Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water. Water which has been treated with chlorine is effective in preventing the spread of disease. General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Control room and schematics of the water purification plant to Bret lake. ... Drinking water Mineral Water Drinking water is water that is intended to be ingested by humans. ... This article is about the medical term. ...

The chlorination of public drinking supplies was originally met with resistance, as people were concerned about the health effects of the practice. The use of chlorine has greatly reduced the prevalence of waterborne disease as it is effective against almost all bacteria and viruses, as well as amoeba. Health effects, health impacts or health risks are an important consideration in many areas, such as hygiene, pollution studies, workplace safety, nutrition and health sciences in general. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... This article is about biological infectious particles. ... Alternate meanings: Amoeboid, Amoebozoa For other uses, see Amoeba (disambiguation). ...

Chlorination is also used to sterilize the water in swimming pools and as a disinfection stage in sewage treatment. It can also apply to the addition of chlorine to other elements, such as gold in the formation of gold chloride. This article needs additional references or sources for verification. ... Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater, both runoff and domestic. ... Gold(III) chloride, traditionally called auric chloride, is one of the most common compounds of gold. ...

History

The technique of purification of drinking water by use of compressed liquefied chlorine gas was developed in 1910 by U.S. Army Major (later Brig. Gen.) Carl Rogers Darnall (1867-1941), Professor of Chemistry at the Army Medical School. Shortly thereafter, Major (later Col.) William J. L. Lyster (1869-1947) of the Army Medical Department used a solution of calcium hypochlorite in a linen bag to treat water. For many decades, Lyster's method remained the standard for U.S. ground forces in the field and in camps, implemented in the form of the familiar Lyster Bag (also spelled Lister Bag). Darnall's work became the basis for present day systems of municipal water purification. The Army is the branch of the United States armed forces which has primary responsibility for land-based military operations. ... Major is a military rank the use of which varies according to country. ... A Brigadier General, or one-star general, is the lowest rank of general officer in the United States and some other countries, ranking just above Colonel and just below Major General. ... Brigadier General Carl Rogers Darnall, MD (25 December 1867, Weston, Texas, USA -18 January 1941, Walter Reed General Hospital, Washington, DC, USA) was a U.S. Army chemist and surgeon credited with originating the technique of liquid chlorination of drinking water. ... Founded by U.S. Army Brigadier General George Miller Sternberg, MD in 1893, the Army Medical School (AMS) was by some reckonings the worlds first school of public health and preventive medicine. ... This article or section needs copy editing for grammar, style, cohesion, tone and/or spelling. ... The Army Medical Department (AMEDD) of the U.S. Army comprises the six medical Special Branches of the Army. ... Calcium hypochlorite is a chemical compound with formula Ca(ClO)2. ...

Chemistry in Water

When chlorine is added to water, it reacts to form a pH dependent equilibrium mixture of chlorine, hypochlorous acid and hydrochloric acid: The correct title of this article is . ... Hypochlorous acid is a weak, unstable acid with chemical formula HOCl. ... The chemical compound hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride gas (HCl). ...

Cl₂ + H₂O → HClO + HCl

Depending on the pH, hypochlorous acid partly dissociates to hydrogen and hypochlorite ions: Dissociation in chemistry and biochemistry is a general process in which complexes, molecules, or salts separate or split into smaller molecules, ions, or radicals, usually in a reversible manner. ... The hypochlorite ion The hypochlorite ion is ClO−. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1. ...

HClO → H⁺ + ClO^-

In acidic solution, the major species are Cl₂ and HOCl while in alkaline solution effectively only ClO^- is present. Very small concentrations of ClO2^-, ClO3^-, ClO4^- are also found^[1].

Drawbacks

Disinfection by chlorination can be problematic, in some circumstances. Chlorine can react with naturally occurring organic compounds found in the water supply to produce dangerous compounds, known as disinfection byproducts (DBPs). The most common DBPs are trihalomethanes (THMs) and haloacetic acids. Due to the carcinogenic potential of these compounds, federal regulations in the United States of America require regular monitoring of the concentration of these compounds in the distribution systems of municipal water systems. However, the World Health Organization has stated that the "Risks to health from DBPs are extremely small in comparison with inadequate disinfection." There are also other concerns regarding chlorine including its volatile nature which causes it to disappear too quickly from the water system, and aesthetic concerns such as taste and odour. Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen; therefore, carbides, carbonates, carbon oxides and elementary carbon are not organic (see below for more on the definition controversy... Trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane (CH4) are replaced by halogen atoms. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ... The World Health Organization (WHO) is a specialized agency of the United Nations (UN) that acts as a coordinating authority on international public health. ... The Parthenons facade showing an interpretation of golden rectangles in its proportions. ... Taste is one of the traditional five senses and refers to the ability to detect the flavor of foodstuffs and other substances (e. ...

Alternatives

Several alternatives to traditional chlorination exist, and have been put into practice to varying extents. Ozonation is used by some municipalities in the United States. Due to current regulations, systems employing ozonation in the United States still must maintain chlorine residuals comparable to systems without ozonation. It has been suggested that Ozone generator be merged into this article or section. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

Disinfection with chloramine is also becoming increasingly common. Unlike chlorine, chloramine has a longer half life in the distribution system and still maintains effective protection against pathogens. The reason chloramines persist in the distribution is due to the relatively lower redox potential in comparison to free chlorine. Chloramine is formed by the addition of ammonia into drinking water to form mono-, di-, and trichloramines. Chloramine (monochloramine) is chemical compound with the formula NH2Cl. ...

Water treated by filtration may not need further disinfection; a very high proportion of pathogens are removed by microorganisms in the filter bed. Disinfection is the destruction of pathogenic and other kinds of microorganisms by physical or chemical means. ...

The advantage of chlorine in comparison to ozone is that the residual persists in the water for an extended period of time. This feature allows the chlorine to travel through the water supply system, effectively controlling pathogenic backflow contamination. In a large system this may not be adequate, and so chlorine levels may be boosted at points in the distribution system, or chloramine may be used, which remains in the water for longer before reacting or dissipating. Chloramine (monochloramine) is chemical compound with the formula NH2Cl. ...

Another method which is gaining popularity is UV disinfection. It leaves no residue in the water. However, this method alone will not remove bacterially produced toxins, pesticides, heavy metals, etc from water. Some bacterial cell walls themselves are toxic to humans, whether dead or alive. Often, multiple steps are taken in commercially sold water. For other uses, see Ultraviolet (disambiguation). ...

See also

• Water fluoridation
• Water pollution
• Sodium hypochlorite
• Symclosene/trichloroisocyanuric acid is the chemical in chlorination tablets

Water fluoridation is the practice of adding fluoride compounds to water with the intended purpose of reducing tooth decay in the general population. ... Raw sewage and industrial waste flows into the U.S. from Mexico as the New River passes from Mexicali, Baja California to Calexico, California Water pollution is a large set of adverse effects upon water bodies such as lakes, rivers, oceans, and groundwater caused by human activities. ... Sodium hypochlorite is a chemical compound with the formula NaClO. A solution of sodium hypochlorite is frequently used as a disinfectant and as a bleaching agent; indeed, often it is simply called bleach, though other chemicals are sometimes given that name as well. ... Trichloroisocyanuric acid (C3Cl3N3O3), also known as Symclosene, trichloro-s-triazinetrione, TCICA, and trichlor, is a chemical compound used as an industrial disinfectant, bleaching agent and a reagent in organic synthesis. ...

References

1. ^ .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", Analytical Sciences, 14, 69, 1998.

External links

• City of Milwaukee, Wisconsin Water Works
• Emergency Disinfection of Drinking Water (US EPA)
• National Pollutant Inventory - Chlorine
• Chlorinated Drinking Water (IARC Monograph)
• NTP Study Report TR-392: Chlorinated & Chloraminated Water (US NIH)
• American Chemistry Council's Chlorine Chemistry Division