Biosolids are the treated materials produced during the processing of wastewater at a wastewater treatment plant (WWTP) (also known as a water resource recovery facility).
Biosolids contain nutrients and organic matter and are used as a soil amendment and conditioner (a beneficial use). A biosolids' quality and their proper use are regulated by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) and the United States Environmental Protection Agency (EPA).
EGLE and the EPA require biosolids to undergo a treatment process and be tested for certain pollutants to protect human health and the environment. Once treated, biosolids can then be applied at agronomic rates, providing a stable and valuable source of plant nutrients and soil structural enhancements.
Per- and polyfluoroalkyl substances (PFAS) are a large group of chemicals used for decades in industrial, commercial, and domestic settings and are found worldwide. Typical materials or processes that use or contain PFAS include firefighting foam, chrome plating, cookware coatings, waterproofing on clothing and carpet, and even food wrappers. Some PFAS, including perfluorooctane sulfonate (PFOS), which is commonly found in biosolids, have been phased out of production in the United States and are no longer approved for use. Even though they have not been used for years, their legacy remains.
WWTPs do not generate PFAS, though they may receive discharges from certain industrial, commercial, or residential sources that have used PFAS. As a result, PFAS may be found in treated wastewater and biosolids. Some of those PFAS are known to travel through water, can linger in the environment, and have the potential to impact the soil, water and crops. In areas where PFAS have been released to the environment, PFAS have been found to build up in the tissue of fish and deer in Michigan and in some instances led to consumption advisories. Some studies have shown that certain PFAS may harm human health, therefore, it is important to minimize exposure to all sources of PFAS in drinking water and food. For more information and referencing, please go to the website (or link) listed below.
Currently, the EPA is working to complete a risk-based evaluation of PFAS in biosolids. In the interim, EGLE has taken a deliberative, disciplined approach which focuses on identifying and reducing significant sources of PFAS entering WWTPs and preventing industrially impacted biosolids from being land applied. These efforts have helped WWTPs reduce PFAS concentrations in their biosolids.
In 2018, EGLE launched the Industrial Pretreatment Program (IPP) PFAS Initiative which has been successful in working with WWTPs to identify, reduce, and monitor sources of PFOS to the WWTP. Since the initial work in 2018, EGLE has seen a substantial reduction in PFOS concentrations at WWTPs with IPPs. Additionally, in 2021, EGLE established an Interim Strategy for the Land Application of Biosolids Containing PFAS. This includes sampling requirements and farmer notification prior to land application as well as source identification and reduction efforts. The Interim Strategy also sets a threshold concentration of PFOS for biosolids to be considered industrially impacted. Any WWTP that exceeds the industrially impacted threshold will not be allowed to land apply their biosolids until PFOS concentrations decrease below the threshold.
Learn more about the IPP PFAS Initiative
Learn more about the Interim Strategy and what EGLE is doing to address PFAS in biosolids
