Shewanella oneidensis MR-1 improving denitrification performance via influencing electron competition and distribution

Abstract Enhancement in denitrification rate with reduced intermediates accumulation has been a great challenge for nitrogen removal from wastewater. In this paper, it was found that the denitrification performance of two denitrifiers, Paracoccus denitrificans and Pseudomonas denitrificans, were both improved in the presence of Shewanella oneidensis MR-1. Data showed the introducing of S. oneidensis MR-1 promoted nitrate reduction rate by 40.3%–50.0% in Par. denitrificans reactors. Meanwhile, it also increased nitrite and nitrous oxide reduction rates by 32.5%–111.0% and 68.8%–694.0% respectively in Pse. denitrificans reactors. Further investigation illustrated S. oneidensis MR-1 generally increased the electron competition capability of nitrogen oxide (NOx) reductases in varying degrees. As the electron distribution to the downstream NOx reductases increased more than that of the upstream ones, it led to reduced intermediates accumulation. Finally, the effectiveness of S. oneidensis MR-1 on augment denitrification performance was also validated in carbon-limited condition.