Which device would you use to quantify solids that settle out of a wastewater sample?

• A. Burette
• B. Beaker
• C. Imhoff cone
• D. Centrifuge

Answer: (C)

Measuring settleable solids relies on letting particles settle by gravity in a specialized, calibrated container. The Imhoff cone is designed for this purpose: its conical bottom concentrates the settled solids, and it has a scale so you can read the volume of solids that collect after a fixed time (usually one hour). After filling with a wastewater sample and letting it stand undisturbed, you read the settled solids directly in milliliters, which can be related to the sample volume for a concentration or percentage value. This method is simple, standardized, and specifically suited for quantifying solids that settle out.

A burette is used for precise liquid dispenses in titrations, not for measuring settled solids. A beaker is too crude and lacks a fixed settling time or scale. A centrifuge can separate solids rapidly but doesn’t provide the gravity-settling measurement in a readable, standardized way.