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Bioremediation is a clean-up technology that uses naturally occurring
microorganisms to degrade hazardous substances into less toxic or
nontoxic compounds.
These microorganisms may:
- Ingest and degrade organic substances as their food and energy
source,
- Degrade organic substances, such as chlorinated solvents or
petroleum products, that are hazardous to living organisms, including
humans, anddegrade the organic contaminants into inert products.
Because the microorganisms already occur naturally in the environment
they pose no contamination risk.
Groundwater Reliance Statistics:
In New Hampshire, approximately 60% of the state's population rely
upon groundwater as a source for drinking water. Approximately 25%
of the state's population uses private wells, most of which are
drilled into bedrock. Of the approximately 2,200 public water supplies
in New Hampshire, it is estimated that at least 85% rely upon groundwater
from fractured bedrock as a source. Similar trends are seen throughout
New England. In general, bedrock aquifers are heavily relied upon
as domestic and small public drinking water sources in much of the
United States.
Bedrock Aquifer Contamination
Statistics:
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Of the 18 Federal
Superfund sites located in New Hampshire, 15 have bedrock
contamination.
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In New Hampshire, there are approximately 400 hazardous
waste sites, 3,000 petroleum sites, and 197 unlined solid waste
landfill, some of which are impacting or have the potential to impact
bedrock aquifers. Of the 18 Federal Superfund sites located in New
Hampshire, 15 have bedrock contamination.
Advantages of Bioremediation:
The remediation of bedrock aquifer contamination is
extremely difficult with existing technologies, such as pump and
treat. This is due to the expense and uncertainty in locating and
removing contamination from fractured bedrock to the degree necessary
to restore groundwater. Therefore, an in situ remediation mechanism
such as biological degradation could be an essential component to
restoring an aquifer to drinking water quality.
The high costs and sometimes limited effectiveness
of conventional remediation technologies have stimulated interest
in bioremediation as an alternative clean-up method. Bioremediation
can be performed directly in the subsurface by using naturally occurring
microorganisms to degrade the contaminants. Bioremediation has been
used to clean-up many groundwater and soil contamination sites.
Keys to the success of bioremediation include insuring that:
- The microorganisms actually degrade the contaminants
to acceptable (less harmful) by-products
- They perform the degradation in an acceptable time
frame, and
- They have adequate supplies of substances they
need to degrade the contaminants.
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bioremediation can be accelerated by supplying
substances to the microorganisms that will stimulate them.
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Finally, the microorganisms must be exposed to favorable
physical and chemical conditions in the subsurface. Biodegradation
of contaminants may occur naturally in the subsurface at fairly
slow rates. These natural processes may be too slow to insure adequate
treatment in an acceptable time frame. However, bioremediation can
be accelerated by supplying substances to the microorganisms that
will stimulate them.
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Site/Treatment Assessment:
Bioremediation must be carefully evaluated before it is considered
acceptable as a treatment alternative at a specific contaminated
site.
Typically, three steps must be taken to assess whether bioremediation
will work:
- Field monitoring must show that the contaminant concentrations
are decreasing.
- Laboratory studies must also corroborate that the subsurface
microorganisms are capable of degrading the contaminants.
- Data must show that the microorganisms are actually degrading
the contaminants in the subsurface at the waste site.
Until recently, there was little evidence that microorganisms
existed in bedrock. Now studies have shown that bacteria exist
in uncontaminated bedrock, living along the fractures that
permeate the rock and in the water that flows through them.
Very little data are available on the implementation or success
of this technique.
Research Directions:
In order to assess whether bioremediation can be used to
clean-up contaminated bedrock:
- Regulatory agencies must have a better understanding of
the microorganisms that live in the bedrock and their ability
to degrade contaminants.
- Protocols must be developed to evaluate whether bioremediation
is an adequate clean-up method.
- Finally, methods to accelerate bioremediation in the bedrock
fractures must be developed.
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