Dynamic Membrane Formation Mechanisms of a Combined Coagulation Dynamic Membrane Process in Treating Polluted River Water at a Constant Pressure

The dynamic membrane formation mechanisms and filtration mechanisms were investigated at 4 cm and 8 cm water head drop (WHD). Flux variation, resistance plot curve shape, the relationship t/V - t and t/V - V were investigated to study the dynamic membrane formation and filtration. And effluent turbidity and particles size distribution were also used to demonstrate the effluent particles size. Based on the flux stability, the dynamic membrane formation time is 120 min and 70 min for 4 cm and 8 cm WHD respectively. According to the forces analysis of a streaming particle, the reason was given about less time is needed for the dynamic membrane formation at higher WHD. Through the analysis of the resistance curve plot and the relationship of t/V - t and t/V - V, the dynamic membrane firstly is formed by cake growth, then small particles were captured by the formed cake, in this stage internal fouling is the dominant mechanism. After the dynamic membrane formation, screening becomes leading operation for particles removal including lager particles and small particles. Turbidity was used to illuminate the suspended solids in the effluent. Effluent turbidity shows that the membrane module occupies the good ability for particles removal before the dynamic membrane formation. Particles size distribution indicates that particles removal ability was formed gradually.