What is the term for the solids that settle at the bottom of a sedimentation tank?

The term for the solids that settle at the bottom of a sedimentation tank is sludge. In wastewater treatment processes, sedimentation tanks are designed to allow suspended solids to settle out of the wastewater due to gravity. The solids that accumulate at the bottom during this process are referred to as sludge. This material consists of organic and inorganic particles that are heavy enough to sink.

In contrast, scum refers to lighter materials that float to the surface, such as fats, oils, and grease. Silt typically describes fine particulate matter that may remain suspended in water, rather than settling. Effluent is the treated water that flows out of the sedimentation tank, which typically contains fewer solids but might still carry some dissolved substances. Understanding these distinctions is essential in recognizing the processes involved in wastewater treatment and the terminology used in this field.