The chapter will explore the treatment of petroleum industry effluents using membrane processes, as alone technologies or combined with activated sludge systems. It begins by discussing the composition and environmental impact of effluents generated by the petroleum industry, emphasizing the challenges posed by high concentrations of oil, grease, salinity, organic matter, and toxic compounds. The chapter then examines the principles and applications of membrane processes, such as microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis and membrane distillation in removing contaminants from these effluents. A detailed analysis is provided on the synergistic potential of integrating membrane processes with activated sludge systems, in a membrane bioreactor, highlighting how this combination can enhance contaminant removal efficiency, reduce fouling, and improve overall treatment performance. Case studies and examples of industrial-scale applications are presented, demonstrating the feasibility, operational challenges, and cost-effectiveness of these treatment strategies. The chapter concludes by discussing future directions, including advancements in membrane materials, fouling mitigation techniques, and the integration of these technologies with emerging approaches to achieve sustainable and efficient treatment of petroleum industry effluents.