What Are Biosolids?
Biosolids are the nutrient-rich organic materials resulting from the treatment of domestic sewage at a wastewater treatment facility. Through biosolids management, solid residue from wastewater treatment is processed to reduce or eliminate pathogens and minimize odors, forming a safe, beneficial agricultural product. Farmers and gardeners have been recycling biosolids for ages. Biosolids can be applied as fertilizer to improve and maintain productive soils and stimulate plant growth. They also are used to fertilize gardens and parks and reclaim mining sites. Biosolids are carefully monitored and must be used in accordance with regulatory requirements. Click here to view facts
Why Do We Have Biosolids?
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We have biosolids as a result of treating sewage sludge (which refers to the solids generated during the treatment of domestic sewage in a treatment plant) in order to meet the land application regulatory requirements. Wastewater treatment technology has made our water safer than ever for recreation and seafood harvesting. Thirty years ago, thousands of American cities dumped their raw sewage directly into the nation's rivers, lakes and bays. Through regulation of this dumping, local governments are now required to treat domestic sewage and to make the decision whether to recycle the solids generated as fertilizer, to incinerate them or to bury them in a landfill. If the solids meet the regulatory requirements for land application and are recycled, they are biosolids.
How Are Biosolids Generated and Processed?
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Biosolids are generated when solids produced during the treatment of domestic sewage are treated further to meet regulatory requirements. The wastewater treatment can actually begin before the wastewater reaches the treatment plant. In many larger wastewater treatment systems, pre-treatment regulations require that industrial facilities pre-treat their wastewater to remove many hazardous contaminants before it is sent to a wastewater treatment plant. Wastewater treatment facilities monitor incoming wastewater streams to ensure their recyclability and compatibility with the treatment plant process.
Sewage sludge is not generated until domestic sewage is treated in a treatment plant, and biosolids are not produced until the sewage sludge meets the land application Part 503 requirements. For these reasons, the treatment of biosolids cannot occur before the domestic sewage reaches the wastewater treatment plant.
Once the wastewater reaches the plant, domestic sewage goes through physical, chemical and biological processes that clean the domestic sewage and remove the solids. If necessary, some of the solids are then treated with lime to raise the pH level to eliminate objectionable odors. Pathogen reduction (reduction of disease-causing organisms, such as bacteria, viruses and parasites) and reduction of other organisms capable of transporting disease for the solids usually occurs in a different process (e.g., a digester).
How Are Biosolids Used?
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After treatment and processing, biosolids can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth. The controlled land application of biosolids completes a natural cycle in the environment. By treating sewage sludge, we create biosolids that can be used as valuable fertilizer instead of taking up space in a landfill or other disposal facility.
If you have a farm and would like free biosolids to fertilize land, please click here to contact us
Do Biosolids Smell?
Biosolids may have their own distinctive odor depending on the type of treatment it has been through. Some biosolids may have only a slight musty, ammonia odor. Others have a stronger odor that may be offensive to some people. Compounds that contain sulfur and ammonia, which are both plant nutrients, cause most odors. Once applied to land, the odor typically dissipates after a short time, depending on weather conditions.
Are Biosolids Good for the Environment?
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Recycling biosolids is good for the environment. Organic matter has been recycled for centuries to improve soil fertility and productivity. When properly applied and managed, biosolids can provide essential plant nutrients, improve soil structure and tilth, add organic matter, enhance moisture retention and reduce soil erosion.
Biosolids recycling is regulated and encouraged by the United States Environmental Protection Agency and state and local authorities. Research and years of recycling experience have demonstrated that properly managed land application of biosolids is environmentally safe.
How Does Charlotte-Mecklenburg Utilities Recycle Biosolids?
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Utilities produces "Class B" biosolids at each of its five wastewater treatment plants. Class B biosolids can be applied to land that produces animal feed crops but not land producing crops for human consumption. Biosolids from four of these plants is recycled through land application on more than 16,000 acres of private farmland in our region. Each of these sites must be permitted with the North Carolina Department of Environment and Natural Resources. This means that in addition to the stringent requirements our biosolids meet, each particular farm where it is applied meets specifications, and the method in which it is applied at each site also is regulated.
Charlotte-Mecklenburg Utilities biosolids program is managed using an EMS which is ISO 14001:2004 certified by an external audit process. The Environmental Management Systems (EMS) emphasizes our commitment to continuous improvement and pollution prevention.