UBC Theses and Dissertations

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UBC Theses and Dissertations

Biological phosphorus removal from municipal wastewater 1981

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BIOLOGICAL PHOSPHORUS REMOVAL FROM MUNICIPAL WASTEWATER by B a r b a r a Anne B a b r o w s k i .A.Sc., 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 , 197 THESIS SUBMITTED I N PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF A P P L I E D SCIENCE i n THE FACULTY OF GRADUATE STUDIES ( D e p a r t m e n t o f C i v i l E n g i n e e r i n g ) We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s-tandard THE UNIVERSITY OF B R I T I S H COLUMBIA A p r i l 1981 (c) B a r b a r a Anne D a b r o w s k i , 19 81 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h C o lumbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s under- s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f C i v i l E n g i n e e r i n g The U n i v e r s i t y o f B r i t i s h Columbia 2075 Wesbrook M a l l Vancouver, Canada V6T 1W5 Date: A p r i l 27, 1981 A B S T R A C T A l a b o r a t o r y s c a l e s t u d y was u n d e r t a k e n 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 m o v i n g " e n h a n c e d " a m o u n t s o f p h o s p h o r u s f r o m m u n i c i p a l w a s t e w a t e r u s i n g s o l e l y b i o l o g i c a l m e a n s . T h e s y s t e m c o n s i s t e d o f a n a n a e r o b i c - a e r o b i c t r e a t - men t s e q u e n c e . S e v e r a l m o d i f i c a t i o n s w e r e s t u d i e d t o o b s e r v e t h e i r e f f e c t o n t h e c a p a b i l i t y o f t h e s y s t e m t o r e m o v e p h o s - p h o r u s . T h e s e i n c l u d e d t e m p e r a t u r e c h a n g e s a n d t h e a d d i t i o n o f a s l u d g e c o n d i t i o n i n g r e a c t o r t o m i n i m i z e n i t r a t e i n p u t t o t h e a n a e r o b i c r e a c t o r a n d t h u s e l i m i n a t i n g t h e p o s s i b l e i n t e r f e r e n c e w i t h t h e r e l e a s e o f p h o s p h o r u s i n t h i s r e a c t o r a n d t h e s u b s e q u e n t u p t a k e i n t h e a e r o b i c r e a c t o r . P a r a m e t e r s s u c h a s C O D , M L S S , DO, O R P , n i t r a t e s , n i t r i t e s , T K N , p H , a l k a l i n i t y , a n d h e a v y m e t a l s w e r e m o n i t o r e d t h r o u g h o u t t h e s t u d y i n a d d i t i o n t o t h e d e t e r m i n a t i o n o f o r t h o p h o s p h a t e s a n d t o t a l p h o s p h a t e s . T h e r e s u l t s show t h a t n i t r i f i c a t i o n a c t i v i t y , o n c e e s t a b l i s h e d i n t h e a e r o b i c r e a c t o r , was e x t r e m e l y d i f f i c u l t t o c u r t a i l due t o t h e s m a l l s c a l e e f f e c t s . The d e n i t r i f i - c a t i o n o f t h e r e t u r n s l u d g e i n t h e s l u d g e c o n d i t i o n i n g r e a c t o r d i d n o t i n i t s e l f r e s u l t i n t h e m a n i f e s t a t i o n o f " e n h a n c e d " p h o s p h o r u s r e m o v a l b y t h e s y s t e m . I t i s h y p o t h e s i z e d t h a t e x c e l l e n t p h o s p h o r u s r e m o v a l (up t o 98%) c a n b e o b t a i n e d u s i n g e s s e n t i a l l y a n a n a e r o b i c - a e r o b i c t r e a t m e n t s cheme o n l y when t h e s y s t e m i s o p e r a t e d a t e x c e p t i o n a l l y l o n g s l u d g e a g e s ( a p p r o x i m a t e l y 86 d a y s i n t h i s s t u d y ) . i i i TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES i x LIST OF FIGURES X ACKNOWLEDGEMENTS x i i SUMMARY x i i i CHAPTER 1 INTRODUCTION 1 1.1 The E f f e c t s o f N u t r i e n t s on the A q u a t i c 2 Environment 1.2 Phosphorus as the L i m i t i n g N u t r i e n t 3 1.3 C o n t r o l o f Phosphorus 5 1.3.1 Phosphorus N a t u r a l l y O c c u r r i n g i n 5 th e A q u a t i c Environment 1.3.2 Sources o f Phosphorus I n p u t t o the 5 A q u a t i c Environment 1.3.3 Phosphorus Forms i n Wastewater 6 1.3.4 P o i n t Source C o n t r o l o f Phosphorus 6 1.3.5 Methods o f P o i n t Source Phosphorus 8 C o n t r o l 1.3.5.1 P h y s i c a l Methods o f 8 Phosphorus C o n t r o l 1.3.5.2 C h e m i c a l Methods o f 9 Phosphorus C o n t r o l 1.3.5.3 B i o l o g i c a l Methods o f 10 Phosphorus C o n t r o l 2 LITERATURE BACKGROUND 11 2.1 Mechanisms o f Phosphorus Uptake 12 i v Page 2.1.1 Normal A s s i m i l a t i o n Mechanism 12 2.1.2 C h e m i c a l P r e c i p i t a t i o n Mechanism 13 2.1.3 Luxury Uptake Mechanism 14 2.2 R e s u l t s and O b s e r v a t i o n s o f S e l e c t e d 18 Phosphorus Removal S t u d i e s 2.2.1 Phosphorus Removal i n C o n v e n t i o n a l 19 A c t i v a t e d Sludge Treatment 2.2.2 Phosphorus Removal v i a M o d i f i e d 20 A c t i v a t e d Sludge Treatment 2.3 O p e r a t i n g C o n d i t i o n s R e q u i r e d f o r 31 Phosphorus Removal 2.4 R e s e a r c h R a t i o n a l e - T h i s Work 35 3 EXPERIMENTAL SYSTEM AND PROCEDURES 37 3.1 P h y s i c a l System C h a r a c t e r i s t i c s 37 3.2 System O p e r a t i o n 38 3.2.1 Raw Sewage Supply 38 3.2.2 System H y d r a u l i c s 40 3.2.2.1 Flow Regime 40 3.2.2.2 Pumping A s p e c t s 49 3.2.3 M i x i n g 49 3.2.4 N i t r o g e n S u p p l y 50 3.2.5 A e r a t i o n 50 3.2.6 L i g h t 50 3.3 Sampling P r o c e d u r e s 51 3.4 A n a l y t i c a l P r o c e d u r e s 53 3.4.1 C h e m i c a l Oxygen Demand (COD) 53 3.4.2 T o t a l Suspended S o l i d s (TSS) 53 3.4.3 Mixed L i q u o r V o l a t i l e Suspended 54 S o l i d s (MLVSS) V Page 3.4.4 A l k a l i n i t y 54 3.4.5 pH 54 3.4.6 Tr a c e M e t a l s .54 3.4.7 N i t r o g e n Forms 55 3.4.7.1 N i t r a t e s and N i t r i t e s 55 3.4.7.2 T o t a l K j e l d a h l N i t r o g e n 56 (TKN) 3.4.8 Phosphate Forms 56 3.4.8.1 Orthophosphates 56 3.4.8.2 T o t a l Phosphates 56 3.5 M o n i t o r i n g P r o c e d u r e s 57 3.5.1 Temperature 57 3.5.2 D i s s o l v e d Oxygen (DO) 57 3.5.3 O x i d a t i o n R e d u c t i o n P o t e n t i a l 59 (ORP) 3.5.4 Flow Rates 59 3.6 H y d r a u l i c R e t e n t i o n Time (HRT) 60 3.7 S o l i d s R e t e n t i o n Time (SRT) 62 3.8 N i t r a t e R e a c t i o n Rates 63 3.9 Orthophosphate R e a c t i o n Rates 64 3.10 AP/ACOD R a t i o 64 3.11 Re s e a r c h Program 65 4 PHASE A: A PRELIMINARY INVESTIGATION OF 66 PARAMETERS AFFECTING THE BIOLOGICAL REMOVAL OF PHOSPHATES FROM WASTEWATER 4.1 D e s c r i p t i o n o f System O p e r a t i n g C o n d i t i o n s 66 4.2 System M o d i f i c a t i o n s 67 4.2.1 Temperature 68 v i Page 4.2.2 Sludge C o n d i t i o n i n g R e a c t o r 68 4.2.3 C l a r i f i e r 69 4.2.4 System Shut-down 69 4.3 R e s u l t s and D i s c u s s i o n 70 4.3.1 C h e m i c a l Oxygen Demand (COD) 70 4.3.2 T o t a l Suspended S o l i d s (TSS) 72 4.3.3 Mixed L i q u o r V o l a t i l e Suspended 74 S o l i d s (MLVSS) 4.3.4 D i s s o l v e d Oxygen (DO) 74 4.3.5 O x i d a t i o n R e d u c t i o n P o t e n t i a l 75 (ORP) 4.3.6 A l k a l i n i t y and pH 75 4.3.7 T r a c e M e t a l s 76 4.3.8 N i t r o g e n Forms 76 4.3.8.1 N i t r a t e s 77 (a) C o n c e n t r a t i o n s 77 (b) N i t r i f i c a t i o n and 79 D e n i t r i f i c a t i o n Rates 4.3.8.2 N i t r i t e s 81 4.3.8.3 T o t a l K j e l d a h l N i t r o g e n 82 (TKN) 4.3.9 Phosphates 82 4.3.9.1 Orthophosphates 8 3 (a) C o n c e n t r a t i o n s 83 (b) P e r c e n t a g e Removals 83 (c) Orthophosphate R e a c t i o n 85 Rates 4.3.9.2 T o t a l Phosphates 88 v i i Page 4.3.10 AP/ACOD R a t i o 88 '4.3.11 H y d r a u l i c R e t e n t i o n Time (HRT) 88 4.3.12 S o l i d s R e t e n t i o n Time (SRT) 89 4.4 C o n d i t i o n s A f f e c t i n g Phosphate Removal 89 5 PHASE B: CONDITIONS REQUIRED FOR THE SUCCESSFUL 94 BIOLOGICAL REMOVAL OF PHOSPHATES FROM WASTEWATER 5.1 D e s c r i p t i o n o f System O p e r a t i n g 94 C o n d i t i o n s 5.2 R e s u l t s and D i s c u s s i o n 95 5.2.1 C h e m i c a l Oxygen Demand (COD) 95 5.2.2 T o t a l Suspended S o l i d s (TSS) 96 5.2.3 Mixed L i q u o r V o l a t i l e Suspended 99 S o l i d s (MLVSS) 5.2.4 D i s s o l v e d Oxygen (DO) 99 5.2.5 O x i d a t i o n R e d u c t i o n P o t e n t i a l 99 (ORP) 5.2.6 A l k a l i n i t y and pH 100 5.2.7 Tr a c e M e t a l s 100 5.2.8 N i t r o g e n Forms 10 2 5.2.8.1 N i t r a t e s 103 (a) C o n c e n t r a t i o n s 103 (b) N i t r i f i c a t i o n and 105 D e n i t r i f i c a t i o n Rates 5.2.8.2 N i t r i t e s 107 5.2.8.3 T o t a l K j e l d a h l N i t r o g e n 107 (TKN) 5.2.9 Phosphates 10 8 5.2.9.1 Orthophosphates 10 8 v i i i Page (a) C o n c e n t r a t i o n s 108 (b) P e r c e n t a g e Removals 110 (c) Orthophosphate R e a c t i o n 112 Rates 5.2.9.2 T o t a l Phosphates 114 5.2.10 AP/ACOD R a t i o 114 5.2.11 H y d r a u l i c R e t e n t i o n Time (HRT) 115 5.2.12 S o l i d s R e t e n t i o n Time (SRT) 115 5.3 C o n d i t i o n s A f f e c t i n g Phosphate R e a c t i o n 116 Rates 6 CONCLUSIONS AND RECOMMENDATIONS 120 6.1 C o n c l u s i o n s 120 6.2 Recommendations 122 REFERENCES 124 APPENDICES 128 APPENDIX I 129 APPENDIX I I 131 i x LIST OF TABLES TABLE TITLE Page 1.1 P o s s i b l e Sources o f Phosphorus I n p u t 7 t o t h e A q u a t i c Environment 3.1 System Dimensions 39 3.2 Sampling Frequency 5 2 3.3 H y d r a u l i c R e t e n t i o n Time 61 I I - l pH and A l k a l i n i t y 134 I I - 2 Raw Sewage Tr a c e M e t a l s 135 I I - 3 T o t a l K j e l d a h l N i t r o g e n 136 I I - 4 T o t a l Phosphates 137 I I - 5 Trace M e t a l s Scan Through System 139 X LIST OF FIGURES FIGURE NO. TITLE Page 3.1 Feed S t o r a g e Drums 41 3.2 Water Bath 42 3.3 A n a e r o b i c R e a c t o r 43 3.4 A e r o b i c R e a c t o r 43 3.5 C l a r i f i e r ( i n i t i a l model) 44 3.6 C l a r i f i e r ( s u b s t i t u t e d model) 45 3.7 Sludge C o n d i t i o n i n g R e a c t o r 46 3.8 I n i t i a l Phosphorus Removal System 47 3.9 M o d i f i e d Phosphorus Removal System 48 3.10 D i s s o l v e d Oxygen Probe A g i t a t i o n 58 Mechanism 4.1 System P e r c e n t a g e COD Removal and 71 A e r o b i c MLSS L e v e l s (Phase A) 4.2 E f f l u e n t N i t r a t e s (Phase A) 78 4.3 N i t r i f i c a t i o n and D e n i t r i f i c a t i o n 80 Rates (Phase A) 4.4 Orthophosphates (Phase A) 84 4.5 P e r c e n t a g e Orthophosphate Removal 86 (Phase A) 4.6 Orthophosphate R e a c t i o n R ates 87 (Phase A) 5.1 System P e r c e n t a g e COD Removal and 97 A e r o b i c MLSS L e v e l s (Phase B) 5.2 E f f l u e n t N i t r a t e s (Phase B) 104 5.3 N i t r i f i c a t i o n and D e n i t r i f i c a t i o n 106 Rates (Phase B) 5.4 Orthophosphates (Phase B) 109 x i T I T L E P e r c e n t a g e O r t h o p h o s p h a t e R e m o v a l ( P h a s e B) O r t h o p h o s p h a t e R e a c t i o n R a t e s ( P h a s e B) F e e d a n d E f f l u e n t COD C o n c e n t r a t i o n E f f l u e n t S u s p e n d e d S o l i d s A P / A C O D R a t i o v s . P e r c e n t P Removed b y S y s t e m x i i ACKNOWLEDGEMENTS I w i s h t o t h a n k my a d v i s o r , D r . W . K . O l d h a m , f o r h i s t e c h n i c a l g u i d a n c e i n t h e p r e p a r a t i o n o f t h i s t h e s i s . Many t h a n k s a r e a l s o due t o D r . D . S . M a v i n i c f o r r e v i e w i n g t h i s m a n u s c r i p t . S u s a n L i p t a k a n d P a u l a P a r k i n s o n w e r e i n v a l u a b l e d u r i n g t h e e x p e r i m e n t a l p o r t i o n o f t h i s s t u d y . Guy K i r c h p r o v i d e d much a p p r e c i a t e d a s s i s t a n c e i n t h e m a i n t e n a n c e o f t h e a p p a r a t u s . The t y p i n g o f t h e o r i g i n a l m a n u s c r i p t was k i n d l y p e r f o r m e d b y my s i s t e r , D o r o t h y . D e s i r e e C h e u n g p a t i e n t l y u p d a t e d t h e f i n a l r e p o r t . The m o r a l s u p p o r t o f my p a r e n t s a n d f r i e n d s i s d e e p l y a p p r e c i a t e d . I n p a r t i c u l a r , I w i s h t o t h a n k C o l l e e n T o m p k i n s , f o r h e r c o m p a n y o n n u m e r o u s t r i p s t o t h e s ewage t r e a t m e n t p l a n t ; B o b S h e p h e r d f o r h i s c o n s t a n t e n c o u r a g e m e n t ; a n d my f a t h e r , f o r o r i g i n a l l y i n t r o d u c i n g me t o t h e f i e l d o f e n v i r o n m e n t a l e n g i n e e r i n g . F u n d i n g b y t h e N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a i s g r e a t f u l l y a c k n o w l e d g e d . x i i i SUMMARY T h i s t h e s i s e x a m i n e s t h e c o n d i t i o n s r e q u i r e d f o r t h e e n h a n c e d b i o l o g i c a l r e m o v a l o f p h o s p h o r u s i n a m o d i f i e d a c t i - v a t e d s l u d g e t r e a t m e n t s c h e m e . The e f f e c t o f p h o s p h o r u s o n t h e a q u a t i c e n v i r o n m e n t a n d r e a s o n s f o r t h e c o n t r o l o f t h i s n u t r i e n t , b y j u d i c i o u s managemen t o f p o i n t s o u r c e d i s c h a r g e s , a r e p r e s e n t e d . M e t h o d s o f c o n t r o l p r e s e n t l y a v a i l a b l e t o t h e w a s t e w a t e r e n g i n e e r i n g d i s c i p l i n e a r e b r i e f l y o u t l i n e d . A n o v e r v i e w o f c u r r e n t l i t e r a t u r e d e a l i n g w i t h t h e e n h a n c e d p h o s p h o r u s r e m o v a l c a p a b i l i t i e s o f s e v e r a l b i o l o g i c a l w a s t e - w a t e r t r e a t m e n t s c h e m e s a n d t h e m e c h a n i s m s i n v o l v e d i n p h o s - p h o r u s u p t a k e a r e d i s c u s s e d . The p h y s i c a l c h a r a c t e r i s t i c s o f t h e s y s t e m i n v e s t i g a - t e d i n t h i s s t u d y , t o g e t h e r w i t h t h e o p e r a t i n g c o n d i t i o n s a n d r e g i m e s , a r e o u t l i n e d . S a m p l i n g , a n a l y s i s , a n d m o n i t o r i n g p r o c e d u r e s a r e a l s o d e s c r i b e d . E q u a t i o n s u s e d t o c a l c u l a t e h y d r a u l i c r e t e n t i o n t i m e s , s o l i d s r e t e n t i o n t i m e s , A P / A C O D r a t i o s , a n d r e a c t i o n r a t e s a r e g i v e n . T h e s t u d y i n v o l v e s two p h a s e s . P h a s e A d e a l s w i t h t h e p r e l i m i n a r y i n v e s t i g a t i o n s u n d e r t a k e n t o d e t e r m i n e t h e r e s p o n s e o f t h e s y s t e m t o v a r i o u s m o d i f i c a t i o n s i n t r o d u c e d t o e n c o u r a g e t h e r e m o v a l o f p h o s p h a t e s . Up t o 55% p h o s p h o r u s r e m o v a l was o b t a i n e d w i t h o u t c h e m i c a l a d d i t i o n . P h a s e A i s c h a r a c t e r i z e d b y c o n s t a n t p h y s i c a l a n d o p e r a t i o n a l a l t e r a t i o n s a i m i n g a t c u r t a i l i n g p o s s i b l e e f f e c t s o f n i t r a t e s ( p a r t i c u l a r l y i n t h e a n a e r o b i c r e a c t o r ) o n t h e p h o s p h o r u s r e l e a s e a n d u p t a k e x i v p h e n o m e n a . T h e d e n i t r i f i c a t i o n o f o x i d i z e d n i t r o g e n s p e c i e s i n t h e s l u d g e r e t u r n was f i n a l l y a c h i e v e d i n t h e s l u d g e c o n d i t i o n i n g r e a c t o r , t h u s p r e c l u d i n g d e n i t r i f i c a t i o n f r o m t a k i n g p l a c e i n t h e a n a e r o b i c r e a c t o r . No i m p r o v e m e n t i n e i t h e r t h e r e l e a s e o r u p t a k e o f p h o s p h o r u s r e s u l t e d h o w e v e r . P h a s e B r e p r e s e n t s t h e p e r i o d o f s t u d y when e n h a n c e d p h o s p h o r u s r e m o v a l was r e a l i z e d . P e r c e n t a g e r e m o v a l s w e r e s i g n i f i c a n t l y h i g h e r t h a n e x h i b i t e d d u r i n g P h a s e A , r e a c h i n g a h i g h o f 98%. T h e r e w e r e no p h y s i c a l m o d i f i c a t i o n s e f f e c t e d d u r i n g P h a s e B . The o n l y s i g n i f i c a n t o p e r a t i n g c h a n g e was t h e m a i n t e n a n c e o f e x c e p t i o n a l l y l o n g s o l i d s r e t e n t i o n t i m e s . 1 CHAPTER 1 INTRODUCTION As the end of the t w e n t i e t h c e n t u r y approaches, the popul a c e today i s becoming i n c r e a s i n g l y aware of the l i m i t s of our environment t o a s s i m i l a t e man's wastes. M u n i c i p a l wastewater, i f i m p r o p e r l y t r e a t e d , may have numerous d e t r i m e n t a l e f f e c t s on the water body i n t o which i t i s d i s c h a r g e d . E a r l y o b j e c t i v e s of m u n i c i p a l t r e a t m e n t schemes aimed at removing b i o d e g r a d a b l e o r g a n i c s and suspended and f l o a t a b l e m a t t e r , as w e l l as the e l i m i n a t i o n of pathogens f o r o b v i o u s h e a l t h reasons. As a b e t t e r u n d e r s t a n d i n g of the e f f e c t s on the environment of wastewater d i s c h a r g e s d e v e l o p s , an i n c r e a s e i n the degree of tr e a t m e n t has become the t r e n d . L i m i t s on n u t r i e n t s ( n i t r o g e n and p h o s p h o r u s ) , t r a c e m e t a l s , r e f r a c t o r y o r g a n i c s , and d i s s o l v e d i n o r g a n i c s o l i d s , have been i n c o r p o r a t e d i n t o the s t a n d a r d s of numerous communities a l l over the w o r l d . T h i s c h a p t e r w i l l i n t r o d u c e the concept of water q u a l i t y d e g r a d a t i o n due t o the a d d i t i o n of n u t r i e n t s from p o i n t s o u r c e s . S i n c e phosphorus i s o f t e n the l i m i t i n g n u t r i e n t , methods by which i t s d i s c h a r g e can be c u r t a i l e d w i l l be p r e s e n t e d . 2 1.1 The E f f e c t s of N u t r i e n t s on the A q u a t i c Environment The impact of n u t r i e n t s on n a t u r a l water b o d i e s i s of g r e a t e r s i g n i f i c a n c e t o l a k e s than r i v e r s because of the a c c u m u l a t i n g p o t e n t i a l of the former. Lakes f a l l i n t o t h r e e major l i m n o l o g i c a l c l a s s e s : o l i g o t r o p h i c , m e s o t r o p h i c , and e u t r o p h i c . O l i g o t r o p h i c l a k e s are r e l a t i v e l y young, h a v i n g a low i n p u t of n u t r i e n t s and a s p a r s e b i o l o g i c a l p o p u l a t i o n . Lakes w i t h h i g h e r l e v e l s of b i o l o g i c a l p r o d u c t i v i t y ( c h a r a c t e r i z e d by the p r e s e n c e of f i s h ) , due t o an adequate n u t r i e n t s u p p l y , a re known as m e s o t r o p h i c . As a d d i t i o n a l n u t r i e n t s a r e added, p r o d u c t i v i t y i n c r e a s e s u n t i l the h a b i t a t i s no l o n g e r o p t i m a l f o r the s p e c i e s p r e s e n t i n the system. At t h i s p o i n t the l a k e becomes e u t r o p h i c . T h i s stage i n l a k e l i f e i s c h a r a c t e r i z e d by e x c e s s i v e b i o l o g i c a l growth, i n p a r t i c u l a r a l g a l blooms. A m u l t i t u d e of problems tend t o r e s u l t . These i n c l u d e t u r b i d i t y and d i s s o l v e d oxygen d e p l e t i o n due t o o r g a n i c m atter decay. A l g a l blooms are a p a r t i c u l a r n u i s a n c e and y i e l d numerous p h y s i c a l and a e s t h e t i c problems i n c l u d i n g f o u l t a s t e and odour of the w a t e r , the d i s r u p t i o n and p o s s i b l e c u r t a i l m e n t of r e c r e a t i o n a l a c t i v i t i e s , and the p r o l i f e r a t i o n of u n d e s i r a b l e b i o l o g i c a l s p e c i e s which t o l e r a t e such p o l l u t e d c o n d i t i o n s . Numerous o t h e r problems occur when the l a k e i s used as a source of water s u p p l y ; c l o g g i n g of i n t a k e s , the n e c e s s i t y f o r an i n c r e a s e i n f i l t e r backwashing f r e q u e n c y , as w e l l as d i c t a t i n g a need f o r c o a g u l a t i o n and c l a r i f i c a t i o n f a c i l i t i e s , ( B l a c k and K h e t t r y ( 1 9 8 0 ) ) , E u t r o p h i c a t i o n a f f e c t s the l i f e - c y c l e s of a l l l e v e l s of the b i o t i c p o p u l a t i o n p r e s e n t i n l a k e s i n c l u d i n g 3 b e n t h o s , p h y t o p l a n k t o n , z o o p l a n k t o n , macrophytes, and f i s h . As n u t r i e n t c o n c e n t r a t i o n s i n a g i v e n l a k e i n c r e a s e , the r e l a t i v e c o n c e n t r a t i o n s of the b i o l o g i c a l p o p u l a t i o n s may s h i f t and p o s s i b l y a l t e r the numbers of s p e c i e s p r e s e n t . 1.2 Phosphorus as the L i m i t i n g N u t r i e n t The t h r e e major n u t r i e n t s r e q u i r e d f o r b i o l o g i c a l growth ar e c a r b o n , n i t r o g e n , and phosphorus. To c o n t r o l the growth of c e r t a i n u n d e s i r a b l e f r e s h water s p e c i e s , the l i m i t i n g n u t r i e n t must f i r s t be i d e n t i f i e d . Subsequent c o n t r o l of t h a t n u t r i e n t i n p u t w i l l c u r t a i l the r a p i d growth of such s p e c i e s . C o n t r o l of carbon i s a w e l l e s t a b l i s h e d p r a c t i c e v i a b i o l o g i c a l wastewater t r e a t m e n t . I t i s i m p o s s i b l e however t o c u r t a i l the a q u a t i c i n p u t of carbon t o t h e e x t e n t t h a t i t w i l l become the l i m i t i n g n u t r i e n t . Even i f t h i s c o u l d be a c h i e v e d , s e v e r a l s p e c i e s of a q u a t i c p l a n t s can u t i l i z e t he b i c a r b o n a t e i o n t o s u s t a i n t h e i r p h o t o s y n t h e t i c f u n c t i o n , which would make t h i s p r a c t i c e f u t i l e ( B l a c k and K h e t t r y ( 1 9 8 0 ) ) . A l g a e r e q u i r e n i t r o g e n i n a combined i n o r g a n i c form f o r growth. In many i n s t a n c e s , c o n t r o l l i n g the i n p u t of t h i s n u t r i e n t t o m a i n t a i n low a l g a l p o p u l a t i o n s t o a g i v e n l a k e or water body i s i r r a t i o n a l . For example, b l u e - g r e e n a l g a e a r e c a p a b l e of f i x i n g d i s s o l v e d n i t r o g e n gas. The s u p p l y of t h i s gas i n such an open system i s v i r t u a l l y i n f i n i t e because of i t s abundant a v a i l a b i l i t y from the atmosphere. B l u e - g r e e n a l g a e t h e r e f o r e a r e a b l e t o t h r i v e under " n i t r o g e n l i m i t i n g " 4 c o n d i t i o n s due to the presence of phosphorus. These algae are a p a r t i c u l a r nuisance i n terms of producing unpleasant t a s t e and odors i n d r i n k i n g water. U n s i g h t l y suspended a l g a l growth may a l s o be manifested (Black and K h e t t r y (1980)). T h i s leaves the c o n t r o l of phosphorus as the only other means of c u r t a i l i n g e u t r o p h i c a t i o n of n a t u r a l water bodies. By l i m i t i n g the phosphorus content i n the a q u a t i c environment, the phosphorus:nitrogen r a t i o would be reduced. Consequently, phosphorus would be r a p i d l y a s s i m i l a t e d i n the growth process of the green algae, to the extent t h a t e v e n t u a l l y the e x i s t e n c e of the n i t r o g e n - f i x i n g blue-green algae would be threatened, and h o p e f u l l y brought under c o n t r o l (Black and K h e t t r y (1980)).. Phosphorus i s g r a d u a l l y being recognized as the l i m i t i n g n u t r i e n t i n the m a j o r i t y of e u r t o p h i c a t i o n s i t u a t i o n s around the world. P o r t e r (1975) r e p o r t s that i n most temperate lakes of the U n i t e d S t a t e s , phosphorus i s l i m i t i n g . Black and K h e t t r y (1980) c i t e numerous examples of b a s i n s i n Canada where the c o n t r o l of phosphorus i s r a p i d l y being c o n s i d e r e d as the only s o l u t i o n to the e s c a l a t i n g r a t e s of e n t r o p h i c a t i o n . Examples of these b a s i n s i n c l u d e : Lake E r i e , O n t a r i o ; Qu'Appelle R i v e r B a s i n , Saskatchewan; S a i n t John R i v e r Basin, New Brunswick; and the Okanagan Basin of B r i t i s h Columbia. The c e n t r a l r e g i ons of South A f r i c a , where f r e s h water i s i n c r i t i c a l l y short supply, are a l s o p o t e n t i a l c a n d i d a t e s f o r e u t r o p h i c a t i o n c o n t r o l by proper phosphorus management tec h n i q u e s . 5 1.3 C o n t r o l of Phosphorus T h i s s e c t i o n w i l l d i s c u s s n a t u r a l l y o c c u r r i n g phosphorus i n the a q u a t i c environment and t y p i c a l raw sewage phosphorus c o n s t i t u e n t s . Reasons f o r e mploying p o i n t s o u r c e c o n t r o l of phosphorus and methods whereby t h i s c o n t r o l can be r e a l i z e d w i l l a l s o be g i v e n . 1.3.1 Phosphorus N a t u r a l l y O c c u r r i n g i n the A q u a t i c Environment A p r a c t i c a l l y i n f i n i t e r e s e r v e of p h o s p h o r u s - c o n t a i n i n g m i n e r a l s i s l o c a t e d i n the e a r t h ' s c r u s t . Most of these however, ar e o n l y t o a v e r y low degree s o l u b l e i n w a t e r . T h i s has r e s u l t e d i n r e l a t i v e l y minor c o n c e n t r a t i o n s of phosphorus d e r i v e d from such s o u r c e s i n " n a t u r a l " water. 1.3.2 Sources of Phosphorus Input t o the A q u a t i c Environment The i n p u t of phosphorus t o a water body may be r o u g h l y d i v i d e d i n t o two forms: the s o l u b l e and the p a r t i c u l a t e . P a r t i c u l a t e P may be b i o l o g i c a l l y i n c o r p o r a t e d i n t o the c e l l p r o t o p l a s m of a q u a t i c o r g anisms, or may be adsorbed onto p a r t i c u l a t e m a t e r i a l . T h i s form of phosphorus may enhance the growth of the r o o t e d a q u a t i c v e g e t a t i o n i n a l a k e environment. S o l u b l e P i s the most r e a d i l y a v a i l a b l e form of phosphorus f o r uptake by the a q u a t i c p o p u l a t i o n . In t h i s c a p a c i t y , s o l u b l e P a c t s as a f e r t i l i z e r , e v e n t u a l l y c o n t r i b u t i n g t o the problems a s s o c i a t e d w i t h e u t r o p h i c a t i o n . B l a c k and K h e t t r y (1980) l i s t e d a summary of phosphorus s o u r c e s , which upon a d d i t i o n t o a 6 n a t u r a l water body may cause e u t r o p h i c a t i o n . These s o u r c e s a r e p r e s e n t e d i n Table 1.1. 1.3.3 Phosphorus Forms i n Wastewater The P c o n c e n t r a t i o n s i n wastewater may be c l a s s e d as t o t a l P, p a r t i c u l a t e P, and s o l u b l e P. Orthophosphates a r e the major c o n s t i t u e n t of the s o l u b l e P f r a c t i o n and a r e the most r e a d i l y a v a i l a b l e form. I n o r g a n i c condensed phosphates a re l a r g e l y d e r i v e d from the d e t e r g e n t i n p u t i n t o m u n i c i p a l wastewater. A f u r t h e r s u b d i v i s i o n may a l s o be made, based on c h e m i c a l r e a c t i v i t y and b i o l o g i c a l a v a i l a b i l i t y . S o l u b l e r e a c t i v e phosphorus, n o n a p a t i t e i n o r g a n i c phosphorus, and c e r t a i n forms of o r g a n i c phosphorus a r e of note s i n c e they have the g r e a t e s t p o t e n t i a l f o r b e i n g u t i l i z e d by the b i o l o g i c a l community i n the wastewater ( W i l l i a m s e t a l . ( 1 9 7 6 ) ) . 1.3.4 P o i n t Source C o n t r o l of Phosphorus From T a b l e 1.1, a l t h o u g h i t i s e v i d e n t t h a t many no n - p o i n t s o u r c e s c o n t r i b u t e t o the P i n p u t t o a n a t u r a l water body, th e s e are d i f f u s e , d i f f i c u l t t o d i s t i n g u i s h or c l a s s i f y , and f o r the most p a r t t h e i r c o n t r o l would r e q u i r e a monumental e f f o r t . To reduce the i n p u t of phosphorus from t h e s e s o u r c e s , a c o n c i o u s e f f o r t must be d i r e c t e d a t prop e r management of f e r t i l i z e r a p p l i c a t i o n t o a g r i c u l t u r a l l a n d , and i n g e n e r a l c o n t r o l l i n g the e x t e n t of man's a c t i v i t i e s p a r t i c u l a r l y i n terms of e x t e n s i v e u r b a n i z a t i o n . P o i n t s o u r c e s , on the o t h e r hand, a r e much more T A B L E 1.1 P O S S I B L E SOURCES OF PHOSPHORUS INPUT TO THE A Q U A T I C ENVIRONMENT ( a c c o r d i n g t o B l a c k a n d K h e t t r y ( 1 9 8 0 ) ) i . M u n i c i p a l w a s t e t r e a t m e n t p l a n t e f f l u e n t s a n d p r i v a t e w a s t e d i s p o s a l i i . U n t r e a t e d i n d u s t r i a l w a s t e s i i i . C h e m i c a l s d e r i v e d f r o m w a t e r t r e a t m e n t i v . S u r f a c e r u n o f f v . G r o u n d w a t e r v i . D e r i v e d f r o m p h y s i c a l , c h e m i c a l , a n d b i o l o g i c a l r e a c t i o n s i n h e r e n t i n t h e a q u a t i c e n v i r o n m e n t v i i . A t m o s p h e r e 8 e a s i l y i d e n t i f i e d and c o n t r o l can be based on s i t e - s p e c i f i c needs. A comprehensive study by the U.S. Environmental P r o t e c t i o n Agency (EPA) i n d i c a t e d that p o i n t source n u t r i e n t l o a d i n g s are i n a r e l a t i v e l y c o n c e n t r a t e d form and are the most r e a d i l y c o n t r o l a b l e ( G a k s t a t t e r et a l . (1978)). The management of p o i n t source waste, i n terms of c o n t r o l l i n g the phosphorus input to the environment d e r i v e d from man's a c t v i t i e s , i s at present the c o n s i d e r e d p r a c t i c a l method. 1.3.5 Methods of P o i n t Source Phosphorus C o n t r o l Depending on the e f f l u e n t r e g u l a t i o n s i n e f f e c t f o r a given p o i n t source d i s c h a r g e , one of three major treatment methods may be s e l e c t e d : p h y s i c a l , chemical, or b i o l o g i c a l . Combinations of these may a l s o be used to s u i t the requirements of d i f f e r e n t p r o j e c t s . 1.3.5.1 P h y s i c a l Methods of Phosphorus C o n t r o l Primary sedimentation and c l a r i f i c a t i o n u s u a l l y r e s u l t s in up to 10% removal of the t o t a l P content from raw sewage. T h i s amount e s s e n t i a l l y r e p r e s e n t s the i n s o l u b l e P f r a c t i o n in wastewater. Because of these low percentage removals, s o l e l y p h y s i c a l sedimentation methods are not s u c c e s s f u l and must be accompanied by e i t h e r chemical or b i o l o g i c a l treatment to y i e l d s i g n i f i c a n t P removal e f f i c i e n c i e s ( i n the 80% removal range). 9 1.3.5.2 Chemical Methods of Phosphorus C o n t r o l A c t i v e removal of P from wastewater i n Canada was encouraged i n 1969 by the I n t e r n a t i o n a l J o i n t Commission (IJC) which recommended that P d i s c h a r g e s i n t o the Great Lakes be reduced to the lowest p r a c t i c a l l e v e l . In 1972 a f u r t h e r s p e c i f i c e f f l u e n t o b j e c t i v e of 1 mg/L t o t a l P was s e t , l e a d i n g to e x t e n s i v e r e s e a r c h i n the f i e l d of p h y s i c a l - c h e m i c a l P removal schemes in Canada,' and p a r t i c u l a r l y i n O n t a r i o . P r e c i p i t a t i n g phosphates with c e r t a i n chemicals, f o l l o w e d by c o a g u l a t i o n and subsequent sedimentation i s a proven method of o b t a i n i n g extremely low e f f l u e n t P l e v e l s . Three chemicals are commonly used f o r t h i s purpose: lime, alum, and f e r r i c c h l o r i d e . The aim of these compounds i s to provide c a t i o n s f o r the p r e c i p i t a t i o n with phosphates. Waste m a t e r i a l s from v a r i o u s i n d u s t i a l o p e r a t i o n s , upon i n i t i a l i n v e s t i g a t i o n , appear to be economically b e n e f i c i a l as a l t e r n a t i v e s to purchased chemicals. Problems with such m a t e r i a l s i n c l u d e t h e i r f l u c t u a t i n g chemical composition and the presence of i m p u r i t i e s such as t r a c e metals ( a f f e c t i n g sludge d i s p o s a l methods). T h e i r a v a i l a b i l i t y may be i n c o n s i s t e n t i n terms of q u a n t i t i e s and t h e i r t r a n s p o r t a b i l i t y from the i n d u s t r y to the wastewater treatment s i t e . In a primary treatment p l a n t such chemicals are u s u a l l y added to a p r e a e r a t i o n u n i t at the head end. In the case of secondary treatment, enhanced P removal i s t y p i c a l l y r e a l i z e d e i t h e r by lime a d d i t i o n to a p r e a e r a t i o n u n i t p r i o r to primary c l a r i f i c a t i o n , or by alum or f e r r i c c h l o r i d e a d d i t i o n d i r e c t l y 10 t o the b i o l o g i c a l r e a c t o r , w i t h subsequent s e d i m e n t a t i o n o c c u r r i n g i n the secondary c l a r i f i e r . J a r t e s t s have proven e x c e l l e n t i n d i c a t o r s of f u l l s c a l e p r e c i p i t a t i o n t e c h n i q u e s . 1.3.5.3 B i o l o g i c a l Methods of Phosphorus C o n t r o l In s t a n d a r d r a t 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 r e c e i v i n g p r i m a r y e f f l u e n t , between 1.0 and 1.5 mg/L of phosphorus i s removed per 200 mg/L of COD removed ( E n v i r o n m e n t a l P r o t e c t i o n Agency ( 1 9 7 6 ) ) . T h i s t r a n s l a t e s t o a r e d u c t i o n i n P of 20% t o 30% a c r o s s the p l a n t f o r a t y p i c a l raw sewage P c o n t e n t of 8 mg/L ( M e t c a l f and Eddy ( 1 9 7 9 ) ) . U n f o r t u n a t e l y such removals are g e n e r a l l y i nadequate s i n c e i n f l u e n t P c o n c e n t r a t i o n s are u s u a l l y h i g h ; thus e f f l u e n t l e v e l s below 1 mg/L of phosphorus are seldom r e a l i z e d . For t h i s reason new approaches have r e c e n t l y been i n i t i a t e d i n the a r e a of b i o l o g i c a l t r e a t m e n t ; these approaches aim a t enhanced phosphorus r e m o v a l . B a s i c a l l y , the m a j o r i t y of new r e s e a r c h i s concerned w i t h the i n c l u s i o n of s t r e s s f u l c o n d i t i o n s which l e a d t o subsequent uptake of P i n amounts g r e a t e r than are r e q u i r e d f o r o r d i n a r y m i c r o b i a l growth. These methods of enhanced b i o l o g i c a l removal of P a r e d i s c u s s e d i n d e t a i l i n Chapter 2. 11 CHAPTER 2 LITERATURE BACKGROUND The r e a l i z a t i o n t h a t n a t u r a l water e u t r o p h i c a t i o n can o f t e n be e f f e c t i v e l y c o n t r o l l e d or a t l e a s t c u r t a i l e d by m a i n t a i n i n g low P c o n c e n t r a t i o n s i n sewage t r e a t m e n t p l a n t e f f l u e n t s , has l e a d t o e x t e n s i v e r e s e a r c h i n t h i s f i e l d . T h i s c h a p t e r w i l l d i s c u s s the r e s u l t s of v a r i o u s s t u d i e s conducted on bench, p i l o t , and f u l l - s c a l e schemes d e s i g n e d f o r the enhanced b i o l o g i c a l removal of P from m u n i c i p a l wastewater. The mechanisms of remo v a l , as proposed by v a r i o u s r e s e a r c h e r s , w i l l be p r e s e n t e d . Case s t u d i e s , t o g e t h e r w i t h t h e i r f i n d i n g s , w i l l be g i v e n as examples of the r e s e a r c h programs b e i n g c o n ducted. Because of the v a r i a t i o n i n the l o c a l c h a r a c t e r i s t i c s and c o n s t i t u e n t s of raw sewage, as w e l l as the seemingly i n e x h a u s t i b l e c o m b i n a t i o n of t r e a t m e n t systems a v a i l a b l e t o the r e s e a r c h e r , comparison of r e s u l t s i s d i f f i c u l t . A l s o , c o n c l u s i o n s d e r i v e d from t h e s e s t u d i e s a re case s p e c i f i c and do not e a s i l y l e n d t hemselves t o u n i v e r s a l a p p l i c a t i o n and ac c e p t a n c e . I t i s " g e n e r a l l y " agreed t h a t c e r t a i n c o n d i t i o n s must be met i n a b i o l o g i c a l t r e a t m e n t scheme t o y i e l d s i g n i f i c a n t l e v e l s of P removal. These w i l l be d e a l t w i t h i n S e c t i o n 2.3 of t h i s c h a p t e r . F i n a l l y , the r a t i o n a l e f o r c h o o s i n g the t r e a t m e n t mode employed i n t h i s s t u d y w i l l be p r e s e n t e d , w i t h r e f e r e n c e t o the work of o t h e r r e s e a r c h e r s . 12 2.1 Mechanisms of Phosphate Uptake There are three schools of thought r e g a r d i n g the method whereby P i s removed in a b i o l o g i c a l treatment u n i t where no chemical a d d i t i o n i s p r a c t i s e d ; these i n c l u d e normal a s s i m i l a t i o n of P by the b i o l o g i c a l s o l i d s , chemical p r e c i p i t a t i o n , and luxury uptake. 2.1.1 Normal A s s i m i l a t i o n Mechanism Proponents of t h i s form of P uptake maintain that P removed v i a a given b i o l o g i c a l treatment scheme i s due to the a s s i m i l a t i o n of P ( i n the v a r i o u s forms i n which i t i s present in the wastewater s u b s t r a t e - See S e c t i o n 1.3.3) by the microorganisms i n the system. The amount a s s i m i l a t e d i s dependent on the growth requirements of the biomass ( H a l l and Engelbrecht (1967), S h e r r a r d and Shroeder (1972)). Conventional a c t i v a t e d sludge treatment i s capable of removing 20 to 30 % of the i n f l u e n t P, t y p i c a l l y y i e l d i n g approximately 3% phosphorus i n the sludge on a dry weight b a s i s (Menar and Jenkins (1970), L e v i n and Shapiro (1965)). Morgan and Fruh (1972) r e p o r t e d 2.5% P content i n sludge using a c t i v a t e d sludge .batch experiments with pH a d j u s t e d to p r e c l u d e the p o s s i b l e p r e c i p i t a t i o n of c a l c i u m phosphate. S e v e r a l r e s e a r c h e r s have found that the P content of sludges can be s i g n i f i c a n t l y g r e a t e r than the above r e p o r t e d l e v e l s . Vacker et a l . (1967) found up to 7% P c o n c e n t r a t e d i n 13 the biomass (on a dry weight b a s i s ) from a f u l l s c a l e a c t i v a t e d sludge p l a n t at San Antonio, Texas. S t u d i e s of m o d i f i e d a c t i v a t e d sludge schemes, i n c o r p o r a t i n g n i t r i f i c a t i o n and/or d e n i t r i f i c a t i o n p rocesses, have y i e l d e d up to 10% P i n the sludge (on a day weight b a s i s ) (Simpkins and McLaren (1978), Timmerman (1979)). Among o t h e r s , these r e s u l t s have prompted f u r t h e r r e s e a r c h of the P removal mechanism. 2.1.2 Chemical P r e c i p i t a t i o n Mechanism The chemical p r e c i p i t a t i o n hypothesis proposes the formation of an i n s o l u b l e c a l c i u m phosphate p r e c i p i t a t e on the a c t i v a t e d sludge f l o e d u r i n g the a e r a t i o n process and subsequent entrapment of the p r e c i p i t a t e i n the z o o g l e a l mass. Calcium in sewage may be i n the form of c a l c i u m ions, p a r t i c u l a t e s a l t s complexed with f a t t y a c i d s , and p a r t i c u l a t e or d i s s o l v e d complexes with phosphorus. Menar and Jenkins (1970) proposed that a c t i v a t e d sludge treatment encourages the i n c r e a s e of both orthophosphate and c a l c i u m i o n s . During a c t i v a t e d sludge treatment, phosphates are h y d r o l y z e d to orthophosphates, thus re n d e r i n g the bound c a l c i u m f r e e f o r the subsequent p r e c i p i t a t i o n p r o c e s s . A d d i t i o n a l c a l c i u m i s obtained from the m i c r o b i a l degradation of f a t t y a c i d s a l t s of c a l c i u m . Release of P i n the c l a r i f i e r i s proposed to be the r e s u l t of the d i s s o l u t i o n of the p r e c i p i t a t e i n the c l a r i f i e r u n i t due to carbon d i o x i d e accumulation and a subsequently lower pH (Menar and Jenkins (1970)). Supporters of t h i s mechanism propose the removal of P i s v i a the r a i s i n g of pH due to carbon d i o x i d e 14 s t r i p p i n g i n the a e r a t i o n basin which, i n schemes designed fo r the enhanced removal of P, i s u s u a l l y at an above average d i s s o l v e d oxygen l e v e l . A d d i t i o n of an a l k a l i n e s o l u t i o n to the contents of the a e r a t i o n basin has a l s o l e a d to e x c e l l e n t P removals (Menar and Jenkins (1970)). S e v e r a l r e s e a r c h e r s d i s a g r e e with t h i s c l a i m however. For example, Barnard (1975), d i d not f i n d any c o r r e l a t i o n of pH with the phosphates in the e f f l u e n t . The f l u c t u a t i o n s i n pH due to C C ^ s t r i p p i n g i n the a e r o b i c u n i t were i n c i d e n t a l in Barnard's study. Thus the pH may not have reached a high enough l e v e l f o r the m a n i f e s t a t i o n of an i n c r e a s e i n the p r e c i p i t a t i o n of phosphates by the a e r o b i c biomass. 2.1.3 Luxury Uptake Mechanism The l u x u r y uptake of P i s d e f i n e d as o c c u r r i n g when m i c r o b i a l growth i s a r r e s t e d due to the lack of a n u t r i e n t other than P and/or the lack of an energy source. In a c t i v a t e d sludge systems a l l n u t r i e n t s are i n abundant supply and organism growth i s c o n t r o l l e d by the input of energy sources (Fuhs and Chen (1975)). Researchers i n t h i s area have m o d i f i e d t h i s d e f i n i t i o n to i n c l u d e s t r e s s c o n d i t i o n s (such as a n a e r o b i o s i s ) as a l s o being capable of producing growth l i m i t i n g c o n d i t i o n s . From experiments on a c t i v a t e d sludge samples, Fuhs and Chen (1975) concluded that P s t o r e d i n the sludge i s i n the form of an a c i d - s o l u b l e g r a n u l a r polyphosphate (sometimes a l s o r e f e r r e d to as an a c i d s o l u b l e f r a c t i o n ) . I n h i b i t i o n of b i o l o g i c a l 15 phosphate accumulation with 2 , 4 - d i n i t r o p h e n o l y i e l d e d r e s u l t s which supported the b i o l o g i c a l luxury uptake mechanism. A s i n g l e organism or s e v e r a l c l o s e l y r e l a t e d forms of the genus A c i n e t o b a c t e r were i s o l a t e d and found capable of s t o r i n g h i g h l y packed m i n e r a l polyphosphates. The authors f u r t h e r determined that these microorganisms grow i n abundance under anaerobic c o n d i t i o n s . T h e i r r e s u l t s i n d i c a t e that the i n c l u s i o n of an anaerobic b a s i n at the head end of an a c t i v a t e d sludge treatment scheme would a i d the growth of f a c u l t a t i v e anaerobic b a c t e r i a . The f u n c t i o n of these organisms would be to produce an energy source i n the form of low-molecular weight i n t e r m e d i a t e s f o r the P accumulating microorganisms ( f o r example, Ac i netobacter ). The c o n v e n t i o n a l a c t i v a t e d sludge process t y p i c a l l y c o n s i s t s of o b l i g a t e aerobes which are unable to produce the intermediate compounds necessary f o r Ac i netobacter growth. A l s o , Ac i n e t o b a c t e r organisms were found incapable of u t i l i z i n g sugars or p o l y s a c c h a r i d e s and would be under heavy c o m p e t i t i o n f o r amino a c i d s i n the c o n v e n t i o n a l a c t i v a t e d sludge p r o c e s s . Thus t h e i r development would, in g e n e r a l , be suppressed. Fuhs and Chen (1975) a t t r i b u t e d the r e l e a s e of P i n the anaerobic stage to the l y s i n g of some Ac i n e t o b a c t e r c e l l s . Timmerman (1979) used s t a i n i n g techniques which i n d i c a t e d the presence of polymetaphosphate compounds (known as v o l u t i n granules) i n c e r t a i n b a c t e r i a l c e l l s . These organisms were l a r g e gram-negative c o c c i c o n t a i n i n g p o l y B-hydroxybutyrate (PHB). Phosphate storage was i n the a c i d s o l u b l e f r a c t i o n ; chromatography techniques recorded numerous ch a i n lengths of 16 polyphosphates i n the e x t r a c t . She suggested that f o r enhanced P uptake to occur, the presence of two organisms i s r e q u i r e d . The microorganisms i n the anaerobic zone would be r e s p o n s i b l e f o r the breakdown of o r g a n i c s f o r the use of a second type of organism (such as A c i n e t o b a c t e r ) a c t i v e i n the ae r o b i c r e g i o n . The l a t t e r organism was p o s t u l a t e d to be i n v o l v e d i n enhanced P and carbonaceous m a t e r i a l removal. Timmerman r e a l i z e d however, that the uptake of o r g a n i c s i n the anaerobic zone was not answered by t h i s approach alon e . I t was f u r t h e r proposed that b a c t e r i a capable of c o n t a i n i n g high c o n c e n t r a t i o n s of P are ab l e to t r a n s p o r t "food" a c r o s s t h e i r membranes i n an anaerobic environment to s a t i s f y energy and c e l l s y n t h e s i s r e a c t i o n s . The or g a n i c s which c o n s t i t u t e t h i s "food" are then a s s i m i l a t e d in the a e r o b i c environment at which p o i n t P uptake a l s o o c c u r s . The presence of PHB was a l s o i d e n t i f i e d i n the anaerobic zone by Osborn et a l . (1979). S t a i n i n g methods showed a decreased presence of polyphosphates s t o r e d i n v o l u t i n granules i n the anaerobic phase. PHB storage was not e x h i b i t e d i n the ae r o b i c zone, while poly P storage was enhanced by a e r o b i c c o n d i t i o n s . Research by Osborn. and N i c h o l l s (1977), a l s o c o n s i d e r e d the mechanism of P uptake and the mode of storage of the P w i t h i n the b a c t e r i a l c e l l . I t was noted that Ac i n e t o b a c t e r was found i n a l l treatment p l a n t s i n the Johannesburg, S.A. area which i n c o r p o r a t e d an anaerobic zone at the head end of the pro c e s s . T h i s o b s e r v a t i o n was supported by Osborn et a l . (1979) who re p o r t e d l a r g e c o n c e n t r a t i o n s of Ac i n e t o b a c t e r i n sludges from Johannesburg S.A treatment p l a n t s . Ac i n e t o b a c t e r was noted 17 by Venter et a l . (1978) t o be p r e s e n t i n g r e a t e s t c o n c e n t r a t i o n s w i t h schemes e x h i b i t i n g enhanced P uptake. The e x c l u s i v e a t t r i b u t i o n of P uptake t o the Ac i n e t o b a c t e r genus, was q u e s t i o n e d by Osborn and N i c h o l l s (1977) i n t h a t a n a e r o b i o s i s per se, and not f e r m e n t a t i o n p r o d u c t s such as a c e t i c a c i d , was deemed the i m p o r t a n t f a c t o r i n enhanced P removal schemes by t h e s e r e s e a r c h e r s . A l s o , extended a n a e r o b i o s i s d i d not a f f e c t the P removal c a p a c i t y of the biomass once a e r a t i o n was resumed. O b l i g a t e aerobes such as Ac i n e t o b a c t e r would f i n d such l o n g a n a e r o b i c p e r i o d s u n f a v o r a b l e , whereas f a c u l t a t i v e m i c r o o r g a n i s m s would e v e n t u a l l y adapt t o t h i s adverse environment. Osborn and N i c h o l l s ( 1 977), i n t h e i r s t u d y of a t r e a t m e n t scheme i n the a n a e r o b i c - a n o x i c - a e r o b i c c o n f i g u r a t i o n , a l s o proposed t h a t f a c u l t a t i v e d e n i t r i f i e r s were i n v o l v e d i n P uptake i n the a n o x i c zone. T h i s zone i s g e n e r a l l y d e f i n e d as c o n t a n i n g n i t r a t e s but b e i n g f r e e of d i s s o l v e d oxygen. However, t h i s form of uptake was s l o w e r than t h a t t y p i c a l of the a e r o b i c zone, and appeared t o cease a l t o g e t h e r upon c o m p l e t i o n of the d e n i t r i f i c a t i o n p r o c e s s . Osborn and N i c h o l l s (1977) m a i n t a i n t h a t s e v e r a l s p e c i e s of b a c t e r i a a r e i n v o l v e d i n P uptake v i a the "polyphosphate o v e r p l u s " mechanism. T h i s phenomenon, o f t e n c o n f u s e d w i t h the l u x u r y uptake mechanism, o c c u r s when m i c r o o r g a n i s m s l a c k i n g the s u p p l y of P a r e suddenly p l a c e d i n a P r i c h environment (Fuhs and Chen ( 1 9 7 5 ) ) . The "phosphate o v e r p l u s " phenomenon i s i n a p p l i c a b l e t o m u n i c i p a l wastewater t r e a t m e n t schemes s i n c e the s u p p l y of P i s g e n e r a l l y over-abundant. Osborn and 18 N i c h o l l s (1977), i n c o n f l i c t w i t h the above s t a t e m e n t , d e f i n e d the r o l e of the a e r o b i c zone as a l l o w i n g the o x i d a t i o n of both carbonaceous matter and ammonia t o o c c u r , w i t h l u x u r y uptake of P t a k i n g p l a c e towards the o u t f l o w end of t h i s zone, due t o n u t r i e n t l i m i t a t i o n . Upon e n t e r i n g the a e r o b i c r e g i o n , o b l i g a t e aerobes ( f o r example, A c i n e t o b a c t e r ) and f a c u l t a t i v e anaerobes have a d i s t u r b e d i n t e r n a l P b a l a n c e , due t o the r e l e a s e which t h e o r e t i c a l l y o c c u r r e d i n the a n a e r o b i c and/or a n o x i c zones. T h i s c o n d i t i o n s t i m u l a t e s the r a p i d a s s i m i l a t i o n of P. F u r t h e r a e r a t i o n i n d u c e s n u t r i e n t l i m i t i n g c o n d i t i o n s c o n d u c i v e t o l u x u r y uptake. Osborn and N i c h o l l s (1977) a l s o observed t h a t l o n g a e r o b i c HRT's appeared t o be b e n e f i c i a l t o the enhanced uptake of P. The l u x u r y P uptake mechanism was a l s o s u p p o r t e d by L e v i n and S h a p i r o (1965), B o r c h a r d t and Azad (1967), C o n n e l l and Vacker (1967), B a r n a r d (1976), and Y a l l et a l . (1972). 2.2 R e s u l t s and O b s e r v a t i o n s of S e l e c t e d Phosphorus Removal S t u d i e s The r e s e a r c h conducted t o date can be d i v i d e d i n t o two c a t e g o r i e s : a) t h a t concerned w i t h the o b s e r v a t i o n of enhanced P removal e f f i c i e n c i e s i n 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 schemes ( S e c t i o n 2.2.1) and b) m o d i f i e d a c t i v a t e d s l u d g e p r o c e s s e s i n c o r p o r a t i n g a n a e r o b i c and/or a n o x i c t r e a t m e n t t o p u r p o s e f u l l y enhance the removal of phosphates from wastewater ( S e c t i o n 2.2.2). 19 2.2.1 Phosphorus Removal i n C o n v e n t i o n a l A c t i v a t e d Sludge Treatment Vacker et a l . (1967) r e p o r t e d up to 96% P removal i n f u l l s c a l 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 t r e a t m e n t . These r e s e a r c h e r s recommended t h a t d i g e s t e r l i q u o r s not be r e c y c l e d t h rough the p l a n t due t o h i g h P c o n t e n t . The DO i n the a e r a t i o n b a s i n was m a i n t a i n e d a t 5 mg/L, which was adequate t o p r e c l u d e P r e l e a s e i n the c l a r i f i e r s ( a l t h o u g h the l i q u i d phase of the r e t u r n sludge was r e p o r t e d t o c o n t a i n up t o 13 mg-P/L of p h o s p h a t e s ) . High n i t r i f i c a t i o n r a t e s g e n e r a l l y c o r e l a t e d w i t h reduced P uptake i n the a e r o b i c u n i t . M i l b u r y e t a l . (1971) i n v e s t i g a t e d the removal of P i n 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 scheme. P r i m a r y e f f l u e n t o r t h o p h o s p h a t e c o n c e n t r a t i o n s f l u c t u a t e d between 7.7 and 9.7 mg-P/L w h i l e the secondary e f f l u e n t P c o n c e n t r a t i o n s were below 1 mg-P/L, w i t h removal e f f i c i e n c i e s of 89% r e a l i z e d . Orthophosphate r e l e a s e of up t o 46 mg-P/L at the head end of the a e r a t i o n tank was r e p o r t e d . S e v e r a l o p e r a t i n g parameters recommended by these r e s e a r c h e r s w i l l be d i s c u s s e d i n S e c t i o n 2.3 . S e v e r a l p r e l i m i n a r y b a t c h type s t u d i e s by S h a p i r o e t a l . (1967), on the P r e l e a s e phenomenon, i n d i c a t e d t h a t the o x i d a t i o n r e d u c t i o n p o t e n t i a l (ORP) must be low (<+150 mV) f o r r e l e a s e t o take p l a c e . The r a t e of r e l e a s e was independent of the mixed l i q u o r c o n c e n t r a t i o n and appeared t o be a r e v e r s i b l e p r o c e s s . F u r t h e r s t u d i e s showed t h a t P r e l e a s e was a l s o 20 t r i g g e r e d by the lowering of pH. Phosphorus r e l e a s e , i n the form of orthophosphates, was p o s t u l a t e d to have been from the a c i d s o l u b l e phosphorus f r a c t i o n of the sludge mass. To prevent P r e l e a s e i n the c l a r i f i e r , h igh DO l e v e l s i n the a e r o b i c u n i t and r a p i d sludge removal from the c l a r i f i e r was recommended. A review of the l i t e r a t u r e shows that enhanced P removal i n c o n v e n t i o n a l a c t i v a t e d sludge i s an u n r e l i a b l e o c c u r r e n c e . Many more i n v e s t i g a t i o n s are needed to catalogue the e f f e c t s of the v a r i a t i o n of the multitude of parameters which p l a y a r o l e in wastewater treatment on the P removal c a p a b i l i t i e s of such systems. 2.2.2 Phosphorus Removal v i a M o d i f i e d A c t i v a t e d Sludge Treatment The l a t e s t r e s e a r c h in t h i s f i e l d has been, to a la r g e degree, a South A f r i c a n endeavour. The c r i t i c a l shortage of water i n that country has spurred the need f o r economical t e r t i a r y treatment schemes. The Bardenpho (BARnard-DENitrification-PHosphorous removal) p r o c e s s , developed by J.L. Barnard i n the e a r l y 1970's, i s perhaps the most famous. T h i s process i s capable of removing up to 95% of n i t r o g e n , 97% of phosphorus and 90% of carbonaceous m a t e r i a l from wastewater v i a a b i o l o g i c a l sequence of plug-flow a c t i v a t e d sludge r e a c t o r s ; these c o n s i s t of two a l t e r n a t i n g a n o x i c - a e r o b i c u n i t s f o l l o w e d by a c l a r i f i e r . The system i s operated i n an extended a e r a t i o n mode. The o r i g i n a l Bardenpho scheme was i n v e s t i g a t e d by Barnard 21 (1974) on a 100 m3/d p i l o t p l a n t , at the Daspoort Sewage Treatment Works i n P r e t o r i a , S.A.. The i n f l u e n t COD was 300 to 600 mg/L. I n f l u e n t orthophosphates were between 5 and 8 mg-P/L. The system y i e l d e d an e f f l u e n t t o t a l P content of <1 mg-P/L. There was no problem with the s e t t l i n g of s o l i d s in the c l a r i f i e r . The system SRT was 16 to 18 days. The SRT was then i n c r e a s e d to gr e a t e r than 25 days and a MLSS content of approximately 6000 mg/L was maintained. At these o p e r a t i n g c o n d i t i o n s , the system y i e l d e d poor P uptake, and s u p e r s a t u r a t i o n of the sludge with P was blamed. An i n t e r c o n n e c t i o n between the f i n a l a e r a t i o n b a s i n and the waste sludge tank was i n e f f e c t d u r i n g t h i s p e r i o d however; t h i s may have had d e l e t e r i o u s e f f e c t s as the P r i c h sludge may have entered the a e r a t i o n b a s i n , c a u s i n g e x c e s s i v e l y high P readings. Venter et a l . (1978) r e p o r t e d enhanced P removal i n a f u l l s c a l e Bardenpho p l a n t only when the e f f l u e n t n i t r a t e l e v e l s were below 2 mg-N/L. No s i g n i f i c a n t drop i n ca l c i u m c o n c e n t r a t i o n was found through the p l a n t , thus s u p p o r t i n g the p u r e l y b i o l o g i c a l uptake mechanism as opposed to chemical p r e c i p i t a t i o n . Further o b s e r v a t i o n s were made on the treatment performance of a modi f i e d Bardenpho scheme with a c i d sludge a d d i t i o n (a source of s h o r t - c h a i n o r g a n i c s ) at the head end of the proc e s s . The r e s u l t s supported the view of Osborn and N i c h o l l s (1977) i n that both of these groups found a c i d sludge a d d i t i o n (designed to st i m u l a t e anaerobic c o n d i t i o n s at the head end of the scheme) of no b e n e f i t . Orthophosphate r e l e a s e of up to 100 mg-P/L was rep o r t e d by Venter et a l . (1978) at the head (anaerobic) end of. 22 the p r o c e s s . The s l u d g e f i l t r a t e of the scheme, which d i d not employ a c i d s l u d g e a d d i t i o n , c o n t a i n e d up t o 700 mg/L of a c e t i c a c i d . P r o l o n g e d p e r i o d s of a n a e r o b i o s i s were found not t o be o p t i m a l f o r the removal of P through the p l a n t . Enhanced P removal was accompanied by low n i t r i f i c a t i o n r a t e s i n the a e r o b i c zone. E f f l u e n t n i t r a t e l e v e l s below 5 mg-N/L were found t o y i e l d a system c a p a b l e of removing the g r e a t e s t amount of P. These r e s e a r c h e r s deemed n e c e s s a r y the i n c l u s i o n of an a n a e r o b i c zone i n a P removing t r e a t m e n t scheme. Subsequent t o h i s i n i t i a l r e s e a r c h , B a r n a r d proposed the a d d i t i o n of an a n a e r o b i c r e a c t o r e i t h e r at the head end of the Bardenpho scheme, t o c o n d i t i o n the biomass f o r enhanced P removal ( r e f e r r e d t o as the M o d i f i e d Bardenpho P r o c e s s ) , or s i m p l y p r i o r t o an a e r o b i c b a s i n i n which n i t r i f i c a t i o n i s s u p p r e s s e d . Both t h e s e schemes were termed Phoredox by B a r n a r d (1976). T h i s p r i n c i p l e i n v o l v e d a h i g h s l u d g e r e c y c l e r a t e , s i n c e the n i t r a t e c o n t e n t i n the s l u d g e of such systems would be t y p i c a l l y low. The s l u d g e r e t u r n was t o be mixed w i t h the fe e d a t the head end of t h e t r e a t m e n t scheme, and then f l o w i n t o the a n a e r o b i c r e a c t o r where phosphorus r e l e a s e would t h e o r e t i c a l l y o c c u r . The mixed l i q u o r would then pass on t o e i t h e r a s t a n d a r d Bardenpho p l a n t f o r d e n i t r i f i c a t i o n or a s i m p l e a e r a t i o n b a s i n i f n i t r i f i c a t i o n i s not a problem. N i c h o l l s (1975) c o n f i r m e d the e f f e c t i v e n e s s of the Phoredox p r i n c i p l e d u r i n g f u l l s c a l e o p e r a t i o n a t the A l e x a n d r a P l a n t ( S . A . ) . Waste s l u d g e was a l l o w e d t o go a n a e r o b i c and was r e c i r c u l a t e d t o the head end of the a e r a t i o n b a s i n . The mixed l i q u o r d i s s o l v e d P c o n t e n t dropped 23 to 0.3 mg-P/L. Some r e - s o l u t i o n of P occur r e d i n the c l a r i f i e r as a r e s u l t of accumulating sludge. The system h y d r a u l i c r e t e n t i o n time was 27 hours. P i l o t s c a l e s t u d i e s by Simpkins (1979) on the modified Bardenpho scheme, i n d i c a t e d that raw sewage COD l e v e l s , although higher than that of s e t t l e d sewage, d i d not y i e l d a p p r e c i a b l y higher P removals. During the p e r i o d of study the AP/ACOD r a t i o s were 0.011 and 0.017 f o r the raw and s e t t l e d i n f l u e n t phases r e s p e c t i v e l y . These r a t i o s are lower than those t y p i c a l l y c orresponding to enhanced P removal. R a t i o s of AP/ACOD of approximately 0.020 y i e l d e d g r e a t e r than 86% P removal i n the study of Simpkins and McLaren (1978). Osborn et a l . (1979) repo r t e d that the enhanced removal of P corresponded to high i n f l u e n t COD l e v e l s i n t h e i r i n v e s t i g a t i o n of the Goudkoppies Works, Johannesburg (S.A.), operated i n the m o d i f i e d Bardenpho mode. These r e s e a r c h e r s c l a i m e d that high n i t r a t e c o n c e n t r a t i o n s d i d not always y i e l d poor process P removal e f f i c i e n c i e s . High DO in the re t u r n sludge appeared to lower the degree of a n a e r o b i o s i s i n the anaerobic zone. Up to 24 mg-P/L r e l e a s e was repor t e d and i t was noted that high r e l e a s e r a t e s corresponded to a low sludge r e t u r n flow. Phosphorus r e l e a s e was observed when e f f l u e n t n i t r a t e c o n c e n t r a t i o n s were below 1 mg-N/L, and was found to be a p r e r e q u i s i t e f o r P removal. The extent of a n a e r o b i o s i s i n the scheme s t u d i e d by Osborn et a l . (1979) was q u e s t i o n a b l e s i n c e t y p i c a l anaerobic r e a c t o r ORP va l u e s were r e p o r t e d as +35 mV. 24 The primary anoxic zone was found to be i n v o l v e d both in d e n i t r i f i c a t i o n and P uptake by these r e s e a r c h e r s . I t was proposed that d e n i t r i f y i n g b a c t e r i a a l s o f u n c t i o n i n a P removal c a p a c i t y . Filamentous organisms p r o l i f e r a t e d when the aerated f r a c t i o n of the system was reduced, y i e l d i n g poor sludge s e t t l i n g c h a r a c t e r i s t i c s . S u b j e c t i n g the e n t i r e treatment plant to a n a e r o b i o s i s f a i l e d to e l i m i n a t e these types of organisms. Poor c l a r i f i e r sludge s e t t l i n g was blamed on o v e r a e r a t i o n i n the secondary a e r a t i o n b a s i n , as w e l l as on high n i t r a t e s (causing d e n i t r i f i c a t i o n with subsequent sludge r i s i n g problems). Dew (1979) s t u d i e d the m o d i f i e d Bardenpho scheme under temperature v a r i a b i l i t y . His r e s u l t s i n d i c a t e P removal i s not a f u n c t i o n of temperature and obtained an o v e r a l l average P removal of 89% (approximately 6.7 mg/L t o t a l P removal based on the average i n f l u e n t t o t a l P c o n c e n t r a t i o n of 7.5 mg/L). The SRT was t y p i c a l l y long, as r e q u i r e d by n i t r o g e n removing systems, ranging from 15 days t o 98 days. Simpkins and McLaren (1978) a l s o i n v e s t i g a t e d a modified Bardenpho p i l o t p l a n t . With an SRT of 15 days, P removal was g r e a t e r than 86%, except when a high mixed l i q u o r r e c y c l e r a t e was i n e f f e c t . The luxury uptake mechanism was supported and i t was c a l c u l a t e d t hat the high P removals c o u l d not have been e x p l a i n e d s o l e l y by the p h y s i c a l - c h e m i c a l p r e c i p i t a t i o n theory of Menar and Jen k i n s (1970). The anaerobic r e l e a s e of P was found to vary with the i n f l u e n t COD c o n c e n t r a t i o n . R a t i o s of AP/ACOD from 0.014 to 0.021 were repor t e d , based on the t o t a l P 25 content of u n f i l t e r e d feed and orthophosphate c o n c e n t r a t i o n s i n f i l t e r e d e f f l u e n t samples. The rate of P uptake i n the a e r o b i c zone was d i r e c t l y p r o p o r t i o n a l to the ra t e of r e l e a s e i n the anaerobic stage. Uptake occurred i n the i n i t i a l anoxic stage and tended to compete with the a e r o b i c stage f o r P. L i t t l e f l u c t u a t i o n of pH was observed. The MLVSS:MLSS r a t i o was 0.70 dur i n g p e r i o d s of enhanced P removal by the p i l o t p l a n t of that study. A r a t i o of 0.85 was obtained at the VCSD Water Reclamation P l a n t , San Ramon, C a l i f o r n i a where phosphorus uptake was t y p i c a l of a c t i v a t e d sludge treatment (Menar and Jenkins (1970)). The average COD of the feed v a r i e d from 250 to 315 mg/L with COD percentage removals exceeding 90%. E f f l u e n t n i t r a t e l e v e l s were t y p i c a l l y l e s s than 5 mg-N/L du r i n g p e r i o d s of s i g n i f i c a n t P removal. Although the t e s t i n g schedule used i n t h i s r e s e a r c h was e x t e n s i v e , (24 hour composite samples were analysed d a i l y ) , and a la r g e data base was compiled, f l u c t u a t i o n s were a problem. Pitman (1980) r e p o r t s e f f l u e n t orthophosphate r e s u l t s from three South A f r i c a n sewage treatment p l a n t s . Data from the Alexandra and O l i f a n t s v l e i p l a n t s i n the Johannesburg (S.A.) area, i n d i c a t e that at comparable i n f l u e n t COD l e v e l s (240 to 820 mg/L),- and a s i m i l a r o p e r a t i n g scheme (a lack of a e r a t i o n at the head end of both treatment p l a n t s ) , enhanced P removal occ u r r e d only at the O l i f a n t s v l e i p l a n t where the SRT was 15 to 20 days. The Alexandra p l a n t SRT was 11 to 15 days. L i m i t e d data i s a l s o presented f o r the Goudkoppies Bardenpho scheme operated at a SRT of between 20 and 22 days. E f f l u e n t n i t r a t e l e v e l s were 26 below 4 mg/L and i n f l u e n t COD ranged from 320 t o 350 mg/L. Phosphorus removals i n the range of 60% were r e p o r t e d d u r i n g the s h o r t s a m p l i n g p e r i o d . The da t a g i v e n does not d i s t i n g u i s h f i l t e r e d from u n f i l t e r e d samples. Pitman (1980), a l s o s t u d i e d the s e t t l i n g c h a r a c t e r i s t i c s of s l u d g e s , when >20% of a p l a n t c o n s i s t s of a n a e r o b i c and/or a n o x i c zones. The r e a s e r c h r e s u l t s y i e l d e d the c o n c l u s i o n t h a t b u l k i n g i n the c l a r i f i e r i s a p o s s i b l e o c c u r r e n c e due t o the a c t i v e growth of f i l a m e n t o u s organisms. Jank e t a l . (1978) a c h i e v e d h i g h P removal e f f i c i e n c i e s i n a p i l o t system o p e r a t e d i n a d e n i t r i f i c a t i o n - n i t r i f i c a t i o n mode, i n c l u d i n g mixed l i q u o r r e c y c l e and methanol a d d i t i o n . The SRT's s t u d i e d were: 5, 10, and 23 days a t 7.5, 15, and 25°C r e s p e c t i v e l y . A system was a l s o i n v e s t i g a t e d w i t h o u t methanol a d d i t i o n and o p e r a t e d a t s l i g h t l y lower SRT's of 4, 8, and 18 days. These a u t h o r s d e t e r m i n e d t h a t enhanced P removal o c c u r r e d i n schemes which employed d e n i t r i f i c a t i o n a t the head end of the system, c o u p l e d w i t h a h i g h i n f l u e n t COD and p e r i o d s of h i g h COD p e r c e n t a g e removals. A l t h o u g h enhanced P removal was r e p o r t e d a t h i g h AP/ACOD r a t i o s , the systems i n v e s t i g a t e d d i d not va r y t o an a p p r e c i a b l e degree, i n terms of t h e i r removal c a p a b i l i t i e s , t o warrant such an o b s e r v a t i o n . In f a c t , a t s i m i l a r o p e r a t i n g c o n d i t i o n s , a g r e a t e r AP/ACOD r a t i o was r e a l i z e d w i t h the scheme which d i d not f a r e as w e l l i n terms of e f f l u e n t P c o n c e n t r a t i o n s than d i d the set-up which i n c l u d e d the a d d i t i o n of methanol. These r e s e a r c h e r s a l s o found t h a t the v a r i a t i o n i n the P c o n t e n t of the s l u d g e was n e g l i g i b l e a t SRT's r a n g i n g from a p p r o x i m a t e l y 27 3 t o 24 days. An a n a e r o b i c stage a t the head end of a treatment scheme was found t o have c o n f l i c t i n g e f f e c t s on the c a p a b i l i t y of the subsequent a e r o b i c stage t o remove h i g h p e r c e n t a g e s of P. M a r a i s (1979a) m a i n t a i n e d t h a t the Bardenpho scheme i s not o p t i m a l f o r the removal of P because of i t s dependency on low TKN:COD r a t i o s . He proposed an a n a e r o b i c - a n o x i c - a e r o b i c sequence i n c o r p o r a t i n g b oth a n o x i c mixed l i q u o r r e c y c l e t o the a n a e r o b i c r e a c t o r and the " c o n v e n t i o n a l " a e r o b i c t o a n o x i c r e c y c l e . Sludge r e t u r n was t o the a n o x i c r e a c t o r . T h i s scheme was c i t e d as ha v i n g a g r e a t e r f l e x i b i l i t y than the Bardenpho i n terms of P removal i n t h a t the TKN/COD f l u c t u a t i o n s i n the i n f l u e n t d i d not d i s r u p t the e f f i c i e n c y of P removed by the p r o c e s s . Maximum a n a e r o b i c s l u d g e mass f r a c t i o n s were a l s o p r e s e n t e d as g u i d e l i n e s t o p r e v e n t i n e f f i c i e n t n i t r i f i c a t i o n i n such schemes. E f f i c i e n c i e s of P removal by the p r o c e s s were not p r e s e n t e d however. MacLaren and Wood (1976) s t u d i e d the P r e l e a s e phenomenon u s i n g a l a b o r a t o r y t r e a t m e n t model i n an a n a e r o b i c - a n o x i c - a e r o b i c c o n f i g u r a t i o n . A SRT of 15 days was m a i n t a i n e d a t an o p e r a t i n g t e m p e r a t u r e of 20°C. An average of 11.4 mg-P/L of o r t h o p h o s p h a t e s was r e c o r d e d i n the a n a e r o b i c u n i t , which was o n l y s l i g h t l y h i g h e r than the f e e d c o n c e n t r a t i o n . P uptake i n t h e a e r o b i c r e a c t o r began i m m e d i a t e l y , y i e l d i n g o r t h o p h o s p h a t e c o n c e n t r a t i o n s of 0.1 mg-P/L i n t h i s u n i t . The e f f l u e n t o r t h o p h o s p h a t e s were r e p o r t e d as 0.4 mg-P/L, i n d i c a t i n g s l i g h t r e l e a s e i n the c l a r i f i e r . The 28 AP/ACOD r a t i o d u r i n g l a b o r a t o r y t e s t i n g was 0.019. F u r t h e r p i l o t p l a n t s t u d i e s by the s e r e s e a r c h e r s , on a m o d i f i e d Bardenpho scheme y i e l d e d no P r e l e a s e when the HRT of the a n a e r o b i c r e a c t o r was m a i n t a i n e d a t 2 h o u r s . I n c r e a s i n g the a n a e r o b i c b a s i n HRT t o 4 hours caused r e l e a s e of up t o 4 mg-P/L and subsequent uptake t o l e v e l s t y p i c a l l y below 1 mg/L t o t a l P. The o p e r a t i n g SRT was 25 days. A drop of SRT t o 15 days d i d not have any d e t r i m e n t a l e f f e c t s i n terms of P remo v a l . The removal of the f i r s t a n o x i c b a s i n from the system, as w e l l as r e t u r n i n g the a n a e r o b i c r e a c t o r t o a 1 hour HRT, d i d not cause a r e d u c t i o n i n the P removal e f f i c i e n c y . F u r t h e r b a t c h e x p e r i m e n t s by these r e s e a r c h e r s s u p p o r t e d the b i o l o g i c a l or l u x u r y P uptake mode. Phosphorus was removed i n the presence of n i t r a t e s and a e r a t i o n . P o p u l a t i o n s e l e c t i o n was c i t e d as the reason f o r the l a c k of P removal i n the i n i t i a l p i l o t p l a n t s t u d i e s . T h i s c o n c l u s i o n c o n f l i c t s w i t h the r e s u l t s r e p o r t e d f o r the bench s c a l e s t u d i e s c onducted by McLaren and Wood (1976), where immediate P removal was o b s e r v e d . Fuhs and Chen (1975) a l s o s u p p o r t e d the requirement f o r an a c c l i m a t i o n p e r i o d t o encourage the a c c u m u l a t i o n of P removing m i c r o o r g a n i s m s . Osborn and N i c h o l l s (1977) i n v e s t i g a t e d the o p e r a t i o n of a p i l o t p l a n t i n an a n a e r o b i c - a n o x i c - a e r o b i c c o n f i g u r a t i o n . The system SRT was 25 days. P i l o t s c a l e s t u d i e s y i e l d e d no improvement i n P removal when a c i d s l u d g e was added t o the tr e a t m e n t p r o c e s s a t the a n a e r o b i c s t a g e . A d d i t i o n of a c e t i c a c i d t o the a n o x i c zone was a l s o found unadvantageous. An a n a e r o b i c zone was deemed i n d i s p e n a b l e f o r the development of 29 v o l u t i n g r a n u l e s i n b a c t e r i a . A comprehensive l i s t of v o l u t i n f o r m i n g b a c t e r i a was p r e s e n t e d i n t h a t r e p o r t . H i g h P removal was a s s o c i a t e d w i t h h i g h MLSS l e v e l s , s i n c e t h i s c o n d i t i o n l e d t o a g r e a t e r c o n c e n t r a t i o n of v o l u t i n c o n t a i n i n g b a c t e r i a . Osborn and N i c h o l l s (1977) agreed t h a t n i t r a t e s must be absent from the a n a e r o b i c zone f o r enhanced P uptake a c r o s s the p l a n t t o o c c u r . I t was proposed t h a t t h i s c o n d i t i o n would m i n i m i z e oxygen a v a i l a b i l i t y t o the d e n i t r i f y i n g s p e c i e s c a u s i n g the r e l e a s e of P through c a t a l y s i s by the enzyme p o l y p h o s p h a t a s e , t h u s a l l o w i n g the a c t i v a t i o n of t h e enzyme p o l y p h o s p h a t e k i n a s e i n P - s t o r i n g b a c t e r i a f o r subsequent uptake of P i n the a e r o b i c r e a c t o r . A maximum n i t r a t e l e v e l of 2 mg-N/L i n the e f f l u e n t from the a e r a t i o n b a s i n was s u g g e s t e d , which c o u l d be a c h i e v e d w i t h s u f f i c i e n t MLSS r e c y c l e t o the a n o x i c r e a c t o r . I n c r e a s i n g the a n a e r o b i c HRT l e a d t o i n c r e a s e d P l e v e l s i n t h i s zone. P e r i o d s g r e a t e r than 2 hours were suggested as h a v i n g p o s s i b l e d e t r i m e n t a l e f f e c t s on the growth of v o l u t i n f o r m i n g b a c t e r i a , which the g e n e r a l consensus i s , a r e e i t h e r s t r i c t or f a c u l t a t i v e a e r o b e s . R e l e a s e of 5 mg-P/L was found t o be adequate f o r subsequent enhanced P uptake i n the a e r o b i c r e a c t o r . Fuhs and Chen (1975) c o u l d not induce P uptake w i t h o u t p r e v i o u s P r e l e a s e under a n a e r o b i c c o n d i t i o n s . The a n a e r o b i c phase per se may not be r e s p o n s i b l e f o r the t r i g g e r i n g of the P r e l e a s e mechanism; h i g h C O 2 c o n c e n t r a t i o n s and a low pH were suggested as imp o r t a n t f a c t o r s . They r e p o r t e d t h a t P r e l e a s e c o u l d be in d u c e d by b u b b l i n g of carbon d i o x i d e t h r o u g h the mixed l i q u o r of the a n a e r o b i c r e a c t o r . However, Osborn and N i c h o l l s 30 (1977) r e p o r t e d t h a t once t h i s " f o r c e d " r e l e a s e o c c u r r e d , subsequent uptake under a e r o b i c c o n d i t i o n s was not r e a l i z e d . H igh DO i n the i n f l u e n t t o the c l a r i f i e r was recommended by Osborn and N i c h o l l s (1977) t o a v o i d a n a e r o b i o s i s , and hence P r e l e a s e , from d e v e l o p i n g i n the s l u d g e b l a n k e t . However, a e r o b i c HRT's l e s s than 4 hours were recommended t o d i s c o u r a g e the c o n t i n u a t i o n of the r e s p i r a t i o n p r o c e s s e s i n the c l a r i f i e r , which were r e p o r t e d t o cause the r e l e a s e of P. L e v i n (1972), proposed a p l u g - f l o w u n i t (known as the P h o - s t r i p p r o c e s s ) which i n c o r p o r a t e d p r i n c i p l e s s i m i l a r t o those proposed by B a r n a r d i n the Phoredox p r o c e s s , except t h a t the c l a r i f i e r u n d e r f l o w was t h i c k e n e d i n L e v i n ' s o p e r a t i o n . T h i c k e n i n g induced a n a e r o b i o s i s , c a u s i n g P t o be r e l e a s e d i n t o the s u p e r n a t a n t which was d e c a n t e d and underwent l i m e p r e c i p i t a t i o n . The t h i c k e n e d a n a e r o b i c s l u d g e was then r e t u r n e d t o the head end of an a e r a t i o n b a s i n . B a r n a r d (1976) c l a i m e d t h a t t h e e s s e n t i a l p a r t of t h i s s t r i p p i n g o p e r a t i o n i s the c r e a t i o n of a n a e r o b i c c o n d i t i o n s i n the s l u d g e and proposed t h a t a p p r o p r i a t e s l u d g e w a s t i n g would remove the P from the system. Vacker et a l . (1967), M i l b u r y e t a l . (1971), and Garber (1972), a l s o a g r e e d t h a t s t r i p p i n g i s an unnecessary o p e r a t i o n . L e v i n ' s r e s u l t s i n d i c a t e t h a t of the P removed, o n l y 25 % i s removed from the system v i a s t r i p p i n g ; the r e m a i n i n g 75% b e i n g removed i n the waste s l u d g e . Timmerman (1979) r e p o r t e d on the s t u d i e s undertaken by A i r P r o d u c t s and C h e m i c a l s , I n c . , u s i n g l a b o r a t o r y s c a l e u n i t s 31 operated i n the a n a e r o b i c - a e r o b i c c o n f i g u r a t i o n . Phosphorus r e l e a s e g r e a t e r than 13 mg-P/L wat noted i n the anaerobic r e a c t o r when the nominal HRT i n t h i s u n i t was maintained at 1.0 hour. Release was found t o be a p r e r e q u i s i t e f o r P uptake. N i t r a t e s i n the o x i c u n i t were not found to be d e t r i m e n t a l to the P uptake mechanism. Only s l i g h t r e l e a s e of P o c c u r r e d i n the c l a r i f i e r . F l u c t u a t i o n s i n i n f l u e n t P c o n c e n t r a t i o n s d i d not a l t e r the high e f f i c i e n c y of removal, once t h i s had been e s t a b l i s h e d (approximately 14 weeks a f t e r s t a r t - u p ) . Due to t h i s lengthy p e r i o d at the beginning of the experiments, where P removal was not i n e f f e c t , the author suggested that ample time must be allowed f o r the development of the necessary P removing organisms. B i o l o g i c a l uptake was supported by a low MLVSS:MLSS r a t i o ( i n the 0.70 range), i n d i c a t i n g that a l a r g e p o r t i o n of the sludge was i n o r g a n i c . The system SRT was not r e p o r t e d . 2.3 Operating C o n d i t i o n s Required f o r P Removal T h i s s e c t i o n w i l l l i s t the c o n d i t i o n s which have become widely accepted as r e q u i r e d f o r the occurance of enhanced P removal i n m o d i f i e d a c t i v a t e d sludge treatment schemes: (a) Plug flow c o n d i t i o n s are one p r e r e q u i s i t e . Barnard (1976) recommends a l e n g t h to width r a t i o of 20:1. M i l b u r y et a l . (1971) obtained P removals i n the 50% range with a bench s c a l e a c t i v a t e d sludge u n i t employing the p l u g flow mode. The e f f e c t i v e n e s s of t h i s mode i s a l s o supported with o b s e r v a t i o n s by Vacker et a l . (19.67), L e v i n et a l . (1972), and Garber (1972). 32 (b) A l l b a s i n s must be c o m p l e t e l y mixed ( B ' r n a r d ( 1 9 7 6 ) ) . (c) The d i s s o l v e d oxygen i n the f i n a l a e r a t i o n b a s i n , p r i o r t o c l a r i f i c a t i o n must be g r e a t e r than i s t y p i c a l f o r 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 t r e a t m e n t . G e n e r a l l y 3 t o 4 mg/L are recommended to a v o i d P r e l e a s e i n the c l a r i f i e r u n i t due t o the onset of a n a e r o b i o s i s i n the s l u d g e b l a n k e t (Vacker et a l . (1967), M i l b u r y et a l . (1971), L e v i n et a l . (1972), Garber (1972), and B a r n a r d ( 1 9 7 6 ) ) . High d i s s o l v e d oxygen i n the f i n a l a e r a t i o n b a s i n a l s o causes carbon d i o x i d e s t r i p p i n g from the mixed l i q u o r , thus i n c r e a s i n g the pH and e n c o u r a g i n g the p o s s i b l e p r e c i p i t a t i o n of P out of s o l u t i o n (Menar and J e n k i n s ( 1 9 7 0 ) ) . B a r n a r d (1976) however, u s i n g a p l u g flow c o m p a r t a m e n t a l i z e d a e r a t e d u n i t , r e p o r t s no improvement i n the P removal e f f i c i e n c y when a l i m e s l u r r y was added t o i n c r e a s e the pH of the mixed l i q u o r t o 8.5. The s e t t l i n g c h a r a c t r i s t i c s i n the c l a r i f i e r a r e a l s o enhanced by h i g h d i s s o l v e d oxygen l e v e l s i n f l u e n t t o t h i s u n i t i n t h a t d e n i t r i f i c a t i o n i s l e s s l i k e l y t o o c c u r , thus m i n i m i z i n g the problem of r i s i n g s l u d g e ( B a r n a r d ( 1 9 7 6 ) ) . D i s s o l v e d oxygen c o n t r o l i s i n g e n e r a l more d i f f i c u l t w i t h bench s c a l e u n i t s than i n f u l l s c a l e o p e r a t i o n s . S m a l l f l u c t u a t i o n s i n the compressed a i r s u p p l y t e n d t o have s i g n i f i c a n t e f f e c t s on the former ( B a r n a r d ( 1 9 7 6 ) ) . (d) N i t i r i f i c a t i o n s h o u l d be m i n i m i z e d as i t c o n t r i b u t e s to h i g h n i t r a t e c o n c e n t r a t i o n s b e i n g r e t u r n e d t o the a n a e r o b i c 33 r e a c t o r , thus r e d u c i n g the degree of P removal. E x c e l l e n t P removal d u r i n g p e r i o d s of low n i t r a t e c o n c e n t r a t i o n s i n the e f f l u e n t was c o n f i r m e d by B a r n a r d (1976). I t must be noted t h a t w h i l e poor phosphorus removal e f f i c i e n c i e s were m a n i f e s t e d s i m u l t a n e o u s l y w i t h a h i g h n i t r i f i c a t i o n r a t e , feed f l o w f l u c t u a t i o n s and e x c e s s i v e d i s s o l v e d oxygen l e v e l s i n the a e r o b i c b a s i n were a l s o a norm. A h i g h n i t r a t e c o n t e n t i n t h i s b a s i n was c o u p l e d w i t h a low P removal e f f i c i e n c y . I t appears t h a t o t h e r forms of n i t r o g e n ( f o r example, ammonia) have no e f f e c t on P removal ( B a r n a r d ( 1 9 7 6 ) ) . In f u l l s c a l 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 t r e a t m e n t , n i t r i f i c a t i o n a c t i v i t y i s , i n g e n e r a l , i n s i g n i f i c a n t s i n c e s l u d g e r e c y c l e r a t i o s are i n the o r d e r of 0.25 (Vacker et a l . (1967), M i l b u r y e t a l . (1971), L e v i n e t a l . (1972), and Garber ( 1 9 7 2 ) ) . A l s o , the f e e d t o f u l l s c a l e o p e r a t i o n s o f t e n a r r i v e s i n a s e p t i c s t a t e , e n c o u r a g i n g the r e a c t i o n of n i t r a t e s i n the r e t u r n sludge w i t h reduced s u b s t a n c e s i n the f e e d . Of c o u r s e , f l u c t u a t i o n s i n the degree of a n a e r o b i o s i s of the f e e d would t r i g g e r e r r a t i c P removal e f f i c i e n c i e s i n a g i v e n system. (e) Reducing c o n d i t i o n s a r e r e q u i r e d at the head end of the t r e a t m e n t scheme. A n a e r o b i o s i s has been found t o y i e l d the r e l e a s e of P which i s a p r e r e q u i s i t e of P removal ( M i l b u r y e t a l . ( 1 9 7 1 ) ) . These r e s e a r c h e r s a l s o c l a i m e d t h a t P uptake was a r e l a t i v e l y slow p r o c e s s . B a r n a r d (1976) r e p o r t e d t h a t P r e l e a s e i s not always a consequence of a n a e r o b i c c o n d i t i o n s . He s u g g e s t e d t h a t the o x i d a t i o n r e d u c t i o n p o t e n t i a l (ORP) may p l a y an i m p o r t a n t r o l e i n the P r e l e a s e phenomenon and t h a t a t some 34 minimum ORP l e v e l P r e l e a s e o c c u r s . Care must be e x e r c i s e d not t o reach such a low ORP t h a t s u l p h a t e s a r e reduced, thus y i e l d i n g odor problems ( B a r n a r d ( 1 9 7 6 ) ) . Barnard's r e s e a r c h i n d i c a t e s t h a t the r e l e a s e of P l e a d s t o subsequent P removal i n the a e r o b i c zone ( B a r n a r d ( 1 9 7 4 ) ) . Complete a n a e r o b i o s i s appears t o be e s s e n t i a l such t h a t the a p p r o p r i a t e s t r e s s c o n d i t i o n s are m a n i f e s t e d . For t h i s reason the i n f l o w of n i t r a t e s to the a n a e r o b i c zone must be c u r t a i l e d i n o r d e r t h a t the ORP i s m a i n t a i n e d at a s u f f i c i e n t l y low l e v e l . M i l b u r y e t a l . (1971) o b t a i n e d P c o n c e n t r a t i o n s of 30 mg-P/L i n f i l t e r e d samples from the a n a e r o b i c end of the t r e a t m e n t scheme s t u d i e d . Fuhs and Chen (1975) s t a t e d t h a t the a n a e r o b i c phase per se d i d not n e c e s s a r i l y s t i m u l a t e P r e l e a s e ; the a c c u m u l a t i o n of carbon d i o x i d e and the r e s u l t i n g low pH were c i t e d as p o s s i b l y h a v i n g an i n f l u e n c e on the r e l e a s e phenomenon. I t was s u g g e s t e d , by t h e s e r e s e a r c h e r s , t h a t the a n a e r o b i c stage may be r e q u i r e d f o r the p r o d u c t i o n of an a p p r o p r i a t e carbon source (by f a c u l t a t i v e anaerobes) which i s r e q u i r e d f o r the growth of P - a c c u m u l a t i n g organisms. P r e l e a s e i n the a n a e r o b i c stage i s a p o s s i b l e r e s u l t of l y s i n g of the P r i c h m i c r o o r g a n i s m s under t h e s e s t r e s s f u l c o n d i t i o n s (Fuhs and Chen ( 1 9 7 5 ) ) . ( f ) The r e t u r n s l u d g e s h o u l d be mixed w i t h the feed (raw or s e t t l e d sewage) at the head end of the p l a n t t o encourage a h i g h oxygen demand, thus improved a n a e r o b i c c o n d i t i o n s (Vacker et a l . (1967), M i l b u r y et a l . (1971), Garber ( 1 9 7 2 ) , L e v i n e t a l . 35 (1972), and B a r n a r d (1976). (g) The b u i l d u p of s o l i d s i n the c l a r i f i e r must be a v o i d e d t o p r e v e n t P r e l e a s e , r e s u l t i n g from a n a e r o b i c c o n d i t i o n s of the sl u d g e ( B a r n a r d ( 1 9 7 4 ) ) . (h) The s u p e r n a t a n t from the sludge d i g e s t e r s s h o u l d not be r e t u r n e d t o the t r e a t m e n t p l a n t because of the h i g h phosphorus c o n c e n t r a t i o n u s u a l l y p r e s e n t t h e r e i n (Vacker e t a l . (1967), M i l b u r y et a l . (1971), Garber (1972), Y a l l et a l . (1972), and L e v i n et a l . (1972)) . ( i ) Garber (1972) proposed t h a t a r e l a t i v e l y h i g h C:P r a t i o i s r e q u i r e d f o r the e s t a b l i s h e m e n t of enhanced P removal c o n d i t i o n s . When the i n f l u e n t carbon c o n t e n t i s h i g h , a h i g h oxygen demand i s e x e r t e d a t the head end of the tre a t m e n t scheme, thus a l l o w i n g a n a e r o b i o s i s t o be e s t a b l i s h e d r a p i d l y and t o a h i g h e r degree than w i t h a low i n f l u e n t carbon c o n t e n t . 2.4 Research R a t i o n a l e - T h i s Work Based on the p r i n c i p l e s d i s c u s s e d e a r l i e r i n t h i s c h a p t e r , a system " d e s i g n e d " f o r the enhanced removal of P was b u i l t and s t u d i e d a t the E n v i r o n m e n t a l E n g i n e e r i n g L a b o r a t o r y a t the U n i v e r s i t y of B r i t i s h C o lumbia. I n i t i a l l y the model c o n s i s t e d of two r e a c t o r s ( 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 ) . The t h e o r y r e g a r d i n g the P removal c a p a b i l i t i e s of t h i s system was based t o a g r e a t e x t e n t on the Phoredox p r i n c i p l e d e s c r i b e d by Barnard ( 1 9 7 6 ) . E s s e n t i a l l y , a n a e r o b i c c o n d i t i o n s were t o be c r e a t e d at 36 the i n f l u e n t end of the system, f o l l o w e d by a p e r i o d of a e r o b i c uptake. Both the sewage f e e d , and the sludge r e t u r n were t o e n t e r the system v i a the a n a e r o b i c zone. N i t r i f i c a t i o n was t o be c u r t a i l e d by m a i n t a i n i n g a low sl u d g e age. The system was then t o be m o n i t o r e d w h i l e o p e r a t i o n a l changes were implemented. The aim of t h i s study was t o make c e r t a i n o p e r a t i o n a l changes t o the system, observe the r e s u l t s i n terms of P removal, and make subsequent m o d i f i c a t i o n s t o improve the e f f i c i e n c y of t h i s removal. Chapter 3 w i l l d e a l w i t h the d e t a i l s of the p h y s i c a l and o p e r a t i o n a l c h a r a c t e r i s t i c s of the system. The r e s u l t s o b t a i n e d w i l l be d i s c u s s e d i n C h a p t e r s 4 and 5. C o n c l u s i o n s and recommendations d e r i v e d from t h i s study a r e p r e s e n t e d i n Chapter 6. 37 CHAPTER 3 EXPERIMENTAL SYSTEM AND PROCEDURES T h i s c h a p t e r d e s c r i b e s the p h y s i c a l and o p e r a t i o n a l c h a r a c t e r i s t i c s of the system used i n t h i s s t u d y , and p r e s e n t s the s ampling p r o c e d u r e s , and sample a n a l y s i s t e c h n i q u e s used. System s t a r t - u p , m o n i t o r i n g p r o c e d u r e s , and v a r i o u s m o d i f i c a t i o n s are d i s c u s s e d . 3.1 P h y s i c a l System C h a r a c t e r i s t i c s The system was i n i t i a l l y d e s i g n e d f o r the e f f i c i e n t removal of phosphates from m u n i c i p a l wastewater, based on i n f o r m a t i o n o b t a i n e d from o t h e r r e s e a r c h (See Chapter 2 ) . Two e n v i r o n m e n t a l l y c o n t r o l l e d rooms were employed; one was m a i n t a i n e d a t 4° C t o f a c i l i t a t e l e n g t h y p e r i o d s of raw sewage s t o r a g e ( S e c t i o n 3.2.1), and another t o house the t r e a t m e n t system a t t e m p e r a t u r e s which c o u l d be i n d e p e n d e n t l y c o n t r o l l e d . I n i t i a l l y the t r e a t m e n t scheme c o n s i s t e d of two r e a c t o r s (an a n a e r o b i c f o l l o w e d by an a e r o b i c ) and a c l a r i f i e r . A t h i r d s l u d g e c o n d i t i o n i n g r e a c t o r was added a t a l a t e r date f o r reasons d i s c u s s e d i n S e c t i o n 4.2.2. The o r i g i n a l c l a r i f i e r p r oved t o be i n e f f i c i e n t i n terms of suspended s o l i d s removal and was s u b s t i t u t e d f o r by another model h a l f way t h r o u g h the s t u d y ( S e c t i o n 4.2.3). 38 A l l components were b u i l t of c l e a r 0.6 cm p e r s p e x ; t h e i r d i m e n s i o n s are g i v e n i n T a b l e 3.1. The r e c t a n g u l a r r e a c t o r s were f i t t e d w i t h a v e r t i c a l perspex p l a t e , 2 cm from the o u t f l o w w a l l w i t h a 12 cm c l e a r a n c e from the r e a c t o r bottom t o the lowest edge of the b a f f l e . The i n i t i a l c l a r i f i e r c o n s i s t e d of a c y l i n d e r w i t h an i n v e r t e d cone f o r m i n g the base. Sludge was withdrawn t h r o u g h t a 0.5 cm opening i n the apex of t h i s cone. I n f l o w t o the c l a r i f i e r was through a 2.5 cm v e r t i c a l c y l i n d e r which extended i n t o the c l a r i f i e r , t o enhance s o l i d s s e t t l i n g c h a r a c t e r i s t i c s . The second "improved" c l a r i f i e r was an i n c l i n e d c y l i n d e r w i t h a f l a t bottom. Sludge w i t h d r a w a l was v i a a 0.5 cm opening a t the l o w e s t p o i n t . 3.2 System O p e r a t i o n 3.2.1 Raw Sewage Supply A p p r o x i m a t e l y 450 l i t r e s of f r e s h , u n s e t t l e d raw sewage was o b t a i n e d b i m o n t h l y d u r i n g the c o u r s e of the s t u d y . The i n i t i a l s o u rce was the L u l u I s l a n d Treatment P l a n t of the G r e a t e r Vancouver R e g i o n a l D i s t r i c t , f o r reasons recommended by Dew (1979). An a n a l y s i s of raw sewage from the Maple Ridge Treatment P l a n t (Maple R i d g e , B.C.) however, i n d i c a t e d much lower t r a c e m e t a l s c o n c e n t r a t i o n than L u l u I s l a n d samples. On t h i s b a s i s the Maple Ridge source was opted f o r a f t e r the i n i t i a l 450 l i t r e s had been used i n the a c c l i m a t i o n p r o c e s s . The raw sewage f e e d was s t o r e d i n two 225 l i t r e , s t a i n l e s s TABLE 3.1 SYSTEM DIMENSIONS LENGTH (cm) WIDTH (cm) HEIGHT (cm) EXPERIMENTAL VOLUME (L) A n a e r o b i c 32.1 9.8 31. 8 5.9 A e r o b i c 55. 9 9.8 31.8 12.4 S l u d g e C o n d i t i o n i n g 24.1 9.8 31. 8 4.6 DIAMETER VOLUME (cm) (L) I n i t i a l C l a r i f i e r 12. 7 4.5 S u b s t i t u t e d C l a r i f i e r 6.4 2.6 40 s t e e l drums a t 4°C ( F i g u r e 3.1). S y n t h e t i c sewage was used t o r a i s e the fee d COD as r e q u i r e d . ( S y n t h e t i c sewage components are l i s t e d i n Appendix I ) . 3.2.2 System H y d r a u l i c s 3.2.2.1 Flow Regime The fee d was pumped to the system, l o c a t e d i n the second e n v i r o n m e n t a l room, out of one drum at a t i m e . The fee d l i n e passed through a water bath t o b r i n g the feed temperature up t o t h a t of the system ( F i g u r e 3.2). The fee d then e n t e r e d the a n a e r o b i c r e a c t o r ( F i g u r e 3.3); f l o w e d by g r a v i t y t o the a e r o b i c r e a c t o r ( F i g u r e 3.4), and on t o the c l a r i f i e r ( F i g u r e s 3.5 and 3.6). I n i t i a l l y the c l a r i f i e r u n d e r f l o w was pumped t o the a n a e r o b i c r e a c t o r . Upon the i n s t a l l a t i o n of the sludge c o n d i t i o n i n g r e a c t o r however ( F i g u r e 3.7), the s l u d g e was r e t u r n e d t o t h i s r e a c t o r and the mixed c o n t e n t s f l o w e d by g r a v i t y t o the a n a e r o b i c r e a c t o r . At the b e g i n n i n g of the s t u d y sludge w a s t i n g was from the sludge r e t u r n l i n e . However; due t o i n c o n s i s t e n t s l u d g e suspended s o l i d s c o n c e n t r a t i o n s , the w a s t i n g p r o c e d u r e was m o d i f i e d ( a f t e r one and h a l f months) such t h a t waste mixed l i q u o r was pumped out of the a e r o b i c r e a c t o r . F i g u r e s 3.8 and 3.9 show s c h e m a t i c s of the f l o w p a t t e r n t h r o u g h the system w i t h o u t and w i t h the s l u d g e c o n d i t i o n i n g r e a c t o r r e s p e c t i v e l y . The change i n c l a r i f i e r s i s a l s o p r e s e n t e d i n thes e f i g u r e s . F I G U R E 3.1: F E E D STORAGE DRUMS 42 F I G U R E 3 . 4 : A E R O B I C REACTOR F I G U R E 3 . 5 : C L A R I F I E R ( I N I T I A L MODEL) F I G U R E 3 . 6 : C L A R I F I E R ( S U B S T I T U T E D MODEL) SLUDGE C O N D I T I O N I N G REACTOR FEED l.5L/h ANAEROBIC REACTOR 5.9L J AEROBIC REACTOR 12.4L WASTE MIXED LIQUOR SLUDGE RETURN (Variable rate ) EFFLUENT CLARIFIER 4.5L WASTE SLUDGE — i FIG.3.8' INITIAL PHOSPHORUS R E M O V A L SYSTEM FIG. 3.9 : M 0 D I Fl E D P H O S P H O R U S R E M O V A L S Y S T E M 49 3.2.2.2 Pumping A s p e c t s Cole-Parmer v a r i a b l e speed p e r i s t a l t i c pumps were employed, t o g e t h e r w i t h Cole-Parmer s i l i c o n e t u b i n g , type 6411. About 50 cm of t h i s t u b i n g was used w i t h i n the "pump head" and extended to the o u t s i d e of the head where a t r a n s i t i o n t o l a r g e r diameter (up t o 2.5 cm) Tygon t u b i n g was made t o m i n i m i z e b l o c k a g e of the l i n e s by l a r g e p a r t i c l e s . Flow c o n t r o l was v i a E a g l e S i g n a l F l e x o p a u s e T i m e r s , each of which was a s s o c i a t e d w i t h one pump (the f e e d , r e c y c l e and w a s t i n g pumps). Many, but s h o r t , ON - OFF c y c l e s were used t o y i e l d a " c o n t i n u o u s " f l o w system, w h i l e a t the same time m i n i m i z i n g the d e p o s i t i o n of s o l i d s i n the t u b i n g by m a i n t a i n i n g a h i g h e r f l o w r a t e . ON-OFF c y c l e s were i n the o r d e r of 10 to 20 c y c l e s per hour, w i t h t y p i c a l ON t i m e s ^ r a n g i n g from 20 t o 40 seconds. 3.2.3 M i x i n g Each r e a c t o r was c o n t i n u o u s l y mixed w i t h a s t a i n l e s s s t e e l p r o p e l l o r powered by a Sargent-Welch cone d r i v e s t i r r e r . M i x i n g was v i g o r o u s , i n or d e r t o p r e v e n t the s e t t l i n g of s o l i d s . The s t o r a g e drums were a l s o mixed c o n t i n u o u s l y when i n use. Some s o l i d s s e t t l i n g s t i l l o c c u r r e d i n these drums however, s i n c e r e s t r i c t e d a c c e s s p r e c l u d e d the use of a l a r g e r p r o p e l l o r . 50 3.2.4 N i t r o g e n Supply The a n a e r o b i c r e a c t o r was c o v e r e d by a f i t t e d perspex cover t o ensure low d i s s o l v e d oxygen l e v e l s i n the mixed l i q u o r . N i t r o g e n gas was c o n t i n u o u s l y b u bbled through the mixed l i q u o r of the a n a e r o b i c r e a c t o r . T h i s gas i s i n e r t and m a i n t a i n e d a p o s i t i v e p r e s s u r e i n the r e a c t o r , p r e v e n t i n g a t m o s p h e r i c a i r from e n t e r i n g , thus a i d i n g i n k e e p i n g the r e a c t o r c o n t e n t s a n a e r o b i c . In f u l l s c a l e t r e a t m e n t t h i s p r a c t i c e would not be r e q u i r e d s i n c e a n a e r o b i o s i s would be e a s i l y a c h e i v e d (and m a i n t a i n e d ) due t o the h i g h e r volume t o s u r f a c e r a t i o than i s i n h e r e n t i n l a b o r a t o r y s c a l e u n i t s . 3.2.5 A e r a t i o n Three F i s h e r Gas D i s p e r s i o n Tubes w i t h f r i t t e d g l a s s c y l i n d e r s c o n n e c t e d , v i a Tygon t u b i n g , t o the b u i l d i n g compressed a i r s u p p l y , p r o v i d e d f i n e bubble a e r a t i o n t o the a e r o b i c r e a c t o r mixed l i q u o r . The a i r f l o w r a t e was a d j u s t e d t o m a i n t a i n the r e q u i r e d d i s s o l v e d oxygen l e v e l (See S e c t i o n 4.3.4 and 5.2.4) u s i n g a p r e s s u r e r e g u l a t o r and a n e e d l e v a l v e . A water t r a p was p r o v i d e d on l i n e t o a v o i d a i r p r e s s u r e f l u c t u a t i o n s . 3.2.6 L i g h t The system was o p e r a t e d i n d a r k n e s s except d u r i n g s a m p l i n g , r o u t i n e d a i l y maintenance, and i n s p e c t i o n p e r i o d s . 51 3.3 Sampling P r o c e d u r e s In g e n e r a l samples were a l l "grab", except the e f f l u e n t samples; i n t h i s case 6 hour c o m p o s i t e s were t a k e n , t o account f o r suspended s o l i d s f l u c t u a t i o n s t h a t o c c u r r e d . Sample p r e - t r e a t m e n t and p r e p a r a t i o n conformed t o the i n d i v i d u a l a n a l y s i s r e q u i r e m e n t s of eae,h of the t e s t s performed as d i s c u s s e d i n S e c t i o n 3.4. A n a l y s i s was done imm e d i a t e l y upon s a m p l i n g i n a l l c a s e s . The raw sewage was sampled upon a r r i v a l a t the l a b o r a t o r y . The f e e d t o the system (raw p l u s s y n t h e t i c sewage) was sampled a t the i n l e t t o the a n a e r o b i c r e a c t o r . Samples of the mixed l i q u o r of each of the r e a c t o r s were taken a t the o u t l e t ends of the r e a c t o r s . The e f f l u e n t was c o l l e c t e d i n a 22.5 l i t r e c o n t a i n e r v i a an o u t l e t l i n e v e r y near the e f f l u e n t e x i t p o i n t from the c l a r i f i e r ( t o a v o i d any problems of s e t t l i n g o c c u r r i n g i n the e f f l u e n t l i n e and subsequent p o s s i b l e e r r o n e o u s r e s u l t s ) . Except f o r suspended s o l i d s , e f f l u e n t c o n c e n t r a t i o n s were assumed t o e q u a l the r e t u r n s l u d g e l e v e l s f o r d i s s o l v e d i m p u r i t i e s . T able 3.2 p r e s e n t s the f r e q u e n c y and type of a n a l y s i s performed d u r i n g the c o u r s e of t h i s s t u d y , as w e l l as i n d i c a t i n g s a m p l i n g p o i n t s . 1 A B L E 3 . 2 S A M P L I N G FREQUENCY PARAMETER N O . OF S A M P L E S PER WEEK S A M P L I N G P O I N T S A l k a l i n i t y 1 A L L * PH 1 A L L * P h o s p h o r u s O r t h o p h o s p h a t e s 3 A L L * T o t a l P h o s p h a t e s 1 F e e d , e f f l u e n t N i t r o g e n N i t r a t e s 1 A L L * N i t r i t e s 1 A L L * S u s p e n d e d S o l i d s MLSS 7 A l l r e a c t o r s , e f f l u e n t O x y g e n BOD 2 F e e d , e f f l u e n t COD 2 F e e d , e f f l u e n t DO C o n t i n u o u s A e r o b i c r e a c t o r DO I r r e g u l a r A n a e r o b i c r e a c t o r , s l u d g e c o n d i t i o n i n g r e a c t o r O x i d a t i o n R e d u c t i o n P o t e n t i a l C o n t i n u o u s A n a e r o b i c r e a c t o r T e m p e r a t u r e C o n t i n u o u s A i r t e m p e r a t u r e F l o w R a t e s 2 F e e d , s l u d g e r e t u r n A L L = F e e d , a n a e r o b i c r e a c t o r , a e r o b i c r e a c t o r , s l u d g e c o n d i t i o n i n g r e a c t o r , a n d e f f l u e n t . 53 3.4 A n a l y t i c a l P r o c e d u r e s 3.4.1 Chemical Oxygen Demand ( COD ) The c h e m i c a l oxygen demand was measured r e g u l a r l y d u r i n g t h i s s t u d y , s i n c e i t s removal i n a g i v e n p r o c e s s can be d i r e c t l y r e l a t e d t o energy and c e l l growth. The a n a l y s i s of t h i s parameter was opted f o r , r a t h e r than BOD or TOC, because of i t s r e l a t i v e r e l i a b i l i t y and s i m p l i c i t y . In a d d i t i o n , a q u i c k v i s u a l i n d i c a t i o n of the l e v e l s of carbonaceous m a t e r i a l p r e s e n t i s a f f o r d e d by t h i s t e s t . The amount of " a v a i l a b l e " s u b s t r a t e was thus o b t a i n e d i n t h i s s t u d y . The d e t e r m i n a t i o n of COD f o l l o w e d the r e q u i r e m e n t s o u t l i n e d i n S t a n d a r d Methods (1976). U n f i l t e r e d samples of raw sewage were a n a l y z e d i m m e d i a t e l y upon a r r i v a l at the l a b o r a t o r y , t o a i d i n the p r o p o r t i o n i n g of the s y n t h e t i c sewage t o the l a r g e s t o r a g e drums. A f e e d COD of between 500 and 700 mg/L was t o have been m a i n t a i n e d i d e a l l y , but l a r g e f l u c t u a t i o n s o c c u r r e d due t o s o l i d s s e t t l i n g i n the s t o r a g e drums (as a r e s u l t of inadequate m i x i n g ( S e c t i o n 3 . 2 . 3 ) ) . Feed samples were not f i l t e r e d p r i o r t o a n a l y s i s . The e f f l u e n t was f i l t e r e d t h r ough a No. 4 Whatman paper f i l t e r . 3.4.2 T o t a l Suspended S o l i d s ( TSS ) Feed, mixed l i q u o r (from each r e a c t o r ) , and e f f l u e n t TSS d e t e r m i n a t i o n s were i n accordance w i t h S t a n d a r d Methods (1976) f o r " T o t a l N o n f i l t e r a b l e R e s i d u e " . 54 3.4.3 Mixed L i q u o r V o l a t i l e Suspended S o l i d s ( MLVSS ) The MLVSS r e s u l t s were o b t a i n e d by a s h i n g the mixed l i q u o r samples on which TSS v a l u e s had been p r e v i o u s l y o b t a i n e d . The procedure i s o u t l i n e d i n S t a n d a r d Methods (1976) under the heading " T o t a l V o l a t i l e R e s i d u e " . 3.4.4 A l k a l i n i t y A l l samples were u n f i l t e r e d . T i t r a t i o n was performed w i t h 0.02N r ^ S C ^ t o a e n d p o i n t pH of 4.8, as suggested i n Sta n d a r d Methods (1976), f o r e x p e c t e d a l k a l i n i t i e s i n the range of 150 mg/L as CaCC>3. 3.4.5 pH The pH v a l u e s were o b t a i n e d at the time of a l k a l i n i t y measurements p r i o r t o t i t r a t i o n . G l a s s e l e c t r o d e s (VanLab 34106-002), i n c o n j u n c t i o n w i t h a s a t u r a t e d c a l o m e l e l e c t r o d e ( F i s h e r C a l omel R e f e r e n c e E l e c t r o d e 13-639-51), were used. E l e c t r o d e c a l i b r a t i o n was w i t h pH 7.0 and 4.0 b u f f e r s o l u t i o n s . Readings were taken w i t h a F i s h e r Accument Model 310 pH meter. 3.4.6 Trace M e t a l s The d e t e r m i n a t i o n of t r a c e m e t a l s f o l l o w e d the r e q u i r e m e n t s of the Methods f o r Chemical A n a l y s i s of Water and Wastes (EPA (1979)) .using a . J a r r e l l Ash 810 Atomic A b s o r p t i o n S p e c t r o p h o t o m e t e r . . 55 3.4.7 N i t r o g e n Forms 3.4.7.1 N i t r a t e s and N i t r i t e s Both of these n i t r o g e n forms were de t e r m i n e d i n d u p l i c a t e on the s u p e r n a t a n t of c e n t r i f u g e d samples, f i l t e r e d t h r o ugh a 0.45 urn membrane f i l t e r and a p p r o p r i a t e l y d i l u t e d . N i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s were o b t a i n e d i n the presence of a cadmium r e d u c t i o n column, f o l l o w e d by n i t r i t e o n l y d e t e r m i n a t i o n w i t h o u t the column. N i t r a t e l e v e l s were then c a l c u l a t e d by s u b t r a c t i o n . The Tech n i c o n Auto A n a l y z e r I I was used and the pr o c e d u r e f o l l o w e d was recommended by the Tech n i c o n I n d u s t r i a l Method 100-70W. A l l v a l u e s were d e t e r m i n e d i n mg-N/L. A comparison of n i t r a t e r e s u l t s was attempted w i t h d u p l i c a t e s b e i n g t e s t e d b oth by the Auto A n a l y z e r method and by u l t r a v i o l e t s p e c t r o p h o t o m e t r y u s i n g a Pye Unicam SP8-100 U l t r a v i o l e t S p ectrophotometer as per Standard Methods (1976). No c o r r e l a t i o n of r e s u l t s c o u l d be d e r i v e d between these two methods, p o s s i b l y due t o phosphate i n t e r f e r e n c e i n the Auto A n a l y z e r (Olson ( 1 9 8 0 ) ) , and d i s s o l v e d o r g a n i c m a t t e r i n t e r f e r e n c e i n the u l t r a v i o l e t d e t e r m i n a t i o n . I t was apparent t h a t the former type of i n t e r f e r e n c e would not be as s i g n i f i c a n t as t h a t of the u l t r a v i o l e t ( s i n c e the cadmium column was w e l l m a i n t a i n e d ) . For t h i s reason the l a t t e r method was not pursued f u r t h e r . 56 3.4.7.2 T o t a i K j e l d a h l N i t r o g e n ( TKN ) The a n a l y s i s of samples f o r TKN c o n c e n t r a t i o n s was performed as o u t l i n e d i n St a n d a r d Methods (1976). T h i s i n c l u d e d p r e l i m i n a r y d i s t i l l a t i o n , f o l l o w e d by a c i d i m e t r i c t i t r a t i o n w i t h 0.02N H 2 S 0 4 . R e s u l t s a r e g i v e n i n mg-N/L and are the sum of the o r g a n i c and ammonia n i t r o g e n forms. 3.4.8 Phosphate Forms 3.4.8.1 Orthophosphates The p r o c e d u r e f o l l o w e d f o r o r t h o p h o s p h a t e d e t e r m i n a t i o n s i s o u t l i n e d i n S t a n d a r d Methods (1976) "Stannous C h l o r i d e Method ". Sta n d a r d s were p r e p a r e d on each day of s a m p l i n g . A Bausch and Lomb S p e c t r o n i c 88 was used t o o b t a i n a b s o r p t i o n r e a d i n g s . Feed samples were u n f i l t e r e d y i e l d i n g t o t a l o r t h o p h o s p h a t e v a l u e s . A l l o t h e r samples (mixed l i q u o r of each r e a c t o r and e f f l u e n t ) were c e n t r i f u g e d and the s u p e r n a t a n t was s u b s e q u e n t l y f i l t e r e d t h r o u g h a 0.45 ym membrane f i l t e r , t o g i v e f i l t e r a b l e o r t h o p h o s p h a t e s . A l l v a l u e s a re g i v e n as mg-P/L and a r e based on the a n a l y s i s of d u p l i c a t e samples. 3.4.8.2 T o t a l Phosphates Feed samples f o r t o t a l phosphate a n a l y s i s were u n f i l t e r e d , w h i l e the e f f l u e n t was f i r s t c e n t r i f u g e d and the s u p e r n a t a n t was f i l t e r e d t h r o u g h a 0.45 ym membrane f i l t e r . Mixed l i q u o r t o t a l p hosphates of the t h r e e r e a c t o r s were not d e t e r m i n e d . The 57 procedure i s g i v e n i n S t a n d a r d Methods (1976). P e r s u l f a t e d i g e s t i o n was f o l l o w e d by t o t a l phosphate d e t e r m i n a t i o n v i a the Stannous C h l o r i d e Method, t o g i v e r e s u l t s i n mg-P/L. As was the case w i t h o r t h o p h o s p h a t e d e t e r m i n a t i o n s , f r e s h s t a n d a r d s were used and a b s o r p t i o n r e a d i n g s were o b t a i n e d v i a a Bausch and Lomb S p e c t r o n i c 88. 3.5 M o n i t o r i n g P r o c e d u r e s T h i s s e c t i o n w i l l d i s c u s s s e v e r a l parameters which were mo n i t o r e d d u r i n g t h i s s t u d y . 3.5.1 Temperature Mixed l i q u o r temperature was mo n i t o r e d w i t h a mercury thermometer. The temperature of the e n v i r o n m e n t a l l y c o n t r o l l e d room was then a d j u s t e d t o m a i n t a i n the r e q u i r e d l i q u i d t e m p e r a t u r e . 3.5.2 D i s s o l v e d Oxygen ( DO ) The a e r o b i c r e a c t o r DO was m o n i t o r e d c o n t i n u o u s l y f o r the d u r a t i o n of t h i s r e s e a r c h work. A Y e l l o w S p r i n g s Instrument Company s u b m e r s i b l e DO probe (Model No. 5740) and Model 54 meter were used. Readings were r e c o r d e d on a c h a r t r e c o r d e r . To pre v e n t membrane f o u l i n g , as w e l l as a i d i n g " f r e s h " l i q u i d t o come i n c o n t a c t w i t h the membrane, the probe was shaken c o n t i n u o u s l y v i a a cam mechanisn ( F i g u r e 3.10). F I G U R E 3 . 1 0 : D I S S O L V E D OXYGEN PROBE A G I T A T I O N MECHANISM 59 The probe was c a l i b r a t e d ( t y p i c a l l y once weekly) a g a i n s t a tap water sample whose DC c o n c e n t r a t i o n had been determined f o l l o w i n g the A z i d e M o d i f i c a t i o n of the Iodometr i c Method, as d e s c r i b e d i n S t a n d a r d Methods (1976) . The a n a e r o b i c and s ludge c o n d i t i o n i n g r e a c t o r DO c o n c e n t r a t i o n s were u s u a l l y measured subsequent to the probe s t a n d a r d i z a t i o n p r o c e d u r e . The DO of the s ludge in the c l a r i f i e r was a l s o determined s p o r a d i c a l l y . 3 . 5 . 3 O x i d a t i o n R e d u c t i o n P o t e n t i a l ( ORP ) The ORP of the a n a e r o b i c r e a c t o r mixed l i q u o r was moni tored c o n t i n u o u s l y . ORP measurements were v i a a F i s h e r p l a t i n u m wire probe (No. 13-639-115) , r e f e r e n c e d to a s a t u r a t e d c a l o m e l e l e c t r o d e (as was used in pH d e t e r m i n a t i o n s ) . Both e l e c t r o d e s were washed t h o r o u g h l y and the r e f e r e n c e e l e c t r o d e was r e f i l l e d w i t h s a t u r a t e d po tas s ium c h l o r i d e s o l u t i o n once weekly . S t a n d a r d i z a t i o n p r o c e d u r e s were a l s o f o l l o w e d on these o c c a s i o n s as o u t l i n e d by the probe m a n u f a c t u r e r s . R e s u l t s were r e c o r d e d u s i n g a c h a r t r e c o r d e r c a l i b r a t e d i n n e g a t i v e m i l l i v o l t (-mV) u n i t s . 3 .5 .4 Flow Rates Both feed and s ludge r e t u r n flow r a t e s were g e n e r a l l y moni tored twice weekly or when f lows were p u r p o s e l y a l t e r e d . The amount of f l u i d ( f eed or r e t u r n s ludge ) d e l i v e r e d i n t o a graduated c y l i n d e r per pumping c y c l e , t imed w i t h a s topwatch , was de termined and r e p o r t e d as L / h . 60 3.6 H y d r a u l i c R e t e n t i o n Time (HRT) Re a c t o r volumes were c o n s t a n t throughout t h i s s t u d y . The feed f l o w r a t e was i d e a l l y m a i n t a i n e d a t a p p r o x i m a t e l y 1.5 L/h; a r a t e which p r o v i d e d an a p p r o p r i a t e F/M r a t i o ( S e c t i o n 4.1), as w e l l as b e i n g r e a s o n a b l e i n terms of the b i m o n t h l y volume of raw sewage t r a n s p o r t e d t o the l a b o r a t o r y . The s o l i d s f l u c t u a t i o n s i n the f e e d f l o w d i c t a t e d t h a t the HRT be a d j u s t e d d u r i n g c e r t a i n p e r i o d s however. For example, h i g h c o n c e n t r a t i o n s of s o l i d s i n the f e e d y i e l d e d a h i g h i n f l u e n t COD, thus n e c e s s i t a t i n g a r e d u c t i o n i n the feed f l o w t o m a i n t a i n a r e a s o n a b l e F/M r a t i o . T h i s , i n t u r n , r e s u l t e d i n l o n g e r l i q u i d r e t e n t i o n i n the system. The sludge r e t u r n f l o w r a t e was a l t e r e d a c c o r d i n g t o the c l a r i f i e r performance and mixed l i q u o r suspended s o l i d s r e q u i r e m e n t s of the r e a c t o r s . Two forms of HRT are p r e s e n t e d i n T a b l e 3.3. The nominal v a l u e s a r e based on the feed r a t e o n l y ( E q u a t i o n 3.1), w h i l e a c t u a l HRT's i n c l u d e the e f f e c t of the sl u d g e r e t u r n f l o w ( E q u a t i o n 3.2). v i • -i I m m R e a c t o r Volume (L) , , . Nominal HRT (h) = F e e d F l o w R a t e ( L / h ) (3-D A c t u a l HRT (h) = c 1 R r C t g r , V ° 1 r T ; i ( L ) P . , T / ^ (3.2) (Feed + Sludge Return) Flow Rate (L/h) TABLE 3.3 HYDRAULIC RETENTION TIME DAY ANAEROBIC REACTOR (hours) AEROBIC REACTOR (hours) SLUDGE CONDITIONING REACTOR ( h o u r s ) * SYSTEM (hours) e x c l u d i n g c l a r i f i e r Nominal A c t u a l Nominal A c t u a l Nominal A c t u a l Nominal A c t u a l 1A-183A Range 3-11 1-3 6-14 3-7 4 1-3 13-29 5-13 T y p i c a l V a l u e 4 2 8 4 4 2 16 8 184A-68B Range 4-6 1-4 8-12 3-9 4-5 1-4 16-23 5-17 T y p i c a l V a l u e 4 3 9 6 4 3 17 12 *Sludge C o n d i t i o n i n g R e a c t o r was o n l y i n o p e r a t i o n from Day 127A. 62 3.7 S o l i d s R e t e n t i o n Time ( SRT ) S i n c e a comprehensive d a t a base of s o l i d s c o n c e n t r a t i o n s i n each r e a c t o r and the e f f l u e n t was d e v e l o p e d , a p r e d e t e r m i n e d d e s i g n SRT c o u l d be m a i n t a i n e d by d a i l y w a s t i n g of an a p p r o p r i a t e amount of mi c r o o r g a n i s m s ( i n i t i a l l y from the sludge r e t u r n l i n e and l a t e r from the a e r o b i c r e a c t o r ) . Sample volumes withdrawn f o r a n a l y s i s , formed a s i g n i f i c a n t p o r t i o n of s o l i d s removed from the system, and were accounted f o r i n the c a l c u l a t i o n of SRT. Poor c l a r i f i e r performance n e c e s s i t a t e d the c o l l e c t i o n of l a r g e composite samples of the e f f l u e n t f o r suspended s o l i d s a n a l y s i s . I t was f e l t t h a t t h i s p r a c t i c e y i e l d e d a b e t t e r e s t i m a t e of the suspended s o l i d s c o n t e n t than p r o v i d e d by grab type samples. Two forms of SRT w i l l be d i s c u s s e d i n t h i s work: the a e r o b i c SRT and the system SRT. Sample c a l c u l a t i o n s f o r t h e s e are g i v e n i n E q u a t i o n s 3.3 and 3.4 r e s p e c t i v e l y . , . „ T _ A e r o b i c R e a c t o r S u s p e n d e d S o l i d s (mg) , A e r o o i c b R i i a ; - S u s p e n d e d S o l i d s W a s t e d f r o m S y s t e m (mg/d) ^.i) . , . _ M a s s o f S u s p e n d e d S o l i d s i n A l l R e a c t o r s (mg) S y s t e m S R I Id) - S u s p e n d e d S o i i d s w a s t e d f r o m S y s t e m (mg/d) (3.4) 63 The e f f l u e n t suspended s o l i d s v a l u e s were averaged over each i n d i v i d u a l p e r i o d f o r which SRT's are g i v e n . A l l s i g n i f i c a n t l y l a r g e samples removed f o r a n a l y s i s were i n c l u d e d i n the SRT c a l c u l a t i o n s . Both a e r o b i c and system SRT's a r e p r e s e n t e d c h r o n o l o g i c a l l y i n a l l the f i g u r e s i n C h a p t e r s 4 and 5. The SRT's quoted are o n l y e s t i m a t e s however, s i n c e o n l y a t the b e g i n n i n g of the s t u d y , when SRT's were s h o r t , was enough time a l l o w e d f o r complete system e q u i l i b r i u m to be a c h i e v e d . At l e a s t one s ludge age, a f t e r a change i n o p e r a t i o n ( f o r example, a temperature change) s h o u l d be m a i n t a i n e d as a r u l e of thumb f o r r e a c h i n g s t e a d y s t a t e c o n d i t i o n s i n a g i v e n t r e a t m e n t system. Gaps i n the SRT d a t a i n d i c a t e p e r i o d s d u r i n g which system o p e r a t i o n was b e i n g a l t e r e d . 3.8 N i t r a t e R e a c t i o n Rates N i t r a t e r e a c t i o n r a t e s were c a l c u l a t e d as per E q u a t i o n 3.5. These r a t e s were based on a c t u a l f l o w r a t e s and c o n s i d e r e d the mass of n i t r a t e s removed d a i l y v i a i n t e n t i o n a l w a s t i n g and s a m p l i n g . When n i t r a t e r e a c t i o n r a t e s were p o s i t i v e , d e n i t r i f i c a t i o n o c c u r r e d i n a g i v e n r e a c t o r , w h i l e n e g a t i v e r a t e s i n d i c a t e d n i t r i f i c a t i o n (See S e c t i o n 4.3.8.1(b), and 5 . 2 . 8 . 1 ( b ) ) . N i t r a t e R e a c t i o n Rate (mg-N/g MLSS/h) N i t r a t e (In-Out) (mg-N/h) R e a c t o r Volume x R e a c t o r MLSS ( L . g . L -1-) ( 3 . 5 ) 64 3.9 Orthophosphate R e a c t i o n Rates E q u a t i o n 3.6 shows the method by which the orthophosphate r e a c t i o n r a t e s , (as r e p o r t e d and d i s c u s s e d i n S e c t i o n 4.3.9.1(c) and 5.2.9.1(c)) were c a l c u l a t e d . The sludge r e t u r n f l o w was i n c l u d e d i n the d e t e r m i n a t i o n of these r a t e s ( i n t h a t a c t u a l f l o w s were c o n s i d e r e d ) , as were the d a i l y wastage and sample volumes removed from the system. Orthophosphate uptake was i n d i c a t e d by p o s t i v e r e a c t i o n r a t e s w h i l e r e l e a s e was denoted by n e g a t i v e v a l u e s . Orthophosphate R e a c t i o n Rate (mg-P/g MLSS/h) = Orthophosphate (In-Out) (mg-P/h) ^ ^^ Re a c t o r Volume x R e a c t o r MLSS ( L . g . L - ^ ) 3.10 AP/ACOD R a t i o S e v e r a l r e s e a r c h e r s have r e f e r r e d t o the AP/ACOD r a t i o as i n d i c a t i v e of the e x p e c t e d P removal c a p a b i l i t i e s of a g i v e n t r e a t m e n t system. T h i s r a t i o was de t e r m i n e d i n t h i s study by c o n s i d e r i n g the change between the u n f i l t e r e d f e e d and f i l t e r e d a e r o b i c r e a c t o r mixed l i q u o r t o t a l phosphate c o n c e n t r a t i o n s . S i n c e o n l y the o r t h o p h o s p h a t e s were a n a l y t i c a l l y d e t e r m i n e d f o r the a e r o b i c r e a c t o r , the c o n v e r s i o n t o t o t a l phosphates was based on the assumption t h a t the o r t h o p h o s p h a t e : t o t a l phosphate r a t i o c a l c u l a t e d f o r the e f f l u e n t was a l s o the same i n the a e r o b i c r e a c t o r . The change i n COD was o b t a i n e d by c a l c u l a t i n g the d i f f e r e n c e between the i n f l u e n t t o and the e f f l u e n t from the system. Note t h a t due t o l a b o r a t o r y a n a l y s i s s c h e d u l i n g , o n l y 65 those Ap/ACOD r a t i o s were c a l c u l a t e d f o r which phosphates and COD d e t e r m i n a t i o n s were w i t h i n a day or so of each o t h e r . . _ T o t a l P ( I n f l u e n t - A e r o b i c R e a c t o r ) ( m g / L ) , AP/ACOD - C 0 D ( I n f l u e n t _ E f f i U e n t ) ( m g / L ) K ' ' 3.11 Research Program The system was o p e r a t e d over a p e r i o d of 10 months. The o p e r a t i o n a l scheme was d i v i d e d i n t o two phases. Phase A i s d i s c u s s e d i n d e t a i l i n Chapter 4 and i s concerned w i t h the s t a r t - u p of the system and the subsequent 8 months of system m o d i f i c a t i o n s i n t e n d e d t o y i e l d s a t i s f a c t o r y phosphorus removal. Such m o d i f i c a t i o n s i n c l u d e d the improvement of c l a r i f i e r d e s i g n , the i n c o r p o r a t i o n of a sl u d g e c o n d i t i o n i n g r e a c t o r and l i q u i d t e m p e r a t u r e changes. Numerous o p e r a t i o n a l and d e s i g n problems w i l l be d i s c u s s e d and r e s u l t s of t h i s p e r i o d p r e s e n t e d . A f u r t h e r two months of s t u d y , Phase B, i n v o l v e d the achievement of enhanced phosphorus removal and the n e c e s s a r y p r e r e q u i s i t e s f o r t h i s t o o c c u r . T h i s second phase i s d i s c u s s e d i n Chapter 5. 66 CHAPTER 4 PHASE A: A PRELIMINARY INVESTIGATION OF PARAMETERS AFFECTING THE BIOLOGICAL REMOVAL OF PHOSPHATES FROM WASTEWATER 4.1 D e s c r i p t i o n of System O p e r a t i n g C o n d i t i o n s T h i s c h a p t e r d e s c r i b e s the o p e r a t i n g c o n d i t i o n s of the system a t s t a r t u p , the subsequent m o d i f i c a t i o n s , and r e s u l t s o b t a i n e d d u r i n g Phase A of the s t u d y . Phase A spans the i n i t i a l 238 days of system o p e r a t i o n . The p h y s i c a l and o p e r a t i o n a l c h a r a c t e r i s t i c s of the system were d i s c u s s e d i n Chapter 3. For r easons d e r i v e d from o t h e r r e s e a r c h (Chapter 2 ) , enhanced P removal was e x p e c t e d and i n t e n s i v e t e s t i n g was t o be undertaken once t h i s phenomenon was o b s e r v e d . S e v e r a l major m o d i f i c a t i o n s of the sysytem were n e c e s s a r y however, as e x p e r i e n c e d i c t a t e d , c a u s i n g numerous d i s r u p t i o n s i n the t e s t i n g s c h e d u l e d e p i c t e d i n T a b l e 3.2. The i n i t i a l raw sewage sour c e was the L u l u I s l a n d Treatment P l a n t ; but because of h i g h m e t a l c o n c e n t r a t i o n s found t h e r e i n , subsequent f e e d sewage was o b t a i n e d from the Maple Ridge Treatment P l a n t . Both the a n a e r o b i c and a e r o b i c r e a c t o r s were seeded w i t h secondary s l u d g e from the Squamish Treatment P l a n t t o encourage the r a p i d development of the biomass. A p p r o x i m a t e l y one month was a l l o w e d f o r system s t a b i l i z a t i o n , w i t h o n l y the mixed l i q u o r s o l i d s b e i n g a c t i v e l y m o n i t o r e d d u r i n g t h i s p e r i o d . To g a i n e x p e r i e n c e w i t h the t e s t i n g p r o c e d u r e s and t o overcome 67 any s a m p l i n g and a n a l y s i s problems, p r e l i m i n a r y t e s t s were a l s o p erformed on s e v e r a l parameters such as COD, n i t r a t e s , n i t r i t e s , t o t a l K j e l d a h l n i t r o g e n , and o r t h o and t o t a l phosphates. Sampling p o i n t s were i d e n t i f i e d and methods were deve l o p e d such t h a t the s a m p l i n g and a n a l y s i s t e c h n i q u e s d e s c r i b e d i n Chapter 3 c o u l d be c l o s e l y adhered t o d u r i n g subsequent months of system o p e r a t i o n . The i n i t i a l d e s i g n parameters were d e v e l o p e d on the assumption t h a t the a n a e r o b i c r e a c t o r biomass d i d not p a r t i c i p a t e i n the a s s i m i l a t i o n of o r g a n i c s . To a v o i d the r e c i r c u l a t i o n of formed n i t r a t e s from the c l a r i f i e r t o the a n a e r o b i c r e a c t o r , an a e r o b i c s l u d g e age of < 5 days ( e x c l u d i n g the c l a r i f i e r ) was m a i n t a i n e d i n i t i a l l y . At the i n f l u e n t f l o w r a t e of 1.5 L/h and an a n t i c i p a t e d B O D 5 of a p p r o x i m a t e l y 200 mg/L, the d e s i g n F/M r a t i o was 0.6 kg B O D 5 a p p l i e d / k g MLVSS/d. The i n i t i a l V o l u m e t r i c L o a d i n g was 0.7 kg B O D 5 a p p l i e d / m 3 / d . 4.2 System M o d i f i c a t i o n s The e f f l u e n t P l e v e l s d i d not approach the a n t i c i p a t e d low c o n c e n t r a t i o n of < 1 mg/L P d u r i n g the i n i t i a l days of the s t u d y . S e v e r a l m o d i f i c a t i o n s of the p h y s i c a l system and o p e r a t i n g c o n d i t i o n s were undertaken d u r i n g Phase A i n an e f f o r t t o f u l f i l l the o b j e c t i v e of the s u c c e s s f u l removal of P. The f o l l o w i n g m o d i f i c a t i o n s were implemented, the e f f e c t s of which w i l l be d i s c u s s e d i n S e c t i o n 4.3. 68 4.2.1 Temperature I n i t i a l l y the l i q u i d t e mperature i n the r e a c t o r s was m a i n t a i n e d a t 18°C. A l t h o u g h the s l u d g e age was low, a t h r i v i n g n i t r i f i e r p o p u l a t i o n was e s t a b l i s h e d i n the a e r o b i c r e a c t o r d u r i n g the f i r s t two months of the s t u d y . Research by B a r n a r d (1976) i n d i c a t e d phosphates c o u l d not be removed s i m u l t a n e o u s l y w i t h h i g h n i t r a t e l e v e l s i n the e f f l u e n t . T h e r e f o r e the c u r t a i l m e n t of n i t r i f i c a t i o n became a major o b j e c t i v e . S i n c e the growth of n i t r i f y i n g a u t o t r o p h i c b a c t e r i a (namely Nitrosomonas and N i t r o b a c t e r ) i s s u s c e p t i b l e t o temperature changes, the t e m p e r a t u r e was lowered on s e v e r a l o c c a s i o n s . T h i s measure was e f f e c t i v e i n r e d u c i n g n i t r i f i c a t i o n r a t e s over a s h o r t time p e r i o d o n l y , e s p e c i a l l y s i n c e the a e r o b i c SRT was i n c r e a s e d as Phase A proceeded (t h u s i m p r o v i n g the c o n d i t i o n s f o r a t h r i v i n g n i t r i f i e r p o p u l a t i o n t o d e v e l o p ) . 4.2.2 Sludge C o n d i t i o n i n g R e a c t o r Temperature changes a l o n e were i n e f f e c t i v e i n l o w e r i n g the n i t r i f i c a t i o n r a t e s i n the a e r o b i c r e a c t o r f o r any a p p r e c i a b l e l e n g t h of t i m e . A s l u d g e c o n d i t i o n i n g r e a c t o r was t h e r e f o r e added t o the system on Day 127A, w i t h the p h y s i c a l c h a r a c t e r i s t i c s d e s c r i b e d i n S e c t i o n 3.1. The aim of t h i s m o d i f i c a t i o n was the p r o v i s i o n of a b a s i n where d e n i t r i f i c a t i o n of the r e t u r n s l u d g e would occur p r i o r t o the s l u d g e e n t e r i n g the a n a e r o b i c r e a c t o r . I t t h e r e b y e nsured t h a t no s i g n i f i c a n t l e v e l s of n i t r a t e s e n t e r e d the a n a e r o b i c r e a c t o r . T h i s measure 69 p r e c l u d e d any p o s s i b l e i n t e r f e r e n c e of r e t u r n e d n i t r a t e s w i t h the r e l e a s e of P i n t h i s r e a c t o r and the subsequent uptake i n the a e r o b i c r e a c t o r . 4.2.3 C l a r i f i e r Numerous problems were e n c o u n t e r e d w i t h the o p e r a t i o n of the system due t o poor c l a r i f i e r p erformance. E x c e s s i v e d e n i t r i f i c a t i o n caused s l u d g e r i s i n g t o the s u r f a c e of the c l a r i f i e r , c a u s i n g suspended s o l i d s t o escape w i t h the e f f l u e n t . The r e s u l t was l a r g e f l u c t u a t i o n s i n mixed l i q u o r suspended s o l i d s i n a l l t h r e e r e a c t o r s due t o the r e t u r n s l u d g e h a v i n g i n c o n s i s t e n t s o l i d s l e v e l s . On Day 175A, a new c l a r i f i e r was i n s t a l l e d w i t h the c h a r a c t e r i s t i c s d e s c r i b e d i n S e c t i o n 3.1. A s i m i l a r c l a r i f i e r showed p r o m i s i n g s e t t l i n g p r o p e r t i e s a t the U n i v e r s i t y of Cape Town ( M a r a i s ( 1 9 7 9 b ) ) . U n f o r t u n a t e l y the problems of poor e f f l u e n t suspended s o l i d s q u a l i t y p r e v a i l e d . These w i l l be d i s c u s s e d i n more d e t a i l i n S e c t i o n 4.3.2. 4.2.4 System Shut-down On Day 160A, the compressed a i r s u p p l y t o the a e r o b i c r e a c t o r was shut o f f , s t i r r i n g was d i s c o n t i n u e d and a l l pumping ceased f o r 12 h o u r s . These measures were undertaken i n o r d e r t o induce complete a n a e r o b i o s i s of the whole system f o l l o w e d by a r e v e r s a l t o pre-shut-down c o n d i t i o n s . T e s t s were performed on the s e t t l e d s u p e r n a t a n t i n each of the u n i t s a t the end of the shut-down p e r i o d , as w e l l as s h o r t l y a f t e r the system was 70 r e s t a r t e d . P e r t i n e n t r e s u l t s w i l l be d i s c u s s e d i n the f o l l o w i n g s e c t i o n . 4.3 R e s u l t s and D i s c u s s i o n The maximum Phase A p e r c e n t a g e removal of pho s p h a t e s was 55% and t h a t of COD was 96%. Throughout the p r e s e n t a t i o n and d i s c u s s i o n of the r e s u l t s o b t a i n e d d u r i n g Phase A, one s h o u l d bear i n mind the t h r e e t e mperature regimes s t u d i e d (as i n d i c a t e d on each of the f o l l o w i n g f i g u r e s ) . Temperature e f f e c t s a re important from the p o i n t of view of the r e a c t i o n r a t e s f o r both n i t r a t e s and phosphates. U n f o r t u n a t e l y , the e f f e c t of temperature on these r a t e s c o u l d not be de v e l o p e d , due t o the s u b s t a n t i a l f r e q u e n t v a r i a t i o n of o t h e r parameters ( e s p e c i a l l y SRT) d u r i n g the cour s e of t h i s phase. A l l parameters w i l l be p r e s e n t e d based on t h e i r c h r o n o l o g i c a l v a r i a t i o n i n the s t u d y . 4.3.1 C h e m i c a l Oxygen Demand ( COD ) Throughout Phase A, i n f l u e n t COD l e v e l s v a r i e d between 140 and 1650 mg/L. A l t h o u g h s y n t h e t i c f e e d s p i k i n g of the raw sewage was p r a c t i s e d t o m a i n t a i n a feed COD of a p p r o x i m a t e l y 600 mg/L, d i f f i c u l t i e s w i t h s t i r r i n g the l a r g e f e e d s t o r a g e drums s t i l l c aused l a r g e COD f l u c t u a t i o n s (See S e c t i o n 3.1.3). I n f l u e n t and e f f l u e n t COD v a l u e s a r e p r e s e n t e d i n Appendix I I , F i g u r e 11-1. Perc e n t a g e removals, as i n d i c a t e d i n F i g u r e 4.1, v a r i e d between 55 and 96%. P e r i o d s of low removal c o r r e s p o n d e d t o low feed COD. TL 72 4.3.2 T o t a l Suspended S o l i d s ( TSS ) F l u c t u a t i o n s i n the f e e d suspended s o l i d s c o n t e n t were p r i m a r i l y a r e s u l t of i n s u f f i c i e n t s t i r r i n g of s t o r a g e drum c o n t e n t s , t y p i c a l l y y i e l d i n g h i g h TSS as the raw sewage l e v e l approached the drum bottom (where s o l i d s c o n c e n t r a t i o n s were h i g h e r due t o s e t t l i n g ) . The c l a r i f i e r was unable t o produce an e f f l u e n t w i t h a c c e p t a b l y low SS, thus p e r c e n t a g e s o l i d s removals are not r e p o r t e d . The e f f l u e n t SS c o n t e n t g e n e r a l l y ranged between 6 and 89 mg/L; sometimes e x c e e d i n g f e e d SS l e v e l s . Due t o these f l u c t u a t i o n s , e f f l u e n t suspended s o l i d s were m o n i t o r e d o n l y f o r the purpose of SRT c a l c u l a t i o n s and are r e p o r t e d i n Appendix I I , F i g u r e I I - 2 . P r o b a b l e reasons f o r the poor performance of the c l a r i f i e r i n c l u d e : s c a l e e f f e c t s , d i s p e r s i o n of the b i o f l o c s i n the a e r a t i o n t a n k , and d e n i t r i f i c a t i o n r e s u l t i n g i n r i s i n g s l u d g e . The l a t t e r i s b e l i e v e d t o have had the g r e a t e s t impact on the h i g h e f f l u e n t SS l e v e l s e n c ountered throughout t h i s s t u d y . Sludge b r i d g i n g o c c u r r e d a c r o s s the bottom cone of the c l a r i f i e r , r e s u l t i n g i n c l e a r l i q u i d f o r m i n g p a r t of the sludge r e t u r n . The a c c u m u l a t i n g s l u d g e was thus a f f o r d e d ample time to. d e n i t r i f y and r i s e . I n c r e a s i n g the sludge r e t u r n caused c l e a r e f f l u e n t t o be pumped out of the c l a r i f i e r , w h i l e sludge a c c u m u l a t i o n around the c l a r i f i e r w a l l s p e r s i s t e d . S i m i l a r problems were e n c o u n t e r e d upon the i n s t a l l a t i o n of the new c l a r i f i e r . A l t h o u g h w a l l e f f e c t s were not as pronounced i n the new c l a r i f i e r i t s e l f , d e n i t r i f i c a t i o n e f f e c t s were 73 v i s i b l e i n the f l o o d e d i n f l u e n t l i n e , e s p e c i a l l y at the j u n c t i o n of t h i s l i n e and the c l a r i f i e r . I t i s not ex p e c t e d t h a t t h i s problem would p r e v a i l i n p i l o t or f u l l s c a l e o p e r a t i o n s . I t i s u n l i k e l y t h a t the poor s l u d g e s e t t l i n g o b s e r v e d d u r i n g Phase A of t h i s s t u d y may have r e s u l t e d from the a c t i v i t y of f i l a m e n t o u s organisms as d e s c r i b e d by Pitman (1980). The a n a e r o b i c zone a l o n e c o n s t i t u t e d 31% of the system volume, and the i n c l u s i o n of the s l u d g e c o n d i t i o n i n g r e a c t o r i n c r e a s e d t h i s t o 46%. U n l i k e the o b s e r v a t i o n s made by Pitman, a d i s t i n c t s l u d g e m a t r i x was e v i d e n t i n t h i s s t u d y , thus p r e c l u d i n g the a c t i v i t y of f i l a m e n t o u s organisms. U n f o r t u n a t e l y , m i c r o s c o p i c e x a m i n a t i o n s of the s l u d g e were beyond the scope of t h i s r e s e a r c h work. The MLSS of the a n a e r o b i c r e a c t o r c l o s e l y p a r a l l e l e d the c o n c e n t r a t i o n s i n the a e r o b i c r e a c t o r , t h e r e f o r e o n l y the l a t t e r v a l u e s a r e p r e s e n t e d i n F i g u r e 4.1. Upon the i n s t a l l a t i o n of the sl u d g e c o n d i t i o n i n g r e a c t o r on Day 127A, the m o n i t o r i n g of the MLSS i n t h i s r e a c t o r was a l s o i n i t i a t e d . MLSS ranged between 1870 mg/L upon i n s t a l l a t i o n , and 7170 mg/L near the end of Phase A. S i n c e the o n l y i n f l o w t o t h i s r e a c t o r o r i g i n a t e d from the un d e r f l o w of the c l a r i f i e r , the s o l i d s c o n c e n t r a t i o n i n t h i s r e a c t o r was h i g h l y dependent on the q u a l i t y of sl u d g e s e t t l e d i n the c l a r i f i e r . When s l u d g e r i s i n g o c c u r r e d , the s l u d g e r e t u r n i n c l u d e d a l a r g e amount of c l e a r e f f l u e n t . T h i s d i l u t e d the s o l i d s i n the sludge c o n d i t i o n i n g r e a c t o r , w i t h subsequent l o w e r i n g of s o l i d s l e v e l s i n the a n a e r o b i c and a e r o b i c r e a c t o r s . T h i s u n r e l i a b l e s o l i d s c o n c e n t r a t i o n i n the sludge r e t u r n was the major reason f o r the s o l i d s f l u c t u a t i o n s i n a l l the 74 r e a c t o r s , c a u s i n g a d d i t i o n a l problems w i t h e s t i m a t i n g d a i l y w a s t i n g volumes. 4.3.3 Mixed L i q u o r V o l a t i l e Suspended S o l i d s ( MLVSS ) The MLVSS t y p i c a l l y c o n s t i t u t e d 87% of MLSS i n a l l t h r e e r e a c t o r s t hroughout Phase A. 4.3.4 D i s s o l v e d Oxygen ( DO ) D i s s o l v e d oxygen l e v e l s were m a i n t a i n e d t y p i c a l l y h i g h e r than r e q u i r e d by c o n v e n t i o n a l (1-2 mg/L) a c t i v a t e d sludge t r e a t m e n t ; i n g e n e r a l between 2.0 and 4.0 mg/L. T h i s was a p r e r e q u i s i t e f o r the p r e v e n t i o n of c l a r i f i e r s l u d g e becoming a n a e r o b i c , c a u s i n g the r e l e a s e of P as w e l l as o t h e r f a c t o r s d i s c u s s e d i n S e c t i o n 2.3. At s t a r t u p , DO c o n t r o l was d i f f i c u l t due t o s o l i d s f l u c t u a t i o n s and problems w i t h d i f f u s e r c l o g g i n g , probe membrane f o u l i n g and f l u c t u a t i o n s i n the l a b o r a t o r y compressed a i r s u p p l y . Subsequent minor o p e r a t i o n a l m o d i f i c a t i o n s (such as t h e p r o v i s i o n of a mechanism t o a g i t a t e the probe) r e s u l t e d i n a r e l i a b l e DO m o n i t o r i n g program (See Sect i o n 3.5.2). The DO i n the a n a e r o b i c r e a c t o r was always below 0.5 mg/L and t y p i c a l l y f l u c t u a t e d about the 0.1 mg/L l e v e l . The a n o x i c r e a c t o r DO was not a c t i v e l y m o n i t o r e d . I n f r e q u e n t DO measurements on the s e t t l e d s l u d g e on the bottom of the c l a r i f i e r i n d i c a t e d l e v e l s i n the neighbourhood of 75 0.3 mg/L, even though the a e r o b i c r e a c t o r DO was r e l a t i v e l y h i g h . 4.3.5 O x i d a t i o n R e d u c t i o n P o t e n t i a l ( ORP ) In g e n e r a l the a n a e r o b i c r e a c t o r was m a i n t a i n e d " t r u l y " a n a e r o b i c d u r i n g Phase A, s i n c e the ORP v a l u e s were f o r the most p a r t below -130 mV, t y p i c a l l y f l u c t u a t i n g between -130 and -520 mV ( l e v e l s above -130mV were o n l y o b s e r v e d on f o u r o c c a s i o n s d u r i n g t h i s phase of s t u d y ) . T h i s i n d i c a t e d t h a t n e g l i g i b l e d i s s o l v e d oxygen and n i t r a t e s were p r e s e n t a t a l l t i m e s . F l u c t u a t i o n s of a p p r o x i m a t e l y 30 mV were obser v e d d u r i n g the ON time of the sl u d g e r e t u r n pump, when the sl u d g e was r e c y c l e d t o the a n a e r o b i c r e a c t o r . These f l u c t u a t i o n s were e l i m i n a t e d upon the i n s t a l l a t i o n of the s l u d g e c o n d i t i o n i n g r e a c t o r . 4.3.6 A l k a l i n i t y and pH A l k a l i n i t y and pH r e s u l t s a r e r e p o r t e d i n Appendix I I Ta b l e I I - l . The a n a e r o b i c r e a c t o r pH was up t o 0.9 u n i t s h i g h e r than the pH of the a e r o b i c r e a c t o r . T h i s i s a t y p i c a l i n t h a t a n a e r o b i o s i s i s , i n g e n e r a l , accompanied by a low pH i n 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 t r e a t m e n t schemes. Beer and Wang (1978) i n d i c a t e however t h a t endogenous n i t r a t e r e s p i r a t i o n , a l t h o u g h y i e l d i n g no carbon d i o x i d e , produces b i c a r b o n a t e s which would t e n d t o b u f f e r the pH. T h i s e x p l a i n s the h i g h pH o b s e r v e d i n the a n a e r o b i c and the s l u d g e c o n d i t i o n i n g r e a c t o r s i n t h i s s t u d y . The a n a e r o b i c r e a c t o r 76 e x h i b i t e d h i g h e r than u s u a l pH because the p r o b a b l e h i g h b i c a r b o n a t e c o n t e n t i n the f l o w from the s l u d g e c o n d i t i o n i n g r e a c t o r a f f o r d e d a h i g h degree of b u f f e r i n g c a p a c i t y . There was no d i s c e r n a b l e t r e n d i n the r a i s i n g or l o w e r i n g of pH upon t r e a t m e n t . In g e n e r a l , a l k a l i n i t y was removed v i a the treatment scheme w i t h the bulk of the removal o c c u r r i n g i n the a e r o b i c r e a c t o r (due i n p a r t t o the n i t r i f i c a t i o n r e a c t i o n s ) . As ex p e c t e d , low pH p a r a l l e l e d low a l k a l i n i t y i n the a e r o b i c r e a c t o r and e f f l u e n t samples. 4.3.7 Trace M e t a l s The c o n c e n t r a t i o n s of t r a c e m e t a l s i n the feed (not s p i k e d w i t h s y n t h e t i c sewage) a r e p r e s e n t e d i n Appendix I I T a b l e 11 -2. Sampling and d i g e s t i o n were performed i m m e d i a t e l y upon a r r i v a l a t the l a b o r a t o r y . There was no a p p r e c i a b l e change i n the f e e d t r a c e m etal c o n c e n t r a t i o n s t hroughout Phase A. I t i s p r o b a b l e t h a t a c c u m u l a t i o n s of the s e m e t a l s i n the sl u d g e i n c r e a s e d w i t h i n c r e a s i n g s l u d g e age. There i s a l s o the p o s s i b i l i t y t h a t a t o x i c i t y t h r e s h o l d was reached, but t h i s a s p e c t was not i n v e s t i g a t e d i n t h i s study (See S e c t i o n 5.2.7). 4.3.8 N i t r o g e n Forms Because r e s u l t s i n t h e l i t e r a t u r e suggest t h a t n i t r a t e s a r e im p o r t a n t i n r e l a t i o n . t o the P r e l e a s e and uptake phenomena, 7.7 t h i s form of n i t r o g e n was mo n i t o r e d e x t e n s i v e l y . N i t r i t e s and t o t a l K j e l d a h l n i t r o g e n were a l s o m o n i t o r e d as so u r c e s of f u r t h e r i n f o r m a t i o n r e g a r d i n g the o p e r a t i n g performance of the system.. 4.3.8.1 N i t r a t e s (a) C o n c e n t r a t i o n s Feed n i t r a t e l e v e l s were t y p i c a l l y <0.02 mg-N/L. An a e r o b i c r e a c t o r c o n c e n t r a t i o n s ( p r i o r t o i n s t a l l i n g the sludge c o n d i t i o n i n g r e a c t o r ) were dependent on the degree of n i t r i f i c a t i o n i n the a e r o b i c r e a c t o r , r e a c h i n g a h i g h of 5.65 mg-N/L. D u r i n g the l a t t e r s t a g e s of Phase A, the n i t r a t e s i n the a n a e r o b i c r e a c t o r were i n g e n e r a l <0.1 mg-N/L as a r e s u l t of the e x c e l l e n t d e n i t r i f i c a t i o n c a p a b i l i t i e s of the s l u d g e c o n d i t i o n i n g r e a c t o r . Due t o the p u r p o s e f u l t emperature c u r t a i l m e n t ( t h a t was p r a c t i s e d d u r i n g the f i r s t 126 days of the study) of n i t r i f i c a t i o n , the a e r o b i c r e a c t o r n i t r a t e l e v e l s f l u c t u a t e d a p p r e c i a b l y . Subsequent t o i n s t a l l i n g the s l u d g e c o n d i t i o n i n g r e a c t o r , such f l u c t u a t i o n s were no l o n g e r an i s s u e . Throughout Phase A, the a e r o b i c r e a c t o r n i t r a t e s p a r a l l e l e d those i n the e f f l u e n t but were, i n g e n e r a l , s l i g h t l y h i g h e r . E f f l u e n t n i t r a t e l e v e l s a r e shown i n F i g u r e 4.2. The attempt a t l i m i t i n g n i t r i f i c a t i o n v i a m a i n t a i n i n g a low slu d g e age, and thus r e c i r c u l a t i n g v e r y low n i t r a t e l e v e l s i n t o SL 79 the anaerobic r e a c t o r d u r i n g the i n i t i a l 127 days of Phase A, was u n s u c c e s s f u l . L i q u i d temperature was lowered twice, to a minimum of 10°C on Day 113A, but the lowest n i t r a t e in the e f f l u e n t (and thus assumed i n the sludge return) was 3.0 mg-N/L (ex c l u d i n g the i n i t i a l 40 days of study d u r i n g which the n i t r i f i e r p o p u l a t i o n was e s t a b l i s h i n g i t s e l f and l i t t l e n i t r i f i c a t i o n o c c u r r e d ) . Upon the i n s t a l l a t i o n of the sludge c o n d i t i o n i n g r e a c t o r , the hig h e s t n i t r a t e c o n c e n t r a t i o n e n t e r i n g the anaerobic r e a c t o r v i a the sludge c o n d i t i o n i n g r e a c t o r , was 0.3 mg-N/L, and t y p i c a l l y was below 0.1 mg-N/L. (b) N i t r i f i c a t i o n and D e n i t r i f i c a t i o n Rates The n i t r i f i c a t i o n and d e n i t r i f i c a t i o n a c t i v i t i e s of the biomass i n each of the three r e a c t o r s are presented c h r o n o l o g i c a l l y i n F i g u r e 4.3. The anaerobic r e a c t o r was i n t e n s i v e l y i n v o l v e d i n d e n i t r i f i c a t i o n u n t i l Day 127A, when the sludge c o n d i t i o n i n g r e a c t o r was i n s t a l l e d . N e g l i g i b l e d e n i t r i f i c a t i o n a c t i v i t y was observed i n the anaerobic r e a c t o r once the sludge c o n d i t i o n i n g r e a c t o r was o p e r a t i o n a l . A maximum d e n i t r i f i c a t i o n r a t e of 7.06 mg-N/g MLSS/h occu r r e d i n the anaerobic r e a c t o r on Day 81A at 18°C. T h i s high value suggests that a h e a l t h y d e n i t r i f i e r p o p u l a t i o n had e s t a b l i s h e d i t s e l f , s i n c e the outflow from t h i s r e a c t o r c o n t a i n e d very low n i t r a t e l e v e l s (0.08 mg-N/L). The anaerobic r e a c t o r d e n i t r i f i c a t i o n r a t e s t y p i c a l l y f l u c t u a t e d about the 0.5 mg-N/g MLSS/h l e v e l . Dew (1979) repo r t e d mean anaerobic d e n i t r i f i c a t i o n r a t e s of 0.53 mg DENITRIFICATION mg N/g M L S S / n NITRIFICATION - mg N/g MLSS/h O O o o b o o Ul o J , 91 »t 30y at 7 C6 ~ 7 2 O o -f- Ul o O O Ol O -1— 3- \ I \ 4- \ O' ro <ji -*- / \ t/i 1 t> •< • n co i x o 5 : 5 I r> t t/i | i n 3J I 33 m 33 a i a n j co -4 | o o - 0 O 1 o o _ L _ A T : o i o u i >ro ! PO Ul u i Iro 01 j M 08 81 ( n i t r a t e + n i t r i t e ) - N / g MLSS/h at 18° C, with a high of 7.8 mg ( n i t r a t e + n i t r i t e ) - N / g MLSS/h recorded at t h i s temperature. N i t r i f i c a t i o n i n the a e r o b i c r e a c t o r f l u c t u a t e d between 0.03 and 2.53 mg-N/g MLSS/h d u r i n g Phase A. The maximum rate was observed on Day 81A, which c o i n c i d e d with the high d e n i t r i f i c a t i o n r a t e observed i n the anaerobic r e a c t o r on t h i s day. Research by Dew (1979), i n d i c a t e d a range of 0 to 1.76 mg ( n i t r a t e + n i t r i t e ) - N / g MLSS/h at 18° C i n the aer o b i c b a s i n of the mo d i f i e d Bardenpho scheme s t u d i e d . E f f l u e n t n i t r a t e c o n c e n t r a t i o n s c l o s e l y p a r a l l e l e d but were g e n e r a l l y lower than those i n the ae r o b i c r e a c t o r , s u p p o r t i n g the v i s u a l o b s e r v a t i o n of d e n i t r i f i c a t i o n o c c u r r i n g i n the c l a r i f i e r system. The d e n i t r i f i c a t i o n r a t e s i n the sludge c o n d i t i o n i n g r e a c t o r f l u c t u a t e d a c c o r d i n g to the amount of n i t r i f i c a t i o n a c t i v i t y i n the ae r o b i c r e a c t o r . Because of the low n i t r a t e content i n the outflow from the sludge c o n d i t i o n i n g r e a c t o r , i t appeared that t h i s r e a c t o r had excess d e n i t r i f y i n g c a p a c i t y and the temperature c o u l d be i n c r e a s e d back up to 14°C, as indeed i t was on Day 138A. 4.3.8.2 N i t r i t e s N i t r i t e c o n c e n t r a t i o n s were determined si m u l t a n e o u s l y with n i t r a t e s . Feed n i t r i t e s were at a l l times <0.07 mg-N/L during 82 Phase A. The a n a e r o b i c r e a c t o r n i t r i t e s were <0.08 mg-N/L. A e r o b i c r e a c t o r n i t r i t e c o n c e n t r a t i o n s were g e n e r a l l y h i g h e r than those of the a n a e r o b i c and s l u d g e c o n d i t i o n i n g r e a c t o r s due t o a g r e a t e r c o n c e n t r a t i o n of o x i d i z e d n i t r o g e n s p e c i e s , r e a c h i n g a maximum of 6.70 mg-N/L on Day 203A a t 14°C. In g e n e r a l however, v a l u e s f l u c t u a t e d around the 1.0 mg-N/L l e v e l . N i t r i t e v a l u e s approached n i t r a t e l e v e l s d u r i n g p e r i o d s of in c o m p l e t e n i t r i f i c a t i o n i n the a e r o b i c r e a c t o r . E f f l u e n t n i t r i t e c o n c e n t r a t i o n s p a r a l l e l e d those of the a e r o b i c r e a c t o r , but were s l i g h t l y l o w e r , due t o d e n i t r i f i c a t i o n i n the c l a r i f i e r u n i t . The sludge c o n d i t i o n i n g r e a c t o r n i t r i t e s never exceeded 0.2 mg-N/L. 4.3.8.3 T o t a l K j e l d a h l N i t r o g e n ( TKN ) Feed TKN c o n c e n t r a t i o n s v a r i e d between 37 and 70 mg-N/L. The e f f l u e n t v a l u e s • ranged from 3 t o 35 mg-N/L. The h i g h e f f l u e n t TKN c o n c e n t r a t i o n on Day 148A o c c u r r e d a t a time when low n i t r i f i c a t i o n r a t e s were r e c o r d e d i n the a e r o b i c r e a c t o r . Appendix I I , Tab l e I I - 3 summarizes the TKN r e s u l t s of t h i s s t u d y . 4.3.9 Phosphates Both o r t h o p h o s p h a t e s and t o t a l phosphates were a n a l y z e d d u r i n g t h i s s t u d y . The methods of phosphate a n a l y s i s were p r e s e n t e d i n S e c t i o n 3.4.8. The e f f i c i e n c y of the treatment scheme, i n terms of P removal, was based on orth o p h o s p h a t e 8 3 d e t e r m i n a t i o n s o n l y . T o t a l phosphate d e t e r m i n a t i o n s were performed so t h a t comparisons w i t h data from o t h e r r e s e a r c h c o u l d be made. 4.3.9.1 Orthophosphates (a) C o n c e n t r a t i o n s As d i s c u s s e d i n S e c t i o n 3.4.8.1, orthophosphate d e t e r m i n a t i o n s were performed on samples f i l t e r e d t hrough a 0.45 ym membrane f i l t e r , e x c ept i n the case of feed samples which were u n f i l t e r e d . C o n c e n t r a t i o n s of o r t h o p h o s p h a t e s i n the f e e d , a l l r e a c t o r s , and the e f f l u e n t a r e g i v e n i n F i g u r e 4.4. The lowe s t o r t h o p h o s p h a t e l e v e l i n the a e r o b i c r e a c t o r of 3.3 mg-P/L o c c u r r e d on Day 28A. T h i s r e l a t i v e l y low r e s u l t c o r r e s p o n d e d t o an u n u s u a l l y h i g h o r t h o p h o s p h a t e c o n c e n t r a t i o n of 13.2 mg-P/L i n the a n a e r o b i c r e a c t o r . A l t h o u g h not as marked, t h i s phenomenon was a l s o o b s e r v e d on Day 218A. I t appears t h a t h i g h o r t h o p h o s p h a t e l e v e l s i n the a n a e r o b i c r e a c t o r , a re a p r e r e q u i s i t e f o r o b t a i n i n g low P c o n c e n t r a t i o n s i n the a e r o b i c r e a c t o r . In g e n e r a l , e f f l u e n t o r t h o p h o s p h a t e l e v e l s s l i g h t l y exceeded t h o s e of the a e r o b i c r e a c t o r ( by up t o 2.9 mg-P/L). (b) P e r c e n t a g e Removals Orthophosphate p e r c e n t a g e removals a re based on a d i f f e r e n c e i n feed and a e r o b i c r e a c t o r samples because of AEROBIC S R T ( d ) 5 10 SYSTEM S R T ( d ) 7 14 12 J 2 ^ 17 T E M P E R A T U R E I 8 ° C I 4 ° C I O ° C 2 5 52 I 4 ° C ^ 2 2 ^ ~5eT 3 0 4 - 2 0 10-h L E G E N D Feed Anaerobic Reactor Aerobic Reactor Sludge Condi t ioning Reactor Ef f luent 4 1 1 50 100 150 T IME - DAYS 2 0 0 2 3 8 F I G . 4 . 4 ' O R T H O P H O S P H A T E S ( P H A S E A ) . 00 85 p o t e n t i a l P r e l e a s e i n the c l a r i f i e r (due t o a n a e r o b i c c o n d i t i o n s d e v e l o p i n g i n the s l u d g e b l a n k e t ) . C l a r i f i e r r e l e a s e of P was s u b s t a n t i a t e d on numerous o c c a s i o n s i n t h i s s t u d y , s i n c e t y p i c a l e f f l u e n t P c o n c e n t r a t i o n s were g r e a t e r than those i n the a e r o b i c r e a c t o r . C a r e f u l d e s i g n and o p e r a t i o n of c l a r i f i e r s i n f u l l s c a l e t r e a t m e n t f a c i l i t i e s would a v o i d such d i s c r e p a n c i e s between the a e r o b i c r e a c t o r and e f f l u e n t P c o n c e n t r a t i o n s . P e r c e n t a g e removals a r e shown i n F i g u r e 4.5. The maximum removals o b t a i n e d o c c u r r e d on Days 28A and 88A when 55% of the i n f l u e n t o r t h o p h o s p h a t e s were removed by the system. (c) Orthophosphate R e a c t i o n Rates The a n a e r o b i c , a e r o b i c and s l u d g e c o n d i t i o n i n g r e a c t o r o r t h o p h o s p h a t e r e a c t i o n r a t e s a r e p r e s e n t e d i n F i g u r e 4.6. In g e n e r a l , the a n a e r o b i c r e a c t o r biomass was i n v o l v e d i n the r e l e a s e of o r t h o p h o s p h a t e s . E s p e c i a l l y h i g h r e l e a s e r a t e s o c c u r r e d s i m u l t a n e o u s l y w i t h the h i g h e r o r t h o p h o s p h a t e removal p e r c e n t a g e s d i s c u s s e d i n S e c t i o n 4.3.8.1. ( b ) . R e l e a s e i n the a n a e r o b i c r e a c t o r was not a f f e c t e d by the i n s t a l l a t i o n of the s l u d g e c o n d i t i o n i n g r e a c t o r and r e s u l t s c o n t i n u e d t o f l u c t u a t e a p p r e c i a b l y (between -0.43 mg-P/g MLSS/h ( n i t r i f i c a t i o n ) and 4.72 mg-P/g MLSS/h). Simpkins (1979) r e p o r t e d a n a e r o b i c r e l e a s e r a t e s of up t o 10 mg-P/g MLSS/h. The o r t h o p h o s p h a t e r e a c t i o n r a t e s i n the a e r o b i c r e a c t o r were a t a l l times i n the form of u p t a k e ; v a r y i n g between 0.02 and 4.37 mg-P/g MLSS/h (compared t o a p p r o x i m a t e l y AEROBIC S R T l d ) 5 10 SYSTEM SRT(d ) 7 14 25 52 T E M P E R A T U R E I 8°C > o UJ CE < I CL </> O I a o I i - cc o 0 I 4 ° C I 0 ° C I4°C L E G E N D Aerobic Reoctor * Ef f luent * * 50 2 0 0 100 150 T IME - DAYS * Indicotes feed versus oerobic reactor removol * * Indicates feed versus effluent removal FIG.4.5^ P E R C E N T A G E O R T H O P H O S P H A T E R E M O V A L ( P H A S E A ) 238 oo CTl a c n O 3 J H X O ~u I o c o T J X J> -t m 33 m > o -I o z J> —i m to x CO m ORTHOPHOSPHATE UPTAKE RATES mgP/gMLSS/h O O ORTHOPHOSPHATE R E L E A S E RATES mg P/g MLSS /h O o I — o Ul o ..\J ..V-H 2 ' f / / ° J> C0| / ui L- / / \ ro / O O o o -4— Ul o ro 6 o ui O b o 00 ' J> 00 33 O m CD 2 O 00 CO 33 X -1 -1 a. a. •—- . - on o O ' I I i I o o 'J. > > c a a. o fD oQ cr (» r> o cr Co X o Q. r& O X r> CD —». O O o rt o 5" JD 33 a o lor "IT -g iro 5 1 ^ Ul ( M ro ;ui ui fro ai i ~ Z.8 88 7 mg-P/g MLSS/h observed by Simpkins ( 1 9 7 9 ) ) . When r e l e a s e r a t e s were r e l a t i v e l y h i g h i n the a n a e r o b i c r e a c t o r , the a e r o b i c uptake r a t e s were a l s o c o m p a r a t i v e l y h i g h . 4.3.9.2 T o t a l Phosphates T o t a l phosphates were m o n i t o r e d o n l y o c c a s i o n a l l y ' and are r e p o r t e d i n Appendix I I , T a b l e I I - 4 . R e s u l t s i n d i c a t e t h a t the r a t i o of or t h o p h o s p h a t e s t o t o t a l phosphates i n u n f i l t e r e d feed samples ranged between 0.58 and 0.99. V i r t u a l l y a l l of the f i l t e r e d e f f l u e n t t o t a l phosphates c o n s i s t e d of o r t h o p h o s p h a t e s . 4.3.10 AP/ACOD Appendix I I , F i g u r e 11-3 summarizes the AP/ACOD r a t i o s f o r t h i s phase of s t u d y . The c a l c u l a t i o n methods used were p r e s e n t e d i n S e c t i o n 3.10. Orthophosphates i n the a e r o b i c r e a c t o r were assumed t o c o n s t i t u t e 100% of t o t a l phosphates. Phase A AP/ACOD r a t i o s v a r i e d from 0.004 t o 0.027, y i e l d i n g P removals of 10% to 52% r e s p e c t i v e l y . For the most p a r t , AP/ACOD r a t i o s were a t the lower end of the range d e t e r m i n e d by o t h e r r e a s e r c h e r s which were d i s c u s s e d i n S e c t i o n 2.2.2. 4.3.11 H y d r a u l i c R e t e n t i o n Time ( HRT ) Both nominal and a c t u a l h y d r a u l i c r e t e n t i o n times m a i n t a i n e d i n each of the t h r e e r e a c t o r s were p r e s e n t e d i n Table 89 3.3. The HRT's were r e l a t i v e l y c o n s t a n t i n each r e a c t o r u n t i l Day 186A, when f l o w s were g e n e r a l l y reduced; t h i s caused s i g h t l y l o n g e r l i q u i d r e t e n t i o n . 4.3.12 S o l i d s R e t e n t i o n Time ( SRT ) As noted both the a e r o b i c and system SRT's are p r e s e n t e d w i t h each f i g u r e i n t h i s c h a p t e r . The days f o r which SRT's are not g i v e n r e p r e s e n t p e r i o d s of system i n s t a b i l i t y (See S e c t i o n 3.7). The s o l i d s r e t e n t i o n t imes were i n c r e a s e d as Phase A proceeded t o a c h i e v e h i g h e r suspended s o l i d s i n the r e a c t o r s , thus i n c r e a s i n g the p o t e n t i a l f o r the growth of v o l u t i n f o r ming b a c t e r i a ( S e c t i o n 2.1.3). 4.4 C o n d i t i o n s A f f e c t i n g Phosphate Removal Due t o d a i l y (and perhaps h o u r l y ) f l u c t u a t i o n s of the i n f l u e n t COD, no e f f e c t of t h i s parameter on the phosphate uptake r a t e i n any of the t h r e e r e a c t o r s c o u l d be a c c u r a t e l y d i s c e r n e d . There was no apparent r o l e p l a y e d by the r e a c t o r MLSS c o n c e n t r a t i o n s , per s e , on the phosphate r e a c t i o n r a t e s . MLVSS was used as an i n d i c a t o r of the v i a b l e biomass i n the system i n terms of phosphate r e l e a s e or upta k e . No knowledge i s c u r r e n t l y a v a i l a b l e r e g a r d i n g the a c t u a l o r g a n i s m i n v o l v e d i n the uptake and r e l e a s e of phosphates (see S e c t i o n 2.1.3); t h u s the c h o i c e of MLVSS i s a r b i t r a r y a t t h i s p o i n t . U n l i k e r e s u l t s r e p o r t e d by Menar and J e n k i n s ( 1 970), enhanced P removal d i d not p a r a l l e l a 90 r e d u c t i o n i n the r a t i o of MLVSS t o MLSS i n the a e r a t i o n tank d u r i n g Phase A. S i n c e the DO i n the r e a c t o r s was m a i n t a i n e d r e l a t i v e l y c o n s t a n t throughout t h i s phase (<0.3 mg/L) i n the a n a e r o b i c and slu d g e c o n d i t i o n i n g r e a c t o r s , and t y p i c a l l y 2 t o 4 mg/L i n the a e r o b i c r e a c t o r , no e f f e c t of t h i s parameter on phosphate r e a c t i o n r a t e s c o u l d be d e t e r m i n e d . Complete a n a e r o b i o s i s (ORP t y p i c a l l y <<-130 mV) was m a i n t a i n e d i n the a n a e r o b i c r e a c t o r ; thus the r e l e a s e of phosphates s h o u l d have o c c u r r e d throughout Phase A ( a c c o r d i n g t o Jank e t a l . ( 1 9 7 8 ) ) . A n a e r o b i c r e l e a s e was a c h e i v e d o n l y s p o r a d i c a l l y however, w i t h subsequent uptake i n the a e r o b i c r e a c t o r a l s o f l u c t u a t i n g a p p r e c i a b l y . At the b e g i n n i n g of Phase A, phosphate r e l e a s e and uptake r a t e s were h i g h (Day 28A). T h i s phenomenon can p r o b a b l y be a t t r i b u t e d t o the i n s t a b i l i t y of the system a t t h a t t i m e . On Day 160A the system was shut down (see S e c t i o n 4.2.4). Phosphate a n a l y s i s of the a n a e r o b i c r e a c t o r c o n t e n t s ( a f t e r the system had been r e s t a r t e d ) i n d i c a t e d the uptake of phosphates i n t h i s u n i t . Uptake c o n t i n u e d d u r i n g the subsequent two weeks. T h i s may have been due t o the a n a e r o b i c biomass a t t e m p t i n g t o overcome the endogenous phase which r e s u l t e d from the shut-down. Upon r e s t a r t i n g the p r o c e s s , a n a e r o b i c r e s p i r a t i o n by the biomass i n t h i s u n i t would have r e s u l t e d i n r a p i d uptake of carbonaceous m a t e r i a l and s i m u l t a n e o u s l y a l s o of pho s p h a t e s . I t may be noted t h a t phosphorus would of c o u r s e be abundant s i n c e the endogenous 91 c o n d i t i o n s d u r i n g the shut-down p e r i o d would have been conducive t o the t r i g g e r i n g of the r e l e a s e phenomenon. No d i s c e r n a b l e e f f e c t s on the b e h a v i o r of the a e r o b i c biomass were observed as a r e s u l t of t h i s system m o d i f i c a t i o n . Phosphate uptake r a t e s i n the a e r o b i c r e a c t o r were r e l a t i v e l y low however. The e f f e c t of pH and a l k a l i n i t y on phosphate r e a c t i o n r a t e s was not s u b s t a n t i a t e d d u r i n g t h i s phase of s t u d y . There i s no e v i d e n c e t h a t a reduced a l k a l i n i t y i n the e f f l u e n t o c c u r e d s i m u l t a n e o u s l y w i t h enhanced P up t a k e , which the proponents of the c h e m i c a l p r e c i p i t a t i o n mechanism m a i n t a i n (Menar and J e n k i n s ( 1 9 7 0 ) ) . Trace metal e f f e c t s may p l a y an i m p o r t a n t r o l e but much more i n f o r m a t i o n i s r e q u i r e d b e f o r e t h e s e can be i s o l a t e d . The f e e d used i n t h i s s tudy c o n t a i n e d r e l a t i v e l y low metal c o n c e n t r a t i o n s . Enhanced removal of P (by c h e m i c a l p r e c i p i t a t i o n ) d i d not m a t e r i a l i z e , even though r e l a t i v e l y h i g h c a l c i u m and magnesium i o n c o n c e n t r a t i o n s were m a n i f e s t e d i n the f e e d d u r i n g Phase A. The c o n t e n t of m e t a l s i n the f e e d was i n g e n e r a l c o n s t a n t ; t h u s t h e i r e f f e c t s may be c o n s i d e r e d as unchanged f o r the d u r a t i o n of t h i s phase of s t u d y . I t i s n e c e s s a r y t o have a b e t t e r m i c r o b i o l o g i c a l u n d e r s t a n d i n g of the e f f e c t s on phosphate r e a c t i o n r a t e s i n wastewater treatment schemes and " t h r e s h o l d " m e t a l s c o n c e n t r a t i o n , b e f o r e t h i s a s p e c t can be a d d r e s s e d . Trace m e t a l s may be h a r m f u l t o the phosphate a c c u m u l a t i n g organisms a t h i g h e r s l u d g e ages s i n c e t h e i r a c c u m u l a t i o n i n the s l u d g e may be s u b s t a n t i a l . A more d e t a i l e d 92 d i s c u s s i o n on the r o l e of t r a c e m e t a l s i s p r e s e n t e d i n S e c t i o n 5.2.7. Numerous r e s e a r c h e r s , t o d a t e , have emphasized the importance of m a i n t a i n i n g a t r u l y a n a e r o b i c r e a c t o r a t the head end of b i o l o g i c a l P removal t r e a t m e n t schemes ( S e c t i o n 2.2). I t was e v i d e n t however, from t h i s work, t h a t s i g n i f i c a n t l e v e l s of n i t r a t e s were r e c y c l e d t o the a n a e r o b i c r e a c t o r v i a the sludge r e t u r n (up t o 16 mg-N/L). These n i t r a t e s were r a p i d l y d e n i t r i f i e d w i t h the a i d of a carbon source d e r i v e d from the raw sewage f e e d . Stemming n i t r i f i c a t i o n i n the a e r o b i c r e a c t o r by t e m p e r a t u r e r e d u c t i o n had i n s i g n i f i c a n t e f f e c t s i n the l o n g term. The s l u d g e c o n d i t i o n i n g r e a c t o r was i n s t a l l e d t o p r o v i d e a b a s i n where d e n i t r i f i c a t i o n of the r e t u r n s l u d g e would take p l a c e p r i o r to the a n a e r o b i c r e a c t o r . In t h i s way, the p o s s i b l e i n t e r f e r e n c e of d e n i t r i f i c a t i o n w i t h the phosphate r e l e a s e mechanism i n the a n a e r o b i c r e a c t o r was a v o i d e d . A l t h o u g h the s l u d g e c o n d i t i o n i n g r e a c t o r was i n v o l v e d i n endogenous d e n i t r i f i c a t i o n , which i s t y p i c a l l y s l o w e r than d e n i t r i f i c a t i o n r a t e s w i t h raw wastewater as a s u b s t r a t e , i t was c a p a b l e of almost c o m p l e t e l y d e n i t r i f y i n g the s l u d g e r e t u r n . The d e n i t r i f i c a t i o n r a t e s i n the a n a e r o b i c r e a c t o r , subsequent t o the i n s t a l l a t i o n of the. s l u d g e c o n d i t i o n i n g r e a c t o r , were n e g l i g i b l e . The r e l e a s e of phosphates i n the a n a e r o b i c zone d i d not change as a r e s u l t of t h i s m o d i f i c a t i o n however. The r e a c t i o n r a t e s g i v e n a r e , i n the case of b oth n i t r a t e s and p h o s p h a t e s , a f u n c t i o n of MLSS l e v e l s m a i n t a i n e d i n each of 93 the r e a c t o r s - thus h i g h MLSS c o n c e n t r a t i o n s y i e l d low r e a c t i o n r a t e s and v i c e v e r s a . T h i s assumption c o u l d be m i s l e a d i n g , e s p e c i a l l y i f i t i s det e r m i n e d a t a l a t e r date t h a t t h a t MLSS i s not the most a p p r o p r i a t e parameter i n r e a c t i o n r a t e s c a l c u l a t i o n s . Temperature e f f e c t s must a l s o be c o n s i d e r e d when d e a l i n g w i t h the magnitudes of the r e a c t i o n r a t e s . 94 CHAPTER 5 PHASE B: CONDITIONS REQUIRED FOR THE SUCCESSFUL BIOLOGICAL REMOVAL OF PHOSPHATES FROM WASTEWATER 5.1 D e s c r i p t i o n of System O p e r a t i n g C o n d i t i o n s T h i s c h a p t e r d e s c r i b e s i n d e t a i l the c o n d i t i o n s n e c e s s a r y f o r the s u c c e s s f u l removal of phosphates from m u n i c i p a l wastewater, as d e t e r m i n e d f o r the c o n f i g u r a t i o n of the system used i n t h i s s t u d y . A l t h o u g h t h e r e were no major p h y s i c a l m o d i f i c a t i o n s d u r i n g t h i s phase, the o p e r a t i o n a l c h a r a c t e r i s t i c s were s i g n i f i c a n t l y a l t e r e d . From the r e s u l t s o b t a i n e d d u r i n g Phase A, i t was apparent t h a t P removal was not o c c u r r i n g w i t h a low s l u d g e age system, even when the i n p u t of n i t r a t e s t o the a n a e r o b i c r e a c t o r was n e g l i g i b l e . Thus Phase B was c h a r a c t e r i z e d by a h i g h mean c e l l r e s i d e n c e p e r i o d . Wasting of mixed l i q u o r from the a e r o b i c r e a c t o r was h a l t e d on Day IB f o l l o w i n g the c o m p l e t i o n of Phase A. No w a s t i n g was p r a c t i s e d u n t i l Day 27B. The l i q u i d t emperature was r a i s e d t o 18° C on Day IB and m a i n t a i n e d a t t h i s l e v e l t h roughout Phase B. These measures were taken t o promote the growth of m i c r o o r g a n i s m s and thus a c h i e v e a h i g h MLSS c o n t e n t i n the r e a c t o r s . A h i g h s l u d g e age would i n t u i t i v e l y promote the e s t a b l i s h m e n t of a l a r g e p o p u l a t i o n of organisms which a r e c a p a b l e of P upta k e . The s l u d g e r e c y c l e r a t e was m a i n t a i n e d t y p i c a l l y a t h a l f the f e e d r a t e . T h i s was n e c e s s a r y s i n c e net s o l i d s growth i s 95 slow a t h i g h s l u d g e ages, y i e l d i n g l i t t l e s e t t l e d sludge i n the c l a r i f i e r . Care a l s o had t o be taken t o a v o i d r e c i r c u l a t i o n of c l e a r e f f l u e n t t o the sludge c o n d i t i o n i n g r e a c t o r w i t h a p o s s i b i l i t y of subsequent d i l u t i o n of a l l t h r e e r e a c t o r s . 5.2 R e s u l t s and D i s c u s s i o n The system removed up t o 98% of phosphates and 96% of COD d u r i n g Phase B. Ma r k e d l y improved P removal was i n i t i a t e d on Day 17B when an unprecedented 92% P removal ( f e e d v e r s u s a e r o b i c r e a c t o r ) was a c h e i v e d . C o n s i s t e n t l y h i g h p e r c e n t a g e removal r a t e s were o b t a i n e d f o r 30 days f o l l o w i n g t h i s o b s e r v a t i o n , w h i l e a h i g h s o l i d s r e t e n t i o n time was m a i n t a i n e d . The s l u d g e age was reduced b e g i n n i n g on Day 40B, by i n c r e a s i n g the w a s t i n g r a t e , i n an e f f o r t t o determine the optimum s l u d g e age below which P removal i s not p o s s i b l e . The system f a i l e d i n terms of i t s c a p a b i l i t y t o remove P on Day 52B, a t an approximate a e r o b i c s l u d g e age of 24 days. A f u r t h e r two weeks of t e s t i n g showed t h a t the system d i d not r e g a i n i t s a b i l i t y f o r enhanced P remo v a l . In f a c t , on t h r e e o c c a s i o n s , P c o n c e n t r a t i o n s of f i l t e r e d samples from the a e r o b i c r e a c t o r were h i g h e r than those i n the u n f i l t e r e d i n f l u e n t samples. 5.2.1 Che m i c a l Oxygen Demand ( COD ) S y n t h e t i c f e e d a d d i t i o n was p r a c t i s e d as d i c t a t e d by the raw sewage COD c o n c e n t r a t i o n s t h r o u g h o u t Phase B. C o n s i s t e n t i n f l u e n t COD c o n c e n t r a t i o n s were not a c h i e v e d however, and 96 values ranged between 180 and 1410 mg/L (Appendix I I , Figure I I - l ) . COD percentage removals f o r the system d u r i n g Phase B v a r i e d from 83 to 96%, with an e x c e p t i o n a l l y low removal of 55% on Day 18B. A c h r o n o l o g i c a l p r e s e n t a t i o n of percentage COD removals d u r i n g Phase B i s given i n F i g u r e 5.1. Once again, as p r e v i o u s l y p o i n t e d out i n S e c t i o n 4.3.1, low COD removals occu r r e d c o n c u r r e n t l y with low i n f l u e n t COD. One reason f o r t h i s occurrence may have been that the i n f l u e n t COD was a t y p i c a l on the given days of sampling. T h i s would have had a p a r t i c u l a r l y n o t i c i b l e e f f e c t , s i n c e the e f f l u e n t was sampled simultaneously with the feed, and would not have yet a d j u s t e d to any increase in i n f l u e n t COD. A l s o , there may be a b a s e l i n e l e v e l of non-biodegradable o r g a n i c s i n the feed, which would be conducive to the above r e s u l t s , i n that a high COD would not n e c e s s a r i l y i n d i c a t e a high amount of a v a i l a b l e carbonaceous m a t e r i a l . 5.2.2 T o t a l Suspended S o l i d s ( TSS ) To achieve a high sludge age, m i c r o b i a l growth was encouraged i n a l l three r e a c t o r s by c o n t r o l l i n g the d a i l y wasting r a t e . The s o l i d s c o n c e n t r a t i o n s i n the anaerobic and a e r o b i c r e a c t o r s were 2500 mg/L at the beginning of Phase B, reaching a peak of 5600 mg/L a f t e r approximately 30 days, and g r a d u a l l y d e c r e a s i n g to 2500 mg/L at the end of t h i s phase (See F i g u r e 5.1). The TSS i n the sludge c o n d i t i o n i n g r e a c t o r ranged from 3570 Q < O O or 1 0 0 > o 2 A E R O B I C S R T Id ) 3 7 S Y S T E M S R T (d ) 8 6 2 4 I ; 5 4 T E M P E R A T U R E I 8 ° C «a . 6 0 0 0 2 0 0 0 2 0 4 0 6 8 T I M E - D A Y S F I G . 5 . 1 : S Y S T E M P E R C E N T A G E C O D R E M O V A L A N D A E R O B I C M L S S L E V E L S ( P H A S E B ) . 98 t o 12,940 mg/L. T h i s l a r g e v a r i a t i o n was p r i m a r i l y due t o poor c l a r i f i e r performance ( S e c t i o n 4.3.2.). Manual, g e n t l e s t i r r i n g of the c l a r i f i e r was p r a c t i s e d ( t y p i c a l l y t w i c e d a i l y ) t o d i s l o d g e the n i t r o g e n gas bubbles t r a p p e d i n the s l u d g e . T h i s a l l e v i a t e d the problem somewhat but c o n d i t i o n s r e v e r t e d t o the adverse a t n i g h t . Because of the s m a l l s i z e , l i t t l e b u f f e r i n g c a p a c i t y was i n h e r e n t i n the system ( t o overcome the f e e d s t r e n g t h f l u c t u a t i o n s and i n c o n s i s t e n c y i n the s l u d g e r e t u r n s o l i d s c o n t e n t ) a d v e r s e l y a f f e c t i n g the system performance. The s m a l l s c a l e pumping system was the major cause of the l a r g e f l u c t u a t i o n s i n feed c o m p o s i t i o n . O f t e n , p a r t i a l b l o c k a g e s of the feed l i n e o c c u r r e d c a u s i n g a f i l t r a t i o n e f f e c t on the f e e d . A l s o such f a c t o r s as c l e a n i n g of the r e a c t o r w a l l s t o d i s l o d g e any biomass a d h e r i n g t o the s u r f a c e s caused shock l o a d i n g on the system. T h i s was a r e s u l t of the r e l a t i v e l y h i g h s u r f a c e area t o volume r a t i o s i n h e r e n t i n a s m a l l s c a l e system, compared t o f u l l s c a l e o p e r a t i o n s . E f f l u e n t TSS c o n c e n t r a t i o n s a r e p r e s e n t e d i n Appendix I I , F i g u r e I I - 2 . D a i l y f l u c t u a t i o n s were common f o r reasons d i s c u s s e d i n S e c t i o n 4.3.2. Because of the poor r e s u l t s o b t a i n e d w i t h t h i s s m a l l s c a l e system, no p e r c e n t a g e removals of suspended s o l i d s t h r o u g h the system a r e p r e s e n t e d . Large s c a l e c l a r i f i c a t i o n would p r e c l u d e the problems encountered w i t h bench s c a l e u n i t s (Barnard ( 1 9 7 4 ) ) . The e x c e s s i v e TSS l o s t i n the e f f l u e n t caused problems w i t h a c h i e v i n g and/or m a i n t a i n i n g h i g h s o l i d s c o n c e n t r a t i o n s i n 99 the r e a c t o r s . Rigorous maintenance of the system was r e q u i r e d to prevent washout. Average e f f l u e n t suspended s o l i d s c o n c e n t r a t i o n s were used in SRT c a l c u l a t i o n s ( S e c t i o n 3.7). 5.2.3. Mixed Liquor V o l a t i l e Suspended S o l i d s ( MLVSS ) On an average b a s i s the v o l a t i l e suspended s o l i d s content t y p i c a l l y c o n s t i t u t e d 84% of the t o t a l suspended s o l i d s f o r a l l three r e a c t o r s d u r i n g t h i s phase. T h i s was s l i g h t l y lower than determined dur i n g Phase A. 5.2.4 D i s s o l v e d Oxygen ( DO ) D i s s o l v e d oxygen l e v e l s i n the a e r o b i c r e a c t o r were t y p i c a l l y maintained between 2 and 4 mg/L d u r i n g t h i s phase. Nightime values were g e n e r a l l y s l i g h t l y higher than day time, due to a l e s s dense sludge r e t u r n (causing d i l u t i o n of r e a c t o r s o l i d s ) . In e f f e c t , nighttime c o n d i t i o n s caused the increase of the F/M r a t i o , thus lowering the oxygen demand. The DO of both the anaerobic and the sludge c o n d i t i o n i n g r e a c t o r s d i d not exceed 0.2 mg/L at any time, and were t y p i c a l l y n e g l i g i b l e . 5.2.5. O x i d a t i o n Reduction P o t e n t i a l ( ORP ) H i g h l y anaerobic c o n d i t i o n s e x i s t e d i n the anaerobic r e a c t o r throughout Phase B. The ORP f l u c t u a t e d between -300 and -500 mV ( t y p i c a l l y approaching the l a t t e r higher v a l u e ) ; w e l l 100 below the a n o x i c c u t - o f f p o i n t of -130 mV. 5.2.6 A l k a l i n i t y and pH Appendix I I , T a b l e I I - l summarizes a l k a l i n i t y and pH data o b t a i n e d d u r i n g Phase B. A l t h o u g h the a l k a l i n i t y of the raw sewage, as a n a l y z e d upon a r r i v a l a t the l a b o r a t o r y , was i n g e n e r a l s i m i l a r t o t h a t t y p i c a l of Phase A, the feed a l k a l i n i t y was h i g h e r throughout Phase B . T h i s can be a c c o u n t e d f o r by the r e l a t i v e l y h i g h a d d i t i o n s of the s y n t h e t i c sewage (which had a h i g h b i c a r b o n a t e c o n t e n t ) d u r i n g Phase B. A l k a l i n i t y was l o s t i n the a e r o b i c r e a c t o r , w h i l e i t was g a i n e d i n the a n a e r o b i c and s l u d g e c o n d i t i o n i n g r e a c t o r s . T h i s o b s e r v a t i o n s u p p o r t s the concept t h a t a l k a l i n i t y i s formed d u r i n g the r e d u c t i o n of n i t r a t e s , a t a r a t e which i s t w i c e t h a t of the a l k a l i n i t y used up d u r i n g the n i t r i f i c a t i o n of ammonia i n a e r o b i c r e a c t i o n s (Beer and Wang ( 1 9 7 8 ) ) . Trends i n pH c o u l d not be s u b s t a n t i a t e d d u r i n g t h i s phase, due t o i n s u f f i c i e n t d a t a and r e s u l t s which were e x t r e m e l y c l o s e i n magnitude; thus i t was d i f f i c u l t t o d i s c o u n t e x p e r i m e n t a l e r r o r . I t can be noted however, t h a t low a e r o b i c r e a c t o r and e f f l u e n t pH v a l u e s o c c u r r e d s i m u l t a n e o u s l y w i t h low a l k a l i n i t i e s . 5.2.7 Trace M e t a l s As d e s c r i b e d i n S e c t i o n 4.3.7, t r a c e m e t a l a n a l y s i s was performed on each f r e s h d e l i v e r y of raw sewage t o the 101 l a b o r a t o r y . Feed t r a c e m e t a l s c o n c e n t r a t i o n s d i d not change a p p r e c i a b l y from those d e t e r m i n e d i n Phase A (Appendix I I , Table I I - 2 ) . On Day 61B a scan was performed of the t r a c e m e t a l c o n t e n t of u n f i l t e r e d samples of the i n f l u e n t , the c o n t e n t s of each r e a c t o r , and the e f f l u e n t (Appendix I I , Table 11-5). The r e s u l t s i n d i c a t e h i g h m e t a l s c o n c e n t r a t i o n s i n the mixed l i q u o r of a l l t h r e e r e a c t o r s , p a r t i c u l a r l y i n the s l u d g e c o n d i t i o n i n g r e a c t o r . Research by N e u f e l d and Hermann (1975) i n d i c a t e s t h a t the r a t i o of m e t al i n the biomass, t o t h a t i n the s u r r o u n d i n g l i q u i d on. a weight b a s i s , may v a r y from 4000 t o 10000 f o r cadmium and z i n c . A U.S. P u b l i c H e a l t h S e r v i c e study (1965) i n d i c a t e d t h a t i f the i n f l u e n t l e v e l s of chromium, copper, n i c k e l , and z i n c exceeded 10 mg/L i n any c o m b i n a t i o n , a 5% decrease i n t r e a t m e n t e f f i c i e n c y ( i n terms of BOD and SS removal) can be e x p e c t e d i n a c t i v a t e d s l u d g e schemes; n i t r i f i c a t i o n was p r a c t i c a l l y e l i m i n a t e d a t these c o n c e n t r a t i o n s . B a r t h et a l . (1967) showed t h a t up t o 60% removal of m e t a l s i s p o s s i b l e w i t h secondary sewage t r e a t m e n t , c a u s i n g the i n f l o w t o the s l u d g e d i g e s t e r s t o c o n t a i n up t o 37 t i m e s the m e t a l s c o n c e n t r a t i o n of the p l a n t i n f l u e n t . Day 61B r e s u l t s i n d i c a t e over 70% removal of i r o n from i n f l u e n t t o e f f l u e n t , w h i l e o t h e r m e t a l p e r c e n t a g e removals were t y p i c a l l y l o w e r . R e s u l t s from t h i s s tudy show t h a t the s ludge r e t u r n m e t a l c o n c e n t r a t i o n (based on the s l u d g e c o n d i t i o n i n g r e a c t o r m e t a l l e v e l s ) were as much as 120 times (as was the case f o r chromium) t h a t of the f e e d . In f a c t , o n l y c a l c i u m and magnesium c o n c e n t r a t i o n s i n the s l u d g e were l e s s than 37 times 102 t h a t i n the f e e d . In the above d i s c u s s i o n , the sludge c o n d i t i o n i n g r e a c t o r m etal c o n c e n t r a t i o n s have been compared w i t h the d i g e s t o r i n f l o w l e v e l s r e p o r t e d i n o t h e r r e s e a r c h work. The f e e d c a l c i u m and magnesium i o n c o n c e n t r a t i o n s were a p p r o x i m a t e l y 8.4 and 2.2 mg/L r e s p e c t i v e l y . Day 61B r e s u l t s show t h a t 8.3 mg/L c a l c i u m and 1.9 mg/L magnesium were p r e s e n t i n the e f f l u e n t . Thus an i n s i g n i f i c a n t r e d u c t i o n of these i o n s o c c u r r e d v i a the system used i n t h i s s t u d y , even though e x c e l l e n t P removals were r e a l i z e d . B a r n a r d (1974) o b t a i n e d enhanced P uptake w h i l e the C a + + and M g + + e f f l u e n t c o n c e n t r a t i o n s were 38 and 18 mg/L r e s p e c t i v e l y ( i n f l u e n t l e v e l s were not r e p o r t e d ) . On t h i s b a s i s , P p r e c i p i t a t i o n seems an u n l i k e l y mechanism. 5.2.8 N i t r o g e n Forms Because of the w i d e l y v a r i a b l e r e s u l t s o b t a i n e d d u r i n g Phase A, the e f f e c t s of the p r e s ence of the v a r i o u s n i t r o g e n forms was not s u b s t a n t i a t e d i n terms of e i t h e r phosphate r e l e a s e or u p t a k e . The m o n i t o r i n g of n i t r a t e s , n i t r i t e s , and t o t a l K j e l d a h l n i t r o g e n was thus c o n t i n u e d d u r i n g Phase B t o s u b s t a n t i a t e these f i n d i n g s . The e f f e c t s of n i t r i f i c a t i o n i n the a e r o b i c r e a c t o r on phosphate uptake r a t e s a l s o r e q u i r e d f u r t h e r c l a r i f i c a t i o n . 103 5.2.8.1 N i t r a t e s (a) C o n c e n t r a t i o n s T y p i c a l feed n i t r a t e l e v e l s d i d not exceed 0.04 mg-N/L. R e l a t i v e l y high values ( f o r example, 15 mg-N/L on Day 13B) most probably r e s u l t e d when feed- s t o r a g e , drum l i q u i d l e v e l s were low, encouraging a i r to be e n t r a i n e d v i a a g i t a t i o n by s t i r r i n g . The anaerobic r e a c t o r n i t r a t e c o n c e n t r a t i o n s v a r i e d from <0.01 to 0.11 mg-N/L. The l a t t e r high value c i t e d i s a t y p i c a l of t h i s phase. I t i s p o s s i b l e that the "sudden" r e d u c t i o n of ae r o b i c sludge age, from 37 days to 24 days, may have t e m p o r a r i l y a l t e r e d the c h a r a c t e r i s t i c s and/or f u n c t i o n s of the biomass. N i t r a t e l e v e l s in the ae r o b i c r e a c t o r d u r i n g Phase B were c h a r a c t e r i z e d by e r r a t i c f l u c t u a t i o n s . Values between 0.25 and 34.2 mg-N/L were recorded. E f f l u e n t n i t r a t e c o n c e n t r a t i o n s p a r a l l e l e d the ae r o b i c r e a c t o r v a l u e s . In g e n e r a l , as was a l s o the case i n Phase A, the e f f l u e n t was t y p i c a l l y lower in n i t r a t e s (as much as 14.3 mg-N/L on Day 48B). T h i s d i f f e r e n c e accounts f o r the f r e q u e n t l y observed d e n i t r i f i c a t i o n i n the c l a r i f i e r u n i t . E f f l u e n t n i t r a t e l e v e l s are given i n F i g u r e 5.2. R e l a t i v e l y low n i t r a t e c o n c e n t r a t i o n s occurred at the high system sludge age of 86 days. T h i s phenomenon was probably caused by the d e s t r u c t i o n of the n i t r i f y i n g p o r t i o n of the biomass due to an e x c e s s i v e l y long anaerobic SRT (Marais (1979a)). The r e d u c t i o n i n system SRT to 104 AEROBIC SRT Id ) 3 7 SYSTEM S R T l d ) 86 TEMPERATURE I8°C TIME - DAYS F I G . 5 . 2 * E F F L U E N T N I T R A T E S ( P H A S E B ) . 105 54 days r e t u r n e d the n i t r a t e s i n the e f f l u e n t (due t o n i t r i f i c a t i o n a c t i v i t y i n the a e r o b i c r e a c t o r ) t o p r e v i o u s l y e l e v a t e d l e v e l s ; The s l u d g e c o n d i t i o n i n g r e a c t o r , whose p r i m a r y f u n c t i o n was the d e n i t r i f i c a t i o n of the c l a r i f i e r u n d e r f l o w , c o n t a i n e d c o n s i s t e n t l y low n i t r a t e l e v e l s , g e n e r a l l y <0.1 mg-N/L. (b) N i t r i f i c a t i o n and D e n i t r i f i c a t i o n Rates The n i t i f i c a t i o n and d e n i t r i f i c a t i o n r a t e s were c a l c u l a t e d as d e s c r i b e d i n S e c t i o n 3.8 and are p r e s e n t e d i n F i g u r e 5.3 f o r each of the r e a c t o r s . D e n i t r i f i c a t i o n was the norm i n the a n a e r o b i c r e a c t o r , a l t h o u g h two i n s t a n c e s of apparent n i t r i f i c a t i o n o c c u r r e d on Days 41B and 48B. These r a t e s were n e g l i g i b l e i n magnitude (<0.007 mg-N/g MLSS/h). At these low r a t e s , f a c t o r s such as sa m p l i n g t e c h n i q u e s and sample p r e p a r a t i o n and a n a l y s i s may p l a y s i g n i f i c a n t r o l e s i n d e t e r m i n i n g whether the a n a e r o b i c biomass a p p a r e n t l y p l a y s a n i t r i f y i n g or a d e n i t r i f y i n g r o l e . The a e r o b i c r e a c t o r m i c r o o r g a n i s m s were i n v o l v e d i n n i t r i f i c a t i o n throughout Phase B. The degree of n i t r i f i c a t i o n was h i g h l y v a r i a b l e , r a n g i n g from <0.01 t o 1.42 mg-N/g MLSS/h. As e x p e c t e d , the low r a t e s c o r r e s p o n d e d t o a low n i t r a t e c o n c e n t r a t i o n i n the a e r o b i c r e a c t o r and v i c e v e r s a . As was p r e v i o u s l y mentioned, the sl u d g e c o n d i t i o n i n g r e a c t o r was i n s t a l l e d t o d e n i t r i f y the r e t u r n s l u d g e . T h i s 106 co CO _ J 5 z £ i z o H < i- AEROBIC SRT(d ) SYSTEM SRT(d) z O £ i= ^ < CO o to 37 86 24 54 TEMPERATURE I 8 ° G 3.00 V 2.50 2 . 0 0 4 - 1.50 1.00-h 0.00 LEGEND IV \ 0.50+- \ \ 44 Anaerobic Reactor Aerobic Reactor Sludge Conditioning Reactor 0 ... -20 40 68 T I M E - DAYS 0.504- — z UJ 6 1.00-L F IG.5.3 8 NITRIFICATION AND DENITRIFICATION RATES ( PHASE B ). 10 7 measure (as d e s c r i b e d i n S e c t i o n 4.3.8.1 (b)) proved s u c c e s s f u l . D e n i t r i f i c a t i o n r a t e s i n t h i s r e a c t o r were l e s s than 0.36 mg-N/g MLSS/h and although of l e s s e r magnitude, were a mir r o r image of the n i t r i f i c a t i o n r a t e s i n the a e r o b i c r e a c t o r . The f u n c t i o n of the c l a r i f i e r c o n t e n t s , i n terms of n i t r i f i c a t i o n or d e n i t r i f i c a t i o n a c t i v i t y , c o u l d not be determined, due to v a r i a t i o n s i n the sludge blanket height and c o n c e n t r a t i o n . The v i s u a l o b s e r v a t i o n of bubbles (assumed to be ni t r o g e n gas) i n the sludge, and the lower n i t r a t e c o n c e n t r a t i o n s i n the e f f l u e n t , as compared to the aerobic r e a c t o r , s t r o n g l y p o i n t to d e n i t r i f i c a t i o n a c t i v i t y in the c l a r i f i e r u n i t . 5.2.8.2 N i t r i t e s Feed n i t r i t e c o n c e n t r a t i o n s were t y p i c a l l y <0.02 mg-N/L throughout Phase B. The anaerobic r e a c t o r n i t r i t e s during t h i s phase were <0.04 mg-N/L. N i t r i t e l e v e l s i n the ae r o b i c r e a c t o r ranged between 0.02 and 4.75 mg-N/L with s i m i l a r c o n c e n t r a t i o n s found i n the e f f l u e n t d u r i n g t h i s phase. The high n i t r i t e c o n c e n t r a t i o n s recorded f o r the ae r o b i c r e a c t o r corresponded to p e r i o d s of incomplete n i t r i f i c a t i o n . The n i t r i t e values in the sludge c o n d i t i o n i n g r e a c t o r were between 0.01 and 0.12 mg-N/L. 5.2.8.3 T o t a l K j e l d a h l N i t r o g e n ( TKN ) Feed TKN c o n c e n t r a t i o n s ranged from 42.7 to 56.6 mg-N/L. The e f f l u e n t v a l u e s v a r i e d between 4.1 and 31.5 mg-N/L (Appendix 108 I I , F i g u r e I I - 3 ) . As observed d u r i n g Phase A, p e r i o d s of low e f f l u e n t TKN o c c u r r e d s i m u l t a n e o u s l y w i t h r e l a t i v e l y h i g h a e r o b i c r e a c t o r n i t r a t e c o n t e n t s . T h i s was a r e s u l t of a l a r g e f r a c t i o n of the TKN h a v i n g been c o n v e r t e d t o o x i d i z e d n i t r o g e n forms of which n i t r a t e s were the major p o r t i o n , throughout t h i s s t u d y . 5.2.9 Phosphates Both o r t h o p h o s p h a t e and t o t a l phosphate c o n c e n t r a t i o n s ( i n p a r t i c u l a r the former) were d e t e r m i n e d d u r i n g t h i s phase of s t u d y . S i n c e s u c c e s s f u l P removal was r e a l i z e d , s a m p l i n g d u r i n g t h i s phase was more f r e q u e n t than t h a t of Phase A. 5.2.9.1 Orthophosphates (a) C o n c e n t r a t i o n s The o r t h o p h o s p h a t e c o n t e n t of the f i l t e r a b l e f r a c t i o n of each r e a c t o r and the e f f l u e n t , as w e l l as the n o n f i l t e r e d f e e d , w i l l be d i s c u s s e d i n t h i s s e c t i o n . These r e s u l t s a r e shown c h r o n o l o g i c a l l y i n F i g u r e 5.4. The u n f i l t e r e d f e e d o r t h o p h o s p h a t e c o n c e n t r a t i o n s were s i m i l a r t o l e v e l s e n c o u n t e r e d d u r i n g Phase A, and ranged between 5.04 and 9.60 mg-P/L. F i l t e r a b l e o r t h o p h o s p h a t e c o n c e n t r a t i o n s i n the a n a e r o b i c r e a c t o r v a r i e d from 12.9 t o 49.5 mg-P/L (whereas Phase A l e v e l s d i d not exceed 13.2 mg-P/L). The a e r o b i c r e a c t o r f i l t e r a b l e o r t h o p h o s p h a t e s d u r i n g Phase B, ranged from AEROBIC SRT( d ) 371 q 2 4 SYSTEM SRTId) $5 "* 5 4 * Feed A n a e r o b i c R e a c t o A e r o b i c R e a c t o r S l u d g e C o n d i t i o n i n E f f l u e n t 0 20 40 68 TIME - DAYS FIG.5.4' ORTHOPHOSPHATES ( PHASE B ) 110 0.14 t o 15.12 mg-P/L. The l a t t e r v a l u e c o r r e s p o n d e d to the f a i l u r e of the system i n terms of P removal ( S e c t i o n 5.2.9.1 ( b ) ) . F i l t e r e d e f f l u e n t o r t h o p h o s p h a t e c o n c e n t r a t i o n s were, i n g e n e r a l , s l i g h t l y h i g h e r than a e r o b i c r e a c t o r l e v e l s , p r o b a b l y as a r e s u l t of P r e l e a s e i n the c l a r i f i e r under a n o x i c c o n d i t i o n s . The o r t h o p h o s p h a t e s of the f i l t e r a b l e p o r t i o n of the slu d g e c o n d i t i o n i n g r e a c t o r c o n t e n t s v a r i e d from 3 t o 76 mg-P/L, compared t o a maximum of 10 mg-P/L d u r i n g Phase A when enhanced P uptake was not a norm. I t appears t h a t h i g h r a t e s of P r e l e a s e i n the s l u d g e c o n d i t i o n i n g r e a c t o r , a r e c o n d u c i v e t o the uptake of P. In g e n e r a l , the f i l t e r a b l e o r t h o p h o s p h a t e c o n c e n t r a t i o n s i n the a n a e r o b i c r e a c t o r were s l i g h t l y h i g h e r than those i n the s l u d g e c o n d i t i o n i n g r e a c t o r d u r i n g Phase B. P e r i o d s of h i g h o r t h o p h o s p h a t e c o n c e n t r a t i o n s i n the s e two r e a c t o r s were c o n c u r r e n t w i t h low v a l u e s i n the a e r o b i c r e a c t o r . (b) P e r c e n t a g e Removals The p e r c e n t a g e of o r t h o p h o s p h a t e s removed d u r i n g Phase A ranged from l e s s than z e r o (when r e l e a s e o c c u r r e d i n the a e r o b i c r e a c t o r ) t o 98%. These removal v a l u e s were de t e r m i n e d by c o n s i d e r i n g the d i f f e r e n c e i n u n f i l t e r a b l e o rthophosphate c o n c e n t r a t i o n s i n the f e e d and f i l t e r a b l e o r t h o p h o s p h a t e l e v e l s i n the a e r o b i c r e a c t o r (See F i g u r e 5.5). R e l e a s e of P i n the c l a r i f i e r was common throughout t h i s phase, c a u s i n g s l i g h t l y lower system P removals. D u r i n g t h i s phase, the system maximum A E R O B I C S R T ( d ) 37 S Y S T E M S R T l d ) 86 1 0 0 - r T E M P E R A T U R E 18° C L E G E N D : A e r o b i c R e a c t o r E f f l u e n t T I M E - D A Y S * I n d i c a t e s f eed v e r s u s a e r o b i c r e a c t o r r e m o v a l I n d i c a t e s feed v e r s u s e f f l u e n t r e m o v a l F IG .5.5 •• PERCENTAGE ORTHOPHOSPHATE REMOVAL (PHASE B ) . 112 o r t h o p h o s p h a t e removal was 95% ( f e e d v e r s u s e f f l u e n t ) . I t i s assumed t h a t f u l l s c a l e o p e r a t i n g c o n d i t i o n s would i n c l u d e an e f f i c i e n t c l a r i f i e r , i n which a n o x i c c o n d i t i o n s , and thus P r e l e a s e would be a v o i d e d . (c) Orthophosphate R e a c t i o n Rates The o r t h o p h o s p h a t e r e a c t i o n r a t e s were c a l c u l a t e d on the b a s i s of the method d e s c r i b e d i n S e c t i o n 3.9. A c h r o n o l o g i c a l p l o t of t h e s e r a t e s , i n each of the r e a c t o r s , d u r i n g Phase B i s g i v e n i n F i g u r e 5.6. Throughout t h i s phase, the a n a e r o b i c r e a c t o r biomass r e l e a s e d phosphates. The r a t e of r e l e a s e f l u c t u a t e d from 0.31 t o 3.34 mg-P/g MLSS/h. Orthophosphate uptake o c c u r r e d i n the a e r o b i c r e a c t o r , except on Day 68B. T h i s day however, c o r r e s p o n d s t o complete system f a i l u r e w i t h r e g a r d t o o r t h o p h o s p h a t e removal ( i n d u c e d by r e d u c i n g the s l u d g e age of the b i o m a s s ) . A e r o b i c r e a c t o r uptake r a t e s v a r i e d between 0.04 and 2.05 mg-P/g MLSS/h d u r i n g Phase B. High r e l e a s e r a t e s i n the a n a e r o b i c r e a c t o r o c c u r r e d s i m u l t a n e o u s l y w i t h enhanced uptake r a t e s i n the a e r o b i c r e a c t o r . A l t h o u g h the r a t e s i n the s l u d g e c o n d i t i o n i n g r e a c t o r were g e n e r a l l y much lower than i n the a n a e r o b i c r e a c t o r , the r e l e a s e of o r t h o p h o s p h a t e s was the norm except f o r Day 68B. R e l e a s e r a t e v a l u e s i n t h i s r e a c t o r ranged between -0.04 ( o r t h o p h o s p h a t e uptake on Day 68B) t o 0.68 mg-P/g MLSS/h. 113 A E R O B I C S R T ( d ) 3 7 2 4 S Y S T E M S R T l d ) 8 6 5 4 T E M P E R A T U R E I 8 ° C 3 . 5 0 - r L E G E N D : 3 . 0 0 4 - 2 . 5 0 - co j 2 . 0 0 4 - 5 0 4 - f i.oo- 0 . 5 0 + / /' / /,-••' 0.00 A n a e r o b i c R e a c t o r A e r o b i c R e a c t o r ' v v\j I i! • i 1 R ! i!| -i—PO: CO CO 2 0 4 0 6 8 I ! \ TI M E - D A Y S " | 0 . 5 0 + - \ A A \ A A 11 1 . 0 0 4 - a. E . 5 0 - \ / \ \ ; i! ^ l\l \ / J \ / v S l u d g e C o n d i t i o n i n g R e a c t o r 2 . 0 0 - 1 - FIG. 5.6= ORTHOPHOSPHATE REACTION RATES ( PHASE B ). 114 5.2.9.2 T o t a l Phosphates T o t a l phosphate d e t e r m i n a t i o n s on u n f i l t e r e d i n f l u e n t samples v a r i e d from 6.5 t o 13.0 mg-P/L d u r i n g t h i s phase of the s t u d y . T h i s i n d i c a t e d t h a t , of the t o t a l phosphates i n the i n f l u e n t , between 62 and 79% were i n the form of o r t h o p h o s p h a t e s . The f i l t e r a b l e t o t a l phosphate l e v e l s i n the e f f l u e n t ranged from 1.6 t o 10.1 mg-P/L. Between 86 and 139% of the t o t a l f i l t e r a b l e phosphates were i n the form of f i l t e r a b l e o r t h o p h o s p h a t e s . R e s u l t s g r e a t e r than 100% were m a i n l y due t o i n a c c u r a c y i n sa m p l i n g and a n a l y s i s . There i s a p o s s i b i l i t y t h a t water e n t e r e d the f l a s k s a t the time of sample c o o l i n g . Only two such o c c a s i o n s were r e c o r d e d . The purpose of the a n a l y s i s of t o t a l phosphates was to compare the sewage c h a r a c t e r i s t i c s used i n t h i s study t o t y p i c a l v a l u e s d e t e r m i n e d by o t h e r r e s e a r c h e r s . I t i s g e n e r a l l y e x p e c t e d t h a t o r t h o p h o s p h a t e s c o n s t i t u t e r o u g h l y 70% of the t o t a l phosphates i n sewage. Thus o r t h o p h o s p h a t e t o t o t a l phosphate r a t i o s found i n t h i s study were t y p i c a l , p a r t i c u l a r l y i n the case of the i n f l u e n t sample r a t i o s . The e f f l u e n t r a t i o s were at the upper l i m i t of ex p e c t e d r e s u l t s . 5.2.10 AP/ACOD R a t i o T o t a l P was used t o c a l c u l a t e the change i n P th r o u g h the system. An e s t i m a t e of the t o t a l P i n the a e r o b i c r e a c t o r was 115 based on t y p i c a l e f f l u e n t t o t a l P: o r t h o p h o s p h a t e r a t i o s , s i n c e t h e s e were not a v a i l a b l e f o r the a e r o b i c r e a c t o r c o n t e n t s . The A P / A C O D r a t i o s a r e p r e s e n t e d i n Appendix I I , F i g u r e 11 -3. The A P / A C O D r a t i o s d e t e r m i n e d d u r i n g Phase B v a r y from 0.005 t o 0.081, y i e l d i n g r e s p e c t i v e P removals of 62% t o 84%. Note t h a t a r e l a t i v e l y "low" A P / A C O D r a t i o of 0.018 y i e l d e d 89% removal of P. T h i s r a t i o o c c u r r e d a t the time i n the study when enhanced removal had a l r e a d y been e s t a b l i s h e d . In g e n e r a l , h i g h e r A P / A C O D r a t i o s were o b t a i n e d d u r i n g the phase of enhanced P removal by t h i s system, than d u r i n g Phase A, when the removal mechanism was not w e l l e s t a b l i s h e d . T h i s f i n d i n g a g r e e s w e l l w i t h r e s u l t s of o t h e r r e s e a r c h e r s ( f o r example, Jank et a l . (1978)) who c l a i m t h a t h i g h A P / A C O D r a t i o s o c c u r s i m u l t a n e o u s l y w i t h h i g h P removal. 5.2.11 H y d r a u l i c R e t e n t i o n Time ( HRT ) T a b l e 3.3, shows HRT's i n a l l t h r e e r e a c t o r s d u r i n g Phase B. The HRT i n each r e a c t o r d u r i n g the i n i t i a l s i x months of Phase A was s l i g h t l y lower than t h o s e m a i n t a i n e d i n Phase B. There was no d i f f e r e n c e i n HRT's between the l a s t two months of Phase A and t h a t of Phase B. 5.2.12 S o l i d s R e t e n t i o n Time ( SRT ) A d i s c u s s i o n of SRT c a l c u l a t i o n s ( b o t h a e r o b i c and system) i s g i v e n i n S e c t i o n 3.7. Phase B was c h a r a c t e r i z e d by l o n g SRT's. A l l w a s t i n g was t e r m i n a t e d on Day I B . A f t e r a b u i l d - u p of 116 s o l i d s had o c c u r r e d i n a l l t h r e e r e a c t o r s , w a s t i n g was resumed and a 37 day a e r o b i c SRT was m a i n t a i n e d . A r e d u c t i o n of SRT on Day 40B o c c u r r e d as s o l i d s w a s t i n g was g r a d u a l l y i n c r e a s e d . 5.3 C o n d i t i o n s A f f e c t i n g Phosphate R e a c t i o n R a t e s As was the case w i t h Phase A, l a r g e f l u c t u a t i o n s of feed COD were a l s o observed d u r i n g Phase B. Thus the e f f e c t s of COD on phosphate r e a c t i o n r a t e s c o u l d not be s u b s t a n t i a t e d d u r i n g the c o u r s e of t h i s s t u d y . I t appears t h a t MLSS c o n c e n t r a t i o n s , per se, i n the r e a c t o r s a re not r e s p o n s i b l e f o r enhanced P rem o v a l . However, the MLSS c o n c e n t r a t i o n s a r e i m p o r t a n t i n terms of a l l o w i n g h i g h s l u d g e ages t o be m a i n t a i n e d w i t h o u t a l t e r i n g the h y d r a u l i c r e t e n t i o n t i m e s and/or r e a c t o r volumes. MLVSS were imp o r t a n t o n l y i n terms of i n d i c a t i n g the c o n c e n t r a t i o n of v i a b l e m i c r o o r g a n i s m s i n the system. The d e t e r m i n a t i o n of the a c t u a l f r a c t i o n of these m i c r o o r g a n i s m s i n v o l v e d i n P uptake and r e l e a s e r e a c t i o n s was beyond the scope of t h i s s t u d y . The d i s s o l v e d oxygen i n the a e r o b i c r e a c t o r was m a i n t a i n e d at l e v e l s comparable t o thos e of Phase A. No c o n c l u s i o n can thus be drawn r e g a r d i n g the p o s s i b l e e f f e c t of DO on the a c t i v i t y of the biomass. A n a e r o b i o s i s i n the a n a e r o b i c r e a c t o r was m a i n t a i n e d ( i n terms of the d i s s o l v e d oxygen l e v e l and n i t r a t e c o n t e n t ) as shown by the o x i d a t i o n r e d u c t i o n p o t e n t i a l r e s u l t s . In g e n e r a l , the ORP l e v e l s were lower (more n e g a t i v e ) than those e x h i b i t e d d u r i n g Phase A. S i n c e the P removal mechanism was not 117 m a n i f e s t e d d u r i n g Phase A, i t i s not p o s s i b l e t o d i s c e r n the r o l e p l a y e d by ORP i n the P removal c a p a b i l i t y of a g i v e n b i o l o g i c a l system. I t i s c l e a r however t h a t ORP v a l u e s of a p p r o x i m a t e l y -300 t o -500 mV are not d e t r i m e n t a l t o the P uptake phenomenon, and may i n f a c t be b e n e f i c i a l . The l a c k of comprehensive pH and a l k a l i n i t y d a t a d u r i n g Phase B has made i t i m p o s s i b l e f o r any r e l a t i o n s h i p t o be drawn r e g a r d i n g the c o r r e l a t i o n of these parameters t o the r e l e a s e and/or uptake of P. There were no d i s c e r n a b l e d i f f e r e n c e s i n i n f l u e n t t r a c e m e t a l c o n c e n t r a t i o n s d u r i n g Phase A and Phase B. The sludge accumulated l a r g e q u a n t i t i e s of t r a c e m e t a l s but t h e s e a c c u m u l a t i o n s a p p a r e n t l y were not d e t r i m e n t a l t o the P r e l e a s e and uptake r a t e s which o c c u r r e d d u r i n g Phase B. By o b s e r v i n g r e a c t i o n r a t e s as opposed t o removal p e r c e n t a g e s , i t becomes c l e a r t h a t n i t r a t e s had no e f f e c t on the a b i l i t y of the a e r o b i c biomass t o remove phosphates. At f i r s t g l a n c e , i t ^ a p p e a r s t h a t o r t h o p h o s p h a t e removal was h i g h o n l y a t t i m e s of low n i t r a t e c o n c e n t r a t i o n s i n the a e r o b i c r e a c t o r ( w i t h consequent low n i t r a t e l e v e l s i n the s l u d g e r e t u r n e d t o the a n a e r o b i c r e a c t o r v i a the s l u d g e c o n d i t i o n i n g r e a c t o r ) . On examining i n d i v i d u a l r e a c t i o n r a t e s however, i n p a r t i c u l a r P uptake r a t e s i n the a e r o b i c r e a c t o r , i t appears t h a t n i t r a t e s d i d not p l a y a r o l e i n r e d u c i n g the P removal c a p a c i t y of the system. T h i s i s c l e a r l y shown by c o n s i d e r i n g the r e s u l t s of Day 58B and 17B. On Day 58B, h i g h n i t r a t e l e v e l s (between 20 and 35 118 mg-N/L) o c c u r r e d i n the a e r o b i c r e a c t o r and the e f f l u e n t , w h i l e a t the same time o r t h o p h o s p h a t e removal was o n l y 38% (based on the i n f l u e n t and the a e r o b i c r e a c t o r ) . The orthophosphate r e a c t i o n r a t e on t h i s day i n the a e r o b i c r e a c t o r was 1.30 mg-P/g MLSS/h. On Day 17B, a t a t s l i g h t l y lower a e r o b i c o r t h o p h o s p h a t e uptake r a t e of (1.09 mg-P/g MLSS/h), 92% P removal o c c u r r e d , w h i l e a t the same time n i t r a t e c o n c e n t r a t i o n s i n the a e r o b i c r e a c t o r were comparable t o those of Day 58B (between 15 and 20 mg-N/L). Thus, the h i g h n i t r a t e c o n t e n t i n the a e r o b i c r e a c t o r , a t comparable o r t h o p h o s p h a t e r e a c t i o n r a t e s , caused two v e r y d i f f e r e n t removal p e r c e n t a g e s t o o c c u r . The two days were o p e r a t e d a t s i m i l a r c o n d i t i o n s except the system SRT on Day 17B was between 56 and 86 days, whereas on Day 58B the system SRT was m a i n t a i n e d a t 54 days. T h e r e f o r e , t h e r e i s s t r o n g e v i d e n c e p r o v i d e d by the r e s u l t s o b t a i n e d d u r i n g t h i s phase t h a t when the SRT i s s u f f i c i e n t l y l o n g , n i t r a t e l e v e l s i n the a e r o b i c r e a c t o r a r e not of consequence, as l o n g as the a n a e r o b i c r e a c t o r i n f l u e n t n i t r a t e s a re s u f f i c i e n t l y c u r t a i l e d . The mass of P removed by the system was 0.102 g on Day 58B and 0.178 g on Day 17B (based on nominal f l o w r a t e s ) . Thus removal amounts and p e r c e n t a g e s appear r e l a t e d . Comparison of o r t h o p h o s p h a t e r e a c t i o n r a t e s i n the a e r o b i c r e a c t o r , and removal p e r c e n t a g e s d e t e r m i n e d f o r i n d i v i d u a l days, does not show a c o r r e l a t i o n due t o f l u c t u a t i o n of the d a t a . Thus p r o c e s s o p t i m i z a t i o n was not a c h e i v e d d u r i n g t h i s phase of the s t u d y . In g e n e r a l however, h i g h removals a r e o n l y p o s s i b l e when r e a c t i o n r a t e s a re g e n e r a l l y h i g h . T h i s can a l s o be s a i d of the 119 a n a e r o b i c and the s l u d g e c o n d i t i o n i n g r e a c t o r s , except i n t h i s c a s e , the r e a c t i o n r a t e s c o n s t i t u t e the r e l e a s e of o r t h o p h o s p h a t e s . The s i g n i f i c a n t l y i n c r e a s e d P r e l e a s e and uptake r a t e s d u r i n g Phase B o c c u r r e d s i m u l t a n e o u s l y w i t h a s i g n i f i c a n t i n c r e a s e of system s o l i d s r e t e n t i o n t i m e . I t appears t h a t the m i c r o o r g a n i s m s r e s p o n s i b l e f o r P r e m o v a l , p r i o r t o Phase B, were washed o u t . D u r i n g Phase B, ample time was g i v e n the b a c t e r i a t o become i n v o l v e d i n the removal mechanism. Phase B r e s u l t s i n d i c a t e t h a t , once the s l u d ge age reaches a p o i n t where enhanced P removal i s e v i d e n t , a r e d u c t i o n i n the SRT (from 86 t o 54 days i n t h i s s t udy) i s p o s s i b l e w i t h o u t any l o s s of P removing biomass a c t i v i t y . F u r t h e r l o w e r i n g of the s l u d g e age i s d e t r i m e n t a l however, as i n d i c a t e d by r e s u l t s subsequent t o Day 48B. A r e d u c t i o n i n s l u d g e age on Day 40B was f o l l o w e d by e i g h t days where the P removal was m a i n t a i n e d a t enhanced l e v e l s . A l t h o u g h f l u c t u a t i o n s were e v i d e n t , the o r t h o p h o s p h a t e r e l e a s e and uptake r a t e s were a l s o r e l a t i v e l y h i g h ( s i m i l a r t o r a t e s e x h i b i t e d d u r i n g the f i r s t f i v e weeks of Phase A ) . Subsequent t o Day 48B however, both the P r e l e a s e and the P uptake r a t e s r e t u r n e d t o t y p i c a l Phase A l e v e l s i n a l l t h r e e r e a c t o r s . The p e r c e n t a g e removals a l s o g r a d u a l l y d i m i n i s h e d , u n t i l Day 62B when the a e r o b i c r e a c t o r biomass was i n v o l v e d i n the r e l e a s e of o r t h o p h o s p h a t e s . N i t r a t e s r e t u r n e d t o the a n a e r o b i c r e a c t o r remained a t the same, r e l a t i v e l y low, l e v e l e n c o u n t e r e d d u r i n g the p e r i o d of enhanced P removal, i n t h a t the d e n i t r i f i c a t i o n by the s l u d g e c o n d i t i o n i n g r e a c t o r biomass d i d not suddenly s t o p . 120 CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 6.1 C o n c l u s i o n s The a n a e r o b i c - a e r o b i c system s t u d i e d i s c a p a b l e of enhanced phosphorus removal, p r o v i d e d a s u f f i c i e n t l y l o n g s o l i d s r e t e n t i o n time i s m a i n t a i n e d . At a system SRT of a p p r o x i m a t e l y 86 days, up t o 98% of phosphates was removed. Once enhanced removal i s a c h i e v e d , subsequent r e d u c t i o n t o a lower system SRT (54 days i n t h i s s t u d y ) appears t o have no d e l e t e r i o u s e f f e c t s on the phosphorus removal c a p a b i l i t i e s of the system. In g e n e r a l , h i g h o r t h o p h o s p h a t e c o n c e n t r a t i o n s were a p r e r e q u i s i t e f o r o b t a i n i n g low P c o n c e n t r a t i o n s i n the a e r o b i c r e a c t o r . Orthophosphate r e a c t i o n r a t e s f o l l o w e d t h i s p a t t e r n a l s o , i n t h a t h i g h r e l e a s e r a t e s i n the a n a e r o b i c r e a c t o r y i e l d e d h i g h uptake r a t e s i n the a e r o b i c r e a c t o r . These phenomena were o n l y o b s e r v e d at h i g h SRT's however. Orthophosphate r e l e a s e r a t e s of up t o 3.34 mg-P/g MLSS/h o c c u r r e d i n the a n a e r o b i c r e a c t o r , w h i l e the a e r o b i c r e a c t o r phosphate uptake r a t e s reached a maximum of 2.05 mg-P/g MLSS/h d u r i n g the p e r i o d of enhanced phosphorus removal by the system. A l t h o u g h the r e l e a s e and uptake r a t e s i n the a n a e r o b i c and a e r o b i c r e a c t o r s reached h i g h e r l e v e l s d u r i n g Phase A of t h i s s tudy (4.72 and 4.37 mg-P/g MLSS/h r e s p e c t i v e l y ) , enhanced system phosphorus removal was not a norm. 121 T y p i c a l a n a e r o b i c r e a c t r r n i t r a t e c o n c e n t r a t i o n s were i n the neighbourhood of 0.1 mg-N/L, thus p r e c l u d i n g the p o s s i b l e i n t e r f e r e n c e of n i t r a t e s w i t h the phosphate r e l e a s e phenomenon throughout the s t u d y . D e n i t r i f i c a t i o n r a t e s i n t h i s r e a c t o r r e ached a maximum of 7.06 mg-N/g MLSS/h d u r i n g Phase A. The i n s t a l l a t i o n of the s l u d g e c o n d i t i o n i n g r e a c t o r v i r t u a l l y e l i m i n a t e d the d e n i t r i f i c a t i o n a c t i v i t y i n the a n a e r o b i c r e a c t o r ; the r e l e a s e of phosphates d i d not o c c u r , as a consequence, however. The p r e s ence of n i t r a t e s or h i g h n i t r i f i c a t i o n r a t e s i n the a e r o b i c r e a c t o r had no d i r e c t b e a r i n g on the phosphate uptake r a t e s i n t h i s u n i t . At comparable n i t r a t e l e v e l s and n i t r i f i c a t i o n r a t e s (15-35 mg-N/L and 0.7-0.9 mg-N/g MLSS/h r e s p e c t i v e l y ) , the phosphate removals were 38% and 92%. The phosphate uptake r a t e s c o r r e s p o n d i n g t o t h e s e removal p e r c e n t a g e s were 1.30 and 1.09 mg-P/g MLSS/h r e s p e c t i v e l y . The AP/ACOD r a t i o s were, i n g e n e r a l , h i g h d u r i n g p e r i o d s of enhanced phosphorus removal by the system. No c o n c l u s i o n s c o u l d be made r e g a r d i n g the e f f e c t s of temperature changes on P u p t a k e , s i n c e t h e s e changes were implemented d u r i n g Phase A of the s t u d y , when enhanced P removal was not a norm. The r o l e p l a y e d by f a c t o r s such as COD, MLSS, a l k a l i n i t y , pH, and t r a c e m e t a l s on the P r e l e a s e / u p t a k e mechanism were not s u b s t a n t i a t e d from r e s u l t s of t h i s s t u d y . E x t e n s i v e d a t a f l u c t u a t i o n s was caused by the d i f f i c u l t y i n a c h i e v i n g system e q u i l i b r i u m . 122 6.2 Recommendations The major problems e n c o u n t e r e d d u r i n g t h i s study i n v o l v e d the e f f e c t s of s i z e on the o p e r a t i o n of the system. P l u g g i n g of t u b i n g and o u t l e t s was a f r e q u e n t o c c u r r e n c e , u s u a l l y s e v e r e l y d i s r u p t i n g the performance of the system. A l a r g e r system would p r e c l u d e these problems. F u r t h e r , the time l a g i n v o l v e d i n o b s e r v i n g the e f f e c t s on the performance of the system, r e s u l t i n g from a p h y s i c a l or o p e r a t i n g change, u s u a l l y was so l o n g t h a t i n e v i t a b l y o t h e r mishaps (such as s p i l l s ) o c c u r r e d i n t h i s time span. I t was thus d i f f i c u l t t o s e p a r a t e the e f f e c t s of the a c t u a l induced change and e f f e c t s of a c c i d e n t a l o c c u r r e n c e s r e s u l t i n g from equipment m a l f u n c t i o n . Because of the presence of r e l a t i v e l y l a r g e p a r t i c l e s i n raw sewage, i t i s recommended t h a t a c o n t i n u o u s f l o w t r e a t m e n t model s h o u l d be o p e r a t e d on the p i l o t p l a n t s c a l e , r a t h e r than on a bench s c a l e . Many a d d i t i o n a l s t u d i e s can be pursued t o b e t t e r d e f i n e the o p e r a t i o n of t h i s phosphorus removal t r e a t m e n t scheme. P r e f e r a b l y , a " d u a l " system s h o u l d be employed where one stream of raw sewage e n t e r s two systems, one of which i s m a i n t a i n e d as the " b a s e l i n e " u n i t , w h i l e the o t h e r undergoes the r e q u i r e d o p e r a t i o n a l changes. To s u b s t a n t i a t e the f i n d i n g s of t h i s s t u d y , the SRT i n f u t u r e s t u d i e s s h o u l d be c a r e f u l l y m a i n t a i n e d a t v a r i o u s l e v e l s . G r a d u a l changes i n SRT s h o u l d be made and the r e s u l t i n g phosphorus removals s h o u l d be a n a l y z e d more f r e q u e n t l y . The minimum SRT n e c e s s a r y f o r enhanced phosphorus uptake s h o u l d be 123 d e t e r m i n e d . Once enhanced phosphorus uptake i s r e a l i z e d , the SRT s h o u l d be f u r t h e r i n c r e a s e d t o d e t e r m i n e i f t h e i e i s a c r i t i c a l SRT beyond which removal w i l l not t a k e p l a c e . A l s o , a g r a d u a l d e c r e a s e i n SRT s h o u l d then be i n v e s t i g a t e d t o s u b s t a n t i a t e the f i n d i n g of t h i s study t h a t , once enhanced removal of phosphorus has been i n i t i a t e d by the system, a r e d u c t i o n of SRT does not reduce the removal c a p a b i l i t i e s . A d d i t i o n a l s t u d i e s s h o u l d be d i r e c t e d a t the o p t i m i z a t i o n of phosphorus removal u s i n g a t w o - r e a c t o r system o n l y (an a n a e r o b i c - a e r o b i c scheme). R e s u l t s from t h i s study i n d i c a t e t h a t the s l u d g e c o n d i t i o n i n g r e a c t o r does not appear n e c e s s a r y f o r enhanced phosphorus removal t o o c c u r . 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( 1 9 7 9 ) , " D e s i g n a n d O p e r a t i n g E x p e r i e n c e w i t h N u t r i e n t R e m o v i n g A c t i v a t e d S l u d g e P l a n t s i n J o h a n n e s b u r g " , P a p e r p r e - s e n t e d a t S e m i n a r o n N u t r i e n t R e m o v a l f r o m M u n i c i p a l E f f l u e n t s , P r e t o r i a . 30. P i t m a n , A.R. ( 1 9 8 0 ) , " S e t t l i n g P r o p e r t i e s o f E x t e n d e d A e r a t i o n S l u d g e " , J o u r n a l W.P.C.F., 5 2 ( 3 ) , pp. 524-536. 31. P o r t e r , K.S. ( 1 9 7 5 ) , " N i t r o g e n P h o s p h o r u s F o o d P r o d u c - t i o n , W a s t e a nd t h e E n v i r o n m e n t " , Ann A r b o r S c i e n c e P u b l i s h e r s , I n c . 32. S h a p i r o , J . , L e v i n , G.V., a n d Z e a , H.G. ( 1 9 6 7 ) , " A n o x i c a l l y I n d u c e d R e l e a s e o f P h o s p h a t e i n W a s t e w a t e r T r e a t m e n t " , J o u r n a l W.P.C.F., 3 9 ( 1 1 ) , pp. 1810^-1818. 33. S h e r r a r d , J .H., a n d S h r o e d e r , E.D., ( 1 9 7 2 ) , " I m p o r t a n c e o f C e l l G r o w t h R a t e a n d S t o i c h i o m e t r y t o t h e R e m o v a l o f P h o s p h o r u s f r o m t h e A c t i v a t e d S l u d g e P r o c e s s " , W a t e r R e s o u r c e s , 6, p. 1051. 34. S i m p k i n s , M.J. ( 1 9 7 9 ) , "The P r e s e n t S t a t u s o f R e s e a r c h o n P h o s p h o r u s R e m o v a l i n S o u t h A f r i c a , w i t h P a r t i c u l a r R e f e r e n c e t o B i o l o g i c a l P r o c e s s e s " , P a p e r p r e s e n t e d a t : T e c h n i c a l T r a n s f e r S e m i n a r : N u t r i e n t R e m o v a l f r o m M u n i c i p a l E f f l u e n t s w i t h S p e c i f i c R e f e r e n c e t o E n e r g y R e q u i r e m e n t s , P r e t o r i a . 35. S i m p k i n s , M.J., and M c L a r e n , A.R. ( 1 9 7 8 ) , " C o n s i s t e n t B i o l o g i c a l P h o s p h a t e a n d N i t r a t e R e m o v a l i n an A c t i v a - t e d S l u d g e P l a n t " , P r o g . Wat. T e c h . , 1 0 ( 5 / 6 ) , pp. 4 3 3 - 4 4 2 . 36. S t a n d a r d M e t h o d s f o r t h e E x a m i n a t i o n o f W a t e r a nd W a s t e w a t e r ( 1 9 7 6 ) , A.P.H.A., 1 4 t h e d i t i o n . 127 Timmerman, M.W. (1979), " B i o l o g i c a l Phosphate Removal from Domestic Wastewater U s i n g A n a e r o b i c / A e r o b i c Treatment", Develop. I n d . M i c r o b i o l . , V o l . 20, p. 285. U.S. P u b l i c H e a l t h S e r v i c e Study (1965), " 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. Dept. H e a l t h , E d u c a t i o n and W e l f a r e , Pub. H e a l t h Serv. P u b l . No. 999-WP-22. V a c k e r , D., C o n n e l l , C.H., and W e l l s , W.N. (1967), "Phosphate Removal t h r o u g h M u n i c i p a l Wastewater Treatment a t San A n t o n i o , Texas", J o u r n a l W.P.C.F., 39 ( 5 ) , pp. 750-771. V e n t e r , S.L.V., H a l l i d a y , J . , and Pitman, A.R. (1978), " O p t i m i z a t i o n o f the Johannesburg O l i f a n t s v l e i Extended A e r a t i o n P l a n t f o r Phosphorus Removal", Prog. Wat.' Tech., 1 0 ( 1 / 2 ) , pp. 279-292. W i l l i a m s , J.D.H., J a q u e t , J.M., and Thomas, R.L. (1972), "Forms o f Phosphorus i n the S u r f i c i a l Sediments o f Lake E r i e " , J o u r . F i s h . Res. Board Can., 33, p. 413. Y a l l , I . , e t a l . (1972), " L o g i c a l Removal o f Phosphates", A p p l i c a t i o n s o f New Concepts o f P h y s i c a l - C h e m i c a l Wastewater Treatment, V a n d e r b i l t U n i v e r s i t y Conf. 128 A P P E N D I C E S 129 A P P E N D I X I SYNTHETIC SEWAGE N a C l 12,000 mg KC1 2,800 mg NaHC0 3 67,200 mg C a C l 2 2,800 mg M g S 0 4 2,000 mg N u t r i e n t B r o t h 10 g Soap 20,000 mg U r e a 12,000 mg S t a r c h 40,000 mg N a 2 H P 0 4 10,000 mg A 1 2 ( S 0 4 ) 18H 20 10,000 mg The a b o v e amounts w e r e d i s s o l v e d i n 4L o f w a t e r t o y i e l d a t h e o r e t i c a l B O D 5 o f 20,000 mg/L. 131 A P P E N D I X I I F I G . H - I : F E E D AND E F F L U E N T COD C O N C E N T R A T I O N FIG. H - 2 • E F F L U E N T S U S P E N D E D S O L I D S 134 TABLE I I - l pH DAY FEED ANAEROBIC REACTOR AEROBIC REACTOR SLUDGE CONDITIONING REACTOR EFFLUENT 23A 7.3 7.5 7.5 7.6 43A 7. 15 7.40 7.05 7. 12 57A 7.19 7. 34 7. 15 7. 22 64A 7.15 7.40 6.90 7. 17 69A 7.10 7.47 6.60 6.80 88A 7.05 7. 37 7.0 7.18 99A 7. 35 7. 52 7.28 7.47 124A 7. 30 7.40 7.20 7.20 186A 7.56 7. 30 6.65 6. 87 6.83 8B 7.75 7. 32 6 .51 6.80 6. 70 23B 7.58 7.30 7. 54 6.94 7.68 47B 7.47 7.37 7.08 7.22 7.29 A L K A L I N I T Y ( m g / L a s C a C 0 3 ) 23A 150 175 160 160 32A 180 180 173 165 4 3A 168 133 78 68 57A 208 131 83 57 64A 213 156 6 5 54 69A 203 159 37 31 88A 207 158 88 75 99A 161 158 120 100 124A 142 157 132 118 186A 150 131 52 100 37 8A 237 221 38 168 22 2 3A 185 225 224 . 239 186 47A 245 298 105 232 99 135 TABLE I I - 2 RAW SEWAGE HEAVY METALS LULU ISLAND SOURCE (mg/L) MAPLE RIDGE SOURCE-PHASE A (mg/L) MAPLE RIDGE SOURCE-PHASE B (mg/L) Low H i g h Low H i g h I r o n 5.5 0.47 1.91 0. 59 2. 59 N i c k e l 0.176 0.002 0.009 0.002 0.005 Chromium 0.208 0.004 <0. 01 0.002 0.003 L e a d 0.370 0.012 0.05 0. 012 0.037 C o p p e r 0. 26 0.13 0. 34 0. 12 0.34 Z i n c 0. 69 0.06 0.26 0.08 0. 19 Manganese 0.17 0. 04 0.09 — — Cadmium 0 .019 0.001 <0.003 — — C a l c i u m 17.0 6.3 12.1 7.96 9.47 M a n g a n e s i u m 4.74 1. 47 3.10 1.98 2.52 TABLE I I - 3 TOTAL KJELDAHL NITROGEN (mg-N/L) DAY FEED EFFLUENT 57A 49.6 9.7 74A 51.4 3.2 9 8A 49.6 19.5 110A 38. 4 20. 4 120A 37.0 16.0 132A 54. 3 24. 2 148A 50.4 35.0 160A 40.6 17. 2 176A 49.4 18 . 7 183A 46.1 9.5 204A 58.6 19.4 211A 51.2 15.0 232A 69.9 12.2 7B 55.7 4.1 2 I B 50.2 30.4 34B 50. 3 31.5 53B 42.7 8.1 137 T A B L E I I - 4 TOTAL PHOSPHATES ( m g - P / L ) DAY FEED ( U n f i l t e r e d ) EFFLUENT ( F i l t e r e d ) 29A 6.7 34A 12.5 5.90 39A 8. 36 5.28 82A 16.6 5.6 103A 6.64 4.99 105A 9.18 5.80 126A 9.68 4.79 181A 8.06 4.64 238A 13.0 6.9 19B 9.50 1. 85 25B 11.40 3. 27 3 I B 10.2 6.25 34B 9.74 4.6 4 IB 6.50 1.59 48B 10.2 2.9 55B 8. 54 3.94 66B 8.8 10.1 138 0.09-j- 0 . 0 8 - 0 .07 - 0.06 - o - 0 .05 - < cr o 0 . 0 4 - - o o < \ 0 . 0 3 - - o. < 0 . 0 2 - - 0.01 - - 0 .00 - 10 A P h a s e A O P h a s e B 20 30 40 50 60 70 80 90 T O T A L P H O S P H A T E P E R C E N T A G E R E M O V A L ( F E E D V E R S U S A E R O B I C R E A C T O R ) 100 FIG. TI - 3 : AP/ACOD RATIO VS. % P REMOVED BY SYSTEM. 139 TABLE I I - 5 HEAVY METALS SCAN THROUGH SYSTEM (DAY 6IB) (mg/L) ELEMENT FEED ANAEROBIC REACTOR AEROBIC REACTOR SLUDGE CONDITIONING REACTOR EFFLUENT C a l c i u m 10.5 38.1 37.5 100. 8.3 C o p p e r 0.27 4.96 6.75 9.5 0.13 I r o n 1.34 21. 8 23.0 82.0 0.32 Z i n c 0.13 2.78 2.67 10. 75 0.07 M a g n e s i u m 2.95 21.6 22.6 75.5 1. 85 L e a d 0.026 0.45 0.47 1.75 0.012 N i c k e l 0.025 0.538 0.567 1.90 0.020 Chromium 0. 010 0.463 0.383 1.28 0.007 Cadmium <0.001 . 0.010 0.010 0.036 <0.001

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