Comparison of O3, UV/O3, and UV/O3/PS processes for marine oily wastewater treatment: Degradation performance, toxicity evaluation, and flocs analysis.

• Light and heavy crude oils and three O 3 -based processes were examined/compared. • UV/O 3 /PS process removed more than 90% of crude oils in 30 min. • 100% of the n -alkanes and PAHs and over 90% of TOC were removed in 1 h in UV/O 3 /PS process. • Acute toxicity of effluent to Vibrio fischeri and Artemia franciscana was significantly reduced. • Flocs characterization revealed the fate of insoluble components during oxidation. Efficient on-site treatment technology is crucial for mitigating marine oily wastewater pollution. This work investigates the ozone (O 3), ultraviolet (UV)/O 3 , UV/O 3 /persulfate (PS) processes for the treatment of marine oily wastewater, including degradation performance, acute toxicity evaluation, and oil flocs analysis in a benchtop circulating flow photoozonation reactor. Degradation performances have been studied by measuring the degradation rate of total oil concentrations, specific oil components (n -alkanes and polycyclic aromatic hydrocarbons (PAHs)), and total organic carbon (TOC). The results show that UV/O 3 /PS could significantly enhance the removal efficiency than the other two processes, with above 90% of removal efficiency in 30 min. Acute toxicity analysis further shows that the wastewater quality is significantly improved by four-fold of the EC 50 of Vibrio fischeri , and the mortality of Artemia franciscana decreases from 100% to 0% after 48 h exposure. Further, the morphology and functional groups of flocs have been further characterized, showing that the floating flocs could be further degraded especially in UV/O 3 /PS process. Our study further raised discussions regarding the future on-site application of O 3 -based systems, based on the results generated from the treatment efficiency, toxicity, and flocs characterization. The regulation of the oxidation strength and optimization of the reaction systems could be a practical strategy for on-site marine oily wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]