If we want to use hard water in textile dye processing first off all we need to remove the hardness of water. There are two types of hardness  (a) Temporary hardness, (b) permanent hardness.

Permanent hardness

 Temporary hardness   

Permanent hardness : Permanent hardness is caused by calcium or magnesium sulphate.

Temporary hardness : Temporary hardness is caused by calcium or magnesium hydrogen carbonate.

 Mg(HCO3)2 + 2Ca(OH)2 → 2MgCO3 +2H2OCaSO4 + Na2CO3 → CaCO3+ Na2SO4    

MgSO4 + Na2CO3 → MgCO3+ Na2SO4  CaSO4 + Na2CO3 → CaCO3+ Na2SO4    

MgSO4 + Na2CO3 → MgCO3+ Na2SO4  MgCO3 + Ca(OH)2 → Mg(OH)2 + CaCO3