Capture the Most Phosphorus
CalPrex™ + AirPrex®
The combination of CalPrex + AirPrex captures 50%+ total phosphorus entering treatment plants, with minimal addition of chemicals.
The CalPrex process harnesses the acidogenic bacteria power to acidify bio-P sludge. Over 60% of phosphorus solubilizes in the acid phase digestion process. Dewatering acidogenically digested sludge isolates the dissolved phosphorus (orthophosphates) in the centrate. The centrate is sent to the CalPrex reactor, where orthophosphates are precipitated by calcium hydroxide. By maintaining a pH solution of 6.5 or below, phosphorus is recovered as brushite (CaHPO4· 2H2O), a market-ready, high-quality fertilizer.
AirPrex converts the remaining orthophosphates in digested sludge to struvite (MgNH4PO4· 6H2O) by air stripping CO2 and adding magnesium chloride. Struvite is another market-ready fertilizer. AirPrex reduces the phosphorus recirculation by 90%.