Pilot Study on Purification of Urban River Water by Using Tidal Flow Constructed Wetland

The pilot-scale tidal flow and vertical subsurface flow constructed wetland systems were built up in Xiannü-Lake Park of Shenyang City for urban river, Weigong River, water purification, their water purifying efficiencies were compared, and the performing conditions of the tidal flow wetland were optimized. The results showed that for the inflow river water with COD_Cr, NH₄⁺-N, TN and TP concentrations of 60.45-93.73, 2.33-4.79, 4.61-8.97 and 0.54-0.80 mg/L, the purifying efficiencies of tidal flow constructed wetland were 45.96%, 35.76%, 30.16% and 33.80%, which were 10.23%, 19.89%, 12.76%, 22.12% higher than those of subsurface flow constructed wetland, respectively. If the pilot-scale tidal flow constructed wetland system was performed following the conditions of “inflow - reacting for 5 h - outflow - being idle for 3 h”, the effluent water quality could meet the fifth grade of the Surface Water Quality Standards. The highest removal efficiencies of COD_Cr and NH₄⁺-N were in the middle layer of the tidal flow constructed wetland, while the highest removal efficiencies of TN and TP were in the top and bottom layers, respectively.