Extensive building closures due to the unprecedented COVID-19 pandemic resulted in long-term water stagnation within the plumbing of large buildings. This study examined water chemical quality deterioration in ten large buildings after prolonged stagnation caused by the closure of a university campus in response to the COVID-19 pandemic. Volume-based and constant-duration flushing protocols were implemented to replace stagnant water with fresh drinking water. The effectiveness of the developed water flushing protocols was examined by monitoring the disinfectant residuals, heavy metal concentrations and temperature for water samples collected from the buildings' point of entry (POE) and select water fixtures. More than 14 m³ of water were flushed in all ten large buildings. The results demonstrated a significantly greater average total chlorine residual concentration in POE water samples collected after flushing (1.1 mg L⁻¹) compared to the stagnant condition (0.6 mg L⁻¹). For water samples collected from fixtures during the extended stagnation, chlorine was absent in 71% of samples from academic buildings and 69% of samples from athletic buildings. The effectiveness of flushing practices is underscored by increasing the median total chlorine concentration from <0.1 to 1.0 mg L⁻¹ in academic buildings and from <0.1 to 0.75 mg L⁻¹ in athletic buildings. Furthermore, the concentrations of Pb, Zn, and Cu had decreased following the water flushing, but the concentration of Fe had increased in some buildings. This study could be beneficial to prepare for prolonged water stagnation events including but not limited to pandemics.

中文翻译：

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因 COVID-19 大流行而延长关闭后重新启用的大型建筑物的自来水质量案例研究

由于史无前例的 COVID-19 大流行，大量建筑物关闭导致大型建筑物的管道内长期积水。这项研究检查了因 COVID-19 大流行而关闭大学校园导致长期停滞后十座大型建筑物的水化学质量恶化情况。实施了基于体积和持续时间的冲洗方案，用新鲜的饮用水代替死水。通过监测从建筑物入口点 (POE) 和选定的水装置收集的水样的消毒剂残留量、重金属浓度和温度，来检查开发的水冲洗方案的有效性。超过 14 m ³十座大型建筑物中的水都被冲走了。结果表明，与停滞条件 (0.6 mg L ^-1 )相比，冲洗后收集的 POE 水样中的平均总氯残留浓度 (1.1 mg L ^-1 )显着更高。对于在长期停滞期间从固定装置收集的水样，来自学术建筑的 71% 的样品和来自运动建筑的 69% 的样品不含氯。通过将学术建筑中的总氯浓度中位数从 <0.1 增加到 1.0 mg L ^-1和从 <0.1 增加到 0.75 mg L ^-1来强调冲洗实践的有效性在运动建筑中。此外，Pb、Zn 和 Cu 的浓度在用水冲洗后有所下降，但在某些建筑物中 Fe 的浓度有所增加。这项研究可能有助于为长期的水停滞事件做好准备，包括但不限于大流行。