[Purification efficiency of four different ecotypes of wetland plants on eutrophic water body]

Four wetland plant species (Acorus calamus, Typha orientalis, Lemna minor, Ceratophyllum demersum) were grown to compare the purification efficiency of wetland plant species alone and in combination on two eutrophic water bodies, high concentration sewage (influent) and low concentration sewage (effluent) in a wastewater treatment plant. The results showed that the concentration of total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) decreased sharply at the beginning of the test, but this decreasing trend slowed down in the late phase. The wetland plants could remove TN, TP and COD from wastewater effectively, but the degree of purification was different among different wetland plant species and among different combinations of these species. The wetland plant species were more effective in reducing TN when used in combination than used alone, and the combination of T. orientalis, L. minor and C. demersum had the highest efficiency in removing TN. The emerged plant species alone were more effective in removing TP in the high concentration sewage, but wetland plant combinations had a higher removal efficiency of TP in the low concentration sewage. In the high concentration sewage, the COD removal efficiency of wetland plants was 85.1%-96.0%, and A. calamus and T. orientalis had the highest removal efficiency. In the low concentration sewage, the COD removal efficiency of wetland plants was 76.9%-94.8%, and the highest removal efficiency was observed in the combination of A. calamus, L. minor and C. demersum. On the whole, the efficiency of wetland plants in removing TN, TP and COD was significantly greater in the high concentration sewage than in the low concentration sewage, and pH was improved in both treatments.