Effects of aeration partition ratio on nitrogen removal performance and the microbial community in the A ² /O process

The partition of the aeration zone is the key factor to control the A ² /O process, and it directly affects nitrogen removal efficiency. In this study, a pilot-scale A ² /O plant was operated for the treatment of real domestic wastewater, which has an effective volume of 10 m ³ . The nitrogen removal efficiency and variations in the microbial community were studied on four different proportions of the aeration zone. Optimal denitrification performance with removal efficiency of 82.7% was achieved with the ratio of anoxic zone (A) to aerobic zone (O) = 5.7/6.6, and the effluent total nitrogen concentration of 9.3 mg L ^–1 . The denitrification rate was the highest at this ratio, and the activated sludge exhibited good settle-ability. The microbial community structure was detected by high-throughput sequencing, the results demonstrated that a large proportion of the anoxic zone provided a more suitable environment for denitrifying bacteria. Thus, the diversity and relative abundance of denitrifying bacteria at the ratio of A/O = 5.7/6.6 (15, 1.54%) were higher than that of A/O = 2.6/6.6 (13, 1.01%) that resulted in overall higher total nitrogen removal efficiency.