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Beneficial Re-Use of Biosolids by Agricultural Land Application

What are biosolids?
Municipal wastewater treatment plants in Tulsa separate the liquid and residual portions of wastewater for processing and treatment. Biosolids are residuals that have undergone additional treatment (stabilization) to prepare them for environmentally acceptable beneficial use or disposal. City of Tulsa biosolids are stabilized and land applied in an environmentally acceptable manner in compliance with EPA regulations 40 CFR Part 503.

Is it safe to land apply biosolids?
Land application is the most common use for biosolids. It has been used for decades and involves spreading the biosolids on the soil surface or injecting the biosolids into the soil. Biosolids enrich the soil by providing organic mater and nutrients needed for crops. Biosolids have been used as a substitute for commercial fertilizers in the United States for over 50 years. While there are many opinions about the use of biosolids, most experts agree that properly applied biosolids will increase crop production and improve the quality of soil without health risk or degradation of the surrounding environment.

How do biosolids help the soil and crops?
Biosolids enrich the soil with essential nutrients and organic matter. Plants need a complex mixture of nutrients, soil, air and water to grow well. Biosolids contain a full range of essential plant nutrients that are released slowly, as the plants need them during the growing season. The organic matter acts as a sponge for water, nutrients and air where soil organisms can prosper and plant roots can better develop. This "sponge" also reduces the possibility of leaching nutrients to the groundwater. The result is improved crop production, less water runoff, less soil erosion and more water conservation.

Biosolids Monitoring:
Land applied biosolids meet strict regulations and quality standards established by the Federal Government Environmental Protection Agency (EPA) and Oklahoma Department of Environmental Quality (ODEQ). These rules set numerical limits for metals in biosolids, pathogen reduction standards, vector attraction reduction, site restrictions, crop planting and harvesting restrictions, and monitoring, record keeping and reporting requirements.

Site Permit & Buffer Zones:

  • Each application site must have a permit approved by ODEQ.

  • Buffer zones are set two hundred fifty (250) feet from residences, any well used for potable water supply or a public water supply surface water intake; one hundred (100) feet from waters of the state, including ponds and drainage ditches; and twenty-five (25) feet from the traveled portion of the public roadway.

  • Buffer zones are set for slopes 5% or greater.

  • Harvesting food, feed and fiber crops are restricted for 30 days after the application of biosolids.

  • Animals are restricted from grazing on the land for 30 days after the application of biosolids.

  • Sod grown on land where biosolids is applied shall not be harvested for one year after the application when the sod is placed on land with high potential for public exposure.

  • Inspections of each application site are made within 18 months after application to ensure that the site operator is keeping their obligations.

How are biosolids applied?

  • For sites not in the City's land application program, approval from ODEQ is required to add the site.

  • Pre-application site inspections and collection of soil samples are performed to determine site suitability.

  • Application rates are determined based on the crop to be harvested.

  • pH adjustment to soil (if needed) and aeration.

  • Application of biosolids

  • Incorporation of biosolids into the soil.

Biosolids application is a Partnership with Landowners
Each project is a partnership between the landowner and the City of Tulsa for the beneficial and economical application of this valuable resource. The landowners provide the site and the City provides the biosolids. Since the City is interested in the most cost effective sites, landowners that assist in the application process are more likely to receive biosolids. Assistance may include hauling of the biosolids from the source, pre-application aeration, spreading biosolids with a manure type spreader, and/or post application incorporation. In all cases, the City provides oversight and record keeping for each project.

To participate in the Biosolids Program, please call or write:
City of Tulsa, Water Pollution Control
175 East 2nd Street, 8th Floor
Tulsa, Oklahoma 74103
(918)-596-9453