Effect of Extracellular Polymeric Substances on Short-Term Membrane Fouling in Submerged Membrane Bioreactor

In order to study the influence of the extracellular polymeric substances(EPS) on the membrane fouling,eight sludge samples with different activities were used for the filtration experiments in a membrane bioreactor(MBR).During which,each experiment was conducted as a short-term filtration experiment with filtration time of 4 h,and the constant driving force used for the filtration was provided by a fixed water head drop of ΔH=78 cm.The results show that the filtration resistance caused by membrane fouling increases with increasing EPS concentration(the Pearson correlation factor rp=0.847),and the content of loosely bound EPS(LB-EPS) has positive correlation with membrane fouling resistance(MBR)(rp=0.753).The FT-IR spectra of the membrane fouling show that the LB protein is the dominant component of the fouling.The experiments also show that the zeta potential,viscosity(μ) and the SVI(sludge volume index) of the sludge well correlate linearly with the membrane fouling resistance,and the LB-EPS content is the main factor causing the variation of the zeta potential,viscosity(μ) and the SVI of the sludge.Through the dynamic analysis of the membrane fouling process,it was found that the filter cake layer formation period is the determinative period of controlling the membrane fouling in MBR,and the resistance of the filter cake increases gradually with increasing the accumulation amount of the EPS adsorbed on the membrane surface.The further analyses also show that LB-EPS and soluble EPS in sludge relate to the amount of EPS adsorbed on the membrane surface,and the FT-IR spectra of pollutants on membrane surface validate that the EPSs are the major pollutants of the membrane surface.