Control of agricultural non-point source pollution in Fuxian lake with riparian wetlands

To control eutrophication caused by agricultural non-point sources, integrated riparian wetlands were constructed and operated to intercept and treat the polluted water flowing into the Fuxian Lake. The influent and effluent mass loadings of total nitrogen (TN), total phosphorus (TP), suspended solid (SS), and chemical oxygen demand (COD) of riparian wetland systems were monitored for nearly one year. In addition, influent and effluent samples of each riparian wetland treatment unit were collected and analyzed for nitrogen (nitrate, nitrite, ammonia, and organic nitrogen) and phosphorus (organic phosphorus and phosphate). Results showed that the wetland systems removed various pollutants. There was a little seasonal change on the COD, SS, TN, and TP removal efficiency. There was no flow in the wetland during the winter. Therefore, the pollutant removal efficiency could not be determined. The nitrogen analysis results showed that ammonia nitrogen and nitrate nitrogen were the main nitrogen species present in the influent and effluent of each wetland functioning unit. Information obtained from this study is helpful in providing a design basis for similar wetland systems to control agricultural non-point source pollution.