Water resource management poses a challenge in the process industry because a large amount of water must be used, even when prices increase. Companies struggle to minimize consumption by reusing wastewater, and the resulting water-reuse-network problem has been actively investigated. With the rising impact of global climate change, it is necessary to develop a sustainable methodology to reduce carbon dioxide emissions in the process industry. This paper proposes a mathematical model for sustainable water reuse networks that explicitly considers CO2 emissions. To construct a sustainable network, emissions due to the construction and operation of the water network and additional water demand due to CO2 capture facilities are incorporated. Actual case studies of steel manufacturing processes and eco-industrial parks are presented to illustrate the applicability of the model.