Recovery of Ammonia and Production of High-Grade Phosphates from Digester Effluents (Municipal and Livestock).

Phosphorus recovery of anaerobically digested swine wastewater and side-stream municipal wastewater via MgCl₂ precipitation was enhanced by combining it with the recovery of NH₃ through gas-permeable membranes and low-rate aeration. The low-rate aeration stripped the natural carbonate in the wastewater and increased pH, which accelerated NH₃ uptake in the gas-permeable membrane system and benefited P recovery. The combined process provided quantitative (ca 100%) P recovery efficiencies. With active NH₃ extraction, the magnesium phosphates produced contained higher P₂O₅ grade (44-46%) and lower N, similar to the composition of the biomineral newberyite.