Anaerobic ammonium oxidation (ANAMMOX) granular sludge was cultured during different operating conditions by an expanded granular sludge bed (EGSB) reactor and up-flow anaerobic sludge bed (UASB) reactors, and the characteristics of the granular sludge and microbial community were compared. The results showed that the flocculent ANAMMOX sludge can be granulated after being operated for 384 days by the EGSB and UASB reactors. The average particle size reached 1.17 mm and 1.21 mm, respectively. The particle size ratio of each range (<0.2, 0.2-1.5, 1.5-3, and>3 mm) was 6.06%, 60.05%, 25.25%, and 8.64% in the EGSB reactor, and 7.40%, 58.90%, 32.04%, and 1.66% in the UASB reactor, respectively. The results of scanning electron microscopy showed that the bacterial flora during different operating conditions were mainly Brevibacterium and Cocci aggregates. High-throughput sequencing results showed that the Shannon index of the EGSB reactor was 7.52, higher than the 7.18 of the UASB reactor on day 384; Proteobacteria was the main phylum of the sludge at each stage, and Planctomycetes increased from 3.30% to 12.30% in the EGSB reactor and 13.30% in the UASB reactor on day 384. The main ANAMMOX genera in the EGSB reactor were Candidatus Brocadia, accounting for 7.53%, followed by Candidatus Kuenenia accounting for 1.61%, whereas in the UASB reactor, Candidatus Kuenenia was the dominant anaerobic ammonia genus, accounting for 7.54%, followed by Candidatus Brocadia, which accounted for 3.69%. The proportion of dominant species was related to the change in environmental factors. The proportion of Candidatus Brocadia was positively correlated with the up-flow rate and nitrogen removal rate (NRR), but negatively correlated with hydraulic retention time (HRT). Candidatus Kuenenia was positively correlated with nitrogen removal efficiency (NRE), NRR, and HRT, but negatively correlated with the up-flow rate.
Keywords: anaerobic ammonium oxidation; culture conditions; granular sludge properties; microbial community structure.