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are innumerable strains of microbes under basic categories of bacteria, yeast or fungi,
which degrade or transform chemicals and compounds into simpler, more desirable, or less
harmful or toxic substances. These bioprocesses have been used for centuries
in the treatment of municipal wastes; wine, cheese and bread making; and for bioleaching
and recovery of metals, such as copper. The use of microorganisms takes advantage of
the fact the microbes, like all living organisms, need nutrients (such as nitrogen,
phosphate, and trace metals), carbon and energy to survive. These beneficial
microbes break down and transform a wide variety of inorganic and organic compounds to
obtain energy for their growth. For example, many species of soil bacteria can use
petroleum hydrocarbons as a food or energy source, transforming them into harmless
substances consisting mainly of carbon dioxide, water and fatty acids. Bioprocess
development has made it possible to greatly accelerate natural bioprocesses by selecting,
concentrating and acclimating microorganisms to degrade or transform many inorganic and
organic contaminants in a matter of weeks or months rather than decades. |
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The foundation of
bioremediation has been the observation that over long periods of time and without human
intervention, nature eliminates both natural and most man made pollution through natural bioprocesses. Bioremediation is a naturally occurring
bioprocess that harnesses microbial and geochemical processes to degrade or transform
(oxidize or reduce contaminants) environmental contaminants to innocuous end
products. Bioremediation processes promote the growth of microbes
that can effectively degrade or transform specific contaminants, converting contaminants
to nontoxic or more easily removed by-products. Because indigenous bacteria are not
always sufficient or suitable, the majority of bioremdiation processes, at field scale,
benefit from the addition of supplemental products used separately or together:
Biostimulation - the process of providing key nutrients, vitamins, enzyme
preparations and other factors to indigenous microbial populations that are necessary to
promote their growth and metabolic activity used to degrade and transform contaminants.
Bioaugmentation – the process of introducing known blends of
microorganism into a contaminated in situ environment or bioreactor to initiate and
sustain a specific bioremediation process.
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 Scientists
have found and isolated microorganisms with better biodegradation and biotransformation kinetics for a variety of
contaminants within broad environmental habitats. Center scientists
have isolated and cultured microbes that express the
qualities needed for field survival and function including the expression of enzymes able
to degrade a broader range of compounds present in contaminated environments. These
microorganisms and enzymes are developed into bioprocesses and bioremediation strategies,
tested at bench-scale and modified to address full-scale site requirements.
Although not a panacea, bioremediation does offer a low-cost permanent
solution for many environmental cleanup situations. It is a natural process
alternative to conventional or traditional methods as incineration,
catalytic destruction, the use of adsorbents, and the physical removal and
subsequent destruction of pollutants. The economics of bioremediation are
usually significantly more favorable than other techniques. The primary
reason is in situ biological treatment there is no need for the hauling and
expensive disposal costs of contaminated soils and high water-content
wastes. |
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integrating proper utilization of natural microbial capabilities with
appropriate engineering designs to provide suitable growth environments,
field implementation of bioprocesses and bioremediation methods can be
successful. However, successful application of bioprocess and bioremediation
techniques must address both the heterogeneous nature of many bioprocess environments and
contaminated waste sites and the complexity of using living organisms. This stresses the
necessity for biotreatability testing, i.e., determination of contaminant
profiles, site environmental and microbial characteristics, key nutrients, etc. to allow
configuration of site specific bioprocess and bioremediation requirements. |
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methods, different strains of bacteria are selected that work
together to degrade or transform specific contaminants. Because site conditions and
types of products and contamination vary greatly,. Products include
only microbes capable of surviving and thriving in difficult environmental situations.
Site-specific bioprocesses and products are not always an instant cure-all,
but in most cases result in a significant bioprocess improvement or a reduction of the
contamination load. Successful process and product use requires close collaboration
between remediation, engineering, and waste management professionals. Site
analysis, biotreatability tests, and treatment goals
are necessary before a project begins, and consistent monitoring during
the treatment phase is critical. The microbiology of any bioprocess or bioremediation
is complex and it is important to have a qualified microbiologist available for all
project aspects. While individual microorganisms for any specific degradation or
transformation may vary considerably, there are several generalizations that can be made
for many bioprocesses:
- Aerobic microbial environments are generally more competition based, whereas anaerobic
communities, usually induce cooperation among organisms because the amount of energy
available is less and organisms have become more specialized and interactive to get their
small piece of energy
- Competitive and noncompetitive environments – in competitive environments there is
a superabundance of resources, there are enough resources and resource heterogeneity
(diversity of carbon resources) so that each organism is successful – the converse is
true in noncompetitive environments where the microbes become spatially isolated
- Bioremediation in noncompetitive environments is often slow because the fastest growing
microbes, on the pollutant, have no way to expand into new niches. This is termed the
isolation factor, and it allows slow or ineffective metabolizers to dominate unless steps
are taken to overcome this physical barrier
- Bioremediation in competitive environments must use selective pressures, such as key
nutrients, water availability, aeration level, pH, oxidation/reduction potentials, etc. to
control or shift the microbial dominance to effective pollutant metabolizers and
transformers
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