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 may be used as fertilizer or soil amendments (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 U.S. 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. Those processes refine the biosolids to be applied at agronomic rates, providing a stable and valuable source of plant nutrients and soil structural enhancements.

In many larger wastewater treatment systems, pretreatment regulations require that industrial facilities pretreat their wastewater to remove many hazardous contaminants before it is sent to a wastewater treatment plant. Wastewater treatment facilities monitor incoming wastewater streams to ensure their compliance with pretreatment regulations and compatibility with the treatment plant process.

Once the wastewater reaches the plant, the sewage goes through physical, chemical, and biological processes that clean the wastewater and remove the solids. If necessary, the solids are then treated with lime (calcium oxide) to raise the pH level to eliminate objectionable odors. The wastewater treatment processes sanitize wastewater solids to control pathogens (disease-causing organisms, such as certain bacteria, viruses, and parasites) and other organisms capable of transporting disease.

Biosolids must meet strict regulations and quality standards. In Michigan, biosolids are beneficially used under requirements established in Michigan's Part 24 Rules.  They govern the use and disposal of biosolids and contain numerical limits for metals, pathogen reduction standards, site restrictions, crop harvesting restrictions and monitoring, recordkeeping, and reporting requirements for land applied biosolids.  

Sewage sludges are residuals from the wastewater treatment plant process that are not beneficially used and are typically disposed of in a landfill or are incinerated.

Some plants will take up PFAS from contaminated soil or water.  At this time, we do not have enough research to predict how much PFAS will end up in a specific crop, and there are no federal standards for PFAS levels in plants. Plant uptake of PFAS appears to vary according to a number of factors, such as:  a) the concentration of PFAS in the soil and water; b) the type of soil; c) the type of plant being grown; d) the amounts of precipitation and irrigation water; and e) other nutrients and components in the soil.

More research is needed to quantify the amount of PFAS that could accumulate in the edible parts of produce and crops grown in soils or irrigated with water contaminated with PFAS, and to determine standards for safe levels. Since people eat a variety of foods, the risk from the occasional consumption of produce grown in soil or irrigated with water contaminated with PFAS is thought to be low. However, because these chemicals can accumulate in the body and people can be exposed from a variety of sources, it is recommended to minimize known PFAS exposures whenever possible.

If you are concerned that your water may contain PFAS and you are on municipal water (meaning, you receive a water bill), view the results of the Michigan Department of Environment, Great Lakes, and Energy (EGLE's) 2018 statewide public water supply sampling effort. (This site also contains results from sampling of schools on their own wells, and many childcare centers and Head Start Programs). If you are concerned that your water may contain PFAS and you are on a private well, visit our Home Sampling Guidance page to learn how you can take and have your own residential water sample analyzed. For other questions, contact the State of Michigan Department of Health and Human Services Environmental Health Hotline at 800-648-6942.

For questions about gardening, visit the Crops, Gardening and Food FAQs. 

Currently, there are no federal or state standards for PFAS in crops.  The Michigan Department of Agriculture and Rural Development (MDARD) has requested guidance regarding PFAS in the food supply from the US Department of Agriculture (USDA) and US Food and Drug Administration (US FDA).

PFAS have been found in materials that are land applied. There currently are no standards for PFAS concentrations in materials for land application.  Historically it has been the role of the US Environmental Protection Agency (USEPA) to establish land application criteria.  EGLE and MPART have requested the USEPA to develop criteria as soon as possible.  Because national standards haven't been developed, Michigan is implementing strategies to identity and reduce sources of PFAS entering municipal wastewater treatment systems, evaluating PFAS concentrations in biosolids prior to land application and PFAS concentrations in biosolids and limiting application rates accordingly.

The Michigan PFAS Action Response Team (MPART) formed a multi-agency Land Application Workgroup with representatives from EGLE, MDHHS and MDARD. This workgroup, along with EGLE's Industrial Pretreatment Program (IPP) staff, are working to understand many complex issues related to PFAS in biosolids and other materials that are land applied.  Specifically, the Land Application Work Group is trying to understand the relationship between PFAS in wastewater treatment plant influent, effluent and biosolids, as well as how PFAS in materials that are land applied might affect surface water, groundwater, and soils.  

Part of EGLE's approach to addressing PFAS in biosolids wastewater and associated residuals is to identify sources of PFAS within wastewater treatment systems and to control or eliminate them at the source.  Preliminary efforts at source control implemented through the Industrial Pretreatment Program PFAS Initiative have been successful in reducing PFAS inputs to wastewater treatment systems thereby reducing the potential for PFAS to accumulate in solids generated at the plant.

In the fall of 2018, EGLE initiated a study of 42 municipal WWTPs to evaluate the presence of PFAS in influents, effluents, and associated residuals (sludge/biosolids).  As part of this initiative, screening of 22 land application sites was conducted to further understand the potential impacts to the environment from land-applied biosolids. The information collected has been used in the development of EGLE's Interim Strategy for Land Application of Biosolids, which contains the PFAS interim strategy. 

EGLE is supporting U.S. Environmental Protection Agency's (USEPA) efforts to complete a risk-based evaluation of PFAS in biosolids.  While the USEPA is completing their evaluation of biosolids, EGLE will continue a deliberative, disciplined approach which focuses on identifying and reducing significant sources of PFAS entering wastewater treatment systems, preventing the land application of industrially impacted biosolids, mitigate (reduce) risks and continue driving PFAS concentrations present in biosolids down as quickly as possible.  

The MPART Land Application Workgroup is now expanding this effort to evaluate PFAS in the land application of other (non-biosolids) residuals.

Industrial sludges are materials generated from industrial facilities and are not considered biosolids, although under certain circumstances they can be land applied under EGLE's and/or MDARD's authority. The MPART Land Application Workgroup is examining the presence and impacts of these types of materials to see if they could be a source of PFAS in soil.

In Michigan, most biosolids used for agriculture are applied to fields that will grow crops such as corn, soybeans, and wheat. 

In some instances, biosolids can be treated in an advanced treatment process to create what is referred to as Class A Exceptional Quality (EQ) biosolids.  EQ biosolids describe biosolids meeting both Class A and Exceptional Quality standards for the level of pathogen reduction, stringent metal limits, and vector attraction standards. EQ biosolids can be used on crops for human consumption as well as home garden and landscape use.

Decades of research and actual application of biosolids have resulted in an overwhelming scientific agreement among qualified researchers that the use of biosolids in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, crop production, and the environment. In fact, the science-based approach used in developing the biosolids standards could serve as a model for policy and regulation in other areas of agricultural production and food safety.