Bringing a sweet touch to dirty work at Devens
Molasses is essential ingredient in effort to clean toxins from soil
The last vestiges of the Green Berets still haven't left Devens. They hold their ground at the former base's airstrip, spread out and dug in. Bombs and bullets can't dislodge them. They can't be starved out. But show up with molasses, and they'll slowly fade away.
A byproduct of turning sugarcane into raw sugar, great for baking and essential to distilling rum, molasses, surprisingly, is the key ingredient in a plan to clean up soil contaminated by Special Forces soldiers who used dry-cleaning fluid to wash their parachutes at the now-defunct Moore Army Airfield.
Years of dumping dry-cleaning fluid into the base's wells resulted in a plume of cancer-causing perchloroethylenes, or PCEs, under the airstrip, which is within the historic boundaries of Ayer. Left alone, the plume could eventually leach into the area's water supplies, specialists said. But thanks to the sticky sweet syrup, the specialists expect that disaster to be avoided.
"It's organic," said Lauri Nehring, a member of People of Ayer Concerned About the Environment, a nonprofit group that has received funding from the federal Environmental Protection Agency to help monitor the cleanup of the base since its decommissioning in 1990. "When we first heard about it, we were like, 'That's weird.' It's kind of fun to talk about."
Molasses is useful for cleaning up toxins for the same reason it's good for gingerbread cookies and shoofly pie: it's tasty. Specialists said the molasses promotes the growth of healthy bacteria that, once their population booms, eventually become voracious enough to eat the excess toxins in the soil.
"Molasses is a simple sugar," said Lynne Welsh, who oversees federal facilities for the state Department of Environmental Protection. "It basically is food for the bacteria that are already naturally in the soil and the ground water. The extra food makes them multiply and once the molasses is used up, then they start to use the PCE and eat it up."
Since 2003, about 460,000 gallons of a mixture of 15 percent molasses and 85 percent water has been injected into a series of wells between Route 2A and the Nashua River, said Robert Simeone, environmental coordinator at Devens for the Pentagon's Base Realignment and Closure Division. Molasses is now injected once a month on the 246-acre area.
The $7 million project is expected to continue for another 20 years, Simeone said. Decades are necessary because PCEs are hard to break down. And once the PCEs break down, their constituent chemicals also need to be consumed and expelled by bacteria until all that's left is harmless ethane and carbon dioxide.
Already, said Simeone, the process is working. "It's going well and there's evidence of that," he said. "We're seeing the breakdown products of PCE."
One of the benefits of the molasses is that while it works, it is neither as costly as siphoning water out of the ground and then pumping it to a treatment plant, nor as disruptive as digging up and transporting mounds of contaminated soil, said EPA environmental engineer Mike Daly.
Molasses is probably more efficient than both options, Daly said, because it is poured into wells that deliver it directly to ground water and the PCE plume. Siphoning or digging usually leaves traces of toxins behind.
"The state of science has shown nature can do a better job than pumping and treating it," said Daly. "Think of squeezing soap out a sponge. You can't squeeze it out of the sponge. It's sort of the same concept. It can be very difficult to get the contamination out through those physical means."
Simeone echoed that sentiment. The airstrip, which is now used by the State Police for driver training, is one of the last remaining, but most polluted, areas on the former base, said Simeone. But compared with another large cleanup project on Devens, the Shepley's Hill Landfill, the molasses treatment is a cinch.
Constantly pumping and treating the arsenic-tainted water from the landfill costs around $500,000 a year and will probably continue indefinitely as the landfill's waste decomposes and releases arsenic amounts that are too large to be released, said Simeone.
The PCE levels from the parachute laundering aren't as dangerous in the short term, said Welsh, but they could be in the future. Since PCEs are heavier than water, she said, they've percolated through the soil and are now resting on bedrock, where slow-moving underground water is pushing them toward the Nashua River. There they could harm wildlife and enter the water supply, she said. The molasses-fed bacteria should eat up the PCEs before they reach the waterway, she said.
The process temporarily reduces oxygen in the ground water and also produces small amounts of excess arsenic, but levels of both will return to normal a few years after the PCEs are gone and officials stop adding molasses, she said. Without molasses or the PCEs as food sources, the bacteria die off until their population returns to normal levels, Welsh said.
The company that injects the molasses, Denver-based
When he was studying how bacteria could cleanse the earth of toxins, Suthersan chose to patent molasses, he said, because of its low cost. Molasses costs 4 to 6 cents a pound, he said, whereas corn syrup runs around 25 cents a pound and milk products cost as much as $8 a pound. "It's one of the cheapest organic substances you can buy," he said.
Other sugary substances that provide fodder for bacteria would work the same way, said Suthersan. Since Arcadis has the right to molasses, other remediation companies have resorted to their version of the same, he said. "Some people are using ice cream."
John Dyer can be reached at email@example.com.