| 摘要 |
PROBLEM TO BE SOLVED: To prevent the leakage of water to be treated to which particulates are added even when hollow fiber membranes are damaged and to suppress the degradation in the quality of permeated water by subjecting the water to be treated to external pressure filtration through the hollow fiber membranes. SOLUTION: The water to be treated side is set at the pressure higher on the outer side of the hollow fiber membranes by using a pressurizing means, such as a pump, and the water to be treated is supplied and is permeated fully or partly to the inner side of the hollow fiber membrane. The impurities larger than the pores of the membranes among the impurities included in the water to be treated are blocked by the skin layers on the outside surfaces of the hollow fiber membranes and are accumulated on the outside surfaces of the hollow fiber membranes. The filtration is continued in this state while the impurities accumulated on the outside surfaces of the hollow fiber membranes are removed by physical washing, such as backflow washing, for passing clean water and gas from the inner side toward the outer side of the hollow fiber membranes and, thereafter, the water contaminated water in the hollow fiber membrane module is once discharged to the outside of the hollow fiber membrane module and the filtration is repeated by again supplying the water to be treated.
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