Inhibition and recovery of UASB-Anammox process: Performance characteristics and microbial community dynamics in response to substrate concentration and dissolved oxygen exposure

Anammox process is a high-efficiency and low-consumption biological nitrogen removal technology that has recently attracted a great deal of attention. Many studies have focused on the changes in the nitrogen removal performance of the anammox process under inhibition. However, little mention has been made of microbial community, metabolic pathways, and the characteristics and differences among different inhibitors. In this study, a UASB-Anammox process was operated for 470 days during which the process underwent substrate inhibition and dissolved oxygen (DO) exposure. Characteristics and differences in performance inhibition and recovery were investigated in terms of process performance, sludge composition, and community structure. A high nitrogen removal rate of 3.72 kg-N/m3/d was achieved at an HRT of 2 h. The results showed that the suppression caused by the two shocks was reversible. DO exposure had a higher effect on anammox activity compared to substrate inhibition. Additionally, the dominant anammox genus changed from Candidatus Kuenenia to Candidatus Brocadia after DO exposure. A low-concentration influent and a short HRT to increase the nitrogen loading rate could effectively avoid the substrate inhibition and enhance nitrogen removal performance. The results provide a deep insight into the inhibition and recovery of anammox process, and also optimize the regulation of process performance.