What does chlorination mean?
Chlorination is the process of adding chlorine or chlorine compounds to a substance — most commonly drinking water, swimming pools, or sewage — in order to disinfect it, killing bacteria, viruses, and other harmful microorganisms. The term also appears in industrial chemistry, where it describes any reaction that introduces chlorine atoms into a molecule. First widely adopted for municipal water supplies in the early twentieth century, chlorination quickly became one of the most consequential public health measures ever implemented, dramatically reducing outbreaks of waterborne diseases such as typhoid and cholera. While highly effective and inexpensive, the practice carries some debate over by-products formed when chlorine reacts with organic matter in water, leading some systems to adopt alternative disinfectants such as ozone or ultraviolet light. Related forms include the verb 'chlorinate' and the adjective 'chlorinated', as in 'chlorinated tap water'.
nounThe process of treating water, sewage, or other substances with chlorine to disinfect it or oxidize impurities. More broadly, the addition of chlorine to a chemical compound.
- The disinfection of water, sewage, or other materials by treatment with chlorine (the dominant everyday sense).
- In chemistry, the introduction of chlorine into a compound by substitution or addition.
"Chlorination of the municipal water supply virtually eliminated typhoid in the city."
"The pool's chlorination system runs automatically every night."
"Chlorination of benzene under UV light yields hexachlorocyclohexane."
Rarely pluralized; usually treated as an uncountable mass noun referring to the process generally.
"Different chlorinations of methane yield different products."
Chlorination of drinking water has been called one of the greatest public health advances of the 20th century — credited with helping extend average human lifespan by decades.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chlorination
The word chlorination derives from 'chlorinate', which combines 'chlorine' — coined from Greek 'chlōros' meaning pale green or yellowish-green, referring to the gas's colour — with the suffix '-ate' denoting a chemical action, plus '-ion' forming a noun of process. Chlorine itself was named in the early nineteenth century after its discovery by Swedish chemist Carl Wilhelm Scheele and subsequent identification as an element by Humphry Davy. Other words sharing the same Greek root include chloride, chlorate, and chlorophyll.
Related word forms
How chlorination is actually used
Technical and formal register; common in public health, municipal engineering, chemistry, and swimming-pool maintenance contexts. In everyday speech people more often say the water is 'chlorinated' than refer to 'chlorination' directly.
Easily confused with chlorination
Chlorine is the greenish-yellow chemical element itself; chlorination is the process of adding or applying it.
Fluoridation adds fluoride to improve dental health, whereas chlorination adds chlorine to kill pathogens.