“Bacteria make enzymes, and it’s these enzymes that do the dirty work of actually breaking down pollutants. So, Scott and his team are experimenting with bacterial enzymes to decontaminate water systems polluted with pesticides and herbicides. Enzymes aren’t alive, so they don’t need nutrients, which means they can be used in places that bacteria won’t survive. They can’t reproduce or adapt, so won’t multiply and disturb delicate ecosystems.”
John Coates’ laboratory at the University of California, Berkeley, hums with activity. Negative 80-degree freezers whirr, liquid nitrogen bubbles, grad students meticulously measure and mix complicated concoctions. But all of this is nothing compared with the commotion going on at a microscopic level.
The Coates lab is growing many different kinds of bacteria, multiplying in petri dishes at mind-boggling rates. But these bacteria aren’t out to harm people or animals. In fact, quite the opposite — they’re hard at work breaking down a dangerous chemical that pollutes waterways across the United States.
The chemical, called perchlorate, comes from rocket fuel, munitions and fireworks. It’s dangerous to humans because it can impair thyroid function. It can also affect the thyroid in freshwater animals like fish and amphibians, even altering gonad development in some animals. But certain bacteria, including several species of Dechloromonasand Azospira, have evolved to use perchlorate to make energy-storing molecules. In the process, they turn it into harmless chloride and oxygen.
Coates is just one of many scientists across the globe who are working to harness the ability of various bacteria to remove harmful pollutants from water. This is no easy task. There are thousands of different pollutants — industrial chemicals, pesticides, herbicides, fertilizers, metals and more — and no one microbe can break down all. Also, because bacteria need special conditions to survive, it can be difficult to incorporate them into water treatment systems.
In spite of these challenges, Coates sees a future full of possibility. “It’s really just a question of sitting down and spinning your brain around all the cool, novel aspects of these organisms and then asking where can we apply this?” he says.
Perchlorate is mostly used in rocket fuels and munitions. Improper storage or disposal of rockets or debris may contaminate the environment. Through leaks or explosions, perchlorate can also pollute waterways near manufacturing plants. It’s water soluble and chemically stable, so it can persist in ground and surface water for decades.
And that’s bad news for people whose drinking water comes from contaminated sources, especially pregnant women and children. Perchlorate has been shown to impair thyroid function; proper thyroid function is essential for normal brain development during the prenatal period and during childhood.
When Coates submitted his first academic paper on perchlorate-degrading bacteria in 1998 (it was published in 1999), there were only a few bacterial species known to be capable of performing this feat. Coates wanted to see if there were more.
“It turns out that the microorganisms that use perchlorate are essentially ubiquitous — they’re not difficult to find. And you can culture them fairly readily. To remediate perchlorate, you just needed to create specific conditions,” he says.
The way to do this is to use something called a bioreactor — a home for bacteria that provides all the nutrients and minerals they need to thrive. It’s similar to a fermenting tank for beer, except instead of yeast
converting sugars into alcohol and carbon dioxide, perchlorate-destroying bacteria turn dangerous perchlorate into harmless chloride and oxygen. Contaminated ground or surface water gets pumped into the bioreactors, which are full of these bacteria. Once the bacteria have broken down the perchlorate, the water is filtered and sterilized to remove bacteria. The decontaminated water can then be sent to consumers or pumped back into the ground.
Thanks to discoveries made by Coates and a legion of other scientists, perchlorate-decontaminating bioreactors have been applied in the real world with great success. Large-scale perchlorate bioreactors are now at work cleaning contaminated water at several sites in California, Kansas, Texas and Utah. These bioreactors are astonishingly efficient: The bioreactor-based groundwater treatment plant in Rialto, California, for example, is capable of decontaminating 2,000 gallons (over 7,500 liters) of perchlorate-polluted water per minute — that’s more than a billion gallons (over 3.7 billion liters) a year. In fact, Coates says that the bacterial removal of perchlorate represents one of the largest-scale bioremediation projects in the world.
Implementing bioreactor technologies isn’t always so straightforward, even when the bioreactor performs well in the lab. A bioreactor designed by Bruce Rittmann, the director of the Swette Center for Environmental Biotechnology at Arizona State University’s Biodesign Institute, was initially used to remove water contaminants like perchlorate and trichloroethene, but can also be used to remove uranium and other metals from water. This kind of contamination can occur around uranium mines and mills, especially older abandoned ones. In people, drinking water contaminated with uranium can cause kidney damage; uranium is also toxic to fish, decreasing their reproductive success.
The bacteria in the bioreactor can’t destroy the uranium, but they can convert it to a form that separates from water. Once the uranium comes out of the solution, it’s much easier to remove —think about the difference between taking a sugar cube out of a glass of water and trying to remove the sugar once it’s dissolved. In tests, Rittmann’s bioreactor removed about 95 percent of the uranium from a contaminated water supply.
Rittmann says it would be relatively straightforward to construct a bioreactor system in currently operational mines that already have some sort of water treatment system in place. However, cleaning up abandoned mines would be more difficult, since they have no such infrastructure. There are about 4,000 abandoned uranium mines in America’s western states.
Note, this is a long story with pictures of the reactors….a good read and hope for our future.