Control On Pollution Of Hoggery Wastewater And Surface Runoff Of Sloping Land In The Catchment Of Maota River

The Danjiangkou Reservoir, with water area of 840 km² and capacity of 8.1 billion stere, is the waterhead of midline project of the famous South-to- North Water Diversion Project. It has the great mission of providing drinking water for Beijing, Tianjin, Hebei, Henan, and the quality of Danjiangkou Reservoir hold the balance of the economy development and zoology safety in the future. There are more than 2000 small watersheds around Danjiangkou Reservoir, by which the population live and do main agricultural production in these small basins. With the development of rural economics, the point and none-point pollution, have affected the rural water condition severity and threatened the water quality of Danjiangkou Reservoir, which induced by hoggery wastewater and nutrient loss from farmland. According to statistics, 70 percent of these small watersheds are located in Shiyan City. The river water quality in Shiyan is good, however, local area and some medium and small rivers exist serious pollution, by monitoring and evaluation of surface water from Shiyan City Water and Water Environment Monitoring Center.We chose a hoggery and a piece of sloping land as the pilot area in the middle reaches of Maota Reservoir in Shiyan City, then designed, constructed and took a series of study, and expected to explore feasible measures to guarantee the rural water quality.Based on the characteristic of the piggery wastewater, we raised a carft of wastewater treatment from small-scale farms in rural areas and devised the water after treatment could be up to standard, preventing to pollute the environment. The hydraulic test was carried, on the aeration condition, we measured and analyzed the velocity distribution characteristics and the standard oxygen transfer rate (SOTR) in oxidation ditch, which laid the foundation for optimizing the hydraulic conditions of oxidation ditch and follow-up sewerage debugging.The pilot-scale hydraulic test proved the distribution of fluid in oxidation ditch under different conditions, and studied the optimal condition. The results show that when aerator rotated to the speed at 100 r/min for anti-clockwise and at 80 r/min for clockwise, regardless of the depth of brushes submerged, the fluid could circulate in the oxidation with enough driving force and without sludge accumulation. In addition, in order to reduce the energy consumption, the aerator could promote fluid flow circulation without dead area when the depth of brushes submerged is 150 mm.A quantity of oxygen transfer tests were conducted on the rotor aerator with horizontal shaft in a pilot -scale oxidation ditch. The submergence depth of brushes and the rotational speed of the aerator seriously affect the SOTR of the aerator. On condition that the submergence depth of brushes is certain, when the aerator rotated anticlockwise, the SOTR and rotational speed were negatively correlated, the SOTR and rotational speed were positively correlated when clockwise. We should flexible adjust the scheme based on the specific circumstances of wastewater during commissioning, and according the conclusions, regulate the speed and submergence depth of brushes to achieve the best results.Based on the water and soil erosion is severity on sloping land, and easily cause agricultural non-point pollution, we carried out pollution prevention and control tests. Combination of the actual situation of the test plots planted maize and soybean, we set several agricultural measures combined with hedgerow, and study the impact of agricultural measures on the control of nitrogen, phosphorus, soil and water loss, crop growth on sloping land as well as the relationship between each other.The experimental results indicated that rainfall, duration and crop growth period are important factors of loss of nutrient, water and soil on sloping land, fertilization before rain will lead to a large numbers of fertilizer loss before they had time to be absorbed by plants. Plant hedgerow could control the loss of water, soil, and nitrogen and phosphorus effectively, which could reduce 31.3% in surface runoff and 53.9% in soil erosion. Hedgerow combined with agricultural measures could effectively reduce the concentration of pollutants in rainfall runoff, compared with the control, treatment plots reduced 2.1%～10.8% and 8.3%～24.9% of the concentrations of SS and COD_Mn respectively, and the loss of nitrogen and phosphorus in hedgerow plots is 27.0%, 73.1% to the control. Balanced fertilization could promote the nutrient absorption by plants, increase crop coverage of the surface to prevent soil erosion, and play an important role in preventing nutrient migration with runoff. Soybean intercropping maize can also weaken the movement of soil nutrients. Hedgerow and balanced fertilization, intercropping effectively weaken the water, soil, fertilizer loss. Based on the hoggery wastewater treatment commissioning and hydraulic test in the oxidation ditch, we have laid some theoretic foundation for wastewater treatment analogical with the test farm. We explored a eco-agricultural model for preventing the rural nonpoint pollution of Shiyan from the runoff experiments on sloping land, which been proved a effective model for preventing nonpoint pollution. This model could make father contribution for water quality and safety of the Danjiangkou Reservoir.