Bio Remediation and Bio Degradation MAIN

8/3/2019 Bio Remediation and Bio Degradation MAIN

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BIOREMEDIATION& BIODEGRADATION


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THE BASIC PROBLEM:RELEASE OF HAZARDOUS MATERIALS

Enormous quantities of organic & inorganiccompounds are released into the environment eachyear as a result of human activities.

The release may be:

Deliberate and well regulated (industrialemissions)

Accidental and largely unavoidable (chemical/oil

spills)

US EPA estimated that in 1980 at least 57 millionsmetric tons of the total waste can be categorizedinto three general groups:


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Heavy metal, Pb, Hg, Cd, Ni and Be canaccumulate in various organs, interfere withnormal enzymatic reactions and cause disease

including cancer

Chlorinated hydrocarbons, also known asorganochlorides including pesticides and other

organic compounds such as PCB (polychlorinatedbiphenyls)

Research proven a positive correlationbetween cancer in lab animals and

organochlorides.

Nuclear waste including radioactive material suchas plutonium which are dangerous for thousands

of years


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Bioremediation can be defined as any process thatuses microorganisms, fungi, green plants or theirenzymes to return the natural environment altered

by contaminants to its original condition.Bioremediation may be employed to attack specific

soil contaminants, such as degradation ofchlorinatedhydrocarbons by bacteria. An example of

a more general approach is the cleanup of oil spillsby the addition of nitrate and/or sulfatefertilisers tofacilitate the decomposition of crude oil by

indigenous or exogenous bacteria.
http://en.wikipedia.org/wiki/Microorganismhttp://en.wikipedia.org/wiki/Fungihttp://en.wikipedia.org/wiki/Phytoremediationhttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Soil_contaminanthttp://en.wikipedia.org/wiki/Chlorinehttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Bacteriumhttp://en.wikipedia.org/wiki/Oil_spillhttp://en.wikipedia.org/wiki/Nitratehttp://en.wikipedia.org/wiki/Sulfatehttp://en.wikipedia.org/wiki/Fertiliserhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Crude_oilhttp://en.wikipedia.org/wiki/Fertiliserhttp://en.wikipedia.org/wiki/Sulfatehttp://en.wikipedia.org/wiki/Nitratehttp://en.wikipedia.org/wiki/Oil_spillhttp://en.wikipedia.org/wiki/Bacteriumhttp://en.wikipedia.org/wiki/Hydrocarbonhttp://en.wikipedia.org/wiki/Chlorinehttp://en.wikipedia.org/wiki/Soil_contaminanthttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Phytoremediationhttp://en.wikipedia.org/wiki/Fungihttp://en.wikipedia.org/wiki/Microorganism


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BIOREMEDIATION

Bioremediation is the application of biological process

principles to the treatment of groundwater, soil andsludges contaminated with hazardous chemicals.

It requires the control and manipulation of microbialprocesses 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 a

particular contaminant

To provide the conditions whereby it can do thismost effectively, thereby eliminating thecontaminant


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The breakdown of organic compounds by micro-

organisms

How might microorganisms attack hazardous organicwastes?

Mineralize compound directly, compound

converted to harmless inorganic molecules suchas carbon dioxide and salts

Of prime importance are microorganisms capableof producing enzymes that will degrade thehazardous chemical (target compound) as

enzymes degrade compounds throughexploitation of the organisms energy need.

Converting compound to some other compound,which may also be toxic and recalcitrant to furtherdegradation

BIODEGRADATION


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Heterotrophic microorganisms are the principal userof organic matter in the biosphere and are key incycling carbon from the organic to the inorganicstate. Provided that sufficient inorganic nutrients as

an energy source and a terminal electron acceptorfor metabolism are present, all naturally occurringorganic material can be biodegraded eventually.

CONCEPTS:


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Simple organic compounds such as acetate maypersist under condition that do not favor microbialactivity. These conditions include extremes intemperature or pH, the presence of toxicants or

antimicrobial agents, the inhibition or exclusion ofmicrobial enzymes, and the lack of water and anelectron acceptor.

CONCEPTS:


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REQUIREMENTS FOR BIOREMEDIATION

MICROORGANISMS

ENERGYSOURCE

ELECTRONACCEPTOR

MOISTURE pH

NUTRIENTS TEMPERATURE

ABSENCE OFTOXICITY

REMOVAL OFMETABOLITIES

ABSENCE OFCOMPETITIVEORGANISMS

BIOREMEDIATION


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Two kinds of cells are recognized, the procaryoticand eucaryotic.

The most important groups to bioremediation arebacteria and fungi.

Microbial Divisions

Procaryotic cell Eucaryotic cell

Bacteria

Blue-green bacteria orcyanobacteria

Plants

Animals

Rotifers

Protozoa

Fungi

Most algae


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Microorganisms destroy organiccontaminants in the course of usingthe chemicals for their own growthand reproduction.

Organic chemicals provide:

carbon, source of cell buildingmaterial, 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 bioremediationare in situ bioremediation and ex situ

bioremediation. In addition, anotheroffshoot of bioremediation isphytoremediation.


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In Situ Bioremediation

In situ bioremediation is when thecontaminated site is cleaned up exactly

where it occurred. It is the most commonly

used type of bioremediation because it isthe cheapestand most efficient, so itsgenerally better to use. There are two maintypes of in situ bioremediation: intrinsic

bioremediation and acceleratedbioremediation.


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Intrinsic Bioremediation

Intrinsic bioremediation usesmicroorganisms already present in theenvironment to biodegrade harmfulcontaminant. 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.


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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 microorganismsgrow more rapidly. Usually themicroorganisms are indigenous, but

occasionally microorganisms that arevery efficient at degrading a certaincontaminant are additionally added.


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Main advantage is that site disturbance isminimized, which is particularly importantwhen the contaminated plume hasmoved under permanent structures.

Biggest limitation of in situ treatment has

been the inability to deal effectively withmetal contaminants mixed with organiccompounds.

The goal of in situ treatment is to manageand manipulate the subsurfaceenvironment to optimize microbial

degradation.


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Land treatments:

Bioventingis the most common in situtreatment and involves supplying airand nutrients through wells tocontaminated soil to stimulate theindigenous bacteria.

In Situ Bioremediation


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In situ biodegradationinvolvessupplying oxygen and nutrients by

circulating aqueous solutions throughcontaminated soils to stimulatenaturally occurring bacteria todegrade organic contaminants.

BioaugmentationBioremediationfrequently involves the addition ofmicroorganisms indigenous orexogenous to the contaminated sites.


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Biosparginginvolves the injection of air

under pressure below the water tableto increase groundwater oxygenconcentrations and enhance the rateof biological degradation ofcontaminants by naturally occurringbacteria. Biosparging increases themixing in the saturated zone and

thereby increases the contactbetween soil and groundwater.


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Ex Situ Bioremediation

Another type of bioremediation is ex situbioremediation, which is whencontaminated land are taken out of thearea to be cleaned up by the organisms.

This type of bioremediation is generallyused only when the site is threatened forsome reason, usually by the spill thatneeds to be cleaned up. Ex situbioremediation is only used whennecessary because its expensive anddamaging to the area, since thecontaminated land is physicallyremoved.


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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


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Bioreactors-Slurry reactors or

aqueous reactors are used for ex situtreatment of contaminated soil andwater pumped up from a

contaminated plume. Bioremediationin reactors involves the processing ofcontaminated solid material (soil,sediment, sludge) or water through an

engineered containment system.


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Phytoremediation

Phytoremediation is the use of plantsto clean up potentially damaging

spills. The plants work with soilorganisms to transform contaminants,such as heavy metals and toxicorganic 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 throughmineralization into inorganic minerals, H2O,

CO2 or CH4.

Mineralization - conversion of an organicsubstrate to inorganic end products


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Growth-linked metabolism biodegradation

provides carbon and energy to support growth.

Maintenance metabolism biodegradation notlinked to multiplication, but to obtaining carbon forrespiration to maintain cell viability; take place only

when organic carbon concentrations very low.

The extent and rate of biodegradation depend onmany factors including pH, temperature, oxygen,

microbial population, degree of acclimation,accessibility of nutrients, chemical structure of thecompound, cellular transport properties andchemical partitioning in growth medium.


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BIODEGRADATION SYSTEM IN BIOREMEDIATION

MICROORGANISMS

GrowthPhysiology

Genetic competenceMetabolic diversity

Enzymologymetabolites

CONTAMINANTSMass transferBioavailability

HydrophobicityRecalcitrance

StructureToxicity

ENVIRONMENTALFACTORS

pHTemperature

MoistureOxygen

NutrientsSoil type


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Microorganisms can be isolated from almostany environmental conditions.

Microbes will adapt and grow at different

temperatures, as well as extreme heat,

desert conditions, in water, with an excessof oxygen, and in anaerobic conditions, withthe presence of hazardous compounds oron any waste stream.

Because of the adaptability of microbes andother biological systems, these can be usedto degrade or remediate environmentalhazards.

Microorganisms


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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 greaterquantities 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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Environmental requirements


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Limitations to biodegradation

Adequate bacterial concentrations (althoughpopulations generally increase if there isfood 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 carriedout 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 highlyspecific. Important site factorsrequired for success include thepresence of metabolically capablemicrobial populations, suitable

environmental growth conditions, andappropriate levels of nutrients andcontaminants.

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 and

shoreline environments.

Case Study: Oil spill Bioremediation


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Oil spill!!

The biggest spill ever occurred during the1991 Persian Gulf war when about 240million gallons spilled from oilterminals and

tankers off the coast of Prince WilliamSound, Alaska. The Exxon Valdez accidentat Bligh Reef in 1989 discharged 40 millionlitres.


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Initial studies showed that the number of oildegrading microorganisms on oiled beaches incomparison with untreated controls increased byas much as 10,000 times.

Oleophilic fertilizer enhanced biodegradation ofoil.

Bioremediation was a useful cleanup alternativethat was used by Exxon on large scale.

Bioremediation to the rescue?


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Oleophilic fertilizer proven to be an

effective nutrient source for oil degradingmicrobial communities.

The beaches are more compatible withlocal wildlife (less tendency for fur andfeathers to become oiled).

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