Flushing Home Plumbing Pipes Contaminated with Aqueous Film-Forming Foam Containing Per- and Polyfluoroalkyl Substances.

Per- and polyfluoroalkyl substances (PFAS) from aqueous film forming foam (AFFF) can be accidentally backflushed into drinking water systems during firefighting operations or at industrial facilities. If this contaminated water enters household plumbing systems, homeowners may need to decontaminate their plumbing. This study examines the persistence of PFAS from AFFF on home plumbing, along with the effects of flushing and stagnation. Two sources of AFFF were investigated, representing older formulations (that contain longer chain PFAS) and newer formulations (that contain shorter chain PFAS). Experiments were conducted in copper, polyvinyl chloride (PVC), and cross-linked polyethylene (PEX) pipes with flushing after contamination followed by intermittent flow and periods of stagnation meant to mimic typical household use. Flushing immediately reduced the PFAS concentration in water leaving the pipe by 99.95% to 99.99%. However, PFAS concentration increased after periods of stagnation, corresponding to slow release of adhered PFAS. Flushing may be a valuable part of the decontamination process, but flushing parameters and duration need to be optimized for local conditions.

Benzene Diffusion and Partitioning in Contaminated Drinking Water Pipes under Stagnant Conditions.

Benzene contamination in drinking water systems affected by wildfires is a problem of emerging concern. Polyethylene pipes used in service lines and premise plumbing are vulnerable to permeation by benzene and can potentially cause challenges in sampling and remediation of contaminated systems. However, the kinetics and equilibria of the uptake of benzene by and release of benzene from pipes of differing polyethylene types and manufacturers are not well studied, leading to additional uncertainty when interpreting sampling data and selecting remediation options. This work addresses this data gap by providing diffusion and partitioning data for benzene and several varieties of polyethylene pipes, including field samples from water distribution systems. All polyethylene pipes that were studied exhibited similar partitioning behavior during benzene uptake and release, but some differences in kinetics were observed among pipes. However, these differences were of minor practical importance in the pipe contamination scenario examined in this work. The results of this study can be used in conjunction with diffusion modeling to inform remediation decisions for benzene-contaminated, polyethylene service lines, and premise plumbing.