Deterministic Integrated Optimization Model for Sewage Collection Networks Using Tabu Search

This paper presents an integrated optimization model for designing sewage collection networks. The layout configuration is designed using the loop-by-loop cutting algorithm. Then, the network with a given layout is hydraulically designed to determine sewer diameters, installation depths, and pump specifications. In both design steps, all technical constraints and criteria are systematically satisfied. Thereby, the optimization of sewer systems becomes totally unconstrained for the applied optimization solver. In this problem, the objective function is the network's construction cost and the decision variables are the parameters of layout generation and sewer specifications. For optimization of the cost function, the tabu search (TS) method as a deterministic combinatorial metaheuristic is developed and coupled to the design solvers. The proposed scheme is able to search adaptively in feasible parts of the problem's decision space as well as to solve the two subproblems of layout generation and sewer sizing simultaneously. Then the model is applied against a benchmark case study. It is found that using the integrated model, the design of sewer networks becomes computationally more efficient and systematic, and it is a very promising approach to attain the global optima.