A cooling water system is widely used in industry, where cooling towers consume large amounts of fresh water each year. In this study, to reduce fresh water consumption of the system, thermal membrane distillation (TMD) is used to treat blowdown water of the cooling tower, and permeate water is sent back to the tower as makeup water. TMD is driven by waste heat of the process stream which is initially cooled by the cooling water system. To obtain the optimal framework with minimum cost, the design and operation of cooling towers and TMD are optimized simultaneously. A case study taken from industry is employed to express the effectiveness of the proposed model. Results show that the optimization model can obtain up to 29.4% reduction on fresh water consumption in comparison with the system without wastewater recovery. Results also indicate that when the water price is higher than 1.067$/ton, the structure with the TMD unit is profitable.