Study on optimization of coagulation-microfiltration combination process of micro-polluted water and membrane fouling

The coagulation-microfiltration(MF) combination process of treating micro-polluted water was studied.The effect of coagulation parameters such as dosage,pH and time were discussed and the results demonstrated that dosage and pH were the critical parameters,while time was not.The coagulation-microfiltration combination process could mitigate membrane fouling.Comparing two filtration methods,it was observed that filtration of coagulation floc suspention was better than filtration of supernatant.The effect of different coagulants on the removal of organics and mitigation membrane fouling in coagulation-microfiltration combination process were also studied.Ferric chloride and polyaluminium chloride(PAC) were used as coagulants.The results suggested that ferric chloride was slightly superior for micro-polluted water on the basis of CODMn and UV254 removal,while PAC was slightly superior on mitigating membrane fouling.By evaluating the recovery effect of the membrane permeability,characteristics of membrane fouling and its cleaning in a coagulation-microfiltration combination process were studied.The results showed that the membrane fouling caused by cake layer,microorganism and organic pollutants and inorganic pollutants accounted for 70%-80%,20%-25%,5%-8%,respectively.The coagulation-microfiltration combination process of micro-polluted water with tap water flushing could restore the membrane permeability effectively.