Field Study II: Pilot Application of nZVI/DC-Combined Methods at Aargau Site

Abstract

Combination of nZVI and electrical field was successfully tested in laboratory and afterwards on several sites in the Czech Republic. With successful references we went abroad to Aargau site in Switzerland (November 2017). Aargau site is characteristic by deep aquifer with bottom in 16–17 meters of depth and 3–4 m of thickness. It is contaminated by chlorinated ethenes in concentrations from 12 to 70 mg/L in total, (especially tetrachloroethene and trichloroethene). In Switzerland we injected NANOFER STAR DC, a product designed for application with direct current (DC). In total, 25 m³ of 10 g/L nZVI was injected via packer system into 5 wells creating a permeable reactive barrier. A system of electrodes was installed directly into the monitoring wells due to very deep groundwater level. Nine-month-long monitoring was held on Aargau site including a tracer test confirming direction of groundwater passing through the barrier. DC application has a positive impact on efficiency and longevity of used nZVI particles. Permeable reactive barrier in Switzerland was able to degrade inflowing chlorinated hydrocarbons concentration in range of 20–69 mg/L with efficiency 92–98% for first 7 months since nZVI application and up to 9 months with efficiency 74%. These results showed a significant improvement of efficiency of this method compared to the conventional use of nZVI.