| With the rapid development of town in China, town water pollution become increasingly worse.Sewage and surface runoff directly discharged can bring severe water environmental problems.Therefore, it is emergent to develop water pollution control technology. Especially in the town,constructed wetland and grassed swales have advantages in treatment domestic wastewater and surface runoff, respectively. Furthermore, these two technologies have characteristics of low investment, easy erection and ecological aesthetics. In order to solve the problem of the town sewage and surface runoff pollution, this study investigate efficiency of tidal flow constructed wetland in treating town sewage and grassed swale in purifying surface runoff. The research contents are as follows: a) Four kinds of constructed wetland, tidal up flow wetland, tidal down flow wetland continuous up flow wetland and continuous down flow wetland were constructed to the assess their purification efficiency in treat town domestic sewage in autumn. b) Two kinds of grassed swale,ryegrass swale and tifway bermudagrass swale, were designed to obtain the optimum operating conditions in treatment of surface runoff.. c) With urface flow ryegrass as reference s, the treatment performance of infiltration ryegrass swale is measured under three kinds of hydraulic load, q1(4m3/m2.d), q2(6 m3/m2.d) and q3(8 m3/m2.d). The main results are as follows:(1)The removal efficiency of COD and TP in tidal flow wetland were higher than those of continuous wetland, which were 30.65% and 14%, respectively. The removal efficiency of NH4+-N and TN of tide up flow is better than thoes of tidal down flow. Continuous down flow is superior to continuous up flow for the two pollutant treatments. During the sampling period, there was no accumulation of nitrate in four types of wetlands. The concentration of nitrite in the tidal up flow and down flow constructed wetlands had the same variation trend. In addition, the concentration of nitrite in the outflow, about 0.02 mg/L,were closer to that of in the inlet of continuous up flow and down flow constructed wetlands. Overall, the tidal flow wetland had a high purified ability in autumn, and this ability is better than that of continuous flow wetland.(2)In the study of optimum operating conditions of surface flow grassed swale. The comprehensive purification capacity of ryegrass swale is superior to tifway bermudagrass swale. Theremoval efficiency of the TSS, TP and TDP was obvious in two kinds of grassed swale. The corresponding efficiency of TN and TDN in ryegrass swale was significantly better than that in tifway bermudagrass swale. The results of orthogonal experiment and range analysis showed the influence degree of those factors from big to small in the order are as follows: hydraulic load, grass height,water depth. The best operating conditions for hydraulic load, grass height and water depth are of0.5m3/m2.d, 15 cm and of 4cm, respectively. These conditions are also suitable for ryegrass swale and tifway bermudagrass swale.(3) In the study of infiltration ryegrass swale, the result showed that the capacity of purification,runoff reduction, strong shock resistance of infiltration grassed swale was stronger than that of surface flow grassed swale. The removal efficiency of particulate pollutants and phosphorus were both high in two grassed swales. And the removal efficiency of two kinds of swales both decreased with the increase of the hydraulic load, which meaned hydraulic load had a strong effect on the removal efficiency for grassed swale. Overall, the removal efficiency of infiltration swale was higher than that of surface flow swale. The removal efficiency of COD, TSS, TP was better in percolation pipe. |
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