Treatment and reclamation of hydrocarbon-bearing oily wastewater as a hazardous pollutant by different processes and technologies: a state-of-the-art review

Hydrocarbon-containing oily wastewater generated by various industries creates a major environmental problem all over the world since petroleum products are commonly used as energy sources and raw materials in various industries. In case of offshore/coastal oil recovery operations, produced water is discharged through either shore side outfalls or coastal rim releases. In many cases, current disposal practices leads to severe environmental pollution by contamination of petroleum hydrocarbon to the surface, ground, and coastal waterways. Therefore, it is necessary to evaluate the performance of various processes for the recovery of petroleum hydrocarbons from wastewater. In this paper, a detailed review on the different separation/treatment processes of oily wastewater is presented. Previous and recent research works are reviewed in the area of oil-water separation from wastewater and also highlight the new developments in these areas. Various separation processes and technologies such as gravity separation, flotation process, membrane process, adsorption process, biological treatment, freeze/thaw process, and photocatalytic oxidation process (PoPs)/advanced oxidation processes (AoPs) are discussed and reviewed. The adsorption properties of a wide variety of porous sorbent materials in oily wastewater treatment, particularly in the area of oil spill cleanup, are also reviewed. The advantages and disadvantages of each process are critically discussed and compared.