A multipurpose optimization model for area-wide sewerage systems

In this paper the goal programming model is given that deals with the optimal scale and location of an area-wide sewerage system, consisting of trunk sewers, treatment plants, and pumping stations. The uncertainty of future wastewater volume is considered, and the regional objectives are evaluated. Hence, the model is composed of several constraints and of three objective functions (goals). The major constraints are the capacity of the treatment plants and the estimated range of wastewater amount in each municipality. The goals are to minimize total cost and environmental impact, while maximizing user satisfaction with the sewerage system. The case study shows that this model can help to decide the location and scale of facilities for sewerage system, giving results that are a good balance of the three goals. Furthermore, the analysis, by varying the settings of the goals or the values of sewerage propagation ratio, shows that the model can simulate changes in the wastewater capacity and its transport routes. Thus, the present model makes it easier for decisionmakers to plan area-wide sewerage systems.