Remediation of non-aqueous phase liquid wastes in groundwater systems containing trapped gas

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Clean water is a national priority. Millions of Canadians depend on clean groundwater as a source of drinking water. In addition, many of the tens of thousands of abandoned properties in Canada remain unused due to the contamination of soil and groundwater by industrial chemicals. Often, the most difficult sites to clean-up are those contaminated by chemicals such as petroleum fuels, solvents, dry cleaning fluids, and coal tar, which are known to present a significant risk to human health. Cleaning up these sites is a challenge due to the complexity of the subsurface, and the physical and chemical behaviour of contaminants. As a result, millions of dollars can be spent to remediate a single site. A detailed understanding of how contaminants move from their source into the surrounding groundwater is critical to engineering successful, cost-effective solutions. There is a need to better understand contamination under realistic conditions. One common condition is the presence of gas bubbles in the subsurface near contaminant sources. Gas bubbles can be created as the water table rises and falls throughout the year, or by many clean-up technologies that treat contamination in place. Gas bubbles are not typically considered, but may significantly affect the lifetime of contaminant sources, the risk to groundwater users, and the movement of contaminants toward the ground surface. For example, past work showed that contaminants may be transferred from a source to groundwater twice as fast in the presence of gas. Research conducted by four Master's and two Doctoral students will include experiments to investigate the formation of gases during the application of clean-up technologies, how gases transfer contaminants to the groundwater, and the effect of contaminant mixtures on gases. The research will also develop new approaches to simulate the interaction between the gas bubbles and contaminants using computer models. Results of this research will lead to more accurate predictions of risk due to site contamination and improved strategies for the application of clean-up technologies. This will provide new insight and tools to the environmental engineering community, which will benefit site owners, property developers, and practitioners.