Effect of booster disinfection on the prevalence of microbial antibiotic resistance and bacterial community in a simulated drinking water distribution system

Booster disinfection was often applied to control the microorganism's growth in long-distance water supply systems. The effect of booster disinfection on the changing patterns of antibiotic resistance and bacterial community was investigated by a simulated water distribution system (SWDS). The results showed that the antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) were initially removed after dosing disinfectants (chlorine and chloramine), but then increased with the increasing water age. However, the relative abundance of ARGs significantly increased after booster disinfection both in buck water and biofilm, then decreased along the pipeline. The pipe materials and disinfectant type also affected the antibiotic resistance. Chlorine was more efficient in controlling microbes and ARGs than chloramine. Compared with UPVC and PE pipes, SS pipes had the lowest total bacteria, ARB concentration, and ARB percentage, mainly due to higher disinfectant residuals and a smoother surface. The significant correlation (rs = 0.77, p < 0.001) of the 16S rRNA genes was observed between buck water and biofilm, while the correlations of targeted ARGs were found to be weak. Bray-Curtis similarity index indicated that booster disinfection significantly changed the biofilm bacterial community and the disinfectant type also had a marked impact on the bacterial community. At the genus level, the relative abundance of Pseudomonas, Sphingomonas, and Methylobacterium significantly increased after booster disinfection. Mycobacterium increased after chloramination while decreased after chlorination, indicating Mycobacterium might resist chloramine. Pseudomonas, Methylobacterium, and Phreatobacter were found to correlate well with the relative abundance of ARGs. These results highlighted antibiotic resistance shift and bacterial community alteration after booster disinfection, which may be helpful in controlling potential microbial risk in drinking water.