Habib Etemadi

In this paper, membrane modification and aeration rate effects on antifouling properties of cellulose acetate (CA) membrane in membrane bioreactor (MBR) systems were examined and the obtained results were compared. In phase I and for membrane modification, zinc oxide (ZnO) nanoparticles, 0–0.75 wt.%, were embedded in CA membrane. In this phase, scanning electron microscopy and contact angle measurements were used to determine the surface properties of the membranes, and optimal nanocomposite membrane was used in MBR for filtration of activated sludge. In phase II, four levels of aeration rate with specific aeration demand per membrane area (SADm) of 1, 2, 3 and 4 m3/ m2 h was used to investigate the effect of aeration rate on CA membrane fouling. The obtained results showed that maximum improvement in hydrophilicity and porosity of CA membrane was observed at 0.5 wt.% loading of ZnO nanoparticles. Also, either low or high aeration rate had a negative influence on permeability and antifouling properties of CA membrane. Under very high aeration rate (SADm > 2 m3/m2 h), the floc and particle breakage occur which these small matters can penetration through the membrane pores and membrane pore blockage or irreversible fouling occurs. By increasing aeration rate, chemical oxygen demand removal was increased and decreased for CA membrane and activated sludge, respectively. Finally, it was observed that the influence of membrane modification on the improvement of antifouling properties of CA membrane was more than optimal aeration rate effect.