CNP Process: CalPrex™ + MagPrex™

THE PROBLEM

Phosphorus is a Limited Resource

Most phosphorus fertilizer used for modern agriculture originates from phosphate rock. Phosphate rock is a non-renewable resource with limited reserves. To ensure sustainable food production for the future, it is critical to expand the recovery and reuse of phosphorus from waste sources. Prior to the development of CalPrex and MagPrex, the methods to effectively recover phosphorus entering a wastewater treatment plant were to chemically acidify sludge or incinerated ash. These processes are prohibitively expensive if only used for fertilizer production.

CalPrex-MagPrex-Flow-Diagram-wLabels

THE SOLUTION

Maximum Phosphorus Recovery, Minimum Sludge Production

The combination of CalPrex + MagPrex 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.

MagPrex 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. MagPrex reduces the phosphorus recirculation by 90%.