Contamination Twodimensional Water Quality Model Study Of Surrounding Area Of Drainage Outlet Of City Rivers

The city rivers are the rivers or river sections passing or originating from the city, including the man power excavated, years developed canals or ditch systems which already have the characteristics of the natural rivers. Currently, China has enhanced the power of treatment of the city rivers. Many city rivers have been comprehensively treated. But the treatments only concern the dredging up, treatments for river banks and surrounding area, thus the river water quality does not change basically comparing the conditions before and after the treatments. This subject is taking the Fu'nan River after the treatment as the object, studying the basic situations of the river contamination, the characteristics of degrading and diffusing of the river pollutants. Taking the Chemical Oxide Demand-COD of the pollutants as the simulative object, the Contamination Twodimensional Water Quality Model Study of city rivers has been established. Also, the moving rules of the pollutants in the rivers have been studied. All these studies have provided the data and theories support for enhancing the self leaning ability of the Fu'nan River body; bettering the river water quality and exact technique execution.The study results demonstrating that:(1) The water quality of Fu'nan River has not been basically changed. The river still has low discharge, slow flow speed. Most of the indexes of the water has surpassed the five kinds standards of the national groundwater environmental quality, which belongs to the five bad water quality. Among which, the BOD average value is 23mg/L, two times surpassing the groundwater five kinds standards; ammonia nitrogen average value is 5.1mg/L, two times surpassing the standards; total phosphorus is 1.1mg/L, five times surpassing the standards; the dissolved oxygen of the water body is low with the averagevalue of 3.8mg/L, while the minimum value is only 1.6mg/L(2) The test for the pollutants' degrading rules gets the degrading coefficient k1, among which the test value of the degrading coefficient k1 of the sewage are 0.197, 0.235, 0.344d^-1; the degrading coefficient of the river is 0.172, 0.26d^-1. The average value k1 of the after many times measurements is 0.242d^-1(3) The tests are taken for measuring the moving and diffusing characteristics of the pollutants in different hydrology conditions, including the pollutants' transverse coefficient of diffusion Dy and longitudinal diffusing Dx coefficient , the Dy and Dx of Fu'nan River in different hydrology conditions have been got. When the flow speed is slow (u - 0.0514m Is), the Dy average value is 0.040m2/s, while the Dx average value is 0.72m² /s; when the flow speed is fast (u = 0.179m Is), the Dy average value is 0.035m² Is, while the Dx average value is 15.1m² Is. Comparing with the relevant literature data, Dy of the pollutants of Fu'nan River is not quite different, but with the affection of the river flow speed, the Dx value is far less than the literature data.(4) After getting the hydrology, water quality data and the data of the degrading and moving characteristics of the pollutants, the various coefficients are put into the twodimensinal water quality model, with the numerical value calculation method, the numerical solutions in different flow speed situations of the water quality model have been got. Also, the COD consistency distributions of various sections of the rivers in two hydrology conditions have been got.When the flow speed is slow, the edge diffusing width of the polluted zone is 1200m that it reaches the opposite bank. When the diffusing consistency is at 2000m, it diffuses to the 40m of the center of the river. Three isoconcentration lines, 0.1, 0.5 and 0.9mg/L have been drawn. For 0.1mg/L concentration line, when it is about 1500m, it diffuses to the opposite bank, while for 0.5mg/L, the maximum diffusing distance in transverse section is about 45m.When the flow speed is fast, when the edge diffusing width of the polluted zone is 2000m, it does not reach the opposite bank. Even at 2000 section, it only diff...