Phosphorus recovery from wastewaters of different sources with magnesium and dolomite lime

The removal and recovery of phosphate from three kinds of typical anaerobic digest wastewater-swine wastewater, chicken manure wastewater and sludge wastewater-with MgO and dolomite lime were investigated. Phosphate recovery efficiencies under different precipitant and reaction time were determined. During the treatment process, the kinetic rates of phosphate removals were determined. X-ray diffraction and scanning electron microscopy were used for precipitates characterization. The results showed that the products consisted of magnesium ammonium phosphate and calcium carbonate. Phosphate could be effectively removed with 200 mg/L of magnesium oxide in 4 h, and 500 mg/L of dolomite lime in 24 h. The removal rates were over 85.0% and 80.0%, respectively. The reaction with dolomite lime was slower, and the solid products obtained in the treatment contained more calcium carbonate than that obtained in the MgO treatment. It was estimated that the material cost for treating 1 m³ wastewater was 0.80 and 0.25 Chinese Yuan (RMB) for magnesium and dolomite lime, respectively. The cost of dolomite lime is lower, making it an ideal chemical.