CalPrex + AirPrex®: Capture the Most P-Recovery

Phosphorus is a Limited Resource

Most phosphorus fertilizer used for modern day 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 AirPrex, the methods to effectively recover phosphorus entering a wastewater treatment plant were chemically acidify sludge or incinerated ash. These processes are prohibitively expensive if only used for fertilizer production.

Maximum Phosphorus Recovery,
Minimum Sludge Production

The combination of CalPrex + AirPrex captures 50%+ total phosphorus entering treatment plants, with a 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 and calcium chloride. 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%.

CalPrex + AirPrex: A Combined Approach

     Reduce Phosphate Recycle Load up to 90%
     Reduce Polymer Consumption up to 30%
     Reduce Disposal Costs up to 20%
     Reduce Maintenance Costs up to 50%
     Recover Over 50% of Total Phosphorus