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

Abstract 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 with 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 L. fusiformis B301 followed , supported by the results of key denitrifying enzymatic activities. Practitioner Points The novel Lysinibacillus fusiformis B301 exhibited the outstanding HN‐AD ability. The novel Lysinibacillus fusiformis B301 simultaneously removed multiple nitrogen species. No nitrite accumulated during the HN‐AD process. Five key denitrifying enzymes were involved in the HN‐AD process. Ammonium nitrogen (83.25%) was converted to gaseous nitrogen by the novel strain.