Chlorination and Types of Chlorination in Water Treatment Process

We all know that chlorination is method in water treatment process adopted for the public water supply system. Here we are discussing about chlorination and types of chlorination. Chlorination provides residual disinfection impacts for long periods. Here we are discussing the types of chlorination. Chlorination is done to achieving the permissible level of chlorine content in public water. It also kills germs and other bacteria.

Types of chlorination

Types of chlorination in the water treatment process

1.Plain Chlorination

Only chlorine treatment and no other treatment. It helps to remove bacteria and colour from water and it also controls the growth of algae. It is used in case of emergencies when full-fledged treatment cannot be given. Also adopted for clean water.


Chlorine is added before raw water enters sedimentation tanks. It helps in reducing the number of coagulants and to improve coagulation. It reduces the taste and odour of water.

It controls the growth of algae. It reduces the bacterial load on filters. It also prevents putrefaction of sludge in settling tanks.

3.Post chlorination

This is the standard form of chlorination in which chlorine is added to water as it leaves filters and before it enters the distribution system. The residual chlorine present in water is useful for its protection against contamination in the distribution system. Residual = 0.1 to 0.2 mg/l

4.Double or multiple chlorinations

It consists of pre-chlorination and post-chlorination. Adopted when raw water is highly contaminated and contains a large amount of bacterial life.

5.Break Point Chlorination

Break Point chlorination gives an idea of chlorine to be added to the water so as to ensure the desired amount of residual chlorine.

6.Super chlorination

The application of chlorine to water beyond the stage of breakpoint is known as super chlorination. It is most commonly added at the end of filtration. It is adopted whenever there is a breakout  of water borne diseases.

When super chlorination is practised, it becomes necessary to remove the excess chlorine by any suitable method of dechlorination before water is supplied to the consumers.


Dechlorination is the process of removing excess chlorine by dechlorinating agents. This is to avoid chlorinous taste from water. Chemicals used for dechlorination are sulphur dioxide, sodium thiosulphate, sodium bio sulphate, activated carbon, potassium permanganate, ammonia etc..

These are the types of chlorination in the water treatment process. Read other posts also if you like this.


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