Spatial and Temporal Dynamics in Attached and Suspended Bacterial Communities in Three Drinking Water Distribution Systems with Variable Biological Stability

Abstract

Microbial presence and regrowth in drinking water distribution systems (DWDSs) is routinely monitored to assess the biological stability of drinking water without a residual disinfectant, but the conventional microbiological culture methods currently used target only a very small fraction of the complete DWDS microbiome. Here, we sequenced 16S rRNA gene amplicons to elucidate the attached and suspended prokaryotic community dynamics within three nonchlorinated DWDSs with variable regrowth conditions distributing similarly treated surface water from the same source. One rural location, with less regrowth related issues, differed most strikingly from the other two urban locations by the exclusive presence of Pseudonocardia (Actinobacteria) in the biofilm and the absence of Limnobacter (Betaproteobacteriales) in the water and loose deposits during summer. There was a dominant seasonal effect on the drinking water microbiomes at all three locations. For one urban location, it was established that the most significant changes in the microbial community composition on a spatial scale occurred shortly after freshly treated water entered the DWDS. However, summerly regrowth of Limnobacter, one of the dominant genera in the distributed drinking water, already occurred in the clean water reservoir at the treatment plant before further distribution. The highlighted bacterial lineages within these highly diverse DWDS communities might be important new indicators for undesirable regrowth conditions affecting the final drinking water quality.

The Bacterial Community Diversity of Bathroom Hot Tap Water Was Significantly Lower Than That of Cold Tap and Shower Water

“…In addition, no significant linear correlations were found between ambient temperature and both Shannon and Inverse Simpson diversity indices of the water samples (p > 0.05) (Table 1). By contrast, previous studies found clear seasonal variations in bacterial communities of cold drinking water (McCoy and VanBriesen, 2012;Henne et al, 2013;Pinto et al, 2014;Prest et al, 2016b;Vavourakis et al, 2020). We hypothesize that the lack of clear seasonal variations in bacterial communities in the current study could be because the HPS simulator delivered temperature-stable tap and shower water to the bathroom.…”

“…Mycobacteriaceae contains a single genus Mycobacterium which is an important drinking water opportunistic pathogen (Good, 1985;Marciano-Cabral et al, 2010;Lu et al, 2017;Wang et al, 2019;Zhang and Lu, 2021). For both cold and hot tap water, the relative abundance of Burkholderiaceae (one dominant family in drinking water and PPSs) (Zeng et al, 2013;Buse et al, 2014;Ferro et al, 2019;Vavourakis et al, 2020) and Xanthobacteraceae (associated with nitrogen fixation) (Oren, 2014) obviously dropped in the second draws (compared with the first draws) (Figure 3). By contrast, the relative abundance of Azospirillaceae (associated with nitrogen fixation) (Sridevi et al, 2012), Obscuribacterales_fa, Moraxellaceae (contains potentially opportunistic pathogens) (Pettersson et al, 1998;Inkinen et al, 2018), and Hyphomonadaceae (contains "strict aerobic and stalked and non-stalked species") (Abraham and Rohde, 2014) significantly increased in the second draws for both cold and hot tap water.…”

“…Monitoring microbial community structures in EWSs is essential to estimate the health risks of water-related microbes (especially opportunistic pathogens), develop strategies to mitigate those risks, and meet increasingly strict drinking water regulations and policies (Hwang et al, 2012;Pinto et al, 2014;Wang et al, 2017;El-Chakhtoura et al, 2018;Perrin et al, 2019;Zhang and Liu, 2019;Zhang and Lu, 2021). Studies have intensely examined microbial community structures in cold tap/drinking water (as well as the corresponding biofilms) from EWSs and linked the structures to various factors such as seasonally changing environmental factors (e.g., ambient temperature, precipitation, and nutrients level) (McCoy and VanBriesen, 2012;Henne et al, 2013;Pinto et al, 2014;Ling et al, 2016;Prest et al, 2016b;Zhang and Liu, 2019;Vavourakis et al, 2020), treatment trains at water utilities (Pinto et al, 2012), disinfectant residual (e.g., free and combined chlorine) levels (Hwang et al, 2012;Waak et al, 2019;Zhang and Lu, 2021), and pipe network flushing (Douterelo et al, 2014;El-Chakhtoura et al, 2018). In addition to cold tap water, the end-consumers frequently contact two essential points of human exposure: hot tap water and shower water (a mixture of cold and hot tap water).…”

Improved Drinking Water Quality after Adding Advanced Oxidation for Organic Micropollutant Removal to Pretreatment of River Water Undergoing Dune Infiltration Near the Hague, Netherlands

“…From the collected water samples, a maximum of 1000 ml was filtered through a polycarbonate membrane filter with a 0.2 µm pore size (Track-etch membrane, Sartorius, The Netherlands). Filters were stored at − 20 • C until further DNA extraction and 16S rRNA amplicon sequencing, which was done as described previously (Vavourakis et al, 2020). Negative controls (water samples of DNase/RNase free water) and positive controls (Zymo DNA mock communities) were also added during filtration and subsequent DNA extraction.…”

Reproducible Microbial Community Dynamics of Two Drinking Water Systems Treating Similar Source Waters

“…Factors influencing the drinking water microbiome are site specific due to the unique type and combination of treatment technologies across DWTPs and DWDS configurations, source water types, and operational practices. − Thus, while the impact of individual treatment process or environmental conditions on the drinking water microbiome may be compared across DWTPs and DWDSs, it is often impossible to perform a paired comparison between drinking water systems due to the inability to control for the type and sequential combination of treatment and distribution practices. For instance, studies have investigated drinking water microbiome dynamics in multiple DWTPs that use similar treatment processes but utilize different source waters or utilize the same source water but different treatment approaches and/or disinfection residual free systems. − In addition, often such comparisons are limited to either the treatment system or the distribution system but rarely encompass a comprehensive source-to-tap analysis. To the best of our knowledge, no study has yet investigated the impact of identical drinking water treatment regimens and similar distribution practices on the drinking water microbiome in the same full-scale systems utilizing similar source waters.…”