Efficient Removal of Ammonia-Nitrogen from Deliming Effluent by using Magnesium Ammonium Phosphate Precipitation Method

Ammonia nitrogen (NH3-N) pollutant has received much attention in the leather industry. An efficient strategy for removal of NH3-N from tannery wastewater was proposed by using a magnesium ammonium phosphate (MAP) precipitation method to remove NH3-N from deliming effluent with the highest NH3-N concentration among all leather-making effluents. Results showed that approximately 80% of NH3-N was removed from deliming effluent when reacting at P/Mg/N mole ratio of 1.2:1.2:1.0 and pH 9.5 for 20 min. The NH3-N and total nitrogen concentrations of tannery wastewater (a composite wastewater of all leather-making effluents) sharply decreased by treating deliming effluent with MAP precipitation, which greatly improved the biological treatment efficiency of tannery wastewater. The residual concentration of NH3-N in the treated tannery wastewater was less than 2 mg/L. The total phosphorus concentration of tannery wastewater increased by less than 0.4 mg/L, indicating that secondary pollution of phosphorus did not occur after MAP precipitation treatment.