In the measurement of settleable solids, which term best describes the solids that settle out under quiet (quiescent) conditions?

• A. Suspended solids
• B. Settleable solids
• C. Dissolved solids
• D. Total solids

Answer: (B)

In this measurement, the key idea is how solids behave when the sample is left undisturbed. The term settleable solids refers to the portion of solids that will settle to the bottom by gravity under quiet, quiescent conditions. This is typically determined by letting the sample stand in a cone or cylinder and measuring how much solids settle in a fixed time (often one hour).

Dissolved solids do not settle at all because they are dissolved in the liquid. Suspended solids are solids that remain dispersed in the water and do not settle during quiescent conditions, with only the portion that actually settles being counted as settleable solids. Total solids is simply the sum of dissolved and suspended solids, not a description of settling behavior.