Exploring Vulnerable Nodes, Impactful Viral Intrusion Sites, and Viral Infection Risk Reductions Offered by Chlorine Boosters in Municipal Drinking Water Networks

Abstract

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.

Measured and Modeled Comparisons of Chemical and Microbial Contaminants in Tap and Bottled Water in a US–Mexico Border Community

“…Hydraulic and water quality modeling of these intrusion events has demonstrated that infection risks may be high for those affected when these events occur but that the spread of contamination in a municipal network may be highly heterogeneous . Modeling efforts have also demonstrated that risks may be higher for municipal networks in rural communities, which tend to be branched as opposed to looped, like networks for urban communities . Chemical contaminants can invade municipal networks, or they may be present as disinfection byproducts (DBPs), such as chloroform, bromodichloromethane, dibromochloromethane, and bromoform, which result from a reaction of hypochlorous or hypobromous acid with organic matter and pose potential cancer risks. , Private well water for drinking can also become contaminated with fecal pathogens and chemical contaminants due to failing septic systems and precipitation runoff .…”