Atlanta (January 20, 2004) — Research conducted at the Georgia Institute of Technology has revealed a new approach for cleaning sites contaminated by toxic solvents-using nature's own bacteria to do the job.
Investigators lead by Assistant Professor Frank Löffler in Georgia Tech's School of Civil and Environmental Engineering have isolated a bacterium they named BAV-1 that can be used to clean toxic sites and prevent cancer-causing substances from reaching drinking water supplies. Löffler's finding was cited as one of the "Top 100 Science Stories of 2003" by the editors of Discover.
Löffler, a microbiologist who maintains a courtesy appointment in Georgia Tech's School of Biology, said the BAV-1 bacterium occurs naturally and appears to present no health risks to people and wildlife. During a multi-year process, Georgia Tech doctoral candidate Jianzhong He was able to isolate the bacterium from samples taken from a polluted site in Michigan.
That area, called the Bachman Road site, had been polluted with tetrachloroethene [PCE] and trichloroethene [TCE], both common solvents that had seeped into the local groundwater. Using a process called bioremediation-the use of microbes to clean up contaminated environments-Löffler's group stimulated the growth of BAV-1 in the surrounding area and monitored the results.
"It turns out that BAV-1 consumed the toxins as a food source, leaving behind only non-toxic by-products once it's finished," Löffler said.
As reported in the scientific journal Nature, researchers found that the bacteria had cleaned the site of poisonous solvents within six weeks, proving that bioremediation can be used to rid toxic sites throughout the country of potentially life-threatening substances.
The Problem at Large
Sites contaminated with chlorinated compounds such as PCE and TCE abound in the United States and many other countries due to the wide use of the solvents through the decades—for example, at dry-cleaning operations. The solvents also are widely used as metal-degreasing agents, especially at military installations.
For many years, disposal of this type of industrial pollution went unregulated, and the solvents were simply dumped or washed away near the sites where they were used. Once they begin to seep into groundwater, the solvents undergo a process that can turn them into even more toxic substances.
Cleaning up these sites is critical if authorities are to prevent the toxins from entering underground aquifers, which are used throughout the country as a source of drinking water.
Dr. Löffler's research group at Georgia Tech studies the fate of pollutants in the environment, with the goal of identifying microorganisms—germs or bacteria—that eat and degrade dangerous chemicals naturally.
"Generally, bacterial degradation means detoxification and, hence, bacteria can be of great help to eliminate toxic waste in the environment and to make our environment cleaner—and keep it that way," Löffler said. "A single handful of forest soil typically contains more bacteria than people who exist on Earth. Many different types of microbes exist, and we try to find those bacteria that detoxify pollutants by collecting samples from contaminated environments, which we then transport to the laboratory for study."
Eventually, such studies will help people, government, and industries to fully exploit the natural potential of the microbial world in coping with the wastes produced by our societies, Löffler said. In addition, research conducted by him and others will lead to the development of novel and environmentally friendlier production processes for common goods.
"The BAV-1 organism is not the only microbe out there that can help," he said. "There are different organisms that target different kinds of contaminants. We specifically look for bacteria that detoxify chlorinated solvents. This BAV-1 is a promising candidate, but there are others out there, too. I predict more interesting microbes will be discovered in the next several years."
BAV-1: The Two Options
In the case of BAV-1, once Löffler's group realized it was present and consuming PCE and TCE at the Michigan location, they wanted to find out how they might use it to speed up the process and detoxify the whole site. During the course of their investigations, the group identified two processes that would work: biostimulation and bioaugmentation.
In situations where BAV-1 already is present in the soil of a contaminated site-as it was at the Michigan site-biostimulation can be used to encourage its detoxifying activity. This is done by providing bacteria what they need most to reproduce and spread-food and nutrients. Once grown in sufficient numbers, the bacteria begin to consume contaminants at increased rates, eventually clearing toxins away completely.
At other contaminated sites where BAV-1 isn't present in the soil, it can be added to the environment through bioaugmentation. In this process, the BAV-1 bacteria are grown off-site in large vessels. Once the bacteria are thriving in large numbers, they then are sent to a site and injected into the ground where they, again, begin to consume contaminants.
At the Michigan test site, both processes worked, although it appears the biostimulation technique took longer to accomplish the job, Löffler said.
Löffler added that innovative engineering solutions focusing on the implementation of the biostimulation and bioaugmentation approaches will further increase the efficiency of both processes. It also might be cheaper—and just as effective—to control contaminated sites by simply containing the spread of the toxic plume, or the area in which substances are moving through the groundwater, he said.
This might be accomplished using biobarriers where BAV-1 microbes are active, Löffler said. With this process, the biobarriers would intersect the path of the toxins moving with the groundwater. The contaminants will be removed in the biobarrier, and clean groundwater will leave the bioactive zone.
The Future of BAV-1 and Bioremediation
According to the U.S. Geological Survey, cleaning up existing environmental contamination in this country alone could cost as much as $1 trillion. Bioremediation stands to play a significant role in that effort because of its potential cost savings.
Simply put, bioremediation allows site clean-up to occur in place, without government agencies or businesses having to spend huge sums of money to remove soil and contaminants, or to restore a site that was heavily disturbed during the typical remediation process.
Löffler and his group have shown that bioremediation can be a successful option. Still, much remains to be learned about how microorganisms interact and perform in different hydrologic environments, he said, and about what type of bacteria might do the most good in a variety of clean-up scenarios.
"What we're doing here in my lab is fundamental research into organisms that degrade contaminants in the environment," Löffler said. "But in order to implement those technologies in the field, to actually clean up a contaminated environment, my knowledge would not be sufficient."
That's where research collaboration becomes important.
"I have to work together with engineers, hydrologists, and geologists, and we then have to come together and implement this technology in the field," Löffler said. "So I think that it's very important to assemble multidisciplinary teams that can then successfully transition basic research findings to contaminated clean-up in the environment."
BAV-1 Research Article in Nature
BAV1.pdf Abobe Acrobat Document=217k
College of Engineering
School of Civil and Environmental Engineering
Assistant Professor Frank Löffler
U.S. Geological Survey: Bioremediation
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