Carbon Injection to Support In-Situ Smouldering Remediation
Abstract
Per- and polyfluoroalkyl substances (PFAS) are a group of anthropogenic contaminants that are growing increasing concern due to their associated negative health affects. The properties of PFAS result in their persistence and stability which present challenges for remediation. Activated carbon is currently the most widely used method for PFAS treatment since carbon microparticle injection can be used for in-situ treatment; however, this method does not result in PFAS destruction. Thermal treatment is a promising post-treatment method that can be used with activated carbon as long as sufficient PFAS-destroying temperatures are achieved (> 900°C). A promising in-situ thermal treatment technology is Self-Sustaining Treatment for Active Remediation (STAR) which uses smouldering combustion to destroy organic contaminants embedded within a porous matrix. This study investigates carbon injection to support STAR for the treatment of PFAS. Four solutions were used (i) 17% colloidal activated carbon (CAC) (ii) 23% CAC (iii) 17% powdered activated carbon (PAC) and (iv) 23% PAC. Smouldering temperatures greater than required PFAS destruction temperature were reached for all carbons if 50 g carbon/kg sand was achieved for both injection and soil-mixing delivery methods. Moreover, emulsified vegetable oil (EVO) was demonstrated to be a successful secondary surrogate fuel to further enhance smouldering temperatures when supplied at a quantity less than or equal to carbon microparticles. These findings present the necessary intermediate laboratory work to evaluate methods that will achieve PFAS treatment through STAR when applied in the field.