Disinfection Byproducts in Intermittent Piped Water Supplies

Intermittent water supply (IWS) is found in many parts of the world, especially in low- and middle-income regions, and is characterized by a loss of distribution system pressure, periods of stagnation, the intrusion of contaminants, repressurization of the piped system when service is resumed after a no-supply period, and the need for consumer water storage. Although we have a robust understanding of the impacts of IWS on microbial water quality, less research emphasis has been placed on the impact of intermittency on chemical water quality, such as the formation of disinfection byproducts (DBPs). Chemical disinfection is commonly used to remove or inactivate waterborne pathogens during drinking water treatment and distribution to protect and improve microbial water quality. However, characteristics of IWS have known or suspected contributions to factors that impact DBP formation during drinking water distribution and household storage, such as the intrusion of organic matter, variable post-chlorine water ages, and growth and/or regrowth of microbial communities. This review discusses the impact of IWS on the formation and fate of DBPs, drawing upon the literature regarding continuous water supply systems and key characteristics of IWS. We call for more frequent monitoring of DBPs in IWS and further investigation of the mechanisms affecting DBP formation and speciation under various IWS conditions.