Pathways, influencing factors and mitigation strategies for N2O emissions in wastewater biochemical treatment

Wastewater treatment is a significant contributor to greenhouse gas emissions, and the generation and emission of nitrous oxide (N2 O) in wastewater biochemical treatment have become a hot research topic. The production mechanism of N2 O generation is complex, and emission characteristics vary widely depending on the processes and operating conditions. While numerous studies have investigated N2 O generation and emission in wastewater biochemical treatment, there is a lack of research on N2 O emission reduction strategies based on the analysis of N2 O generation pathways. This paper systematically discusses the primary pathways of N2 O production in wastewater biochemical treatment process, including NH2 OH oxidation, nitrifier denitrification, heterotrophic denitrification, and abiotic pathways. The factors influencing N2 O production are described, including wastewater characteristics such as carbon source, nitrogen source, salinity, process parameters such as dissolved oxygen, reflux ratio, and the distribution of microbial communities. This paper summarizes corresponding mitigation strategies, highlighting the effective reduction of N2 O production and emission through process optimization, coupling different biochemical processes, and enriching microbial communities with low N2 O production levels. Current research challenges and future development directions are assessed, emphasizing that model construction remains an effective method to study N2 O production and emission biochemical treatment of wastewater, with broad prospect in N2 O recovery research. © 2025 Harbin Institute of Technology. All rights reserved.