Pilot scale struvite recovery trials from a full-scale anaerobic digester supernatant at the City of Penticton Advanced Wastewater Treatment Plant

Pilot-testing of a fluidized bed reactor used to recover phosphate in the form of struvite from a full-scale anaerobic digester supernatant was conducted on site, at the City of Penticton Advanced Wastewater Treatment Plant (AWWTP). The main objective of this study was to demonstrate the ability of the reactor, developed by the UBC phosphate recovery team, to remove at least 70 % of the phosphate in the supernatant from a full-scale digester fed with a combination of primary and secondary sludge, from a biological nutrient removal wastewater treatment plant. Results showed that the reactor was capable of removing over 80 % of the phosphate from the digester supernatant. The operation of the reactor could easily be controlled to achieve any desired level of phosphorus removal up to 90%. Reactor operation was relatively trouble free after an initial commissioning period. By the end of the experiment, it was possible to leave the reactor unattended for periods of up to 5 days without incident. Analysis of the recovered struvite crystals showed essentially pure struvite (>99 % by weight) with small amounts of calcium (