Removal of struvite to prevent problems associated with its accumulation in wastewater treatment works.

Deposition of struvite within the infrastructure of wastewater treatment works can cause significant operating difficulties. A laboratory-scale, two-stage, continuously stirred tank reactor was developed to remove struvite to prevent problems associated with its deposition. Before any experimental work was conducted, the mixing regime within the system was determined using a pH-tracer response method. Perfect mixing conditions were achieved once the stirring speed reached 500 rpm. Experiments were conducted examining the effects of various process parameters such as retention time, pH, recycling rate, and ammonium concentration. By increasing the hydraulic retention time, the residual magnesium concentration decreased, with the optimum conditions occurring at 125 minutes.