Environmental impacts and economic assessment of a large-scale pilot plant for micropollutants removal: Granular activated carbon vs. coupled advanced oxidation process-granular activated carbon treatments

Water scarcity requires efficient use, but also protection of surface water quality. Micropollutants are poorly removed in conventional wastewater treatment plants (WWTPs), necessitating the implementation of quaternary treatments to avoid their discharge. This study evaluates the environmental impacts and the cost of six treatment scenarios in a large-scale pilot plant (4–19 m³ d⁻¹) at Heiderscheidergrund WWTP (Luxembourg): stand-alone granular activated carbon (GAC) (fresh (F) and regenerated (R)), photo-Fenton (PF)+GAC (F and R), and UV/H₂O₂+GAC (F and R). The environmental impacts were evaluated using Life Cycle Assessment (LCA), which identified five principal impacts: global warming (GHG), photochemical ozone formation (POCP), human toxicity - cancer effects (HTP-C), resource depletion - energy carriers (E-RD), and water resource depletion (W-RD) as the most affected categories. The overall ranking of impacts across scenarios was: PF+FGAC > PF+RGAC > UV/H₂O₂+FGAC > UV/H₂O₂+RGAC > FGAC > RGAC. Electricity was the main contributor in almost all cases, whereas chemical reagents were more relevant in toxicity-related impacts. Sensitivity analysis revealed that replacing the current electric mix with 100 % renewables reduced GHG by up to 72 %, whereas 100 % fossil energy increased it by up to 173 %. For GAC, W-RD was particularly sensitive to the activation method, with alternative datasets increased up to 473 % in the fresh GAC scenario. Cost assessment showed stand-alone GAC as the cheapest option and coupled AOP-GAC systems incurring higher costs, mainly from energy. This integrated evaluation provided quantitative evidence to support the selection of sustainable quaternary treatments in line with European Union water resilience objectives. • Electricity use dominated most impact categories across all treatments. • Renewable mix reduced GWP by up to 72 %; fossil mix increased it by 173 %. • Water depletion strongly depended on the GAC activation process. • UV/H 2 O 2 +GAC achieved the best balance between impact and cost. • Regenerated GAC showed the lowest overall environmental impacts.