LAUSR

Abstract Nitrous oxide (N2O) is largely produced during wastewater treatment. However, there is a lack of review on linking N2O production and mitigation with microbial communities in wastewater treatment. In this study, various microbial communities contributing to N2O turnovers are reviewed according to their functions in nitrogen cycle, including ammonia oxidizing bacteria and archaea, comammox bacteria, autotrophic denitrifying bacteria, heterotrophic denitrifying bacteria and non-denitrifying N2O reducers. Their metabolic pathways and enzymatic reactions of N2O production are demonstrated, including nitrifier denitrification, nitritation, archaeal N2O production and denitrification pathways. The N2O emission factor of the nitrifier denitrification pathway is generally higher than nitritation pathway, and that of denitrifying bacteria depends on species and electron acceptors. The mitigation strategies are developed according to the dominating microbial communities. Overall, this review illustrates a comprehensive characteristic of N2O production by microbial communities in wastewater treatment, which could contribute to the development of effective N2O mitigation strategies.