Hybrid/integrated treatment technologies for oily wastewater treatment

Managing oily wastewater generated by various sources has become one of the top priorities globally due to the severe and catastrophic effects caused in the case of improper management. So far, several technologies such as adsorption, flotation, coagulation/flocculation, advanced oxidation processes, membrane filtration, and biological methods have been used to treat oily wastewater. However, it is difficult to efficiently treat oily wastewater by individual methods due to the complexity of the organic matter, inadequate contaminants removal, and economic considerations. Therefore an efficient and broadly applicable approach for effectively separating various oil/water emulsions remains highly desired. Considering the particular features of each method, the integration of oily wastewater treatment processes provides an opportunity for minimizing the disadvantages of individual methods. Depending on costs, discharge standards, and wastewater characteristics, different designs may be applied for pretreatment and posttreatment stages in hybrid systems. The focus of this work is to review and evaluate current hybrid technologies available for treating oily wastewater based on treatment efficiency, cost-effectiveness, environmental friendliness, and footprint. Finally, the challenges of using hybrid technologies and research gaps are addressed for future studies.