The objective of this paper is to introduce an optimization approach to the design of an integrated system of multi-effect distillation (MED) and membrane distillation (MD). Brine from the MED system is further treated in the MD network to enhance the recovery of fresh water and to reduce brine disposal. The desalination system is thermally integrated with an industrial facility to use excess process heat to reduce the cooling load for the industrial process and to decrease the heating load for the desalination system. A superstructure-based optimization formulation is developed and solved to determine the key design and operating variables. A case study is solved to illustrate the usefulness of the proposed approach. (C) 2017 Elsevier B.V. All rights reserved.