MBBR模拟

Vol.:(0123456789)13BioprocessandBiosystemsEngineering(2018)41:1573–1587 dynamicsimulationof a two-stagepre-denitrificationMBBRsystemunder increasingorganicloadingratesHudson B. Carminati1 ·Paula S. Lima1 ·Argimiro R. Secchi1 ·João P. Bassin1Received:25April2018/Accepted:9July2018/Publishedonline:24July2018©Springer-VerlagGmbHGermany,partofSpringerNature2018AbstractBiofilm-basedwastewatertreatmentsystemshavebecomeattractiveduetotheirnumerousadvantageswhencomparedtoothersuspendedgrowthprocesses.However,themathematicalmodelingofthesereactorsisrelativelycomplex,sinceithastoconsiderawiderangeofphenomenatoaccuratelydescribetheprocessbehavior.Thisworkdealswiththemodelingofatwo-stageMBBRsystemruninpre-denitrificationmodefortheremovaloforganicmatterandnitrogenfromwastewater.Themodeldevelopmenttookintoaccountdiffusivephenomenaandkineticsinahomogeneousbiofilmcomposedofdifferentbacterialfunctionalgroups(namelyheterotrophsandnitrifiers).Thethicknessofthebiofilmwastreatedasavariable,giventhatdetachmentofadheredbiomasstookplace.Thesuspendedbiomassfractionwasalsoconsideredtoremovethepollut-antsbymeansofMonod-typekineticsassociatedwiththeactivatedsludgemodel.Thedynamicbehaviorofthecomponentsinvolvedinthesystemandtheirspatialdistributioninthebiofilmobtainedfromsimulateddatashowedgoodagreementwiththosereportedintheliterature,demonstratingthereproducibilityofthemodelandencouragingfutureapplicationsinfull-scaleMBBRplants.KeywordsMoving-bedbiofilmreactor ·Biofilm ·Nitrogenremoval ·DynamicsimulationAbbreviationListofsymbolsABiofilmsurfacearea(L2)bDecayrate(T−1)SSolublesubstrateconcentration(M L−3)CmSaturatingconcentrationofoxygenintheliquidphase(M L−3)DDiffusioncoefficient(L2 T−1)fBiomassfractioninthebiofilmfpFractionoftheinertbiomassintheinactiveportionofthebiofilmixbN/CODmassratiokExternalmasstransfercoefficient(L2 T−1)KHalf-saturationcoefficient(M L−3)kLaOxygenmasstransfercoefficient(T−1)LBiofilmthickness(L)mMassofbiomass(M)MMiMolecularweight(M N−1)PPressure(M L−1 T−2)QFlowrate(L3 T−1)rConversionrate(M L−3 T−1)RUniversalconstantofgases(M L2 T−2 Θ−1 N−1)tTime(T)TTemperature(θ)VReactorvolume(L3)XBiomassconcentration(M L−3)xMolarfractionYYieldcoefficientzSpatialvariableinthebiofilm(L)δBoundarylayerthickness(L)λShearlossrate(T−1)μMaximumspecificrate(T−1)νStoichiometriccoefficientρMBiofilmmeandensity(M L−3)ρProcessrate(M L−3)Subscripts1Anoxicreactor2AerobicreactoraAnoxicprocessfAnaerobicprocesshHydrolysisprocess*Joã[e-mail];[e-mail]1ChemicalEngineeringProgram,COPPE,UniversidadeFederaldo RiodeJaneiro,P.O.Box 68502,Rio de Janeiro 21941-972,Brazil1574BioprocessandBiosystemsEngineering(2018)41:1573–158713oAerobicprocessAAutotrophicbiomassHHeterotrophicbiomassIInertbiomassNHAmmoniaNONitratenitrogenO2OxygenSReadilyorslowlybiodegradablesubstrateairFeedairinInfluentstreameqEquilibriumconditioniComponent(solubleorbiomass)jProcessSuperscriptsBBiofilmphaseGGasphaseIInterfacebiofilm-bulkLBulkphaseIntroductionAmongtheprioritypollutantstoberemovedfromwaste-watersareorganicmatterandnutrients(e.g.,nitrogenandphosphorus),astheycausestrongimpactsonreceivingwaterbodiessuchasexcessiveoxygenconsumptionandeutrophication[1,2].Thewastewatertreatmentprocesseshaveundergoneconstantimprovementstomeettheincreas-inglystringenteffluentdischargelimitsimposedbyenviron-mentallegislations[3].Basedonattachedbiomassgrowth,biofilmreactorshaveattractedmuchattentionoverthelastyearsinthewastewatertreatmentsector.Oneofthegrowingbiofilmtechnologyisthemoving-bedbiofilmreactor(MBBR)[4,5],whichreliesontheuseofsmallandfreelymovingcarriermediathatsupportbacterialgrowth.Givenitshighflexibility,thisprocesscanbeeas-ilyimplementedinexistingtreatmentplants.Usually,thehighestfractionofbiomassinMBBRsystemsisattachedtothecarriers,butsuspendedsolidscanbepresentundersomeoperatingconditions(e.g.,highorganicloadingrate),evenatlowhydraulicretentiontimes(HRT)[6–8].Forchemicaloxygendemand(COD)removal,severalaerobicMBBRtankscanbeoperatedinseries,dependingontheappliedorganicload.Whennitrogenremovalisrequired,atwo-ormulti-stagereactorconfigurationisoftenusedbycombininganoxicandaerobictanks.Oneexampleisthepre-denitrificationdesign,inwhichaninternalrecirculationofthemixedliquorfromtheaerobictotheanoxictankiscarriedout[9,10].AlthoughthebiofilmsystemssuchastheMBBRarereportedtooperatestablywithsatisfactoryperformance[7,8],thepredictionofthebehaviorofwastewatertreatmentplantsunderdifferentoperatingconditionsisnotstraight-forward.Inaddition,theimplementationofnewwastewatertreatmentplantsortheimprovementoftheexistingonesarealwayschallenging.Forthesepurposes,modelingandsimu-lationofthetreatmentfacilityareusuallyperformed[11,12].However,themodelingofMBBRsystemsisquitecom-plex,sinceitmustadmittheexistenceofdifferentphases(solid,gas,andliquid)withinthereactor,differentzones(aerobic,anoxic,andanaerobic)withinthebiofilm,vari-ationsinthebiofilmthickness,distinctmicrobialkinetics,amongseveralotheraspects[13,14].Itisimpor