Aeration system design in integrated fixed-film ac

Aeration system design in integrated fixed-film activated sludge (IFAS)Aerationsystemdesigninintegratedfixed-filmactivatedsludge(IFAS)andmovingbedbiofilmreactors(MBBR)usingstainlesssteelpipediffusers,manifold,anddownpipesChandlerJohnson1,JoshuaP.Boltz21ChiefTechnologyOfficer,WorldWaterWorks,Inc.,4000S.W.113thSt.,OklahomaCity,OK731732BiofilmTechnologiesPracticeLeader,CH2MHILL,Inc.,4350W.CypressSt.,Ste.600,Tampa,FL33605(jboltz@ch2m.com)ABSTRACTAerobicintegratedfixed-filmactivatedsludge(IFAS)andmovingbedbiofilmreactors(MBBRs)useanengineeredaerationsystemconsistingofstainless-steelpipediffusers,manifold(orsubmergedairheader),downpipes,andmanuallyoperatedair-flowcontrolvalves.Theso-calledmedium-bubblediffuserhasalargediameter(i.e.,4-mm)orificethatissituatedalongtheundersideofthestainlesssteelpipediffuser.Therefore,medium-bubblediffusersarenotassusceptibletoscalingandfoulingasfine-bubblediffusers,andoperationalexperiencehasproventhatmedium-bubblediffusersrequiresignificantlylessmaintenanceth