Bioremediation uses microorganisms, plants, or their enzymes to degrade contaminants in soil. Contaminants include chlorinated solvents, heavy metals, pesticides, and hydrocarbons from industrial activities. Bioremediation occurs through biodegradation, mineralization, or cometabolism. Strategies include intrinsic bioremediation, biostimulation, bioaugmentation, landfarming, and phytoremediation. A case study describes how nutrients were added to Alaskan shoreline to stimulate indigenous bacteria and enhance biodegradation of crude oil after a large spill.
2. Introduction
• Strategy or process that uses microorganisms, plants, or microbial or plant
enzyme to detoxify contaminants in the soil and other environments is called
Bioremediation.
• Any substance in the soil that exceeds naturally-occurring levels and poses
human & soil health risks is a soil contaminant. (Soil Science Society of America)
• Contaminants include:
Chlorinated Solvents (TEC and PCE)
Trinitrotoluene (TNT)
Heavy metals such as chromium and lead
Pesticides
Aromatic hydrocarbons (benzene , toluene etc.)
Polyaromatic hydrocarbons (creosote mixture)
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4. Bioremediation Processes
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Biodegradation: Partial and sometimes
total, transformation or detoxification of
contaminants by microbes and plants
Mineralization: Complete conversion of
an organic contaminant to its inorganic
constituent by a single or multiple
species.
Cometabolism: Transformation of a
contaminant without providing it Carbon
or energy for degrading microbes.
5. Criteria for Bioremediation
• Organisms must have necessary catabolic activity to degrade contaminants
at a reasonable rate.
• The target contaminant must be bioavailable (e.g. not sorbed as a bound
residue).
• The site must have soil condition conducive to organism growth or activity.
• Not much expensive.
• Magnitude, toxicity and area of contamination
Failure to meet any one of these criteria cause rejection of bioremediation
approach.
Many compounds can not be degraded at a reasonable rate, such are referred
as Recalcitrant compounds e.g. Humus
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6. Biological Mechanisms ofTransformation
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Conversion
Conversion of
contaminants to
mineralized end
product
CO2, H2O & Salts
Biotransformation
Biotransformation,
where end product is
not mineral
TEC to DEC
Biodegradation
Involves the process
of extracting energy
from organic
chemicals via
oxidation of organic
chemicals
9. Intrinsic Bioremediation
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• Intrinsic bioremediation use indigenous microorganism to degrade
contaminant.
• No human intervention involved in this.
• Cheapest means of bioremediation.
• Most commonly used method.
• Too slow degradation.
10. Biostimulation
• Microbes are motivated to start the process of bioremediation
• Addition of nutrients to stimulate indigenous bacteria.
Bioventing
• Gaseous stimulants such as Oxygen & Methane are added passively
• It stimulate indigenous microbes activity
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11. Bioaugmentation
• Inoculation of microorganisms to facilitate bioremediation.
• Organisms are selected for their high degrading potential.
• Wild-type or genetically modified species.
A single species
Consortium of several species
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12. Landfarming
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• Incorporation of wastes into the
surface of non-contaminated soil.
• There is a thick clay layer to prevent
leachate from contaminating ground
water.
• Soil is plowed or disking
• Uniform distribution of fertilizer &
microbial inoculant
13. Composting
• Microorganisms are used in constructed
piles of soils or windrows to degrade
contaminants.
• Piles are physically mixed and moistened
to promote microbial activity.
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14. Phytoremediation
• Use of plants to remove or transform contaminants
• Affects directly or indirectly
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Hyper
accumulating
heavy metals
Stimulating
microbes in
rhizosphere
16. Biostimulation Example
• In U.S.,Alaska there was release of over 40million liters crude oil. Over
1500km of shoreline in the sound and Gulf of Alaska were contaminated to
varying degrees.
• Oil is rich with carbon and low in N & P
• A stable water in oil emulsion having N/P with 7.3/0.8 ratios was applied in
form of Inipol
• A thin layer of inipol was applied at shore at 300ml/sq. m
• Crude oil destabilize Inipol to release its N
• Increase the activity of indigenous hydrocarbon degrading bacteria.
• Enhance degradation of petroleum
• Passive bioremediation also occurred
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Inipol
Water in oil
formulation
Honey like
appearance
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Significance
of
Bioremediati
on
Less hazardous
No waste
generated
Natural
Process
Less expensive
Not suitable for
more than one
contaminant soil
Can be carried
out on Site
Takes few
months to years
Release of
contaminants in
environment
Climate issue
Advantages
Disadvantages
