Question

Explain the principle behind the supply of drinking water in a city.

Answer 1

Supply of drinking water in a city

• We all know that a city's water supply comes from a neighboring river or lake. In general, water collected from a river or lake in a reservoir contains suspended contaminants and must be cleansed before being distributed to towns.
• This is done at a location known as waterworks, which is located along a river or lake's bank.

Principle of Supply of drinking water in a city

• To remove suspended contaminants and destroy germs in the water, the supply water is filtered through sedimentation, decantation, loading, filtration, and chlorination.

Sedimentation

• The process of settling down heavy insoluble particles in a mixture of water is called sedimentation.

Decantation

• The process of transferring clear liquid after sedimentation, without disturbing the sediment (insoluble heavy particle) is called decantation.

Loading Tank-

• The water from the sedimentation tank is sent to the loading tank. Now, alum is added to the water. The suspended clay particles present in the water get dissolved in the alum. Due to this, the alum becomes heavy and settles down at the bottom of the loading tank.

Filtration

• The process of separating suspended solid matter from a liquid, by causing the latter to pass through the pores of a filter is called filtration.

Chlorination Tank

• The clear water is then passed to the chlorination tank where a measured quantity of chlorine is added to the water to kill the germs present in the water.
• This process is called disinfecting the water or sterilisation of water. Now, disinfected water can be used for drinking purposes.