Patent ID: 7470366

Claim:
A water purification system, comprising: a reverse osmosis unit capable of separating a supply stream of feed water into an RO permeate stream and an RO reject stream; a nanofiltration membrane for receiving the RO reject stream from said reverse osmosis unit and for removing non-monovalent salt impurities from the RO reject stream to produce a treated stream; and, an electrodeionization unit for producing an EDI product stream of purified water and comprising a diluting compartment for receiving a diluting feed stream from said RO permeate stream and a concentrating compartment for receiving the treated stream and for outputting a concentrate effluent stream; wherein the system produces an EDI product stream without using a recycle pump for recycling the concentrate effluent stream back to said concentrating compartment or said reverse osmosis unit; and further wherein said water purification system thereby reduces overall consumption of said feed water.