A UK industry and government supported research project aims to develop a new approach for cleaning up soils contaminated with metal and organic pollutants by combining electrokinetic and microbiological techniques.
Land tainted with a mix of organic and metal substances is estimated to make up to 50% of contaminated sites worldwide.
However the presence of metals in these soils severely inhibits the organisms used in the biodegradation of organics in soil. Usual methods capable of dealing with these soils, such as site excavation, soil incineration, landfill disposal and soil washing with chemical agents, are seen as increasingly environmentally unsound, time consuming or costly.
The new technique works by applying a low voltage direct current to the soil, encouraging ionic movement. This movement frees the metals allowing them to migrate with water from the soil and forces them to concentrate near strategically placed electrodes in the soil.
The movement reduces metal toxicity so the heterotrophic bacteria which biodegrade carbon based molecules can be stimulated and introduced into the soil. Specialised acid producing bacteria are also introduced to speed up the process of metal removal from the soil.
Metal rich water, which is collected at the electrodes, is then free to be pumped out and microbiologically precipitated so that clean water can be reintroduced into the now decontaminated soil.
The project aims to develop a cost effective and rapid method for soil remediation. It is being undertaken with the support of a Department of Trade and Industry LINK programme, biotechnology company IBS Viridian, EA Technology and the Oxford Centre for Environmental Biotechnology (University of Oxford and Institute of Virology and Environmental Microbiology).