Strategic implementation of upflow microbubble airlift photocatalytic process to control heavy metal resistant-MDR bacteria and the associated genes in wastewater

Abstract

The emergence of multidrug resistance (MDR) and heavy metal resistance (HMR) in bacterial pathogens and genes through mobile genetic elements (MGEs) from wastewater effluents needs to be eradicated using green technology. HMR is critical to controlling antimicrobial resistance but has been neglected in most photocatalytic disinfection (PCD) studies. Advanced photocatalysis in antimicrobial studies requires a strategic approach to enhance the disinfection efficiency. This study applied an optimized upflow airlift photocatalytic reactor (UAPR) with microbubble air and blue light to remove the antimicrobial resistance (HMR–MDR bacteria (HMR–MDRB), HMR genes (HMRGs), antibiotic resistant genes (ARGs) and MGEs) and inhibit pathogenicity in a mixed culture of high-strength HMR–MDRB isolated from wastewater. Stable dissolved oxygen (DO) supplementation and blue light significantly affected the HMRGs and MGE reduction, resulting in enhanced disinfection activity (30 %) and reaction time (60 min) required for the complete inactivation of HMR-MDRB mixed culture. The process effectively reduced the blaNDM-1 (3.37 log), pbrT (2.18 log), intl1 (2.16 log), and tn916/1545 (4.07 log), with a PCD rate constant (kg) of 0.0515 min−1, 0.0359 min−1, 0.0292 min−1, and 0.0662 min−1, respectively. Process mechanism studies showed that the stable supplementation of DO was a critical factor in controlling the type of reactive oxygen species (ROS), resulting in type II ROS, 1O2, as the critical free radical contributing to the reduction of ARGs and integron, whereas h+ was the ROS for pbrT and transposon.