Patent ID: 7132052

Claim:
A water softener comprising: a cation exchange resin tank fluidly couple for discharging spent brine comprising monovalent and divalent ions; a fluid mixer valve couple to the resin tank and to a water tank to dilute the spent brine to a desire concentration of a regenerant salt; an ion-separation device fluidly couple to the fluid mixer valve to receive the dilute spent brine and separate the diluted spent brine into first and second streams, the first stream substantially comprising monovalent ions and the second stream substantially comprising divalent ions; and a reverse osmosis (RO) membrane fluidly couple to the ion-separation device to receive the first stream from the ion-separation device and produce a concentrate stream of monovalent ions and substantially demineralized water; wherein the concentrate stream monovalent ions is collected for reuse as regenerant salt.