What type of chlorine is often employed for disinfection in water treatment facilities?

Free chlorine is commonly used for disinfection in water treatment facilities because it is an effective and efficient agent for killing harmful pathogens and microorganisms. When chlorine is added to water, it exists in two main forms: free chlorine and combined chlorine. Free chlorine consists of hypochlorous acid (HOCl) and hypochlorite ions (OCl-), both of which are powerful disinfectants that can penetrate microbial cell walls and disrupt vital cellular functions, thus effectively inactivating bacteria, viruses, and other pathogens.

Using free chlorine in treatment processes provides operators with flexibility, as it can be easily monitored and adjusted to meet specific water quality standards. Additionally, free chlorine typically has a rapid reaction time, making it especially suitable for disinfection purposes. This efficacy and speed are crucial in ensuring safe drinking water and maintaining public health.

While chloramine and combined chlorine do serve disinfection purposes, they are not as effective against certain pathogens as free chlorine. Chloramine is often used as a secondary disinfectant due to its longer-lasting residual properties in distribution systems but is less potent for immediate disinfection. Fluoride, on the other hand, is not used for disinfection but rather for the prevention of dental caries and does not have a role in pathogen in