6/11/20
States Can Learn from Michigan’s Work on PFAS in Wastewater and Biosolids
“Other states can learn from these experiences and avoid excessive costly testing and impacts on most wastewater and biosolids programs.”
In late April and June 2020, the Michigan Department of Environment, Great Lakes, and Energy (EGLE) released a summary of two years of investigation of PFAS in the state’s wastewater and biosolids and the actions taken to address them.
Michigan was one of the first states to take significant actions on PFAS, with widespread testing that uncovered numerous major industrial and fire-fighting sites impacted by PFAS. (This EWG map shows how much more testing Michigan has done compared to other states; only New Jersey has a similar density of testing to date.)
Michigan EGLE now recognizes that PFAS are found at background levels in all wastewater, because the chemicals are being measured in waters in at tiny levels – parts per trillion (ppt) – and because they have been in such widespread use in a wide variety of consumer and business products since the mid-1900s. Wastewater treatment facilities (WWTF) are not producers or sources of PFAS; they receive them from households and businesses - and sometimes from industries. Data from Michigan and elsewhere find some PFAS in every wastewater test, but they are found at far higher levels in a relatively few facilities that receive sewer discharges from industries that use large amounts of PFAS in their operations, such as metal platers. It became clear to Michigan’s environmental agency that reducing PFAS impacts from wastewater or biosolids was going to be most significant when such large industrial discharges are addressed first. While other states went out and tested all wastewater and biosolids randomly, at considerable cost, Michigan focused on industrial discharges to WWTFs.
Michigan effluent data from 42 WWTPs with IPP programs for which comprehensive data were developed. Click to enlarge.
After some preliminary investigations, in February, 2018, Michigan EGLE decided to focus on the 95 wastewater treatment facilities with formal Industrial Pretreatment Programs (IPP). This proved to be an exemplary decision. Put the focus on where the highest potential risk lies and where the money and effort spent can reduce the greatest amount of potential risk in the near term. AECOM was contracted to conduct testing of these facilities’ influent, effluent, biosolids, and, when indicated, sites where biosolids had been applied. See the current summary report. Michigan EGLE plans to release a complete report with further data later this summer.
From the report: “Some key observations that were made during the IPP PFAS Initiative as of January 2020 are:
“A total of 68 out of 95 WWTPs with IPPs either have no sources or have sources but have discharges at or less than the PFOS water quality values.
“A total of 93 out of 95 WWTPs were able to complete the initial screening of their industrial users within 1 year of starting the initiative. Most were able to complete the initial screening within 6 months.
“Low levels of PFOS (approximately 3 to 7 ng/L) were detected in wastewater even when no significant industrial sources were present. This suggests that there are background levels of PFAS in domestic sanitary sewage in most communities.
“Depending on the PFOS concentrations in the effluent, sampling is being required semiannually, quarterly, and monthly at 22, 19, and 10 WWTPs, respectively.
“Source reduction efforts have resulted in substantial drops in PFOS concentrations being discharged at the WWTPs….”
PFOS concentrations in biosolids from 42 WWTPs targeted for likely PFAS concerns. Michigan EGLE uses 150 ppb as the point separating industrially-impacted biosolids from average typical biosolids. The 150 ppb demarcation is not a risk-based value. Click to enlarge.
Further investigation by Michigan EGLE and AECOM looked at 42 treatment plants’ biosolids and found an average PFOS level of 195 parts per billion (ppb), with a median concentration of 13 ppb. As has been seen elsewhere, there was clearly a difference between industrially-impacted biosolids and the large majority of typical, average biosolids. Only six of the 42 Michigan facilities that were targeted because of likely PFAS concerns were found to be significantly impacted by industrial discharges. Those then became the focus of subsequent efforts.
Focusing on these six industrially-impacted wastewater facilities, and an additional four, Michigan EGLE facilitated industry source control upstream of the treatment plants. Dischargers of PFAS, like metal platers, installed pretreatment systems, such as granulated activated carbon (GAC), to reduce the levels going to the wastewater facilities. In one case, the amount of landfill leachate taken in by the wastewater treatment facility, which has relatively high PFAS levels and, in that one case, was a relatively high percentage of the total wasteawater flow, was reduced. In another case, a leak that let in firefighting foam was eliminated.
Initial summary data on PFAS, PFOS, and PFOA in matrices at the land application sites in Michigan expected to have highest PFAS impacts because of use of industrially-impacted biosolids and/or high cumulative application rates. Further data will be included in a follow-on report expected in summer 2020. Click to enlarge.
The final stage of the investigation was looking at biosolids land application sites where the industrially-impacted biosolids had been utilized, in some case for many years, with comparison to long-term sites using biosolids with average PFAS levels. Of the six facilities with industrial impacts, two sent their biosolids to landfills, and they continue to do so. The other four suspended their land application programs during the investigation, and they and sites of four other land application programs were further evaluated. The report concluded: “Screening of agricultural fields that received biosolids applications found significantly higher PFAS concentrations in various environmental matrices associated with WWTPs with elevated levels of PFAS in their biosolids. However, site-specific environmental conditions were determined to be very important when evaluating potential impacts and exposure pathways. Some agricultural fields that had land-applied biosolids from WWTPs with high PFAS impacts did not have high PFAS concentrations in environmental matrices (soils, surface waters, groundwater, etc.). Also, significantly lower PFAS concentrations were detected at land application sites receiving less impacted biosolids. Additional information will be included in a detailed report expected in the summer of 2020.”
The summary data (right) show minimal PFOA and PFOS groundwater and surface water impacts from average (“lower-impacted WWTPs”) biosolids, while industrially-impacted biosolids with high PFAS levels impacted groundwater and surface waters more. However, even with the biosolids most impacted by industrial discharges, the maximum concentration in groundwater was still below the 70 ppt EPA health advisory level for PFOA and PFOS separately (except for one unusual perched groundwater sample noted in the table’s footnote; unclear what that is about).
Now, with testing confirming that those facilities that had industrial impacts are now producing biosolids with more average PFAS levels, Michigan EGLE is supporting the impacted facilities in restarting their biosolids land application programs.
Michigan’s experience illuminates a cost-effective approach to addressing PFAS in wastewater and biosolids. Other states can learn from these experiences and avoid excessive costly testing and impacts on most wastewater and biosolids programs:
All wastewater and biosolids contain PFAS. That is a known fact. Further random, widespread testing programs are unnecessary and do nothing to advance understanding. Wisconsin wastewater treatment facilities recognized this in the fall of 2019, when they declined a state request to test wastewater and biosolids. There are still no formal, consistent EPA-approved analytical methods for PFAS in non-potable water (e.g. wastewater) and solids (e.g. biosolids). Therefore, data compiled from different labs may not be comparable and have to be treated as qualitative. And there remains limited understanding about what the test results mean. How much PFAS is acceptable in wastewater and biosolids? Until that is understood, there is nothing to which to compare test results.
There is a clear difference between wastewater and biosolids that are industrially impacted and the vast majority that are not. For example, for PFOS, the PFAS chemical that is the most prevalent, persistent, and concerning, Michigan found that 150 parts per billion (ppb) seems to be the dividing line between average biosolids and those that are clearly industrially impacted. That 150 ppb number is not a risk-based number; it just shows up clearly in Michigan data and, NEBRA confirms, in other biosolids PFAS data. Michigan found just 6 facilities with significant industrial impacts, and Michigan is a state with relatively high levels of industry.
PFOA and, especially, PFOS, are worth focusing on for now. They are the most researched, most concerning (as long-chain PFAS), and most ubiquitous from decades of use. Addressing them - especially PFOS, as Michigan did - can yield immediate known significant reductions in potential risk. Other PFAS - short-chain, etc. – are addressed somewhat in the process, even as further research clarifies their potential risks.
The concern about PFAS in wastewater is the potential to cause surface waters to exceed risk-based limits. Michigan has about the most extreme surface water standard anywhere: 11 or 12 parts per trillion (ppt) for PFOS, focused on drinking water and protecting a local fish species, respectively. Because of dilution, typical wastewater effluent, which sometimes exceeds that level of PFOS, is not considered a significant concern.
The concern about PFAS in biosolids is the potential for leaching to groundwater, impacting groundwater above drinking water standards. Again, typical biosolids that are not industrially impacted do not impact groundwater at levels exceeding the U. S. EPA 70 ppt drinking water advisory level (and even lower regulatory levels). Even the industrially impacted Michigan biosolids did not cause exceedances, according to initial data in the Michigan report.
Source control of PFAS is the answer. At this stage of understanding of PFAS, focusing on industrially-impacted wastewater and biosolids is cost-effective and reduces disruptions of typical wastewater and biosolids programs. Michigan experiences lead to this conclusion. And New Hampshire, another state that has aggressively tested for PFAS, is now focusing on helping wastewater facilities work upstream with industries and other users of large amounts of PFAS, so as to reduce the amounts that enter wastewater in the first place. Such efforts do not threaten the vast majority of wastewater programs. Other states can leap-frog past random, widespread testing and focus on helping wastewater treatment facilities identify and proactively work with any of their industries that may use large amounts of PFAS, in order to reduce PFAS discharges.
Spend resources on research to understand if there is any significant public health concern from PFAS in wastewater and biosolids. Money saved from random, widespread testing is better spent advancing field research. For example, there remains little field research to indicate if biosolids applications are actually creating any significant issues. Limited investigations by several states - including the recent Michigan report – indicate that even long-term (20 - 30 years) land application sites are not impacting groundwater above the 70 ppt EPA public health advisory for drinking water. However, a few sites in states, like Vermont, do have impacts above those states’ extremely low standards of 20 ppt or less. Set the standards extremely low, and impacts will be found, not only from biosolids, but also from landfills and other waste management operations, septage management, septic systems, and car washes and other small businesses.
“Put the focus on where the highest potential risk lies and where the money spent can reduce the greatest amount of potential risk in the near term.”