ABSTRACT
The use of permeable reactive barriers (PRB) for the treatment of contaminated groundwater is gaining interest as an alternative to conventional (pump and treat) methods. Laboratory experiments investigating the potential for treatment of arsenic contaminated groundwater through the use of potential reactive barrier materials were conducted. For this investigation, arsenic contaminated groundwater collected from a mine located in Ontario, Canada, was passed through laboratory columns of 100% zero valent iron and a mixture containing 20% zero valent iron. During the experiments, the influent groundwater contained between 5 and 15 mg/L of dissolved arsenic. Flow through the columns (0.2 to 0.4 pore volumes/day; PV/day or ~25 to 65 m/a) was several times the groundwater velocity measured at the mine site where the water was collected (10 m/a). Results indicate that the reactive mixture is capable of removing the dissolved arsenic to below current drinking water limits (0.05 mg/L) for considerably more than 90 pore volumes, the current progress of the experiment. After treating 90 PV of water containing an average of 10 mg/L As, concentrations exceeding 0.1 mg/L of As migrate less than 5 cm into the reactive material and concentrations exceeding 0.05 mg/L do not move more than 12 cm into the reactive material. In terms of a field application (e.g. 1 m thick) in situ PRB installation, this represents the equivalent of years or decades of treatment before replacement.
