During the purification of water, if chlorine is applied beyond the stage of break-point, then the water is called as ____.

A. Super chlorinated

B. Pre-chlorinated

C. Post chlorinated

D. Double chlorinated

Answer: Option A – Super chlorinated


  • 1. Plain chlorination:

    • This term is used to indicate that only the chlorine treatment and no other treatment has been given to the raw water

    • It is used for clean water, i.e turbidity between 20 – 30 mg/l

    • Dose is 0.5 mg/l

    2. Pre-chlorination:

    • It is the process of applying chlorine to the water before filtration or rather before sedimentation and coagulation.

    • Normal dose is 5 to 10 mg/l and pre- chlorination is always followed by post chlorination

    3. Post chlorination:

    • It is the normal standard process of applying chlorine in the end, when all other treatments have been completed.
  • 4. Double chlorination:

    • It simply means that the water has b chlorinated twice

    5. Break-point chlorination:

    • It means an extent of chlorine is ado water.

    • It represents that much dose of chlorination, beyond which any further additional chlorine will appear as free residual chlorine.
  • 6. Super-chlorination:

    • When excess chlorine (5 to 15 mg/l) is added during an epidemic such that it gives a residual of 1 to 2 mg/l beyond breakpoint is called super chlorination.

    • If chlorine is applied beyond the stage of break-point, then the water is called super-chlorinated.

    • It is most commonly added at the end of filtration.

    7. Dechlorination

    • When chlorine residue is high, excess chlorine will be removed by dechlorinating agent.

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