Find in Library

Nitrogen removal through heterotrophic nitrification–aerobic denitrification (HN–AD) has been acknowledged as one of the most efficient and cost-effective nitrogen removal processes. This study involved the isolation of a novel HN–AD bacterium (<i>Rhodococcus</i> sp. S2) from landfill leachate. <i>Rhodococcus</i> sp. S2 exhibited high nitrogen removal performance under aerobic conditions without the accumulation of nitrite as an intermediate. The maximum removal efficiencies for NH₄⁺-N, NO₂⁻-N, and NO₃⁻-N were found to be 99.97 ± 0.3%, 99.79 ± 0.14%, and 83.53 ± 0.31%, respectively. Additionally, <i>Rhodococcus</i> sp. S2 demonstrated simultaneous nitrifying and denitrifying capabilities and showed a preference for utilizing NH₄⁺-N in mixed nitrogen sources. The optimal nitrogen removal conditions for <i>Rhodococcus</i> sp. S2 were as follows: sodium acetate as a carbon source, a C/N ratio of 16, a shaking speed of 200 rpm, a pH of 9, and a temperature of 35 °C. Genome sequencing results revealed the presence of nitrate reductases (<i>NarG</i>), nitrate oxidoreductase (<i>NxrA</i>), and nitrite reductase (<i>NirBD</i>) in <i>Rhodococcus</i> sp. S2, providing further evidence of its HN–AD capability. In treating raw wastewater under the aforementioned experimental conditions, S2 achieved a maximum TN removal efficiency of 57.16 ± 0.52% with the addition of sodium acetate as a carbon source. These results suggest that <i>Rhodococcus</i> sp. S2 might be a promising candidate for wastewater nitrogen removal.