ABSTRACT

Chlorine in some form is the most widely used disinfection medium for drinking water, wastewater, and foods, and is also commonly used in swimming pools, cooling water systems, and surface sanitizing. It is applied as gaseous chlorine, sodium and calcium hypochlorites, monochloramine, and chlorinated isocyanurates or chlorine dioxide. Chlorinated organic disinfection by-products (DBPs) being somewhat hydrophobic are more easily detected at lower concentrations, so there is a tendency to focus on them. Some halogenated DBPs have potential theoretical risks from long-term exposures at low concentrations, whereas the oxidized non-halogenated product alcohols, aldehydes, ketones, and carboxylic acid by-products are considered not to be unique in our oxygenated environment. Concentrated hypochlorite also spontaneously produces several inorganic by-products, including chlorite, chlorate and perchlorate, and ultimately chloride when those have been chemically reduced. Bromate is produced during chlorine production electrolysis if bromide is present in the salt.