Different Constructed Wetlands for Treatment of Micro-polluted Raw Water

Four kinds of constructed wetlands,including plug-flow subsurface constructed wetland,to-and-fro subsurface constructed wetland,surface-flow constructed wetlands with reed and cattail,were constructed to treat micro-polluted raw water from Yellow River.The removal efficiencies of TN and COD were investigated.The results show that the plug-flow subsurface constructed wetland and to-and-fro subsurface constructed wetland have no obvious difference in removal of TN and nitrate nitrogen.The treatment efficiency of subsurface constructed wetlands is lower than that of surface-flow constructed wetlands.The removal rates of TN and nitrate nitrogen in surface-flow constructed wetland with cattail are 84.33% and 76.32% respectively,which is better than those in surface-flow constructed wetland with reed.Four kinds of wetlands have the COD removal rate of 30% to 65% without obvious difference.The constructed wetlands have an obvious purification for micro-polluted raw water from Yellow River,the effluent can satisfy the water quality standard for the city water supply source.