Photocatalysis as a potential tertiary treatment of urban wastewater: new photocatalytic materials

Heterogeneous UV-photocatalytic process has been studied as tertiary treatment of real municipal wastewater. Wastewater photocatalytic treatment was carried out using several materials previously developed as photocatalysts: volcanic ashes and nanostructured titania supported over volcanic ashes. Both material activities in particles were compared with Degussa TiO₂ (powder). Photocatalyst amount influence was studied by varying it between 2 and 10 g L⁻¹. Wastewater decontamination process was evaluated measuring the chemical oxygen demand evolution with phototreatment time in order to choose the best photocatalytic material and its optimal operation concentration. Moreover, the photocatalytic results obtained were compared with those obtained from photolysis and adsorption studies in wastewater using the same operation conditions. In addition, analyses of main wastewater parameters were made in order to evaluate the complete water decontamination process. Possibility of using photocatalysts in particles shows the main advantage of continuous photocatalyst separation from the water effluent once the decontamination process has finished. Good photocatalytic activities were observed, and it allows to conclude that heterogeneous photocatalysis is an effective method for municipal wastewater treatment, achieving water disinfection and phosphates removal.