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TINY BUGS TAKE THE BITE OUT OF HAZARDOUS WASTE

SHARE TINY BUGS TAKE THE BITE OUT OF HAZARDOUS WASTE

Scientists at the Idaho National Engineering Laboratory are cultivating waste-munching "super bugs" that may contribute in a major way to solving the world's chemical pollution problems.

"In terms of waste cleanup parlance, this is probably the hottest bug in the world," said Patrick Dugan, director of the Center for Bioprocessing Technology at the lab's Idaho Research Center in Idaho Falls.Dugan was talking about pseudomonas, a living microorganism that scientists at EG&G Idaho Inc., through a complex set of experiments and processes, are coaxing into eating increasingly concentrated solutions of common hazardous chemicals.

Each year, said Dugan, industry produces thousands of gallons of liquids called scintillation cocktails, used in testing soil and water samples and in disease diagnosis. The cocktails usually contain a combination of hazardous chemicals such as zylene and toluene, along with any of several low-level radioactive substances.

Under the right conditions, pseudomonas, which is found naturally in soil, can render the two hazardous chemicals harmless by breaking down the chains of carbon that link molecules within.

"This organism goes after carbon," Dugan said. "This is what it eats."

The biodegradation process, as it's known, can make the remaining radioactive part of the cocktail a lot easier to dispose of safely.

After metabolizing the waste into mostly carbon dioxide and water, said Dugan, the microbes remain in their natural state and won't hurt the environment.

Here's how the scientists are wooing the bugs to do their bidding.

First, said Dugan, they select a microbe found to metabolize a given chemical. They study the biological factors that enable the microbe to eat what it does. Then, they build a bioreactor chamber in which they place the microbe and the chemical.

By manipulating the amount of chemical the bug is fed, along with air, temperature, moisture and fertilizer levels, they carefully engineer the ideal environment in the chamber that will cause the bug to eat the maximum amount of waste chemical in the highest concentration.

The design of the bioreactor is also important and at the research center scientists are experimenting with two types - liquid-feed and vapor-phase.

In vapor-phase bioreactors under development at the center, EG&G microbiologist Robert Rogers said, a nutrient solution similar to crop fertilizer is dripped on the microbes, which grow on thousands of thimble-sized plastic cages piled in a tube. The thimbles provide lots of surface area for the microbe to grow on. Vaporized zylene is piped in the bottom of the tube as fast as the microbes can digest it.

Liquid-feed bioreactors at the lab are similar, except that the waste chemicals are dripped in from the top of the tube.

Scientists may also try to combine the two kinds of bioreactors to achieve greatest efficiency.

"The question now is, `Can you gear it up to handle waste on a large, industrial scale?' " Dugan said. That's the ultimate goal of the research team.

EG&G's interest in the technology was spurred by recent federal legislation restricting the disposal of mixed radioactive and hazardous wastes. Also propelling the technology is the possibility of selling it to companies with waste disposal problems.

Rogers said biotechnology probably will work well in the degradation of common liquid methylated benzenes such as zylene and toluene, and also in getting rid of chloronated solvents contained in dry cleaning fluids, degreasers and paint strippers.

In the case of the chlorinate pollutants, the methylosinus bug, which grows on methane gas, looks the most promising in research so far. Future research may focus on genetically engineering more potent strains of microbes that can break down specific chemicals even faster under the right conditions.