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Anaerobic treatment analysis of concentrated hog wastes 1972

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ANAEROBIC TREATMENT ANALYSIS OF CONCENTRATED HOG WASTES by LES NEMETH 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 , 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department 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 as c o n f o r m i n g to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF A p r i l , BRITISH 1972 COLUMBIA I n 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 o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e 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 , I a g r e e t h a t t h e 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 a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may b e g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r b y h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f < C < I > ' 1 L JAJ6> The 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 V a n c o u v e r 8, C a n a d a A B S T R A C T Due to the deve lopment o f i n t e n s i v e l i v e s t o c k p r o d u c t i o n methods - n a m e l y , h i g h - d e n s i t y c o n f i n e m e n t f e e d i n g - a n i m a l was te s t r a d i t i o n a l l y l o o k e d upon as " n a t u r a l " o r " b a c k g r o u n d " w a s t e s , a r e now b e i n g s u b j e c t t o t he same r e s t r i c t i o n s , as r e g a r d s d i s p o s a l , ^ as i n d u s t r i a l w a s t e s . As a r e s u l t was te t r e a t m e n t o f some n a t u r e has become n e c e s s a r y . Such t r e a t m e n t methods wou ld r e d u c e the amount o f s o l i d s r e q u i r i n g d i s p o s a l and make the l i q u i d p o r t i o n more a c c e p t a b l e f o r d i s p o s a l t o w a t e r c o u r s e s o r f o r r e - u s e . A n a e r o b i c l a g o o n i n g i s one such method o f was te t r e a t m e n t o f c o n c e n t r a t e d a n i m a l w a s t e s . An i n v e s t i g a t i o n on a l a b o r a t o r y - s c a l e o f t he e f f e c t s o f v a r i o u s p a r a - m e t e r s on the a n a e r o b i c d e c o m p o s i t i o n o f hog waste was u n d e r t a k e n . I n c l u d e d i n t h i s s t u d y was the e f f e c t o f v a r i e d d e t e n t i o n t imes and t e m p e r a t u r e s on such waste c h a r a c t e r i s t i c s as oxygen demand, s o l i d s , n u t r i e n t s and gas com- p o s i t i o n and p r o d u c t i o n . The f i n a l outcome o f t h i s p rogram was t o add some deg ree o f o p t i m i z a t i o n to the a n a e r o b i c was te t r e a t m e n t method and to d e v e l o p i m p r o v e d d e s i g n g u i d e l i n e s r e l a t e d to t h i s s p e c i f i c f i e l d . A l l recommendat ions p r e s e n t e d a r e ba sed on l a b o r a t o r y f i n d i n g s . C o r - r e l a t i o n between l a b o r a t o r y - s c a l e r e s u l t s and f i e l d - s c a l e r e s u l t s was no t a t t e m p t e d i n t h i s p o r t i o n o f the s t u d y . i i TABLE OF CONTENTS L I ST OF TABLES v i L I ST OF FIGURES v i i ACKNOWLEDGEMENT v i i i CHAPTER I INTRODUCTION 1 1.1 G e n e r a l D i s c u s s i o n 1 1.2 D e s i g n and L a y o u t o f T rea tment F a c i l i t i e s 3 1.3 Fundamenta l s o f A n a e r o b i c Lagoons 5 1.4 Compar i son o f F i e l d Lagoon and L a b o r a t o r y D i g e s t e r 6 1.5 Need f o r Improved D e s i g n C r i t e r i a 8 CHAPTER I I LITERATURE REVIEW 11 2.1 G e n e r a l D i s c u s s i o n 11 2.2 S o l i d s 12 2.3 Tempera tu re 14 2.4 pH and N u i s a n c e Odours 15 2.5 Gas P r o d u c t i o n and C o m p o s i t i o n 15 2.6 D e t e n t i o n Time 17 2.7 S u c c e s s f u l Lagoon D e s i g n and O p e r a t i o n 17 CHAPTER I I I EXPERIMENTAL PROCEDURE 20 3.1 G e n e r a l D i s c u s s i o n . . . . . 20 3.2 E s t a b l i s h i n g and O p e r a t i n g the Mode l D i g e s t e r U n i t s • 22 3.3 D i g e s t e r T e m p e r a t u r e s 23 3.4 T e s t i n g P r o c e d u r e f o r the I n f l u e n t and E f f l u e n t . . . 24 i i i 3.5 T e s t i n g P r o c e d u r e f o r the E v o l v e d Gas 25 3.6 Summary 28 CHAPTER IV THE EFFECT OF DETENTION TIME 29 4.1 I n t r o d u c t i o n 29 4.2 G e n e r a l D i s c u s s i o n . . . . . 29 4 .3 Ave rage Raw Waste C h a r a c t e r i s t i c s 31 4.4 D i s c u s s i o n o f R e s u l t s 31 4.5 Gas P r o d u c t i o n and C o m p o s i t i o n 39 CHAPTER V THE EFFECT OF TEMPERATURE 46 5.1 I n t r o d u c t i o n 46 5.2 G e n e r a l D i s c u s s i o n 46 5.3 D i s c u s s i o n o f R e s u l t s 47 5.4 S t a b i l i t y o f the D i g e s t e r s 49 5.5 Gas P r o d u c t i o n and C o m p o s i t i o n 50 CHAPTER VI SETTLING - VS - BIOLOGICAL DEGRADATION 54 6.1 I n t r o d u c t i o n 54 6.2 G e n e r a l D i s c u s s i o n 55 6.3 Methane P r o d u c t i o n R e l a t e d to .COD, BOD and VS R e d u c t i o n 57 6.4 D i s c u s s i o n o f R e s u l t s • • 66 CHAPTER V I I NUTRIENTS 70 7.1 I n t r o d u c t i o n 70 7.2 Average Raw Waste and E f f l u e n t C h a r a c t e r i s t i c s . . . . 71 7.3 Ammonia-N T o x i c i t y 71 7.4 E f f e c t o f Tempera tu re on T o t a l Phospha te and Ammonia-N Removal 74 7.5 E f f e c t o f D e t e n t i o n Time on T o t a l Phospha te and Ammonia-N Removal . 76 7.6 N i t r o g e n o u s Oxygen Demand 78 CHAPTER V I I I CONCLUSIONS AND RECOMMENDATIONS 80 8.1 I n t r o d u c t i o n 80 8.2 C o n c l u s i o n s . 80 8.3 Recommendations f o r D e s i g n 83 8.4 Recommendations f o r F u t u r e S t u d i e s 84 BIBLIOGRAPHY . . 86 APPENDIX A LABORATORY RESULTS 89 APPENDIX B EFFECT OF DETENTION TIME ON COD, B0D 5 AND SOLIDS REMOVAL 105 APPENDIX C EFFECT OF TEMPERATURE ON COD, BOD5 AND SOLIDS REMOVAL 110 APPENDIX D EFFECT OF DETENTION TIME AND TEMPERATURE ON AMMONIA-N AND TOTAL PHOSPHATE REMOVAL 115 APPENDIX E SAMPLE CALCULATIONS 120 L I ST OF TABLES T a b l e Page I F IELD STUDY DESIGN PARAMETERS FOR ANAEROBIC LAGOONS TREATING HOG WASTES 13 I I AVERAGE RAW WASTE CHARACTERISTICS 32 I I I AVERAGE EFFLUENT CHARACTERISTICS 33 IV PER CENT REMOVAL OF COD, BOD 5 , TS AND VS " . . . 34 V EFFLUENT pH AND ALKALINITY 38 VI DAILY GAS PRODUCTION AS RELATED TO DETENTION TIME 40 V I I GAS COMPOSITION FOR 3 0 ° , 2 5 ° AND 1 8 - 2 3 ° C DIGESTERS (RAW WASTE ADDED DAILY) 43 V I I I GAS COMPOSITION FOR 3 0 ° , 2 5 ° AND 1 8 - 2 3 ° C DIGESTERS (NO RAW WASTE ADDITION) 43 IX PER CENT REMOVAL OF COD, BOD 5 , TS AND VS 48 X DAILY GAS PRODUCTION AS RELATED TO TEMPERATURE 52 XI PER CENT COD REDUCED BY BIOLOGICAL ACTION 60 X I I PER CENT BOD 5 REDUCED BY BIOLOGICAL ACTION 61 X I I I PER CENT VS REDUCED BY BIOLOGICAL ACTION 62 XIV AVERAGE RAW WASTE CHARACTERISTICS 72 XV AVERAGE EFFLUENT CHARACTERISTICS 73 XVI PER CENT REMOVAL OF TOTAL PHOSPHATE AND AMMONIA-N AS AFFECTED BY TEMPERATURE 75 XV I I PER CENT REMOVAL OF TOTAL PHOSPHATE AND AMMONIA-N AS AFFECTED BY DETENTION TIME 77 v i L I ST OF FIGURES F i g u r e Page 1-1 PLAN AND ELEVATION VIEWS OF THE LAGOON FAC IL IT IES 4 1-2 SECTION OF F IELD ANAEROBIC LAGOON 7 1-3 SECTION OF LABORATORY ANAEROBIC DIGESTER 7 1-4 AERIAL VIEW OF HOG BARNS AND ANAEROBIC LAGOONS 9 1-5 LABORATORY ANAEROBIC DIGESTER 9 3 - 1 CHROMATOGRAM OF DIGESTER GAS 27 4 - 1 TOTAL DAILY GAS PRODUCTION AS RELATED TO RAW WASTE ADDITION 41 6-1 PER CENT OF COD REMOVED BY BIOLOGICAL REDUCTION AS COMPARED TO THE OVERALL COD REMOVAL OVER A RANGE OF LDTs 63 6-2 PER CENT OF BODg REMOVED BY BIOLOGICAL REDUCTION AS COMPARED TO THE OVERALL BOD 5 REMOVAL OVER A RANGE OF LDTs 64 6 - 3 PER CENT OF VS REMOVED BY BIOLOGICAL REDUCTION AS COMPARED TO THE OVERALL VS REMOVAL OVER A RANGE OF LDTs 65 7- 1 LONG TERM BOD CURVE FOR RAW PIG WASTE 79 v i i A C K N O W L E D G E M E N T The a u t h o r i s d e e p l y g r a t e f u l t o h i s s u p e r v i s o r , D r . W.K. Oldham f o r h i s g u i d a n c e and encouragement d u r i n g the p r e p a r a t i o n and c o m p l e t i o n o f t h i s s t u d y . The a u t h o r i s a l s o g r a t e f u l f o r the h e l p and a s s i s t a n c e r e c e i v e d f rom h i s l o v i n g w i f e , E i j a - R i i t t a and f rom Bob Cameron, L i z a M c D o n a l d , A d r i a n Duncan and Bob Warman. T h i s i n v e s t i g a t i o n was s u p p o r t e d by the Depar tment o f N a t i o n a l H e a l t h and W e l f a r e . V a n c o u v e r , B.C. A p r i l , 1972 v i i i C H A P T E R I INTRODUCTION 1.1 G e n e r a l D i s c u s s i o n In t he p a s t d e c a d e , f o r a number o f r e a s o n s , f a r m e r s have f ound i t n e c e s s a r y to c o n c e n t r a t e g r e a t e r numbers o f a g r i c u l t u r a l a n i m a l s o n t o more c o n f i n e d l a n d a r e a s [ l ] . A l o n g w i t h the new c o n c e p t s o f f a r m i n g , t h e s e f a r m e r s a r e c o n f r o n t e d w i t h new p r o b l e m s , one o f wh i ch i s d i s p o s a l o f t he r e s u l t i n g a n i m a l w a s t e s . P r e v i o u s to t h i s when l a r g e a r e a s o f l a n d were a v a i l a b l e , t r a d i t i o n a l l a n d d i s p o s a l o f a n i m a l was te s was a s u i t a b l e s o l u t i o n . But l a n d d i s p o s a l methods f o r the newly d e v e l o p i n g h i g h d e n s i t y , c o n f i n e m e n t farms a r e no l o n g e r a c c e p t a b l e due p r i m a r i l y t o : ( i ) the d i m i n i s h e d r e l a t i v e v a l u e o f a n i m a l was te s as a f e r t i l i z e r ; ( i i ) t he q u a n t i t y o f raw waste b e i n g t oo g r e a t f o r d i r e c t l a n d d i s p o s a l w i t h o u t c r e a t i n g n u i s a n c e c o n d i t i o n s ; ( i i i ) t he p o l l u t i o n p rob lems c r e a t e d by was te s r e a c h i n g s u r r o u n d i n g w a t e r c o u r s e s o r g round w a t e r s . As a r e s u l t , the need f o r waste management by a l t e r n a t e methods has become e s s e n t i a l [ 2 ] , D u r i n g the p a s t t e n y e a r s t he a l t e r n a t i v e to was te d i s p o s a l by t r a d i t i o n a l manure s p r e a d i n g has been b i o l o g i c a l waste t r e a t m e n t . Those was te t r e a t m e n t schemes wh i ch have been u t i l i z e d s u c c e s s f u l l y a r e : (1) a c t i v a t e d s l u d g e sys tems (2) o x i d a t i o n d i t c h e s 1 2 (3) a e r a t e d l a g o o n s ( m e c h a n i c a l a e r a t i o n ) (4) a n a e r o b i c l a g o o n s . F i e l d s t u d i e s on a l l o f t h e s e t r e a t m e n t p r o c e s s e s have shown t h a t the e f f l u e n t p r o d u c e d can con fo rm to s t a n d a r d s s e t by most r e g u l a t o r y a g e n c i e s . I t seems t h e n t h a t the t r e n d i n d e s i g n f o r f u t u r e " f a c t o r y - f a r m s " i s w e l l o u t l i n e d . In o r d e r to comply to the s t a n d a r d s o f the a p p r o p r i a t e r e g u l a - t o r y a g e n c y , i n c a se s where l a n d d i s p o s a l i s no l o n g e r a d e q u a t e , some f o rm o f b i o l o g i c a l waste t r e a t m e n t i s n e c e s s a r y . The N a t i o n a l Hog C e n t r e a t A b b o t s f o r d , B.C. i s the f i r s t l a r g e - s c a l e h i g h d e n s i t y h o g - r a i s i n g f a c i l i t y t o be e s t a b l i s h e d i n the F r a s e r V a l l e y . From t h i s i n s t a l l a t i o n 2 2 , 0 0 0 m a r k e t a b l e hogs p e r y e a r w i l l be b o r n , weaned, and f i n i s h e d w i t h i n b u i l d i n g s whose t o t a l f l o o r a r e a i s 1 0 0 , 0 0 0 s q . f t . The r e s u l t i n g vo lume and s t r e n g t h o f waste f rom such an i n d u s t r y i s c o n s i d e r a b l e . As t h i s was te i s t o be d i s c h a r g e d i n t o the F r a s e r R i v e r , the P r o v i n c i a l P o l l u t i o n C o n t r o l B r anch (PPCB) s t i p u l a t e d t h a t was te t r e a t m e n t be p r o v i d e d . However, beca u se knowledge o f the was te l o a d o r c h a r a c t e r i s t i c s was l a c k i n g , the deg ree o f t r e a t m e n t to be p r o v i d e d was n o t s p e c i f i c a l l y s t i p u l a t e d . The N a t i o n a l Hog C e n t r e r e t a i n e d a c o n - s u l t i n g f i r m wh i ch s t u d i e d numerous t r e a t m e n t schemes and d e r i v e d a w o r k i n g a r rangement w h i c h was a g r e e a b l e to b o t h the PPCB and N a t i o n a l Hog. The f i r m ' s s t u d y o f t r e a t m e n t schemes took i n t o c o n s i d e r a t i o n a n t i c i p a t e d waste c h a r a c t e r i s t i c s , t r e a t m e n t e f f i c i e n c i e s , l a n d a r e a r e q u i r e m e n t s , i n i t i a l c a p i t a l o u t l a y and p r e s e n t l a n d v a l u e s . The f i n a l p r o p o s a l i n - v o l v e d t r e a t m e n t by a n a e r o b i c l a g o o n s . The o v e r a l l p l a n s i n c l u d e d b u i l t - i n v e r s a t i l i t y so t h a t m e c h a n i c a l a e r a t i o n d e v i c e s c o u l d be i n s t a l l e d i f 3 t r e a t m e n t e f f i c i e n c y had to be i n c r e a s e d . 1.2 D e s i g n and Layou t o f T rea tment F a c i l i t i e s (a) D e s i g n The t r e a t m e n t a c c e p t e d by the PPCB, c o n s i s t e d o f a t h r e e - c e l l s y s t e m . The f i r s t two c e l l s , o r p r i m a r y l a g o o n s , a r e o f 300,000 c u . f t . c a p a c i t y each w i t h a w a t e r d e p t h o f 15 f e e t . These were b u i l t t o a c t as s e t t l i n g ponds w i t h the added b e n e f i t o f a n a e r o b i c b i o l o g i c a l a c t i v i t y . D u r i n g r o u t i n e fa rm o p e r a t i o n the two p r i m a r y ponds a r e u sed a l t e r n a t e l y one " r e s t i n g " w h i l e t he o t h e r i s i n s e r v i c e . Removal f r e q u e n c y o f accumu- l a t e d s l u d g e f rom a l t e r n a t e c e l l s was e s t i m a t e d t o be e v e r y t h r e e t o f i v e y e a r s . T h i s removed s l u d g e wou ld be w e l l d e g r a d e d , r e d u c e d i n vo lume and s u i t a b l e f o r l a n d d i s p o s a l . The t h i r d c e l l o f the s y s tem was d e s i g n e d f o r 100,000 c u . f t . c a p a c i t y w i t h a wa te r d e p t h o f 11 f e e t . I t a c c e p t s t he l i q u i d o v e r f l o w f rom w h i c h e v e r p r i m a r y c e l l i s i n use and p r o v i d e s f u r t h e r d e t e n t i o n f o r the s u p e r n a t a n t . A n a e r o b i c d e c o m p o s i t i o n o f t he d i s s o l v e d and c o l l o i d a l o r g a n i c s c o n t i n u e s i n t h i s c e l l . The o v e r f l o w f r om t h i s f i n a l c e l l i s c o n t i n u a l l y c h l o r i n a t e d and d i s c h a r g e d to the F r a s e r R i v e r . I t i s t o t h i s t h i r d c e l l t h a t m e c h a n i c a l a e r a t i o n d e v i c e s w i l l be added i f an i n c r e a s e i n t r e a t m e n t e f f i c i e n c y becomes n e c e s s a r y . (b) Layou t The p l a n and e l e v a t i o n v i ews o f the l a g o o n f a c i l i t i e s a r e i l l u s t r a t e d i n F i g u r e 1-1. 4 P R I M A R Y L A G O O N S S E C T I O N O F L A G O O N FIGURE 1-1 PLAN fie ELEVATION VIEWS OF THE LAGOON FAC IL IT IES 1.3 Fundamenta l s o f A n a e r o b i c Lagoons The o b j e c t i n l a g o o n i n g o f c o n c e n t r a t e d a n i m a l was tes i s t o s t a b i l i z e to some deg ree the i n c o m i n g o r g a n i c s by b i o l o g i c a l means. The b i o l o g i c a l a n a e r o b i c p r o c e s s may be g e n e r a l l y d e s c r i b e d as t h r e e - p h a s e ( i ) H y d r o l y s i s o f complex m a t e r i a l ; ( i i ) A c i d p r o d u c t i o n - c o n v e r s i o n o f complex o r g a n i c s i n the raw waste to m o s t l y a c i d i n t e r m e d i a t e - p r o d u c t s by a c i d - f o r m i n g b a c t e r i a ; ( i i i ) Gas p r o d u c t i o n - c o n v e r s i o n o f the a c i d i n t e r m e d i a t e - p r o d u c t s t o methane and c a r b o n d i o x i d e l a r g e l y by methane f o r m i n g b a c t e r i a . In o r d e r f o r t h i s s y s tem t o be s u c c e s s f u l , the. raw was te must have a h i g h f o o d v a l u e so as t o s u s t a i n the m e t a b o l i c a c t i v i t y o f t h e b a c t e r i a . The f o o d v a l u e i s measured by the c o n c e n t r a t i o n o f b i o c h e m i c a l oxygen demand (BOD) and v o l a t i l e su spended s o l i d s (VSS) . The h i g h e r t h e s e v a l u e s a r e the more s u i t a b l e the f o o d s o u r c e i s f o r a n a e r o b i c d i g e s t i o n . I n i t i a l l y the s o l i d s i n a n i m a l was te s a r e i n s u s p e n s i o n and a l a r g e p o r t i o n o f the s o l i d s s e t t l e ou t i n the p r i m a r y l a g o o n . However, as opposed t o the u s u a l s e p a r a t i o n and r e m o v a l o f s e t t l e d s o l i d s , the s e t t l e d s o l i d s a r e a l l o w e d to a c c u m u l a t e i n the l a g o o n and the a c c u m u l a t e d s o l i d s p r o v i d e a s u i t a b l e s u b s t r a t e f o r a n a e r o b i c breakdown. The o v e r l y i n g waste w a t e r c o n t a i n i n g d i s s o l v e d and c o l l o i d a l s o l i d s b l a n k e t s the s e t t l e d s o l i d and s e r v e s two i m p o r t a n t f u n c t i o n s : ( i ) i t has a h i g h oxygen demand wh i ch p r e v e n t s 6 d i f f u s i o n o f f r e e oxygen to the bo t tom d e p o s i t s , a n d ; ( i i ) i t p r o v i d e s a b u f f e r i n g mechanism t h r o u g h d i l u t i o n and d i s p e r s i o n f o r shock was te l o a d i n g s . Under t h e s e c o n d i t i o n s the a n a e r o b i c b a c t e r i a t h r i v e i n the l a g o o n s and degrade the o r g a n i c s o l i d s w i t h c o n s e q u e n t p r o d u c t i o n o f methane ( C H ^ , c a r b o n d i o x i d e ( C 0 2 ) and t r a c e g a s e s . The e v o l v e d gas b u b b l e s t o the s u r f a c e and f i n a l l y d i f f u s e s t o the a t m o s p h e r e . A n a e r o b i c l a g o o n i n g t h e n i s a combined t w o - p a r t p r o c e s s o f (1) s o l i d s r e m o v a l and c o n c e n t r a t i o n by s e t t l i n g and (2) o r g a n i c s r e - d u c t i o n by b i o l o g i c a l means. I t s h o u l d be n o t e d t h a t the r e s u l t i n g e f f l u e n t s t r e n g t h i s s t i l l c o n s i d e r a b l e due i n p a r t t o r e s u s p e n s i o n o f s o l i d s by gas a g i t a t i o n and to i n c o m p l e t e breakdown o f the o r g a n i c s . A c r o s s - s e c t i o n o f a t y p i c a l l a g o o n i s shown i n F i g u r e 1-2. 1.4 Compar i son o f F i e l d Lagoon and L a b o r a t o r y D i g e s t e r L a b o r a t o r y - s c a l e a n a e r o b i c r e a c t i o n v e s s e l s were b u i l t t o s i m u - l a t e the p r i m a r y f i e l d l a g o o n . F o l l o w i n g the work w i t h l a b d i g e s t e r s t he sub sequent s t e p would be f i e l d s t u d i e s wh i ch wou ld be c o n d u c t e d to c o r - r e l a t e the l a b - s c a l e and f u l l - s c a l e r e s u l t s . I f s u c c e s s f u l i n t h i s a r e a o f the work i t would become p o s s i b l e to t e s t the a n a e r o b i c t r e a t a b i l i t y o f most a n i m a l was te s i n the l a b o r a t o r y and d e t e r m i n e w i t h a c c e p t a b l e a c c u r a c y the d e s i g n c r i t e r i a t h a t must be u sed on the f u l l - s c a l e i n s t a l l a t i o n s t o a c h i e v e a g i v e n t r e a t m e n t e f f i c i e n c y . A c r o s s - s e c t i o n o f the l a b o r a t o r y 7 RAINFALL RAW WASTE EVAPORATION A T M O S P H E RE ^ EVOLVED GAS AGITATED SUPERNATANT / / / / , SLU D G E SUPERNATANT S ludge — C o n s i s t s o f s e t t l e d s o l i d s p l u s a n a e r o b e s A g i t a t e d S u p e r n a t a n t — I n c l u d e s d i s s o l v e d and c o l - l o i d a l s o l i d s ; r e - s u s p e n d e d s o l i d s due to gas a g i t a t i o n ; p l u s a n a e r o b e s C r u s t — C o n s i s t s o f v o l a t i l e m a t t e r p l u s g r a i n h u l l s , h a i r , and wood f i b r e s E v o l v e d Gas — C o n s i s t s o f CH^, C0 2 p l u s t r a c e gases Atmosphere — 0 2 , N 2 p l u s t r a c e gases FIGURE 1-2 SECTION OF F IELD ANAEROBIC LAGOON EVAPORATION EVOLVED GAS '////X. R U S I////, RAW WASTE ATMOSPHERE SUPERNATANT Atmosphere — C H 4 , C 0 2 p l u s t r a c e gases FIGURE 1-3 SECTION OF LABORATORY ANAEROBIC DIGESTER d i g e s t e r i s shown i n F i g u r e 1-3 and can be compared to the f i e l d f a c i l i t y i l l u s t r a t e d i n F i g u r e 1-2. An a e r i a l v i ew o f the fa rm and a p h o t o g r a p h o f the l a b o r a t o r y s e t - u p a r e shown i n F i g u r e s 1-4 and 1-5. 1.5 Need f o r Improved D e s i g n C r i t e r i a G u i d e l i n e s f o r t he d e s i g n o f t he a n a e r o b i c l a g o o n s i n u se a t t he N a t i o n a l Hog C e n t r e were d e t e r m i n e d f rom knowledge o f t r e a t m e n t e f f i c i e n c i e s o f o p e r a t i n g f a c i l i t i e s i n the U n i t e d S t a t e s and f rom d e s i g n g u i d e l i n e s w h i c h had e v o l v e d o v e r the y e a r s f rom e x p e r i e n c e w i t h t h e s e l a g o o n s . W i t h the many u n c e r t a i n t i e s i n v o l v e d i n t he d e s i g n and o p e r a t i o n o f a n a e r o b i c l a g o o n s f o r c o n c e n t r a t e d a n i m a l was te s and beca u se o f a l a c k o f d e f i n i t e d e s i g n p a r a m e t e r s f o r l a g o o n s , t h i s l a b o r a t o r y s t u d y was u n d e r - t a k e n to d e v e l o p i m p r o v e d d e s i g n g u i d e l i n e s . The g e n e r a l d e s i g n o f a l a g o o n can be s i m p l e i f no c o n s i d e r a t i o n i s g i v e n t o the w o r k i n g s w i t h i n the l a g o o n . The d e s i g n e r , g i v e n the a v e r a g e c h a r a c t e r i s t i c s and f l o w o f the raw w a s t e , the r e q u i r e d e f f l u e n t q u a l i t y (as s e t by the r e g u l a t o r y agency ) and the f i e l d s t u d y d a t a c o l l e c t e d on s i m i l a r e x i s t i n g f a c i l i t i e s can d e t e r m i n e a w o r k a b l e l a g o o n vo lume f o r adequa te t r e a t m e n t . C o n s i d e r i n g o n l y the " i n " and " o u t " was te v a l u e s i s n o t w h o l l y a d e q u a t e . E s s e n t i a l i t e m s wh i ch a r e m i s s i n g i n such a d e s i g n method a r e : ( i ) the r a t e o f b u i l d - u p o f s o l i d s and hence the r e q u i r e d f r e q u e n c y o f s l u d g e r e m o v a l ; ( i i ) the r a t e o f o r g a n i c s o l i d s d e s t r u c t i o n by a n a e r o b i c b a c t e r i a ; AERIAL VIEW OF HOG BARNS AND ANAEROBIC LAGOONS FIGURE 1-4 LABORATORY ANAEROBIC DIGESTER FIGURE 1-5 10 ( i i i ) the effect of solids build-up on treatment efficiencies; (iv) the effect of temperature on the waste treatment operation; (v) the effect of gas evolution in mixing the lagoon contents and on the quality of the lagoon effluent. These then were some of the specific points which this research study centered on. Included with the study and related to the above points were the effects of such parameters as raw waste loading rate and nutrient concentration. In the f i n a l analysis the purpose of this study was to provide information which would assist in optimizing c r i t e r i a for the design of anaerobic treatment for concentrated animal wastes. C H A P T E R I I LITERATURE REVIEW 2.1 G e n e r a l D i s c u s s i o n E a r l y manure l a g o o n s were o f t e n m i s t a k e n l y p a t t e r n e d a f t e r a e r o b i c l a g o o n s w i t h o u t due c o n s i d e r a t i o n t o the a n i m a l waste c h a r a c t e r - i s t i c s o r the p r i n c i p l e s i n v o l v e d i n t r e a t i n g such w a s t e s . R e c e n t l i t e r a t u r e on d e s i g n c r i t e r i a f o r l a g o o n s s p e c i f i c a l l y s t a t e s t h a t manure pond d e s i g n s h o u l d be ba sed on vo lume c o n s i d e r a t i o n s r a t h e r than on s u r f a c e r e l a t i o n s h i p s so commonly u s e d to d e s i g n waste w a t e r ponds [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ] . As a n a e r o b i c b a c t e r i a need n e i t h e r s u n l i g h t n o r oxygen f o r s u r v i v a l , s u r - f a c e a r e a r e q u i r e m e n t s need n o t even be c o n s i d e r e d i n t h i s scheme o f t r e a t - ment d e s i g n . C o n s e q u e n t l y , p r e s e n t d e s i g n methods have been d e v e l o p e d on a v o l u m e t r i c b a s i s . Some o f the p a r a m e t e r s wh i ch have been q u o t e d f o r d e s i g n i n g l a g o o n f a c i l i t i e s a r e : ( i ) c u . f t . o f l a g o o n / l b . o f a n i m a l ; ( i i ) l b . BOD/cu. f t . o f l a g o o n / d a y ; ( i i i ) l b . v o l a t i l e s o l i d s ( V S ) / c u . f t . o f l a g o o n / d a y . In the f i r s t c a s e , a l l t h a t i s r e q u i r e d to d e t e r m i n e the l a g o o n volume i s the t o t a l we i gh t o f a n i m a l s t o be accommodated w h i l e the second and t h i r d d e s i g n p r o c e d u r e s r e q u i r e some knowledge o f the a n i m a l waste c h a r a c t e r i s t i c s and the amount o f waste p r o d u c e d p e r day . Of t h e s e t h r e e d e s i g n p a r a m e t e r s , the f i r s t two a r e g a i n i n g w i d e r a c c e p t a n c e . T h i s i s due to the f a c t t h a t l i v e s t o c k manures u s u a l l y c o n t a i n l a r g e q u a n t i t i e s 11 12 o f hay s t ems , g r a i n h u l l s and s i m i l a r n o n - b i o d e g r a d a b l e bu t v o l a t i l e m a t t e r . Thus the l b . V S / c u . f t . o f l a g o o n / d a y i s i n a p p r o p r i a t e and l e s s r e l i a b l e i n d e t e r m i n i n g adequate l a g o o n s i z e s . Some o f the v a l u e s o b t a i n e d f r om f i e l d r e s e a r c h and w h i c h have been u sed f o r d e s i g n a r e o u t l i n e d i n T a b l e I. Removal e f f i c i e n c i e s r e p o r t e d on a few o f the above l a g o o n s by t h e s e same r e s e a r c h e r s show: 75-80% t o t a l s o l i d s (TS) r e m o v a l , 85-90% VS and c h e m i c a l oxygen demand (COD) r e m o v a l , 60-70% BOD r e m o v a l . I t s h o u l d be n o t e d however t h a t t h e s e v a l u e s a r e m i s l e a d i n g and one must n o t l o s e s i g h t o f t he f a c t t h a t l a g o o n i n g e s s e n t i a l l y a f f o r d s p r i m a r y t r e a t m e n t f o r t he i n c o m i n g was te and the e f f l u e n t i s s t i l l r a t h e r p o t e n t . 2.2 S o l i d s R e l a t e d to the h i g h p e r c e n t r e m o v a l o f VS f o r c o n c e n t r a t e d a n i m a l was tes i s the d e c r e a s e i n e f f e c t i v e waste r e t e n t i o n c a p a c i t y o f t he l a g o o n due to s o l i d s a c c u m u l a t i o n [ 9 ] . The s l u d g e b u i l d - u p r a t e has been found to be a f u n c t i o n o f b o t h the l o a d i n g r a t e o f VS , the r a t e o f b i o l o g - i c a l d e g r a d a t i o n o f VS and a l s o to some e x t e n t to the washout o f VS. But even a b a l a n c e d m i c r o b i a l p o p u l a t i o n w i l l n o t r e d u c e a l l the o r g a n i c m a t e r i a l to gaseous e n d - p r o d u c t s and i n e v i t a b l y a f i n i t e s e r v i c e l i f e f o r waste l a g o o n s w i l l be r e a c h e d ( i . e . s o l i d s b u i l d - u p w i l l become a p r o b l e m ) . Two a l t e r n a t i v e s o l u t i o n s to t h i s p r o b l e m o f f e r e d by p r e s e n t d e s i g n 13 TABLE I F IELD STUDY DESIGN PARAMETERS FOR ANAEROBIC LAGOONS TREATING HOG WASTES R e f e r e n c e // R e s e a r c h e r R e q u i r e d Lagoon Volume 5 8 9 H a r t & T u r n e r C l a r k Dornbush & A n d e r s o n H a r t & T u r n e r R i c k e t t s W i l l r i c h Anon W i l l r i c h Eby W i l l r i c h C u r t i s Wh i te Dornbush Dornbush & A n d e r s o n 2 . 5 - 5 . 0 l b VS/1000 f t 3 / d a y 475 f t 3 / h o g 130-170 f t 3 / h o g 124 f t 3 / a n i m a l 0 .3 f t 3 / l b a n i m a l 1.6 f t 3 / l b a n i m a l 0 .9 f t 3 / l b a n i m a l 1.8 f t 3 / l b a n i m a l 0 . 4 - 1 . 4 f t 3 / l b a n i m a l 1 .0 -2 .0 f t 3 / l b a n i m a l 75-100 f t 3 / h o g 10-20 l b BOD/1000 f t 3 / d a y 15-20 l b BOD/1000 f t 3 / d a y 5-10 l b VS/1000 f t 3 / d a y 14 p r o c e d u r e a r e : (1) p e r i o d i c d r e d g i n g w i t h o u t c o n s i d e r a t i o n o f s l u d g e d e p t h ; (2) d e s i g n i n g a g i v e n s l u d g e s t o r a g e l i f e i n t o the l a g o o n s by e s t i m a t i n g the c u . f t . o f s l u d g e p r o d u c e d / 1 0 0 l b . a n i m a l / y e a r [ 3 ] , and the r a t e o f s o l i d s d e g r a d a t i o n . From t h i s a d r e d g i n g f r e q u e n c y o f t he l a g o o n c o u l d t h e n be c a l c u l a t e d b a s e d on a p r e - d e t e r m i n e d l e v e l f o r maximum s o l i d s b u i l d - u p . The s e c o n d e s t i m a t e assumes a c o n s t a n t s o l i d s c o n c e n t r a t i o n f o r the s l u d g e . T h i s i s a rough e s t i m a t e o n l y , f o r as the s l u d g e a c c u m u l a t e s w i t h i n the pond i t compacts and o c c u p i e s l e s s s p a c e . T h i s wou ld a l t e r any o r i g i n a l d e s i g n e s t i m a t e f o r c l e a n o u t f r e q u e n c y . 2.3 T e m p e r a t u r e B i o l o g i c a l a c t i v i t y under a n a e r o b i c c o n d i t i o n s i s e x t r e m e l y t e m p e r a t u r e s e n s i t i v e [ 3 , 5 , 8 , 9 ] . As r e p o r t e d f rom l a b o r a t o r y s t u d i e s and v e r i f i e d by f i e l d s t u d i e s , a n a e r o b i c a c t i o n i s v i g o r o u s under summer t e m - p e r a t u r e c o n d i t i o n s ( 2 5 - 3 5 ° C ) w i t h l i t t l e a c t i v i t y under w i n t e r t e m p e r a t u r e c o n d i t i o n s ( 0 - 1 0 ° C ) . Of e q u a l c o n c e r n i s the r a t e a t wh i ch t e m p e r a t u r e f l u c t u a t i o n s o c c u r w i t h i n the t r e a t m e n t s y s t e m . I t has been d e t e r m i n e d t h a t a s l ow r a t e o f t e m p e r a t u r e change a l l o w s a n a e r o b i c b a c t e r i a t o a d j u s t somewhat to the new c o n d i t i o n s and to c o n t i n u e b i o l o g i c a l a c t i v i t y . On the o t h e r h a n d , 15 r a p i d t e m p e r a t u r e f l u c t u a t i o n s have been f ound to c o m p l e t e l y a r r e s t a n a e r - o b i c , a c t i o n [ l 2 J . In o r d e r to p r o v i d e p r o t e c t i o n and i n s u l a t i o n a g a i n s t r a p i d t e m p e r a t u r e c h a n g e s , l a g o o n d e s i g n c r i t e r i a s h o u l d i n c l u d e m i n i m i z i n g expo sed s u r f a c e a r e a and m a x i m i z i n g d e p t h . 2.4 pH and N u i s a n c e Odours D u r i n g the o p e r a t i o n o f a s u c c e s s f u l l a g o o n the pH s h o u l d be m a i n t a i n e d n e a r n e u t r a l w i t h an optimum range f rom 6 . 8 - 7 . 2 . V a r i a n c e s f rom t h e s e c o n d i t i o n s r e s u l t i n ma lodourous c o n d i t i o n s and d e c r e a s e d b i o - l o g i c a l a c t i v i t y . Dornbush [ 9 ] d e s c r i b e s t h i s s i t u a t i o n : "Meager i n f o r m a t i o n seems t o p o i n t t he a c c u s - i n g f i n g e r a t s l u d g e a c c u m u l a t i o n s on the b o t t o m o f l a g o o n s as b e i n g a ma jo r s o u r c e o f n u i s a n c e o d o r s . W i th low t e m p e r a t u r e s o r an i n a d e q u a t e p o p u l a t i o n o f methane f o r m e r s , the f i r s t s t a g e o f d i g e s t i o n , t h a t o f a c i d f o r m a t i o n , w i l l p r o c e e d w i t h i n the s l u d g e a c c u m u l a t i o n s . The r e s u l t i n g o r g a n i c a c i d s wou ld q u i c k l y e x c e e d the l i m i t e d b u f f e r i n g w i t h i n the s l u d g e d e p o s i t s and the pH wou ld b e g i n t o d rop to f u r t h e r l i m i t the p e r f o r m a n c e o f t he methane f o r m e r s . O r g a n i c a c i d s wou ld be e x p e c t e d t o a c c u m u l a t e and an a c i d s l u d g e bank o r " p o c k e t " wou ld d e v e l o p . I t i s h y p o t h e s i z e d t h a t t h e s e a c i d s l u d g e banks a r e a ma jo r s o u r c e o f o d o r s i n l a g o o n s . Odors w i l l be p r o d u c e d i n the a c i d s l u d g e u n t i l t h i s l o c a l i z e d " p i c k l i n g " e n v i r o n m e n t i s a l t e r e d e i t h e r t h r o u g h d i s p e r s i o n by m i x i n g , pH a d j u s t m e n t , o r deve lopment o f an adequate p o p u l a t i o n o f methane f o r m e r s t o b r e a k down the a c i d s . " 2.5 Gas P r o d u c t i o n and C o m p o s i t i o n M c C a r t y [ l l ] o u t l i n e s the r e l a t i o n s h i p between waste s t a b i l i - z a t i o n and methane gas f o r m a t i o n a s : 16 From t h i s e q u a t i o n i t i s t h e o r e t i c a l l y p o s s i b l e to p r e d i c t the q u a n t i t y o f methane p r o d u c e d f rom a knowledge o f the waste c h e m i c a l c o m p o s i t i o n d u r i n g c o m p l e t e breakdown o f the w a s t e . The u l t i m a t e oxygen demand o f methane gas may be d e s c r i b e d as f o l l o w s : CH, + 2C> CC- + 2H 0 (2) 4 2 2 2 E q u a t i o n (2) a l l o w s p r e d i c t i o n o f COD o r BOD L ( u l t i m a t e BOD) s t a b i l i z a t i o n f rom the vo lume o f methane p r o d u c e d . T h i s c h e m i c a l e q u a t i o n shows one mole o f methane i s e q u i v a l e n t to two mo les o f oxygen . F u r t h e r c a l c u l a t i o n shows t h a t 5.62 c u . f t . CH^ (STP) w i l l be p r o d u c e d p e r l b . o f oxygen u t i l i z e d . Measured v a l u e s f o r methane p r o d u c t i o n p e r pound o f COD o r BOD^ s t a b i l i z a t i o n f o r a w ide v a r i e t y o f was tes f r om p u r e l a b o r a t o r y s u b s t r a t e s t o complex was te s have shown the v a l i d i t y o f t h i s r e l a t i o n s h i p and the c l o s e a c c u r a c y w i t h wh i ch i t can be u s e d to p r e d i c t methane p r o - d u c t i o n [ 1 0 , 1 1 ] . Gas a g i t a t i o n i s a l s o i m p o r t a n t . Gas a g i t a t i o n appea r s t o improve the l a g o o n a c t i o n by r e d i s t r i b u t i n g and mak ing a v a i l a b l e u n d i g e s t e d o r g a n i c m a t e r i a l f o r b a c t e r i a l u t i l i z a t i o n [ 3 , 4 , 5 ] . D e s i g n f o r m e c h a n i c a l m i x i n g i s t h e r e f o r e u s u a l l y no t n e c e s s a r y i f v i g o r o u s b i o l o g i c a l a c t i v i t y can be m a i n t a i n e d . Gas m i x i n g w i t h i n the l a g o o n i s i n d i c a t e d by the c o n - s t a n t r a i s i n g o f bo t tom s l u d g e to the l a g o o n s u r f a c e [ 7 ] , W i th r e g a r d to gas c o m p o s i t i o n , the gaseous e n d - p r o d u c t s c o n - s i s t o f methane , c a r b o n d i o x i d e and t r a c e g a s e s . T a i g i n i d e s [ 6 ] , s t u d y i n g 17 a n a e r o b i c d i g e s t i o n o f hog was tes a t 3 5 ° C , r e p o r t e d t h a t d u r i n g s u c c e s s f u l a n a e r o b i c t r e a t m e n t o f swine was te s 59% o f the gas was methane and 40% c a r b o n d i o x i d e . 2.6 D e t e n t i o n Time In a d d i t i o n t o the o r g a n i c l o a d i n g t o the l a g o o n i n g s y s tem m e n t i o n e d i n s e c t i o n 2 . 1 , t he was te r e t e n t i o n t ime must a l s o be g i v e n c o n s i d e r a t i o n . E c k e n f e l d e r [ l O ] s t a t e s t h a t : " . . . s u f f i c i e n t t ime must be a v a i l a b l e i n the r e a c t o r t o p e r m i t g rowth o f t he o r g a n i s m s o r t hey w i l l be washed out o f the s y s t e m . " I t has been d e t e r m i n e d t h a t t he methane b a c t e r i a g rowth r a t e gove rn s and t h a t f o r d e t e n t i o n t imes o f l e s s t han 7 days some o r gan i sms w i l l b e g i n to be washed out o f the t r e a t m e n t s y s t e m . 2.7 S u c c e s s f u l Lagoon D e s i g n and O p e r a t i o n Recommended g e n e r a l p r o c e d u r e s f o r hog was te l a g o o n d e s i g n and o p e r a t i o n a r e summar ized f rom the a v a i l a b l e l i t e r a t u r e [ 5 , 8 , 9 , 1 0 ] and a r e as f o l l o w s : (a) D e s i g n - ( i ) vo lume r e q u i r e m e n t s s h o u l d be b a s e d on 3 / 4 - l % c u . f t . / l b . a n i m a l ; 10 -20 l b . BOD/1000 c u . f t . / d a y o r 3 . 5 - 7 . 0 l b . VS/1000 c u . f t . / d a y w i t h c o n s i d e r a t i o n f o r s l u d g e vo lume b u i l d - u p (15-20 c u . f t . / l O O l b . h o g / y e a r ) ; 18 ( i i ) r a p i d t e m p e r a t u r e f l u c t u a t i o n s wh i ch a d v e r s e l y a f f e c t methane p r o d u c i n g b a c t e r i a s h o u l d be m i n i m i z e d i n t he l a g o o n by m i n i m i z i n g the exposed s u r f a c e a r e a and m a x i m i z i n g the d e p t h ; ( i i i ) i n o r d e r to a v o i d s e v e r e r e t a r d a t i o n o f b i o l o g i c a l a c t i v i t y t he t e m p e r a t u r e i n the l a g o o n s h o u l d n o t drop be low a s p e c i f i e d minimum ( i . e . 2 0 ° C ) ; ( i v ) i n o r d e r to p r e v e n t the p o s s i b l e c o n - t a m i n a t i o n o f s u r r o u n d i n g w a t e r s u p p l i e s t he s o i l c h a r a c t e r i s t i c s and l o c a t i o n o f t he l a g o o n s h o u l d be c o n s i d e r e d w i t h r e g a r d t o i n f i l t r a t i o n , g round w a t e r t a b l e and u n c o n t r o l l e d r u n o f f due t o s t o r m s ; (v) the r e t e n t i o n banks o f the l a g o o n s h o u l d be s l o p e d a d e q u a t e l y t o e n s u r e s o i l s t a b i l i t y ; ( v i ) the raw was te s h o u l d be d i s c h a r g e d i n t o the c e n t r a l a r e a o f t he l a g o o n t h r o u g h submerged i n l e t s . B a f f l e s s h o u l d be p r o v i d e d a t t he o u t l e t s t o d e c r e a s e the p o s s i b i l i t y o f s h o r t - c i r c u i t i n g ; ( v i i ) a f e n c e s h o u l d be p r o v i d e d a round the l a g o o n as a s a f e t y p r e c a u t i o n . O p e r a t i o n - ( i ) i f p o s s i b l e t he o p e r a t i o n o f the l a g o o n s h o u l d commence i n l a t e s p r i n g o r e a r l y summer to t ake advantage o f the n a t u r a l warming t r e n d to a i d i n e s t a b l i s h i n g a v i a b l e b a c t e r i a c u l t u r e ; ( i i ) t he pH range s h o u l d be between 6.8 and 7.4 s i n c e the b a c t e r i a a r e most a c t i v e a t n e u t r a l pH ; ( i i i ) t he d e s i g n w a t e r l e v e l s h o u l d be m a i n - t a i n e d so t h a t t h e s o l i d s a r e c o v e r e d a t a l l t imes and n o t i n d i r e c t c o n t a c t w i t h a t m o s p h e r i c oxygen . T h i s a l l o w s immed ia te and c o n t i n u o u s a n a e r o b i c d i g e s t i o n o f s o l i d s . C H A P T E R I I I EXPERIMENTAL PROCEDURE 3.1 G e n e r a l D i s c u s s i o n A l l n e c e s s a r y i n i t i a l p r e p a r a t i o n s had been c o m p l e t e d i n advance o f the s t a r t i n g t ime f o r t h i s s t u d y . T h i s i n c l u d e d a l i t e r a t u r e i n v e s t i g a t i o n on hog was te c h a r a c t e r i s t i c s and t r e a t m e n t , a p rogram f o r t he f i e l d c o l l e c t i o n o f raw was tes and d e s i g n o f a t e n t a t i v e s e t o f e x - p e r i m e n t s f o r the a n a l y s i s o f b o t h raw waste and e f f l u e n t s a m p l e s . The e x p e r i m e n t a l p r o c e d u r e s u sed a r e o u t l i n e d i n S t a n d a r d Methods [ 15 ] and f u r t h e r e x p l a i n e d i n C h e m i s t r y f o r S a n i t a r y E n g i n e e r s [ 1 6 ] , A d d i t i o n a l p r e p a r a t i o n s i n c l u d e d the a s semb ly o f f o u r mode l d i g e s t e r s o f 25 l i t r e c a p a c i t y c o n s t r u c t e d f rom t r a n s p a r e n t a c r y l i c p l a s t i c ( F i g u r e 1 -5 ) , the d e s i g n o f a gas c o l l e c t i o n a p p a r a t u s and the d e s i g n o f a s u i t a b l e method f o r gas a n a l y s i s . T h r e e o f the d i g e s t e r u n i t s were t e m p e r a t u r e c o n t r o l l e d w h i l e the t e m p e r a t u r e o f the f o u r t h d i g e s t e r was a l l o w e d t o m a i n t a i n amb ient room t e m p e r a t u r e ( 1 8 ° - 2 3 ° C ) . E x t e r n a l h e a t i n g t a p e s r e g u l a t e d by a t h e r m o - s t a t mechanism were used to m a i n t a i n two o f the d i g e s t e r t e m p e r a t u r e s ( 2 5 ° C and 3 0 ° C ) . S i n c e the ambient l a b o r a t o r y t e m p e r a t u r e was c o n t i n u a l l y above 1 8 ° C , the 10°C d i g e s t e r u n i t was c o o l e d by i n t e r n a l c o o l i n g c o i l s . The t y p e o f t h e r m o s t a t mechanism used w i t h t h i s u n i t was i d e n t i c a l to t h a t i n the h e a t e d d i g e s t e r s . In t h i s c a s e however the t h e r m o s t a t s i m p l y a c t i v a t e d a c o o l i n g wa te r c i r c u l a t i o n pump as r e q u i r e d . 20 21 W i th the 25 l i t r e c a p a c i t y o f the d i g e s t e r u n i t s t o work w i t h , some range o f d e t e n t i o n t imes had to be d e c i d e d upon. An upper l i m i t o f 50 days was cho sen b e c a u s e i t r e p r e s e n t e d a r e a l i s t i c f i g u r e i n terms o f t he f i e l d l a g o o n s a t A b b o t s f o r d . Work ing f rom t h i s upper l i m i t , the d e - t e n t i o n t imes were to be d e c r e a s e d o v e r a p e r i o d o f months i n a s t e p w i s e manner to some l ower l i m i t . T h i s l o w e r l i m i t was e x p e c t e d to be the p o i n t a t w h i c h t r e a t m e n t e f f i c i e n c y wou ld be m a r k e d l y r e d u c e d . The i n i t i a l d e - t e n t i o n t ime r e p r e s e n t e d a d a i l y f e e d i n g r a t e o f % l i t r e o f raw was te to each d i g e s t e r . E q u i p p e d w i t h t h i s o u t l i n e the a im t h e n was to c o l l e c t s u f f i - c i e n t and s a t i s f a c t o r y e x p e r i m e n t a l d a t a t h r o u g h the v a r i o u s d e t e n t i o n p e r i o d s . T h i s r e p r e s e n t e d d a i l y and week ly waste s a m p l i n g , c o m p l e t i n g e x p e r i m e n t s i n d u p l i c a t e and t r i p l i c a t e , and r e - r u n n i n g e x p e r i m e n t s where l a r g e changes o r d i s c r e p a n c i e s i n the raw was te o r e f f l u e n t c h a r a c t e r i s t i c s o c c u r r e d . I t was a n t i c i p a t e d t h a t t h i s t e s t i n g p rogram wou ld d e t e r m i n e the e f f e c t s o f s e t t l i n g , t e m p e r a t u r e , and d e t e n t i o n t ime on the a n a e r o b i c d i g e s t i o n p r o c e s s . F o r c l a r i t y t he e x p e r i m e n t a l p r o c e d u r e i s d i v i d e d i n t o f o u r ma jo r h e a d i n g s : ( i ) e s t a b l i s h i n g and o p e r a t i n g the mode l d i g e s t e r u n i t s ; ( i i ) d i g e s t e r t e m p e r a t u r e s ; ( i i i ) t e s t i n g p r o c e d u r e f o r the e f f l u e n t and i n f l u e n t ; ( i v ) t e s t i n g p r o c e d u r e f o r t he e v o l v e d ga s . 22 3.2 E s t a b l i s h i n g and O p e r a t i n g the Mode l D i g e s t e r U n i t s A number o f months were r e q u i r e d to e s t a b l i s h a v i a b l e c u l t u r e o f a n a e r o b i c b a c t e r i a i n the d i g e s t e r s wh i ch wou ld a c t p r e d i c t a b l y t o i m - p o s e d l o a d i n g s . D u r i n g tho se months , f a m i l i a r i t y was g a i n e d w i t h the waste c h a r a c t e r i s t i c s and w i t h the r e q u i r e d l a b t e c h n i q u e s . The f i r s t a t t empt a t c u l t u r i n g the anaerobes f a i l e d due t o an e x c e s s i v e raw waste f e e d i n g r a t e . In o r d e r to r e c t i f y t h i s s i t u a t i o n w i t h o u t the a i d o f c h e m i c a l s the d i g e s - t o r s were a l l o w e d t o " s i t " w i t h no f u r t h e r a d d i t i o n o f raw was te u n t i l the a n a e r o b e s were a c t i v e a g a i n . Once the b a c t e r i a r e - e s t a b l i s h e d t h e m s e l v e s a f e e d i n g program was begun. I n i t i a l l y a low f e e d i n g r a t e was u s e d . The f e e d i n g r a t e was i n c r e a s e d p r o g r e s s i v e l y u n t i l the d i g e s t e r s o p e r a t e d s u c - c e s s f u l l y a t 400 mg B 0 D 5 / l i t r e o f d i g e s t e r / d a y . The re was no c o m p r e h e n s i v e d a t a g a t h e r i n g a t t e m p t e d a t t h i s t i m e . D u r i n g the i n t e n s i v e t e s t p e r i o d t h a t f o l l o w e d , f e e d i n g o f the d i g e s t e r s was done d a i l y w i t h the e x c e p t i o n o f d o u b l e doses on F r i d a y s and Mondays i n o r d e r to compensate f o r t he l a c k o f f e e d i n g on the weekends. F e e d i n g was done i n a manner w h i c h e s s e n t i a l l y e x c l u d e d e n t r y o f a t m o s p h e r i c oxygen to the d i g e s t e r . T h i s was a c c o m p l i s h e d by s i m u l t a n e o u s l y d r a i n i n g o f f a volume o f e f f l u e n t and a d d i n g an e q u a l volume o f raw w a s t e . The d i g e s t e r gas l i n e was c l o s e d d u r i n g t h i s o p e r a t i o n i n o r d e r to m a i n t a i n p o s i t i v e p r e s s u r e w i t h i n the d i g e s t e r . S i n c e m e c h a n i c a l m i x i n g was n o t u sed on any o f the u n i t s i n o r d e r t o s i m u l a t e f i e l d c o n d i t i o n s , t he s o l i d s a c c u m u l a t i o n was q u i t e n o t i c e a b l e . The s o l i d s a c c u m u l a t i o n however gave l i t t l e t r o u b l e d u r i n g the f e e d i n g o r s a m p l i n g p r o c e d u r e . Any a t t e m p t s to d i r e c t l y measure s o l i d s 23 b u i l d - u p p r o v e d f r u i t l e s s becau se o f gas l e n s f o r m a t i o n s w h i c h s e p a r a t e d and l i f t e d the s l u d g e c o n t i n u a l l y , and because o f c r u s t f o r m a t i o n s a t the l i q u i d s u r f a c e . 3.3 D i g e s t e r T e m p e r a t u r e s Of the t h r e e d i g e s t e r u n i t s i n i t i a l l y o n - l i n e , two were t e m - p e r a t u r e c o n t r o l l e d by t h e r m o s t a t u n i t s . U s i n g the p r e v i o u s l y d e s c r i b e d a r rangement f o r t e m p e r a t u r e c o n t r o l , the t e m p e r a t u r e and t e m p e r a t u r e s e n s i t i v i t y f o r t h o s e two d i g e s t e r u n i t s was 2 5 ± 1 ° C and 3 0 ± 1 ° C . The t h i r d u n i t was o p e r a t e d a t room t e m p e r a t u r e w i t h no t h e r - most c o n t r o l . F o r t h i s u n i t , t h r o u g h the S p r i n g and Summer months o f t e s t i n g the ave rage t e m p e r a t u r e o f t he d i g e s t e r c o n t e n t s g r a d u a l l y i n - c r e a s e d and t h e n t h r o u g h l a t e Summer and F a l l months s l o w l y f e l l o f f . The minimum-maximum d i g e s t e r t e m p e r a t u r e s r e c o r d e d d u r i n g t h i s p e r i o d were 17°C and 25°C w i t h the u s u a l range o f 1 8 - 2 3 ° C . The f q u r t h d i g e s t e r u n i t was c o m p l e t e d l a t e r , and was i d e n t i c a l t o the o t h e r t h r e e e x c e p t t h a t c o o l i n g c o i l s o f c o p p e r t u b i n g l i n e d the i n s i d e p e r i m e t e r o f the d i g e s t e r . C o o l i n g w a t e r was f o r c e d t h r o u g h t h e s e l i n e s by a t h e r m o s t a t i c a l l y c o n t r o l l e d pump. The c o n t r o l l e d t e m p e r a t u r e was m a i n t a i n e d a t 1 0 ± 1 ° C . The one d i f f i c u l t y e n c o u n t e r e d w i t h t h i s u n i t was t h e r m a l l a y e r i n g between the bo t tom s l u d g e and the o v e r l y i n g l i q u i d l a y e r . T h i s p r o b l e m was c au sed by poo r v e r t i c a l p o s i t i o n i n g o f the c o o l i n g c o i l s . In o r d e r to remedy t h i s s i t u a t i o n , the d i g e s t e r c o n t e n t s were o c c a s i o n a l l y s t i r r e d . 24 During the start-up of the fourth digester, seeding material from the other three digesters was u t i l i z e d with a supplement of raw waste. The l i q u i d temperature was gradually lowered from 20°C to 10°C over a one month period. Using the previously o u t l i n e d feeding procedure a b a c t e r i a l culture acclimated to 10°C was established. From then on the t e s t i n g and feeding procedure used on t h i s digester was the same as that f o r the other three. With t h i s u n i t , however, sludge build-up was even more pronounced than i n the heated digesters. By early F a l l the build-up had i n t e r f e r e d with the sampling and feeding procedure. At t h i s point some sludge was drained and discarded. This was done only once with t h i s digester. 3.4 Testing Procedure for the Influent and E f f l u e n t As required during the study, eight-hour composite samples of raw waste were obtained from the o u t f a l l sewer at the hog farm. About 100 to 150 l i t r e s of raw waste were c o l l e c t e d on each occasion. Sampling was done from the sewer l i n e leading from the barns at the manhole c l o s e s t to the point of discharge into the lagoons (Figure 1-1). The f i l l e d carboys were deli v e r e d to a r e f r i g e r a t e d storage f a c i l i t y at UBC. R e f r i g e r a t i o n was necessary i n order to minimize b a c t e r i a l growth and a c t i v i t y . The carboys of raw waste were then used i n d i v i d u a l l y f o r feeding and t e s t i n g purposes. For the analysis of the raw waste samples, a grab sample of mixed raw waste was taken from each carboy being used. The samples taken for t e s t i n g of the s e t t l e d l i q u i d portion of the digesters were also grab samples. This sampling however, was done 25 r e g u l a r l y d u r i n g the m i d d l e o f each week. In t he e v e n t t h a t t e s t i n g was d e l a y e d f o r one o r more days f o r e i t h e r raw waste o r e f f l u e n t , the samples were i m m e d i a t e l y r e f r i g e r a t e d u n t i l the a n a l y s i s was p e r f o r m e d . T e s t s i n t r i p l i c a t e were p e r f o r m e d on b o t h the m ixed raw was te and d i g e s t e r s u p e r n a t a n t . The e x p e r i m e n t a l p r o c e d u r e s f o l l o w e d a r e o u t l i n e d i n the t w e l f t h e d i t i o n o f S t a n d a r d Methods [ 1 5 ] . The t e s t s p e r f o r m e d w e r e : (1) Phospha te (page 231) (2) A l k a l i n i t y (page 369) (3) T o t a l and O r g a n i c K j e l d a h l N i t r o g e n (page 402 & 404) (4) B i o c h e m i c a l Oxygen Demand (BOD) (page 415) (5) pH V a l u e (page 422) (6) T o t a l and V o l a t i l e S o l i d s (TS & VS) (page 423) (7) C h e m i c a l Oxygen Demand (COD) (page 510) I t was a l s o n e c e s s a r y due to the h i g h was te s t r e n g t h , t o d i l u t e the t e s t s a m p l e s . Through r e p e a t e d t r i a l s the d i l u t i o n f a c t o r s f o r t he raw was te and the e f f l u e n t f rom each d i g e s t e r were d e t e r m i n e d . These v a l u e s r e m a i n e d f a i r l y c o n s t a n t t h r o u g h o u t the sub sequen t t e s t i n g p e r i o d . F o r p u r p o s e s o f a c c u r a t e c o n t r o l a l l d i l u t i o n s were made u s i n g a p p r o p r i a t e p i p e t t e s , v o l u m e t r i c f l a s k s and d i s t i l l e d w a t e r . 3.5 T e s t i n g P r o c e d u r e f o r the E v o l v e d Gas A p r o p e r l y f u n c t i o n i n g a n a e r o b i c d i g e s t e r e v o l v e s p r i m a r i l y CH4 and C 0 2 , w i t h t r a c e s o f some o t h e r g a s e s . In the case o f a f l o w - t h r o u g h sy s tem w i t h a u n i f o r m f e e d , the two p r i m a r y ga ses would be e v o l v e d 26 i n a r e l a t i v e l y c o n s t a n t r a t i o f o r the g i v e n o p e r a t i n g c o n d i t i o n s . D e t e r - m i n a t i o n o f t h i s r a t i o d u r i n g t e s t i n g wou ld p o s s i b l y a i d i n showing (1) any u p s e t o r i n b a l a n c e i n the d i g e s t e r by the v a r i a t i o n i n the gas r a t i o , (2) the e f f e c t o f t e m p e r a t u r e on the c o m p o s i t i o n o f the e v o l v e d ga s . A c t u a l a n a l y s i s o f the c o n s t i t u e n t s o f t he e v o l v e d gas was c o m p l e t e d on a r e s e a r c h gas ch romatog raph w i t h a t h e r m a l c o n d u c t i v i t y d e t e c t o r u n i t . The d e t e c t o r was t e m p e r a t u r e programmed. A f t e r some l i t e r a t u r e r e v i e w , a s e r i e s o f co lumns and p a c k i n g s were t e s t e d w i t h s t a n d a r d gas samples o f CH^, C O 2 , H 2 S and N H 3 . The p a c k - i n g f i n a l l y d e c i d e d upon was cho sen becau se i t s e p a r a t e d most e f f e c t i v e l y t he gas c o n s t i t u e n t s and a l s o gave d i s t i n g u i s h a b l e peaks f o r t h e s e gas c o n s t i t u e n t s . A t y p i c a l gas chromatogram i s shown i n F i g u r e 3 - 1 . The d e t a i l s o f t he mode l and columns a r e : Mode l - H e w l e t t - P a c k a r d 5752B Column - 16 ' * 1/8" <{> SS P a c k i n g i n Column - 8' P o r o p a c k Q 50 -80 Mesh + 8 ' P o r o p a c k R 50 -80 Mesh Gas f o r the p u r p o s e o f a n a l y s i s was c o l l e c t e d i n a g l a s s chamber f i t t e d w i t h a gas s a m p l i n g p o r t . The samples were then e x t r a c t e d w i t h a s y r i n g e and a n a l y z e d on the gas c h r o m a t o g r a p h . T e s t i n g a t the s t a r t was done t h r e e t imes week ly bu t as the s t u d y p r o g r e s s e d a week l y a n a l y s i s was deemed s u f f i c i e n t . Measurement o f the r a t e o f gas p r o d u c t i o n and t o t a l p r o d u c t i o n o f gas d u r i n g a 24 h o u r p e r i o d was a c c o m p l i s h e d t h r o u g h a w a t e r - g a s d i s p l a c e - 27 8 -1 7 - G A S ANALYS I S FOR D I G E S T E R * 3 - l 8 ° - 2 3 ° C 6 - 5 - INJECT ION P O R T T C D E T E C T O R IN IT IAL T E M R P T G C G A S P R E S S U R E C H A R T S P E E D I 3 9 ° C I 8 0 ° C 5 0°C I O ° C / M I N . 4 8 ps i 0.5 IN./MIN. 4 - 3 - 2 - C 0 2 I - N/ A 1 1 3 4 5 6 T I M E (MIN.) T~ 9 -1 10 FIGURE 3-1 C H R O M A T O G R A M O F D I G E S T E R G A S 28 ment mechanism (see F i g u r e 1 -5) . By t h i s method, w a t e r wh i ch had p r e v i o u s l y been i n c o n t a c t w i t h d i g e s t e r gas i n o r d e r t h a t the w a t e r be s a t u r a t e d w i t h d i s s o l v e d d i g e s t e r g a s , was c o n t a i n e d i n a r i g i d p l a s t i c t u b e . As gas e v o l v e d , an e q u a l vo lume o f w a t e r was d i s p l a c e d . (The c o n f i g u r a t i o n o f the p l a s t i c tube was d e s i g n e d ' so t h a t a m i n i m a l back p r e s s u r e a c t e d on the d i g e s t e r s y s t e m . ) The d i s p l a c e d w a t e r was t h e n c o l l e c t e d i n a g r a d u a t e d c y l i n d e r and the vo lume measu red . A r e c o r d was a l s o k e p t o f t he t ime r e - q u i r e d to d i s p l a c e a s p e c i f i c vo lume o f w a t e r , e n a b l i n g p e r i o d i c r a t e d e t e r m i n a t i o n s f o r gas p r o d u c t i o n . D u r i n g each 24 hou r t e s t p e r i o d a r e c o r d was k e p t o f t he a v e r a g e room t e m p e r a t u r e and l o c a l a t m o s p h e r i c p r e s s u r e so t h a t c o n v e r s i o n t o STP c o u l d be made. Due to the c r u d e n e s s o f t h i s equ ipment the r e s u l t s o b t a i n e d were p r i m a r i l y v a l u a b l e f o r c o m p a r i s o n o f d i g e s t e r o p e r a t i o n r a t h e r t h a n f o r a b s o l u t e v a l u e s o f gas p r o d u c t i o n . 3.6 Summary M i n o r d i f f i c u l t i e s were e n c o u n t e r e d i n a l l a r e a s d u r i n g the s t u d y b u t none o f t h e s e a d v e r s e l y a f f e c t e d o r changed the o b j e c t i v e s o f the p rog ram. The e x p e r i m e n t a l d a t a i s shown i n A p p e n d i x A. D i s c u s s i o n and c o n c l u s i o n s w i t h r e g a r d to t h e s e r e s u l t s a r e p r e s e n t e d i n the s u b - sequent c h a p t e r s . C H A P T E R I V THE EFFECT OF DETENTION TIME 4.1 I n t r o d u c t i o n The need f o r d e t e r m i n i n g an optimum d e t e n t i o n t ime f o r the raw was te i s t w o f o l d . The r e q u i r e d d e t e n t i o n t imes must be s u f f i c i e n t t o : ( i ) p r o v i d e adequa te s e t t l i n g t ime f o r p a r t i c u l a t e m a t t e r ; ( i i ) p r o v i d e i n t i m a t e b i o l o g i c a l c o n t a c t t ime i n o r d e r t h a t s u b s t a n t i a l b a c t e r i a l d e g r a d a t i o n o f o r g a n i c s can t ake p l a c e . In t h i s r e g a r d t h r e e a r e a s were i n v e s t i g a t e d : (1) i n f l u e n t and e f f l u e n t c o n c e n t r a t i o n s o f v a r i o u s waste p a r a m e t e r s ; (2) f l u c t u a t i o n s o r changes i n e f f l u e n t c h a r a c t e r i s t i c s ; (3) gas c o m p o s i t i o n as a f f e c t e d by the l o a d i n g r a t e . 4;2 G e n e r a l D i s c u s s i o n In o r d e r to s t u d y the e f f e c t s o f d i f f e r e n t h o l d i n g p e r i o d s on swine was te s i t was n e c e s s a r y to d e t e r m i n e a b r o a d y e t p r a c t i c a l range o f d e t e n t i o n t imes f o r t h e s e t e s t s . As p r e v i o u s l y m e n t i o n e d , an upper l i m i t o f 50 days was chosen to match the a p p r o x i m a t e f i e l d l a g o o n d e t e n t i o n t ime and the l o w e r l i m i t was to be d e t e r m i n e d e x p e r i m e n t a l l y . S o l i d s were a l l o w e d to s e t t l e and a c c u m u l a t e i n t he d i g e s t e r s i n o r d e r to s i m u l a t e the f i e l d l a g o o n s . Due to the c o n s t a n t d a i l y accumu- l a t i o n o f s o l i d s , the l i q u i d d e t e n t i o n t ime (LDT) was no t c o n s t a n t ( i . e . 29 30 the LDT c a l c u l a t e d at the s t a r t of a s p e c i f i c feeding rate was reduced over a period of time because an increasing portion of the t o t a l volume was oc- cupied by the accumulated s o l i d s , thereby reducing the l i q u i d volume). No r e s t r i c t i o n however was placed on the detention time for the s e t t l e d s o l i d s ( s o l i d s detention time (SDT) >> LDT). As previously stated, attempts at measuring the gradual build-up of s e t t l e d s o l i d s were unsuccessful. Thus no adjustment f a c t o r was determined to c a l c u l a t e the actual average LDT. It should be noted that SDT i s an important parameter to be considered with regard to anaerobic b i o l o g i c a l a c t i v i t y . However, any measurements of the sludge build-up and subsequent c a l c u l a t i o n of the av- erage sludge age was impossible due to continuous gas lens formations i n the sludge and overturning of the sludge. In t h i s study therefore the possible e f f e c t s on anaerobic d i g e s t i o n of sludge age was not further pursued. In the following presentations the t h e o r e t i c a l LDT (based on t o t a l digester volume and the volume of raw waste added d a i l y ) i s tabled opposite the removal e f f i c i e n c i e s rather than the true or a c t u a l LDT. This however, provided at the l e a s t a conservative estimate of removal e f f i c i e n - c ies at the stated detention time (e.g. If the t h e o r e t i c a l LDT i s 50 days, the true average LDT because of s o l i d s build-up would be less than 50 days. The removal e f f i c i e n c i e s tabled for a t h e o r e t i c a l LDT of 50 days would probably be equal to or le s s than the removal at a true average LDT of 50 days.) During the t e s t i n g two primary c h a r a c t e r i s t i c s of the raw waste and e f f l u e n t were monitored: 31 ( i ) COD and BOD 5 , ( i i ) TS and VS and two s e c o n d a r y c h a r a c t e r i s t i c s : ( i i i ) t o t a l and o r g a n i c n i t r o g e n , ( i v ) t o t a l p h o s p h a t e . I tems ( i ) and ( i i ) a r e o f p r i m a r y i m p o r t a n c e i n s t a n d a r d waste t r e a t m e n t p o l i c y ( i . e . r e d u c i n g p a r t i c u l a t e d i s c h a r g e i n t o , and oxygen d e - p l e t i o n i n , r e c e i v i n g w a t e r s ) . Items ( i i i ) and ( i v ) a r e i m p o r t a n t beca u se o f n u t r i e n t r e q u i r e m e n t s f o r the a n a e r o b i c d i g e s t i o n p r o c e s s and beca u se o f n u t r i e n t a d d i t i o n t o r e c e i v i n g w a t e r s . N u t r i e n t s w i l l be f u r t h e r d i s c u s s e d i n C h a p t e r V I I . 4 .3 Ave rage Raw Waste C h a r a c t e r i s t i c s In c a l c u l a t i n g the a v e r a g e v a l u e s p r e s e n t e d i n T a b l e s I I and I I I o n l y t h o s e e x p e r i m e n t a l r e s u l t s were c o n s i d e r e d w h i c h were r e c o r d e d a f t e r t he a p p r o p r i a t e t h e o r e t i c a l LDT had e l a p s e d f rom the s t a r t o f a g i v e n f e e d - r a t e p h a s e . The f i n a l r e s u l t s o f p e r c e n t r e m o v a l b a s e d on t h e o r e t i c a l LDT a r e p r e s e n t e d i n T a b l e IV. These r e s u l t s a r e a l s o g r a p h i c a l l y i l l u s - t r a t e d i n A p p e n d i x B. 4.4 D i s c u s s i o n o f R e s u l t s (a) S o l i d s From the r e s u l t s i n T a b l e IV the f o l l o w i n g comments can be made: ( i ) e x c l u d i n g the r e s u l t s f o r LDT = 6 d a y s , 32 TABLE I I • AVERAGE RAW WASTE CHARACTERISTICS* T h e o r e t i c a l LDT (Days) BOD 5 O g / i O COD (mg/A) TS (mg/A) VS (mg/4) 50 9175 29550 - - 25 9760 29900 28195 20800 12.5 9950 32770 27150 19020 6 9950 4 9 1 0 0 * * 39700 31800 * V a l u e s f o r raw waste used i n the c a l c u l a t i o n s f o r the r e s u l t s i n T a b l e IV. * * T h e h i g h COD v a l u e i s due to the h i g h v o l a t i l e s o l i d s c o n c e n t r a t i o n i n the f i n a l raw was te s amp le s . I t was a l s o n o t e d t h a t the m a j o r i t y o f the s o l i d s were f e e d c h i p s and sawdust wh i ch r a p i d l y s e t t l e d out when a sample was l e f t t o s t a n d . The B0D 5 v a l u e d i d n o t change to such an e x t e n t as d i d the o t h e r c h a r a c t e r i s t i c s , i n d i c a t i n g t h a t a l a r g e p o r t i o n o f the v o l a t i l e s o l i d s was e s s e n t i a l l y n o n - b i o d e g r a d a b l e . TABLE I I I AVERAGE EFFLUENT CHARACTERISTICS* Temp, o f D i g e s t e r ( ° C ) T h e o r e t i c a l LDT (Days) COD (mg/A) BOD 5 (mg/A) TS (mg/A) VS (mg/A) 30 50 5025 1010 25 5275 1170 7470 4265 12.5 7540 1590 7060 3995 6 6630 1095 6350 3660 25 50 5615 1100 _ _ 25 5390 1170 7470 4160 12.5 7375 1690 7330 3995 6 5645 1195 5560 3020 18 -23 50 5760 1190 _ 25 5500 1465 7330 3950 12.5 7210 1940 7060 3710 6 5890 1790 5560 3020 10 50 _ _ — 25 10665 5515 7610 4370 12.5 15730 7265 8280 4850 6 11295 5820 5560 3180 * T h e a v e r a g e v a l u e s f o r t h e 6 day LDT were o b t a i n e d f r om 2 s a m p l e s . TABLE IV PER CENT REMOVAL OF COD, BOD 5 , TS AND VS Temp, o f T h e o r e t i c a l A v e r a g e Removal (%)* D i g e s t e r LDT ( ° C ) (Days) COD BOD 5 TS VS 30 50 83.0 89.0 - • - 25 82.5 88.0 73.5 79.5 12 .5 77.0 84.0 74.0 79.0 6 86 .5 89 .0 84 .0 88.5 25 50 81.0 88.0 _ _ 25 82.0 88.0 ' 73.5 80.0 12.5 77.5 83 .0 73.0 79.0 6 88.5 88.0 86 .0 9 0 . 5 18 -23 50 80.5 87.0 25 81.5 85.0 74.0 81.0 12.5 78.0 80.5 74.0 80.5 6 88.0 82.0 86 .0 90.5 10 50 _ 25 64 .5 43 .5 73.0 79.0 12.5 52.0 27.0 69.5 74.5 6 77.0 41 .5 86.0 9 0 . 0 * T h e v a l u e s f o r p e r c e n t r e m o v a l f o r t he 6 day LDT a r e q u e s t i o n a b l e due t o t h e u n u s u a l l y h i g h s o l i d s c o n t e n t s i n t h e l a s t two raw was te samp les u s e d . 35 i n c r e a s i n g the LDT f rom 12.5 to 25 days i n the f o u r d i g e s t e r s d i d no t s i g n i f i c a n t l y improve s o l i d s r e m o v a l ; ( i i ) f o r the 6 day LDT i n the 30, 25 and 1 8 - 2 3 ° C d i g e s t e r s , the p e r c e n t r e m o v a l f o r VS was 8 8 . 5 - 9 0 . 5 % and f o r TS was 84 -86%. Comparab le r e m o v a l s o f VS and TS o c c u r r e d i n the 10°C d i g e s t e r . As e x p l a i n e d p r e v i o u s l y t h e s e u n u s u a l r e s u l t s f o r the 6 day LDT were p r o b a b l y due to the u n u s u a l l y h i g h s o l i d s c o n c e n t r a t i o n s i n the f i n a l raw was te s a m p l e s , (b) Oxygen Demand R e s u l t s s i m i l a r t o t h o s e o b t a i n e d f o r s o l i d s r e m o v a l were r e - c o r d e d f o r COD and B0D 5 r e m o v a l ( see T a b l e I V ) . O b s e r v a t i o n s to n o t e were : ( i ) i n c r e a s i n g the LDT f rom 12.5 to 50 days i n the 30, 25 and 1 8 - 2 3 ° C d i g e s t e r s o n l y i m p r o v e d COD r e m o v a l 3 .5 -6% and B0D 5 r e m o v a l 5 - 6 . 5 % ; ( i i ) o v e r a r ange o f 12 .5 -25 days LDT f o r the 10°C d i g e s t e r , COD and B0D 5 r e m o v a l s i g n i f i c a n t l y i m p r o v e d ; ( i i i ) f o r the 6 day LDT i n the f o u r d i g e s t e r s , the p e r c e n t r emova l s a r e u n u s u a l l y h i g h due p r o b a b l y to the h i g h s o l i d s c o n t e n t i n the f i n a l raw waste s a m p l e s . 36 From t h e s e o b s e r v a t i o n s , . i t i s a p p a r e n t t h a t t he r a p i d 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 t h i s was te i s an i m p o r t a n t f a c t o r i n t r e a t m e n t . W i th the h i g h c o n c e n t r a t i o n o f s e t t l e a b l e VS i n the w a s t e , u n t r e a t e d d i s c h a r g e s c o u l d have a d v e r s e e f f e c t s upon r e c e i v i n g w a t e r s i n the fo rm o f oxygen d e p l e t i o n and deve lopment o f s l u d g e b a n k s . C o n s e q u e n t l y , f o r t r e a t m e n t o f t h i s t ype o f w a s t e , where 65-70% o f t he TS a r e o r g a n i c , r e m o v a l o f VS by s e t t l i n g s h o u l d be a p r ime d e s i g n f e a t u r e . The r e m o v a l o f s o l i d s wou ld n o t o n l y r e d u c e the o r g a n i c l o a d i n t he e f f l u e n t bu t the removed s o l i d s wou ld a l s o p r o v i d e an adequate f o o d s o u r c e f o r f u r t h e r b i o l o g i c a l d e g r a d a t i o n . T h i s d e g r a d a t i o n p r o c e s s c o u l d be a c c o m p l i s h e d by a n a e r o b i c means. Two f u r t h e r p o i n t s to n o t e as shown by the e x p e r i m e n t a l r e s u l t s a r e : ( i ) f o r oxygen demand r e m o v a l d e t e n t i o n t ime i s more c r i t i c a l a t low t e m p e r a t u r e s ( 1 0 ° C ) as compared to h i g h e r t e m p e r a t u r e s ( 2 0 - 3 0 ° C ) ; ( i i ) f o r the f o u r d i g e s t e r s , the i n c r e a s e i n p e r c e n t r e m o v a l o f s o l i d s as the LDT i s e x t e n d e d may be a t t r i b u t e d to l o n g e r s e t t l i n g t ime and improved s e t t l i n g c o n d i t i o n s due to l e s s v i g o r o u s gas a g i t a t i o n ; and to f u r t h e r b i o l o g i c a l r e d u c t i o n o f su spended VS beca u se o f i n c r e a s e d c o n t a c t t i m e . (c) pH and A l k a l i n i t y Two q u a l i t y p a r a m e t e r s were m o n i t o r e d to h e l p d e t e c t changes i n the e f f l u e n t c h a r a c t e r i s t i c s . These p a r a m e t e r s , pH and a l k a l i n i t y , 37 a l s o a i d e d i n c h a r t i n g p o s s i b l e changes i n b a c t e r i a l a c t i v i t y . R e s u l t s f o r pH and a l k a l i n i t y a r e shown i n T a b l e V and shown g r a p h i c a l l y i n A p p e n d i x A. As shown i n T a b l e V ( i ) i n c r e a s i n g the LDT f o r a l l d i g e s t e r s f rom 6 to 50 d a y s , r e s u l t e d i n changes o f pH o n l y . 2 - . 3 u n i t s . However, t he v a r i a b i l i t y i n the d a i l y pH r e a d i n g s were more n o t i c e a b l e as LDT d e c r e a s e d ; ( i i ) the i n c r e a s e i n v a r i a b i l i t y o f the pH f o r the d i g e s t e r e f f l u e n t s d u r i n g the 6 day LDT (see A p p e n d i x A) can be a t t r i b u t e d t o 16% o f the t o t a l d i g e s t e r c o n t e n t s b e i n g d i s p l a c e d d a i l y by raw w a s t e . Random t e s t i n g o f the raw waste pH gave v a l u e s r a n g i n g f rom 6 . 5 - 7 . 5 ; ( i i i ) w i t h r e g a r d to a l k a l i n i t y c o n c e n t r a t i o n o f the e f f l u e n t d u r i n g the 6 day LDT, the r e s u l t s c l e a r l y show t h a t d i s p l a c i n g 16% by vo lume o f the d i g e s t e r c o n t e n t s w i t h raw waste ( the a l k a l i n i t y c o n c e n t r a t i o n o f wh i ch was much l o w e r ) m a r k e d l y a f f e c t e d the r e s u l t s f o r the f o u r d i g e s t e r s . From t h e s e o b s e r v a t i o n s f o r pH and a l k a l i n i t y , the lower l i m i t f o r d e t e n t i o n t ime i s p r i m a r i l y d e t e r m i n e d by the p e r c e n t by volume o f the TABLE V EFFLUENT pH AND ALKALINITY Temp, o f D i g e s t e r ( ° C ) T h e o r e t i c a l LDT (Days) pH A l k a l i n i t y (mg/A) 30 25 18-23 10 50 7.4 - 7.5 - 25 7.4 - 7.6 6800 - 8100 12.5 7.5 - 7.6 7000 - 7600 6 7.3 7.4 5700 - 6100 50 7.3 7.4 _ 25 7.4 — 7.5 6800 - 7900 12 .5 7.4 - 7.5 6900 - 7600 6 7.3 - 7.4 5500 - 6000 50 7.3 _ 7.4 25 7.3 - 7.4 6800 - 7700 12 .5 7.3 - 7.5 6800 - 7400 6 7.2 -• 7.3 4900 - 5700 50 25 6.8 - 6.9 5200 - 6100 12.5 6.6 - 6.9 5000 - 5700 6 6.6 - 6.8 3600 - 3800 3 9 digester contents that the raw waste displaces. Because of the v a r i a b i l i t y of the raw waste c h a r a c t e r i s t i c s and the quantity of raw waste added d a i l y , the digester contents are s i g n i f i c a n t l y a f f e c t e d during the addition of raw waste ( i . e . the pH and a l k a l i n i t y of the digester contents becomes as v a r i - able as the raw waste pH and a l k a l i n i t y ) . This i n turn i n i t i a t e s a sequence of events. A greater portion of the anaerobic b a c t e r i a are washed out d a i l y from the system; the optimum pH range f o r the b a c t e r i a i s not c o n s i s t e n t l y maintained; and, the b u f f e r i n g mechanism provided by the digester contents against low raw waste pH i s reduced. As a r e s u l t the b i o l o g i c a l balance of anaerobic b a c t e r i a i s progressively destroyed, p o t e n t i a l l y causing upset conditions i n the d i g e s t i o n process. 4.5 Gas Production and Composition For each detention time, t o t a l gas volume produced and gas composition were recorded. The object here was to monitor changes i n gas constituents and i n gas volumes i n order to i n d i c a t e the l e v e l of b i o l o g i c a l a c t i v i t y . (a) Volume The t o t a l gas production per day from the 30, 25 and 18-23°C digesters increased as the raw waste loading rate was increased (see Table VI and Figure 4-1). Since the t o t a l gas produced i s r e l a t e d to the bac- t e r i a l population and to the quantity of substrate added per unit time, the r e s u l t i s then as expected. During the 4 A/day loading rate (6 days LDT), the d a i l y gas production (based on l i n e a r extrapolations of the r e s u l t s from lower TABLE VI DAILY GAS PRODUCTION AS RELATED TO DETENTION TIME Gas P r o d u c t i o n Gas P r o d u c e d Temp, o f T h e o r e t i c a l T o t a l D a i l y Gas P r i o r t o Raw f r o m Raw Waste D i g e s t e r LDT P r o d u c t i o n (1) Waste A d d i t i o n Added D a i l y ( ° C ) (Days) ( m £ / d a y @ STP) (2) (1 -2 ) (mi,/day @ STP) ( m £ / d a y @ STP) 30 50 6250 4430 1820 25 12000 9260 2740 12.5 24700 19500 5200 6 28000 20900 7100 25 50 6600 4890 1710 25 9800 7350 2450 12 .5 19500 15600 3900 6 25000 18800 6200 18-23 50 5600 4100 1500 25 9600 7700 1900 12.5 17250 14300 2950 6 22750 17750 5000 10 50 _ _ 25 500 250 250 12.5 1250 600 650 6 — _ _  42 f e e d i n g r a t e s ) was n e v e r a c h i e v e d (see F i g u r e 4 - 1 ) . The f a l l i n g o f f o f the t o t a l vo lume o f gas p r o d u c e d i n d i c a t e d t h a t a t t h i s h i g h l o a d i n g r a t e : ( i ) the b i o l o g i c a l s y s tem was u n a b l e t o manage the i n c r e a s e d l o a d ; ( i i ) such a l a r g e p o r t i o n o f the d i g e s t e r c o n t e n t s was d i s p l a c e d d a i l y t h a t b a c t e r i a wash -ou t was o c c u r r i n g ; ( i i i ) the i n c r e a s e d v a r i a b i l i t y i n pH and a l k a l i n i t y caused by the raw waste d i s p l a c i n g 16% o f the d i g e s t e r c o n t e n t s was a d v e r s e l y a f f e c t i n g the b i o l o g i c a l s y s t e m . The r e s u l t s t o n o t e f o r the 10°C d i g e s t e r were the l a c k o f gas p r o d u c t i o n and the i n s e n s i t i v i t y o f gas p r o d u c t i o n to a l l l o a d i n g r a t e s . At t h i s t e m p e r a t u r e the methane b a c t e r i a b a r e l y f u n c t i o n i r r e s p e c t i v e o f the l o a d i n g r a t e . (b) C o m p o s i t i o n i The gas a n a l y s i s f o r the 30, 25 and 1 8 - 2 3 ° C d i g e s t e r s d u r i n g the t e s t p e r i o d d i d no t v a r y a p p r e c i a b l y even though the l o a d i n g r a t e was i n c r e a s e d f o u r t imes (Append ix A ) . The r e s u l t s t h r o u g h the t e s t p e r i o d f o r t h e s e d i g e s t e r s a r e shown i n T a b l e V I I . The a n a l y s i s f o r the c o n s t i t u e n t s o f the gas d i d no t i n d i c a t e any b i o l o g i c a l up se t f o r the h i g h l o a d i n g r a t e s even though the r e s u l t s f o r pH, a l k a l i n i t y and gas p r o d u c t i o n d i d p o i n t to t h i s . The p e r c e n t a g e o f CHi+ and CO2 gas t o the t o t a l e v o l v e d gas i s t h e r e f o r e c h a r a c t e r i s t i c o f the s u b s t r a t e ( i . e . s p e c i f i c s p e c i e s o f b a c t e r i a once e s t a b l i s h e d i n the 43 TABLE V I I GAS COMPOSITION FOR 3 0 ° , 2 5 ° AND 1 8 - 2 3 ° C DIGESTERS (RAW WASTE ADDED DAILY) Gas % C o m p o s i t i o n * Extreme L i m i t s A v e r a g e CH^ 66-71 68 C 0 2 28-32 30 N 2 0 . 4 - 1 . 0 0 .8 H 2 S 0 . 2 - 0 . 5 0 .3 H 2 0 0 . 4 - 1 . 5 0 .9 TABLE V I I I GAS COMPOSITION FOR 3 0 ° , 2 5 ° AND 18- DIGESTERS (RAW WASTE ADDITION TERMINATED) -23°C Gas C o m p o s i t i o n % * Extreme L i m i t s CH^ 49-55 co 2 42-49 N 2 0 . 5 - 1 . 5 H 2 S N/D H 2 0 0 . 5 - 1 . 5 *The combined p e r c e n t a g e o f CH^ and C 0 2 gas t h r o u g h t h i s p e r i o d was 97 -99%. 44 d i g e s t e r s a t t h e s e t e m p e r a t u r e s w i l l c o n t i n u e to p r o d u c e gas o f t h i s s p e - c i f i c n a t u r e because o f the t y p e o f raw waste b e i n g added) and does n o t n e c e s s a r i l y i n d i c a t e u p s e t c o n d i t i o n s ( see A p p e n d i x A ) . The r e s u l t s o f t he gas a n a l y s e s f o r the 10°C d i g e s t e r , w h i c h was the l e a s t a c t i v e o f the d i g e s t e r s , were h i g h l y v a r i a b l e and the CO2 p e r c e n t a g e o f t he e v o l v e d gas had n o t i c e a b l y i n c r e a s e d . I t a p p e a r s t h a t under t h e s e c i r c u m s t a n c e s the i n c r e a s e i n the v a r i a b i l i t y o f the gas com- p o s i t i o n c o u p l e d w i t h the i n c r e a s e i n t he p e r c e n t CO2 o f the gas a r e i n d i c a t o r s o f u p s e t c o n d i t i o n s w i t h i n the d i g e s t e r . A f t e r t he raw was te l o a d i n g was t e r m i n a t e d , r e c o r d s were k e p t o f the gas c o m p o s i t i o n and p r o d u c t i o n d u r i n g the f o l l o w i n g f i v e months . The gas c o m p o s i t i o n changed m a r k e d l y i n the f i r s t twenty days b u t e v e n - t u a l l y s t a b i l i z e d . F o r the r e s u l t s d u r i n g t h i s p e r i o d o f the s t u d y see T a b l e V I I I . These r e s u l t s s u b s t a n t i a t e d the t h e o r y t h a t the r a t i o o f CH^ and CO2 i s s u b s t r a t e s p e c i f i c and does n o t n e c e s s a r i l y i n d i c a t e b i o l o g i c a l u p s e t . I t appea r s f rom t h i s t h a t the c h a r a c t e r i s t i c s u b s t r a t e b e i n g u t i - l i z e d by the b a c t e r i a had changed ( i . e . o r g a n i c s wh i ch were more d i f f i c u l t t o d e g r a d e ) . The a c i d - f o r m e r s p r o d u c e d i f f e r e n t i n t e r m e d i a t e p r o d u c t s and p o s s i b l y because o f t h i s , the g a s - f o r m e r s p r o d u c e CHi+ and C 0 2 i n d i f f e r e n t p e r c e n t a g e s . ( In o r d e r to v e r i f y t h i s t h e o r y , however , f u r t h e r a n a l y s i s o f i n t e r m e d i a t e p r o d u c t s o f d i g e s t i o n wou ld have to be u n d e r t a k e n . T h i s was no t done i n t h i s s t u d y . ) (NOTE : - T a i g i n i d e s [ 6 ] r e p o r t i n g on d i g e s t i o n o f hog was tes a t 35°C showed a gas a n a l y s i s o f 59% C H 4 and 40% C 0 2 p l u s t r a c e g a s e s . S i n c e v i g o r o u s a n a e r o b i c a c t i o n was n o t e d i n T a i g i n i d e s ' s t u d y and s i m i l a r l y i n t h i s s t u d y , the d i f f e r e n t r a t i o o f CHi+ to CO2 can be a t t r i b u t e d to the d i f f e r e n c e s i n the raw waste c o m p o s i t i o n and i s n o t an i n d i c a t o r o f " p o o r 1 o r " g o o d " a n a e r o b i c d i g e s t i o n . ) C H A P T E R V THE EFFECT OF TEMPERATURE 5.1 I n t r o d u c t i o n A n o t h e r i m p o r t a n t p a r a m e t e r w h i c h must n e c e s s a r i l y be c o n s i d e r e d i n the a n a e r o b i c d i g e s t i o n p r o c e s s i s t e m p e r a t u r e . The t e m p e r a t u r e a f f e c t s t he r a t e a t wh i ch the was te i s a s s i m i l a t e d and r e d u c e d . B e s i d e s the t e m p e r - a t u r e i t s e l f , t e m p e r a t u r e f l u c t u a t i o n s a r e a l s o c r i t i c a l to the a n a e r o b i c p r o c e s s [ 1 2 ] . Because methane b a c t e r i a a r e v e r y s e n s i t i v e to t e m p e r a t u r e c h a n g e s , the range and f r e q u e n c y o f t e m p e r a t u r e f l u c t u a t i o n s d e t e r m i n e s whether a n a e r o b i c d e g r a d a t i o n can be m a i n t a i n e d . In t h i s r e g a r d t h r e e i t e m s w i l l be d i s c u s s e d , (1) i n f l u e n t and e f f l u e n t c o n c e n t r a t i o n s o f v a r i o u s waste p a r a m e t e r s ; (2) d i g e s t e r s t a b i l i t y ; and (3) gas p r o d u c t i o n and c o m p o s i t i o n . 5.2 G e n e r a l D i s c u s s i o n The t e m p e r a t u r e s d e c i d e d upon f o r the d i g e s t e r s were such t h a t t h e s e t e m p e r a t u r e s c o v e r e d the e x p e c t e d range o f low and h i g h t e m p e r a t u r e c o n d i t i o n s f o r l a goons i n t he F r a s e r V a l l e y . The s p e c i f i c t e m p e r a t u r e s c h o s e n , as p r e v i o u s l y m e n t i o n e d , were 1 0 ° , 2 5 ° and 3 0 ° C . The room t e m p e r - a t u r e d i g e s t e r v a r i e d f rom 1 8 - 2 3 ° C . I t was on the room t e m p e r a t u r e d i g e s - t e r t h a t the e f f e c t s o f s m a l l t e m p e r a t u r e f l u c t u a t i o n s were to be s t u d i e d . The h e a t i n g and c o o l i n g a p p a r a t u s f o r the d i g e s t e r s , s a m p l i n g t e c h n i q u e s f o r the raw waste and d i g e s t e r e f f l u e n t , and the c h e m i c a l e x - p e r i m e n t s and a n a l y t i c a l t e c h n i q u e s have p r e v i o u s l y been d e s c r i b e d i n 46 47 C h a p t e r I I I and IV. The f i n a l r e s u l t s as r e l a t e d to t e m p e r a t u r e a r e p r e s e n t e d i n the f o l l o w i n g T a b l e IX and a r e a l s o g r a p h i c a l l y i l l u s t r a t e d i n A p p e n d i x C. The c a l c u l a t i o n s f o r t h e s e r e s u l t s were c a r r i e d ou t i n the manner d e s c r i b e d i n C h a p t e r IV. 5.3 D i s c u s s i o n o f R e s u l t s (a) S o l i d s From the r e s u l t s i n T a b l e IX, t h r o u g h the r ange o f t e m p e r a t u r e s f rom 10°C t o 3 0 ° C , the v a r i a t i o n i n p e r c e n t r e m o v a l f o r TS was 1-4.5% and f o r VS was 2 -5 .5% . W i t h t h i s t y p e o f w a s t e , where the m a j o r i t y o f the s o l i d s r e a d i l y s e t t l e o u t , v a r y i n g the d i g e s t e r t e m p e r a t u r e does no t s i g - n i f i c a n t l y improve the s u p e r n a t a n t q u a l i t y w i t h r e g a r d s to s o l i d s r e m o v a l . (b) Oxygen Demand F o r the r e s u l t s f rom 6 to 50 days LDT, the e f f e c t o f t e m p e r a t u r e on t h e r e m o v a l o f b o t h COD and B0D 5 was m a r k e d l y s i m i l a r . (See T a b l e IX . ) These o b s e r v a t i o n s were n o t e d : ( i ) as the LDT i s i n c r e a s e d f rom 12.5 days to 50 d a y s , the e f f e c t o f i n c r e a s e d t e m p e r a t u r e becomes more s i g n i f i c a n t ; ( i i ) the 1 8 - 2 3 ° C d i g e s t e r f u n c t i o n e d n e a r l y as w e l l as the .hea ted d i g e s t e r s and s i g n i f i c a n t l y b e t t e r t h a n the 10°C d i g e s t e r ; ( i i i ) b a c t e r i a l a c t i v i t y a p p e a r s t o be a s t e p f u n c t i o n o f t e m p e r a t u r e : (a) 10°C o r l e s s minimum a c t i v i t y TABLE IX PER CENT REMOVAL OF COD, BOD 5 , TS AND VS T h e o r e t i c a l Temp, o f A v e r a g e Removal (%) LDT D i g e s t e r (Days) ( ° C ) COD BOD 5 TS VS 50 30 83 .0 89.0 - - 25 81.0 88.0 - - 1 8 - 2 3 80.5 87.0 - - 10 - - - - 25 30 82.5 88.0 73.5 79.5 25 82.0 88.0 73.5 80.0 18 -23 81 .5 85.0 74.0 81.0 10 64 .5 43 .5 73.0 79.0 12.5 30 77.0 84.0 74.0 79.0 25 77.5 83 .0 73.0 79.0 18 -23 78.0 80.5 74.0 80.5 10 52 .0 27 .0 69 .5 74.5 6 30 86.5 89.0 84 .0 88.5 25 88 .5 88.0 86.0 9 0 . 5 18 -23 88 .0 82.0 86 .0 90 .5 10 77.0 41 .5 86.0 90 .0 * T h e v a l u e s f o r p e r c e n t r e m o v a l f o r the 6 day LDT a r e q u e s t i o n a b l e due to the u n u s u a l l y h i g h s o l i d s c o n t e n t i n t h e l a s t two raw was te samples u s e d . 49 (b) 1 0 - 2 0 ° C t r a n s i t i o n range where the b a c t e r i a l a c t i v i t y r a p i d l y i n c r e a s e s (c) 2 0 - 3 0 ° C l e v e l l i n g o f f o r p l a t e a u i n the b a c t e r i a l a c t i v i t y . The e x t e n t t o w h i c h the oxygen demand i s r e d u c e d d u r i n g the t r e a t m e n t o f t he waste depends on the n a t u r e o f the o r g a n i c s and the a c t i v - i t y o f the b a c t e r i a . In the range o f t e m p e r a t u r e s f rom 2 0 - 3 0 ° C the b a c t e r i a l p o p u l a t i o n appea r s t o f u n c t i o n a c t i v e l y w i t h a b a l a n c e d p o p u l a t i o n o f a c i d - f o r m i n g and g a s - p r o d u c i n g b a c t e r i a wh i ch r e d u c e o r g a n i c s t o t h e i r r e s p e c t i v e e n d - p r o d u c t s . However, i t i s a p p a r e n t f rom the n o t i c e a b l e d rop i n the p e r c e n t r e m o v a l o f e i t h e r BOD5 o r COD t h a t between 20 and 10°C a change o c c u r s . . In the low t e m p e r a t u r e range ( l e s s t han 1 0 ° C ) , i t appea r s t h a t the b i o l o g i c a l sequence o f a c i d - f o r m a t i o n to gas p r o d u c t i o n i s no l o n g e r c a r r i e d t h r o u g h . F o r examp le , t he t o t a l d a i l y gas p r o d u c t i o n f o r t h e 10°C d i g e s t e r was a t the most o n e - t e n t h t h a t p r o d u c e d f rom the o t h e r t h r e e d i g e s t e r s i n d i c a t i n g t h a t t he methane b a c t e r i a w h i c h c o n v e r t the i n t e r m e d i a t e - p r o d u c t s t o gaseous e n d - 4 p r o d u c t s no l o n g e r f u n c t i o n to the same deg ree as i n the o t h e r t h r e e d i g e s - t e r s . I t s h o u l d a l s o be n o t e d t h a t the a l k a l i n i t y o f t he 10°C d i g e s t e r was c o n s i s t e n t l y l ower than the a l k a l i n i t y o f t he e f f l u e n t f rom the o t h e r d i - g e s t e r s and o f the raw waste s a m p l e s , i n d i c a t i n g i n c o m p l e t e a n a e r o b i c d i g e s t i o n w i t h p r o b a b l e v o l a t i l e a c i d b u i l d - u p i n the d i g e s t e r c o n t e n t s . 5.4 S t a b i l i t y o f the D i g e s t e r s C o n s i d e r i n g the pH and a l k a l i n i t y v a l u e s o f the e f f l u e n t , a l o n g w i t h the t o t a l d a i l y gas p r o d u c t i o n as b e i n g measures o f the s t a b i l i t y o f the d i g e s t e r s ( i . e . a c t i v e a n a e r o b i c d e g r a d a t i o n ) , changes i n t e m p e r a t u r e 50 must be r e c o g n i z e d as an i m p o r t a n t v a r i a b l e . In the 2 0 - 3 0 ° C range i t was found t h a t : ( i ) t he pH v a l u e o f the e f f l u e n t was c o n s i s t e n t l y between 7 . 3 - 7 . 6 ; ( i i ) t he a l k a l i n i t y c o n c e n t r a t i o n o f the e f f l u e n t was s i g n i f i c a n t l y g r e a t e r t h a n the a l k a l i n i t y c o n c e n t r a t i o n o f the i n c o m i n g w a s t e ; ( i i i ) the d a i l y gas p r o d u c t i o n was a lways v i g o r o u s . From the above ment i oned d a t a (see a l s o T a b l e V and A p p e n d i x A) i t was c o n c l u d e d t h a t t he 30°C d i g e s t e r was o p e r a t i n g under the most s t a b l e c o n d i t i o n s o f the t h r e e . I t was f ound t h a t t h r o u g h o u t the t e s t p e r i o d the 30°C d i g e s t e r c o n s i s t e n t l y had the h i g h e s t d a i l y gas p r o d u c t i o n and m a i n - t a i n e d t h e h i g h e s t e f f l u e n t pH a t 7 . 4 - 7 . 6 . F o r the 10°C d i g e s t e r the pH was n e v e r g r e a t e r than 7, the gas p r o d u c t i o n was m i n i m a l compared to the o t h e r t h r e e d i g e s t e r s , and the e f - f l u e n t a l k a l i n i t y c o n c e n t r a t i o n was r e p e a t e d l y l o w e r t h a n the i n c o m i n g raw waste a l k a l i n i t y due t o the a c c u m u l a t i o n o f e x c e s s o r g a n i c a c i d s . A l l o f t h e s e c o n d i t i o n s i n d i c a t e d t h a t the 10°C d i g e s t e r was b i o l o g i c a l l y u n s t a b l e . 5.5 Gas P r o d u c t i o n and C o m p o s i t i o n The m e t a b o l i c a c t i v i t y o f b a c t e r i a i s a f u n c t i o n o f t e m p e r a t u r e [ l l , 1 8 ] . S i n c e the a c t i v i t y f o r methane b a c t e r i a gove rn s the r a t e a t wh i ch gas i s p r o d u c e d i n an a n a e r o b i c d i g e s t e r , the t o t a l d a i l y gas p r o d u c t i o n f rom each d i g e s t e r was a n t i c i p a t e d to be a f u n c t i o n o f t e m p e r a t u r e . F o r each t e m p e r a t u r e , t o t a l gas vo lume p r o d u c e d and gas com- p o s i t i o n were r e c o r d e d . As m e n t i o n e d i n the p r e v i o u s c h a p t e r the o b j e c t 51 o f t h i s was to m o n i t o r the l e v e l o f b i o l o g i c a l a c t i v i t y . (a) Volume From the e x p e r i m e n t a l r e s u l t s r e c o r d e d i n T a b l e X, t e m p e r a t u r e d e f i n i t e l y a f f e c t s the d a i l y volume o f gas p r o d u c e d . (See a l s o F i g u r e 4 - 1 . ) (b) C o m p o s i t i o n As p r e v i o u s l y m e n t i o n e d i n C h a p t e r IV ( a l s o see T a b l e V I I and A p p e n d i x A ) , t h rough the t e m p e r a t u r e range 2 0 - 3 0 ° C the gas c o m p o s i t i o n was c o n s i s t e n t . Through t h i s t e m p e r a t u r e range the a c t i v i t y and s p e c i f i c t y p e s o f b a c t e r i a a r e v e r y s i m i l a r . The 1 0 °C d i g e s t e r , however , was n o t as c o n s i s t e n t w i t h r e g a r d s t o the c o m p o s i t i o n o f e v o l v e d gas (Append ix A ) . The a n a l y s i s o f gas f rom t h i s d i g e s t e r showed t h a t C 0 2 i n c r e a s e d to 42-49% as compared to 28-32% C 0 2 f o r t he warmer d i g e s t e r s . T h i s i n c r e a s e can be r e l a t e d to the drop i n pH o f t he d i g e s t e r e f f l u e n t , combined w i t h the drop i n the a l k a l i n i t y c o n c e n - t r a t i o n between the i n c o m i n g raw was te and the e f f l u e n t (Append ix A ) . E s s e n t i a l l y a l l a l k a l i n i t y measured i n the d i g e s t e r was i n the fo rm o f b i c a r b o n a t e a l k a l i n i t y . The c h e m i c a l e q u i l i b r i a i n the d i g e s t e r r e s u l t i n g f rom t h i s b i c a r b o n a t e a l k a l i n i t y may be r e p r e s e n t e d as H + + HCO3 t H 2 C 0 3 t C 0 2 ( a q . ) + H 2 0 C 0 2 ( a q . ) t C 0 2 ( g a s ) As t he pH d ropped i n the d i g e s t e r , a g r e a t e r p o r t i o n o f t he b u f f e r c a p a c i t y was u t i l i z e d and c o n s e q u e n t l y the c h e m i c a l e q u i l i b r i a s h i f t e d to the r i g h t r e l e a s i n g a d d i t i o n a l C 0 2 g a s . I f t h i s dynamic e q u i l i b r i u m a p p l i e d to the 10°C d i g e s t e r , i t p r o v i d e s an e x p l a n a t i o n f o r the i n c r e a s e d p e r c e n t a g e o f C 0 2 i n the e v o l v e d ga s . The v a r i a t i o n i n the gas c o m p o s i t i o n ( i . e . f l u c t u a t i o n s i n the p e r 52 TABLE X DAILY GAS PRODUCTION AS RELATED TO TEMPERATURE T h e o r e t i c a l LDT (Days) Temp. ( ° C ) T o t a l D a i l y Gas P r o d u c t i o n (A/day @ STP) (1) Gas P r o d u c t i o n P r i o r t o Raw Waste A d d i t i o n ( m £ / d a y @ STP) (2) Gas P r o d u c e d f r om Raw Waste Added D a i l y ( 1 -2 ) (mA/day @ STP) 50 30 25 18-23 10 6250 6600 5600 4430 4890 4100 1820 1710 1500 25 30 25 18-23 10 12000 9800 9600 500 9260 7350 7700 250 2740 2450. 1900 250 12.5 30 25 18-23 10 24700 19500 17250 1250 19500 15600 14300 600 5200 3900 2950 650 30 25 18-23 10 28000 25000 22750 20900 18800 17750 7100 6200 5000 53 cent of C 0 2 gas) could conceivably have been caused by the variation in the alkalinity of the raw waste. McCarty [ l l ] states that the indicators of unbalanced treatment in a digester are: (i) increased volatile acids concentration and C 0 2 percentage in gas; ( i i ) decreased pH, total gas production and waste stabilization. These indicators were present in the 10°C digester but not in the other three. C H A P T E R V I SETTLING - VS - BIOLOGICAL DEGRADATION 6.1 I n t r o d u c t i o n Removal o f o r g a n i c s f rom the raw was te added d a i l y t o the d i - g e s t e r s was f ound to be due to two f a c t o r s (1) s e t t l i n g and (2) b i o l o g i c a l d e g r a d a t i o n . S e t t l i n g i s s t r i c t l y a p h y s i c a l phenomena and any r e m o v a l o f o r g a n i c s i s a c h i e v e d o n l y by s e p a r a t i o n . Hence the o r g a n i c l o a d has n o t been d i s p o s e d o f , but m e r e l y c o n c e n t r a t e d . A n a e r o b i c d e g r a d a t i o n r e d u c e s the was te l o a d by c o n v e r t i n g o r g a n i c s t o gaseous e n d - p r o d u c t s [ l l , 1 8 , 1 9 , 2 0 ] . B i o l o g i c a l r e d u c t i o n o f was te depends t o v a r y i n g d e g r e e s o n : ( i ) t e m p e r a t u r e , w h i c h a f f e c t s t he b i o l o g i c a l a c t i v i t y ; ( i i ) c h a r a c t e r i s t i c s o f the waste ( i . e . t y p e s o f o r g a n i c s , t o x i c s u b s t a n c e s , e t c . ) , w h i c h d e t e r m i n e the ea se w i t h w h i c h b a c t e r i a can degrade o r s t a b i l i z e the w a s t e ; ( i i i ) c o n t a c t t ime between the waste and b a c t e r i a , wh i ch d e t e r m i n e s the p e r c e n t o f the t o t a l o r g a n i c s r e d u c e d . The a n a e r o b i c t r e a t m e n t may be d e s c r i b e d as a t h r e e - s t e p p r o c e s s i n v o l v i n g ( i ) h y d r o l y s i s o f complex m a t e r i a l ( i i ) a c i d p r o d u c t i o n ( i i i ) methane f e r m e n t a t i o n . 54 55 In the f i r s t s t e p , complex o r g a n i c s a r e c o n v e r t e d to l e s s com- p l e x s o l u b l e o r g a n i c compounds by e n z y m a t i c h y d r o l y s i s . In the s e c o n d s t e p , t h e s e h y d r o l y s i s p r o d u c t s a r e f e r m e n t e d to s i m p l e o r g a n i c compounds ( p r e - d o m i n a n a t l y v o l a t i l e f a t t y a c i d s ) by a group o f f a c u l t a t i v e and a n a e r o b i c b a c t e r i a c o l l e c t i v e l y c a l l e d " a c i d - f o r m e r s " . In the t h i r d s t e p , the s i m p l e o r g a n i c compounds a r e f e r m e n t e d to methane and c a r b o n d i o x i d e by a group o f s u b s t r a t e - s p e c i f i c s t r i c t a n a e r o b e s c a l l e d "methane f o r m e r s " . Thus o r g a n i c was te m a t e r i a l s a r e c o n v e r t e d e f f e c t i v e l y to b a c t e r i a l p r o t o p l a s m and gaseous e n d - p r o d u c t s o f CH^, C 0 2 and t r a c e g a s e s . The r e s u l t i s t h a t f o r some o r g a n i c s an a b s o l u t e r e m o v a l i s a c h i e v e d t h r o u g h c o n v e r s i o n to gaseous e n d - p r o d u c t s . In a c t u a l waste t r e a t m e n t p r a c t i c e , no t a l l o r g a n i c s can be t a k e n t h r o u g h t h i s c h a i n o f e v e n t s , as some o r g a n i c s i n the raw was te a r e r e s i s t a n t t o b i o l o g i c a l b reakdown. Hence f o r a c t u a l was te t r e a t m e n t , t o t a l r e m o v a l o f o r g a n i c s i s n o t p r a c t i c a l l y p o s s i b l e . 6.2 G e n e r a l D i s c u s s i o n W i t h r e g a r d t h e n to the raw waste s t u d i e d and i t s t r e a t m e n t , s i n c e b u i l d - u p o f s e t t l e d s o l i d s f rom the d a i l y a d d i t i o n o f raw was te i s i n e v i t a b l e , the s o l u t i o n i s t o c o n t r o l t o some d e g r e e , d e p e n d i n g on d i f - f e r e n t c i r c u m s t a n c e s , the r a t e o f s o l i d s b u i l d - u p and t h e r e b y r e c e i v e maximum b e n e f i t f rom the a n a e r o b i c l a g o o n i n g s y s t e m . The re a r e t h r e e p o s s i b l e a l t e r n a t i v e s i n c o n t r o l l i n g the r a t e o f s o l i d s b u i l d - u p i n l a g o o n s f o r t r e a t m e n t o f c o n c e n t r a t e d a n i m a l w a s t e s . These a r e : ( i ) an e x t e n d e d h o l d i n g p e r i o d where a l a r g e p e r c e n t a g e o f the o r g a n i c s a r e b i o l o g i c a l l y r e d u c e d , and the r e m a i n i n g s o l i d s a r e h e l d 56 " i n d e f i n i t e l y " i n the l a g o o n . F o r a t r e a t - ment sy s tem of t h i s t y p e , however the c o s t f o r the r e q u i r e d l a n d a r e a and o f c o n s t r u c t i o n o f t h e s e l a goons c o u l d be p r o h i b i t i v e . ( i i ) a v e r y b r i e f d e t e n t i o n p e r i o d where e s s e n t i a l l y o n l y s e t t l e a b l e waste m a t e r i a l s a re removed and o n l y a s m a l l f r a c t i o n o f t he d e g r a d a b l e o r g a n i c s a r e r e d u c e d by b a c t e r i a . The s l u d g e b u i l d - u p i n t h i s c a se wou ld be r a p i d and f u r t h e r t r e a t m e n t o f the e f f l u e n t wou ld p r o b a b l y be r e q u i r e d . A l s o , an a d d i t i o n a l method o f d i s p o s a l f o r the a c c u m u l a t e d s o l i d s wou ld be needed ( e . g . l a n d d i s p o s a l by f r e q u e n t t r u c k i n g o f the s o l i d s ) , ( i i i ) a compromise on the above two ext remes ( i . e . a l a g o o n i n g sy s tem w i t h a c t i v e a n a e r o b i c d i g e s t i o n , and a l i m i t e d s l u d g e s t o r a g e c a p a c i t y w i t h a p rogram f o r the p e r i o d i c d i s p o s a l o f the a c c u m u l a t e d s l u d g e ) . As an examp le , l a n d d i s p o s a l o f the s l u d g e p r o d u c e d c o u l d be c o - o r d i n a t e d t o s u i t the r e q u i r e - ments o f s u r r o u n d i n g f a r m s . In s t u d y i n g c o n c e n t r a t e d a n i m a l was tes and c o n s i d e r i n g the above t h r e e a l t e r n a t i v e s , two q u e s t i o n s were r a i s e d wh i ch r e q u i r e d an swer s : (1) What p e r c e n t o f the t o t a l COD, BOD and VS o f the raw waste was removed by s e t t l i n g and what p e r c e n t by b i o l o g i c a l a c t i v i t y ? (2) What t e m p e r a t u r e s and l e n g t h o f LDT wou ld p r o v i d e a b a l a n c e between r e m o v a l by s e t t l i n g and by b i o l o g i c a l d e g r a d a t i o n ? 6.3 Methane P r o d u c t i o n R e l a t e d to COD, BOD and VS R e d u c t i o n From p r e v i o u s work done on a n a e r o b i c t r e a t m e n t M c C a r t y [ l l ] has shown f rom t h e o r e t i c a l c o n s i d e r a t i o n s s u p p o r t e d by e x p e r i m e n t a l e v i d e n c e t h a t a maximum o f 5.62 c u . f t . o f methane gas w i l l be p r o d u c e d p e r pound o f COD o r u l t i m a t e BOD r e d u c e d (0.35 m l . o f methane/mg o f COD o r B 0 D L ) . From the f o l l o w i n g f o r m u l a the r e d u c t i o n o f COD o r B 0 D L t o methane can be c a l - c u l a t e d : Cm = 5 .62F (1) where F = pounds o f B 0 D L o r COD r e d u c e d p e r day Cm = c u b i c f e e t o f CH1+ p r o d u c e d p e r day F o r VS r e d u c t i o n E c k e n f e l d e r [ l O ] r e p o r t s the f o l l o w i n g : " . . . T h e r e p o r t e d gas p r o d u c t i o n f o r v o l a t i l e s o l i d s (VS) r e d u c t i o n i n a w e l l o p e r a t i n g a n a e r o b i c d i g e s t i o n t ank i s 17 to 20 f t 3 / l b o f VS d e s t r o y e d w i t h a methane c o n t e n t o f about 65 p e r c e n t . T h i s i s e q u i v a l e n t t o 5 t o 7 f t 3 o f COD d e s t r o y e d wh i ch i s c l o s e to the v a l u e r e p o r t e d by Lawrence and M c C a r t y . I t i s s i g n i f i c a n t a t t h i s p o i n t t h a t t h e s e v a l u e s a r e a maximum, as suming comp le te c o n v e r s i o n o f the s o l i d s t o methane. V o l a t i l e s o l i d s r e d u c t i o n can o c c u r by l i q u e f a c t i o n and c o n v e r s i o n to v o l a t i l e a c i d s w i t h o u t any COD r e d u c t i o n . Under t h e s e c o n d i t i o n s , the methane y i e l d p e r u n i t o f v o l a t i l e s o l i d s r e d u c t i o n may be v e r y l o w . " From the f o l l o w i n g f o r m u l a the r e d u c t i o n o f VS can be c a l c u l a t e d : C f c = KP (2) where P pounds o f VS r e d u c e d p e r day c u b i c f e e t o f gas p r o d u c e d p e r day k = 17-22 f t 3 g a s / l b VS r e d u c e d o r 1 .06-1 .37 ml gas/mg VS r e d u c e d In o r d e r to use f o r m u l a e 1 and 2, the f o l l o w i n g i n f o r m a t i o n was n e c e s s a r y ( i ) week l y a n a l y s i s o f the e v o l v e d gas on a gas ch romatog raph i n o r d e r to d e t e r m i n e the C H 4 p e r c e n t a g e ; ( i i ) measurement o f the d a i l y gas p r o d u c t i o n f o r each o f the s p e c i f i c L D T ' s . D u r i n g the measurements a r e c o r d was k e p t o f the ave rage room t e m p e r a t u r e and a v e r a g e l o c a l a t m o s p h e r i c p r e s s u r e . T h i s was done so as to e n a b l e c o n - v e r s i o n o f the c o l l e c t e d d a t a to STP; ( i i i ) measurement o f the r a t e a t wh i ch gas was p r o - duced d u r i n g a t e s t r u n . Read ing s were t aken e v e r y 15 m i n u t e s . W i th t h i s d a t a the d a i l y vo lume o f gas p r o d u c e d c o u l d then be s e p a r a t e d i n t o components - t h a t p r o d u c e d f rom the a c - cumu l a ted s l u d g e , and t h a t p r o d u c e d f rom the d a i l y a d d i t i o n o f raw w a s t e ; ( i v ) measurement o f the ave rage d a i l y a d d i t i o n o f VS f o r e a c h LDT. From the above d a t a and as suming t h a t measured c h e m i c a l and b i o c h e m i c a l oxygen demand a r e e q u i v a l e n t and i n t e r c h a n g e a b l e , e x p e r i m e n t a l v a l u e s o f 59 F and P c o u l d be d e t e r m i n e d . The f i n a l r e s u l t s wou ld then make p o s s i b l e a c o m p a r i s o n between the p e r c e n t r e d u c t i o n o f COD, BOD^ and VS to gaseous e n d - p r o d u c t s and the p e r c e n t removed by s e t t l i n g . E x p e r i m e n t a l r e s u l t s a r e g i v e n i n T a b l e s X I , X I I , and X I I I and F i g u r e s 6 - 1 , 6-2 and 6 - 3 . F o r t he c a l c u l a t i o n s u s i n g e q u a t i o n s 1 and 2, see A p p e n d i x E. In o r d e r to e x p l a i n the r a t i o n a l e f o r F i g u r e s 6 - 1 , 6-2 and 6 - 3 , an example f o r each w i l l be g i v e n . Case I - COD F o r the r e s u l t s o b t a i n e d f o r g i v e n c o n d i t i o n s o f (1) Tempera tu re = 25°C (2) LDT = 25 days ( i n t h i s c a se a l o a d i n g o f l £ / d a y o f raw was te ) the maximum amount o f the measured raw was te COD l o a d t h a t was b i o l o g i c a l l y r e d u c e d to gaseous e n d - p r o d u c t s was a p p r o x i m a t e l y 18.5% and 63 .5% o f t he measured COD l o a d o f t he raw was te was removed by s e t t l i n g . Case I I - BOD 5 F o r the same g i v e n c o n d i t i o n s as Case I, the maximum amount o f the measured raw was te BOD 5 l o a d t h a t was b i o l o g i c a l l y r e d u c e d to gaseous e n d - p r o d u c t s was a p p r o x i m a t e l y 51% and 27% o f the measured BOD 5 l o a d was removed by s e t t l i n g . Case I I I - VS F o r the same g i v e n c o n d i t i o n s as Case I, a s suming the c o n s t a n t k to be c o r r e c t , a p p r o x i m a t e l y 15% o f the measured raw waste VS l o a d was b i o - l o g i c a l l y r e d u c e d and 65% o f the measured VS l o a d was removed by s e t t l i n g . F o r a l l o f the above c a s e s , the sum of the two p e r c e n t a g e s t o t a l s the TABLE XI PER CENT" COD REDUCED BY BIOLOGICAL ACTION Average Temp. L o a d i n g Raw Waste COD* ( ° C ) Ra te ( £ / d a y ) Cone. L o a d i n g ( m g / £ ) (mg/day) 30 1/2 29350 14675 1850 66.5 1225 3490 24 1 25450 25450 2750 68 1870 5330 21 2 32400 64800 5200 66.5 3445 9815 15 4 50000 200000 7100 68 4830 13765 7 25 1/2 29350 14675 1700 67 .5 1145 3265 22 1 25450 25450 2450 68 1665 4745 18.5 2 32400 64800 3900 67.5 2620 7475 11.5 4 50000 200000 6200 68 4215 12015 6 18-23 1/2 29350 14675 1500 71 1060 3015 20.5 1 25450 25450 1900 69.5 1315 3750 14.5 2 32400 64800 2950 68 2005 5715 9 4 50000 200000 5000 69 3450 9835 5 10 1 25450 25450 250 51 125 355 1.5 2 32400 64800 650 43 270 760 1 * A v e r a g e Raw Waste COD added d u r i n g t h i s p a r t of the t e s t i n g . * * T h i s i s the a d j u s t e d v a l u e wh i ch takes i n t o c o n s i d e r a t i o n the gas p roduced f rom the accumu la ted d i g e s t e r s l u d g e ( see T a b l e V I ) * * * k = 2.85 mg COD/mj! CH^ o Average V o l . F * * * % of Gas Produced % Cm , . of Raw Waste from Raw Waste C H 4 (mil/day) V.-kjCm; C 0 D A d d e d * * (mg/day) L o a d i n g (mA/day) TABLE X I I PER CENT BOD c REDUCED BY BIOLOGICAL ACTION Temp. ( ° C ) L o a d i n g Rate Average Raw Waste B0D 5 * Ave rage V o l . of Gas P roduced f rom Raw Waste % CH Cm (mil/day) p ft** max (=k 1Cm) % of Raw Waste BOD, (A/day) Cone. ( m g / £ ) L o a d i n g (mg/day) A d d e d * * (nU/day) (mg/day) L o a d i n g 30 1/2 9200 4600 1850 66.5 1225 3490 76 1 9300 9300 2750 68 , 1870 5330 57 2 10850 21700 5200 66.5 3445 9815 45 4 10700 42800 7100 68 4830 13765 32 25 1/2 9200 4600 1700 67.5 1145 3265 71 1 9300 9300 2450 68 1665 4745 51 2 10850 21700 3900 67.5 2620 7475 34.5 4 10700 42800 6200 68 4215 12015 28 18-23 1/2 9200 4600 1500 71 1060 3015 65.5 1 9300 9300 1900 69.5 1315 3750 40.5 2 10850 21700 2950 68 2005 5715 26.5 4 10700 42800 5000 69 3450 9835 23 10 1 9300 9300 250 51 125 355 4 2 10850 21700 650 43 270 760 3.5 * Ave rage Raw Waste BOD^ added d u r i n g t h i s p a r t o f the t e s t i n g . * * T h i s i s the a d j u s t e d v a l u e wh ich takes i n t o c o n s i d e r a t i o n the gas p roduced f rom the accumu la ted d i g e s t e r s l u d g e ( see T a b l e VI ) *** k± = 2.85 mg BOD/mA C H 4 TABLE X I I I PER CENT VS REDUCED BY BIOLOGICAL ACTION Temp, ( ° C ) L o a d i n g Rate (A/day) Average Raw Waste VS* Cone. L o a d i n g ( m g / £ ) (mg/day) c t * * (Average V o l . o f Gas P roduced f r o m Raw Waste added) (ml/day) (=k 2c t) (mg/day) % of Raw Waste VS Reduced Range Avg . 30 1/2 - - 1850 1350 - 1740 - - 1 15300 15300 2750 2010 - 2600 13.2 - 17 15 2 22500 45000 5200 3800 - 4900 8.5 - 11 10 4 35000 140000 7100 4900 - 6700 3.5 - 5 4 25 1/2 _ 1700 1240 1600 _ _ 1 15300 15300 2450 1790 - 2310 11.5 - 15 13 2 22500 45000 3900 2850 - 3680 6.5 - 8 7 4 35000 140000 6200 4530 - 5850 3 - 4 3 18-23 1/2 _ 1500 1100 1415 _ _ 1 .15300 15300 1900 1390 - 1790 9 11.5 10 2 22500 45000 2950 2150 - 2780 5 6 5 4 35000 140000 5000 3650 - 4710 2.5 - 3.5 3 10 1 15300 15300 250 185 _ 235 1 1.5 = 1 2 22500 45000 650 475 — 615 1 1.5 = 1 Average Raw Waste VS added d u r i n g t h i s p a r t o f t e s t i n g . * * T h i s i s the a d j u s t e d v a l u e which takes i n t o c o n s i d e r a t i o n the gas p roduced f r om the accumu la ted d i g e s t e r s l u d g e ( see T a b l e VI) * * * k 9 = 0 ,73 - 0 .94 mg VS/mA gas produced (65 - 70% CH.) 63 • • 3 0 °C DIGESTER c — • o 25 °C DIGESTER A 4 18-23 °C DIGESTER 100 -i A - — - A 10 °C DIGESTER F I G U R E 6 - 1 PERCENT OF COD REMOVED BY BIOLOGICAL REDUCTION AS COMPARED TO THE OVERALL COD REMOVAL OVER A RANGE OF LDTs. 64 • • 3 0 °C DIGESTER o o 25 °C D IGESTER A A I 8 - 2 3 ° C DIGESTER 100 i * — 1 0 °C DIGESTER L D T (DAYS) F IGURE 6 - 2 PERCENT OF B 0 D 5 REMOVED BY BIOLOGICAL REDUCTION AS COMPARED TO T H E OVERALL B O D 5 REMOVAL OVER A RANGE OF L D T s . 65 • • 30 °C DIGESTER o o 25 °C DIGESTER A • 1 8 - 2 3 ° C DIGESTER 100 n 10 °C DIGESTER PERCENT OF V S REMOVED BY BIOLOGICAL REDUCTION AS COMPARED TO T H E O V E R A L L VS REMOVED OVER A RANGE OF L D T s . 66 measured o v e r a l l r e m o v a l . 6 .4 D i s c u s s i o n o f R e s u l t s These r e s u l t s were n o t e d : (a) Tempera tu re ( i ) F o r the range o f t e m p e r a t u r e s s t u d i e d , s e q u e n t i a l d rop s i n r e m o v a l e f f i c i e n c y r e s u l t e d as the t e m p e r a t u r e d e c r e a s e d . T h i s was as e x p e c t e d , s i n c e the l e v e l o f b i o l o g i c a l a c t i v i t y i s more i n t e n s e a t e l e v a t e d t e m p e r a t u r e s and a g r e a t e r p o r t i o n o f the o r g a n i c m a t t e r i s t h e r e - f o r e m e t a b o l i z e d d u r i n g a s p e c i f i e d t ime p e r i o d . ( i i ) The r a p i d drop i n the a c t i v i t y o f t he b a c t e r i a between 20°C to 10°C i s o f s i g n i f i c a n c e . I t appea r s t h a t even a t the modera te t e m p e r a t u r e s o f 10°C methane f e r m e n t a t i o n i s s e v e r e l y r e t a r d e d . However, comp le te a n a e r o b i c a c t i v i t y does no t n e c e s - s a r i l y c e a s e . The h y d r o l y s i s p r o c e s s and o r g a n i c a c i d p r o d u c t i o n s t i l l c o n t i n u e s , a l t e r i n g the d i g e s t e r c o n t e n t s . Thus when the t e m p e r a t u r e f i n a l l y does i n c r e a s e , methane f e r m e n t a t i o n can c o n t i n u e . T h i s o b s e r v a t i o n was n o t e d w i t h the 10°C d i g e s t e r . Gas p r o d u c t i o n i n c r e a s e d m a r k e d l y w i t h i n 2-3 days a f t e r the r e f r i g e r a t i o n u n i t was d i s c o n n e c t e d and the d i g e s t e r t e m - p e r a t u r e i n c r e a s e d to the l a b t e m p e r a t u r e o f a p p r o x i m a t e l y 2 0 ° C . ( i i i ) A l l o w i n g the t e m p e r a t u r e to f l u c t u a t e f rom 1 8 ° - 2 3 ° C d i d n o t a d v e r s e l y a f f e c t b i o l o g i c a l a c t i v i t y . A s m a l l e r p e r c e n t o f t he o r g a n i c s were m e t a b o l i z e d as com- p a r e d to the 25°C and 30°C d i g e s t e r b u t t h i s was e x p e c t e d becau se o f the l o w e r a v e r a g e t e m p e r a t u r e . The p e r c e n t r e m o v a l was much above the r e s u l t s o b t a i n e d f o r the 10°C d i g e s t e r . D e t e n t i o n Time ( i ) From the r e s u l t s f o r b i o l o g i c a l r e d u c t i o n o f VS and COD, i t i s a p p a r e n t t h a t a l a r g e p o r t i o n o f the VS and COD l o a d o f t he raw waste i s n o t amenable to b i o l o g i c a l a c t i o n F o r COD r e d u c t i o n , a l e v e l l i n g o f f o c c u r s a f t e r 25 days LDT and any f u r t h e r i n c r e a s e i n the d e t e n t i o n t ime i s o f l i t t l e b e n e f i t T h i s wou ld a l s o appea r to be the case f o r VS r e d u c t i o n . ( i i ) E x t e n d i n g the b i o l o g i c a l c o n t a c t t ime m a r k e d l y a f f e c t s t he b i o l o g i c a l r e - d u c t i o n o f the BOD 5 l o a d a t t e m p e r a t u r e s above 2 0 ° C . ( i i i ) T h e r e appea r s t o be l i t t l e b e n e f i t f o r e x t e n d e d b i o l o g i c a l c o n t a c t t ime a t t e m p e r a t u r e s 10°C o r l e s s . O r g a n i c s Removal ( i ) I n c l u d e d i n t he was te c o m p o s i t i o n a r e a g g r e g a t e d complex o r g a n i c s such as f e e d c h i p s , wood f i b r e s , swine h a i r s , seeds and g r a i n h u l l s w h i c h a r e e s s e n t i a l l y n o n - b i o d e g r a d a b l e . These a r e r e a d i l y s e p a r a b l e f r om the d i g e s t e r s u p e r n a t a n t and a r e c o n - c e n t r a t e d i n t he s l u d g e and scum l a y e r s . From the d a t a f o r VS r e m o v a l the i n d i c a t i o n t h a t a s i g n i f i c a n t p o r t i o n o f the o r g a n i c s i n the d i g e s t e r s a r e o f t h i s n a t u r e and hence w i l l a c c u m u l a t e i n the d i g e s t e r , ( i i ) R e d u c t i o n o f o r g a n i c s by b a c t e r i a i s t em- p e r a t u r e s e n s i t i v e and i s s i g n i f i c a n t l y r e d u c e d a t t e m p e r a t u r e s be low 2 0 ° C . ( i i i ) The r a p i d i n c r e a s e i n the b i o l o g i c a l r e - d u c t i o n o f the BOD 5 l o a d by e x t e n d i n g the c o n t a c t t ime i n d i c a t e s t h a t the measured BOD 5 l o a d o f the raw waste p r o v i d e s a r e a d i l y a v a i l a b l e f o o d s o u r c e f o r the b a c t e r i a . C H A P T E R V I I NUTRIENTS 7.1 I n t r o d u c t i o n I t i s g e n e r a l l y a g r e e d today t h a t p h o s p h a t e s and n i t r o g e n com- pounds a r e p r i m a r y c o n t r i b u t o r s to e u t r o p h i c a t i o n i n n a t u r a l b o d i e s o f w a t e r and a t the same t ime a r e n e c e s s a r y i n any b i o l o g i c a l t r e a t m e n t schemes. D u r i n g t h i s s t u d y the p o s s i b l e e f f e c t s o f t h o s e two n u t r i e n t s were c o n s i d e r e d i n l i g h t o f the above two p o i n t s . The " i n " and " o u t " c o n c e n t r a t i o n s o f am- m o n i a - n i t r o g e n and p h o s p h a t e were m o n i t o r e d i n an a t t empt to answer a number o f q u e s t i o n s . (1) W i l l t he a m m o n i a - n i t r o g e n c o n c e n t r a t i o n i n t he d i g e s t e r c o n t e n t s and raw waste a f f e c t a n a e r o b i c t r e a t m e n t ? (2) What e f f e c t s do d e t e n t i o n t ime and t e m p e r a t u r e have on the e f f l u e n t c o n c e n t r a t i o n s o f p h o s p h a t e a r e ammon i a -n i t r o gen ? (3) What p e r c e n t o f t he t o t a l b i o l o g i c a l oxygen demand w i l l be due to n i t r o g e n e o u s oxygen demand? In o r d e r to measure the c o n c e n t r a t i o n s and e f f e c t s o f the above two n u t r i e n t s , c h e m i c a l and gas a n a l y s e s were c a r r i e d o u t . The c h e m i c a l t e s t s a r e o u t l i n e d i n S t a n d a r d Methods [ 15 ] and w e r e : ( i ) t o t a l K j e l d a h l - N ( i i ) o r g a n i c K j e l d a h l - N ( i i i ) t o t a l pho spha te 70 (NOTE - the a r i t h m e t i c d i f f e r e n c e between t o t a l and o r g a n i c K j e l d a h l - N c o n c e n t r a t i o n s d e t e r m i n e s the ammonia K j e l d a h l - N c o n c e n t r a t i o n . ) 7.2 Ave rage Raw Waste and E f f l u e n t C h a r a c t e r i s t i c s The d a t a p r e s e n t e d i n T a b l e s XIV and XV a r e a ve rage v a l u e s as m e n t i o n e d p r e v i o u s l y , i n c a l c u l a t i n g t h e s e ave rage v a l u e s o n l y t h o s e r e s u l t s were c o n s i d e r e d i n the c a l c u l a t i o n o f a v e r a g e v a l u e s w h i c h were r e c o r d e d a f t e r the a p p r o p r i a t e t h e o r e t i c a l LDT had e l a p s e d . M c C a r t y i n h i s p a p e r e n t i t l e d A n a e r o b i c Waste T r e a t m e n t "Ammonia may be p r e s e n t d u r i n g t r e a t m e n t e i t h e r i n the fo rm o f t he ammonium i o n ( N H ^ ) o r as d i s s o l v e d ammonia gas ( N H 3 ) . These two forms a r e i n e q u i l i b r i u m w i t h each o t h e r , the r e l a t i v e c o n c e n t r a t i o n o f each d e p e n d i n g upon the pH o r h y d r o g e n i o n c o n c e n t r a t i o n as i n d i c a t e d by the f o l l o w i n g e q u i l i b r i u m e q u a t i o n : When the h y d r o g e n i o n c o n c e n t r a t i o n i s s u f f i c i e n t l y h i g h (pH o f 7.2 o r l o w e r ) , the e q u i l i b r i u m i s s h i f t e d to the l e f t so t h a t i n h i b i t i o n i s r e l a t e d to ammonium i o n c o n c e n t r a t i o n . A t h i g h e r pH l e v e l s , the e q u i l i b r i u m s h i f t s t o the r i g h t and the ammonia gas c o n c e n t r a t i o n may become i n h i b i t o r y . The ammonia gas i s i n h i b i t o r y a t a much l ower c o n c e n t r a t i o n than the ammonium i o n . " T h i s summary i s g i v e n by M c C a r t y on ammonia t o x i c i t y : 7.3 Ammonia-N T o x i c i t y Fundamenta l s [ l l ] s t a t e s : % NH 3 + H + Ammonia N i t r o g e n C o n c e n t r a t i o n (mg/A) E f f e c t on A n a e r o b i c T r e a t m e n t 50-200 200-1000 1500-3000 Above 3000 B e n e f i c i a l No A d v e r s e E f f e c t I n h i b i t o r y a t H i g h e r pH L e v e l s T o x i c 72 TABLE XIV AVERAGE RAW WASTE CHARACTERISTICS* T h e o r e t i c a l T o t a l O r g a n i c T o t a l Ammonia LDT Phospha te K j e l d a h l - N K j e l d a h l - N K j e l d a h l - N (Days) (mg/A) (mg/A) (mg/A) (mg/A) 50 2195 660 2435 1775 25 2040 750 2740 1990 12.5 2060 705 2285 1580 6** 3000 920 2310 1390 * V a l u e s f o r raw waste u sed i n c a l c u l a t i o n s f o r the r e s u l t s i n T a b l e XV I . * * T h e u n u s u a l l y h i g h v a l u e s f o r the 6 day LDT a p p e a r e d to be due to the h i g h s o l i d s c o n c e n t r a t i o n i n the f i n a l raw waste s a m p l e s . 73 TABLE XV AVERAGE EFFLUENT CHARACTERISTICS Temp, o f T h e o r e t i c a l T o t a l O r g a n i c T o t a l Ammonia D i g e s t e r LDT Phospha te K-N K-N K-N ( ° C ) (Days) (mg/A) (mg/A) (mg/A) (mg/A) 30 50 800 200 1810 1610 25 730 255 2190 1935 12.5 670 265 2130 1865 6 680 240 1740 1500 25 50 740 210 1850 1640 25 810 265 2155 1890 12.5 690 255 2095 1840 6 550 220 1600 1380 18-23 50 660 220 1850 1630 25 700 260 2100 1840 12.5 620 255 2070 1815 6 530 210 1500 1310 10 50 - - ~ " 25 670 265 2030 1765 12.5 790 315 2070 1755 6 750 195 1360 1165 74 F o r a l l f o u r d i g e s t e r s o v e r the e n t i r e d u r a t i o n o f the l a b s t u d y , the c o n - c e n t r a t i o n o f ammonia n i t r o g e n i n the raw waste and e f f l u e n t f l u c t u a t e d between 1300-2000 mg/A ( w i t h the pH a lways l e s s than 7 . 6 ) . The e f f e c t o f ammonia i n t h i s ca se a c c o r d i n g to the above c h a r t wou ld be to cause l i t t l e a d v e r s e e f f e c t s . From a l l i n d i c a t i o n s d u r i n g the s t u d y no c o m p l i c a t i o n s were e n c o u n t e r e d i n terms o f ammonia t o x i c i t y u p s e t t i n g n o r m a l a n a e r o b i c d i g e s t i o n . 7.4 E f f e c t o f Tempera tu re on T o t a l Phospha te and Ammonia-N Removal From the r e s u l t s i n T a b l e XV I , (see a l s o A p p e n d i x D) the f o l l o w i n g o b s e r v a t i o n s were n o t e d : ( i ) T o t a l pho spha te r e m o v a l - t he ave rage p e r c e n t r e m o v a l o f p h o s p h a t e appear s n o t t o be a f f e c t e d by t e m p e r a t u r e . Through the range o f t e m p e r a t u r e s f rom 1 0 - 3 0 ° C , the ave rage p e r c e n t r e m o v a l o f p h o s - p h a t e v a r i e d 6-7% and d i d n o t i n d i c a t e any dependency on t e m p e r a t u r e as was the ca se f o r COD and B0D 5 r e - m o v a l . ( i i ) Ammonia-N r e m o v a l - d a t a o b t a i n e d i s i n s u f f i c i e n t to d e t e r m i n e i f t e m p e r a t u r e does a f f e c t the ave rage pe r c e n t r e m o v a l o f ammonia-N. However the p o i n t to n o t e i s t h a t the maximum p e r c e n t r e m o v a l was a p p r o x i m a t e l y 15% wh ich i n d i c a t e s t h a t the ammonia-N i s p r i m a r i l y d i s s o l v e d and n o t removab le by s e t t l i n g . TABLE XVI PER CENT REMOVAL OF TOTAL PHOSPHATE AND AMMONIA-N AS AFFECTED BY TEMPERATURE T h e o r e t i c a l T e m p e r a t u r e Ave rage Removal (%) LDT ( ° C ) (Days) T o t a l Ammonia-N Phospha te 50 30 25 18-23 10 25 30 25 18-23 10 12.5 30 25 18-23 10 30 25 18-23 10 63.5 66.5 70 9.5 7.5 8 64 60.5 65.5 67 3 5 7.5 11.5 67.5 66.5 70 61 .5 0 0 0 0 77.5 81.5 82.5 75 0 0.5 5.5 16 T h e r e f o r e the 15% o f ammonia-N t h a t i s removed i s p r o b a b l y removed t h r o u g h two mechan i sms: ( i ) b i o l o g i c a l up take ( i i ) a d s o r p t i o n o f ammonia-N i n the c o l l e c t e d s l u d g e 7.5 E f f e c t o f D e t e n t i o n Time on T o t a l Phospha te and Ammonia-N Removal • From the r e s u l t s i n T a b l e XV I I ( see a l s o A p p e n d i x D ) , the f o l l o w i n g o b s e r v a t i o n s were n o t e d : ( i ) Pho spha te r e m o v a l - t w o - t h i r d s o f the p h o s p h a t e c o n c e n t r a t i o n i s r a p i d l y removed by s e t t l i n g . The r e m a i n i n g pho spha te i s p r e s e n t i n d i s s o l v e d form and f u r t h e r r e m o v a l wou ld l i k e l y r e q u i r e c h e m i c a l t r e a t m e n t , ( i i ) Ammonia-N r e m o v a l - the ammonia n i t r o g e n i n b o t h the i n c o m i n g raw waste and the e f f l u e n t i s p r e s e n t i n t he fo rm o f ammonium i o n ( N H ^ ) o r as d i s s o l v e d ammonia gas ( N H 3 ) , and cannot t h e r e f o r e be removed by s e t t l i n g . Based on t h i s t h e n e x t e n d i n g the d e t e n t i o n p e r i o d i s no t the s o l u t i o n to ammonia-N r e m o v a l . As p r e v i o u s l y m e n t i o n e d , the s m a l l deg ree o f r e m o v a l o f ammonia-N can be a t t r i b u t e d to (1) b i o l o g i c a l u p t a k e and (2) a d s o r p t i o n i n the d i g e s t e r s l u d g e . TABLE XV I I PER CENT REMOVAL OF TOTAL PHOSPHATE AND AMMONIA-N AS AFFECTED BY DETENTION TIME Temp, o f T h e o r e t i c a l Average Removal (%)* D i g e s t e r LDT ( ° C ) (Days) T o t a l Ammonia-N Pho spha te 30 50 63.5 9.5 25 64 3 12.5 67.5 0 6 77.5 0 25 50 66 .5 7.5 25 60.5 5 12.5 66.5 0 6 81.5 0.5 18 -23 50 70 8 25 65 .5 7.5 12.5 70 0 6 82.5 5.5 10 50 _ _ 25 67 11.5 12.5 61.5 0 6 75 6 * T h e s e r e s u l t s o f p e r c e n t r e m o v a l f o r the 6 day LDT a r e q u e s t i o n a b l e due t o the u n u s u a l l y h i g h VS c o n t e n t o f the raw waste samples u s e d . The r e s u l t s a r e ba sed on o n l y two t e s t s a m p l e s . 78 7.6 N i t r o g e n o u s Oxygen Demand The r e s u l t s f rom the s i n g l e l o n g term BOD t e s t c o m p l e t e d on the raw was te F i g u r e 7-1 i n d i c a t e d t h a t : ( i ) c a r b o n a c e o u s BOD o f the raw was te was between 10 ,000 -10 ,500 mg/A. T h i s a c c o u n t e d f o r 70-75% o f the t o t a l measured BOD; ( i i ) n i t r o g e n o u s oxygen demand o f the raw was te was between 4000-4500 mg/A mak ing up the o t h e r 25-30% o f the t o t a l measured BOD. D u r i n g the t r e a t m e n t i n the d i g e s t e r s the c a r b o n a c e o u s BOD was m e a s u r a b l y r e d u c e d but maximum r e d u c t i o n f o r ammonia-N c o n c e n t r a t i o n was 15% ( i . e . l i t t l e r e d u c t i o n o f the n i t r o g e n o u s BOD). C o n s e q u e n t l y , i f a s i m i l a r l o n g term BOD t e s t was c a r r i e d ou t on the d i g e s t e r e f f l u e n t t h e s e r e s u l t s c o u l d be e x p e c t e d : ( i ) c a rbonaceous BOD o f t he e f f l u e n t wou ld be r e d u c e d to 1000-1500 mg/A. T h i s wou ld a c c o u n t f o r a p p r o x - i m a t e l y 20 -30%; ( i i ) n i t r o g e n o u s BOD r e d u c e d o n l y t o a p p r o x i m a t e l y 3500-4000 mg/A wou ld now a c c o u n t f o r 70-80% o f the t o t a l m e a s u r a b l e BOD. T h i s i s a s i g n i f i c a n t r e s u l t i n terms o f the p o t e n t i a l added oxygen demand the e f f l u e n t w i l l e x e r t on any r e c e i v i n g w a t e r . LONG TERM BOD CURVE FOR RAW PIG WASTE FIGURE 7-1 C H A P T E R V I I I CONCLUSIONS AND RECOMMENDATIONS 8.1 I n t r o d u c t i o n The a n a e r o b i c . d e c o m p o s i t i o n o f c o n c e n t r a t e d a n i m a l was tes i s a f f e c t e d by v a r i o u s p a r a m e t e r s such a s : ( i ) r e a c t i o n t e m p e r a t u r e , ( i i ) d e t e n t i o n t ime , ( i i i ) waste c h a r a c t e r i s t i c s . The l a b o r a t o r y p rogram a s s e s s e d the e f f e c t s on hog waste t r e a t - ment o f t h e s e p a r a m e t e r s by measurements o f the f o l l o w i n g : ( i ) i n l e t and o u t l e t c o n c e n t r a t i o n s o f n u t r i e n t s , oxygen demand and s o l i d s ; ( i i ) gas p r o d u c t i o n and c o m p o s i t i o n . T h i s l a b s t u d y has p r o v i d e d some v a l u a b l e i n s i g h t i n t o the m e c h a n i c s o f a n a e r o b i c d i g e s t i o n o f c o n c e n t r a t e d a n i m a l w a s t e s . I t i s hoped t h e r e f o r e t h a t i t w i l l p r o v i d e d e s i g n e n g i n e e r s w i t h a d d i t i o n a l i n f o r m a t i o n to be used i n the o p t i m a l d e s i g n o f waste t r e a t m e n t f a c i l i t i e s . The f o l l o w i n g c o n c l u s i o n s and recommendat ions stem f rom the r e s u l t s o b t a i n e d t h r o u g h t h i s l a b s t u d y . 8.2 C o n c l u s i o n s (A) Tempera tu re - the t e m p e r a t u r e o f the d i g e s t e r c o n t e n t s w i t h r e g a r d to the waste s t u d i e d i s the p r i m a r y f a c t o r i n d e t e r m i n i n g the o p e r a t i n g e f f i c i e n c y o f a n a e r o b i c d i g e s t i o n . The f e r m e n t a t i o n k i n e t i c s w i l l c o n t i n u e to o p e r a t e s a t i s f a c t o r i l y as l o n g as the t e m p e r a t u r e i s m a i n t a i n e d above 2 0 ° C . However i n d e c r e a s i n g the t e m p e r a t u r e f r om 20°C to 1 0 ° C , the a c t i v i t y o f the- methane o r gan i sms i s m a r k e d l y r e d u c e d and f o r t e m p e r a t u r e s 10°C and b e l o w , the methane f e r m e n t a t i o n p r o c e s s and c o n s e q u e n t gas p r o d u c t i o n w i l l drop to z e r o . When t h i s o c c u r s , the d i g e s t e r does l i t t l e e l s e than a c t as a s e t t l i n g b a s i n . D e t e n t i o n Time - d e t e n t i o n t i m e , o r b i o l o g i c a l c o n t a c t t i m e , i s s i g n i f i c a n t when r e l a t e d w i t h t e m p e r a t u r e . W i th i n c r e a s i n g c o n t a c t t ime f o r t e m p e r a t u r e s f r om 20° to 3 0 ° C , an i n c r e a s i n g p o r t i o n o f the r e d u c e a b l e o r g a n i c m a t t e r i s c o n v e r t e d to s t a b l e e n d - p r o d u c t s . F o r t e m p e r a t u r e s l e s s t h a n 2 0 ° C , d e t e n t i o n t ime i s even more c r i t i c a l i n terms o f p r o v i d i n g s u f f i c i e n t t ime f o r maximum s o l i d s r e m o v a l by s e t t l i n g and a c h i e v i n g s i g n i f i c a n t r e d u c t i o n s i n oxygen demand. (As m e n t i o n e d a b o v e , r e d u c t i o n o f r e d u c e a b l e o r g a n i c s v i r t u a l l y c e a s e s a t t e m p e r a t u r e s l e s s t han 1 0 ° C . ) S e t t l i n g vs B i o l o g i c a l D e g r a d a t i o n - w i t h t h i s p a r - t i c u l a r w a s t e , i n a d d i t i o n to the i n o r g a n i c m a t t e r , a l a r g e p r o t i o n o f o r g a n i c m a t t e r i s i n e r t t o b i o l o g i c a l r e d u c t i o n . I t i s thus o b v i o u s t h a t the n o n - r e d u c e a b l e o r g a n i c s o l i d s add to the s o l i d s a c c u m u l a t i o n p r o b l e m . In t h i s r e g a r d adequate s o l i d s s t o r a g e i n the c e l l d e s i g n and p e r i o d i c d r e d g i n g o f the a n a e r o b i c c e l l s w i l l be n e c e s s a r y . N u t r i e n t C o n c e n t r a t i o n - a l a r g e p e r c e n t a g e o f t he n u t r i e n t l o a d o f ammonia-N and t o t a l p h o s p h a t e i s d i s s o l v e d and t h e r e f o r e canno t be f u r t h e r removed by s e t t l i n g . The d i g e s t i o n p r o c e s s a l s o does n o t a c h i e v e f u r t h e r n u t r i e n t r e d u c t i o n . In t h i s r e g a r d t h e r e f o r e , t o a c h i e v e f u r t h e r improvement i n t he e f f l u e n t q u a l i t y an a d d i t i o n to the a n a e r o b i c p r o c e s s w i l l be r e q u i r e d ( i . e . c h e m i c a l t r e a t m e n t a n d / o r n i t r i f i c a t i o n and d e n i t r i f i c a t i o n ) . Gas P r o d u c t i o n and C o m p o s i t i o n - w i t h r e g a r d t o t h i s w a s t e , gas p r o d u c t i o n i s a f u n c t i o n o f t e m p e r a t u r e ( t h i s f o l l o w s f rom the known f a c t t h a t the b i o l o g i c a l a c t i v i t y i s a f u n c t i o n o f t e m p e r a t u r e ) ; the gas c o n - s t i t u e n t s d u r i n g a c t i v e a n a e r o b i c d i g e s t i o n s h o u l d t e s t 97-99% methane and c a r b o n d i o x i d e . The r a t i o o f methane and c a r b o n d i o x i d e gas i s c h a r a c t e r i s t i c o f the s u b s t r a t e b e i n g added and does no t n e c e s s a r i l y i n d i c a t e u p s e t c o n d i t i o n s . O r g a n i c L o a d i n g - w i t h r e g a r d to t h i s s p e c i f i c was te t r e a t m e n t , o r g a n i c l o a d s o f 10.4 to 82.4 l b B O D 5 / 1000 f t 3 / d a y d i d no t i n d u c e d i g e s t e r u p s e t . However the p e r c e n t o f the t o t a l l o a d r e d u c e d d e c r e a s e d w i t h the i n c r e a s i n g o r g a n i c l o a d . C o n v e n t i o n a l recommended v a l u e s range f rom 10-20 l b BOD5/ IOOO f t 3 / d a y , and 83 compar ing t h i s w i t h the e x p e r i m e n t a l d a t a , c o n v e n t i o n a l d e s i g n p r a c t i s e i s a t l e a s t c o n s e r v a t i v e . 8.3 Recommendat ions f o r D e s i g n These recommendat ions b a s e d on the l a b o r a t o r y s t u d y w i t h o u t any c o r r e l a t i o n to f u l l - s c a l e r e s u l t s , w h i c h to d a t e have no t been c a r r i e d o u t , a r e p r e s e n t e d f o r t r e a t m e n t o f c o n c e n t r a t e d hog was te by a n a e r o b i c d i g e s t i o n : ( i ) i n d e s i g n i n g an a n a e r o b i c c e l l s y s tem f o r a g i v e n a r e a , a f a c t o r to c o n s i d e r i s c l i m a t i c c o n d i t i o n s ; ( e . g . F o r c o l d c l i m a t e s where the mean maximum t e m p e r a t u r e f r e q u e n t l y does n o t e x c e e d 2 0 ° C , a l a r g e r l a g o o n vo lume w i l l be r e q u i r e d as compared to warm c l i m a t e s beca u se l e s s s o l i d s w i l l be r e - duced and more a c c u m u l a t e d . ) ; ° ( i i ) i n o r d e r t o m a i n t a i n c o n t i n u o u s a c t i v e a n a e r o b i c d i g e s t i o n the t e m p e r a t u r e o f the d i g e s t e r c o n t e n t s s h o u l d n o t drop be low 2 0 ° C , u n l e s s a h i g h e r e f f l u e n t oxygen demand can be t o l e r a t e d d u r i n g the c o l d e r o p e r a t i n g p e r i o d ; ( i i i ) the r e q u i r e d pH range s h o u l d p r e f e r a b l y be between 7 . 2 - 7 . 6 ; ( i v ) due to the n a t u r e o f t he w a s t e , two c e l l s i n s e r i e s would p r o b a b l y p r o v i d e a b e t t e r t r e a t m e n t sy s tem than one c e l l o f the same t o t a l vo lume. The i n i t i a l c e l l would p r o v i d e p r i m a r y s e t t l i n g and v i g o r o u s 84 dig e s t i o n of the s o l i d s , and the second c e l l with l e s s vigorous overturning of the sludge would provide quiescent conditions for further removal of s o l i d s by s e t t l i n g plus a d d i t i o n a l anaerobic treatment; (v) enough volume should be provided for sludge accumulation to ensure that the LDT does not become so short that required b a c t e r i a are washed out ( i . e . because of the r e l a t i v e growth rate of methane organisms some methane b a c t e r i a w i l l be washed out i f LDT drops below 7 days). 8.4 Recommendations f o r Future Studies (A) Separation of S e t t l e d Solids and Supernatant This study would determine i f separation of the supernatant and the s e t t l e d s o l i d s during the di g e s t i o n process w i l l improve the q u a l i t y of the e f f l u e n t . This would e n t a i l having two c e l l s i n s e r i e s with a t o t a l volume equivalent to the volume of the s i n g l e c e l l used i n t h i s study. The primary c e l l would contain the accumulated s o l i d s and sludge; the secondary c e l l the supernatant. By providing quiescent conditions for the supernatant, improved e f f l u e n t q u a l i t y through s o l i d s s e t t l i n g could be achieved. (B) Determination of the Rate and Degree of B i o l o g i c a l Reduction of the Concentrated Animal Waste Oxygen Demand and V o l a t i l e Solids This study would consist of a s e r i e s of batch anaerobic vessels regulated at various temperatures. An i n i t i a l measurement of the COD, BOD and VS of the completely mixed digester contents would be required. 85 F o l l o w i n g t h i s , week ly a n a l y s i s o f the d i g e s t e r c o n t e n t s and e v o l v e d gas p l u s measurement o f gas p r o d u c t i o n would be c a r r i e d o u t . From t h i s a d e t e r m i n a t i o n o f the deg ree o f r e d u c t i o n t h a t can be e x p e c t e d w i t h such a was te and the b i o l o g i c a l r a t e o f r e d u c t i o n as r e l a t e d to such a was te c o u l d be a c c o m p l i s h e d . (C) Ammonia-N Removal In t h i s r e s p e c t , a s t u d y r e l a t e d s p e c i f i c a l l y t o n i t r o g e n o u s oxygen demand r e m o v a l f rom the d i g e s t e r s u p e r n a t a n t wou ld be w o r t h w h i l e . T h i s s t u d y wou ld i n c l u d e a two c e l l s y s tem as m e n t i o n e d p r e v i o u s l y . The s e c o n d c e l l wou ld i n c o r p o r a t e m e c h a n i c a l a e r a t i o n o r c h e m i c a l t r e a t m e n t i n o r d e r t o a c h i e v e ammonia-N r e m o v a l . (D) S l udge C h a r a c t e r i s t i c s Because a c c u m u l a t i o n o f s l u d g e pose s a p r o b l e m i n terms o f e v e n t u a l d i s p o s a l , a s t u d y r e l a t e d to the c h e m i c a l and p h y s i c a l c h a r a c t e r - i s t i c s o f s l u d g e , the e x t e n t to wh i ch the s l u d g e can be b i o l o g i c a l l y r e d u c e d and the e f f e c t o f d e t e n t i o n on r e d u c i n g the s l u d g e volume wou ld be w o r t h w h i l e i n more f u l l y u n d e r s t a n d i n g the o v e r a l l p i c t u r e f o r t r e a t m e n t o f c o n c e n t r a t e d a n i m a l w a s t e s . B I B L I O G R A P H Y Townshend, A. R., R e c h e r t , K. A . , and N o d w e l l , J . H. Status Report on Water P o l l u t i o n Control F a c i l i t i e s for Farm Animal Wastes in the Province of Ontario, A n i m a l Waste Management ( 1969 ) , C o r n e l l U n i v e r s i t y , pp . 131-149. L o e h r , Raymond C. The Challenge of Animal Waste Management, A n i m a l Waste Management (1969 ) , C o r n e l l U n i v e r s i t y , pp . 1 7 - 2 2 . H a r t , Samuel A . , and T u r n e r , M a r v i n E. Waste S t a b i l i s a t i o n Ponds for A g r i c u l t u r a l Wastes, Advances i n Water Q u a l i t y Improvement I ( 1968 ) , E d i t e d by G l o y n a and E c k e n f e l d e r , U n i v e r s i t y o f Texas P r e s s , pp . 457 -463 . W i l l r i c h , T . L. Primary Treatment of Swine Wastes by Lagooning, N a t i o n a l Symposium on A n i m a l Wastes Management (1966 ) , P r o c e e d i n g s , M i c h i g a n S t a t e U n i v e r s i t y , pp . 7 0 - 7 4 . C u r t i s , D a v i d R. Design C r i t e r i a for Anaerobic Lagoons for Swine Manure Disposal, N a t i o n a l Symposium on A n i m a l Waste Management ( 1966 ) , P r o c e e d i n g s , M i c h i g a n S t a t e U n i v e r s i t y , pp . 7 5 - 8 0 . T a i g i n i d e s , E. P . , Baumann, E. R., J o h n s o n , H. P . , and Hazen , T . E. Anaerobic Digestion of Hog Wastes, J o u r n a l o f A g r . E n g i n e e r i n g R e s e a r c h ( B r i t i s h ) , V o l . 8, No. 4 ( 1963 ) , p p . 327 -333 . H a r t , Samuel A. Animal Manure Lagoons, A Questionable Treatment System, 2nd I n t e r n a t i o n a l Symposium f o r Waste T r e a t m e n t Lagoons (1970 ) , pp . 320 -325 . W h i t e , James E. Current Design for Anaerobic Lagoons, 2nd I n t e r n a t i o n a l Symposium f o r Waste T r e a t m e n t Lagoons ( 1970 ) , p p . 360 -363 . D o r n b u s h , James N. State of the Art-Anaerobic Lagoons, 2nd I n t e r n a t i o n a l Symposium f o r Waste T r e a t m e n t Lagoons ( 1970 ) , p p . 382 -387 . E c k e n f e l d e r , W. W. Water Q u a l i t y E n g i n e e r i n g f o r P r a c t i s i n g E n g i n e e r s (1970 ) , Barnes & N o b l e , I n c . , New Y o r k . M c C a r t y , P. L. Anaerobic Waste Treatment Fundamentals, P u b l i c Works (September-December 1964 ) . 86 87 [ 12 ] B u s w e l l , A. M. Discussion - B i o l o g i c a l Formation of Methane, I n d u s t r i a l and E n g i n e e r i n g C h e m i s t r y , V o l . 48 , No. 9 ( 1956 ) , page 1443. [13 ] T a i g i n i d e s , E. P . , and Hazen , T . E. Properties of Farm Animal Excreta, T r a n s a c t i o n s o f the ASAE, V o l . 9 , No. 3 (1966 ) , p p . 374 -376 . [14 ] Schmid , Lawrence A . , and L i p p e r , R a l p h I. Swine Wastes, Characterization, and Anaerobic Digestion, A n i m a l Waste Management ( 1969 ) , C o r n e l l U n i v e r s i t y , p p . - 5 0 - 5 7 . [15 ] APHA, AWWA, WPCF S t a n d a r d Methods f o r the E x a m i n a t i o n o f Water and Wastewater ( 1965 ) , A m e r i c a n P u b l i c H e a l t h A s s o c i a t i o n , I n c . , 12th E d i t i o n . [ 16 ] Sawyer, C l a i r N . , and M c C a r t y , P e r r y L. C h e m i s t r y f o r S a n i t a r y E n g i n e e r s ( 1967 ) , M c G r a w - H i l l , 2nd E d i t i o n , New Y o r k . [17 ] R i c h , L i n v i l G . , U n i t P r o c e s s e s o f S a n i t a r y E n g i n e e r i n g ( 1963 ) , John W i l e y and Sons I n c . , New Y o r k . [ 18 ] M c K i n n e y , Ross E. M i c r o b i o l o g y f o r S a n i t a r y E n g i n e e r s ( 1962 ) , M c G r a w - H i l l , New Y o r k . [ 19 ] B a r k e r , H. A. B i o l o g i c a l Formation of Methane, I n d u s t r i a l and E n g i n e e r i n g C h e m i s t r y , V o l . 48, No. 9 ( 1956 ) , p p . 1438-1442. [ 20 ] P f e f f e r , John T . Anaerobic Lagoons - Theoretical Considerations, 2nd I n t e r n a t i o n a l Symposium f o r Waste T r e a t m e n t Lagoons ( 1970 ) , p p . 3 1 0 - 320. [ 21 ] E c k e n f e l d e r , W. W., and O ' C o n n o r , D. J . B i o l o g i c a l Waste T r e a t m e n t , Pergamon P r e s s ( 1 9 6 1 ) , New Y o r k . A P P E N D I C E S a APPENDIX A LABORATORY RESULTS 89 pH OF THE EFFLUENT AS R E L A T E D TO THE FEEDING RATE. O pH OF THE EFFLUENT AS R E L A T E D TO THE FEEDING RATE. pH OF THE EFFLUENT AS RELATED TO THE FEEDING RATE . VO r-2 7 1 7 0 6 9 PH 6 81 6-7 6-6 Digester * 4 - I O ° C 6 b o HI* o > 6 l a CO o od c o o Y ? . . ( 6 VS n <? 6': • O 6": 6-5 1 I / D a y 2 I /Day 4 I/Day JL 10 20 30 4 0 SO 6 0 70 8 0 90 100 110 Time ( Days) 120 130 140 ISO 160 170 160 190 pH OF E F F L U E N T AS R E L A T E D TO FEEDING R A T E . D i g e s t e r * l - 3 0 ° C 40 —I I— #2 - 2 5 ° C — n — #3 _ • I8°C- 35 — I I — #4 -- I 0 ° C 30 u R.W. COD V 2 I /Day 1 I/Day 21/Day <4J/Day ..o «•• • o o- I I I 1 I I 1 i i i i i i i i i i i i 0 10 20 30 40 50 60 70 80 9 0 100 110 120 130 140 ISO >60 170 180 190 Time ( Days) COD OF RAW WASTE 8 EFFLUENT AS RELATED TO THE FEEDING RATE . VO 16 V 2 l / D a y 11 /Day 2 I/Day 41/Day Time ( Days) B O D 5 OF RAW WASTE a EFFLUENT AS RELATED TO THE FEEDING R A T E VO v/i so 45 40 35 b 3 ° 25 E IA ? 2 0 o <n 2 o 10 Diges te r * I - 3 0 ° C — I I — * 2 - 2 5 ° C — " — * 3 - I 8 ° C - 2 3 ° C — H — * 4 - I 0 ° C Total Solids Raw Waste V2 I/Day 1 I/Day 2 l /Doy , j * y D S y J L J I I L ' ' I L 10 2 0 3 0 40 50 60 70 80 9 0 100 110 120 130 140 ISO 160 170 180 190 T i m e ( D a y s ) TS OF RAW WASTE S EFFLUENT AS RELATED TO THE FEEDING RATE . 40 " 35 O M - 30 o» E 25 •o o in 2 0 o o >5 10 D i g e s t e r * I - 3 0 ° C — II — * 2 - 2 5 ° C :4b — II — 3 " I 8 ° C " 2 3 ° C II * 4 - I 0 ° C V 2 1/ Day V o l a t i l e S o l i d s Raw Waste 1 I /Day 21/Day 10 20 3 0 4 0 50 6 0 7 0 8 0 9 0 100 T i m e ( Days) 110 120 130 140 ISO 160 170 180 190 VS OF RAW WASTE 8 EFFLUENT AS RELATED TO THE FEEDING RATE . I 2 0 0 0 10 20 30 40 SO 60 60 9 0 100 110 Time ( D a y s ) 120 130 140 ISO 160 170 180 190 L KJELDAHL N OF RAW WASTE 8 E F F L U E N T AS RELATED TO THE FEEDING RATE. I O O O I 9 0 0 8 0 0 ~ 7 0 0 | E " e o o l c <B t> O ~Z SOOl z JC O 4 0 0 | y 3 0 0 [ c o w 2 0 0 | O Digester * l - 3 0 ° C Raw Waste Organic Kjeldahl Nitrogen • n- o o- 100 _L 2 - 2 5 ° C II 3 - i e ° C - 23°C II * 4 - 10 ° C Ln V 2 1/ Day 1 I/Day 2 I/Day 4 I/Day J L • 0 20 30 4 0 50 60 70 80 9 0 100 110 120 130 140 I S O 160 170 180 190 T ime ( Days) ORGANIC K.N OF RAW WASTE 8 EFFLUENT AS RELATED TO THE FEEDING RATE . - 3000 2750 2 500 2250 g 2000 <p jj 1750 a CO o a. isoo Digester * I - 3 0 ° C — I I — * 2 - 2 5 ° C — I I — * 3 " I 8 ° C - 2 3 ° C II o 1250 . * 4 - I 0 ° C V2 1/ Doy 7T Total Phosphate Raw Waste 1 1/ Day 2 l /Doy 4 l/Daj 1000 750 5 0 0 10 20 30 40 50 60 70 T O T A L PHOSPHATE OF RAW WASTE 8 EFFLUENT AS RELATED TO THE FEEDING RATE . S Ti me ( Days) ALKALINITY OF RAW WASTE 8 EFFLUENT AS RELATED TO THE FEEDING RATE . 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 T i m e (Days ) i— o T O T A L GAS P R O D U C E D FOR SPECIFIC F E E D I N G R A T E . 100 90 80 70 £ 60 ° 50 o w 40 u Q> a . 30 2 0 I 0 V 1/ Day 2 1 I / D a y . 2 I/Day 41/Day 0 I / Day Digester =#= I - 3 0 ° C » # 2 - 2 5 ° C " * 3 - I 8 - 2 3 ° C - „ ^ 4 _ | 0 o c 20 40 60 80 100 120 140 160 180 T i m e ( Days) 200 220 240 260 280 300 320 o % M E T H A N E GAS OF T O T A L GAS COMPOSITION . 100 90 i r V I/ Day 2 T 1 1 T 1 I/Day 2 1 / D o y 41 /Day 0 1 / Day 8 0 _ 70 - 6 0 a H - 50 o c a> o 40 i_ a . 3 0 2 0 I 0 Digester # i - 3 0 ° C - „ 4^ 2 - 2 5 ° C — « # 3 - l 8 - 2 3 ° C •• # 4 - I O ° C 20 40 60 80 100 120 140 160 180 2 0 0 220 240 260 280 300 320 Time (Days) % C A R B O N DIOXIDE OF T O T A L GAS COMPOSITION. o -F - APPENDIX B EFFECT OF DETENTION TD1E ON COD, BOD 5 AND SOLIDS REMOVAL 105 % C O D AND BOD5 REMOVED (AVG) b COD AND BOD5 REMOVED (AVG) O _L_ O _ i o o _J cn O cn O 1 o L_ 00 o I _ 10 o o o r o - - 1 O I m r~ 0 m - 1 OJ -r\ O -n m 0 0 —1 > -< .e>_ 0 CO 0 D E T cn_ O m z TIO  cn_ 0 z - 1 M E O 0 z 0 0 p 0 CD 0 - - O O cn CP o~ CO 0 r~ ro_ 0 O CO r-R E M  O - 1 OJ_ 0 V A O  D A r~ -< CO 0 cn_ O cn O " ->i O 0 > 0 rn CO - 1 0 CD m O O aj O O U> z P ro r£ < t cn 0 0 % TS AND VS REMOVED (AVG) O ro O 1 01 o o I cn o I cn O 1 O I 00 o _ J _ 10 o 1 o o o m co —t m vo z p ro ro cn o o ZOT % COD AND BOD5 REMOVED (AVG) 1 m m -n m o - 1 o rn —t m 2 m o 0 4 - ro O f- O OJ H O CO cn O cn. O o OJ o I o cn o I cn o 3 1 CO o V O o o CD m co —i m JO z p OJ CO I ro OJ o o % TS AND VS REMOVED (AVG) o P p CO p o cn CP CO p o CO m 2 P % ro P D OJ H P CO cn P cn P P P ro cu P L_ 4> _2_ cn _2_ cn 5 1 00 _2_ CO _9_ CD m co —i m 3) z p 01 CO I ro Oi o o 801 LDT (DAYS) LDT (DAYS) THE E F F E C T OF DETENTION TIME ON COD, B O D 5 S SOLIDS REMOVAL o APPENDIX C EFFECT OF TEMPERATURE ON COD, BOD5 AND SOLIDS REMOVAL 110 100 9 0 - o 80- > < ~ 70" o UJ leo- UJ cc tn Q 50- o m LDT = 5 0 DAYS £ 40- < Q O 30" 20- 10 0 —\— 10 —T— 30 20 TEMP ( ° C ) 100 1 901 80 0 € 0 UJ > o 1 50- CO > Q z < to 40H 30 20 10 L D T =50 DAYS ( S A M P L E S NOT T A K E N ) .10 TEMP ( — i — 20 ° C ) 30 T H E EFFECT OF TEMPERATURE ON COD, B 0 D 5 AND SOLIDS REMOVAL 3TT   A P P E N D I X D E F F E C T OF D E T E N T I O N T I M E AND T E M P E R A T U R E ON A M M O N I A - N AND T O T A L P H O S P H A T E R E M O V A L 115 9TT  8TT 6IT APPENDIX E SAMPLE CALCULATIONS 120 121 CASE I - COD Cm = ml o f C H 4 p r o d u c e d p e r day k x = 2.85 mg COD/mA C i \ F = mg o f COD r e d u c e d p e r day f o r Temp. = 30°C LDT = 50 days COD r e d u c e d : F = k x Cm = 2 .85(1225) = 3490 mg/day L o a d i n g o f COD = 14675 mg/day % COD b i o l o g i c a l l y r e d u c e d : 3490 14675 X 1 0 0 = 2 4 % . 122 CASE I I - BOD 5 Cm = ml o f CH^ p r o d u c e d p e r day k x = 2.85 mg B O D 5 / m £ CH^ F = mg o f B0D 5 r e d u c e d p e r day f o r Temp. = 30°C LDT = 5 0 days B0D 5 r e d u c e d : F = k x Cm = 2 .85 (1225) = 3490 mg/day L o a d i n g o f B0D 5 = 4600 mg/day % B0D 5 b i o l o g i c a l l y r e d u c e d : 3490 4600 * 1 0 0 = 7 6 % 123 CASE I I I - VS C f c = ml o f gas p r o d u c e d p e r day k 2 = 0 . 7 3 - 0 . 9 4 mg VS/ml gas p r o d u c e d (65-70% CH^) P = mg o f VS r e d u c e d p e r day f o r Temp. = 30°C LDT = 25 day VS r e d u c e d : P = k 2 C t ( i ) f o r k 2 = 0 .73 P = 0 .73 (2750) = 2010 ( i i ) f o r k 2 » 0 .94 P = 0 .94 (2750) = 2600 L o a d i n g o f VS = 15300 mg/day % VS b i o l o g i c a l l y r e d u c e d : x 100 = 13.2% ( f o r k 2 = 0 .73 ) 2600 15300 x 100 = 17% ( f o r k ? = 0 .94 )

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