Transcript Advanced Environmental Biotechnology

Groundwater Pollution
Bioremediation – Cleaning up
simple organic chemicals
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Pollution of air, water and soil
is a worldwide problem
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Picture: http://upload.wikimedia.org/wikipedia/commons/b/b3/Pollution_over_east_China.jpg
The pollution of groundwater
by organic chemicals affects
an estimated 300,000 to
400,000 contaminated sites in
the USA alone
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Picture: http://commons.wikimedia.org/wiki/Image:Drainage_nitrates_vers_HondeghemFr_2003_04_09.jpg
Problems occur when there is
too much of something in the
environment
Carbon dioxide emissions in thousands of metric tons
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http://commons.wikimedia.org/wiki/Image:Countries_by_carbon_dioxide_emissions_world_map.PNG
Bioremediation is when
organisms either
metabolize or fix
contaminants
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Contaminant
Organisms
Less harmful
chemicals
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Contaminant
Organisms
Contaminants
are fixed
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Bioremediation is
any process that
uses
microorganisms,
fungi, green plants
or their enzymes to
return the
contaminated
environment to its
original condition.
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Because there
is too much of
something we
need to either
reduce it or
immobilize
(fix) it
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Reducing pollution can mean
degrading it or changing its form
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Contaminant
Organisms
Less harmful
chemicals
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Bioremediation of chlorinated
ethenes uses microorganisms to
break down contaminants to less
toxic end products
PCE (Tetrachloroethene), which contains four chlorine
atoms, is degraded from PCE to TCE to DCE
(dichloroethene) to VC (vinyl chloride) to ethene. DCE and
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VC are toxic but ethene is not toxic.
The organisms make
chemical reactions happen
Balance these reactions
Benzene (a component of gasoline)
2C6H6 + 15O2
?CO2 + ?H2O
Alanine (an amino acid)
4C3H4NH2O2H + 15O2
12CO2 + 14H2O + ?
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The organisms make chemical
reactions happen
Balance these reactions
Benzene (a component of gasoline)
2C6H6 + 15O2
12CO2 + 6H2O
Alanine (an amino acid)
4C3H4NH2O2H + 15O2
12CO2 + 14H2O + 2N2
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These chemical equations are
used to calculate how many
other chemicals need to be
added
150 kg of analine need to be
degraded.
How much oxygen needs to be
supplied?
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Atomic weights
N=14 O=16 H=1 C=12
C3H4NH2O2H = 89
4C3H4NH2O2H needs 15O2
150 / 89 x 4 = X / 32 x 15
X = 202 kg O2
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Bioremediation might be
improved
We could add more or
better organisms to the
soil (bioaugmentation)
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We could help the
organisms grow by
changing things in
the environment
(biostimulation)
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How could we stimulate the
growth of microorganisms?
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How could we stimulate the
growth of microorganisms?
We could add nutrients, change the
pH, change the temperature, and
add or remove oxygen.
Eg Benzene
2C6H6 + 15O2
12CO2 + 6H2O
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Other Names
Bioremediation is also called
enhanced (늘리다) bioremediation or
engineered bioremediation.
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Aerobic bioremediation
usually involves oxidative
processes
Contaminants may be partially
oxidized to less toxic by-products
Contaminants may be fully oxidized
to chemicals such as carbon dioxide
and water
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BTEX (Benzene, Toluene,
Ethylbenzene, and Xylenes) are
monoaromatic hydrocarbons
which are in petroleum and
petroleum products such as
gasoline.
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If there is enough oxygen more
degradation can happen
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… and so on
What does each
number stand
for?
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If there is enough oxygen they
can degrade to water and
carbondioxide
2C6H6 + 15O2
12CO2 + 6H2O
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See the redox
reaction. This
gives the cell
energy.
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Oxidation can occur without O2
oxygen
Oxidation is when a chemical
accepts an electron of another
chemical.
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Aerobic is often faster than
anaerobic degradation
However, many compounds can only
be metabolized under reductive
conditions.
Then anaerobic metabolism is
needed.
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Reductive Dehalogenation
One type of anaerobic
bioremediation is reductive
dehalogenation where the
contaminants are made less toxic by
removal of halogens such as
chlorine or nitro groups.
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Remember the degrading of
tetrachloroethene
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Anaerobic = no oxygen
Tetrachloroethene is reduced with eH2 is the electron donor
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Reduction of Halogens
Highly electrophilic compounds
such as halogenated aliphatics and
explosives often are bioremediated
through reductive processes that
remove the electrophilic halogen or
nitro groups.
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At many contaminated sites,
organisms naturally exist that
can degrade the contaminants
But not all sites have organisms that
work.
Some sites don’t have the right
conditions (such as electron acceptors)
for fast degradation of the contaminants.
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How can we engineer the
conditions to stimulate
bioremediation?
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We can engineer the conditions
Engineered bioremediation involves
supplying oxygen (or other electron
acceptor), water, and nutrients at the
correct rate so that the naturally
existing microorganisms are
stimulated to degrade the
contaminants.
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How can we follow what is
happening?
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Signs of Biological Activity
Biological activity will result in
decreased oxygen concentration (for
aerobic processes) and increased
metabolites (e.g. ethene from the
reductive dechlorination of
tetrachloroethene).
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Contaminant
Organisms
Less harmful
chemicals
We can count this, this or this.
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Types of Contaminants
Bioremediation is commonly used for:
Organic contaminants
Some inorganic pollutants such as ammonia,
nitrate, and perchlorate
Changing the valence states of heavy metals
to convert them into immobile or less toxic
forms. (eg mobile hexavalent chromium into
immobile and less toxic trivalent chromium)
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Perchlorates are the salts of perchloric
acid (HClO4).
They are commonly found in rocket fuel
and explosives, often those used by the
military.
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Advantages of Bioremediation
It may result in complete degradation of
organic compounds to nontoxic byproducts.
Not much equipment is needed
It can be in-situ or ex-situ.
In-situ bioremediation is safer because
contaminated soils don’t have to be moved.
In-situ bioremediation does not change the
natural surroundings of the site.
Low cost compared to other remediation
technologies.
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Advantage 우위
Toxic
≠
nontoxic (not toxic)
equipment 설비
in-situ 원위치
≠
ex-situ
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Disadvantages of Bioremediation
There could be partial degradation to
metabolites that are still toxic and/or more
mobile in the environment.
Biodegradation is easily stopped by toxins and
environmental conditions.
We have to always measuring biodegradation
rates.
It may be difficult to control volatile organic
compounds during ex-situ bioremediation
process
Generally requires longer treatment time as
compared to other remediation technologies.
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Partial 불완전한
Mobile 가동성의
Rate 속도, 진도
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Processes
Bioremediation processes may be directed
towards accomplishing:
–complete oxidation of organic contaminants
(called mineralization),
–biotransformation of organic chemicals into
smaller parts, or
–reduction of halo- and nitro- groups by transferring
electrons from an electron donor (eg a sugar or
fatty acid) to the contaminant, resulting in a less
toxic compound.
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Order of Acceptors
Usually electron acceptors are used by
bacteria in order of their thermodynamic
energy yield :
oxygen,
nitrate,
iron,
sulfate,
carbon dioxide.
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Order of Acceptors
Residual NAPL
Mobile
LNAPL
Pool
Methanogenesis
Aerobic
Respiration
Dentrification
Sulfate
Reduction
Iron (III) Reduction
Plume of
Dissolved Fuel
Hydrocarbons
(Source: W,R, N, & W, 1999.)
(Adapted from Lovley et al., 1994b.)
Ground
Water
Flow
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http://mn.water.usgs.gov/bemidji/results/fact-sheet.pdf
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Reduction Zones
Oxygen and nitrate are highly
energetic but they are used rapidly.
Their reduction zones frequently do
not go deeply into contaminated
zones particularly in heavily polluted
areas.
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The major nutrients needed
include carbon, hydrogen,
oxygen, nitrogen and
phosphorous.
The amount which needs to be added
depends on what is already there.
Generally, the C to N to P ratio (w/w)
required is 120:10:1.
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Not Too Much Toxin
Too much contaminant can be toxic to
microbes.
Some may be toxic even at low
concentrations.
We can try to dilute contaminants.
We can try to find acclimated microbes.
We can try to change the bioavailability
of the toxin.
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BIOREMEDIATION OF CONTAMINATED SITES
Karl J. Rockne and Krishna R. Reddy
University of Illinois at Chicago
Department of Civil and Materials Engineering
842 West Taylor Street
Chicago, Illinois 60607, USA
http://www.uic.edu/classes/cemm/cemmlab/bio
remed-india2003.pdf#search='BIOREMEDIATION%20OF%2
0CONTAMINATED%20SITES'
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