Drastic reduction of trihalomethane concentration
in domestic water supply systems

Summary

Disinfection stage that guarantees the safety of drinking water in epidemiological terms is mandatory in the process of water treatment. One of the main disinfection methods is chlorination with chlorine or hypochlorites. As a result, chlororganics are generated in drinking water. Some representatives of this class of compounds – trihalomethanes pose a danger to human health, producing a carcinogenic, mutagenic effect, and accumulating in the body. In this regard, the sanitary legislation strictly regulates the concentration of these compounds in drinking water, and the standards for them continuously toughen. Reducing the concentration or limiting the generation of trihalomethanes in drinking water has been an urgent task, and for the purpose of solving this task a number of technical methods are proposed. A promising method of water disinfection is presented that provides for almost complete elimination of trihalomethane generation; namely processing water with «Chlorine dioxide and chlorine» disinfectant, obtained in local automated installations of «DH-100» type. As the practice of implementing this method at more than 50 water treatment facilities in Russia and Kazakhstan has shown, the method provides for reducing trihalomethane concentrations, including water supply sources containing bromides, up to their complete elimination, while ensuring complete disinfection and safety of drinking water.

Key words

potable water , disinfection , bioreactor , water treatment , ozone , trihalomethanes , chlororganic compounds , chlorine , chlorine dioxide , preammoniation , hypochlorites , bromides

Chlororganic and bromorganic compounds in drinking water:
methods of their removal

Summary

Pilot tests of biosorption membrane technology that allows reducing trihalomethanes concentration in drinking water by both preventing from their formation and by removing them from treated water were carried out. Biosorption membrane pretreatment of the Don River water provides for 1.4–1.5 reduction of toxic chlororganic and bromorganic compounds formation during post chlorination of water. Advanced water treatment in a biosorption membrane reactor ensures reducing the concentration of chlororganic compounds formed during primary chlorination. The average efficiency of reducing chloroform concentration in the biosorption membrane reactor was 45%, that of dichlorobromomethane – 82%, and of chlorodibromomethane – 89%, whereas filters provided for 23% chloroform reduction efficiency and 33% of dichlorobromomethane and chlorodibromomethane reduction efficiency, respectively. Additional treatment of the Don water in the biosorption membrane reactor after physical and chemical pretreatment provided for the post treatment efficiency (organics removal) of 33% for COD, 35% for permanganate value, and 34.3% for color. At the same time the efficiency of organics removal in filters was 19% for COD, 9% for permanganate value, and 10% for color. The highest post treatment efficiency in both cases was reached for turbidity removal. The efficiency of turbidity reduction in the biosorption membrane reactor was 91%, in filters – 58%. The results of long-term studies carried out for two years in the pilot plant with the Don River water showed that the development of biosorption membrane technologies was a promising direction of improving natural water treatment processes, in particular, for preventing from formation of chlororganic and bromorganic compounds during chlorination.

Key words

powdery activated carbon , natural water treatment , trihalomethanes , biosorption membrane technology , chlororganic and bromorganic compounds