Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
Environ Sci Technol. 2017 Mar 21;51(6):3318-3326. doi: 10.1021/acs.est.6b04994. Epub 2017 Mar 7.
Partial replacement of lead service lines (LSLs) often results in the excessive long-term release of lead particulates due to the disturbance of pipe scale and galvanic corrosion. In this study, a modeling approach to simulate the release and transport of particulate and dissolved lead from full and partially replaced LSLs is developed. A mass-transfer model is coupled with a stochastic residential water demand generator to investigate the effect of normal household usage flow patterns on lead exposure. The model is calibrated by comparing simulation results against experimental measurements from pilot-scale setups where lead release under different flow rates and water chemistry scenarios was reported. Applying the model within a Monte Carlo simulation framework, partial replacement of the LSL was predicted to result in releasing spikes with significantly high concentrations of particulate lead (1011.9 ± 290.3 μg/L) that were five times higher than those released from the simulated full LSL. Sensitivity analysis revealed that the intensity of flow demands significantly affects particulate lead release, while dissolved lead levels are more dependent on the lengths of the stagnation periods. Preflushing of the LSL prior to regulatory sampling was found to underestimate the maximum monthly exposure to dissolved lead by 19%, while sampling at low flow rates (<5.2 LPM) was found to consistently suppress the high spikes induced by particulate lead mobilization.
部分更换铅服务管 (LSL) 通常会导致由于管道结垢和电偶腐蚀的干扰而导致铅颗粒的过度长期释放。在这项研究中，开发了一种建模方法来模拟从全和部分更换 LSL 中释放和传输颗粒状和溶解铅。质量传递模型与随机居民用水量生成器耦合，以研究正常家庭使用流量模式对铅暴露的影响。该模型通过将模拟结果与报告不同流速和水化学情景下铅释放的试点规模设置中的实验测量值进行比较来校准。在蒙特卡罗模拟框架内应用该模型，预测部分更换 LSL 将导致释放出具有显著高浓度颗粒状铅 (1011.9 ± 290.3 μg/L) 的峰值，比从模拟的全 LSL 中释放的铅高出五倍。敏感性分析表明，水流需求的强度显著影响颗粒状铅的释放，而溶解铅水平更取决于停滞期的长度。在监管采样之前进行 LSL 预冲洗被发现低估了溶解铅的最大月暴露量 19%，而在低流速 (<5.2 LPM) 下采样则一直抑制由颗粒状铅迁移引起的高峰值。
