Which chemical is most commonly used for water disinfection?

Chlorine is the most commonly used chemical for water disinfection due to its effectiveness in killing bacteria, viruses, and other pathogens that could lead to waterborne diseases. It has been a standard disinfectant in water treatment for many decades because of its strong oxidizing properties, which allow it to effectively eliminate microorganisms. Additionally, chlorine remains active in the water for an extended period, providing residual protection as the water travels through distribution systems, helping to prevent any recontamination.

While other disinfectants, such as ozone and chloramine, are also used in certain situations, chlorine's cost-efficiency, ease of use, and long-standing history in water treatment processes make it the primary choice for disinfection in many water utilities. Fluoride, on the other hand, is primarily added to water for the purpose of dental health, not disinfection.