Stagnation trigger changes to tap water quality in winter season: Novel insights into bacterial community activity and composition

The drinking water distribution system is important for water supply and it affects the quality of the drinking water. Indoor pipeline water quality is regulated by physical, hydraulic and biological elements, such as indoor temperature and stagnation. In this work, the effects of indoor heating and overnight stagnation on the variation in bacterial com-munity structure and the total cell count were assessed by full-length 16S rRNA gene sequencing and flow cytometry, respectively. The results exhibited that the average intact cell count was 6.99 x 10(4) cells/mL and the low nucleic acid (LNA) bacteria was 4.48 x 10(4) cells/mL after stagnation. The average concentration of total and intracellular adeno-sine triphosphate (ATP) was 3.64 x 10(-12) gATP/mL and 3.13 x 10(-17) gATP/cell in stagnant water, respectively. The growth of LNA cells played a crucial role in increasing ATP. The dominant phylum observed was Proteobacteria (87.21 %), followed by Actinobacteria (8.25 %). Opportunistic pathogens increased the risk of disease in stagnant water (up to 1.2-fold for Pseudomonas sp. and 5.8-fold for Mycobacterium sp.). Meanwhile, structural equation model (SEM) and redundancy analysis (RDA) also illustrated that water temperature, residual chlorine and Fe significantly affected the abundance and composition of bacterial community. Taking together, these results show response of tap water quality to overnight stagnation and indoor heating, and provide scientific basis for drinking water security management in winter season.

Automated summary

This study assessed the effects of indoor heating and overnight stagnation on bacterial community structure and cell count in the drinking water distribution system. It found that the growth of low nucleic acid (LNA) cells played a crucial role in increasing adenosine triphosphate (ATP). Opportunistic pathogens increased the risk of disease in stagnant water and water temperature, residual chlorine and iron significantly affected the abundance and composition of bacterial community.