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Using nodal infection risks to guide interventions following accidental intrusion due to sustained low pressure events in a drinking water distribution system

Fatemeh Hatam, Mirjam Blokker, Marie-Claude Besner, Gabrielle Ebacher and Michèle Prévost

Article (2019)

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Abstract

Improving the risk models to include the possible infection risk linked to pathogen intrusion into distribution systems during pressure-deficient conditions (PDCs) is essential. The objective of the present study was to assess the public health impact of accidental intrusion through leakage points in a full-scale water distribution system by coupling a quantitative microbial risk assessment (QMRA) model with water quality calculations based on pressure-driven hydraulic analysis. The impacts on the infection risk of different concentrations of Cryptosporidium in raw sewage (minimum, geometric mean, mean, and maximum) and various durations of intrusion/PDCs (24 h, 10 h, and 1 h) were investigated. For each scenario, 200 runs of Monte Carlo simulations were carried out to assess the uncertainty associated with the consumers' behavioral variability. By increasing the concentrations of Cryptosporidium in raw sewage from 1 to 560 oocysts/L for a 24-h intrusion, or by increasing the duration of intrusion from 1 to 24 h, with a constant concentration (560 oocysts/L), the simulated number of infected people was increased by 235-fold and 17-fold, respectively. On the first day of the 1-h PDCs/intrusion scenario, a 65% decrease in the number of infected people was observed when supposing no drinking water withdrawals during low-pressure conditions at nodes with low demand available (<5%) compared to no demand. Besides assessing the event risk for an intrusion scenario, defined as four days of observation, the daily number of infected people and nodal risk were also modeled on di�erent days, including during and after intrusion days. The results indicate that, for the case of a 1-h intrusion, delaying the start of the necessary preventive/corrective actions for 5 h after the beginning of the intrusion may result in the infection of up to 71 people.

Uncontrolled Keywords

QMRA; sustained pressure drops; accidental intrusion; infection risk fromCryptosporidium; pressure-driven hydraulic analysis

Subjects: 1000 Civil engineering > 1000 Civil engineering
1500 Environmental engineering > 1500 Environmental engineering
1500 Environmental engineering > 1501 Water quality, pollution
Department: Department of Civil, Geological and Mining Engineering
Research Center: CIEP - Industrial Chair on Drinking Water
Funders: NSERC Industrial Chair on Drinking Water / Chaire industrielle CRSNG en eau potable
PolyPublie URL: https://publications.polymtl.ca/4936/
Journal Title: Water (vol. 11, no. 7)
Publisher: MDPI
DOI: 10.3390/w11071372
Official URL: https://doi.org/10.3390/w11071372
Date Deposited: 05 Jul 2022 11:57
Last Modified: 11 May 2023 06:55
Cite in APA 7: Hatam, F., Blokker, M., Besner, M.-C., Ebacher, G., & Prévost, M. (2019). Using nodal infection risks to guide interventions following accidental intrusion due to sustained low pressure events in a drinking water distribution system. Water, 11(7), 1372 (17 pages). https://doi.org/10.3390/w11071372

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