High-rate nitrogen removal and microbial community of an up-flow anammox reactor with ceramics as biomass carrier

• A NLR and NRR of 1.16 g N L−1 d−1, 1.0 g N L−1 d−1 were achieved at HRT 1.5 h.
• The DO had little influence on nitrogen removal efficiency even it was 1.0 mg L−1.
• With the decrease in HRT, an enhanced for TN removal performance was achieved.
• Candidatus Jettenia asiatica showed high anammox activity even at 20 ± 2 °C.

Nitrogen removal performance and responsible microbial community of anammox process at low temperatures, and long term effect of dissolved oxygen (DO) on the performance of anammox process were investigated in a biofilm reactor, which was operated at 33 ± 1 °C (159 d) and 20 ± 2 °C (162 d) with an influent DO concentration of 0.7–1.5 mg L−1. Nitrogen removal recovered to 70% after 2 wk with the temperature drastically decreasing from 33 ± 1 °C to 20 ± 2 °C. At 20 ± 2 °C, the average effluent (NH4+–N + NO2−–N) concentration was 0.08 ± 0.08 mg L−1 at a hydraulic retention time of 1.5 h. A total nitrogen removal efficiency of the reactor of 1.0 g N L−1 d−1 was obtained for up to one month while the nitrogen loading rate was 1.16 g N L−1 d−1. Results of T-RFLP and 16S rRNA phylogenic analysis revealed that Candidatus Jettenia asiatica, as confirmed to adapt to low temperature, was considered to be responsible for the stable and high nitrogen removal performance.