In this study, we used modeling with stochastic demands to assess free chlorine concentrations in premise plumbing systems. Different occupancy scenarios and the use of automated purging devices at the fixtures were assessed. Chlorine concentrations were highly variable, so three novel metrics were proposed to assess the temporal distribution of chlorine residuals: the initial chlorine concentrations at fixtures for each use, the percentage of time a fixture was exposed to low chlorine concentrations (below 0.1 mg/L), and the durations of the low chlorine events. Showers, particularly those with lower occupancy, often had near-zero chlorine residuals. The chlorine residuals were below a 0.1 mg/L threshold 75% of the time for the one-person household but only 55% in a two-person household. 12-h scheduled purging reduced the percentage of time with low chlorine to 29% for the one-person household. Lower chlorine residuals in the water supply, smaller pipes, and longer service pipes resulted in substantially lower median chlorine concentrations at the fixtures. The choice of decay coefficients also had a large impact on the percentage of time with low chlorine. Overall, this research provides a new methodology to quantify and assess the highly variable chlorine concentrations in premise plumbing systems and the impacts of purging devices.

中文翻译：

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评估随机需求和装置净化对场所管道系统中游离氯残留的影响

在这项研究中，我们使用随机需求建模来评估场所管道系统中的游离氯浓度。对不同的占用场景以及固定装置自动净化设备的使用进行了评估。氯浓度变化很大，因此提出了三个新颖的指标来评估氯残留物的时间分布：每次使用的固定装置的初始氯浓度、固定装置暴露于低氯浓度（低于 0.1 mg/L）的时间百分比，以及低氯事件的持续时间。淋浴间，尤其是使用率较低的淋浴间，氯残留量往往接近于零。单人家庭中 75% 的时间氯残留量低于 0.1 mg/L 阈值，而两人家庭中只有 55% 的时间低于 0.1 mg/L 阈值。对于单人家庭来说，12 小时定期净化将低氯时间百分比减少至 29%。供水中的氯残留量较低、管道较小、服务管道较长，导致固定装置的中位氯浓度大幅降低。衰减系数的选择也对低氯时间的百分比有很大影响。总体而言，这项研究提供了一种新的方法来量化和评估场所管道系统中高度可变的氯浓度以及净化装置的影响。