Water Quality Modeling of Perfluorooctanoic Acid in a Water Distribution System

FWRJ Water Quality Modeling of Perfluorooctanoic Acid in a Water Distribution System

Christopher C. Baggett and Saheb Mansour-Rezaei

Perfluorooctanoic acid (PFOA) is a man-made chemical that has been used in numerous industries since the 1940s. The PFOA is persistent in the environment and remains in the human body for years after exposure, leading to adverse health effects.

The PFOA and perfluorooctanesulfonic acid (PFOS) are a part of a larger group of chemicals called per- and polyfluoroalkyl substances (PFAS), which have been used in consumer products and industrial applications, such as food packaging, clothing, firefighting foams, and upholstery. Both PFOA and PFOS have been the most extensively produced and studied of these chemicals. Studies have found PFOA in the blood samples of the general human population and wildlife.

As part of the third Unregulated Contaminant Monitoring Rule (UCMR 3), The U.S. Environmental Protection Agency (EPA) conducted sampling and analysis of water systems for 30 unregulated contaminants, including PFAS, between 2013 and 2015. Due in part to the confirmed presence of PFAS in water samples and the possibility of adverse health impacts associated with drinking water containing PFAS, EPA established a drinking water health advisory level for PFAS in 2016. Epidemiology studies, however, have demonstrated that humans are at an increased risk of developing certain types of health issues due to drinking water with PFAS concentrations less than the EPA level.

Some states have established maximum contaminant levels (MCLs), which are much lower than EPA’s PFAS drinking water health advisory level. In June 2022, EPA released a new health advisory (HA) for four PFAS: Interim HAs for PFOA and PFOS, and Final HAs for GenX chemicals and perfluorobutanesulfonic acid (PFBS). Table 1 presents a summary of the EPA and state drinking water values for PFAS in parts per trillion (ppt).

Table 1. U.S. Environmental Protection Agency Health Advisory and States Levels for Per- and Polyfluoroalkyl Substances

Regulatory Agency PFOA PFOS PFHxS PFNA PFHpA PFDA PFBS GenX

ppt ppt ppt ppt ppt ppt ppt ppt

United States EPA Health Advisories* Connecticut Department of Public Health Florida Department of Environmental Protection Maine 0.004 0.02

16 10 49 12

70 (Sum of 2) 2,000 10

Division of Environmental and Community Health Massachusetts Department of Environmental Protection New Hampshire Department of Environmental Services New Jersey NJ Drinking Water Standards New York DH Drinking Water Standards Rhode Island DEP Drinking Water Standards Vermont 20 (Sum of 6)

20 (Sum of 6)

12 15 18 11

14 13 13

10 10

20 (Sum of 6)

DH Drinking Water and Groundwater 20 (Sum of 5) Standards *Health advisories are nonenforceable and nonregulatory and reflect EPA’s assessment of the best available peerreviewed science. The interim updated health advisories replace the 2016 final health advisories for PFOA and PFOS, which were both set at 70 ppt. The EPA is reviewing and will respond to the Science Advisory Board (SAB) comments as the agency moves forward to develop maximum contaminant level goals (MCLGs) to support the Safe Drinking Water Act National Primary Drinking Water Regulation for PFOA and PFOS, which is expected to be proposed later in 2022. Christopher C. Baggett, P.E., is senior project manager, and Saheb Mansour-Rezaei, Ph.D., P.E., is lead project engineer, with WrightPierce in Tampa.

Chemicals Cause Concern for the Water Industry

The concentrations of PFOA are a growing concern in water distribution systems. Water quality models provide a costeffective tool to estimate temporal and spatial variations of PFOA concentrations within water distribution systems. The concept of water quality modeling was preliminarily introduced to the utility industry in the early 1980s. The usability of these models was greatly improved in the 1990s with development of Windows-based commercial water distribution system models.

Today, water distribution system models are commonly used to replicate the behavior of real-world systems. The following water quality models have been developed: S Clark and Boutin (2001) evaluated the applicability of water quality models to simulate formation and propagation Continued on page 40