Water Purification

Welcome to class.

Water Purification

Bad water can be made safe for drinking by the process called purification.  Purification of water has a lot of processes involved. These are:

  1. Sedimentation and decantation
  2. Filtration
  3. Coagulation
  4. Chlorination, and fluoridation/Heating.

Sedimentation and decantation: the dirty or contaminated water in a bucket or cup is placed on a balanced table for some hours for the undissolved heavy particles in the water to settle down at the bottom of the cup or bucket. This is called Sedimentation. After these hours, the water is transferred into another cup or bucket, in a way that the undissolved particles remain at the bottom the cup/ bucket. This is called decantation.

Filtration: the clearer water obtained after sedimentation and decantation can then be filtered by pouring it on a filter bed in order to remove the undissolved tiny particles that still remain in the water.

Coagulation: a potash alum can now be introduced to the water in order to coagulate (i.e to bring together all the dissolved particles in the water). After application of coagulant (potash alum), the dirts will cluster together at the bottom of the container and these dirts can now be removed by decantation or filtration.

Potash/ Alum

Chlorination and fluoridation or heating: measurable amount of chlorine and fluorine is introduced into the water to kill germs and prevent goiter respectively. An alternative way of killing germs in water is by heating. When the water is heated, the heat will kill the germs in the water because micro-organism cannot survive under such high temperature

After all these processes, the water is safe for drinking.


  1. What is water purification?
  2. Which of the following substances is not used in water purification? (a) potash alum (b) chlorine (c) fluorine (d) acid
  3. Separation techniques can be used to purify water (true/ false)
  4. Mention 4 processes that are involved in water purification.

We have come to the end of the class. If you have any question ask using the comment box. see you in the next class. 

Get more class notes, videos, homework help, exam practice etc on our app [CLICK HERE]

Upgrade your teaching with ready-made & downloadable class notes on our app [CLICK HERE]

Leave a Reply

Your email address will not be published. Required fields are marked *

Don`t copy text!