N2O reduction bacterial microbial community structure data
The N2O reduction rate is affected by the electron competition among denitrifying enzymes, limiting the potential to mitigate nitrous oxide (N2O) emissions using heterotrophic denitrifying bacteria during wastewater treatment. To overcome the interference of electron competition on the N2O reduction rate, it is essential to conduct in-depth research on how different types and combinations of electron acceptors (EAs) affect the structure of denitrifying communities and their corresponding N2O reduction capabilities and electron competition mechanisms. In this study, three denitrifying communities were enriched from activated sludge biomass with different EA: NO3- (R1), N2O (R2), and NO3- + N2O (R3). The N2O reduction capabilities were analyzed through electron competition batch tests, denitrification gene abundance, and microbial community structure. Electron competition caused suppression of the N2O reduction rate in all three reactors, regardless of the operating SRT (with and without biomass retention). The N2O reduction rate inhibition in R3 was lower than in R1 and R2 under both SRT modes, implying that R3 has adapted to EA competition during the enrichment process, and its electron flux directed towards NOS is less affected under conditions of EA competition. The study also showed that, NosZ II type N2O-reducers tend to be enriched when N2O serves as the sole EA, whereas nosZ I type N2O-reducers are more prone to enrichment when NO3- or NO3- + N2O are used as electron acceptors. Additionally, the genus Flavobacterium seems to play a significant role in alleviating the suppression of the N2O reduction rate caused by electron competition. This study revealed that enriching denitrifying communities with combinations of EAs can alleviate the inhibition of N2O reduction caused by electron competition.