Demonstrating the CalPrex System for High-Efficiency Phosphorus Recovery


As utilities face stringent nutrient effluent regulations, phosphorus recovery has become a high priority for water resource recovery facilities (WRRFs). Many WRRFs that have implemented biological phosphorus removal in their treatment processes have seen detrimental effects on biosolids dewatering, primarily with struvite issues. Although phosphorus is a beneficial contributor to biosolids for land application, maintaining an adequate balance of phosphorus in the biosolids product is a concern for utilities. One option for alleviating these issues is to remove the phosphorus before dewatering by using a phosphorus precipitating process like the CalPrex® technology. During the CalPrex® process, brushite, a calcium phosphate mineral, is precipitated by reacting soluble phosphorus at pH 6.5 with calcium hydroxide. The brushite is then extracted to produce a valuable fertilizer that is interchangeable with other phosphorus fertilizers in the market.

This webcast will discuss the findings of Demonstrating the CalPrex System for High-Efficiency Phosphorus Recovery (project 5004), a pilot evaluation led by a collaboration of four utilities: Madison Metropolitan Sewerage District, Metro Wastewater Reclamation District, Milwaukee Metropolitan Sewerage District, and Massachusetts Water Resources Authority. The study sought to validate the CalPrex® technology, conducted a cost/benefit analysis of full-scale implementation at the partner facilities, and explored the end use viability of the brushite product.