Advanced oxidation processes for the degradation of dissolved organics in produced water: A review of process performance, degradation kinetics and pathway

Produced water from oil and gas exploration is one of the major challenges posed by the energy sector due to the large volumes generated daily and the potential hazardous effects of the organic and inorganic constituents of produced water on the ecosystem. Although reuse and dilution through discharge in large water bodies may reduce this challenge, there is a continuous need for a proper treatment prior to disposal. Advanced oxidation processes (AOPs) are promising, efficient and eco-friendly technologies that utilize in-situ generated powerful oxidizing species such as hydroxyl radicals (•OH), sulfate radicals (SO4•−), superoxide radicals (O2•−) and others for a rapid and effective remediation of organic pollutants from wastewater. This critical review presented a concise overview of the recent literature (2010–2020) related to the treatment of dissolved organics in produced water by different AOPs. The sources, composition and natural attenuation of dissolved hydrocarbons in produced water were enumerated and their potential toxicity to aquatic organisms were examined. The fundamental principles, advantages, and drawbacks of different AOPs based on chemical, photochemical and electrochemical oxidation, as well as their applications to real and synthetic produced waters were presented and compared. Degradation byproducts generated during the treatment of produced water using AOPs and the reaction pathways were also discussed. Finally, the barriers/challenges that must be overcome for a successful scale-up and full-scale implementation of these treatment technologies were listed.