This paper aims to evaluate the efficiency of a multilayer configuration of a permeable reactive barrier (PRB) made up of granular mixtures of zero valent iron (ZVI) and lapillus. The latter is a volcanic material used to disperse ZVI particles. A high dispersion of ZVI improves the long-term hydraulic conductivity but can significantly reduce reactivity due to the lower amount of ZVI. In this research, the performance of two different combinations of a two-layer configuration was studied by means of long-term column tests. The first layer, named “pre-treatment layer”, had a thickness of 4 cm and a volumetric ratio (ZVI/lapillus) of 10:90 or 05:95, while the second layer had a volumetric ratio (ZVI/lapillus) of 20:80. A single layer configuration made only of the 20:80 ZVI/lapillus was used as a benchmark. The three tests were performed using a multi-contaminated solution of copper, nickel and zinc. Test results showed an early loss of the hydraulic conductivity in the single layer configuration and an increase of PRB longevity by 68 % in the presence of the pre-treatment layer. The pre-treatment zone containing 10 % ZVI delayed the clogging phenomenon, while the zone with 5 % ZVI ensured both the correct long-term hydraulic behavior and a removal efficiency higher than 77.6 % for Nickel and 99 % for copper and zinc at 23 cm of thickness for at least two months.

本文旨在评估由零价铁 (ZVI) 和青金石颗粒混合物组成的可渗透反应屏障 (PRB) 的多层结构的效率。后者是一种用于分散ZVI颗粒的火山材料。ZVI 的高度分散可改善长期导水率，但由于 ZVI 含量较低，会显着降低反应性。在本研究中，通过长期柱测试研究了两层配置的两种不同组合的性能。第一层称为“预处理层”，厚度为 4 cm，体积比（ZVI/lapillus）为 10:90 或 05:95，而第二层的体积比（ZVI/lapillus）为20:80。仅由 20:80 ZVI/lapillus 制成的单层配置用作基准。这三个测试是使用铜、镍和锌的多重污染溶液进行的。测试结果表明，单层配置中的水力传导率会提前丧失，并且在存在预处理层的情况下，PRB 寿命增加了 68%。含有 10% ZVI 的预处理区域延迟了堵塞现象，而含有 5% ZVI 的区域确保了正确的长期水力行为，并且在 23 cm 处镍去除率高于 77.6%，铜和锌去除率高于 99%厚度至少两个月。