Remediation of groundwater contaminated by chromium and arsenic at sites in the UK and Alaska

Groundwater pollution by potentially toxic metals is an on-going issue in areas with a legacy of industrial or mining activity. Remediation of hexavalent chromium (Cr(+6)) to the less mobile and less toxic trivalent form (Cr(+3)) by chemical reduction may have the undesirable effect of mobilising other metal contaminants present in soil and groundwater. Arsenic, for example, can also be chemically reduced from the pentavalent As(+5) species, which is largely immobile, to the highly mobile trivalent As(+3) species, if a remediation process is set up with the sole purpose of addressing chromium contamination. The mobility of metal species, such as arsenic, is controlled by a wide range of chemical and bio-chemical parameters, as shown in Figure 1. This project will investigate the electro-chemical and bio-chemical environment needed to optimise remediation of mixed chromium and arsenic plumes, with an emphasis on nanoscale bio-mineralisation and bio-sorbants