EffectsofaNitrification/DenitrificationInhibitionCompoundonBiologicalWastewaterTreatment

MatthewPreisser1,KateNewhart2,andTzahiCath21AuburnUniversity,2ColoradoSchoolofMines

Introduction Distributedwastewatertreatmenthasthepotentialtocutenergycostsandconservewaterbyreusingtreatedwaterclosertothepointofgeneration.Sincedistributedwatertreatmentplantstraditionallyhavesmallercapacitythantheircentralizedcounterparts,pollutantscanhaveagreatereffectoneffluentquality.Thisworkexaminestheeffectsofaknownnitrificationanddenitrificationinhibitoronwatertreatment:sodiumazide.Inbiologicalwastewatertreatment,nitrificationanddenitrificationarenecessaryprocessestoconvertammoniainrawwastewaterintobioavailablenitrateandsubsequentlynitrogengasforcompletenitrogenremoval.Theremovalofnitrogenfromwastewaterisimportanttopreventdamagetoreceivingecosystems,andcrucialinthecaseofwaterreusetoprotectthehealthofconsumers.ExperimentalOverview Sodiumazide(NaAz)hasbeenstudiedasanitrification-inhibitor,inparticularabacteriostatic3herbicide1,2.Ifusedtotreatlargeswathsofcrops,distributedwastewatertreatmenthasthepotentialtotreattheagriculturalrunoff.Understandingtheeffectsofherbicidesonbiologicalwastewatertreatmentisnecessarytopreventaninterruptionineffluentquality.Fortheseexperiments,apuresolutionofNaAzwasusedtoinduceabiologicalperturbationinabatch,activatedsludgesystem.

Abenchscalejartestwith2Lreactorswereinitiallydosedwithreturnactivatedsludgefromademonstration-scalesequencing-batchmembranebioreactor(SB-MBR).After20minutesofsettling,effluentwaterqualitywasmeasuredusingvariousHach‘Test-N-Tube’tests(HachCompany,Loveland,CO),includingnitrate,totalnitrogen,ammonia,andchemicaloxygendemand(COD).Totalsuspendedsolidsoftheactivatedsludgeandconductivity,pH,andalkalinityoftheeffluentwerealsomeasured.Inthebenchscaletests,thehydraulicresidencetimewaskeptat24hoursbyremoving1Lofeffluentsupernatantwateranddosingwith1Lofraw,municipalwastewaterevery12hours.Threemainexperimentsweredevelopedandexecutedforthisproject,andaredescribedbelow.PulseDisturbance–Thefirstexperimentwasconductedasabenchscalejartest,wherevaryingconcentrationsofNaAz(0,0.1,1,10,100,1000ppm)weredosedasingletimeinsix2Ljars/bioreactors.Thisexperimentcanbeusedtorepresentasingledisturbance,suchasfromastormrunoffevent.PressDisturbance–Thesecondexperimentconductedmanipulatedthesamebenchscalejartest,whereNaAzwasdosedoverthecourseof72hours.Thisexperimentcanbeusedtorepresentacontinualdosingofanherbicideupstreamofawastewatertreatmentfacility.

SensorNetworkTest–Ammoniumandnitrateprobesweretestedinoneofthe2Lbioreactorsduringapulsedisturbancetotestitsfunctionality.ResultsExperiment1:PulseDisturbance ApulseinputofNaAzresultedinnearcompleteinhibitionofnitrificationatconcentrationsabove100ppm.Dosingofthesystemoccurredinthemorningof6/15.Thisisshownintheincreasedammonialevels(Figure1)anddecreasednitratelevels(Figure2).Qualitatively,athigherconcentrationsthesettleabilityofbioreactorsdecreasedwithincreasedconcentration(Figure3.)

Figure1:AmmoniaconcentrationsofeffluentwaterduringapulsedisturbanceofNaAz

Figure2:NitrateconcentrationsofeffluentwaterduringapulsedisturbanceofNaAz

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Figure3:Qualitativedifferencesinsettleabilityofbioreactorsdosedduringapulsedisturbanceat0and1000ppmExperiment2:PressDisturbance Bioreactorsweredosedoverthecourseof72hourswithNaAzinconcentrationsrangingfrom0to100ppm.TotalsuspendedsolidsorTSS(Figure4)decreasedovertimeduringthedosingperiodforbioreactorsdosedabove50ppm,whichcorrelateswithadecreaseinmicrobialactivity.

Figure4:GraphoftotalsuspendedsolidsorTSS(mg/L)duringapulsedisturbancewherebioreactorsweredosedfor72hourswithNaAz

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Experiment3:SensorNetwork Nitrateandammoniumprobes(VernierTechnologyandSoftware,Beaverton,Oregon)wereplacedina2Lbioreactorthatunderwentapulsedisturbanceat75ppm.DatawascollectedeverysecondovermultipledaysusinganArduinomicroprocessor.Abuildupofabiofilmandformationofairbubblesunderthemembranesoftheprobesshowedthatsensorsinanactivatedsludgesystemmustbemaintainedproperlytoensureaccuratereadingsovertime.Conclusions

• NaAzcompletelyinhibitsnitrificationatconcentrationsabove100ppm,inbothapulseandpressdisturbance

• NaAzandotherrelatedagriculturalproductshavethepotentialtoseriouslyharmthemicrobialecologyofbiologicalwastewatertreatmentsystems

• Sensornetworksinactivatedsludgesystemswillneedmorebenchscaletestingtodetermineamaintenance/calibrationscheduleinordertoimproveperformance

• COD,pH,alkalinity,andconductivityarenotasbeneficialtodetectperturbationeventsbecauseoftheirabilitytorecovertosteadystatevalues,comparedtonitrateandammoniumlevelswhicharemorepermanentlychanged

FutureWork

• Applyinganinhibitioncompoundtothepilotscalesequencingbatchmembranebioreactor(SB-MBR)locatedatMinesPark

• Examiningtheeffectsofacommercialgradeherbicide/fertilizerasanitrificationinhibitortounderstandtheeffectofamorecomplexmatrix

• Furtherdevelopmentandimplementationofthefaultdetectionprogramandsensornetwork

References1Tu,A.,Kim,M.,andKim,DJ.(2013).SelectiveinhibitionofammoniaoxidationandnitriteoxidationlinkedtoN2Oemissionwithactivatedsludgeandenrichednitrifiers.JournalofMicrobiologyBiotechnology23(5):719-723.2Chefetz,B.,Stimler,K.,ShechterM.,andDrori,Y.(2006).Interactionsofsodiumazidewithtriazineherbicides:Effectonsorptiontosoils.Chemosphere65(2):352-357.3Lichstein,H.C.;Soule,M.H.(1943).StudiesoftheEffectofSodiumAzideonMicrobicGrowthandRespiration:I.TheActionofSodiumAzideonMicrobicGrowth.JournalofBacteriology.47(3):221–230.