Comparison of the new Cl 2 /O 3 /UV process with different ozone- and UV-based AOPs for wastewater treatment at pilot scale: Removal of pharmaceuticals and changes in fluorescing organic matter.

This work critically compared the removal of fluorescing PARAFAC components and selected pharmaceuticals (carbamazepine, fluoxetine, gemfibrozil, primidone, sulfamethoxazole, trimethoprim) from a tertiary wastewater effluent by different UV- and ozone-based advanced oxidation processes (AOPs) operated at pilot-scale. Investigated AOPs included UV/H ₂ O ₂ , UV/Cl ₂ , O ₃ , O ₃ /UV, H ₂ O ₂ /O ₃ /UV, and the new Cl ₂ /O ₃ /UV. AOPs comparison was accomplished using various ozone doses (0-9 mg/L), UV fluences (191-981 mJ/cm ² ) and radical promoter concentrations of Cl ₂  = 0.04 mM and H ₂ O ₂  = 0.29 mM. Chlorine-based AOPs produced radical species that reacted more selectively with pharmaceuticals than radical species and oxidants generated by other AOPs. Tryptophan-like substances and humic-like fluorescing compounds were the most degraded components by all AOPs, which were better removed than microbial products and fulvic-like fluorescing substances. Removal of UV absorbance at 254 (UV ₂₅₄ ) nm was always low. Overall, chlorine-based AOPs were more effective to reduce fluorescence intensities than similar H ₂ O ₂ -based AOPs. The Cl ₂ /O ₃ /UV process was the most effective AOP to degrade all target micro-pollutants except primidone. On the other hand, the oxidation performance of pharmaceuticals by other ozone-based AOPs followed the order H ₂ O ₂ /O ₃ /UV > O ₃ /UV > O ₃ . UV/Cl ₂ process outcompeted UV/H ₂ O ₂ only for the removal of trimethoprim and sulfamethoxazole. Correlations between the removal of pharmaceuticals and spectroscopic indexes (PARAFAC components and UV ₂₅₄ ) had unique regression parameters for each compound, surrogate parameter and oxidation process. Particularly, a diverse PARAFAC component for each investigated AOP resulted to be the most sensitive surrogate parameter able to monitor small changes of pharmaceuticals removal.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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