PFAS Testing in Landfill Leachate: Preparing for New York’s Proposed Rule

If adopted, New York’s proposed landfill leachate treatment requirements would create a substantial treatment and verification challenge for covered facilities. Solid waste professionals impacted by the new rule need to determine how to efficiently generate the analytical data needed to select treatment technologies, evaluate performance, and assess the fate of PFAS in concentrates and other residuals. In this post, we examine how to:

• Establish baseline concentrations and appropriate reporting limits
• Select methods and analytical strategies for each sample stream
• Evaluate PFAS beyond routine targeted analyte lists
• Track PFAS into concentrates pre and post treatment or destruction

What New York’s Proposed Landfill Leachate Rule Includes—and What It Doesn’t

The New York State Department of Environmental Conservation (NYSDEC) has proposed amendments to 6 NYCRR Parts 360 and 363 that would require active municipal solid waste landfills and qualifying construction and demolition debris landfills with leachate collection systems to treat leachate before discharge to a water resource recovery facility or other authorized discharge location. Rather than setting a fixed effluent limit, the proposal would require treatment to reduce the concentration of listed contaminants by at least 99.9% before treated effluent is discharged. The proposal also addresses management of concentrated treatment residuals.

The proposed treatment requirements cover a broad range of landfill leachate contaminants, including PFAS and 1,4-dioxane, but questions remain about which individual compounds would be subject to the treatment requirement. NYSDEC left room to include PFAS beyond PFOA and PFOS, creating uncertainty about whether facilities should prepare to evaluate technologies against a broader range of PFAS compounds rather than a small number of currently regulated compounds.

Furthermore, the proposal does not mandate a single treatment technology. NYSDEC’s supporting analysis considers an approach that combines multistage reverse osmosis, granular activated carbon treatment of RO permeate, evaporation and solidification of concentrate streams, and thermal oxidation of vapor effluent. This illustrative treatment train is neither a prescribed system for every facility nor an assurance of effectiveness across all leachate conditions. Ultimately, technology selection must be supported by site-specific data, including data on the residuals generated by treatment.

Each of these features has analytical consequences. A percentage-based target makes reporting limits a performance question, not just a laboratory detail. An open-ended analyte list argues for looking beyond routine targeted methods. And a multistage treatment train means PFAS must be followed into every residual the process creates – not just the treated effluent.

Baseline Data Defines Your Reporting Limit Requirements

Because the proposed requirement is a percentage reduction, the treatment target moves with the starting concentration. Facilities therefore need to identify not only which PFAS to evaluate but also how low their analytical program must reliably measure to demonstrate a 99.9% reduction.

Initial characterization of raw leachate provides the baseline for setting those targets. Lower influent concentrations translate into lower effluent targets. A compound present at 1,000 ng/L in raw leachate would need to be shown at or below 1 ng/L after treatment; a compound present at 50 ng/L would need to be shown at or below 0.05 ng/L. Facilities should work with their laboratory to use baseline data to establish appropriate methods and reporting limits before treatment testing begins. These reduction targets stretch analytical reporting and detection limits in complex matrices such as raw leachate, foamate, and RO concentrate.

Therefore, complexities are created as a “not detected” result does not mean zero. If the reporting limit exceeds the concentration needed to demonstrate the intended reduction, the result may not technically substantiate treatment performance.

At a minimum, the facility and laboratory should define the following in the project plan:

• PFAS analytes to be quantified and treatment-performance objectives
• Baseline influent concentrations and expected concentrations in treated effluent and concentrates
• Reporting limits goals to evaluate the intended reduction
• Appropriate analytical methods for each sample stream
• Analytical strategies that address these complex matrices without unnecessarily elevating reporting limits
• Criteria for comparing results when different methods are used for raw and treated samples

Where different methods are used, comparisons should account for differences in analyte coverage, preparation, and reporting limits. Establishing these criteria in advance helps ensure that analytical variability is suitable for evaluating   treatment performance.

Discuss Data Quality Objectives with Your Laboratory

Matrix interferences and recovery outliers of spiked surrogates are a common cause of elevated reporting limits. Landfill leachate and concentrated PFAS streams can present analytical challenges. Dilutions may be necessary to bring concentrations within an instrument’s calibration range or address matrix effects.

For example, it is not uncommon for 5: 3 FTCA to be present at ppm levels in raw leachate samples. When an analyte is over the instrument’s calibration range, the value is considered estimated. Estimated values are not always useful when evaluating mass balance or treatment efficacy in complex pilot studies. Laboratories will dilute a sample to get these higher concentration analytes into an appropriate calibration range.  This can cause elevated reporting limits.  PFAS compounds that were present at lower concentrations can now become non-detect. To maintain the validity of the data for both lower- and higher-concentration PFAS, it is common practice for the Pace ® Treatability Center of Excellence to employ two dilution schemes and report a combination of both runs. This allows the end user of the data to evaluate PFAS results generated from multi-stream pilots more effectively. Clients should work with their laboratory team before submitting study samples to discuss expected concentrations, matrix characteristics, and the data needed from each stream. Pace ® has put together an internal team dedicated to these complex studies that includes PFAS subject matter experts, pilot study project managers, and operational staff dedicated to complex matrices to ensure success of these projects. Depending on the study, separate analytical runs or different dilution levels may be appropriate, as previously discussed. The objective is to jointly determine a strategy that produces usable data without unnecessarily sacrificing the sensitivity needed to evaluate treatment.

Use Your Entire Analytical Toolbox – Not Just One Method

EPA 1633A is often the go-to method for targeted PFAS analysis in non-potable liquids. Other methods can also be employed in conjunction with EPA 1633A, depending on the matrix, expected concentrations, turnaround needs, and study objectives.

ASTM D8421, for example, provides another targeted analytical option for non-potable water and has been validated in challenging matrices, including landfill leachate. It can offer faster results, making it useful when timely data are needed to guide pilot operation or process adjustments. In one study, we used ASTM D8421 for raw samples for a faster turnaround and EPA 1633A for treated samples to achieve lower reporting limits.

The PFAS toolbox also extends beyond conventional targeted analysis. Ultrashort-chain PFAS are receiving increasing attention, yet these compounds are not covered by routine methods such as EPA 1633A. A laboratory-developed procedure for ultrashort-chain PFAS analysis available through Pace® can help fill this gap can help fill this gap, providing a broader picture of PFAS present in leachate and their fate during treatment or destruction. Including this analysis where appropriate can also establish baseline data and help facilities assess whether their treatment approach addresses compounds beyond those currently monitored.

Total oxidizable precursor analysis, or TOP Assay, addresses a different gap: precursors that may not be measured by routine targeted analysis. The assay oxidizes susceptible precursors into terminal PFAS that can then be measured. Comparing results before and after oxidation reveals precursor contributions that the initial targeted result may not show. As a complementary tool in a treatment study, TOP Assay can help answer whether an apparently successful reduction in targeted compounds leaves an oxidizable precursor pool behind.

Lastly, EPA 1621/AOF offers a complementary screening tool by measuring adsorbable organic fluorine (AOF) in aqueous samples. It provides a broader organofluorine measurement, but it does not identify individual PFAS. Non-PFAS fluorinated compounds can also contribute to the result. AOF is suitable to be used alongside targeted and ultrashort-chain analyses rather than used as a replacement for them or described as a measurement of “all PFAS.”

Considering the entire PFAS analytical toolbox allows a fit-for-purpose treatment study: rapid targeted results where operational decisions require them, greater sensitivity where treatment targets demand it, and expanded coverage where required or useful.

Follow PFAS Into Concentrates and Residuals

NYSDEC’s proposal would require proper disposal of the concentrated residual waste resulting from treatment, making residuals management part of compliance planning. A treatability study should therefore identify sampling points throughout the process, not simply at the raw-leachate inlet and treated-water outlet. Depending on the treatment train, those points may include:

• Raw leachate and pretreated leachate
• Treated liquid or membrane permeate
• RO reject or other concentrate
• Regenerant and spent treatment media
• Solids and other process residuals
• Feed and outputs from a destruction process

Data from these streams help operators determine where PFAS mass accumulates, how much residual material must be managed, and whether an on-site destruction step warrants evaluation. Applying the expanded analytical toolbox to these streams can also show whether precursors or ultrashort-chain compounds are concentrating in residuals that targeted results alone would not reveal.

Put Specialized Treatability Expertise to Work

The Pace® PFAS Treatability Studies Center of Excellence was established to help clients evaluate and validate PFAS removal, remediation, and destruction technologies across complex matrices. Our work combines analytical expertise with support for clients piloting treatment programs and destruction processes.

For landfill operators and all solid waste professionals preparing for New York’s proposed requirements, that expertise can help align the analytical program with the decisions ahead: which treatment train to evaluate, what sensitivity is needed, how to manage difficult matrices, and what evidence is required to support removal or destruction claims.

Contact the Pace® PFAS Treatability Studies Center of Excellence to discuss an analytical strategy for your landfill leachate, treated streams, and concentrates with one of our specialists.