What is the difference between biosolids and sludge?

Biosolids are treated sewage sludge. Sludge is typically 3% solids (97% liquids) whereas biosolids are typically 15-90% solids. Because of the treatment and production process, pathogen levels Biosolids are much lower than in sludge.

Regulators, such as State departments of Health and Environment strictly control the application, production and quality of biosolids.