Removal Efficiency Of Nitrogen And Phosphorus On Composite Constructed Wetland Demonstration Project

Constructed wetland has the benefits of low investment and low energy consumption. Itcan not only degrade the organic pollutants strongly, but also remove TN and TP effectlywhich can not be removed by traditional secondary treatment. It mainly studies on removingnitrogen and phosphorus of polluted city watercourse by different composite constructedwetlands, and provide design basis for building Wei River wetlands.Subject to demonstration project, this study mainly carries out the followings: Bymonitoring the removal efficiency of TN and TP by constructed wetland under different T,PH, HRT, HLR and pollution load, and analyse the impacting factors of artificial wetlandson TN and TP removal; By monitoring the removal efficiency of TN and TP by constructedwetland after the treatment of those different impacting factors for one year, and analyse howthe removal efficiency of TN and TP by constructed wetland change with the plants,substrate, combined process, climatic conditions, hydraulic conditions, and pollution load,and study the best combination technology and dynamic model to remove TN, TP; Bymonitoring NH4-N, TN, TP of inlet and outlet selectively at all levels of wetland bed for oneyear, and study the treatment effect of NH4-N, TN, TP by composite constructed wetlandsand the differences between wetland and traditional process, indicate the improvements ofthe demonstration project.The result proves that：(1)The removal efficiency of TN and TP is affected by plants, substrates, microbe,temperature, PH, HTR and HLR.. On the whole, these factors change with seasons, andconstructed wetland has higher treatment efficiency of TN and TP in summer than winter. (2)Different plants and different substrate combinations have different removalefficiency of TN and TP. In a year when planted with Typha, TN and TP average removalefficiency of the wetland are high up to70%and80%, which is higher12%-15%thanplanted with reeds and ryegrass. When there is sludge of water supply plant as substrate inconstructed wetland, TN and TP average removal efficiency of the wetland are high up to40%and50%, which is higher10%-30%than that filling with sludge.(3)Different technological combinations have different removal efficiency of TN andTP, and the difference is not evident. When the wetland’s flow pattern is the two stages ofundercurrent pattern plus surface flow, TN and TP average removal rate are60%and70%,which is higher10%-30%than other compound artificial wetland.(4) Different Hydraulics have different removal efficiency of TN and TP. The properbleHRT for demonstration project should be3d; and when HLR is0.03m~3/m~2*d, thedemonstration project has preferable TN and TP removal efficiency.(5) Different contaminant loads have different removal efficiency of TN and TP.During the range of TN2200-3000mg/m~2and TP120-280mg/m~2, the TN and TP removalefficiency has the same trend with contamination loading growth.