Struvite formation to remove phosphorus from anaerobic swine lagoon effluent

Because of increased concern about surface water eutrophication From nutrient-enriched agricultural runoff many regulatory agencies are encouraging swine producers to decrease application rates of waste-based P. Increasingly strict regulations have created the need for phosphorus removal and/or reduction from anaerobic swine lagoon effluent. Struvite (MgNH4PO4. 6H(2)O) naturally forms in pipes and pumps of anaerobic lagoon systems that use recycled flush water to transport waste. Although struvite formation is generally considered a nuisance, encouragement of struvite precipitation and subsequent removal of the precipitate is a promising mechanism for efficient nutrient removal from swine lagoon effluent. In addition to reducing soluble phosphate concentrations, struvite can be used as a slow-release fertilizer and would therefore be a valuable waste by-product. Struvite production is used in a few locations to recover phosphorus from industrial and municipal wastewater, but it has not yet been successfully adapted to swine waste treatment. This study focuses on optimizing the chemical environment of swine lagoon effluent in order to efficiently precipitate and recover struvite. Effects of Mg and P concentrations and solution pH on P removal and precipitation kinetics are reported. Effective struvite precipitation would reduce effluent P concentrations, thereby allowing swine producers to recover nutrients for off-farm sale and minimize undesirable P accumulation in soil.