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Aerobic biostabilization of a high-strength landfill leachate Uloth, Victor Charles 1976

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AEROBIC BIOSTABILIZATION OF A HIGH-STRENGTH LANDFILL LEACHATE  by  V i c t o r Charles Uloth B . A . S c , U n i v e r s i t y o f W a t e r l o o , 1973  A THESIS SUBMITTED IN PARTIAL FULFILMENT  OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED  SCIENCE  I n the.Department of C i v i l Engineering  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 t o t h e required standard  The U n i v e r s i t y o f B r i t i s h F e b r u a r y , 1976  Columbia  In  presenting  an  advanced  the I  Library further  for  degree shall  agree  scholarly  by  his  of  this  written  thesis  in  at  University  the  make  that  it  thesis  purposes  for  freely  may  be  It  financial  University  Civil of  a  *e  for  J"fH\l  3Q  j  gain  Columbia  MIL  British for  extensive by  the  understood  Engineering  British  of  available  permission.  of  fulfilment of  granted  is  2075 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5  D  partial  permission  representatives.  Department The  this  shall  reference  Head  be  requirements  Columbia,  copying  that  not  the  of  copying  agree  and  of my  I  this  that  study. thesis  Department or  for  or  publication  allowed without  my  11  ABSTRACT  One p a r t i c u l a r l y u n d e s i r a b l e a s p e c t i s the contamination  o f water passing through the l a n d f i l l s i t e .  p o t e n t i a l adverse environmental recognized  o f s o l i d waste d i s p o s a l  on l a n d  The  e f f e c t s o f these " l e a c h a t e s " have been  t o the extent that t h e i r c o n t r o l  and t r e a t m e n t  of a great deal o f c u r r e n t research i n water p o l l u t i o n T h i s s t u d y was i n i t i a t e d t o i n v e s t i g a t e  i s the subject  control.  the p o s s i b i l i t y of reducing  the amounts o f oxygen demanding m a t e r i a l i n a h i g h - s t r e n g t h l a n d f i l l l e a chate by a e r o b i c b i o l o g i c a l methods, w i t h o u t any p r i o r removal o f t h e heavy metals contained  i n that leachate.  t i m e was a l s o i n v e s t i g a t e d  The e f f e c t  of v a r y i n g s o l i d s  detention  and t h e d i s t r i b u t i o n o f t h e heavy m e t a l s i n  the e f f l u e n t s was examined. U s i n g v e r y h i g h mixed l i q u o r v o l a t i l e suspended s o l i d s t i o n s , 8,000 t o 16,000 mg/1, and a c o m b i n a t i o n mixing, a n t i c i p a t e d  o f a i r and m e c h a n i c a l  foaming problems were c o n t r o l l e d  o p e r a t i o n was m a i n t a i n e d  concentra-  and s t a b l e  digester  a t s o l i d s d e t e n t i o n times as low as 10 days.  For  i n f l u e n t COD c o n c e n t r a t i o n s between 44,000 and 52,000 mg/1, s e t t l e d e f f l u e n t COD removal i n c r e a s e d m a r g i n a l l y from 96.8 t o 99.2 p e r c e n t , as t h e s o l i d s d e t e n t i o n t i m e i n c r e a s e d from 10 t o 60 days.  M i x e d l i q u o r COD  removal s i m i l a r l y i n c r e a s e d from 51.5 t o 75.7 p e r c e n t .  Increasing the  s o l i d s d e t e n t i o n t i m e from 10 t o 20 days, s i g n i f i c a n t l y improved t h e q u a l i t y o f t h e s e t t l e d e f f l u e n t w i t h r e s p e c t t o oxygen demanding  material.  A t s o l i d s d e t e n t i o n times g r e a t e r t h a n 20 days, and w i t h i n f l u e n t ' BOD^ between 32,000 and 38,000 mg/1, s e t t l e d e f f l u e n t B0D  5  averaged 58.1 mg/1,  as opposed t o s e t t l e d e f f l u e n t BOD5 g r e a t e r t h a n 125 mg/1 when t h e s o l i d s d e t e n t i o n t i m e was 10 days o r l e s s . The  l e a c h a t e feed used i n these s t u d i e s c o n t a i n e d a v a r i e t y o f  heavy m e t a l s i n c l u d i n g aluminum (41.8 m g / l ) , cadmium (0.39 m g / l ) , chromium (1.9 m g / l ) , copper (0.24. m g / l ) , l e a d (1.44 m g / l ) , n i c k e l (0.65 m g / l ) , and z i n c (223 m g / l ) .  Most o f t h e s e m e t a l s i n c l u d i n g aluminum, cadmium,  chromium, n i c k e l and z i n c were almost c o m p l e t e l y removed by the s e t t l i n g biological floe. extent.  Others were a s s o c i a t e d w i t h the s l u d g e s o l i d s t o a l e s s e r  A n a l y s i s o f the k i n e t i c parameters a s s o c i a t e d w i t h t h e b i o s t a b i -  l i z a t i o n p r o c e s s i n d i c a t e d t h a t the h i g h heavy m e t a l c o n c e n t r a t i o n s i n t h e mixed l i q u o r s i n h i b i t e d the a c t u a l b i o l o g i c a l removal o f oxygen demanding m a t e r i a l i n the d i g e s t e r s t e s t e d .  The s e t t l i n g b i o l o g i c a l f l o e  was  found, however, t o remove g r e a t e r t h a n 97 p e r c e n t o f t h e mixed l i q u o r and g r e a t e r t h a n 96 p e r c e n t o f t h e mixed l i q u o r COD times were m a i n t a i n e d g r e a t e r t h a n 20 days.  when s o l i d s d e t e n t i o n  Therefore, f o r best treatment  r e s u l t s a s o l i d s d e t e n t i o n time o f a t l e a s t 20 days i s recommended and food t o m i c r o - o r g a n i s m r a t i o s h o u l d be k e p t below 0.15 day.  BOD,,  the  lb.BOD^/lb.MLVSS/  iv  T A B L E OF CONTENTS  Page ABSTRACT  .  .  LIST  OF TABLES  LIST  OF FIGURES  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . . .  .  i i  •  ' *  ACKNOWLEDGMENT  .  .  .  .  .  '.  .  '.  .  .  v i  v i i  ix  CHAPTER 1  INTRODUCTION  2  GENERAL  REVIEW  .  OF AEROBIC  Process  .  .  .  .  .  BIOSTABILIZATION  .  2-1  General  2-2  Design  2-3  Factors Affecting Aerobic Biostabilization  2-4  Heavy M e t a l  2-5  Previous Studies of B i o l o g i c a l  2-6  .  4  .  7  Leachate .  1  4  Removal by A c t i v a t e d  Summary  .  Description  Equations  Landfill  •  .  .  Sludge  .  Treatment .  .  .  .  .  .  8 14  of  .  .  .  .  17  '  20 .  3  RESEARCH  RATIONALE AND EXPERIMENTAL  4  SYSTEM DESIGN AND EXPERIMENTAL o f t h e Treatment  DESIGN  PROCEDURE  .  .  .  .  .  .  22  .  4-1  Design  4-2  Leachate  4-3  pH C o n t r o l  28  4-4  Nutrient Balance  28  4-5  Metal  4-6  Acclimatization-Metal  4-7  Aerobic Biostabilization  4-8  Summary  Source  System  24  and C h a r a c t e r i s t i c s  Concentrations  .  24  .  .  .  .  .  .  .  Removal Study  .  Efficiency .  .  .  .  . .  . .  Studies .  .  .  .  .  . .  25  31 .  31  .  .  34  .  .  37  V  Page CHAPTER 5  DISCUSSION  39  5-1  Removal o f Oxygen Demanding M a t e r i a l  5-2  Volatile  5-3  6  OF RESULTS  . Metal  .  .  .  .  39  Suspended S o l i d s  55  Removal and D i s t r i b u t i o n  5-4  Settled  Effluent  5- 5  Kinetic  Parameters  58  Characterization and E f f i c i e n c y  .  .  Predictions  . .  .  71  .  CONCLUSIONS AND RECOMMENDATIONS 6- 1  Conclusions  6-2  Recommendations  7  REFERENCES  8  APPENDICES  .  .  .  .  .  .  80 .  f o rFuture .  ' 76  .  .  .  Studies .  .  .  .  .  ..  80  . . .  .  .  82  .  .  .  84 86  Appendix A  Solids  Tests  Results  Appendix B  BOD5  Appendix C  pH o f E f f l u e n t s  Test Results  Studies  .  During  During  Studies  Studies  and Mixed L i q u o r s .  .  .  .  .  Studies  -. .  .  . .  87 92  During .  .  .  98  .  .  102  .  106  Appendix D  Oxygen Uptake R a t e s D u r i n g  Appendix E  D e t e r m i n a t i o n o f K i n e t i c Parameters From "Extended A e r a t i o n " E f f i c i e n c y Study Data  L I S T OF T A B L E S  Page TABLE I II III  COMPOSITION OF T Y P I C A L LEACHATES DESIGN PARAMETERS CONTINUOUS  VI VII VIII  IX  DOSE OF METAL THAT WILL G I V E  (CONTINUOUS DOSAGE)  XI  XIII XIV  EFFICIENCY  .  .  .  .  .  .  .  .  .  5  .  .  12  .  .  . .  15 .  .  BOD :N:P RATIOS DURING STUDY 5  T Y P I C A L B O D T E S T R E S U L T S FOR MIXED LIQUOR E F F L U E N T S FROM D I G E S T E R S A, B AND C, AND FOR L E A C H A T E FEED .  15 .  29  .  30  .  42  5  COMPARISON  OF  BOD5  T E S T RESULTS ON S E T T L E D  EFFLUENTS  SEEDED BOD D I L U T I O N WATER  .  ORGANIC CARBON REMOVAL E F F I C I E N C Y STUDY  DURING  .  .  45  "SHORTER DETENTION T I M E " 55  METAL D I S T R I B U T I O N A T END OF A C C L I M A T I Z A T I O N - M E T A L STUDY  .  .  62  METAL D I S T R I B U T I O N A T END OF E F F I C I E N C Y STUDIES SUMMARY OF METAL REMOVAL  K I N E T I C PARAMETERS  MIXED LIQUOR BOD E F F I C I E N C Y STUDY  5  DETERMINED  DURING  .  .  66  BY S E T T L I N G B I O L O G I C A L FLOC  DURING E F F I C I E N C Y S T U D I E S C H A R A C T E R I S T I C S OF L E A C H A T E FEED AND  E F F I C I E N C Y STUDY DATA XVI  2  .  SETTLED  . . . EFFLUENTS'  FROM AEROBIC B I O S T A B I L I Z A T I O N E F F I C I E N C Y S T U D I E S XV  .  COMPOSITION OF L E A C H A T E F E E D USED DURING STUDY NUTRIENT ADDITIONS AND  REMOVAL XII  . .  SIGNIFICANT  E F F E C T S OF METALS ON MIXED LIQUOR SOLIDS  U S I N G UNSEEDED AND X  .  D I S T R I B U T I O N OF METALS THROUGH THE A C T I V A T E D SLUDGE PROCESS  V  .  FOR A C T I V A T E D SLUDGE PROCESSES  REDUCTION I N AEROBIC TREATMENT IV  . ' ..  .  69 .  72  FROM "EXTENDED A E R A T I O N "  . '  77  "SHORTER D E T E N T I O N T I M E " 79  vii  LIST OF FIGURES Page FIGURE 1  SCHEMATIC OF LABORATORY AEROBIC DIGESTERS  .  .  .  2  BOD5 OF MIXED LIQUORS AND SETTLED EFFLUENTS vs SOLIDS DETENTION TIME  40  PERCENT BOD5 REMOVALS vs SOLIDS DETENTION TIME  4  COD OF MIXED LIQUORS DURING "SHORTER DETENTION TIME" EFFICIENCY STUDY  47  COD OF SETTLED EFFLUENTS DURING "SHORTER DETENTION TIME" EFFICIENCY STUDY  48  COD OF MIXED AND SETTLED EFFLUENTS v s SOLIDS DETENTION TIME  49  7  PERCENT COD REMOVALS vs SOLIDS DETENTION TIME  50  8  COD OF MIXED AND SETTLED EFFLUENTS v s FOOD TO MICROORGANISM RATIO  .  52  PERCENT COD REMOVALS vs FOOD TO MICRO-ORGANISM RATIO  .  54  6  9 10 11  12  13  14  15  .  .  26  3  5  .  .  .  .  41  .  STEADY STATE MIXED LIQUOR VOLATILE SUSPENDED SOLIDS CONCENTRATIONS v s SOLIDS DETENTION TIME . . .  .  57  EFFLUENT TOTAL SOLIDS CONCENTRATION DURING THE ACCLIMATIZATION-METAL REMOVAL STUDY  59  MIXED LIQUOR TOTAL SOLIDS CONCENTRATIONS vs TIME FROM STARTUP-  88  MIXED LIQUOR SUSPENDED SOLIDS CONCENTRATIONS v s TIME FROM START UP:  89  MIXED LIQUOR VOLATILE SUSPENDED SOLIDS CONCENTRATIONS v s TIME FROM START UP  90  SETTLED EFFLUENT TOTAL SOLIDS CONCENTRATION DETENTION TIME  91  vs SOLIDS  16  BOD5 OF SETTLED EFFLUENTS DURING ACCLIMATIZATION STUDY  .  93  17 .  BOD5 OF SETTLED EFFLUENTS DURING EFFICIENCY STUDIES .  .  94  18  BOD5 OF MIXED LIQUORS DURING EFFICIENCY STUDIES  .  .  95  19  BOD OF MIXED LIQUORS vs FOOD TO MICRO-ORGANISM RATIO  .  96  s  V 111  Page  FIGURE 20  PERCENT B0D REMOVAL vs FOOD TO MICRO-ORGANISM RATIO  21  pH OF SETTLED EFFLUENTS DURING ACCLIMATIZATION STUDY  22  pH OF MIXED LIQUORS DURING "EXTENDED AERATION" EFFICIENCY STUDY  100  pH OF MIXED LIQUORS DURING "SHORTER DETENTION TIME" EFFICIENCY STUDY  101  23  5  92  <  .  24  OXYGEN UPTAKE RATES DURING ACCLIMATIZATION STUDY  25  OXYGEN UPTAKE RATES DURING "EXTENDED AERATION" EFFICIENCY STUDY  104  OXYGEN"UPTAKE RATES DURING "SHORTER DETENTION TIME" EFFICIENCY STUDY  105  DETERMINATION OF K AND K USING BOD5 DATA FROM "EXTENDED AERATION" EFFICIENCY STUDY  108  DETERMINATION OF Y AND b USING BOD5 DATA FROM "EXTENDED AERATION" EFFICIENCY STUDY  110  26 27 28  .  .  99  103.  s  ACKNOWLEDGMENT  The a u t h o r w i s h e s t o s i n c e r e l y thank h i s s u p e r v i s o r , D r . D.S. Mavinic,  f o r h i s guidance, i n t e r e s t and encouragement d u r i n g t h i s s t u d y .  The a u t h o r i s a l s o v e r y g r a t e f u l f o r t h e a d v i c e and a s s i s t a n c e  received  from h i s l o v i n g w i f e , Susanne; Dr. R.D. Cameron; Mrs. E l i z a b e t h McDonald and t h e t e c h n i c i a n s i n t h e p o l l u t i o n c o n t r o l l a b o r a t o r y , Mary Mager and Susan H a r p e r .  The a u t h o r would a l s o l i k e t o thank t h e N a t i o n a l  Research  C o u n c i l , as he was s u p p o r t e d d u r i n g t h i s s t u d y by a NRC P o s t g r a d u a t e Scholarship.  Equipment f o r t h i s work was p r o v i d e d under NRC R e s e a r c h  Grant Number A-8945.  CHAPTER 1  INTRODUCTION Over t h e y e a r s t h e r e has been a s u b s t a n t i a l i n c r e a s e i n t h e volume o f s o l i d waste b e i n g generated  throughout t h e w o r l d .  Although  enormous  amounts o f money have been spent on t h e development o f a l t e r n a t i v e d i s p o s a l methods such as i n c i n e r a t i o n , composting and r e c y c l i n g , s a n i t a r y l a n d f i l l s and garbage dumps r e m a i n t h e most p o p u l a r method o f d i s p o s a l f o r s o l i d w a s t e s . One o f t h e major problems p r e s e n t e d  by t h e o p e r a t i o n o f a s o l i d waste  l a n d f i l l , p a r t i c u l a r l y i n high r a i n f a l l c l i m a t e s , i s the production of leachate.  L e a c h a t e i s produced when s u r f a c e o r groundwater:, becomes  as i t passes t h r o u g h  the layers of refuse i n a l a n d f i l l .  contaminated  I f the leachate  e n t e r s nearby s u r f a c e o r groundwaters, a s e r i o u s p o l l u t i o n p r o b l e m may result.  The magnitude o f t h e p o l l u t i o n p r o b l e m w i l l depend l a r g e l y on t h e  s t r e n g t h and q u a n t i t y o f l e a c h a t e produced, as w e l l as on t h e d i l u t i o n a f f o r d e d by r e c e i v i n g w a t e r s . of leachate strength (1).  T a b l e I i l l u s t r a t e s t h e observed  variability  The q u a l i t y and q u a n t i t y o f l e a c h a t e depends on  the amount and c o m p o s i t i o n o f t h e r e f u s e , t h e h y d r o g e o l o g y o f t h e s i t e , t h e age o f t h e l a n d f i l l , and t h e c l i m a t e .  The d e l e t e r i o u s e f f e c t s o f l e a c h a t e s  on r e c e i v i n g w a t e r s has been w e l l documented i n t h e l i t e r a t u r e With the recent p o p u l a r i t y o f environmental  matters,  (1,2,3).  the importance  o f l e a c h a t e as a p a r t i c u l a r l y u n d e s i r a b l e a s p e c t o f s o l i d w a s t e d i s p o s a l on l a n d has been r e c o g n i z e d t o such an e x t e n t chosen and designed  to minimize  that disposal s i t e s are u s u a l l y  leachate production.  Design  precautions  e n t a i l d i v e r s i o n o f s u r f a c e water from t h e l a n d f i l l s i t e , p r e v e n t i o n o f groundwater c o n t a c t w i t h r e f u s e , and s e a l i n g and s l o p i n g t h e s u r f a c e t o minimize  or e l i m i n a t e p r e c i p i t a t i o n i n f i l t r a t i o n .  T h i s method o f c o n t r o l i s  v e r y e f f e c t i v e i n a r i d o r s e m i - a r i d c l i m a t e s where p r e c i p i t a t i o n i s m i n i m a l .  TABLE I COMPOSITION OF TYPICAL LEACHATES Parameter BOD  Range o f V a l u e s o r C o n c e n t r a t i o n s ( L a n d f i l l s and T e s t L y s i m e t e r s ) 9  5  T o t a l Carbon T o t a l O r g a n i c Carbon  715 22,350 715 - 22,350  Total Solids Total Volatile Solids Total Dissolved Solids  •1,000 _ 45,000 1,000 - 23,157 0 - 42,300  Acidity Alkalinity Aluminum Arsenic Bar ium Beryllium Calcium Cadmium Chloride Chromium Copper Iron Lead Magnesium Manganese Mercury Molybdenum Nitrogen - t o t a l - NH Nickel Phosphorus - t o t a l Potassium Sodium Sulphates Sulphides Titanium Vanadium Zinc 3  Tannin-like  Odour  0 0  _  0 0 0 0 5 0 34 0 0 0.2 0 165 0.06 0 0 0 0 0.01 0 2.8 0 1 0 0 0 0  _  -  -  -  -  -  9,560 20,900 122 11.6 5.4 0.3 4,000 0.19 2,800 33.4 10 5,500 5.0 15,600 1,400 0.064 0.52 2,406 1,106 0.80 154 3,770 7,700 1,826 0.13 5.0 1.4 1,000  3.7 - 8.5  H  Colour  55,000  0 - 90,000  COD  P  -  78 - 1,278  compounds'L.. _..;.••>••>  0 - 12,000  (chloroplatinate) not  detectable to ter:  a l l v a l u e s except those f o r pH, c o l o u r and odour a r e i n mg/1.  3  However, many l a n d f i l l s i t e s a r e l o c a t e d i n areas where p r e c i p i t a t i o n r a t e s a r e h i g h and where a v a i l a b l e s o i l cover m a t e r i a l i s u n s u i t a b l e f o r s e a l i n g the l a n d f i l l a g a i n s t i n f i l t r a t i n g p r e c i p i t a t i o n .  I n a d d i t i o n , urban  develop-  ment has r e s u l t e d i n keen c o m p e t i t i o n f o r t h e a v a i l a b l e l a n d s by a l l potent i a l u s e r s and so l e s s than i d e a l p a r c e l s o f l a n d have o f t e n been chosen for  landfill  sites.  The p e r c o l a t i o n o f w a t e r through  the refuse g r e a t l y increases the  r a t e o f b i o c h e m i c a l s t a b i l i z a t i o n o f t h e l a n d f i l l and thus decreases t h e time r e q u i r e d f o r c o n s o l i d a t i o n and s e t t l i n g o f t h e l a n d f i l l .  Although  such a l a n d f i l l s i t e may be used f o r b u i l d i n g c o n s t r u c t i o n o r r e c r e a t i o n a l purposes much sooner t h a n a s e a l e d l a n d f i l l , t h e l e a c h a t e produced i s h i g h l y contaminated  and must t h e r e f o r e be c o l l e c t e d f o r subsequent  treatment.  C o l l e c t i o n o f t h e l e a c h a t e b e f o r e i t e n t e r s ground o r s u r f a c e w a t e r s can be a c c o m p l i s h e d  by c a r e f u l l a n d f i l l d e s i g n and s i t e s e l e c t i o n .  development o f s u i t a b l e treatment much c u r r e n t r e s e a r c h .  The  methods, however, remains t h e t o p i c o f  T h i s s t u d y was i n i t i a t e d t o i n v e s t i g a t e a e r o b i c  b i o s t a b i l i z a t i o n of a high-strength l a n d f i l l p o t e n t i a l r e c e i v i n g w a t e r p o l l u t i o n problems.  l e a c h a t e as a means o f r e d u c i n g  CHAPTER 2  GENERAL REVIEW OF AEROBIC BIOSTABILIZATION  2-1  General Process D e s c r i p t i o n A e r o b i c p r o c e s s e s i n c l u d e a c t i v a t e d s l u d g e , t r i c k l i n g f i l t e r s and  a e r o b i c s t a b i l i z a t i o n ponds.  The a c t i v a t e d s l u d g e p r o c e s s i s used a l m o s t  exclusively i n large c i t i e s .  T r i c k l i n g f i l t e r s a r e o f t e n used i n s m a l l  c i t i e s and f o r h i g h - s t r e n g t h , r e a d i l y b i o d e g r a d a b l e i n d u s t r i a l w a s t e s . A e r o b i c ponds a r e used i n s m a l l c i t i e s where l a r g e l a n d areas :lare . a v a i l a b l e . The p r i n c i p l e s _behind a l l t h r e e p r o c e s s e s a r e s i m i l a r .  However, s i n c e v a r i a  t i o n s o f t h e complete-mix a c t i v a t e d s l u d g e system were used i n t h i s s t u d y , the  f o l l o w i n g d i s c u s s i o n w i l l be d i r e c t e d t o t h a t p r o c e s s . The a c t i v a t e d s l u d g e p r o c e s s was developed i n England i n 1914 and  was so named because  i t i n v o l v e d t h e p r o d u c t i o n o f an a c t i v a t e d mass o f  micro-organisms c a p a b l e o f a e r o b i c a l l y s t a b i l i z i n g o r decomposing waste.  The a e r o b i c environment  i n an a c t i v a t e d s l u d g e a e r a t i o n b a s i n i s  m a i n t a i n e d by t h e use o f d i f f u s e d o r m e c h a n i c a l a e r a t i o n . t e n t s a r e r e f e r r e d t o as t h e mixed l i q u o r . the  an o r g a n i c  A f t e r t h e waste  The r e a c t o r coni s treated i n  r e a c t o r , t h e r e s u l t i n g b i o l o g i c a l mass:is s e p a r a t e d from t h e l i q u i d i n  a s e t t l i n g tank o r c l a r i f i e r .  A p o r t i o n o f the s e t t l e d b i o l o g i c a l solids, i s  u s u a l l y r e c y c l e d , t h e r e m a i n i n g mass i s wasted.  A p o r t i o n o f the micro-  organisms must be wasted, o t h e r w i s e t h e mass o f m i c r o - o r g a n i s m s would keep i n c r e a s i n g u n t i l t h e system c o u l d no l o n g e r c o n t a i n them.  The l e v e l a t  w h i c h t h e b i o l o g i c a l mass s h o u l d be k e p t depends on t h e d e s i r e d t r e a t m e n t e f f i c i e n c y and o t h e r c o n s i d e r a t i o n s r e l a t e d t o growth k i n e t i c s .  The m i c r o -  organism c o n c e n t r a t i o n s g e n e r a l l y maintained i n three types:of: a c t i v a t e d Sludge t r e a t m e n t systems., a r e l i s t e d i n Table. 11(4) .  TABLE I I DESIGN PARAMETERS FOR ACTIVATED SLUDGE PROCESSES  Solids Process Detention M o d i f i c a t i o n Time,0 ,Days  Food To Microorganism R a t i o , U, lb. BOD /lb.MLVSS/Day 5  Volumetric Loading, lb.BOD /1000 c u . f t . 5  Mixed Liquor V o l a t i l e Suspended S o l i d s , mg/1iter  Recycle Ratio  Conventional  5 - 15  0.2 - 0.4  20 - 40  1,200 - 2,400  0. 25 - 0.50  Complete M i x  5 - 15  0.2 - 0.6  50 - 120  2,400 - 4,800  0. 25 - 1.00  0.05 - 0.15  10 - 25  2,400 - 4,800  0. 75 - 1.50  Extended Aeration  20 - 30  To d e s i g n and o p e r a t e an a c t i v a t e d s l u d g e system e f f i c i e n t l y , n e c e s s a r y t o u n d e r s t a n d t h e importance o f t h e m i c r o - o r g a n i s m s systems.  it is  i n the  I n n a t u r e , t h e k e y r o l e o f t h e b a c t e r i a i s t o decompose o r g a n i c  m a t t e r produced  by o t h e r l i v i n g organisms.  I n the a c t i v a t e d sludge process,  the b a c t e r i a a r e t h e most i m p o r t a n t m i c r o - o r g a n i s m s  because t h e y a r e r e -  sponsible f o r the decomposition o f the organic m a t e r i a l i n the i n f l u e n t . In  t h e mixed l i q u o r .tank, a p o r t i o n o f t h e o r g a n i c waste m a t t e r i s used by  a e r o b i c and f a c u l t a t i v e b a c t e r i a t o o b t a i n energy remainder  o f t h e o r g a n i c m a t e r i a l i n t o new c e l l s .  f o r the synthesis of the Thus, a p o r t i o n o f t h e  o r g a n i c m a t t e r i s o x i d i z e d t o low energy compounds such as NO^., SO^ and CC>2, Thfc remainder  i s synthesized into c e l l u l a r  While b a c t e r i a a r e t h e micro-organisms organic waste organisms  material. t h a t a c t u a l l y degrade t h e  i n the i n f l u e n t , the metabolic a c t i v i t i e s o f other micro-  a r e a l s o i m p o r t a n t i n t h e a c t i v a t e d - s l u d g e system.  p r o t o z o a and r o t i f e r s a c t as e f f l u e n t p o l i s h e r s .  F o r example,  P r o t o z o a consume d i s -  p e r s e d b a c t e r i a t h a t have n o t f l o c c u l a t e d , and r o t i f e r s consume any s m a l l b i o l o g i c a l f l o e p a r t i c l e s t h a t have n o t s e t t l e d . F u r t h e r , w h i l e i t i s i m p o r t a n t t h a t b a c t e r i a decompose t h e o r g a n i c waste as q u i c k l y as p o s s i b l e , i t i s a l s o i m p o r t a n t t h a t t h e y form a s a t i s f a c t o r y f l o e , which i s a p r e r e q u i s i t e f o r the e f f e c t i v e s e p a r a t i o n o f the b i o l o g i c a l s o l i d s i n the s e t t l i n g u n i t .  I t has been o b s e r v e d t h a t as t h e  s o l i d s d e t e n t i o n o r mean c e l l r e s i d e n c e t i m e i s i n c r e a s e d , t h e 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 e b i o l o g i c a l f l o e a r e enhanced. i s t h a t , as t h e mean age o f t h e c e l l s duced and t h e m i c r o - o r g a n i s m s  i n c r e a s e s , t h e s u r f a c e charge i s r e -  s t a r t t o produce  e x t r a c e l l u l a r polymers,  t u a l l y becoming " e n c a p s u l a t e d " i n a s l i m e l a y e r . polymers  The r e a s o n f o r t h i s  even-  The p r e s e n c e o f t h e s e  and t h e s l i m e promotes t h e f o r m a t i o n o f f l o e p a r t i c l e s t h a t c a n be  removed r e a d i l y by g r a v i t y s e t t l i n g .  T y p i c a l v a l u e s o f mean c e l l r e s i d e n c e  7  or s o l i d s d e t e n t i o n t i m e used i n t h e d e s i g n and o p e r a t i o n o f a c t i v a t e d s l u d g e processes  2-2  a r e a l s o shown i n T a b l e I I (4).  Design Equations : . I n t h i s s t u d y t h e b i o l o g i c a l s o l i d s r e t e n t i o n t i m e , 0 , arid t h e  food t o m i c r o - o r g a n i s m r a t i o , U, were used as b a s i c d e s i g n parameters. Lawrence and M c C a r t y (5) have d e f i n e d  f o r c o m p l e t e l y mixed,  no-recycle  systems as t h e r e c i p r o c a l o f t h e n e t s p e c i f i c growth r a t e as f o l l o w s :  JL = Y K S - b 0  K C  where  s  +  (1)  S  Y = growth y i e l d  coefficient,  K = maximum r a t e o f s u b s t r a t e u t i l i z a t i o n p e r u n i t w e i g h t o f m i c r o organisms,  (T"l),  S = concentration of substrate surrounding  t h e m i c r o - o r g a n i s m s , (M/L ) ,  b = m i c r o - o r g a n i s m decay o r endogenous r e s p i r a t i o n c o e f f i c i e n t , (T ^) , K  s  = s u b s t r a t e c o n c e n t r a t i o n when  dS/dt = K , (M/L ) , X 2  dS = r a t e o f m i c r o b i a l s u b s t r a t e u t i l i z a t i o n per u n i t volume, and •' d t X  = m i c r o b i a l mass c o n c e n t r a t i o n o r mixed l i q u o r v o l a t i l e suspended s o l i d , MLVSS, c o n c e n t r a t i o n , ( M / L ) . 3  An e x p r e s s i o n f o r t h e mixed l i q u o r m i c r o b i a l mass c o n c e n t r a t i o n , X, c a n be d e r i v e d f o r s t e a d y - s t a t e c o n d i t i o n s by p e r f o r m i n g on t h e r e a c t o r .  The e q u a t i o n  a s u b s t r a t e mass  balance  i s as f o l l o w s :  X =• Y ( S - S j ) (2) i + be. c = i n f l u e n t waste c o n c e n t r a t i o n , (M/L ) , and 0  where  S  3  Q  S-]^ = e f f l u e n t waste c o n c e n t r a t i o n , (M/L ) . The  parameters, Y, b, K and K  s  were d e t e r m i n e d u s i n g t h e r e s u l t s o f SL ...  p r e l i m i n a r y "extended a e r a t i o n " e f f i c i e n c y s t u d y and then, e q u a t i o n s  1 and  8  2 were used t o p r e d i c t the performance  o f t h e u n i t s a t lower  solids  detention times. 2-3  Factors A f f e c t i n g Aerobic B i o s t a b i l i z a t i o n A p p l i c a t i o n and s t u d y o f a e r o b i c t r e a t m e n t methods over a number o f  y e a r s have demonstrated  t h a t c e r t a i n f a c t o r s may  f a v o u r a b l e e f f e c t s on a e r o b i c d i g e s t i o n .  S i n c e the process i s c a r r i e d  by a h i g h l y d i v e r s e group o f m i c r o - o r g a n i s m s , must be m a i n t a i n e d d u r i n g d i g e s t i o n .  have f a v o u r a b l e o r unout  c e r t a i n optimum c o n d i t i o n s  Among t h e f a c t o r s most o f t e n c o n s i d e r e d  i n d e s i g n i n g an a e r o b i c s t a b i l i z a t i o n p r o c e s s a r e pH,  temperature,  r e q u i r e m e n t s , n u t r i e n t r e q u i r e m e n t s , and waste t o x i c i t y . s t a n d i n g o f t h e f a c t o r s t h a t e f f e c t the p r o c e s s was  oxygen  Because an  under-  necessary i n order to  d e s i g n and s u c c e s s f u l l y o p e r a t e the d i g e s t e r s , t h e most i m p o r t a n t f a c t o r s were examined. (a)  pH and A l k a l i n i t y - To m a i n t a i n a s t a b l e , b i o l o g i c a l p o p u l a t i o n , the pH s h o u l d be m a i n t a i n e d between 6.5 t h i s recommended range may  drop.  , NO^  Values o u t s i d e of  i n h i b i t the growth o f a e r o b i c b a c t e r i a  o r even cause t h e i r d e s t r u c t i o n . and o x i d i z e d , SO^  and 9.0.  and CO2  As the o r g a n i c w a s t e i s decomposed may  be formed r e s u l t i n g i n a pH  For t h i s r e a s o n i t i s recommended t h a t the i n f l u e n t w a s t e  s h o u l d c o n t a i n 0.5  l b . o f a l k a l i n i t y per l b . o f BOD5 t o be removed.  I f s u f f i c i e n t a l k a l i n i t y i s n o t .present i n t h e i n f l u e n t , i t may  be  n e c e s s a r y t o add b u f f e r i n g agents t o m a i n t a i n t h e pH i n t h e d e s i r e d range. (b)  Temperature - The  temperature dependence o f the b i o l o g i c a l  r a t e constant i s v e r y important i n a s s e s s i n g the o v e r a l l of a b i o l o g i c a l treatment process.  reaction-  efficiency  Temperature not o n l y i n f l u e n c e s  the m e t a b o l i c a c t i v i t i e s o f the m i c r o b i a l p o p u l a t i o n , but a l s o  has  a p r o f o u n d e f f e c t on such f a c t o r s as gas  t r a n s f e r r a t e s and  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 the b i o l o g i c a l s o l i d s .  The  the  temperature  e f f e c t on the r e a c t i o n r a t e of a b i o l o g i c a l p r o c e s s i s u s u a l l y  ex-  p r e s s e d i n the f o l l o w i n g form: Ky_ =  * < " > T  (3)  20  K20 where K^,  = r e a c t i o n rate at  K20  =  <t>  r e a c t i o n r a t e a t 20°C, = temperature-activity coefficient,  T = temperature,  <j> v a r i e s between 1.00  From t h e s e r e l a t i v e l y low v a l u e s i t i s evident  and  °C.  For a c t i v a t e d s l u d g e p r o c e s s e s ,  ficient,  T°C,  and  1.03.  of the t e m p e r a t u r e - a c t i v i t y  coef-  t h a t r e l a t i v e l y l a r g e t e m p e r a t u r e changes  would be r e q u i r e d t o s i g n i f i c a n t l y a f f e c t t r e a t m e n t e f f i c i e n c y . Oxygen Requirements - To m a i n t a i n  aerobic conditions  the d i s s o l v e d oxygen l e v e l must be k e p t above 1-2 a d d i t i o n , the a i r s u p p l y  i n the  mg/litre.  reactor, In  r a t e must be adequate t o s a t i s f y the BOD  the w a s t e , t o s a t i s f y the endogenous r e s p i r a t i o n o f the s l u d g e ganisms, and  t o p r o v i d e adequate m i x i n g .  ism r a t i o s g r e a t e r t h a n 0.3, 900  c u b i c f e e t per l b . of  F o r food t o m i c r o - o r g a n -  removed.  ' l b . of BOD^  i n c r e a s e a i r use  removed.  t o 1,200  t o 1,800  A minimum a i r f l o w o f a p p r o x i m a t e l y 3  to avoid s o l i d s d e p o s i t i o n (4).  prolonged  cubic feet  f e e t per minute per f o o t o f tank l e n g t h i s r e q u i r e d t o adequate m i x i n g and  to  A t l o w e r food t o m i c r o -  o r g a n i s m r a t i o s , endogenous r e s p i r a t i o n , n i t r i f i c a t i o n and aeration periods  or-  the a i r r e q u i r e m e n t s amount t o 500  BOD5  of  per  cubic  maintain  10.  (d)  N u t r i e n t Requirements - I f any b i o l o g i c a l system i s t o f u n c t i o n p r o p e r l y , n u t r i e n t s r e q u i r e d by t h e m i c r o - o r g a n i s m s must be a v a i l a b l e i n adequate amounts.  N i t r o g e n and phosphorus". • a r e t h e n u t r i e n t s  required i n highest concentrations.  S i n c e t h e s e m a t e r i a l s may be  absent i n some w a s t e s , i t i s i m p o r t a n t may have t o be added.  t o know t h e amounts w h i c h  Sawyer (6) e s t a b l i s h e d a r a t i o o f n i t r o g e n  t o phosphorus:, t o BOD^ w h i c h s h o u l d be m a i n t a i n e d organisms a r e t o f u n c t i o n e f f e c t i v e l y . ranging 150:1  from 17:1 t o 32:1 and  as b e i n g adequate.  B O D r ^ P  i f aerobic  micro-  He c i t e d B0D^:N r a t i o s  r a t i o s r a n g i n g from 90:1 t o  These r a t i o s have been a d j u s t e d  through  usage t o B0D5:N:P o f 100:5:1 and have g e n e r a l l y r e s u l t e d i n s a t i s f a c t o r y performance. (e)  Waste T o x i c i t y - Because t h e incoming waste i s more o r l e s s u n i - . f o r m l y d i s p e r s e d i n a complete-mix r e a c t o r , i t c a n , i n c o m p a r i s o n t o t h e c o n v e n t i o n a l , p l u g - f l o w , a c t i v a t e d s l u d g e r e a c t o r , more e a s i l y w i t h s t a n d shock l o a d s o f o r g a n i c and t o x i c m a t e r i a l s . t h i s reason, The  a complete-mix r e a c t o r was chosen f o r t h i s  For  study.  t e r m t o x i c , however, i s v e r y r e l a t i v e and t h e c o n c e n t r a t i o n  a t w h i c h any s u b s t a n c e i s t o x i c o r i n h i b i t i n g t o a e r o b i c d i g e s t i o n may v a r y from a f r a c t i o n o f a mg/l t o s e v e r a l thousand mg/l.  At  some low c o n c e n t r a t i o n s , s t i m u l a t i o n o f a c t i v i t y i s u s u a l l y a c h i e v e d . T h i s s t i m u l a t o r y c o n c e n t r a t i o n may range from a f r a c t i o n o f a mg/l f o r heavy metals t o over a hundred mg/l f o r sodium and c a l c i u m s a l t s . As t h e c o n c e n t r a t i o n i s i n c r e a s e d above s t i m u l a t o r y c o n c e n t r a t i o n s , the r a t e o f b i o l o g i c a l a c t i v i t y begins  t o decrease.  A point i s  t h e n reached where i n h i b i t i o n i s a p p a r e n t and t h e r a t e o f b i o l o g i c a l a c t i v i t y i s l e s s than t h a t a c h i e v e d  i n t h e absence o f t h e s u b s t a n c e .  F i n a l l y , a t some h i g h c o n c e n t r a t i o n , t h e b i o l o g i c a l a c t i v i t y may  11  approach z e r o . M i c r o - o r g a n i s m s have t h e a b i l i t y t o adapt t o some e x t e n t , t o the i n h i b i t o r y c o n c e n t r a t i o n o f most s u b s t a n c e s . a d a p t a t i o n , however, i s a l s o r e l a t i v e .  The e x t e n t o f  I n some cases t h e a c t i v i t y  a f t e r a c c l i m a t i z a t i o n may approach t h a t o b t a i n e d i n t h e absence o f the i n h i b i t o r y s u b s t a n c e , w h i l e i n o t h e r c a s e s , t h e l e v e l o f a c t i v i t y w i l l remain much lower than t h a t o b t a i n e d i n t h e absence o f I n h i b i t o r y substances. B a r t h e t a l . (7) conducted.a  comprehensive  s t u d y on t h e e f f e c t s  o f heavy m e t a l s on a c o n v e n t i o n a l a c t i v a t e d s l u d g e p r o c e s s .  However,  t h e i r s t u d y i n v o l v e d o n l y f o u r m e t a l s , namely chromium, copper, n i c k e l and z i n c .  D u r i n g each r u n , an e x p e r i m e n t a l p i l o t - p l a n t  and a c o n t r o l u n i t r e c e i v i n g no m e t a l were compared.  unit  The m e t a l was  added c o n t i n u o u s l y t o a c o n s t a n t sewage feed o f t h e e x p e r i m e n t a l unit.  Two weeks o f a c c l i m a t i o n were a l l o w e d b e f o r e d a t a on t h e  q u a l i t y o f t h e f i n a l e f f l u e n t were c o l l e c t e d .  T h i s time  interval  was r e q u i r e d f o r t h e m e t a l c o n c e n t r a t i o n i n t h e a c t i v a t e d s l u d g e t o b u i l d up t o a c o n d i t i o n o f o p e r a t i n g e q u i l i b r i u m .  The f i n a l  from b o t h u n i t s was a s s a y e d d a i l y f o r BOD, COD, suspended turbidity.  effluent  s o l i d s and  The r u n f o r any s e l e c t e d m e t a l dosage was c o n t i n u e d • f o r  60 days t o o b t a i n s u f f i c i e n t d a t a .  The v a l u e s f o r t h e two u n i t s  were t h e n compared as f r e q u e n c y d i s t r i b u t i o n c u r v e s and t h e c o n t i n uous doses o f each m e t a l t h a t w i l l g i v e s i g n i f i c a n t r e d u c t i o n i n a e r o b i c t r e a t m e n t e f f i c i e n c y were thus determined. a r e summarized i n T a b l e I I I ( 7 ) .  Their results  TABLE I I I CONTINUOUS DOSE OF METAL THAT WILL GIVE SIGNIFICANT REDUCTION I N AEROBIC TREATMENT EFFICIENCY  Concentration in Influent mg/l  Metal Chromium ( V I )  10  Copper  1  Nickel  1 t o 2.5  Zinc  5 t o 10  In a d d i t i o n ,  mixed doses o f t h e f o u r m e t a l s were a p p l i e d  c o n c e n t r a t i o n s , so as t o i n v e s t i g a t e The  Waste  possible  synergistic  r e s u l t s o f t h e s e s t u d i e s showed t h a t t h e a c t i v a t e d  of a b i o l o g i c a l treatment p l a n t can t o l e r a t e ,  at different effects.  s l u d g e phase  i n the i n f l u e n t  sewage,  chromium, copper, n i c k e l and z i n c , up t o a t o t a l heavy m e t a l concentration  o f 10 mg/l.; E i t h e r  s i n g l y o r i n c o m b i n a t i o n , heavy m e t a l  c o n c e n t r a t i o n s o f t h i s magnitude caused ; o n l y a 5 p e r c e n t in o v e r a l l plant e f f i c i e n c y In a d d i t i o n  reduction  (7).  Kampf ( 8 ) , a German r e s e a r c h e r , has d e v e l o p e d a 3-  s t a g e method f o r e x a m i n i n g t h e e f f e c t o f t o x i c compounds on a c t i vated sludge.  Based on measurements o f oxygen consumption u s i n g  the Warburg r e s p i r o m e t e r , s t a g e 1 measures t h e d i r e c t . i n h i b i t i o n : o f r e s p i r a t i o n by t o x i c s u b s t a n c e s ; Stage 2, w h i c h examines t h e r e c o v e r y o f t h e s l u d g e and t h e d u r a t i o n and i n t e n s i t y o f h a r m f u l e f f e c t s the  t o x i c l o a d has been i n t e r r u p t e d ,  respiration  after  measures t h e i n h i b i t i o n o f  i n s l u d g e from a p a r a l l e l s t a g e 1 sample a f t e r m i x i n g  with fresh nutrient  s o l u t i o n ; i.Stage  3, used':.to.indicate the..a  t o x i c i t y of the substrate a f t e r contact w i t h the activated  sludge,  13  measures the  i n h i b i t i o n of r e s p i r a t i o n i n f r e s h s l u d g e when exposed  t o a t o x i c s o l u t i o n s e p a r a t e d from a s t a g e 1 sample by c e n t r i f u g ing.  The  method has  and aluminum.  been used t o examine the e f f e c t s o f magnesium  Only h i g h c o n c e n t r a t i o n s  oxygen consumption.  of magnesium a f f e c t e d  C o n c e n t r a t i o n s of about 2,850 mg  o f magnesium  c h l o r i d e per l i t r e were p r a c t i c a l l y h a r m l e s s , w h i l e the concentration  t e s t e d , 20,000 m g / l i t r e , i n h i b i t e d r e s p i r a t i o n by  about 25 p e r c e n t , and  the o r i g i n a l r a t e of r e s p i r a t i o n was  r a p i d l y when the s l u d g e was solution.  The  s e p a r a t e d and  hours.  r e s p i r a t i o n r a t e of a c t i v a t e d s l u d g e was,  o f 100 mg  of  the s e p a r a t e d s l u d g e r e g a i n e d i t s r e s p i r a t o r y a c t i v i t y  higher  however, per  the m i c r o - o r g a n i s m s became a c c l i m a t i z e d a f t e r s e v e r a l  I n the second s t a g e , even a f t e r long p e r i o d s  provided  restored  exposed t o f r e s h n u t r i e n t  i n h i b i t e d by aluminum (as s u l p h a t e ) i n c o n c e n t r a t i o n s l i t r e , but  highest  the c o n c e n t r a t i o n  t h a n 160  mg  o f aluminum was  per l i t r e .  aluminum t e s t e d , 320  mg  The  per l i t r e ,  highest  not  contact, slowly,  significantly  concentration  of  caused i r r e v e r s i b l e damage.  N e u f e l d and Hermann (9) i n v e s t i g a t e d the e f f e c t o f mercury, cadmium and  z i n c on a c c l i m a t e d  a c t i v a t e d sludge.  o f 30,  300  o f each m e t a l , t h e y found t h a t i t  was  100,  and  1,000  mg/1  U s i n g shock doses  p o s s i b l e to°maintain a t h r i v i n g c u l t u r e o f a c t i v a t e d b i o t a i n ~  the p r e s e n c e o f l e v e l s of mercury, cadmium and higher  t h a n p r e v i o u s l y thought p o s s i b l e .  evaluated  z i n c t h a t a r e much  K i n e t i c parameters were  a t s e v e r a l heavy m e t a l c o n c e n t r a t i o n s .  For cadmium and  z i n c , the maximum r a t e of s u b s t r a t e u t i l i z a t i o n per u n i t w e i g h t o f m i c r o - o r g a n i s m s , K, was  found t o be v i r t u a l l y c o n s t a n t u n t i l a  threshold concentration  of m e t a l i n the s l u d g e , about 25 mg/1  cadmium or 8 mg/1  o f z i n c , was  reached.  Beyond t h i s t h r e s h o l d ,  of K  14  d e c r e a s e d l i n e a r l y when p l o t t e d r e l a t i v e t o m e t a l i n t h e mg/gm VSS,  on l o g - l o g paper.  No t h r e s h o l d e f f e c t was  t h e case o f mercury and i t was m e t a b o l i c r a t e i n a way  floe,  observed i n  c o n c l u d e d t h a t mercury a f f e c t s  t h a t may  the  be t o t a l l y c o u n t e r a c t e d by i n -  c r e a s i n g the c o n c e n t r a t i o n o f o r g a n i c s u b s t r a t e , (f)  D e t e n t i o n Time - D e t e n t i o n t i m e , w h i c h i s c l o s e l y r e l a t e d t o l o a d i n g r a t e e x p r e s s e d i n terms o f t h e food t o m i c r o - o r g a n i s m r a t i o ,  has  been shown t o a f f e c t t h e e f f i c i e n c y o f a e r o b i c b i o s t a b i l i z a t i o n . d e t e n t i o n time d e c r e a s e s , t h e l o a d i n g r a t e i n c r e a s e s .  As  As t h e d e t e n -  t i o n time d e c r e a s e s , an i n c r e a s i n g p e r c e n t a g e o f b a c t e r i a i s removed each day w i t h t h e e f f l u e n t .  E v e n t u a l l y a l i m i t i n g d e t e n t i o n time  i s reached when the b a c t e r i a a r e b e i n g removed from the a s . f a s t as . t h e y can r e p r o d u c e t h e m s e l v e s .  system  T h i s minimum s o l i d s  d e t e n t i o n time can be p r e d i c t e d , i f Y, b, K, K  g  and S  Q  a r e known  u s i n g the e q u a t i o n (5) :  1 Q  c min.  =  Y K S K  s  +  (4)  b  0  S  D  U s i n g the r e s u l t s o f a p r e l i m i n a r y s t u d y a t " s a f e " c o n s e r v a t i v e d e t e n t i o n t i m e s , the minimum s o l i d s d e t e n t i o n time cari^ be p r e d i c t e d and d e t e n t i o n times i n t h e f i n a l e f f i c i e n c y s t u d y can  then  be s e t above the p r e d i c t e d minimum. 2-4  Heavy M e t a l Removal by A c t i v a t e d  Sludge  The c o m p l e t e l y mixed, a e r o b i c b i o l o g i c a l t r e a t m e n t p r o c e s s has been shown t o have a c a p a b i l i t y f o r l o n g - t e r m removal o f heavy m e t a l i o n s t h a t i s s u p e r i o r to anaerobic processes  (7,10).  B a r t h et a l .  (7)  investigated  t h e removal o f chromium, copper, n i c k e l and z i n c by a c t i v a t e d s l u d g e . r e s u l t s are.. summarized i n T a b l e IV ( 7 ) .  I t was  Their  a l s o found t h a t t h e e f f e c t s  o f t h e metals on t h e mixed l i q u o r a r e apparent range.  even i n t h e 1 t o 2 mg/1  D u r i n g f i v e years, o f s t u d y , no b u l k i n g was encountered  f e d system.  i n the metal  The f l o e i n t h e f i n a l s e t t l e r s e t t l e d q u i c k l y w h i l e c o n t r o l  u n i t s f r e q u e n t l y bulked.  T a b l e V (7) shows t h e e f f e c t s , o f a c o m b i n a t i o n o f  the f o u r metals on t h e v o l a t i l e s o l i d s c o n t e n t o f t h e mixed l i q u o r .  TABLE IV DISTRIBUTION OF METALS THROUGH THE ACTIVATED SLUDGE PROCESS (CONTINUOUS DOSAGE)  Cr ( V I ) (15 mg/1)  Outlet Primary  Sludge  2.4  Cu (10 mg/1)  Ni (10 mg/1)  9  Zn (10 mg/1)  2.5  14  Excess A c t i v a t e d Sludge  27  55  15  63  Final  56  25  72  11  M e t a l Unaccounted f o r  15  15  11  12  Average E f f i c iency o f Pro• cess i n Removing M e t a l  44-:  75  28  89  Range o f Removal 'Ef-f i c l e n c i e s  18-58  Percent of Metal  Effluent  Fed  50-80  12-76  74-97  TABLE V EFFECTS OF METALS ON MIXED LIQUOR SOLIDS Analys i s Percent Volatile Solids  Control Unit 66.7  Mixed L i q u o r From Metal Mixture Metal Mixture 8.9 mg/1 4.9 mg/1 57.9  61.3  Metal Mixture 2.0 mg/1 63.8  16  M o u l t o n and Shumate (11) i n d i c a t e d t h a t o v e r a l o n g p e r i o d , an a c c l i m a t e d , a c t i v a t e d s l u d g e system r e t a i n e d 80 t o 85 p e r c e n t o f t h e i n f l u e n t copper f e d t o i t a t a c o n c e n t r a t i o n o f 50 mg/l.  J a c k s o n e t a l . (12)  i n a s u r v e y o f m e t a l s removal by a c t i v a t e d s l u d g e , l i s t e d r e p o r t s o f copper removals r a n g i n g from 54 t o 93 p e r c e n t , chromium removals from 10 t o 100 p e r c e n t , and z i n c removals from 60 t o 100 p e r c e n t .  T o t a l i n f l u e n t metal  c o n c e n t r a t i o n s f o r t h i s r e p o r t , however, were l e s s t h a n 10 mg/l. N e u f e l d and Hermann (9) a l s o i n v e s t i g a t e d t h e u p t a k e o f mercury, cadmium and z i n c by a c c l i m a t e d a c t i v a t e d s l u d g e .  U s i n g shock doses o f 30,  100, 300 and 1000 mg/l o f each m e t a l , t h e y i n v e s t i g a t e d t h e m e t a l d i s t r i b u t i o n between t h e s e t t l e d s l u d g e and c l e a r s u p e r n a t a n t v e r s u s t i m e .  Mercury,  cadmium and z i n c were removed r a p i d l y from aqueous s o l u t i o n by t h e b i o l o g i cal floe.  A l t h o u g h e v e n t u a l e q u i l i b r i u m was  a c h i e v e d a f t e r about 2 weeks  o f c o n t a c t , no s i g n i f i c a n t i n c r e a s e i n t h e p e r c e n t m e t a l removal c o u l d be o b s e r v e d a f t e r 3 hours o f c o n t a c t .  A t doses up t o 300 mg/l, a f t e r 3 h o u r s ,  95 p e r c e n t o f t h e mercury, 73 p e r c e n t o f t h e cadmium, and 53 p e r c e n t o f t h e z i n c were removed oh t h e b i o l o g i c a l  floe.  U s i n g s l u g doses up t o 25 mg/l o f cadmium, copper, l e a d and  nickel  . i n a s y n t h e t i c waste f e e d , Cheng e t a l . (13) a l s o s t u d i e d t h e heavy m e t a l u p t a k e by a c c l i m a t e d s l u d g e w i t h t i m e .  I t was  found t h a t under a e r o b i c  c o n d i t i o n s , m e t a l u p t a k e by t h e biomass  i s c h a r a c t e r i z e d by a v e r y r a p i d  phase o f 3 t o 10 minutes f o l l o w e d by a l o n g - t e r m , slow-phase, u p t a k e . lower m e t a l c o n c e n t r a t i o n s , m e t a l was  At  c o n c l u d e d t o be t a k e n up by t h e  b i o f l o c t h r o u g h the f o r m a t i o n o f m e t a l - o r g a n i c complexes.  At higher metal  c o n c e n t r a t i o n s , m e t a l i o n p r e c i p i t a t i o n from s o l u t i o n may  occur i n a d d i t i o n  to sludge uptake.  The h i g h m o l e c u l a r w e i g h t e x o c e l l u l a r polymers o f t h e  b i o f l o c , which i n c l u d e p o l y s a c c h a r i d e s , p r o t e i n s , r i b o n u c l e i c a c i d ,  and  17  d e o x y r i b o n u c l e i c a c i d , p r o v i d e many f u n c t i o n a l g r o u p i n g s t h a t may a c t as binding s i t e s f o r the metals. Cheng e t a l .  (13) found t h a t m e t a l uptake by t h e biomass depends on  s e v e r a l f a c t o r s , i n c l u d i n g pH and t h e c o n c e n t r a t i o n o f o r g a n i c m a t t e r and m e t a l s p r e s e n t i n t h e system.  Higher i n i t i a l concentrations o f metal ions  or mixed l i q u o r v o l a t i l e suspended s o l i d s i n c r e a s e t h e o v e r a l l u p t a k e .  In  g e n e r a l , t h e uptake c a p a c i t y i n c r e a s e s w i t h i n c r e a s i n g pH, up t o a v a l u e a t which metal hydroxide p r e c i p i t a t i o n occurs.  Among t h e m e t a l s s t u d i e d , t h e  p r e f e r r e d o r d e r o f uptake by a c t i v a t e d s l u d g e , w i t h average p e r c e n t removal i n b r a c k e t s , was found t o be l e a d (90%) > copper (89%) > cadmium (80%) > n i c k e l (58%) a t mixed l i q u o r v o l a t i l e suspended s o l i d s c o n c e n t r a t i o n s between 1600 and 1800 mg/1. The l a r g e - s c a l e a c c u m u l a t i o n o f heavy m e t a l s by a c t i v a t e d s l u d g e , w i t h i t s subsequent removal i n t h e secondary c l a r i f i e r , would appear t o o f f e r a v e r y p r o m i s i n g method o f t r e a t i n g l a n d f i l l 2-5  therefore leachate.  P r e v i o u s S t u d i e s o f B i o l o g i c a l Treatment o f L a n d f i l l L e a c h a t e A s t u d y by Poorman (14) was e s t a b l i s h e d t o i n v e s t i g a t e t h e p o s s i -  b i l i t y o f r e d u c i n g t h e amounts o f oxygen demanding m a t e r i a l i n l e a c h a t e by a n a e r o b i c d i g e s t i o n w i t h o u t any p r i o r removal o f heavy m e t a l s .  The e f f e c t s  of v a r i e d d e t e n t i o n time and c h a n g i n g c h a r a c t e r i s t i c s o f t h e l e a c h a t e were also studied. for  BOD^ removals r a n g i n g from 80 t o 96 p e r c e n t were a c h i e v e d  d e t e n t i o n times r a n g i n g from 5 t o 20 days and i n f l u e n t B0D5's r a n g i n g  from 11,000 t o 16,000 mg/1.  COD removals ranged from 65 t o 79 p e r c e n t f o r  i n f l u e n t v a l u e s r a n g i n g from 23,000 t o 33,000 mg/1.  A v a r i e t y o f metals  i n c l u d i n g aluminum, cadmium, chromium, copper, l e a d , mercury, n i c k e l and 1  z i n c were p r e s e n t i n t h e l e a c h a t e .  T h e i r c o n c e n t r a t i o n s covered a broad  range w i t h z i n c b e i n g t h e h i g h e s t a t 65 mg/1.  The a n a e r o b i c d i g e s t i o n  18  p r o c e s s was not a d v e r s e l y a f f e c t e d by t h e s e m e t a l s .  Some o f t h e m e t a l s ,  n o t a b l y aluminum, cadmium, mercury, n i c k e l and z i n c , were e s s e n t i a l l y comp l e t e l y a s s o c i a t e d w i t h the s l u d g e , w h i l e o t h e r s were p r i m a r i l y a s s o c i a t e d w i t h the s e t t l e d  effluent.  B o y l e and Ham  (15) i n v e s t i g a t e d the b i o l o g i c a l t r e a t a b i l i t y o f  l a n d f i l l l e a c h a t e w i t h t o t a l s o l i d s c o n c e n t r a t i o n s between 4,000 and 7,800 mg/l.  P r o c e s s e s e v a l u a t e d i n t h e l a b o r a t o r y i n c l u d e d a n a e r o b i c and a e r o b i c  b i o l o g i c a l treatment of leachate, a e r o b i c treatment of s e l e c t e d o f l e a c h a t e and domestic wastewater  combinations  i n a simulated a c t i v a t e d sludge t r e a t -  ment p l a n t , and a n a e r o b i c f o l l o w e d by a e r o b i c p o l i s h i n g t r e a t m e n t o f l e a c h ate.  A n a e r o b i c t r e a t m e n t o f raw l e a c h a t e was  g r e a t e r than 90 p e r c e n t BOD  most p r o m i s i n g , p r o v i d i n g  r e d u c t i o n f o r h y d r a u l i c d e t e n t i o n times g r e a t e r  t h a n 10 days a t temperatures  i n the range o f 23° t o 30°C.  Temperature was  found t o g r e a t l y a f f e c t the a n a e r o b i c s t a b i l i z a t i o n o f l e a c h a t e i n t h e range o f 23° t o 11°C. BOD  A temperature  c o e f f i c i e n t o f 1.111  removal r a t e s i n l a b o r a t o r y v e s s e l s .  e f f l u e n t s produced  was  estimated for  Aerobic p o l i s h i n g of anaerobic  a more s t a b l e e f f l u e n t s u i t a b l e f o r s u r f a c e w a t e r  dis-  charge.  A e r o b i c t r e a t m e n t a l s o proved t o be p r o m i s i n g , r e s u l t i n g i n BOD  removals  i n excess o f 90 p e r c e n t and COD  removals :greater t h a n 80 p e r c e n t  a t a p p r o x i m a t e l y 23°C and a t l o a d i n g s o f l e s s t h a n 30 lb.BOD^/day/1,000-cu. ft.  BOD  removal dropped  t o 80 p e r c e n t as t h e l o a d i n g was  l b .B0D5/day/l,000 c u . f t . and COD to micro-organism  r a t i o o f about 0.25  i n g problems were encountered foam s o l u t i o n was  removal dropped  t o 74 p e r c e n t a t a food  mg BOD^/mg MLVSS/day.  S e r i o u s foam-  throughout t h e s t u d y , even though an a n t i -  added t o the a e r o b i c u n i t s .  organism r a t i o exceeded 1.5,  i n c r e a s e d t o 87  When t h e food t o m i c r o -  s l u d g e b u l k i n g problems were a l s o  No m e t a l a n a l y s e s were g i v e n and no e f f o r t was d i s t r i b u t i o n i n the mixed l i q u o r  effluents.  encountered.  made t o d e t e r m i n e t h e m e t a l  A d d i t i o n a l l a b o r a t o r y s t u d i e s i n d i c a t e d t h a t l e a c h a t e c o u l d be added t o domestic wastewater  i n an "extended  p l a n t a t a l e v e l up t o 5 p e r c e n t by volume  aeration" activated ( l e a c h a t e COD  mg/1) w i t h o u t s e r i o u s l y i m p a i r i n g e f f l u e n t q u a l i t y .  sludge  ='.10,000  A t g r e a t e r than 5 per-  c e n t by volume, l e a c h a t e a d d i t i o n s r e s u l t e d . i n g r e a t l y i n c r e a s e d e f f l u e n t BOD and COD, i n c r e a s e d oxygen uptake r a t e s , and p o o r e r mixed  liquor  settling. Cook and Foree (16) i n v e s t i g a t e d a e r o b i c b i o s t a b i l i z a t i o n o f a medium-strength leachate.  (B0D  5  = 9,500 mg/1, COD = 17,500 mg/1) s a n i t a r y  landfill  T h e i r s t u d y was d e s i g n e d t o d e t e r m i n e t h e s u s c e p t i b i l i t y t o  treatment o f a t y p i c a l s a n i t a r y l a n d f i l l  l e a c h a t e by a e r o b i c b i o l o g i c a l  methods, t o e v a l u a t e t r e a t m e n t p r o c e s s e s f o r p o l i s h i n g o f t h e e f f l u e n t s from a e r o b i c b i o l o g i c a l t r e a t m e n t , and t o p e r f o r m a 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 z a t i o n o f t h e l e a c h a t e and t r e a t e d e f f l u e n t s .  To a c c o m p l i s h t h e s e  o b j e c t i v e s , l a b o r a t o r y s c a l e t r e a t m e n t u n i t s (2 l i t r e volume) were o p e r a t e d under v a r i o u s o r g a n i c l o a d i n g , n u t r i e n t a d d i t i o n t h e i r performance  and pH c o n d i t i o n s , and  was e v a l u a t e d by a n a l y t i c a l t e s t i n g .  The r e s u l t s o f t h i s  s t u d y i n d i c a t e d t h a t a e r o b i c b i o l o g i c a l t r e a t m e n t was a v e r y e f f e c t i v e means of.  s t a b i l i z i n g a " t y p i c a l " sanitary l a n d f i l l  leachate.  The b e s t o p e r a -  t i o n a l c o n d i t i o n s were found t o be a d e t e n t i o n time o f 10 days (COD l o a d i n g = 98.5 lb.COD/day/1,000 - c u . f t . ) , w h i c h r e s u l t e d i n a MLVSS c o n c e n t r a t i o n o f 4,400 mg/1 o r g r e a t e r ( f o o d t o m i c r o - o r g a n i s m r a t i o = 0.216 lb.BOD^/lb. MLVSS/day) i n t h e c o m p l e t e l y mixed, no r e c y c l e , systems e v a l u a t e d .  With  t h e s e two o p e r a t i o n a l c o n d i t i o n s , COD s t a b i l i z a t i o n e f f i c i e n c y o f g r e a t e r t h a n 97 p e r c e n t was a c c o m p l i s h e d .  The BOD5 o f t h e s e t t l e d e f f l u e n t was  reduced t o l e s s t h a n 26 mg/1 (99.7 p e r c e n t r e m o v a l ) , i n d i c a t i n g almost, complete b i o l o g i c a l s t a b i l i z a t i o n . e s t a b l i s h e d and m a i n t a i n e d .  A s t a b l e m i c r o b i a l p o p u l a t i o n was  The mixed l i q u o r was c h a r a c t e r i z e d by v e r y  20  good s e t t l i n g p r o p e r t i e s and e f f i c i e n t n u t r i e n t removal was The  obnoxious odour o f the raw  above 7.6 was  maintained  l e a c h a t e was  i n each u n i t .  accomplished.  c o m p l e t e l y removed and a  A e r o b i c b i o l o g i c a l treatment  pH units  w i t h d e t e n t i o n times o f 2 days and 5 days f a i l e d as i n d i c a t e d by s h a r p l y i n c r e a s i n g e f f l u e n t COD centrations. The  T h i s f a i l u r e was  mg/l  240 mg/l.  of i r o n remaining  s h a r p l y d e c r e a s i n g MLVSS con-  p r e d i c t e d by t h e o r e t i c a l  removal o f o n l y t h r e e metals was  the raw l e a c h a t e was  was  c o n c e n t r a t i o n s and  examined.  The  determinations.  i r o n c o n c e n t r a t i o n -in  A l l o f the 10 day u n i t s had  in their settled effluent.  l e s s than  T h i s l a r g e i r o n removal  a t t r i b u t e d m a i n l y t o c h e m i c a l p r e c i p i t a t i o n a t the h i g h pH  i n the 10 day u n i t s . mg/l.  The  L e s s t h a n 430 mg/l  10 day u n i t s .  c a l c i u m c o n c e n t r a t i o n i n the raw  maintained  feed was  1,200  remained i n any o f t h e s e t t l e d e f f l u e n t s from t h e  As the pH i n t h e s e 10 day u n i t s i n c r e a s e d from 7.6  to  t h e c a l c i u m c o n c e n t r a t i o n i n the s e t t l e d e f f l u e n t s dropped f r o m 430 t o 20 mg/l.  The magnesium c o n c e n t r a t i o n i n t h e raw  T h i s c o n c e n t r a t i o n was b i o l o g i c a l treatment  10  l e a c h a t e was  8.4, mg/l  170  mg/l.  not s i g n i f i c a n t l y r e d u c e d because the pH i n the  u n i t s was  not h i g h enough t o cause p r e c i p i t a t i o n o f  the magnesium as magnesium h y d r o x i d e . The  e f f l u e n t p o l i s h i n g r e s u l t s showed t h a t a c t i v a t e d c a r b o n  v e r y e f f e c t i v e i n r e d u c i n g the r e s i d u a l COD o r g a n i c c a r b o n and c o l o u r . moval, but had  2-6  (by a p p r o x i m a t e l y  The use o f b l e a c h was  l i t t l e e f f e c t on  was  40 p e r c e n t ) ,  effective i n colour re-  COD.  Summary A e r o b i c d i g e s t i o n i s s e n s i t i v e t o a number o f f a c t o r s and  t h e r e f o r e be d e s i g n e d w i t h t h e s e i n mind.  Optimum n u t r i e n t  should  requirements  and s u i t a b l e o p e r a t i n g t e m p e r a t u r e s f o r a e r o b i c m i c r o - o r g a n i s m s have been w e l l e s t a b l i s h e d and can r e a d i l y be s a t i s f i e d .  pH may  a l s o be  controlled  t h r o u g h t h e a d d i t i o n o f b u f f e r s and a c i d s o r bases. s u p p l i e d t o keep t h e r e a c t o r s a e r o b i c .  Enough oxygen must b  I f l o a d i n g r a t e s a r e k e p t low  enough, a e r o b i c b i o s t a b i l i z a t i o n i s a v e r y e f f e c t i v e means o f s t a b i l i z i n g medium-strength l a n d f i l l concentrations  leachate.  The e f f e c t o f i n c r e a s e d heavy m e t a l  i n a s t r o n g l a n d f i l l l e a c h a t e , on t h e a e r o b i c  treatment  e f f i c i e n c y a t v a r i o u s d e t e n t i o n t i m e s , must, however, be examined and t h e degree t o w h i c h t h e s e heavy m e t a l s may be c o n c e n t r a t e d s l u d g e must be d e t e r m i n e d .  i n the s e t t l e d  CHAPTER 3 (  RESEARCH RATIONALE AND  EXPERIMENTAL DESIGN  The development o f methods o f s a t i s f a c t o r i l y t r e a t i n g  landfill  l e a c h a t e s i s a major g o a l o f an on-going r e s e a r c h program c u r r e n t l y b e i n g conducted a t the U n i v e r s i t y o f B r i t i s h Columbia. program, a n a e r o b i c  d i g e s t i o n , chemical treatment  been i n v e s t i g a t e d by r e s e a r c h p e r s o n n e l ing.  As p a r t o f t h a t r e s e a r c h and peat t r e a t m e n t  i n the Department o f C i v i l  To complete the i n v e s t i g a t i o n o f the most obvious  t i v e s , t h i s s t u d y was  have  treatment  i n i t i a t e d t o d e t e r m i n e the t r e a t a b i l i t y o f  Engineeralternalandfill  l e a c h a t e by a e r o b i c d i g e s t i o n . Although  the c o m p o s i t i o n o f l a n d f i l l  leachate varies widely,  s t u d i e s have shown t h a t i n v a r i a b l y , l e a c h a t e has v e r y h i g h BOD w e l l as numerous heavy m e t a l s  o f .varying c o n c e n t r a t i o n .  v a l u e s , as  Because the p r e s e n c e  o f l a r g e amounts o f oxygen demanding m a t e r i a l s i s a major c o n c e r n , i n r i v e r s w i t h f i s h , BOD treatment  process.  be c o n s i d e r e d .  The  previous  r e d u c t i o n must be the prime g o a l o f any  especially leachate  For t h i s r e a s o n a l l forms o f b i o l o g i c a l t r e a t m e n t e f f e c t s o f heavy metals  on the p r o c e s s and  their  must distri-  b u t i o n i n the r e s u l t i n g s l u d g e and l i q u i d e f f l u e n t s a r e a l s o o f v i t a l  interest  and t h e r e f o r e r e q u i r e i n v e s t i g a t i o n . Although  the p r e s e n c e o f heavy m e t a l s  i s g e n e r a l l y believed to  cause more problems d u r i n g a e r o b i c d i g e s t i o n than d u r i n g a n a e r o b i c d i g e s t i o n , advantages c l a i m e d f o r a e r o b i c d i g e s t i o n as compared to a n a e r o b i c d i g e s t i o n include (4): (a) v o l a t i l e - s o l i d s r e d u c t i o n a p p r o x i m a t e l y  equal to that obtained anaero-  bically; (b) lower BOD  concentrations i n supernatant  (c) p r o d u c t i o n o f an o d o u r l e s s , h u m u s - l i k e ,  liquor; b i o l o g i c a l l y s t a b l e end  product  23  t h a t c a n be d i s p o s e d  of e a s i l y ;  (d) p r o d u c t i o n o f a s l u d g e w i t h e x c e l l e n t d e w a t e r i n g (e) r e c o v e r y o f more o f t h e b a s i c f e r t i l i z e r v a l u e s (f)  characteristics; i n the s l u d g e ;  fewer o p e r a t i o n a l problems; and  (g) lower c a p i t a l c o s t . The major d i s a d v a n t a g e  of the a e r o b i c d i g e s t i o n process  appears t o be t h e  h i g h e r power c o s t a s s o c i a t e d w i t h s u p p l y i n g t h e r e q u i r e d oxygen. The p u r p o s e s o f t h i s s t u d y were t o d e t e r m i n e t h e s u s c e p t i b i l i t y t o treatment  o f a h i g h - s t r e n g t h , l a n d f i l l l e a c h a t e by a e r o b i c b i o l o g i c a l  methods, t o d e t e r m i n e where and t o what e x t e n t m e t a l s i n t h e l e a c h a t e might be c o n c e n t r a t e d ,  and t o c h a r a c t e r i z e t h e s e t t l e d e f f l u e n t s o b t a i n e d  from  the a e r o b i c b i o s t a b i l i z a t i o n p r o c e s s . The s t u d y was c a r r i e d out i n t h r e e phases. removal study was d e s i g n e d  The a c c l i m a t i z a t i o n - m e t a l  t o produce an a c c l i m a t i z e d m i c r o b i a l p o p u l a t i o n  f o r use i n t h e subsequent a e r o b i c b i o s t a b i l i z a t i o n e f f i c i e n c y s t u d i e s and t o s t u d y t h e long-term,  m e t a l removal c a p a c i t y o f t h e s e t t l i n g b i o l o g i c a l f l o e .  The a e r o b i c b i o s t a b i l i z a t i o n e f f i c i e n c y s t u d i e s were d e s i g n e d  to determine  the e f f e c t o f i n c r e a s i n g s o l i d s d e t e n t i o n t i m e and o r g a n i c l o a d i n g on t r e a t ment e f f i c i e n c y and m e t a l removal.  Based on e s t i m a t e s  of the steady  state  mixed l i q u o r v o l a t i l e suspended s o l i d s l e v e l s , s o l i d s d e t e n t i o n times were s e l e c t e d t o g i v e o r g a n i c l o a d i n g s i n t h e range recommended tion.  f o r extended a e r a -  U s i n g t h e r e s u l t s o f t h i s "extended a e r a t i o n " e f f i c i e n c y s t u d y , t h e  minimum s o l i d s d e t e n t i o n time f o r t h e system was p r e d i c t e d and t h e s o l i d s d e t e n t i o n times t o be used i n t h e " s h o r t e r d e t e n t i o n . t i m e " were then s e t above t h i s p r e d i c t e d minimum.  study  A t t h e c o n c l u s i o n o f each phase  o f the study, s e t t l e d e f f l u e n t s were c o l l e c t e d sequent c h a r a c t e r i z a t i o n .  efficiency  f o r m e t a l a n a l y s i s and sub-  CHAPTER 4  SYSTEM DESIGN AND EXPERIMENTAL PROCEDURE  4-1  D e s i g n o f t h e Treatment System The  i n v e s t i g a t i o n o f t h e t h e o r y o f a e r o b i c b i o s t a b i l i z a t i o n and  p r e v i o u s attempts  a t a e r o b i c a l l y t r e a t i n g l a n d f i l l l e a c h a t e (15,16) p r o v i d e d  the b a s i c i n f o r m a t i o n needed t o d e s i g n t h e system.  I t was d e c i d e d t h a t a  s i n g l e stage bench s c a l e system would be used t o e v a l u a t e t h e a e r o b i c b i o s t a bilization  o f h i g h - s t r e n g t h l a n d f i l l l e a c h a t e , because o f i t s s i m p l i c i t y and  ease o f o p e r a t i o n . : A f t e r i n v e s t i g a t i n g p r e v i o u s models used i n s i m i l a r s t u d i e s , i t was d e c i d e d t o use t h r e e d i g e s t e r s each o f 10 l i t r e s c a p a c i t y . T h i s d e c i s i o n was based on t h e f a c t t h a t : (1) they were r e a d i l y a v a i l a b l e i n the l a b o r a t o r y , (2) s i m i l a r u n i t s had s u c c e s s f u l l y been used i n p r e v i o u s s t u d i e s , and ( 3 ) l e a c h a t e volumes a v a i l a b l e were i n s u f f i c i e n t t o use l a r g e r digesters.  The d i g e s t e r s were made from l a r g e g l a s s b o t t l e s .  The bottom o f  each b o t t l e was removed and t h e necks were f i t t e d w i t h l a r g e rubber The  stoppers.  s t o p p e r s were s e c u r e d u s i n g heavy s t a i n l e s s s t e e l w i r e but no w i r e was  a l l o w e d i n s i d e t h e d i g e s t e r s , thus p r e v e n t i n g any unknown a d d i t i o n s o f m e t a l to  the d i g e s t e r contents.  fitted  A porous g l a s s , c o a r s e - b u b b l e ,  a i r d i f f u s e r was  i n t h e bottom o f each d i g e s t e r and a i r was p r o v i d e d f o r each u n i t  from t h e l a b o r a t o r y compressed a i r system. Because o f t h e h i g h c o n c e n t r a t i o n s o f metals i n t h e l e a c h a t e foaming problems were a n t i c i p a t e d .  feed,  To c o n t r o l foaming, w h i l e m a i n t a i n i n g  adequate m i x i n g , i t was f e l t t h a t a c o m b i n a t i o n s h o u l d be employed i n t h e d i g e s t e r s .  o f a i r and m e c h a n i c a l  Consequently,  mixing  an a d j u s t a b l e clamp was  p l a c e d on t h e a i r l i n e t o each d i g e s t e r t o c o n t r o l a i r f l o w and an e l e c t r i c d r i v e n s t i r r e r was p r o v i d e d i n each d i g e s t e r t o ensure u n i f o r m o f food and m i c r o - o r g a n i s m s .  distribution  M i x i n g speeds were s e t a p p r o x i m a t e l y  equal i n  25  a l l t h r e e d i g e s t e r s and a i r f l o w r a t e s were a d j u s t e d t o m a i n t a i n a e r o b i c c o n d i t i o n s w h i l e m i n i m i z i n g foaming.  A s c h e m a t i c o f t h e s e d i g e s t e r s i s shown  i n F i g u r e 1. To c o n t a i n any foam w h i c h might be produced d e c i d e d t o use o n l y 4.5  d u r i n g the s t u d y , i t was  l i t r e s o f mixed l i q u o r , thus a l l o w i n g f o r about 8  i n c h e s o f foam i n each d i g e s t e r . c i t y t o the b i o l o g i c a l system.  An a n t i f o a m a g e n t * was  a l s o tested for tox-  V a r i o u s doses o f the a n t i f o a m agent were addled  to t e s t u n i t s , but even i n v e r y l a r g e doses the oxygen uptake r a t e s o f t e s t and c o n t r o l u n i t s remained e q u a l a f t e r s e v e r a l h o u r s . e v e r , never reached the p r o p o r t i o n s a n t i c i p a t e d and  Foaming problems,  i t was  how-  n e c e s s a r y t o add  the a n t i f o a m agent t o o n l y the h i g h e s t loaded d i g e s t e r t e s t e d . S i n c e t h e c o n v e n t i o n a l a c t i v a t e d s l u d g e p r o c e s s i s not i n f l u e n c e d by s m a l l temperature  changes, and s i n c e the r e a c t o r s were t o be  o p e r a t e d d u r i n g the summer, i t was necessary.  The  temperature  f e l t t h a t temperature  o f the mixed l i q u o r s was  of  c o n t r o l s were not  measured f r e q u e n t l y  o throughout  significantly  o  the s t u d y and found t o v a r y between 21  and 25 C.  The  temperature  t h e mixed l i q u o r appeared t o be a f f e c t e d more by the a i r f l o w r a t e t h r o u g h  t h e d i g e s t e r t h a n by the ambient a i r t e m p e r a t u r e ,  d e c r e a s i n g as t h e a i r f l o w -  rate increased. 4-2  Leachate The  Source and  Characteristics  l e a c h a t e used as f e e d i n t h i s s t u d y was -  generated  meter c o n s t r u c t e d a t the U n i v e r s i t y o f B r i t i s h Columbia,  from a  lysi-  as p a r t o f an  on-  g o i n g program t o c h a r a c t e r i z e l a n d f i l l l e a c h a t e s and m o n i t o r v a r i a t i o n s i n t h e i r composition w i t h time, r a i n f a l l meters.,  The program was  r a t e , c o v e r m a t e r i a l and o t h e r p a r a -  i n i t i a t e d by Dr. R.D.  *Dow C o r n i n g a n t i f o a m e m u l s i o n DB-31.  Cameron, o f the Department o f  Electric  E l e c t r i c motor driven stirrer  motor  0  •  Volumetric graduation ( on m a sking  Plastic  tape)  Porous, G l a s s , Coarse bubble diffuser  tubing  A d j u s t a b l e screw  Oil - free air  Figure  1  SCHEMATIC  OF  LABORATORY  Rubber  clamp  AEROBIC  stopper  J3 DIGESTERS  Civil  Engineering, Details  U.B C. 0  of the lysimeter are:  (1)  Dimensions  - 14 f e e t  (2)  Cover m a t e r i a l  (3)  T o t a l weight o f garbage  (4)  Depth  (5)  Weight (density) b e f o r e  (6)  Rainfall  rate  (7)  Moisture  content  (8)  Percentage composition  - 2 feet  o f garbage  Textiles  Glass  feet final  mixed  - 47.6  - 5.4 - 3.6  rocks  and d i r t  by  technicians  tion in  research  this  - 1.4  - 100  from t h i s  4 weeks  per year  - 9.8  lysimeter  was c o l l e c t e d  i n leachate  i n the laboratory  study and s t o r e d  returned  The 4 C temperature has been composition.  t o produce a composite sample,  program.  weekly,  o  a t 4 C.  t o m i n i m i z e changes  every  y a r d (wet)  - 8.7  t h e l a b and s t o r e d  adequate  - 884 l b . / c u b i c  o f garbage:  o to  cover  a n d c e r a m i c s - 7.0  Total  Leachate  - 3420 l b s .  - 4.7  Metals  Ash,  fuel  - 34.77„  products  Cardboard  i n diameter  - 11.8  Garden waste  Wood  - 8  4 feet  o f hog  - 15 i n c h e s  Food waste  Paper  deep,  as p a r t  Composite  samples were  i n 20 1 p o l y e t h y l e n e  Samples  w h i c h was  of the leachate  found were  analysed  characteriza-  t h e n mixed f o r u s e o b o t t l e s a t 4 C.  120  litres  of high-strength l a n d f i l l  f i v e month p e r i o d f o r use One  i n the a e r o b i c b i o s t a b i l i z a t i o n  20 l i t r e b o t t l e was  m e t a l removal s t u d y .  l e a c h a t e were thus c o l l e c t e d over a  s e l e c t e d f o r use  I t s composition  i n the  The  c o m p o s i t e was  As  the  the r e m a i n i n g  l e a c h a t e were mixed t o form a l a r g e c o m p o s i t e w h i c h was efficiency studies.  acclimatization-  i s shown i n T a b l e V I .  a c c l i m a t i z a t i o n - m e t a l removal s t u d y drew t o an end,  treatment  study.  100  1 of  used t h r o u g h o u t  the  pumped i n t o 20 1 p o l y -  o e t h y l e n e b o t t l e s and a g a i n before  feeding.  The  s t o r e d at 4 C to minimize  composition  biological  activity  o f t h e c o m p o s i t e l e a c h a t e sample i s a l s o  shown i n T a b l e V I . 4-3  pH C o n t r o l Because the pH o f t h e l e a c h a t e was  pH c o n t r o l might be n e c e s s a r y .  w e l l below 6.5,  t h e r e f o r e adjusted to approximately  pH o f the mixed l i q u o r was liquors,  r o s e from 7.2  l e a c h a t e feed was and a l l through  7.2  monitored d a i l y .  t o g r e a t e r t h a n 8.3  stopped.  felt  From day  in 2 litre  batches,  using calcium hydroxide.  The  I n 9 days the pH o f a l l mixed and  t h u s , pH a d j u s t m e n t o f  the  10 on i n t h e a c c l i m a t i z a t i o n s t u d y  t h e e f f i c i e n c y s t u d i e s , o n l y n u t r i e n t s were added t o  l e a c h a t e feed and no a t t e m p t was  that  A t t h e s t a r t o f the a c c l i m a t i z a t i o n - m e t a l  removal s t u d y , the pH o f t h e l e a c h a t e f e e d , p r e p a r e d was  i t was  the  made t o c o n t r o l the pH o f the mixed  liquors.  4-4  N u t r i e n t Balance In o r d e r t o m a i n t a i n a B0D,_:N:P r a t i o o f 100:5:1, a d d i t i o n a l  gen and phosphorus ; were r e q u i r e d . t h i s purpose. and  A mixture  S e v e r a l c h e m i c a l s were c o n s i d e r e d  o f mono-basic ammonium phosphate  di-ammonium phosphate ((OTI^)2HPO4) was  both n i t r o g e n and  nitrofor  ((NH^H^PO^.)  s e l e c t e d because i t s u p p l i e d  phosphorus.; i n forms s u i t a b l e f o r u t i l i z a t i o n by  aerobic  29  TABLE V I COMPOSITION OF LEACHATE FEED USED DURING STUDY  Concentration mg/l During A c c l i m a t i z a t i o n M e t a l Removal S t u d y  Parameter  Concentration mg/l During E f f i c i e n c y Studies  42,000  36,000  58,000  48,000  Carbon  18,400 16  15,400 11  Total Solids Total V o l a t i l e Solids Total Dissolved Solids  34,900 21,500 34,500  26,600 17,800 25,700  Acidity Alkalinity  6,600 10,200  5,640 7,640  BOD  5  COD T o t a l Carbon Total Inorganic  Aluminum Arsenic Barium Beryllium Boron Calcium Cadmium Chloride Chromium Copper Iron Lead Magnesium Manganese Mercury Nitrogen - t o t a l - NH Nickel Phosphorus - t o t a l Potassium Sodium Sulphates Zinc 3  T a n n i n - l i k e compounds  * pH *not i n mg/l  60.2 4.1 1.3 trace 7.40 1,924 0.43 1,650 2.3. 0.17 1,260 1.79 378 46.0 0.012 1,370 938 0.61 22.2 1,610 1,720 1,020 227  41.8 3.6 0.7 trace 7.30 1,394 0.39 1,620 1.9 0.24 960 1.44 310 41.0 0.012 . 1,080 725 0.65 19.8 1,060 1,250 1,070 223  943  578  5.09  5.02  30  micro-organisms  and i t was f e l t t h a t pH o f t h e l e a c h a t e f e e d c o u l d be  b u f f e r e d around 7.2 by s e l e c t i o n !.o£ .the p r o p e r molar r a t i o s o f t h e s e two salts.  An e x a c t r a t i o o f 5:1 f o r N:P c o u l d , however, n o t be a c h i e v e d u s i n g  t h e s e two s a l t s , so a B0D^:N r a t i o o f 20:1 was aimed f o r i n e s t a b l i s h i n g required nutrient additions.  S i n c e t h e a n a l y s i s o f t h e l e a c h a t e feed used  i n t h e a c c l i m a t i z a t i o n - m e t a l removal  s t u d y was n o t complete when t h e s t u d y  began, n u t r i e n t a d d i t i o n s were e s t i m a t e d from p r e v i o u s l a b a n a l y s e s on t h e 4-week composite  samples.  S i m i l a r l y , t h e a n a l y s i s o f t h e composite  leachate  feed used i n t h e e f f i c i e n c y s t u d i e s was n o t complete when these' s t u d i e s began.  T h e r e f o r e , t h e same amounts o f each s a l t were added d u r i n g t h e f i r s t  h a l f o f t h e e f f i c i e n c y s t u d y ("extended a e r a t i o n " e f f i c i e n c y s t u d y ) . N u t r i e n t a d d i t i o n s were t h e n reduced d u r i n g t h e f i n a l h a l f o f t h e e f f i c i e n c y study ("shorter detention time" e f f i c i e n c y study).  The r e s u l t i n g n u t r i e n t  a d d i t i o n s and B0D :N:P r a t i o s a r e shown i n T a b l e V I I . c  TABLE V I I NUTRIENT ADDITIONS AND B0D :N:P RATIOS DURING STUDY c  Study Phase  Ammonium Phosphate A d d i t i o n , mg/1  Di-Ammonium Phosphate A d d i t i o n , mg/1  BOD :N:P R a t i o in L e a c h a t e Feed  AcclimatizationM e t a l Removal Study  630  2,900  100:4.85:2.05'  "Extended A e r a t i o n " E f f i c i e n c y Study  630  2,900  100:6.37:3.12  1,462  100:5:1.3  "Shorter Detention Time" E f f i c i e n c y Study  4-5  Metal  Concentrations  No attempt was made t o m o d i f y m e t a l c o n c e n t r a t i o n s .  I t was  felt  t h a t t h e b e s t approach would be t o u s e l e a c h a t e as produced and o b s e r v e the e f f e c t s  o f the very h i g h metal c o n c e n t r a t i o n s on the e f f i c i e n c y  aerobic b i o s t a b i l i z a t i o n  4-6  process.  A c c l i m a t i z a t i o n - M e t a l Removal S t u d y This phase o f t h e r e s e a r c h program was d e s i g n e d  t o produce an a c c l i m a -  t i z e d m i c r o b i a l population f o r use i n the aerobic b i o s t a b i l i z a t i o n s t u d i e s and t o study t h e long-term, biological  efficiency  m e t a l removal c a p a c i t y o f t h e s e t t l i n g  floe.  To s e t " s a f e " h y d r a u l i c d e t e n t i o n times was n e c e s s a r y  f o r use i n t h i s s t u d y , i t  t o e v a l u a t e a number o f c o n v e n t i o n a l d e s i g n parameters.  and Ham (15) found a e r o b i c treatment  of l a n d f i l l  Boyle  l e a c h a t e p r o m i s i n g when  l o a d i n g s were kept below 30 lb.BOD^/day/1,000 c u b i c . f e e t . (16)  of the  Cook and F o r e e  found, however, t h a t BOD removals were s t i l l e x c e l l e n t when l o a d i n g s  were i n c r e a s e d t o about 100 lb.COD/day/1,000 c u b i c f e e t ,  provided  food t o  m i c r o - o r g a n i s m r a t i o s were k e p t r e l a t i v e l y low (around 0.22 lb.BOD^/lb.MLVSS/ day).  F o r t h i s reason,  t h e v o l u m e t r i c BOD and COD l o a d i n g r a t e s and food t o  m i c r o - o r g a n i s m r a t i o s , assuming a MLVSS c o n c e n t r a t i o n o f 4,000 mg/l, were e v a l u a t e d a t a number o f c o n v e n i e n t  h y d r a u l i c d e t e n t i o n times.  With a  h y d r a u l i c d e t e n t i o n time o f 45 days, COD l o a d i n g was a n t i c i p a t e d t o be about 81 lb.COD/day/1,000 c u b i c f e e t r e s u l t i n g  i n an i n i t i a l  o r g a n i s m r a t i o o f about 0.23 lb/BOD /lb.MLVSS/day. 5  food t o m i c r o -  Thus, a 45 day h y d r a u -  l i c d e t e n t i o n t i m e was s e t f o r t h e h i g h e s t l o a d e d d i g e s t e r and h y d r a u l i c d e t e n t i o n times 90 days.  f o r t h e o t h e r two d i g e s t e r s were c o n v e n i e n t l y s e t a t 60 and  S i n c e no suspended s o l i d s were t o be w i t h d r a w n d u r i n g t h e a c c l i m a -  t i z a t i o n study,  t h e s o l i d s d e t e n t i o n times  t h e . l e n g t h o f t h a t study.(56  days).  i n a l l t h r e e u n i t s were e q u a l t o  (a)  S t a r t Up  - About 15 1 o f w a s t e a c t i v a t e d s l u d g e were o b t a i n e d  the C e n t r a l Sewage Treatment P l a n t i n Squamish, B.C., n o r t h o f Vancouver.  The  plant t r e a t i n g a mixture  l i g h t i n d u s t r i a l waste.  sludge treatment"  miles  Squamish Sewage Treatment P l a n t i s a  "package a c t i v a t e d s l u d g e t r e a t m e n t " domestic and  some 40  from  of  A survey o f "package a c t i v a t e d  p l a n t s i n the Vancouver a r e a had  duce the most s u i t a b l e a c t i v a t e d s l u d g e  f o r use  shown i t t o pro-  in this  study.  • The mixed l i q u o r v o l a t i l e suspended s o l i d s c o n c e n t r a t i o n i n the s l u d g e sample was  d e t e r m i n e d and enough s l u d g e was  i n each d i g e s t e r t o p r o v i d e 4.5  then placed  1 o f mixed l i q u o r w i t h a v o l a t i l e  suspended s o l i d s c o n c e n t r a t i o n o f 3,960 mg/1.  The  r e q u i r e d volumes  o f l e a c h a t e feed w i t h n u t r i e n t s added and pH a d j u s t e d t o about were t h e n added t o each d i g e s t e r : 100 ml t o D i g e s t e r D j , 75 ml D i g e s t e r E",  and 50 ml t o D i g e s t e r F".  d i g e s t e r was  then a d j u s t e d t o 4.5  f l o w was  i n i t i a t e d and a d j u s t e d  a b l e clamps on the a i r l i n e s .  The  to  t o t a l volume i n each  1 u s i n g d i s t i l l e d water.  Air  i n each d i g e s t e r u s i n g the a d j u s t S t i r r e r s i n each d i g e s t e r were t h e n  t u r n e d on and s t i r r i n g speeds s e t a p p r o x i m a t e l y (b)  7.2  equal.  D i g e s t e r O p e r a t i o n and T e s t i n g - At 24 h o u r : i n t e r v a l s the w a t e r l o s t by e v a p o r a t i o n was o f the d i g e s t e r s and  replaced w i t h d i s t i l l e d water.  The  sides  the s t i r r e r s i n each d i g e s t e r were s c r a p e d  remove a l l a d h e r i n g m i c r o - o r g a n i s m s , w h i c h were thus r e t u r n e d the mixed l i q u o r and  t h e n the c o n t e n t s were c o m p l e t e l y mixed.  to  to The  o * oxygen uptake r a t e i n each d i g e s t e r was 3.0  ml o f mixed l i q u o r , w h i c h was  then measured a t 20 C u s i n g  subsequently  * u s i n g a YSI Model 53 B i o l o g i c a l Oxygen M o n i t o r Temperature C i r c u l a t o r , Model F J .  r e t u r n e d t o the  and a Haake C o n s t a n t  diges-  t e r from w h i c h i t was o b t a i n e d .  A f t e r t h e oxygen u p t a k e r a t e i n  each d i g e s t e r had been d e t e r m i n e d , t h e a i r and s t i r r e r s i n a l l t h r e e d i g e s t e r s were shut o f f and t h e b i o l o g i c a l f l o e s were a l l o w e d to s e t t l e .  The s e t t l i n g t i m e r e q u i r e d t o o b t a i n an adequate volume  o f c l e a r s u p e r n a t a n t i n c r e a s e d as b i o l o g i c a l s o l i d s a c c u m u l a t e d i n t h e d i g e s t e r s , b u t t h e d i g e s t e r s were never a l l o w e d t o s i t more t h a n a n hour w i t h o u t a i r .  A f t e r s e t t l i n g , t h e r e q u i r e d volume o f  c l e a r s u p e r n a t a n t was w i t h d r a w n from each d i g e s t e r u s i n g v o l u m e t r i c p i p e t t e s : 100 ml from D i g e s t e r D 7 5  ml from D i g e s t e r E a n d  50  ml from D i g e s t e r F•". Volumes o f l e a c h a t e f e e d e q u a l t o t h e volumes removed were t h e n added t o each d i g e s t e r .  A i r t o t h e d i g e s t e r s was  t u r n e d back on and t h e s t i r r i n g speeds were a g a i n s e t e q u a l .  The  pH o f t h e s e t t l e d e f f l u e n t from each d i g e s t e r was measured and recorded.  E v e r y 5 days t h e t o t a l s o l i d s c o n c e n t r a t i o n s i n t h e  s e t t l e d e f f l u e n t s were d e t e r m i n e d .  The BOD^'s o f t h e s e t t l e d  e f f l u e n t s were .determined e v e r y 7 days. As i n d i c a t e d , l e a c h a t e f e e d f o r t h e s e u n i t s was p r e p a r e d i n 2 l i t r e volumes  and s t o r e d a t 4°C u n t i l needed.  pH a d j u s t m e n t on t h e  i n i t i a l f e e d caused a g r e a t p o r t i o n o f t h e m e t a l s t o s e t t l e o u t o f the leachate feed.  When t h e pH o f a l l 3 u n i t s c l i m b e d t o g r e a t e r  t h a n 8.3 a f t e r 9 days o f o p e r a t i o n , t h e pH a d j u s t m e n t o f t h e l e a c h a t e f e e d was d i s c o n t i n u e d .  The a d d i t i o n o f n u t r i e n t s a l o n e s t i l l  caused a p o r t i o n o f t h e m e t a l s t o s e t t l e o u t o f t h e l e a c h a t e .  Thus,  t h r o u g h o u t t h i s s t u d y , f e e d was brought out o f t h e r e f r i g e r a t o r , a l l o w e d t o warm up f o r about an hour t o reduce any t e m p e r a t u r e shock t the system and t h e n t h o r o u g h l y mixed j u s t p r i o r t o t h e d a i l y  feeding.  A f t e r 56 days, 500 ml o f mixed l i q u o r were w i t h d r a w n from each digester.  100 ml o f each mixed l i q u o r were d i g e s t e d f o r m e t a l  a n a l y s i s f o l l o w i n g t h e recommended EPA method (17) and t h e b a l a n c e : was a l l o w e d t o s e t t l e .  C l e a r s u p e r n a t a n t s were t h e n w i t h d r a w n f o r  metal a n a l y s i s .  4-7  Aerobic B i o s t a b i l i z a t i o n E f f i c i e n c y Studies S o l i d s t e s t s near t h e end o f t h e a c c l i m a t i z a t i o n - m e t a l  removal  s t u d y i n d i c a t e d MLVSS l e v e l s i n D i g e s t e r s D", E', and F" o f a p p r o x i m a t e l y 11,800, 10,900 and 7,600 mg/1 r e s p e c t i v e l y .  W h i l e t h e s e MLVSS l e v e l s a r e  g r e a t l y i n excess o f t h e recommended range f o r a c t i v a t e d s l u d g e p r o c e s s e s , no attempt was made t o s i g n i f i c a n t l y reduce t h e b i o l o g i c a l s o l i d s c o n c e n t r a t i o n s because: (1) t h e b i o l o g i c a l f l o e s s t i l l s e t t l e d w e l l , (2) t h e s e t t l e d e f f l u e n t s had v e r y low BOD^ and g r e a t l y reduced  metal  concentrations, (3) Cook and Foree (16) c r e d i t e d t h e i r h i g h MLVSS l e v e l s ( >4,400 mg/1) w i t h h e l p i n g c o n t r o l and reduce t h e foaming problem, and (4) i t was f e l t t h a t t h e b i o l o g i c a l s o l i d s l e v e l s would drop t o s u i t a b l e l e v e l s i f t h e r e was n o t enough food i n t h e l e a c h a t e f e e d t o m a i n t a i n s u c h h i g h MLVSS c o n c e n t r a t i o n s . A g a i n , t o s e t " s a f e " s o l i d s d e t e n t i o n times f o r u s e i n t h e f i r s t h a l f o f t h e s e e f f i c i e n c y s t u d i e s , v o l u m e t r i c BOD and COD l o a d i n g r a t e s and a n t i c i p a t e d food t o m i c r o - o r g a n i s m  r a t i o s ' were c a l c u l a t e d .  Assuming a  maximum MLVSS c o n c e n t r a t i o n o f 10,000 mg/1, a 30 day : s o l i d s d e t e n t i o n time r e s u l t e d . i n a food t o m i c r o - o r g a n i s m  r a t i o o f about 0.12, a BOD l o a d i n g  r a t e o f about 75 lb.BOD /day/l,000 c u b i c f e e t and COD l o a d i n g o f about 102 5  lb.COD/day/1,000 c u b i c f e e t .  The COD l e a d i n g was t h e r e f o r e v e r y c l o s e t o  the maximum recommended by Cook and Foree organism r a t i o was expected t o remain  (16) and t h e food t o m i c r o -  i n t h e range recommended f o r extended  35  a e r a t i o n and below t h e range f o r c o n v e n t i o n a l complete mix a c t i v a t e d s l u d g e treatment (see Table I I ) .  A s o l i d s d e t e n t i o n time o f 30 days was t h e r e -  f o r e s e t f o r t h e h i g h e s t l o a d e d d i g e s t e r , D i g e s t e r D, i n t h e f i r s t h a l f o f the a e r o b i c b i o s t a b i l i z a t i o n e f f i c i e n c y s t u d i e s .  S o l i d s d e t e n t i o n times  f o r D i g e s t e r s E and F were t h e n s e t a t 45 and 60 days r e s p e c t i v e l y , t o c o v e r t h e range o f food t o m i c r o - o r g a n i s m r a t i o s recommended f o r extended a e r a t i o n , 0.05 t o 0.15 lb.BOD^lb.MLVSS/day. (a)  D i g e s t e r O p e r a t i o n and T e s t i n g - A t 24 hour i n t e r v a l s , t h e w a t e r l o s t by e v a p o r a t i o n was r e p l a c e d w i t h d i s t i l l e d w a t e r , t h e s i d e s and s t i r r e r s i n each d i g e s t e r were s c r a p e d , and t h e oxygen u p t a k e r a t e a t 20°C was d e t e r m i n e d f o r each d i g e s t e r .  The r e q u i r e d  volumes  o f mixed l i q u o r were t h e n w i t h d r a w n from each d i g e s t e r u s i n g l a r g e - t i p opening', b a c t e r i o l o g i c a l p i p e t t e s : 150 ml from D i g e s t e r D, 100 ml from D i g e s t e r E, and 75 ml from D i g e s t e r F.  Volumes o f l e a c h a t e  feed e q u a l t o t h e volumes o f mixed l i q u o r s . removed were t h e n added t o each d i g e s t e r . measured  The pH o f t h e mixed l i q u o r from each d i g e s t e r was  and r e c o r d e d .  E v e r y 3 o r 4 days, t h e MLSS c o n c e n t r a t i o n ,  MLVSS c o n c e n t r a t i o n and t o t a l s o l i d s c o n c e n t r a t i o n i n t h e l i q u o r e f f l u e n t were d e t e r m i n e d .  The  BOD5  mixed  o f t h e mixed l i q u o r and  s e t t l e d e f f l u e n t s were d e t e r m i n e d e v e r y 7 days.  These  parameters  were used t o d e t e r m i n e when s t e a d y s t a t e o p e r a t i o n was a c h i e v e d . A f t e r 30 days, s e t t l e d e f f l u e n t s from each d i g e s t e r were c o l l e c t e d d a i l y and c o m p o s i t e d f o r subsequent e f f l u e n t zation.  characteri-  A f t e r 35 days, 200 ml o f mixed l i q u o r were w i t h d r a w n from  each d i g e s t e r .  100 ml o f each mixed l i q u o r were wet-ash  f o l l o w i n g t h e recommended EPA p r o c e d u r e ( 1 7 ) .  digested  S m a l l samples o f  each mixed l i q u o r were t h e n w i t h d r a w n f o r COD a n a l y s i s and t h e b a l a n c e o f t h e samples was a l l o w e d t o s e t t l e .  The s e t t l e d  effluents  36  were t h e n c o l l e c t e d f o r m e t a l a n a l y s i s .  The a n a l y t i c a l  procedures  employed f o r a l l t e s t s used i n t h i s s t u d y a r e o u t l i n e d i n t h e t h i r t e e n t h e d i t i o n o f S t a n d a r d Methods (18) and f u r t h e r e x p l a i n e d i n Chemistry  f o r S a n i t a r y Engineers  (19).  Metal concentrations  were determined u s i n g a J a r r e l l - A s h MV 500 A t o m i c A d s o r p t i o n Spectrophotometer. (b)  T r a n s i t i o n t o " S h o r t e r D e t e n t i o n Time" Study - A n a l y s i s o f t h e MLVSS c o n c e n t r a t i o n and mixed l i q u o r BOD^ d a t a c o l l e c t e d d u r i n g t h e "extended  a e r a t i o n " e f f i c i e n c y s t u d y , p r e d i c t e d a minimum s o l i d s  d e t e n t i o n t i m e o f 6.46 days ( s e e A p p e n d i x E ) . A c t i v a t e d s l u d g e t r e a t m e n t p l a n t s a r e u s u a l l y d e s i g n e d w i t h s o l i d s d e t e n t i o n times 3 o r 4 times t h e p r e d i c t e d minimum.  T h e r e f o r e , because c o n s i d e r -  a b l e p e r s o n a l judgment was i n v o l v e d i n t h e s e l e c t i o n o f t h e k i n e t i c parameters  used t o determine  t h e minimum s o l i d s d e t e n t i o n t i m e ,  and because foaming problems were s t i l l a n t i c i p a t e d a t s h o r t e r det e n t i o n t i m e s , a s o l i d s d e t e n t i o n time o f 10 days was s e t f o r t h e h i g h e s t loaded d i g e s t e r .  D e t e n t i o n t i m e s o f 20 and 30 days,  a p p r o x i m a t e l y 3 and 4 times t h e p r e d i c t e d minimum, were t h e n chosen for the remaining u n i t s .  To m i n i m i z e t h e shock t o any u n i t , i t was  d e c i d e d t o g r a d u a l l y i n c r e a s e t h e l o a d i n g on each and t o make t h e h i g h e s t l o a d e d d i g e s t e r i n t h e "extended o  a e r a t i o n " e f f i c i e n c y study,  the h i g h e s t l o a d e d d i g e s t e r i n t h e " s h o r t e r d e t e n t i o n t i m e " iency study.  effic-  T h e r e f o r e , over t h e n e x t 7 days, t h e volume o f mixed  l i q u o r w i t h d r a w n and l e a c h a t e feed added t o each u n i t was g r a d u a l l y i n c r e a s e d : from 150 ml p e r day t o 450 m l p e r day f o r D i g e s t e r D, from 100 ml p e r day t o 225 ml p e r day f o r D i g e s t e r E, and from 75 ml p e r day t o 150 ml p e r day f o r D i g e s t e r F.  37  (c)  " S h o r t e r D e t e n t i o n Time" E f f i c i e n c y Study - The same d a i l y p r o c e d u r e used i n t h e "extended a e r a t i o n " e f f i c i e n c y s t u d y was employed t h i s study.  during  B r i e f l y , each day, a f t e r r e p l a c i n g w a t e r l o s t by  e v a p o r a t i o n and measuring t h e oxygen u p t a k e r a t e i n each d i g e s t e r , the  r e q u i r e d volumes o f mixed l i q u o r were w i t h d r a w n from each  d i g e s t e r : 450 ml from D i g e s t e r A, 225.ml from D i g e s t e r B, and 150 ml from D i g e s t e r C.  Volumes o f l e a c h a t e feed e q u a l t o t h e volumes o f  mixed l i q u o r w i t h d r a w n were t h e n added t o each d i g e s t e r . The pH o f t h e mixed l i q u o r from each d i g e s t e r was measured and recorded d a i l y .  E v e r y 3 o r 4 days t h e MLSS c o n c e n t r a t i o n , MLVSS  c o n c e n t r a t i o n and t o t a l s o l i d s c o n c e n t r a t i o n i n t h e mixed were d e t e r m i n e d .  The BOD^ o f t h e mixed and s e t t l e d e f f l u e n t s was.  d e t e r m i n e d e v e r y 7 days. of  liquor  However, because t h e r e was some e v i d e n c e  i n h i b i t i o n i n t h e mixed l i q u o r  BOD5  t e s t s and because t h o s e t e s t  r e s u l t s were v e r y e r r a t i c , . ; , t h e COD o f t h e mixed and s e t t l e d e f f l u e n t s was - d e t e r m i n e d e v e r y 3 o r 4 days i n i t i a l l y ,  and e v e r y 7  days a f t e r s t e a d y s t a t e o p e r a t i o n was a c h i e v e d . '  A f t e r 35 days, 100 ml o f each mixed l i q u o r was d i g e s t e d f o r  metal a n a l y s i s (17).  One l i t r e o f each mixed l i q u o r was t h e n w i t h -  drawn f o r s e t t l i n g t e s t s and t h e s e t t l e d e f f l u e n t s were c o l l e c t e d for  4-8  m e t a l a n a l y s i s and c h a r a c t e r i z a t i o n .  Summary A l o n g , c a r e f u l , a c c l i m a t i z a t i o n p e r i o d produced mixed l i q u o r s  v e r y h i g h v o l a t i l e suspended s o l i d s c o n c e n t r a t i o n s .  with  Prudent s e l e c t i o n o f  s o l i d s d e t e n t i o n times f o r t h e "extended a e r a t i o n " e f f i c i e n c y s t u d y r e s u l t e d i n s t a b l e o p e r a t i o n w i t h i n 3 weeks, as i n d i c a t e d by t h e mixed l i q u o r BOD^ and VSS c o n c e n t r a t i o n s .  A short t r a n s i t i o n period to shorter detention  38  times r e s u l t e d a g a i n i n s t a b l e o p e r a t i o n , a t t h e s e new w i t h i n 3 weeks.  d e t e n t i o n times,  W e l l b a l a n c e d and s t a b l e a e r o b i c b i o s t a b i l i z a t i o n e f f i c i e n c y  s t u d i e s were conducted  f o r 35 days f o r t h e s e two s e t s o f d i g e s t e r s .  The  h i g h suspended s o l i d s l e v e l s and t h e c o m b i n a t i o n o f a i r and m e c h a n i c a l mixi n g e f f e c t i v e l y c o n t r o l l e d foaming and o n l y a t t h e l o w e s t ( d e t e n t i o n time t e s t e d was  i t n e c e s s a r y t o add a c h e m i c a l a n t i f o a m agent.  CHAPTER 5  DISCUSSION OF RESULTS  5-1  Removal o f Oxygen Demanding M a t e r i a l (a)  BODc;  Removal - I t was o r i g i n a l l y i n t e n d e d t o u s e  BODrj  data  through-  out t h e s t u d y t o i n d i c a t e t h e e f f i c i e n c i e s o f t h e u n i t s t e s t e d . * F i g u r e 2 shows t h e BOD's o f " t h e mixed l i q u o r s " a n d s e t t l e d as a f u n c t i o n o f t h e s o l i d s d e t e n t i o n t i m e .  effluents  F i g u r e 3 shows t h e  p e r c e n t BOD,, removal as a f u n c t i o n o f t h e s o l i d s d e t e n t i o n t i m e .  i From t h e s e two f i g u r e s , i t c a n be seen t h a t t h e mixed l i q u o r BOD^ d a t a were v e r y / e r r a t i c j... v a r y i n g randomly from 2,040 t o 3,680 mg/1. Throughout t h e s t u d y , t h e mixed l i q u o r BOD^ c o n c e n t r a t i o n s d e t e r mined, u s i n g t h e s t a n d a r d BOD^ t e s t , i n d i c a t e d BOD^ removals ing  from 89.3 t o 93.7 p e r c e n t .  would be v e r y e n c o u r a g i n g ,  rang-  W h i l e such h i g h l e v e l s o f t r e a t m e n t  t h e r e l i a b i l i t y o f t h e BOD,, t e s t on a  w a s t e c o n t a i n i n g such h i g h heavy m e t a l c o n c e n t r a t i o n s i s v e r y questionable. T a b l e V I I I shows t y p i c a l BOD^ t e s t r e s u l t s f o r t h e mixed l i q u o r e f f l u e n t s from D i g e s t e r s A, B and C, as w e l l as one s e t o f BOD5 r e s u l t s f o r the leachate feed. the c a l c u l a t e d  BOD5  As t h e d i l u t i o n f a c t o r  o f each sample d e c r e a s e s .  cative of biological inhibition.  test  decreases,  This trend i s i n d i -  A t d i l u t i o n s g r e a t e r ; t h a n . 2 .times  t h e g r e a t e s t d i l u t i o n used f o r t h e d e t e r m i n a t i o n o f t h e mixed l i q u o r BOD,., t h e same i n h i b i t i o n may be observed results.  i n the l e a c h a t e feed  S i n c e m e t a l c o n c e n t r a t i o n s i n t h e mixed l i q u o r s were v e r y  c l o s e t o those i n t h e l e a c h a t e f e e d , i t i s h i g h l y p r o b a b l e t h a t  180  Settled  effluents i  T  r  160 140 „ 120 I O O  ^  E I  80  «  a  O  60  A v e r a g e for d e t e n t i o n times over i O d a y s = 5 8 . I mg/litre  CO  O  40 20 0  J  10  Mixed 3,800i 1  15  L  20  Solids  25  I I  1  O  1  40  45  —days  C  50  55  60  1  I.I  1  1.1  i  O  —  O  3,400  — —  3,200 3,000  —  2,600  —  o  2,800 O m  35  d e t e n t i o n time,0  liquor effluents  3,600  a>  _L  30  —  2,400 2,200 2,000  — * Values shown on graphs are averages over l a s t 14-21 days of each run (see Appendix B)  I  5  I  I  10  !  15  20  Solids  Figure 2  BOD  1 25  1 30  detention  1 35  1 40  0 45  1 50  o1 55  time,0 ~days c  OF M I X E D L I Q U O R S AND S E T T L E D vs SOLIDS DETENTION TIME  EFFLUENTS  1  60  41  100  tr  99.8 /CN  — —  Settled effluents  °  X /o'  99.6  •o  Q>  99.4  . C o cx X UJ  ^ 99.2 o > o  E 99.0 to  a o  Mixed I i quor • effluents  95r  (D  93  9I  • •  89  87 h  85  83 i.  10  20  30  40  1  1  50  60  70  Solids detention time, 0c - days  Figure  3  PERCENT  BOD  REMOVALS v s S O L I D S  DETENTION  TIME  80  TABLE V I I I ..-TYPICAL BOD TEST RESULTS FOR MIXED LIQUOR EFFLUENTS 5  FROM DIGESTERS A, B AND C, AND FOR LEACHATE FEED  Sample Source  ML o f Sample i n 300 ML BOD B o t t l e ( D i l u t i o n ; Factor in Brackets)  Dissolved Oxygen Depletion mg/1  BOD 5 mg/1 Accepted Average  Mixed L i q u o r E f f l u e n t from Digester A 0 = 10 days  0.10 "0.'20 0.30 0.30 0.50 0.70  (3,000:1) (1,500:1) (1,000:1) (1,000:1) ( 600:1) ( 429:1)  1.38 2.20 2.94 3.03 4.54 5.40  4,140 3,300 2,940 3,030 2,724 2,320  Mixed Liquor E f f l u e n t from Digester B 0 = 20 days  0.10 0.20 0.30 0.30 0.50 0.70  (3,000:1) (1,500:1) (1,000:1) (1,000:1) ( 600:1) ( 429:1)  1.47 2.60 3.50 3.60 4.73 5.82  4,410 3,900 3,500 3,600 2,838 2,494  Mixed L i q u o r E f f l u e n t from Digester C 0 = 30 days  0.10 0.20 0.30 0.30 0.50 0.70  (3,000:1) (1,500:1) (1,000:1) (1,000:1) ( 600:1) ( 429:1)  1.70 2.52 3.40 3.50 4.69 5.85  5,100 3,780 3,400 3,500 2,814 2,507  Leachate Feed  0.010 0.020 0.020 0.030 0.040 0.050  (30,000:1) (15,000:1) (15,000:1) (10,000:1) ( 7,500:1) ( 6,000:1)  0.97 2.23 2.28 3.52 3.72 3.96  29,100 33,450 35,100 35,200 27,900 23,600  c  c  c  1  2,998  J  3,667  J  i j  3,560  •-34,580  43  heavy m e t a l i n h i b i t i o n o f b i o l o g i c a l a c t i v i t y r e s u l t e d highly variable and  BOD5  test results.  i n t h e observed  S i n c e the m e t a l s c o n c e n t r a t i o n s  BOD5 o f t h e s e t t l e d s u p e r n a t a n t s were v e r y low,  t h a t the m e t a l s and a l a r g e p e r c e n t a g e o f the l i q u o r s , were bound t o t h e b i o l o g i c a l f l o e .  BOD5  i t was b e l i e v e d o f the  mixed  S i n c e no method c o u l d be  found t o remove t h e i n h i b i t i n g heavy m e t a l s w i t h o u t removing b i o l o g i c a l s o l i d s and hence of o b t a i n i n g r e l i a b l e  test results  BOD5  I n t h e s t a n d a r d BOD mg/l  d i l u t i o n offered the only feasible  BOD5,  5  f o r the mixed  method  liquors.  t e s t , a n oxygen d e p l e t i o n o f a t l e a s t 0.50  is required for s t a t i s t i c a l r e l i a b i l i t y .  B l a n k s o f t h e BOD  d i l u t i o n w a t e r used, g e n e r a l l y had oxygen d e p l e t i o n s between 0.15 and  0.30 mg/l a f t e r 5 days.  effluents  resulted  in highly  v e r y c l o s e t o 0.50 mg/l.  H i g h e r d i l u t i o n s o f the mixed variable  liquor  r e s u l t s w i t h oxygen d e p l e t i o n s  The h i g h v a r i a b i l i t y a t t h e s e h i g h e r  d i l u t i o n s may have been due t o s a m p l i n g v a r i a b i l i t y o r t o t h e oxygen d e p l e t i o n o f the BOD d i l u t i o n w a t e r , as o b s e r v e d i n b l a n k tests. tent,  Nevertheless, since higher d i l u t i o n s did not give consiss t a t i s t i c a l l y - r e l i a b l e r e s u l t s , and s i n c e t h e t r e n d  i n Table  V I I I  was n o t always o b s e r v e d w i t h a l l mixed l i q u o r  the BOD,, v a l u e s o b t a i n e d u s i n g d i l u t i o n f a c t o r s and  because o f t h e p r o b l e m i n o b t a i n i n g c o n s i s t e n t , BODcj  samples,  between 1,000:1  1,500:1 were a c c e p t e d f o r the mixed l i q u o r e f f l u e n t s .  reliable  indicated  However,  statistically-  r e s u l t s , w i t h o u t any e v i d e n c e o f b i o l o g i c a l  inhibi-  t i o n , i t was d e c i d e d t h a t COD r e s u l t s w o u l d be u s e d t o i n d i c a t e t h e e f f i c i e n c y o f the u n i t s The effluent  tested.  BOD^ o f t h e s e t t l e d e f f l u e n t s  was v e r y low;  BOD^'s r a n g i n g between 27.1 and 128.9 mg/l.  w i t h average Several  d i l u t i o n s o f each s e t t l e d e f f l u e n t were u s e d . i n t h e BOD^ t e s t s  44  and no evidence of i n h i b i t i o n was apparent i n the r e s u l t s . mixed l i q u o r  BOD5  I f the  r e s u l t s are accepted, the s e t t l i n g b i o l o g i c a l f l o e  removed an average of 97.5 percent of the mixed l i q u o r  BOD5.  The  a c t u a l percent removal by the s e t t l i n g b i o l o g i c a l f l o e i s probably even, higher.  O v e r a l l , better than 99.6 percent of the i n f l u e n t  was removed i n a l l s e t t l e d e f f l u e n t s .  BOD5  As shown i n Figure 3,  .two curves may.be drawn though the .percent BOD.,, removal data f o r settled effluents.  Curve 1 was the BOD^ data f o r s e t t l e d  from Digesters D, E and F.  effluents  During t h i s study, the mixed l i q u o r was  allowed to s e t t l e f o r about a h a l f an hour before s e t t l e d analysis.  effluent  samples were withdrawn f o r  BOD5  Curve 2 uses the  data f o r s e t t l e d e f f l u e n t s  from Digesters A, B and C. During t h i s  BOD5  study, the mixed l i q u o r was allowed to s e t t l e f o r at least an hour before s e t t l e d e f f l u e n t samples were withdrawn f o r BOD^ and COD analysis.  The extra time was required to obtain adequate volumes  of s e t t l e d e f f l u e n t  f o r both t e s t procedures; As can be seen i n  both Figures 2 and 3, the longer s e t t l i n g time r e s u l t e d overall  BOD5  removal and lower s e t t l e d e f f l u e n t  BOD5.  times over 20 days, the BOD^ of the s e t t l e d e f f l u e n t s  i n greater For detention averaged"58.1  mg/1. Because the s e t t l i n g b i o l o g i c a l f l o e was observed to remove a very large percentage of both the mixed l i q u o r  BOD5  and s o l i d s , it  was suspected that the very low s e t t l e d e f f l u e n t BOD,, might be due to an absence of micro-organisms i n the s e t t l e d e f f l u e n t .  For t h i s  reason,  effluent  BOD5  tests were p e r i o d i c a l l y conducted on s e t t l e d  samples using unseeded BOD d i l u t i o n water and BOD d i l u t i o n water seeded w i t h enough domestic sewage to cause an oxygen d e p l e t i o n o f  45  about 0.50 mg/l a f t e r 5 days. shown i n T a b l e I X .  T y p i c a l r e s u l t s from t h e s e t e s t s a r e  As o n l y t h e BOD^ o f s e t t l e d e f f l u e n t  from  D i g e s t e r A was s i g n i f i c a n t l y i n c r e a s e d by s e e d i n g t h e BOD d i l u t i o n water, the  o f a l l s e t t l e d e f f l u e n t s was d e t e r m i n e d u s i n g un-  BOD5  seeded BOD d i l u t i o n w a t e r . and  The v a l u e s r e p o r t e d i n f o l l o w i n g  f i g u r e s and I n F i g u r e s 2 and 3 a r e t h e r e s u l t s o f BOD  tables  tests  u s i n g unseeded BOD d i l u t i o n w a t e r .  TABLE I X COMPARISON OF BOD5 TEST RESULTS ON SETTLED EFFLUENTS USING UNSEEDED AND SEEDED BOD DILUTION WATER  Settled Effluent Source Digester Effluent BOD ,mg/l - using unseeded BOD d i l u tion water  0  A  =  0  B  =  0  C  =  0  D  =  0  E  =  F 0 = c 60 days  c 10 days  c 20 days  162.6  32.4  27.1  83.2  65.9  77.0  208.6  28.7  24.9  88.2  68.9  79.5  c 30 days  c 30 days  c 45 days  5  - using seeded BOD d i l u tion water  (b)  COD Removal - Because i t was o r i g i n a l l y i n t e n d e d t o use BOD5 d a t a t h r o u g h o u t t h e s t u d y t o i n d i c a t e o p e r a t i o n a l s t a b i l i t y and r e m o v a l e f f i c i e n c i e s , t h e COD o f t h e mixed l i q u o r s and s e t t l e d e f f l u e n t s from D i g e s t e r s D, E and F was checked o n l y a t t h e end o f t h e "extended a e r a t i o n "  e f f i c i e n c y study.  During  the " s h o r t e r d e t e n t i o n  46  t i m e " e f f i c i e n c y s t u d y , t h e COD o f b o t h t h e mixed l i q u o r s and settled effluents  from D i g e s t e r s A, B, and C was- m o n i t o r e d .  Figures  4 and 5 show t h e COD o f t h e mixed  l i q u o r s and s e t t l e d  respectively,  From these f i g u r e s , i t can be seen  during that study.  t h a t t h e COD r e s u l t s on mixed  l i q u o r e f f l u e n t s were more  than t h e COD r e s u l t s on s e t t l e d e f f l u e n t s . v e r y h i g h mixed  l i q u o r suspended  (20,500 t o 25,000 mg/1)  effluents,  variable  However, c o n s i d e r i n g t h e  s o l i d s l e v e l s i n these  units  and t h e r e s u l t i n g s a m p l i n g problems, t h e  o b s e r v e d v a r i a b i l i t y o f t h e mixed l i q u o r COD t e s t r e s u l t s i s n e i t h e r s u r p r i s i n g nor excessive. The mixed l i q u o r and s e t t l e d e f f l u e n t COD r e s u l t s o v e r t h e l a s t 14 t o 17 days were averaged.  COD t e s t s were a l s o conducted on the  mixed l i q u o r and s e t t l e d e f f l u e n t s  from D i g e s t e r s D, E, and F a t  the end o f t h e "extended a e r a t i o n " e f f i c i e n c y s t u d y . t h e COD o f t h e mixed l i q u o r s and s e t t l e d e f f l u e n t s the s o l i d s d e t e n t i o n t i m e . 48,250 mg/1.  F i g u r e 6 shows  as a f u n c t i o n o f  The COD o f t h e i n f l u e n t l e a c h a t e averaged  T h i s h i g h COD was s u b s t a n t i a l l y  b o t h t h e mixed l i q u o r s and s e t t l e d e f f l u e n t s creasing s o l i d s detention time.  reduced.  The COD o f  decreased w i t h i n -  The s e t t l i n g b i o l o g i c a l f l o e r e -  moved an average o f 96.4 p e r c e n t o f t h e mixed  l i q u o r COD. A t s o l i d s de-  t e n t i o n times;.less 'than' 20 days, however, s e t t l e d e f f l u e n t rose • very s h a r p l y .  COD  S e t t l e d e f f l u e n t COD a t s o l i d s d e t e n t i o n times  g r e a t e r t h a n 20 days was l e s s than 600 mg/1. F i g u r e 7 shows t h e p e r c e n t COD removal as a f u n c t i o n o f t h e s o l i d s detention time.  M i x e d l i q u o r COD removal i n c r e a s e d from 51.5 t o  75.7 p e r c e n t as t h e s o l i d s d e t e n t i o n time was i n c r e a s e d from 10 t o 60 d a y s .  S e t t l e d e f f l u e n t COD removal i n c r e a s e d s l i g h t l y from 96.8  47  1  25,000  23,000  21,000  E  19,000  Digester A 0 = IOdays c  o o  17,000  I 5,000 Digester C 0 = 30days C  13,000  Figure  Dotted lines indicate averages used in tables and on other graphs i _ J l _L 1 10 14 18 22 26 30 Time from start up - days 4  COD OF M I X E D L I Q U O R S DURING E F F I C I E N C Y STUDY  "SHORTER D E T E N T I O N  34 TIME'  48  2,400  2,000  1,600 Digester A 0 =IOdays  a)  c  E I  1,200  Q O O  800 Digester B ©c=20day  400  Digester C |0 =3Odays c  Dotted lines indicate averages used in tables and on other graphs 8  Figure  5  12 16 20 24 Time from start up - days  COD OF S E T T L E D E F F L U E N T S T I M E " E F F I C I E N C Y STUDY  DURING  28  32  "SHORTER D E T E N T I O N  36  Mixed liquor effluents 24,000 21,000 £  I8,000h-  10  15  20 Solids  Figure  6  25  30  35  40  d e t e ntion t i m e , ©  COD OF M I X E D AND DETENTION TIME  SETTLED  45 c  50  55  60  - days  EFFLUENTS v s SOLIDS  50  Figure  7  PERCENT  COD  REMOVALS  v s SOLIDS DETENTION  TIME  51  t o 99.2 p e r c e n t as the s o l i d s d e t e n t i o n t i m e i n c r e a s e d from 10 t o 60 days.  A t s o l i d s d e t e n t i o n t i m e g r e a t e r t h a n 20 days,  e f f l u e n t COD  removal was  g r e a t e r than 98.7  percent.  g e n e r a l l y o b s e r v e d t h a t the s e t t l i n g c h a r a c t e r i s t i c s  settled  I t has been of the b i o l o g i -  c a l f l o e a r e enhanced as the s o l i d s d e t e n t i o n t i m e i n c r e a s e s ( 4 ) . As the mean age o f the c e l l s i n each d i g e s t e r i n c r e a s e s , t h e m i c r o organisms  i n the b i o l o g i c a l f l o e produce more e x t r a c e l l u l a r  and e v e n t u a l l y become, " e n c a p s u l a t e d " i n a s l i m e l a y e r .  polymers  I t appears,  t h e r e f o r e , t h a t t h e p r e s e n c e o f t h e s e e x t r a c e l l u l a r polymers and the s l i m e l a y e r promote b o t h BOD suspended  and COD  r e m o v a l , when v e r y h i g h v o l a t i l e  s o l i d s levels are maintained.  I n the 10 day s o l i d s d e t e n -  t i o n t i m e u n i t , t h e s e t t l i n g b i o l o g i c a l f l o e removed 93.5 p e r c e n t of t h e mixed l i q u o r COD. the  s e t t l i n g b i o l o g i c a l f l o e removed 97.0 p e r c e n t o f the mixed  l i q u o r COD. COD  I n t h e 20 day s o l i d s d e t e n t i o n t i m e u n i t ,  A d e c r e a s e o f b e t t e r t h a n 800 mg/1  therefore resulted  i n settled  effluent  from i n c r e a s i n g t h e s o l i d s d e t e n t i o n t i m e  from 10 t o 20 days. Because v e r y h i g h v o l a t i l e suspended  s o l i d s c o n c e n t r a t i o n s were  m a i n t a i n e d i n a l l s i x d i g e s t e r s , a l o o k a t COD  removal as a f u n c t i o n  of the food t o m i c r o - o r g a n i s m r a t i o i s d e s i r a b l e b o t h f o r d e s i g n purposes and f o r a comparison o f the r e s u l t s w i t h t h o s e o b t a i n e d by other researchers. settled effluents The COD  F i g u r e 8 shows the COD  o f the mixed l i q u o r  and  as a f u n c t i o n o f t h e food t o m i c r o - o r g a n i s m r a t i o .  o f the mixed l i q u o r and s e t t l e d e f f l u e n t s  i n c r e a s e s as t h e  o r g a n i c l o a d i n g o r food t o m i c r o - o r g a n i s m r a t i o i n c r e a s e s .  As. t h e  food t o m i c r o - o r g a n i s m r a t i o i s i n c r e a s e d , t h e i n c r e m e n t a l r i s e i n s e t t l e d e f f l u e n t COD mixed l i q u o r COD  i n c r e a s e s , w h i l e the incremental i n c r e a s e i n  decreases.  These c o n t r a s t i n g c u r v e s p r o b a b l y  Settled effluents  0.02 0.04 0.06 0.08 0.10  0.12  Food / micro - organism  r a t i o , lb. B O D / l b . M L V S S / . d a y  0.14  0.16 0.18  0.20 0.22  0.24  5  Mixed liquor effluents  a)  £ I8,000H o> 1 5 , 0 0 0 E Q O O  0.02 0.04 0.06 0.08 0.10 0.12 0.i4 0.16 0.18 0.20 0.22 0.24 Food / m i c r o - o r g a n i s m r a t i o , lb. B 0 D / l b . M L V S S / d a y 5  Figure  8  COD OF M I X E D AND S E T T L E D MICRO-ORGANISM RATIO  EFFLUENTS  vs  FOOD  TO  53  i n d i c a t e t h a t the q u a l i t y o f the s e t t l e d e f f l u e n t i s a f f e c t e d more by the s l u d g e age ( 0  ). t h a n by the food t o m i c r o - o r g a n i s m r a t i o . c  F i g u r e 9 shows the p e r c e n t COD  removal f o r b o t h t h e mixed  liquor  and s e t t l e d e f f l u e n t s as a f u n c t i o n o f the o r g a n i c l o a d i n g . p e r c e n t COD ratio.  The'  removal d e c r e a s e s w i t h i n c r e a s i n g food t o m i c r o - o r g a n i s m  A t food t o m i c r o - o r g a n i s m r a t i o s l e s s than 6.12  lb.MLVSS/day, b e t t e r t h a n 59 p e r c e n t o f the i n f l u e n t COD  lb.BOD^/ i s removed  i n t h e mixed l i q u o r and b e t t e r t h a n 98 p e r c e n t o f t h e i n f l u e n t i s removed i n the s e t t l e d e f f l u e n t .  As t h e food t o m i c r o - o r g a n i s m  r a t i o i n c r e a s e s t o g r e a t e r t h a n 0.20  lb.B0D5/lb.MLVSS/day, the p e r -  c e n t COD  T h i s t r e n d was a l s o o b s e r v e d  removal d e c r e a s e s r a p i d l y .  by B o y l e and Ham  (15) and Cook and F o r e e ( 1 6 ) , even though  s t r e n g t h l a n d f i l l l e a c h a t e s were used i n t h e i r (c)  COD  lower  studies,  O r g a n i c Carbon Removal - T o t a l c a r b o n i n the raw l e a c h a t e averaged 15,400 mg/1, was  o f w h i c h 15,389 mg/1  i n o r g a n i c carbon.  was  o r g a n i c c a r b o n and 11  mg/1  The t o t a l c a r b o n and t o t a l i n o r g a n i c c a r b o n  i n t h e s e t t l e d e f f l u e n t s from D i g e s t e r s A, B, and C were d e t e r mined* as p a r t o f the s e t t l e d e f f l u e n t c h a r a c t e r i z a t i o n The r e s u l t s a r e summarized i n T a b l e X.  program.  From t h e s e r e s u l t s ,  i t is  apparent t h a t a l a r g e amount o f o r g a n i c m a t t e r was .removed/from, t h e s e t t l e d e f f l u e n t s of a l l u n i t s .  The removal o f o r g a n i c c a r b o n  i n c r e a s e d r a p i d l y as t h e s o l i d s d e t e n t i o n t i m e i n c r e a s e d from 10 t o 20 days.  Removal o f o r g a n i c c a r b o n was  g r e a t e r t h a n 98 p e r c e n t a t  s o l i d s detention times, ( 0  ) , g r e a t e r than 20 days, and thus c c o n f i r m e d the o b s e r v e d COD removal e f f i c i e n c i e s .  u s i n g a Beckman Model 915-A. T o t a l O r g a n i c Carbon A n a l y s e r .  54  100  99 o o o  98  (fl  97  U  o>  -•c o  Settled effluents  Q. K  96  £  o  95"  6 80r-  0)  o  o  75  70  65  60  55  50  Mixed liquor effluents J  45  0.03  0.06  0.09  0.12  Food to micro-organism Figure  9  PERCENT  0.15  0.18  0.21  0.24  ratio,lb.BODg/lb.MLVSS/day  COD REMOVALS v s FOOD TO M I C R O - O R G A N I S M R A T I O  55  TABLE X ORGANIC CARBON REMOVAL DURING "SHORTER DETENTION TIME" EFFICIENCY STUDY Raw L e a c h a t e D i g e s t e r A D i g e s t e r B D i g e s t e r C 30 10 20  S e t t l e d E f f l u e n t Source S o l i d D e t e n t i o n Time, days T o t a l Carbon, mg/1 T o t a l O r g a n i c Carbon, mg/1 . T o t a l ..Inorganic .Carbon,mg/1. Percent Organic Removal  15,400 15,389 .11  933 683 ,25.0  513 268 245  454 221 233  95.6  98.3  98.6  Carbon  N  T o t a l i n o r g a n i c c a r b o n i n t h e l e a c h a t e f e e d was o n l y 11 mg/1. T o t a l i n o r g a n i c c a r b o n i n t h e s e t t l e d e f f l u e n t s , however, v a r i e d between 230 and 250 mg/1. carbon,  This increase i n e f f l u e n t inorganic  r e s u l t s from t h e b i o d e g r a d a t i o n o f o r g a n i c c a r b o n t o c a r b o n  d i o x i d e and w a t e r .  As c a r b o n d i o x i d e was formed by t h e d e s t r u c t i o n  of organic m a t e r i a l s i n the leachate feed, a p o r t i o n o f the released gas d i s s o l v e d i n t h e mixed l i q u o r w a t e r and was c o n v e r t e d t o carbonate  and b i c a r b o n a t e m e t a l l i c s a l t s .  The h i g h pH m a i n t a i n e d  i n t h e s e u n i t s (8.5 - 8.8) would promote both t h e f o r m a t i o n o f i n s o l u b l e carbonates,  such as c a l c i u m c a r b o n a t e ,  gaseous c a r b o n d i o x i d e t o t h e atmosphere.  and t h e r e l e a s e o f  I t i s therefore l i k e l y  t h a t t h i s narrow range o f t o t a l i n o r g a n i c c a r b o n c o n c e n t r a t i o n s i s caused by s a t u r a t i o n o f t h e s e t t l e d e f f l u e n t s w i t h s o l u b l e and b i c a r b o n a t e m e t a l l i c 5-2  carbonate  salts.  V o l a t i l e Suspended S o l i d s The mixed l i q u o r t o t a l s o l i d s , t o t a l suspended s o l i d s , and v o l a t i l e  suspended s o l i d s were m o n i t o r e d  during the e f f i c i e n c y studies.  The r e s u l t s  o f t h o s e t e s t s a r e i l l u s t r a t e d i n A p p e n d i x A. reached steady s t a t e values w i t h i n  A l l 3 parameters  4 weeks o f s t a r t u p .  A l t h o u g h t h e sus-  pended s o l i d s l e v e l s m a i n t a i n e d i n a l l u n i t s were s e v e r a l mended l e v e l s f o r a c t i v a t e d and  t i m e s t h e recom-  s l u d g e systems, t h e mixed l i q u o r s  settled  well  t h e s e t t l i n g b i o l o g i c a l f l o e removed a l a r g e p e r c e n t a g e o f t h e mixed  l i q u o r COD and BOD . 5  mg/l  generally  .'"to 25,000 mg/l.  volatile.  S t e a d y s t a t e MLSS c o n c e n t r a t i o n s ranged f r o m 14,500 An a v e r a g e 64 p e r c e n t o f t h e s e suspended s o l i d s were  The mixed l i q u o r s s e t t l e d q u i c k l y  t o produce s l u d g e s w i t h t o t a l  suspended s o l i d s c o n c e n t r a t i o n s around 45,000 mg/l.  S e t t l i n g was e s s e n -  t i a l l y complete a f t e r 2 h o u r s . F i g u r e 10 shows t h e s t e a d y s t a t e mixed l i q u o r v o l a t i l e suspended s o l i d s c o n c e n t r a t i o n s as a f u n c t i o n  o f the s o l i d s d e t e n t i o n time.  The s t e a d y  s t a t e MLVSS c o n c e n t r a t i o n d e c r e a s e s as t h e s o l i d s d e t e n t i o n t i m e i n c r e a s e s . As  previously  discussed, increasing  t h e s o l i d s d e t e n t i o n t i m e from 10 t o 20  days i n c r e a s e d t h e removal o f mixed l i q u o r COD by t h e s e t t l i n g b i o l o g i c a l f l o e , from 93.5 t o 97.0 p e r c e n t .  A t s o l i d s d e t e n t i o n times g r e a t e r t h a n 20  days, t h e s e t t l i n g b i o l o g i c a l f l o e c o n s i s t e n t l y 97.5  removed between 96.5 and  p e r c e n t o f t h e mixed l i q u o r COD even though t h e MLVSS c o n c e n t r a t i o n s  s t e a d i l y decreased.  This fact supports the previously  drawn c o n c l u s i o n  t h a t s o l i d s d e t e n t i o n t i m e o r s l u d g e age i s v e r y i m p o r t a n t i n d e t e r m i n i n g s e t t l e d e f f l u e n t c o m p o s i t i o n , and t h a t i n c r e a s i n g  the s o l i d s d e t e n t i o n time  from 10 t o 20 days s i g n i f i c a n t l y improves t h e q u a l i t y o f t h e s e t t l e d effluent. The that highly  v e r y low s e t t l e d e f f l u e n t s t a b i l i z e d microbial  o r g a n i c c a r b o n , COD, and BOD5  masses e x i s t e d  i n a l l units.  indicate  Microscopic  e x a m i n a t i o n o f t h e mixed l i q u o r s c o n f i r m e d t h e presence o f v a r i o u s forms o f bacteria,  p r o t o z o a , f u n g i and r o t i f e r s  i n a l l units.  F u n g a l growth was  16,000  14,000  £ \  12,000}-  E  I; 10,000  +c Q> U  o  o  8,000  Ul  in  > s  6,000  4,000h  2,000h  10  0  15  20  25 30 35 40 Solids detention t i m e , 0 - d a y s  45  50  c  Figure  10  STEADY S T A T E M I X E D L I Q U O R V O L A T I L E DETENTION TIME  SUSPENDED  S O L I D S CONCENTRATIONS  v s SOLIDS  58  v e r y l i m i t e d and  thus d i d not  a d v e r s e l y a f f e c t the  settling  characteristics  of the b i o l o g i c a l f l o e s . . A l a r g e number of free-swimming c i l i a t e s were observed.stalked  S i n c e free-swimming c i l i a t e s use  p r o t o z o a , and  much more energy t h a n f i x e d  or  t h e r e f o r e r e q u i r e much more food, t h e s e m i c r o s c o p i c  e x a m i n a t i o n s c o n f i r m the o b s e r v e d h i g h mixed l i q u o r BOD^  and  COD  concentra-  tions. 5-3  'Metal Removal •and'Di'stribut i o n The  a t the end  metal d i s t r i b u t i o n w i t h i n  of both sets of e f f i c i e n c y s t u d i e s .  m e t a l removal by the acclimatization-metal  f l o e were of s p e c i a l They can  removal s t u d y .  Any  examined d u r i n g  the  d i s t r i b u t i o n of m e t a l s w i t h i n  the m e t a l removal e f f i c i e n c y o f the  the  biological  i n t e r e s t for three reasons:  need f o r a d d i t i o n a l be  t r e a t m e n t of the  o f t o x i c i t y can  be  settled effluents  c o n c e n t r a t e d , the p o s s i b i l i t y  assessed.  Acclimatization-Metal  Removal Study - To  removal c a p a c i t y o f the c o n c e n t r a t i o n i n the  s t u d y the  long-term metal  s e t t l i n g b i o l o g i c a l f l o e , the  s e t t l e d e f f l u e n t s was  b i o l o g i c a l s o l i d s were removed, h y d r a u l i c as the b a s i s of t h i s s t u d y . centration  t o remove  identified.  Depending on where the heavy m e t a l s a r e  (a)  overall  disposal.  heavy m e t a l s can (3)  The  the  examined  p r o v i d e i n f o r m a t i o n heeded t o d e c i d e .on a s a t i s f a c t o r y method  of sludge (2)  In a d d i t i o n ,  s e t t l i n g b i o l o g i c a l f l o e was  mixed l i q u o r e f f l u e n t and  (1)  the mixed l i q u o r e f f l u e n t was  monitored.  t i m e from s t a r t . u p .  from t h e  function  of the  t h a t the  t o t a l s o l i d s c o n c e n t r a t i o n i n the  Since  d e t e n t i o n t i m e was  F i g u r e 11 shows the  o f the s e t t l e d e f f l u e n t s  total solids no used  t o t a l s o l i d s con-  three digesters,  From F i g u r e 11  as  i t i s evident  settled effluents  in-  a  8,000h O Digester D',hydraulic detention time <y 7,000  n  <^  —  H  —  I I —  F  f'  1  t  8  45days  — I I —  — n —  — II —  =  60  — I I —  — I I —  — II —  =  90  —"—>  — "  —  E 6,000 I c  Z  5 000JS  5 F i g u r e 11  10  15  20  25 30 35 40 Time from start up — days  45  50  EFFLUENT TOTAL SOLIDS CONCENTRATION DURING ACCLIMATIZATION-METAL REMOVAL STUDY  55 VO  60  c r e a s e s as t h e h y d r a u l i c d e t e n t i o n t i m e decreases.  Similarly, i t  was found t h a t t h e BOD^ o f t h e s e t t l e d e f f l u e n t s i n c r e a s e d as t h e h y d r a u l i c d e t e n t i o n time d e c r e a s e d ( s e e Appendix B) even though t h e MLVSS c o n c e n t r a t i o n s time.  increased w i t h decreasing:hydraulic  A f t e r 30 days, t h e t o t a l s o l i d s c o n c e n t r a t i o n s  e f f l u e n t s began t o l e v e l o f f .  detention  i n the s e t t l e d  A f t e r 56 days o f o p e r a t i o n ,  biological  s o l i d s had accumulated i n t h e d i g e s t e r s t o t h e e x t e n t t h a t i t was d i f f i c u l t t o o b t a i n t h e r e q u i r e d volumes o f c l e a r s u p e r n a t a n t D i g e s t e r s D' and E'", even a f t e r one h o u r o f s e t t l i n g .  from  At this  time  samples o f t h e mixed l i q u o r s and s e t t l e d e f f l u e n t s from each d i g e s t e r were c o l l e c t e d f o r m e t a l a n a l y s i s .  The mixed l i q u o r samples were  "wet-ash" d i g e s t e d , f o l l o w i n g t h e recommended EPA p r o c e d u r e ( 1 7 ) . However, when t h e d i g e s t e d samples were f i l t e r e d p r i o r t o m e t a l a n a l y s i s , c o n s i d e r a b l e p a r t i c u l a t e m a t t e r was o b s e r v e d on t h e . f i l t e r s . To check t h e e f f i c i e n c y o f t h e d i g e s t i o n p r o c e s s and t o check t h e a c c u r a c y  f o r meta-1 r e c o v e r y ,  o f t h e subsequent m e t a l a n a l y s i s , a  m a t e r i a l b a l a n c e was d e v e l o p e d , u s i n g t h e r e s u l t s o f t h e t o t a l s o l i d s c o n c e n t r a t i o n t e s t s on t h e s e t t l e d e f f l u e n t s . t h i s m a t e r i a l balance,  i t was assumed t h a t :  the net  metal  metal  influent  concentration  concentration  metal  in  i n day 56  concentration  feed  The  leachate  In developing  settled effluent  ^weighted a v e r a g e t o t a l solids concentration throughout study  X'.  ' t o t a l s o l i d s concentrat i o n i n day 56 ^settled effluent  c o n c e n t r a t i o n o f each m e t a l i o n e x p e c t e d i n each mixed  was t h e n d e t e r m i n e d by m u l t i p l y i n g t h e n e t i n f l u e n t m e t a l  liquor concentra-  t i o n t o each d i g e s t e r by 56 days and d i v i d i n g by t h e r e s p e c t i v e  61  d i g e s t e r s h y d r a u l i c d e t e n t i o n time.  The r a t i o o f t h e  mixed l i q u o r m e t a l c o n c e n t r a t i o n t o t h a t d e t e r m i n e d b a l a n c e was  analysed  by t h i s mass  then used t o check the m e t a l a n a l y s i s and m e t a l  recovery  u s i n g t h e "wet-ash" d i g e s t i o n p r o c e s s . ,- The l a r g e number o f s u b s t a n c e s  i n l e a c h a t e and t h e i r p o s s i b l y  h i g h c o n c e n t r a t i o n s , can produce i n t e r f e r e n c e s r e s u l t i n g i n e r r o r s i n the d e t e r m i n a t i o n o f i n f l u e n t m e t a l c o n c e n t r a t i o n s . many i n s o l u b l e m e t a l - s l u d g e  When t h e  complexes w h i c h might be formed, a r e  c o n s i d e r e d , the p o s s i b i l i t y o f f u l l m e t a l r e c o v e r y by any d i g e s t i o n process  i s very s l i g h t .  sludge  I n l i g h t o f t h e s e problems  t h e s i m p l i c i t y o f the m a t e r i a l b a l a n c e a p p l i e d , i t was  and  decided that  t h e m e t a l d i s t r i b u t i o n r e s u l t s would be c o n s i d e r e d a c c e p t a b l e i f a p p l i c a t i o n o f the m a t e r i a l b a l a n c e a c c o u n t e d 110 p e r c e n t o f t h e i n f l u e n t m e t a l .  f o r between 90  To meet t h i s c r i t e r i o n ,  and i t was  found n e c e s s a r y t o use n i t r o u s o x i d e - a c e t y l e n e flames f o r aluminum, c a l c i u m , i r o n , and manganese a n a l y s e s .  The a i r - a c e t y l e n e flame,  n o r m a l l y employed i n a t o m i c a b s o r p t i o n a n a l y s i s f o r m e t a l s , used f o r a l l o t h e r m e t a l s .  was  These p r o c e d u r a l m o d i f i c a t i o n s f o r  m e t a l a n a l y s i s were s i m i l a r l y employed i n t h e m e t a l a n a l y s e s formed a t t h e end o f each e f f i c i e n c y  per-  study.  The r e s u l t s o f t h e m e t a l a n a l y s e s and t h e a p p l i c a t i o n o f the simple m a t e r i a l balance, along w i t h i n f l u e n t c o n c e n t r a t i o n s , are shown i n T a b l e X I .  A p p l y i n g the a c c e p t a b i l i t y c r i t e r i o n p r e v i o u s l y  mentioned, i t can be seen from the l a s t column i n T a b l e X I t h a t none o f the averages f o r any m e t a l l i e v e r y f a r o u t s i d e t h e a c c e p t a b l e range.  Cadmium, chromium, i r o n , and magnesium r e c o v e r y were, how-  e v e r , r a t h e r low.  When t h e d i g e s t e r s were t a k e n a p a r t a t t h e end  of  the s t u d y , l a r g e clumps o f m e t a l were found s e t t l e d below t h e c o a r s e -  TABLE X I METAL DISTRIBUTION AT END OF ACCLIMATIZATION-METAL REMOVAL STUDY  Metal  Digester  Influent Concentration mg/1  Mixed Liquor Concentration mg/1  Settled Effluent Concentration mg/1  Percent o f Metal, Associated With ' Sludge S o l i d s  Concentration Expected i n Mixed Liquor (From; M a t e r i a l Balance) mg/1  Percent o f Influent Metal Accounted For  75.0 58.0 40.3  0.4 0.0 0.0  99.47 100 100  74.5 56.2 37.4  100.6 103.2 107.6  60.2  Aluminum  Er  F'  0.430  Cadmium ET  F^  •  0.02 0.01 0.00  95.35 97.22 100  2,140 1,670 1,140  194 130 127  90.93 92.21 88.86  2,224 1,720 1,138  96.5 97.2 100.1  2.43 1.85 .1.30  0.07 0.05 0.04  97.11 97.29 96.92  2.81 2.12 1.42  86.4 87.1 91.7  99.12 98.75 97.67  1,557 1,168 775  83.6 80.6 98.7  0.430 0.360 0.240  0.517 0.395 0.267  83.7 91.3 89.9  1,924  Calcium D" E' F* Chromium  2.31.  D' Ef F^1,260  Iron D'' '  f: F*  1,300 940 765  11.4 11.7 17.8  /continued..  TABLE X I c o n t i n u e d  Metal  Digester  Influent Concentration mg/l 1.79  Lead  2.02 1.58 1.05  D"  E: F  >  378  Magnesium D* E? F* Manganese  D'" E*  276 240 179  46.0 50.4 38.8 ' 26.0  F'  0.44 0.39 0.29  Percent o f Metal Associated With Sludge S o l i d s 78.22 75.32 72.38  Concentration Expected i n Mixed Liquor (From M a t e r i a l Balance) mg/l i.84 i.42 0.98  0.667 0.495 0.350  D" E? F* -  1,610  Potassium  1,043 880 678  Dr  F*  D' E" F"  227  252 200 142  Percent o f Influent Metal Accounted For 108.0 110.0 106.0  159.0 115.4 87.4  42.39 51.92 51.17  33i.4 277.2 195.1  88.3 89.5 93.1  1.3 0.7 0.6  97.48 98.20 97.69  56.1 42.5 28.3  90.1 91.5 91.8  0.090 0.090 0.055  86.51 81.82 84.29  1,020 862 662  2.21 2.05 2.06  0.61:-  Nickel  Zinc  Mixed Liquor Concentrat ion mg/l  Settled Effluent Concentration mg/l  7.6 5.5 7.7  96.19 97.25 94.57  6.674 6.506 0.351 l i 111 938 698 275.8 208.2 137.7  99.1 98.1 99.7 96.6 96.2 98.0 91.6 96.1 103.0  bubble d i f f u s e r s .  T e s t s w i t h a magnet i n d i c a t e d  t h a t t h o s e clumps  were p r i m a r i l y  i r o n , but t h e y p r o b a b l y a l s o c o n t a i n e d o t h e r m e t a l  precipitates.  T h i s o b s e r v a t i o n c o u l d account f o r many o f t h e low  mixed  l i q u o r m e t a l c o n c e n t r a t i o n s d e t e r m i n e d i n t h i s phase o f the  study. E x a m i n a t i o n o f T a b l e X I i n d i c a t e s t h a t most o f t h e m e t a l s checked a r e a s s o c i a t e d w i t h t h e s l u d g e s o l i d s . precipitated,  These m e t a l s may  be  adsorbed t o t h e b i o l o g i c a l f l o e , o r d i s s o l v e d i n t h e  l i q u i d f r a c t i o n o f t h e s l u d g e , but t h e y would be removed from the f i n a l c l a r i f i e r w i t h the s e t t l e d " sludge.  B e t t e r t h a n 95 p e r c e n t o f  the mixed l i q u o r aluminum, cadmium, chromium, i r o n , manganese, and z i n c were removed by t h e s e t t l i n g b i o l o g i c a l f l o e s . 95 p e r c e n t o f the mixed  Between 70  and  l i q u o r c a l c i u m , l e a d , and n i c k e l were a s s o c i  a t e d w i t h the s l u d g e s o l i d s . Between 42 and 52 p e r c e n t o f t h e mixed moved by s e t t l i n g .  l i q u o r magnesium was  re-  I t i s l i k e l y t h a t the h i g h pH m a i n t a i n e d i n t h e  t h r e e d i g e s t e r s caused a p o r t i o n o f t h e i n f l u e n t magnesium s a l t s t o p r e c i p i t a t e and s u b s e q u e n t l y t o s e t t l e out o f t h e mixed l i q u o r w i t h the s e t t l i n g b i o l o g i c a l f l o e s . L e s s t h a n 3 p e r c e n t o f t h e mixed l i q u o r p o t a s s i u m was the s e t t l i n g b i o l o g i c a l f l o e s . b i o l o g i c a l t r e a t m e n t system.  removed by  P o t a s s i u m passes r i g h t t h r o u g h t h e The mixed l i q u o r p o t a s s i u m  remained  v i r t u a l l y c o m p l e t e l y d i s s o l v e d and a s s o c i a t e d w i t h the l i q u i d t i o n o f t h e mixed  liquor.  frac-  S i m i l a r r e s u l t s would be e x p e c t e d f o r  sodium. From the f i f t h column i n T a b l e X I i t can a l s o be seen t h a t t h e c o n c e n t r a t i o n o f any p a r t i c u l a r m e t a l i n the s e t t l e d e f f l u e n t a l l y decreases w i t h i n c r e a s i n g h y d r a u l i c d e t e n t i o n time.  gener-  This trend  65  however, i s due t o the d e c r e a s i n g mixed l i q u o r m e t a l c o n c e n t r a t i o n s . The MLVSS c o n c e n t r a t i o n s i n d i g e s t e r s D E a n d i m a t e l y 11,800, 10,900 and 7,600 mg/l r e s p e c t i v e l y .  F w e r e  approx-  From t h e s i x t h  column o f T a b l e X I i t i s e v i d e n t t h a t i n c r e a s i n g MLVSS c o n c e n t r a t i o n s d i d n o t i n c r e a s e t h e m e t a l removal by t h e s e t t l i n g b i o l o g i c a l  floes  and s i m i l a r l y , t h a t i n c r e a s i n g h y d r a u l i c d e t e n t i o n time d i d n o t n i f i c a n t l y ..improve m e t a l removal by t h e s e t t l i n g b i o l o g i c a l S o l i d s d e t e n t i o n times i n a l l u n i t s were e q u a l a s no 7  s o l i d s were removed d u r i n g t h i s s t u d y .  sig-  floes.  biological  These r e s u l t s a r e , t h e r e f o r e ,  c o n s i s t e n t w i t h t h e r e s u l t s observed i n the removal o f oxygen demanding material. From t h e f o u r t h column o f T a b l e X I i t may s e t t l i n g r e s u l t e d i n mixed  be n o t e d t h a t  daily  l i q u o r m e t a l c o n c e n t r a t i o n s i n D i g e s t e r D'  exceeding those i n the l e a c h a t e feed. s e t t l i n g b i o l o g i c a l f l o e s remained  S i n c e m e t a l removal by t h e .  c o n s i s t e n t l y h i g h i n a l l of the  u n i t s t e s t e d , no l i m i t c o u l d be s e t on t h e m e t a l removal c a p a c i t y o f the s e t t l i n g b i o l o g i c a l f l o e .  I t i s c l e a r from t h e s e r e s u l t s , how-  e v e r , t h a t a s e t t l i n g , a c t i v a t e d s l u d g e f l o e may  e f f e c t i v e l y be used  as a p h y s i c a l t r e a t m e n t method f o r good removal o f v e r y h i g h c o n c e n t r a t i o n s o f a number o f m e t a l s .  The  f a c t t h a t most heavy m e t a l s a r e  c o n c e n t r a t e d i n the s l u d g e means, however, t h a t a g r e a t d e a l o f c a r e must be t a k e n i n d i s p o s i n g o f t h a t s l u d g e , (b)  E f f i c i e n c y S t u d i e s - The c o n c e n t r a t i o n s o f m e t a l s i n the mixed  liquor  and s e t t l e d e f f l u e n t s from a l l t h r e e d i g e s t e r s were d e t e r m i n e d a t t h e end o f each s e t o f e f f i c i e n c y s t u d i e s . T a b l e X I I shows t h e r e s u l t s o f t h o s e m e t a l a n a l y s e s a l o n g w i t h the i n f l u e n t l e a c h a t e m e t a l c o n c e n t rations.  From t h e f o u r t h column i t can be seen t h a t mixed  liquor  TABLE X I I METAL DISTRIBUTION AT END OF EFFICIENCY STUDIES  Metal  Digester  Percent of Settled M e t a l Removed Mixed Liquor Effluent Influent By S e t t l i n g Concentration Concentration Concentration me/1 B i o l o g i c a l Floe mg/1 mg/1 41.8  Aluminum  41.00 •40.60 36.60 38.40 38.40 37.60  A "B C D E F Cadmium  1.02 0.64 0.31 0.31 0.00 0.00  0.39 0.384 0.388 0.352 0.374 0.369 0.334  A B C D E F  0.012 0.009 0.005 0.010 0.008 0.005  97.51 98.42 99.15 99.19 100 100  96.88 97.68 98.58 97.33 97.83 98.50  1,394  Calcium  1,394 1,392 1,200 1,630 1,640 1,160  A B C D E F Chromium  28.0 20.6 20.8 84.0 63.8 75.0  97.99 98.52 98.27 94.85 96.11 93.53  1.9. A B C D E F  1.87 1.85 1.78 1.85 1.78 1.38.  0.14 0.06 0.06 0.06 0.04 0.04  92.51 96.76 96.63 96.76 97.75 97.10  13.6 2.9 1.45 1.45 0.50 0.10  98.61 99.70 99.84 99.84 99.94 99.99'  960  Iron A B C D E F  980 973 887 888 847 782  /continued..  67  TABLE X I I c o n t i n u e d  Metal  Digester  Lead A B C D ,E . F Magnesium  ...  Settled Influent Mixed Liquor Effluent Concentration Concentration Concentration me/1mg/l mg/l  Percent of M e t a l Removed ' By S e t t l i n g B i o l o g i c a l Floe  •1.44 1.39 1.22 1.10 1.35 -1.12 1.06  0.28 0.20 0.16 0.22 0.14 0.11  79.85 83.61 85.45 83.70 .87.. 50 89.62  306 289 244 278 244 193  139 91 85 112 96 98  54.57 68.51 65.16 59.71 60.65 49.22  40.50 36.10 32.50 38.60 34.30 27.70  1.73 0.68 0.45 0.45 0.18 0.11  95.73 98.12 98.62 98.83 99.47 99.60  0.640 0.640 0.640 0.620 0.620 0.540  0.190 0.180 0.120. 0.150 0.150 0.080  70.31 71.87 81.25 75.80 75.80 85.19  828 792 710 744 716 762  690 715 660 680 615 570  16.67 9.72 7.58 8.60 14.11 15.18  1.81 1.42 0.60 0.86 0.25 0.17  99.08 99.23 99.63 99.60 99.86 99.88  310 A B C D E F  Manganese  41.0 A B C D E F 0.65  Nickel A B C D E F Potassium  1,'060 A B C D E F  Zinc A B C D E F  •  223 197.3 183.4 160.3 215.4 179.1 137.1  68  calcium concentrations at the end of the "extended a e r a t i o n " e f f i c i e n c y study exceeded those i n the leachate feed.  Those calcium  concentrations, however, are l e s s than those i n the leachate feed used i n the a c c l i m a t i z a t i o n - m e t a l removal study (1,924 mg/1) and therefore, i n d i c a t e that calcium concentrations i n the mixed l i q u o r were dropping to approach those i n the new leachate feed. A l l other mixed l i q u o r metal concentrations were l e s s than or equal to those i n the leachate feed.  I n the highest loaded u n i t s i n each  study, the mixed l i q u o r metal concentrations were very close to those i n the leachate feed.  As the loading rate decreases i n each  set, the concentration of metal i n the mixed l i q u o r s decreases, • as would be expected.  Since the same u n i t s were used i n each study,  the metal concentrations i n each "shorter detention time" d i g e s t e r more c l o s e l y approach the metal concentrations i n the leachate: feed, than do those i n the same digesters during the "extended a e r a t i o n " e f f i c i e n c y study. Table X I I I summarizes the d i g e s t e r operating parameters and the r e s u l t i n g metal removal e f f i c i e n c i e s .  As i n the a c c l i m a t i z a t i o n -  metal removal study, the s e t t l i n g b i o l o g i c a l f l o e s removed b e t t e r than 95 percent of the mixed l i q u o r aluminum, cadmium, chromium, i r o n , manganese-and z i n c .  Mixed l i q u o r calcium and lead removal  e f f i c i e n c i e s increased s l i g h t l y i n most d i g e s t e r s during the e f f i c iency s t u d i e s , while average mixed l i q u o r n i c k e l removal decreased slightly. Between 49 and 68 percent of the mixed l i q u o r magnesium was r e moved w i t h the s e t t l i n g b i o l o g i c a l s o l i d s .  I t i s very l i k e l y that  the s l i g h t l y higher pH's maintained during the e f f i c i e n c y studies account f o r t h i s s l i g h t improvement i n magnesium removal over that  TABLE X I I I SUMMARY OF METAL REMOVAL BY SETTLING BIOLOGICAL FLOC DURING EFFICIENCY STUDIES Digester S o l i d s D e t e n t i o n Time, Days  A 10  B 20  C 30  24,250 16,100  22,650 15,100  20,800 13,500  19,550 10,590  97.51  98.42  99.15  99.19  Cadmium  96.88  97.68  98.58  97.33  97.83  98.50  Calcium  97.99  98.52  98.27  94.85  96.11  93.53  Chromium  92.51  96.76  96.63 .  96.76  97.75  97.10  Iron  98.61  99.70  99.84  99.84  99.94  99.99  Lead  79.85  83,61  85.45  83.70  87.50  89.62  Magnesium  54.57  68.51  65.16  59.71  60,65  49.22  Manganese  95.73  98.12  98.62  98.83  99.47  99.60  Nickel  70.31  71.87  81.25  75.80  75.80  85.19  Potassium  16.67  9.72  7.58  8.60  14.11  15.18  Zinc  99.08  99.23  99.63  99.60  99.86  99.88  S t e a d y - S t a t e MLSS C o n c e n t r a t i o n , m g / l S t e a d y - S t a t e MLVSS C o n c e n t r a t i o n , m g / 1 Percent of Mixed Liquor Metal C o n c e n t r a t i o n s Removed by S e t t l i n g Biological Floe: Aluminum  . D 30  E 45  F 60  20,300 11,880  14,300 8,100  100  100  70  o b s e r v e d i n t h e a c c l i m a t i z a t i o n - m e t a l removal s t u d y . T a b l e X I I I a l s o shows t h a t o n l y between 7.6 and 16.7 p e r c e n t o f t h e mixed l i q u o r p o t a s s i u m was a s s o c i a t e d  w i t h the sludge s o l i d s .  W h i l e p o t a s s i u m removal d u r i n g t h e e f f i c i e n c y s t u d i e s  increased  o v e r t h a t observed i n t h e a c c l i m a t i z a t i o n - m e t a l removal s t u d y , t h e results s t i l l  i n d i c a t e t h a t p o t a s s i u m passes r i g h t t h r o u g h t h e  a c t i v a t e d s l u d g e , t r e a t m e n t p r o c e s s and t h a t i t remains a l m o s t comp l e t e l y a s s o c i a t e d w i t h t h e l i q u i d f r a c t i o n o f t h e mixed  liquor.  From t h e e f f i c i e n c y s t u d y r e s u l t s and t h o s e o b s e r v e d a t t h e end o f t h e a c c l i m a t i z a t i o n - m e t a l removal s t u d y , i t may be c o n c l u d e d t h a t t h e o r d e r o f mixed l i q u o r m e t a l r e m o v a l by t h e s e t t l i n g  biological  f l o e , w i t h average p e r c e n t removal i n b r a c k e t s , i s as f o l l o w s : aluminum (99.3) and i r o n (99.3) > cadmium (97.7) (81.7)  > z i n c (98.4)  > chromium (96.5)  > n i c k e l (79.2)  > manganese  > c a l c i u m (94.6)  > magnesium (55.9)  (98.2)  > lead  > potassium (8.7).  The p e r c e n t removal f o r a l l m e t a l s i s g e n e r a l l y c o n s i d e r a b l y h i g h e r t h a t t h a t o b s e r v e d by o t h e r r e s e a r c h e r s (9,11,12,13). pH and v o l a t i l e suspended  The h i g h e r  s o l i d s l e v e l s used i n t h i s s t u d y c o u l d  account f o r t h i s i n c r e a s e d m e t a l removal by t h e s e t t l i n g  biological  f l o e , a l t h o u g h i t may be o b s e r v e d from T a b l e X I I I t h a t d e c r e a s i n g MLVSS c o n c e n t r a t i o n s from 16,100 t o 8,100 mg/l d i d n o t a d v e r s e l y a f f e c t t h e mixed l i q u o r m e t a l removal by t h e s e t t l i n g floe.  Indeed, i t : may  be  biological  o b s e r v e d t h a t i n most c a s e s , t h e p e r c e n t  m e t a l removal i n D i g e s t e r A r e p r e s e n t s t h e l o w e s t v a l u e i n any u n i t tested.  This trend again suggests that i n c r e a s i n g the s o l i d s deten-  t i o n t i m e from 10 t o 20 days, o r higher, s i g n i f i c a n t l y improves t h e s e t t l i n g c h a r a c t e r i s t i c s of the b i o l o g i c a l s o l i d s , with higher  BOD5,  subsequent  COD, o r g a n i c c a r b o n , and m e t a l removal by t h e s e t t l i n g  71  biological floe.  5-4  Settled Effluent The  Characterization  leachate feed to a l l u n i t s  d u r i n g the  e f f i c i e n c y s t u d y was  dark g r e e n i n c o l o u r , w i t h a f a i r l y s t r o n g o b n o x i o u s odour. ents from a l l the u n i t s  t e s t e d was  l e a c h a t e was  settled effluents  e f f i c i e n c y study d i g e s t e r s are  t e r i z e d i n T a b l e XIV. c o n c e n t r a t i o n s and  e f f l u e n t , the  (a)  a l m o s t c o m p l e t e l y removed.  A l s o shown i n T a b l e XIV  the proposed B.C.  s p e c i f i c discharges (1). t e s t was  are  the  - As  oxygen demanding m a t e r i a l  f r o m the  leachate  previously  d i s c u s s e d , the removal  s e t t l e d e f f l u e n t s was  the COD  o f the  For  Solids  - The  generally the  to  BOD5  o f the  mg/1 mg/1.  settled  and It is  effluents  s a t i s f y r e g u l a t o r y agency r e q u i r e m e n t s , i f adequate s e t t l i n g  t i m e i s a l l o w e d i n the (b)  averaged 58.1  remained l e s s t h a n 625  e v i d e n t from t h e s e r e s u l t s t h a t the may  signifi-  s o l i d s d e t e n t i o n times g r e a t e r t h a n  of the s e t t l e d e f f l u e n t s  settled effluent  of  excellent.  q u a l i t y o f the s e t t l e d e f f l u e n t w i t h r e s p e c t  oxygen demanding m a t e r i a l . 20 days, the BOD^  for  sample.  I n c r e a s i n g the s o l i d s d e t e n t i o n t i m e from 10 t o 20 days, improved the  charac-  shown f o r a s p e c i f i c s e t t l e d  performed due. t o a s h o r t a g e of the  Oxygen Demanding M a t e r i a l  cantly  The  further  influent  The  P o l l u t i o n C o n t r o l Board g u i d e l i n e s  Where no numbers a r e  not  efflu-  l i g h t brown t o y e l l o w i n c o l o u r .  obnoxious odour o f the raw from the  Settled  very  final  clarifier.  t o t a l s o l i d s c o n c e n t r a t i o n s i n the  decreased w i t h i n c r e a s i n g  total solids results  indicate  settled  effluents  s o l i d s d e t e n t i o n time.  that increasing  the  Again,  solids  d e t e n t i o n t i m e from 10 t o 20 days o r h i g h e r s i g n i f i c a n t l y improves the e f f l u e n t  quality.  A l t h o u g h the  sample volumes o b t a i n e d were  TABLE XIV CHARACTERISTICS OF LEACHATE FEED AND SETTLED EFFLUENTS FROM AEROBIC BIOSTABILIZATION EFFICIENCY STUDIES ; Characteristics ( a l l , except p H , i n mg/1)  Leachate Feed  Digester A  5  Digester B  Digester C  Digester D  Digester . E  Digester F  BOD COD T o t a l Carbon T o t a l O r g a n i c Carbon  36,000 48,000 15,400 15,389  128.9 1,547 933 683  32.4 594.2 513 268  27.1". 456.4 454 221  90.8 610.4  65.7 427.8  -  -  -  Total Solids  26,600  6,050  5,200  4,980  5,160  4,870  4,450  pH Acidity Alkalinity  5.02 5,640 7,640  8.80 0.0 1,320  8.73 0.0 1,210  8.50 0.0 1,080  Aluminum Arsenic Cadmium Calcium Chromium Iron Lead Magnesium Manganese Nickel P o t a s s ium Selenium Zinc  '41.8 3.62 0.39 1,394 1.9, 960 1.44 310 41.0 0.65.:; 1,060 0.450 223  1.02  0.64  0.31  0.012 28.0 0.14 13.6 0.28 119 1.73 0.19:' 690  0.009 20.6 0.06 2.9 0.20 91 0.68 0.180 715  0.005 20.8 0.06 1.45 0.16 85 0.45 0.12t 660  1.81  1.42  0.60  5  -  -  -  -  -  -  -  8.80 0.0 857 0.31 0.265 0.010 84.0 0.06 1.45 0.22 112 0.45 0.15C680 0.036 0.86  -  8.74 0.0 728 0.00 0.26 0.008 63.8 0.04 , 0.50 0.14 96 0.18 0.15 615  -  0.25  74.9 385.5  8.60 0.0 542 0.00 0.26 O.OOf 75.0 0.04 0.10 0.11 98 0.11 0.08: 570  -  0.17  P.C.B» U-> Requirements 45  6.5-8.5  0.5 0.05 0.005 0.10 0.3 0.05 150 0.05 0.3  0.5  /continued...  TABLE XIV  continued...  Characteristics ( a l l , except p H , i n mg/1)  Leachate Feed  Digester A  Total Nitrogen*  1,770 1,390  29.4  T o t a l Phosphoruss*  ' '868 ,362  12.0  Digester B 23.9  5.46  Digester C  Digester D  Digester E  Digester F  P.CB. Requirements  70.4  39.4  22.9  15.0  32.4  25.8  20.3  4.5  13.4  3.11  * n u t r i e n t a d d i t i o n s t o t h e l e a c h a t e f e e d were d e c r e a s e d d u r i n g t h e " s h o r t e r d e t e n t i o n t i m e " study.  efficiency  74  not s u f f i c i e n t t o a c c u r a t e l y d e t e r m i n e t h e suspended s o l i d s t r a t i o n s i n the s e t t l e d e f f l u e n t s ,  concen-  t e s t s showed t h a t suspended s o l i d s  c o n c e n t r a t i o n s i n a l l s e t t l e d e f f l u e n t s were low ( l e s s t h a n 100 m g / l ) , b u t may, i n many c a s e s , exceed P o l l u t i o n C o n t r o l Board r e quirements.  F o r t h i s r e a s o n some form o f e f f l u e n t p o l i s h i n g  may be  necessary. (c)  pH, A l k a l i n i t y and A c i d i t y - pH was checked d a i l y . i l l u s t r a t e d i n A p p e n d i x C.  Because pH f l u c t u a t e d  The r e s u l t s a r e considerably, the  v a l u e s shown i n T a b l e X I V a r e a p p r o x i m a t e a v e r a g e s o v e r t h e l a s t 15 t o 20 days o f each s t u d y . The pH o f t h e l e a c h a t e f e e d was 5.02, p r o b a b l y p r i m a r i l y t h e r e s u l t o f o r g a n i c a c i d s produced i n t h e l a n d f i l l . d i g e s t e r u n i t s was m a i n t a i n e d  The pH i n a l l  a t g r e a t e r t h a n 8.5.  These r e l a t i v e l y  h i g h pH v a l u e s u n d o u b t e d l y a i d e d i n t h e p r e c i p i t a t i o n o f many m e t a l s such as i r o n , c a l c i u m and magnesium. The a c i d i t y o f t h e l e a c h a t e f e e d was c o m p l e t e l y d e s t r o y e d , i n d i c a t i n g t h a t t h e o r g a n i c a c i d s were n e u t r a l i z e d .  The a l k a l i n i t y  o f t h e l e a c h a t e f e e d was a l s o s u b s t a n t i a l l y reduced. of the s e t t l e d e f f l u e n t s time.  decreases  The a l k a l i n i t y  with increasing solids  detention  T h i s t r e n d i s p r o b a b l y caused by t h e a d s o r p t i o n o f p r e c i p i -  t a t e d metal carbonates  by t h e b i o l o g i c a l f l o e ( c a r b o n a t e  form o f a l k a l i n i t y ) and by t h e p r o d u c t i o n o f o r g a n i c a c i d digester.  i s one i n each  As t h e s o l i d s d e t e n t i o n time i n c r e a s e s , more o f t h e  organic matter  i n t h e l e a c h a t e f e e d s h o u l d be u t i l i z e d and thus t h e  a l k a l i n i t y of the s e t t l e d e f f l u e n t s  should decrease w i t h i n c r e a s i n g  s o l i d s d e t e n t i o n time, (d)  Metals  - The metal c o n c e n t r a t i o n s i n t h e l e a c h a t e f e e d a r e s i g n i f i -  75  c a n t l y reduced, but t h e s e t t l e d e f f l u e n t s s t i l l  do n o t s a t i s f y t h e  e f f l u e n t r e q u i r e m e n t s s e t by t h e P o l l u t i o n C o n t r o l Board.  Metal  concentrations i n the s e t t l e d e f f l u e n t g e n e r a l l y decrease w i t h i n c r e a s i n g s o l i d s d e t e n t i o n t i m e , as do t h e mixed t r a t i o n s a t t h e end o f each s t u d y .  l i q u o r metal  concen-  A s o l i d s d e t e n t i o n time o f o n l y  10 days i s r e q u i r e d t o s a t i s f y t h e P.C.B. e f f l u e n t r e q u i r e m e n t s f o r • -magnesium and n i c k e l , w h i l e - s o l i d s d e t e n t i o n times o f a t l e a s t 30 days a r e r e q u i r e d t o s a t i s f y t h o s e r e q u i r e m e n t s f o r cadmium, chromium and z i n c . and mixed in for  Even w i t h t h e s l u d g e age as l o n g as 60 days,  l i q u o r metal c o n c e n t r a t i o n s s i g n i f i c a n t l y l e s s than those  t h e l e a c h a t e f e e d , t h e P o l l u t i o n C o n t r o l Board e f f l u e n t s t a n d a r d s a r s e n i c , l e a d and manganese cannot be met.  For t h i s reason,  some form o f e f f l u e n t p o l i s h i n g s h o u l d be d e v e l o p e d .  Carbon a d s o r p -  t i o n o r i o n exchange columns would appear t o be most p r o m i s i n g f o r m e t a l removal i n t h e s e low c o n c e n t r a t i o n r a n g e s , (e)  N u t r i e n t s - U s i n g t h e lower l e a c h a t e f e e d c o n c e n t r a t i o n s i n T a b l e XIV as a g u i d e l i n e , i t would appear t h a t a s o l i d s d e t e n t i o n time o f at  l e a s t 30 days i s n e c e s s a r y t o o b t a i n s e t t l e d e f f l u e n t n i t r o g e n  and phosphorus  c o n c e n t r a t i o n s l e s s t h a n t h e maximums a l l o w e d by  regulating agencies. u n i t s was s t i l l  However, s i n c e t h e mixed  f a i r l y h i g h , micro-organisms  were n o t g i v e n enough time t o use a l l  liquor  BOD5  in all  i n those d i g e s t e r s  the nutrients  supplied.  Reducing n u t r i e n t a d d i t i o n s d u r i n g the " s h o r t e r d e t e n t i o n time" e f f i c i e n c y s t u d y improved t h e q u a l i t y o f t h e s e t t l e d e f f l u e n t s w i t h respect to nutrient concentrations, without adversely a f f e c t i n g the b i o l o g i c a l e f f i c i e n c y o f those d i g e s t e r s .  I t may be c o n c l u d e d ,  t h e r e f o r e , t h a t n u t r i e n t a d d i t i o n s t o t h e l e a c h a t e f e e d were e x c e s s i v e and t h a t t h o s e a d d i t i o n s might be s u b s t a n t i a l l y r e d u c e d ,  thus  76  l o w e r i n g the c o s t o f l e a c h a t e  treatment.  Cook and Foree (16) have shown t h a t i t i s p o s s i b l e t o a e r o b i c a l l y t r e a t a medium-strength l a n d f i l l o f 100:3.95:0.18 w i t h o u t any stabilization efficiency.  l e a c h a t e w i t h a B0D5:N:P r a t i o  s i g n i f i c a n t reduction i n aerobic bio-,  Without n u t r i e n t a d d i t i o n s , the  leachate  feed used i n these e f f i c i e n c y s t u d i e s would have had a B0D5:N:P ...ratio o f 100,: 2.,02:0.55. feed may  S i n c e much o f the ammonia i n t h e  have been s t r i p p e d out o f the h i g h pH mixed l i q u o r s  b u b b l i n g , t h r o u g h t h e d i g e s t e r s , i t may n i t r o g e n i n some form t o t h e ' l e a c h a t e  have been n e c e s s a r y feed.  phosphorusv r e q u i r e m e n t s "nutrient-deficient"  5-5  to  add  in satisfactory  n i t r o g e n and phosphorus . l e v e l s i n t h e s e t t l e d e f f l u e n t s , s i g n i f i c a n t r e d u c t i o n i n treatment  by a i r  However, s i n c e r e d u c e d  n u t r i e n t a d d i t i o n s t o the l e a c h a t e feed might r e s u l t  any  leachate  without  e f f i c i e n c y , the n i t r o g e n  and  f o r a e r o b i c b i o s t a b i l i z a t i o n of such  w a s t e s s h o u l d be more t h o r o u g h l y i n v e s t i g a t e d .  K i n e t i c Parameters and E f f i c i e n c y P r e d i c t i o n s The  results  o f t h e "extended a e r a t i o n " e f f i c i e n c y s t u d y were used  t o d e t e r m i n e t h e k i n e t i c parameters a s s o c i a t e d w i t h a e r o b i c b i o s t a b i l i z a - • t i o n of t h i s high-strength l a n d f i l l  leachate.  These k i n e t i c parameters  were then used t o p r e d i c t t h e minimum s o l i d s d e t e n t i o n t i m e f o r l e a c h a t e treatment  (see A p p e n d i x E) and  " s a f e " s o l i d s d e t e n t i o n times were  chosen f o r t h e " s h o r t e r d e t e n t i o n t i m e " e f f i c i e n c y s t u d y . parameters thus d e t e r m i n e d a r e summarized i n T a b l e XV. t h e k i n e t i c - p a r a m e t e r s d e t e r m i n e d by Cook and F o r e e (16) o f a medium-strength l a n d f i l l treatment  l e a c h a t e , and  p l a n t d e s i g n (4) a r e a l s o  The  For  then  kinetic  comparison,  f o r the  treatment  t h o s e commonly used i n sewage  presented.  77  TABLE XV KINETIC PARAMETERS DETERMINED FROM "EXTENDED AERATION" EFFICIENCY STUDY DATA Range o f V a l u e s N o r m a l l y Employed i n Sewage T r e a t ment P l a n t D e s i g n (4)  Kinetic Parameter  V a l u e Determined For a MediumStrength L a n d f i l l Leachate (16) 0.4 mgVSS/mgCOD • ,  0.332 mgVSS/mgBOD  0.05 d a y  0.0025 d a y "  Y  0.40-0.67 mgVSS/mgB0D  b  0.05-0.09 d a y  K  3.0-6.0 mgBOD /mgVSS/day 0.60  K  5  - 1  5  s  - 1  5  5  mgCOD/mgVSS/day 0.75  175 mgCOD/1  20-200 mgB0D /l  V a l u e Determined From T h i s "Extended A e r a t i o n " E f f i c i e n c y S t u d y Data  1  mgBOD /mgVSS/day 5  21,375 mgB0D /l 5  S i n c e t h e BOD^ d a t a from t h e "extended a e r a t i o n " e f f i c i e n c y showed a g r e a t d e a l o f s c a t t e r , when p l o t t e d t o determine  study  these k i n e t i c  para-  m e t e r s , c o n s i d e r a b l e p e r s o n a l judgment was i n v o l v e d i n o b t a i n i n g t h e e s t i mates shown i n T a b l e XV.  B i o l o g i c a l i n h i b i t i o n made a c c u r a t e d e t e r m i n a t i o n  o f mixed l i q u o r BOD,, i m p o s s i b l e .  However, t h a t i n h i b i t i o n was n o t always  e v i d e n t i n t h e "extended a e r a t i o n " e f f i c i e n c y s t u d y BOD^ t e s t s .  Attempts  t o a n a l y s e t h e COD data from t h e "extended a e r a t i o n " e f f i c i e n c y s t u d y  proved  even more u n s a t i s f a c t o r y , as even g r e a t e r s c a t t e r p r e v e n t e d any r e l i a b l e e s t i m a t i o n o f t h e s e k i n e t i c parameters. parameter v a l u e s a p p e a r i n g  Thus, a l t h o u g h t h e a c c u r a c y o f t h e  i n T a b l e XV i s somewhat q u e s t i o n a b l e , an a n a l y s i s  o f t h o s e v a l u e s s h o u l d g i v e some i n s i g h t i n t o what i s happening i n t h e digesters. The  low growth y i e l d c o e f f i c i e n t , Y, i n d i c a t e s t h a t o n l y 0.332 mg  o f b i o l o g i c a l suspended s o l i d s were produced f o r each mg o f BOD^ d e s t r o y e d . T h i s low v a l u e may be t h e r e s u l t o f u n d e r e s t i m a t i n g t h e mixed l i q u o r BOD^ o r o f b i o l o g i c a l i n h i b i t i o n caused by t h e h i g h mixed l i q u o r , h e a v y m e t a l concentrations.  78  The  endogenous r e s p i r a t i o n o r a u t o - o x i d a t i o n c o e f f i c i e n t , b, i s  a l s o v e r y low.  The micro-organisms  i n t h e mixed l i q u o r e n t e r t h e endogenous  growth phase o n l y when t h e food c o n c e n t r a t i o n i n t h e mixed l i q u o r i s t o o low t o m a i n t a i n l o g a r i t h m i c growth.  D u r i n g endogenous r e s p i r a t i o n ,  u t i l i z e t h e p r o t o p l a s m o f s i m i l a r micro-organisms growth.  cells  t o o b t a i n energy f o r  The BOD,, o f a l l mixed l i q u o r s i n t h e "extended a e r a t i o n " e f f i c i e n c y  - study,, exceeded .2,000 mg/l and,,there f o r e , .there was no need f o r a u t p - o x i d a t i o n t o occur.  T h i s f a c t i s r e f l e c t e d by t h e v e r y low v a l u e o f b.  The maximum r a t e o f s u b s t r a t e u t i l i z a t i o n p e r u n i t w e i g h t organisms, plants.  K, i s lower than n o r m a l l y observed  i n domestic  sewage  o f microtreatment  The low v a l u e o f K i n d i c a t e s b i o l o g i c a l i n h i b i t i o n , p r o b a b l y due  t o t h e v e r y h i g h heavy m e t a l c o n c e n t r a t i o n s i n t h e mixed l i q u o r . K  g  i n d i c a t e s t h e s u b s t r a t e (BOD5) c o n c e n t r a t i o n when t h e r a t e o f  s u b s t r a t e u t i l i z a t i o n per u n i t weight maximum, K.  K  s  has been observed  o f micro-organisms  i s one h a l f t h e  t o v a r y w i t h t h e type o f waste.  As t h e  c o m p l e x i t y o f t h e waste i n c r e a s e s o r as t h e b i o d e g r a d a b i l i t y o f t h e w a s t e decreases, K  g  increases.  Here t h e v e r y h i g h v a l u e a g a i n i n d i c a t e s b i o l o g i -  c a l i n h i b i t i o n , and suggests  t h a t v e r y h i g h MLVSS c o n c e n t r a t i o n s a r e neces-  s a r y t o g e t r e a s o n a b l e r e d u c t i o n s i n t h e i n f l u e n t l e a c h a t e B0D__. Although  these e s t i m a t e s o f t h e k i n e t i c parameters may n o t be v e r y  a c c u r a t e , t h e y may be used t o p r e d i c t t h e b e h a v i o u r s o l i d s d e t e n t i o n time i s decreased. ( 2 ) , as p r e s e n t e d 11,900 mg/l.  o f t h e d i g e s t e r s as t h e  Use o f t h e s e parameters i n e q u a t i o n  i n s e c t i o n 3-2, p r e d i c t s a maximum MLVSS c o n c e n t r a t i o n o f  The f a c t t h a t a l l MLVSS c o n c e n t r a t i o n s i n t h e " s h o r t e r d e t e n -  t i o n t i m e " e f f i c i e n c y s t u d y exceeded t h i s p r e d i c t e d maximum would  indicate  t h a t t h e p r e d i c t e d v a l u e o f t h e growth y i e l d c o e f f i c i e n t i s low.  Neverthe-  l e s s , t h e k i n e t i c parameter e s t i m a t e s were then used i n e q u a t i o n ( 1 ) , t o p r e d i c t t h e mixed l i q u o r  B0D . s  A comparison o f the e x p e r i m e n t a l l y  determined  79  and p r e d i c t e d mixed l i q u o r higher estimates  BOD5  values  i s presented  i n T a b l e XVI.  Using  o f the growth y i e l d c o e f f i c i e n t would r e s u l t i n lower  d i c t e d mixed l i q u o r  BOD5  pre-  concentrations.  TABLE X V I MIXED LIQUOR B0D  Digester  5  DURING "SHORTER DETENTION TIME" EFFICIENCY STUDY E x p e r i m e n t a l l y Determined Mixed L i q u o r BOD5 7o Removal  Solids Detention Time,Days  P r e d i c t e d Values Mixed L i q u o r BOD5 7o Removal  A  10  2,805 mg/1  92.15  17,700 mg/1  50.5  B  20  3,676 mg/1  89.72  6,250 mg/1  82.5  C  30  3,582 mg/1  89.98  3,790 mg/1  89.3  The  p r e d i c t e d mixed l i q u o r  e x p e r i m e n t a l l y determined v a l u e .  BOD5  i n D i g e s t e r C i s v e r y c l o s e t o the  However, t h i s would be e x p e c t e d as d a t a  from a s i m i l a r 30 day s o l i d s d e t e n t i o n t i m e u n i t was used t o e s t i m a t e k i n e t i c parameters.  the  As p r e v i o u s l y d i s c u s s e d , heavy m e t a l i n h i b i t i o n p r e -  v e n t e d any a c c u r a t e d e t e r m i n a t i o n o f mixed l i q u o r BOD^. v a l u e s i n T a b l e XVI, however, i n d i c a t e  The p r e d i c t e d  the g e n e r a l t r e n d w h i c h s h o u l d have  been observed and the':.value-;.o.f^increasing the s o l i d s d e t e n t i o n time from 10 t o 20 /days o r higher.:  Trends s i m i l a r t b a t h a t - i n d i c a t e d  v a l u e s o f mixed l i q u o r  BOD5  s e t t l e d effluent B0D  5  b y the p r e d i c t e d  were o b s e r v e d i n the mixed l i q u o r COD and  and COD r e s u l t s .  CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS  6-1  Conclusions  (1)  A e r o b i c b i o s t a b i l i z a t i o n i s an e f f e c t i v e means o f s t a b i l i z i n g a high-strength l a n d f i l l leachate. v o l a t i l e suspended  U s i n g v e r y h i g h mixed  liquor  s o l i d s c o n c e n t r a t i o n s (8,000 t o 16,000 mg/1),  s t a b l e d i g e s t e r o p e r a t i o n c a n be m a i n t a i n e d a t s o l i d s d e t e n t i o n times as s h o r t as 10 days, p r o v i d e d food t o m i c r o - o r g a n i s m  ratios  a r e k e p t below 0.22 l b . B O D ^ l b . V S S / d a y . (2)  F o r i n f l u e n t COD c o n c e n t r a t i o n s between 44,000 and 52,000 mg/1, s e t t l e d e f f l u e n t COD removal  i n c r e a s e s s l i g h t l y from 96.7 t o 99.1  p e r c e n t as t h e s o l i d s d e t e n t i o n time i s i n c r e a s e d from 10 t o 60 days. 75.7  Mixed l i q u o r COD removal s i m i l a r l y i n c r e a s e s from 51.5 t o p e r c e n t as t h e food t o t h e m i c r o - o r g a n i s m r a t i o d e c r e a s e s  from 0.22 t o 0.06 (3)  F o r i n f l u e n t B0D  5  settled effluent  lb.B0D /lb.VSS/day. 5  c o n c e n t r a t i o n s between 32,000 and 38,000 mg/1, BOD^ removal g r e a t e r t h a n 99.6 p e r c e n t i s p o s s i b l e  a t s o l i d s d e t e n t i o n times g r e a t e r t h a n 10 days. (4)  F o r i n f l u e n t o r g a n i c c a r b o n c o n c e n t r a t i o n s between 15,250 and 15,550 mg/1, s e t t l e d e f f l u e n t  removals o f g r e a t e r t h a n 95 p e r c e n t  may be e x p e c t e d when food t o m i c r o - o r g a n i s m r a t i o s a r e m a i n t a i n e d l e s s t h a n 0.22 (5)  lb.B0D /lb.VSS/day. 5  The s e t t l i n g b i o l o g i c a l f l o e removes g r e a t e r t h a n 97 p e r c e n t o f t h e mixed l i q u o r  BOD5  and g r e a t e r t h a n 96 p e r c e n t o f t h e mixed  COD when h i g h v o l a t i l e suspended  liquor  s o l i d s c o n c e n t r a t i o n s (8,000 t o  16,000 mg/1) a r e m a i n t a i n e d i n t h e mixed  liquor.  81  (6)  I n c r e a s i n g t h e s o l i d s d e t e n t i o n time from 10 t o 20 days i n c r e a s e s the removal o f mixed l i q u o r COD from 93.5  t o 97.0  by the s e t t l i n g b i o l o g i c a l  p e r c e n t and s i g n i f i c a n t l y improves the  floe  quality  o f t h e s e t t l e d e f f l u e n t s w i t h r e s p e c t t o oxygen demanding m a t e r i a l . " A t s o l i d s d e t e n t i o n times g r e a t e r t h a n 20 days, B0D  5  averaged 58.1  (7) -Most o f t h e .metals biological floe.  settled  effluent  mg/l. i n t h e mixed l i q u o r were removed by t h e s e t t l i n g pH's  g r e a t e r t h a n 8.5 were m a i n t a i n e d  ina l l  u n i t s t e s t e d w i t h o u t any pH a d j u s t m e n t t o t h e l e a c h a t e f e e d . h i g h pH v a l u e s u n d o u b t e d l y  The  a i d e d m e t a l removal, as d i d t h e h i g h  MLVSS c o n c e n t r a t i o n s . B e t t e r t h a n 95 p e r c e n t o f the mixed l i q u o r aluminum, cadmium, chromium, i r o n , manganese and z i n c were removed by t h e s e t t l i n g biological floe.  B e t t e r than 90 p e r c e n t o f t h e mixed l i q u o r  cium and around 80 p e r c e n t o f b o t h t h e mixed l i q u o r l e a d and were a s s o c i a t e d w i t h t h e s l u d g e s o l i d s .  On t h e average,  calnickel  however,  o n l y 56 p e r c e n t o f t h e magnesium i n t h e mixed l i q u o r was  removed  by s e t t l i n g , and b e t t e r t h a n 90 p e r c e n t o f mixed l i q u o r  potassium  remained i n the s e t t l e d  effluents.  Even though t h e l e a c h a t e used i n t h i s s t u d y c o n t a i n e d v e r y h i g h c o n c e n t r a t i o n s o f v a r i o u s heavy m e t a l s , t h e r e was instability attributable  to these metals.  no i n d i c a t i o n  of  This i n d i c a t e s that,  f o r a h i g h - s t r e n g t h waste, c o n t a i n i n g r e l a t i v e l y h i g h  concentra-  t i o n s o f m e t a l s , a b i o l o g i c a l community can be a c c l i m a t e d  and  r e s u l t i n a s t a b l e system. S i n c e a l l o f t h e heavy m e t a l s a r e not c o m p l e t e l y i n the sludge s o l i d s , a d d i t i o n a l  treatment  concentrated  i s n e c e s s a r y t o remove  82  the m e t a l r e m a i n i n g  i n the s e t t l e d e f f l u e n t s .  a h i g h p e r c e n t a g e o f the metals  In addition,  i s ; a s s o c i a t e d w i t h the s l u d g e , t h e  l a t t e r s h o u l d be d i s p o s e d o f i n a manner such t h a t the p o t e n t i a l o f t h e s e metals (8)  because  pollution  i s minimized.  A n a l y s i s o f k i n e t i c parameters i n d i c a t e s t h a t the heavy m e t a l s i n the mixed l i q u o r s s e r i o u s l y  i n h i b i t e d the b i o l o g i c a l e f f i c i e n c y o f  -the u n i t s t e s t e d - a n d .suggests t h a t v e r y h i g h .mixed l i q u o r suspended s o l i d s c o n c e n t r a t i o n s may be n e c e s s a r y a b l e mixed l i q u o r  BOD5  volatile  to o b t a i n reason-  reductions.  (9) . The v e r y h i g h mixed l i q u o r m e t a l c o n c e n t r a t i o n s i n h i b i t e d b i o l o g i c a l a c t i v i t y i n the  BOD5  t e s t s t o the e x t e n t t h a t i t was i m p o s s i b l e  t o o b t a i n a c c u r a t e mixed l i q u o r  BOD5  results.  For t h i s r e a s o n , COD  removal and/or o r g a n i c c a r b o n removal s h o u l d be u s e d t o c h a r a c t e r i z e the e f f i c i e n c y o f b i o l o g i c a l treatment  p r o c e s s e s , when the  feed  t o such systems c o n t a i n s h i g h c o n c e n t r a t i o n s o f i n h i b i t i n g heavy metals. (10)  BOD^iNiP r a t i o s o f 100:5:1 o r b e t t e r were used i n t h e s t u d i e s and proved s a t i s f a c t o r y . settled effluents  indicated,  Analyses  efficiency  o f the n u t r i e n t s i n the  however, t h a t the n i t r o g e n and  phos-  phorus, a d d i t i o n s t o the l e a c h a t e f e e d were e x c e s s i v e and might be s u b s t a n t i a l l y reduced without a d v e r s e l y a f f e c t i n g  treatment  efficiency. 6-2  Recommendations f o r F u t u r e  Studies  S i n c e v e r y l i t t l e work has been done on the use o f a e r o b i c .bios t a b i l i z a t i o n as a method o f t r e a t i n g l a n d f i l l l e a c h a t e , a d d i t i o n a l are necessary. (1)  studies  These s h o u l d i n c l u d e :  An i n v e s t i g a t i o n  i n t o methods o f d i s p o s i n g o f the s l u d g e , s o as t o  m i n i m i z e t h e p o l l u t i o n p o t e n t i a l o f t h e heavy m e t a l s . (2)  An i n v e s t i g a t i o n o f a d d i t i o n a l t r e a t m e n t methods polishing,  for effluent  t o reduce t h e heavy m e t a l c o n c e n t r a t i o n s and r e s i d u a l  oxygen demanding m a t e r i a l i n t h e s e t t l e d e f f l u e n t s . (3)  An i n v e s t i g a t i o n o f t h e n i t r o g e n and phosphorus., a e r o b i c micro-organisms  (4)  requirements o f  i n the d i g e s t i o n process.  An i n v e s t i g a t i o n o f t h e e f f i c i e n c y o f a e r o b i c b i o s t a b i l i z a t i o n o f a h i g h - s t r e n g t h l a n d f i l l l e a c h a t e when much o f t h e heavy m e t a l s a r e removed by p r i o r c h e m i c a l t r e a t m e n t o f t h e l e a c h a t e .  CHAPTER 7  REFERENCES 1.  Cameron, R.D., "The E f f e c t s o f S o l i d Waste L a n d f i l l L e a c h a t e s on R e c e i v i n g Water", paper p r e s e n t e d a t the 1975 B r i t i s h Columbia Water and Waste A s s o c i a t i o n C o n f e r e n c e , H a r r i s o n Hot S p r i n g s , B.C., 14 pages, A p r i l 1975.  2.  Hughes, G., Tremblay, J . , Anger, H., D'Cruz, J . , " P o l l u t i o n o f Ground- w a t e r Due t o M u n i c i p a l Dumps", T e c h n i c a l " B u l l e t i n No. 42, I n l a n d Waters Branch, Department o f Energy, Mines and R e s o u r c e s , Ottawa, Canada, 98 pages, 1971.  3.  Z a n o n i , A.E., "Groundwater P o l l u t i o n from S a n i t a r y L a n d f i l l s and R e f u s e Dump Grounds - A C r i t i c a l Review", Department o f N a t u r a l Resources7 Madison, W i s c o n s i n , 43 pages, 1971.  4.  M e t c a l f , L. and Eddy, H., Wastewater E n g i n e e r i n g : C o l l e c t i o n , . ment, D i s p o s a l , M c G r a w - H i l l Book Company, 1972.  Treat-  5.  Lawrence, A.W. and M c C a r t y , P.L., "A U n i f i e d B a s i s f o r B i o l o g i c a l Treatment D e s i g n and O p e r a t i o n " , J o u r n a l o f the S a n i t a r y E n g i n e e r i n g D i v i s i o n , P r o c e e d i n g s o f the A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s , • page 757, 1970.  6.  Sawyer, C.N., B a c t e r i a N u t r i t i o n and S y n t h e s i s , B i o l o g i c a l Treatment o f Sewage and I n d u s t r i a l Waste, Volume 1, R e i n h o l d P u b l i s h i n g Company, New York, 1956.  7.  B a r t h , E.F., E t t i n g e r , M.B., S a l o t t o , B.V. and McDermott, G.N., "Summary R e p o r t on the E f f e c t s o f Heavy M e t a l s on the B i o l o g i c a l Treatment P r o c e s s e s " , J o u r n a l Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 37, page 86, J a n u a r y 1965.  8.  Water P o l l u t i o n A b s t r a c t s , e d i t e d by Department o f the Environment, London, E n g l a n d , Volume 44, page 456, O c t o b e r 1971.  9.  N e u f e l d , R.D. and Hermann, E.R., "Heavy M e t a l Removal by A c c l i m a t e d A c t i v a t e d S l u d g e " , J o u r n a l Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . ' 47, page 310, F e b r u a r y 1975.  10.  " I n t e r a c t i o n o f Heavy M e t a l s and B i o l o g i c a l Sewage Treatment P r o c e s s e s " , U.S. Department o f H e a l t h , E d u c a t i o n and W e l f a r e , P u b l i c H e a l t h , S e r v i c e P u b l i c a t i o n Number 999-WP-22, 1965.  11.  M o u l t o n , E. and Shumate, K., "The P h y s i c a l and B i o l o g i c a l E f f e c t s o f Copper on A e r o b i c B i o l o g i c a l Waste Treatment P r o c e s s e s " , Proceedings o f the 18th I n d u s t r i a l Waste C o n f e r e n c e , Purdue U n i v e r s i t y , E x t . S e r v . 115,.West L a f a y e t t e , I n d i a n a , page 602, 1963.  85  12.  J a c k s o n , S. and Brown, V., " E f f e c t o f T o x i c Wastes on Treatment P r o c e s s e s and W a t e r c o u r s e s " , Water P o l l u t i o n C o n t r o l , London, page 292, June 1970.  13.  Cheng, M.H., P a t t e r s o n , J.W„ and M i n e a r , R.A., "Heavy M e t a l s Uptake by A c t i v a t e d Sludge", J o u r n a l Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 47, page 362, F e b r u a r y 1975.  14.  Poorman, B.L. " T r e a t a b i l i t y o f L e a c h a t e from a S a n i t a r y L a n d f i l l by A n a e r o b i c D i g e s t i o n " , M a s t e r o f A p p l i e d S c i e n c e T h e s i s , Department o f C i v i l E n g i n e e r i n g , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 75 pages, A p r i l 1974.  15.  B o y l e , W.C. and Ham, R.K., " B i o l o g i c a l T r e a t a b i l i t y o f L a n d f i l l L e a c h a t e " , J o u r n a l Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 46, page 860, May 1974.  16.  Cook, E.N. and Foree, E.G., " A e r o b i c B i o s t a b i l i z a t i o n o f S a n i t a r y L a n d f i l l L e a c h a t e " , J o u r n a l Water P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 46, page 380, F e b r u a r y 1974.  17.  "Methods f o r C h e m i c a l A n a l y s i s o f Water and Wastes', U.S. E n v i r o n m e n t a l P r o t e c t i o n Agency, Water Q u a l i t y L a b o r a t o r y , C i n c i n n a t i , Ohio, 1971.  18.  A.P.H.A., A.W.W.A., W.P.C.F., S t a n d a r d Methods f o r t h e E x a m i n a t i o n o f Water and Wastewater, 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 . , 1 3 t h E d i t i o n , 1971.  19.  Sawyer, C.N. and M c C a r t y , P.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 , M c G r a w - H i l l Book Company, 2nd E d i t i o n , 1967.  86  CHAPTER 8  APPENDICES  87  APPENDIX  SOLIDS  TESTS  RESULTS  A  DURING  STUDIES  88  28,000h  18,000  I 6,000  12  16  Time from Figure  12  MIXED LIQUOR TOTAL START UP  20 start up  S O L I D S CONCENTRATIONS  v s T I M E FROM  89  26,000  24,000  DIGESTER  16,000  14,000*  8  12  16  Time from Figure  13  MIXED LIQUOR S T A R T UP  SUSPENDED  SOLIDS DETENTION DAYS  O  A  0  B  10 20  Q  @  c D  30 30  •  E  ^  F  45 60  20  24  start up — days  S O L I D S C O N C E N T R A T I O N S v s T I M E FROM  90  18,000  I 6,000  2 14,000  SOLI DS DIGESTER  O  8,000  6,000  DETENTION DAYS  @  A B  10 20  Q  c  30  ©  D  30  •  E  45  ^  F  60  Dotted lines indicate averages used to calculate F/M ratios J I I J L_ 8 12 16 20 Time from  Figure  14  MIXED LIQUOR V O L A T I L E T I M E FROM START UP  24  28  32  36  start up — days  SUSPENDED  SOLIDS CONCENTRATIONS v s  8,000r-  10  15  20 25 30 35 40 Solids detention time, 0 - days  45  50  55  60  C  Figure  15  SETTLED  EFFLUENT  TOTAL' S O L I D S CONCENTRATION  v s SOLIDS DETENTION  TIME  vo  92  APPENDIX B  BODr TEST RESULTS DURING  STUDIES  Figure  16  BOD c; OF  SETTLED  EFFLUENTS  DURING  ACCLIMATIZATION  STUDY  9.4  240 SOLIDS DIGESTER  200  DETENTION T I M E , DAYS  O ®  A 8  10 20  Q  c  30  ©  D  30  •  E  45  ^  F  60  160  •  20  80  40  * Dotted lines indicate averages used in tables and on other graphs  Tigure  17  1  I  4  8  BOD  5  I  I  12 16 Time from  OF S E T T L E D  I  I  20 24 start up - days  EFFLUENTS  28  DURING E F F I C I E N C Y  32  STUDIES  95  4.800H  4,000  3,200 a>  E  I  2,4 001  IO  O O  m SOLIDS  1,600  DIGESTER  DETENTION  TIME,  DAYS  800  O  A  1 0  ®  B  20  Q  C  30  ©  D  30  •  £  45  ^  F  60  * Dotted lines indicate averages used in tables and on other graphs 8  Figure  18  BOD_  12 16 20 24 Time from start up-days  OF MIXED LIQUORS  DURING EFFICIENCY  28  32  STUDIES  2,200  2,000  0.02  0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 Food / micro - organism ratio, lb. BOD /lb. MLVSS/day 5  Figure  19  BOD _ OF M I X E D L I Q U O R S v s FOOD TO M I C R O - O R G A N I S M  RATIO  0.22  0.24 VO ON  Settled effluents  I O O I —  •  • —  99.8  \ 99.6  -  o o  \  •  \  in  T3  <o  99.4  \  X3 c ~ o cx UJ  I  99.21  o > o  E  v U  99.0" 95i  Mixed liquor  •  Q  effluents  O  CD  93  9 I  •  •  89  87  85  83  1 0.03  0.06  0.09  0.12  0.15  0.18  0.21  0.24  Food / micro - organism ratio, lb. B O D / l b . M L V S S / d a y 5  F i g u r e 20  PERCENT RATIO  B0D  5  REMOVAL  vs  FOOD  TO  MICRO-ORGANISM  98  •_  •  APPENDIX C  pH OF EFFLUENTS AND MIXED LIQUORS DURING  STUDIES  Fipurp  71  nil  OF  SF.TTT.F.D E F F L U E N T S  DURING  ACCLIMATIZATION  STUDY  100  101  4  8  12 Time from  Figure  23  pH OF MIXED LIQUORS EFFICIENCY  STUDY  16  20  24  28  32  start up - d a y s DURING "SHORTER  DETENTION  TIME"  APPENDIX D  OXYGEN UPTAKE RATES DURING  STUDIES  Time from F i e u r e 24  start up - days  OXYGEN UPTAKE RATES DURING ACCLIMATIZATION STUDY  104  Figure  25  OXYGEN UPTAKE RATES EFFICIENCY  STUDY  DURING "EXTENDED  AERATION"  O  4  Digester A, s o l i d s detention time = lOdays  8  12  16  Time from OXYGEN UPTAKE RATES EFFICIENCY  STUDY  20  24  28  32  start up - days DURING "SHORTER  DETENTION  TIME"  106  APPENDIX E  DETERMINATION  OF KINETIC  PARAMETERS  "EXTENDED AERATION" EFFICIENCY  FROM  STUDY DATA  10?  Determining K and K AS_ At  Rate of food u t i l i z a t i o n  S -S o 1 0 C  AS At  I t can be shown that:  K X S K  +S  s  [MONOD EQUATION]  1  1  (AS/At) . K S. X K + S, s 1  Rearranging the above equation:  K or X I P l o t t i n g (^g/At) v  DIGESTER  0  c days  K  s  Vij s  K  K should y i e l d a s t r a i g h t l i n e with slope _s_ and intercept K.  g"  s  (AS/At)  X mg VSS/1  S o mg/i  S  m  / l  g  X  V s ,  AS/At  l  mg/  (AS/At)  (10" )/( g/^  x  3  m  m  g  VSS  /mg/day  D  30  10,589  35,750  3,454  1,076  0.290  9.85  E  45  11,869  35,750  2,036  750  0.491  15.83  F  60  8,121  35,750  2,194  559  0.456  13.71  The above data i s plotted i n Figure 27. K = 0.75  m  and  g  B0D  K = 21,375 s  5/mg m  g  From that graph i t was estimated that:  VSS/day  / l  Determining Y and b: A b i o l o g i c a l solids balance y i e l d s the equation: AX At  AS Y  At  Dividing each side by X: l^U*!  bX  =  Y  _  b  1/ 'K.  „JLUo  20  18  16 o  ^  14  o» E  S  > cn E  12 Slope 10  Ks _ 28,500 K  K = 0.75.mg/mgVSS/day  co  <  K=  2l,375mg/litre  s  8  I n t e r c e p t = —=1.33 /. K = 0.75  0.1  0.2  mg/litre/day mg M L V S S / l i t r e 0.4  0.3 1/S  Figure  27  0.5  0.6  0.7  0.8  10 -3 1  mg/litre  D E T E R M I N A T I O N OF K AND K U S I N G BOD5 DATA FROM A E R A T I O N " E F F I C I E N C Y STUDY s  "EXTENDED  109  .^•^/A) v s . - ^ — — ^ should therefore y i e l d a s t r a i g h t l i n e t  A plot-of  w i t h slope Y and i n t e r c e p t , -b.  AS...  /At =  S - S' o 1  AX, ... /At  X. - Xo 1  Assuming v o l a t i l e .suspended s o l i d s concentration i n the leachate feed are negligible, X  Q  =0, then: A X  and  DIGESTER  0  c days  AX/At X  = X  l  1 0  AX/At = 1 X 0 days  /At  1  c  X mg VSS  /;L m  g  S o / l  S  m  l g/1  AS  m  g  AS/At X  /At  / l /day  m g /  m g VSS/ day  ,D  30  0.0333  10,589  35,750  3,454  1,076  0.107  E.  45  0.0222  11,869  35,750  2,036  750  0.063  F  60  0.0166  8,121  35,750  2,194  59  0.069  The above data i s p l o t t e d i n Figure 28.  From that graph i t i s evident that the  estimated values of Y and b depend a great deal on personal judgement. "best" values estimated by the author are: Y = 0.332 mg VSS/mg B0D and  b = 0.0025 day"  5  1  Estimation of Minimum S o l i d s Detention Time:  c min..  s o  Therefore, minimum s o l i d s detention time, 0 . =6.46 days ' c mm. ;  ;  The  0.04  0.03  0.02h  Slope = Y = 0.332  0.01  0.0  0.02  V . b = - 0 . 0 0 2 5 day  0.03 -I  0.04  J 0.06  0.05 A  S  / v  A  t  mg VSS mg  L 0.07  J  0.08  L 0.09  0.10  . mg/mg VSS/day  -0.0! h  -0.02  0.03 Figure  28  DETERMINATION OF Y AND b USING BOD  5  DATA FROM "EXTENDED AERATION" EFFICIENCY  STUDY  

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