Water chlorination

Water chlorination disinfects water by adding chlorine or chlorine compounds that inactivate disease-causing microorganisms. It is widely used in drinking-water treatment and distribution.

Hypochlorous acid: A weak acid, HOCl, that is a highly effective chlorine-based disinfectant in water. It is the principal active disinfectant formed when chlorine dissolves in water.
Drinking water treatment: The processes used to make water safe and suitable for human consumption. Chlorination is one disinfection step within the broader treatment of drinking water.
John Snow: An English physician whose investigations linked cholera to contaminated water in nineteenth-century London. His work helped establish the public-health case for controlling waterborne disease.
Typhoid fever: A bacterial infection caused by Salmonella enterica serovar Typhi, often transmitted through contaminated food or water. Disinfecting public water supplies helped reduce transmission of this waterborne disease.
Ozonation: Water treatment that uses ozone gas to oxidize contaminants and inactivate microorganisms. Ozone disinfects without leaving the persistent distribution-system residual typical of chlorine.
Chlorine demand: The amount of chlorine consumed by reactions with substances in water before a residual remains. Organic matter and other compounds can consume chlorine before it reaches microorganisms.
Water distribution system: The pipes, storage facilities, and equipment that deliver treated water to users. A chlorine residual can limit microbial regrowth as water travels through the network.
Jersey City water disinfection: The 1908 introduction of routine water filtration and chlorination in Jersey City, New Jersey. The system became an early, prominent example of municipal chlorination in the United States.
Cholera: An acute diarrheal disease caused by toxigenic Vibrio cholerae and commonly spread through contaminated water. Chlorination can interrupt the waterborne transmission route that drives cholera outbreaks.
Ultraviolet germicidal irradiation: The use of ultraviolet light to damage microbial genetic material and prevent reproduction. UV can inactivate pathogens without adding a chemical disinfectant, but provides no lasting residual.

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