Question

Water form lakes and rivers is _ before it is supplied to our houses

Answer 1

Water from lakes and rivers is $\green{\boxed{purified}}$ before it is supplied to our homes.

★ ADDITIONAL INFORMATION:

Stages of water purification on a large scale:

• Sedimentation: Water pumped from the source (river, lake or dam) is allowed to stand in large tanks, called settling tanks, for a few hours. Mud, sand and other suspended particles settle down. The addition of a small quantity of potash alum (K2SO4 . A12(SO4)3 . 24H2O) helps the suspended particles to settle down quickly. The solid that settles at the bottom of the tank is called sediment. That is why these tanks are also called sedimentation tanks. The water over the sediment layer is more or less clean.
• Filtration: The water from the sedimentation tank is filtered through layers of sand and gravel. Filtration is also done through activated charcoal, which affords better-quality water. Activated charcoal is a special type of charcoal made by heating ordinary charcoal in vacuum. This charcoal holds the impurities strongly.
• Chlorination: The filtered water is then treated with chlorine gas, which kills germs. This process is known as chlorination.