EPA Method 304B

2028METHOD304B:DETERMINATIONOFBIODEGRADATIONRATESOFORGANICCOMPOUNDS(SCRUBBEROPTION)1.0ScopeandApplication.1.1Applicability.Thismethodisapplicableforthedeterminationofbiodegradationratesoforganiccompoundsinanactivatedsludgeprocess.Thetestmethodisdesignedtoevaluatetheabilityofanaerobicbiologicalreactionsystemtodegradeordestroyspecificcomponentsinwastestreams.Themethodmayalsobeusedtodeterminetheeffectsofchangesinwastewatercompositiononoperation.Thebiodegradationratesdeterminedbyutilizingthismethodarenotrepresentativeofafull-scalesystem.Full-scalesystemsembodybiodegradationandairemissionsincompetingreactions.Thismethodmeasuresbiodegradationinabsenceofairemissions.TheratesmeasuredbythismethodshallbeusedinconjunctionwiththeprocedureslistedinappendixCofthisparttocalculatethefractionemittedtotheairversusthefractionbiodegraded.2.0SummaryofMethod.2.1Aself-containedbenchtopbioreactorsystemisassembledinthelaboratory.Asampleofmixedliquorisaddedandthewastestreamisthenfedcontinuously.Thebenchtopbioreactorisoperatedunderconditionsnearlyidenticaltothetargetfull-scaleactivatedsludgeprocess,exceptthatairemissionsarenotafactor.Thebenchtop2029bioreactortemperature,dissolvedoxygenconcentration,averageresidencetimeinthereactor,wastecomposition,biomassconcentration,andbiomasscompositionofthetargetfull-scaleprocessaretheparameterswhichareduplicatedinthelaboratorysystem.Biomassshallberemovedfromthetargetfull-scaleactivatedsludgeunitandheldfornomorethan4hourspriortouseinthebenchtopbioreactor.Ifantifoamingagentsareusedinthefull-scalesystem,theyshallalsobeusedinthebenchtopbioreactor.Thefeedflowingintoandtheeffluentexitingthebenchtopbioreactorareanalyzedtodeterminethebiodegradationratesofthetargetcompounds.Thechoiceofanalyticalmethodologyformeasuringthecompoundsofinterestattheinletandoutlettothebenchtopbioreactorarelefttothediscretionofthesource,exceptwherevalidatedmethodsareavailable.3.0Definitions.[Reserved]4.0Interferences.[Reserved]5.0Safety.5.1Ifexplosivegasesareproducedasabyproductofbiodegradationandcouldrealisticallyposeahazard,closelymonitorheadspaceconcentrationofthesegasestoensurelaboratorysafety.Placementofthebenchtop2030bioreactorsysteminsidealaboratoryhoodisrecommendedregardlessofbyproductsproduced.6.0EquipmentandSupplies.NOTE:Figure304B-1illustratesatypicallaboratoryapparatususedtomeasurebiodegradationrates.WhilethefollowingdescriptionreferstoFigure304B-1,theEPArecognizesthatalternativereactorconfigurations,suchasalternativereactorshapesandlocationsofprobesandthefeedinlet,willalsomeettheintentofthismethod.Ensurethatthebenchtopbioreactorsystemisself-containedandisolatedfromtheatmospherebyleak-checkingfittings,tubing,etc.6.1BenchtopBioreactor.Thebiologicalreactionisconductedinabiologicaloxidationreactorofatleast6-literscapacity.Thebenchtopbioreactorissealedandequippedwithinternalprobesforcontrollingandmonitoringdissolvedoxygenandinternaltemperature.Thetopofthebenchtopbioreactorisequippedforaerators,gasflowports,andinstrumentation(whileensuringthatnoleakstotheatmosphereexistaroundthefittings).6.2Aerationgas.Aerationgasisaddedtothebenchtopbioreactorthroughthreediffusers,whichareglasstubesthatextendtothebottomfifthofthereactordepth.Apureoxygenpressurizedcylinderisrecommendedinorder2031tomaintainthespecifiedoxygenconcentration.Installablower(e.g.,DiaphragmType,15SCFHcapacity)toblowtheaerationgasintothebenchtopbioreactordiffusers.Measuretheaerationgasflowratewitharotameter(e.g.,0-15SCFHrecommended).Theaerationgaswillrisethroughthebenchtopbioreactor,dissolvingoxygenintothemixtureintheprocess.Theaerationgasmustprovidesufficientagitationtokeepthesolidsinsuspension.Provideanexitfortheaerationgasfromthetopflangeofthebenchtopbioreactorthroughawater-cooled(e.g.,Allihn-type)verticalcondenser.Installthecondenserthroughagas-tightfittinginthebenchtopbioreactorclosure.Designthesystemsothatatleast10percentofthegasflowsthroughanalkalinescrubbercontaining175mLof45percentbyweightsolutionofpotassiumhydroxide(KOH)and5dropsof0.2percentalizarinyellowdye.Routethebalanceofthegasthroughanadjustablescrubberbypass.Routeallofthegasthrougha1-Lknock-outflasktoremoveentrainedmoistureandthentotheintakeoftheblower.Theblowerrecirculatesthegastothebenchtopbioreactor.6.3WastewaterFeed.Supplythewastewaterfeedtothebenchtopbioreactorinacollapsiblelow-densitypolyethylenecontainerorcollapsiblelinerinacontainer(e.g.,20L)equippedwithaspigotcap(collapsiblecontainersorlinersofothermaterialmayberequireddue2032tothepermeabilityofsomevolatilecompoundsthroughpolyethylene).Obtainthewastewaterfeedbysamplingthewastewaterfeedinthetargetprocess.Arepresentativesampleofwastewatershallbeobtainedfromthepipingleadingtotheaerationtank.Thissamplemaybeobtainedfromexistingsamplingvalvesatthedischargeofthewastewaterfeedpump,orcollectedfromapipedischargingtotheaerationtank,orbypumpingfromawell-mixedequalizationtankupstreamfromtheaerationtank.Alternatively,wastewatercanbepumpedcontinuouslytothelaboratoryapparatusfromableedstreamtakenfromtheequalizationtankofthefull-scaletreatmentsystem.6.3.1R