US EPA

8177693 

Meetings & Symposia 

Degradation of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in aqueous film forming foam (AFFF)-impacted groundwater and soil by oxidation methods 

Yao, Y; Volchek, K; Brown, CE; Vogan, J; Burdick, J; Ross, I; Pancras, T; Ptacek, C; Thomson, N; Groza, L; Ma, J; Baldwin, JR 

2016 

Environment Canada 

39th AMOP Technical Seminar on Environmental Contamination and Response 

383-407 

English 

A bench-scale treatability study on the degradation of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in aqueous film forming foam (AFFF)-impacted groundwater and soil was conducted. Its specific focus was on the use of oxidation technologies. It was part of Environment and Climate Change Canada (ECCC)'s Technology Feasibility Study for the Remediation of Poly- and Perfluorinated Alkyl Substances (PFAS)-Contaminated Sites. The actual groundwater and soil samples were collected from a typical firefighting training site in Canada. The groundwater was used as is and the soil was mixed with tap water to simulate soilwashing effluent prior to the addition of reactants. Three oxidation methods were tested, including two formulations of persulfate and permanganate (known as [Smart Combined In-Situ Oxidation and Reduction] ScisoR® technology), while the third oxidant recipe comprising a manganese mineral plus hydrogen peroxide (H2O2) catalyst. The degradation of PFOS appeared to be effective using both ScisoR® 1 and ScisoR® 2 methods, in which the removal of PFOS using ScisoR® 1 was 97% for both groundwater and the soil/tap water mixture. The PFOS concentrations normally decreased at early times, then increased and reached peak concentrations around 48 hrs, and then decreased again. These observations suggest that degradation and formation of PFOS occurred concurrently under the oxidative conditions. PFOA was also found to be degradable under the ScisoR® conditions, but groundwater and soil borne precursor oxidation likely contributed to its generation in the experimental work such that it appeared to have a lower degradation rate compared to PFOS under the same conditions. In addition, PFOA was observed to be generated as a transient degradation intermediate during PFOS removal under the oxidative conditions. The transient formation of PFOA likely exceeded the rate at which the ScisoR® methods could remove this contaminant and likely reflects the presence of significant precursor mass, currently undetected. The results indicate that treatment efficiencies of PFOS/PFOA depend on multiple factors, including the original concentrations of these compounds and their precursors, their degradation rates, dosage of oxidants and reaction time, etc. Removal of PFOS/PFOA with the manganese mineral tests with different concentrations of H2O2 appeared effective at early times when the oxidant was present. However, re-dosage of H2O2 did not lead to continuous degradation of PFOS/PFOA. Further work is required to improve the current oxidation techniques for more effective PFAS (particularly PFOA) removal and to obtain an improved understanding of the reaction mechanisms of PFOS/PFOA and other PFCs, as well as relevant precursors and degradation by-products. 

Technology, Directorate