Toray Industries, Inc.

Wakako Ogiwara

Hiroo Takabatake

Masahide Taniguchi

Provided is a fresh water production method applying a combined water-treatment technology employing a plurality of semi-permeable membrane units, the method enabling prevention of problems caused by growth of a biofilm and allowing effective use of an injected chemical agent and an injected neutralizing agent. The fresh-water production method produces fresh water by treatment of source water by a semi-permeable membrane treatment device, the concentrated water resulting from the treatment by the semi-permeable membrane treatment device is mixed with other source water, and the water mixture is treated by a second semi-permeable membrane treatment device. A first chemical agent is injected continuously or intermittently into the source water and a second chemical agent is injected continuously or intermittently into the source water.

Fresh water production method

A water producing system which is provided with a semi-permeable membrane treatment process Ato produce membrane permeate Aand concentrate A, a semi-permeable membrane treatment processBwhich is equipped with a treatment target water B branching means for branching treatment target water Binto two or more to produce a membrane Band concentrate B, and a semi-permeable membrane treatment process Cwhich is equipped with a first water mixing means for mixing one of the treatment target water B with at least part of the concentrate A, and subjects the mixed water to the semi-permeable membrane treatment to produce membrane permeate Cand concentrate C, thereby producing fresh water from a plurality of kinds of raw water which differ in osmotic pressure.

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Otsu, Japan

Wakako Ogiwara