Sourcesofmatri省略treatmentsystemMEdwards

BRIEFCOMMUNICATIONS1274ChineseScienceBulletinVol.50No.12June2005ChineseScienceBulletin2005Vol.50No.1212741276Sourcesofmatrix-boundphosphineinadvancedwastewatertreatmentsystemDINGLili1,LIANGHanwen1,ZHUYixin1,MOWeiheng1,WANGQiang1,RENHongqiang1,WANGXiaorong1,M.Edwards2&D.Glindemann21.StateKeyLaboratoryofPollutionControlandResourceReuse,SchoolofEnvironment,NanjingUniversity,Nanjing210093,China;2.VirginiaPolytechnicInstituteandStateUniversity,418DurhamHall(0246),Blacksburg,VA24061,USACorrespondenceshouldbeaddressedtoWangXiaorong(email:[e-mail])DOI:10.1360/982005-302Phosphine(PH3),ahighlytoxicandreductivegas,hasbeenexploredinbiogases[1,2]anditprovesalsotobeubiquitouseveninremoteatmosphericairataconcentrationintheorderof(pg—ng)/m3[3].Formorethanonehundredyears,sourcesandmechanismsofbiologicalphosphineformationinnaturalandengineeredenvironmentshavebeeninvestigatedanddiscussed[4].Anaerobicenvironmentswerereportedtobethemainsourceofphosphineemission[16].Matrix-boundphosphine,whichisdefinedastheamountofphosphinegasliberatedduringacidicorcausticdigestionofsolidsandsludgelikeenvironmentalsamples,hasbeendefinedbyGassmannandGlindemann[5].Morerecentstudieshavedemonstratedthatmatrix-boundphosphineoccurredinanaerobicdigestedsludge,manure,paddyfield,sedimentofreservoir,soilsandfluvialandmarinesediments[57,9].Previousresearchontheroleofphosphineinwastewatertreatmenthasturnedattentionalmostonlytotheanaerobicdigestionsystems,andmorethan85%ofphosphineinanaerobicdigestionsystemswasclaimedtobematrix-boundphosphine[8].Inthispaper,5differentwastewatertreatmentstagesfromafullscaleadvancedwastewatertreatmentplantareinvestigatedforthepotentialexistenceofmatrix-boundphosphineinanaerobicsludge,anoxicsludge,aerobicsludge,chemicalphosphateprecipitationsludgeanddigestedsludge.Resultsshowedthatallsourcescontainedmatrix-boundphosphine.Inparticular,thesludgesamplesweretakenfromthewastewatertreatmentsystem(WWTS)ofWuxiLionNathanTaihushuiBreweryCo.Ltd.inJiangsu,China.Thesystem,designedtotreat1200m3/dofbrewerywastewater,includesbiologicalnutrientremovalandchemicalphosphorusremovalprocesses,asillustratedinFig.1.Rawwastewater,afterpHadjustment,flowsintotheUpflowAnaerobicSludgeBlanket(UASB)reactor,andthenissequentiallyreceivedbyanaerobic,anoxic(withnitrateandnooxygen)andaerobicreactors.Intheanoxicstage,denitrificationoccurswhenitreceivesrecycledliquidfromtheaerobicreactorandreturnedsludgefromthesecondarysettler.Intheaerobicstage,phosphateisovertakenbyPolyphosphateAccumulatingOrganisms(PAOs)andthenremovedincombinationwithbiomassremoval.Therestofthewastesludgewhichissedimentedfromthesettlerisdigestedanaerobicallyanditseffluentistreatedbychemicalprecipitationwithaluminiumchlorideasprecipitant.Thetemperatureofthesystemis29.Fivelocationsofsampling()areshowninFig.1.SamplingdateswereApril14andOctober20,2004.Thesystemwasinastableoperationmodeduringthesamplingperiod.TheCODconcentrationofinfluentwas2371mg/LinApriland1618mg/LinOctober.DissolvedOxygen(DO)intheanaerobic,anoxicandaerobicstageswas0,3.7and5.0mg/Lrespectively.Fourtotwelvesludgesamplespersamplingpointweretakenandrefrigeratedindarkuntilanalysis.Matrix-boundphosphinewastestedfollowingthemethodbyGassmann[9];SuspendedSolids(SS)andVolatileSuspendedSolids(VSS)weremeasuredaccordingtostandardmethods[10].Fig.2showsconcentrationsofmatrix-boundphosphine,pH,SSandVSScontentsinthesamplesoffivestagesinAprilandOctober.Matrix-boundphosphinevariedsubstantiallywiththechangeofsamplingseasonandsamplinglocation.InApril,themaximumofmeanmatrix-Fig.1.Schematicdiagramoftheadvancedwastewatertreatmentsystem.,Samplingstages;UASB,upflowanaerobicsludgeblanket.BRIEFCOMMUNICATIONSChineseScienceBulletinVol.50No.12June20051275Fig.2.Meanmatrix-boundphosphineconcentration(a),pH(b)andsuspendedsolids(SS)aswellasvolatilesuspendedsolids(VSS)(c)ofvarioussludges.Anaero,anaerobicsludge;Anox,anoxicsludge;Aero,aerobicsludge;Digest,digestedsludge;Chem,chemicalprecipitationsludge.boundphosphine(66.2ngPH3/kgwetsludge)wasobservedinanaerobicsludgeoftheUASBreactor,fol-lowedbydigestedsludge(59.7ngPH3/kgwetsludge).Inaerobicsludge,thisvaluewasashighas45.4ngPH3/kgwetsludge.Chemicalprecipitationsludgeandanoxicsludgehadasimilarconcentration,of40.3and40.1ngPH3/kgwetsludge.InApril,ofallsources,theorderofmeanmatrix-boundphosphineconcentrationwas:anaerobicdigestedaerobicchemicalprecipitation≈anoxic.InOctober,thematrix-boundphosphineconcentrationdroppedsignificantlyinallsludgesampleswiththemaximumof18.6ngPH3/kgwetsludgeobtainedinaerobicsludge,whichisabout41%ofthevalueofthesamesludgeinApril.Slightlylowervalueswerefoundinanaerobicsludge(14.5ngPH3/kgwetsludge)andanoxicsludge(14.0ngPH3/kgwetsludge).Themeanlevelinchemicalprecipitationsludgewas8.09ngPH3/kgwetsludge.Indigestedsludge,theleveldecreaseddramaticallyto1.84ngPH3/kgwetsludge.InOctober,theorderofphosphineconcentrationwas:aerobicanaerobic≈anoxicchemicalprecipitationdigested.Ofallsamplestestedineitherseason,thehighestmatrix-boundphosphineconcentrationwasfoundalwaysintheanaerobicsludge.ThepHvalueofthe