Coupling UVC254 nm-LED/H2O2 and Fenton processes for disinfection and contaminants of emerging concern removal in continuous mode for wastewater reclamation in accordance with EU 2020/741

A novel strategy based on the sequential combination of UVC254 nm-LED/H2O2 and the Fenton process at neutral pH in continuous flow mode for wastewater reclamation has been assessed. The concentration of Escherichia coli (E. coli) reached water class A according to the European Union (EU) Regulation 2020/741 (<= 10 CFU/100 mL) and a 87 +/- 2 % of the contaminants of emerging concern (CECs) load was removed, complying with the new proposal regarding Urban Wastewater Treatment (Directive COM (2022) 541). To reach these results, initially the municipal wastewater secondary effluent was kept under UVC254 nm-LED/H2O2 process with a hydraulic residence time (HRT) of 5 min, a liquid depth of 5-cm and 1.8 mmol L-1 of H2O2. In the sequence, addition of Fe2+ to the outside of the UVC254 nm-LED reactor was added to acquire the desired concentration of 1.8 mmol L-1 Fe2+ (Fenton process). To obtain the same disinfection and CECs degradation by only UVC254 nm-LED/H2O2 process, 45 min-HRT were necessary. These results show that the coupled processes are the best strategy, given the reduction in HRT (from 45 to 5 min) and total cost (from 1.79 to 0.54 <euro> m(-3)). In addition, new research on the application at pilot scale will encourage to evaluate the long-term toxicity of the reclaimed wastewater and to identify the main transformation products of the most abundant CECs.