Mechanismkineticsandapplication

Mechanism,kineticsandapplicationstudiesonenhancedactivatedsludgebyinteriormicroelectrolysisXiaoyiYang*,YuXue,WennaWangDepartmentofThermalEnergyEngineering,BeiHangUniversity,XueyuanRoad37#,Haidian,District,Beijing100083,PRChinaarticleinfoArticlehistory:Received5May2008Receivedinrevisedform18July2008Accepted19July2008Availableonline2September2008Keywords:InteriormicroelectrolysisEnhancedactivatedsludgeBiologicaltreatmentGalvaniccellreactionKineticsabstractEnhancedactivatedsludgebyinteriormicroelectrolysis(EAIM)wasstudiedtotreattextilewastewater,kinetics,mechanismandapplicationofwhichwerealsodiscussedincomparisonwithtraditionalacti-vatedsludgeandinteriormicroelectrolysis,respectively.Theresultsofkineticsstudyindicatedthreedif-ferentprocessesallfollowedfirst-orderkineticswell.InEAIM,threeimpactfactorstakeeffectsonCODremoval,whichareflocculation,activatedsludgeandelectrophoresisandredox.IntermsofassumptionofnointeractionamongthreeCODremovalmechanisms,49.6%ofthetotalCODremovalisascribedtoflocculation,30.1%toactivatedsludgeand20.3%toelectrophoresisandredox.EAIMshoweditsadvan-tagesinCODremovalefficiency,extensiveadaptabilitytocomplexcompositionandwiderangeofpH.EAIM-aerobicprocessprovidedanefficientandeconomicperformancefordealingwithtextilewastewater.2008ElsevierLtd.Allrightsreserved.1.IntroductionChemicalagentsanddyesusedindye,textileindustryarechar-acterizedbyhardoxidation,baddecolonizationandpoorbiodegra-dationduetograduallystrictrequirementstothequalityoftheproduct.Thosechemicalsisdischargedintowastewaterindiffer-entprocessstagesoftextileindustry,thusdifficultiesofwastewa-tertreatmentarebeingenhancedandaccordinglymostofthetraditionalmethodsarebecominginadequate(Haoetal.,2000;Fernandesetal.,2004;Sakalisetal.,2005)andunsatisfiedtotherequirementofenvironment.Inaddition,inventionsofnewmate-rialsaredevelopingrapidly.Therefore,itisaveryimportantandcomplexproblemtotreatpoorbiodegradablewastewaterbyaneconomicallyandenvironmentallyacceptablemanner.Thetextileindustryaloneconsumes10%oftheworldsurfactantproduction.Thepresenceofsmallamountofsurfactantinwaste-waterishighlyvisiblebecausetheyinducefoamingandsubse-quentlytheloweroxygenconcentrationinwater.Oneofthemostimportantaspectassociatedwiththetreatmentoftextilewastewateristheremovalofsurfactant.Accordingly,itisneces-sarytopretreattextilewastewaterbeforeaerobictreatment.Chemicalcoagulation–flocculation,chemicaloxidation,activated-carbonadsorptionandanaerobicbiologicaltechnology,usuallycombinedwithasecondaryactivatedsludgetreatmentprocess,havebeenstudiedtotreattextilewastewater(RottandMinke,1999;Georgiouetal.,2003).However,chemicalcoagulationpro-duceslargeamountsofsludgeandsubsequentlyimposeshandlinganddisposalproblems,andchemicaloxidationandactivated-car-bonadsorptionareveryexpensive.Therefore,apretreatmenttech-nologybeforeaerobictreatmentisanimportantthemeintextilewastewatertreatment.Interiormicroelectrolysisalsocalledironchipsfiltrationhasbeenusedtopretreatindustrialwastewaterduetoextensiveadaptabilitytowidevariationsofcompositionsofwastewater(Yupingetal.,2006).Especially,ithasbeenstudiedontreatmentofpoorbiodegradablewastewater,includingpesticidewastewater(Huifangetal.,2003),pharmacywastewater(YongguangandJian,2001;Honglietal.,2005)anddyewastewater(ChuanandJie,2003;Cangcangetal.,2005).Fromachemicalpointofview,wasteironchipscontainingalmost3.5%carbonformnumerousgalvaniccellsbetweenironandcarboninwastewater,whichresultsingal-vaniccellreaction.Productsreleasedfromgalvaniccellreactionin-cludehydroxyl,atomichydrogenandFe(II).Thosenewproductshavehighactivitiesandareeasytoreactwithcontaminants.Fur-thermore,thosehighactivatedproductsandnumerousgalvaniccellreactionsleadtoelectro-flocculationandconsequentlyremovecontaminants.Fromabiologicalpointofview,ironisanimportantandindispensablecomponentofbiomoleculewhichundergoesre-doxincells(Jeaneetal.,2001),andFe(II)isoftenusedinactivatedsludgetreatmentplantsasacoagulant.Thus,itcouldbepromisingtocombineinteriormicroelectrolysiswithactivatedsludgeto-getherinasamereactor.Physical,chemicalandbiologicalactionsalltakeeffectsoncontaminantsremovalandonlycheapironchipscostadditionallyintheprocess.Inthispaper,enhancedactivatedsludgebyinteriormicroelectrolysiswasstudiedandremoval0960-8524/$-seefrontmatter2008ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2008.07.035*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](X.Yang).BioresourceTechnology100(2009)649–653ContentslistsavailableatScienceDirectBioresourceTechnologyjournalhomepage:ficiencyofcontaminants,mechanismandkineticsofEAIMwerealsodiscussed.2.Methods2.1.SamplesAstextilewastewaterisnotonlywidevariationofcompositionofwastewater(Mohanaetal.,2007)butalsothelargestwatercon-sumers(Wijetungaetal.,2008),textilewastewatersampleswereusedfortheentirestudy.Textilewastewaterwasobtainedfromarealtextilefactory(Tianjin).InTable1,mainwastewatercharac-teristicsoftextilewastewateraresummarized.ConsideringBOD/CODratios,wastewatershowedve