Regardless of where the water comes from, the presence of contaminants is often a problem. Surface water, either from lakes or rivers, is often more concentrated in certain types of organic contaminants such as micro-organisms. Among these micro-organisms, we can find pathogens, bacteria, viruses or any other organic contaminants. To deal with these types of contaminants, several technologies have been developed over the years. Among water disinfection technologies, chlorination is probably the most widespread.

Chlorination is a chemical disinfection technique that deactivates microorganisms that can be dangerous to health. To proceed with water chlorination, it is sufficient to add chlorine or one of its derivatives to the water. When added to water, the oxidizing power of chlorine attacks the DNA of microorganisms in order to deactivate them and prevent them from reproducing. In some cases, a filtration step must be added to remove the dead bodies from the water.

It is important to note that chlorination is the addition of chlorine to water. Knowing this, chlorine can be added in all its forms: liquid, gaseous or solid. In addition to the different physical states of chlorine, its derivatives can also be added to water. Generally speaking, the two most common types of chlorination are the addition of standard chlorine or the use of chloramine.

Furthermore, when chlorine is added to water, the addition of a dechlorination step may be necessary to avoid problems associated with too high a chlorine residual. To sum up, when chlorine is added to water, two sub-categories of chlorine are created: free chlorine and combined chlorine. The combination of these two categories is what we call total chlorine.

Finally, if you would like to learn more about chlorine, chlorartion and dechlorination, here are some articles on the subject:

- Chloramine and reverse osmosis membranes

- Free chlorine, combined chlorine or total chlorine: what are the differences?

- Chlorine or chlorine dioxide: what are the differences?

- What is dechlorination?

- How to choose the best dechlorination solution in pharmaceuticals