PFAS in Biosolids

PFAS and Biosolids – A Dynamic Regulatory Puzzle

July 10, 2024

By: Heather Lord, Ph.D

The high nutrient content of biosolids makes them valuable for fertilizing agricultural land and for use in commercial soil amendments. Concerns around per- and polyfluoroalkyl substances (PFAS) in biosolids have spurred new controls around the production, use and sale of these products. This blog takes a look at the current status of the issue.

Introduction to Biosolids and Their Use

Biosolids are a byproduct of wastewater treatment, and the beneficial reuse of this byproduct as a fertilizer or soil amendment is practiced globally. Annual production approximately 700,000 dry tonnes in Canada ( and 6 million dry tonnes in the United States ( In the U.S., 60% are beneficially reused, and 40% are disposed either through incineration or landfilling. Restrictions on the beneficial reuse of biosolids in North America have, to date, focused on pathogen and metals content. Restrictions and regulations related to PFAS in biosolids have recently been introduced. 

PFAS Concerns and Regulatory Changes

The unique chemical properties, ubiquitous nature and poorly understood compositions of PFAS products present challenges for managing PFAS in the wastewater-treatment process. As with most organic contaminants, current wastewater-treatment processes do not reduce the PFAS loadings of influent streams prior to release as either liquid effluent or biosolids. In fact, because much of the composition of commercial PFAS products is unknown, they cannot be measured with conventional testing and, in many cases, are unstable and can transform into known PFAS during the treatment process. Therefore, measured PFAS concentrations in effluent and biosolids can appear to be increased relative to influent loadings. Of the PFAS compounds that can be measured, the more water-soluble PFAS are primarily present in the effluent stream, and the less water-soluble compounds that prefer to bind to solids and organic matter are dominant in biosolids.  

In a 2014 Canadian study, influent, effluent and biosolids from 20 wastewater treatment plants (WWTPs) were evaluated for PFAS. PFOA was the dominant PFAS in effluent (2 ng/L to 140 ng/L) and PFOS was dominant in final treated biosolids at 2 µg/kg to 17,000 µg/kg. The next highest concentration PFAS in biosolids were PFOA, PFNA and PFDA (Guerra 2014). The authors noted that industrial wastewater inputs can have a disproportional impact on PFAS loadings in biosolids, suggesting that source control upstream of WWTPs is warranted. In a 2013 U.S. study, biosolids from 94 WWTPs in 32 states were evaluated (Venkatesan and Halden 2013). PFOS was again the dominant PFAS found at an average of 400 µg/kg. The next highest PFAS were PFOA, PFDA and PFUnDa. In a 2020 study of 11 commercially available biosolid-based soil amendment products, PFOS was seen as the dominant PFAS in all products tested at 2 to 90 µg/kg (Lazcano 2020). 

Regulatory Responses to PFAS in Biosolids

On April 10, 2024, the US EPA established that there was no safe level of PFOS or PFOA in drinking water. Long-term land application of biosolids containing PFAS is known to result in elevated PFOS and PFOA in the upper soil horizons. Leaching of predominantly PFOA to groundwater is also seen (Johnson 2022). The concerns this raises for human and wildlife exposure has spurred regulatory responses to mitigate potential harm. 

In the U.S., the recent promulgation of US EPA Method 1633 has provided states the ability to regulate industrial wastewater discharges of PFAS through NPDES permits along with the ability to require testing of biosolids prior to land application.  A 2023 publication from the Environmental Council of the States (ECOS) provides a snapshot of the actions being taken by the states.   At that time, 34 states had established policies on management of PFAS in biosolids. Maine has enacted a ban on land application of biosolids and Michigan has banned land application if PFOS exceeds 125 ppb. Six states require monthly, quarterly or annual testing. Colorado and Michigan have implemented trigger levels of 50 ppb for source assessment and reporting. Four states have implemented industry-specific WWTP monitoring, and 12 states have implemented monitoring downstream of land application sites. 

In Canada, the federal departments responsible for Health, Environment and Food have taken a coordinated approach to biosolids regulation through the June 2024 publication of an interim PFOS limit of 50 ppb for commercial trade in biosolids.  Of note, Canadian federal agencies regulate the importation and sale of biosolids, while the provinces regulate biosolids manufacture, use and disposal. Further restrictions on PFAS in biosolids through provincial regulation are anticipated. 

Montrose’s Expertise in PFAS Management

Control of PFAS in biosolids will enable the continued beneficial reuse of nutrient-rich, safe biosolids for residential, agricultural and commercial benefit. Montrose is well positioned throughout North America to assist clients in navigating the dynamic landscape of biosolids PFAS management. Whether for state-of-the-art PFAS testing services, treatment systems design and construction, support for biosolids management programs to ensure products meet or exceed current and future regulatory requirements, or the provision of expertise in dispute resolution, Montrose has the experts needed to put the pieces of the biosolids PFAS puzzle in order.  


  • Guerra, P., M. Kim, L. Kinsman, T. Ng, .M Alaee, and S.A. Smyth. “Parameters affecting the formation of perfluoroalkyl acids during wastewater treatment” J. Hazard. Mater., Vol. 272, (2014) 148–154. 
  • Johnson, G.R. “PFAS in soil and groundwater following historical land application of biosolids.” Water Research, Vol. 211, (2022) 118035. 
  • Lazcano, R.K., Y.J. Choi, M.L. Mashtare, and L.S. Lee. “Characterizing and comparing per- and polyfluoroalkyl substances in commercially available biosolid and organic non-biosolid-based products” Environ. Sci. Technol., Vol. 54, (2020) 8640−8648. 
  • Venkatesan, A.K., and R.U. Halden. “National inventory of perfluoroalkyl substances in archived U.S. biosolids from the 2001 EPA National Sewage Sludge Survey.” J. Hazard. Mater., Vol. 252-253, (2013) 413–418. 

Heather Lord, Ph.D
Senior Associate Forensic Chemist
Dr. Lord is a Senior Associate Forensic Chemist and supports the continued expansion of Environmental Standards’ forensic chemistry practice. She specializes in forensic method development, evaluation, and specification, as well as critical data review and interpretation, involving multiple lines of evidence, for sites impacted by hydrocarbons, PFAS and other contaminant classes. She provides consultation to design and execute forensic response programs as components of HSE management systems and site investigations. Heather received her B.S. degree in Environmental Biology with Chemistry minor from the University of Guelph. She received her Ph.D. in Analytical Chemistry from the University of Waterloo in 2005 and has published an impressive body of work on her research in the applications of numerous techniques for environmental and biological analytical chemistry.

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