Optimal Control of Combined Sewer Overflows

Combined sewer networks carry wastewater and stormwater together. Capacity limitation of these sewer networks results in combined sewer overflows (CSOs) during high-intensity storms. Untreated CSOs when directly discharged to the nearby natural water bodies cause many environmental problems. Controlling existing urban sewer networks is one possible way of addressing the issues in urban wastewater systems. However, it is still a challenge, when considering the receiving water quality effects. This paper presents an evolutionary constrained multi-objective optimization approach to control the existing combined sewer networks. The control of online storage tanks was taken into account when controlling the combined sewer network. The developed multi-objective approach considers two important objectives, i.e. the pollution load to the receiving water from CSOs and the cost of the wastewater treatment. The proposed optimization algorithm is applied here to a realistic interceptor sewer system to demonstrate its effectiveness.