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The effects of temperature, pH and retention time on volatile fatty acids production from primary… Gupta, Ashok Kumar 1986

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THE EFFECTS OF TEMPERATURE, pH AND RETENTION TIME ON VOLATILE FATTY ACIDS PRODUCTION FROM PRIMARY SLUDGE  by ASHOK KUMAR GUPTA B . S c . ( C i v i l Engg.) 1980, M . S c . ( C i v i l of D e l h i , D e l h i ,  Engg.) 1982, U n i v e r s i t y India  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF v MASTER OF APPLIED SCIENCE  in FACULTY OF GRADUATE STUDIES DEPARTMENT OF CIVIL ENGINEERING We a c c e p t t h i s t h e s i s as c o n f o r m i n g  to the S q u i r e d  standard  UNIVERSITY OF B R I T I S H COLUMBIA January,1986 ©  ASHOK KUMAR GUPTA, J a n u a r y , 1 9 8 6  In  presenting  this  degree at the  thesis  in  University of  partial  fulfilment  of  this  department  or  thesis for by  his  scholarly purposes may be  or  her  representatives.  permission.  CiVMU  gM5fr.  The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3  Date  DE-6(3/81)  JaMx^a/t-A-j '  that the  for  an advanced  Library shall make it  agree that permission for extensive  It  publication of this thesis for financial gain shall not  Department of  requirements  British Columbia, I agree  freely available for reference and study. I further copying of  the  is  granted  by the  understood  that  be allowed without  head of copying  my or  my written  ABSTRACT  A alternate British  typical  anaerobic  (VFA's)  to  the  phosphorus  At  the  full-scale  at  a  pilot-scale been  aerobic  (UBC)  overall  has  and  Columbia  acids  biological  has  removal  indicated  that  zone  at  VFA's  research  at  least  to  addition  to  of  the  University  of  of  volatile  plant  at  the  fatty  improves  treating  weak  the  sewage.  K e l o w n a , B.C., and  fermentation  add  consists  processes  when  removal  U B C , anaerobic  produce  process  Bio-P  at  phosphorus  removal  the  of  efficiency,  biological  to  z o n e s . Recent  anaerobic  facility  used  phosphorus  of  primary  anaerobic  zone  sludge  of  these  processes.  The knowledge  of  V F A ' s ) to  help  effects  of  short-chain Oxidation to  used  reactors  the  achieve  pilot  phase  VFA's  of  optimum  temperature,  primary  potential  between  A  completely  random  were  run  on  the a  fed  fill  time  once  and sludge also  3 X 3 X 2  a day  with  plant.  ii  pH  on  the the  were  studied  factorial  in  primary  a  improve  the  production  of  fermenter.  The  production  of  at  throughout  production  sequence. basis  to  (the  of  monitored  O R P and the  draw  was  digestion  and o p e r a t i o n  experimental and  research  anaerobic  (ORP) w a s  relationship  determine  this  sewage  the  to  of  design  retention  from  r o o m . Reactors were UBC  objective  acid  reduction  explore  was  primary  of  lab-scale. the  VFA's.  experimental  Three  study  litre  design  anaerobic  temperature-controlled  sludge  brought  from  the  iii Results improved  with  showed  the  increase in temperature  low  temperatures  the  increase in retention  9 days at 30°C  (10°C  and 20°C)  t i m e ; however  7.0, was not  net  to  net  production  range  of  10°C  V F A production  extension of  the  consistently to  improved  retention  consistent with both retention  was observed between  30°C. At  V F A production. The effect  and had a confounding effect. At  a relationship  VFA  in the  the  appeared detrimental  control, at a value of temperature  that  10°C and 20°C  with  time  to  of  pH  time  and  temperatures,  ORP and V F A production. No  definite  relationship between the net V F A production and ORP was found at 30° C.  Table of  Contents  ABSTRACT  ii  LIST OF T A B L E S  vi  LIST OF FIGURES  vii  ACKNOWLEDGEMENT  .„'  ix  1.0 INTRODUCTION 1.1.  1  E X C E S S BIOLOGICAL  1.2. ANAEROBIC  PHOSPHORUS R E M O V A L  DIGESTION  4  1.3. OPTIMIZATION OF ACID FORMERS 1.4.  METHANOGEN  1  5  INHIBITION  .7  2.0 RESEARCH OBJECTIVES  9  3.0 DESIGN OF EXPERIMENTS  12  3.1.  EXPERIMENTAL DESIGN  12  3.2.  SEQUENCE OF EXPERIMENTS  13  4.0 EXPERIMENTAL FACILITIES  16  4.1.  EXPERIMENTAL  SET-UP  16  4.2.  FEED USED IN THE STUDY  16  4.2.1  COLLECTION A N D S T O R A G E OF THE FEED  16  4.2.2  MAINTENANCE  18  4.3.  EXPERIMENTAL PROCEDURE  4.3.1 4.4.  OF THE COD OF THE FEED  18  FILL A N D DRAW R E A C T O R S :  SAMPLING  AND ANALYSIS  4.4.1  SAMPLING  4.4.2  ANALYTICAL  4.4.2.1  18  VOLATILE  20 !  TECHNIQUES FATTY  USED  ACIDS  iv  20 20 21  V  4.4.2.2 5.0 R E S U L T S  TOTAL AND  ORGANIC  21  DISCUSSION  5.1.  RESULTS  5.2.  STATISTICAL  22 22  ANALYSIS  5.2.1  STANDARDIZED  5.2.2  ANALYSIS  OF  5.2.3  DUNCAN'S  MULTIPLE  5.3.  CARBON  23  ERRORS  23  VARIANCE  (ANOVA)  RANGE  27  TEST  33  DISCUSSION  33  5.3.1  TOTAL  VFA  5.3.2  ACETIC  5.3.3  PROPIONIC  ACID  5.3.4  EFFECT  OF  pH  5.3.5  EFFECT  OF  TEMPERATURE  49  5.3.6  EFFECT  OF  RETENTION  50  5.3.7  BEST  5.3.8  MICROBIOLOGICAL  ACID  AT  .„  40  PRODUCTION  43  CONTROL  46  TIME  OF  TREATMENT  EXPLANATION  VARIABLES  FOR  THE  5.3.10  DAILY  5.3.11  OXIDATION  CONCLUSIONS  BETWEEN  SOLUBLE  TOC  AND  VFA  VFA  58  POTENTIAL(ORP)  61  RECOMMENDATIONS  CONCLUSIONS  6.2.  RECOMMENDATIONS  APPENDIX  OF  REDUCTION  6.1.  REFERENCES  OF  55  PRODUCTION  AND  50  51  PRODUCTION  6.0  BEHAVIOUR  30 ° C  RELATIONSHIP  37  PRODUCTION  COMBINATION  REACTOR 5.3.9  PRODUCTION  73 73 .....74 76  I  80  List of Tables Table  Page  Table 3.1 Layout  of  Sequence of  Experiments  Table 4.1 Typical Characteristics of the  14  influent primary sludge  19  Table 5.1 Summary of  Results for  10°C Temperature  Run  24  Table 5.2 Summary of  Results for  20°C Temperature  Run  25  Table 5.3 Summary of  Results for  30°C Temperature  Run  26  Table 5.4 Standardized Errors  28  Table 5.5 A n a l y s i s of Variance for  Net A c e t i c A c i d Production  29  Table 5.6 A n a l y s i s of  Net Propionic A c i d Production  30  Variance for  Table 5.7 A n a l y s i s of Variance for Total Table 5.8 Ranking of  Means of  Different Operating  Net Volatile  Fatty A c i d Production  Net A c e t i c A c i d Production  Conditions  using Duncan's Multiple  .31  Under Range Test  34  Table 5.9 Ranking of Means of Net Propionic A c i d Production Under Different Operating Conditions using Duncan's Multiple Range Test  35  Table 5.10 Ranking of Means of Total Net V F A Production Different Operating Conditions using Duncan's Multiple  36  vi  Under Range Test  List of Figures Figure  Page  Fig. 2.1 Causes and Effects  11  Fig. 4.1 Sketch of  17  Anaerobic Reactor (Adapted from Comeau, 1984)  Fig. 5.1 Total Net V F A Concentration v s . Retention Time at Controlled pH  38  Fig. 5.2 Total Net V F A Concentration v s . Retention Time at Uncontrolled pH .39 Fig. 5.3 Net A c e t i c A c i d Concentration v s . Retention Time at Controlled pH  ..41  Fig. 5.4 Net A c e t i c A c i d Concentration v s . Retention Time at Uncontrolled pH  42  Fig. 5.5 Net Propionic A c i d Concentration v s . Retention Time at Controlled pH  44  Fig. 5.6 Net Propionic A c i d Concetration v s . Retention Time at Uncontrolled pH Fig. 5.7 Total Net V F A concentration  45 v s . Soluble Total Organic Carbon  56  Fig. 5.8 Net Daily Production of Total V F A v s . Retention Time at Controlled pH Fig. 5.9 Net Daily Production of Total V F A v s . Retention Time at Uncontrolled pH  59 60  Fig. 5.10 Relationship Between Mean ORP v s . Net A c e t i c A c i d Production  62  Fig. 5.11 Relationship Between Mean ORP v s . Net Propionic A c i d Production ..63  vii  viii Fig. 5.12 Relationship Between Mean ORP v s . Total Net V F A Production  64  Fig. 5.13 Relationship Between ORP and Net V F A production for and Controlled pH Operation  10°C 66  Fig. 5.14 Relationship Between ORP and Net V F A production and Uncontrolled pH Operation  for  10°C  Fig. 5.15 Relationship Between ORP and Net V F A production and Controlled pH Operation  for  Fig. 5.16 Relationship Between ORP and Net V F A production and Uncontrolled pH Operation  for  Fig. 5.17 Relationship Between ORP and Net V F A production and Controlled pH Operation  for  67 20°C 68 20°C 69  Fig. 5.18 Relationship Between ORP and Net V F A production for and Uncontrolled pH Operation  30°C 70 30°C 71  ACKNOWLEDGEMENT I  am  sincerely  guidance the  thankful  to  and encouragement  moral  support  Timothy bringing due  Ma  primary  thank  during  this  Dr. W .  study.  Sue Jasper,  help  in  sludge  from  the pilot  and to  I  K.  also  Oldham,  for  acknowledge  the f e l l o w  graduate  his  deeply student,  stages of this research.  their  to Fred K o c h , Y v e s  discussions short  also for  supervisor,  and assistance received from  P. F. C o l e m a n , at the v a r i o u s  I  my  the  Susan  lab  work  plant  C o m e a u and T. V a s s o s  D r . D. S . M a v i n i c  time.  ix  for  Liptak, and  every  Paula Barry  week.  f o r their  reviewing  Parkinson and Rabinowitz  Thanks  are a l s o  participation  the t h e s i s  for  in  in the a  very  CHAPTER 1 INTRODUCTION  Phosphorus recent  past. This  an  essential  in  danger  are  is m a i n l y  component  of  wastewater include  removal  phosphorus  presently  of  technology with the  treatment  removal. A  have  been  number  of  a n d h a s , in a v e r y  the c h e m i c a l of  chemical  short  precipitation, inorganic  plants  owing  residues  to  is  (which  to  techniques  the w o r l d . O f biological  very  promising  to be f a v o u r a b l y  compared  the latter's often  a  existing years  in the e x c e s s  process  time, come  Many  recent  around  is  b o d i e s are  precipitation  shown  biological  in  in the  wastewater  water  enrichment.  upgraded  treatment  attention  from  the r e c e i v i n g  i n t e r e s t ' is b e i n g  process. This  removal  phosphorus  in u s e in the v a r i o u s  removal  problem  where  due t o  facilities  late, h o w e v e r , considerable phosphorus  considerable  because phosphorus  eutrophication  treatment  has r e c e i v e d  expensive  pose  nature  difficult  and  disposal  problems).  1.1. EXCESS BIOLOGICAL PHOSPHORUS REMOVAL  According (1959  )  in  metabolic  India,  phosphorus the  concluded  Levin first  and Shapiro  reported  in  the  that,  in  the  of  aeration.  a biological  Levin  mechanism  (1965),  phosphorus  waste  r e m o v a l , the m a g n i t u d e  intensity  hypothesize  who  requirements  investigators  to  where  o f the r e m o v a l and for  1  Shapiro  in  sludge they  et a l .  excess  of  plant.  These  observed  excess  appeared to be linked to  (1965)  P uptake.  w a s Sastry  removal  activated  plant  it  were  H o w e v e r , it  the  first  to  w a s Barnard  2 (1974,1976)  who  exhibiting mixed  intensity He  noted  that  the  excess P removal  was  that  liquor  had  that  stated  first  been  subjected  P release from  that  anaerobic  to  the  P  common  feature  at  point  some  an  anaerobic  sludge  release  back  is  a  to  of in  all  the  p r o c e s s , the  condition the  processes  of  such  supernatant  prerequisite  for  an  occured.  the  excess  biological P removal. A anaerobic  Bio-P  in  carbon  certain  substrates  bacterial  simultaneously, phosphorus carbon  compound  Fukase  et  (1985)  of  released  as  zone  phosphate  from  phosphorus  amount  of  is  and  an  store  it  the  released  1984). Hence, the  of  and  under  by  aerobic under of  biological  alternate  inorganic  fatty  (1979), Fukase  form  added  can be correlated with the amount (Wentzell,  of  acids  a  et  anaerobic zone,  can  anaerobic  stored  al.  (1980),  and  Arvin  et  between  of  some  be  phosphorus  bacteria  p o o l s . The correlated  phosphorus  in the removal  the take  amount  with  the  in  turn  conditions, which  V F A available  the  conditions. When  polyphosphate zone  and  as a  al. (1982)  amount  of  (PHB)  relationship  the  aerobic in  Deinema  forms  (VFA's) are  poly-j3-hydroxybutyrate  (1984).  solution  followed  phosphorus  free or  volatile  Osborn  some  acids  into  in  and  is  fatty  uptake  as  Comeau  there  solution  such as  consists  is released. PHB has been reported  and  phosphate  process  absence of  cells  Nicholls  that  volatile  anaerobic  of  by  a l . (1982)  observed  amount  removal  and aerobic zones. In the  oxygen, simple stored  typical  anaerobic zone capacity  of  a  plant can be improved by the addition of V F A in the anaerobic zone.  In North A m e r i c a , COD values of the wastewaters quite readily  low  (in the 200-300mg/l  biodegradable  range). Siebritz et  COD comprises  about  are generally  al. (1982) found  20% of  the  total  that  the  COD of  the  3 South A f r i c a n wastewaters. If same is true for North American wastewaters, then  the  readily  wastewaters effect  of  readily  biodegradable  would a  GOD  concentration  be in the range of  recycle  rate  biodegradable is  of  1:1  zone  reduced to  anaerobic  P release, assuming  North  40-60mg/l. Allowing  with  respect  COD concentration  anaerobic  in  to  available  the  to  minimum  that  enters  no  nitrate  for  the  influent  the  2 0 - 3 0 m g / l , the  American dilution  flow,  organisms required  the  in  to  zone  the the  ensure  (Rabinowitz  and Oldham, 1985). Therefore, to ensure that the specific substrates  required  for  bacteria  in  the  excess biological  the  anaerobic  concentration  zone,  in  the  P removal the  addition  influent  synthetic V F A or by primary Rensink phosphorus removal report  that the  in  British  the  al.  from 45% to of  of  be  VFA's  is  increased  almost  either  by  the  essential. V F A the  addition  used  acetic  acid  addition  to  improve  97%. Oldham (1984) and Rabinowitz primary  C o l u m b i a , primary  a pilot-scale  sludge  was  (1985)  sludge can be used succesfully  fatty acids. At the f u l l - s c a l e biological phosphorus at  of  fermentation.  (1984)  K e l o w n a , B.C., and  rich fermentor  can sludge  fermentation  produce volatile plant  et  mechanism is available to  facility  purposefully  at  the  liquor was used as a V F A source in the  removal  University  fermented  and  to  the  of acid  anaerobic zone  of  bioreactor.  To than  methane  digestion  maintaining  impact  much of a  about  the  production,  and the  Unfortunately,  known  optimize  viable  use  improved of  the  digestion  anaerobic  digestion  knowledge products  of  acid  of  methane  production,  for  the  on the  research on anaerobic  population  optimizing  of  while  acid  rather  phase  of  process is required.  digestion  formers.  VFA's  is f o c u s s e d on  However, suppresing  little  is  methane  4  production, to  1.2.  maximize  the  matter  is  converted  molecular least 1.  oxygen.lt  three  Fermentative  2.  acids 3.  VFA's.  groups  to  short  hydrolyzed  by  amino  acids.  by  these  The fatty  acids  (VFA's),  are  and  neutral  1971). acetic  the  acid  and  of  p r o c e s s requiring  at  organic  polymers  convert  these  acetate, carbon  dioxide  of  of  enzymes to  acids  to  volatile  (Woods  dioxide  et  anaerobic  and  a l . , 1980).  digestion  is  the to  complex  simple  simple are  soluble  sugars  the  only  organic  while  substrate  compounds. proteins  compounds  that  are are  enzymes.  carbohydrates, amino  formation  most  the  phase  of  short  compounds, hydrogen  The  absence  hydrogen;  portion  extra-cellular  to  the  organic  phase.  Fatty  of  which  and c a r b o n  hydrolyzed  fermentation  leads  other  Mah,  produced  extra-cellular  to  which  acids;  catabolize  insoluble  are  in  in  stage  complex  bacteria  dioxide  methane  starch  attacked  fatty  which  and  hydrolyzed not  chain  acid-forming  I n i t i a l y , the  dioxide  a three  hydrolyze  non-methanogenic  c a l l e d the  carbon  process  bacteria:  acetogenic  produce  biological  and  which  bacteria  The  Cellulose  of  acetate, carbon  hydrogen  a  c o n s i d e r e d as  bacteria  Methanogenic  commonly  be  producing  to  is  methane  can  simpler  Hydrogen  digestion to  metabolic  produce  and  of  ANAEROBIC DIGESTION  Anaerobic  is  availability  common propionic  and  chain carbon  short-chain, a c i d . Other  acids  and  volatile dioxide volatile  important  long fatty  chain acids  (Chynoweth fatty  acids  acids  produced  5 are  formic  although  acid,  butyric  produced  in this  oxidized by all known dioxide to  methane Short  phase  becomes  acid,  voleric  phase, is barely  methanogenic  chain  volatile  substrate  for  Acetic  acid  the  acid  methane  organisms  catabolizing  is  a  in nature  methane  are required  acetic  isovaleric  detectable  acid.  because  bacteria during the  acid  fatty  a  acids  group  V F A ' s to very  strictly  Hydrogen,  it  is  rapidly  reduction  of  carbon  important  acid  in  the  intermediary.  via the  methyl  is also a major  propionic  are  forming  methanogenic dioxide. Approximately  group  of  intermediary.  digestion, the acid  acid  anaerobic  methane and carbon  in anaerobic  and  produced  of  is produced  (McCarty, 1964). Propionic  many  and  (Mah et al., 1977).  bacteria. These bacteria ferment  70% of  acid  the  groups most  acetic  Although  of  bacteria  important  in  fermentation.  1.3. OPTIMIZATION OF ACID FORMERS  Little bacteria the  known  in conjunction  important  studies ,1965;  is  using Ghosh  1979,1982). optimize  with  information soluble and  about  the  substrates  Hence, the  optimization  suppression of on  Pohland,  the  such  1974;  usefulness  the design and operation  acid as  of  has  glucose et  the  al.,  the fermenter studies  acid  producing  formers.  Most  been  obtained  (Andrews  and  1984;  results  a substrate, is questionable. There are few  the  methane  phase  Cohen of  the  of  from  using primary  from  Pearson  Zoetemeyer these  of  et  studies,  al., to  sludge as  available where  primary  sludge has been used as a substrate to study the the acid phase. Important among them (1968),  are the studies  Chynoweth  and  done by Eastman and Ferguson (1981), O'Rouke  Mah  (1971)  and  Borchardt  (1971).  Important  6  observations studies  made  using  in the  primary  sludge  Andrews using  soluble  exceedingly being  studies  and  with  a s the  have  soluble  (1965) found  a minumum  s u b s t r a t e , as w e l l  s u b s t r a t e , are  Pearson  substrate,  rapid  using  cell  and  discussed  Ghosh  that  the  as  the  below.  and  Pohland  fermentation  residence time  in  (1974),  step  of  only  a few  concluded  that  the  is  hours  required.  Andrews volatile  acid  by  variation  the  relative  and  more  report  produced of  the  from  production  the  Pearson a  organism  strongly  that  and  of  on  (1965)  given  the  distribution  substrate  residence  individual  of  time.  fatty  culture  pH  the  also  may  be  markedly  Zoetemeyer  acids depends  value.  volatile  is  and  found  that  dilution  rate  Ferguson  affected  of  influenced  (1982)  o n the  Eastman  acids  type  by  (1981)  operating  conditions, especially pH.  Carbohydrates acid  phase  time  and  times  (Eastman hence  and  et  (1981),  reported  the  covert  different  carbon  al.  lipid  (1975),  sources  are  degraded  in  the  require  a  longer  detention  degradation  occurs  at  short  detention  quoted  Uribelarrea  arid  Pareilleux  of  22  by  non-methanogenic  (cellulose, proteins,  organisms  able  to  carbohydrates  etc.)  into  optimum  for  acid  acids.  from  raw  to sludge  optimum  oxidation-reduction  -510  (calomel  mV  of  existence  According production  materials  and M a h , 1971).  Bissele  fatty  nitrogenous  F e r g u s o n , 1981). L i p i d s  inhibition  (Chynoweth  volatile  and  ref.).  Borchardt  (1971),  the  digestion  is  around  potential  for  acid  7.  In  the  production  pH same  was  study,  the  reported  as  7 McCarty (1963) and Andrews and Pearson (1965) found that degradation of  butyric  acid by the methanogenic bacteria occurs at a faster  rate than acetic acid and much faster than propionic very low butyric  1.4.  a c i d ; this results in a  concentration and often no detection is p o s s i b l e .  METHANOGEN INHIBITION  Methanogenic conditions. The optimal  bacteria are extremely  pH range for  the  pH  is  maintained  between  between  6.6  7.6. When  about 6.2, the acid condition exhibits acute toxicity  fermentative  to  the  and  pH of  interesting  of  7.0 and 7.2.  is quite satisfactory as long  6.6, there  is  inhibition  environmental  is between  below  It  is signifiant  sensitive to  methanogens  McCarty (1964) reports that the gas production as  the  methanogenic  note  that this  pH does not  bacteria will  continue  to  stop  pH  drops  bacteria. At  a  to these bacteria.  acid production. The  produce acids until the  pH drops  to  anaerobes, even a small amount  of  4.5 or 5.0 (Pfeffer, 1974). As molecular highly  oxygen can be inhibitory  reduced  that optimum -530  methanogens are strict  mV  environment redox potential  (calomel  minimum  for  ref.  aeration, studied  for  but  completely  when inhibited.  with an E ^ of by volume.  the One  E^  growth.  Dirisian  methane formers  electrode, the  these bacteria. Hence they  their  (E^-.)).  effect  w a s t e s . When operating with an occured,  to  of  reached  system  of  was  - 5 0 0 m V ; the o f f - g a s  ORP on  -360  et  the  al.  (1971)  treatment  mV, some methane mV,  methane  completely  from  a l . (1963)  found  is between -520 mV and  Converse  -435  et  require a  of  swine  production  production  anaerobic,(no  using  was  aeration),  this s y s t e m was 51.1% methane  8  Ammonia, concentrations. ammonia  At  nitrogen  concentrations regardless  of  particularly when  concentrations and  above pH  greater  3000  mg/l  Methanogens minimum  cell  residence  low  2.5  to  as  fermentation Ferguson and  operation.  requires  very  and  active  are  the  time  very  1500  7.4, N H  and 3  ammonium  for  (Andrews  and  longer  that, in gas  slow  reported  much  little  than  form,  3  is  inhibitory  3000  mg/l,  can  become  ion  itself  at  high  of  total  inhibitory. At becomes  toxic  1961).  days  (1981) r e p o r t  pH=6,  operation  4  NH  between  a pH  (McCarty,  in  a  organisms.  methane  producing  Pearson,  1965),  cell ~ residence  batch  production  methanogenesis  growing  test  using  took  place  started  only  primary  on  the is  eighth  twentieth  as  methane  Eastman sludge  the the  bacteria active  time.  by  Although  at  and 35°C  day  of  day  of  CHAPTER 2  RESEARCH OBJECTIVES  As the  acid  design  phase and  information of  discussed of  the m e t h a n e  The  and  studied  on  objective  on a control  production,  acetic  acid, propionic  It potential a  of  can  was  exists  acid time  not only  also  the  net  acid, butyric  also  between a  fatty  the t r e a t m e n t  volatile  related  achieve  the  study  and  of  the  optimization  the o p t i m i z a t i o n  was  production  of  optimum  much  to  about  knowledge  of the methane  pH. The  formers.  to  from  of  explore primary  effect  of  the sludge  pH  was  (i.e. p H , t e m p e r a t u r e  and  situation.  variables respect  production  to net total  of  the  volatile  individual  acids  fatty (e.g.  acid).  to  the s t u d y ,  relationship,  be u s e d a s a c o n t r o l  with  decided  (ORP) throughout  relationship  there  but  this  (pH=7) vs. no control  effect  is  known  of  to  Unfortunately,  suppresion  retention  retention time) w a s studied acid  is  improved  required  digestion  with  net v o l a t i l e  is  fermenter.  bacteria. Little  temperature,  The  the  anaerobic  main  chapter,  digestion  in c o n j u n c t i o n  between  fermenter  of  forming  the' acid f o r m e r s  relationship  anaerobic  operation available  in t h e p r e v i o u s  in o r d e r  fatty  it w o u l d  parameter  monitor  acid be  to explore  oxidation  useful  to VFA  reduction  the p o s s i b i l i t y  (VFA) production  to monitor  9  the  determine  and  ORP.  whether  production.  of If  ORP  10 The phase  of  anaerobic  fermenter. This sewage  basic  would  treatment  wastewater, with  two  while the  HRT  have  a  completely  Before the  causes  variables). Figure  amount of  the  these  treatment shows  the  used  and  to  by  causes  and  in  the  from  a a  substrate.  retention  the  type  time  of  (HRT)  organisms  organisms.  Because  of  simplify  i t , it w a s  decided  to  same  instead  experiments,  variables)  acid  the  the  used  the  e f f i c i e n c y of  phosphorus  hydraulic  governs  of  production  biological  remove  and  having is  VFA  soluble, simple  food  study  system  of  to  former  of  the  designing  2.1  improving  (SRT)  The  retention time  (or  the  designed  time  an u n d e r s t a n d i n g  maximize  being  concentration  mixed  achieve  in  parameters.  nature  to  helpful  retention  c o n f u s i o n , the t e r m  know  to  be  governs  exploratory  digestion  a low  different  the  was  plant  Sludge are  purpose  and  SRT of  it  the  effects  and  SRT  was  and  very  effects in the  HRT.  (or  To  avoid  HRT.  important  to  performance  present  study.  C A U S E S  E F F E C T S  RETENTION TIME  NET A C E T I C ACID PRODUCTION  SOME MECHANISM  TEMPERATURE  WITH/WITHOUT pH CONTROL  >  NET PROPIONIC ACID PRODUCTION  NET T O T A L VFA PRODUCTION  Figure 2.1 : C A U S E S AND E F F E C T S .  CHAPTER 3  DESIGN  To  know  treatment  variables,  statistical  basis.  3.1. EXPERIMENTAL  A design  whether it  was  completely Since  combinations  were  allocated  the  randomization controller  the  execution was  is  any  to  restricted  interaction  design  were  s t u d i e d . Three  time  and 2 conditions  design  the  X  3  was  the  between  experiments  2  throughout  experiments.  controlled  conditions  factorial  the  random,  However,  limitations  the  of  of each  pH, temperature  methane  periods  were  for  3,  of  temperature  studied. The details  not studied  of  pH  and retention  are g i v e n  and  9  because  retention  of the p o s s i b i l i t y  below:  of volatile  times. of  Higher  significant  formation.  TEMPERATURE: V o l a t i l e f a t t y a c i d s was  6  complete  and retention  days  studied  design,  (availability  fatty  retention  a  treatment  experimental  on the p r o d u c t i o n  was  on  experimental  RETENTION TIME: T h e e f f e c t o f r e t e n t i o n t i m e acids  the  room).  combinations  o f pH w e r e  X  completely  b y , equipment  a l l , eighteen  time  3  randomly  of  and a temperature  In  decided  randomized  used.  to  there  DESIGN  was  prior  OF EXPERIMENTS  studied. Keeping  in m i n d  production  at three  the c l i m a t i c c o n d i t i o n s  12  different  temperatures  in B r i t i s h  C o l u m b i a , it  13  was  decided  to cover  temperatures  that w e r e  pH:  It  pH  of  the  uncontrolled  pH  is  well-known  the r e a c t o r  studied  of  only was  combination  variations  layout  described  a  single  limited  effect  such  as  conditioning,  it w a s  each  it w a s  to study  decided  volatile  pH  fatty  a c i d s , the  the pH e f f e c t f o r '  c o n d i t i o n . The  control  Statistics  is g i v e n  in  ideal  Table  3.1, t h e  of  nesting  temperature  each  run's  temperature  culture  conditioning  with  decided  to  reduce  intermix  design  limited  room.  3.1. T o  Hence,  was  by  the  complete  retention  time  X  value.  would  to  random  particular  compromise  However,  in T a b l e  was  controlled  this  layout  of  experiments  at the U n i v e r s i t y  aforementioned  layout  was  limitations.  3.2.  SEQUENCE OF EXPERIMENTS As  is  evident  s e t , three  of  be to pH  the  X  confound retention  possibility  the c o n t e n t s  from  anaerobic  w a s checked  British  the best  time  each  o f the e x p e r i m e n t  of  run t o time  of  the three  X  culture reactors  experimental run.  The  In  of  temperature  by  of  interactions.  run.  30°C.  the p r o d u c t i o n  randomization  temperature  of  1 0 ° C t o 3 0 ° C . T h e three  and  a n d the c o n t r o l l e d  within a single  The  between  with  pH c o n d i t i o n  because  randomization  run  from  are 1 0 ° C , 2 0 ° C  falls. Hence,  layout  compromised  pH  that  complete  the  availability  studied  range  w a s 7.  A obtained  the t e m p e r a t u r e  Columbia  one, given  Table  3.1, s i x  reactors  were  out b y the  Department  and c o n f i r m e d  the s e v e r e  sets  of  operating.  that the  equipment  experiments Details  of  and  were each  14  T a b l e 3.1  Layout o f Sequence o f Experiments  REACTOR# 1  REACTOR# 2  REACTOR# 3  1  9/10/pHu  3/10/pHu  9/10/pHc  2  9/30/phu  6/30/pHu  3/30/pHc  3  9/30/pHc  6/3 0/pHc  3/30/pHu  4  6/20/pHc  9/20/pHc  9/20/pHu  5  3/20/pHc  3/20/pHu  6/20/pHu  6  6/10/pHc  6/10/pHu  3/10/phc  RUN #  KEY: R e t e n t i o n Time ( d a y s ) / T e m p e r a t u r e ° C / pH C o n t r o l l e d or Uncontrolled  15  set  of experiments  are g i v e n  FIRST SET; T h e f i r s t had  9  had  uncontrolled  days  days  SECOND  set of experiments  retention  retention  time  pH but o n l y  time  reactor  had a  reactor  also  reactor  h a d three  days  FOURTH  time  and nine  also had  h a d three  h a d three six days  first  second The  reactor  was  reactor  time. The third reactor  also had 9  was performed  retention  pH. The time.  second  The  third  ot 3 0 ° C .  The first  pH. The second  time. The third  reactor  reactor  had  time.  20°C.  The first  pH. The second  reactor  reactor  also  days. The third reactor  experiments  retention  had s i x had  days  controlled  had u n c o n t r o l l e d  time time  w a s also  run at 2 0 ° C .  and controlled  The first  pH. The second  reactor  pH. The third  reactor  but u n c o n t r o l l e d  and uncontrolled pH.  a n d last  set of experiments  w a s run at s i x d a y s  was also  retention  and c o n t r o l l e d  retention  retention  time  days  The first  time.  set of  days  run at 3 0 ° C .  and c o n t r o l l e d pH.  time  run at  was  and uncontrolled  but s i x  w a s nine  retention  retention  third reactor  days  time  days  time  days  reactor  9  pH  retention  set  SIXTH SET: T h e s i x t h The  experiments  set o f experiments  FIFTH SET; T h e f i f t h reactor  of  and c o n t r o l l e d  days  retention  pH but s i x d a y s  p H , but the r e t e n t i o n pH  time  pH and three  SET: T h i s  retention  of  retention  days  had c o n t r o l l e d  uncontrolled  set  had u n c o n t r o l l e d  THIRD SET: T h e t h i r d  also  3 days  pH. The second  reactor  and c o n t r o l l e d pH.  retention  h a d nine  w a s run at 1 0 ° C . T h e f i r s t  and uncontrolled  SET: T h e s e c o n d  reactor  below.  retention  run at s i x d a y s  w a s run at three  days  were  time  retention retention  conducted  and controlled  time time  at 1 0 ° C . pH. The  but u n c o n t r o l l e d p H . and controlled pH.  16  CHAPTER 4 EXPERIMENTAL FACILITIES  4.1. EXPERIMENTAL SET-UP As three  identical  discussed anaerobic  Three used  as  bung  with  openings  order  t o r e p l a c e the v o l u m e  were  maintained  using  dilute  4.1.  4.2.  a  needle  NaOH.  of  conditions  an  was  opening  attached  were  of sample mixed  at  capacity  room.  each  were  a  rubber  probe, thermometer  and a  with  by  of  a  septum  was  a  n i t r o g e n - f i l l e d b a l l o o n , in  withdrawn  b y an inert g a s . R e a c t o r s  all  times  by  sketch  the a n a e r o b i c  of  a  controlled  ensured  covered  to  controlled  A  2.8-litre  run c o n s i s t e d  Fisher  by  means  Automatic reactors  of  Titrator is  magnetic Model  shown  in  380 Figure  .  FEED USED IN THE STUDY  4.2.1  COLLECTION  AND  Primary British was  that  completely  pH w a s  '  flasks  f o r a pH p r o b e , O R P  tube. A d d i t i o n a l y ,  to  experimental  s e t up in a t e m p e r a t u r e  Erlenmeyer  used  stirrers. The  3, e a c h  reactors. Anaerobic  sealed  insert  reactors  Pyrex  anaerobic  feeding/wasting  in C h a p t e r  Columbia  STORAGE  sludge  was  used  c o l l e c t e d in s e a l e d  from as  plastic  OF T H E F E E D  the B i o - P feed  pilot  throughout  containers  16  from  plant the  at t h e U n i v e r s i t y  study.  the p i l o t  Primary  plant  every  of  sludge week  ,n  F i g . 4.1  Sketch  of  Anaerobic  Reactor  (Adapted  from  Comeau,  1984)  18 and  stored  4.2.2  in the  laboratory  MAINTENANCE  OF  THE  Preliminary showed range.  that To  have  decided to analysis week.  the  concentrated  4.3.  the  If  by  the  constant  until  OF  of  sludge  COD  of  before  of  removing  primary  sludge  feeding  characteristics  of  1800  at 2000  of  analysis  was to  then  the  influent  pilot  plant  to  2400  mg/l  the  study, this  primary was  a  by  COD  primary  it  was  end,  COD  sludge  done  diluted  achieve  the  mg/l  mg/l. To  batch  COD  supernatant  feeding.  from  throughout  new  sludge  daily  sludge  in the  sludge  operation,  for  FEED  varied  the  r e q u i r e d , the  needed  THE  the  quality  state  mg/l. Typical  in T a b l e  of  steady  feeding.  COD  analysis  performed  During  2000  a  maintain  was  before  COD  at 4 ° C  every  every  water value  sludge  day  or  was  close are  to  given  4.1.  EXPERIMENTAL PROCEDURE At  the  beginning  obtained  from  the  Columbia  Bio-P  pilot  AND  DRAW  of  the  flow-through  study,  a  fermenter  plant. This  culture  mixed at  was  microbial  the  used  culture  University to  start  of  the  was  British  anaerobic  reactors.  4.3.1  FILL  Reactors feeding the  was  basis  mixed contents  at  of all and  done the  were  once  day.  on  wasted  used to  a  fill  Sludge  retention  the  was  run  per  desired  times, hence  REACTORS:  and  wasting  time. A s sludge  carry-out  the  was  draw  basis.  volume  was  reactors the  calculated  were  same  the n e c e s s a r y  Wasting  as  tests.  and on  completely the  reactor  19  T a b l e 4.1  Typical Characteristics of the Influent Sludge  MEAN VALUE  PARAMETER U n f i l t e r e d COD (mg/L) T o t a l Suspended S o l i d s  (mg/L)  Alkalinity  (mg/L a s C a C 0 )  Acetic Acid  3  (mg/L)  Propionic Acid Butyric Acid  (mg/L)  (mg/L)  RANGE  2000.0  1950 .0 t o 2 0 3 0 . 0  1000.0  0 950 .0 t o 1 1 0 0 .  6.8  PH  Primary  260.0  6 .5 t o  6. 9  240 .0 t o 2 7 0 . 0  20.0  14 .0 t o  nil  nil  nil  nil  2 5 .0  20  At reactors  were  possibility  4.4.  the  of  and  e x p e r i m e n t a l run, the c o n t e n t s redistributed. This  was  done  of  to  the  three  reduce  the  microbial culture.  ANALYSIS  SAMPLING  of  ensure  that  c o n d i t i o n s , each  retention  times  run, s t e a d y  Because  reactors  the  represent TOC,  the  and  analysis.  alkalinity Replicate  error. A l t h o u g h day,  Hence  no  for  state  of  pH  purpose  membrane activity  filters  of  occured  for  and during  readings  data  was  was  for  was  analysis,  VFA's  wasting  volatile  acids  were the  immediately storage  frozen  of  and  were to  the  ascertain quite  new  least  two  In  each  7  days.  of  to  fatty  acids,  steady  state  the  sampling  24-hour  period.  and  feeding  ensure  used  during  the ORP  of  frequently  filtered  period. Aliqouts  a  were  volatile  over  set  the s c h e d u l e d  period  during to  observed  at  samples  monitored  one  a  for  day  for  to  commenced.  for  Samples  were  fatty  was  done  per  acclimated  operated  mixed, waste  once  done  variation  r e c o r d e d just b e f o r e  Samples  was  were  gathering  reactors.  collected  significant  the  data  sampling  the  sampling and  set-up  completely  were  ORP  microorganisms  detailed  were  contents  the  experimental  before  experimental  were  each  c o n d i t i o n i n g the  To  the  of  inter-mixed  SAMPLING AND  4,4.1  set  end  readings  every  day.  through  that the  pH  no same  0.45/nm  biological samples  21  were  used  for TOC  4,4.2  ANALYTICAL  analysis.  TECHNIQUES  Analyses accordance meter  with  with  combined  combined  reference used  to  4.4.2.1  probe  pH  VOLATILE  (1982),  packing was  for  used  propionic acetic  for and  acid  of  adding  TOTAL  As  915A  The  TOC  out  in  using  pH  one  probe.  Broadley  James  Ag/AgCI pH  as  meters  phosphoric  c/0.3%  Model Just  were  acid  a  were  #  pure)  and  obtain  a  1%  the  5750)  reagent-grade  butyric  the  acid  Model  4  include acetic,  8 7 9 0 0 , 5MI) w e r e injection,  Bulletin 3  Packard  from  gas  20M/0.1%H PO  analysed  prepared  before  acid, to  carbowax  acids  by  in the S u p e l c o  (Hewlett  (96%  75N  determined  described  volatile fatty  samples.  Total  a  scale  were  chromatograph  propionic  acid  used  pH  was  to  (98% inject  brought  solution.  CARBON  mentioned  analysis.  in  using  expanded  (VFA's)  carbo-pack  gas  (Hamilton  ORGANIC  monitored  with  junction,  320  the p r o c e d u r e  60/80  pure),  pre-filtered  4.4.2.2  Model  Model  carried  electrodes  measured  peripheral  Acids  to  all analyses.  (99.9%  3, .by  TOC  a  was  were  pH w a s  reference  butyric acids. Standards  below  for  Fatty  column. A  pure). M i c r o s y r i n g e s 1.0jul  with  The  COD  ACIDS  according  the  (ORP)  and  ORP.  FATTY  using  (1980).  and  Accumet  and  Volatile  751E  glass  couple. Fisher measure  Methods"  potential  ORP  chromatography  alkalinity, solids  "Standard  Oxidation-Reduction Corp.  for  USED  earlier, aliquots  Organic  analyzer.  Carbon  of  was  the  VFA  determined  samples by  were  using  used  Beckman  22  CHAPTER 5  RESULTS AND  DISCUSSION  5.1. RESULTS  Fermenter stable. No seven  significant  days  period  Only from  the  found  below  and  of  than  concentration  temperature  detection  limit  (which  P e a r s o n ( 1 9 6 5 ) , the  bacteria  occurs  propionic  acid;  and  no  often  production 30°  C  acetic  C  was  acid  mg/l,  controlled 84  temperature  production 10°  maximum  and  mg/l  5  temperature  operation  parameter  for  at  a  which  mg/l  (35 for  sludge. was  3  was  over  than  rate  acetic  corresponding  quite  the  final  acid to  combination.  the  uncontrolled  the  in  this  also  22  always  McCarty(1963)  butyric  very  produced  was  per  acetic  acid  acid  low  9  production days  by  and  butyric  Maximum pH, 9  days  accounted  pH, 3  noted  retention  experiment.  uncontrolled  combination.  a  be  the much acid  possible.  pH  mg/l)  in  the  to  acid  mg/l). A s  faster results  found  Butyric  of  d e t e c t i o n is  net  acid were  degradation  combination, which  production was  in any  propionic primary  103  state  analysis.  the  The  steady  observed  of  and  was  during  were  a c e t i c a c i d and  the  methanogenic  experiment  trends  fermentation  Andrews  faster  behaviour  net  for  this  time, 30°  propionic  retention time  Lowest  days  in  the  lowest  propionic  retention  time  C  acid and net acid and  23  The final the  7  days  of  experiment  production and  pH  in t h e d i f f e r e n t  each  was  sampling  30° C  stable  ORP  during  the steady  and  5.3  data  record  5.2.  STATISTICAL  for  pH r e c o r d e d  acid  retention  at 6 d a y s  in  net V F A time  and 3 0 ° C  listed  in  were  are  reactors  the reactors very  was  were  also  strictly  l o w . The highest  reference) while  summarized  temperature is g i v e n  within  days,  within  Sampling  error  ( M S ) error  error error  is  errors,  Table  days  square  square  all the  ORP  the l o w e s t  in  Tables  5.1, 5.2  run r e s p e c t i v e l y . in A p p e n d i x  Complete  1.  ERRORS  standardized  samples, between  in  ANALYSIS  are  experimental mean  the  reference).  o f t h e net V F A p r o d u c t i o n  production,  mean  average  during  total  was -265mv(Ag/AgCI  the experiment  10°C, 20°C  The  the  stable  t o the h i g h e s t  period. Since  in a l l the r e a c t o r s  of  STANDARDIZED  occurs  acetic  potential  state  was -395mv(Ag/AgCI  Results  between  reduction  in the e x p e r i m e n t  recorded  5.2.1  corresponded  (152 m g / l as  -  anaerobic, ORP values recorded  quite  temperature).  Oxidation very  was  p e r i o d . The l o w e s t  5.63 w h i c h  in the s t u d y  reactors  5.4. T h e  while  calculated sampling  experimental  for  error  error  the is  net  the  VFA  variation  is t h e v a r i a t i o n  that  reactors.  is c a l c u l a t e d as t h e s q u a r e and number  calculated  and  as  number  as  the  of  days  of  samples  square  root  samples  root  o f the r a t i o o f  taken  per d a y , w h i l e  of  the ratio  collected.  Mean  o f the square  Table  Ret. Time (days)  Average pH  5.1  Summary o f  Net A c e t i c Acid (mg/L)  Mean  Results  Net P r o p i o n i c Acid (mg/L)  Mean  Range  for  10  C Temp.  T o t a l N e t VFA (mg/L a s Acetic Acid)  Mean  Range  Run  Mean Sol. TOC (mg/L)  * Mean ORP (mV)  Range  3  6.43  44  34 -  50  5  3 -  7  48  37 -  56  93  -263  3  7.00  48  38 -  56  19  13 -  28  63  54 -  79  98  -274  6  5.97  50  42 -  55  20  15 -  25  66  58 -  73  108  -303  6  7.00  60  53 -  70  31  25 -  15  85  77 -  93  118  -326  9  5.93  53  46 "  60  19  15 -  23  68  61 -  78  110  -295  9  7.00  71  63 -  80  31  25 -  40  97  85 - 104  123  -385  *: A g / A g C l r e f .  T a b l e 5.2  Ret. Time (days)  Summary o f R e s u l t s f o r 2 0 ° C Temp. Run  Net  Acetic Acid (mg/L)  Average PH  Mean  Range  Net P r o p i o n i c Acid (mg/L)  Mean  Range  T o t a l N e t VFA (mg/L a s Acetic Acid)  Mean  *  Mean Sol. TOC (mg/L)  Mean ORP (mV)  Range  3  6.25  48  41 -  54  18  11 -  22  63  53 -  70  104  -342  3  7.00  63  57 -  68  31  25 -  36  88  78 -  95  113  -358  6  5.88  79  70 -  84  29  22 -  33  103  95 - 110  118  -366  6  7.00  74  67 -  82  43  37 -  48  109  98 - 118  135  -391  9  6.01  66  60 -  70  60  55 -  65  115  105 - 122  140  -378  9  7.00  82  75 -  86  48 -  56  124  114 - 129  143  -359  *: A g / A g C l r e f .  52  J  T a b l e 5.3  Ret. Time (days)  Summary o f R e s u l t s f o r 3 0 ° C Temp. Run  Acetic Acid (mg/L)  Net  Propionic Acid (mg/L)  Range  Mean  Range  Net Average PH  Mean  T o t a l N e t VFA (mg/L a s Acetic Acid)  Mean  Mean Sol. TOC (mg/L)  Mean ORP (mV)  Range  5.89  75  68  82  47  42  50  113  104  121  130  -396  3  7.00  77  70  84  32  28  36  103  94  111  123  -352  3  5.63  88  78  95  80  75  88  152  140  160  163  -354  6  7.00  94  84  100  73  70  77  153  142  163  162  -376  6  6.13  35  30  40  84  80  95  103  95  116  123  -391  9  7.00  103  95  110  42  35  46  137  123  147  153  -334  9  *: A g / A g C l r e f .  27  errors  used  propionic  in  and  the  total  calculation VFA  of  standardized  productions  are  given  in  errors  for  net  acetic,  Tables  5.5,  5.6  the  experimental  and  5.7  respectively.  error. Since all  In  a l l c a s e s , the  the  experimental  sampling error  error was  is  the  less  larger  than  e r r o r , it  has  been  used  in  the s t a t i s t i c a l t e s t s .  5.2.2  ANALYSIS  OF  To treatment variance 5.5, 5.6 of  variables (ANOVA)  and  VFA  values the  know  5.7  conclusions  total  VARIANCE  (pH, was  Handbook  from  analysis  Tables  (95%  (or  v a r i a t i o n that  days  occurs  to  e.g. f o r  Within  Days  Days  (95%  confidence  has  been  S t a t i s t i c s , CRC  5.7), the  mean  sqaures  within days  errors  net t o t a l  ^  the  R e t e n t i o n T i m e , pH caused VFA  >  F  by  _  S  t  a  t  i  s  t  j  c  (  9  5  (108,126)  |  }  and  interval) from  (1966)  ratio of is  mean  experimental  error  and  C  type  than  Temperatures  (Table  %  of  greater  the s a m p l i n g  production  the  obtained  Press  and  interval) value. Hence  and  the  Tables  acetic, propionic  5.5, 5.6  the  =  net  (ANOVA)  data.  variance  (Tables  the  when  g r e a t e r than  Between  variance  cases  for  analysis  production of  F-Statistics  P r o b a b i l i t y and  confidence  analysis;  M S  of  for  VFA  interpretations  respectively.  all three  F-Statistic  its  net  between  Temperature),  the a n a l y s i s  the  M S  and  of  squares(MS) between  laboratory  Time  interaction  o u t l i n e the r e s u l t s  the  is  any  the  of  constant)  Retention  is  on  drawn  in  there  performed  For  held  whether  production  used  (ANOVA")  and 5.7).  =  1  4  are  subsequent  28  Table  5.4  Standardized  PARAMETER  Errors  SAMPLING ERROR (mg/L)  EXPERIMENT ERROR (mg/L)  Net A c e t i c A c i d Production (mg/L)  ±1.72  ±2.24  Net P r o p i o n i c A c i d Production (mg/L)  ±1.47  ±1.59  Net T o t a l V o l a t i l e F a t t y A c i d s Production (mg/L as Ac. Acid)  ±2.11  ±2.76  29  T a b l e 5.5  Analysis of Variance f o r net A c e t i c Acid  Production  3x3x2 FACTORIAL WITH NESTED C L A S S I F I C A T I O N WITH EQUAL NUMBER OF SAMPLES TAKEN EACH DAY  Deg. o f Freedom (df)  Sum o f Squares (SS)  Mean Squares (MS)  17  81881.86  4816.58  137.02  Sign.  R e t e n t i o n Time  2  9369.31  4684.65  133.26  Sign.  Temperature  2  24782.64 12391.32  352.49  Sign.  pH  1  13906.29 13906.29  395.59  Sign.  R e t . Time x Temp.  4  8414.48  2103.62  59.84  Sign.  Ret.  2  11571.50  5785.75  164.59  Sign.  Temp, x pH  2  3517.93  1758.96  50.04  Sign.  R e t . Time x pH x Temp.  4  10319.71  2579.93  73 .39  Sign.  Between Days w i t h i n Reactors  108  3796.57  35.15  5.95  Sign.  Between S a m p l e s w i t h i n Days  126  744.00  5.90  Sources o f Variations  Between Reactors  Time x pH  F  STAT  F  TEST  30  T a b l e 5.6  Analysis of Variance f o rnet P r o p i o n i c Production  Acid  3x3x2 FACTORIAL WITH NESTED C L A S S I F I C A T I O N WITH EQUAL NUMBER OF SAMPLES TAKEN EACH DAY  Sources o f Variations  Sum o f Squares  (ss)  Mean Squares (MS)  1.22E+05  7182.84  466.92  Sign.  2  2.67E+04 13358.65  868.37  Sign.  2  6.38E+04 31920.80  2074.99  Sign.  pH  1  4.63E+03  4630.29  301.05  Sign.  R e t . Time x Temp.  4  1.08E+04  2712.18  176.30  Sign.  R e t . Time x pH  2  4.32E+03  2159.65  140.39  Sign.  Temp, x pH  2  1.36E+04  6820.54  443.36  Sign.  R e t . Time x pH x Temp.  4  2.69E+03  673.49  43 .78  Sign.  Between Days within Reactors  108  1.66E+03  15.38  3.54  Sign.  Between S a m p l e s w i t h i n Days  126  5.47E+02  4.34  Between Reactors Retention  17 Time  Temperature  i 1  Deg. o f Freedom (df)  •  F  STAT  F  TEST  31  Table  5.7  Analysis Volatile  of Variance Fatty Acids  f o r T o t a l Net Production  3x3x2 FACTORIAL WITH NESTED C L A S S I F I C A T I O N WITH EQUAL NUMBER OF SAMPLES TAKEN EACH DAY  Sources of Variations  Between Reactors  Deg. o f Freedom (df)  Sum o f Squares (SS)  Mean Squares (MS)  F  STAT  F  TEST  17  224008  13177  250.07  Sign.  R e t e n t i o n Time  2  49756  24878  472.13  Sign.  Temperature  2  131248  65624  1245.39  Sign.  PH  1  12718  12718  241.35  Sign.  R e t . Time x Temp.  4  18933  4733  89.83  Sign.  R e t . Time x pH  2  3066  1533  29.09  Sign.  Temp, x pH  2  1767  883  16.76  Sign.  R e t . Time x pH x Temp.  4  6520  1630  30.93  Sign.  B e t w e e n Days w i t h i n Reactors  108  5691  53  5.92  Sign.  Between Samples w i t h i n Days  126  1121  9  32  Another  important  production  caused  greater  than  squares  between  is  greater  reactor  thing  is  (95%  cases  (Tables  (Table  of  5.5,  mean  (95%  C.l.)  Hence,  the  because  value.  squares  If  another  the  For  and  ratio  between  the  the  reactor  time  in  ratio  mean  the  of  a  In  all  in  case  „,.„ „_ 250.07  _ >  _ _ . . F-Statistic(95%  is  total  is  mean  reactors in  one  change the  squares  example,  VFA  time  within  reactors of  net  production  because  within  of  days  VFA  the  the  retention  temperature.  of  days  or  between  C.l.) v a l u e , then  Reactors  in  three  between  greater  than  VFA  production  of  into  if of  is  eight  than is  cases  how  effect  the  other  a  two.  change the  interaction to  dependent  (95% on  5.5,  _ ,. C.l.)  =  , 1.69  total  VFA  5.5, 5.6 in  one  ratio the  pH,  values  and  and  5.7),  production  the  the  5.7). T h e  parameter the  mean  of  retention  reactors,  of  reactors  other  is  mean  squares  not  two  5.7),  and  variation step  is  is to  dependent  on  the  squares  due  to  between of  time  first  reactors  a change  in  is one  v a r i a b l e s . In a l l the  (pH)x(Ret.Time)x(Temp.) (Table  is  variables.  in  between  between  C.l.) v a l u e , t h e n the e f f e c t  the 5.6  treatment  changes  (Tables  If  productions  of  variation  of  F-Statistic  s i g n i f i c a n t ; e.g. f o r  VFA  the  sources  the  (Tables  net  because  the  (pH)x(Ret.Time)x(Temp.)  parameter  the  clarify  caused  partitioned examine  in  c h a n c e , but  temperature  =  Days  variation  To  three  mean  5.7)  change  5.7),  '^Between  greater  chance.  in  squares  ^^Between  values  and  the  temperature  by  pH, retention  5.6  the  that  whether  pH,  occur  F-Statistic than  is  the  t o the  combination  F-Statistic  varying  would  different  to  examine  reactors  some  reactors  by  which  than  to  interaction  is  33  (pH)x(Ret.Time)x(Temp,) '^Between  Because seven  the  5.2.3  will  DUNCAN'S  Range  test, to  nature  of  in  Table  one  the  mean  and  accounting together.  column as  of  F  _  S  t  a  t  j  s  t  i  c  (  9  5  %  c  ,  }  =  2  5  data  Table  shown  examined  production. This  then  the  other  in the T a b l e  using was  interaction. Results for  net  example,  5.8  discussed  was  acetic, of  statistically  For  significant,  5.7.  TEST  Combinations for  is  s i g n i f i c a n t , as  acid  5.10  respectively.  pH,  done this  were  to  VFA  clarify  the  are  and  total  VFA  time  and  productions,  have  combinations found  Multiple  test  retention  following  they  Duncan's  propionic,  indifferent  the  because  of  to  shown  are  listed  be  statistically  the  relationship  VFA  production.  above.  9  days  Ret. T i m e / 2 0 ° C  temp./ uncontrolled  3  days  Ret. T i m e / 2 0 ° C  temp./ c o n t r o l l e d pH,  6  days  Ret. T i m e / 1 0 ° C  temp./ controlled  pH, and  pH  DISCUSSION  The among  three  Statistical to  RANGE  production  5.9  grouped  indifferent  5.3.  rank  5.8,  temperatures,  in  VFA  interaction  be  (pH)x(Ret.Time)x(Temp.)  production,  been  automatically  MULTIPLE  Net  >  Days  (pH)x(Ret.Time)x(Temp.)  sources  ^  =  layout  control  analysis  of  of  this  variables the  (pH)x(Ret.Time)x(Temp.)  data  study and  enables their  shows  interaction  effects  that, in is  us  all  to  clarify  on  net  cases,  significantly  the  variation  greater  than  due the  Table 5.8  Ranking o f Means o f Net A c e t i c A c i d P r o d u c t i o n Under D i f f e r e n t O p e r a t i n g C o n d i t i o n s U s i n g Duncan's M u l t i p l e Range T e s t  9/30/U 6/30/U  9/20/U  3/30/C  3/20/C  6/10/C  6/30/C > 9/30/C > 9/20/C > 3/30/U > 6/20/U > 6/10/C > 3/10/C > 3/10/U 6/2 0/C  KEY:  R e t e n t i o n time  9/10/C  3/20/U  (days)/Temp. °C/pH C o n t r o l l e d o r U n c o n t r o l l e d .  Table  5.9  R a n k i n g o f Means o f N e t P r o p i o n i c A c i d Production Under D i f f e r e n t O p e r a t i n g C o n d i t i o n s U s i n g Duncan's M u l t i p l e Range T e s t  3/30/C  6/10/U  9/10/C  3/10/C  9/30/U > 6/30/U > 6/30/C > 9/20/U > 9/20/C > 3/30/U > 6/20/C > 6/10/C > 9/10/U > 3/10/U 9/30/C  3/20/C 6/20/U  KEY:  Retention  time  ( d a y s ) / T e m p . °C/pH C o n t r o l l e d o r U n c o n t r o l l e d .  3/20/U  Table 5.10  Ranking o f Means o f T o t a l Net VFA P r o d u c t i o n Under D i f f e r e n t Operating Conditions using Duncan's M u l t i p l e Range T e s t  9/20/C 6/20/U  9/10/U 9/20/U  6/10/U  9/30/C > 6/30/C > 6/30/U > 3/30/C > 3/20/C > 3/20/U > 9/20/U 3/30/U 6/20/C  6/10/C  3/10/C 3/10/U  9/10/C KEY:  R e t e n t i o n time (days)/Temp. °C/pH C o n t r o l l e d o r U n c o n t r o l l e d .  37  experimental variation  error  we  temperature  or  would and  variable  dependent  on  get  if  on  the  e f f e c t s of  variation  pH). T h i s  treatment  the  the  result  the  values  of  of  confounded  with  the  main  caused  the  the  parameter  between  the  be  the  studied  effect  i.e.  under  study.  reactors  (the  retention  of  change  production,  is  time, in  very  variables.  one much  Therefore,  separately.  effect In  under  effect  studies  its  the  same  treatment  parameter  parameters  the  acids  two  within  is  would  truth,  study  that be  it  and  interactions  is  viewed caused  the  as by  conditions  are if the  within  reactor.  5.3.1  TOTAL  VFA  PRODUCTION  Information VFA  concentration  values  (Figs.  5.1  and  e x a m p l e , at  total  VFA  net  when  the  pH  5.1).  If  the  two  reactors and  uncontrolled  obtained  for  d a t a . For  mg/l  cannot  single  that  fatty  other  days had  confirms  the  the p a r a m e t e r s  folly  interaction  reactors  volatile  The  by  all  between  each 5.2)  control  agrees  was  was  retention time (having  153 pH  mg/l).  if  (103  well  days  with  the  mg/l  as  production 6  mg/l  the  mean  temperature  statistical and  total  analysis  time  pH  of  the  u n c o n t r o l l e d p H , the  acid  (Fig. 5.2).  jumped  as  becomes is  total  net  and  to  137  However, mg/l  d a y s , the d i f f e r e n c e b e t w e e n  conditions)  retention  113  time,  acetic  significantly more and  the  of  retention time  reduced to pH  plots  retention  a d d e d , the is  the  of  103  different  r e a c t o r has  the c o n t s r o l l e d r e a c t o r  set  30°C, 9  production  from  insignificant  dropped net V F A  acetic acid).  to  3  (Fig. the (152  days,  the  production  than  38  160 JO < U  cu u  < <  CD  -i  150-j  140 130 120  no  3  100 9080-  6  c o  706050  O  -i  Legend  40> ,*o  CD  30  A  A t 10° c  20 ^  X  A t 20° c  10  •  A t 30' C  0 3  4  5  6  Retention Time (Days)  7  8  9  10  Fig. 5.1 Total Net V F A Concentration v s . Retention Time at Controlled pH  39  160 TS  <  150  o  130-  % o  120-  < < CD  Legend  HO  110 -  A  M 10° c  X  At 20° c  •  Af 30' C  x  •  100 9080-  u c o o  70 60 50 40  302010 0  3  4  5  6  7  Retention Time (Days)  F i g . 5.2  T o t a l Net V F A  Concentration  vs. Retention Time  8  at U n c o n t r o l l e d  10  pH  40  Repeating days  retention  uncontrolled at  30°C  to  6  days,  much  to  the  3  the  124  (103  days,  the  20°C,  tested  (3, 6 and  ACETIC  to  e x a m p l e , at with  no  study jumped  to  retention production but to  much 3  103 time of  smaller  days,  and  mg/l,  the  the  the  acetic  a c i d ) . If  we  significant  two  (63  5.2),  controlled as  was  still  and  shown  is  dropped  significant  but  retention  reactors '(having  different  88  drop  9  the  vs.  more  and  retention time is  produces  (Fig.  5.1  a  much  mg/l  VFA's  as  than  acetic  the  acid)  uncontrolled  and  5.2),  larger  pH  the  same  degree.  At  pattern all  controlled reactor  occurs  three  produces  as  was  retention much  times  more  net  reactor.  9 was  the  35  mg/l,  highest to  6  c o n t r o l l e d and (94 net  vs.  88  acetic  net  acetic  r e t e n t i o n t i m e , the  when  reduced  pH, retention time  e f f e c t on  days  However  is  magnitude  reactors  the  5.1  between  two  between  more  a confounding  5.4).  same  (Figs.  PRODUCTION  control  (Fig.  as  interaction between  30°C  pH  mg/l  uncontrolled  have  the  the  20°C  difference  a c e t i c a c i d ) . If  between  9 d a y s ) , the  The  of  for  comparison.  to  ACID  not  as  109  30°C  but  than the  significant  but  reactor  10°C  at  procedure  difference  controlled  found  found  vs.  the  At  5.3.2  a  mg/l  becomes  reactor, unlike  VFA's  shows  difference  conditions)  and  same  conditions,  vs.  smaller  time pH  time  pH  (115  the  the pH  control  achieved days,  If  net  temperature  production  acetic  production  study  the (Fig.  between  the  was For  production in  this  production 5.3).  If  acetic  the acid  reactors  is  still  retention time  is  further  reduced  reactors  (having  production  pH  acid  also.  achieved  added,  this  difference  the  acid  was  in  uncontrolled  mg/l). acid  lowest  and  in  the  two  significant,  41  110  ioo H 90 80  H  70-  o  60  H  .2  50  A  X ^  40H Z  S  30  Legend A At 10° c X At 20° c  H  2010-  • 2  -r 4  5  6  7  At 3 0 ' C 8  10  Retention Time (days)  F i g . 5.3  Net  Acetic Acid  Concentration  vs. Retention Time  at C o n t r o l l e d  pH  42  100 90  ^ 6 )  rj) 8 0 E. o 70  c o  o  "o  60 H 50  < o U <  d)  c o  CD  40 A 30 H  Legend 20 H A At 10° c 10  4  X At 20° c • At 3 0 ' C 2  F i g . 5.4 PH  Net  Acetic Acid  3  4 5 6 7 Retention Time (days)  Concentration  vs. Retention Time  8  at  10  Uncontrolled  43  different  pH  conditions)  At in  the  net  reactors mg/l). reactor but  the  not  the  times net  more  and  (3,  addition  of  in  the  uncontrolled  pH,  effect  on  the  of  net  net  control  added.  to  uncontrolled  shown  at  30°C  days,  the  reactor  vs.  uncontrolled (74  At  (81  pH  3  net  vs. days  acetic  79  66 pH  mg/l),  retention acid  than  as  5.4).  was  At  found  all  controlled  the  reactor  at three  30°C,  but  retention  produces  more  reactor.  mg/l  acetic time  propionic  propionic for  all time,  with  retention 31  net  retention  19  20  difference  PRODUCTION  5  from  and  more  occurs  pH  between  days  pattern  the  retention  9  mg/l).  mg/l).  days),  case  to  v s . 75  significant  small.  much  and  days  and  was  9  6  very  5.3  3  from  control  and  is  (Figs.  pH  improved  improved  same  the  at  days  the  to  produces  v s . 66  the  10°C,  example,  6  (82  ACID  confounding At  reactor  degree  6  PROPIONIC  5.6).  pH  was  controlled  two  a  controlled  as  than  the  shows  the  dropped  acid  between  10°C,  interaction  have  acetic  reactor  As the  of  is  a c e t i c a c i d than  5.3.3  production  d i f f e r e n t (71  time  time  lesser  tested  retention  retention  controlled  much  days  magnitude  At a  significantly  same  uncontrolled  to  not  the  difference  the  9  acid  to  produces  the  time,  acetic  but If  20°C,  is  mg/l  and  acid  acid  the  net  19  temperature  to  as  net 31  pH  found  to  well  (Figs.  5.5  with  the  studied.  For  of  propionic  control. Similarly  propionic mg/l,  production,  was  times  production of  VFA  improves  retention  addition the  total  production  three  the  and  production  the  times, and  acid  acid  acid for  production  respectively, when  pH  44  90  \  CO  80-  Legend A At 10° c  70  X  J ,  • At 3 0 ' C  6  60  o o  50  c  <  d  At 20° c  40  o  Q_  % c  o  2  30 20 10  3  F i g . 5.5 PH  Net P r o p i o n i c  Acid  4  5  6  7  9  10  Retention Time (days)  Concentration  vs. Retention  Time  at  Controlled  45  F i g . 5.6 PH  Net  Propionic  Acid  Concetration  vs. Retention T i m e  at  Uncontrolled  46  At  20°C,  production  improved  control. At  6  to  days  produce  However, Controlled reactor  pH  (52  addition  9  the  pH  73  when  pH  acid  (from  to  5.3,4  84  confounding production.  for  was  mg/l)  pH  for  3  with  the  as  acetic  and  pH  effect  with  5.2).  controlled the  propionic  addition  of  reactor  reverse  pattern  a c i d than  acid  the  was  uncontrolled  10°C,  pH  as  control, total and  acid  production  three  retention  dropped  6  pH  pH  found reactor.  was  observed.  the  uncontrolled  days  more.  The  of  pH  value  of  47  retention  retention  dropped times  from  days  addition  to  68  a  temperature control  and  to  the  studied.  For  mg/l  and  respectively,  the  production  with  32  times  time,  drop  dropped  in  the  by  50%  control.  for  and  9  net  VFA  production  97  mg/l  days  3  6  to  the  improved  acid,  as  7  was  retention  improved  control  acetic  Similarly, for  acid,  9  much  pH  mg/l  of  the  propionic  the  and  At  the  from  temperature.  the  net  CONTROL  of  63  pH  production  was  e x a m p l e , pH  to  time,  with  than  net  all  days  s i g n i f i c a n t l y . For 48  acid  propionic  added.  Control  At  mg/l  a l s o , the  less  acid  production  OF  31  time,  net  control  mg/l  42  EFFECT  the  propionic  control  propionic  time  retention  mg/l).  30°C,  80  to  produced  At  from  18  retention  reactor  net  days  propionic  days  e x a m p l e , the to  from  net  v s . 60  of  3  retention  more  at  and  time  net  the days  retention  on  have  the  net  a VFA  production  total  VFA  production  retention  time  and  net  total  to  VFA  times, with  improved  acetic  found  acid,  from  66  the to  respectively  10°C  addition 85 (Figs.  mg/l 5.1  47  At improving time (63  the  did  net  the  vs.  higher  pH  total  VFA  controlled  88mg/l  significant  temperatures,  as  improvement  improving VFA  the  net  production  control, VFA  while  production  significant  effect  9  pH  retention production much  However,  At  controlled  (measured  acetic  3  pH  in the  acid  acid  t i m e , the  greater  days  pH  in  Therefore  retention  control  and there  no  mg/l),  loss  time, control  was  the are  was  103  the  of  insignificant  but  the s a m e  net  time,  no  on  the  30°C,  the  at  a  acid  reactor  producing  (47  32  vs.  acid  and  control  propionic magnitude  at  production.  from  mg/l  between  mg/l).  production  acid  ( F i g s . 5.3  and  the  in  propionic  improved  of  net pH  effect  the  propionic  addition  in  with  insignificant  reactor  84  change  acid  e x a m p l e , at is  from  effective t i m e , the  significant  mg/l  acetic of  no  observed.  in a c e t i c  production  dropped with  VFA  was  retention  uncontrolled  increase  reactor) to  mg/l  a  not  increase  6 days  controlled  the  acid  production  5.6).  between  than  acetic  42  the  total  there  acetic  small  acids. For  77  in  retention  net  retention  production  vs.  than  a  have  acid  more  as  production  to  effective  3 days  was  days mg/l  d i f f e r e n t . w i t h the  uncontrolled  r e a c t o r ) to  sign.  (75  the  uncontrolled 6  days  was  103  propionic  acetic  retention  pH,  propionic  At  and  3  control. At  found  on  propionic  at 9 d a y s  controlled  VFA  was  significantly  net  the  the  of  was  more  of  control  time  net  for  times,  control  time, only pH  not  concentration.  pH  to  with  in the t o t a l  production  113  retention  pH  VFA  the  is  only  retention  production. At  achieved  of  total  pH  significantly  higher  also  from  days  was  change  of  VFA  decreased at  net  30°C  total  Control relative  at  at  of  20°C,  produce  acid);  in the  Similarly,  control  production. At reactor  acetic  the  35  mg/l  5.4),  while  (measured  in  (Figs. 5.5  and  acids  changes  but  opposite  the  total  VFA  48  production  in the t w o  Effects production  can  environmental temperatures the  of  be  the  the  at 3 0 °  10°  C,  approximately  20°  not  under  provided, will  and  1980). T h i s  it  will  controlled  with to  a  the  the  net  VFA  degree  undergoing  methane  of  at  producing  acid  maximum  producing  temperatures  temperature  that the  acid producing  stress  enzymatic  value  of  be  optimum  means  this  account  might  population  an  increase  agrees  cells  into  on  of  different  bacteria  in  bacteria  is  growth  of  C.  have  enhance  interaction  taking  presence  environmental  subsequently  operation was  C  much  by  the  Psychrophiles  Gaudy,  temperature  bacterial  psychrophilic.  and  and  possible  operated  At  pH  explained  stress and  reactors  reactors.  the  at  C,  activities  VFA  in  As  about  and  if  VFA  production  of  the  acid  C  (Gaudy  optimum  bacterial  Results  described  7,  15°  bacterial population  the  production.  explanation. of  10°  of  for  cell,  is  which  the  10°  C  earlier, when  the  pH  was  of  pH  is  found  to  improve  significantly.  At psychrophilic.  20° As  temperatures  for  means  acid  under  that  considerable  respond  positively  optimum  pH  does  not  controlled  C,  most  mentioned growth  of  producing  to  the  pH.  any  C  and  bacteria  environmental  conditions. A s show  20°  earlier.the  stress  presence  of  described  significant  at  producing psychrophiles  optimum this and  high may  b e f o r e , the in  be  stress  results  the  in  VFA  of  a  15° are  C.  C  production  It  already  position  caused 20°  are  maximum  of  temperature not  again  have  temperature  environmental  increase  bacteria  by  to the  operation at  the  49  Mesophiles C  and  This is  an  At  30°  have  a  that  mainly  the  VFA  is  this  hypothesis.  can  in  be  the  the  bacterial  As net  VFA  activities  in  supporting  the  by  taking  can  total  net  of  between reactor In  to  having  this  115  mg/l  5.2).  The  was and  30°C.  activities  as  run  control the  operated  does  to  30°  methanogenic  30°  which  C,  stress.  not  If  increase  the  bacterial  agree  with  improvement  was  the  value  of  7. T h i s  presence  C. T h i s  substrate, which  bacterial  1980).  in  possible at  pH  at  45°  Gaudy,  r e g i m e , it s h o u l d  significant  account  and  environmental  would  the  neutralize  to  increased  cell.  A  detailed  b a c t e r i a in the  of  methanogenic  due  the  enzymatic explanation  30°  C  operated  chapter.  found  to  total  VFA  The  case,  reasons  have  very  the at  for  net  w i t h the  exception  20°C the  to drop  total 103 in  pronounced  productions.  consistently only  a  VFA mg/l the  As  in  behaviour  and  30°C  pH  net  total  VFA  of  net  the  temperature.  dropped  acetic acid  on  temperature,  the  production as  effect  e x p e c t e d , the  increase  was  retention time, uncontrolled  acetic acid  main  the  improved  9 days  particular as  pH  mesophilic.  TEMPERATURE  production 10°C  no  controlled  later in t h i s  acetic, propionic  VFA  with  producing  Temperature the  at  much  is  approximately  bacteria  temperature  earlier,  of  (Gaudy  enzymatic  C  VFA's  C  a temperature  reactors  use  37°  under  into  in the  presence  OF  30°  growth  producing  increased  production  acid  given  acid  such  of  production the  EFFECT  to  for  about  be  mentioned  bacteria  increased  not  under  VFA  population  r e a c t o r s , is  will  results  explained  methanogenic  5.3.5  of  due  bacterial population  temperature  population  the  production  However,  producing  of  provided  cell.  acid  temperature  mesophilic, pH  noticed  the  maximum  optimum  means  optimum  C  at  from  30°C  (Fig.  production  was  50  the  unexpected  drop  production  dropped  temperature  from  abnormal  in  of  net  from  20°C  behaviour  production  the  60  to  is  acetic  acid  mg/l  30°C  given  to  (Fig. later  acetic, propionic  35  5.4). in  and  p r o d u c t i o n . The mg/l  with  net  acetic  the  acid  increase  in  A  possible  explanation  for  this  this  chapter.  Otherwise,  the  net  total  VFA  consistently  improved  with  temperature.  5.3.6  EFFECT  OF  RETENTION  Retention  time  temperature  on  the  net  temperature,  the  net  total  retention 30°C,  (for  net  total  the  raised time  time  from was  3  to  further  to  103  mg/l  as  to  137  mg/l  as  A  possible  5.3.7  BEST  6  days  value  production.  6  acetic acetic  it  acid  increased  for  the the  COMBINATION  OF  the  did  18  time not  total  (153 make  is  VFA mg/l  any  of  given  and  20°C  increase  in  tested).  However,  at  the  pH  with  an  retention when  reactor  reactor  time  the  dropped  was  retention from  152  from  153  and  5.2).  retention  time  and  (Fig. 5.1  later in t h i s  chapter.  VARIABLES  pH, temperature  concentration as  with  production  controlled  TREATMENT  combinations  net  net  effect  10°C  decreased  uncontrolled pH  At  times  when  subsequently  for  confounding  improved  retention  9 d a y s . The  acid  a  production.  days  production  to  have  production  9  days.but  to  VFA  VFA  increased  maximum  7  total  and  VFA  found  explanation  retention of  6  was  microbiological  Of t e s t e d , the  3,  TIME  acetic  significant  was  achieved  a c i d ) . The change  and  in  at  control the  net  of  30°C pH total  and to  a  VFA  51  Maximum at  30°C, 9 days  and  9  days  production  retention  (84  control net  al  to  VFA  distribution et  discussed  of  a  of  7  production.  for  (1982) and  Eastman the  found  that  pH  fatty  acids.  5.3.8  MICROBIOLOGICAL  affected  the  acids  the  mg/l), w a s  maximum  not  have  it  achieved  p H , at  30°C  propionic  acid  relative  significant  both  of  FOR  THE  maximum  effect  affects  have  distribution  EXPLANATION  the  the  acid concentrations.  (1981)  p H . In  a  for  clearly shows  certainly  propionic  Ferguson  of  combinations  productions  However,  and  effect  best  does  the a c e t i c a c i d and  about  arrived  the  above  of  the  the  on  the  relative  Zoetemeyer  at  the  studies,  individual  BEHAVIOUR  that  similar it  was  volatile  OF  REACTOR  days  retention  30^C  As time,  30°C  mentioned  reactor  the  study  behaviour  at  (Fig. these  Methane  The  to  grow  quite  found  pH,  m g / l , the  lowest  35  be  given,  9  the  net  acetic  production for  the  taking  acid  recorded fermenter  into  account  bacteria.  are  methane  slowly  explanation  can  producing  bacteria  of  that, at  uncontrolled  conditions  methane  pH  was  microbiological  producing  optimum  bacteria  A  operating  Methane  and  dropped  5.4).  the p o t e n t i a l a c t i v i t y o f  conditions.  e a r l i e r , it  temperature  production unexpectedly in  (103  c o n t r o l l e d pH. U n c o n t r o l l e d  accounted  propionic  value  conclusions  AT  and  production  e a r l i e r , the  a c e t i c and  pH  total  time,  acid  mg/l).  VFA, of  acetic  retention time  As net t o t a l  net  very  sensitive  formers  compared  lies to  to  environmental  between  7  acid-producing  and  7.2.  bacteria  52  and  so  a  adequate for  longer  retention  population  methane  for  the  producing  and  Pearson,1965).  minimum  cell  residence  on  average  values  bacteria acids for  the  3.1,  acetic  reduction  the  to  the  McCarty(1969)  the  degradation  (about  -391mV  Methane 390mV of  vs.  Lower  total as  forming  McCarty  (1963), than  is  and  the  acid.  to  at  9  days  production  result  of  the  use  bacteria. A c c o r d i n g acetic  acid  propionic  is  the  much  of to  acid. Average  an  readily in  the  time  with  The  also  is  of  acetic  Lawrence  and  conditions  are  b a c t e r i a , the  rate  was  very  of  Pearson  degradable reactor  was  study. (  -  probability temperature.  reactor as  low  -435mV  high  30°C  acid  of  different.  acid.  a  the  rate  acetic  E^.  and  and  butyric  in the w h o l e  uncontrolled  Andrews  pH  and  degradation  recorded  acetic  predicted  days  are  the  bacteria  residence  4.2  reactor  at  days(  methanogenic  However,  time  the  more  cell  to that o f  occur  retention in  the  methanogenic  minimum  reported  C, the  environmental  uncontrolled  ref.), the  35°  to  of  time  4  methane  acid  rate  comparable  the  to  McCarty,1969).  propionic  favourable  is  in  been  VFA  the  methane  formers  acid  2.5  of  minimum  increase  acid, assimilating  residence  an  McCarty(1969),  for  ref.) ( P f e f f e r , 1979). H e n c e , t h e r e  formation  net  interpreted  has  to  maintain  acetic, propionic  propionic  when  vs. Ag/AgCI  Ag/AgCI  methane  that  potential  production  retention time  and  of  and  growth  of  to  cell  temperature. A t  (Lawrence  acid  propionic  Redox  the  found  that  propionic  of  for  solids  C  them  between  Lawrence  Pearson(1965),  than  reported  for  30°  and  reported  to  and  was  for  Minimum  r e s p e c t i v e l y . The  acetic  higher  been  assimilation  days  Andrews  much  provided  the  in t e m p e r a t u r e t o  According is  2.7  present.  required  minimum  assimilation  of  has  substrate  for  3.2,  acid  degradation  of  of  required  According  time  of  responsible  are  acid  type  is  substrate  bacteria  Andrews  depends  time  may  substrate (1965) by  be by and  methane  6.13,  which  53  is  not  a  favourable  McCarty(1969), propionic  the  acid  there w a s  pH  for  unfavourable  degradation  probably  no  Results  more  loss  of  and  Pearson(1965).  Andrews  and  Pearson's  Moreover, sludge  has  production acid in  they  used  been  the  used.  acetic acid  from  2.4  to  acid  can  be  acid  by  acid  for  this  produced  fermentation with  establish  could  be  utilization  due of  production pathways  the  a  shift  different  existing  is  while  also  of  acid per  experiments  in  the  that  in  for  to the  the  reserves types  of  microorganisms.  is  of  or  the  acid  change  work  was  of of  only  one  necessary.  study  primary  of  methane  and  propionic  a" sudden  decrease  acid  a  net  SRT  increase  in  was  increased  which  propionic  acid,  and  the  net  one  meq  of  metabolized,  Andrews  in the  of  nature  time. However,  in  they  f e r m e n t a t i o n . The  microorganisms  existing  acids,  the  meq/l. Since  residence change  was  valeric  2.2  a  by  findings  start  acid, from  valeric  type by  acetic  when  only  there w a s  respect  the  there  volatile  of  the  the  present  that of  formers,  meq  affects  used  of  meq/l.  was  they  accompanied  known  to  between  that  observed  5.7  only  reason  endogenous  of of  exact  to  feed  methane  Pearson(1965) concluded  producing not  is  study  concentration. However,  produced  propionic  this  and  degradation. Therefore,  comparable  difference  production was  The  decrease  quite  main  Lawrence  production.  relative concentrations  days.  measured  acid  to  conditions  acetic acid  statistical design  concentration  4.3  the  are  The  They  a f f e c t e d the  net  than  synthetic  differently. Methane  propionic  and  no  According  environmental  study  and  hence  formers.  in p r o p i o n i c  this  Andrews  temperature, and  methane  changes  in  could change  present,  microorganisms the  acid  with  the the  metabolic  54  In the c o n t r o l l e d r e a c t o r , the net t o t a l improved  because  potential  in the c o n t r o l l e d  redox  potential  E  -  c  (  pH  is  for  close  not only acid  producing  is  7. H e n c e ,  optimum  produced  volatile  controlled  acid  is  acids.  pH, might  b a c t e r i a , thus  the  from  the l o n g e r eventual the  compensated  giving  a higher  at the c o n t r o l l e d pH is  propionic  acid  assimilating  In  their  (4.5,  study  5.7,  they  6.0,  is  al.(1982)  6.4, all  6.9,  7.9).  the  C) and c o n c l u d e d  between  the  5.7  and  6.0.  In  optimum  methane  as  other  volatile by  acid  so  can acids.  the  acid  methane  of  a l l the  produced,  lost  to  at  methane  V F A production. The loss  under  pH acid  bacteria  the m e t a b o l i s m  acetic  effect seven  of  a c t i v i t y o f the  favourable  the  environmental  optimum their  influence  of  pH  on  conditions  pH  of  in an a n a e r o b i c  instead  controlled  that  the  well  substrate,  glucose  However,  seven  in  studied  dissimilation of studied  methane  McCarty(1969).  also  et al.(1982a) s t u d i e d  studied  temperature(30° glucose  they  Zoetemeyer  5.0,  design,  on acidogenic  first  glucose.  et  for  as  due t o the i n c r e a s e d  and  -360mV,  controlled  f o r the a c e t i c a c i d  bacteria  reported by Lawrence  Zoetemeyer temperature  methane  is  v o l a t i l e a c i d s , b y the  net t o t a l  acid  lowest  the  formers  but a l s o  chain  extra  ref.). The  Borchardt(1971),  primary  product  Redox  pH  in  production  production.  Optimum  conditions  both  acid  production)  Pearson(1965),  propionic  c o n d i t i o n s , as  to  dioxide  Therefore, have  1979).  and carbon  an  (Ag/AgCI  methane  and  acid  methane  pH  for  Andrews  methane  with  7.2. A c c o r d i n g  is  to  -334mV  ref.)(Pfeffer  bacteria, and f r o m  bacteria. A c e t i c  forming  and  to  was  (concurrently  formers  According  produce Acetic  7  in the net a c e t i c  reactor  Ag/AgCI  between  were  formers.  other  vs.  the a c i d  reactor  the i n c r e a s e  reported  315mV  formers  of  volatile  of  pH  digestor.  acidogenesis of  using  conditions  and  of  c o n t r o l l e d pH experimental at  a  single  pH f o r the a c i d i f i c a t i o n o f next  study,  Zoetemeyer  et  55  al.(1982b)  studied  the  e f f e c t of  with  fourteen  conditions  60°  C  used. A l l  being  of  5.8, w h i c h  in  their  that  the  and  38°  and  for  see  design,  it  biological been  on  the  30°C,  not  a  pH  the  acidification of  pH  =  being  Zoetemeyer  et  conclusions condition  of  al.(1982) on  if  production as  an  a  that is  If  a  indicator of  is  range  between  C  to  controlled  pH  concluded  C  and  design  using  in  and  pH  can  studied  separately.  optimum  for  VFA  In  not  basis  of are  such not  SOLUBLE  was  correct.  experiments  about  but pH  studied  Therefore the  it for of by the  optimum  defensible.  TOC  AND  measured  VFA  in  between  total  organic  relationship  does  exist, TOC  the net t o t a l  means  acceptance  temperatures  an one  It  optimum  o t h e r w o r d s , the  necessarily  of  production;  same.  fourteen  study,  have  effect  the  the  C.  factorial experimental  the  all  53°  C  experiments  Hence,  be  36°  et al.(1982) w i t h t h i s  temperature  be  glucose  between  51°  t e m p e r a t u r e s , the  carbon  21°  production. not  glucose,  they  is  other  pH  of  a  experiments  study, that  of  acidification of  statistical  this  was  BETWEEN  organic  range  at  at  for  and  relationship  exists.  may  the  temperature  Total determine  5.8  optimum  RELATIONSHIP  In  in a range  mesophilic  using  production  mean  acidogenesis  for  Zoetemeyer  of  VFA  glucose  drawn  by  pH  these  statistically  the  of  necessarily  5.8  done  proved  VFA  of  thermophilic  systems.  on  the  conducted  optimum  basis  importance  effect  parameter  used  the  the  studies  the  has  interactive  On  the  the t w o  with  5.3.9  be  t e m p e r a t u r e w i t h i n the  can  does  to  were  optimum C,  at  experiments  study.  dealing  that  the  found  on  controlled temperatures  previous  Comparing one  was  of  temperature  VFA  PRODUCTION  all  carbon  production.  the and  experiments total  measurements  net can  to VFA be  56  170 160 150 140 130 120110100 9080 70 60-  5040  30  Legend A  20-  Soluble T O C  X Unaccounted  10-  TOC  10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160  Mean Net Total VFA Prod, (mg/l Acetic Acid)  F i g . 5.7  Net  Total  VFA  concentration  vs.  Soluble  Total  Organic  Carbon  57  The production Fig.  5.7  soluble  relationship  between  in the f e r m e n t e r s  that  total  VFA  T O C . The  is  shown  production  following  =  0.659x  +  TOC  F i g . 5.7. It  an  for  using  soluble  in  has  equation  c o e f f i c i e n t , r=0.98) w a s obtained  y  total  almost  the  and total is  quite  linear  line  of  the m e t h o d  clear  from  relationship  with  best  of  net V F A  fit  (correlation  least-squares.  60  where,  To in  the  acid  propionic VFA  TOC  was  =  Soluble  x  =  Total  determine  phase  acids,  total  y  is  it  production then  plotted  contributed  by total  VFA  VFA  cone,  in  as  acid  (mol. wt. =  mg/l  the  to  to  the  TOC  the  production acid  60) has t w o c a r b o n  by  the  calculated 24/60  (as  of  acid.  the  acetic  remainder  VFA  multiplying  each  molecule  and  by  the  of  the  production.  by  atoms(at. w t . -  mattter  contributed  the  net  acetic  the o r g a n i c  TOC  values;  total  was  of  production  subtract  soluble  against  acetic  c o n e , in m g / l as  the s o l u b i l i z a t i o n  due  decided  from  in m g / l  net V F A  whether  purely  was  TOC  TOC  total of  net  acetic  12)).  Hence, Unaccounted  A production best  fit  method,  TOC  relationship  is a l s o  =  TOC -  between  24/60(Total  unaccounted  p l o t t e d in F i g . 5.7.The  (correlation  Coeff.,  r=0.88)  net V F A  was  following obtained  TOC  cone.)  and  equation using  net  total  VFA  f o r the line o f  the  least-squares  58  y'  =  0.255x  +  60  where, y' x  A the  increase  very  in other  solubilized  in  about  the  acetic, fatty  (like  in  process,  compounds  5.3,10  being  total  mass  mg/day in  time  5.8  value  and  acids  but  No  was  definite  done.  VFA  cannot  OF  produced  5.9  raising  at 3 0 ° C  of  and  It  was  only  VFA  They  may  be  with  means  that  also  being  be  drawn  analysis other  are  significant of  TOC  can  as  for  volatitle  known  to  to  BIO-P  the  some  other  which  varying  be  organic  out.  f e r m e n t e r , through  per  unit  is  time  of  temperature s t u d y , the  for  interest  varies.  u n c o n t r o l l e d pH  respectively. These  3 days  acid  possibility  c y c l e d , it  mg/day, improves  the  observed.  not  acid.  unaccounted  etc.), w h i c h  are  be r u l e d  acetic  VFA  are  c o n t r o l l e d and  and  they  as  conclusion  products,  was  as  of  propionic  u n d e r t a k e n . The  sludge  c o n d i t i o n s . In t h i s  observed  acid  a fixed volume  p r o d u c t i o n , in and  the  production  amount.  phase, was  primary  the  c o n e , in m g / l  unidentified  PRODUCTION  of  for  Figs.  VFA  pH  of  in  VFA  acetic  produced  Given volumes  net  butyric  acid  analysis  DAILY  VFA  valeric, isovaleric, isobutyric  the  no  net  increase  these  and  -24/60(VFA)  Total  small  of  propionic  produced  total  very  nature  acids  =  than  a  TOC  small  the  something  =  clearly  consistently  maximum  the net  retention time.  by  how  the  production  have  show  been that  lowering  controlled  daily  know  total  conditions  plots  both  Net  to  daily  and  production  the  in  plotted  net  total  retention  uncontrolled of  VFA  was  59  Acetic Acid)  150-r  m  • ( 9//day TJ O  130120-  c  X  At 2 0 °  •  At 3 0 ° C  100 90807050-  VFA Pr  t  Legend A At 10° c  140 -  o  <  150-  40-  o  30^  50-  Net  201003  4  5  6  7  8  9  10  Retention Time (Days)  F i g . 5.8 Net D a i l y PH  Production of Total V F A v s . Retention T i m e  at C o n t r o l l e d  60  VFA Pr  po. o  Legend A At 10° c  140130120110-  X  At 20° c  •  At 30° C  o cn  Co  J ,  150 -  o O  /day As Acetic Acid)  160 q  80706050-  4030-  o  "'l""T  Net  20-  o  2  3  4  5  6  7  10  Retention Time (Days)  F i g . 5.9 Net D a i l y U n c o n t r o l l e d pH  Production of Total V F A  vs. Retention Time  at  61  In on  the  considering  potential effectiveness  in a f u l l - s c a l e t r e a t m e n t 1.  If  an  for  unlimited  the  were  purpose) mass  then  of  the  VFA's  If  important  available  mass  produced  in  criteria  for  as  in  of  OXIDATION  ORP of  steady  in  the  reactors  ORP  state  As  is  5.1  and  Hence,  paramount  form  -265  mentioned  throughout  the  is  that design  the  the  substrate  volume used  of for  the  main  of  VFA's  the this  greatest  phosphorus  sludge  of  total VFA's  the  governing  to  the  biological  availability  important and  the  is  substrate  sizing  from  concentration  maximization  is  in  as  provide  fermenter  simple  the  mind.  being  to  the  primary  it  the  of to  in  most  concentration the  biological  temperature  of  the  importance.  were  noticed to  of  kept  5.9).  anaerobic  5.2  in a l l the  were  then  process  POTENTIAUORPI  measurements analysis  and  removal  be  if  would  feeding  experiments  available  was  production  Since  low,  REDUCTION  readings  varied  monitored  Figs.  process. is  the  input  facility.  tank  5.8  sludge,  the  were  system  for  complete-mix  must  fermenter.and  in F i g s .  primary  points  existing  time,  phosphorus  sludge  in the  maximize  wastewaters  P-removal  5.3.11  shown  removal  shown  fermenter  (as  complete-mix  biological  retention  unit  these  following  an  per  to  of  primary  shorter  of  the  the  (eg.  maximizing  phosphorus municipal  of  fixed  process  is  of  organisms  removal it  results  p l a n t , the  source  anaerobic  fermenter  2.  the  18  quite  reactors. No  over  -395mV  the  during  the  trends  of  period  (Ag/AgCI  earlier,  experiments  stable  of  7  to  explore  the  any  days.  ref.) in t h i s  oxidation-reduction  final  7  days  variations  ORP  in  the  study.  potential  possibility  of  using  was it  62  F i g . 5.10  Relationship  Between  Mean ORP  v s . Net  Acetic Acid  Production  63  F i g . 5.11  Relationship  Between  Mean ORP  vs. Net  Propionic  Acid  Production  64  180  -i  20  J  CD Z  —  i -400  1  1  -380  -360  1 -340  1 -320  1 -300  1 -280  1— -260  ORP (mV). Ag/AgCI REF.  F i g . 5.12  Relationship  Between  Mean ORP  v s . T o t a l Net V F A  Production  65  as  an  indicator  acetic, propionic 5.11  and  5.12  definite  and  one  variables,  relationship Figs. for  5.13  production.  total  VFA  draw  the  5.18  production  both  cases,  the  at  critical 10°C  acetic low  and  acid  measured  ORP  is  affected  by  the  vs.  the  as  -385mV  net  acetic  total acid  lowered  from  operation (Ag/AgCI  at  of  temperature between  temperature  5.14  show  and  the  and  and  ORP  was  associated  was  ORP  somewhere  total  VFA  pH.  But  keep  at  on  acid  reduced  close  to  only  between and  production  combinations. VFA  between  production  the  a  production  pH.  relationship  acetic  The  VFA  pH  VFA  net  discern  ORP.  net  net  r e a c t o r , the  to  5.10,  t e m p e r a t u r e , pH  uncontrolled  and  below  -300mV  controlled  increasing,  pH with  total  net  p H , the  even  when  and  net  conditions.  In  lower  In  VFA  -300mV, for  ORP  ORP.  production  indicating acid  net  that  production  production  the  ORP  was  of as  ( A g / A g C I ref.).  net  20°C  temperature increased  dropped  propionic  -366mV  ref.) f o r  20°C  production  production  while  sets  ORP  net  Figs.  relationship  and  lies  VFA  -366mV,  explore  definite  controlled  Similarly, for the  to  relationships  of  uncontrolled  and  and  no  and  when  ORP  production  and  in  impossible  for  pH  dropping  acid  is  10°C  a higher  uncontrolled  started the  at  net  it  ORP  plotted  is  different combinations  VFA  examination,  been  there  different  F i g s . 5.13  have  between  that  decided  show  Relationships  production  the  is  since  it w a s  for to  between  can  two. However,  other  VFA  respectively. Upon  relationship  conclusion the  of  to (Fig.  net V F A  when acid  with  the  uncontrolled  decreasing  ORP  production  -378mV 5.15),  and  was  (Ag/AgCI  ref.).  critical  ORP  the  production.  ORP.  further  increased For was  pH  as  (Fig. But  the  lowered the  the  5.16),  ORP  controlled  around  net than was pH  -360mV  66  F i g . 5.13 R e l a t i o n s h i p B e t w e e n ORP C o n t r o l l e d pH O p e r a t i o n  and Net V F A  production  for  10°C  and  67  70-,  u o o  %  60 H  u o  8  5 0 H  cn J , 40  c  q  ~o D  30  Legend  o A  Q.  20 H  Total VFA  X Acetic Acid O  Propionic Acid  > C D  io H  -310  -300  -290  -280  -270  •260  Mean ORP (mv)  Fig. 5.14 Relationship Between ORP and Net V F A production Uncontrolled pH Operation  for  10°C and  F i g . 5.15 R e l a t i o n s h i p B e t w e e n C o n t r o l l e d pH O p e r a t i o n  ORP  and  Net  VFA  production  for 20°C  and  69  F i g . 5.16 R e l a t i o n s h i p B e t w e e n ORP U n c o n t r o l l e d pH O p e r a t i o n  and  Net  VFA  production  for 20°C  and  70  F i g . 5.17 R e l a t i o n s h i p B e t w e e n C o n t r o l l e d pH O p e r a t i o n  ORP  and  Net  VFA  production  for  30°C  and  71  F i g . 5.18 R e l a t i o n s h i p B e t w e e n U n c o n t r o l l e d pH O p e r a t i o n  ORP  and  Net  VFA  production  for 30°C  and  72  At uncontrolled and  net  30°C  p H , no  VFA  definite  production  McCarty(1969),  the  methane  ORP  be  production lay  between  that  the  Hence,  -334mV  to  -396mV  a  in  pairs  (CO2/H2)  concentration  is  from  which  (1979)  control  acids  method.  explain  has  at  the  lack  of  a  Lawrence  and  acetic  30°C it  methane  , the  is  higher  acid  (1979), the  ref.)for'  at  ref.). M o r e o v e r , active  ORP  for  (Ag/AgCI  as  mean  Pfeffer  methanogenesis  expressed  phase by  if the and  of  widely  within  doubt  anaerobic  a wide  differ  concentration  (CO2/H2/CH4), fatty  of  to  conducted  more  well  also  ORP known  temperatures.  occuring definite  at  30°C  relationship  ORP.  generated  carried out. However,  useful  vs.  -315mV  are  to  required  According  (Ag/AgCI  as  between  According  time  experiments  might  externally will the  as  probability  methanogenic are  low  days.  controlled  observed  5.18).  residence 4.2  the  for  was  and  bacteria  higher  production  ORP  as  forming  reactors,  the  is  all  Hughes  differ  bacteria  In  is  VFA  cell  occur.  there  between  5.17  least  methane  operated  (Fig.  at  to  and,  relationship  minimum  assimilating must  temperature  the  range at  the  digestion. of  significance The  organisms  main  and  different times. They  methane  measurements ATP,  about  were  measurements  bacteria, where combined of  ORP  redox  thus  their  will  also  reduction  w i t h gas might  of  yield,  become  a  73  CHAPTER  CONCLUSIONS AND  6.1.  1.  following 'conclusions  Of  the  the  maximum  any  18  combinations  Temperature,  the  of  determined  in  the  seems  to  and  retention  Hence,  the one  of  made  from  the  discussion  of  temperature the  At  lower  helped  to  pH  was  propionic  total  VFA  a value  VFA  are  achieved of  interactive  of  at 7  pH  tested,  30°C  did  and  not  6  make  production.  change  in  their  in  other  two  variables.  the  net  VFA  on  (10°C), net  of  Net  the  to  net  effect  was  and  one In  effects  on  variable  is  essence  production  then,  cannot  be  isolation.  The  and  time, temperature  pH  time  parameter  ( 3 0 ° C ) , it d o e s  control  of  total  the  values  improve  temperature 6.  be  concentration  control  temperature  acetic 5.  lower  VFA  in the  production. on  retention  change  pH  effect  At  total  of  t i m e . The  significant  dependent  4.  net  retention  VFA  3.  can  results:  days  2.  RECOMMENDATIONS  CONCLUSIONS  The the  6  total  not  found  control VFA  a f f e c t the to  affect  of  pH  to  production. net  the  a  value  But  at  production  relative  net  of  7  higher  significantly. production  of  acids.  production  between  the  10°C  consistently to  temperature  (10°C  improve  net  the  improved  with  the  increase  in  30°C. and  VFA  20°C)  the  production/  73  increase  in  retention  time  74  7.  Extending  the  detrimental  8.  to  by  methane  A  definite  production a  11.  30°C and  net  The  use  of  to  be  VFA  the  at  30°C  because  soluble  total  some at  of  appears  its  TOC  for  use  to  as  and  total  TOC  can  be  substrate  specific sewage  20°C.  lowering  of  net be  production,  relationship  and  definite  VFA  the of  10°C  no  net  form  w i t h the  temperature,  ORP  production  determined  ORP  increased  days  exist. Therefore, soluble  of  be  and  9  between  to  been to  to  bacteria.  found  has  seems  production At  VFA  indicator  production  10.  net  time  relationship was  viable  There  the  producing  relationship 9.  retention  used  once  and  as the  process.  between  On  VFA  average,  net  VFA  net  VFA  ORP.  relationship  was  observed  between  VFA  production  appears  production.  ORP  mesurements  doubtful  unless  as  indicator  temperature  of  and  pH  values  this  study,  are  taken  into  account.  6.2. RECOMMENDATIONS 1.  Because  of  the  of  of  temperature  each  were  studied.  retention  time  combinations 2.  There  is  pH  butyric  requires  acids all the  and  retention  should  for  of  studies,  variables  products  nature  and  future  and  of  digestion. This  monitored  In  a potential  unidentified  and  exploratory  for a  be  formed  time, even  for  the  two  three  to  with  acid  VFA's  other  lower  of  pH  temperature, the  optimum  production.  the  the  Gas  of  determine  net V F A  conditions  conditions  conditions  dealing  compounds. at  and  studied  during  analysis other  more  maximum  study  time  only  investigation phase than  production  of  the  anaerobic  acetic, should  temperatures, to  of  propionic also  be  provide  an  overall  mass  balance  related to  the f a t e o f  organic  carbon  substrate.  76  REFERENCES 1.  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Z o e t e n m e y e r , R.J., V a n Den H e u v e l , J.C., and C o h e n , A., "pH on A c i d o g e n i c D i s s i m i l a t i o n of Glucose in an A n a e r o b i c W a t e r R e s e a r c h , 16(1982), 3 0 3 - 3 1 1 .  47.  Z o e t e m e y e r , R. J . , A r n o l d y , P., C o h e n , A., and B o e l h o u w e r , C., " I n f l u e n c e o f T e m p e r a t u r e o n the A n a e r o b i c A c i d i f i c a t i o n o f G l u c o s e in a M i x e d Culture Forming Part of a Two-Stage Digestion Process.", Water R e s e a r c h , 16(1982), 3 1 3 - 3 2 1 .  Influence Digestor",  80  APPENDIX  DAILY  NET  VOLATILE  FATTY  ACIDS  PRODUCTION  DATA  RECORD  DAYS  TREATMENT VARIABLES  NET  NET  NET  IN  *******************  ACETIC  PROP.  VFA  STEADY  RET.  pH  ACID  ACID  PROD.  STATE  TIME  C/U  PROD.  PROD,  (mg/L  TEMP. C  (mg/L)  (mg/L)  as acet ic acid)  1  9  10  U  50  15  62.2  1  9  10  U  52  18  66.6  2  9  10  U  59  23  77.6  2  9  10  U  46  20  62.2  3  9  10  U  54  17  67.8  3  9  10  U  60  20  76.2  4  9  10  u  48  18  62.6  4  9  10  u  49  15  61 . 2  5  9  10  u  54  15  66.2  5  9  10  u  55  22  72.8  6  9  10  u  50  20  66.2  6  9  10  u  53  1  6  66.0  7  9  10  u  55  22  72.8  80  10  u  50  19  65.4  1  3  10  u  48  5  52. 1  1  3  1 0  u  42  5  46. 1  2  3  10  u  40  6  44.9  2  3  1 0  u  50  6  54.9  3  3  10  u  35  4  38.2  3  3  10  u  48  4  51.2  4  3  10  u  50  5  54. 1  4  3  10  u  50  7  55.7  5  3  10  u  45  6  49.9  5  3  10  u  38  3  40.4  6  3  10  u  48  4  51 . 2  6  3  10  u  34  4  37.2  7  3  10  u  45  5  49. 1  7  3  10  u  46  5  50. 1  1  9  10  C  75  30  99.3  1  9  10  C  78  32  103.9  2  9  10  C  70  35  98.4  2  9  1 0  C  65  28  87.7  3  9  10  C  70  40  102.4  3  9  10  C  80  25  100.3  4  9  10  c  63  27  84.9  4  9  10  c  75  28  97.7  5  9  10  c  75  33  101.8  5  9  10  c  68  33  94.8  10  c  68  35  96.4  10  c  70  38  100.8  10  c  75  28  97.7  10  c  66  27  87.9  30  U  33  84  101.1  30  U  30  80  94.9  30  u  32  88  103.4  30  u  35  80  99.9  30  u  40  93  115.4  30  u  38  82  104.5  30  u  39  81  104.7  30  u  30  82  96.5  30  u  33  80  97.9  30  u  34  85  102.9  30  u  33  84  101.1  30  u  36  95  113.0  30  u  38  86  107.7  30  u  37  82  103.5  30  U  90  83  157.3  30  U  95  80  159.9  30  U  82  85  1 50.9  30  U  85  78  148.2  30  U  86  76  147.6  30  U  90  76  1 5.1 . 6  30  U  93  79  1 57. 1  30  U  85  88  1 56.4  30  U  90  80  154.9  30  U  88  80  152.9  30  U  89  75  1 49.8  30  U  78  77  1 40.4  30  U  85  80  149.9  30  U  89  83  1 56.3  30  C  70  30  94.3  30  C  75  28  97.7  30  C  78  30  102.3  30  C  75  32  100.9  30  C  79  30  103.3  30  C  81  33  107.8  30  C  82  34  109.6  30  C  72  34  99.6  30  C  70  33  96.8  30  C  77  30  101.3  30  C  77  33  103.8  30  C  79  28  101 . 7  30  C  80  36  109.2  30  C  84  33  110.8  30  C  100  40  1 32.4  30  C  110  45  146.5  30  c  95  35  123.4  30  c  105  40  137.4  30  C  1 06  40  1 38.4  30  C  108  45  144.5  30  C  1 05  42  1 39. 1  30  C  95  43  129.9  30  C  1 05  45  141.5  30  C  99  40  131.4  30  C  1 08  43  142.9  30  C  1 00  45  1 36.5  30  C  1 05  42  1 39. 1  30  C  100  46  137.3  30  C  90  70  146.8  30  C  85  70  141.8  30  C  92  73  151.2  30  C  94  75  154.8  30  C  96  75  1 56.8  30  C  98  73  1 57.2  30  C  98  75  1 58.8  30  C  90  74  1 50.0  30  C  92  72  150.4  30  C  84  72  1 42.4  30  C  94  75  1 54.8  30  C  98  73  157.2  30  C  99  73  1 58.2  30  C  100  77  162.4  30  U  70  48  108.9  30  U  68  44  103.7  30  U  78  43  1 12.9  30  U  79  46  116.3  30  U  80  49  119.7  30  U  75  50  115.5  30  U  74  49  113.7  30  U  75  50  115.5  30  U  71  45  107.5  30  U  82  48  120.9  30  U  80  47  118.1  30  U  74  42  1 08. 1  30  U  74  48  112.9  30  U  72  47  110.1  20  C  72  39  103.6  20  C  68  37  98.0  20  C  67  40  99.4  20  C  75  42  109. 1  20  C  78  44  113.7  20  C  82  43  116.9  20  C  82  44  117.7  20  C  70  41  103.2  20  C  70  40  102.4  20  C  72  44  107.7  20  C  75  48  113.9  20  C  74  48  112.9  20  C  78  44  113.7  20  76  45  112.5  20  C  80  55  124.6  20  C  78  56  123.4  20  C  75  48  113.9  20  C  84  52  126.2  20  C'  85  51  126.4  20  C  86  53  129.0  20  C  85  50  125.5  20  C  78  50  118.5  20  C  80  50  120.5  20  C  80  51  121.4  20  C  83  54  126.8  20  C  84  53  127.0  20  C  86  53  129.0  20  C  80  49  1 19.7  20  U  63  58  110.0  20  U  60  58  107.0  20  U  65  61  114.5  20  U  68  57  114.2  20  U  70  62  120.3  20  U  70  62  120.3  20  U  69  65  121.7  20  U  60  55  104.6  20  U  63  59  110.8  20  U  63  61  112.5  20  U  65  56  110.4  20  U  69  62  119.3  20  u  69  60  117.6  20  u  70  62  1 20.3  20  C  63  28  85.7  20  C  65  28  87.7  20  C  68  30  92.7  20  C  57  34  84.6  20  C  65  32  90.9  20  C  63  32  88.9  20  C  60  27  81 . 9  20  C  58  25  78.3  20  C  67  30  91 .3  20  C  63  33  89.8  20  C  59  32  84.9  20  C  65  32  90.9  20  C  66  36  95.2  20  C  66  29  89.5  20  U  50  20  66.2  20  U  46  18  60.6  20  U  48  22  65.8  20  U  41  1 5  53.2  20  U  52  1 1  60.9  20  U  53  18  67.6  20  U  52  20  68.2  20  U  44  18  58.6  20  U  42  1 5  54.2  20  U  45  20  61.2  20  U  47  18  61 . 6  20  U  52  18  66.6  20  U  50  20  66.2  20  U  54  20  70.2  20  U  75  25  95.3  20  U  22  22  95.8  20  U  80  28  102.7  20  U  70  33  96.8  20  U  84  30  108.3  20  U  84  31  109. 1  20  U  82  28  104.7  20  U  78  25  98.3  20  U  78  30  102.3  20  U  82  26  1 03. 1  20  U  72  33  98.8  20  U  81  29  104.5  20  U  84  32  109.9  20  U  80  30  104.3  10  C  60  30  84.3  10  C  62  31  87.1  10  C  59  35  87.4  10  C  58  33  84.8  10  c  53  29  76.5  10  c  65  25  85.3  10  c  61  30  85.3  10  c  59  32  84.9  10  c  64  30  88.3  10  c  57  34  84.6  10  c  59  31  84. 1  10  c  56  33  82.8  10  c  70  28  92.7  10  c  60  30  84.3  10  u  48  20  64.2  10  u  43  25  63.3  10  u  53  18  67.6  10  u  52  22  69.8  10  u  54  20  70.2  10  u  49  1 7  62.8  1 0  u  50  19  65.4  10  u  50  19  65.4  1 0  u  42  20  58.2  1 0  u  50  25  70.3  10  u  53  24  72.5  10  u  55  19  70.4  1 0  u  52  15  64.2  10  u  45  18  59.6  10  C  45  15  57.2  10  C  38  19  53.4  10  c  43  22  60.8  1 0  c  52  22  69.8  10  c  48  1 3  58.5  10  c  51  1 3  61 . 5  10  c  52  20  68.2  10  c  48  1 6  61 . 0  1 0  c  40  1 7  53.8  10  c  45  20  61 . 2  1 0  c  56  28  78.7  10  c  50  20  66.2  10  c  50  18  64.6  10  c  48  21  65.0  

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