Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Total Chlorine

Last updated: September 24, 2019

What Does Total Chlorine Mean?

Total chlorine is the sum of combined and free chlorine. In all instances, the level of total chlorine will always be above or equal to free chlorine levels. The most common levels of free chlorine present in drinking water are 0.2 to 2.0 mg/L, but can be up to 5.0 mg/L.

Total chlorine is usually measured in wastewater that has undergone treatment.


Corrosionpedia Explains Total Chlorine

Chlorine that is present in water consists of two forms: combined and free. The latter performs the job of oxidizing contaminants and killing bacteria. When chlorine is added to water, it is added as free chlorine. Total chlorine is the sum of both free and combined chlorine.

When free chlorine comes into contact with various forms of contaminants, the chlorine is transformed to combined chlorine, also known as chloramines. This type of chlorine has very little ability to sanitize and oxidize.

When chlorine is added to water, various reactions take place and most of the chlorine initially reacts with metals and organic materials in water that is not accessible for disinfection, referred to as "chlorine demand" of the water. The rest of the chlorine concentration following the chlorine demand is referred to as the total chlorine, that is subdivided to the two types mentioned above.

The levels of total chlorine, free chlorine and combined chlorine should be measured accurately to identify the amount of appropriate solutions that should be added to water in order to maintain the residual of free chlorine present in the water. In a more wide-scale basis, the main goal is the proper disinfection of piped water treatment systems.


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