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Copperhill Biosolids Project

Frequently Asked Questions

What are biosolids?

Every day, wastewater treatment facilities across the country treat billions of gallons of wastewater generated by homes and businesses. The treatment process produces liquid and solid residues that must be managed in an environmentally responsible manner. After treatment, these solids can yield biosolids, which are defined by the U.S. Environmental Protection Agency (EPA) as “nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility … that can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth.”


What are the different classes of biosolids?

The EPA categorizes biosolids as Class A Exceptional Quality, Class A, and Class B. The difference between these types depends on the quality of the material, and the distinction helps ensure safe use. Class A Exceptional Quality are the highest quality of biosolids and approved for use in gardens that grow food. Class A biosolids are the next highest-level quality. They can be applied to land safely and are popular among home gardeners as compost or fertilizer. Class B biosolids are lower quality than Class A but are still approved as a compost or soil improvement for farmland. Class A Exceptional Quality biosolids meet the most stringent pollutant, pathogen, and vector attraction reduction requirements.


Is it safe to use biosolids?

Yes. Biosolids are among the most carefully controlled amendments in agriculture. They are also one of the most in-demand and effective because they are rich in both nutrients and organic matter. Biosolids have been applied to farms and mine reclamation sites for decades, and numerous studies have shown the benefits and safety of this practice.


What are some of the benefits of biosolids land application?

The benefits of biosolids for both soil and vegetation are numerous and well recognized. Biosolids provide primary nutrients (nitrogen and phosphorous) and secondary nutrients such as calcium, iron, magnesium, and zinc. Unlike some chemical fertilizers, biosolids provide nitrogen that is released slowly over the growing season.


Why not just landfill?

Communities across the country are experiencing higher costs for landfill space. At the same time, additional landfill space is becoming harder to obtain due to zoning and siting restrictions. When biosolids are used beneficially, it extends the life of current landfills and reduces the need for expansion.



What is the history of biosolids at Copperhill Industries?

The Copperhill Industries property that lies along Highway 68 near Copperhill, Tennessee is part of the Copper Basin Mining District Federal Superfund site. From the late 1800s until the 1980s, mining, processing, chemical manufacturing, and waste disposal occurred within the Copper Basin Mining District Superfund site. These operations left the site barren with no vegetation or topsoil. Beginning in 2016, Copperhill Industries began reclaiming portions of the site. Reclaiming the land was particularly challenging because of low soil pH and a lack of organic matter, which plants need to survive. After reclamation efforts with chemical fertilizer failed, Class B biosolids from Moccasin Bend Wastewater Treatment Plant in Chattanooga were land applied to portions of the site in 2018. Reclamation with the Class B biosolids was very successful. However, reclamation with Class B biosolids stopped in late 2022. A very small amount of Class B biosolids remain on the property and are planned to be land applied this summer.


What is the current use of biosolids at Copperhill Industries?

In spring 2023, Denali Water Systems proposed a pilot project to produce Class A Exceptional Quality biosolids. The Class A Exceptional Quality biosolids are used to establish vegetation and reclaim the site.


Is copper still mined at Copperhill Industries?

No, copper mining operations ceased when the mine closed in 1988.


What is being done about odors?

Every step of Denali’s operation is designed to reduce odor. These steps include sourcing the material, transportation, treatment with lime, and land application.



The biosolids are sourced from different wastewater treatment plants than the material applied previously. This material has gone through a different treatment process that can lead to a decrease in odor.


Denali has designed routes so trucks avoid traveling through busy or commercial areas.

Treatment with lime

Upon delivery to Copperhill Industries property, biosolids are treated with lime. This process is carefully controlled and monitored so that the material achieves Class A Exceptional Quality status.  The lime causes a chemical reaction that may release a small amount of odor for a short period of time in the immediate processing area. 

Land application

Copperhill Industries applies the Class A Exceptional Quality biosolids to locations that are far from neighboring residents so that any odors that may be present are reduced.


Where can residents go for more resources on biosolids?


United States Environmental Protection Agency:


A Plain English Guide to the EPA Part 503 Biosolids Rule:


Tennessee Biosolids Management Rules:


Who can I contact for more information?

For more information about biosolids at Copperhill Industries, contact Denali at

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