Question

Which one of the following processes is used in the purification of water in a municipal water treatment system?

• A. sedimentation, sublimation and filtration
• B. Evaporation and filtration
• C. Sedimentation and distillation
• D. Sedimentation, filtration and chlorination

Answer 1

The correct option is D

Sedimentation, filtration and chlorination

Explanation for correct answer: (D) Sedimentation, filtration and chlorination:

• A wastewater treatment plant is a facility that treats wastewater from industrial sources.
• Water is passed through huge sedimentation tanks where solid wastes such as faeces settle down.
• Then the water is filtered by passing through a layer of sand and gravel to remove various pollutants.
• Then the water is put in a chlorination tank where chlorine is added to water to remove bacteria and viruses.

Explanation for incorrect answers:

(A) sedimentation, sublimation and filtration:

• As discussed earlier, the processes of sedimentation and filtration are involved in water treatment.
• Sublimation is a process by which a solid is converted directly to vapour state on heating. This process is not involved in water purification.

(B) Evaporation and filtration:

• As discussed earlier, the processes of filtration is involved in water treatment.
• Evaporation is the process by which water is converted to vapour state at any temperature below it's boiling point. This process is not involved in water purification.

(C) Sedimentation and distillation:

• As discussed earlier, the processes of sedimentation is involved in water treatment.
• Distillation is a process of separating the dissolved solid impurities from a liquid by boiling. But it is not possible to use this process in large scales as in waste water treatment plants.

Therefore, the correct answer is (D) Sedimentation, filtration and chlorination.