Multiple choice

A water treatment plant treating 10 mld of water requires 20 mg/I of filter Alum, Al2 (SO4)3.18 H2O. The water has 6 mg/l of alkalinity as CaCo3 (Al = 26.97, S = 32, O = 16, H = 1, Ca = 40, and C = 12).

Total alkalinity requirement (106 mg per day as CaCO3) matching filter Alum, shall be

  1. 180

  2. 120

  3. 90

  4. 60
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The alkalinity requirement is based on the stoichiometry of the reaction between alum and alkalinity. 1 mg of alum reacts with 0.45 mg of alkalinity as CaCO3. For 20 mg/l of alum and 10 mld, the calculation yields 90 mg/l equivalent.

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