The existence of perfluoroalkyl substances (PFASs) in surface waters is a worldwide problem due to their toxicity and persistence in the environment. To date, the application of advanced oxidation processes (AOPs) for the removal of PFAS by conventional treatment processes is not fully understood. AOPs have shown promise for the degradation of PFASs in pure water backgrounds. However, there is still limited data available on the effectiveness of AOPs in real water backgrounds at environmentally relevant concentrations. Therefore, the main goal of this research was to screen the effectiveness of selected commercially available AOPs (UV, UV+H2O2, O3/H2O2) processes for the removal of PFAS contaminants from groundwater. Bench-scale UV, UV+H2O2, and O3/H2O2 experiments were performed at the highest applicable concentrations of oxidant/UV dose at 4 hr contact time. Additionally, UV experiments were conducted with a commercially available pilot scale photocatalytic reactor in the presence of 1 g/L of catalyst, one commercially available (Cat#1), one novel (Cat#2), and a combination of both (Cat#1 +Cat#2). The groundwater was collected from a PFAS contaminated well in CA and measured according to method EPA 533. The results showed that the total PFAS concentrations increased from 920 ng/L to 3150 ng/L and 1961 ng/L following UV and UV/H2O2 treatment, respectively. This suggests the presence of long chain (&gt;C8) PFAS, which are not detected by EPA 533, that are oxidized to carboxylic acids (i.e., PFOA, PFHxA, PFPeA, PFBA). On the other hand, O3/H2O2 did show degradation of PFOA (85%) but formed shorter chain carboxylic acids. The total PFAS measured after UV/Cat#1, UV/Cat#2, and UV/Cat#1+Cat#2 increased to 2768, 2358, and 1525 ng/L, respectively. All three tested UV/Cat combinations showed complete removal of PFDA, PFNA, PFPeS, and PFBS. While UV/Cat#1 treatment showed degradation for PFOS (42%), UV/Cat#2 treatment had complete removal for PFOS and PFHxS, and ~90% removal for PFOA. The combination of both catalysts during UV treatment showed complete removal of PFOS and PFHxS and ~94% removal for PFOA. Overall, the results suggest that AOPs do transform longer-chain PFAS to shorter-chain PFAS under extreme commercially available operating conditions. Since EPA Method 533 only captures specific PFAS, groundwaters with a large concentration of non-detected PFAS species have the risk of forming detectable PFAS and thus increasing total PFAS during treatment.

Screening to identify commercially available advanced oxidation processes to remove PFASs from groundwater

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