High enrichment of heterotrophic nitrification-aerobic denitrification bacterial community achieved by shortening anoxic feeding duration in the sequencing batch reactor: feeding mode effect and mechanism

Heterotrophic nitrification-aerobic denitrification (HN-AD) has attracted increasing attentions due to its novel advantages of aerobic total inorganic nitrogen (TIN) removal in a single reactor. However, the low relative abundance of the HN-AD bacterial community within activated sludge confines the practical utilization of HN-AD. This study explored the effects of feeding modes (anoxic feeding for 10 min or 1 min compared with aerobic feeding), on nitrogen removal and the functional bacterial population in sequencing batch reactors. Aerobic feeding (shortening anoxic feeding duration to 0 min) led to the highest TIN removal (88.42 ± 4.00 %). Shortening anoxic feeding duration from 10 min to 1 min also increased TIN removal efficiency from 53.16 ± 7.48 % to 73.31 ± 5.92 %. High-throughput sequencing revealed the relative abundance of HN-AD functional bacteria within the aerobic feeding reactor, which increased more than 8.30 times compared with that in the reactor with anoxic feeding for 10 min, the dominant HN-AD bacteria were Comamonadaceae with a relative abundance of 13.90 %. Stoichiometric calculations showed the proportion of organic matter utilized by HN-AD bacteria increased up to 70.78 % with aerobic feeding, suggesting that high carbon availability could be the reason behind the improved TIN removal and HN-AD bacterial enrichment. The results demonstrated that the feeding mode of sequencing batch reactors significantly influenced the HN-AD bacterial population. This study proposed a methodology on highly enriched HN-AD bacteria by altering feeding mode to shorten the anoxic feeding duration, to achieve efficient nitrogen removal while reducing costs and energy consumption.