UV Treatment: Standard Practice, PFAS Limitation
Ultraviolet (UV) disinfection is a standard advanced treatment process that inactivates pathogens without chemical residuals. Some treatment operators wonder whether UV treatment also contributes to PFAS removal. The straightforward answer: conventional low-pressure UV treatment at standard disinfection doses has essentially no effect on PFAS—these compounds are among the most UV-resistant organic molecules known.
The C–F Bond and UV Resistance
PFAS compounds do not absorb UV light at the 254 nm wavelength used in conventional UV disinfection systems. The C–F bonds that make PFAS environmental pollutants also prevent UV photolysis under normal treatment conditions. Studies of conventional UV disinfection confirm <5% PFAS reduction—statistically indistinguishable from zero removal under treatment plant operating conditions.
Vacuum UV and High-Energy Photolysis
Vacuum UV (VUV) at wavelengths below 200 nm can initiate PFAS photolysis, but vacuum UV is not used in standard water treatment due to equipment complexity and oxygen absorption limitations in air. High-energy UV at very high doses combined with oxidants (UV/H2O2 or UV/persulfate) can destroy some PFAS compounds but requires substantially higher UV doses than disinfection practice and remains a research-stage technology for water treatment applications.
UV as Part of Multi-Barrier Treatment
UV treatment remains valuable in PFAS treatment trains for its disinfection function—preventing pathogen risks that might otherwise require additional chemical disinfectants. However, utilities implementing UV to address PFAS should understand it provides zero PFAS removal benefit and cannot substitute for adsorption or membrane treatment in PFAS compliance strategies.