An integrated simulation-optimization approach for dynamic design of the urban wastewater collection systems

In this study, an integrated simulation-optimization approach is developed for dynamic design of the urban wastewater collection systems. The proposed approach consists of the mutual integration of the United States Environmental Protection Agency (US-EPA) Storm Water Management Model (SWMM) and heuristic harmony search (HS) optimization approach within the simulation-optimization framework. Unlike the previous approaches for solving the wastewater collection system design problems, the proposed approach simulates the hydraulic flow process by considering the unsteady flow conditions based on the dynamic-wave approach. In this way, the flow process encountered in practice is simulated more accurately. The developed SWMM-based dynamic simulation model is then integrated into an HS-based optimization model. The main objective of the HS based optimization model is to determine the slope of the pipes by minimizing the total system cost. During the optimization process, all the physical and managerial constraints of the problem are considered by means of the penalty function approach. The applicability of the proposed approach is evaluated by solving two example problems. Identified results indicated that the proposed approach not only efficiently solves the dynamic design problem, but also provides comparable results with those obtained by using different approaches in literature.