Mitigating nitrous oxide emissions from low carbon to nitrogen ratio wastewater treatment: Utilizing sugarcane...

Sugarcane bagasse was recycled to produce fermentation liquid (FL) as a supplementary carbon source that was added to constructed wetlands (CWs) for regulating influent carbon to nitrogen ratio (C/N), and then being applied to investigate nitrogen transformations and greenhouse gas emissions. Results showed that this FL achieved faster NO₃^--N removal and lower N₂O fluxes than sucrose did, and the lowest N₂O flux (67.6 μg m^-2h^-1) was achieved when FL was added to CWs in a C/N of 3. In contrast, CH₄ emissions were higher by the FL addition than by the sucrose addition, although the fluxes under both additions were in a lower range of 0.06-0.17 mg m^-2h^-1. The utilization of FL also induced significant variations in microbial communities and increased the abundance of denitrification genes. Results showed the application of FL from sugarcane bagasse can be an effective strategy for improving nitrogen removal and mitigating N₂O emissions in CWs.