Optimal Design of Sensor Placement in Water Distribution Networks

Abstract

In this study we provide a methodology for the optimal design of water sensor placement in water-distribution networks. The optimization algorithm used is based on a simulation-optimization approach and not on the topological structure of the system. Further the proposed optimization model is based on a single objective function approach which incorporates multiple factors such as the time of detection of a contaminant in the system, the contaminated water volume, the population affected and the reliability of the optimal sensor system design. In this sense the proposed model mimics a multi-objective approach without the artificial control of the preference among multiple objectives using weighting functions, which is a common solution method for multi-objective problems. A reliability constraint concept is also introduced into the optimization model such that the minimum number of sensors and their optimal placement can be identified in order to satisfy a pre-specified reliability criterion for the network. An improved genetic algorithm is proposed for the solution of the model. The algorithm works on a subset of the complete set of junctions present in the system (junction sub-domain) and the final solution is obtained through the evolution of sub-domains. The proposed algorithm is applied to two test networks to assess four quantitative design objectives: (i) minimization of the expected detection time; (ii) minimization of the expected populationaffected prior to detection; (iii) minimization of the expected contaminated water demand prior to detection; and, (iv) maximization of the expected likelihood of detection. The results of the proposed solution are discussed comparatively with the outcome of other solutions that were submitted to the WDSA symposium (2006). These comparisons indicate that the model proposed here is an effective approach in solving this problem.