| Chaohu is located in the middle of Anhui province, near the Yangtze River and surrounded by the chaohu Lake. In recent years, with the development of urban economic construction, the rivers and lakes are polluted varying degrees surrounding Chaohu, especially the river through the city is polluted most serious. It affects people’s daily life. This research object of the river around the city is typically polluted river and the most major river systems in Chaohu. The river is divided into two parts of east, west. The water are bad V class and polluted seriously, Total Nitrogen and Total Phosphorus are severely exceed the standard.According to the characteristics of river, pollution load, using COD instead of BOD, the Dobbins-Camp water quality model was used to calculate supplementing water of the minimum flow rate and the minimum flow, in order to optimize the technology of water supplement regulation in Chaohu.Three sampling points were selected apart in the east and west rounding river. There are a total of six sampling points. COD degradation coefficient k1 and precipitation coefficient k3 was measured by BOD culture method. Then COD degradation coefficient k1 was modified. It was founded that COD degradation coefficient of the east rounding river was greater than the west rounding river. The reason that the east rounding river water pollution condition is more serious. Because of a lot of pollutants in the river, the river oxygen consumption was faster. Then COD degradation coefficient k1 was greater.Through the laboratory simulation determination of sediment oxygen consumption rate, it was founded that sediment oxygen demand and time was in a linear relationship:the east rounding river at 7℃ of △O=0.0740t+0.4394, at 15℃ of △O=0.1602t-0.1534, at 28℃ of △O=0.2316t. The west rounding river at 7℃ of △O=0.0899t+0.3661, at 15℃ of △O=0.1522t+0.2651, at 28℃ of △O=0.2088t+0.4600.Per unit time per unit area of the sediment oxygen consumption rate p1 and temperature T was in a linear relationship. Under the condition of 13℃,29℃,16℃ and 5℃, per unit time per unit area of the sediment oxygen consumption rate of the east rounding river were 17.255mg/(m2·h),31.857mg/(m2·h),19.993mg/(m2·h) and 9.955mg/(m2·h) respectively. Under the condition of 13℃,29℃,16℃ and 5℃, per unit time per unit area of the sediment oxygen consumption rate of the west rounding river were 17.986mg/(m2·h),29.956mg/(m2·h),20.230mg/(m2·h) and 12.001mg/(m2·h) respectively.Atmospheric oxygen and photosynthesis are contained in the water reaeration. Formula was used in this paper. According to the east and west rounding river depth range, Churchill formula was used to calculate the Atmospheric oxygen flow rate k2. Black and white bottle experiment was used to identify the oxygen in photosynthesis characteristics. The light intensity can be regarded as the same influence in spring and autumn. The determination results were that for the east rounding river, in summer the oxygen production rate was 1.237mg/L-d and the oxygen consumption rate was 0.303mg/L·d; in autumn the oxygen production rate was 0.723mg/L·d and the oxygen consumption rate was 0.273mg/L; in winter the oxygen production rate was 0.573mg/L·d and the oxygen consumption rate was 0.283mg/L·d. For the west rounding river, in summer the oxygen production rate was 0.850mg/L·d and the oxygen consumption rate was 0.223mg/L·d; in autumn the oxygen production rate was 0.715mg/L·d and the oxygen consumption rate was 0.195mg/L·d; in winter the oxygen production rate was 0.353mg/L·d and the oxygen consumption rate was 0.168mg/L·d.Through the simulation experiment of sediment release of anaerobic conditions and natural conditions, it was founded that COD release at 20℃ was most, at 5℃ was least. The reason that it was not beneficial for microorganism to decompose organism or the minerals to adsorb organism at 20℃. Therefore, a large number of organism was released into the water. The concentration of COD was greater. TN、TP release at 30℃ was most, at 5℃ was least. The reason that organic nitrogen and phosphorus would be decomposed by microorganism when the temperature gone up. In addition, the electric potential of redox was lower by the reduction of dissolved oxygen. Fe3+ was reduced to Fe2+. Phosphorus was released from sediment. Therefore, the higher the temperature is, the more TN and TP released from sediment. Under the anaerobic conditions, sediment release concentration of COD、TN and TP were greater than the natural conditions. The reason that under the anaerobic conditions the organism would not be decomposed by aerobic microorganism. Anaerobic decomposition of organism was not beneficial for nitrification and denitrification. Because of the decrease of dissolved oxygen, Fe3+ was reduced to Fe2+. Therefore, the amount of sediment release the quantity of COD, TN and TP were more.Calculate supplementing water of the minimum flow rate and the minimum flow to maintain DO≥3mg/L, COD≤30mg/L for class Ⅳ. The results were in spring, summer, autumn, winter the four seasons as following. the minimum flow rate of the east rounding river were 0.0063m/s,0.0136m/s,0.0070m/s,0.0035m/s; the west rounding river were 0.0155m/s,0.0220m/s,0.0070m/s,0.0163m/s,0.0055m/s; the minimum flow of the east rounding river were 0.2232m3/s,0.4896m3/s,0.2520m3/s, 0.1260m3/s; the west rounding river were 1.3175m3/s,1.8700m3/s,1.3855m3/s, 0.4675m3/s. |
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