Mechanism analysis and influence of pH on fouling properties of EPS from membrane fouling layer

Solution pH influences the surface charge and structure of solute as well as those of membrane,consequently heavily affects the interaction between solute and membrane,deposited amount of solute on membrane surface and membrane flux.Extracellular polysaccharides(EPS) are one of important foulants of membrane surface in membrane bioreactor(MBR).EPS were obtained from membrane fouling layer of treating wastewater MBR.Based on the determination of membrane flux,filtration resistances and deposited amount of EPS on the membrane surface as well as the mechanism analysis of membrane fouling,the influence of solution pH on the PVDF membrane fouling of EPS obtained was investigated.The membrane fouling caused by EPS in MBR follows the model of deposition resistance.EPS deposition on membrane surface leads to membrane fouling.As pH of EPS solution increases,the repulsion between EPS and membrane surface goes up,depositing resistance of filtration goes down and deposited amount of EPS increases.When pH is 7.0,deposited resistance of filtration,deposited amount of EPS and flux are 3.34×1011 m-1,1.25 g/m2 and 9.8%,respectively.