ena-STUDY-WDRC KAUST-13-06-2016-11:45:20:868-250
Fate and persistence of a pathogenic NDM-1-positive Escherichia coli strain in anaerobic and aerobic sludge microcosms
The presence of emerging biological contaminants in reclaimed wastewater has introduced new challenges when implementing wastewater reuse, as such emerging pollutants might impose a potential risk to the public health. To evaluate the effectiveness in the removal of such contaminants by the conventional wastewater treatment process, the fate and decay kinetics of Escherichia coli strain PI7 and its plasmid encoded antibiotic resistance genes (ARGs) were assessed in microcosms representing anaerobic and aerobic biological treatment units. E. coli PI7 decayed at a significantly slower rate in the anaerobic condition. Approximate half-lives of E. coli PI7 were 34 h and 5.1 h in the anaerobic and aerobic microcosms, respectively. In the aerobic microcosms, 1 in every 10000 E. coli cells were identified to be recalcitrant to decay and persist indefinitely in the sludge. While extracellular DNA quickly degraded in the liquid fractions of aerobic sludge, ARGs associated with the E. coli PI7 were detected to have transferred to other native microorganisms in the sludge. In contrast, no DNA decay was detected in the anaerobic sludge water matrix throughout the 24 h sampling period, highlighting the potential risk of ARG environmental dispersion associated with anaerobically treated wastewater effluents. This study points at the limited ability of biological treatment units to remove emerging biological contaminants, and emphasizes the importance in the implementation of advance membrane separation technologies to achieve effective pathogen containment.
The presence of emerging biological contaminants in reclaimed wastewater has introduced new challenges when implementing wastewater reuse, as such emerging pollutants might impose a potential risk to the public health. To evaluate the effectiveness in the removal of such contaminants by the conventional wastewater treatment process, the fate and decay kinetics of Escherichia coli strain PI7 and its plasmid encoded antibiotic resistance genes (ARGs) were assessed in microcosms representing anaerobic and aerobic biological treatment units. E. coli PI7 decayed at a significantly slower rate in the anaerobic condition. Approximate half-lives of E. coli PI7 were 34 h and 5.1 h in the anaerobic and aerobic microcosms, respectively. In the aerobic microcosms, 1 in every 10000 E. coli cells were identified to be recalcitrant to decay and persist indefinitely in the sludge. While extracellular DNA quickly degraded in the liquid fractions of aerobic sludge, ARGs associated with the E. coli PI7 were detected to have transferred to other native microorganisms in the sludge. In contrast, no DNA decay was detected in the anaerobic sludge water matrix throughout the 24 h sampling period, highlighting the potential risk of ARG environmental dispersion associated with anaerobically treated wastewater effluents. This study points at the limited ability of biological treatment units to remove emerging biological contaminants, and emphasizes the importance in the implementation of advance membrane separation technologies to achieve effective pathogen containment.