Tastes great! UF scientists find bacteria that improve foul-tasting water

November 23, 2004

GAINESVILLE, Fla. — For thirsty consumers tired of choking down water with an earthy or musty flavor, the solution may lie within the water itself, a team of University of Florida researchers has found. The team has identified a type of bacterium that can quickly and inexpensively remove a foul-tasting, foul-smelling compound. Their findings appear in the current issue of the journal Water Research.

The culprit is an organic compound, 2-methylisoborneol, or MIB, released by blue-green algae that bloom in water reservoirs during the summer. Though harmless to humans, MIB gives the water a funky quality and has proved to be a headache for water treatment facilities worldwide.

“It’s not a North American problem, or a southern versus northern problem,” said Angela Lindner, a UF professor of environmental engineering and a principal author on the paper. “There have been outbreaks of this particular alga which spits out this chemical in Australia and in Japan. It can be a problem if you get your drinking water from a surface-water reservoir, usually a big lake, as opposed to groundwater aquifers, which are our general source of water.”

The researchers’ isolated strain belongs to the genus Bacillus, a group of bacteria found nearly everywhere in nature — and in this case, in the very same lake water as the MIB. The bacterium removes MIB-related odors simply by modifying the compound and lopping off the parts of its structure that produce unpleasant smells. “It’s just changing its structure, and the structure affects the properties,” she said.

The mystery species is genetically similar to several known species, but further testing will be necessary to identify it completely, Lindner said. The key, however, is not in finding one magical bacterium to do the job, but in locating a useful local species within any contaminated water supply, she said. This research can therefore serve as a template for other scientists working on the MIB problem.

An Australian scientist who has seen the UF study is now working on isolating local microbes for a similar study. “It wouldn’t be helpful to send him our strain because the conditions of their water may not be conducive for this microorganism to thrive,” Lindner said. “The idea was that if we want them to be able to develop these systems at any facility, it should come from the water source that they’re working with.”

Many water treatment plants use activated carbon to remove MIB and other compounds, a method that is effective but can be cost prohibitive, Lindner said. Other methods, such as chlorination and sedimentation, can eliminate other bad-tasting compounds but don’t remove MIB, she said.

The problem has been particularly severe in Florida’s Manatee County, a beach community that gets a portion of its water from shallow Lake Manatee. Searching for alternative methods for water treatment, Manatee County proposed a cooperative research effort with UF scientists. The primary focus of the cooperation was on tailoring activated carbon to specifically remove the intractable MIB, with the bacterial study a small part of the larger project.

However, it may now be possible to combine bacterial and activated carbon methods to produce a more inexpensive method for treatment, said Bruce MacLeod, water quality supervisor at Manatee County Utilities. “We have figured out how to do it with carbon, but it costs upwards of $16,000 a day,” he said. “We’re interested in investigating any way that this might be useful. It would be great for us and for the whole water industry.”

“There’s definitely a stigma on using biological populations in water-treatment plants. You’re adding something you traditionally want to remove,” said Chance Lauderdale, the study’s research assistant and a former UF graduate student in environmental engineering. “It’s kind of unknown, and it’s something that people are slowly getting used to. And activated carbon methods are useful, but microbiology could potentially be more cost effective because it’s renewable. It’s not something you’ll have to replace periodically.”

Using bacteria to eliminate MIB-related odors is a tricky proposition, and the first step was to determine whether it was even possible. The “odor threshold” for MIB — where it’s been removed to the point where there is no more smell or taste — is extremely low, Lindner said.

“It’s hard to get anything out of the water to that concentration using biological methods. Other biological studies have shown they can remove it but not below to where you can’t smell it anymore,” she said.

To assess that, the MIB-depleting bacterium was taken directly from Lake Manatee. Over the course of a year, Lauderdale isolated and nurtured a pure bacterial culture from the lake that, when placed in vials with untreated lake water, cleaned up the smelly compound and left no scent behind. Using average MIB levels in the lake as a starting point, the entire cleanup took about five days.

Although the results of the study are very promising, it’s only the first step, according to Lindner and Lauderdale. For one thing, they’ve isolated the bacterium but haven’t yet identified the species – or what chemical processes the bacteria go through when consuming MIB.

“In terms of actual (chemical) products, that will be our next step,” Lindner said. “We don’t know what our microbe is capable of doing. It’s obviously removing it very well, but whether it goes through the same pathway we’ve seen in other studies or not, we don’t know.”

Another step will be a small-scale pilot study to look at how the bacteria behave under more natural conditions, Lauderdale said.