Thermal hydrolysis (raising water/sewage to very high temperatures and pressures) can also break down PFAS and other bad stuff like pharmaceutical compounds. The Washington, D.C. Blue Plains water treatment plant uses this technology to safely convert septic sludge to fertilizer, sold under the brand name Bloom:
https://en.wikipedia.org/wiki/Blue_Plains_Advanced_Wastewate...
https://bloomsoil.com/faqs/#what-is-bloom
edit: As I Google to double-check my recollection, I'm finding mixed but encouraging reports on this technique's effectiveness. For instance this 2021 paper:
https://www.sciencedirect.com/science/article/abs/pii/S22133...
>To our best knowledge, there are only two studies that have evaluated fate of PFAS in sludge before and after HTL. In a report presented by Mitroshkov et al. [19], 15 PFAS were quantified in five sludge samples before HTL. After HTL, concentrations of the majority of these PFAS were below detection limit of the GC/MS/MS. However, the authors did not report the HTL operating conditions used in this study. In addition, PFSAs including PFOS, the commonly recognized most recalcitrant PFAS, were not targeted in this work.
>In another study, degradation of five PFAS (i.e., PFOA, 7:3 FTCA, 8:2 FTUCA, 8:2 FTS, PFOS) in sludge by HTL was conducted [35]. Among the five, each spiked at 1000 µg/kg, the first three were degraded > 99% at 350 °C for 90 min. Degradation of 8:2 FTS and PFOS was 34% and 67%, respectively. It was found that undegraded PFAS partitioned to the biocrude phase, which may negatively impact the quality and use of these biocrude in the real world.
>Compared to PFAS in water only, more degradation was observed when these PFAS were spiked to sludge. It was speculated that metal ions and mineral solids in the sludge might have contributed to enhanced PFAS degradation [35].