[Fast Start-Up ANAMMOX Operation Strategy and Flora Characteristics of a Biofilter]

To achieve the rapid start-up of anaerobic ammonia oxidation (ANAMMOX) reaction at room temperature and sludge granulation, a small amount of ANAMMOX sludge was inoculated by an upflow biological filter reactor, and ANAMMOX was started by stage variable load and shortening hydraulic residence time (HRT) operation strategy. The reaction was evaluated, and the nitrogen removal characteristics of the biofilter were evaluated. The results showed that the biofilter started the ANAMMOX reaction in a medium-temperature (25-29℃) environment for 22 days. After 97 days of culture, the total nitrogen volume removal rate (NRR) reached 5.64 kg·(m³·d)^-1, the total nitrogen (TN) removal rate was close to 80%, and the average particle size of the granular sludge was 4.5 mm. High-throughput sequencing analysis showed that the biofilter formed a layered structure of nitrifying bacteria-heterotrophic bacteria, anaerobic ammonium oxidation bacteria (AAOB), and AAOB-heterotrophic bacteria from bottom to top. The various microflora synergistically denitrified, creating a low dissolved oxygen (DO) stable environment for AAOB, and the dominant population Candidatus Kuenenia (AF375995.1) was enriched. In addition, the removal process of pollutants along the path and the characteristics of sludge along the process were analyzed, and it was verified that the sludge in the reaction zone had good ANAMMOX activity. An ANAMMOX-biofilter reactor achieves rapid start-up of the ANAMMOX reaction, sludge granulation, and efficient operation by effectively maintaining the amount of bacteria and stabilizing the reaction conditions.