Investigation of the Removal of Several Micropollutants Presenting Different Ozone Reactivities from Natural Potable Water Matrix by the Application of Ozonation with the Use of SiO2 and Al2O3 as Catalysts

Abstract

The aim of this study was to investigate the correlation between solid materials and micropollutants, aiming to enhance the removal of the latter during the application of the ozonation process. For that purpose, two solid materials (SiO2 and Al2O3) presenting catalytic activity were used for the removal of eight micropollutants from natural potable water, containing them either separately or in a mixture, by ozonation. The studied micropollutants, presenting different physicochemical properties, are atrazine, ibuprofen, p-CBA (ozone-resistant compounds), benzotriazole, caffeine (with moderate ozone reactivity), carbamazepine, fluoxetine, paracetamol (easily oxidized by ozone). The residual concentrations of carbamazepine, paracetamol, and fluoxetine were found to be lower than 5.9 μg/L, 1.2 μg/L, and 15.5 μg/L, respectively, after 1 min of oxidation time in all studied systems. In contrast, benzotriazole and caffeine removal was enhanced by the addition of catalysts; in both cases the best catalyst was SiO2. Regarding the ozone-resistant compounds, both examined materials enhanced the removal of ibuprofen and p-CBA; however, the best was found to be SiO2 and Al2O3, respectively. In contrast, Al2O3 cannot be considered as an effective catalyst for the removal of atrazine, which presents chemical affinity only with SiO2 and for this reason it can be removed to a higher extent by its presence. Similar results were observed in the study of the mixture, although in this system, the residual concentration of all micropollutants was found to be under the detection limit after the application of catalytic ozonation.

Evaluation of Heterogeneous Catalytic Ozonation Process for the Removal of Micropollutants from Water/Wastewater: Application of a Novel Pilot-Scale Continuous Flow System

“…In the case of atrazine, the achieved degradation rates in the catalytic ozonation system reach 77%; however, the application of single ozonation appears to be better, regarding the removal of this organic compound, as it presents higher degradation rate (85%). The inhibition of atrazine removal during ozonation through the presence of a solid material (alumina, calcite, dolomite, goethite, pearlite, PET, zeolite) was also noticed by the authors during previous relevant studies [21,36,37], implying that in order for a material to act as an efficient catalyst in the heterogeneous catalytic ozonation process, especially in the case of ozone-resistant compounds, it must not only be able to increase the production of hydroxyl radicals but also be able to bring the pollutant into a closer encounter with these radicals in order for it to be efficiently oxidized [37], i.e., to present higher (or at least good) affinity both with the micropollutant and with the ozone/radicals. Namely, although ozone is adsorbed on the surface of the catalyst, promoting the formation of hydroxyl radicals, atrazine molecules are not adsorbed on the catalytic surface, indicating that the mechanism of this organic pollutant's degradation mainly includes its oxidation in the liquid phase.…”

Assessing the Effects of Ozonation on the Concentrations of Personal Care Products and Acute Toxicity in Sludges of Wastewater Treatment Plants

“…Ozonation carries the inherent danger of producing toxic oxidation by-products because chemical compounds are often not mineralized entirely but transformed into unknown intermediates instead [ 36 , 39 ]. It has been reported that adverse effects occurring after the ozone reactor are possibly due to the formation of toxic oxidation by-products [ 40 , 41 ]. Since there was no significant correlation when using H. azteca toxicity to test ozonation in sludge before and after treatment, chronic toxicity tests can be used to evaluate growth/reproductive effects in the future.…”