Life cycle assessment of UVC-based advanced oxidation processes as quaternary treatments: Clostridium spp. inactivation and comparison with CECs removal

In this work, Life Cycle Assessment has been applied for the evaluation of UVC-based photochemical treatments to deal with wastewater treatment plant effluents. In particular, UVC photolysis, UVC/H₂O₂ combination and UVC/H₂O₂/Fe(II) (namely photo-Fenton) were tested at pH ca. 7.5. Clostridium spp. was chosen as target species to test disinfection. Both, UVC/H₂O₂ and photo-Fenton were able to decrease Clostridium spp. below detection limit in 5 min. Best results were reached with H₂O₂ concentration of 21 mM. Coupling coagulation-flocculation with the photochemical process was tested for effluents with high organic load and turbidity. Global warming potential selected UVC photolysis as the best treatment for disinfection from the environmental point of view, despite its lower efficiency. However, when CECs removal was considered using acetaminophen as target contaminant, photo-Fenton was the most efficient and the most sustainable option. Finally, LCA was applied to the experimental work performed in the laboratory, showing that the effect of reactions was negligible vs. sample collection and transportation, as well as analytical procedures which accounted for more than 99 % of the impact.