Bugs provide solution to MTBE groundwater
contamination
Petaluma, CA— Although half of the states
in the United States have banned methyl tertiary butyl ether (MTBE)
in gasoline because it contaminates groundwater, past spills and
underground storage tank leaks will continue to impair groundwater
quality in parts of the country for years or decades to come.
Helping to address this problem are bioreactors
from Environmental Resolutions, Inc. (ERI) now being used at dozens
of locations, which show that naturally occurring microorganisms
concentrated in state-of-the-art bioreactors can effectively clean
contaminated groundwater sites. “Microorganisms have been
used more and more in groundwater remediation in recent years as
water industry practitioners learn more about the microorganisms’
vast treatment capabilities,” said Joe O’Connell, president
of ERI. He added that bioreactors are more frequently being embraced
by water industry officials as a treatment tool since bioreactors
can clean both MTBE and related chemicals such as tertiary butyl
alcohol (TBA) and other gasoline components.
ERI worked with Drs. Edward Schroeder, Daniel
Chang and Kate Scow at the University of California at Davis to
develop a compact, practical, and effective bioreactor technology
to treat groundwater. Bioreactor-based water treatment involves
pumping groundwater out of the ground, mixing it with active microorganisms
in a bioreactor system, and discharging the newly treated water.
The discharge is either sent back into the ground, to a municipal
sewer system, or into surface water.
The bioreactor groundwater treatment technology
developed by ERI and UC Davis includes an aboveground tank containing
trillions of microorganisms, primarily bacteria that attach themselves
to the surfaces of fine grains of sand. The grains are distributed
throughout the tank by the upward flow of the water passing through
the tank for treatment. As the contaminated water mixes with them,
the microorganisms consume MTBE and other dissolved gasoline components
as food. During the water’s 20-minute journey through the
bioreactor, the microorganisms destroy the gasoline chemicals, converting
them to carbon dioxide and water, thus eliminating the contamination.
ERI bioreactors can treat a wide range of contaminant
concentrations because of the way their distinct water recycle loop
dilutes water coming out of the ground. ERI’s bioreactors
have handled extremely high concentrations (up to a million parts
per billion of gasoline constituents), reducing them to non-detectable
levels. Laboratory analyses of water samples leaving ERI bioreactors
are able to detect little if any MTBE or other gasoline traces.
Microorganisms, like people, require oxygen and
essential nutrients to survive, grow and multiply. Bioreactors have
systems that provide these essential materials to the microorganisms
as they treat the contaminated water. Microorganisms in a bioreactor
ecosystem have the ability to adapt to changes in water temperature,
water flow rate and contaminant concentrations, which often fluctuate
over time.
ERI bioreactors have been deployed at over 30
MTBE sites. The bioreactors are quiet and odor-free and can be efficiently
moved along with their microbial communities to new treatment sites.
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