Objective To investigate the purification effect of a combined system of rotating biological contactors and hybrid constructed wetlands on polluted river water, as well as the emission characteristics of greenhouse gases during the treatment process, and to provide technical support for the application and promotion of biological and ecological technology.

Methods With Liangtan River treatment project as the subject of investigation, the effect of the combined process in removing pollutants was analyzed, and the headspace and static box method were used to investigate the release pattern of greenhouse gases during the treatment process.

Results Throughout the year, the combined process showed a removal rate exceeding 90% for ammonia nitrogen (NH₄⁺-N), with an effluent concentration that met the Class Ⅱ standard in the Environmental Quality Standards for Surface Water(GB 3838-2002), and it also showed a good effect in removing total nitrogen(TN), total phosphorus(TP), and chemical oxygen demand(COD) and basically reached the Class Ⅴ standard. CO₂ was the primary greenhouse gas emitted by the combined process, and the release amount of gases displayed significant seasonal variations with greater emissions during the warm season. In addition, global warming potential (GWP) reached 2.00×10⁴ g/d in the warm season, which was 2.10 times that in the cold season. The mean annual emissions of N₂O, CH₄, and CO₂ were 2.61, 70.64, and 1.77×10⁴ mg/(m³·d), respectively.

Conclusion The combined process of rotating biological contactors and hybrid constructed wetlands shows a synergistic effect in achieving efficient pollutant purification and greenhouse gas emission reduction during the treatment of polluted river water.