Professor James Gossett, director of the School of Civil and  Environmental Engineering, pioneered in-situ bioremediation of  groundwater that has been contaminated with chlorinated ethenes, the  second-most-common groundwater pollutant in North America (after  petroleum hydrocarbons). These toxic synthetic chemicals, used as drycleaning  solvents and industrial degreasing agents, used to be flushed  down drains or indiscriminately dumped after use.

Gossett and one of his students reported the first complete  reductive dechlorination of perchloroethylene, or PCE, to nontoxic ethene  gas by an anaerobic bacterium. He and another Cornell colleague,  a microbiologist, isolated the organism that performs the anaerobic  transformation, Dehalococcoides ethenogenes strain 195. The product  of this transformation, ethene, also known as ethylene, is considered  environmentally benign. In fact, it is a natural substance in plants that  causes fruit to ripen. Strain 195 and its close relatives have now been  found at PCE-contaminated sites all over the world.

More recently, Gossett has switched research emphasis to aerobic  oxidation of lesser-chlorinated ethenes, investigating the potential of  bacteria to derive energy and growth from oxidation of these important  pollutants. He and colleagues have isolated a dozen organisms that live  by complete degradation of vinyl chloride under aerobic conditions, as  well as a unique organism that can derive its energy and growth from  oxidation of cis-dichloroethene (cDCE) to carbon dioxide.

Strain 195 and other microorganisms may be at work at pollution sites, a possibility that Gossett and Professor Ruth Richardson, also in Civil and Environmental Engineering, can investigate now that they know what to look for. “Strain 195 is a metabolically talented organism,” says Richardson, who brings the skills of microbiology and molecular biology to environmental engineering. “The genome of strain 195 suggests a deep dependence on chlorinated organic compounds—but also a great versatility in this appetite. In light of these insights, it is not surprising that relatives of strain 195 have consistently shown up in cultures that degrade PCE—as well as PCBs, dioxins, and chlorinated benzenes,” Richardson adds.

“And that will tell us whether some enhancement would be helpful or whether the problem will take care of itself,” Gossett explains.

Leonard Lion, professor in Civil and  Environmental Engineering, and Claude  Cohen, professor in Chemical and Biomolecular  Engineering, are collaborating to develop  nanoscale polymer particles that can be injected  into soil contaminated by coal tar wastes to trap  contaminants and carry them to the surface.

Lion and Cohen envision using the particles  to improve upon what’s called pump-and-treat  remediation. This method pumps contaminated  groundwater to the surface, removes  contaminants, and then reinjects the cleaned  water underground.

The particle surface chemistry is designed  so the particles, with an average diameter of  approximately 60 nanometers, can travel with  water through the soil without getting stuck.  The chemistry of the interior of the polymer  particles is designed to foster scavenging of  organic contaminants that would otherwise cling  to the soil. The polymer particles would replace  surfactants sometimes used in the pump-andtreat  process. After the particles carry their cargo  to the surface, they can be relieved of their toxic  loads and used again.