Nitrogen removal efficiency of surface flow constructed wetland for treating slightly polluted river water

Restoration and water quality improvement of malodorous as well as slightly polluted rivers have been the global focus for environmental protection research and the development and construction of sponge cities. To date, constructed wetlands have been proven to be one of efficient methods to improve water quality. Nitrogen removal efficiency is a crucial indicator for the performance evaluation in slightly polluted river water treatment. Therefore, current study aimed to investigate the N removal efficiency of 3-stage surface flow constructed wetlands for water treatment. Results show that after a prolonged operation period, constructed wetlands were able to remove NH₄⁺-N, NO₃^--N, and TN by 38.4%, 22.3%, and 29.1%, respectively. Further investigations were carried out to investigate the removal efficiency of various N species in the 3-stage wetlands. Findings reveal that NH₄⁺-N was mainly treated in wetland #1 (W1) and wetland #2 (W2), while NO₃^--N and TN were in wetland #2 (W2) and wetland #3 (W3). Results also reveal that the influencing factors such as hydraulic retention time (HRT), water temperature (WT), and additional carbon source have significant effect on the removal performance of constructed wetlands.