Microbial communities in premise plumbing systems were investigated after more than 2 months of long-term stagnation, during a subsequent flushing event, and during post-flush stagnation. Water samples were collected from showers in buildings supplied with chlorinated groundwater, untreated groundwater, and chloraminated surface water. The building supplied with chlorinated groundwater generally had the lowest bacterial concentrations across all sites (ranging from below quantification limit to 5.2 log copies/L). For buildings supplied with untreated groundwater, bacterial concentrations (5.0 to 7.6 log copies/L) and microbial community diversity index (ACE) values were consistent throughout sampling. Nontuberculous mycobacteria (NTM) and Legionella pneumophila were not detected in any groundwater-supplied buildings. Total bacteria, Legionella spp., and NTM were abundant in the surface water-supplied buildings following long-term stagnation (up to 7.6, 6.2, and 7.6 log copies/L, respectively). Flushing decreased these concentrations by ∼1 to >4 log units and reduced microbial community diversity, but the communities largely recovered within a week of post-flush stagnation. The results suggest that buildings supplied with disinfected surface water are more likely than buildings supplied with treated or untreated groundwater to experience deleterious changes in microbiological water quality during stagnation and that the water quality improvements from flushing with chloraminated water, while substantial, are short-lived.
|Original language||English (US)|
|Number of pages||11|
|Journal||Environmental Science and Technology|
|State||Published - Apr 4 2023|
Bibliographical noteFunding Information:
The authors thank the personnel at the suburban school and youth camp for their assistance with building access and sampling. The authors also thank Scott Bernardson, Kirk Hall, and Tony Gutterman from Facilities Management at theUniversity of Minnesota for their assistance with building access and sampling. The authors would also like to thank personnel at the Minnesota Department of Health (MDH), especially Anita Anderson, Kim Larsen, and Alex Bartley, for guidance in the development of a sampling and flushing plan. Finally, the authors thank MDH for the financial support of this research.
© 2023 American Chemical Society.
- Legionella pneumophila
- Legionella spp.
- nontuberculous mycobacteria
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't