Variability of Non-Regulated Disinfection By-Products in Distribution Systems: Impact of the Storage Tank

In this chapter, the spatial variability of non-regulated disinfection by-products (DBPs) in drinking water – haloacetonitriles (HANs), haloacetaldehydes (HAs), haloketones (HKs), chloropicrin (CP) and cyanogen chloride (CNCl) – was investigated in four distribution systems in the Québec City area. Attention was directed to the impact, on DBP levels, of water that is re-chlorinated in distribution system storage tanks. The results show that when there was a storage tank as part of the distribution system, flow through this led to an increase in targeted DBP levels except for CNCl for which levels were systematically lowest at sites located after the storage tank. However, for most DBP families, the variability within the storage tank was different from month to month. Moreover, the impact on DBP levels of water flowing through the storage tank differed between the four systems under study. This study highlights that, as for regulated DBPs (trihalomethanes-THMs and haloacetic acids-HAAs), the selection of the sampling locations for non-regulated DBP monitoring represents a considerable challenge.