for National Geographic News
A microorganism too small to see with the naked eye may be the answer to one of the U.S. Department of Energy's largest environmental problems: hundreds of billions of gallons of groundwater contaminated with uranium and other toxic chemicals.
The microorganism, called Geobacter sulferreducens, has a unique metabolismit passes electrons onto metals to get energy from its food in the same way that we humans breathe in oxygen to break down our food.
In the electron transfer process, the microorganism changes the metals from their dissolved, or soluble, form to a solid, or insoluble, form. This causes the metal to fall out of the groundwater.
"Basically what that allows us to do is to take uranium dispersed in a large area, filter it out from the water, and capture it in a discreet zone so that it is easy to excavate or otherwise extract," said Derek Lovley, a microbiologist at the University of Massachusetts Amherst.
In 1987, Lovley discovered that Geobacter uses iron oxideessentially rustto survive. He has since found some 30 different species of the organism and learned they can be coaxed to "breathe" all kinds of metals.
Working with the U.S. Department of Energy, Lovley and his colleagues are in the third year of a project designed to coax Geobacter to thrive on uranium in contaminated groundwater.
Teresa Fryberger, director of the U.S. Department of Energy's Environmental Remediation Sciences Division, said approaches like Geobacter to cleanup contaminated groundwater are needed to overcome the limitations of current technologies.
Currently the department pumps contaminated groundwater to the surface, treats it to remove contaminants, and then re-injects it to the ground.
"In most cases it cannot completely remove the contamination and is not capable of resolving groundwater contamination problems such as those resulting from uranium contamination at many DOE [Department of Energy] sites," Fryberger said.
The problem of uranium-contaminated groundwater dates back to the Cold War when mines and mills throughout the United States produced millions of tons of uranium oxide, or yellowcake, to build nuclear bombs.
When the mills shut down in the 1970s, radioactive wastes were left behind. Today this waste is seeping into and contaminating the nation's groundwater. People who drink the water are at risk of kidney damage and cancer.
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