Benefits of employing a disinfectant residual in distribution systems

Since the beginning of the 20th century, the widespread use of chlorine to disinfect drinking water has resulted in a dramatic decrease in water-related disease. Additional tools to disinfect water, including ozone, chlorine dioxide, chloramines, and even ultraviolet light further increase the arsenal available to combat pathogenic microbes, although their use lags far behind that for free chlorine. For many years the taste of chlorine in drinking water has been equated with the guarantee of its safety. The progress against waterborne disease, however, has not been without its downside as science recognize the concern of disinfection by-products (DBPs) and customers raise their expectations for water without chlorinous tastes or odors. Now, at the turn of the next millennium, consideration is being voiced to whetherit is time to abandon the use of chemical disinfectants altogether, at least in the water delivered to customers. It is the position of this paper that this approach is premature and that control of water quality is such that one can not guarantee that water distributed without a residual disinfectant isn't subject to recontamination or microbial degradation prior to the customer's tap. Rather than to abandon the approach (disinfection) that has led to such public health milestones, researchers should focus their efforts to make compatible the goal of residual disinfection without tastes, odors, and minimal DBP levels. [ABSTRACT FROM AUTHOR]