电絮凝DomesticWastewaterElectrocoagulation

ENVIRONMENTALENGINEERINGSCIENCEVolume25,Number2,2008©MaryAnnLiebert,Inc.DOI:10.1089/ees.2006.0132TreatmentofDomesticWastewaterbyElectrocoagulationinaCellwithFe–FeElectrodesUgurKurt,1M.TalhaGonullu,2FatihIlhan,3KamilVarinca4EnvironmentalEngineeringDepartmentYildizTechnicalUniversity,34349,IstanbulTurkeyABSTRACTInthisstudy,thepotentialtotreatdomesticwastewater(DWW)usinganelectrocoagulation(EC)processwastestedontwodifferentsamples,oneofwhichwasheavilyloaded[380mgchemicaloxygendemand(COD)/L];theotherwasweaklyloaded[260mgCOD/L].ThesamplesweresuppliedfromtheIstanbul-YenikapiDWWpretreatmentplant.TheexperimentalstudieswereconductedwithinanelectrolysiscellwithFe–Feelectrodes.Inthiscell,underoptimumoperationalconditionsintheformofelectricalpowerandelectrolysistime,pollu-tantremovalefficiency(asCOD),suspendedsolids(SS)andcharacteristicsofformedsludgeweretested.Attheendofthesestudies,theoptimumoperationalconditionsfoundforelectricalpowerwas0.6WforbothDWWsamples,andelectrolysistimesweredeterminedas15minforheavilyloadedDWW(HLDWW)and8minforweaklyloadedDWW(WLDWW).Energyconsumptioninoptimumelectricalchargeconditionswas0.4kWh/m3HLDWWand0.2kWh/m3WLDWW.TheremovalefficiencyofCODandSSwereobtainedandshowntobeover60and70%,respectively.Thelevelofsludgeproductionwas1.5–2%duringtheoptimalre-actiontime,andsludgevolumewasdecreased50%usingH2O2.Keywords:COD;domesticwastewater;electrocoagulation;electricityconsumption;sludgereduction153*Correspondingauthor:YildizTechnicalUniversity,EnvironmentalEngineeringDepartment,34349,Istanbul,Turkey.Phone:[phone],ext.2347;Fax:[phone];E-mail:[e-mail]CANCREATESEVEREWATERPOLLUTIONprob-lemsforaquaticlifebecauseofitsvariouscontents.Al-thoughwastewaterscanbecomposedofvarioussources,itismostcommonlycomposedofdomesticwastewaters(DWWs).Currently,DWWisgenerallytreatedbyaeratedbiologicalmethods.Activatedsludge,beingthemostpopularmethod,produceshighqualityeffluent—90%biologicaloxygende-mand(BOD)andsuspendedsolids(SS)removal(MetcalfandEddy,2003).Butthiscommonlyusedmethodhassomedis-advantages,suchasrequiringcontinuousairsupply,highop-eratingcosts(skilledlabor,energy,etc.),sensitivityagainstshocktoxicloads,longertreatmenttime,andnecessarysludgedisposal.Somelab-basedstudieshavebeencarriedouttotreatDWWchemicallybycoagulation.Chemicaloxygendemand(COD)treatmentbetweentheratiosof55and75%,especiallyifitincludesSSsubstancesinthewastewater,canberealizedbythismethod(Debik,1999).Thechemicalsthatarecon-sumedinthistypeoftreatmentandthechemicalcharacteris-ticsofthesludgeproducedarethemostsignificantproblemsencounteredusingthismethod.Fromanenvironmentalpointofview,thesewagetreat-mentprocessisstillfarfrombeingenvironmentallysus-tainable.Basedonadeskstudy,astructuralapproachisgivenonhowtoachieveamoresustainabletreatmentpro-cess.Someofthepossibilitiesaretheimprovementofthemitigationoftoxicpollutants,high-temperaturesludgetreat-mentprocesses,andmembraneseparationprocesses(Rulkens,2006).Electrochemicaltreatmentmethodscanbementionedinthiscontextalso.Electrochemicaltreatmentseemstobeapromisingtreat-mentmethodduetoitshigheffectiveness,itslowermain-tenancecost,lessneedforlaborandrapidachievementofresults(Fengetal.,2003).Electrocoagulation-flotationtreatmentisinvestigated,asithasgreaterabilityforthere-movalofCODandSSfromeffluentsincomparisonwithtreatmentbyconventionalcoagulation(Jiangetal.,2002).Attheendofthestudiesidentifyingthemostappropri-atetreatmentalternatives,electrocoagulation(EC)isshowntobeoneofthebestmethodsforthewastewater.Reusingofwastewaterhasbecomeanabsolutenecessity,sothereisanurgentneedtodevelopinventive,moreeffective,andlow-costtechniquesfortreatmentofwastewater(Fengetal.,2003).Electrochemicaltreatmenttechniquesareoneofthese.Ahostofverypromisingtechniquesbasedonelec-trochemicaltechnologyarebeingdeveloped,andexistingonesarebeingimprovedthatdonotrequirechemicaladdi-tions(Mollahetal.,2001).ECcanbeusedtoremoveirons,silicates,humus,dissolvedoxygen(Chen,2004),reducecopper(ComninellisandPulgarin,1993)anddecolorize(Bechtoldetal.,2002).EChasalsobeenappliedsuccess-fullytotreatpotablewater,food,andproteinwastewater,yeastwastewater,urbanwastewater,restaurantwastewater,tarsand,andoilshalewastewater,nitratecontainingwaste-water,heavymetals,textiledyes,fluorine,polymericwastes,organicmatterfromlandfillleachate,suspendedparticles,chemicalandmechanicalpolishingwastes,aqueoussus-pensionsofultrafineparticles,andphenolicwaste(Mollahetal.,2004).Presently,ECtechnologiesaremoreefficientandmorecompact.RemovalmechanismsoftheECprocessincludecoagulation,adsorption,precipitation,andflotation(Kobyaetal.,2003).Similarly,theeffectofDCelectricfieldsonCODinaerobicmixedsludgeprocesseshasbeeninvestigated,andoptimumoperationalconditionswerede-termined(Alshawabkehetal.,2004).Inanotherstudy,re-movalofnitrogencompoundshasbeensuccessfullyreal-izedusingarotatingelectrobiologicalcontactor;aninterestingstudy,inwhichover83%efficiencyoftheden-itrificationwasobservedatanitrificationefficiencyof68.9%(KrzemieniewskiandRodzi