Insight into the characteristics of microbial communities in a single-stage anammox reactor under different oxygen conditions

Stable partial nitritation and anammox (PN/A) are highly related to the interaction of microorganisms, but the characteristics of the microbial community and its link to system stability remain unclear. In this study, a stable PN/A system was obtained under a micro-aerobic condition in a lab-scale reactor. The characteristics of the microbial community in the stable PN/A were investigated and compared to unstable (anoxic and over-aerated) conditions using a high-throughput analysis. Under the micro-aerobic condition, the highest community richness was observed as well as the most abundant microbial correlation network. Comparatively, the microbial community diversity was lower under the anoxic condition (two-stage anammox process) and the over-aerated condition (unstable PN/A operation), and the correlation network structure was simpler as well. Further analysis suggested that micro-aerobic conditions (DO concentration less than 0.1 mg L-1) could drive a complicated microbial community through the enrichment of both aerobic and anaerobic bacteria, which might determine the stable nitrogen removal performance. Overall, this study confirms the succession divergence of microbial communities under different DO conditions and provides a better understanding of the link between the microbial community and PN/A operation.

Automated summary

This study achieved a stable partial nitritation and anammox system in a lab-scale reactor under micro-aerobic conditions, where the highest microbial community richness and most abundant microbial correlation network were observed. In contrast, lower microbial community diversity and simpler correlation network structures were found under anoxic and over-aerated conditions. This suggests that micro-aerobic conditions play a key role in driving a complex microbial community and determining stable nitrogen removal performance.