SBR法处理垃圾渗滤液的反硝化过程中NO2积累的研究英文孙洪伟

BIOTECHNOLOGYANDBIOENGINEERINGChineseJournalofChemicalEngineering,17(6)1027—1031(2009)NitriteAccumulationduringtheDenitrificationProcessinSBRfortheTreatmentofPre-treatedLandfillLeachate*SUNHongwei(孙洪伟),YANGQing(杨庆),PENGYongzhen(彭永臻)**,SHIXiaoning(时晓宁),WANGShuying(王淑莹)andZHANGShujun(张树军)KeyLaboratoryofBeijingWaterQualityScienceandWaterEnvironmentRecoveryEngineering,BeijingUniver-sityofTechnology,Beijing100124,ChinaAbstractThenitriteaccumulationinthedenitrificationprocessisinvestigatedwithsequencingbatchreactor(SBR)treatingpre-treatedlandfillleachateinanoxic/anaerobicup-flowanaerobicsludgebed(UASB).Nitriteac-cumulatesobviouslyatdifferentinitialnitrateconcentrations(64.9,54.8,49.3and29.5mg·L－1)andlowtempera-tures,andthetwobreakpointsontheoxidation-reductionpotential(ORP)profileindicatethecompletionofnitrateandnitritereduction.Usually,thenitratereductionrateisusedasthesoleparametertocharacterizethedenitrifica-tionrate,andnitriteisnotevenmeasured.Foraccuracy,thetotaloxidizednitrogen(nitrate+nitrite)isusedasameasure,thoughdetailscharacterizingtheprocessmaybeoverlooked.Additionally,batchtestsareconductedtoinvestigatetheeffectsofC/Nratiosandtypesofcarbonsourcesonthenitriteaccumulationduringthedenitrifica-tion.Itisobservedthatcarbonsourceissufficientforthereductionofnitratetonitrite,butforfurtherreductionofnitritetonitrogengas,isdeficientwhenC/Nisbelowthetheoreticalcriticallevelof3.75basedonthestoichiome-tryofdenitrification.Fivecarbonsourcesusedinthiswork,exceptforglucose,maycausethenitriteaccumulation.Fromexperimentalresultsandcitedliterature,itisconcludedthatAlcaligenespeciesmaybecontainedintheSBRactivated-sludgesystem.Keywordslandfillleachate,nitriteaccumulation,denitrification,C/Nratio,carbonsource,sequencingbatchreactor1INTRODUCTIONConventionalbiologicaldenitrificationinvolvesaseriesofbiologicalreductionprocesses,giveninEq.(1).Inthisprocess,nitrateisconvertedtonitrogengasbynitratereductase(NaR),nitritereductase(NiR),nitricoxidereductase(NoR),andnitrousoxidereduc-tase(N2oR),correspondingly[1].3NO−NNaR⎯⎯⎯→2NO−NNiR⎯⎯⎯→NONoR⎯⎯⎯→N2O2NoR⎯⎯⎯→N2(1)Nitriteisoneoftheintermediatesofnitratere-ductionprocess.Itisgenerallyconsideredthatreduc-tionrateofnitriteishigherenoughthanthatofnitrate,sothatnitriteaccumulationwillnotoccurduringthedenitrificationprocess[2].However,nitriteaccumula-tionindenitrificationisfrequentlyobserved[3-9],probablyduetothelowerreductionrateofnitritewithrespecttothatofnitrate.Nitriteaccumulationiscausedbymicrobialcommunitieswithdifferentchar-acteristicsfornitrateandnitritereduction.Somedeni-trifierswithdifferentdenitrificationabilityaresum-marizedinTable1.Thepreviousstudiesonnitriteaccumulationindenitrificationhavesomeshortcomings.First,nitriteaccumulationismainlyobservedinthetreatmentofmunicipalwastewater,nitrogenfertilizerindustry,andsimulatedwastewater,butithasnotbeenreportedonhighstrengthlandfillleachate.Second,theinforma-tionondenitrificationkineticsisnotprovide.Finally,thereisnotaccurateandsimplemethodtoindicatethecompletionofdenitrificationtoavoidthedischargeofReceived2009-01-15,accepted2009-06-06.*SupportedbytheNationalNaturalScienceFoundationofChina(50978003),theNaturalScienceFoundationofBeijing(8091001),theFundingProjectforAcademicHumanResourcesDevelopmentinInstitutionsofHigherLearningUndertheJurisdictionofBeijingMunicipality(PHR20090502),andtheStateKeyLaboratoryofUrbanWaterResourceandEnviron-ment(HIT)(QAK200802).**Towhomcorrespondenceshouldbeaddressed.E-mail:[e-mail];[e-mail]1SummaryofcharacteristicsofdenitrifiersfornitrateandnitritereductionSpeciesDenitrificationcharacteristicofbacteriaReductionratescomparisonPflavobacteriumsp①nitratereduction,nitritereduction,nonitriteaccumulation32Red,NO-NRed,NO-NrrPfluorescens①nitratereduction,nitritereduction,nitriteaccumulation32Red,NO-NRed,NO-NrrAlcaligene②nitratereduction,nitriteaccumulation,nitriteastheonlyfinalproduct-AcinetobcterPseudomonas②nitratereduction,nitritereduction,nonitriteaccumulation,forcoexistingnitrateandnitritepreferentialreductionofnitrite32Red,NO-NRed,NO-NrrAlcaligenesnitratereduction,nitritereduction,nitriteaccumulationwithglucose32Red,NO-NRed,NO-Nrr①Ref.[5];②Ref.[9].Chin.J.Chem.Eng.,Vol.17,No.6,December20091028moreharmfulnitriteintothereceivingwaterbody.Therefore,theobjectivesofthisworkareasfollows.(1)Toinvestigatenitriteaccumulationduringdenitri-ficationatdifferentinitialnitrateconcentrationsandlowtemperatures,(2)toperfectdenitrificationkineticswiththetotaloxidizednitrogen(nitrate+nitrite),(3)todevelopanaccurateandsimplemethodtoindicatethecompletereductionofnitrateandnitritebyusingORPasprocesscontrolparameter,and(4)toinvesti-gatetheeffectsofvariouscarbonsourcesandC/Nratiosonthenitriteaccumulationindenitrification.2MATERIALSANDMETHODS2.1LandfillleachateTheleachateusedwassampledeverymonthfromBeijingLiulitunMunicipalSolidWaste(MSW)SanitaryLandfill.Itwaspre-treatedbyananoxic/anaerobicup-flowanaerobicsludgebed(UASB)forremovinghighconcentratedorganics.TheeffluentoftheUASBreactorwasusedastheinfluentofthe