| Hollow fiber UF membrane with 1 105 and 2 104Da were used to treat the secondary effluent from Xi'an Bei Shi Qiao Sewage Purification center. The study investigated the characteristics of UF for the removal of turbidity, organic substances and bacteria. When MWCO of UF membrane is different, the removal efficiency of UF membrane for waste is different and the permeate flux decline with operation time is also different. At the same time the study investigated the effect of backwashing, feed-water recovery and pressure on membrane resistance.In order to realize automatic control of the UF system and date acquisition and improve the accuracy of experiment result, the UF automatic system was used to meet the need of continuous experiment.The results show that UF can almost remove the turbidity completely. The permeate turbidity is lower than 0.5NTU when raw water turbidity isl.82~3.56 NTU. UF also performs physical disinfection well. It can achieve 99% removal efficiency of bacteria and E.coli. UF can remove organic substances in wastewater, but the removal efficiency is not high. Compared with UF membrane with 1 105Da, UF membrane with 2 104Da can remove organic substances in wastewater more effectively, but the difference is not obvious. In the initial period of a filtration circle, the permeate flux decline of UF membrane with 2x 104Da is larger, but the permeate flux decline is smaller afterwards.The results show that membrane fouling can be prevented more or less by backwashing. Lower feed-water recovery and higher pressure can keep higher flux. By the analysis of membrane fouling mathematic model, a conclusion can be drown that in the initial period of a filtration circle , permeate flux decline is resulted mainly by membrane pore blocking ;while in the final period, mainly by cake formation. Based on this, a two-stage mathematic model for the description mechanism of membrane fouling was proposed.
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