Hardness is one of the main properties of water. Water softening methods are the removal of hardness from water. There are two types of hardness that affect water, that is temporary hardness and permanent hardness
The temporary hardness can be removed by boiling or by adding lime. The permanent hardness can be removed by lime soda process, zeolite process or demineralization process.
Water Softening methods and its Treatment Process
1. Lime soda process
Lime and sodium carbonate are used to remove permanent hardness from water. Quick lime Cao or hydrated lime can be used for water softening.
Advantages of lime soda process
- Ph value increases and the corrosion of the distribution system decreases.
- The process is suitable for turbid, chalybeate and acidic waters for which zeolite process cannot be used
- Less quantity of coagulant will be required for coagulation.
- Removal of iron and manganese to some extent.
- There is a likelihood of killing of pathogenic bacteria in this process.
- Better for excessively hard waters.
Disadvantages of lime soda process
- A large quantity of sludge is formed in this process which needs to be disposed of by some suitable method.
- In this process, recarbonation is required. By lime soda process water of zero hardness cannot be produced.
2. Zeolite process
Zeolite is a complex compound of aluminum, silica, and soda. Hard water is passed through a bed of ion exchange material or ion exchanger commonly known as zeolite. Calcium and magnesium are removed from water as these are substituted by sodium by the ion exchange process.
By zeolite process, the hardness of water is reduced almost to zero
Advantages of zeolite process
- Sludge is not formed and there is no problem of sludge disposal
- Does not require any skilled supervision.
- It is possible to reduce the hardness of water to zero. This is useful for softening of water to be used for boilers and certain textile industries.
Disadvantages of zeolite process.
- Cannot be adopted for highly turbid water.
To improve the quality of water demineralization is another method in water softening technique. It is similar to zeolite process with the difference that in the demineralization process the metallic ions such as calcium, magnesium, etc.. are exchanged for hydrogen ions.
The ion exchanger is prepared with carbonaceous material or resin. The effluent obtained in the demineralization process is free from minerals and it has a quality almost equal to that of distilled water used for industries.
These are the water softening methods done in the water treatment plant or laboratory.