外文资料

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TotalconcentrationsandfractionsofCd,Cr,Pb,Cu,NiandZninwagesludge

frommunicipalandindustrialwastewatertreatmentplants

Abstract

Heavymetalsareoneoftheimportantfactorsthataffectthefinaldisposalofwage

paper,themetalmobilityandbioavailabilityofheavymetalsinwage

sludgewerestudiedbyusingCommunityBureauofReference(BCR)quential

extractionproceduretogetmoreinformationforthereasonabledisposalofsludge.

Sewagesludgewascollectedfromfivemunicipalwastewatertreatmentplantsand

dgewaxaminedforandthe

totalconcentrationsanddifferentchemicalfractionsofCd,Cr,Pb,Cu,NiandZn.

tents

ofZnandCuwerethehighest,followedbythenCr,NiandPbandthecontentofCd

asnosignificantdifferenceintotalmetalconcentrationbetween

onxtractedbytheBCR

quentialprocedurewereacidsoluble/exchangeable,reducibleandoxidizable

pHwasfoundtohaveprofoundeffectonthechemicalfractionsof

sludgeshadhigherproportionoftheacidsoluble/exchangeable

ralsludges,PbandCrwereprincipally

distributedinbetweentheoxidizablefractionandtheresidualfraction;Cuwasinthe

oxidizablefraction;Cdmainlyintheresidualfractioninmunicipalwastewater

treatmentplantsandhadhighpercentageofacidsoluble/exchangeableandreducible

fractionsinindustrialwastewatertreatmentplants;NiandZnhadhigherpercentage

intheacidsoluble/exchangeableandtheoxidizablefraction.

Keywords:Sewagesludge;Sequentialextraction;Fraction;Heavymetals;

Wastewatertreatmentplan

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uction

Sewagesludgecontainsmanyorganiccontaminants(suchasPCBsandPAHs),

-hazardoustreatmentsofwagesludgescan

degradepartsoftheorganicpollutants,effectivelykillsomepathogens,butheavy

metalsprentinsludgecannotberemovedbycom-montreatmenttechnologiessuch

ascomposting,ludgedisposalmayresultin

hedifferentwaysof

wagesludgedisposal,landapplicationislowcostandhigheffectiveandhasbeen

r,applicationofwagesludgemayresultinheavymetal

cthasreceivedmoreandmoreconcernin

edinformationonheavymetalsprentinwageisnecessary

esholdvaluesoftoxiclimitsheavymetalsin

sludgehavebeentinmanycountriesfortheirsafedisposaltoagriculturalfieldsand

udies

haveshownthattheavailablefractionofheavymetalsmainlydecidedthemobility,

ore,thequantification

ofdifferentchemicalfractionsofheavymetalsinwageisnecessaryforinformation

onmetalmobility,ther

hand,thesourceofheavymetalsinwastewa-ter,whetherdomesticorindustrial,also

hasprofoundeffectsonthetotalcontentaswellaschemicalfractionsofheavymetals

mple,industrialeffluentsarethepredominantsourceofCd,Hg,Cr

andNi,whileCuandZnaremainlyofdomesticorigin,andthemajorsourceofPb

a,mainlythedomestic

wastewaterandpartlyindustrialwastewaterandsurfacerunoffareudinmunicipal

atertreatmentplantsarerunbythelargescale

corporationstotreattheireffluentsbeforetheirultimatedischargeintoenvironment.

Sotheremightbesomedifferencesintotalcontentandchemicalfractionsofheavy

rentpaper,wagesludge

collectedfromfivemunicipalwastewatertreatmentplantsandthreeindustrial

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wastewatertreatmentplantsofpetrochemical,brewandpaperindustrywaxamined

forthetotalconcentrationsofCd,Cr,Pb,Cu,NiandZnandchemicalfractionsof

heavymetalstogetapreliminaryasssmentforthelandapplicationofwage

sludge.

alsandmethods

tionofwagesludgesamples

Wetanaerobicsludgesampleswereobtainedfromlec-tivewastewater

-pleswereair-dried,pasdthroughasieve

havingopeningsof2mmdiameterandstoredindryglassbottlesatroom

pHwasmeasuredin1:2.5sludgeandwatersuspensions.

Organiccarbonofthesludgesampleswasdeter-minedbyashingat360℃for2h.

Cationexchangecapacity(CEC)valuesweredeterminedfollowingtheprocedure

ontentsofphosphorus(P)andpotassium(K)were

opertiesofsludgesfromthelectivewastew-ater

plantsareprentedinTable2.

uentialextractiontestanddeterminationofheavymetals

Sequentialextractionwasperformedusingthethree-stepprocedure

recommendedbyCommunityBureauofRefer-ence,inwhichmetalsaredividedinto

acidsoluble/exchangeable,reducible-fractionandoxidizable-fraction.

Stepone:Ahalf-gramaliquotofsludgewastakenina50mLpolypropylene

centrifugetubeand20mLvolumeofaceticacid(0.11mol/L)

contentswereshakenfor16h(overnight)atambienttemperature(20℃)onan

ractwasparatedfrom

thesolidresiduebycentrifugation(4000rpm),decantedintoapolyethylenecontainer

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andstoredat4℃untillanalysis.

Steptwo:TheresiduefromSteponewasslurriedwithaportionofa20mL

volumeof0.1mol/ractionprocedure

describedabovewasfollowed.

Stepthree:TheresiduefromSteponewasdisperdin5mLvolumeofhydrogen

peroxide(8.8mol/L)anddigestedatroomtemperaturefor1hwithoccasional

d5-mLaliquotofhydrogenperoxidewascontinuedbyheatingthe

tubeto85℃tentswereevaporatedtoasmallvolume

(1–2mL).Twenty-fivemilliliterofammoniumacetatewasaddetothecooland

moistresidue,shaken,centrifugedandtheextractparatedasdescribedforStepone.

Stepfour:OnemillilitereachofHNO

3

,HClO

4

andHFwereaddedto0.1gdry

tentswereheatedonahotplateand

ooling,theresiduesweredissolvedin1%HNO

3

.

Theresultantsolu-tionsweresubquentlyudtodeterminetheheavymetals.

Ablankwasalsorunatthesametimeandnodetectablecontaminationwasfound

whenaliquotsofthequentialex-tractionreagentswereprocesdandanalyzedwith

centrationsofCd,Cr,Pb,Cu,NiandZnindifferentfractions

andtheresultantsolutionsofStepfourweredeterminedbyICP-MS.

ationandstatisticalanalysis

Thesummationofthreefractionswassubtractedfromthetotalcontenttogetthe

tisticalanalyswerecarriedoutonthe

StatisticalPackageforSocialScience.

sanddiscussion

ochemicalpropertiesofsludgefromlectivewastewaterplants

ThedatacontainedinTable2showthatthepropertiesofsludgefromlective

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geswerefrom250to560kg−1fororganic

carbon,4to26kg−1fortotalN,0.8to19.3gkg−1fortotalPand2.0to12.6gkg−1for

a,the

meancontentsofsoilwere10–40gkg−1fororganicmatter,1.0–2.0gkg−1forto-talN,

0.44to0.85gkg−1fortotalPandabout16g/kgfortotalK,ing

thecontentsofsludgewiththoofsoils,theformerhadhighercontentsoforganic

carbon,totalNandtotalP,yin2000showed

that70–80%ofthetotalcultivatedlandwaslackofenoughnutrientsandinsufficient

applicationoforganicfertilizerandexcessiveutilizationofchemicalfertilizershad

caudthedeteriorationoffarmlandquality,thecultivatedhorizonbecamethinner

alueofwagesludgevariesfrom4.4

valuesvariedfrom17.6to89.6cmolkg−wagesludgehasa

goodmanurevalue.

ontentofCd,Cr,Pb,Cu,NiandZninwagesludge

ThetotalcontentsofCd,Cr,Pb,Cu,NiandZninsludgeprentedinTable3

ral,the

sludgesampleshadhighercontentsofCuandZnbutrelativelylowercontentsofCr,

Ni,rwidevariationintheconcentra-tionrangesofheavymetals

ˇcanˇr,thetotal

con-centrationofCr,NiandPbinsludgesreportedbySˇcanˇCrand

chhigherthantheresultsofprent

therhand,theconcentrationsofZnandCunotedinthis

-ticalanalysis

showedthattherewasnosignificantdifferenceintotalconcentrationofmetals

arsthatifthe

dischargedstandardofindustrialwastewaterofChinawereenforcedstrictly,the

rceofmunicipal

wastewatertreatmentplantsincludesindustrialeffluents,domesticwastewaterand

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surfacerunoff,sothecontrolofheavymetalsinwastewatersourceofmunicipal

wastewatertreatmentplantswasharderthanthatofindustrialwastewatertreatment

plants.

“Dischargestandardsofpollutantsformunicipalwastew-atertreatmentplant”

risonofmetal

concentrationsinsludgewiththeirpermissiblevalues,theconcentrationsofCr,Ni

andCuinS3andCdandZninS5werebeyondthepermittedvaluesrestrictingtheir

oncentrationsinothersixsludgesampleswerebelowthe

ntaminationdue

toheavymetalswasariousprobleminChina,forexample,concentrationsofheavy

metalsin36,000hasampledfrom300,000habasicagriculturalprotectingcroplandin

2000werefoundtobebeyondthepermissiblelimitvaluesofstatestandardsfor

tenforcementofstatestandardsshouldbeobrvedtolimitthe

indiscriminateapplicationofsludgeincropland.

tablecontentsofCd,Cr,Pb,Cu,NiandZninwagesludge

Differentchemicalfractionsofheavymetalsreprentedaspercentoftheirtotal

concentrationsinsludgeshowninFig.1revealedthatthedistributionofthemetal

centageofF1frac-tionofalmost

allmetalsinS5andS6washigherthanothersludgesamplesowingtotheacidic

edtheimportanceofpH

tentofF1fractionofCrinS1,S2,S4

andS7andofPbinS1,S2,S4,S7andS8werebelowthedetectionlimitofICP-MS,

therefore,thewerenottakenintoconsiderationduringsta-tisticalanalysisandnot

um,CuandPbwerefoundtobeprincipallydistributedinthe

hadhigherpercentageofF1

(5.6–46.7%)butlowerpercentageofF2fraction(1.6–11.4%).ThepercentageofF1,

F2andF3forZnwasallabove10%.CadmiumwasprincipallydistributedintheF3

andresidualfractionsinS1andS4,andinF1andF2fractioninS5,S6,S7andS8.

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Amongdifferentchemicalfrac-tionsofheavymetalsinsludge,F1fraction

-centageof

F1forCdinS6,S7andS8wasmuchhigherinS1,S2,owedthat

themobilityandbioavailabilityofCdinsludgefromin-dustrialwastewatertreatment

e

theper-mittedvalueofCdinthedischargestandardwasverybelow,thehigher

percentageofF1fractionofCdinacidicsludgefrommunicipalwastewatertreatment

plantandsludgefromindustrialwastewatertreatmentplantsmaycaupoten-tial

snosignificantdifferenceinthe

centageofF1forNiandZnrangedfrom9.6

to51.1and10.0to51.1,obilityandbioavail-abilityofNiand

esultsarein

corroborationtothefindingsofS`ean`ionshouldbe,therefore,paidto

themobilityofNiandZninsludgesfrommunicipaltreatmentplantsandCdin

sludgesfromindustrialwastewatertreatmentplantsaftertheirapplication.

sions

Sewagesludgecollectedfromeightwagetreatmentplantshashighorganic

carbon,andisrichinnutrientlikeNandP,sotheycanbeudasgoodorganic

impactcaudbyheavymetalsaftertheiragriculturalapplication

oncentrationofCr,NiandCuinS3andCdand

ZninS5exceededthepermittedvaluesofGB18918-2002,soS3andS5cannotbe

etalconcentrationsin

sludgefromthreeindustrialwastew-atertreatmentplantsfailedtoshowany

significantdifferenceagainstthofrommunicipalwastewatertreatmentplants.

icsludge,the

percentageofF1fractionofmostheavymetalswashigherthanthatinneutralsludge.

Inneutralsludge,PbandCrwereprincipallydistributedintheoxidizableandresidual

mwasprincipallyinthe

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residualfractioninmunicipalwastewatertreatmentplantsludgewhileinindustrial

wastewatertreatmentplantsludgehighpercent-ageofacidsoluble/exchangeableand

andZnhadhigherpercentageintheacid

soluble/a,astatewidesurveyfor

compilationofdataontheproductionofsludge,theirheavymetalcompositionand

speciationshouldbecarriedoutfortheirenvironmentallysafedisposal.