Tuningofactiva省略itetemperaturesZhihuaLi

TuningofactivatedsludgeinwinterbasedonrespirogramprofilesunderstandardandsitetemperaturesZhihuaLi1,⁎,ZhenyuHang1,QianZhang1,ShuangshuangZhang1,TianyuZhang2,HanqingYu3,⁎1.SchoolofEnvironmentalandMunicipalEngineering,Xi'anUniversityofArchitectureandTechnology,Xi'an710055,China2.DepartmentofMathematicalSciences,MontanaStateUniversity,Bozeman,MT59717-2400,USA3.CASKeyLaboratoryofUrbanPollutantConversion,DepartmentofChemistry,UniversityofScience&TechnologyofChina,Hefei230026,ChinaARTICLEINFOABSTRACTArticlehistory:Received24September2018Revised14December2018Accepted17December2018Availableonline27December2018RespirogramsofactivatedsludgeOURTxandOUR20xweremeasuredundersite(T)andstandard(20°C)temperatures,respectively,andthepredictedstandardtemperaturerespirogramOUR20x,calwasalsocalculatedusingtheArrheniusequation.Theserespirogramprofilesrevealmoreinformationthaneffluentquality.AdecreaseofOUR20xisacriticalalarmsignalforthelossofpollutantremovalcapacity,andasuddenincreaseofthepredictedvalueOUR20x,calisanalarmsignalfortheunrecoverabledeteriorationofbiomass.ThesignofOUR20x–OUR20x,calcanbeusedforselectionoftuningstrategies.Forexample,anegativevalueofOUR20x–OUR20x,calindicatesthatdoublingbiomassisdifficult,thusstrategiessuchasextendingthereactiontimewithlimitedavailablebiomassispreferred.ThefindingsinthisstudyelucidatedtherespirationprofileofactivatedsludgeunderchangesoftemperatureandcanbeeffectivelyusedforthestableoperationofWastewaterTreatmentPlantsundercoldtemperaturesandseasonalvariations.©2018TheResearchCenterforEco-EnvironmentalSciences,ChineseAcademyofSciences.PublishedbyElsevierB.V.Keywords:ActivatedsludgeColdtemperatureshockingOxygenuptakerate(OUR)RespirogramSeasonalvariationsIntroductionTemperatureisoneoftheimportantfactorsinfluencingtheactivityandmicrobialcommunitystructureofactivatedsludge(Dongetal.,2016;Juetal.,2014;Zhangetal.,2019)andhasbeenextensivelyinvestigated,especiallyfornitrifi-cationsystems(Chenetal.,2018;Delatollaetal.,2009;Hoangetal.,2014a;Mannuccietal.,2014;Sunetal.,2015;Youngetal.,2017;Zhangetal.,2014).Approximately20%ofthenitrificationrateat20°Ccouldberetainedat1°Cwhenapropertemperaturedecreasestepwasused(Hoangetal.,2014a;Youngetal.,2017).Theeffectoftemperatureonthekineticpropertiesofactivatedsludgecanbewell-describedusingtheArrheniusequation(HwangandOleszkiewicz,2007;Mannuccietal.,2014).μT¼μ20θT−20ðÞð1Þwhereθisthetemperaturecorrectionfactor;μT(day−1)andμ20(day−1)arethespecificgrowthratesatthesitetemperature(T°C)and20°C,respectively.Thetemperaturecorrectionfactorθ,takingnitrificationasanexample,hasbeenextensivelyinvestigatedundervariousconditions(Hoangetal.,2014a;HwangandOleszkiewicz,2007;Mannuccietal.,2014;Youngetal.,2017;JOURNALOFENVIRONMENTALSCIENCES79(2019)330–338⁎Correspondingauthors.E-mails:[e-mail],(ZhihuaLi),[e-mail].(HanqingYu).©2018TheResearchCenterforEco-EnvironmentalSciences,ChineseAcademyofSciences.PublishedbyElsevierB.V.Availableonlineat).Itvariesoverawiderangefrom1.03to1.60dependingontemperaturechangerate,temperaturerangeanddurationofcold-shocking(Table1).ItisreasonabletocompensateforthedecreasedrateμTunderalowtempera-turewiththeenrichmentofbiomass;therefore,methodssuchasextendingthesludgeretentiontime(SRT)andbio-augmentationarefrequentlyemployed(HeadandOleszkiewicz,2004;Hoangetal.,2014b;Peietal.,2014;Wuetal.,2008).MarginaleffectsexistforextendingSRT;i.e.,afterreachingacertainlevel,increasingSRTdoesnotleadtofurtherincreaseinthenitrificationcapability,andmayevenworsenthebioactivitywhenrecoveringfromalowtempera-turetoahightemperature(HeadandOleszkiewicz,2004).Bio-augmentationiseffectiveforcompensatingthedeficiencyofSRT;however,theeffectsdependmoreonhydraulicretentiontime(HRT)thanSRT,andtheenhancementofnitrificationwilldisappearquicklyoncethebio-augmentationisceased(HeadandOleszkiewicz,2004;Peietal.,2015),whichmakessuchamethodexpensiveduringwinteroperation.Therefore,takingpropertuningmeasuresunderlowtemperatureremainsachallenge.Cold-shockingisalsoencounteredduringseasonalvaria-tions(HwangandOleszkiewicz,2007;Juetal.,2014),e.g.,fromautumntowinter,resultinginfluctuationsineffluentconcentrations,andthetemperaturecorrectionfactorθincreasessignificantlywhenthetemperaturedecreasestoacriticaltemperature(Table1).Thesignificanceorimplicationsofthevariationofθisstillunderdiscussion.Also,themeasuredactivityofnitrificationhasbeenfoundtoremainunchangedorbecomeevenhigherintheinitialperiodofdecreasingtemperature(Hoangetal.,2014b),whichdoesnotfollowtheArrheniusequation.Themechanismforsuchbehaviorremainsunclearandinvitesfurtherinvestigation.Therespirogramisfrequentlyemployedforthedescrip-tionoftheactivityofsludge,fortheevaluationoftherobustnessofactivatedsludgesystemsandforestimationoftherecoverypotential(Huangetal.,1985;Lietal.,2018a),thusitnaturallyservesasabasisfortheselectionoftuningstrategiesundercoldtemperatureshock.Therefore,thisstudyevaluateddiffe