| 摘要 |
PROBLEM TO BE SOLVED: To provide a purified water production system and a method performing an inexpensive and stable membrane filter operation, even in the case that algae generate in raw water. SOLUTION: The purified water production system 10 alternately performs a filter process and a washing process with chlorine at a normal operation time not generating a large quantity of algae, and a washing process without chlorine is performed between the filter process and the washing process with chlorine at an alga-generating time when a large quantity of algae generate. In the washing process, with chlorine backward washing with permeated water added with a chlorine type oxidant is performed, and in the washing process without chlorine, backward washing with the permeated water not added with the chlorine type oxidant is performed. Then, algae stuck to the filter membrane 18 are peeled off and removed by the washing process without chlorine and then when the washing process with chlorine is performed, cells of the algae are not destroyed by chlorine and the filter membrane 18 can be washed without clogging.
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