Select the correct order of processes used for water purification in waterworks.
1. Filtration
2. Chlorination
3. Suspended impurity sedimentation
4. Solid impurity sedimentation
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 4-3-1-2.
The correct order of water purification processes in waterworks is: solid impurity sedimentation → suspended impurity sedimentation → filtration → chlorination (4 → 3 → 1 → 2). First, large solid particles settle at the bottom by gravity. Next, finer suspended impurities are removed through sedimentation, often aided by coagulants like alum. The water is then filtered through layers of sand, gravel, or other media to eliminate remaining small particles. Finally, chlorination is done to disinfect the water by killing harmful microorganisms. This sequence ensures that the water becomes clean, clear, and safe for human consumption before distribution.