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1、BioproccssBiosystEng25(2002)103-109DOI10.1007s00449002-0286-9AerobictreatmentofdairywastewaterwithsequencingbatchreactorsystemsXiujinLi,RuihongZhangAbstractPerformancesofsingle-stageandtwo-stagesequencingbatchreactor(SBR)systemswereinvestigatedfortreatingdairyWaSteWater.Asingle-stageSBRsystemwastest
2、edwith10,000mg/1chemicaloxygendemand(COD)influentatthreehydraulicretentiontimes(HRTs)of1,2,and3daysand20,000mg/1CODinfluentatfourHRTsof1,2,3,and4days.A1-dayHRTwasfoundsufficientfortreating10,000-mg/1CODwastewater,withtheremovalefficiencyof80.2%COD,63.4%totalsolids,66.2%volatilesolids,75%totalKjeldah
3、lnitrogen,and38.3%totalnitrogenfromtheliquideffluent.Two-dayHRTwasbelievedsufficientfortreating20,000-mg/1CODdairywastewaterifcompleteammoniaoxidationisnotdesired.However,4-dayHRTneedstobeusedforachievingcompleteammoniaoxidation.Atwo-stagesystemconsistingofanSBRandacomplete-mixbiofilmreactorwascapab
4、leofachievingcompleteammoniaoxidationandcomparablecarbon,solids,andnitrogenremovalwhileusingatleast1/3lessHRTascomparedtothesingleSBRsystem.KeywordsAerobic,dairy,wastewater,sequencingbatchreactorIntroductionDairywastewateriscurrentlydisposedofmainlythroughlandapplicationwithlittleornopretreatmentinC
5、aliforniaintheUnitedStates.Duetoincreasingawarenessofthegeneralpublicaboutpotentialadverseimpactofanimalwastesonenvironmentalqualityandrecentdevelop-Received:2October2001/Accepted：6February2002Publishedonline：5April2002Springer-Verlag2002XLi()DepartmentofEnvironmentalEngineering,BeijingUniversityofC
6、hemicalTechnology,I00029fBeijing,ChinaE-mail：bdujinTelu+86-010-64427356Fax：+86-010-644%781R.ZhangBiologicalandAgriculturalEngineeringDepartment,UniversityofCaliforniaatDavis,CA95616,USAThisresearchwassupportedinpartbytheCaliforniaEnerg),CommissionandtheAgriculturalExperimentStationoftheUniversityofC
7、alifornia,Davis,USA.10：mentsinenvironmentalregulationsforgaseous-emissioncontrolandnutrientmanagement,alternativewastewatertreatmentmethodsbecomeattractiveoptionsfordairyproducers.Asequencingbatchreactor(SBR)isabiologicaltreatmentreactorthatusesaerobicbacteriatodegradeorganiccarbonandremovenitrogenp
8、resentinthewastewater.Ifdesignedandoperatedproperly,itmaybecomeapromisingalternativefortreatinganimalwastewatertocontrolOdorSandreducesolidsandnutrientcontents.TheSBRtreatswastewaterinsmallbatchesandfitswellwithmostanimalwastewatercollectionsystems.Itisatime-orientedsystemandoperatesoverrepeatedcycl
9、esoffivephases-fill,react,settle,decant,andidle.ThemajorfactorsthatcontroltheperformanceofSBRsincludeorganicloadingrate,hydraulicretentiontime(HRT),solidsretentiontime(SRT),dissolvedoxygen(DO),andinfluentcharacteristicssuchaschemicaloxygendemand(COD),solidscontent,andcarbon-to-nitrogenratio(CN),etc.
10、DependingonhowtheseparametersarecontroDed,theSBRcanbedesignedtohaveoneormoreofthesefunctions:carbonoxidation,nitrification,anddenitrification1,2.Carbonoxidationanddenitrificationarecarriedoutbyheterotrophicbacteriaandnitrificationisbyautotrophicbacteria.TheSBRhasbeensuccessfullyusedinthetreatmentofm
11、unicipalandindustrialwastewater,wherethehightreatmentperformanceresultedinexcellenteffluentquality3,4.Itisconsideredtobeasuitablesystemforwastewatertreatmentapplicationsinsmallcommunities5.TheSBRisarelativelynewtechnologyforagriculturalapplications.PreviousresearchontheSBRforanimalwasteWaSprimarilyc
12、oncentratedonswinewastewatertreatment.Severalresearchers6,7,8reportedtheperformanceofSBRintreatingswinewastewaterwithCODandsuspendedsolids(SS)intherangeof1,614-2,826mg/1and175-3,824mg/1,respectively.SatisfactoryremovalofCODandSSfromthewastewaterwasachievedwithHRTsof22-30h.Fernadesetal.9studiedtheSBR
13、fortreatinghighlyconcentratedswinemanurewithabout4%totalsolids(TS).TheinfluentCOD,NH3-N,andtotalKjeldahlnitrogen(TKN)wereashighas31,175mg/1,1,265mg/1,and2,580mg/1,respectively.Theirresultsindicatedthatabove97%COD,99%NH3-N,and93%TKNremovalefficiencieswereachievedintheliquideffluentatHRTsof6and9daysan
14、dSRTofover20days.Tametal.10researchedSBRfortreatmentofwastewaterfromamilkingcenterandreportedthatthewastewaterwith919-1,330mg/1CODand15-37mg/1NH3-NcouldbesuccessfullytreatedwithaHRTof20h.StudiesontheSBRfortreatingdairymanurearcnotwelldocumentedintheliterature.PreviousresearchfindingsabouttheSBRfortr
15、eatmentofswinemanureandothertypesofwastewaterprovidevaluablereferencesforthetreatmentofdairywastewater.However,duetothedifferencesinthecharacteristicsofdairywastewaterfromothertypesofwastewater,researchisneededtodevelopdesignandoperationalguidelinesfortheSBRintreatingdairywastewaterofvariouscharacte
16、ristics.TheobjectivesofthisstudyarctoinvestigatetheeffectsofwastewaterCharaCteriStics,HRT,SRT,andorganicloadingrateontheperformanceoftheSBRsystemintreatingdairywastewaterforcarbonandsolidsremovalandnitrogenconversion,anddevelopdesignandoperationalguidelinesfortheSBRsysteminsingle-andmultiple-stageco
17、nfigurations.2Materialsandmethods2.1DairymanurecollectionandpreparationDairymanurewascollectedontheDairyResearchFarmOftheUniversityofCaliforniaatDavis.Duetorunoffofurineonthefeedlot,theco11ectedmanurewasmainlyfecesandcontainedarelativelylowcontentofammonianitrogen.Themanurewasslurriedwithadditionofw
18、aterandthenscreenedtwiceWithtwosieveswithopeningsof44and2x2mm,respectively,toremovelargeparticles.,hescreenedmanurewastransportedimmediatelytothelaboratoryandstoredinafreezerat-20untiluse.TheTSandCODofthescreenedmanurewere30,000-40,000mg/1and35,000-50,000mgl,respectively.Whenneeded,thestoredmanurewa
19、sthawedandthendilutedwthtapwatertoobtainadesiredCODconcentration.Duetorelativelylowammoniacontentoftherawmanureascomparedtotypicallevelsinthemanurecollectedondairyfarms,ureawasaddedtoincreasetheNH3-Ninthepreparedmanurefrom100-125mg/1to500-550mg/1.Thepreparedmanurewasthenputintoa50-1feedingtankhoused
20、inarefrigeratorat4fordailyuse.Thefeedingtankhadanagitatortomixthewastewaterduringthefeedingofthereactors.2.2ExperimentalsetupandoperationBothsingle-stageandtwo-stagetreatmentsystemsweretested.Thesingle-stageSBRsystemconsistedofanSBRandasolids-settlingtankinscries.ThewastewaterwasfirstfedintotheSBRfo
21、rtreatmentandtheeffluentoftheSBR,includingbothsludgeandliquid,wasthendischargedintoasettlingtank,whereliquidwasseparatedfromsludgebygravitysettlingandcharacterizedasliquideffluentofthesystem.Thetwo-stagesystemconsistedofanSBR(first-stagereactor),aSOIidS-Settlingtank,andacomplete-mixbiofilmreactor(CM
22、BR)(second-stagereactor)connectedinseries.Theliquideffluentobtainedfromthesolids-settlingtankwasusedasinfluentofCMBRandfurthertreatedintheCMBRforachievingcompletenitrification.Thetwo-stageSBR-CMBRsystemisshowninFig.1.Eachsystemwasfedanddecantedtwiceadayfor12hineachtreatmentcycle.Alltheperistalticpum
23、psusedforfeedinganddecantingwereoperatedautomaticallyWithadigitaltimecontroller.ThetimesequencefordifferentoperationsduringeachtreatmentcycleoftheSBRwas13minfill,11hand4-8minreact,40minsettle,1-3mindecant,and10minidle.TheCMBRwasoperatedasacomplete-mixreactorandhadlongSRTprovidedbytheattachedgrowthon
24、thepolyethylenepelletsplacedinthereactor.Theplasticpelletshadlightdensity(920kgm3)andwerekeptfluidizedwiththeairflow.EachpelletWaS10mmindiameterand10mminheight,withacrossinsidethecylinderandlongitudinal6nsontheoutside,providingalargesurfaceareaforbacterialattachment.Thefillingvolumeofthepelletsintot
25、aloccupiedapproximately18%ofliquidvolume(31)inthereactor.TheSBRandCMBRreactorsweremadefromtransparentacrylicandhadatotalvolumeof61each,with51cmheightand12cmdiameter.Duringtesting,theliquidvolumeofeachreactorwas31.Eachreactorwasaeratedusingpressurizedairatacontrolledflowrate.Inordertominimizethewater
26、evaporationinthereactor,theairwashumidifiedbytravelingthroughwaterntainedina15-1jarpriortoenteringthereactor.TheairWaSevenlydistributedintothewastewaterthroughfourairstonediffusersinstallednearthebottomofthereactor.AllthereactorswereinitiallyseededwiththeactivatedsludgeobtainedfromtheUCDavisWastewat
27、erTreatmentPlantandallowedtoacclimateforabout2monthsbeforeformalexperimentswerestarted.Itnormallytookabout4weeksforeachSBRreactortoreachasteadystatewhenanewoperatingconditionwasintroduced.ThesteadystatewasdefinedtobeastatewhentheweeklyvariationsofeffluentCOD,TS,NH3-N,andpHwerelessthan5%.TheSeparamet
28、ersweremonitoredtwiceaweek.TheCMBRhadbeenfullyacclimatedwithdilutedairywastewaterforabout6monthsandhadnitrificationbacteriawellestablishedbeforebeingconnectedwiththeSBR.Themixedliquorsuspendedsolids(MLSS)intheCMBRwasabout10,000mg/1,whichwascalculatedfrombothsuspendedgrowthandattachedgrowthsolids.Ino
29、rdertodeterminetheammoniaemissionfromSBRduetoaeration,ammoniaintheexitingairofSBRwascollectedbyabsorbingitin0.3Nboricacidsolutionfor24hundereachtestingcondition.2.3ExperimentalplanandsystemperformanceevaluationTheexperimentwascarriedoutintwophases.,I,hefirstphasewasforstudyingtheeffectsofinfluentcha
30、racteristics,URT,andcorrespondingSRTandloadingrateontheperformanceofthesingle-stageSBRsystem.Thesecondphasewastoevaluatetheperformanceofatwo-stageSBR-CMBRsystem.Thetwosystemswerethencomparedintermsofcarbonandsolidsremovalandnitrogenconversionefficiencies.Withthesingle-stageSBRsystem,threeHRTs(1,2and
31、3days)weretestedforWaSteWaterof10,000mg/1CODandfourHRTs(1,2,3and4days)forwastewaterof20,000mg/1COD.Forthewastewaterof10,000mg/1COD,thecorrespondingloadingrateandSRTforthethreeHRTswere10,5,and3.3gCOD/l/dayand8,12,andStage I: SBRStage II: CMBRExhaust airFeed tankDifTuscrir supphHumidifierFlUidDitTuser
32、Elow meter,Sludge efuenlSettling tankExhaustcluctFig. 1. Laboratory set for a two-stage SBR-CMBR system for dairy wastewater treatment15days,respectively.Forthewastewaterof20,000mg/】COD,thecorrespondingloadingrateandSRTforthefourHRTswere20,10,6.7,and5gCOD/l/dayand1.5,3,4,and6days,respectively.Withth
33、etwo-stageSBRsystem,2dayswasusedfirstasthesystemHRT,with1dayforthefirst-stageandIdayforthesecond-stageforbothinfluents,andthen2.5dayswasusedwith2daysforthefirststageand0.5daysforthesecondstage.Anairflowrateof41/minwasappliedforallruns,遥ichwasabletomaintaindissolvedoxygen(DO)intheSBRandCMBRabove3mgl.
34、TheperformanceofthetreatmentsystemsWa$evaluatedintermsofcarbonandsolidsremovalandnitrogenconversionefficiencies.TheparametersanalyzedincludedTS,volatilesolids(VS),COD,SCOD(solubleCOD),TKN,NH5-N,NO2-N,andNO3-N.TwokindsofretnovaJ/conversionefficiencieswereusedtointerprettheresultsforcarbonandsolidsrem
35、ovalandnitrogenoxidation.Oneefficiency,Et,isbasedontheremovalfromtotaleffluent(includingbothsludgeandliquideffluentgenerated),reflectingtheremovalefficiencythroughbiologicalprocessalone.Theotherefficiency,E,wasksedontheremovalfromliquideffluent,i.e.,supernatant,representingtheremovalefficiencythroug
36、hbothbiologicalprocessandsludgeseparation.Forthesingle-stageSBRsystem.,thetotaleffluentwastheeffluentfromtheSBRandtheliquideffluentwasthesupernatantdecantedfromthesolidssettlingtank.Forthetwo-stageSBR-CMBRsystem,thetotaleffluentwasthecombinationofsludgefromthesettlingtankandthefinaleffluentfromCMBR1
37、andtheliquideffluentwastheliquideffluentofCMBR.Mostofpreviousresearchonlyreportsremovalefficiencyfromliquideffluent（三）Actually,EIdoesnotreflecttherealcapabilityofasystem,forremovingvariousconstituentsfrom,wastewater,becausepartoftheseconstituentsarecontainedinthesludgethatisseparatedfromtheliquideff
38、luentanddischargedasaseparatesludgestream.Therefore,Etneedstobeusedinordertoassesstherealcapabilityofasystem.forremovingvariousconstituentsfrom.wastewater.2.4SamplingandanalyticalmethodsAftereachreactorreachedsteadystateundertestingconditions,samplesweretakenfromtheinfluent,mixedliquor,totaleffluent
39、,andliquideffluentofthereactorthreetimesaweek(everyotherday)foranalysesofCOD,SCOD,TS,VS,NH3-N1NO2-N1NO3-N,andTKN.Theremovalefficiencies,ElandEt,werecalculatedbasedonthedatafrominfluent,liquideffluent,andtotaleffluentofthesystems.TheseparationofsludgeandliquidinthettaeffluentoftheSBRwasperformedbyset
40、tlingtheeffluentina1-1graduatedcylinderfor2handthendecantingtheliquidfractionabovethesludge-Iiquidinterfaceline.TheCOD,SCOD,TS,VS,andTKNweremeasuredaccordingtoAPHAstandardmethods11.TheCODmeasuredinthisstudywasCODcrThepHwasmeasuredwithanACCllmetpHmeter(FisherScientific,Pittsburgh,Pa.).TheNH3-Nwasmeas
41、uredwithagas-sensingelectrodeandthepHmeter.TheDOinthereactorswasmonitoredonadailybasiswthaDOmeter(YSIModel58,FisherScientific,Pittsburgh,Pa.).TheNO2-NwasanalyzedwiththeHACHmethod,usingaDR/2000spectrophotometer12.TheNO3-Nwasmeasuredwiadiffusion-conductivityanalyzer13.3Resultsanddiscussion3.1Performan
42、ceofthesingle-stageSBRsystem3.1.1RemovalofcartoonandsolidsTheperformancedata.oftheSBRfor10,000tng/1CODinfluentCODof10,000areshowninTable1.WiththeincreaseofHRTfrom1to3days,theCOD,SCOD,TS,andVSintheliquideffluentbecamelower,yieldingbettereffluentqualityduetoincreasedbiologicalconversionandimprovedslud
43、gesettleability,asIndicatedbytheincreasedremovalefficiencies(EandEJ.However,而erewasnoParameters Influent (mg/1)1-day HRT2-day HRT3-day HRTLiquid Total EI EtLiquid Total ElBtLiquid Total El Eteffluent effluent (%)(%)CffIUent effluent (%)(%)effluent effluent (%)(%)(mg/1)(mg/1)(mg/1)(mg/1)(mg/1)(mg/1)T
44、able 1. Einucnt quality and treatment efficiencies of SBR for 10/)00 mg/1 COD influentCOD10,0001,9806,500SCOD2,9141,4571457TS6,6562,4365,232VS5,1081,7243,361TKN780195365TN780481607NH3-N510120120NO3-NO37NO1-NO249PH8.16.80 0 4 2 2 2 5 45.50.21.34.53.22.76.016250550857388054 方*万141 2L h2,h0 19 9 4 8 53
45、 5 7 4 5 9 0JMQ 2 3 5 1 5,k53.2.2.8.03 5 4 4 62.6 6 &9.8 5 6 7 7 3 7.72.7工.64.4& 63.6 43.9.4 5 2 3 5 2 7086054050 72106774 8,4,44,41 4 2L h2,h0 8 8 7 8 6 03 2 9 6 3 9 79M。J 3 54,h53.79.4.0.7.63 s & 6矢6 5 2 3 5 2 8 3 9.7,6.82 3 1 L3.Z8.9.6 8 5 6 7 7 3 8significantdifferenceintermsofcarbonandsolidsrem
46、ovalsandliquideffluentqualityforthethreeHRTs.Forexample,theincreaseofCODand,SremovalefficiencyEwas5.1%and0.3%,andEtwas5.7%and2.0%,respectively,whenHRTincreasedfrom1to3days.Therefore,1-dayHRTwasbelievedtobesufficientfortreatingthedairywastewaterwith10,000mg/1CODforitsSatiS启CtOryremovalefficiencyandre
47、lativelyshortHRT.At1-dayHRT,theremovalefficiencyfromtheliquideffluent()was80.2%forCOD,63.4%forTS,and66.2%forVS.TheseremovalswereduetobothbiologicalconversionintheSBRandsludgeseparationintheso)ids-settlingtank.TheremovalduetobiologicalconversionaloneintheSBR,asmeasuredbyEx,was45.0%forCOD,21.4%forTS,a
48、nd34.2%forVS.EtWaSsignificantlygreaterthansuggestingthatthesludgeseparationafterSBRtreatmentisnecessaryforachievingsignificantcarbonandsolidsremovalfromthedairywastewater.Itwasfoundthataerobictreatmentgreatlyenhancedtheflocculationandscttleabilityofthesolidsinthewastewater.Goodsettleabilityofsludgewasimportantforachievinghighcarbonandsolidsremovalefficiency.TheperformancedataoftheSBRfor20,000mg/1CODinfluentareshowninTable2.The1-dayHRTWaStestedfirst.Itwasfoundthatitwasimpossi
