Effect of Ca2+ and Fe3+ Addition on Nitrification-Denitrification Process in a Membrane Bioreactor

Study on the effect of Ca2+ and Fe3+ addition on nitrification-denitrification process in a submerged membrane bioreactor was conducted. The removal rate of total nitrogen and ammonia nitrogen was investigated. The result indicated that the ammonia nitrogen and total nitrogen removal rate increased from 75% to 85% and 55% to 75%, respectively, as the calcium concentration ranging from 0 to 150 mg/L, which indicated that the nitrification and denitrification process were promoted. Ferric ion of 50 mg/L obtained a considerable increase in TN removal from 55% to 70% ,with an increase of ammonia nitrogen removal rate from 75% to 83%. However, ferric ion concentration ranging between 100 mg/L and 150mg/L caused a decrease of both total nitrogen and ammonia nitrogen removal efficiency, indicating that the activity of nitrifying and denitrifying bacteria was inhibited.