& Biosolids
Biosolids
Field Green® biosolids are treated using a process called anaerobic digestion. This is a biological process where beneficial microorganisms feed on wastewater solids at high temperatures in an oxygen-free environment. This treatment process effectively reduces pathogens (disease-causing organisms), decreases the amount of solids, and stabilizes the material.
During the digestion process, over a third of the solids are broken down by microorganisms
and converted to biogas. This biogas is primarily methane and carbon dioxide. WLSSD uses this
methane-rich biogas as a fuel to heat the plant and to run microturbines that generate electricity.
After digestion, excess water is removed to prepare Field Green® for land application. The final product looks and feels like moist soil and has an ammonia-like odor. Monitoring is conducted to ensure product quality.
After dewatering, the biosolids are ready for distribution to land application sites. Field Green® is delivered and spread by WLSSD staff five days a week year-round. The material is hauled in a truck with a self-unloading trailer and is spread using a manure spreader pulled by a tractor. Land application sites are located primarily in Carlton and St. Louis Counties.
