Abstract
The growth of the bacterial community harbored in indoor drinking water taps is regulated by external environmental factors, such as indoor temperature. However, the effect of indoor heating on bacterial regrowth associated with indoor drinking water taps is poorly understood. In the present work, flow cytometry and community-level sole-carbon-source utilization techniques were combined to explore the effects of indoor heating on water bacterial cell concentrations and community carbon metabolic profiles in building tap pipes during the winter season. The results showed that the temperature of water stagnated overnight (“before”) in the indoor water pipes was 15–17 °C, and the water temperature decreased to 4–6 °C after flushing for 10 min (“flushed”). The highest bacterial cell number was observed in water stagnated overnight, and was 5–11 times higher than that of flushed water. Meanwhile, a significantly higher bacterial community metabolic activity (AWCD590nm) was also found in overnight stagnation water samples. The significant “flushed” and “taps” values indicated that the AWCD590nm, and bacterial cell number varied among the taps within the flushed group (p < 0.01). Heatmap fingerprints and principle component analyses (PCA) revealed a significant discrimination bacterial community functional metabolic profiles in the water stagnated overnight and flushed water. Serine, threonine, glucose-phosphate, ketobutyric acid, phenylethylamine, glycerol, putrescine were significantly used by “before” water samples. The results suggested that water stagnated at higher temperature should be treated before drinking because of bacterial regrowth. The data from this work provides useful information on reasonable utilization of drinking water after stagnation in indoor pipes during indoor heating periods.
Highlights
Building indoor water pipes are the most important drinking water facility related to potable water quality and public health [1,2]
Flow cytometry and BIOLOG techniques were used to reveal the effects of the indoor heating process on building tap pipe water bacterial cell concentrations and community carbon metabolic profiles
The highest bacterial cell number was observed in water stagnated overnight, which is 5–11 times higher than that of flushed water
Summary
Building indoor water pipes are the most important drinking water facility related to potable water quality and public health [1,2]. Recent publications have suggested that drinking water pipeline materials, including metal pipes and polymer pipes [8,9], household stagnation [10] and temperature [3] may increase the bacterial regrowth associated with indoor water pipes [10]. BIOLOG-ECO microplates contain 31 different sole carbon sources including carbohydrates, carboxylic acids, amino acids, polymers, phenolic compounds, and amines [4]. These carbon sources are utilized by water bacteria, and the metabolic profiles can be used to evaluate the community functional diversity [4]
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