Treatment of Polluted River Water Using a Combined Coagulation-Dynamic Membrane Process

A combined coagulation/dynamic membrane process was investigated for treating polluted river water. Polyaluminum chloride (PAC) was selected as coagulant based on jar tests, and the optimal dose was 100 mg/L. Effluent turbidity was studied as the marker of a dynamic membrane formation, and the removal of chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN) were surveyed to evaluate the process performance. The formation time of the dynamic membrane varied depending on the different influent turbidity. The COD removal efficiency was above 65% after 10 min operation and 70% after 60 min operation. TP was effectively reduced to less than 0.7 mg/L after formation of a dynamic membrane. The TN removal efficiency was less than 20%, as nitrogen is not effectively removed by coagulation/filtration processes. The majority of pollutants removal was attributed to the chemical coagulation - flocculation and dynamic membrane filtration, but filamentous bacteria also play a role.