Abstract: 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.

Abstract: A water producing system which is provided with a semi-permeable membrane treatment process A100 to produce membrane permeate A3 and concentrate A, a semi-permeable membrane treatment processB200 which is equipped with a treatment target water B branching means for branching treatment target water B2 into two or more to produce a membrane B5 and concentrate B6, and a semi-permeable membrane treatment process C300 which 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 C7 and concentrate C8, thereby producing fresh water from a plurality of kinds of raw water which differ in osmotic pressure.

Abstract: A water producing system which is provided with a semi-permeable membrane treatment process A100 to produce membrane permeate A3 and concentrate A, a semi-permeable membrane treatment process 8200 which is equipped with a treatment target water B branching means for branching treatment target water B2 into two or more to produce a membrane B5 and concentrate B6, and a semi-permeable membrane treatment process C300 which 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 C7 and concentrate C8, thereby producing fresh water from a plurality of kinds of raw water which differ in osmotic pressure.

Abstract: A pure water production apparatus and method are provided that effectively use an isobaric type energy recovery unit that can efficiently recover energy against feed water variation. In a pure water producing method supplying and having a plurality of kinds of feed water with different water qualities permeated through a semi-permeable membrane to produce the pure water, a portion (referred to as first feed water) of the plurality of kinds of feed water supplied to a semi-permeable membrane unit comprising the semi-permeable membrane is boosted by utilizing an isobaric type energy recovery unit that recovers pressure energy of concentrate discharged from the semi-permeable membrane unit, the rest (referred to as second feed water) of the plurality of kinds of feed water is boosted by a high pressure pump, and the boosted first and second feed water are supplied together to the semi-permeable membrane unit.

Abstract: 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.