Anaerobictreatmentofvinassesbyasequentiallymixedmo

AnaerobictreatmentofvinassesbyasequentiallymixedmovingbedbiofilmreactorC.Sheli*andR.Moletta***LaboratoryofEnvironmentalTechnology,CollegeofGeo-explorationScienceandTechnology,JilinUniversity,ChaoyangCampus,Changchun130026,China**Polytech’Savoie,Universite´deSavoie,CampusScientifiqueSavoieTechnolac,77376LeBourgetdulac,FranceAbstractWinedistillerywastewater,commonlycalledvinasses,wastreatedbyananaerobicmovingbedbiofilmreactor(AMBBR)with32.9litreavailablevolume.Thereactorwasfilledwith66%cylindricalpolyethylenesupportswithdensity0.84gcm23asabiofilmcarrier.Thereactorwassequentiallymixedbyasubmergedcentrifugalpumpfixedtothebottom,andeachmixingtimejustlasted1.25minutes.Theorganicloadingrate(OLR)ofthereactorwereincreasedfrom1.6to29.6gsCODl21d21(solublechemicaloxygendemands2sCOD)andhydraulicretentiontime(HRT)wasdecreasedfrom6.33to1.55daysaccordingly.SolubleCODremovalefficiencywas81.3–89.2%atanOLRof29.6gsCODl21d21.Attheendoftheexperiment,83.4%totalbiomasswasattachedonsupportandthespecificdensityofsupportinthereactorwas0.93–1.05gcm23,whichincreasedbyabout10.7–25%comparedwiththatatthebeginningofthestudy.KeywordsAnaerobicmovingbedbiofilmreactor;anaerobictreatmentsequentialmixing;vinassesIntroductionAnaerobicdigestionhasbeenprovedasuccessfultechnologytotreathighstrengthorganicwastewater.TechnologiessuchasanaerobicSBR(Ruizetal.,2002),anaerobicfluidized-bedreactor(Dura´nandCabrero,1991;Pe´rezetal.,1999),anaerobicinversefluidizedbed(Garcı´a-Bernetetal.,1998;Garcı´a-Calderonetal.,1998)andupflowanaerobicsludgeblanket(UASB)(GoodwinandStuart,1994;Espinosaetal.,1995;WolmaransanddeVilliers,2002)hasbeenshowedtoperformwellwhenusedtotreatwinevinasses,sugarbeet,sugarcaneandwhiskydistillerywastewaters.Anaerobicflui-disedbedreactorsusessmallfluidisedparticlestoinducethecellimmobilisation.UASBperformanceismainlydeterminedbytheformationandactivityofthegranulesludge.Movingbedbiofilmreactor(MBBR)isawell-knowntechnologyinaerobictreatment.Inthisreactor,thebiofilmgrowsonmobilesupportandtheagitationcouldbedonebyaerationorbymechanicalsteering.Itincorporatestheadvantagesofbiofilmtechnology,anditisacompactreactor.Thereactorisfilledwiththeespeciallydesignedplasticmediawhichprovidesthelargespecificsurfaceareaforbacteriatogrow.Thedensityofthemediawithbiofilmshouldbesimilartothedensityofwater(densityofone)inordertospendlessenergyforagitation.TheMBBRprocesshasbeenusedtotreatmunicipalandindustrialwastewatersforCODremovalandnitrificationanddenitrification(Ødegaardetal.,1994).Afewanaerobicmovingbedbiofilmreactors(AMBBRs)havebeenusedaspre-treat-mentofpaper-makingwastewater(JahrenandØdegaard,1999)andhighstrengthcanevinasses(JahrenandØdegaard,2000).Theanaerobicdigestionprocessesproducebiogaswhichcanbeuseasmicro-mixingofthewastewaterinthedigester.Inthisstudy,wehavetestedthefeasibilityusingthesequentially-mixedanaerobicAMBBRtotreatvinasses,withsequencingmechanicalagitationformacro-mixing.WaterScience&TechnologyVol56No2pp1–7QIWAPublishing20071doi:10.2166/wst.2007.465MaterialsandmethodsDigesterThereactorwasmadeofaPlexiglasscylinder(23.8cmdiameterand89cmheight),withaworkingvolumeof32.9litres(Figure1).Thereactorwasfilledwith66%cylindricalpolyethylenesupports‘Bioflow9’wfromRaushert(diameter9mm,height7mmandrealdensity0.84gcm23)asbiofilmcarrier.Theavailablespecificbiofilmsurfaceareaofthecarrierwasabout528m2m23beforebiofilmformation.ThesequentialmixingofthereactorwascarriedoutbyasubmergedSupermacen-trifugalpumpfixedonthebottomofthereactor.Themixingtimeswassetto2–8timesperhour(accordinglyincreasedwithorganicloadingrateintheexperiment),andthedur-ationofeachmixingtimeonlylastedfor1.25minutes.Thisdurationwasabletomoveallthemediainthereactor.ThereactorwasfedwithMasterflexCole-Parmerperistalticpump,andthefeedingtankwasmixedwithamechanicalstirrer.Hydraulicretentiontimewasadjustedthroughcontrollingtheflowrateofthefeedingofinfluent.Asimplewaterdisplacementgasmeterwasusedtomeasuretheproducedbiogasvolume,whereacounterregisteredaunitafteracertainvolumeofthesolutioncontain-ingNa2SO4andH2SO4wasdisplaced(MolettaandAlbagnac,1982).WastewaterandseedsludgeTwokindsofrawwinevinassesfrom100m3storagetankswereusedaswastewatertofeedthereactor.ThecharacteristicsofthevinasseswerepresentedinTable1.LowstrengthvinasseswithanaverageCODconcentrationof16.19gl21wasfedthereactorfromday1to49,andhighstrengthvinasseswithanaverageconcentrationof45.5gl21CODwasdilutedbeforefeedingfromday50to116andday154to187.Undilutedhighstrengthvinasseswasthenfedthereactor.TraceelementsFe,Ni,Cowereonlycontinuouslyaddedfromday178to181toacceleratetheperformanceofthereactorintheformsofFeCl2·4H2O,NiCl2·6H2OandCoCl2·6H2O,andtheirconcen-trationswere50mgl–1,10mgl21and10mgl21,respectivelyintheinfluent.ThepHofinfluentwasadjustedtoover6.7,mostlyover7.0,with20%NaOHsol-utionbeforeday178.Thereafter,theinfluentpHadjustmentwasalsomadebeforefeed-ing,buttheinfluentpHwasbelow6.7andrangedfrom4.03to5.75afterday195.Seedsludgeofthereactorcamefromtheanaerobicsludgetankofanotherreactortotreatthesamekindofvinasses.SS,VSSandVSS/SSratioofthesludgewere36.8gl21,SupportBiogasGasmeterStirr