Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Gerhard, Jason I.

Abstract

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants, ubiquitous in the environment, and are challenging to remediate. Self-sustaining Treatment for Active Remediation (STAR) destroys organic contaminants embedded in porous media using smouldering combustion. Self-sustaining smouldering conditions allow the reaction to propagate through the contaminated media without external energy. This study explored STAR as a remediation option for PFAS-impacted granular activated carbon (GAC) and PFAS-contaminated soil. Three smouldering mixtures were used (i) PFAS-spiked GAC and sand, (ii) PFAS-spiked soil and GAC, (iii) PFAS-contaminated field site soil and GAC. Smouldering temperatures were greater than 900˚C, destroying the GAC. Post-treatment PFAS concentrations of the sand, soil, and ash were near or below detection limits (0.5 μg/kg). Analysis of emissions demonstrated hydrogen fluoride and shorter-chain PFAS were produced suggesting PFAS had been mineralized and altered during smouldering. Results suggest STAR is an effective remediation technique for PFAS-impacted soils and PFAS-saturated GAC.

Summary for Lay Audience

Non-stick pans, waterproof clothing, fast-food wrappers, and stain-resistant carpets are some of the countless products that are made with a group of man-made chemicals called PFAS. PFAS are also included in foams used at airports and military sites to extinguish fires. The sites that have used the foam and manufactured PFAS has led to PFAS getting into the environment. PFAS chemicals do not naturally breakdown so they accumulate in the environment and people, where they are suspected to cause various health problems. To remove PFAS from drinking water, carbon filters are most commonly used. However, at the end of their lifespan, few disposal options are available. Also, no methods currently exist that are effective at removing PFAS compounds attached to soil. STAR is a heat-based treatment option for soils that has been shown to destroy other contaminants. STAR requires little energy to operate, allowing STAR to be cheap and useful method to clean-up contaminated soils. This research, for the first time, explored using STAR as a treatment option to remove PFAS from polluted soils and carbon filter material. STAR technology can bring contaminated soils and carbon filter material to extreme temperature (900˚C or greater), destroying the carbon filter material and breaking down the PFAS. Results showed that after using STAR, no PFAS remained in the soil. Compounds released into the air were either non-toxic or could be absorbed to other carbon filters that could be treated later. This research demonstrated STAR is an option to treat carbon filter material and soil contaminated with PFAS, removing these toxic compounds from the environment.

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