发布时间 : 星期一 文章Fungi immobilization for landfill leachate treatment--2010更新完毕开始阅读
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QIWAPublishing2010WaterScience&Technology—WST|62.6|2010
Fungiimmobilizationforland?llleachatetreatment
JenjiraSaetangandSandhyaBabel
ABSTRACT
Thispaperinvestigatedtreatmentofland?llleachatecollectedfromNonthaburiland?llsite,Thailand,byusingimmobilizedwhiterotfungi,namely,TrametesversicolorBCC8725andFlavodon?avusBCC17421.EffectsofpHandco-substrateswereinvestigatedatdifferentcontacttimes.Threetypesofco-substratesascarbonsourceusedinthisstudyareglucose,cornstarchandcassava.Treatmentef?ciencywasevaluatedbasedoncolor,BOD,andCODremoval.InitialBODandCODwerefoundtobe5,600and34,560mg/L,respectively.TheoptimumpHwasfoundtobe4,theoptimumco-substrateconcentration(glucose,cornstarchandcassava)was3g/Landtheoptimumcontacttimewas10daysforbothtypesoffungi.Additionofglucose,cornstarchandcassavaasco-substrateatoptimumconditionscouldremove78,74,and66%ofcolor,respectivelyforT.versicolorand73,68,and60%,respectively,forF.?avus.Moreover,forT.versicolor,BODandCODreductionof69and57%,respectively,couldbeachievedatoptimumconditionswhenusingglucoseasaco-substrate.ForF.?avus,BODandCODreductionof66and52%,respectivelywereobtainedwhenusingglucoseasaco-substrate.Whiterotfungicanbeconsideredpotentiallyusefulinthetreatmentofland?llleachateastheycanhelpinremovingcolor,BODandCODduetotheirbiodegradativeabilities.
Keywords
JenjiraSaetang
SandhyaBabel(correspondingauthor)EnvironmentalTechnologyProgram,
SirindhornInternationalInstituteofTechnology,ThammasatUniversity,
RangsitCampus,P.O.Box22,Pathumthani12121,Thailand
E-mail:sjenjira@yahoo.com;
sandhya@siit.tu.ac.th
|biodegradation,color,co-substrate,immobilization,land?llleachate,whiterotfungi
INTRODUCTION
In
Thailand,
more
than
14
million
tons/year
or
conditions.Fungicanbeusedinpelletformbutthemaindisadvantagewithpelletcultureistheinternalmasstransportresistanceimposedduetothediffusionofoxygenandothernutrientspresent,aswellasthebiosyntheticactivity(Wittleretal.1986).Moreover,therearenorealisticmeansbywhichthestructureofthepelletscanbecontrolledtoreducethediffusionresistanceintheirinternalstructure,whichoftenimpairstheirbiosyntheticef?ciency(Prasadetal.2005).Therefore,searchforotherformssuchasintheimmobilizedformoversomemediacanbeanalternative.
Theimmobilizedcultureisexpectedtoimprovethemasstransferofoxygenandnutrientsforfungalmyceliabyprovidingalargeattachingsurfacearea.Polyurethanefoamservesasasupportmaterialforfungitomultiplyandgrow.Theadvantagesofusingimmobilizedmicroorganismsfor
40,000tons/dayofmunicipalsolidwasteisproducedinurbanareasalloverthecountrywithanannualincreasingrateofabout3%(PollutionControlDepartment2005).Undertropicalclimaticconditions,heavyrainfallduringmonsoonseasonyieldshugeamountsofleachatetobetreated,whereasthecapacityoftheexistingtreatmentsystemisusuallylimited.Inadequatelytreatedwateristhendischargedintothenearbywaterbody,causingseverepollutionproblems(Chiemchaisri&Srisukphun2003).Theutilizationofbiodegradativeabilitiesofsomewhiterotfungiseemstobepromising.Researchersarenowfocusingonwhiterotfungiforuseinbioremediationprocessessincetheseorganismshavetheabilitytodegradeawiderangeofenvironmentalpollution(Pointing2001).Theuseoffungiconstitutesanalternativemodeoftreatmentinaerobic
doi:10.2166/wst.2010.816
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J.SaetangandS.Babel|Fungiforleachatetreatmentpollutantdegradationarewell-known(Cassidyetal.1996).Besidesbeingeconomicallycheaperandeasiertohandle,theimmobilizedfungusisreusableforseveralbatches.Thedecolorizationcanbeachievedbytwomechanisms,eitherbyadsorptionoroxidativedegradationbytheenzymes(Fu&Viraraghavan2001).Whilemanystudieshavebeencarriedoutonbiodecolorization,forexample,decolorizationoftextiledyesandtheiref?uentsusingwhiterotfungi(Sathiyamoorthietal.2007),biologicaltreatmentofapulpandpaperindustryef?uentbyFomeslividusandTrametesversicolor(Selvametal.2002),anddegradationoflignininpulpmillwastewatersbywhite-rotfungionbio?lm(Wuetal.2005),noattentionhasbeenpaidtothetreatmentofleachatebywhiterotfungi.Thus,thisstudywasundertakentoexplorethepossibilityofusingwhiterotfungiforland?llleachatetreatment.Trametesversicolorwaschoseninthisstudybecauseofthepreviouslyshownpotentialfordecolorizationandorganictreatment(Benitoetal.1997).
Thisstudyinvestigatesland?llleachatetreatmentusingimmobilizedwhiterotfungi,namelyTrametesversicolorandFlavodon?avusonpolyurethanefoam(PUF)inbatchexperiments.Effectsofco-substratesascarbonsource,suchasglucose,cassavaandcornstarch,onthetreatmentef?ciencywereinvestigated.Treatmentef?ciencywasmeasuredintermsofcolor,BODandCODremoval.
METHODOLOGY
Fungiandleachatecollection
TwotypesoffungiusedinthisexperimentwereT.versicolorBCC8725andF.?avus17421whichwereobtainedfromBIOTECHCentralResearchUnit,ThammasatUniversity,Pathumthani,Thailand.Thefungiweregrowninculturetubesat258Cfor1weekcontainingpotatodextroseagar(PDA).
Freshleachatewascollectedfromapipeasdischargedfromland?lltothestabilizationpondinNonthaburiland?llsite(opendumpsite),Thailandandwasusedforthestudy.Theleachatewasstoredat48Ctoavoidanydecomposition.
WaterScience&Technology—WST|62.6|2010
Sub-cultureoffungi
Potatodextroseagarwasusedasaculturemedia.Theboiledagarwaspouredintoculturetubeswithcaps.Thetubeswerethenkeptinautoclaveat1218Cfor15minandcooleduntilsolidi?ed.ThefungiwasspreadoverthePDAintheculturetube.Temperaturewascontrolledat258Cfor1week.Sub-culturewasdoneonceaweektoobtainactivefungi.
Leachatecharacterizationbeforetreatment
Theleachatewas?lteredtoremovesuspendedsolidsbeforemeasurementandwasanalyzedforpH,SS,COD,BOD5,NH3-NaccordingtotheStandardMethodsfortheExam-inationofWaterandWastewater20thEdition(1998).Theheavymetals:Ni,Cr,Cd,Pb,andHg,wereanalyzedusingtheInductivelyCoupledPlasmaSpectroscopy(ICPOptima2100DV).ThecoloroftheleachatewasmeasuredbyusingADMITristimulusFilterMethod(HewlettPackardSpectrophotometerModel8452ADiodeArray).
MycelialsuspensionandimmobilizationoffungionPUFMycelialsuspension
Mycelialsuspensionwaspreparedbypunchingfourpiecesoffungifromtheculturetubebyusingthesterileloopin100mlofsterilepotatodextrosebroth(PDB).Cottonplugswereusedtoclosethe?asksandwereagitatedfor24hoursonaotaryshakerat150rpm.
PUFsterilization
80piecesofPUFwere?rstputintothe1,000mlPDBin2,000ml?askssothatPUFwasnottoocrowded.The?askswerepluggedwiththecottonandthensterilizedinautoclavefor15minutespriortouse.
FungiimmobilizationonPUF
To1,000mlofPDBcontaining80piecesofPUF,100mlofmycelialsuspensionwasaddedina2,000ml?ask.The
?asks
were
kept
at
the
ambient
temperature
(30–338C).ThePUFwerecoveredwithfungalmycelium
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J.SaetangandS.Babel|FungiforleachatetreatmentWaterScience&Technology—WST|62.6|2010
within4days.TenpiecesofPUFwithimmobilizedfungiwereusedforeachvaryingcondition.
variedbyusing1NNaOHand1NHClsolutiontopH3,4,5andone?askwasusedasacontrol.The?askswerepluggedwithcottonandcoveredwithaluminumfoil.All?askswereshakenat150rpmfor1to5daysandcolorremovalwasobserved.pHwasmonitoredonadailybasisandchangeswererecorded.Allprocessesweredoneundersterileconditionsatambienttemperature.
Biomassgrowthoffungi
To?ndthebiomassgrowth,10piecesofpolyurethanefoamcoveredwithfungalmyceliumforfourdaysinPDB(asabove)wereplacedin100mLofleachate.Thegrowthoffungiwasdeterminedeverydaybyweighingthe?askbeforeandafterthegrowthfor16days.Thisprovidedthebiomassgrowthinbothattachedandsuspendedform.Co-substrates(glucose,cornstarchandcassava)atdifferentconcentrationswerealsoaddedtoseetheeffectongrowthoffungi.Allprocessesweredoneundersterileconditionatambientairtemperature(30–338C).
Effectofco-substratesconcentrationoncolorremovalLeachate(100ml)wasadjustedtotheoptimumpHand10piecesofPUFwithimmobilizedfungiwerethenadded.Concentrationofco-substrate(glucose,cassava,andcornstarch)wasvariedat1,2,3g/L.Forglucose,higherco-substrateconcentrationsat4and5g/Lwerealsotested.Inone?ask,noco-substratewasadded(control).All?askswereshakenat150rpmfor15daysto?ndtheeffectofcontacttime.Theleachatewas?lteredandcolorremovalwasmonitored.
Batchexperiment
Batchexperimentswereconductedto?ndouttheoptimumpH,optimumdoseforeachco-substrateandtheeffectofcontacttime.Optimumconditionsarede?nedasconditionswheremaximumcolorremovalwasachieved.EffectofpHoncolorremoval
TenpiecesofPUFwithimmobilizedfungiwereputin?askscontaining100mlofleachate.ThepHineach?askwas
DeterminationofleachateatoptimumconditionRemovalofcolor,BODandCODwereanalyzedandcomparedwiththeleachatebeforetreatmentattheoptimumconditionsofpH,concentrationofco-substrateandcontacttime.
Table1
|Characteristicsofland?llleachate
Unit
Industrialef?uentstandard(PCD1996)
Value
Parameters
1.pH2.Color
3.Suspendedsolids(SS)
4.Biochemicaloxygendemand(BOD5)5.Chemicaloxygendemand(COD)6.Ammonia-nitrogen
7.TotalheavymetalconcentrationCdCr(Total)PbHgNi
Note:ND?Notdetectable.
–ADMImg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/L
5.5–9.0Nostandard
,50(notexceed150),20(notexceed60),120(notexceed400)TKN,100(notexceed200),0.03,0.25,0.2,0.005,1.0
5.339005,5265,60034,560182.101.2031.502.501.60ND
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J.SaetangandS.Babel|FungiforleachatetreatmentRESULTSANDDISCUSSION
Determinationofland?llleachatecharacteristicsThephysicalandchemicalcharacteristicsoffreshleachateascollectedfromNonthaburiland?llsitearecomparedwithindustrialef?uentstandardsinThailandandareshowninTable1.
Theresultsshowedthattheleachatewasquiteacidic.Thecolorofleachatewasblackwithahighamountofsuspendedsolids.Theammonianitrogenconcentrationwasnotveryhighindicatingthattheleachatewasfresh.Theheavymetalconcentrationswerebeyondthestandards.Crconcentrationparticularlywasveryhighwiththemaximumof31.5mg/L,exceedingtheIndustrialEf?uentStandardwhichis0.25mg/L.ThismightbeduetothemixingofsolidwastewithsometoxicwasteandalsoduetolowpHwhichincreasesthesolubilityofheavymetals.
Biomassgrowthoffungi
Asthefungineedtobesuppliedwithanexternalcarbonsource(Cerniglia1997),biomassgrowthoffungiinleachatewasstudiedbyvaryingdifferenttypesofco-substratesat1–3g/Landwithoutco-substrateaddition.Fungifollowedatypicalpatternofgrowthinresponsetothecarbonsourceintheenvironment.Typically,asingleunitoffunguswouldgrowrapidlyatthebeginning.Theexponentialphaseisfollowedbythestationaryphase.Similargrowthpatternswereobservedinthestudydonebyotherresearchers(Carlile&Watkinson1994).Afterthat,astheorganicmatterintheformofnutrientssuchasglucosebecamedepleted,growthoffungididnotincreasemuch.Thefungiconsumeandgrowsreadilyonavailablecarbonsourcesattheinitialstagesofgrowthandthenproducesecondarymetabolitesandextracellularenzymesforbiodegradationinthepresenceoflowconcentrationofnitrogen(Gramss&Ziegenhagen1999).
FromFigure1,itcanbeseenthatthebiomassgrowthwasstronglyin?uencedbytheconcentrationofco-substrates.Attheendoftheexperiment,thebiomassgrowthofT.versicolorwithglucose,cornstarch,cassavaandwithoutadditionofco-substratewas0.2378,0.2267,0.1348and0.0877gwetweight,respectively.Glucoseisthe
WaterScience&Technology—WST|62.6|2010
e0.25tG1ahcG2ae0.2G3l foCS1 lm0.15CS2 00CS310.1 rC1ep C2m0.05aC3rG0Control12345678910111213141516Day (s)
Figure1
|BiomassgrowthofT.versicolorinleachateatvaryingco-substrateconcentration(Note:G?Glucose;CS?Cornstarch;C?Cassavaat1,2,3g/Landw/o?withoutco-substrate).
mostfavorableco-substrate.Itisamonomericsugarthatfungicaneasilytransportintocellsanduseasenergy.Cassavaisacomplexsubstrateandfungihadtoproduceanenzymetodegradethemintomonomer?rstbeforetransportingintocells.Fungineedhighenergytoproduceenzymesandsecreteextracellularenzymestodegradecomplexorganics.
F.?avusrequiredmoretimetogrowascomparedtoT.versicolor.Thefungigrewalmostthesameratewith
differenttypesofco-substrateuntilDay5.However,glucose,cornstarch,cassavaandwithoutadditionwerestillthemosttoleastfavorableco-substrates(sameasinT.versicolor)after15daystimeperiod.
Attheendoftheexperiment,thebiomassgrowthofF.?avuswithglucose,cornstarch,cassava,andwithoutco-substrateadditionwas0.2223,0.2075,0.1598and0.0841gwetweight,respectively(Figure2).Highergrowthwithco-substratesindicatesthatadditionalcarbonsourcesservesasasourceoffoodforfungi.However,thefungicanalsogrowintheleachatewithoutco-substrateindicatingthatorganiccompoundspresentintheleachatecansupportthegrowthbutthegrowthisverylowascomparedwithco-substrate.
0.25etG1ahcG2a0.2elG3 foCS1 lm0.15CS2 00CS31 0.1rC1ep C2m0.05aC3rG0Control12345678910111213141516Day (s)
Figure2
|BiomassgrowthofF.?avusinleachateatvaryingco-substrateconcentration(Note:G?Glucose,CS?Cornstarch,C?Cassavaat1,2,3g/Landw/o?withoutco-substrate).