Taryn McKnight

PFAS in Water Reuse: Navigating Analytical Complexities and Treatment 

Taryn McKnight, Vice President and PFAS Practice Leader, Eurofins Environment Testing (USA) 

As water reuse projects increasingly encounter PFAS contamination challenges, the intersection of regulatory requirements and analytical limitations creates critical operational and compliance obstacles. With EPA's January 2025 guidance including quarterly PFAS monitoring in NPDES permits and states applying drinking water MCLs to reuse applications, water recycling facilities face unprecedented analytical and treatment validation demands.  Current PFAS analytical methodologies present significant compromises in capturing the complete PFAS picture for water reuse applications. While conventional methods like EPA Method 1633A can measure approximately 40 discrete PFAS with part-per-trillion sensitivity, many additional PFAS remain undetected due to lacking analytical reference standards. This analytical gap becomes particularly problematic when validating treatment technologies for potable reuse applications, where demonstrating complete removal efficiency or destruction is essential for public health protection and regulatory compliance.  This presentation examines how comprehensive multi-method analytical approaches can address these challenges in water reuse contexts. We will present case study data from municipal and industrial water reuse facilities where influent, effluent, and recycle streams were analyzed using targeted PFAS analysis (LC-MS/MS and GC-MS/MS), Total Oxidizable Precursor (TOP) Assay, Adsorbable Organofluorine (AOF) by combustion ion chromatography, and non-target analysis. This multi-method strategy reveals how different analytical techniques complement each other to provide a more complete understanding of PFAS fate through facilities and treatment processes.  Key findings demonstrate critical insights for water reuse facility operations. The data illustrate where conventional single-method approaches may provide false confidence in treatment performance and where supplementary analytical tools become essential for comprehensive risk assessment. With growing investment in PFAS-specific treatment technologies for water reuse applications, this analytical framework provides essential guidance for facilities navigating the evolving regulatory landscape while ensuring protection of public health and environmental resources. The presentation will offer practical recommendations for analytical program design that balances regulatory compliance requirements with operational decision-making needs.

Taryn McKnight, Vice President and PFAS Practice Leader for Eurofins Environment Testing in the U.S., has nearly 25 years of experience in the environmental testing industry. As one of the company's subject matter experts on PFAS, Ms. McKnight contributes to multiple organization and agency workgroups to address PFAS challenges, including her role as co-chair of the NGWA subcommittee to develop PFAS Sampling Guidance and a PFAS Forensics White Paper. With her expertise, she provides technical guidance to clients in setting up programs to achieve their site-specific objectives, and to agencies with understanding their analytical options and data usability considerations for water reuse applications.