2003. Optimization of phosphorus precipitation from swine manure slurries to enhance recovery

to force the precipitation of phosphorus and reduce the concentration of soluble phosphorus (PO4 3–) in two swine wastes. One of the swine wastes tested contained a high concentration of PO4 3 – (initially ~ 1,000 mg/L), and the other swine waste tested contained a low concentration of PO4 3 – (initially ~230 mg/L). The precipitation reactions were performed to determine the required reaction time, pH, magnesium addition rate and seed material for future precipitate recovery work. For the high and low concentration waste, a 10-minute reaction time at a pH of 8.6 was sufficient to remove 98 and 96 % of the PO4 3 – from solution. A molar ratio of Mg2+:PO4 3 – of 1.6:1 was determined to be effective for PO4 3 – removal from both the low and high strength wastes. At a molar ratio of 1.6:1, the PO3 – in the high concentration waste was reduced from 590 to 12 mg/L. In the low concentration waste, the PO4 3 – concentration was reduced from 157 to 15 mg/L. Seeding the reaction did not significantly enhance the recovery process