Scrubbing bubbles clean up soil

USA Today (Society for the Advancement of Education), June, 1995

Super-tiny bubbles made from an ingredient commonly found in shampoos and soaps are highly effective in cleaning up hazardous wastes in soils. Louisiana State University engineers report. "Look on the label of your shampoo bottle and you'll find the bubble-making ingredient. It's called `sodium lauryl sulfate,'" Dipak Roy, professor of civil engineering, points out. "It's also a component in household detergents and soaps." The compound works as a surface-active agent or surfactant, reducing friction between surfaces, loosening and dissolving oily wastes much the same way detergents clean fabric in the washing machine.

The micro-bubble surfactant can be used to clean soils containing many types of chemicals, especially imbedded oily wastes that pump-and-treat procedures leave behind, indicates David Constant, director of LSU's Hazardous Waste Research Center. "You can just keep pumping and pumping where the waste is bound up in the soil and subsurfaces and it won't come out. You can go on for years - decades - trying to remove it. The use of this of this special surfactant can speed that up."

The researches took a regular surfactant and put it in a bubble generator - a kind of agitating machine - to make tiny gas-filled bubbles that have double layers of a soapy film. The bubbles must be just the right size, because the greater the surface area, the greater their efficiency.

When pumped under high pressure, they make their way through the soil by opening channels within it. The mobilized micro-bubbles push their soapy surfaces against stubborn organic contaminants imbedded in the soil and make them soluble. The bubbles trap the oily waste and hold it inside as they travel through the soil.

"In the field we plan to pump the bubble emulsion through contaminated zones by using injection wells and then collect the waste in recovery wells," Roy explains. "Once we take it out and it's above ground in tanks, then we can think of all types of treatment. It could be a chemical treatment, a biological one, or it could be incineration."