Removal of antibiotic resistant bacteria and antibiotic resistance genes by an electrochemically driven UV/chlorine process for decentralized water treatment

Abstract

The UV/chlorine (UV/Cl2) process is a developing advanced oxidation process and can efficiently remove antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). However, the transportation and storage of chlorine solutions limit the application of the UV/Cl2 process, especially for decentralized water treatment. To overcome the limitation, an electrochemically driven UV/Cl2 process (E-UV/Cl2) where Cl2 can be electrochemically produced in situ from anodic oxidation of chloride (Cl−) ubiquitously present in various water matrices was evaluated in this study. >5-log inactivation of the ARB (E. coli) was achieved within 5 s of the E-UV/Cl2 process, and no photoreactivation of the ARB was observed after the treatment. In addition to the ARB, intracellular and extracellular ARGs (tetA, sul1, sul2, and ermB) could be effectively degraded (e.g., log(C0/C) > 4 for i-ARGs) within 5 min of the E-UV/Cl2 process. Atomic force microscopy showed that the most of the i-ARGs were interrupted into short fragments (< 30 nm) during the E-UV/Cl2 process, which can thus effectively prevent the self-repair of i-ARGs and the horizontal gene transfer. Modelling results showed that the abatement efficiencies of i-ARG correlated positively with the exposures of •OH, Cl2−•, and ClO• during the E-UV/Cl2 process. Due to the short treatment time (5 min) required for ARB and ARG removal, insignificant concentrations of trihalomethanes (THMs) were generated during of the E-UV/Cl2 process, and the energy consumption (EEO) of ARG removal was ∼0.20‒0.27 kWh/m3-log, which is generally comparable to that of the UV/Cl2 process (0.18–0.23 kWh/m3-log). These results demonstrate that the E-UV/Cl2 process can provide a feasible and attractive alternative to the UV/Cl2 process for ARB and ARG removal in decentralized water treatment system.