Abstract: A method for treating phosphate-containing wastewater, such as phosphogypsum pond water. The method includes the steps of: (a) adding a first cation to the wastewater to precipitate fluorosilicate from the wastewater; (b) adding a second cation to the wastewater to precipitate fluoride from the wastewater; (c) raising the pH of the wastewater to precipitate the second cation from the wastewater; (d) removing residual silica from the wastewater; and (e) precipitating phosphate from the wastewater. The precipitated fluorosilicate may be sodium fluorosilicate. The precipitated phosphate may be struvite.

Abstract: A method for treating, and recovering phosphate compounds from, phosphate-containing wastewater. The method includes the steps of: (a) removing fluoride from the wastewater; (b) recovering a phosphate compound from the wastewater by maintaining supersaturation conditions for the phosphate compound; and (c) polishing the wastewater. A silica removal step may be optionally performed after step (a) and before step (b).

Abstract: A method for treating, and recovering phosphate compounds from, phosphate-containing wastewater. The method includes the steps on (a) removing fluoride from the wastewater; (b) recovering a phosphate compound from the wastewater by maintaining supersaturation conditions for the phosphate compound; and (c) polishing the wastewater. A silica removal step may be optionally performed after step (a) and before step (b).

Abstract: A method for treating, and recovering phosphate compounds from, phosphate-containing wastewater. The method includes the steps of: (a) removing fluoride from the wastewater; (b) recovering a phosphate compound from the wastewater by maintaining super saturation conditions for the phosphate compound; and (c) polishing the wastewater. A silica removal step may be optionally performed after step (a) and before step (b).

Abstract: Methods and apparatus for precipitating dissolved materials from a solution involve reduction of fines. In an embodiment, the method comprises: introducing a solution into a reactor, causing the dissolved materials in the solution to precipitate into crystals under a first reaction condition, adjusting the reaction condition from the first reaction condition to a second reaction condition, maintaining the reaction condition in the second reaction condition to cause a sub-population of the crystals to dissolve, and adjusting the reaction condition from the second reaction condition to the first reaction condition. In an embodiment, the apparatus comprises a reaction tank, a recycling path and at least an acid injector which is configured for dosing an acid into solution flow in the recycling path.

Abstract: Methods and apparatus for precipitating dissolved materials from a solution involve reduction of fines. In an embodiment, the method comprises: introducing a solution into a reactor, causing the dissolved materials in the solution to precipitate into crystals under a first reaction condition, adjusting the reaction condition from the first reaction condition to a second reaction condition, maintaining the reaction condition in the second reaction condition to cause a sub-population of the crystals to dissolve, and adjusting the reaction condition from the second reaction condition to the first reaction condition. In an embodiment, the apparatus comprises a reaction tank, a recycling path and at least an acid injector which is configured for dosing an acid into solution flow in the recycling path.

Abstract: A method for treating phosphate-containing wastewater, such as phosphogypsum pond water. The method includes the steps of: (a) adding a first cation to the wastewater to precipitate fluorosilicate from the wastewater; (b) adding a second cation to the wastewater to precipitate fluoride from the wastewater; (c) raising the pH of the wastewater to precipitate the second cation from the wastewater; (d) removing residual silica from the wastewater; and (e) precipitating phosphate from the wastewater. The precipitated fluorosilicate may be sodium fluorosilicate. The precipitated phosphate may be struvite.

Abstract: A method for treating, and recovering phosphate compounds from, phosphate-containing wastewater. The method includes the steps of: (a) removing fluoride from the wastewater; (b) recovering a phosphate compound from the wastewater by maintaining super saturation conditions for the phosphate compound; and (c) polishing the wastewater. A silica removal step may be optionally performed after step (a) and before step (b).

Abstract: Formation of scale in a wastewater treatment system upstream of a struvite precipitation reactor is inhibited by injection of one or more of CO2 and H3PO4. The injection may be performed at multiple locations. Injection may be controlled based on one or more of pH, fluid flow and fluid pressure. Scale may be inhibited while maintaining production of precipitated struvite.