Question

7. Arrange the general steps for the purification of drinking water in a sequence.

(1) filtration

(2) chlorination

(3) Sedimentation

(4) addition of chemicals

• A. 1 3 2 4
• B. 3 1 2 4
• C. 3 4 1 2
• D. 1 2 4 3

Answer 1

The correct option is C

3 4 1 2

Explanation:

The process of purification of drinking water is as follows:

1. Sedimentation: River water is pumped into settling tanks and left to settle naturally. Sedimentation is the process by which suspended impurities settle after standing.
2. Addition of chemicals: In this process, lime and alum are added to the water chamber. Alum and lime are stirred using massive mechanical blades. This water is then poured into a sedimentation tank. The processes of suspended impurities are accelerated by alum. Some bacteria are caught and eliminated during this precipitation process.
3. Filtration: The resulting pure water is pumped through a sand and gravel filter which gets rid of contaminants in the suspension.
4. Chlorination: The addition of bleaching powder produces chlorine, which aids in the killing of harmful bacteria, and the resulting pure water is stored in storage tanks.

Hence (C) will be the correct option with sequence 3412.