Hard Water – Definition, Types and 5 Effect of Hard water

Hard water and soft water is the two type of water contain in difference sources on the basis of dissolved impurities present in water and its behavior towards soap. Water that produce lather with soap easily and contain  little or none of the dissolved salt ions like Cl^–, SO₄^—, CO₃^—, HCO₃^– etc., of calcium (ca⁺⁺) or magnesium (Mg⁺) is called soft water. For examples, tap water, river water, spring or underground water, sea water, well water etc.

Hard water is water that does not produce lather with soap easily and contain dissolved salt ions like Cl^–, SO₄^—, CO₃^—, HCO₃^– etc., of calcium (ca⁺⁺) or magnesium (Mg⁺). For examples, tap water, river water, spring or underground water, sea water, well water etc.

What is Hardness of Water?

Hardness of water is due presence of appreciable concentrations of soluble bicarbonate, chlorine and sulphate of calcium and magnesium. When hard water is added with soap [is Na or K salt of fatty acids e.g. sodium stearate (C₁₇H₃₅COONa), sodium palmitate (C₁₅H₃₁COONa),] then Ca⁺⁺ and Mg⁺⁺ ions of hard water react with the soap forming water insoluble scum or curds of calcium or magnesium salts of fatty acids, and no lather is produced until all Ca⁺⁺ and Mg⁺⁺ ions are completely precipitated. 

Due to these reaction, hard water is unfit for washing purpose.

Types of Hardness

Based on the nature of dissolved ions, hardness of water is classified as,

• Temporary hardness of water
• Permanent hardness of water

Temporary Hardness 

This type of hardness is due to presence of soluble bicarbonates of calcium and magnesium in water. It is called temporary hardness because it is removed by simply boiling. The presence of soluble bicarbonates of calcium and magnesium in water are due to following some reactions. Rain water dissolves CO₂ from the atmosphere and form dil. Solution of H₂CO₃.

The water flows over the rock and reacts with CaCO₃ or MgCO₃ present in the rocks to form soluble bicarbonates of Ca⁺⁺ and Mg⁺⁺.

Permanent Hardness of Water

This type of hardness is due to the presence of soluble sulphate and chloride of calcium and magnesium. Water becomes permanently hard when it flows over the rocks which contain sulphate or chloride of calcium or magnesium (CaSO₄, CaCl₂, MgSO₄, MgCl₂).

Effect of Hard Water

Mineral Deposit Formation

When hard water is heated, the minerals in the water can create a scale buildup on the insides of pipes, boilers, and other hot water-using appliances. This buildup can block water flow and decrease efficiency.

Stains

Due to the minerals in the water interacting with surfaces, hard water can leave stains on fixtures, sinks, and appliances. These stains can be hard to get rid of and can appear dirty or discolored on surfaces.

Reduced Appliance Lifetime

Mineral deposits in appliances such as water heaters and dishwashers can shorten their lifetime and necessitate more frequent fixes and replacements.

Skin and Hair

Hard water can create dry skin and hair that’s not silky. While it may appear that you are washing away the soap, hard water does not eliminate soap from your body. As a result, the detergent is left behind, absorbing your skin’s natural moisture and oils.

Soaps and detergents

Soaps and detergents respond negatively with hard water. It produces a curdy substance rather than a thick and foamy lather. To fight the negative impacts of hard water, more soap and detergent are required.

Removal of hardness of water

By Boiling

When temporary hard water is boiled, calcium or magnesium bicarbonates decompose to give calcium or magnesium carbonate, which is water insoluble and precipitates out.

However boiling method would costly on large scale.

By adding Lime  (Clark’s process) 

Temporary hardness can be removed by the addition of calculated amount of slaked lime. Excess of lime further creates the problem of hardness as.

Both these two  method can’t remove the permanent hardness of water.

By addition of washing soda (Na₂CO₃) can remove both temporary and permanent hardness.

We know that, water containing CO₂ gas is capable of dissolving lime stone or chalk slowly if it present in large quantities in soils in the form of limestone or chalk hills.

This reaction is responsible for the formation of caves.

By ion exchange method

 In this method, the ions responsible for the hardness of water are exchanged by Na⁺, K⁺, or H⁺ ions of ion-exchanger compounds. This method removes both temporary and permanent hardness of wter. Ion exchanger are the complex salts containing Na⁺,  K⁺, or H⁺ in their salts. Ion exchangers are:

• Inorganic ion exchanger

• Organic ion exchanger 

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