Simultaneous removal of micropollutants, antibiotic resistant bacteria, and antibiotic resistance genes using graphitic carbon nitride under simulated solar irradiation

Abstract

The prevalence of micropollutants (MPs) and antibiotic resistance in aquatic environments has raised increasing concern for public health and ecological security. Conventional wastewater treatment processes have limited efficiency to remove these emerging contaminants. Recently, photocatalytic processes have been proposed as a promising solution to achieve enhanced performance, but there are very few studies focusing on simultaneous removal of both chemical and biological contaminants. To test the technical feasibility of a “one-stop” photocatalytic process, we evaluated the photocatalytic performance of a urea-based graphitic carbon nitride (g-C3N4) for simultaneous removal of multiple MPs, as well as antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). After a 10 min treatment under simulated solar irradiation, five MPs including sulfamethoxazole, diclofenac, mecoprop, benzotriazole, and carbamazepine (10 µg/L each) were effectively removed from spiked MilliQ water (88% of total removal efficiency) and real wastewater effluent (83% of total removal efficiency), respectively. In addition, 6.2-log reduction (complete inactivation) and 4.3-log reduction of ARB were observed after 60 min reaction in MilliQ water and real wastewater effluent, respectively. Moreover, ARB lost their self-repair function after the treatment. Lastly, atomic force microscopy images and qPCR analysis revealed that, not only the abundance of ARB but also extracellular ARGs (e-ARGs) decreased over the treatment peroid. Experiments trapping reactive species suggested that superoxide radicals (O2•-) and holes (h+) were the major active radicals contributing to contaminants degradation. The effective treatment performance for both chemical and biological contaminants, low manufacturing costs and ease of use make g-C3N4 a promising catalyst for application in the tertiary wastewater treatment processes.