Air to stop contamination

A tanker overturns at Gardermoen airport and thousands of litres of aircraft fuel leak out. threatening the groundwater. The fire brigade is called out to save the day - using compressed air!

This scenario could become a reality in a few years if Atle Dagestad (31), a Ph.D.-student at NTH's Dept. of Geology and Mineral Resources Engineering succeeds with his research project. Dagestad is trying to determine if injection of ordinary air can reduce the extent of contamination. At the end of May he started field trials in a 50 x 50 m area at Gardermoen. Preliminary laboratory tests at NTH have produced promising results.

The idea is deceptively simple. Dagestad demonstrates the principle in his own 1.2 x 2.4 m sandbox at NTH, pumping compressed air under a metre-thick water-saturated layer of sand. After only a few seconds, bubbles appear on the surface, which is soon covered in water that has been forced upwards.

What has happened is that the injected air has created an "airlock" in the pores in the sand. The air forces moisture out of all gaps and forms an impenetrable barrier that would prevent oil spills, for example, from spreading. Dagestad can also imagine other applications, such as reducing the entry of water into building trenches. The method is simple and, just as important, cheap. Normally, the alternative would be to drive piles into the earth to create a physical wall. A further advantage of the compressed-air method is that the oxygen in the air helps to raise the level of bacteriological activity in the soil, accelerating the natural breakdown of contaminants.

Dagestad is working on a Ph.D.-thesis based on this method, which has never been tried before to prevent pollution. He started the project a year ago, and if all goes well should be finished in two or three years.