Aerobic-moving-bed-biofilm-reactor-treating-thermomechanical-pulping-whitewater-under-thermophilic

WaterResearch36(2002)1067–1075AerobicmovingbedbiofilmreactortreatingthermomechanicalpulpingwhitewaterunderthermophilicconditionsSigrunJ.Jahrena,*,JukkaA.Rintalab,HallvardØdegaardaaDepartmentofHydraulicandEnvironmentalEngineering,NorwegianUniversityofScienceandTechnology,N-7034Trondheim,NorwaybDepartmentofBiologicalandEnvironmentalScience,UniversityofJyv.askyl.a,P.O.Box35,FIN-40351Jyv.askyl.a,FinlandReceived20April1999;receivedinrevisedform17April2001;accepted15June2001AbstractThecontinuouslyoperatedlaboratoryscaleKaldnesmovingbedbiofilmreactor(MBBR)wasusedforthermophilic(551C)aerobictreatmentofTMPwhitewater.IntheMBBR,thebiomassisgrownoncarrierelementsthatmovealongwiththewaterinthereactor.Inoculationwithmesophilicactivatedsludgegave60–65%SCODremovalfromthefirstdayonwards.Duringthe107daysofexperiment,the60–65%SCODremovalswereachievedatorganicloadingratesof2.5–3.5kgSCODm�3d�1,thehighestloadingratesappliedduringtherunandHRTof13–22h.Carbohydrates,whichcontributedto50–60%oftheinfluentSCOD,wereremovedby90–95%,whilelessthan15%ofthelignin-likematerial(30–35%ofSCODin)wasremoved.Thesludgeyieldwas0.23gVSSgSCODremoved�1.Theresultsshowthattheaerobicbiofilmprocesscanbesuccessfullyoperatedunderthermophilicconditions.r2002ElsevierScienceLtd.Allrightsreserved.Keywords:Aerobic;Biofilm;Movingbedbiofilmreactor;Thermophilic;Thermomechanicalpulpingwhitewater1.IntroductionThermomechanicalpulp(TMP)isproducedbyrefiningwoodchipsattemperaturesabove1001C.TheyieldoftheTMPprocessis93–97%basedondrywood[1]implyingthat30–70kgton�1islosttothewater.TheorganiccompoundsinTMPwhitewaterconsistoflignin(40%),carbohydrates(40%)andextractives(20%)[2].Thermomechanicalpulpingwhitewateriswarm,nor-mallywithtemperaturesbetween501Cand801C,withaCODof1000–5600mgL�1[3].Processwatertreatmentathightemperaturewouldomitcoolingoftheprocesswaterandallowthetreatedwatertobereusedintheprocessesatthemillwithoutheating.Thus,investmentsincoolingfacilitiessuchascoolingtowersmaybeminimisedorevenavoided.Highermaintenanceenergyrequir