Monitoring and Occurrence of PFAS in Drinking Water | AAAS EPI Center
inform and engage the community is also essential, and should include plans for how to respond to the PFAS detections above or below the federal- and state-specific criteria. Identifying Sampling Locations to Determine Sources of Contamination Analytical costs, complex water matrices, and trace PFAS concentrations and cross contamination can make sampling efforts costly and challenging. To allocate time and resources appropriately, develop a robust PFAS sampling plan . Figure 2 presents an example of PFAS travel routes from sources of contamination to the community, and recommended sampling components. One component of a sampling plan is to provide a “ Community Impact Assessment ” to sample treated drinking water at the WTP or within the distribution system to identify which communities are impacted. If PFAS are found, more sampling should take place over weeks to months after the contamination is identified to determine the risk to public health. A second component of a PFAS sampling plan is to conduct “ WTP Sampling ” at the WTP surface water intake(s) and/or groundwater well(s). The length of time an intake should be sampled depends on the location, as some sites are more impacted by seasonal changes than others. For surface water plants, the intake(s) should be sampled multiple times over an extended period (e.g., six to nine months) to account for seasonality or other variations in water quality typically associated with surface water sources. For groundwater sampling, a few samples over a short period (e.g., weeks to months) may be adequate to determine typical PFAS concentrations. If PFAS are not detected in raw (untreated) water samples after several sampling events, sampling frequency may be reduced (e.g., yearly) to check for PFAS contamination. The surface water intake and/or groundwater well sampling frequencies in the monitoring plan should be determined based on how variable the water sources are. Frequency can range from weekly to monthly depending on results of initial data collection. A third component of a PFAS sampling plan is “ Discharger Tracking and Source Water Identification ”. The purpose of this component is to better understand the sources of PFAS contamination in drinking water. Discharger tracking and source water identification includes sampling locations throughout the WTP source water such as tributaries that discharge into a river or lake, or additional groundwater well locations. Discharger tracking and source water identification should also include an evaluation of potential sources of contamination such as airports, firefighting training facilities, manufacturing facilities, landfills, and WWTPs. WTP source water contamination by PFAS is usually localized, meaning contaminants are likely to occur where a primary source discharges or infiltrates into a WTP source water. However, it is not always clear where those sources of contamination are located. Additional sampling components may be conducted as necessary to evaluate less obvious contamination sources, including secondary sources such as waste management units (e.g., landfills) that receive PFAS wastes. Sampling efforts should continue to monitor all possible PFAS contamination sources that can be identified. It is difficult to identify all contamination sources, but detailed sampling at multiple points upstream and downstream of potential sources can help to identify the contamination sites by comparing
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