Nitrous oxide recovery from wastewater via microbial denitrification

Nitrous oxide (N₂O), a potent greenhouse gas, poses a significant threat to global climate change. For a long time, researchers have predominantly focused on mitigating N₂O emissions from various sources in wastewater. However, the potential of N₂O for other applications and as a valuable energy resource has largely been overlooked. The microbial denitrification process, a key pathway in the nitrogen cycle, naturally produces N₂O as an intermediate product. The understanding of the mechanisms governing N₂O production and recovery during denitrification, particularly the metabolic pathways of heterotrophic and autotrophic denitrification, is improving but still incomplete. In this review, the latest advancements in N₂O recovery during microbial denitrification have been summarized. The review emphasizes the distinct metabolic pathways of heterotrophic and autotrophic denitrification, highlighting the factors influencing N₂O production in each pathway (e.g., inhibition of nitrous oxide reductase activity and carbon source regulation). Furthermore, the application potential of various emerging bioprocesses in N₂O recovery has been explored. While these processes have shown high N₂O recovery efficiency at laboratory scale, their practical application in wastewater treatment systems requires further development. Additionally, the recent research progress in N₂O collection technologies has been reviewed (e.g., gas stripping and membrane-contactor). This review will provide guidance for the future application of N₂O recovery via microbial denitrification, offering an integrated solution for synergistic greenhouse gas mitigation and resource recovery in wastewater treatment process.