Research On The Relationship Between Extracellular Polymeric Substances And Membrane Fouling In MBR

Membrane bioreactors(MBR) have many advantages, but membrane fouling remains a major obstacle to their wide application. Extracellular polymeric substances (EPS) has been reported as an important factor governing membrane fouling. This research studies the effect of effluent quality on the different of aeration rates(2,4,6mg/L) and the sludge concentration(2,4.5,6,8,10g/L), examines the composition of EPS attached on membrane surface and in sludge mixed liquor at the same time, and concludes the relationship between EPS and membrane fouling. EPS mentioned above include soluble EPS(EPSs), loosely bound EPS(LB), tightly bound EPS(TB). The main experimental results and conclusions are as follows.①When dissolved oxygen concentration is 4mg/L and the mixed-liquor suspended solids is 4.5-6g/L, the pollutants removal rate is highest and the membrane fouling rate is lowest compared to the other conditions;②When dissolved oxygen concentration is higher (6mg/L) or the mixed-liquor suspended solids is lower (2g/L), EPSs and other dissolved organic matters in the gel layer on the membrane surface is the main reason for membrane fouling;③When dissolved oxygen concentration is lower (2mg/L) or the mixed-liquor suspended solids is higher (8g/L), EPSs, LB and zoogloea aggregate each other to form compact sludge layer which cause membrane fouling severely;④When dissolved oxygen concentration and the mixed-liquor suspended solids are appropriate, sludge floc will form dynamic membrane on the membrane surface, which can adsorb and degrade small soluble organics in sewage so as to alleviate the membrane fouling;⑤There is a linear relationship between polysaccharides and proteins of EPS in the mixed-liquor suspended solids and on the membrane surface and membrane fouling rate. With the increasing of proportion of proteins, membrane fouling rate is higher.