Table Of ContentWastewater
Purification
Aerobic Granulation
in
Sequencing
Batch Reactors
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Wastewater
Purification
Aerobic Granulation
in
Sequencing
Batch Reactors
Edited by
Yu Liu
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
© 2008 by Taylor & Francis Group, LLC
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CRC Press
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Library of Congress Cataloging-in-Publication Data
Wastewater purification : aerobic granulation in sequencing batch reactors /
editor, Yu Liu.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-4200-5367-8 (hardback : alk. paper)
1. Sewage--Purification--Microbial granulation process. 2.
Sewage--Purification--Sequencing batch reactor process. I. Liu, Yu.
TD765.65.W37 2006
628.3’2--dc22 2007030300
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Contents
Preface .....................................................................................................................vii
Contributors ..............................................................................................................xi
Chapter 1 AerobicGranulationatDifferentCarbonSourcesand
Concentrations ......................................................................................1
Qi-Shan Liu and Yu Liu
Chapter 2 AerobicGranulationatDifferentShearForces .................................25
Qi-Shan Liu and Yu Liu
Chapter 3 AerobicGranulationatDifferentSBRCycleTimes ..........................37
Zhi-Wu Wang and Yu Liu
Chapter 4 AerobicGranulationatDifferentSettlingTimes ...............................51
Lei Qin and Yu Liu
Chapter 5 RolesofSBRVolumeExchangeRatioandDischargeTimein
AerobicGranulation ...........................................................................69
Zhi-Wu Wang and Yu Liu
Chapter 6 SelectionPressureTheoryforAerobicGranulationin
SequencingBatchReactors ................................................................85
Yu Liu and Zhi-Wu Wang
Chapter 7 GrowthKineticsofAerobicGranules .............................................111
Qi-Shan Liu and Yu Liu
Chapter 8 DiffusionofSubstrateandOxygeninAerobicGranules ................131
Yong Li, Zhi-Wu Wang, and Yu Liu
Chapter 9 TheEssentialRoleofCellSurfaceHydrophobicityin
AerobicGranulation .........................................................................149
Yu Liu and Zhi-Wu Wang
v
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vi Contents
Chapter 10 EssentialRolesofExtracellularPolymericSubstancesin
AerobicGranulation .........................................................................181
Yu Liu and Zhi-Wu Wang
Chapter 11 InternalStructureofAerobicGranules ............................................195
Zhi-Wu Wang and Yu Liu
Chapter 12 BiodegradabilityofExtracellularPolymericSubstances
ProducedbyAerobicGranules ........................................................209
Zhi-Wu Wang and Yu Liu
Chapter 13 CalciumAccumulationinAcetate-FedAerobicGranules ...............223
Zhi-Wu Wang, Yong Li, and Yu Liu
Chapter 14 InfluenceofStarvationonAerobicGranulation ..............................239
Yu Liu, Zhi-Wu Wang, and Qi-Shan Liu
Chapter 15 FilamentousGrowthinanAerobicGranularSludgeSBR ..............259
Yu Liu and Qi-Shan Liu
Chapter 16 ImprovedStabilityofAerobicGranulesbySelecting
Slow-GrowingBacteria ....................................................................287
Yu Liu and Zhi-Wu Wang
Chapter 17 PilotStudyofAerobicGranulationforWastewaterTreatment .......301
Qi-Shan Liu and Yu Liu
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Preface
Biogranulationisaprocessofmicrobialself-immobilization,anditcanbedivided
intotwogeneralgroups,thatis,anaerobicandaerobicgranulation.Anaerobicgran-
ulation has been studied extensively for decades, whereas the interest in aerobic
granulationwasstartedjustafewyearsago.Aerobicgranulationisanenvironmental
biotechnology developed for the purpose of high-efficiency wastewater treatment.
The distinguishing characteristics of aerobic granules attribute superiority to this
technology in comparison with the conventional activated sludge processes. Thus
far,intensiveresearchhasbeenconductedtounderstandthemechanismofaerobic
granulation in sequencing batch reactor (SBR) and its application in treating a
wide variety of municipal and industrial wastewater. Obviously, the basic research
of aerobic granulation has promoted this technology from laboratory study to the
present pilot- and full-scale applications. This book aims to discuss the up-to-date
researchandapplicationofthisenvironmentalbiotechnologytailoredforenhanced
wastewaterpurification.
First, chapter 1 presents experimental evidence showing that aerobic granula-
tioninSBRisindeedinsensitivetothesubstratetypeanditsconcentrationapplied,
although the carbon source seems to influence the physical properties and micro-
bial diversity of mature aerobic granules. It appears from this chapter that aerobic
granulationtechnologyisapplicabletothepurificationofawidespectrumofwaste-
water.HydrodynamicshearforceresultingfromintensiveaerationinSBRplaysan
essential role in aerobic granulation. Chapter 2 elaborates on how hydrodynamic
shearforcewouldinfluenceaerobicgranulation,withspecialfocusonshearforce-
associated changes in microbial activity, cell surface property, and production of
extracellular polysaccharides. Hitherto, almost all successful aerobic granulations
areachievedinSBRthatisfeaturedbyitscyclicoperation.Chapter3furtherlooks
intotheroleofSBRcycletimeinaerobicgranulation.
Chapter4focusesonunderstandingtheroleofsettlingtimeinaerobicgranula-
tion, which is a unique operating parameter of SBR as compared to conventional
activated sludge reactors. Settling time is shown as an essential driving force of
aerobic granulation. Aerobic granulation would fail if settling time is not properly
controlled. Aerobic granulation seems to be an effective defensive or protective
strategyofthemicrobialcommunityagainstexternalselectionpressure.Chapter5
identifies the volume exchange ratio and discharge time of SBR as two other pos-
sibledrivingforcesofaerobicgranulationinSBR.Further,chapter6showsthatall
the major selection pressures identified so far can be unified to an easy concept of
theminimalsettlingvelocitythatultimatelydeterminesaerobicgranulationinSBR.
Thisselectionpressuretheoryoffersusefulguidesforup-scaling,manipulating,and
optimizingaerobicgranularsludgeSBR.
Aerobicgranulationisagradualprocessthatcanbequantitativelydescribedas
changeingranulesizeinthecourseofSBRoperation.Inthisregard,somekinetic
vii
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viii Preface
models have been developed and presented in chapter 7. Because of the large size
of the aerobic granule, mass diffusion limitations exist in the aerobic granule.
Chapter8 looks into the diffusion behaviors of substrate and dissolved oxygen in
aerobic granules and presents a comprehensive modeling system, which describes
the dynamic diffusion of substrate and oxygen in various-sized aerobic granules.
Thismodelsystemcanprovideaneffectiveandusefultoolforpredictingandopti-
mizingtheperformanceofaerobicgranularsludgeSBR.
Itisbelievedthatcell-to-cellself-aggregationinitiatesaerobicgranulation.Cell
surface hydrophobicity serves as an essential affinity force that initiates the first
contactofcelltocell.Existingevidenceshowsthatanumberofcultureconditions
can induce cell surface hydrophobicity. Chapter 9 discusses the factors known to
influencecellsurfacehydrophobicity.Furthermore,athermodynamicinterpretation
of the role of cell surface hydrophobicity in aerobic granulation is also given. The
enrichmentcultureofhighlyhydrophobicbacteriathusappearstogreatlyfacilitate
aerobic granulation. Chapter 10 discusses the essential roles of extracellular poly-
saccharidesintheformationandmaintenanceofstructuralstabilityofaerobicgran-
ules.Itappearsthatboththequantityandthequalityofextracellularpolysaccharides
determinethematrixstructureandintegrityofaerobicgranules.
Chapter11revealsthattheinternalstructureoftheaerobicgranuleexperiencesa
shiftfromhomogenoustoheterogeneousastheaerobicgranulegrowstoabigsizedue
to mass diffusion limitation. Uneven distributions of granule biomass, extracellular
polysaccharides, and cell surface hydrophobicity are also discussed in chapter11.
Chapter 12 mainly focuses on biodegradability of extracellular polysaccharides pro-
ducedbyaerobicgranules.Onlynonbiodegradableextracellularpolysaccharidescan
play a crucial protective role in the granule integrity stability, while biodegradable
extracellular polysaccharides accumulated at the central part of the aerobic granule
canserveasanadditionalenergyreservoirwhenanexternalcarbon sourceisnolonger
available for microbial growth.Chapter 13provides a plausible explanation for the
observedhighcalciumaccumulationinacetate-fedaerobicgranulesfrombothexperi-
mentalandtheoreticalaspects.Itisshownthatthecalciumionmaynotbeanessential
elementrequiredforsuccessfulaerobicgranulation.
Unlike the continuous activated sludge process, a substrate periodic starvation
exists in aerobic granular sludge SBR due to its cyclic operation. Chapter 14 dis-
cussesdifferent,evencontroversial,viewswithregardtotheroleofsuchaperiodic
starvationinaerobicgranulation.Asfilamentousgrowthhasbeenfrequentlyobserved
inaerobicgranules,chapter15looksintocausesandcontroloffilamentousgrowth
in aerobic granular sludge SBRs. In view of its industrial application, long-term
stabilityofaerobicgranularsludgeSBRremainsamainconcern.Forthispurpose,
chapter 16 sheds light on the possible operation strategy that can help improve the
stability of aerobic granules, including the selection of slow-growing bacteria and
controlofgranuleage.Afternearlytenyearsoflaboratoryresearch,aerobicgranu-
lation technology has achieved pilot- and full-scale applications. Chapter17 shows
thatsuccessfulaerobicgranulationcanbeachievedinpilot-scaleSBRusingfreshor
storedaerobicgranulesasseeds.
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Preface ix
ThisbookpresentsreadersallaspectsofaerobicgranulationinSBR.Thesuc-
cessfultestofthistechnologyinpilot-scalestudyforeseesitspromisingapplication
inpracticalwastewatertreatment.Isincerelyhopethatthepublicationofthisbook
willprovideaplatformforthefurtherdevelopmentofthistechnologyandpromote
itsquickapplicationinthewastewatertreatmentindustry.
YuLiu
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Contributors
Yu Liu, Ph.D. Lei Qin, Ph.D.
SchoolofCiviland SchoolofChemicaland
EnvironmentalEngineering EnvironmentalEngineering
NanyangTechnologicalUniversity ShanghaiUniversity
Singapore People’sRepublicofChina
Zhi-Wu Wang, Ph.D. Yong Li, M.Eng.
SchoolofCiviland SchoolofCiviland
EnvironmentalEngineering EnvironmentalEngineering
NanyangTechnologicalUniversity NanyangTechnologicalUniversity
Singapore Singapore
Qi-Shan Liu, Ph.D.
SingaporePolytechnic
Singapore
xi
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1
Aerobic Granulation at
Different Carbon Sources
and Concentrations
Qi-Shan Liu and Yu Liu
CONTENTS
1.1 Introduction.....................................................................................................1
1.2 AerobicGranulationwithAcetateandGlucose.............................................2
1.2.1 MicroscopicObservationofAerobicGranulation...............................2
1.2.1.1 SeedSludge............................................................................2
1.2.1.2 FormationofCompactAggregatesafterOperationfor
OneWeek...............................................................................2
1.2.1.3 FormationofGranularSludgeafterOperationfor
TwoWeeks.............................................................................3
1.2.1.4 AppearanceofMatureGranulesafterOperationfor
ThreeWeeks...........................................................................4
1.2.2 CharacteristicsofGlucose-andAcetate-FedAerobicGranules.........5
1.2.2.1 Morphology............................................................................5
1.2.2.2 SludgeSettleability.................................................................5
1.2.2.3 GranulePhysicalStrengthandBiomassDensity...................7
1.2.2.4 CellSurfaceHydrophobicity..................................................7
1.2.2.5 MicrobialActivity..................................................................7
1.2.2.6 StorageStabilityofAerobicGranules...................................7
1.3 AerobicGranulationonOtherCarbonSources..............................................9
1.4 AerobicGranulationatDifferentCODConcentrations.................................9
1.4.1 EffectofCODConcentrationonthePropertiesof
AerobicGranules...............................................................................10
1.4.2 EffectofCODConcentrationontheReactorPerformance..............15
1.5 AerobicGranulationatDifferentSubstrateN/CODRatios..........................15
1.5.1 EffectofN/CODRatioonthePropertiesofAerobicGranules........16
1.5.2 EffectofN/CODRatioonPopulationDistribution...........................18
1.6 Conclusions...................................................................................................20
References................................................................................................................20
1.1 INTRODUCTION
Granulation is a process in which microorganisms aggregate to form a spherical,
densebiomass.Granuleshavebeengrownsuccessfullyineitheranaerobicoraerobic
1
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