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Two-stage treatment of a landfill leachate: aerobic biostabilization with lime-magnesium polishing 1980

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TWO-STAGE TREATMENT OF A L A N D F I L L L E A C H A T E : A E R O B I C B I O S T A B I L I Z A T I O N WITH L I M E - M A G N E S I U M P O L I S H I N G b y P h i l l i p Thomas Wong B . A . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1977 A T H E S I S SUBMITTED I N P A R T I A L F U L F I L M E N T OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF A P P L I E D S C I E N C E i n THE F A C U L T Y OF GRADUATE S T U D I E S (The D e p a r t m e n t o f C i v i l E n g i n e e r i n g ) We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE U N I V E R S I T Y OF B R I T I S H COLUMBIA J u n e 19 80 @ P h i l l i p Thomas W o n g , 19 80 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t 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 study. 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 copying 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 granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s under- stood t h a t copying or p u b l i c a t i o n of 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 allowed without my w r i t t e n p e r m i s s i o n . Department of C i v i 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 Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date June 9, 19 80 ABSTRACT Leachate i s produced when water p e r c o l a t e s through l a n d - f i l l s , e x t r a c t i n g suspendable and s o l u b l e o r g a n i c and i n o r g a n i c c o n s t i t u e n t s from the r e f u s e beds. T h i s may l e a d t o s e r i o u s s u r f a c e and/or ground water p o l l u t i o n . Recently, the c o n t r o l and treatment of le a c h a t e has been the s u b j e c t o f a gr e a t d e a l of r e s e a r c h , p a r t i c u l a r l y a t the U n i v e r s i t y o f B r i t i s h Columbia T h i s study was i n i t i a t e d as a follow-up t o s e v e r a l o f those p r e v i o u s s t u d i e s . I n v e s t i g a t e d were the t r e a t a b i l i t y of medium strength' -,(BOD5 f-6'8090, mg/L) l e a c h a t e by a e r o b i c ; b i o s t a - b i l i z a t i o n , a t a n u t r i e n t l o a d i n g o f BOD,_:N:P of 100:3.2:1.1, b and then p o l i s h i n g o f the f i r s t stage e f f l u e n t s by lime- magnesium c o a g u l a t i o n . In the b i o l o g i c a l treatment stage, the ranges o f ambient a i r temperature and sludge age s t u d i e d were 5° t o 25°C and 5 to 20 days, r e s p e c t i v e l y . In the b i o s t a b i l i z a t i o n phase, a BODj-:N:P l o a d i n g o f 100:3.2:1.1 was found to be "adequate" f o r treatment, w h i l e the s t a n d a r d n u t r i e n t l o a d i n g of 100:5:1 was found to be "e x c e s s i v e " . This was e v i d e n t by the much hi g h e r n i t r i t e - n i t r a t e c o n c e n t r a t i o n i n the e f f l u e n t o f the BOD,-:N:P = 100:5:1 r e a c t o r . Organic removal by the f i r s t stage u n i t s was e x c e l - l e n t . B 0 D 5 and COD removals of a t l e a s t 99.4 and 9 6.4 percen t , r e s p e c t i v e l y , were achieved under a l l c o n d i t i o n s i n v e s t i g a t e d , except f o r the two u n i t s c l o s e to washout c o n d i t i o n s (the 5-day sludge age u n i t s a t 10° and 5°C). Temperature and sludge age a l s o had minimal e f f e c t s on the removal o f metals, except under the two c o n d i t i o n s mentioned above; removals were g r e a t e r than 90 percent, f o r most of the metals monitored. The r e a c - t o r s o n l y reduced magnesium c o n c e n t r a t i o n s by 32.5 t o 52.7 percen t , mainly because the mixed l i q u o r pH's (about 8.5) were not h i g h enough f o r magnesium p r e c i p i t a t i o n as magnesium hydroxide. For the lime-magnesium p o l i s h i n g s tep, samples were dosed w i t h lime t o pH l e v e l s o f 10.0, 10.7, and 11.4. Magnesium doses of 0, 10, 20, 35 and 50 mg/L were then added t o the sam- p l e s a t each pH l e v e l . In g e n e r a l , removals of i m p u r i t i e s were not enhanced s i g n i f i c a n t l y by these magnesium a d d i t i o n s . T h i s was due, i n p a r t , to the i n i t i a l low c o n c e n t r a t i o n s of con- taminants; i n a d d i t i o n , t h e r e a l r e a d y e x i s t e d g r e a t e r than 20 mg/L of magnesium i n the samples. A e r o b i c b i o s t a b i l i z a t i o n , at a sludge age g r e a t e r than 15 days, a t BOD^:N:P = 100:3.2:1.1, and l i q u i d temperatures o f a t l e a s t 3°C, f o l l o w e d by lime p r e c i p i t a t i o n (to pH g r e a t e r than or equal to 10.0), i s capable o f reducing most contami- nants o f a medium s t r e n g t h l e a c h a t e (BOD^ = 8090 mg/L) to l e v e l s below l o c a l (Province o f B r i t i s h Columbia) p o l l u t i o n c o n t r o l o b j e c t i v e s . TABLE OF CONTENTS i v Page ABSTRACT i i LIST OF TABLES ' v i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS i x CHAPTER 1 INTRODUCTION 1 2 BACKGROUND 5 2-1 A e r o b i c B i o s t a b i l i z a t i o n 5 2-1.1 D e s c r i p t i o n o f the A c t i v a t e d Sludge Process . . . 5 2-1.2 Previous Research 9 2-2 P h y s i c a l - C h e m i c a l Treatment 16 2-2.1 Chemical P r e c i p i t a t i o n and C o a g u l a t i o n / 16 2- 2.2 Lime-Magnesium Process . . . . 19 2- 3 Other Treatment Processes and Methods 22 3 EXPERIMENTAL SYSTEM AND METHODS . . . . . 24 3- 1 Leachate Source and C h a r a c t e r i s t i c s 24 3-2 B i o l o g i c a l Treatment System 26 3- 2.1 The B i o l o g i c a l Reactors . . . 26 3-2.2 The Experimental Apparatus . . 26 3-2.3 Oper a t i o n of the Reactors . . 27 (a) O p e r a t i o n a l Parameters . . 27 (b) A c c l i m a t i o n 30 (c) Daily? O p e r ating Procedure 31 3-3 Lime-Magnesium Treatment System . .-. 32 V TABLE OF CONTENTS (continued) CHAPTER Page 4 RESULTS AND DISCUSSION 35 4-1 A c t i v a t e d Sludge Treatment Phase . 35 4-1.1 Mixed L i q u o r C h a r a c t e r i s t i c s and K i n e t i c s 35 4-1.2 Removal o f Organic M a t e r i a l and S o l i d s 41 4-1.3 Removal of Metals 4 7 4-1.4 Removal o f N u t r i e n t s . . . . 51 4- 2 Lime-Magnesium C o a g u l a t i o n Phase . 55 5 CONCLUSIONS AND RECOMMENDATIONS . . . . 63 5- 1 Conclusions 63 5-2 Recommendations 65 REFERENCES . 68 APPENDICES 71 A Determination o f B i o l o g i c a l Treatment K i n e t i c C o e f f i c i e n t s . . 72 B Supplementary R e s u l t s . 81 v i LIST OF TABLES Table No. T i t l e Page 1 Composition o f T y p i c a l Leachates 3 2 P a r t i a l Data Summary o f N u t r i e n t Requirement Study by Temoin 14 3 Leachate C h a r a c t e r i s t i c s 25 4 K i n e t i c C o e f f i c i e n t s o f T h i s and Previous I n v e s t i g a t i o n s 36 5 Mixed L i q u o r C h a r a c t e r i s t i c s 38 6 Organic M a t e r i a l ( i n Terms o f BOD 5 and COD) and S o l i d M a t e r i a l C o n c e n t r a t i o n s ( i n E f f l u e n t s ) and Removals 42 7 Comparison o f COD values o f F i l t e r e d E f f l u e n t s and Two-Hour' S e t t l e d E f f l u e n t s from the Reactors a t 5 C 45 8 Comparison o f Oxygen Demanding M a t e r i a l Removals under Various N u t r i e n t Loadings and F/M Ra t i o s 46 9 Metal Removal E f f i c i e n c i e s o f the B i o l o g i c a l Reactors 48 10 Metal C o n c e n t r a t i o n s o f the A e r o b i c a l l y B i o s t a b i l i z e d E f f l u e n t s 50 11 N i t r o g e n (TKN, NH , and N0 2~N0 ) and Phosphorus ( T o t a l ; C o n c e n t r a t i o n s ( i n E f f l u e n t s ) and Removals by the B i o l o g i c a l Reactors 52 12 pH, A c i d i t y , A l k a l i n i t y , and Lime Dosages Required o f the Samples Used f o r Lime- Magnesium C o a g u l a t i o n 56 13 E f f l u e n t Organic M a t e r i a l ( i n Terms o f BOD,. and COD), Suspended S o l i d s , and T o t a l Phosphorus C o n c e n t r a t i o n s and Removals by C o a g u l a t i o n 57 14 Metal C o n c e n t r a t i o n s o f the F i n a l E f f l u e n t s P o l i s h e d by the Lime-Magnesium Process . . . 60 v i i LIST OF TABLES (continued) 15 Metal Removals by Lime-Magnesium C o a g u l a t i o n 61 16 Computation Table f o r the G r a p h i c a l Determination of K i n e t i c C o e f f i c i e n t s . . . 75 17 K i n e t i c C o e f f i c i e n t s and Minimum Mean C e l l R e t e n t i o n Times . 80 18 A c i d i t y , A l k a l i n i t y , TC and TOC Con c e n t r a t i o n s and Removals by the B i o l o g i c a l Reactors 83 v i i i LIST OF FIGURES F i g u r e No. T i t l e Page 1 T y p i c a l Laboratory Reactor 28 2 MLVSS versus Sludge Age 40 3 Determination o f k and K a t Room Temperature 76 4 Determination o f Y and b a t Room Temperature 76 5 Determination o f k and K a t 15°C 77 s 6 Determination o f Y and b a t 15°C 77 7 Determination o f k and K a t 10°C 7 8 s 8 Determination of Y and b a t 10°C 78 9 Determination o f k and K a t 5°C 79 s 10 Determination o f Y and b at 5°C 79 11 Mixed L i q u o r COD versus .Sludge Age 82 i x ACKNOWLEDGEMENTS The author wishes to express h i s g r a t i t u d e t o h i s a d v i s o r , Dr. D.S. Mavi n i c , f o r h i s p a t i e n t guidance and advice d u r i n g the p r e p a r a t i o n o f t h i s t h e s i s . He would a l s o l i k e t o thank Dr. W.K. Oldham f o r r e v i e w i n g t h i s t h e s i s . The author i s a l s o very g r a t e f u l to Susan L i p t a k , Paula Parkinson,and Sue Jackman o f the C i v i l E n g i n e e r i n g Environmental Laboratory f o r t h e i r g r e a t a s s i s t a n c e . F i n a n c i a l support from the N a t i o n a l Research C o u n c i l o f Canada i s g r a t e f u l l y acknowledged. 1 CHAPTER 1 INTRODUCTION S a n i t a r y l a n d f i l l s and t h e i r m o d i f i c a t i o n s have long been accepted as a " s a t i s f a c t o r y " method of s o l i d waste d i s - p o s a l . Although o t h e r techniques such as composting and resource recovery are more en v i r o n m e n t a l l y d e s i r a b l e , the s i m p l i c i t y and low c o s t o f l a n d f i l l s have l e d to t h e i r popu- l a r i t y . A l s o , i t i s the only " f i n a l " s o l i d waste d i s p o s a l method c u r r e n t l y i n use; u n l i k e composting, i n c i n e r a t i o n , p y r o l y s i s , and resource recovery, l a n d f i l l i n g does not y i e l d a r e s i d u e which r e q u i r e s f u r t h e r d i s p o s a l . Most problems a s s o c i a t e d w i t h m u n i c i p a l s o l i d waste l a n d f i l l s have been overcome. Continuous compaction and d a i l y cover have minimized v e c t o r problems, l e s s e n e d a i r b o r n e l i t t e r , and reduced odour problems. However, the g e n e r a t i o n of l e a c h a t e i s a problem of growing concern. Leachate i s produced when water p e r c o l a t e s through l a n d - f i l l s , e x t r a c t i n g suspendable and s o l u b l e o r g a n i c and i n o r g a n i c c o n s t i t u e n t s from the r e f u s e beds. Although the l e a c h a t e u s u a l l y undergo some degree o f s e l f p u r i f i c a t i o n b a c t e r i o l o - g i c a l l y and c h e m i c a l l y , the l a r g e amounts o f e x t r a c t e d m a t e r i a l can l e a d to a g r o s s l y p o l l u t e d l i q u i d . The q u a n t i t y and qua- l i t y o f l e a c h a t e produced i s dependent on a number o f p h y s i c a l v a r i a b l e s - some o f these are: the amount, composition, par- t i c l e s i z e , and moisture content of the r e f u s e , the degree o f compaction of the r e f u s e , the depth o f the r e f u s e beds, the 2 hydrogeology of the s i t e , and the c l i m a t e o f the r e g i o n . Table 1 (6) i l l u s t r a t e s the wide range o f composition o f t y p i c a l l e a c h a t e s . S i n c e l e a c h a t e may be a s e r i o u s source o f s u r f a c e and/or ground water p o l l u t i o n , environmental agencies are not allow- i n g l e a c h a t e g e n e r a t i o n and movement to go unchecked. There are t h r e e a l t e r n a t i v e s a v a i l a b l e f o r the e l i m i n a t i o n o r m i n i - m i z a t i o n o f the l e a c h a t e problem; these are the r e d u c t i o n o f le a c h a t e p r o d u c t i o n , l e a c h a t e r e c i r c u l a t i o n , and the c o l l e c t i o n and treatment o f l e a c h a t e b e f o r e d i s c h a r g e . E l i m i n a t i n g o r mi n i m i z i n g l e a c h a t e p r o d u c t i o n i n v o l v e s good s i t e s e l e c t i o n and design, w i t h proper c o n s t r u c t i o n and o p e r a t i o n . Measures employed may i n c l u d e m i l l i n g and b a l i n g of r e f u s e , s u r f a c e water c o n t r o l , ground water c o n t r o l , and/or chemical i m m o b i l i z a t i o n . However, wit h some o f the above mea- sures , l o n g term maintenance may be r e q u i r e d and the p o t e n t i a l f o r l e a c h a t e p r o d u c t i o n remains (mainly because o f the reduced r a t e o f waste s t a b i l i z a t i o n due to the absence o f wa t e r ) . A l s o , i n areas o f high p r e c i p i t a t i o n , these methods may be i n e f f e c t i v e o r the c o s t s o f employing such methods may be pro- h i b i t i v e l y h i g h . A p r o m i s i n g new technique f o r a c c e l e r a t i n g the r a t e o f waste s t a b i l i z a t i o n i s l e a c h a t e r e c i r c u l a t i o n . The volume o f le a c h a t e i s reduced d u r i n g the s t a b i l i z a t i o n p e r i o d and a f t e r t h i s s h o r t p e r i o d , l e a c h a t e s t r e n g t h i s g r e a t l y reduced. How- ever, a f t e r waste s t a b i l i z a t i o n , the r e c i r c u l a t e d l e a c h a t e 3 TABLE 1 (6) COMPOSITION OF TYPICAL LEACHATES Range o f Values o r C o n c e n t r a t i o n s * Parameter ( L a n d f i l l s and Tes t Lysimeters) BODp. 9 - 55 000 COD 0 - 90 000 T o t a l Carbon 715 - 22 350 T o t a l Organic Carbon 715 - 22 350 T o t a l S o l i d s 1 000 - 45 000 T o t a l V o l a t i l e S o l i d s 1 000 - 23 157 T o t a l D i s s o l v e d S o l i d s 0 - 42 300 A c i d i t y 0 - 9 560 A l k a l i n i t y 0 — 20 900 Aluminum 0 - 122 A r s e n i c 0 - 11.6 Barium 0 - 5.4 B e r y l l i u m 0 - 0.3 Calcium 5 - 4 000 Cadmium 0 - 0.19 C h l o r i d e 34 - 2 800 Chromium 0 - 33.4 Copper 0 - 10 Iron 0.2 - 5 500 Lead 0 - 5.0 Magnesium 165 - 15 600 Manganese 0.06 - 1 400 Mercury 0 - 0.064 Molybdenum 0 — 0.52 N i t r o g e n - t o t a l 0 - 2 406 - NH 3 0 - 1 106 N i c k e l 0.01 - 0.80 Phosphorus - t o t a l 0 - 154 Potassium 2 .8 - 3 770 Sodium 0 - 7 700 Sulphates 1 - 1 826 Sulphides 0 - 0.13 Ti t a n i u m 0 - 5.0 Vanadium 0 - 1.4 Zinc 0 - 1 000 pH 3.7 - 8.5 T a n n i n - l i k e compounds 78 - 1 278 Colou r ( c h l o r o p l a t i n a t e ) 0 - 12 000 Odour not d e t e c t a b l e t o t e r r i b l e * A l l valu e s except those f o r pH, c o l o u r and odour are i n mg/L. 4 should be c o l l e c t e d f o r u l t i m a t e treatment and d i s p o s a l . However, t h i s method has obvious shortcomings under c o n t i n u - i n g f i l l o p e r a t i o n and/or high p r e c i p i t a t i o n a reas. The l a s t a l t e r n a t i v e i s the c o l l e c t i o n and treatment of the l e a c h a t e generated. I t i s to t h i s end t h a t t h i s study and many oth e r r e s e a r c h p r o j e c t s at the U n i v e r s i t y o f B r i t i s h Columbia have been c a r r i e d out. T h i s i n v e s t i g a t i o n i s a follow-up t o s e v e r a l o f those p r e v i o u s s t u d i e s . The purpose o f t h i s study was to e v a l u a t e the t r e a t a b i l i t y o f a l e a c h a t e by a e r o b i c b i o s t a b i l i z a t i o n at a n u t r i e n t l o a d i n g of BOD5:N:P of 100:3.2.:1.1 and then p o l i s h i n g the e f f l u e n t s from the a e r o b i c treatment process by p h y s i c a l - c h e m i c a l treatment (through lime-magnesium c o a g u l a t i o n ) . In the b i o - l o g i c a l treatment stage, the ranges o f ambient a i r temperature and sludge age (or mean c e l l r e s i d e n c e time) i n v e s t i g a t e d were 5° to 25 PC and 5 t o 2 0 days r e s p e c t i v e l y . Temoin (31), i n a p r e v i o u s study, found 100:3.19:1.11 to be the optimum n u t r i e n t l o a d i n g . S e v e r a l i n v e s t i g a t o r s (19, 20, 27) have found lime-magnesium c o a g u l a t i o n to be an e f f e c t i v e method i n the treatment o f wastewaters. 5 CHAPTER 2 BACKGROUND 2 - 1 A e r o b i c B i o s t a b i l i z a t i o n 2 - 1.1 D e s c r i p t i o n o f the A c t i v a t e d Sludge Process A c t i v a t e d sludge i s an a e r o b i c suspended-growth t r e a t - ment p r o c e s s . The b i o l o g i c a l f l o e s , kept i n suspension by a e r a t i o n and perhaps mechanical mixing, are p r i m a r i l y respon- s i b l e f o r the removal o f o r g a n i c s i n the wastewater. Under normal o p e r a t i n g c o n d i t i o n s , b a c t e r i a are the dominant primary feeders i n the a c t i v a t e d sludge p r o c e s s . The s p e c i e s o f the b a c t e r i a i s dependent on the nature o f the o r g a n i c waste and the environmental c o n d i t i o n s i n the a e r a t i o n tanks. The primary b a c t e r i a are maintained i n the de- c l i n i n g o r endogenous growth phases, c a u s i n g them to d i e , l y s e , and thereby r e l e a s e t h e i r c e l l contents to s o l u t i o n . In t h i s p r o c e s s , raw o r g a n i c matter i s converted to energy or s y n t h e s i z e d and r e s y n t h e s i z e d by v a r i o u s groups o f bac- t e r i a . A l s o common i n a c t i v a t e d sludge are protozoans, the secondary f e e d e r s . The b a c t e r i a s y n t h e s i z e the o r g a n i c mat- t e r , and the protozoans consume the b a c t e r i a . Other s p e c i e s o f organisms p r e s e n t i n the " z o o g l e a l mass" may i n c l u d e y e a s t s , molds, worms, alg a e , r o t i f i e r s , nematodes, and i n s e c t l a r v a e . 6 In a d d i t i o n to o r g a n i c removal, some degree o f metal removal i s o b t a i n e d . The mechanism by which metal removal i s a c h i eved i n a c t i v a t e d sludge i s a combination o f f l o c - c u l a t i o n and s e t t l i n g ( 5). The average composition of the c e l l t i s s u e i n the zoo- g l e a l mass i s taken as C^H^NO^ An elemental a n a l y s i s o f b a c t e r i a l c e l l s , t h a t i n c l u d e s the phosphorus requirement, i s , however, C 6 g H 8 7 ° 2 3 N 1 2 P (29). O x i d a t i o n , s y n t h e s i s , and endogenous r e s p i r a t i o n are the met a b o l i c r e a c t i o n s t h a t occur. The chemical s t o i c h i o m e t r i c equations f o r these r e - s p e c t i v e r e a c t i o n s are as f o l l o w s : C H 0 + 0„ — C0„ .+ H 00 + energy . . . . . . (1) C H O + 0„ + NH_, + energy x y z 2 3 — - C0 2 + H 2 P + C 5H 7N0 2 .... . . . . . . . (2) C 5H 7N0 2 + 50 2 — - 5C0 2 + 2H 20 + NH^ . .,. . . . . . . (3) In the presence o f enzymes, about o n e - t h i r d o f the o r g a n i c matter removed i s o x i d i z e d to C0 2 and H 20 i n or d e r t o pro v i d e energy f o r the s y n t h e s i s o f the remaining t w o - t h i r d s o f the or g a n i c matter t h a t i s converted to c e l l m a t e r i a l . For e f f i c i e n t b i o l o g i c a l wastewater treatment, i t i s g e n e r a l l y accepted t h a t a n u t r i e n t l o a d i n g l e v e l (BOD,. :N:P) of approximately 100:5:1 must be maintained (11). I f i n s u f - f i c i e n t n u t r i e n t s are a v a i l a b l e , filamentous b a c t e r i a can predominate, r e s u l t i n g i n sludge b u l k i n g and incomplete c o n v e r s i o n of o r g a n i c s t o end products (8, 29). Normally, 7 t h i s i s not a problem when t r e a t i n g domestic sewage s i n c e n u t r i e n t s are pr e s e n t i n s u f f i c i e n t q u a n t i t y . I n d u s t r i a l wastewaters, however, o f t e n are d e f i c i e n t and r e q u i r e n i t r o - gen and phosphorus supplements. The q u a n t i t y o f n u t r i e n t s added i s of concern. Insuf- f i c i e n t n u t r i e n t s l e a d t o problems as d e s c r i b e d p r e v i o u s l y , but excess n u t r i e n t a d d i t i o n s can a l s o l e a d to d i f f i c u l t i e s . Some of these are: (i) r i s i n g sludge ( d e n i t r i f i c a t i o n o f excess n i t r o g e n i n the r e a c t o r , where NOj and NO^ are converted t o N j " gas. which becomes trapped i n the sludge mass, cau s i n g poor s e t t l i n g i n the c l a r i f i e r ) , ( i i ) h i g h l e v e l s o f n i t r o g e n and phosphorus i n the f i n a l e f f l u e n t , which are i n excess o f l o c a l p o l l u t i o n con- t r o l standards and w i l l f e r t i l i z e r e c e i v i n g waters, and ( i i i ) h i g h e r c o s t s than necessary (both c a p i t a l c o s t s f o r storage and chemical f e e d i n g equipment and o p e r a t i n g c o s t s f o r the purchase of c h e m i c a l s ) . Temperature i s another f a c t o r t h a t a f f e c t s the e f f i - c i e n c y o f the a c t i v a t e d sludge p r o c e s s . B i o l o g i c a l m e t a b o l i c a c t i v i t y g e n e r a l l y decreases w i t h d e c r e a s i n g temperature. The temperature e f f e c t on the r e a c t i o n r a t e i s u s u a l l y des- c r i b e d by the m o d i f i e d A r r h e n i u s equation (22): 8 K e (T-20) (4) 20 where K, r e a c t i o n c o n s t a n t a t temperature T K 20 r e a c t i o n constant a t 20°C e temperature s e n s i t i v i t y c o e f f i c i e n t 1.056 f o r a temperature between 20° and 30°C 1.135 f o r a temperature between 4° and 2 0°C Other f a c t o r s a f f e c t i n g a c t i v a t e d sludge performance are sludge age, pH, and d i s s o l v e d oxygen. pH should be maintained w i t h i n a range o f 6.5 to 9.0 (11). The d i s s o l v e d oxygen l e v e l should be above 1.5 to 2.0 mg/L, f o r a e r o b i c c o n d i t i o n s to e x i s t . G e n e r a l l y , as sludge age decreases, e f f l u e n t q u a l i t y worsens. In i n v e s t i g a t i n g t r e a t a b i l i t y systems i n v o l v i n g the a c t i - v a t e d sludge process, t h r e e o p e r a t i o n a l procedures are commonly used: continuous flow, f i l l - a n d - d r a w , and b a t c h . The c o n t i n - uous flow system i s favoured, s i n c e i t more c l o s e l y s i m u l a t e s the f u l l - s c a l e p r o c e s s , as w e l l as providing'more comprehensive data. However, bench-scale, continuous flow r e a c t o r s are prone to o p e r a t i n g d i f f i c u l t i e s such as clogged t u b i n g and breakdown o f pumps. The f i l l - a n d - d r a w method, on the o t h e r hand, r e q u i r e s f a r l e s s mechanical equipment and i s t h e r e f o r e a much s i m p l i e r and t r o u b l e f r e e system to operate; A l s o , the k i n e t i c s o f a f i l l - a n d - d r a w system are s i m i l a r t o t h a t o f a plug-flow, f u l l - s c a l e system. Batch r e a c t o r s are o n l y use- f u l f o r determining trends and approximating design v a l u e s . 9 I t i s f o r the above reasons, p l u s the importance of t y i n g i n t o p r e v i o u s l e a c h a t e t r e a t a b i l i t y work performed under the f i l l - a n d - d r a w system, t h a t the f i l l - a n d - d r a w method has been used f o r t h i s i n v e s t i g a t i o n . 2 - 1.2 Previous Research The e a r l i e s t known a e r o b i c " b i o s t a b i l i z a t i o n o f l e a c h a t e " study was c a r r i e d out by Boyle and Ham (4). T h e i r 5-day sludge age u n i t s achieved 90, 93, and 80 p e r c e n t BODr. remo- v a l s f o r BOD 5 l o a d i n g s of 0.019, 0.036, and 0.087 l b B O D 5 / d a y / f t 3 (0 . 30 , ' 0 . 58 , and 1.39 kg BODg/day/m.3)..,. resp e c - " ' t i v e l y . T h e i r 1-day sludge age u n i t never performed e f f e c t - i v e l y d u r i n g one month o f o p e r a t i o n . Sludge b u l k i n g pro- blems predominated, r e s u l t i n g i n poor q u a l i t y e f f l u e n t . T h i s was a t t r i b u t e d t o an e x c e s s i v e l y , h i g h v o l u m e t r i c l o a d i n g of 3 3 0.330 l b BOD 5/day/ft (5.29 kg BOD5/day/m ) and a food-to- microorganism (F/M) r a t i o exceeding 1.5 kg BOD^/day/kg MLVSS. The u n i t s were operated on a f i l l - a n d - d r a w b a s i s . Although the a e r o b i c treatment s t u d i e s were encouraging, s e v e r a l disadvantages of the p r o c e s s , i n c l u d i n g h i g h power r e q u i r e - ments and foaming problems, caused Boyle and Ham to d i r e c t the major t h r u s t of t h e i r p r o j e c t toward anaerobic treatment. Cook and Foree (9) e v a l u a t e d the treatment of l e a c h a t e by a e r o b i c b i o s t a b i l i z a t i o n under v a r i o u s o r g a n i c l o a d i n g s , n u t r i e n t a d d i t i o n s , and pH c o n d i t i o n s . The l e a c h a t e used i n this study was of "medium" s t r e n g t h . Some c h a r a c t e r i s t i c s of the raw l e a c h a t e were: 10 COD = 15,800 mg/L BOD 5 = 7,100 mg/L pH = 5.4 BOD5:N:P = 100:2.5:0.18 S i x bench-scale a e r o b i c u n i t s were used t o e v a l u a t e the b i o l o g i c a l s t a b i l i z a t i o n of the l e a c h a t e . Four u n i t s were d a i l y f i l l - a n d - d r a w systems o p e r a t i n g w i t h v a r i o u s lime and n u t r i e n t a d d i t i o n s and a 10-day sludge age (0.044 l b BOD^/day/ 3 3 f t o r 0.70 kg BOD5/day/m ). An a d d i t i o n a l f i l l - a n d - d r a w u n i t was run a t a 5-day sludge age and the l a s t u n i t was a continuous feed system, w i t h a 2-day sludge age. Both o f these u n i t s f a i l e d , as p r e d i c t e d by the o p e r a t i o n a l and k i n e t i c c h a r a c t e r i s t i c s determined. The t h e o r e t i c a l d e t e n t i o n time f o r f a i l u r e was c a l c u l a t e d to be 5.3 days. The 10-day u n i t s a l l performed w e l l . COD removals-iwere from 9 7.6 p e r c e n t f o r the u n i t f e d le a c h a t e o n l y , t o 9 8.1 perce n t f o r the u n i t w i t h lime and n u t r i e n t s added. The BODj. of the e f f l u e n t s were a l l below 26 mg/L, corresp o n d i n g to removal e f f i c i e n c i e s o f a t l e a s t 99.7 perc e n t . The s e t - t l i n g p r o p e r t i e s of the mixed l i q u o r were very good. The range o f sludge volume i n d i c e s (SVI) was from 39 t o 55, w i t h the lime supplemented u n i t s having the lowest S V I 1 s . The range f o r t o t a l suspended s o l i d s (TSS) and v o l a t i l e suspended s o l i d s (VSS) i n the e f f l u e n t were 39 to 77 mg/L and 24 to 57 mg/L, r e s p e c t i v e l y . 11 The r e m o v a l o f t h r e e m e t a l s was e x a m i n e d . I r o n c o n c e n - t r a t i o n s w e r e r e d u c e d f r o m 2 40 mg/L t o l e s s t h a n 10 mg/L, i n a l l o f t h e 1 0 - d a y r e a c t o r s . Cook a n d F o r e e a t t r i b u t e d t h e h i g h r e m o v a l s m a i n l y t o c h e m i c a l p r e c i p i t a t i o n a t t h e h i g h pH's. C a l c i u m r e m o v a l s w e r e much h i g h e r i n t h e t w o u n i t s w i t h a pH o f 8.4. T h i s was due t o t h e p r e c i p i t a t i o n o f t h e c a l c i u m as c a l c i u m c a r b o n a t e a t t h i s h i g h pH. The mag- n e s i u m c o n c e n t r a t i o n s w e r e n o t r e d u c e d s i g n i f i c a n t l y . The pH was n o t h i g h enough t o c a u s e p r e c i p i t a t i o n o f t h e m a g n e s i u m as m a g n e s i u m h y d r o x i d e . The r e m o v a l t h a t d i d o c c u r was due t o s e t t l i n g o u t o f i n s o l u b l e . m a g n e s i u m . M o s t o f t h e t o t a l K j e l d a h l n i t r o g e n (TKN) was r e m o v e d i n t h e 10-day u n i t s a n d NO^-N was p r o d u c e d i n t h e n u t r i e n t s u p p l e m e n t e d u n i t s . The m i x e d l i q u o r c o n c e n t r a t i o n s o f TKN w e r e l o w e r t h a n t h e c o n c e n t r a t i o n s f o r t h e l e a c h a t e , w i t h a n d w i t h o u t a d d e d NH^-N, i n d i c a t i n g t h a t some ammonia s t r i p - p i n g h a d t a k e n p l a c e . A l m o s t a l l o f t h e p h o s p h o r u s was f o u n d t o be t i e d up i n t h e m i c r o b i a l masses, a n d s e t t l e d s l u d g e . The n u t r i e n t a d d i t i o n s t h a t w e r e made w e r e i n t h e f o r m o f ammonia n i t r o g e n a n d o r t h o p h o s p h a t e . ..> The r e s u l t s o f Cook a n d F o r e e 1 s s t u d y showed t h a t n u t r i e n t a d d i t i o n s w e r e n o t n e e d e d f o r s u c c e s s f u l t r e a t m e n t o f t h e l e a c h a t e . P a l i t a n d Q a s i m (24) s t u d i e d t h e b i o l o g i c a l t r e a t m e n t k i n e t i c s o f l a n d f i l l l e a c h a t e . T h e i r s t u d y was c o n d u c t e d w i t h d i l u t e l a n d f i l l l e a c h a t e ( d i l u t e d COD = 365 mg/L), u s i n g a b e n c h - s c a l e c o n t i n u o u s f l o w a c t i v a t e d s l u d g e u n i t . 12 They concluded t h a t l e a c h a t e can be b i o l o g i c a l l y t r e a t e d i n an a c t i v a t e d sludge p l a n t . Poor s o l i d s - l i q u i d s e p a r a t i o n was encountered s e v e r a l times d u r i n g the experiment. I t was suggested t h a t the a d d i t i o n o f n u t r i e n t s would enhance removal e f f i c i e n c i e s . There have a l s o been s e v e r a l l e a c h a t e t r e a t a b i l i t y (by a e r o b i c s t a b i l i z a t i o n ) s t u d i e s done a t the U n i v e r s i t y o f B r i t i s h Columbia. The f i r s t i n v e s t i g a t o r was U l o t h (33). He attempted t o t r e a t h i g h s t r e n g t h l e a c h a t e (BOD,. = 35000 mg/L) u s i n g very h i g h mixed l i q u o r v o l a t i l e suspended s o l i d s c o n c e n t r a t i o n s (8000 to 16000 mg/L). P r o v i d e d t h a t F/M r a t i o s were kept below 0.22 kg BODg/day/kg MLVSS, s t a b l e r e a c t o r o p e r a t i o n s were maintained a t s o l i d s d e t e n t i o n times as s h o r t as 10 days. COD removals i n c r e a s e d from 9 6.7 to 99.1 p e r c e n t f o r sludge ages from 10 to 60 days.. G r e a t e r than 99.6 percent BODj. removals were p o s s i b l e f o r s o l i d s d e t e n t i o n times over 10 days. Metal removals were a l s o h i g h . U l o t h a t t r i b u t e d t h i s to the hig h pH's ( g r e a t e r than 8.5) and VSS c o n c e n t r a t i o n s of the mixed l i q u o r s . BOD^:N:P r a t i o s o f 100:5:1 or"';lower were used. A n a l y s i s o f the e f f l u e n t s i n d i - cated t h a t the n i t r o g e n and phosphorus a d d i t i o n s were exces- s i v e and t h e r e f o r e , might be s u b s t a n t i a l l y reduced without i m p a i r i n g treatment e f f i c i e n c y . The b i o l o g i c a l r e a c t o r s o f t h i s , and a l l subsequent s t u d i e s a t the U n i v e r s i t y o f B r i t i s h Columbia, were operated on a f i l l - a n d - d r a w b a s i s . S e t t l i n g was complete a f t e r 2 hours f o r t h i s study. 13 An i n v e s t i g a t i o n by Temoin (31) was a follow-up to the work of U l o t h . Temoin was concerned w i t h the n i t r o g e n and phosphorus requirements f o r the s u c c e s s f u l treatment o f high s t r e n g t h l e a c h a t e through a e r o b i c b i o s t a b i l i z a t i o n . With an ^optimal" sludge age o f 20 days and o p e r a t i n g a t room tempera- t u r e , the n u t r i e n t l o a d i n g (BOD,_:N:P) was v a r i e d from 100:3.19:0.12 to 100:5:1.1. The most e f f e c t i v e treatment was achieved w i t h a l o a d i n g o f 100:3.19:1.11. A p a r t i a l summary (21) of Temoin's r e s u l t s are shown i n Table 2. Two main types of b a c t e r i a were found i n the mixed l i - quors. One was a zoo g l e a l form common to domestic sewage treatment p l a n t s . The second was actinomycete Geodermatophi- l i u s . T h i s b a c t e r i a had never b e f o r e been i s o l a t e d i n a se- wage treatment p l a n t . The r e a c t o r s w i t h the h i g h phosphorus l o a d i n g s (271 mg/L) a l l had 90% Geodermatophilius and 10% z o o g l e a l f l o e . As the phosphorus l o a d i n g decreased, the zoo- g l e a l form s t a r t e d t o predominate. When n u t r i e n t l o a d i n g were s u f f i c i e n t l y reduced, sludge b u l k i n g o c c u r r e d . For :5/this study, s e t t l i n g f o r e f f l u e n t s was g i v e n 2h hours. The two most r e c e n t l e a c h a t e treatment s t u d i e s at the U n i v e r s i t y of B r i t i s h Columbia were c a r r i e d out by Z a p f - G i l j e (34) and Graham (14). These s t u d i e s were done c o n c u r r e n t l y . They t r e a t e d a medium s t r e n g t h l e a c h a t e (COD = 19000 mg/L) by a e r o b i c b i o s t a b i l i z a t i o n ! w i t h sludge ages ranging from 6 to 25 days and temperatures r a n g i n g from 5° to 2 5°C. N u t r i e n t l o a d i n g s were s l i g h t l y i n excess o f BODj-:N:P = 100:5:1. T A B L E 2 (31) P A R T I A L DATA SUMMARY OF NUTRIENT REQUIREMENT STUDY BY TEMOIN N U T R I E N T LOADING OF REACTOR B O D c : N : P E F F L U E N T CONCENTRATIONS BODj- (mg /L ) TSS (mg /L ) C r (mg /L ) Fe (mg/L) Pb (mg /L ) Zn (mg /L ) L e a c h a t e F e e d 19330 990 0. 365 960 0.167 49.5 . 100:5.03:1.11 82 380 0.050 25.2 0.011 1.31 100:3.98:1.11 55 133 0.033 9 .72 0.006 0.630 100:3.19:1.11 36 47 0.035 4.27 0.003 0.295 100:3.98:0.32 300 1805 0.103 27. 3 0.023 2.10 100:3.98:0.12 1430 245 0.040 13.5 0.005 0.726 100:3.19:0.12 560 160 0.033 6.73 0.015 0.543 15 Z a p f - G i l j e then a l s o employed a e r o b i c b i o s t a b i l i z a t i o n as a p o l i s h i n g step f o r h i s f i r s t stage b i o s t a b i l i z e d e f f l u e n t s . Graham's second stage p o l i s h i n g o f h i s e f f l u e n t s was by lime p r e c i p i t a t i o n . Removal o f o r g a n i c m a t e r i a l i n the f i r s t stage was e x c e p t i o n a l l y good, w i t h b e t t e r than 99% BOD 5 and 95% COD removals. Metal removals were b e t t e r than 90% f o r most of the metals monitored. For the temperature and sludge age ranges s t u d i e d , the d i f f e r e n c e s i n performance o f the r e a c - t o r s were not very s i g n i f i c a n t . The e x c e p t i o n t o t h i s was at the lowest temperature, p a r t i c u l a r l y a t the lower sludge ages, where r e a c t o r i n s t a b i l i t y was observed. The s e t t l i n g c h a r a c t e r i s t i c s o f a l l the mixed l i q u o r s were h i g h l y v a r i a b l e . Hence, Z a p f - G i l j e f i l t e r e d the samples i n o r d e r to o b t a i n a c o n s i s t e n t e f f l u e n t , whereas Graham c o l l e c t e d both 2-hour s e t t l e d and f i l t e r e d e f f l u e n t s . Whatman No.. 4 f i l t e r ' p a p e r was used. Z a p f - G i l j e found b i o l o g i c a l p o l i s h i n g o f the f i r s t stage e f f l u e n t s n o t o f e a s i b l e a t hig h temperatures, due t o the low r e s i d u a l c o n c e n t r a t i o n o f biodegr a d a b l e o r g a n i c s . I t was only m a r g i n a l a t the lowest temperature i n v e s t i g a t e d (9°C), where 4 5 p e r c e n t BOD,- and 80 per c e n t COD removal, p l u s a r e d u c t i o n o f some metal c o n c e n t r a t i o n s was achieved. Graham found lime p o l i s h i n g to be e f f e c t i v e ; however, the lime dosages r e q u i r e d were o f t e n very h i g h . 16 2 - 2 P h y s i c a l - C h e m i c a l Treatment 2 - 2.1 Chemical P r e c i p i t a t i o n and C o a g u l a t i o n Chemical p r e c i p i t a t i o n i n v o l v e s the a d d i t i o n of chemi- c a l s to a l t e r the s t a t e of d i s s o l v e d and suspended matter and f a c i l i t a t e t h e i r removal by sedimentation. In some cases the change i s s l i g h t , and removal i s e f f e c t e d by entrap- ment w i t h i n a p r e c i p i t a t e c o n s i s t i n g p r i m a r i l y o f the coagulant i t s e l f (22). S e v e r a l i n v e s t i g a t o r s have conducted chemical treatment of l e a c h a t e experiments. Ho e t a l . (16) used l i m e , sodium s u l f i d e , alum, and f e r r i c c h l o r i d e as t h e i r p r e c i p i t a t i o n and c o a g u l a t i o n c h e m i c a l s . The b e s t r e s u l t s were o b t a i n e d with lime. However, metal and c o l o u r removals were p o s s i b l e o n l y a t h i g h chemical doses. No s i g n i f i c a n t o r g a n i c removals were ob t a i n e d and a l a r g e amount o f sludge was produced. The r e s u l t s i n d i c a t e d t h a t a combination of b i o l o g i c a l treatment to reduce o r g a n i c l e v e l s , f o l l o w e d by lime p r e c i p i t a t i o n was promising. V a r i o u s chemicals u s i n g v a r i o u s combinations of pH and dosage were t r i e d by Cook and Foree (9). The chemicals used were: hydrated l i m e , alum, f e r r i c c h l o r i d e , f e r r i c s u l f a t e , p o l y e l e c t r o l y t e , and sodium hydroxide. From the s t u d i e s performed, Cook and Foree concluded t h a t suspended s o l i d s and c o l o u r c o u l d be e f f e c t i v e l y reduced, but because of the high c o n c e n t r a t i o n o f s o l u b l e o r g a n i c s , the t o t a l o r g a n i c s t r e n g t h c o u l d not be s i g n i f i c a n t l y reduced. 17 Thornton and Blanc (32) examined the treatment o f l e a c h a t e by chemical c o a g u l a t i o n and p r e c i p i t a t i o n w i t h regard t o removals o f b i o c h e m i c a l oxygen demand, i r o n , c a lcium, magnesium, suspended s o l i d s , and c o l o u r . I n i t i a l t e s t s on a low s t r e n g t h l e a c h a t e (COD = 50 33 mg/L) i n v o l v e d the use o f alum and lime, with removal of c o l o u r and sus- pended s o l i d s as a measure o f chemical e f f e c t i v e n e s s . At doses of 300 mg/L, suspended s o l i d s removals were a p p r o x i - mately 50% f o r alum and 75% f o r lime. Due to the s u p e r i o r performance of lime over alum, a l l f u r t h e r t e s t s were conduct- ed w i t h l i m e . A h i g h e r s t r e n g t h l e a c h a t e (COD = 12923 mg/L) was a l s o used i n order t o determine the e f f e c t s o f i n c r e a s e d l e a c h a t e s t r e n g t h on lime requirements. For t h i s l e a c h a t e , a 9 00 mg/L lime dose was only e f f e c t i v e f o r a 60% removal o f suspended s o l i d s . From t h e i r s t u d i e s , Thornton and Blanc concluded t h a t s u b s t a n t i a l r e d u c t i o n s i n c o l o u r , suspended s o l i d s , and m u l t i v a l e n t c a t i o n s can be achieved by lime p r e c i p i t a t i o n . These r e d u c t i o n s were a f u n c t i o n of the a l k a l i n i t y o f the sample and the a b i l i t y o f lime to r a i s e the pH f o r the pre - c i p i t a t i o n o f c a l c i u m carbonate and metal hydroxides. However, s i g n i f i c a n t removals o f o t h e r d i s s o l v e d s o l i d s and s o l u b l e o r g a n i c s , which c o n s t i t u t e the major p o r t i o n o f BOD, were not achieved by the lime treatment. Bjorkman;. (3) , a t the U n i v e r s i t y o f B r i t i s h Columbia, conducted a comprehensive study on the p h y s i c a l - c h e m i c a l 18 treatment and d i s i n f e c t i o n of l e a c h a t e . The chemicals s t u d i e d were: lime, alum, f e r r i c c h l o r i d e , f e r r i c s u l f a t e , powdered a c t i v a t e d carbon, and ozone. Supplemental to the chemicals, three high molecular weight s y n t h e t i c polymers were t e s t e d as c o a g u l a t i o n and s e t t l i n g enhancers. The COD of the l e a c h a t e s t u d i e d was 14000 mg/L. Bjorkman achieved the b e s t o v e r a l l treatment u s i n g 110 mg/L ozone, f o l l o w e d by 2350 mg/L o f l i m e . T h i s r e s u l t e d i n d i s i n f e c t i o n and the f o l l o w i n g removals: 9 7.9% of pretreatment t u r b i d i t y , 90% of c o l o u r , 20% of COD, 26% o f Cu, 99.98% of Fe, 0% o f K, 99.8% of Mn, 0% o f Na, 98.5% of P, 39% o f Pb, and 99.9% o f Zn. From the above i n v e s t i g a t i o n s , i t i s apparent t h a t p h y s i c a l - c h e m i c a l treatment of l e a c h a t e by i t s e l f does not appear to be f e a s i b l e . I t can o n l y be c o s t e f f e c t i v e i f coupled w i t h o t h e r pretreatment p r o c e s s e s , t h a t would sub- s t a n t i a l l y reduce oxygen demanding m a t e r i a l f i r s t . In a d d i - t i o n , l i m e , which appears to be the most f a v o u r a b l e chemical, i s r e q u i r e d i n such massive dosages t h a t the c o s t s and sludge generated would make the chemical treatment o f raw l e a c h a t e a poor a l t e r n a t i v e . Ho e t a l . (16) added lime i n s u f f i c i e n t doses to r a i s e the pH to 9.0 and 11.0, f o r l e a c h a t e p r e t r e a t e d a n a e r o b i - c a l l y f o r 10 days, as w e l l as o t h e r samples t r e a t e d a n e r o b i - c a l l y f o r 10 days and then a e r o b i c a l l y f o r 5 a d d i t i o n a l days. For the a n a e r o b i c a l l y t r e a t e d l e a c h a t e , a lime dose o f 19 2700 mg/L was r e q u i r e d t o r a i s e the pH to 11.0. A t t h i s dose, e s s e n t i a l l y complete i r o n removal and about 10 percent COD removal were achieved. For the a n a e r o b i c a l l y - a e r o b i c a l l y t r e a t e d l e a c h a t e , a h i g h lime dose o f 1400 mg/L removed e s s e n t i a l l y a l l o f the i r o n and 30 percent o f the COD. Before lime p r e c i p i t a t i o n , the c o n c e n t r a t i o n s were COD = 55 8 and 366 mg/L and Fe = 20.0 and 15.0 mg/L, f o r the anaerobic and a n a e r o b i c - a e r o b i c e f f l u e n t s , r e s p e c t i v e l y . Graham (14) a l s o i n v e s t i g a t e d the p o l i s h i n g of a b i o - l o g i c a l l y s t a b i l i z e d l e a c h a t e by lime p r e c i p i t a t i o n . He found t h a t the dosage o f lime r e q u i r e d t o achieve adequate o r g a n i c removals was dependent upon the i n f l u e n t COD, a l k a - l i n i t y , and the t o t a l suspended s o l i d s of the sample. To e f f e c t i v e l y reduce r e s i d u a l o r g a n i c s and metals i n the b i o - t r e a t e d e f f l u e n t s , h i g h lime dosages were o f t e n r e q u i r e d . 2 - 2.2 Lime-Magnesium Process Chemical p r e c i p i t a t i o n and c o a g u l a t i o n by the lime - magnesium process i n v o l v e s p r e c i p i t a t i o n , a d s o r p t i o n , com- p l e x a t i o n , c h e l a t i o n , f l o c c u l a t i o n and entrapment i n the removal of d i s s o l v e d , c o l l o i d a l , and suspended matter from waters and wastewaters. For the removal o f heavy metals, the primary mechanism i s d i r e c t p r e c i p i t a t i o n o f i n s o l u b l e metal hydroxides. A d s o r p t i o n , f l o c c u l a t i o n and entrapment are the important mechanisms i n the removal o f o r g a n i c s . T h i s removal i s p a r t l y due to the i n - s i t u p r e c i p i t a t i o n o f magnesium hydroxide, a g e l a t i n o u s f l o e , which a i d s s o l i d s 20 removal as i t s e t t l e s . In t h i s way, the lime-magnesium pro- cess o f f e r s b e t t e r treatment than lime treatment alone (19, 27) . The magnesium a d d i t i o n i s i n the form of a magnesium s a l t , p r e f e r a b l y magnesium carbonate. T h i s i s so t h a t both magnesium hydroxide and c a l c i u m carbonate w i l l p r e c i p i t a t e out. The chemistry o f the lime-magnesium process i s very s i m i l a r t o t h a t o f water s o f t e n i n g . The f o l l o w i n g equations summarize the process (27): C0 2 + Ca(OH) 2 —--• CaC0 3l + HO (5) C a ( H C 0 3 ) 2 + Ca(OH) 2 — - 2CaC0 3» + 2H 20 (6) Mg(HC0 3) 2 + Ca(OH) 2 — MgC0 3 + CaCO^ + 2H 20 . . . (7) MgC0 3 + Ca(OH) 2 — Mg(0H) 2l + CaCO^ . . . . . . . (8) MgS0 4 + Ca(OH) 2 - — Mg(OH ) 2 l + CaS0 4 (9) Equations • (5) and (6) show the necessary c o n v e r s i o n of a l l the CC>2 and HCC>3 to C0 3~ and E^O b e f o r e the OH c o n c e n t r a t i o n (or pH) can i n c r e a s e . The c o n v e r s i o n o f magnesium b i c a r b o n - ate ( i f any present) and c a l c i u m hydroxide t o p r e c i p i t a t e d magnesium hydroxide and c a l c i u m carbonate i s i l l u s t r a t e d i n Equations (7) and (8). A r e a c t i o n such as Equation (9) occurs when magnesium i s not added i n the form o f magnesium carbonate o r i f noncarbonate magnesium/hardness i s pr e s e n t . I t should be noted t h a t when magnesium carbonate i s the coagulant, there i s no i n c r e a s e i n d i s s o l v e d s o l i d s . 21 Another s t r o n g f e a t u r e of t h i s process i s t h a t magnesium carbonate t r i h y d r a t e (MgCO^1 3H 20) and lime can be recovered from the sludge and r e c y c l e d . B l a c k et a l . r e c e n t l y developed a r e l a t i v e l y simple and i n e x p e n s i v e method f o r the r e c o v e r y of magnesium (27). The method i n v o l v e s : the s e l e c t i v e r e - moval of Mg(OH) 2 (to s o l u b l e Mg(HCO^) 2), from the primary sludge by c a r b o n a t i o n , the c l a r i f i c a t i o n o f the MgfHCO^^ s o l u t i o n ( u s u a l l y by f i l t r a t i o n ) , f o l l o w e d by h e a t i n g to 35°to 40°C and then a e r a t i o n , a t which time MgCG^-3H20 p r e c i p i t a t e s out. , The p r e c i p i t a t e can then be vacuum f i l - t e r e d and d r i e d . . The sludge can then be r e c a l c i n e d to r e - cover l i m e . Recovery and r e c y c l e of magnesium and lime i s an important economic f a c t o r , a f f e c t i n g both chemical and sludge h a n d l i n g c o s t s . I f recovery i s not p r a c t i s e d , sludge dewatering c o u l d be d i f f i c u l t because of the g e l a t i n o u s na- t u r e of the Mg(OH) 2 f l o e . Most e a r l y a p p l i c a t i o n s of the lime-magnesium process have been i n water treatment. Magnesium compounds as coagu- l a n t s have not been used e x t e n s i v e l y because of t h e i r high c o s t s . However, the advent o f mandatory w a t e r - s o f t e n i n g sludge e l i m i n a t i o n i n many areas and the magnesium recovery i n n o v a t i o n by Black e t a l . means a new low-cost source of magnesium. Rush (27) r e p o r t s t h a t a number of i n v e s t i g a t i o n s i n pulp and paper m i l l wastewater c l a r i f i c a t i o n have been con- ducted. They found t h a t magnesium hydroxide formed i n - s i t u 22 allowed much lower doses o f lime to be used than i f lime were used alone i n the removal o f COD, suspended s o l i d s , and c o l o u r . Rush a l s o found t h a t b e t t e r d e c o l o u r i z 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 c o u l d be achieved u s i n g low magnesium and lime c o n c e n t r a t i o n s , as opposed t o t h r e e to f i v e times as much lime alone. Rush (27) r e p o r t s DuBose's p i l o t p l a n t treatment s t u d i e s of raw m u n i c i p a l wastes showed t h a t much g r e a t e r r e d u c t i o n s i n phosphate, suspended s o l i d s , and c o l o u r , and ten to t h i r t y - p e r c e n t more COD c o u l d be removed w i t h r e c y c l e d magnesium b i c a r b o n a t e and l i m e , r a t h e r than lime alone. He a l s o found t h a t the s u p e r i o r i t y of the lime-magnesium process over lime alone was even more pronounced wi t h i n c r e a s i n g wastewater s t r e n g t h . MacLean (20) a p p l i e d lime-magnesium c o a g u l a t i o n to remove heavy metals from m u n i c i p a l wastewaters. He found t h a t the e f f e c t o f magnesium was most s i g n i f i c a n t when used i n c o n j u n c t i o n w i t h low lime treatment (pH = 10.0). Leung (19) s t u d i e d the removal o f trace.;, o r g a n i c s from m u n i c i p a l wastewaters by the lime-magnesium p r o c e s s . His r e s u l t s i n d i - c ated t h a t enhanced removal, due to the presence o f magnesium, was minimal. 2 - 3 Other Treatment Processes and Methods While a e r o b i c b i o s t a b i l i z a t i o n and the lime-magnesium p r e c i p i t a t i o n and c o a g u l a t i o n are the o n l y treatment processes examined i n t h i s i n v e s t i g a t i o n , i t i s important to r e c o g n i z e 23 t h a t there are a number of o t h e r treatment a l t e r n a t i v e s a v a i l a b l e . The f o l l o w i n g i s a b r i e f s y nopsis o f p r e v i o u s i n v e s t i g a t i o n s of these a l t e r n a t i v e l e a c h a t e treatment p r o c e s s e s . Boyle and Ham (4) and Poorman (25) s t u d i e d anaerobic treatment o f raw l e a c h a t e . Although reasonably good t r e a t - ment e f f i c i e n c i e s were obta i n e d , h i g h r e s i d u a l BOD,, values (165 to 3000 mg/L) i n d i c a t e d f u r t h e r e f f l u e n t treatment was necessary to meet a p p r o p r i a t e d i s c h a r g e l e v e l s . P h y s i c a l - c h e m i c a l treatment schemes have a l r e a d y been d i s c u s s e d i n the p r e v i o u s s e c t i o n . These do not appear to be a v i a b l e a l t e r n a t i v e f o r t r e a t i n g raw l e a c h a t e , because o f poor oxygen demanding matter removal. Although s o l u b l e o r g a n i c s can be removed by a c t i v a t e d carbon a b s o r p t i o n (9, 16, 18), c o s t e f f e c t i v e n e s s would probably r u l e t h i s process out. Boyle and Ham (4) and Temoin (31) looked a t combined treatment of l e a c h a t e with domestic sewage. Boyle and Ham found t h a t l e a c h a t e a d d i t i o n s o f a t l e a s t 5 p e r c e n t by volume (leachate COD = 10000 mg/L) c o u l d be added to an extended a e r a t i o n p l a n t , without s e r i o u s l y i m p a i r i n g e f f l u e n t q u a l i t y . Temoin combined leachate (BODj. = 19 330 mg/L) w i t h domestic sewage i n p r o p o r t i o n s v a r y i n g from 0 to 20 p e r c e n t o f t o t a l volume o f l e a c h a t e p l u s sewage. Very e f f e c t i v e treatment of a l l the combined wastewaters was found. 24 CHAPTER 3 EXPERIMENTAL SYSTEM AND METHODS 3 - 1 Leachate Source and C h a r a c t e r i s t i c s The l e a c h a t e used i n t h i s study was generated from f i v e o f s i x t e e n s i m u l a t e d l a n d f i l l s or " l y s i m e t e r s " at the U n i v e r s i t y of B r i t i s h Columbia. These l y s i m e t e r s are p a r t of a long-term r e s e a r c h program to i n v e s t i g a t e the produc- t i o n and composition o f l e a c h a t e with time, p r e c i p i t a t i o n , cover m a t e r i a l , r e c y c l i n g o f l e a c h a t e and oth e r parameters. T h i s program was i n i t i a t e d i n 19 71 by Dr. R.D. Cameron of the Department o f C i v i l E n g i n e e r i n g . At the end of January \. <• 1979, w a t e r i n g o f the l y s i m e t e r tanks was d i s c o n t i n u e d . The f i v e tanks (tanks H, R, T, W, and X) producing the h i g h e s t s t r e n g t h l e a c h a t e s were watered f o r 2% weeks i n June o f 19 79 to generate enough l e a c h a t e f o r t h i s i n v e s t i g a t i o n . The w a t e r i n g r a t e o f 5.65 Imperial g a l l o n s (25.7 l i t r e s ) twice a week was e q u i v a l e n t to 90 inches (2 30 mm) of p r e c i - p i t a t i o n per yea r . Leachate was c o l l e c t e d twice a week and s t o r e d i n 20 l i t r e p o l y e t h y l e n e c o n t a i n e r s a t 4°C to r e t a r d b i o l o g i c a l a c t i v i t y . When 450 l i t r e s of l e a c h a t e were c o l l e c t e d , a l l o f the le a c h a t e was combined, w e l l mixed and r e - s t o r e d at 4°C i n order t o have a c o n s i s t e n t wastewater to use through- out the study p e r i o d . The c h a r a c t e r i s t i c s of t h i s l e a c h a t e are shown i n Table 3. 25 TABLE 3 LEACHATE CHARACTERISTICS PARAMETER CONCENTRATION* PH 5-4 BOD 5 8090 COD 13000 TSS 460 TVSS 280 TS 6910 TVS 3680 A c i d i t y as CaC0 3 (pH = 8.3) 2060 A l k a l i n i t y as CaC0 3 (pH = 3.7) 3160 Carbon - TC 3820 - TOC 3800 N i t r o g e n as N - TKN 172 - NH 3 130 - N0 2-N0 3 <0.05 Phosphorus - t o t a l 5.3 Cadmium 0.22 Calci'um 495 Chromium 0.08 Iron 955 Lead 0.03 Magnesium 39 .2 Manganese 9.46 N i c k e l 0.083 Zinc 27.0 * A l l u n i t s i n mg/L, except pH. 26 3 - 2 B i o l o g i c a l Treatment System 3 - 2.1 The B i o l o g i c a l Reactors Bench-scale, d a i l y f i l l - a n d - d r a w (or semi-continuous) r e a c t o r s were used i n the f i r s t stage treatment o f the l e a - chate. These r e a c t o r s were employed t o simulate a f u l l - s c a l e , p l u g - f l o w , a c t i v a t e d sludge p r o c e s s . The reasons f o r u s i n g t h i s type o f system are many. Some of these f a c t o r s are: (i) t here are fewer o p e r a t i o n a l problems w i t h a f i l l - a n d - draw system than with a continuous flow system. For example, pumps and timers can m a l f u n c t i o n and f l u i d l i n e s can c l o g up, ( i i ) the apparatus was a v a i l a b l e s i n c e p r e v i o u s l e a c h a t e r e s e a r c h had been c a r r i e d out a t the U n i v e r s i t y o f B r i t i s h Columbia u s i n g t h i s equipment, and ( i i i ) u s i n g t h i s system allows f o r the t y i n g i n of t h i s i n v e s t i g a t i o n to p r e v i o u s r e s e a r c h performed a t the U n i v e r s i t y o f B r i t i s h Columbia. 3 - 2.2 The Experimental Apparatus Nine, 10 l i t r e g l a s s j a r s w i t h t h e i r bottoms removed, were used as r e a c t o r s . Rubber stopp e r s , w i t h coarse bubble g l a s s d i f f u s e r stones f i t t e d through them, were p l a c e d i n the necks of the j a r s . O i l - f r e e a i r was s u p p l i e d t o the r e a c t o r s by the l a b o r a t o r y compressed a i r system. A c o n s t a n t a i r flow was maintained with an a i r r e g u l a t o r on the a i r supply l i n e . S ince one a i r supply l i n e s erved f o u r o r f i v e 27 r e a c t o r s , a: v uniform r a t e o f a i r to each r e a c t o r was ensured by a d j u s t a b l e screw clamps on the a i r l i n e to each i n d i v i d u a l u n i t . Mechanical, s u r f a c e , c one-drive s t i r r e r s produced complete mixing and uniform d i s t r i b u t i o n of food and micro- organisms w i t h i n the r e a c t o r s and helped t o reduce foaming. A schematic diagram o f a t y p i c a l r e a c t o r i s shown i n F i g u r e 1. 3 - 2.3 Operation of the Reactors (a) O p e r a t i o n a l Parameters The c o n t r o l parameters i n t h i s i n v e s t i g a t i o n were mean c e l l r e t e n t i o n time (MCRT) or sludge age (© c) and temperature (T). The sludge ages i n v e s t i g a t e d were 20, 15, 10 and 5 days. This study o f sludge ages was done a t ambient a i r temperatures of 19° to 24° (room temperature), 15°, 10°, and 5°C. These r e a c t o r s had a n u t r i e n t l o a d i n g r a t e o f BOD<.:N:P of 100:3.2:1.1. In a d d i t i o n t o these u n i t s , a c o n t r o l u n i t a t room temperature w i t h a sludge age o f 20 days and the con- v e n t i o n a l B0D5:N:P l o a d i n g r a t e o f 100:5:1 was operated. The parameters monitored i n c l u d e d : pH, COD, TSS, TVSS, TS, and TVS of the mixed l i q u o r ; pH, BOD 5, COD, TSS, TVSS, TS, TVS, a c i d i t y , a l k a l i n i t y , carbon (TC and TOC), n i t r o g e n (TKN, NH^, and NOj.-NO^) , t o t a l phosphorus, and a number o f metals (Cd, Ca, Cr, Fe, Pb, Mg, Mn, N i , and Zn) i n e f f l u e n t s f i l t e r e d through Whatman No. 4 f i l t e r paper. I n i t i a l l y S V I 1 s were a l s o monitored. T h i s was abandoned s i n c e the r e s u l t s were not meaningful. They ranged from 25 t o 28 volumetric grodua tion porous glass air diffuser flexible plastic tubing o i I - free air electric motor driven st i rrer rubber stopper adjustable screw clamp to other reactors FIGURE I T Y P I C A L LABORATORY REACTOR 29 55; the lowest SVI's corresponded to the worst s e t t l i n g s ludges. These values were low s i n c e much of the sus- pended s o l i d s remained suspended. BOD,, t e s t i n g on the mixed l i q u o r s was not done. Pre- vious r e s e a r c h (14, 33, 34) had shown t h a t apparent b i o l o - g i c a l i n h i b i t i o n (probably due to high metal c o n c e n t r a t i o n s ) r e s u l t e d i n h i g h l y v a r i a b l e mixed l i q u o r BOD,, t e s t v a l u e s . (The BOD,, t e s t s of t h e i r e f f l u e n t s showed no s i g n of i n h i b i - t i o n over a wide range of d i l u t i o n s . ) A l l t e s t s were performed a c c o r d i n g to Standard Methods (1). The Wet Ash d i g e s t i o n procedure f o r metals a n a l y s i s was taken from Methods f o r Chemical A n a l y s i s o f Water and Wastes 01:3). The l a b o r a t o r y instruments used f o r a n a l y s i s were: i) F i s h e r Accumet Model 210 pH Meter f o r pH determina- t i o n s , i i ) Yellow Springs Instrument Co., Inc., YSI Model 54 Oxygen Meter f o r BOD^ d e t e r m i n a t i o n s , i i i ) S a r t o r i u s Model 2442 balance f o r s o l i d s d e t e r m i n a t i o n s , iv) Technicon^Auto.'. A n a l y z e r I I f o r NO^NO^ de t e r m i n a t i o n s , v) Bausch and Lomb S p e c t r o n i c 88 f o r t o t a l phosphorus d e t e r m i n a t i o n s , v i ) Perkin-Elmer 703 Atomic A b s o r p t i o n Spectrophotometer f o r metals a n a l y s i s , and v i i ) J a r r e l l Ash 810 Atomic A b s o r p t i o n Spectrophotometer f o r metal a n a l y s i s when hig h s e n s i t i v i t y was r e q u i r e d . 30 (b) A c c l i m a t i o n The b a c t e r i a l seed used i n t h i s i n v e s t i g a t i o n was a c t i v a t e d sludge from the Mamquam sewage treatment p l a n t i n Squamish, B.C. T h i s had a l s o been the source o f seed f o r s e v e r a l p r e v i o u s s t u d i e s . The MLVSS of the seed was approximately 13000 mg/L, much h i g h e r than the expected MLVSS of the experimental r e a c t o r s . I t was f e l t t h a t by d i l u t i n g the seed, the r e a c t o r s would a c c l i m a t e and reach steady s t a t e c o n d i t i o n s f a s t e r . T herefore, the r e a c t o r s were s t a r t e d up wit h about 2.5 l i t r e s of seed and 2.5 l i t r e s o f d i s t i l l e d water. The r e a c t o r s were then a e r a t e d and s t i r r e d o v e r n i g h t . Over the next f i v e days, the amount of l e a c h a t e feed was g r a d u a l l y i n c r e a s e d d a i l y (with the e q u i v a l e n t volume of mixed l i q u o r withdrawn j u s t b e f o r e feeding) u n t i l the volume added c o r r e - sponded to the sludge age of each u n i t . A r e g u l a r o p e r a t i n g procedure ( d e s c r i b e d i n the next s e c t i o n ) was then f o l l o w e d f o r 24 days b e f o r e t e s t i n g was s t a r t e d . T h i s was to a l l o w the microorganisms to become a c c l i m a t e d and the MLVSS to s t a b i l i z e . I n i t i a l l y , nine r e a c t o r u n i t s were s t a r t e d up; f i v e a t room temperature and f o u r a t 15°C (as d e s c r i b e d i n 3 - 3.1 ( a ) ) . When t e s t i n g a t these temperatures was > complete, the room temperature u n i t s were shut down and the c o l d room tem- pe r a t u r e g r a d u a l l y dropped to 10°C over t h r e e days. The u n i t s were then a c c l i m a t e d to the temperature f o r 10 days. 31 By the end of t h i s p e r i o d , steady s t a t e c o n d i t i o n s were reached. COD and TVSS of the mixed l i q u o r s and e f f l u e n t s were c o n t i n u a l l y monitored. " S t a b i l i z e d " COD and TVSS values were used as an i n d i c a t o r of steady s t a t e c o n d i t i o n s . When o p e r a t i o n at 10°C was complete, the same proce- dure was used f o r the 5°C run. (c) D a i l y O p e r a t i n g Procedure A f t e r the i n i t i a l 5-day s t a r t up p e r i o d , a r e g u l a r d a i l y o p e r a t i n g procedure was f o l l o w e d . Thi s procedure con- s i s t e d o f : i ) Take l e a c h a t e out of the 4°C c o l d room and l e a v e at room temperature f o r up to an hour b e f o r e f e e d i n g the r e a c t o r s . (The time i n t e r v a l depended on what tempera- t u r e the r e a c t o r s were a t . T h i s was so t h a t the micro- organisms i n the mixed l i q u o r would not r e c e i v e a tem- p e r a t u r e shock.) i i ) Scrape r e a c t o r w a l l and s t i r r i n g bar to prevent s i g n i - f i c a n t l o s s of s o l i d s from the mixed l i q u o r , i i i ) Turn o f f mixers and a i r supply. Top r e a c t o r s o f f to 5.0 L with d i s t i l l e d water to r e p l a c e e v a p o r a t i o n l o s s . Turn mixers and a i r back on. iv) Withdraw the a p p r o p r i a t e volume of mixed l i q u o r from each u n i t . Allow to s e t t l e f o r about h a l f an hour and then f i l t e r through Whatman No. 4 f i l t e r paper. v) P i p e t a p p r o p r i a t e volume of n u t r i e n t feed ( d i l u t e d (NH„) oHP0„ and NH.C1) to each u n i t . 32 vi ) Add the a p p r o p r i a t e amount of l e a c h a t e to each r e a c t o r (250, 333, 500 and 1000 ml to the 20, 15, 10, and 5- day sludge age un i t s , r e s p e c t i v e l y ) . When t e s t i n g was r e q u i r e d , some o f the mixed l i q u o r from step (iv) was used. Any f i l t e r e d e f f l u e n t not used i n t e s t i n g was;stored at 4°C f o r the lime-magnesium p o l i s h i n g phase. The frequency of t e s t i n g was approximately twice a week f o r pH, BOD,., COD, TSS, TVSS, TS, and TVS. The a n a l y s i s f o r the o t h e r monitored parameters was done at the end o f opera- t i o n o f the r e a c t o r s at each temperature. 3 - 3 Lime-Magnesium Treatment System The t e s t i n g procedure f o l l o w e d was l a r g e l y adopted from the methods developed by MacLean (20). He used Rush's (27) re s e a r c h as a b a s i s and i n v e s t i g a t e d the time and mixing speed r e q u i r e d f o r pH s t a b i l i z a t i o n , r a p i d mixing, f l o c c u l a - t i o n and s e t t l i n g . A l s o examined were the methods and dosages of magnesium and lime a d d i t i o n . The volumes of e f f l u e n t c o l l e c t e d from the b i o l o g i c a l r e a c t o r s were l i m i t e d . I t was f e l t t h a t r a t h e r than attempt to p o l i s h each e f f l u e n t , a much more comprehensive study c o u l d be done by combining s e v e r a l e f f l u e n t s . Hence, the f i l t e r e d e f f l u e n t s from a l l the 20, 15 and 10-day r e a c t o r s were combined t o form SAMPLE 1 (low strength) and a l l the 5-day r e a c t o r e f f l u e n t s formed SAMPLE 2 (high s t r e n g t h ) . A l l j a r t e s t i n g was done a t room temperature on a Phipps and B i r d Laboratory S t i r r e r . 33 Lime (Ca(0H)2) was added i n the powdered form. T h i s procedure was adopted because MacLean (20) found t h a t dry- reagent grade Ca(0H) 2 gave b e t t e r r e p r o d u c i b i l i t y than a lime s l u r r y . Presumably, t h i s i s due to s l u r r y s e t t l i n g . The lime dosages used were such as to r a i s e the sample pH to 10.0, 10.7, and 11.4. 3 ++ Magnesium was added as a 10 mg/L Mg s o l u t i o n , pre- pared by d i s s o l v i n g 1.01 grams of reagent grade MgSO^-7H2P i n 100 ml o f d i s t i l l e d water. MacLean (20) found b e t t e r removal was o b t a i n e d when c o a g u l a t i o n was performed u s i n g M g + + than Mg(0H) 2. T h i s f o l l o w s the g e n e r a l l y accepted theory t h a t the magnesium must be added i n the i o n i c form so t h a t i t p r e c i p i t a t e s " i n - s i t u " , f o r optimum removal. The Mg + + dosages used were 0, 10, 20, 35, and 50 mg/L. The lime-magnesium c o a g u l a t i o n t e s t sequence used con- s i s t e d o f the f o l l o w i n g procedure: i) For each run, a s e t o f 6 , 3-1.0 l i t r e samples were measured i n t o 1 l i t r e beakers, u s i n g a 1 l i t r e g r a- duated c y l i n d e r . One o f the samples was used to c a l c u l a t e the Ca(OH) 2 dosage. The sample was mixed a t 10 0 rpm and the pH was c o n s t a n t l y monitored to a pH of 10.0, 10.7, o r 11.4. The lime requirement was c a l c u l a t e d and f i v e such doses were measured out. i i ) 0.0, 1.0, 2.0, 3.5, and 5.0 ml of the M g + + s o l u t i o n were p i p e t t e d i n t o the remaining f i v e samples. These a d d i t i o n s corresponded t o 0, 10, 20, 35 and 50 mg/L Mĝ *~, r e s p e c t i v e l y . The samples were s t i r r e d f o r 1 34 minute at 100 rpm to d i s p e r s e the Mg i o n s , i i i ) The lime a d d i t i o n s were made and the samples were g i v e n a 15 minute r a p i d mix a t 100 rpm f o r pH s t a b i l i z a t i o n , i v ) The samples were gi v e n a 10 minute f l o c c u l a t i o n p e r i o d a t 15 to 20 rpm. v) The samples were given a 30 minute s e t t l i n g p e r i o d at 0 rpm. A f t e r s e t t l i n g , the f o l l o w i n g analyses were done on the supernatants: pH, BOD 5, COD, TSS, TVSS, t o t a l phosphorus, and a number of metals (Cd, Ca, Cr, Fe, Mg, Mn, N i , and Zn). The a n a l y t i c a l procedures f o r these analyses are as d e s c r i b e d p r e v i o u s l y . Lead (Pb) was not i n c l u d e d s i n c e the Pb concen- t r a t i o n s o f a l l the f i r s t stage e f f l u e n t s were a l r e a d y below the minimum d e t e c t i o n l e v e l . Due to the nature o f the j a r t e s t procedure, l e s s than 1 l i t r e o f each supernatant was a v a i l a b l e f o r t e s t i n g . T h i s l i m i t e d the number o f analyses which c o u l d be performed. Hence, o n l y the parameters which were c o n s i d e r e d e s s e n t i a l were determined. Lack of sample p r o h i b i t e d d e terminations of a l k a l i n i t y , TS, TVS, carbon and n i t r o g e n (which were per- formed i n the a e r o b i c b i o l o g i c a l phase). 35 CHAPTER 4 RESULTS AND DISCUSSION 4 - 1 A c t i v a t e d Sludge Treatment Phase 4 - 1.1 Mixed L i q u o r C h a r a c t e r i s t i c s and K i n e t i c s The k i n e t i c c o e f f i c i e n t s k, K g, Y, and b, as d e f i n e d i n Appendix A, are f i x e d f o r a s p e c i f i e d waste b i o l o g i c a l com- munity, and a p a r t i c u l a r s e t of environmental c o n d i t i o n s . The determinations of the k i n e t i c c o e f f i c i e n t s and minimum sludge ages are shown i n Appendix A. For comparison, c o e f - f i c i e n t s from p r e v i o u s i n v e s t i g a t i o n s are i n c l u d e d w i t h the values from t h i s study i n Table 4. ^The c a l c u l a t e d minimum sludge ages (the mean c e l l r e s i d e n c e time a t which r e a c t o r f a i l u r e o c c u r s , due to the biomass b e i n g removed./fas t e r : than i t can reproduce) were 1.8, 1.8, 4.0, and 5.4 f o r room temperature, 15°, 10°, and 5°C, r e s p e c t i v e l y . The above temperatures are ambient a i r temperatures. Room temperatures ranged from 19° to 25°C. The mixed l i q u o r . temperatures were from 2° to 5°C f-lower than the ambient a i r temperatures. The h i g h e r temperatures had the g r e a t e s t d i f - ferences between the l i q u i d and a i r temperatures. The reason f o r t h i s temperature d i f f e r e n c e i s the compressed a i r used to pr o v i d e oxygen to the r e a c t o r s . The a i r was c o l d and i t co o l e d the mixed l i q u o r s , thus more than compensating f o r the heat of r e s p i r a t i o n . TABLE 4 KINETIC COEFFICIENTS OF THIS AND PREVIOUS INVESTIGATIONS KINETIC COEFFICIENTS INVESTIGATIVE .?'AUTHORS LEACHATE COD (mg/L) BASIS FOR KINETIC COEFFICIENTS k (days "*") K s: (mg/L) Y b (days "*") T y p i c a l A c t i v a t e d Sludge Process (22) BOD,. 5.0 60 : 0.6 0.06 Cook and Foree (9) 15800 COD 0.60 175 - 0.4 0.05 P a l i t and Qasim (24) 365 COD 1.8 182 ' 0.59 0.115 Ul o t h (33) 48000 BOD 5 0.75 - 21375. 0. 332 0.0025 Z a p f - G i l j e (34) 19250 s o l u b l e BOD.. 0.74 19.6 0.374 0.015 Th i s I n v e s t i g a t i o n a t Room Temp. 13000 s o l u b l e BOD,. 1.16 81. 8 0.49 0 .009 This I n v e s t i g a t i o n a t 15°C 13000 s o l u b l e BODr 1.12 63.8 0.51 0.018 This I n v e s t i g a t i o n a t 10°C 13000 s o l u b l e BODr b 0.51 34.6 0.51 0.006 This I n v e s t i g a t i o n a t 5°C 13000 s o l u b l e BODr- 0.35 17.0 0.55 0.002 Note: a l l temperatures are room temperature unless s t a t e d otherwise. 3 7 The values f o r maximum r a t e o f s u b s t r a t e u t i l i z a t i o n per u n i t weight of microorganisms, k, are lower than t h a t i n a t y p i c a l a c t i v a t e d sludge p r o c e s s . T h i s i s probably due, i n p a r t , to h i g h metal c o n c e n t r a t i o n s c a u s i n g b i o l o g i - c a l i n h i b i t i o n . The value o f k a l s o decreased w i t h d e c r e a s i n g temperature. T h i s was expected, s i n c e b i o l o g i c a l r e a c t i o n r a t e s slow down as temperature i s lowered. The s u b s t r a t e c o n c e n t r a t i o n when the r a t e of s u b s t r a t e u t i l i z a t i o n per u n i t weight o f c e l l s i s on e - h a l f the maximum, K g, a l s o decreased w i t h d e c r e a s i n g temperature. T h i s i s due to k d e c r e a s i n g w i t h temperature. The growth y i e l d c o e f f i c i e n t , Y, i n c r e a s e d w i t h decreas- i n g temperature. T h i s i s because a t lower temperatures, h i g h e r MLVSS's were maintained (with no s o l i d s r e c y c l e ) and l e s s s u b s t r a t e was u t i l i z e d . T h i s c o u l d be due, i n p a r t , t o psychro- p h i l i c organisms becoming more dominant as temperature de- creased. Table 4 a l s o i n d i c a t e s Y i s dependent on the s t r e n g t h of the le a c h a t e feed. The endogenous decay c o e f f i c i e n t s , b, are q u i t e low. Th i s i s the case f o r most h i g h s t r e n g t h l e a c h a t e s s i n c e almost a l l of the c e l l s are i n the log-growth phase (due to the l a r g e amount o f o r g a n i c s a v a i l a b l e ) . Thus, t h e r e i s no heed f o r a u t o - o x i d a t i o n to occur. Mixed l i q u o r pH, COD, and s o l i d s were monitored about twice a week throughout the i n v e s t i g a t i o n . The r e s u l t s are presented i n Table 5 . No mixed l i q u o r BODj. analyses were TABLE 5 MIXED LIQUOR CHARACTERISTICS REACTOR DESCRIPTION PH COD (mg/L) TSS (mg/L) TVSS (mg/L) TS (mg/L) TVS (mg/L) F/M (days - 1) T(°C) 9 c(days) Room Temp. 20* 8.3 4700 5940 3630 7050 3620 0.111 20 8.6 4480 5980 3490 6660 3400 0.116 15 8.6 4730 5820 3470 6560 3390 0.155 10 8.6 5030 6240 3650 6960 3600 0.222 5 8.5 5810 6540 4000 7420 3930 0.405 15 20 8.5 4900 6050 3690 6610 3640 0.110 15 8.5 5000 5750 3430 6710 3550 0.157 10 8.5 5200 5940 3520 6990 3840 0.2 30 5 8.4 6200 6250 3790 7560 4190 0.427 10 20 8.6 5380 6070 3810 7010 4040 0.106 15 8.7 6050 6530 3860 7360 4100 0.140 10 8.7 6540 6960 4220 8300 4800 0.192 5 . 8.5 6880 6300 4040 7050 4450 0.400 5 20 8.5 6310 6580 4070 7420 4300 0.099 15 8.4 6590 6820 4350 7670 4490 0.124 10 8.4 10460 7300 4790 7970 4770 0.169 5 8.3 6710 6240 4320 7710 4910 0.375 * reactor nutrient loading B0D5:N:P = 100:5:1, a l l others are 100:3.2:1 Note: the figures presented are mean values obtained from 2 to 4 analyses. As a typical example of the ranges obtained, the ranges of the 10-day, 15°C reactor were: pH = 8.4 to 8.5, COD=4840 to 5470 mg/L, TSS = 5710 to 6270 mg/L, TVSS = 3200 to 3770 mg/L, TS = 6740 to 7310 mg/L, and TVS = 3390 to 3940 mg/L. 39 performed s i n c e p r e v i o u s i n v e s t i g a t i o n s (14, 33, 34) have shown t h a t b i o l o g i c a l i n h i b i t i o n made ac c u r a t e d e t e r m i n a t i o n of mixed l i q u o r BODj. i m p o s s i b l e . In g e n e r a l , a l l s o l i d s l e v e l s i n c r e a s e d w i t h d e c r e a s i n g sludge age and/or temperature. The TVSS/TSS r a t i o i n c r e a s e d from 0.59 to 0.65 as the temperature decreased from room temperature to 5°C. The mixed l i q u o r v o l a t i l e suspended s o l i d s (MLVSS) are p l o t t e d i n F i g u r e 2. As can be seen i n F i g u r e 2, a t the lowest sludge age and lower temperatures, the s o l i d s l e v e l s s t a r t e d to drop. The most dramatic change was at 5 days and 5°C. T h i s i s e x p l a i n e d by the f a c t t h a t the r e a c t o r was on the verge o f "washout" c o n d i t i o n s . As p r e - v i o u s l y s t a t e d , the minimum sludge age a t 5°C was c a l c u l a t e d to be 5.4 days. C u l t u r a l a c c l i m a t i o n o f the sewage sludge took about 4 weeks. For the f i r s t 2 weeks, severe foaming problems o f a l l the mixed l i q u o r s were encountered. A f t e r t h i s time, f o r the d u r a t i o n of t h i s study, foaming problems p e r s i s t e d o n l y i n the 5-day sludge age r e a c t o r s . Temperature a c c l i m a t i o n , as measured by mixed l i q u o r COD and MLVSS, was complete w i t h i n two weeks. T h i s confirms the f i n d i n g s of Graham (14), Z a p f - G i l j e (34), and B e n e d i c t and C a r l s o n (2). B e n e d i c t and C a r l s o n used endogenous r e s p i - r a t i o n r a t e per gram o f biomass s o l i d s as the i n d i c a t o r o f steady s t a t e c o n d i t i o n s . The s e t t i e a b i l i t y o f the mixed l i q u o r s was poor. Set- t l i n g problems a l s o o c c u r r e d i n the i n v e s t i g a t i o n s by Graham (14) and Z a p f - G i l j e (34). Z a p f - G i l j e used documentation from 5000 3 0 0 0 1 — J : " ' ' 5 10 15 2 0 S L U D G E A G E , 6 C (days) o FIGURE 2 MLVSS VERSUS SLUDGE AGE 41 l i t e r a t u r e t o a r g u e t h a t t h e s l u d g e b u l k i n g i s a n e f f e c t o f t h e f i l l - a n d - d r a w p r o c e s s . H e n c e , i n o r d e r t o o b t a i n an e f f l u e n t c o m p a r a b l e t o t h a t o f a c o n t i n u o u s f l o w r e a c t o r , Graham a n d Z a p f - G i l j e u s e d g r a v i t y f i l t r a t i o n t h r o u g h Whatman No. 4 f i l t e r p a p e r . T h i s a u t h o r f o l l o w e d t h e same p r o c e d u r e . The Whatman No. 4 f i l t e r p a p e r h a s a h i g h f i l t e r s p e e d a n d r e t a i n s c o a r s e a n d g e l a t i n o u s p r e c i p i t a t e s . 4 - 1.2 R e m o v a l a n d O r g a n i c M a t e r i a l a n d S o l i d s T a b l e 6 shows t h e r e m o v a l e f f i c i e n c i e s o f BOD^, COD, an d s o l i d m a t e r i a l f r o m t h i s s t u d y . A l l r e a c t o r s r e d u c e d BOD^ l e v e l s b y a t l e a s t 9 9.4 p e r c e n t , e x c e p t t h e 9 c = 5-day r e a c t o r s a t 5° a n d 10°C. A l t h o u g h t h e i r B ODY ' S w e r e c o n s i d e r a b l y h i g h e r , t h e minimum p e r c e n t a g e remo- v a l was s t i l l 9 7.7 p e r c e n t . COD r e m o v a l r a t e s r a n g e d f r o m 9 8.9 t o 9 3.2 p e r c e n t . As w i t h t h e BOD 5 l e v e l s , t h e COD l e v e l s o f t h e 0 c = 5 d a y s r e a c t o r s w e r e s i g n i f i c a n t l y h i g h e r t h a n t h e r e s t . Of t h e s o l i d s , much h i g h e r r e m o v a l r a t e s o f s u s p e n d e d s o l i d s , r a t h e r t h a n t o t a l s o l i d s , o c c u r r e d . T h i s was p r o b a b l y l a r g e l y due t o s u s p e n d e d s o l i d s b e i n g f i l t e r e d o u t by t h e Whatman No. 4 f i l t e r p a p e r . Once a g a i n , t h e 5-day s l u d g e age r e a c t o r s , a t t h e two l o w e s t t e m p e r a t u r e s , e x h i b i t e d s u b s t a n t i a l l y l o w e r r e m o v a l r a t e s . As e x p e c t e d , t h e g e n e r a l t r e n d was d e c r e a s i n g r e m o v a l r a t e s o f o r g a n i c s a n d s o l i d s w i t h d e c r e a s i n g s l u d g e age a n d / o r t e m p e r a t u r e . H owever, o f t h e c o n d i t i o n s i n v e s t i g a t e d ( s l u d g e TABLE 6 ORGANIC MATERIAL (IN TERMS OF BOD,- AND COD) AND SOLID MATERIAL CONCENTRATION (IN EFFLUENTS) AND REMOVALS REACTOR BOD.. COD TSS TVSS TS TVS DESCRIPTION J T 6 c mg/L % mg/L % mg/L % mg/L % mg/L % mg/L % <°C) (days) REMOVAL REMOVAL REMOVAL REMOVAL REMOVAL REMOVAL Leacha te Feed 8090 13000 460 280 6910 3680 RT 20* 7 >99.9 148 98.9 4 99.1 4 98.6 1660 76.0 420 88.6 20 9 99.9 173 98.7 8 98.3 5 98.2 1080 84.4 280 92.4 15 11 99 .9 200 98.5 10 97.8 6 97.9 1060 84. 7 290 92.1 10 25 99.7 209 98.4 11 97.6 6 97.9 1040 84.9 290 92.1 5 44 99 .5 365 97.2 22 9 5.2 11 96.1 1340 80.6 490 86.7 15 20 7 >99 .9 216 98.3 7 98.5 7 97.5 1050 84.8 290 92.1 15 9 99.9 252 98.1 16 96.5 9 96.8 1150 83.4 320 91. 3 10 20 99.8 271 97.9 18 96.1 8 97.1 12 30 82.2 330 91.0 5 51 99.4 462 96.4 23 95.0 14 95.0 1340 80.6 480 87.0 10 20 9 99.9 201 98.5 9 98.0 6 97.9 1080 84.4 300 91. 8 15 16 99. 8 215 98.3 6 98.7 5 98.5 1080 84.4 310 91.6 10 17 99.8 308 97.6 8 98.3 5 98.5 1100 84.1 350 9 0.5 5 112 98. 6 633 95.1 55 88.0 36 87.1 1480 78.6 660 82.1 5 20 14 99.8 270 97.9 14 97.0 8 97.1 1140 83.5 400 89.1 15 20 99.8 317 97.6 8 98.3 5 98.5 1150 83.4 420 88.6 10 42 99.5 425 96.7 23 95.0 10 96.4 1240 82.1 500 86.4 5 188 97.7 888 93.2 148 67.8 72 74.3 1780 74.2 840 77.2 * reactor nutrient loading BOD5:N:P = 100:5:1, a l l others are 100:3.2:1.1 Note: the concentration figures presented are the mean concentrations obtained from 2 to 4 analyses. As a typical example of the ranges obtained, the ranges of the 10-day, 15°C reactor were: BOD5 = 15 to 24 mg/L, COD = 245 to 310 mg/L, TSS = 13 to 22 mg/L, TVSS = 4 to 10 mg/L, TS = 1090 to 1440 mg/L, and TVS = 286 to 362 mg/L. 43 ages from 5 t o 20 days and temperatures o f 5 WC to room tem- perature) the o v e r a l l removal r a t e s were very s i m i l a r ; the exceptions o c c u r r e d f o r the lowest sludge age r e a c t o r s at 5° and 10°C. Even though these two r e a c t o r s were approaching washout c o n d i t i o n s , they performed s u r p r i s i n g l y w e l l . They . s t i l l had an average BOD^ removal o f 9 8 p e r c e n t , COD removal of 94 pe r c e n t , and s o l i d s removal of about 75 p e r c e n t . The most s t r i n g e n t o f the B r i t i s h Columbia p o l l u t i o n c o n t r o l o b j e c t i v e s (10) (Level AA, r e c e i v i n g waters are streams, r i v e r s , and e s t u a r i e s w i t h d i l u t i o n r a t i o s from 20 to 200:1) allows e f f l u e n t BODr = 30 mg/L and SS = 40 mg/L. 3 A l l e f f l u e n t s , except from the two r e a c t o r s near washout, met or were c l o s e to these g u i d e l i n e s . The Whatman No. 4 f i l t e r paper used t o g r a v i t y f i l t e r e f f l u e n t s r e t a i n s coarse and g e l a t i n o u s p r e c i p i t a t e s . As sludge b u i l d s up on the f i l t e r paper, more and more s o l i d s would be f i l t e r e d out due to s t r a i n i n g , impingement on sludge p a r t i c l e s , and f l o c c u l a t i o n . Some o f the these s o l i d s f i l - t e r e d out would probably not s e t t l e out i n a c l a r i f i e r under f i e l d c o n d i t i o n s i n a continuous flow a c t i v a t e d sludge system. T h e r e f o r e , i n order t o o b t a i n e f f l u e n t of a q u a l i t y as comparable as p o s s i b l e t o t h a t which would be o b t a i n e d under f i e l d c o n d i t i o n s , the f i l t e r paper was changed f r e q u e n t l y . The only o t h e r a l t e r n a t i v e f o r t h i s poor s e t t l i n g mixed l i q u o r was to al l o w s e v e r a l hours of s e t t l i n g time. This was not f e a s i b l e due to time c o n s t r a i n t s and the po'ssible development 'of anaerobic " c o n d i t i o n s . 44 As a check t o a s c e r t a i n t h a t f i l t r a t i o n was not respon- s i b l e f o r the high removal r a t e s o b t a i n e d , COD t e s t s were run on f i l t e r e d e f f l u e n t s and e f f l u e n t s o b t a i n e d by a l l o w i n g the mixed l i q u o r s t o s e t t l e f o r 2 hours. These e f f l u e n t s were c o l l e c t e d a t the same time from the r e a c t o r s a t 5°C., ; The r e s u l t s are t a b u l a t e d i n Table 7. G e n e r a l l y , the d i f f e r e n c e s i n removal r a t e s were w i t h i n 0.5 per c e n t . The e x c e p t i o n was f o r the 5-day r e a c t o r , which had a di s c r e p a n c y o f 2.3 perc e n t . Temoin (31) and Graham (14) found s e t t l e d e f f l u e n t BOD's to be 2 to 4 times h i g h e r than f i l t e r e d e f f l u e n t BOD 5 ( f o r the r e a c t o r s which performed e f f e c t i v e l y ) . The d i f f e r e n c e s i n r e - moval r a t e s o f these f i l t e r e d and s e t t l e d BOD^'s were w i t h i n 0.2 per c e n t . In view of these minor d i f f e r e n c e s , i t i s f e l t t h a t the f i l t e r i n g procedure used i s q u i t e a c c e p t a b l e i n the context o f t h i s study. In o r d e r to determine the e f f e c t s o f the n u t r i e n t l o a d i n g l e v e l , a s u i t a b l e b a s i s o f comparison to oth e r s t u d i e s must be used. S i n c e the c h a r a c t e r i s t i c s and s t r e n g t h o f the l e a - chates and the MLVSS l e v e l s i n the pr e v i o u s l e a c h a t e treatment s t u d i e s v a r i e d g r e a t l y , the most r e l e v a n t parameter i s the food-to-microorganism (F/M) r a t i o . Table 8 pr e s e n t s a compari- son of oxygen demanding m a t e r i a l removal of a number of a e r o b i c b i o s t a b i l i z a t i o n s t u d i e s , w i t h v a r i o u s n u t r i e n t l o a d i n g s and F/M r a t i o s (at room temperature). From Table 8, i t i s d i f f i c u l t to draw c o n c l u s i o n s o f the e f f e c t on the removal o f o r g a n i c matter by the n u t r i e n t l o a d - i n g l e v e l . From the l i m i t e d data a v a i l a b l e , i t appears t h a t n u t r i e n t l o a d i n g has l i t t l e , i f any, e f f e c t on the o r g a n i c T A B L E 7 COMPARISON OF COD V A L U E S OF F I L T E R E D E F F L U E N T S AND TWO-HOUR S E T T L E D E F F L U E N T S FROM THE REACTORS AT 5°C SLUDGE COD OF E F F L U E N T S A G E , F I L T E R E D S E T T L E D FOR 2 HOURS d a y s m g / L % REMOVAL m g / L % REMOVAL 20 294 9 7 . 7 . 338 9 7 . 4 15 342 9 7 . 4 398 9 6 . 9 10 465 9 6 . 4 521 9 6 . 0 5 914 9 3 . 0 1212 9 0 . 7 TABLE 8 COMPARISON OF OXYGEN DEMANDING MATERIAL REMOVALS UNDER VARIOUS NUTRIENT LOADINGS AND F/M RATIOS INVESTIGATIVE AUTHORS NUTRIENT LOADING, BOD5:N:P F/M, kg BOD5/day kg MLVSS SLUDGE AGE, days EFFLUENT BOD,. EFFLUENT COD mg/L % REMOVAL mg/L % REMOVAL Cook and 100:3.9:0.18 0.161 10 26 99.6 360 97.6 Foree (9) 100:11:1.6 0.141 10 10 99.9 310 98.0 Uloth (33) 100:5:1.3 0.119 20 32 99.9 594 98.8 Temoin (31) 100:3.19:0.12 0.148 20 56 99 .7 569 98.1 100:3.98:0.12 0.137 20 85 99.6 1162 96.2 100:3.98:0.32 0.124 20 28 99 .9 585 98.1 100:3.19:1.11 0.117 20 14 >99.9 476 98.4 100:3.98:1.11 0.123 20 26 99 .9 335 98.9 100:5.03:1.11 0.119 20 44 99.8 273 99.1 Zapf-Gilje 100:5:1 0.174 20 6 >99.9 300 98.4 (34) 100:5:1 0.345 9 20 99.9 470 97.6 100:5:1 0.487 6 26 99.8 580 97.0 Graham (14) 100:5:1 0.175 25 4 >99.9 331 98.3 100:5:1 0.293 15 10 99.9 352 98.2 This Inves- 100:5:1 0.111 20 7 >99.9 148 98.9 tigation 100:3.2:1.1 0.116 20 9 99.9 173 98.7 100:3.2:1.1 0.155 15 11 99.9 200 98.5 100:3.2:1.1 0.222 10 25 99.7 209 98.4 100:3.2:1.1 0.405 5 44 99.5 365 97.2 Note: Cook and Foree's and Uloth's effluents are settled effluents. A l l others are f i l t e r e d effluents. A l l reactors were at room temperature. 47 removal e f f i c i e n c y o f the p r o c ess, except a t very low phospho- rus l e v e l s . A much more comprehensive study, c o v e r i n g a wider range of l o a d i n g s , and w i t h emphasis on the lower n u t r i e n t l o a d i n g l e v e l s i s r e q u i r e d b e f o r e more d e f i n i t i v e c o n c l u s i o n s can be made. T h i s would i n c l u d e the e f f e c t s o f n u t r i e n t l o a d i n g and the minimum l o a d i n g l e v e l b e f o r e process e f f i c i e n c y i s im- p a i r e d . A l s o , a s e r i e s of these t e s t s should be conducted a t v a r i o u s o r g a n i c l o a d i n g l e v e l s o r sludge ages t o determine i f the e f f e c t o f n u t r i e n t l o a d i n g changes as F/M changes. S h e r r a r d and Shroeder (29) and S i k e s and Nieminen (30) have found t h a t the n u t r i e n t requirements o f a f o o d - p r o c e s s i n g wastewater and a K r a f t - m i l l e f f l u e n t were a f u n c t i o n of the sludge age. 4 1.3 Removal of Metals Many d i f f e r e n t f a c t o r s a f f e c t the removal of metals i n the a c t i v a t e d sludge p r o c e s s . These may be d i v i d e d i n t o p l a n t o p e r a t i n g parameters, p h y s i c a l or chemical f a c t o r s , and b i o l o - g i c a l f a c t o r s . O perating parameters which have been shown to a f f e c t metal removal are SVI, sludge age, suspended s o l i d s r e - moval, d i s s o l v e d oxygen c o n c e n t r a t i o n , and s e t t l i n g time. Phy- s i c a l and chemical f a c t o r s a f f e c t i n g metal removal are tempera- t u r e , pH, metal i o n c o n c e n t r a t i o n , metal s o l u b i l i t y , metal valency, c o n c e n t r a t i o n o f complexing agents, and p a r t i c l e s i z e . The main b i o l o g i c a l f a c t o r i s the c o n c e n t r a t i o n of b a c t e r i a l e x t r a c e l l u l a r polymers (5). The metal removal e f f i c i e n c i e s o f the b i o l o g i c a l r e a c t o r s are presented i n Table 9. In g e n e r a l , temperature and MCRT, i n the ranges s t u d i e d , had minimal e f f e c t on the removal of metals. However, s i m i l a r to the o r g a n i c removal d i s c u s s e d TABLE 9 METAL REMOVAL EFFICIENCIES OF THE BIOLOGICAL REACTORS REACTOR DESCRIPTION PERCENT REMOVAL OF THE METAL T(°C) © c(days) Cd Ca Cr Fe Pb Mg Mn N i Zn R.T. 20* >9 8.2 66.3 91.3 >99.9 >80.0 35.8 97.3 71.1 99 .7 20 >98 .2 88.2 87.5 99.8 >80.0 48 .6 99.0 69.9 99.7 15 >98.2 91.3 86.3 >99 .9 >80 .0 52.7 99 .4 66.3 99.7 10 >98.2 92.0 82.5 >99.9 >80.0 47.3 98 . 8 59.0 99 .6 5 >98.2 93.0 81. 3 99.3 >80.0 47.1 98.0 51.8 98.8 15 20 >98.2 87.7 87.5 >99.9 >80.0 50.6 98.5 65.1 99.7 15 >9 8. 2 89.2 86.3 >99.9 >80.0 49 .4 98.3 38.6 99.2 10 >9 8.2 89.9 81.3 >99.9 >80.0 42.7 97.7 56.6 99 .4 5 >9 8.2 90.9 62.5 99.4 >80.0 41.7 96.2 51.8 98.8 10 20 >98 .2 89.6 82 .5 >99.9 >80 .0 41.4 98.5 53.0 99.4 15 >98 .2 91.1 82.5 >99.9 >80.0 45.5 98.7 48.2 99 .5 10 >98 .2 90.6 81.3 >99 .9 >80.0 41.7 98.4- 54 .2 99.4 5 73.6 88.4 77.5 97.7 >80.0 35.3 94.9 47.0 96.1 5 20 95.6 89.9 81.3 >99.9 >80.0 43.5 98.1 51.8 99 .5 15 95.6 90.8 77.5 >99.9 >80.0 43.5 98.4 53.0 99 .7 10 95.6 89.1 78.8 99 .6 >80.0 36.6 97.9 42.2 99.3 5 73.6 88.3 72.5 97.2 >80.0 32.5 93.1 27.7 96.0 * r e a c t o r n u t r i e n t l o a d i n g BOD,-:N:P = 100:5:1, a l l others are 100:3.2:1.1 49 e a r l i e r , s e v e r a l metal removals were s i g n i f i c a n t l y lower f o r the 5-day sludge age r e a c t o r s a t 10° and 5°C. These i n c l u d e d cadmium, i r o n , manganese, and z i n c . Chromium and n i c k e l con- c e n t r a t i o n s appear dependent on sludge age and temperature. The percent removals ranged from 87.5 and 69.9 at G c= 20 days and T = room temperature t o 72.5 and 2 7.7 a t 9 c = 5 days and T = 5°C f o r chromium and n i c k e l , r e s p e c t i v e l y . The e x c e l l e n t removal of most metals i s presumed to be l a r g e l y due to two mechanisms. As found by ot h e r r e s e a r c h e r s (5, -7, 9, 34), hig h m o l e c u l a r weight e x t r a c e l l u l a r polymers of the b i o f l o c p r o v i d e d many f u n c t i o n a l groupings t h a t a c ted as b i n d i n g s i t e s f o r the metals. T h i s r e s u l t e d i n metal uptake by the sludge, w i t h subsequent removal by sludge s e t t l i n g . A l s o , because of hi g h pH l e v e l s i n the mixed l i q u o r , metal hydroxide and metal carbonate p r e c i p i t a t i o n probably o c c u r r e d . Of the metals analyzed, magnesium had the lowest percentage removal. The reason f o r t h i s was t h a t the pH was not h i g h enough t o cause chemical p r e c i p i t a t i o n o f magnesium hydroxide. Table 10 prese n t s the r e s i d u a l metal c o n c e n t r a t i o n s o f the e f f l u e n t s and the s t r i c t e s t o b j e c t i v e s of the l o c a l p o l l u - t i o n c o n t r o l board (10). I f the two r e a c t o r s c l o s e to washout are not i n c l u d e d , then n e a r l y a l l o f the o b j e c t i v e s are met under n e a r l y a l l o p e r a t i n g c o n d i t i o n s . Only i r o n and magne- sium c o n c e n t r a t i o n s g r e a t l y exceed the o b j e c t i v e s ; and even then, t h i s u s u a l l y o c c u r r e d under the low sludge age and/or temperature c o n d i t i o n s . Although most i r o n removals exceeded 99.9 percent, the very high i r o n c o n c e n t r a t i o n (955 mg/L) i n TABLE 10 METAL CONCENTRATIONS OF THE AEROBICALLY BIOSTABILIZED EFFLUENTS REACTOR DESCRIPTION METAL CONCENTRATION (mg/L) T(°C) 0 c(days) Cd Ca' Cr Fe Pb Mg Mn Ni Zn Leach? it e Feed 0.22 495 0.08 955 0.03 39.2 9.46 0.083 27.0 R.T. 20* <0.004 167 0.007 0.21 <0.006 25.1 0.253 0.024 .0,07 20 <0.004 58.2 0.010 1.70 <0.006 20.1 0.096 0.025 0.09 15 <0 .004 43.0 0.011 0.75 <0.006 18 .5 0.061 0.028 0.09 10 <0.004 39.8 0.014 0.85 O.006 20.6 0 .114 0.034 0.11 5 <0.004 34.8 0.015 7.10 <0.006 20.7 0.187 0.040 0.33 15 20 <0.004 60. 7 0.010 0.47 O.006 19.3 0.140 0.029 0.09 15 <0.004 53.3 0.011 0.57 <0.006 19 .8 0.157 0.051 0.22 10 <0.004 49.9 0.015 0.87 <0.006 22.4 0.215 0.036 0.15 5 <0.004 45.2 0.030 6.07 <0.006 22. 8 0.364 0.040 0.32 10 20 <0.004 51.4 0.014 2.0 8***<0.006 22.9 0.140 0.039 0.16 15 <0.004 44. 3 0.014 0.24 <0.006 21.3 0.126 0.043 0.13 10 <0.004 46.5 0.015 0.78 <0.006 22.8 0.154 0.038 0.15 5 0.058 57.6 0.018 21.7 <0.006 25.3 0.487 0.044 1.04 5 20 0.009 49.9 0.015 0.73 <0.006 22.1 0.178 0.040 0.13 15 0.009 45.3 0.018 0.67 <0.006 22 .1 0 .153 0.039 0.09 10 0.009 54.0 0.017 3.80 <0.006 24.8 0.202 0.048 0.20 5 0.058 57.9 0.022 26.8 <0 .006 26.4 0.654 0.060 1.09 PCB** 1 0.005 0.1 0.3 0.05 0.05 0.3 0.5 * r e a c t o r n u t r i e n t l o a d i n g BOD5:N:P = 100:5:1, a l l others are 100:3.2:1.1 ** B r i t i s h Columbia P o l l u t i o n C o n t r o l O b j e c t i v e s (10), L e v e l AA O b j e c t i v e s *** sample contaminated- 51 the l e a c h a t e probably r e s u l t e d i n the hig h e f f l u e n t concen- t r a t i o n s . From the l i m i t e d data, i t appears t h a t the n u t r i e n t l o a d i n g s used made l i t t l e d i f f e r e n c e i n metal removal e f f i - v c i e n c i e s . 4 - 1.4 Removal of N u t r i e n t s The removals of the b a s i c n u t r i e n t s , n i t r o g e n and phos- phorus, are presented i n Table 11. S i n c e the g r e a t e s t concern i s the n u t r i e n t c o n c e n t r a t i o n of the i n f l u e n t l e a c h a t e feed and o f the f i n a l e f f l u e n t , the n u t r i e n t supplements added (to b r i n g the n u t r i e n t l o a d i n g to the proper l e v e l ) are not i n c o r p o r a t e d i n the c a l c u l a t i o n of the percentage removals. T h i s method o f c a l c u l a t i o n i s a l s o more c o n s e r v a t i v e ( i n terms o f percentage removals) than i f the n u t r i e n t a d d i t i o n s were i n c l u d e d . T o t a l K j e l d a h l n i t r o g e n (TKN) removals were e x c e l l e n t . Except f o r the 5°C, 5-day sludge age reactor-removals were a l l g r e a t e r than 94.8 percen t , c o r r e s p o n d i n g t o a r e s i d u a l of 8.9 mg/L. Ammonia n i t r o g e n (NH^) removals were a l s o h i g h . R e s i d u a l c o n c e n t r a t i o n s were a l l below 1.0 mg/L (the minimum d e t e c t i o n l e v e l f o r the sample s i z e used) except f o r the 5°C, 5-day r e a c t o r . The p e r c e n t removals o f TKN and NH^ f o r the low temperature, low sludge age r e a c t o r were 78.8 and 82.3 percent, r e s p e c t i v e l y . The major d i f f e r e n c e between the c o n t r o l - r e a c t o r (BOD5:N:P = 100:5:1) and the oth e r r e a c t o r s (BOD5:N:.P = 100:3.2:1.1) was the e f f l u e n t n i t r i t e - n i t r a t e n i t r o g e n TABLE 11 NITROGEN (TKN, NH^, AND NOj-NO ) AND PHOSPHORUS (TOTAL) CONCENTRATIONS (IN EFFLUENTS) AND REMOVALS BY THE BIOLOGICAL REACTORS REACTOR TKN M NH. NO~-NO-, TOTAL PHOSPHORUS DESCRIPTION 3 2 3 T e c mg/L % * * mg/L 9- * * o mg/L 9- ** o mg/L 9- * * o <°C) (days) REMOVAL REMOVAL REMOVAL REMOVAL Leacha te Feed 172 130 . • <0.05 5.3 R.T. 20* 5.4 96.9 < 1 >99.2 43 < 0 0.07 98.7 20 4.9 97.2 < 1 >99 .2 0.17 < 0 0.28 94.7 15 5.3 96.9 < 1 >99 .2 0.12 < 0 0.15 97.2 10 5 . 8 96.6 < 1 >99.2 0.07 < 0 0.13 97.5 5 6.7 96.1 < 1 >99.2 <0.05 0.68 87.2 15 20 6.0 96.5 < 1 >99.2 0.16 < 0 v - x 0.29 94.5 15 6.5 96.2 < 1 >99.2 0.18 < 0 0.24 95.5 10 7.0 95.9 < 1 >99 .2 0.06 < 0 0.15 97.2 5 7.4 95. 7 < 1 >99 .2 <0.05 . 0.61 88. 5 10 20 5.9 96.6 < 1 >99 .2 0.11 < 0 0.19 96 .4 15 6.2 96.4 < 1 >99.2 0.12 < 0 0.14 97.4 10 8.1 95.3 < 1 >99.2 0.12 < 0 0.19 96 .4 5 8.1 95.3 < 1 >99.2 0.16 < 0 1.66 68.7 5 20 7.3 95.8 < 1 >99.2 0.12 < 0 0.15 97.2 15 8.1 95.3 < 1 >99 .2 0.06 < 0 0 .19 96.4 10 8.9 94.8 < 1 >99.2 0.09 < 0 0.36 93.2 5 36.4 78. 8 23 82. 3 0.19 < 0 2.52 52.5 * r e a c t o r n u t r i e n t l o a d i n g BOD5:N:P - 100:5:1 , a l l others are 100:3.2:1.1 ** Note: the n u t r i e n t a d d i t i o n s are not i n c l u d e d i n the % removals, 7 - f s V - R F M O V A T - ELEACHATE FEED] - [EFFLUENT] ( i e . ts REMOVAL - — (-LEACHATE FEED] X 1 0 0 ° ] to 53 (NOj-NO^) c o n c e n t r a t i o n s . The c o n t r o l - r e a c t o r e f f l u e n t c o n c e n t r a t i o n , was 4 3 mg/L, whereas the c o n c e n t r a t i o n s of a l l o t h e r e f f l u e n t s were below 0.2 mg/L. T h i s i n d i c a t e s t h a t n i t r i f i c a t i o n o c c u r r e d i n the c o n t r o l - r e a c t o r and not enough excess n i t r o g e n was p r e s e n t i n the BOD^:N:P = 100:3.2:1.1 loaded r e a c t o r s f o r n i t r i f i c a t i o n t o occur. T h i s r e s u l t i s s i g n i f i c a n t . I t i s evidence t h a t a BODj.:N r a t i o of 20:1 i s 'low. With t h i s n i t r o g e n l o a d i n g l e v e l , i n a d d i t i o n to unnecessary chemical c o s t s , problems c o u l d a r i s e w i t h r i s i n g sludge i n the s e t t l i n g tank. T h i s oc- curs w h e n . n i t r i t e s and n i t r a t e s are converted to n i t r o g e n gas, which then becomes trapped i n the sludge mass. The sludge then becomes buoyant, l e a d i n g to poor s o l i d s - l i q u i d s e p a r a t i o n i n the c l a r i fiber.. The n i t r o g e n a d d i t i o n s were i n the form of NH^ (as diam- monium hydrogen phosphate and ammonium c h l o r i d e ) . E c k e n f e l d e r and O'Connor (12) s t a t e t h a t when a n u t r i t i o n a l supplement i s r e q u i r e d f o r b i o l o g i c a l p r o c e s s e s , ammonia n i t r o g e n s h o u l d be used, s i n c e i t i s r e a d i l y a s s i m i l a b l e . H a t t i n g h (15) r e p o r t s t h a t s e v e r a l i n v e s t i g a t o r s have found t h a t a l l i n o r - ganic n i t r o g e n and only a p o r t i o n of o r g a n i c n i t r o g e n i s a v a i l a b l e f o r sludge growth. The p o r t i o n o f o r g a n i c n i t r o g e n a v a i l a b l e v a r i e d w i d e l y , depending on the waste. U l o t h (33) suggested t h a t , d u r i n g h i s i n v e s t i g a t i o n , much o f the ammonia i n h i s l e a c h a t e feed may have been s t r i p p e d out o f the h i g h pH mixed l i q u o r by the vigorous a e r a t i o n . Cook and Foree (9) a l s o encountered some ammonia s t r i p p i n g d u r i n g t h e i r s t u d i e s . 54 T h e r e f o r e , i t appears t h a t although a n i t r o g e n l o a d i n g o f BOD^:N = 100:3.2 was a p p l i e d to the r e a c t o r s i n t h i s i n v e s t i g a t i o n , not a l l of the n i t r o g e n was a v a i l a b l e f o r m i c r o b i a l a s s i m i l a t i o n i f any ammonia s t r i p p i n g d i d occur. This leads to the q u e s t i o n o f " s i m i l a r i t y " o f the n u t r i e n t l o a d i n g s o f t h i s i n v e s t i g a t i o n and t h a t o f Temoin's (31) optimum of BOD5:N:P = 100:3.19:1.11. Temoin r e p o r t s t h a t h i s l e a c h a t e TKN = 616 mg/L, but does not r e c o r d what p o r t i o n of t h i s i s NH^ n i t r o g e n . Thus, although the a v a i l a b l e n i t r o - gen l o a d i n g s were probably s i m i l a r , the s i m i l a r i t y cannot be f u l l y v e r i f i e d . The removal o f phosphorus was good. E x c l u d i n g the 5-day sludge age r e a c t o r s , a l l removals were g r e a t e r than 9 3.2 percent. The 5-day r e a c t o r removals ranged from 87.2 to 52.5 p e r c e n t - p r o g r e s s i v e l y worse as the temperature decreased. As expected, the c o n t r o l r e a c t o r , which had the l e a s t phos- phorus added, demonstrated the be s t removal. Not i n c l u d i n g the two r e a c t o r s near washout, a l l r e s i d u a l phosphorus l e v e l s met the l o c a l p o l l u t i o n c o n t r o l "AA" l e v e l o b j e c t i v e (10) of 1.5 mg/L. A p o s s i b l e e x p l a n a t i o n as t o why the low BOD^:N:P l o a d - i n g o f 100:3.2:1.1 was so e f f e c t i v e i n the treatment o f the le a c h a t e c o u l d be the presence o f the actinomycete Geoder- m a t o p h i l i u s b a c t e r i a , mentioned p r e v i o u s l y . As r e p o r t e d , d u r i n g Temoin's (31) i n v e s t i g a t i o n , a t the h i g h e r phosphorus l o a d i n g o f BOD:P = 100:1.11, 9 0 percent o f the b i o l o g i c a l f l o e c o n s i s t e d o f Geodermatophilius, which had never been 55 i s o l a t e d i n a sewage treatment system b e f o r e (to t h i s author's knowledge). Although the Geodermatophilius c e l l t i s s u e com- p o s i t i o n i s probably s i m i l a r to t h a t of b a c t e r i a common to a c t i v a t e d sludge p l a n t s , the metabolism of the Geodermatophi- l i u s c o u l d be s u f f i c i e n t l y d i f f e r e n t to account f o r t h i s d i f - f e r ence i n n u t r i e n t requirements (26) . Unfortunately,/no m i c r o s c o p i c examination of the mixed l i q u o r was done i n t h i s study to c o n f i r m the presence o f the Geodermatophilius. T h i s v e r t i f i c a t i o n was not done because t h i s author d i d not l e a r n of the Geodermatophilius u n t i l a f t e r the completion of the l a b o r a t o r y p o r t i o n of t h i s study. 4 - 2 Lime-Magnesium C o a g u l a t i o n Phase The i n i t i a l pH, a c i d i t y , a l k a l i n i t y and lime dosages r e q u i r e d f o r the samples t h a t underwent the lime-magnesium process are shown i n Table 12. The lime dosages shown were determined by adding lime u n t i l the pH s t a b i l i z e d a t the de- s i r e d l e v e l . As the M g + + dose i n c r e a s e d , the f i n a l pH dropped. The drop i n pH was about 0.1 pH u n i t s a t the low lime (pH = 10.0), low magnesium (0 mg/L) dose, up to 1.0 pH u n i t s a t the high lime (pH = 11.4)> h i g h magnesium (50 mg/L) dose. T h i s i n d i c a t e s t h a t MgtOH^/ and probably o t h e r metal hydroxide p r e c i p i t a t e s , formed. The r e s u l t s o f o r g a n i c m a t e r i a l , suspended s o l i d s , and phosphorus c o n c e n t r a t i o n s and removals appear i n Table 13. A l - though the p e r c e n t removals o f BOD,- from the lower s t r e n g t h sam- p l e (SAMPLE 1) are f a i r l y h i g h ( p a r t i c u l a r l y a t the h i g h lime T A B L E 12 p H , A C I D I T Y , A L K A L I N I T Y , AND L I M E DOSAGES REQUIRED OF THE SAMPLES USED FOR L I M E - M A G N E S I U M COAGULATION PARAMETER SAMPLE 1 SAMPLE 2 pH 7 . 7 7 . 2 A c i d i t y t o pH = 8 . 3 a s C a C 0 3 (mg /L ) 16 37 A l k a l i n i t y t o pH = 3 . 7 a s C a C 0 3 (mg /L ) 384 414 C a ( O H ) 2 D o s a g e ( m g / L ) f o r pH 1 0 . 0 228 329 C a ( O H ) 2 D o s a g e (mg /L ) f o r pH 1 0 . 7 307 408 C a ( O H ) 2 D o s a g e (mg /L ) f o r pH 1 1 . 4 4 3 3 549 TABLE 13 EFFLUENT ORGANIC MATERIAL (IN TERMS OF BOD5 AND COD), SUSPENDED SOLIDS, AND TOTAL PHOSPHORUS CONCENTRATIONS AND REMOVALS BY COAGULATION SAMPLE DESCRIPTION BOD5 COD TSS TVSS TOT AL P SAMPLE Mg +* DOSE % % % mg/L % mg/L % NUMBER pH (mg/L) mg/L REMOVAL mg/L REMOVAL mg/L REMOVAL REMOVAL REMOVAL 1 7.7 Not 7.5 204 6 3 0.19 P o l i s h e d 0.08 58 10.0 0 3.5 53 194 5 48 <0 3 0 10 3.5 53 196 4 47 <0 2 33 0.08 58 20 3.0 60 192 6 77 <0 3 0 0.06 68 . 35 3.3 56 188 8 54 <0 3 0 0.08 58 50 2.9 61 192 6 63 <0 4 <0 0.10 47 10.7 0 3.3 56 192 6 33 <0 3 0 0.09 53 10 2.0 73 192 6 24 <0 2 33 0.09 53 20 2.0 73 194 5 24 <0 4 <0 0.09 53 35 2.0 73 190 7 42 <0 5 <0 0.09 53 50 2.1 72 190 7 29 <0 2 33 0.07 63 11.4 0 2.0 73 192 6 36 <0 4 <0 0.10 47 10 1.7 77 190 7 58 <0 7 <0 0.06 68 20 1.6 79 190 7 74 <0 10 <0 0.09 53 35 1.3 83 186 9 105 <0 12 <0 0.10 47 50 1.5 80 186 9 105 <0 13 <0 0.09 53 2 7.2 Not P o l i s h e d 52 462 100 58 1.14 10.0 0 45 13 421 9 92 8 15 74 0.51 55 10 36 31 433 6 109 <0 19 67 0.64 44 20 41 21 425 8 83 17 13 78 0.44 61 35 36 31 421 9 82 18 17 71 0.45 61 50 37 39 437 5 102 <0 20 66 0.51 55 10.7 0 27 48 433 6 98 2 18 69 0.63 45 10 27 48 449 3 101 <0 17 71 0.63 45 20 29 44 433 6 102 <0 18 69 0.65 43 35 28 46 431 7 96 4 16 72 0.72 37 50 30 42 429 7 98 2 24 59 0.58 49 11.4 0 50 4 421 9 71 29 24 59 0.52 54 10 41 21 413 11 54 46 21 64 0.36 68 20 40 23 401 13 48 52 19 67 0.29 75 35 41 21 397 14 42 58 15 74 0.28 75 50 x 31 423 8 51 49 22 64 0.26 77 Ln 58 dosage) , the ab s o l u t e removals were very low. A BOD,, removal of j u s t 6 mg/L r e s u l t e d i n a 80 per c e n t removal. For the h i g h e r s t r e n g t h sample (SAMPLE 2 BOD 5 = 52 mg/L), almost 50 percent BOD,, removal was achieved a t the medium lime dose (pH = 10.7). The maximum COD removal o b t a i n e d f o r e i t h e r sample was 14 per c e n t . T h i s i n d i c a t e s t h a t the lime-magnesium process was much more e f f e c t i v e i n removing b i o l o g i c a l l y degrad- ab l e o r g a n i c matter, than b i o l o g i c a l l y r e s i s t a n t o r g a n i c matter. The reason f o r t h i s i s not apparent. However, i t i s not an item of extreme importance s i n c e the primary concern i s BOD,. - t h i s i s an i n d i c a t i o n of the oxygen demand by the e f - f l u e n t on r e c e i v i n g waters. F o r SAMPLE 1, the suspended s o l i d s l e v e l s were i n c r e a s e d (<0 percent removal) up to about s e v e n t e e n - f o l d by the coagu- l a t i o n p r o c e s s . T h i s was due to the i n i t i a l low suspended s o l i d s l e v e l s and the f a c t t h a t some of the chemicals added remained suspended. The removal of t o t a l suspended s o l i d s was g e n e r a l l y poor f o r SAMPLE 2. At the hig h lime dosage, however, "reasonable" removals o f up to 58 per c e n t were ach i e v e d . The removal o f t o t a l phosphorus d i d not f o l l o w a t r e n d with the v a r y i n g lime and magnesium dosages; but, the h i g h e s t three percentage removals d i d occur a t the hi g h lime and h i g h e s t t h r e e magnesium dosages f o r SAMPLE 1. The range o f t o t a l phosphorus removal was from 3 7 t o 77 p e r c e n t . The h i g h e s t phosphorus r e s i d u a l remaining was 0.72 mg/L, w e l l below the l o c a l "AA" l e v e l (10) o f 1.5 mg/L. 59 The r e s u l t s o f t h e m e t a l c o n c e n t r a t i o n s a n d r e m o v a l s a r e p r e s e n t e d i n T a b l e s 14 and 15. I n g e n e r a l , t h e r e m o v a l s d i d n o t i n c r e a s e m a r k e d l y w i t h i n c r e a s i n g l i m e a n d / o r m a g n e s i u m d o s a g e s . T h i s was p r o b a b l y d u e , i n p a r t , t o t h e v e r y l o w i n i t i a l c o n c e n t r a t i o n s o f t h e m e t a l s . F rom T a b l e 1 5 , t h e r e - l a t i v e o r d e r o f m e t a l r e m o v a l e f f i c i e n c i e s w e r e : C d , Mn, F e , Zn, C r , N i , C a , a n d Mg. As e x p e c t e d , Ca and Mg h a d t h e l o w e s t r e m o v a l s s i n c e t h e s e m e t a l s w e r e a d d e d t o t h e s a m p l e s f o r t h e c o a g u l a t i o n p r o c e s s . F rom T a b l e 14, o n l y i r o n c o n c e n t r a t i o n s o f e f f l u e n t s f r o m SAMPLE 2 s u b s t a n t i a l l y e x c e e d e d t h e l o c a l l e v e l "AA" o b j e c t i v e s . ( 1 0 ) . A l s o , s e v e r a l o f t h e e f f l u e n t s f r o m SAMPLE 2 e x c e e d e d t h e a l l o w a b l e Mn c o n c e n t r a t i o n o f 0.05 mg/L. The l e v e l "AA" o b j e c t i v e s a r e met f o r a l l t h e p a r a m e t e r s m e a s u r e d f o r t h e e f f l u e n t s o f SAMPLE 1. I n g e n e r a l , r e m o v a l s w e r e n o t e n h a n c e d s i g n i f i c a n t l y b y t h e ma g n e s i u m a d d i t i o n s . G r e a t e r t h a n 20 mg/L o f M g + + was a l r e a d y p r e s e n t i n b o t h s a m p l e s , b e f o r e a n y ma g n e s i u m a d d i - t i o n ; h e n c e , magnesium h y d r o x i d e p r e c i p i t a t i o n o c c u r r e d e v e n i n t h e s a m p l e s w i t h o u t m a g n e s i u m a d d i t i o n s . T a b l e 14 shows a g a i n i n c o n c e n t r a t i o n s o f Ca a n d Mg f o r some o f t h e e f f l u e n t s . T h i s i n d i c a t e s t h a t some o f t h e Ca an d Mg a d d e d r e m a i n e d i n s o l u t i o n a n d d i d n o t p r e c i p i t a t e o u t as CaCO^ a n d M g f O H ^ - T h e r e f o r e , two means o f i m p r o v i n g r e m o v a l s b y t h e l i m e - c o a g u l a t i o n p r o c e s s a r e a p p a r e n t . The f i r s t w o u l d b e t o i n c r e a s e t h e l i m e d o s a g e t o a pH l e v e l o f , s a y , 1 2 . 0 . T h i s w o u l d l e a d t o g r e a t e r p r e c i p i t a t i o n o f M g ( 0 H ) 2 a n d t h e o t h e r m e t a l l i c h y d r o x i d e s . The p r e c i p i t a t i o n 60 TABLE 14 METAL CONCENTRATIONS OF THE FINAL EFFLUENTS POLISHED BY THE LIME-MAGNESIUM PROCESS SAMPLE DESCRIPTION METAL CONCENTRATION (mg/L) SAMPLE Mg++ DOSE NUMBER PH (mg/L) Cd Ca Cr Fe Mg Mn - Ni Zn 1 Not Polished <0.001 40 0.011 0.66 20.1 0.10 0.039 0.16 10.0 0 <0.001 20 0.007 0.21 17.4 0.01 0.035 0.08 10 <0.001 32 0.007 0.17 29.0 0.01 0.034 0.09 20 <0.001 33 0.010 0.18 39.3 0.01 0.039 0.09 35 <0.001 42 0.005 0.22 54.0 0.02 0.038 0.16 50 <0.001 45 0.006 0.13 65.4 0.01 0.037 0.07 10.7 0 <0.001 22 0.006 0.14 16.1 0.02 0.033 0.10 10 <0.001 26 0.006 0.14 25.5 0.02 0.031 0.09 20 <0.001 38 0.006 0.17 35.3 0.02 0.030 0.23 35 <0.001 45 0.007 0.15 50.6 0.02 0.031 0.14 50 <0.001 44 0.007 0.13 63.5 0.02 0.030 0.42 11.4 0 <0.001 31 0.007 0.19 14.1 0.03 0.030 0.11 10 <0.001 38 0.007 0.18 20.0 0.03 0.030 0.14 20 <0.001 45 0.008 0.17 26.0 0.03 0.028 0.11 35 <0.001 59 0.007 0.14 35.5 0.02 0.028 0.43 50 <0.001 68 0.007 0.28 52.9 0.02 0.028 0.19 2 Not Polished 0.004 44 0.016 20.4 23.2 0. 38 0.041 0.79 10.0 0 0.001 36 0.011 6.8 19.9 0.10 0.038 0.22 10 0.001 39 0.010 10.8 30.3 0.09 0.039 0.19 20 0.002 40 0.010 6.7 39.5 0.08 0.037 0.23 35 0.002 38 0.009 6.7 54.3 0.08 0.037 0.23 50 0.002 43 0.008 6.5 65.1 0.08 0.035 0.30 10.7 0 0.001 34 0.010 9.9 17.2 0.19 0.034 0.20 10 0.001 37 0.013 10.7 28.6 0.14 0.032 0.34 20 0.001 39 0.010 10.3 38.7 0.13 0.033 0.29 35 <0.001 40 0.009 9.7 51.7 0.12 0.033 0.32 50 <0.001 38 0.013 8.5 61.5 0.10 0.031 0.25 11.4 0 <0.001 23 0.011 7.8 10.7 0.17 0.029 0.18 10 <0.001 21 0.011 4.2 11.8 0.10 0.025 0.15 20 <0.001 25 0.007 3.4 16.3 0.08 0.025 0.09 35 <0.001 26 0.008 2.0 23.6 0.05 0.016 0.17 50 <0.001 34 0.009 3.2 52.5 0.06 0.027 0.28 P.C.B . Objectives* 1 0.005 0.1 0.3 0.05 0.3 0.5 * B r i t i s h Columbia Pollution Control Objectives (10), Level AA Objectives 61 TABLE 15 METAL REMOVALS BY LIME-MAGNESIUM COAGULATION SAMPLE DESCRIPTION PERCENT REMOVAL OF THE METAL SAMPLE Mg + + DOSE NUMBER' PH (mg/L) Cd Ca Cr Fe Mg Mn N i Zn 1 10.0 0 50 36 68 13 90 10 50 10 20 36 74 <0 90 13 44 20 18 9 73 <0 90 0 44 35 <0 55 67 <0 80 3 Mo 50 <0 45 80 <0 90 5 56 10.7 0 45 45 79 20 80 15 38 10 35 45 79 <0 80 21 44 20 5 45 74 <0 80 23 0 35 <0 36 77 <0 80 21 13 50 <0 36 80 <0 80 23 0 11.4 0 23 36 71 30 70 23 32 10 5 36 73 1 70 23 13 20 <0 27 74 <0 70 26 32 35 <0 36 79 <0 80 26 <0 50 <0 27 58 <0 80 26 <0 2 10.0 0 66 18 31 67 14 74 7 72 10 62 11 38 47 <0 76 5 76 20 58 9 38 67 <0 79 10 71 35 61 14 44 67 <0 79 10 71 50 61 2 50 68 <0 79 15 62 ' 10.7 0 67 23 38 51 26 50 17 75 10 69 16 19 48 <0 63 22 57 20 73 11 38 50 <0 66 20 63 35 89 9 44 52 <0 68 20 59 50 89 14 19 58 <0 74 24 68 11.4 0 >90 48 31 62 54 55 29 77 10 >90 53 31 79 50 74 39 81 20 >90 43 56 83 30 79 39 89 35 >90 41 50 90 <0 87 61 78 50 >90 23 44 84 <0 84 34 65 62 of Mg(0H)2 would a l s o a i d i n the removal of o r g a n i c s and suspended s o l i d s (as d i s c u s s e d i n S e c t i o n 2 - 2.2). Secondly, i f the a l k a l i n i t i e s o f the.samples were r a i s e d by adding carbonate, a l l (as much as p r a c t i c a l l y pos- ++ s i b l e ) of the Ca would p r e c i p i t a t e out as CaCO^- Calcium carbonate i s s o l u b l e t o the extent o f about 17 mg/L (28), whereas C a + + c o n c e n t r a t i o n s were as h i g h as 68 mg/L (= 170 mg/L as CaCO^) i n the e f f l u e n t s , thus i n d i c a t i n g a carbonate d e f i - c i e n c y . The b e s t method of i n c r e a s i n g the carbonate c o n c e n t r a - t i o n would be through the use o f r e c y c l e d magnesium, i n the form o f MgCO^'Sl^O. In some cases though, t h i s carbonate may not be s u f f i c i e n t and more may have to be added. Although the a l k a l i n i t y o f SAMPLES 1 and 2 were around 400 mg/L, i t appears t h a t much o f i t was not due to the carbonate system. I t should be noted t h a t the r e s u l t s form the lime-magnesium phase are very p r e l i m i n a r y . The l a c k of sample volume l i m i t e d the j a r t e s t i n g t o j u s t one run. A more d e t a i l e d study i s r e - q u i r e d b e f o r e more d e f i n i t i v e c o n c l u s i o n s can be drawn. 63 CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 5 - 1 Conclu s i o n s 1) A e r o b i c b i o s t a b i l i z a t i o n i s an e f f e c t i v e means o f removing contaminants from a medium s t r e n g t h l e a c h a t e (BOD,- = 809 0 mg/L). 2) In the ranges o f temperature (ambient a i r temperatures from 25° to 5°C and corresponding l i q u i d temperatures from 18° to 3°C) and sludge ages (from 20 to 5 days) i n v e s t i g a t e d , the removals o f contaminants were onl y nomi- n a l l y dependent on temperature and sludge age. The excep- t i o n s were when the sludge ages were c l o s e to or lower than the "minimum" sludge age as p r e d i c t e d by the k i n e t i c p ara- meters a t a given temperature. T h i s o c c u r r e d f o r the 5-day sludge age r e a c t o r s a t 10° and 5°C. 3) The treatment performance of the r e a c t o r s was e x c e l l e n t . E x c l u d i n g the two r e a c t o r s c l o s e to washout c o n d i t i o n s , f i l t e r e d e f f l u e n t s (using Whatman No. 4 f i l t e r paper) met the most s t r i n g e n t l o c a l p o l l u t i o n c o n t r o l o b j e c t i v e s (10) f o r n e a r l y a l l of the parameters monitored, under n e a r l y a l l o p e r a t i o n a l c o n d i t i o n s . Only i r o n and magnesium con- c e n t r a t i o n s g r e a t l y exceeded the o b j e c t i v e s , and even then, t h i s u s u a l l y only o c c u r r e d under adverse c o n d i t i o n s (low sludge age and/or temperature). 4) For the l e a c h a t e t r e a t e d , a B0D5:N:P l o a d i n g of 100:3.2:1.1 was "adequate". The e f f i c i e n c i e s o f the r e a c t o r s under t h i s l o a d i n g were comparable to the c o n t r o l - r e a c t o r , which 64 had a standard l o a d i n g o f 100:5:1. The c o n v e n t i o n a l BODj-:N = 20:1 l o a d i n g was found to be low. In the c o n t r o l r e a c t o r , the s u r p l u s n i t r o g e n , not a s s i m i l a t e d by the microorganisms, r e s u l t e d i n n i t r i f i c a t i o n . T h i s was e v i d e n t by the n i t r i t e - n i t r a t e c o n c e n t r a t i o n o f 4 3 mg/L i n the c o n t r o l r e a c t o r e f f l u e n t . The n i t r i t e - n i t r a t e c o n c e n t r a t i o n s o f a l l the oth e r r e a c t o r s were below 0.2 mg/L. 5) The a d d i t i o n s o f magnesium i n the lime-magnesium process d i d not enhance removal e f f i c i e n c i e s s i g n i f i c a n t l y . T h i s was due, i n p a r t , to the i n i t i a l low c o n c e n t r a t i o n s o f contaminants and a l s o because there a l r e a d y e x i s t e d g r e a t e r than 2 0 mg/L of magnesium i n the samples. B e t t e r performance of the lime-magnesium^process c o u l d be accom- p l i s h e d by i n c r e a s i n g the lime dosage (to pH = 12j-/ f o r b e t t e r magnesium hydroxide p r e c i p i t a t i o n ) and/or r a i s i n g the a l k a l i n i t y by adding carbonate ( f o r b e t t e r c a l c i u m carbonate p r e c i p i t a t i o n ) . 6) A e r o b i c b i o s t a b i l i z a t i o n a t a sludge age g r e a t e r than 15 days and l i q u i d temperature o f a t l e a s t 3°C, f o l l o w e d by lime p r e c i p i t a t i o n (to pH g r e a t e r than or equal to 10.0) i s capable o f r e d u c i n g contaminants o f a medium s t r e n g t h l e a c h a t e (BODr = 809 0 mg/L), to l e v e l s below the l o c a l (Province of B r i t i s h Columbia) p o l l u t i o n c o n t r o l objec- t i v e s . 65 5 - 2 Recommendations 1) Although a low BOD5:N:P l o a d i n g o f 100:3.2:1.1 has been shown t o be e f f e c t i v e , an even lower n u t r i e n t l o a d i n g may be j u s t as e f f e c t i v e . Although Temoin (31) d i d a t - tempt to o p t i m i z e the n u t r i e n t l o a d i n g l e v e l , a more comprehensive study i s r e q u i r e d . In p a r t i c u l a r , BOD^:N loadings of l e s s than 100:3.19 and B0D 5:P l o a d i n g s between 100:0.32 and 100:1.11 should be more thoroughly i n v e s t i - gated. The e f f e c t o f sludge age (or F/M r a t i o ) on n u t r i e n t requirements a l s o warrants f u r t h e r r e s e a r c h . 2) In c o n j u n c t i o n with the above recommendation, a study o f the s t o i c h i o m e t r y o f the l e a c h a t e treatment process should be conducted. As p r e v i o u s l y d i s c u s s e d , the Geodermatophilius organism may have a d i f f e r e n t metabolism, and thus, p o s s i - b l y , d i f f e r e n t n u t r i t i o n a l requirements than the p o p u l a t i o n of microorganisms normally found i n a domestic a c t i v a t e d sludge p l a n t . By f o l l o w i n g a procedure as o u t l i n e d (with minor m o d i f i c a t i o n s ) i n Experiment XVIII - 1 o f "Envir o n - mental E n g i n e e r i n g U n i t Operations and U n i t Processes Laboratory Manual" (2 3), the s t o i c h i o m e t r y o f the processes can be determined. T h i s w i l l not onl y c o n f i r m or deny d i f f e r e n t metabolisms as a reason f o r the low n u t r i e n t r e - quirements, but w i l l a l s o l e a d to a b e t t e r understanding o f the p r o c e s s . In a d d i t i o n , an assay o f the Geodermatophilius should be done to c o n f i r m t h a t the carbon-hydrogen-nitrogen- oxygen content i s s i m i l a r t o t h a t o f the microorganisms normally p r e s e n t i n an a c t i v a t e d sludge p l a n t (CVH-NOi) . 66 3) The problem of poor s o l i d s - l i q u i d s e p a r a t i o n should be addressed i n more d e t a i l . S e t t l i n g problems have been encountered i n a number of " a e r o b i c b i o s t a b i l i z a t i o n of l e a c h a t e " s t u d i e s . Good sludge s e t t l e a b i l i t y i s extremely c r u c i a l i n the o p e r a t i o n of the p r o c e s s . Z a p f - G i l j e (34) and Graham (14) a t t r i b u t e the s e t t l i n g problems mainly to the repeated shock l o a d i n g s of the f i l l - a n d - d r a w procedure, r a t h e r than to biomass r e a c t i o n t o the f e e d . Although t h i s i s l i k e l y to be an important reason, i t i s q u e s t i o n a b l e whether t h i s i s the major cause. P a l i t and Qasim (24) ran a continuous flow system and sludge b u l k i n g o c c u r r e d s e v e r a l times. Cook and Foree (9), U l o t h (33), and Temoin (31) a l l used the f i l l - a n d - d r a w procedure without any s e r i o u s s e t t l i n g problems. E c k e n f e l d e r and Ford (11) l i s t e x c e s s i v e o r g a n i c l o a d - i n g as a p o s s i b l e cause of sludge b u l k i n g . The F/M r a t i o s were l e s s than 0.17 ^? BOD 5/day f Q r three t r o u b l e f r e e kg MLVSS s t u d i e s mentioned above. The systems of P a l i t and Qasim (24), Z a p f - G i l j e (34) and Graham (14) a l l had F/M r a t i o s g r e a t e r than 0.17 k g BOD^/day^ I n i n v e s t i g a t i o n kg MLVSS the lower sludge age (5 and 10 days) r e a c t o r s experienced s e t t l i n g problems. These r e a c t o r s a l l had F/M r a t i o s c l o s e t o or exceeding 0.17. The h i g h e r sludge age (15 and 20 days) r e a c t o r s a l l had F/M r a t i o s l e s s than 0.16. 6 7 The a b o v e e v i d e n c e seems t o i n d i c a t e t h a t F/M l o a d i n g m i g h t b e more i m p o r t a n t t h a n t h e mode o f o p e r a t i o n ( c o n t i n u o u s f l o w o r f i l l - a n d - d r a w ) . A n o t h e r p o s s i b l e f a c t o r may b e t e m p e r a t u r e . The t h r e e s t u d i e s i n w h i c h no s e t t l i n g p r o b l e m s w e r e e n c o u n - t e r e d w e r e o p e r a t e d a t room t e m p e r a t u r e . The s t u d i e s o f Z a p f - G i l j e , Graham a n d t h i s i n v e s t i g a t i o n w e r e o p e r a t e d a t t e m p e r a t u r e s r a n g i n g f r o m 5° t o 2 5°C. As t e m p e r a t u r e d e c r e a s e d , s l u d g e s e t t l e a b i l i t y g rew w o r s e . T h u s , t h e e f f e c t o f t e m p e r a t u r e a n d / o r t h e e f f e c t o f d i f f e r e n t o r - g a n i s m s p e c i e s ( i e . m e s o p h i l e s v e r s u s p s y c h r o p h i l e s ) s h o u l d b e i n v e s t i g a t e d f u r t h e r . .4) The l i m e - m a g n e s i u m p r o c e s s s h o u l d be i n v e s t i g a t e d more c o m p r e h e n s i v e l y . Two a d d i t i o n a l a s p e c t s t h a t s h o u l d be i n c l u d e d a r e a l i m e d o s a g e t o r a i s e t h e pH l e v e l t o 1 2.0, a n d a d d i n g c a r b o n a t e t o t h e s a m p l e s , t o i m p r o v e t h e ++ ++ r e m o v a l s o f Ca a n d Mg a s CaCO^ a n d M g ( O H ) 2 . 5) The q u a l i t y a n d q u a n t i t y o f l e a c h a t e g e n e r a t e d i s h i g h l y v a r i a b l e f r o m s e a s o n t o s e a s o n . The s t r e n g t h o f t h e l e a c h a t e a l s o d e c r e a s e s a s t h e age o f a l a n d f i l l i n c r e a s e s . T h e r e f o r e , r a t h e r t h a n h a v i n g a s e p a r a t e l e a c h a t e t r e a t - ment f a c i l i t y , i t seems r e a s o n a b l e t h a t a s a v i n g s i n t r e a t - ment c o s t s m i g h t be r e a l i z e d i f l e a c h a t e c o u l d b e t r e a t e d , a l o n g w i t h d o m e s t i c w a s t e w a t e r , i n e x i s t i n g a c t i v a t e d s l u d g e p l a n t s . 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K., " B i o l o g i c a l T r e a t a b i l i t y of L a n d f i l l Leachate", J o u r n a l of the Water P o l l u t i o n C o n t r o l F e d e r a t i o n , Vol. 46, No. 5, May 1974, pp. 860- ' 872. 5. Brown, M. J . and L e s t e r , J . N., "Metal Removal i n A c t i v a t e d Sludge: The Role of B a c t e r i a l E x t r a c e l l u l a r Polymers", Water Research, V o l . 13, No. 9, 1979, pp. 817-837. 6. Cameron, R. D., "The E f f e c t s of S o l i d Waste L a n d f i l l Leachates on R e c e i v i n g Waters", paper presented at the 19 75 B r i t i s h Columbia Water and Waste A s s o c i a t i o n Conference, H a r r i s o n Hot S p r i n g s , B. C , A p r i l 1975, 14 pages. 7. Cheng, M. H., P a t t e r s o n , J . W., and Minear, R. A., "Heavy Metals Uptake by A c t i v a t e d Sludge", J o u r n a l o f the Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 47, No. 2, February 1975, pp. 362-376. 8. C l a r k , J . W., Viessman, W., and Hammer, M. J . , "Water Supply and P o l l u t i o n C o n t r o l " / . I n t e r n a t i o n a l Textbook Company, Scranton, 2nd e d i t i o n , 19 71. 9. Cook, E. N. and Foree, E. G., "Aerobic B i o s t a b i l i z a t i o n of S a n i t a r y L a n d f i l l Leachate", J o u r n a l of the Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 46, No. 2, February 1974, pp. 380-392. 10. Department of Lands, F o r e s t s , and Water Resources, "Report on P o l l u t i o n C o n t r o l O b j e c t i v e s f o r M u n i c i p a l Type Waste Discharges i n B r i t i s h Columbia", Water Resources S e r v i c e , V i c t o r i a , B r i t i s h Columbia, September 1975. 11. E c k e n f e l d e r , W. W. and Ford, D. L., "Water P o l l u t i o n C o n t r o l " , Jenkins Book P u b l i s h i n g Company, A u s t i n and New York, 1970. 69 12. E c k e n f e l d e r , W. W.: and O'Connor, D. J . , " B i o l o g i c a l Waste Treatment", Pergamon Pr e s s , New York, 1961. 13. EPA, "Methods f o r Chemical A n a l y s i s o f Water and Wastes", EPA-600/4-79-02, March 1979. 14. Graham, D. W., " B i o l o g i c a l Chemical Treatment o f Leachate", M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, f i n a l r e p o r t i n p r o g r e s s . 15. H a t t i n g h , W. H. J . , "The N i t r o g e n and Phosphorus Requirements o f Microorganisms i n A c t i v a t e d Sludge", Ph.D. t h e s i s , U n i v e r s i t y o f B r i t i s h Columbia, August 1962. 16. Ho, S., Boyle, W. C , and Ham, R. K. , "Chemical T r e a t - ment of Leachates from S a n i t a r y L a n d f i l l s " , J o u r n a l of the Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 46, No. 7, J u l y 1974, pp. 1776-1791. 17. Lawrence, A. W. and McCarty, P. L., " U n i f i e d B a s i s f o r B i o l o g i c a l Treatment Design and Operation", J o u r n a l of the S a n i t a r y E n g i n e e r i n g D i v i s i o n , V o l . 96, No. SA3, June 1970, pp. 757-778. 18. Lee, C. J . , "Treatment o f a M u n i c i p a l L a n d f i l l Leachate", M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, January 19 79. 19. Leung, Y.-C, "The Removal o f Organics from M u n i c i p a l Wastewaters by Lime-Magnesium Coagulation'!, M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, June 1978. 20. MacLean, B. H., "The Removal of Heavy Metals from M u n i c i p a l Wastewaters by Lime-Magnesium C o a g u l a t i o n " , M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, June 1977. 21. M a v i n i c , D. S., "Leachate Treatment Schemes - Research Approach", paper presented at the EPA S o l i d and Haz- ardous Waste Research D i v i s i o n , F i f t h Annual Research Symposium, Orlando, F l o r i d a , March 19 79, 17 pages. 22. M e t c a l f and Eddy, Inc., "Wastewater E n g i n e e r i n g : T r e a t - ment, D i s p o s a l , Reuse", McGraw-Hill Book Company, 2nd e d i t i o n , 19 79. 23. O'Connor, J . T., ed., "Environmental E n g i n e e r i n g U n i t Operations and U n i t Processes Laboratory Manual", A s s o c i a t i o n of Environmental E n g i n e e r i n g P r o f e s s o r s , July.1972. 24. P a l i t , T. and Qasim, S. R., " B i o l o g i c a l Treatment K i n e t i c s of L a n d f i l l Leachate", J o u r n a l of the E n v i r o n - mental E n g i n e e r i n g D i v i s i o n , V o l . 10 3, No. EE2, A p r i l 1977, pp. 353-366. 70 25. Pborman, B. L., " T r e a t a b i l i t y o f Leachate from a San- i t a r y L a n d f i l l by Anaerobic D i g e s t i o n " , M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, A p r i l 19 74. 26. Ramey, W. D. , Department of M i c r o b i o l o g y , U n i v e r s i t y of B r i t i s h Columbia, p e r s o n a l communication, A p r i l 19 80. 27. Rush, R. J . , "Magnesium-Lime Process f o r D e c o l o u r i z a t i o n of K r a f t M i l l E f f l u e n t s " , M.A.Sc. t h e s i s , U n i v e r s i t y o f B r i t i s h Columbia, A p r i l 1976. 28. Sawyer, C.N. and McCarty, P. L., "Chemistry f o r S a n i t a r y Engineers", McGraw-Hill Book Company, 2nd e d i t i o n , 19 67. 29. S h e r r a r d , J . H. and Schroeder, E. D., "S t o i c h i o m e t r y of I n d u s t r i a l B i o l o g i c a l Wastewater Treatment", J o u r n a l o f the Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 48, No. 4, A p r i l 1976, pp. 742-747. 30. S i k e s , J . E. G., and Nieminen, G. A., "Economic Consid- e r a t i o n s i n the S e l e c t i o n o f a B i o l o g i c a l Treatment System", 19 75 Environment Improvement Conference, Canadian Pulp and Paper A s s o c i a t i o n , October 1975. 31. Temoin, P. E., " N u t r i e n t Requirements f o r B i o s t a b i l i - z a t i o n of a L a n d f i l l Leachate", M.A.Sc. t h e s i s , Univer- s i t y of B r i t i s h Columbia, f i n a l r e p o r t i n p r o g r e s s . 32. Thornton, R. J . and Blanc, F. C , "Leachate Treatment by C o a g u l a t i o n and P r e c i p i t a t i o n " , J o u r n a l of >• the E n v i - ronmental E n g i n e e r i n g D i v i s i o n , V o l . 99, No. EE4, August 197 3, pp. 5 35-544. 33. U l o t h , V. C., "Aerobic B i o s t a b i l i z a t i o n o f a High- St r e n g t h L a n d f i l l Leachate", M.A.Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, February 1976. 34. Z a p f - G i l j e , R., " E f f e c t s o f Temperature on Two-Stage B i o s t a b i l i z a t i o n of L a n d f i l l Leachate", M.A.Sc. t h e s i s , U n i v e r s i t y o f B r i t i s h Columbia, October 19 79. APPENDICES 72 APPENDIX A Determination o f B i o l o g i c a l Treatment K i n e t i c C o e f f i c i e n t s The r e l a t i o n s h i p between b i o l o g i c a l growth and sub- s t r a t e u t i l i z a t i o n i s formulated i n two b a s i c equations by Lawrence and McCarty (17). The f i r s t e q u a t i o n , developed e m p i r i c a l l y from waste treatment s t u d i e s , d e s c r i b e s the r e l a t i o n s h i p between net r a t e o f growth and r a t e o f s u b s t r a t e u t i l i z a t i o n : dX where = net growth r a t e o f microorganisms per u n i t volume of r e a c t o r (mass per volume-time) Y = growth y i e l d c o e f f i c i e n t (mass o f micro- organisms per mass o f s u b s t r a t e u t i l i z e d ) dF dt r a t e o f m i c r o b i a l s u b s t r a t e u t i l i z a t i o n per u n i t volume (mass per volume-time) b = microorganism decay c o e f f i c i e n t (time "*") X = m i c r o b i a l mass c o n c e n t r a t i o n (mass per volume The second equation r e l a t e s the r a t e o f m i c r o b i a l sub- s t r a t e u t i l i z a t i o n to the c o n c e n t r a t i o n o f microorganisms and the c o n c e n t r a t i o n o f s u b s t r a t e surrounding the micro^ organisms: dF = kxs. dt K +S (A.2) s where k = maximum r a t e of s u b s t r a t e u t i l i z a t i o n _^ per u n i t weight o f microorganisms (time ) S = c o n c e n t r a t i o n o f s u b s t r a t e surrounding the microorganisms (mass per volume) 73 = h a l f v e l o c i t y c o e f f i c i e n t , equal to the s u b s t r a t e concent (mass per volume) s e c t r a t i o n when dF/dt = {h)1<L Using the two b a s i c equations, the k i n e t i c c o e f f i c i e n t s Y, b, k, and K g can be g r a p h i c a l l y determined from l a b o r a t o r y data (22). D i v i d i n g both s i d e s o f Equation A . l by X g i v e s : dX/dt = Y dF/dt _ b ( A . 3 ) A X S u b s t i t u t i n g dX/dt 1 , dF _ S o ~ S x " e a n a dt e c c (where S Q = c o n c e n t r a t i o n of s u b s t r a t e i n i n f l u e n t ) i n t o Equation A.3 g i v e s : 1 ( S o " S ) c c 1 S -S The r e f o r e , from a p l o t o f versus ^ — ' the y - i n t e r c e p t c c = - b and the sl o p e = Y dF o Rearranging Equation A.2 and s u b s t i t u t i n g = c g i v e s : X9^ K . 1 C - v i + k (A. 5) S -S k ' S o X© T h e r e f o r e , from a p l o t o f c versus . _1, the y - i n t e r c e p t S -S S 1 K ° = T- and the s l o p e = s * F" A f t e r the k i n e t i c c o e f f i c i e n t s have been determined, the M t h e o r e t i c a l minimum mean c e l l r e t e n t i o n time, 9 , a t which ' c process f a i l u r e o c c u r s , can be c a l c u l a t e d . 74 A m a t e r i a l s balance f o r a r e a c t o r i s w r i t t e n as (17): /Net Rate of Change\ = ( G r o w t h R a t e ) _ ( W a s h o u t R a t e ) \of M i c r o b i a l Mass J V ( f l ) n = ( Y f ~ b X ) V " Q X • ' • ( A ' 6 ) where V = r e a c t o r volume (volume) Q = flow r a t e (volume per time) When steady s t a t e c o n d i t i o n s e x i s t , ("^r) = 0, \ 'n t h e n 1_ = Y dlZdt _ b m m m ( A > 7 ) c s i n c e Q/V = 6 c when there i s no r e c y c l e . S u b s t i t u t i n g Equation A.2 i n t o E quation A.7 g i v e s : 1 _ YkS~ 0 k +S c s: - b , (A. 8) M When 0 = 9 * (the mean c e l l r e s i d e n c e time a t which the c c microorganisms are washed out of the system f a s t e r than they can reproduce), the e f f l u e n t waste c o n c e n t r a t i o n , S, i s equal to the i n f l u e n t waste c o n c e n t r a t i o n , S Q. Hence, , YkS 1 = 2 - - b (A.9) k +S C s o The l a b o r a t o r y data used to determine the k i n e t i c c o e f - f i c i e n t s i s shown i n Table 16. The g r a p h i c a l d e t e r m i n a t i o n o f the c o e f f i c i e n t s i s shown i n F i g u r e s 3 to 10. The k i n e t i c M i n Table 17, c o e f f i c i e n t r e s u l t s and the c a l c u l a t e d © c ' s are t a b u l a t e d TABLE 16 COMPUTATION TABLE FOR THE GRAPHICAL DETERMINATION OF KINETIC COEFFICIENTS REACTOR DESCRIPTION S o (mg/L) S (mg/L) X (mg/L) 1 e c (days "*•) 1 : s (L/mg) S -S o xe c xe c (days ) S -S o (day s) T (°C) 6 c (days) R.T. 20 8090 9 3490 0.050 0.111 0.116 8.64 15 8090 11 3470 0.067 0.091 0.155 6.44 10 8090 25 3650 0.100 0.040 0.221 4.53 5 8090 44 4000 0.200 0.023 0.402 2.49 15 20 8090 7 3690 0.050 0.14 3 0.110 9.13 15 8090 .9 3430 0.067 0.111 0.157 6. 37 10 8090 20 3520 0.100 0.050 0.229 4. 36 5 809 0 51 3790 0.200 0.020 0.424 2. 36 10 20 8090 9 3810 0.050 0.111 0.106 9.43 15 8090 16 3860 0.067 0.063 0.139 7.17 10 8090 17 4220 0.100 0.059 0.191 5.23 5 8090 112 4040 0.200 0.009 0.395 2. 53 5 20 8090 14 4070 0.050 0.071 0.099 10.08 15 8090 20 4350 0.067 0.050 0.124 8.09 10 8090 42 479 0 0.100 0.024 0.168 5.95 5 8090 188 4320 0.200 0.005 0. 366 2.73 Note: S and S are s o l u b l e BODr c o n c e n t r a t i o n s o 5 DETERMINAT ION OF k AND K g AT ROOM T E M P E R A T U R E .'. b = 0. 0 0 9 doys 0 0.1 0.2 0.3 0.4 0.5 (days " 1 ) F I G U R E 4 DETERMINATION OF Y AND b AT ROOM T E M P E R A T U R E DETERMINATION OF k AND K 8 AT IO°C 0.20h 0.15 - 0.10 (A >» o -|<D 0.05 0.00 -0.05 s l o p e " Y = 0.51 y - i n t e r c e p t = - b = - 0 . 0 0 6 d a y s b = 0. 0 0 6 days _J L -1 0.2 0.3 0.4 S o " S (days" 1) X 0C F I G U R E 8 DETERMINATION OF Y AND b AT I0°C 8 10 in co o - / K s x slope : - j p = 57.0  d7 8 L / m g / .". K e = 6 3 . 8 m g / L / y - i n t e r c e p t = = 0. 8 9 days .'. k = 1.12 d a y s " 1 1 1 1 0.20 0. 15 0.04 0.08 S l m g ' 0.12 0.16 7 0. 10 (A >» a TJ _|CD 0.05 0.00 - 0 . 0 5 F I G U R E 5 DETERMINAT ION OF k AND K, AT 15° C 0,2 S o " S 0.4 0.5 x e T ( d a y r l ) F I G U R E 6 DETERMINATION OF Y AND b AT I5°C F I G U R E 9 DETERMINAT ION OF k AND K $ AT 5°C 0 . 2 0 0 .15 0.10 tn >» o -|<D 0  0 5 r s lope = Y = 0 . 5 5 0 . 0 0 f -I a y - intercept = - b = - 0 . 0 0 2 d a y s - 0 . 0 5 .'. b = 0 . 0 0 2 days - I 0. I 0.2 0.3 0 . 4 F I G U R E 10 DETERMINATION OF Y AND b AT 5°C vo TABLE 17 KINETIC COEFFICIENTS AND MINIMUM MEAN CELL RETENTION TIMES £ c ; t; s TEMPERATURE (°C) k (days ^) K s. (mg/L) Y b (days "*") c (days) R.T. 1.16 81. 8 0.49 • 0.009 1.8 15 1.12 63.8 0.51 0.018 1.8 10 0.51 34.6 0.51 0.006 4.0 5 0. 3.4 17.0 0.55 0.002 5.4 Appendix B Supplementary R e s u l t s 4000 1— 1 1 1 I I 5 10 15 20 SLUDGE A 6 E , 6 C ( days) K comment-three replicate samples were analyzed FIGURE II MIXED LIQUOR COD VERSUS SLUDGE AGE 00 NJ TABLE 18 AC ID I TY , A LKAL IN I TY , TC, AND TOC CONCENTRATIONS AND REMOVALS BY THE BIOLOGICAL REACTORS REACTOR nRRPRTPTION ACID ITY ALKAL IN ITY 1 PC 1 Tr roc T e mg/L as CaCO., % mg/L as C a C 0 3 % mg/L % mg/L % (°C) c (day s ) (pH = 8.3) REMOVAL (PH = 3.7) REMOVAL REMOVAL REMOVAL L e a c h a t e F e e d 2060 3160 3820 3800 R.T. 2 0 * 0 100 148. 9 5 . 3 101 97 . 4 55 98 . 6 20 0 100 335 89.4 142 9 6 . 3 67 9 8 . 2 15 0 100 350 88.9 149 9 6 . 1 67 9 8 . 2 10 0 100 363 88 .5 175 95 .4 89 9 7 . 7 5 0 100 338 89 . 3 226 94 .1 142 9 6 . 3 15 20 0 100 345 89 .1 162 9 5 . 8 81 97 .9 15 0 100 373 88 .2 177 95 . 4 86 9 7 . 7 10 0 100 387 87 .8 190 9 5 . 0 92 97 . 6 5 0 100 39 3 87.6 271 92 .9 180 9 5 . 3 10 20 0 100 415 86.9 170 9 5 . 5 74 9 8 . 1 15 0 100 390 87 .7 182 95 . 2 88 9 7 . 7 10 0 100 388 87 .7 223 94 . 2 129 96 . 6 5 0 100 39 3 87.6 371 9 0 . 3 281 9 2 . 6 5 20 0 100 411 87 .0 217 9 4 . 3 117 96 .9 15 0 100 390 87 .7 232 93.9 135 96 .4 10 0 100 412 87.0 278 92 .7 177 9 5 . 3 5 0 100 493 84 .4 473 87.6 366 90 . 4 * r e a c t o r n u t r i e n t l o a d i n g B O D 5 : N : P = 1 0 0 : 5 : 1 , a l l o t h e r s a r e 1 0 0 : 3 . 2 : 1 . 1

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