Roles of MnO2 on performance, sludge characteristics and microbial community in anammox system

The long-term impacts of MnO2 on performance, sludge characteristics and microbial community of biogranule-based anaerobic ammonium oxidation (anammox) process were evaluated in an up-flow anaerobic sludge blanket reactor. It was found that the total nitrogen removal efficiency of reactor was fluctuated between 90%–93% at 1–200mgL−1 MnO2. Notably, the specific anammox activity was increased to maximum value of 657.3±10.6mgTNg−1VSSd−1 at 50mgL−1 MnO2 and then slightly decreased, but still higher than that achieved at 0–15mgL−1 MnO2, which had similar variation trends to the content of heme c and extracellular polymeric substances in anammox granules. High throughput sequencing indicated that MnO2 could improve the microbial richness and diversity of anammox granules and Candidatus Kuenenia was always the dominant species, and its abundance continued to increase to 21.3% at the end of operational experiment. Therefore, MnO2 could be applied to enhance the anammox process and the optimal influent MnO2 concentration was lower than 50mgL−1 in view of the reactor performance and cost issues. [Display omitted] •Long-term impacts of MnO2 on microbial community in anammox system were investigated for the first time.•The best reactor performance was achieved when the influent MnO2 concentration was within 50mgL−1.•The SAA, heme c content, EPS and VS had the similar varying trends to NRR.•Relative abundance of “Ca. Kuenenia” increased with continuous addition of MnO2.