Permanent Hardness of Water

The hardness of water is determined by the concentration of minerals in the water. It contains mainly salts of magnesium and calcium. Normally hard water is not a serious threat to life. But sometimes, it is better to detect and remove it. Hardness causes residues in the dishwasher, less foam with detergents and soap, wearing out of clothes, and less water pressure through taps are some of the common signs to take an appointment for softening of water in the home. There are no severe health issues regarding hard water, but it might cause dry skin and hair.

How can you detect the hardness of water?

The hardness of water may not seem very visible. But when we closely observe, we can feel the hardness of the water.

• Stains in sink and tub

• Clothes wear out easily

• Dull colours of clothes

• White, chalky residue on dishes and pipes

• Dry skin and dry hair

• Hard water will not form lather with soap

Hard water problems

We’ve discussed the signs of hardness. Let’s discuss the problems of having hard water. We don’t want our daily water use to make us feel bad, right? When you have hard water, sulphur might cause a rotten egg smell. It will have a musty odour and taste. Hard water will have a metallic smell and taste also. Hard water causes discolouration and cloudiness. Rusting of iron and steel is enhanced with hard water. In industrial cases, hard water causes corrosion, deterioration of equipment, build-ups in pipes, low flow pressure, etc.

TYPES OF HARDNESS IN WATER:

1)Temporary hardness.

2)Permanent hardness.

TEMPORARY HARDNESS:

Temporary hardness is due to the presence of bicarbonates of calcium and magnesium. It can be easily removed by boiling.

PERMANENT HARDNESS:

Permanent hardness is due to chlorides and sulphates of calcium and magnesium. This type of hardness cannot be removed by boiling. There are several methods of eliminating permanent hardness, like:

WASHING SODA METHOD

Water is treated with a specified amount of washing soda (Na, CO2), which transforms calcium and magnesium chlorides and sulphates into their respective carbonates, which precipitate.                          

Ca(HCO3)2 + Na2CO3    Boil   CaCO3 + 2NaHCO3

Mg(HCO3)2 + Na2CO3     Boil  MgCO3 + 2NaHCO3

CALGON PROCESS

Calgon is a marketing term for sodium hexametaphosphate, a complex salt. It is applied in the softening of hard water. Calgon generates a complex anion whenever it ionises:

Na2(Na4 P6 O 18) ⟶2Na++ Na4P6O2-18

The calcium and magnesium ions in hard water expel sodium ions from the anion of Calgon once Calgon is added to it.

Ca2+ + Na4P6O2-18    2Na+ + CaNa2 P6 O2-18

ION EXCHANGE METHOD

Hard Water is cleaned with silicate salt to exchange sodium with calcium and other minerals.

SYNTHETIC RESIN METHOD

It excels in the ion exchange approach to removing all types of cations and anions.

Clark’s method- Example

The last important method of removing the hardness of water is Clark’s method. It removes salts of magnesium and calcium by adding cold lime. It is performed using change in Ph.

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2O.

Clark’s process is also known as cold lime softening. If we are elaborating the process of Clark’s process, it will be

CO2 + Ca(OH)2 → CaCO3  + H2O

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3  + 2H2O

Mg(HCO3)2 + 2Ca(OH)2 → Mg(OH)2  + 2CaCO3  + 2H2O

Clark’s method- Questions

1. What happens in Clark’s process?

When hydrated lime is added to the water, the following reaction occurs, where those products are easy to remove.

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2O.

2. What is the disadvantage of Clark’s process?

The waste produced after this process is hard to remove. So the disposal of waste is also an extra cost.

CONSEQUENCES OF HARD WATER

• Precipitation of soap scum

• Fading of laundry

• Precipitation of some dyes such as calcium or magnesium salts

• Plaque accumulation and clogging of pipes

• Coagulation of some types of print pastes

• Incompatibility with chemicals in finishing recipes

Conclusion

There are two types of hard water. The hardness of water caused by calcium bicarbonate is known as temporary hardness. Other salts of calcium and magnesium cause permanent hardness. This dissolution of minerals occurs during regular water cycles, and the grade of hardness sometimes depends on the geological area.

Hardness causes residues in the dishwasher, less foam with detergents and soap, wearing out of clothes, and less water pressure through taps are some of the common signs to take an appointment for softening of water in the home.

There are no severe health issues regarding hard water, but it might cause dry skin and hair. Temporary hardness can be removed by boiling, but permanent hardness can’t.