Membrane aeration bioreactors for wastewater treatment: completely mixed and plug-flow operation

A laboratory scale membrane aeration bioreactor (MABR) with a void volume o f 1.351 was tested for its ability to treat synthetic wastewater. The MABR process couples aerobic biological wastewater treatment with the bubbleless mass transfer of pure oxygen through hollow fibre membranes. The biofilm t hat was formed on the surface of the hollow fibres utilised oxygen transfer red from the fibre lumen for the degradation of organics transferred from t he synthetic wastewater flowing over the biofilm. When operated as a comple tely mixed reactor at an organic loading rate of 24.5 kg chemical oxygen de mand (COD)/m(3)/day and a hydraulic retention time of 34 min, an 89% COD re moval efficiency was achieved. During plug flow operation, 86% COD removal efficiency was obtained at an organic loading rate of 5.8 kg COD/m(3)/day a nd a hydraulic retention time of 47 min. Regular membrane cleaning to contr ol biomass growth was necessary to prevent channeling. The ability of the r eactor to operate under plug flow conditions demonstrated that the biofilm plays a significant role in oxygen mass transfer. (C) 1999 Elsevier Science S.A. All rights reserved.