About twenty-five years ago, the environmental engineers working for Gainesville Regional Utilities’ Kanapaha Wastewater Treatment Plant in Alachua County, Florida, made a serendipitous discovery while monitoring the plant effluent being injected into the drinking water aquifer. Some fifteen hundred feet underground, the water, which had been “treated” to drinking water standards by the plant, to comply with state regulations, had, according to the data they compiled, undergone what they referred to as “polishing.” Something was consuming the allowable contaminants in drinking water as it traveled through the porous limestone. In other words, there was biological activity going on in the dark where no living things, presumably, exist.
Since then biota have not only been discovered living around the volcanic vents deep in the Pacific Ocean, but microbes have actually been put to work in what is called bioremediation. A story in Miller-McCune provides the particulars.
The architect of this innovative program is one Terry Hazen, one time alligator hunter, sailor and jungle explorer (looking for E.coli).
After graduating from Michigan State University and Wake Forest, Hazen
… took his newly minted degree to the University of Puerto Rico in 1979, lured not just by the chance to cruise the Caribbean in his 27-foot sailboat but by the opportunity to explore how microbes, like the bacterium E. coli, survive in tropical environments. E. coli was thought to always signal the presence of human waste, but Hazen guessed that wasn’t the case in warmer climes.
While in Puerto Rico, Hazen overturned the almost universal assumption that the microbe E. coli was always associated with human feces. By collecting water from pristine streams and the leaves of bromeliads in the top of the rainforest canopy, he proved that E. coli was indigenous to the Puerto Rican environment. During his eight years on the island, Hazen rose to tenured full professor and chairman of the Department of Biology at the University of Puerto Rico in Rio Piedras, with more than 30 publications within four years — all before he was 30.
His study of life underground came somewhat later.
While drilling in the Savannah River Site, Hazen noticed methanotrophs, or microbes that consume methane, 2,000 feet below — which surprised scientists because the rock there was thought to lack the nutrients to support life. These microbes possessed an almost magical property. They produced a powerful enzyme that could break down more than 300 types of toxic organic contaminants and convert them into carbon dioxide and water.
I might note at this point that the Waste Water Plant in Gainesville has since been renamed the Kanapaha Water Reclamation Facility and, as noted in the link above, continues to receive kudos for its achievements. Perhaps it’s time we also rename the microbes who do the cleaning. “Bugs” seems doubly inappropriate now that the world of computers considers them a menace. Perhaps we could call them “live-in scrubbies.”
In 1995, the DOE sent Hazen to spearhead the cleanup of an abandoned oil refinery in southern Poland where oil had been dumped in open ponds for more than a century, forming what Hazen called a “sludge lagoon.” He showed that cleaning up such sites could be done quickly, to a high standard, just by providing the right mix of air and food to indigenous microbes, which cleaned up the oil-soaked dirt by doing what comes naturally. The project showcased the DOE’s expertise and served as the training ground for bioremediation teams all over Europe.
The underground microbes do need to be fed to spur their proliferation.
Hazen’s team began feeding the Hanford microbes in 2004. They injected 40 pounds of nutrients — a viscous, honey-like substance — into the wells and a few days later began taking samples of water and soil to be analyzed in Hazen’s Berkeley lab. Within three weeks, it was clear that the microbes were enjoying the new diet and thriving; the population boomed 1,000-fold and “the chromium levels were undetectable,” Hazen says, holding back a triumphant smile. “It lasted for almost four years.”
In 2008, after the hexavalent chromium levels rose again to 100 parts per billion, Hazen’s team fed the microbes a second meal of about 10 pounds of nutrients. Within 24 hours the odor of hydrogen sulfide — rotten egg gas — began wafting out of the wells. It’s the “sweet smell of success,” says Hazen with a smile, an indication that the toxic chromium was now being downgraded into the relatively harmless form that will cling to sediments and stay out of water — and out of the Columbia River, an important breeding ground for salmon. Hazen notes that there seems to be some type of “memory response” that occurs when the microbes are fed a second time, triggering a faster reaction.
Hydrogen sulfide is, of course, a smell well known all over the South. Some refer to it as “the smell of money” when it wafts from paper mills and pine stump refineries.
Hazen’s approach exploits a fundamental mechanism of metabolism. When humans digest food, they take electrons from the foods they eat and pass them off to the oxygen they breathe in. Similarly, microbes in the soil metabolize the nutrients that come through the wells, strip off some of the electrons and, through a series of chemical reactions, transfer the electrons to an electron acceptor. But different microbes have evolved to breathe different substances. Some microbes breathe oxygen, some nitrate, some carbon dioxide, and others breathe chromium.
Hazen anticipates that the microbial-remediation approach used at Hanford will become increasingly important. Studies in the last decade have shown that even ultra-low concentrations of many contaminants — like petroleum products — can disrupt the reproductive systems of humans and other animals, suggesting that many sites will need to meet a higher standard of cleanup. The only way to reach safe levels may involve the use of microbes. “Methanotrophs can get contaminants to parts per trillion and basically degrade until there is nothing there,” Hazen says.
While I highly recommend you read the whole article, especially for the projected future uses of the microbes, I want to close with the following:
Although Hanford ranks as one of the worst, it is just one of more than 70,000 or so dangerously contaminated sites scattered across the United States. Cleanup traditionally involves costly measures like carting dirty soil to distant decontamination plants or entombing toxic material in pits, a process that is often ineffective, Hazen says, because the tombs inevitably leak. The price tag to clean up all these sites is estimated at $1.7 trillion.
$1.7 trillion is significantly less than we spend each year on health care to produce a more sickly population and just a bit more than we spent to kill hundreds of thousands of Iraqis over eight years, with no positive effect. Talk about misplaced priorities.