<p>The aim of this work is to develop an intelligent and robust decision support system (DSS). Thirteen indicators have been applied, and they are on the basis of the main pillars of the sustainability policy, which involve the environmental impacts, economic aspects, social issues, and technical performances. The DSS involves the simultaneous evaluation of criteria and alternative (SECA) technique and the quintic fuzzy set theory to obtain the weights of the indicators and the prioritization of the decision options. The findings obtained from the present work show that the sequence of preference of the demulsification techniques under scrutiny is as follows: chemical demulsification, electrical demulsification, biological demulsification, microwave irradiation demulsification, and membrane demulsification as the first to fifth options. Therefore, chemical demulsification has been recognized as the sustainable and optimal demulsification technique for water-in-oil (W/O) and oil-in-water (O/W) emulsions in Iran’s oil and gas industry. The development of this demulsification technique should be highly promoted to help the processes of the studied industry in Iran. The results point to this work could give robust and reliable findings for selecting the optimal demulsification technique, and they are expected to have an important effect on the oil and water separation process for the oil and gas industry.</p> Graphical Abstract <p></p>