PFAS & Your Water: Drinking Water Monitoring & Treatment
How much PFAS is in our community’s drinking water?
Six PFAS compounds are the focus of the EPA’s regulations on PFAS in drinking water. Our most recent monitoring data, completed during the fourth quarter of 2024, detected PFOA at 3.4 ppt and PFOS at 3.2 ppt in our finished drinking water. PFHxS and PFBS were not detected during fourth quarter sampling but have been detected in the past. HFPO-DA (Gen-X) and PFNA have never been detected in our treated drinking water. Maximum, minimum, and average values detected of these six PFAS compounds in drinking water since 2018 are:
One part per trillion (ppt) can be visualized as one grain of sand in an Olympic-size swimming pool.
Over the last five years, we have detected an additional five PFAS compounds in our treated drinking water. Details on the results of each PFAS compound detected in our treated and source water are summarized in the dashboard below.
What is OWASA doing about PFAS?
We are working toward strategies to further reduce levels of PFAS in our drinking water. In the near term, we are improving a part of our current treatment process; in the long term, we are:
Monitoring: We are continuing to monitor our water supply, drinking water, wastewater, and biosolids. Monitoring provides data for research, helps us understand our water and our current treatment effectiveness on PFAS, and informs our solutions.
Engineering a Solution:
We are optimizing the use of an existing part of our treatment process (powdered activated carbon, or “PAC”) and have achieved reductions in PFAS compounds beyond those we see with our previous treatment. However, this will not be enough to meet our goals. While PAC is helping in the meantime, achieving our goals for PFAS levels and meeting the EPA’s Maximum Contaminant Levels (MCLs) for PFAS will still require a major new treatment facility.
In spring 2024, we began pilot testing a combination of two technologies that small-scale testing showed would work well on OWASA’s source water: Granulated Activated Carbon (GAC) and Ion Exchange (IX).Our pilot project showed both technologies are performing well to remove PFAS from our drinking water. However, we have a number of other criteria to consider when selecting a technology:
• How long the media (substance/material) works before it needs to be replaced;
• Capital (construction) and operational costs;
• Ease of operation;
• PFAS disposal;
• How the treatment technology impacts other aspects of OWASA’s drinking water quality; and
• The technology’s long-term adaptability to future advances.
We will announce the technology we will move forward with for PFAS treatment in January 2025
.
Design and Construction: Concurrent to the pilot testing, we have started about 12 to 14 months of design for a new treatment process and facilities that will be followed by 18 to 24 months of construction. We anticipate enhanced treatment for PFAS removal being online in 2028/2029.
Holistic Response: While the EPA’s proposed standard is focused on drinking water and our near-term focus is on drinking water treatment, our ultimate response will include addressing PFAS throughout our system.
Tributaries of Cane Creek Reservoir
While working to investigate PFAS levels in Cane Creek Reservoir source water, OWASA conducted monitoring of tributaries that feed the reservoir. In some areas, this monitoring showed much higher levels of PFAS than in the water taken in from Cane Creek Reservoir at our intakes for several compounds. The levels of PFAS found in the tributaries is not what is in the water entering the treatment plant nor in your drinking water. Our monitoring suggests that the presence of PFAS in Cane Creek Reservoir could be from another municipality’s previous biosolids land application practices in the watershed.
The map below shows where our samples were taken and the levels detected for individual compounds, relative to previously used biosolids land application fields.