6评估厌氧消化最佳稀释比

Assessmentofoptimumdilutionratioforbiohydrogenproductionbyanaerobicco-digestionofpressmudwithsewageandwaterB.Radjarama,⇑,R.Saravananeb,1aDepartmentofCivilEngineering,PondicherryEngineeringCollege,Puducherry605014,IndiabEnvironmentalEngineeringLaboratory,DepartmentofCivilEngineering,PondicherryEngineeringCollege,Puducherry605014,IndiaarticleinfoArticlehistory:Received21March2010Receivedinrevisedform16November2010Accepted17November2010Availableonline26November2010Keywords:PressmudSewageUASBBiohydrogenCo-digestionabstractAnaerobicco-digestionofpressmudwithwaterorsewageatratiosof1:7.5,1:10and1:12.5wereper-formedincontinuouslyfedUASBreactorsforhydrogenproduction.Ataconstanthydraulicretentiontimeof30h,thespecifichydrogenproductionratewas187mL/gvolatilesolids(VS)reducedduringmax-imumbiohydrogenproductionof7960mL/dayata1:10ratioofpressmudtosewage.Chemicaloxygendemand(COD)andVSreductionsof61%and59%werenotedonpeakbiohydrogenyield.ApHrangeof5–6wassuitableatambienttemperatureforentireprocess;alowerpHwasinhibitory.Co-digestionofacidicpressmudwithsewagecontrolledpHforfermentation.Hencepressmudcanbeexploitedforbio-hydrogenproduction.2010ElsevierLtd.Allrightsreserved.1.IntroductionHydrogenisapromisingalternativetocarbon-basedfuelsbe-causeitisclean,renewableandhasahighenergyyieldof122kJ/g(ChangandLin,2004).Atpresent,hydrogenisproducedmainlyfromfossilfuels,biomassandwaterusingchemicalorbio-logicalprocesses.Onesuchbiologicalprocessisanaerobichydro-genfermentationwhichcanutilizehighlyconcentratedorganicwastewaterandbiomass,suchasmunicipalsolidwastesandsew-agesludgeasrawmaterial(DasandVeziroglu,2001).Pressmudisanotherpotentialwastesourceforhydrogenproduction.About4%ofcrushedsugarcaneisconvertedtopressmud,andannuallyabout4.2milliontonsofpressmudisavailablefromthesugarindustryinIndia(SaravananeandRadjaram,1998).Itisanacidic,thusmildlycorrosive,compressedfibrouswastethatcontains5–15%sugar(ParthaandSivasubramanium,2006)and84%isbio-degradable.EarlierstudiesonpressmudexaminedthefeasibilityofmethaneproductionbymethanogenesisatpHof8(SaravananeandRadjaram,1998).Incontrast,hydrogenproductionisfavoredatanacidpH(G´omezetal.,2006;Mohanakrishnaetal.,2010).Asasemi-solidmaterial,pressmudcannotbefermentedunlesswaterorsewageisadded.Fermentationcanbecarriedoutinanupflowanaerobicsludgeblanket(UASB)processsincethisanaero-bictreatmentsystemhasahightreatmentefficiencyandashorthydraulicretentiontime(HRT)(ChangandLin,2004).Fermenta-tioninacontinuousstirredtankreactordoesnotseempracticalsincethistypeofreactorwasunabletomaintainhighleveloffer-mentativebiomassforhydrogenproductionanditsspecifichydro-genproductionratewaslow(Yuetal.,2002).Dilutionisakeyparameterinanaerobicfermentationaslowdilutionleadstoprod-uctinhibitionandhighdilutionleadstowashoutofbiomassinreactor(HanandShin,2004).Inthepresentstudywaterandsew-agewereusedtodilutepressmudtoallowefficientfermentation.2.Methods2.1.SeedSeedsludgewascollectedfromamunicipalwastewatertreatmentplantmaintainedbythePublicWorksDepartment,Pondicherry,India.ItwassievedthroughawiremeshofØ0.5mmtoremovesolidmaterialsthatmayblocktheflowinthepump.Cowdungwasmixedwithwaterata1:2ratioanddigestedunderanaerobicconditionsfor30daysatapHbetween5and6byaddingHCl/NaOHasneeded.Thedigestwasfilteredthroughwiremesh(Ø0.5mm)toremovefibrousmaterials,mixedwithseedsludgeat4:1ratio,andheatedto70Cfor1htoinhibitthemethanogens,andusedasseed.Thecharacteristicsoftheseed(fermentedcowdungdilutedwithsludge)aregiveninTable1.0960-8524/$-seefrontmatter2010ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2010.11.075⇑Correspondingauthor.Tel.:[phone],mobile:[phone];fax:[phone].E-mailaddresses:[e-mail](B.Radjaram),[e-mail](R.Saravanane).1Tel.:[phone]x210,mobile:[phone];fax:[phone].BioresourceTechnology102(2011)2773–2780ContentslistsavailableatScienceDirectBioresourceTechnologyjournalhomepage::7.5ofpressmudandwaterwasnecessarytoobtainahydrogenfermentationsubstratethatcanbefilteredandulti-matelyusedinacontinuousflowsystem.Therefore,feedsforreac-torR1werepreparedforthreeseriesofexperimentsbydiluting4kgpressmudwith30,40and50Lofwatertoobtaindilutionratiosof1:7.5,1:10,and1:12.5,respectively.FeedsforreactorR2werepreparedatthesamedilutionratiosbyaddingsewageinsteadofwater.Thepressmud/sewageandpressmud/watermixtureswereallowedtosoakfor4h,filteredthroughwiremesh(Ø0.5mm)toremovefibersandthefiltratewasfedintothereac-tors.ThecharacteristicsofthefeedsubstratearegiveninTable1.2.3.BioreactorsystemTwoUASBreactorsofvolume20Leachwereusedinthisstudy.Thecylindricalplexiglasreactorshadaninternaldiameter10cmandaheightof190cm(H/D10)withagasliquidseparatoratthetop(diameter,20cm;height,20cm)withaneffluentportat15cmfromthebottomofthegasliquidseparator.Sevensamplingportswereevenlyfixedovertheentireheightofthecolumnat25-cminterval.Thegasliquidseparatorhousedaninvertedf