Methods to Remove of Temporary Hardness of Water

Question: Describe different methods to remove temporary hardness of water.

Answer.

Methods to remove temporary hardness

Generally, there are two methods to remove temporary hardness.

1. By boiling

2. By adding slaked lime (Clark’s method)

1. By boiling

Temporary hardness of water can be removed by boiling. During the boiling of hard water, soluble calcium and magnesium hydrogen carbonates are converted into their insoluble carbonates which are separated by filtration. Thus, calcium and magnesium ions are removed as insoluble carbonates and water becomes soft.

However, this method is too expensive for removal of temporary hardness of water at large scale.

2. By adding slaked lime (Clark’s method)

In Clark’s method, slaked lime (Ca(OH)₂) is added to temporary hard water. The slaked lime reacts with soluble calcium and magnesium hydrogen carbonates to form their insoluble carbonates which are separated by method of filtration. This method is for large removal of temporary hardness of water.

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