Thermal remediation of multicomponent NAPL contamination in highly heterogeneous subsurface systems

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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.