Application of solar photocatalytic ozonation for the degradation of emerging contaminants in water in a pilot plant

Aqueous mixtures of six commonly detected emerging contaminants (acetaminophen, antipyrine, bisphenol A, caffeine, metoprolol and testosterone), selected as model compounds, were treated by different solar-driven photochemical processes including photolysis, photocatalytic oxidation with Fe(III) or TiO2, photo-Fenton and single, photolytic and photocatalytic ozonations. Experiments were carried out in a compound parabolic collector photoreactor. It was found that photolysis and photocatalytic oxidation using Fe(III) are not effective for the complete removal of the selected contaminants, while TiO2 photocatalysis, photo-Fenton, single, photolytic and photocatalytic ozonations can rapidly remove them and decrease total organic carbon to some extent. The combination of photocatalytic oxidation and ozonation considerably enhances the system efficiency by reducing the ozone demand and energy requirements to completely remove the contaminants. Results also demonstrate that, at the operational conditions applied in this work, the contaminant removal and mineralization by ozone processes takes place in the slow kinetic regime, therefore the application of the ozone combined processes studied instead of single ozonation is recommended. Kinetic considerations on the application of solar photocatalytic processes for mineralization have been also assessed. (C) 2014 Elsevier B.V. All rights reserved.