Co-remediation of hexavalent chromium and arsenic polluted groundwater using crab processing waste products

Groundwater samples containing elevated concentrations of Cr(VI) and As(III) were collected from boreholes in the Glasgow area that were known to contain waste in-fill from chromite ore processing (COPR). As Cr(VI)pollution is usually addressed by chemical reduction to the less mobile and toxic Cr(III) species, there is concern whether this will cause other contaminants such as arsenic to become mobile from the reduction of the less-mobile As (V) to the more toxic As (III).
Chromium speciation was determined using ICP-MS and colourimetry, then compared to analysis after laboratory-scale remediation by passing samples through columns containing mixtures of sorbants, including crab processing waste, chitosan and zero-valent iron under different redox conditions. Arsenic speciation was determined by IC-ICP-MS and anodic stripping voltammetry and monitored for each experiment. Results are presented on the effectiveness of different sorbants to reduce the mobility of Cr(VI) as an alternative to chemical reduction, and rated on consequential arsenic mobility.