Patent ID: 7871522

Claim:
A system for producing high quality water from saline water or alternately producing power from two aqueous streams of different salt concentrations, which system comprises: a semipermeable membrane element capable of operating in either an RO or a PRO mode, which element has a first subchamber and a second subchamber separated by semipermeable membrane, said element also having an inlet and an outlet connected to said first subchamber and first and second ports connected to said second subchamber, a hydroturbine power generator, first conduit means connecting said outlet from said first subchamber of said element to said hydroturbine, means for delivering a liquid feedstream of high salt concentration water from a source of such saline water under high pressure which includes a second conduit leading to said first subchamber inlet, third conduit means having first and second branches connected to said first port of said second subchamber, means for supplying low salt concentration water to said second subchamber through said first branch, while said second branch serves as a discharge tube for aqueous permeate, and control means connected to said high salt concentration water feedstream delivery means and to said low salt concentration water supplying means for alternately operating said system either in a power-producing PRO mode wherein said first branch of said third conduit means operatively connects said low salt concentration water supply means to said first port of said second chamber so that water passes through said membrane to dilute high salt concentration water in the first chamber, and wherein at least some of a dilute stream exiting from said first chamber outlet flows through said first conduit means to said hydroturbine generator, or in a high quality water-producing RO mode wherein said first branch is closed to flow and said second discharge branch of said third conduit means is operatively connected to said second subchamber for flow of permeate therethrough, which permeate has passed through said membrane from the first chamber to which high salt concentration water is supplied.