Chlorination: Essential for Safety, Neutral for PFAS
Chlorine disinfection is fundamental to drinking water safety, preventing waterborne disease by inactivating bacteria, viruses, and protozoa. For PFAS, however, chlorination—whether using free chlorine, chloramines, or chlorine dioxide—has no meaningful effect on concentrations of fully perfluorinated terminal PFAS compounds.
Chemical Stability of PFAS Against Oxidation
Chlorine and its disinfection byproducts are oxidizing agents, but PFAS are highly resistant to chemical oxidation. The C–F bond that makes PFAS environmentally persistent prevents oxidative cleavage under the conditions used in drinking water disinfection. Studies confirm that chlorine doses of 2–10 mg/L—far exceeding typical treatment doses—achieve <5% reduction of PFOA and PFOS concentrations.
Chlorination of PFAS Precursors
An important nuance is that chlorination may partially oxidize some PFAS precursor compounds, altering their structure without fully mineralizing them. Some chlorinated transformation products have different health profiles from their precursors, and chlorination may convert some non-regulated precursors to regulated terminal PFAS—potentially increasing reportable PFAS concentrations in finished water.
Disinfection Byproducts and PFAS Together
Utilities adding chlorine to source waters with high PFAS concentrations must still manage disinfection byproduct (DBP) formation alongside PFAS treatment. High-NOM source waters requiring higher chlorine doses for DBP compliance create additional treatment complexity. Treatment optimization for both DBPs and PFAS represents a multi-parameter challenge that conventional treatment cannot address with chlorination alone.