Effective attenuation of extracellular antibiotic resistance gene risks in wastewater by capacitive deionization

Abstract

Despite the effective inactivation on antibiotic resistant bacteria, current water and wastewater treatment technologies are often ineffective in removing antibiotic resistance genes (ARGs), which remain active outside cells, known as extracellular ARGs (eARGs). eARGs can persist for a long time and facilitate bacterial transformation in receiving environments, thereby, posing a threat to public health. This study applied capacitive deionization (CDI), as a promising desalination technology, for eARGs removal from wastewater. Results showed that CDI using carbon electrodes was significantly more effective than activated carbon adsorption in removing eARGs, with the removal efficiency and rate constant that are 2.1–11.2 times (p < 0.05) and 2.5–13 times (p < 0.05) higher. In the flow-by mode, CDI achieved the highest removal of eARGs (3.5 log) in just 15 min. Furthermore, CDI treatment significantly decreased the frequency of horizontal gene transfer (HGT) and increased potential for natural degradation, thereby reducing the risk of eARGs propagation. The high electric field (>1000 V/m) applied in CDI induces DNA conformational damage and DNA sequence mutations, which are the main mechanisms for removing eARG. This study will provide technical guidance and theoretical support for the removal of eARG in wastewater.