Surface water — rivers, lakes, and reservoirs — serves as the drinking water source for the majority of US public water systems. These sources are particularly vulnerable to PFAS contamination from point source discharges, agricultural runoff, and atmospheric deposition, presenting significant treatment challenges for utilities dependent on them.
PFAS in Rivers and Downstream Utilities
Rivers receiving discharges from PFAS-using industries, WWTP effluent, or stormwater runoff from PFAS-contaminated sites carry PFAS to downstream drinking water intakes. Utilities drawing from impacted rivers face PFAS concentrations that vary with flow conditions, upstream industrial activity, and precipitation patterns. River-dependent utilities must treat variable influent PFAS concentrations while maintaining compliance with fixed MCLs at all times — a more dynamic challenge than treating relatively stable groundwater sources.
Reservoir Management
Drinking water reservoirs accumulate PFAS from watershed sources over time. Unlike flowing river contamination, reservoir PFAS may concentrate through evaporation and seasonal stratification affects PFAS distribution within the water column. Treatment strategies must account for the full range of PFAS concentrations that may be drawn from reservoir intakes at different depths and seasons.
Treatment Train Design for Surface Water PFAS
Surface water treatment plants already employ coagulation, sedimentation, filtration, and disinfection for turbidity and microbial control. PFAS treatment is typically added as an additional stage — most commonly GAC contactors following conventional treatment — rather than replacing existing unit processes. The existing treatment train provides some PFAS co-removal through coagulation of PFAS-laden particles and organic matter, reducing the load on dedicated PFAS treatment stages.