Comparison of Oxygen Transfer and Uptake Between an Integrated Fixed-Film Activated Sludge (IFAS) Process and a Conventional Activated Sludge Process (ASP)

摘要

Integrated fixed-film activated sludge (IFAS) processes are a combination of biofilm reactorsand activated sludge processes, achieved by introducing and retaining biofilm carrier mediain activated sludge processes. We tested a full-scale IFAS process equipped withAnoxKaldnes media and coarse-bubble aeration. This process operated independently inparallel with an existing full-scale activated sludge process. Both processes achieved thesame percent removal of COD and ammonia, despite the double hydraulic load and doubleoxygen demand on the IFAS process. In order to prevent kinetic limitations associated withdissolved oxygen (DO) diffusional gradients through the IFAS biofilm and to avoid mediacoalescence on the reactor surface and promote biofilm contact with the substrate, high DOand high mixing requirements are specified for the IFAS system. These require an elevatedair flux in the IFAS process, which was much higher than that of the parallel activated sludgeprocess. Even though the air used per unit load removed should be the same for bothprocesses, the IFAS reactors were characterized by higher air flux and air use per unit loadtreated due to the high DO and mixing requirements. This directly affected the energyfootprint for aeration, which in this case was much higher for the IFAS system than activatedsludge.