Microbial contamination in distributed drinking water purifiers induced by water stagnation

Recovery of microbiological quality of long-term stagnant tap water in university buildings during the COVID-19 pandemic

“…It was observed that water retention would result in increased HPC values, which was consistent with the findings of previous studies ( Pepper et al, 2004 ). However, compared with short-term stagnation ( Chen et al, 2020 ), much more culturable bacteria were detected in this work due to the much longer retention. According to the issued data by the local administration, the HPCs were usually zero CFU/mL.…”

“…During the beginning days of this study, the 16s rRNA genes were at log 7-9 copies/L, and most of the cultural bacteria were at log 1-4 CFU/mL. Since the stagnant period was over 4 months, which obviously exceeded the bacterial growth cycles in most natural and artificial circumstances, it could be inferred that the bacterial biomass would be in a pseudo-steady state ( Chen et al, 2020 ), i.e., the dead bacterial cell numbers should be equivalent to the newly-divided cells, during most time of the stagnant. Therefore, another problem for LTSW was the accumulation of endotoxin produced by the in-situ lysis of the bacteria.…”

“…Microbial growth during water stagnation is well documented ( Lautenschlager et al, 2010 ; Ling et al, 2018 ). For example, Chen et al (2020) showed that the colony of total bacteria increased to >500 CFU/mL after short stagnation in water purifiers. Moreover, the stagnation was highly related to the occurrence of waterborne pathogenic microorganisms ( Schwake et al, 2016 ; Kinsey et al, 2017 ).…”

Is flushing necessary during building closures? A study of water quality and bacterial communities during extended reductions in building occupancy

“…Previous research has indicated that stagnation of drinking water can be associated with increased chemical and microbial contaminants, such as plumbing metals (e.g., lead, copper), disinfection byproducts, nitrifying organisms, and opportunistic pathogens (e.g., Legionella pneumophila, non-tuberculous mycobacteria, Pseudomonas aeruginosa; Lytle and Schock, 2000;Council, 2006;Rhoads et al, 2016;CDC, 2020;Nisar et al, 2020). These elevated chemical and microbial contaminants can result from physicochemical changes caused by increased water age, including disinfectant residual decay, temperatures trending toward ambient, destabilization of corrosion scale and biofilm, release of metals, and changes in the composition and concentration of bioavailable nutrients (Ling et al, 2018;Chen et al, 2020). Poor water quality is a particular concern in building plumbing compared to pipes within distribution systems because of longer water age and higher surface-areato-volume ratios, which may lead to increased metal leaching from pipe materials, enhanced biofilm formation, and greater decay rates of disinfection residuals (Zlatanović et al, 2017).…”

Microbial diversity in full-scale water supply systems through sequencing technology: a review

“… 126 Moreover, the composition and content of microorganisms in household faucet water change greatly, even if stopped overnight. 138 Chen et al 139 studied the effect of water stagnation on microbial pollution in a water purifier; the results showed that the growth of microorganisms in the water purifier was faster than in a DWDS, and the size of the microorganisms decreased with an increase in stagnation time. This suggests that microbial contamination caused by stagnation should be carefully considered in the design and usage guidance of building water supply systems (BWSSs) to ensure healthy drinking water.…”