| Based on the Qingpu modern agriculture zone, the drainage of paddy fields select hydrophy tes which can intercept nitrogen and phosphorus efficiently, aiming to build an eco-ditch-wetl and drainage system, reduce contaminants in water from the process, especially content of N and P, thus preventing the agricultural nonpoint source pollution caused by Reduction of water withd rawal of farmland and eutrophication caused by discharging to the river directly. The main resear ch results are as follows:(1) Based on the experiments, it is not obvious that haptophytes purify water of low polluti on load. It will work when the hydraulic retention time is controlled in 2 days. As a result, it re quires tracking to study the quality of drainage water sufficiently and timely adjustment of operat ing parameters, especially hydraulic retention time. When applied to ditches and wetland ecology construction, pollution load of the soil itself, the purification of water is also good. It is adequate to use the traditional earth ditch as a drainage ditch, in an economic point of view, as soil itsel f can purify the water under low pollution load with good effect; but in the ecological point of view, the plants with humidity resistance, cold resistance and high-temperature resistance should b e selected and planted in ditch on both sides to conserve water and soil which will improve the ecological environment. When the rice field drainage in the high pollution load (after a large nu mber of chemical fertilizers and pesticides has been applied), the soil itself can not-intercept nitro gen and phosphorus sufficiently with its low purification capacity. At this time, large amounts of nitrogen and phosphorus enter the water to the rivers and lakes with the rice fields, causing eutr ophication. Lying appropriate aquatic plants within trench can slow down the flow rate of paddy water, intercept nitrogen and phosphorus to improve the water soluble oxygen, steady the role of PH of the water. For example, vetiver plays a dominant role in controlling medium phosphorus p ollution; iris has a more moderately strong effect to control nitrogen pollution; cattail plays a mo re dominant role on the removal of high concentration of loading COD. As a result, aquatic plan ts have larger effect on the hydraulic retention time of removal of pollutants. So what kind of pl ants are good or not can not one-sided, only on the water quality and HRT be designed by treat ment contaminated water to can be chosen the right varieties.(2) The ecological ditch conducted a 5-day test run at the end of the project, after the trial run, the canals basically universalizing its expected processing quality. After HRT for 5 days, th e removal rate of the main pollutant N, P, COD reached more than 30%, even 50% or more. By the data of the trial run, the layout-combination of emergent aquatic & flowing water make the eco-ditch play a more water pollution purification of large capacity in the non-rainfall conditions.(3) The follow-up ecological functions of wetland water desalination reflect the comprehensiv e functions, including the wetland water purification, ecological restoration, cultural transmission a nd other functions in one.Construction of the ecological drainage system is divided into four steps, selection of aquatic plants - infrastructure of ecological ditches-ditches plant layout-construction of the wetlands included. The selection of aquatic plants is comparatively successful; the test run of eco-ditch is more stable and functional. The wetland ecosystem is relatively sound, while the whole system se ries more smoothly. After the 2011 implementation of Phaseâ…¡, construction of rise field drainage system will be more complete.
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