Water cleaning process may not be the best answer
Utah State University students are researching ways to clean up a pollutant in the groundwater near Hill Air Force Base.
The pollutant is trichloroethylene (TCE), which was used by the base during World War II to keep jets clean and is currently used in dry cleaning, said Bruce Bugbee, professor of crop physiology. TCE can potentially cause cancer if consumed, he said.
“They would just spray it on the jets so the jets would be nice and clean,” he said. “But it just seeps into the ground and doesn’t go away. It got into the drinking water near Hill Air Force Base last fall.”
However, there hasn’t been any TCE found in the groundwater so far this year, Bugbee said.
One way to remove TCE from the groundwater is by using a process called phytoremediation, which involves using plants, mainly trees, to clean out pollutants from soil and water, Bugbee said.
“Phytoremediation is using plants to clean up polluted soil, for example if there was an oil spill,” he said. “It’s getting the trees to grow deep roots down into the groundwater, soak it up and get it out.
“Think of trees as a biological filter,” he said. “They can take up TCE in their roots and degrade it.”
USU has been working on the TCE research for eight years. One of the projects involves growing bacteria-free plants to measure the carbohydrates and proteins the roots leak out, Bugbee said.
“We grow plants that are sterile, with no bacteria at all in them,” he said. “Then we can measure what comes out of it. It’s a big challenge, but we can grow them for a few months without bacteria.
USU is one of the few places in the world that knows how to do it, he said.
To grow bacteria-free plants, the seeds are soaked in Clorox, grown in sand and watered with sterile nutrients, Bugbee said. In addition, the air the plants use is filtered.
Many bacteria need plants to grow, and the bacteria that grows nears plants could be used to help break down the TCE, Bugbee said, so it is important to understand the relationship between the roots and the bacteria.
Another experiment is being done with dwarf fruit trees to see how TCE affects them.
“We’re putting the TCE in the trees and looking at how it moves up the plants to see if any gets in the peaches and apples,” Bugbee said. “We’ve done a lot of other studies with trees to see how well they can take it up and degrade it.”
So far, the research has shown that plants can absorb TCE and break it down, but not as well as some people believe, Bugbee said.
“A lot of people want to believe trees are the answer,” he said. “It’s a very attractive concept. In some ways, we’re at odds with members of the scientific community about how effective trees are at filtering groundwater.
“It’s quite a controversy,” he said. “There are a lot of people with differing opinions about how effective phytoremediation is.”
Bugbee said phytoremediation doesn’t work as well because plants don’t want to absorb it in their roots.
“Plants don’t like dry cleaning fluid going up them any more than people do,” he said. “They’re not taking it up that fast.”
Phytoremediation is not a “magic bullet” that will solve everything, Bugbee said. But it can help if it’s combined with other processes. Another way to clean the TCE out of the water would be to pump the groundwater up and filter it, but the cost would be great.
“Phytoremediation is like a two-edged sword,” he said. “On one hand, you get plants to clean it up. But you don’t want it to get into your fruits and vegetables. Planting a row of trees around Hill Air Force Base could be feasible though.”
For more information students can visit the Crop Physiology Laboratory’s Web site at www.usu.edu/cpl.
-kcartwright@cc.usu.edu