Interplay of Biologically Active Carbon Filtration and Chlorine-Based Disinfection in Mitigating the Dissemination of Antibiotic Resistance Genes in Water Reuse Distribution Systems

Abstract

Appropriate management approaches are needed to minimize the proliferation of antibiotic resistance genes (ARGs) in reclaimed water distribution systems (RWDSs). Six laboratory-scale RWDSs were operated over 3 years receiving influent with or without biologically active carbon (BAC) filtration + chlorination, chloramination, or no disinfectant residual. Shotgun metagenomic sequencing was applied toward comprehensive characterization of resistomes, focusing on total ARGs, ARG mobility, and specific ARGs of clinical concern. ARGs such as aadA, bacA, bla OXA , mphE, msrE, sul1, and sul2 were found to be particularly sensitive to varying RWDS conditions. BAC filtration with chlorination most effectively achieved and maintained the lowest levels of nearly all metagenomically derived antibiotic resistance indicators. However, BAC filtration or addition of residual disinfectants alone tended to increase these indicators. Biofilm and sediment compartments harbored ARGs in disinfected systems, presenting a concern for their release to bulk water. Relative and absolute abundances of most ARGs tended to decrease with water age (up to 5 days), with notable exceptions in BAC-filtered chloraminated and no residual systems. Superchlorination of unfiltered water especially raised concerns in terms of elevation of clinically relevant and mobile ARGs. This study revealed that BAC filtration and disinfection must be carefully coordinated in order to effectively mitigate ARG dissemination via RWDSs.

Mapping the Terrain for Pathogen Persistence and Proliferation in Non-potable Reuse Distribution Systems: Interactive Effects of Biofiltration, Disinfection, and Water Age

“…Moreover, we observed that pathogen gene markers tended to be enriched in the biofilm in the chlorine condition and the presence in the biofilm at P0 may have shielded these FPs and non-FPs from disinfectants. − Notably, the genera of WHO priority pathogens that appear to have been enriched in the chlorinated condition are characterized by flexible genomes capable of acquiring new genes conferring antibiotic resistance and virulence . In this respect, it is worth noting that a parallel study of antibiotic resistance in these RWDSs found that the unfiltered, chlorinated waters also enriched antibiotic resistance genes and mobile genetic elements known to be associated with these pathogens …”

“…76 In this respect, it is worth noting that a parallel study of antibiotic resistance in these RWDSs found that the unfiltered, chlorinated waters also enriched antibiotic resistance genes and mobile genetic elements known to be associated with these pathogens. 77 It is acknowledged that some portion of the detections reported in this study do not represent viable microorganisms as this is an inherent limitation of molecular methods. However, this limitation does not explain the overall trends observed in this study.…”

Characteristics of Antibiotic Resistance Genes and Antibiotic-Resistant Bacteria in Full-Scale Drinking Water Treatment System Using Metagenomics and Culturing

“…Previous studies have reported that tetA could be removed using free chlorine, and this is similar to our results ( Amarasiri et al, 2020 ). However, some researchers have demonstrated that the abundance of sul 1 and sul 2 increased after chlorination ( Liu et al, 2018 ; Zhu et al, 2021 ). Subsequently, the shift of these ARGs remains controversial when chlorine is used.…”

Antimicrobial Resistance Monitoring of Water Environments: A Framework for Standardized Methods and Quality Control

“… 29 Research has also brought to light concerns about regrowth of resistant microorganisms in distribution systems, particularly in situations of nonpotable recycled water. 30 , 31 Thus, wastewater, recycled water, and impacted receiving waters have been identified as key candidate monitoring points for AMR in the environment 32 − 34 ( Figure 1 ).…”