Contaminant intrusion in water distribution systems: An ingress model

Abstract

In a water distribution system, low or negative pressure may occur under normal operation of the system and may lead to contaminant intrusion. To assess the risk associated with contaminant intrusion, exposure assessment is required. To have more accurate intrusion exposure assessment, the effects of the surrounding soil on the intrusion rate must be considered. This research proposes a model to create a more realistic estimation of intrusion rate. A two‐level factorial design was used to screen the effect of pipe internal pressure, soil porosity, average diameter of soil particles, size of the leak point, and pipe burial depth. The Buckingham p theorem was applied to group the influential factors into a set of dimensionless p parameters. The relationship among the p parameters was obtained by using the numerical data generated by a two‐dimensional finite element model for flow in a saturated zone surrounding a pipe. A regression analysis was then applied to find the best fit for the data.

Impact of Orifice-to-Pipe Diameter Ratio on Leakage Flow: An Experimental Study

“…The outflow experiments were conducted using the 3 mm orifice with three pipe diameters (25,50, and 100 mm) discharging into air, as shown in Figure 7. The pipe pressure was controlled at 10 m, and the main pipe velocity was changed to a certain range using the same test system.…”

“…A comprehensive understanding of the relationship between leakage and various factors can help predict the leakage flow rate and reduce the losses in order to improve the reliability of a water supply network [23,24]. However, to the authors' knowledge, the only study dealing with the effect of pipe wall curvature on the flow rate through leak openings was performed by using a 2D computational fluid dynamics (CFD) model to estimate the intrusion rate into the pipelines [25].…”

Contaminant intrusion in water distribution systems

“…An external contaminant may enter a distribution system through a leaky junction ( i ) when the internal pipe head ( H int i ) is lower than the external piezometric head ( H ext i ). The intrusion flow rate at a typical junction can be estimated by using either the original orifice equation (Besner et al, 2011; McInnis, 2004) or the equation proposed by Mansour‐Rezaei and Naser (2013). The model of Mansour‐Rezaei and Naser can provide a more realistic estimate of intrusion rates because it takes into account the characteristics of soil surrounding a pipe.…”