Permeable Reactive Barrier with Zerovalent Iron Grit for the Remediation of Metal Contaminated Groundwater with High Mineralization: A Comprehensive Field Assessment

A large-scale field trial was conducted at a metal-contaminated site to evaluate the effectiveness of a permeable reactive barrier (PRB) containing zerovalent iron (ZVI) grit for remediating groundwater with high concentration and mineralization of metals. The work was based on laboratory and field investigations, which indicated that iron grit was the only economically viable solution. An extensive network of monitoring wells was used to observe the site before and after PRB installation, focusing on: (i) metal mass discharge using passive mass flux samplers; (ii) impact on microbiota; (iii) metal capture and material characterization with scanning electron microscopy. Seven months after the installation of the PRB, the average mass fluxes of Zn, Pb, and Ni in the outflow decreased by 82%, 72%, and 79%, respectively, compared to concentrations before the installation. The average Mn mass flux increased by approximately 67% due to the dissolution of Mn oxides, and gradually declined over time following the PRB installation. The treatment did not cause any apparent harmful side effects on the present microbiota. Results indicate this setup might also be appropriate for other locations dealing with high groundwater mineralization, though the Mn leaching should be further investigated.