Describe the various process involved in purification of water.
The purification of water means making the unhealthy water potable. The purification of water involves following steps - Screening - The first step of purification of water is screening. In this step, the floating matter of large size present in the water is removed. Screening prevents the pumps and other equipments from the possible damage due to floating matter of sewage. Aeration - The process of exposing large surface of water to the atmospheric air is called aeration. After screening, water is collected in a large aeration tank and aerated by compressed air. This process removes volatile substances and gases like Hydrogen sulfide and carbon dioxide causing bad taste and odor. It increases the oxygen level in water. Due to aeration, precipitate of iron and magnese is formed which are separated from water. Sedimentation - The process by which suspended particles settle down under the action of gravity is known as sedimentation. Now, aerated water is placed in the sedimentation t