| The Danjiangkou Reservoir is the waterhead of midline project of the famous South-to-North Water Diversion Project. And it takes the important task of providing drinking water for Beijing, Tianjin, Hebei and other provinces. So the water quality has attracted a wide spread attention. In recent years, the test results showed that the water quality of the Danjiangkou Reservoir was good overall. However, parts of the index were more than the water quality standard. Shiyan city belongs to the underdeveloped mountainous areas of the central of China. Shiyan city,85%of whose land area is in the Danjiangkou Reservior watershed, is the most sensitive area of the waterhead of the midline project. In this study, we chose a hoggery and a piece of sloping land in the village of Liao, the region of Maojian and a piece of vegetable base in Shiqiao village, the region of Zhangwan, Shiyan City of Hubei as the pilot area of representative catchment. We chose different ecological measures to control different sources of pollution and study the effects of these measures for agricultural wastewater pollution.(1) We adopted the oxidation ditch process for piggy wastewater strengthening treatment from the characteristics of high pollutant concentration. Integrating the results of the four activated sludge culture, we can conclude that sludge floc already occured in the oxidation ditch after 3-5 days exposure nausea. And its SV30 can reach 5%in 10 days. Based on the pollutants removal rates of the ditch, we presumed that disinfection solution was toxic to the bacteria. The trend of mixed liquor suspended solids (MLSS) changed with the influent. But the concentrations of COD, nitrogen and phosphorus were all higher than their set values.(2) We raised vegetative buffer strips (VBS) to control agricultural non-point source pollution. To test the effects of different plants comprising a VBS of 2 meters width, we conducted a series of tests on surface runoff characteristics. The result showed that:â‘ Relative to the middle of Amorpha fruticosa, the VBS had significant effects in intercepting both runoff and erosion. And the average removal rates were 97.2%for runoff and 97.5%for erosion. Under the condition of this study, the minimum suspended solid (SS) average removal rate of the VBS was more than 65%. The ammonium-N average removal rate of the whole VBS was 77.2%. On contrast, the average removal rate for total phosphorus was 36.89%.â‘¡By comparing the different treatment of the VBS, we can conclude that:Under different VBS treatments, the erosion was more during the winter wheat growing season. And it showed a decreasing trend during the summer corn growing season. There are ammonium-N and nitrate-N two forms water-solubility N in runoff. The result showed that nitrate-N was the main form. And Amorpha fruticosa VBS showed better interception effect. Test proved that particulate phosphorus was the major form of phosphorus in runoff. Shrub-grass VBS and Amorpha fruticosa VBS had better interception rate and no significant difference between the two. Under different VBS, water-solubility N and total phosphorus loss in each pilot runoff were significant different. In the condition of long duration and greater than 100 millimeter rainfall, the shrub-grass VBS removal effects was better than Amorpha fruticosa and Trifolium VBS only for erosion and nitrogen and phosphorus.(3) We took denitrification wall to control and study the nitrate-N removal effect of this technology of the setting of two different substrates and widthes. And the result showed that the ammonium-N average concentration were 0.43 mg/L,2.86mg/L, 0.37mg/L before, during and after the denitrification. We can conclude that although the ammonium-N produced in the wall from time to time, the ammonium-N was not significantly different in effluent from in influent. It proved that the denitrification and ammoniation theory was also suitable for the process of denitrification wall. The results of 2009 showed that the nitrate-N removal effects of the pine sawdust and mushroom culture wood chip was little different of the same width, and the average removal rates of the two substrates were 83.86%and 83.74%. The removal rates of the two substrates in the setting of lm width were higher than of the other two widthes. |
