Effect of coagulation on mechanism of ultrafiltration membrane fouling and flux recovery by backwashing

摘要

Application of ultrafiltration in the treatment of industry wastewater is typically limited by fouling, which is mainly caused by pore blocking, pore constriction, caking or all the mechanisms integrated. In this study ultrafiltration combined with coagulation was employed to treat the secondary effluent of textile wastewater. The effect of coagulation on the efficiency of backwashing and fouling mechanisms was investigated in ultrafiltration. Compared to ultrafiltration alone, ultrafiltration combined with coagulation provided high flux recovery. A rapid decrease of flux took place at the beginning due to internal pore constriction, followed by cake development on the surface of the membrane. With increased coagulation addition, the flux became large, and cake development was no longer the dominant mechanism of the flux decline. In order to analyze the mechanism of membrane fouling,the cake filtration model, which was derived from Darcy's law, was established whether the coagulation was added or not. It was shown that cake filtration model had good fit of the data when coagulation was not added. However, the model changed with some deviation as coagulation was present.