Robust design of wastewater systems at regional level

Wastewater systems are of crucial importance in the promotion of sustainable development. Their implementation is very complex because there are many different issues to be considered simultaneously (environmental, economical, social, and technical). The Water Framework Directive (WFD) brought new challenges to the definition of appropriate designs for such systems. In particular, they should be determined so that they are capable of performing well even during extreme events. Therefore, the uncertainty inherent to the water environments where the wastewater systems are included must be considered since the beginning of the decision processes where these systems are dealt with. In this paper is presented a robust optimization model for helping to define the configuration of sewer networks and the location and size of the treatment plants where the effluent carried by the sewers will be processed before being discharged into some water body. Its application to a case study illustrates how the model can be used to analyze the implications of increasing the reliability of wastewater systems upon the costs of these systems.