| 摘要 |
A method of operating a membrane separator comprising a raw-water tank and, disposed therein, a membrane module constituted of many exposed hollow-fiber membranes, in which the burden to be imposed on the filter membranes is lessened and cleaning is effectively conducted to thereby secure a high recovery and enable a stable membrane filtration operation. The method of operating the membrane separator is characterized by comprising: a filtration step in which a differential pressure is applied to the upstream side (raw-water side) of the hollow fiber membranes and the downstream side (treated-water side) thereof to thereby filtrate the raw water; a physical cleaning step comprising conducting gas cleaning in which a gaseous cleaning medium is jetted into the upstream-side membrane module and back-pressure water cleaning in which a back-wash medium is fed from the downstream side of the hollow fiber membranes and passed through the hollow fiber membranes to the raw-water side thereof; and a drainage step in which the discharge water inside the tank is discharged from the system, the drainage step being conducted after the filtration step and the physical cleaning step are repeatedly conducted two or more times.
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