Utilizing Biosolids on Agricultural Land
Biosolids are solid, semisolid and liquid residues generated during the treatment of sanitary sewage, or domestic sewage, in treatment works treating domestic sewage (TWTDS). The term was introduced by the wastewater treatment industry in 1991 to describe the residuals or solids created during the biological treatment of wastewater (hence “bio-solids”). The U.S. Environmental Protection Agency (USEPA) recently adopted the name “biosolids” to differentiate high quality treated sewage sludge from raw sewage sludge and from sewage sludge containing large amounts of pollutants. Therefore, sewage sludges must be processed to meet USEPA standards for beneficial reuse before they can be called biosolids. The Michigan Department of Environmental Quality (MDEQ) has also adopted this term for rules made effective in November 1999.
Like animal manure, biosolids are part of the natural cycle of life. They contain inorganic and organic compounds removed during wastewater treatment. The beneficial use of biosolids for land application allows for the nutrient content and soil amendment properties of these residuals to be used advantageously for sustained crop production. For decades, sewage sludge has been used with great success on agricultural lands throughout the world. Land application has been increasingly regulated to protect human health and the environment from various constituents that can be found in biosolids, such as bacteria, viruses and other pathogens (i.e., disease-causing organisms), metals (e.g., cadmium and lead), toxic organic chemicals (e.g., PCBs) and nutrients (the most important being nitrogen and phosphorus). Forty years of research and demonstration projects on applying biosolids to land have provided a good scientific basis for the safe use and return of biosolids in our environment.