What is the term for deposits of foreign materials on the bottoms of bodies of water or wastewater collection lines?

The term for deposits of foreign materials on the bottoms of bodies of water or wastewater collection lines is "sludge." Sludge refers to a semi-solid material that accumulates in the bottom of tanks, basins, or treatment vessels during the wastewater treatment process. It typically consists of a mixture of organic and inorganic materials, suspended solids, and microorganisms that have settled out of the water column due to gravity. This accumulation plays a significant role in treatment processes, as managing and properly handling sludge is essential for the overall efficiency and effectiveness of wastewater treatment operations.

Biosolids, while related to sludge, specifically refer to treated sludge that is safe for land application and can be used as a soil amendment. Settled solids may refer to various materials that have accumulated through sedimentation but does not encompass the biological and chemical complexities associated with sludge. Floating solids pertain to materials that do not sink to the bottom, which is contrary to the nature of sludge.

The correct terminology emphasizes the significance of understanding the various components and processes in wastewater treatment, highlighting the role of sludge as a critical material requiring management in treatment plants.