Treatment and Transformation of Nitrogen Pollutants in Polluted River Water Using a Combination of Macrophyte Pond and Subsurface Flow Constructed Wetland

Nitrogen pollution in medium-to-small rivers often brings about eutrophication to lakes. In this work, a composite technique consisting of retention pond (RP)-subsurface flow constructed wetland (SFCW)-stabilization pond (SP) was proposed in the present study. Results showed that RP-SFCW-SP can effectively remove COD, TN, and NH 4 + -N in the polluted river water. The hydraulic load and pollution load had little effect on the performance of RP-SFCW-SP. Temperature had no influence on the removal of NH 4 + -N, but slightly reduced TN removal in winter. Ecological kinetic models were used to analyze nitrogen transformation. Nitrogen mass balance and weight analysis showed that all the three units had high nitrification rates, which played a major role in the removal of NH 4 + -N. TN removal in RP and SP was mainly achieved by hydrophyte absorption. While nitrification-denitrification in SFCW played a major role in TN removal. The results showed that RP-SFCW-SP can be utilized to practically treat polluted river waters