Regional Wastewater System Planning under Population Dynamics Uncertainty

Abstract

Regional wastewater systems are used for the collection and treatment of the wastewater generated in a region and aimed at guaranteeing surface water quality. The volumes of wastewater to process depend on future population and thus are affected by the uncertainty inherent to population dynamics. In this article, we present a robust approach to the planning of regional wastewater systems under population dynamics uncertainty. The approach searches for the optimal configuration of the sewer networks and for the best location, type, and size of the possible pump stations and treatment plants to include in the system. It assumes uncertainty to be described by a given number of discrete scenarios of known probabilities and relies on discrete nonlinear optimization models whose objective is to minimize the expected regret of solutions with respect to total costs. As demonstrated through a case study developed for the North Baixo Mondego area in central Portugal, the results obtained through the proposed approach provide clear insights into the wastewater system planning decisions to make and do not require excessive computational effort.