Abstract

Oily sludge has been an emerging concern as a waste product in the petroleum industry. It is generated in huge amounts in both upstream and downstream industries. Oily sludge is a very complex matrix with a wide range of constituents including light and heavy petroleum hydrocarbons (PHCs), solids, water and different kinds of heavy metals such as nickel and vanadium. Since oily sludge has proven to expose dangers to the public health and the environment, it has been considered as hazardous waste and its treatment before disposal has been essential. Oily sludge is a very stable water-in-oil suspension that is naturally emulsified by PHCs and small solid particles, and hence its treatment is a challenging issue. The objective of this study is to present the electrokinetic method as a sustainable approach to the successful treatment of oily sludge. To achieve this purpose, a novel design of the EK reactor was proposed to undergo further investigation. The optimization of the EK reactor design was conducted on a small scale. The new design was applied to larger scales with the required modifications. In order to enhance phase separation and obtain a higher quality of recovered material, different additives were introduced into the system. Ferric chloride proved to be the most effective one according to the qualitative and quantitative study. The large-scale EK reactor (20 L) achieved 35% of water recovery and 15% of oil recovery while it reduced the disposable volume by 35% after 150 hours of operation. The optimal conditions and configurations of the batch system were used to design an innovative continuous-flow reactor. The new reactor aimed to attain a higher recovery of oil and water and lower energy consumption during a 24-h retention period. A water recovery of 31% and an oil recovery of 11% was accomplished after 24 hours as a result of the successful operation of the novel system. The developed EK systems are ready to be applied at full scale to treat industrial and municipal sludge.