Study On Water Environmental Capacity In Yizheng

Environmental capacity is a basic concept in environmental science,and it reflects the bearing capacity to the pollutant under certain environmental targets. It is important to determine the size of the environmental capacity for total capacity control and water environmental planning.Based on the water function classification, the pollution control units are partitioned. Then the important point sources such as industrial pollution, living pollution and a part of non-point source pollution are investigated in each pollution control unit. And the COD and NH3-N quantities entering river of control units are calculated.For parameter estimation, a new parameter estimation optimization criterion function (PEOCF) has been established on minimum deviation of the absolute value of relative errors. Then combied with genetic algorithm, a parameter estimation method is designed. It is applied to water quality model parameter estimation and P-III curve multi-parameter estimation of precipitation. The COD degeneration coefficients of rivers in Yizheng are evaluated, and also a good result of P-III curve multi-parameters estimation of precipitation are obtained, with the relative errors between predicted and measured values being in±10%.QUAL2K model V2.07 is a new water quality model published by United States Environmental Protection Agency in March 2006. This paper attempts to use this model for water quality simulation. The COD and NH3-N concentration distribution in Yiyang River, Xupu River, Long River, Yanshan River and Yicheng River under different guarantees rate conditions have been simulated by QUAL2K water quality model, within results'relative error between±20%.According to the results of the concentrations distribution along distance, the environmental capacity of any outfall arbitrary point can be calculated. Then the surplus environmental capacity of COD and NH3-N of the five rivers are calculated. Adding together the surplus environmental capacity and the present quantity of pollutant emission, total environmental capacity under the different guarantees rate is obtained. The result indicats that total COD environmental capacity of Yizheng is 52063.33 t/a, 35141.70 t/a, 18771.56 t/a, 11040.69 t/a, 8885.30 t/a; total NH3-N environmental capacity of the five rivers is -8368.54 t/a, -4089.62 t/a, -897.40 t/a, 307.46 t/a, 509.64 t/a, respectively under 10%, 25%, 50%, 75% and 90% five kind of different guarantees rate condition.