Date of Award

Spring 1-1-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil, Environmental & Architectural Engineering

First Advisor

John S. McCartney

Second Advisor

Angela Bielefeldt

Third Advisor

Dobroslav Znidarcic

Abstract

The goal of this study is to understand the conditions in which heat collected from soil borehole thermal energy storage (SBTES) systems can be used for thermally enhanced vapor extraction. SBTES systems consist of an array of closely-spaced vertical geothermal boreholes, and are used for storing heat collected from solar thermal panels. The temperature of the soil in these systems is expected to reach values ranging from 40 to 60 ◦C. Although thermal enhancement of soil vapor extraction (SVE) has been investigated in several studies, they typically involved temperatures in the range of 100-300 ◦C and the role of relatively low temperatures such as those in SBTES systems has not been thoroughly evaluated. Although the temperature is not significant, the heat is from a renewable source and can be applied for a long duration for low cost. The experimental approach used in this study involves column tests in which a vacuum is used to draw air through an unsaturated soil column contaminated with diesel fuel at residual saturation. Three tests were performed in which the soil column was heated to different temperatures and a vacuum was imposed to result in a constant upward air flow rate through the soil column. The data collected, including the air flow rates, the soil temperature and dielectric permittivity, and the total petroleum hydrocarbon in the gas phase at different locations, indicates that moderate increases in temperatures lead to small increases in the removal of diesel from the unsaturated soil layer. However, the increases observed in the amount removed did not lead to a significant change in the percent of initial diesel removed. These results confirm that moderate increase in temperature are not sufficient to significantly improve diesel remediation from a low-permeability silt. However it does demonstrate a potential for integrating SBTES systems with subsurface remediation strategies for more volatile contaminants to provide a sustainable approach for the reuse of contaminated sites.

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