Water produced with the oil, which contains a mixture of organic and inorganic compounds, is the largest residue in the upstream oil industry. With the increase of extraction from oil and gas reservoirs, the volume of this water is increasing day by day and its improper discharge on land and sea will cause many environmental problems. So far, various methods have been used to treat the produced water in marine areas, but most of them are only suitable for primary pollution removal and a more efficient treatment system is needed to make the produced water reusable or discharge into the environment. One of the most important factors in determining the operating method in offshore platforms is space constraints. The use of intensive chemical and physical methods in oil rigs has been common in the past and today. In this paper, CFU technology, which has been used in marine areas since 2000, is introduced as the most suitable water treatment system in comparison with other technologies used. Proper separation efficiency, flexibility, insensitivity to various fluctuations, low cost and low space required by this system, have forced oil companies to use this technology more than before.