Permeable Barriers to Remove Cd and Cr from Groundwater

Abstract

Laboratory investigations were conducted on permeable barrier media for in-situ removal of divalent cadmium (Cd) and hexavalent chromium (Cr⁺⁶) from contaminated groundwater. Permeable barriers are in-situ treatment systems placed in the ground, down-gradient from a plume or source of groundwater contamination. They are designed to allow the groundwater to flow through them while retaining contaminants. This investigation sought to develop low cost, yet effective, barrier materials to expand the breadth of potential permeable barrier applications. The batch studies used a bottle point isotherm procedure to evaluate various combinations of powdered activated carbon (PAC), calcium carbonate (CaCO₃), and ferric oxide (Fe₂O₃). Silica sand was used as the inert media filler matrix. A 1:1:1 combination of PAC, agricultural limestone, and ferric oxide mixed at a 1:4 ratio with sand was selected for a column experiment based on data developed during the batch studies. Results of the column investigation indicated that the batch study sorption projections were low. This column investigation was conducted as the one-dimensional case for subsequent use of the media in a trench-based permeable barrier.