bioremediation of contaminated soil by microorganisms.

1. Bioremediation of Contaminated Soils

2. Introduction
Bioremediation
of
Contaminated
Soils
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• Bioremediation could simply be defined as a biological process of the
decontamination of contaminated environment
• 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)

3. Sources of Contaminants in land
Bioremediation
of
Contaminated
Soils
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• IndustrialActivity
• AgriculturalActivities
• Waste Disposal
• Accidental Oil Spillage
• Acid Rain

6. In-situ remediation
• in-situ bioremediation is applied to eliminate the pollutants in contaminated
soils and groundwater.
• It is a superior method for the cleaning of contaminated environments
because it saves transportation costs and uses harmless microorganisms to
eliminate the chemical contaminations
• These microorganisms are better to be of positive chemotactic affinity
toward contaminants.
• Another advantage of in situ bioremediation is the feasibility of synchronous
treatment of soil and groundwater.
• Continuous treatment of contaminated soil and ground water
• Minimal exposure of public
• Economical
• There are two types of in situ bioremediation:
i) Intrinsic in situ bioremediation
ii) Engineered in situ bioremediation.

7. • Intrinsic bioremediation is the process of converting environmental
pollutants into the non-toxic forms through the inherent abilities of naturally
occurring microbial population.
• This process is most effective in the soil and water as these biomes always
have high chance of being fully contaminated by contaminants and toxins.
• This process is usually employed in underground places as such underground
petroleum tanks.
• There is escalating attention on intrinsic bioremediation for control of all or
some of the contamination at waste sites.
• The natural ability of micro-organisms to degrade the contaminants should
be examined and tested at laboratory and in field trails prior its use for
intrinsic bioremediation.
Intrinsic in situ bioremediation

8. Conditions for intrinsic in situ bioremediation
• Flow of ground water throughout the year
• Carbonate minerals to buffer acidity produced during biodegradation
• Dispense of electron acceptors and nutrients for microbial growth
• pH, pollutant concentration, temperature and nutrient availability decides
whether or not bioremediation takes place.
• The microbial growth during bioremediation of the waste is hindered by
presence of metals such as Hg, Pb, As and cyanide as toxic concentration.
• Degradation of pollutants using bacteria in ground water relies on the type
and concentration of compounds, electron acceptor and time period for
which bacteria was exposed to contamination.

10. 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
Bioremediation
of
Contaminated
Soils
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11. Biological Mechanisms ofTransformation
Bioremediation
of
Contaminated
Soils
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Conversion of
contaminants to
mineralized end
product
CO2, H2O &
Salts
Biotransformation,
where end product is
not mineral
TEC to DEC
Conversion Biotransformation Biodegradation
Involves the process
of extracting energy
from organic
chemicals via
oxidation of organic
chemicals

12. Engineered in situ bioremediation
• This type of bioremediation is performed through the introduction of
certain microorganisms to a contamination site.
• As the conditions of contamination sites are most often unfavorable for the
establishment and bioactivity of the exogenously amended
microorganisms.
• Therefore the environment is modified in a way so that improved physico-
chemical conditions are provided.
• Oxygen, electron acceptors, and nutrients (for example nitrogen and
phosphorus) are required to enhance microbial growth.

13. Bioremediation
of
Contaminated
Soils
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Biostimulation
• Microbes are motivated to start the process of bioremediation
• Biostimulation involves the modification of the environment to stimulate
existing bacteria capable of bioremediation.
• This can be done by addition of various forms of rate limiting nutrients and
electron acceptors, such as phosphorus, nitrogen, oxygen, or carbon (e.g. in the
form of molasses).
• Biostimulation can be used where the bacteria necessary to degrade the
contaminants are present but conditions do not favor their growth.
• The major disadvantage is its dependency on environmental factors that
controls its potentiality. Secondly, when the contaminants are firmly
engrossed to the soil particles or the contaminant is non biodegradable,
then biostimulation cannot be executed.

14. Bioventing
• Bioventing is a type of in situ bioremediation technique that stimulates the aerobic
degradation process.
• It enhances the intrinsic capability of indigenous microflora to degrade the organic
contaminants adsorbed to soil by introducing oxygen into an unsaturated zone.
• Bioventing generally is performed using blowers. However, at some sites, it may be
possible to perform bioventing by relying on barometric changes or tidal fluctuations
as opposed to using blowers; this process is commonly referred to as passive
bioventing.
• By delivering oxygen into an unsaturated zone, it improves the innate capacity of
indigenous microorganisms to break down organic pollutants adsorbed to soil.
• Through vertical and horizontal wells, air is injected directly into the contaminated
zone. Only the amount of air needed for degradation is used in this procedure. It also
reduces pollutant volatilization and discharge into the environment.
• Bioventing can be done in two ways: actively or passively.
• The gas exchange from the vent wells is simply affected by atmospheric pressure in
passive bioventing, whereas in active bioventing, air is driven into the ground by a
blower, maybe in connection with a vacuum extraction of the gas.

15. Most Common Procedure
1. Air Injection: The blowers inject air or remove soil vapors from a series of
vent wells. The number, position, and depth of the wells are determined by
a variety of geological and engineering criteria.
2. Vapor Extraction: When vapors are extracted, a negative pressure is created,
causing atmospheric air to be sucked into the subsurface. Extraction reduces
vapor intrusion into neighboring structures, but injecting air might worsen it
due to increased subsurface pressure and the establishment of preferential
routes.
3. System Operation: Therefore, during the first months of operating a system
designed for soil gas extraction, vapor treatment utilizing thermal or
catalytic oxidation or granular activated carbon (GAC) may be required at
many sites. Changes in subsurface pressures and concentrations of oxygen,
carbon dioxide, and total petroleum hydrocarbons are monitored using soil
gas monitoring sites.

16. 4. Respiratory Tests: During the application of
the full-scale treatment, in-situ respiratory tests
are performed on a regular basis.
5. Baseline Test: A baseline test is conducted
immediately before or at the start of treatment,
and subsequent tests can be performed quarterly
to annually to assess changes in degradation
rates over time.
6. Shutting Off Systems: After air has been
delivered into the vadose zone for at least 24
hours, the test is started by shutting off the
bioventing system.
7. Recording: Over the course of one to five days,
oxygen, carbon dioxide, and petroleum
hydrocarbon concentrations are recorded. When
the oxygen concentration falls below 5%, the test
is usually finished.
8. Calculation: The rate of biodegradation can be
determined using the rate of oxygen or carbon
dioxide usage.

17. Bioaugmentation
Bioremediation
of
Contaminated
Soils
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• Bioaugmentation is defined as “the introduction of cultured microorganisms
into a contaminated environment in order to enhance bioremediation of
pollutants.”
• Organisms are selected for their high degrading potential.
• Bioaugmentation works by increasing the level of active microbes and
microorganisms within the treatment environment.
• These microorganisms are already working to transform contaminants into less
harmful compounds, but each microorganism can only handle this
transformation up to a certain rate.
• Wild-type or genetically modified species.
A single species
Consortium of several species

18. • Bioaugmentation is used to degrade specific soil and groundwater
contaminants.
• stearothermophilus, Penicillium sp., Aspergillus sp., Flavobacterium,
Arthrobacter, Pseudomonas, Streptomyces, Saccharomyces, etc.
• Activated sludge systems are generally based on microorganisms like
bacteria, protozoa, nematodes, rotifers, and fungi, which are capable of
degrading biodegradable organic matter.

19. Bioslurping
• Bioslurping uses elements of both, bioventing and free product recovery, to address
two separate contaminant media by simultaneously recovering free product and
bioremediation the vadose zone of soils. Bioslurping can enhance free-product
recovery without extracting vast quantities of ground water.
• Bioslurping is the adaptation and application of vacuum-enhanced dewatering
technologies to remediate hydrocarbon-contaminated sites.

21. Ex situ bioremediation

22. Landfarming
Bioremediation
of
Contaminated
Soils
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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

23. Composting
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Bioremediation
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• Microorganisms are used in constructed
piles of soils or windrows to degrade
contaminants.
• Piles are physically mixed and moistened
to promote microbial activity.

24. Phytoremediation
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Bioremediation
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• Use of plants to remove or transform contaminants
• Affects directly or indirectly
Hyper
accumulating
heavy metals
Stimulating
microbes in
rhizosphere

25. Biostimulation
Example
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Bioremediation
of
Contaminated
Soils
• 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
Inipol
Water in oil
formulation
Honey like
appearance
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26. Significance
of
Bioremediati
on
Lesshazardous
No waste
generated
Natural
Process
Less expensive
Not suitable for
more than one
contaminant soil
Can be carried
out onSite
Takes few
months to years
Release of
contaminants in
environment
Climate issue
Advantages
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Bioremediation
of
Contaminated
Soils
Disadvantages