Abstract: The degradation of trace ammonia nitrogen in water by ammonia-magnesium phosphate precipitation method was studied, and the effects of reaction time, NH₄⁺/PO₄^3-/Mg²⁺ molar ratio and other factors on the degradation of ammonia nitrogen were discussed. The results showed that when 1 L of ammonia nitrogen in water when the initial concentration of 2 μg/mL, to optimize the reaction conditions as follows: Input N, P, Mg of the mole ratio of 1∶1.1∶1.4, the reaction time of 90 min, the water ammonia nitrogen removal rate can reach 78.12%. When it was applied to the ammonia nitrogen degradation of Jiuqu river, the degradation rate of ammonia nitrogen in water was reduced to 70.02% due to the various impurities in the water.

Key words: magnesium ammonium phosphate, ammonia nitrogen, method of precipitation, ammonia nitrogen degradation