Optimization for maintenance of water distribution system using stochastic search algorithms

Abstract

Water distribution systems are complex interconnected networks consisting of pipes, junction joints and pumps that require extensive planning to ensure that water is delivered to the consumers without service interruptions. All water distribution systems deteriorate over time. It is not economically viable to replace all deteriorating pipelines in old water distribution systems. Therefore maintenance is essential to improve the service level and maximize the reliability of aging water distribution systems. The objective of this study is to propose a maintenance decision model to obtain a near-optimal maintenance strategy that minimizes the total discounted maintenance cost over a defined planning horizon subject to the water distribution system availability constraint. Various maintenance alternatives like replacement and rehabilitation of water distribution pipe network are considered in the study. The cost terms which are relevant to the maintenance problem under study are described by a set of non linear equations. Stochastic Search Algorithms have created an immense interest among researchers to solve this type of complex combinatorial optimization problems. In this study, the application of stochastic search algorithms such as Simulated Annealing technique, Tabu Search approach and Genetic Algorithms, to solve the water distribution system maintenance optimization problem is demonstrated. The study considers a real-life water distribution system in Chennai, India. A systematic failure study of the pipe network together with the pumping system components to identify the potential failure modes of the water distribution system is carried out. A Monte Carlo simulation approach is used to assess the infrastructure availability of the water distribution system. The results obtained from the present study provide insights into the working of the proposed stochastic search algorithms and their application to solve water distribution system maintenance problems.