Bioremediation uses microorganisms to degrade contaminants in soil and water. It is more cost effective than other remediation methods like incineration. There are three main techniques - in situ treats contamination on site, ex situ treats excavated material on or off site, and ex situ slurry treats soil-water mixtures in bioreactors or ponds. Specific in situ methods include land farming, bioventing, biosparging, and bioaugmentation which introduce oxygen and nutrients to stimulate microbes. Ex situ methods are composting, biopiles, and bioreactors which accelerate degradation through aeration and temperature/nutrient control.

1. BIOREMEDIATION
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2. INTRODUCTION
• Bioremediation is defined as the use of biological treatment
systems to destroy or reduce the concentration of hazardous
wastes from contaminated sites.
• Economical, safety
• Cost-effective, permanent solution to clean up soils
contaminated with xenobiotic compounds
• At least six times cheaper than incineration and three times
cheaper than confinement
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3. Introduction
• New and exciting field
• Performed off-site when contamination is superficial, but it
will have to be in situ when the contaminants have reached
the saturated zone
• General components and characteristics
Microbial systems
Type of contaminant
Geological and chemical conditions at the contaminated site
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5. Advantages
• Can be done on site
• Minimum site disruption is caused
• Eliminates transportation costs and liabilities
• Eliminates long-term liabilities
• Uses biological system, often less expensive
• Can be coupled with other treatment techniques
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6. Disadvantages
• Some chemical compounds are not biodegradable
• Extensive monitoring required
• Each site has specific requirements
• Potential production of toxic unknown sub-products is
possible
• Strong scientific support is needed
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7. BIOREMEDIATION
TECHNIQUES
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8. Bioremediation techniques
• Divided into 3 categories :
In-situ, ex-situ and ex-situ slurry
• In situ - soil and associated ground water is treated in place
without excavation
• Ex situ – excavated prior to treatment
• Ex situ slurry – creation and maintenance of soil- water
slurry as bioremediation medium
• Slurry can be maintained either in a bioreactor or in a pond
lagoon 8

9. In situ remediation
techniques
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10. In situ remediation techniques
• Bioremediation on land
• Land farming
• Bioventing
• Biosparging
• Bioaugmentation
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11. Bioremediation on land
• Depend on the area contaminated, the properties of the
compounds involved, the conc of contaminants, time required
to complete the bioremediation
• The contamination can be treated on site or the contaminated
material excavated and treated on or off site.
• If contaminant is water soluble a pump-and-treat technique
used
• Introduced into contaminated areas and removed at another
site to be treated on or off site
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12. Land farming
• The simplest of the on-site treatment
• Involve mixing of the soil by ploughing or some form of
mechanical tilling
• Ploughing increases the O₂ levels in the soil and distributes
contaminants more evenly, which increases the rate of
degradation.
• Nutrients added to increase biodegradation
• 4-6 months required to remove contaminants such as PAHs
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13. Land farming
• Method is best suited for shallow contamination of soil
surface
• Treatment area is lined and dammed to retain any
contaminated leachate
• Rate of degradation depends on the microbial pollution, the
type and level of contamination, and the soil type
• Avg half-life for the degeneration of diesel fuel and heavy oils
is in the order of 54 days with this type of system
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14. Land farming
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15. Bioventing
• In situ process, which combines an increased oxygen supply
with vapour extraction
• A vacuum is applied at some depth in the contaminated soil
• This draws air down into the soil from holes drilled around
the site and sweeps out any volatile organic compounds
• Nutrient supplementation can be provided by running
nutrients into trenches dug across the site
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16. Bioventing
• The increased supply of air will increase the rate of natural
degradation by the aerobic micro-organisms.
• Only effective for reasonably volatile compounds, where soil is
permeable
• Vapour extracted may need some form of treatment
• One biological solution is the use of biofilters
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18. Biosparging
• Process to increase the biological activity of the soil by
increasing the supply of oxygen by sparging air or oxygen
into the soil
• Air injection replaced by pure oxygen – increase degradation
rates
• The expense of treatment limited its application to highly
contaminated sites but on-site degradation of oxygen has
reduced costs
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19. Biosparging
• Hydrogen peroxide used on a number of sites but it can be
toxic at low concentrations to MO
• This process is similar to soil vapor extraction, which can be
used for volatile contaminants
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20. Bioaugmentation
• The addition of nutrients injected into contamination well
below the surface can be used to stimulate the indigeneous
microbial population.
• This technique can be combined with the addition of specific
MO
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21. Ex situ remediation
techniques
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22. Ex situ remediation techniques
• If the contaminated material is excavated it can be treated on
or off site, which is often a more rapid method of de-
contaminating the area
• The techniques include
– Composting
– Biopile process
– Bioreactors
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23. Composting
• Solid-phase treatment carried out after extraction
• Composting materials such as straw, bark and wood chips is
mixed with the contaminated soil and piled into heaps
• Process work in the same way as normal system which rise the
temp to 60° C and above cause microbial activity
• higher temp encourages the growth of thermophilic bacteria
• Increased costs of this type of system restrict it to highly
contaminated materials
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24. Composting
• Organic materials added vegetables, fruit and garden waste
• Added at a conc of 33-75%
• Temp above 70° C achieved after 6-22 days of incubation,
with turning every 7 days and 84-86% of the contamination
was removed by day 40 compared with 35% in untreated soil.
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25. Biopile process
• Soil heaped into piles within a lined area to prevent leaching
• Piles covered with polythene and liquid nutrients applied to
the surface
• Aeration improved by applying suction to the base of the pile
as in a composting system
• Leachate collected by pipes at the base and recycled if
necessary
• Space limited
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26. Biopile process
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27. Bioreactors
• Soil extracted from a contaminated site can be treated as a
solid waste or a liquid leachate in bioreactors of various
designs.
• Control of parameters such as temp, pH, mixing and O₂
supply – improve degradation rates
• Used for Solid waste slurries can be solid-bed, fluidized bed,
and stirred tank bioreactors
• When treating liquid leachates and contaminated ground
water all those reactors – waste water treatment are used
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28. Bioreactors
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