Question

The purpose of re-carbonation after water softening by the lime soda process is
the
1. Removal of excess soda from water
2. Removal of non carbonate hardness from water
3. Recovery of lime from the water
4. Conversion of precipitate to soluble form of water.​

Answer 1

Answer:

your answer is no. 3

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Answer 2

The correct option is 4. Conversion of precipitate to soluble form of water.​

Explanation:

• Recarbonation is a typical method for lowering the pH of water.
• When water is treated with lime soda, the pH of the water increases to 10 or even higher.
• Also, the water becomes supersaturated with calcium carbonate, which is critical for lowering the pH, stabilising the water, and preventing the formation of carbonate scale in filter sand and distribution pipes.
• As a result, the water should be recarbonated by injecting carbon dioxide into it, which is the process of stabilising water by lowering the pH to 8.7 and converting CaCO3 precipitates to water-soluble foams.