title: Laboratory and in-situ reductions of soluble phosphorus in swine waste slurries.
abstract: Laboratory and field experiments were conducted using magnesium chloride (MgCl2) to force the precipitation of struvite (MgNH4PO4 x 6H2O) and reduce the concentration of soluble phosphorus (SP) in swine waste. In laboratory experiments, reductions of SP of 76% (572 to 135 mg P l(-1)) were observed in raw swine manure after addition of magnesium chloride (MgCl2) at a rate calculated to provide a 1.6:1 molar ratio of magnesium (Mg) to total phosphorus. Adjusting the pH of the treated manure to pH 9.0 with sodium hydroxide (NaOH) increased SP reduction to 91% (572 to 50 mg P l(-1)). X-ray diffraction of the precipitate recovered from swine waste slurry treated only with MgCl2 confirmed the presence ofstruvite. The molar N:P:Mg ratio of the recovered precipitate was 1:1.95:0.24, suggesting that compounds in addition to struvite were formed. In a field experiment conducted in a swine manure holding pond, a 90% reduction in SP concentration was observed in approximately 140,000 l of swine manure slurry treated before land application with 2,000 l MgCl2 (64% solution) at ambient slurry temperatures ranging from 5 to 10 degrees C.
authors.affiliation: University of Tennessee, Department of Agricultural and Biosystems Engineering, Knoxville 37901-1071, USA.
authors.forename: R T
authors.initials: RT
authors.lastname: Burns
authors.forename: L B
authors.initials: LB
authors.lastname: Moody
authors.forename: F R
authors.initials: FR
authors.lastname: Walker
authors.lastname: Raman
mesh_terms: D000383:Agriculture; D000818:Animals; D011232:Chemical Precipitation; D015636:Magnesium Chloride / Q000737:chemistry; D017616:Magnesium Compounds / Q000737:chemistry; D008372:Manure; D010710:Phosphates / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*; D012995:Solubility; D000069877:Struvite; D013552:Swine
chemical_list: D017616:Magnesium Compounds; D008372:Manure; D010710:Phosphates; D015636:Magnesium Chloride; D010758:Phosphorus; D000069877:Struvite