| As the biggest developing country with the largest population, China has been facing serious water scarcity. In addition, the uneven temporal and spatial distribution of water severely worsens the water scarcity problem. Construction of Water Diversion Project have a great significance in water scarcity alleviation and even overall economic development, but it also brought many adverse impacts on the eco-environment and society. Once a water pollution accident breaks out in the middle route open channel of the South-to-North Water Transfer (SNWT), the characteristics and developing mechanism of the flow fields and pollutant concentration distributions caused by the accident must be quickly determined in order to take effective measures against the accident. Based on the field investigation and model experiment, this paper studied on the regularity of pollutant transport under the sudden water pollution accidents and put forward the treatment measures for the pollution incident. The main research contents are as follows:(1) This paper studied on the diffusion of the pollutant in model channel with NaCl, red ink, ammonia nitrogen and oil as tracer. The results of the tracer experiments show that in the flow of water through 6.85×10-3 m3/s, the concentration of different tracers have a same trend. Relative to the initial section at 0.5m, the dilution of different tracers have reached 90%when the cross section is 2.5m.(2) Without considering the attenuation of contaminants, the paper research on the longitudinal dispersion coefficient of the channel through three kinds of tracers. It shows that in the flow of water through 6.85×10-3 m3/s, the calculation result by tracer model test (2.44m2/s) is almost the same as that calculated from the Elder experience analysis (2.411 m2/s) under the same conditions. To a certain extent, it can reflect the actual situation of the field channel.(3) The results of field investigation show that the sediment concentration was in range between 0.2 and 0.8 kg/m3, and the water turbidity was in range between 0.8 and 1.7 NTU. According to the test by the Construction and Administration Bureau of MRSN, the water quality of the water diversion project met Class II of Chinese Surface Water Quality Standard. In addition, the thickest ices on the water surface were 0.9 cm, and ice could go through the ice booms just when its thickness was less than 0.1cm, which had no effect on the operation of the gates.(4) Based on the measured data and the theoretical formula, the results show that the longitudinal dispersion of the pollutant is approximately normal distribution. For the pollution of ammonia nitrogen in practical engineering, the study has derived a quadratic function relation between the time length of pollution and the cross section of the channel through the formula of one dimensional water quality model, and the coefficients of the function relation are all about the expression of the parameter w. In engineering practice, oil and other insoluble contaminants can take the means of filtration and oil skimming to deal with. In addition, for the soluble pollutants, the pollution of water can be control by separated treatment based on the relationship between the time length of pollution and the cross section.(5) In accordance with the model test, there is provided a multi-point sampler comprising a fixing device, a collection device, a control device and the power device. The instrument is extremely simple in operation and takes up a small volume in the water, so that the instrument has a small disturbance to the water flow in experiment. In addition, the multi-point sampler can take water samples at the same time which further enables the samples to be drawn reliably. |
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