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ArticleEvaluationoftheeffectsofAlkylPhenoliccompoundsonkineticcoefficientsandbiomassactivityinMBBRbymeansofrespirometrictechniquesBijanBina1,2,FarzanehMohammadi2,3,⁎,MohammadMehdiAmin1,2,HamidRezaPourzamani1,2,ZeynabYavari2,31EnvironmentResearchCenter,ResearchInstituteforPrimordialPreventionofNon-communicableDisease,IsfahanUniversityofMedicalSciences,Isfahan,Iran2DepartmentofEnvironmentalHealthEngineering,SchoolofHealth,IsfahanUniversityofMedicalSciences,Isfahan,Iran3StudentResearchCommittee,IsfahanUniversityofMedicalSciences,Isfahan,IranabstractarticleinfoArticlehistory:Received1May2017Receivedinrevisedform26July2017Accepted26July2017Availableonline19September2017ThepresenceofAlkylPhenols(APs)inaquaticsystemsisconsideredasoneoftheenvironmentalconcernsinrecentdecadeswhicharegenerallyusedassurfactants.APsareendocrinedisruptorsandestrogen-mimicking,causingharmfuleffectssuchasfeminizationandcarcinogenesisonaquaticenvironmentandhumanhealth.ThemostcommerciallyimportantAPsare4-NonylPhenol(4-NP)and4-tert-OctylPhenol(4-t-OP).Movingbedbiofilmreactor(MBBR),whichcombinedattachedandsuspendedgrowthadvantages,isanadvancedbiologicaltreatmentprocessformunicipalandindustrialwastewatersthathasdrawnconsiderableattentionfrommanyresearcherstoremovetoxicpollutantsfromwastewater.TheaimofthisresearchwastoevaluateBacterialactivitiesandkineticcoefficientsinthepresenceofAPs.Thisstudywascarriedoutusinglaboratory-scaleMBBRfedwithsyntheticwastewatercontaining4-NPand4-t-OP.Thereactorwasoperatedatdifferentloadsofchemicaloxygendemand(COD)andAPsanddifferenthydraulicretentiontime(HRT).TherespirometrictechniquewasappliedtoinvestigatetheeffectofAPsonheterotrophicandautotrophicactivityandkineticcoefficientsinbiomassobtainedfromMBBR.Respirometrictechniquedemonstratesareliabletoolinordertoassessthebiofilmkineticcoefficientsandbiomassviabilitytoinsertinthemathematicalmodels.Thecalculatedkineticparameterswereintherangeofconventionalandextendedaerationactivatedsludgeprocesses.TheresultsdemonstratethatAPshavesignificantinhibitoryeffectsonactivityandgrowthrateofheterotrophicandautotrophicbacteria,heterotrophshavebeenlessaffectedbythepresenceof4-NPand4-t-OP,andthesecompoundshadgreaterinhibitoryeffectsonautotrophicbacteria.©2017TheChemicalIndustryandEngineeringSocietyofChina,andChemicalIndustryPress.Allrightsreserved.Keywords:AlkylPhenolsAutotrophsHeterotrophsKineticcoefficientsMBBRRespirometrictechniques1.IntroductionAlkylPhenolEthoxylates(APEs)areamongtheextensivelyusednonionicsurfactantsandwidelyusedinconsumerproductssuchasdetergents,lubricants,phenolicresins,rubberandplastic,polymers,antioxidants,heatstabilizersandothermaterials[1].APswhicharethemetabolitesofAPEsaremorestable,moretoxicwithstrongerxenoestrogeniceffectsandmorelipophilicpropertiesthantheirparents.ThemostimportantandwidelyusedAPsare4-NPand4-t-OP[2]whichhaveharmfuleffectsonhumanhealthandenvi-ronment.Thesecompoundscanleadtocanceroustumor,reproductivedisorder,immunesystemdisorderandobesity[3].APsareregularlyfoundinwastewaterandcommonlydetectedinwaterresourcesreceivingwastewatereffluents[4]thereforethefateandpresenceofAPsinwaterresources,andwastewaterswererecentlyreportedindifferentpapers[1,5].Accordingtoconductedresearches,thereareabout0.25to193μg·L−14-NPindomesticwastewaterwithamedianof16.7μg·L−1,while4-t-OPhasbeenshownfromanundetectablerangeto23μg·L−1withamedianof1μg·L−1[6–8].Amongvariousprocessesduringthepastdecade,MBBRhasbeensuccessfullyappliedforthetreatmentofmunicipalandindustrialwastewater.Attachedgrowthofbiofilmonthecarriersisthefunda-mentalofMBBR[9].Movingbedbiofilmreactorsaredesignedtooffertheadvantagesoftheattachedbiomassprocesses(compact,simplicityofoperation,highandstableremovalefficiency,highsurfaceareaformicrobialgrowth)withoutitsdrawbacks(clogging,requirementforbackwashing,sludgerecyclingandbulking)[10].TheMBBRprocesscouldeliminate4-NPand4-t-OPpollutantsmorethan90%[11,12].Inthisprocessheterotrophsarefacedwithstarvationstatusduetohighbiomassconcentrationandhighcellretentiontime(SRT),andthus,physiologicalconditionsarenotappropriateforthegrowthofChineseJournalofChemicalEngineering26(2018)822–829⁎Correspondingauthorat:DepartmentofEnvironmentalHealthEngineering,SchoolofHealth,IsfahanUniversityofMedicalSciences,Isfahan,Iran.E-mailaddress:fm_1363@yahoo.com(F.Mohammadi).©2017TheChemicalIndustryandEngineeringSocietyofChina,andChemicalIndustryPress.Allrightsreserved.ContentslistsavailableatScienceDirectChineseJournalofChemicalEngineeringjournalhomepage:[13,14].Modelingisareliablewaytodescribeandpredicttheperformanceofbiologicaltreatmentprocesses.Kineticcoefficientsarerequiredfordevelopingamodelwithsuitablecapabilityforthedesignofbiologicalprocesses.Typesofsubstrate,microorganismsandenvironmentalconditionsinthebioreactorsignificantlyaffectthek