Petrochemical industry is a great water consumer sector, producing wastewater with complex composition and at high volumes (around 1,750 millions of m3 per year). In order to introduce the circular economy concept into the petrochemical sector, LIFE-REWATCH project aims to demonstrate, at pilot scale, a technology available to treat and reuse the produced wastewater into the same facility. In order to achieve the goals of LIFE-REWATCH, experts on the wastewater treatment from Fundació Eurecat, DuPont Water Solutions and Veolia Water Technologies Ibérica has been formed an interdisciplinary group. The treatment scheme includes five stages: (i) Actiflo coagulation-ballasted flocculation process, (ii) AnoxKaldnes moving bed biofilm reactor (MBBR), (iii) DuPont Ultrafiltration process, (iv) DuPont FILMTEC Reverse Osmosis and (v) DuPont Ion Exchange Resins technology. The prototype is located on Dow Chemical Ibérica’s (DCI) petrochemical complex in Tarragona (Spain) and treats the produced wastewaters from olefins steam cracker and octene plant. Initially, MBBR was started to get successful biofilm formation and steady state conditions. Secondly, Actiflo commenced last week. Actiflo is treating the effluent of the MBBR and the operational conditions will be optimized during the following weeks. DuPont Ultrafiltration is planned to be started this week and will also be optimized in the short term to allow the operation of reverse osmosis downstream.