Introduction to Bioaugmentation
In industry, often the biomass present needs reinforcements
to increase its degradation efficiency. A method currently in use
is bioaugmentaion, which adds microorganisms that have been
isolated and selectively adapted to degrade specific compounds
to existing biomass (Huban, Plowman, 74). The benefit of this
method is that the microorganisms added are able to degrade
contaminants not broken down by biomass already present in the
pond, resulting in improved treatment of wastewater.
Bioaugmentation changes the species composition of existing
biomass by adding bacteria from natural sources or environmental
isolates. Many natural bacteria can be found in the contaminated
soils and water of sludge storage areas and lagoons. (75) For
example, if bacteria was needed to degrade aliphatic
hydrocarbons, a likely source would be storage area for the
sludge produced in the degradation process.
Example of Metabolic Pathway
The samples taken from storage facilities contain many
different strains of bacteria, so the particular strain needed
must be isolated. The method of isolation is to create an
environment containing the organic compunds of interest and see
which strains are able to survive and grow in their presence.
After the candidate strains are isolated, they are tested to see
which strains in the processing of degradation consume the most
oxygen, oxidize the target compound, and produce the largest
quantities of gas. (Huban, Plowman, 75). The next phase of theprocess is to remove minor strains to increase overall efficiency. From the sample strains remaining, the concentration of the target compound can be increased or more of these strains can be isolated to obtain the desired activity. A concern with
bioaugmentation is the saprophytic bacteria, which is found in
the majority of the stains isolated. Some of the bacteria, under
certain conditions, are pathogens that can cause infection (76).
The safety method used to combat this problem is to subject the
stains to antibiotics, to see if these remedies will work.
Case Study Example
The usefulness of bioaugmentation is its cost-effectiveness.
In one particular example, an anerobic digestor serving a 100-
million-gal/d facility had a 10 ft layer of scum and grease that
contained almost 20% total solids (77). It was estimated that
physical removal of the scum would cost $1,000,000. When the
appropriate microorganisms were added, isolated, and produced
using the bioaugmenatation precedure described above, the
percentage of solids decreased from 20% to 1.5% at a cost of less
than $50,000 (78). It is important to note that in this example,
a food source of nitrate salts was added as well as the "grease
bugs" to digest the sludge in the anaerobic environment.
Future Direction of Bioaugmentation
The latest technological advances in the bioaugmentation
consist of genetic fingerprinting and molecular markers to
determine the interactions between augmented organisms and native
organisms (existing biomass). In addition, there are some
prospects for genetically engineered microorganisms. These
advances in genetic engineering would involve splicing genes from
one organism into another the genes that code specificdegradative enzymes (81).A possible application would be in situations where the contaminent levels of the wastewater are below the levels needed for microorganism enzyme production.
Genetic engineering could make it possible to alter the gene
structure so the microorganisms produces the correct enzyme in
the presence of some other contaminent already present in high
concentration within the wastewater.
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- "Huban, Christopher and Robert Plowman". Bioaugmentation: Put Microbes
to Work Chemical Engineering Magazine. March 1997. Pgs 74-82.