Life cycle assessment of the thermal oxidation and pyrolysis of granular activated carbon loaded with perfluorooctane sulfonic acid (PFOS)

Granular activated carbon (GAC) has been widely used to remove per- and polyfluoroalkyl substances (PFAS) from contaminated drinking water . The spent GAC can be thermally destroyed or regenerated for reuse. To understand how innovations in thermal treatment can reduce environmental impact of PFAS-laden GAC, we performed a life cycle assessment (LCA) of the thermal oxidation and pyrolysis of perfluorooctane sulfonic acid (PFOS) loaded onto GAC with and without the use of calcium additives. The functional unit for the study was 1 kg of clean GAC, and the system boundary included transportation, thermal oxidation or regeneration and reuse of GAC, and treatment of the waste byproducts. Two underlying assumptions were made based on prior research: (1) the regeneration and post-performance of the GAC was 100 % for all scenarios, and (2) the additive eliminated volatile organic fluorine (VOF) products of incomplete destruction (PIDs) and captured hydrofluoric acid (HF). Without an additive, the LCA indicated that regeneration and reuse have an overall lower environmental impact than thermal oxidation. The highest impact comes from the need for an afterburner to treat the VOF. Using hydrated lime as an additive decreases the temperature and time required for mineralization of PFAS, reducing the environmental impact in all categories. This is attributed to not needing post-processes to handle VOF and HF. The results underscore the importance of choosing the appropriate management practice for PFAS-laden GAC, with the goal of reducing environmental impacts while maximizing the destruction and mineralization efficiency of PFAS. • Regeneration is always a better option compared to oxidation. • Using additives provides the lowest overall environmental impact. • Operating the afterburner has the highest environmental impact.