Divergent Bacterial Communities in Water and Sediment of Chlorinated Drinking Water Storage Tanks

Properly operated and maintained drinking water distribution system (DWDS) storage tanks are crucial for allocating safe drinking water, but varying operational processes and infrequent maintenance can result in water quality degradation, including disinfectant residual loss, sediment accumulation, bacterial growth, and potential contamination. This study assessed how the physical, chemical, and hydraulic characteristics of representative chlorinated DWDS tanks relate to bacterial communities in water and sediment; investigated water quality variation by depth within tanks; and explored the infrastructure and management characteristics influencing bacterial community composition in tanks. Bulk water and sediment samples were collected from seven tanks in a chlorinated DWDS system, and 16S rRNA gene amplicon sequencing was used to characterize the bacterial community. Bulk water and sediment communities were distinct, dominated by Alphaproteobacteria and Gammaproteobacteria, respectively. Spatial variations as a function of distance from the treatment plant, tank-specific characteristics, and sediment accumulation were found to shape bacterial communities within tanks. Total coliforms and <i>Escherichia coli</i> were undetectable in all water samples, but genetic signatures indicated the presence of multiple genera associated with opportunistic pathogens (OPs). This study aims to establish a deeper understanding of the bacterial community within DWDS tanks and the impact that tank conditions and characteristics have on DWDS water quality.