BIOREMEDIATION

Introductory conceptCONVENTIONAL METHOD:

• Concept of dig n dump

• Insufficient method

• The toxic materials from these “dig n dump” sites have begun to leak into water

sources and into areas that sustain human life.

• 1891 the first biological sewage treatment plant was created in Sussex, UK.

• The word “bioremediation” did not appear in peer-reviewed scientific literature

until 1987.

CONCEPT:

• Bioremediation is the transformation or degradation of contaminants into non-

hazardous or less hazardous chemicals.

• Bacteria are generally used for bioremediation, but fungi, algae and plants have also

been used.

• Bioremediation is not a new technology.

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• Increases in environmental contamination lead to aprogressive deterioration of environmental quality.

• The increasing size of the human population requiresthe need for a biological approach to improveenvironmental conditions.

• Exposure to pest control and environmental chemicalremediation is increasing because environmentalrelease of biotechnology agents is becoming moreof biotechnology agents becomingaccepted.

• Therefore, it is important to have reliable data onpotential health effects of these agents.

WHAT IS CONTAMINATION ?• Any substance causing harm directly or indirectly to any

living form ,process is called contamination and substancecausing contamination are called contaminants.

• Human population releases toxicants such as detergents,fertilizers, propellants, pesticides, refrigerants, and manyother chemicals.

• Feces and urine contain biological nitrogen waste and areproduced by animals.

• Radioactive compounds yield other radioactive metabolites,which can be as hazardous or more so than the parentcompound.

• Heavy metals are utilized in many industrial processes andproducts.

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ENVIRONMENTAL CONTAMINANTS

Pollutants

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naturally occurring‐compounds in theenvironment that arepresent in unnaturally highconcentrations.

Examples: crude oil refined oil phosphates heavy metals

Xenobiotics chemically synthesized

compounds that havenever occurred innature.

Examples: pesticides herbicides plastics

What is Bioremediation?• By definition, bioremediation is the use of living organisms,

primarily microorganisms, to degrade the environmentalcontaminants into less toxic forms. The use of bacteria andfungi and plants to break down or degrade toxic chemicalcompo nds that ha e acc m lated in the en ironment.

• Bioremediation is the productive utilization of livingsystems to degrade, detoxify, transform, immobilize orstabilize toxic environmental contaminants.

• inMi b th t lilive i

andil d

groundwaterd t lik tto eat

certain harmful chemicals, such as those found in gasolineand oil spills. When microbes completely digest thesechemicals, they change them into water and harmlessgases such as carbon dioxide.

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General equation of bioremediation

Microbes + contaminants + electron acceptor= CO2+ H20 + biomass

Thus, bioremediation is defined as the processwhereby organic wastes are biologically degradedunder controlled conditions to an innocuousstate, or to levels below concentration limitsestablished by regulatory authorities.

Principles of bioremediationIn year 2000, Tate summarized the principles of

bioremediation:1 The relationship ofof comparative biochemistry

applies equally to cultures of microbes and thosepresent in the soil.

2. The microbial growth requirements are the samewhether in the laboratory culture or in the field.

3. The ecological factors need to accommodate thepresence of other microbes and adapt to thephysical and chemical properties of the soil.

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Aerobic and Anaerobic bioremediation

Various factors controls bioremediation

1. Availability of micro organisms such as bacteria,‐fungi etc which are capable of bioremediation

2. Availability of contaminants3. Environmental factors such as:i. Type of soilii. Temperatureiii. pHiv. Oxygen

v. Electron acceptorsvi. Nutrients

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Factor

Microbialpopulation

Oxygen

Water

Desired Conditions

Suitable kinds of organisms that can biodegrade allof the contaminants

Enough to support aerobic biodegradation (about2% oxygen in the gas phase or 0.4 mg/liter in thesoil water)

Soil moisture should be from 50–70% of the waterholding capacity of the soil

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NutrientsNi h h lf a

nd

d h i

to support good microbial growth

Temperature Appropriate temperatures for microbial growth (0–

pH40˚C)Best range is from 6.5 to 7.5

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Important organisms involved inbioremediation

• Metabolizing Microbes– Indigenous microbes – those found naturally at a

polluted site– Bacteria

• Pseudomonas• E.coli

– Algae and fungi• Fusarium oxysporum• Mortierella hyaline

Bioremediation Technology

• Technologies can be generally classified as in situ or exsitu.

IN SITU: It involves treating the contaminated material atthe site. It is an application of biological treatment to thecleanup of hazardous chemicals in the soil and surface orsubsurface waters.

EX SITU: It involves the removal of the contaminatedmaterial to be treated elsewhere. In this processgenerally the excavated soil is placed in a lined above‐ground treatment area and aerated following processingto enhance the degradation of organic contaminants bythe indigenous microbial population.

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Examples of bioremediation technologies are

1. Phytoremediation2. Bioventing3. Bioleaching4. Landfarming5. Bioreactors6. Composting7. Bioaugmentation8. Rhizofiltration9. Biostimulation.

Types of in situ bioremediation

1. BIOVENTING2. IN SITU BIODEGRADATION3. BIOSPARGING4. BIOLEACHING5. BIOAUGMENTATION6. PHYTOREMEDIATION

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1. BIOVENTING:

• Bioventing is an In-Situ remediation technology

• Uses indigenous microorganisms to biodegrade organic constituents adsorbed to soils in

the unsaturated zone.• In Bioventing, the activity of the indigenous bacteria is enhanced by inducing air (or

oxygen) flow into the unsaturated zone (using extraction or injection wells) and, ifnecessary, by adding nutrients.

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2. IN SITU BIODEGRADATION/ BIOSTIMULATION:

It involves supplying oxygen and nutrients by circulatingaqueous solutions through contaminated soils to stimulatenaturally occurring bacteria to degrade organic contaminants.It can be used for soil and groundwater Generally thistechnique includes conditions such as the infiltration of water‐containing nutrients and oxygen or other electron acceptorsfor groundwater treatment.

Biostimulation is the addition of nutrients, oxygen or otherelectron donors and acceptors to the coordinated site in orderto increase the population or activity of naturally occurringmicroorganisms available for bioremediation.

3. BIOSPARGING: It involves the injection of air under pressure belowthe water table to increase groundwater oxygen concentrationsand enhance the rate of biological degradation of contaminantsby naturally occurring bacteria. It can be used to reduceconcentrations of petroleum constituents that are dissolved ingroundwater.

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4. BIOLEACHING:

It is the extraction of specific metals from their ores through the useof living organisms.

Benefits of bioleaching

• Simple and inexpensive process.

• Ecofriendly process

• No need for high pressure or temperature

• Leaching residues less active than in physico-chemical processes

• Pretreatment of refractory gold in ores where high arsenic content concentrares.

• Operating the bioleaching plant is very simple, as bacteria do most of the work

• Relatively low cost

• Thiobacillus ferrooxidans, Leptospirillum ferrooxidans

and Thermophilic species of Sulfobacillus, Acidianus andSulfolobus

• These bacteria tolerate acids and metabolize sulphur.• The particular bacteria use a chemical reaction known as

“Oxidation reaction” to convert metal sulphide crystalsinto sulphates and sheer metals.

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1 Th b t i idi f i (F 2+) d l h (S)to produce ferric iron (Fe3+) and sulphate (SO42-)

2. The Fe3+ in turn reacts with the sulphide minerals toproduce Fe2+ and S

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5 . BIOAUGMENTATION:

It frequently involves the addition of microorganisms indigenous or

exogenous to the contaminated sites. Microorganisms can

biotransform or biodegrade contaminants. The microorganisms

added can be a completely new species or more members of a

species that already exists at the site.

For this approach to be successful in the field, the seedmicroorganisms

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• b bl d d l• maintain genetic stability and viability during storage,• survive in foreign and hostile environments,• effectively compete with indigenous microorganisms,• and move through the pores of the sediment to the contaminants

6. PHYTOREMEDIATION

Phytoremediation is the use of living green plants for reduction and/or removal ofcontaminants from contaminated soil, water, sediments, and air.

Advantages:• Low cost• The possibility of phytomining

• Eco friendly

Limitations:• Phytoremediation is limited to the surface area and depth occupied by the

roots.• Time consuming

• The survival of the plants is affected by the toxicity of the contaminated landand the general condition of the soil.

• Bio-accumulation of contaminants, especially metals, into the plants whichthen pass into the food chain, from primary level consumers upwards or

requires the safe disposal of the affected plant material.

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How does it work:

Modes of phytoremediation:

PHYTODEGRADATION: The process PHYTOEXTRACTION: The use of plantswhere plants are able to metabolically to extract contaminants from the

degrade organic pollutants environment

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PHYTOSTIMULATION: Enhancementof soil microbial activity for the

degradation of contaminants, typicallyby organisms that associate with roots.

PHYOTVOLATILISATION: The use ofplants to volatilise pollutants from

polluted soils and water

PHYTOSTABILISATION: Use of plants toreduce bioavailability and migration of

contaminants

RHIZOFILTRATION: The uptake ofcontaminants by the roots of plants

which are immersed in water

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In situ bioremediation:Advantages:

1. It does not requires removal of the contaminants from the contaminated site.

2. Less time consuming.3. Less costly.

4. No potential danger involved.

Disadvantages:

1. As the site is not contained,therefore it is harder to control conditions and

monitor the progress.

Types of Ex situ bioremediation

• These techniques generally involve the excavation or removal ofcontaminated soil/water from the site.

1. LANDFARMING/ BIOFARMING2. COMPOSTING3. BIOPILES4. BIOREACTORS

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3. LAND/ BIO FARMING: It is a simple technique in whichcontaminated soil is excavated and spread over a preparedbed and periodically tilled until pollutants are degraded.

• Contaminated soils are mixed with soil amendments such as soil bulking agentsand nutrients, and then they are tilled into the earth.

• The material is periodically tilled for aeration.LIMITATIONS:

• Large space requirements• Time consuming• Leaching problem

2. COMPOSTING: It is a technique that involves combiningcontaminated soil with nonhazardous organic amendantssuch as manure or agricultural wastes. The presence of theseorganic materials supports the development of a rich

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microbial population and elevated temperaturecharacteristic of composting.

3. BIOPILES are a hybrid of landfarming and composting.Essentially, engineered cells are constructed as aeratedcomposted piles. Typically used for treatment of surfacecontamination with petroleum hydrocarbons they are arefined version of landfarming that tend to control physicallosses of the contaminants by leaching and volatilization.Biopiles provide a favorable environment for indigenousaerobic and anaerobic microorganisms.

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4. Bioreactors.• A bioreactor may refer to any manufactured or engineered device

or system that supports a biologically active environment. It is avessel in which a chemical process is carried out. Bioreactors arealso designed to treat sewage and wastewater.

• Bioremediation in reactors involves the processing of contaminatedsolid material (soil, sediment, sludge) or water through anengineered containment system.

• A slurry bioreactor may be defined as a containment vessel andapparatus used to create a three-phase (solid, liquid, and gas)mixing condition to increase the bioremediation rate of soil boundand water-soluble pollutants as a water slurry of the contaminatedsoil and biomass (usually indigenous microorganisms) capable ofdegrading target contaminants.

Ex situ bioremediation:

Advantages:

1. Removes the contaminants and place them in a contained environment.

2. This contained environment allows easy monitoring and maintenance and

thus makes whole process faster.

Disadvantages:

1. Removal of contaminants from the contaminated sites is time

consuming,costly and potentially dangerous.

2. Increased exposure to the toxic material.

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Advantages of Bioremediation:

1) Bioremediation is a natural process.

2) It is cost effective.

3) T iToxic h i l are d t d or removedd from

environment and not just merely separated.

4) Low capital expenditure.

5) Less energy is required as compared to other

technologies

6) Less manual supervision.

Disadvantages

1) The process of bioremediation is slow. Time

required is in day to months.

2) Heavy metals are not removed.

3) For in situ bioremediation site must have soil

with high permeability.

4) It does not remove all quantities of

contaminants.

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Recombinant DNA technology andbioremediation

• Genetically engineered microorganisms (GEMs) haveshown potential for the bioremediation of soil and

l d treatment

Example:‐1. Enterobacteragglomerans DK3 containing plasmid RP 4 Tn 4371 ,‐

encodes for Biophenyl degradation. This donor strain whenadded to the soil disappears quickly, but the plasmid istransferred to the other microbes present, which carry out thebiophenyl degradation.

2. The bacterium Deinococcus radiodurans (the most radioresistantorganism known) has been modified to consume and digesttoluene and ionic mercury from highly radioactive nuclear waste

Conclusion• Bioremediation is cost effective and is a beneficial addition to chemical‐

and physical methods of managing wastes and environmentalpollutants.

• Biodegradative treatment offers a savings of 60 to 90% over landfilldisposal costs.

• New tools and techniques for use of bioremediation in situ in biofilters,and in bioreactors are contributing to the rapid growth of this field.

• It is clear that new bioremediation technologies that can better monitorand control many types of societal wastes are emerging.

• Genetically engineered microbes will require further study to clarifyissues of safety and containment.

• Perhaps the larger problem facing policy makers in the future is how todecide where available bioremedial dollars will benefit human andenvironmental health the most.

• Target cleanup goals have been judged to be highly unrealistic in somecases. At most of these sites remedial efforts are as yet incomplete, andsome efforts have had little effect.

• Bioremediation will play an increasingly important role as a result ofnew and emerging techniques and processes.

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