This study aimed to investigate the performance of direct (UV) and hydrogen peroxide-assisted (UV/H2O2) photolysis applied to MBR permeate as a pre-treatment for nanofiltration systems treating petroleum refinery wastewater. The MBR permeate was subjected to UV and UV/H2O2 (C:H2O2 1:1, 1:2 and 1:3) in order to reduce the membrane fouling potential of nanofiltration in the polishment stage. The process that promoted the lower fouling potential was chosen as pre-treatment for nanofiltration process. The results showed that MBR permeate COD removal efficiency of 80% is enough for membrane fouling mitigation and that C:H2O2 ratio of 1:3 with retention time of 60 min is the best technical and economic condition for that. The H2O2/UV showed potential for the mitigation of flux decline due to membrane fouling, improvement in membrane cleanability, which consequently prolongs the NF membrane lifespan. The total operational cost (OpEx) for the H2O2/UV was estimated to be 0.231 US$/m(3) and the integration of H2O2/UV to NF process represents savings of 20% of CapEx and 20% of OpEx. Finally, the MBR-H2O2/UV - NF process produces high quality water that can be reused in the refinery process, such as in cooling systems.