Improvement of the Design and Purification Performance of Surface-flow Constructed Wetland

The technical design of small-scale surface-flow constructed wetland system was described with details of some associated purification effects of municipal wastewater with different concentrations.Plots were composed of three stages in series and some reforms were adopted in the design of the constructed wetland.Depths of the wetland was increased in order to form an anaerobic region in every plot,which had the same function as anaerobic tank and reduced the area of the wetland system.The new substrate,ceramic pellet,replaced soil and gravel as the stuffing of the wetland.Two kinds of wastewater with low and high concentrations were purified in two stages.The low concentration sewage was treated in the first stage,and the high concentration sewage in the second stage.For these two sewages,the average removal rates of COD in the 3rd plot were 86.98% and 93.69%,the reductions of TN were 84.27%,72.76% respectively,and the concentrations of NO~-_(2)-N and NO~-_(3)-N were low,the mean removal rates of PO~(3-)_(4)were 92.17%,95.78%,and removal rates of TP were 91.33% and 95.46%.The treatment efficiency of this surface-flow constructed wetland was influenced by temperature and the climate and was an effective technology in improving the water quality and restoring the aquatic ecosystems.