This study explored the ability of orthophosphate addition to limit lead release from lead service lines delivering high pH, low alkalinity water. We built pipe loop reactors with lead pipes harvested from Providence, RI, and we operated them with high pH and low alkalinity water of a composition similar to that in Providence. Orthophosphate addition decreased the release of both dissolved and particulate lead to the water. The most substantial decreases in total lead concentrations occurred after 15 weeks of orthophosphate addition, which was associated with the formation of calcium-lead-phosphorus (Ca-Pb-P) solids as part of the pipe scale. Pre-existing hydrocerussite (Pb3(CO3)2(OH)2(s)) in the scale of the lead pipe appeared to promote the formation of a Ca-Pb-P solid similar to phosphohedyphane (Ca2Pb3(PO4)3(Cl,F,OH)(s)). Continuous orthophosphate addition was also associated with the formation of a calcium phosphate solid with features like those of fluorapatite (Ca5(PO4)3F(s)) on the outermost layer of the scale. Through promoting the formation of these new solids within and on top of the scales, orthophosphate addition limited release of dissolved and particulate lead. These results demonstrate the ability of orthophosphate to control lead release at higher pH conditions than those for which it has typically been used. In addition to the formation of phosphate solids, PbO2(s), which was not present on the as-received pipes, was formed due to the constant supply of free chlorine in the laboratory-scale experiment.

中文翻译：

---

在高pH，低碱度的水中，正磷酸盐对管道垢中铅释放的影响。

这项研究探索了添加正磷酸盐的能力，以限制铅从铅输送管线中释放铅的能力，该铅输送管线输送高pH，低碱度的水。我们使用从罗德岛州普罗维登斯（Providence）收获的铅建造了管道环流反应器，并在高pH和低碱度水（与普罗维登斯（Providence）相似）的条件下运行它们。正磷酸盐的加入减少了溶解和颗粒状铅向水中的释放。在添加正磷酸盐15周后，总铅浓度出现了最大幅度的下降，这与管道水垢中钙铅磷（Ca-Pb-P）固体的形成有关。铅管中预先存在的水陶粒（Pb3（CO3）2（OH）2（s））似乎促进了Ca-Pb-P固体的形成，类似于磷庚烷（Ca2Pb3（PO4）3（Cl， F，OH））。连续添加正磷酸盐还与磷酸钙固体的形成有关，该固体具有在鳞片最外层具有类似氟磷灰石（Ca5（PO4）3F（s））的特征。通过促进水垢内和水垢上方这些新固体的形成，正磷酸盐的添加限制了溶解的铅和颗粒状铅的释放。这些结果证明了在比通常使用的磷酸盐更高的pH条件下，正磷酸盐能够控制铅的释放。除了形成磷酸盐固体外，由于实验室规模实验中不断供应游离氯，还形成了原样管道中不存在的PbO2。