Powdered Activated Carbon Treatment of PFAS‐Containing Washwater From Aircraft Hangar Pipe Rinsing

ABSTRACT The decontamination of thousands of pipes in fire suppression systems, for example, aircraft hangars and firetrucks exposed to aqueous film forming foam (AFFF), may generate large volumes of PFAS‐laden water requiring treatment. This study investigated the use of powdered activated carbon (PAC) to remove PFAS from washwater used to rinse pipes from aircraft hangar pipe contaminated with AFFF. The untreated washwater contained 249 µg/L of total PFAS. The concentrations were highest for 6:2 FTS (178 µg/L), PFHxA (48 µg/L), PFOA (9.5 µg/L), and PFPeA (6.2 µg/L). PFAS was removed from washwater during 24‐h adsorption experiments conducted over a range of adsorbent masses. Temporal increases were observed between the 2‐ and 4‐h total PFAS concentrations during most of the experiments, corresponding to some PFAS species being displaced during complex competitive adsorption mechanisms. After 24 h in the presence of 0.23 g of PAC per liter of solution, removals of 6:2 FTS and PFHxA, two of the short‐chain PFAS, were 95% and 86%, respectively. For long‐chain PFAS, PFOA and PFOS were removed to below their quantitation limits (i.e., 1 and 0.01 µg/L, respectively) in most cases. However, removal of 8:2 FTS was only 52% in the presence of 0.0575 grams of PAC, despite having a relatively high Log K ow and dipole moment values, also pointing to the complexity of PAC adsorption mechanisms in AFFF contaminated water. To the authors’ knowledge, this is the first study to report the use of PAC to treat AFFF washwater, a niche but important matrix.