Biodegradation-and-kinetics-of-aerobic-granules-un

ENVIRONMENTALBIOTECHNOLOGYBiodegradationandkineticsofaerobicgranulesunderhighorganicloadingratesinsequencingbatchreactorYaoChen&WenjuJiang&DavidTeeLiang&JooHwaTayReceived:1January2008/Revised:15February2008/Accepted:15February2008/Publishedonline:11March2008#Springer-Verlag2008AbstractBiodegradation,kinetics,andmicrobialdiversityofaerobicgranuleswereinvestigatedunderahighrangeoforganicloadingrate6.0to12.0kgchemicaloxygendemand(COD)m−3day−1inasequencingbatchreactor.Theselectionandenrichingofdifferentbacterialspeciesunderdifferentorganicloadingrateshadanimportanteffectonthecharacteristicsandperformanceofthematureaerobicgranulesandcausedthedifferenceongranularbiodegradationandkineticbehaviors.Goodgranularcharacteristicsandperformancewerepresentedatsteadystateundervariousorganicloadingrates.Largeranddenseraerobicgranulesweredevelopedandstabilizedatrelativelyhigherorganicloadingrateswithdecreasedbioactivityintermsofspecificoxygenutilizationrateandspecificgrowthrate(μoverall)orsolidretentiontime.Thedecreaseofbioactivitywashelpfultomaintaingranulestabilityunderhighorganicloadingratesandimprovereactoroperation.Thecorrespondingbiokineticcoefficientsofendogenousdecayrate(kd),observedyield(Yobs),andtheoreticalyield(Y)weremeasuredandcalculatedinthisstudy.Astheincreaseoforganicloadingrate,adecreasednetsludgeproduction(Yobs)isassociatedwithanincreasedsolidretentiontime,whilekdandYchangedinsignificantlyandcanberegardedasconstantsunderdifferentorganicloadingrates.KeywordsAerobicgranule.Sequencingbatchreactor.PCR-DGGE.Biokinetics.Specificoxygenutilizationrate.SolidretentiontimeIntroductionHigh-strengthwastewatersproducedbyindustrieshavegrownrapidlyintherecentyears,anditisimperativetodevelopsuitablesolutionstomeetthedischargeregula-tions.Variousanaerobicandaerobicsystemswereappliedforthetreatmentofhigh-strengthwastewaters(Ahnetal.2007;Kurianetal.2006;Lacalleetal.2001;LefebvreandMoletta2006;Thompsonetal.2001).Recentstudieshaveshownthataerobicgranulationtechnologyhasgreatpotentialsandcanbeappliedinthetreatmentofhigh-strengthorganicwastewaterforeconomicalandtechnicaladvantages(Liuetal.2003;Moyetal.2002).Comparedwithconventionalactivatedsludge,aerobicgranulationisatypicalself-immobilizationofthebacteriaunderaerobicconditions.Withregularclear-outshape,compact,andstrongmicrobialstructure,aerobicgranuleshaveadvan-tagesoffaststart-up,goodsettlingability,highbiomassretention,andabilitytowithstandhighorganicloadingconditions.Mostaerobicgranuleshavebeensuccessfullycultivatedinthesequencingbatchreactors(SBR).TheperiodicaloperationalconditionsofSBRcontributeafeast–faminemodeltomicroorganism’sgrowth,whichplaysatriggerroleforaerobicgranulation(Tayetal.2001).Thesludgeproductionandkineticsofaerobicgranulesundersucharepeatedcycleoperationalconditionareimportanttotheprocessdesignandoptimization.Liuetal.(2005)reportedsomekineticparametersofaerobicgranulesbasedononly1-weekexperiment,anditwasdifficulttoextendtofurtherApplMicrobiolBiotechnol(2008)79:301–308DOI10.1007/s00253-008-1421-6Y.Chen:W.JiangCollegeofArchitectureandEnvironment,SichuanUniversity,Chengdu610065,People’sRepublicofChinaY.Chen:D.T.Liang:J.H.Tay(*)InstituteofEnvironmentalScienceandEngineering,NanyangTechnologicalUniversity,Singapore637723,Singaporee-mail:[e-mail].(2004)usedalinearphenomeno-logicalequationmainlytodescribethesize-dependentgrowthofaerobicgranulesunderdifferentoperationalconditions.Theinfluenceofcycletimeonkineticbehaviorsofsteady-stateaerobicgranulesinSBRwasstudiedbyLiuandTay(2007).However,theinformationofbiokineticsofaerobicgranulesunderdifferentorganicloadingrates(OLRs)intheSBRreactorwaslimitedandrequiredfurtherinvestigation.Thestressedsubstrateloadingisanimportantoperationalparameterthatsignificantlyinfluencestheaerobicgranula-tion.ItwasfoundthatOLRcouldexertamicrobialselectionpressureongranulationprocessandaffecttheperformanceofgranulesbyselectionandenrichingdifferentbacterialspecies(Moyetal.2002).ThemicrobialadaptationtodifferentOLRswouldfurtherinfluencethebiodegradationandbacterialcommunitystructure.Therefore,themainobjectiveofthisstudywastoinvestigatethebiodegrada-tion,kinetics,andmicrobialdiversityofaerobicgranulesatsteadystatesunderahighrangeofOLRsinSBRreactor.ThisworkwouldbeusefulforbetterunderstandingofthemechanismandmicrobialadaptationofaerobicgranulationunderhighOLRs.MaterialsandmethodsExperimentalsetupOnecolumn-typeacrylicreactorwithaninternaldiameterof52mmandaworkingvolumeof1.1lwasusedastheSBRreactortocultivateaerobicgranules.Fineairbubblesforaerationwereintroducedthroughanairdiffuserinthebottomofthecolumn,andtheairflowrateof4.0lmin−1wasapplied,whichresultedinasuperficialupflowairvelocityof3.2cms−1inthereactor.Thereactorwasoperatedat4hpercyclesequentially:5minofinfluentfilling,225minofaeration,5minofsettling,and5minofeffluentwithdrawal.Thehydraulicretentiontimewaskeptat8h,andOLRwasincreasedbyincrementsof3.0kgchemicaloxygendemand(COD)m−3day−1from6.0to12.0kgCODm−3day−1.MediumThesyntheticwastewaterconsistedofsodiumacetateassolec