An Integrated Simulation-Optimization Approach for Dynamic Design of the Urban Wastewater Collection Systems

In this study, a simulation-optimization approach is proposed for dynamic design of the urban wastewater collection systems. The proposed approach consists of the mutual integration of the Storm Water Management Model (SWMM), developed by the U.S. Environmental Protection Agency (US-EPA) and the heuristic Harmony Search (HS) optimization approach. Unlike the previous approaches developed to solve wastewater collection system design problems, the proposed approach simulates the hydraulic flow process by considering unsteady state flow conditions based on the dynamic wave model. The objective of the HS based optimization model is to determine the pipe slopes so that the total system cost is minimized. After determining the pipe slopes, the corresponding pipe diameters were determined by developing an internal solution approach. All the physical and managerial constraints that should be considered during the search process have been considered by means of the penalty function approach. The applicability of the proposed approach was evaluated by solving two example problems. Identified results indicated that the proposed approach can effectively solve the dynamic design problems of the wastewater collection systems.