Study on Improvement of Pollutants Removal Efficiency by Partial Aeration in Wavy Subsurface-flow Constructed Wetland

Dissolved oxygen(DO) in constructed wetlands is considered to be the key restrictive factor for the removal of NH+4-N and COD.Therefore,three partial aeration measures including influent preaeration,aeration in the foreside of wetland and aeration in the backside of wetland,were adopted to intensify pollutants removal in the wavy subsurface-flow constructed wetland(W-SFCW).The experiment results show the influent preaeration has not an apparent effect,while the other two methods can improve the distribution of DO in the wetland,and the removal effects of COD and NH+4-N are remarkable.The removal rates of COD and NH+4-N in the wetland aerated in the foreside reach 62.12% and 93.5% respectively,while those in the wetland aerated in the backside reach 58.09% and 96.6% respectively.In the wetland aerated in the foreside,the removal of COD and NH+4-N is caused by the exterior aeration,while in the wetland aerated in the backside,the removal of COD is mainly caused by the ecological effect of wetland,and the exterior aeration is only used in the nitrification of NH+4-N.Therefore,from the point of view of oxygen demand and energy consumption,the wetland aerated in the backside is better.When the hydraulic load of wetlands reaches 0.8 m3/(m2·d),organic loading and NH+4-N loading reach 56 to 112 gCOD/(m2·d) and 20 to 28 g/(m2·d) respectively.