Landfillleachatetreatmentwithsequencingbatchreacto

Desalination191(2006)86–910011-9164/06/$–Seefrontmatter©2006PublishedbyElsevierB.V.PresentedattheInternationalCongressonMembranesandMembraneProcesses(ICOM),Seoul,Korea,21–26August2005.*Correspondingauthor.LandfillleachatetreatmentwithsequencingbatchreactorandmembranebioreactorNiinaLaitinen*,AnteroLuonsi,JariVilenPirkanmaaRegionalEnvironmentCentre,P.O.Box297,33101Tampere,FinlandTel.+358407594675;Fax[phone];email:[e-mail]15March2005;accepted25August2005AbstractLandfillleachatefromacompostingfieldofaFinnishmunicipalwastelandfillwastreatedwithsequencingbatchreactor(SBR)andasubmergedmembranebioreactor(MBR)fedbatchwise.Theaveragequalityoftheleachatewas475mg/lsuspendedsolids,1240mg/lBOD7,10mg/lphosphorus,and210mg/lammoniumnitrogen.HydraulicretentiontimesinSBRvariedfromfourtoninedaysandinMBRfromtwotofivedays.SolidsretentiontimesinSBRwerefrom10to40daysandinMBRfrom35toover60days.ThesludgeconcentrationinSBRvariedfrom6.6to10g/landinMBRfrom7.3to9.3g/linnormalconditions.InSBR,suspendedsolidsconcentrationineffluentwasupto89%smallerthaninfluentsuspendedsolidsconcentration.However,sometimesbulkingreducedtheefficiency.ThepreliminaryresultswithMBRstart-upshowedthatitisfreefrombulkingproblemsandcomparedtofeedconcentrationtheretentionwasover99%ofsuspendedsolids.ItalsoincreasedtheretentionsofbothBOD7andammoniumnitrogento97%andreducedvariations.Phosphorusretentionwas88%.Keywords:Landfillleachate;Membranebioreactor;Sequencingbatchreactor;Nitrification1.IntroductionInmodernwastetreatment,thequalitiesofwastewaters,spillwaters,andleachates,producedindifferentpartsofwastetreatmentprocessvaryconsiderablywithwastequalities.Thepossibletreatmentmethodstobeconsideredare:treatmentwithmunicipalwastewaterandseparatetreatmentofallorsomeofthewastewaterfractions[1].Sofar,mostFinnishlandfillsdonottreattheirwaste-watersseparatelybutconductthemintoamuni-cipalwastewatertreatmentplant.Ifthetreatmentplantissmall,e.g.thehighnitrogencontentofdoi:10.1016/j.desal.2005.08.012N.Laitinenetal./Desalination191(2006)86–9187thelandfillwastewatersmaycausesomeopera-tionalproblems.Moreover,thenationalbiowastestrategyasksfordecreasingtheamountoforganicwastetolandfillssothattheamountofbiode-gradablematerialtolandfillswillbein200675%orlessoftheamountin1994,in200950%orlessandin201635%orless[2].Thusincreasingamountsoforganicwastearetreatedseparatelyindigestersorincompostingplants.AccordingtoKettunenetal.[3]thewastewatersoriginatingfromtheorganicwastetreatmenthashighestorganicmatterandnitrogenconcentrations.Theintensifiedtreatmentincompostingplantswithinternalwaterrecyclingleadtowastewatersmuchstrongerthanthoseoriginatingfromopencom-postingfieldsandthustheseparatetreatmentofthesewastewatersfororganicmatterandnitrogenremovalisreasonable.Inthisstudysequencingbatchreactor(SBR)andadual-tankmembranebioreactor(MBR)processeswerestudiedforthetreatmentoflandfillleachatefromacompostingfield.TheSBRtechnologyisanactivatedsludgeprocessdesignedtooperateundernon-steadystateflowconditionsandthereisadegreeofflexibilityassociatedwithworkinginatimeratherthaninaspacesequence[4].Accordingtoliterature[5],membranebio-reactoroffersatreatmentmethodforachievementofhighqualitytreatedwaterwithreducedsludgeproduction.TheSBRsystemseemssuitablefortreatingtheleachatefrombiologicalwastetreatmentinwhichthevolumesandconcentrationsoftheproducedwatercanvaryconsiderablywithtime.Previously,theSBRhasbeensuccessfullyappliedforthetreatmentofconcentratedwaste-watersfrommilkfarms[6].Moreover,theprocesscanbemodifiedsothatbothnitrificationandde-nitrificationcanbeachievedinthesameunit.However,inSBRprocessthesludgemustsettleandincaseofdisturbancessludgebulkingcanreducethequalityofproducedwater.Withmem-brane,bulkingisnoproblemandthequalityofproducedwaterismuchmorestable.Thetreat-mentoflandfillleachateswithMBRhasbeenmentionedtobeespeciallypromisingfieldforMBRsinEuropewithexistingreferenceplantsinGermany,France,andHolland[7].Witgensetal.[8,9]havestudiedtheuseofmembranebio-reactorsfortheremovalofendocrinedisruptersfromlandfillleachate.Ahnetal.[10]havepre-sentedacasestudyofanadvancedlandfillleachatetreatmentprocessusingmembranebio-reactorandreverseosmosisforagedlandfill,inwhichleachatethecarbontonitrogenratiowasunbalancedforproperbiologicaloperation.SetiadiandFairus[11]usedanactivatedsludge-membranesystem,inwhichthemembraneunitplacedoutsidetheactivatedsludgetank,forthetreatmentofhazardouswastelandfillleachate.2.ExperimentalThemunicipalwastelandfillleachate(Table1)fromanopenditchnexttocompostingfieldwastreatedinasequencingbatchreactor(SBR)andinadual-tankmembranebioreactor(MBR)fedbatchwise.Asimplifiedflowsheetoftheequip-mentusedispresentedinFig.1.TheSBRwasoperatedinnitrification/denitrificationtank,thetotaloperationalvolumeofwhichwasapproxi-mately165l.WhenoperatedasSBRthefollowingstepsweredoneina24-hcycle:feeding,reaction,Table1AveragequalityofcompostingfieldleachateusedasfeedParameterLeachatepH7.2±0.2Conductivity,mS/m450±130Suspendedsolids,mg/l480±260BOD7,mg/l1300±300CODCr,mg/l2200±230T