Michigan’s Biosolids Program is regulated by the Michigan Department of Environment, Great Lakes, and Energy’s (EGLE) Water Resources Division (WRD), under Part 24, Land Application of Biosolids (Part 24 Rules), promulgated pursuant to Part 31, Water Resources Protection, of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended. You may contact EGLE’s Biosolids Program staff with questions about Michigan's Biosolids Program Rules and regulations.
Biosolids are organic material produced during the treatment of domestic sewage at a Wastewater treatment plant (WWTP). A WWTP separates liquids from settleable solids. Solids are pulled out of the waste stream, while the rest of the liquid is safely treated to be discharged into the environment. Settled solids that are treated further to reduce pathogens may be able to be land applied to a farmer’s benefit. Residuals such as biosolids can provide essential nutrients comparable to commercial products.
Biosolids are organic materials resulting from the treatment of domestic sewage in a wastewater treatment facility. After solids have settled, the WWTP may stabilize the collected solids by digestion or another method to reduce or eliminate pathogens. Many WWTP's opt to further treat their solids in order to participate in the beneficial use land application program. WWTP’s that don’t participate in the biosolids land application have the option to landfill or incinerate collected solids.
Biosolids do not come from septic tanks, industrial or food processing facilities, or animals.
Biosolids are most often land applied in bulk to agricultural fields. Biosolids can also be used in silviculture (applied to trees), mine reclamation, and when treated to Class A Exceptional Quality (EQ) standards, sold, or given away for the public to use. All places where biosolids are applied are reviewed by the Biosolids staff at EGLE, and must meet management criteria such as slope, isolation distances from water and buildings, and agronomic rate. Most biosolids applied in Michigan are injected below the surface to limit transmission of pathogens.
Farmers apply biosolids to their land because biosolids can provide the soil with important macronutrients such as nitrogen, phosphorus, and potassium (N, P, K) like those found in conventional fertilizers. Micronutrients such as zinc, copper, and molybdenum can also be found in biosolids. Using recommendations from soil tests, farmers apply nitrogen found in biosolids at a rate needed by the crops they will be planting. Soils low in organic matter can also benefit from the carbon content received by biosolids land application. Furthermore, there is an economic benefit in using biosolids over commercial fertilizer, as biosolids are often supplied at no cost to the farmer.
The Part 24 Rules outline limitations that directly or indirectly protect the environment and natural resources. See table below for a summary of regulatory requirements. The following table compares the different classifications of biosolids land applied in Michigan:
| Type of Biosolids/Class of Pathogens | Meet Ceiling Concentration for Pollutants (Table 1) | Meet Pollutant Concentration Limits (Table 3) | Site Restrictions | General Requirements and Management Practices |
|---|---|---|---|---|
| Class A EQ | Yes | Yes | No | Yes |
| Class A | Yes | Yes | No | Yes |
| Class B | Yes | Yes | Yes | Yes |
Table definitions:
EGLE currently requires the monitoring of the following pollutants:
Other chemicals can be detected in biosolids, but the above metals were determined to have potential to impact public health and are therefore limited. Not all chemicals detected in biosolids have been determined to negatively impact public health and are not included. For more information about how the EPA determines what should be included, please refer to the EPA’s Biosolids Website.
PFAS is being monitored according to strategies developed by the emerging pollutants section (EPS). Michigan Biosolids PFAS-Related information can be found at Michigan.gov/Biosolids.
In addition to biosolids, wastewater treatment plants are required to monitor the water that is discharged into surface water for a number of pollutants. In order to ensure they are able to meet discharge limits, many treatment facilities implement industrial pretreatment programs (IPP) to limit the amount of pollutants coming into the facility. More information about pollutants monitored at the waste water treatment plant can be found at Michigan.gov/EGLEnpdes and Michigan.gov/IPP.
If a pollutant in biosolids surpasses a certain threshold, it is required that the lifetime amount of that pollutant is tracked on that field. If any pollutant exceeds the amount in the table below, land application of those solids is forbidden. This is also referred to as Table 1 of R 323.2409(5)(a):
| Pollutant | Ceiling Concentration in milligrams per kilogram (on a dry weight basis) |
|---|---|
| Arsenic | 75 |
| Cadmium | 85 |
| Copper | 4300 |
| Lead | 840 |
| Mercury | 57 |
| Molybdenum | 75 |
| Nickel | 420 |
| Selenium | 100 |
| Zinc | 7500 |
Setbacks (isolation distances) from drinking water wells must be accounted for when a site is being considered for the land application of biosolids. For Class B injected or surface-applied biosolids with incorporation, land appliers must maintain the following isolation distances: 100 feet from domestic wells, 100 feet from homes or commercial buildings, and 50 feet from any surface waters.
If you have concerns regarding well water quality, contact EGLE’s Drinking Water and Environmental Health Division (DWEHD) to discuss how to analyze well samples. You can also contact your local health department for more information.
Due to the close contact humans have with their pets, it is recommended that both people and pets avoid areas of biosolids land application for at least 30 days. This reduces the chance that any residual pathogens will be transferred to you, your home, or other people.
If the biosolids land applied are liquid, they generally contain a substantial amount of water. Tanker trucks are used to transport the biosolids from the WWTP to the location of land application. Usually liquid biosolids are generally 2-10% solid, meaning that up to 98% of what is being applied is water content. To deliver the nutrients required to the field, it may take numerous trips to deliver the biosolids.
Additionally, biosolids must be land applied at an agronomic rate that cannot exceed the recommended nitrogen, phosphorus, potassium (NPK) value for the crops grown at a specific biosolids site. Biosolids sites must have a soil analysis no less than two years old on file that provides these recommendations. If the biosolids are not being applied above agronomic rate, it is unlikely that too much is being applied.
Agronomic Rate is the calculated biosolids application rate (dry weight basis) which provides the amount of plant-available nitrogen (PAN) needed by the crop or vegetation grown on the land; which minimizes the amount of nitrogen that passes below the root zone of the crop or vegetation grown; and which considers the amounts of phosphate (P2O5) and potash (K2O) added by the biosolids as part of the total nutrient management plan.
Refer to the Michigan State University’s Extension office publication, “Utilizing Biosolids on Agricultural Land,” for more information on agricultural rate.
The following documents must be submitted to WRD Biosolids staff within 10 days of initial land application activity.
Staff will review the documents in accordance with the Part 24 Rules and ensure consistency and completeness. In addition, facilities land applying biosolids are now required to sample annually for PFAS compounds. Biosolids PFAS sampling is required to be submitted two weeks prior to the initial land application for that calendar year.
It is the responsibility of the Biosolids Generator (the City, Village, Township, County, LLC, etc. that generates the biosolids) to ensure that biosolids being land applied in Michigan are being handled in accordance with the Part 24 Rules and the approved Residual Management Program (RMP). Many Biosolids Generators hire third party contractors to handle, sample, and apply biosolids on behalf of the generator. It is the responsibility of anyone generating, treating, land applying or otherwise handling biosolids to be compliant with Part 24 rules.
Generally, biosolids should not emit odors different than farm activity of similar nature. The presence of odors does not indicate that there is danger to human health or the environment, and the odor can be different depending on the treatment process. However, the odor should not be excessive. If there is concern about odor that is experienced during and/or after biosolids land application, contact Biosolids Staff or contact EGLE’s Air Quality Division (AQD) district office.
Biosolids land application sites can be identified by using the Site Map Explorer function of the WRD’s MiEnviro Portal (MiEnviro) database. All new biosolids sites are entered into MiEnviro by the WRD’s Biosolids Staff. This allows anyone to view biosolids sites and download documents that are accessible to the public. If there is not a biosolids site in the area of concern on the Site Map Explorer, other unrelated land application activity may be taking place such as manure spreading, septage application, or other beneficial use materials.
Contacting the local health department is another way to know if a site receiving land application is designated for biosolids. More resources on land application programs in Michigan are provided at the end of this document. Staff maps will provide the contact for specific regions of Michigan.
Biosolids are regulated federally through Title 40 Code of Federal Regulations (CFR) Part 503, Standards for the Use or Disposal of Sewage Sludge and are regulated in Michigan through the Part 24 Rules. Contact biosolids staff or nearby waste water treatment plants for more information. The following links provide more information:
