有机污染场地热强化多相抽提修复的模拟研究

Simulation study on thermal enhanced multi-phase extraction remediation of organically contaminated sites

多相抽提(multi-phase extraction,MPE)技术已成为地下有机污染修复领域的研究热点,而数值模型可以对MPE过程中污染物的迁移、转化进行高效精准预测.本研究通过对多孔介质内多相流基本物理概念的描述及迁移规律的推导分析,构建MPE修复数学模型,并对华东地区某有机污染场地MPE修复过程进行模拟概化,再现了修复过程中有机污染物的迁移、转化特征,同时对其进行细致分析,为地下有机污染修复提供理论基础和科学依据.结果表明,MPE过程中污染物在压力驱动下向抽提井方向迁移至饱和带,饱和度锋面存在明显向下收缩的趋势.模拟计算结果与实际监测值有较好的相关性,污染物的总去除率达93%,修复效果较好.此外还设置了不同MPE修复方案,模拟研究温度、抽提井压力对有机污染物去除率的影响,结果表明,有机污染物的去除率随着温度和抽提井压力的升高而升高,低温低压时低渗透层中残留的污染物难以抽出,导致其总去除率降低.

Multi-phase extraction(MPE)has become a hot topic in the field of subsurface organic pollution remediation.Numerical models can predict the transport and transformation of pollutants during MPE with high efficiency and accuracy.In this study,a mathematical model for MPE remediation was constructed by describing the basic physical concepts of multi-phase flow in porous media and deriving the transport law.The model also presented the transport and transformation characteristics of organic pollutants in the remediation process by simulating and generalizing the MPE remediation process at an organic contaminated site in East China.Meanwhile,a detailed analysis was carried out to provide a theoretical basis and scientific basis for the remediation of subsurface organic pollution.The results suggested that the contaminants driven by pressure migrated towards the extraction wells into the saturation zone and that there was a clear tendency for the saturation front to shrink downwards during the MPE process.More notably,the simulated results correlated well with actual on-site monitoring values,and the total removal of pollutants reached 93%,suggesting a favorable remediation effect.In addition,different MPE scenarios were set up to simulate the influence of temperature and extraction well pressure on the removal of organic pollutants.It was noted that the removal of organic pollutants increased with the temperature and extraction well pressure.However,the organic pollutants trapped in low-permeability layer were difficult to be extracted at low temperature and low pressure,which reduced the total removal.