Rapid Start-Up of Anammox Process with a Stepwise Strategy: System Performance, Microbial Community Succession and Mechanism Exploration

Anammox has emerged as a primary alternative to conventional biological nitrogen removal because of its excellent nitrogen removal performance and minimal energy utilization. However, the slow growth and reproduction of anammox bacteria (AnAOB) leads to an overlong start-up period, which severely restricts the full-scale promotion and application of anammox in wastewater treatment plants. Therefore, in this study, a sequencing batch biofilm reactor (SBBR) equipped with combined packing was used to investigate the rapid start-up of the anammox process. The result showed that the anammox reactor started successfully in only 75 days using a stepwise strategy, and the total nitrogen removal rate (TNRR) increased from 0.02 kg N m-3 d-1 on day 1 to 0.23 kg N m-3 d-1 on day 75. The primary AnAOB was Candidatus Kuenenia with a relative abundance of 37.20% at the end of the start-up of the anammox reactor. Denitrifying bacteria, nitrifying bacteria, and hydrolytic bacteria were also detected in the reactor. The synergistic interactions between AnAOB and these bacteria facilitated the efficient removal of pollutants. This study can offer a potential approach for the start-up of anammox in domestic wastewater treatment plants, which is conducive to achieving widespread application of anammox.