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UBC Theses and Dissertations

Detoxification of bleached kraft mill effluents by foam separation Ng, Kong Seng 1977

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DETOXIFICATION OF BLEACHED KRAFT MILL EFFLUENTS BY FOAM SEPARATION by KONG SENG B.Sc. Eng., N a t i o n a l Taiwan U n i v e r s i t y 1967 M . E . S c , U n i v e r s i t y o f Western O n t a r i o 1969 IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN THE DEPARTMENT OF CHEMICAL ENGINEERING FACULTY OF GRADUATE STUDIES WE ACCEPT THIS THESIS AS CONFORMING TO THE REQUIRED STANDARD THE UNIVERSITY OF BRITISH COLUMBIA June, 1977 A THESIS SUBMITTED Kong Seng Ng, 1977 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the requ i rement s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h Co lumb ia , I a g ree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s tudy . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d that c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i thout my w r i t t e n p e r m i s s i o n . Department o f C h e m i c a l E n g i n e e r i n g The U n i v e r s i t y o f B r i t i s h Co lumbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 D a t e December 9, 1977 ABSTRACT i Foam s e p a r a t i o n has been s u c c e s s f u l l y d e v e l o p e d on a 4-1 l a b o r a t o r y column, an 80-1 f i e l d column i n s t a l l a t i o n and a 6000 g a l p i l o t p l a n t t r o u g h t y p e system as a n o v e l p r o c e s s f o r d e t o x i f y i n g b l e a c h e d k r a f t m i l l e f f l u e n t s . T o x i c s u r f a c e a c t i v e m a t e r i a l s such as r e s i n and u n s a t u r a t e d f a t t y a c i d s c o l l e c t a t t h e g a s - l i q u i d i n t e r f a c e o f r i s i n g a i r b u b b l e s and c o n -c e n t r a t e i n t h e foam. The h i g h l y t o x i c c o l l a p s e d foam r e p r e s e n t s 1-2% by volume o f t h e i n f l u e n t and i s s u b s e q u e n t l y d e t o x i f i e d by b i o l o g i c a l t r e a t m e n t . P r o c e s s p a r a m e t e r s c o n t r o l l i n g d e t o x i f i c a t i o n e f f i c i e n c y a r e pH, g a s - l i q u i d i n t e r f a c i a l a r e a , i n i t i a l t o x i c i t y l e v e l and mode o f o p e r a t i o n . The g a s - l i q u i d i n t e r f a c i a l a r e a and pH a r e o f utmost im-p o r t a n c e . F o r a t y p i c a l e f f l u e n t w i t h MST o f 3-4 h r , a p p r o x i m a t e l y 20-2 30 m / l o f i n t e r f a c i a l a r e a g i v e n t o an e f f l u e n t a t pH > 7.0 a r e r e q u i r e d f o r d e t o x i f i c a t i o n . Foam s e p a r a t i o n i s u n i v e r s a l l y a p p l i c a b l e and r e l i a b l e f o r de-t o x i f y i n g k r a f t whole m i l l e f f l u e n t . Over 80% o f 205 samples f r o m 10 Can a d i a n m i l l s were d e t o x i f i e d . A 1 g a l / m i n , one and two s t a g e c o n t i n -uous f l o w systems d e t o x i f i e d o v e r 90% o f samples a t pH 8 and 1-2 h r r e t e n t i o n t i m e o v e r 80 days o f o p e r a t i o n p e r i o d . S tudy o f d e t o x i f i c a t i o n mechanism i n d i c a t e d t h a t foam f r a c t i o n a t i o n a c c o u n t s f o r 77.5% o f d e t o x i f i c a t i o n , v o l a t i z a t i o n f o r 5.4% and u n i d e n t -i f i e d mechanisms f o r 17.1%. Depending on t h e mode o f o p e r a t i o n , up t o 5% o f e f f l u e n t volume was d i s c h a r g e d as foam. The foam volume c o u l d be red u c e d t o < 2% by i n c r e a s i n g foam r e t e n t i o n t i m e and e n h a n c i n g i n t e r n a l r e f l u x . C o l l a p s e d foam was r e a d i l y d e t o x i f i e d by a b i o d i s c o r a e r a t e d lagoon process. I n a d d i t i o n t o d e t o x i f i c a t i o n , foam s e p a r a t i o n removed 20-60% o f suspended s o l i d s , 66% r e s i n a c i d s , 12% B0D 5 ( 1 0 % TOC), 8% c o l o r and 80% f o a m i n g t e n d e n c y . Suspended s o l i d s r e m o v a l c o u l d be i n c r e a s e d t o 88% i f an e x p e n s i v e d i s s o l v e d a i r system were used f o r b u b b l e g e n e r a t i o n . C o m m e r c i a l l y a v a i l a b l e equipment f o r foam g e n e r a t i o n and foam b r e a k i n g was r e v i e w e d . J e t a e r a t o r s and t u r b i n e systems were a s s e s s e d as most s u i t a b l e f o r c o m m e r c i a l a p p l i c a t i o n . P i l o t p l a n t e v a l u a t i o n o f t h i s equipment i n d i c a t e d t h a t r e l i a b l e and c o n s i s t e n t o p e r a t i o n c o u l d be o b t a i n e d . The r e s u l t s were used t o e s t a b l i s h e m p i r i c a l f o r m u l a e f o r use i n p r o c e s s s c a l e up. 2 D u r i n g a 4 month c o n t i n u o u s f l o w s t u d y , a p p r o x i m a t e l y 5-7 m / l o f g a s - l i q u i d i n t e r f a c i a l a r e a was p r o v i d e d t o d e t o x i f y 80-100 g a l / m i n o f m i l l A e f f l u e n t w i t h MST o f 6-10 h r . The d e t o x i f i c a t i o n s u c c e s s r a t e o f a l a r g e number o f samples i n c r e a s e d f r o m 50 t o 86 and t o 100% as t h e o p e r a t i o n changed from 1 t o 2 t o 3 s t a g e s . The foam produced by t h e p i l o t p l a n t was c o l l a p s e d by a 12" d i a m e t e r t u r b i n e a t 100% e f f i c i e n c y a l l t h e t i m e . C o s t s o f foam s e p a r a t i o n were examined f o r a p r o j e c t e d 3 s t a g e foam s e p a r a t i o n p r o c e s s , t r e a t i n g 25 M g a l / d a y o f b l e a c h e d k r a f t whole m i l l e f f l u e n t . C a p i t a l c o s t s f o r pH c o n t r o l , foam g e n e r a t i o n , foam b r e a k i n g and foam t r e a t m e n t were e s t i m a t e d a t $2.26 M. O p e r a t i n g c o s t s were e s t i m a t e d a t $2.,35/ton o f p u l p . i i i TABLE OF CONTENTS Page A b s t r a c t i T a b l e o f C o n t e n t s . . i i i L i s t o f T a b l e s v i i i L i s t o f F i g u r e s x l L i s t o f A p p e n d i c e s x i v Acknowledgements x v i x N o m e nclature x v i i i CHAPTER I : POLLUTION PROBLEMS IN KRAFT INDUSTRY 1 CHAPTER I I : RATIONALE OF FOAM SEPARATION PROCESS AS A MEANS OF DETOXIFYING KRAFT MILL EFFLUENTS 5 A. T o x i c Components o f K r a f t M i l l E f f l u e n t s 5 B. E x i s t i n g D e t o x i f i c a t i o n P r o c e s s e s 10 1. P h y s i c o - c h e m i c a l p r o c e s s e s 10 a. A d s o r p t i o n 10 b. C o a g u l a t i o n - f l o c c u l a t i o n 12 c. C h e m i c a l o x i d a t i o n 13 2. B i o l o g i c a l t r e a t m e n t p r o c e s s e s 1^ 3. C o n c l u s i o n s 15 C. P o t e n t i a l R o l e o f Foam S e p a r a t i o n P r o c e s s f o r D e t o x i -f i c a t i o n o f K r a f t M i l l E f f l u e n t s 15 CHAPTER I I I : LITERATURE REVIEW OF FOAM SEPARATION PROCESSES . . 19 A. C l a s s i f i c a t i o n o f Foam S e p a r a t i o n P r o c e s s e s 19 B. P r i n c i p l e o f Foam S e p a r a t i o n 21 1. F i l m f o r m a t i o n 21 2. A d s o r p t i o n 22 3. Foam s e p a r a t i o n mechanisms 23 a. Foam f r a c t i o n a t i o n 23 b. F r o t h f l o t a t i o n 24 i v C. F a c t o r s A f f e c t i n g Foam S e p a r a t i o n 26 1. C h e m i c a l n a t u r e and c o n c e n t r a t i o n 29 2. P H 30 3. Gas f l o w r a t e 30 4. B u b b l e s i z e 31 5. Temperature 31 6. V i s c o s i t y 32 7. Column h e i g h t 32 8. Foam r e m o v a l 32 D. Mode o f O p e r a t i o n 33 E. A p p l i c a t i o n s . 34 CHAPTER IV: MATERIALS AND METHODS 39 A. Scope o f Study 3 9 B. Source and Type o f E f f l u e n t s 45 1. L a b o r a t o r y s t u d i e s 45 2. F i e l d s t u d i e s 4 6 3. P i l o t p l a n t s t u d i e s 47 C. Foam S e p a r a t i o n Systems - Equipment and O p e r a t i o n . . . . 47 1. L a b o r a t o r y System 47 a. Foam g e n e r a t i o n ->4 b. Foam volume r e d u c t i o n 54 c. Foam c o l l a p s i n g 56 2. Foam s e p a r a t i o n s y s t e m i n s t a l l e d a t m i l l s i t e ( F i e l d system) a. pH c o n t r o l ^ b. Pumping s t a t i o n 59 c. A i r d i s p e r s i o n s y s t e m 61 d. Foam f r a c t i o n a t i o n columns 63 e. Foam c o l l a p s i n g 67 f . Treatment and d e t o x i f i c a t i o n o f c o l l a p s e d foam 67 3. P i l o t p l a n t foam s e p a r a t i o n s y s t e m 71 a. E f f l u e n t d e l i v e r y 71 b. pH c o n t r o l 74 c. Foam f r a c t i o n a t i o n s y s t e m 74 d. Foam h a n d l i n g s y s t e m 77 D. A n a l y s e s 78 E. D e t e r m i n a t i o n o f D e t o x i f i c a t i o n Mechanisms $4 CHAPTER V: RESULTS AND DISCUSSIONS 8 7 A. T r e a t a b i l i t y S t u d i e s 87 V 1. S e l e c t i v e d e t o x i f i c a t i o n o f v a r i o u s p r o c e s s streams . . 87 a. U n b l e a c h e d w h i t e w a t e r 89 b. A c i d b l e a c h e f f l u e n t 91 c. C a u s t i c e x t r a c t i o n e f f l u e n t 92 2. E f f e c t o f c a u s t i c e x t r a c t i o n e f f l u e n t a d d i t i o n on d e t o x i f i c a t i o n o f a c i d b l e a c h e f f l u e n t 94 3. E f f e c t o f s y n t h e t i c s u r f a c t a n t on d e t o x i f i c a t i o n o f u n b l e a c h e d w h i t e w a t e r 97 4. D e t o x i f i c a t i o n o f combined m i l l e f f l u e n t 99 5. S e l e c t i o n o f most s u i t a b l e p r o c e s s streams f o r foam s e p a r a t i o n t r e a t m e n t 102 B. P r o c e s s P a r a m e t e r s f o r Optimum D e t o x i f i c a t i o n by Foam S e p a r a t i o n 107 1. E f f e c t o f pH 108 2. E f f e c t o f t e m p e r a t u r e 109 3. E f f e c t o f column h e i g h t 113 4. E f f e c t o f a e r a t i o n r a t e and G/L r a t i o 115 5. E f f e c t o f b u b b l e d i a m e t e r and g a s - l i q u i d i n t e r f a c i a l a r e a 117 6. E f f e c t o f i n f l u e n t t o x i c i t y l e v e l on t r e a t m e n t t i m e and g a s - l i q u i d i n t e r f a c i a l a r e a r e q u i r e m e n t 120 7. E f f e c t o f mode o f o p e r a t i o n and r e t e n t i o n t i m e r e q u i r e d 124 8. E f f e c t o f s t a g i n g 127 C. E f f e c t o f V a r i a b i l i t y i n E f f l u e n t C h a r a c t e r i s t i c s on D e t o x i f i c a t i o n 130 D. D e t o x i f i c a t i o n R e l i a b i l i t y o f a Foam S e p a r a t i o n P r o c e s s . . 133 E. Mechanisms o f D e t o x i f i c a t i o n 134 1. E f f e c t o f gas ton d e t o x i f i c a t i o n L 136 2. R e l a t i v e c o n t r i b u t i o n o f foam s e p a r a t i o n , v o l a t i z -a t i o n and o t h e r mechanisms t o d e t o x i f i c a t i o n 138 3. C u m u l a t i o n o f r e s i n a c i d s i n foam 141 F. Combined D e t o x i f i c a t i o n and F i b r e Removal by Foam S e p a r a t i o n P r o c e s s 143 1. D i s p e r s e d a i r s y s t e m 144 2. D i s s o l v e d a i r f l o t a t i o n s y s t e m 147 G. B e n e f i c i a l S i d e E f f e c t s o f Foam S e p a r a t i o n P r o c e s s 152 1. R e s i n a c i d s r e m o v a l 152 2. Suspended s o l i d s r e m o v a l 152 3. B0D 5 and TOC r e m o v a l 153 4. C o l o r r e m o v a l 153 5. Foaming tendency r e m o v a l 153 v i H. Treatment o f Foam 156 1. Foam c h a r a c t e r i s t i c s 156 2. R e d u c t i o n o f foam volumes 160 a. E f f e c t o f foam h e i g h t 162 b. E f f e c t o f foam r e c y c l i n g 164 3. Breakage o f foam 166 a. E f f e c t o f r o t a t i o n speed and t i p speed o f t u r b i n e on foam c o l l a p s i n g e f f i c i e n c y 167 b. Power consumption 171 4. Foam d i s p o s a l 171 a. I n c i n e r a t i o n 174 b. C h e m i c a l t r e a t m e n t 174 c. B i o l o g i c a l t r e a t m e n t 174 CHAPTER V I : THEORETICAL ASSESSMENT OF MAJOR OPERATING EQUIPMENT. . 178 A. Assessment o f Foam G e n e r a t i o n System 178 1. S p e c i f i c c r i t e r i a f o r equipment s e l e c t i o n . . . . . . 178 2. S e l e c t i o n o f most p r o m i s i n g foam g e n e r a t i o n system. . 179 a. F o r c e d a i r d i f f u s i o n 179 b. A i r e n t r a i n m e n t 181 c. M e c h a n i c a l s h e a r 183 d. H y d r a u l i c s h e a r 184 e. H i g h p r e s s u r e a e r a t o r 185 3. S e l e c t i o n o f t h e b e s t foam g e n e r a t i o n s y s t e m . . . . 185 a. Bubble s i z e 186 b. R e l i a b i l i t y o f equipment . 189 c. Economy 192 d. C o n c l u s i o n 193 B. Assessment o f Foam B r e a k i n g System 193 1. S p e c i f i c c r i t e r i a f o r equipment s e l e c t i o n 193 2. S e l e c t i o n o f most p r o m i s i n g foam b r e a k i n g system. . . 194 a. A i r j e t 194 b. S o n i c p r e s s u r e 194 c. Thermal method 196 d. L i q u i d s p r a y 196 e. O r i f i c e foam b r e a k e r 197 f . M e c h a n i c a l f o r c e s 197 3. S e l e c t i o n o f b e s t t u r b i n e foam b r e a k i n g s y s t e m . . . 198 CHAPTER V I I : PILOT PLANT OPERATION 2 0 4 A. P i l o t P l a n t Foam S e p a r a t i o n P r o c e s s 204 B. I n f l u e n t C h a r a c t e r i s t i c s 205 C. O p t i m i z a t i o n o f O p e r a t i o n a l P a r a m e t e r s f o r D e t o x i f i c a t i o n o f M i l l A's W h o l e m i l l E f f l u e n t 2 0 7 1. G a s - l i q u i d i n t e r f a c i a l a r e a and number o f j e t s r e q u i r e d 2 (- ) 7 v i i o no 2. Foam minimization D. E f f e c t of Staging on D e t o x i f i c a t i o n Success Rate and 211 Foam C h a r a c t e r i s t i c s E. Foam Breaking Performance 215 F. Summary of P i l o t Plant Operation 217 CHAPTER VIII: PROPOSAL AND ECONOMICS OF A FOAM SEPARATION PLANT FOR DETOXIFYING KRAFT MILL EFFLUENT . '218 A. Process Description 218 B. S p e c i f i c a t i o n and Design Considerations of Various Process Elements 221 1. E f f l u e n t screening and pumping system 221 2. pH control 223 3. Foam generation system 223 a. Foam separation tank 223 b. Foam generator 224 c. Blower capacity 226 4. Foam handl ing 226 a. Foam breaking system 227 b. Foam treatment system 228 C. Proposal For A 25 MGD Foam Separation Plant 228 D. Estimation of Operating Cost 232 CHAPTER IX: SUMMARY AND CONCLUSIONS 235 REFERENCES ,245 v i i i L IST OF TABLES T a b l e Page 1. R e p o r t e d T o x i c V a l u e s o f S u l p h u r Compounds . . . . . . 6 2. T o x i c Components i n K r a f t M i l l I n d i v i d u a l and Combined P r o c e s s Streams 8 3. C h a r a c t e r i s t i c s o f D i f f e r e n t Foam S e p a r a t i o n O p e r a t i o n s 36 4. A p p l i c a t i o n o f Foam S e p a r a t i o n P r o c e s s 37 5. E f f e c t o f Foam S e p a r a t i o n on D e t o x i f i c a t i o n o f I n d i v i d u a l P r o c e s s Streams 90 6. E f f e c t o f S u r f a c t a n t A d d i t i o n On D e t o x i f i c a t i o n o f Unbleached White Water 98 7. T o x i c i t y Removal o f Combined M i l l E f f l u e n t By Foam S e p a r a t i o n I d 8. Foam S e p a r a t i o n Time R e q u i r e d F o r D e t o x i f y i n g V a r i o u s Combined E f f l u e n t s 103 9. E f f e c t o f Bubble D i a m e t e r , G a s - L i q u i d R a t i o , and I n t e r f a c i a l A r e a on D e t o x i f i c a t i o n H 9 10. E f f e c t o f O p e r a t i o n Mode and R e t e n t i o n Time On C o n t i n u o u s D e t o x i f i c a t i o n o f K r a f t M i l l E f f l u e n t s . . . 126 11. D e t o x i f i c a t i o n P e r f o r m a n c e (mean v a l u e ) Of a S i n g l e S t a g e v s 2-Stage System I 2 8 12. S u c c e s s Rate i n D e t o x i f y i n g B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t s By Foam S e p a r a t i o n 131 13. D e t o x i f i c a t i o n R e l i a b i l i t y o f a S i n g l e Stage C o n t i n u o u s Foam S e p a r a t i o n System Over 63 Days o f O p e r a t i o n 135 14. Foam S e p a r a t i o n o f B l e a c h e d K r a f t M i l l E f f l u e n t W i t h D i f f e r e n t Gases I 3 7 15. R e l a t i v e C o n t r i b u t i o n To D e t o x i f i c a t i o n by V a r i o u s Mechanisms 1^9 i x 16. E f f e c t o f Foam S e p a r a t i o n On R e s i n A c i d s Removal . . . . 142 17. Removal o f F i b r o u s Suspended S o l i d s a t D i f f e r e n t L o a d i n g s By a D i s p e r s e d A i r System 145 18. Removal o f Suspended S o l i d s by a D i s p e r s e d A i r Foam S e p a r a t i o n System a t M i l l S i t e . 146 19. Removal o f F i b r o u s Suspended S o l i d s From B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t By D i s s o l v e d A i r F l o t a t i o n . . 150 20. BOD5 and TOC R e d u c t i o n by Foam S e p a r a t i o n 154 21. C o l o r Removal by C o n t i n u o u s Foam S e p a r a t i o n System . . . 155 22. E f f e c t o f Foam S e p a r a t i o n on Foaming Tendency R e d u c t i o n . 158 23. Average C h a r a c t e r i s t i c s o f I n f l u e n t and C o l l a p s e d Foam . 161 24. E f f e c t o f Foam H e i g h t on Foam Volume D i s c h a r g e d . . . . 163 25. E f f e c t o f Foam R e c y c l i n g on D e t o x i f i c a t i o n i n a C o n t i n u o u s System 1^5 26. C r i t i c a l T i p Speed F o r Foam C o l l a p s i n g . i 7 0 27. C h e m i c a l Treatment o f C o l l a p s e d Foam 175 28. Treatment o f C o l l a p s e d Foam by an A e r a t e d Lagoon and B i o d i s c System 1^6 29. C h a r a c t e r i s t i c s o f V a r i o u s Foam G e n e r a t i n g Equipment . . 180 30. Comparison o f Most P r o m i s i n g Foam G e n e r a t i n g Equipment 188 31. A v e r a g e A i r B u b b l e S i z e s P r o d u ced By a J e t A e r a t o r i n B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t 19° 32. Comparison o f V a r i o u s Foam B r e a k i n g D e v i c e s 195 33. E f f e c t o f I m p e l l e r Geometry o f a 3-Blade T u r b i n e on Foam C o l l a p s i n g E f f i c i e n c y and Power Consumption . . . . 203 34. I n f l u e n t C h a r a c t e r i s t i c s D u r i n g P i l o t P l a n t O p e r a t i o n . . 206 35. Average Foam G e n e r a t i o n C h a r a c t e r i s t i c s i n a Staged Foam S e p a r a t i o n System w i t h 2 t o 6 J e t A e r a t o r s i n O p e r a t i o n 210 X 36. D e t o x i f i c a t i o n S u c c e s s Rate o f V a r i o u s C o n t i n u o u s Foam S e p a r a t i o n Systems 2 1 3 37. E f f i c i e n c y o f Foam B r e a k i n g by a 3-Blade Vaned D i s c T u r b i n e 2 1 6 38. P r o c e s s S p e c i f i c a t i o n F o r a 25 MGD I n t e g r a t e d Foam S e p a r a t i o n P l a n t 2 2 2 39. Comparison o f Foam S e p a r a t i o n P r o c e s s t o A e r a t e d Lagoon P r o c e s s 2 3 3 xi LIST OF FIGURES Figure Page 1. Chemical Structure of Resin Acid Derivatives 17 2. Classification of Foam Separation 20 3-a. Adsorption of Surface Active Molecules on Gas-Liquid Interface 25 -b. Mechanism of Froth Flotation 25 4. Three Foam Lamellae Coming Together In a Plateau Border and Forming Angles of 120° With Each Other . . 28 5. Modes Of Operation of Various Foam Separation System . 35 6-a. Overall View of Laboratory Foam Separation Equipment . 49 -b. Sintered Glass Gas Disperser Inserted to the Bottom of the Foam Separation Column 49 7. A Single Column Used for Laboratory Foam Separation Studies 50 8. Foam Separation System with Kenics Aerator 51 9. Mechanical Dispersion of Air by a Turbine 53 10. Dissolved Air Flotation System 55 11. Reduction of Foam by Recycling (enriching mode) . . . 57 12. Foam Collapsing System Using Vacuum Rupture Technique 58 13. Process Flow Sheet For Foam Separation at Mill Site. . 60 14-a. Plastic Disc Air Dispersion Discs 62 -b. Ceramic Air Dispersion Tubes 62 -c. Porous Alundum Plate Air Dispersion Media 62 15. Field Foam Separation Column Installed With Ceramic Tube Air Dispersers 64 16. Foam Separation Column Installed at Mill Site . . . . 65 17. Picture of Field Foam Separation Column in Operation . 6 6 x i i 18. Foam B r e a k i n g by Water Spray System 68 19. B i o d i s c System f o r Treatment o f C o l l a p s e d Foam . . . . 70 20. P i l o t P l a n t Foam S e p a r a t i o n System (100 g a l / m i n ) . . . . 7 2 21. O v e r a l l View o f 100 g a l / m i n Foam S e p a r a t i o n P i l o t P l a n t I n s t a l l e d a t M i l l A 7 3 22-a. J e t A e r a t o r T e s t i n g U n i t 7 6 -b. J e t A e r a t o r i n O p e r a t i o n 7 6 23. M e c h a n i c a l T u r b i n e Foam B r e a k i n g System 7 ^ 24. L a b o r a t o r y Set-up f o r I n v e s t i g a t i o n o f D e t o x i f i c a t i o n Mechanisms 85 25. R e l a t i v e C o n t r i b u t i o n t o D e t o x i f i c a t i o n by Foam F r a c t i o n a t i o n , V o l a t i z a t i o n and Unknown Mechanisms. . . 86 26. E f f e c t o f pH on Foaminess o f C a u s t i c E x t r a c t i o n E f f l u e n t 88 27. E f f e c t o f E f f l u e n t C o m p o s i t i o n on t h e pH Requirement f o r D e t o x i f i c a t i o n 95 28. Time R e q u i r e d f o r D e t o x i f i c a t i o n o f V a r i o u s E f f l u e n t M i x t u r e s from M i l l B 104 29. Time R e q u i r e d f o r D e t o x i f i c a t i o n o f V a r i o u s W h o l e m i l l E f f l u e n t s 106 30. E f f e c t o f pH on D e t o x i f i c a t i o n by Foam S e p a r a t i o n . . . 110 31. E f f e c t o f Temperature I l l 32. E f f e c t o f Column H e i g h t on D e t o x i f i c a t i o n 114 33. E f f e c t o f A e r a t i o n R a t e 116 34. C o r r e l a t i o n Between T o x i c i t y o f I n f l u e n t and Treatment Requirement <-121 35. C o r r e l a t i o n Between T o x i c i t y and G a s - L i q u i d I n t e r -f a c i a l A r e a R e q u i r e d f o r D e t o x i f i c a t i o n (mean v a l u e s ) . 123 36. E f f e c t o f Foaming Tendency on Suspended S o l i d s Removal By a D i s p e r s e d A i r Foam S e p a r a t i o n System 148 x i i i 37. D e t o x i f i c a t i o n o f B l e a c h e d K r a f t M i l l E f f l u e n t by a D i s s o l v e d A i r System 151 38. R e d u c t i o n o f Foaming Tendency D u r i n g T o x i c i t y Removal . . 15V 39. Foaming Tendency R e d u c t i o n by C o n t i n u o u s Foam S e p a r a t i o n 159 40. C r i t i c a l RPM Requirement f o r V a r i o u s T u r b i n e S i z e s . . . . 169 41. Power Consumption by a 38 cm T u r b i n e Foam B r e a k e r . . . . 172 42. E f f e c t o f R o t a t i o n Speed and T u r b i n e D i a m e t e r on Power Consumption 173 43. S u r f a c e A e r a t o r 182 3 44. B u b b l e s S i z e s Produced by J e t A e r a t o r a t 5 f t /min A i r Load i 8 7 45. J e t A e r a t o r i n O p e r a t i o n 191 46. P r i n c i p a l F o r c e s I n v o l v e d i n B r e a k i n g Foam by T u r b i n e . . 199 47. T u r b i n e s o f V a r i o u s Shapes 201 48. E f f e c t o f G a s - L i q u i d I n t e r f a c i a l A r e a F o r D e t o x i f i c a t i o n o f K r a f t M i l l E f f l u e n t s 2 0 9 49. F l o w Sheet o f Foam S e p a r a t i o n P l a n t F o r D e t o x i f y i n g K r a f t M i l l E f f l u e n t 2 2 0 50. P r o p o s e d Foam S e p a r a t i o n P l a n t 51. L a y o u t o f Foam G e n e r a t i o n Tank, J e t A e r a t o r and T u r b i n e Foam B r e a k e r 23-*-52. I n s t a l l a t i o n o f J e t System i n Foam S e p a r a t i o n Tank . . . . A p p e n d i x XTX x i v LIST OF APPENDICES Ap p e n d i x I . E f f l u e n t C o m p o s i t i o n v s pH Requirement f o r D e t o x i f i c a t i o n . . . 254 I I . T o x i c i t y o f S e l e c t e d C a t i o n i c S u r f a c t a n t s t o F i s h a t 50 ppm C o n c e n t r a t i o n 255 I I I . C o r r e l a t i o n Between I n i t i a l T o x i c i t y and G a s - L i q u i d I n t e r f a c i a l A r e a R e q u i r e d f o r D e t o x i f i c a t i o n • • 256 I V - a . O p e r a t i n g D a t a o f a S i n g l e Stage C o n t i n u o u s Foam S e p a r a t i o n System 257 -b. O p e r a t i n g D a t a o f a Two Stage C o n t i n u o u s Foam S e p a r a t i o n System 258 V-a. D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l A by Foam S e p a r a t i o n 259 -b. D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l B by Foam S e p a r a t i o n 260 - c . D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l C by Foam S e p a r a t i o n 261 -d . D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l D by Foam S e p a r a t i o n 262 -e. D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l E by Foam S e p a r a t i o n 263 - f . D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l F by Foam S e p a r a t i o n 264 -g . D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l G by Foam S e p a r a t i o n 265 -h. D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l H by Foam S e p a r a t i o n 266 - i . D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l I by Foam S e p a r a t i o n 267 - j . D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t From M i l l J by Foam S e p a r a t i o n 268 XV A p p e n d i x V l - a . C o n t i n u o u s D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t s by Foam S e p a r a t i o n i n a S i n g e Stage Column ( w i t h seven 5" d i a m e t e r , 65 y p o r e s i z e p l a s t i c a i r d i f f u s e r s i n a 180-1 column) 269 -b. C o n t i n u o u s D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t s by Foam S e p a r a t i o n i n a S i n g l e Stage Column ( w i t h f o u r 5" d i a m e t e r , 25 y p o r e s i z e p l a s t i c a i r d i f f u s e r s i n a 180-1 column) 271 - c . C o n t i n u o u s D e t o x i f i c a t i o n o f B l e a c h e d K r a f t W h o l e m i l l E f f l u e n t s by Foam S e p a r a t i o n i n a S i n g l e Stage Column ( w i t h f o u r 1' l e n g t h , 3" d i a m e t e r , 25 y p o r e s i z e c e r a m i c d i f f u s e r s i n a 180-1 column) 272 V l l - a . D e t e r m i n a t i o n o f D e t o x i f i c a t i o n Mechanisms - M i l l F 273 -b. D e t e r m i n a t i o n o f D e t o x i f i c a t i o n Mechanisms - M i l l G . . . . . 274 - c . D e t e r m i n a t i o n o f D e t o x i f i c a t i o n Mechanisms - M i l l I 275 V I I I . T o x i c i t y Removal by a D i s s o l v e d A i r Foam S e p a r a t i o n 276 System I X - a . E f f e c t o f Foam S e p a r a t i o n on Foaming Tendency R e d u c t i o n o f M i l l B E f f l u e n t s 277 -b. E f f e c t o f Foam S e p a r a t i o n on Foaming Tendency R e d u c t i o n o f M i l l F E f f l u e n t s 278 X-a. C h a r a c t e r i s t i c s o f Foam Produced by 25 y P l a s t i c D i f f u s e r i n a C o n t i n u o u s Foam S e p a r a t i o n System 279 -b. C h a r a c t e r i s t i c s o f Foam P r o d u c e d by a 25 y Ceramic D i f f u s e r s i n a C o n t i n u o u s Foam S e p a r a t i o n System 280 X I . C r i t i c a l R o t a t i o n Speed (RPM) and T i p Speed R e q u i r e d F o r Foam C o l l a p s i n g 281 X I I . Power Data o f Foam B r e a k i n g System 282 X I I I . E f f e c t o f F l o c c u l a t i o n on D e t o x i f i c a t i o n o f K r a f t M i l l E f f l u e n t s 283 xv i A p p e n d i x X l V - a . Treatment o f C o l l a p s e d Foam by 1-day and 3-day R e t e n t i o n A e r a t e d Lagoon 284 -b. Treatment o f C o l l a p s e d Foam by 2-hr and 4-hr R o t a t i n g B i o d i s c Systems 285 XV. I n f l u e n t C h a r a c t e r i s t i c s o f M i l l A E f f l u e n t s 286 XVI. T o x i c i t y o f T r e a t e d Samples as a F u n c t i o n o f I n t e r f a c i a l A r e a P r o d u c e d D u r i n g Foam S e p a r a t i o n 287 X V I I . E f f e c t o f S t a g i n g a t C o n s t a n t G a s - L i q u i d I n t e r f a c i a l A r e a on D e t o x i f i c a t i o n P erformance o f J e t Foam G e n e r a t i o n System 288 X V I I I . Foam B r e a k i n g P e r f o r m a n c e by a T u r b i n e System 289 X l X - a . S i z i n g o f S c r e e n i n g and Pumping Equipment 290 -b. pH C o n t r o l System 292 - c . S i z i n g o f Foam S e p a r a t i o n System 293 -d . S i z i n g o f Foam D i s p o s a l System 299 XX. L i s t o f P u b l i c a t i o n s 301 ACKNOWLEDGEMENT The a u t h o r i s most i n d e b t e d t o Dr. R.M.R. B r a n i o n , Department o f C h e m i c a l E n g i n e e r i n g , U n i v e r s i t y o f B r i t i s h C o l umbia and D r s . J.C. M u e l l e r and C C . Walden o f t h e D i v i s i o n o f A p p l i e d B i o l o g y , B.C. Re-s e a r c h C o u n c i l f o r t h e i r g u i d a n c e and encouragement t h r o u g h o u t t h e p e r i o d o f t h i s s t u d y . The a u t h o r i s a l s o g r a t e f u l t o h i s e m p l o y e r , B. R e s e a r c h f o r t h e use o f a l l r e s e a r c h f a c i l i t i e s and t o numerous s t a f f t h e A p p l i e d B i o l o g y D i v i s i o n o f B.C. R e s e a r c h i n p a r t i c u l a r t o Mr. L. R i e g e r , Mr. R. W i l s o n , Mr. P. Temoin, Mr. L. G u t i e r r e z and Mrs. P. MacLeod f o r t h e i r c a p a b l e t e c h n i c a l a s s i s t a n c e . Thanks a r e a l s o due t o Mr. R. Wiseman, t e c h n i c a l d i r e c t o r and management o f Northwood P u l p M i l l , P r i n c e George, B.C; and Mr. N. E c k s t e i n , s e n i o r p r o c e s s e n g i n e e r and management o f Harmac P u l p M i l l ( M a c M i l l a n - B l o e d e l L t d . ) f o r t h e i r c o - o p e r a t i o n and a s s i s t a n c e d u r i n g o n - s i t e s t u d i e s . T h i s r e s e a r c h was made p o s s i b l e by g r a n t s f r o m t h e C o u n c i l o f F o r e s t I n d u s t r y , E n v i r o n m e n t a l Committee - P u l p and P a p e r , and CPAR program o f t h e C a n a d i a n F o r e s t r y S e r v i c e . NOMENCLATURE S u r f a c e t e n s i o n (dynes/cm) C h e m i c a l p o t e n t i a l (dynes-cm/g-mole) S u r f a c e e x c e s s (g-mole/cm 3) A c t i v i t y c o e f f i c i e n t Gas c o n s t a n t A b s o l u t e t e m p e r a t u r e P r o p o r t i o n a l i t y c o n s t a n t i = l , 2 , 3 , 4 R o t a t i o n speed o f t u r b i n e (rpm) Dia m e t e r o f t u r b i n e (cm) T i p v e l o c i t y (cm/sec) Foaming tendency (min) Foaming s t a b i l i t y (min) Volume of foam E f f i c i e n c y o f foam b r e a k i n g Power co n s u m p t i o n ( w a t t s ) Foam b r e a k i n g c a p a c i t y ' ( f t 3 / m i n ) B u b b l e d i a m e t e r (mm) Time o f a e r a t i o n (min) Treatment t i m e r e q u i r e d I n f l u e n t t o x i c i t y (MSTrhrs) CHAPTER 1 POLLUTION PROBLEMS IN KRAFT INDUSTRY 1 The p r o c e s s o f m a n u f a c t u r i n g p u l p and paper r e q u i r e s an enormous amount o f w a t e r . I n Canada, a t y p i c a l b l e a c h e d k r a f t p u l p m i l l consumes an a v e r a g e of 30,000 t o 40,000 g a l o f w a t e r p e r t o n of p u l p p r o d u c e d . Up t o 25% o f t h e wood c h i p s may be d i g e s t e d by t h e c o o k i n g c h e m i c a l s , c o n v e r t e d i n t o v a r i o u s c h e m i c a l compounds and d i s c h a r g e d t o t h e r e c e i v -i n g w a t e r s i n d i l u t e form. These c h e m i c a l compounds a r e c o n s i d e r e d as p o l l u t a n t s . The c h a r a c t e r i s t i c s and t y p e s o f p o l l u t a n t s however, a r e h i g h l y complex and a r e s t i l l i n t h e p r o c e s s of b e i n g i d e n t i f i e d . N e v e r -t h e l e s s , t h e s e p o l l u t a n t s can be c l a s s i f i e d i n t h e form o f t h e f o l l o w i n g e f f e c t s : pH i n b a l a n c e suspended s o l i d s c o n c e n t r a t i o n b i o c h e m i c a l oxygen demand (BOD) t o x i c i t y c o l o r . The g r e a t e s t i m p a c t o f d i s c h a r g i n g u n t r e a t e d k r a f t m i l l e f l f u e n t t o t h e a d j a c e n t e n vironment i s p r i m a r i l y due t o r e l e a s e o f tremendous volume o f waste a t a s i n g l e p o i n t . The c u m u l a t i v e , e f f e e t o f v a r i o u s p o l l u t a n t s w i l l c o n s e q u e n t l y l o w e r t h e q u a l i t y o f r e c e i v i n g w a t e r s and damage t h e e c o l o g y o f t h e s u r r o u n d i n g s . A t p r e s e n t t h e F e d e r a l and P r o v i n c i a l a u t h o r i t i e s have e s t a b l i s h e d e f f l u e n t d i s c h a r g e g u i d e l i n e s f o r pH, suspended s o l i d s , BOD,, and t o x i c i t y ; t h e d e g r e e o f r e m o v a l r e q u i r e d f o r each m i l l however i s s e t a c c o r d i n g t o i n d i v i d u a l c i r c u m -2 s t a n c e s s u c h as g e o g r a p h i c a l l o c a t i o n s , t y p e and age o f t h e m i l l , e t c . I n g e n e r a l , p u l p and paper m i l l s a c r o s s Canada a t t e m p t t o meet t h e pH s t a n d a r d by c o n t r o l l e d d i s c h a r g e o f v a r i o u s a c i d and a l k a l i n e sewers c o u p l e d w i t h c h e m i c a l t r e a t m e n t where n e c e s s a r y , t o a c h i e v e t h e p e r m i t -a b l e pH l e v e l s . Suspended s o l i d s s t a n d a r d s a r e met by s e d i m e n t a t i o n w i t h o r w i t h o u t c h e m i c a l a i d s . The d e s i g n o f t h e s e two p h y s i c a l - c h e m i c a l t r e a t m e n t p r o c e s s e s a r e q u i t e s t a n d a r d and t h e i r p e r f o r m a n c e s a r e r e a s o n a b l y c o n s i s t e n t (1). The r e m o v a l o f BOD^ i s a c c o m p l i s h e d by b i o l o g i c a l t r e a t m e n t p r o -c e s s e s where t h e BOD!^ m a t e r i a l s a r e b i o d e g r a d e d by m i c r o - o r g a n i s m s (2) t o CC^, w a t e r and c e l l mass. N u t r i e n t s and o t h e r e n v i r o n m e n t a l f a c t o r s must be m a i n t a i n e d a t s u i t a b l e l e v e l s . A good b i o l o g i c a l s y s t e m must a l s o i n c o r p o r a t e s p e c i a l d e s i g n s t o p r o v i d e p r o t e c t i o n a g a i n s t shock l o a d s s u c h as s p i l l s and p r o c e s s changes d u r i n g p u l p m i l l o p e r a t i o n s . These a r e t o e n s u r e p r o p e r f u n c t i o n i n g o f t h e b iomass. W i t h r e g a r d t o d e t o x i f i c a t i o n , a l t h o u g h s e v e r a l t e c h n i q u e s have been p r o p o s e d , none o f them i s y e t e c o n o m i c a l l y v i a b l e . The k r a f t i n d u s t r y p r e s e n t l y r e l i e s c o m p l e t e l y on t h e p r o p e r p e r f o r m a n c e o f t h e i r b i o l o g i c a l waste t r e a t m e n t s y s t e m t o a c h i e v e t h e s i d e e f f e c t o f d e t o x -i f i c a t i o n . S i n c e t h e b i o - p r o c e s s e s a r e n o t d e s i g n e d f o r t o x i c i t y r e -m o v al, p r o p e r s a f e g u a r d s have n o t been c o n s i d e r e d t o e n s u r e optimum per f o r m a n c e . As a r e s u l t , r e m o v a l o f t o x i c i t y i s n o t a l w a y s c o n s i s t e n t (3). K r a f t m i l l e f f l u e n t s a r e h i g h l y c o l o r e d due t o t h e p r e s e n c e o f l a r g e amounts o f l i g n i n d e r i v a t i v e s . An a d v e r s e e f f e c t on f i s h l i f e has n o t been d e m o n s t r a t e d . C u r r e n t s t u d i e s a r e r e l a t e d m a i n l y t o t h e e f -f e c t s o f c o l o r d i s c h a r g e (4, 5) on l i g h t t r a n s m i s s i o n and i n t u r n on p r i m a r y p r o d u c t i v i t y o f p h o t o s y n t h e t i c a q u a t i c f l o r a . A t p r e s e n t , no s t a n d a r d has been s e t t o r e g u l a t e t h e d i s c h a r g e o f c o l o r compounds. However, i n a n t i c i p a t i o n o f t h e more s t r i n g e n t r e g u l a t i o n , s e v e r a l major r e s e a r c h s t u d i e s on c o l o r r e m o v a l have r e c e n t l y been i n i t i a t e d . Most n o t a b l e a r e t h e development o f m a s s i v e l i m e ( 6 , 7 , 8 ) , i o n f l o t a t i o n (9,10) and ozone (11,12) t r e a t m e n t p r o c e s s e s . These p r o c e s s e s s t i l l r e q u i r e s u b s t a n t i a l development work b e f o r e c o m m e r c i a l i z a t i o n can be a c h i e v e d . C o n s i d e r i n g t h e e f f l u e n t g u i d e l i n e s and t h e t e c h n o l o g i e s a v a i l a b l e t o d a t e , one o f t h e most p r e s s i n g p r oblems f a c i n g t h e p u l p and paper i n d u s t r y i s t h e r e m o v a l o f t o x i c i t y . A t p r e s e n t t h e F e d e r a l Government t o x i c i t y s t a n d a r d c a l l s f o r d i s c h a r g e o f an e f f l u e n t c a p a b l e o f s u s t a i n -i n g 80% f i s h s u r v i v a l i n a 65% e f f l u e n t o v e r 96-hr. I n 1971, t h e P o l -l u t i o n C o n t r o l Board o f B r i t i s h C o l u m b i a e s t a b l i s h e d l e v e l A and B e f -f l u e n t t o x i c i t y g u i d e l i n e s f o r c o a s t a l m i l l s ( 1 3 ) . The l e v e l A t o x i c i t y o b j e c t i v e r e q u i r e s 50% f i s h s u r v i v a l i n 45% e f f l u e n t c o n c e n t r a t i o n o v e r 9 6 - h r s , whereas f o r l e v e l B, t h e e f f l u e n t c o n c e n t r a t i o n i s 12.5%. The m i l l s a r e r e q u i r e d t o meet th e l e v e l A s t a n d a r d i n t h e n e a r f u t u r e . The f e d e r a l and p r o v i n c i a l l e v e l A s t a n d a r d s can o n l y be met by i m p l e m e n t i n g some form o f waste t r e a t m e n t system. S i n c e a b i o l o g i c a l t r e a t m e n t p r o c e s s i s t h e b e s t known method o f s i m u l t a n e o u s BOD,, and t o x i c i t y r e m o v a l , even though d e t o x i f i c a t i o n i s n o t n e c e s s a r i l y c o n s i s t e n t , t h e p r o c e s s has been widely a d o p t e d by t h e i n d u s t r y . However, i n most c o a s t a l m i l l s , B0D5 r e m o v a l i s n o t c o m p u l s o r y due t o t h e l a r g e d i l u t i o n i n v o l v e d when d i s c h a r g i n g t o m a r i n e w a t e r and as l a n d i s a l w a y s s c a r c e , a b i o l o g i c a l t r e a t m e n t p r o c e s s i s n o t a s u i t a b l e c h o i c e . An a l t e r n a t i v e a p p r o a c h , s u c h as p h y s i c a l s e p a r a t i o n t e c h n i q u e would be more p r a c t i c a l . 5 CHAPTER I I RATIONALE OF FOAM SEPARATION PROCESS . AS A MEANS OF DETOXIFYING KRAFT MILL EFFLUENTS A. TOXIC. COMPONENTS OF KRAFT MILL EFFLUENTS The t o x i c a n t s i n k r a f t m i l l e f f l u e n t have been shown t o v a r y w i t h t h e t y p e o f wood f u r n i s h ( s o f t - o r hardwood) and p r o c e s s c o n d i t i o n s . A l a r g e number o f c h e m i c a l compounds a r e known t o c o n t r i b u t e t o t h e o v e r -a l l t o x i c i t y . I n a r e c e n t r e v i e w ( 1 4 ) , i t has been s u g g e s t e d t h a t t o x i -c a n t s c o n s i s t s m a i n l y o f soaps o f r e s i n and f a t t y a c i d s , t e r p e n e s ; s u l p h u r compounds (hydrogen s u l p h i d e , sodium h y d r o s u l p h i d e , sodium t h i o s u l p h a t e , d i m e t h y l s u l p h i d e , m e t h y l m e r c a p t a n ) ; c h l o r i n a t e d l i g n i n r e s i d u e s ; c h l o r i n a t e d g u a i a c o l s and c a t e c h o l s ; t e t r a c h l o r o - o - b e n z o -q u i n o n e ; t r i c h l o r o v e r a t r o l e ; 4 - ( P - t o l y l ) - l - l p e n t a n o l ; a c e t o n e ; m e t h y l e t h y l k e t o n e , p i n e n e s , d d t e r p i n e and t e r p i n e o l . B a s i c a l l y , t h e t o x i c m a t e r i a l s can be c l a s s i f i e d as v o l a t i l e and n o n v o l a t i l e s u b s t a n c e s . The v o l a t i l e compound a r e m o s t l y s u l f u r com-pounds ( 1 5 ) . The t y p e , and t h e c o n c e n t r a t i o n l e t h a l t o f i s h (16) a r e shown i n T a b l e 1. The maximum c o n c e n t r a t i o n s o f v o l a t i l e t o x i c a n t s t o l e r a b l e by f i s h w i t h o u t c a u s i n g d e a t h range from 0.3 t o 1 mg/1. The l e t h a l c o n c e n t r a t i o n i s a p p r o x i m a t e l y 1 - 3 mg/1. The c o n c e n t r a t i o n s t h a t e x i s t i n f r e s h e f f l u e n t n o r m a l l y exceed t h e l e t h a l l e v e l . However t h e y a r e u n s t a b l e and can be removed by a i r o r steam s t r i p p i n g . T h i s t y p e o f t o x i c a n t i s n o t t h e s u b j e c t o f t h i s s t u d y . LC50: C o n c e n t r a t i o n o f e f f l u e n t a t w h i c h 50% o f t e s t f i s h k i l l e d a f t e r 96-hr e x p o s u r e . 6 TABLE 1 REPORTED TOXIC VALUES (15,16) OF SULPHUR COMPOUND S u l p h u r Compound C h e m i c a l Formula * C r i t i c a l C o n c e n t r a t i o n (mg/1) L e t h a l C o n c e n t r a t i o n (mg/D *** LC50-48 h r (mg/1) Hydrogen s u l p h i d e H2S 0.3-0.5 1.0 -M e t h y l mercaptan CH 3SH 0.5-0.9 0.9-1.2 -D i m e t h y l s u l p h i d e ( C H 3 ) 2 S - - 2.3 D i m e t h y l d i s u l p h i d e ( C H 3 ) 2 S 2 - - 4.0 D i m e t h y l s u l p h o x i d e ( CH 3) 2SO - - 5.4 Sodium s u l p h i d e Na 2S 1.0 3.0 1.75 Sodium H y d r o s u l p h i d e NaHS 0.3 1.8 -Sodium T h i o s u l p h a t e N a 2 S 2 0 3 5.0 — — Maximum c o n c e n t r a t i o n t o l e r a b l e by t e s t f i s h w i t h o u t c a u s i n g d e a t h . Minimum c o n c e n t r a t i o n r e q u i r e d t o k i l l 100% of t e s t f i s h . C o n c e n t r a t i o n r e q u i r e d t o k i l l 50% o f Daphnia a f t e r 48 h r o f exposure. 7 Among t h e n o n - v o l a t i l e s , r e s i n a c i d s were f i r s t r e p o r t e d as t o x i c c o n s t i t u e n t s ( 1 7 ) . O ther t o x i c a n t s and t h e i r c o n t r i b u t i o n s t o t o x i c i t y were n o t i d e n t i f i e d u n t i l r e c e n t l y . The t o x i c a n t s a r e o r g a n i c i n n a t u r e . T a b l e 2 shows t h e t y p e s and c o n c e n t r a t i o n o f t o x i c a n t s p r e s e n t i n i n d i v i d u a l and combined e f f l u e n t s treams from s e v e r a l C a n a d i a n k r a f t m i l l s . I n d i v i d u a l t o x i c a n t s i s o l a t e d (18) f r o m t h e s e e f f l u e n t s k i l l f i s h a t 0.2 - 2 mg/1. Most p r o c e s s s t r e a m s c o n t a i n more t h a n 2 d i f -f e r e n t t o x i c a n t s , t h e i r combined c o n c e n t r a t i o n s (19) i n t h e s e streams a r e up t o 10 t i m e s g r e a t e r t h a n t h e i n d i v i d u a l l e t h a l c o n c e n t r a t i o n s ( 2 0 , 2 1 ) . I n woodroom e f f l u e n t , t h e c o n c e n t r a t i o n s o f t o x i c a n t s v a r y w i d e l y w i t h t h e wood f u r n i s h e s , t h e degree and n a t u r e o f w a t e r r e c y c l e , t h e e x t e n t o f d e b a r k i n g and t e m p e r a t u r e o f t h e wash w a t e r . The pH c o n d i t i o n a t w h i c h d e b a r k i n g i s u n d e r t a k e n i s a l s o i m p o r t a n t because more r e s i n s w o u l d be d i s s o l v e d a t an a l k a l i n e pH. A p p r o x i m a t e l y 10 - 50 mg/1 o f r e s i n a c i d s , d e p e n d i n g on (22) whether hardwood o r s o f t wood a r e u s e d , can be f o u n d . The r e s i n a c i d s , composed m a i n l y o f a b i e t i c , d e h y d r o -a b i e t i c , i s o p i m a r i c and p a l u s t r i c a c i d s a c c o u n t f o r about 80% o f t h e t o x i c i t y (18) o f k r a f t m i l l e f f l u e n t s . A s m a l l f r a c t i o n o f u n s a t u r a t e d f a t t y a c i d and d i t e r p e n e a l c o h o l s were a l s o f o u n d t o c o n t r i b u t e t o t h e o v e r a l l t o x i c i t y . The major u n s a t u r a t e d f a t t y a c i d s were o l e i c , l i n o -l e i c , l i n o l e n i c , and p a l m i t o l e i c . S a t u r a t e d f a t t y a c i d s a r e n o t t o x i c a t c o n c e n t r a t i o n s o f up t o 20 mg/1 ( 2 0 ) . I n t h e p u l p i n g e f f l u e n t ( u n b l e a c h e d w h i t e w a t e r ) , r e s i n a c i d c o n -c e n t r a t i o n r a n g e s from 14 - 20 mg/1, w h i c h i s a l s o r e s p o n s i b l e f o r TABLE 2 TOXIC COMPONENTS IN KRAFT MILL INDIVIDUAL AND COMBINED PROCESS STREAMS Type of Chemical Compounds* (Sodium salts) Lethal Concentration (mg/1) 96-hr LC50 Woodroom Effluent Concentration of Toxicants (mg/1) Kraft Unbleached Whitewater Kraft Plant Caustic Effluent Bleach Effluent Acid Effluent Maximum Cone. in Bleached Kraft Wholemill Effluent Naturally Occuring Resin Acids(abietic, dehydroabietic, palu-s t r i c , plmaric) 0.4-1.1 10 - 50 14 - 20 Trace 0 8 Chlorinated Lignin 1.3-2.2 ^  * Chlorine Atoms/ l i g n i n unit Chlorinated Resin Acids(Mono & dichloro-dehydroabietic) 0.6 - - (0-6.8) 2 Unsaturated Fatty Acids (Oleic, l i n o l e i c , l i n o -l e r i c , palmitolelc) 2.5-8 0.3-2 7 - - 2 Chlorinated Phenolics (Tri & Tetrachloro-guaico]) 0.3-0.8 - - (0.4-2.3: - 0.7 Diterpene Alcohols (Pimarol, dehydroabietol abietol) 0.3-1.8 Trace - - - 1 Epoxystearic acid 1.5 - - 1.5-17 _ Juvabiones** 0.8-2.0 - - - 3 * P u r i f i c a t i o n of chlorinated l i g n i n have not achieved. * Present only i n f i r species. '9 80% o f t h e t o x i c i t y ( 1 8 ) . Under v i g o r o u s wood d i g e s t i o n c o n d i t i o n s , up t o 7 mg/1 o f f a t t y a c i d s were found i n t h e e f f l u e n t . These two c h e m i c a l components a c c o u n t f o r v i r t u a l l y a l l t h e t o x i c i t y i n u n b l e a c h e d w h i t e w a t e r . Two e n t i r e l y d i f f e r e n t waste s t r e a m s , namely c a u s t i c e x t r a c t i o n and a c i d b l e a c h ^ e f f l u e n t s a r e d i s c h a r g e d f r o m t h e b l e a c h p l a n t . T o x i c a n t s (20) i n t h e c a u s t i c e x t r a c t i o n e f f l u e n t a r e m a i n l y c h l o r i n a t e d r e s i n a c i d s (1 - 6.8 mg/1) c h l o r i n a t e d p h e n o l i c s (0.4 - 2.3 mg/1) and epoxy-s t e a r i c a c i d (1.5 - 1.7 mg/1). These compounds a r e n o t found i n t h e a c i d b l e a c h e f f l u e n t . I n s t e a d , s i g n i f i c a n t q u a n t i t i e s o f c h l o r i n a t e d l i g n i n d e r i v a t i v e s a r e b e l i e v e d t o be p r e s e n t and t o be r e s p o n s i b l e f o r t h e t o x i c i t y o f a c i d b l e a c h e f f l u e n t . T h e i r c h e m i c a l s t r u c t u r e and c o n c e n t r a t i o n have n o t y e t been f u l l y i d e n t i f i e d . However, i t has been r e p o r t e d t h a t 1.2 t o 2.2 c h l o r i n e atoms were d e t e c t e d f o r e v e r y l i g n i n u n i t p r e s e n t ( 2 3 ) . A l t h o u g h o n l y l i m i t e d d a t a a r e a v a i l a b l e , t h e t o x i c a n t s p r e s e n t i n a l l i n d i v i d u a l p r o c e s s s t r e a m s a r e e x p e c t e d t o be p r e s e n t i n t h e t o t a l combined e f f l u e n t . The c a l c u l a t e d c o n c e n t r a t i o n s o f d i f f e r e n t t o x i c a n t s i n combined whole m i l l e f f l u e n t a r e shown i n T a b l e 2. The major t o x i c components a r e n a t u r a l l y o c c u r r i n g and c h l o r i n a t e d r e s i n a c i d s (up t o 8 and 2 mg/1 r e s p e c t i v e l y ) and u n s a t u r a t e d f a t t y a c i d s (up t o 2 mg/1). J u v a b i o n e d e r i v a t i v e s (up t o 5 mg/1) a l t h o u g h e x i s t i n g i n h i g h c o n c e n -t r a t i o n s , were o n l y found i n m i l l s p r o c e s s i n g f i r s p e c i e s ( 2 0 ) . F o r t y p i c a l k r a f t whole m i l l e f f l u e n t , t h e t o t a l combined c o n c e n t r a t i o n o f t o x i c a n t s i s e s t i m a t e d t o be 18.7 mg/1, a p p r o x i m a t e l y 10 - 20 t i m e s greater than the l e t h a l concentration of i n d i v i d u a l components. B. EXISTING DETOXIFICATION PROCESSES In recent years, because of the enforcement of t o x i c i t y discharge guidelines, removal of t o x i c i t y from e f f l u e n t s has become of concern to the k r a f t industry. Most d e t o x i f i c a t i o n processes have been developed on a t r i a l and error basis and o v e r a l l have not been very successful. Of those processes which show promise i n r e l i a b l y detoxifying the ef-f l u e n t , only a l i m i t e d few were economically v i a b l e . These processes can be b r i e f l y categorized into physico-chemical and b i o l o g i c a l t r e a t -ment processes. 1. Physico-Chemical Processes a. Adsorption Adsorption i s based on operations i n which s p e c i f i c substances are separated from s o l u t i o n upon contact with another i n s o l u b l e phase, the adsorbent s o l i d . Physical adsorption occurs as a r e s u l t of p h y s i c a l or intermolecular forces of a t t r a c t i o n between the gaseous adsorbate and the s o l i d adsorbent. This type of adsorption, also known as "van der Waals" adsorption, i s a r e a d i l y r e v e r s i b l e phenomenon. Chemisorption i s the r e s u l t of chemical i n t e r a c t i o n between the s o l i d and the adsorbed substance. The adhesive force involved i s generally greater than that of physical adsorption. Moreover, the process i s frequently i r r e v e r s -i b l e and, on desorption, the o r i g i n a l substance- often w i l l be found to have undergone a chemical change. 11 A c t i v a t e d c a r b o n i s t h e most common a d s o r b e n t used t o p h y s i c a l l y a d s o r b t h e p o l l u t a n t s f r o m i n d u s t r i a l e f f l u e n t s . T h i s p r o c e s s i s c h a r a c t e r i z e d by s h o r t r e t e n t i o n t i m e (< 4 h r ) , s i m p l e o p e r a t i o n and i t does n o t g e n e r a t e d i f f i c u l t y i n t h e d i s p o s i n g o f s l u d g e s ( 2 4 ) . Carbon i s e f f e c t i v e i n re m o v a l o f t o x i c i t y f rom t h e e f f l u e n t (25) , b u t v e r y l i t t l e BOD r e m o v a l i s a c c o m p l i s h e d . R e c e n t l y a c a r b o n a d s o r p t i o n p r o -c e s s u s i n g 300 mg/1 o f powder c a r b o n and combined w i t h 300 mg/1 of alum has been p r o p o s e d (26) . A f t e r pH a d j u s t m e n t and f o l l o w e d by a e r a t i o n , t h e t o x i c i t y , BOD,, and c o l o r o f k r a f t m i l l e f f l u e n t s were c o n c u r r e n t l y removed. However, t h e c o s t i s h i g h and t h e p r o c e s s may r e q u i r e an alum and c a r b o n r e g e n e r a t i o n system. D e t o x i f i c a t i o n s t u d i e s have a l s o been u n d e r t a k e n w i t h f l y a s h ( m u l t i c l o n e r e j e c t s f r o m t h e hog f u e l b o i l e r ) w i t h a c e r t a i n d e g r e e o f s u c c e s s ( 2 7 ) . Because o f t h e u n c e r t a i n t i e s i n f l y a s h s u p p l y , t h i s method c o u l d o n l y be used f o r s e l e c t e d waste streams and by a l i m i t e d number o f m i l l s . Use o f p e a t moss f o r t o x i c i t y a d s o r p t i o n (27) was n o t s u c c e s s f u l . P o l y m e r i c r e s i n s , s u c h as Rohm and Haas XAD-2 have been e x t r e m e l y s u c c e s s f u l i n a d s o r b i n g t o x i c i t y ( 2 8 ) . An a d s o r b e n t r e g e n e r a t i o n s y s t e m and subsequent d i s p o s a l o f t h e t o x i c m a t e r i a l s a r e r e q u i r e d . The c o s t o f t h i s s ystem would be h i g h e r t h a n f o r t h e c a r b o n system. 1 b. C o a g u l a t i o n - F l o c c u l a t i o n The words c o a g u l a t i o n and f l o c c u l a t i o n a r e o f t e n used i n t e r c h a n g e -a b l y i n waste w a t e r t r e a t m e n t t e c h n o l o g y . I n t h e t r e a t m e n t o f e f f l u -e n t s , c o a g u l a t i o n u s u a l l y i n v o l v e s t h e r e d u c t i o n o f s u r f a c e c h a r g e s and t h e f o r m a t i o n o f complex h y d r o u s o x i d e s . T h i s p r o c e s s i s g e n e r a l l y i n s t a n t a n e o u s i n t h e i n t e r a c t i o n between c o a g u l a n t and s o l i d p a r t i c l e s . T y p i c a l c o a g u l a n t s a r e alum and heavy m e t a l s . I n most was t e w a t e r a p p l i c a t i o n s , s o l u b l e p o l y m e r s a r e used as f l o c c u l a n t s e i t h e r s o l e l y o r a f t e r t h e a d d i t i o n o f c o a g u l a n t s . These p o l y m e r s may be n a t u r a l p r o -d u c t s , e.g., guar gum and m o d i f i e d l i g n o s u l p h o n e s , o r s y n t h e t i c , e.g., p o l y a c r y l a m i d e and p o l y e t h y l e n i m i n e . T y p i c a l l y , t h e m o l e c u l a r w e i g h t o f 6 6 t h e s e p o l y m e r s i s between <2 x 10 and 20 x 10 . P o l y e l e c t r o l y t e s a r e l i n e a r o r b r a n c h e d p olymer m o l e c u l e s w i t h i o n i z a b l e f u n c t i o n a l g r o u p s . When t h e s e groups d i s s o c i a t e , t h e polymer m o l e c u l e s become charged e i t h e r p o s i t i v e l y ( c a t i o n i c ) o r n e g a t i v e l y ( a n i o n i c ) . N o n i o n i c p o l y e l e c t r o l y t e s a r e t h o s e w i t h o u t i o n i z a b l e f u n c t i o n a l g r o u p s . At a g i v e n t e m p e r a t u r e , t h e c o n f i g u r a t i o n o f t h e polymer m o l e c u l e i s dependent on t h e number o f p o t e n t i a l c h a r g e s i t e s on t h e polymer c h a i n , t h e e x t e n t t o w h i c h t h e s e s i t e s a r e i o n i z e d and t h e i o n i c s t r e n g t h o f t h e s o l u t i o n . U n f o r t u n a t e l y , because d e t a i l e d i n -f o r m a t i o n p e r t a i n i n g t o t h e p h y s i c a l and c h e m i c a l n a t u r e o f t h e com-m e r c i a l p r o d u c t s a r e c l o s e l y guarded by each m a n u f a c t u r e r , t h e s e l e c t i o n o f a s u i t a b l e p o l y e l e c t r o l y t e i s m o s t l y based on e x p e r i e n c e and s t i l l r e m a i n s as an a r t . A number o f s t u d i e s have been u n d e r t a k e n u s i n g s e v e r a l p o l y e l e c t r o -l y t e s ( 2 9 ) , and heavy m e t a l compounds, e.g. l i m e , alum and f e r r i c c h l o -r i d e (30) as f l o c c u l a n t s . Removal o f t o x i c i t y (31,31) can be o b t a i n e d a t a c o s t o f $5 - $ 6 /ton o f p u l p . S l u d g e h a n d l i n g a p p ears t o be t h e m a j o r problem. c. C h e m i c a l O x i d a t i o n A i r and m o l e c u l a r oxygen a r e t h e most common o x i d a n t s f o r g e n e r a l i n d u s t r i a l u s e s . However, a t ambient t e m p e r a t u r e s and p r e s s u r e s , t h e s e o x i d a n t s a r e i n e f f e c t i v e f o r t h e t r e a t m e n t o f p u l p and paper e f f l u e n t s . The e f f i c i e n c y o f t h e s e o x i d a n t s c a n , however, be improved by o p e r a t i o n s a t e l e v a t e d t e m p e r a t u r e and p r e s s u r e . C a t a l y t i c o x i d a t i o n has been t r i e d t o improve t h e o x i d a t i o n e f f i c i e n c y o f o r g a n i c s i n d i l u t e aqueous s o l u t i o n s . I n g e n e r a l , a c a t a l y s t o r promoter i s used t o i n i t i a t e t h e o x i d a t i v e r e a c t i o n . U l t r a v i o l e t and gamma i r r a d i a t i o n s have been s t u d i e d as p r o m o t e r s o f c h e m i c a l o x i d a t i o n o f p u l p and paper m i l l e f f l u -e n t s . These p r o c e s s e s a r e r e l a t i v e l y s o p h i s t i c a t e d and cannot be j u s t -i f i e d e c o n o m i c a l l y . Among t h e gaseous o x i d a n t s , ozone has been i n v e s t i g a t e d (11,12,32) most t h o r o u g h l y f o r r e m o v a l o f v a r i o u s c a t e g o r i e s o f p o l l u t a n t s f r o m k r a f t m i l l e f f l u e n t . I t has been r e p o r t e d t h a t a c u t e t o x i c i t y o f k r a f t m i l l e f f l u e n t s c o u l d be removed d u r i n g o z o n a t i o n . However, d e t o x i f i -c a t i o n was a t t r i b u t e d t o c o n c u r r e n t foam s e p a r a t i o n r a t h e r t h a n c h e m i c a l d e g r a d a t i o n o f t o x i c a n t s . Treatment c o s t s were e s t i m a t e d t o range between $7 - $45 p e r t o n o f p u l p . D u r i n g t h e p r o c e s s , t h e c o l o r and BOD^ o f k r a f t m i l l e f f l u e n t were a l s o removed by 80% and 70% r e s p e c t -i v e l y ( 1 2 , 3 2 ) . 2. B i o l o g i c a l Treatment P r o c e s s e s B i o l o g i c a l p r o c e s s e s a r e p r i m a r i l y d e s i g n e d f o r BOD^ r e m o v a l (33) and have become t h e o n l y p r a c t i c a l f orm o f d e t o x i f i c a t i o n t e c h n i q u e c u r r e n t l y i n use. The e f f i c i e n c y o f d e t o x i f i c a t i o n by b i o l o g i c a l t r e a t m e n t i s a s s o c i a t e d w i t h BOD^ r e m o v a l ( 3 3 , 3 4 ) . I n a r e c e n t s t u d y , i t has been shown t h a t most t o x i c a n t s i s o l a t e d from k r a f t m i l l e f f l u e n t a r e b i o d e g r a d a b l e ( 3 5 ) . However, c h l o r i n a t e d c o n s t i t u e n t s e x c e p t t e t r a -c h l o r o g u a i a c o l compounds a r e more r e s i s t a n t t o b i o d e g r a d a t i o n t h a n r e s i n and f a t t y a c i d d e r i v a t i v e s . To a c h i e v e h i g h s u c c e s s r a t e o f d e t o x i f i -c a t i o n , b i o l o g i c a l p r o c e s s e s must be o p e r a t e d a t s u i t a b l e r e t e n t i o n t i m e w i t h adequate n u t r i e n t , d i s s o l v e d oxygen and mixed l i q u o r suspended s o l i d s c o n c e n t r a t i o n s ( 3 6 ) . The o p e r a t i n g c o s t o f t h e s e p r o c e s s e s r a n g e s from $2 -.4 p e r t o n o f p u l p . E x p e r i e n c e i n p u l p and paper m i l l s ( e Northwood p u l p m i l l , P r i n c e George, B.C. and Weyerhaeuser P u l p M i l l , Kamloops, B.C.) s u g g e s t s t h a t h i g h d e t o x i f i c a t i o n s u c c e s s r a t e can be o b t a i n e d c o n s i s t e n t l y by p r o p e r o p e r a t i o n o f t h e t r e a t m e n t s y s t e m i I n most m i l l s , d e t o x i f i c a t i o n f a i l u r e s can be r e l a t e d t o n e g l i g e n c e , l a c k o f s u i t a b l y t r a i n e d o p e r a t o r s , f r e q u e n t p r o c e s s changes i n t h e m i l l and v a r i a t i o n o f e n v i r o n m e n t a l f a c t o r s . 3. C o n c l u s i o n s The upper c o s t l i m i t f o r a d e t o x i f i c a t i o n p r o c e s s t o be a c c e p t a b l e t o t h e k r a f t p u l p i n d u s t r y , s h o u l d n o t exceed t h e c o s t o f b i o l o g i c a l t r e a t m e n t p r o c e s s i . e . , $2 - 4 / t o n of p u l p . Most p h y s i c o - c h e m i c a l t r e a t m e n t p r o c e s s e s f o r d e t o x i f i c a t i o n a r e s t i l l i n t h e development s t a g e . Treatment c o s t s f o r a l l p r o c e s s e s a r e i n t h e $6 - 20 r a n g e , i . e . f a r beyond t h e e c o n o m i c a l l e v e l . M o r e o v e r , subsequent s l u d g e d i s p o s a l u s u a l l y p r e s e n t s a p r o b l e m . From b o t h economic and t e c h n i c a l p o i n t s o f v i e w , none of t h e p h y s i c o - c h e m i c a l methods have d e v e l o p e d t o a com-m e r c i a l l y v i a b l e p r o c e s s . I n t h e p a s t , b i o l o g i c a l d e t o x i f i c a t i o n t e c h n i q u e s were p r a c t i s e d w i t h o u t t h e f u l l u n d e r s t a n d i n g o f t h e c h e m i s t r y o f t o x i c a n t s . A t p r e s e n t , w i t h more t o x i c a n t s b e i n g ' i d e n t i f i e d , d e t o x i f i c a t i o n p e r f o r m a n c e of b i o -l o g i c a l p r o c e s s e s has been improved. The l a r g e s t drawback o f b i o l o g i c a l p r o c e s s however, i s t h e l a r g e l a n d a r e a r e q u i r e m e n t . F o r m i l l s w h i c h a r e hampered by s h o r t a g e o f l a n d and f o r c o a s t a l m i l l s who a r e n o t r e -q u i r e d t o remove e f f l e u n t BOD,., a r a p i d d e t o x i f i c a t i o n p r o c e s s w h i c h can g u a r a n t e e r e l i a b l e d e t o x i f i c a t i o n i s s t i l l h i g h l y d e s i r a b l e . C. POTENTIAL ROLE OF FOAM SEPARATION PROCESS FOR DETOXIFICAITON OF KRAFT MILL EFFLUENTS Foaming has a l w a y s been a s s o c i a t e d w t i h t h e p u l p i n g p r o c e s s (19,37) and w i t h i t s e f f l u e n t d i s c h a r g e s . I t i s a f r u s t r a t i n g and t r o u b l e s o m e o p e r a t i o n c h a r a c t e r i s t i c . The f o a m i n g tendency o f t h e e f f l u e n t depends on t h e p u l p i n g p r o c e s s and wood s p e c i e s and v a r i e s w i t h each p r o c e s s s t r e a m . Over t h e y e a r s , a g r e a t d e a l o f a t t e n t i o n has been g i v e n t o f o a m i n g c h a r a c t e r i s t i c s o f p u l p and p a p e r m i l l e f f l u e n t s . Foaming t e c h n o l o g y has been i n v e s t i g a t e d i n s e v e r a l s t u d i e s f o r r e d u c t i o n o f B0D 5 ( 3 8 ) , c o l o r ( 2 9 , 3 9 ) , f o a m i n g t e n d e n c y ( 3 8 ) , r e s i n a c i d s (40) and suspended s o l i d s w i t h v a r i a b l e d e g r e e s o f s u c c e s s . Some r e d u c t i o n o f t o x i c i t y as a r e s u l t o f f o a m i n g , b u t n o t a s u b s t a n t i a l one, has a l s o been r e p o r t e d i n d i l u t e b l a c k l i q u o r ( 4 1 ) , s u l p h i t e m i l l e f f l u e n t (42) and k r a f t m i l l e f f l u e n t (43) i n e a r l i e r s t u d i e s . However, t h e c a u se o f t o x i c i t y r e d u c t i o n was n o t c l e a r when t h e s e o b s e r v a t i o n s were made. I n r e c e n t y e a r s , i t has been o b s e r v e d t h a t d u r i n g b i o l o g i c a l t r e a t -ment p r o c e s s e s , c o p i o u s amounts o f s t a b l e foam ( a c c u m u l a t i n g up t o d e p t h s o f s e v e r a l f e e t ) a r e p r o d u c e d w h i c h c o v e r t h e e n t i r e a e r a t i o n pond d u r i n g t h e a e r a t i o n p r o c e s s ( 4 4 ) . These foams a r e p r o d u c e d , c o l -l a p s e d , d r i e d and r e d i s p e r s e d t o t h e pond a c c o r d i n g t o changes i n e f f l u -e n t c h a r a c t e r i s t i c s and c l i m a t i c c o n d i t i o n s . I t i s now b e l i e v e d t h a t t h e foams when r e t u r n e d t o t h e e f f l u e n t w i l l cause i r r e g u l a r d e t o x i f i -c a t i o n r e s u l t s (45) o f t h e b i o l o g i c a l t r e a t m e n t system. To d a t e , among t h e t o x i c components i d e n t i f i e d i n k r a f t m i l l e f -f l u e n t , major t o x i c a n t s , s u c h as a l l n a t u r a l l y o c c u r i n g ( F i g u r e 1) and c h l o r i n a t e d r e s i n a c i d s , f a t t y a c i d s . a n d c h l o r i n a t e d l i g n i n d e r i v a t i v e s b e l o n g t o t h e group o f c a r b o x y l i c a c i d s . These a r e a l l s u r f a c e a c t i v e compounds. S u r f a c e a c t i v e compounds a r e known t o r e d u c e s u r f a c e t e n s i o n and promote foaming (46,47) i n a s o l u t i o n . Under s u i t a b l e c o n d i t i o n s , t h e y can be s e p a r a t e d by foaming as a r e s u l t o f t h e i r own s u r f a c e F i g u r e I CHEMICAL STRUCTURE OF RESIN ACIDS ABIETIC ACID CH 3 COOH NEOABIETIC ACID CH 3 COOH LEVOPIMARIC ACID CH 3 COOH DEHYDROABIETIC ACID CH, COOH 18 a c t i v i t y o r by r e a c t i n g w i t h n o n - s u r f a c e a c t i v e m a t e r i a l s ( t o x i c o r non-t o x i c ) t o form new s u r f a c e a c t i v e complexes w h i c h a r e t h e n removed f r o m t h e b u l k o f t h e s o l u t i o n by f o a m i n g . I t i s p o s t u l a t e d t h a t r e s i n a c i d s , f a t t y a c i d s and o t h e r n o t as y e t i d e n t i f i e d t o x i c compounds, s u r f a c e a c t i v e o r n o t , may c o n c e n t r a t e i n d e p e n d e n t l y i n t h e foam o r r e a c t t o f o r m a complex p r i o r t o a t t a c h m e n t t o t h e foam. Removal o f foam w i l l r e s u l t i n r e m o v a l o f t o x i c i t y . Recent s t u d i e s have documented t h e v a l i d i t y o f t h i s h y p o t h e s i s : 1. S e p a r a t i o n o f foam f r o m k r a f t m i l l e f f l u e n t removed up t o 65% o f t h e r e s i n a c i d c o n t e n t ( 4 0 ) . 2. A n o n - a c t i v e b i o l o g i c a l t r e a t m e n t s y s t e m (extreme pH and N 2 a e r a t i o n t o p r e v e n t t h e growth o f m i c r o b e s ) under f o a m i n g c o n d i t i o n s , d e t o x i f i e d a k r a f t m i l l e f f l u e n t t o a degree comparable t o an a c t i v e b i o d e g r a d a t i o n s y s t e m (48) i n t h e l a b o r a t o r y . A l t h o u g h t h e s o l u b i l i t y , f o a m i n g c h a r a c t e r i s t i c s and l e t h a l c o n c e n -t r a t i o n s o f i n d i v i d u a l t o x i c compound v a r y and a r e dependent on pH, tem-p e r a t u r e and s y n e r g i s t i c e f f e c t o f each t o x i c component, t h e s e s u r f a c e a c t i v e compounds can be a d s o r b e d o n t o t h e g a s - l i q u i d i n t e r f a c e ( b u b b l e ) by p r o v i d i n g s u i t a b l e c h e m i c a l and p h y s i c a l c o n d i t i o n s . Thus t h e i r c o n c e n t r a t i o n i n s o l u t i o n can be r e d u c e d t o a l e v e l w h i c h i s n o t t o x i c t o f i s h . Based on t h e s e p r e l i m i n a r y d a t a , i t i s p r o p o s e d t o e v a l u a t e and o p t i m i z e foam s e p a r a t i o n as an a l t e r n a t i v e t o e x i s t i n g t e c h n i q u e s f o r d e t o x i f i c a t i o n . CHAPTER I I I LITERATURE REVIEW OF FOAM SEPARATION PROCESSES A. CLASSIFICATION OF FOAM SEPARATION PROCESSES Foam s e p a r a t i o n i s a c h e m i c a l e n g i n e e r i n g p r o c e s s t h a t s e l e c t i v e l y s e p a r a t e s t h e s u r f a c e a c t i v e components o f a s o l u t i o n a t t h e s u r f a c e s o f a s c e n d i n g b u b b l e s . Foam s e p a r a t i o n b e l o n g s t o t h e group o f " a d s o r p t i v e b u b b l e s e p a r a t i o n methods" (49) t h a t may be c o n v e n i e n t l y c l a s s i f i e d i n t o foam f r a c t i o n a t i o n and f r o t h f l o t a t i o n ( F i g u r e 2). Foam f r a c t i o n a t i o n s e p a r a t e s d i s s o l v e d s u b s t a n c e s from homogeneous s o l u t i o n s by s e l e c t i v e a d s o r p t i o n o f one o r more s o l u t e s w i t h t h e a i d o f s u r f a c t a n t s on t h e g a s - l i q u i d i n t e r f a c e w h i l e f r o t h f l o t a t i o n s e p a r a t e s i n s o l u b l e sub-s t a n c e s from h e t e r o g e n e o u s systems. F r o t h f l o t a t i o n i s f u r t h e r s u b d i v i d e d i n t o seven c a t e g o r i e s : 1 . Ore f l o t a t i o n i s a s o l i d - s o l i d s e p a r a t i o n t e c h n i q u e . T h i s t e c h -n i q u e i s m a i n l y used f o r s e p a r a t i o n o f m i n e r a l o r e s . 2. M a c r o f l o t a t i o n i s t h e re m o v a l o f m a c r o s o p i c p a r t i c l e s by foamin g . 3. M i c r o f l o t a t i o n i s t h e r e m o v a l o f m i c r o s c o p i c p a r t i c l e s , e s p e c i a l l y m i c r o o r g a n i s m s and c o l l o i d a l m a t e r i a l s by foamin g . 4. A d s o r b i n g c o l l o i d f l o t a t i o n i s t h e r e m o v a l o f d i s s o l v e d m a t e r i a l t h a t i s f i r s t a d s o r b e d on c o l l o i d a l p a r t i c l e s . The major o b j e c t i v e b e i n g t h e r e m o v a l o f t h e d i s s o l v e d m a t e r i a l r a t h e r t h a n t h e c o l -l o i d a l p a r t i c l e s . 5 . I o n f l o t a t i o n i s t h e r e m o v a l o f s u r f a c e i n a c t i v e i o n s ( c o l l i g e n d ) by t h e a d d i t i o n o f an o p p o s i t e l y c h a r g e d s u r f a c t a n t ( c o l l e c t o r ) i n 20 F i g u r e 2 CLASSIFICATION OF FOAM SEPARATION FOAM SEPARATION FOAM FRACTIONATION FROTH FLOTATION ORE I FLOTATION I MACRO-FLOTATION MICRO-FLOTATION ABSORBING COLLOID FLOTATION ION FLOTATION MOLECULAR FLOTATION PRECIPITATE FLOTATION s t o i c h i o m e t r i c amounts. The i n s o l u b l e i o n - s u r f a c t a n t complex i s t h e n f l o a t e d o u t . A t h i g h c o n c e n t r a t i o n s , a p r e c i p i t a t e i s formed w h i c h i s s u b s e q u e n t l y removed by p a r t i c u l a t e f l o t a t i o n . A t l o w e r c o n c e n t r a t i o n s , t h e c o l l e c t o r a d s o r b s on t h e b u b b l e s and h o l d s t h e c o l l i g e n d t o them. 6. M o l e c u l a r f l o t a t i o n i s t h e r e m o v a l o f s u r f a c e i n a c t i v e m o l e c u l e s t h r o u g h t h e use o f a s u r f a c t a n t w h i c h y i e l d s an i n s o l u b l e complex w h i c h i s t h e n f l o a t e d o u t . 7. P r e c i p i t a t e f l o t a t i o n i n v o l v e s t h e f o r m a t i o n o f p r e c i p i t a t e s p r i o r t o a d d i t i o n o f s u r f a c t a n t . S i n c e f l o c c u l a n t s a r e used f r e q u e n t l y , t h e o v e r a l l c h a r g e on t h e m a t e r i a l t o be removed i s r e d u c e d . The s u r f a c t a n t i s r e q u i r e d o n l y t o r e a c t w i t h o u t e r m o s t l a y e r o f t h e p r e c i p i t a t e s r e s u l t i n g i n s u r f a c t a n t r e q u i r e m e n t l e s s t h a n s t o i -c h i o m e t r i c amount. B. PRINCIPLES OF FOAM SEPARATION 1. F i l m F o r m a t i o n The most w i d e l y b e l i e v e d t h e o r y o f f i l m f o r m a t i o n i s t h e " b a l a n c e d l a y e r " t h e o r y ( 5 0 ) . The h y p o t h e s i s was t h a t below t h e s u r f a c e , when two b u b b l e s were formed, a foam f i l m i s formed as two b u b b l e s a p p r o a c h each o t h e r . I n t h e s o l u t i o n , t h e m e c h a n i c a l f o r c e , t h a t b r o u g h t t h e s e s u r -f a c e s t o g e t h e r e n c o u n t e r s i n c r e a s i n g r e s i s t a n c e as t h e l i q u i d l a y e r between them becomes t h i n n e r . The r e s i s t a n c e a r i s e s f r o m t h e d i f f e r e n c e i n c o n c e n t r a t i o n between t h e s u r f a c e l a y e r and t h e mass o f t h e s o l u t i o n . S o l u t e i s e i t h e r p o s i t i v e l y o r n e g a t i v e l y a d s o r b e d on t h e s u r f a c e . T h i s c o n c e n t r a t i o n d i f f e r e n c e i s s p o n t a n e o u s , and t h e r e f o r e r e q u i r e s t h e e x p e n d i t u r e o f work on t h e s y s t e m t o r e s t o r e t h e q u a l i t y o f c o n c e n -t r a t i o n . T h i s t h e o r y e x p l a i n s why p u r e l i q u i d s and s a t u r a t e d s o l u t i o n s do n o t foam. S i n c e a d s o r p t i o n does n o t o c c u r i n t h e s e s o l u t i o n s , r e -s i s t i n g f o r c e s cannot a r i s e t o p r e v e n t c o a l e s c e n c e and t h e c onsequent d i s a p p e a r a n c e o f s u r f a c e . 2. A d s o r p t i o n The f u n d a m e n t a l e q u a t i o n f o r a d s o r p t i o n (51) was d e v e l o p e d by G i b b s . I t r e l a t e s t h e degree o f a d s o r p t i o n a t t h e boundary between 2 phases to t h e change i n i n t e r f a c i a l t e n s i o n a t t h a t boundary and com-p o s i t i o n o f t h e two phases. F o r e q u i l i b r i u m c o n d i t i o n s a t c o n s t a n t t e m p e r a t u r e , and where t h e r a d i u s o f c u r v a t u r e o f t h e boundary s u r f a c e i s l a r g e compared t o t h e t h i c k n e s s o f t h e i n t e r f a c i a l t r a n s i t i o n l a y e r , t h e e q u a t i o n i s : dy + F i d y i + + r . d y . = 0 Y= S u r f a c e t e n s i o n o f s o l u t i o n , dynes/cm y= C h e m i c a l p o t e n t i a l o f t h e components i n the b u l k phase, dynes-cm/g-mole 2 r= E x c e s s s u r f a c e c o n c e n t r a t i o n o f components g-mole/cm I n a system c o n t a i n i n g one s o l v e n t and one s o l u t e , t h e s u r f a c e e x c e s s c o n c e n t r a t i o n o f t h e s o l v e n t 1^ = z e r o , and t h e e q u a t i o n becomes: dy dy + r 2 d y 2 = 0 o r T2= -The c h e m i c a l p o t e n t i a l o f a s o l u t e i s d e f i n e d a s : y.= y. + RT I n a. where i i * l y^= i C h e m i c a l p o t e n t i a l o f component i i n t h e s u r f a c e phase (dynes-cm/g-mole) u^.= C h e m i c a l p o t e n t i a l o f component i n t h e s u r f a c e phase under s t a n d a r d c o n d i t i o n s (dynes-cm/g-mole) 3 a^= A c t i v i t y o f component i (g-mole/cm ) R = Gas c o n s t a n t T = A b s o l u t e t e m p e r a t u r e By d i f f e r e n t i a t i o n : dp. = RT d i n a. x 1 hence 1 2 RT d i n a. l I n p r a c t i c e , t h e d i f f i c u l t i e s i n m e a s u r i n g s m a l l changes i n y a c c u r a t e l y and t h e u n c e r t a i n t i e s i n i d e n t i f y i n g t h e s p e c i f i c s u r f a c t a n t s and e v a l u -a t i n g t h e i r a c t i v i t y c o e f f i c i e n t s have s e v e r e l y l i m i t e d t h e u t i l i z a t i o n o f t h i s e q u a t i o n as a q u a n t i t a t i v e t o o l . However, a t below c r i t i c a l m i c e l l e c o n c e n t r a t i o n s ( d i l u t e s o l u t i o n ) , a^ approaches c ^ ( c o n c e n t r a t i o n o f s o l u t e ) r - 1 dy To = - „„ x — 2 RT d I n c The G i b b s a d s o r p t i o n e q u a t i o n i n d i c a t e s t h a t t h e s u r f a c e e x c e s s o f dy d Y a s o l u t e depends on c . A l a r g e n e g a t i v e v a l u e o f ^ w i l l mean h i g h c o n c e n t r a t i o n s a t t h e g a s - l i q u i d i n t e r p h a s e ( 5 2 ) . 3. FOAM SEPARATION MECHANISMS a. Foam F r a c t i o n a t i o n Foam f r a c t i o n a t i o n o f s o l u t e s o c c u r s when gas i s d i s p e r s e d i n t o a s o l u t i o n c o n t a i n i n g m a t e r i a l w h i c h has a d i f f e r e n t s u r f a c e a c t i v i t y (53) t h a n t h e b u l k l i q u i d . I n an aqueous phase, s u r f a c e a c t i v e m a t e r i a l p o s s e s s i n g h y d r o p h i l i c ( p o l a r g r o u p s ) and h y d r o p h o b i c ( n o n - p o l a r g r o u p s ) p r o p e r t i e s w i l l m i g r a t e t o t h e b u b b l e - l i q u i d i n t e r f a c e b e c a u s e t h i s a r -rangement p r o v i d e s h i g h e r s t a b i l i t y t h a n t h e homogeneous s o l u t i o n . F i g u r e 3-a i l l u s t r a t e s t h e o r i e n t a t i o n o f s u r f a c e a c t i v e m o l e c u l e s on a b u b b l e . The m o l e c u l e s a r r a n g e t h e m s e l v e s i n s u c h a p o s i t i o n t h a t t h e h y d r o p h i l i c ends o f t h e m o l e c u l e s r e m a i n i n t h e aqueous phase and t h e h y d r o p h o b i c ends p r o t r u d e i n t o t h e gaseous phase. D u r i n g c o n t i n u o u s o p e r a t i o n , b u b b l e s f l o a t t o t h e t o p o f t h e l i q u i d and f o r m a foam b l a n k e t . I f t h e foam p r o d u c e d i s s t a b l e , t h e s u r f a c e a c t i v e m a t e r i a l w i l l be a c c u m u l a t e d i n t h e foam l a y e r and c a n be removed f r o m t h e mother s o l u t i o n . S o l u t e s w h i c h by t h e m s e l v e s have l i t t l e o r no f o a m i n g a b i l i t y , may be s u c c e s s f u l l y foam f r a c t i o n a t e d by a d d i n g f o a m i n g a g e n t s . These a g e n t s (54) a r e r e q u i r e d t o f o r m e i t h e r e l e c t r o s t a t i c bonds o r c h e l a t e s w i t h t h e s o l u t e s . F o r i n s t a n c e , o r g a n i c (55) and i n o r g a n i c i o n s c a n be foam f r a c t i o n a t e d (56) by t h e a i d o f c a t i o n i c o r a n i o n i c s u r f a c t a n t s , i . e . by u s i n g a s u r f a c t a n t o f t h e o p p o s i t e c h a r g e . I n some s i t u a t i o n s , t h e c h a r g e o f a s o l u t e may be changed by a change i n pH and made s u s -c e p t i b l e t o foam f r a c t i o n a t i o n . b. F r o t h F l o t a t i o n F r o t h f l o t a t i o n removes i n s o l u b l e , suspended m a t t e r . A i r b u b b l e s a r e i n t r o d u c e d i n t o a h e t e r o g e n e o u s m i x t u r e o f l i q u i d s and s o l i d s . The t i n y b u b b l e s s e r v e as s i t e s f o r t h e a t t a c h m e n t o f t h e suspended m a t t e r 25 F i g u r e 3 a. ADSORPTION OF SURFACE ACTIVE MOLECULES ON GAS-LIQUID INTERFACE HYDROPHILIC END HYDROPHOBIC END b. MECHANISM OF FROTH FLOTATION 4 A O 4 _ O HYDROPHOBIC PARTICLES HYDROPHILIC PARTICLES O O 7 o n 4 O 9 o „ O o o ( 5 7 ) w h i c h p o s e s s e s h y d r o p h o b i c p r o p e r t i e s . F i g u r e 3-b i l l u s t r a t e s how t h e o p e r a t i o n o f f r o t h f l o t a t i o n i s e f f e c t e d . Due t o d i f f e r e n c e s i n d e n s i t y , t h e b u b b l e - p a r t i c l e c o n g l o m e r a t e w i l l r i s e t o t h e t o p and c o n c e n t r a t e i n t o a f r o t h l a y e r . The f r o t h t o g e t h e r w i t h t h e suspended s o l i d s can t h e n be removed. c. F a c t o r s A f f e c t i n g Foam S e p a r a t i o n The e f f e c t i v e n e s s o f foam s e p a r a t i o n depends on t h e a d s o r p t i v e c h a r a c t e r i s t i c s o f t h e sys t e m and p r o p e r t i e s o f t h e s u r f a c t a n t s . Foam c h a r a c t e r i s t i c s a r e f r e q u e n t l y d e s c r i b e d by t h e f o l l o w i n g terms ( 5 8 ) : Vf E x p a n s i o n R a t i o L i q u i d C o n t e n t Fo am D e n s i t y — p x Foaming Tendency : V I V I Vf V I Vf V f x t Vg G a s / l i q u i d i n t e r f a c i a l a r e a S = ^ x ^ assumes s p h e r i c a l b u b b l e s V I x d Where: Vf = Volume o f foam V I = Volume o f l i q u i d c o n t a i n e d i n t h e foam p = D e n s i t y o f l i q u i d Vg = Volume o f gas i n t r o d u c e d a t t i m e t h = t h i c k n e s s o f l i q u i d f i l m d = b u b b l e d i a m e t e r S = g a s - l i q u i d i n t e r f a c i a l a r e a / u n i t l i q u i d volume. The e f f i c i e n c y o f foam s e p a r a t i o n i s governed by t h e r a t i o o f t h e c o n c e n t r a t i o n o f t h e s o l u t e i n t h e foam phase t o t h a t o f t h e b u l k l i q u i d ( e n r i c h m e n t r a t i o ) . A maximum e n r i c h m e n t r a t i o c o r r e s p o n d s t o maximum p u r i f i c a t i o n and minimum foam p r o d u c t i o n . I n o r d e r t o o b t a i n a h i g h e n r i c h m e n t r a t i o , t h e foam on w h i c h s u r f a c t a n t i s a d s o r b e d must be r e a s o n a b l y s t a b l e ; t h e e n t r a i n e d l i q u i d s h o u l d be e a s i l y d r a i n e d o u t (5 3 , 5 4 ) . Foam s t a b i l i t y r e l a t e s t o t h e c a p a b i l i t y o f foam t o m a i n t a i n t h i c k w a l l s o f l i q u i d w h i c h r e s i s t e x t e r n a l s t r e s s e s and t o r e p a i r random t h i n s p o t s t h u s p r e v e n t i n g foam b r e a k a g e by t h e p r e s e n c e o f e l e c t r o s t a t i c s u r f a c e f o r c e s . Foam p e r s i s t s so l o n g as t h e l i q u i d f i l m s c o n s t i t u t i n g i t e x i s t . A s t a b l e foam can w i t h s t a n d l a m e l l a r t h i n n i n g w i t h o u t r u p -t u r i n g . Those f a c t o r s (59) w h i c h a f f e c t t h e development and s t a b i l i t y o f foams a r e : t h e n a t u r e and c o n c e n t r a t i o n o f t h e sys t e m components, tem-p e r a t u r e , p r e s s u r e and pH. These f a c t o r s i n t u r n d e t e r m i n e t h e s e c -o n dary v a r i a b l e s s u c h as v i s c o s i t y , s u r f a c e t e n s i o n and b u b b l e s i z e . T h e i r r e l a t i v e c o n t r i b u t i o n and i n t e r a c t i o n t o foam s t a b i l i t y a r e ex-t r e m e l y complex. The s e l e c t i o n o f optimum v a l u e s f o r t h e s e f a c t o r s s e e k s t o p r o v i d e a d i f f e r e n t s u r f a c e f i l m c o n c e n t r a t i o n from t h a t o f t h e b u l k l i q u i d and t o c r e a t e a h i g h s u r f a c e v i s c o s i t y i n t h e s u r f a c e l a y e r . Foam d r a i n a b i l i t y r e f e r s t o t h e f o r m a t i o n o f a d r y foam as a r e s u l t o f s u c t i o n and g r a v i t a t i o n a l f o r c e s . When a foam i s formed, l i q u i d d r a i n a g e (60) o c c u r s i n s t a n t l y w i t h i n t h e p l a t e a u b o r d e r s and l a m e l l a r w a l l s ( F i g u r e 4 ) . D r a i n a b i l i t y i s a f f e c t e d by i n t r a l a m e l l a r l i q u i d c o n -c e n t r a t i o n , b u b b l e s i z e , v i s c o s i t y and s u r f a c e t e n s i o n . 28 F i g u r e 4 THREE FOAM LAMELLAE COMING TOGETHER IN A PLATEAU BORDER AND FORMING ANGLES OF 120° WITH EACH OTHER Foam s t a b i l i t y and d r a i n a b i l i t y can be improved by t h e f o l l o w i n g methods ( 5 8 ) : - I n c r e a s e t h e b u l k v i s c o s i t y I n c r e a s e t h e s u r f a c e v i s c o s i t y Lower t h e s u r f a c e t e n s i o n - I n c r e a s e t h e s u r f a c e e l a s t i c i t y - I n c r e a s e t h e s u r f a c e c o n c e n t r a t i o n - P r e v e n t e v a p o r a t i o n . S p e c i f i c p a r a m e t e r s t h a t have an i m p o r t a n t e f f e c t on t h e degree o f s e p a r a t i o n a r e p r e s e n t e d as f o l l o w s : 1. C h e m i c a l N a t u r e and C o n c e n t r a t i o n I n g e n e r a l , t h e f o a m i n e s s o f aqueous s o l u t i o n s o f i n o r g a n i c com-pounds i s s m a l l compared t o aqueous s o l u t i o n s o f many a l c o h o l s , o r g a n i c a c i d s , and o r g a n i c s a l t s . F o r a s i n g l e s o l u t e , t h e r e i s an i d e a l c o n -c e n t r a t i o n where t h e most s t a b l e foam w i l l be formed. I f t h e co n c e n -t r a t i o n o f a s u r f a c t a n t i s t o o h i g h , i t s m o l e c u l e s can group t o g e t h e r so t h a t t h e h y d r o c a r b o n c h a i n s a r e c l o s e t o g e t h e r and away from t h e s o l v e n t l i q u i d ( 6 1 ) . Such a g r o u p i n g i s u s u a l l y r e f e r r e d t o as a m i c e l l e . Maximum foam s t a b i l i t y o c c u r s a t t h e c r i t i c a l m i c e l l e c o n c e n t r a t i o n ( 4 5 ) . M i c e l l e f o r m a t i o n has a d e t r i m e n t a l e f f e c t on s u c c e s s f u l s e p a r a -t i o n because o f t h e l o s s o f s u r f a c e a c t i v i t y ( 6 2 ) . Low c o n c e n t r a t i o n o f s u r f a c t a n t i s a l s o u n d e s i r a b l e as t h e s t a b i l i t y o f t h e foam cannot be m a i n t a i n e d . F o r multi-component s o l u t i o n s , foam s t a b i l i t y may i n c r e a s e o r d e c r e a s e as t h e c o n c e n t r a t i o n changes. 2. pH A l m o s t a l l i n v e s t i g a t o r s r e f e r t o t h e i m p o r t a n c e o f pH on foam s e p a r a t i o n . I n g e n e r a l t h e e f f e c t o f pH can be summarized (63,64) as f o l l o w s : pH changes may a f f e c t t h e s o l u b i l i t y o f t h e s u r f a c t a n t and s u r f a c e t e n s i o n o f t h e s o l u t i o n . The s t a b i l i t y o f t h e foam may change l e a d i n g t o r e d i s p e r s i o n . A change may o c c u r i n t h e c h a r g e o f c o l l i g e n d , due t o h y d r o l o s i s o r f o r m a t i o n o f o t h e r complexes. - V a r i a t i o n o f pH can l e a d t o p r e c i p i t a t i o n o f a c o l l i g e n d . Changes may o c c u r i n t h e i o n i z a t i o n o f t h e c o l l e c t o r ; ( S u r f a c e a c t i v e agent used t o f o r m a complex w i t h m a t e r i a l s t o be removed) a c i d o r a mines, may l o s e t h e i r c h a r g e a t l o w o r h i g h pH v a l u e s . They e i t h e r t h e n cease t o be c o l l e c t o r s , o r t h e i r mode o f c o l -l e c t i o n changes. 3. Gas F l o w Rate W i t h a c o n s t a n t b u b b l e d i a m e t e r , t h e volume o f gas p r o v i d e d de-t e r m i n e s t h e s u r f a c e a r e a a v a i l a b l e f o r s u r f a c t a n t a d s o r p t i o n . I n -c r e a s i n g a i r f l o w i n c r e a s e s t h e r a t e o f s u r f a c t a n t r e m o v a l . However, t h i s w i l l r e d u c e t h e r e t e n t i o n o f t h e foam i n t h e column, p e r m i t t i n g more l i q u i d e n t r a i n m e n t and r e d u c i n g t h e e n r i c h m e n t r a t i o (65) . The volume o f foam g e n e r a t e d w i l l a l s o be g r e a t e r . 31 4. Bubble S i z e I n foam s e p a r a t i o n t h e g a s - l i q u i d i n t e r f a c i a l a r e a r e q u i r e d f o r r e m o v a l of a u n i t c o n c e n t r a t i o n of a s p e c i f i c s u r f a c t a n t i s c o n s t a n t . T h e r e f o r e , t h e s i z e s o f t h e b u b b l e s produced d i c t a t e t h e amount o f a i r r e q u i r e d ( b l o w e r c a p a -c i t y ) t o p r o d u c e t h i s g a s - l i q u i d i n t e r f a c e . The b u b b l e s i z e s s h o u l d p r e f e r a b l y be as s m a l l as p o s s i b l e . S m a l l b u b b l e s , however a r e more c o s t l y t o p r o d u c e . The a d s o r p t i o n p r o p e r t i e s o f b u b b l e s o f d i f f e r e n t s i z e s a r e b a s i c a l l y t h e same on a per u n i t a r e a b a s i s b u t t h e a s c e n t r a t e s o f b u b b l e s a r e d i f f e r e n t . As a r e s u l t , s m a l l e r b u b b l e s w i l l have a l o n g e r b u b b l e - l i q u i d c o n t a c t t i m e . I n foam s e p a r a t i o n of t o x i c i t y ( r e s i n a c i d s and f a t t y a c i d s r e m o v a l ) , i t i s assumed t h a t a d s o r p t i o n o f t o x i c a n t s on t h e i n t e r f a c e i s i n s t a n t a n e o u s , t h e r e f o r e t h e a s c e n t r a t e due t o b u b b l e s i z e d i f f e r e n c e s h o u l d n o t be an i m p o r t a n t f a c t o r i n d e t e r m i n i n g g a s - l i q u i d i n t e r f a c i a l a r e a . 5 . Temperature Foam s t a b i l i t y u s u a l l y d e c r e a s e s w i t h i n c r e a s i n g t e m p e r a t u r e . T h i s i s due p r i m a r i l y t o t h e d e c r e a s e d v i s c o s i t y o f t h e s u r f a c e l a y e r s and i n c r e a s e d gas p r e s s u r e s w i t h i n t h e b u b b l e s . A l t h o u g h i t has been known t h a t t h e r e i s a c r i t i c a l t e m p e r a t u r e above w h i c h a s o l u t i o n c o n t a i n i n g s u r f a c t a n t s w i l l n o t foam, v e r y l i t t l e a t t e n t i o n has been g i v e n t o t h i s i n most s t u d i e s . I n t h e o r y , t h e b e h a v i o r of s u r f a c e a c t i v e compounds i s g r e a t l y a f f e c t e d by t e m p e r a t u r e . Above t h e c r i t i c a l m i c e l l e c o n c e n t r a t i o n , t h e s o l u b i l i t y o f s u r f a c t a n t s i n c r e a s e s m a r k e d l y w i t h t e m p e r a t u r e . The t e m p e r a t u r e a t w h i c h t h e s u r f a c t a n t s o l u b i l i t y i s e q u a l t o c r i t i c a l m i c e l l e c o n c e n t r a t i o n i s d e f i n e d as " K r a f t - P o i n t " (66). I n c r e a s e d t e m p e r a t u r e w i l l d e c r e a s e v i s c o s i t y and i n c r e a s e t h e d r a i n a g e r a t e i n t h e foam f i l m . T h e r e f o r e t h e foams a r e u n s t a b l e and e a s i l y r u p t u r e d . H i g h temp-a t u r e s a l s o cause p r e f e r e n t i a l e v a p o r a t i o n w i t h i n t h e l i q u i d f i l m s . I f t h e l i q u i d i s e v a p o r a t e d , t h e c o n c e n t r a t i o n o f t h e s o l u t e may be i n -c r e a s e d u n t i l t h e b u b b l e s c o l l a p s e . 6. V i s c o s i t y Foam s t a b i l i t y i s h i g h l y dependent on v i s c o s i t y . H i g h v i s c o s i t y r e d u c e s foam d r a i n a g e and may r e d u c e e n r i c h m e n t i f t h e foam i s removed q u i c k l y . However, s l o w d r a i n a g e w i l l c ause t h e gas b u b b l e s t o r e m a i n i n c o n t a c t w i t h t h e b u l k o f t h e l i q u i d l o n g e r . T h i s i s b e n e f i c i a l t o s u r f a c t a n t a d s o r p t i o n . 7. Column H e i g h t The h e i g h t o f t h e column a f f e c t s t h e mass t r a n s f e r o f t h e s u r -f a c t a n t s from t h e b u l k s o l u t i o n t o t h e g a s - l i q u i d i n t e r f a c e . I n gen-e r a l , minimum column h e i g h t w i l l depend on b u b b l e s i z e . I n c r e a s i n g column h e i g h t p e r m i t s l o n g e r b u b b l e - l i q u i d c o n t a c t and w i l l enhance foam e n r i c h m e n t . A s t u d y c o n d u c t e d by G o l d b e r g (67) s u g g e s t e d t h a t a minimum column h e i g h t o f 10 cm would be s u f f i c i e n t f o r s u r f a c t a n t a b s o r p t i o n . 8. Foam Removal Removal o f s u r f a c t a n t cannot be r e a l i z e d w i t h o u t t h e f o r m a t i o n o f foam. U n s t a b l e foams must be removed as t h e y a r e formed, t h e r e b y de-c r e a s i n g d r a i n a g e and e n r i c h m e n t . M o d e r a t e l y s t a b l e foams may b r e a k and p r o v i d e i n t e r n a l r e f l u x w h i c h i n c r e a s e s e n r i c h m e n t . F o r s t a b l e foams e x t e r n a l r e f l u x i s r e q u i r e d t o i n c r e a s e e n r i c h m e n t . So t h e method o f foam r e m o v a l depends on t h e foam c h a r a c t e r i s t i c s and t h e e x t e n t o f e n r i c h m e n t d e s i r e d . D. Mode o f O p e r a t i o n There a r e two g e n e r a l c o n f i g u r a t i o n s f o r foam s e p a r a t i o n equipment: t h e column t y p e and t h e t r o u g h t y p e . F o r s m a l l - s c a l e and l a b o r a t o r y o p e r a t i o n s , t h e column t y p e s e p a r a t o r i s t h e most common t y p e i n use t o d a y . The f e e d l i q u o r i s f e d t o t h e s i d e o f t h e column j u s t b e l o w t h e foam l i q u i d i n t e r f a c e . P orous s p a r g e r s a r e p l a c e d n e a r t h e bottom o f t h e column t o d i s p e r s e t h e gas. The ac c u m u l a t e d foam i s removed from t h e t o p o f t h e column. From p r a c t i c a l c o n s i d e r a t i o n s t h e t r o u g h system i s most s u i t a b l e f o r c o m m e r c i a l o p e r a t i o n s because o f s i m p l e r c o n s t r u c t i o n t h a n a t a l l f o aming column. The f e e d i s i n t r o d u c e d a t one end of a h o r i z o n t a l c o v e r e d t r o u g h and i s d i s c h a r g e d n e a r t h e o p p o s i t e end. D e v i c e s gen-e r a t i n g f i n e b u b b l e s a r e spaced a l o n g t h e bottom and t h e foam a c c u -m u l a t e s i n t h e space between t h e f o a m - l i q u i d i n t e r f a c e and t h e t r o u g h c o v e r . A v e r t i c a l b a f f l e h o l d s t h e l i q u i d i n t h e t r o u g h w h i l e a l l o w i n g t h e foam t o s p i l l o v e r i n t o a chamber f o r e v e n t u a l d i s c h a r g e . The foam t r a v e l s v a r i a b l e d i s t a n c e s d e p e n d i n g on where i t was g e n e r a t e d . F r o t h f l o t a t i o n i s done m o s t l y i n t r o u g h - t y p e systems. B o t h d i s s o l v e d a i r and d i s p e r s e d a i r a r e used t o c r e a t e t h e r e q u i r e d b u b b l e s u r f a c e . The column foamer i s more v e r s a t i l e t h a n t h e t r o u g h t y p e . F i g u r e 5 shows t h r e e a d d i t i o n a l modes o f o p e r a t i o n o f a column foamer. The o p e r -a t i o n a l c h a r a c t e r i s t i c s and t h e e q u a t i o n s used (51) f o r e s t i m a t i o n o f t h e s u r f a c t a n t c o n c e n t r a t i o n i n t h e t r e a t e d e f f l u e n t and i n t h e foam a r e summarized (68) i n T a b l e 3. F o r e n r i c h i n g p u r p o s e s , ( F i g u r e 5-b) a p o r t i o n o f t h e c o l l a p s e d foam i s r e t u r n e d i n t o t h e foam f r a c t i o n o f t h e column as e x t e r n a l r e f l u x . T h i s o p e r a t i o n w i l l e n r i c h t h e n e t o v e r f l o w and r e d u c e foam p r o d u c t i o n . F o r s t r i p p i n g a c t i o n ( F i g u r e 5-c) t h e f e e d i s i n immediate c o n t a c t w i t h t h e foam. Some o f t h e s u r f a c t a n t s a r e removed b e f o r e e n t e r i n g t h e l i q u i d p o o l . T h i s o p e r a t i o n p u r i f i e s t h e bot t o m p r o d u c t b u t g r e a t l y i n c r e a s e s t h e foam volume. The combined e n r i c h i n g and s t r i p p i n g mode ( F i g u r e 5-d) i s o p e r a t e d by d i r e c t i n g t h e f e e d t h r o u g h t h e foam b l a n k e t and c o n c u r r e n t l y r e t u r n i n g p a r t o f t h e c o l l a p s e d foam as e x t e r n a l r e f l u x . C o n s e q u e n t l y , t h e n e t o v e r f l o w i s e n r i c h e d , t h e bo t t o m p r o d u c t and t h e volume o f foam m i n i m i z e d . E. A p p l i c a t i o n s C o n v e n t i o n a l l y , foam s e p a r a t i o n has been used f o r t h e s e p a r a t i o n (69) and p u r i f i c a t i o n o f n a t u r a l l y s u r f a c e a c t i v e s u b s t a n c e s , p r o t e i n s , enzymes ( 7 0 ) , f a t t y a c i d s ( 7 1 ) , s a l t s and d e t e r g e n t s ( 7 2 ) . The use o f foam s e p a r a t i o n i n p o l l u t i o n c o n t r o l f o r t h e r e c o v e r y and f r a c t i o n a t i o n o f s u r f a c e i n a c t i v e m a t e r i a l s i s a r e c e n t development (73,74,75). T a b l e 4 summarizes t h e t y p e s o f a n i o n s , c a t i o n s , d y e s , f a t t y a c i d s and d e t e r -g e n t s , p r o t e i n s and enzymes t h a t have been removed by foam s e p a r a t i o n ( 7 6 ) . 35 F i g u r e 5 MODES OF OPERATION OF VARIOUS FOAM SEPARATION SYSTEMS (a) Simple Q FOAM COLLAPSED FOAM • DRAIN FRACTION (W) (b) Enriching f FOAM | 0 = ( R + ')D o a° °° RD a o o aa REFLUX ME T U OVERHEAD PRODUCT "0-oz; - . » DRAIN GAS FRACTION (W) FEED (c) Stripping FOAM 4>0 Oo O o GAS | (G) COLLAPSED FOAM (D) * DRAIN FRACTION (W) (d) Combined FOAM GAS ' (G) Q=(Q+I)D REFLUX (RD) NET OVERHEAD PRODUCT (D) DRAIN FRACTION (W) TABLE 3 CHARACTERISTICS OF DIFFERENT FOAM SEPARATION OPERATIONS (51,64) Mode of Operation Features Results * Equations for estimation of column performance Simple -Feed into l i q u i d pool -Countercurrent contact of gas and feed -Volume of foam removed i s a function of foam height „ n , 6 G TW CQ * °" + Q d C » - S - W - " Enriching -Feed into l i q u i d pool -Part of collapsed foam returned to foam layer as external reflux -Countercurrent contact of gas and liquid(feed+ l i q u i d drainage from foam) - Enriches the net foam overflow - Reduces volume of foam removed n ic cn 0.59.GTW C w = C F -(6.59 - R + 1) F d Stripping -Feed into foam blanket -No reflux -Countercurrent gas-l i q u i d contact - P u r i f i e s bottom product -Increases foam volume -Decreases enrichment r _ _ . 6,59 GTW LQ ~ C F + Q d C w = c - 6-59 GTW F w d Combined -Feed at lower part of foam layer -Part of collapsed foam returned to foam layer -Countercurrent gas-l i q u i d contact -Enriches the net foam overflow - P u r i f i e s bottom product -Moderate foam production r _ 6.59 GTf(R+1) CD C F + Q d r 6.59 G T F  C W C F " W d C = Concentration of surfactant w = output from column T = Surface concentration D = net collapsed foam overflow F = Feed R = reflux r a t i o Q =? Collapsed foam flow rate d = average bubble diameter TABLE 4 APPLICATION OF FOAM SEPARATION PROCESS Types o f M a t e r i a l s Removed S p e c i f i c Examples S u r f a c t a n t Requirement Remarks P r o t e i n s and Enzymes C h o l i n e s t e r a s e , D e x t r i n s , D i a t a s e F i s h s c a l e s , Hemoglobin, Hop R e s i n s , P e p s i n , R e n n i n , T y r o s i n a s e , Urease, M e t a p r o t e i n , Egg W h i t e s ; albumin No Best s e p a r a t i o n a t i s o e l e c t r i c pH A n i o n s 1-Chloromethyl n a p t h a l e n e , 1-Naphthoic a c i d , Phosphates, f e r r o c y a n i d e , S i l i c a t e , P h e n o l a t e C a t i o n i c S u r f a c t a n t Recovery o f s u r f a c t a n t may be r e q u i r e d C a t i o n s Ag, Be, Ca, Co, Cu, Fe, K, Mg, Mn, N i , Ra, Sm, S r , U, V, Th, Zn A n i o n i c S u r f a c t a n t F a t t y a c i d s and d e t e r g e n t s L a u r y l s u l f a t e , S u l f o n a t e s , M y r i s t i c a c i d , N o n y l i c a c i d , O l e i c a c i d , P a l m i t i c a c i d , R i c i n i c a c i d S a p o n i n , S t e a r i c a c i d , Decanoic a c i d , L a u r i e a c i d , t r i t o n . No M i s c e l l a n e o u s Amyl and L a u r y l a l c o h o l . Sugar j u i c e s . A p p l e and beer p r o t e i n s . G o n a d o t i o p i c hormones. Dyes. No Examples of c o m m e r c i a l a p p l i c a t i o n s o f foam s e p a r a t i o n p r o -c e s s e s a r e t h e c o n c e n t r a t i o n o f p r o t e i n s f r o m d i l u t e s o l u t i o n s (69) and t h e r e m o v a l o f d e t e r g e n t compounds i n sewage (77,78,79). Foam s e p a r -a t i o n u s u a l l y i s c o n d u c t e d w i t h 5 t o 10 min r e t e n t i o n t i m e s and G/L r a t i o s o f 3 t o 6. F o r r e m o v a l o f a n i o n s and c a t i o n s , a d d i t i o n o f a s u r f a c t a n t o f o p p o s i t e c h a r g e (69, 71) t o f o r m a foamable m e t a l - s u r -f a c t a n t complex i s r e q u i r e d . The p r o c e s s t h e r e f o r e i s more c o m p l i c a t e d . I n t h e p u l p and paper i n d u s t r y , foam s e p a r a t i o n has been i n v e s t -i g a t e d f o r BOD r e m o v a l ( 3 8 , 8 0 ) . F r o t h f l o t a t i o n i s w i d e l y used f o r r e m o v a l o f suspended s o l i d s (81) and b i o l o g i c a l s o l i d s ( 8 2 ) . Foam f r a c t i o n a t i o n i s p r a c t i s e d f o r r e c o v e r y o f t a l l o i l (83) f r o m b l a c k l i q u o r . An i o n f l o t a t i o n p r o o e s s (29,39) has been p r o p o s e d f o r t h e r e m o v a l o f c o l o r f r o m k r a f t m i l l e f f l u e n t . Other a p p l i c a t i o n s i n c l u d e o i l r e c o v e r y f r o m r e f i n e r y w a s t e s , g r e a s e and suspended s o l i d s r e m o v a l f r o m f o o d p r o c e s s i n g , r e m o v a l o f c o l l o i d a l m a t e r i a l s (84) and c o n c e n -t r a t i o n o f a l g a e (85) f r o m l a g o o n d i s c h a r g e s . ~r-CHAPTER IV MATERIALS AND METHODS A. SCOPE OF STUDY The r e s e a r c h program was c a r r i e d o u t i n f o u r p h a s e s : Phase I . - T r e a t a b i l i t y and o p t i m i z a t i o n s t u d i e s u s i n g a 4 ii l a b o r a -t o r y foam s e p a r a t i o n system. Phase I I . - I d e n f i c a t i o n o f p r o c e s s o p e r a t i o n a l p roblems i n a 80 I foam s e p a r a t i o n column i n s t a l l e d a t m i l l s i t e . Phase I I I . - V e r i f i c a t i o n o f p r o c e s s c o n d i t i o n s and d e t o x i f i c a t i o n r e -l i a b i l i t y o f foam s e p a r a t i o n p r o c e s s i n a 6000 g a l t r o u g h t y p e foam s e p a r a t i o n system. Phase IV. - Assessment o f c a p i t a l and o p e r a t i n g c o s t s . 1. T r e a t a b i l i t y o f V a r i o u s P r o c e s s Sewers D u r i n g t h e m a n u f a c t u r e o f b l e a c h e d p u l p , v a r i o u s p r o c e s s sewers d i s c h a r g e w a s t e s o f d i f f e r e n t c h a r a c t e r i s t i c s . I n g e n e r a l , u n b l e a c h e d w h i t e w a t e r and c a u s t i c e x t r a c t i o n e f f l u e n t a r e more t o x i c t h a n a c i d e f f l u e n t (86) and combined e f f l u e n t and a l s o d i f f e r i n foaming t e n d e n -c i e s ; i n f a c t , o n l y whole m i l l e f f l u e n t s p o s s e s s e x c e s s i v e f o a m i n g t e n -d e n c i e s . E x p e r i m e n t s were d e s i g n e d t o a s s e s s t h e a m e n a b i l i t y o f i n -d i v i d u a l and combined w a s t e streams t o d e t o x i f i c a t i o n by foam s e p a r -a t i o n . The f e a s i b i l i t y o f u s i n g s y n t h e t i c s u r f a c t a n t s f o r enhancement o f t h e foam s e p a r a t i o n p r o c e s s was a l s o i n c l u d e d i n t h e e v a l u a t i o n program. The most e a s i l y t r e a t a b l e i n d i v i d u a l and combined e f f l u e n t s t r e a m s were s e l e c t e d f o r subsequent s t u d i e s . 2 . U n i v e r s a l A p p l i c a b i l i t y o f Foam S e p a r a t i o n P r o c e s s Wood f u r n i s h e s , p u l p i n g and b l e a c h i n g p r o c e d u r e s , w a t e r usage and o t h e r p r o c e s s m o d i f i c a t i o n s f o r p r o d u c t i o n o f b l e a c h e d k r a f t p u l p v a r y f r o m m i l l t o m i l l a c r o s s Canada. E f f l u e n t c h a r a c t e r i s t i c s t h e r e f o r e a l s o d i f f e r and may n o t be e q u a l l y s u s c e p t i b l e t o d e t o x i f i c a t i o n by foam s e p a r a t i o n . I n o r d e r t o e v a l u a t e t h e a p p l i c a b i l i t y o f t h e p r o c e s s t o the e n t i r e i n d u s t r y , d a i l y e f f l u e n t d i s c h a r g e s f r o m a l a r g e number o f Can a d i a n m i l l s were sampled o v e r a one month p e r i o d . Under s t a n d a r d i z e d c o n d i t i o n s , e f f l u e n t s were t r e a t e d a t d i f f e r e n t t i m e i n t e r v a l s . The s u c c e s s r a t e and t h e t r e a t m e n t t i m e r e q u i r e d f o r d e t o x i f i c a t i o n were c a l c u l a t e d . A t t e m p t s were made t o i d e n t i f y t h e r e a s o n s f o r o c c a s i o n a l d e t o x i f i c a t i o n f a i l u r e s i n s p e c i f i c i n s t a n c e s . 3. O p t i m i z a t i o n o f V a r i o u s P r o c e s s P a r a m e t e r s U s i n g e f f l u e n t s from s e v e r a l m i l l s , t h o s e p r o c e s s v a r i a b l e s t h a t were i m p o r t a n t i n foam s e p a r a t i o n were o p t i m i z e d . F a c t o r s s t u d i e d were pH, a e r a t i o n r a t e ( G / L ) , g a s - l i q u i d i n t e r f a c i a l a r e a , t e m p e r a t u r e , t r e a t m e n t t i m e , column h e i g h t and mode o f o p e r a t i o n . The optimum c o n -d i t i o n s f o r d e t o x i f i c a t i o n were d e t e r m i n e d f o r s e v e r a l m i l l s and t h e r e s u l t s were used f o r development o f a c o n t i n u o u s f l o w s y s t e m f o r on-s i t e o p e r a t i o n . 4 . D e t o x i f i c a t i o n Mechanisms The p r i n c i p a l mechanisms i n v o l v e d i n d e t o x i f i c a t i o n by foam s e p -a r a t i o n were s t u d i e d t o g a i n a b e t t e r u n d e r s t a n d i n g o f t h e p r o c e s s and to c o n t r o l b e t t e r t h e p r o c e s s p a r a m e t e r s . S e v e r a l e x p l a n a t i o n s have been p o s t u l a t e d f o r t h e mechanisms c o n t r o l l i n g d e t o x i f i c a t i o n , namely: s t r i p p i n g , v o l a t i z a t i o n , o x i d a t i o n and foam f r a c t i o n a t i o n . A t t e m p t s were made t o d e t e r m i n e t h e r e l a t i v e c o n t r i b u t i o n o f v a r i o u s mechanisms by s e p a r a t i n g t h e e f f l u e n t i n t o a foam f r a c t i o n , a vapour f r a c t i o n and a t r e a t e d e f f l u e n t f r a c t i o n . 5 . F e a s i b i l i t y o f Combined D e t o x i f i c a t i o n w i t h Suspended S o l i d s Removal D i s s o l v e d a i r f l o t a t i o n has been used w i d e l y f o r suspended s o l i d s r e m o v a l . D u r i n g foam s e p a r a t i o n , a p r o c e s s s i m i l a r t o f l o t a t i o n , one would e x p e c t t h a t t h e b u b b l e s c o u l d be used f o r c o n c u r r e n t t o x i c i t y and suspended s o l i d s r e m o v a l . An assessment was made as t o whether t h e c o n d i t i o n s s u i t a b l e f o r d e t o x i f i c a t i o n were c o m p a t i b l e w i t h c o n d i t i o n s f o r good suspended s o l i d s r e m o v a l . 6. B e n e f i c i a l S i d e E f f e c t s o f Foam S e p a r a t i o n Foam s e p a r a t i o n i s known t o be c a p a b l e o f c o n c e n t r a t i n g a v a r i e t y o f m a t e r i a l s i n t h e foam f r a c t i o n . D u r i n g t h e d e t o x i f i c a t i o n p r o c e s s , p o l l u t a n t s o t h e r t h a n - t o x i c a n t s may a l s o be removed s i m u l t a n e o u s l y . P o l l u t i o n p a r a m e t e r s o f i n t e r e s t t h a t were s t u d i e d , i n c l u d e d BOD, TOC, f o a m i n g t e n d e n c y , r e s i n a c i d s , and c o l o r . 7. P r o c e s s R e l i a b i l i t y A f t e r d e t e r m i n a t i o n o f p r o c e s s a p p l i c a b i l i t y and optimum p r o c e s s p a r a m e t e r s i n t h e l a b o r a t o r y , t h e r e s u l t s were v e r i f i e d i n an 8 0 - g a l l o n c a p a c i t y foam s e p a r a t o r o p e r a t e d c o n t i n u o u s l y a t 1 g a l / m i n f o r s e v e r a l months a t a m i l l s i t e . E f f l u e n t s o f c h a n g i n g c h a r a c t e r i s t i c s were c o n -t i n u o u s l y f e d t o t h e sy s t e m and d e t o x i f i c a t i o n p e r f o r m a n c e was c o r r e -l a t e d t o i n f l u e n t t o x i c i t y , o p e r a t i n g c o n d i t i o n s , m i l l u p s e t s and m i l l o p e r a t i n g p r a c t i c e s . I n t h e c o u r s e o f t h e i n v e s t i g a t i o n , foam g e n e r a t i o n r a t e s and o p e r -a t i o n d i f f i c u l t i e s were s t u d i e d and c o r r e c t e d t o improve t h e p e r f o r m a n c e o f t h e p r o c e s s . C o l l a p s e d foam was a l s o c o l l e c t e d and c h a r a c t e r i z e d f o r foam volume, l i q u i d c o n t e n t and t o x i c i t y f o r foam d i s p o s a l s t u d i e s . 8. S e l e c t i o n o f Foam G e n e r a t i o n Systems I n t h e foam s e p a r a t i o n p r o c e s s , s u f f i c i e n t g a s - l i q u i d i n t e r f a c i a l a r e a must be g e n e r a t e d f o r a d s o r p t i o n o f s u r f a c e a c t i v e s u b s t a n c e s . The s u r f a c e a r e a can be e s t i m a t e d from: F o r s p h e r i c a l b u b b l e s , . -. Vgas x 6 > 9 i-i \ I n t e r f a c i a l A r e a = „_ " . . -p ——• -(nr7l) V l i q x b u b b l e d i a m e t e r T h i s e q u a t i o n s u g g e s t s t h a t a t c o n s t a n t l i q u i d volume, t h e s m a l l e r t h e b u b b l e d i a m e t e r , t h e s m a l l e r t h e volume o f gas needed t o g e n e r a t e t h e r e q u i r e d s u r f a c e a r e a f o r d e t o x i f i c a t i o n . However, p r o d u c t i o n o f s m a l l b u b b l e s u s u a l l y r e q u i r e s h i g h e n e r g y i n p u t s .arid, may not be economical f o r c o m m e r c i a l o p e r a t i o n . T h e r e f o r e , s e v e r a l t y p e s o f com-m e r c i a l foam g e n e r a t i n g equipment were t e s t e d and compared w i t h r e s p e c t t o b u b b l e s i z e s , horsepower r e q u i r e m e n t and d e t o x i f i c a t i o n p e r f o r m a n c e . The d a t a a r e i m p o r t a n t f o r t h e d e s i g n o f any l a r g e s c a l e s y s t e m and f o r e s t i m a t i o n o f o p e r a t i n g c o s t s . 9. R e d u c t i o n and B r e a k i n g o f Foam An a v e r a g e 750 t p d k r a f t m i l l d i s c h a r g i n g 25 MGD o f e f f l u e n t w i l l p r o duce l a r g e amounts o f foam w h i c h must be c o l l a p s e d by some p r a c t i c a l means. The s u i t a b i l i t y o f v a r i o u s modes o f o p e r a t i o n and foam b r e a k i n g d e v i c e s a v a i l a b l e on t h e market was i n v e s t i g a t e d f o r a p p l i c a t i o n i n a foam s e p a r a t i o n o p e r a t i o n . The most e f f i c i e n t and e c o n o m i c a l s y s t e m was s e l e c t e d and d e s i g n p a r a m e t e r s p e r t i n e n t t o k r a f t m i l l e f f l u e n t were d e v e l o p e d . 10. D i s p o s a l o f Foam H y p o t h e t i c a l l y , i f foam f r a c t i o n a t i o n i s t h e main mechanisms o f d e t o x i f i c a t i o n , t h e t o x i c s u b s t a n c e s w i l l be c o n c e n t r a t e d i n t h e foam. F u r t h e r t r e a t m e n t w i l l be r e q u i r e d p r i o r t o d i s p o s a l . Assuming t h a t a minimum o f 1 - 2% o f t h e i n f l u e n t i s c o n v e r t e d t o foam, t h e t o t a l volume o f c o l l a p s e d foam f r o m a 25 MGD p l a n t i s e s t i m a t e d a t a p p r o x i m a t e l y 250,000 - 500,000 g a l / d a y . A l t h o u g h s e v e r a l a p p r o a c h e s a r e a v a i l a b l e f o r t r e a t m e n t and d i s p o s a l o f t h i s h i g h l y c o n c e n t r a t e d m a t e r i a l , o n l y a few a r e p r a c t i c a l . P h y s i c a l d e s t r u c t i o n t e c h n i q u e s s u c h as e v a p o r -a t i o n f o l l o w e d by i n c i n e r a t i o n appear t o be t h e most e f f e c t i v e f r o m a t e c h n i c a l v i e w p o i n t , b u t may be t o o c o s t l y t o o p e r a t e . I n c o n s i d e r -a t i o n o f t h e economics, o n l y t h e l e s s e x p e n s i v e b i o l o g i c a l t r e a t m e n t ( a e r a t e d l a g o o n o r b i o d i s c p r o c e s s e s ) and c h e m i c a l t r e a t m e n t t e c h n i q u e s ( f l o c c u l a t i o n - c o a g u l a t i o n ) were s t u d i e d . 11. P i l o t P l a n t O p e r a t i o n F o l l o w i n g l a b o r a t o r y and f i e l d s i t e s t u d i e s on t h e f e a s i b i l i t y o f foam d e t o x i f i c a t i o n t e c h n i q u e s , t h e most s u i t a b l e equipment s e l e c t e d f o r foam g e n e r a t i o n and foam b r e a k i n g was i n s t a l l e d i n a 100 g a l / m i n p i l o t p l a n t . A f t e r s u c c e s s f u l d e m o n s t r a t i o n s o f t h e s u i t a b i l i t y o f t h e s e l e c t e d equipment, a two-month c o n t i n u o u s s t u d y was c o n d u c t e d t o v e r i f y t h e d e t o x i f i c a t i o n p e r f o r m a n c e o f foam s e p a r a t i o n p r o c e s s and t o o b t a i n d e s i g n p a r a m e t e r s f o r a l a r g e s c a l e i n s t a l l a t i o n . 12. E v a l u a t i o n o f P r o c e s s P o t e n t i a l A f t e r c o m p l e t i o n o f t h e l a b o r a t o r y , f i e l d and p i l o t p l a n t s t u d i e s , t h e t e c h n i c a l and e c o n o m i c a l p o t e n t i a l o f t h e foam s e p a r a t i o n p r o c e s s as a means o f d e t o x i f i c a t i o n were e v a l u a t e d . The c a p i t a l and o p e r a t i n g c o s t s were compared t o b i o l o g i c a l t r e a t m e n t p r o c e s s e s , i n p a r t i c u l a r t o t h e a e r a t e d l a g o o n t r e a t m e n t w h i c h i s used most commonly f o r BOD r e -moval and d e t o x i f i c a t i o n o f k r a f t m i l l e f f l u e n t s . 45 B. SOURCE AND TYPE OF EFFLUENTS D u r i n g t h e i n i t i a l phase o f l a b o r a t o r y i n v e s t i g a t i o n , i n d i v i d u a l p r o c e s s e f f l u e n t s , o b t a i n e d from m i l l s A,B,C and D were foam s e p a r a t e d . F o r t h e r e m a i n d e r o f t h e l a b o r a t o r y s t u d y , combined w h o l e m i l l e f f l u e n t f r o m 10 C a n a d i a n m i l l s (A t o J ) was used. F o r f i e l d and p i l o t p l a n t s t u d i e s , combined w h o l e m i l l e f f l u e n t f r o m m i l l s F and A were u s e d t h r o u g h o u t . 1. L a b o r a t o r y S t u d i e s As i n d i v i d u a l p r o c e s s s t r e a m s , u n b l e a c h e d w h i t e w a t e r , c a u s t i c e x-t r a c t i o n s t a g e e f f l u e n t and a c i d b l e a c h e d e f f l u e n t were o b t a i n e d . W h o l e m i l l e f f l u e n t c o n s i s t i n g o f a l l t h e major and mi n o r p r o c e s s s t r e a m s was o b t a i n e d f r o m 10 Canadian m i l l s , t h e code names, l o c a t i o n , wood f u r n i s h e s and t y p e o f e f f l u e n t s o b t a i n e d f o r t h e l a b o r a t o r y s t u d i e s a r e shown below: L o c a t i o n o f P r i n c i p a l Wood Type o f E f f l u e n t s M i l l M i l l F u r n i s h O b t a i n e d A B.C. Coast 18% f i r , 46% he m l o c k 36% c e d a r I n d i v i d u a l p r o c e s s s t r e a m s w h o l e m i l l e f f l u e n t B B.C. Co a s t 43.4% f i r 3% hemlock 16.3% c e d a r I n d i v i d u a l p r o c e s s s t r e a m s w h o l e m i l l e f f l u e n t C B.C. I n t e r i o r 50% s p r u c e , 45% p i n e , 5% f i r I n d i v i d u a l p r o c e s s streams w h o l e m i l l e f f l u e n t D B.C. I n t e r i o r 36% s p r u c e , 33% p i n e 31% o t h e r s I n d i v i d u a l p r o c e s s s t r e a m s w h o l e m i l l e f f l u e n t E B.C. Coast F i r , c y p r e s s , s p r u c e , p i n e and hemlock W h o l e m i l l e f f l u e n t 46 F B.C. I n t e r i o r G B.C. I n t e r i o r H B.C. C o a s t I O n t a r i o J Quebec 60% s p r u c e , 16% p i n e 12% b a l s a m and o t h e r s 50% s p r u c e , 4 5 % p i n e 5% o t h e r s 50% hemlock, 32% f i r , 18% c e d a r 80% j a c k p i n e and 20% s p r u c e 46% p o p l a r , 27% maple, 17% b i r c h and 10% so f t w o o d W h o l e m i l l e f f l u e n t W h o l e m i l l e f f l u e n t W h o l e m i l l e f f l u e n t W h o l e m i l l e f f l u e n t W h o l e m i l l e f f l u e n t The samples were s h i p p e d i m m e d i a t e l y t o t h e l a b o r a t o r y and s t o r e d i n a 2°C w a l k - i n r e f r i g e r a t o r . I n o r d e r t o m i n i m i z e any d e t e r i o r a t i o n i n e f f l u e n t q u a l i t y , t h e y were used f o r e x p e r i m e n t as soon as p o s s i b l e . 2. F i e l d S t u d i e s F i e l d s t u d i e s were c o n d u c t e d a t t h e combined e f f l u e n t o u t f a l l o f m i l l F; an i n t e r i o r B.C. m i l l . The m i l l p r o d u c e d an a v e r a g e o f 750 t p d o f b l e a c h e d k r a f t p u l p u s i n g t h e CEDED b l e a c h i n g sequence and d i s c h a r g e a p p r o x i m a t e l y 25 MGD o f e f f l u e n t t o t h e F r a s e r R i v e r . The e f f l u e n t s were t o x i c , p o s s e s s e d good f o a m a b i l i t y and appe a r e d s u i t a b l e f o r foam s e p a r a t i o n . The e f f l u e n t was n e u t r a l i z e d i n t h e m i l l w i t h l i m e mud and s l a k e d l i m e t o about pH 4.5, t h e n w i t h sodium h y d r o x i d e t o pH 7. The suspended s o l i d s o f n e u t r a l i z e d e f f l u e n t were removed i n a 4-hr r e t e n t i o n p r i m a r y c l a r i f i e r ; t h e c l a r i f i e r o v e r f l o w was e n r i c h e d w i t h ammonium phosphate 47 and u r e a t o a BOT^/N/P r a t i o o f about 100/2.5/0.7 and d i s c h a r g e d t o a 5-day r e t e n t i o n a e r a t e d l a g o o n system. W h o l e m i l l e f f l u e n t e n t e r i n g t h e m i l l ' s b i o t r e a t m e n t l a g o o n was tapped and pumped t o t h e f i e l d foam s e p -a r a t i o n p l a n t . 3. P i l o t P l a n t S t u d i e s P i l o t p l a n t s t u d i e s were c o n d u c t e d a t t h e combined e f f l u e n t o u t f a l l o f m i l l A on Vancouver I s l a n d . The m i l l p r o d u c e d a p p r o x i m a t e l y 1000 t p d o f b l e a c h e d k r a f t p u l p and d i s c h a r g e d 60 MGD o f e f f l u e n t . The wood f u r n i s h e s were 18% f i r , 46% hemlock and 36% c e d a r ; a CEHCHDED b l e a c h i n g sequence was used. The e f f l u e n t s were m o d e r a t e l y t o x i c t o f i s h . The pH o f t h e e f f l u e n t r a n g e d f r o m 3-5. C. FOAM SEPARATION SYSTEMS - EQUIPMENT AND OPERATION 1. L a b o r a t o r y System L a b o r a t o r y s t u d i e s were done u s i n g a d i s p e r s e d a i r foam f r a c t i o n -a t i o n s ystem, a h e l i c a l a e r a t o r s y s t e m , a t u r b i n e and a h i g h p r e s s u r e f l o t a t i o n system. a. Foam G e n e r a t i o n ( i ) Foam F r a c t i o n a t i o n Column D i s p e r s e d A i r System A s e r i e s o f foam f r a c t i o n a t i o n columns, 180 cm h i g h , were c o n -s t r u c t e d from 7.5 cm d i a m e t e r m e t h a c r y l a t e p l a s t i c t u b i n g ( F i g u r e 6-a ) . Two s i n t e r e d g l a s s t u b e s ( F i g u r e 6-b), 1 i n c h i n l e n g t h , 1/2 i n c h i n d i a m e t e r , (45 y p o r e s i z e ) were i n s e r t e d i n t h e b o t t o m o f t h e column f o r d i s p e r s i o n o f a i r i n t o t h e s o l u t i o n . I n F i g u r e 7, t h e s e t up o f a l a b o r a t o r y system, c o m p l e t e w i t h a u t o m a t i c pH and t e m p e r a t u r e c o n t r o l , gas and l i q u i d f e e d and vacuum s u c t i o n i s shown. Most e x p e r i m e n t s i n t h e l a b o r a t o r y were done b a t c h - w i s e . Four l i t r e s o f raw e f f l u e n t were a d j u s t e d t o t h e d e s i r e d pH, poured i n t o t h e foam f r a c t i o n a t i o n column, warmed up t o t h e t e m p e r a t u r e r e q u i r e d and t h e n foam f r a c t i o n a t e d f o r a s p e c i f i e d l e n g t h o f t i m e . Foam f r a c t i o n a t i o n was a c h i e v e d by d i s p e r s i n g a i r t h r o u g h t h e e f -f l u e n t a t 500 ml/min, u n l e s s o t h e r w i s e i n d i c a t e d . The foam g e n e r a t e d was c o n t i n u o u s l y removed a t 60 cm foam h e i g h t by vacuum s u c t i o n . A f t e r t r e a t m e n t , t h e foam f r a c t i o n a t e d e f f l u e n t was sampled f o r a n a l y s i s . H e l i c a l A e r a t o r Foam G e n e r a t i o n System A K e n i c s a e r a t o r s y s t e m c o n s i s t s o f a s e r i e s o f a l t e r n a t i n g r i g h t and l e f t hand h e l i c e s c o n t a i n e d i n a p i p e . These h e l i c e s a r e o r i e n t e d so t h a t each l e a d i n g edge i s a t 90° t o t h e t r a i l i n g edge o f t h e one ahead. A s c h e m a t i c d i a g r a m i s g i v e n i n F i g u r e 8. F o r b u b b l e g e n e r a t i o n a i r i s mixed w i t h t h e l i q u i d and t h e n pumped a t h i g h speed t h r o u g h a p i p e . B u b b l e s i z e i s c o n t r o l l e d by t h e v e l o c i t y o f t h e a i r - l i q u i d m i x t u r e . FIGURE 6-a FIGURE 6-b OVERALL VIEW OF LABORATORY FOAM SINTERED GLASS GAS DISPERSER SEPARATION EQUIPMENT INSERTED IN THE BOTTOM OF WO 50 F i g u r e 7 A SINGLE COLUMN USED FOR LABORATORY FOAM SEPARATION STUDIES A Vacuum ^ suction 7,5 cm Treated effluent F i g u r e 8 FOAM SEPARATION SYSTEM WITH KENICS AERATOR o°OOoq RECIRCULATION PUMP ST FOAM REMOVAL HELICAL AERATOR (see Detail A ) Tj ROTAMETER AIR / o o o / B U B B L E o ° o / MIXTURE LIQUID 8 AIR (DETAIL A) KENICS AERATOR 52 F o r l a b o r a t o r y s t u d i e s , a 1.25 cm d i a m e t e r , 30 cm l o n g K e n i c s A e r a t o r c o n s i s t i n g o f 6 l e f t - and 6 r i g h t - h a n d h e l i c a l e l e m e n t s was i n -s t a l l e d a t t h e b o t t o m o f a f o a m - f r a c t i o n a t i o n column ( F i g u r e 7 ) . Four l i t r e s o f e f f l u e n t were t r e a t e d b a t c h - w i s e . L i q u i d was drawn f r o m t h e b o t t o m o f t h e column and pumped a t 2 f t / s e c t h r o u g h t h e h e l i c a l a e r a t o r b a c k i n t o t h e column. A i r was me t e r e d t o t h e h i g h v e l o c i t y s y s t e m a t 250 ml/min. Foam was removed c o n t i n u o u s l y by vacuum s u c t i o n a t 60 cm foam h e i g h t . ( i i ) T r o ugh Type Foam F r a c t i o n a t i o n Tank T u r b i n e System A l a b o r a t o r y - s i z e d t u r b i n e s y s t e m was use d . I t c o n s i s t e d o f a 15 l i t r e g l a s s r e c t a n g u l a r v e s s e l , a s h a f t w i t h a 7.5 cm d i a m e t e r i m p e l l e r f i t t e d w i t h f o u r 1.5 cm x 1.5 cm b l a d e s and an a i r f e e d l i n e l e a d i n g b e n e a t h t h e i m p e l l e r ( F i g u r e 9 ) . The s y s t e m d i s p e r s e s a i r by s h e a r i n g t h e a i r b u b b l e s . B u b b l e s i z e i s c o n t r o l l e d by t h e r o t a t i o n a l speed o f t h e i m p e l l e r . F o r e ach e x p e r i m e n t , 10 l i t r e s o f e f f l u e n t were t r e a t e d . A i r was metered a t 500 ml/min i n t o t h e sy s t e m , and d i s p e r s e d by t h e i m p e l l e r a t a p p r o x i m a t e l y 1000 rpm. Foam was m a n u a l l y removed f r o m t h e s u r f a c e o f t h e l i q u i d a t 2 min i n t e r v a l s . 53 F i g u r e 9 MECHANICAL DISPERSION OF AIR BY A TURBINE 54 ( i i i ) H i g h P r e s s u r e Foam F r a c t i o n a t i o n Column D i s s o l v e d A i r F l o t a t i o n System F i g u r e 10 shows a d i s s o l v e d a i r f l o t a t i o n s y s t e m used i n t h e l a b -o r a t o r y . The b a t c h system c o n s i s t e d o f an 8 l i t r e c a p a c i t y p r e s s u r i z -a t i o n t a n k . Under h i g h p r e s s u r e (20 - 80 p s i g ) , a i r was d i s s o l v e d i n t o t h e e f f l u e n t by s p l a s h i n g t h e e f f l u e n t on a 3" d i a m e t e r p l a t e l o c a t e d 2" b e l o w t h e top o f t h e p r e s s u r i z a t i o n t a n k . A f t e r 5 min o f c o n t i n u o u s c i r c u l a t i o n t h e e f f l u e n t was r e l e a s e d v e r y s l o w l y t o an 8 l i t r e f l o t -a t i o n c e l l f o r foam g e n e r a t i o n . b. Foam Volume R e d u c t i o n I n s p e c i f i c i n s t a n c e s , t h e foam volume t o be d i s c h a r g e d was c o n -s i d e r e d t o be t o o l a r g e t h e r e f o r e subsequent d i s p o s a l would n o t be e c o n o m i c a l l y f e a s i b l e . Methods f o r r e d u c i n g t h e volume o f foam w h i c h were i n v e s t i g a t e d i n t h i s s t u d y , i n v o l v e d i n t e r n a l and e x t e r n a l r e f l u x e s o f t h e c o l l a p s e d foam. The s t u d y o f foam r e d u c t i o n was u n d e r t a k e n i n a 350 cm h i g h , 7.5 cm d i a m e t e r foam s e p a r a t i o n column. The l i q u i d volume t r e a t e d was 4-1 (90 cm column h e i g h t ) . Maximum foam h e i g h t was 260 cm. ( i ) I n t e r n a l R e f l u x The volume o f t h e foam d i s c h a r g e d was g r a d u a l l y r e d u c e d by i n -c r e a s i n g t h e h e i g h t o f t h e foam r e t e n t i o n column p r i o r t o d r a w - o f f . FIGURE 10 DISSOLVED AIR FLOTATION SYSTEM 56 Under n o r m a l o p e r a t i n g c o n d i t i o n s ( A i r f l o w = 500 ml/min; a i r d i f f u s e r p o r e s i z e = 45 u ) , a l l t h e foam p r o d u c e d was b r o k e n s p o n t a n e o u s l y and r e s u l t e d i n f o r m a t i o n o f a gummy s o l i d m a t e r i a l a t a h e i g h t o f 250 cm above t h e l i q u i d l e v e l . ( i i ) E x t e r n a l R e f l u x The e x t e r n a l r e f l u x s y s t e m i s a l s o r e f e r r e d t o as " e n r i c h m e n t mode o p e r a t i o n " i n foam s e p a r a t i o n p r o c e s s e s . The s e t - u p o f t h e equipment i s shown i n F i g u r e 11. The same column d e s i g n e d f o r i n t e r n a l r e f l u x o p e r -a t i o n was used e x c e p t t h a t foam was removed a r b i t r a r i l y a t 60 cm above t h e l i q u i d l e v e l and c o l l a p s e d e x t e r n a l l y . A measured f l o w o f c o l l a p s e d foam was s p r a y e d c o n t i n u o u s l y back i n t o t h e column on t o p o f t h e foam l a y e r . The amount o f foam r e t u r n e d was c o n t r o l l e d a t r e c y c l e r a t i o s o f 0.1 t o 1.0. c. Foam C o l l a p s i n g A vacuum system c o n s i s t i n g o f an e d u c t o r and a 4-1 c a p a c i t y vacuum j a r was used ( F i g u r e / 1 2 ) . The vacuum l i n e was l i n k e d t o a foam r e m o v a l p o r t 60 cm above t h e l i q u i d s u r f a c e o f a 7-1 c a p a c i t y foam s e p a r a t i o n column, exposed t o a t m o s p h e r i c c o n d i t i o n . The a p p l i e d s u c t i o n c o u p l e d w i t h c o n t i n u o u s a e r a t i o n f o r c e d t h e foam t o f l o w t o t h e vacuum j a r . Foam was c o l l a p s e d due t o t h e e x p a n s i o n i n volume i n t h e vacuum j a r and t h e s t i r r i n g e f f e c t o f a m a g n e t i c b a r . I n s i t u a t i o n s where foamin g was e x c e s s i v e , s m a l l amounts o f c h e m i c a l "defoamers were added t o a s s i s t foam b r e a k i n g . The method o f vacuum s u c t i o n was used m a i n l y i n t h e l a b o r a -t o r y . Figure ii REDUCTION OF FOAM BY RECYCLING ( ENRICHING MODE ) Whole mill ef fluent T effluent F i g u r e 12 FOAM COLLAPSING SYSTEM USING VACUUM RUPTURE TECHNIQUE 59 2. Foam S e p a r a t i o n System I n s t a l l e d a t M i l l S i t e ( F i e l d System) A 1 g a l / m i n c o n t i n u o u s f l o w foam s e p a r a t i o n p l a n t was i n s t a l l e d on-s i t e a t t h e o u t f a l l o f M i l l F a t an I n t e r i o r B.C. M i l l . The equipment was i n s t a l l e d i n a 12' x 50' m o b i l e t r a i l e r . The foam s e p a r a t i o n s y s t e m c o n s i s t e d o f 3 s e p a r a t e columns, each w i t h 80 g a l c a p a c i t y and w i t h i n d i v i d u a l o p e r a t i o n a l c o n t r o l e l e m e n t s . S u p p o r t i n g equipment i n c l u d e d 3 0 0 - g a l and 5 0 0 - g a l pH a d j u s t m e n t t a n k s , an e f f l u e n t pumping s t a t i o n 3 w i t h f l o w c o n t r o l and a 6 f t /min compressor . F i g u r e 13 shows a f l o w s h e e t o f t h e foam s e p a r a t i o n p r o c e s s . a. pH C o n t r o l Raw e f f l u e n t was pumped from t h e m i l l ' s d i s c h a r g e t o a s m a l l head t a n k , w h i c h o v e r f l o w e d t o t h e sewer. The head t a n k g r a v i t y f e d a 5 x 5 x 4 f t wooden t a n k used f o r pH a d j u s t m e n t . The o p e r a t i n g volume o f t h i s t a n k was 600 g a l and r e t e n t i o n t i m e was 3 h r . I t was e q u i p p e d w i t h a l o w speed L i g h t n i n m i x e r and an a u t o m a t i c pH c o n t r o l s y s t e m ( G r e a t L a k e s pH m e t e r , M o d e l 6 0 ) . The pH o f t h e e f f l u e n t was m a i n t a i n e d a t 8 by a d d i n g 25% NaOH s o l u t i o n . F o r s t a n d b y p u r p o s e , a 300 g a l pH a d j u s t m e n t t a n k was k e p t n e a r b y . b. Pumping S t a t i o n E f f l u e n t f r o m t h e pH t a n k was d e l i v e r e d by t h r e e J a b s c o I m p e l l e r pumps t o t h e foam f r a c t i o n a t i o n column. I n i t i a l l y t h e f l o w r a t e was F i g u r e 13 PROCESS FLOW SHEET FOR FOAM SEPARATION AT MILL SITE Air o 61 c o n t r o l l e d by d i s c h a r g i n g e x c e s s l i q u i d t h r o u g h a b y p a s s i n g s y s t e m b u t because o f p l u g g i n g problems i n t h e v a l v e s , t h i s c o n t r o l was r e p l a c e d by an i n t e r m i t t e n t programmed t i m e r and p r o p e r s i z i n g o f t h e pumps. To e n s u r e a c c u r a t e l i q u i d f l o w r a t e e n t e r i n g t h e sy s t e m , a Brook r o t a m e t e r was i n s t a l l e d f o r d a i l y c a l i b r a t i o n . c. A i r D i s p e r s i o n System The a i r r e q u i r e d f o r foam g e n e r a t i o n was g e n e r a t e d o n - s i t e by a 6 3 3 f t /min co m p r e s s o r , a 2 f t /min system was used as stand-by. The a i r was d e l i v e r e d by 1/2" d i a m e t e r h i g h d e n s i t y p l a s t i c t u b i n g t o t h e a i r chamber b u i l t a t t h e bottom o f t h e column. F o u r d i f f e r e n t t y p e s o f po r o u s gas d i f f u s e r s were i n s e r t e d i n t h e a i r chamber f o r foam g e n e r a t i o n . Seven, 5 - i n c h d i a m e t e r , 1 / 1 6 - i n c h t h i c k , p orous p l a s t i c d i s c s ( B e l -A r t P r o d u c t s ) ( F i g u r e 14-a) - Nom i n a l P o r e S i z e : 65u 2 T o t a l n o m i n a l a i r d i s p e r s i o n a r e a : 0.95 f t F o u r , 1 - f t l o n g , 3 - i n c h d i a m e t e r , p o r o u s c e r a m i c t u b e s ( N o r t o n Company ( F i g u r e 14-b) No m i n a l Pour S i z e : <25u 2 T o t a l n o m i n a l a i r d i s p e r s i o n a r e a : 3.14 f t FIGURE 14-a FIGURE 14-b FIGURE 14-c PLASTIC DISC AIR CERAMIC AIR DISPERSION POROUS ALUNDUM PLATE DISPERSION MEDIA TUBES AIR DISPERSION MEDIA 63 One, 1 8 - i n c h d i a m e t e r , 1 1 / 2 - i n c h t h i c k p orous Alundum p l a t e ( N o r t o n Company) ( F i g u r e 14-c) - N o m i n a l P o r e S i z e : 65u T o t a l n o m i n a l a i r d i s p e r s i o n a r e a : 1.77 f t 2 F i g u r e 15 shows a foam f r a c t i o n a t i o n column w i t h porous c e r a m i c t u b e s i n p l a c e . d. Foam F r a c t i o n a t i o n Columns Three 80 g a l c a p a c i t y foam f r a c t i o n a t i o n columns (1.5 f t d i a m e t e r , 6 f t h e i g h t ) made o f m e t h a c r y l a t e p l a s t i c were u s e d . The columns were eq u i p p e d w i t h f e e d i n l e t p o r t s , a i r d i s p e r s i o n media a t t h e bo t t o m and foam d i s c h a r g e p o r t s . The d i m e n s i o n s o f each column a r e shown i n F i g u r e 16. Two systems were o p e r a t e d c o n t i n u o u s l y whereas t h e t h i r d s y s t e m was h e l d i n r e s e r v e ( F i g u r e 1 7 ) . The columns were o p e r a t e d a t a c o n s t a n t l i q u i d h e i g h t o f 4 f t w i t h a l i q u i d volume o f a p p r o x i m a t e l y 45 g a l . E f f l u e n t was f e d i n a t t h e l i q u i d - f o a m i n t e r f a c e and d i s c h a r g e d a t t h e b o t t o m o f t h e s y s t e m v i a a s t a n d - p i p e l e v e l c o n t r o l . A i r was d i s p e r s e d i n t o t h e l i q u i d a t t h e bo t t o m o f t h e column v i a a i r d i s p e r s i o n media. FIGURE 15 FIELD FOAM SEPARATION COLUMN INSTALLED WITH CERAMIC TUBE AIR DISPERSERS 65 F i g u r e 16 FOAM SEPARATION COLUMN INSTALLED AT MILL SITE 1.5' Foam separator F o a m remova l FIGURE 17 PICTURE OF FIELD FOAM SEPARATION COLUMN IN OPERATION 67 e. Foam C o l l a p s i n g The foam s e p a r a t i o n s y s t e m o p e r a t e d a t t h e f i e l d - s i t e p r o d u c e d up t o 30 1/min o f foam. I n t h i s s y stem, foam was e x p e l l e d from a 180 1 op-e r a t i n g c a p a c i t y , foam column t h r o u g h a 3 - i n d i a m e t e r foam p o r t opened 6 - i n above t h e l i q u i d l e v e l . The t o p o f t h e foam column was c l o s e d t o f o r c e t h e foam t o f l o w o u t from t h e system. A w a t e r s p r a y n o z z l e , w h i c h was more e f f e c t i v e and s i m p l e r t h a n a vacuum sy s t e m , was used f o r foam c o l l a p s i n g ( F i g u r e 1 8 ) . The i m p a c t f o r c e o f t h e w a t e r j e t s as t h e y i m p i n g e d on t h e foam, and t h e i r d i l u t i o n e f f e c t s caused t h e foam t o - c o l l a p s e . f . Treatment and D e t o x i f i c a t i o n o f C o l l a p s e d Foam The foam produced f r o m t h e f i e l d foam s e p a r a t i o n s y s t e m was sub-j e c t e d t o v a r i o u s c h e m i c a l and b i o l o g i c a l t r e a t m e n t s . C h e m i c a l t r e a t -ment methods i n v o l v e d f l o c c u l a t i o n - c o a g u l a t i o n o f p o l l u t a n t s . B i o -l o g i c a l t r e a t m e n t methods i n v o l v e d r o t a t i n g b i o d i s c and a e r a t e d l a g o o n t r e a t m e n t s . ( i ) C h e m i c a l Treatment The foam removed from t h e column was c o l l a p s e d . To t h e c o l l a p s e d foam a s u i t a b l e amount o f l i m e (at pH 1 0 ) , alum ( a t pH 5.5), o r f e r r i c s u l p h a t e (pH 5.5) was added. A f t e r a d d i t i o n o f the' p a r t i c u l a r c h e m i c a l , t h e pH was a d j u s t e d t o t h e l e v e l o p t i m a l f o r f l o c c u l a t i o n - c o a g u l a t i o n . These s t u d i e s were c o n d u c t e d w i t h 3-1 o f c o l l a p s e d foam i n a P h e l p s and F i g u r e 18 FOAM BREAKING BY WATER SPRAY SYSTEM B i r d s l a b o r a t o r y f l o c c u l a t o r . The w a s t e s were a g i t a t e d by a 3 - i n c h p a d d l e a t 100 rpm f o r 10 min and 30 rpm f o r 20 min. The f l o e s formed were a l l o w e d t o s e t t l e f o r 2 h r . C l a r i f i e d e f f l u e n t s were d e c a n t e d f o r subsequent t o x i c i t y a n a l y s i s . ( i i ) B i o l o g i c a l Treatment P r i o r t o any e x p e r i m e n t s , t h e c o l l a p s e d foam was a d j u s t e d t o pH 7 and e n r i c h e d w i t h ammonium s u l p h a t e and p h o s p h o r i c a c i d a c c o r d i n g t o B0D,.:N:P = 100:5:1. Treatment t e m p e r a t u r e was m a i n t a i n e d a t 22 ± 3 C. M i c r o b i a l growth was d e v e l o p e d by t r e a t i n g a b a t c h o f e f f l u e n t f o r one week b e f o r e t h e c o n t i n u o u s o p e r a t i o n was begun. The i n o c u l u m was ob-t a i n e d f r o m a n e a r - b y a c t i v a t e d s l u d g e system. R o t a t i n g B i o d i s c An 8-1 c a p a c i t y , bench s c a l e , c o n t i n u o u s f l o w b i o d i s c u n i t was used ( F i g u r e 1 9 ) . The u n i t c o n s i s t e d o f a t r o u g h d i v i d e d i n t o t h r e e compart-ments. On t h e top o f t h e t r o u g h , 75 c l o s e l y spaced d i s c s , 25 i n each compartment were s u p p o r t e d by a s h a f t and r o t a t e d g e n t l y by a l o w sp e e d , gear d r i v e motor. Each 8 - i n d i a m e t e r , l / 8 - i n t h i c k , p l e x i g l a s s d i s c 2 2 had a s u r f a c e a r e a o f 0.72 f t , g i v i n g a t o t a l s y s t e m a r e a o f 55 f t . The l o w e r p o r t i o n o f each d i s c was submerged i n t h e waste b e i n g t r e a t e d , w h i l e t h e upper p o r t i o n r o t a t e d i n t h e a i r . A b i o l o g i c a l s l i m e d e v e l -oped on t h e d i s c s . The waste p a s s i n g t h r o u g h t h e d i s c s f l o w s p a r a l l e l t o t h e a d j a c e n t f a c e s o f t h e d i s c s . The d r a g f o r c e s g e n e r a t e d by t h e s l o w r o t a t i o n i m p a r t e d a l i f t i n g a c t i o n t o t h e waste and caused t h e waste s o l u t i o n n e a r t h e d i s c t o f l o w i n a c i r c u l a r p a t t e r n . FIGURE 19 BIODISC SYSTEM FOR TREATMENT OF COLLAPSED FOAM o 71 A e r a t e d Lagoon A 20-1 o p e r a t i n g c a p a c i t y r e c t a n g u l a r shaped t a n k (1 x w x d = 13-x 1 1 - x 1 0 - i n ) was us e d as an a e r a t e d l a g o o n . A m a s t e r f l e x pump de-l i v e r e d t h e c o l l a p s e d foam t o i t c o n t i n u o u s l y f o r b i o l o g i c a l o x i d a t i o n . L a b o r a t o r y compressed a i r was us e d t o p r o v i d e oxygen f o r m i c r o b i a l 3 growth. A p p r o x i m a t e l y 100 cm /min o f a i r was d i f f u s e d t h r o u g h t h r e e f r i t t e d g l a s s t u b e s submerged a t t h e bo t t o m o f t h e t a n k . The a v e r a g e d i s s o l v e d oxygen l e v e l was m a i n t a i n e d a t 3 mg/1 and mixed l i q u o r s u spend-ed s o l i d s were m o n i t o r e d r e g u l a r l y . The a e r a t e d l a g o o n system was o p e r a t e d a r b i t r a r i l y a t . 3-day r e t e n t i o n t i m e s u s i n g t h e same e f f l u e n t and under t h e same c o n d i t i o n as t h a t used i n t h e b i o d i s c system. < 3. P i l o t P l a n t Foam S e p a r a t i o n System The p i l o t p l a n t was d e s i g n e d t o p r o c e s s a maximum o f 100 g a l / m i n o f e f f l u e n t . The p r i n c i p l e s y s t e m components c o n s i s t e d o f a 500 g a l c a p a c i t y pH c o n t r o l s ystem, a 6000 g a l c a p a c i t y foam g e n e r a t i o n s y s t e m and a 300 "gal c a p a c i t y foam c o l l a p s i n g s y s tem. F i g u r e 20 g i v e s t h e d i m e n s i o n o f t h e foam s e p a r a t i o n system. A 12 x 50 f t t r a i l e r was i n -s t a l l e d ( F i g u r e 21) n e a r t h e p i l o t p l a n t t o house t h e pH c o n t r o l s y s t e m , a i r b l o w e r s and l a b o r a t o r y f a c i l i t i e s . a. E f f l u e n t D e l i v e r y A p p r o x i m a t e l y 80 - 100 g a l / m i n o f w h o l e m i l l e f f l u e n t was pumped fro m t h e m i l l s ' main d i s c h a r g e sewer and d e l i v e r e d t h r o u g h 200 f t o f 2-i n d i a m e t e r p o l y e t h y l e n e p i p e t o t h e p i l o t p l a n t system. The e f f l u e n t s F i g u r e 20 PILOT PLANT FOAM SEPARATION SYSTEM ( lOOga l /m in ) Influent Stand-pipe Head tank with pH control 2 Line 100 g p m Pump N 3 FIGURE 21 OVERALL VIEW OF 100 gal/min FOAM SEPARATION PILOT PLANT INSTALLED AT MILL A entered a 500 gal capacity head tank (1 x w x d = 4- x 4- x 5-ft) for pH adjustment and were then pumped to the foam separation plant. Excess i n f l u e n t s to the pH c o n t r o l system and treated e f f l u e n t s from the foam generation plant were discharged to the ocean. b. pH Control The pH of the e f f l u e n t was adjusted to between 7 and 8 i n the head tank p r i o r to foam separation. Overall retention time was 5-7 min. pH monitoring and addition of caustic s o l u t i o n (25% concentration) was co n t r o l l e d by a Model 60 Great Lake I n d u s t r i a l pH Monitor. A 1/3 hp L i g h t n i n Mixer activated by a 60-min i n t e r v a l programmable timer pro-vided intermittent a g i t a t i o n (to reduce foaming i n pH tank). The pH > adjusted e f f l u e n t was then pumped to the foam generation tank. c. Foam Fra c t i o n a t i o n System The foam f r a c t i o n a t i o n system comprised a foam generation tank, an a i r d e l i v e r y system and foam generation equipment. ( i ) Foam Generation Tank A plywood tank, coated with water proof paint was constructed on-s i t e . The tank measured 20 f t i n length, 6 f t i n width and 8 f t i n height and was operated with a 6 f t depth of l i q u i d . The tank was subdivided with wooden walls into three equal sections. The walls were removable and allowed conversion of the system into a one, two or three s t a g e system as r e q u i r e d . Depending on t h e s e t - u p , t h e t o t a l r e t e n -t i o n t i m e , t h e volume o f t h e e f f l u e n t t r e a t e d and t h e number o f s t a g e s c o u l d be v a r i e d . The pH a d j u s t e d i n f l u e n t e n t e r e d t h e t a n k a t a r a t e o 80- 100 g a l / m i n , c o r r e s p o n d i n g t o 60-75 min t o t a l r e t e n t i o n t i m e and 20 25 min r e t e n t i o n t i m e p e r s t a g e . The t a n k was f i l l e d w i t h e f f l u e n t a t a l l t i m e s . However, f o r s i n g l e s t a g e o p e r a t i o n , o n l y t h e e f f l u e n t i n t h e 1 s t s t a g e was a e r a t e d f o r foam f o r m a t i o n . F o r two and t h r e e s t a g e o p e r a t i o n , t h e a e r a t o r s i n t h e second and t h i r d s t a g e were a l s o used. E f f l u e n t s f l o w e d s u c c e s -s i v e l y t h r o u g h a 15- x 61- cm o p e n i n g from t h e f i r s t t o t h e s e c o n d and t h e n t o t h e t h i r d s t a g e . The top o f t h e foam g e n e r a t i o n t a n k was c o v e r e d by p l a s t i c and p r o t e c t e d by a shed. The f r o n t o f t h e t a n k was open t o a l l o w foam t o s p i l l t o t h e a d j a c e n t foam b r e a k i n g system ( F i g u r e 2 1 ) . ( i i ) Foam G e n e r a t i n g Equipment N i n e , c o m m e r c i a l s i z e , 2" d i a m e t e r , j e t a e r a t o r s were i n s t a l l e d i n t h e 3-stage foam g e n e r a t i o n t a n k . A d i a g r a m o f a u n i t i s shown i n F i g u r e 22-a. F i b u r e 22-b shows t h e f o r m a t i o n o f a h o r i z o n t a l j e t plume ( b u b b l e - l i q u i d m i x t u r e ) by s u c h a j e t a e r a t o r . The f l u i d was pumped t h r o u g h t h e j e t n o z z l e a t 2 f t / s e c v e l o c i t y by a 1/2 hp, 20 g a l / m i n c a p a c i t y r e c i r c u l a t i o n pump a t t a c h e d t o t h e j e t . A i r was s u p p l i e d t o t h e j e t a t 10 p s i p r e s s u r e and mixed w i t h t h e m o t i v e f l u i d i n t h e 76 F i g u r e 2 2 a JET AERATOR TESTING UNIT -STARTER 2' O.D. FOR HOSE CONNECTION PUMP 3/-< 5% SIDE VIEW TOP VIEW F i g u r e 2 2 b JET AERATOR IN OPERATION JET PLUME 77 j e t chamber. F i n e b u b b l e s were produced by s h e a r i n g a c t i o n and t u r -b u l e n c e and d i s c h a r g e d f r o m t h e j e t n o z z l e t o t h e l i q u i d . B u b b l e s i z e s and foam volume were r e g u l a t e d by t h e a i r f l o w r a t e and t h e f l u i d v e l -o c i t y t h r o u g h t h e n o z z l e . ( i i i ) A i r S u p p l y System Two 5-hp, 550 v o l t r o t a r y vaned b l o w e r s were i n s t a l l e d t o s u p p l y a i r f o r foam g e n e r a t i o n . Each b l o w e r was r a t e d a t 50 cfm, a t 1 atm p r e s s u r e and c o n n e c t e d t o a 2 - i n common a i r l i n e . An o r i f i c e p l a t e was i n s t a l l e d f o r a i r f l o w measurement. The a i r l i n e was a t t a c h e d t o a m a n i f o l d t o s u p p l y a i r t o t h e n i n e j e t a e r a t o r s . A n o n - r e t u r n a b l e c h e c k - v a l v e was i n s t a l l e d i n t h e a i r l i n e t o p r e v e n t b a c k f l o w o f l i q u i d . d. Foam H a n d l i n g System ( i ) Foam Removal jam I n t h i s s y s t e m , no m e c h a n i c a l d e v i c e was i n s t a l l e d t o a s s i s t f o r e m o v a l . Foam was e x p e l l e d e a s i l y f r o m t h e s y s t e m by s p i l l a g e t h r o u g h a s i d e - o p e n i n g o f t h e c l o s e d t o p foam g e n e r a t i o n t a n k . New foam c o n -t i n u o u s l y emerged f r o m t h e l i q u i d , and pushed o l d foam s l o w l y t o t h e e x i t and toward t h e foam b r e a k i n g t a n k . The t r a v e l d i s t a n c e v a r i e d f r o m 0 t o 20 f t d e p e n d i n g upon t h e number o f s t a g e s used and t h e l o c a t i o n o f t h e s t a g e i n t h e t a n k where t h e foam was p r o d u c e d . 78 ( i i ) Foam B r e a k i n g The foam b r e a k i n g s y s t e m c o n s i s t e d o f a 300 g a l ( 3 - x 3- x 4 - f t ) wooden t a n k , f i t t e d w i t h a t u r b i n e and was d e s i g n e d t o p e r m i t d i s c h a r g e o f l i q u i f i e d foam o n l y ( F i g u r e 2 3 ) . Foam s p i l l e d f r o m t h e o p e n i n g o f t h e foam g e n e r a t i o n system i n t o t h e foam c o l l e c t i o n t a n k and was b r o k e n m e c h a n i c a l l y by t u r b i n e due t o c o m b i n a t i o n o f i m p a c t , s h e a r and c e n t r i -f u g a l f o r c e s . The t u r b i n e foam b r e a k e r was b a s i c a l l y a 3 -blade vaned d i s c d r i v e n by a 1/3 hp motor a t 1800 rpm. I t was mounted c e n t r a l l y , a p p r o x i m a t e l y 1 - f t above t h e t a n k bottom. The s i z e of vaned d i s c and b l a d e number were changed t o accommodate d i f f e r e n t volumes o f foam i n p u t . D. ANALYSES T o x i c i t y was d e t e r m i n e d by u s i n g j u v e n i l e r a i n b o w t r o u t Salmo  g a i r d n e r i , as t h e t e s t f i s h . The f i s h were t a k e n from a homogeneous p o p u l a t i o n o f h a t c h e r y - r e a r e d f i s h , a c c l i m a t e d t o l a b o r a t o r y c o n d i t i o n s of w a t e r and t e m p e r a t u r e . B i o a s s a y s were done a t 12 - 15°C, pH 7 ± 0.2 and oxygen s a t u r a t i o n . When a i r was i n a d e q u a t e , p u r e oxygen was used t o m a i n t a i n oxygen s a t u r a t i o n . E f f l u e n t samples f r o m l a b o r a t o r y t e s t were b i o a s s a y e d w i t h f i v e t o t e n f i s h i n 3 l i t r e g l a s s j a r s , a t f i s h l o a d i n g s o f 1 - 1.5 g/1. E f f l u e n t samples from t h e f i e l d and p i l o t p l a n t systems were b i o a s s a y e d w i t h F i g u r e 23 MECHANICAL TURBINE FOAM BREAKING SYSTEM 10 - 20 f i s h i n 20 l i t r e s o f e f f l u e n t a t t h e same f i s h l o a d i n g s as i n t h e l a b o r a t o r y t e s t . T o x i c i t y was d e t e r m i n e d a c c o r d i n g t o one o f two p r o c e d u r e s : M edian S u r v i v a l Time (MST) - The median s u r v i v a l t i m e o f a f i s h p o p u l a t i o n was d e t e r m i n e d on 100% e f f l u e n t c o n c e n t r a t i o n o v e r a 24-h p e r i o d . E f f l u e n t s were c l a s s e d as n o n - t o x i c when a l l f i s h s u r -v i v e d a 24-h e x p o s u r e p e r i o d . S t a t i c F e d e r a l G u i d e l i n e f o r T o x i c i t y - F i s h were exposed t o 65% e f f l u e n t c o n c e n t r a t i o n s f o r 96-h. The e f f l u e n t met F e d e r a l Tox-i c i t y r e q u i r e m e n t s , f o r a s t a t i c m o n i t o r i n g b i o a s s a y , i f more t h a n 80% o f f i s h s u r v i v e d . BOD g was a n a l y s e d a c c o r d i n g t o t h e S t a n d a r d Methods f o r Waste and Wastewater A n a l y s i s ( 8 7 ) . TOC ( T o t a l O r g a n i c Carbon) was d e t e r m i n e d by a Beckman Model 905 TOC A n a l y s e r . Suspended S o l i d s were d e t e r m i n e d by c e n t r i f u g i n g a l i q u o t s o f e f f l u e n t a t 10,000 rpm f o r 10 m i n , t r a n s f e r r i n g t h e s o l i d s cake t o a GF/A g l a s s f i b r e f i l t e r , r i n s i n g i t w i t h d i s t i l l e d w a t e r and d r y i n g a t 105°C f o r 15-h and w e i g h i n g . R e s i n A c i d s were d e t e r m i n e d by a gas c h r o m a t o g r a p h i c t e c h n i q u e ( 8 8 ) . C o l o r was d e t e r m i n e d by a s p e c t r o p h o t o m e t r y method ( 8 9 ) . E f f l u e n t F l o w was c o n t r o l l e d by u s i n g a p r e r a t e d pump o f known c a p a c i t y and v e r i f i e d by m e a s u r i n g t h e t i m e r e q u i r e d t o f i l l up a t a n k o f f i x e d c a p a c i t y . A i r F l o w was measured by u s i n g r o t a m e t e r s . F o r h i g h a i r f l o w measure-ments an o r i f i c e p l a t e was u s e d . P r e s s u r e and t e m p e r a t u r e o f t h e a i r measured a t t h e b l o w e r d i s c h a r g e d were d e t e r m i n e d and used f o r c o n v e r -s i o n o f a i r f l o w t o s t a n d a r d c o n d i t i o n s . B u b b l e S i z e s and B u b b l e D i s t r i b u t i o n s were d e t e r m i n e d by p h o t o g r a p h i c t e c h n i q u e . I n t h e l a b o r a t o r y and f i e l d column i n s t a l l a t i o n , b u b b l e s i z e s were d e t e r m i n e d by d i r e c t l y p h o t o g r a p h i n g t h e foam l i q u i d i n t e r f a c e and c r u d e l y e s t i m a t i n g an a v e r a g e b u b b l e s i z e . I n t h e p i l o t p l a n t s t u d y , an a c c u r a t e method was employed. A 1.8- x 0.6- x 1.2-m t a n k a t t a c h e d w i t h a t r a n s p a r e n t 40- x 6- x 90-cm r e c t a n g u l a r box was u s e d . The a e r a t o r was i n s t a l l e d i n t h e t a n k . The b u b b l e s g e n e r a t e d by t h e a e r a t o r s p a r t i a l l y e n t e r e d t h e box. Under r e l a t i v e l y q u i e s c e n t c o n d i t i o n s , p h o t o g r a p h s were t a k e n u s i n g an Olympus 0M-2 a u t o m a t i c a p e r t u r e c o n t r o l l e d , s i n g l e - l e n s r e f l camera. S t r o n g back and t o p i l l u m i n a t i o n (2000 w a t t s ) and h i g h s h u t t e r speed (1/1000 s e c ) were employed. P i c t u r e n e g a t i v e s were p r o j e c t e d on a s c r e e n f o r measurement o f t h e b u b b l e d i a m e t e r s . A s e c t i o n o f t h e s l i d e r e p r e s e n t a t i v e t o t h e o v e r a l l p i c t u r e was s e l e c t e d and a mean d i a -meter based on a t l e a s t 200 b u b b l e s was c a l c u l a t e d . G a s / L i q u i d r a t i o was d e t e r m i n e d by d i v i d i n g gas f l o w r a t e by l i q u i d f l o w r a t e . G a s - L i q u i d I n t e r f a c i a l A r e a . g e n e r a t e d by a j e t a e r a t o r was d e t e r m i n e d f r o m t h e a i r f l o w r a t e , l i q u i d f l o w r a t e and t h e mean b u b b l e d i a m e t e r , 82 assuming s p h e r i c a l b u b b l e s . -r t c • i , _ Gas f l o w r a t e x 6 , . . 3 , 2 , . . . I n t e r f a c i a l a r e a p r o d u c t i o n r a t e = :— r — ; — x 10 (m /mm) mean b u b b l e d i a m e t e r I n t e r f a c i a l A r e a P r o d u c e d = I n t e r f a c i a l A r e a P r o d u c t i o n R a t e , 2 . ... U n i t volume of e f f l u e n t p r o c e s s e d L i q u i d F l o w R a t e 3 Foam F l o w Rate was c a l c u l a t e d from t h e t i m e r e q u i r e d t o f i l l a 5 - f t v e s s e l . L i q u i d E n t r a i n e d i n Foam was d e t e r m i n e d by m e a s u r i n g t h e l i q u i f i e d volume o f 20 l i t e r s o f foam: L i q u i d e n t r a i n e d (%) = ^ l i q u i d x V foam C o n v e r s i o n o f I n f l u e n t t o Foam was d e t e r m i n e d by t h e f o r m u l a „ . F l o w r a t e o f foam x l i q u i d c o n t e n t /„ c o n v e r s i o n = — . j x 100 Flow r a t e o f i n f l u e n t Foaming Tendency was measured as t h e r e s i d e n c e t i m e f o r each foam b u b b l e e n t r a p p e d i n t h e foam l a y e r (46) by a e r a t i n g 4 l i t r e s o f e f f l u e n t f o r 4 min a t 500 ml/min. Foaming . £ V foam a f t e r 4 min o f a e r a t i o n Tendency * Gas f l o w r a t e Foaming S t a b i l i t y was d e t e r m i n e d by m e a s u r i n g t h e foam volume r e m a i n i n g a f t e r 4 min o f r e t e n t i o n i n t h e foaming column. Foaming # _ V foam a f t e r 4 min r e t e n t i o n S t a b i l i t y ' t Gas f l o w r a t e Foam B r e a k i n g E f f i c i e n c y was d e f i n e d as t h e r a t i o o f volume o f foam c o l l a p s e d t o o r i g i n a l volume. . /<V\ Vfoam — V r e s i d u a l foam , E f f x c x e n c y U) = 775 x 100 Vfoam R o t a t i o n Speed was d e t e r m i n e d by u s i n g a model 134(3776) P h o t o l a s t i c I n c . s t r o b o s c o p e . T i p Speed of t h e t u r b i n e was c a l c u l a t e d by t h e f o r m u l a : „ . . TT D x rpm , V t i p = 77;— E— cm/sec. o i l Power was measured by a model 432 Weston E l e c t r i c I n s t r u m e n t Watt meter. 84 E. DETERMINATION OF DETOXIFICATION MECHANISMS A 7-1 l a b o r a t o r y foam s e p a r a t i o n column c o n t a i n i n g 4-1 o f l i q u i d , a 3-1 foam c o l l e c t i o n j a r and a 6-1 v a p o r c o n d e n s i n g system were used t o s e p a r a t e t h e t r e a t e d e f f l u e n t , c o l l a p s e d foam and v a p o r r e s p e c t i v e l y . The s e t - u p o f t h e equipment i s shown i n F i g u r e 24. The s t a n d a r d c o n d i t i o n s a p p l i e d f o r d e t e r m i n a t i o n o f d e t o x i f i c a t i o n mechanisms were pH 9.5, room t e m p e r a t u r e s (22 ± 3°C) and 500 ml/min a e r a -t i o n r a t e t h r o u g h 45 u f r i t t e d g l a s s f o r 1-h. Foam was c o l l a p s e d by p a s s i n g t h r o u g h g l a s s w o o l (foam b r e a k e r ) t o a 3-1 c o l l e c t o r . V apors were condensed i n a f l a s k immersed i n an a c e t o n e - d r y i c e (CO2) b a t h . I n a l l e x p e r i m e n t s foaming was c o m p l e t e l y d i m i n i s h e d a f t e r t r e a t m e n t . P r i o r t o t h e e x p e r i m e n t s a s e r i e s o f d i l u t i o n s o f t o x i c e f f l u e n t s were b i o a s s a y e d f o r t o x i c i t y . The MST was p l o t t e d a g a i n s t % e f f l u e n t c o n c e n t r a t i o n . F i g u r e 25 shows an example f o r d e v e l o p i n g a s t a n d a r d t o x i c i t y c u r v e . The r e l a t i v e c o n t r i b u t i o n by v a r i o u s mechanisms was d e t e r m i n e d by f r a c t i o n a t i n g t h e same e f f l u e n t under a s t a n d a r d s e t o f c o n d i t i o n s i n t o t r e a t e d e f f l u e n t , foam and condensed v a p o r f r a c t i o n s . B i o a s s a y was done on t r e a t e d e f f l u e n t a l o n e , t r e a t e d e f f l u e n t p l u s t h e foam f r a c t i o n , and t r e a t e d e f f l u e n t p l u s b o t h t h e foam and condensed v a p o r f r a c t i o n s . The MST of t h e r e c o n s t i t u t e d e f f l u e n t s were equated t o p e r c e n t c o n c e n t r a t i o n o f t h e raw e f f l u e n t w h i c h y i e l d e d t h e same MST v a l u e s ( F i g u r e 2 5 ) . F i g u r e 2 4 LABORATORY SET-UP FOR INVESTIGATION OF DETOXIFICATION MECHANISMS 00 U l F i g u r e 25 RELATIVE CONTRIBUTION TO DETOXIFICATION BY FOAM FRACTIONATION, VOLATILIZATION AND UNKNOWN MECHANISMS lOO-i r -§ 8 0 si gdeo ^ 2 0 H Foam fractionation Toxicity curve of diluted raw effluent Toxicity O Untreated effluent 100% O Treated effluent + foam + vapor 84% A Treated effluent + foam 72% Loss by unidentified mechanism 16% _L 1 0 0 2 0 0 TOXICITY, 300 MST 400 in minutes 500 600 Note: The toxicity fractions are determined as percent effluent equivalents, i. e., toxicity of a fraction is compared to the percent dilution of raw effluent, which yields the same toxicity. CHAPTER V RESULTS AND DISCUSSION A. TREATABILITY STUDIES 1. S e l e c t i v e D e t o x i f i c a t i o n o f V a r i o u s P r o c e s s Streams The t h r e e major p r o c e s s streams i n a b l e a c h e d k r a f t m i l l a r e un-b l e a c h e d w h i t e w a t e r from t h e p u l p i n g d i s c h a r g e ; c a u s t i c e x t r a c t i o n s t a g e e f f l u e n t s and a c i d b l e a c h e f f l u e n t s from t h e b l e a c h p l a n t d i s -c h a r g e . These t h r e e e f f l u e n t streams d i f f e r i n waste c h a r a c t e r i s t i c s and r e p r e s e n t up t o 75% o f t h e combined w h o l e m i l l e f f l u e n t . The t o x -i c i t y and t h e f o a m i n e s s o f t h e e f f l u e n t s measured f r o m a group o f samples v a r y w i t h each p r o c e s s s t r e a m i n t h e f o l l o w i n g manner: T o x i c i t y C a u s t i c E x t r a c t i o n U n b l e a c h e d w h i t e A c i d B l e a c h (MST:hr) E f f l u e n t ( 1 . 3 - 2 . 1 ) > Water(1.6-2.1) > E f f l u e n t ( 0 . 3 - 8 . 5 ) Foaminess C a u s t i c E x t r a c t i o n U nbleached w h i t e A c i d B l e a c h (£ t:min) e f f l u e n t (>6) > w a t e r (4-5) > E f f l u e n t (2-5) C a u s t i c e x t r a c t i o n e f f l u e n t i s t h e most t o x i c o f t h e i n d i v i d u a l p r o c e s s streams ( 8 6 ) . I t s f o a m i n e s s i s governed by t h e pH o f t h e e f f l u -e n t . When th e pH was r e d u c e d from i n i t i a l 10 t o 4, t h e e f f l u e n t was n o t foamable. However, as t h e pH d e c r e a s e d f u r t h e r t o 3, t h e foaming t e n d e n c y o f t h i s w a s t e s t r e a m i n c r e a s e d a b r u p t l y t o 6 min ( F i g u r e 26) and r e m a i n e d c o n s t a n t . The f o a m i n e s s and t o x i c i t y o f t h e u n b l e a c h e d w h i t e w a t e r a r e s l i g h t l y l o w e r t h a n t h e c a u s t i c e x t r a c t i o n e f f l u e n t but h i g h e r t h a n t h e a c i d b l e a c h e f f l u e n t . The f o a m i n g c h a r a c t e r i s t i c s o f t h e s e two s t r e a m s , however, a r e n o t a f f e c t e d as s e v e r e l y as c a u s t i c ex-F i g u r e 2 6 EFFECT OF pH ON FOAMINESS OF CAUSTIC EFFLUENT 89 t r a c t i o n e f f l u e n t by changes i n pH. These t h r e e i n d i v i d u a l p r o c e s s s treams were s u b j e c t e d t o foam s e p a r a t i o n t r e a t m e n t s and a s s e s s e d f o r d e t o x i f i c a t i o n . The r e s u l t s a r e p r e s e n t e d i n T a b l e 5. a. Unbleached W h i t e Water The major t o x i c m a t e r i a l s i n u n b l e a c h e d w h i t e w a t e r o r i g i n a t e d f r o m e v a p o r a t o r c o n d e n s a t e and r e s i d u a l b l a c k l i q u o r ( 9 0 ) . The MSTs of t h e f o u r b a t c h e s o f samples o b t a i n e d were i d e n t i c a l i n i n i t i a l t o x i c i t y , and range d from 1 t o 2 h r ( T a b l e 5 ) . The e f f l u e n t s were s u b j e c t e d t o foam s e p a r a t i o n a t pH A and 9.5. D u r i n g t h e p r o c e s s o f a e r a t i o n , u n s t a b l e foams were pr o d u c e d . They c o l l a p s e d s p o n t a n e o u s l y and r a p i d l y b e f o r e r e a c h i n g t h e foam r e m o v a l p o r t . T a b l e 5 shows t h a t a f t e r foam s e p -a r a t i o n t r e a t m e n t a t b o t h pH t h e MST remained a t 1.1-2.1 and 0.7-3 h r s , i . e . r e d u c t i o n o f t o x i c i t y was n o t a c h i e v e d . S i n c e foam s e p a r a t i o n t r e a t m e n t i n v o l v e s t h e s p a r g i n g o f a i r t h r o u g h t h e w a s t e s , v o l a t i l e t o x i c a n t s would be e x p e c t e d t o be s t r i p p e d out from t h e e f f l u e n t a f t e r p r o l o n g e d a e r a t i o n . Among t h e n o n - v o l a t i l e s a r e n a t u r a l l y o c c u r i n g r e s i n a c i d s w h i c h r e p r e s e n t 80% o f t h e t o x i c i t y (20) and u n s a t u r a t e d f a t t y a c i d s w h i c h a r e r e s p o n s i b l e f o r t h e r e m a i n i n g t o x i c i t y ( 2 3 ) . These t o x i c a n t s a r e s u r f a c e a c t i v e and s h o u l d be foam s e p a r a b l e . However, t h e foams were n o t s t a b l e enough t o f a c i l i t a t e f r a c t i o n a t i o n o f t o x i c a n t s p r o p e r l y . T h i s o b s e r v a t i o n a g r e e s w i t h r e -p o r t e d r e s u l t s on t h e f o a m i n e s s o f c o m m e r c i a l sodium a b i e t a t e and r o s i n ( m a i n l y a b i e t i c a c i d ) s o l u t i o n a t v a r i o u s pH c o n d i t i o n s ( 9 1 ) . TABLE 5 EFFECT OF FOAM SEPARATION ON DETOXIFICATION OF INDIVIDUAL PROCESS STREAMS I n d i v i d u a l Source T o x i c i t y (MST, h r ) P r o c e s s Stream of E f f l u e n t Raw E f f l u e n t A f t e r Foam S e p a r a t i o n ( M i l l ) Waste a t pH 2.5 4.0 9.5 A 2.1 2.2 3.0 Unbleached B 1.1 - 0.5 0.7 w h i t e w a t e r C 1.2 - 0.4 1.1 D 1.6 - 0.5 0.8 A 8.5 4.8 3.7 • NT A c i d b l e a c h B 5.2 4.8 2.1 24.0 e f f l u e n t C 0.7 0.7 0.6 0.6 D 0.3 0.2 0.8 0.5 C a u s t i c e x t . e f f l u e n t A C D 2.1 0.7 0.3 NT NT 24.0 4.5 1.9 1.1 1.8 0.9 0.3 NT: N o n t o x i c Treatment C o n d i t i o n s : Volume = 4 l i t e r s Gas d i s p e r s i o n medium = S i n t e r e d g l a s s P o r e s i z e = 45 u A e r a t i o n r a t e = 500 ml/min Treatment t i m e = 5 h r NT = N o n t o x i c b. A c i d B l e a c h . E f f l u e n t 91 Two samples o f a c i d b l e a c h e f f l u e n t were o b t a i n e d f r o m M i l l s A and B (B.C. c o a s t ) and t h e o t h e r two were t a k e n f r o m m i l l s C and D (B.C. i n t e r i o r ) . The c o a s t a l m i l l samples were t a k e n from t h e m i l l o u t f a l l s and were r e l a t i v e l y f r e e o f c h l o r i n e due t o v i g o r o u s m i x i n g a t t h e s a m p l i n g p o i n t . These samples were n o t v e r y t o x i c (MST = 5-8 h r s ) and f o a m i n g was moderate. The i n t e r i o r m i l l samples were t a k e n d i r e c t l y f r om t h e b l e a c h p l a n t . The t o x i c i t i e s o f t h e s e two samples (MST = 1-2 h r ) approached t h a t o f u n b l e a c h e d w h i t e w a t e r . However, foamin g t e n d -ency was o n l y a f r a c t i o n h i g h e r . The foam produced by a l l samples was m o d e r a t e l y s t a b l e w i t h i n t h e t e s t e d r ange o f pH 2.5 - 9.5. Most of t h e foam c o l l a p s e d b e f o r e r e a c h i n g t h e foam r e m o v a l p o r t and formed scum on to p o f t h e foam. Only a s m a l l p o r t i o n o f t h e foam was removed. The l e s s t o x i c a c i d b l e a c h e f f l u e n t s f r o m M i l l s A and B were s a t i s f a c t o r i l y d e t o x i f i e d a t a l k a l i n e pHs ( T a b l e 5) even though foaming was n o t s a t i s -f a c t o r y . I n t h e s e e f f l u e n t s i t would appear t h a t r e m o v a l o f o n l y a f r a c t i o n o f any t o x i c a n t s r e d u c e d t h e e f f l u e n t t o a n o n - t o x i c l e v e l . D e t o x i f i c a t i o n can be a t t r i b u t e d p a r t i a l l y t o t h e a i r s t r i p p i n g of any v o l a t i l e m a t e r i a l s , i n c l u d i n g r e s i d u a l c h l o r i n e . The f o r m a t i o n o f scum a l s o s u g g e s t e d t h a t p r e c i p i t a t i o n / i o n f l o t a t i o n was p a r t l y r e s p o n s i b l e f o r d e t o x i f i c a t i o n . I n c o n t r a s t , even though f o a m i n g was s l i g h t l y b e t t e r on h i g h l y t o x i c samples (C and D ) , d e t o x i f i c a t i o n was e x t r e m e l y d i f f i c u l t . P r e s e n t l y a v a i l a b l e l i t e r a t u r e i n d i c a t e s t h a t c h l o r i n a t e d l i g n i n d e r i v a t i v e s a r e t h e major t o x i c a n t s (23,92) i n a c i d b l e a c h e f f l u e n t . I n k r a f t p u l p c h l o r o l i g n i n , t h e a c i d i c groups o f t h e components a r e r a t h e r s t r o n g , w h i c h i s t o be e x p e c t e d f o r h y d r o x y c h l o r o q u i n o n e s . They can be n e u t r a l i z e d by h y d r o l y s i s o f t h e c h l o r i n e f r o m t h e c h l o r o l i g n i n , w h i c h r e q u i r e s a l k a l i n e c o n d i t i o n s ( 9 3 ) . At pH 9.5 d u r i n g foam s e p a r -a t i o n , t h e c h l o r i n e m o i e t y o f t h e c h l o r o l i g n i n can be s t r i p p e d by a e r -a t i o n and s h o u l d r e s u l t i n l o w e r t o x i c i t y o f t h e e f f l u e n t . Recent s t u d i e s (94) have i n d i c a t e d t h a t t h e t o x i c i t y o f a c i d b l e a c h e f f l u e n t can be c o m p l e t e l y removed by s i m p l y a d j u s t i n g t h e pH t o b a s i c c o n d i -t i o n s . One p o s s i b l e e x p l a n a t i o n why t h e more t o x i c a c i d b l e a c h e f f l u e n t samples were n o t d e t o x i f i e d c o u l d be a t t r i b u t e d t o t h e g r o u p i n g o f t h e s u r f a c t a n t s i n t o m i c e l l a r s t r u c t u r e s . Due t o t h e r e s u l t a n t l o s s o f s u r f a c e a c t i v i t y , t h e t o x i c a n t s would n o t be removed. T h i s h y p o t h e s i s , however has n o t been v e r i f i e d e x p e r i m e n t a l l y . c. C a u s t i c E x t r a c t i o n E f f l u e n t I n t h e a l k a l i n e e x t r a c t i o n s t a g e o f b l e a c h i n g , s a p o n i f i c a t i o n o f f a t t y and r e s i n a c i d s i n t o sodium s a l t s t a k e s p l a c e as does a m i c e l l a r s o l u b i l i z a t i o n o f t h e more o r l e s s h y d r o p h o b i c c o n s t i t u e n t s o f t h e r e s i n s ; i . e . , t h e u n s a p o n i f i a b l e s and t h e r e m a i n i n g f a t t y a c i d e s t e r s . T h i s m i c e l l a r s o l u b i l i z a t i o n i s e f f e c t e d by s u r f a c e a c t i v e f a t t y and r e s i n a c i d soaps. The c r i t i c a l m i c e l l e c o n c e n t r a t i o n (CMC) f o r r e s i n soaps i s r e p o r t e d t o be 0.02 m o l e s / 1 (95) and 0.002 moles/1 f o r f a t t y a c i d s (95,96,97). W i t h a 50 - 50 m i x t u r e , t h e CMC i s 0.002 M / l ( 9 8 ) . U s i n g t h i s f i g u r e , i t has been c a l c u l a t e d t h a t t h i s m i c e l l a r c o n c e n -t r a t i o n i s exceeded i n t h e k r a f t c o o k i n g o f p i n e . I n t h e c a u s t i c e x -t r a c t i o n s t a g e o f t h e p u l p b l e a c h i n g p r o c e s s h a l f o f t h e soaps a r e l i k e l y t o form m i c e l l e s whereas i n a d i l u t e p u l p s u s p e n s i o n s u c h as i n t h e a l k a l i n e w a s h i n g s t a g e of b l e a c h i n g a f t e r c h l o r i n a t i o n , no m i c e l l e s w ould be formed ( 9 9 ) . On t h i s b a s i s and s i n c e t h e wood f u r n i s h e s i n t h e s e t h r e e m i l l s d i d n o t c o n t a i n p i n e , i t was assumed t h a t m i c e l l e s were n o t p r e s e n t i n c a u s t i c e x t r a c t i o n e f f l u e n t . The f o a m i n e s s o f c a u s t i c e x t r a c t i o n e f f l u e n t ( F i g u r e 26) g r e a t l y depends on t h e pH c o n d i t i o n . I n f o r m a t i o n a v a i l a b l e t o d a t e i n d i c a t e s t h a t t h e major t o x i c a n t s a r e m a i n l y n e g a t i v e l y c h a r g e d c h l o r i n a t e d p h e n o l i c s , r e s i n and s t e a r i c a c i d d e r i v a t i v e s . C a u s t i c e x t r a c t i o n e f f l u e n t foams c o p i o u s l y a t e x t r e m e l y low a c i d pHs. The a c i d pHs r e -q u i r e d t o i n d u c e foaming s u g g e s t s t h e p r e s e n c e o f l a r g e q u a n t i t i e s o f n o n - t o x i c c a t i o n i c t y p e , s u r f a c e a c t i v e compounds. These c a t i o n i c t y p e s u r f a c t a n t s can r e a c t w i t h t h e n e g a t i v e l y c h a r g e d t o x i c m a t e r i a l s ( T a b l e 2) t h e r e b y s u p p r e s s i n g t h e i r foaming c a p a b i l i t i e s a t a l k a l i n e pHs. C a u s t i c e x t r a c t i o n e f f l u e n t i s h i g h l y r e s p o n s i v e t o foam s e p a r a t i o n ( T a b l e 5 ) . D e t o x i f i c a t i o n was g overned c o m p l e t e l y by t h e pH o f t r e a t -ment. As e x p e c t e d , a t pH 4 and 9.5 where foaming was n o t p o s s i b l e , t o x i c i t y c o u l d n o t be removed. .At pH 2.5, f o a m i n g was abundant and l a r g e amounts o f b r o w n i s h scum were formed. Foaming s t i l l p e r s i s t e d 94 a f t e r 10 h r o f a e r a t i o n . Out o f t h r e e samples t r e a t e d , two samples were c o m p l e t e l y d e t o x i f i e d , t h e t h i r d was p a r t i a l l y d e t o x i f i e d t o a s u b s t a n t -i a l l y l o w t o x i c l e v e l (MST i n c r e a s e d f r o m 0.3 h r t o 24 h r ) . I t a p p e a r s t h a t i f more t i m e were g i v e n f o r r e m o v a l o f r e s i d u a l foam, t h e t h i r d sample would a l s o have been d e t o x i f i e d . I t i s s p e c u l a t e d t h a t c a u s t i c e x t r a c t i o n e f f l u e n t c o n t a i n s a s u i t -a b l e s u r f a c t a n t s e r v i n g as a c o l l e c t o r w h i c h forms a c o l l i g e n d w i t h t h e n e g a t i v e l y c h a r g e d t o x i c m a t e r i a l s . A t a c i d pHs, some t o x i c components w i l l a l s o be p r e c i p i t a t e d . The f o r m a t i o n o f l a r g e q u a n t i t i e s o f scum s u g g e s t t h a t p r e c i p i t a t e f l o t a t i o n o c c u r s c o n c u r r e n t l y w i t h i o n f l o t -a t i o n . 2. E f f e c t o f C a u s t i c E x t r a c t i o n E f f l u e n t A d d i t i o n on D e t o x i f i c a t i o n  o f A c i d B l e a c h E f f l u e n t C a u s t i c e x t r a c t i o n e f f l u e n t i s t h e o n l y i n d i v i d u a l p r o c e s s s t r e a m t h a t c o u l d be d e t o x i f i e d by foam s e p a r a t i o n . I t would appear t h a t c a u s -t i c e x t r a c t i o n e f f l u e n t c o n t a i n s some n e c e s s a r y s u r f a c t a n t w h i c h can combine (by means o f p r e c i p i t a t i o n , c h e l a t i o n , o r c o m p l e x i n g ) w i t h t h e t o x i c s u r f a c e a c t i v e compounds and o t h e r n o t y e t i d e n t i f i e d n o n - s u r f a c e a c t i v e m a t e r i a l s and make them foamable. An e x p e r i m e n t was d e s i g n e d t o u t i l i z e t h e s u r f a c t a n t s o f t h e c a u s t i c e x t r a c t i o n e f f l u e n t f o r d e t o x i -f i c a t i o n o f a c i d b l e a c h e f f l u e n t . A p p e n d i x I r e c o r d s t h e d e t o x i f i c a t i o n d a t a o f a s e r i e s o f c a u s t i c - a c i d e f f l u e n t m i x t u r e s o f d i f f e r e n t p r o p o r -t i o n s a f t e r foam s e p a r a t i o n t r e a t m e n t a t pH 2.5, 7.0 and 9.5. These r e s u l t s a r e shown i n F i g u r e 27. F i g u r e 27 EFFECT OF EFFLUENT COMPOSITION ON THE pH REQUIREMENT FOR DETOXIFICATION 0 20 40 60 80 100 Acid Effluent 100 80 60 40 20 0 Caustic Effluent 96 The MST o f t h e u n t r e a t e d m i x t u r e s v a r i e d from 0.3 t o 2.8 h r . A t pH 2.5, 100% c o n c e n t r a t i o n c a u s t i c e x t r a c t i o n e f f l u e n t , w h i c h foamed c o p i -o u s l y , was c o m p l e t e l y d e t o x i f i e d . O ther e f f l u e n t m i x t u r e s d i d n o t p r o d u c e a s t a b l e foam. D e t o x i f i c a t i o n d e c r e a s e d as t h e p e r c e n t a g e o f a c i d b l e a c h e f f l u e n t i n c r e a s e d . T o x i c i t y c o u l d n o t be removed i n a c i d -c a u s t i c e f f l u e n t m i x t u r e s o f p r o p o r t i o n s g r e a t e r t h a n 60:40. A t pH 7.0 some r e d u c t i o n of t o x i c i t y was o b s e r v e d i n e f f l u e n t w i t h < 50% c a u s t i c e f f l u e n t . A t pH 9.5 f o a m i n g and scum f o r m a t i o n were d i r e c t l y p r o p o r -t i o n a l t o t h e e x t e n t of d e t o x i f i c a t i o n . E f f l u e n t s c o n t a i n i n g 60 - 80% a c i d b l e a c h . e f f l u e n t had t h e g r e a t e s t f o a m i n e s s , formed most scum, and d e t o x i f i e d c o m p l e t e l y . The r e l a t i o n s h i p of d e t o x i f i c a t i o n pH w i t h e f f l u e n t c o m p o s i t i o n d e m o n s t r a t e s t h e d i f f e r e n c e s i n t h e c o n c e n t r a t i o n s and t y p e s o f s u r f a c e a c t i v e t o x i c m a t e r i a l s c o n t a i n e d i n a c i d and c a u s t i c b l e a c h e d e f f l u e n t . N e v e r t h e l e s s , t h e s e s u r f a c e a c t i v e s u b s t a n c e s c o u l d a l l be foamed out f r o m t h e combined e f f l u e n t by t h e use o f s u i t a b l e c o l l e c t o r s p r e s e n t i n t h e e f f l u e n t because complete d e t o x i f i c a t i o n o c c u r s . I t would appear t h a t t h e c o l l e c t o r and c o l l i g e n d a r e p r e s e n t i n a t l e a s t s t o i c h i o m e t r i c r a t i o s i n t h e 20 - 35% r ange o f c a u s t i c e f f l u e n t and t h e 60 - 80% range of a c i d b l e a c h e f f l u e n t . Because o f t h e v a r i a t i o n s i n t o x i c a n t c o n -c e n t r a t i o n s due t o d i f f e r e n t p r o c e s s c o n d i t i o n s and t h e r a t i o o f c a u s t i c t o a c i d e f f l u e n t d i s c h a r g e i n d i f f e r e n t m i l l s , i t i s d i f f i c u l t t o de-t e r m i n e t h e e x a c t s t o i c h i o m e t r i c r e l a t i o n s h i p between c o l l e c t o r and c o l l i g e n d i n t h e s e e f f l u e n t s . T h e r e f o r e a c o m m e r c i a l foam s e p a r a t i o n p r o c e s s f o r r e m o v a l o f t o x i c i t y f r o m b l e a c h p l a n t e f f l u e n t s h o u l d i n -c o r p o r a t e s u f f i c i e n t s u r g e c a p a c i t y t o m a i n t a i n a p r o p e r r a t i o o f a c i d -c a u s t i c e f f l u e n t w h i c h would be r e q u i r e d t o e f f e c t d e t o x i f i c a t i o n . 3. E f f e c t o f S y n t h e t i c S u r f a c t a n t s on D e t o x i f i c a t i o n o f U n b l e a c h e d  W h i t e Water I n m i l l s where o n l y u n b l e a c h e d p u l p i s m a n u f a c t u r e d , u n b l e a c h e d w h i t e w a t e r i s t h e major t o x i c s t r e a m . Under t h i s s i t u a t i o n , u s i n g c a u s t i c e f f l u e n t as a s o u r c e o f s u r f a c t a n t f o r f l o t a t i o n c annot be r e a l i z e d . S i n c e most t o x i c compounds i n k r a f t m i l l e f f l u e n t s ( T a b l e 2) a r e n e g a t i v e l y c h a r g e d c a r b o x y l i c o r g a n i c compounds, a d d i t i o n of a c a t i o n i c s u r f a c t a n t w o u l d most l i k e l y a i d d e t o x i f i c a t i o n . I d e a l l y , s u c h s u r f a c t a n t s s h o u l d be n o n - t o x i c and r e a d i l y b i o d e g r a d a b l e . S e v e r a l c o m m e r c i a l l y a v a i l a b l e c a t i o n i c s u r f a c t a n t s were s c r e e n e d f o r t o x i c i t y a t 50 ppm c o n c e n t r a t i o n . I n A p p e n d i x I I , i t i s shown t h a t 5 o u t o f 15 c a t i o n i c s u r f a c t a n t s ( t e r t i a r y amines and q u a r t e r n a r y ammionium s a l t s ) t e s t e d , were n o n - t o x i c . They were added t o u n b l e a c h e d w h i t e w a t e r a t 50 mg/1 c o n c e n t r a t i o n and t r e a t e d by foam s e p a r a t i o n a t pHs 5, 7 and 9.5. A c o n t r o l sample a e r a t e d under t h e same c o n d i t i o n but w i t h o u t s u r f a c t a n t was compared f o r d e t o x i f i c a t i o n . T a b l e 6 shows t h e r e s u l t s o f t h e s e e x p e r i m e n t s . The c o n t r o l sample foamed m o d e s t l y . S e p a r a t i o n o f foam a t pH 7 was n o t e f f e c t i v e i n d e t o x i f y i n g t h e sample. I n t h e p r e s e n c e o f 50 ppm o f TABLE 6 EFFECT OF SURFACTANT ADDITION ON DETOXIFICATION OF UNBLEACHED WHITE WATER MST o f Raw E f f l u e n t ( h r ) MST o f Foam S e p a r a t e d E f f l u e n t ( h r ) W i t h o u t S u r f a c t a n t (pH:7.0) W i t h 50 ppm o f C a t i o n i c S u r f a c t a n t S u r f a c t a n t S p e c i e s pH 5 pH 7 pH 9.5 3 5 He x a d e c y l T r i m e t h y l Ammonium Bromide ** N.T. 6 8 3 5 B e n z y l H e x a d e c y l -d i m e t h y l Ammonium C h l o r i d e N.T. N.T. 24 0.8 1 Ethomeen 425* 11 8 6 0.8 1 Amine T* 6 1 7.0 0.8 1 * V a r i q u a t 450 N.T. 2.5 0.8 T e r t i a r y Amine and Q u a t e r n a r y Ammonium S a l t s , Treatment time= 4 h r A e r a t i o n r a t e = 500 ml/min NT = Not t o x i c . 99 c a t i o n i c s u r f a c t a n t , however, foami n g was g r e a t l y enhanced and t h e ex-t e n t o f t o x i c i t y r e m o v a l improved under most pH c o n d i t i o n s . Three s u r f a c t a n t s namely: H e x a d e c y l T r i m e t h y l Ammonium Bromide; B e n z y l Hex-a d e c y l - d i m e t h y l Ammonium C h l o r i d e and V a r r i q u a t 450 d e t o x i f i e d ' e f f l u e n t c o m p l e t e l y a t s l i g h t l y a c i d pHs. A t a l k a l i n e pHs, t h e c o m p l e x i n g e f f e c t o f t h e s u r f a c t a n t s was a d v e r s e l y a f f e c t e d . Removal o f t h e t o x i c a n t s became i n e f f e c t i v e . The s u c c e s s o f u s i n g s u r f a c t a n t f o r d e t o x i f i c a t i o n r e p r e s e n t s an a l t e r n a t i v e a p p r o a c h f o r d e t o x i f y i n g e f f l u e n t s w h i c h a r e t o x i c b u t n o t foamable. However, l a r g e q u a n t i t i e s o f s u r f a c t a n t s w o u l d be r e q u i r e d . S u p p o s i n g t h a t u n b l e a c h e d w h i t e w a t e r ( a p p r o x i m a t e l y 4 - 5 M g a l / d a y from a 750 TPD p u l p m i l l ) were t r e a t e d by foam s e p a r a t i o n and w i t h 50 ppm s u r f a c t a n t dosage a t $1 - 1.50/lb o f s u r f a c t a n t c o s t : t h e n foam s e p a r a t i o n o f u n b l e a c h e d w h i t e w a t e r would c o s t $3.5 - 5.0/ton o f p u l p ; w h i c h i s u n e c o n o m i c a l . T h e r e f o r e , methods of r e c o v e r i n g t h e s u r f a c t a n t would have t o be d e v e l o p e d t o r e d u c e t h e t r e a t m e n t c o s t t o an a c c e p t a b l e l e v e l . 4. D e t o x i f i c a t i o n o f Combined M i l l E f f l u e n t A l a r g e number o f combined m i l l e f f l u e n t s were t a k e n d i r e c t l y f r o m 5 m i l l s . These e f f l u e n t s were d i f f e r e n t i n terms o f make-up o f t h e v a r i o u s w a s t e s t r e a m s b u t had i n common a c a u s t i c e x t r a c t i o n e f f l u e n t . The t o x i c i t y o f t h e s e e f f l u e n t s ranged from 1.3 t o 7 h r MST. S i n c e t h e s t u d y was aimed a t e x a m i n i n g t h e t r e a t a b i l i t y o f e f f l u e n t o b t a i n e d f r o m d i f f e r e n t s o u r c e s , foam s e p a r a t i o n t r e a t m e n t t i m e was a r b i t r a r i l y c hosen a t 8 h r , i n e x c e s s of what woul d be r e q u i r e d f o r a t y p i c a l e f f l u e n t . D e t o x i f i c a t i o n r e s u l t s as a f u n c t i o n of e f f l u e n t c o m p o s i t i o n a r e p r e s e n t e d i n T a b l e 7. I n g e n e r a l , a l l e f f l u e n t s foamed w e l l a t b o t h a c i d and a l k a l i n e pHs d u r i n g t h e f i r s t two h o u r s o f e x p e r i m e n t . Among th e 16 s a m p l e s , 15 were d e t o x i f i e d by foam s e p a r a t i o n a t pH 9.5. These e f f l u e n t s were o b t a i n e d from M i l l s A, B, C , D and E. As i n d i c a t e d i n T a b l e 7, a l t h o u g h t h e e f f l u e n t c o n s t i t u e n t s d i f f e r e d , a l l combined e f f l u e n t s were d e t o x i f i e d a t pH 9.5. O n l y t h e M i l l C sample w h i c h c o n s i s t e d of a l l major and m i n o r e f f l u e n t s t r e a m s e x c e p t u n b l e a c h e d w h i t e w a t e r c o u l d n o t be d e t o x i f i e d . However', t h i s e f f l u e n t was p a r t i a l l y d e t o x i f i e d a t pH 4.0 (60% f i s h s u r v i v a l ) . S i n c e t h e s e e f f l u e n t samples were o b t a i n e d d i r e c t l y f r o m t h e m i l l d i s c h a r g e p i p e l i n e s and p r o c e s s e d as soon as t h e y were r e c e i v e d , t h e c h a r a c t e r i s t i c s o f t h e s e e f f l u e n t s . . a n d t h e r e s p o n s e t o foam s e p a r a t i o n a r e b e l i e v e d t o be t y p i c a l . Thus, i t can be assumed t h a t i n g e n e r a l , foam s e p a r a t i o n t r e a t m e n t i s e f f e c t i v e f o r d e t o x i f y i n g combined m i l l e f f l u e n t waste s t r e a m s . TABLE 7 TOXICITY REMOVAL OF COMBINED MILL EFFLUENT BY FOAM SEPARATION M i l l Type of Effluent MST of Raw Effluent (hr) MST (hr) of Treated Effluent at pfl (No.of Detoxified Sample^ 4.0 9.5 (No. of samples treated) A Total combined effluent excluding acid bleached effluent 3.0 3.0 N.T. 1/1 Wholemill effluent 4.2 2.5 6.0 - N.T N.T. N.T. 3/3 B Unbleached white water + acid bleach effluent + caustic extraction effluent 3.7 72 N.T. 1/1 Wholemill effluent 5.0 4.5 - N.T N.T. 2/2 C Total combined effluent excluding unbleached 1.3 60% Survival 1.2 1/1 D Wholemill effluent 4.8 3.5 860 80% Survival N.T. 2/2 E Wholemill effluent 7.0 2.5 3.8 4.0 4.5 3.2 -N.T. N.T. N.T. N.T. N.T. N.T. 6/6 Process condition: treatment- time = 8 hr Sparger pore size = 45y Air flow = 500 ml/ml 102 5. S e l e c t i o n o f Most S u i t a b l e P r o c e s s Streams f o r Foam S e p a r a t i o n  Treatment Foam s e p a r a t i o n r e s u l t s on combined and i n d i v i d u a l p r o c e s s s t r e a m s i n d i c a t e t h a t c a u s t i c e x t r a c t i o n e f f l u e n t by i t s e l f and o t h e r w a s t e st r e a m s when mixed w i t h i t can be d e t o x i f i e d by foam s e p a r a t i o n . S i n c e t h e volumes of k r a f t m i l l e f f l u e n t d i s c h a r g e d a r e enormous, i t w o u l d be d e s i r a b l e t o t r e a t o n l y t h o s e combined w a s t e streams w h i c h a r e most r e s p o n s i v e t o foam s e p a r a t i o n and can be d e t o x i f i e d r a p i d l y . The v i a -b i l i t y o f a foam s e p a r a t i o n p r o c e s s i s d e t e r m i n e d by f o u r i m p o r t a n t f a c t o r s : c h e m i c a l and p r e t r e a t m e n t r e q u i r e m e n t s , volume of e f f l u e n t t o be t r e a t e d and t h e e f f e c t i v e n e s s o f t h e foaming t e c h n i q u e on d e t o x i f i c a t i o n ; t r e a t m e n t t i m e and l a n d a r e a r e q u i r e m e n t s ; economics of a foam s e p a r a t i o n o p e r a t i o n . V a r i o u s p r o c e s s s t r e a m s were o b t a i n e d f r o m a p u l p m i l l and mixed a c c o r d i n g t o t h e p r o p o r t i o n s i n w h i c h t h e y a r e found i n t h e m i l l t o form a combined e f f l u e n t . The pH's o f v a r i o u s e f f l u e n t were a d j u s t e d t o c o n d i t i o n s where d e t o x i f i c a t i o n was most e f f e c t i v e . T a b l e 8 shows t h e r e l a t i v e magnitude of volume d i s c h a r g e d , t h e t i m e r e q u i r e d t o d e t o x i f y t h e s e e f f l u e n t m i x t u r e s , t h e pH r e q u i r e m e n t f o r t r e a t m e n t , and t h e amount of foam removed. F i g u r e 28 p l o t s t h e MST of t h e e f f l u e n t d u r i n g t h e p r o g r e s s o f foam s e p a r a t i o n . TABLE 8 FOAM SEPARATION TIME REQUIRED FOR DETOXIFYING VARIOUS COMBINED EFFLUENTS C o m p o s i t i o n % o f T o t a l Volume D i s c h a r g e d I n i t i a l T o x i c i t y (MST, h r ) pH f o r Treatment Time to Complete D e t o x i f i c a t i o n ( h r ) Foam Volume removed (% c o n v e r s i o n of i n f l u e n t ) Whole m i l l e f f l u e n t 100 8 9.5 0.25 5 Acid:UWW:caustic (2:0.7:1) 76 12 9.5 4.0 4.5 A c i d : c a u s t i c (2:1) 67 6 9.5 6.0 10 C a u s t i c e x t r a c t i o n 21 1 2.5 17.0 20 F i g u r e 28 TIME REQUIRED FOR DETOXIFICATION OF VARIOUS EFFLUENT MIXTURES FROM MILL B 0 2 4 6 17 TIME, hours 105 Among t h e v a r i o u s p o s s i b l e c o m b i n a t i o n s , w h o l e m i l l e f f l u e n t s were d e t o x i f i e d most r e a d i l y . A f t e r 15-min of t r e a t m e n t , 5% of t h e e f f l u e n t t r e a t e d was removed as foam, t o x i c i t y was r e d u c e d f r o m 8-hr MST t o a n o n t o x i c l e v e l . A l t h o u g h t h e combined a c i d , ;UWW .and . c a u s t i c . ' . e x t r a c t i o n e f f l u e n t s were th e l e a s t t o x i c , a t r e a t m e n t t i m e of up t o 4-hr was r e q u i r e d t o e f f e c t d e t o x i f i c a t i o n . However, because foam f o r m a t i o n i s l e s s abundant, o n l y 4.5% o f t h e i n f l u e n t was t r a n s f o r m e d t o foam. W i t h combined a c i d : c a u s t i c e f f l u e n t , about 10% of t h e e f f l u e n t was t r a n s -formed i n t o foam o v e r 6-hr of foam s e p a r a t i o n . Foam s e p a r a t i o n e f f e c t -i v e l y p r o d uced a n o n t o x i c e f f l u e n t . C a u s t i c e x t r a c t i o n e f f l u e n t a l o n e was most d i f f i c u l t t o d e t o x i f y and a l s o p r o duced t h e most foam ( 2 0 % ) . Up t o 17-hr o f t r e a t m e n t had t o be g i v e n t o a c h i e v e a s i g n i f i c a n t l e v e l o f t o x i c i t y r e d u c t i o n . F our a d d i t i o n a l e x p e r i m e n t s were c o n d u c t e d on w h o l e m i l l e f f l u e n t s w i t h MST's r a n g i n g from 1-hr t o 8-hr. F o r t h e l e s s t o x i c samples (MST:4-8 h r ) t r e a t m e n t t i m e ( F i g u r e 29) r e q u i r e d f o r d e t o x i f i c a t i o n was i n t h e n e i g h b o r h o o d o f 0.25-hr. F o r more t o x i c e f f l u e n t s (MST = 1 h r ) 2-hrs o f t r e a t m e n t d e t o x i f i e d t h e e f f l u e n t . I n a c t u a l o p e r a t i o n , i t i s u n l i k e l y t h a t c a u s t i c e x t r a c t i o n e f f l u -ent would be t r e a t e d a l o n e because l a r g e amounts o f a c i d would be r e -q u i r e d t o r e d u c e t h e pH t o 2.5. M o r e o v e r , a f t e r t r e a t m e n t , n e u t r a l i z -a t i o n would be needed p r i o r t o d i s c h a r g e . I n a d d i t i o n , t h e much l a r g e r amount o f foam produced might p r e s e n t a g r e a t e r d i s p o s a l p r o b l e m . The r e s u l t s ( T a b l e 8) c l e a r l y i n d i c a t e t h a t i t i s more p r a c t i c a l t o t r e a t F i g u r e 29 TIME REQUIRED FOR DETOXIFICATION OF VARIOUS WHOLE MILL EFFLUENTS TIME, hours 107 combined w h o l e m i l l e f f l u e n t because of t h e f o l l o w i n g a d v a n t a g e s : even w i t h o u t foam s e p a r a t i o n t r e a t m e n t , t h e e f f l u e n t w o u l d r e q u i r e n e u t r a l i z a t i o n t o pH 6.5 t o 8.0, p r i o r t o d i s c h a r g e . T h e r e f o r e , b r i n g i n g t h e pH t o t h e o p e r a t i n g c o n d i t i o n (pH 7.0 o r 9.5) r e p r e -s e n t s o n l y a m i n o r a d j u s t m e n t : a f t e r t r e a t m e n t , t h e f i n a l pH a l w a y s r e m a i n s a r o u n d 7-8 w h i c h w o u l d a l l o w d i r e c t d i s c h a r g e t o t h e w a t e r c o u r s e : - w h o l e m i l l e f f l u e n t d e t o x i f i e d much more r a p i d l y t h a n c a u s t i c e f f -l u e n t . T h i s compensates f o r t h e l a r g e r volumes i n v o l v e d . - t h e volume o f foam f o r d i s p o s a l i s s u b s t a n t i a l l y r e d u c e d : a l l t o x i c o r p o t e n t i a l l y t o x i c w a s t e s a r e i n c l u d e d i n w h o l e m i l l e f f l u e n t and can be t r e a t e d . B. PROCESS PARAMETERS FOR OPTIMUM DETOXIFICATION BY FOAM SEPARATION D u r i n g t h e f e a s i b i l i t y s t u d i e s d i s c u s s e d i n S e c t i o n V-A, i t was d e m o n s t r a t e d t h a t t h e p r e s e n c e o f s u r f a c t a n t s i s n e c e s s a r y t o s u s t a i n f oaming. The c o r r e c t e f f l u e n t c o m p o s i t i o n and s u i t a b l e pH c o n d i t i o n s a r e e s s e n t i a l f a c t o r s c o n t r o l l i n g t h e s u c c e s s of t h e d e t o x i f i c a t i o n o f k r a f t w h o l e m i l l e f f l u e n t . Many o t h e r v a r i a b l e s a l s o a f f e c t t h e p e r -formance and e f f i c i e n c y of foam s e p a r a t i o n . The r e l a t i v e i m p o r t a n c e o f each v a r i a b l e depends,on t h e c h a r a c t e r i s t i c s o f t h e w a s t e . These v a r i -a b l e s were examined i n a s e r i e s of b a t c h and c o n t i n u o u s e x p e r i m e n t s . Most p a r a m e t e r s were s t u d i e d i n a b a t c h system. Those v a r i a b l e s t h a t a r e i n t e r r e l a t e d a r e d i s c u s s e d under t h e same h e a d i n g . The b a t c h ex-p e r i m e n t s were done under t h e f o l l o w i n g s t a n d a r d c o n d i t i o n s w i t h a l l o p e r a t i n g v a r i a b l e s e x c e p t one h e l d c o n s t a n t . System = 4 1 l a b o r a t o r y foam s e p a r a t i o n column Waste = b l e a c h e d k r a f t w h o l e m i l l e f f l u e n t pH = 9 . 5 A e r a t i o n r a t e = 500 ml/min G/L = 4-10 Temperature = 30 ± 2°C S p a r g e r p o r e s i z e = 45 u (mean b u b b l e d i a m e t e r = 1 mm) Column h e i g h t = 90 cm Foam h e i g h t = 60 cm Treatment t i m e = 30 min. 1. E f f e c t of pH Most t o x i c a n t s c o n t a i n e d i n b l e a c h e d k r a f t , w h o l e m i l l e f f l u e n t s a r e n e g a t i v e l y c harged c a r b o x y l i c compounds ( T a b l e 2 ) . Changes i n pH may change th e c h a r g e on t h e t o x i c compounds, enhance h y d r o l y s i s o f s u r f a c t -a n t s and/or a f f e c t t h e s u r f a c e t e n s i o n and foam p r o p e r t i e s . As a r e s u l t , a d s o r p t i o n o f t o x i c a n t s on t h e b u b b l e s and t h e e x t e n t o f t o x -i c i t y r e m o v a l can be v a r i e d . The i n t e r a c t i o n s of t o x i c s u r f a c e a c t i v e compounds i n k r a f t m i l l e f f l u e n t s a r e h i g h l y complex. A l t h o u g h t h e pH e f f e c t has been d e m o n s t r a t e d q u i t e e x t e n s i v e l y d u r i n g t h e t r e a t a b i l i t y s t u d i e s ( S e c t i o n V-A-2), t o d e t e r m i n e t h e r ange o f pH t h a t w o u l d be s u i t a b l e f o r r e m o v a l of t h e m a j o r i t y of t o x i c s u r f a c t a n t s , foam s e p -a r a t i o n t r e a t m e n t s f o r s e v e r a l more b a t c h e s o f e f f l u e n t s were r e p e a t e d between pH's o f 2 and 10. 109 The r e s u l t s o f foam s e p a r a t i o n on e f f l u e n t s from t h r e e d i f f e r e n t m i l l s ( F i g u r e 3 0 ) , c o n f i r m e d t h a t d e t o x i f i c a t i o n i s pH dependent. The c r i t i c a l pH's f o r d e t o x i f i c a t i o n f o r M i l l s D, F and G, were 9 and 7 r e -s p e c t i v e l y . The v a r i a t i o n i n pH r e f l e c t e d t h e d i f f e r e n c e s i n t h e q u a n t -i t y and c h a r a c t e r i s t i c s o f t h e c o n s t i t u e n t s o f t h e t o x i c compounds. Below t h e c r i t i c a l pH l e v e l , a l t h o u g h some r e d u c t i o n o f t o x i c i t y c o u l d be a c h i e v e d , c o m p l e t e d e t o x i f i c a t i o n was n o t o b t a i n e d . The f o a m i n e s s a l s o d e c r e a s e d s u b s t a n t i a l l y w i t h d e c r e a s i n g pH v a l u e . A f t e r t r e a t m e n t , t h e pH o f t h e e f f l u e n t d e c r e a s e d by 0.5 t o 1 pH u n i t . The c h e m i c a l s used f o r pH a d j u s t m e n t s h o u l d be s e l e c t e d c a r e f u l l y . I n most p u l p m i l l s , l i m e w i l l be used because i t i s r e a d i l y a v a i l a b l e and e c o n o m i c a l t o u s e . However, t h e q u a n t i t y a p p l i e d s h o u l d be c a r e -f u l l y d e t e r m i n e d and s h o u l d n o t exceed t h e maximum l e v e l where p r e c i p i -t a t i o n w o u l d o c c u r . O t h e r w i s e s e v e r e s c a l i n g by c a l c i u m d e p o s i t s on t h e equipment w i l l o c c u r . I n c o n s i d e r a t i o n o f t h i s l i m i t a t i o n as w e l l as t h e economics o f t h e s i t u a t i o n i t i s a d v i s a b l e t o add l i m e t o r a i s e t h e pH t o j u s t below t h e t r o u b l e s o m e l e v e l ( e . g . pH 6 ) . F u r t h e r pH a d j u s t -ment s h o u l d be made by c a u s t i c a d d i t i o n . 2. E f f e c t o f Temperature I n a s o l u t i o n c o n t a i n i n g s u r f a c e a c t i v e compounds, changes i n t e m p e r a t u r e a f f e c t t h e s o l u b i l i t y o f t h e s u r f a c t a n t s and s u r f a c e t e n s i o n o f t h e s o l u t i o n . T h e r e f o r e , s e p a r a t i o n o f t o x i c m a t e r i a l s by foam f r o m k r a f t m i l l e f f l u e n t s c o u l d a l s o be a f f e c t e d by t e m p e r a t u r e . F i g u r e 31 F i g u r e 30 EFFECT OF pH ON TOXICITY REMOVAL n o N T 1200-8 0 0 -400 Mill D (clarified effluent) Raw NT 1200-c £ 800 c »- 400 co z -fh Mill F (unclarified effluent) pH Raw > NT x c 2 1200 800 400 -it Mill F (clarified effluent) PH Raw NTJ I200r-800 400 it Mill 6 (clarified effluent) Raw o pH •it- PH 9.5 9.5 9.5 9.5 F i g u r e 31 EFFECT OF TEMPERATURE •xo. •xo •xo Initial M S T (hr) - Mill A = 12 - Mill B = 8 Treatment Time = 15 min pH=9,5 G/L = 0.95 30 50 TEMPERATURE, °C 70 i l l u s t r a t e t h e e f f e c t o f t e m p e r a t u r e o v e r t h e range o f 10 - 70°C f o r 2 samples. O t h e r t e m p e r a t u r e s , w h i c h a r e u n l i k e l y t o o c c u r e i n t h e m i l l , were n o t c o v e r e d i n t h i s s t u d y . The r e s u l t s i n d i c a t e t h a t f o r d e t o x i -f i c a t i o n o f k r a f t m i l l e f f l u e n t , t h e t e m p e r a t u r e e f f e c t i s s i g n i f i c a n t o n l y a t low l e v e l . A t 500 ml/min a e r a t i o n r a t e and 15 m i n u t e s t r e a t m e n t t i m e , foam s e p a r a t i o n a t t e m p e r a t u r e s < 10°C was n o t as e f f e c t i v e as t r e a t m e n t a t h i g h e r t e m p e r a t u r e s . Between 20 - 70°C, e f f l u e n t s were de-t o x i f i e d w i t h o u t d i f f i c u l t y . O ther s t u d i e s on p u r e s u r f a c t a n t s have v e r i f i e d t h a t i n c r e a s e s i n t e m p e r a t u r e cause i n c r e a s e s i n f r a c t i o n a t i o n ( 1 0 0 ) . However, t h e r e s u l t i s i n c o n t r a d i c t i o n t o G i b b s a d s o r p t i o n "1 dv e q u a t i o n ( x = — ) where s u r f a c e e x c e s s i s supposed t o d e c r e a s e c RT d i n e w i t h i n c r e a s i n g t e m p e r a t u r e . D e t o x i f i c a t i o n by foam s e p a r a t i o n i s a combined p r o c e s s of s o l u t e f r a c t i o n a t i o n and s o l i d f l o t a t i o n , as e v i d e n c e d by t h e f o r m a t i o n o f f r o t h and scum i n t h e foam. I t i s p o s s i b l e t h a t h i g h e r t e m p e r a t u r e s promote f o r m a t i o n o f p r e c i p i t a t e s and/or i o n complexes. T h e r e f o r e as l o n g as t h e t e m p e r a t u r e i s n o t t o o h i g h t o d e s t r o y t h e s t a b i l i t y o f t h e foam f i l m , d e t o x i f i c a t i o n w i l l improve. D u r i n g t h i s e x p e r i m e n t , t h e e f f e c t o f e v a p o r a t i o n on t h e f i l m became n o t i c e a b l e o n l y a t t e m p e r a t u r e s g r e a t e r t h a n 70°C. A t such h i g h t e m p e r a t u r e s foams were d e s t a b i l i z e d and c o l l a p s e d r e a d i l y . S i n c e i n p r a c t i c e t h e t e m p e r a t u r e o f k r a f t m i l l d i s c h a r g e s a v e r a g e s 30 t o 40°C, t h i s r ange of t e m p e r a t u r e would be s u i t a b l e t o s u p p o r t t h e f o r m a t i o n of s t a b l e foam f i l m s . Temperature wou l d t h e n n o t p r e s e n t a p r o b l e m i n foam s e p a r a t i o n o f t o x i c i t y . 113 3. E f f e c t of Column H e i g h t The column h e i g h t o f t h e foam s e p a r a t i o n s y s t e m a f f e c t s t h e mass t r a n s f e r and c o n t a c t t i m e of t h e b u b b l e s i n t h e l i q u i d . F o r most p u r e s u r f a c t a n t s , t h e d i f f e r e n c e i n t r a n s f e r r a t e s can be g r e a t ( 1 0 1 ) . F o r a two component system, mass t r a n s f e r can be p r e d i c t e d by u s i n g one o f s e v e r a l e s t a b l i s h e d t h e o r e t i c a l p r i n c i p l e s (102, 1 0 3 ). However, t h e s e p r i n c i p l e s a r e n o t a p p l i c a b l e t o p u l p m i l l e f f l u e n t s w h i c h c o n t a i n a good m i x t u r e o f s u r f a c e a c t i v e s u b s t a n c e s o f d i f f e r e n t c h e m i c a l c h a r a -c t e r i s t i c s . I n o r d e r t o i n v e s t i g a t e whether column h e i g h t i s of s i g n i f i c a n c e i n d e t o x i f i c a t i o n p r o c e s s , a s e r i e s of c o n t i n u o u s f l o w e x p e r i m e n t s were r u n w i t h l i q u i d h e i g h t s v a r i e d from 11 - 120 cm. The r e s u l t s ( F i g u r e 32) i n d i c a t e t h a t a minimum o f 11 cm and 22 cm were a l l t h e l i q u i d h e i g h t r e q u i r e d f o r d e t o x i f i c a t i o n o f m i l l s A and B e f f l u e n t s h a v i n g an i n i t i a l MSTs o f 5 h r s (A) and 24 h r s (B) r e s p e c t i v e l y . The l i q u i d h e i g h t r e -q u i r e m e n t a g r e e s c l o s e l y w i t h p u b l i s h e d d a t a (67) on s u r f a c t a n t r e m o v a l . I n a c o n t i n u o u s p r o c e s s , t h e h e i g h t of t h e foam s e p a r a t i o n column can be d i v i d e d i n t o 2 r e g i o n s ( 6 5 ) ; a m i x i n g zone j u s t around t h e f e e d p o i n t and a zone below i t i n w h i c h l i q u i d moves c o u n t e r c u r r e n t t o t h e a i r . I t i s g e n e r a l l y r e c o g n i z e d t h a t s o l u t e t r a n s f e r o c c u r s m a i n l y i n t h e c o u n t e r c u r r e n t r e g i o n . Below a c e r t a i n h e i g h t , t h e c o u n t e r c u r r e n t r e g i o n d i s a p p e a r s , t h e two r e g i o n s t h e n become one m i x i n g zone and t h e n h e i g h t a f f e c t s s e p a r a t i o n . F i g u r e 32 EFFECT OF COLUMN HEIGHT ON DETOXIFICATION o o Mill I Mill B I A xo—XO—XO——XO •XO •xo •xo xo Initial MST (hr) -Mill A = 12 -Mill B = 8 Treatment Time = 15 min pH = 9.5 G/L = 0.95 1 1 1 40 80 HEIGHT OF LIQUID, cm 120 115 From t h i s s t u d y , t h i s c o n d i t i o n would appear t o o c c u r a t l i q u i d h e i g h t s o f 22 cm and 11 cm ( F i g u r e 3 2 ) . The l i q u i d h e i g h t r e q u i r e m e n t o f a foam s e p a r a t i o n system i s p r o p o r t i o n a l t o t h e e f f l u e n t t o x i c i t y . I n g e n e r a l , t h e a v e r a g e t o x i c i t y o f p u l p m i l l e f f l u e n t i s seldom l e s s t h a n 2 h r MST and i n o r d e r t o m i n i m i z e l a n d u t i l i z a t i o n , c o m m e r c i a l foam s e p a r a t i o n s y s t e m w o u l d be b u i l t a t l e a s t 5 - 10 f t i n h e i g h t , t h e minimum h e i g h t o f 22 cm and t h e c o u n t e r c u r r e n t b u b b l e - l i q u i d c o n t a c t can be met a t a l l t i m e . 4. E f f e c t o f A e r a t i o n R a t e and G/L R a t i o P r o v i d e d c o n s t a n t b u b b l e d i a m e t e r ( c o n s t a n t gas s p a r g e r p o r e s i z e ) a r e p r o d u c e d , a u n i t amount o f s u r f a c e a c t i v e m a t e r i a l c o n t a i n e d i n t h e e f f l u e n t would r e q u i r e a c o n s t a n t amount o f l a i r b u b b l e s u r f a c e f o r com-p l e t e r e m o v a l o f s u r f a c t a n t s from t h e e f f l u e n t . S i n c e t h e t o x i c m a t e r -i a l s i n k r a f t m i l l e f f l u e n t s a r e s u r f a c e a c t i v e , t h e minimum a i r r e -q u i r e m e n t s h o u l d i n c r e a s e w i t h t h e t o x i c i t y . F i g u r e 33 i l l u s t r a t e s de-t o x i f i c a t i o n r e s u l t s by foam s e p a r a t i o n t r e a t m e n t f o r t h r e e b a t c h e s o f e f f l u e n t s h a v i n g MSTs o f 2.5, 5 and 8 - h r s . R e g a r d l e s s o f i n i t i a l t o x i c i t y l e v e l , t h e r e s u l t s s u g g e s t t h a t t o x i c i t y r e d u c t i o n was go v e r n e d by t h e a i r f l o w r a t e . The c r i t i c a l a e r a t i o n r a t e r e q u i r e d was c o n t r o l l e d by the e f f l u e n t t o x i c i t y . The most t o x i c e f f l u e n t f r o m M i l l G w h i c h had an i n i t i a l MST o f 2.5 h r , r e q u i r e d 1000 ml/min o f a e r a t i o n (G/L = 4) t o a c h i e v e d e t o x i f i c a t i o n by foam s e p a r a t i o n . The l e s s t o x i c e f f l u e n t f r o m M i l l B (MST - 5 h r ) r e q u i r e d a minimum a e r a t i o n r a t e o f 500 ml/min (G/L = 2) whereas t h e TOXICITY ( M S T , hours) 9TT 117 l e a s t t o x i c e f f l u e n t from M i l l C (MST = 8 h r ) was d e t o x i f i e d by a e r a t i n g a minimum o f 250 ml/min (G/L = 1) o f a i r . The a i r r e q u i r e m e n t f o r a foaming system can a l s o be d e t e r m i n e d by t h e G/L r a t i o ( d e t e r m i n e d by t r e a t m e n t t i m e , gas and l i q u i d f l o w r a t e s ) . Each v a r i a b l e d e t e r m i n i n g G/L, i . e . t r e a t m e n t t i m e and a i r f l o w r a t e can be v a r i e d and w i l l n o t a f f e c t t h e amount of s u r f a c t a n t s removed. How-e v e r , i t s h o u l d be r e a l i z e d t h a t h i g h a i r f l o w p r o d u c e s wet foam and w i l l l o w e r t h e e n r i c h m e n t r a t i o . M o r e o v e r , s e v e r e t u r b u l e n c e i n t h e f oaming column w i l l r e s u l t . T h i s c o n d i t i o n may be d e t r i m e n t a l b ecause t h e t o x i c foam-scum may be r e d i s p e r s e d i n t o t h e e f f l u e n t and t h e foam f l o w r a t e may be e x c e e d i n g l y l a r g e . T h e r e f o r e , when l a r g e G/Ls a r e en-c o u n t e r e d , i t would be d e s i r a b l e t o c o n s i d e r t h e advantage o f i n c r e a s i n g t h e t r e a t m e n t t i m e s s l i g h t l y so t h a t t h e a e r a t i o n r a t e can be d e c r e a s e d t o a more manageable l e v e l . 5. E f f e c t of B u b b l e D i a m e t e r and G a s / L i q u i d I n t e r f a c i a l A r e a The g a s - l i q u i d i n t e r f a c i a l a r e a a p p l i e d t o a foam s e p a r a t i o n s y s t e m i s c o n t r o l l e d by t h e G/L r a t i o . The same g a s - l i q u i d i n t e r f a c e c a n be c r e a t e d by e i t h e r s p a r g i n g l a r g e amounts of a i r i n b i g b u b b l e s o r s m a l l volumes of a i r i n s m a l l b u b b l e s . Thus, t h e s m a l l e r t h e b u b b l e s i z e p r o d u c e d , t h e l e s s a i r b l o w e r c a p a c i t y r e q u i r e d . S i n c e i t i s e x p e c t e d t h a t t h e t o t a l i n t e r f a c i a l a r e a r e q u i r e d f o r d e t o x i f i c a t i o n s h o u l d i n c r e a s e w i t h i n c r e a s e d i n f l u e n t t o x i c i t y l e v e l , t h e e x t e n t o f t o x i c i t y a d s o r p t i o n i n foam w i l l be a f u n c t i o n o f t h e g a s - l i q u i d i n t e r f a c e gen-e r a t e d p e r u n i t t i m e . I n a s e r i e s o f b a t c h e x p e r i m e n t s , t h e foam generation system, foam separation time and air flow rates were changed to obtain different bubble diameters and G/L ratios. Although i t i s recognized that small bubbles ascent slower than big bubbles and this should enhance adsorption of toxicants, this factor was not considered in this study since i t was assumed that transfer of toxicants to the interface was instantaneous. Table 9 shows that with a coarse dispersion medium, producing approx-imately 4 mm diameter bubbles (estimated crudely by direct photographing of bubbles i n the column), a G/L ratio of 30 was necessary to detoxify a typical effluent within 1.5 hr treatment time. By choosing a finer dis-persion medium, producing bubbles of approximately 1.5 mm diameter, the necessary G/L ratio for detoxification could be reduced to 10 within a similar treatment time. A third system, producing 1 mm diameter bubbles detoxified waste of similar toxicity even at a lower G/L ratio of 7. A l -though the three systems operated at different aeration rates, G/L ratios and bubble diameters the total gas-liquid interfacial areas cumulated over the whole experiment was similar within the range of 41 to 46 m / l . Iden-t i c a l experiments using a helical aerator (Kenics System) and a, turbine system producing 0.07 mm diameter bubbles (G/L = 3-4) and a dissolved air system producing 0.07 mm diameter bubbles (G/L = 0.3) created a gas-liquid 2 interfacial area of 24 - 33 m / l compared to the porous'diffuser systems, the variations of gas-liquid interfacial area was less than a factor of 2 whereas the G/L was reduced by a factor of 100 from 30 to_0.3. The data confirm that the same detoxification results can be obtained by reducing the G/L ratio given and with smaller bubble sizes. There i s a minimum limit however, to which the G/L could be reduced because in commercial aeration systems, the cost of bubble generation usually increases with the reduction in bubble sizes. Therefore, the TABLE 9 EFFECT OF BUBBLE DIAMETER, GAS-LIQUID RATIO AND INTERFACIAL AREA ON DETOXIFICATION Experiment No. T o x i c i t y Type o f Sparger Used A e r a t i o n (1/min) Treatment Time R e q u i r e d F o r D e t o x i f i c a t i o n (hr) * E s t i m a t e d Bubble Diameter (mm) G a s / L i q u i d R a t i o G a s / L i q u i d I n t e r f a c i a l A r e a ( m 2 / l ) I n f l u e n t MST (hr ) T r e a t e d E f f l u e n t ( h r ) 1 4.3 NT** Seven 5" d i a m e t e r 65n pore s i z e p l a s t i c d i s c s 60 1.5 4.0 30 46.3 2 4.7 NT Four 5" d i a m e t e r 25y pore s i z e p l a s t i c d i s c s 30 1.0 1.5 10 41.2 3 2.0 NT Four 1' l o n g <25y pore s i z e c e r a m i c tubes 10 18 2.0 1.0 1.0 1.0 7 6 41.1 37.0 4 1.8 NT Seven 1 1 l o n g 0.5" d i a m e t e r h e l i c a l a e r a t o r s 4 3.0 0.75 4 32.9 5 1.4 4.8 NT NT 3" d i a m e t e r 4-blade t u r b i n e 1 1 0.5 0.75 0.75 4 3 32.9 24 6 5.0 NT 40 p s i , d i s s o l v e d a i r f l o t a t i o n system (4 p a s s e s ) A i r s a t -u r a t i o n a t 40 p s i 0.07 0.3 25.2 *• Bubble d i a m e t e r and g a s - l i q u i d i n t e r f a c e were e s t i m a t e d from photographs ( S e c t i o n IV-D) and l i t e r a t u r e d a t a . ** NT = N o n - t o x i c ; 100% f i s h s u r v i v a l i n 100% e f f l u e n t c o n c e n t r a t i o n a f t e r 24 h r s . Note: E x p e r i m e n t s No. 1 - 4 done i n 180 1 columns a t f i e l d s i t e ; b a t c h o p e r a t i o n Experiment No. 6 done i n l a b o r a t o r y u s i n g a 4 1 f l o t a t i o n u n i t . 120 G/L r a t i o c o u l d be r e d u c e d o n l y t o t h a t minimum below w h i c h f u r t h e r r e -d u c t i o n o f b u b b l e s i z e s w o u l d n o t be e c o n o m i c a l . The above i n d i c a t e s t h a t d e t o x i f i c a t i o n e f f i c i e n c y depends on t h e t o t a l i n t e r f a c i a l a r e a produced p e r u n i t volume of w a s t e t r e a t e d . The p r o d u c t i o n o f i n t e r -f a c i a l a r e a can be c o n t r o l l e d i n i t i a l l y by s e l e c t i o n of a gas d i s p e r s i o n s y s t e m , w h i c h p r o d u c e s gas b u b b l e s o f t h e r e q u i r e d d i a m e t e r and t h e n , by a d j u s t i n g t h e G/L r a t i o a c c o r d i n g l y . 6. E f f e c t of I n f l u e n t T o x i c i t y L e v e l on Treatment Time and G a s - L i q u i d  I n t e r f a c i a l A r e a Requirement Under a g i v e n s e t of c o n d i t i o n s , t r e a t m e n t t i m e r e q u i r e d i n a b a t c h o p e r a t i o n a p pears t o depend on t h e i n i t i a l t o x i c i t y o f t h e e f f l u e n t . I n F i g u r e 34, t h e t i m e n e c e s s a r y t o d e t o x i f y e f f l u e n t s by foam s e p a r a t i o n i s p l o t t e d a g a i n s t t h e i n i t i a l t o x i c i t y . R e g r e s s i o n a n a l y s i s i n d i c a t e s t h a t t h e d a t a f i t s t h e form o f a power c u r v e . The c o r r e l a t i o n c o e f f i c -i e n t was c a l c u l a t e d as r = 0.81. Y = 41.84 X " ° - 7 1 where X = i n f l u e n t t o x i c i t y i n MST (min) Y = t r e a t m e n t t i m e The e x p r e s s i o n c o u l d be used t o p r e d i c t t r e a t m e n t t i m e r e q u i r e d f o r d e t o x i f i f i c a t i o n . U s i n g t h i s e q u a t i o n and c a l c u l a t i n g t h e w o r s t c a s e s where e f f l u e n t s of 100 min and 50 min MSTs a r e foam s e p a r a t e d , t h e p r e d i c t e d t r e a t m e n t t i m e s f o r d e t o x i f i c a t i o n a r e 1.6 and 2.6 h r s . DURATION OF FOAM FRACTIONATION FOR COMPLETE DETOXIFICATION (hours) o — ro OJ 01 o H O o X o -n Z3o E° m co —I 4* o o " a . i.o 3 o o o o o o H m m T3 a>Q< xcornoo c o o 2 m 3 J O H C/>><0 • < 3 § r~ r~ r r r " r - r - r rn o cu > o t> • © 23 o Co HP i n H Z — 33 m <a 4* m[3] z m H Z mO o x S o m Is I n g e n e r a l , t h e MST o f t h e m a j o r i t y o f t h e e f f l u e n t s e x ceeds 100 m i n and seldom f a l l s b elow 50 min. T h e r e f o r e , maximum t r e a t m e n t t i m e r e q u i r e d i s n o t e x p e c t e d t o be g r e a t e r t h a n 3 h r s . A t t h e s p e c i f i c a i r f l o w r a t e g i v e n and assuming b u b b l e s o f 1 mm mean d i a m e t e r s were p r o d u c e d , t h e t o t a l g a s - l i q u i d i n t e r f a c e g e n e r a t e d o v e r t h e p e r i o d o f t r e a t m e n t t i m e r e q u i r e d f o r d e t o x i f i c a t i o n was c a l c u l a t e d f o r a group o f samples f r o m M i l l s E , .F, G and H (Appendix I I I ) . F i g u r e 35 p l o t s t h e g a s - l i q u i d i n t e r f a c i a l a r e a g e n e r a t e d as a f u n c t i o n o f t h e mean t o x i -c i t y o f t h e v a r i o u s sample g r o u p s . The r e s u l t s produce a s e r i e s o f s t r a i g h t l i n e s but n o t p a r a l l e l t o each o t h e r . I n g e n e r a l , i t was f o u n d t h a t g a s - l i q u i d i n t e r f a c i a l a r e a r e q u i r e m e n t i n c r e a s e d l i n e a r l y w i t h t h e i n i t i a l t o x i c i t y o f t h e e f f l u e n t . However, t h e s l o p e s o f t h e c u r v e s v a r i e d from m i l l t o m i l l i n d i c a t i n g t h a t t h e d e t o x i f i c a t i o n r e q u i r e m e n t s f o r foam s e p a r a t i o n a r e d i f f e r e n t f o r each m i l l . F o r example, e f f l u e n t s 2 f r o m M i l l s F. and G w i t h an MST o f 3 h r r e q u i r e d 50 m / l i n t e r f a c i a l a r e a , 2 whereas M i l l E e f f l u e n t w i t h t h e same i n i t i a l t o x i c i t y needed 100 m / l . I n c o n t r a s t , t h i s i n t e r f a c i a l a r e a was n o t s u f f i c i e n t t o d e t o x i f y M i l l H e f f l u e n t where l a r g e q u a n t i t i e s o f defoamer were p r e s e n t when t h e samples were o b t a i n e d f r o m t h e m i l l . Thus, r e q u i r e m e n t f o r d e t o x i f i c a t i o n by foam s e p a r a t i o n needs t o be a s s e s s e d f o r each m i l l . D e t e r m i n a t i o n o f t h e m i n i m a l g a s - l i q u i d i n t e r f a c i a l a r e a i s an i m p o r t a n t d e s i g n c o n s i d e r -a t i o n o f t h e foam s e p a r a t i o n p r o c e s s . T y p i c a l MST v a l u e s o f most b l e a c h e d k r a f t m i l l e f f l u e n t s v a r y f r o m 100 - 800 min; w i t h an ave r a g e o f 200 - 300 min. A foam s e p a r a t i o n s y s -tem d e s i g n e d t o p r o v i d e o n l y s u f f i c i e n t i n t e r f a c i a l a r e a f o r re m o v i n g a v e r a g e t o x i c i t y l o a d s w i l l f a i l t o d e t o x i f y when i n f l u e n t t o x i c i t y F i g u r e 35 CORRELATION BETWEEN TOXICITY AND GAS-LIQUID INTERFACIAL AREA REQUIRED FOR DETOXIFICATION (MEAN VALUES) 600i GAS-LIQUID INTERFACIAL AREA im^/l) REQUIRED FOR DETOXIFICATION 124 exceeds t h e av e r a g e . Thus f o r a p r o p e r d e s i g n some measure o f t o x i c i t y v a r i a t i o n as w e l l as ave r a g e v a l u e s a r e r e q u i r e d . F o r a t t a i n m e n t o f a s a t i s f a c t o r y d e t o x i f i c a t i o n r a t e , w h i c h meets r e g u l a t o r y r e q u i r e m e n t s , t h e s y s t e m t h e r e f o r e w i l l have t o be d e s i g n e d t o h a n d l e t o x i c i t y w e l l i n e x c e s s o f t h e a v e r a g e l o a d s . F o r example, i f a system f o r M i l l E was d e s i g n e d t o h a n d l e t o x i c i t y l e v e l s o f MST - 100 min i n s t e a d o f 250 min, 2 2 t h e i n t e r f a c i a l a r e a r e q u i r e d would be 145 m / l i n s t e a d o f 30 m / l ; a f i v e f o l d i n c r e a s e . Such a d r a s t i c i n c r e a s e o f i n t e r f a c i a l a r e a r e -qui r e m e n t might p r o v e t o be p r o h i b i t i v e l y c o s t l y . Thus, u t i l i z a t i o n o f su r g e c a p a c i t y and m i n i m i z a t i o n o f t h e f r e q u e n c y w i t h w h i c h e x c e s s i v e l y t o x i c l o a d s have t o be h a n d l e d p r o b a b l y w i l l be e s s e n t i a l t o e l i m i n a t e t h e need f o r i m p r a c t i c a l l y h i g h i n t e r f a c i a l a r e a g e n e r a t i o n r e q u i r e -ments . 7. E f f e c t o f Mode o f O p e r a t i o n and R e t e n t i o n Time R e q u i r e d Three d i f f e r e n t modes of foam s e p a r a t i o n o p e r a t i o n , namely: s i m p l e , s t r i p p i n g and e n r i c h i n g modes ( S e c t i o n I I I ) were i n v e s t i g a t e d . T o t a l r e f l u x , a s p e c i a l case o f e n r i c h m e n t o p e r a t i o n was a l s o s t u d i e d t o de-t e r m i n e what t y p e o f o p e r a t i o n would be most s u i t a b l e f o r d e t o x i f i c a t i o n of k r a f t m i l l e f f l u e n t . The e x p e r i m e n t s were con d u c t e d u s i n g e f f l u e n t h a v i n g an o r i g i n a l MST o f 305 min. The system was o p e r a t e d under c o n -t i n u o u s f l o w c o n d i t i o n s f o r 8 h r s i n a 4 1 l a b o r a t o r y column, a t r e -t e n t i o n t i m e s o f 10 min, 15 min, 25 min and 40 min. Foam was w i t h d r a w n 60 cm above t h e l i q u i d l e v e l . Among t h e s e v a r i o u s modes of o p e r a t i o n ( T a b l e 10) e f f l u e n t s were d e t o x i f i e d more r e a d i l y u s i n g a s t r i p p i n g mode. A r e t e n t i o n t i m e o f 15 min p e r m i t t e d 80% f i s h s u r v i v a l . A t 25 min r e t e n t i o n t i m e , t h e e f f l u e n t was c o m p l e t e l y d e t o x i f i e d . Under t h e same c o n d i t i o n s , s i m p l e mode and e n r i c h m e n t mode o p e r a t i o n s b o t h a l l o w e d 20% and 80% f i s h s u r v i v a l a t 15 min and 25 min r e t e n t i o n t i m e and complete d e t o x i f i c a t i o n a t 40 min r e t e n t i o n t i m e . An i n t e r e s t i n g r e s u l t was o b t a i n e d by o p e r a t i n g t h e column a t t o t a l r e f l u x where foams were r e t u r n e d c o m p l e t e l y i n t o s o l i d gummy m a t e r i a l s . D e t o x i f i c a t i o n r e s u l t s a t 25 min and 40 min r e t e n t i o n t i m e were compar-a b l e t o t h e s i m p l e mode o p e r a t i o n . The o v e r a l l r e s u l t s s u g g e s t t h a t a s t r i p p i n g mode o p e r a t i o n w o u l d appear t o have s l i g h t advantage because o f t h e l o w e r r e t e n t i o n t i m e r e -qu i r e m e n t . However, because t h e e f f l u e n t s were f e d on top o f t h e foam, l a r g e amounts o f l i q u i d were e n t r a i n e d i n t h e foam. By i n c r e a s i n g r e -t e n t i o n t i m e , t h e foam volume d i s c h a r g e d c o u l d be r e d u c e d q u i t e sub-s t a n t i a l l y ( f r o m 30 t o 12% as r e t e n t i o n t i m e i n c r e a s e d from 10 t o 40 min) as a r e s u l t o f b e t t e r l i q u i d d r a i n a g e . Even a t t h e h i g h e s t r e -t e n t i o n t i m e (40 min) t e s t e d , t h e foam volumes were s t i l l 4 - 1 2 t i m e s g r e a t e r t h a n s i m p l e mode ( 3 % volume) and e n r i c h i n g mode ( 1 . 2 % volume) o p e r a t i o n s . I n d e s i g n i n g a c o m m e r c i a l foam s e p a r a t i o n p l a n t , s t r i p p i n g mode o p e r a t i o n i s n o t recommended because o f t h e l a r g e foam volume i n v o l v e d . TABLE 10 EFFECT OF OPERATION MODE AND RETENTION TIME ON CONTINUOUS DETOXIFICATION OF KRAFT MILL EFFLUENTS O p e r a t i o n P r o c e s s C o n d i t i o n MST o f E f f l u e n t a f t e r Treatment (min) Foam Volume (%) D i s c h a r g e d (60 cm foam h e i g h t ) Mode Feed P o s i t i o n R e t e n t i o n Time (min) G/L Simple I n f l u e n t : f e e d a t g a s - l i q u i d i n t e r f a c e 10 1.2 800 8.5 15 2 5000 7.0 25 4 ** 80% S u r v i v a l 5.3 40 4.8 N o n t o x i c 3.0 S t r i p p i n g I n f l u e n t : f e e d on top of foam l a y e r 10 1.2 1000 30 15 2 **80% S u r v i v a l 21 25 4 N o n t o x i c 16 40 4.8 N o n t o x i c 12 E n r i c h i n g (Normal o p e r a t i o n I n f l u e n t : f e e d a t gas l i q u i d i n t e r f a c e C o l l a p s e d foam: 50% r e t u r n e d t o foam l a y e r 10 1.2 600 6.7 15 2 5000 4.5 25 4 **80% S u r v i v a l 2.3 40 4.8 N o n t o x i c 1.2 E n r i c h i n g ( T o t a l r e f l u x ) I n f l u e n t : f e e d a t g a s - l i q u i d i n t e r f a c e C o l l a p s e d foam: . 100% r e t u r n e d t o foam l a y e r 10 1.2 500 (Scum f o r m a t i o n ) 15 2 1000 (Scum f o r m a t i o n ) 25 4 70% S u r v i v a l (Scum f o r m a t i o n ) 40 4.8 N o n t o x i c (Scum f o r m a t i o n ) Volume o f foam s e p a r a t i o n column :4 1 MST of u n t r e a t e d e f f l u e n t : 305 min Note: ^ ''MST cannot be de t e r m i n e d when f i s h s u r v i v a l exceeds 50% a f t e r 96 h r s exposure. The t o t a l r e f l u x system o f f e r s t h e advantage o f c o n v e r t i n g l a r g e volumes o f foam t o a s m a l l volume of scum. However, t h e system must be o p e r a t e d w i t h c a r e because o f t h e c o l l a p s e d foams a r e h i g h l y c o n c e n t r a t e d i n t o x i c m a t e r i a l . When r e t u r n i n g t o t h e foam l a y e r f o r r e f l u x , t h e r e i s a l ways a danger o f l i q u i d c h a n n e l l i n g w i t h i n t h e foam. Once t h i s o c c u r s , t h e t o x i c m a t e r i a l s w i l l be r e d i s p e r s e d i n t o t h e s o l u t i o n . I n comparing t h e c o m p l e x i t i e s and d i s a d v a n t a g e s o f v a r i o u s o p e r -a t i o n modes, d e t o x i f i c a t i o n e f f i c i e n c i e s and foam volume, i t seems l o g i c a l t o use o n l y t h e s i m p l e o r t h e e n r i c h i n g modes f o r l a r g e s c a l e foam s e p a r a t i o n o p e r a t i o n s . 8. E f f e c t o f S t a g i n g I n o r d e r t o i n v e s t i g a t e t h e n e c e s s i t y of s t a g i n g i n a c o n t i n u o u s foam s e p a r a t i o n , a two s t a g e system u s i n g two 180-1 columns c o n n e c t e d i n s e r i e s was o p e r a t e d a t t h e l o w e s t p o s s i b l e G/L r a t i o and a s s e s s e d f o r d e t o x i f i c a t i o n p e r f o r m a n c e . A s i n g l e s t a g e column o p e r a t e d under s i m -i l a r c o n d i t i o n s was run_ s u b s e q u e n t l y f o r c o m p a r i s i o n . The system was o p e r a t e d c o n t i n u o u s l y f o r 15 days. I n t h e t w o - s t a g e system, t h e a i r f l o w and r e t e n t i o n t i m e i n each column was 2.3 1/min and 30 min r e s p e c t -i v e l y : t h e s e were a p p r o x i m a t e l y h a l f o f t h e s i n g l e s t a g e s y s t e m , i . e . t h e o v e r a l l G/L and r e t e n t i o n t i m e were i d e n t i c a l . The o p e r a t i n g c o n -d i t i o n s and d a i l y t o x i c i t y d a t a f o r each column a r e p r e s e n t e d i n Ap-p e n d i x IV a-b. D e t o x i f i c a t i o n r e s u l t s f o r t h e two systems a r e compared i n T a b l e 11. TABLE 11 DETOXIFICATION PERFORMANCE (MEAN VALUE) OF A SINGLE STAGE VERSUS 2 STAGE SYSTEM Parameter S i n g l e Stage System Two Stage System 1 s t Stage 2nd Stage O v e r a l l R e t e n t i o n time (min) 58 29 29 58 G/L 8 4.65 4.65 9.3 I n f l u e n t MST (min) 252 277 - -(No. o f Samples D e t o x i f i e d ) (No. o f Samples T r e a t e d ) 5/8 0/14 13/14 13/14 % o f T r e a t e d e f f l u e n t meeting Fed. T o x i c i t y s t a n d a r d . 63 0 91 91 Foam P r o d u c t i o n (% volume d i s c h a r g e d ) 6.8 3.7 0.9 4.6 Gas d i f f u s e r : Four f i n e bubble ceramic d i f f u s e r , 1* lo n g , 3 " d i a m e t e r O p e r a t i o n E l a p s e d Time: 15 days. 129 The s i n g l e s t a g e system o p e r a t i n g a t an a v e r a g e G/L o f 8 and 58 m i n r e t e n t i o n t i m e d e t o x i f i e d 63% o f t h e samples (5 out o f 8 s a m p l e s ) . The foam d i s c h a r g e d ( c o l l a p s e d volume) a v e r a g e d t o 6.8% o f t h e i n f l u e n t v o l -ume. W i t h a 2-stage system, d e t o x i f i c a t i o n r a t e s improved d r a m a t i c a l l y t o 9 1 % (13 o u t of 14 samples were d e t o x i f i e d ) . M o r e o v e r , o v e r a l l foam d i s c h a r g e d was o n l y 4.6% o f i n f l u e n t , about 30% l e s s t h a n t h a t o f t h e s i n g l e s t a g e system. The r e d u c t i o n i n foam d i s c h a r g e was due t o i n -c r e a s e d foam r e t e n t i o n as a r e s u l t o f l o w e r a i r f l o w (G/L = 4 . 6 ) i n each column. The a v e r a g e foam g e n e r a t i o n i n t h e f i r s t s t a g e was 3.7% a g a i n s t 0.9% i n t h e second s t a g e . A l t h o u g h t h e f i r s t s t a g e removed most o f t h e foamable m a t e r i a l s , d e t o x i f i c a t i o n was i n c o m p l e t e . T h i s i s i n d i c a t e d by t h e p o o r f i s h s u r v i v a l r a t e . The second s t a g e removed t h e r e m a i n i n g s m a l l amounts of t o x i c m a t e r i a l s and b r o u g h t t h e e f f l u e n t t o t h e non-t o x i c l e v e l . The r e s u l t s i n d i c a t e t h a t a l t h o u g h on t h e o v e r a l l , t h e same G/L and r e t e n t i o n t i m e were a p p l i e d t o t h e s i n g l e s t a g e system, t h e t w o - s t a g e a c h i e v e d a f a r b e t t e r d e t o x i f i c a t i o n r a t e (92% v s 63%) and l o w e r foam d i s c h a r g e r a t e s . S t a g i n g o f a foam s e p a r a t i o n system a s s u r e s c o m p l e t e r e m o v a l o f foam and t h u s p r e v e n t s t h e t o x i c scums and r e s i d u a l foams t o r e t u r n t o t h e l i q u i d phase. Each foam s e p a r a t i o n column r e -sembles a back mix r e a c t o r , a l t h o u g h t h e c o n c e n t r a t i o n i s u n i f o r m i n each r e a c t o r , t h e r e i s n e v e r t h e l e s s a change i n c o n c e n t r a t i o n as f l u i d moves f r o m r e a c t o r t o r e a c t o r , i . e . t h e c o n c e n t r a t i o n d r o p s t o a l o w e r v a l u e . As t h e number o f back mix r e a c t o r s i n c r e a s e d , t h e s y s t e m ap-p r o a c h e s a p l u g f l o w system ( 1 0 4 ) . 130 Since the effectiveness of the foam separation process i s con-centration ( t o x i c i t y ) dependent, a plug flow reactor would be more ef-f i c i e n t because the concentration of reactants ( i n t h i s case MST) de-creases progressively as f l u i d passes through the system. C. EFFECT OF VARIABILITY IN EFFLUENT CHARACTERISTICS ON DETOXIFICATION The waste c h a r a c t e r i s t i c s of bleached k r a f t m i l l e f f l u e n t s obtained from various Canadian m i l l , d i f f e r according to wood furnishes and modi-f i c a t i o n i n the various m i l l s process conditions. An extensive sampling program therefore was conducted to investigate the e f f e c t of e f f l u e n t v a r i a b i l i t y on foam separation of t o x i c i t y . A t o t a l of 205 batches of samples were obtained at d i f f e r e n t times from eight B.C., one Ontario and one Quebec m i l l s . Wood furnishes used i n these m i l l s included f i r , hemlock, cedar, spruce, pine, cypress, balsam, poplar, maple and b i r c h . None of the m i l l s processed exactly the same wood furnishes. Water usage ranged from 29,000 to 48,000 gal/ton of pulp. Additives i n the e f f l u e n t were mostly chemical defoamers and usually consisted of more than two d i f f e r e n t types. Almost a l l samples obtained were tox i c to f i s h . Over 90% of the MSTs were i n the range of 2 - 6 hr. Each batch of sample was subdivided and treated under established foaming conditions with treatment times of 0.25 - 5 hr. For the ma-j o r i t y of the samples, foam ceased to occur a f t e r treatment. The r e -ductions i n t o x i c i t y are shown i n Appendix V a-j and are summarized i n Table 12. TABLE 12 SUCCESS RATE IN DETOXIFYING BLEACHED KRAFT WHOLEMILL EFFLUENTS BY FOAM SEPARATION M i l l Principal Wood Furnish No. of Samples Toxicity (MST) in Influent, hr Treatment Time Required to Detoxify (hr) No.of Samples Detoxified * Success Rate(%) of Detoxification 100% Test cone. 65% Test cone. 100% Test cone. 65% Test cone. Mean ± SD Range A 18% F i r , 46% Hemlock 36% Cedar 8 9.7+6.5 1.2-24 0.25 7 8 88 100 B 43.4% F i r , 40.3% Hemlock, 16.3% Cedar 18 9.8±7.4 0.5-24 0.5 - 3 12 15 67 83 C 50% Spruce, 45% Pine, 5% F i r 19 1.4±0.9 0.2- 4 1 - 3 16 - 84 -D 36% Spruce, 33% Pine, 31% others 20 2.3±1.6 0.3-6.5 0.25 - 2 13 - 65 -E F i r , Cypress, Spruce, Pine and Hemlock 20 1.2±1.3 0.2-6.0 0.5 - 4.5 16 - 80 -F 60% Spruce, 16% Pine, 12% Balsam & Others 64 4.2±4.8 0.5-NT 0.25 - 2 54 - 84 -G 50% Spruce, 45% Pine, 5% others 18 4.2±3.0 0.7-12 0.25 - 1 22 22 100 100 H 50% Hemlock, 32% F i r and 18% Cedar 19 6.0±4.1 0.5-17 2 - 5 17 - 100 -I 80% Jackpine and 20% Spruce 10 1.8±1.0 0.5- 4 2 10 10 100 100 J 46% Poplar, 27% Maple, 17% Birch & 10% Softwood 9 3.4±3.5 0.1-NT 1 - 5 6 7 77 89 Overall 205 0.25 - 5 173 52 83 93 * Based on no. of samples with 100% f i s h survival on 100% effluent after 24 hr . ** Over 80% f i s h survival i n 65% effluent after 96 hr of exposure (Federal Toxicity Test). Note: M i l l s A - H from B.C.; M i l l I from Ontario; M i l l J from Quebec. The m a j o r i t y of t h e samples, r e g a r d l e s s of when and where t h e y were t a k e n were d e t o x i f i e d w i t h i n 3 h r as a r e s u l t o f foam s e p a r a t i o n . F o r h i g h l y t o x i c e f f l u e n t , d e t o x i f i c a t i o n c o u l d be a c h i e v e d by e x t e n d i n g t h e t r e a t m e n t t i m e t o 5 h r . The p e r c e n t a g e o f t h e samples d e t o x i f i e d from each m i l l d i f f e r e d s l i g h t l y . A t 100% t e s t c o n c e n t r a t i o n , t h e b e s t r e s u l t s were f r o m m i l l s G, H, and I where 100% s u c c e s s was a c h i e v e d . F o u r m i l l s (A, C, E, and F) a c h i e v e d an 80 - 90% s u c c e s s and t h e r e -m a i n i n g t h r e e a c h i e v e d a" 65 - 80% s u c c e s s . O v e r a l l 173 o u t o f 205 samples were d e t o x i f i e d and an o v e r a l l s u c c e s s r a t e f o r a l l 10 m i l l s o f 83%. A d d i t i o n a l b i o a s s a y s were done on samples from 5 m i l l s (A, B, G, I and J ) u s i n g t h e F e d e r a l T o x i c i t y s t a n d a r d (80% s u r v i v a l i n 65% e f f l u e n t o v e r 96 h r ) . D e t o x i f i c a t i o n s u c c e s s r a t e s on t h i s b a s i s r e a c h e d 94%, about 11% h i g h e r t h a n w i t h t h e more s t r i n g e n t MST t e s t i n 100% e f f l u e n t c o n c e n t r a t i o n . Among t h o s e samples w h i c h d i d n o t pass t h e t o x i c i t y t e s t s , sub-s t a n t i a l t o x i c i t y r e d u c t i o n was a c h i e v e d (MST >1000 m i n ) . I n most of t h e s e samples, f o a m i n g was s t i l l p o s s i b l e a f t e r 5-hr o f t r e a t m e n t . T h i s i n d i c a t e s t h a t i f l o n g e r t r e a t m e n t t i m e were g i v e n t o p e r m i t complete foam r e m o v a l and i f a l l samples were t e s t e d i n 65% e f f l u e n t , t h e y would have p a s s e d t h e f e d e r a l t o x i c i t y t e s t . I n a few i s o l a t e d i n s t a n c e s , a d e t o x i f i c a t i o n f a i l u r e c o u l d be t r a c e d t o b l a c k l i q u o r s p i l l s and b l e a c h p l a n t breakdowns. Under such 133 c o n d i t i o n s , t h e e f f l u e n t c o m p o s i t i o n w o u l d n o t be c o m p a t i b l e w i t h t h e e s t a b l i s h e d foam s e p a r a t i o n p r o c e s s and w o u l d p r o b a b l y r e q u i r e com-p l e t e l y d i f f e r e n t c o n d i t i o n s f o r d e t o x i f i c a t i o n . I n g e n e r a l , t h e r e s u l t s l e a d t o t h e c o n c l u s i o n t h a t t h e v a r i a b i l i t y o f wood f u r n i s h e s , p r o c e s s m o d i f i c a t i o n s , w a t e r usage and o t h e r f a c t o r s r e l a t i n g t o p u l p i n g and b l e a c h i n g do n o t s e r i o u s l y a f f e c t t h e amena-b i l i t y o f t h e e f f l u e n t t o d e t o x i f i c a t i o n by foam s e p a r a t i o n . However, t h e s e v a r i a t i o n s a f f e c t t h e t o x i c i t y l e v e l o f t h e e f f l u e n t and t h e r e b y a f f e c t t h e t r e a t m e n t c o n d i t i o n s r e q u i r e d . O v e r a l l , t h i s s a m p l i n g program has c o n f i r m e d t h e e f f e c t i v e n e s s and u n i v e r s a l a p p l i c a b i l i t y o f t h e foam s e p a r a t i o n p r o c e s s f o r d e t o x i f y i n g k r a f t whole m i l l e f f l u e n t . D. DETOXIFICATION RELIABILITY OF A FOAM SEPARATION PROCESS The c h a r a c t e r i s t i c s of p u l p m i l l e f f l u e n t s a r e n o t c o n s t a n t due t o t h e c o m p l e x i t y o f m i l l o p e r a t i o n , o c c a s i o n a l s p i l l s and b l e a c h i n g changes. F o r c o m m e r c i a l a p p l i c a t i o n a foam s e p a r a t i o n p r o c e s s must pr o d u c e e f f l u -e n t s w h i c h meet t o x i c i t y s t a n d a r d s a l l t h e t i m e on e f f l u e n t s o f e v e r -c h a n g i n g c h a r a c t e r i s t i c s . I n o r d e r t o a s s e s s t h e r e l i a b i l i t y o f t h e p r o c e s s , a 180 1 c a p a c i t y , c o n t i n u o u s f l o w , foam s e p a r a t i o n column was i n s t a l l e d i n M i l l F and o p e r a t e d c o n t i n u o u s l y o v e r a 63 day p e r i o d . The system was o p e r a t e d as a s i n g l e s t a g e column i n t h e s i m p l e mode t h r o u g h -out t h e s t u d y . The G/L r a t i o and g a s - l i q u i d i n t e r f a c i a l a r e a s were v a r i e d by c h a n g i n g t h e d e s i g n o f t h e a e r a t i o n system t o p r o v i d e d i f -f e r e n t b u b b l e s i z e s . Samples were t a k e n and b i o a s s a y e d d a i l y o n - s i t e . The o p e r a t i n g d a t a w i t h d i f f e r e n t a e r a t o r s and a e r a t i o n r a t e s a r e g i v e n i n A p p e n d i x V I a-c. The i n f l u e n t t o x i c i t y c o v e r e d a wide r a n g e , (MST = 0.8 - 24 h r ) and av e r a g e d 4 h r . The r e s u l t s o f d e t o x i f i c a t i o n under d i f f e r e n t p r o c e s s c o n d i t i o n s a r e summarized i n T a b l e 13. When t h e system was o p e r a t e d a t G/L o f 33 - 48 and a t 1.6 - 2.L h r s r e t e n t i o n t i m e , t h e c o r r e s p o n d i n g 2 g a s - l i q u i d i n t e r f a c i a l a r e a s (>40 m / l ) e s t i m a t e d by s i m p l e p h o t o g r a p h i c t e c h n i q u e exceeded t h e minimum r e q u i r e m e n t f o r e f f l u e n t s o f a v e r a g e d t o x i c i t y ( m i l l E o f F i g u r e 2 4 ) . D u r i n g t h e 28 days o f c o n t i n u o u s op-e r a t i o n , a l l samples met t h e t o x i c i t y s t a n d a r d 100% of t h e t i m e . As t h e G/L r a t i o was d e c r e a s e d t o t h e 8 - 1 2 ra n g e t h e i n t e r f a c i a l a r e a g e n e r -a t e d became o n l y m a r g i n a l l y s u f f i c i e n t . A t t h i s i n i t i a l l e v e l , t h e d e t o x i f i c a t i o n s u c c e s s r a t e dropped t o 75 and 63% i n d i c a t i n g t h a t t h e system was o p e r a t i n g under s u b - o p t i m a l c o n d i t i o n s . • Over t h e 63 days o f e l a p s e d o p e r a t i o n t i m e , i t has been documented t h a t i f adequate G/L r a t i o s , g a s - l i q u i d i n t e r f a c i a l a r e a s and r e t e n t i o n t i m e s were p r o v i d e d , c o n s i s t e n t d e t o x i f i c a t i o n o f e f f l u e n t s o f v a r y i n g c h a r a c t e r i s t i c s c o u l d be o b t a i n e d . However, adequate s a f e t y m a r g i n s i n g a s - l i q u i d i n t e r f a c i a l a r e a have t o be d e s i g n e d i n t o t h e sy s t e m , t o m a i n t a i n h i g h o p e r a t i n g r e l i a b i l i t y . E. MECHANISMS OF DETOXIFICATION Foam s e p a r a t i o n i n v o l v e s a d s o r p t i o n o f s u r f a c e a c t i v e m a t e r i a l s o n t o t h e g a s - l i q u i d i n t e r f a c e . D u r i n g t h e p r o g r e s s o f foam s e p a r a t i o n , s e v e r a l o t h e r mechanisms such as a i r s t r i p p i n g , v o l a t i l i z a t i o n , and TABLE 13 DETOXIFICATION RELIABILITY OF A SINGLE STAGE CONTINUOUS FOAM SEPARATION SYSTEM OVER 63 DAYS OF OPERATION O p e r a t i o n P e r i o d ( d a y s ) O p e r a t i n g C o n d i t i o n s G/L Gas-L i q u i d I n t e r f a c e G enerated ( m 2 / l ) I n f l u e n t T o x i c i t y (MST:hr) No. of Samples Taken *No. o f Samples D e t o x i -f i e d S u c c e s s Rate o f D e t o x i -f i c a t i o n A i r D i f f u s e r Gas Fl o w R a t e (1/min) L i q u i d F l o w Rate (1/min) R e t e n t i o n Time ( h r ) 12 65 u pore s i z e p l a s t i c d i s c s 65 1.5 2.1 48.0 72 3.0 12 12 100 16 65 M pore s i z e p l a s t i c d i s c s 60 1.8 1.6 33.0 49 3.0 17 17 100 24 25 u pore s i z e p l a s t i c d i s c s 45 3.1 1.0 12.5 42 8.0 24 18 75 11 <25 u pore s i z e c e r a m i c t u b e s 25 3.0 1.0 8.0 30 4.2 8 5 63 Note: A l l numbers i n d i c a t e d a r e mean v a l u e s o f a l l the samples t a k e n . O p e r a t i o n : M i l l F b l e a c h e d k r a f t w h o l e m i l l e f f l u e n t . C o n t i n u o u s o n - s i t e s t u d y 180 1 column Treatment pH = 8.0 * A s s e s s e d f o r F e d e r a l t o x i c i t y s t a n d a r d : o v e r 80% o f f i s h s u r v i v e d i n 65% e f f l u e n t o v e r 96 h r . 136 o x i d a t i o n o f t o x i c a n t s c o u l d a l s o o c c u r and c o n t r i b u t e t o t h e r e d u c t i o n of t o x i c i t y . The r e l a t i v e i m p o r t a n c e of t h e s e v a r i o u s mechanisms was i n v e s t i g a t e d i n a s e r i e s o f e x p e r i m e n t s d e s i g n e d t o i d e n t i f y t h e m a j o r mechanisms c o n t r o l l i n g t h e d e t o x i f i c a t i o n p r o c e s s and t h e p r o b l e m s a s -s o c i a t e d w i t h subsequent d i s p o s a l o f foam. The raw e f f l u e n t s were t r e a t e d under c o n d i t i o n s where t h e e f f l u e n t would be d e t o x i f i e d . P r e -l i m i n a r y e x p e r i m e n t s examined t h e e f f e c t o f gas used and t h e t o x i c i t y o f t h e v a r i o u s f r a c t i o n c o l l e c t e d d u r i n g foam s e p a r a t i o n . Subsequent e x p e r i m e n t s d e t e r m i n e d t h e r e l a t i v e c o n t r i b u t i o n o f t h e v a r i o u s mech-anisms and t h e c o n c e n t r a t i o n of t o x i c s u r f a c e a c t i v e m a t e r i a l s i n t h e foam. 1. E f f e c t o f Gas on D e t o x i f i c a t i o n The t i m e s r e q u i r e d t o d e t o x i f y two samples o f b l e a c h e d k r a f t w h o l e -m i l l e f f l u e n t w i t h i n f l u e n t MST v a l u e s o f 222 and 360 min were d e t e r -mined on p a r a l l e l systems u s i n g a i r , oxygen and n i t r o g e n as t h e foam p r o d u c i n g g a s e s . A f t e r 1-hr o f t r e a t m e n t a l l t h e f oamable m a t e r i a l s had been removed. T a b l e 14 shows t h a t a l l samples were d e t o x i f i e d r e g a r d -l e s s o f t h e gas used f o r foam s e p a r a t i o n i n d i c a t i n g t h a t o x i d a t i o n i s o f m i n o r s i g n i f i c a n c e . When th e foam f r a c t i o n was r e t u r n e d t o t h e t r e a t e d e f f l u e n t , t h e r e c o n s t i t u t e d e f f l u e n t became t o x i c w i t h MST r a n g i n g f r o m 281 - 430 min. The l o s s of t o x i c i t y was s m a l l and c o u l d be due t o some c h e m i c a l d e g r a d a t i o n of t o x i c a n t s o r t o s t r i p p i n g . S i n c e t h e r e c o n -s t i t u t e d e f f l u e n t s were t o x i c a g a i n and t h e v a r i a t i o n s i n MST were i n s i g n i f i c a n t , s e p a r a t i o n of foam was presumed t o be t h e major r e a s o n TABLE 14 FOAM SEPARATION OF BLEACHED KRAFT MILL EFFLUENT WITH DIFFERENT GASSES Gas T o x i c i t y (MST i n min) U n t r e a t e d E f f l u e n t T r e a t e d E f f l u e n t R e c o n s t i t u t e d E f f l u e n t T r e a t e d E f f l u e n t + Foam F r a c t . T r e a t e d E f f l u e n t + Foam F r a c t . + Cond. Vapor F r a c t A i r 222 NT 281 208 360 NT 400 400 Oxygen 222 NT 317 350 360 NT 380 380 N i t r o g e n 222 NT 317 337 360 NT 430 380 NT - Non t o x i c (100% s u r v i v a l o f f i s h i n 100% e f f l u e n t f o r 24 h r ) 138 f o r t o x i c i t y r e d u c t i o n . W i t h t h e a d d i t i o n o f t h e condensed v a p o r f r a c t i o n t o t h e r e c o n s t i t u t e d e f f l u e n t , t h e e f f l u e n t s became s l i g h t l y more t o x i c (208 - 400 min) and were a l s o n o t a f f e c t e d by t h e gas s p e c i e s u s e d . These v a r i a t i o n s , however may be a t t r i b u t e d p a r t i a l l y t o t h e e r r o r s o f t h e b i o a s s a y t e c h n i q u e employed. 2. R e l a t i v e C o n t r i b u t i o n o f Foam S e p a r a t i o n , V o l a t i z a t i o n and O t h e r  Mechanisms t o D e t o x i f i c a t i o n The r e l a t i v e c o n t r i b u t i o n o f v a r i o u s mechanisms t o d e t o x i f i c a t i o n ( S e c t i o n IV-E) was d e t e r m i n e d f o r 20 samples t a k e n f r o m two B.C. m i l l s and one O n t a r i o m i l l . The samples were s u b j e c t e d t o foam s e p a r a t i o n u n t i l d e t o x i f i e d . The c o n d i t i o n s o f t r e a t m e n t f o r i n d i v i d u a l m i l l s and th e t o x i c i t i e s o f v a r i o u s r e c o n s t i t u t e d e f f l u e n t s a r e g i v e n i n A p p e n d i x V I I a-c. The r e s u l t s a r e sumamrized i n T a b l e 15. A l t h o u g h t h e r e l a t i v e c o n t r i b u t i o n o f v a r i o u s d e t o x i f i c a t i o n mech-anisms v a r i e d from sample t o sample, i n g e n e r a l t h e b u l k o f t o x i c i t y was c o n c e n t r a t e d i n t h e foam. Foam s e p a r a t i o n r e s p o n s i b l e f o r an a v e r a g e o f 77.5% o f t o x i c i t y r e d u c t i o n , r a n g i n g from 60 - 90% and 85 - 95% f o r m i l l F, G and I samples r e s p e c t i v e l y . I n k r a f t m i l l e f f l u e n t , t h e c o n c e n -t r a t i o n s o f t o x i c s u r f a c e a c t i v e t o x i c a n t s ( T a b l e 2) seldom exceed 20 mg/1 and y e t c o p i o u s foaming i s an i n h e r e n t c h a r a c t e r i s t i c o f k r a f t m i l l e f f l u e n t . I t would appear t h a t t h e foam i s produced by s u r f a c t a n t s i n th e e f f l u e n t o f w h i c h t h e t o x i c s u r f a c t a n t s a r e p r o b a b l y o n l y a mi n o r f r a c t i o n . TABLE 15 RELATIVE CONTRIBUTION TO DETOXIFICATION BY VARIOUS MECHANISMS No. o f I n i t i a l Foam Removed To D e t o x i f i c a t i o n % (v/v) R e l a t i v e C o n t r i b u t i o n to D e t o x i f i c a t i o n by (%) MILL Samples A n a l y z e d T o x i c i t y MST (min) Foam S e p a r a t i o n V o l a t i l i z a t i o n Unknown Mechanisms F 10 Range 70 - 450 3.1 - 9.1 60 - 95 1 - 13 3 - 39 Mean ± SD 307 ± 135 6.5 ± 9.3 71 ± 12 5 ± 4 24 ± 12 G 5 Range 30 - 120 7.9 - 20.8 70 - 90 0 - 14 10 - 29 Mean + SD 58 ± 36 15.7 ± 5.8 79 ± 9 4.6 ± 5 17.2 ± 11 I 5 Range 60 - 105 10.0 - 25.1 85 - 95 5 - 9 0 - 8 Mean ± SD 78 ± 17 18.2 ± 5.8 89 ± 4 7 ± 2 4 ± 3 OVERALL 20 Range 30 - 450 3.1 - 25.1 60 - 9 5 0 - 14 0 - 39 Mean ± SD 188 ± 155 12.2 ± 7.1 77.5 ± 13.0 5.4 ± 4.0 17 ± 1 4 . 0 140 Gas s t r i p p i n g of t o x i c m a t e r i a l s ( v o l a t i l i z a t i o n ) w h i c h removed o n l y 5.4% o f t h e t o x i c i t y i s o f m i n o r i m p o r t a n c e . I t has been r e p o r t e d (105) however, t h a t i n a f r e s h e f f l u e n t v o l a t i l e compounds a r e m a j o r t o x i c i t y c o n t r i b u t o r s . C o n c e i v a b l y , t h e s e v o l a t i l e compounds c o u l d have escaped d u r i n g shipment and t h e 1-day o f a v e r a g e s t o r a g e t i m e b e f o r e p r o c e s s i n g . A p p r o x i m a t e l y 17% o f t h e t o x i c i t y , removed by foam f r a c t i o n a t i o n , c o u l d n o t be a c c o u n t e d f o r i n r e c o n s t i t u t e d t r e a t e d e f f l u e n t s . P r e -sumably some form o f c h e m i c a l change i s p r i m a r i l y r e s p o n s i b l e . Because t h e t o x i c c o n s t i t u e n t s c o n s t i t u t e a r e l a t i v e l y m i n u t e f r a c t i o n on a w e i g h t b a s i s , i t i s d i f f i c u l t t o r u l e out v i r t u a l l y any p o s s i b i l i t i e s . F o r example, m o l e c u l a r r e a r r a n g e m e n t o f t h e r e s i n a c i d , a b i e t i c a c i d , t o t h e more t h e r m o d y n a m i c a l l y s t a b l e d e h y d r o a b i e t i c a c i d , would r e s u l t i n a d i m i n u t i o n o f t o x i c i t y (18, 20, 1 06 ) . O x i d a t i o n o f u n s a t u r a t e d f a t t y a c i d t o t h e c o r r e s p o n d i n g oxy o r p e r o x y f o r m s , presumably a l s o would a c h i e v e t h e same r e s u l t . However, b o t h t o x i c m o i e t i e s , i . e . r e s i n and u n s a t u r a t e d f a t t y a c i d s , p r e sumably would c o l l e c t i n t h e foam. More r e c e n t l y , i t has been shown t h a t t h e t o x i c i t y o f c h l o r o l i g n i n , t h e major o f f e n d e r i n a c i d b l e a c h e f f l u e n t d e c r e a s e d q u i t e s u b s t a n t i a l l y when t h e s o l u t i o n was made a l k a l i n e ( 9 4 ) . C o m b i n a t i o n of a l l t h e s e f a c t o r s i s b e l i e v e d t o be r e s p o n s i b l e f o r t h e 17% l o s s of t o x i c i t y . A l t h o u g h b i o -a s s a y v a l u e s a r e l e s s a c c u r a t e t h a n most c h e m i c a l a s s a y s , a c u m u l a t i v e e r r o r i n b i o a s s a y p r o c e d u r e s would be e x p e c t e d t o show an i n c r e a s e i n t o x i c i t y f o r some r e c o n s t i t u t e d samples. T h i s d i d n o t o c c u r w i t h i n t h e l i m i t s o f v a r i a b i l i t y i n t h e t o x i c i t y t e s t . 141 I n c o n c l u s i o n , o v e r a l l r e s u l t s s u g g e s t t h a t foam f r a c t i o n a t i o n , i . e . c o n c e n t r a t i o n o f t o x i c i t y i n t h e foam, i s t h e major d e t o x i f i c a t i o n mechanism and a c c o u n t s f o r about 77% o f t o x i c i t y r e m o v a l . 3. C u m u l a t i o n o f R e s i n A c i d s i n Foam E i g h t samples were a n a l y z e d f o r r e s i n a c i d s c o n t e n t b e f o r e and a f t e r foam s e p a r a t i o n ( T a b l e 1 6 ) . The a v e r a g e r e s i n a c i d s c o n t e n t o f t h e raw e f f l u e n t s , h a v i n g i n i t i a l MSTs o f 100 - 600 min, was 3.4 mg/1. There appeared t o be no d i r e c t r e l a t i o n between t h e r e s i n a c i d s c o n -c e n t r a t i o n and t h e t o x i c i t y o f t h e e f f l u e n t . T h i s , p r o b a b l y i s due t o t h e p r e s e n c e o f many o t h e r t o x i c a n t s w h i c h a l s o c o n t r i b u t e t o t h e t o x -i c i t y o f t h e e f f l u e n t . A f t e r a sample was d e t o x i f i e d by foam s e p a r -a t i o n , a 60% r e d u c t i o n i n r e s i n a c i d s was a c h i e v e d ; t h e a v e r a g e r e s i n a c i d s c o n c e n t r a t i o n was r e d u c e d t o 1.4 mg/1. The r e s i n a c i d s c o n t e n t s o f t h e foams were n o t a n a l y z e d . There i s no doubt however, t h a t t h e r e s i n were t r a n s f e r r e d t o g e t h e r w i t h many o t h e r s u r f a c e a c t i v e m a t e r i a l s i n t o t h e foam f r a c t i o n . A r e c e n t a n a l y s i s o f a foam-scum sample ob-t a i n e d f r o m a k r a f t m i l l a e r a t e d l a g o o n i n d i c a t e s t h a t r e s i n a c i d s had ac c u m u l a t e d t o c o n c e n t r a t i o n s o f up t o 9000 mg/1 ( 4 5 ) . T h i s foam sample a l s o c o n t a i n e d up t o 6000 mg/1 o f o r g a n i c s u b s t a n c e s i n c l u d i n g a l c o h o l s , a l d e h y d e s , and k e t o n e d e r i v a t i v e s . The l e t h a l c o n c e n t r a t i o n (LC50) o f t h e s e o r g a n i c s i s between 2 - 1 3 mg/1. TABLE 16 EFFECT OF FOAM SEPARATION ON RESIN ACIDS REMOVAL TOXICITY (MST) RESIN ACIDS EFFLUENT Influent (min) Treated Effluent . (min) Influent (mg/1) Treated Effluent (mg/1) % Removed 255 NT 2.8 1.0 64.3 240 NT 2.6 1.1 57.7 M i l l F 160 NT 3.2 1.2 62.5 120 NT 5.1 1.9 62.7 100 NT 3.3 1.7 48.5 600 NT 3.4 1.4 58.8 M i l l A 600 NT 3.6 1.2 66.7 500 NT 3.0 1.0 66.7 No of Samples 8 8 8 8 8 Mean ± SD 322±211 - 3.4±0.8 1.3±0.3 61±6 F. COMBINED DETOXIFICATION AND FIBRE REMOVAL BY FOAM SEPARATION PROCESS There i s a s i m i l a r i t y between t h e mechanisms o f f r a c t i o n a t i o n o f s o l u b i l i z e d components and f l o t a t i o n o f suspended p a r t i c l e s by fo a m i n g . I n b o t h p r o c e s s e s , a i r b u b b l e s a r e a l l o w e d , t o r i s e t h r o u g h t h e s o l u t i o n and produce a f o a m - f r o t h on t h e l i q u i d s u r f a c e . The f r a c t i o n a t i o n p r o -c e s s i n v o l v e s a d s o r p t i o n o f s u r f a c e a c t i v e t o x i c s u b s t a n c e s a t t h e g a s -l i q u i d i n t e r f a c e . The f l o t a t i o n p r o c e s s a t t r a c t s t h e h y d r o p h o b i c s u s -pended p a r t i c l e s t o t h e b u b b l e s and s e p a r a t e s them f r o m t h e s o l u t i o n by f l o a t i n g them t o t h e s u r f a c e ( 1 0 8 ) . Foam f r a c t i o n a t i o n p r o c e s s i f p r o p e r l y o p e r a t e d c o u l d be made c o m p a t i b l e w i t h c o n c u r r e n t suspended s o l i d s r e m o v a l . At p r e s e n t , t h e p u l p and paper i n d u s t r y i s r e q u i r e d t o r e d u c e t h e suspended s o l i d s l e v e l i n t h e i r waste d i s c h a r g e s t o < 50 mg/1 p r i o r t o d i s c h a r g e . I n s t a l l a t i o n o f a c l a r i f i e r i s n e c e s s a r y . I f foam s e p a r -a t i o n were adopted f o r c o m m e r c i a l a p p l i c a t i o n , combined t o x i c i t y -suspended s o l i d s r e m o v a l i n one p r o c e s s would be of i n t e r e s t . S i n c e t h e suspended s o l i d s i n k r a f t m i l l e f f l u e n t c o n s i s t o f l a r g e amounts o f f i b r o u s m a t e r i a l s and because o f economics any foam s e p a r a t i o n w o u l d most l i k e l y be o p e r a t e d u s i n g a d i s p e r s e d a i r foam g e n e r a t i o n s y s t e m , t h i s s t u d y was u n d e r t a k e n w i t h p a r t i c u l a r emphasis on f i b r e r e m o v a l by a d i s p e r s e d a i r foam s e p a r a t i o n system. F o r c o m p a r i s o n , a d i s s o l v e d a i r system was a l s o o p e r a t e d . 1. D i s p e r s e d A i r System 144 Known amounts o f f i b r e were added t o an e f f l u e n t w h i c h had an o r i g i n a l suspended s o l i d s l e v e l o f 116 mg/1. T h i s gave a s e r i e s o f e f f l u e n t samples w i t h suspended s o l i d s r a n g i n g f r o m 116 t o 738 mg/1. These e f f l u e n t samples were foam s e p a r a t e d f o r r e m o v a l of suspended s o l i d s under t h e same c o n d i t i o n s w h i c h w o u l d d e t o x i f y t h e e f f l u e n t . Removal of f i b r e s a f t e r 1-hr of t r e a t m e n t t i m e ranged from 19% t o 62% ( T a b l e 1 7 ) . I n g e n e r a l when t h e suspended s o l i d s l e v e l was below 200 mg/1, a maximum of 39% r e m o v a l was a c h i e v e d . R e s i d u a l SS l e v e l s s t i l l ranged from 94 - 108 mg/1 and c o u l d n o t meet t h e e f f l u e n t d i s -c h a r g e g u i d e l i n e s . A t h i g h e r suspended s o l i d s l e v e l s (260 - 739 mg/1), t h e d e g r e e o f r e m o v a l improved t o about 60%; however, t h e suspended s o l i d s r e m a i n i n g i n t h e e f f l u e n t i n c r e a s e d up t o 380 mg/1. I n T a b l e 18, t h e r e s u l t s o f s i m i l a r e x p e r i m e n t s u n d e r t a k e n i n t h e f i e l d u s i n g v a r i o u s t y p e s o f a i r d i s p e r s i o n media and on f r e s h p r i m a r y c l a r i f i e d e f f l u e n t s a r e shown. The b u b b l e d i a m e t e r produced ranged from 0.75 - 3 mm d i a m e t e r . However foam s e p a r a t i o n y i e l d e d s i m i l a r low p e r -c e n t a g e s o f SS r e m o v a l . Suspended s o l i d s o f t h e i n f l u e n t r a n g e d f r o m 87 t o 121 mg/1; t h e y were r e d u c e d t o 51 - 83 mg/1 and a v e r a g e d 65 mg/1 a f t e r 1-hr t r e a t m e n t ; i . e . a r e d u c t i o n of 21 - 55% (38% a v e r a g e r e -d u c t i o n ) . A l t h o u g h t h e r e m o v a l of suspended s o l i d s was s u b s t a n t i a l , t h e f i n a l c o n c e n t r a t i o n s t i l l exceeded t h e d i s c h a r g e d g u i d e l i n e . 145 TABLE 17 REMOVAL OF FIBROUS SUSPENDED SOLIDS AT DIFFERENT LOADINGS BY A DISPERSED AIR SYSTEM Experiment Suspended S o l i d s (mg/1) B e f o r e Treatment A f t e r Treatment % Removal 1 116 94 19 2 145 108 26 3 162 105 35 4 174 106 39 5 260 166 36 6 486 183 62 7 498 210 58 8 608 380 46 9 738 306 59 O p e r a t i n g C o n d i t i o n s : B a t c h o p e r a t i o n Volume: 4 l i t r e pH: 8 • A i r D i f f u s e r : 45u pore s i z e s i n t e r e d g l a s s R e t e n t i o n Time: 1 h r G/L: 7 T o x i c i t y (MST): B e f o r e Treatment = 300 min A f t e r Treatment = N o n - t o x i c TABLE 18 REMOVAL OF SUSPENDED SOLIDS BY A DISPERSED AIR, FOAM SEPARATION SYSTEM AT MILL SITE A i r D i s p e r s i o n System E s t i m a t e d Bubble S i z e Treatment C o n d i t i o n s - Suspended S o l i d s (mg/1) (mm) Time ( h r ) G/L I n i t i a l F i n a l % Removal Four 5 i n c h d i a m e t e r p l a s t i c d i s c s (25u pore s i z e ) 3 1 1 7 1.4 115 87 75 56 35 36 Four 1 f t l e n g t h 3 i n c h d i a m e t e r c e r a m i c tubes (<25y p o r o s i t y ) 1 0.5 1 : i 6 6 12 87 115 115 56 57 51 35 50 55 Seven 1 f t l o n g 1/2 i n c h d i a m e t e r h e l i c a l a e r a t o r 0.75 I 1.5 1.4 2.1 121 96 83 76 31 21 Range Mean S t d . Dev. 87-121 105 14.6 51-83 64.9 12.7 21-55 37.7 11.5 B a t c h O p e r a t i o n Volume: 180 l i t r e pH: 8.0 E f f l u e n t : B l e a c h e d k r a f t w h o l e m i l l e f f l u e n t B e f o r e t r e a t m e n t : MST = 0.8 - 2 h r A f t e r t r e a t m e n t : N o n t o x i c . 147 The c a p a c i t y o f t h e d i s p e r s e d a i r foam s e p a r a t i o n p r o c e s s f o r rem o v i n g f i b r e depends on t h e foaming c h a r a c t e r i s t i c s o f t h e i n f l u e n t ; 1. e., s u r f a c t a n t c o n c e n t r a t i o n . I n an e x p e r i m e n t w i t h 500 mg/1 f i b r e i n s u s p e n s i o n , a r e a s o n a b l e r e l a t i o n s h i p between i n i t i a l f o a m i n g t e n d e n c y and p e r c e n t f i b r e r e m o v a l under a g i v e n s e t of o p e r a t i n g c o n d i t i o n s was o b s e r v e d ( F i g u r e 36). As the 1 foaming tendency ( E t ) i n c r e a s e d t o 5.0 m i n w h i c h i s t y p i c a l f o r b l e a c h e d k r a f t w h o l e m i l l e f f l u e n t s , t h e r e m o v a l o f suspended s o l i d s improved t o 43%. B u t , as i n t h e p r e v i o u s e x p e r i m e n t s , r e s i d u a l f i b r e l e v e l s i n t h e t r e a t e d e f f l u e n t remained h i g h (> 250 mg/1) i n t h e t r e a t e d e f f l u e n t . G e n e r a l l y , f i b r o u s suspended m a t t e r can be f l o a t e d by a d i s p e r s e d a i r system, as l o n g as some foaming tendency r e m a i n s i n t h e s u b s t r a t e . When a l l foaming t e n d e n c y i s removed, f u r t h e r r e m o v a l o f f i b r e becomes i m p o s s i b l e . I n c o n c l u s i o n , foam s e p a r a t i o n by a d i s p e r s e d a i r system can remove a s u b s t a n t i a l amount o f f i b r e s d u r i n g t h e d e t o x i f i c a t i o n p r o c e s s . However, t h e e x t e n t o f f i b r e r e m o v a l depends on t h e foaming tendency and t h e suspended s o l i d s l e v e l o f t h e was t e . S u f f i c i e n t r e d u c t i o n o f s u s -pended s o l i d s t o meet e f f l u e n t d i s c h a r g e g u i d e l i n e s was n o t a c h i e v e d i n any i n s t a n c e . 2. . D i s s o l v e d A i r F l o t a t i o n System I t has been shown i n S e c t i o n B-5 t h a t d i s s o l v e d a i r f l o t a t i o n can a l s o be used t o c r e a t e foam f o r t h e p u r p o s e of s e p a r a t i n g t o x i c i t y f r o m k r a f t m i l l e f f l u e n t s . T h e r e f o r e , d i s s o l v e d a i r f l o t a t i o n systems may be F i g u r e 36 EFFECT OF FOAMING TENDENCY ON SUSPENDED SOLIDS REMOVAL BY A DISPERSED AIR FOAM SEPARATION SYSTEM 149 more s u i t a b l e f o r c o m b i n i n g p r i m a r y c l a r i f i c a t i o n w i t h d e t o x i f i c a t i o n t h a n d i s p e r s e d a i r foam s e p a r a t i o n s y s t e m s . A s e r i e s o f samples w i t h suspended s o l i d s r a n g i n g f r o m 70 - 450 mg/1 were s u b j e c t e d t o d i s s o l v e d a i r f l o t a t i o n . The r e s u l t s o f s u s -pended s o l i d s r e m o v a l a r e p r e s e n t e d i n T a b l e 19. D u r i n g t h e f i r s t p r e s s u r i z a t i o n and f l o t a t i o n c y c l e , suspended s o l i d s c o u l d be r e d u c e d t o l e s s t h a n 56 mg/1 r e g a r d l e s s o f i n i t i a l SS l e v e l ; t h e r e d u c t i o n s ranged from 53 - 88%. F u r t h e r t r e a t m e n t o f t h e c l a r i f i e d e f f l u e n t by a second f l o t a t i o n c y c l e p r o duced more b u b b l e s and i n t e r f a c i a l a r e a . However, o n l y m a r g i n a l r e d u c t i o n i n r e s i d u a l SS l e v e l s was a c h i e v e d ; i . e . a second c y c l e i s u s e f u l o n l y f o r r e d u c i n g t o x i c i t y . O v e r a l l , r e m o v a l o f suspended s o l i d s by d i s s o l v e d a i r f l o t a t i o n was f a r more e f f e c t i v e and r e l i a b l e t h a n by t h e d i s p e r s e d a i r foam s e p a r a t i o n . The d i s s o l v e d a i r f l o t a t i o n a p p l i e d i n t h i s e x p e r i m e n t a l s o d e t o x i f i e d t h e e f f l u e n t d u r i n g t h e p r e s s u r i z a t i o n and f l o t a t i o n p r o c e s s . I n F i g u r e 37, t h e r e d u c t i o n of t o x i c i t y i s p l o t t e d a g a i n s t g a s - l i q u i d r a t i o , p r e s s u r i z a t i o n c y c l e s and i n t e r f a c i a l a r e a a p p l i e d . I n t h e f i r s t c y c l e , t o x i c i t y was r e d u c e d from an MST o f 150 -200 min t o 1000 - 1200 min. I n t h e second and t h i r d 2 c y c l e , c o r r e s p o n d i n g t o 10 and 15 m / l o f t o t a l i n t e r f a c i a l a r e a , e f f l u -e n t s were c o m p l e t e l y d e t o x i f i e d . The number o f p r e s s u r i z a t i o n c y c l e s needed f o r d e t o x i f i c a t i o n i s r e l a t e d t o t h e i n f l u e n t t o x i c i t y and g a s -l i q u i d i n t e r f a c e r e q u i r e m e n t (Appendix V I I I ) . P r e l i m i n a r y r e s u l t s c l e a r l y i n d i c a t e t h a t t h i s p r o c e s s i s c a p a b l e o f r e d u c i n g suspended s o l i d s t o low l e v e l s and of removing t o x i c i t y i n t h e same o p e r a t i o n . TABLE 19 REMOVAL OF FIBROUS SUSPENDED SOLIDS FROM BLEACHED KRAFT WHOLEMILL EFFLUENT BY DISSOLVED AIR FLOTATION Suspended S o l i d s i n E f f l u e n t (mg/1) Suspended S o l i d s i n E f f l u e n t A f t e r 1 s t C y c l e 2nd C y c l e (mg/1) % Removed (mg/1) % Removed 70 33 53 . 27 61 106 33 69 28 74 141 56 60 43 70 215 50 77 50 77 334 54 84 57 83 450 55 88 55 88 O p e r a t i n g C o n d i t i o n s : P r e s s u r e : 40 p s i g 5 min p r e s s u r i z a t i o n 10 min f l o t a t i o n T o x i c i t y : I n i t i a l MST: 350 min 1 s t C y c l e : 1440 min 2nd C y c l e : Non-Toxic F i g u r e 37 DETOXIFICATION OF BLEACHED KRAFT MILL EFFLUENT BY A DISSOLVED AIR SYSTEM 0 1 0.05 1 0.10 0.15 0.20 0.25 1 0.30 0 1 1 1 1 2 3 No. OF CYCLES 1 1 4 1 Ln r—' 0 4 8 12 n 16 GAS-LIQUID, m2/L interface 20 152 However, t h e energy r e q u i r e m e n t s f o r p r o d u c i n g i n t e r f a c i a l a r e a by a d i s s o l v e d a i r s y s t e m p r o b a b l y would be t o o h i g h compared t o d i s p e r s e d a i r system. G.' BENEFICIAL SIDE EFFECTS OF FOAM SEPARATION PROCESS Other t h a n d e t o x i f i c a t i o n , foam s e p a r a t i o n c o u l d e f f e c t r e m o v a l o f a l a r g e number of o t h e r p o l l u t a n t s . I n t h e c o u r s e o f t h i s s t u d y , numer-ous samples were t a k e n f r o m b a t c h and c o n t i n u o u s r u n s and a n a l y z e d f o r s e v e r a l p o l l u t i o n p a r a m e t e r s . Some r e s u l t s have been p r e s e n t e d i n e a r l i e r s e c t i o n s . 1. R e s i n A c i d Removal As documented e a r l i e r i n T a b l e 16, t h e r e s i n a c i d c o n t e n t o f t h e t r e a t e d e f f l u e n t ranged from 2.6 - 5.1 mg/1 and av e r a g e d 3.4 mg/1. A f t e r foam s e p a r a t i o n , r e s i n a c i d c o n t e n t was r e d u c e d t o 1 - 1.9 mg/1 and a v e r a g e d 1.3 mg/1. The aver a g e r e s i n a c i d r e m o v a l was 62%. S i n c e t h e l e t h a l c o n c e n t r a t i o n o f r e s i n a c i d i s i n t h e range o f 1 - 2 mg/1, t h e r e s u l t s o f t h i s a n a l y s i s p a r t l y e x p l a i n t h e mechanism o f d e t o x i f i -c a t i o n . 2. Suspended S o l i d s Removal The e f f e c t o f foam s e p a r a t i o n on suspended s o l i d s r e m o v a l has been c o v e r e d i n S e c t i o n F. A d i s s o l v e d a i r system i s more e f f e c t i v e t h a n a d i s p e r s e d a i r system. Removal o f suspended s o l i d s by a d i s p e r s e d a i r sys t e m ranged from 19 - 62% ( T a b l e 17 and 18) and depended on foaming 153 t e n d e n c y and i n i t i a l suspended s o l i d s c o n c e n t r a t i o n . However, w i t h a more s o p h i s t i c a t e d d i s s o l v e d a i r s y s t e m , suspended s o l i d s were r e d u c e d t o 52 - 88% ( T a b l e 19) and met t h e e f f l u e n t d i s c h a r g e g u i d e l i n e s . 3. BOD5 and TOC Removal Among e i g h t samples a n a l y z e d ( T a b l e 20) foam s e p a r a t i o n r e d u c e d t h e BOD,, from an aver a g e o f 170 mg/1 (range = 70 - 278 mg/1) t o 150 mg/1, a 12% r e d u c t i o n . The r e d u c t i o n o f t o t a l o r g a n i c c a r b o n a v e r a g e d 11% ( f r o m 317 t o 285 mg/1). The BOD,, ( o r TOC) removed d u r i n g foam s e p a r a t i o n p r o c e s s a ppears t o be i n s i g n i f i c a n t and a g r e e s w i t h p u b l i s h e d d a t a (37, 42). 4. C o l o r Removal The r e s u l t s o f c o l o r r e m o v a l t r i a l s a r e shown i n T a b l e 21. The c o l o r was re d u c e d from an i n i t i a l v a l u e o f 3540 - 5510 t o 2990 - 4960 u n i t s and a v e r a g e 12.3% r e m o v a l . The r e d u c t i o n o f c o l o r was p r o b a b l y caused by p a r t i a l r e m o v a l o f t u r b i d i t y as a r e s u l t o f suspended s o l i d s r e m o v a l . The r e d u c t i o n s a r e t o o s m a l l t o have any p r a c t i c a l s i g n i f i -c a n ce. 5. Foaming Tendency Removal The foaming tendency o f i n d u s t r i a l e f f l u e n t s , p a r t i c u l a r l y p u l p m i l l e f f l u e n t s i s a e s t h e t i c a l l y , an u n d e s i r a b l e c h a r a c t e r i s t i c . D u r i n g t h e p r o c e s s o f d e t o x i f i c a t i o n , t h e foaming tendency (E ) was r e d u c e d TABLE 20 B0D 5 AND TOC REDUCTION BY FOAM SEPARATION B e f o r e Treatment A f t e r Treatment % Removal BOD5,ppm TOC,ppm BOD5,ppm T0C,ppm BOD5 TOC 205 449 184 395 10.2 12.0 130 317 110 288 15.3 9.1 220 573 195 535 16.8 6.6 125 195 115 164 8.0 15.9 160 340 150 325 6.2 4.4 170 185 160 167 5.8 9.7 278 293 230 244 17.2 16.7 70 190 58 165 17.1 13.1 P r o c e s s C o n d i t i o n s : 4 1 b a t c h system 500 ml/min a e r a t i o n pH = 9.5 Treatment f i n e : 60 min. TABLE 21 COLOUR REMOVAL BY CONTINUOUS FOAM SEPARATION SYSTEM C o l o u r o f . A Feed Stream (APHA U n i t s ) G/L C o l o u r o f E f f l u e n t Stream (APHA U n i t s ) % Removal 3540 0.83 3230 8.7 0.83 2990 15.5 0.83 3190 9.8 0.83 3310 6.5 0.83 3230 8.7 5510 2.5 4170 24.3 2.5 4330 21.4 2.5 4720 14.3 5310 2.5 4960 6.6 2.5 4720 11.1 2.5 4890 7.9 Av •. 12. 3 M i l l A whole m i l l e f f l u e n t O p e r a t i o n : 4 1 c o n t i n u o u s f l o w system R e t e n t i o n t i m e : 30 min. s u b s t a n t i a l l y . F i g u r e 38 shows an example of t h e e f f e c t o f foam s e p -a r a t i o n on foaming tendency d u r i n g l a b o r a t o r y b a t c h t r e a t m e n t f o r t o x -i c i t y r e m o v a l . A sample w i t h an i n i t i a l MST v a l u e o f 240 min c o u l d be d e t o x i f i e d w i t h i n 20 min o f t r e a t m e n t . D u r i n g t h e same p e r i o d , t h e foaming t e n d -ency o f t h e e f f l u e n t d e c r e a s e d f r o m an i n i t i a l v a l u e o f E = 6.0 m i n t o 3 min; and a f t e r 30 min o f t r e a t m e n t i t was r e d u c e d t o E = 1.0 min. t h i s same p a t t e r n o f foaming t e n d e n c y r e d u c i o n was o b s e r v e d w i t h a l l samples examined. As A p p e n d i c e s IX a-b and T a b l e 22 i n d i c a t e , t h e foam- 1 i n g t e ndency o f raw m i l l e f f l u e n t s ranged f r o m E = 0.9 t o E = 6.0 min. A f t e r t o x i c i t y was removed by foam s e p a r a t i o n , t h e foaming tendency i n -v a r i a b l y was l e s s t h a n 1.0 min. At t h i s l e v e l , foams were u n s t a b l e and c o l l a p s e d r a p i d l y . D u r i n g c o n t i n u o u s o p e r a t i o n , t h e foami n g tendency o f t h e t r e a t e d e f f l u e n t s d i s c h a r g e d was s l i g h t l y h i g h e r t h a n t h o s e t r e a t e d by b a t c h system. F i g u r e 39 shows t h a t a t s t e a d y s t a t e o p e r a t i o n , t h e foaming t e n d e n c y was r e d u c e d from-2.5-6 min t o 0.8-1 min. H. TREATMENT OF FOAM I . Foam C h a r a c t e r i s t i c s The q u a l i t y o f foam d i s c h a r g e d from a foaming system i s d e t e r m i n e d by a number o f o p e r a t i n g p a r a m e t e r s s u c h as a i r f l o w , b u b b l e s i z e , and foam h e i g h t . I n A p p e n d i c e s X-a and X-b t h e d a i l y foam f l o w r a t e s o f F i g u r e 38 REDUCTION OF FOAMING TENDENCY DURING TOXICITY REMOVAL N T IT 1600 •- 12001 H CO 2 t 800| o X o 400 Toxicity Batch operation pH : 9,5 Aeration '. 500 ml/min Air dispenser .' 45p pore size v Foaming tendency o^, o 10 20 30 TREATMENT TIME, min. 40 50 o a z UJ o z 2 2 8 TABLE 22 EFFECT OF FOAM SEPARATION ON FOAMING TENDENCY REDUCTION Foam Separation System Source of Samples No. of Samples TOXICITY (MST:hr) FOAMING TENDENCY,min Influent (mean±S.D.) Treated Effluent Influent (mean+S.D.; Treated Effluent (mean) BATCH OPERATION Vol: 4 l i t r e Gas Disperser: 45 u sintered glass pH: 7.0 Aeration: 500 ml/min Treatment time: 0 ?S-9 h r M i l l B 11 8 ± 4.8 (Range: 2.5-18) Nontoxic 3 ± 1.6 (Range: 0.5-3.0) 1.0 BATCH OPERATION Vol: 4 l i t r e Gas Disperser: 45 u sintered glass pH: 9.5 Treatment time: 0.25-2 hr M i l l F 10 4.8 ± 2.4 (Range:3.2-9.0) Nontoxic 4.6 ± 0.8 (Range: 3.2-5.8) 1.0 F i g u r e 39 FOAMING TENDENCY REDUCTION BY CONTINUOUS 6.0-1 FOAM SEPARATION Mill A Wholemill Effluent pH = 9,5 <>CK]ttO Q^!W>t>0 O-6/L =2.5 ooo-o ZSr/jfiflntV 1 •A 6 / L = 0,833 J 0 4 8 12 16 20 24 28 HOURS AFTER INITIATION OF CONTINUOUS OPERATION 160, two, c o n t i n u o u s foam s e p a r a t i o n systems i n s t a l l e d w i t h p l a s t i c and c e r -amic d i f f u s e r s were measured. The volume o f foam p r o d u c e d by p l a s t i c d i f f u s e r s when removed a t 30 cm foam h e i g h t was e q u i v a l e n t t o an a v e r a g e o f 6.3% o f t h e i n f l u e n t f l o w . W i t h a f i n e c e r a m i c d i f f u s e r p r o d u c i n g 1 mm b u b b l e s , even though t h e o p e r a t i n g G/L was r e d u c e d t o 4.5 (50% o f t h e p l a s t i c d i f f u s e r s y s t e m ) , t h e foam volume was 5.6% o f t h e i n f l u e n t f l o w volume. The c o l l a p s e d foams were a l s o c h a r a c t e r i z e d f o r BOD^ and t o x -i c i t y . As T a b l e 23 i n d i c a t e s , BOD,, c o n t r i b u t i n g m a t e r i a l s a r e e n r i c h e d by a f a c t o r of 1.2 t o 1.5. The low e n r i c h m e n t r a t i o s u g g e s t t h a t t h e m a j o r i t y o f t h e BOD,, m a t e r i a l s a r e n o t s u r f a c e a c t i v e . The i n c r e a s e i n BOD,, was due, a t l e a s t i n p a r t t o t h e c o n c e n t r a t i o n of suspended s o l i d s . I n c o m p a r i s o n , t o x i c i t y i n c r e a s e d by a f a c t o r o f 4 t o 8 ( i n terms o f MST d e c r e a s e ) from i n i t i a l 4.5 t o 7.5 h r i n t h e i n f l u e n t t o 0.5 t o 2 h r i n t h e foam. These r e s u l t s d i r e c t l y c o n f i r m t h a t t h e t o x i c , s u r f a c e a c t i v e compounds a r e n o t degraded. Thus f u r t h e r t r e a t m e n t o f t h e foam p r i o r t o d i s c h a r g e would be r e q u i r e d . 2. R e d u c t i o n o f Foam Volumes U s i n g t h e s ystem, d e s c r i b e d i n t h i s t h e s i s , d e t o x i f i c a t i o n o f b l e a c h e d k r a f t m i l l e f f l u e n t s t r a n s f o r m s 5 t o 6% o f t h e i n f l u e n t f l o w i n t o a h i g h l y t o x i c waste s t r e a m . Treatment of 25 MGD of e f f l u e n t t y p i c a l o f a 750 t p d p u l p m i l l w o u l d p r o d u c e 125,000 - 150,000 g a l o f c o l l a p s e d foam f o r u l t i m a t e d i s p o s a l . R e d u c t i o n o f t h e foam volume t o 1 - 2% o f t h e i n f l u e n t (25,000 - 50,000 g a l / d a y ) i s c o n s i d e r e d TABLE 23 AVERAGE CHARACTERISTICS OF INFLUENT AND COLLAPSED FOAM Foam S e p a r a t i o n System Number of Samples O b t a i n e d Waste C h a r a c t e r i s t i c s A i r D i s p e r s e r s O p e r a t i n g C o n d i t i o n s Type o f Sample Suspended S o l i d s (mg/1) B0D 5 (mg/1) T o x i c i t y (MST:hr) % o f I n f l u e n t C o n v e r s i o n t o Foam Four 25y 1 f t l o n g , 3 i n d i a m e t e r c e r a m i c tubes R e t e n t i o n time = 30±6 min G/L=4.4+1.0 5 I n f l u e n t Range 17 - 80 215-265 2.5-5.0 -Mean!S.D. 42 ± 25 230± 22 4.5+1.2 -A C o l l a p s e d Foam Range - 214-290 0.3-3.2 2.4-13.2 Mean±S.D. - 253± 38 2.1+1.0 5.614.8 Four 25y 5 i n d i a m e t e r p l a s t i c d i s c s L — R e t e n t i o n time = 59±2,5min G/L=12.2 4.0 10 I n f l u e n t Range 38-99 122-293 0.5-24 -MeanlS.D. 57±17 220161 7.5+ 9 -A C o l l a p s e d Foam Range - 227-450 0.2-1.7 1.5-13.2 MeantS.D. - 346188 0.610.5 6.314.2 Foam o b t a i n e d under c o n d i t i o n s w h i c h d e t o x i f i e d a l l samples i n a 180 1 column a t m i l l s i t e . 162 p r a c t i c a l and a c c e p t a b l e by most m i l l s f o r subsequent t r e a t m e n t . Because o f t h i s s e v e r a l f a c t o r s such as t h e e f f e c t s o f foam h e i g h t , and o f foam r e c y c l i n g on t h e t o t a l foam volume r e d u c t i o n were i n v e s t i g a t e d . a. E f f e c t o f Foam H e i g h t The foam h e i g h t above t h e l i q u i d a t w h i c h foam i s removed d e t e r -mines t h e degree o f i n t e r n a l r e f l u x i n t h e foam l a y e r and c o n t r o l s t h e " d r y n e s s " and t h e volume o f foam t o be removed. A s e r i e s o f e x p e r i m e n t s w i t h a 7 l i t r e foaming column was r u n , i n w h i c h t h e foam h e i g h t ( d i s -t a n c e f r o m t h e l i q u i d - f o a m i n t e r f a c e t o t h e foam d i s c h a r g e p o r t ) was v a r i e d from 30 t o 60, 80, 120 and 150 cm. A d d i t i o n a l e x p e r i m e n t s were a l s o c o n d u c t e d by i n c r e a s i n g t h e foam h e i g h t t o a l e v e l (250 cm) where t h e r a t e o f foam d e s t r u c t i o n by c o a l e s c e n c e and d r a i n a g e i s e q u a l t o t h e r a t e o f foam p r o d u c t i o n i . e . no foam was removed. The foam removed d u r i n g t r e a t m e n t was c o l l a p s e d and t h e l i q u i d volume measured. Then t h e p e r c e n t o f t h e t o t a l t r e a t e d l i q u i d volume was c a l c u l a t e d . T a b l e 24 shows t h a t foam s e p a r a t i o n d e t o x i f i e d a l l s a m p l e s , r e g a r d l e s s o f foam h e i g h t . However, t h e volume of foam removed d u r i n g t h i s e x p e r i m e n t d e c r e a s e d from an ave r a g e 5.2% a t t h e l o w e s t foam h e i g h t (30 cm) t o 2.1% a t the h i g h e s t foam h e i g h t (150 cm). T a b l e 24 a l s o shows t h a t a t a foam h e i g h t o f 250 cm, t h e c o n d i t i o n of t o t a l r e f l u x was a c h i e v e d i . e . no foam was discharged,, Even a t t h i s extreme c o n d i t i o n , c o m plete d e t o x i f i c a t i o n was a c h i e v e d . The t o t a l r e f l u x column i s t h e o r e t i c a l l y an i n f i n i t e l y l o n g r e f l u x column. A foam h e i g h t o f 250 cm was s u f f i c i e n t t o a c h i e v e t h i s g o a l . Foams TABLE 24 EFFECT OF FOAM HEIGHT ON FOAM VOLUME Foam Height (cm) k T o x i c i t y A f t e r Treatment MST (min) Collapsed Foam Removed (ml) Influent Conversion % (v/v) to Foam Run # 1 Run // 2 Run # 1 Run // 2 Run # 1 Run // 2 Average 30 NT NT 200 220 5.0 5.5 5.25 60 NT NT 175 180 4.3 4.5 4.40 80 NT NT 140 160 3.5 4.0 3.75 120 NT NT 100 110 2.5 2.8 2.65 150 NT NT 75 95 1.8 2.4 2.10 250(Total Reflux) NT NT 0 0 0 0 0 NT = Non-toxic (100% Survival of f i s h i n 100% effluent for 24 hr) Influent T o x i c i t y : MST = 1.5 hr Operating Conditions: Volume: 4 l i t r e s Aeration rate: 500 ml/min A i r disperser: 45u pore size sintered glass G/L: 4 pH : 8 Treatment time: 30 min 164 were t u r n e d c o m p l e t e l y i n t o s o l i d gummy m a t e r i a l s and d e t o x i f i c a t i o n was e q u i v a l e n t t o systems w h i c h d i s c h a r g e d foam. I n t h e b a t c h s y s t e m , t h e c o n c e n t r a t i o n o f s u r f a c t a n t i n t h e foam n e v e r r e a c h e d a c o n s t a n t v a l u e . The c o n c e n t r a t i o n o f t o x i c i t y i n t h e l i q u i d p o o l d e c r e a s e d w i t h t i m e u n t i l e v e n t u a l l y i t was so low t h a t no foam c o u l d r e a c h t h e t o p o f t h e column. P r a c t i c a l l y a l l s u r f a c t a n t s were c o n c e n t r a t e d i n t h e scum. I n c o n c l u s i o n , t h e n by a l l o w i n g t h e l i q u i d c o n t e n t o f t h e foam t o d r a i n i n t o t h e foam column, t h e n e t volume of foam t o be removed f r o m t h e system c o u l d be m i n i m i z e d . I t woul d a p p e a r , t h a t by p r o p e r l y c o n -t r o l l i n g t h e foam h e i g h t o v e r t h e l i q u i d , t h e d r y n e s s and t h e r e b y t h e volume o f foam r e q u i r i n g d i s p o s a l c o u l d be s i g n i f i c a n t l y r e d u c e d . b. E f f e c t o f Foam R e c y c l i n g R e c y c l i n g o f c o l l a p s e d foam a l s o c o n c e n t r a t e s t h e t o x i c a n t s i n t h e foam phase and t h e r e b y r e d u c e s t h e volume r e q u i r i n g d i s p o s a l . The e f f e c t o f r e c y c l i n g foam and o p e r a t i n g t h e c o n t i n u o u s foam s e p a r a t i o n s y s t e m i n an " e n r i c h i n g mode" ( F i g u r e 7) was s t u d i e d on e f f l u e n t s a t f o u r l e v e l s o f t o x i c i t y . Foam was r e c y c l e d a t r a t i o s o f z e r o t o 1. T a b l e 25 shows t h a t f o r e f f l u e n t s o f a l l l e v e l s o f t o x i c i t y , a foam r e c y c l i n g r a t i o as h i g h as 0.8 can be o p e r a t e d w i t h o u t s a c r i f i c i n g d e t o x i f i c a t i o n e f f i c i e n c y , i . e . a l l e f f l u e n t s were d e t o x i f i e d . A t t h i s c o n d i t i o n , t h e n e t foam d i s c h a r g e d r a n g e d from 0.5 - 1.2% o f t h e i n f l u -e n t compared t o 2.5-6% d i s c h a r g e d when foam was n o t r e c y c l e d . TABLE 25 EFFECT OF FOAM RECYCLING ON DETOXIFICATION IN A CONTINUOUS SYSTEM Foam R e c y c l i n g R a t i o MST•of E f f l u e n t a t Steady S t a t e Net Foam d i s c h a r g e d (%) Un t r e a t e d , m i n T r e a t e d , m i n 0 600 240 180 NT NT NT 2.5 3.75 6.00 0.4 840 NT 0.45 0.6 840 240 NT NT 0.30 1.50 0.8. 600 240 180 NT NT NT 0.5 0.75 1.20 *1.0 840 600 240 180 NT NT 960 1620 0 0 0 0 A T o t a l r e f l u x = no foam was d i s c h a r g e d O p e r a t i o n : C a p a c i t y = 3 1 A e r a t i o n = 750 ml/min G/L = 7 . 5 A i r d i s p e n s e r = 45 u pore s i z e R e t e n t i o n time = 30 min Foam h e i g h t = 60 cm O p e r a t i o n w i t h a r e c y c l e r a t i o o f one approaches a t o t a l r e f l u x s ystem. D e t o x i f i c a t i o n o f e f f l u e n t s o f r e l a t i v e l y low t o x i c i t y , e.g. 600 - 800 min MST, was n o t a f f e c t e d by t h e co m p l e t e r e t u r n o f t h e c o l -l a p s e d foam. A l l t o x i c a n t s a c c u m u l a t e d as gummy scums f l o a t i n g on t h e t o p o f t h e foam d u r i n g t h e p r o c e s s . P r e s u m a b l y , t h e 100% r e c y c l i n g system remained n o n - t o x i c o n l y because t h e d u r a t i o n o f t h e t e s t was s h o r t . F o r l o n g e r o p e r a t i o n , i t i s p r o b a b l e t h a t d i s p e r s i o n o f t o x i c scum i n t o t h e e f f l u -e n t would o c c u r . W i t h t h e more t o x i c e f f l u e n t s (MST:180 - 240 min) up t o 80% o f t h e c o l l a p s e d foam c o u l d be r e c y c l e d w i t h o u t any t o x i c i t y b r e a k - t h r o u g h . The n e t volume o f c o l l a p s e d foam was l e s s t h a n 1.2%. When 100% o f foam was r e c y c l e d , t r e a t e d e f f l u e n t s were m a r g i n a l l y t o x i c . These e x p e r i m e n t s were done on a c o n t i n u o u s s c a l e under c o n t r o l l e d l a b o r a t o r y c o n d i t i o n s . The r e d u c t i o n o f foam volume by o p e r a t i n g l a r g e -s c a l e systems i n an e n r i c h i n g mode may be l e s s e f f e c t i v e . N e v e r t h e l e s s , by c o m b i n i n g t h e two t e c h n i q u e s , i . e . o p e r a t i n g foam s e p a r a t i o n systems a t a maximum foam h e i g h t and r e c y c l i n g p a r t o f t h e c o l l a p s e d foam, i t appears t e c h n i c a l l y f e a s i b l e t o r e d u c e t h e n e t volume o f foam t o 1 - 2% of t h e i n f l u e n t . 3. Breakage o f Foam As t h e q u a n t i t y o f foam d e a l t w i t h i n t h e l a b o r a t o r y was s m a l l , foam b r e a k a g e was e a s i l y a c h i e v e d by vacuum s u c t i o n o r ' b y p a s s i n g t h e 167 foam t h r o u g h a packed bed f i l l e d w i t h g l a s s o r s t e e l w o o l . M e c h a n i c a l b r e a k a g e by a r a p i d l y s p i n n i n g m a g n e t i c b a r o r a g i t a t o r was a l s o e f f e c -t i v e . The c o l l a p s e d foam volume produced i n t h e f i e l d u n i t amounted t o 3 0.5 - 1.0 f t /min/column. Breakage o f foam was most e f f e c t i v e l y done by means of p e r i o d i c a d d i t i o n o f a c h e m i c a l ( s i l i c o n e ) defoamer c o u p l e d w i t h c o n t i n u o u s s p r a y i n g w i t h a s t r o n g j e t of w a t e r . However, b o t h methods s e r i o u s l y changed t h e p r o p e r t i e s o f t h e c o l l a p s e d foam, and c o u l d n o t be a p p l i e d i f foam r e c y c l i n g were p r a c t i c e d f o r r e d u c t i o n o f foam volume. I n v i e w o f t h e tremendous volume o f foam p r o d u c e d i n a c o m m e r c i a l s i z e foam s e p a r a t i o n p l a n t and t h e p o s s i b i l i t y o f o p e r a t i n g a foam r e c y c l i n g s ystem, an e f f i c i e n t and c o m m e r c i a l l y a c c e p t a b l e means of foam b r e a k i n g i s d e s i r a b l e . Of t h o s e methods e v a l u a t e d (109) a mech-a n i c a l t u r b i n e was a s s e s s e d as most u s e f u l . Foam b r e a k i n g by a t u r b i n e system was examined b r i e f l y i n an on-s i t e c o n t i n u o u s f l o w e x p e r i m e n t . Foam was produced a t a r a t e o f 6 - 42 3 f t /min, c o n t a i n i n g 2 - 3% o f l i q u i d . E x p e r i m e n t s were c o n d u c t e d w i t h a v a r i a b l e speed 1/3 hp motor f i t t e d w i t h 15 t o 38 cm d i a m e t e r vaned d i s c t u r b i n e s . a. E f f e c t o f R o t a t i o n Speed and T i p Speed o f T u r b i n e on Foam C o l l a p s i n g E f f i c i e n c y I n t h e o r y , foam c o l l a p s i n g e f f i c i e n c y s h o u l d i n c r e a s e w i t h t h e r o t a t i o n a l speed ( 1 0 9 ) . There i s a c r i t i c a l r o t a t i o n a l speed a t w h i c h 100% o f t h e foam w i l l be c o l l a p s e d . A p p e n d i x X I p r e s e n t s t h i s c r i t i c a l speed r e q u i r e m e n t f o r f o u r d i f f e r e n t t u r b i n e s i z e s a t 5 foam l o a d s . The r e s u l t s ( F i g u r e 40) show t h a t t h e c r i t i c a l r o t a t i o n speed r e q u i r e d t o c o l l a p s e 100% o f t h e foam ranged from 700 t o 1700 rpm.' I t d e c r e a s e d w i t h i n c r e a s i n g t u r b i n e d i a m e t e r , b u t i n c r e a s e d as foam l o a d i n c r e a s e d . The c o r r e s p o n d i n g mean c r i t i c a l t i p speed ranged from 1430 cm/sec t o 2200 cm/sec as foam f l o w v a r i e d from 6.2 t o 42 f t /min. However, a t c o n s t a n t foam f l o w , t h i s c r i t i c a l t i p speed ( T a b l e 26) d i d n o t v a r y s i g n i f i c a n t l y as a f u n c t i o n o f rpm and d i s c d i a m e t e r ( f o r 23-38 cm t u r - ' b i n e ) . The maximum t i p speed r e q u i r e m e n t was a p p r o x i m a t e l y 2200 cm/sec. I t would appear t h a t t i p speed, w h i c h i s d e t e r m i n e d by r o t a t i o n speed and t u r b i n e d i a m e t e r i s the major c o n t r o l l i n g p a r a m e t e r f o r foam b r e a k -i n g . I n F i g u r e 40, i t has been shown t h a t p l o t s o f c r i t i c a l rpm as a f u n c t i o n o f d i s c d i a m e t e r a r e s t r a i g h t l i n e s w i t h t h e same s l o p e (30 rpm/cm) f o r v a r i o u s foam l o a d s . T h i s f a m i l y o f v i r t u a l l y p a r a l l e l c u r v e s a l l o w s t e n t a t i v e e x t r a p o l a t i o n t o v a l u e s n o t measured i n t h e p i l o t p l a n t . An e m p i r i c a l e q u a t i o n r e l a t i n g rpm, foam f l o w and d i s c d i a m e t e r was d e v e l o p e d based on t h i s o b s e r v e d r e l a t i o n s h i p : N = 390 F - 30 D + 1850 o r F = 2.6 x 10"3N + 7.7 x 10_2D - 4.7 where F = foam b r e a k i n g c a p a c i t y i n m 3/min N = r o t a t i o n speed i n rpm D = d i a m e t e r o f t u r b i n e i n cm. A l t h o u g h t h i s e q u a t i o n was d e v e l o p e d w i t h t u r b i n e s r a n g i n g from 15 t o 38 cm i n d i a m e t e r , o p e r a t i n g between 700 - 1700 rpm, i t can w i t h F i g u r e 4 0 CRITICAL R. R M. REQUIREMENT FOR VARIOUS TURBINE SIZES 18001 T 1600 2 1400[ o_ or o UJ £ \200\ in < o £ 10001 800 600 FOAM FLOW m3/min (ft3/min) X 1.19 (42) A 0,69 (24.5) "O 0.45 (15.9) D 0.33 (11.7) 0.18 (6.2) 10 20 30 TURBINE DIAMETER (cm) 40 50 170 T A B L E 2 6 C R I T I C A L T I P S P E E D * F O R F O A M C O L L A P S I N G Foam Flow m3/min (fc 3/min) C r i t i c a l Tip Speed (cm/sec) of Turbine 23 cm (9")diameter 31 cm (12")diamPrPr 38 cm Range Mean ± S.D. 0.18 (6.2) 1436 1436 1396 1396-1436 1432 ± 23 0.33 (11.7) 1675 1914 1795 1675-1914 1795 ± 120 0.45 (15.9) 1795 1818 1914 1795-1914 1842 ± 63 0.69 (24.5) 1854 2233 2393 1854-2393 2160 ± 277 1.2 (42.0) 1914 2300 2500 1914-2393 2180 ± 244 * Speed at which a l l foams entering the system were collapsed. c a u t i o n be used t o e s t i m a t e t h e foam b r e a k i n g c a p a c i t y o f t u r b i n e s o f d i f f e r e n t d i a m e t e r s and r o t a t i o n a l speeds p r o v i d e d t h e s e a r e n o t t o o d i f f e r e n t from t h e ranges t e s t e d . b. Power Consumption D u r i n g t h e s t u d y o f foam b r e a k i n g e f f i c i e n c y w i t h v a r i o u s foam l o a d s , t h e power consumed by a 31 cm and a 38 cm t u r b i n e o p e r a t i n g a t 100% foam b r e a k i n g e f f i c i e n c y ( a l l foam c o l l a p s e d ) was measured. The r e s u l t s a r e p r e s e n t e d i n A p p e n d i x X I I . A t y p i c a l power c u r v e f o r a 38 cm t u r b i n e i s p l o t t e d i n F i g u r e 41. The power consumed was f o u n d t o depend on rpm, foam f l o w r a t e and t u r b i n e d i a m e t e r . F o r s c a l e up p u r -p o s e s , t h e power d a t a were f i t t e d t o d i f f e r e n t e q u a t i o n s . L i n e a r r e -g r e s s i o n a n a l y s i s produced t h e f o l l o w i n g d i m e n s i o n a l r e l a t i o n s h i p : f = 51.7 x 10 ~ 1 7 x N 3 D 5 + 51.2 r where P = Power i n w a t t s F = Foam f l o w i n m 3/min N = rpm D = T u r b i n e d i a m e t e r i n cm as t h e b e s t f i t , w i t h a c o r r e l a t i o n c o e f f i c i e n t o f 0.81 ( F i g u r e 4 2 ) . T h i s e q u a t i o n may s e r v e as a b a s i s f o r p r e d i c t i n g t h e power r e q u i r e m e n t s f o r a c o m m e r c i a l s i z e p l a n t . 4. Foam D i s p o s a l S e v e r a l methods were examine f o r u l t i m a t e d i s p o s a l o f c o l l a p s e d foam. S e l e c t i o n o f s u i t a b l e method depends g r e a t l y on t h e volume and 1.0 F i g u r e 41 POWER CONSUMPTION BY A 38cm (15") TURBINE FOAM BREAKER 0.8 5 2 0.6 13 CO z o o cc 0.41 U J o 0_ Foom Breaker '/3hp, 15", 3 blade varied drive turbine Rotation speed - 1800 rpm 0.2 Foam Flow m?/min. ( f t 3 / min.) 1.19(42) .69 (24.5) 0.45(15.9) no load 0 500 1000 ROTATION SPEED (r.p.m.) 1500 2000 NJ NET POWER CONSUMPTION ( Watts/mVmin) oo c h a r a c t e r i s t i c s o f t h e foam. a. I n c i n e r a t i o n The foam c o u l d be i n c i n e r a t e d p r o v i d e d i t s volume was l o w and t h e s o l i d c o n t e n t was h i g h enough t o j u s t i f y t h e c o s t . The economic f e a s i -b i l i t y o f i n c i n e r a t i o n would depend on t h e volumes t o be h a n d l e d , on t h e c h a r a c t e r i s t i c s o f t h e c o l l a p s e d foam, t h e a v a i l a b i l i t y o f s u f f i c i e n t e v a p o r a t i o n and i n c i n e r a t i o n c a p a c i t y , and o t h e r f a c t o r s . T h i s a p p r o a c h has n o t been e v a l u a t e d i n d e t a i l . b. C h e m i c a l Treatment A l t h o u g h c h e m i c a l f l o c c u l a n t s were r e p o r t e d t o be e f f e c t i v e i n d e t o x i f y i n g k r a f t m i l l e f f l u e n t a t r e a s o n a b l y low dosage (Appendix X I I I ) T a b l e 27 shows t h a t a p p l i c a t i o n o f up t o 10 g/1 o f l i m e , 1 g/1 o f alum o r 1 g/1 o f f e r r i c s u l p h a t e was i n e f f e c t i v e i n d e t o x i f y i n g t h e c o l l a p s e d foam ( T a b l e 2 6 ) . The main r e a s o n c o u l d be a t t r i b u t e d t o i n s u f f i c i e n t dosage due t o t h e h i g h i n i t i a l t o x i c i t y o f t h e c o l l a p s e d foam. c. B i o l o g i c a l Treatment I n t h e f i e l d column i n s t a l l a t i o n , a p p r o x i m a t e l y 5% o f t h e i n f l u e n t was c o n v e r t e d t o foam h a v i n g an MST v a l u e o f 0.7-1.8 h r . The foams were c o l l e c t e d and s u b j e c t e d t o b i o d e g r a d a t i o n . T a b l e 28 summarizes t h e r e s u l t s o f d e t o x i f i c a t i o n o f c o l l a p s e d foam by an a e r a t e d l a g o o n and a r o t a t i n g d i s c system ( F i g u r e 9 ) . The d a i l y d a t a a r e p r e s e n t e d i n A p p e n d i x XIV a-b . The a e r a t e d l a g o o n t r e a t m e n t d e t o x i f i e d s a t i s f a c t o r i l y when op-e r a t e d a t 3-day but n o t a 1-day's r e t e n t i o n t i m e . The 1-day r e t e n -TABLE 27 CHEMICAL TREATMENT OF COLLAPSED FOAM C h e m i c a l T o x i c i t y of C o l l a p s e d Foam, MST ( h r ) Type Dosage B e f o r e A f t e r (g/1) Treatment Treatment 1 0.25 0.60 Lime 2 0.40 0.50 (PH:12) 7 0.40 0.70 10 0.40 0.80 0.1 0.40 0.60 Alum 0.2 0.40 0.75 (pH:6.5) 0.4 0.25 1.30 1.0 0.25 2.30 0.1 0.40 0.75 F e r r i c C h l o r i d e 0.2 0.40 0.90 (pH:6.5) 0.4 0.25 1.00 1.0 1.00 4.00 TABLE 28 TREATMENT OF COLLAPSED FOAM BY AN AERATED LAGOON AND BIODISC SYSTEM B i o l o g i c a l Treatment System No. o f Samples B0D 5 (mg/1) T o x i c i t y , MST ( h r ) B e f o r e Treatment A f t e r Treatment % Removal B e f o r e Treatment No. o f Samples D e t o x i f i e d D e t o x i f i c a t i o n S uccess Rate % A e r a t e d l a g o o n 1-day r e t e n t i o n 3-day r e t e n t i o n 7 178 51 71 1.8 2 28 9 370 16 95 0.7 9 100 R o t a t i n g b i o d i s c 2-hr r e t e n t i o n 4-hr r e t e n t i o n 7 178 13 92 1.8 1 14 9 214 20 91 0.8 9 100 t i o n , a e r a t e d l a g o o n t r e a t m e n t r e d u c e d BOD,- f r o m an a v e r a g e o f 71%, f r o m 178 t o 51 mg/1; 3-day r e t e n t i o n , a e r a t e d l a g o o n t r e a t m e n t by 95%, f r o m 370 t o 16 mg/1. However, t h e 1-day system d e t o x i f i e d o n l y 28% of t h e foam samples compared t o 100% f o r t h e 3-day system. The r o t a t i n g b i o l o g i c a l d i s c t r e a t m e n t d e t o x i f i e d 14 and 100% o f 2 t h e samples a f t e r 2 ( h y d r a u l i c l o a d : 0 . 4 5 g a l / f t /day) and 4-hr ( h y -2 d r a u l i c l o a d : 0.22 g a l / f t /day) r e t e n t i o n t i m e s r e s p e c t i v e l y . C o r r e s -p o n d i n g BOD,, r e m o v a l was 91 and 92% r e s p e c t i v e l y . The r e s u l t s i n d i c a t e t h a t b o t h b i o l o g i c a l t r e a t m e n t p r o c e s s e s a r e f e a s i b l e f o r t h e t r e a t m e n t o f c o l l a p s e d foam. However, t h e c o l l a p s e d foam i s c o n c e n t r a t e d w i t h s u r f a c e a c t i v e t o x i c a n t s , i f a e r a t e d l a g o o n i s i n s t a l l e d f o r r e m o v a l o f BOD,, and t o d i s p o s e o f t o x i c i t y , f o a m i n g can be e x c e s s i v e i n a l a r g e s c a l e o p e r a t i o n , as a r e s u l t , a s u i t a b l e method o f foam c o n t r o l , such as a d d i t i o n o f c h e m i c a l defoamers o r i n s t a l l a t i o n o f m e c h a n i c a l foam b r e a k i n g system would be r e q u i r e d . I n c e r t a i n s y s t e m s , where r e f l u x o f c o l l a p s e d foam i s p r a c t i c e d , t h e foam d i s c h a r g e d s h o u l d be more t o x i c e.g. MST: 10 - 20 m i n , b i o -d e g r a d a t i o n t e c h n i q u e f o r foam d e t o x i f i c a t i o n w o u l d s t i l l be a p p l i c a b l e i n v i e w o f t h e h i g h d e t o x i f i c a t i o n s u c c e s s r a t e documented i n T a b l e 28. However, t h e r e t e n t i o n t i m e o f t h e l a g o o n may have t o be i n c r e a s e d ( o r h y d r a u l i c l o a d i n g o f t h e b i o d i s c system d e c r e a s e d ) t o i n c r e a s e t h e de-t o x i f i c a t i o n c a p a b i l i t y CHAPTER IV THEORETICAL ASSESSMENT OF MAJOR OPERATING EQUIPMENT D e s i g n o f a c o m m e r c i a l s i z e s e p a r a t i o n p l a n t i n v o l v e s two key u n i t o p e r a t i o n s , namely; foam g e n e r a t i o n and foam b r e a k i n g . From an e n g i -n e e r i n g s t a n d p o i n t , t h e equipment s h o u l d be r e a d i l y a v a i l a b l e , r u g g e d , u n s o p h i s t i c a t e d , r e q u i r i n g m i n i m a l maintenance and be e c o n o m i c a l t o use. A. ASSESSMENT OF FOAM GENERATION SYSTEM 1. S p e c i f i c C r i t e r i a f o r Equipment S e l e c t i o n The f o l l o w i n g d e s i g n c h a r a c t e r i s t i c s a r e c o n s i d e r e d c r i t i c a l f o r foam g e n e r a t i o n equipment: R a t e o f g a s - l i q u i d i n t e r f a c e g e n e r a t i o n = 20 m 2 / l ( F i g u r e 35) B u b b l e s i z e = 1 mm G a s / l i q u i d r a t i o c a l c u l a t e d = 7 B u b b l e - l i q u i d c o n t a c t t i m e = l o n g ( u p t o 1 hour) D e t o x i f i c a t i o n o f t y p i c a l k r a f t m i l l e f f l u e n t r e q u i r e s about 20 m 2 / l o f g a s - l i q u i d i n t e r f a c e and l e s s t h a n 1-hr o f r e t e n t i o n t i m e . The r e q u i r e d i n t e r f a c i a l a r e a can be a c h i e v e d by e i t h e r s p a r g i n g l a r g e q u a n t i t i e s o f c o a r s e a i r b u b b l e s o r s m a l l e r volumes of f i n e a i r b u b b l e s . The b u b b l e s i z e p r o duced by t h e equipment i s e x p e c t e d t o be c o n t r o l l a b l e a t a mean b u b b l e d i a m e t e r o f 1 mm. Systems p r o d u c i n g s m a l l e r b u b b l e s 179 a r e n o t c o n s i d e r e d e c o n o m i c a l l y f e a s i b l e due t o t h e l a r g e energy r e -q u i r e m e n t . I n o r d e r t o enhance a d s o r p t i o n o f t o x i c m a t e r i a l s o n t o t h e g a s - l i q u i d i n t e r f a c e , l o n g b u b b l e c o n t a c t t i m e s a r e h i g h l y d e s i r a b l e . F u r t h e r m o r e , r e d i s p e r s i o n o f t h e produced foam s h o u l d be m i n i m i z e d . 2. S e l e c t i o n o f Most P r o m i s i n g Foam G e n e r a t i o n System Foam i s g e n e r a t e d by d i s p e r s i n g a gas i n t o a l i q u i d . Commercial gas d i s p e r s i o n equipment ( a e r a t o r s ) has been m a n u f a c t u r e d p r i m a r i l y f o r oxygen t r a n s f e r i n b i o l o g i c a l waste t r e a t m e n t systems. I n d e s i g n i n g an aerator (110) oxygen t r a n s f e r i s maximized by ( I ) g e n e r a t i n g t h e l a r g e s t p r a c t i c a l i n t e r f a c i a l a r e a between a g i v e n l i q u i d volume and a i r , ( i i ) p r e v e n t i n g b u i l d - u p o f t h i c k i n t e r f a c i a l f i l m s o r by b r e a k i n g them down t o keep t h e t r a n s f e r c o e f f i c i e n t h i g h , ( i i i ) m a i n t a i n i n g t h e l o n g e s t p o s s i b l e e x p o s u r e t i m e . The above c o n s i d e r a t i o n s a r e c o m p a t i b l e w i t h d e s i g n o f a foam g e n e r a t i n g d e v i c e . On t h e b a s i s o f m e c h a n i c a l d e s i g n , f i v e d i f f e r e n t t y p e s o f gas d i s p e r s i n g p r i n c i p l e s can be a p p l i e d t o foam g e n e r a t i o n . The c h a r a c t e r i s t i c s o f o p e r a t i o n o f each a r e summarized i n T a b l e 29. The equipment r e p r e s e n t a t i v e o f each s y s t e m and i t s p o t e n t i a l a p p l i c a t i o n f o r foam g e n e r a t i o n have been a s s e s s e d based on p e r f o r m a n c e s and o p e r a t i o n p r i n c i p l e s . a. F o r c e d A i r D i f f u s i o n A i r i s b u b b l e d i n t o w a t e r t h r o u g h o r i f i c e s , n o z z l e s i n t h e a i r p i p -i n g , d i f f u s e r p l a t e s , o r s p a r g e r s . D i f f u s e d a e r a t i o n equipment ( F i g u r e 6-b and 14) can be c l a s s e d i n t o two g e n e r a l t y p e s , namely: c o a r s e TABLE 2 9 CHARACTERISTICS OF VARIOUS FOAM GENERATING EQUIPMENT Characteristics Foam Generator Forced Diffusion (fine bubble diffuser) Surface Mechanical Shear Hydraulic Shear High Pressure Bubble size range (mui) 0.5 - 1.5 - 0.5 - 1.5 0.5 - 1.5 0.03 - 0.1 Ai r Requirement (xlO 3 ft 3/min)* 3.6-10.8 - 3.6 - 10.8 3.6- 10.8 0.22 - 0.72 hp/100 gal of effluent** 0.1 - 0.13 0.04 0.2 0.10 0.40 Plugging Problem Serious None None None None Maintenance Required Frequent cleaning Replacement Frequent servicing if gear box, motor Frequent servicing of gear box, motor Routine inspection of c i r c u l a t i n g pumps Frequent inspection of pressurization system, compressor. I n s t a l l a t i o n Simple Simple Simple Simple Sophisticated Operation Simple Simple Simple Simple Sophisticated Relative Cost Magnitude Economical Economical Moderately expensive Medium Expensive to produce 20 i o 2 / l / l i of gas-liquid i n t e r f a c i a l area. * from l i t e r a t u r e (4) and plant operator. oo o 1 8 1 b u b b l e d i f f u s e r s and f i n e b u b b l e d i f f u s e r s . O n l y t h e f i n e b u b b l e de-v i c e s a r e s u i t a b l e f o r p r o d u c t i o n o f t h e g a s - l i q u i d i n t e r f a c i a l a r e a r e q u i r e d f o r foam d e t o x i f i c a t i o n . These t y p e s o f d i f f u s e r s a r e gen-e r a l l y f a b r i c a t e d of a porous medium such as carborundum, p l a s t i c o r t i g h t l y wrapped s a r a n . B u b b l e s i z e s as s m a l l as 0.5 mm d i a m e t e r can be g e n e r a t e d . The f i n e b u b b l e d i f f u s e r i s e c o n o m i c a l t o use and s i m p l e t o o p e r a t e , however, p l u g g i n g of p o r e s o c c u r s r e a d i l y as a r e s u l t o f i n -adequate f i l t r a t i o n of a i r , growth o f b i o m a s s , o r suspended s o l i d de-p o s i t s and s c a l i n g . A h i g h degree of m a i n t e n a n c e may be r e q u i r e d t o keep t h e u n i t s o p e r a t i v e . These d i f f u s e r systems a r e g e n e r a l l y a v a i l -a b l e i n t h e form of 2 - f t l o n g , 3 - i n d i a m e t e r t u b e s ( F i g u r e 14-b) o r 6 - i n d i a m e t e r domes/discs ( F i g u r e 1 4 - a ) . F i n e b u b b l e g e n e r a t i o n i s u s u a l l y most e f f e c t i v e when t h e d i f f u s e r s a r e i n s t a l l e d a t t h e b ottom o f a l o n g n a r r o w b a s i n . T h i s c o n f i g u r a t i o n promotes p l u g f l o w and i n c r e a s e s g a s -l i q u i d c o n t a c t t i m e . However, t h e c o n s t r u c t i o n c o s t of t h e w a s t e t r e a t m e n t system may i n c r e a s e . D e s p i t e s e v e r a l a d v a n t a g e s , f i n e b u b b l e d i f f u s e r s r e q u i r e f r e q u e n t c l e a n i n g and r e p l a c e m e n t . Thus t h e i r p e r f o r m a n c e i s n o t c o n s i s t e n t . T h i s l i m i t a t i o n s e r i o u s l y r e s t r i c t s t h e use o f porous d i f f u s e r s i n foam g e n e r a t i o n . b. A i r E n t r a i n m e n t T h i s t y p e o f d e v i c e i s b e s t r e p r e s e n t e d by a s u r f a c e a e r a t o r w h i c h b r i n g s w a s t e w a t e r t o t h e s u r f a c e f o r c o n t a c t w i t h a i r . F i g u r e 43 shows a t y p i c a l d e s i g n o f s u r f a c e a e r a t o r ( 1 1 1 ) . The b l a d e d o r p a d d l e - s u r f a c e 182 F i g u r e 43 SURFACE AERATOR 183 a e r a t o r pumps l i q u i d f rom b e n e a t h t h e b l a d e s and s p r a y s t h e l i q u i d a c r o s s t h e w a t e r s u r f a c e . The b r u s h a e r a t o r u t i l i z e s a r o t a t i n g s t e e l b r u s h w h i c h s p r a y s l i q u i d f r o m r o t a t i n g b l a d e s w i t h m i x i n g a c h i e v e d by an induced, v e l o c i t y below t h e r o t a t i n g element. A d r a f t tube i s em-p l o y e d i n some d e s i g n . The s u r f a c e a e r a t o r o f f e r s h i g h oxygen t r a n s f e r w i t h l ow horsepower r e q u i r e m e n t s (0.04 hp/1000 g a l ) . M a i n t e n a n c e i s m a i n l y r e l a t e d t o s e r v i c i n g o f t h e gear box and motor. A s u r f a c e a e r -a t o r r e q u i r e s s u f f i c i e n t a r e a f o r p r o p e r a e r a t i o n and t h e r e f o r e i s most e f f e c t i v e i n a s h a l l o w b a s i n . The major drawback o f t h e s u r f a c e a e r a t o r f o r use as a foam g e n e r -a t o r i s t h e mechanism of b u b b l e p r o d u c t i o n . I n most s y s t e m s , a i r i s e n t r a i n e d and foam i s c r e a t e d as t h e s p r a y r e - e n t e r s t h e c o n t e n t s o f t h e ta n k . The s t r e a m o f a i r - l i q u i d m i x t u r e w i l l i m p i n g e on t h e foam s u r -f a c e . S i m i l a r t o a l i q u i d s p r a y , t h e t o x i c foam w i l l be c o l l a p s e d and r e t u r n e d t o t h e l i q u i d . T h i s mechanism i s d e t r i m e n t a l t o d e t o x i f i -c a t i o n . L i m i t e d d a t a i s a v a i l a b l e on t h e s i z e and volume o f b u b b l e s p r o d u c e d . However, because a i r i s n o t i n t r o d u c e d d i r e c t l y i n t o t h e e f f l u e n t , foam g e n e r a t i o n c a p a c i t y i s low. c. M e c h a n i c a l Shear The most p r o m i s i n g m e c h a n i c a l s h e a r t y p e g a s - d i s p e r s i o n d e v i c e ( F i g u r e 8) i s t h e submerged t u r b i n e m i x e r . T h i s s y s t e m i s w i d e l y used i n f e r m e n t a t i o n and sewage t r e a t m e n t systems. The gas i s d i s c h a r g e d f r o m a p i p e o r s p a r g e r r i n g b e n e a t h t h e r o t a t i n g b l a d e s o f an i m p e l l e r . The d e s i g n o b j e c t i v e s a r e t o p r o v i d e , by m e c h a n i c a l s h e a r and 184 f l u i d s h e a r a c t i o n , s u f f i c i e n t f o r c e s t o c r e a t e a f i n e b u b b l e d i s t r i -b u t i o n and maximize t h e a i r r e t e n t i o n i n t h e system. The m e c h a n i c a l a c t i o n i s n e c e s s a r y t o keep t h e system f u l l y mixed as w e l l as t o i n j e c t a i r t o c r e a t e t h e g a s - l i q u i d i n t e r f a c e . B a l a n c e between a i r f l o w and i m p e l l e r speed i s c r i t i c a l . Under s u i t a b l e a i r l o a d and r o t a t i o n speed ( t i p speed) o f t h e b l a d e , b u b b l e s i z e s o f 0.5 - 1.5 mm can be p r o d u c e d . A submerged t u r b i n e system i s a f i x e d u n i t a e r a t i o n d e v i c e and u s -u a l l y i s i n s t a l l e d i n a deep b a s i n . The system i s most s u i t a b l e f o r s h o r t r e t e n t i o n t i m e , w a s t e t r e a t m e n t p l a n t s where l a n d i s a t a premium. These advantages must be t r a d e d o f f a g a i n s t h i g h e r horsepower r e q u i r e -ments (0.2 hp/1000 g a l ) . The maintenance r e q u i r e m e n t s a r e s i m i l a r t o s u r f a c e a e r a t o r s . T u r b i n e systems a r e easy t o o p e r a t e , r e l i a b l e i n p r o d u c i n g f i n e b u b b l e s and a r e n o n - p l u g g i n g . They would be good systems f o r foam g e n e r a t i o n . d. H y d r a u l i c Shear The h y d r a u l i c s h e a r f o r c e d e v e l o p e d by t u r b u l e n t a c t i o n o f w a t e r ' i n a tube i s an e f f e c t i v e means o f gas d i s p e r s i o n . B u b b l e s i z e , i s co n -t r o l l e d by t h e l o a d i n g o f a i r and t h e v e l o c i t y o f t h e l i q u i d t r a v e l l i n g i n s i d e t h e tu b e . To produce 1 mm mean b u b b l e d i a m e t e r s , t h e pumping system s h o u l d be i n s t a l l e d t o m a i n t a i n t h e l i q u i d v e l o c i t y a t >5 f t / s e c t h r o u g h t h e t u b e . The power r e q u i r e m e n t (0.1 hp/1000 g a l ) i s l o w e r t h a n f o r t u r b i n e system b u t h i g h e r t h a n f o r po r o u s media and s u r f a c e a e r a t i o n systems. Some d e s i g n s a r e c a p a b l e o f p r o d u c i n g b u b b l e s o f 0.1 mm d i a m e t e r ( 1 1 2 ) . The b e s t h y d r a u l i c s h e a r system c a n be r e p r e s e n t e d by h e l i c a l ( F i g u r e 8) and t h e j e t a e r a t o r s ( F i g u r e 2 2 ) . B o t h systems a r e n o n - p l u g g i n g , s i m p l e t o use and g e n e r a t e l a r g e i n t e r f a c i a l a r e a s . M a i n t e n a n c e r e q u i r e m e n t s a r e much l o w e r t h a n f o r a i r d i f f u s e r s and t u r b i n e s . These a e r a t i o n systems would be s u i t a b l e f o r foam g e n e r a t i o n . e. H i g h P r e s s u r e A e r a t o r The most common system i s based on t h e p r i n c i p l e o f d i s s o l v e d a i r p r o c e s s . A i r and l i q u i d a r e p r e s s u r i z e d t o g e t h e r a t 40 t o 80 p s i and due t o i t s g r e a t e r s o l u b i l i t y a t h i g h e r p r e s s u r e s , t h e a i r d i s s o l v e s . Upon r e l e a s e o f t h e p r e s s u r e , t h e a i r becomes i n s o l u b l e p r o d u c i n g bub-b l e s and, i f c o n d i t i o n s a r e r i g h t , foam would be c r e a t e d . B u b b l e s i z e r a n g e s f r o m 30 t o 120 u i n d i a m e t e r a c c o r d i n g t o t h e p r e s s u r e a p p l i e d , s u r f a c t a n t c o n c e n t r a t i o n and mode o f o p e r a t i o n . The p r o c e s s u t i l i z e s v e r y s m a l l amounts of a i r b u t r e q u i r e s an e x t r e m e l y l a r g e energy i n p u t (0.4 hp/1000 g a l ) . Compared t o o t h e r a l t e r n a t i v e s , o p e r a t i n g c o s t s a r e c o n s i d e r e d h i g h . The d i s s o l v e d a i r sy s t e m i s q u i t e s o p h i s t i c a t e d t o b u i l d and o p e r a t e . T h i s system would n o t be e c o n o m i c a l t o o p e r a t e . 3. S e l e c t i o n o f t h e B e s t Foam G e n e r a t i o n System P r e l i m i n a r y e x a m i n a t i o n i n d i c a t e d t h a t t h e t u r b i n e ( m e c h a n i c a l s h e a r s y s t e m ) , o r h e l i c a l and j e t a e r a t o r s ( h y d r a u l i c s h e a r system) would be t h e most p r o m i s i n g systems f o r foam g e n e r a t i o n . The s i z e o f b u b b l e s produced by a l l t h r e e systems can be v a r i e d by c h a n g i n g t h e op-e r a t i n g c o n d i t i o n s . W i t h r e s o n a b l e power i n p u t s , a b u b b l e d i a m e t e r o f 1 mm and 20 m 2 / l o f g a s - l i q u i d i n t e r f a c i a l a r e a can be a c h i e v e d . The e f f e c t i v e n e s s o f d e t o x i f i c a t i o n w i t h t u r b i n e systems o r w i t h h e l i c a l s ystems ( T a b l e 10) has been documented e a r l i e r i n C h a p t e r IV. The b u b b l e s i z e s ( F i g u r e 44) produced by t h e j e t a e r a t o r a r e much s m a l l e r (0.57-1.16 mm d i a m e t e r u s i n g an a c c u r a t e p h o t o g r a p h i n g t e c h n i q u e as d e s c r i b e d i n S e c t i o n IV-D). Thus;the d e t o x i f i c a t i o n e f f i c i e n c y o f t h e foam s e p a r a t i o n p r o c e s s u s i n g j e t a e r a t o r s i s e x p e c t e d t o be a t l e a s t comparable t o a t u r b i n e o r h e l i c a l system. To s e l e c t t h e b e s t system f o r c o m m e r c i a l i n s t a l l a t i o n , t h e s e s y s -tems a r e compared i n d e t a i l i n T a b l e 30 i n terms o f c o n s i s t e n c y i n p r o d u c i n g f i n e b u b b l e s , equipment r e l i a b i l i t y and c o s t s . a. B u b b l e S i z e L a b o r a t o r y e x p e r i m e n t s i n d i c a t e d t h a t t u r b i n e a e r a t i o n p r o d u c e d a c o n s i s t e n t l y n a r r o w range o f b u b b l e s i z e s ( T a b l e 30) w i t h a p p r o x i m a t e l y 50% o f them <_,1 mm b u b b l e d i a m e t e r . Due t o t u r b u l e n t c o n d i t i o n , bub-b l e - e f f l u e n t c o n t a c t was adequate d u r i n g t h e o p e r a t i o n . I n c o n t r a s t , a c t u a l t e s t i n g u s i n g a r e g u l a r - t y p e h e l i c a l a e r a t o r p r o d u c e b u b b l e s r a n g i n g from 1 - 3 mm i n d i a m e t e r ( T a b l e 30) w h i c h q u i c k l y r o s e t o t h e s u r f a c e . To produce t h e same g a s - l i q u i d i n t e r f a c i a l a r e a as a t u r b i n e s ystem, a l a r g e number o f a d d i t i o n a l a e r a t o r s and FIGURE 44 BUBBLE SIZES AT 5 f t 3 / m i n AIRLOAD PER JET AERATOR ( in bleached k ra f t wholemi l l e f f l u e n t ) 2 H 6 i i i 8 10 Scale (mm) 00 188 TABLE 30 COMPARISON OF MOST PROMISING FOAM GENERATING EQUIPMENT Operating Characteristics Turbine Aerator Hel i c a l Aerator Jet Aerator Probability of producing 1 mm bubble diameter under normal operating conditions >50% <50% 100% V e r i f i c a t i o n of bubble size Laboratory Experiment Demonstration of test model V e r i f i c a t i o n by a test model P o s s i b i l i t y of producing >1 mm diameter bubbles due to poor performance Sl i g h t l y possible Highly possible S l i g h t l y possible Consequence of producing >1 mm diameter bubbles Increase aeration rate Increase the No. of aerators and aeration rate Increase aeration rate Gas-liquid contact time Long Short Longest RELIABILITY Simplicity of the system More sophisticated Simple Simple Ins t a l l a t i o n Sophisticated Easy Easy Ease of operation Easy Easy Easy P o s s i b i l i t y of breakdown Highly possible Minimal Minimal Maintenance required On gearbox, bear-ing and motor Minimal On pump P o s s i b i l i t y of corrosion On a l l mechanical components None On pump ECONOMY of foam generating equipment (25 MGD plant) No. of aerators required * 15 312 12 hp required 1430 680 1328 Capital Cost ($) 375,000 250,000 ** 550,000 Operating Cost ($/ton of pulp) 0.49 0.21 0.42 * Assuming 1 mm bubble diameter are produced. ** Cost based on production of 1 mm mean bubble diameter. According to actual testing, mean bubble size i s >2 mm and the ca p i t a l cost w i l l be at least doubled. b l o w e r s would be r e q u i r e d t o compensate f o r t h e l a r g e b u b b l e s i z e and s h o r t b u b b l e r e t e n t i o n t i m e . T h i s would c r e a t e d e s i g n and i n s t a l l a t i o n p r o b l e m s . A l t h o u g h t h e b u b b l e s i z e can be r e d u c e d by pumping t h e e f f l u e n t t h r o u g h t h e a e r a t o r , w i t h a 2 - f t d i a m e t e r , 5 - f t l o n g c o m m e r c i a l s i z e a e r a t o r , a pumping c a p a c i t y o f 6000 g a l / m i n would be r e q u i r e d f o r each a e r a t t o b r i n g t h e l i q u i d v e l o c i t y t o t h e 5 f t / s e c r e q u i r e d f o r f i n e b u b b l e p r o d u c t i o n . The a d d i t i o n a l c o s t cannot be e c o n o m i c a l l y j u s t i f i e d . D e m o n s t r a t i o n o f t h e j e t a e r a t o r showed t h a t t h i s s y s t e m p r o d u c e d t h e most u n i f o r m and s m a l l e s t b u b b l e s . I n T a b l e 31, t h e mean and r a n g e o f b u b b l e s i z e s i n k r a f t m i l l e f f l u e n t a r e g i v e n as a f u n c t i o n o f a i r l o a d p e r j e t . Mean b u b b l e d i a m e t e r remained v i r t u a l l y unchanged a t 0.6 mm ( F i g u r e 44) when t h e a i r l o a d was < 5 f t 3 / m i n . At h i g h e r a i r l o a d s , t h e b u b b l e s i z e s i n c r e a s e d and r e a c h e d a c o n s t a n t s i z e o f a p p r o x i m a t e l y 1.2 mm. When t h e k r a f t m i l l e f f l u e n t was r e p l a c e d by w a t e r , t h e b u b b l e s i z e i n c r e a s e d a p p r o x i m a t e l y by 300%. These f i n e b u b b l e s a r e d i s c h a r g e d i n a s t r o n g plume ( F i g u r e 4 4 ) . The c o n t a c t t i m e o f t h e b u b b l e s i s e x t e n d e d because t h e b u b b l e s t r a v e l h o r i z o n t a l l y b e f o r e r i s i n g v e r -t i c a l l y t o t h e s u r f a c e . Of t h e t h r e e systems c o n s i d e r e d , t h e j e t a e r a t o r a p p e a r s most c o n -s i s t e n t i n p r o d u c i n g f i n e b u b b l e s . b. R e l i a b i l i t y o f Equipment The t u r b i n e a e r a t o r i s t h e most s o p h i s t i c a t e d o f t h e t h r e e systems compared i n terms o f d e s i g n and i n s t a l l a t i o n . W i t h o u t p r o p e r c a r e , t h e l a r g e number o f m e c h a n i c a l components c o u l d cause m e c h a n i c a l f a i l u r e . R o u t i n e s e r v i c i n g i s r e q u i r e d . The system i s c o n s t r u c t e d o f m e t a l , TABLE 31 AVERAGE AIR BUBBLE SIZES PRODUCED BY A JET AERATOR IN BLEACHED KRAFT WHOLEMILL EFFLUENT A i r f l o w / j e t Bubble Diameter (mm) ( s t d f t 3 / m i n ) Range Mean ± S.D. 1.1 0.43-0.86 0.57 ± 0.11 1.8 0.47-0.70 0.63 ± 0.10 3.1 0.4-0.80 0.58 ± 0.10 3.9 0.44-0.89 0.61 ± 0.14 5.0 0.48-0.71 0.61 ± 0.13 5.5 0.59-0.78 0.74 ± 0.09 6.0 0.56-1.94 0.88 ± 0.18 14.3 0.76-1.01 0.85 ± 0.11 21.5 0.38-2.01 1.24 ± 0.35 50.0 0.56-1.45 1.16 ± 0.17 O p e r a t i n g c o n d i t i o n : J e t : 5 cm d i a m e t e r n o z z l e 1/2 hp, 20 g a l / m i n r e c i r c u l a t i o n pump FIGURE 45 JET AERATOR IN OPERATION 192 t h e r e f o r e e x p e n s i v e a l l o y s o r s t a i n l e s s s t e e l s must be used. Conse-q u e n t l y , l a b o u r c o s t s and d e p r e c i a t i o n based on t h e s e r v i c e l i f e ex-p e c t a n c y o f t h e equipment w i l l be h i g h . The d e s i g n o f t h e h e l i c a l s ystem i s t h e s i m p l e s t and most depend-a b l e . I t i s made o f p l a s t i c m a t e r i a l w i t h no m e c h a n i c a l moving p a r t s . O p e r a t i o n i s t r o u b l e f r e e and r e q u i r e s minimum mai n t e n a n c e . I t i s non-c o r r o s i v e and u n l i k e l y t o b r e a k down. A d d i t i o n o r r e p l a c e m e n t o f h e l -i c a l a e r a t o r s i s easy. The j e t a e r a t i o n system a l s o o f f e r s s i m p l e , easy o p e r a t i o n and minimum mai n t e n a n c e expenses. The j e t s a r e made o f f i b e r g l a s s a r i d . a r e a l s o n o n - c o r r o s i v e . The r e c i r c u l a t i o n pump w i l l r e q u i r e p e r i o d i c i n -s p e c t i o n . W i t h advances i n pump e n g i n e e r i n g o v e r t h e p a s t few decades, c o n t i n u o u s r e l i a b l e o p e r a t i o n i s a l m o s t a s s u r e d . c. Economy Based on t h e p r e s e n t i n f o r m a t i o n and assuming t h a t 1 mm b u b b l e d i a m e t e r can be produced by a l l t h r e e foam g e n e r a t i o n s y s t e m s , t h e number of u n i t s r e q u i r e d t o pro d u c e 20 m 2 / l o f g a s - l i q u i d i n t e r f a c e and c a p i t a l c o s t o f each system were o b t a i n e d f r o m v a r i o u s m a n u f a c t u r e r s . I n s t a l l a t i o n o f t h e t u r b i n e a e r a t o r , w i t h r e q u i r e m e n t o f 1,430 hp, i s e s t i m a t e d a t $375,000. The h e l i c a l s ystem i s t h e c h e a p e s t t o i n s t a l l ($250,000) and o p e r a t e . I t r e q u i r e s t h e l e a s t horsepower (680 h p ) . However, t h i s s ystem most l i k e l y w i l l p r o d u c e 2 - 3 mm d i a m e t e r b u b b l e s . 193 Under t h i s a s s u m p t i o n , t h e e s t i m a t i o n w i l l be s e v e r a l t i m e s h i g h e r . The j e t a e r a t o r s ystem, r e q u i r i n g 1328 hp i s e s t i m a t e d t o c o s t $550,000. O p e r a t i n g c o s t s a r e e s t i m a t e d a t $0.49/ton of p u l p f o r t u r b i n e a e r a t i o n , $0.21/ton f o r t h e h e l i c a l s ystem and $0.42/ton f o r t h e j e t a e r a t i o n s y s -tem. A l t h o u g h h a v i n g a h i g h e r c a p i t a l c o s t , t h e o p e r a t i n g c o s t o f j e t a e r a t i o n i s s l i g h t l y l o w e r t h a n f o r t u r b i n e a e r a t i o n because o f l o w e r d e p r e c i a t i o n . d. C o n c l u s i o n Among th e t h r e e most p r o m i s i n g a e r a t i o n s y s t e m s , t h e j e t a e r a t o r p r o d u c e s s m a l l b u b b l e s most r e l i a b l y and p r o v i d e s t h e l o n g e s t c o n t a c t t i m e between b u b b l e s and e f f l u e n t . M i x i n g of t h e t a n k c o n t e n t s i s most c o m p l e t e . The system i s easy t o i n s t a l l , r e l i a b l e i n o p e r a t i o n and t h e c o s t i s comparable t o a t u r b i n e system. T h e r e f o r e , a j e t a e r a t o r s y s t e m i s recommended f o r c o m m e r c i a l o p e r a t i o n . B. ASSESSMENT OF FOAM BREAKING SYSTEMS 1. S p e c i f i c C r i t e r i a f o r S e l e c t i o n o f Foam B r e a k i n g Systems A 25 MGD p l a n t w i l l p r oduce a t l e a s t 2000 f t 3 / m i n of foam ( 1 - 2 % l i q u i d c o n t e n t ) w h i c h s p r e a d s e v e n l y o v e r a l a r g e l i q u i d s u r f a c e . Foams f l o w p o o r l y and must be c o l l a p s e d as soon as t h e y a r e p r o duced i n o r d e r t o p r e v e n t t h e r e d i s p e r s i o n o f t h e t o x i c m a t e r i a l s . The equipment f o r c o l l a p s i n g such huge q u a n t i t i e s of foam s h o u l d be a b l e t o cause t h e 194 foam t o f l o w i n t o t h e foam b r e a k i n g a r e a , remove t h e foam from t h e t a n k and e f f e c t i v e l y c o n v e r t t h e foam i n t o a f r e e l y f l o w i n g l i q u i d . 2. S e l e c t i o n , o f Most P r o m i s i n g Foam B r e a k i n g Systems S e v e r a l foam d e s t r u c t i o n t e c h n i q u e s have been d i s c u s s e d i n t h e l i t e r a t u r e . Many of t h e s e d i s c u s s i o n s a r e co n c e r n e d o n l y w i t h l a b o r a -t o r y e x p e r i m e n t a l work. Some o f t h e s e t e c h n i q u e s have n e v e r been t e s t e d on a l a r g e s c a l e . The p r i n c i p l e s o f o p e r a t i o n , a p p l i c a t i o n , and t h e i r s u i t a b i l i t y f o r i n s t a l l a t i o n i n foam s e p a r a t i o n p l a n t a r e summarized i n T a b l e 32. a. A i r J e t Foam can be b r o k e n by e x p o s u r e t o a s t r o n g c u r r e n t from an a i r j e t (112, 1 1 3 ) . B u r s t i n g o f t h e b u b b l e s i n t h e foam o c c u r s as a r e s u l t o f e v a p o r a t i o n and impact f o r c e s . F o r a l a r g e s c a l e i n s t a l l a t i o n , i t would n o t be m e c h a n i c a l l y f e a s i b l e t o s u b j e c t a l a r g e foam s u r f a c e t o t h e number of a i r j e t s , o p e r a t i n g a t e x t r e m e l y h i g h a i r f l o w s w h i c h a r e n e c e s s a r y t o b r e a k t h e foam. A t p r e s e n t , t h i s method i s e x c l u s i v e l y u sed f o r l a b o r a t o r y work. b. S o n i c P r e s s u r e , Sound waves of t h e p r o p e r f r e q u e n c y can c o l l a p s e foam by means o f a c o m b i n a t i o n o f a c o u s t i c p r e s s u r e , r a d i a t i o n p r e s s u r e , i n d u c e d r e s o n a n t v i b r a t i o n s and t u r b u l e n c e p r oduced by t h e s o n i c wave ( 1 1 4 ) . U s u a l l y 195 TABLE 32 COMPARISON OF VARIOUS FOAM BREAKING DEVICES Foam B r e a k i n g System O p e r a t i n g P r i n c i p l e Commercial I n s t a l l a t i o n P r a c t i c a b i l i t y f o r P u l p M i l l A p p l i c a t i o n A i r Impact f o r c e , E v a p o r a t i o n None I m p r a c t i c a l S o n i c P r e s s u r e V a r i o u s a c o u s t i c p r e s s u r e s None I m p r a c t i c a l Thermal E v a p o r a t i o n , C h e m i c a l d e g r a d a t i o n None I m p r a c t i c a l O r i f i c e Impact f o r c e None I m p r a c t i c a l L i q u i d Spray Sudden p r e s s u r e change, d i l u t i o n Yes I m p r a c t i c a l M e c h a n i c a l F o r c e s - W h i r l i n g P a d d l e - C e n t r i f u g a l - T u r b i n e Shear, Impact, Compression and T e n s i o n F o r c e s None F e r m e n t a t i o n i n d u s t r y and P u l p and Paper i n d u s t r y . I m p r a c t i c a l S u i t a b l e S u i t a b l e 196 s i r e n s w i t h a wide f r e q u e n c y r a n g e , and w h i s t l e s tuned t o a p a r t i c u l a r band a r e e f f e c t i v e ( 1 1 5 ) . A c o u s t i c v i b r a t i o n s e.g., 0.7 o r 11 k c a t 150 db a r e r e p o r t e d t o d i s i n t e g r a t e foam. A t p r e s e n t , i t i s n o t e c o n o m i c a l t o use s o n i c t e c h n i q u e s f o r c o n t r o l l i n g l a r g e volumes o f foam. c. Thermal Method Foam may be c o l l a p s e d by h e a t i n g i t . The h i g h t e m p e r a t u r e w i l l d e c r e a s e t h e s u r f a c e v i s c o s i t y w h i c h weakens t h e b u b b l e f i l m . I n some i n s t a n c e s , d e g r a d a t i o n o f s u r f a c t a n t s p r e s e n t i n foam f i l m may a l s o o c c u r . E v a p o r a t i o n o f t h e s o l v e n t w i l l r e s u l t i n t h i n n i n g o f t h e f i l m and a change i n t h e c o n c e n t r a t i o n o f t h e foaming s u b s t a n c e s ( 1 1 6 ) . I n a c t u a l p r a c t i c e , foam i s c o l l a p s e d by h e a t i n g e l e m e n t s p l a c e d d i r e c t l y o v e r t h e s u r f a c e o f foam ( 1 1 7 ) . Heat t r e a t m e n t i s i n d i r e c t , and l e s s e f f e c t i v e on an energy i n p u t b a s i s , t h a n o t h e r systems. I n v i e w o f t h e huge volume of foam (2000 f t 3 / m i n ) produced f r o m k r a f t m i l l e f f l u e n t s , t h e r m a l t r e a t m e n t cannot be r e g a r d e d as an e c o n o m i c a l l y v i a b l e method. d. L i q u i d S p r a y S p r a y i n g foam w i t h a s t r o n g w a t e r j e t , i n most c a s e s i s an e f f e c -t i v e means of foam c o l l a p s i n g . Foam bre a k a g e i s caused by a c o m b i n a t i o n o f v a r i o u s f o r c e s and p r o g r e s s i v e d i l u t i o n o f t h e foam l i q u i d ( 1 1 8 ) . T h i s t e c h n i q u e , however, i s o n l y s u i t a b l e i n s i t u a t i o n s where r e c o v e r y o r r e f l u x o f foam i s n o t r e q u i r e d and where d i l u t i o n o f foam does n o t c o n s t i t u t e a d i s p o s a l p r o b l e m . The system has been a p p l i e d s u c c e s s f u l l y i n t h e Los A n g e l e s County S a n i t a t i o n D i s t r i c t Water R e c l a m a t i o n P l a n t r 197 (119) and i n a f i e l d s c a l e k r a f t m i l l foam s e p a r a t i o n p r o c e s s ( F i g u r e 1 7 ) . F o r l a r g e s c a l e foam s e p a r a t i o n o f k r a f t m i l l e f f l u e n t , as a means of d e t o x i f i c a t i o n , foam must be c o l l e c t e d f o r subsequent t r e a t m e n t . L i q u i d s p r a y i s t h e r e f o r e n o t s u i t a b l e . e. O r i f i c e Foam B r e a k e r The e f f e c t i v e n e s s o f foam bre a k a g e by an o r i f i c e i s a t t r i b u t e d t o t h e s h a r p p r e s s u r e changes as t h e foam p a s s e s t h r o u g h t h e o r i f i c e . A t a p r e s s u r e d i f f e r e n c e o f 7 p s i , foam drawn t h r o u g h a 2.5 mm d i a m e t e r o r i f i c e i s c o l l a p s e d e f f e c t i v e l y ( 1 2 0 ) . However, t h i s s ystem i s n o t e c o n o m i c a l l y v i a b l e f o r l a r g e s c a l e foam b r e a k i n g due t o t h e l a r g e power r e q u i r e m e n t s f o r pumping gas. I n a d d i t i o n , t h e s m a l l o r i f i c e u sed may cause p l u g g i n g p r o b l e m s . f . M e c h a n i c a l F o r c e s S u b j e c t i n g t h e foam t o sudden p r e s s u r e changes can cause i t t o c o a l e s c e , become u n s t a b l e and b u r s t ( 1 2 1 ) . These p r e s s u r e changes can be a c h i e v e d by c o m p r e s s i o n , s h e a r , c o m p a c t i o n and t e n s i o n f o r c e s t h r o u g h v a r i o u s k i n d s o f c o m m e r c i a l l y a v a i l a b l e equipment. F o r d r y and u n s t a b l e foam, a w h i r l i n g p a d d l e o r r o t a t i n g r o d (122) can c r e a t e s u f f i c i e n t i m p a c t and s h e a r f o r c e s f o r foam c o l l a p s i n g . F o r wet and s t a b l e foam a p e r f o r a t e d , c e n t r i f u g a l b a s k e t (123) i s e f f e c t i v e . The foam i s b r o k e n by sudden p r e s s u r e changes as t h e foam l e a v e s t h e b a s k e t . P r o p e r l y s e l e c t e d t u r b i n e b l a d e s , r o t a t i n g a t h i g h speed (2000 rpm) can c r e a t e s u f f i c i e n t l y h i g h s t r e s s e s on t h e foam t o cause r u p t u r i n g . ( 1 2 4 ) . T u r b i n e 198 t y p e foam b r e a k e r s a r e a v a i l a b l e i n t h e market and have been r e p o r t e d t o r e l i a b l y c o l l a p s e foams from b l a c k l i q u o r o x i d a t i o n t o w e r s ( 1 2 5 ) . Foam b r e a k i n g i s i n s t a n t a n e o u s and e f f e c t i v e . T h i s system appears s u i t a b l e f o r a foam s e p a r a t i o n p l a n t . 3. S e l e c t i o n o f b e s t T u r b i n e Foam B r e a k i n g System P r e l i m i n a r y a n a l y s i s i n d i c a t e s t h a t m e c h a n i c a l f o r c e s c r e a t e d by t u r b i n e b l a d e s were a b l e t o c o l l a p s e foam s u c c e s s f u l l y . The e f f e c t i v e -n e s s o f a t u r b i n e f o r foam b r e a k i n g has a l s o been v e r i f i e d a t a f i e l d s i t e ( T a b l e 26) as d e s c r i b e d i n C h a p t e r V. Foams, were b r o k e n by a com-b i n a t i o n o f a t l e a s t t h r e e major f o r c e s : S u c t i o n , c e n t r i f u g a l and s h e a r f o r c e s ( 1 2 6 ) . These f o r c e s a r e d e t e r m i n e d by t h e r o t a t i o n a l speed and d i a m e t e r o f t h e b l a d e , as i n d i c a t e d by t h e f o l l o w i n g f o r m u l a e : 3 S u c t i o n f o r c e = ND Shear r a t e = K N 1 , 5 D 2 , 5 2 C e n t r i f u g a l f o r c e = K 3 N 2D = K 4 V where K i = C o n s t a n t , i = 1,2,3,4 N = R o t a t i o n speed D = Di a m e t e r o f b l a d e V t i p = T i p speed A l l t h r e e f o r c e s a r e c o n c u r r e n t l y i n v o l v e d i n foam b r e a k i n g . F i g u r e 46 i l l u s t r a t e s t h e mechanism by w h i c h t h e p r i n c i p a l f o r c e s i n -v o l v e d i n b r e a k i n g foam a c t . The b l a d e s r o t a t i n g a t h i g h speed p r o d u c e a s u c t i o n f o r c e w h i c h draws the foam i n t o t h e d i s c . Near t h e i m p e l l e r F i g u r e 46 PRINCIPAL FORCES INVOLVED IN BREAKING FOAM BY TURBINE TURBINE FOAM BREAKER (zzr TZ3 Suction Force o ° O o ( - ) o 0 0 0 Foam Foam Blade Contact Area Centrifugal Force Liquid Foam Breakage Rupture 200 i s a zone of rapid r a d i a l and tangential currents, high turbulence, and intense shear. The foams are spun and accelerated as they leave the d i s c . Due to c e n t r i f u g a l force, the liquid,content of the foam i s accelerated f a s t e r than the gas and so i s separated. The foam f i l m i s stretched and a weak region co n s i s t i n g of t h i n foam fi l m s i s created. As the foam c i r c u l a t e s and tr a v e l s along the blades, these weak regions w i l l eventually rupture under tension or be beaten by the blades and then rupture. The combined e f f e c t of the various forces causes foam to break within seconds. During mechanical foam breaking, several other factors are also responsible for some foam breaking. These include c o l l i s i o n s among the foams, smashing of foams on the walls of the foam tank etc. These f a c t o r s , however, are not considered as s i g n i f i c a n t as suction, shear and c e n t r i f u g a l forces. A turbine impeller operates l i k e a pump without a casing. Con-v e n t i o n a l l y , turbines are used for l i q u i d mixing and gas dispersion. They can be c l a s s i f i e d into two basic designs; the a x i a l discharging type and the r a d i a l discharging type. Both types contain many v a r i -ations and subtypes for s p e c i f i c a p p l i c a t i o n s . The blades may be str a i g h t or curved, pitched or v e r t i c a l . The impeller may be open or semi-open. Figure 47 i l l u s t r a t e s some of the conventional turbines and more popular modifications (127). t The a x i a l flow type turbines, e.g. s t r a i g h t blade, pitched blade, high shear and curved blades are not desirable. These systems discharge the foam d i r e c t l y , reduce the foam-blade contact time and shear rate, which are e s s e n t i a l for foam breaking. Among the r a d i a l discharge type 201 F i g u r e 4 7 TURBINES OF VARIOUS SHAPES I. STRAIGHT BLADE 2. PITCHED BLADE 3. HIGH SHEAR 202 t u r b i n e s , t h e d i s c , s a w t o o t h and r a d i a l t u r b i n e s a r e n o t s u i t a b l e b e cause of poor s u c t i o n and low c e n t r i f u g a l f o r c e s . The b e s t systems a r e t h e d i s c f l a t b l a d e and t h e vaned d i s c t u r b i n e s . They combine good pumping, h i g h s h e a r and c e n t r i f u g a l f o r c e d u r i n g h i g h speed r o t a t i o n . T a b l e 33 compares t h e p e r f o r m a n c e of v a r i o u s t y p e s o f t u r b i n e foam b r e a k i n g systems. The r e s u l t s i n d i c a t e t h a t t h e r e a r e no r e a l d i f f e r e n c e s between p e r f o r m a n c e o f t u r b i n e s . However, a i v e r t i c a l 3-blade -vaned d i s c s ystem i s c o n s i d e r e d t h e b e s t c h o i c e i n terms o f : f o a n u b r e a k i n g - e f f i c i e n c y , power co n s u m p t i o n and s i m p l e d e s i g n . T h i s s y s t e m would be s u i t a b l e f o r c o m m e r c i a l o p e r a t i o n . TABLE 33 EFFECT OF IMPELLER GEOMETRY OF A 3 BLADE TURBINE ON FOAM COLLAPSING EFFICIENCY AND POWER CONSUMPTION D e s i g n o f I m p e l l e r Vaned d i s c ( v e r t i c a l b l a d e ) Vaned d i s c (45° p i t c h ) - c l o c k w i s e Vaned d i s c ( t a p p e r e d b l a d e ) Curved vaned d i s c - c l o c k w i s e D i s c f l a t b l a d e t u r b i n e • T O Foam C o l l a p s i n g E f f i c i e n c y 81 82 7 7 8 1 80 Power Consumption (KW) Loaded 0.35 0.35 0.35 0.38 0.50 O p e r a t i n g C o n d i t i o n s : D i s c <j) = 31 cm(12") No. o f b l a d e s = 3 rpm = 1800 O p e r a t i o n = C o n t i n u o u s Foam f l o w = 0.50 m 3/min (17.6 cfm) L i q u i d e n t r a i n e d = 1.4% 204 CHAPTER V I I PILOT PLANT OPERATION D a t a e s t a b l i s h e d d u r i n g l a b o r a t o r y and f i e l d s t u d i e s were used f o r d e s i g n i n g a 6000 g a l c a p a c i t y foam s e p a r a t i o n p i l o t p l a n t . The main i n t e n t was t o v e r i f y t h e d e t o x i f i c a t i o n p r i n c i p l e s p r e v i o u s l y d i s c u s s e d and t o a s s e s s t h e s u i t a b i l i t y o f t h e s e l e c t e d foam g e n e r a t i n g and foam c o l l a p s i n g equipment. T h i s i n f o r m a t i o n i s r e q u i r e d f o r s i z i n g and c o s t -i n g o f a f u l l s i z e c o m m e r c i a l foam s e p a r a t i o n p l a n t . The p i l o t p l a n t s e l e c t e d was equipped w i t h a j e t a e r a t i o n system f o r foam g e n e r a t i o n , and a t u r b i n e f o r foam b r e a k i n g . I t was l o c a t e d n e a r t h e o u t f a l l o f M i l l A on Vancouver I s l a n d . A. PILOT PLANT FOAM SEPARATION PROCESS The p i l o t p l a n t was a 3 - s t a g e , t r o u g h t y p e d e s i g n ( F i g u r e 20) w h i c h p r o c e s s e d 80 - 100 g a l / m i n o f b l e a c h e d k r a f t whole m i l l e f f l u e n t . Re-t e n t i o n t i m e and a i r f l o w r a t e s o f t h e system v a r i e d f r o m 20 - 80 min 3 and 50 - 100 f t /min r e s p e c t i v e l y . The pH of t h e e f f l u e n t was con-t r o l l e d o n l y when d e t o x i f i c a t i o n p e r f o r m a n c e was b e i n g m o n i t o r e d . The v a r i a t i o n s i n gas and l i q u i d f l o w r a t e s , r e t e n t i o n t i m e and pH produced foams of d i f f e r e n t c h a r a c t e r i s t i c s . The p i l o t p l a n t was o p e r a t e d o v e r a p e r i o d o f 8 months. Throughout t h e s t u d y , i n f l u e n t c h a r a c t e r i s t i c s , foam b r e a k i n g e f f i c i e n c y and d e t o x i f i c a t i o n i n each s t a g e were d e t e r -mined a t r e g u l a r i n t e r v a l s . B. INFLUENT CHARACTERISTICS 205 D u r i n g t h e f i r s t month of p i l o t - p l a n t o p e r a t i o n , i n f l u e n t and foam samples were t a k e n each day a t c o n v e n i e n t i n t e r v a l s . The i n f l u e n t was a n a l y z e d f o r pH and foaming t e n d e n c y ; foam was a n a l y z e d f o r volume, d e n s i t y , s t a b i l i t y and l i q u i d c o n t e n t . The t o x i c i t y o f t h e i n f l u e n t was d e t e r m i n e d l e s s f r e q u e n t l y . The d a t a a r e t a b u l a t e d i n A p p e n d i x XV and summarized i n T a b l e 34. The pH o f t h e m i l l e f f l u e n t v a r i e d w i d e l y f r o m 3.0 t o 9.5 dep e n d i n g upon m i l l o p e r a t i o n , and o v e r t h e e x p e r i m e n t a l p e r i o d a v e r a g e d 4.8. The foaming t e n d e n c y o f t h e e f f l u e n t was i n f l u -enced by pH. I t v a r i e d from 4.2 t o 6.5 min and averaged 5.3 min. Out o f a t o t a l o f 43 samples, t e n were a n a l y z e d f o r t o x i c i t y . MSTs range d from 200 t o 800 min and a v e r a g e d 433 min. U s i n g t h i s e f f l u e n t , and w i t h t h e foam s e p a r a t i o n p l a n t o p e r a t i n g a t an a v e r a g e r e t e n t i o n 2 t i m e o f 67 min and a G/L of 9.8, a p p r o x i m a t e l y 30 m / l i t e r o f g a s - l i q u i d 3 i n t e r f a c e was p r o d u c e d . Foam p r o d u c t i o n a v e r a g e d 18.4 f t /min. The l i q u i d c o n t e n t of t h e foam averaged 1.5% and foaming s t a b i l i t y a v e r a g e d 4.2 min. The foaming tendency and t h e foaming s t a b i l i t y o f t h e i n f l u e n t were t y p i c a l o f and s i m i l a r t o t h o s e o b s e r v e d on e f f l u e n t from o t h e r w e s t e r n C a n a d i a n k r a f t m i l l s ( 4 0 ) . C o n v e r s i o n o f i n f l u e n t t o foam was 3%, l o w e r t h a n t h e range o b s e r v e d d u r i n g an e a r l i e r f e a s i b i l i t y s t u d y (up t o 5 % ( S e c t i o n V-D) on e f f l u e n t s f r o m an i n t e r i o r B.C. m i l l , foam s e p a r a t e d i n a 180 1 column). T h i s was due t o t h e d e s i g n o f t h e p i l o t p l a n t w h i c h p e r m i t t e d l o n g e r r e t e n t i o n t i m e s r e s u l t i n g i n b e t t e r foam d r a i n a g e . TABLE 34 INFLUENT CHARACTERISTICS DURING PILOT PLANT OPERATION I n f l u e n t C h a r a c t e r i s t i c s (mean±S.D.) P r o c e s s C o n d i t i o n s (mean±S.D.) Foam C h a r a c t e r i s t i c s (mean±S.D.) No. of Weeks No. of Samples PH Foaming Tendency (min) T o x i c i t y (MST, min) G/L R e t e n t i o n Time (min) Foam Flow ( f t 3 / m i n ) L i q u i d E n t r a i n e d (%) Foaming S t a b i l i t y (min) I n f l u e n t C o n v e r s i o n t o Foam (%) 1 s t week 6 6.9 ±2.4 5.6 ±0.3 -12.2 ±0.5 74.8 ±2.8 18.55 ±3.15 1.7 ±0.4 5.0 ±0.3 3.7 ±0.9 2nd week 9 4.4 ±1.1 5.5 ±0.7 - 11.1 ±0.6 67.8 ±3.6 18.9 ± 3.85 1.6 ±0.5 4.7 ±1.0 3.3 ±1.3 3r d week 4.7 ±1.1 5.1 ±0.6 506± 220 8.5 ±2.8 65.4 17.5 ± 10.85 1.4 ±0.2 4.0 ±1.0 2.6 ±1.8 4 t h week 9 3.6 ±0.7 5.4 ±0.5 277±198 9.7 ±2.4 65.4 19.25 ± 4.9 1.5 ±0.3 3.6 ±1.1 3.2 ±1.1 O v e r a l l 43 4.8 ±1.6 5.3 ±0.6 433±210 9.8 ±2.6 67.2 ±3.7 18.36 ±7.77 1.5 ±0.3 4.2 ±1.1 3.0 ±1.5 O C. OPTIMIZATION OF OPERATIONAL PARAMETERS FOR DETOXIFICATION OF MILL A"S WHOLEMILL EFFLUENT 207 I n a foam s e p a r a t i o n p r o c e s s , maximum g a s - l i q u i d i n t e r f a c i a l a r e a g e n e r a t i o n i s d e s i r a b l e f o r a d s o r p t i o n o f t o x i c s u r f a c e a c t i v e com-p o n e n t s . However, i n terms of economics, t h e number o f foam g e n e r a t i n g u n i t s r e q u i r e d t o p r o d u c e t h a t i n t e r f a c i a l a r e a and t h e r e l a t e d foam volume d i s c h a r g e d must be r e d u c e d t o a minimum. C r i t i c a l d e s i g n c o n -s i d e r a t i o n s a f f e c t i n g t h e s e two f a c t o r s a r e t h e j e t a e r a t o r d i s t r i b u t i o n and t h e s t a g i n g o f t h e system. 1. G a s - L i q u i d I n t e r f a c i a l A r e a and Number of J e t s R e q u i r e d I t has been r e p o r t e d t h a t under t h e c o n d i t i o n s where b u b b l e c o a l -e s c e n c e and a i r p o c k e t f o r m a t i o n d i d n o t o c c u r , maximum i n t e r f a c i a l a r e a 2 3 (1450 m /min) was g e n e r a t e d w i t h 5 f t /min o f a i r l o a d p e r j e t ( 1 2 8 ) . S i n c e changes i n b u b b l e s i z e s a r e n o t v e r y s e n s i t i v e t o t r e a t m e n t t i m e o r j e t submergence ( 1 2 8 ) , t h e n o p e r a t i o n a t an optimum a i r l o a d o f 5 3 f t /min p e r j e t i s in d e p e n d e n t of t h e p o s i t i o n o f t h e j e t i n t h e foam g e n e r a t i o n t a n k and s t a g i n g o f t h e system. A c c o r d i n g t o e a r l i e r s t u d i e s , t h e g a s - l i q u i d i n t e r f a c i a l a r e a r e -qu i r e m e n t f o r d e t o x i f i c a t i o n i s d i r e c t l y p r o p o r t i o n a l t o t h e i n i t i a l t o x i c i t y o f t h e e f f l u e n t ( F i g u r e 3 5 ) . F o r M i l l A's w h o l e m i l l e f f l u e n t and w i t h i n f l u e n t t o x i c i t y ranged from MST: 360 - 600 m i n , t h e r e d u c t i o n o f t o x i c i t y a f t e r foam s e p a r a t i o n and t h e g a s - l i q u i d i n t e r f a c i a l a r e a - 208 a p p l i e d were c a l c u l a t e d ( r e f e r t o M a t e r i a l s and Methods s e c t i o n ) and g i v e n i n App e n d i x X V I . I n F i g u r e 48 t h e t o x i c i t y o f t h e t r e a t e d e f f l u -e nt i s p l o t t e d a g a i n s t G/L r a t i o and g a s - l i q u i d i n t e r f a c i a l a r e a . W i t h i n c r e a s i n g g a s - l i q u i d i n t e r f a c i a l a r e a a p p l i e d , t h e t o x i c i t y was p r o -g r e s s i v e l y r e d u c e d . Most o f t h e samples were c o m p l e t e l y d e t o x i f i e d a t 2 o r above 6 m / l o f g a s - l i q u i d i n t e r f a c i a l a r e a ( a t G/L o f 1 ) . T h i s i n t e r f a c i a l a r e a r e q u i r e m e n t a g r e e s w i t h e a r l i e r r e s u l t s o b t a i n e d i n a l a b o r a t o r y system ( S e c t i o n V-B). The p i l o t p l a n t system was o p e r a t e d a t 80 g a l / m i n o f e f f l u e n t f l o w . 3 A t an o p e r a t i n g a i r l o a d i n g o f 5 f t /min p e r j e t , b u b b l e s o f 0.6 mm mean 2 2 d i a m e t e r , were produced g i v i n g a p p r o x i m a t e l y 1450 m /min ( o r 3.5 m / l ) o f i n t e r f a c i a l a r e a . Two a e r a t o r s ( -r-— = 1.75), t h e r e f o r e w o u l d appear t o be adequate t o g e n e r a t e s u f f i c i e n t g a s - l i q u i d i n t e r f a c i a l a r e a . 2. Foam M i n i m i z a t i o n 3 I f two j e t a e r a t o r s were o p e r a t e d a t an a i r l o a d o f 5 f t /min p e r j e t i n a s i n g l e s t a g e system, p r o c e s s i n g 80 g a l / m i n o f M i l l A w h o l e m i l l 3 e f f l u e n t t h e y would p r o d u c e 22.5 f t /min o f foam ( T a b l e 3 5 ) . I t has been documented t h a t i n a m u l t i p l e s t a g e s y s t e m t h e m a j o r i t y o f t h e foam i s p r o duced i n t h e f i r s t s t a g e w i t h l e s s b e i n g produced i n t h e 2nd and 3 r d s t a g e s ( S e c t i o n V-A-8). As a r e s u l t , i n c r e a s i n g t h e foam t r a v e l l i n g d i s t a n c e e i t h e r by s t a g i n g o r p r o p e r d i s t r i b u t i o n o f t h e j e t s w o u l d r e -duce t h e foam volume d i s c h a r g e d . T a b l e 35 a l s o shows t h a t i f one a e r -a t o r was i n s t a l l e d i n each s t a g e , t h e r e b y i n c r e a s i n g t h e foam p a t h F i g u r e 48 EFFECT OF GAS-LIQUID INTERFACIAL AREA ON DETOXIFICATION OF KRAFT MILL EFFLUENTS Non-toxic Level Foam Generation System : Jet Aerator Air Load : O.I4m3/min per jet (5ft^min) Fluid Velocity : 60 cm/sec 10 15 20 GENERATED INTERFACIAL AREA ( m 2/I ) 25 30 TABLE 35 AVERAGE FOAM GENERATION CHARACTERISTICS OF A 1-3 STAGE FOAM SEPARATION SYSTEM I n f l u e n t C h a r a c t e r i s t i c s : - B l e a c h e d k r a f t whole m i l l e f f l u e n t - pH a d j u s t e d t o 7.0 - 8.0 - Flow = 100 g a l / m i n O p e r a t i o n C h a r a c t e r i s t i c s : - Foam g e n e r a t i o n system w i t h 1 t o 3 e q u a l l y s i z e d s t a g e s - A i r l o a d per j e t = 3.5-23.1 ( f t 3 / m i n / j e t ) 1 Stage System 2 Stage System 3 Stage System T o t a l Number (0-6 f t Foam T r a v e l l i n g D i s t . ) (0-12 f t Foam T r a v e l l i n g D i s t ) (0-18 f t Foam T r a v e l l i n g D i s t ) of J e t A e r a t o r s i n t h e System Maximum Foam P r o d u c t i o n ( f t 3 / m i n ) Foam L i q u i d C o n t e n t (%) I n f l u e n t C o n v e r t e d t o Foam (%) Maximum Foam P r o d u c t i o n ( f t 3 / m i n ) Foam L i q u i d Content (%) I n f l u e n t Converted to Foam (%) Maximum Foam P r o d u c t i o n ( f t 3 / m i n ) Foam L i q u i d C ontent (%) I n f l u e n t C o n v e r t e d t o Foam (%) 2 23 1.20 2.46 14.1 1.38 1.81 - - -3 24 1.27 2.71 23.7 1.08 2.08 17.3 0.90 1.13 4 - - - 20.8 1.13 2.16 ]4.8 0.84 0.98 6 — — — 26.5 0.68 1.47 18.0 0.75 1.26 211 f r o m 0 - 6 f t t o 0 - 12 f t , t h e q u a n t i t y o f d i s c h a r g e d foam c o u l d be 3 r e d u c e d by 40% t o 14.1 f t /min. A d d i t i o n a l e x p e r i m e n t s u s i n g 3 - 6 j e t s i n a 3 s t a g e o p e r a t i o n ( i n c r e a s i n g t h e foam p a t h from 0 - 12 t o 0 - 18 f t ) a l s o showed an a d d i t i o n a l 20 - 30% foam r e d u c t i o n ( T a b l e 35) when compared t o a 2-stage system. S t a g i n g o f t h e foam f r a c t i o n a t i o n s y s t e m w i l l a l s o d e c r e a s e t h e foam's l i q u i d c o n t e n t . The a v e r a g e foam l i q u i d c o n t e n t i n a two s t a g e s y s t e m was 1.1%, w h i l e t h e a v e r a g e foam l i q u i d c o n t e n t i n a s i n g l e s t a g e system was 1.5%. The r e d u c t i o n o f foam p r o d u c t i o n and foam l i q u i d c o n t e n t a c h i e v e d by u s i n g a 3-stage s y s t e m i n s t e a d o f a s i n g l e s t a g e system r e d u c e d t h e p e r c e n t a g e o f i n f l u e n t c o n -v e r t e d t o foam f r o m 2 . 4 5 - 2 . 7 1 % t o 0.98 - 1.26% t h u s m i n i m i z i n g t h e foam h a n d l i n g p r o b l e m . The o v e r a l l r e s u l t s s u g g e s t t h a t f o r d e t o x i f y i n g M i l l A e f f l u e n t , a 2 - j e t , 2 -stage s y s t e m i s s a t i s f a c t o r y t o p r o v i d e t h e c r i t i c a l i n t e r f a c i a l a r e a and t o m i n i m i z e foam o u t p u t . D. EFFECT OF STAGING ON DETOXIFICATION SUCCESS RATE AND FOAM CHARACTERISTICS I n t h e p r e v i o u s s e c t i o n , i t was e s t a b l i s h e d t h a t , p r o c e s s i n g o f 80 g a l / m i n o f M i l l A w h o l e m i l l e f f l u e n t r e q u i r e s two j e t a e r a t o r s o p e r a t i n g 3 a t an assumed a i r l o a d o f 5 f t /min p e r j e t . T h i s c o n d i t i o n would 2 p r o v i d e 6 m / l o f i n t e r f a c i a l a r e a (G/L<1) s u f f i c i e n t f o r d e t o x i f i c a t i o n by foam s e p a r a t i o n . I n a d d i t i o n , d e s i g n c o n s i d e r a t i o n s s u g g e s t t h a t s t a g i n g o f the system; i . e . w i t h one j e t i n s t a l l e d p e r s t a g e i s bene-f i c i a l f o r foam r e d u c t i o n . I n o r d e r t o d e t e r m i n e t h e c o m p a t i b i l i t y o f s t a g i n g w i t h d e t o x i f i c a t i o n and foam m i n i m i z a t i o n , t h e p i l o t p l a n t was o p e r a t e d as a 1, 2 and 3 s t a g e system. A i r f l o w s and j e t c o n f i g u r a t i o n s 2 were a d j u s t e d t o m a i n t a i n 5 - 7 m / l o f g a s - l i q u i d i n t e r f a c i a l a r e a . Grab and c o m p o s i t e samples were t a k e n from each s t a g e f o r b i o a s s a y a n a l y s i s and foam c h a r a c t e r i z a t i o n . The d a t a a r e t a b u l a t e d i n A p p e n d i x X V I I and summarized i n T a b l e 36. The r e s u l t s s u g g e s t t h a t a t a s e l e c t e d c r i t i c a l g a s - r l i q u i d i n t e r -2 f a c i a l a r e a (6 m / l ) , c o n s i s t e n t d e t o x i f i c a t i o n was a c h i e v e d . D e t o x i f i -c a t i o n s u c c e s s r a t e , however was dependent upon t h e number o f s t a g e s i n o p e r a t i o n . I t i n c r e a s e d from 50 t o 86 t o 100% as t h e o p e r a t i o n s t a g e s i n c r e a s e d from 1 t o 2 and t h e n t o 3 s t a g e s . The l o w d e t o x i f i c a t i o n r a t e i n t h e s i n g l e s t a g e o p e r a t i o n may be p a r t i a l l y a t t r i b u t e d t o t h e v a r i -a b i l i t y o f t h e i n f l u e n t t o x i c i t y and t h e l o w number o f samples examined. I f t h e number o f samples were d o u b l e d , a s l i g h t l y h i g h e r d e t o x i f i c a t i o n r a t e may be o b t a i n e d . C o n c u r r e n t w i t h t h e improved d e t o x i f i c a t i o n s u c c e s s r a t e , foam 3 o u t p u t d e c r e a s e d w i t h i n c r e a s i n g s t a g e number, from 13.8 f t /min i n a 3 1-stage s y s t e m t o 12.4 and 10.9 f t /min i n a 2- and 3-stage system. As documented i n S e c t i o n V I I C-2, t h e r e d u c t i o n i n foam f l o w i s a t t r i b u t e d t o an i n c r e a s e i n foam t r a v e l l i n g d i s t a n c e ( i n c r e a s e d t i m e f o r foam d r a i n a g e ) w i t h an i n c r e a s e i n number o f o p e r a t i o n s t a g e s . T a b l e 36 a l s o l i s t s t h e MST v a l u e s o f c o l l a p s e d foam. MSTs ranged f r o m 15 - 20 min i n a s i n g l e s t a g e system t o 10 - 20 min i n a t h r e e s t a g e system-. The r e s u l t s c o n f i r m e d e a r l i e r f i n d i n g s t h a t t h e t o x i c m a t e r i a l s a r e c o n c e n t r a t e d i n t h e foam. TABLE 36 DETOXIFICATION SUCCESS RATE OF VARIOUS CONTINUOUS FOAM SEPARATION SYSTEMS System No. o f J e t s i n Each Stage* ( l s t / 2 n d / 3 r d ) No. o f Samples Taken I n t e r f a c i a l A r e a C r e a t e d (mean:m 2/l) Foam C h a r a c t e r i s t i c s D e t o x i f i c a t i o n Success Rate (%) Flow Rate (mean:ft 3/min; T o x i c i t y (MST :min) 1 s t Stage 2nd Stage 3rd Stage 1-Stage l/O/O 4 6.2 (Range: 5.5-7.8) 13.8 (Range: 10.6-17.7) 15-20 50 - -2-Stage 1/1/0 14 7.1 (Range: 5.5-7.8) 12.4 (Range: 0.4-14.1) 15-30 57 86 -3-Stage 1/1/1 2/1/1 3/3/3 4 7.5 (Range: 7.3-7.6 10.9 (Range: 0.7-14.1) 10-20 50 100 100 * V a r i o u s j e t c o n f i g u r a t i o n s . 214 F o r d e t o x i f i c a t i o n p u r p o s e s , s t a g i n g o f t h e system i s c r u c i a l f o r a c h i e v i n g a h i g h s u c c e s s r a t e . I t p e r m i t s p r o g r e s s i v e r e d u c t i o n o f t o x i c i t y from s t a g e t o s t a g e and encourages b e t t e r g a s - l i q u i d c o n t a c t i n t h e e f f l u e n t . T h i s c o n d i t i o n i s c o m p l e t e l y c o m p a t i b l e w i t h t h e r e q u i r e -ment f o r foam m i n i m i z a t i o n . The MST o f M i l l A e f f l u e n t u s u a l l y ranged from 6 - 10 h r . A two 3 j e t s y stem ( 5 f t /min a i r l o a d p e r j e t ) o p e r a t i n g i n a two s t a g e foam s e p a r a t i o n p l a n t w o u l d p r o v i d e minimum c o n d i t i o n s f o r d e t o x i f i c a t i o n o f 80 g a l / m i n o f whole m i l l e f f l u e n t . However, i n o r d e r t o e n s u r e a co n -s i s t e n t l y h i g h s u c c e s s r a t e and s t i l l m a i n t a i n minimum foam o u t p u t , i t i s recommended t h a t a two s t a g e system, w i t h two j e t s i n t h e 1 s t s t a g e and one j e t i n t h e 2nd s t a g e be used . F o r e f f l u e n t s f r o m o t h e r m i l l s and h i g h e r t o x i c l o a d s , a s i m i l a r s t u d y w o u l d be r e q u i r e d t o d e t e r m i n e t h e p r o p e r number o f j e t s and s t a g i n g r e q u i r e m e n t s o f t h e system. I n t h i s p i l o t p l a n t system, t h e j e t a e r a t o r s were o p e r a t e d a t an 3 2 a i r l o a d o f 5 f t /min p e r j e t , p r o d u c i n g 1450 m /min o f i n t e r f a c i a l a r e a (0.6 min mean b u b b l e d i a m e t e r ) i n o r d e r t o d e m o n s t r a t e t h e f i n e b u b b l e p r o d u c t i o n c a p a b i l i t y o f t h e j e t . T h i s a i r l o a d i s s t i l l w e l l below t h e d e s i g n a i r l o a d o f j e t s (50 f t /min o f a i r f l o w ) a v a i l a b l e f o r p r o -d u c t i o n o f g a s - l i q u i d i n t e r f a c i a l a r e a ( 1 2 8 ) . The r e m a i n i n g a i r l o a d c a p a c i t y p e r j e t c o u l d have been u t i l i z e d t o produce more i n t e r f a c i a l a r e a t o d e t o x i f y more t o x i c e f f l u e n t s w i t h o u t c h a n g i n g o t h e r o p e r a t i n g p a r a m e t e r s . I n c o m m e r c i a l o p e r a t i o n , t h e j e t ought t o be o p e r a t e d a t 3 maximum d e s i g n a i r l o a d o f 50 f t /min(128). A t t h i s a i r l o a d , t h e d i s p e r s e d 215 a i r b u b b l e s a v e r a g e 1.2 mm (128) and g a s - l i q u i d i n t e r f a c i a l a r e a would 2 be produced a t a r a t e o f 4500 m /min (assuming 60% o f t h e a i r e n t e r i n g t h e j e t was d i s p e r s e d i n t o f i n e b u b b l e s ) . E. FOAM BREAKING PERFORMANCE 3 The foam s e p a r a t i o n p i l o t p l a n t p r o duced a maximum of 23 f t /min 3 (0.94 m /min) o f foam c o n t a i n i n g 1 - 1.5% o f l i q u i d . T h i s l a r g e amount o f foam had t o be l i q u i f i e d f o r b e t t e r h a n d l i n g and subsequent t r e a t -ment. Throughout t h i s s t u d y , t h e t e c h n i c a l and e c o n o m i c a l f e a s i b i l i t y o f a 3-blade vaned d i s c t u r b i n e i n b r e a k i n g foam was s t u d i e d . The foam b r e a k e r was f i t t e d w i t h a 30 cm d i a m e t e r d i s c and powered by a 1/3 hp motor r o t a t i n g a t 1800 rpm. The c o r r e s p o n d i n g t i p v e l o c i t y was 3600 cm/sec e x c e e d i n g t h e p r e v i o u s l y e s t a b l i s h e d minimum r e q u i r e m e n t f o r e f -f e c t i v e foam b r e a k i n g ( S e c t i o n V - H - I I I ) . The foam p r o p e r t i e s and foam b r e a k i n g e f f i c i e n c y were m o n i t o r e d o v e r 40 days o f o p e r a t i o n . The r e s u l t s o f foam b r e a k i n g a r e p r e s e n t e d i n A p p e n d i x X V I I I . I n T a b l e 37, t h e range and mean v a l u e s o f t h e foam b r e a k i n g d a t a 3 a r e p r e s e n t e d . Foam f e e d r a t e v a r i e d from 3.2 - 23 f t /min, l i q u i d c o n -t e n t v a r i e d from 1.06 - 2.92% and foaming s t a b i l i t y r anged 3.1 - 5.6 min. R e g a r d l e s s o f foam c h a r a c t e r i s t i c s , foam was e f f e c t i v e l y and c o n s i s t e n t l y b r o k e n by t h e t u r b i n e a c h i e v i n g 100% b r e a k i n g e f f i c i e n c y o v e r 40 days of o p e r a t i o n . No o p e r a t i n g p r o b l e m was e v e r e n c o u n t e r e d . The r e s u l t s v e r i f i e d t h a t t h e t u r b i n e foam b r e a k e r i s r e l i a b l e , rugged and e f f e c t i v e f o r l a r g e s c a l e foam b r e a k i n g . TABLE 37 AVERAGE EFFICIENCY OF FOAM BREAKING BY A 3-BLADE VANED DISC TURBINE SYSTEM Day o f O p e r a t i o n Foam C h a r a c t e r i s t i c s Foam B r e a k i n g E f f i c i e n c y (%) Flow Rate ( f t 3 / m i n ) L i q u i d C ontent (%) Foam S t a b i l i t y (min) 1 2.22 2.56 11.2 100 2 10.91 1.88 4.0 100 3 12.64 1.33 9.6 100 5 13.59 2.92 - 100 6 18.04 2.04 10.2 100 8 18.00 1.32 - 100 10 21.00 1.5 10.7 100 14 21.04 1.26 11.1 100 .22 14.47 1.51 11.2 100 26 23.76 1.06 10.2 100 30 20.72 1.06 10.9 100 35 16.31 0.62 6.2 100 40 16.31 0.62 11.3 100 O p e r a t i o n : Type: 3 b l a d e , 30 cm d i a m e t e r vaned d i s c t u r b i n e R o t a t i o n Speed: 1800 rpm T i p v e l o c i t y : 3600 cm/sec. 217 F. SUMMARY OF PILOT PLANT OPERATION The p i l o t p l a n t work c o v e r i n g t h e o p e r a t i o n and p e r f o r m a n c e o f t h e foam s e p a r a t i o n p r o c e s s o v e r an 8 month o p e r a t i n g p e r i o d , i n d i c a t e d t h a t t h e equipment s e l e c t e d f o r foam g e n e r a t i o n and foam b r e a k i n g was s u i t -a b l e f o r l a r g e s c a l e o p e r a t i o n . The f o l l o w i n g c o n c l u s i o n s a r e drawn: O p e r a t i o n o f t h e foam d e t o x i f i c a t i o n p r o c e s s i s ea s y , s i m p l e and r e q u i r e s l i t t l e o p e r a t o r a t t e n t i o n ; J e t a e r a t o r s p roduce s u f f i c i e n t l y f i n e b u b b l e s t h a t a r e n e c e s s a r y f o r good and p r a c t i c a l foam g e n e r a t i o n ; Foam b r e a k i n g i s a c h i e v e d e f f i c i e n t l y by a t u r b i n e ; - D e t o x i f i c a t i o n i s c o n s i s t e n t and r e l i a b l e ; The foam produced i s h i g h l y t o x i c . The r e s u l t s i n d i c a t e t h a t foam s e p a r a t i o n i s a t e c h n i c a l l y v i a b l e p r o c e s s f o r d e t o x i f i c a t i o n o f k r a f t m i l l e f f l u e n t . o CHAPTER V I I I 218 PROPOSAL AND ECONOMICS OF A FOAM SEPARATION PLANT FOR DETOXIFYING KRAFT MILL EFFLUENT Based on t h e r e s u l t s o b t a i n e d from l a b o r a t o r y and p i l o t p l a n t o p e r a t i o n , a foam s e p a r a t i o n p l a n t has been p r o p o s e d f o r a 750 ton/day C a n a d i a n b l e a c h e d k r a f t m i l l d i s c h a r g i n g 25 MGD o f e f f l u e n t . The econ-omics of t h e p l a n t a r e a s s e s s e d i n terms t h a t a r e as r e l e v a n t t o Canad-i a n o p e r a t i n g c o n d i t i o n s as p o s s i b l e . The major and a u x i l i a r y o p e r a t i n g equipment r e q u i r e d f o r e f f e c t i v e t o x i c i t y r e m o v a l and foam b r e a k i n g were used as t h e b a s i s f o r e s t i m a t i n g c a p i t a l and o p e r a t i n g c o s t s . A. PROCESS DESCRIPTION D e t o x i f i c a t i o n by foam s e p a r a t i o n i n v o l v e s t h e a d s o r p t i o n o f t o x i c s u r f a c e a c t i v e components on a g a s - l i q u i d i n t e r f a c e . The a d s o r p t i o n i s t o be c a r r i e d o u t on a c o n t i n u o u s b a s i s i n a t r o u g h t y p e foam s e p a r a t i o n t a n k w i t h p r o v i s i o n s f o r r e f l u x i n g t h e c o l l a p s e d foam. S t a g i n g i s r e -q u i r e d t o promote g a s - l i q u i d c o n t a c t and enhance t h e s e p a r a t i o n o f t o x i -c a n t s . The foam s e p a r a t i o n p l a n t d e s i g n e d f o r a 750 ton/day b l e a c h e d k r a f t m i l l d e t o x i f y i n g e f f l u e n t s o f 3 - 4 h r s MST i s d e s c r i b e d as f o l l o w s : C a p a c i t y = 25 MGD P r o c e s s C y c l e = C o n t i n u o u s f l o w R e a c t o r = 3 s t a g e t r o u g h t y p e c o m p lete w i t h foam g e n e r a t i o n and c o l l a p s i n g systems. 219 P r o c e s s e l e m e n t s : E f f l u e n t pumping pH c o n t r o l S c r e e n i n g A i r s u p p l y Foam g e n e r a t i o n Foam c o l l a p s i n g Foam t r e a t m e n t . O p e r a t i n g c o n d i t i o n s : E f f l u e n t f l o w r a t e : 17,000 g a l / m i n R e t e n t i o n t i m e : 60 min G/L i n t e r f a c e : 20 m / l ( F i g u r e 3 5 ) . F i g u r e 49 shows t h e f l o w s h e e t o f t h e p r o p o s e d 25 MGD foam s e p -a r a t i o n p l a n t . W h o l e m i l l e f f l u e n t i s d i s c h a r g e d a t a c i d i c pH c o n d i t i o n s and i s a d j u s t e d by l i m e mud and s l a k e d l i m e t o pH o f 5 t o 6. The e f f l u -e n t s f l o w t h r o u g h a t r a v e l l i n g s c r e e n f o r r e m o v a l o f c h i p s and k n o t s and e n t e r t h e foam s e p a r a t i o n system. P r i o r t o g e n e r a t i o n o f foam, t h e pH i s i n c r e a s e d t o 7 - 8 by ad-d i t i o n o f l i m e mud and s l a k e d l i m e f o l l o w e d by c a u s t i c s o l u t i o n . The pH a d j u s t e d e f f l u e n t f l o w s t o t h e f i r s t s t a g e o f a 3-stage r e c t a n g u l a r foam g e n e r a t i o n t a n k by g r a v i t y . The t a n k p r o v i d e s a t o t a l r e t e n t i o n t i m e o f 1 h r , (20 m i n / s t a g e ) . Foam i s g e n e r a t e d a t a G/L r a t i o s u f f i c i e n t t o 2 p r o v i d e 20 m / l o f g a s - l i q u i d i n t e r f a c e f o r a v e r a g e t o x i c i t y l o a d s . The system s h o u l d be d e s i g n e d t o p r o v i d e c o m p l e t e d e t o x i f i c a t i o n i n 2 s t a g e s The 3 r d s t a g e would s e r v e as a p r o t e c t i o n a g a i n s t u n u s u a l l y h i g h t o x i -c i t y l o a d s and t o p r o v i d e f u r t h e r s e p a r a t i o n o f foam i f r e q u i r e d . F i g u r e 4 9 FLOW SHEET OF FOAM SEPARATION PLANT FOR DETOXIFYING KRAFT MILL EFFLUENT SCREENING 1 Caustic Solution Foam Reflux pH CONTROL FOAM Tl I I SEPAF AT ION REATMFJv T I I Collapsed Foam 1 Nutrients BIOLOGICAL TREATMENT Detoxified Collapsed Foam Air Supply Detoxified Effluent 221 The foams r i s e t o t h e chamber above t h e l i q u i d s u r f a c e and a r e c o n t i n u o u s l y pumped and c o l l a p s e d by m e c h a n i c a l foam b r e a k e r s i n s t a l l e d on t o p o f t h e foam s e p a r a t i o n tank. Beneath t h e t a n k c o v e r , a f i n e s p r a y i n g system i s used f o r r e f l u x o p e r a t i o n . C o l l a p s e d foam i s pumped t o a 3-day r e t e n t i o n l a g o o n f o r b i o l o g i c a l d e t o x i f i c a t i o n . S h o u l d t h e foam volume become e x c e s s i v e , i t would be r e c y c l e d t o t h e foam l a y e r i n t h e foam s e p a r a t o r f o r i n t e r n a l r e f l u x . The t o t a l amount o f foam s h o u l d n o t exceed 2%, by volume, o f t h e i n f l u e n t . D e t o x i f i e d foam i s r e c y c l e d t o t h e foam s e p a r a t i o n s y s t e m f o r t h e p u r p o s e o f p r o t e c t i n g e f f l u e n t q u a l i t y s h o u l d b i o d e g r a d a t i o n f a i l . B. SPECIFICATIONS AND DESIGN CONSIDERATIONS OF VARIOUS PROCESS ELEMENTS The p r i n c i p l e o p e r a t i o n s i n t h e foam s e p a r a t i o n p r o c e s s a r e e f f l u -e nt pumping, pH c o n t r o l , foam g e n e r a t i o n , foam b r e a k i n g and foam h a n d l -i n g . The d a t a and s p e c i f i c a t i o n s f o r each o p e r a t i o n a r e shown i n T a b l e 38. 1. E f f l u e n t S c r e e n i n g and Pumping System I n e v i t a b l y , p u l p m i l l e f f l u e n t w i l l o c c a s i o n a l l y i n c l u d e l a r g e and s m a l l p i e c e s of woody m a t e r i a l s . L a r g e p a r t i c l e s s u c h as c h i p s o r k n o t s may cause equipment f a i l u r e . F o r s a f e t y measures, i t would be a d v i s a b l e t o i n s t a l l a c o a r s e t r a v e l l i n g s c r e e n . F i n e p a r t i c l e s s u c h as f i b r e s ( a p p r o x i m a t e l y 100 mg/1) a r e f l o t a b l e by foam. M o r e o v e r , t h e y w i l l p a s s t h r o u g h most c o m m e r c i a l s i z e equipment w i t h o u t c a u s i n g o p e r a t i n g p r o b -lems. T h e r e f o r e , i n s t a l l a t i o n o f a c l a r i f i e r f o r f i b r e r e m o v a l i s n o t TABLE 38 222 PROCESS SPECIFICATION FOR A 25 M GAL/DAY INTEGRATED FOAM SEPARATION PLANT P r i n c i p a l Design Purpose: Removal of acute t o x i c i t y from bleached kraft m i l l effluent to meet Federal t o x i c i t y Standard. Side Benefits: 10-15% BOD5 removal 50-60% foaming tendency reduction. I n f l u e n t : Flow: 25 M gal/day (17,000 gal/min) pH : 3 - 5 Temperature: 30-35°C Foaming tendency: 5.9 - 12 min Toxicity: MST 180-240 min B0D5 : 100 - 200 mg/1 Suspended s o l i d s : 70 mg/1 pH C o n t r o l : Method: Lime mud, slaked lime followed by NaOH End point: 7.0-8.0 Mixing: mechanical agitation. Foam S e p a r a t i o n P r o c e s s : Design: 3 stage trough type system Flow rate: 17,000 gal/min Retention time: 60 min (20 min/stage). Volume of tank: 5,500 f t 3 (1,840 ft 3/stage) Gas-liquid interface requirement: 20 m 2/l Foam generation equipment: Jet aerators (50 ft 3/min a i r load per jet) Bubble diameter: 1.2 mm Gas to l i q u i d r a t i o : 6 (Gas flow rate: 13,600 ft 3/min) Rate of gas-liquid interface generated: 1.36 x 10 s m2/min. Foam C o l l a p s i n g : Foam breaking equipment: Mechanical, agitator (1800 rpm) with 3 blade vaned disc turbine (61 cm diameter) Design: Restricted l i q u i d draw-off system Foam flow: 1800 ft 3/min Foam l i q u i d content: 1.5% C o l l a p s e d Foam Treatment : Treatment System: 3-day aerated lagoon Flow rate: 200 gal/min Volume of tank: 4600 f t 3 Toxicity of influent: MST = 1 5 - 3 0 min B0Ds of influent: 400 mg/1 T rea ted Whole M i l l E f f l u e n t : Flow: 17,000 gal/min pH : 7.0 - 8.0 Foam tendency: 2 - 6 min Temperature: 30 - 35°C Toxicity : Non toxic BOD5 : 130 - 150 mg/1 mandatory. The s c r e e n e d e f f l u e n t can be h a n d l e d by a c o n v e n t i o n a l pumping system. P r a c t i c a l e x p e r i e n c e s u g g e s t s t h a t t h e e f f l u e n t q u a l i t y i s s u c h t h a t i t can be p r o c e s s e d by foam s e p a r a t i o n w i t h o u t s o p h i s -t i c a t e d p r e t r e a t m e n t . 2 . pH C o n t r o l The foam s e p a r a t i o n p r o c e s s must be o p e r a t e d a t pH o f > 7 i n o r d e r t o e f f e c t d e t o x i f i c a t i o n . The pH can be b r o u g h t t o t h e d e s i r e d l e v e l by l i m e o r c a u s t i c . However, i f t h e p r o c e s s i s o p e r a t e d a t h i g h e r pH (above 8 ) , t h e c a l c i u m l e v e l must be k e p t below t h e c o n c e n t r a t i o n where p r e c i p i t a t i o n o c c u r s . I n most C a n a d i a n m i l l s , e f f l u e n t pHs a r e a d j u s t e d t o 5 w i t h l i m e p r i o r t o d i s c h a r g e . T h i s c a l c i u m l e v e l has n o t c r e a t e d o p e r a t i o n problems i n t h e p i l o t p l a n t . To e n s u r e t r o u b l e f r e e o p e r a t i o n and t o m i n i m i z e d e t o x i f i c a t i o n f a i l u r e , i t i s recommended t h a t t h e pH o f t h e e f f l u e n t s h o u l d be a d j u s t e d w i t h l i m e t o pH 5 - 6 and c a u s t i c used f o r f u r t h e r n e u t r a l i z a t i o n . 3. Foam G e n e r a t i o n System a. Foam S e p a r a t i o n Tank S t a g i n g o f t h e system i s recommended. I t p e r m i t s s e q u e n t i a l r e -moval o f t o x i c a n t s and would be b e n e f i c i a l t o d e t o x i f i c a t i o n . The r e t e n t i o n t i m e o f t h e p r o c e s s c o n t r o l s t h e amount of foam d i s c h a r g e d . S h o r t r e t e n t i o n t i m e s , a l t h o u g h r e d u c i n g t h e volume o f t h e foam s e p -a r a t o r , w i l l i n c r e a s e t h e g a s - l i q u i d c o n t a c t t i m e and i n c r e a s e t h e 224 volume of foam d r a s t i c a l l y . E x p e r i m e n t a l r e s u l t s i n d i c a t e t h a t a 3-s t a g e system ( 1 s t and 2nd s t a g e s f o r d e t o x i f i c a t i o n , 3 r d s t a g e f o r p r o t e c t i o n ) w i t h a r e t e n t i o n t i m e o f 1 h r (20 m i n / s t a g e } s u i t s a l l r e -q u i r e m e n t s . The foam s e p a r a t o r s h o u l d have a c l o s e d t o p w i t h a minimum 3 - f t foam h e i g h t t o a l l o w f o r l i q u i d d r a i n a g e . P r o v i s i o n s h o u l d a l s o be made f o r t h e i n s t a l l a t i o n o f a foam b r e a k e r on t o p o f t h e c o v e r . To i n s t a l l t h e d i r e c t i o n a l j e t s y s t e m , a c h a n n e l t y p e foam s e p a r a t i o n t a n k , s e m i -c i r c u l a r a t b o t h ends i s p r e f e r r e d . T h i s w i l l a l l o w t h e plume o f t h e a i r - l i q u i d m i x t u r e ( F i g u r e 45) t o f l o w f r e e l y i n t h e c h a n n e l and e x t e n d b u b b l e r e t e n t i o n i n t h e l i q u i d phase. T r a n s f e r o f t o x i c a n t s t o t h e g a s-l i q u i d i n t e r f a c e would be enhanced. b. Foam G e n e r a t o r 2 F o r t h e a v e r a g e k r a f t m i l l e f f l u e n t , a p p r o x i m a t e l y 20 m / l o f g a s -l i q u i d i n t e r f a c i a l a r e a i s r e q u i r e d f o r t o x i c i t y a d s o r p t i o n . The a i r c a p a c i t y r e q u i r e m e n t i s minimum w i t h equipment t h a t p r o d u c e s t h e f i n e s t b u b b l e s . However, most f i n e b u b b l e p r o d u c i n g equipment i s h i g h i n c a p i t a l and energy c o s t s , t h e r e f o r e , economic f a c t o r s s h o u l d be c o n -s i d e r e d i n o r d e r t o d e c i d e what b u b b l e s i z e i s most s u i t a b l e . Most o f t h e c o m m e r c i a l l y a v a i l a b l e equipment can p r o d u c e b u b b l e s i z e s i n t h e r a n g e of 0.5 - 3 mm. P r o d u c t i o n o f an a v e r a g e 1 mm d i a m e t e r b u b b l e appears t o be a r e a s o n a b l e o b j e c t i v e , i n terms o f energy and economy. 225 T h e o r e t i c a l assessment of v a r i o u s a e r a t o r s (Chapber V I ) s u g g e s t e d t h a t a j e t a e r a t o r system would be most s u i t a b l e f o r p r o d u c i n g 1 mm d i a -meter b u b b l e s . A j e t a e r a t o r system depends on pumps, b l o w e r s and a s e r i e s o f j e t m i x i n g systems t o p r o d u c e b u b b l e s . The s i z e s a r e i n -v e r s e l y p r o p o r t i o n a l t o t h e energy i n p u t and a r e a f f e c t e d by t h e f o l -l o w i n g f a c t o r s : C o n t r o l l i n g P a r a m e t e r s G a s - l i q u i d i n t e r f a c i a l a r e a t o be g e n e r a t e d , Amount o f a i r r e q u i r e d , Shear f o r c e , b u b b l e s i z e and power c o n s u m p t i o n , B u b b l e s i z e and g a s - l i q u i d c o n t a c t t i m e , P a t t e r n of t h e plume o f f i n e b u b b l e s and g a s - l i q u i d c o n t a c t . F a c t o r Number o f j e t u n i t s B l o w e r c a p a c i t y Pumping c a p a c i t y L i q u i d submergence Geometry o f t h e t a n k The f i r s t t h r e e f a c t o r s a r e i n t e r r e l a t e d and must be d e t e r m i n e d f o r a p e r f o r m a n c e optimum where a t e c o n o m i c a l c o s t , a maximum g a s - l i q u i d i n t e r f a c i a l a r e a i s p r o d u c e d . F o r most i n d u s t r i a l a p p l i c a t i o n s t h e l i q u i d v e l o c i t y a t t h e j e t o u t l e t (50 f t / s e c ) i s c r i t i c a l f o r p r o d u c i n g f i n e b u b b l e s ; a l i q u i d submergence o f 15 f t i s c o n s i d e r e d adequate t o promote a i r d i s p e r s i o n and t o p r o v i d e adequate g a s - l i q u i d c o n t a c t t i m e . Among t h e v a r i o u s models a v a i l a b l e t h e d i r e c t i o n a l l y mixed j e t a e r a t o r i system i s t h e p r e f e r r e d d e s i g n . T h i s system e j e c t s f i n e b u b b l e s h o r -i z o n t a l l y and r e t a i n s t h e b u b b l e s i n t h e l i q u i d f o r t h e l o n g e s t p o s s i -226 b l e r e t e n t i o n t i m e . The b u b b l e s i z e s p r o d u c e d a r e s m a l l and m i x i n g i s c o m p l e t e . c. B l o w e r C a p a c i t y 2 To produce 20 m / l o f g a s - l i q u i d i n t e r f a c i a l a r e a and u s i n g j e t a e r a t o r s y stems, t h e a i r r e q u i r e m e n t f o r b u b b l e s o f 1.2 mm d i a m e t e r i s e s t i m a t e d t o be 4 t i m e s t h e l i q u i d f l o w r a t e . To be c o n s e r v a t i v e t h e foam s e p a r a t i o n p r o c e s s s h o u l d be o p e r a t e d a t a G/L o f 6. The t o t a l a i r 3 r e q u i r e m e n t i s e s t i m a t e d t o be 13,600 f t /min f o r a 25 MGD p l a n t . The p r e s s u r e drop a c r o s s t h e j e t ( 1 - i n d i a m e t e r ) i s n e g l i g i b l e . O n l y l i q u i d head and f r i c t i o n i n t h e a i r p i p i n g and a i r header c o n -t r i b u t e s i g n i f i c a n t l y t o p r e s s u r e d r o p . C o n v e n t i o n a l c e n t r i f u g a l t y p e a i r b l o w e r s r a t e d a t o p e r a t i n g p r e s s u r e s o f 10 t o 15 p s i w o u l d appear t o be s u i t a b l e . 4. Foam H a n d l i n g Based on t h e r e s u l t s o f t h e p i l o t p l a n t t e s t s , i t i s r e a s o n a b l e t o assume t h a t 1.2% o f t h e i n f l u e n t w i l l be t r a n s f o r m e d t o foam c o n t a i n i n g 3 1.5% o f l i q u i d , i . e . n o t more t h a n 2000 f t /min o f foam w i l l be p r o -duced. The foams must be removed, c o l l a p s e d and t r e a t e d p r i o r t o d i s -p o s a l . 227 a. Foam B r e a k i n g System To e l i m i n a t e t h e i n s t a l l a t i o n o f an e x p e n s i v e foam s c r a p i n g s y s t e m and assuming t h a t t h e foam does n o t f l o w , a foam b r e a k e r s h o u l d be mounted on top of t h e foam s e p a r a t o r . I t must pump, c o l l a p s e and d i s -c h a r g e t h e l i q u i f i e d foam t o a t r e a t m e n t system. T h r e e f a c t o r s s h o u l d be c o n s i d e r e d f o r s e l e c t i o n o f a s u i t a b l e system: F a c t o r C o n t r o l l i n g P a r a m e t e r S u c t i o n f o r c e R a t e o f pumping t h e foams f o r c o n t a c t o f b l a d e . C e n t r i f u g a l f o r c e S t r e t c h i n g t h e f i l m , c r e a t e t h i n s p o t f o r foam r u p t u r e . Shear f o r c e F o r r u p t u r e o f foam f i l m . The p i l o t p l a n t s y s t e m used t o e v a l u a t e m e c h a n i c a l foam b r e a k e r s i n d i c a t e s t h a t a 3 - b l a d e , t u r b i n e , vaned d i s c system o p e r a t i n g a t >2200 cm/sec t i p speed i s e f f i c i e n t f o r foam b r e a k i n g . Foam l o a d and power r e q u i r e m e n t o f a 3-blade t u r b i n e were g i v e n by ( S e c t i o n V-H-3) F = (2.6 x 1 0 _ 3 N + 7.7 x 10" 2D - 4.7) 3 where: F = foam l o a d (m /min) N = r o t a t i o n speed (rpm) D = d i a m e t e r o f t u r b i n e (cm) P = F x (51.7 x 1 0 _ 1 7 N 3 D 5 + 51.2) P = w a t t s F o r c o m m e r c i a l i n s t a l l a t i o n s , a 2 4 - i n (62 cm) d i a m e t e r vaned d i s c t u r b i n e p o s i t i o n e d on t h e top o f t h e foam s e p a r a t o r w o u l d be most s u i t -a b l e . 228 S h o u l d foaming become e x c e s s i v e and t h e volume o f foam exceed 2%, r e f l u x o f foam would be r e q u i r e d . I n c r e a s e d foam h e i g h t i s i n g e n e r a l e f f e c t i v e i n p r o m o t i n g foam c o a l e s c e n c e , s e l f d e s t r u c t i o n and r e d u c i n g t h e t o t a l f l o w r a t e . A l t e r n a t i v e l y , t h e s p a c i n g and p o s i t i o n o f t h e foam b r e a k e r c o u l d be a l t e r e d t o i n c r e a s e t h e t r a v e l d i s t a n c e of foam t o t h e e f f e c t i v e s u c t i o n r e g i o n . N e v e r t h e l e s s , i n s t a l l a t i o n o f a f i n e s p r a y foam r e c y c l i n g system on top o f t h e foam l a y e r would be a d v i s a b l e i n t h e e v e n t t h a t foaming became e x c e s s i v e l y h i g h . b. Foam Treatment System The c o l l a p s e d foam i s c o n c e n t r a t e d i n BOD,., suspended s o l i d s , t o x -i c i t y and i s h i g h l y foamable. F o r a 25 MGD p l a n t , c o l l a p s e d foam i s d i s c h a r g e d a t a r a t e o f 250,000 t o 500,000 g a l / d a y . A b i o l o g i c a l t r e a t -ment p r o c e s s i s p r e f e r r e d because o f i t s h i g h d e t o x i f i c a t i o n e f f i c i e n c y and low o p e r a t i n g c o s t . T r e a t e d e f f l u e n t s a r e pumped back t o t h e foam g e n e r a t i o n t a n k t o p r o t e c t t h e s y s t e m a g a i n s t o p e r a t i o n f a i l u r e . C. PROPOSAL FOR A 25 MGD FOAM SEPARATION PLANT A 25 MGD foam s e p a r a t i o n p l a n t , based on t h e most u p - t o - d a t e d e s i g n d a t a , has been p r o p o s e d i n a r e c e n t s t u d y ( 1 2 9 ) . The major and a u x i l -i a r y o p e r a t i n g equipment r e q u i r e d , t h e power c o n s u m p t i o n , and t h e c a p i t a l c o s t e s t i m a t e d f o r d e t o x i f y i n g : t y p i c a l k r a f t m i l l e f f l u e n t of MST: 3-4 h r s a r e r e p r o d u c e d i n ^ A p p e n d i c e s X I X a-d f o r r e f e r e n c e . T h i s system would be i n s t a l l e d w i t h a d i r e c t i o n a l j e t a e r a t o r f o r foam g e n e r a t i o n and a t u r b i n e f o r foam b r e a k i n g . C o s t f i g u r e s were 229 o b t a i n e d from equipment s u p p l i e r s . F i g u r e 50 shows a s c h e m a t i c d i a g r a m o f t h e prop o s e d system. F i g u r e 51 shows t h e l a y o u t o f t h e foam ge n e r -a t i o n t a n k w i t h a j e t a e r a t o r and a t u r b i n e foam b r e a k e r . The power r e -q u i r e m e n t s and i n s t a l l e d c a p i t a l c o s t s a r e e x t r a c t e d f r o m A p p e n d i x X I X a-d and summarized as f o l l o w s : No. HP C o s t P r o c e s s E l e m e n t s C a p a c i t y R e q u i r e d T o t a l I n s t a l l e d Pump_Ln_ S_ta_tion ( A p p e n d i x X l X - a ) E f f l u e n t C o l l e c t i o n Tank C/W S c r e e n 50,000 g a l 1 - 200,000 Pump - 5,000 g a l / m i n 5 200 250,000 £H_Cmit_r_l_S_s_em (A p p e n d i x X l X - b ) t o c o n t r o l pH a t 7 1 200,000 F_oam_Sej3a.ra.tion (Appendix X I X - c ) Foam Tank 1.23 M G a l 1 - 330,000 J e t A e r a t o r ( D i r e c t i o n a l l y mixed) 24 j e t s / u n i t 12 - 350,000 R e c i r c u l a t i o n Pump 5000 g a l / m i n 13 540 2 00,000 3 Blower 4500 f t /min 3 900 2 50,000 F_oam_Tr_e_tment (Appendix X l X - d ) Foam b r e a k e r 170 f t 3 / m i n 13 240 180,000 3 day a e r a t e d l a g o o n 2.2 M g a l 1 45 300 ,003 T o t a l 1,925 $ 2,260,000 The p l a n t c o s t i s e s t i m a t e d a t $ 2 . 3 M w i t h 1925 horsepower r e -qu i r e m e n t . F o r c o m p a r i s o n p u r p o s e s , t h e c a l c u l a t i o n was r e p e a t e d assuming e f f l u e n t s were t w i c e as t o x i c (MST:1.5-2 h r ) and h a l f as t o x i c (6-8 h r ) a t h e t y p i c a l e f f l u e n t , i . e . MST: 3-4 h r . The c o r r e s p o n d i n g c a p i t a l c o s t s e s t i m a t e d a t $3.06M(3365 Hp) and $1.46 M(1205 hp) r e s p e c t i v e l y . F i g u r e 50 SCHEMATIC DIAGRAM OF FULLY INTEGRATED FOAM SEPARATION PILOT PLANT Influent pH ADJUSTMENT SYSTEM FOAM COLLECTION TANK Nontoxic effluent FOAM TREATMENT SYSTEM Nontoxic effluent to sewer 1x3 CO o 231 F i g u r e 51 LAYOUT OF FOAM SEPARATION SYSTEM Air line (by pen) (non wt. bearing) baffle Blowers Air main (by others) Foam breaker shown in one of the stages Stage No. 3 26.4m M.I3m PLAN VIEW scale: none D. ESTIMATION OF OPERATING COST The o p e r a t i n g c o s t o f d e t o x i f y i n g t y p i c a l e f f l u e n t s o f a 3-4 h r MST i s e s t i m a t e d as f o l l o w s : $/day P l a n t C o s t : .$ 2,260,000 C a p i t a l w i t h 15 y e a r s l i f e C a p i t a l R e c o v e r y f a c t o r Taxes and I n s u r a n c e 13.5% 3.0% 16.5% 1,021.6 Power C o s t * ( l c/Kwh) C h e m i c a l C o s t = l . l c / 1 0 0 g a l ( 1 2 9 ) 354.9 303.0 M a i n t e n a n c e = ( 5 % o f c a p i t a l ) L a b o r ( i n c l u d e o v e r h e a d = 4 h r / d a y 51.1 a t $16/hr) 32.0 T o t a l 1,762.6 O p e r a t i n g Cost = $2.35/ton o f p u l p (7c/1000 g a l ) R e p e a t i n g t h e same p r o c e d u r e , t h e o p e r a t i n g c o s t s f o r d e t o x i f y i n g a more t o x i c e f f l u e n t (MST:1.5 - 2 h r s ) and a l e s s t o x i c e f f l u e n t (MST:3-6 h r s ) a r e e s t i m a t e d a t $3.20/ton o f p u l p (9.6C/1000 g a l ) and $1.66/ton o f p u l p (5C/1000 g a l ) r e s p e c t i v e l y . The o p e r a t i n g c o s t o f a foam s e p a r -a t i o n system f o r d e t o x i f y i n g t y p i c a l e f f l u e n t i s e s t i m a t e d a t $2.35/ton o f p u l p o r 7C/1000 g a l . The e s t i m a t e d c o s t i s comparable t o an a e r a t e d l a g o o n system ($2.5 - 3.0/ton o f p u l p ) c u r r e n t l y w i d e l y used f o r BOD^and c o n c u r r e n t t o x i c i t y r e m o v a l . T a b l e 39 compares t h e c h a r a c t e r i s t i c s o f t h e two p r o c e s s e s . An a e r a t e d l a g o o n i s a b i o l o g i c a l t r e a t m e n t p r o c e s s , d e s i g n e d p r i m a r i l y * Power C o s t / d a y = 1985 Hp x 0.745 ^ x 24 h r x lc/KWH = $354.9 233 TABLE 39 COMPARISON OF FOAM SEPARATION PROCESS TO AERATED LAGOON PROCESS Nature of Process Ae r a t e d Lagoon ( B i o l o g i c a l ) Foam S e p a r a t i o n ( P h y s i c o - c h e m i c a l ) pH of o p e r a t i o n 7 - 8 7 - 8 R e t e n t i o n time 3 - 5 days 1 - 2 h r Op e r a t i n g temperature 10 - 40 C 10 - 70 C N u t r i e n t requirement BODs:N:P= 100:5:1 None Recovery to shock l o a d slow Rapid S i m p l i c i t y of o p e r a t i o n Simple Simple Performance BOD5 removal T o x i c i t y removal 60 - 85 Z 80 - 100% 10 - 20 % 90 - 100 % Cost (per ton of pulp) f o r d e t o x i f y i n g average e f f l u e n t of 3 - 4 hr MST 1 $2.5 - 3.0 $2.35* For e f f l u e n t s o f MST: 1.5 - 2 hrs : Cost = $3.20/ton of pulp MST: 6 - 8 hrs : Cost = $1.66/ton of pulp t o remove 60 - 80%. o f B 0 D 5 > d e t o x i f i c a t i o n i s a b e n e f i c i a l s i d e e f f e c t . The s y s t e m r e q u i r e s 3 - 5 days r e t e n t i o n t i m e , a d d i t i o n o f n u t r i e n t s and i s s u s c e p t i b l e t o shock l o a d . The s u c c e s s r a t e o f de-t o x i f i c a t i o n c an r e a c h 80 - 100% i f o p e r a t e d p r o p e r l y . ( 3 3 ) . The d i s -t i n c t a d v a n t a g e s o f a foam s e p a r a t i o n p r o c e s s , (a p h y s i c a l s e p a r a t i o n t e c h n i q u e ) a r e t h e s h o r t r e t e n t i o n . r e q u i r e m e n t (<1 h r ) , t h e h i g h s u c c e s s r a t e o f d e t o x i f i c a t i o n (90 - 1 0 0 % ) , and t h e r a p i d r e c o v e r y f r o m s h o c k l o a d s . However, t h e p r o c e s s o n l y removes 10 - 1 5 % o f BOD,.. S i n c e t h e c o s t o f t h i s foam d e t o x i f i c a t i o n p r o c e s s , ( $2.35/ton) d e t o x i f y i n g e f f l u e n t s o f >3 - 4 h r MST i s comparable t o t h a t o f an a e r a t e d l a g o o n p r o c e s s (130) , i t would appear t h a t f o r t h o s e m i l l s w h i c h a r e n o t r e q u i r e d t o remove BOD,., such as i s t h e c a s e f o r t h o s e l o c a t e d on t h e c o a s t , foam s e p a r a t i o n i s a s u i t a b l e p r o c e s s f o r t o x i c i t y r e m o v a l . F o r more t o x i c e f f l u e n t , c o s t o f foam s e p a r a t i o n i s s l i g h t l y h i g h e r ($3.20/ton) t h a n an a e r a t e d l a g o o n p r o c e s s . I n a s i t u a t i o n where l a n d s u p p l y i s a p r o b l e m , foam s e p a r a t i o n s t i l l r e p r e s e n t s a v i a b l e a l t e r n a t i v e . 235 CHAPTER IX SUMMARY AND CONCLUSIONS 1. The p o l l u t a n t s d i s c h a r g e d from a b l e a c h e d k r a f t m i l l c o n s i s t o f numerous o r g a n i c and i n o r g a n i c m a t e r i a l s . N e v e r t h e l e s s , t h e y can be summarized a s : - pH i n b a l a n c e - suspended s o l i d s - B i o c h e m i c a l Oxygen Demand (BOD) t o x i c i t y c o l o r . A l a r g e number o f p u l p m i l l s i n Canada have a l r e a d y i n s t a l l e d n e u t r a l i z a t i o n s y s t e m s , c l a r i f i e r s , and b i o l o g i c a l t r e a t m e n t p r o c e s s e s f o r m e e t i n g t h e F e d e r a l and P r o v i n c i a l pH, suspended s o l i d s and BOD d i s c h a r g e g u i d e l i n e s . The t e c h n o l o g y f o r t o x i c i t y and c o l o r r e m o v a l a r e s t i l l under development. 2. A t p r e s e n t , t o x i c i t y r e m o v a l i n t h e k r a f t i n d u s t r y r e l i e s com-p l e t e l y on t h e p r o p e r p e r f o r m a n c e o f t h e i r b i o l o g i c a l t r e a t m e n t s y s t e m ( f o r r e m o v a l o f BOD,.) t o a c h i e v e c o n c u r r e n t d e t o x i f i c a t i o n . C o n d i t i o n s f o r o p t i m a l BOD,, r e m o v a l a r e n o t n e c e s s a r i l y c o m p a t i b l e w i t h d e t o x i -f i c a t i o n ; t h e r e f o r e d e t o x i f i c a t i o n s u c c e s s r a t e s a r e n o t a l w a y s s a t -i s f a c t o r y . F o r c o a s t a l m i l l s w h i c h a r e n o t r e q u i r e d t o remove t h e BOD,. and f o r m i l l s w i t h l a n d s h o r t a g e p r o b l e m s , b i o l o g i c a l t r e a t m e n t p r o -236 c e s s e s ( e . g . 5-day a e r a t e d l a g o o n and 24-hr low r a t e a c t i v a t e d s l u d g e s y stems) a r e n o t s u i t a b l e . An a l t e r n a t i v e r a p i d , r e l i a b l e d e t o x i f i -c a t i o n p r o c e s s i s d e s i r e d . A t p r e s e n t , t h e i m p a ct of k r a f t m i l l e f f l u e n t c o l o r t o t h e r e -c e i v i n g w a t e r has n o t been w e l l e s t a b l i s h e d . Removal o f c o l o r t h e r e f o r e i s o f low p r i o r i t y . 3. The m ajor t o x i c compounds i n k r a f t m i l l e f f l u e n t s a r e n a t u r a l l y o c c u r i n g and c h l o r i n a t e d r e s i n a c i d s (up t o 8 and 2 mg/1 r e s p e c t i v e l y ) and u n s a t u r a t e d f a t t y a c i d s (up t o 2 mg/1). O t h e r t o x i c a n t s i n c l u d e c h l o r i n a t e d l i g n i n , p h e n o l i c s , a l c o h o l s , e p o x y s t e a r i c a c i d s and j u v a -b i o n e s . A t y p i c a l combined w h o l e m i l l e f f l u e n t c o n t a i n s t o x i c a n t s , 10 -20 t i m e s g r e a t e r t h a n t h e l e t h a l c o n c e n t r a t i o n o f i n d i v i d u a l compounds. These t o x i c m a t e r i a l s a r e m o s t l y o r g a n i c c a r b o x y l i c compounds and can be d e s t r o y e d by c h e m i c a l o r b i o l o g i c a l means. S e v e r a l p r o c e s s e s e.g. c a r b o n a d s o r p t i o n , c h e m i c a l f l o c c u l a t i o n and o z o n a t i o n have been p r o p o s e d as a l t e r n a t i v e s t o b i o l o g i c a l d e t o x i f i c a t i o n p r o c e s s e s . How-e v e r , t h e c o s t s , e s t i m a t e d a t $6 - 20 p e r t o n of p u l p , a r e 2 - 5 t i m e s g r e a t e r t h a n t h e c o s t s of b i o l o g i c a l t r e a t m e n t . Thus t h e s e p r o c e s s e s a r e n o t e c o n o m i c a l l y v i a b l e . 4. The t o x i c a n t s ( m a i n l y c a r b o x y l i c compounds) a r e s u r f a c e a c t i v e compounds. S u r f a c e a c t i v e compounds a r e known t o r e d u c e s u r f a c e t e n s i o n and promote foaming i n a s o l u t i o n . Under s u i t a b l e c o n d i t i o n s , t h e y can be s e p a r a t e d by foaming as a r e s u l t of t h e i r own s u r f a c e a c t i v i t y . Removal of foam s h o u l d r e s u l t i n r e m o v a l o f t o x i c i t y . T h i s h y p o t h e s i s was v e r i f i e d i n a s t u d y where a n o n - a c t i v e b i o l o g i c a l t r e a t m e n t s y s t e m (extreme pH and ^ a e r a t i o n ) under foaming c o n d i t i o n s , d e t o x i f i e d k r a f t m i l l e f f l u e n t t o a degree comparable t o an a c t i v e b i o l o g i c a l s y s t e m i n t h e l a b o r a t o r y . Based on t h e s e p r e l i m i n a r y d a t a and t h e o r e t i c a l c o n s i d e r a t i o n s , a foam s e p a r a t i o n p r o c e s s was d e v e l o p e d as an a l t e r n a t i v e t o e x i s t i n g t e c h n i q u e s f o r d e t o x i f i c a t i o n . The f e a s i b i l i t y and p r o c e s s p a r a m e t e r s were s t u d i e d i n a 4-1 l a b o r a t o r y foaming columns and a 180-1 f i e l d s i t e column i n s t a l l a t i o n . The r e s u l t s were v e r i f i e d i n a 6000 g a l c a p a c i t y 3 -stage p i l o t p l a n t a t a B.C. c o a s t a l m i l l . 5. D e t o x i f i c a t i o n by foam s e p a r a t i o n was i n v e s t i g a t e d on t h r e e i n -d i v i d u a l p r o c e s s s t r e a m s , namely: u n b l e a c h e d w h i t e w a t e r , a c i d b l e a c h e d e f f l u e n t and c a u s t i c e x t r a c t i o n e f f l u e n t p l u s v a r i o u s combined e f f l u -e n t s . O n l y c a u s t i c e f f l u e n t and i t s combined e f f l u e n t s were r e s p o n s i v e t o foam s e p a r a t i o n t r e a t m e n t . C a u s t i c e x t r a c t i o n e f f l u e n t c o n t a i n e d t h e n e c e s s a r y s u r f a c t a n t and c o u l d be used t o f a c i l i t a t e d e t o x i f i c a t i o n o f o t h e r e f f l u e n t s t r e a m s . However, t h e p r o p o r t i o n o f v a r i o u s e f f l u e n t s t r e a m s p r e s e n t i n t h e combined e f f l u e n t was i m p o r t a n t . F o r a c i d b l e a c h e d e f f l u e n t , d e t o x i f i c a t i o n was e f f e c t i v e i n t h e p r e s e n c e of 20 -35% o f c a u s t i c e f f l u e n t . Two s y n t h e t i c c a t i o n i c s u r f a c t a n t s ( q u a r -t e r n a r y ammonium and amine s a l t s ) c o u l d r e p l a c e c a u s t i c e f f l u e n t f o r c o l l e c t i o n of t o x i c m a t e r i a l s i n u n b l e a c h e d w h i t e w a t e r . 238 6. V a r i o u s combined e f f l u e n t s were a s s e s s e d i n a b a t c h s y s t e m w i t h v a r i a b l e t r e a t m e n t t i m e s , pH and % o f t o t a l volume t r e a t e d . The o p e r -a t i n g c o n d i t i o n s r e q u i r e d t o a c h i e v e d e t o x i f i c a t i o n a r e p r e s e n t e d as f o l l o w s : E f f l u e n t Stream C a u s t i x e x t r a c t i o n C a u s t i c E x t + A c i d B l e a c h e f f l u e n t T reatment Time ( h r ) 17 pH Requirement 2.5 9.5 % T o t a l E f f l u e n t T r e a t e d 20% 50% C a u s t i c E x t + A c i d B l . E f f . + U.W.W. Combined W h o l e m i l l 4 0.25 9.5 9.5 67% 100% Combined w h o l e m i l l e f f l u e n t was s e l e c t e d f o r a l l subsequent t r e a t -ment because of t h e v e r y s h o r t t r e a t m e n t t i m e (0.25 h r ) r e q u i r e d t o e f f e c t d e t o x i f i c a t i o n . I n a d d i t i o n , s i n c e 100% o f t h e e f f l u e n t d i s -c h a r g e d i s t r e a t e d , t h e p r o c e s s e d e f f l u e n t may comply w i t h e f f l u e n t t o x -i c i t y d i s c h a r g e o b j e c t i v e s . 7. P r o c e s s p a r a m e t e r s f o r d e t o x i f i c a t i o n o f whole m i l l e f f l u e n t were i n v e s t i g a t e d on a l a r g e number o f samples. F o r an a v e r a g e e f f l u e n t , t h e f o l l o w i n g c o n d i t i o n s were n e c e s s a r y t o . e f f e c t d e t o x i f i c a t i o n . P r o c e s s P a r a m e t e r C o n d i t i o n pH >7.0 Temperature >10°C Column h e i g h t >20 cm G/L 7 - 10 2 G a s / l i q u i d i n t e r f a c i a l a r e a >20 m / l 239 8. R e s u l t s o f a c o n t i n u o u s s t u d y l e d t o s e v e r a l i m p o r t a n t c o n c l u s i o n s . a. G a s - l i q u i d r a t i o , b u b b l e s i z e and a e r a t i o n r a t e a r e i n t e r -r e l a t e d . These f a c t o r s can v a r y b u t w i l l n o t a f f e c t d e t o x i f i c a t i o n e f f i c i e n c y p r o v i d e d t h e r e q u i r e d g a s - l i q u i d i n t e r f a c i a l a r e a i s p r o -duced. b. The amount o f t o x i c a n t s p r e s e n t i s r e f l e c t e d i n t h e MST v a l u e o f t h e e f f l u e n t . The g a s - l i q u i d i n t e r f a c i a l a r e a r e q u i r e d t o e f f e c t de-t o x i f i c a t i o n i s d i r e c t l y p r o p o r t i o n a l t o t h e MST v a l u e . On a t y p i c a l o e f f l u e n t o f 250 - 350 min MST, 20 - 30 m / l o f i n t e r f a c e i a l a r e a a r e r e q u i r e d . c. A s i m p l e mode i s recommended f o r n o r m a l o p e r a t i o n o f t h e foam d e t o x i f i c a t i o n u n i t . I f foaming becomes e x c e s s i v e , an e n r i c h m e n t mode w i t h i t s b u i l t - i n foam r e f l u x s y s t e m i s p r e f e r r e d . A s t r i p p i n g mode i s n o t s u i t a b l e due t o l a r g e volumes o f foam p r o d u c t i o n . d. D e t o x i f i c a t i o n by foam s e p a r a t i o n i s c o n c e n t r a t i o n dependent. T h e r e f o r e s t a g i n g w i l l be b e n e f i c i a l t o t o x i c i t y r e m o v a l . A 2- s t a g e s y s t e m d e t o x i f i e d 91% o f a l a r g e number of samples compared t o 63% w i t h a s i n g l e s t a g e system. 9. The e f f e c t of v a r i a b i l i t y i n e f f l u e n t c h a r a c t e r i s t i c s on foam de-t o x i f i c a t i o n was s t u d i e d on 205 samples o b t a i n e d from 10 C a n a d i a n k r a f t m i l l s . Under t h e e s t a b l i s h e d foam s e p a r a t i o n c o n d i t i o n s , 170 (80%) samples were d e t o x i f i e d r e g a r d l e s s o f e f f l u e n t v a r i a t i o n . The t r e a t m e n t t i m e r e q u i r e d c o u l d be e x p r e s s e d by: Y = 41.84 X ~ ° . 7 1 where Y = t r e a t m e n t t i m e X = e f f l u e n t MST The r e s u l t s s u g g e s t t h a t foam s e p a r a t i o n of t o x i c i t y f r o m k r a f t m i l l e f f l u e n t i s a p r o c e s s u n i v e r s a l l y a p p l i c a b l e t o t h e b l e a c h e d k r a f t i n d u s t r y . 10. A 180-1 c a p a c i t y column, o p e r a t e d f o r 3 months i n f i e l d s i t e , c o n -s i s t e n t l y and r e l i a b l y d e t o x i f i e d t h e e f f l u e n t s . A t G/Ls of 33 - 48 and 1.6 t o 2.1 h r o f r e t e n t i o n t i m e , 100% o f t h e samples were d e t o x i f i e d . Under s u b - o p t i m a l o p e r a t i o n (G/Ls of 8 - 12 and 1 h r r e t e n t i o n t i m e ) 65 - 75% o f t h e e f f l u e n t s were d e t o x i f i e d . 11. I n v e s t i g a t i o n of t h e d e t o x i f i c a t i o n mechanism on t w e n t y d i f f e r e n t samples o b t a i n e d from t h r e e m i l l s showed t h a t foam f r a c t i o n a t i o n a c -c o u n t e d f o r 77.5% t o x i c i t y r e m o v a l ; v o l a t i l i z a t i o n f o r 5.4% and unknown mechanisms f o r 17.1%. 12. Foam s e p a r a t i o n o f t o x i c i t y can be combined w i t h r e m o v a l o f f i b r o u s suspended s o l i d s . The most s u i t a b l e s y s t e m f o r a combined p r o c e s s i s t h e d i s s o l v e d a i r f l o t a t i o n system. L a b o r a t o r y s t u d i e s i n d i c a t e t h a t suspended s o l i d s c o u l d be r e d u c e d f r o m 450 mg/1 t o l e s s t h a n 55 mg/1 (88% r e m o v a l ) i n one p r e s s u r i z a t i o n c y c l e o p e r a t i n g a t 40 p s i g ; c o m p l e t e d e t o x i f i c a t i o n o f t y p i c a l e f f l u e n t s of MST v a l u e s o f 5 - 6 h r was a c h i e v e d a f t e r 2 - 3 r e p r e s s u r i z a t i o n c y c l e s . However, t r e a t m e n t c o s t s a r e n o t e c o n o m i c a l l y j u s t i f i a b l e . D i s p e r s e d a i r foam g e n e r a t i n g systems were l e s s e f f e c t i v e i n r e - ' moving suspended s o l i d s . Under c o n d i t i o n s w h i c h p r o v i d e d f o r c o m p l e t e d e t o x i f i c a t i o n , o n l y 19 - 62% o f f i b r o u s suspended s o l i d s c o u l d be 241 removed; t h e r e s i d u a l suspended s o l i d l e v e l i n t r e a t e d e f f l u e n t s , however, s t i l l exceeded 90 mg/1. The foam s e p a r a t i o n p r o c e s s a l s o removed 66% o f r e s i n a c i d s , 12% o f B0D 5 (10% TOC), 8% o f c o l o r and 80% o f t h e foaming t e n d e n c y . 13. Foam s e p a r a t i o n o f t o x i c i t y y i e l d s foam as a b y - p r o d u c t . A s i n g l e s t a g e p r o c e s s p r o d u c e s about 4 - 5% o f t h e e f f l u e n t volume as foam. The foam volume w h i c h must be removed depends on t h e o p e r a t i o n mode o f t h e system. However, e f f l u e n t s w i t h h i g h e r t o x i c i t y , r e q u i r e g r e a t e r volumes of foam r e m o v a l f o r d e t o x i f i c a t i o n . The volume of foam can e f f e c t i v e l y be r e d u c e d t o l e s s t h a n 1 - 2% by i n c r e a s i n g t h e foam h e i g h t i n t h e foaming column, i m p r o v i n g i n t e r n a l r e f l u x , o r by r e c y c l i n g c o l l a p s e d foam t o t h e foaming column. The foam, i s e n r i c h e d i n BOD,, and t o x i c i t y . BOD,, of t h e foam ran g e d f r o m 214 - 450 mg/1; t o x i c i t y MST v a l u e s from 13 - 192 min. The en-r i c h m e n t r a t i o i s 1.2 and 8 r e s p e c t i v e l y . Treatment by a 3-day r e -t e n t i o n a e r a t e d l a g o o n and by a 4-hr r e t e n t i o n t i m e r o t a t i n g b i o l o g i c a l d i s c system d e t o x i f i e d t h e c o l l a p s e d foam. C h e m i c a l t r e a t m e n t by p r e -c i p i t a t i o n d i d n o t remove t o x i c i t y . 14. C o m m e r c i a l l y a v a i l a b l e foam g e n e r a t i n g and foam c o l l a p s i n g e q u i p -ment were e v a l u a t e d f o r a p r o p o s e d a p p l i c a t i o n t o a 25 MGD (750 t p d ) p l a n t . 242 a. Foam G e n e r a t i o n F i v e c a t e g o r i e s of foam g e n e r a t i o n equipment were a s s e s s e d : f o r c e d a i r d i f f u s i o n system - h y d r a u l i c s h e a r a e r a t o r s u r f a c e a e r a t o r - h i g h p r e s s u r e a e r a t o r . - m e c h a n i c a l s h e a r a e r a t o r A j e t a e r a t i o n system ( h y d r a u l i c s h e a r a e r a t o r ) i s recommended. I t i s s i m p l e t o o p e r a t e , easy t o m a i n t a i n and e c o n o m i c a l t o use. The b u b b l e s i z e s p r oduced a r e a p p r o x i m a t e l y 1.2 mm i n d i a m e t e r and r e m a i n i n c o n t a c t w i t h t h e s o l u t i o n f o r a l o n g t i m e . b. Foam C o l l a p s i n g W i t h r e g a r d t o foam c o l l a p s i n g , t h e f o l l o w i n g systems were a s -s e s s e d : a i r j e t - l i q u i d s p r a y s o n i c p r e s s u r e - o r i v i c e foam b r e a k e r t h e r m a l t r e a t m e n t - m e c h a n i c a l f o r c e s . I n v i e w of t h e c o p i o u s q u a n t i t i e s o f foam p r o d u c e d from k r a f t m i l l e f f l u e n t s foam c o l l a p s i n g by m e c h a n i c a l f o r c e s such as i m p a c t , compres-s i o n and s h e a r f o r c e s w o u l d be most s u i t a b l e . C ommercial systems w h i c h a r e b e i n g s u c c e s s f u l l y a p p l i e d , and a r e a v a i l a b l e i n t h e market a r e o f t h e c e n t r i f u g a l - t u r b i n e t y p e . They a r e w i d e l y a p p l i e d f o r foam c o n t r o l i n t h e f e r m e n t a t i o n and t h e p u l p and paper i n d u s t r y . The foam b r e a k i n g 243 c a p a c i t y and power con s u m p t i o n can be p r e d i c t e d by t h e f o l l o w i n g r e -l a t i o n s h i p s e s t a b l i s h e d d u r i n g t h i s s t u d y : -3 -2 Foam b r e a k i n g c a p a c i t y : F = 2.6 x 10 N + 7.7 x 10 D - 4.7 \ P -17 3 5 Power con s u m p t i o n : — = 51.7 x 10 N D + 5 1 . 2 r where N = rpm 3 F = foam b r e a k i n g c a p a c i t y (m /min) D = t u r b i n e d i a m e t e r (cm) p = power ( w a t t s ) 15. A p i l o t p l a n t s t u d y was u n d e r t a k e n t o a s s e s s o p e r a t i o n a l r e l i -a b i l i t y . A j e t a e r a t o r system and a t u r b i n e system were i n s t a l l e d i n a 6000 g a l c a p a c i t y foam g e n e r a t i o n t a n k , p r o c e s s i n g 80 - 100 g a l / m i n o f m i l l A combined e f f l u e n t . The sy s t e m was o p e r a t e d o v e r 4 months as a 1, 2 and 3 s t a g e system. The g a s - l i q u i d i n t e r f a c i a l a r e a g e n e r a t e d was 2 k e p t c o n s t a n t a t 5 -.7 m 11 (G/L = 1 ) . The j e t a e r a t o r p r oduced a c o p i o u s amount o f f i n e b u b b l e s c o n -s i s t e n t l y and r e l i a b l y . W i t h an i n f l u e n t t o x i c i t y o f 2.5 - 6 h r MST, t h e g a s - l i q u i d i n t e r f a c i a l a r e a p r o v i d e d r e s u l t e d i n a d e t o x i f i c a t i o n s u c c e s s r a t e o f 50, 86 and 100% as t h e number o f o p e r a t i o n a l s t a g e s i n c r e a s e d from 1 t o 2 and t h e n t o 3 s t a g e s . The foam was h i g h l y con-c e n t r a t e d i n t o x i c m a t e r i a l s , i t s MST ran g e d from 15 t o 20 min. D u r i n g t h e p r o c e s s o f d e t o x i f i c a t i o n , a 3 b l a d e , 1 2 - i n d i a m e t e r vaned d i s c t u r b i n e (1800 rpm, 300 cm/sec t i p speed) r e l i a b l y c o l l a p s e d 3 up t o 42 f t /min of foam o v e r 8 months of c o n t i n u o u s o p e r a t i o n . F i b r e s c o l l e c t e d i n t h e foam d i d n o t cause o p e r a t i o n a l p r o b l e m s . 16. A 25 MGD f u l l y i n t e g r a t e d foam s e p a r a t i o n p l a n t c o n s i s t i n g o f foam g e n e r a t i o n , foam c o l l a p s i n g and foam d i s p o s a l was d e s i g n e d and t h e o p e r a t i n g equipment s e l e c t e d . C a p i t a l c o s t i n s t a l l e d and o p e r a t i n g c o s t s were e s t i m a t e d t o be $2.3 M and $2.35/ton o f p u l p . The c o s t i s comparable t o t h a t o f an a e r a t e d l a g o o n p r o c e s s and l o w e r t h a n t h e h i g h r a t e b i o l o g i c a l p r o c e s s e s . 17. 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O f t e n 2051526. 113. Gaden J r . , E.L. and V. K e v o r k i a n . 1956. Foams i n C h e m i c a l T e c h n o l o g y . Chem. Eng. (Oct. 1956):173. 114. Dosey, A.E. 1959. C o n t r o l o f Foam D u r i n g F e r m e n t a t i o n By The A p p l i c a t i o n o f S o n i c Energy. B i o t e c h , and B i o e n g . 1 ( 3 ) : 2 8 9 . 115. Adams. F.R. 1958. U l t r a s o n i c C o a t i n g C o l o r Refoaming. TAPPI. 41(5):173A. 116. G a s t r o c k , E.A. and J.D. R e i d . 1963. A n t i f o a m i n g D e v i c e f o r Use i n C o n c e n t r a t i o n of Nonflammable L i q u o r s . I n d . Eng. Chem. 10 ( 8 ) : 4 4 0 . 117. Poncha, R.P. and B.L. K a r g e r . 1965. S t u d i e s of R e c o v e r y by Foam F r a c t i o n a t i o n on 1-Naphthylamine. A n a l . Chem. _3_7 ( 3 ) : 4 2 2 . 118. E c k s t e i n , N. 1977. P r i v a t e Communication Harmac P u l p M i l l ( M a c M i l l a n - B l o e d e l L t d . ) Vancouver I s l a n d , B.C. 119. M i e l e , R. 1964. 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B l a c k L i q u o r O x i d a t i o n a t G r e a t Lakes Paper Company L t d . P u l p Paper Mag. Canada. 71:T45. 126. Leamy, C H . 1973. S c a l e - u p of Gas D i s p e r s i o n M i x e r s . Chem. Eng. 80(24):115. 127. H o l l a n d , F.A. and F.S. Chapman. 1966. L i q u i d M i x i n g and P r o -c e s s i n g i n S t i r r e d Tanks. R e i n h o l d Pub. Corp. N.Y. 128. Ng, K.S. and C C Walden. 1977. P i l o t P l a n t E v a l u a t i o n of a J e t Foam G e n e r a t i o n System. CPAR P r o j e c t 508-2, Canadian F o r e s t r y S e r v i c e , Ottawa, Canada. 129. Ng, K.S. and C C Walden. 1975. Study o f Foam S e p a r a t i o n as a Means of D e t o x i f y i n g B l e a c h e d K r a f t M i l l E f f l u e n t s . CPAR P r o j e c t 233-3, C a n a d i a n F o r e s t r y S e r v i c e , Ottawa, Canada. 130. Ekons, C o n s u l t i n g E n g i n e e r s . 1972. C o s t o f E f f l u e n t Treatment a t D i f f e r e n t P u r i f i c a t i o n L e v e l s . Paper Trade J . 1 5 6 ( 4 1 ) : 50. 254 APPENDIX I EFFLUENT COMPOSITION VS pH REQUIREMENT FOR DETOXIFICATION E f f l u e n t MST o f MST o f E f f l u e n t T r e a t e d C o m p o s i t i o n U n t r e a t e d Sample a t ( h r ) C a u s t i c A c i d (hr) pH 2.5 pH 7.0 pH 9.5 100 0 1.4 * 80% S u r v i v a l 2.2 1.0 80 20 2.2 72 4.2 2.4 67 33 0.3 <24 4.6 4.9 50 50 0.3 5.7 24 24 33 67 1.7 4.2 24 * 80% s u r v i v a l ** 20 80 2.7 3.7 24 NT 0 100 1.7 6.3 24 24 MST v a l u e cannot be o b t a i n e d because over 50% o f f i s h s u r v i v e d a f t e r 96 h r s e x p o s u r e . NT = Not t o x i c . APPENDIX II 255 TOXICITY OF SELECTED CATIONIC SURFACTANTS TO FISH AT 50 ppm CONCENTRATION T o x i c 1 - H e x a d e c y l p y r i d i n i u m C h l o r i d e Ethomeen S/20 Arquad 2HT-75 Dehyquart CDB Hyamine 2389 R o c c a l MC-14 Ammonyxl T N o n - t o x i c H e x a d e c y l t r i m e t h y l Ammoniumbromide B e n z y l h e x a d e c y l d i m e t h y l Ammonium C h l o r i d e Ethomeen C/25 Amine T. V a r i q u a t 450 The s u r f a c t a n t s a r e c o n s i d e r e d n o n - t o x i c a t t e s t c o n c e n t r a t x o n when o v e r 80% o f t h e f i s h s u r v i v e d a f t e r 96 h r s ex p o s u r e . APPENDIX III CORRELATION BETWEEN INITIAL TOXICITY AND GAS-LIQUID INTERFACIAL AREA REQUIRED FOR DETOXIFICATION  Treatment Time (hr) No. of Samples I n i t i a l MST, min (meantS.D.) I n t e r f a c i a l Area Required for D e t o x i f i c a t i o n * (m 2/l) MILL E 0.50 1 255 22.5 3.00 7 147± 97 135.0 4.00 3 40± 10 180.0 4.50 9 33± 22 202.5 MILL F 0.25 28 265±177 11.25 0.50 4 257±156 22.50 1.00 10 150± 79 45.00 2.00 17 110± 65 90.00 MILL G 0.25 7 309±111 11.25 0.50 7 281±230 22.50 1 .00 4 217±176 45.00 2 .00 4 53± 21 90.00 MILL H 2.00 6 538±299 90.00 3.00 6 343±132 135.00 4.00 5 283±175 180.00 A i r dispersion system: sintered glass 45 p pore size average bubble diameter, 1.5 mm APPENDIX IV-a OPERATING DATA OF A SINGLE STAGE CONTINUOUS FOAM SEPARATION SYSTEM Volume: 180 l i t r e s , Four 1' length, 3" Diameter Ceramic tubes, Pore s i z e : < 25 u Day of Operation Treatment Conditions Toxic i t y Foam Volume pH Retention time (hr) G/L * Influent (MST, min) Treated effluent (% Survival i n 65% effluent over 96 hr) (% of Influent converted to foam) Nov. 1 8.8 1.0 8 702 80 2.7 4 9.6 1.0 9 120 90 7.7 5 8.3 1.2 9 - 100 8.01 7 - - - 300 100 -8 9.2 0.97 7 150 0 7.01 9 10.0 0.97 7 252 100 3.6 10 9.4 1.0 9 48 0 10.7 11 8.1 0.8 8 192 60 8.5 Range Mean ± SD 8.1 - 10 9±0.7 0.8 - 1.0 0.97 ±008 7-9 8±1 48-702 252±215 0-100 2.7 - 10.2 6.8±2.7 50% of f i s h were k i l l e d at the s p e c i f i c mean surviv a l time indicated APPENDIX IV-b OPERATING DATA OF A 2 STAGE CONTINUOUS FOAM SEPARATION SYSTEM Volume: 180 l i t r e s e ach, Four 1' Length 3" Diameter Ceramic Tubes, Pore S i z e : <25 y Treatment C o n d i t i o n s T o x i c i t y Foam Volume f/ o f i n f l i i P n t Day o f ** T r e a t e d E f f l u e n t /a/ rt * t J / ro/ f f ~l . • c o n v e r t e d t o foam) (% S u r v i v a l i n 65% e r r l u e n t O p e r a t i o n pH G/L T o t a l I n f l u e n t o v er 96 h r ) 1 s t 2nd R e t e n t i o n ^ MST Time ( h r ) (min) 1 s t Stage 2nd Stage Stage Stage Dec. 6 6.0 9.4 0.88 600 40 100 - -7 8.0 7.3 0.85 402 . 10 100 — — 8 8.0 7.3 0.85 300 0 100 — — 9 8.0 9.5 0.92 - - — — — 10 8.0 9.5 0.92 180 0 70 — — 11 8.1 8.2 0.95 300 0 100 2.5 0.8 12 8.0 8.8 0.90 350 20 100 2.8 0.7 13 8.0 7.6 0.80 210 0 100 5.2 1.7 14 8.0 8.6 0.83 252 0 100 — — 15 8.0 10.8 1.15 300 10 80 3.9 0.9 16 8.2 10.6 1.33 220 0 100 2.5 0.3 17 8.8 11.4 1.10 120 0 100 — — 18 8.0 11.0 1.17 - - 100 4.7 1.0 19 8.0 9.2 0.96 240 30 100 3.1 0.9 20 8.0 10.0 0.98 192 0 100 5.0 1.1 Range 6.0-8.8 7.3-11.4 0.80-1.17 120-600 0-40 70-100 2.5-5.2 0.3-1.7 Mean ± SD 8.0±0.6 9.3± 1.3 0.97±0.14 277±125 - — 3.7±1.1 0.9±0.4 * R e t e n t i o n time and G/L i n each s t a g e i s 50% of the t o t a l . 50% o f f i s h were k i l l e d a t the s p e c i f i c mean s u r v i v a l time i n d i c a t e d . NJ CO 259 APPENDIX V (a)  DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL A BY FOAM SEPARATION Date Treatment To x i c i t y - i n 100% Test Concentration(MST:min) % of Fish ^Treated Effluent Time (hr) Before Treatment After Treatment Survived in65% Effluent over 96 hr Meets Toxicity Standards July 24 0.25 1440 NT 100 Yes 25 0.25 90 1440 100 Yes 27 0.25 480 NT 100 Yes 28 0.25 600 NT 100 Yes 30 0.25 450 NT 100 Yes - 0.25 450 NT 100 Yes - 0.25 720 NT 100 Yes Augus t 18 0.25 420 NT 100 Yes Range - 90 - 1440 1440-NT - -Mean ± S D 0.25 581 + 390 - 100 -Federal t o x i c i t y standard i s met when over 80% of f i s h survived i n 65% effluent over 96 hrs. 260 APPENDIX V (b)  DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL B BY FOAM SEPARATION Date Treatment Toxicity of Effluent i n 100% Test Cone.(MST:min) % of Fish Survived i n * Treated Effluent Time (hr) I n i t i a l (min) Final (min) 65% Effluent over 96 hr Meets Toxicity S tandard October 31 1.5 1440 NT 100 Yes 25 1.5 1080 NT 100 Yes 29 1.5 150 NT 100 Yes November 5 3 600 NT 100 Yes 6 0.5 420 NT 100 Yes 8 0.5 360 NT 100 Yes 9 0.5 600 NT 100 Yes 12 3 30 NT 100 Yes 13 3 1320 1440 100 Yes 15 0.5 1440 NT 100 Yes 18 3 600 1200 80 Yes 19 1 420 NT 100 Yes 20 3 120 1080 0 No 21 0.5 500 NT 100 Yes 22 3 270 1080 20 No 25 3 330 1200 70 No 26 3 300 1080 . 80 Yes 27 1 600 NT 100 Yes Range 0.5 - 3 30 - 1440 1200-NT 0 - 100 -Mean ± SD 1.9 ± 1.2 588 ± 442 - - -* Federal t o x i c i t y standard i s met when over 80% of f i s h survived i n 65% effluent over 96 hrs. 261 APPENDIX V (c)  DETOXIFICATION QF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL C BY FOAM SEPARATION Date Treatment Time (hr) T o x i c i t y o f E f f l u e n t i n 100% T e s t C o n c e n t r a t i o n B e f o r e Treatment A f t e r Treatment J a n . 16 1 240 NT 17 3 60 NT 18 3 150 NT 19 3 30 NT 24 3 30 NT 26 3 40 500 29 3 25 600 30 3 15 NT 31 3 60 NT Feb. 1 2 105 NT 2 3 75 1200 5 2 90 NT 6 2 100 NT 7 2 120 NT 8 2 165 NT 9 2 90 NT • 12 3 65 NT 13 3 65 NT 14 3 105 NT Range 1 - 3 15 - 240 500-NT Mean ± S D 2.5 ± 0.5 86 ± 55 -APPENDIX V (d)  DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL D BY FOAM SEPARATION Date Treatment Time (h r ) T o x i c i t y 100% T e s t of E f f l u e n t i n Cone.(MST:min) B e f o r e Treatment A f t e r Treatment May 9 1 240 NT 10 1 180 NT 14 1 240 NT 15 2 405 NT 16 2 140 1080 18 2 255 702 22 2 105 NT 23 2 100 NT 24 1 120 NT 25 1 75 NT 28 2 20 195 29 2 65 720 30 2 120 1080 31 2 15 NT June 1 1 150 NT 4 2 45 NT 5 0.25 240 NT 6 2 40 1080 7 2 150 1080 11 2 90 NT Range 0.25 - 2 20 - 405 195 - NT Mean ± S D 1.5 + 0.5 140 ± 97 -DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL E BY FOAM SEPARATION Date Treatment Time (hr) T o x i c i t y o f E f f l u e n t i n 100% T e s t Cone.(MST:min) B e f o r e Treatment A f t e r Treatment J a n . 16 4.5 45 NT 17 4 30 NT 18 4 50 NT 19 4.5 45 NT 22 4 40 NT 25 4.5 20 NT 26 4.5 15 NT 29 4.5 15 NT 30 3 360 NT 31 3 140 NT Feb. 1 3 120 NT 2 3 105 NT 5 3 75 NT 7 3 90 NT 8 4.5 70 1200 9 4.5 60 1200 12 3 140 NT 13 0.5 255 NT 14 4.5 10 1080 15 4.5 20 1080 Range 0.5 - 4.5 10 - 360 1080 - NT Mean ± S D 3.5 ± 1.0 74 ± 79 -APPENDIX V (f) 264 DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL F BY FOAM SEPARATION Treatment Toxicity (MST) Date T l ne (h r) I n i t i a l (min) Final (min) February 3 0 .5 250 NT 11 2 30 NT 12 2 95 NT 15 2 95 1200 17 1 250 NT 18 1 80 NT 19 2 50 NT 20 1 65 NT 21 2 75 NT 22 . 2 80 NT 24 2 150 1320 25 1 150 NT 28 1 135 NT March 1 0 .5 150 NT 7 1 120 NT May 8 0 .25 840 NT 9 0 25 1080 NT 11 0 25 NT NT 14 0 .25 300 NT 15 0 25 120 NT 16 0 25 270 NT 17 0 25 255 NT 18 0 25 240 NT 19 0 25 240 NT 21 0 25 150 NT 22 0 25 180 NT 23 0 25 540 NT 24 0 25 150 NT 26 0 25 300 NT 28 0 25 60 NT 29 2 110 1440 30 1 210 NT 31 2 200 1320 June 2 2 90 1320 4 0 25 240 NT 5 0 25 120 NT 6 0. 25 30 NT 7 0 5 150 NT 8 1 100 NT 9 0 25 30 NT 11 2 60 1440 12 2 45 NT 13 2 50 NT 19 0. 25 240 NT July 11 2 240 1440 12 0. 25 240 NT 13 0. 25 360 NT 14 0. 25 180 NT 15 2 240 1440 16 0. 5 480 NT 17 0. 25 150 NT 18 0. 25 390 NT 19 0. 25 180 NT 20 0. 25 NT NT 21 0. 25 1440 NT 22 2 150 360 23 0. 25 360 NT 24 0. 25 210 NT 25 0. 25 540 NT October 1 0. 25 450 NT 4 . 0. 25 1440 NT 11 1 300 NT 16 2 120 1080 17 1 90 NT Range 0.25 - 2 1440 - NT 360 - NT Mean + S D 0.9 ± 0.4 254 ± 285 -265 APPENDIX V (a) DETOXIFICATION OF BLEACHED KRAFT. WHOLEMILL EFFLUENT  FROM MILL G BY FOAM SEPARATION Date Treatment Toxicity of Effluent i n 100% Test Cone. (MST:min) % of Fish Survival i n 'Treated Effluent Meets Federal Time (hr) Before After 65% Effluent Treatment Treatment u v s r r?o Toxicity Standard May: 14 1 120 NT 100 Yes 15 0.25 450 NT 100 Yes 17 1 480 NT 100 Yes 18 1 150 NT 100 Yes 22 1 120 NT 100 Yes 23 0.25 420 NT 100 Yes 24 0.50 105 NT 100 Yes 25 0.50 120 NT 100 Yes 28 0.50 420 NT 100 Yes 29 0.50 90 NT 100 Yes 30 0.25 220 NT 100 Yes 31 0.50 720 NT 100 Yes June: 1 0.25 210 NT 100 Yes 4 0.50 180 NT 100 Yes 5 0.25 390 NT 100 Yes 6 0.50 330 NT 100 Yes 7 0.25 290 NT 100 Yes 8 0.25 180 NT 100 Yes Nov: 15 2 100 NT 100 Yes 16 2 80 NT 100 Yes 19 2 40 NT 100 Yes 21 2 40 NT 100 Yes Range 0 25-2.0 40-720 - - -Mean 0 76±0.58 252+179 - - -Federal t o x i c i t y standard i s met when over 80% of f i s h survived i n 65% effluent over 96 hrs. APPENDIX V (h)  DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL H BY FOAM SEPARATION Date Treatment Time (hr) T o x i c i t y o f E f f l u e n t i n 100%Test Cone.(MST:min) . B e f o r e Treatment A f t e r Treatment J a n . 23 5 35 1440 24 5 30 1440 25 4 375 NT Feb. NT 1 4 360 NT 2 4 480 NT 5 3 180 NT 6 3 300 NT 7 2 1080 NT 8 3 540 NT 9 2 600 NT 12 2 540 NT 13 2 360 NT 14 2. 210 NT 15 2 435 NT 16 3 435 NT 21 4 70 NT 22 4 130 NT 23 3 360 NT 26 3 240 NT Range 2 - 5 30 - 1080 1440 - NT Mean ± SD 3 ± 1 357 ± 246 •-267 APPENDIX V ( j )  DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL I BY FOAM SEPARATION Date Treatment T o x i c i t y o f E f f l u e n t i n 100% T e s t Cone.(MST:min) % of F i s h S u r v i v a l i n 65% E f f l u e n t o v e r 96 h r ^ T r e a t e d E f f l u e n t Meets F e d e r a l T o x i c i t y S t a n d a r d Time (h r ) B e f o r e Treatment A f t e r Treatment Nov. 2 150 NT 100 yes 28 2 150 NT 100 yes 29 2 150 NT 100 yes Dec. 3 2 30 NT 100 yes 4 2 90 NT 100 yes 5 2 60 NT 100 yes 6 2 75 NT 100 yes 10 2 105 NT 100 yes 11 2 75 NT 100 yes 18 2 75 NT 100 yes 19 2 240 NT 100 yes Range - 30-240 - - -Mean ± SD 105+ 60 - - -F e d e r a l t o x i c i t y s t a n d a r d i s met when o v e r 80% o f f i s h s u r v i v e d i n 65% e f f l u e n t o ver 96 h r s . 268 APPENDIX IV (j)  DETOCIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT FROM MILL J BY FOAM SEPARATION Treatment T o x i c i t y o f E f f l u e n t i n 100% T e s t Cone.(MST:min) % of F i s h S u r v i v a l i n 65% E f f l u e n t over 96 h r * T r e a t e d E f f l u e n t Date Time (hr) B e f o r e Treatment A f t e r Treatment Meets F e d e r a l T o x i c i t y S t a n d a r d Nov 28 1 600 NT 100 yes 30 3 180 NT 100 yes Dec 3 5 4 1080 0 yes 4 3 5 NT 100 no 5 3 5 1440 80 yes 18 1 210 NT 100 yes 19 1 240 NT 100 yes 20 1 360 NT 100 yes Range 1-5 4-600 1080-NT 0-100 -Mean±SD 2±2 2011209 - - -* F e d e r a l t o x i c i t y s t a n d a r d i s met when over 80% of f i s h s u r v i v e d i n 65% e f f l u e n t o ver 96 h r APPENDIX VI (a) CONTINUOUS DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENTS BY FOAM SEPARATION IN A SINGLE STAGE SYSTEM (With Seven 5 " Diameter 65)J pore size P l a s t i c A i r Diffusers i n a 1 8 0 - 1 column) Treatment Conditions Toxicity of Effluent Date Gas Flow (1/min) Liquid Flow (1/min) Retention Time (hr) Before Treatment After Treatment (June) pH G/L % of Fish Survived i n 65%Effluent over 96hr Meets Federal Toxi-c i t y Standard 14 8.5 39 1.55 25.8 1.92 250 100 yes 15 8.0 39 1.50 26.6 1.97 60 100 yes 16 - 60 - - - 60 100 yes 18 8.0 60 1.65 36.4 1.80 160 100 yes 19 8.2 59 1.60 36.2 1.83 150 100 yes 20 8.0 79 1.60 48.2 1.83 516 100 yes 21 8.4 80 0.80 98.0 3.66 100 100 yes 22 - - - - - 720 100 yes 23 8.0 - 1.40 - 2.10 90 100 yes 24 8.0 80 2.05 39.0 1.45 210 100 yes 25 8.0 80 1.20 66.5 2.47 75 100 yes 26 8.0 80 1.40 57.0 2.10 120 100 yes Range 8.0-8.5 39-80 0.8-2.05 25-98 1.45-3.66 60-720 100 -MeantS D 8.1+0.2 65±16 1.5±0.3 48+23 2.1 ±0.6 210+205 100 -APPENDIX VI(a) Continued CONTINUOUS DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENTS BY FOAM SEPARATION IN A SINGLE STAGE SYSTEM (With Seven 5" Diameter 65u Pore Size P l a s t i c A i r Diffusers in a 180-1 column) Treatment Conditions Toxicity of Effluent Date (July) Gas Flow Liquid Flow (1/min) G/L Retention Before After Treatment pH (1/min) Time (hr) Treatment Z ot Fish Survived i n 65%Effluent over 96hr Meets Federal Toxi-city Standard 11 8.0 60 1.90 31.8 1.53 120 100 Yes 12 8.0 60 1.80 33.2 1.62 330 90 Yes 13 8.0 59 1.80 33.3 1,62 120 100 Yes 14 8.0 60 1,90 31.8 1.53 220 100 Yes 15 8.0 61 1.85 32.4 1.58 576 100 Yes 16 8 5 60 1.85 32.4 1.58 220 100 Yes 17 8.0 60 1.85 32.4 1.58 100 90 Yes 18 8.0 60 1.84 32.8 1.58 282 100 . Yes 19 8.0 60 1.80 33.4 1.62 260 80 Yes 20 8.5 60 1.80 33.4 1.62 132 80 Yes 21 8.0 64 1.76 35.8 1.65 1000 90 Yes 22 8 0 60 1.75 34.0 1.67 - 100 Yes 23 8.0 - 1.80 - 1.62 350 - -24 8.0 60 1.60 37.5 1.83 360 100 Yes 25 8.0 60 1.80 33.3 • 1.62 180 100 Yes 26 8.0 60 1.90 31.5 1.53 120 100 Yes 27 8 0 60 1.60 33.3 1.62 - 100 Yes Range 8.0 -8.5 59 -64 1.60-1.90 31.5-37.5 7.53-1.83 102-1000 80 - 100 -Mean±S D 8.0510.16 60.25+ 1.06 1.80±0.08 33 ± 1.5 1.60+0.07 294+ 238 - -N3 O APPENDIX VI(b) CONTINUOUS DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENT BY FOAM SEPARATION IN A SINGLE STACE SYSTEM (With Four 5" Diameter 25p Pore Size P l a s t i c Diffusers in a 180-1 column) Treatment Conditions Toxicity of Effluent Date Gas Flow Liquid Flow Retention After Treatment pH Before % of Fish Sur- Meets Federal (1/min) (1/min) G/L Time (hr) Treatment vived i n 65% Toxicity Effluent over96h Standard Aug. 23 8.0 60 2.9 10.4 1.00 180 90 Yes 24 8.0 60 2.9 10.4 1.00 1080 100 Yes 25 8.0 60 2.9 10.4 1.00 300 0 No 26 8.8 60 2.9 10.4 1.00 1440 80 Yes 27 8.0 60 2.9 10.4 1.00 800 100 Yes Sept. 25 8.2 29 4.0 7.3 0.73 120 100 Yes 26 10.0 29 4.0 7.3 0.73 582 100 Yes 27 9.2 27 3.2 8.5 1.10 680 40 No 28 8.0 33 4.2 7.8 0.70 120 90 Yes 30 8.0 25 3.2 7.8 0.92 360 90 Yes Oct. 1 8.2 31 3.2 9.7 0.91 500 50 No 3 8.0 36 2.4 15.0 1.20 250 100 Yes 4 7.4 50 2.0 17.8 1.04 160 100 Yes 5 8.0 48 3.0 16.0 0.98 120 100 Yes 6 8.0 48 2.9 16.6 1.01 350 0 No 8 8.0 50 3.1 16.2 0.94 190 80 Yes 10 8.7 50 - 16.0 1.00 138 100 Yes 11 8.2 47 3.2 14.7 0.91 108 80 Yes 13 8.2 - - - - 300 100 Yes 15 8.1 46 3.0 15.3 0.97 120 0 No 16 8.4 45 2.8 16.0 1.05 1440 100 Yes 17 8.6 50 2.8 17.8 1.05 162 0 No 18 8.2 48 - - 600 100 Yes 19 8.4 52 - - - 1440 100 Yes Range 7.4-10.0 25 -60 2.8-4.2 7.3-17.8 0.70-1.22 108-1440 0-100 -Mean ± SD 8.3+ 0.5 45.4±11.6 3.1±0.5 12.5± 3.8 0.96+0.12 480± 446 - -N J APPENDIX VI(e) CONTINUOUS DETOXIFICATION OF BLEACHED KRAFT WHOLEMILL EFFLUENTS BY FOAM SEPARATION IN A SINGLE STAGE SYSTEM (With Four 1' Length, 3" Diameter 25u Pore Size Ceramic Tubes in a 180-1 column) Treatment Conditions Toxicity of Effluent Date After Treatment pH Gas Flow (1/min) Liquid Flow (1/min) G/L Retention Time (hr) Before Treatment % of Fish Survived i n 65ZEffluent over 96hr Meets Federal Toxi-c i t y Standard Nov. 1 8.8 25 2.8 8 1.00 702 80 yes 4 9.6 27 2.9 9 1.00 120 90 yes 5 8.3 27 2.9 9 1.02 - 100 yes 7 _ - - - 300 100 yes 8 9.2 20 3.0 7 0.97 150 0 no 9 10.0 22 3.0 7 0.97 252 100 yes 10 9.4 26 3.0 9 1.00 48 0 no 11 8.1 30 3.6 8 0.80 192 60 no Range 8.1-10 25-30 2.8 - 3.6 7-9 0.80-1.00 48-702 0-100 -MeantS D 9 ±0.7 25± 3 3.0 ± 0.3 8±1 0.97±0.08 252±215 - -APPENDIX VII(a) DETERMINATION OF DETOXIFICATION MECHANISMS - MILL F MST (min) of Diluted Raw Influent MST (min) of Various Reconstituted Fractions Relative Detox Contrib i f i c a t i o ution to n (1) Foam SAMPLE 100% 90% 80% 70% 60% Treated E f f l u -ent Treated E f f l u -ent + foam Treated Effluent + foam + vapour Foam Separa-tion Volat-i l i z a -t ion Unknown Mechan-isms Removed % (v/v) 1 435 555 1275 _ 1215 NT 525 510 90 2 8 5.8 2 330 285 - 870 1110 NT 1230 1170 60 2 39 -3 420 630 780 960 NT NT 540 480 72 1 27 -4 70 80 - 110 250 NT 250 200 60 2 38 -5 300 330 270 330 540 NT 405 120 70 8 22 4.3 6 300 420 690 870 NT NT 1440 990 62 7 31 3.1 7 420 240 210 1140 1200 NT 135 300 71 9 20 .6.3 8 240 135 160 285 780 ' NT 360 150 67 13 20 6.3 9 450 720 960 1200 NT NT 1320 1320 68 5 27 9.1 10 105 120 135 180 330 NT 105 75 95 2 3 7.0 Range 70-450 80-720 135-1275 110-1200 250-NT - 150-1440 75-1320 60-95 1-13 3-39 3.1-9.1 Mean+SD 307+135 352+235 560+ 428 660+ 447 - - 631+ 505 531± 463 71+12 5+ 4 24±12 6.5±1.3 LO APPENDIX VII(b) DETERMINATION OF DETOXIFICATION MECHANISMS - MILL G MST (min) of Diluted Raw Influent MST (min) of Various Reconstituted Fractions Relative Contribution to Detoxi f i c a t i o n (%) Foam Sample 100% 90% 80% 70% 60% Treated Effluent Treated Effluent + Foam Treated Effluent + Foam + Vapor Foam Separation V o l a t i l -i z a t i o n Unknown Mechan-isms Removed %(v/v) 1 120 140 195 320 480 NT 200 220 71 0 29 2 60 55 90 125 165 NT 120 75 70 14 16 14.9 3 40 50 120 180 330 NT . 80 50 84 6 10 7.9 4 40 50 60 75 NT NT 50 40 90 0 10 20.8 5 30 70 75 110 120 NT 95 85 76 3 21 19.2 Range 30-120 50-140 60-195 75-320 120-NT - 50-200 40-220 70-90 0-14 10-29 7.9-20.8 Mean ± SD 58+ 36 73± 38 108+ 53 162± 96 274+143 - 109± 57 94± 72 78+ 9 4.6± 5 17.2111 15.7± 5.8 ro -o APPENDIX VII(c) DETERMINATION OF DETOXIFICATION MECHANISMS - MILL I MST (min) of Dilutee i Raw Influent MST (min) of Various Reconstituted Fractions Relative Contribution to Detoxification (%) Sample 100% 90% 80% 70% . 60% Treated E f f l u -ent Treated E f f l u -ent + foam Treated Effluent + foam + vapour Foam Separa-tion Volat-i l i z a -t i o n Unknown Mechanisms Foam Removed % (v/v) 1 60 75 130 160 270 NT 95 65 85 9 6 15.5 2 75 90 140 240 - NT 110 105 86 6 8 18.7 3 75 105 150 180 - NT 95 75 95 5 0 10.0 4 105 120 150 180 - NT 120 110 90 7 3 21.8 5 75 90 90 210 - NT 90 80 90 7 3 25.1 Range 60-105 75-120 90-150 160-210 - - 90-120 65-110 85-95 5-9 0-8 10.0-25.1 MeantSD 78± 17 96+ 21 132+ 25 194± 30 - - 102+ 13 87± 20 89± 4 7±2 4+3 18.2+ 5.8 ro APPENDIX VIII TOXICITY REMOVAL BY A DISSOLVED AIR FOAM SEPARATION SYSTEM T o x i c i t y (MST) No of C y c l e s R e q u i r e d f o r D e t o x i f i c a t i o n T o t a l A i r * D i s s o l v e d (1) G/L Foam Removed % (v/v) I n f l u e n t (min) T r e a t e d E f f l u e n t (min) 105 NT 4 1.024 0.26 -210 NT 3 0.768 0.19 3.8 300 NT 2 0.512 0.13 2.8 420 NT 2 0.512 0.13 2.5 580 NT 2 0.512 0.13 3.3 O p e r a t i o n 4 1 D i s s o l v e d A i r B a t c h O p e r a t i o n pH: 8.0 P r e s s u r i z a t i o n : 5 min a t 40 p s i g F l o t a t i o n t i m e : 10 min Bubble S i z e : 0.3 mm * T o t a l d i s s o l v e d a i r has been c a l c u l a t e d , based on ml of a i r d i s s o l v e d a t 40 p s i g and number o f p r e s s u r i z a t i o n c y c l e s a p p l i e d . APPENDIX I X ( a ) EFFECT OF FOAM SEPARATION-ON. FOAMING TENDENCY REDUCTION OF MILL B EFFLUENTS Date MST of 100% (min) E f f l u e n t Foaming Tendency E t (min) B e f o r e Treatment A f t e r Treatment I n i t i a l F i n a l O c t o ber 25 29 1080 150 NT* NT 3.66 3.66 <1.Q <1.0 November 5 6 8 9 12 15 19 21 27 600 420 360 600 30 720 420 300 600 NT NT NT NT NT NT NT NT NT 3.54 4.58 3.55 1.64 1.42 1.42 0.92 3.12 6.06 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 Range Mean ± S.D. 150 - 1080 480 ± 287 .... -0»92-6.06 3.12 1.68 -NT: N o n - t o x i c O p e r a t i o n : Volume: 4 l i t e r s A e r a t i o n : 500 ml/min pH: 7.0 Treatment Time: 0.5-3 h r APPENDIX IX (b) EFFECT OF FOAM SEPARATION ON FOAMING TENDENCY REDUCTION OF MILL F EFFLUENTS MST o f 100% E f f l u e n t Foaming Tendency Date (min) E t (min) B e f o r e A f t e r I n i t i a l F i n a l J u l y 15 240 NT 5.22 1.0 17 150 NT 4.58 1.0 18 390 NT 5.50 1.0 19 180 NT 4.76 1.0 23 360 NT 4.76 1.0 24 210 NT 5.86 1.0 25 540 NT 5.40 1.0 October 1 450 NT 3.26 1.0 11 300 NT 4.20 1.0 17 90 NT 3.20 1.0 Range 90 - 540 - 3.20 - 5.86 -Mean ± S.D. 291 + 143 4.66 ± 0.90 NT = N o n - t o x i c O p e r a t i o n : Volume: 4 l i t e r s A e r a t i o n : 500 ml/min pH: 8.0 Treatment Time: 0.25 - 2 h r APPENDIX X (a) CHARACTERISTICS OF FOAM PRODED BY 25y PLASTIC DIFUSER IN A CONTINUOUS FOAM SEPARATION SYSTEM O p e r a t i n g C o n d i t i o n : Column: 180 1, Gas D i s p e r s e r : Four 25y pore s i z e , 5" di a m e t e r p l a s t i c d i s c s , pH: 8.0, R e t e n t i o n Time: 59 ± 2.5 min, G/L: 12.2 ± 4.0. Date Raw I n f l u e n t BOD5 (mg/1) Susp. S o l i d s (mg/1) T o x i c i t y MST (min) Foam Separated E f f l u e n t BOD5 (mg/1) T o x i c i t y C o l l a p s e d Foam C h a r a c t e r i s t i c s BOD5 (mg/1) T o x i c i t y MST ( min) I n f l u e n t Conversion! to Foam October 8 9 11 13 16 19 20 November 5 6 7 10 13 15 250 165 218 144 50 57 40 65 41 293 122 212 285 291 218 54 64 58 99 38 61 190 60 110 300 1440 1440 Range Mean ± S..D. No. o f Samples 122 - 293 220 ± 61 10 38 - 99 57 ± 17 11 300 48 348 30 30 - 1440 447 ± 538 10 N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. 260 445 375 450 267 388 243 310 462 227 375 36 36 15 13 30 90 25 100 50 18 5.6 4.0 6.1 1.5 8.0 13.2 8.5 227 - 450 346 ± 88 11 13 - 100 38 ± 27 10 1.5 - 13. 6.3 ± 4. 7 N.T. = N o n - t o x i c Foam h e i g h t : 30 cm E s t i m a t e d b u b b l e d i a m e t e r : 1.5 mm N3 NO APPENDIX X (b) CHARACTERISTICS OF FOAM PRODUCED BY A 25y CERAMIC DIFFUSER IN A FOAM SEPARATION SYSTEM O p e r a t i n g C o n d i t i o n : Column: 180 l i t r e s , 1 s t s t a g e of t h e 2 s t a g e system, Gas D i s p e r s e r : Four <25y pore s i z e , 1 f t l o n g Ceramic Tubes, pH: 8.0, R e t e n t i o n Time: 30 ± 6.0 min, G/L: 4.4 ± 1.0 Raw I n f l u e n t Foam Separated E f f l u e n t Foam C h a r a c t e r i s t i c s Date B0D5 (mg/1) Susp. S o l i d s (mg/1) T o x i c i t y MST (min) BOD5 (mg/1) T o x i c i t y BOD5 (mg/1) T o x i c i t y MST (min) I n f l u e n t C o n v e r s i o n to Foam December 8 11 12 13 15 16 230 265 210 230 215 61 31 20 45 80 17 300 300 350 150 300 220 180 200 175 210 160 N.T. N.T. N.T. N.T. N.T. N.T. 290 255 214 120 120 18 192 144 144 13.6 6.2 3.2 2.4 2.4 Range Mean ± S.D-No. o f Samples 215 - 265 230 ± 22 5 17 - 80 42 ± 25 6 150 - 300 270 ± 72 6 160 - 210 185 ± 20 5 -214 - 290 253 ± 38 3 18 - 192 123 ± 58 6 2.4 - 13.6 5.6 ± 4.8 5 N.T. = N o n - t o x i c Foam h e i g h t : 30 cm E s t i m a t e d b u b b l e d i a m e t e r : 1 mm 00 o 281 APPENDIX XI CRITICAL ROTATION SPEED (RPM) AND TIP SPEED* REQUIREMENT FOR FOAM COLLAPSING Foam Flow m^ /min (ft3.min) Turbine Diameter cm (in) 15 (6") 23 (9") 31 (12") 38 (15") rpm Tip Speed rpm Tip Speed rpm Tip. Speed rpm Tip Speed 0.18 (6.2) 1500 1197 1200 1436 900 1436 700 1396 0.33 (11.7) 1550 1236 1400 1675 1200 1914 900 1795 0.45 (15.9) 1640 1308 1500 1795 1140 1818 960 1914 0.69 (24.5) - - 1440 1854 1400 2233 1200 2393 1.20 (42.0 - - 1600 1914 1450 2300 1250 2500 Liquid Content = 1.5 ± 0.3% Foam Collapsing Efficiency = 100% Tip Speed in cm/sec. APPENDIX XI I 282 POWER DATA OF FOAM BREAKING SYSTEM Foam Flow Rotation Speed N(RPM) Turbine Diameter D(cm) Power Consumption \T 3 n 5 F(m3/min) Loaded Turbine PL (Watts) Unloaded Turbine (Po(W) Net Power Cons. P=PL-Po(W) IN U (RPM3 x cm 5 x 10 1 7) P/F Watt md/min 0.18 1200 31 225 210 15 0.46 83 0.18 1300 31 230 220 10 0.58 56" 0.18 1400 31 240 228 12.5 0.72 69 0.18 1500 31 260 240 20 0.89 111 0.18 1600 31 280 260 20 1.08 111 0.69 1400 31 270 230 40 0.72 58 0.69 1520 31 270 230 40 0.92 58 1.19 1200 31 270 210 60 0.46 50 1.19 1300 31 325 220 105 0.58 88 1.19 1400 31 400 228 170 0.72 143 1.19 1500 31 475 240 235 0.89 197 0.45 1300 38 435 355 80 1.77 178 0.45 1340 38 450 360 90 1.93 200 0.45 1400 38 455 375 80 2.2 178 0.45 1440 38 460 380 80 2.43 178 0.45 1500 38 475 395 80 2.71 178 0.45 1520 38 480 390 90 2.85 200 0.45 1600 38 495 415 80 3.29 178 0.69 1200 38 420 335 85 1.38 123 0.69 1300 38 460 355 105 1.77 152 0.69 1400 38 500 375 125 2.20 181 0.69 1500 38 535 395 140 2.71 203 0.69 1600 38 590 415 175 3.29 254 1.19 1200 38 430 335 95 1.38 80 1.19 1300 38 475 355 120 1.77 101 1.19 1400 38 525 375 150 2.20 126 1.19 1500 38 600 395 205 2.71 172 1.19 1600 38 690 415 275 3.29 231 APPENDIX XIII EFFECT OF FLOCCULATION ON DETOXIFICATION OF KRAFT MILL EFFLUENTS F l o c c u l a n t MST o f E f f l u e n t (min) Sludge Volume (% v/v) S p e c i e s Cone, (mg/1) U n t r e a t e d T r e a t e d F e r r i c C h l o r i d e 100 200 500 210 80% S u r v i v a l 100% S u r v i v a l 80% S u r v i v a l * Poor S e t t l i n g 0.3% 1.3% 100 500 240 60% S u r v i v a l 100% S u r v i v a l — Lime 1000 2000 210 100% S u r v i v a l 100% S u r v i v a l 7% 7.2%. 1000 2000 5000 240 1000 m i n ( 2 0 % S u r v i v a l ) 80% S u r v i v a l 80% S u r v i v a l — Alum 100 500 240 420 min 800 min (20% S u r v i v a l ) * Poor S e t t l i n g 1% F l o e s i n c o l l o i d a l form. 284 APPENDIX XIV (a)  TREATMENT OF COLLAPSED FOAM BY 1-DAY AND 3-DAY  RETENTION AERATED LAGOONS Retention Time: 1 day Collaps ed Foam Day Before Treatment After Treatment B0D5 (mg/1) Toxicity MST (hr) B0D5 Cmg/1) Toxicity MST (hr) 1 140 2.0 20 NT 3 140 1.5 5 2 4 255 2.0 90 20 5 175 0.25 85 1 6 180 2.3 55 4 7 - 0.45 - 60% Survival 8 - 4.0 - NT Range 140 - 255 0.25 - 4.0 5 - 8 5 1 - NT Mean ± S D 178 + 47 1.8 ± 1.3 51 ± 38 -Retention Time: 3 days 1 445 0.6 8 NT 3 375 0.6 48 NT 5 450 0.4 15 NT 7 300 0.4 12 NT 8 267 0.2 10 NT 11 - 0.5 - NT 12 - 1.5 - NT 13 - 1.5 - NT 28 388 0.4 6 NT Range 267 - 450 0.2 - 0.6 6 - 48 -Mean ± S D 370 ± 75 0.7 ± 0.5 16.5 ± 15.8 Note: MLSS ^ 1000 mg/1 285 APPENDIX XIV (b) TREATMENT OF COLLAPSED FOAM BY 2-HR AND 4 -HR ROTATING BIODISC SYSTEMS Hydraulic Retention Load: 0.45 ga l / f t 2 / d a y Time: 2 hr Collapsed Foam * Day Before Treatment After Treatment B0D5 (mg/1) Toxi c i t y MST (hr) B0D5 (mg/1) Toxi c i t y MST (hr) 1 140 2.0 30 20% Survival a f t e r 24 hrs 3 140 1.5 15 40% Survival 4 255 2.0 10 24 5 175 0.25 10 10% Survival 6 180 2.3 3 20% Survival 7 - 0.45 - 24 8 - 4.0 - NT Range 140 - 255 0.25 - 2.3 3 - 30 24 - NT Mean ± S D 178 ± 47 1.8 ± 1.3 13.6 ± 10.1 -2 Hydraulic Load: 0.22 g a l / f t /day Retention Time: 4 hr 1 267 0.5 - NT 2 - 1.5 - NT 3 - 1.5 - NT 18 243 0.4 23 NT 19 200 - 45 NT 22 262 - 16 NT 25 227 0.8 12 NT 27 175 0.25 11 NT 30 125 - 14 NT Range 125 - 267 0.25 - 1.5 11 - 45 -Mean ± S D 214 ± 51 0.83 ± 0.55 20.2 ± 12.9 -The system was operated for 7 days, pri o r to taking any samples. APPENDIX XV INFLUENT CHARACTERISTICS UNDER VARYING PROCESS CONDITIONS Da te I n f l u e n t C h a r a c t r i s t i c s P r o c e s s C o n d i t i o n s Foam C h a r a c t e r i s t i c s pH T o x i c i t y (MST:min) Foaming T e n d e n c i e s (min) A i r F l ow ( f t 3 / m i n ) L i q . F l o w ( f t 3 / m i n ) G /L R e c e n t i o n T ime (min) F l o y Ra te ( £ t J / m i n ) L i q u i d E n t r a i n e d i n Foam(%) Foaming S t a b i l i t y (min) C o n v e r s i o n o f I n f l u e n t to foam(X) 19/2 7.2 _ 5.6 98 7.77 13.1 30.5 13.77 1.3 4.7 2.6 9.5 - 5.2 98 8.54 12.0 73.7 20.47 1.6 5.0 3.9 II 9.2 _ 6.1 98 8.54 12.0 73.7 23.30 1.4 5.2 3.9 20/2 7.0 - 5.2 98 8.54 12.0 73.7 17.65 1.3 5.2 2.7 3.9 - 5.7 98 8.54 , 12.0 73.7 19.06 2.0 4.7 4.5 it 4.0 - 5.7 98 8.54 12.0 73.7 16.94 2.4 5.4 4.8 Range 4.0-9.5 - 5.2-5.7 98 7.77-8.54 12.0-13.1 73.7-80.5 13.77-23.30 1.5-2.4 4.7-5.4 2.6-4.8 Mean 6.9 - 5.6 98 8.47 12.2 74.8 18..71 1.7 5.0 3.7 S.D. 2.4 - 0.3 0 0.35 0.5 2.8 3.18 0.4 0.3 0.9 23/2 4.1 - 5.9 98 8.12 12.4 76.3 21.18 1.9 5.4 5.0 " 3.6 - 5.7 98 8.35 11.3 69.0 21.18 1.8 4.3 4.3 " 3.0 - 6.5 98 8.85 11.3 69.0 21.18 1.4 5.6 3.4 24/2 6.4 - 5.9 98 8.87 10.7 . 65.4 20.47 1.1 5.6 2.4 4.5 - 4.3 98 8.87 10.7 65.4 19.06 2.5 3.7 5.0 6.0 - 5.9 98 8.85 11.2 69.0 . 13.77 1.5 5.6 2.3 4.0 - 5.4 98 8.87 10.7 65.4 12.36 1.1 4.1 1.4 11 3.7 - 4.4 98 8.87 10.7 65.4 17.65 1.3 3.1 2.4 25/2 4.0 - 5.8 98 8.87 10.7 65.4 24.0 1.4 5.2 3.5 Range 3.0-6.4 - 5.4-6.5 98 8.12-8.87 10.7-12.4 65.4-76.3 12.36-24.0 1.1-2.5 3.1-5.6 1.4-5.0 Mean 4.0 - 5.5 98 8.30 11.1 76.3 19.06 1.6 4.7 3.3 S.D. 1.1 - 0.7 0 0.25 0.6 3.6 3.88 0.5 1.0 1.3 8/3 3.3 - 5.5 98 9.50 10.7 65.4 30.71 1.2 5.4 3.9 II 4.0 200 5.1 98 9.50 10.7 65.5 30.71 1.2 4.4 3.9 " 4.5 - 5.1 98 9.50 10.7 65.4 30.71 1.2 4.2 3.9 9/3 4.1 800 4.4 98 9.50 10.7 65.4 10.94 1.1 2.4 1.3 6.5 - 4.2 100 9.50 11.2 65.4 10.94 1.1 3.3 1.3 3.5 - 4.4 100 9.50 11.2 65.4 10.94 1.1 4.0 1.3 10/3 4.5 480 5.9 100 9.50 11.2 65.4 10.94 1.1 5.8 1.3 11/3 4.5 - 5.4 105 9.50 11.7 65.4 40.96 1.3 4.5 7.7 " 3.9 - 5.3 50 9.50 5.6 65.4 20.47 1.5 4.3 3.2 3.9 600 5.8 50 9.50 5.4 65.4 13.06 1.5 4.8 2.1 3.9 - 5.8 50 9.50 5.5 65.4 7.77 1.5 4.3 . 1.2 12/3 4.1 - 5.1 50 9.50 .5.5 65.4 8.47 1.5 4.4 j 1.3 4.1 _ 5.1 48 9.50 5.4 65.4 6.35 1.5 4.4 !| 1.0 4.1 _ 5.1 48 9.50 5.3 65.4 6.35 1.5 . 4.4 j 1.0 5.8 _ 4.4 50 9.50 5.6 65.4 16.94 1.4 2.6 1 2.5 5.8 _ 4.4 50 . 9.50 5.4 65.4 14.12 1.4 2.6 j 2.1 5.8 - 4.4 100 9.50 10.9 65.4 25.52 1.4 2.6 I 3.7 5.8 450 4.4 100 9.50 11.1 65.4 - _ 2.6 j 7.0 - 5.1 100 . 9.50 11.1 65.4 22.25 1.3 2.6 3.0 Range 3.3-7.0 200-800 4.2-5.9 48-105 9.50 5.3-11.7 65.4 j 6.25-40.96 1.2-1.3 2.4-5.3 1.0-7.7 Mean 4.7 506 5.1 . 32.3 9.50 8.5 65.4 17.65 1.4 4.0 2.6 S.D. 1.1 220 0.6 24.7 - 2.3 0 I 10.94 0.2 1.0 1.3 16/3 3.6 - 6.1 50 9.50 5.6 65.4 19.77 1.9 1.3 3.9 it 3.6 - 6.1 50 9.50 5.5 65.4 16.59 1.9- 1.8 3.7 3.3 - 5.3 100 9.50 11.1 65.4 30.71 1.7 4.5 \ 5.5 3.3 5.3 98 9.50 10.9 65.4 22.24 1.3 4.5 3.0 " 3.3 I 150 5.3 97 9.50 10.7 65.4 15.53 1.3 4.5 2.1 r i 3.5 5.3 97 9.50 10.7 65.4 13.77 1.3 4.5 1.9 17/3 3.8 5.0 98 9.50 10.9 65.4 22.24 1.4 3.5 3.3 19/3 3.0 I 420 4.7 98 9.50 10.9 65.4 17.65 1.4 3.3 2.6 " 5.3 360 5.8 98 9.50 10.9 65.4 17.65 1.4 3.3 2.6 Range 3.0-5.3 150-420 4.7-6.1 50-100 9.50 5.5-11.7 65.4 13.77-30.71 . 1.3-1.9 1.3-4.5 1.9-5.5 tlean 3.6 277 5.4 87.3 9.50 9.7 65.4 19.42 1.5 3.6 3.2 S.D. 0.7 198 0.5 21.2 - 2.4 0 4.94 0.3 1.1 1.1 APPENDIX XVI 287 TOXICITY OF TREATED SAMPLES AS A FUNCTION OF INTERFACIAL AREA PRODUCED DURING FOAM FRACTIONATION I n f l u e n t c h a r a c t e r i s t i c s : O p e r a t i n g C o n d i t i o n s : - B l e a c h e d k r a f t whole m i l l e f f l u e n t - R e t e n t i o n t i m e = 40 min - pH a d j u s t e d t o 7.0 - 8.0 - 2 s t a g e system - Flow = 0.3 m 3/min I n t e r f a c i a l No. o f MST o f Ar e a Samples T r e a t e d E f f l u e n t (m 11) T e s t e d (min) 0 1 360 2.8 1 2900 2.8 1 3600 3.8 1 2200 4.0 1 1440 4.0 4 2200 4.0 8 N.T. 4.8 1 N.T. 8.4 1 N.T. 14.6 1 N.T. 18.6 1 N.T. APPENDIX XVII EFFECT OF STAGING AT CONSTANT GAS-L IQUID INTERFACIAL AREA ON DETOXIFICATION PERFORMANCE OF J E T FOAM GENERATION SYSTEM Jet Aeration System Operation Liquid flow rate pH : 7 - 8 Retention time: 100 gal/min 20 min/stage Type: 2" diameter j e t c/w submersible pump Flui d v e l o c i t y : 60 cm/sec through j e t nozzle. Stage Sample No. Type of Sample Taken Comp. Grab Grab Grab Foam Separation System No. of Jets 1st Stage Comp. Comp. Comp. Comp. 2nd Stage 3rd Stage Total Air Load (ft 3/min) l Comp. 1 1 -2 Comp. 1 1 3 Comp. 1 1 4 Grab 1 1 5 Comp. 1 1 § 6 Grab 1 1 Ul 7 Comp. 1 1 -cn 8 Grab 1 1 -0) 9 Comp. 1 1 -M 4 10 Grab 1 1 -4J C/l 11 Comp. 1 1 -O 12 Grab 1 1 — 13 14 Comp. Grab 1 1 1 1 -7.4 7.4 11.3 11.3 Retention Time (min') 9.2 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 12.7 12.7 12.7 9.2 10.7 10.6 10.6 20 20 20 20 G/L 0.7 0.7 1.1 1.1 Gas-Liquid I n t e r f a c i a l Area (m 2/l) Flow Rate «t 3/min) 5.3 5.3 7.1 7.1 Foam Characteristics 10.7 11.3 15.4 18.2 Toxicity (LT50:min) 15 15 17 20 Toxi c i t y (LT50:min) of Effluent Feed >480<1380 >480<1380 380 600 After Foam Separation 1st Stagd 5760 Nontoxic 2900 Nontoxic Number os samples taken No. of samples detoxified Detoxification success rate 4 2 50% 40 0.9 5. 5 3.3 40 1.1 7 1 12.6 40 1.1 7 1 13.8 40 1.1 7 1 13.8 40 1.1 7 1 13.0 40 1.1 7 1 13.1 40 1.1 7 1 12.6 40 1.1 7 1 13.8 40 1.1 7 1 12.4 40 1.1 7 1 11.9 40 1.1 7 .1 13.3 40 1.2 7 .8 12.4 40 1.2 7 .8 14.1 40 1.2 7 .8 15 30 30 17 17 17 17 15 15 15 15 17 17 18 >480<1380 >480<1380 2000 >480<1380 400 >480<1380 >480<1380 >480<1380 >480<1380 3880 420 1440 420 360 3160 Nontoxic Nontoxic 4300 Nontoxic 4300 Nontoxic 5000 Nontoxic Nontoxic 2880 Nontoxic Nontoxic 1440 2nd Stagd 3rd Stage Number of samples taken No. of samples detoxified Detoxification success rate 60 0.9 7 3 7.9 60 1.0 7 6 9.2 60 1.0 7 6 13.6 60 1.0 7 6 13.0 10 15 20 20 >480< 960 600 >480< 960 420 Number of samples taken No. of samples detoxified Detoxification success rate 14 8 57% Nontoxic 5760 Nontoxic 4000 4 3 50% Nontoxic Nontoxic Nontoxic 4760 Nontoxic Nontoxic Nontoxic Nontoxic Nontoxic Nontoxic Nontoxic Nontoxic Nontoxic 2880 14 12 86% Nontoxic Nontoxic Nontoxic Nontoxic 3 3 100% Nontoxic Nontoxic Nontoxic Nontoxic 3 3 100% APPENDIX XV I I I FOAM BREAKING PERFORMANCE BY A TURBINE SYSTEM Operation: Type : 3 blade 30 cm diameter vaned disc Rotation speed: 1800 rpm Power : 1/3 hp Tip Velocity : 3600 cm/sec Day of Operation Influent Characteristics Foam Characteristics Foam Sampling (hrs) pH Foam tendency (min) Foam flow (ft3/min) Foam liquid content (%: v/v) Foam stability (Z=:min) Breaking Efficiency (%) 1 5 7.2 6.0 2.22 2.56 5.6 100 2 1 2 3 8.0 8.0 8.0 4.5 4.8 4.8 10.45 10.98 11.26 2.43 1.70 1.52 3.7 3.7 4.6 100 100 100 Average 8.0 4.7 10.91 1.88 4.0 100 3 1 2 8.0 7.0 5.4 6.1 12.78 12.50 1.52 1.33 4.5 5.3 100 100 Average 8.0 5.8 12.64 1.43 4.8 100 * 3 4 5 7.2 7.2 5.1 5.6 13.91 13.24 1.32 1.34 4.5 5.1 100 100 Average 7.2 5.4 13.59 1.33 4.8 100 4 1 2 3 4 5 6 8.0 8.0 8.0 8.0 8.0 8.0 -12.11 12.99 12.80 11.58 10.59 11.75 1.43 1.06 0.82 0.67 1.20 0.90 -100 100 100 100 100 100 Average 8.0 - 12.00 1.01 - 100 5 1 2 3 4 5 6 8.0 8.0 8.0 8.0 8.0 8.0 -15.07 15.36 17.44 19.13 17.47 18.32 2.6 2.75 3.29 3.36 3.04 3.04 -100 100 100 100 100 100 Average 8.0 - 17.13 2.92 - 100 . 6 3* 7.2 5.6 18.04 2.04 5.1 100 7 1 2 3 4 5 8.0 8.0 8.0 8.0 8.0 -13.45 16.45 16.34 17.65 23.62 0.75 0.67 0.67 1.00 0.86 -100 100 100 100 100 Average 8.0 • 17.51 0.79 - 100 8 1 2 3 5 6 8.0 8.0 8.0 8.0 8.0 -18.04 13.89 17.23 22.31 25.14 1.36 1.32 1.28 2.53 1.51 -100 100 100 100 100 Average 8.0 - 18.00 1.32 - 100 10 6 8.0 5.7 21.00 1.5 5.3 100 14 . 4 8.0 6.2 21.04 1.26 5.6 100 16 3 7.2 5.5 - 0.57 5.1 100 22 2 7.3 6.0 14.47 1.51 5.6 100 26 4 8.0 5.6 23.76 1.06 5.1 100 30 4 8.0 6.2 20.72 1.06 5.4 100 35 2 8.0 6.6 16.31 0.62 3.1 100 40 3 8.0 6.6 • 16.31 0.62 5.6 100 290 APPENDIX XlX-a SIZING OF SCREENING AND PUMPING EQUIPMENT A pumping s t a t i o n b a s i c a l l y c o n s i s t s o f a t r a v e l l i n g s c r e e n submerged i n an e f f l u e n t c o l l e c t i o n chamber t o s e p a r a t e t h e u n d i g e s t e d wood c h i p s f r o m t h e e f f l u e n t and a pumping sy s t e m c a p a b l e o f d e l i v e r i n g 17,000 g a l / m i n o f e f f l u e n t . A. EFFLUENT COLLECTION CHAMBER Bas is : .To accomodate a p p r o x i m a t e l y 50,000 g a l o f e f f l u e n t w i t h a 3 min r e t e n t i o n t i m e . Se lect ion of Equipment: C o n c r e t e t a n k o f d i m i n s e i o n 1 x w x d = 100' x 10' x 8'. Capita l Cost: $70,000 T„,. + , r w + . C a p i t a l C o s t $70,000 ___ I n s ta l led Cost: — * ,no, = „',— = $117,000 B. TRAVELLING SCREEN Bas is : To s e p a r a t e t h e wood c h i p s and k n o t s f r o m t h e e f f l u e n t . Se lec t i on : 0.5' o p e n i n g , 10 f t / m i n v e l o c i t y , 10' x 8' t r a v e l l i n g s c r e e n I n s t a l l a t i o n : 5' submergence i n e f f l u e n t c o l l e c t i o n chamber. Capita l Cost: $50,000 c o m p l e t e w i t h motor , „ r , l l n j r ^ c + . C a p i t a l C o s t $50,000 6 o o n n n I n s ta l led Cost: — c — 7 7 ^ = — = $83,000 oU/o U . o 291 C. PUMPS Bas is : 17,000 g a l / m i n f l o w r a t e Maximum Head = 25 f t Four pumps, each r a t e d a t 5000 g a l / m i n E l e c t r i c i t y = l c / k w h Estimation of Power Requirement n~v,i, - 5000 g a l / m i n ,„ . l b o c . 1 1 i r . c f t - l b Work = . & , ,- '.i x 62.4 x 25 f t = 1.1 x 10° : 7.4 g a l / f t " * f t 6 mm A t 70% e f f i c i e n c y , „ , work 1.1 x 1 0 6 . _, , Estxma t e d BHp = 3 3 ( ) 0 0 x Q > 7 = 2 3 . 1 x 1 0 3 = 4 7 ' 6 Hp r e q u i r e d = E s t i m a t d BPH x S a f e t y F a c t o r = 47.6 x 1.3 = 61.9 S e l e c t i o n ; Four 5000 g a l / m i n pump Power = 65 hp/pump, 260 hp t o t a l Type = S i n g l e s t a g e , d r y p i t , v e r t i c a l t u r b i n e . Capita l Cost* $150,000 asuming t h a t c o s t i n s t a l l e d i s 60% of C a p i t a l . In s ta l led Cost: C a p i t a l C o s t = $150,000 = $ 2 5 0 5 o o o ov/o U.o Power C o s t / d a y = HP r e q u i r e d x 0.745 x 24 h r x r^ = 4 x 50 x 0.745 x l c = $35.76 D. SUMMARY Total Cost Requirement of Screening and Pumping F a c i l i t y Ins ta l led Cost: $450,000 Total HP: 260 Power Consumption: $35.76/day. 292 . APPENDIX XlX-b pH CONTROL SYSTEM A t p r e s e n t , t h e pH o f t h e f i n a l combined e f f l u e n t i n a k r a f t m i l l i s most commonly c o n t r o l l e d by a two - s t a g e p r o c e s s . I n i t i a l l y , l i m e mud i s added t o t h e a c i d sewer t o i n c r e a s e t h e pH t o a p p r o x i m a t e l y 3.0. A t pH g r e a t e r t h a n 3.0, n e u t r a l i z a t i o n by l i m e mud becomes i n e f f e c t i v e . I n s t e a d , s l a k e d l i m e o r c a l c i u m h y d r o x i d e i s added t o t h e a c i d sewer i n s u c h a way t h a t t h e pH o f t h e combined m i l l e f f l u e n t w i l l be a p p r o x i m a t e l y 5 t o 6. To i n c r e a s e t h e pH t o 7.0, a c o n d i t i o n where d e t o x i f i c a t i o n by foam s e p a r a -t i o n i s most e f f e c t i v e , a d d i t i o n of c a u s t i c s o l u t i o n w i l l be r e q u i r e d . T h i s can be done i n t h e f i r s t s t a g e o f t h e foam g e n e r a t i o n t a n k . A. Caustic Storage Tank Duty: To s t o r e 7 days s u p p l y o f 25% c a u s t i c a t a r a t e o f 846 g a l / d a y ( 1 2 9 ) . Se lec t i on : 7000 g a l g l a s s l i n e d s t o r a g e t a n k w i t h c o v e r . B. Caustic Feed Pump Duty: To pump 0.6 g a l / m i n o f c a u s t i c a g a i n s t 5 f t of head. Se lec t i on : 3 g a l / m i n n o n - c o r r o s i v e pump. C. pH Cont ro l l e r Duty: To c o n t r o l pH a t 7.0. Se lec t i on : U n i l o c pH. sys t e m c o m p l e t e w i t h c o n t r o l e l e m e n t s . D. Summary Total Cost Requirement of pH Control System Capita l Cost: $150,000 Ins ta l led Cost: $200,000 293 APPENDIX XIX-c SIZING OF FOAM SEPARATION SYSTEM A. FOAM GENERATION TANK Bas is : 3-stage c h a n n e l shaped sy s t e m s e m i - c i r c u l a r a t b o t h ends. Cover t o p r o v i d e i n s t a l l a t i o n o f foam b r e a k e r . Each s t a g e w i t h c e n t r a l b a f f l e . Estimation of Foam Generation Tank R e t e n t i o n t i m e = 1 h r L i q u i d volume = (17,000 x 60) g a l .= 1.02 M g a l . Gassed Volume = 1.0 2 x 1.2 M g a l = 1.23 M g a l - i : " % 1 0 6 f t 3 = 136,500 f t 3 Volume o f each s t a g e = 45,500 f t 3 L i q u i d d e p t h = 20 f t Foam h e i g h t = 3 f t F r e e b o a r d = 2 f t O v e r a l l d i m e n s i o n (1 x w x d) = 150 ' x 86.5' x 20' Tha l a y o u t o f t h e syst e m i s shown i n F i g u r e 48. C o n s t r u c t i o n : - Common w a l l c o n s t r u c t i o n i s most a p p l i c a b l e . - V a l v e s a r e i n s t a l l e d t o c o n t r o l t h e g r a v i t y f l o w between each s t a g e . - Walkway above common w a l l s h o u l d be i n s t a l l e d f o r s e r v i c i n g o f pumps. Assuming c o n s t r u c t i o n c o s t a t $ 6 5 / y d 3 c a p a c i t y I n s t a l l e d C o s t : 1 3 6 > ^ 0 0 x $65 = $330,000. 294 B. JET AERATOR Bas is : S i z e o f j e t a e r a t o r = 1" d i a m e t e r g a s - l i q u i d i n t e r f a c e = 20 m 2 / l G/L = 6 A i r l o a d i n g = 50 f t 3 / m i n p e r j e t Estimation of Jet Aerat ion Systems: T o t a l a e r a t i o n r e q u i r e m e n t = G/L x l i q u i d f l o w r a t e , 17000 g a l / m i n  b X 7.48 g a l / f t 3 = 13600 f t 3 / m i n 13600 3 Number o f j e t a e r a t o r u n i t s r e q u i r e d = 91 u n i t s A e r a t i o n r e q u i r e d / s t a g e = — ^ — f t 3 / m i n = 4545 f t 3 / m i n Se l ec t i on : Commercial j e t a e r a t i o n systems c a n be b u i l t w i t h 24 1 - i n d i a m e t e r u n i t s on a common he a d e r . F o u r j e t a e r a t o r systems each w i t h 24 j e t u n i t s a r e s e l e c t e d and i n s t a l l e d i n each s t a g e . INSTALLATION: I n s t a l l e d a t t h e bot t o m o f t h e b a s i n , as shown i n F i g u r e 52 a t 1 7 - f t submergence. Each system i s c o n n e c t e d t o a r e c i r c u l a t i o n pump and a i r b l o w e r . Capita l Cost: $200,000 c o m p l e t e w i t h p i p i n g and s u p p o r t s . I n s ta l led Cost: C a p i t a l C o s t = $200,000 = $ 3 5 0 5 0 0 0 bv/o O.o 295 B. JET AERATOR Bas is : S i z e o f j e t a e r a t o r = 1" d i a m e t e r g a s - l i q u i d i n t e r f a c e = 2 0 m 2 / l G/L = 6 a i r l o a d i n g = 50 f t 3 / m i n p e r j e t Estimation of Jet Aerat ion Systems: To p r o d u c e b u b b l e s o f 1 mm d i a m e t e r , a minimum l i q u i d submergence o f 15' and a i r t o power r a t i o o f >1 i s r e q u i r e d . T o t a l a e r a t i o n r e q u i r e m e n t = G/L x l i q u i d f l o w r a t e , 1700 g a l / m i n b X 7.48 g a l / f t 3 = 13600 f t 3 / m i n A e r a t i o n r e q u i r e d / s t a g e = -*-3600 f t 3 / m - ^ n = 4 5 4 5 f t 3 / m i n Number o f j e t a e r a t o r u n i t s r e q u i r e d = 91 u n i t s . S e l e c t i o n : Commercial j e t a e r a t i o n systems can be b u i l t w i t h 24 1 - i n d i a m e t e r u n i t s on a common h e a d e r . Four j e t a e r a t o r s y s t e m s , each w i t h 24 j e t u n i t s a r e s e l e c t e d . INSTALLATION: I n s t a l l e d a t t h e bottom o f t h e b a s i n , as shown i n F i g u r e 52 a t 1 7 - f t submergence. Each s y s t e m i s c o n n e c t e d t o a r e c i r c u l a t i o n pump and a i r b l o w e r . Capita l Cost: $200,000 c o m p l e t e w i t h p i p i n g and s u p p o r t s . I n s ta l led Cost: ^ p i t a l C o s t = $200,000 = $ 3 5 0 0 0 0 OU/a 0.6 296 F i g u r e 5 2 INSTALLATION OF JET SYSTEM IN FOAM SEPARATION TANK PUMP RETRIEVAL GUIDE BARS 4.6m -AIR LINE •DMJA o o o o o o o o oflo o o o o o o o o o ojlp O . SUPPORT 297 RECIRCULATION PUMP Bas is : L i q u i d v e l o c i t y o f 50 f t / s e c t h r o u g h t h e j e t i s r e q u i r e d t o produce 1 mm b u b b l e d i a m e t e r and promote g a s - l i q u i d c o n t a c t t i m e . Estimation of Pumping Requirement C r o s s s e c t i o n a l a r e a o f 1" j e t u n i t = ir x ( ^ j j ) f t 2 = 0.01 f t 2 S i n c e each j e t a e r a t i o n s y s t e m c o n s i s t s o f 24, 1" j e t s , t o t a l c r o s s s e c t i o n a l a r e a = 0.24 f t 2 . F o r each j e t a e r a t o r s y s t e m , t h e pumping r a t e r e q u i r e d t o a c h i e v e 50 f t / s e c v e l o c i t y = c r o s s s e c t i o n a l a r e a x l i q u i d v e l o c i t y = 0.24 x 50 f t 3 / s e c = 12 f t 3 / s e c = 720 f t 3 / m i n = 720 x 7.48 g a l / m i n = 5385 g a l / m i n . A 5500 g a l / m i n pump i s used, w i t h l i q u i d submergence o f 17' and 70% e f f i c i e n c y . T, . j 7;20 x 62.4 x 17 0 0 E s t i m a t e d BHp = 3 3 0 0 0 x 0 . 7 = 33 HP r e q u i r e d = E s t i m a t e d BHP x S a f e t y F a c t o r (1.3) = 33 x 1.3 hp = 42.9 hp. S e l e c t i o n : S u b m e r s i b l e c e n t r i f u g a l pump r a t e d a t 45 hp, 5500 g a l / m i n No. o f pumps: 12, 1 s t a n d b y T o t a l HP = 540 C a p i t a l C o s t : $120,000 „ o C a p i t a l C o s t $ 40,000 n n n I n s t a l l e d C o s t : — ? , n v = - — T T ^ T — = $200,000 bU/o U.o Power c o s t / d a y = 4 5 x 12 x 0.745 x 24 x l c = $96.55. BLOWER CAPACITY Bas is : A e r a t i o n r e q u i r e m e n t / s t a g e = 4545 f t 3 / m i n Estimation of Blower Capacity: P r e s s u r e drop o f l i q u i d head = ^ ^ x 14.7 p s i = 7.6 p s i P r e s s u r e drop o f a i r h e a d e r , b l o w e r p i p i n g , b r a n c h c o n n e c t i o n and a i r s u p p l y l i n e s = 1 p s i 1 p s i P r e s s u r e drop a c r o s s j e t a e r a t o r = 0 p s i 0 p s i T o t a l 8.6 p s i . A 10 p s i b l o w e r i s r e q u i r e d , a t an e f f i c i e n c y o f 70% RHP = P s i x ( f t 3 / m i n ) x 144 = 10 x 4545 x 144 = 33000 x 0.7 23100 . * T o t a l HP r e q u i r e m e n t = 283 . x 3 = 849 S e l e c t i o n : C e n t r i f u g a l t y p e b l o w e r r a t e d a t 10 p s i 300 hp, 4500 f t 3 / m i n a i r f l o w . No. o f b l o w e r s = 3, 1 s t a n d b y T o t a l HP = 900. C a p i t a l C o s t : $150,000 I n s t a l l e d C o s t : C a p i t a l C o s t = $ 1 5 ^ 0 0 0 = Q Q Power c o s t / d a y = 900 x 0.745 x 24 x l c = $160.92. SUMMARY Total Cost Requirement of Foam Generator The t o t a l c o s t i n s t a l l e d and power r e q u i r e m e n t areshown as f o l l o w s : Foam G e n e r a t i n g Element Horsepower I n s t a l l e d C o s t J e t A e r a t o r - $350,000 Pump 540 120,000 Blower 900 250,000 T o t a l 1440 $ . 720,000 299 APPENDIX XIX-d SIZING OF FOAM DISPOSAL SYSTEM A. FOAM BREAKER Bas is : I n f l u e n t c o n v e r s i o n t o foam = 1.2% L i q u i d c o n t e n t = 1.5% Foam f l o w r a t e = 1800 f t 3 / m i n Foam b r e a k e r = 2 f t d i a m e t e r , 1800 rpm, 3-blade vaned d i s c t u r b i n e Estimation of Foam Breaking Capacity Foam b r e a k i n g c a p a c i t y o f a 3 b l a d e t u r b i n e i s g i v e n (128) by: _ 3 F = (2.6 x 10 3 N + 7.7 x 10 2 D - 4.7) ™ mm where N = r o t a t i o n speed, rpm D = d i a m e t e r o f t u r b i n e , cm f t ' mxn F = (2.6 x 10 'd x 1800 + 7.7 x 10 z x 31-4.7) x 35.3 x = 173 f t 3 / m i n . T o t a l No.of foam b r e a k e r s r e q u i r e d = = 10 F o r s a f e t y measures, 12 w i l l be i n s t a l l e d . The power o f each u n i t i s g i v e n by (128): P = F x (51.7 x 10~ 1 7 N 3D 5 + 51.2) Watts = 173 x (51.7 x 10~ 1 7 x 18003 x 2 5 + 51.2) x HP = 16.7 HP Se lec t i on : 3 b l a d e vaned d i s c t u r b i n e 2 ' d i a m e t e r r a t e d a t 20 hp, 1800 rpm T o t a l HP = 240 C a p i t a l C o s t = $110,000 T . -i J /-i _ C a p i t a l C o s t $110,000 n n n I n s t a l l e d C o s t = — r , r = - — z f — r — = $180,000 0.6 0.6 Power/day = 240 x 0.745 x 24 x l c = $42.9 300 B. FOAM TREATMENT BY AERATED LAGOON Bas i s : C o l l a p s e d foam f l o w = 200 g a l / m i n BOD 5 r e d u c e d f r o m 400 mg/1 t o 50 mg/1 Se lec t i on : Volume o f 3-day a e r a t e d l a g o o n = 200 x 1440 x 3 = 0.86 M g a l BOD 5 d e s t r o y e d = 2 0 0 M l x 6 0 m i n x 350 mg/1 x h r min 3.8 1 / g a l x 2.205 x 1 0 ~ 6 lb/mg = 35.5 l b Oxygen t r a n s f e r o f s u r f a c e a e r a t o r = 1 l b / h p - h r 35 5 Horsepower = — = 35.5, a 45 Hp u n i t i s chosen. I n s t a l l e d C o s t : $300,000 (1) Power c o s t / d a y = 45 x 0.745 x 24 x l c = $8.04 C. SUMMARY Total Cost Requirement of Foam Disposal System Ins ta l led Cost: $480,000 Total HP: 405. Power Consumption: $72.4/day. 301 APPENDIX XX LIST OF .PUBLICATIONS 1. Z a j i c , J . E . , and K.S. Ng (1 9 6 9 ) . B i o c h e m i c a l Uranium L e a c h i n g . Dev. i n I n d . M i c r o b i o l . , 11: 413. 2. Ng, K.S., J.E. Z a j i c , and D.F. M a n c h e s t e r ( 1 9 7 2 ) . E f f e c t o f SO Removal on B i o d e g r a d a b i l i t y o f A r b i s o B l a c k L i q u o r . P r o c . o f 7 t h Can. P o l l . Res. Sym. 3. Ng, K.S., J.C. M u e l l e r and C C . Walden ( 1 9 7 3 ) . D e t o x i f i c a t i o n o f K r a f t M i l l E f f l u e n t s by Foam S e p a r a t i o n . P u l p P a p e r Mag. Can. 7 4 ( 5 ) : T263. 4. Ng, K.S., J.C. M u e l l e r and C C . Walden ( 1 9 7 4 ) . P r o c e s s P a r a m e t e r s o f Foam D e t o x i f i c a t i o n f o r K r a f t E f f l u e n t s . P u l p Paper Mag. Can. 75(7) : T263. 5. Ng, K.S., and J.C. M u e l l e r ( 1 9 7 5 ) . Foam S e p a r a t i o n - A T e c h n i q u e f o r Water P o l l u t i o n Abatement. Water and Sewage Works ( J u n e , 1975): 48. 6. Ng, K.S., J.C. M u e l l e r and C C Walden ( 1 9 7 6 ) . Foam S e p a r a t i o n F o r Deto-x i f i c a t i o n o f B l e a c h e d - K r a f t M i l l E f f l u e n t s . J . Water P o l l . Cont. Fed. 4 8 ( 3 ) : 458. . 7. M u e l l e r , J . C , and K.S. Ng (1 9 7 6 ) . Foam S e p a r a t i o n - A N o v e l T e c h n i q u e f o r D e t o x i f i c a t i o n o f K r a f t E f f l u e n t s . P r o g . Water Tech. 8 ( 2 / 3 ) : 259. 8. Ng, K.S., and P. Temoin ( 1 9 7 7 ) . D e s i g n C o n s i d e r a t i o n s o f Foam S e p a r a t i o n P r o c e s s f o r D e t o x i f y i n g K r a f t E f f l u e n t s . P u l p Paper Mag. Can. 78(2) : T29. 9. Ng, K.S., J.C. M u e l l e r and C C . Walden ( 1 9 7 7 ) . Foam B r e a k i n g - A Key p r o c e s s i n D e t o x i f i c a t i o n o f K r a f t M i l l E f f l u e n t s by Foam S e p a r a t i o n . Can. J . of Chem. Eng. 5 5 ; 439. 10. Ng, K.S. and L. G u t i e r r e z ( 1 9 7 7 ) . M e c h a n i c a l Foam B r e a k e r s - A Means f o r Foam C o n t r o l i n Sewage and I n d u s t r i a l Waste Tr e a t m e n t . J . Water P o l l . Cont. Fed., ( i n p r e s s ) . 11. Ng, K.S., J.C. M u e l l e r and C C . Walden ( 1 9 7 7 ) . Ozone Treatment of K r a f t M i l l Wastes. J . Water P o l l . C o n t . F e d . ( i n p r e s s ) . 12. Ng, K.S.,:.L. G u t i e r r e z and J.C. M u e l l e r ( 1 9 7 7 ) . T o x i c i t y Removal By Foam S e p a r a t i o n - P i l o t P l a n t Assessment o f M a j o r O p e r a t i o n Equipment and D e t o x i f i -c a t i o n R e l i a b i l i t y . ( P r e s e n t e d a t PNPCA C o n f e r e n c e , P o r t l a n d , Oregon). LIST OF PUBLICATIONS 1. Zajic, J.E., and K.S. Ng. (1969). Biochemical Uranium Leaching. Dev. in Industrial Microbiol., 11:413. 2. Ng, K.S., J.E. Zajic, D.F. Manchester and Y.K. Ng. (1972). Effect of S0 2 Removal on Biodegradability ofiArbiso Black Liquor. Proc. of 7th Can. Poll. Res. Sym. 3. Ng, K.S., J.C. Mueller and CC. Walden. (1973). Detoxification of Kraft M i l l Effluents by Foam Separation. Pulp Paper Mag. Can. 74(5):T187. 4. Ng, K.S., J.C. Mueller and CC. Walden. (1974). Process Parameters of Foam Detoxification for Kraft Effluents. Pulp Paper Mag. Can.75(7):T263. 5. Ng, K.S. and J.C Mueller. (1975). Foam Separation - A Technique for Water Pollution Abatement. Water and Sewage Works (June, 1975):48. 6. Ng, K.S., J.C. Mueller and C C Walden. (1976). Foam Separation For Detoxi-fication of Bleached Kraft M i l l Effluents. J. Water Poll. Cont. Fed.48(3);458. 7. Mueller, J.C. and K.S. Ng. (1976). Foam Separation - A Novel Technique for Detoxification of Kraft Effluents. Prog. Water Tech. 8(2/3);259. 8. Ng, K.S. and P. Temoin. (1977). Design Considerations of Foam Separation Process for Detoxifying Kraft Effluents. Pulp Paper Mag. Can. 78(2);T29. 9. Ng, K.S. J.C. Mueller and CC. Walden. (1977). Foam Breaking - A key process in foam separation process. Can. J. for Chem. Eng. 55:439.: 10. Ng, K.S. and L. Gutierrez. (1977). Mechanical Foam Breakers - A means for foam control in sewage and industrial waste treatment. J. Water Poll. Cont. Fed. (in press). 11. Ng, K.S., J.C. Mueller and CC. Walden. (1977). Ozone Treatment of Kraft M i l l Wastes. J. Water Poll. Cont. Fed. (in press). 12. Ng, K. S. and L. Gutierrez. (1977). Toxicity Removal by Foam Separation -Pilot plant assessment of major operating equipment and detoxification r e l i a -b i l i t y , (accepted for presentation at the 1977 PNWPCA conference, Portland, Oregon). 

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