Chromium clean-up

Scientists at Brighton University have developed a new way to treat chromium VI contaminated soil that could save industry and developers millions of pounds.

It involves placing contaminated soil in a specially kitted-out industrial skip, placing two arrays of iron electrodes at opposite ends of the skip and applying a low-intensity electric current.

The toxic chromium VI contaminant in the soil moves in response to the electric field and is transformed to low-toxicity chromium (III), and together with iron derived from the sacrificial electrodes, the chromium is effectively locked within an 'iron curtain' that can be subsequently removed.

The low-energy method is called Ferric Iron Remediation and Stabilisation (FIRS) and has been developed by Dr Laurence Hopkinson and Prof Andy Cundy at Brighton University's School of Environment and Technology.

They have developed the system for commercial use on chromium VI and other metallic contaminants in collaboration with Churngold Remediation, although the system can be applied to a much wider range of problem pollutants.

Current methods of decontaminating soil tend to be expensive and labour-intensive. Many, for instance, require the removal of soil to landfill sites, which has been subject to heavy taxing and restriction under UK and European Union (EU) regulations.

Pilot studies on more than 500m³ of soil have shown that FIRS was able to reduce the level of hexavalent chromium, one of the most common and toxic heavy metal contaminants found in heavy clay soil in industrial and mining areas, by up to 85 per cent over 42 days. 

Electrokinesis was also used to reduce contamination in soil water through an electrokinetic holding tank in the skip, in the process yielding purified water which comfortably surpasses the EU's 0.05mg/L maximum contaminant level of Cr(VI) in drinking water.

Initial research into FIRS was funded by the Engineering and Physical Sciences Research Council with further funding for scale-up of the technology provided via the government's Knowledge Transfer Partnership scheme and Churngold Remediation.