Effect of phosphorus limitation on the anammox process under different nitrogen concentrations

Abstract

The effect of phosphorus limitation on the nitrogen removal performance of the anammox process was investigated using continuous feeding reactors. When the phosphorus supply was stopped under an influent nitrogen concentration of 256 mg-N L−1, a high nitrogen conversion rate of 1.88 kg-N m−3 d−1 was maintained for 17 days. However, during the next 25 days, the nitrogen conversion rate decreased by 16.5%. Subsequently, nitrogen removal activity was recovered entirely by re-adding 0.1 mg-P L−1 of phosphorus. Similar tests were performed at different influent nitrogen concentrations. The results showed that the minimum phosphorus concentrations (MPC) in the influent required to maintain anammox activity at influent nitrogen concentrations of 379 and 502 mg-N L−1 were 0.2 and 0.3 mg L−1, respectively. These results indicate that the MPC increased with N concentration, with an MPC/N of 0.0005. A microbial community analysis based on the 16S rRNA gene amplicon sequencing revealed that two genera of anammox bacteria (Candidatus Kuenenia and Candidatus Jettenia) were presented. The dominant anammox bacteria changed from Candidatus Kuenenia to Candidatus Jettenia after the phosphorus-limitation tests.