The preceding reactions are examples of other types of reactions (such as combination, combustion, and single-replacement reactions), but they’re all redox reactions. They all involve the transfer of electrons from one chemical species to another. Redox reactions are involved in combustion, rusting, photosynthesis, respiration, batteries, and more.
The sum of the two propagation steps corresponds to the balanced chemical equation for the overall reaction. There are three possible termination steps: the combination of (1) two bromine atoms, (2) two ethyl radicals, or (3) an ethyl and a bromine radical:
Bladder cancer risks for smokers and non-smokers exposed to chlorinated water Years at a residence Cases Controls Odds ratio Cases Controls Odds ratio Reference/comments served by chlorinated (95% CI) (95% CI) water A.
Bladder cancer risks and duration of exposure to chlorinated surface water in five interview-based incident case-control studies Years of Odds 95% CI Comments Reference exposure to ratio chlorinated surface water A.
Study participants exposed to chlorinated water sources for more than 40 years were found to have twice the risk of bladder cancer (OR = 2.0; 95% CI = 1.3-3.1) compared with participants exposed to unchlorinated groundwater sources.
2.4.3 Chloramine reactions Chloramination of drinking-water produces THMs (if chloramine is formed by chlorination followed by ammonia addition), HAAs, chloral hydrate, hydrazine, cyanogen compounds, nitrate, nitrite, organic chloramines and 1,1-dichloropropanone (1,1-DCPN) (Dlyamandoglu & Selleck, 1992; Kirmeyer et al., 1993, 1995).
Hoigne & Bader (1994) described the kinetics of reaction between chlorine dioxide and a wide range of organic and inorganic compounds that are of concern in water treatment.
Several researchers have shown that monochloramine readily transfers its chlorine at a comparatively rapid rate to organic amines to form organohalogen amines (Isaac & Morris, 1983; Bercz & Bawa, 1986).
In a national survey of the water supplies of 70 communities serving about 38% of the population in Canada, conducted in the winter of 1976-1977, chloroform concentrations in treated water of the distribution system 0.8 km from the treatment plant, determined by the gas sparge technique, averaged 22.7 µg/litre.
In addition to this, chlorine dioxide is more selective in typical water treatment applications, as evidenced by its somewhat lower disinfectant demand as compared with chlorine.
The reaction of aqueous chlorine or monochloramine with organic nitrogen may form complex organic chloramines (Feng, 1966; Morris et al., 1980; Snyder & Margerum, 1982).
Treatment of phenol-laden source waters with chlorine dioxide does not produce the typical chlorophenolic taste and odour compounds that are produced when the water is treated using chlorine and is effective in removing existing tastes and odours of this type.
2.7.2 Chloramine organic by-products When Suwannee River (USA) fulvic acid was reacted with aqueous solutions of 15N-labelled chloramine and 15N-labelled ammonia, lyophilized products exhibiting nuclear magnetic resonances between 90 and 120 ppm were observed, denoting the formation of amides, enaminones and aminoquinones (Ginwalla & Mikita, 1992).
The limited research that has been conducted in aqueous solutions indicates that these intermediates decompose readily in water to form products such as aldehydes, ketones, carboxylic acids and ketoacids.
Sodium hypochlorite is stored at pH greater than 12 to prevent rapid decomposition, and most of the sodium hypochlorite is present as hypochlorite ion.