An Efficient Simulated Annealing Algorithm for Regional Wastewater System Planning

Planning solutions for wastewater system problems are often sought at a local level-that is, each city develops its own solution. However, in many cases, it would be possible to find solutions that are better both from the economic and the environmental viewpoints if they were looked for at a regional level. In this article, we present an efficient simulated annealing (SA) algorithm for solving a regional wastewater system planning model. The model is aimed at determining the minimum-cost configuration for the system that will drain the wastewater generated by the population centers of a region, while complying with all relevant regulations. In particular, the system must ensure that the wastewater discharged from each treatment plant will not exceed a given maximum amount, consistent with the water quality standards defined for the receiving water body. The SA algorithm is termed efficient because its parameters were calibrated to ensure optimum or near-optimum solutions to the model within reasonable computing time. The calibration was performed using a particle swarm algorithm for a large set of test instances designed to replicate real-world problems.