Planning regional wastewater systems across borders

Abstract

Regional wastewater systems are aimed at guaranteeing surface water quality by properly collecting and treating the wastewater generated in the population centers of a region. But the most suitable planning regions are often divided by political or social boundaries and may include upstream–downstream surface water quality conflicts. A cross-border planning approach allows for the coordination of pollution control and can embrace both economic and environmental considerations. In this paper, a methodology for wastewater system planning across borders is presented. An optimization model is used to identify reference solutions for negotiation between parties, regarding the layout of the infrastructure to be included in the system. The model takes into account costs and water quality in the receiving water body, and is therefore able to meet surface water quality standards in the shared waterway. A heuristic method is used to solve the model, based on a simulated annealing algorithm enhanced with a local improvement procedure. A region designed to replicate a real-world problem containing two countries is used as a case study. The transboundary wastewater system planning approach is compared with the consideration of separate systems for each country. The features of the transboundary solutions are discussed, with particular focus on the basis of the asymmetries in willingness to pay and different cost allocations.