Improved Optimization Strategies for Generating Practical Water-Usage and -Treatment Network Structures

A design procedure to generate practical structures for the water-usage and -treatment networks is presented in this paper. The optimization strategies used in the proposed procedure are developed on the basis of a modified version of the existing nonlinear programming model. In particular, a systematic method is used to incorporate additional design options and a fixed number of repeated treatment units into the superstructure. Also, to account for the possible existence of unrecoverable solutes, the inequality constraints on their concentrations are added in the revised model formulation. To enhance convergence efficiency, a reliable method is developed in this work to produce a good initial guess. The advantages of this initialization technique are demonstrated with several examples adopted from the literature. Finally, several useful solution techniques to manipulate the structural properties of water networks are provided at the end of this paper. The effectiveness of our approach for creating favorable network structures is shown in the results of case studies.