Recovery of magnesium ammonium phosphate from ammonia nitrogen wastewater by chemical precipitation

Batch experiments of magnesium ammonium phosphate (MAP) precipitation were conducted to examine the optimal conditions for recovering MAP from simulated NH₄⁺-N wastewater. The experimental results indicated that the precipitates consisted mainly of MAP when the pH was maintained between 8.0 and 11.0. The precipitates, produced at pH 10 and the molar ratio of n (NH₄⁺):n (Mg²⁺):n (PO₄^3-) was 1:1.4:1, were pure MAP, 3.14 g MAP was attained from 1 L simulated wastewater and the removal rate of NH₄⁺-N could reach 91.5%. It is shown that the application of chemical precipitation method can be promoted for the cost of it could be considerably decreased by recovering MAP.