Polluted water at Hill Air Force Base examined
A suspected carcinogen was found in the groundwater at a United States Air Force Base, and Utah State University is coming to the rescue.
Ryan Dupont, USU professor of civil and environmental engineering, is heading up a research project to find a way to rid the groundwater at Hill Air Force Base of a chemical called trichloroethylene (TCE).
The TCE in question was used as a degreasing agent years ago, and was improperly disposed of, as were many chemicals 30 years ago, Dupont said. The fact that TCE is nonflammable and non-biodegradable adds to the problem; TCE will not go away by itself. This is where Dupont and his team of students and professors come in.
Although TCE is only a suspected carcinogen, there are other definite health risks that can come as a result from exposure to the chemical. According to the Agency for Toxic Substances and Disease Registry’s Web site at www.atsdr.cdc.gov, drinking large amounts of TCE “may cause nausea, liver damage, unconsciousness, impaired heart function, or death.” Even drinking small amounts of TCE for a prolonged amount of time may cause liver and kidney damage, impaired immune system function, and impaired fetal development in pregnant women, according to the Web site, although the extent of some of these effects is not yet clear.
“There’s a very low standard for TCE in drinking water,” Dupont said.
The level that has been deemed safe is .005 mg/L. In some areas, the concentration of TCE in the groundwater is almost 1,000 times the recommended amount. The average concentration of TCE around Hill AFB is 1 to 2 mg/L, with some areas that have up to 5 mg/L.
TCE is composed of hydrogen, carbon and chlorine. In order to make the groundwater safe to drink again, Dupont and his researchers must come up with a way to get rid of the three chlorine atoms, changing it from TCE to ethylene.
Dupont said, “Part of the challenge is to get rid of something bad and not do something worse.”
Removing one chlorine atom causes TCE to become dichloroethylene, which is slightly more of a probable carcinogen than TCE. Removing another chlorine atom causes it to become vinylchloride, which is a known carcinogen. To make the water safe again, the last chloride particle must be removed, making the substance ethylene.
Scientists have found that adding everyday substances to the groundwater such as glucose, vegetable oil and molasses, will eventually clean the soil, but it is not known if the results would be consistent or not.
Another solution that has been found is the addition of carbon and a solution of microbes. Although the microbes do work, the problem is that they are expensive, and they don’t move very well in certain conditions. For example, in the area where the microbe/carbon solution worked, the groundwater would only move 6 feet in 60 days. The challenge, Dupont said, is to devise a remediation strategy that will effectively and quickly deal with the 3,000-foot long plume of groundwater at Hill AFB. Dupont said a better solution needs to be found before the time and money it would take to clean the entire area is invested.
“The use of the microbe/carbon donor solution appears optimal for this site,” Dupont said. “But again, the engineering challenge is in making the system work for the very large plumes that exist around Hill.”
Right now, in the Utah Water Research Laboratory, Dupont and a group of students and other professors are doing just that. They have gathered six cylinder samples of the soil at the site. At the moment, they are replicating the level of TCE found in the groundwater so they can test their hypotheses. Rachel Winters, a junior majoring in environmental engineering, said she loves working on the project, because “it helps to reassure me that this is what I want to do for a living.”
According to Hill Air Force Base’s Web site, the “ground-water problems are being addressed, and vapor problems in homes are being monitored as needed to ensure the well being of area residents. Alternative water supplies have been provided to ensure that residents are not using the groundwater.”
-sophisan@cc.usu.edu