Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7d. Ex Situ PFAS Water Treatment Technologies

Formatted Title:

Non-Organic On-Site Regeneration of Per- and Polyfluoroalkyl Substances-Laden Granular Activated Carbon

Background/Objectives:

Poly- and perfluoroalkyl substances (PFAS), also known as “forever chemicals”, are a complex group of over 4800 manufactured chemicals that are ingredients in various everyday products. The presence of carbon-fluorine bond renders these compounds chemically and thermally stable. While most PFAS treatment methods primarily focus on source removal, the challenge of handling residual PFAS remains. Adsorption via granular activated carbon (GAC) is widely used to remove PFAS. However, once GAC becomes saturated with PFAS, it necessitates further treatment. Thermal reactivation of spent GAC holds promise for PFAS destruction, albeit with substantial energy requirements and the need to transport spent GAC to reactivation facilities. The patented Fluorinse® process offers an innovative solution. This process successfully regenerates the media onsite by employing a sequence of fluids, leading to the precipitation of PFAS. These precipitates can then be effectively eliminated using innovative destruction technologies, such as supercritical water oxidation (SCWO). Notably, the regenerated GAC has demonstrated the same capacity as virgin GAC.

Approach/Activities:

To validate the practicality and effectiveness of our regeneration solution, including its application for PFAS remediation, we conducted a comprehensive series of bench-scale experiments including rapid small-scale column tests (RSSCTs). The experiments included, but were not limited to, regenerating carbon substrates using calcium hydroxide and calcium chloride, comparing sorption isotherms of fresh and regenerated activated carbon for PFAS, and evaluating the performance of our regeneration system for capturing contaminants from complex samples closely resembling groundwater. We further advanced our investigation by conducting column testing with small columns loaded with GAC, establishing a comprehensive regeneration column protocol, and applying our innovative approach to unground spent F400 GAC. To ascertain practicality and scale-up potential, three columns were utilized: one with fresh GAC, one with spent GAC regenerated, and one with unused GAC pretreated using the regeneration process. The study also examined the role of surfactants and agglomerating agents in aiding regeneration efficiency as well as the effects of co-contaminants (e.g., humic acid) on regeneration. In addition, we tested the efficacy of regeneration solution on municipal water facility – GAC and water from site. PFAS were measured by LC-MS/MS EPA Method 537.1.

Results/Lessons Learned:

The column test results were in line with the beaker test results. RSSCT results indicated 76% recovered capacity testing GAC and water from a partner water facility. In parallel experiments, influent from another partner water treatment facility with ~ 100 ppt PFAS was successfully treated using regenerated GAC to < 14 ppt for numerous cycles. For these experiments, the regenerated GAC capacity consistently ranged from 95% to 100%. These findings underscore the system's ability to effectively regenerate and maintain its pollutant capture capabilities. This technology exhibits considerable scalability potential and can be tailored for implementation at new sites with subsequent optimization. Furthermore, it offers adaptability for integration into existing sites. At the forthcoming Battelle conference, we intend to present the results achieved including fluorine mass balances, highlighting the efficacy of our approach, encompassing insights on the regeneration solution and agglomeration. Additionally, we will make every effort to provide preliminary findings regarding the performance of various destruction technologies such as electrochemical oxidation and supercritical water oxidation (SCWO) on PFAS destruction in the residuals.

George Adamson

Affiliation

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(Group 1, Poster Board #270) Non-Organic On-Site Regeneration of Per- and Polyfluoroalkyl Substances-Laden Granular Activated Carbon