wk2-bioremediation and bio degradation

8/8/2019 Wk2-Bioremediation and Bio Degradation

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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).

wk2-bioremediation and bio degradation

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