Study on Purification Effect of Sewage by Constructed Wetland in Lianhua Lake

Taking compound constructed wetland in Lianhua lake as research object,the purification efficiency of COD,TN and TP by the constructed wetland was analyzed to provide technical support for establishment of constructed wetlands in northeast China.The results show that the purification efficiency of COD in vertical subsurface flow wetland is better than that in horizontal subsurface flow wetland.Compared with the surface flow wetland,subsurface flow wetland has the better removal efficiency of COD.The constructed wetland in Lianhua lake has significant purification efficiency of TN.In various wetland units,down-flow wetland has the lowest removal rate of TN.the purification efficiency of TP in vertical subsurface flow wetland is better than that in horizontal subsurface flow wetland.The surface flow wetland shows the best performance in removal of TP.The substrate in horizontal subsurface flow wetland is easy to be blocked,and its purification function is affected.The constructed wetland shows the best performance in removal of COD and TP in August and September and in removal of TN in July,August and late September.The removal rate of TP in late October becomes negative.