Distribution water — Disinfection

Disinfection is the process of producing pathogen-free "drinking" water (for human consumption).

This operation has long been associated with the simple injection of a disinfectant (chemical reagent) into previously clarified water.

In fact, we can see that all treatment operations, especially those designed to remove colloids or suspended solids from raw water, physically contribute to this disinfection; they are also beneficial, as prior clarification improves the effectiveness of the reagent.

A distinction must also be made between "active" disinfection (bactericidal effect), which ensures the elimination of germs in a relatively short time, before feeding the network, and "passive" or safety disinfection, which consists of maintaining a minimum concentration of disinfectant (residual) in the distribution network and up to the sampling points (residual effect, see § 1.3).

To maintain this residual over long periods of time, the presence of dissolved organic matter is undesirable, as many of these molecules contribute to the accelerated degradation of the disinfectant; moreover, some of them can lead to the formation of undesirable by-products that are toxic or generate bad tastes.