Q1: Chlorination of water is done for the removal of

ANS:D - hardness.

For the evaporation and measurement of settlable solids, the apparatus typically used is an Imhoff cone. An Imhoff cone is a specialized device designed for the determination of settleable solids in water and wastewater samples. It consists of a conical-shaped container with a stopcock at the bottom to allow for controlled draining of the sample. The Imhoff cone is graduated to measure the volume of settleable solids that accumulate over a specific period, typically 1 hour. The procedure involves filling the Imhoff cone with a representative sample of water or wastewater and allowing it to settle for a specified duration, usually 1 hour. During this time, settleable solids in the sample will settle to the bottom of the cone under the influence of gravity. After the settling period, the volume of settleable solids, usually expressed in millimeters (mm), is measured directly on the graduated scale of the Imhoff cone. The settleable solids are then typically reported as millimeters of settled solids per liter of sample (mm/L) or as a percentage of the sample volume.