Mitigation of antibiotic resistance: the efficiency of a hybrid subsurface flow constructed wetland in the removal of resistant bacteria in wastewater

This research investigates the effectiveness of a lab-scale hybrid subsurface flow constructed wetland (HSSFCW) for removing wastewater contaminants, including antibiotic-resistant bacteria (ARB), genes (ARGs) and antibiotics. The results suggested that HSSFCW demonstrated a high removal efficiency for COD (89%) and BOD (88.9%), while lower efficiencies were observed for salts, TDS, EC, and TKN. Further, various bacteria such as <i>Enterobacter cloacae, Serratia liquefaciens</i> and <i>Serratia odorifera</i> were detected in the plant rhizosphere, while <i>Acinetobacter baumanii</i> and <i>Staphylococcus spp.</i> were identified as biofilm formers on the wetland media. The mean removal efficiency of 70.44, 65.99, 70.66 and 51.49% was observed for total heterotrophic bacteria; Cefixime (Cef)-, Ciprofloxacin (Cip)-, and Linezolid (Lzd)-resistant bacteria. Upon chlorination of effluent samples, Cef-, Cip- and Lzd-resistant bacteria were effectively inactivated at 30, 15 and 7.5 mg Cl₂ min/L, respectively. The wetland achieved a removal efficiency of 83.85% for Cip and 100% for Lzd at week 12 with <i>p</i> = 0.040 and <i>p</i> < 0.001, respectively. Further, a log reduction of 0.66 for <i>16S</i>, 0.82 for <i>blaTEM</i>, 0.61 for <i>blaCTX,</i> and 0.48 for <i>blaOXA</i> was observed. Thus, HSSFCW was observed to be efficient in removing organic contaminants, ARBs, ARGs and antibiotics from domestic wastewater and can be upgraded under natural environments.