Multi-objective Optimization of Combined Sewer Systems Using SWMM 5.0

Combined sewer overflows (CSOs) are frequent in many cities during stormy weather. CSOs are not only an environmental issue but also induce an adverse aesthetic view for major cities, worldwide. Many engineering solutions have been proposed by researchers to reduce, if possible to avoid CSOs; however, most of these solutions require sewer network capacity enhancement. Therefore, most of the proposed engineering solutions are based on structural measures. However, they are not the best solutions since most of these measures require new structural components and thus capital requirement. Therefore, if possible, control of existing combined sewer networks to minimize the CSOs and their adverse environmental effects would be an ideal solution. However, a holistic control algorithm based on environmental concerns is yet to be tabled. Therefore, this paper presents an improved approach in control of existing combined sewer systems to minimize the adverse environmental effects due to the combined sewer overflows. A multi-objective optimization approach was developed, considering flows and water quality in combined sewer flows and the wastewater treatment costs. The presented multi-objective optimization approach shows a considerable improvement in controlling urban wastewater systems compared to the previous work by the same author. The improved algorithm has advantages in solution space of multi-objective optimization approach. Furthermore, it eliminates achievement of infeasible solutions unlike the other constrained multi-objective optimization approaches.