Recovery of ammonia and phosphate minerals from swine wastewater using gas-permeable membranes.

Gas-permeable membrane technology is useful to recover ammonia (NH) from liquid manures. In this study, phosphorus (P) recovery via MgCl precipitation was enhanced by combining it with NH recovery through gas-permeable membranes. Anaerobically digested swine wastewater containing approximately 2300 mg NH-N L and 450 mg P L was treated using submerged membranes plus low-rate aeration to recover the NH from within the liquid and MgCl to precipitate the P. The experiments included a first configuration where N and P were recovered sequentially and a second configuration with simultaneous recovery. The low-rate aeration reduced the natural carbonate, increased pH and accelerated NH uptake by the gas-permeable membrane system, which in turn benefited P recovery. Phosphorus removal efficiency was >90% and P recovery efficiency was about 100%. With higher NH capture, the recovered P contained higher PO content (37-46%, >98% available), similar to the composition of the biomineral newberyite (MgHPO·3HO).