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

Diverse
pathogens can potentially persist and proliferate in reclaimed
water distribution systems (RWDSs). The goal of this study was to
evaluate interactive effects of reclaimed water treatments and water
age on persistence and proliferation of multiple fecal (e.g., Klebsiella, Enterobacter) and non-fecal (e.g., Legionella,
mycobacteria) gene markers in RWDSs. Six laboratory-scale RWDSs were
operated in parallel receiving the influent with or without biologically
active carbon (BAC) filtration + chlorination, chloramination, or
no disinfectant residual. After 3 years of operation, the RWDSs were
subject to sacrificial sampling and shotgun metagenomic sequencing.
We developed an in-house metagenome-derived pathogen quantification
pipeline, validated by quantitative polymerase chain reaction and
mock community analysis, to estimate changes in abundance of ∼30
genera containing waterborne pathogens. Microbial community composition
in the RWDS bulk water, biofilm, and sediments was clearly shaped
by BAC filtration, disinfectant conditions, and water age. Key commonalities
were noted in the ecological niches occupied by fecal pathogen markers
in the RWDSs, while non-fecal pathogen markers were more varied in
their distribution. BAC-filtration + chlorine was found to most effectively
control the widest range of target genera. However, filtration alone
or chlorine secondary disinfection alone resulted in proliferation
of some of these genera containing waterborne pathogens.