Removal Of Chromium From Groundwater Using Permeable Barriers: An Aquifer Simulation Studyby Mark D. Schmidt, Univ of New Mexico, Albuquerque, NM, USA,
Stephen P. Shelton, Univ of New Mexico, Albuquerque, NM, USA,
Abstract: Previous efforts to remediate groundwater contaminated by chromium-bearing industrial wastes have involved post-extraction methods, whereby groundwater is pumped to the surface treated and returned to the aquifer. This practice has proven effective for removing soluble pollutants. However, it is often costly and labor intensive and requires treating large volumes of water. Also, institutional obstacles such as ground and surface water discharge permits and groundwater rights must be considered. An alternative to conventional remediation methods is the in situ permeable barrier process, which intercepts soluble contaminants from solution but allows groundwater to flow through. Trench-based barriers, backfilled with reactive media, result in the direct adsorption of chemical species or the oxidation or reduction of chemical species followed by precipitation. Laboratory studies were conducted to determine the technical feasibility of using trench-based media to remove chromium from groundwater. In batch tests various doses of candidate media and 10g of silica sand were added to glass vials containing a chromium solution. Candidate media included powder-activated carbon, ferric oxide and agricultural limestone. Adsorption isotherms were plotted from batch test results. In aquifer simulation tests a chromium-containing solution was passed through an aquifer simulation model containing silica sand and a vertical barrier of candidate media. Removal of soluble hexavalent chromium (Cr(VI)) to concentrations less than the maximum contaminant level (MCL) for total chromium in drinking water (0.05 mg/l) was demonstrated with all candidate media in the aquifer simulation model. Adsorption appeared to be the principle mechanism of removal for all candidate media considered. Information gained from experience with the physical model was used in developing a computer generated, 1-D solute transport model to predict the movement of hexavalent chromium in an aquifer system.
Subject Headings: Water treatment | Chromium | Aquifers | Groundwater pollution | Water discharge | Solubility | Simulation models
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