Question

What is the role of chlorine in water treatment?

Answer 1

Hint: Chlorination is the first step that comes into our mind when we think of water purification. This is because, chlorination is a very cheap, most effective and well-established step.

Complete step by step solution:
- First of all, what is water treatment? It is a process which is used to improve the quality of water and makes it fit for our end use. The end use can be drinking, irrigation, industrial water supply, river flow maintenance, etc. Water treatment involves removal of contaminants, undesirable components or harmful pathogens. This treatment is very crucial for human health, as it destroys disease causing components from water.

- The water from lakes, rivers and groundwater contains many microorganisms. Among that some microorganisms are very harmful, as these can cause water-borne disease. These are known as pathogens. These water borne diseases include cholera, typhoid and dysentery.

- Inorder to combat water borne disease, many disinfection methods such as coagulation, sedimentation, filtration and chlorination are used. These methods will inactivate those harmful pathogens.

- Among this chlorination is the most important method, as it is very cheap and easily accessible. Its use had been started centuries ago and is still going on. It has been proven very effective against many bacteria and viruses.

- Chlorine inactivates these pathogens by damaging its cell membrane. Once the cell membrane is weakened, chlorine enters the cell and disrupts the cell respiration and DNA activity.

Additional Information:
- Chlorine is the chemical element which is represented by the symbol Cl.
- Atomic number of Chlorine is 17.
- It belongs to the halogen group and it is the second lightest element among the halogens.
- It is a yellow-green gas at the room temperature.

Note: - Chlorine can be toxic not only for microorganisms, it can also disrupt human health.
- Chlorine can be irritant to the eyes, nasal passage and respiratory systems.
- Chlorine gas must be handled carefully because it can cause acute health effects and can be fatal at concentration as low as 1000 ppm.
- Trihalomethane, which is the by-product of chlorination, is a carcinogen and it has been a topic of concern. It can cause bladder, rectal and colon cancer.