Question

Describe “breakpoint chlorination” and why is it necessary?

Answer 1

Breakpoint chlorination consists of a continual addition of chlorine to the water upto the
the point where the chlorine enquiry is met and all present ammonia is oxidized so that only free chlorine remains.
This is usually applied for disinfection but it also has other benefits such as smell and taste control. in order
to reach the breakpoint a superchlorination is applied . To achieve this uses chlorine concentrations which largely e
exceed the 1mg/L concentration required for disinfection.
All chlorine reacts with any organic materials present until they are destroyed. Chlorine then reacts with amino acids
or urea. These compouds come from proteins or from urine in pool water. The products of this reaction are called chloramines.
It is these products which gives pools their characteristic smell.

There are three stages of chloramines.
a. Monochloramine (0.4ppm combined chlorine is maximum before you cause eyebum)
b. Dichoramine (causes smell and chlorine odour)
c. Trichloramine(reduced oxidation algae encouraged, time to super chlorinated)

The trichloramines are suspected of causing the most health and odour problems.If more chlorine
is aded the chlorramines are themselves broken down until there is nothing left to react.