Thermal remediation of multicomponent NAPL contamination in highly heterogeneous subsurface systems

热修复方法包括热水冲洗、蒸汽冲洗(SF)、电阻加热(ERH)和导热加热(TCH)。到目前为止，对高度非均质地下系统(如Smithville裂隙岩层)的热修复研究很少，无论是在实验室或现场规模，还是通过数值模拟。通过热修复去除多组分非水相液体(NAPL)，特别是同时含有高挥发性和低挥发性有机化合物的NAPL的速率限制传质预测目前也没有被很好地理解。研究的总体目标是确定SF、ERH和TCH在从非均质土壤、裂隙粘土和裂隙岩石系统中去除多组分非水相液体源的有效性。特别是，将确定用于从低渗透性区域去除多组分NAPL源的特定组分以及相关的吸附和水相有机化合物的三种热修复方法的有效性。加热过程中土壤性质的变化将被确定，并与去除率相关。关于通过热修复从多组分NAPL中去除特定有机成分的传质限制将被描述。还将确定在不同的水文地质环境下利用三种热修复技术向下调动致密的NAPL的潜力。这项研究将包括实验室规模的热修复研究和计算机模拟，这项研究将对理解复杂非均质体系中多组分NAPL源区热量对传质的影响做出重要贡献。这将使对各种热修复方法用于现场修复的有效性进行更现实的评估。由于这些过程中的不确定性目前是实施热修复方法的障碍，预计这将导致更广泛地应用热修复方法，从而清理更多不适合使用其他方法修复的地点。

Thermal remediation methods include hot water flushing, steam flushing (SF), electrical resistance heating (ERH), and thermal conductive heating (TCH). To date, there has been little research conducted on thermal remediation in highly heterogeneous subsurface systems (e.g. Smithville fractured rock site), either at the lab or field scale, or with numerical modelling. Prediction of rate limited mass transfer associated with the removal of multicomponent nonaqueous phase liquids (NAPL) by thermal remediation, particularly NAPL containing both high and low volatility organic compounds is also not currently well understood.The overall objective of the research is to determine the effectiveness of SF, ERH, and TCH for removal of multicomponent NAPL sources from heterogeneous soils, fractured clay, and fractured rock systems. In particular, the effectiveness of the three thermal remediation methods for removing specific components of the multicomponent NAPL source and the associated sorbed and aqueous phase organic compounds from the low permeability regions will be determined. Changes in soil properties during heating will be determined and related to removal rates. Mass transfer limitations with respect to removal of specific organic components from multicomponent NAPL by thermal remediation will be characterized. The potential for downward mobilization of dense NAPL with the three thermal remediation techniques for various hydrogeological settings will also be determined. The research will involve bench scale thermal remediation studies and computer modelling.This research will make significant contributions to the understanding of the impact of heat on mass transfer from multicomponent NAPL source zones in complex heterogeneous systems. This will allow more realistic evaluations of the effectiveness of the various thermal remediation methods for site remediation. As the uncertainty in these processes is currently a barrier to implementation of thermal remediation methods, it is expected that this will lead to more widespread application of thermal remediation methods, resulting in cleanup of more sites not amenable to remediation using other methods.