The purpose of this study was to select the appropriate reactive media for chromate reduction to treat groundwater (high pH) with permeable reactive barriers. The study addresses groundwater contamination for three chromium refining sites located in Hudson County, New Jersey. The use of iron (Fe⁰) as a reactive medium was studied and found to be insufficient for use in permeable reactive barriers because of the high pH conditions of groundwater at these sites. Pyrite and iron (Fe⁰)-pyrite mixtures were studied as viable reactive media by considering their passivation kinetics, reductive capacities and solubility properties.

Column experiments were carried out with different volumetric ratios of pyrite and iron (Fe⁰)-pyrite mixtures with combination of aquifer materials (sand) to calculate the maximal chromium accumulation necessary to accurately estimate the capacities of reactive media. The iron (Fe⁰)-pyrite mixture was found to be suitable for treating chromate-contaminated groundwater at the high pH conditions. The reactive media capacities of these mixtures were found to be satisfactory for successful use of permeable reactive barriers to treat the three sites.

We recommend the use of iron (Fe⁰)-sand mixture as a reactive medium for the Allied Signal site (#NJL 000005033) and iron (Fe⁰)-pyrite sand mixture as the reactive medium for both the P.P.G (#NJL 000005017) and the Chemical Land Holding sites.