Valve isolation placement to mitigate contaminant spreading in water distribution network

Abstract

A water distribution network (WDN) is a complex system that supplies drinking water from water treatment plants to consumers. WDN consists of various elements that ensure an efficient and reliable water supply. Among all these elements, valves are critical components that control the flow and pressure within the network and can isolate segments (the smallest parts of the WDN that can be isolated without interrupting service in the entire WDN) for maintenance or repair purposes. There are several studies in the literature on the optimal positioning of valves, in general the proposed methods are treated as optimization problems with one or more objectives aimed at reducing installation costs while ensuring high system reliability of the WDN (Creaco et al., 2010). In recent years, water distribution networks have become increasingly vulnerable to contamination risks (WHO, 2014). Various factors contribute to this vulnerability, such as malfunctions in chlorination equipment, low pressure, contaminants entering water tanks and inadvertent connections between drinking and non-drinking water sources. When contamination is detected, the quickest remedial action that a water utility can take is to isolate the water section by closing gate valves. The objective of this study is to find the optimal placement of gate valves in the water distribution network (WDN) to address the vulnerability of water quality, effectively isolate the contamination and minimize the residual concentration of contaminants. The proposed methodology is based on community detection algorithms used by sociologists to detect community structures in social networks (Traag, 2014). A community C can be described as a group of nodes with a high density of links between them and low density of links between different groups (or communities). In this work, the community detection algorithm proposed by Girvan and Newman (2002) is used to identify groups of densely connected nodes in the WDN, and then isolation valves are placed on the boundary pipes between the different groups of nodes without performing hydraulic simulations. Different edge weights are tested to improve the placement of the isolation valves and reduce the risk of water pollution. The proposed methodology will be tested on a real water distribution network in southern Italy.