Why lime is added during coagulation step of water treatment?

It increases the pH.

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It decreases the pH.

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It adds taste to water.

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It adds colour to the water.

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Solution

The correct option is A
It increases the pH.

Water treatment follows six steps: Aeration, coagulation, clariflocculation, filtration, chlorination and storage. During coagulation, alum is added due to which sedimentation of solid waste occurs. The pH of the water decreases due to the addition of the alum. Therefore lime, which is alkaline in nature, is added to this water to increase its pH.

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