Which of the following best describes the process of sedimentation in water treatment?

Sedimentation is a key process in water treatment that involves the gravitational settling of suspended particles to the bottom of a container, typically a sedimentation tank or basin. When raw water is collected, it often contains various impurities such as silt, clay, and organic matter. The purpose of sedimentation is to allow these particles to settle out from the water by utilizing gravity, which helps to improve the water quality before further treatment processes occur.

During sedimentation, the water is held still for a period of time, allowing heavier particles to sink to the bottom. This results in a clearer, more purified water layer on top, which can then be further treated through processes such as filtration or disinfection. By effectively removing suspended solids, sedimentation reduces the load on subsequent treatment steps and helps ensure the production of safe drinking water.

The other options do not accurately reflect the process of sedimentation. Adding chemicals to water is part of coagulation or flocculation, whereas evaporation pertains to the removal of excess water as vapor, and cooling water involves lowering its temperature, neither of which describe the settling of particles.