Question

Name the steps involved in the purification of drinking water supplied in cities and towns

Answer 1

The water source for our towns and cities are river, lakes or underground water which contains suspended and dissolved impurities.

To remove these impurities steps involved are: 
1. Loading and sedimentation: to settle the suspended impurities to form sediment for this purpose potash alum is added.
2. Filtration: The water still contains lighter suspended impurities which are removed by filtration through sand and gravel. In cities, groundwater is drawn from a tube well or submersible pumps which have filters fitted in them. This clear water still contains germs. 
3. Chlorination: To kill germs water is passed into the chlorination tank where it is treated with chlorine to kill germs. Water is now potable i.e. safer for drinking and supplied to homes.