Analyzing PFAS in wastewater discharge requires a new method

May 10, 2023
Draft Method 1633 shows immense promise an a protocol for analyzing PFAS in wastewater.

The U.S. EPA’s 2021-2024 PFAS Strategic Roadmap calls for further efforts to research, restrict, and remediate per- and polyfluoroalkyl substances (PFAS) that are discharged into the environment.

To support that mission, the agency has been in search of new test methods for PFAS in matrices other than potable water. One method in particular has been singled out for its promise: Draft Method 1633. In December of last year EPA released its third draft of the method.

There exist two programs that are driving the development of Draft Method 1633, and it is importat that wastewater professionals gain knowledge about the latest changes in the 3rd Draft.

NPDES: a primary driver

One of the primary programs driving the development of Draft Method 1633 is the National Pollutant Discharge Elimination System (NPDES).

Created in 1972 by the Clean Water Act (CWA), NPDES is a permitting program designed to regulate the discharge of pollutants into the nation’s waterways. States can petition EPA to administer their own NPDES program, and the majority of states have received partial or full approval.

On Dec. 5th of 2022, EPA issued a memo to states providing guidance on addressing discharges in NPDES permits which strongly recommended using Draft Method 1633 to monitor for the 40 PFAS detectable by the method. Draft Method 1621, a method for analyzing Total Organic Fluorine, may also be used.

NPDES permitting also offers an established vehicle for monitoring and assessing the problem of PFAS in biosolids without the need to wait for new legislation to control the issue.

Also known as wastewater sludge, biosolids are a by-product of wastewater treatment. EPA estimates that roughly half of the biosolids produced in the U.S. are land-applied as soil amendments. When biosolids are produced from the treatment of wastewater containing PFAS, and no effort is made to address PFAS contamination, the biosolids are likely to be contaminated as well.

When used for agricultural purposes, PFAS can migrate from these biosolids to local ground and surface waters. It can also contaminate the food supply through plant uptake and animal consumption of plants grown in contaminated soil.

In April of 2022, EPA issued guidance to the states, recommending the regular monitoring of biosolids for PFAS. Again, Draft Method 1633 is the preferred method.

Effluent guidelines program

EPA also seems likely to encourage the use of Draft Method 1633 development through its Effluent Limitation Guidelines (ELGs). As described by EPA, ELGs are “national, technology-based regulations developed to control industrial wastewater discharges to surface waters and into publicly owned treatment works . . . intended to represent the greatest pollutant reductions that are economically achievable for an industry.”

The CWA requires EPA to publish a plan for new and revised ELGs every two years.

The most recent of those plans, Plan 15, calls for EPA to set effluent guidelines for PFAS in landfill leachate, following a study of landfills conducted by EPA in 2021 which indicated that ELGs for landfill leachate were warranted.

That study found that 95% of landfill leachate contained PFAS. If the landfill is unlined, this leachate can directly contaminate local soils and groundwater. If the landfill has a leachate collection system, the leachate is often sent to the local wastewater treatment facility. Since traditional wastewater treatment does not destroy PFAS and can convert PFAS precursors into terminal PFAS, discharge from these facilities may contain PFAS.

Plan 15 also calls for a detailed study of PFAS in wastewater discharge from textile mills and industrial discharge sent to publicly owned treatment works. Draft Method 1633 is expected to cover both of these matrices when finalized and will likely be specified as the preferred or required method for future ELGs as well as effluent research initiatives.

Unpacking the 3rd draft

The 3rd Draft of Draft Method 1633, published in December 2022, includes the “final” quality control (QC) protocols for wastewater — although there may be further adaptations and clarifications in the 4th Draft and in the final method. The final version of Method 1633 is also expected to include QC protocols for all non-potable waters, including landfill leachate, and cover a variety of solids, including soil, sediment, biosolids, and biota.

What follows is a rundown of some of the changes in the 3rd Draft, as well as a few insights into what may change before the method is finalized.

Section 1.6 acknowledges that some PFAS analytes do not perform well. During the single lab validation phase, Pace Analytical noted potential problems with the FOSA and FOSE compounds, particularly in biota samples.

Section 7.1.17 includes a note specifying that stacked solid phase extraction (SPE) cartridges will be allowed in place of SPE plus dispersive carbon for wastewater matrices. The note goes on to say that this flexibility may be extended to other matrices in subsequent revisions, so wastewater professionals should keep a close eye on future drafts to see if that is the case.

Section 11.0 requires labs to prescreen in the absence of source-specific knowledge, but the lack of specificity leaves a lot of unanswered questions. Are labs required to report the prescreening data? If not, how will this requirement be enforced? Does an educated guess constitute source-specific knowledge?

Appendix A contains a suggested screening protocol, but notes that other procedures can be used. The lack of defined protocols raises the question of how reliable the data coming from other approaches may be. Pace will look for these issues to be cleared up in future drafts.

Section allows for a trained analyst to omit the total suspended solids (TSS) analysis in aqueous samples by simple visual inspection.

Section 11.2.4 suggests centrifugation may be used but is not explicit. In Pace’s opinion, this will need to be clarified in future drafts or it will be a point of contention with the data and likely lead to considerable variability between labs’ Standard Operating Procedures. In the world of environmental compliance, variability between lab methods is problematic.

Table 5 (not shown here) sets Laboratory Control Sample (LCS) acceptance limits (referred to as OPR targets in the draft), and Table 8 sets the EIS recovery acceptance limits for wastewater. Once again, analysts will have to wait for future drafts for these limits in other matrices.

Furthermore, despite wide acceptance ranges for many compounds, the 3rd Draft states that some laboratories will still struggle to achieve results within the specified ranges. In some cases, Extracted Internal Standard (EIS) recovery limits for real-world wastewater samples are actually narrower than the EIS recovery limits for LCS samples prepared from clean reagent water.

It does not make much sense for sample acceptance criteria to be wider for clean water than for presumably more complicated wastewater samples. Tables 5 and 8  may see further changes before finalization.

A useable & useful method

Defining protocols across such a wide array of matrices is understandably challenging, and there may be many further changes before Draft Method 1633 is finalized. 

Nevertheless, Draft Method 1633 is already a useful tool for analyzing PFAS in wastewater for qualified labs. Once finalized, it will be immensely helpful in understanding the prevalence of these compounds and their spread throughout the environment. 

About the Author

Nick Nigro

Nick Nigro is a product manager at Pace Analytical, responsible for PFAS operations at seven emerging contaminant centers of excellence within Pace’s nationwide network of environmental testing laboratories.

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