Influence des paramètres structurels et opérationnels sur la qualité de l'eau dans un réseau de distribution

Influence des paramètres structurels d'un réseau sur la qualité de l'eau -- Influence des paramètres hydrauliques d'un réseau sur la qualité de l'eau -- Influence des paramètres physico-chimiques d'un réseau sur la qualité de l'eau -- Modélisation du fonctionnement hyraulique et de la qualité de l'eau dans les réseaux de distribution -- Utilisation des systèmes d'information géoréférencée (SIG) et autres technologies pour optimiser la gestion des réseaux de distribution -- Développement et mise en place d'une approche intégrée : détails techniques et expérimentaux -- Utilistion d'une approche intégrée afin d'expliquer la qualité de l'eau d'un réseau de distribution (article scientifique) -- Utilisation de l'approche intégrée pour expliquer les épisodes de coliformes et les concentrations de chlore en réseau (résultats complémentaires) -- Explications relatives à l'évolution du chlore en réseau

Risk evaluation of drinking water distribution system contamination due to operation and maintenance activities

Pathogenic microorganisms responsible for waterborne disease outbreaks -- Mechanisms of microorganisms introduction into distribution systems -- Impact of disinfectant residual on microbial intrusion -- Risks related to accidental intrusion of microorganisms in distribution systems -- Research objectives and methodology -- Critical review of the literature on distirbution system intrusion -- Efficacy o fdisinfectant residual against microbial intrusion in distribution systems; a review of existing studies -- The fate of microorganisms experimentally introduced into drinking water systems -- Laboratory -- or bench-scale systems -- Pilot-scale systems -- Full-scale test distirbution system -- Discussion : what can be learned from these experiments? Assessing the effect of distribution system O & M on water quality -- Impact of water mian repairs on water quality -- Negative pressure events and water quality -- Integration of data was found useful to explain water quality variations -- Loss in system's physical integvrity : field assessment of the impact on water quality -- Loss in system's hydraulic integrity : field assessment of the impact on water quality -- Benefits for the water industry

Negative pressures in full-scale distribution system: field investigation, modelling, estimation of intrusion volumes and risk for public health

International audienceVarious investigations encompassing microbial characterization of external sources of contamination (soil and trenchwater surrounding water mains, flooded air-valve vaults), field pressure monitoring, and hydraulic and transient analyses were conducted in the same distribution system where two epidemiological studies showing an increase in gastrointestinal illness for people drinking tap water were conducted in the 1990's. Interesting results include the detection of microorganisms indicators of fecal contamination in all external sources investigated but at a higher frequency in the water from flooded air-valve vaults, and the recording of 18 negative pressure events in the distribution system during a 17-month monitoring period. Transient analysis of this large and complex distribution system was challenging and highlighted the need to consider field pressure data in the process

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

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