基于随机水质模型的水功能区COD超标风险分析

由于水环境系统中存在诸多不确定因素,建立在物理简化基础上的确定性水质模型并不能反映水质变化过程的不确定性。为了弥补确定性水质模型的局限性,本文根据随机微分方程理论,假设水质模型中的耗氧系数、沉降系数、复氧系数服从双侧截尾正态分布,建立了考虑随机效应的水质模型。将模型应用于COD超标风险分析,分别计算了不同水文、水质条件下COD浓度的概率分布。结果表明:当三道营来水COD浓度为16、17、18 mg/L时,超标概率为分别在0.3、0.6、0.8左右。

Study on risk analysis of COD exceed standard in water function zone based on stochastic water quality model

Because of existence of many uncertain factors in water environmental system,the model established on the basis of the physical simple does not reflect the uncertainty of water quality and water quality change. In order to compensate the limitations of deterministic model of water quality,the paper supposed oxygen coefficient, sedimentation coefficient and reaeration coefficient to obey the doubly truncated normal distribution hypothesis in water quality model according to the theory of stochastic differential equation,and set up one-dimensional COD model considering random effect.The model was used to risk analysis of COD exceed the standard.The paper calculated the probability distribution of COD in different condition. The result showed that when the COD is 16, 17, 18 mg/L, the risk probability over standard is about 0.3, 0.6,0.8.