Application of Proposed EPA PFAS Methods for Wastewater
Dr. Amanda Miller, Ph.D., Analytical Research Scientist, NCASI
The Environmental Protection Agency (EPA) has published multiple drafts of Method 1633 for analysis of Per- and Polyfluorinated Substances (PFAS) in aqueous matrices, including wastewater. Both Method 1633 and laboratory method 537M (modified) by isotope dilution were included and are currently used for the analysis of PFAS analytes in wastewater discharged under National Pollution Discharge Elimination System (NPDES) permits. Non-targeted methods EPA Method 1621 and Total Oxidizable Precursors (TOP) assay were also investigated, these methods are comprehensive in their analysis and currently outside the scope of NPDES permits. We contracted the analysis of replicate pulp and paper industry-associated waters (influent, effluent, synthetic wastewater, river water, and blanks) at a total of eight EPA-accredited laboratories with the various PFAS methodologies to (1) enhance our understanding of the applicability and relevance of Method 1633 compared to existing targeted and emerging non-targeted PFAS methods and (2) evaluate the capabilities of EPA-accredited contract laboratories and consistency of reported results. We reviewed Level IV reports to evaluate adherence to test methods (i.e., sample preparation protocols and QA/QC measures), and identify reporting biases, false positives, and QA/QC intricacies. Upon reviewing EPA Method 1633 reported data, inconsistencies in the initial sample handling protocols among certified laboratories were associated with disparities in reported concentrations of PFAS analytes in replicate samples. The inconsistency occurred when total suspended solids (TSS) data was greater than 50 mg total mass causing some laboratories to subsample from the sampling bottle or dilute the sample, with both actions not advised according to Method 1633. Among the 13 commonly detected PFAS compounds in the same influent sample measuring 1500 mg/L TSS, concentrations ranged from non-detect to 110 ng/L, with labs having to dilute the sample or extract to deal with the interferant to achieve passing QC typically reporting non-detects. Comparative PFAS concentrations across methods are reported for each sample type. These findings have significant implications for stakeholders and emphasize the need for refinement of sample preparation protocols among certified laboratories. Such refinement is particularly important when analyzing complex matrices such as pulp and paper industry wastewaters, and instrumental in achieving water quality objectives.
Dr. Amanda Miller started working as an Analytical Research Scientist at the NCASI Laboratory in June 2023. She graduated with her Ph.D. in Chemistry from the University of Nebraska-Lincoln. At the University of Nebraska-Lincoln, she conducted multiple research projects, which utilized analytical techniques such as High-Performance Liquid Chromatography and Mass Spectrometry. Her dissertation work focused on the identification and biological function of natural products from Lysobacter and related Gram-negative bacteria. She received both the Molecular Mechanism of Disease Predoctoral Fellowship and the Marjorie Langell Outstanding Graduate Research Assistant Award for her research.
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