Breakpoint Chlorination

Posted by on Monday, February 13, 2012 Under: Disinfection
A few people struggle to fully understand the concept of what is known as 'breakpoint chlorination' during the pool plant operators course. In basic terms, as far as pool plant operators are concerned, breakpoint chlorination describes the point at which there is twice the amount of free chlorine than combined chlorine.

Imagine a swimming pool that has high levels of pollution. If you were to introduce some much-needed chlorine into the pool, it would quickly end up as combined chlorine as it literally combines with bacteria etc. and becomes useless as a disinfectant as soon as it does so. In fact, combined chlorine as now classed as pollution and it's combined chlorine that makes peoples eyes sting. So, in a nutshell; combined chlorine is something we want as little of as possible, as close to zero as we can possibly get it and certainly no more than 1mg/l.

As all the chlorine we have introduced has become combined chlorine, we need to add some more. We always need to have some chlorine available in order to quickly neutralize contamination. This is referred to as 'free chlorine'. This is the good stuff and we want it in our swimming pool. To be precise, we need the free chlorine levels to be at least double the combined chlorine levels. Free Chlorine is measured with the DPD 1 test, Total Chlorine is measured with the DPD 3 test, and Combined Chlorine is the difference between the two.

But, if the chlorine we introduce turns into combined chlorine, how are we, as pool plant operators, supposed to maintain twice the amount of free chlorine than combined chlorine? Well, that's simple:

  • Get people into the habit of taking a shower before swimming so that there is less bacteria available for the chlorine to combine with;
  • Dilute the swimming pool water with enough fresh water (30 litres per bather, per day);
  • Ensure enough chlorine is being dosed into the swimming pool (an automated system is always recommended for any type of commercial facility);
  • Make sure that the pool turnover time is fast enough for your type of pool;
  • Male sure your not overloading your pool.
Not of the above is particularly difficult, and if you follow these steps, you should have no problem achieving breakpoint chlorination.

In : Disinfection 

Tags: "breakpoint chlorination" "free chlorine" "combined chlorine" "total chlorine" "dpd 1" "dpd 3"