Question

Purification of water on small annd medium scale

Answer 1

Answer:

Explain it well at first

Explanation:

Answer 2

Answer:

Boiling is the oldest and satisfactory method of purification of water on small scale. Boiling for 5 to 10 minutes kills bacteria, spores, cysts and ova of intestinal parasites. It also removes hardness of water and soft water is produced.

Purification of water on a large scale!

Water is purified on a large scale in establishments that are known as waterworks. Usually, the following steps are taken to purify water.

1. 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.

2. 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.

3. Chlorination:

The filtered water is then treated with chlorine gas, which kills germs. You can see for yourself that alum helps the suspended particles of water to settle down quickly. Take two similar glasses containing equal volumes of muddy water and label them A and B. (You can prepare muddy water by mixing a teaspoonful of mud from your garden with the water in the glass.)

Crush a small crystal of alum (which you can obtain from a store) between the folds of a paper and add it to A. Stir the water in the two glasses and allow them to stand side by side. Within a short while, you will find that the mud has settled down with clear water above it in glass A, but the water is still not clear in glass B.