Treatment of water to remove certain ions therefrom

Claim 1

A two stage method of treating water to reduce concentrations of sulfate and hardness for use in a physical separation process where minerals contained in makeup water are concentrated by removing substantially pure water, producing sulfate ion concentrations in excess of 1500 ppm, consisting of the following steps: a. Conducting a portion of said concentrated mineral rich process water to a first reaction chamber, adding calcium hydroxide to the first reaction chamber in an amount sufficient to substantially increase calcium ion concentration and to produce hydroxide ion concentration in excess of 1000 ppm as calcium carbonate and in the presence of solid calcium sulfate precipitate calcium sulfate, and removing portion of solid calcium sulfate from the first reaction chamber; b. Transferring only the supernatant water from the first reaction chamber, to the second reaction chamber, adding raw makeup water to the second reaction chamber, the amount of raw water being several times greater than the amount of supernatant water from the first reaction chamber, together with sufficient amount of carbon dioxide or bicarbonate, to react with essentially all the hydroxide brought from the first reaction chamber forming carbonate and precipitate essentially all of the formed calcium carbonate; c. Transferring only the supernatant water from the second reaction chamber to said physical separation process; d. adding sufficient sulfuric acid to said physical separation process to prevent scaling therein; e. treating said supernatant water in said physical separation process to yield substantially pure water and a makeup water containing carbonate and sulfate hardness.