Disinfection by-product

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Disinfection by-products (DBPs) form when organic materials in source water react with chemical treatment agents at the drinking water treatment plant ^[1], ^[2].

For example, chlorinated disinfectants (e.g. free chlorine, chlorine dioxide) introduced into the water to destroy pathogenic microbes and form a residual chlorine component such that drinking water may reach the consumer tap safe from microbial contamination, may react with naturally present fulvic and humic acids to produce a range of DBPs including trihalomethanes, haloacetic acids and many others. Residual chlorine may also react further within the distribution network if it comes into contact with organic material accumulated there e.g. as biofilms. In addition to being highly influenced by the types of organic and inorganic matter in the source water, the different species and concentrations of DBPs vary according to e.g. chlorine dosing at the drinking water disinfection stage, the time since dosing, temperature, pH of the water ^[3].

[edit] Occurrence

DBPs are present in most drinking water supplies that have been subject to chlorination, chloramination or ozonation. Many hundreds of DBPs exist in treated drinking water and while the exact figure is not known, at least 600 have been identified. The low levels of many of these DBPs, coupled with the analytical costs in testing water samples for them, means that in practice only a handful of DBPs are actually monitored.

[edit] Health effects

Exposure to DBPs has been associated with cancers, adverse birth outcomes and some birth defects.

[edit] References