Search

To comprehensively understand the profile of free-living bacteria and potential bacterial pathogens in sewage treatment plants (STPs), this study applied high-throughput sequencing-based metagenomics approaches to investigate the effects of activated sludge (AS) treatment process and ultraviolet (UV) disinfection on the community of bacterial pathogens in two full-scale STPs. A total of 23 bacterial genera were identified as free-living bacteria, and 243 species/OTU97% were identified as potential bacterial pathogens, 6 of which were confidently detected in the STPs (with the total abundances ranging from 0.02 to 14.19%). Both diversity and relative abundance of the detected bacterial pathogens decreased obviously after AS treatment process (p < 0.05), and increased slightly after sedimentation (p < 0.05). UV disinfection shows no obvious effects on the total relative abundance of the free-living pathogenic bacteria in sewage. Although large amounts of the particle-bound pathogens were eliminated through the sewage treatment process, the STPs could not effectively remove the free-living bacterial pathogens, and some pathogenic bacteria (e.g., Pseudomonas aeruginosa) present in the effluent had higher relative abundance after UV disinfection. Overall, the results extend our knowledge regarding the community of potential pathogens (especially free-living pathogens) in STPs. [ABSTRACT FROM AUTHOR]

As antibiotic resistance continues to spread globally, there is growing interest in the potential to limit the spread of antibiotic resistance genes (ARGs) from wastewater sources. In particular, operational conditions during sludge digestion may serve to discourage selection of resistant bacteria, reduce horizontal transfer of ARGs, and aid in hydrolysis of DNA. This study applied metagenomic analysis to examine the removal efficiency of ARGs through thermophilic and mesophilic anaerobic digestion using bench-scale reactors. Although the relative abundance of various ARGs shifted from influent to effluent sludge, there was no measureable change in the abundance of total ARGs or their diversity in either the thermophilic or mesophilic treatment. Among the 35 major ARG subtypes detected in feed sludge, substantial reductions (removal efficiency >90 %) of 8 and 13 ARGs were achieved by thermophilic and mesophilic digestion, respectively. However, resistance genes of aadA, macB, and sul1 were enriched during the thermophilic anaerobic digestion, while resistance genes of erythromycin esterase type I, sul1, and tetM were enriched during the mesophilic anaerobic digestion. Efflux pump remained to be the major antibiotic resistance mechanism in sludge samples, but the portion of ARGs encoding resistance via target modification increased in the anaerobically digested sludge relative to the feed. Metagenomic analysis provided insight into the potential for anaerobic digestion to mitigate a broad array of ARGs. [ABSTRACT FROM AUTHOR]