[Membrane filtration characteristics and its influencing factors in coagulation-microfiltration combination process for water purification].
A coagulation-microfiltration combination process was used to treat micro-polluted raw water in the intermittent operation mode. The effect of the operational parameters such as filtration time and aeration intensity, on the membrane filtration characteristics was investigated. An indicator J/p, defined as flux per unit pressure, was employed. At all the experimental conditions, J/p always fell down fast at first owing to membrane fouling, and then decreased slowly. But the initial decreasing rate and relative stable value of J/p in the latter period depended on the different operational parameters. J/p was greatly influenced by the filtration time, then the ratio of the filtration time to the ceasing time. Under the condition the filtration time was shortened by 1/2, the flux will increase by two times; when the ratio of filtration time/ceasing time was shortened, the flux was increased by only 50%. Higher J/p value could be achieved at the filtration time of 15 min and the ratio of filtration time/ceasing time of 3.8. Increased aeration intensity could enhance J/p to some extent. In the experiments, when the aeration intensity was increased from 2 to 4 m3/h, the membrane permeability was increased by about 15%; and the membrane permeability would not increased if the aeration intensity was continuously increased to 6 m3/h. Primary inorganic elements on the membrane surface at the present experimental condition were found to be Si and Ca from the element analysis.