Formation of volatile chlororganic compounds in the process
of the Don River water disinfection with chlorine-containing agents

Summary

Various oxidants are used for water purification and disinfection, including chlorine and its derivatives (hypochlorites, chloramines, bleach, etc.), ozone, less often chlorine dioxide, hydrogen peroxide, potassium permanganate, etc. Traditionally, the sanitary and epidemiological safety of drinking water is ensured by chlorination owing to the sanitary and hygienic reliability, prolonged bactericidal action, relative simplicity and economic efficiency of the method. While disinfecting water, an agent containing active chlorine is used, which, upon entering into a substitution reaction with organic substances present in water, forms toxic compounds belonging to the group of trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform, etc.). The Don River water is characterized by the presence of bromides (0.18–0.2 mg/dm³) resulting in the formation of bromine-containing volatile chlororganic compounds. The water treatment facilities of the Industrial District of Novocherkassk have introduced the technology of «Chlorine dioxide and chlorine» disinfectant production based on the redox reaction between chlorate and sodium chloride in acid environment. The use of liquid chlorine and sodium hypochlorite for the disinfection of the Don River water leads to the formation of volatile chlororganic compounds with dibromochloromethane and chlorodibromomethane dominated. Preammoniation of water with a chlorine to ammonium sulfate ratio of 4:1 is an effective way to reduce the concentrations of volatile chlororganic compounds to 0.02–0.1 MPC while using liquid chlorine or sodium hypochlorite. Chlorate-chloride technology of producing chlorine dioxide in acid environment instead of «Chlorine dioxide and chlorine» agent generates 100% hypochlorite solution in the hypochlorous acid format that, in the absence of water preammoniation, is capable of forming volatile chlororganic compounds in concentrations exceeding the MPC.

Key words

sodium hypochlorite , water disinfection , chlorine water , chlorine dioxide , bromine-containing trihalomethanes , preammoniation , chlorate-chloride production of chlorine dioxide