Removal and Reuse of Ammonia and Phosphate by Precipitation of Struvite

The objective of this research was to efficiently remove ammonia from industrial wastewaters by precipitation of struvite. Struvite (MgNH₄PO₄) causes problems when it precipitates as a scale, which often occurs in anaerobic digesters and in nutrient-rich industrial wastewaters. Several processes have been patented for the removal of ammonia by precipitation of struvite. The emphasis in this research was on the engineering aspects of the process; i.e. minimizing cost and difficulty, minimizing the use of hazardous materials, and maximizing potential reuse of the residual struvite. The precipitation environment was optimized in terms of thermodynamic equilibria and kinetic parameters that controlled the granular structure of the precipitate. The resulting solid was a relatively pure struvite residual, easily separable and dewatered, and appropriate for reuse.