Realization of nitrite accumulation in a sulfide-driven autotrophic denitrification process: Simultaneous nitrate and sulfur removal

The study was based on the removal of nitrate and sulfide, and aimed to nitrite accumulation. The process of autotrophic denitrification driven by sulfide as an electron donor was investigated in a sequencing batch reactor. The research showed that autotrophic denitrification successfully started on day 22, and the removal rates of NO3-N and S2--S were 95.8% and 100%, respectively, when the S/N molar ratio was 1.45. When the S/N ratio was reduced to 0.94, the phenomenon of NO2--N accumulation was observed. NO2--N continuously accumulated, and the maximum accumulation rate was 55.3% when the S/N ratio was 0.8. In the batch test, the study showed that NO2--N accumulation was optimal when the S/N ratio was 0.8, and the NO2--N concentration increased with increasing NO3--N concentration at the same S/N ratio. Microbial communities also changed based on the high-throughput analysis, and Proteobacteria (59.5%-84%) was the main phylum. Arenimonas (11.4%-28.2%) and uncultured_f_ Chromatiaceae (5.7%-27.5%) were the dominant bacteria, which complete denitrification and desulfurization throughout the operating system. Therefore, this study provided a theoretical basis for the simultaneous removal of NO3--N and S-2(-)-S, as well as the accumulation of nitrite, and provided material support for anaerobic ammonia oxidation technology. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrates that autotrophic denitrification can effectively remove nitrate and sulfide while achieving nitrite accumulation; the accumulation rate of nitrite varies under different S/N ratios; changes in microbial community structure are closely related to the autotrophic denitrification process.