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NSA192009 Pages: 3
Describe the various steps involved in sewage treatment. (10)
Write any four disadvantages of hard water. (4)
Write the principle and procedure of estimation of permanent and temporary
hardness of water by complexometric titration.
50 mL sewage water sample after reaction with 20 mL 2 ९2120; required
12.4 mL of 0.2 N ferrous ammonium sulphate solution. For blank titration 20
mL (൦൩0: required 20.4 mL of 0.2 N ferrous ammonium sulphate solution. (6)

Calculate the COD of the sample.

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