Nitrogen Removal by Simultaneous Anammox and Denitrification under Low Temperature: Preliminary Batch Trials

Abstract

 The simultaneous anaerobic ammonium oxidation (anammox) and heterotrophic denitrification (SAD) process has been proposed for the nitrogen removal from domestic wastewater. In the SAD process, anammox bacteria are inoculated into the denitrification reactor. Nitrate is reduced to nitrite by heterotrophic denitrifiers. Then, nitrite is partly intercepted by anammox bacteria from heterotrophic denitrifiers and is reduced to N₂ using ammonium. The purpose of this study was to investigate the possibility of nitrogen removal by the SAD process in the 24－h batch mode at 20℃. Both samples of anammox sludge acclimated at 20℃ and activated sludge collected from a wastewater treatment plant were inoculated to 20mL synthetic wastewater at 1500 mg－MLSS/L, respectively. The nitrogen removal of 49－80% in the SAD process was demonstrated in a wide range of the C/N ratio of 0.4－1.5 with synthetic wastewater containing 70 mg－N/L nitrate, 50 mg－N/L ammonium, and acetate as the sole carbon source. The nitrogen removal in the SAD process was higher than the typical denitrification process at lower C/N ratio. However, the nitrogen removal in the SAD process at 20℃ was much slower than that obtained at 33℃ in a previous study (Park et al., J. Biosci. Bioeng., 123, 505－511) and highly depended on the activity of the heterotrophic denitrifiers. The high nitrite-producing activity of heterotrophic denitrifiers will be needed for developing the efficient SAD process at low temperature.