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FAQ: Land Application of Biosolids

Land applying biosolids
Environment, Great Lakes, and Energy

FAQ: Land Application of Biosolids

Biosolids are nutrient-rich organic materials, which remain following the treatment of domestic sewage at a wastewater treatment plant (WWTP).  Biosolids undergo additional treatment processes to stabilize the materials and kill pathogens prior to being utilized as a soil amendment and conditioner.  Michigan’s Biosolids Program is regulated by EGLE’s Water Resources Division (WRD), under the authority of Part 31 of the Water Resources Protection of the Natural Resources and Environmental Protection Act, 1994 PA 451, Michigan’s Part 24 Administrative Rules.

Do you have a question about Michigan's Biosolids Program and regulations? Contact our biosolids program specialists.

  • EGLE has developed answers to commonly asked questions related to PFAS in biosolids, which can be found on EGLE's PFAS and biosolids land application page.

  • There are certain circumstances when additional samples need to be collected beyond that required in Table 7.  One of those circumstances is described in Rule 2406(1), which requires that a person collect and analyze representative samples for the biosolids that are applied to the land.  Therefore, if a facility land applies seasonally (i.e., spring and fall), then data collected prior to the spring hauling period would not necessarily be representative of the material hauled in the fall.  Under this scenario, 1 sample would need to be collected before each hauling period (total of 2 samples) in order for the data to be representative of the material land applied.  If a generator removes biosolids monthly or more frequently, monitoring is required at least once per month each month that the biosolids are removed.  Rule 2412(3) does allow the permittee to petition EGLE for a reduced sample frequency after 2 years of monitoring.

  • The double sampling requirement is not based on the reporting year or calendar year; it is based only on the frequency of sampling.  Therefore, in the scenario presented, if your fourth quarterly sample is above Table 3 concentrations, then you would be required to begin the double sample frequency for the parameter over the Table 3 concentrations.  In other words, instead of collecting your sample every 3 months (quarterly), you would need to double that frequency and collect your next sample approximately 1½ months later.  If this sample result came below a Table 3 concentration, you would then return to the regular first quarterly sampling.  If this first quarterly sample was again above Table 3 concentrations, then you would need to continue the double sample frequency (every 1½ months) until concentrations are at or below Table 3 concentrations.

  • The federal requirements contained in Title 40 of the Code of Federal Regulations (CFR), Section 122.21(q)(7)(ii), state, in part, that biosolids applicants ". . . must provide data from a minimum of three samples taken within four and one-half years prior to the date of the permit application.  Samples must be representative of the sewage sludge and should be taken at least one month apart.  Existing data may be used in lieu of sampling done solely for the purpose of the application."

    Therefore, a minimum of 3 samples is required for facilities without prior analytical data.  However, additional samples could be required under certain circumstances, as in the case of:  (a) a facility land applying over 320 dry tons, (b) to obtain representative data as in a lagoon with 4 or more separate cells (unit processes), or (c) a facility with metals concentrations in excess of Table 3 concentrations.

  • For a lagoon not accepting additional wastewater or sludge, waiting between samples is not necessary.  The objective is to obtain representative samples from the entire lagoon.  This could be composite samples taken from multiple locations of the lagoon, or multiple samples analyzed separately and then averaged.  In a wastewater stabilization lagoon where solids will be removed from the bottom of one of the cells, the cell should not accept additional wastewater and then use the above composite or multiple samples.

  • Yes, as long as the 3 samples were composites collected from multiple areas of the same cell and the material is well mixed prior to land application.  The average of the three composite samples should be representative of the material to be land applied.

  • Michigan Part 24 Rules defines agronomic rate, in part, as "the calculated biosolids application rate which provides the amount of plant-available nitrogen (PAN) needed by the crop or vegetation grown on the land . . ."  The two most commonly utilized methods for calculating PAN in Michigan are the 1 year PAN and the multiyear PAN methods.  Michigan recommends facilities utilize the multiyear PAN, which involves calculating the amount of mineralized nitrogen that becomes available from land application having occurred to the site in the previous 3 years. 

    Guidance on calculating multiyear PAN can be obtained from Appendix E of the RMP Development Document.

    Calculating agronomic rate also requires determining the nitrogen needs of the crop for a realistic yield goal.  Nitrogen needs of the intended crop can either be obtained from Michigan State University Cooperative Extension Bulletin or directly from the soil test.  However, if you base application rates on the soil test, you need to make sure those nitrogen recommendations are consistent with those of Michigan State University.

    Determining realistic yield goals can be more difficult.  Field records are the best source for crop yield estimates.  Where field records are not available, you can make first-year estimates for a project using Natural Resource Conservation Service (NRCS) soil surveys or county production averages.  County production averages can be obtained from the Internet at

  • Determining the accurate acreage of a land application site is a critical component of accurately applying biosolids at the agronomic rate.  Simply relying on the farmer's estimate of acreage is not recommended as farmers will frequently over estimate and sometimes underestimate useable acreages.  EGLE suggests that land applying facilities or their land application contractor double check the farmer's estimate of useable acreage with commonly available measurement tools such as a Global Positioning System or a computer-based mapping program.  The NRCS offers a free Internet site that allows access to aerial photographs overlaying soils mapping program that includes a useful site measuring function.

  • When the land application period lasts for more than 2 consecutive days, EGLE has found that the percent solids analysis provided on the analytical report for metals and nutrients is often not representative of the percent total solids of biosolids actually land applied.  Because Rule 2406(1) requires that a person collect and analyze representative samples, EGLE typically does require daily percent total solids analysis, unless information can be provided demonstrating that the initial data is representative (i.e., mechanical plant with good mixing).  The daily percent solids results should be utilized when calculating daily application rates and reporting dry tons land applied.

    A related issue regarding lagoon cleaning projects is that the composite samples collected for the RMP approval often overestimate the concentration of available nutrients and underestimate the total percent solids of the biosolids being applied to land after a few days of cleaning operations inside the lagoon.  This phenomenon is likely due to the mixing of the biosolids with the clay particles from upper portions of clay liners disrupted from equipment working inside the lagoon.  To address this situation and provide the most representative data possible (in addition to the sampling for metals, nutrients, and fecal coliform prior to beginning the project), EGLE has begun requiring the sample plan in the lagoon RMP to include a commitment to analyze a minimum of 2 additional composite samples for available nutrients in addition to the daily percent solids collected during the course of the lagoon cleaning.  This data should then be used in reporting dry tons and nutrients land applied.

    For more clarification on this requirement, please contact your EGLE Biosolids Specialist.

  • Temporarily transferring a site is not allowed, but you may relinquish a site to another facility.  Rule 2413(2)(c) states, in part, that ". . . biosolids from other sources may be land applied to a site only after that site is relinquished in writing to another generating facility."  The facility relinquishing the site must sign an agreement, and the facility receiving the site will need to submit a new site ID package indicating on the site ID form that this is a "repermit."  The signed relinquishing form and the revised site ID form with all the attachments should be submitted to the EGLE District Office just as it is done for a new site.  If, after 1 growing season, the original facility wishes to enroll the land application site back into their program, they must follow the same procedure.

  • Yes, it is acceptable as long as an original hard copy of the signature page is later submitted to EGLE and the facility receives a copy of the entire approved RMP.  The facility should be instructed to retain a copy of the entire RMP and understand its contents, as the generator is ultimately responsible for the enforceable commitments in the RMP.

  • The Part 24 Rules defines the term municipal well (type I and IIA wells), in part, by stating "As defined and specified in Act No. 399 of the Public Acts of 1976, as amended . . ."  Since the Part 24 Rules definition of the term municipal well cross references Act 399, it is thereby interpreted the same as "public water supply (type I and IIA wells)."  Therefore, the 2,000-foot required setback requirement in the Part 24 Rules applies to any type I or type IIA public water supply well.

    EGLE provides the following suggested ways to identify the location of potential public water supplies from any prospective biosolids land application sites.

    • Drive around any sites to closely survey the surrounding area for potential public water supplies such as schools, restaurants, industries, and condo developments.
    • Include a sentence in the 10-day notification letter to the township and county health department specifically requesting that you be advised if any public water supplies exist within 2,000 feet of the proposed site.