Treatment of Contaminated Ground with In-Ground Barrier Walls

There is a large number of contaminated sites in the UK which has in many cases also resulted in extensive contamination of the groundwater. There are two ways of dealing with this problem: one way is to use a risk-based approach (see Remediation of Brownfield Sites) and the other is to treat the contaminated ground and groundwater by removing the contamination. One risk-based approach is to contain pollutants from such a site within a physical barrier, but more recently we have been examining the use of 'reactive' barriers. Such reactive barriers intercept the flow of contaminated groundwater or contaminant plume so that clean water emerges through the barriers. Such barriers do not just contain the contaminants, but clean them up.

This is a relatively new field of research and we are examining a range of different materials to determine their effectiveness in reactive barriers. Activated carbon and iron filings are known to work, but these products are expensive. We are looking at the use of waste materials such as granulated tyres and wood shavings: using materials such as these would solve more than one problem, and would provide a sustainable solution.

This type of cleaning up process can also be speeded up by funnelling groundwater through the barrier wall that will clean it up. However, any such barrier material is likely to get saturated and need replacing, so as a further refinement we are also considering using isolated microorganisms (bacterial strains) in the barriers which eat the contaminants and hence continue to grow. Such microorganisms need optimum conditions in which to live so we have to determine what these conditions are and how we can supply them.

Another aspect of our research involves effective installation methods for such barrier systems. There are construction problems involved with just digging a trench and putting the barrier in, so we are looking at how you can add barrier materials directly by mixing them into the soil using augers similar to those used for conventional piling works. This method has proved to be cost-effective and it reduces the risk by eliminating exposure of contaminated material to the surface and also eliminates off-site disposal. We are looking at the applicability of different auger design in different ground conditions and at optimising the mixing conditions.

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Telephone - +44 01223 332715

Other environmentally related projects:

Remediation of Brownfield sites

Waste minimisation and re-use

Geoenvironmental response to climate change

Geoenvironmental sustainability