General Multiobjective Model and Simulated Annealing Algorithm for Waste-Load Allocation

Abstract

Waste-load allocation (WLA) is a difficult problem with multiobjective features, which requires models that consider a full range of competing goals to identify good and practical solutions. In this study, a general and multiobjective optimization model was proposed. This model integrates different decision variables related to multiple waste-removal efficiencies and outflow discharges into water bodies. This model also considered an equity measure and limits for the concentration of dissolved oxygen and biochemical oxygen demand. A simulated annealing (SA) algorithm and the enhanced stream water quality simulation model (QUAL2E) were used to solve the WLA problem. This approach was applied to the Santa Maria da Vitória River watershed in the state of Espírito Santo, Brazil. Computational results have demonstrated that the proposed optimization model with the SA metaheuristic and QUAL2E could effectively incorporate the expectations and conflicting objectives, providing various good solutions to support decision makers.