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Until recently, drinking water suppliers have emphasized theuse of sophisticated techniques at the treatment plant toensure good water quality. Such an approach, however,may be risky if water quality significantly deteriorates in thedistribution system. This study tracked the fate of chlorine dioxide(ClO2) and its major inorganic by-products, chlorite andchlorate ions (ClO2- and ClO3-),in a full-scale distributionsystem.In a network fed by a treatment plant using ClO2 in postdisinfection,ClO2- concentrations decreased with increasing waterresidence time, most likely because of the ion's chemical instabilityand reactions with the pipe material's ferrous ion. In the twonetworks fed by plants using free chlorine in postdisinfection,ClO2- levels were below the method detection limit (MDL). ClO3-concentrations in the first network were either below the MDL orstable at low levels in cold water and decreased slightly withincreasing residence time in warm water. ClO3- levels in the othertwo networks showed significant variations, some of which maybe attributable to microbial biomass.Increasingly stringent regulations under the Disinfectants/DisinfectionByproducts Rule are forcing water suppliers to reconsidertheir use of chlorine. This study's findings should help drinkingwater providers more accurately assess the feasibility of usingClO2 as an alternative disinfectant. Includes 83 references, table, figure.

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Edition: Vol. 94 - No. 7 Published: 07/01/2002 Number of Pages: 10File Size: 1 file , 220 KB