Chlorination of water

Wastewater. Phenol is a toxic poUutant to the waterways and has an acute toxicity (- 5 m g/L) to fish. Chlorination of water gives chlorophenols, which impart objectionable odor and taste at 0.01 mg/L. Biochemical degradation is most frequently used to treat wastewater containing phenol. Primary activated sludge, along with secondary biological treatment, reduces phenol content to below 0.1 mg/L (69). 

Pyrene is a common PAH contaminant and may occur in drinking water. Chlorination of water with or without bromide that may be present in coastal environments has been examined. Both chlorinated and brominated pyrenes with halogen substituents at the 1,3-, 1,6-, and 1,8-positions were found, and could putatively be produced by reaction of pyrene with hypochlorous acid and hypochlorite (Hu et al. 2006). 

Ohya T, Kanno S. 1987. Formation of cyanogen chloride during the chlorination of water containing aromatic compounds and ammonium ion. J Pharm Sci 76(11). 

The chlorination of water is usually carried out by adding chlorine gas, sodium hypochlorite, or calcium hypochlorite to the water in low concentrations. The active antibacterial agent in each case is hypochlorous acid, HClO(aq). For example, when chlorine gas is added to water, hypochlorous acid is formed by the following reaction. 

Some people object to the chlorination of water, and prefer to drink bottled spring water. There is controversy over the level of risk associated with chlorination, and over the possible benefits of spring water. For example, hypochlorous acid reacts with traces of organic materials in the water supply. These reactions can produce toxic substances, such as chloroform. Supporters of chlorination believe that these substances are present at very low, safe levels, but opponents of chlorination disagree. Complete the following practice problems to help you decide on your own opinion of chlorination. 

Research and assess the most recent information you can find on the health and safety aspects of the chlorination of water. Are you in favour of chlorination, or opposed to it Explain your answer. 

Chemical/Physical. Hypochlorite ions, formed by the chlorination of water for disinfection purposes, may react with acetone to form chloroform. This reaction is expected to be significant within the pH range of 6 to 7 (Stevens et al., 1976). 

Chlorination of water containing bromide ions converted phenol to 2,4,6-tribromophenol. Bromodichlorophenol, dibromochlorophenol, and tribromophenol have also been reported to form from the chlorination of natural water under simulated conditions (Watanabe et al., 1984). 

Chlorination of waters containing two phenylurea-type herbicides, isoproturon and diuron, results in the formation of THMs. The reaction of the phenylurea-type herbicide isoproturon with chlorine produced compounds that still contained the aromatic ring of the herbicide with the urea side-chain unmodified. The formation of chlorinated and brominated derivatives was related to the bromide concentration present in the water [113]. 

Uses. One of four common trihalomethanes formed after chlorination of water supplies in the past used to make fire extinguisher fluids. 

Uses. As a reagent for albumin detection in making herbicides. It is found as a by-product after chlorination of water containing humic materials. 

White phosphorus reacts rapidly with chlorine to form phosphorus trichloride, which finally hydrolyzes and oxidizes to form phosphoric acids (EPA 1991). Chlorination of water, therefore, further shortens the half-life of phosphorus in water. 

Rappe C, Swanson SE, Glas B. 1989c. Formation of PCDDs and PCDFs by the chlorination of water. Chemosphere 19 1875-1880. 

Chlorination of water containing organics will create trihalo-methanes (THMs) ... 

The most important alternative to chlorination of water is ozonization in which the above-mentioned disadvantages occur to a much lesser extent. However, the higher cost of ozonization is a problem. Ozonization helps subsequent flocculation and biological degradation on activated charcoal. About 0.2 to 1.0 g of ozone is required per of water, in exceptional cases up to 3 g/m. A further alternative is treatment with chlorine dioxide (from sodium chlorite and chlorine), in which there is less formation of organochloro-compounds than in the case of chlorination (see Section 1.7.4.2.5). 

Krasovskii GN and Egorova NA (2003) Chlorination of water as a high hazard to human health. Gigiena i San-itariia 1 17-21. 

Chloroform is a volatile, low-molecular weight, lipophilic compound and a chlorinated trihalo-metheane. Most of the chloroform produced in the United States is used to make fluorocarbon 22 (HCFC 22) and the rest is produced for export and miscellaneous uses. In the past it was used as an inhalation anesthetic and as an extraction for, fats, oils, greases and other products, as a dry cleaning spot remover, in fire extinguishers, and as a fumigant. It is available as emulsions, spirits, tinctures, and chloroform water. Chloroform is also formed as a by-product of chlorination of water, wastewater, and swimming pool. Other sources include pulp and paper mills, hazardous waste sites, and sanitary landfills. 

Vaccines have become modern medical miracles along with bypass surgery and the CAT scan, but with this difference—vaccines have saved more lives and prevented more deaths than any other modern medical intervention since the chlorination of water and the pasteurization of milk. 

Depending on pH and redox potential the following forms can occur in water Clj, HCIO, CIO and Cl . In the presence of ammonia nitrogen, chloramines are formed during the chlorination of water. In neutral media primarily HCIO reacts ... 

An example of the chlorination of water containing organic matter is the reaction of guaiacol alcohol with chlorine (Fig. 3.20), or the oxidation reaction of the phenolic nucleus during chlorination ... 

Morris, J.C. Formation of halogenated organics by chlorination of water septics. A review Draft report to Office of Research and Development, EPA (RD 683), Washington 1975. 

PROBABLE FATE photolysis, could be important, only identifiable transformation process if released to air is reaction with hydroxyl radicals with an estimated half-life of 8.4 months oxidation, has a possibility of occurring, photooxidation half-life in air 42.7 days-1.2 yrs hydroiysis too slow to be important, first-order hydrolytic half-life 275 yrs voiatilization likely to be a significant transport process, if released to water or soil, volatilization will be the dominant environmental fate process, volatilization half-life from rivers and streams 43 min-16.6 days with a typical half-life being 46 hrs sorption adsorption onto activated carbon has been demonstrated bioiogicai processes moderate potential for bioaccumulation, biodegradation occurs in some organisms, in aquatic media where volatilization is not possible, anaerobic degradation may be the major removal process other reactions/interactions may be formed from haloform reaction after chlorination of water if sufficient bromide is present... 

PROBABLE FATE photolysis occurs in aqueous alkali, photolysis may occur near surface of waters and in atmosphere oxidation probably cannot compete with biodegradation, complete oxidation by Pseudomonas isolated from activated sludge hydrolysis not an important process volatilization too slow to be important, evaporation half-life 73 days sorption slight potential for adsorption by lipophilic materials, may adsorb to sediments if released in water biological processes no bioaccumulation more resistant to biodegradation than phenol, complete removal by biodegradation in 13-36 days in river waters other reactions/interactions chlorination of water eould further chlorinate the compound... 

PROBABLE FATE photolysis, possible, but cannot compete with microbial biodegradation oxidation, any oxidation which occurs is too slow to be important hydrolysis not an important process, first-order hydrolytic half-life 3.4 yrs volatilization not expected to be an important process sorption sorption will not remove significant amounts biological processes rapid microbial degradation is the principal fate of 2,4-DCP other reactions/interactions chlorination of water may produce further chlorination of 2,4-DCP... 

PROBABLE FATE photolysis, photooxidation of volatized phenol and photoylis of phenolic anion may both take place at moderate rates, atmospheric and aqueous photolytic half-life 1.9-7.2 days oxidation metal-catalyzed oxidation may take place in highly aerated waters, photooxidation half-life in water 3.2-160 days, photooxidation half-life in air 2.28-22.8 hrs hydrolysis not important volatilization very little, if any, volatilization of phenol occurs sorption not important biological processes no bioaccumulation, but very extensive biodegradation in natural waters other reactions/interactions chlorination of water may produce chloro-phenols... 

A primary premise relating to the development of an engineering discipline is that it is required by an established industry. The chemical-process industries in the United States popularly are assumed to have developed after the First World War. Up to that time Germany is credited with being the preeminent chemical power. This is not so. Many developments that we assume are modem were firmly established by 1908, the year AIChE was founded. In that year the United States began the first large-scale chlorination of water William H. Walker... 

J. C. Morris and B. Baum, "Precursors and Mechanisms of Haloform Formation in the Chlorination of Water Supplies," chapter in Wafer Chiorinafion, Vol. 2, R. L. Jolley, H. Gorchev, and D. H. Hamilton, Jr., eds., Ann Arbor Science, Ann Arbor, Mich., 1978. 

This is formed during the chlorination of water and during the breakdown of other chlorinated hydrocarbons (CHCs). 

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