Patent ID: 7560031

Claim:
A process for treatment of pond water from phosphoric acid production comprising the steps of: performing a first liming stage comprising the steps of: increasing the pH of the pond water to form a first liming stage precipitate; and separating the first stage precipitate from the aqueous solution to obtain a clarified water, wherein the first stage clarified water has a phosphorus and fluorine concentration of P 1 and F 1 ; performing a product generation stage comprising the steps of: mixing the clarified water with solids from a final liming stage to form a product generation stage precipitate, and separating the product generation stage precipitate from the aqueous solution to obtain a solid product and a re-clarified water wherein the solid product contains di-calcium phosphate values precipitated from the pond water; wherein the product generation aqueous solution has a phosphorus and fluorine concentration of P 2 and F 2 , such that the concentration of P 1 minus the concentration of P 2 divided by the concentration of F 1 minus the concentration of F 2 is greater than 100; performing a final liming stage comprising the steps of: adding lime to increase the pH of re-clarified water to form a final liming stage precipitate; separating the final stage precipitate from the water to form the solids from the final liming stage and the clarified treated water, wherein the solids from the final liming stage are the solids added in the product generation stage; and directing the clarified treated water for further use, treatment, or disposal.