Removal of Micropollutants by Persulfate-Based Processes: the Role of Reactive Oxygen Species and Evaluation for WWTP Effluent Reclamation

Abstract Ten representative micropollutants (MPs) from the European Union's watch list of substances, the pharmaceuticals amoxicillin (AMX), ciprofloxacin (CFX), desvenlafaxine (DVF), sulfamethoxazole (SMX) and trimethoprim (TMX), and the fungicides fluconazole (FLZ), imazalil (IMZ), penconazole (PNZ), prochloraz (PCZ) and tebuconazole (TBZ), have been selected to evaluate their removal using Advanced Oxidation Processes (AOPs) based on the activation of persulfate by UV irradiation (UV/PS) and heat (PS/heat). These MPs with different physicochemical properties are commonly found in wastewater treatment plant (WWTP) effluents and can have negative effects on the environment and human health even at low concentrations. Second-order rate constants (k SO4 ) for the reaction of each MP with sulfate radicals (SO 4 · − ) were determined, varying between (2.73 ± 0.05) × 10 10 M −1 s −1 for CFX, and (3.5 ± 0.1) × 10 8 M −1 s −1 for FLZ. Radical scavenging experiments confirmed that the role of hydroxyl radicals (HO·) was dominant in the degradation of most MPs, while SO 4 · − contributed significantly to the removal of SMX, AMX, and CFX. The effect of the effluent organic matter (EfOM) was negative, especially for the PS/heat process. Disinfection by UV/PS and UV irradiation alone applied to WWTP effluents showed high levels of E. coli elimination. Finally, the productivity of each process was estimated in terms of energy efficiency, indicating that the processes tested remain economically viable for quaternary treatment targeting persistent pollutants. Results show that the UV/PS system is more efficient than the UV/heat process in terms of MPs removal, resulting in lower costs.