In the United States, as many as 45 million people are affected by health-related water-quality standards violations. The most frequent violation is fecal contamination, and rural areas are the most affected. A large percentage of waterborne disease outbreaks have been traced to municipal drinking water distribution systems, so it is increasingly important to ensure suitable water quality for communities served by these systems.

Water treatment facilities commonly use chlorine for disinfection purposes. But sometimes one treatment is not enough due to contaminant intrusions. A second chlorine booster may help, but this can also cause taste and odor complaints, as well as potentially increase disinfectant byproduct concentrations. Researchers Seungyub Lee, Amanda M. Wilson, Emily Cooksey, Dominic Boccelli, and Marc P. Verhougstraete wanted to determine the optimal locations for secondary chlorine boosters when required.

In their study, “Exploring Vulnerable Nodes, Impactful Viral Intrusion Sites, and Viral Infection Risk Reductions Offered by Chlorine Boosters in Municipal Drinking Water Networks” published in the Journal of Water Resources, Planning and Management, the authors compared risk reductions offered by chlorine boosters in two networks. They used two water distribution systems as case study networks; a branched system without a tank; and a looped system with a tank and assumed continuous contamination as a worst-case scenario. Learn more about how this work can assist in identifying vulnerable points in drinking water systems and the optimal locations for risk reduction strategy implementations at The abstract is below.


The effects of drinking water system infrastructure on water quality and health following intrusion events have not been extensively studied. This study proposes a coupling of hydraulic and water-quality modeling with quantitative microbial risk assessment (QMRA) to characterize microbial infection risks. Two networks were considered based on their network configuration. We assumed a continuous intrusion of enterovirus under three scenarios. The location of vulnerable and influential nodes in a looped and a branched network were compared, followed by a comparison of chlorine booster placement to reduce infection risks. The most vulnerable nodes in the branched network were generally downstream of the intrusion site, whereas those for the looped network were in the middle of the network due to tank dynamics. Influential injection nodes for the looped network were also in the middle of the network but mostly located at the upstream nodes for the branched network. A single chlorine booster yielded a risk reduction (47.6%) for the branched network, greater than for the looped network (nearly none). Two chlorine boosters reduced the looped network risks more notably (63%). The generalizability of these results to other networks likely depends upon specific network hydraulics and variability in municipal drinking water use. This work will help public water system managers in identifying vulnerable points in their distribution system and optimal locations for risk reduction strategy implementation.

Read the paper in full in the ASCE Library: