Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor.

"High-concentration" and "low-concentration" bench-scale batch plasma reactors were used to effectively degrade per- and polyfluoroalkyl substances (PFAS) at a high concentration (∼100 mg/L) and a low concentration (<1 µg/L), respectively, in ion exchange (IX) regenerant still bottom (SB) solutions. In the SBs, numerous PFAS were detected with a wide concentration range (∼0.01 to 100 mg/L; total oxidizable precursors (TOP) ∼4000 to 10000 mg/L). In the "high-concentration" plasma reactor, the concentrations of PFAS precursors and long-chain perfluoroalkyl acids (PFAAs) (≥6C for PFSAs and ≥8C for perfluorocarboxylic acids (PFCAs)) were decreased by >99.9% in 2 h, and short-chain PFAAs (<6C for perfluorocarboxylic acids (PFSAs) and <8C PFCAs) were decreased by >99% in 6 h of treatment. Subsequently, a "low concentration" plasma reactor was used to remove additional PFAAs. In this reactor, the addition of CTAB (cetrimonium bromide, a cationic surfactant) caused short-chain PFAAs, other than PFBA, to be removed to below detection limits in 90 min of treatment time. Overall, >99% of the TOP present in SBs was removed during the treatment. Fluorine recovery of 47 to 117% was obtained in six SB samples. Energy requirement (EE/O) for the treatment of PFOA and PFOS from SBs ranged from 380 to 830 kWh/m3.

Rapid Removal of Poly- and Perfluorinated Compounds from Investigation-Derived Waste (IDW) in a Pilot-Scale Plasma Reactor.

A pilot-scale plasma reactor installed into an 8 × 20 ft2 mobile trailer was used to rapidly and effectively degrade poly- and perfluoroalkyl substances (PFAS) from liquid investigation-derived waste (IDW; development and purge water from monitoring wells) obtained from 13 different site investigations at Air Force installations. In the raw water, numerous PFAS were detected in a wide concentration range (∼10-105 ng/L; total oxidizable precursors (TOP) ∼102-105 ng/L, total fluorine by combustion ion chromatography ∼102 to 5 × 106 ng F/L). The concentration of total PFAS (12 perfluorocarboxylic acids (PFCAs) and perfluoroalkyl sulfonates (PFSAs)) in the 13 samples ranged between 2.7 and 1440 µg/L and the concentration of perfluorooctane sulfonate (PFOS) plus perfluorooctanoic acid (PFOA) ranged between 365 and 73700 ng/L. Plasma-based water treatment resulted in rapid perfluoroalkyl acids (PFAAs) removal from 4 L individual IDW samples with faster rates for longer-chain PFCAs (C ≥ 8) and PFSAs (C ≥ 6) than for PFCAs and PFSAs of shorter chain length. In 9 of the 13 IDW samples, both PFOS and PFOA were removed to below United States Environmental Protection Agency's (USEPA's) health advisory concentration level (HAL) concentrations in <1 min, whereas longer treatment times (up to 50 min) were required for the remaining four IDW samples due to either extremely high solution electrical conductivity, which decreased the plasma-liquid contact area (one IDW sample) or high concentrations of PFAAs and their precursors; the latter was found to be converted to PFAAs during the treatment. Overall, 36-99% of the TOP concentration present in the IDWs was removed during the treatment. There was no effect of non-PFAS co-contaminants on the degradation efficiency. Overall, the results indicate that plasma-based water treatment is a viable technology for the treatment of PFAS-contaminated IDW.