Biosolids

Biosolids are a nutrient-rich organic material created from the biological and physical treatment of wastewater. Biosolids can be used to improve soil structure, water retention, and are also used as a slow-release fertilizer.

After proper handling and management techniques, biosolids are the final by-product of all settleable and floatable materials that enter the wastewater treatment facility. They are biologically processed in large digestors to further reduce or eliminate pathogens. Biosolids are rich in nutrients such as Nitrogen, Potassium, Calcium, Phosphorus, and many other highly beneficial compounds. Once dried, these solids can be of great beneficial use on agricultural lands and are a great soil amendment substitute to store-bought fertilizers. The final product can look and smell just like dirt.

The quality of biosolids can be classified in several different ways. The Board of Public Utilities can produce a Class “B” product, which can only be used for agricultural benefits and has several restrictions on their end use. The Board of Public Utilities can also produce a Class “A” product that is very similar to fertilizer you can buy at your local stores. These solids can be applied to yards, gardens, parks, and flower beds. Biosolids can also be added during the composting process of plant-based materials. Class “A” solids have virtually no restrictions on their end use.

Dependent upon quality, biosolids can be classified in several different ways. The Board of Public Utilities produces two types of biosolids.

• Class A - A biosolid product that is very similar to the fertilizer you can buy at your local stores. These solids can be applied to yards, gardens, parks, and flower beds. They can also be added during the composting process of plant-based materials. Class “A” solids have virtually no restrictions on their end use.
• Class B - A biosolid product that can only be used for agricultural benefits and has several restrictions on their end use.

Any settleable or floatable solids that enter the wastewater treatment plant are stored in large digestors for anywhere between 30 and 60 days. These digestors are held at a constant temperature, comparable to the human body. During this process, the waste product is stabilized, and methane gas is produced. This gas is recycled back into the heating of the digestors. Once the sludge meets several different criteria, it is then dewatered into a “cake” using two large screw presses. The solids are then handled in large drying beds for further drying, eventually reaching a total solids concentration of at least 75%.

On average, the Board of Public Utilities produces 1,200 dry metric tons (DMT) per year. The BOPU currently uses land application as our primary method of disposal.

The Board of Public Utilities has recently replaced our aging centrifuges with slow rotating screw presses which have allowed the Board of Public Utilities to produce a better “cake” and a better biosolids product. The Board of Public Utilities is starting to explore the possibility of adding a drying technology that will produce the final product in several hours, compared to the current process, which takes at least two years. This process would allow the Board of Public Utilities to offer a Class “A” product to the public for beneficial uses almost instantly.

After proper handling and management techniques, biosolids are the final by-product of all settleable and floatable materials that enter the wastewater treatment facility. They are biologically processed in large digestors to further reduce or eliminate pathogens. Biosolids are rich in nutrients such as Nitrogen, Potassium, Calcium, Phosphorus, and many other highly beneficial compounds. Once dried, these solids can be of great beneficial use on agricultural lands and are a great soil amendment substitute to store-bought fertilizers. The final product can look and smell just like dirt.

Any settleable or floatable solids that enter the wastewater treatment plant are stored in large digestors for anywhere between 30 and 60 days. The digestors maintain a constant temperature, comparable to the human body. During this process, the waste product is stabilized, and methane gas is produced. This gas is recycled back into the heating of the digestors. Once the sludge meets several different criteria, it is then dewatered into a “cake” using two large screw presses. The solids are then handled in large drying beds for further drying, eventually reaching a total solids concentration of at least 75%.

Please email or call the Biosolids program at the Board of Public Utilities with any questions.

Email: biosolids@cheyennebopu.org
Phone: (307) 637-0866