Perfluorooctanoic Acid (PFOA) Incorporated into Iron Particles Promoted the Formation of Disinfection Byproducts under Drinking Water Conditions

Perfluorooctanoic acid (PFOA) is an emerging persistent organic pollutant that is frequently detected throughout the drinking water supply system. Here, we first found that PFOA could significantly increase the formation of disinfection byproducts (DBPs) in unlined iron pipes (UIPs) during the distribution process. The increased DBPs were not due to the reaction of PFOA itself with free chlorine, but the in situ formed Fe-PFOA complex played a key role. Notably, PFOA could enhance iron release from UIPs and was greatly incorporated into the iron particles to form Fe-PFOA complex. The center dot OH generated by the Fe-PFOA heterogeneous reaction could break large dissolved organic matter into small molecules that had higher reactivity with chlorine. In addition, DBP precursors with more aromatic structures were favorable for forming strong Fe-pi interactions with Fe-PFOA complex, resulting in more center dot OH for the formation of aromatic DBPs. The cytotoxicity test showed that the viability of cells exposed to DBPs from UIPs with 100 ng/L PFOA was 46.9%, while that without PFOA was 67.91%. Overall, this study provided a new perspective on the risk of PFOA, with a focus not on PFOA itself but on its potential to promote DBP-associated toxicity in iron-based drinking water distribution pipes.

Automated summary

The study found that perfluorooctanoic acid (PFOA) significantly increased the generation of disinfection byproducts (DBPs) in unlined iron pipes (UIPs), not through its reaction with free chlorine, but through the formation of Fe-PFOA complex. PFOA enhanced iron release from UIPs and was incorporated into iron particles to form the complex, which generated center dot OH that broke down large organic matter into small molecules reacting with chlorine. Precursors with aromatic structures favored the formation of aromatic DBPs through Fe-pi interactions with Fe-PFOA complex. Cytotoxicity tests revealed that DBPs from UIPs with 100 ng/L PFOA had a viability of 46.9%, while that without PFOA had a viability of 67.91%.