Study on Water Environmental Capacity and Total Quantity Control of Pollutants of Changhe River in Urban Area of Huanggang

Increasingly serious problem of water pollution in Changhe river results from the development of economy and society and urbanization in Huanggang city.The urban reaches of Changhe river polluted seriously acting as the object of research,based on full investigation of water environment in the present situation,functions of water environment and water pollutants load of the river,it calculates the water environmental capacity of the river by means of one-dimensional mathematical water quality model.And then backward inference method is used to calculate the maximal allowable amount of every pollutant discharged.At the same time,it puts forward a program of controlling total quantity and reduction of pollutants discharged in Changhe river basin,which provides scientific basis for control of water pollution in basin.The results show that in the event that water quality of urban reaches is up to the standard of gradeⅢ,the water environmental capacity of COD,NH3-N and TP will be 4534.42t/a,331.78t/a and 34.04t/a respectively in urban reaches of Changhe river.As the actual pollution load of COD,NH3-N and TP is 2.09times,2.20times,1.46times respectively as large as water environmental capacity,the actual pollution load has exceeded its permissible pollution bearing capacity.In order to improve water quality of river downstream,it is necessary that the reduction rate of COD,NH3-N and TP discharged in Huangzhou district should be 35.3%,33.9%and 13.0%respectively on the basis of present emissions.