电絮凝Electrocoagulationinthetreatmentofindustr

•VISIONS•SCIENCE•TECHNOLOGY•RESEARCHHIGHLIGHTSDissertation19VTTSCIENCE19ElectrocoagulationinthetreatmentofindustrialwatersandwastewatersISBN978-951-38-7940-2(softbacked.)ISBN978-951-38-7941-9(URL:)ISSN2242-119X(softbacked.)ISSN2242-1203(URL:)ElectrocoagulationinthetreatmentofindustrialwatersandwastewatersChemicalcoagulationiscommonlyusedinrawwaterandwastewatertreatmentplantsforthedestabilisationofpollutantssothattheycanberemovedinthesubsequentseparationprocesses.Themostcommonlyusedcoagulationchemicalsarealuminiumandironmetalsalts.Electrocoagulationtechnologyhasalsobeenproposedforthetreatmentofrawwatersandwastewaters.Withthistechnology,metalcationsareproducedontheelectrodesviaelectrolysisandthesecationsformvarioushydroxidesinthewaterdependingonthewaterpH.Inadditiontothismainreaction,severalsidereactions,suchashydrogenbubbleformationandthereductionofmetalsoncathodes,alsotakeplaceinthecell.Inthisresearch,theapplicationsofelectrocoagulationwereinvestigatedinrawwatertreatmentandwastewaterapplications.ElectrocoagulationinthetreatmentofindustrialwatersandwastewatersMikkoVepsäläinenVTTSCIENCE19ElectrocoagulationinthetreatmentofindustrialwatersandwastewatersMikkoVepsäläinenThesisforthedegreeofDoctorofScience(Technology)tobepresentedwithduepermissionforpublicexaminationandcriticisminchambermusicaudito-riumattheConcertandCongressHouseMikaeli,Mikkeli,Finlandonthe2ndofNovember,2012atnoon.ISBN978-951-38-7940-2(softbacked.)ISSN2242-119X(softbacked.)ISBN978-951-38-7941-9(URL:)ISSN2242-1203(URL:)Copyright©VTT2012JULKAISIJA–UTGIVARE–PUBLISHERVTTPL1000(Tekniikantie4A,Espoo)02044VTTPuh.020722111,faksi0207227001VTTPB1000(Teknikvägen4A,Esbo)FI-2044VTTTfn.+35820722111,telefax+358207227001VTTTechnicalResearchCentreofFinlandP.O.Box1000(Tekniikantie4A,Espoo)FI-02044VTT,FinlandTel.+35820722111,fax[phone]KopijyväOy,Kuopio20123ElectrocoagulationinthetreatmentofindustrialwatersandwastewatersMikkoVepsäläinen.Espoo2012.VTTScience19.96p.+app.50p.AbstractChemicalcoagulationiscommonlyusedinrawwaterandwastewatertreatmentplantsforthedestabilisationofpollutantssothattheycanberemovedinthesub-sequentseparationprocesses.Themostcommonlyusedcoagulationchemicalsarealuminiumandironmetalsalts.Electrocoagulationtechnologyhasalsobeenproposedforthetreatmentofrawwatersandwastewaters.Withthistechnology,metalcationsareproducedontheelectrodesviaelectrolysisandthesecationsformvarioushydroxidesinthewaterdependingonthewaterpH.Inadditiontothismainreaction,severalsidereactions,suchashydrogenbubbleformationandthereductionofmetalsoncathodes,alsotakeplaceinthecell.Inthisresearch,theapplicationsofelectrocoagulationwereinvestigatedinrawwatertreatmentandwastewaterapplications.Thesurfacewaterusedinthisresearchcontainedhighconcentrationsofnatu-ralorganicmatter(NOM).Theeffectofthemainparameters–currentdensity,initialpH,electricchargepervolume,temperatureandelectrolysiscellconstruc-tion–onNOMremovalwereinvestigated.Inthewastewatertreatmentstudies,theremovalofmalodoroussulphidesandtoxiccompoundsfromthewastewatersanddebarkingeffluentswerestudied.Also,themainparametersofthetreatment,suchasinitialpHandcurrentdensity,wereinvestigated.Aluminiumelectrodeswereselectedfortherawwatertreatment,whereaswastewatersanddebarkingeffluentweretreatedwithironelectrodes.Accordingtoresultsofthisstudy,aluminiumismoresuitableelectrodematerialforelectrocoagulationapplicationsbecauseitproducesAl(III)species.MetalionsandhydroxidesproducedbyironelectrodesarelesseffectiveinthedestabilisationofpollutantsbecauseironelectrodesproducemoresolubleandlesschargedFe(II)species.However,Fe(II)canbeeffectiveinsomespecialapplications,suchassulphideremoval.Theresultingmetalconcentrationisthemainparameteraffectingdestabilisationofpollutants.Currentdensity,treatmenttime,temperatureandelectrolysiscellconstructionaffectthedissolutionofelectrodesandhencealsotheremovalofpollutants.However,itseemsthattheseparametershaveminimalsignificanceinthedestabilizationofthepollutantsbesidesthiseffect(inthestudiedrangeofparameters).InitialpHandfinalpHhaveaneffectonthedissolutionofelectrodes,buttheyalsodefinewhataluminiumorironspeciesareformedinthesolutionandhaveaneffectontheȗ-potentialofallchargedspeciesinthesolution.Accordingtotheresultsofthisstudy,destabilisationmechanismsofpollutantsbyelectrocoagulationandchemicalcoagulationaresimilar.4OptimumDOCremovalandlowresidualaluminiumcanbeobtainedsimultane-ouslywithelectrocoagulation,whichmaybeasignificantbenefitofelectrocoagula-tioninsurfacewatertreatmentcomparedtochemicalcoagulation.Surfacewatertreatmentwithelectrocoagulationcanproducehighqualitywater,whichcouldbeusedaspotablewaterorfreshwaterforindustrialapplications.Inwastewatertreatmentapplications,electrocoagulationcanbeusedtoprecipitatemalodoroussulphidestopreventtheirreleaseintoair.Technologyseemstobeabletoremovesometoxicpollutantsfromwastewaterandcouldbeusedaspretreatm