TechnologytSolutions Natural attenuation gets a boost
Sandr a Dwor at zek
now offer tests to determine whether vinyl-chloride-metabolizing Dehalo coccoides organisms are already The use of microbes for cleaning up Both Edwards and Löffler played present at sites with chlorinated chlorinated compounds has recently key roles in the technology’s speedy contaminants. When they are, the gained momentum, largely because development. Edwards first discovsites are generally treated with “bioof the growing use of mixed cultures ered a consortium of microbes that stimulation”, which involves adding of Dehalococcoides bacteria that can naturally broke down PCE and TCE compounds that can serve as elecreliably transform chlorinated coninto ethene without accumulating tron donors to inspire the microbes taminants into nontoxic ethene. any vinyl chloride more than a deto go to work on the contaminants. Researchers are currently Materials being used as biotrying to extend the techstimulants include emulsinology to target carbon tetfied vegetable oil, lactate, rachloride, chloroform, and molasses, and chitin. trichloroethane. When Dehalococcoides Since 1999, the U.S. EPA BAV1 is not found, cultures has approved “monitored can be added, such as Shaw natural attenuation” as a Environmental’s Shaw Deremedy for many classes chlorinating Culture, SDC-9, of contaminants but not the Bio-Dechlor Inoculum for chlorinated solvents. from Regenesis, and GeoSynThat is because some natutec’s KB-1. Once any of these rally occurring microbes cultures are added to sites can transform chlorinated with chlorinated contamicontaminants like perchlonants, they “do really well— roethylene (PCE) and trithere’s something going on Some strains of Dehalococcoides bacteria can break down chloroethylene (TCE) into in the real world that makes chlorinated solvents into nontoxic ethene. vinyl chloride, which is a huthem extremely happy,” Löfman carcinogen. fler says. “There are fewer This is a serious concern becade ago, with colleagues now at failures with this technology than cause “there are probably tens of GeoSyntec. She named the consorany other technology for the same thousands of contaminated chloritium KB-1 “after my mother’s red group of contaminants,” he adds. nated solvents sites” in the world, pickup truck [Kick Butt] that surprisBioaugmentation also tends to cost estimates David Major, a principal ingly had a lot of ‘zip’—just like the less than the conventional alternain the Toronto offices of GeoSynculture.” In 2002, KB-1 became the tives of thermal stripping and in situ tec. Chlorinated solvents are used in first commercially available culture chemical oxidation, says Rob Steffan dry cleaning, by automotive service for bioaugmentation of chlorinated of Shaw Environmental. shops, in the fabrication of electronsolvents. All of these benefits have resulted ics and pharmaceutical products, A year later, Löffler and his colin bioaugmentation’s use throughand by the military. leagues were the first to report their out the U.S. as well as in Denmark Bioaugmentation, or the addition success in isolating an organism, and Sweden. GeoSyntec has plans to of microbes for remediation purDehalococcoides strain BAV1, capaapply the technology in the U.K. and poses, moved rapidly for chlorinated ble of metabolizing vinyl chloride to Switzerland, says Phil Dennis, techsolvents because “there are not a lot produce ethene (Nature 2003, 424, nology manager of the company’s of good alternatives out there. . . . 62–65). The finding “meant that reSiREM division. People are willing to try even someductive dechlorination could be pro“Generally, there are no regulations thing that’s quite early on in the deductive because organisms that use against the use of naturally occurring velopment stage,” explains Elizabeth vinyl chloride and convert it to ethorganisms in the U.S., [although] deEdwards of the University of Toronto. ene exist. We could also show that pending on the state, you may need a “The entire application moved pretty [the Dehalococcoides BAV1] organpermit to bioaugment,” Major notes. quickly from the laboratory to the isms were present at some sites but “Regardless, you need to show regulafield,” agrees Frank Löffler of Geornot at all sites,” Löffler explains. tors that what you are adding is bengia Institute of Technology’s school of A few environmental engineering eficial, necessary, and safe.” civil and environmental engineering. firms and commercial laboratories —KELLYN BETTS © 2007 American Chemical Society
JANUARY 1, 2007 / Environmental Science & Technology n 15
