Experimentation Study Of Pre-Treatment Of Light-Polluted Raw Water By Constructed Wetlands System

In this study, we used constructed wetlands to light-polluted raw water in the progress pretreatment. We have studied the removal efficiency of COD, TN, TP, ammonia, in the light-polluted raw water from Yellow river with altogether four kinds of wetlands (direct-flow Subsurface Flow Wetlands, to-and-fro-flow Subsurface Flow Wetlands, Surface Flow Wetlands with reed and Surface Flow Wetlands with Cattail). The experiment operated from June to December, 2005. The removal rates of COD and TN in the four experiment systems were satisfied. The experiment indicated that the removal rates of COD and TN in the two different subsurface wetland areas were 30%~65%, respectively under high hydraulic loading rate (4m/d). The removal rate of TN in the two different surface wetland areas was above 56%, but that of COD was under 10%. It is obvious that, the removal effect of COD in subsurface wetland is better than that in surface wetland. But the surfaces removed more TN.The outflow water quality under the planed load met the China standard for surface water resources (GB3838-2002).We increased the inflow load, and test the pre-treatment effect of subsurface wetlands. We increased the inflow load to 6.4m/d. On this condition, the removal rates of COD and TN in subsurface wetlands were 25%~62%, and around 30%.In winter, the removal efficiency of TN decreased obviously, but that of COD was still all right. And in winter, the raw water quality was better, so the outflow water quality still met GB3838-2002.