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Image of food to waste process

Biosolids are the processed, nutrient-rich organic byproduct resulting from the treatment of sewage.  Biosolids are created as a side stream of the wastewater treatment process. 

The treatment of biosolids can begin before the wastewater reaches the sewage treatment plant. The St. Vrain Sanitation District (the District) requires that some industrial facilities pre-treat their wastewater to remove many hazardous contaminants before it is sent to the wastewater treatment plant. Wastewater treatment facilities monitor incoming wastewater streams to ensure their recyclability and compatibility with the treatment plant process.

Once the wastewater reaches the plant, the volume goes through physical and biological processes that treat the wastewater and remove solids. The District’s wastewater treatment process sanitizes wastewater solids by extended exposure to a high temperature to control pathogens (disease-causing organisms, such as certain bacteria, viruses, and parasites) and other organisms capable of transporting disease. The final product is a nutrient-rich substance, Class A Biosolids, that meets or exceeds state and federal regulations (40 CFR Part 503, colorado REG 64)

Biosolids Use

image of Class A Biosolids

After treatment and processing, biosolids can be recycled and applied as a soil amendment to improve and maintain productive soils and stimulate plant growth. The controlled land application of biosolids completes a natural cycle in the environment.  Farmers and gardeners have been recycling biosolids for ages.  The application of biosolids reduces the need for chemical fertilizers.  Agricultural use of biosolids, which meet strict quality criteria and application rates, have been shown to produce significant improvements in plant growth and yield. Nutrients found in biosolids, such as nitrogen, phosphorus and potassium and trace elements such as calcium, copper, iron, magnesium, manganese, sulfur, and zinc, are necessary for plant growth. The use of biosolids reduces fertilizer costs and replenishes the organic matter that has been depleted over time. The organic matter improves soil structure by increasing the soil's ability to absorb and store moisture.  The organic nitrogen and phosphorous found in biosolids are used very efficiently because these nutrients are released slowly throughout the growing season. This enables plants to absorb the nutrients as they grow. This efficiency lessens the likelihood of groundwater pollution of nitrogen and phosphorous.

Across the country, about 50% of all biosolids are being recycled to land. These biosolids are used on less than one percent of the nation's agricultural land.

Biosolids Safety

The National Academy of Sciences has reviewed current practices, public health concerns, and regulatory standards, and has concluded that "the use of these materials in the production of crops for human consumption when practiced in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, to crop production and to the environment."

The federal biosolids rule Is contained in 40 CFR Part 503. Biosolids that are to be land applied must meet these strict regulations and quality standards.  The Part 503 rule governing the use and disposal of biosolids contains numerical limits, for metals in biosolids, pathogen reduction standards, site restriction, crop harvesting restrictions and monitoring, record keeping and reporting requirements for land-applied biosolids.

There are different rules for different classes of biosolids. Class A biosolids produced by the District contain no detectible levels of pathogens. Class A biosolids meet strict vector attraction reduction requirements and have low levels of metals.  In general, exceptional quality (Class A) biosolids used in small quantities by the general public have no buffer requirements, crop type, crop harvesting, or site access restrictions. When used in bulk, Class A biosolids are subject to buffer requirements, but not to crop harvesting restrictions.

For More Information on Class A Biosolids:

Contact the St Vrain Sanitation District Wastewater

Treatment Plant at:

6501 County Road 26
Longmont, Colorado 80504
Phone: 303-776-4639

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