Bioremediation uses microorganisms like bacteria and fungi to degrade contaminants in soil and water. It works by stimulating natural microbial activity to break down harmful pollutants into harmless substances. Various technologies can be used including treating excavated soil in biopiles or bioreactors, injecting nutrients and oxygen into contaminated groundwater and soil, and planting vegetation that helps remove toxins from the environment. The microbes metabolize the pollutants for food and energy through aerobic or anaerobic processes, transforming contaminants into less toxic or non-toxic forms.

1. BIOREMEDIATION

2. DefinitionDefinition
 Bioremediation is defined as the processBioremediation is defined as the process
whereby organic wastes are biologicallywhereby organic wastes are biologically
degraded under controlled conditions to andegraded under controlled conditions to an
innocuous state, or to levels belowinnocuous state, or to levels below
concentration limits established by regulatoryconcentration limits established by regulatory
authorities.authorities.
 It uses naturally occurring microorganisms likeIt uses naturally occurring microorganisms like
bacteria and fungi or plants to degrade orbacteria and fungi or plants to degrade or
detoxify substances hazardous to humandetoxify substances hazardous to human
health and/or the environment.health and/or the environment.

3. - Concept

4. Bioremediation – Concept (Contd..)Bioremediation – Concept (Contd..)
Recent studies in molecular biology and ecology offerRecent studies in molecular biology and ecology offer
opportunities for more efficient biological processes toopportunities for more efficient biological processes to
clean-up of polluted water and land areasclean-up of polluted water and land areas
 Bioremediation allows natural processes to clean up
harmful chemicals in the environment.
 Microscopic “bugs” or microbes that live in soil and
groundwater like to eat certain harmful chemicals.
 When microbes completely digest these chemicals,
they change them into water and harmless gases
such as carbon dioxide.

5. SchematicSchematic
Bioremediation is an option that offers the possibility
to destroy or render harmless various contaminants
using natural biological activity.

6. Bacteria
Fungi
Fungi
Actinomycetes Actinomycetes Actinomycetes

7. Bioremediation - Basic factsBioremediation - Basic facts
 The microorganisms may be indigenous to a contaminated areaThe microorganisms may be indigenous to a contaminated area
or they may be isolated from elsewhere and brought to theor they may be isolated from elsewhere and brought to the
contaminated sitecontaminated site
 Contaminant compounds are transformed by living organismsContaminant compounds are transformed by living organisms
through reactions that take place as a part of their metabolicthrough reactions that take place as a part of their metabolic
processes.processes.
 Biodegradation of a compound is often a result of the actions ofBiodegradation of a compound is often a result of the actions of
multiple organisms.multiple organisms.
 Microorganisms must enzymatically attack the pollutantsMicroorganisms must enzymatically attack the pollutants
 Bioremediation can be effective only where environmentalBioremediation can be effective only where environmental
conditions permit microbial growth and activityconditions permit microbial growth and activity
 Manipulation of environmental parameters needed for microbialManipulation of environmental parameters needed for microbial
growth and degradation to proceed at a faster rate.growth and degradation to proceed at a faster rate.

8. FACTORS OF BIOREMEDIATIONFACTORS OF BIOREMEDIATION
The control and optimization of bioremediationThe control and optimization of bioremediation
processes is a complex system of many factors.processes is a complex system of many factors.
 existence of a microbial populationexistence of a microbial population
 availability of contaminants to the microbialavailability of contaminants to the microbial
populationpopulation
 the environment factors (type of soil,the environment factors (type of soil,
temperature, pH, the presence of oxygen ortemperature, pH, the presence of oxygen or
other electron acceptors, and nutrients).other electron acceptors, and nutrients).

9. MICROBIAL POPULATIONSMICROBIAL POPULATIONS
 Microorganisms can be isolated from almost anyMicroorganisms can be isolated from almost any
environmental conditions. Microbes will adapt andenvironmental conditions. Microbes will adapt and
grow at subzero temperatures, as well as extremegrow at subzero temperatures, as well as extreme
heat, desert conditions, in water, with an excess ofheat, desert conditions, in water, with an excess of
oxygen, and in anaerobic conditions, with theoxygen, and in anaerobic conditions, with the
presence of hazardous compounds or on any wastepresence of hazardous compounds or on any waste
stream.stream.
 The main requirements are an energy source and aThe main requirements are an energy source and a
carbon source. Because of the adaptability ofcarbon source. Because of the adaptability of
microbes and other biological systems, these can bemicrobes and other biological systems, these can be
used to degrade or remediate environmentalused to degrade or remediate environmental
hazards.hazards.

10. Types of microorganismsTypes of microorganisms
 Aerobic. Grows in presence of oxygen, degradeAerobic. Grows in presence of oxygen, degrade
pesticides and hydrocarbons, both alkanes andpesticides and hydrocarbons, both alkanes and
polyaromatic compounds. Many of these bacteria use thepolyaromatic compounds. Many of these bacteria use the
contaminant as the sole source of carbon and energy.contaminant as the sole source of carbon and energy.
Examples Pseudomonas, Alcaligenes, Sphingomonas,Examples Pseudomonas, Alcaligenes, Sphingomonas,
Rhodococcus, and Mycobacterium.Rhodococcus, and Mycobacterium.
 Anaerobic. Grows in absence of oxygen. are not asAnaerobic. Grows in absence of oxygen. are not as
frequently as aerobic, degrade polychlorinated biphenylsfrequently as aerobic, degrade polychlorinated biphenyls
(PCBs), dechlorination of the solvent trichloroethylene(PCBs), dechlorination of the solvent trichloroethylene
(TCE), and chloroform.(TCE), and chloroform.
 Methylotrophs. Aerobic bacteria that grow utilizingMethylotrophs. Aerobic bacteria that grow utilizing
methane for carbon and energy. The initial enzyme in themethane for carbon and energy. The initial enzyme in the
pathway for aerobic degradation, methanepathway for aerobic degradation, methane
monooxygenase, has a broad substrate range and ismonooxygenase, has a broad substrate range and is
active against a wide range of compounds, including theactive against a wide range of compounds, including the
chlorinated aliphatics trichloroethylene and 1,2-chlorinated aliphatics trichloroethylene and 1,2-
dichloroethane.dichloroethane.

11. BiostimulationBiostimulation
Although the microorganisms are present in contaminated soil,Although the microorganisms are present in contaminated soil,
they cannot necessarily be there in the numbers required forthey cannot necessarily be there in the numbers required for
bioremediation of the site. Their growth and activity must bebioremediation of the site. Their growth and activity must be
stimulated.stimulated.
 Biostimulation usually involves the addition of nutrients andBiostimulation usually involves the addition of nutrients and
oxygen to help indigenous microorganisms.oxygen to help indigenous microorganisms.
 These nutrients are the basic building blocks of life and allowThese nutrients are the basic building blocks of life and allow
microbes to create the necessary enzymes to break down themicrobes to create the necessary enzymes to break down the
contaminants. All of them will need nitrogen, phosphorous, andcontaminants. All of them will need nitrogen, phosphorous, and
carbon.carbon.
 Carbon is the most basic element of living forms and is neededCarbon is the most basic element of living forms and is needed
in greater quantities than other elements. In addition toin greater quantities than other elements. In addition to
hydrogen, oxygen, and nitrogen it constitutes about 95% of thehydrogen, oxygen, and nitrogen it constitutes about 95% of the
weight of cells.weight of cells.
 Phosphorous and sulfur contribute with 70% of the remainders.Phosphorous and sulfur contribute with 70% of the remainders.
The nutritional requirement of carbon to nitrogen ratio is 10:1,The nutritional requirement of carbon to nitrogen ratio is 10:1,
and carbon to phosphorous is 30:1.and carbon to phosphorous is 30:1.

12.  For degradation it is necessary that bacteriaFor degradation it is necessary that bacteria
and the contaminants be in contact. This isand the contaminants be in contact. This is
not easily achieved, as neither the microbesnot easily achieved, as neither the microbes
nor contaminants are uniformly spread in thenor contaminants are uniformly spread in the
soil.soil.
 Some bacteria are mobile and exhibit aSome bacteria are mobile and exhibit a
chemotactic response, sensing thechemotactic response, sensing the
contaminant and moving toward it.contaminant and moving toward it.
 Other microbes such as fungi grow in aOther microbes such as fungi grow in a
filamentous form toward the contaminant.filamentous form toward the contaminant.
 It is possible to enhance the mobilization ofIt is possible to enhance the mobilization of
the contaminant utilizing some surfactantsthe contaminant utilizing some surfactants
such as sodium dodecyl sulphatesuch as sodium dodecyl sulphate
Biostimulation (Contd..)Biostimulation (Contd..)

14. The Science – How Does it Work?The Science – How Does it Work?
Microbial MetabolismMicrobial Metabolism refers to all the chemical reactions thatrefers to all the chemical reactions that
happen in a cell or organism. All living processes are based on ahappen in a cell or organism. All living processes are based on a
complex series of chemical reactions.complex series of chemical reactions.
Anabolism – BuildingAnabolism – Building complex molecular structures simpler mol.complex molecular structures simpler mol.
In anabolism, chemicals taken up by the microorganism areIn anabolism, chemicals taken up by the microorganism are
used to build various cell parts. Carbon and nitrogen are theused to build various cell parts. Carbon and nitrogen are the
basic chemicals in the proteins, sugars and nucleic acids thatbasic chemicals in the proteins, sugars and nucleic acids that
make up microbial cells. Microorganisms take up carbon andmake up microbial cells. Microorganisms take up carbon and
nitrogen from the soil, water, and air around them. In order tonitrogen from the soil, water, and air around them. In order to
take up nutrients and make them into cell parts, atake up nutrients and make them into cell parts, a
microorganism needs energy. This is where catabolism comes in.microorganism needs energy. This is where catabolism comes in.
Catabolism – BreakingCatabolism – Breaking complex molecules into simpler mol.complex molecules into simpler mol.
Catabolism allows microorganisms to gain energy from theCatabolism allows microorganisms to gain energy from the
chemicals available in the environment. Although mostchemicals available in the environment. Although most
microorganisms are exposed to light and to chemical energymicroorganisms are exposed to light and to chemical energy
sources, most rely on chemicals for their energy. Whensources, most rely on chemicals for their energy. When
chemicals break down, energy is released. Microorganisms usechemicals break down, energy is released. Microorganisms use
this energy to carry out cellular functions, such as thosethis energy to carry out cellular functions, such as those
involved in anabolism.involved in anabolism.

15. Mid
Research

16. Super bugSuper bug
Pseudomonas putida.
Dr. Ananda Mohan ChakrabortyDr. Ananda Mohan Chakraborty

17.  Natural AttenuationNatural Attenuation
 Aerobic/AnaerobicAerobic/Anaerobic
biodegradationbiodegradation
 BiopilesBiopiles
 Land TreatmentLand Treatment
 BioscrubbersBioscrubbers
 Methanotrophic Process (in Situ)Methanotrophic Process (in Situ)
 Plant Root UptakePlant Root Uptake
(Phytoremediation)(Phytoremediation)
 Solid Phase BioremediationSolid Phase Bioremediation
 Bio Wall for PlumeBio Wall for Plume
Decontamination (In Situ)Decontamination (In Situ)
 BiodegradationBiodegradation
 CompostingComposting
 BioreactorsBioreactors
 DehalogenationDehalogenation
 Binding of MetalsBinding of Metals
 Fungi Inoculation ProcessFungi Inoculation Process
 Slurry Phase bioremediationSlurry Phase bioremediation
 Bioventing (Chapter 7: BMPs forBioventing (Chapter 7: BMPs for
Vapor (Extraction)Vapor (Extraction)
 Bioremediation of MetalsBioremediation of Metals
(Changing the Valence)(Changing the Valence)
Different kinds of bioremediation technologies are currently being used for soil
treatment and many more innovative approaches involving bioremediation are being
developed. considering the similarity in their cross-media transfer potential, listed below
are a few examples of bioremediation technologies and processes:
Kinds of Bioremediation

18. Key Features of BioremediationKey Features of Bioremediation
 Most bioremediation treatment technologies destroy the contaminants inMost bioremediation treatment technologies destroy the contaminants in
the soil matrix.the soil matrix.
 These treatment technologies are generally designed to reduce toxicityThese treatment technologies are generally designed to reduce toxicity
either by destruction or by transforming toxic organic compounds intoeither by destruction or by transforming toxic organic compounds into
less toxic compounds.less toxic compounds.
 Indigenous micro-organisms, including bacteria and fungi, are mostIndigenous micro-organisms, including bacteria and fungi, are most
commonly used. In some cases, wastes may be inoculated with specificcommonly used. In some cases, wastes may be inoculated with specific
bacteria or fungi known to biodegrade the contaminants in question.bacteria or fungi known to biodegrade the contaminants in question.
Plants may also be used to enhance biodegradation and stabilize thePlants may also be used to enhance biodegradation and stabilize the
soil.soil.
 The addition of nutrients or electron acceptors (such as hydrogenThe addition of nutrients or electron acceptors (such as hydrogen
peroxide or ozone) to enhance growth and reproduction of indigenousperoxide or ozone) to enhance growth and reproduction of indigenous
organisms may be required.organisms may be required.
 Field application of bioremediation may involve:Field application of bioremediation may involve:
– ExcavationExcavation
– Soil handlingSoil handling
– Storage of contaminated soil pilesStorage of contaminated soil piles
– Mixing of contaminated soilsMixing of contaminated soils
– Aeration of contaminated soilsAeration of contaminated soils
– Injection of fluidInjection of fluid
– Extraction of fluidExtraction of fluid
– Introduction of nutrients and substratesIntroduction of nutrients and substrates

19. Bioremediation - technology description
Bioremediation involves the use of micro-organisms to chemically
degrade organic contaminants. Aerobic processes use organisms
that require oxygen to be able to degrade contaminants. In come
cases, additional nutrients such as nitrogen and phosphorous are
also needed to encourage the growth of biodegrading organisms. A
biomass of organisms – which may include entrained constituents
of the waste, partially degraded constituents, and intermediate
biodegradation products – is formed during the treatment process
(USEPA, 1990d29
)
Although bioremediation is applied in many different ways, the
description of typical solid phase bioremediation, composting,
bioventing, and traditional in situ biodegradation is provided here,
besides the description of a few common bioremediation
technologies.

20. Solid Phase Bioremediation
The solid phase bioremediation treatment can be
conducted n lined land treatment units or in composting
piles. A lined land treatment unit consists of a prepared
bed reactor with a leachate collection system and
irrigation and nutrient delivery systems,. The unit may
also contain air emission control equipment. The soil is
placed on land lined with an impervious layer, such as
soil, clay, or a synthetic liner.

21. Bioventing
Bioventing uses relatively low-flow soil aeration techniques to
enhance the biodegradation of soils contaminated with organic
contaminants. Although bioventing is predominantly used to treat
unsaturated soils, applications involving the remediation of
saturated soils and groundwater (augmented by air sparging) are
becoming more common . Generally, a vacuum extraction, an air
injection, or a combination of both systems is employed. An air
pump, one or more air injections or vacuum extraction probes, and
emissions monitors at the ground surface level are commonly
used.

22. A basic bioventing system includes a well and a blower,
which pumps air through the well and into the soil.

23. Landfarming
Ex situ processes also include landfarming, which
involves spreading contaminated soils over a large area.
Bioremediation may also be conducted in a bioreactor, in
which the contaminated soil or sludge is slurried with
water in a mixing tank or a lagoon. Bioremediation
systems require that the contaminated soil or sludge be
sufficiently and homogeneously mixed to ensure
optimum contact with the seed organisms.

24. It is a full-scale technology in which excavated
soils are mixed with soil amendments, placed on a
treatment area, and bioremediated using forced
aeration. It is a hybrid of landfarming and
composting.
The basic biopile system includes a treatment bed,
an aeration system, an irrigation/nutrient system
and a leachate collection system.
Biopile treatment

26. Bioreactors
Bioreactors function in a manner that is similar to sewage
treatment plants. There are many ways in which a bioreactor can
be designed; but most are a modification of one of two systems. In
the first system, which is often referred to as a trickling filter or
fixed media system.
The second common bioreactor design uses a sealed vessel to
mix the contaminants, amendments and micro-organisms.
Recent research has expanded the capabilities of this technology,
which along with its generally lower cost, has led to bioremediation
becoming an increasingly attractive cleanup technology.

28. It is a technique that involves combining
contaminated soil with nonhazardous
organic amendants such as manure or
agricultural wastes. The presence of these
organic materials supports the
development of a rich microbial
population and elevated temperature
characteristic of composting.
Composting

32. Composition of a microbial cell (%).
Carbon 50 Sodium 1
Nitrogen 14 Calcium 0.5
Oxygen 20 Magnesium 0.5
Hydrogen 8 Chloride 0.5
Phosphorous 3 Iron 0.2
Sulfur 1 All others 0.3
Potassium 1

33. Biotreatment of metal and radionuclide:Biotreatment of metal and radionuclide:
There are many metal tolerant microbes which are capable of
accumulating and transforming toxic metals and thus helps in
detoxification processes. A number of processes involved in metal
removal by different tolerant microorganisms. These includes –
• Precipitation of heavy metals and radionuclides by production of
extra cellular materials which interact with metal cations
forming insoluble precipitate;
• Biotransformation of metals and radio nuclides either by
oxidation, reduction or alkylation reactions;
• Intercellular accumulation or extra cellular accumulation

34. The major mechanisms for bacterial metal precipitation
is through the formation of hydrogen sulphide and the
immobilization of the metal cations as metal sulphides.
Aerobic bacteria like Citrobactor sp produces metal
sediment as phosphate salt through phosphatase
reactions, where hudrogen phosphate is formed from
organic phosphates, such hydrogen phosphate (HPO4=
)
subsequently precipitates metals and radionuclides (such
as lead, cadmium and uranium). The sulphur reducing
bacteria viz. Desulfovibrio and Desulfotomaculam
produce metal sediment in anaerobic environment

35. In contrary several microorganisms transforms metals and
radionuclides by oxidation, reduction or alkalanation reactions.
Ferrous (Fe2+
) and manganous (Mn2+
) compounds can be deposited
through oxidation reactions catalysed by species of bacteria, fungi,
algae and protozoa. For example Leptothrix is very common ferro-
manganese oxidizing bacteria produces Fe(OH)3
and MnO2
within a
surface bound exopolymer. Similarly Thiobacillus ferrooxidans and
Leptospirillum ferrooxidans can solubilize metal from minerals
allowing the extraction and recovery of metals such as Cu, Cd, Gold
and uranium from low grade ores. All these are oxidative reactions.
On the other hand several microbes help in reduction of metal likes
mercury, iron, manganese, selenium, arsenic and thus reduces the
toxicity of metal ions. Identically tin, selenium and lead can be
volatilized by bacteria through the production of alkylated metals.
The major bacteria like Pseudomonous and Corynebacterium and
fungi like Alterneria alternata perform these reactions in presence of
methylating agents

36. Bioaccumulation of metals by microbes are quite well known.
Microbes often accumulate metals in intercellular region by active
transport or extracellular surface binding. Filamentous fungi like
Aspergillus niger and Penicillium species are quite well known for
their bioadsorption. A variety of biopolymers like polysaccarides,
protein and polyphenolics has proformed metal binding
properties. Metal binding proteins such as metallothioneins
(cystine rich small peptides) and phytochelations appears to be
commonly produced by microbes. In addition in certain categories
of microbes metal chelating agents ex siderophores are known. The
siderophores are catechol or hydroxamate derivatives.

37. Several microbes are now well recognized as aromatic
degrading organism. Sometime they acts individually or acts
together called consortium. A wide variety of bacteria and
fungi can carry out aromatic transformation, both partial
and complete, under a variety of environmental conditions.
The bacteria Pseudomonous putida or fungi like
Phanesochaete chrysosporium are well known for arotic
compound biotransformation reactions. Under aerobic
conditions the most common initial transformation is a
hydroxylation that involves the incorporation of molecular
oxygen. The enzymes involved in these initial
transformations are either monooxygenases or
dioxygenases.
Biodegradation of Aromatics:

38. Fig.1: Incorporation of oxygen into the aromatic ring by the dioxygenase enzyme,
followed by meta or ortho ring cleavage

39. Fig.2: Fungal monooxygenase incorporation of oxygen into the aromatic
ring

40. Fig.3: Anaerobic biodegradation of aromatic compounds by a consortium of anaerobic bacteria.
coo-
benzoate
Anaerobic biodegradation
CH3 COO- CH4 + CO2
Methanogenic bacteria
acetate

41. Methods of Bioremediation:
There are two broad classes of bioremediation-
1. In-situ bioremediation – Onsite treatment for
detoxification
2. Ex-situ bioremediation- Of site treatment toxic materials
3. Sometimes bioremediation takes place by natural ways &
means called Intrinsic bioremediation or natural
attenuation.

43. Summary of strategiesSummary of strategies

44. There are many instances where bioremediation technology received
better appreciation and viable technology. But there are numbers
environmental conditions that influence the bioremediation processes.
These include the oxygen availability and nutrient availability for
microbial actions in on site treatment areas. Thus bioventing (a
technique used to add oxygen directly to a contaminated site through
external aeration pipeline or air spraying through forceful injection at
contaminated site. The primary nutrient like sources of C, N, P needs
to be added in contaminated site for rapid microbial biodegradation
process as needed. Surfactant addition has been proposed as a
technique for increasing the bioavailability and hence biodegradation
of contaminants. The details of various bioremediation techniques are
given below:

45. Fig.4:
(a) In situ bioremediation in vadose
zone and groundwater,
(b) Bioventing and biofilteration in
vadose zone
(c) Bioremediation in the
groundwater by air sparging.

46. If appropriate biodegrading microorganisms are not
present in soil or if microbial populations have been
reduced because of contaminant toxicity, specific
microorganisms can be added as “introduced organisms”
to enhance the existing populations. This process is known
as bioaugmentation. Scientist is now capable of creating
‘super bugs’ organisms that can degrade pollutants at
extremely rapid rates. Such organisms can be developed
through successive adaptations under laboratory
condition or can be genetically engineered.

47. Table: Current Status of Bioremediation
(National Research Council, 1993)

48. Future Research Areas in BioremediationFuture Research Areas in Bioremediation
 More research needs to be done in order to completelyMore research needs to be done in order to completely
understand the complex microbial processes which makeunderstand the complex microbial processes which make
bioremediation possible, especially the bioremediation of metals.bioremediation possible, especially the bioremediation of metals.
 Researchers are trying to understand why some microorganismsResearchers are trying to understand why some microorganisms
are better at degrading one kind of chemical than another.are better at degrading one kind of chemical than another.
 The development of better in situ bioremediation strategies areThe development of better in situ bioremediation strategies are
also being studied. In situ treatments would be ideal since theyalso being studied. In situ treatments would be ideal since they
cost less and are less disturbing to the environment. Currently,cost less and are less disturbing to the environment. Currently,
in situ treatments are problematic because naturally existingin situ treatments are problematic because naturally existing
external conditions are too difficult to control (dense soil, coldexternal conditions are too difficult to control (dense soil, cold
conditions, etc.).conditions, etc.).
 Methods for better delivery of nutrients or microorganisms in situMethods for better delivery of nutrients or microorganisms in situ
and ex situ are being developed.and ex situ are being developed.

49. Advantages of bioremediationAdvantages of bioremediation
 Bioremediation is perceived by the public as an acceptable waste treatmentBioremediation is perceived by the public as an acceptable waste treatment
process. Microbes able to degrade the contaminant increase in numbers whenprocess. Microbes able to degrade the contaminant increase in numbers when
the contaminant is present; when the contaminant is degraded, thethe contaminant is present; when the contaminant is degraded, the
biodegradative population declines.biodegradative population declines.
 It is safe as the residues for the treatment are usually harmless products andIt is safe as the residues for the treatment are usually harmless products and
include carbon dioxide, water, and cell biomass.include carbon dioxide, water, and cell biomass.
 It is useful for the complete destruction of a wide variety of contaminants. ThisIt is useful for the complete destruction of a wide variety of contaminants. This
eliminates the chance of future liability associated with treatment and disposal ofeliminates the chance of future liability associated with treatment and disposal of
contaminated material.contaminated material.
 Instead of transferring contaminants from one environmental medium toInstead of transferring contaminants from one environmental medium to
another, for example, from land to water or air, the complete destruction ofanother, for example, from land to water or air, the complete destruction of
target pollutants is possible.target pollutants is possible.
 It can often be carried out on site, without disruption of normal activities, noIt can often be carried out on site, without disruption of normal activities, no
need to transport waste off site.need to transport waste off site.
 It does not require too much of sophisticated equipments.It does not require too much of sophisticated equipments.
 Bioremediation can prove less expensive than other technologies that are usedBioremediation can prove less expensive than other technologies that are used
for clean-up of hazardous waste.for clean-up of hazardous waste.

50. Disadvantages of bioremediationDisadvantages of bioremediation
 Bioremediation is limited to those compounds that areBioremediation is limited to those compounds that are
biodegradable. Not all compounds are susceptible to rapid andbiodegradable. Not all compounds are susceptible to rapid and
complete degradation.complete degradation.
 Biological processes are often highly specific. Important siteBiological processes are often highly specific. Important site
factors required for success include the presence of metabolicallyfactors required for success include the presence of metabolically
capable microbial populations, suitable environmental growthcapable microbial populations, suitable environmental growth
conditions, and appropriate levels of nutrients and contaminants.conditions, and appropriate levels of nutrients and contaminants.
 It is difficult to extrapolate from bench and pilot-scale studies toIt is difficult to extrapolate from bench and pilot-scale studies to
full-scale field operations.full-scale field operations.
 Research is needed to develop and engineer bioremediationResearch is needed to develop and engineer bioremediation
technologies for complex mixtures of contaminants that are nottechnologies for complex mixtures of contaminants that are not
evenly dispersed in the environment.evenly dispersed in the environment.
 Bioremediation often takes longer than other treatment options,Bioremediation often takes longer than other treatment options,
such as excavation and removal of soil or incineration.such as excavation and removal of soil or incineration.

51. The problems of on site bioremediation by microbes are often
failed for two major reasons.
First, the introduced microbe often cannot establish a niche
in the environment. In fact, these introduced organisms often do
not survive in a new environment beyond a few weeks.
Second, there are difficulties in delivering the introduced
organisms to the site of contamination, because microorganisms
like contaminants, can be strongly sorbed by solid surfaces. An
overall scenario in current status of Bioremediation is given in
below table.
Limitation of Bioremediation:

52. Bioremediation status in India
The country has, so far, identified 172 abandoned dump sites
located in various states which require remediation. So far,
bioremediation in India appears techno economically feasible
because of the prevailing tropical climate almost throughout
the year in most of the States and Union Territories.
Phytoremediation in India is being extensively used for
restoration of environmental quality. However, there exists
ample scope to modify the process through biostimulation and
bioaugmentation as well as through better understanding of
the behavior of microbial community. Also, the potential for
generation of carbon credit through phytoremediation
intervention as well as through solid waste composting
(instead of land filling) needs to be identified and applied
wherever possible.

53. THANK YOUTHANK YOU