BIOREMEDIATION

Prof. S. C. Santra

Department of Environmental Science

University of Kalyani

Definition as per EPADefinition as per EPA

Bioremediation is defined as the process Bioremediation is defined as the process whereby organic wastes are biologically whereby organic wastes are biologically degraded under controlled conditions to an degraded under controlled conditions to an innocuous state, or to levels below innocuous state, or to levels below concentration limits established by regulatory concentration limits established by regulatory authorities. authorities.

It uses naturally occurring microorganisms like It uses naturally occurring microorganisms like bacteria and fungi or plants to degrade or bacteria and fungi or plants to degrade or detoxify substances hazardous to human detoxify substances hazardous to human health and/or the environment.health and/or the environment.

- Concept

Bioremediation – Concept (Contd..)Bioremediation – Concept (Contd..)

Recent studies in molecular biology and ecology offer Recent studies in molecular biology and ecology offer opportunities for more efficient biological processes to opportunities 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.

SchematicSchematic

Bioremediation is an option that offers the possibility to destroy or render harmless various contaminants

using natural biological activity.

BacteriaFungi

Fungi

Actinomycetes Actinomycetes Actinomycetes

Bioremediation - Basic facts Bioremediation - Basic facts The microorganisms may be indigenous to a contaminated area The microorganisms may be indigenous to a contaminated area

or they may be isolated from elsewhere and brought to the or they may be isolated from elsewhere and brought to the contaminated sitecontaminated site

Contaminant compounds are transformed by living organisms Contaminant compounds are transformed by living organisms through reactions that take place as a part of their metabolic through reactions that take place as a part of their metabolic processes.processes.

Biodegradation of a compound is often a result of the actions of Biodegradation 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 environmental Bioremediation can be effective only where environmental

conditions permit microbial growth and activityconditions permit microbial growth and activity

Manipulation of environmental parameters needed for microbial Manipulation of environmental parameters needed for microbial growth and degradation to proceed at a faster rate.growth and degradation to proceed at a faster rate.

FACTORS OF BIOREMEDIATIONFACTORS OF BIOREMEDIATION

The control and optimization of bioremediation The 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 population existence of a microbial population

availability of contaminants to the microbial availability of contaminants to the microbial populationpopulation

the environment factors (type of soil, the environment factors (type of soil, temperature, pH, the presence of oxygen or temperature, pH, the presence of oxygen or other electron acceptors, and nutrients).other electron acceptors, and nutrients).

MICROBIAL POPULATIONSMICROBIAL POPULATIONS

Microorganisms can be isolated from almost any Microorganisms can be isolated from almost any environmental conditions. Microbes will adapt and environmental conditions. Microbes will adapt and grow at subzero temperatures, as well as extreme grow at subzero temperatures, as well as extreme heat, desert conditions, in water, with an excess of heat, desert conditions, in water, with an excess of oxygen, and in anaerobic conditions, with the oxygen, and in anaerobic conditions, with the presence of hazardous compounds or on any waste presence of hazardous compounds or on any waste stream.stream.

The main requirements are an energy source and a The main requirements are an energy source and a

carbon source. Because of the adaptability of carbon source. Because of the adaptability of microbes and other biological systems, these can be microbes and other biological systems, these can be used to degrade or remediate environmental used to degrade or remediate environmental hazards. hazards.

Types of microorganismsTypes of microorganisms Aerobic. Grows in presence of oxygen, degrade Aerobic. Grows in presence of oxygen, degrade

pesticides and hydrocarbons, both alkanes and pesticides and hydrocarbons, both alkanes and polyaromatic compounds. Many of these bacteria use the polyaromatic 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 as Anaerobic. Grows in absence of oxygen. are not as frequently as aerobic, degrade polychlorinated biphenyls frequently 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 utilizing Methylotrophs. Aerobic bacteria that grow utilizing methane for carbon and energy. The initial enzyme in the methane for carbon and energy. The initial enzyme in the pathway for aerobic degradation, methane pathway for aerobic degradation, methane monooxygenase, has a broad substrate range and is monooxygenase, has a broad substrate range and is active against a wide range of compounds, including the active against a wide range of compounds, including the chlorinated aliphatics trichloroethylene and 1,2-chlorinated aliphatics trichloroethylene and 1,2-dichloroethane.dichloroethane.

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 for they cannot necessarily be there in the numbers required for bioremediation of the site. Their growth and activity must be bioremediation of the site. Their growth and activity must be stimulated.stimulated.

Biostimulation usually involves the addition of nutrients and Biostimulation 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 allow These nutrients are the basic building blocks of life and allow microbes to create the necessary enzymes to break down the microbes to create the necessary enzymes to break down the contaminants. All of them will need nitrogen, phosphorous, and contaminants. All of them will need nitrogen, phosphorous, and carbon.carbon.

Carbon is the most basic element of living forms and is needed Carbon is the most basic element of living forms and is needed in greater quantities than other elements. In addition to in greater quantities than other elements. In addition to hydrogen, oxygen, and nitrogen it constitutes about 95% of the hydrogen, 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.

For degradation it is necessary that bacteria For degradation it is necessary that bacteria and the contaminants be in contact. This is not and the contaminants be in contact. This is not easily achieved, as neither the microbes nor easily achieved, as neither the microbes nor contaminants are uniformly spread in the soil. contaminants are uniformly spread in the soil.

Some bacteria are mobile and exhibit a Some bacteria are mobile and exhibit a chemotactic response, sensing the chemotactic response, sensing the contaminant and moving toward it.contaminant and moving toward it.

Other microbes such as fungi grow in a Other microbes such as fungi grow in a filamentous form toward the contaminant. filamentous form toward the contaminant.

It is possible to enhance the mobilization of It is possible to enhance the mobilization of the contaminant utilizing some surfactants the contaminant utilizing some surfactants such as sodium dodecyl sulphatesuch as sodium dodecyl sulphate

Biostimulation (Contd..)Biostimulation (Contd..)

The Science – How Does it Work?The Science – How Does it Work?

Microbial MetabolismMicrobial Metabolism refers to all the chemical reactions that refers to all the chemical reactions that happen in a cell or organism. All living processes are based on a happen in a cell or organism. All living processes are based on a complex series of chemical reactions. complex series of chemical reactions.

Anabolism – Building Anabolism – Building complex molecular structures simpler mol.complex molecular structures simpler mol. In anabolism, chemicals taken up by the microorganism are used to In anabolism, chemicals taken up by the microorganism are used to

build various cell parts. Carbon and nitrogen are the basic chemicals build various cell parts. Carbon and nitrogen are the basic chemicals in the proteins, sugars and nucleic acids that make up microbial in the proteins, sugars and nucleic acids that make up microbial cells. Microorganisms take up carbon and nitrogen from the soil, cells. Microorganisms take up carbon and nitrogen from the soil, water, and air around them. In order to take up nutrients and make water, and air around them. In order to take up nutrients and make them into cell parts, a microorganism needs energy. This is where them into cell parts, a microorganism needs energy. This is where catabolism comes in. catabolism comes in.

Catabolism – Breaking Catabolism – Breaking complex molecules into simpler mol.complex molecules into simpler mol. Catabolism allows microorganisms to gain energy from the Catabolism allows microorganisms to gain energy from the

chemicals available in the environment. Although most chemicals available in the environment. Although most microorganisms are exposed to light and to chemical energy microorganisms are exposed to light and to chemical energy sources, most rely on chemicals for their energy. When chemicals sources, most rely on chemicals for their energy. When chemicals break down, energy is released. Microorganisms use this energy to break down, energy is released. Microorganisms use this energy to carry out cellular functions, such as those involved in anabolism. carry out cellular functions, such as those involved in anabolism.

Mid

Research

Super bugSuper bug

Pseudomonas putida. Dr. Ananda Mohan ChakrabortyDr. Ananda Mohan Chakraborty

Natural AttenuationNatural Attenuation Aerobic/Anaerobic Aerobic/Anaerobic

biodegradationbiodegradation BiopilesBiopiles Land TreatmentLand Treatment BioscrubbersBioscrubbers Methanotrophic Process (in Situ)Methanotrophic Process (in Situ) Plant Root Uptake Plant Root Uptake

(Phytoremediation)(Phytoremediation) Solid Phase BioremediationSolid Phase Bioremediation Bio Wall for Plume Bio 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 for Bioventing (Chapter 7: BMPs for

Vapor (Extraction)Vapor (Extraction) Bioremediation of Metals Bioremediation 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

Key Features of BioremediationKey Features of Bioremediation Most bioremediation treatment technologies destroy the contaminants Most bioremediation treatment technologies destroy the contaminants

in the soil matrix.in the soil matrix. These treatment technologies are generally designed to reduce toxicity These treatment technologies are generally designed to reduce toxicity

either by destruction or by transforming toxic organic compounds into either by destruction or by transforming toxic organic compounds into less toxic compounds.less toxic compounds.

Indigenous micro-organisms, including bacteria and fungi, are most Indigenous micro-organisms, including bacteria and fungi, are most commonly used. In some cases, wastes may be inoculated with specific commonly 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 the Plants may also be used to enhance biodegradation and stabilize the soil.soil.

The addition of nutrients or electron acceptors (such as hydrogen The addition of nutrients or electron acceptors (such as hydrogen peroxide or ozone) to enhance growth and reproduction of indigenous peroxide 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

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.

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.

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.

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

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.

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

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.

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

Composition of a microbial cell (%).

Carbon 50 Sodium 1Nitrogen 14 Calcium 0.5Oxygen 20 Magnesium 0.5Hydrogen 8 Chloride 0.5Phosphorous 3 Iron 0.2Sulfur 1 All others 0.3Potassium 1

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

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

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

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.

 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:

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

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

Fig.3: Anaerobic biodegradation of aromatic compounds by a consortium of anaerobic bacteria.

coo-

benzoate

Anaerobic biodegradationCH3 COO- CH4 + CO2

Methanogenic bacteria

acetate

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.

Summary of strategiesSummary of strategies

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:

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.

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.

Table: Current Status of Bioremediation

(National Research Council, 1993)

Future Research Areas in BioremediationFuture Research Areas in Bioremediation More research needs to be done in order to completely More research needs to be done in order to completely

understand the complex microbial processes which make understand 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 microorganisms Researchers 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 are The development of better in situ bioremediation strategies are also being studied. In situ treatments would be ideal since they also being studied. In situ treatments would be ideal since they cost less and are less disturbing to the environment. Currently, in cost less and are less disturbing to the environment. Currently, in situ treatments are problematic because naturally existing situ treatments are problematic because naturally existing external conditions are too difficult to control (dense soil, cold external conditions are too difficult to control (dense soil, cold conditions, etc.). conditions, etc.).

Methods for better delivery of nutrients or microorganisms in situ Methods for better delivery of nutrients or microorganisms in situ and ex situ are being developed. and ex situ are being developed.

Advantages of bioremediationAdvantages of bioremediation Bioremediation is perceived by the public as an acceptable waste treatment process. Microbes able to degrade Bioremediation is perceived by the public as an acceptable waste treatment process. Microbes able to degrade

the contaminant increase in numbers when the contaminant is present; when the contaminant is degraded, the the contaminant increase in numbers when the 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 and include carbon dioxide, water, and It is safe as the residues for the treatment are usually harmless products and include carbon dioxide, water, and cell biomass.cell biomass.

It is useful for the complete destruction of a wide variety of contaminants. This eliminates the chance of future It is useful for the complete destruction of a wide variety of contaminants. This eliminates the chance of future liability associated with treatment and disposal of contaminated material.liability associated with treatment and disposal of contaminated material.

Instead of transferring contaminants from one environmental medium to another, for example, from land to Instead of transferring contaminants from one environmental medium to another, for example, from land to water or air, the complete destruction of target pollutants is possible.water or air, the complete destruction of target pollutants is possible.

It can often be carried out on site, without disruption of normal activities, no need to transport waste off site. It can often be carried out on site, without disruption of normal activities, no 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 used for clean-up of hazardous waste.Bioremediation can prove less expensive than other technologies that are used for clean-up of hazardous waste.

Disadvantages of bioremediationDisadvantages of bioremediation

Bioremediation is limited to those compounds that are Bioremediation is limited to those compounds that are biodegradable. Not all compounds are susceptible to rapid and biodegradable. Not all compounds are susceptible to rapid and complete degradation.complete degradation.

Biological processes are often highly specific. Important site Biological processes are often highly specific. Important site factors required for success include the presence of metabolically factors required for success include the presence of metabolically capable microbial populations, suitable environmental growth capable 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 to It 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 bioremediation Research is needed to develop and engineer bioremediation technologies for complex mixtures of contaminants that are not technologies 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.

 

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:

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.

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