Landfill-leachate-treatment-with-sequencing-batch-reactor-and-membrane-bioreactor

88N.Laitinenetal./Desalination191(2006)86–91settlinganddecanting.Fortheperiodof24h,21.5htheunitwasaerated,2hwassettling,and30minwasneededfordecantingandfeeding.AtthebeginningofAugustanaircontrolvalvewasinstalledtonitrification/denitrificationtankenabl-ingbettercontroloftheaerationandattheendofAugust,after61daysofoperation,theaeratedtimewasdecreasedto17.5h,andtimeforsettlingwasincreasedto3h.WhenMBRwasoperatedthenitrification/denitrificationtankhadavolumeof120landMBRtank60l.ThecyclesforaerationintheSBRunitwerethesameasinSBRoperation.TheMBRunitwasZeeWeed®10(ZW10)unitfromZenon.ZeeWeedZW10isfullyautomizedmembranebioreactorunitinwhichthemembranesaresub-mergedtoanaeratedtank.Membranefoulingispreventedbyairscouring(airflow2Nm³/h)andwithperiodicalbackwashingofthemembranes.Intheseexperiments,thebackwashingwasdonefor10severy60s.Membraneareaintheunitwas0.93m².AnewZeeWeed®500membrane(nominalporesizeof0.04µm)wasusedintheexperiments.Themembranewascleanedpriortousewith200ppmsodiumhypochloritesolutionandrinsedthoroughlywithwater.TheleachatewasanalyzedforpH,conduc-tivity,suspendedsolids,volatilesuspendedsolids,biologicaloxygendemand(BOD7),chemicaloxy-gendemand(CODCr),totalorganiccarbon(TOC),totalandsolublephosphorus,totalnitrogen,totalammonia(NH3+NH4–N),andnitrate-nitritenitrogen(NO3+NO2–N),alkalinity,andturbidity.ListofanalysesispresentedinTable2.Fromthesupernatantorpermeatealmostthesamesetofanalysesweremade.Themixedliquorwasana-lyzedforpH,suspendedsolidsandvolatilesus-pendedsolids.FromanalysesitmustbementionedthatBOD7wasanalyzedwithoutallylthioureaandincaseofeffluents,thevaluesincludesomeoxygenconsumptionfromnitrification.Itwasalsoob-servedthatthetotalnitrogenanalysisofthesuper-natantandpermeategavevaluessmallerthanex-pectedfromthetotalammoniaandtotalnitrite/nitratenitrogenconcentrations.TheoxidizerusedFig.1.AsimplifiedflowsheetofusedSBRandMBRequipment.ForSBRoperationonlynitrification/denitrificationtankwasusedandforMBRoperationthewholeequipmentwasinuse.Abbreviations:Nitr.=nitrific