Azeolite bed exhausted by softening of 4000 litres of hard water requires 10 litres of 15%NACl solution for regeneration. Calculate the hardness of water sample.

Solution :

Find out of amount of NaCl in brine solution used in process & then convert it in to CaCO3 equivalent.

Amount of NaCl consumed by Zeolite bed=10% NaCl= 100 g/ Lit

So, 10 liter solution contain = 10 x 100= 1000 g of NaCl

Convert it into CaCO3 equivalent

1000 g of NaCl= 1000x 50/58.5 g of CaCO3 equivalent= 854.70 g of CaCO3 equivalent

Zeolite bed on softening 4000 litres of hard water, required 10 litres of 10% NaCl Which is equivalent to 854.70 g of CaCO3 equi.

4000 liter hard water contain= 854.70 g of CaCO3 equi.

Therefore, 

1 lit $=\frac{ 854.70\times 1000}{4000}$ mg of  CaCO3

 213.5 PPM