Master of Engineering Science
Civil and Environmental Engineering
Gerhard, Jason I.
Per- and polyfluoroalkyl substances (PFAS) are a large group of anthropogenic compounds. Long-term use has led to widespread environmental contamination, and PFAS source zones will require cleanup.
Self-sustaining Treatment for Active Remediation (STAR) is a thermal treatment technology that employs smouldering combustion as a method of soil treatment. Smouldering can be self-sustaining and is thus more energy-efficient. Previous research applying STAR to PFAS-contaminated soil and granular activated carbon (GAC) showed promise, as PFAS were removed from soil.
This study clarified the potential of STAR as a treatment option for PFAS. This study is unique in how thoroughly it characterized the fluorine mass balance of the thermal system and demonstrated how calcium oxide as a soil amendment would limit the release of potentially harmful byproducts. Furthermore, it demonstrated a high degree of PFAS mineralization. Altogether, this study provides both new science and engineering options for effective smouldering treatment of PFAS-contaminated soils.
Summary for Lay Audience
PFAS are a large family of chemicals that possess several unique characteristics. Their unique properties means that they are used in a wide variety of consumer products since being introduced in the 1950s. PFAS are also used in the manufacturing of other goods, and as an ingredient in firefighting foams. Locations where this foam has been used for training – airports, military bases, firefighter schools, and oil refineries – can have significant PFAS contamination in nearby soil and groundwater. The characteristics of PFAS are such that they will not naturally breakdown in the environment, and PFAS exposure has been linked with numerous health issues. PFAS can bioaccumulate in human tissue, and it is estimated that most humans have some quantity of PFAS in their bodies.
The health risks of PFAS and the extent of their environmental contamination means that contaminated sites will require cleanup. The unique characteristics of PFAS that often make them useful in their various applications also make cleanup difficult. Currently, the most popular methods of treatment for PFAS-contaminated soil are excavation followed by landfilling or incineration. These methods are expensive, ineffective, and unsustainable. STAR is a treatment option for PFAS-contaminated soils that has shown great promise. STAR uses smouldering combustion to destroy PFAS and remove it from contaminated soil. The application of smouldering allows STAR to be an energy efficient alternative to other thermal treatment technologies. However, the destruction of PFAS can create harmful byproducts and greenhouse gases that must be managed. This study demonstrated for the first time a better understanding of how PFAS react to thermal treatment. Methods of limiting the release of harmful by-products were also explored. Results showed that the addition of small amounts of calcium oxide greatly reduced the amount of by-products emitted, while still effectively treating the PFAS in the soil. This study further demonstrated the viability of STAR as a treatment option for PFAS-contaminated soils.
Harrison, Brian Gerald, "Self-sustaining Smouldering Combustion of Granular Activated Carbon Contaminated with Per- and Polyfluoroalkyl Substances – Fluorine Mass Balance and Enhanced Methods of Mineralization" (2022). Electronic Thesis and Dissertation Repository. 8538.
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Available for download on Monday, January 01, 2024