Degradation of antibiotics and profiling of transformation products upon peracetic acid–mediated treatment of electrochlorinated groundwater in a flow–through reactor

Abstract

Preventing the formation of hazardous chlorinated transformation products (Cl–TPs) when applying the electrochemical advanced oxidation processes (EAOPs) is a major challenge for ensuring their broader scale-up. In this context, the addition of peracetic acid (PAA) can potentially contribute to reduce the risk of Cl–TPs, but the associated transformation pathways remain insufficiently understood. Here, PAA–mediated electrochlorination process was found to reduce typical Cl-TPs (e.g., chloroform below 60 μg L^–1) by 26.9%~80.8%. Under optimized conditions, an innovative PAA–based treatment in a single-pass flow–through electrochemical reactor achieves the removal of four mixed antibiotics with low specific energy consumption (5.3 Wh mmol^–1). The antibiotics concentration in the effluent remained below the detection limit within 10 operation cycles. In addition, reductions in Cl–TPs were achieved in both simulated and actual groundwater, meeting the 2022 Chinese drinking water quality standards. Fourier transform ion cyclotron resonance mass spectrometry (FT−ICR MS) revealed that PAA–based electrochlorination preferentially removed highly unsaturated heavy byproducts (O/C <0.3, MW >400 Da), and the CHOCl formulae number decreased by 59%. The transformation pathways of Cl–TPs were mainly identified as decarbonylation, dihydroxylation, and hydrogenation. Moreover, the possible halogenation pathways number showed a significant decrease of 77.9%. These findings provide deeper insights into the degradation mechanisms and Cl–TPs minimization during PAA−mediated electrochemical antibiotic degradation, shedding light on the transformation processes in diverse environmental scenarios.