Given the increased focus on PFAS from a regulatory perspective, various federal, state, non-profits, and private organizations have focused on continuing to fund research to fill necessary knowledge gaps and advance the current science. In 2021, there were continued peer-reviewed research studies that were published which a focus on solid waste related topics. These studies focused on the disposal of municipal solid waste (MSW), treatment of landfill leachate, management of treatment residuals (e.g., spent treatment media and regeneration), fate of PFAS during waste collection, food waste characterization, and recycling. These studies further supported previous research observations and filled various knowledge gaps as outlined below:
- Compost: Food waste was shown to contain PFAS and supported the detection of PFAS in compost at higher levels with food waste relative to compost without food waste (Thakali & MacRae, 2021). It is still unknown how the cycling of PFAS in food waste might impact composting and other management strategies.
- Fate and Transport of PFAS at Landfills: The potential contribution of PFAS in groundwater near a landfill and the potential health risks to humans from perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in the groundwater was found to be low via the drinking exposure pathway. Further studies are needed to assess the comprehensive exposure pathways of PFASs from landfills to humans while taking into consideration the relative exposure via food consumption and other daily exposure (Xu et al., 2021). Daily exposure from consumer products was highlighted in the PFAS Exposure Factsheet Explores Consumer Use.
- Waste Collection: PFAS found in waste collection vehicle leachate was compared to PFAS in aged landfill leachate. It was shown that precursor transformations to perfluroroalkyl acids (PFAAs) already began to occur during waste collection to disposal at the landfill (Liu et al., 2021).
- Landfill Liners: The transport of PFOS through a single composite liner made of a geomembrane over a geosynthetic clay liner (GCL) and an attenuation layer was predicted through modeling studies. Results predicted that in the event of no leakage there would be no concerns of groundwater quality being impacted and meeting regulatory limits (Rowe & Barakat, 2021). If the liner was comprised (e.g., there are holes or wrinkles), the impact on groundwater quality will be dependent on the length of impacted area and geomembrane properties.
- Leachate Treatment: The focus of research in this area continue to focus on innovative treatment, evaluation of onsite vs. off treatment, and management of treatment residuals.
- Onsite and offsite (e.g., discharge to a WWTP) environmental, human health, and economic performances were evaluated for various leachate treatment scenarios through life cycle assessment and life cycle cost assessment. Results showed that the onsite scenario offered benefits from human health and economic perspectives, while the offsite scenario generally performed better from an environmental perspective but will vary based on the initial PFAS concentration, removal needs, and volume treated (Feng et al., 2021).
- When electricity is applied to water, aqueous electrons, known as plasma, are produced to remove PFAS. Plasma-based technology continues to be shown as a viable technology for the treatment of PFAS-contaminated landfill leachates (Singh et al., 2021).
- A literature review on sorption media disposal highlighted that there is still limited information on the sorption as well as desorption processes. Due to the wide range of PFAS compounds present in liquid and gaseous waste streams, predicting the retainment of PFAS on the media. Compounding the sorption issue is that retainment can be affected by solution characteristics (e.g., dissolved organic matter, pH, and ionic strength). PFAS can also compete with other compounds present in a waste stream (Kah et al., 2021). Research has shown that shorter-chain compounds are more likely to desorb during treatment. There are still knowledge gaps in fully understanding the fate of PFAS associated with treatment media after disposal.
- A 'Concentrate-&-Destroy' technology was tested to treat PFAS from a model landfill leachate. This approach focused on developing a media can also act as a photocatalyst. The latter is used to degrade PFAS in the presence of ultraviolet light. The media containing PFAS was then successfully treated using a combination of ultraviolet light and hydrogen peroxide, which are known to be strong oxidations (Tian et al., 2021).
- Thermal Treatment: An indirect study that provides potential insight to the performance of thermal treatment of MSW was evaluated by measuring the concentration of PFAS in MSW prior to combustion and in fly and bottom ashes. High PFAS levels were found in leachate from waste prior to combustion (21.4-682 ng/mL; mean 215 ng/mL) while lower concentrations were detected in fly (1.46-87.6 ng/g) and bottom (3.11-77.4 ng/g) ashes. The lower levels in fly and bottom ashes suggest that incineration was able to destroy a majority of PFAS during incineration. Relatively lower levels of PFASs in fly and bottom ashes indicated that high-temperature incineration destroyed most of the PFASs. A similar observation was published in a prior study by Solo-Gabriel et al., (2020).
- Occupational Exposure: The potential exposure to PFAS during recycling was evaluated in China. The study showed that there were higher levels of PFAS in sorters relative to workers with other job assignments (e.g., managers). These results suggest that sorters may be directly exposed to PFASs but further investigations are needed (Peng et al., 2022). It is important to keep in mind that workers in China might be exposed to more PFAS relative to the U.S. due to the continued use. In addition, there is limited information on PFAS in recyclables.
To further advance PFAS research, various federal, state, and non-profit entities have funded studies specifically focused on solid waste. These entities have funded over $7 millions dollars in research since 2019. In 2019, the U.S. EPA funded $6 million dollars in research to address “Practical Methods to Analyze and Treat Emerging Contaminants (PFAS) in Solid Waste, Landfills, Wastewater/Leachates, Soils, and Groundwater to Protect Human Health and the Environment”. This research continued in 2021 at 8 institutions across the U.S. These projects focus on understanding treatment methods to remove and destruction PFAS in leachate and other wastewaters, characterization and quantification of PFAS in landfill leachate and gas, groundwater, and biosolids, and the presence of PFAS in waste disposed at landfills and the effects of different management approaches on the presence of these compounds in leachate. These projects are estimated to end this year.
The Environmental Research & Education Foundation continues to fund PFAS research by adding two projects in 2021, totaling just under $500,000 in funding, focused on the disposal of PFAS-containing special wastes (North Carolina State University) and solid waste combustion treat at landfills (University of Vermont, Sanborn Head & Associates, Weston Solutions, and North Carolina State University). These projects will add to the existing research on destructive and concentrating treatment approaches for PFAS in leachate and other liquid waste streams as well as understanding the ability for conventional liners to control the migration of PFAS beyond the landfill. Since 2020, EREF is funding just over $1 million dollars in PFAS research specifically addressing solid waste needs.
The Hinkley Center for Solid and Hazardous Waste Management is a State of Florida funding agencies that focuses on solid and hazardous waste management research. They have also directed research funding towards PFAS in 2021 through the funding of a project titled “Remediation of Perfluoroalkyl Substances in Landfill Leachate via Solar Photocatalysis (Florida Polytechnic University)”. Since 2019, they have funded a total of 6 projects that have primarily focused on leachate treatment and the fate of PFAS in landfills.
These research projects are not only imperative to fill necessary knowledge gaps to fully understand the needs to management PFAS but will also address emerging regulatory actions by the U.S. EPA. In October, the U.S. EPA released their PFAS Strategic Roadmap: EPA's Commitments to Action 2021-2024 that outlines how the agency, as a whole, would approach addressing PFAS across multiple sectors and industries. In the same month, EPA announced that it would be taking the necessary steps to evaluate four PFAS compounds (PFOA, PFOS, PFBS, and GenX) under the Resource Conservation and Recovery Act (RCRA) and strengthening the ability to clean up PFAS contamination across the country through the RCRA corrective action process. The Preliminary Effluent Guidelines Program Plan 15 guidelines specifically identify the need to understand how landfill leachate contributes to WWTP influent and effluent quality and to broaden the focus beyond PFOA and PFOS to 40 PFAS compounds.
This year will be an exciting time to see the wrap up of innovative and transformative research that will advance key areas for the solid waste industry to be equipped to continue to proactively manage PFAS-containing wastes.
Feng, D., Song, C., Mo, W. 2021. Environmental, human health, and economic implications of landfill leachate treatment for per- and polyfluoroalkyl substance removal. Journal of Environmental Management, 289, 112558.
Kah, M., Oliver, D., Kookana, R. 2021. Sequestration and potential release of PFAS from spent engineered sorbents. Science of The Total Environment, 765, 142770.
Liu, S., Zhao, S., Liang, Z., Wang, F., Sun, F., Chen, D. 2021. Perfluoroalkyl substances (PFASs) in leachate, fly ash, and bottom ash from waste incineration plants: Implications for the environmental release of PFAS. Science of The Total Environment, 795, 148468.
Peng, L., Xu, W., Zeng, Q., Sun, F., Guo, Y., Zhong, S., Wang, F., Chen, D. 2022. Exposure to perfluoroalkyl substances in waste recycling workers: Distributions in paired human serum and urine. Environment International, 158, 106963.
Rowe, R.K., Barakat, F.B. 2021. Modelling the transport of PFOS from single lined municipal solid waste landfill. Computers and Geotechnics, 137, 104280.
Singh, R.K., Brown, E., Mededovic Thagard, S., Holsen, T.M. 2021. Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor. Journal of Hazardous Materials, 408, 124452.
Thakali, A., MacRae, J.D. 2021. A review of chemical and microbial contamination in food: What are the threats to a circular food system? Environmental Research, 194, 110635.
Tian, S., Xu, T., Fang, L., Zhu, Y., Li, F., Leary, R.N., Zhang, M., Zhao, D., Soong, T.-Y., Shi, H. 2021. A ‘Concentrate-&-Destroy’ technology for enhanced removal and destruction of per- and polyfluoroalkyl substances in municipal landfill leachate. Science of The Total Environment, 791, 148124.
Xu, C., Liu, Z., Song, X., Ding, X., Ding, D. 2021. Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in multi-media around a landfill in China: Implications for the usage of PFASs alternatives. Science of The Total Environment, 751, 141767.