Transcript bioremediation - Portal UniMAP

BIOTECHNOLOGY
AND ENVIRONMENT
CHAPTER CONTENTS
• What Is Bioremediation?
• Bioremediation Basics
• Cleanup Sites and Strategies
• Applying Genetically Engineered Strains to
Clean Up the Environment
• Environmental Disasters: Case Studies in
Bioremediation
• Future Strategies and Challenges for
Bioremediation
WHAT IS BIOREMEDIATION?
• Biodegradation - the use of living organisms such as
bacteria, fungi, and plants to degrade chemical
compounds
• Bioremediation – process of cleaning up
environmental sites contaminated with chemical
pollutants by using living organisms to degrade
hazardous materials into less toxic substances
WHY IS BIOREMEDIATION
IMPORTANT??
The quality of life directly related to the cleanliness and
health of environment.
Environmental chemicals can influence our genetics:
some chemicals can act as mutagens- leading to
disease conditions- reason to concern on the
consequences of environmental chemicals on
human and animals.
- Bioremediation is Way to clean up the environment
thru cheaper and cleaner approach.
- To convert harmful pollutants into relatively harmless materials
such as carbon dioxide, chloride, water, and simple organic
molecules
- Bioremediation can be conducted at the site of
contamination- complete clean up is possible.
WHAT IS BIOREMEDIATION?
• Biotechnological approaches are essential for;
•
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Detecting pollutants
Restoring ecosystems
Learning about conditions that can result in human diseases
Converting waste products into valuable energy
BIOREMEDIATION BASICS
• What needs to be cleaned up?
• Soil, water, air, and sediment
• Pollutants enter environment in many different ways
• Tanker spill, truck accident, ruptured chemical tank at
industrial site, release of pollutants into air
• Eg: leaking of chemical tanker. Initially,
only contaminate surface and
subsurface soils; however, if large
amounts of chemicals released and
undetected, chemicals may move
deeper into the soils.
• Following heavy rains, these chemicals
may create runoff that can
contaminate the adjacent surface
water supplies; ponds, river
• Chemicals may leak into the ground
creating leachate.
• Leachate can cause contamination of
subsurface water- common source of
drinking water.
BIOREMEDIATION BASICS
• Chemicals in the Environment
• Carcinogens
– Compounds that cause cancer
• Mutagens
• Cause skin rashes, birth defects
• Poison plant and animal life
BIOREMEDIATION BASICS
BIOREMEDIATION BASICS
• Fundamentals of Cleanup Reactions
• Microbes convert chemicals into harmless substances by
either
• Aerobic metabolism (require oxygen) or anaerobic metabolism
(do not require oxygen)
• Both processes involve oxidation and reduction reactions
• Oxidation – removal of one or more electrons from an atom or
molecule
• Reduction –addition of one or more electrons to an atom or
molecule
• During redox reaction, oxidizing agents (electron acceptor)
accept electrons and become reduced.
BIOREMEDIATION BASICS
AEROBIC BIODEGRADATION
• In environments such as surface water and soil, O2 is
readily available
• Aerobic bacteria degrade pollutants by oxidizing
chemical compounds.
• O2 can oxidized variety of chemicals including organic
molecules such as petroleum products.
• In the process, O2 is oxidized into water.
• Microbes can further degrade the compounds into
simpler molecules; CO2 and methane.
• Bacteria derived energy from the process, producing
more bacterial cells.
ANAEROBIC DEGRADATION
• In some environments where O2 is lacking,
biodegradation may take place thru anaerobic
biodegradation.
• Also requires redox reaction but using other
molecules as electron acceptors.
• Fe3+ , SO42+ , NO3- are common electron acceptors.
METABOLIZING MICROBES
• Ability of microbes to degrade different chemicals
effectively depends on many conditions
• Types of chemical, temp, zone of contamination,
nutrients influence the effectiveness and rates of
biodegradation/
• The search for useful microbes for bioremediation is
often carried out at the site of contamination.
• Anything living in a polluted sites will have
developed the resistance to the polluting
chemicals.
• Indigenous microbes- found naturally in the
contaminated area.
• Indigenous microbes
• The most common and effective microbes for
bioremediation
Indigenous
microbes found
naturally in the
contaminated
site
Isolated, grown
and studied in
the lab
Released back
into the cleanup
environments in
large scale
BIOREMEDIATION BASICS
• Stimulating Bioremediation
• Many indigenous microbes are very effective in
biodegradation
• There are a few strategies used to enhance the
effectiveness of the microbes.
• Nutrient enrichment (fertilization) – fertilizers are added to a
contaminated environment to stimulate the growth of
indigenous microorganisms that can degrade pollutants.
- Adding more nutrients, more microbes and grow rapidly,
therefore, increases the rate of reaction.
• Bioaugmentation (seeding) –bacteria are added to the
contaminated environment to assist indigenous microbes with
biodegradative processes
• Phytoremediation: using plants to clean up the
contaminated soils.
• Chemical pollutants are taken up by roots of the
plants as they absorb water from the contaminated
soil.
• The contaminated plants are disposed off or
burned.
• It can be low-cost, effective and low-maintainance
approach.
• Disadvantages: only surface layers can be cleaned
up and may take several years to clean up.
CLEANUP SITES AND STRATEGIES
Ex situ bioremediation
(removing of
contaminated soil to
other locations for
treatments)
Soil cleanup
In situ bioremediation
(cleaning up at the
contamination site
without removal of soil
to other location)
Preferred method; Less expensivesoil and water does not have to
excavated or pump out of the site
and larger area can be treated.
In situ
bioremediation
Those that require
aerobic
degradation:
involve bioventing
Rely on stimulating
microbes in the
contaminated soil or water
Bioventing: pumping air/H2O2 into the contaminated soil. H2O2 is used
because it can be degraded into water and O2 easily to provide microbes with
source
of
o2.
Fertilizers may also be added to stimulate the growth of bacteria and degrading
activities
• Disadvantages of in situ bioremediation: not
suitable for solid clay and dense rocky soils.
• Soils that have been contaminated with chemicals
persist for long periods of time can take years to
clean up this way
EX SITU BIOREMEDIATION
Slurry-phase
bioremediation
Moving contaminated
soil to another site,
mixing with fertilizer and
water in bioreactors in
which conditions can be
controlled and
monitored.
Solid phase
bioremediation
(Composting,
landfarming and biopiles)
More time consuming
and requires a large
amount of space.
Ex situ bioremediation
SOLID PHASE BIOREMEDIATION
composting
landfarming
biopiles
•Degrade household
wastes, degrade
chemical pollutant in
contaminated soils.
•Hay, strawa added to
soil to provide bacteria
with nutrients that help
bacteria to degrade
chemicals.
•Spreading
contaminated soils on
a pad so that water
and leachates can
leak out of the soil.
•Primary goal: to collect
leachate so that
polluted water cannot
further contaminate
the environment
•When chemical in the
soil can evaporate
easily and when
microbes in the soil pile
degrade the pollutant
rapidly
•A few bulking agents
are added and fans
and piping systems are
used to pump air into or
over the pile.
•As chemicals in the pile
evaporate, the
vacuum airflow pull the
chemical vapors away
from pile and released
into the air/filter.
9.3 CLEANUP SITES AND STRATEGIES
CLEANUP SITES AND STRATEGIES
Bioremediation
of water
Wastewater
treatment
Groundwater
cleanup
WASTEWATER TREATMENT
• It is a well known application of bioremediation
• The purpose is to remove;
• Human sewage
• fecal material
• paper wastes
• Soaps
• Detergents
• Other household chemicals
WASTEWATER TREATMENT: IN
TYPICAL SEPTIC SYSTEM
Human sewage and
wastewater from a
household move thru
plumbing system out to
septic tank
Resulting sludge can be
used as fertilizers
Feces and paper wastes
are ground and filtered
into small particle. Settle
out into a tanks to create
mud like material- sludge
Sludge is pumped into
anaerobic digester tanks.
Anaerobe microbes
degrade the sludge
producing methane gas.
Water flow out of the
tank called effluent and
sent to aerating tanksaerobic bacteria oxidize
organic materials in the
effluent
Effluent is passed into
activated sludge system –
tank containing
microbes. Effluent then
disinfected with chlorine
and released to lake/river
CLEANUP SITES AND STRATEGIES
GROUNDWATER CLEANUP
• Groundwater- source of drinking water may be
contaminated with pollutants.
• Polluted groundwater can be difficult to clean up
because it get trapped in soil and rocks.
• Ex situ and in situ approaches are used in combination.
• For eg: groundwater contaminated by gasoline/oil
• These pollutants rise onto the surface of the aquifer,
• It can be directly pumped out but the portion mixed
with groundwater must be pumped to the surface and
passed thru bioreactors
• Inside bioreactor: bacteria in biofilms growing over a
screen degrade the pollutants
• The clean water containing fertilizer, bacteria pumped
back into the aquifer for in-situ hybridization.
CLEANUP SITES AND STRATEGIES
CLEANUP SITES AND STRATEGIES
• Turning Wastes into Energy
• Wastes from landfills are used to produce energy
• Scientists are working to produce bioreactors that
contain anaerobic bacteria that can convert food
wastes into soil nutrients and methane gas.
• Methane gas used to produce electricity
• Soil nutrients can be sold commercially as fertilizers
• Anaerobes in sediment that use organic molecules to
generate energy
• Electicigens – electricity-generating microbes
APPLYING GENETICALLY
ENGINEERED STRAINS TO CLEAN UP
THE ENVIRONMENT
• Many indigenous microbes cannot degrade certain
types chemicals: highly toxic compounds.
• Radioactive compounds- kill microbes thus
preventing biodegradation.
• The development of genetic engineering- enable
scientists to create genetically engineered microbes
that capable of improving bioremediation process.
PETROLEUM EATING BACTERIA
• Created in 1970s
• Isolated strains of pseudomonas from contaminated soils
• Contained plasmids that encoded genes for breaking
down the pollutants
9.4 APPLYING GENETICALLY
ENGINEERED STRAINS TO CLEAN UP
THE ENVIRONMENT
• E. coli to clean up heavy metals
• Copper, lead, cadmium, chromium, and mercury
• Genetically modified strain of E. coli that can degrade heavy
metals.
• Biosensors – bacteria capable of detecting a variety
of environmental pollutants
• Genetically Modified Plants and Phytoremediation
• Plants that can remove RDX and TNT
ENVIRONMENTAL DISASTERS: CASE
STUDIES IN BIOREMEDIATION
jet fuel and
Hanahan,
south carolina
80,000 gallons kerosene leaked.
After series of clean up- spill could
not contained from soaking thru
the sandy soil and contaminating
the water
after 10 years, reached residential
areas- removing contaminated
soil was impractical- large area
Scientists found that indigenous
microbes were degrading the
fuel and adding fertilizers
increasing the rate of
biodegradation
FUTURE STRATEGIES AND
CHALLENGES FOR BIOREMEDIATION
• Recovering Valuable Metals
- Metals such as copper, nickel, boron and gold.
- Many microbes can convert metal products into
insoluble substances called metal oxides that will
accumulate in their cells/cell surface.
- For eg: many manufacturing processes using silver
and gold plating techniques that create waste
solutions with suspended gold/silver particles.
Microbes can be used to recover this metals.
FUTURE STRATEGIES AND
CHALLENGES FOR BIOREMEDIATION
• Bioremediation of radioactive wastes
- Removing radioactive wastes from environment.
- Although radioactive kill materials kill a majority of
microbes, some strains of bacteria have
demonstrated a potential for degrading
radioactive chemicals.
- For eg: Geobacter can reduce soluble uranium in
groundwater into insoluble uranium effectively,
immobilizing the radioactivity.