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BiochemicalEngineeringJournal58–59(2011)79–86ContentslistsavailableatSciVerseScienceDirectBiochemicalEngineeringJournaljournalhomepage:ficationofhighnitratestrengthwastewaterGraceM.Nisolaa,MarkC.F.R.Redillasa,EulsaengChob,MidoekHana,NamjongYooc,Wook-JinChunga,∗aEnergyandEnvironmentFusionTechnologyCenter(E2FTC),DepartmentofEnvironmentalEngineeringandBiotechnology,MyongjiUniversity,Yongin,SouthKoreabKoreaEnvironmentInstitute,DivisionofWaterandEnvironmentalStrategyResearchGroup,Seoul,SouthKoreacIlshinEnvironmentalEngineeringCo.Ltd.,Seoul,SouthKoreaarticleinfoArticlehistory:Received6October2010Receivedinrevisedform18May2011Accepted25August2011Availableonline3September2011Keywords:LimestoneDenitrificationNitrateremovalSulfuroxidationPackedbedOystershellsabstractThreepackingmaterialsforsulfuroxidizingdenitrificationpackedbedsystemsseededwithacclimatedanoxicsludgewereevaluated.Twoporousmediawerepreparedviathermalfusionwithsodiumbicar-bonateasporogen:sulfurfusedwithpowdered(1)calciumcarbonate(CaCO3)(SCa)and(2)oystershell(SCr).Randomlypackedsulfurandlimestonegranules(S+L)mediawereusedasthecontrol.ResultsrevealedthatSCristhemostsuitablemediaasitexhibitedthehighestnitrateremovalsandlowestnitriteaccumulation.Ithasmacrovoidalporeswhichfacilitatedmicrobialattachment.Additionally,SCrhadthehighestCaCO3loadingperunitvolumeandhighestmediadissolutionratewhichwasfavorabletoavertpHdecrease.Butduetohighdenitrificationactivity,highsulfatelevelsinSCrmaynecessitateapost-treatmentsteppriortoeffluentdischarge.Duetopoorbiomassattachment,S+Lismostsensi-tivetochangeinfluidflowcondition.Ashydraulicretentiontimeisdecreased,S+Lexhibitedintensiveandirreversibleperformancedecline.InferiordenitrificationperformanceofSCawasmainlyduetolowCaCO3loadingperunitvolume,lowdissolutionkineticsandlowalkalinityconsumptionbydenitrifiers.UsingmodifiedStover–Kincannonkineticmodel,overallperformanceanddenitrificationcapacitiescanbearrangedasSCrS+LSCa.©2011ElsevierB.V.Allrightsreserved.1.IntroductionSulfuroxidizingdenitrification(SOD)featuresseveraladvan-tagesovertheconventionalheterotrophicdenitrification.AutotrophicSODmicroorganismsrequireinorganiccarbonsourcetherebyeliminatingthenecessityoforganiccarbonsupply[1,2].Whileachievinghighnitrate(NO3−–N)removalrates,biomassyieldsinSOD(0.40–0.57gVSS/gNO3−–N)aregenerallylowerthanheterotrophicdenitrification(0.8–1.2gVSS/gNO3−–N)therebyalleviatingtheinconvenienceofexcessbiomassproduction[3–5].ThereareseveralknownmicroorganismscapableofcarryingoutSODbutthemostcommonspeciesareThiobacillusdenitrifi-cansandThiomicrospiradenitrificans,whicharetypicallyfoundinsoil,sewageandpondsystems[1,6].Awell-knownstoichiomet-ricequationforsulfur-basedautotrophicdenitrificationisshowninEq.(1),whereinNO3−–Nreductiontonitrogen(N2)gasiscon-comitantwithinorganiccarbon(CO2)utilizationandsulfur(S0)∗Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddresses:[e-mail](G.M.Nisola),[e-mail](M.C.F.R.Redillas),[e-mail](E.Cho),[e-mail](M.Han),[e-mail](N.Yoo),[e-mail](W.-J.Chung).oxidationtosulfate(SO42−)[1,7].55S0+20CO2+50NO3−+38H2O+4NH4+→4C5H7O2N+55SO42−+25N2+64H+(1)Butlikeothertreatmentmethods,SODhasitsowndisadvan-tages.Withhigherstringencyinwaterqualitystandards,dischargelimitsforSO42−ladenwastewaterwereproposedorhavebeenrecentlyimplementedincertaincountries[8].Thus,SO42−ionsinSODeffluentsmayrequireadditionalpost-treatmentpriortoitsdisposal.Furthermore,SODconsumesalkalinityashydroniumionsaresimultaneouslygeneratedwithS0oxidation[9].Thuswithoutsufficientalkalinitysupply,thepHmaynotbemaintainedwithintheoptimalrange(pH=6–8)forthegrowthofSODmicroorgan-isms[10].ThelimitationsofSODhavebeenaddressedinliteraturethroughprocessoptimization,variationinprocessconfigurationsanddevelopmentofsuitableSODmedia[1,7,11,12].ParticularlyinSODmediadevelopment,theuseofelementalsulfur(S0)asasubstratehasbeenproposedbyseveralstudiesasitbearsnotoxicityandproducesminimalSO42−incontrasttoaque-oussulfursourceslikethiosulfateandsulfite[1,13,14].TheSODmediamustsupplybothalkalinityandsulfursources.Randomlypackedlimestone(CaCO3)andS0pelletsweretestedbyseveral1369-703X/$–seefrontmatter©2011ElsevierB.V.Allrightsreserved.doi:10.1016/j.bej.2011.08.01680G.M.Nisolaetal./BiochemicalEngineeringJournal58–59(2011)79–86studiesandfounditsatisfactory[1,15–19].ThemostrecentSODmediaisthethermallyfusedsulfurandCaCO3(SC)pelletswhereinhighdenitrificationrate(207gNO3−–N/dayton)wasachieved[20].However,thelowsurfaceareaoffusedSCpelletsmayleadtoinsuf-ficientmicrobialattachmentandwastewater-mediacontactwhichcouldconsequentlylimittheSODperformance[21].Withfewstud-iesonSODmediadevelopment,enhancementsonmediapropertiesmustbegivenspecialattention.Inthisstudy,newreactiveporousmediaweredevelopedasSODpackingmaterials.AlkalinitysourcesCaCO3orpowderedoys-tershells(POS)werethermallyfusedwithS0powder.Mediaporositieswereincreasedusingsodiumbicarbonate(NaHCO3)asporogen.Randomlypacked