PFAS – The Next Wastewater Utility Challenge?
WWTPs have come under scrutiny for discharging PFAS to the environment. The unique physio-chemical properties of PFAS compounds make them difficult to remove using conventional wastewater treatment technologies. So what does that mean for wastewater utility managers?
July 31, 2019
Per- and poly-fluoroalkyl substances (PFAS) have entered the national consciousness due to concerns over their levels in finished drinking water, their ubiquity and longevity in the environment, and potential risks to human and wildlife health from exposure to harmful levels. Wastewater treatment plants (WWTPs) have come under scrutiny for discharging PFAS to the environment in their treated effluent and through land application of contaminated biosolids, even though they are usually not the original source of these compounds. The unique physio-chemical properties of PFAS compounds make them difficult to remove using conventional wastewater treatment technologies. In fact, because the traditional treatment process can break down polyfluorinated precursor compounds into shorter perfluorinated compounds, it is not uncommon to have higher concentrations of two key PFAS chemicals (PFOA, perfluorooctanoic acid and PFOS, perfluorooctane sulfonate) in the treated effluent than in the influent. Wastewater treatment plants have also been implicated as sources of airborne PFAS.
The unique physio-chemical properties of PFAS compounds make them difficult to remove using conventional wastewater treatment technologies.
The goal of this article is to provide wastewater treatment plant operators and utility managers with the most recent and relevant information for planning operations, capital investments and engaging effectively with local communities and regulators on PFAS-related topics.
The Regulatory Environment
In February, the USEPA announced a Comprehensive PFAS Action Plan (1), indicating that they intend to develop maximum contaminant levels (MCLs) for PFOA and PFOS in drinking water and to take steps to classify PFAS as hazardous substances. These actions have the potential to affect wastewater utilities in two key ways:
- By requiring higher levels of treatment to protect downstream public water supplies and/or expanded source water protection measures; and
- By limiting disposal options for biosolids containing PFAS.
Bipartisan legislation requiring USEPA to develop MCLs for drinking water passed the Senate in June 2019 as part of the National Defense Authorization Act. However, it stops short of directing USEPA to designate PFAS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) or Superfund. However, this provision was included in a PFAS-related amendment to a defense spending bill in the House of Representatives that was passed in July 2019.
USEPA announced a Comprehensive PFAS Action Plan indicating that they intend to develop MCLs for PFOA and PFOS in drinking water and to take steps to classify PFAS as hazardous substances.
States are also developing their own standards for PFAS in surface waters. The standards could be drivers for new permit limits and/or additional monitoring requirements for WWTPs. In turn, these requirements could result in costly investments in new treatment technologies to achieve a higher level of PFAS removal. Additional (and expensive) monitoring is also likely to accompany any new requirements.
Conventional wastewater treatment processes tend to “treat” many PFAS chemicals by partitioning them into the biosolids, which poses its own challenge and is discussed below. PFAS is a broad class of chemicals, with over 3,000 individual compounds. Of these, only 24 are routinely measured. It is not unusual for one or more of these 24 compounds to have higher concentrations in a WWTP treated effluent than in the influent. The treatment process allows some of the thousands of PFAS potentially present in an influent to be transformed or degraded into one of the PFAS chemicals that is quantified in analytical testing (2).
One strategy to address this treatment conundrum is to minimize the amount of PFAS entering the WWTP treatment process. Investigations have been undertaken in some states to identify and address sources of PFAS. Once identified, leverage can be applied through the industrial pre-treatment permitting program (IPP) to require industrial sources to reduce or eliminate PFAS prior to discharge into the sewer system. Common industrial sources typically include metal platers and landfills. However, putting additional pretreatment requirements on industrial sources could have economic consequences for the community and operational implications for the WWTP, which means this strategy must be carefully considered and supported with monitoring data.
Another potential strategy is to employ additional treatment technology to remove PFAS prior to discharge. To date, drinking water suppliers have used granular activated carbon (GAC) and reverse osmosis (RO) as the most effective treatment strategies, but both can be expensive to implement. These technologies or some variant of them have been tested in wastewater treatment as well (3). It is important to understand that these techniques will still leave the utility with the problem of contaminated material disposal. There are also destructive techniques, such as electrochemical oxidation and incineration, which destroy the chemical structure of PFAS (4). However, most of these methods are in the research and development stage, in a pilot testing phase on a small scale, or in the case of incineration, tend to be cost prohibitive.
PFAS have been found in wastewater sewage sludge and much of this sludge is processed into biosolids and applied on agricultural lands. Land application is mutually beneficial – the WWTP has a cost effective method of disposing of biosolids, while the farmer enriches their soil with nutrient-rich material. However, land application of municipal biosolids can be a potential source of PFAS contamination in waterways through runoff from these fields. Research has already shown that PFAS can leach out of land-applied biosolids and percolate into underlying aquifers (5,6).
PFAS have been found in wastewater sewage sludge and much of this sludge is processed into biosolids and applied on agricultural lands.
There are currently no standards regulating PFAS levels in biosolids. Most states are taking a measured approach to respond to PFAS in biosolids, starting with collecting data on PFAS in biosolids (Michigan and Maine, for example). As noted above, USEPA’s Action Plan and House bill includes plans to classify PFAS as hazardous substances. This action could greatly affect the ability to cost effectively dispose of biosolids containing PFAS through land application. The National Association of Clean Water Agencies (NACWA), which advocates on behalf of the wastewater industry, views biosolids as the chief area where PFAS could affect WWTPs (7). They are currently working to ensure that land application disposal is preserved if PFAS are classified as hazardous substances. The Water Environment Federation (WEF) and Water Research Foundation (WRF) are also actively researching PFAS treatment in wastewater and characterizing the potential risk to human health from land-applied biosolids.
Protecting Drinking Water Supplies
Surface waters often serve as public water supplies. WWTP effluent containing high levels of PFAS that are discharged upstream of a drinking water intake may pose a threat to the downstream public. Effectively removing PFAS in drinking water requires the same technologies used to remove them from wastewater, which is an expensive proposition. Much like the strategy of limiting discharges to WWTP through control at the source, an additional measure of protection to public water supplies can be achieved by limiting PFAS in upstream discharges.
Surface waters often serve as public water supplies. WWTP effluent containing high levels of PFAS that are discharged upstream of a drinking water intake may pose a threat to the downstream public.
Source water protection plans are an avenue to force upstream dischargers to reduce the level of PFAS in their discharges. A similar mechanism, through the wellhead protection program, can be employed to provide better protection of groundwater-sourced public water supplies.
Summary & Conclusion
The science of PFAS source identification and management, as well as the regulatory landscape addressing these chemicals, is rapidly evolving. It seems certain that regulatory pressures will continue to increase for addressing areas of known and suspected contamination, requiring implementation of management strategies that reduce potential future impacts.
Although most municipal wastewater utilities have not yet had to deal with PFAS issues, we recommend a proactive approach, starting with an initial PFAS risk evaluation. This initial risk evaluation is intended to provide municipal decision-makers with some idea of where their PFAS risks lie, as well as give them recommendations for next steps to inform proactive planning for PFAS response.
An initial risk evaluation can provide municipal decision-makers with information on potential PFAS risks and recommendations for next steps for a proactive planning PFAS response.
LimnoTech has managed multiple PFAS investigations at a range of facilities and can provide assistance if your facility is interested in proactively addressing this complex issue.
This article is the fifth in a series of articles authored by LimnoTech staff on PFAS-related issues. Follow us on LinkedIn or Twitter (@LimnoTech) and check the News and Media page on our website for more information and updates. Links to the other PFAS articles in this series are provided below:
The latest publication of the LimnoTech Currents newsletter, PFAS – Like Nothing We’ve Seen Before, also focuses on PFAS and covers a range of topics, including aviation and AFFF, potential issues and areas of concern for municipalities, analysis methods and laboratory considerations, and current regulations.
Carrie Turner, PE, is a senior project engineer at LimnoTech. Carrie specializes in developing affordable and sustainable solutions for our clients dealing with pollution-related issues. She has 20 years of experience evaluating impacts of pollutant sources on watersheds and in waterways using innovative data and modeling analyses that build on her extensive work in environmental chemistry before joining LimnoTech. Carrie also uses her chemistry background to design and implement sampling programs, conduct laboratory audits, validate data, write Quality Assurance Project Plans, and develop customized databases and data management frameworks that integrate spatial, physical and chemical data by linking them with GIS systems for analysis and visualization.