| Urban watershed is of great significance quality of life of residents and urban ecology environment. At present, waters pollution problems, especially eutrophication, affect water ecology and urban landscape. Controlling outer source pollution is the key measures to prevent eutrophication. Athought Constructed Wetland are widely used to control water pollution around the world, it have some shortcoming, such as a bigger floor area, inefficient in nitrogen and phosphorous removal and the reoxygenation capacity etc. So Terrace-filter Constructed Wetland (TFCW), a new type of vertical-flow Constructed Wetlands system is discovered and researched in productive experiment and demonstrating project. Main research contents include the following:â‘ Make comparison for the ability of NH4+-N and PO43- adsorption, the performance of steel slag is the best of five kinds of matrix, and its adsorptive capacity is an order of magnitude higher than other matrix. Freundlich adsorption equation description can be taken used to express the NH4+-N and PO43- uniform temperature adsorption curve. When NH4+-N and PO43- are being coexistent state, they have a competition relation in steel slag matrix adsorption site position. Because of NH4+-N's existence, PO43- adsorption quality reduces to half. When the PO43- concentration is low, slightly affection is put on NH4+-N adsorption. But with the increase of equilibrium concentration, its influence strengthens gradually.â‘¡In productive experiments, investigation on the pollutant removal efficiency of eight different combinations of configuration, substrates and plants indicates that the optimum process is B. Through orthogonal experiment to determine the factors of primary and secondary order impact the pollutants removal in process B and its optimum operating conditions (A3B3C2D1) and the control of parameters; The experimental results of water distribution indicates that: triangular weir is superior to perforated pipe in the reoxygenation capacity, but inferior in distribution uniformity of water, resulting in the effect of pollutant degradation in slightly worse; In the aspect of substrates and plants, steel slag is a better wetland substrates, which shows obviously removal efficiency for nitrogen, TN and TP, and promote the reaction of nitrification and denitrification; In all experimental plants, Canna is the most suitable kind for wetland for effective in nitrogen and phosphorus removal.â‘¢The research of the reoxygenation capacity of different wetlands bed in demonstrating project show that the average reoxygenation is First-class wetlands 0.49mg/L, Second-class 0.45mg/L, Third-class 1.50mg/L; investigation on the effect of aspect ratio of wetlands on the pollutants removal indicates that when aspect ratio in the following range does not affect the pollutants removal: First-class wetlands 1.8~3.2, Second-class 2.2~4.2, Third-class 2.8~5.4; The analysis of the degradation model of pollutants shows that the kA are COD1.12, NH4+-N1.13,TN0.51,TP0.64. Different pollutants are removed in different places: COD and ammonia nitrogen mainly in the First-class, TN mainly in the second-class by denitrification, TP shows different removal efficiency in different wetlands beds due to pollution load. Under the conditions of stable operation, the average removal rates of COD, ammonia nitrogen, TN and TP are 75%, 75.5%, 47% and 55%, respectively,and the effluent quality of wetland better than grade-one standard B of "Discharge Standards of Pollutant for Municipal Wastewater Treatment Plant "(GB18918-2002), and the running costs is $0.221 per cubic meter.The research shows that the Terrace-filter Constructed Wetland (TFCW) system overcome the disadvantage of the traditional Constructed Wetlands, broadens the scope of application of Constructed Wetland and provides more technical selection for water restoration and wastewater treatment.
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