In industry, waste water is used, treated, and reused in vast amounts. A current trend is to combine the treatment operations and water usage of processing units in a single network, in order to increase efficiency. Designing and operating such an integrated network at minimal cost can be challenging. For example, an accurate mathematical model of such optimization problems yields a Mixed Integer Non-Linear Programming (MINLP), which is hard to solve. In this thesis, different modeling approaches are compared that solve this problem. Several linearization strategies are applied in order to obtain a Mixed Integer Linear Program (MIP). The focus of this research is on modeling approaches rather than search algorithms.