Produced water is the largest waste stream acquired in the recovery of oil and gas. Water treatment technologies have achieved significant progress in the treatment of conventional water in the recent years, hence reducing the burden of dealing with this byproduct and therefore removing the restriction of the production from unconventional resources. In order to efficiently develop these unconventional reservoirs, the tertiary recovery method (Enhanced Oil Recovery) can be used. This thesis focuses on a chemical flooding method entitled polymer flooding. The OMV Exploration & Production GmbH has a polymer flooding project, where a polymer solution is injected into two wells in the Matzen oilfield for several years. The water-soluble polymer is added to the injection water to increase the viscosity which leads to improving the volumetric sweep efficiency aspect of the oil recovery. After some time of continuous injection, the produced oilfield water contains back-produced polymer. However, it is important to treat and remove the back-produced polymer from the water so that the injection pressure stays as low as possible. Tests have shown that the back-produced polymer affects the efficiency of the dissolved flotation units in the OMV water treatment plant, which is only designed to treat conventional water. In this thesis, a pilot plant called micro-bubble flotation was tested. This pilot plant has a multi-chamber flotation unit with the combination of both dissolved gas flotation and induced gas flotation. This unit was tested for the treatment of back-produced polymer and compared with the dissolved flotation unit in the OMV water treatment plant. The unit can operate up to a flow rate of 33 m3/h. The tests were done with a low flow rate of 1.2 m3/h, which is the rate of the well containing back-produced polymer. Additionally, a higher flow rate of 13 m3/h was done also, which reflects the conventional wells flow rate. Different amounts of chemicals were analyzed during the time of this pilot plant trial. The pilot plant is supplied with formation water coming from nine different wells of an underground oil reservoir in the 8. TH Tortonian reservoir, which is located in the Matzen oilfield. Different trials were tested within the pilot plant: conventional water with different flow rates with and without chemicals, back-produced polymer water with and without chemicals. Samples were taken on a daily basis from all sample points (inlet to outlet) and the water phase was analyzed according to different parameters such as oil-in-water concentration, total suspended solids, polymer content and turbidity.