Chlorination

Agents for chlorinating swimming pool water

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The chlorination is the displacement of water with chlorine or chlorine compounds for disinfection of drinking water , utility and waste water , the water treatment in swimming pools , the (preventive) or mildew control for bleaching . Chlorination is also a textile finishing process and, in the USA, a disinfection process for chickens after slaughter.

Chlorination should not be confused with chlorination . The technical goal of chlorination is the production of organic-chemical compounds ( chloroalkanes , dichloroalkanes, carboxylic acid chlorides etc.) that contain chlorine.

Chemistry of chlorination

When chlorine is introduced into water, an equilibrium of chlorine, hypochlorous acid and hydrochloric acid is formed, depending on the pH value :

${\displaystyle \mathrm {Cl_{2}+H_{2}O\to \ HClO+HCl} }$

Depending on the pH value , the hypochlorous acid partially dissociates into oxonium and hypochlorite ions:

${\displaystyle \mathrm {HClO+H_{2}O\to \ H_{3}O^{+}+ClO^{-}} }$

In acidic solution the most important species are Cl ₂ and HClO, while in alkaline solution predominantly ClO ^- is present, in addition to very small concentrations of ClO ₂ ^- , ClO ₃ ^- , ClO ₄ ^- .

application

Water treatment

Effectiveness of chlorine dioxide and chlorine (concentration determined iodometrically ) against the bacterium Staphylococcus aureus : Percentage of bacteria killed at different pH values after 20 minutes of disinfection with chlorine dioxide or chlorine

The chlorination of drinking water is used for disinfection in water treatment , whereby chlorine is added in the form of chlorine gas , chlorine dioxide or sodium hypochlorite . The maximum concentration values ​​that apply here are set out in a list maintained by the Federal Environment Agency. Ozonation and the use of UV radiation are considered alternatives to disinfecting swimming pool or drinking water . In Germany, the DGUV issues extensive recommendations and regulations for the chlorination of water.

Textile finishing

Chlorination is the oldest process for the felt and shrink-free finishing ( textile finishing ) of wool through the action of acidic chlorine or hypochlorite solutions.

Disinfection of broilers

In the USA, slaughtered chickens are subjected to chlorination for the purpose of disinfection (“ chlorinated chickens ”). The process is not approved in the European Union (as of 2014).

See also

• Chlorination
• Javel water

Individual evidence

1. ^ GM Fair, J. Corris, SL Chang, I. Weil, and RP Burden. The behavior of chlorine as a water disinfectant. J. Am. Water Works Assoc. 40.1948: 1051-1061.
2. ↑ Shunji Nakagawara, Takeshi Goto, Masayuki Nara, Youichi Ozaqa, Kunimoto Hotta and Yoji Arata, Spectroscopic Characterization and the pH Dependence of Bactericidal Activity of the Aqueous Chlorine Solution . In: Analytical Sciences , 14 , 69, 1998.
3. ↑ Huang Junli, Wang Li, Ren Nanqi, Ma Fang and Juli: Disinfection effect of chlorine dioxide on bacteria in water. In: Water Research , 1997, 31 (3) , pp. 607-613; doi: 10.1016 / S0043-1354 (96) 00275-8 .
4. ↑ ^{a b} Announcement of the list of treatment materials and disinfection processes in accordance with Section 11 of the Drinking Water Ordinance. (PDF; 245 kB) Federal Environment Agency , December 2019, accessed on March 26, 2020 . 
5. ↑ Article “Chlorination”. In: Umweltlexikon.katalyse.de . Catalysis Institute, 1990, accessed March 26, 2020 .  
6. ↑ DGUV Information 207-023 | Checklist for chlorination facilities using chlorine gas and their installation rooms in bathrooms. (PDF; 164 kB) German Statutory Accident Insurance , September 2015, p. 8 , accessed on March 26, 2020 . 
7. ↑ DGUV Information 203-086 | Chlorination of drinking water. (PDF; 1.1 MB) German Statutory Accident Insurance , March 2017, accessed on March 26, 2020 . 
8. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 1: A-Cl. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1979, ISBN 3-440-04511-0 , pp. 732-733.