Author(s): Alba Hernandez-Zanoletty; Inmaculada Polo-Lopez; Isabel Oller; Sixto Malato; Ana Ruiz-Delgado; Samira Nahim-Granados; Jenny Flores; Oscar Cabezuelo; M. Luisa Marin; F. Bosca

Linked Author(s): Alba Hernández-Zanoletty

Keywords: Solar photocatalysis; Riboflavin; Wastewater purification; Rose Bengal; TiO2

Abstract: The treatment and reuse of urban wastewater is currently an actual alternative to mitigate water problems in terms of water stress, scarcity and/or bad quality in many areas around the world. Advanced Oxidation Processes (AOPs) have proven to be effective as tertiary treatments for the reduction or elimination of hazardous chemical compounds such as contaminants of emerging concern (CECs) and pathogenic microorganisms including antibiotic resistant bacteria and genes (ARG and ARB). Among AOPs, photocatalytic processes based on semiconductors and organic photocatalysts driven by sunlight have gained attention of researchers due to its good characteristics and effectiveness demonstrated for water purification. Nevertheless, important limitations on the up-scale still need investigation such as the catalyst separation or recovery after the water treatment. In this regard, the immobilization of catalysts to facilitate their recovery and recycling is one of the most investigated solutions. In fact, this concept has been applied to the heterogenization of semiconductors such as TiO₂ or organic photocatalysts on silica materials to improve the solar photocatalytic efficiency in aqueous solution. The aim of this study is to evaluate new immobilized photocatalysts, Riboflavin and Rose Bengal covalently bound to glass wool and TiO₂ supported on glass wool, for decontamination and disinfection of simulated effluents of urban wastewater (UWW). Preliminary tests were carried out under different operating conditions in a solar simulator SUNTEST XLS+ (Atlas Material Testing Solutions) with 30 W/m² irradiation average. The experimental set-up is composed of a UV-transparent tubular reactor (14 mm diameter) filled with 1 g/L of each corresponding immobilized photocatalyst. Water flows at 108 mL/min. Demineralized water spiked with sulfamethoxazole (SMX) (at 1 mg/L initial concentration) and Escherichia coli and Enterococcus faecalis (10⁶ CFU/mL initial concentrations each) were used as model of CECs and waterborne pathogens for the assessment of the photocatalytic efficiency of both immobilized photocatalysts. Prior to each experiment, the photocatalysts were washed to avoid any residual contamination. Results showed that riboflavin (10.9 g/L) was the best option for water disinfection, reaching 4 Log Reduction Value (LRV) in 100 min for E. coli and E. faecalis. On the other hand, the best result for water decontamination (SMX removal 75% in 120 min) was obtained with the TiO₂ photocatalyst (7.6 g/L) supported on glass wool, which also showed a large number of cycles of efficient reuse activity. Following working plan will be focused on testing the new immobilized photocatalysts in different photoreactor designs and optimize the mechanism of action, with a mixture of several different pollutants (CECs and pathogens) in natural water and actual UWW treatment plant effluents.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022915

Year: 2022