There are 1,305 Superfund Sites on the United States Environmental Protection Agencies National Priorities List that may require remediation due to the environmental or human health risks associated with subsurface contamination. The contaminants present at these sites and others vary with respect to their physical and chemical properties which dictate the selection of appropriate remediation technologies. In-Situ Thermal Desorption (ISTD) has been studied as a remediation technique for removing many recalcitrant contaminants from soil. ISTD involves passing electrical current through heating elements in wells and removing contaminants through heater/vacuum wells. Heating occurs by heat conduction through the soil. At high temperatures, even relatively low volatility contaminants can be vaporized, removed by vacuum and treated with an on-site recovery system. The main objective of this research was to design and test a laboratory apparatus scaled to a typical ISTD field site and to use it to conduct experiments that could be used to aid in the validation of the STARS numerical simulator. A dimensional analysis was done on the governing energy balance equation to determine the most important scaling groups for the ISTD process so the laboratory experiments could be scaled up to the field. The laboratory apparatus was modeled after a symmetry element of the hexagonal field pattern and a triangular glass prism was constructed for heated sandpack experiments. Temperature data was measured in dry sand, sand partially saturated with water, and sand with both water and PCE added to it. The apparatus was made of glass so that the behavior of the PCE contaminant could be observed when the sand was heated. / text

A numerical model was utilized to assess the effects of elevated temperature on the application of in situ chemical oxidation (ISCO) and enhanced in situ bioremediation (EISB) for the subsurface remediation of trichloroethene (TCE) and tetrachloroethene (PCE). Temperature adjustment of the contaminant physicochemical properties as well as the chemical/biological reactions associated with ISCO and EISB were accounted for in the model domain. ISCO reaction rates were estimated using Arrhenius principles; microbial growth rates for EISB were estimated using non-linear fits to published literature data. The results from this study showed that temperature did provide remedial benefits to ISCO and EISB treatment during the short-term timeframe of oxidant/substrate injection. During these time periods, heated ISCO and EISB treatment exhibited greater DNAPL mass removal and mass flux reduction compared to heated abiotic dissolution. In the long term, after oxidant/substrate injection was terminated, the treatment enhancements achieved by ISCO and EISB were negated. Permeability (k) reduction due to rind formation (ISCO) and bioclogging (EISB) inhibited DNAPL dissolution and contributed to greater dissolution tailing effects. Tailing effects caused by ISCO were more severe compared to EISB since rind formation contributed to permanent k reduction; partial k recovery was observed in the EISB scenarios due to biomass decay. Even though higher temperatures were beneficial to ISCO and EISB during the short-term oxidant/substrate injection period, treatment efficacy was ultimately controlled by the detrimental by-products (rind from ISCO and biomass from EISB) formed as a result of the associative chemical/biological reactions. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-02-10 18:59:23.177