Water is purified before it is used in cooking, washing, drinking and for farming.Purification of water involves the following steps:
(a) Alum is added in water containers and water is left undisturbed for few hours. The suspended impurities settle down through the process known as loading. The clean water is then separated by decantation.
(b) Water is boiled before drinking. If water is boiled for about 20 minutes at about 100°C, the germs present in it are killed.
(c) The water from rivers and lakes is pumped and collected in a reservoir or water tank. Heavy particles (such as rocks, stones, etc.) are allowed to settle down through a process called sedimentation in a container. This tank is known as sedimentation tank.
(d) The water is allowed to pass through a container which has gravel and sand acting as a sieve to filter impure substances. The water gets free from dirt and various other impurities by the process called filtration.
