Trihalomethanes chlorine dioxide

Under drinking water plant treatment conditions, humic materials and/ or resorcinol do not produce trihalomethanes with chlorine dioxide even when a slight excess of chlorine (1 percent to 2 percent) is present. Also, saturated aliphatic compounds are not reactive with chlorine dioxide. Alcohols are oxidized to the corresponding acids. 

Chlorine dioxide has been used widely in Europe since the early 1940 s as a drinking water disinfectant. More recently the USA has suggested the use of chlorine dioxide to reduce the formation of chloro-organic compounds particularly chloroform and other trihalomethanes (THM s) which are known carcinogens(7). 

Chlorine dioxide is a very reactive compound and will not exist in the environment for long periods of time. In air, sunlight will quickly break apart chlorine dioxide into chlorine gas and oxygen. In water, chlorine dioxide will react quickly to form chlorite ions. In water treatment systems, chlorine dioxide will not form certain harmful compounds (e.g., trihalomethanes) when it reacts with dissolved organic compounds. Chlorine dioxide does form other disinfection byproducts, such as chlorite and chlorate ions. 

Other DBFs (e.g., lower chlorinated organics, chlorate, and chlorite) which may be found in drinking water treated with chlorine dioxide (Aieta and Berg 1986 Chang 1982 Stevens 1982). Suh and Abdel-Rahman (1985) reported that the presence of CIO2 and HOCl (CI2 dissolved in water) inhibit the formation of trihalomethanes, and the degree of inhibition depends on the ratio of CIO2 to HOCl. 

Carvalho, E. R. (2003). Study of trihalomethanes formation from aquatic humic substances treated by chlorine and chlorine dioxide. Ph.D. thesis, University of Sao Paulo-USP, Brazil. 

Chlorine. Chlorine is a well known disinfectant for water and wastewater treatment, however, it can react with oiganics to form toxic chlorinated compounds such as the trihalomethanes bromodichloromethane, dibromochloromethane, chloroform [67-66-3], and bromoform [75-25-2]. Chlorine dioxide [10049-04A] may be used instead since it does not produce the troublesome chlorinated by-products as does chlorine. In addition, by-products formed by chlorine dioxide oxidation tend to be more readily biodegradable than those of chlorine, however, chlorine dioxide is not suitable... 

Chlorine has been the most widely used disinfectant in the United States however, it produces trihalomethanes (THMs) and other halogenated organic compounds in drinking water. Because of this, water suppliers are beginning to utilize other disinfectants, such as ozone, chlorine dioxide, and monochioramine, or combinations of disinfectants, such as ozone followed by chlorine. 

See also Bromoform Chlorine Chlorine Dioxide Chlorobenzene Chloroform Organochlorine Insecticides Polychlorinated Biphenyls (PCBs) Trihalomethanes. 

It is common for water suppliers to use disinfectants such as chlorine, chloramines and chlorine dioxide to kill microorganisms such as giardia and E coli. Levels of disinfectants used may be higher after rainstorms in summer months. By-products include trihalomethanes, haloacetic acids, bro-mate, and chlorite. Levels of disinfection products and by-products are regulated. 

Residual chlorine dioxide is lost by evaporation hence, chlorite, chlorate and chloride are the principal residues expected. The chloride generated as a result of treatment with ASC is negligible compared with the chloride already present in food. The use of chlorine to disinfect water supplies results in formation of by-products such as trihalomethanes. However, chlorine dioxide acts as an oxidizing agent and therefore does not form trihalomethanes or by-products other than chlorite and chlorate ions. The residues of the food-grade acids (e.g. phosphate, citrate, malate, sulfate) are commonly present in food and have previously established acceptable daily intakes (ADIs). Therefore, the Committee focused the toxicological evaluation on ASC, chlorite and chlorate. 

Chlorine dioxide is frequently employed for disinfecting drinking water, as this prevents or noticeably reduces the formation of so-called haloforms or trihalomethanes. 

Chlorine dioxide is fast replacing aqueous CI2, particularly in pulp and paper manufacture, because the reaction of CIO2 with organic materials does not appear to form carcinogenic trihalomethanes (THMs) as side-products and because CIO2 is 10... 

In this connection, many drinking water utilities are changing their primary disinfectants from chlorine to alternative disinfectants, such as ozone, chlorine dioxide, and chloroamines, which reduce regulated trihalomethanes and some organochlorine compound levels but, at the same time, often increase levels of other potentially toxicologi-cally important compounds, such as inorganic oxyhalide by-products (bromate, chlorite, and chlorate). Some of them have been classified as probable human carcinogens. 

The extensive use of chlorine to purify water has recently been shown to result in the formation of chlorinated hydrocarbons. Low molecular weight compounds, such as the haloforms (HCX3), also called trihalomethanes (THM), are volatile and have been shown to be carcinogenic. They have been detected in drinking water and in the air of enclosed swimming pools. Thus, several alternate disinfectants (such as ozone, chlorine dioxide, UV, and ferrates) have been crmsidered as alternates to chlorine. Of these, the use of ozone has been most developed. 

Lykins BW, Griese MH (1986) Using chlorine dioxide for trihalomethane control. J Am Water... 

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