Abstract: A water producing system is provided that produces fresh water by treating treatment target water A at a first semipermeable membrane treatment plant, that mixes concentrate resulted by the treatment carried out at the first semipermeable membrane treatment plant with treatment target water B, and that treats the mixed water at a second semipermeable membrane treatment plant to produce fresh water. A bypass line allows the treatment target water A to be mixed with the treatment target water B or the concentrate while bypassing the first semipermeable membrane treatment plant, so that the second semipermeable membrane treatment plant can operate even when any trouble occurs at the first semipermeable membrane treatment plant and treatment cannot be carried out thereby.

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.

Abstract: Disclosed is a fresh water generator for fresh water production, which is effective to prevent a membrane life from becoming worse by suppressing the load on the membrane of a second semi-permeable membrane treatment facility when the concentrated water produced by the treatment of a first semi-permeable membrane treatment facility, and water to be treated with different osmotic pressure there from are mixed and treated with the second semi-permeable membrane treatment facility by the fresh water generator which comprises a means for storing the concentrated water produced from the first semi-permeable membrane treatment facility and water (B) to be treated, which is separately supplied in a storage tank A and a storage tank B in such a manner that the flow rate (mixture ratio) of the concentrated water to the water (B) to be treated is maintained constant, and supplying the concentrated water and the water (B) to be treated from each of the storage tanks to the second semi-permeable membrane treatment facili

Abstract: A method is provided for precisely predicting the temporal variation of a membranous filtration resistance, the temporal variation of a transmembrane pressure, the temporal variation of a membranous filtration flux, or the temporal variation of a membranous filtration flowrate as occurs in filtrating a liquid to-be-filtrated with a membrane, in a membranous filtration method wherein the liquid to-be-filtrated is filtrated by the separation membrane with the transmembrane pressure as a driving force. The variation of the membranous filtration resistance, the transmembrane pressure or the membranous filtration flowrate (flux) with time is predicted in a case where the membranous filtration is continued while controlling the membranous filtration flowrate (flux) or the transmembrane pressure to a set value.

Abstract: A fine bubble diffusing tube that can generate fine bubbles evenly and uniformly even when the diffusing tube has a long length, a fine bubble diffusing device using such a tube and a submerged membrane separation apparatus are produced. The fine bubble diffusing tube is provided with a cylindrical supporting tube 1, and an elastic sheet 2 with fine slits formed therein, with the elastic sheet 2 being placed to cover the outer circumference of the supporting tube 1, so that, upon supplying a gas to a space between the elastic sheet 2 and the supporting tube 1, the fine slits of the elastic sheet 2 are opened to generate fine bubbles, and the supporting tube 1 has a length L of 1000 mm or more in the longitudinal direction, with gas supply units 4 serving as gas flow inlets being attached to the two ends of the supporting tube.

Abstract: A submerged membrane separation apparatus is provided that includes a separation membrane module and fine bubble diffusing tubes placed vertically below the module that can evenly and uniformly produce fine bubbles from vertically below the separation membrane module, even when the separation membrane module is large.