Established remediation techniques (pump and treat) often rely on pumping large amounts of contaminated water out of the ground, flushing the pollutants with it. However, these techniques require large volumes of water and may need to be operated for many years. The cost of treating the contaminated water and the time required make this approach very expensive -- and serves only to contain the contaminated groundwater.
The approach developed by the Georgia Tech team could allow remediation engineers to directly address pollution mass removal, with recovery rates exceeding 90 percent.
"Our approach is to aggressively treat the source zone where the actual spill occurred and remove the compound, then separate and treat or recycle it above ground," Pennell explained. "We are trying to remove the long-term source of groundwater contamination in a manner that will produce the most results for the least cost. It's generally not economically feasible to treat the entire aquifer."
One issue that all such solvent remediation efforts must address is containing the problem. Because these chlorinated compounds are heavier than water, removal efforts can inadvertently drive them deeper into the ground if underground water supplies lack natural boundaries such as impermeable clay or bedrock.
To keep the dense nonaqueous phase liquids (DNAPL) from flowing deeper into the earth, engineers have injected alcohols such as n-butanol into the pollution mass to lower its density. They have also injected surfactant chemicals food or pharmaceutical quality agents similar to those used in whipped toppings and shampoos which reduce the interfacial tension to separate the solvent from soil particles.
The patent-pending technique developed by Pennell and collaborators C. Andrew Ramsburg, Tohren C.G. Kibbey and Kim F. Hayes combines both approaches, making the
Contact: John Toon
Georgia Institute of Technology Research News