The behavior of membrane fouling initiation on the crossflow membrane bioreactor system

A membrane bioreactor (MBR) system (i.e. an activated sludge system where the clarifier has been replaced with membrane filtration) has many advantages compared with the conventional activated sludge process. However a serious problems that has prevented this technology from reaching its potential is membrane fouling. In this study, the biomass was cultivated under three conditions: normal (high dissolved oxygen, DO); bulking; and normal conditions with low DO concentration. Membrane filtration tests were performed with cellulose acetate (CA), sulfonated polyethersulfone (SPES) and polyethersulfone (PES) membranes, respectively. Relatively hydrophobic PES membranes fouled more seriously than hydrophilic CA membranes. This phenomenon was especially significant under bulking conditions. Ultimate flux was almost equal for all three membrane types however, since the PES and SPES started with higher initial fluxes. Effluent quality was not affected by membrane fouling/flux but did deteriorate at low DOs.