2025 Volume 61 Issue 1 Pages 11-18
Tidal flow constructed wetlands (TFCWs) with a rhythmic sequential cycle of filled/wet and drained/dry phases can enhance nitrogen removal in wastewater treatment. However, the performance and mechanisms of nitrogen removal by TFCWs in the treatment of actual wastewater have not been investigated. In this study, a pilot-scale TFCW with common reed plants was established at a sewage treatment plant and operated with a 6－h filled/wet and 2－h drained/dry cycle for 11 months. Efficient substrates (pumice and zeolite materials)-to-sewage oxygen supply and organic compound removal were observed during the filled/wet period, and then the sewage was changed from aerobic to anaerobic conditions. Efficient nitrification and denitrification were also observed during the filled/wet period. Owing to efficient nitrification and denitrification, the pilot-scale TFCW showed higher nitrogen removal performance (37.9 g total-dissolved inorganic nitrogen/m2/d) than previous conventional CWs. The nitrogen mass balance analysis revealed that microbial reactions (82.97%), plant uptake (0.98%), substrate adsorption (0.05%), and discharge in effluent (15.99%) were the main factors affecting total inorganic nitrogen inflow in the TFCW over 11 months of treating actual sewage (26.11 kg), indicating that microbial nitrification and denitrification reactions play a major role in nitrogen removal.
