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PFAS Statewide Investigation Network: Community Water Supply Sampling
In 2021, Illinois Environmental Protection Agency (Illinois EPA) completed a statewide investigation into the prevalence and occurrence of Per- and Polyfluoroalkyl Substances (PFAS) in finished, or treated, drinking water at 1,428 entry points to the distribution system representing 1,749 community water supplies (CWS) across Illinois. The purpose of this investigation was to support the potential development and promulgation of maximum contaminant level (MCL) standards in Illinois for certain PFAS, and to respond to scientific data regarding the effects of PFAS on public health. Samples were analyzed using United States Environmental Protection Agency (U.S. EPA) Method 537.1. Illinois EPA, in conjunction with U.S. EPA, developed a Quality Assurance Project Plan (QAPP) for this investigation network. The QAPP also contains a Standard Operating Procedure (SOP) for sample collection.
Before conducting sampling at a CWS, Illinois EPA staff contacted the CWS Responsible Operator in Charge to schedule a time to collect the samples for PFAS analyses. There was no cost to CWS for this sampling.
Illinois EPA provided CWS owners and operators with the results of this sampling. If PFAS were present in concentrations above minimum reporting levels (MRLs), or the lowest concentration a laboratory can reliably detect, Illinois EPA returned to collect a confirmation sample at the distribution system entry point(s). This is where source, or treated, drinking water enters the pipes to the distribution system that provides water to customers. Based on the results of the confirmation sampling, additional evaluation or actions were taken to protect human health and the environment. Illinois EPA’s sample analyses included a total of 18 PFAS, each with an MRL of 2 nanograms per liter (ng/L) or parts per trillion (ppt) using U.S. EPA Method 537.1, listed on the chart below.
Illinois EPA Sample Collection Dissemination of Results
Illinois EPA representatives collected samples from the entry point(s) of the CWS distribution systems for analyses. Illinois EPA followed a strict chain-of-custody protocol and used the same laboratory for all sample analyses to ensure to U.S. EPA Method 537.1 was followed uniformly. Following sample validation and review by Illinois EPA, Illinois EPA provided analytical results to the CWS. The analytical results are available in Illinois EPA’s Drinking Water Watch system and on the PFAS Investigation Network Interactive Dashboard and Map.
In instances where PFAS chemicals were detected, the numbers listed above reflect the number of entry points where one or more PFAS chemical was confirmed through additional sampling. Fifteen entry points had initial detections that were not confirmed. Four of the fifteen unconfirmed entry points were taken out of service after the initial sample.
CWS Owner and Operator Sampling/PFAS Analysis
Owner/operators (o/o) conducting their own sampling for PFAS should contact the Bureau of Water for information on validated drinking water analytical methods. In addition, CWS o/o should use a laboratory accredited by the National Environmental Laboratory Accreditation Conference (NELAC) to analyze for PFAS. NELAC has an online database that can be used to search for labs to analyze PFAS in drinking water.
Source Water Assessment
Now is a good time for CWS o/o to review and ensure their contingency plans are up to date and to review the Source Water Assessment and Protection (SWAP) Fact Sheet. The SWAP Fact Sheet that Illinois EPA developed includes potential contamination sources and the susceptibility of the source water to contamination, but the CWS may need to update its SWAP Fact Sheet with current information.
Response to PFAS present in CWS entry points
Illinois EPA notified the CWS of any confirmed PFAS detections in drinking water. The CWS then informed consumers of these sample results through direct mailing, distribution of notices directly to customers, posting on the CWS website or other means. During confirmation sampling, Illinois EPA provided information to the CWS on treatment and source water options to assist the CWS as they address the presence of PFAS in drinking water. If PFAS were identified in finished water during the PFAS Statewide Sampling Investigation, Illinois EPA requested the CWS to monitor quarterly for PFAS analytes in both finished and raw water, and may also have included other system specific efforts to eliminate or reduce the presence of PFAS in finished drinking water.
CWS Treatment
The owners/operators of CWS can obtain technical information on the removal of PFOA, PFOS, and other PFAS on the U.S. EPA website.
CWS Permits
A change in source or treatment will require the CWS to obtain construction and operating permits from Illinois EPA. Pilot studies may be required to determine design parameters for treatment units for PFAS removal. Parameters such as loading rates, contact times, media selection, media life, maintenance, monitoring constituents and frequencies, and disposal considerations must be justified to obtain a construction permit. Corrosion control studies may be required. Information on treatment considerations can be found on the U.S. EPA PFAS website.
PFAS Investigation Network Interactive Dashboard and Map