Effect of micro-aeration stirring on nitrogen removal in anammox reactor

Bottom micro-aeration was adopted for the Anammox reactor with the aim of enhancing the mass transfer and reducing the chemical oxygen demand (COD) in the reactor, thereby improving the nitrogen removal performance of the Anammox reactor. Under the condition of hydraulic retention time (HRT) of 17.1 h, the removal efficiencies of COD and nitrogen-containing pollutants in the Anammox reactor were investigated at 1.5 L/h, 12 L/h, and 45 L/h aeration rates respectively. The differences of microbial communities under aeration rates of 12 L/h and 45 L/h were analyzed by high-throughput sequencing. The results showed that COD removal efficiency was 63.4%, total nitrogen (TN) removal efficiency, nitrogen removal contribution from Anammox, and specific anaerobic ammonia oxidation activity (SAA) were 72.9%, 92.4%, and 0.25 ± 0.012 g-N/g-VSS/d respectively. These results indicate that a proper aeration rate can enhance the removal of both carbon and nitrogen in the reactor. Furthermore, at an aeration rate of 12 L/h, the abundance of Planctomycetes, a phylum containing anaerobic ammonium-oxidizing bacteria (AnAOB), reached 11.21%, and the abundance of the genus Candidatus Brocadia was 8.99%, both of which were higher than the values of 1.24% and 0.73% at an aeration rate of 45 L/h, respectively. This indicates that excessive aeration can inhibit the activity of AnAOB and reduce the nitrogen removal ability of the Anammox reaction. This study illustrates the impact of varying aeration rates on the carbon removal and nitrogen removal performance of an Anammox reactor, providing references for the practical engineering application of aeration in Anammox reactors.