Microfiltration membrane bioreactors (MF MBRs) have been extensively applied in wastewater treatment. Polysaccharide has been known to contribute significantly to organic fouling of NW membranes. In this study, the influences of ionic strength, divalent cations (Ca2+ and Mg2+) and organic foulant composition on polysaccharide fouling of NW membranes were investigated. Interfacial interaction parameters analysis showed that the cohesion and adhesion energies of polysaccharide increased with higher ionic strength, presence of divalent cations, and higher mass ratio of polysaccharide to protein. Fouling experiments indicated that MF membrane fouling by polysaccharide was also enhanced with increasing ionic strength, divalent cations addition, and higher polysaccharide concentration. Measured interaction energies confirmed the trends of the fouling profiles. Since the MF membrane surfaces were not completely coated with polysaccharide and some of the clean membrane remained exposed after fouling, it was consistently shown that feed solutions that induced higher fouling rates were associated with greater attractive and lower repulsive interaction energies among the polysaccharide molecules and between polysaccharide molecules and clean MF membrane. (C) 2013 Elsevier Ltd. All rights reserved.