Study on the Treatment for High Concentration of Ammonia Nitrogen in Piggery Wastewater by MAP

Magnesium-ammonium-phosphate precipitation method (MAP) is a newly-developed technique to remove ammonia nitrogen from wastewater. In this study, MAP method has been studied by using MgCl₂-6H₂O and Na₂HPO₄-12H₂O as precipitators for treating highly concentrated ammonia nitrogen wastewater. The effect of pH value, formulas of precipitation and precipitator ratio on MAP precipitation efficiency has been examined. A lab scale study is conducted to optimize the reaction conditions by single factor experimentation and cross experimentation. The experimental results indicates that the effluent ammonia nitrogen and removal rate reaches 36.66 mg/L and 95.15% respectively when pH is 9.5,the mole ratio n(PO₄ ^3- ) : n(NH₄ ⁺) : n(Mg₂ ⁺) is controlled at 1 : 1 : 1.2 and the reaction time is controlled at 10 minutes.