水平潜流人工湿地流场数值模拟与结构优化分析

Numerical simulations of flow field and analyses of optimal structure for horizontal subsurface flow constructed wetlands

为了解决传统水平潜流人工湿地在床体结构设计方面的随意性与经验化问题,以流场均匀分布为目标,利用数值模拟方法对人工湿地床体结构参数进行优化,包括人工湿地基质填充厚度、床体长宽比例、构建尺度、主体填料区的分层填充方式,解析基质结构的配置规律,实现各参数的定量化。模拟结果表明,填料的分层配置对流场分布的影响很大。在基质厚度为0.6 m,长宽比为5∶3,且填料按照渗透系数指数规律分层填充的情况下,流场分布较均匀。在此基础上,根据模拟结果所确定的结构参数构建潜流人工湿地小试装置,并与传统结构人工湿地进行对照,对模拟结果进行验证。实验结果表明,当水力停留时间(HRT)为36 h时,分层填充与单层填充方式的人工湿地对COD、TP和TN的平均去除率分别为64.89%、82.72%、69.69%和29.84%、39.15%、31.83%,结构优化后的人工湿地净化效果得以显著提升。

A simulation-based design approach is used to find the optimal substrate structure of horizontal subsurface flow constructed wetlands for avoiding the arbitrary and empirical problems during the substrate structure design.The simulation scheme,describing variable filling depth,the aspect ratio,the constructed size and the layered filling styles,quantifies the structure parameters and matching rules.The simulation results showed that the substrate matching approach is a crucial factor for the flow field distribution.With 0.6m thickness and 5 ∶ 3aspect ratios,the uniform flow field distribution in wetlands is linked with the exponential equation for the permeability coefficients.Two pilot-scale SSCWs（traditional design and optimal design） were constructed according to the simulation parameters to verify the simulation results,it showed that with the HRT of 36 h,the mean removal rates of COD,TP and TN in optimal design SSCW were 64.89%,82.72%,69.69%,respectively,in contrast,which were 29.84%,39.15% and 31.83% in the traditional design SSCWs.It indicated that the removal efficiencies of SSCWs were improved significantly after structure optimization.