Multiphysics of bubbles and nanoparticles in porous media: Novel approaches to the remediation of subsurface environments contaminated by chlorinated organic substances

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Soil and groundwater at abandoned industrial facilities (brown-field sites) in Canada remain contaminated by chlorinated volatile organic compounds (VOCs), long after the use of these chemicals has ceased. Chlorinated organics are denser than water, causing subsurface contamination deep below the water table. Their intermediate by-products are believed to be potent carcinogens and are thus a major threat to groundwater resources. The success of many remediation strategies is limited by the difficulty of introducing a gas phase uniformly within VOC source zones below the water table, as would be necessary for transferring a VOC into the flowing gas phase or for supplying reactive gases (e.g., oxygen, hydrogen, methane) for use by contaminant-degrading bacteria. The overall aim of the proposed research is to develop radically new alternatives to present-day strategies for the remediation of a wide spectrum of subsurface environments (e.g., contamination deep below the water table and in fractured rock) compromised by VOCs. The proposed research program derives its novelty from the use of gas-supersaturated water injection (SWI) as the means for introducing a mobile gas-phase in situ. In this process, gas is not injected but exsolved in situ from injected water that contains an excess of dissolved gas (analogous to opening a can of soda pop). Using a synergy of experimentation and modeling at both the microscopic (pore-level) and macroscopic (continuum) scales, we address the following questions. Firstly, what mechanisms govern the interaction of flowing gas bubbles with VOC blobs trapped within soil and rock and how do we predict the extent of VOC removal by volatilization and/or mobilization at practically relevant scales? Secondly, how do we harness the interactions between flowing bubbles and hydrophobic nanoparticles to generate foam in situ and how can such a foam be used to remediate contaminated subsurface environments? In summary, this research program will develop innovative technologies that could increase the competitive advantage of Canadian companies active in the area of site redevelopment.displace a residual oil phase, (ii) improve sweep efficiency during SWI and (iii) control the emplacement of nano-scale zero-valent iron nanoparticles. We will complement these studies by experiments in 1D and 2D sand packs and rock cores with an aim to validate a continuum-scale model ofthree-phase flow with non-equilibrium inter-phase mass transfer that could serve as a tool for the design offield-scale tests.The proposed research program will integrate experiments and modeling at scales ranging from the scale of asingle gas-liquid interface (dynamic surface tension during irreversible adsorption of nanoparticles) to the porenetwork scale (oil gangion-gas bubble dynamics) to macroscopic 1D and 2D domains. It will provide HQPtraining for 2 PhD, 2MASc and 2 undergraduate co-op students, offering unique opportunities for discoveriesin technological fields not limited to soil remediation, but including enhanced oil recovery and geologicalsequestration of carbon dioxide.