Two-step optimization approach for design of a total water system

The development of the two-step optimization approach, as seen in Part I of the paper, can then be extended to a total water system. The total water system comprises two subsystems: namely, water-using units and wastewater treatment system. In this paper, the proposed approach utilizes mixed integer linear programming (MILP) and nonlinear programming (NLP) in the two-step optimization approach to generate multiple optimum solutions, called "class of good solutions", for the total water system design problem. A case study from the literature is used to illustrate the proposed approach, and comparisons with the results from the current techniques were then made to demonstrate the proposed method's strength.