|DUBE, PATRICK - Former ARS Employee|
|GARCIA-GONZALEZ, MARIA - Instituto Tecnológico Agrario De Castilla Y León (ITACYL)|
Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2017
Publication Date: 1/31/2017
Citation: Vanotti, M.B., Dube, P., Szogi, A.A., Garcia-Gonzalez, M.C. 2017. Recovery of ammonia and phosphate minerals from swine wastewater using gas-permeable membranes. Water Research. 112:137-146.
Interpretive Summary: Conservation and recovery of nitrogen and phosphorus from animal wastes and municipal effluents is important because of economic and environmental reasons. In this paper we present a novel technology for separation and recovery of ammonia and phosphorus from liquid swine manure. Phosphorus recovery via magnesium precipitation was enhanced by combining it with ammonia recovery through gas-permeable membranes and low-rate aeration. The combination destroyed the natural carbonate alkalinity in the wastewater and increased pH, which accelerated ammonia uptake in the gas-permeable membrane system and improved the phosphate recovery. The process provided 100% phosphorus recovery efficiencies. Surprisingly, the magnesium phosphates produced contained very-high phosphate grade (46% P2O5) similar to commercial triple superphosphate fertilizer and consistent with the composition of a rare biomineral called newberyite that is found in guano deposits. This is an important finding because we were able to produce from wastes a valuable phosphate product with high P2O5 content favored by the fertilizer industry. An U.S. Patent was filed on the process.
Technical Abstract: Gas-permeable membrane technology is useful to recover ammonia from liquid manures. In this study, phosphorus (P) recovery via magnesium chloride precipitation was enhanced by combining it with ammonia recovery through gas-permeable membranes. Anaerobically digested swine effluent containing approximately 2300 milligrams (mg) ammonium nitrogen (N) per liter and 450 mg P per liter was treated using submerged membranes and low-rate aeration to recover the ammonia from within the liquid and magnesium chloride 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 alkalinity, increased pH and accelerated ammonia uptake by the gas-permeable membrane system, which in turn benefited P recovery. Phosphorus removal efficiency was > 90%, P recovery efficiency was about 100% and plant availability > 98%. With higher ammonia capture, the recovered P contained higher P content (37-46% P2O5 fertilizer grade), similar to the composition of the biomineral newberyite (MgHPO4.3H2O).