In this study is presented the result obtained for the treatment of waste water from the medical sector using membrane filtration system. Polyethersulfone (PES) membranes were obtained using Dimethylformamide DMF like solvent, with different concentration to determine the rejection variation of different dyes. Membranes were obtained by the immersion precipitation method and permeation properties were determined by dead end technique. The results show that the membranes filtration method can by improved to reduce the cost of the water treatment from the medical sector. Using DMF solvent membranes with a smaller concentration of polymer have a good rejection results in comparison with other membranes obtained with different solvents.