Which term describes treated sewage sludge used as a soil conditioner?

• A. Compost
• B. Sludge
• C. Biosolids
• D. Manure

Answer: (C)

Handling sewage solids from wastewater treatment involves processing them to reduce pathogens and contaminants so they can be reused safely. The term biosolids refers to the treated, stabilized sewage sludge that is approved for land application as a soil conditioner. It signals that the material has undergone processing to meet safety standards and provides nutrients and organic matter to soil. This distinguishes biosolids from raw sludge, which hasn’t been treated to acceptable standards; compost, which is a product from the aerobic decomposition of various organic wastes; and manure, which is animal waste not derived from human wastewater. In practice, biosolids are stabilized through processes like digestion or lime treatment and must meet regulatory pollutant limits before use.