河流污染混合区特性计算方法及排污口分类准则Ⅰ：原理与方法

A computational method for the characteristics of pollutant mixing zone in rivers and the sewage outfall classification criteria Ⅰ. Principles and methods

在连续点源离岸排放条件下,从考虑河流纵向移流、横向扩散的简化二维方程解析解出发,对基于环境扩散的宽阔河流探讨了污染混合区的计算方法。给出了污染混合区边界曲线的标准方程及无量纲形式;分别给出了离岸系数0≤η≤2和η>2两种类型污染混合区5个特征点各参数及面积与离岸系数η的关系曲线,分析了各参数的变化规律,提出了以离岸系数η作为判据的分类参数和临界条件。给出了河流岸边、离岸与中心排放的分类判别准则:(1)当0≤η≤0.7时,简化为岸边(近岸)排放类型;(2)当0.7<η<2.3时,称为离岸排放类型;(3)当η≥2.3时,简化为中心排放类型。对河流离岸排放提出了达到全断面均匀混合距离的计算公式,比现行公式有所改进。为河流排污口位置的优化设计和控制排污量计算提供了分类、简便、快捷的理论方法,具有重要实用价值。

Upon the condition that continuous point source is discharged off-bank in rivers those are wide according to their environmental diffusion, calculation method for the pollutant-mixing zone was derived from the simplified two-dimensional transport equation which considers the longitudinal advection and trans-vers diffusion. Standard and non-dimensionalized equations for the boundary of the pollutant-mixing zone were obtained. Two kinds of pollutant-mixing zone were identified by the off-bank coefficient：0≤η≤2 and η〉2. Relations between the five characteristic parameters, plus the area of the zone, and η were found. The changing pattern of the parameters was analyzed. The off-bank coefficient η was proposed as the classification parameter, providing the criteria for the categorization. The classification criteria for river bank,off-bank and river center discharge types are：① for 0≤η≤0.7,the outfall can be simplified as the type of river bank （near-bank） discharge;② for 0.7〈η〈2.3, it is named the type of off-bank dis-charge;③ for η≥2.3, the outfall can be simplified as the type of river center discharge. The current equation of the distance has been improved to reach full section uniform mixing in off-bank river dis-charge. The result provides classified, simple and convenient theoretical method for the optimization of out-fall location and for the pollution load control calculation thus has important practical value.