Patent ID: 9428412
Filing Date: 2016-08-30
CPC Classification: B01D,C01B,C02F

Claim Text:
1. A process for treatment of a feedwater stream with reverse osmosis membrane separation equipment, to produce a low solute containing product stream and a high solute containing reject stream, said process comprising: (a) providing a feedwater stream containing solutes therein, said solutes comprising (i) hardness, (ii) alkalinity, and (iii) at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution, said at least one molecular species comprising one or more of (1) at least some TOC, or (2) at least some silica, or (3) at least some boron; (b) effectively eliminating the tendency of said feedwater to form scale when said feedwater is concentrated at a selected pH, by treating the feedwater stream in a hydrogen form cation exchange resin to (i) remove substantially all hardness from said feedwater stream, (ii) remove substantially all alkalinity from said feedwater stream, and (iii) remove dissolved carbon dioxide created during removal of said hardness and of said alkalinity; (c) raising the pH of the product from step (b) to a selected pH of ten (10) or more, by adding a selected alkali thereto, to urge said at least one molecular species which is sparingly ionized when in neutral or near neutral pH aqueous solution toward increased ionization; (d) passing the product from step (c) above through continuously operated reverse osmosis membrane separation equipment, to concentrate said feedwater at a recovery rate of ninety percent (90%) or more; (e) maintaining a stable normalized production rate of said product stream; and (f) maintaining a stable silica rejection rate in said reverse osmosis membrane separation equipment.