Efficiency of ozonation and sulfate radical - AOP for removal of pharmaceuticals, corrosion inhibitors, x-ray contrast media and perfluorinated compounds from reverse osmosis concentrates

Xenia A M Mutke; Philipp Swiderski; Felix Drees; Orkan Akin; Holger V Lutze; Torsten C Schmidt

doi:10.1016/j.watres.2024.121346

Efficiency of ozonation and sulfate radical - AOP for removal of pharmaceuticals, corrosion inhibitors, x-ray contrast media and perfluorinated compounds from reverse osmosis concentrates

Water Res. 2024 May 15:255:121346. doi: 10.1016/j.watres.2024.121346. Epub 2024 Feb 29.

Authors

Xenia A M Mutke¹, Philipp Swiderski¹, Felix Drees¹, Orkan Akin¹, Holger V Lutze², Torsten C Schmidt³

Affiliations

¹ Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141, Essen, Germany.
² Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141, Essen, Germany; IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany; Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany; Department of Civil and Environmental Engineering, Institute IWAR, Chair of Environmental Analytics and Pollutants, Technical University of Darmstadt, Franziska-Braun-Straße 7, 64287, Darmstadt, Germany.
³ Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141, Essen, Germany; IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany; Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany.

PMID: 38569355
DOI: 10.1016/j.watres.2024.121346

Abstract

This study investigated the elimination of pharmaceuticals, corrosion inhibitors, x-ray contrast media and perfluorinated compounds from reverse osmosis concentrates during ozonation and UV/persulfate processes. Second-order rate constants for the reactions of candesartan, irbesartan, methyl-benzotriazole, and chloro‑benzotriazole with sulfate radical (SO₄^·-) were determined for the first time. Experiments were conducted in buffered pure water, in buffered water added with the matrix substituents chloride, carbonate, NOM, and reverse osmosis concentrate with spiked micropollutants (MP). UV/persulfate eliminated all MP to a higher extent than ozonation in RO concentrates due to the higher yield of oxidative species and photolytic degradation. Compounds with electron-rich moieties such as carbamazepine, diclofenac, metoprolol, and sulfamethoxazole were completely eliminated with small ozone doses (< 0.5 mg O₃ / mg DOC) and with a small fluence (< 5000 J m^-2) in UV/persulfate processes. Photosensitive compounds with high reactivity towards hydroxyl radicals (^·OH) and SO₄^·- like the x-ray contrast media Iopamidol, Iohexol, and Amidotrizoic acid were successfully eliminated with a reasonable fluence in UV/persulfate, whereas these compounds persist in ozonation at common ozone dosages. However, much higher fluences and ozone dosages were required for the least reactive compounds like the class of benzotriazoles. Comparing the application of both oxidative processes to the RO concentrate, ozonation has the disadvantage of forming bromate. The energy input of both processes strongly depends on the target compounds to be eliminated. For the elimination of compounds such as sulfamethoxazole, ozonation is a feasible technique, whereas UV/persulfate is better suited for the elimination of recalcitrant compounds such as x-ray contrast media. In general, oxidative process treatment of RO concentrate could be applied to partly abate micropollutants before discharge.

Keywords: Hydroxyl radical; Micropollutants; Ozone; PFAS; Reverse osmosis concentrate; Sartans; Sulfate radical.