Q1: Imhoff cone is used to measure

ANS:D - settleable solids.

The Imhoff cone is specifically designed to measure settleable solids in wastewater. Settleable solids are particles in wastewater that can settle out of suspension under the influence of gravity within a specific period. These solids typically include suspended particles, organic matter, and inorganic materials that settle to the bottom of a container when allowed to stand. The Imhoff cone is a conical-shaped glass or plastic container with a calibrated scale marked on its side. Wastewater samples are poured into the Imhoff cone, and the container is allowed to stand for a specified settling period, usually one hour. During this time, settleable solids in the sample settle to the bottom of the cone, forming a distinct layer. After the settling period, the volume of settled solids, known as the "sludge volume," is measured using the calibrated scale on the Imhoff cone. This measurement provides an indication of the settleable solids content in the wastewater sample and is used to assess the sedimentation characteristics of the wastewater. Therefore, the Imhoff cone is specifically used to measure settleable solids in wastewater samples.