Question

describe with the help of the diagram the treatment of water by lime soda process!? ​

Answer 1

Answer:

Lime soda process: In lime-soda process, hard water is treated with lime (CaO or Ca (OH)2) firstly, after that with soda. In this process, the hardness is removed by sedimentation as calcium carbonate or magnesium hydroxide.

Answer 2

Explanation:

If process is carried out at room temperature it is called cold lime soda process.

1) Cold process i) Batch process

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ii) Cold Continuous process:-

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Coagulant is necessary because at room temperature precipitate is finally divided. But do not settle easily & cannot easily filtered.

NaAlO2+2H2O−−→NaOH+Al(OH)3

Mechanical stirrer is used to increase mixing & rate of precipitate formation

ii) Hot continuous process-

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It is carried out at temperature 80−150∘c. It is used when small quantity of water is required. But it takes place at low hardness ie. 15-25 ppm. Due to hot condition-

i) Reactions take place faster.

ii) No need of coagulant

iii) Hardness is low

iv) Dissolved gases are expelled out at high temperature

Advantages:- i) It is more economical

ii) Less amount of coagulant is required.

iii) It increases pH value, there by corrosion is reduced.

iv) Also Fe, Mn & minerals are reduced.

v) Pathogenic bacteria are reduced.

Disadvantages:-

i) The hardness is 50-60 ppm by cold process & about 15-30 ppm by hot process

ii) Careful operation & skilled supervision are required.

iii) Disposal of large quantity of sludge formed during process is a problem