[Removal Efficiency and Mechanism of Ammonia Nitrogen in a Low Temperature Groundwater Purification Process].

. For the same period, the amount of ammonia nitrogen removal via oxidation continued to increase, with higher quantities removed in the upper filter layer than in the lower filter layer. Dissolved oxygen(DO) is the limiting factor in the further increase in the removal of ammonia nitrogen by oxidation. With an increase in the filtration rate, the adsorption time of ammonia nitrogen by iron oxides was shortened, and the adsorption amount was reduced. Meanwhile, the shortening of EBCT reduced the ammonia nitrogen removed by nitrification under the action of nitrifying bacteria in the unit volume of the filter material. Based on these findings, it is recommended that the thickness of the filter layer should be increased to improve ammonia nitrogen removal performance.