Optimizing Struvite Production for Phosphate Recovery in WWTP

Struvite, a crystalline structure comprised of ions of magnesium $\left({\mathrm{Mg}}^{+2}\right)$ , ammonium $({\mathrm{NH}}_4–\mathrm{N})$ , and phosphate $({\mathrm{PO}}_4–\mathrm{P})$ , is commonly encountered in wastewater treatment plants (WWTPs) through struvite encrustation. The gradual accumulation of this crystal in pipes and fittings leads to high costs due to downtime and replacement of parts. Technologies that are used to reduce this problem are ideally located in biological nutrient removal plants downstream of anaerobic digesters, as high levels of ${\mathrm{NH}}_4–\mathrm{N}$ and ${\mathrm{PO}}_4–\mathrm{P}$ typically characterize anaerobic digester supernatants. In 2003–2004, two technical-scale, struvite recovery studies were conducted on-site at the City of Penticton, B.C., Canada and the City of Richmond, B.C., Canada using a novel technology developed by the environmental engineering group at the University of British Columbia. The results of these studies showed an average reduction of 80% in phosphate and a dense, spherical product, 5–10 times larger than any commercially available struvite to date. Overall, the recovery of struvite has enormous commercial potential, which results in WWTP becoming more sustainable, concurrently reducing problems typically associated with their operation.