Understanding the microbiota in drinking water distribution networks – from municipal to indoor water supply systems
"A drinking water distribution system can be viewed as an ecosystem that is comprised of diverse microorganisms interacting with each other and the environment. These microorganisms are central to water quality integrity during distribution. This study investigated the diversity, structure, and spatio-temporal variation of microbial communities in the municipal distribution system and indoor plumbing. The Champaign-Urbana water distribution system, which received conventionally treated and disinfected groundwater, was used as a model system. High throughput sequencing (454 pyrosequencing and Illumina Mi-seq sequencing) was used to study the diversity, and flow cytometry was used to quantify microbial abundance. For the municipal distribution system, the study focused on the biofilm component. Microbial communities were sampled from household water meters (n=213). Tap water communities (n=20) were also sampled for comparisons. A positive correlation between OTU abundance and occupancy was observed. Highly abundant and prevalent OTUs were observed and defined as ""core populations"" in the biofilm and suspended communities. The biofilm core population overlapped with the suspended community and formed a ""shared core population,"" including taxa related to methano-/methylotrophy and aerobic heterotrophy. Despite that, the biofilm community differed from the suspended community by specific core populations and lower diversity and evenness. Multivariate tests indicated seasonality as the main contributor to community structure variation. Indoor plumbing has smaller pipelines and is prone to stagnation, therefore biological growth is expected. However, the magnitude of biological growth and the possible community composition change is not clear. Thus, we examined the impact of stagnation on the community composition in the tap water community. We treated three dormitory buildings in Champaign-Urbana as natural laboratories and conducted a controlled stagnation test. Our results showed that the microbial abundance increased from <103 cells/mL to ~105 cells/mL after a week-long stagnation. The community structure of post-stagnation water significantly differed from the pre-stagnation water. Multivariate analysis showed a significant difference between stagnant and fresh tap water communities. The building, floor, and faucet of sample collection were also shown as significant sources of variation, yet to a lesser degree than stagnation. Temporal variation did not significantly influence the community structure. The post-stagnation communities further exhibited differentiation by flow volumes, which again indicate the influence from the pipeline structure. Methylotrophy and aerobic heterotrophy-related taxa were observed in the post-stagnation communities. Overall, this study has demonstrated that spatiotemporal experiments combined with hypothesis testing can lead to new understanding of drinking water supply systems. Source water community, seasons, and water use (stagnation) were shown to profoundly influence microbial communities in the distribution system. Our findings further showed taxa indicative of a certain carbon source and cell count gradients indicative of stagnation. These findings suggest that the microbiota in the distribution system is a valuable source of information within the distribution system and can be harnessed to complement current monitoring."
Drinking water, microbiome, disinfection, Miseq, unified neutral theory of biodiversity
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign