20.4 Emerging Contaminants, PFAS & Advanced Analytical Methods
Key Takeaways
- PFAS are a large family of synthetic fluorinated compounds whose carbon-fluorine bonds resist conventional treatment and environmental degradation.
- EPA finalized national primary drinking water regulations for several PFAS in 2024, setting maximum contaminant levels of 4.0 parts per trillion for PFOA and PFOS.
- PFAS sampling requires specific field precautions, because common items such as certain waterproof clothing, food packaging, and PTFE-containing materials can contaminate the sample.
- Granular activated carbon, ion exchange, and reverse osmosis are the three treatment technologies EPA identifies as effective for PFAS removal.
- The Unregulated Contaminant Monitoring Rule collects occurrence data on contaminants that lack standards, and it is how EPA builds the record for future regulation.
20.4 Emerging Contaminants, PFAS & Advanced Analytical Methods
The Need-to-Know Criteria added "emerging contaminants (e.g., microplastics, PFAS)" to the laboratory analysis content area, reflecting how quickly this area has moved from research topic to compliance obligation.
What PFAS Are
Per- and polyfluoroalkyl substances (PFAS) are a family of thousands of synthetic compounds built around chains of carbon atoms bonded to fluorine. The carbon-fluorine bond is among the strongest in organic chemistry, which is exactly why these compounds are useful — and exactly why they persist.
Uses: non-stick cookware, stain- and water-resistant textiles, food packaging, cosmetics, industrial processes, and aqueous film-forming foam (AFFF) used in firefighting.
Sources of drinking water contamination: fire training areas at airports and military installations, industrial discharges, landfill leachate, and land-applied biosolids.
| Property | Consequence |
|---|---|
| Extremely persistent | Do not break down; the "forever chemicals" label |
| Mobile in groundwater | Travel far from the source |
| Bioaccumulative | Build up in blood and organs |
| Not removed by conventional treatment | Coagulation, sedimentation, filtration, and chlorination are ineffective |
[!IMPORTANT] Conventional treatment does not remove PFAS. A plant with excellent turbidity removal and disinfection performance provides no PFAS barrier whatsoever. This is a genuine change in how operators must think about their treatment train — the multiple-barrier approach as historically configured does not address these compounds.
The Regulations
In 2024 EPA finalized national primary drinking water regulations for several PFAS.
| Compound | MCL |
|---|---|
| PFOA | 4.0 parts per trillion (ng/L) |
| PFOS | 4.0 parts per trillion |
| PFHxS | 10 parts per trillion |
| PFNA | 10 parts per trillion |
| HFPO-DA (GenX chemicals) | 10 parts per trillion |
| Mixtures of PFHxS, PFNA, HFPO-DA, and PFBS | Hazard Index of 1 |
The maximum contaminant level goals for PFOA and PFOS are zero, reflecting the conclusion that no level is considered without risk.
The Hazard Index is worth understanding because it is a different regulatory structure from a simple concentration limit. Each of the four compounds in the mixture is divided by its own health-based water concentration, and the resulting ratios are summed. A total of 1 or greater is an exceedance, even where no individual compound exceeds its own value — the approach recognizes that these compounds act together.
Systems must monitor, report results in the Consumer Confidence Report, and install treatment where the standards are exceeded, on the compliance schedule the rule establishes.
Sampling for PFAS
PFAS sampling has requirements unlike any other parameter, because the contamination risk comes from the sampler's own equipment and clothing.
| Prohibited or avoided | Reason |
|---|---|
| PTFE (Teflon) tubing, tape, and caps | Fluoropolymer — a direct PFAS source |
| Waterproof or water-resistant clothing and boots | Commonly treated with PFAS |
| Fabric softener on laundered field clothing | May contain PFAS |
| Certain food packaging and wrappers on site | Grease-resistant coatings contain PFAS |
| Some sunscreens, cosmetics, and insect repellents | May contain PFAS |
| Glass sample containers for some methods | PFAS adsorb to glass; HDPE or polypropylene is specified |
Field practice includes field reagent blanks to demonstrate that the sampling process itself did not introduce contamination, powder-free nitrile gloves changed between samples, and no pre-rinsing of the bottle.
Analytical methods are EPA Method 533 and Method 537.1 for drinking water, both using liquid chromatography with tandem mass spectrometry. Reporting limits are in the parts per trillion, and only laboratories specifically certified for the method may produce compliance data.
Treating PFAS
EPA identifies three best available technologies:
| Technology | Notes |
|---|---|
| Granular activated carbon (GAC) | Effective, particularly for longer-chain PFAS such as PFOA and PFOS; shorter-chain compounds break through sooner |
| Ion exchange (anion resin) | PFAS-selective resins; high capacity; often single-use |
| Reverse osmosis / nanofiltration | Very effective across the range; produces a concentrate stream |
[!WARNING] Every one of these technologies concentrates the PFAS rather than destroying it. Spent GAC, spent resin, and RO concentrate all contain the removed compounds, and disposal is a genuine and unresolved challenge. High-temperature incineration, specialized landfilling, and emerging destruction technologies are all under active development and regulatory scrutiny. Treating PFAS therefore creates a residuals management obligation that must be planned from the outset — a point directly connected to the residuals handling covered earlier in this guide.
Other Emerging Contaminants
| Contaminant | Concern |
|---|---|
| Microplastics | Particles under 5 mm from textiles, tire wear, and plastic breakdown; no federal drinking water standard; standardized analytical methods still developing |
| Pharmaceuticals and personal care products | Detected at nanogram-per-liter levels; primarily a wastewater effluent and reuse concern |
| 1,4-Dioxane | Solvent stabilizer; very difficult to remove, requiring advanced oxidation; not removed by GAC or air stripping |
| Hexavalent chromium | Regulated federally as total chromium; California has a separate standard |
| Cyanotoxins | Health advisories for microcystins and cylindrospermopsin |
| Manganese | Health-based advisory in addition to the aesthetic secondary standard |
| Nitrosamines (NDMA) | A chloramination byproduct; relevant to systems that chloraminate |
The Unregulated Contaminant Monitoring Rule
UCMR is the mechanism by which EPA collects national occurrence data on contaminants that have no standard. Every five years EPA designates a list, and large systems plus a representative sample of small systems monitor for them and report the results to a national database.
The purpose is regulatory: UCMR data becomes the occurrence record supporting a decision to regulate, and the PFAS standards finalized in 2024 rest substantially on UCMR monitoring data. For an operator, UCMR monitoring is a real obligation with specified sampling locations and schedules, and its results appear in the Consumer Confidence Report even though no standard applies.
A conventional surface water plant with excellent turbidity removal, effective disinfection, and full compliance with all existing standards receives a PFOA result of 9 parts per trillion. What does this indicate about the treatment train?
A field technician preparing to collect PFAS samples arrives wearing a water-resistant jacket and waterproof boots, and plans to use PTFE-lined bottle caps. What is the problem?
A utility installs granular activated carbon to remove PFAS and meets the drinking water standards. What obligation does this create that must be planned in advance?