"Forever chemicals" in wastewater increasingly challenges water utilities. Here ar esome validated methods for detecting and quantifying PFAS concentrations.

As concerns continue to grow about PFAS compounds in wastewater streams, treatment plant operators have become responsible for detecting and monitoring those compounds.

Crucial to those duties is selection of an appropriate test method for PFAS, which are synthetic chemicals characterized by their resistance to heat, water and oil. Being highly stable and difficult to destroy, they can build up in the environment and in the bloodstreams and tissues of animals, humans and plants. Studies show a likely link between some PFAS, particularly PFOA and PFOS, and numerous health issues.

PFAS can enter wastewater streams through various pathways including industrial discharges, landfill leachate ultimately processed at wastewater treatment plants and municipal storm drainage systems in combined sewer systems.

PFAS-containing runoff is a particular problem on sites where aqueous film-forming foam has been used to fight and train for chemical fires. Therefore, airports and military and industrial sites are often strong contributors of PFAS to municipal sewer systems. Common household and industrial cleaners can also contain PFAS, so even the graywater from homes and commercial buildings can contribute the compounds to wastewater.

REGULATORY MONITORING

The National Pollutant Discharge Elimination System and the Effluent Limitations Guidelines program were established as part of the Clean Water Act in 1972. Although awareness of the dangers of PFAS in wastewater has been building over several decades, these programs have only recently addressed PFAS in a significant way.

States can petition the EPA to administer their own NPDES programs, and most have received partial or full approval to do so. In December 2022, the EPA published a memo containing recommendations for dealing with PFAS in wastewater discharges and biosolids to states authorized to administer NPDES permitting. States have been somewhat slow to adapt to the recommendations, but that will change as more water quality restrictions are enacted.

ELGs are national regulatory standards for municipal wastewater treatment plants and for wastewater discharged to surface waters. The EPA updates its ELG Plan every two years. Plan 15, released in January 2023, calls for ELGs to be set for discharge from landfills. Once promulgated, these will be the first federal PFAS-related ELGs for wastewater discharge.

Plan 15 also calls for more research on PFAS in wastewater from textile mills and industrial wastewaters sent to municipal treatment plants. Investigation of the need for ELGs in other industries is ongoing.

Of course, compliance with existing legislation is not the only justification for wastewater analysis. Many industrial entities and municipal wastewater treatment plants are expanding their testing to assess potential liabilities and help prepare for future regulatory requirements.

PFAS TEST METHODS

Wastewater is challenging to analyze for PFAS due to varying solids content and the inherent complexity of the sample matrix. Accurate analysis requires special equipment and techniques. Still, significant progress has been made on standardizing and validating PFAS test methods. Here are some common methods used to analyze wastewater samples.

EPA Method 1633

The biopersistence of PFAS makes it important to have standard procedures for measuring their presence in a wide range of matrices. Method 1633 offers a standardized approach to measure 40 PFAS compounds in matrices including wastewater, surface water, groundwater, soil, biosolids/sludge, sediment, landfill leachate and biological tissues.

Finalized in January 2024, Method 1633 includes standard procedures for analyzing PFAS in all target matrices. It will also play a vital role in EPA efforts to study, monitor and regulate PFAS in nearly all matrices and regulatory programs, except drinking water.

EPA Method 1621

Also finalized in January of 2024, this screening method is designed to detect adsorbable organic fluorine in aqueous matrices by combustion ion chromatography. It measures adsorbable organic fluorine in nonpotable water; high levels indicate that targeted testing may be warranted. Method 1621 also can detect organic fluorine concentrations in nonpotable water from the many PFAS not detectable by targeted methods such as EPA 1633.

ASTM D8421 and D8535/EPA 8327

This method was developed by the American Society for Testing and Material to provide a fast, robust way to analyze PFAS in aqueous and solid matrices. It uses liquid chromatography/tandem mass spectrometry, with optional isotope dilution to minimize the impacts of sample matrix interference on quantification and thus improve data quality.

This method has several advantages. Turnaround time is faster, and it is often less expensive than other methods that are more procedurally challenging. In addition, the aqueous method requires only a 15 mL sample, saving significant field collection time and shipping costs. These benefits make the method attractive for wastewater programs.

Total Oxidizable Precursors (TOP Assay)

PFAS precursors are compounds that can degrade to terminal PFAS under the right conditions, including traditional wastewater treatment processes. TOP Assay oxidizes PFAS precursors, most of which are not currently measured by targeted techniques, converting them to their terminal PFAS compounds that then can be measured.

The increase in PFAS measured after the TOP Assay oxidation is a gross estimate of the total concentration of PFAS precursors present in a sample. TOP Assay is particularly useful in forensic studies designed to identify the source of elevated PFAS in treated wastewater.

VALUE OF OPTIONS

Standardized and validated methods for analyzing PFAS in nonpotable liquids give wastewater dischargers and regulatory entities reliable data for informed decision-making.

However, wastewater covers a wide range of nonpotable liquids with varying levels of suspended solids, and not all decisions require the same data. Multiple options enable utilities to choose a method that best meets their requirements in terms of compliance, targeted analytes, data quality, speed and cost.

Those seeking to have wastewater analyzed should work with a laboratory that is familiar with the methods available and can help them choose wisely.