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Modelling of membrane enhanced biological phosphorus removal : determining model parameters Zhang, Zhe 2004

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MODELLING OF MEMBRANE ENHANCED BIOLOGICAL PHOSPHORUS REMOVAL: DETERMINING MODEL PARAMETERS by  ZHE ZHANG B.Eng., Shenyang Architecture and Civil Engineering Institute, 1987 A THESIS S U B M I T T E D IN P A R T I A L F U L F I L L M E N T O F T H E REQUIREMENTS FOR T H E D E G R E E O F M A S T E R O F APPLIED in  T H E F A C U L T Y O F G R A D U A T E STUDIES (Department of Civil Engineering)  We accept this thesis as confirming to the required standard  T H E U N I V E R S I T Y O F BRITISH C O L U M B I A March 2004 © Zhe Zhang, 2004  SCIENCE  Library Authorization  In presenting this thesis in partial fulfillment of the requirements for a n a d v a n c e d degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.  ZHt  ZHAhJGr  Name of Author (please print)  Degree: Department of  /V[ /-\ S  Date (dd/mm/yyyy)  Year:  c  CiV-ii  The University of British Columbia Vancouver, B C C a n a d a  Ln^n  2 i> o  4  ABSTRACT  Parameter determination and wastewater characterization are c r u c i a l for m o d e l i n g o f the m e m b r a n e enhanced b i o l o g i c a l phosphorus r e m o v a l process ( M E B P R ) . T h e b a t c h test is a preferred approach for assessing the m o d e l components. S l u d g e samples f r o m an M E B P R and a s i m p l i f i e d U n i v e r s i t y o f C a p e T o w n , S o u t h A f r i c a ( U C T ) processes w e r e a n a l y z e d i n p a r a l l e l to estimate the g r o w t h y i e l d , decay rate and m a x i m u m specific g r o w t h rate o f the heterotrophic b i o m a s s , i n a d d i t i o n to i n v e s t i g a t i n g the difference b e t w e e n the t w o processes i n terms o f the m i c r o b i a l activity, b y c o m p a r i n g the g r o w t h y i e l d , decay coefficient and m a x i m u m s p e c i f i c g r o w t h rate o f the heterotrophic b i o m a s s . M e t h o d s reported i n the literature w e r e used i n this study. C a r b o n , nitrogen and phosphorus fractions o f influent wastewater at the U B C p i l o t plant w e r e characterized to p r o v i d e the b a s i c i n f o r m a t i o n p r i o r to c o m p u t e r s i m u l a t i o n .  T h i s study presents and discusses results o f parameter  estimation and  wastewater  characterization f r o m a v a i l a b l e data. A s l i g h t l y l o w e r g r o w t h y i e l d v a l u e w a s o b s e r v e d i n the M E B P R process c o m p a r e d w i t h the s i m p l i f i e d U C T process. T h e m o d e l d e c a y coefficient results based o n the t w o processes were v e r y close. H o w e v e r , different values o f m a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s w e r e f o u n d between the M E B P R simplified  U C T processes.  The  concentrations  of  readily biodegradable  and  substrate  the and  fermentation products w e r e i n the t y p i c a l range; and the ratios o f C O D / T K N and C O D / T P i n the wastewater w o u l d a l l o w for excellent nitrogen and phosphorus r e m o v a l i n the M E B P R process;  11  w h i l e the h i g h e r fractions o f inert particulate matter and s l o w l y b i o d e g r a d a b l e substrates i n the wastewater m a y affect the performance o f the M E B P R process.  T h e e x p e r i m e n t a l results suggested that characterization is v e r y important for m o d e l i n g the m e m b r a n e enhanced b i o l o g i c a l phosphorus r e m o v a l process, and the parameters that are wastewater-specific must be determined for the use o f m o d e l i n g . M o r e studies o n the shear force, mass transfer, and m i x i n g c o n d i t i o n s i n the M E B P R process s h o u l d be c o n d u c t e d to investigate their effects o n m i c r o b i a l activities.  iii  T A B L E OF CONTENTS  Abstract  ii  Table of Content  iv  List of Tables  vii  List of Figures  viii  Abbreviations  x  Acknowledgements CHAPTER I  C H A P T E R II  xv Introduction  1  1.1 G e n e r a l  1  1.2 D i r e c t i o n o f R e s e a r c h  8  1.3 S c o p e o f D i s s e r t a t i o n  9  Background and Literature Review  11  2.1 B i o l o g i c a l N u t r i e n t R e m o v a l Process  11  2.2 M e m b r a n e B i o r e a c t o r  19  2.3 D e s c r i p t i o n o f A c t i v a t e d S l u d g e M o d e l N o . 2  C H A P T E R III C H A P T E R IV  •  22  2.4 W a s t e w a t e r Treatment Processes i n U B C P i l o t Plant  40  2.5 Parameter E s t i m a t i o n and W a s t e w a t e r C h a r a c t e r i z a t i o n  45  Research Objectives  68  Materials and Methods  69  4.1 E x p e r i m e n t a l D e s i g n  69  iv  4.2 E x p e r i m e n t a l A p p a r a t u s 4.3 M e t h o d o l o g i e s  72 •  76  4.4 D a t a Q u a l i t y A s s u r a n c e and C o n t r o l ( Q A / Q C ) 4.5 Statistical A n a l y s i s  CHAPTER V  87 •  Results and Discussion  88  5.1 H e t e r o t r o p h i c G r o w t h Y i e l d  88  5.2 H e t e r o t r o p h i c D e c a y R a t e  94  5.3 M a x i m u m S p e c i f i c G r o w t h R a t e o f H e t e r o t r o p h i c B i o m a s s  99  5.4 W a s t e w a t e r C a r b o n fractions 5.5 Wastewater N i t r o g e n F r a c t i o n s  C H A P T E R VI  C H A P T E R VII  87  105 Ill  5.6 W a s t e w a t e r P h o s p h o r u s F r a c t i o n s  114  Conclusions and Recommendations  118  6.1 C o n c l u s i o n s  118  6.2 R e c o m m e n d a t i o n s for Further S t u d y  122  Engineering Significance  123  REFERENCES  124  APPENDICES A p p e n d i x 1. D e t e r m i n a t i o n o f H e t e r o t r o p h i c G r o w t h Y i e l d  133  A p p e n d i x 2. D e t e r m i n a t i o n o f D e c a y C o e f f i c i e n t for H e t e r o t r o p h i c B i o m a s s  137  A p p e n d i x 3. D e t e r m i n a t i o n o f the M a x i m u m S p e c i f i c G r o w t h R a t e o f H e t e r o t r o p h y  141  A p p e n d i x 4. D e t e r m i n a t i o n o f R e a d i l y B i o d e g r a d a b l e C O D  146  A p p e n d i x 5. D e t e r m i n a t i o n o f Particulate Inert C O D  152  A p p e n d i x 6. D e t e r m i n a t i o n o f Influent C O D F r a c t i o n s  157  v  A p p e n d i x 7. D e t e r m i n a t i o n o f Influent N i t r o g e n F r a c t i o n s A p p e n d i x 8. D e t e r m i n a t i o n o f Influent P h o s p h o r u s F r a c t i o n s  VI  LIST OF TABLES  T a b l e 2.1 S u m m a r y o f B i o l o g i c a l N i t r o g e n R e m o v a l Process Z o n e s  17  T a b l e 2.2 S o l u b l e and Particulate C o m p o n e n t s i n A S M 2  25  T a b l e 2.3 S t o i c h i o m e t r i c M a t r i x e s for D i s s o l v e d C o m p o n e n t s i n A S M 2  32  T a b l e 2.4 S t o i c h i o m e t r i c M a t r i x e s for Particulate C o m p o n e n t s i n A S M 2  33  T a b l e 2.5 T y p i c a l S t o i c h i o m e t r i c Constants i n A S M 2  34  T a b l e 2.6 T y p i c a l C o n v e r s i o n Factors i n A S M 2  34  T a b l e 2.7 T y p i c a l V a l u e s for the S t o i c h i o m e t r i c C o e f f i c i e n t o f A S M 2  35  T a b l e 4.1 O p e r a t i o n C o n d i t i o n and C o n f i g u r a t i o n o f U B C P i l o t Plant  71  T a b l e 4.2 P r e s e r v a t i o n o f S a m p l e s  71  T a b l e 4.3 Initial E x p e r i m e n t a l C o n d i t i o n s for H e t e r o t r o p h i c G r o w t h Y i e l d Tests  77  T a b l e 4.4 I n i t i a l E x p e r i m e n t a l C o n d i t i o n s for H e t e r o t r o p h i c D e c a y R a t e Tests  79  T a b l e 4.5 Initial E x p e r i m e n t a l C o n d i t i o n s for Tests o f M a x i m u m S p e c i f i c G r o w t h R a t e o f Heterotrophic Biomass  80  T a b l e 4.6 I n i t i a l E x p e r i m e n t a l C o n d i t i o n s for R e a d i l y B i o d e g r a d a b l e C O D Tests  82  T a b l e 4.7 Initial E x p e r i m e n t a l C o n d i t i o n s for Inert S o l u b l e C O D Tests  83  T a b l e 4.8 I n i t i a l E x p e r i m e n t a l C o n d i t i o n s for Particulate Inert C O D Tests  84  T a b l e 5.1 G r o w t h Y i e l d Test R e s u l t s  91  T a b l e 5.2 R e p o r t e d and Tested G r o w t h Y i e l d V a l u e s for M e m b r a n e B i o r e a c t o r s  92  T a b l e 5.3 R e s u l t s o f T r a d i t i o n a l and M o d e l D e c a y C o e f f i c i e n t for H e t e r o t r o p h i c  97  Biomass @ 2 0 ° C T a b l e 5.4 R e s u l t s o f M a x i m u m S p e c i f i c G r o w t h R a t e for H e t e r o t r o p h i c B i o m a s s @ 2 0 ° C  102  T a b l e 5.5 R e s u l t s o f R e a d i l y B i o d e g r a d a b l e C O D Tests  106  T a b l e 5.6 R e l a t i o n s h i p B e t w e e n E x p e c t e d B i o l o g i c a l N i t r o g e n R e m o v a l E f f i c i e n c y  116  and Influent O r g a n i c M a t t e r to N i t r o g e n R a t i o s T a b l e 5.7 C O D to P h o s p h o r u s R e m o v a l R a t i o s for V a r i o u s B P R processes  117  T a b l e 6.1 R e s u l t s o f Parameter E s t i m a t i o n @ 2 0 ° C  121  T a b l e 6.2 R e s u l t s o f W a s t e w a t e r C h a r a c t e r i z a t i o n  121  vii  LIST O F FIGURES  F i g u r e 2.1 O v e r a l l B i o - P R e m o v a l M e c h a n i s m s  14  F i g u r e 2.2 P r o c e s s S c h e m a t i c o f the U C T P r o c e s s  16  F i g u r e 2.3 M o d i f i e d U C T P r o c e s s  17  F i g u r e 2.4 C O D F r a c t i o n a t i o n i n A S M 2  37  F i g u r e 2.5 N i t r o g e n F r a c t i o n a t i o n i n A S M 2  39  F i g u r e 2.6 P h o s p h o r u s F r a c t i o n a t i o n i n A S M 2  40  F i g u r e 2.7 S c h e m a t i c L a y o u t o f U B C P i l o t P l a n t  42  F i g u r e 2.8 P r o c e s s S c h e m a t i c o f M E B P R P r o c e s s at U B C P i l o t Plant  43  F i g u r e 2.9 P r o c e s s S c h e m a t i c o f the S i m p l i f i e d U C T Process at U B C P i l o t Plant  43  F i g u r e 2.10 S c h e m a t i c Representation o f the T r a d i t i o n a l A p p r o a c h to M o d e l i n g B i o m a s s  48  D e c a y and L o s s o f V i a b i l i t y F i g u r e 2.11 S c h e m a t i c Representation o f the L y s i s : g r o w t h A p p r o a c h to M o d e l i n g  49  B i o m a s s D e c a y and L o s s o f V i a b i l i t y F i g u r e 2.12 P l o t o f E q u a t i o n 4.18 to D e t e r m i n e the T r a d i t i o n a l D e c a y C o e f f i c i e n t for  53  Heterotrophic Biomass F i g u r e 2.13 B a t c h T e s t to E s t i m a t e the M a x i m u m S p e c i f i c G r o w t h R a t e o f H e t e r o t r o p h i c  57  Biomass F i g u r e 2.14 L o g a r i t h m i c F o r m o f the R e l a t i v e O x y g e n U p t a k e F i g u r e 2.15 R e s p i r a t i o n Test to D e t e r m i n e the C o n c e n t r a t i o n o f R e a d i l y B i o d e g r a d a b l e Substrate Sso F i g u r e 4.1 O U R T e s t E q u i p m e n t and S k e t c h D i a g r a m  74  F i g u r e 4.2 B a t c h T e s t R e a c t o r s and S k e t c h D i a g r a m  75  F i g u r e 5.1 C O D V a r i a t i o n i n A H e t e r o t r o p h i c G r o w t h Y i e l d Test ( M E B P R )  89  F i g u r e 5.2 D e t e r m i n a t i o n o f the Heterotrophic G r o w t h Y i e l d ( M E B P R )  90  F i g u r e 5.3 H e t e r o t r o p h i c D e c a y C o e f f i c i e n t o f the M E B P R Process  96  F i g u r e 5.4 H e t e r o t r o p h i c D e c a y C o e f f i c i e n t o f the U C T Process  96  F i g u r e 5.5 M a x i m u m S p e c i f i c G r o w t h R a t e o f Heterotrophic B i o m a s s ( M E B P R )  100  viii  F i g u r e 5.6 L o g a r i t h m i c F o r m o f R e l a t i v e O U R for the M E B P R P r o c e s s  100  F i g u r e 5.7 M a x i m u m S p e c i f i c G r o w t h R a t e o f H e t e r o t r o p h i c B i o m a s s ( U C T )  101  F i g u r e 5.8 L o g a r i t h m i c F o r m o f R e l a t i v e O U R for the U C T P r o c e s s  101  F i g u r e 5.9 N i t r o g e n Concentrations i n the Influent S a m p l e s  113  F i g u r e 5.10 N i t r o g e n C o n c e n t r a t i o n s i n A n Influent S a m p l e  113  F i g u r e 5.11 Ortho-phosphate & T o t a l P h o s p h o r u s i n the Influent S a m p l e s  115  F i g u r e 5.12 C o m p a r i s o n o f the Ortho-phosphate & T o t a l P h o s p h o r u s C o n c e n t r a t i o n s i n  115  the Influent S a m p l e s  ix  ABBREVIATIONS  /P  fraction o f inert particulate f o r m e d d u r i n g heterotrophic d e c a y ( m g C O D ) ( m g cell C O D ) "  1  fsi  fraction o f inert C O D i n particulate substrate  fxi  fraction o f inert C O D generated i n b i o m a s s decay  Pj  process rate  |1H  s p e c i f i c g r o w t h rate o f heterotrophic m i c r o o r g a n i s m s (d" )  Umax  m a x i m u m specific g r o w t h rate o f heterotrophic m i c r o o r g a n i s m s (d" )  1  1  0  temperature coefficient  0c  m e a n c e l l residence t i m e or s o l i d retention t i m e (d)  AER  aerobic z o n e  ANA  anaerobic z o n e  ANO  anoxic zone  A/O™  P h o r e d o x process  A /0™  anaerobic/anoxic/aerobic process  AR  r e c y c l e o f denitrified m i x e d l i q u o r f r o m the end o f the a n o x i c z o n e  ASIM  Activated Sludge SIMulation program  ASM1  Activated Sludge M o d e l N o . 1  ASM2  Activated Sludge M o d e l N o . 2  ASM3  Activated Sludge M o d e l N o . 3  b'n  traditional decay coefficient o f heterotrophic m i c r o o r g a n i s m s (d" )  2  1  x  bn  m o d e l decay coefficient o f heterotrophic m i c r o o r g a n i s m s (d~ )  BOD  biochemical oxygen demand (mg L " )  B N R  b i o l o g i c a l nitrogen r e m o v a l  CAS  c o n v e n t i o n a l activated sludge  COD  chemical oxygen demand (mg L " )  CTKN  total k j e l d a h l nitrogen ( m g L " )  CTN  total nitrogen ( m g L " )  DO  d i s s o l v e d o x y g e n ( m g O2 L " )  G C  gas chromatography  HRT  h y d r a u l i c residence t i m e  IAWPRC  International A s s o c i a t i o n o n W a t e r P o l l u t i o n R e s e a r c h a n d C o n t r o l  IAWQ  International A s s o c i a t i o n o n W a t e r Q u a l i t y  J'NSF  nitrogen content ( N ) o f s o l u b l e substrate S F  I'NSI  N content o f inert s o l u b l e C O D S i  / BM  N content o f b i o m a s s X H , X P A O , a n d X A U T  J'NXI  N content o f inert particulate C O D X i  I'NXS  N content o f particulate substrate X s  tPBM  p h o s p h o r u s ( P ) content o f b i o m a s s X H , X P A O , a n d X U T  I'PXS  i s P content o f particulate substrate X s  I'PXI  i s P content o f inert s o l u b l e C O D S\  /psF  is P content o f s o l u b l e substrate SV  /  i s P content o f inert s o l u b l e C O D S\  N  P S I  1  1  1  1  1  A  M B R  m e m b r a n e bioreactor  M E B P R  m e m b r a n e enhanced b i o l o g i c a l p h o s p h o r u s r e m o v a l process  MLSS  m i x e d l i q u o r suspended s o l i d s ( m g L " ) 1  xi  MLVSS  m i x e d l i q u o r v o l a t i l e suspended solids ( m g L " )  NR  denitrified m i x e d l i q u o r  OUR  o x y g e n u t i l i z a t i o n rate  PE  p r i m a r y effluent  PAOs  phosphate a c c u m u l a t i n g organisms  PHAs  p o l y h y d r o x y a l k a n o i c acids  PHB  p o l y - a -hydroxybutyrate  Poly-P  polyphosphate  Q  f l o w rate ( L m i n " )  RAS  return activated sludge  ro2  respiration rate ( m g O 2 1 / ' h r " )  s?  s o l u b l e components  S?o  influent concentration o f s o l u b l e components  S  fermentation product, equal to acetate ( m g C O D L " )  1  1  1  A  SALK  a l k a l i n i t y o f the wastewater [ m o l ( H C O 3 ) L " ]  SBRSIM  s e q u e n c i n g batch reactor s i m u l a t i o n  S  fermentable, r e a d i l y biodegradable organic substrates ( m g C O D L " )  1  1  F  s,  inert s o l u b l e organic matter ( m g C O D L " )  SMP  s o l u b l e m i c r o b i a l products  SN2  dinitrogen ( m g N L " )  SNH4  a m m o n i a + a m m o n i a nitrogen ( m g N L " )  SN03  nitrite + nitrate nitrogen ( m g N L " )  So2  d i s s o l v e d o x y g e n ( m g O2 L " )  Sp04  i n o r g a n i c s o l u b l e phosphorus, p r i m a r i l y ortho-phosphate ( m g P L " )  S  r e a d i l y biodegradable substrate, s u m o f S A + S F ( m g C O D L " )  1  1  1  1  1  1  1  s  xii  SSSP  s i m u l a t i o n o f single-sludge processes  STKN  soluble Kjeldahl nitrogen -  STP  s o l u b l e phosphorus  SRT  s o l i d s retention t i m e (d)  T  temperature ( ° C )  TSS  total suspended s o l i d s  U B C  University o f British Columbia  U C T  University o f Cape T o w n  V F A  v o l a t i l e fatty acids  VIP  V i r g i n i a Initiative P l a n t  V  reactor v o l u m e ( L )  v  volume o f mixed liquor (L)  VSS  v o l a t i l e suspended s o l i d s  v  v o l u m e o f wastewater ( L )  W A S  waste activated sludge  x?  particulate components  X?o  particulate c o m p o n e n t i n influent  XAUT  nitrifying organisms  X  heterotrophic o r g a n i s m s ( m g C O D L " )  mI  " WW  1  H  XI  inert particulate o r g a n i c m a t e r i a l ( m g C O D L " )  XMeOH  m e t a l - h y d r o x i d e s ( m g T S S L " ) , assumed to be c o m p o s e d o f F e ( O H ) 3 i n A S M 2  XjyieP  metal-phosphate, M e P 0 4 ( m g T S S L " ) , assumed to be c o m p o s e d o f F e P O 4 i n  1  1  1  ASM2  X  M L S S concentration ( m g C O D L " ) 1  M  T  XPAO  phosphate-accumulating organisms: P A O (mg C O D L " )  XPHA  p o l y h y d r o x y a l k a n o i c a c i d , is a c e l l u l a r internal storage product o f p h o s p h o r u s  1  a c c u m u l a t i n g organisms, P A O ( m g C O D L " ) 1  A p  particulate phosphorus, ( m g P L " )  Xpp  poly-phosphate, a c e l l u l a r internal i n o r g a n i c storage product o f p h o s p h o r u s  r  T  1  a c c u m u l a t i n g organisms, P A O ( m g P L " ) , 1  Xs  s l o w l y biodegradable substrate ( m g C O D L " )  XJKN  particulate K j e l d a h l n i t r o g e n  XTSS  total suspended s o l i d s , T S S ( m g T S S L " )  YH  heterotrophic g r o w t h y i e l d ( m g cell m g ~ ' C O D )  Yobs  observed g r o w t h y i e l d ( m g c e l l mg" C O D )  1  1  1  xiv  ACKNOWLEDGMENTS  I w o u l d l i k e to express m y p r o f o u n d gratitude to m y supervisor D r . E r i c R . H a l l for h i s g u i d a n c e and support t h r o u g h this project. I w o u l d l i k e to thank Professor J i m A t w a t e r for h i s suggestions and c o m m e n t s o n this thesis. T h a n k s are also extended to D r . P i e r r e B e r u b e for h i s k n o w l e d g e and references regarding this research.  I w o u l d also l i k e to a c k n o w l e d g e m y friends and colleagues i n 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 group at U B C w i t h o u t w h o m this thesis w o u l d not have c o m p l e t e d . M y thanks are g i v e n to S u s a n H a r p e r and P a u l a P a r k i n s o n for their n e v e r - e n d i n g assistant i n laboratory analysis. M y thanks also go to F r e d A . K o c h for h i s efforts i n m a i n t a i n i n g the p i l o t plant processes. T h e t e c h n i c a l support f r o m Scott J a c k s o n and B i l l L e u n g o f the C i v i l E n g i n e e r i n g t e c h n i c a l staff is e s p e c i a l l y appreciated.  F i n a l l y , I w i s h to g i v e this thesis to m y father i n m e m o r y o f h i s l o v e , care and support t h r o u g h h i s life e s p e c i a l l y at h i s final days w i t h o u t h i s encouragement a c c o m p l i s h e d this research.  xv  I w o u l d not  have  CHAPTER I  INTRODUCTION  1.1 General  The  membrane  enhanced  combination o f membrane  biological  phosphorus  removal  (MEBPR)  process  filtration and b i o l o g i c a l nutrient r e m o v a l ( B N R ) processes,  is  a  in a  m a n n e r that the m e m b r a n e replaces the secondary c l a r i f i e r for separating the s o l i d s f r o m the effluent.  P o t e n t i a l benefits o f the M E B P R process are h i g h q u a l i t y effluent, m o r e efficiency,  s m a l l footprint, and reduced cost. O p t i m i z e d process c o n f i g u r a t i o n and operating c o n d i t i o n s o f the M E B P R system are required to m a i n t a i n the desired nutrient r e m o v a l w h i l e a c h i e v i n g the e c o n o m i c benefits. T h e o n l y systematic approach to o p t i m i z e the process d e s i g n is m o d e l i n g ; therefore  the  estimation  of  important  kinetic  and  stoichiometric  parameters  and  the  characterization o f wastewater are required for use i n m o d e l i n g .  Modeling processes,  is an essential  t o o l for d e s i g n i n g and o p t i m i z i n g wastewater  e s p e c i a l l y for c o m p l i c a t e d systems  treatment  s u c h as b i o l o g i c a l nutrient r e m o v a l and  its  m o d i f i c a t i o n s , for e x a m p l e , the M E B P R process. S i n c e a large n u m b e r o f reactions take p l a c e w i t h i n the system, computer s i m u l a t i o n is a convenient w a y to o p t i m i z e the process d e s i g n and operation. W a s t e w a t e r  characterization is required to p r o v i d e the b a s i c c o n d i t i o n s p r i o r to  computer s i m u l a t i o n o f the M E B P R process.  1  Membrane enhanced biological phosphorus removal process and issues The membrane  enhanced  b i o l o g i c a l phosphorus  r e m o v a l process  is p r o p o s e d as a  process that takes full advantage of, a n d a v o i d s the p r o b l e m s associated w i t h , the m e m b r a n e bioreactor ( M B R ) a n d b i o l o g i c a l nutrient r e m o v a l ( B N R ) processes; the process s h o u l d b e able to o p t i m i z e d to achieve h i g h carbon and nutrient r e m o v a l e f f i c i e n c y i n a n e c o n o m i c a l w a y .  T h e M E B P R process i s t w o processes w o r k i n g i n c o n j u n c t i o n w i t h o n e another, rather than as connected b u t independent unit operations. T h e o p t i m u m operating c o n d i t i o n s o f M B R and B N R processes are not e x a c t l y the same o r are even different i n s o m e aspects. F o r e x a m p l e , a longer S R T favors carbon a n d nitrogen r e m o v a l , a n d s o l i d s r e d u c t i o n for a n M B R ; h o w e v e r , a v e r y l o n g S R T affects the phosphorus r e m o v a l e f f i c i e n c y d u e to r e l e a s i n g s o l u b l e phosphate to the process caused b y b i o m a s s decay.  T h e fundamental differences i n the b i o l o g y o f a n M B R c o m p a r e d to an activated sludge process are not yet clear (Stephenson  et al., 2 0 0 0 ) , p a r t i c u l a r l y for those m i c r o o r g a n i s m s  associated w i t h b i o l o g i c a l phosphorus r e m o v a l processes. A l i m i t e d amount o f i n f o r m a t i o n i s a v a i l a b l e o n h o w the floe structure, respiration rate, species d i v e r s i t y a n d o f f gas p r o d u c t i o n are affected b y changes i n operation ( C i c e k et al., 1 9 9 9 ; Stephenson et al., 2 0 0 0 ) . I n p a r t i c u l a r increased shear a n d the absence o f a clarifier w e r e cited as reasons for the differences b e t w e e n the M B R a n d the activated sludge process (Stephenson et al, 2 0 0 0 ) .  T h e a p p l i c a t i o n o f the M E B P R process has not been reported i n the literature, e v e n t h o u g h M B R a n d B N R processes h a v e been u s e d successfully. B i o l o g i c a l nutrient r e m o v a l has been u s e d successfully for treatment o f b o t h m u n i c i p a l a n d i n d u s t r i a l wastewater since i t w a s d e v e l o p e d i n the 1 9 7 0 ' s . T h e B N R process i s a m o d i f i c a t i o n o f the activated sludge process to  incorporate a n o x i c and/or anaerobic zones to p r o v i d e n i t r o g e n and/or p h o s p h o r u s r e m o v a l . H o w e v e r , there are issues affecting its performance. In s u c h a system, b i o m a s s separation f r o m the final effluent is u s u a l l y through sedimentation as i n the c o n v e n t i o n a l activated sludge system; the effluent q u a l i t y is affected b y the p h y s i c a l properties o f the sludge and b y the configuration and operation o f the sedimentation process. S e d i m e n t a t i o n does not w o r k w e l l for anaerobic systems due to gas bubbles f l o a t i n g sludge to the surface. In aerobic  systems,  denitrification c a n o c c u r , r e s u l t i n g i n nitrogen gas r a i s i n g sludge to the surface. F i l a m e n t o u s m i c r o o r g a n i s m s cause sludge b u l k i n g i n a secondary clarifier  (Stephenson  et al.,  2000).  Therefore, an alternative approach is desired for separating b i o m a s s from final effluent; and a m e m b r a n e for s o l i d separation w o u l d a v o i d s u c h p r o b l e m s i n a s o l i d separation  membrane  bioreactor.  With  the  development  o f membrane  technology, membranes  are often u s e d  replacement for sedimentation, i.e. for separation o f b i o m a s s i n b i o l o g i c a l processes.  as  a  Many  advantages o f M B R have been reported i n the literature s u c h as c o m p l e t e suspended s o l i d s r e m o v a l f r o m effluent, n o sludge b u l k i n g c o n c e r n , zero or r e d u c e d sludge p r o d u c t i o n and a s m a l l plant footprint (Stephenson et al,  2 0 0 0 ) . H o w e v e r , u n s o l v e d p r o b l e m s associated w i t h  M B R systems still l i m i t their applications i n the market, s u c h as aeration l i m i t a t i o n s , m e m b r a n e f o u l i n g and m e m b r a n e costs. P h o s p h o r u s r e m o v a l was not s h o w n to be i m p r o v e d i n an M B R c o m p a r e d to a c o n v e n t i o n a l system ( Y o o n et al., 2 0 0 0 ) . It w o u l d be an i n n o v a t i v e a p p r o a c h to c o m b i n e the advantages o f an M B R and B N R , and to compensate for the disadvantages o f each i n a single system.  I f an M B R is c o m b i n e d w i t h a B N R process, sludge b u l k i n g w i l l no l o n g e r b e a p r o b l e m , and the o v e r a l l costs o f the process m a y be reduced due to the absence o f s e c o n d a r y 3  clarifiers, the s m a l l footprint and reduced sludge p r o d u c t i o n i n the process. T h u s , it is p o s s i b l e to achieve b o t h nutrient r e m o v a l and c o m p l e t e s o l i d s - l i q u i d separation i n an M E B P R system, and consequently to p r o d u c e h i g h q u a l i t y effluent. T h i s approach w o u l d also be able to p r o v i d e additional benefits b y r e c o v e r i n g phosphorus from d o w n s t r e a m for reuse. Therefore, it w i l l be p a r t i c u l a r l y attractive i n the market for p r o v i d i n g h i g h q u a l i t y effluent and r e d u c i n g the o v e r a l l cost o f a wastewater treatment plant. O n e w a y to achieve this g o a l is to o p t i m i z e the d e s i g n and operation o f the M E B P R process b y c o m p u t e r s i m u l a t i o n .  Computer  simulation  C o m p u t e r s i m u l a t i o n w i t h an appropriate m o d e l has been used to study whether  a  treatment plant is capable o f b i o l o g i c a l carbon and nutrient r e m o v a l . It is a p o w e r f u l w a y to o p t i m i z e d e s i g n and operation o f the M E B P R process. C o m p u t e r s i m u l a t i o n is a c c o m p l i s h e d b y the f o l l o w i n g several steps ( C h e n g et al., 1999): selection o f an appropriate m o d e l , characterization o f the wastewater, c a l i b r a t i o n o f the m o d e l , -  v e r i f i c a t i o n o f the c a l i b r a t i o n , and computer s i m u l a t i o n s w i t h different operating parameters.  S e l e c t i n g an appropriate m o d e l i s the first step o f computer s i m u l a t i o n . T h e m o d e l s h o u l d effectively simulate the process, and it s h o u l d be easy to use. S e c o n d l y , to a p p l y the m o d e l for use  i n the d e s i g n and operation o f the M E B P R  wastewater-specific  and concentrations  o f important  process, parameters that  components  i n the influent must  are be  evaluated. F o r those parameters that do not change v e r y m u c h , the default values i n the m o d e l can be used.  A f t e r the characterization step, parameters and concentrations o f influent w i l l be r u n i n computer to predict the results. T h e differences between predicted results and measured values o f an effluent are u s e d to v e r i f y the c a l i b r a t i o n to a reasonable value. T h e n different o p e r a t i n g parameters w i l l be u s e d to p r o d u c e the desired results. B a s e d o n i n f o r m a t i o n f r o m the M E B P R process, and incorporated i n a computer p r o g r a m , any c o n c e i v a b l e case can be s i m u l a t e d as noted b y H e n z e et al. (2000).  For  some  models,  such  as  A S M 1 and  ASM2,  it  is  difficult  to  determine  the  concentrations o f the v a r i o u s constituents i n a bioreactor because o f the c o m p l e x i t y o f the m o d e l s . S e v e r a l organizations h a v e d e v e l o p e d computer codes for s o l v i n g the  simultaneous  m a s s balance equations for the constituents i n the m o d e l s , a l l o w i n g their p r e d i c t i o n for a v a r i e t y o f b i o r e a c t o r configurations. F o r e x a m p l e S S S P ( B i d s t r u p et al,  1988), S B R S I M ( O l e s and  W i l d e r e r , 1991) were d e v e l o p e d for i m p l e m e n t a t i o n o f A S M N o . l ( A S M 1 ) , w h i l e A S I M ( G u j e r et al,  1994) i m p l e m e n t s A S M 1 and A S M 2 m o d e l s .  Activated sludge model T h e m o d e l i n g o f b i o l o g i c a l wastewater treatment systems deals w i t h c o m p l e x systems for the r e m o v a l o f o r g a n i c matter, nitrogen and phosphorus. B e c a u s e o f the interactions w i t h i n s u c h systems, the m a t h e m a t i c a l m o d e l s d e p i c t i n g t h e m are quite c o m p l e x , w h i c h has detracted f r o m their use ( H e n z e et al,  1987). R e a l i z i n g the benefits to be d e r i v e d from the m a t h e m a t i c a l  m o d e l i n g , w h i l e r e c o g n i z i n g the reluctance o f m a n y engineers  to use it, the  International  A s s o c i a t i o n o n W a t e r P o l l u t i o n R e s e a r c h and C o n t r o l ( I A W P R C ) d e v e l o p e d the p r a c t i c a l m o d e l A c t i v a t e d S l u d g e M o d e l N o . 1 ( A S M 1 ) , for realistic p r e d i c t i o n o f the performance o f a s i n g l e sludge system c a r r y i n g out carbon o x i d a t i o n , 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 ( H e n z e et  al,  2 0 0 0 ) . B a s e d o n A S M 1 , the International A s s o c i a t i o n o n W a t e r Q u a l i t y ( I A W Q ) d e v e l o p e d the 5  A c t i v a t e d S l u d g e M o d e l N o . 2 ( A S M 2 ) . A S M 2 is an e x t e n s i o n o f A S M 1 , and it incorporates a l l o f the processes i n c l u d e d i n A S M 1 , p l u s b i o l o g i c a l phosphorus r e m o v a l . It is m u c h larger than A S M 1 and m o r e c o m p l e x , i n c l u d i n g 19 components and 19 process rate equations that require 22 s t o i c h i o m e t r i c coefficients and 42 k i n e t i c parameters.  G r a d y et al. (1999) s u m m a r i z e d the differences b e t w e e n A S M 1 and A S M 2 . First, s o m e processes i n A S M 1 were s i m p l i f i e d i n A S M 2 to m i n i m i z e its size. F o r e x a m p l e , a m m o n i f i c a t i o n o f s o l u b l e organic n i t r o g e n and h y d r o l y s i s o f particulate o r g a n i c nitrogen w e r e a s s u m e d to o c c u r in  stoichiometric  proportion  to  soluble  substrate  removal  and  hydrolysis  of  slowly  biodegradable o r g a n i c matter.  S e c o n d , the processes h a p p e n i n g under anaerobic c o n d i t i o n s are quite different i n the two  m o d e l s . A S M 1 assumed that m i c r o b i a l g r o w t h and h y d r o l y s i s stopped under anaerobic  c o n d i t i o n s , although decay and lysis c o n t i n u e d . T h i s is inadequate for b i o l o g i c a l p h o s p h o r u s r e m o v a l . C o n s e q u e n t l y , A S M 2 i n c l u d e s fermentation, uptake o f acetate for f o r m a t i o n o f p o l y - a hydroxybutyrate ( P H B ) and other p o l y h y d r o x y a l k a n o i c acids ( P H A s ) , and release o f s o l u b l e phosphate f r o m h y d r o l y s i s o f polyphosphate.  T h i r d , the scope o f activities o f the c o m m o n heterotrophic bacteria was e x p a n d e d . T h e y ferment r e a d i l y biodegradable substrate, p r o d u c i n g acetate under anaerobic c o n d i t i o n s , but g r o w under aerobic and a n o x i c c o n d i t i o n s u s i n g b o t h r e a d i l y fermentable However, A S M 2  substrate and acetate.  is not capable o f m o d e l i n g a t o t a l l y anaerobic system because  common  heterotrophic bacteria cannot g r o w t h under anaerobic c o n d i t i o n s . A S M 2 can o n l y m i m i c the performance o f an anaerobic z o n e i n a system w i t h aerobic and a n o x i c zones ( G r a d y et 1999). 6  al.  F i n a l l y , several s i m p l i f y i n g assumptions were m a d e i n A S M 2 w i t h respect to phosphatea c c u m u l a t i n g organisms  ( P A O s ) g r o w t h . T h e y were assumed  to g r o w o n l y under  aerobic  c o n d i t i o n s and to use o n l y stored P H B s as a substrate for g r o w t h .  T h e m o s t significant change f r o m A S M 1 to A S M 2 w a s the fact that the b i o m a s s w a s assigned c e l l internal structure. H o w e v e r , A S M 2 o n l y considers the average c o m p o s i t i o n o f the b i o m a s s , it is not capable o f d i s t i n g u i s h i n g the c o m p o s i t i o n ( c e l l internal structure) o f i n d i v i d u a l cells, since it i s based o n average properties o f the p o p u l a t i o n as m e n t i o n e d b y H e n z e et al. (2000).  A S M 2 c a n be used for d y n a m i c s i m u l a t i o n o f c o m b i n e d b i o l o g i c a l processes for carbon, nitrogen a n d phosphorus r e m o v a l . A l s o , A S M 2 c o u l d b e used as a conceptual p l a t f o r m f o r further m o d e l development. T h u s , it w a s selected for m o d e l i n g the M E B P R process i n this research. H o w e v e r , it has m a n y l i m i t a t i o n s . F o r e x a m p l e , the results f r o m cases b e y o n d the n o r m a l range m a y not always be v a l i d . Therefore, wastewater  characterization a n d m o d e l  parameter determination are c r u c i a l for computer s i m u l a t i o n .  Wastewater characterization and model parameters  determination  W a s t e w a t e r characterization a n d m o d e l parameter determination are r e q u i r e d p r i o r to computer  s i m u l a t i o n to p r o v i d e the basic  conditions  for the s i m u l a t i o n o f a p a r t i c u l a r  wastewater a p p l i c a t i o n . T h e q u a l i t y o f the m o d e l predictions w i l l depend o n the q u a l i t y o f the wastewater  characterization  a n d o n the c a l i b r a t i o n o f the m o d e l . T h e m o r e  detailed the  characterization, the m o r e r e l i a b l e the results obtained from the m o d e l i n g effort w i l l b e ( H e n z e et al., 2000). A f t e r iterative c a l i b r a t i o n a n d v e r i f i c a t i o n , s i m u l a t i o n i s a c c o m p l i s h e d w i t h  7  different operating parameter values to a c h i e v e the desired objectives. T h u s , the u n d e r s t a n d i n g o f wastewater characteristics and the d e t e r m i n a t i o n o f m o d e l parameters are necessary.  A s a result o f variations i n h u m a n activities, m u n i c i p a l wastewater treatment systems experience d i u r n a l variations i n the f l o w a n d concentration o f the wastewater entering t h e m . The  wastewater c o m p o s i t i o n influences the actual system performance ( H e n z e et al., 2 0 0 0 ) .  W a s t e w a t e r c o m p o s i t i o n is determined b y wastewater input to the sewer, sewer s y s t e m type (separate o r  c o m b i n e d ) , and  the  transformation  processes  o c c u r r i n g i n the  sewer.  The  wastewater input to the sewer can change due to r a i n , i n d u s t r i a l a c t i v i t y and the habits o f the p o p u l a t i o n connected to the sewer system. A detailed k n o w l e d g e o f the influent to a wastewater treatment system w i l l a l l o w for a g o o d p r e d i c t i o n o f the performance o f the system. T h u s , k i n e t i c and s t i o c h i o m e t r i c parameter d e t e r m i n a t i o n and wastewater characterization w e r e the major interests o f this research.  1.2 Direction of Research  T h i s research is the first step o f m o d e l i n g the m e m b r a n e enhanced b i o l o g i c a l p h o s p h o r u s r e m o v a l process. T h e major tasks w e r e wastewater  characterization and m o d e l  parameter  determination; the results w e r e u s e d for c o m p a r i n g the M E B P R and s i m p l i f i e d U C T processes i n terms o f the m i c r o b i a l activity. M o s t o f the efforts focused o n fundamental studies to determine k e y s t o i c h i o m e t r i c and k i n e t i c parameters i n A S M 2 ; these studies w e r e based o n the s i m p l i f i e d U C T a n d M E B P R processes operated i n the U B C p i l o t plant. T h e purposes o f this research were: •  to g a i n k n o w l e d g e o n wastewater c o m p o s i t i o n s i n the influent,  8  •  to e x p l o r e the difference b e t w e e n the s i m p l i f i e d U C T and M E B P R processes i n terms o f the m i c r o b i a l activities b y c o m p a r i n g the k i n e t i c and s t o i c h i o m e t r i c parameters, and  •  to p r o v i d e the b a s i c c o n d i t i o n s , e.g. a database, for future process d e s i g n and c o m p u t e r s i m u l a t i o n o f the M E B P R process.  T h e major tasks o f this research w e r e : •  to selected appropriate approaches for wastewater characterization and m o d e l parameter estimations,  •  to establish a n a l y t i c a l methods for e s t i m a t i o n o f particular parameters,  •  to d e s i g n and construct the r e q u i r e d testing apparatus,  •  to conduct the required e x p e r i m e n t a l tests, and  •  to d o c u m e n t the results and m a k e r e c o m m e n d a t i o n s .  1.3 Scope of Dissertation  T h e dissertation is set out i n 6 chapters. C h a p t e r 1 introduces the issues o f this research. T h e b a c k g r o u n d i n f o r m a t i o n and p r e v i o u s research related to m o d e l i n g o f the M E B P R process is r e v i e w e d i n C h a p t e r 2 to p r o v i d e necessary i n f o r m a t i o n for understanding the process d e s i g n and o p t i m i z a t i o n . A c t i v a t e d sludge m o d e l N o . 2 is described i n C h a p t e r 2 for the purpose o f selecting the m o s t important components  and parameters to be e x a m i n e d . T h e  alternative  approaches for wastewater characterization and parameter estimation, as w e l l as the related references from literature are d i s c u s s e d i n C h a p t e r 2. Presented i n Chapter 3 are the objectives o f this research. T h e detailed e x p e r i m e n t a l procedures  9  for wastewater  characterization and  parameter e s t i m a t i o n are described i n C h a p t e r 4 and the A p p e n d i c e s . R e s u l t s are reported and d i s c u s s e d i n C h a p t e r 5, and C h a p t e r 6 makes r e c o m m e n d a t i o n s for future research.  10  C H A P T E R II  Background and Literature Review  In this chapter, the b a c k g r o u n d i n f o r m a t i o n and p r e v i o u s research r e l a t i n g to b i o l o g i c a l nutrient r e m o v a l , m e m b r a n e technologies, wastewater characterization and m o d e l parameter determination are r e v i e w e d to p r o v i d e necessary i n f o r m a t i o n for M E B P R process d e s i g n and optimization.  2.1 Biological Nutrient Removal Process  T h e m e c h a n i s m s , recent development, process c o n f i g u r a t i o n o f the b i o l o g i c a l nutrient r e m o v a l process, and the factors affecting the system performance are r e v i e w e d i n this section.  B i o l o g i c a l nutrient r e m o v a l ( B N R ) processes are m o d i f i c a t i o n s o f the activated s l u d g e process that incorporate a n o x i c and/or anaerobic zones to p r o v i d e n i t r o g e n and/or p h o s p h o r u s r e m o v a l ( G r a d y et al., 1999). M a n y B N R variants h a v e been d e v e l o p e d , representing a w i d e range o f nutrient r e m o v a l c a p a b i l i t i e s .  Removal  o f nutrients  from  wastewater  p r i o r to discharge is b e i n g r e q u i r e d m o r e  frequently under the pressure o f p r o b l e m s caused b y eutrophication, and excess nutrient r e m o v a l is a central issue i n wastewater treatment plant d e s i g n . A n u m b e r o f approaches h a v e e v o l v e d since the early 1 9 7 0 ' s . I n i t i a l l y the processes m o s t u s e d w e r e b i o l o g i c a l n i t r i f i c a t i o n  for  a m m o n i a o x i d a t i o n and c o n t r o l , b i o l o g i c a l d e n i t r i f i c a t i o n u s i n g m e t h a n o l for n i t r o g e n r e m o v a l ,  11  and c h e m i c a l p r e c i p i t a t i o n for phosphorus r e m o v a l . In recent years, b i o l o g i c a l nutrient r e m o v a l has been considered as a r e l a t i v e l y l o w - c o s t t e c h n o l o g y ( M e t c a l f & E d d y , 1991), and a n u m b e r o f b i o l o g i c a l treatment processes have been d e v e l o p e d for r e m o v a l o f phosphorus alone or i n c o m b i n a t i o n w i t h nitrogen.  N i t r o g e n r e m o v a l is n o r m a l l y a c h i e v e d through the processes o f n i t r i f i c a t i o n i n a e r o b i c zones and d e n i t r i f i c a t i o n i n a n o x i c zones w i t h i n a single-sludge system, w i t h c a r b o n o x i d a t i o n o c c u r r i n g i n b o t h zones. B y r e v i e w i n g the h i s t o r y o f the processes, G r a d y et al. (1999) i n d i c a t e d that the t w o concepts incorporated into this approach w e r e the r e c i r c u l a t i o n o f n i t r a t e - N to an i n i t i a l a n o x i c z o n e to a l l o w the use o f r e a d i l y biodegradable substrate for d e n i t r i f i c a t i o n , a n d the use o f a second a n o x i c z o n e for a d d i t i o n a l d e n i t r i f i c a t i o n u s i n g s l o w l y b i o d e g r a d a b l e substrate and b i o m a s s decay. These concepts are n o w w i d e l y u s e d i n b i o l o g i c a l n i t r o g e n r e m o v a l .  W i t h the d e v e l o p m e n t o f nitrogen r e m o v a l systems, enhanced p h o s p h o r u s r e m o v a l w a s observed i n certain full-scale activated sludge systems (Sedlak, 1 9 9 1 ; R a n d a l l et al,  1992).  B a r n a r d ( 1 9 7 5 , 1976) created an effective and cost c o m p e t i t i v e single-sludge n i t r o g e n r e m o v a l system (four-stage B a r d e n p h o process), b y integrating aerobic and a n o x i c zones, w i t h nitrate r e c i r c u l a t i o n . H e also added an i n i t i a l anaerobic z o n e to h i s n i t r o g e n r e m o v a l system to r e m o v e b o t h n i t r o g e n and phosphorus i n a process n o w k n o w n as the five-stage B a r d e n p h o process. S i n c e that t i m e , a great deal has been  d i s c o v e r e d about  the m e c h a n i s m s , m i c r o b i o l o g y ,  s t o i c h i o m e t r y , and k i n e t i c s o f B N R systems, and m a n y process variants h a v e b e e n d e v e l o p e d .  12  Mechanisms  of nitrogen and phosphorus  removal  T w o p r i n c i p a l m e c h a n i s m s for the r e m o v a l o f n i t r o g e n are a s s i m i l a t i o n a n d n i t r i f i c a t i o n denitrification  (Metcalf & Eddy,  1991). In the a s s i m i l a t i o n process, a m m o n i a - n i t r o g e n is  incorporated into c e l l mass, w h i l e a p o r t i o n o f this a m m o n i a - n i t r o g e n w i l l b e returned to the wastewater o n the death a n d l y s i s o f the c e l l . In n i t r i f i c a t i o n - d e n i t r i f i c a t i o n , the r e m o v a l o f nitrogen is a c c o m p l i s h e d i n t w o c o n v e r s i o n steps. •  Nitrification:  a m m o n i a - n i t r o g e n is o x i d i z e d to the intermediate product, nitrite, b y  autotrophic bacteria (Nitrosomonas),  a n d then nitrite is converted to nitrate b y another  bacteria genera (Nitrobacter) under aerobic c o n d i t i o n s .  Nitrosomonas  bacteria  Ammonia (NH ) 3  Nitrobacter  Nitrite (N0 ~)  •  Nitrate ( N 0 " )  2  bacteria  Nitrite (N0 ~) 2  •  ^  3  D e n i t r i f i c a t i o n : u n d e r a n o x i c c o n d i t i o n s , n i t r i t e - N is converted to n i t r o g e n gas for removal  b y heterotrophic bacteria that u t i l i z e n i t r a t e - N as their t e r m i n a l electron  accepter. Nitrate ( N 0 " ) 3  —  •  N0 " ~ • NO 2  _  •  N  2  0 — • Nitrogen Gas ( N ) 2  B i o l o g i c a l p h o s p h o r u s r e m o v a l is a c c o m p l i s h e d b y creating c o n d i t i o n s favorable for the g r o w t h o f P A O s , w h i c h have the interesting characteristics o f concentrating phosphate i n polyphosphate  (Poly-P)  granules  when  they  are c y c l e d  between  aerobic  and  anaerobic  c o n d i t i o n s . T h e enrichment o f the b i o m a s s w i t h P A O s a l l o w s phosphorus r e m o v a l f r o m the wastewater v i a b i o m a s s wastage ( G r a d y et al, W e n t z e l et al,  1986; A r u n et al,  1999). M a n y researchers ( C o m e a u et al., 1986;  1988; G r a d y et al,  13  1999) h a v e discussed the m e c h a n i s m o f  b i o l o g i c a l phosphorus r e m o v a l extensively. B a s e d o n the w o r k o f L o t t e r et al. (1986) and G r a d y et al. (1999), the o v e r a l l m e c h a n i s m m a y be s u m m a r i z e d as f o l l o w s ( F i g u r e 2.1).  V o l a t i l e fatty a c i d  Phosphorus  Phosphorus  Carbon dioxide  \  4  C a r b o n storage  Oxygen  Poly-P  Poly-P  C a r b o n storage  P h o s p h o r u s r e m o v a l bacteria  P h o s p h o r u s r e m o v a l bacteria  Aerobic  Anaerobic  F i g u r e 2.1 O v e r a l l B i o - P r e m o v a l m e c h a n i s m s (adapted from G r a d y et al., 1999)  •  Sequential exposure o f the m i x e d l i q u o r to anaerobic and aerobic zones gives the P A O s a c o m p e t i t i v e advantage over o r d i n a r y heterotrophic bacteria, w h i c h are not able to take u p o r g a n i c matter under anaerobic c o n d i t i o n s , but w h i c h can carry out  fermentation  reactions, r e s u l t i n g i n the f o r m a t i o n o f v o l a t i l e fatty acids ( V F A s ) (Lotter et al., 1986). •  U n d e r anaerobic c o n d i t i o n s , the P A O s are able to transport V F A s into the c e l l and store t h e m as P H B and other p o l y h y d r o x y a l k a n o i c acids ( P H A s ) , u s i n g energy cleavage o f intracellular polyphosphate, releasing s o l u b l e phosphate to the  from  the  wastewater  ( G r a d y et al. 1999). •  U n d e r the aerobic and a n o x i c c o n d i t i o n s , the P A O s g r o w b y u s i n g the stored P H A as a c a r b o n and energy source or b y u s i n g nitrate and nitrite as alternative electron acceptors, a l l o w i n g a n o x i c c o n d i t i o n s to be used as w e l l for f o r m i n g P o l y - P from s o l u b l e phosphate i n the wastewater (Lotter et al,  1986; G r a d y et al. 1999).  14  •  P h o s p h o r u s is r e m o v e d f r o m the system b y w a s t i n g sludge w i t h P A O s , w h i c h c o n t a i n h i g h concentrations o f P o l y - P at the e n d o f the aerobic z o n e (Lotter et al, 1986; G r a d y etal. 1999).  It m a y b e stated that the essential requirements for b i o l o g i c a l phosphorus r e m o v a l are sequential exposure o f the m i x e d l i q u o r to anaerobic and aerobic c o n d i t i o n s , the presence o f V F A s i n the anaerobic zone, a n d the w i t h d r a w a l o f W A S w h i l e the m i x e d l i q u o r i s i n the aerobic z o n e . Therefore, these requirements s h o u l d b e incorporated i n the B N R process d e s i g n and o p t i m i z a t i o n .  Processes selection and bioreactor  configuration  B e f o r e b e g i n n i n g a computer s i m u l a t i o n , a b a s i c process must have been assumed. T h e process selection depends o n the degree o f n i t r o g e n and/or phosphorus r e m o v a l r e q u i r e d , the characteristics o f the wastewater, the size o f the plant a n d site restrictions, etc. H o w e v e r , the k e y consideration i n the selection a n d d e s i g n o f B i o - P processes i s the control o f n i t r a t e - N a d d i t i o n to the anaerobic z o n e ( G r a d y et al., 1999). O n e approach to m i n i m i z e nitrate r e c y c l e to the anaerobic z o n e i s to a l l o w the return activated sludge ( R A S ) to denitrify under  endogenous  conditions. Increasing the residence t i m e o f the R A S i n the clarifier, as i n A 10 process ( R a n d a l l et al, 1992), i s one s u c h e x a m p l e .  T w o other processes  that e l i m i n a t e n i t r a t e - N r e c y c l e to the anaerobic z o n e are the  U n i v e r s i t y o f C a p e T o w n , S o u t h A f r i c a ( U C T ) ( E k a m a et al, 1983; S e d l a k 1 9 9 1 ; R a n d a l l et al, 1992) a n d the V I P ( D a i g g e r et al, 1988; S e d l a k 1 9 9 1 ; R a n d a l l et al, 1992) processes. F i g u r e 2.2 p r o v i d e s a process schematic o f the U C T process, w h i c h w a s p r o p o s e d to ensure that n o  15  nitrate entered the anaerobic zone. R A S is r e c y c l e d to the a n o x i c z o n e and the n i t r i f i e d m i x e d l i q u o r ( N R ) f r o m the aerobic z o n e is also directed to the a n o x i c z o n e to increase the o v e r a l l degree o f n i t r o g e n r e m o v a l . A s e c o n d r e c y c l e o f d e n i t r i f i e d m i x e d l i q u o r f r o m the e n d o f the a n o x i c z o n e ( A R ) to the anaerobic z o n e is required to p r o v i d e the m i c r o o r g a n i s m s needed there. S i n c e it w a s difficult to c o n t r o l the nitrates at the end o f the a n o x i c z o n e , the m o d i f i e d U C T process ( F i g u r e 2.3) w a s proposed.  Effluent  Influent  F i g u r e 2.2 Process schematic o f the U C T process ( G r a d y et al., 1999)  T h e m o d i f i e d U C T process has t w o a n o x i c zones. T h e first receives and denitrifies the R A S and the other receives and denitrifies the N R . T h e process i s able to ensure that n o nitrate enters the anaerobic zone, and it m a k e s c o n t r o l o f the N R to the d o w n s t r e a m a n o x i c z o n e less c r i t i c a l , and r e l a t i v e l y h i g h N R rates c a n be u s e d to ensure that the f u l l d e n i t r i f i c a t i o n c a p a b i l i t y o f this z o n e is used. H o w e v e r , an o v e r s i z e d upstream a n o x i c z o n e is r e q u i r e d to ensure that complete  d e n i t r i f i c a t i o n occurs. Therefore,  it increases  the  overall  process  volume  c o m p l e x i t y ( G r a d y et al., 1999). T h e f u n c t i o n o f each z o n e is s u m m a r i z e d i n T a b l e 2 . 1 .  16  and  AR  NR Effluent  Influent  F i g u r e 2.3 M o d i f i e d U C T process ( G r a d y et al,  1999)  T a b l e 2.1 S u m m a r y o f b i o l o g i c a l n i t r o g e n r e m o v a l process zones Zone Anaerobic  Function To  a l l o w P A O s release  stored P H A and take u p V F A s  i n the  absence o f o x y g e n and nitrates to achieve m a x i m u m P - r e m o v a l capabilities H i g h concentration o f V F A w i l l m a x i m i z e o v e r a l l P - r e m o v a l i n shortest t i m e First  R e m o v e nitrates entering the bioreactor from R A S or P E ( p r i m a r y  Anoxic  effluent) before i n t r o d u c t i o n to the anaerobic z o n e Nitrates are used b y heterotrophic bacteria i n the R A S instead o f O2, for respiration V F A s i n the P E are u s e d preferentially i n this reaction  Second  C o n v e r t nitrates f o r m e d i n the aerobic z o n e to n i t r o g e n gas, w h i c h is  Anoxic  released to the atmosphere T h e internal r e c y c l e l i n e is u s e d to transfer the nitrates to the a n o x i c zone A t the end o f aerobic zone, the o x y g e n concentration must minimized  i n order to m a x i m i z e d e n i t r i f i c a t i o n capacity i n  be the  second a n o x i c z o n e Theoretically, percentage  of  a higher nitrates  internal r e c y c l e rate transfers to  the  anoxic  zone  for  a  higher  denitrification.  H o w e v e r , the p r a c t i c a l upper l i m i t appears to be about 3 x the P E f l o w rate, due to the negative i m p a c t o f D O that is also returned. Aerobic  T o degrade any o r g a n i c c a r b o n that has not been u t i l i z e d d u r i n g denitrification i n the a n o x i c z o n e T o o x i d i z e a l l a m m o n i a to nitrates b y autotrophic bacteria T o take up and store P i n the f o r m o f P o l y - P  17  Factors affecting BNR process  performance  M a n y factors that affect the p e r f o r m a n c e o f B N R  process are s i m i l a r to those that affect  activated sludge systems ( G r a d y et al., 1999). T h e s e factors are s o l i d s retention t i m e ( S R T ) , the ratio o f wastewater o r g a n i c matter to nutrient concentrations, the c o m p o s i t i o n o f o r g a n i c matter i n wastewater,  the effluent total suspended solids l e v e l s , and e n v i r o n m e n t a l factors s u c h as  temperature, p H , and D O concentration.  S o l i d s retention t i m e p l a y s the same r o l e i n B N R processes  as i n activated sludge.  H o w e v e r , the S R T i n the separate zones are o f m o r e interest than the total S R T , since they c o n t r o l what o c c u r s i n those zones ( L i n e r and G r a d y , 1997). T h e aerobic S R T w a s d e f i n e d as the fraction o f the total system S R T that is aerobic. B e c a u s e the S R T is defined i n terms o f the m a s s o f b i o m a s s i n a system, the fraction o f the system S R T that is aerobic is e q u i v a l e n t to the fraction o f the b i o m a s s i n the system that is m a i n t a i n e d under aerobic c o n d i t i o n s , fxwi, A E R ( G r a d y et al., 1999). C o n s e q u e n t l y : ( X T * V ) A V E / ( X T * V ) s y s t e m = / X M , A V E = e , A E R / ec M  M  c  (2.1)  L i k e w i s e , w i t h the fractions those are a n o x i c : ( X M T * V ) A N X / ( X M T * V ) s s t e m fxM, =  y  A N X ~ ec, A N x / ec  (2.2)  and anaerobic: ( X M T * V ) A N A / ( X M T * V ) s t e m =yxM, A N A  =  y s  ec, A N A / e c  (2.3)  W h e r e X M T is the b i o m a s s c o n c e n t r a t i o n i n any g i v e n z o n e , V is the reactor v o l u m e o f e a c h z o n e ; ec, A E R is the S R T o f aerobic z o n e , ec, A N X is the a n o x i c S R T , s i m i l a r l y , ec, A N A is the anaerobic S R T , a n d e c is the system S R T .  The  anaerobic S R T c a n d r a m a t i c a l l y affect a B N R system t h r o u g h o r g a n i s m s e l e c t i o n .  A n increase i n the anaerobic S R T w i l l a l l o w increased fermentation o f b i o d e g r a d a b l e o r g a n i c 18  matter i n the anaerobic zone, r e s u l t i n g i n increased p r o d u c t i o n o f V F A s and increased b i o l o g i c a l phosphorus r e m o v a l . D a i g g e r et al. (1988) and S a d i c k et al. (1992) reported that anaerobic p l u s a n o x i c S R T s i n the 2 to 3 day range have been successful i n some p i l o t - and f u l l - s c a l e B N R processes. G r a d y et al. (1999) suggest that the anaerobic S R T s h o u l d be at least 0.5 days. It s h o u l d be m e n t i o n e d that longer S R T s i n B N R systems a l l o w m o r e c o m p l e t e m e t a b o l i s m o f organic  matter,  which  can  increase  nitrogen  r e m o v a l , but  these m a y  adversely  impact  phosphorus r e m o v a l .  T h e concentration o f biodegradable o r g a n i c matter relative to the nutrient c o n c e n t r a t i o n i n the influent c a n d r a m a t i c a l l y affect the performance o f a B N R system. I f a  wastewater  contains insufficient o r g a n i c matter for r e m o v i n g a l l o f the phosphorus, p h o s p h o r u s w i l l be present i n the process effluent at a concentration d e t e r m i n e d b y the relative concentrations o f phosphorus and o r g a n i c matter i n the influent. T h e c o m p o s i t i o n o f the o r g a n i c matter present i n a wastewater, p a r t i c u l a r l y its b i o d e g r a d a b i l i t y , also affects the performance o f B N R process. A h i g h p o r t i o n o f V F A s i n wastewater w i l l result i n r a p i d uptake b y the P A O s and a r e l a t i v e l y s m a l l anaerobic S R T c a n be used. A n u m b e r o f e n v i r o n m e n t a l factors affect the B N R process significantly.  These factors  are temperature,  p H , d i s s o l v e d o x y g e n concentration,  mixing  energy, and bioreactor and aerator configurations.  2.2 M e m b r a n e Bioreactor  In this section, the d e v e l o p m e n t and advantages  o f m e m b r a n e bioreactors  nutrient r e m o v a l and the m i c r o b i a l a c t i v i t y i n M B R s are r e v i e w e d .  19  (MBR),  Development of membrane Membrane  bioreactors  bioreactors  (MBRs)  have  been  developed  by combining  membrane  t e c h n o l o g y w i t h b i o l o g i c a l reactors for the treatment o f wastewaters. M e m b r a n e bioreactors w i t h a n o x i c stages h a v e been u s e d for nitrate r e m o v a l ( S u w a et al., 1992). A n a e r o b i c processes are suitable for h i g h strength wastewaters ( R o s s et al., 1992).  F u l l - s c a l e c o m m e r c i a l aerobic M B R processes first appeared i n N o r t h A m e r i c a i n the late 1970s a n d then i n Japan i n the early 1980s, w i t h anaerobic processes entering the i n d u s t r i a l wastewater market at around the same t i m e i n S o u t h A f r i c a . T h e aerobic M B R process has successfully treated b o t h i n d u s t r i a l a n d m u n i c i p a l wastewater. T h e v e r y h i g h q u a l i t y o f the treated water from a n M B R process i s c o m m o n (Stephenson et al., 2 0 0 0 ) . M a n y advantages o f M B R s have b e e n reported i n the literature.  Advantages of MBRs •  H i g h e r r e m o v a l efficiencies c o m p a r e d to the activated sludge processes ( C o t e et al., 1997).  •  P r o v i d e stable c o n d i t i o n s for the g r o w t h o f s p e c i a l i z e d m i c r o o r g a n i s m s that are able to r e m o v e s l o w l y degradable c o m p o n e n t s (Stephenson et al., 2 0 0 0 ) .  •  C a n be operated at l o w H R T s a n d l o n g S R T s w i t h o u t washout o f b i o m a s s .  •  M e a n n i t r i f i c a t i o n a c t i v i t y for M B R s has been demonstrated to b e m o r e than d o u b l e that o f the equivalent activated sludge plant ( Z h a n g et al, 1997).  •  N o filaments o r s l u d g e - b u l k i n g p r o b l e m s .  •  P r o d u c e less sludge than other c o m p a r a b l e wastewater treatment process d u e to their operation at r e l a t i v e l y l o n g S R T s a n d l o w sludge l o a d i n g rates.  20  Nutrient removal in MBRs T o t a l n i t r o g e n r e m o v a l through the i n c l u s i o n o f a n a n o x i c z o n e i s c o m m o n i n M B R systems. S u w a et al. (1992) a n d C h i e m c h a i s r i et al. (1992) reported h i g h e r n i t r i f i c a t i o n a n d denitrification rate i n M B R s . T h e performance o f M B R s has been s h o w n to b e dependent o n b o t h a n o x i c a n d aerobic c y c l e t i m e , a n d the ratio o f the b i o l o g i c a l o x y g e n d e m a n d to the total nitrogen concentration ( B O D / T N ) o f the wastewater. T o t a l n i t r o g e n r e m o v a l d r o p p e d f r o m > 8 0 % to < 5 0 % o n decreasing the B O D / T N ratio f r o m >2 to <1 ( N a h et al, 2 0 0 0 ) . G h y o o t a n d Verstraete (1999) f o u n d that M B R s a c h i e v i n g 9 0 % n i t r o g e n r e m o v a l c o u l d b e operated at d o u b l e the l o a d i n g rates w i t h m e t h a n o l instead o f acetic a c i d .  P h o s p h o r u s r e m o v a l i n M B R s i s a major area o f interest, as the need to reduce nutrient loads b e c o m e s m o r e important. R e p o r t e d phosphorus r e m o v a l s range from 1 1 . 9 % ( C o t e et al., 1997) to 75%o ( U e d a a n d H a t a , 1999). A s s i m i l a t i o n alone does not account for a l l o f the reported phosphorus r e m o v a l . H o w e v e r , stable phosphorus r e m o v a l has been demonstrated b y m e t a l c o a g u l a t i o n d o s i n g a c h i e v i n g a r e m o v a l e f f i c i e n c y o f 8 0 % ( B u i s s o n et al,  1998). P h o s p h o r u s  r e m o v a l w a s not i m p r o v e d i n an M B R c o m p a r e d to a c o n v e n t i o n a l system ( Y o o n et al., 2 0 0 0 ) . E n h a n c e d b i o l o g i c a l phosphorus r e m o v a l c a n be a c h i e v e d b y the a d d i t i o n o f a n anaerobic z o n e at the front o f a n activated sludge plant a n d r e t u r n i n g sludge w i t h o u t nitrate from the aerobic z o n e ( Y e o m a n et al,  1988). T h e r e is no reason this c o u l d not b e a p p l i e d to a M B R system  (Stephenson et al., 2 0 0 0 ) .  Microbial  activity in MBR  T h e fundamental b i o l o g y o f a n M B R i s not yet clear (Stephenson et al, 2 0 0 0 ) . O n l y a l i m i t e d amount o f i n f o r m a t i o n is a v a i l a b l e . T h e floe i n a n M B R has b e e n s h o w n to b e s m a l l a n d 21  active, w i t h a h i g h v o l a t i l e fraction i n the m i x e d l i q u o r and a great d i v e r s i t y o f species, e s p e c i a l l y i n terms o f f r e e - s w i m m i n g bacteria ( C i c e k et al., 1999).  Z h a n g et al. (1997) c o m p a r e d four M B R s w i t h four c o n v e n t i o n a l activated sludge processes. T h e s i z e distributions o f the floes w e r e s m a l l e r i n the M B R s at 7-40 (J.m c o m p a r e d w i t h 7 0 - 3 0 0 u m i n activated sludge. T h e s m a l l e r floe size encountered i n the M B R process accounted for the i m p r o v e d n i t r i f i c a t i o n rate. C i c e k et al. (1999) reported few filamentous o r g a n i s m s , nematodes and ciliates i n M B R s operated at a 30-day sludge age c o m p a r e d to an activated sludge system operated at 20-day sludge age. V a r i a t i o n s i n c o n d i t i o n s s u c h as shear stress, mass transfer, m i x i n g and the absence o f a clarifier were cited as reasons. In contrast, G h y o o t and Verstraete (1999) noted h i g h e r concentrations o f p r o t o z o a , p a r t i c u l a r l y flagellate and free ciliates, i n a submersed-membrane operated at the same sludge age.  M B R c o m p a r e d to an activated sludge system  E n z y m e a c t i v i t y w a s also seen to be h i g h e r i n the M B R and  this was attributed to washout i n the activated sludge system ( C i c e k et al., 1999; Stephenson et al, 2 0 0 0 ) .  2.3 Description of Activated Sludge Model No. 2  In this section, the b a s i c concepts and m o d e l presentation o f A S M 2 are described; m o d e l c o m p o n e n t s , processes and parameters as w e l l as wastewater characterization o f A S M 2 are also reviewed.  22  r  Basic concepts and model presentation The  Activated  Sludge Model  No.2  ( A S M 2 ) presents a b a s i c concept for d y n a m i c  s i m u l a t i o n o f a c o m b i n e d b i o l o g i c a l treatment process for carbon, nitrogen and p h o s p h o r u s r e m o v a l ( H e n z e et al,  2G00). F o r a realistic s i m u l a t i o n o f such a process, a large n u m b e r o f  reactions b e t w e e n a large n u m b e r o f components must be accounted for i n A S M 2 . T h e reactions must be representative  o f the most important fundamental processes  occurring within  the  system. F u r t h e r m o r e , the m o d e l s h o u l d quantify b o t h the k i n e t i c s and s t o i c h i o m e t r y o f each process. In order to trace a l l the interactions o f the system components w h i l e c o n v e y i n g the maximum  amount  o f i n f o r m a t i o n , m a t r i x notation  is used  to  present  the  kinetics  and  s t o i c h i o m e t r i c parameters o f A S M 2 . In this section, m a t r i x notation, v a r i o u s c o m p o n e n t s , the b i o l o g i c a l process as w e l l as k i n e t i c and s t o i c h i o m e t r i c parameters, c h e m i c a l p r e c i p i t a t i o n o f p h o s p h o r u s and wastewater characterization i n the A S M 2 m o d e l are r e v i e w e d b r i e f l y .  ASM2  u t i l i z e s m a t r i x notation for the presentation o f the b i o k i n e t i c m o d e l , because  m a t r i x notation is the o n l y p o s s i b l e m e t h o d to o v e r v i e w the c o m p l e x transformations a m o n g the components ( H e n z e et al, 2 0 0 0 ) . T h e m a t r i x is set u p i n t w o steps.  The  first step is to identify the components o f relevance i n the m o d e l . Particulate  constituents are g i v e n the s y m b o l X and the s o l u b l e components S. Subscripts are u s e d to specify i n d i v i d u a l components, w h i c h are denoted b y i n d e x i. T h e second step i n d e v e l o p i n g the m a t r i x is to identify the b i o l o g i c a l processes o c c u r r i n g i n the system. T h e transformation processes are characterized w i t h the i n d e x j respectively. Process rates are denoted b y py; s t o i c h i o m e t r i c coefficients are presented i n the f o r m o f a s t o i c h i o m e t r i c coefficient m a t r i x v,-,-, w h i c h sets out the mass relationships b e t w e e n the c o m p o n e n t s i n the i n d i v i d u a l processes. T h e  23  rate o f p r o d u c t i o n o f the c o m p o n e n t /, r „ i n a l l p a r a l l e l processes m a y be c o m p u t e d f r o m the sum: n = X vji • p) o v e r a l l processes j  (2.1)  Where Vji = s t o i c h i o m e t r i c coefficient for the c o m p o n e n t / i n process j [ M , M * " ] 1  C o n t i n u i t y equations are the m a t h e m a t i c a l equivalent o f the p r i n c i p l e that i n c h e m i c a l reactions, elements, electrons (or C O D ) and net e l e c t r i c a l charges m a y neither b e f o r m e d n o r destroyed. A c o n t i n u i t y equation, w h i c h is v a l i d for a l l processes j and a l l m a t e r i a l c subject to continuity, m a y be w r i t t e n as:  X Vp • id = 0 o v e r a l l components i  (2.2)  Where: id = c o n v e r s i o n factor to convert the units o f c o m p o n e n t i to the units o f the m a t e r i a l c, to w h i c h c o n t i n u i t y i s to be a p p l i e d [ M M , " ' ] C  Components  in the model  A S M 2 is m o r e c o m p l e x than A S M 1 and i n c l u d e s m o r e components to characterize the wastewater  as w e l l as the activated sludge. A total o f ten s o l u b l e c o m p o n e n t s ,  particulate components  characterize the wastewater  and  ten  and sludge ( T a b l e 2.2). S o m e o f the  components are defined b y their interactions w i t h the b i o m a s s and require bioassays for their analysis, since these c o m p o n e n t s m a y not be differentiated b y filtration t h r o u g h 0.45 (xm m e m b r a n e filters ( H e n z e et al., 2 0 0 0 ) . A l l c o m p o n e n t s are assumed to be h o m o g e n e o u s and distributed t h r o u g h the system o f interest.  24  T a b l e 2.2 S o l u b l e and particulate c o m p o n e n t s i n A S M 2 S o l u b l e components •  s  Particulate c o m p o n e n t s XAUT  A  X  SALK  H  SF  x,  SI  XivieOH  SN2  XMeP  SNH4  XpAO  SN03  XpHA  So2  Xpp  Sp04  X  Ss  s  XTSS  In A S M 2 , the fermentation products, S , are defined as the end products o f fermentation. A  It is assumed as acetate for a l l s t o i c h i o m e t r i c c a l c u l a t i o n s ; h o w e v e r , i n r e a l i t y a w h o l e range o f other fermentation products is p o s s i b l e . R e a d i l y b i o d e g r a d a b l e C O D is the fermentable, r e a d i l y b i o d e g r a d a b l e o r g a n i c substrate, S F . T h i s fraction o f the s o l u b l e C O D (Ss) is d i r e c t l y a v a i l a b l e for b i o d e g r a d a t i o n b y heterotrophic organisms. It is assumed that S F m a y serve as a substrate for fermentation;  therefore  it does not  i n c l u d e fermentation  products.  Readily  biodegradable  substrate was i n t r o d u c e d i n A S M 1 . In A S M 2 , it is replaced b y the s u m o f S F and S . Inert A  s o l u b l e o r g a n i c m a t e r i a l , S i , cannot be further degraded i n treatment plants, a l t h o u g h its concentration c a n be i n f l u e n c e d b y p h y s i c a l / c h e m i c a l p h e n o m e n a  s u c h as a d s o r p t i o n  and  v o l a t i l i z a t i o n . It i s assumed as part o f the influents and it is also a s s u m e d to be p r o d u c e d through h y d r o l y s i s o f particulate substrates X . T h e presence o f S i i n the m a t r i x is s i m p l y to s  r e m i n d us that wastewater contains non-biodegradable s o l u b l e C O D , w h i c h passes t h r o u g h the bioreactor unaffected b y b i o l o g i c a l a c t i v i t y ( G r a d y et al,  1999).  Inert particulate organic material, X i , undergoes no r e a c t i o n i n a b i o l o g i c a l reactor, but m a y be f l o c c u l a t e d onto the activated sludge. X i m a y be a fraction o f the influent or m a y be p r o d u c e d t h r o u g h b i o m a s s decay. It is an important class o f o r g a n i c substrate i n m a n y  25  wastewaters. T h e concentration o f X i i n the bioreactor depends o n the m a g n i t u d e o f the S R T relative to the H R T . X s is s l o w l y biodegradable substrates, w h i c h are h i g h m o l e c u l a r w e i g h t c o l l o i d a l and particulate o r g a n i c c o m p o u n d s that m u s t undergo h y d r o l y s i s external to the c e l l before they are a v a i l a b l e for degradation. It is assumed that the products o f h y d r o l y s i s ( S F ) m a y be fermented. Its concentration must be determined e x p e r i m e n t a l l y .  T h e nitrogen fractions s i m u l a t e d b y A S M 2 are total K j e l d a h l nitrogen ( T K N ) , a m m o n i a , nitrate and nitrite. N i t r a t e p l u s nitrite nitrogen, S N O 3 , is assumed to i n c l u d e nitrate as w e l l as nitrite nitrogen. It is f o r m e d b y aerobic g r o w t h o f autotrophic bacteria and is lost as it serves as the electron acceptor for a n o x i c g r o w t h o f heterotrophic bacteria. A m m o n i u m p l u s a m m o n i a nitrogen, S N H 4 , is assumed to be a l l N H / for the balance o f the electrical charge. A m m o n i a is the substrate for autotrophic n i t r i f y i n g bacteria, and it is the preferred f o r m o f nitrogen for b i o m a s s g r o w t h . A m m o n i a is f o r m e d b y a m m o n i f i c a t i o n o f s o l u b l e organic nitrogen, S N S , w h i c h is the last s o l u b l e nitrogen constituent. Inorganic s o l u b l e phosphorus, Spew, is p r i m a r i l y orthophosphates. F o r the b a l a n c e o f electrical charges, it is assumed that S PO4 consists o f 5 0 % H P 0 " , and 5 0 % H P 0 " , independent o f p H . 2  2  4  4  Biological  processes  ASM2  is an e x t e n s i o n  o f the Activated  Sludge Model  No.l  (ASM1).  Additional  b i o l o g i c a l processes are i n c l u d e d i n A S M 2 to deal w i t h b i o l o g i c a l phosphorus r e m o v a l . A total o f nineteen processes are used to describe the o v e r a l l treatment process.  T h e b i o l o g i c a l processes described i n A S M 2  are based o n the average b e h a v i o r o f  different m i c r o o r g a n i s m s , and are d e s c r i b e d as b a l a n c e d g r o w t h processes to reduce m o d e l c o m p l e x i t y . O n l y three groups o f m i c r o o r g a n i s m s are assumed to represent a vast v a r i e t y o f 26  unknown  species  to  avoid  describing unbalanced  growth o f cells;  the  three groups  of  m i c r o o r g a n i s m s are heterotrophic organisms, X H , p h o s p h o r u s - a c c u m u l a t i n g o r g a n i s m s ( P A O ) , X P A O , a n d n i t r i f y i n g o r g a n i s m s (autotrophic organisms), X U T - E a c h group is r e s p o n s i b l e for A  transformation  o f v a r i o u s substrates  i n the process. In a d d i t i o n , each b i o l o g i c a l  process  described i n A S M 2 represents a large n u m b e r o f processes that act u p o n a v a r i e t y o f substances, w h i c h i n the m o d e l are s u m m a r i z e d i n terms o f C O D . In order to s i m p l i f y A S M 2 , it is assumed that these substances c o n t a i n a constant fraction o f nitrogen and phosphorus. F o r e x a m p l e , the h y d r o l y s i s o f particulate, b i o d e g r a d a b l e organic n i t r o g e n is i n c l u d e d as a separate process i n A S M 1 but not i n A S M 2 . It is assumed that X s contains a constant fraction o f n i t r o g e n /  N X s  , and  p h o s p h o r u s Z'PX - W i t h o u t this s i m p l i f y i n g a s s u m p t i o n , s i x m o r e h y d r o l y s i s processes and t w o s  m o r e particulate c o m p o n e n t s w o u l d be r e q u i r e d ( H e n z e et al., 2 0 0 0 ) .  H y d r o l y s i s processes a n d processes o f facultative heterotrophic o r g a n i s m s The  heterotrophic  organisms  X H are  responsible  for  the  hydrolysis o f  slowly  b i o d e g r a d a b l e substrate X , the aerobic degradation o f fermentable o r g a n i c substrates S F , a n d o f s  fermentation products S , the a n o x i c o x i d a t i o n o f S F and S A  A  and the r e d u c t i o n o f nitrate SNO3  (denitrification), and the anaerobic fermentation o f S F to S . In a d d i t i o n , these o r g a n i s m s are A  subject to decay a n d l y s i s . T h e s e processes are s u m m a r i z e d here.  a) H y d r o l y s i s processes M a n y h i g h m o l e c u l a r w e i g h t , c o l l o i d a l or particulate o r g a n i c substrates  cannot  be  u t i l i z e d d i r e c t l y b y m i c r o o r g a n i s m s . T h e s e substrates must be m a d e a v a i l a b l e b y c e l l external e n z y m a t i c reactions, w h i c h are c a l l e d h y d r o l y s i s processes ( H e n z e et al., 2 0 0 0 ) . It has b e e n r e c o g n i z e d that h y d r o l y s i s reactions p l a y t w o important roles i n b i o c h e m i c a l reactors  for  wastewater treatment. First, they are responsible for the s o l u b i l i z a t i o n o f c e l l u l a r c o m p o n e n t s 27  released as a result o f c e l l l y s i s , p r e v e n t i n g their b u i l d u p i n the system. S e c o n d l y , m a n y b i o c h e m i c a l operations receive particulate o r g a n i c m a t e r i a l , i n w h i c h case h y d r o l y s i s is essential to b r i n g about the desired biodegradation. H y d r o l y s i s has important i m p a c t s o n the o u t c o m e o f b i o l o g i c a l operations; h o w e v e r , r e l a t i v e l y few studies have sought to understand the k i n e t i c s a n d mechanisms  o f h y d r o l y s i s ( G r a d y et al.,  1999). B a s e d o n e x p e r i m e n t a l e v i d e n c e , three  h y d r o l y s i s processes are d i s t i n g u i s h e d i n A S M 2 , d e p e n d i n g o n the a v a i l a b l e electron acceptors. T h e s e processes are listed as f o l l o w i n g . 1.  A e r o b i c h y d r o l y s i s o f s l o w l y biodegradable substrate.  2.  A n o x i c h y d r o l y s i s o f s l o w l y b i o d e g r a d a b l e substrate.  3.  A n a e r o b i c h y d r o l y s i s o f s l o w l y b i o d e g r a d a b l e substrate.  It is p r o p o s e d that o n l y heterotrophic o r g a n i s m s m a y catalyze h y d r o l y s i s . T y p i c a l l y h y d r o l y s i s is s l o w e r under a n o x i c (denitrifying) o r anaerobic (fermentation) c o n d i t i o n s than under aerobic c o n d i t i o n s . It is assumed that s l o w l y biodegradable substrate, X s , is degraded to r e a d i l y degradable substrate, S F , w h i l e a s m a l l fractionTsi o f inert o r g a n i c m a t e r i a l S i is released d u r i n g h y d r o l y s i s . In order to s i m p l i f y A S M 2 , it is assumed that s l o w l y b i o d e g r a d a b l e substrate X  s  and the fermentable substrates, S F , c o n t a i n constant fractions o f n i t r o g e n a n d p h o s p h o r u s . A s  m e n t i o n e d i n A S M 2 , it is a difficult task to estimate h y d r o l y s i s rate constants under different electron acceptor c o n d i t i o n s because some o f the processes are not w e l l characterized, and the rates r e m a i n to be studied.  b) Processes o f facultative heterotrophic o r g a n i s m s i n c l u d e the f o l l o w i n g . 4.  A e r o b i c g r o w t h o f heterotrophic o r g a n i s m s o n fermentation substrates S F -  5.  A e r o b i c g r o w t h o f heterotrophic o r g a n i s m s o n fermentation products S A -  6.  A n o x i c g r o w t h o f heterotrophic o r g a n i s m s o n fermentation substrates S F 28  7.  A n o x i c g r o w t h o f heterotrophic organisms o n fermentation products S A (denitrification).  8.  F e r m e n t a t i o n . U n d e r anaerobic  conditions, readily biodegradable  substrates S F are  transformed into fermentation products S A 9.  L y s i s o f heterotrophic o r g a n i s m s . T h i s process represents the s u m o f a l l d e c a y processes o f the heterotrophic organisms.  Process o f p h o s p h o r u s - a c c u m u l a t i n g organisms P h o s p h o r u s - a c c u m u l a t i n g o r g a n i s m s , X P A O , have the potential to a c c u m u l a t e p h o s p h o r u s i n the f o r m o f poly-phosphate X  p p  . It is assumed that P A O cannot denitrify and that they c a n  o n l y g r o w o n c e l l u l a r internal stored o r g a n i c materials, X  P H  A - B o t h these assumptions are v e r y  severe restrictions o f A S M 2 and m a y lead to further extensions ( H e n z e , et al., 2 0 0 0 ) . 10. Storage o f X energy o f X  P H  p p  A - P A O release phosphate, Spo4, f r o m poly-phosphate, X , w h i c h b e c o m e s a v a i l a b l e f r o m the h y d r o l y s i s o f X  p p  p p  , and u t i l i z e the  , i n order to store c e l l  external fermentation products, S , i n the f o r m o f c e l l internal o r g a n i c storage m a t e r i a l A  XpHA11. Storage o f poly-phosphate. Storage o f ortho-phosphates, X  p p  , requires the P A O to o b t a i n  energy, w h i c h m a y be gained f r o m the respiration o f X H A P  12. G r o w t h o f p h o s p h o r u s - a c c u m u l a t i n g o r g a n i s m s . These o r g a n i s m s are assumed to g r o w o n l y at the expense o f c e l l internal o r g a n i c storage products X P H A 13. 14. and 15. L y s i s o f p h o s p h o r u s - a c c u m u l a t i n g o r g a n i s m s and their storage products. D e a t h , endogenous respiration and maintenance a l l results i n a loss or d e c a y o f a l l fractions o f P A O .  29  N i t r i f i c a t i o n processes N i t r i f i c a t i o n is assumed to b e a one-step process, f r o m a m m o n i u m , S N H 4 , d i r e c t l y to nitrate, SNO3- T h e intermediate c o m p o n e n t , nitrite, is not i n c l u d e d as a m o d e l c o m p o n e n t . N i t r i f i c a t i o n reduces a l k a l i n i t y . A l k a l i n i t y i s used to a p p r o x i m a t e the c o n t i n u i t y o f e l e c t r i c a l charge i n a b i o l o g i c a l reaction. It is i n t r o d u c e d i n order to o b t a i n an e a r l y i n d i c a t i o n o f p o s s i b l e l o w p H c o n d i t i o n s , w h i c h m i g h t i n h i b i t s o m e b i o l o g i c a l process. S i k i s a s s u m e d to b e bicarbonate, A  H C 0 " , only. 3  16. G r o w t h o f n i t r i f y i n g o r g a n i s m s . N i t r i f y i n g o r g a n i s m s c o n s u m e a m m o n i u m as a substrate and a nutrient, a n d p r o d u c e nitrate under a e r o b i c c o n d i t i o n s .  17. L y s i s o f n i t r i f y i n g o r g a n i s m s . T h e d e c a y p r o d u c t s o f l y s i s ( X s a n d u l t i m a t e l y , S F ) contribute to the increased g r o w t h a n d o x y g e n c o n s u m p t i o n o f heterotrophs  during  endogenous r e s p i r a t i o n o f nitrifiers.  Chemical precipitation  ofphosphates  In a d d i t i o n to the b i o l o g i c a l p h o s p h o r u s r e m o v a l process, A S M 2 i n c l u d e s t w o c h e m i c a l processes,  which  m a y be used  to m o d e l c h e m i c a l p r e c i p i t a t i o n o f p h o s p h o r u s .  A  high  concentration o f released ortho-phosphate from a b i o l o g i c a l nutrient r e m o v a l s y s t e m a n d metals present i n the wastewater m a y result i n c h e m i c a l p r e c i p i t a t i o n o f p h o s p h o r u s . T h i s r e a c t i o n m a y contribute to a l o w effluent c o n c e n t r a t i o n o f ortho-phosphate; therefore, A S M 2 suggests a v e r y s i m p l e p r e c i p i t a t i o n m o d e l , w h i c h m a y b e calibrated for a v a r i e t y o f situations. F o r this purpose, two  processes are i n c l u d e d i n A S M 2 . H o w e v e r , these processes c a n b e deleted, i f c h e m i c a l  p r e c i p i t a t i o n i s not o f any interest.  30  18. and 19. P r e c i p i t a t i o n and r e d i s s o l u t i o n o f phosphate Spo4- It is assumed that they are r e v e r s i b l e processes, w h i c h at steady state w o u l d be i n e q u i l i b r i u m a c c o r d i n g to: XivieOH + Spo4 <=> XjvieP  (2.3)  W h e r e : XivieOH is c o m p o s e d o f ferric h y d r o x i d e , F e ( O H ) 3 XMeP i s c o m p o s e d o f ferric phosphate, FePC>4  T h e s t o i c h i o m e t r i c s o f the processes i n t r o d u c e d i n A S M 2 are r e v i e w e d i n T a b l e 2.3 and T a b l e 2.4 for the p u r p o s e o f presenting a clear picture o f A S M 2 m o d e .  31  on on on on on on h- H — f  oo oo  > > >  < <  <  <  lew  > >  > >  00  < o <D  -t-»  id  00  o 00  <2 o  o  o  o  2  o CL,  > > >  OO  <  00  o  oo  z  00 (D  o o  I  ao  o -a <u J> z  *o 00 on t-i  o  •*  •*  -»  z z z > > >  z ^  < 00  I  OO  S S I  •a  X  I  T-  I  S O  X  < X  o  •s 00  X CL,  o  o  §  CO  u. u_  on g on on 'on .52 S  o  2 OS  P  1& 3  PH  . a n oo .2 .2  O  x .2 -S o o„ o B o c3 B  ,b ^  C  •5 -a -c >  (N  m  Tf  X  X  X o  tn §  o <  o  s  §•2  on S O ."X  aj  § O O 2O _fl « «  3 to O  i—i  <  $ %  O  H  s  s  00 00  on  +->  -L->  O P  in vo  s  o t-i  o  cd  »-i  o  ' 00 00  f-i  g B  o on -~  < HJ h-l h-t  O  =0  on  <3> 05 —' —'  r-' -S oo -H  o  S  Model parameters K i n e t i c s a n d s t o i c h i o m e t r i c parameters u s e d to describe the b i o l o g i c a l nutrient r e m o v a l process are m a i n l y b a s e d o n M o n o d k i n e t i c s for a l l c o m p o n e n t s that c a n i n f l u e n c e the r e a c t i o n rate. T a b l e s 2.5 a n d 2.6 present s u m m a r i e s o f t y p i c a l s t o i c h i o m e t r i c coefficients i n A S M 2 a n d the c o n v e r s i o n factors r e q u i r e d for use w i t h the c o n t i n u i t y equations. T a b l e 2.7 is a list o f the d e f i n i t i o n s and t y p i c a l v a l u e s o f the k i n e t i c parameters i n the A S M 2 m o d e l .  Table 2.5 T y p i c a l s t o i c h i o m e t r i c constants i n A S M 2 (adapted f r o m A S M 2 ) Typical  Definition  Constants  Units  values /si  F r a c t i o n o f inert C O D i n particulate substrate  0.00  g C O D (gCODT  1  YH  Y i e l d coefficient  0.63  g C O D (g C O D ) "  1  /XI  F r a c t i o n o f inert C O D generated i n b i o m a s s decay  0.10  g C O D (g C O D ) "  1  0.63  g C O D (g C O D ) "  1  Y i e l d coefficient ( b i o m a s s /  TPAO Tp04  PHA)  P P requirement (S o4 release) for P H A storage P  PHA  TpHA  0.20  requirement for P P storage  Y i e l d coefficient (biomass/ nitrate)  TAUT  0.40 0.24  gP(g  COD)'  g C O D (g  1  COD)  gCOD (gNV  1  1  Table 2.6 T y p i c a l c o n v e r s i o n factors i n A S M 2 (adapted f r o m A S M 2 ) Definition  Conversion  Units  Typical values  factors *NSI  N i t r o g e n ( N ) content o f inert s o l u b l e C O D S i  0.01  gN(gCOD)-  1  Z'NSF  N content o f s o l u b l e substrate Sp  0.03  gN(gCOD)"  1  0.03  gN(gCOD)  1  N content o f inert particulate C O D  J'NXI  X\  Z'NXS  N content o f particulate substrate X s  0.04  gN(g  *NBM  N content o f b i o m a s s XH, X P A O , and X A U T  0.07  gN(gCOD)-  1  ips\  P h o s p h o r u s (P) content o f inert s o l u b l e C O D Si  0.00  gP(gCOD)-  1  IPSP  P content o f s o l u b l e substrate S  0.01  gP(gCOD)-  1  0.01  gP(gCOD)-  1  1  F  P content o f inert particulate C O D  X\  COD)"  ipxs  P content o f particulate substrate Xs  0.01  gP(gCOD)  ZPBM  P content o f b i o m a s s XH, XPAO,  0.02  gP(g  XAUT  COD)"  1  1  JTSSXI  TSS  to X I ratio  0.75  g T S S ( g COD)"  ZTSSXS  TSS  to X  0.75  g T S S (g C O D ) "  1  0.90  gTSS (gCOD)"  1  ZTSSBM  TSS  s  ratio  to b i o m a s s ratio f o r X n , X P A O , a n d X A U T  34  1  T a b l e 2.7 T y p i c a l values for the s t o i c h i o m e t r i c coefficient o f A S M 2 ( H e n z e et al, 1995) 20 C  Temperature Hydrolysis:  Units  U  3.00 0.60 0.10 0.20 0.50 0.10  d"  Heterotrophic organisms: M a x i m u m growth rate on substrate M a x i m u m rate for fermentation <7fe Reduction factor for denitrification £N03 Rate constant for lysis b Saturation/inhibition coefficient for oxygen K02 Saturation coefficient for growth on S K Saturation coefficient for fermentation o f S Saturation coefficient for S (acetate) K Saturation/inhibition coefficient for nitrate ^N03 Saturation coefficient for ammonia (nutrient) •^NH4 Saturation coefficient for phosphorus (nutrient) Saturation coefficient for alkalinity KALK  6.0 3.0 0.80 0.40 0.20 4.00 20.00 4.00 0.50 0.05 0.01 0.10  d" g C O D (g C O D ) - d"  Phosphorus -accumulating organisms: Rate constant for storage o f P H A (base: X ) <?PH Rate constant for storage o f P P qpp M a x i m u m growth rate f^p AO Rate constant for lysis o f X o b?AO Rate constant for lysis o f X b Rate constant for lysis o f X bpHA Saturation coefficient o f S 2 K02 Saturation coefficient for S (acetate) K Saturation coefficient for ammonia Knm Saturation coefficient for phosphorus i n P P storage KPS Saturation coefficient for phosphorus i n growth K Saturation coefficient for alkalinity KALK Saturation coefficient for poly-phosphate KPP M a x i m u m ratio o f X p / X p KM AX Inhibition coefficient for P H A K\PP Saturation coefficient for P H A KpftA  3.00 1.50 1.00 0.20 0.20 0.20 0.20 4.00 0.05 0.20 0.01 0.10 0.01 0.34 0.02 0.01  g C O D ( g P A O ) " d" g P P (g P A O ) " d 1 d" d" d' d" g 0 nf g COD rn gNm" gPrn" gPni mole H C 0 n f gPP(gPAO)g P P (gPAO)" gPP (gPAO) g P H A (g P A O ) "  M a x i m u m growth rate Decay rate Saturation coefficient for oxygen Saturation coefficient for ammonia Saturation coefficient for alkalinity Saturation coefficient for phosphorus  1.00 0.15 0.50 1.00 0.50 0.01  d" d g 0 m" gNm" mole HCO3" m" gPm"  Rate constant for P precipitation Rate constant for redissolution Saturation coefficient for alkalinity  1.0 0.6 0.50  m ( g F e ( O H ) ) " d" d mole H C 0 " m"  fN03  K02 K  x  Hydrolysis rate constant A n o x i c hydrolysis reduction factor Anaerobic hydrolysis reduction factor Saturation/inhibition coefficient for oxygen Saturation/inhibition coefficient for nitrate Saturation coefficient for particulate C O D  H  F  f  F  A  A  P P  A  P A  P P  P P  P H A  0  A  K  P  P  AO  1  g 0 m" gNm' gCOD(gCOD)3  2  3  1  d g 0 rn g C O D m' g COD rn g C O D m" gNm" gNm" gPrn mole H C 0 - m" 1  3  2  3  3  3  3  3  3  3  3  1  1  1  1  1  3  2  3  3  3  3  _  3  3  1  1  1  1  Nitrifiers: MAUT &AUT  K02 -^NH4 -^ALK ^P  1  1  3  2  3  3  3  Precipitation: ^PRE KRED ^ALK  35  1  3  1  3  1  3  3  1  1  Wastewater  characterization  A s m e n t i o n e d i n the p r e v i o u s section, i n A S M N o . 2 , characterization i s p r o p o s e d i n terms o f o r g a n i c matter, n i t r o g e n a n d p h o s p h o r u s fractions i n m u n i c i p a l wastewater as w e l l as a l k a l i n i t y a n d d i s s o l v e d o x y g e n , a n d those fractions are d i v i d e d into v a r i o u s sub-fractions.  O r g a n i c fractions ( C O D ) The  >  total o r g a n i c matter content  i n wastewater  can be measured  as C O D , CTCOD-  K n o w l e d g e o f the influent C O D fractions i s o f p r i m a r y i m p o r t a n c e i n d e t e r m i n i n g the o x y g e n d e m a n d , sludge wastage, d e n i t r i f i c a t i o n c a p a c i t y o f excess b i o l o g i c a l P r e m o v a l , a n d the related magnitudes o f the fractions c a n differ greatly b e t w e e n wastewaters. T h e total C O D i n the A S M 2 is s u b d i v i d e d into the f o l l o w i n g c o m p o n e n t s ( F i g u r e 3.1) (2.4)  CTCOD - S A + S F + SI + X I + X s + X H + X P A O + X H A + X A U T P  F i g u r e 2.4 s h o w s a t y p i c a l d i s t r i b u t i o n o f C O D i n p r i m a r y effluent from m u n i c i p a l wastewater treatment. It also s h o w s v a r i o u s a n a l y t i c a l techniques r e c o m m e n d e d b y A S M 2 f o r m e a s u r i n g parts o f the C O D . N o t a l l the c o m p o n e n t s  s h o w n i n F i g u r e 2.4 are o f equal  i m p o r t a n c e . T h e concentration o f autotrophy i n the influent i s v e r y s m a l l i n m o s t cases, a n d this is also b e l i e v e d to b e the case for the p h o s p h a t e - a c c u m u l a t i n g b i o m a s s , X  P A  o - Stored poly-  h y d r o x y a l k a n o a t e , X P H A , i s c l o s e to zero i n r a w wastewater. T h i s m e a n s that the total C O D fractionation  i n m a n y cases c a n b e s i m p l i f i e d to  CTCOD - S  In  A  (2.5)  + Sp + S I + X I + X s + X H  cases w h e r e the heterotrophic  biomass  i s n e g l i g i b l e or i n c l u d e d i n the s l o w l y  degradable suspended organics, X s , E q u a t i o n 2.5 c a n b e reduced to (2.6)  CTCOD — S A + SF + SI + X I + X S  36  T h e i n c l u s i o n o f X H i n X s does not affect the m o d e l i n g s i g n i f i c a n t l y , but it affects value o f the y i e l d coefficient Y  H  (a s m a l l y i e l d coefficient m u s t be chosen).  Effluent analysis  VFA  Model  Analytical  soluble  soluble  COD  COD  Respiration test  Total COD X  Model s  calibration  XAUT ~XPHA ^PAO  X,  Respiration test Model calibration  X,  F i g u r e 2.4 C O D fractionation i n A S M 2 ( H e n z e et al,  37  1995)  N i t r o g e n fractions A s s h o w n i n F i g u r e 2.5, the total n i t r o g e n concentration i n m u n i c i p a l wastewater, C T N , c a n be characterized as CTN  =  C T K N + >SNO3 = XJKN + STKN +>SNO3  (2-7)  Where: CTKLN is total K j e l d a h l nitrogen, ^ T K N is particulate K j e l d a h l nitrogen, and it is the s u m o f nitrogen b o u n d to a l l the other o r g a n i c particulate fractions X  T  K  N  = {X * {  /NXI) + ( X * INXS) + ( * H + X S  P A O  +X ) AVT  /NBM  (2.8)  SJKN is s o l u b l e K j e l d a h l nitrogen, and it is d o m i n a t e d b y a m m o n i a - n i t r o g e n , 5NH4 STKN  =S  N H  4 + ( S * *'NSF) + F  (5, * i sO N  (2-9)  C h a r a c t e r i z a t i o n o f the n i t r o g e n fractions is not as detailed as for o r g a n i c matter. O n e o f the reasons is that the m a j o r part o f the n i t r o g e n i n wastewater is present as a m m o n i a , w h i c h has n o c o u p l i n g to the o r g a n i c c o m p o n e n t s . F o r the r e m a i n i n g nitrogen, m o s t o f w h i c h is c o u p l e d to the o r g a n i c components, it is sufficient to use f i x e d nitrogen fractions for the v a r i o u s C O D c o m p o n e n t s as s h o w n i n A S M 2 ( H e n z e et al., 2 0 0 0 ) .  38  -3  Nitrite + Nitrate  *SN03  Analytical  SNH4  Total  soluble  Ammonia  nitrogen  Kjeldahl  CTN  nitrogen  Model soluble Kjeldahl nitrogen  STKN  Total Kjeldahl nitrogen CTKN  S F * *NSF  >I *  *NBS  Analytical particulate Kjeldahl nitrogen  X s * Z'NXS X\ * Z'NXI XH  *  iNBM  ^TKN  G a s analysis  15  F i g u r e 2.5 N i t r o g e n fractionation i n A S M 2 ( H e n z e et al,  1995)  P h o s p h o r u s fractions A s s h o w n i n F i g u r e 2.6, the total phosphorus concentration i n r a w m u n i c i p a l wastewater c a n be d i v i d e d into these fractions: CTP  =  X r p + Sjp  (2.10)  Xpp is particulate phosphorus; it i n c l u d e s i n o r g a n i c and organic phosphorus. X  T P  = (0.205* X  M e  p ) + X p + ( X * /PXS) + ( * i * z i ) + ( X + X P  s  PX  SJP is s o l u b l e phosphorus, w h i c h i n c l u d e s 39  H  P  A  O  +X  A U T  ) * IBPM  (2.11)  S  TP  (2.12)  = S 4 + ( S F * Z'PSF) + ( S i * Z'PSI) ?0  F o r m u n i c i p a l wastewater, E q u a t i o n s 2.11 a n d 2.12 can be a p p r o x i m a t e d b y Xjp = ( X s * z'pxs) + ( X i * /pxi)  (2.13)  Sjp = SpQ4  (2.14)  gm  gm"  3  >P04  3.6  Ortho-  Model  Total  phosphate  soluble  phosphorus  phosphorus Analytically soluble  ~f) 0.3  1.25  S F * /PSF  X s * ipxs  >i *  X A U T * i PBM  0.25 ~0  Organic phosphorus  ~0 0.6  phosphorus  hs\  X H * 2pBM  q  'PXI  ~XpAO * ' P B M  Suspended phosphorus  X p * 0.205 F e  Figure 2.6 P h o s p h o r u s fractionation i n A S M 2 ( H e n z e et al., 1995)  2.4 Wastewater Treatment Processes in U B C Pilot Plant  T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a ( U B C ) p i l o t plant is a research f a c i l i t y that has b e e n used for U B C student research projects since the 1980s. It p r o v i d e s an o p p o r t u n i t y to d e v e l o p new  theories and processes, and to o p t i m i z e process designs and system operations. It is a  m o d u l a r system i n w h i c h reactor zones a n d r e c y c l e rates c a n be adjusted to p r o v i d e a v a r i e t y o f d e s i r e d c o n f i g u r a t i o n s and operating c o n d i t i o n s . In recent years, it has b e e n 40  focused  on  b i o l o g i c a l nutrient r e m o v a l ; m o s t recently u s i n g a m e m b r a n e enhanced b i o l o g i c a l p h o s p h o r u s r e m o v a l process.  Sources of wastewater U B C p i l o t plant receives d o m e s t i c wastewater f r o m residences o n the southeastern part o f the U B C campus and a part o f the wastewater f r o m office b u i l d i n g s o f U B C . R a w wastewater is c o l l e c t e d a n d transported to the p i l o t plant b y p u m p i n g into t w o storage tanks t w i c e a day, a n d the p r i m a r y effluent p r o d u c e d there i s p u m p e d into each train (train A a n d B ) at a constant f l o w rate o f 2 L m h f . 1  Process  configurations T w o systems were operated i n p a r a l l e l for c o m p a r i s o n o f different process  designs  ( F i g u r e 2.7). S i d e A o f the plant w a s the M E B P R process. It consisted o f three i n - l i n e a n d c o m p l e t e l y m i x e d bioreactors w i t h m o v e a b l e baffles. A total o f s i x Z e e W e e d m e m b r a n e s w e r e installed i n the aerobic z o n e to replace the secondary clarifier for suspended s o l i d s r e m o v a l f r o m the final effluent. Z e n o n E n v i r o n m e n t a l Inc. manufactured the m e m b r a n e s ; the m a t e r i a l o f the m e m b r a n e s  w a s a h o l l o w - f i b e r , c h l o r i n e tolerant a n d h y d r o p h i l i c p r o p r i e t a r y p o l y m e r  ( Z e n o n ) . T h e return sludge w a s p u m p e d f r o m the aerobic z o n e to the a n o x i c z o n e w i t h r e c y c l e ratio  1:1 (return activated sludge f l o w rate i s 1.0 times the average influent f l o w  rate).  A n a e r o b i c r e c y c l e w a s also h e l d constant at a p p r o x i m a t e l y 1:1 ( F i g u r e 2.8). T h e c o n f i g u r a t i o n o f B - s i d e w a s s i m i l a r to the A - s i d e , i n that anaerobic, a n o x i c , a n d aerobic zones w e r e separated.  S i d e B w a s a s i m p l i f i e d c o n f i g u r a t i o n o f the U n i v e r s i t y o f C a p e T o w n ( U C T ) process w i t h a traditional secondary clarifier, w h e r e the returned activated sludge ( R A S ) w a s r e c y c l e d b a c k to the a n o x i c z o n e ( F i g u r e 2.9). Influent entered the anaerobic z o n e f r o m the p r i m a r y 41  clarifier, and f r o m the anaerobic z o n e into the a n o x i c zone, then to the aerobic z o n e . R e t u r n sludge was p u m p e d f r o m the u n d e r f l o w o f a secondary clarifier to the a n o x i c z o n e to p r o v i d e nitrate and nitrite for d e n i t r i f i c a t i o n , and then b y the anaerobic r e c y c l e to contact influent i n the anaerobic zone.  Anaerobic recycle 1:1  Membrane  r Anaero bic  Anoxic  zone  zone  o  o  A e r o b i c zone O O  Effluent  i A-side  R e c y c l e 1:1 (based o n average influent f l o w rate)  B-side Anaerobic recvcle 1:1 S e c o n d a r y clarifier r Anaero bic  Anoxic  zone  zone  A e r o b i c zone  /  \  Effluent R e c y c l e 1:1  Influent  F i g u r e 2.7 S c h e m a t i c layout o f U B C p i l o t plant  42  2.5 Parameter Estimation and Wastewater Characterization  M a n y approaches have been d e v e l o p e d to determine the g r o w t h y i e l d , d e c a y rate a n d maximum  specific g r o w t h rate o f heterotrophic b i o m a s s as w e l l as s o m e o f the influent  wastewater components. A n u m b e r o f those methods w e r e selected for the use w i t h the m o d e l A S M N o . 2 and are r e v i e w e d i n the sub-sections.  D e t e r m i n a t i o n o f heterotrophic g r o w t h y i e l d H e t e r o t r o p h i c g r o w t h y i e l d is an important s t i o c h i o m e t r i c parameter to p r e d i c t sludge p r o d u c t i o n and o x y g e n d e m a n d i n a wastewater treatment process. H e t e r o t r o p h i c g r o w t h y i e l d must be k n o w n before characterization c a n be done. A n y errors i n this estimate w i l l  be  compensated for i n the determination o f other parameters or influent concentrations, s u c h as r e a d i l y b i o d e g r a d a b l e substrate and decay coefficient o f heterotrophic b i o m a s s . T h e true g r o w t h y i e l d ( Y ) is defined as the amount o f b i o m a s s f o r m e d per unit o f substrate r e m o v e d w h e n a l l energy expenditure is for synthesis. ( G r a d y et al,  1999). It is c o m m o n i n e n v i r o n m e n t a l  engineering practice to express Y i n terms o f the amount o f s o l u b l e C O D r e m o v e d f r o m the wastewater i f the electron d o n o r is an o r g a n i c c o m p o u n d . T h u s , y i e l d s are s o m e t i m e s expressed as the amount o f b i o m a s s C O D f o r m e d per u n i t mass o f substrate C O D r e m o v e d f r o m  the  wastewater.  T h e e n g i n e e r i n g practice o f m e a s u r i n g bacterial g r o w t h relies o n e s t i m a t i n g changes i n bacterial b i o m a s s ( i n terms o f m g C O D o r m g V S S ) as a function o f t i m e ( E k a m a et al, H e n z e et al,  1986;  1987). T h i s a l l o w s o b s e r v a t i o n o f YH directly, as b i o m a s s is g r o w n o n o n l y the  45  s o l u b l e components o f the wastewater. T h e approach for the determination o f heterotrophic g r o w t h y i e l d has been i m p r o v e d b y a n u m b e r o f researchers ( H e n z e et al., 1987; S l a d e et 1991; G r a d y et al,  al.,  1999), and the m e t h o d described above also w a s r e c o m m e n d e d b y the  I A W P R C T a s k G r o u p for the use i n the A S M m o d e l s . T h i s m e t h o d was u s e d i n the present study and is described b e l o w .  T h e k e y to d e t e r m i n i n g Yw d u r i n g a batch test i s to p r o v i d e sufficient substrate to a l l o w the bacteria p e r f o r m i n g the b i o d e g r a d a t i o n to f u l l y d e v e l o p their p r o t e i n s y n t h e s i z i n g and e n z y m e system. G r a d y et al. (1999) suggested that this c o u l d be a c c o m p l i s h e d w h e n the i n i t i a l substrate to b i o m a s s concentration is at least 2 0 w h e n b o t h concentrations are expressed as C O D . S i n c e the K s values for i n d i v i d u a l substrates tend to be less than 10 m g L " as C O D 1  ( G r a d y et al,  1999), a s o l u b l e substrate concentration (S o) o f 2 0 m g L " as C O D has b e e n 1  S  p r o v e n to be successful b y experiments ( B r o w n et al,  1990). C o n s e q u e n t l y , the i n i t i a l b i o m a s s  concentration s h o u l d be o n the order o f 1 m g L " as C O D . In this case, the i n i t i a l b i o m a s s 1  concentration applies o n l y to b i o m a s s that is active i n b i o d e g r a d a t i o n o f the test c o m p o u n d . T h o s e suggestions have been considered i n the Y H test procedures i n the present study.  H o w e v e r , these estimates depend o n detecting changes i n the b i o m a s s c o n c e n t r a t i o n w i t h methods that are inaccurate and insensitive. P o l l a r d et al. (1998) estimated Y  H  using a  t h y m i d i n e assay. T h e p r i n c i p a l o f the t h y m i d i n e assay relies o n the fact that w h e n bacteria d e c o m p o s e o r g a n i c matter they p r o d u c e n e w b i o m a s s . T h e in situ rate o f synthesis o f this n e w b i o m a s s is m a r k e d w i t h r a d i o a c t i v e l y l a b e l e d t h y m i d i n e . T h e advantage o f u s i n g t h y m i d i n e to track n e w c e l l f o r m a t i o n is that it i s o n l y used b y bacteria for D N A synthesis; n o n - g r o w i n g  46  cells do not synthesize D N A . A l s o , t h y m i d i n e is not i n v o l v e d i n other m e t a b o l i c pathways. S o it represents a direct measurement o f g r o w t h that is independent o f c e l l death, d i l u t i o n and g r a z i n g b y p r o t o z o a . H o w e v e r , due to the l i m i t a t i o n o f a v a i l a b l e equipment, this m e t h o d c o u l d not be used i n this research.  D e c a y o f heterotrophic m i c r o o r g a n i s m s T h e heterotrophic decay rate (b) is v e r y important for p r e d i c t i o n s o f sludge p r o d u c t i o n and o x y g e n demands  i n a b i o l o g i c a l treatment system. It s h o u l d be d e t e r m i n e d before  estimation o f m a x i m u m s p e c i f i c g r o w t h rate o f heterotrophic b i o m a s s . T w o approaches  the have  been i n t r o d u c e d to describe this coefficient. T h e traditional approach that d e s c r i b e d the b i o m a s s decay has b e e n u s e d for m a n y years and has f o u n d m a n y a p p l i c a t i o n s . Its m a i n attributes are its s i m p l i c i t y and f a m i l i a r i t y . Its m a i n weakness is its i n a b i l i t y to easily h a n d l e the situation i n w h i c h the nature o f the t e r m i n a l electron acceptor is c h a n g i n g ( G r a d y et al., 1999). T h e s e c o n d m o d e l addresses that situation, w h i c h is the l y s i s : r e g r o w t h approach.  T h e important concepts i n c o r p o r a t e d i n the traditional approach are that the a c t i v e b i o m a s s i s destroyed as a result o f " d e c a y " and the electrons r e m o v e d as a result o f the o x i d a t i o n o f the c a r b o n to c a r b o n d i o x i d e pass to the electron acceptor. Furthermore, not a l l o f the b i o m a s s is totally o x i d i z e d and a p o r t i o n is left as b i o m a s s debris ( J e w e l l and M c C a r t y , 1 9 7 1 ; M c C a r t y and B r o d e r s e n , 1962; M c K i n n e y ,  1962). F i g u r e 2.10 illustrates the traditional a p p r o a c h for  m o d e l i n g b i o m a s s d e c a y and loss o f v i a b i l i t y .  47  Growth Loss o f C O D Soluble  Biomass  substrate Ss  X  B  0 0  2  + NH  C0  3  2  2  Decay  + H 0 2  Loss o f C O D C0  2  +H 0 + NH 2  3  F i g u r e 2.10 S c h e m a t i c representation o f the traditional approach to m o d e l i n g b i o m a s s d e c a y and loss o f v i a b i l i t y ( G r a d y et al, 1999)  The  events  involved  i n the traditional approach  are expressed  b y the f o l l o w i n g  s t o i c h i o m e t r y based o n a C O D balance: B i o m a s s C O D + [-(1-7D)] 0  2  equivalents electron acceptor  fo b i o m a s s debris C O D (2.15)  W h e r e fo i s the fraction o f active b i o m a s s c o n t r i b u t i n g to the b i o m a s s debris, X . D  T h e rate e x p r e s s i o n o f decay o f b i o m a s s is first order w i t h respect to the b i o m a s s concentration,  X: B  r  XB  = -b'*X  (2.16)  B  W h e r e b ' i s the traditional decay coefficient, w i t h units o f hr" , a n d the rate o f p r o d u c t i o n o f 1  b i o m a s s debris, Xu, i s : rxo = b*f X D  (2.17)  B  C o n s i d e r i n g the rate o f p r o d u c t i o n o f b i o m a s s debris, the rate o f o x y g e n (electron acceptor) u t i l i z a t i o n associated w i t h b i o m a s s decay i s : rso = (1 - / D ) b' * X  B  ( C O D units) = -(l-f )b' D  48  *X  B  (0  2  units)  (2.18)  A c c o r d i n g to the l y s i s r e g r o w t h approach, v i a b l e b i o m a s s can either d i e or be i n a c t i v a t e d , l e a d i n g to dead and n o n v i a b l e b i o m a s s . Furthermore, a l l b i o m a s s can undergo l y s i s , a l t h o u g h at different rates for different types, l e a d i n g to s o l u b l e and particulate organic matter ( G r a d y et al., 1999). T h e particulate organic matter is h y d r o l y z e d to s o l u b l e organic matter, and the s o l u b l e organic matter from either source can be used b y the v i a b l e b i o m a s s for n e w g r o w t h as illustrated in Figure 2.11.  Growth Soluble  Loss o f C O D  substrate Ss  \.  ^  O2+NH3  Biomass  w  X  B  CO2 + H2O  D e c a y and l y s i s N o loss o f C O D  Hydrolysis N o loss o f C O D Particulate substrate X s  Figure 2.11 S c h e m a t i c representation o f the l y s i s : g r o w t h approach to m o d e l i n g b i o m a s s decay and loss o f v i a b i l i t y ( G r a d y et al., 1999)  T h e C O D - b a s e d s t o i c h i o m e t r y o f the l y s i s : r e g r o w t h approach o f D o l d et al. (1980) is: Biomass C O D  (1 -f ) D  particulate C O D + / '  D  b i o m a s s debris C O D  (2.19)  W h e r e / o is the fraction o f active b i o m a s s c o n t r i b u t i n g to b i o m a s s debris. A s i n the traditional approach, the rate o f loss o f b i o m a s s C O D to death and l y s i s is c o n s i d e r e d to be first order w i t h respect to the active b i o m a s s concentration, r B = -b*X X  X: B  (2.20)  B  W h e r e b is the decay coefficient, w i t h units o f hr"  49  In a m a n n e r s i m i l a r to the traditional approach, the rate o f p r o d u c t i o n o f b i o m a s s debris i s : rxn = b*f X D  (2.21)  B  A n d the rate o f p r o d u c t i o n o f particulate substrate C O D ( X s ) is: rxs  = ( l - / D ) * * * B  (2.22)  W h e r e t h e / b is n u m e r i c a l l y different from  f. D  T h e net effect o f the t w o approaches is the same because a g i v e n amount o f b i o m a s s w i l l be lost f r o m a bioreactor regardless o f h o w w e r e c o g n i z e the actual events o c c u r r i n g ( G r a d y et al., 1 9 9 9 ) . In the l y s i s : r e g r o w t h approach, carbon is c y c l e d w i t h i n the system several times to achieve the same loss o f b i o m a s s that the traditional approach achieves i n one pass. Therefore, b must be n u m e r i c a l l y larger than b '. S i m i l a r l y , fo  must be n u m e r i c a l l y s m a l l e r than fo since the  same amount o f b i o m a s s debris is u l t i m a t e l y f o r m e d f r o m the loss o f a g i v e n amount o f b i o m a s s b y decay. D o l d et al. ( 1 9 8 0 ) reported the relation between the four parameters to be: f'D*b=f *b'  (2.23)  0  Furthermore: / D = [(1-Y)/(1-Y*/D)]/D  '  (2-24)  W h e r e / • has a v a l u e o f around 0 . 2 for t y p i c a l b i o m a s s f o u n d i n b i o c h e m i c a l operations for wastewater treatment, and fo  is suggested to be around 0 . 0 8 ( D o l d and M a r a i s , 1 9 8 6 ; H e n z e et  al., 1 9 9 5 ; G r a d y et al., 1 9 9 9 )  T h e v a l u e o f the decay coefficient is v e r y dependent o n b o t h the species o f o r g a n i s m s i n v o l v e d and the substrate o n w h i c h it is g r o w n . T h e latter effect is p r o b a b l y due to the nature o f the energy reserves synthesized d u r i n g g r o w t h . T h e v a l u e o f b also depends to s o m e o f extent o n the rate at w h i c h the b i o m a s s is g r o w n . T h e relationship o f b ' a n d b also depends o n Y ( D o l d and  50  M a r a i s , 1986), and H e n z e et al. (1987) suggested that E q u a t i o n 4.13 b e used to convert b ' v a l u e s to b values. b = b'/[\-Y(\-f )]  (2.25)  D  W i d e ranges o f this coefficient h a v e b e e n reported, so it m u s t b e d e t e r m i n e d for a particular wastewater.  H i s t o r i c a l l y , m a n y investigators h a v e used  a m e t h o d that i n v o l v e s  m e a s u r i n g the change i n T S S o r V S S concentration o v e r t i m e for the d e t e r m i n a t i o n o f decay coefficient o f heterotrophic b i o m a s s {bw), but the O U R technique has b e e n s h o w n to g i v e m o r e r e p r o d u c i b l e results p r o v i d e d proper precautions are taken ( M a r a i s a n d E k a m a , 1976). E k a m a et al. (1986) d e v e l o p e d a n approach based o n the O U R test, w h i c h i s r e c o m m e n d e d b y the I A W P R C a n d I A W Q groups for use w i t h the A S M 1 a n d A S M 2 m o d e l s .  In the O U R approach, b i o m a s s is r e m o v e d f r o m o n e o f the c o m p l e t e l y m i x e d reactors (also k n o w n as a c o n t i n u o u s - f l o w stirred tank reactor) a n d put into a b a t c h reactor w h e r e it i s aerated, and the O U R i s measured m a n y times o v e r a p e r i o d o f several days. G e n e r a l l y , the longer the experiment i s r u n , the m o r e accurate the assessment o f b n w i l l b e . T h e slope o f a p l o t o f the natural l o g a r i t h m o f the o x y g e n uptake rate versus t i m e w i l l b e the traditional d e c a y coefficient ( M a r a i s a n d E k a m a , 1976). I n the O U R test, p r o p e r precautions s h o u l d b e taken. p H s h o u l d b e m a i n t a i n e d at a constant v a l u e near neutrality, a n d n i t r i f i c a t i o n s h o u l d b e i n h i b i t e d d u r i n g the test b y the a d d i t i o n o f 2 0 m g L " o f t h i o u r e a ( O r h o n a n d A r t a n , 1994) o r b y the 1  a d d i t i o n o f 0.16 g n i t r i f i c a t i o n i n h i b i t o r ( f o r m u l a 2 5 3 3 ) p e r 3 0 0 m L o f s a m p l e ( S o z e n et al., 1998).  51  T w o m e t h o d s that use the data o n the change i n O U R o v e r t i m e h a v e been used for the d e t e r m i n a t i o n o f b. F o r the t r a d i t i o n a l decay approach as discussed above, E q u a t i o n 2.26 determines the rate o f o x y g e n u t i l i z a t i o n associated w i t h decay. O U R = -r Where r  s o  (O2 units)  = (1 - / ) V- X D  B  (2.26)  is the rate o f o x y g e n u t i l i z a t i o n associated w i t h decay, / • is the fraction o f a c t i v e  s o  b i o m a s s c o n t r i b u t i n g to the b i o m a s s debris, b' is the t r a d i t i o n a l decay coefficient, w i t h units o f hr" , a n d X 1  B  The  is the a c t i v e b i o m a s s concentration.  o n l y r e a c t i o n i n the b a t c h reactor is b i o m a s s decay because there is n o s o l u b l e  substrate present. B y substituting the appropriate term o n the mass b a l a n c e o f b i o m a s s g i v e s the Equation 2.27: DX /dt B  = -b'X  (2.27)  s  w h i c h w h e n integrated o v e r t i m e t g i v e s equation 2 . 2 8 : X V=X -z-  (2.28)  Vi  B  m  W h e r e X B O is the i n i t i a l b i o m a s s c o n c e n t r a t i o n at t i m e t = 0 . B y substitution o f E q u a t i o n 2 . 2 8 into E q u a t i o n o f 2 . 2 6 , g i v e s the o x y g e n uptake rate i n the reactor at any t i m e t is g i v e n as: O U R | t = ( 1 - / ) V- X D  B  0  • e-*  (2.29)  In the absence o f n o n l i n e a r techniques, E q u a t i o n 2.29 m a y be transformed, a l l o w i n g a l i n e a r least squares t e c h n i q u e to be used. l n ( O U R ) | , = l n [ ( l - / ) V- X D  B 0  ] - b't  (2.30)  52  \  T h e alternative approach is to plot l n ( O U R ) versus t i m e a n d use linear least squares to o b t a i n the slope, w h i c h i s -b'. T h i s i s s h o w n i n F i g u r e 2.12. O n c e the v a l u e o f t r a d i t i o n a l d e c a y coefficient b' has been obtained, the decay coefficient c a n b e calculated w i t h E q u a t i o n 2.25.  b=  b1[l-Y(l-f )]  (2.25)  D  Intercept = L n [ ( l - / ) ] 6 ' X D  B O  ]  S l o p e = -V  Time (hrs)  F i g u r e 2.12 P l o t o f E q u a t i o n 2.30 to determine-the traditional decay coefficient for heterotrophic b i o m a s s ( G r a d y et al., 1999)  T h e temperature effect w a s corrected for b y u s i n g a reference temperature o f 2 0 ° C b y Equation 2.31. b = b *Q ~ . {T  (2.31)  T20)  20  W h e r e 6 is the temperature coefficient o f 1.029 for b i o m a s s decay ( G r a d y et ah, 1999).  A e r o b i c g r o w t h rate o f heterotrophic m i c r o o r g a n i s m s T h e m a x i m u m specific g r o w t h rate, ju, i s referred to as a specific rate coefficient because it defines the rate o f b i o m a s s g r o w t h i n terms o f the concentration o f active b i o m a s s present. C o n s e q u e n t l y , the m a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s , JUH, i s w r i t t e n i n terms o f heterotrophic b i o m a s s g r o w t h o n organic substrate. T h e m a i n f u n c t i o n o f the jUu i s to  53  a l l o w the m a x i m u m O U R to be predicted. Therefore, this parameter must be evaluated for use w i t h the A S M 2 m o d e l .  A  number  o f different  types o f experiments  have  been  performed  to  develop  a  relationship between the specific g r o w t h rate coefficient and the concentration o f substrate. It is found that / / i n i t i a l l y increases r a p i d l y as the substrate concentration is increased, but then / / approaches a m a x i m u m , w h i c h is c a l l e d the m a x i m u m s p e c i f i c g r o w t h rate. N o one yet k n o w s enough about the m e c h a n i s m s o f b i o m a s s g r o w t h to propose a m e c h a n i s t i c equation that w i l l characterize  growth  exactly ( G r a d y et  al.,  1999).  The  c o m m o n l y accepted  equation  for  characterization o f b i o m a s s g r o w t h is the M o n o d equation ( E q u a t i o n 2.32), i n w h i c h the g r o w t h rate depends o n the concentration o f the l i m i t i n g nutrient, w h i c h c a n be the c a r b o n source, the electron donor, the electron acceptor, nitrogen, or any other factor needed for o r g a n i s m g r o w t h .  M = M«***Ss/(Ks  + Ss)  W h e r e fi is the specific g r o w t h rate, / /  (2.32)  m a x  is the m a x i m u m specific g r o w t h rate, K% is the h a l f  saturation coefficient, and Ss is the concentration o f substrate.  E v e n though the o r i g i n a l w o r k w a s done i n batch reactors, and the M o n o d equation w a s d e v e l o p e d for pure culture o f bacteria g r o w i n g o n single organic substrates, it c a n be u s e d for m o d e l i n g b i o c h e m i c a l operations for wastewater treatment ( A n d r e w s , 1 9 7 1 ; C h i u et al.,  1972;  L a w r e n c e and M c C a r t y , 1970). It is r e c o g n i z e d that the values obtained f r o m m i x e d culture systems are i n reality average values r e s u l t i n g f r o m the presence o f m a n y interacting species ( C h i u et al., 1972; G h o s h and P o h l a n d 1971). C o n s e q u e n t l y , it has been r e c o m m e n d e d that / / be characterized b y ranges, rather than b y single values, just as was r e c o m m e n d e d for Y ( G r a d y et  54  al,  1999). M o n o d k i n e t i c s have been the u n d e r l y i n g basis for d e s c r i b i n g m i c r o b i a l g r o w t h i n  M B R s ( C h a i z e and H u y a r d , 1991; W e n et al,  The m a x i m u m  1999; Stephenson et al,  specific g r o w t h rate o f heterotrophic  2000).  biomass,  JUH, determines  the  m a x i m u m o x y g e n requirement o f a b i o l o g i c a l system. T h e m a i n f u n c t i o n o f JUH is to a l l o w the m a x i m u m O U R to be predicted. T h e v a l u e o f the specific heterotrophic g r o w t h rate is v e r y dependent o n the nature o f the organisms and the substrate. It appears to be i n f l u e n c e d b y the c o n f i g u r a t i o n o f the reactor and the temperature. It is difficult to evaluate accurately, but that i s not c r i t i c a l because the m o d e l is not v e r y sensitive to the v a l u e o f flw ( H e n z e et al,  Ekama  et  al  (1986)  hypothesized  that  the  maximum  specific  2000).  growth  rate  of  m i c r o o r g a n i s m s is p r o p o r t i o n a l to the m a x i m u m O U R and to the fraction o f v i a b l e b i o m a s s i n the sludge. T h e y measured the m a x i m u m O U R and estimated the fraction o f the active v o l a t i l e b i o m a s s . H e n z e et al (2000) suggested that measures o f JM s h o u l d b e based u p o n o x y g e n uptake measurements rather than c e l l g r o w t h or substrate r e m o v a l . S i n c e the concentration o f r e a d i l y biodegradable substrate i n the effluent f r o m an activated sludge process is generally quite l o w , it is not c r i t i c a l to the predictions o f b i o m a s s concentration and O U R that jUy\ be m o d e l e d w i t h h i g h accuracy; i.e. an error factor o f 2 or 3 w i l l h a v e little i m p a c t o n m o d e l p r e d i c t i o n s .  T w o respirometric procedures w e r e r e c o m m e n d e d for d e t e r m i n i n g JUH v a l u e s b y H e n z e et al. (1987). O n e was d e v e l o p e d b y L a m b et al. (1964) and refined b y C h u d o b a et al C e c h et al.  (1985).  C o a g u l a t e d and filtered wastewater  (1985) and  as a substrate is injected  into  a  respirometer at a n u m b e r o f concentrations. T h e net o x y g e n uptake rate ( O U R ) i n response to an  55  injection is p r o p o r t i o n a l to the substrate u t i l i z a t i o n rate, w h i c h i n turn is p r o p o r t i o n a l to the g r o w t h rate, w i t h the y i e l d b e i n g the p r o p o r t i o n a l i t y factor. T h e m a x i m u m s p e c i f i c g r o w t h rate can be c a l c u l a t e d b y E q u a t i o n 2 . 3 3 , after the s p e c i f i c o x y g e n uptake rate ( S O U R ) and 7 H have b e e n determined. T  H  JUH = —  — (SOUR)  (2.33)  (1-TH)  T h e t e c h n i q u e d e v e l o p e d b y E l l i s et al. (1996) relies o n a single substrate i n j e c t i o n w i t h d e t e r m i n a t i o n o f the k i n e t i c parameters b y fitting the theoretical o x y g e n c o n s u m p t i o n c u r v e to the observed o x y g e n c o n s u m p t i o n c u r v e . In the m e t h o d o f E l l i s et al. (1996), m a s s b a l a n c e equations for substrate u t i l i z a t i o n and b i o m a s s g r o w t h i n a b a t c h reactor are w r i t t e n t h r o u g h an appropriate  m o d e l and s o l v e d b y u s i n g a s s u m e d  theoretical  substrate  and  biomass  curves  can  values for the parameters. be  converted  into  an  T h e resulting  equivalent  oxygen  c o n s u m p t i o n c u r v e b y u s i n g a C O D balance. T h e theoretical data c u r v e is then c o m p a r e d to the actual data c u r v e and the parameter values are adjusted u n t i l the best agreement is a c h i e v e d b e t w e e n the theoretical and actual curves.  K a p p e l e r a n d G u j e r ( 1 9 9 2 ) d e v e l o p e d a s i m p l e batch test m e t h o d w i t h  centrifuged  wastewater and a v e r y s m a l l a m o u n t o f activated sludge. T h e respiration o f s u c h a b a t c h test is s h o w n i n F i g u r e 2 . 1 3 . T h e O U R is r e c o r d e d u n t i l a distinct drop i n the rate o c c u r s . U s i n g the slope o f the natural l o g a r i t h m o f the relative respiration rate versus time, the m a x i m u m s p e c i f i c g r o w t h rate is c a l c u l a t e d . In this m e t h o d , o x y g e n respiration increases due to u n l i m i t e d g r o w t h o f heterotrophic b i o m a s s d u r i n g the first stage o f the test. Subsequently, o x y g e n uptake decreases to  56  a l o w l e v e l because o f l i m i t i n g concentrations o f r e a d i l y b i o d e g r a d a b l e substrates. T h e o x y g e n respiration rate at this l e v e l is d o m i n a t e d b y g r o w t h o n substrate released b y h y d r o l y s i s .  InWOMtO)] 1 T  3  '  0 8  Slope: 7.5 d-1 .2 0.6 a. ZD c  °* 0.4 +  X O  £  0.2  Temperature: 24 °C  t  SRT: 9 days •  With addition of nitrification inhibitor —4 1 i  «  120  60  180  240  Time (minutes)  F i g u r e 2.13 B a t c h test to estimate the m a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s ( K a p p e l e r and Gujer, 1992)  The  o x y g e n respiration i n a b a t c h test w i t h neither substrate n o r o x y g e n l i m i t a t i o n is  expressed b y : roi (0 = - [ ( 1 - F H ) / T H ] - / / H X Where 7  H  H  (0 - (1-/ )-&H-*H(0 d  (2.34)  is the heterotrophic g r o w t h y i e l d , JUH is the m a x i m u m s p e c i f i c g r o w t h rate, XH i s the  concentration o f heterotrophic b i o m a s s , fo  is the fraction o f active heterotrophic  biomass  c o n t r i b u t i n g to b i o m a s s debris, bn is the heterotrophic decay rate, and t is the t i m e .  In this case, the o x y g e n uptake rate o n l y depends o n heterotrophic b i o m a s s . T h u s , the mass b a l a n c e for heterotrophic b i o m a s s i n a b a t c h test c a n be w r i t t e n as f o l l o w s :  57  dX /dt = (MH-b )-X (t) H  H  (2.35)  H  Integration o f E q u a t i o n 2.35 w i t h X H (to) = X o leads to: H  X (t)=X -eQiH- )-t  (2.36)  bH  H  m  A f t e r c o m b i n i n g E q u a t i o n 2.34 a n d 2.36, the o x y g e n r e s p i r a t i o n i s :  roi (t) =  -[(\-Y )/Y ]JUH H  (1-/P>6H]- X ^(ju )-t bH  -  H  H  H  (2.37)  T h e i n i t i a l respiration at t = 0 i s :  roi (to) = - [ ( 1 - T H ) / T ] - / / H H  -  (H?)b \ X H  m  (2.38)  B y c o m p a r i n g E q u a t i o n 2.37 w i t h E q u a t i o n 2.38, the r e s p i r a t i o n o f heterotrophic b i o m a s s at a n y time without limitations is: roi(t)/ro (to) 2  = e(jUH- )-t  (2.39)  b  T h e l o g a r i t h m i c f o r m o f E q u a t i o n 2.39 i s : ln[r  0 2  (0/ roi (*o)] = <Jte- bu)t  (2.40)  E q u a t i o n 2 . 4 0 represents a straight l i n e w i t h ( / / - &H) as slope as s h o w n i n F i g u r e 2.14, w h i c h H  c a n b e determined g r a p h i c a l l y o r b y m a t h e m a t i c a l methods.  T h e temperature effect i s corrected to a reference temperature o f 2 0 ° C b y E q u a t i o n 2 . 3 1 , w i t h a 8 o f 1.094 for aerobic g r o w t h o f heterotrophic b i o m a s s ( G r a d y et al., 1999).  58  800 -r  3 600  400 •  a i  200 fTemperarurt: 24 C 8  S R T : 9 days  With addition of uitrifkatiofl ichibiior  0 0  60  120  180  240  300  360  Time (minutes) F i g u r e 2.14 L o g a r i t h m i c f o r m o f the relative o x y g e n uptake ( K a p p e l e r a n d G u j e r , 1992)  Wastewater  characterization  C h a r a c t e r i z a t i o n o f a c o m p l e x wastewater i n a m a n n e r suitable for use w i t h A S M 2 i s c o m p l i c a t e d i n c o m p a r i s o n w i t h the routine measurements u s u a l l y m a d e at wastewater treatment plants. In m a n y wastewater treatment plants, influents are n o r m a l l y characterized i n terms o f the concentration  of TSS, V S S ,BOD  5 ;  a m m o n i a - N , total K j e l d a h l  nitrogen and alkalinity; a  d i s t i n c t i o n i s s e l d o m m a d e b e t w e e n the s o l u b l e and particulate phases d u r i n g measurement o f B O D , C O D , a n d T K N ( G r a d y et al, 1999). H o w e v e r , characterization i n A S M 2 i s p r o p o s e d i n 5  terms o f o r g a n i c , nitrogen a n d phosphorus fractions i n m u n i c i p a l wastewater as w e l l as a l k a l i n i t y and d i s s o l v e d o x y g e n , a n d those fractions are d i v i d e d into v a r i o u s sub fractions, the details o f w h i c h are r e v i e w e d i n C h a p t e r 2 .  59  It  is important  to  recognize  that the  distinction between  the  slowly  and  readily  biodegradable substrates is o p e r a t i o n a l l y defined and does not necessarily correspond to r e a d i l y distinguishable p h y s i c a l characteristics, s u c h as s o l u b l e and particulate, i n spite o f the s y m b o l s used i n the m o d e l ( G r a d y et al.,  1999). T h u s , characterization o f the wastewater  must  be  a c c o m p l i s h e d e x p e r i m e n t a l l y . A n u m b e r o f researchers have investigated v a r i o u s approaches for determining  those  components,  characterizing wastewater  and  some  of  i n the A S M m o d e l s .  these  methods  T h e procedures  were  recommended  for  for q u a n t i f i c a t i o n o f the  concentration o f inert s o l u b l e organic matter (Si), as w e l l as a few other fractions are r e v i e w e d here.  D e t e r m i n a t i o n o f the r e a d i l y biodegradable substrate, S F T h e r e a d i l y (fermentable) biodegradable substrate, S F , is c o m p o s e d o f s m a l l m o l e c u l e s that can be m e t a b o l i z e d directly, or q u i c k l y f e r m e n t e d / h y d r o l y z e d before b e i n g m e t a b o l i z e d . T h e components c a n be s o l u b l e proteins and carbohydrates and s i m i l a r e a s i l y degradable c o m p o u n d s . In A S M 2 , the s o l u b l e substrate, Ss, is d i v i d e d into t w o parts, S A , v o l a t i l e acids/fermentation products, and Sp, r e a d i l y (fermentable) biodegradable substrate. T h u s the s o l u b l e substrate, Ss, is the s u m o f these t w o parts.  A  determination o f Ss c a n be m a d e b i o l o g i c a l l y , c h e m i c a l l y , p h y s i c a l l y or p h y s i c a l -  c h e m i c a l l y . It c a n be m a d e i n d i r e c t l y through the o x y g e n uptake rate ( O U R ) as o r i g i n a l l y done b y E k a m a and M a r a i s (1977), w h i c h i n v o l v e s a bioassay. D u e to the d i f f i c u l t i e s associated w i t h that assay, a n u m b e r o f alternatives have been p r o p o s e d ( K a p p e l e r and Gujer, 1992; O r h o n and A r t a n , 1994; W e n t z e l et al., 1995; R a u n k j  r et ah, 1996). A p h y s i c a l determination c a n be m a d e  60  b y ultrafiltration or gelfiltration, u s i n g c u t - o f f values around 1000 D a l t o n s ( D o l d et al,  1986). It  m i g h t also b e estimated f r o m the anaerobic h y d r o l y s i s potential o f the organic matter (Johansson, 1994).  In  the O U R procedure,  Ss c a n be determined b y m e a s u r i n g the change i n o x y g e n  u t i l i z a t i o n rate ( O U R ) i n a s i n g l e c o m p l e t e l y m i x e d reactor operated at an S R T o f 2 days w h i l e r e c e i v i n g a d a i l y c y c l i c square w a v e feeding pattern w i t h 12 hours o f feed f o l l o w e d b y 12 hours w i t h o u t feed ( E k a m a et al,  1986; H e n z e et al,  1987). A f t e r the reactor has been operated for a  sufficient p e r i o d to establish a stable response pattern, several measurements o f the O U R s h o u l d be m a d e d u r i n g a c o m p l e t e c y c l e . W h e n the feed is stopped, the O U R w i l l drop r a p i d l y because any a c c u m u l a t e d r e a d i l y b i o d e g r a d a b l e substrate is q u i c k l y used. T h e O U R then d e c l i n e s s l o w l y u n t i l the s l o w l y biodegradable  substrate is exhausted.  A t this point, the O U R w i l l  reflect  endogenous m e t a b o l i s m and decay. T h u s the i m m e d i a t e drop i n O U R is associated o n l y w i t h the s o l u b l e substrates. T h e concentration c a n be determined b y a s s u m i n g a y i e l d factor ( E k a m a et al,  1986; K r i s t e n s e n et al,  Alternatively,  1992).  a batch  test w i t h activated  sludge  biomass  and  unfiltered  influent  wastewater i n a C O D ( m g L " ) / V S S ( m g L " ) ratio o f a p p r o x i m a t e l y 1 to 2 w a s carried out to !  1  determine the s o l u b l e b i o d e g r a d a b l e substrate concentration i n influent, Ss ( K a p p e l e r and G u j e r , 1992). D u r i n g the first p e r i o d the o x y g e n uptake rate decreases r a p i d l y , because the s o l u b l e substrate is q u i c k l y exhausted l e a d i n g to the substrate l i m i t a t i o n as r e v i e w e d p r e v i o u s l y . A t this stage the O U R w i l l be d o m i n a t e d b y the g r o w t h o n the substrate released b y h y d r o l y s i s and less b y endogenous respiration. Therefore Ss c a n be calculated a c c o r d i n g to E q u a t i o n 2.41 f r o m the  61  difference between total respiration and respiration due to hydrolysis substrate and endogenous respiration. Figure 2.15 shows a resulting oxygen respiration o f this approach. Ss  =  [Jl"02, tot "  ko2, baseline -  = [A0 -(V 2  w w  +V  m L  respiration]/(l  ~  YH)  (2.41)  ) / V ]/(1 - Y ) ww  H  Where: A 0 = mass o f oxygen consumed by Ss (area under O U R curve), 2  V  =  volume o f wastewater in the mixture, and  =  volume o f mixed liquor in the mixture.  w w  V L m  (g 02/m3'd) 1000 T  Time (minutes')  Figure 2.15 Respiration test to determine the concentration o f readily biodegradable substrate Sso (Kappeler and Gujer, 1992)  It should be mentioned that a period with elevated respiration longer than half an hour might already cause heterotrophic growth and a non-negligible amount o f hydrolyzed substrate that influences correct interpretation o f the respiration curve (Kappeler and Gujer, 1992). If the  62  concentration o f v o l a t i l e a c i d , S , has been measured then S F c a n be d e t e r m i n e d A  from  the  difference o f Ss and S . A  T h e concentration o f S F c a n also be estimated b y c h e m i c a l p r e c i p i t a t i o n f o l l o w e d b y C O D measurements. T h e p r e c i p i t a t i o n c a n be m a d e w i t h z i n c sulphate ( M a m a i s et al., 1993) or other precipitants l i k e p o l y m e r i z e d a l u m i n u m c h l o r i d e ( H e n z e and H a r r e m o e s ,  1992). T h e  p h y s i c a l and c h e m i c a l m e t h o d for S F d e v e l o p e d b y M a m a i s et al. (1993), is m u c h q u i c k e r than the o r i g i n a l b i o a s s a y and gives results that correlated w e l l w i t h the o r i g i n a l b i o a s s a y for d o m e s t i c wastewater. In this m e t h o d , samples o f r a w wastewater are f l o c c u l a t e d b y a d d i n g Z n S 0 4 , m i x i n g v i g o r o u s l y for 1 m i n u t e , and adjusting the p H to 10.5 w i t h N a O H . T h e s e samples are then a l l o w e d to settle quiescently before a s a m p l e o f clear supernatant is w i t h d r a w n and filtered through a 0.45 | i m m e m b r a n e filter. T h e s o l u b l e fraction after p r e c i p i t a t i o n has a c o m p o s i t i o n : S = S  A  + S + Si . F  (2.42)  > f  W h e r e the S i f is the inert C O D i n the filtrate, it is s m a l l and less than 1 0 % o f C O D i n the ;  filtrate  for m u n i c i p a l wastewater ( H e n z e , 1992). In m a n y cases it is close to S i . T h e f l o c c u l a t i o n step r e m o v e s c o l l o i d a l o r g a n i c matter that otherwise w o u l d pass through the filter and be m e a s u r e d as " s o l u b l e " m a t e r i a l . T h e C O D o f the  filtrate  is the total s o l u b l e C O D o f the  wastewater.  S u b t r a c t i o n o f the inert s o l u b l e C O D , S i , p r o v i d e s the v a l u e o f the s o l u b l e b i o d e g r a d a b l e C O D , Ss. T h e r e a d i l y biodegradable C O D , S F was then calculated b y subtraction o f the acetic a c i d concentration, SA-  A major advantage o f this m e t h o d is that m o r e samples c a n be a n a l y z e d , g i v i n g a better measure o f the l o n g - t e r m average  concentration o f the r e a d i l y b i o d e g r a d a b l e  63  C O D i n the  wastewater,  than  can be  obtained  with  the  bioassay.  This  approach  has  been  used  or  r e c o m m e n d e d b y m a n y researchers ( G r a d y et al., 1999; H e n z e et al., 2 0 0 0 ) .  D e t e r m i n a t i o n inert s o l u b l e o r g a n i c matter, S i Inert s o l u b l e organics consist o f m o l e c u l e s o f v a r y i n g size. T h e m a j o r part o f the s o l u b l e inert organics is large m o l e c u l e s , w h i l e a s m a l l fraction is c o m p o s e d o f l o w and m e d i u m - s i z e inert m o l e c u l e s . T h e determination o f this fraction depends o n the assumptions u n d e r l y i n g the d e f i n i t i o n o f this substrate i n the m o d e l used. In A S M 2 , a l l s o l u b l e inert substrate is assumed to be present i n the influent, and the s o l u b l e inert substrate p r o d u c e d d u r i n g the process is not considered.  T h e concentration o f S i can be evaluated i n m a n y w a y s . It c a n be determined b y a l o n g term B O D test ( H e n z e et a l . , 2 0 0 0 ) . T h e s o l u b l e C O D r e m a i n i n g after 20 days o f o x i d a t i o n c a n be regarded as equivalent to S i ( E k a m a et a l . , 1986; B j e r r e et a l . 1995). It c a n also b e d e t e r m i n e d f r o m continuous l a b - or p i l o t - s c a l e experiments w i t h a h i g h s o l i d s retention time. In this case, the major part ( 9 0 - 9 5 % ) o f the s o l u b l e C O D i n the effluent w i l l be inert and thus represent S i ( H e n z e et a l . , 1995). T h o s e methods are not p o s s i b l e i n this research due to the l i m i t a t i o n o f a v a i l a b l e time.  H e n z e (1992) suggested a s i m p l e b a t c h test m e t h o d to estimate S i . A n aliquot o f the m i x e d l i q u o r is r e m o v e d f r o m one o f bioreactors operating at an S R T o f 10 days or m o r e and aerated i n a separate batch reactor. T h e s o l u b l e C O D is m e a s u r e d o v e r t i m e u n t i l it reaches a stable r e s i d u a l v a l u e ; the final residual is the inert m a t e r i a l , and that v a l u e c a n b e c o n s i d e r e d to  64  be equivalent to the concentration o f inert s o l u b l e C O D i n the influent ( H e n z e , 1992; G r a d y et al,  1999). L e s o u e f et al. (1992) determined S i as the final s o l u b l e C O D concentration at the end  o f the g r o w t h y i e l d test, w h e n the s o l u b l e C O D was constant and it was assumed that a l l o f the s o l u b l e b i o d e g r a d a b l e C O D h a d been u t i l i z e d .  Inert s o l u b l e C O D c a n be determined as the t r u l y s o l u b l e C O D r e m a i n i n g i n the effluent f r o m a bioreactor operated w i t h a l o n g S R T ( M a m a i s et al,  1993). T h e t r u l y s o l u b l e C O D i s  obtained b y f l o c c u l a t i n g an effluent s a m p l e f r o m the bioreactor w i t h the longest S R T w i t h ZnS0  4  at p H 10.5 ( f o r m i n g Z n ( O H )  2  floe) p r i o r to filtration through a 0.45 u m m e m b r a n e  filter.  T h e f l o c c u l a t i o n step effectively r e m o v e s c o l l o i d a l o r g a n i c matter that m i g h t pass t h r o u g h the filter,  l e a v i n g o n l y S i , and G r a d y et al. (1999) and H e n z e et al. (2000) r e c o m m e n d e d this  method.  A l l o f the above techniques p r o d u c e a p p r o x i m a t i o n s o f S i . B a c t e r i a p r o d u c e s o l u b l e m i c r o b i a l products as they degrade o r g a n i c matter. C o n s e q u e n t l y , part o f the inert o r g a n i c matter r e m a i n i n g w i l l a c t u a l l y be o f m i c r o b i a l o r i g i n . H o w e v e r , because the m o d e l s e m p l o y e d i n A S M 2 do not e x p l i c i t l y account for s o l u b l e m i c r o b i a l products ( S M P ) , it is acceptable to c o n s i d e r S M P as part o f the inert s o l u b l e C O D i n m o s t case. G e r m i r l i et al (1991) d e v e l o p e d an e x p e r i m e n t a l procedure for i n d u s t r i a l wastewater to take the S M P into account, h o w e v e r it requires a l o n g adaptation t i m e . It m a y be u s e d i n situations i n w h i c h it is necessary to e x p l i c i t l y account for s o l u b l e m i c r o b i a l products.  65  D e t e r m i n a t i o n o f inert particulate matter, X i T h i s fraction c a n be estimated through a batch test ( K a p p e l e r and G u j e r , 1992), b y c a l i b r a t i o n o f the m o d e l w i t h respect to observed sludge p r o d u c t i o n ( H e n z e et al., 1987), o r b y the tedious c o n t i n u o u s technique described b y E k a m a et al. (1986). F o r c o m p u t e r p r o g r a m s based o n a defined s o l i d s retention t i m e , X i can be f o u n d b y c a l i b r a t i o n o f the m i x e d l i q u o r concentration m e a s u r e d i n an activated sludge tank ( H e n z e et al., 2 0 0 0 ) . B j e r r e et al. (1995) determined X i as the particulate matter left after 2 0 days o f aeration m i n u s the products f r o m the b i o m a s s ( 2 0 % o f the b i o m a s s ) . L e s o u e f et al. (1992) evaluated X i d u r i n g the S i test. It w a s carried out i n a b a t c h test w i t h wastewater alone. A f t e r c o n t i n u o u s aeration o f a filtered s a m p l e for several days, a final C O D l e v e l is reached, S i . T h e b i o d e g r a d a b l e matter r e m a i n i n g i n the filtrate contains r a p i d l y and s l o w l y biodegradable substances. In parallel, a n o n - f i l t e r e d s a m p l e w a s aerated c o n t i n u o u s l y , the inert particulate matter X i w a s estimated as the difference b e t w e e n the total C O D o f the aerated non-filtered sample m i n u s the created b i o m a s s m i n u s the s o l u b l e inert C O D , S i .  T h e particulate mass created b y the b i o d e g r a d a t i o n o f the r e m a i n i n g matter i n the filtrate w a s c a l c u l a t e d as the difference between the final total C O D o f the filtered s a m p l e m i n u s the final s o l u b l e C O D o f the experiment w i t h the filtered sample, S i . T h e o b s e r v e d y i e l d o f b i o m a s s p r o d u c t i o n per u n i t mass o f degraded C O D w a s then calculated b y p u t t i n g the mass created into r e l a t i o n w i t h the C O D degraded.  T h e c a l c u l a t i o n o f the b i o m a s s f o r m e d b y the r e m o v a l o f the degradable particulate matter w a s based o n the non-filtered sample: the difference b e t w e e n the i n i t i a l total C O D a n d the  66  soluble final C O D corresponded to the converted substrate. M u l t i p l i e d b y the y i e l d , this gave the created b i o m a s s . T h e inert particulate matter w a s the difference between the final C O D o f the non-filtered sample, from w h i c h w a s deducted the s o l u b l e inert fraction, X j , and the p r o d u c e d b i o m a s s . T h u s E q u a t i o n 2.43 determined X s . T o t a l influent C O D = C O D  = X  T 0  s o  + X  l  0  + S  s o  + S  1 0  (2.43)  Determination o f s l o w l y biodegradable C O D S l o w l y b i o d e g r a d a b l e C O D , X s , is n o r m a l l y c a l c u l a t e d b y a C O D m a s s b a l a n c e a r o u n d the influent wastewater as r e c o m m e n d e d b y H e n z e et al. (1987). X s can be f o u n d as the difference between the total C O D and the other fractions as s h o w n i n E q u a t i o n 2.44. X  s  = C O D T O - SAO - S o - S, - X , F  0  (2.44)  0  W h e r e the s l o w l y biodegradable o r g a n i c matter i n c l u d e d the b i o m a s s fraction. T h e total influent C O D can be measured and the concentrations o f Ss, S i and X i i n influent can be estimated b y the procedures described p r e v i o u s l y . T h e s l o w l y degradable o r g a n i c substrate can also be estimated based o n batch o r continuous experiments, but these estimates w i l l not be v e r y accurate ( E k a m a etal., 1986; K a p p e l e r and G u j e r , 1992).  67  C H A P T E R III  Research Objectives  A s m e n t i o n e d i n Chapter I, the purposes o f this research w e r e to identify the m o s t important parameter values for use w i t h the A S M 2 m o d e l , to g a i n k n o w l e d g e o n wastewater c o m p o s i t i o n s i n the influent, and i n a d d i t i o n , to e x p l o r e the difference b e t w e e n the M E B P R a n d s i m p l i f i e d U C T processes i n terms o f the m i c r o b i a l activities b y c o m p a r i n g the k i n e t i c a n d s t o i c h i o m e t r i c parameter values, a n d to p r o v i d e d b a s i c c o n d i t i o n s , e.g. a database for future process d e s i g n and c o m p u t e r s i m u l a t i o n o f the M E B P R process.  T o achieve these purposes, the objectives o f this research were: •  to determine the values o f s u c h important parameters  as g r o w t h rate, m o d e l d e c a y  coefficient, and m a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s for the M E B P R and U C T processes, •  to determine the C O D fractions i n the influent, i n c l u d i n g r e a d i l y b i o d e g r a d a b l e C O D , V F A s , inert s o l u b l e C O D , inert particulate C O D , and s l o w l y b i o d e g r a d a b l e C O D ,  •  to determine the nitrogen fractions i n the influent, e.g. a m m o n i a nitrogen, N H / , nitrite and nitrate ( N 0 + N 0 ) , total nitrogen, T K N , and 3  •  2  to determine the phosphorus fractions ( P 0 ~ and T P ) i n the influent. 3  4  68  C H A P T E R IV  The  Materials and Methods  experiment  results  for this research  were  used  primarily  to  provide useful  i n f o r m a t i o n b y estimating values o f m o d e l parameters and concentrations o f influent wastewater components for further o p t i m i z a t i o n o f the M E B P R process i n the U B C p i l o t plant. T h e s e parameters w e r e estimated for the M E B P R and U C T processes r u n i n p a r a l l e l , to c o m p a r e the differences i n terms o f the m i c r o b i a l activities b e t w e e n the t w o processes. A l l experiments w e r e p e r f o r m e d i n 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 o f the C i v i l E n g i n e e r i n g D e p a r t m e n t at the U n i v e r s i t y o f B r i t i s h C o l u m b i a .  M o d e l parameters a n d wastewater fractions w e r e d e t e r m i n e d u s i n g the m e t h o d o l o g i e s described b y the A S M N o . 2 procedures o r b y alternative b a t c h test methods p r o p o s e d b y a v a r i e t y o f researchers for use w i t h the m o d e l A S M N o . 2. T h e routine c h e m i c a l analyses o f m o d e l components w e r e c o m p l e t e d f o l l o w i n g Standard M e t h o d s ( A P H A  et al.,  1998), o r  Q u i c k c h e m M e t h o d s . E x p e r i m e n t a l tests a n d analyses w e r e c o n d u c t e d u s i n g v a r i o u s e q u i p m e n t that is d i s c u s s e d b e l o w . D e t a i l e d e x a m p l e s and c a l c u l a t i o n s u s e d for each m o d e l c o m p o n e n t s are l i s t e d i n A p p e n d i c e s .  4.1 Experimental Design  T h e e x p e r i m e n t w a s designed as a series o f lab scale b a t c h tests. It w a s c a r r i e d out i n two phases. In the first phase, the laboratory scale b a t c h reactors w e r e designed, a n d the b a t c h  69  test m e t h o d o l o g i e s w e r e refined u s i n g wastewater a n d sludge samples c o l l e c t e d f r o m the U B C p i l o t plant. I n the s e c o n d phase, parameters  were  estimated,  the influent wastewater  and similar  operating  w a s characterized, a n d m o d e l  conditions were  maintained  for the  experiments.  Operating conditions of the UBC pilot plant T h e operating c o n d i t i o n s o f the M E B P R a n d U C T processes were set to s i m i l a r values i n order to c o m p a r e the m o d e l parameter values determined f r o m the t w o processes ( T a b l e 4.1). H o w e v e r , the S R T c o u l d b e changed a c c o r d i n g to the research objectives. Process v o l u m e s w e r e f i x e d d u r i n g the testing; process flow rates w e r e measured a n d adjusted at least t w i c e p e r w e e k . A e r o b i c D O concentrations w e r e c h e c k e d , r e c o r d e d a n d adjusted i f necessary. A e r o b i c sludge w a s wasted d a i l y a n d v o l u m e s w e r e v a r i e d d e p e n d i n g o n m i x e d l i q u o r ( M L S S ) a n d effluent suspended s o l i d s concentrations. W a s t a g e v o l u m e s w e r e adjusted w e e k l y a c c o r d i n g to the m o s t recent w e e k l y aggregated s o l i d s data to meet the desired S R T o f the t w o processes.  Sampling and preservation of samples T h e test m e d i a w e r e influent wastewater, effluent a n d sludge f r o m the M E B P R a n d the s i m p l i f i e d U C T processes at the U B C p i l o t plant. T h e wastewater to the U B C p i l o t plant i s p r e d o m i n a n t l y m u n i c i p a l sewage. W a s t e w a t e r w a s c o l l e c t e d every w e e k (between September and O c t o b e r 2 0 0 1 , a n d January to A p r i l 2 0 0 2 ) for the d e t e r m i n a t i o n o f a m m o n i a , nitrate a n d nitrite, ortho-phosphate,  T K N , T P and V F A concentrations. S a m p l e s for these tests w e r e  preserved i m m e d i a t e l y after s a m p l i n g , as s u m m a r i z e d i n T a b l e 4 . 2 , a n d then t h e y w e r e a n a l y z e d triplicate. T h e a n a l y t i c a l procedures are i n t r o d u c e d i n the f o l l o w i n g sections.  70  T a b l e 4 . 1 . O p e r a t i o n c o n d i t i o n and c o n f i g u r a t i o n o f U B C p i l o t plant M E B P R Process  U C T process  Influent Q  2.0  2.0  R e t u r n sludge Q  2.0  2.0  2.0  2.0  0  0  1386  1386  252  252  378 756  378 756  11.6  11.6  Anaerobic zone  2.1  2.1  A n o x i c zone  3.2  3.2  A e r o b i c zone  6.3 17-25  6.3 17-25  50 (approx)  4 0 (approx)  Process f l o w rate ( L m i n " ) 1  s  Anaerobic recycle Q A n o x i c recycle Q  a  r  Total v o l u m e o f bioreactor ( L ) Anaerobic zone A n o x i c zone A e r o b i c zone H R T (hr.) (based o n Q ) System H R T  S R T (day) Process sludge wastage ( L day" ) 1  2-3  2-3 A e r o b i c D O concentration ( m g 0 L " ) Note: Clarifier solids were not included in the calculation of HRT and SRT. 1  2  T a b l e 4.2 P r e s e r v a t i o n o f samples Parameter  Filtration  Sample volume  (0.45 i m m e m b r a n e filter)  (mL)  Preservation  VFA  Yes  1 (half vial)  Add H P 0  TKN/TP  No  20  A d d 5% H S 0  NH  Yes  4  NO /P0 x  4  Yes  10 .  10  3  4  2  A d d 5% H S 0 2  to p H < 2 4  4  to p H < 2 to p H <2  1 drop o f p h e n y l m e r c u r i c acetone  T h e tests for heterotrophic g r o w t h y i e l d , decay rate, m a x i m u m g r o w t h rate and r e a d i l y b i o d e g r a d a b l e C O D w e r e carried out i m m e d i a t e l y after s a m p l i n g , i n reactors or respirometers. T h e s e tests for d e t e r m i n i n g m o d e l parameter values were r u n i n p a r a l l e l w i t h the b i o m a s s the M E B P R processes.  from  and U C T processes, i n order to demonstrate any differences b e t w e e n the t w o T h e methods, procedures, and apparatus are i n t r o d u c e d i n the f o l l o w i n g sections,  and the details are g i v e n i n the appendices.  71  4.2 Experimental Apparatus  E q u i p m e n t w a s set u p i n the U B C 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 and the U B C p i l o t plant. T w o sets o f equipment (Figures 4.1 and 4.2) w e r e designed and refined for the e s t i m a t i o n o f k i n e t i c and s t o i c h i o m e t r i c parameters as w e l l as the e s t i m a t i o n o f concentrations o f v a r i o u s wastewater components.  T h e O U R test system ( F i g u r e 4.1) w a s u s e d to carry out the b a t c h tests for the determination o f the decay rate, m a x i m u m specific g r o w t h rate and r e a d i l y b i o d e g r a d a b l e C O D concentration b y respirometry. T h e respirometers w e r e constructed f r o m a c r y l i c t u b i n g sealed to an a c r y l i c base. T h e respirometer w a s topped w i t h a c o n i c a l l i d as a vent, and to m i n i m i z e the surface area at the top o f the respirometer. A d i s s o l v e d o x y g e n probe w a s inserted into each respirometer  at the top, and an air s u p p l y diffuser w a s p l a c e d i n the b o t t o m o f each  respirometer. A i r f r o m the diffusers p r o v i d e d fine-bubble aeration. A laboratory stir plate a n d m a g n e t i c stir bars were used to m a i n t a i n the respirometer contents i n suspension. R e s p i r o m e t e r s w e r e kept i n the temperature-controlled c h a m b e r to m a i n t a i n the contents at the temperature o f the p i l o t plant reactors ( A p p e n d i c e s 2 and 3).  T h e b a t c h reactors w e r e used to estimate the g r o w t h y i e l d o f heterotrophic b i o m a s s , s o l u b l e inert C O D and particulate inert C O D , a c c o r d i n g to the selected procedures. A s illustrated i n F i g u r e 4.2, a s i m p l e b a t c h reactor w a s constructed f r o m a c r y l i c t u b i n g sealed to an a c r y l i c base, a n d the v o l u m e o f the reactor w a s a p p r o x i m a t e l y 1 liter. T h e diffuser w a s p l a c e d i n the b o t t o m o f each reactor, and the air s u p p l y w a s adjusted to m a i n t a i n the d i s s o l v e d o x y g e n at 4-6 m g O2 L " d u r i n g the tests. A m a g n e t i c stir plate a n d stir bars w e r e u s e d to keep the contents 1  o f the reactors i n suspension. T h e water loss due to evaporation w a s accounted for, a n d w a s 72  replaced w i t h d i s t i l l e d water stored i n the temperature-controlled chamber, p r i o r to s a m p l i n g . T h e temperatures are s h o w n i n T a b l e s 4 . 3 , 4.7 and 4.8 i n S e c t i o n 4 . 3 .  73  each  4.3 Methodologies  In this section, the selected methods for the experiments are i n t r o d u c e d . S o m e o f the m o d e l components c a n b e determined b y standard procedures, w h i l e m a n y m o d e l c o m p o n e n t s cannot be measured d i r e c t l y o r p r e c i s e l y . In s o m e cases, the a n a l y t i c a l procedures are not yet standardized, due to a need for further understanding and d e v e l o p m e n t ( H e n z e et al., 2 0 0 0 ) .  Estimation of kinetic and stoichiometric A s reviewed i n Chapter  parameters  1, m o d e l parameter  determinations  are r e q u i r e d p r i o r to  c o m p u t e r s i m u l a t i o n to p r o v i d e the b a s i c c o n d i t i o n s for s i m u l a t i o n for a p a r t i c u l a r wastewater a p p l i c a t i o n . I n this research, the g r o w t h y i e l d , decay rate a n d m a x i m u m specific g r o w t h rate o f heterotrophic bacteria w e r e evaluated because these parameters are important a n d p a r t i c u l a r to the wastewater studied.  D e t e r m i n a t i o n o f heterotrophic g r o w t h y i e l d The  heterotrophic g r o w t h y i e l d tests were based o n a m e t h o d d e s c r i b e d b y m a n y  researchers ( H e n z e et al,  1 9 8 7 ; Slade et al,  1991; G r a d y et al,  1999).  A 0.5 L s a m p l e o f  influent wastewater w a s filtered through a G6 G F / C glass fiber filter for pre-filtration, then t h r o u g h a 0.45 p m m e m b r a n e filter to r e m o v e suspended m a t e r i a l . T h e filtered wastewater w a s p l a c e d into a 1-L batch reactor a n d the i n i t i a l s o l u b l e C O D o f the reactor contents w a s d e t e r m i n e d i n triplicate samples. T h e pre-determined amount o f b i o m a s s f r o m the U C T o r M E B P R process i n the U B C p i l o t plant w a s then added into the reactor a c c o r d i n g to the i n i t i a l s o l u b l e C O D : b i o m a s s ratio o f 50-100:1 (details refer to A p p e n d i x 1), then the i n i t i a l total C O D o f the reactor contents w a s measured. T h e actual values a n d i n i t i a l b a t c h test c o n d i t i o n s are given i n Table 4.3. 76  H e t e r o t r o p h i c g r o w t h y i e l d tests were r u n i n duplicate. Reactors w i t h the m i x t u r e o f wastewater and b i o m a s s f r o m the U C T and M E B P R processes were run i n p a r a l l e l for 5-8 days i n the  temperature-controlled  chamber  at the  U B C Environmental Engineering Lab. The  temperature was m a i n t a i n e d constant at the temperature o f the p i l o t plant reactor. T h e reactor contents w e r e stirred c o n t i n u o u s l y u s i n g a laboratory stir plate and a m a g n e t i c stir bar, and air was s u p p l i e d u s i n g a r o u n d stone diffuser through the reactor. C a r e was taken to scrape the w a l l g r o w t h o n the side o f the reactor and aeration t u b i n g w i t h a bottlebrush r e g u l a r l y for k e e p i n g cells i n suspension. W a t e r loss i n each reactor was calculated and compensated for w i t h d i s t i l l e d water a d d i t i o n before t a k i n g samples. D u p l i c a t e samples w e r e r e m o v e d from the reactor t w i c e d a i l y for several days and a n a l y z e d for s o l u b l e and total C O D .  Table 4.3 Initial e x p e r i m e n t a l c o n d i t i o n s for heterotrophic g r o w t h y i e l d tests Initial s o l u b l e C O D : b i o m a s s ratio  Liquid volume  (mg C O D L" ) (mg C O D L ' ) ' '  (mL)  50  500  50  1  pH  Temperature  Test date  (°Q 7  16  500  7  16  50 50  500  7.8  13  500  7.8  13  70  500  8  13  70  500  8  13  100  500  8  13  100  500  8  13  80  500  7.9  15  80  500  7.9  15  Oct-12-01 Feb-25-02 Mar-01-02 Apr-08-02 Apr-24-02  T h e heterotrophic b i o m a s s 7 , was estimated b y o b s e r v i n g the C O D o f c e l l m a t e r i a l H  f o r m e d d u r i n g r e m o v a l o f s o l u b l e substrate. T h e b i o m a s s C O D was calculated as the difference between the total C O D and the s o l u b l e C O D , and the y i e l d was determined from the E q u a t i o n 4 . 1 , and 4.2. A B i o m a s s C O D = total C O D - s o l u b l e C O D  77  (4.1)  A Biomass C O D  Y =  -  H  (4.2)  A Soluble C O D  T h e 7 H w a s determined b y p l o t t i n g the b i o m a s s C O D as a f u n c t i o n o f the s o l u b l e C O D r e m o v e d a n d t a k i n g the slope o f the r e s u l t i n g l i n e ( G r a d y et al., 1999).  D e c a y o f heterotrophic m i c r o o r g a n i s m s T h e b a t c h r e s p i r o m e t r i c m e t h o d o f E k a m a et al. (1986) o u t l i n e d i n A S M 1 ( H e n z e et al., 1987) w a s u s e d to determine the d e c a y coefficient. B i o m a s s r e m o v e d f r o m the a e r o b i c z o n e o f the M E B P R o r U C T process w a s p l a c e d into 2, 2 - L respirometers i n the temperature-controlled c h a m b e r to m a i n t a i n the contents at the temperature o f the p i l o t plant reactors. T a b l e 4.4 s h o w s the e x p e r i m e n t a l c o n d i t i o n s . S a m p l e s f r o m the t w o processes were tested i n duplicate. T h e reactor contents were c o n t i n u o u s l y stirred and aerated, a n d the decrease o f d i s s o l v e d o x y g e n was recorded a n d l o g g e d d i r e c t l y b y a computer. T h e O U R w a s calculated o v e r 11 to 15 days. p H w a s m a i n t a i n e d at a constant v a l u e near 7.5 b y a d d i n g a l k a l i n i t y ( s o d i u m bicarbonate), a n d n i t r i f i c a t i o n w a s i n h i b i t e d d u r i n g the test b y the a d d i t i o n o f 0.16 g n i t r i f i c a t i o n i n h i b i t o r f o r m u l a 2533 ( s u p p l i e d b y H A C H C o m p a n y ) per 3 0 0 m L o f sample. T h e respirometer contents w e r e topped u p d a i l y w i t h d i s t i l l e d water to compensate for evaporative losses.  T h e slope o f a p l o t o f the natural l o g a r i t h m o f the o x y g e n uptake rate versus t i m e i s the traditional decay coefficient, b'. T h e m o d e l decay coefficient, b w a s c a l c u l a t e d f r o m the traditional d e c a y coefficient u s i n g E q u a t i o n 2.25. T h e c o e f f i c i e n t , / ^ , w a s a s s u m e d to b e 0.08 i n the present study for use w i t h the A S M 2 .  T h e temperature effect w a s corrected f o r b y u s i n g a  reference temperature o f 2 0 ° C b y E q u a t i o n 2 . 3 1 . b = b o*Q ~ (T  (2.31)  T20)  2  78  W h e r e 0 is the temperature coefficient o f 1.029 for b i o m a s s d e c a y ( G r a d y et al., 1999).  T a b l e 4.4 E x p e r i m e n t a l c o n d i t i o n s for heterotrophic d e c a y rate tests Test date  Sample  Reactor  sources  Volume (L)  May-7-02 May-24-02 June-12-02  UCT  2  Alkalinity Temperature (°C) 17.5  pH  NaHC0  7.5  Nitrification inhibitor  3  formula 2533  (g) Yes  (0.16g)(300 mL)" Yes  Yes  2  17.5 18.5  7.5 7.5  Yes Yes  Yes  MEBPR  2  18.5  7.5  Yes  Yes  UCT UCT  2 2  18  Yes  18  7.5 7.5  Yes  Yes Yes  MEBPR  2  19  7.5  Yes  Yes  MEBPR  2  19  7.5  Yes  Yes  MEBPR UCT  2  1  A e r o b i c g r o w t h rate o f heterotrophic m i c r o o r g a n i s m s T h e m a x i m u m g r o w t h rate o f heterotrophic b i o m a s s w a s d e t e r m i n e d u s i n g the a p p r o a c h d e v e l o p e d b y K a p p e l e r a n d G u j e r (1992). A batch test w i t h centrifuged wastewater and a v e r y s m a l l amount o f activated sludge b i o m a s s f r o m the M E B P R o r U C T process w a s carried out i n parallel w i t h i n t w o respirometers i n a temperature-controlled chamber.  T a b l e 4.5 s h o w s the  experimental c o n d i t i o n s .  A 2 - L s a m p l e o f influent wastewater w a s centrifuged at a r e l a t i v e centrifugal force o f 1560  g, and the C O D o f the centrifuged s a m p l e w a s then measured. S l u d g e samples f r o m the  U C T and M E B P R processes w e r e aerated for m e a s u r i n g the endogenous O U R . T h e M L S S a n d MLVSS  concentrations o f sludge samples w e r e estimated.  Wastewater and biomass were  m i x e d into a 2 - L respirometer i n a C O D : V S S ratio o f 4 : 1 . N i t r i f i c a t i o n w a s i n h i b i t e d d u r i n g the test b y the a d d i t i o n o f 0.16 g n i t r i f i c a t i o n i n h i b i t o r ( f o r m u l a 2 5 3 3 ) per 300 m L o f sample. T h e reactors w e r e p l a c e d into a temperature-controlled c h a m b e r to m a i n t a i n the contents at the temperature o f the p i l o t plant reactors. T h e reactor contents w e r e c o n t i n u o u s l y stirred a n d  79  aerated, and the O U R was measured i m m e d i a t e l y after m i x i n g . T h e air s u p p l y w a s shut off, and the D O concentration was recorded and registered b y a c o m p u t e r for 5 minutes. T h e air s u p p l y was turned o n again and D O concentration was m a i n t a i n e d b e t w e e n 4-6 m g 0  L " . O U R was 1  2  measured at 10-minute intervals u n t i l a sharp decease i n rate was observed. T h e m a x i m u m specific g r o w t h rate was c a l c u l a t e d f r o m the slope (jU  max  - b^) o f the relative O U R versus t i m e  a c c o r d i n g to the E q u a t i o n 2.40, u s i n g the &H v a l u e determined p r e v i o u s l y : ln[r  0 2  (t)l r  02  (to)] = (//  max  - b )-t  (2.40)  H  T h e temperature effect was corrected to a reference temperature o f 2 0 ° C b y E q u a t i o n 2 . 3 1 , w i t h a 0 o f 1.094 for aerobic g r o w t h o f heterotrophic b i o m a s s ( G r a d y et al., 1999).  T a b l e 4.5 Initial e x p e r i m e n t a l c o n d i t i o n s for tests o f the m a x i m u m s p e c i f i c g r o w t h rate o f heterotrophic b i o m a s s Biomass Test date  4/11/02 4/12/02  Sources  5/10/02 5/13/02 5/14/02 5/15/02  Reactor  Nitrification  C O D : b i o m a s s ratio  volume  inhibitor formula  (mg C O D L ) (mg C O D L'y'  (L)  2533  UCT  2.6  2  Yes  17  MEBPR  2  2  Yes  17  UCT  2.6  2  Yes  17.5  1.9 2.9  2  Yes  17.5  2  Yes  18  UCT  3.9  2  Yes  19  MEBPR 4/19/02  C e n t r i f u g e d influent  MEBPR  (0.16g)(300 mL)"  Temperature (°C) 1  UCT  6.3  2  Yes  17.5  MEBPR  9.8  2  Yes  17  UCT  4.8  2  Yes  20.5  MEBPR  4.7  2  Yes  21  UCT  3.9  2  Yes  20  MEBPR  3.8  2  Yes  20.5  5/16/02  UCT  5.2  2  Yes  17  5/22/02  UCT  4.5  2  Yes  17  UCT  4.4  2  Yes  16.5  MEBPR  4.7  2  Yes  16.5  5/28/02  80  Wastewater  characterization  D e t e r m i n a t i o n o f the r e a d i l y biodegradable substrate, S F In this study, t w o methods were used for the determination o f r e a d i l y b i o d e g r a d a b l e substrate. O n e w a s the aerobic batch m e t h o d d e s c r i b e d b y E k a m a et al. (1986) a n d K a p p e l e r a n d G u j e r (1992); the other o n e w a s a r a p i d p h y s i c a l - c h e m i c a l assay d e v e l o p e d b y M a m a i s et al. (1993).  a). A e r o b i c b a t c h m e t h o d A predetermined amount o f wastewater s a m p l e w a s m i x e d w i t h a k n o w n amount o f b i o m a s s a c c o r d i n g to a n i n i t i a l C O D ( m g L " ) : V S S ( m g L " ) ratio o f a r o u n d 0.1 to 0.2. T h e 1  1  m i x t u r e w a s p l a c e d into a respirometer i n a temperature-controlled c h a m b e r to m a i n t a i n the reactor contents at the temperature o f the p i l o t plant reactors. T h e contents w e r e aerated u s i n g a r o u n d stone diffuser a n d stirred c o n t i n u o u s l y u s i n g a magnetic m i x e r a n d a m i x i n g bar. T a b l e 4.6 s h o w s the e x p e r i m e n t a l c o n d i t i o n s for the aerobic batch m e t h o d .  T h e O U R test started i m m e d i a t e l y after s a m p l e m i x i n g , a n d the air s u p p l y w a s turned off. T h e change i n D O concentration w a s m o n i t o r e d for 5 minutes o r u n t i l the D O concentration reached 1 m g 0  L " . A f t e r w a r d s , the air s u p p l y w a s turned o n , a n d the D O concentration w a s 1  2  m a i n t a i n e d b e t w e e n 4 to 6 m g 0  L " . T h e O U R w a s measured several times at 10-minute 1  2  intervals u n t i l a distinct slope f o l l o w e d b y a flatter slope o f O U R w a s o b s e r v e d . T h e area under the O U R c u r v e c o r r e s p o n d i n g to the s o l u b l e biodegradable C O D c o n c e n t r a t i o n o f the influent wastewater w a s calculated a c c o r d i n g to E q u a t i o n 2 . 4 1 .  81  Table 4.6 Initial e x p e r i m e n t a l c o n d i t i o n s for r e a d i l y biodegradable C O D tests (batch method) Test date  M i x e d liquor V S S  Influent C O D  (mgU )  (mgU )  C O D / V S S ratio i n reactors  Feb-21-02  7555  371  0.02  Apr-8-02  5550  396  0.11  1.5 2.0  Apr-22-02  5050  445  0.08  1.5  5050  445  0.08  2.0  5175  446  0.129  1.5  5175  446  0.129  2.0  1  Apr-30-02  1  Reactor volume (L)  b). P h y s i c a l - c h e m i c a l m e t h o d T h e influent and effluent samples f r o m the U C T and M E B P R processes w e r e f l o c c u l a t e d b y an a d d i t i o n o f 100 g L " o f z i n c sulfate s o l u t i o n , and m i x e d v i g o r o u s l y for a p p r o x i m a t e l y 1 1  m i n u t e . T h e p H o f each s a m p l e was then adjusted  to 10.5 w i t h a 6 M s o d i u m h y d r o x i d e  s o l u t i o n . S a m p l e s were settled for a few minutes to separate the supernatant f r o m the c o l l o i d a l matter. T h e supernatant w a s w i t h d r a w n w i t h a syringe from each s a m p l e and filtered t h r o u g h 0.45 u i n m e m b r a n e  filters to r e m o v e a l l o f the flocculated m a t e r i a l , and the filtrates  were  measured as s o l u b l e C O D . Therefore, the v a l u e o f s o l u b l e biodegradable C O D w a s determined based o n the difference b e t w e e n the test results o f the influent and effluent samples.  The  concentration o f r e a d i l y biodegradable C O D , SF, was calculated a c c o r d i n g to E q u a t i o n 2.42.  D e t e r m i n a t i o n inert s o l u b l e o r g a n i c matter. Si In the present study, the s o l u b l e inert C O D w a s determined b y the procedures o f L e s o u e f et al. (1992). T h e unfiltered wastewater samples w e r e aerated for over 8-10 days, and s o l u b l e C O D was a n a l y z e d p e r i o d i c a l l y u n t i l the final s o l u b l e C O D was reached. T h e c o n c e n t r a t i o n o f Si was calculated from the s o l u b l e inert C O D at the end o f the tests b y a s s u m i n g that a l l o f the s o l u b l e b i o d e g r a d a b l e C O D h a d been u t i l i z e d . T h e final s o l u b l e C O D w a s c o n s i d e r e d to be the inert s o l u b l e C O D i n the influent ( L e s o u e f et al., 1992).  82  A v o l u m e o f 500 m L unfiltered wastewater s a m p l e w a s p l a c e d i n a 1-L reactor. T h e reactor contents were stirred c o n t i n u o u s l y b y u s i n g a laboratory stir plate and a m a g n e t i c stir bar, and the air was s u p p l i e d b y u s i n g a r o u n d stone diffuser through the reactor. A n i n i t i a l soluble  C O D was  determined  as  described  i n the  heterotrophic  growth  yield  test.  A  predetermined amount o f b i o m a s s from the aerobic z o n e o f the M E B P R process was seeded a c c o r d i n g to an i n i t i a l V S S ( m g L ) : C O D ( m g L ' ) ratio o f 1:50-100 i n each reactor, and the 1  -  i n i t i a l total C O D w a s determined. T h e tests w e r e carried out i n p a r a l l e l for m o r e than 10 days. S a m p l e s f r o m the reactors were measured as s o l u b l e C O D p e r i o d i c a l l y u n t i l a final s o l u b l e C O D was observed. T h e s o l u b l e inert C O D o f the influent was d e t e r m i n e d as the final s o l u b l e inert C O D after aeration. T h e i n i t i a l e x p e r i m e n t a l c o n d i t i o n s are s h o w n i n T a b l e 4.7.  T a b l e 4.7 Initial e x p e r i m e n t a l c o n d i t i o n s for the inert s o l u b l e C O D tests Reactor volume  Initial s o l u b l e C O D / b i o m a s s (mg C O D L " ) (mg C O D L" )" 1  1  1  pH  Temperature  Test date Oct-12-01  (mL)  50  500  7  (°C) 16  50  500  7  16  50  500  7 '  16  50  500  7  16  50  500  8  13  Feb-15-02  50  500 500  7.8  70  8  13 13  Mar-01-02  70  500  8  13  100  500  8  13  100  500  8  13  80  500  7.9  15  Oct-25-01  Feb-25-02  Apr-08-02 Apr-24-02  D e t e r m i n a t i o n o f inert particulate matter, X i T h e procedure o f L e s o u e f et al. (1992) w a s used to estimate the inert particulate C O D i n the present study. A sample o f influent wastewater was filtered t h r o u g h a 0.45 i m m e m b r a n e filter to r e m o v e any suspended matter, and a v o l u m e o f 500 m L filtrate w a s stirred and aerated i n a 1-L reactor. A n i n i t i a l s o l u b l e C O D w a s determined as d e s c r i b e d i n the heterotrophic  83  g r o w t h y i e l d test. A p r e d e t e r m i n e d amount o f b i o m a s s from the aerobic z o n e o f the M E B P R process was seeded a c c o r d i n g to an i n i t i a l V S S ( m g L " ) : C O D ( m g L" ) ratio around 1:50-100 1  1  i n each reactor, and an i n i t i a l total C O D was then determined. A t the same t i m e , a non-filtered s a m p l e was r u n i n p a r a l l e l for 8-10 days. S a m p l e s from the t w o reactors were a n a l y z e d as s o l u b l e and total C O D p e r i o d i c a l l y u n t i l a final s o l u b l e C O D was observed. T h e inert particulate C O D o f the influent was d e t e r m i n e d b y the difference b e t w e e n the final total C O D o f the n o n filtered s a m p l e and the b i o m a s s g r o w t h , m i n u s the s o l u b l e inert C O D . T h e i n i t i a l e x p e r i m e n t a l c o n d i t i o n s are l i s t e d i n T a b l e 4.8.  T a b l e 4.8 Initial e x p e r i m e n t a l c o n d i t i o n s for the particulate inert C O D tests Initial s o l u b l e C O D : b i o m a s s ratio  Reactor volume  (mg C O D L ' ) (mg C O D L )  pH  Temperature  Test date  (°C) 16  Oct-12-01  (mL)  1  50  500  50  500  50  500 500  100 100 80  7 7  16  7  16  8  13  500  8  13  500  7.9  15  Oct-25-01 Apr-08-02 Apr-24-02  Determination o f s l o w l y biodegradable C O D In the present study, the s l o w l y b i o d e g r a d a b l e C O D , X s , was determined b y C O D m a s s b a l a n c e f o l l o w i n g the a p p r o a c h o f H e n z e et al. (1987). X s was found as the difference b e t w e e n the total C O D and the other X  s o  = COD™ - S  A 0  fractions.  - S o- S F  l 0  - X  (2.44)  I 0  W h e r e the s l o w l y b i o d e g r a d a b l e o r g a n i c matter i n c l u d e d the b i o m a s s  Conventional chemical analysis Chemical oxygen demand  84  fraction.  S a m p l e s w e r e a n a l y z e d for C O D a c c o r d i n g to Standard M e t h o d s ( A P H A et al,  1998).  T h e C O D analysis f o l l o w e d the c h e m i s t r y procedure o u t l i n e d i n m e t h o d 5 2 2 0 D o n a H A C H DR/2000  spectrophotometer.  Suspended solids T h e total and v o l a t i l e suspended s o l i d s were measured b y procedures 2 5 4 0 D and 2 5 4 0 E i n Standard M e t h o d s ( A P H A et al,  1998).  O x y g e n uptake rate O x y g e n uptake rate tests were carried out i n respirometers i n p a r a l l e l to increase the, a c c u r a c y o f the test results. D u r i n g O U R tests, the air s u p p l y was shut o f f and the decrease i n d i s s o l v e d o x y g e n w a s recorded. T h e D O concentrations were m o n i t o r e d o n a d i s s o l v e d o x y g e n meter ( Y S I M o d e l 54). T h e D O change was l o g g e d every second. S i n c e the respirometer w a s airtight, it w a s assumed that the actual respiration rate o f the tested b i o m a s s at any t i m e d u r i n g the b a t c h  test d i d not  depend  o n o x y g e n input. T h e gradient  o f the  dissolved oxygen  concentration therefore represented the actual o x y g e n uptake rate o f the b i o m a s s .  V o l a t i l e fatty acids V o l a t i l e fatty acids ( V F A s ) are c l a s s i f i e d as water-soluble fatty acids that c a n b e d i s t i l l e d at atmospheric pressure.  T h e y i n c l u d e water-soluble fatty acids w i t h up to s i x c a r b o n atoms.  T h e concentration o f v o l a t i l e acids, S A c a n be determined b y m e a s u r i n g V F A s u s i n g a gas c h r o m a t o g r a p h i c m e t h o d . In the present study, V F A s tests f o l l o w e d the procedures i n G C B u l l e t i n 751 p r o v i d e d b y S u p e l c o Inc. T h e preserved s a m p l e was injected into a v i a l and d i r e c t l y a n a l y z e d b y gas chromatography ( G C ) . S a m p l e s w e r e a n a l y z e d i n triplicate.  85  N i t r o g e n ( N H / , N Q + N O ? , and T K N ) and p h o s p h o r u s ( P Q " and T P ) 3  3  4  A m m o n i a ( N H / ) , nitrite and nitrate ( N O x ) and p h o s p h o r u s ( P O 4 ) i n the 3  filtrate  of  samples were a n a l y z e d , u s i n g a L a c h a t Q u i c k c h e m 8 0 0 0 A u t o m a t e d I o n A n a l y z e r a n d a L a c h a t X Y Z sampler, a c c o r d i n g to the Standard M e t h o d s , o r Q u i c k c h e m m e t h o d s as the f o l l o w i n g : N H 4 - N , Standard M e t h o d s 4 5 0 0 - N H - H f l o w i n j e c t i o n analysis (proposed), phenolate m e t h o d , +  3  measured i n the range o f 2.0-100 m g N L /  1  at 6 3 0 n m w a v e l e n g t h ; nitrite and nitrate ( N O ) , x  Standard M e t h o d s 4 5 O O - N O 3 - I C a d m i u m r e d u c t i o n f l o w i n j e c t i o n m e t h o d (proposed), m e a s u r e d i n the range o f 1-100 m g N L "  at 5 2 0 n m w a v e l e n g t h ; and phosphate ( P 0 " - P ) , Q u i c k c h e m  1  3  4  m e t h o d N o . 10-115-01 - 1 - Z (ascorbic a c i d m e t h o d , m e a s u r e d i n the range o f 0.5-50.00 m g P L "  1  at 880 n m w a v e l e n g t h ) .  T o measure T K N and T P , 5 m L o f each s a m p l e was put into a 7 5 - m L d i g e s t i o n tube for digestion. A series o f standards, w h i c h i n c l u d e d b l a n k s , 2 0 0 , 4 0 0 , 800 and 1000 ( | l g N + | i g P ) were prepared w i t h a N O / P C » 4 7 N H 4 3  +  x  standard s o l u t i o n . T w o r o c k s and 10 m L o f d i g e s t i o n  reagent w e r e added into each s a m p l e and standard. T h e samples, b l a n k s a n d standards w e r e then digested w i t h T K N / T P a c i d i c d i g e s t i o n reagent (made o f 2 0 0 m L o f H 2 S 0  4  and 134 g K2SO4 i n  1 L o f d i s t i l l e d water) at 1 4 0 ° C for 3.5 hours, and then at 3 6 0 ° C for a d d i t i o n a l 3.5 hours. A f t e r these digested samples and standards were c o o l e d d o w n to the r o o m temperature, they w e r e m i x e d w i t h d i s t i l l e d water to the top o f testing tubes and preserved at the r o o m temperature before  tests. T h e preserved T K N samples  were  a n a l y z e d for N H 4 - N  a c c o r d i n g to  +  the  Q u i c k c h e m m e t h o d N O . 1 0 - 1 0 7 - 0 6 - 2 - D . T P samples w e r e a n a l y z e d for PO4 " a c c o r d i n g to the 3  Quickchem method N O . 10-115-01-1-H.  86  4.4 Data Quality Assurance and Control (QA/QC)  The  Q A / Q C p r o g r a m i n c l u d e d duplicates i n m o s t o f the runs a n d replicate runs. F o r  e x a m p l e , t w o respirometers w e r e operated w i t h i d e n t i c a l e x p e r i m e n t a l c o n d i t i o n s i n m a x i m u m specific g r o w t h rate test i n A p r i l temperature,  11, 2002 (e.g. i n i t i a l s o l u b l e C O D : b i o m a s s ratio, p H ,  n i t r i f i c a t i o n inhabitation, aeration, m i x i n g , and the s a m p l i n g technique). T h e  acceptable measurements w e r e then averaged for final report and analysis. T h e measurements o f most parameters s u c h as V F A , N H / , N O x , PO4 ", T K N a n d T P i n c l u d e d c o n t r o l a n d s a m p l e 3  triplicates.  4.5 Statistical Analyses  Statistical  analyses  included  c a l c u l a t i o n s o f the  mean,  standard  deviation on  the  measured results o f p r e v i o u s experiments. T h e e x p e r i m e n t a l results i n the present study w e r e also reported b y u s i n g 9 5 % confidence intervals.  87  CHAPTER V  Results and Discussion  In this chapter the e x p e r i m e n t a l results are presented and d i s c u s s e d to p r o v i d e an insight o f g r o w t h y i e l d , d e c a y coefficient and m a x i m u m s p e c i f i c g r o w t h rate o f heterotrophic b i o m a s s i n the M E B P R  process b y c o m p a r i n g w i t h the results  obtained f r o m  the U C T process.  M e a n w h i l e , the c o m p o s i t i o n s o f the wastewater are also presented to p r o v i d e the r e q u i r e d i n f o r m a t i o n for further c o m p u t e r s i m u l a t i o n .  5.1 Heterotrophic Growth Yield  H e t e r o t r o p h i c g r o w t h y i e l d is a m o s t important s t o i c h i o m e t r i c parameter i n the m o d e l s o f A S M . It p l a y s an important r o l e i n p r e d i c t i o n o f sludge p r o d u c t i o n and o x y g e n d e m a n d i n a wastewater treatment process. A n accurate e s t i m a t i o n o f this parameter is v e r y important.  F i g u r e 5.1 is a t y p i c a l c u r v e o b s e r v e d d u r i n g heterotrophic g r o w t h y i e l d tests. A t the b e g i n n i n g o f the test, a s m a l l amount o f b i o m a s s g r e w r a p i d l y o n a large amount o f substrate and the amount o f b i o m a s s f o r m e d was i n the absence o f decay. T h i s gave an accurate estimate o f Y . T o achieve this result, care was taken to set the ratio o f the i n i t i a l s o l u b l e C O D i n the H  s a m p l e to the  seeded  biomass  concentration to as h i g h a v a l u e as p o s s i b l e (100:1)  r e c o m m e n d e d b y G r a d y et al. (1999).  88  as  -v  0  1  24  1  1  1  1  1  43  72  96  120  144  Time (hr.) - * — S o l u b l e C O D — a — P a r t i c u l a t e C O D — ± — P a r t i c u l a t e C O D formed  F i g u r e 5.1 C O D v a r i a t i o n i n a heterotrophic g r o w t h y i e l d test for the M E B P R process ( A p r i l 8, 2 0 0 2 )  D u r i n g the first 24 hours, e v e n t h o u g h the o b s e r v e d y i e l d ( Y b ) w a s h i g h , substrate 0  s  r e m o v a l w a s i n c o m p l e t e , as s h o w n i n F i g u r e 5.1 and 5.2, and little excess b i o m a s s synthesized.  H o w e v e r , at l o n g e r times, m o r e excess b i o m a s s w a s generated  because  increased g r o w t h a n d substrate r e m o v a l , a l l w i t h a r e l a t i v e l y h i g h o b s e r v e d y i e l d . A f t e r  was of the  i n i t i a l g r o w t h phase, a decrease i n b i o m a s s g r o w t h w a s o b s e r v e d after 72 hours o f testing; less excess b i o m a s s w a s o b s e r v e d because m o r e o f it w a s o x i d i z e d through decay, m a i n t e n a n c e energy needs, etc. A s the t i m e w a s increased further, the substrate c o n c e n t r a t i o n b e c a m e s m a l l relative to the i n i t i a l c o n c e n t r a t i o n so that the difference o f t h e m b e c a m e essentially constant. T h i s o c c u r r e d at about 72 h r for the values used to generate this graph. A further increase i n testing t i m e increased the i m p o r t a n c e o f decay, c a u s i n g Y b a n d the net p r o d u c t i o n o f b i o m a s s 0  s  to d e c l i n e as s h o w n b y the d e c r e a s i n g C O D b e t w e e n 72 h r a n d 92 h r i n F i g u r e 5.1. B e y o n d the p o i n t o f 92 hr, s l i g h t l y increased particulate C O D and s o l u b l e C O D w e r e o b s e r v e d . T h i s w a s l i k e l y because  s o l u b l e C O D w a s released due to b i o m a s s decay and b i o m a s s re-grew b y  u t i l i z i n g the s o l u b l e C O D as w e l l as b y a c c u m u l a t i n g b i o m a s s debris i n the reactor. 89  Soluble COD removed (mg COD/L)  F i g u r e 5.2 D e t e r m i n a t i o n o f the heterotrophic g r o w t h y i e l d o f M E B P R process ( A p r i l 8, 2 0 0 2 )  T h e total b i o m a s s concentration i n the test w o u l d not go to zero as the t i m e w a s increased, because substrate was c o n t i n u a l l y b e i n g r e - s u p p l i e d b y b i o m a s s death and l y s i s , w h i c h caused the fluctuation o f s o l u b l e C O D and b i o m a s s concentration as s h o w n i n F i g u r e 5.1 as w e l l as i n other Y H tests. H o w e v e r it d i d approach a l i m i t , although the active b i o m a s s b e c a m e quite s m a l l as discussed i n the literature ( G r a d y et al,  1999).  It was s h o w n that o n l y w h e n the testing t i m e was v e r y short and the b i o m a s s was g r o w i n g v e r y r a p i d l y w o u l d most substrate be u s e d for g r o w t h , a l l o w i n g the o b s e r v e d y i e l d to approach the true g r o w t h y i e l d . F o r a l l other situations, a significant amount o f energy must b e e x p e n d e d for maintenance and other purposes associated w i t h decay, thereby l o w e r i n g the o b s e r v e d y i e l d . T h e data i n F i g u r e 5.1 were c a r e f u l l y selected to o m i t the data b e y o n d 72 h r for p l o t t i n g the curve i n F i g u r e 5.2 to determine the v a l u e o f heterotrophic g r o w t h y i e l d .  90  A l l o f the test results are s h o w n i n T a b l e 5.1. T h e g r o w t h y i e l d o f heterotrophic b i o m a s s as f o u n d to be (at 9 5 % o f c o n f i d e n c e l e v e l ) : MEBPR  0.50 ( ± 0.16) k g C O D ( k g C O D ) " @ 2 0 ° C  UCT  0.59 ( ± 0.28) k g C O D ( k g C O D ) "  n = 9  1  1  @ 20°C  n=10  Table 5.1 G r o w t h y i e l d test results Date Oct-12-01  Y  H  (UCT)  (MEBPR)  R  2  (%)  Temperature ( ° C )  76 80  98 95  0.42  87  0.37  68 94  13 13  95  0.51  0.80  0.46 0.62  99 94  13  86 . 97  97  13 13  0.37  96  0.52  96  15  0.63  79  0.47  92  15  0.72  Mar-01-02  0.79 0.50  Apr-08-02  0.53 0.62  s  H  0.53  Feb-25-02  Sample mean  Y  0.62  0.41  88 97  0.56  Apr-24-02  R " (%)  13  0.50 0.08  0.59 0.14  Note: the units of Y  H  16 16  are kg COD (kg COD)"  1  S l i g h t l y s m a l l e r g r o w t h y i e l d s w e r e observed for the M E B P R process c o m p a r e d w i t h the U C T process i n m o s t cases, although s o m e results w e r e s i m i l a r . T h i s is i n agreement w i t h other research. Stephenson et al. (2000) i n d i c a t e d that the o v e r a l l g r o w t h y i e l d s for M B R s are s i m i l a r to those f r o m c o n v e n t i o n a l m u n i c i p a l wastewater treatment systems, t y p i c a l l y b e t w e e n 0.1 to 0.35 k g M L S S k g C O D " ( T a b l e 5.2). H o w e v e r , i n s o m e cases the g r o w t h y i e l d has b e e n 1  reported to be c l o s e to, o r greater than, i n c o n v e n t i o n a l processes ( C h a i z e and H u y a r d , 1 9 9 1 ; M u r a k a m i et al., 2 0 0 0 ) . C a n a l e s et al. (1994) reported that g r o w t h y i e l d for an M B R treating d o m e s t i c wastewater w a s 0.56 k g k g " C O D under n o r m a l operating c o n d i t i o n s . R a m a n a t h a n 1  and G a u d y (1971) and G r a d y et al. (1999) reported that Y H for aerobic heterotrophs d e g r a d i n g carbohydrates w a s i n the range o f 0.48-0.72 k g k g " C O D . K a p p e l e r a n d G u j e r ( 1 9 9 2 ) suggested 1  91  a y i e l d o f 0.67 k g kg" C O D for d o m e s t i c wastewater based o n b a t c h tests. S t r o t m a n n et al (1999) reported a y i e l d range o f 0.7-0.87 k g k g " C O D for a n activated sludge system. I n A S M 2 , 1  Y  ranges f r o m 0.46 to 0.69 k g k g " C O D , and the t y p i c a l v a l u e r e c o m m e n d e d i n A S M 2 i s 0.63 1  H  k g k g " C O D for m u n i c i p a l wastewater. T h e g r o w t h y i e l d results f r o m this study agree w e l l w i t h 1  the reported values i n literature.  T a b l e 5.2 R e p o r t e d and tested g r o w t h y i e l d values for m e m b r a n e bioreactors Wastewater  S R T (day)  Y  (kg k g ' C O D )  Reference  1  H  Municipal  50  0.2  B u i s s o n et al., 1998  Municipal  25  Municipal Urban  50  0.26 0.2  T r o u v e et al, 1994 B u i s s o n et al, 1998  10  0.34  B o u h a b i l a et al, 1998  Urban  20  0.2  B o u h a b i l a et al, 1998  Municipal Municipal  20  0.1 0.25  C o t e etal, 1997  50  Domestic  -  0.6  Domestic  100  Municipal  -  0.56 0.2  F a n e r a / . , 1998 M u r a k a m i etal,  1999  C h a i z e and H u y a r d , 1991  Municipal 17-25 0.50 Note: source of this table is from Stephenson et al. (2000) and the present study.  C o t e etal, 1 9 9 7 Present study  P o t e n t i a l reasons for the s l i g h t l y l o w e r g r o w t h y i e l d i n the M E B P R process versus the U C T process are discussed here. O n e reason m i g h t b e the different o r g a n i s m species present i n the t w o processes, w h i c h c a n affect the g r o w t h y i e l d (Stephenson et al, 2 0 0 0 ) , a n d the h i g h e r forms o f m i c r o o r g a n i s m s that have been f o u n d i n M B R s  ( C i c e k et a l . , 1999; G h y o o t a n d  Verstraete, 1999), since g r a z i n g m i c r o o r g a n i s m s c o n s u m e bacteria as f o o d , c a u s i n g a decreased Y . T h e other e n v i r o n m e n t a l c o n d i t i o n s c o u l d also cause this result s u c h as the h i g h shear forces for i m p r o v i n g mass transfer and m i x i n g i n M B R m a y cause breakage o f c e l l s ( M e i j e r et al, 1993; S h i m i z u et al, 1994; W i s n i e w s k i and G r a s m i c k , 1997; K i m et al, 2 0 0 1 ) .  92  A s i m i l a r p h e n o m e n o n was f o u n d i n the research o f G h y o o t and Verstraete (1999) w h o noted h i g h e r concentrations o f p r o t o z o a , p a r t i c u l a r l y flagellates and free ciliates, i n a submersed m e m b r a n e M B R w h e n c o m p a r e d to an activated sludge system operating at the same sludge age. It has been f o u n d that p r o t o z o a and rotifers p l a y c r u c i a l roles i n c o n s u m i n g particulate organics, i n c l u d i n g s c a v e n g i n g o f bacteria. O t h e r larger b i o l o g i c a l species s u c h as  nematode  w o r m s and insect larvae m a y contribute to the c o n s u m p t i o n o f particulate organic matter ( G r a d y etal,  1999).  It has been f o u n d that not o n l y the species o f o r g a n i s m affects Y (Payne, 1970), but also that the nature o f the substrate influences the y i e l d ( H a d i l i p e t r o u et al., 1964). A l t h o u g h the purpose o f this research w a s not to investigate the factors affecting Y  H  , it is essential to  understand their i n f l u e n c e d u r i n g e x p e r i m e n t a l tests and to ensure an accurate estimate o f Y H . It is also important i n the interpretation o f the test results. T h e g r o w t h environment, i n c l u d i n g m e d i a c o m p l e x i t y , type o f t e r m i n a l electron acceptor, p H and temperature w i l l a l l affect Y ( H e i j n e n and v a n D i j k e n , 1992). G r a d y et al. (1999) reported that the y i e l d has a m a x i m u m v a l u e around p H 7 because that is o p t i m a l for m a n y p h y s i o l o g i c a l functions. Temperature also affects Y ( M u c k and G r a d y , 1974); h o w e v e r , because o f the uncertainty associated w i t h the i m p a c t o f temperature o n Y , most engineers assume it to be independent o f temperature o v e r the n o r m a l p h y s i o l o g i c a l temperature range.  It is reasonable to predict that the l o w e r Y H w o u l d l e a d to less sludge p r o d u c t i o n i n the MEBPR  process.  L u b b e c k e et al.  (1995) and D a v i e s et al.  (1998) observed l o w sludge  p r o d u c t i o n i n M B R s , and they reported that about 7 0 % less sludge p r o d u c t i o n was generated i n an M B R than i n a c o n v e n t i o n a l activated sludge system ( C A S ) at the same space l o a d i n g . G h y o o t and Verstraete (1999) reported the sludge y i e l d o f an M B R system w a s 2 0 - 3 0 % l o w e r 93  than that o f a C A S system for a s i m i l a r c o n d i t i o n s o f S R T a n d o r g a n i c l o a d i n g rate, d u e to increased quantities o f predators, such as protozoa a n d metazoa i n the M B R .  In the present study, it w a s noted that the difference i n Y H values obtained f r o m the t w o processes w a s not as large as the range reported i n the literature. T h e reasons for the decreased Y  H  s h o u l d be investigated further for better understanding o f the m i c r o b i a l activities i n the  M E B P R process..  5.2 Heterotrophic Decay Rate  T h e heterotrophic decay coefficient is one o f the most important k i n e t i c coefficients i n A S M 2 , a n d it c a n b e u s e d to predict the sludge p r o d u c t i o n and o x y g e n d e m a n d o f a n activated sludge process. A change i n bH has a large effect o n the predicted b i o m a s s concentration. A h i g h decay coefficient means that the bioreactor w i l l b e m o r e efficient i n o x i d i z i n g the substrate to carbon d i o x i d e , i.e. decreased b i o m a s s p o p u l a t i o n due to b i o m a s s d e c a y i n absence o f substrate; consequently, the b i o m a s s concentration w i l l be l o w a n d the o x y g e n requirement w i l l b e h i g h . T h e v a l u e o f the d e c a y coefficient i s v e r y dependent o n b o t h the species o f o r g a n i s m s i n v o l v e d and the substrates o n w h i c h they are g r o w i n g . T h i s effect w i l l b e e s p e c i a l l y p r o n o u n c e d at l o n g S R T s , therefore, it i s v e r y important to evaluate this parameter for a p a r t i c u l a r treatment system.  In the present study, the traditional decay coefficient w a s evaluated b y the m e t h o d p r o p o s e d b y E k a m a et al. (1986). S l u d g e samples f r o m the M E B P R a n d U C T processes w e r e aerated i n t w o 2 - L respirometers i n p a r a l l e l to investigate the differences b e t w e e n the t w o processes i n t e r m o f decay coefficients. N i t r i f i c a t i o n i n h i b i t o r ( F o r m u l a 2 5 3 3 ) w a s added to  94  prevent any p o s s i b l e interference i n d u c e d b y n i t r i f i c a t i o n , and p H w a s c o n t r o l l e d a r o u n d 7 . 5 b y a d d i n g a l k a l i n i t y . O U R w a s measured over 1 5 days.  F i g u r e 5.3 and F i g u r e 5 . 4 s h o w t y p i c a l results f r o m b a t c h decay tests u s i n g b i o m a s s f r o m the M E B P R a n d U C T processes. D u r i n g the endogenous phase, there w a s no external input o f substrates. T h e b i o m a s s w a s left o n its o w n and a l l the substrate w a s i n i t i a l l y generated through the processes decreased  slowly  and  o f decay and h y d r o l y s i s . B i o m a s s concentration a n d r e s p i r a t i o n rate continuously,  while  inert  particulate  matter  and  biomass  debris  accumulated.  T h e detailed results o f these tests are l i s t e d i n T a b l e 5.3 and A p p e n d i x 2 . B e c a u s e the decay coefficient w a s estimated at a v a r i o u s temperatures i n different seasons, the tests results w e r e adjusted b y the A r r h e n i u s equation. A s m a l l v a l u e o f 9 has been used for the effect o f temperature o n decay, w i t h a v a l u e o f 1 . 0 2 9 ( D o l d et al., 1 9 8 0 ) . T h i s v a l u e w a s u s e d to correct the m o d e l decay coefficient, Z?H, to a temperature o f 2 0 ° C w i t h E q u a t i o n 4 . 1 9 .  6tf=&2o'*e (T  T20)  (4.19)  95  y = -0.0871X + 7.0818 R = 0.96 2  7 6 X O J  5  4 3 2 1 0 -i—i—i—i—i—i—i—i—i—i 1—i—i—i—i—i—i—i—i—i 0 1 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 1 4 1 5 1 6 1 7 1 8 1 9 T i m e (day)  F i g u r e 5.3 H e t e r o t r o p h i c decay coefficient o f the M E B P R process (June 12, 2 0 0 2 , B )  y = -0.1451x +4.5971 R = 0.95 2  0  1  2  3  4  5  6  7  8  9  10  11  12 13  14  15 16  Time (day)  F i g u r e 5.4 H e t e r o t r o p h i c decay coefficient o f the U C T process (June 12, 2 0 0 2 , A )  96  A s r e v i e w e d i n C h a p t e r II, most studies h a v e used the traditional decay concept to quantify the impacts o f maintenance, etc. o n m i c r o b i a l systems, h o w e v e r , b i o m a s s decay i n A S M 2 was described b y the l y s i s : r e g r o w t h concept instead; so the traditional decay coefficient (b)  determined b y the traditional approach was converted to the m o d e l decay coefficient (b)  using Equation 4.13: Z> = M [ l - Y ( l - / b ) ]  W h e r e the v a l u e offo  (4-13)  w a s assumed to be 0.08.  T a b l e 5.3 R e s u l t s o f traditional and m o d e l decay coefficient for heterotrophic b i o m a s s @ 2 0 ° C Test data  T r a d i t i o n a l decay rate bn (day" ) M o d e l decay rate b UCT 0.09 0.15 0.15 0.16 0.14 0.03  May-7-02 May-24-02 June-12-02 Sample mean  s  MEBPR 0.12 0.21 0.12 0.09 0.13 0.04  H  (day" ) p H  UCT  MEBPR  0.20 0.34 0.34  0.22 0.33 0.23 0.17 0.24  0.36 0.31 0.06  7.5 7.5 7.5 7.5  0.06  T h e traditional decay coefficient o f heterotrophic b i o m a s s was found to be (at the 9 5 % o f confidence): MEBPR  b  H  UCT  b  H  =0.13 ( ± 0 . 0 8 ) d a y  @20°C  n = 4  = 0.14 ( ± 0.06) day" @ 2 0 ° C  n = 4  1  1  Therefore, the m o d e l decay coefficient o f heterotrophic b i o m a s s was found to be (at the 9 5 % o f confidence): MEBPR  b = 0.24 ( ± 0 . 1 2 ) day" @ 2 0 ° C  n = 4  UCT  b  n = 4  1  H  = 0.31 ( ± 0 . 1 2 ) day" @ 2 0 ° C 1  H  97  It is s h o w n i n T a b l e 5.3 that the bn obtained for the t w o processes are s i m i l a r . T h e m o d e l decay coefficient was 0.17-0.33 day" w i t h a m e a n o f 0.24 day" for the M E B P R process, and 1  0.2-0.36 day" w i t h a m e a n v a l u e o f 0.31 day 1  1  1  for the U C T process at 2 0 ° C . It c a n be f o u n d that  either the ranges o f the t w o data sets or the v a r i a t i o n o f the t w o distributions are v e r y s i m i l a r .  R e s u l t s f r o m this study fell w i t h i n the range o f the reported values i n the literature. T h e s a m p l e average v a l u e o f traditional decay coefficient b n was 0.14 day" for the U C T process and 1  0.13 day" for the M E B P R process at 2 0 ° C . S i m i l a r results were found f r o m the literature as 1  D o l d and M a r a i s (1986) r e v i e w e d the literature c o n c e r n i n g b a and c o n c l u d e d that i n aerobic and a n o x i c wastewater treatment systems a t y p i c a l v a l u e for heterotrophic b i o m a s s d e c a y is 0.24 day" . R e p o r t e d values o f b 1  v a r y w i d e l y , r a n g i n g f r o m 0.05 day" for d o m e s t i c sewage i n the 1  H  U S A to 1.6 day" for s o m e f o o d - p r o c e s s i n g wastes ( H e n z e et al., 1987). H e n z e et al. (1987) 1  reported a t y p i c a l m o d e l decay coefficient v a l u e for m u n i c i p a l wastewater o f 0.62 day"  1  in  A S M 1 . M e t c a l f and E d d y (1991) suggested a t y p i c a l decay coefficient o f 0.05-0.06 day"  at  1  2 0 ° C for c o n v e n t i o n a l activated sludge processes and aerobic processes. K a p p e l e r and G u j e r (1992) suggested a v a l u e o f 0.4 day" . W e n et al. (1999) reported b 1  to be 0.08 day" at 3 0 ° C i n 1  H  a c e r a m i c m e m b r a n e side-stream aerobic bioreactor treating r a w wastewater. F a n et al. (1996) reported 0.05 day" for an M B R at 3 0 ° C . T h e m o d e l decay coefficient r e c o m m e n d e d i n A S M 2 is 1  0.4 day" at 2 0 ° C . It i s this w i d e range that l e d to the r e c o m m e n d a t i o n that the d e c a y coefficient 1  be m e a s u r e d for each wastewater treatment situation under c o n s i d e r a t i o n ( H e n z e et al., 1987).  98  5.3 Maximum Specific Growth Rate of Heterotrophic Biomass  T h e m a x i m u m specific g r o w t h rate o f heterotrophic  b i o m a s s , (XH, determines  the  m a x i m u m o x y g e n requirement o f a b i o l o g i c a l treatment system. T h e m a i n f u n c t i o n o f (IH is to a l l o w the m a x i m u m O U R to be predicted. It is difficult to evaluate accurately, but that is not c r i t i c a l because the m o d e l is not v e r y sensitive to the values u s e d ( H e n z e et al., 2 0 0 0 ) .  T h e m a x i m u m specific g r o w t h rate was evaluated u s i n g the r e s p i r o m e t r i c technique o f K a p p e l e r and G u j e r (1992) as described i n C h a p t e r I V and A p p e n d i x 3. T h e e x p e r i m e n t a l e v a l u a t i o n was p e r f o r m e d u s i n g p a r a l l e l respirometers m a i n t a i n e d at the temperature o f the U B C p i l o t plant. S l u d g e samples w e r e aerated for 3-3.5 hours to achieve stable steady state respiration c o n d i t i o n s before a d d i n g fresh wastewater. A f t e r the endogenous r e s p i r a t i o n rate w a s measured, a centrifuged wastewater sample was added and the O U R was recorded for about 3 hours. A total o f 13 samples o f centrifuged influent wastewater and b i o m a s s f r o m the M E B P R and U C T processes were tested u s i n g C O D / V S S ratios o f about 4. T y p i c a l results are s h o w n i n F i g u r e s 5.5 to 5.7.  A s s h o w n i n F i g u r e 5.5 and F i g u r e 5.7, o x y g e n respiration increased due to the u n l i m i t e d g r o w t h o f heterotrophic b i o m a s s to a m a x i m u m d u r i n g the first 2 to 3 hours o f the test, f o l l o w e d b y a sharp decrease to a l o w l e v e l because o f l i m i t i n g concentrations o f r e a d i l y b i o d e g r a d a b l e substrates. T h e o x y g e n respiration rate at this l e v e l w a s d o m i n a t e d b y g r o w t h o n substrate released b y h y d r o l y s i s . B e c a u s e the respirometers were airtight d u r i n g the O U R tests the o x y g e n uptake rate o n l y depended o n heterotrophic b i o m a s s as r e v i e w e d i n C h a p t e r II; therefore (|1H bn) c o u l d be determined f r o m the slope i n F i g u r e 5.6 and 5.8 a c c o r d i n g to E q u a t i o n 4.28.  99  350  -i  300 250 -„ _l CM  O 200 a,  E, 150 -  CC  O  100 50 0 -50  100  150  200  250  300  Time (min.)  F i g u r e 5.5 M a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s for the M E B P R process (May 13,2002)  200  F i g u r e 5.6 L o g a r i t h m i c f o r m o f relative O U R for the M E B P R process ( M a y 11, 2 0 0 2 )  100  F i g u r e 5.7 M a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s for the U C T process ( A p r i l 11, 2 0 0 2 )  F i g u r e 5.8 L o g a r i t h m i c f o r m o f relative O U R for the U C T process ( A p r i l 11, 2 0 0 2 )  101  ln[r  0 2  (t)/ r  0 2  (to)] = (LX - b ) t h  (4.28)  H  T h e m a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s w a s determined u s i n g E q u a t i o n 5.1: S l o p e = | i - bn'  (5.1)  H  W h e r e bn = 0.13 day"'for the M E B P R process and 0.14 day"'for U C T process. T h e s e average values w e r e d e t e r m i n e d i n the decay tests o f this study.  The  temperature  effect w a s c o n s i d e r e d i n the determination o f p: . T h e tests w e r e H  c o n d u c t e d at the temperature o f the aerobic zones o f the U B C p i l o t plant, and the v a l u e o f | I H w a s adjusted to 2 0 ° C u s i n g the A r r h e n i u s equation. A c c o u n t i n g for the i m p a c t o f temperature o n the aerobic g r o w t h o f heterotrophy, G r a d y et al. (1999) reported an average v a l u e o f 0 for a large database is 1.094. T h i s v a l u e w a s used i n this study. T h e m a x i m u m specific g r o w t h rate results are listed i n T a b l e 5.4.  Table 5.4 R e s u l t s o f m a x i m u m specific g r o w t h rate for heterotrophic b i o m a s s @ 2 0 ° C Date  (P-rnax •b H )  (day" )  UCT  MEBPR  4/11/02  14.1  4/12/02  16.0  5/10/02  7.7  1  P-max  UCT  (day" ) 1  MEBPR  14.3 16.2  9.1  F / M ratio UCT  MEBPR  2.6 9.3  7.8  2.6  1.9  3.9  5/13/02  5.7  1.75  5.8  9.8  15.0  7.9  15.1  1.9 8.0  6.3  5/14/02  4.8  4.7  5/15/02  17  11.7  17  11.8  3.9  3.8  5/16/02  10  5/28/02  5.5  Sample mean p :  13.2 10.7  m a x  s  5.2  5.6  10.8  11.9 4.16  8.36 2.94  4.4  Note: The value of b was 0.14 day" for the U C T , and 0.13 day" for the M E B P R process. H  102  4.7  T h e values o f (IH w e r e found to be (at the 9 5 % o f confidence l e v e l ) : (J-max for M E B P R process  8.36 ( ± 5.88) day" @ 2 0 ° C  n = 5  (l  11.9 ( ± 8.4) day" @ 2 0 ° C  n = 8  1  for U C T process  m a x  1  T h e m a x i m u m specific g r o w t h rate o f heterotrophy w a s found to v a r y i n the range o f 5.6 to 17.0 day" w i t h a m e a n v a l u e o f 11.9 day" for the U C T process, and the range o f 1.9 to 11.8 1  1  day" w i t h a m e a n v a l u e o f 8.36 day" for the M E B P R process. 1  1  S o m e results compare w e l l w i t h literature values, but others are m a r k e d l y h i g h e r than the p: range o f 0.12-0.55 hr" (2.88-13.2 day" ) s u m m a r i z e d b y G r a d y et al. ( 1 9 9 9 ) . A s i m i l a r 1  1  H  result was found i n the research o f Stanyer (1997). K a p p e l e r and G u j e r (1992) f o u n d that p:  H  v a r i e d i n the range o f 1-8 day" for t y p i c a l settled d o m e s t i c sewage o f S w i t z e r l a n d . H e n z e et al. 1  (1995) reported a t y p i c a l v a l u e o f (IH to be 6 day" for p r i m a r y effluent at 2 0 1  C in A S M 2 . Sozen  et al. (1998) reported a  range o f 3.4-6.5 day" for synthetic sewage a n d different  mixtures  and  under  aerobic  1  anoxic  conditions.  The  maximum  wastewater  specific growth  rate  of  heterotrophy depends strongly o n the species o f m i c r o o r g a n i s m s present and the substrate u p o n w h i c h the m i c r o o r g a n i s m s are g r o w i n g . T h e unstable operation o f the p i l o t processes m a y h a v e altered  the n o r m a l f u n c t i o n o f the m i c r o o r g a n i s m s .  D o m e s t i c wastewater  is a c o m p l e x  substrate, and the m i c r o b i a l c o m m u n i t i e s i n wastewater treatment systems are also c o m p l e x , c o n t a i n i n g m a n y m i c r o b i a l species. T h i s m a k e s it v e r y difficult to generalize about parameter values and the parameters s h o u l d be characterized b y ranges rather than b y a s i n g l e v a l u e ( G r a d y et al,  1999). It is suggested that care s h o u l d be exercised i n the use o f values c o n s i d e r e d  to be t y p i c a l .  103  T h e v a l u e o f the specific g r o w t h rate o f heterotrophic b i o m a s s has been reported to be i n f l u e n c e d b y the c o n f i g u r a t i o n o f the reactor. F o r e x a m p l e , some reactors tend to select microorganism  species that can g r o w r a p i d l y (higher p: ), whereas H  s o m e reactors  select  m i c r o o r g a n i s m s that are g o o d scavengers o f substrate ( C h u d o b a et al., 1985; D o l d et al., 1986).  C h u d o b a et al. (1985) also p o i n t e d out that the b a t c h assays t y p i c a l l y u s e d to measure k i n e t i c characteristics, are i n f l u e n c e d b y the ratio o f the i n i t i a l substrate to the  biomass  concentration (So/Xo) i n the reactor. T h e y r e c o m m e n d e d that these ratios s h o u l d be less than 2. Others ( E l l i s et al., 1996; G r a d y et al., 1999) s i m i l a r l y e x p l a i n e d that So/Xo m u s t be l o w for k i n e t i c g r o w t h parameters to represent those o f the o r i g i n a l treatment environment. T h e greater the So/Xo ratio, the greater the change i n the bacterial c o m m u n i t y a w a y f r o m the o r i g i n a l wastewater environment, and the m o r e l i k e l y it is that the measured k i n e t i c s w i l l reflect the characteristics o f the fastest g r o w i n g bacteria ( P o l l a r d et al., 1998). In the present study, w h e n the So/Xo was too l o w , the i n i t i a l O U R plateau was absent, the curve was n a r r o w and t a l l w i t h few measurements a v a i l a b l e to characterize the i n i t i a l O U R . T h e s e investigations s h o w e d that the So/Xo c o u l d be c r u c i a l .  T h e batch system adopted i n this study ( K a p p e l e r and Gujer, 1992) was c r i t i c i z e d b y N o v a k et al. (1994), o n the p r e s u m p t i o n that it is l i k e l y to create a m i c r o b i a l g r o w t h m e d i u m that is totally different from the c o n d i t i o n s associated w i t h the activated sludge g r o w i n g i n continuous systems. T h e y noted that batch reactors w o u l d favor the fast g r o w i n g group i n the b i o m a s s and generate an u n r e a l i s t i c a l l y h i g h JJ,  h  alternative technique maximum  v a l u e . N o v a k et al. (1994) p r o p o s e d  an  o f m a t h e m a t i c a l s i m u l a t i o n and b a t c h c u l t i v a t i o n for e s t i m a t i o n o f  s p e c i f i c g r o w t h rate o f heterotrophic b i o m a s s . T h e estimation w a s based  104  on  m a t h e m a t i c a l c a l i b r a t i o n o f c o n t i n u o u s l y operated systems, a n d the m e t h o d w a s c o m p a r e d w i t h a batch test m e t h o d . C o m p a r i n g the t w o methods, a difference b e t w e e n o b t a i n e d results w a s found  (//Hmax  - 4 day" from the N o v a k et al. (1994) m e t h o d , a n d 1  = 10 day" f r o m the 1  //Hmax  b a t c h m e t h o d ) . T h e y e x p l a i n e d that under b a t c h testing c o n d i t i o n s ( h i g h So/Xo ratio) fasterg r o w i n g m i c r o o r g a n i s m s c o u l d be favored i n their g r o w t h .  T h u s , this c o m p l i c a t e s k i n e t i c  analysis and requires that experiments to determine k i n e t i c parameters  be conducted w i t h  systems that m i m i c the p h y s i c a l c o n f i g u r a t i o n to b e e m p l o y e d i n the f u l l - s c a l e facilities ( G r a d y et al,  1999). T h e m e t h o d o f N o v a k et al. (1994) w a s not u s e d i n the present study d u e to the  l i m i t a t i o n o f t i m e for m o d e l s i m u l a t i o n , a n d K a p p e l e r a n d G u j e r (1992) m e t h o d w a s u s e d . A s r e v i e w e d i n C h a p t e r I V , it i s difficult to evaluate JUH accurately, but it i s n o t c r i t i c a l because A S M 2 i s not v e r y sensitive to this v a l u e .  5.4 Wastewater C a r b o n Fractions  T h e o r g a n i c matter i n wastewater is s u b d i v i d e d into f i v e parts: fermentation products, r e a d i l y b i o d e g r a d a b l e o r g a n i c substrate,  inert s o l u b l e o r g a n i c matter,  s l o w l y biodegradable  substrate a n d inert particulate o r g a n i c matter i n A S M 2 . It is c o m m o n to express these fractions i n C O D terms. T h e results o f the detailed wastewater characterization analysis are l i s t e d i n A p p e n d i x 6.  Readily biodegradable COD, 5> and Volatile Acids, SA S o l u b l e b i o d e g r a d a b l e C O D w a s measured u s i n g the r a p i d p h y s i c a l - c h e m i c a l m e t h o d o f M a m a i s et al. (1993) a n d the aerobic b a t c h test m e t h o d ( E k a m a et al,  1986; Kappeler and  Gujer, 1992). R e a d i l y biodegradable C O D w a s c a l c u l a t e d f r o m the difference o f the s o l u b l e  105  b i o d e g r a d a b l e C O D (Ss) and v o l a t i l e acids ( S A ) . T h e detailed results are s h o w n i n A p p e n d i x 4. T h e results o f the p h y s i c a l - c h e m i c a l determination m e t h o d s c o m p a r e d w e l l w i t h the aerobic batch test m e t h o d as s h o w n i n the T a b l e 5.5.  T a b l e 5.5 R e s u l t s o f r e a d i l y b i o d e g r a d a b l e C O D tests Method  n  Sample source  Ss ( S + S ) (mg L" )  (mgL- )  (mgL )  Physical-chemical  MEBPR  61  18  43  9  Batch Aerobic  MEBPR  61  13  48  6  A  F  1  SA  SF 1  1  In the p h y s i c a l - c h e m i c a l m e t h o d , the fraction o f r e a d i l y biodegradable C O D ( S F ) o f the total influent C O D w a s f o u n d to be (at the 9 5 % o f c o n f i d e n c e l e v e l ) : S  F  fraction:  10% ( ± 6 % )  S  F  concentration  43 ( ± 3 8 ) m g L  Range 3 - 1 3 % Range 1 4 - 7 0 m g L "  - 1  n = 9 1  n = 9  In the batch aerobic m e t h o d , the concentration and fraction o f r e a d i l y b i o d e g r a d a b l e C O D ( S ) o f the total influent C O D w e r e f o u n d to be (at the 9 5 % o f confidence l e v e l ) : F  S  F  fraction  1 0 % ( ± 6%)  S  F  concentration  48 ( ± 32) m g L "  As  s h o w n i n T a b l e 5.5, the  Range 7 - 1 6 % R a n g e 27 - 72 m g L "  1  n = 6 1  n = 6  S F values obtained b y the p h y s i c a l - c h e m i c a l m e t h o d  c o m p a r e d w e l l w i t h those f r o m the b a t c h aerobic m e t h o d , and those data also agreed w e l l w i t h values reported i n the literature. H e n z e et al. (1992) reported a range o f this fraction u p to 2 0 % o f the total C O D . K a p p e l e r and G u j e r (1992) reported this fraction to be 1 1 % for m u n i c i p a l wastewater. R e a d i l y b i o d e g r a d a b l e C O D f r o m the test o f B j e r r e et al. (1995) w a s 25 m g L " . 1  K r i s t e n s e n et al. (1998) reported a range o f S F b e t w e e n 9 % and 3 4 % o f total C O D . T h e t y p i c a l  106  range for r e a d i l y b i o d e g r a d a b l e substrate r e c o m m e n d e d b y A S M 2 is 1 0 - 2 0 % o f the total C O D for m u n i c i p a l wastewater, i n g o o d agreement w i t h the results f r o m this study.  v o l a t i l e acids concentration ( S A ) and S A fraction i n the total influent C O D w e r e  The f o u n d to be:  S A concentration  19 ( ± 1 0 ) m g L "  S  5% (± 4%)  A  fraction  R a n g e 8 - 50 m g L "  1  1  Range 2 - 1 0 %  n = 23 n = 23  T h e results c o m p a r e w e l l w i t h the values reported f r o m literature. T h e t y p i c a l range for v o l a t i l e acids is 2 - 1 0 % o f the total C O D ( H e n z e et al, 2000). A s m e n t i o n e d i n the d i s c u s s i o n o f m e c h a n i s m s o f b i o l o g i c a l nitrogen and phosphorus r e m o v a l , the b i o d e g r a d a b l e o r g a n i c matter p l a y s the k e y r o l e i n nutrient r e m o v a l . A h i g h p o r t i o n o f V F A s i n wastewater w i l l result i n r a p i d uptake b y the P A O s and a r e l a t i v e l y s m a l l anaerobic S R T can be used. It has been estimated that at least 25 m g L " as C O D o f r e a d i l y biodegradable substrate must be a v a i l a b l e i n the anaerobic 1  z o n e to generate sufficient V F A s to a l l o w adequate b i o l o g i c a l p h o s p h o r u s r e m o v a l ( S i e b r i t z et al,  1983).  The  r e a d i l y b i o d e g r a d a b l e substrate concentration i n the influent w i l l also affect  the  d e n i t r i f i c a t i o n rate i n an i n i t i a l a n o x i c zone. D e n i t r i f i c a t i o n is r a p i d w h e n r e a d i l y b i o d e g r a d a b l e substrate is a v a i l a b l e , thus, this fraction i n the influent wastewater w i l l s i g n i f i c a n t l y affect the performance o f a B N R system. T h e e x p e r i m e n t a l results s h o w that the concentrations o f r e a d i l y b i o d e g r a d a b l e C O D and V F A i n the wastewater o f interest were t y p i c a l c o m p a r i n g w i t h the range  in A S M 2 ;  it w i l l  be  further  a p p r o v e d i n the  107  following  section that the  readily  b i o d e g r a d a b l e C O D to T K N or T P ratios i n the influent wastewater at the U B C p i l o t plant w o u l d a l l o w adequate nitrogen and phosphorus r e m o v a l i n the M E B P R process.  Soluble inert COD Inert s o l u b l e C O D , S i , is defined as the o r g a n i c fraction that cannot be further degraded i n treatment plants. It is assumed to be part o f the influent and it is also assumed to be the p r o d u c e d b y h y d r o l y s i s o f particulate substrates.  Inert s o l u b l e C O D w a s determined f r o m inert particulate C O D tests and f o l l o w e d the methods o f L e s o u e f et al. (1992). T h e influent wastewater samples were aerated i n a b a t c h reactor for 8-10 days, and samples were r e m o v e d and a n a l y z e d t w i c e a day for s o l u b l e C O D u n t i l it reached a stable l e v e l . T h e final s o l u b l e C O D concentration was c o n s i d e r e d to be the inert particulate C O D i n the influent. T h e detailed results are s h o w n i n A p p e n d i x 6. T h e inert s o l u b l e C O D concentration and the fraction o f total C O D were f o u n d to be (at the 9 5 % o f confidence l e v e l ) : Si concentration  6 0 ( ± 20) m g L "  S, fraction  16% ( ± 6 % )  R a n g e 45 - 71 m g L "  1  Range 1 3 - 2 2 %  1  n = 10 n=10  G e n e r a l l y , the inert s o l u b l e C O D measured i n the present study c o m p a r e d w e l l w i t h the results o f K a p p e l e r and G u j e r (1992). T h e y reported the range o f S i to be 10-20 % o f total C O D . H e n z e et al. (1992) suggested that S i s h o u l d be i n the range o f 2 0 - 2 5 % o f total C O D for m u n i c i p a l r a w wastewater. B j e r r e et al. (1995) reported the inert s o l u b l e C O D i n their research as 55 m g L " . H o w e v e r , l o w e r ranges o f S i can also be f o u n d i n the literature. E k a m a et al. 1  (1986) estimated a v a l u e o f S i as 5 % o f total C O D for r a w wastewater i n S o u t h A m e r i c a . H e n z e  108  et al. (1992) reported a v a l u e b e i n g 2 % o f total C O D i n D e n m a r k , and a range o f this fraction as 8-11%  o f total r a w wastewater i n S w i t z e r l a n d . T h e t y p i c a l range o f S i r e c o m m e n d e d b y A S M 2  is 5-10 % o f total p r i m a r y effluent C O D .  It s h o u l d be m e n t i o n e d that the reported values for this fraction has b e e n m e a s u r e d w i t h m a n y different methods, most o f methods i n c l u d i n g elements o f e s t i m a t i o n i n their procedures as r e v i e w e d i n C h a p t e r I V . Therefore, care must be taken for the interpretation o f the results. In the present study, the inert s o l u b l e C O D w a s determined f r o m the inert particulate C O D tests i n order to o b t a i n c o m p a r a b l e results w i t h X i . S i n c e these tests w e r e u s u a l l y r u n o v e r 8-11 days, and the v a l u e o f S i m i g h t be h i g h e r than the m e t h o d r e c o m m e n d e d b y I A W P R C  group i n  A S M 2 , i n w h i c h the s o l u b l e C O D r e m a i n i n g after 2 0 days o f o x i d a t i o n c o u l d b e regarded as equivalent to S i ( E k a m a et al., 1986).  Inert particulate  COD  T h e inert particulate C O D was determined b y the m e t h o d o f L e s o u e f et al. (1992) as described i n C h a p t e r I V and A p p e n d i x 5. T h e detailed results are s h o w n i n A p p e n d i x 5. T h e concentration and fraction o f inert particulate C O D were found to be (at the 9 5 % o f c o n f i d e n c e level): X , concentration  103 ( ± 100) m g L  Si fraction  23% (±18%)  _ 1  R a n g e 53 - 192 m g I / Range 1 3 - 3 8 %  1  n = 6 n = 6  M a n y researchers have characterized this fraction either i n r a w or p r i m a r y wastewaters. E k a m a et al. (1986) f o u n d the fraction o f inert particulate C O D i n r a w wastewater to b e 1 3 % o f the total C O D . H e n z e et al. (1987) suggested this fraction i n r a w wastewater b e i n g 1 1 - 2 0 % o f  109  total C O D . S i m i l a r l y , K a p p e l e r and G u j e r (1992) o b s e r v e d the X j fraction i n r a w wastewater to be 8-10% o f the total C O D . S o m e researchers evaluated this fraction i n p r i m a r y effluent, and X i was reported to l i e b e t w e e n 4 % and 1 3 % o f the total C O D ( E k a m a et al, 1992 and L e s o u e f et al,  1986; H e n z e et al.,  1992). T h e t y p i c a l values for this fraction r e c o m m e n d e d b y A S M 2 l i e  i n the range o f 10%> to 1 5 % o f the total C O D i n p r i m a r y effluent. B j e r r e et al. (1995) f o u n d the inert particulate C O D i n their research to be 33 m g L " . 1  G e n e r a l l y , the fraction o f inert particulate inert C O D i n this study is h i g h e r than the t y p i c a l range. T h e major i m p a c t o f particulate substrate o n the d y n a m i c response o f a system i s i n the u t i l i z a t i o n o f o x y g e n . B e c a u s e o f the nature o f h y d r o l y s i s , the i m p a c t o f the presence o f particulate substrate is to d a m p e n the system response, thereby r e d u c i n g the peak o x y g e n requirement. In a d d i t i o n , the need for h y d r o l y s i s to m a k e substrate a v a i l a b l e causes a t i m e l a g i n the occurrence o f the m a x i m u m and m i n i m u m o x y g e n c o n s u m p t i o n rates. T h i s result s h o u l d b e taken into c o n s i d e r a t i o n i n the process design and o p t i m i z a t i o n .  Slowly biodegradable  COD  S l o w l y b i o d e g r a d a b l e substrates are the o r g a n i c fraction that m u s t undergo c e l l external hydrolysis  before  they  are  available  for  degradation.  The  slowly  biodegradable  COD  concentration and the fraction were determined b y the difference b e t w e e n the total C O D and the other fractions. T h e detailed results are s h o w n i n A p p e n d i x 6. T h e concentration and fraction o f the s l o w l y biodegradable C O D were f o u n d to be (at the 9 5 % o f c o n f i d e n c e l e v e l ) : X  s  concentration  2 2 7 ( ± 54) m g L "  X  s  fraction  56% ( ± 1 4 % )  1  Range 1 9 9 - 2 7 7 m g L " Range 5 3 - 6 8 %  110  1  n = 4 n = 4  M a n y researchers have characterized the fraction o f X s i n r a w wastewater. E k a m a et al. (1986) obtained a v a l u e o f 6 2 % o f the total C O D . H e n z e et al. (1987) reported the range o f X  s  as 4 0 - 4 9 % o f the wastewater C O D . K a p p e l e r and G u j e r (1992) found the range o f X s to l i e b e t w e e n 5 3 % and 6 0 % o f the total C O D . B j e r r e et al. (1995) estimated the s l o w l y b i o d e g r a d a b l e C O D i n their, research as 115 m g L " . T h e s l o w l y biodegradable C O D fraction i n p r i m a r y 1  effluent is r e l a t i v e l y l o w c o m p a r e d w i t h the fraction i n r a w wastewater. L e s o u e f et al. (1992) and H e n z e et al. (1992) observed this fraction to be between 4 1 - 4 3 % o f the total C O D , and E k a m a et al. (1986) reported a v a l u e o f 6 0 % i n p r i m a r y effluent. T h e t y p i c a l v a l u e o f the s l o w l y biodegradable C O D is 3 0 - 6 0 % o f the total C O D i n p r i m a r y effluent ( H e n z e et al,  2000).  T h e s l o w l y biodegradable substrate i n this study is r e l a t i v e l y h i g h i n c o m p a r i s o n to the literature data as s h o w n above. A h i g h concentration o f this fraction w i l l s i g n i f i c a n t l y affect the performance o f a B N R system. D e n i t r i f i c a t i o n is m u c h s l o w e r w h e n o n l y s l o w l y b i o d e g r a d a b l e substrate is present, because the use o f s l o w l y biodegradable substrate is c o n t r o l l e d b y the rate o f h y d r o l y s i s , w h i c h is r e l a t i v e l y s l o w under a n o x i c c o n d i t i o n s . It s h o u l d be c o n s i d e r e d i n the M E B P R process o p t i m i z a t i o n .  5.5 Wastewater Nitrogen Fractions  T h e total n i t r o g e n i n r a w m u n i c i p a l wastewater is d o m i n a t e d b y reduced nitrogen, either i n the f o r m o f a m m o n i a or as a m i n o groups i n o r g a n i c substances. In general, there is no need to characterize the n i t r o g e n fractions i n as m u c h detail as for organic fractions ( H e n z e et al,  1995).  In the present study, the n i t r o g e n fractions were measured as a m m o n i a , nitrite p l u s nitrate, T K N and T N a c c o r d i n g to the procedures described i n the C h a p t e r I V . T h e detailed results are s h o w n  111  i n A p p e n d i x 7. T h e concentrations and fractions o f these components were f o u n d to be (at the 9 5 % o f confidence l e v e l ) : R a n g e 18 - 36 m g L  n = 17  A m m o n i a concentration  25 ( ± 8) m g L "  NO2" & N O V concentration  0.15 ( ± 0 . 2 ) m g L "  T K N concentration  44.8 ( ± 1 0 ) m g L "  1  R a n g e 36 - 55 m g L "  1  n - 18  T N concentration  45.1 ( ± 10) m g L "  1  R a n g e 48 - 55 m g L "  1  n = 18  1  1  R a n g e 0.03 - 0 . 4 5 m g L "  1  n = 17  T h e concentration o f each nitrogen fraction is s h o w n i n F i g u r e 5.9, and the detailed results are g i v e n i n A p p e n d i x 7.  T o t a l K j e l d a h l nitrogen i n r a w m u n i c i p a l wastewater i n c l u d e s o r g a n i c r e d u c e d n i t r o g e n and a m m o n i a . A m m o n i a i n r a w m u n i c i p a l wastewater has its p r i m a r y o r i g i n i n urea. A m m o n i a is the d o m i n a t i n g reduced nitrogen component, and accounts n o r m a l l y for 6 0 - 7 0 % o f the total K j e l d a h l nitrogen ( H e n z e et al., 1995). T h e a m m o n i a n i t r o g e n i n this study w a s about 5 6 % o f the total nitrogen as s h o w n i n F i g u r e 5.10, and it is l o w e r than the n o r m a l range. O x i d i z e d n i t r o g e n i n r a w m u n i c i p a l wastewater c a n have its o r i g i n i n i n f i l t r a t i o n water. T h e nitrite p l u s nitrate concentration has been reported to be i n the range o f 0-1 m g L " i n the literature ( H e n z e 1  et al,  1995), and this is c o m p a r e d w e l l w i t h the results f r o m this study.  112  ^  60  ft ft  » 50  30  •  A  t"  ft  ft ft ft  § 40 09  i  *  ft  A  ft  1  •  • • • •  » o 10 0 - .g-in 9/16/01  1  .  11/5/01  12/25/01  g ——H2  m  B 3B IB 8  —JBB-S—BP  2/13/02  S-S—3  4/4/02  5/24/02  Tested date •  Ammonia  •  NOx * T K N • TN  F i g u r e 5.9 N i t r o g e n concentrations i n the influent samples  - 6 0 » 50 |  40  TKN i Ammonia-;  g> 10 NOx 9/20/01 Tested date • Ammonia a NOx a T K N H T N  F i g u r e 5.10 N i t r o g e n concentrations i n an influent s a m p l e  113  5.6 Wastewater Phosphorus F r a c t i o n  T o t a l phosphorus i n r a w m u n i c i p a l wastewater is i n the phosphate f o r m ; either as i n o r g a n i c o r as o r g a n i c b o u n d phosphorus. T h e major part o f o r g a n i c b o u n d p h o s p h o r u s is o f p h y s i o l o g i c a l o r i g i n . T h e total phosphorus fractions are h e a v i l y i n f l u e n c e d b y the use o f phosphorus i n detergents. P h o s p h o r u s f r o m detergents c a n account for u p to 5 0 % o f the total phosphorus  concentration i n r a w wastewater.  Much  o f the ortho-phosphate  in municipal  wastewater has it o r i g i n i n detergents and other h o u s e h o l d c h e m i c a l s ( H e n z e et al., 2 0 0 0 )  T h e r e is n o need to characterize phosphorus fractions i n as m u c h detail as for the o r g a n i c fractions. T o t a l phosphorus was measured b y traditional c h e m i c a l a n a l y t i c a l m e t h o d s d e s c r i b e d i n C h a p t e r I V . T h e ortho-phosphate and total phosphorus concentrations w e r e f o u n d to be (at the 9 5 % o f confidence l e v e l ) : Ortho-phosphate concentration 3.4 ( ± 1.0) m g L "  1  T o t a l phosphorus concentration 4.6 ( ± 1.2) m g L "  1  R a n g e 2.8 - 4.5 m g L "  1  R a n g e 2.8 - 5.4 m g L "  1  n=18 n = 18  F i g u r e 5.11 s h o w s the v a r i a t i o n o f the v a r i o u s p h o s p h o r u s concentrations tested d u r i n g the study p e r i o d , and the detailed results are listed i n A p p e n d i x 8.  T h e ortho-phosphate fraction w a s about 63-73% o f the total p h o s p h o r u s i n this study, and i n s o m e cases this fraction w a s as h i g h as 9 1 - 9 6 % o f the total phosphorus ( F i g u r e 5.12). T h e s e results are h i g h e r than the t y p i c a l range f o u n d i n A S M 2 , w h i c h is 6 0 % o f the total phosphorus. Therefore, it is suggested again that characterization o f influent wastewater is v e r y important for a particular wastewater o f interest.  114  •  •  Q_  B  E.  4  •B  3  O  •  •  (TJ  2 4 1 4 0  -I  :  1  7/28/01  1  9/16/01  1  1  11/5/01  12/25/01  r  2/13/02  4/4/02  5/24/02  Test date • Ortho-phosphate • Total phosphrous  F i g u r e 5.11 Ortho-phosphate & total p h o s p h o r u s concentrations i n the influent samples  6 5 4  S  2  o  1-H:  u  iH I  I  1  2  3  4  5  6  7  )  9  10  11  12  1  I ..... I  I  13  14  15  16  1  1  17 18  Test ID 01 Ortho-phosphate H Total phosphorus  F i g u r e 5.12 C o m p a r i s o n o f the Ortho-phosphate & total phosphorus concentrations i n the influent samples  115  T h e concentration o f biodegradable matter relative to the nutrient concentration i n the influent c a n d r a m a t i c a l l y affect the performance  o f a B N R system. T h e C O D / T K N  ratio  obtained from this study is 9.3, and this v a l u e s h o u l d a l l o w excellent n i t r o g e n r e m o v a l as i n d i c a t e d b y T a b l e 5.6. T a b l e 5.6 presents general guidance c o n c e r n i n g the a m e n a b i l i t y o f v a r i o u s wastewaters  to b i o l o g i c a l n i t r o g e n r e m o v a l p r o v i d e d b y G r a d y et al. (1999). It w a s  suggested that these values c o u l d be used to choose candidate treatment processes, and to determine h o w d i f f i c u l t it m a y be to achieve g o o d nitrogen r e m o v a l . A c t u a l l y , g u i d e l i n e s s u c h as these are c o n s i d e r e d to be conservative ( R a n d a l l et al., 1992). That is, adequate p e r f o r m a n c e can be obtained at l o w e r than the r e c o m m e n d e d C O D / T K N ratio i n practice ( G r a d y et  al.,  1999).  T a b l e 5.6 R e l a t i o n s h i p between expected b i o l o g i c a l nitrogen r e m o v a l e f f i c i e n c y and influent organic matter to nitrogen ratios ( G r a d y et al., 1999) Nitrogen removal efficiency  C O D : T K N (mg C O D ) (mg N)"'  Poor  <5  Moderate  5-7  Good  7-9  Excellent  >9  T h e C O D : total phosphorus ( T P ) , and B O D : 5  T P ratios are often u s e d to j u d g e  the  phosphorus r e m o v a l potential o f a wastewater (Tetreault et al., 1986; S e d l a k 1 9 9 1 ; and R a n d a l l et al,  1992). I f a wastewater contains sufficient o r g a n i c matter for r e m o v i n g p h o s p h o r u s , the  effluent phosphorus concentration w i l l generally be l o w w h e n it is treated i n a B P R process. However,  i f a wastewater  contains  insufficient o r g a n i c matter for r e m o v i n g a l l o f  the  phosphorus, phosphorus w i l l be present i n the process effluent at a concentration d e t e r m i n e d b y the relative concentrations o f phosphorus and o r g a n i c matter i n the influent. T h e B O D 5 to phosphorus r e m o v a l ( A P ) ratio is often u s e d to characterize the capabilities o f B P R systems ( S e d l a k , 1991). T a b l e 5.7 p r o v i d e s t y p i c a l range for C O D : A P for a variety o f B P R process. 116  Table 5.7 C O D to phosphorus r e m o v a l ratios for v a r i o u s B P R processes ( G r a d y et al., 1999) T y p e o f B P R process  C O D : A P ratio (mg C O D ) (rngP)"  H i g h efficiency (e.g., A / O ™ w i t h o u t  nitrification, V I P , U C T )  M o d e r a t e efficiency (e.g., A / O ™ and A / 0 ™ w i t h nitrification) 2  L o w efficiency (e.g., B a r d e n p h o )  1  26-34 34-43 >43  A l o w v a l u e for the ratio indicates an efficient process since little o r g a n i c matter is required to r e m o v e a unit o f phosphorus. H i g h l y efficient B P R processes such as the U C T process require o n l y 2 6 - 3 4 m g C O D to r e m o v e one m g o f phosphorus. A s d i s c u s s e d above, a BPR  process  will  achieve g o o d performance  o f it is operates under p h o s p h o r u s - l i m i t e d  c o n d i t i o n s . T h a t is, the C O D : A P ratio o f the influent i s greater than the C O D : A P v a l u e i n T a b l e 5.7 for the process b e i n g used ( G r a d y et al.,  1999). T h e C O D : A P ratio o b t a i n e d f r o m  the  present study was 93, and it is m u c h h i g h e r than the values s h o w n i n T a b l e 5.7. Therefore, the organic matter to phosphorus ratio for the influent to the U B C p i l o t plant s h o u l d a l l o w g o o d performance for phosphorus r e m o v a l i n the s i m p l i f i e d U C T and M E B P R processes at the U B C p i l o t plant.  117  C H A P T E R VI  Conclusions and Recommendations  6.1 Conclusions  M o d e l i n g is an essential t o o l for d e s i g n and o p t i m i z i n g o f wastewater processes,  especially  modifications,  such  for as  the  complicated MEBPR  biological process.  nutrient  Parameter  removal  systems  determination  and  treatment and  their  wastewater  characterization i n this study p r o v i d e d useful i n f o r m a t i o n and a database for further c o m p u t e r simulation.  T h e heterotrophic g r o w t h y i e l d f r o m this study was f o u n d to be 0.50 m g m g " ' f o r the M E B P R process and 0.59 m g m g " for the U C T process, and these results correlated w e l l w i t h 1  the t y p i c a l range r e c o m m e n d e d b y the I A W Q T a s k G r o u p i n the A S M 2 researchers.  as w e l l as other  T h e v a l u e o f heterotrophic g r o w t h y i e l d obtained f r o m the M E B P R process w a s  l o w e r than the v a l u e determined from the U C T process, and s i m i l a r results h a v e b e e n reported i n the literature.  T h e m o d e l decay rate was f o u n d to be 0.17-0.33 day" w i t h a m e a n o f 0.24 day" for the 1  1  M E B P R process, and 0.2-0.36 day" w i t h a m e a n v a l u e o f 0.31 day" for the U C T process at 1  1  2 0 ° C . T h o s e results meet w e l l w i t h the reported values. T h e r e w a s no significant difference found i n the v a l u e o f b\\ b e t w e e n the t w o processes. T h i s p o i n t is supported b y results i n the literature.  118  In the test o f the m a x i m u m specific g r o w t h rate o f heterotrophic b i o m a s s , a m u c h w i d e r LLH range was obtained c o m p a r e d w i t h ranges reported i n the p r e v i o u s research literature. T h e [in w a s f o u n d to v a r y i n the range o f 5.6 to 17 day" , w i t h a m e a n v a l u e o f 11.9 day" for the U C T 1  1  process, and b e t w e e n 1.9 to 11.8 day" , w i t h a m e a n v a l u e o f 8.36 day" for the M E B P R process. 1  1  T h i s gives a clear i n d i c a t i o n that \±H is quite site-specific and m o d e l - s p e c i f i c and m a y be affected b y c o m p o u n d s w i t h an i n h i b i t o r y effect; thus quite a large range can exist. It is further suggested the process s h o u l d be stable d u r i n g the tests to p r o v i d e the n o r m a l l i v i n g c o n d i t i o n s for the m i c r o o r g a n i s m s .  The  p h y s i c a l - c h e m i c a l m e t h o d for d e t e r m i n i n g the r e a d i l y b i o d e g r a d a b l e C O D w a s  m u c h q u i c k e r than the b a t c h aerobic methods and gave results that correlated w e l l w i t h the aerobic m e t h o d for the tested d o m e s t i c wastewater. T h e fraction o f r e a d i l y b i o d e g r a d a b l e C O D accounted for 3 - 1 6 % o f the total influent C O D , w h i l e the V F A concentration w a s 2 - 1 0 % i n the tested wastewater; these results c o m p a r e d w e l l w i t h the values r e c o m m e n d e d b y I A W P R C i n the m o d e l o f A S M 2 .  T h e e x p e r i m e n t a l results  s h o w e d that the c o n c e n t r a t i o n o f r e a d i l y  biodegradable substrate and fermentation products i n the wastewater o f interest w o u l d a l l o w adequate n i t r o g e n and phosphorus r e m o v a l i n the M E B P R process.  T h e tested wastewater contained a s l i g h t l y h i g h e r l e v e l o f inert s o l u b l e C O D than the default range p r o v i d e d i n A S M 2 . It was found that S i ranged b e t w e e n 45-71 m g L " w i t h a m e a n 1  v a l u e o f 6 0 m g L " , a c c o u n t i n g for 1 3 - 2 2 % o f the total C O D i n the influent. 1  119  T h e inert particulate C O D w a s f o u n d to be 53-192 m g L " and accounted for 1 3 - 3 8 % o f 1  the total C O D , w i t h a m e a n v a l u e o f 2 3 % . T h i s fraction was h i g h e r than the v a l u e r e c o m m e n d e d b y the I A W P R C group. T h e presence o f particulate substrate m a y d a m p e n the system response, and reduce the peak o x y g e n requirement. It s h o u l d be c o n s i d e r e d i n the process design. T h e particulate inert C O D test is tedious and t i m e c o n s u m i n g , and it is not able to d i s t i n g u i s h active b i o m a s s f r o m b i o m a s s debris.  A large amount o f s l o w l y b i o d e g r a d a b l e matter existed i n the influent, and it accounted for  5 6 % o f the total C O D . T h i s  fraction w a s r e l a t i v e l y h i g h c o m p a r e d w i t h the  range  r e c o m m e n d e d for A S M 2 . A h i g h concentration o f s l o w l y b i o d e g r a d a b l e matter m a y affect the performance o f the M E B P R process because the h y d r o l y s i s o f s l o w l y b i o d e g r a d a b l e substrate is r e l a t i v e l y s l o w under a n o x i c c o n d i t i o n s . It s h o u l d be c o n s i d e r e d i n the M E B P R  process  optimization.  T h e total n i t r o g e n and phosphorus fractions i n wastewater were h i g h e r than the t y p i c a l range. T h e ratios o f C O D / T K N and C O D / A P obtained f r o m this study s h o u l d a l l o w e x c e l l e n t nitrogen and p h o s p h o r u s r e m o v a l i n the M E B P R process.  Presented  i n T a b l e s 6.1  and 6.2  are the results  wastewater characterization i n the present study.  120  o f the parameter  e s t i m a t i o n and  Table 6.1 R e s u l t s o f parameter estimation @ 2 0 ° C Parameter Y b  Sample mean  Standard deviation (s)  0.50 0.59  (day ) 1  H  (day ) 1  H  Mmax ( d a y ) 1  n  Process  0.08  9  MEBPR  0.14  10  UCT  0.24  0.06  4  MEBPR  0.31  0.06  4  UCT  8.36  2.94  5  MEBPR  11.9  4.16  8  UCT  Table 6.2 Results o f wastewater characterization Parameter  Sample mean  Standard deviation (s)  n  SA(mgL-')  19 5  8.9 2  23 23  45  16  16  10 103  3  16  50  6 6  S (%) S (mg L' ) A  1  F  •  S (%) X , (mgL" ) F  1  X , (%) Si ( m g L )  23 60  9 10  Si (%) Xs^gL" )  16  3  1.0 10  227  27  4  56  7 4  17  0.1  17  5  18  1  1  X NH  + 4  (%) (mgN L' ) s  25  1  N 0 " & N 0 " (mg N L" ) T K N ( m g N L" )  0.15 44.8  T N ( m g N L" )  1  2  3  1  4  15.1  5  18  1  3.4  0.5  18  TP ( m g P L )  4.6  0.6  18  1  P0  3 4  " (mgPU ) 1  E x p e r i e n c e obtained from this study shows that parameter determination and wastewater characterization are v e r y important i n the activated sludge m o d e l , a n d must b e d e t e r m i n e d i n a particular wastewater  a p p l i c a t i o n . H o w e v e r , determination  k i n e t i c parameters i s not necessary.  121  o f a l l other  stiochiometric and  6.2 Recommendations for F u r t h e r Study  •  Studies o n the shear force, mass transfer, and m i x i n g c o n d i t i o n s i n the M E B P R process s h o u l d be conducted to investigate their effects o n m i c r o b i a l activities.  •  M o r e accurate methods are essential to quantitatively analyze the o b s e r v e d y i e l d .  •  M o r e accurate methods, such as D N A tests w o u l d be b e n e f i c i a l to identify the m a j o r species presented i n each z o n e o f the M E B P R and U C T processes and analysis the pattern o f their g r o w t h and decay, therefore to find out the difference b e t w e e n  the  M E B P R and U C T process i n terms o f the m i c r o b i a l activities. •  A l t h o u g h ranges o f Y  H  i n literature p r o v i d e an i d e a o f the magnitudes to be expected,  designs s h o u l d o n l y be based o n estimates o f Y H obtained f r o m laboratory and p i l o t scale studies o f the particular waste to be treated because it is wastewater-specific. •  T h e w i d e range o f \IH obtained f r o m this study p r o v i d e d strong p r o o f o f the general understanding that the g r o w t h o f heterotrophy is wastewater-specific and s h o u l d b e observed for a p e r i o d i n v o l v i n g a statistically m e a n i n g f u l n u m b e r o f experiments for the characterization o f a g i v e n d o m e s t i c sewage.  •  E x p e r i m e n t a l results o f this study suggested that the p h y s i c a l - c h e m i c a l m e t h o d gives a better measure o f the l o n g - t e r m average concentration o f the r e a d i l y b i o d e g r a d a b l e C O D i n the wastewater c o m p a r e d w i t h the b a t c h aerobic m e t h o d .  •  S o l u b l e inert C O D obtained f r o m the lab scale b a t c h test s h o u l d be d o u b l e c h e c k e d w i t h effluent s o l u b l e C O D from the wastewater treatment process w i t h an S R T o v e r 25 days.  •  T h e inert particulate matter i n the influent wastewater at U B C p i l o t plant w a s r e l a t i v e l y h i g h , based o n the a v a i l a b l e data. T h i s s h o u l d be c o n s i d e r e d i n the process o p t i m i z a t i o n .  122  C H A P T E R VII  Engineering Significance  T h e parameter d e t e r m i n a t i o n and wastewater characterization for m o d e l i n g o f m e m b r a n e enhanced b i o l o g i c a l phosphorus r e m o v a l process i n this study w o u l d m a k e a c o n t r i b u t i o n i n the wastewater treatment process s e l e c t i o n and processes d e s i g n .  T h e parameters and wastewater characteristics obtained f r o m this study w o u l d p r o v i d e references for a d e s i g n engineer to choose adequate v a l u e s o f m o d e l parameters for m o d e l i n g o f a wastewater treatment process, e s p e c i a l l y for a M E B P R process o r a U C T process.  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Water Science and Technology 3 5 (6): 37-44, 1997.  132  wastewater  Appendix 1  Determination of Heterotrophic Growth Yield  Heterotrophic growth yield, Y  H  , was estimated b y the m e t h o d d e s c r i b e d b y H e n z e et al.  ( 1 9 8 7 ) , Slade et al. ( 1 9 9 1 ) and G r a d y et al. ( 1 9 9 9 ) . T h e v a l u e o f g r o w t h y i e l d w a s d e t e r m i n e d b y p l o t t i n g the b i o m a s s C O D as a function o f the s o l u b l e C O D r e m o v a l and t a k i n g the s l o p e o f the r e s u l t i n g l i n e ( G r a d y et al.,  1 9 9 9 ) . E x p e r i m e n t w a s conducted d u p l i c a t e based o n t w o  p a r a l l e l processes at the U B C p i l o t plant. O n e w a s the s i m p l i f i e d U C T process; w h i l e the other w a s the m e m b r a n e enhanced b i o l o g i c a l phosphorus r e m o v a l process ( M E B P R ) .  Procedures  1.  A t one day before Y H test, take 2 0 0 m L o f b i o m a s s f r o m each aerobic reactor o f the U C T and M E B P R processes at U B C p i l o t plant, and test M L S S i and M L V S S i concentrations.  2.  A t the day o f Y H test, take 2 0 0 m L o f b i o m a s s f r o m each aerobic reactor o f the U C T and M E B P R processes at U B C p i l o t plant, and test M L S S 2 and M L V S S 2 concentrations.  3.  T h e M L V S S 2 results w i l l be obtained one day later, so estimate this v a l u e b y a s s u m i n g the active fraction o f the second sample is a p p r o x i m a t e l y the same as the first sample.  4.  F i l t e r 2 . 5 L o f the influent wastewater f r o m the U B C p i l o t plant w i t h v a c u u m t h r o u g h G6 GF/C  glass fiber filters for pre-filtration, then t h r o u g h 0 . 4 5 m e m b r a n e filters to r e m o v e  suspended s o l i d s a n d a part o f c o l l o i d a l matter. 5.  F i l l 5 0 0 m l o f the filtered wastewater i n reactors A , B , C and D . C o n t i n u o u s l y stir the reactor contents b y u s i n g a stir plate and m a g n e t i c stir bar, and aerate the contents b y u s i n g a r o u n d stone diffuser. P l a c e these reactors into a temperature c o n t r o l l e d c h a m b e r to m a i n t a i n the contents at the temperature o f the p i l o t - p l a n t reactors.  6.  W i t h d r a w 1 0 m l o f reactor contents from each reactor. F i l t e r t h r o u g h 0 . 4 5 u\m p o r e s i z e m e m b r a n e filters, a n d take triplicate samples to determine the i n i t i a l s o l u b l e C O D .  7.  A d d m i x e d l i q u o r from the aerobic z o n e o f U C T process to reactor A a n d B a c c o r d i n g to the i n i t i a l s o l u b l e C O D : b i o m a s s ratio o f 1 : 5 0 - 1 0 0 . E s t i m a t e the amount o f b i o m a s s added into the reactor b y the f o l l o w i n g equation: [Initial s o l u b l e C O D ( m g / L ) * V r e a c t o r ( L ) ] / [ M L V S S ( m g / L ) * V b i o m a s s ( L ) ] = 5 0 - 1 0 0 : 1 2  133  S i m i l a r l y , add m i x e r l i q u o r from M E B P R process to reactor C and D . 8.  Stir the reactor contents v i g o r o u s l y for a f e w m i n u t e s to disperse the b i o m a s s a n d r e m o v e 10 m l o f each s a m p l e u s i n g a w i d e m o u t h pipette to determine the i n i t i a l total C O D i n triplicate.  9.  C o m p e n s a t e water losses w i t h d i s t i l water before t a k i n g samples.  10. R e m o v e duplicate samples at regular intervals for measurement o f the total a n d s o l u b l e C O D i n each reactor. Stir the reactor contents v i g o r o u s l y u n t i l a l l b i o m a s s floe are dispersed sufficiently  well  to  allow  representative  sampling. Determine  total  C O D . Remove  a p p r o x i m a t e l y 6 m l o f the reactor contents and filter through a 0.45 (xm m e m b r a n e filter. T a k e duplicate samples to d e t e r m i n i n g s o l u b l e C O D from the filtrate. 11. Repeat (7) at regular intervals u n t i l the s o l u b l e C O D is f i n a l l y stable. 12. F o r each s a m p l i n g t i m e calculate the changes o f particulate and s o l u b l e C O D . 13. P l o t the b i o m a s s C O D as a f u n c t i o n o f the s o l u b l e C O D r e m o v e d and take the s l o p e o f the resulting line. T h e slope is Y  H  ( G r a d y et al, 1999).  Experimental Results of Heterotrophic Growth Yield  Table A 1. Growth yield test results Date  Y (UCT) k g kg" C O D H  R  (%)  Y  H  (MEBPR)  k g kg" C O D  (%)  1  1  0.41  88  0.62  0.56  97  0.53  76 80  0.72  98  0.79  95  0.42  68  13  0.5  87  0.37  94  13  0.53  95  0.51  99  13  Apr-08-02  0.62  86  0.46  94  13  0.8  97  0.62  97  13  Apr-24-02  0.37  96  0.52  96  15  0.63  79  0.47  92  15  Oct-12-01 Feb-25-02 Mar-01-02  Sample mean  s  16 16 13  0.59 0.14  0.50 0.08  134  E x a m p l e of C a l c u l a t i o n Date: A p r i l 8, 2 0 0 2 Test m e d i a : influent wastewater + b i o m a s s f r o m M E B P R process  Step 1 Calculate the changes in soluble and particulate COD with time: A S o l u b l e C O D = s o l u b l e C O D at t i m e 0 - s o l u b l e C O D at t i m e t A P a r t i c u l a t e C O D = (total - soluble) C O D at t i m e t - (total - s o l u b l e ) C O D at t i m e 0 A t t i m e t = 2 2 hr, A S o l u b l e C O D = 145 - 100 = 45 m g L "  1  A P a r t i c u l a t e C O D = (130 - 100) - (148 - 145) = 2 7 m g L "  Time  1  T o t a l C O D S o l u b l e C O D Particulate C O D A S o l u b l e C O D (mgL- )  0  148  145  3  0  0  22  130 116  100  30  27  55  61  45 90  69 93  116  46 45  70 58  99  103  100  67 55  143.5  118  48  70  97  67  46.5  1  1  (mgL" )  (mgL )  (mgL ) 1  (mgL" )  AParticulate C O D  (hr)  1  1  58  A S o l u b l e C O D = s o l u b l e C O D at t i m e 0 - s o l u b l e C O D at t i m e t A P a r t i c u l a t e C O D - (total - soluble) C O D at t i m e t - (total - s o l u b l e ) C O D at t i m e 0 A t t i m e t = 2 2 hr, A S o l u b l e C O D = 145 - 100 = 45 m g L "  1  A P a r t i c u l a t e C O D = (130 - 100) - (148 - 145) = 2 7 m g L "  1  Step 2 Evaluate COD change trend P l o t C O D changes w i t h t i m e , a n d find out the p e r i o d d u r i n g w h i c h particulate C O D increased based o n the s o l u b l e C O D r e m o v e d i n the absence o f b i o m a s s decay, e. g . t = 0 - 93 hr.  135  COD variation in reactor D  144 T i m e (hr.)  •Sol. C O D  J — Parti. C O D —&r- P a r t . C O D A  Step 3. Calculate YH Select the data o f s o l u b l e and particulate C O D (at t = 0 , 2 2 , 4 6 . 5 , 6 9 , 9 3 hr) i n the absence o f b i o m a s s decay, and p l o t the particulate C O D f o r m e d based o n s o l u b l e C O D r e m o v a l , and the r e s u l t i n g slop is the heterotrophic g r o w t h y i e l d , Y H = 0 . 6 2 .  Figure 5.2 Heterotrophic growth yield of MEBPR April 8,2002  Soluble COD removed (mg COD/L)  136  Appendix 2  Determination of Decay Coefficient for Heterotrophic Biomass  T h e m e t h o d o f H e n z e et al. (1987) w a s used for the d e t e r m i n a t i o n o f d e c a y coefficient o f heterotrophic b i o m a s s . T h e d e c a y coefficient was calculated f r o m the change o f the o x y g e n u t i l i z a t i o n rate o f b i o m a s s o v e r 11 days. T h e experiment was c o n d u c t e d i n p a r a l l e l w i t h the b i o m a s s f r o m the s i m p l i f i e d U C T and M E B P R processes.  Procedures 1.  C o l l e c t a p p r o x i m a t e l y 2 L o f m i x e d l i q u o r f r o m the U C T and 2 L o f m i x e d l i q u o r f r o m the M E B P R process and transfer t h e m to the respirometer A and B .  2.  A d d n i t r i f i c a t i o n i n h i b i t o r ( f o r m u l a 2533) a c c o r d i n g to 0.16 g per 3 0 0 m l o f s a m p l e to each respirometer to prevent n i t r i f i c a t i o n .  3.  p H w a s m o n i t o r e d p e r i o d i c a l l y to ensure that it was constant and r e m a i n e d near neutrality b y a d d i n g s o d i u m bicarbonate.  4.  C o n t i n u o u s l y stir each reactor contents b y u s i n g a stir plate and m a g n e t i c stir bar, and aerate the contents b y u s i n g a r o u n d stone diffuser. P l a c e these reactors  into a  temperature  c o n t r o l l e d c h a m b e r to m a i n t a i n the contents at the temperature o f the p i l o t - p l a n t reactors. 5.  M e a s u r e the o x y g e n uptake rate p e r i o d i c a l l y for several days.  6.  T o p the respirometer contents d a i l y w i t h d i s t i l l e d water to compensate for evaporative losses.  7.  P l o t the natural l o g a r i t h m o f the o x y g e n uptake rate against t i m e . T h e slope o f the l i n e defines the t r a d i t i o n a l d e c a y coefficient, b'n-  8.  D e t e r m i n e the m o d e l d e c a y coefficient b y u s i n g the f o l l o w i n g equation: b ' H  b  H  = 1-  Where: f  p  Y (l-/p) H  - fraction o f b i o m a s s that forms particulate decay products (f = 0.08) assumed b y the p  I A W P R C model.  137  Experimental Results of Traditional Decay Coefficient of Heterotrophic Biomass  Table A 2. Test results of traditional decay coefficient Data May-7-02  S a m p l e sources  R  (%)  2  pH  b  (day ) @20°C 1  H  92  7.5  0.09  0.107 ( 1 7 . 5 ° C )  95  7.5  0.115  0.148 ( 1 8 . 5 ° C )  96  7.5  0.154  0.203 ( 1 8 . 5 ° C )  96  7.5  0.212  UCT  0.145 ( 1 8 ° C )  95  7.5  0.154  UCT  0.154 ( 1 8 ° C )  95  7.5  0.163  0.116 ( 1 9 ° C )  95  7.5  0.119  0.087 ( 1 9 ° C )  96  7.5  0.09  UCT MEBPR  June-12-02  (day ) 1  H  0.084 ( 1 7 . 5 ° C )  UCT MEBPR  May-24-02  b  MEBPR MEBPR Sample mean @20°C 5  0.14 0.03  0.13 0.04  Table A 3. Results of model decay rate Data  S a m p l e sources  May-7-02  (day' ) @ 2 0 ° C 1  H  pH 7.5  0.202 ( 1 7 . 5 ° C )  0.22  7.5  0.324 ( 1 8 . 5 ° C )  0.34  7.5  0.382 ( 1 8 . 5 ° C )  0.33  7.5  UCT  0.317 ( 1 8 ° C )  0.34  7.5  UCT  0.337 ( 1 8 ° C )  0.36  7.5  MEBPR  0.219 ( 1 9 ° C )  0.23  7.5  MEBPR  0.164 ( 1 9 ° C )  0.17  7.5  UCT MEBPR  Sample mean @ 2 0 ° C  b  0.184(17.5°C) MEBPR  June-12-02  (day' ) 1  H  0.20  UCT  May-24-02  b  0.31  0.24  s 0.06 0.06 Note: The growth yield Y was 0.51 (mg COD) (mg COD)" for M E B P R process, and 0.59 (mg COD) (mg COD)' for U C T process in the calculation of model decay coefficient, b . 1  H  H  138  E x a m p l e of C a l c u l a t i o n  D a t e : J u n e 12, 2 0 0 2  Test m e d i a : b i o m a s s c o l l e c t e d f r o m M E B P R process  Step 1 Calculate OUR O U R ( m g 0 2 / L hr) = [ ( D O , - D 0 ) / t , + ( D 0 - D 0 ) / t + ...+ ( D 0 - D O ) / t ] / 6 0 2  2  3  2  5  6  F o r e x a m p l e at t = 0 - 5 m i n , the results w a s c a l c u l a t e d as: O U R = [(7.16 - 4 . 7 ) / l + (4.7 - 4 . 1 ) / 1 + . . . + (3.2 - 2 . 6 8 ) / l ] / 6 0 = 53.67 ( m g 0  Test t i m e  T i m e (min)  D O m g L"  13:30  0  7.16  13:31  1  4.7  13:32  2  4.1  0.6  13:33  3  3.71  0.39  13:34  4  3.2  0.51  13:35  5  2.68  0.52  1  A D O (mg L" ) 1  5  L" hr ) 1  2  O U R (mg 0  - 1  L"' hr ) - 1  2  2.46  53.76  Step 2 Calculate InOUR changes with time T i m e (min.)  T i m e (day)  O U R ( m g 0 2 L " ' hr"') O U R ( m g 0 2 L " hr" ) 1  InOUR  0  0  53.76  1290.24  7.163  90  0.0625  19.08  457.92  6.126  447  0.310  20.16  483.84  6.182  1922  1.335  17.64  423.36  6.048  7007  4.866  6.36  152.64  5.028  9849  6.840  7.08  169.92  5.135  13375  9.288  5.24  125.76  4.834  14629  10.159  5.6  134.4  4.901  17136  11.9  4.8  115.2  4.747  18529  12.867  4.2  100.8  4.613  19935  13.844  3.48  83.52  4.425  21463  14.905  3.6  86.4  4.459  23445  16.281  3.24  77.76  4.354  26357  18.303  1.68  40.32  3.697  28673  19.912  1.92  46.08  3.830  Step 3 Calculate traditional decay coefficient, bn" P l o t I n O U R versus t i m e as the f o l l o w i n g curve, a n d the s l o p o f the r e s u l t i n g l i n e i s the traditional d e c a y coefficient brf = 0 . 1 1 6 (day"') at 1 9 ° C . W h e n i t w a s c o n v e r t e d to the temperature o f 2 0 ° C , V @ 2 0 = 0 . 1 1 6 * 1 . 0 2 9  ( 2 0  "  1 9 )  139  = 0.119 day" . 1  Heterotrophic decay rate of MEBPR process June 12,2002(A)  = 3H  2 10  i 0  i  i  1 2 3  i  i  i  4 5 6  i  i  7 8  i  i  i  i  i  i  i  i  i  i  i  9 10 11 12 13 14 15 16 17 18 19 20 Time (day)  Step 4 Calculate model decay coefficient,  bn@20°C  b = b 'l[\ - Y ( 1 - / P ) ] = - 0 . 1 1 6 / [ 1 - 0.51(1-0.08) = 0.219 ( d a y ) @ 1 9 ° C 1  H  b =b  H  20  H  h  *9  ( T 2 C  ^  T )  i  = 0 . 2 1 9 * 1 . 0 2 9 (20-19) = 0.23 (day" ) @ 2 0 ° C 1  140  Appendix 3  Determination of Maximum Specific Growth Rate of Heterotrophic Biomass  The method  described b y K a p p e l e r and G u j e r (1992) w a s used  to determine  the  m a x i m u m s p e c i f i c g r o w t h rate for heterotrophic b i o m a s s . T h i s parameter was determined b y s i m p l e batch test w i t h centrifuged wastewater and a v e r y s m a l l amount o f b i o m a s s . T h e o x y g e n u t i l i z a t i o n rate w a s recorded u n t i l a distinct drop i n the rate occurs. U s i n g the slope o f the natural l o g a r i t h m o f the relative respiration rate versus time, the m a x i m u m s p e c i f i c g r o w t h rate w a s calculated.  Procedures 1.  Centrifuged  2 L o f influent  wastewater  i n a speed  o f 3240  n  (min) . -1  Withdraw  a  predetermined amount o f m i x e d l i q u o r f r o m the U C T system. M i x the centrifuged influent wastewater and the m i x e d l i q u o r i n the respirometer A a c c o r d i n g to the C O D : V S S r a t i o n around 4 : 1 . In the same w a y w i t h d r a w m i x e d l i q u o r from M E B P R process and put into the respirometer B . 2.  A d d n i t r i f i c a t i o n i n h i b i t o r ( f o r m u l a 2 5 3 3 ) a c c o r d i n g to 0.16 g per 3 0 0 m l o f s a m p l e to each respirometer to prevent n i t r i f i c a t i o n .  3.  P l a c e reactors into a temperature c o n t r o l l e d chamber  to m a i n t a i n the contents at  the  temperature o f the U B C p i l o t - p l a n t reactors. 4.  S t i r the respirometer contents b y u s i n g a stir plate and a magnetic stir bar.  5.  A e r a t e the respirometer  contents b y u s i n g a r o u n d stone diffuser.  Insert a  calibrated  d i s s o l v e d o x y g e n probe l i n k e d to a computer. Stop aeration u n t i l the d i s s o l v e d o x y g e n concentration o f wastewater reaches 6 m g L " . 1  6.  A l l o w the D O probe to equilibrate for 30 seconds and then record the change i n d i s s o l v e d o x y g e n concentrations u n t i l the d i s s o l v e d o x y g e n decreases to 1 m g L " . 1  7.  T u r n o n the air s u p p l y to re-aerate the respirometer contents to m a i n t a i n a d i s s o l v e d o x y g e n concentration above 4 m g L " . M e a s u r e O U R for 5 minutes at 5-7 m i n u t e intervals u n t i l a 1  d i s c e r n i b l e decrease i n rate is observed.  141  8.  T h e o x y g e n respiration s h o u l d increase due to u n l i m i t e d heterotrophic abrupt decrease i n the O U R is detected, w h i l e concentration  g r o w t h u n t i l an  o f readily  biodegradable  substrate b e c o m e s l i m i t i n g . 9.  P l o t the relative o x y g e n uptake rate, lnr(t)/r(to), against time. T h e slope ( | l x -bpi) o f relative m a  O U R versus t i m e is related to the m a x i m u m s p e c i f i c g r o w t h rate a c c o r d i n g to the equations outline b y K a p p e l e r and G u j e r (1992). T h e a d d i t i o n o f decay coefficient and the slope o f the straight l i n e determine the m a x i m u m specific g r o w t h rate  142  Experimental Results: Maximum Specific Growth Rate of Heterotrophy  Table A 4 . Results of maximum specific growth rate of heterotrophy Time  B i o m a s s Sources  4/11/02  UCT  4/12/02  UCT  (M-H-•b H ) ( d a y ) 1  10.8 12.8 7.3  MEBPR MEBPR  4/19/02  16.7  F / M ratio  Temperature °C  95%  2.6  17  R  2  92%  2.6  17.5  91%  1.9  17.5  88%  2.9  18  5/10/02  UCT  7  96%  3.9  19  5/13/02  UCT  4.5  96%  6.3  17.5  95%  9.8  17  5/14/02  UCT  87%  4.8  20.5 21  5/15/02  UCT  MEBPR  1.6 15.7 8.6  MEBPR 17  12.2  MEBPR  87%  4.7  98%  3.9  20  87%  3.8  20.5  5/16/02  UCT  10  90%  5.2  17  5/28/02  UCT  4  95%  4.4  16.5  92%  4.7  16.5  MEBPR  7.8  Table A 5 . Results of maximum specific growth rate of heterotrophy @ 2 0 ° C Time  B i o m a s s Sources  4/11/02  UCT  4/12/02  UCT  5/10/02 5/13/02  UCT  14.1  15.0  UCT  8.0  4.7 3.9  17 11.7  9.8 4.8  15.1  17 MEBPR  6.3 1.9  7.9  1.9 3.9  5.8 1.75  MEBPR  2.6 9.3  7.8  5.7  F / M ratio 2.6  16.2 9.1  7.7  UCT  5/15/02  14.3  16.0  MEBPR 5/14/02  1  H  MEBPR UCT  Mday )  (M-H-b ) ( d a y ' )  11.8  3.8  5/16/02  UCT  10  13.2  5.2  5/28/02  UCT  5.5  5.61  4.4  Sample mean  UCT  11.9  s  UCT  4.16  MEBPR  10.7  10.8  4.7  8.36 MEBPR  2.94  Note: The value of b was 0.14 day for U C T , and 0.13 day' for M E B P R process for the calculation of U , 1  H  143  E x a m p l e of C a l c u l a t i o n  Date: M a y 13, 2 0 0 2 Test m e d i a : influent wastewater and b i o m a s s c o l l e c t e d f r o m U C T process T=  17.5 ° C  Step 1 Calculate OUR C a l c u l a t e O U R u s i n g the same m e t h o d as i n the decay rate d e t e r m i n a t i o n i n A p p e n d i x 2 : O U R (mg 0 2 / L hr) = [ ( D O , - D 0 ) / t i + ( D 0 - D 0 ) / t + . . . + ( D O - D 0 ) / t ] / 6 0 2  2  3  2  s  In T a b l e A 9, e.g., w h e n t = 0 m i n , O U R = 4.68 ( m g 0  Test t i m e  T i m e (min)  D O mg/L  13:29 13:30  0  6.08  1 2  5.99  13:31 13:32 13:33 13:34  6  5  I/'hr').  2  A D O (mg/L)  3  5.91 5.79  0.09 0.08 0.12  4  5.76  0.03  5  5.69  0.07  O U R ( m g 0 / L hr) 2  4.68  Step 2 Plot OUR changes versus time  Step 3 Calculate relative OUR S p e c i f i c o x y g e n uptake rate S O U R = O U R ( m g 0  u ' d " ) * 10 (g M L V S S ) " 1  2  3  R e l a t i v e O U R = In [r (t)/r (to)]. F o r e x a m p l e , w h e n t = 9 m i n , M L V S S = 2525 m g L " ' = 2.525 g L " , 1  S O U R = 118.08/2.525 = 4 6 . 7 6 m g ( M L V S S d)"  1  144  1  S O U R at any t i m e d u r i n g the test w a s c a l c u l a t e d a n d l i s t e d i n the f o l l o w i n g table.  OUR ( m g 0 / L hr)  0  4.68  112.32  44.483  0  2  (mg  OUR 0 L d )  Relative O U R  Time (min.)  1  SOUR mg ( M L V S S dV  1  2  Ln[r(t)/r(t )]  1  0  9  4.92  118.08  46.764  0.050  39  5.52  132.48  52.467  0.165  70  6.36  152.64  60.451  0.307  80  5.76 7.32  138.24  54.749  0.208  175.68 172.8  69.576 68.436  0.447  198.72  0.571  120 140 190  7.2  0.431  200  8.28 8.52  204.48  78.701 80.982  220  10.2  244.8  96.950  230  7.44  70.717  0.779 0.464  240  9.96  178.56 239.04  94.669  0.755  0.599  Step 4 Determine maximum specific growth rate of heterotrophy P l o t relative O U R versus t i m e , the slop ((XH - bn) o f the r e s u l t i n g l i n e w a s 4.5 at 1 7 . 5 ° C . C o n v e r t e d it to 2 0 ° C b y a s s u m i n g 0 = 1.094 ( G r a d y et al, 1999). For example, when assuming b  = 0.14 ( d a y ) , L i = 4.5 * 1 . 0 9 4 1  H  ( 2 0  H  "  20°C.  Logarithmic form of relative OUR for UCT process May 13, 2002  0  50  100  150  Time (min.)  145  200  1 7 5 )  + 0.14 = 5.8 ( d a y ' ) at  Appendix 4  Determination of Readily Biodegradable C O D  T w o methods w e r e u s e d to determine the concentration o f r e a d i l y b i o d e g r a d a b l e C O D . O n e was the r a p i d p h y s i c a l - c h e m i c a l m e t h o d ( M a m a i s et al., 1993), and the other w a s aerobic b a t c h test m e t h o d ( E k a m a et al., 1986 and K a p p e l e r and Gujer, 1992).  Physical - chemical method T h i s m e t h o d i n v o l v e s r e m o v a l o f the c o l l o i d a l matter that n o r m a l l y passes t h r o u g h a 0. 4 5 | i m m e m b r a n e filter b y f l o c c u l a t i o n and p r e c i p i t a t i o n . T h e filtered samples c o n t a i n total influent s o l u b l e C O D f r o m w h i c h the n o n - r e a d i l y biodegradable s o l u b l e C O D is subjected to y i e l d the r e a d i l y b i o d e g r a d a b l e C O D .  1.  C o l l e c t 5 0 0 m l o f influent wastewater s a m p l e f r o m the storage tank i n U B C p i l o t plant, and take 500 m l o f effluent s a m p l e from the U C T and M E B P R processes separately.  2.  F l o c c u l a t e 100 m l o f those samples b y a d d i n g 1 m l o f 100-g L " z i n c sulfate solutions. M i x 1  v i g o r o u s l y w i t h a m a g n e t i c stir plate and stir bar for a p p r o x i m a t e l y 1 m i n u t e . 3.  A d j u s t the p H o f these samples to 10.5 b y u s i n g a 6 M o f s o d i u m h y d r o x i d e s o l u t i o n and a l l o w these samples to settle for a few minutes.  4.  W i t h d r a w the clear supernatant f r o m each s a m p l e w i t h a syringe and filter t h r o u g h a 0.45 | i m pore size filter. D e t e r m i n e the C O D o f each s a m p l e i n triplicate.  5.  T h e C O D o f the influent filtered supernatant CODSOL,  is the influent total t r u l y s o l u b l e C O D ,  and the C O D o f the effluent filtered supernatant  is the influent n o n - r e a d i l y  biodegradable C O D , Si. 6.  T h e s o l u b l e substrate C O D is determined b y the f o l l o w i n g equation: S  7.  I f the  s  acetic  = CODSOL-S,  acid  concentration  S A , has  substrate S F c a n be found as: S F = Ss - S A -  146  been  measured  then  readily  biodegradable  Experimental Results of Readily Biodegradable C O D  Table A 6. Readily biodegradable C O D test results - Physical chemical method Ssi S a m p l i n g data ( m g L " ) 1  UCT  SFI  Ss2 (mgU )  SF2 (mgU )  MEBPR  MEBPR  SFI  (mgL ) UCT 1  1  (%)  1  SF2  SA  (%)  (mgU ) 1  Sep-20-01  56  33  9  37  14  4  23  Oct-25-01 Oct-26-01  61  40  10  49  28  7  21  45 77  14 57  3 13  45 91  14 70  31 20  77  55  3 16 11  73  61 42  15 11  12  50 67  54  12  13  64 61  51  11  13  10  18  Feb-18-02 Apr-3-02 Apr-8-02  45  57  11  Apr-15-02 Apr-22-02 Apr-30-02 Sample mean  52  65 60  40  12 10  43  8  2.7  3.2  s  22  Calculation of Readily Biodegradable C O D - Physical & Chemical Method  Data: A p r i l 30, 2002 Test m e d i a : influent wastewater a n d sludge from U C T a n d M E B P P process  Step L Determine the influent total truly soluble and non-readily biodegradable  COD  Test the influent filtered supernatant to obtain the total t r u l y s o l u b l e C O D : COD oL=89mgL  l  S  Test the effluent filtered supernatant to get the influent non-biodegradable C O D S r 24 m g L '  1  Step 2. Calculate the soluble substrate COD  fraction  Ss = C O D S O L - S i = 89 - 25 = 6 4 m g L "  Influent total C O D , C O D  T o t  = 446 m g L"  1  1  T h e s o l u b l e biodegradable C O D fraction o f total C O D w a s 6 4 / 4 4 6 = 1 4 %  Step 5. Calculate the readily biodegradable COD  fraction  R e a d i l y biodegradable C O D i s the difference between the s o l u b l e biodegradable C O D a n d the V F A concentration S A - V F A concentration w a s tested separately, S = 1 3 m g L " . 147 1  A  R e a d i l y biodegradable C O D , S = S - S = 64 - 13 = 51 m g L " . 1  F  s  A  F r a c t i o n o f r e a d i l y biodegradable C O D o f total C O D = 51/446 = 1 1 % .  Aerobic batch test method A predetermined amount o f wastewater w i t h a k n o w n C O D strength is m i x e d w i t h a p r e v i o u s l y aerated v o l u m e o f settled m i x e d l i q u o r . T h e o x y g e n u t i l i z a t i o n rate i s . m o n i t o r e d u n t i l it drops to a l o w e r plateau l e v e l . T h e area beneath the O U R c u r v e is used to calculate the s o l u b l e substrate Ss. I f the acetic a c i d concentration S A , has been measured then r e a d i l y b i o d e g r a d a b l e substrate S F can be found as S F = Ss - S A -  1.  C o l l e c t 2 L o f m i x e d l i q u o r sample f r o m the aerobic z o n e i n the M E B P R process a n d b r i n g t h e m to the lab. C o n t i n u o u s l y m i x e d and aerated samples to keep t h e m fresh.  2.  C a l i b r a t e and zero a D O meter.  3.  C o l l e c t 3 L o f influent wastewater s a m p l e and determine the s a m p l e C O D . D e t e r m i n e the V S S concentration o f the m i x e d l i q u o r s a m p l e and calculate the C O D : V S S ratio.  4.  M i x a k n o w n v o l u m e o f well-aerated m i x e d l i q u o r s a m p l e w i t h a k n o w n v o l u m e o f wastewater  i n each  respirometer  to  o b t a i n the  C O D : V S S ratio  desired. F i l l  each  respirometer w i t h the m i x t u r e and insert a m a g n e t i c m i x i n g bar. 5.  P l a c e these respirometers o n a m a g n e t i c stir plate i n a temperature-controlled c h a m b e r to m a i n t a i n the contents at the temperature o f the p i l o t plant aerobic zones. Start the m i x e r at s l o w speed to keep s o l i d s m i x e d c o m p l e t e l y .  6.  Insert a calibrated d i s s o l v e d o x y g e n probe l i n k e d to a c o m p u t e r into each respirometer. A e r a t e reactor contents w i t h a r o u n d stone diffuser u n t i l the d i s s o l v e d o x y g e n o f wastewater is a p p r o x i m a t e l y 6 m g / L .  7.  A l l o w the probe to equilibrate for at least 3 0 seconds and then r e c o r d the changes i n the d i s s o l v e d o x y g e n for 5 minutes or u n t i l D O reaches 1 m g L " . 1  8.  T u r n o n the air s u p p l y to m a i n t a i n the D i s s o l v e d O x y g e n concentration a b o v e 4 m g O2 L " .  9.  M e a s u r e O U R every 15 minutes.  1  10. C o n t i n u e measurements u n t i l the O U R c u r v e that is attributable to the s o l u b l e substrate COD, S . s  11. I f the  acetic  acid  concentration  S A , has  substrate S F c a n be f o u n d as: S F = Ss - S . A  148  been  measured  then  readily biodegradable  Experimental Results of Readily Biodegradable C O D  Table A 7. Readily biodegradable C O D test results - O U R method Biomass Sampling Time  Source  (%)  (mgL" )  (%)  MEBPR  45  12  17  (%) 3  (mg L" )  Feb-21-02  28  8  1  Ss  SA  S  Ss (mgL" )  1  SF  A  SF 1  Apr-8-02  MEBPR  39  10  12  3  27  7  Apr-22-02  MEBPR  76  17  13  3  63  14  Apr-30-02  MEBPR MEBPR  85 56  19 12  13 13  3 3  72 43  MEBPR  65  14  13  3  52  16 10 12  11 12 13 3 48 61 3.2 s 17 Note: The growth yield was 0.59 (mg COD) (mg COD)" for U C T process, and 0.51 (mg COD) (mg COD)" is for M E B P R process for this calculation. Sample mean  1  1  Example of Calculation  Date: A p r i l 30, 2 0 0 2 Test m e d i a : influent wastewater and b i o m a s s c o l l e c t e d f r o m M E B P R process V o l u m e o f wastewater = 9 0 0 m l V o l u m e o f biomass = 600 m l T o t a l v o l u m e = 1500 m l V S S C o n c e n t r a t i o n = 5175 m g L " Total C O D = 446 m g L "  1  1  C O D / V S S ratio = 0.129  Stepl  Calculate OUR  C a l c u l a t e O U R u s i n g the same m e t h o d as i n the decay rate determination i n A p p e n d i x 2 : O U R (mg 0  L " hr" ) = [ ( D O , - D 0 ) / t ! + ( D 0 - D 0 ) / t + . . . + ( D 0 - D O ) / t ] / 6 0 1  2  1  2  2  3  Step 2 Plot OUR changes versus time  149  2  5  6  5  Readily biodegradable COD of MEBPR process April 30,2002 (A)  Step 3 Calculate the area under the OUR curve T h e plateau i n this c u r v e i s 3.48 m g O2 L " hr" . 1  1  T h e area i s c a l c u l a t e d b y the f o l l o w i n g equation: A r e a = ( O U R i + OUR2)/2 * ( T i m e 2 - T i m e 1), S u m the area to o b t a i n the total area under the curve.  T i m e (min.)  O U R ( m g 0 L " hr" )  Area  0  39.72  488.28  1  2  1  13  35.4  559.98  30 45  30.48  473.4  32.64  423.54  58  32.52  488.7  73  32.64  517.44  89  32.04  463.68  105  25.92  333.48  119  21.72  386.58  136  23.76  238.32  148  15.96  170.88  164  5.4  81  179 194  5.4  81.9  5.52  81.6  210  4.68  57.12  224  3.48  Total  4845.9  150  Step 4 Calculate the area due to the readily biodegradable COD T o t a l area m i n u s the area d u e to the b a c k g r o u n d respiration as i n d i c a t e d b y the plateau. T h e b a c k g r o u n d area is 3.48 m g 0 2 L " hr" 2 2 4 minutes. 1  1  T h e area d u e to s o l u b l e biodegradable C O D is 4 8 4 5 . 9 - 3.48*224 = 4066.38 m g 0 2 * m i n L " hr" 1  1  Step 5 Calculate the soluble biodegradable COD concentration A s s u m i n g Y H = 0.51 Ss = [ A 0 2 / (1 - Y h ) ] * ( V + V b  Ss = area* ( 1 - Y h ) * ( V + V b  The  w w  w w  )/V  )/V  w w  w w  = 4 0 6 6 . 3 8 * (1-0.51)* (900+600)/(900*60) = 5 6 m g 0 L "  fraction o f r e a d i l y biodegradable C O D ( S + V F A ) i n the total influent C O D i s 5 6 / 4 4 6 = F  0.12  Step 6 Calculate the readily biodegradable COD concentration, SF R e a d i l y biodegradable C O D = s o l u b l e biodegradable C O D - concentration o f V F A T h e concentration o f V F A i n influent w a s measured as 13 m g L " S  F  1  2  = S - V F A = 56 - 13 = 43 m g L "  1  1  s  T h e r e a d i l y biodegradable C O D fraction o f total C O D = 4 3 / 4 4 6 = 1 0 %  151  Appendix 5  Determination of Particulate Inert C O D  The b a t c h m e t h o d o f L e s o u e f et al. (1992) was used to determine the influent particulate COD.  A f t e r i s o l a t i n g residue o n a glass fiber filter, a refractory p o r t i o n w a s m e a s u r e d  b i o d e g r a d i n g a l l the filtrate. T h e inert s o l u b l e substrate was determined after  after  continuous  aeration o f a filtered sample for several days u n t i l a final C O D l e v e l was a c h i e v e d . T h e matter r e m a i n i n g i n the filtrate contained r e a d i l y and s l o w l y biodegradable substrate. A n o n - f i l t e r e d s a m p l e was aerated c o n t i n u o u s l y i n p a r a l l e l , the inert particulate matter w a s estimated f r o m the difference b e t w e e n the total C O D o f the aerated non-filtered sample, less the created b i o m a s s and the s o l u b l e inert  COD.  Procedures 1.  C o l l e c t a 3.5 L o f influent wastewater s a m p l e f r o m the storage tank i n U B C p i l o t plant.  2.  F i l t e r the wastewater sample w i t h v a c u u m through a G 4 G F / C glass fiber to r e m o v e any suspended matter.  3.  F i l l reactor A , B , C , and D w i t h 500 m l o f the filtered wastewater. Stir reactor contents b y u s i n g a m a g n e t i c m i x e r and a m a g n e t i c m i x i n g bar, and aerate t h e m b y u s i n g a r o u n d stone diffuser.  4.  D e t e r m i n e the i n i t i a l s o l u b l e C O D . R e m o v e a p p r o x i m a t e l y 6 m l o f each reactor  contents  w i t h a syringe and filter t h r o u g h a 0.45 | i m pore size m e m b r a n e filter. R e m o v e t r i p l i c a t e samples o f the filtrate for the s o l u b l e C O D determination. 5.  A d d a predetermined amount o f m i x e d l i q u o r f r o m the aerobic z o n e o f the U C T process to reactor A and B , w h i l e a predetermined amount o f m i x e d l i q u o r f r o m the aerobic z o n e o f M E B P R process to reactor C and D .  6.  F i l l reactor E and F w i t h 500 m l o f unfiltered influent wastewater and stir t h e m u s i n g a m a g n e t i c m i x e r and m a g n e t i c m i x i n g bar. A e r a t e the rector contents b y u s i n g a r o u n d stone diffuser.  7.  A d d a predetermined amount o f m i x e d l i q u o r f r o m the U C T process to R e a c t o r E , w h i l e a predetermined amount o f m i x e d l i q u o r f r o m the aerobic z o n e o f the M E B P R process to reactor F .  152  8.  Stir the reactor contents v i g o r o u s l y for a few m i n u t e s to disperse the b i o m a s s a n d r e m o v e triplicate C O D samples u s i n g a w i d e m o u t h pipette to determine the i n i t i a l total C O D .  9.  P l a c e these reactors i n a temperature-controlled c h a m b e r to m a i n t a i n the contents at the temperature o f the U B C p i l o t - p l a n t reactors.  10. A e r a t e reactor contents for several days and p e r i o d i c a l l y w i t h d r a w samples f r o m  each  reactor for the measurement o f the total a n d s o l u b l e C O D u n t i l a final C O D l e v e l is reached. C o m p e n s a t e evaporative losses w i t h d i s t i l l e d . Stir the reactor contents v i g o r o u s l y u n t i l a l l b i o m a s s floe are dispersed sufficiently w e l l to a l l o w representative s a m p l i n g . 11. T h e inert particulate matter is the difference b e t w e e n the final total C O D o f the n o n - f i l t e r e d sample, m i n u s the s o l u b l e inert C O D and the p r o d u c e d b i o m a s s .  153  Experiment Results of Inert Particulate C O D  Inert particulate C O D test results S a m p l i n g date P r o c e s s T o t a l C O D ( m g L " ' ) X i ( m g L / ' ) X | fraction (%) 10/12/01  UCT  503  192  38  MEBPR  503  145  29  10/25/01  MEBPR  408  24  4/8/02  UCT MEBPR  396 396  97 54 76  4/24/02  MEBPR  398  53  13  434  103  23  50  9  Sample mean s  14 19  Calculation of Particulate Inert C O D  D a t a : A p r i l 24, 2 0 0 2  Test m e d i a : influent wastewater and b i o m a s s c o l l e c t e d f r o m M E B P R process  Step 1. Determine the total COD and filtered COD of influent wastewater sample D a t e T i m e (hr) T o t a l C O D S o l u b l e C O D 4.24  0  398  120  4.25  34.5  310  65  4.26  57  301  59  4.27  86  280  54  4.28  110.5  53  4.3  127  249 223  53  COD variation of unfiltered sample 500 i _  400  H .  I 300 § u  200 -  A  100 ?  o -• 0  20  40  60  80  100  120  140  Time (hr.) —•—Total COD of unfiltered sample —s— Soluble COD of unfiltered sample 154  T o t a l C O D o f influent w a s 398 m g L " . 1  T h e filtered C O D o f influent w a s l 2 0 m g L " . 1  Step 2 Determine the total and filtered COD of the filtered and unfiltered sample after a final COD level has been reached  D a t e T i m e (hr) T o t a l C O D S o l u b l e C O D 4.08  0  124  117  4.09 4.1  34.5  96  73  57  96  4.11  86  93  61 53  4.12 4.14  110.5 127  88 86  49 45  T o t a l C O D o f the unfiltered S a m p l e after aeration w a s 223 m g L " . 1  T h e filtered C O D o f the filtered sample after aeration w a s 53 m g L " . 1  T o t a l C O D o f the filtered s a m p l e after aeration w a s 8 6 m g L " . 1  T h e filtered C O D o f the filtered sample after aeration w a s 4 5 m g L " . 1  COD variation of filtered sample  0  20  40  60  80  100  120  140  Time (hr.) -Total COD of filtered sample —a—Soluble COD of filtered sample  Step 3 Determine the particulate inert COD concentration of the influent wastewater S o l u b l e inert C O D S i = S o l u b l e C O D o f the total sample after aeration = 53 m g L " , o r 1  155  Si = 9 0 % o f the effluent s o l u b l e inert C O D = 28 m g L '  Apparent yield A p p a r e n t y i e l d for determine the matter r e m a i n i n g i n the filtrate: Y i e l d = Particulate C O D formed/biodegradable matter r e m a i n i n g i n the filtrate Particulate C O D f o r m e d b y degradation o f matter r e m a i n i n g i n the filtrate: total C O D o f filtered sample after aeration - s o l u b l e C O D o f filtered sample after aeration = 86 - 45 = 41 m g L"  1  B i o d e g r a d a b l e matter r e m a i n i n g i n the filtrate: i n i t i a l filtered C O D o f total s a m p l e - S i = 1 2 0 - 53 = 67 m g L "  1  A p p a r e n t y i e l d = 33/67 = 0.49  Biomass formed B i o m a s s debris fraction was about 2 0 % o f the total particulate C O D f o r m e d , so the b i o m a s s f o r m e d was: (1 - 20%)*41 = 33 m g L "  1  Inert particulate C O D : F i n a l C O D = Si + X i + y i e l d (initial total C O D - S i - X i ) 249 = 53 + X , +0.49(398 - 53 - X , ) X i = 53mg L"  1  Particulate inert C O D content i n influent w a s 28/398 = 7%, and s o l u b l e inert C O D content i n influent was 53/398 = 1 3 % .  156  Appendix 6  Determination of Influent C O D Fractions  S a m p l i n g data T o t a l C O D S ( V F A ) A  Sep-20-01  380  23  S % S S % 6 33 9 A  14  380 Sep-27-01  341  35  10  Oct-12-01  503 503  50  10  5 7 4  Oct-16-02  530  Oct-25-01  408 416  21 21  Oct-26-01  420  31  Jan-30-02  425 411  16 22  505  21  4  440  20  440  Feb-4-02 Feb-12-02 Feb-15-02 Feb-18-02  F  5  40  F  28 14  7 3  192 145  38 29  71 68  14 14  70  17  277  68  97  24  71  17  199  48  5  57  13  66  16  20  5  70  16  17  7  45 49  19 22  210 216  53  227 27  56 7  435  234  Mar-1-02 Mar-19-02  453  18  4  508 485  14  3  22  5  55  11  Apr-8-02  396 396  12 12  3  45  11  3  61  15  Apr-12-02  341 8  2  42  11  223  Apr-15-02  395  Apr-19-02  413  Apr-22-02  445  13  3  54  12  445  13  3  59  13  52  12 11  Apr-24-02  398  Apr-30-02  446  13  3  s  S,%  X  s  X % s  5  371  Sample mean  s,  10  Feb-25-02  Apr-3-02  X,%  4  Feb-21-02  Mar-25-02  Xi  446  13  3  51  446  13  3  42  9  418 67  19 8.9  5 2  45 16  10 3  157  76 54  19 14  53 53  13 13  53  13  53  13  103 50  23 9  60 10  16 3  55  Appendix 7  Determination of Influent Nitrogen Fractions  Sampling d a t a N H ( m g N L"') N Q " & N Q " (mg N L"') T K N (mg N L / ' ) T N (mg N L"') +  4  2  3  0.1  55.2  55.3  0.08  51.2  51.3  0.13 0.03 0.05  39.4 41.3 39.2  39.5 41.4  Oct-26-01  35 24 23  Jan-21-02  28  41.7  41.9  Jan-30-02 Feb-4-02  26 27  0.19 0.45  36 47.4  36.4 47.5  Feb-12-02  26  46.2  46.4  Feb-18-02 Feb-25-02  21  0.19 0.22 0.21 0.04  49.1 42.1  49.3 42.2  Mar-19-02  25 18  42.7  42.7  Mar-25-02  21  47  Apr-3-02  26  0.04 0.2  47 32.1  Sep-20-01  36  Sep-27-01 Oct-12-01 Oct-25-01  0.17  48 43  Apr-8-02  27  Apr-15-02  22  0.13  38.9  39.3  45.3  Apr-22-02  23  50.3  Apr-30-02  25  0.11 0.14  39 50.4  48.2  49.2  Sample mean  25 4  0.15 0.1  44.8 5  45.1 5  s  158  Appendix 8  Determination of Influent Phosphorus Fractions S a m p l i n g data PO4 " ( r a g P U ) 1  TP(mgPU')  Sep-20-01  4.5  4.7  Sep-27-01  4.1. 4.1  4.5  Oct-25-01 Oct-26-01 Jan-21-02  3.4 3  4.7 4.5  3.3  4.3  Jan-30-02  3.1  4.1  Feb-4-02 Feb-12-02  3.3 3.3  4.7 5.3  Feb-18-02  3.3  4.8  Feb-25-02 Mar-19-02  3.1 3.4  3.5 5.3  Mar-25-02 Apr-3-02  3.1  2.8 5.4  Apr-8-02 Apr-15-02  2.9 2.8  4.6 4.6  Apr-22-02  3.6  4.5  Oct-12-01  3.8  4.6  Apr-30-02  3.6  4.7  Sample mean  3.4  4.6  5  0.5  0.6  159  

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