Control of TN and TP by the Pond and Wetland Integrated System

Abstract

Agricultural non-point source (NPS) pollution is an important pollution source and has been a serious threat to water quality safety; by contrast, point source pollution has been gradually controlled. In this chapter, we studied the control effect of artificial pond–wetland coupled systems on the reduction in total nitrogen (TN), total phosphorus (TP), and other pollutants in the Shenxi River watershed in Anji County by continuous sampling and monitoring. Results showed that from May to October in 2012, TN concentration was 3.7–6.4 mg/L, the TN removal rate was 9.9–63.4 % for artificial water ponds at the mouth of Zhongzhang River, and the removal efficiency of TN was strongly influenced by water TN concentration. For the artificial channel connected to the Zhongzhang River, water TN concentration was within the range of 2.5–5.1 mg/L, the TN removal rate was 5.0–48.1 %, and all TP removal rates were more than 30 % for the artificial ponds in Hongcun and Shenxi villages. At high water TP concentration of the artificial ponds, the removal effect was improved and the purification efficiencies of TN and TP were satisfactory in Hongcun village and Shenxi River downstream wetlands. The TN removal rate reached 25.0–96.0 %, whereas the TP removal rate was within the range of 21.8–98.1 %. Generally, the annual average TN removal rate was 60.4 % for the combined system of artificial pond–wetland, and the highest rate reached 86.8 %; meanwhile, the average TP removal rate was 78.6 %, and the highest rate reached 94.9 %. Therefore, the effect of combined artificial wetland system on nutrient reduction was rather good and helpful for NPS pollution management in the Shenxi River watershed.