Enhanced Water Age Performance Assessment in Distribution Networks

Abstract

Water age is frequently used as a surrogate for water quality in distribution networks and is often included in modelling and optimisation studies, though there are no reference values or standard performance functions for assessing the network behaviour regarding water age. This paper presents a novel methodology for obtaining enhanced system-specific water age performance assessment functions, tailored for each distribution network. The methodology is based on the establishment of relationships between the chlorine concentration at the sampling nodes and simulated water age. The proposed methodology is demonstrated through application to two water distribution systems in winter and summer seasons. Obtained results show a major improvement in comparison with those obtained by published performance functions, since the water age limits of the performance functions used herein are tailored to the analysed networks. This demonstrates that the development of network-specific water age performance functions is a powerful tool for more robustly and reliably defining water age goals and evaluating the system behaviour under different operating conditions.

Characterizing stochastic water age in premise plumbing systems using conventional and advanced statistical tools

“…In previous studies on water distribution systems, researchers created "performance indexes" where they correlated water age to an index that reflected one or more water quality parameters. [24][25][26][27] Several studies found that, at around 10 hours, there was a sharp decrease in water quality, 24,25,27 though this depended on the temperature and the distribution system layout, and initial water quality. With similar indexes for specific premise plumbing systems, the water age could be more directly linked to the quality.…”

“…This is especially true for microbial quality, where the quality remains high while the chlorine residual persists and water temperatures are unfavorable for growth (low or high), but can rapidly decline once chlorine dissipates and temperatures become favorable. [24][25][26][27] Given this rapid decline in quality, the average water age may not reflect the average water quality. Therefore, a statistical approach maybe more valuable than exploring average flows.…”

Assessing the Impact of Stochastic Demands and Fixture Purging on Free Chlorine Residuals in Premise Plumbing Systems

“…They found similar trends with higher initial chlorine concentrations leading to a higher percentage of nodes above a certain concentration of chlorine. Past research has also found the chlorine supply to the service line to be very low or nondetect at times . Overall, the trends remained the same for the influent chlorine concentrations, with the purging decreasing the amount of time a fixture spent with low chlorine, especially for the shower.…”

“…Zhang and Edwards found higher chlorine decay in metallic pipes that corrode at high rates, such as cast-iron, galvanized-iron, copper, and old lead pipes than in relatively inert pipes, such as plastic, glass, and stainless steel pipes. If the temperature is higher, chlorine decays faster. − The overall free chlorine decay also depends on the TOC in the water and the pH, with lower pH and TOC values leading to more effective disinfection, though lower pH can lead to pipe corrosion, which, in turn, can affect the k w . , …”

“…Also, we focused on the cold system, as this was easier to model and was more likely to reveal meaningful trends. Free chlorine residual in hot water pipes would likely be zero, both due to long stagnation times in the hot water heater , and high chlorine dissipation rates at high temperatures. − The model assumed that cold water in the premise plumbing system was at room temperature. This is reasonable as water in pipes quickly equilibrates with room temperature.…”