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研究报告

摘要：将人工湿地视为在纵向分散活塞流反应器(PFD)的主流道上并联一个n级串联完全混合反应器(CSTRs)所组成的系统.在这一物理概念的基础上,推导了模拟人工湿地水力停留时间分布(RTD)的CSTRs＋PFD并联模型.模型所包含的4个参数(串联CSTRs个数n,串联CSTRs容积占系统总容积的百分数z,进入串联CSTRs的流量占总流量百分数f,PFD的分散数D)对RTD的峰值时间、峰值高度、平均停留时间、停留时间分布方差具有良好的调节作用.与传统模型相比,该模型能更准确地反映不同人工湿地的特征水流规律.模型采用基于流量的无量纲时间变量,可应用于非稳态变流量下人工湿地RTD的模拟.用前期示踪剂试验所获得的5条水平潜流人工湿地的RTDs对该模型进行验证,当这4个参数取值为z＝0.41、f＝0.57、n＝3、D＝0.667时,该模型计算所得RTD与实测RTDs拟合程度良好,较传统PFD或CSTRs模型能更好地反映该人工湿地RTD早期高峰、峰值集中、尾部倾斜拖长的流态特征.

Abstract：The non-ideal flow of constructed wetland (CW) could be modeled by a plug flow with dispersion (PFD) reactor combined with a continuous stirring tank reactor (CSTR) in parallel. Based on this concept, a new model, CSTRs＋PFD parallel model, was developed to simulate the residence time distribution (RTD) of CW. This model had 4 parameters (n, number of CSTRs; z, the volume percentage of CSTRs; f, the influent percentage flow into CSTRs; and D, the dispersion number of PFD), with which the mode, peak value, mean residence time and variance of RTD can be adjusted properly, and it could present the characteristic flow pattern of different CW more precisely than traditional models. Flow-weighted dimensionless time was adopted in this model which can be applied in both variable and steady flow CW systems. Five experimental RTDs from previous tracer study of a subsurface horizontal CW were used to test the model. When the 4 parameters were set as z＝0.41,f＝0.57,n＝3,D＝0.667, the CSTRs＋PFD parallel model produced RTD function that fitted reasonably well with the experimental data. Compared with traditional model such as PFD and CSTRs, this model can produce a concentrated early sharp rise peak and a leaned and extended long tail which is characteristic of the RTD in this CW.