Abstract: Embodiments described herein provide systems and methods for a phosphate processing system with integrated sub-systems, such as a phosphoric acid plant, precipitation system, crystallizer system, rinsing system, granulation system, pond water system, organics removal system, and/or exhaust treatment system. Such sub-systems can be integrated with each other by using one or more output streams from one or more sub-systems as one or more input streams for one or more sub-systems. In some embodiments, the phosphate processing system can produce phosphoric acid, struvite containing fertilizer, fertilizer using recycled struvite, magnesium or fluoride containing compositions using recycled magnesium or fluoride, and other components using phosphoric acid collected from a phosphoric acid and gypsum composition or using sludge collected from a waste stream, for example.

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 fertilizer comprises a slow release source of phosphorus and a slow release source of sulfur. The slow release source of phosphorus may be struvite. The slow release source of sulfur may be polyhalite. The fertilizer may further contain a fast release source of phosphorus such as a water-soluble phosphorus-containing material. The fertilizer may be in the blended form or in the co-granular form. A number of methods may be used to make such co-granular fertilizers.

Abstract: Methods and apparatus for precipitating dissolved materials from an aqueous solution are provided. In an embodiment, the method comprises: introducing the aqueous solution into a reactor and introducing a source of magnesium (Mg) into the reactor in a quantity sufficient to cause the dissolved materials to precipitate into crystals. The source of Mg is introduced into the reactor in the form of particles of a Mg-containing material. The source of Mg has a solubility in the aqueous solution of less than about 1 g/L. Alternatively, the concentration of Mg in the reactor is less than about 0.03 mol/L. In an embodiment, the apparatus comprises a reaction tank having an inlet and an outlet and a hydration tank associated with the reaction tank and configured for hydrating a source of Mg in an aqueous solvent and introducing the source of Mg as a hydrated slurry into the reaction tank.

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: Apparatus and methods for removing solutes from wastewater are disclosed. An embodiment provides a reactor tank having a manifold located at or near an interface between a lower (upstream) section having a first cross-section and a higher (downstream) section having a second cross-section smaller than the first cross section. An inlet for wastewater to enter the reactor tank is located in or below the first cross-section. A recycling path is provided for removing wastewater from the manifold and recycling at least part of the removed wastewater into the reactor tank. An outlet for water to exit the reactor tank is located downstream from the manifold.

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: 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: Apparatus and methods for removing solutes from wastewater are disclosed. An embodiment provides a reactor tank having a manifold located at or near an interface between a lower (upstream) section having a first cross-section and a higher (downstream) section having a second cross-section smaller than the first cross section. An inlet for wastewater to enter the reactor tank is located in or below the first cross-section. A recycling path is provided for removing wastewater from the manifold and recycling at least part of the removed wastewater into the reactor tank. An outlet for water to exit the reactor tank is located downstream from the manifold.

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: A reaction tank useful for precipitating struvite from aqueous solutions such as wastewater comprises an aeration system. The aeration system includes air diffusers in the reaction tank. The air diffusers are located at a level below an outlet of the reaction tank. The airflow control mechanism comprises means for automatically controlling the flow of the stripping gas from the diffusers. The airflow control mechanism may be configured to automatically control the flow of stripping gas in response to a signal from a sensor measuring the pH of the aqueous solution the alkalinity of the aqueous solution or the concentration of dissolved carbon dioxide in the aqueous solution.