Hardness of water

What is hardness of water?

The hardness of water is defined as a measure of the amount of magnesium and calcium salts dissolved in water. These components enter water predominantly via the weathering of rocks. Greater the quantity of magnesium and calcium in the water more is the hardness of water.

Types of hardness of water

The hardness of water can be classified into two types. They are:

Temporary and Permanent hardness of water

Difference between the temporary and permanent hardness of water is given in the below table:

Temporary hardness of water Permanent hardness of water
It is also called alkaline hardness. It is also called non-alkaline hardness.
It can be removed by the process of boiling. It can be removed by chemicals.
It is caused due to the dissolved bicarbonates of magnesium and calcium. Hence, also known as carbonate hardness. It is caused due to the dissolved sulphates and chlorides of magnesium, calcium, etc. Hence also known as non-carbonate hardness.
Hardness can be removed in a cost-effective way. Removal of the hardness of water is expensive.

Causes of hardness of water

The hardness of water is mainly caused due to the presence of the following compounds in water:

  • Calcium bicarbonate – Ca(HCO3)2
  • Calcium sulphate – CaSO4
  • Magnesium bicarbonate – Mg(HCO3)2
  • Magnesium sulphate – MgSO4
  • Magnesium chloride – MgCl2
  • Aluminium compounds
  • Magnesium nitrate – Mg(NO3)2
  • Calcium chloride – CaCl2
  • Manganese salts
  • Calcium nitrate – Ca(NO3)2

How to remove Permanent hardness of water?

The following are different methods used to remove the permanent hardness of water.

Method 1 – Soda

Soda helps remove temporary as well as the permanent hardness of water. It is a cost-effective process and easy to use. Therefore, it is considered as an ideal substance for water softening at home.

Method 2 – Base exchange method

It is a chemical process through which softening of permanent hard water is achieved on a large scale for household intend. It is one of the common and effective ways to soften hard water.

Method 3 – Softening agents

  • Borax – Water containing 20 % hardness is softened by using borax. It is often used to achieve low alkalinity of the soap solution.
  • Soap – It is widely used as a softening agent. But, using soap as a softening agent is spendthrift as the process is expensive when compared to the soda method.

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