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University of Nebraska–Lincoln

UNL Extension in Lancaster County

Natural Resources

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Regulations for Safe Use of Biosolids

by Barb Ogg, PhD, UNL Extension Educator

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Technological advances in processing wastewater and the careful application of biosolids allow the beneficial use of biosolids while minimizing the risk of human health problems and environmental contamination. In 1993, the U.S. Environmental Protection Agency (EPA) established specific wastewater processes and application procedures required to permit land application of biosolids. These regulations were the culmination of 30 years of carefully designed studies conducted at many land grant universities throughout the U.S. These regulations, known as Standards for the Disposal and Utilization of Sewage Sludge, Part 503, are also referred to as the Part 503 rule. 

The Part 503 rule addresses wastewater operational standards (to reduce pathogens), pollutant limits (heavy metals), management practices, monitoring, recordkeeping and reporting.

Pathogens. All biosolids that are land-applied must be processed to reduce the amounts of pathogens to safe levels. Biosolids that are suitable for horticultural or lawn application (Milorganite®, for example) are called "Class A" biosolids. Because Class A biosolids are processed with some type of heat treatment, they can be applied safely to food crops or to areas of frequent human contact.

Biosolids produced by the City of Lincoln are applied to crop fields or areas where direct human exposure is infrequent. These biosolids are classified by the EPA as “Class B” biosolids. At the Theresa Street Wastewater Facility, time and temperature processing in anaerobic digesters significantly reduces pathogens, but the pathogens are not completely destroyed. Class B requirements for land application also include site restrictions that prevent crop harvesting and restrict animal grazing for certain periods of time until environmental conditions have further reduced pathogens. 

Heavy metals. The EPA 503 Regulations established ceiling concentrations for 10 metals that are usually found in municipal wastewater. The concentrations were determined using a sophisticated risk analysis based on experiments that examined potential health hazards to humans. Fourteen pathways, each examining a possible route of exposure, were carefully studied. Some of these pathways were very complicated. For example, one pathway examined the effect of applying metal-contaminated biosolids to soil grown to forage plants that were fed to livestock that ultimately ended up as human food. To understand this pathway better, scientists studied the uptake of metal-contaminated soil by different crops that might be fed to livestock. In other experiments, scientists fed contaminated feed directly to animals and examined the meat, milk, and body organs of the livestock. Results of these and many other experiments were used to determine the maximum concentrations of metals that can be safely present in sludge and soil. 

Environmental protection. The second aspect of the Part 503 rules involves careful application to prevent environmental contamination. The Part 503 rules include the following application restrictions: 

—Biosolids must be applied at agronomic rates, based on the nitrogen requirements of the next crop. The purpose of this regulation is to prevent over-application, which could result in nitrates leaching into ground water. Compliance with this regulation requires soil tests to determine fertilizer needs of each field and frequent analysis of the nitrogen concentration in biosolids.

—Setback distances restrict the application of biosolids near rivers, streams and other water ways to prevent contamination of surface waters from nutrient overloading and/or pollutants. 

—Municipalities must monitor application rates and field locations, keep records and calculate loading rates of pollutants and submit annual reports detailing field applications.

Local regulations. Many biosolids programs have state or local regulations that may be more restrictive than the EPA regulations or may address local concerns about the application. These regulations may concern proximity to housing developments, acreages, schools and/or the timely incorporation of biosolids. Because municipal biosolids contains human waste, there is a natural tendency for the public to be concerned about its use. But, when biosolids meets EPA regulations regarding pathogen and metal standards and when responsible application practices are followed, the benefits of biosolids far outweigh the likelihood of health problems or environmental contamination. Municipalities, like the city of Lincoln, are working hard to make sure that their wastewater solids are safe and applied in a responsible manner.


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PHOTO Credit: Vicki Jedlicka

Lincoln's biosolids recycling program is a joint collaboration between the City of Lincoln, Public Works and Utilities Department and University of Nebraska-Lincoln Extension in Lancaster County with assistance from the University of Nebraska Agronomy Department, Lincoln/Lancaster County Health Department and the Natural Resources Conservation Service.


Contact Information

University of Nebraska-Lincoln in Lancaster County
Barb Ogg or David Smith
Web site: lancaster.unl.edu
444 Cherrycreek Road, Suite A, Lincoln, NE 68528 | 402-441-7180