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BIOREMEDIATION
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Man is a rational being and is curious to
exploit/discover new things in the
environment. In order for him to understand
the life in a better aspect and try to solve
the mystery of the nature/environment.
While exploiting the environment, humanactivities resulted to pollution and
RELEASE OF certain HAZARDOUS
MATERIALS.
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Bioremediation came as an option that
offers the possibility to destroy or render
harmless various contaminants usingnatural biological activity.
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Bioremediation
the branch of biotechnology that
uses biological process to
overcome environmental problems.
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Bioremediation can be defined
as any process that uses:microorganisms, fungi, green
plants or their enzymes to return the
natural environment altered bycontaminants to its original condition.
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Bioremediation may be
employed: to attack specific soil contaminants, such as
degradation of chlorinated hydrocarbons by
bacteria.
An example of a more general approach is the
cleanup of oil spills by the addition of nitrateand/or sulphate fertilisers to facilitate the
decomposition of crude oil by indigenous or
exogenous bacteria.
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How might microorganisms
attack hazardous organicwastes?
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Slide 9
L2 The design of bioremediation process involves the optimization and control of select portions of biochemical cycles. The biochemical
transformation requires catalysts. Microorganisms are the catalyst generator and enzymes are the catalysts. These enzymes result in
degradative (catabolic) reactions to provide energy and material for synthesis of additional microbial cells.
Lecturer, 7/10/2008
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Cont.
Of prime importance are microorganismscapable of producing enzymes that will
degrade the hazardous chemical (targetcompound) as enzymes degradecompounds through exploitation of theorganisms energy need.
Converting compound to some othercompound, which may also be toxic andrecalcitrant to further degradation
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REQUIREMENTS FOR BIOREMEDIATION
MICROORGANISMS
ENERGY
SOURCE
ELECTRON
ACCEPTOR
MOISTURE pH
NUTRIENTS TEMPERATURE
ABSENCE OF
TOXICITY
REMOVAL OF
METABOLITIES
ABSENCE OF
COMPETITIVE
ORGANISMS
BIOREMEDIATION
L3
L4
L5
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THE BASIC PROBLEM:
RELEASE OF HAZARDOUS MATERIALS
Enormous quantities of organic & inorganic
compounds are released into the environment each
year as a result of human activities.
The release may be:
Deliberate and well regulated (industrial
emissions)
Accidental and largely unavoidable (chemical/oil
spills)
US EPA estimated that in 1980 at least 57 millions
metric tons of the total waste can be categorized
into three general groups:
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Slide 12
L1 This include organic chemicals, inorganic chemicals, biological organisms and radionuclides.Lecturer, 7/10/2008
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Heavy metal, Pb, Hg, Cd, Ni and Be can
accumulate in various organs, interfere with
normal enzymatic reactions and cause diseaseincluding cancer
Chlorinated hydrocarbons, also known as
organochlorides including pesticides and other
organic compounds such as PCB (polychlorinated
biphenyls)
Research proven a positive correlation
between cancer in lab animals and
organochlorides.
Nuclear waste including radioactive material such
as plutonium which are dangerous for thousands
of years
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BIOREMEDIATION
Bioremediation is the application of biological processprinciples to the treatment of groundwater, soil andsludges contaminated with hazardous chemicals.
It requires the control and manipulation of microbial
processes in surface reactors or in the subsurface.
The contaminants can be biodegraded in situ orremoved and placed in bioreactor (at or off thecontamination sites).
Idea:
To isolate microbes that can degrade or eat aparticular contaminant
To provide the conditions whereby it can do this
most effectively, thereby eliminating thecontaminant
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Simple organic compounds such as acetate may
persist under condition that do not favor microbial
activity. These conditions include extremes in
temperature or pH, the presence of toxicants or
antimicrobial agents, the inhibition or exclusion of
microbial enzymes, and the lack of water and an
electron acceptor.
CONCEPTS:
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Two kinds of cells are recognized, the procaryoticand eucaryotic.
The most important groups to bioremediation are
bacteria and fungi.
Microbial Divisions
Procaryotic cell Eucaryotic cell
BacteriaBlue-green bacteria or
cyanobacteria
PlantsAnimals
Rotifers
Protozoa
FungiMost algae
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Microorganisms destroy organiccontaminants in the course of using
the chemicals for their own growth
and reproduction. Organic chemicals provide:
carbon, source of cell building
material, electrons, source of energy
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Metabolism is defined by the nature of the redoxreaction
Metabolism modes are divided into two; aerobicand anaerobic
Cells catalyze oxidation of organic chemicals(electron donors), causing transfer of electronsfrom organic chemicals to some electron
acceptor
Electron acceptors:
In aerobic oxidation, acceptor is oxygen
In anaerobic, acceptor is:-nitrate
-manganese
-iron
-sulfate
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TYPES OF BIOREMEDIATION
The two main types of bioremediation
are in situ bioremediation and ex situ
bioremediation. In addition, anotheroffshoot of bioremediation is
phytoremediation.
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In Situ Bioremediation
In situ bioremediation is when the
contaminated site is cleaned up exactly
where it occurred. It is the most commonly
used type of bioremediation because it is
the cheapest and most efficient, so its
generally better to use. There are two main
types of in situ bioremediation: intrinsic
bioremediation and acceleratedbioremediation.
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Intrinsic Bioremediation
Intrinsic bioremediation usesmicroorganisms already present in theenvironment to biodegrade harmful
contaminant. There is no humanintervention involved in this type ofbioremediation, and since it is the cheapestmeans of bioremediation available, it is themost commonly used. When intrinsicbioremediation isnt feasible, scientists turnnext to accelerated bioremediation.L8
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Slide 22
L8 IB relies on the intrinsic (naturally occurring)supplies of electron acceptors, nutrients, and other necessary materialsto develop
biologically active zone and prevent the migration of contaminants away from the source.
Involves no engineered measures to increase the supply rates of oxygen, nutrients or other stimulants.Lecturer, 7/11/2008
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Accelerated Bioremediation
In accelerated bioremediation, eithersubstrate or nutrients are added to the
environment to help break down thetoxic spill by making the microorganisms
grow more rapidly. Usually the
microorganisms are indigenous, but
occasionally microorganisms that arevery efficient at degrading a certain
contaminant are additionally added.
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Main advantage is that site disturbance is
minimized, which is particularly important
when the contaminated plume hasmoved under permanent structures.
Biggest limitation of in situ treatment has
been the inability to deal effectively with
metal contaminants mixed with organic
compounds.
The goal of in situ treatment is to manage
and manipulate the subsurface
environment to optimize microbial
degradation.
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Land treatments:
Bioventingis the most common in situ
treatment and involves supplying airand nutrients through wells to
contaminated soil to stimulate the
indigenous bacteria.
In Situ Bioremediation
L6
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Slide 25
L6 contaminants are trapped in the unsaturated zone (also known as vadose zone) above the water table, the easiest way to supply
oxygen is by pulling air through the unsaturated soil.
vacuum pumps create negative pressure that sweeps air through the soil and past the contaminated soil.
by passing air through the unsaturated zone evaporates moisture and can dessicate the soil enough that microbiological activity isslowed down or prevented.Lecturer, 7/11/2008
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In situ biodegradation involves
supplying oxygen and nutrients by
circulating aqueous solutions through
contaminated soils to stimulate
naturally occurring bacteria to
degrade organic contaminants.
Bioaugmentation Bioremediation
frequently involves the addition of
microorganisms indigenous or
exogenous to the contaminated sites.
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Biosparginginvolves the injection of air
under pressure below the water tableto increase groundwater oxygen
concentrations and enhance the rate
of biological degradation ofcontaminants by naturally occurring
bacteria. Biosparging increases the
mixing in the saturated zone and
thereby increases the contactbetween soil and groundwater.L7
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Slide 27
L7 Originally developed in Europe, and has become a popular means of engineered bioremediation in North America for strictly aerobic
biodegradation.
Biosparging can strip volatile contaminants from the saturated zone into the unsaturated zone and a vapor-capture system.
Not effective when low-permeability geological zones trap or divert the gas flow.Lecturer, 7/11/2008
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Slide 28
L9 Most applicable for small, heavily contaminated sources and when a rapid site cleanup is desired.
Excavation incurs major costs and potentially increases exposure to workers and those who reside nearby.Lecturer, 7/11/2008
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Landfarmingis a simple technique in whichcontaminated soil is excavated and spreadover a prepared bed and periodically tilleduntil pollutants are degraded.
Compostingis a technique that involvescombining contaminated soil with non-hazardous organic compounds such as
agricultural wastes. The presence of theseorganic materials supports the developmentof a rich microbial population and elevatedtemperature characteristic of composting.
Ex Situ Bioremediation
L10
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Slide 29
L10 LF is a simple, low tech form of ex situ bioremediation.contaminated solids are mixed into the surface layer of topsoil. nutrients and
moisture can be added initially and throughout the treatment period to optimize conditions for microbial growth.Lecturer, 7/11/2008
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Bioreactors-Slurry reactors oraqueous reactors are used forex situ
treatment of contaminated soil and
water pumped up from a
contaminated plume. Bioremediationin reactors involves the processing of
contaminated solid material (soil,
sediment, sludge) or water through an
engineered containment system.
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Phytoremediation
Phytoremediation is the use of plants
to clean up potentially damaging
spills. The plants work with soilorganisms to transform contaminants,
such as heavy metals and toxic
organic compounds, into harmless or
valuable forms.
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Biodegradation
Biodegradation microbial catalyzedreduction in complexity of chemicals
Involves the breakdown of organiccompounds either through biotransformationinto less complex metabolites or through
mineralization into inorganic minerals, H2O,
CO2 or CH4.
Mineralization - conversion of an organicsubstrate to inorganic end products
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BIODEGRADATION SYSTEM IN BIOREMEDIATION
MICROORGANISMS
Growth
Physiology
Genetic competence
Metabolic diversity
Enzymology
metabolites
CONTAMINANTS
Mass transfer
Bioavailability
HydrophobicityRecalcitrance
Structure
Toxicity
ENVIRONMENTAL
FACTORS
pH
Temperature
Moisture
Oxygen
Nutrients
Soil type
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Although the microorganisms are present incontaminated soil, they cannot necessarilybe there in the numbers required forbioremediation of the site. Their growth andactivity must be stimulated.
Biostimulation usually involves the additionof nutrients and oxygen to help indigenousmicroorganisms.
These nutrients are the basic building
blocks of life and allow microbes to createthe necessary enzymes to break down thecontaminants.
Nutrients
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Carbon is the most basic element of
living forms and is needed in greater
quantities than other elements.
In addition to hydrogen, oxygen, and
nitrogen it constitutes about 95% of theweight of cells.
The nutritional requirement of carbon to
nitrogen ratio is 10:1, and carbon tophosphorous is 30:1.
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Limitations to biodegradation
Adequate bacterial concentrations (althoughpopulations generally increase if there is
food present)
Electron acceptors Nutrients (e.g., nitrogen and phosphorus)
Non-toxic conditions
Minimum carbon source
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Relative biodegradability
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Advantages of bioremediation
Bioremediation is a natural process and istherefore perceived by the public as anacceptable waste treatment process
Many compounds that are legallyconsidered to be hazardous can be
transformed to harmless products. Instead of transferring contaminants from
one environmental medium to another, forexample, from land to water or air, thecomplete destruction of target pollutants is
possible.
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Bioremediation can often be carried
out on site, often without causing a
major disruption of normal activities. Bioremediation is less expensive
Advantages of bioremediation
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Disadvantages of bioremediation
Bioremediation is limited to thosecompounds that are biodegradable.
There are some concerns that the
products of biodegradation may bemore persistent or toxic than theparent compound.
It is difficult to extrapolate from bench
and pilot-scale studies to full-scalefield operations.
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Bioremediation often takes longerthan other treatment options
Biological processes are often highly
specific. Important site factorsrequired for success include the
presence of metabolically capable
microbial populations, suitable
environmental growth conditions, andappropriate levels of nutrients and
contaminants.
Disadvantages of bioremediation
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As a result of the petroleum industry millionsof tons of these compounds enter the oceansevery year. Many hydrocarbons dissolveslowly in water. Others such as the aromaticcompounds like benzene are more soluble,
and these are toxic to living cells.
While accidental releases may contribute toonly a small percentage of the oil released
into the marine environment large accidentaloil spills receive much attention and evokeconsiderable public concern because theycan result in contamination of ocean andshoreline environments.
Case Study: Oil spill Bioremediation
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Oil spill!!
The biggest spill ever occurred during the
1991 Persian Gulf war when about 240
million gallons spilled from oil terminals and
tankers off the coast of Prince WilliamSound, Alaska. The Exxon Valdez accident
at Bligh Reef in 1989 discharged 40 million
litres.
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Initial studies showed that the number of oil
degrading microorganisms on oiled beaches in
comparison with untreated controls increased by
as much as 10,000 times.
Oleophilic fertilizer enhanced biodegradation of
oil.
Bioremediation was a useful cleanup alternative
that was used by Exxon on large scale.
Bioremediation to the rescue?
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Oleophilic fertilizer proven to be aneffective nutrient source for oil degrading
microbial communities.
The beaches are more compatible with
local wildlife (less tendency for fur and
feathers to become oiled).