Author(s)

J. A. Zeferino, M. da Conceição Cunha & A. P. Antunes

Abstract

This paper describes a multiobjective approach for the siting and sizing of the components of a regional wastewater system. This approach can be particularly helpful for the coherent and harmonious implementation of the Water Framework Directive. Three criteria are considered for finding efficient solutions. A simulated annealing algorithm improved by a local search algorithm is used and the results of three case studies are presented and compared. Keywords: wastewater systems, multiobjective models, simulated annealing. 1 Introduction The worldwide concern about water and sanitation has been expressed in initiatives like the United Nations Millennium Development Goals. The target to reduce by half the population without sustainable access to safe drinking water and basic sanitation is incorporated in the goal to ensure environmental sustainability. If this target is to be met appropriate wastewater systems have to be implemented. These systems are often designed at a local level. However, better solutions both from the economic and the environmental points of view can be obtained with regional planning. This work describes a multiobjective approach to regional wastewater system planning. In this type of system, global cost is usually the criterion that is optimized, making it a single-objective problem. The other indicators for achieving a sustainable development are often included as problem constraints, considering some upper and lower limits. However, for some indicators, these limits may be difficult to establish, which can make them easier to handle as criteria. Since the criteria to be optimized are usually incommensurable, it is impossible to find a solution where all these criteria are optimized

Keywords

wastewater systems, multiobjective models, simulated annealing.