Sites ranging from munitions disposals to landfills to local gas stations were the topic of environmental scientist Rebecca Brellenthin’s discussion of her career in environmental preservation at last Friday’s weekly Science Forum.
“Challenges of environmental restoration: construction, preservation and enhanced biodegradation” was the topic of the forum where Brellenthin guided the audience through three different sites facing environmental woes. One of the sites was A.C. Thompson Field in Jackson, Miss.
The area was originally a fire training facility from 1964 to 1978 and afterwards it became an area of contamination. Studies of the area found trace elements of 1.1-Dichloroethene in the groundwater. 1.1-Dichloroethene is an organo-chloride that is a highly flammable, colorless liquid that has a striking odor and is insoluble in water. Exposure to it results in sedation, inebriation, convulsions, spasms and even unconsciousness. For Brellenthin’s team, the basic problem with breaking it down was figuring out a way to remove the chlorine found in the substance.
Before Brellenthin and her team began to clean up the area, they had to assess the problems they would face. The team identified three problems. They had to find the main source of contamination, deal with the constant threat of hurricanes and handle the land’s unfavorable topography.
To break down the 1.1-Dichloroethene, the team used a Hydrogen Release Compound, which slowly diminishes the chlorine. The team injected HRC into the groundwater, which immediately released lactic acids into the contaminated area. The lactic acids then metabolized with the assistance of microbes and thus created hydrogen atoms. This chemical reaction is a natural process known as reductive dechlorination.
“We had to dechlorinate the contaminant until it was safe,” Brellenthin said.
How this works is chlorinated hydrocarbons are biologically degraded under anaerobic conditions, meaning conditions without oxygen. Then the anaerobic microbes remove the chlorine in the contaminant and replace it with hydrogen. Ultimately, the process creates non-toxic compounds such as ethane gas.
The team used HRC because it is a low-cost and effective means of removing chlorinated contaminants. It is also a long-term natural process that works well into an 18-month period. This eliminates the need for additional treatments and costs. HRC is also a very ecologically safe method that is not hazardous to any of the area’s plants and animals.
The area met state regulations and was considered stable. An audience member asked how such a contaminated area did not leak into other sources of water.
“It was the fat clays, fat silts and the slate layers that kept the contamination isolated,” said Tess Rottero, A.C Thompson Field site manager.
Brellenthin’s experience working with contamination also extends to Knoxville. She worked on a site on Magnolia Avenue which was once a gas station. The station had more than 20,000 gallons of waste that hadn’t been cleaned for decades.
“It was the 1950s. There were no regulations,” Brellenthin said.
She also said she was doubtful that the environment could ever be free of contamination, noting that she considered human ignorance to be the biggest environmental concern facing the world. Yet, Brellenthin said she now feels there is generally greater environmental know-how.
Audience member Rottero said she was hopeful that there would be fewer contamination concerns in the future.
“Hopefully, as a society, we are getting smarter. Our industry will not go away. We are using safe compounds in dry cleaning, and we are banning old chemicals,” Rottero said.
She added that as society’s awareness increases, waste clean-up and recycling will minimize the frequency and degree of environmental degradation.
