Decomposition of EPS on the membrane surface and its influence on the fouling mechanism in MBRs

This study is aimed at elucidating the mechanism of the change of molecular weight distribution of EPS by bacterial activities after being attached on the membrane surface and the influence of EPS on the membrane surface on membrane fouling in a laboratory-scale MBR reactor. Change of EPS amount after accumulation on the membrane surface was measured under a non-substrate-fed condition. High molecular weight EPS (more than 1,000 kDa) accumulated on the membrane surface was found to be decomposed to smaller molecular-weight EPS and was finally mineralised decreasing the filtration resistance of the membrane. This natural recovery mechanism from fouling was explained by a mathematical model considering the production and decomposition of high- and lowmolecular weight EPS on the membrane surface.