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PFAS and Biosolids / Land Application
PFAS and Biosolids / Land Application
What are biosolids?
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.
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 plants 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 separate out the solids. Solids intended for land application (i.e., biosolids) undergo additional treatment processes to stabilize the materials and kill pathogens (disease-causing organisms, such as certain bacteria, viruses, and parasites) prior to being utilized as a soil amendment and conditioner.
What is the difference between biosolids and sewage sludge?
Biosolids must meet strict regulations and quality standards. In Michigan, biosolids are beneficially used under requirements established in Michigan's Part 24 Administrative Rules. The rules 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.
Will crops be contaminated if they are grown in soil or irrigated with water containing PFAS?
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 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 collect and have your own residential water sample analyzed. For other questions, contact the Michigan Department of Health and Human Services (MDHHS) Drinking Water Hotline at 844-934-1315.
For questions about gardening, visit the Crops, Gardening and Food FAQs.
Are there food standards for PFAS in crops?
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).
Are there PFAS in materials that are land applied?
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 EPA to establish land application criteria. EGLE and the Michigan PFAS Action Response Team (MPART) have requested the EPA 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 limiting application rates accordingly.
What research is being done on PFAS and materials that are land applied?
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 Water Resources Division 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.
What is Michigan doing to understand and address PFAS in biosolids and industrial byproducts?
Part of EGLE's approach to addressing PFAS in biosolids 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 29 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 Containing PFAS.
EGLE is supporting the EPA's efforts to complete a risk-based evaluation of PFAS in biosolids. While the EPA 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 and industrial byproducts/sludges.
What about materials other than biosolids that are land applied?
Industrial byproducts/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.
Which crops can be planted on biosolid-applied fields?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.
What is the consensus in the scientific community about the safety of using biosolids for food crop production?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.