Types of Chlorination

◆Types of Chlorination◆

1) Plain Chlorination

• If Turbidity of water is less than 10NTU or 20-30 mg/l. only this disinfection is provided in the form of chlorination which is known as plain chlorination.

• The dose of chorine = 0.5 mg/l (act as residual chlorine)

2) Pre chlorination

• When organic impurities in water are very high, then chlorination is provided on or before filtration.

• Does of chlorine = 5-10mg/l. at coagulation
 = .1- .5mg/l at filtration.

3) Post Chlorination

When chlorination is provided after filtration, when water is provided pre-chlorination the amount of chlorine should be such that the residual chlorine
must be 0.2mg/l with 10 min. contact period.

4) Double Chlorination

The Combination of pre & post chlorination is known as Double chlorination.

5) Super Chlorination

• When excess chlorine (5-50 mg/l) is added for disinfection, it is known as super chlorination. It is done for epidemic water→ Residual Cl → 1-2 mg/l.

• Excess chlorine after disinfection is removed out of water such that residual chlorine should be 0.2 – 0.5 mg/l. It is known as DE chlorination.

• It can be done by adding Activated carbon or sodium thiosulphate.