In this paper, a new systematic design methodology has been developed for thes imultaneous energy and water minimization in multiple-contaminant systems that also feature maximum re-use of water. In addition to allowing re-use of water in multiple-contaminant systems, issues about heat losses and flowrate changes inside unit operations have also been incorporated in this new design method. To implement such a design, two new design aspects are introduced; new method for â€œNon-isothermal Mixingâ€ point identification and new â€œSeparate Systemâ€ generation. The first aspect involves â€œnon-isothermal mixingâ€, which enables direct heat recovery between water streams, and therefore allows the reduction of the number of heat transfer units. The other aspect is the generation of â€œseparate system â€œin heat exchanger network design. The flexibility of mixing and splitting of water streams allows separate systems to be created as a cost-effective series of heat-exchanger units between freshwater and wastewater streams. The new design aspects have been illustrated with two examples.