Microbes on a mission
Microbes on a mission
It’s invisible to most of us, but one of the most prevalent organic groundwater contaminants on Earth is something called trichloroethylene (TCE), a toxic chlorinated solvent that was in wide industrial use between 1940 and the early 1970s.
“It’s everywhere,” says Elizabeth Edwards, professor of chemical engineering and applied chemistry at the University of Toronto, who learned about TCE as a PhD student at Stanford University and when working for a private-sector environmental remediation company in Ontario. “It seems that every industrial manufacturer on the planet that has been operating for more than 20 years has it.”
TCE is now present in deep groundwater and aquifers across the planet, and unlike hydrocarbons, which can be naturally degraded over time by various microbes, a toxic plume of underground TCE can persist in perpetuity.
Until recently, only expensive band-aid solutions existed to address the problem, such as capturing groundwater, pumping it to the surface and treating it. “Finding a way to turn off those pumps and destroy the mass of chemicals on your site so that you don’t have this legacy problem anymore,” says Edwards, “was what was needed.”
By sequencing the genomes of bacteria that were cultured from dirt samples taken from several contaminated sites — a process known as metagenomics — Edwards and collaborators were able to determine which naturally occurring micro-organisms could completely neutralize TCE. They then developed a way to grow large quantities of those microbes that can be injected in liquid solution deep underground, where they eat their way through the toxins.
Incubated in Edwards’ lab, the idea was commercialized in 2001 by SiREM, a company in Guelph, Ont., and has since been deployed at over 350 sites worldwide. It remains the only such technology that has passed all the regulatory tests necessary for use in Canada. Customers typically include large industries with a history of manufacturing or utilizing solvents like TCE, which is used to degrease metal parts when assembling automobiles or airplanes.
This work is just the tip of the iceberg, says Edwards, who is the director of the University of Toronto’s BioZone, a multidisciplinary research centre for applied biotechnology research. Moving forward, Edwards plans to explore various microbial processes that take place in the absence of oxygen, including the mechanics of human digestion, how to use microbes to make biofuels and how to convert garbage into usable energy. “If we could exploit those processes more fully,” she says, “we could recycle waste and get waste to energy, and that will have even more of an impact on the planet than cleaning up TCE in groundwater.”
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