Per- and Polyfluoroalkyl Substances (PFAS) are a class of over 6,000 persistent,
bioaccumulative, mobile, and toxic environmental contaminants that are ubiquitous in
wastewater and stormwater. PFAS exposure is linked to adverse human health outcomes and
lethal and sublethal toxicity in aquatic species. PFAS discharges in wastewater effluent draw
increasing scrutiny from states, including Iowa, and federal regulatory rule making is underway.
The best-studied and most frequently regulated PFAS are perfluoroalkyl acids (PFAAs). PFAAs
are also the terminal transformation products of many precursor PFAS with more complex head
groups. Wastewater treatment processes can transform many precursor species into PFAAs;
however, precursor species are less likely to be researched, monitored, or regulated than their
terminal transformation products.
We propose to investigate whether shorter hydraulic retention times during wastewater treatment
will result in less precursor transformation and therefore a greater discharge of PFAS which are
“invisible” to standard measurement protocols. Proper accounting of often-unmeasured precursor
PFAS—which may contribute to aquatic toxicity and can transform into terminal PFAAs in the
environment—will provide a more comprehensive understanding of PFAS discharge to
environmental waters from stormwater and wastewater. This improved understanding will enable
more informed treatment design and the establishment of effective and equitable regulations.