1. Bioremediation
The Natural Way to Reduce pollution
Presented By: Tenzin Dolma
BMS 2nd Year
SRCASW, DU
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2. Introduction
The use of bacteria and fungi and plants to
break down or degrade toxic chemical
compounds that have accumulated in the
environment at excess levels to bring them to
normal levels which are considered acceptable.
It involves :
(1) a minor change in an organic molecule leaving the main structure
still intact
(2) fragmentation of a complex organic molecule
in such a way that the fragments could be reassembled to yield the
original structure
(3) complete mineralization
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3. The release of the pollutants can be
• Deliberate and well regulated (industrial emissions)
• Accidental and largely unavoidable (chemical/oil spills)
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4. What Makes Bioremediation a Promising Approach?
•Permanence , the waste are completely degraded
• Low cost, 60-90% less than other technologies
Two Ways of Metabolization
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5. In situ Ex situ
• Relies on indigenous microbial • Ex-situ Bioremediation requires
fauna of subsurface soil and pumping of the groundwater or
ground water. The microbes at excavation of contaminated soil
the contaminated site can prior to remediation treatments.
degrade the waste. • It suffers from costs associated
• Degradation continues till a limit problems with solid handling
but we can add nutrients and is process e.g. excavation,
called “enhanced insitu screening and fractionation,
bioremediation.” mixing, homogenizing and final
• Eg. Exxon Valdez oil spill Alaska disposal. (i) solid-phase system
(including land treatment and soil
piles) i.e. composting, and (ii)
slurry-phase systems (involving
treatment of solid-liquid
suspensions in bioreactors).
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6. Requirem ents for
Biorem ediation:
Microbes
Energy Electron
Source Acceptor
Moisture pH
Nutrients Temperature
Absence Of
Absence Of Removal Of
Competitive
Toxicity Metabolites
Bacteria
Bioremediation
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7. Above groundbioreactors
• Same technology as fermenters.
Treats excavated soil or ground
water with high levels of
contaminants.
• Contaminated soil+ water=
slurry Reactor
• Bacterial inoculum may be from
indigenous indigenous site,
activated sludge or sewage.
• Genetically engineered
organisms are used. Bioreactors
can be used in series to
accomplish the degradation.
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8. Land Farming
• Pretreated or untreated oily sludge from refinery wastes mixed with
soil is subjected to insitu bioremediation.
• Conditions: Flat landfarm, light and loamy soil for proper aeration ,
clay layer to prevent ground water seepage. Temperature and
precipitaion is foreseen too. ( 20 to 30 degree)
• Inorganic fertilizers are applied to raise the pH to about 7.8.
• Cons: Slow and incomplete, Heavy metal accumulation, the land
farm used intensively can’t be used for agriculuture and livestock
grazing later.
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9. Composting
• It is the emerging trend with a low cost
in decontaminating the soils which were
wasted with discharges from explosive
industries. Alternative to incineration.
• Anaerobes can degrade RDX and HMX.
• Example: Desulfovibrio species use the
explosives as N source , Klebsiella
pneumoniae degrades RDX to CO2, H20
and formaldehyde.
• Degradation of 90%..80 days, 55 degree
celsius . In 150 days, 18000mg to 74 mg
per kg.
• Eg. Desulphovibrio species( RDX and
HMX), Klebsiella pneumoniae (RDX)
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10. Super Bug
•Oil spills cause devastation to the environment
killing sea life, birds, and coastal plants.
Spraying areas of contamination with oil-eating
microbes accelerates the degradation of the oil.
•The very first superbug was created by
Chakrabarty and co-workers reported the
development of a new strain of bacterium by
transfer of plasmids and named it superbug
which could utilize a number of toxic organic
chemicals like octane, hexane, xylene, toluene,
camphor and naphthalene. This superbug
making it the first genetically engineered
microorganism to be patented. This superbug
was then used for cleaning an oil spill in Texas
in 1990.
• Eg. Alcanivorax borkumensis, Deinococcus
radiodurans, Pseudomonas putida
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11. Phytoremediation
• Phytoremediation is the use of plants to clean up potentially damaging spills.
The plants work with soil organisms to transform contaminants, such as heavy
metals and toxic organic compounds, into harmless or valuable forms.
• ≈350 plant species naturally take up toxic materials
• Sunflowers used to remove radioactive cesium and strontium from Chernobyl site
• Water hyacinths used to remove arsenic from water supplies in Bangladesh, India
• Transgenic plants as Arabidopsis thaliana hybrids are used.
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12. Mycoremediation:
• Mushroom mycelium release
enzymes that can break the
chemical bonds of many
petrochemicals and toxins.
Some mushrooms can also
uptake heavy metals—they
must then be harvested and
treated as toxic waste.
Different species work best
for specific toxins.
• A substrate, often wood
chips, sterilized straw or
cardboard, is inoculated with
mushroom spawn of a
beneficial species.
Inoculated substrate can
also be used as a filter for
flowing water. Some Presentaion@ Tenzin Dolma
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of fungi will attack

13. Pros and Cons
• Pros
i. Inexpensive method
ii. No maintenance expenses and aesthetically
pleasing
• Cons
i. Only surface soil (root zone) can be treated
ii. Clean up take several years
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14. Thank you!!!
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15. References
• Alexdaner N.Glazer and Hiroshi Nikaido ,
Microbial Biotechnology, 2nd Edition
• Microbes and Society, Benjamin S. Weeks
• Prescott microbiology, McGraw-Hill
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