Roles of reactive oxygen species in antibiotic resistant bacteria inactivation and micropollutant degradation in Fenton and photo-Fenton processes

Reactive oxygen species play a critical role in degrading chemical or biological contaminants in advanced oxidation processes. However, it is still not clear whether conventional Fenton and photo-Fenton processes generate different reactive oxygen species, respectively. This study revealed the roles of reactive oxygen species (ROS) for simultaneous removal of antibiotic resistant bacteria (ARB) and recalcitrant micropollutant using three processes, i.e., conventional Fenton, photo-Fenton, and ethylenediamine-N, N'-disuccinic acid (EDDS) modified photo-Fenton. Both chemical scavengers and electron paramagnetic resonance spectroscopy confirmed the generation of various ROS and their contribution towards bacterial inactivation and micropollutant degradation. Results showed ARB and carbamazepine (CBZ) elimination efficiency in the order: EDDS modified photo-Fenton process > photo-Fenton process > Fenton process. The ARB detection limit (6-log ARB) was observed within 10 min at lower doses of 0.1 mM Fe3+, 0.2 mM EDDS, and 0.5 mM hydrogen peroxide (H2O2). With the same dose, it took longer (60 min) to remove CBZ, while 2.5 times higher H2O2 dose (1.25 mM) removed around 99% of CBZ within 10 min treatment. The present study highlighted that the hydroxyl radical (HO•) plays a dominant role, while singlet oxygen (1O2) and superoxide radical anion (O2•-) exhibit moderate effects to remove the hazards. Our findings provide mechanistic insights into the role of various reactive oxygen species on degrading micropollutants and inactivating ARB.