BIOREMEDIATION
Arkajit Ganguly, Assistant Professor, Department of
Microbiology, Brindavan College, Bangalore -94.
"Remediate" means to solve a problem, and
"bio-remediate" means to use biological organisms to solve an
environmental problem related to contaminated soil or groundwater.
The rapid expansion and increasing
sophistication of the different industries in the past century has meant that
there has been an increasing amount and complexity of toxic waste which pollute
the environment. Bioremediation provides
a technique for cleaning up environmental pollution by enhancing the same
biodegradation processes that occur in nature. Depending on the site and its
contaminants, bioremediation may be safer and less expensive than alternative
solutions such as incineration or land filling of the contaminated materials. Bioremediation uses microorganisms (both bacteria and
fungi) to degrade organic contaminants in soil, groundwater, sludge, and
solids. The microorganisms break down contaminants by using them as an energy
source or co-metabolizing them with an energy source.
There are three types of bioremediation
strategies involving microorganisms:
1) Natural attenuation – In some cases, natural populations of
microorganisms adapt to the contaminant conditions and are able to convert the
contaminants to non-hazardous end products
2) Biostimulation – In some cases, natural
populations can be stimulated to degrade contaminants (e.g. Addition of
nutrients to enhance microbial growth)
3) Bioaugmentation – In some cases it is
necessary to add the microbial organisms that are capable of degrading the
contaminant rapidly.
Bioremediation may be conducted in situ or ex
situ. In situ processes treat soil and groundwater in place, without
removal or transportation offsite. This approach may be advantageous since the
costs of materials handling and some environmental impacts may be reduced.
However, in situ processes may be limited by the
ability to control or manipulate the physical and chemical environment during
bioremediation. Ex situ processes, on the other hand, involve
the removal of the contaminated media to a treatment area Still there are
various other factors that affect the process of bioremediation. These include contaminant
concentration, contaminant bioavailability, pH, temperature, nutrients, etc.
Though bioremediation provides a good cleanup strategy for
some types of pollution, but as expected, it will not work in all cases. For
example, bioremediation may not provide a feasible strategy at sites with high
concentrations of chemicals that are toxic to most microorganisms. The success of a bioremediation of a contaminated
site highly depends on characterization and monitoring completed before and
during its implementation.
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