Why Granular Carbon Beds and Ion-Exchange Resins Are Documented Differently for PFAS
A common misconception is that all treatment methods targeting per- and polyfluoroalkyl substances (PFAS) perform similarly. Granular activated carbon (GAC) and ion-exchange resins are two primary technologies used in PFAS treatment, but their documented effectiveness varies due to chemical interactions and selectivity differences.
GAC adsorbs certain PFAS compounds effectively, particularly longer-chain chemicals, whereas ion-exchange resins can target a broader range of fluorinated compounds, including some shorter-chain substances. Documentation for these technologies reflects tested capabilities through controlled trials, showing distinctions in the types and amounts of PFAS reduced. Understanding these differences helps households evaluate solutions when existing equipment cannot meet their treatment needs.
How the UCMR5 Survey Differs from UCMR3 in Compounds Tested and Detection Levels
The EPA’s Unregulated Contaminant Monitoring Rule (UCMR) surveys assess the presence of emerging contaminants like PFAS but evolve over time. UCMR5, conducted for the Bend Water Department through 2023 and into 2024, includes a refined list of PFAS compounds and improved detection limits compared to UCMR3.
For instance, UCMR5 monitored 20 samples for PFOA, PFOS, and other fluorinated compounds with reporting levels often at parts per trillion (ng/L, nanograms per liter). This contrasts with UCMR3’s earlier monitoring, which included fewer compounds and generally higher reporting thresholds. The updated survey provides more precise data, capturing lower-level detections that inform residents about the presence of 'forever chemicals' in their public water system.
How Seasonal and Multi-Year Variation Shows in the Record
The Bend Water Department’s data from May 2023 to August 2024 shows variation across 20 samples. Some compounds, such as PFOA, were detected above the method reporting level in only a few samples, with the highest PFOA measurement recorded at 7.9 ng/L (0.0079 µg/L). Other PFAS compounds like PFOS, PFHxS, and PFNA were not detected above reporting levels during this period.
These findings reflect surface water variability and treatment effectiveness over time rather than a steady-state condition. Factors such as seasonal changes in water sources, environmental inputs, and system operations can affect concentrations. The multi-sample approach provides a snapshot rather than a constant level, emphasizing the importance of periodic testing for individual households seeking to understand their own water quality.
What the Measured Range Means Against Federal Standards, and What It Does Not Mean
The EPA’s federal maximum contaminant levels (MCLs) for PFAS compounds, effective in 2024, are set to 4.0 ng/L (parts per trillion) for PFOA and PFOS, and higher for other compounds. In Bend’s public water system, only one PFOA sample slightly exceeded this standard, at 7.9 ng/L, with no PFOS detections above 4.0 ng/L.
This data does not imply any individual household’s water contains these levels or that detections above reporting limits equate to health violations. A detection shows the instrument measured a substance at a certain sensitivity but does not alone determine safety or regulatory noncompliance. Moreover, the data represent the public system’s supply, not specific home plumbing conditions, which would require direct testing.
What You Should Write Down Before Asking Anyone for Treatment Advice
- Date and location of any water testing results you receive
- Specific PFAS compounds reported, including units (ng/L or parts per trillion)
- Type of water source (surface water or groundwater)
- Whether your household has a history of relying on treatment equipment for PFAS
- Previous equipment’s type and known limitations or failure modes
- Whether your water provider publishes any notices about PFAS monitoring or related advisories
Having this information handy will allow a more focused discussion about treatment needs and options appropriate for your household.
Closing: Making Informed Choices About PFAS Treatment After Equipment Failure
We clarified that EPA’s data for Bend Water Department in Deschutes County shows measured PFAS at varying low levels with one PFOA result above the upcoming federal MCL; however, these system-wide figures do not define any individual home’s water quality. Understanding differences in treatment technologies and the evolution of monitoring programs helps guide your next steps.
Where previous equipment no longer performs as needed, the Pentair PFAS Forever Chemicals Filter ships ready to configure and offers a documented approach to reducing a broad range of these persistent compounds in residential water supplies.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2024-08-14. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for BEND WATER DEPARTMENT (OR4100100), OR: 200 results across 10 listed contaminants, 6 detections above the reporting level; 1 results above a 2024 federal MCL
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