Bugs Have Surprising Appetite For Pollution Microbes Convert Toxic Pollutant Into Harmless Chemical

The bugs that scientists are using to clean up the Idaho National Engineering and Environmental Laboratory have a bigger appetite for pollution than anyone guessed.

The first real-world experiment using microbes to clean up groundwater contamination at the site has surprised almost everyone with its effectiveness. The results could help drive a more natural approach to cleaning up pollution there.

The microbes are working on a plume of contaminated groundwater from an old injection well at Test Area North. The bugs, as scientists lovingly call them, occur naturally in the rocks and water underneath Earth’s surface.

With a new source of food being injected into the aquifer, they have begun to convert a toxic pollutant into a harmless chemical given off by fruit.

Scientists say results of the test look promising so far. Early estimates suggest microbes will clean up the contamination twice as fast as more traditional methods, which pump the water out of the ground and treat the toxic chemicals.

“In the first five months, we’ve seen tremendous transformations,” said lead project scientist Kent Sorenson. “This is really, really neat stuff. It’s going to be a cited study.”

The groundwater project at Test Area North is the largest experiment using microbes to combat pollution at the site. It is the first time researchers are applying theories and processes tested in the laboratory in a real aquifer.

At Test Area North, researchers are targeting a plume of trichloroethene, one of the waste products that was injected directly into the aquifer through a well until 1972.

TCE is a colorless liquid that was widely used as a degreaser to clean machinery. The solvent has been found to cause cancer in laboratory animals, and is one of the most common and long-lived pollutants found in groundwater today.

“It’s not just some weird thing that exists only at the INEEL,” Sorenson said. “It’s a huge problem in municipal areas all over the country.”

There are no records showing what quantities of chemicals and wastes were sent through the injection well at Test Area North. Officials estimate between 500 and 30,000 gallons of TCE may have been used and disposed as waste in the injection well.

Over time, the TCE became mixed with sewage and other sludges, forming a sticky goo around the well that continues to pollute the groundwater. The plume of contamination now extends for two miles.

Traditional pump and treat methods weren’t making much of a dent in the problem. In 18 months of continuous pumping, probably less than 1 percent of the TCE was recovered.

About four years ago, scientists turned to microbes as a possible solution. Through an entirely natural process, they can transform TCE into a harmless compound called ethene.

But the microbes need a food source to make that happen, and a clean basalt aquifer doesn’t offer much lunch. “The bugs that were there were limited because they didn’t have any food,” Sorenson said. “They were just down there starving.”

Beginning in January, scientists started injecting sodium lactate, a natural compound used in food preservatives, into the aquifer. The syrupy liquid had proved to be a good source of food in laboratory tests.

Then they started measuring concentrations of TCE and ethene in surrounding monitoring wells to see whether the microbes were working.

In the closest monitoring well, concentrations of the toxic chemical have plummeted by almost 10 times. In the last six weeks, concentrations of ethene, the harmless chemical, have skyrocketed.

Those changes suggest the bacteria are fed, happy and working their pollution-busting transaction. In another well, TCE concentrations have dropped so low that it can no longer be detected.

The one-year study will last until November. Because they don’t know how much TCE is in the aquifer, INEEL scientists say they don’t have a very good idea about how long it will take to address all the pollution.

But they do seem to be making progress in an environment that scientists once thought was nearly impossible to clean up, said technical project manager Lance Peterson.

“The scope is a daunting thing,” he said. “But we’ve been able to use all the resources of the INEEL to make it happen.”

This sidebar appeared with the story: CLEANING UP Natural remedies Scientists are working on several projects using natural processes to clean up man-made contamination from decades of nuclear research at the INEEL. Bacteria found in cow manure are being used to help break down chunks and pieces of TNT, which remain in the soil from the site’s days as a naval proving ground. Argonne National Laboratory began planting weeds and 4,000 willow trees recently to extract radioactive cesium and toxic metals from the soil there. The plants, which can exist in mildly polluted soils and take up contaminants in their roots and leaves, will be periodically harvested and incinerated. “These are alternative remediation approaches that eliminate transportation costs and kind of use Mother Nature to address environmental problems,” said Lockheed Martin spokesman Erik Simpson.