Effects of Sedimentation and Aeration on Antibiotic Resistance Induction in an Activated Sludge Process

摘要

The influent of municipal wastewater treatment plant (WWTP) can contain micropollutants such as antibiotics, chlorine, detergents, and biocides. In vitro studies have shown that these micropollutants may induce antibiotic resistance in bacteria. Previous studies have reported increases or decreases of antibiotic resistant bacteria between the influent and effluent of WWTP in an unpredictable manner. Thus, the triggers of resistance induction in WWTP are still unknown. To investigate the effects of unit operations in WWTP on antibiotic resistance induction, we incubated sixteen strains of E. coli susceptible to norfloxacin under simulated conditions of the primary sedimentation tank (PST) and aeration tank (AeT) in sterilized and filtered wastewater from PST and AeT at 25℃ for 1 and 6 hours, respectively, which are typical hydraulic retention time of each tank. The minimum inhibition concentration (MIC) towards norfloxacin was compared before and after incubation to evaluate the occurrence of induction. We found that resistance to norfloxacin was more likely to increase in AeT than in PST. Higher growth was observed in strains that showed the largest increase in MIC. The longer contact time with the wastewater and the aeration are factors that appeared to induce antibiotic resistance in an activated sludge process.