Simultaneous nitrogen removal via heterotrophic nitrification and aerobic denitrification by a novel Lysinibacillus fusiformis B301.

Simultaneous nitrogen removal via heterotrophic nitrification and aerobic denitrification (HN-AD) has received widespread attention in biological treatment of wastewater. This study reported a novel Lysinibacillus fusiformis B301 strain, which effectively removed nitrogenous pollutants via HN-AD in one aerobic reactor while no nitrite accumulated. It exhibited the optimal nitrogen removal efficiency under 30°C, citrate as the carbon source and C/N ratio of 15. The maximum nitrogen removal rates were up to 2.11 mgNH 4 + -N/(L·h), 1.62 mgNO 3 - -N/(L·h), and 1.41 mgNO 2 - -N/(L·h), respectively, when ammonium, nitrate and nitrite were employed as the only nitrogen source under aerobic conditions. Ammonium nitrogen was preferentially consumed via HN-AD in the coexistence of three nitrogen species, and the removal efficiencies of total nitrogen were up to 94.26%. Nitrogen balance analysis suggested that 83.25% of ammonium was converted to gaseous nitrogen. The HD-AD pathway catalyzed by Lysinibacillus fusiformis B301 followed NH 4 + → N H 2 OH → NO 2 - → NO 3 - → NO 2 - → N 2 , supported by the results of key denitrifying enzymatic activities.