under HSBC Climate Partnership

Green ChemistrySeries

Module I 1 : Bioremediation

and Phytoremediation

Organised by

WWF-India's

Des

ign

ed b

y: M

r. A

shis

h R

ohil

la

1.0 Introduction

2.0 How does bioremediation work?

3.0

4.0 When and where should one apply bioremediation technology?

5.0 Phytoremediation

01

05

09

12

16

1.1 Bioremediation - definition and historical account

1.2 Bioremediation - an introduction

2.1 Introduction

2.2 Types of bioremediation

2.3 Advantages and disadvantages of bioremediation

3.1 Bioremediation in nature

3.2 Essential factors for bioremediation

3.3 How much time does bioremediation take?

3.4 The process

4.1 When can one use bioremediation?

4.2 Bioremediation in municipal wastewaters

4.3 Bioremediation in industrial CETPs and tanneries

4.4 Bioremediation products

5.1 What is phytoremediation?

5.2 Where did phytoremediation originate?

5.3 Applications of phytoremediation

5.4 Mechanisms for phytoremediation

5.5 Determining which plant to use

5.7 Applicability

CONTENTS

Green Chemistry SeriesModule II: Phytoremediation

Bioremediation and

Written and compiled by:

Dr. Anjana Pant,

Dr. Alka Tangri

Dr. Subhash Awasthi

Conceptualized by:

Ms. Arundhati Das

Dr. Anjana Pant

Edited by:

Mr. Anshuman Atroley

Published June, 2011

This manual has been prepared by WWF-India

with technical support from PII & EM and BIPCC

Process of bioremediation

1.0 Introduction

2.0 How does bioremediation work?

3.0

4.0 When and where should one apply bioremediation technology?

5.0 Phytoremediation

01

05

09

12

16

1.1 Bioremediation - definition and historical account

1.2 Bioremediation - an introduction

2.1 Introduction

2.2 Types of bioremediation

2.3 Advantages and disadvantages of bioremediation

3.1 Bioremediation in nature

3.2 Essential factors for bioremediation

3.3 How much time does bioremediation take?

3.4 The process

4.1 When can one use bioremediation?

4.2 Bioremediation in municipal wastewaters

4.3 Bioremediation in industrial CETPs and tanneries

4.4 Bioremediation products

5.1 What is phytoremediation?

5.2 Where did phytoremediation originate?

5.3 Applications of phytoremediation

5.4 Mechanisms for phytoremediation

5.5 Determining which plant to use

5.7 Applicability

CONTENTS

Green Chemistry SeriesModule II: Phytoremediation

Bioremediation and

Written and compiled by:

Dr. Anjana Pant,

Dr. Alka Tangri

Dr. Subhash Awasthi

Conceptualized by:

Ms. Arundhati Das

Dr. Anjana Pant

Edited by:

Mr. Anshuman Atroley

Published June, 2011

This manual has been prepared by WWF-India

with technical support from PII & EM and BIPCC

Process of bioremediation

Table 1.1 Compounds degraded by anaerobic conditions (Alexander 219)

Table 2.1 Relationship of available oxygen to bacteria numbers (Flathman 313)

Table 5.1 Partial listing of plants and chemicals they can remediate.

Table 5.2 Partial listing of current remediation possibilities

Table 6.1 Growth parameters of Azadirachta indica as influenced by Cr(VI) in nutrient medium after

120h of treatment.

Table 6.2 Accumulation of Cr* in A. indica treated with tannery sludge in pot experiment.

Table 6.3 Accumulation of Cr (VI) in different parts of A. indica in field experiment.

Fig. 1.1 Bioremediation triangle (adapted from King 20)

Fig. 4.2 Sewage carrying drains polluting the Ganges

(a) Sisamau, Kanpur; (b) Assi, Varanasi

Fig. 5.1 Phytoremediation process

Fig. 6.1 Phytoremediation site: Some of the Plants are still preserved

Fig. 6.2

and phytoremediation technology to treat chrome bearing biological and primary sludge

recovered from tannery effluent in CETP process. Picture as on April 2011.

Fig. 6.3 A. indica grown at various concentrations of chromium (VI).

Fig. 6.4 Accumulation of chromium (VI) in different parts of A. indica.

Fig. 6.5 Growth of A. indica plants in tannery sludge amended soil

Annexure 1. Phyto-remedial-technology technical and regulatory guidance and decision trees, revised

List of Figures

List of Annexures

A Pictorial view of CETP Unnao showing tree plantation under integrated bioremediation

List of Tables

6.0 Case Studies

References

Annexure I.

24

31

6.1 Case Study 1. Phytoremediation in CETP Banthar

6.2 Case Study 2. A Tamil Nadu experience

Phyto-remedial-technology technical and regulatory 33

guidance and decision trees, revised

Table 1.1 Compounds degraded by anaerobic conditions (Alexander 219)

Table 2.1 Relationship of available oxygen to bacteria numbers (Flathman 313)

Table 5.1 Partial listing of plants and chemicals they can remediate.

Table 5.2 Partial listing of current remediation possibilities

Table 6.1 Growth parameters of Azadirachta indica as influenced by Cr(VI) in nutrient medium after

120h of treatment.

Table 6.2 Accumulation of Cr* in A. indica treated with tannery sludge in pot experiment.

Table 6.3 Accumulation of Cr (VI) in different parts of A. indica in field experiment.

Fig. 1.1 Bioremediation triangle (adapted from King 20)

Fig. 4.2 Sewage carrying drains polluting the Ganges

(a) Sisamau, Kanpur; (b) Assi, Varanasi

Fig. 5.1 Phytoremediation process

Fig. 6.1 Phytoremediation site: Some of the Plants are still preserved

Fig. 6.2

and phytoremediation technology to treat chrome bearing biological and primary sludge

recovered from tannery effluent in CETP process. Picture as on April 2011.

Fig. 6.3 A. indica grown at various concentrations of chromium (VI).

Fig. 6.4 Accumulation of chromium (VI) in different parts of A. indica.

Fig. 6.5 Growth of A. indica plants in tannery sludge amended soil

Annexure 1. Phyto-remedial-technology technical and regulatory guidance and decision trees, revised

List of Figures

List of Annexures

A Pictorial view of CETP Unnao showing tree plantation under integrated bioremediation

List of Tables

6.0 Case Studies

References

Annexure I.

25

33

6.1 Case Study 1. Phytoremediation in CETP Banthar

6.2 Case Study 2. A Tamil Nadu experience

Phyto-remedial-technology technical and regulatory 35

guidance and decision trees, revised

Bioremediation: the use of biological organisms to clean up contaminated soil and water

Contaminants: anything that creates an unclean environment

Contaminant transport: waste movement from the generated site to a new site

In situ: within the site

Ex situ: External to the site

Leachate: a solution formed by the leaching of contaminants through soil layers.

Leaching: the dissolving, by a liquid solvent, of soluble material from its mixture with an insoluble solid;

leaching is an industrial separation operation based on mass transfer

Migration: movement of the contaminant from one location within the ground to another location.

Migration can occur within the soil and /or groundwater.

Phytoremediation: the use of plants and trees to clean up contaminated soil and water

Rhizosphere: area surrounding the root system

Transpiration: loss of water from a plant by evaporation

Translocation: a change in location (of pollutant)

Uptake: absorption of a contaminant into the surface of a medium (medium can be soil, plants, etc.)

Vadose zone: region of aeration above the water table. This zone also includes the capillary fringe above the

water table, the height of which varies by the grain size of the sediments from being absent to many hundreds of

feet, depending upon several factors.

Glossary of Technical Terms List of Abbreviations

BTEX: Benzene, Toluene, Ethylbenzene, and Xylenes (Volatile Organic Compounds or

VOC's in petroleum derivatives

BOD: Biological Oxygen Demand

CETP: Common Effluent Treatment Plant

COD: Chemical Oxygen Demand

GAC: Granulated Activated Carbon

ITRC: Interstate Technology and Regulatory Council

NBRI: National Botanical Research Institute

OM&M: Operational, Maintenance & Monitoring

PCB: Polychlorinated biphenyl

RO: Reverse Osmosis

SVOCs: Semi-Volatile Organic Compounds

TDS: Total Dissolved Solids

VOCs: Volatile Organic Compounds

Bioremediation: the use of biological organisms to clean up contaminated soil and water

Contaminants: anything that creates an unclean environment

Contaminant transport: waste movement from the generated site to a new site

In situ: within the site

Ex situ: External to the site

Leachate: a solution formed by the leaching of contaminants through soil layers.

Leaching: the dissolving, by a liquid solvent, of soluble material from its mixture with an insoluble solid;

leaching is an industrial separation operation based on mass transfer

Migration: movement of the contaminant from one location within the ground to another location.

Migration can occur within the soil and /or groundwater.

Phytoremediation: the use of plants and trees to clean up contaminated soil and water

Rhizosphere: area surrounding the root system

Transpiration: loss of water from a plant by evaporation

Translocation: a change in location (of pollutant)

Uptake: absorption of a contaminant into the surface of a medium (medium can be soil, plants, etc.)

Vadose zone: region of aeration above the water table. This zone also includes the capillary fringe above the

water table, the height of which varies by the grain size of the sediments from being absent to many hundreds of

feet, depending upon several factors.

Glossary of Technical Terms List of Abbreviations

BTEX: Benzene, Toluene, Ethylbenzene, and Xylenes (Volatile Organic Compounds or

VOC's in petroleum derivatives

BOD: Biological Oxygen Demand

CETP: Common Effluent Treatment Plant

COD: Chemical Oxygen Demand

GAC: Granulated Activated Carbon

ITRC: Interstate Technology and Regulatory Council

NBRI: National Botanical Research Institute

OM&M: Operational, Maintenance & Monitoring

PCB: Polychlorinated biphenyl

RO: Reverse Osmosis

SVOCs: Semi-Volatile Organic Compounds

TDS: Total Dissolved Solids

VOCs: Volatile Organic Compounds

1.1 Bioremediation – Definition and Historical Account

The term 'Bioremediation' has been used to describe the process of using microorganisms to degrade or remove

hazardous components of the wastes from the environment (Glazer and Nikaido 1995). Bioremediation has

been described as “a treatability technology that uses biological activity to reduce the concentration or toxicity

of a pollutant. It commonly uses processes by which microorganisms naturally transform or degrade chemicals

in the environment”.

This use of microorganisms (most often bacteria) to destroy or transform hazardous contaminants is not new.

Microorganisms have been used since 600 B.C. by the Romans and others to treat their wastewater. Although

the same technology is still used today to treat wastewater it has been expanded to treat an array of other

contaminants. In fact, bioremediation has been used commercially for around 30 years. The first commercial

use of a bioremediation system was in 1972 to clean up a Sun Oil pipeline spill in Ambler, Pennsylvania

(National Research Council 1993). Since 1972, bioremediation has become a well-developed way of cleaning

up different contaminants. A survey prepared by the Environmental Protection Agency in 1992 received

information on 240 cases of bioremediation in the United States (Alexander 1994). Most of these cases involved

treating contaminated soil or groundwater.

1.2 Bioremediation – an Introduction

Bioremediation is defined as the use of living organisms, primarily microorganism to degrade the

environmental contaminant into less toxic form. It uses naturally occurring bacteria and fungi or plants to

degrade or detoxify substances hazardous to human health or environment. The microorganism may be

indigenous to a contaminated area or may be isolated from elsewhere and brought to a contaminant site.

Contaminant compounds are transformed by living organism through reactions that take place as a part of their

metabolic processes (Vidali, 2011). Biodegradation of a compound is often a result of action of multiple

organisms. When microorganisms are added to a contaminated site to enhance degradation then the process is

called bioaugmentation (described in detail under types of bioremediation).

For bioremediation to be effective, microorganisms must enzymatically attack pollutants and convert them to

harmless products. As bioremediation can be effective only where environment conditions permit microbial

growth and activity, its application may involve manipulation of environmental parameters to allow microbial

growth and degradation to proceed at a faster rate.

The key indicators showing bioremediation in progress:

(a) Biological Oxygen Demand (BOD): Biological Oxygen Demand (BOD) is the amount of oxygen

required by microorganisms to completely degrade the organic matter to carbon dioxide and water. The

rise in BOD leads to a fall of Dissolved Oxygen (DO) levels and hence the wastewater becomes septic.

1 2

1.0 Introduction

1

A high BOD indicates the presence of a large number of microorganisms, which suggests a high

level of pollution.

(b) Chemical Oxygen Demand (COD): Chemical Oxygen Demand (COD) is the amount of

oxygen required by microorganisms to completely degrade the chemical matter. It is expressed

in milligrams per liter (mg/L), which indicates the mass of oxygen consumed per liter of

solution.

(c) Dissolved Oxygen (DO): The dissolved oxygen (DO) is oxygen that is dissolved in water. The

oxygen dissolves by diffusion from the surrounding air; aeration of water that has tumbled over

falls and rapids; and as a waste product of photosynthesis. A simplified formula for

Photosynthesis (in the presence of light and chlorophyll) is given below:

Carbon dioxide + Water-------------->Oxygen + Carbon-rich foods

Co H O O C H O2 2 2 6 12 6

Fish and aquatic animals cannot split oxygen from water (H2O) or other oxygen-containing

compounds. Only green plants and some bacteria can do that through photosynthesis and

similar processes. Virtually all the oxygen we breath is manufactured by green plants.

(d) Total Suspended Solids (TSS): TSS includes solid materials, including organic and inorganic,

that are suspended in the water. These would include silt, plankton and industrial wastes. High

concentrations of suspended solids can lower water quality by absorbing light. Waters then

become warmer and lessen the ability of the water to hold oxygen necessary for aquatic life.

(e) Sulphides: The presence of sulphide (as hydrogen sulphide) in water results in disagreeable

taste and odour; an aesthetic objective of ≤ 0.05 mg/L (≤ 50 µg/L) (expressed as hydrogen

sulphide) has therefore been established. Sulphides are also generated by sulphate-reducing

bacteria through anaerobic decomposition of sewage, algae, naturally deposited organic matter

and the sulphur found in fungicides, pesticides and fertilizers. Sulphides are also present in

industrial wastes from petroleum and petrochemical plants, gas works, paper mills, heavy

water plants and tanneries.

(f) Coliforms: Coliform bacteria include a wide range of aerobic and facultative anaerobic, gram-

negative, non-spore-forming bacilli. Escherichia coli and thermo-tolerant coliforms are a

subset of the total coliform group that can ferment lactose at higher temperatures. Traditionally,

coliform bacteria were regarded as belonging to the genera Escherichia, Citrobacter, Klebsiella

and Enterobacter, but the group is more heterogeneous and includes a wider range of genera.

The total coliform group includes both faecal and other species. Untreated or partially treated

sewage inherently contains coliforms with a predominance of faecal coliforms and organic

matter provides nutrients to enhance their growth. This increases the septicity of the water.

1.1 Bioremediation – Definition and Historical Account

The term 'Bioremediation' has been used to describe the process of using microorganisms to degrade or remove

hazardous components of the wastes from the environment (Glazer and Nikaido 1995). Bioremediation has

been described as “a treatability technology that uses biological activity to reduce the concentration or toxicity

of a pollutant. It commonly uses processes by which microorganisms naturally transform or degrade chemicals

in the environment”.

This use of microorganisms (most often bacteria) to destroy or transform hazardous contaminants is not new.

Microorganisms have been used since 600 B.C. by the Romans and others to treat their wastewater. Although

the same technology is still used today to treat wastewater it has been expanded to treat an array of other

contaminants. In fact, bioremediation has been used commercially for around 30 years. The first commercial

use of a bioremediation system was in 1972 to clean up a Sun Oil pipeline spill in Ambler, Pennsylvania

(National Research Council 1993). Since 1972, bioremediation has become a well-developed way of cleaning

up different contaminants. A survey prepared by the Environmental Protection Agency in 1992 received

information on 240 cases of bioremediation in the United States (Alexander 1994). Most of these cases involved

treating contaminated soil or groundwater.

1.2 Bioremediation – an Introduction

Bioremediation is defined as the use of living organisms, primarily microorganism to degrade the

environmental contaminant into less toxic form. It uses naturally occurring bacteria and fungi or plants to

degrade or detoxify substances hazardous to human health or environment. The microorganism may be

indigenous to a contaminated area or may be isolated from elsewhere and brought to a contaminant site.

Contaminant compounds are transformed by living organism through reactions that take place as a part of their

metabolic processes (Vidali, 2011). Biodegradation of a compound is often a result of action of multiple

organisms. When microorganisms are added to a contaminated site to enhance degradation then the process is

called bioaugmentation (described in detail under types of bioremediation).

For bioremediation to be effective, microorganisms must enzymatically attack pollutants and convert them to

harmless products. As bioremediation can be effective only where environment conditions permit microbial

growth and activity, its application may involve manipulation of environmental parameters to allow microbial

growth and degradation to proceed at a faster rate.

The key indicators showing bioremediation in progress:

(a) Biological Oxygen Demand (BOD): Biological Oxygen Demand (BOD) is the amount of oxygen

required by microorganisms to completely degrade the organic matter to carbon dioxide and water. The

rise in BOD leads to a fall of Dissolved Oxygen (DO) levels and hence the wastewater becomes septic.

1 2

1.0 Introduction

1

A high BOD indicates the presence of a large number of microorganisms, which suggests a high

level of pollution.

(b) Chemical Oxygen Demand (COD): Chemical Oxygen Demand (COD) is the amount of

oxygen required by microorganisms to completely degrade the chemical matter. It is expressed

in milligrams per liter (mg/L), which indicates the mass of oxygen consumed per liter of

solution.

(c) Dissolved Oxygen (DO): The dissolved oxygen (DO) is oxygen that is dissolved in water. The

oxygen dissolves by diffusion from the surrounding air; aeration of water that has tumbled over

falls and rapids; and as a waste product of photosynthesis. A simplified formula for

Photosynthesis (in the presence of light and chlorophyll) is given below:

Carbon dioxide + Water-------------->Oxygen + Carbon-rich foods

Co H O O C H O2 2 2 6 12 6

Fish and aquatic animals cannot split oxygen from water (H2O) or other oxygen-containing

compounds. Only green plants and some bacteria can do that through photosynthesis and

similar processes. Virtually all the oxygen we breath is manufactured by green plants.

(d) Total Suspended Solids (TSS): TSS includes solid materials, including organic and inorganic,

that are suspended in the water. These would include silt, plankton and industrial wastes. High

concentrations of suspended solids can lower water quality by absorbing light. Waters then

become warmer and lessen the ability of the water to hold oxygen necessary for aquatic life.

(e) Sulphides: The presence of sulphide (as hydrogen sulphide) in water results in disagreeable

taste and odour; an aesthetic objective of ≤ 0.05 mg/L (≤ 50 µg/L) (expressed as hydrogen

sulphide) has therefore been established. Sulphides are also generated by sulphate-reducing

bacteria through anaerobic decomposition of sewage, algae, naturally deposited organic matter

and the sulphur found in fungicides, pesticides and fertilizers. Sulphides are also present in

industrial wastes from petroleum and petrochemical plants, gas works, paper mills, heavy

water plants and tanneries.

(f) Coliforms: Coliform bacteria include a wide range of aerobic and facultative anaerobic, gram-

negative, non-spore-forming bacilli. Escherichia coli and thermo-tolerant coliforms are a

subset of the total coliform group that can ferment lactose at higher temperatures. Traditionally,

coliform bacteria were regarded as belonging to the genera Escherichia, Citrobacter, Klebsiella

and Enterobacter, but the group is more heterogeneous and includes a wider range of genera.

The total coliform group includes both faecal and other species. Untreated or partially treated

sewage inherently contains coliforms with a predominance of faecal coliforms and organic

matter provides nutrients to enhance their growth. This increases the septicity of the water.

3 4

Waste water consists of organic matter which is the single largest component responsible for air, water and soil

pollution.

There are three essential components needed for bioremediation. These three components are microorganisms,

food, and nutrients. These three main components shown in Figure 1.1 are known as the bioremediation

triangle.

Microorganisms are found almost everywhere on earth with the exception of active volcanoes. So a lack of food

and nutrients are usually the missing ingredients that prevent successful bioremediation. Microorganisms find

the food they eat in the soil or water where they live. However, a contaminant can become an additional food

source for the microorganisms. The contaminant serves two useful purposes for the microbes:

(a) provides a source of carbon needed for growth, and

(b) the microbes obtain energy by breaking chemical bonds and transferring electrons away from the

contaminant.

This is known as an oxidation-reduction reaction. The contaminant that loses electrons is oxidized and the

chemical that gains the electrons (electron acceptor) is reduced. The energy gained from the electron transfer is

used along with the carbon and some electrons to produce more cells. Microbes generally use oxygen as an

electron acceptor but nitrate, sulphate, iron, and CO are also commonly used. The use of oxygen as an electron 2

acceptor is called aerobic respiration. The major byproducts of aerobic respiration are carbon dioxide, water,

and an increase in the microbe population.

Anaerobic respiration uses nitrate, sulphate, iron, or CO as the electron acceptors instead of oxygen. Anaerobic 2

respiration can occur after the oxygen has been depleted by aerobic respiration or where there is not sufficient

1

oxygen in the first place. The process of anaerobic degradation has been ignored for many years.

However, recently it has been gaining more attention. Table 1.1 shows several contaminants that can be

degraded using this anaerobic respiration process.

Food

NutrientsNitrogen, Phosphorus,

electron acceptorsMicrobes

Organisms

Figure 1.1: Bioremediation Triangle (adapted from King 20)

Carbon Tetrachloride Tetrachloroethylene

Chloroform Phenols

Vinyl Chloride Benzoates

DDD Toluene

DDT Ethylbenzene

TCE Xylene

Tetrachlorethane PCBs

Table 1.1: Compounds Degraded by Anaerobic Processes (Alexander 1994)

3 4

Waste water consists of organic matter which is the single largest component responsible for air, water and soil

pollution.

There are three essential components needed for bioremediation. These three components are microorganisms,

food, and nutrients. These three main components shown in Figure 1.1 are known as the bioremediation

triangle.

Microorganisms are found almost everywhere on earth with the exception of active volcanoes. So a lack of food

and nutrients are usually the missing ingredients that prevent successful bioremediation. Microorganisms find

the food they eat in the soil or water where they live. However, a contaminant can become an additional food

source for the microorganisms. The contaminant serves two useful purposes for the microbes:

(a) provides a source of carbon needed for growth, and

(b) the microbes obtain energy by breaking chemical bonds and transferring electrons away from the

contaminant.

This is known as an oxidation-reduction reaction. The contaminant that loses electrons is oxidized and the

chemical that gains the electrons (electron acceptor) is reduced. The energy gained from the electron transfer is

used along with the carbon and some electrons to produce more cells. Microbes generally use oxygen as an

electron acceptor but nitrate, sulphate, iron, and CO are also commonly used. The use of oxygen as an electron 2

acceptor is called aerobic respiration. The major byproducts of aerobic respiration are carbon dioxide, water,

and an increase in the microbe population.

Anaerobic respiration uses nitrate, sulphate, iron, or CO as the electron acceptors instead of oxygen. Anaerobic 2

respiration can occur after the oxygen has been depleted by aerobic respiration or where there is not sufficient

1

oxygen in the first place. The process of anaerobic degradation has been ignored for many years.

However, recently it has been gaining more attention. Table 1.1 shows several contaminants that can be

degraded using this anaerobic respiration process.

Food

NutrientsNitrogen, Phosphorus,

electron acceptorsMicrobes

Organisms

Figure 1.1: Bioremediation Triangle (adapted from King 20)

Carbon Tetrachloride Tetrachloroethylene

Chloroform Phenols

Vinyl Chloride Benzoates

DDD Toluene

DDT Ethylbenzene

TCE Xylene

Tetrachlorethane PCBs

Table 1.1: Compounds Degraded by Anaerobic Processes (Alexander 1994)

5 6 2

2.0 How does Bioremediation work?

2.1 Introduction

There are also several nutrients that must be accessible to the microorganisms for bioremediation to be

successful. These include moisture, nitrogen, phosphorus, and other trace elements. Microorganisms like other

organisms need moisture to survive and grow. In addition, microbes depend on the moisture to transport food to

them since they do not have mouths. The optimal moisture content for microbes in the vadose zone has been

determined to be between 10 and 25% (King, 1998). Besides moisture, nitrogen (ammonia) and phosphorus

(orthophosphate) are two major nutrients needed for the microorganisms. The microorganisms also require

minor elements such as sulphur, potassium, magnesium, calcium, manganese, iron, cobalt, copper, nickel, and

zinc (King, 1998). However, these minor elements are usually available in the environment in sufficient

amounts where nitrogen and phosphorus may be lacking and need to be added.

There are many contaminants susceptible to bioremediation. Petroleum hydrocarbons, in particular, benzene,

toluene, ethylbenzene, and xylene (BTEX), the major components of gasoline, have been biodegraded using

this technology. In addition, alcohols, ketones, and esters are well established as being biodegradable by

microorganisms. Many other contaminants are emerging as treatable using bioremediation such as halogenated

aliphatics, halogenated aromatics, polychlorinated biphenyls, and nitroaromatics (National Research Council

1993).

2.2 Types of Bioremediation

Bioremediation can be broken into two main types:

a) Intrinsic and

b) Engineered.

a) Intrinsic bioremediation: Intrinsic bioremediation is also known as natural attenuation or passive

bioremediation. Intrinsic bioremediation is preferred to engineered bioremediation primarily because the

cost is much lower. Intrinsic bioremediation consists of allowing the natural occurring microorganisms to

degrade the contaminants without implementing any engineered steps to enhance the process. There are

four main requirements that must be met for intrinsic bioremediation to be successful. These four

requirements are:

1. Sufficient microorganisms that can biodegrade the contaminant,

2. Required nutrients are available,

3. Suitable environmental conditions exist and,

4. Sufficient time to allow the natural process to degrade the contaminant.

Table 2.1: Relationship of Available Oxygen to Bacteria Numbers (Flathman 313)

This method is different from depending only on the natural because intrinsic

bioremediation must degrade the microorganisms faster than the growth of contaminant. This requires

good monitoring to determine the location and concentration of the contaminants, the number of

microbes, and other appropriate parameters.

b) Engineered bioremediation: Engineered bioremediation is also known as enhanced bioremediation.

Engineered bioremediation is a process that adds to or enhances the natural process of degradation.

Generally it is used when any one of the four necessary conditions for intrinsic bioremediation is not

available or when the process needs to be completed faster. An example of engineered bioremediation is to

install wells to circulate fluids and nutrients to stimulate the microorganisms.

Within engineered bioremediation there are two types:

(i) Biostimululation: In case of biostimulation, the environment is modified to favour the growth of

existing microbes like addition of missing nutrients, oxygen and so on. There are also several nutrients that

must be accessible to the microorganisms for bioremediation to be successful. These include moisture,

nitrogen, phosphorus, and other trace elements. Microorganisms like other organisms need moisture to

survive and grow. In addition, microbes depend on the moisture to transport food to them since they do not

have mouths. The optimal moisture content for microbes in the vadose zone has been determined to be

between 10 and 25% (King 1998). Besides moisture, nitrogen (ammonia) and phosphorus (orthophosphate)

are two major nutrients needed for the microorganisms.

Bacterial countMaximum

Available Oxygen (ppm) Total Heterotrophic Gasoline-Utilizing

Bacteria Bacteria

4 28 (air) 5 x 10 1 x 10

6 540 (O ) 5.5 x 10 7 x 102

7 7112 (250 ppm H O ) 7.5 x 10 2.7 x 102 2

8 7200 (500 ppm H O ) 2.1 x 10 3.1 x 102 2

Correlation Coefficient, r 0.97 0.93

* - ppm = path per million 1 ppm = 1 mg/litre

bacterial population

5 6 2

2.0 How does Bioremediation work?

2.1 Introduction

There are also several nutrients that must be accessible to the microorganisms for bioremediation to be

successful. These include moisture, nitrogen, phosphorus, and other trace elements. Microorganisms like other

organisms need moisture to survive and grow. In addition, microbes depend on the moisture to transport food to

them since they do not have mouths. The optimal moisture content for microbes in the vadose zone has been

determined to be between 10 and 25% (King, 1998). Besides moisture, nitrogen (ammonia) and phosphorus

(orthophosphate) are two major nutrients needed for the microorganisms. The microorganisms also require

minor elements such as sulphur, potassium, magnesium, calcium, manganese, iron, cobalt, copper, nickel, and

zinc (King, 1998). However, these minor elements are usually available in the environment in sufficient

amounts where nitrogen and phosphorus may be lacking and need to be added.

There are many contaminants susceptible to bioremediation. Petroleum hydrocarbons, in particular, benzene,

toluene, ethylbenzene, and xylene (BTEX), the major components of gasoline, have been biodegraded using

this technology. In addition, alcohols, ketones, and esters are well established as being biodegradable by

microorganisms. Many other contaminants are emerging as treatable using bioremediation such as halogenated

aliphatics, halogenated aromatics, polychlorinated biphenyls, and nitroaromatics (National Research Council

1993).

2.2 Types of Bioremediation

Bioremediation can be broken into two main types:

a) Intrinsic and

b) Engineered.

a) Intrinsic bioremediation: Intrinsic bioremediation is also known as natural attenuation or passive

bioremediation. Intrinsic bioremediation is preferred to engineered bioremediation primarily because the

cost is much lower. Intrinsic bioremediation consists of allowing the natural occurring microorganisms to

degrade the contaminants without implementing any engineered steps to enhance the process. There are

four main requirements that must be met for intrinsic bioremediation to be successful. These four

requirements are:

1. Sufficient microorganisms that can biodegrade the contaminant,

2. Required nutrients are available,

3. Suitable environmental conditions exist and,

4. Sufficient time to allow the natural process to degrade the contaminant.

Table 2.1: Relationship of Available Oxygen to Bacteria Numbers (Flathman 313)

This method is different from depending only on the natural because intrinsic

bioremediation must degrade the microorganisms faster than the growth of contaminant. This requires

good monitoring to determine the location and concentration of the contaminants, the number of

microbes, and other appropriate parameters.

b) Engineered bioremediation: Engineered bioremediation is also known as enhanced bioremediation.

Engineered bioremediation is a process that adds to or enhances the natural process of degradation.

Generally it is used when any one of the four necessary conditions for intrinsic bioremediation is not

available or when the process needs to be completed faster. An example of engineered bioremediation is to

install wells to circulate fluids and nutrients to stimulate the microorganisms.

Within engineered bioremediation there are two types:

(i) Biostimululation: In case of biostimulation, the environment is modified to favour the growth of

existing microbes like addition of missing nutrients, oxygen and so on. There are also several nutrients that

must be accessible to the microorganisms for bioremediation to be successful. These include moisture,

nitrogen, phosphorus, and other trace elements. Microorganisms like other organisms need moisture to

survive and grow. In addition, microbes depend on the moisture to transport food to them since they do not

have mouths. The optimal moisture content for microbes in the vadose zone has been determined to be

between 10 and 25% (King 1998). Besides moisture, nitrogen (ammonia) and phosphorus (orthophosphate)

are two major nutrients needed for the microorganisms.

Bacterial countMaximum

Available Oxygen (ppm) Total Heterotrophic Gasoline-Utilizing

Bacteria Bacteria

4 28 (air) 5 x 10 1 x 10

6 540 (O ) 5.5 x 10 7 x 102

7 7112 (250 ppm H O ) 7.5 x 10 2.7 x 102 2

8 7200 (500 ppm H O ) 2.1 x 10 3.1 x 102 2

Correlation Coefficient, r 0.97 0.93

* - ppm = path per million 1 ppm = 1 mg/litre

bacterial population

7 8 2

• It is also cost-effective and can easily compete with other treatment methods.

• It involves no use of energy hence it is climate friendly completely cutting down the cost of energy.

Because of this reason, it can be implemented in remote areas with no electricity.

• Involves no infrastructure costs or civil structures hence can be quickly started with no preparation

time.

• Microbes able to degrade the contaminant increase in numbers when the contaminant is

present(subtrate dependent); when the contaminant is degraded, the microbial population declines and

dies.

However, bioremediation have some disadvantages as well.

• Bioremediation cannot be used on all contaminated areas. It is limited to only those compounds that are

biodegradable and not all compounds are susceptible to rapid and complete degradation.

• There are some sites where the necessary ingredients for the process that cannot be made available to

the microorganisms. Bioremediation may not be a possibility there; even if it may not be economically

feasible.

• Often the greatest problem is that bioremediation involves microorganisms which people cannot see

and thus often do not understand. Moreover, bacteria are also often linked to diseases and infection.

Therefore it may not be accepted easily.

• Biological processes are often highly specific to site conditions.

There are two basic ways to provide oxygen for bioremediation:

(a) Physical and,

(b) Chemical.

The physical method forces air or pure oxygen into the contaminated soil or ground water while the

chemical method provides oxygen through the introduction of another substance such as hydrogen

peroxide, which release oxygen.

(ii) Bioaugmentation: Bioaugmentation is used where the desired microbes are in low numbers in

undesirable. Bioaugmentation process involves the addition of certain specific micro

organisms to the system to enhance the overall metabolism process. The concept is based on the fact that

there are Biologically degradable solids within the wastewater. Biological treatment generally involves the

use of intrinsic bacteria which are present in the wastewater. They are usually present in very small numbers

and may or may not be able to biodegrade a specific contaminant. The indigenous population may act but

not quickly enough to prevent the spread of the contaminant. If a rapid response is important, the reliance on

small numbers of the indigenous microbial population is not appropriate. The solution for this lies in

Bioaugmentation. In this method, the microbes are augmented or added to the site to enhance their numbers

so that they outnumber the undesirable ones. This is the type that we commonly use for treatment of

municipal wastewater.

2.3 Advantages and Disadvantages of Bioremediation

Advantages of bioremediation include

• Bioremediation can often be carried out on site mostly without causing a major disruption of normal

activities. This also eliminates the need to transport waste/wastewater off site and the potential threats

to human health and the environment that can arise during transportation.

• 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 from hazardous to non-

hazardous. The fact that the contaminant is destroyed/metabolised rather than translocated to another

site is another advantage. This minimises the long-term liability of the agency responsible for the

contamination.

• The residues from the treatment are usually harmless and include carbon dioxide, water, and cell

biomass.

• Bioremediation is a natural process.

comparison to

7 8 2

• It is also cost-effective and can easily compete with other treatment methods.

• It involves no use of energy hence it is climate friendly completely cutting down the cost of energy.

Because of this reason, it can be implemented in remote areas with no electricity.

• Involves no infrastructure costs or civil structures hence can be quickly started with no preparation

time.

• Microbes able to degrade the contaminant increase in numbers when the contaminant is

present(subtrate dependent); when the contaminant is degraded, the microbial population declines and

dies.

However, bioremediation have some disadvantages as well.

• Bioremediation cannot be used on all contaminated areas. It is limited to only those compounds that are

biodegradable and not all compounds are susceptible to rapid and complete degradation.

• There are some sites where the necessary ingredients for the process that cannot be made available to

the microorganisms. Bioremediation may not be a possibility there; even if it may not be economically

feasible.

• Often the greatest problem is that bioremediation involves microorganisms which people cannot see

and thus often do not understand. Moreover, bacteria are also often linked to diseases and infection.

Therefore it may not be accepted easily.

• Biological processes are often highly specific to site conditions.

There are two basic ways to provide oxygen for bioremediation:

(a) Physical and,

(b) Chemical.

The physical method forces air or pure oxygen into the contaminated soil or ground water while the

chemical method provides oxygen through the introduction of another substance such as hydrogen

peroxide, which release oxygen.

(ii) Bioaugmentation: Bioaugmentation is used where the desired microbes are in low numbers in

undesirable. Bioaugmentation process involves the addition of certain specific micro

organisms to the system to enhance the overall metabolism process. The concept is based on the fact that

there are Biologically degradable solids within the wastewater. Biological treatment generally involves the

use of intrinsic bacteria which are present in the wastewater. They are usually present in very small numbers

and may or may not be able to biodegrade a specific contaminant. The indigenous population may act but

not quickly enough to prevent the spread of the contaminant. If a rapid response is important, the reliance on

small numbers of the indigenous microbial population is not appropriate. The solution for this lies in

Bioaugmentation. In this method, the microbes are augmented or added to the site to enhance their numbers

so that they outnumber the undesirable ones. This is the type that we commonly use for treatment of

municipal wastewater.

2.3 Advantages and Disadvantages of Bioremediation

Advantages of bioremediation include

• Bioremediation can often be carried out on site mostly without causing a major disruption of normal

activities. This also eliminates the need to transport waste/wastewater off site and the potential threats

to human health and the environment that can arise during transportation.

• 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 from hazardous to non-

hazardous. The fact that the contaminant is destroyed/metabolised rather than translocated to another

site is another advantage. This minimises the long-term liability of the agency responsible for the

contamination.

• The residues from the treatment are usually harmless and include carbon dioxide, water, and cell

biomass.

• Bioremediation is a natural process.

comparison to

3.1 Bioremediation in nature

Natural bioremediation has been occurring for millions of years. Biodegradation of dead vegetation and dead

animals is a kind of bioremediation. It is a natural part of the carbon, nitrogen, and sulphur cycles. Chemical

energy present in waste materials is used by microorganisms to grow while they convert organic carbon and

hydrogen to carbon dioxide and water.

When bioremediation is applied by people, microbial biodegradation processes are said to be managed.

However, bioremediation takes place naturally and often it occurs prior to efforts to manage the process. One

of the first examples of managed bioremediation was land farming (refers to the managed biodegradation of

organic compounds that are distributed onto the soil surface, fertilised, and then tilled). Many petroleum

companies have used it. High-molecular-weight organic compounds (i.e., oil sludges and waste) are spread

onto soil and then tilled into the ground with fertilizer, as part of the managed bioremediation process. Good

conditions for microbial biodegradation are maintained by controlling soil moisture and soil nutrients. In 1974,

R.L. Raymond was awarded a patent for the bioremediation of gasoline. This was one of the first patents

granted for a bioremediation process.

3.2 Essential Factors for Bioremediation

Microbial population: Suitable kinds of organisms that can biodegrade specifies or all of the contaminants

are essential. This could include a single consortium containing many strains which

degrade various strains like sulphate reducing strain, nitrate reducing strain and so on

based on the nature of waste to be treated.

Water/Moisture: The moisture in the medium should be 50–70% of the water holding capacity of the

medium. This is because microbes grow and multiply optimally in these situations.

Nutrients: Nitrogen, phosphorus, sulphur, and other nutrients to support good microbial growth.

Microbes grow in the presence of nutrients and break them down into simpler and less

hazardous components. Nutrients are required to have a good population of microbes.

Temperature: Appropriate temperatures for microbial growth (0–40˚C) is essential. This is the

broad range for bioremediation to occur. However this range narrows down when you

consider specific microbial consortia.

pH: Best range is from 6.5 to 7.5. This too, just like temperature, can vary with the

specific microbial consortia that are used.

9 10 3

3.3 How much time does bioremediation take ?

The time taken for bioremediation of a site depends on several factors. The most important ones are given as

follows.

a) Type and amount of harmful chemicals present

b) Size and depth of the polluted area

c) Type of medium (water/soil) and the conditions present

d) Above ground or underground

It can take a few months or even several years for microbes to eat enough of the harmful chemicals to clean up

the site.

3.4 The Process

A. Feasibility Assessment and Budgeting:

Feasibility assessment is the first and the key step in determining whether the environmental and physical

conditions will suit the process of bioremediation or not and in terms of costing vs. results, if it would be the best

solution. Thus, in this step one determines the range of environmental conditions like pH, temperature and

nutrient availability. The chemical analysis of waste to find the waste profile is also done to ascertain if the

organisms will survive optimally to treat the waste. The analysis of microbes in waste can give valuable insights

into the best products to use for bioremediation. The feasibility also considers factors like flow rate, volume of

wastewater and retention time which play a key role in bioremediation. These can be manipulated to some

extent with minor changes to make bioremediation more effective.

B. Baseline data:

Once the feasibility and budgeting is done, there needs to be a comprehensive analysis of the waste for

parameters that would be used as indicators of improvement in the monitoring plan. The baseline data has to be

done with a good deal of planning otherwise it can topple the entire monitoring plan. This is based on 2

strategies:

1. Physical Conditions: Any change in physical condition of the site needs to be monitored as it can affect

the pace and pathway of bioremediation. The key physical parameters are pH, temperature, Colour,

Biological and Chemical Oxygen Demand, if in a stream, lake or pond then dissolved oxygen too and

Sulphides and Total Suspended Solids

2. Contaminant Analysis: The presence of contaminants can be assessed by the chemical analysis. The

objective of Bioremediation is to reduce/eliminate the levels of hazardous contaminants and thus they

need to be monitored to see if they are being eliminated or not. These could be chemicals, heavy metals or

3.0 Process of Bioremediation

3.1 Bioremediation in nature

Natural bioremediation has been occurring for millions of years. Biodegradation of dead vegetation and dead

animals is a kind of bioremediation. It is a natural part of the carbon, nitrogen, and sulphur cycles. Chemical

energy present in waste materials is used by microorganisms to grow while they convert organic carbon and

hydrogen to carbon dioxide and water.

When bioremediation is applied by people, microbial biodegradation processes are said to be managed.

However, bioremediation takes place naturally and often it occurs prior to efforts to manage the process. One

of the first examples of managed bioremediation was land farming (refers to the managed biodegradation of

organic compounds that are distributed onto the soil surface, fertilised, and then tilled). Many petroleum

companies have used it. High-molecular-weight organic compounds (i.e., oil sludges and waste) are spread

onto soil and then tilled into the ground with fertilizer, as part of the managed bioremediation process. Good

conditions for microbial biodegradation are maintained by controlling soil moisture and soil nutrients. In 1974,

R.L. Raymond was awarded a patent for the bioremediation of gasoline. This was one of the first patents

granted for a bioremediation process.

3.2 Essential Factors for Bioremediation

Microbial population: Suitable kinds of organisms that can biodegrade specifies or all of the contaminants

are essential. This could include a single consortium containing many strains which

degrade various strains like sulphate reducing strain, nitrate reducing strain and so on

based on the nature of waste to be treated.

Water/Moisture: The moisture in the medium should be 50–70% of the water holding capacity of the

medium. This is because microbes grow and multiply optimally in these situations.

Nutrients: Nitrogen, phosphorus, sulphur, and other nutrients to support good microbial growth.

Microbes grow in the presence of nutrients and break them down into simpler and less

hazardous components. Nutrients are required to have a good population of microbes.

Temperature: Appropriate temperatures for microbial growth (0–40˚C) is essential. This is the

broad range for bioremediation to occur. However this range narrows down when you

consider specific microbial consortia.

pH: Best range is from 6.5 to 7.5. This too, just like temperature, can vary with the

specific microbial consortia that are used.

9 10 3

3.3 How much time does bioremediation take ?

The time taken for bioremediation of a site depends on several factors. The most important ones are given as

follows.

a) Type and amount of harmful chemicals present

b) Size and depth of the polluted area

c) Type of medium (water/soil) and the conditions present

d) Above ground or underground

It can take a few months or even several years for microbes to eat enough of the harmful chemicals to clean up

the site.

3.4 The Process

A. Feasibility Assessment and Budgeting:

Feasibility assessment is the first and the key step in determining whether the environmental and physical

conditions will suit the process of bioremediation or not and in terms of costing vs. results, if it would be the best

solution. Thus, in this step one determines the range of environmental conditions like pH, temperature and

nutrient availability. The chemical analysis of waste to find the waste profile is also done to ascertain if the

organisms will survive optimally to treat the waste. The analysis of microbes in waste can give valuable insights

into the best products to use for bioremediation. The feasibility also considers factors like flow rate, volume of

wastewater and retention time which play a key role in bioremediation. These can be manipulated to some

extent with minor changes to make bioremediation more effective.

B. Baseline data:

Once the feasibility and budgeting is done, there needs to be a comprehensive analysis of the waste for

parameters that would be used as indicators of improvement in the monitoring plan. The baseline data has to be

done with a good deal of planning otherwise it can topple the entire monitoring plan. This is based on 2

strategies:

1. Physical Conditions: Any change in physical condition of the site needs to be monitored as it can affect

the pace and pathway of bioremediation. The key physical parameters are pH, temperature, Colour,

Biological and Chemical Oxygen Demand, if in a stream, lake or pond then dissolved oxygen too and

Sulphides and Total Suspended Solids

2. Contaminant Analysis: The presence of contaminants can be assessed by the chemical analysis. The

objective of Bioremediation is to reduce/eliminate the levels of hazardous contaminants and thus they

need to be monitored to see if they are being eliminated or not. These could be chemicals, heavy metals or

3.0 Process of Bioremediation

4.1 When can one use Bioremediation?

While bioremediation is a very useful technology, it cannot possibly work under all situations. There are

specific situations where it works best. Hence one needs to conduct a quick feasibility assessment before actual

implementation. This assessment can give us insights into the following:

a) Will bioremediation work in the given situation;

b) If yes then, will it be the best option or are there better technologies in the situation;

c) What would it cost to do bioremediation

d)Would it be economical to use bioremediation

Under situations where the above situations are present, one needs to do a thorough study of the nature of

wastewaters to be certain as to which microbes should be used.

4.2 Bioremediation in Municipal wastewater

Figure 4.2: Sewage carrying drains polluting the Ganges

(a) Sisamau, Kanpur; (b) Assi, Varanasi

1211 4

even organic waste. BOD is an indicator depicting level of the presence of biodegradable contaminants,

COD indicates the presence of chemical contaminants, Sulphides indicates presence of sulphur and

excessive nutrients too are pollutants in their own way. These can be monitored and then progressively

compared with baseline data. All parameters may not be appropriate for all sites and situations , these have

to be chosen with care.

C. Treatment plan:

Based on the level of chemical contaminants, other pollutants and physical environmental conditions, the

treatment plan has to be carefully decided. A contaminated site is not the best place for organisms or bacteria

hence to establish them, there needs to be an initial shock dosing for their survival. Once the bacteria establish

themselves, the dosages have to be reduced slowly until you reach the maintenance dose which continues. This

dose takes into account their natural death and multiplication.

D. Monitoring Plan:

The process of bioremediation needs to be monitored to ensure that it is on and taking place the way it has been

planned and the contaminant is progressively decreasing. This is done by monitoring the process of

bioremediation using several parameters which serve as an evidence to the process. The parameters for the

monitoring plan are the ones that are decided during the baseline data collection phase. The periodicity of this

data is also important and should be based on good judgment.

3

4.0 When and where should one apply Bioremediation Technology?

(b)

(a)

4.1 When can one use Bioremediation?

While bioremediation is a very useful technology, it cannot possibly work under all situations. There are

specific situations where it works best. Hence one needs to conduct a quick feasibility assessment before actual

implementation. This assessment can give us insights into the following:

a) Will bioremediation work in the given situation;

b) If yes then, will it be the best option or are there better technologies in the situation;

c) What would it cost to do bioremediation

d)Would it be economical to use bioremediation

Under situations where the above situations are present, one needs to do a thorough study of the nature of

wastewaters to be certain as to which microbes should be used.

4.2 Bioremediation in Municipal wastewater

Figure 4.2: Sewage carrying drains polluting the Ganges

(a) Sisamau, Kanpur; (b) Assi, Varanasi

1211 4

even organic waste. BOD is an indicator depicting level of the presence of biodegradable contaminants,

COD indicates the presence of chemical contaminants, Sulphides indicates presence of sulphur and

excessive nutrients too are pollutants in their own way. These can be monitored and then progressively

compared with baseline data. All parameters may not be appropriate for all sites and situations , these have

to be chosen with care.

C. Treatment plan:

Based on the level of chemical contaminants, other pollutants and physical environmental conditions, the

treatment plan has to be carefully decided. A contaminated site is not the best place for organisms or bacteria

hence to establish them, there needs to be an initial shock dosing for their survival. Once the bacteria establish

themselves, the dosages have to be reduced slowly until you reach the maintenance dose which continues. This

dose takes into account their natural death and multiplication.

D. Monitoring Plan:

The process of bioremediation needs to be monitored to ensure that it is on and taking place the way it has been

planned and the contaminant is progressively decreasing. This is done by monitoring the process of

bioremediation using several parameters which serve as an evidence to the process. The parameters for the

monitoring plan are the ones that are decided during the baseline data collection phase. The periodicity of this

data is also important and should be based on good judgment.

3

4.0 When and where should one apply Bioremediation Technology?

(b)

(a)

13 14 4

Chromium is widespread in a tannery environment as it is used for tanning (apart from electroplating, chromate

manufacturing and wood preservation) (Papp, 2001) The conventional treatment methodology for soils and

groundwater systems contaminated with hexavalent chromium is pumping of the contaminated material,

addition of chemical reductant, precipitation followed by sedimentation, or ion exchange and/or adsorption.

These are practiced both in situ and ex situ systems (Zahir, 1996). These physico-chemical methods incur from

high costs associated with energy and chemical consumption. The search for new and innovative technology for

the remediation of Cr(VI) pollution has attracted the attention on the biotransformation potential of certain

microorganisms. Microbial reduction of toxic hexavalent chromium to less soluble trivalent form as a normal

function of their metabolism seems to be a potential method for the remediation of Cr(VI) contamination. Many

microbes have been reported to reduce Cr(VI) under either aerobic or anaerobic conditions. In addition some

species are capable of reducing Cr(VI) both aerobically and anaerobically depending on the oxidation reduction

potential (ORP) of the environment. The physiological mechanisms responsible for Cr(VI) reduction appear to

vary significantly among various organisms. In some cases intracellular enzymes were responsible for Cr(VI)

biotransformation, where as in other cases Cr(VI) reduction took place extracellularly. The carbon

source/electron donor preferences also varied considerably depending on the microbial consortia employed.

Though many studies have been carried out for the treatment of Cr(VI) contaminated water/wastewater, not

much research has been carried out on the remediation of Cr(VI) contaminated soils either using in situ or ex situ

bioremediation techniques. Turick et al. (1998) demonstrated the Cr(VI) reduction in a contaminated soil by

indigenous microbial consortium under anaerobic condition. Organic amended soils have been reported to

reduce Cr(VI) in ground water from 1mg/L to less than 50g/L. Under anaerobic conditions, indigenous

microbes have reduced 65% of Cr(VI) from contaminated soil with the addition of glucose.

Information available on the ex situ treatment of Cr(VI) contaminated soil is scarce. For small volumes of highly

contaminated soil, ex situ remediation is still a promising alternative. For ex situ treatment, basically three steps

have to be optimized, leaching of Cr(III) and Cr(VI), transformation of Cr(VI) to Cr(III) and subsequent

removal of Cr(III) from the system.

4.4 Bioremediation Products:

There are several suppliers of bioremediation products present in the indian market.These products utilized for

bioremediation are usually patented. These products are usually:

• A consortium of live micro-organisms in the form of dry solid/concentrated solution/sometimes also

tablets,

• Can be easily activated in aqueous medium,

• Are either dripped into the water or sprayed at requisite concentrations and alternatively/

additionally applied as slow release tablets,

Almost all urban centres discharge their wastewaters [untreated /partially treated / treated] in the water courses.

Thus the major source of organic pollution in fresh water bodies is still sewage or domestic wastewater. In India,

not all the cities have conventional sewage treatment facilities.Even in towns and cities where such facilities do

exist, there are issues like insufficient treatment capacity, suboptimal operational performance of the units, and

frequent electrical outages that hamper the operation of sewage treatment plants.

A wide gap between domestic sewage generated and treatment capacity in almost all Indian cities results in the

untreated sewage to flow into the river and other water bodies.At the same time conventional treatment

technologies require high operational and maintenance cost. Hence there is a need to identify sustainable

wastewater treatment approach to fill the gap and reduce the load on conventional treatment processes and

demonstrate the benefits to the key stakeholders.

Wastewater consists of organic matter which is the single largest component responsible for air, water and soil

pollution due to its decomposition under anaerobic conditions (devoid of oxygen) and thus a high BOD. This

can be easily used by microbes as food and thus degraded and metabolised very effectively thus reducing the

BOD, Total Suspended Solids, Sulphides and also coliforms (primarily by competition for the same resources).

WWF-India successfully demonstrated in situ bioremediation in a drain in Kanpur, and then ex situ at

Allahabad. In industrial applications too, often municipal wastewaters are added to increase the nutrient value

for microbes and thus allowing them to multiply and grow better.

4.3 Bioremediation in Industrial CETPs and Tanneries

Effluents from textile, leather, tannery, electroplating, galvanizing, dyes and pigment, metallurgical and paint

industries and other metal processing and refining operations at small and large-scale sector contains

considerable amounts of toxic metal ions. These metal ions pose problems to the water environment by

discharging mine water from underground and open pit mines Moncur et al 2005 . The potential impacts from

leaching operations on the environment are most likely to be experienced as changes to surface and groundwater

quality. The principal pathways by which leached contaminants can enter into groundwater are leakage or spills

from storage ponds, leach pad liners, subsequent leaching to groundwater, storm water run-on/off, uncontrolled

leaching from heaps and dumps following closer (Moncur et al 2005).

In the growing Indian economy both the Government and industry are concerned about the treatment of the

effluents. These concerns are exemplified due to the investment constraints on small scale and medium scale

industries in erecting waste treatment plants. Under such a constraint CETPs are being considered as a common

facility. Since the nature of effluents and their chemical composition is very diverse, CETPs face a grave

challenge in treating such effluents. Chemical oxygen demand (COD) and ammoniacal nitrogen are the main

concerns at the CETP. The bacterial consortium developed have been reported to lower the COD from an initial 38000 mg/l to 1500 mg/l at flask level and from 3000 mg/l to 1400 mg/l at a pilot plant of size 25 m on site.

Bacterial consortium are generally developed using the bacteria isolated from the soil and wastewater in the

premises of CETP, and the same bacterial consortium used at site.

( )

13 14 4

Chromium is widespread in a tannery environment as it is used for tanning (apart from electroplating, chromate

manufacturing and wood preservation) (Papp, 2001) The conventional treatment methodology for soils and

groundwater systems contaminated with hexavalent chromium is pumping of the contaminated material,

addition of chemical reductant, precipitation followed by sedimentation, or ion exchange and/or adsorption.

These are practiced both in situ and ex situ systems (Zahir, 1996). These physico-chemical methods incur from

high costs associated with energy and chemical consumption. The search for new and innovative technology for

the remediation of Cr(VI) pollution has attracted the attention on the biotransformation potential of certain

microorganisms. Microbial reduction of toxic hexavalent chromium to less soluble trivalent form as a normal

function of their metabolism seems to be a potential method for the remediation of Cr(VI) contamination. Many

microbes have been reported to reduce Cr(VI) under either aerobic or anaerobic conditions. In addition some

species are capable of reducing Cr(VI) both aerobically and anaerobically depending on the oxidation reduction

potential (ORP) of the environment. The physiological mechanisms responsible for Cr(VI) reduction appear to

vary significantly among various organisms. In some cases intracellular enzymes were responsible for Cr(VI)

biotransformation, where as in other cases Cr(VI) reduction took place extracellularly. The carbon

source/electron donor preferences also varied considerably depending on the microbial consortia employed.

Though many studies have been carried out for the treatment of Cr(VI) contaminated water/wastewater, not

much research has been carried out on the remediation of Cr(VI) contaminated soils either using in situ or ex situ

bioremediation techniques. Turick et al. (1998) demonstrated the Cr(VI) reduction in a contaminated soil by

indigenous microbial consortium under anaerobic condition. Organic amended soils have been reported to

reduce Cr(VI) in ground water from 1mg/L to less than 50g/L. Under anaerobic conditions, indigenous

microbes have reduced 65% of Cr(VI) from contaminated soil with the addition of glucose.

Information available on the ex situ treatment of Cr(VI) contaminated soil is scarce. For small volumes of highly

contaminated soil, ex situ remediation is still a promising alternative. For ex situ treatment, basically three steps

have to be optimized, leaching of Cr(III) and Cr(VI), transformation of Cr(VI) to Cr(III) and subsequent

removal of Cr(III) from the system.

4.4 Bioremediation Products:

There are several suppliers of bioremediation products present in the indian market.These products utilized for

bioremediation are usually patented. These products are usually:

• A consortium of live micro-organisms in the form of dry solid/concentrated solution/sometimes also

tablets,

• Can be easily activated in aqueous medium,

• Are either dripped into the water or sprayed at requisite concentrations and alternatively/

additionally applied as slow release tablets,

Almost all urban centres discharge their wastewaters [untreated /partially treated / treated] in the water courses.

Thus the major source of organic pollution in fresh water bodies is still sewage or domestic wastewater. In India,

not all the cities have conventional sewage treatment facilities.Even in towns and cities where such facilities do

exist, there are issues like insufficient treatment capacity, suboptimal operational performance of the units, and

frequent electrical outages that hamper the operation of sewage treatment plants.

A wide gap between domestic sewage generated and treatment capacity in almost all Indian cities results in the

untreated sewage to flow into the river and other water bodies.At the same time conventional treatment

technologies require high operational and maintenance cost. Hence there is a need to identify sustainable

wastewater treatment approach to fill the gap and reduce the load on conventional treatment processes and

demonstrate the benefits to the key stakeholders.

Wastewater consists of organic matter which is the single largest component responsible for air, water and soil

pollution due to its decomposition under anaerobic conditions (devoid of oxygen) and thus a high BOD. This

can be easily used by microbes as food and thus degraded and metabolised very effectively thus reducing the

BOD, Total Suspended Solids, Sulphides and also coliforms (primarily by competition for the same resources).

WWF-India successfully demonstrated in situ bioremediation in a drain in Kanpur, and then ex situ at

Allahabad. In industrial applications too, often municipal wastewaters are added to increase the nutrient value

for microbes and thus allowing them to multiply and grow better.

4.3 Bioremediation in Industrial CETPs and Tanneries

Effluents from textile, leather, tannery, electroplating, galvanizing, dyes and pigment, metallurgical and paint

industries and other metal processing and refining operations at small and large-scale sector contains

considerable amounts of toxic metal ions. These metal ions pose problems to the water environment by

discharging mine water from underground and open pit mines Moncur et al 2005 . The potential impacts from

leaching operations on the environment are most likely to be experienced as changes to surface and groundwater

quality. The principal pathways by which leached contaminants can enter into groundwater are leakage or spills

from storage ponds, leach pad liners, subsequent leaching to groundwater, storm water run-on/off, uncontrolled

leaching from heaps and dumps following closer (Moncur et al 2005).

In the growing Indian economy both the Government and industry are concerned about the treatment of the

effluents. These concerns are exemplified due to the investment constraints on small scale and medium scale

industries in erecting waste treatment plants. Under such a constraint CETPs are being considered as a common

facility. Since the nature of effluents and their chemical composition is very diverse, CETPs face a grave

challenge in treating such effluents. Chemical oxygen demand (COD) and ammoniacal nitrogen are the main

concerns at the CETP. The bacterial consortium developed have been reported to lower the COD from an initial 38000 mg/l to 1500 mg/l at flask level and from 3000 mg/l to 1400 mg/l at a pilot plant of size 25 m on site.

Bacterial consortium are generally developed using the bacteria isolated from the soil and wastewater in the

premises of CETP, and the same bacterial consortium used at site.

( )

5.1 What is Phytoremediation?

Phytoremediaton is the process using plants to clean up the environment. The word phytoremediation comes

from the Greek word phyto, meaning “plant” and the Latin word remediare, meaning “to remedy”. This word is

generally used to describe any system where plants are introduced into an environment to remove

contaminants from it. Phytoremediation is done in a variety of ways. Plants can be introduced into an

environment and allowed to absorb/uptake contaminants into its leaves and roots. These plants can then be

harvested to either recover the contaminants or dispose off the plant parts as hazardous waste. There have even

been studies where these plants have transformed the contaminants into harmless substances through the

process of and then once harvested can be used for mulch, animal feed, paper, etc. In some instances (especially

if trees are being used) the plants are left in the environment and allowed to grow and mature as normal.

Phytoremediation is the use of plants and trees to clean up contaminated soil and water. This technology is

currently in its infancy, and more research needs to be done before it is widely used as a remediation technique.

However, the future seems promising. Currently, majority of research is concentrated on determining the best

plant for the job, quantifying the mechanisms by which the plants transform pollutants, and determining which

contaminants are amenable to phytoremediation. Polluted sites are being studied, and phytoremediation

technology seems to be a promising technology for a variety of contaminants. This technology is useful for soil

and water remediation. Whilst the technology has historically been applied to soil clean-up, it can also be

applied to the treatment of tannery waste. This article provides an overview of the technique, together with

information concerning the specific application to the leather industry (ie the use of reed beds).

Phytoremediation uses various types of

plants to remove, transfer, stabilize,

and/or destroy contaminants in the soil

and groundwater. There are several

different types of phytoremediation

mechanisms. These are:

1. Rhizosphere biodegradation:In this

process the plant releases natural

substances through its roots, supplying

nutrients to microorganisms in the soil.

T h e m i c r o o rg a n i s m s e n h a n c e

biological degradation.

Fig 5.1 : Phytoremediation in CETP, Banthar

15 16 54

• Shelf life of the product is limited,

• The microorganisms multiply rapidly in the conditions presence of organic waste,

• The products effectively control odour generation by eliminating formation of hydrogen sulphide

gas and reduce BOD.

5.0 Phytoremediation

Contaminant* Taken Up- Dissolved in Transpiration Water or as Vapor Adsorbed through Roots- Translocated in Xylem

* Or an intermediate from rhizoderadation

Treatment Zone

5.1 What is Phytoremediation?

Phytoremediaton is the process using plants to clean up the environment. The word phytoremediation comes

from the Greek word phyto, meaning “plant” and the Latin word remediare, meaning “to remedy”. This word is

generally used to describe any system where plants are introduced into an environment to remove

contaminants from it. Phytoremediation is done in a variety of ways. Plants can be introduced into an

environment and allowed to absorb/uptake contaminants into its leaves and roots. These plants can then be

harvested to either recover the contaminants or dispose off the plant parts as hazardous waste. There have even

been studies where these plants have transformed the contaminants into harmless substances through the

process of and then once harvested can be used for mulch, animal feed, paper, etc. In some instances (especially

if trees are being used) the plants are left in the environment and allowed to grow and mature as normal.

Phytoremediation is the use of plants and trees to clean up contaminated soil and water. This technology is

currently in its infancy, and more research needs to be done before it is widely used as a remediation technique.

However, the future seems promising. Currently, majority of research is concentrated on determining the best

plant for the job, quantifying the mechanisms by which the plants transform pollutants, and determining which

contaminants are amenable to phytoremediation. Polluted sites are being studied, and phytoremediation

technology seems to be a promising technology for a variety of contaminants. This technology is useful for soil

and water remediation. Whilst the technology has historically been applied to soil clean-up, it can also be

applied to the treatment of tannery waste. This article provides an overview of the technique, together with

information concerning the specific application to the leather industry (ie the use of reed beds).

Phytoremediation uses various types of

plants to remove, transfer, stabilize,

and/or destroy contaminants in the soil

and groundwater. There are several

different types of phytoremediation

mechanisms. These are:

1. Rhizosphere biodegradation:In this

process the plant releases natural

substances through its roots, supplying

nutrients to microorganisms in the soil.

T h e m i c r o o rg a n i s m s e n h a n c e

biological degradation.

Fig 5.1 : Phytoremediation in CETP, Banthar

15 16 54

• Shelf life of the product is limited,

• The microorganisms multiply rapidly in the conditions presence of organic waste,

• The products effectively control odour generation by eliminating formation of hydrogen sulphide

gas and reduce BOD.

5.0 Phytoremediation

Contaminant* Taken Up- Dissolved in Transpiration Water or as Vapor Adsorbed through Roots- Translocated in Xylem

* Or an intermediate from rhizoderadation

Treatment Zone

17 18 5

2. Phyto-stabilization: In this process chemical compounds produced by the plant immobilise contaminants,

rather than degrade them.

3. Phytoaccumulation (also called phytoextraction): In this process plant roots adsorb the contaminants

along with other nutrients and water. The contaminant mass is not destroyed but ends up in the plant shoots

and leaves. This method is used primarily for waste containing metals. At one demonstration site, water-

soluble metals are taken up by plant species selected for their ability to take up large quantities of Lead (Pb).

The metals are stored in the plant's aerial shoots, which are harvested and either smelted for potential metal

recycling/recovery or are disposed of as a hazardous waste. As a general rule, readily bioavailable metals

for plant uptake include Cadmium, Nickel, Zinc, Arsenic, Selenium, and Copper. Moderately bioavailable

metals are Cobalt, Manganese, and Iron. Lead, Chromium, and Uranium are not very bioavailable. Lead can

be made much more bioavailable by the addition of chelating agents to soils. Similarly, the availability of

uranium and radio-cesium 137 can be enhanced using citric acid and ammonium nitrate, respectively.

4. Hydroponic Systems for Treating Water Streams (Rhizofiltration): Rhizofiltration is similar to phyto-

accumulation, but the plants used for cleanup are raised in greenhouses with their roots in water. This

system can be used for ex-situ groundwater treatment. That is, groundwater is pumped to the surface to

irrigate these plants. Typically hydroponic systems utilize an artificial soil medium, such as sand mixed

with perlite or vermiculite. As the roots become saturated with contaminants, they are harvested and

disposed of.

5. Phytovolatilization: In this process plants take up water containing organic contaminants and release the

contaminants into the air through their leaves.

6. Phytodegradation: In this process plants actually metabolise and destroy contaminants within plant

tissues.

7. Hydraulic Control: In this process trees indirectly remediate by controlling groundwater movement.

Trees act as natural pumps when their roots reach down towards the water table and establish a dense root

mass that takes up large quantities of water. A poplar tree, for example, pulls out of the ground 30 gallons of

water per day, and a cottonwood can absorb up to 350 gallons per day (1gallon= 4.5 litres).

The plants most used and studied are poplar trees. The U.S. Air Force has used poplar trees to contain

trichloroethylene (TCE) in groundwater. In Iowa, EPA demonstrated that poplar trees acted as natural pumps to

keep toxic herbicides, pesticides, and fertilisers out of the streams and groundwater. The US Army Corps of

Engineers has experimented with wetland plants to destroy explosive compounds in the soil and groundwater.

Submersed and floating-leafed species (coontail and pondweed, and arrowhead, respectively) decreased

trinitrotoluene (TNT) to 5% of original concentration. Submersed plants were able to decrease Royal

Demolition Explosive (RDX) levels by 40%, and when microbes were added, RDX decreased by 80%.

Sunflowers, using rhizo filtration, were used successfully to remove radioactive contaminants from pond water

in a test at Chernobyl, Ukraine

The range of biological treatments for environmental problems, as described by the term phytoremediation,

actually consists of several specific processes is summarised below:

1. Phytoextraction - Uptake of substances from the environment, with storage in the plant

(phytoaccumulation)

2. Phytostabilisation - Reducing the movement or transfer of substances in the environment. For

example, limiting the leaching of substances contaminating soil

3. Phytostimulation - Enhancement of microbial activity for the degradation of contaminants,

typically around plant roots

4. Phytotransformation - Uptake of substances from the environment, with degradation occurring

within the plant (phytodegradation)

5. Phytovolatilisation - Removal of substances from the soil or water with release into the air,

possibly after degradation

6. Rhizofiltration - The removal of toxic metals from groundwater

Phytoremediation takes advantage of the nutrient utilisation processes of the plant to take in water and nutrients

through roots, transpire water through leaves, and act as a transformation system to metabolise organic

compounds, such as oil and pesticides. Alternatively they may absorb and bio-accumulate toxic trace elements,

including heavy metals such as lead, cadmium and selenium. Heavy metals are closely related to the elements

plants use for growth. Phytoremediation is an affordable technology that is most useful when contaminants are

within the root zone of the plants (top three to six feet of the soil). For sites with contamination spread over a

large area, phytoremediation may be the only economically feasible technology.

5.2 Where did Phytoremediation originate?

The concept of using plants to clean up their environment is not a new one, but most research in this area was

strictly in studying those few wild plants that actually grew in waste infested areas. It wasn't until Dr. Ilya

Raskin, a Russian born US educated scientist, came along that phytoremediation was actually born. Dr. Raskin,

who not only came up with this new technology involving plants, but also named it, came to the United States in

1976. In 1989, he encountered a company called Envirogen Inc. which used microorganisms to degrade and

clean up oils and chemicals in soil. Dr. Raskin became interested in finding a similar technology to clean up

heavy metals, which these microorganisms fail to do. It was at this point that Dr. Raskin remembered some

reading he did back home. He states: “I remembered reading Russian papers from the 1930's and 1940's about

geobotany, in which they prospected for minerals by looking at the plants. Some plants have a high capability of

accumulating metals from the soil.” These plants gave a clue to what minerals were under the surface, but

couldn't these same plant to use to absorb the metals from the soil? It was then that phytoremediation was born.

Dr. Raskin spent many hours finding those plants that best took metals from their environment.

17 18 5

2. Phyto-stabilization: In this process chemical compounds produced by the plant immobilise contaminants,

rather than degrade them.

3. Phytoaccumulation (also called phytoextraction): In this process plant roots adsorb the contaminants

along with other nutrients and water. The contaminant mass is not destroyed but ends up in the plant shoots

and leaves. This method is used primarily for waste containing metals. At one demonstration site, water-

soluble metals are taken up by plant species selected for their ability to take up large quantities of Lead (Pb).

The metals are stored in the plant's aerial shoots, which are harvested and either smelted for potential metal

recycling/recovery or are disposed of as a hazardous waste. As a general rule, readily bioavailable metals

for plant uptake include Cadmium, Nickel, Zinc, Arsenic, Selenium, and Copper. Moderately bioavailable

metals are Cobalt, Manganese, and Iron. Lead, Chromium, and Uranium are not very bioavailable. Lead can

be made much more bioavailable by the addition of chelating agents to soils. Similarly, the availability of

uranium and radio-cesium 137 can be enhanced using citric acid and ammonium nitrate, respectively.

4. Hydroponic Systems for Treating Water Streams (Rhizofiltration): Rhizofiltration is similar to phyto-

accumulation, but the plants used for cleanup are raised in greenhouses with their roots in water. This

system can be used for ex-situ groundwater treatment. That is, groundwater is pumped to the surface to

irrigate these plants. Typically hydroponic systems utilize an artificial soil medium, such as sand mixed

with perlite or vermiculite. As the roots become saturated with contaminants, they are harvested and

disposed of.

5. Phytovolatilization: In this process plants take up water containing organic contaminants and release the

contaminants into the air through their leaves.

6. Phytodegradation: In this process plants actually metabolise and destroy contaminants within plant

tissues.

7. Hydraulic Control: In this process trees indirectly remediate by controlling groundwater movement.

Trees act as natural pumps when their roots reach down towards the water table and establish a dense root

mass that takes up large quantities of water. A poplar tree, for example, pulls out of the ground 30 gallons of

water per day, and a cottonwood can absorb up to 350 gallons per day (1gallon= 4.5 litres).

The plants most used and studied are poplar trees. The U.S. Air Force has used poplar trees to contain

trichloroethylene (TCE) in groundwater. In Iowa, EPA demonstrated that poplar trees acted as natural pumps to

keep toxic herbicides, pesticides, and fertilisers out of the streams and groundwater. The US Army Corps of

Engineers has experimented with wetland plants to destroy explosive compounds in the soil and groundwater.

Submersed and floating-leafed species (coontail and pondweed, and arrowhead, respectively) decreased

trinitrotoluene (TNT) to 5% of original concentration. Submersed plants were able to decrease Royal

Demolition Explosive (RDX) levels by 40%, and when microbes were added, RDX decreased by 80%.

Sunflowers, using rhizo filtration, were used successfully to remove radioactive contaminants from pond water

in a test at Chernobyl, Ukraine

The range of biological treatments for environmental problems, as described by the term phytoremediation,

actually consists of several specific processes is summarised below:

1. Phytoextraction - Uptake of substances from the environment, with storage in the plant

(phytoaccumulation)

2. Phytostabilisation - Reducing the movement or transfer of substances in the environment. For

example, limiting the leaching of substances contaminating soil

3. Phytostimulation - Enhancement of microbial activity for the degradation of contaminants,

typically around plant roots

4. Phytotransformation - Uptake of substances from the environment, with degradation occurring

within the plant (phytodegradation)

5. Phytovolatilisation - Removal of substances from the soil or water with release into the air,

possibly after degradation

6. Rhizofiltration - The removal of toxic metals from groundwater

Phytoremediation takes advantage of the nutrient utilisation processes of the plant to take in water and nutrients

through roots, transpire water through leaves, and act as a transformation system to metabolise organic

compounds, such as oil and pesticides. Alternatively they may absorb and bio-accumulate toxic trace elements,

including heavy metals such as lead, cadmium and selenium. Heavy metals are closely related to the elements

plants use for growth. Phytoremediation is an affordable technology that is most useful when contaminants are

within the root zone of the plants (top three to six feet of the soil). For sites with contamination spread over a

large area, phytoremediation may be the only economically feasible technology.

5.2 Where did Phytoremediation originate?

The concept of using plants to clean up their environment is not a new one, but most research in this area was

strictly in studying those few wild plants that actually grew in waste infested areas. It wasn't until Dr. Ilya

Raskin, a Russian born US educated scientist, came along that phytoremediation was actually born. Dr. Raskin,

who not only came up with this new technology involving plants, but also named it, came to the United States in

1976. In 1989, he encountered a company called Envirogen Inc. which used microorganisms to degrade and

clean up oils and chemicals in soil. Dr. Raskin became interested in finding a similar technology to clean up

heavy metals, which these microorganisms fail to do. It was at this point that Dr. Raskin remembered some

reading he did back home. He states: “I remembered reading Russian papers from the 1930's and 1940's about

geobotany, in which they prospected for minerals by looking at the plants. Some plants have a high capability of

accumulating metals from the soil.” These plants gave a clue to what minerals were under the surface, but

couldn't these same plant to use to absorb the metals from the soil? It was then that phytoremediation was born.

Dr. Raskin spent many hours finding those plants that best took metals from their environment.

19 20

5.3 Applications of Phytoremediation

Phytoremediation can and has been used to clean up metals, pesticides, solvents, explosives, crude oil,

polyaromatic hydrocarbons, land fill leachates, agricultural runoff, acid mine drainage, and radioactive

contamination.

Phytoremediation is an environmentally friendly, safe and cost effective way to clean up contaminants. Early

estimates on the costs have shown that plants could do the same job as a group of engineers for one tenth of the

cost. The plants are also more pleasing to look at than many such operations are. The soil or water need not be

gathered in a stored as hazardous waste, requiring large amounts of land, money, and manpower.

Plants can be raised, watered, and then harvested with less manpower. If need be, the storage of the harvested

plants as hazardous waste would incur lesser amount. The main drawback of the use of this technology is that it

isn't good for all sites. If the contamination runs too deep or the contaminant concentration is too large, the plants

alone can't efficiently remediate the contaminated site.

Sites where phytoremediation has been used include Chernobyl where sunflowers were used to remove cesium

137 and strontium 90. Hybrid poplars have been used in Whitewood Creek in South Dakota to absorb arsenic

from mine wastes and in Maryland to remove trichloroethylene and polycyclic aromatic compounds from

groundwater.

5.4 Mechanisms for Phytoremediation

Phytoremediation uses one basic concept - the plant takes the pollutant through the roots. The pollutant can be

stored in the plant (phyto-extraction), volatized by the plant (phyto-volatization) metabolized by the plant

(phyto-degradation), or any combination of the above. However, Phytoremediation is more than just planting

and letting the foliage grow; the site must be engineered to prevent erosion and flooding and maximize pollutant

uptake. There are 3 main planting techniques for phytoremediation.

1. Growing plants on the land, like crops. This technique is most useful when the contaminant is within the

plant root zone, typically 3 - 6 feet (Ecological Engineering, 1997), or the tree root zone, typically 10-15

feet (T. Crossman, personal communication, November 18, 1997).

2. Growing plants in water (aquaculture). Water from deeper aquifers can be pumped out of the ground

and circulated through a "reactor" of plants and then used in an application where it is returned to the

earth (e.g. irrigation).

3. Growing trees on the land and constructing wells through which tree roots can grow. This method

can remediate deeper aquifers in-situ. The wells provide an artery for tree roots to grow toward the

water and form a root system in the capillary fringe

5.5 Selection of PlantThe majority of current research in the phytoremediation field revolves around determining which plant works

most efficiently in a given application. Not all plant species will metabolise, volatise, and/or accumulate

pollutants in the same manner. The goal is to ascertain which plants are most effective at remediating a given

pollutant.

5

Research has yielded some general guidelines for groundwater phytoremediation plants. The plant must grow

quickly and consume large quantities of water in a short time. A good plant would also be able to remediate more

than one pollutant because pollution rarely occurs as a single compound. Phytoremediation has been shown to

work on metals and moderately hydrophobic compounds such as BTEX compounds, chlorinated solvents,

ammunition wastes, and nitrogen compounds. Table 5.1 shows a partial listing of plants and which pollutants

they are capable of remediating. Table 5.2 shows a partial listing of current remediation projects to give the

reader an idea of remediation possibilities.

Sunflowers absorb lead, arsenic, zinc, chromium, copper, and manganese, and were successfully used to clean

up uranium and strontium-90 from contaminated soil in the Ukraine after the Chernobyl disaster, the worst

nuclear power plant accident in history. The common mulberry tree (M. rubra) has been shown to release

chemicals that support the growth of bacteria that break down PCBs, and willow trees absorb cadmium, zinc,

and copper. For removing lead from soil, most members of the Brassica family will do the trick, Kale, mustard

greens, collards, broccoli, and so forth. The water hyacinth naturally absorbs pollutants from water, including

cadmium, chromium, mercury, lead, zinc, cesium, strontium-90, uranium, and pesticides. It is extremely fast

growing and has lovely blossoms, mostly lavender to pink. It originated in South America but is now an invasive

species all over the place. Water Hyssop (Bacopa monnieri) removes not only lead, but mercury, cadmium and

chromium from bogs and wetlands, and makes a lovely ground cover for muddy shores. It has small ucculent

leaves, and dainty white flowers.

Plant Chemicals

Arabidopsis Mercury

Bladder campion Zinc, Copper

Brassica family (Indian Mustard & Broccoli) Selenium, Sulphur, Lead, Cadmium, Chromium, Nickel, Zinc, Copper,

Cesium, Strontium

Buxaceae (boxwood) Nickel

Compositae family Cesium, Strontium

Euphorbiaceae Nickel

Tomato plant Lead, Zinc, Copper

Trees in the Populus genus Pesticides, Atrazine, (Poplar, Cottonwood) Trichloroethylene (TCE),

Carbon tetrachloride, Nitrogen compounds, 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5 triazine (RDX)

19 20

5.3 Applications of Phytoremediation

Phytoremediation can and has been used to clean up metals, pesticides, solvents, explosives, crude oil,

polyaromatic hydrocarbons, land fill leachates, agricultural runoff, acid mine drainage, and radioactive

contamination.

Phytoremediation is an environmentally friendly, safe and cost effective way to clean up contaminants. Early

estimates on the costs have shown that plants could do the same job as a group of engineers for one tenth of the

cost. The plants are also more pleasing to look at than many such operations are. The soil or water need not be

gathered in a stored as hazardous waste, requiring large amounts of land, money, and manpower.

Plants can be raised, watered, and then harvested with less manpower. If need be, the storage of the harvested

plants as hazardous waste would incur lesser amount. The main drawback of the use of this technology is that it

isn't good for all sites. If the contamination runs too deep or the contaminant concentration is too large, the plants

alone can't efficiently remediate the contaminated site.

Sites where phytoremediation has been used include Chernobyl where sunflowers were used to remove cesium

137 and strontium 90. Hybrid poplars have been used in Whitewood Creek in South Dakota to absorb arsenic

from mine wastes and in Maryland to remove trichloroethylene and polycyclic aromatic compounds from

groundwater.

5.4 Mechanisms for Phytoremediation

Phytoremediation uses one basic concept - the plant takes the pollutant through the roots. The pollutant can be

stored in the plant (phyto-extraction), volatized by the plant (phyto-volatization) metabolized by the plant

(phyto-degradation), or any combination of the above. However, Phytoremediation is more than just planting

and letting the foliage grow; the site must be engineered to prevent erosion and flooding and maximize pollutant

uptake. There are 3 main planting techniques for phytoremediation.

1. Growing plants on the land, like crops. This technique is most useful when the contaminant is within the

plant root zone, typically 3 - 6 feet (Ecological Engineering, 1997), or the tree root zone, typically 10-15

feet (T. Crossman, personal communication, November 18, 1997).

2. Growing plants in water (aquaculture). Water from deeper aquifers can be pumped out of the ground

and circulated through a "reactor" of plants and then used in an application where it is returned to the

earth (e.g. irrigation).

3. Growing trees on the land and constructing wells through which tree roots can grow. This method

can remediate deeper aquifers in-situ. The wells provide an artery for tree roots to grow toward the

water and form a root system in the capillary fringe

5.5 Selection of PlantThe majority of current research in the phytoremediation field revolves around determining which plant works

most efficiently in a given application. Not all plant species will metabolise, volatise, and/or accumulate

pollutants in the same manner. The goal is to ascertain which plants are most effective at remediating a given

pollutant.

5

Research has yielded some general guidelines for groundwater phytoremediation plants. The plant must grow

quickly and consume large quantities of water in a short time. A good plant would also be able to remediate more

than one pollutant because pollution rarely occurs as a single compound. Phytoremediation has been shown to

work on metals and moderately hydrophobic compounds such as BTEX compounds, chlorinated solvents,

ammunition wastes, and nitrogen compounds. Table 5.1 shows a partial listing of plants and which pollutants

they are capable of remediating. Table 5.2 shows a partial listing of current remediation projects to give the

reader an idea of remediation possibilities.

Sunflowers absorb lead, arsenic, zinc, chromium, copper, and manganese, and were successfully used to clean

up uranium and strontium-90 from contaminated soil in the Ukraine after the Chernobyl disaster, the worst

nuclear power plant accident in history. The common mulberry tree (M. rubra) has been shown to release

chemicals that support the growth of bacteria that break down PCBs, and willow trees absorb cadmium, zinc,

and copper. For removing lead from soil, most members of the Brassica family will do the trick, Kale, mustard

greens, collards, broccoli, and so forth. The water hyacinth naturally absorbs pollutants from water, including

cadmium, chromium, mercury, lead, zinc, cesium, strontium-90, uranium, and pesticides. It is extremely fast

growing and has lovely blossoms, mostly lavender to pink. It originated in South America but is now an invasive

species all over the place. Water Hyssop (Bacopa monnieri) removes not only lead, but mercury, cadmium and

chromium from bogs and wetlands, and makes a lovely ground cover for muddy shores. It has small ucculent

leaves, and dainty white flowers.

Plant Chemicals

Arabidopsis Mercury

Bladder campion Zinc, Copper

Brassica family (Indian Mustard & Broccoli) Selenium, Sulphur, Lead, Cadmium, Chromium, Nickel, Zinc, Copper,

Cesium, Strontium

Buxaceae (boxwood) Nickel

Compositae family Cesium, Strontium

Euphorbiaceae Nickel

Tomato plant Lead, Zinc, Copper

Trees in the Populus genus Pesticides, Atrazine, (Poplar, Cottonwood) Trichloroethylene (TCE),

Carbon tetrachloride, Nitrogen compounds, 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5 triazine (RDX)

21 22 5

Pennycress Zinc, Cadmium

Sunflower Cesium, Strontium 90, Uranium, Chromium, Zinc

genus Lemna (Duckweed) Explosives wastes

Parrot feather Explosives wastes

Pondweed, arrowroot, coontail TNT, RDX

Perennial rye grass Polychlorinatedphenyls (PCP's), olyaromatichydrocarbons (PAH's)

Table 5.1. Partial listing of plants and chemicals they can remediate.

Plant Chemicals Clean-up numbers Source

Pondweed, TNT & RDX 0.016-0.019 mg of TNT / L per day Betts, 1997

Arrowroot, & 0.133 - 0.291 mg RDX / L per day

Coontail

Poplars Nitrates from From 150 mg/L to 3 mg USEPA, 1996

fertilizers / L in under 3 years

Mustard Greens Lead 45% of the excess was removed Ecological & Pumpkin

Vines Engineering, 1997

Halophytes Salts Reduced the salt levels in the Ecological

soils by 65% Engineering, 1997

Pennycress Zinc & 108 lb / acre per year Chaney, 1995

Cadmium & 1.7 lb / acre per year

— Hydrocarbons From TPH concentrations

greater than 100 ppm to

TPH concentrations less

than 10 ppm in less than

a year.

Poplar Trees Atrazine Lab: 91% of the atrazine Burken & Schnoor, 1997

was taken up in 10 days

Indian Mustard Lead(II), Lab: Concentration in Salt et al, 1997

Seedlings Strontium(II), the plant was

Cadmium(II), 2000-100 times

Nickel(II), the concentration

Cesium(i), in solution

Cromium (IV)

Sugar Beet Nitroglycerin Lab: From 1.8mM GTN Goel et al, 1997

cell cultures (GTN) to undetectable levels in 20 hours

Table 5.2. Partial listing of current remediation possibilities

5.6 Advantages and Limitations of Phytoremediation:

Advantages

1. Aesthetically pleasing.

2. Solar driven.

3. Works with metals and slightly hydrophobic compounds, including many organics.

4. Can stimulate bioremediation in the soil closely associated with the plant root. Plants can stimulate

microorganisms through the release of nutrients and the transport of oxygen to their roots.

5. Relatively inexpensive - reduced to one- third (Wantanbe, 1997).

6. Even if the plants are contaminated and unusable, the resulting ash is approximately 20-30 tons per

5000 tons soil (Black, 1997).

7. Planting vegetation on a site also reduces erosion by wind and water

8. Can leave usable topsoil intact

21 22 5

Pennycress Zinc, Cadmium

Sunflower Cesium, Strontium 90, Uranium, Chromium, Zinc

genus Lemna (Duckweed) Explosives wastes

Parrot feather Explosives wastes

Pondweed, arrowroot, coontail TNT, RDX

Perennial rye grass Polychlorinatedphenyls (PCP's), olyaromatichydrocarbons (PAH's)

Table 5.1. Partial listing of plants and chemicals they can remediate.

Plant Chemicals Clean-up numbers Source

Pondweed, TNT & RDX 0.016-0.019 mg of TNT / L per day Betts, 1997

Arrowroot, & 0.133 - 0.291 mg RDX / L per day

Coontail

Poplars Nitrates from From 150 mg/L to 3 mg USEPA, 1996

fertilizers / L in under 3 years

Mustard Greens Lead 45% of the excess was removed Ecological & Pumpkin

Vines Engineering, 1997

Halophytes Salts Reduced the salt levels in the Ecological

soils by 65% Engineering, 1997

Pennycress Zinc & 108 lb / acre per year Chaney, 1995

Cadmium & 1.7 lb / acre per year

— Hydrocarbons From TPH concentrations

greater than 100 ppm to

TPH concentrations less

than 10 ppm in less than

a year.

Poplar Trees Atrazine Lab: 91% of the atrazine Burken & Schnoor, 1997

was taken up in 10 days

Indian Mustard Lead(II), Lab: Concentration in Salt et al, 1997

Seedlings Strontium(II), the plant was

Cadmium(II), 2000-100 times

Nickel(II), the concentration

Cesium(i), in solution

Cromium (IV)

Sugar Beet Nitroglycerin Lab: From 1.8mM GTN Goel et al, 1997

cell cultures (GTN) to undetectable levels in 20 hours

Table 5.2. Partial listing of current remediation possibilities

5.6 Advantages and Limitations of Phytoremediation:

Advantages

1. Aesthetically pleasing.

2. Solar driven.

3. Works with metals and slightly hydrophobic compounds, including many organics.

4. Can stimulate bioremediation in the soil closely associated with the plant root. Plants can stimulate

microorganisms through the release of nutrients and the transport of oxygen to their roots.

5. Relatively inexpensive - reduced to one- third (Wantanbe, 1997).

6. Even if the plants are contaminated and unusable, the resulting ash is approximately 20-30 tons per

5000 tons soil (Black, 1997).

7. Planting vegetation on a site also reduces erosion by wind and water

8. Can leave usable topsoil intact

23 24 5

Limitations

1. Can take many growing seasons to clean up a site, the success of phytoremediation may be seasonal,

depending on location. Other climatic factors will also influence its effectiveness.

2. Phytoremediation requires a large surface area of land for remediation.

3. The toxicity and bioavailability of biodegradation products is not always known. Degradation by-

products may be mobilized in groundwater or bio-accumulated in animals. Additional research is

needed to determine the fate of various compounds in the plant metabolic cycle to ensure that plant

droppings and products do not contribute toxic or harmful chemicals into the food chain.

4. Disposal of harvested plants can be a problem if they contain high levels of heavy metals.

5. Plants that absorb toxic materials may contaminate the food chain.

6. Returning the water to the earth after aquaculture must be permitted.

7. Less efficient for hydrophobic contaminants, which bind tightly to soil.

8. Phytoremediation is not effective for strongly adsorbed contaminants such as polychlorinated

biphenyls (PCBs).

5.7 Applicability

Phytoremediation is used for the remediation of heavy metals, radionuclides, pesticides, explosives, fuels,

volatile organic compounds (VOC's) and semi-volatile organic compounds (SVOCs).

6.0 Case Studies

6.1 Case Study 1. Phytoremediation of solid waste in CETP Banthar

Phytoremediation: Phytoremediation is the use of certain features of plants, such as their biological processes or physical characteristics, to remediate contaminated media. It can include a number of methods that can address a variety of contaminants and media depending upon the cases concerned. This process immobilizes the contaminants in the local soil. For optimum effectiveness, the various forms of phytoremediation require different characteristics in the plants used. In general, terrestrial plants are more likely to be effective for phytoremediation than aquatic plants because their root systems are larger. This technique can be used to contain, remove, extract, or destroy contaminants.

Fig 6.1 Phytoremediation site: Some of the Plants are still preserved

Some green plants/trees at CETP Unnao used for waste treatment through Phytoremedaition Technology along with NBRI

Lucknow (detailed data lies with NBRI Lucknow). CETP Unnao further studied that Indian mustard and grasses (such as ryegrass

and prairie grasses) are found very effective in phyto-stabilisation process.

Introduction:

Leather industry is one of the important industries in India as it earns a significant proportion of foreign

exchange. It is also the major reason for the environmental invasion of chromium (Cr). The effluent and sludge

disposed from these industries into recipient water bodies and onto land has led to extensive degradation of

environment. Cleaning up of the Chromium contaminated sites is a challenging task. Phytoremediation

23 24 6

Limitations

1. Can take many growing seasons to clean up a site, the success of phytoremediation may be seasonal,

depending on location. Other climatic factors will also influence its effectiveness.

2. Phytoremediation requires a large surface area of land for remediation.

3. The toxicity and bioavailability of biodegradation products is not always known. Degradation by-

products may be mobilized in groundwater or bio-accumulated in animals. Additional research is

needed to determine the fate of various compounds in the plant metabolic cycle to ensure that plant

droppings and products do not contribute toxic or harmful chemicals into the food chain.

4. Disposal of harvested plants can be a problem if they contain high levels of heavy metals.

5. Plants that absorb toxic materials may contaminate the food chain.

6. Returning the water to the earth after aquaculture must be permitted.

7. Less efficient for hydrophobic contaminants, which bind tightly to soil.

8. Phytoremediation is not effective for strongly adsorbed contaminants such as polychlorinated

biphenyls (PCBs).

5.7 Applicability

Phytoremediation is used for the remediation of heavy metals, radionuclides, pesticides, explosives, fuels,

volatile organic compounds (VOC's) and semi-volatile organic compounds (SVOCs).

6.0 Case Studies

6.1 Case Study 1. Phytoremediation of solid waste in CETP Banthar

Phytoremediation: Phytoremediation is the use of certain features of plants, such as their biological processes or physical characteristics, to remediate contaminated media. It can include a number of methods that can address a variety of contaminants and media depending upon the cases concerned. This process immobilizes the contaminants in the local soil. For optimum effectiveness, the various forms of phytoremediation require different characteristics in the plants used. In general, terrestrial plants are more likely to be effective for phytoremediation than aquatic plants because their root systems are larger. This technique can be used to contain, remove, extract, or destroy contaminants.

Fig 6.1 Phytoremediation site: Some of the Plants are still preserved

Some green plants/trees at CETP Unnao used for waste treatment through Phytoremedaition Technology along with NBRI

Lucknow (detailed data lies with NBRI Lucknow). CETP Unnao further studied that Indian mustard and grasses (such as ryegrass

and prairie grasses) are found very effective in phyto-stabilisation process.

Introduction:

Leather industry is one of the important industries in India as it earns a significant proportion of foreign

exchange. It is also the major reason for the environmental invasion of chromium (Cr). The effluent and sludge

disposed from these industries into recipient water bodies and onto land has led to extensive degradation of

environment. Cleaning up of the Chromium contaminated sites is a challenging task. Phytoremediation

25 26 6

involves the use of selective green plants to remove/reduce effect of toxic substances from the environment. The

use of plants has been investigated for a wide variety of chemical substances, including metal and organic

contaminants, in various media, most commonly soil and water. It is an emerging technology that can be

considered for remediation of contaminated sites because of its cost effectiveness, aesthetic advantages, and

long term utility as an innovative technology for wastewater and solid waste management. Though many small

herbs have been successfully proved to accumulating heavy metal ions like chromium, the burden of harvesting

and disposing the one season plants poses greater difficulty in applying the bioremediation. Hence large plants

with long period of life and soil covering and transpiration potentials could be the best choice. On this basis an

attempt was made to treat saline and chrome contaminated hazardous solid waste using Arjuna indica, Acacia,

Eucalyptus and other trees at CETP Unnao, under the technical guidance of Dr. S. Awasthi, CEO,

CETP/UTPCC, where about 1000 trees were grown applying hydroponic studies, pot culture and by field

experiments for the remediation of chromium contamination with the collaboration of National Botanical

Research Institute (NBRI) Lucknow.

Fig 6.2 A Pictorial view of CETP Unnao having planted certain trees under integrated bioremediation and phtoremediation technology

to treat chrome bearing biological and primary sludge recovered from tannery effluent in CETP process. Picture status as on April 2011.

Methodology for Phytoremediation of chrome waste:

Chromium concentrations were selected based on previous hydroponic studies of annual plants (Shanker et al.,

2004). Chromium was used at levels such as 10, 25, 50, 100, 150 mM in the experiments. Soil amended with

various levels of tannery sludge (10%, 20%, 40%, 60%, 80% and 100%) was prepared and filled into the pots

and a pot with only garden soil served as control. All the experiments were conducted in duplicate sets. Based on

these results, field trials were conducted to evaluate the metal accumulation.

Measurement of chromium content (mg/Kg) was made on plant parts according to Jones et al. (1991).

Results and Discussion:

Plants have the genetic potential to clean up soil contaminated with toxic metals. Some plants can take up,

translocate, and tolerate increased levels of certain heavy metals that could be toxic to any other known

organisms. Identification of metal hyper-accumulator species has been an impetus for Phytoremediation

research. In the present study, a significantly high accumulation of heavy metals was found in various parts of

the Azadirachta indica, grown on hydroponic and tannery sludge amended soil. It was observed that under

normal control conditions, the concentration of Cr in various parts of the plant was < 1 mg/Kg dry weight (DW)

of plant tissues. The accumulation of hexavalent chromium Cr (VI) in hydroponics experiment of Azadirachta

indica was found maximum in shoots followed by roots and leaves which increased with increase in chromium

amendments (Fig.7.3).

Fig. 6.3. Azadirachta indica grown at various concentrations of chromium (VI).

Of the total amount of chromium accumulated by Azadirachta indica 95.16% was in the shoots and 4.63% in

roots. However, chromium accumulation in the leaf was quiet low or very negligible when compared to stem

and roots (Fig.6.4).

25 26 6

involves the use of selective green plants to remove/reduce effect of toxic substances from the environment. The

use of plants has been investigated for a wide variety of chemical substances, including metal and organic

contaminants, in various media, most commonly soil and water. It is an emerging technology that can be

considered for remediation of contaminated sites because of its cost effectiveness, aesthetic advantages, and

long term utility as an innovative technology for wastewater and solid waste management. Though many small

herbs have been successfully proved to accumulating heavy metal ions like chromium, the burden of harvesting

and disposing the one season plants poses greater difficulty in applying the bioremediation. Hence large plants

with long period of life and soil covering and transpiration potentials could be the best choice. On this basis an

attempt was made to treat saline and chrome contaminated hazardous solid waste using Arjuna indica, Acacia,

Eucalyptus and other trees at CETP Unnao, under the technical guidance of Dr. S. Awasthi, CEO,

CETP/UTPCC, where about 1000 trees were grown applying hydroponic studies, pot culture and by field

experiments for the remediation of chromium contamination with the collaboration of National Botanical

Research Institute (NBRI) Lucknow.

Fig 6.2 A Pictorial view of CETP Unnao having planted certain trees under integrated bioremediation and phtoremediation technology

to treat chrome bearing biological and primary sludge recovered from tannery effluent in CETP process. Picture status as on April 2011.

Methodology for Phytoremediation of chrome waste:

Chromium concentrations were selected based on previous hydroponic studies of annual plants (Shanker et al.,

2004). Chromium was used at levels such as 10, 25, 50, 100, 150 mM in the experiments. Soil amended with

various levels of tannery sludge (10%, 20%, 40%, 60%, 80% and 100%) was prepared and filled into the pots

and a pot with only garden soil served as control. All the experiments were conducted in duplicate sets. Based on

these results, field trials were conducted to evaluate the metal accumulation.

Measurement of chromium content (mg/Kg) was made on plant parts according to Jones et al. (1991).

Results and Discussion:

Plants have the genetic potential to clean up soil contaminated with toxic metals. Some plants can take up,

translocate, and tolerate increased levels of certain heavy metals that could be toxic to any other known

organisms. Identification of metal hyper-accumulator species has been an impetus for Phytoremediation

research. In the present study, a significantly high accumulation of heavy metals was found in various parts of

the Azadirachta indica, grown on hydroponic and tannery sludge amended soil. It was observed that under

normal control conditions, the concentration of Cr in various parts of the plant was < 1 mg/Kg dry weight (DW)

of plant tissues. The accumulation of hexavalent chromium Cr (VI) in hydroponics experiment of Azadirachta

indica was found maximum in shoots followed by roots and leaves which increased with increase in chromium

amendments (Fig.7.3).

Fig. 6.3. Azadirachta indica grown at various concentrations of chromium (VI).

Of the total amount of chromium accumulated by Azadirachta indica 95.16% was in the shoots and 4.63% in

roots. However, chromium accumulation in the leaf was quiet low or very negligible when compared to stem

and roots (Fig.6.4).

27 28 6

Fig. 6.4. Accumulation of Chromium (VI) in different parts of A. indica.

Presence of Cr in the external environment does not lead to any changes in the growth and development pattern

of the plants at the initial low concentrations. While, Hasselgren (1999) found stem biomass production of three

willow clones was enhanced by sludge application rate; it also led to more uniform growth and a greater shoot

number than in control plants. But Sinapsis alba showed reduction in plant height at 200 – 400 mg chromium per

kilogram soil (Hanus and Tomas, 1993).

Parameter Control Cr (VI) Cr (VI) Cr (VI) Cr (VI) Cr (VI)(10 µM) (25 µM) (50 µM) (100 µM) (150 µM)

Shoot 9.48 ±0.6 9.12 ±0.1 8.42 ±0.6 7.63 ±0.3 6.91 ±0.5 6.75 ±0.6length (cm)

Root 6.97 ±0.1 4.06 ±0.4 4.29 ±0.2 3.87 ±0.1 3.98 ±0.2 3.06 ±0.4length (cm)

Total leaf 16.3 ±2.1 16.7 ±0.9 15.6 ±1.1 14.68 ±1.9 14.7 ±2.3 13.73 ±2.3area (cm2)

Shoot dry 0.028 ±0.003 0.028 ±0.006 0.029 ±0.006 0.024 ±0.004 0.015 ±0.006 0.012 ±0.006weight (g)

Root dry 0.099 ±0.009 0.056 ±0.018 0.052 ±0.018 0.045 ±0.07 0.043 ±0.018 0.041 ±0.018weight (g)

Table 6.1 Growth parameters of Azadirachta indica as influenced by Cr(VI) in nutrient medium after

120 h of treatment.

500

400

300

200

100

25 50 100 150

mg

\Kg

dry

wt

Chromium concentration (mM)

0 5 10

Shoot Root

In pot studies also the test plant accumulated higher amount of chromium in the stem followed by roots and

leaves; but the chromium accumulation in the shoot was over 2 and 28 fold when compared to the root and leaf

respectively (Table 6.2). The accumulation of Cr increased with increase in sludge amendments and exposure

periods as observed by Hasselgren (1999). Whereas, Huffman and Allaway (1973) have reported as much as

98% chromium accumulation in the roots of bean plants. The reason for the high accumulation in roots of the

plants could be because chromium is immobilized in the vacuoles of the root cells (Shanker et al., 2004). Khan

(2000) further reported the potential of mycorhiza in protecting tree species Populus euroamericana, Acacia

arabica and Dalbergia sissoo against the harmful effects of chromium contaminated tannery effluent polluted

soil.

Plant Tannery sludge ( % )parts

10 20 40 60 80 100

Root 48.43 ± 0.90 71.43 ± 0.95 94.26 ± 0.86 110.40 ± 0.72 253.03 ± 1.35 341.66 ± 1.60

Shoot 242.13 ± 1.55 451.43 ± 1.25 597.93 ± 0.47 785.26 ± 1.27 896.36 ± 2.85 1021 ± 2.25

Leaves 17.03 ± 1.15 21.93 ± 0.41 25.50 ± 0.72 29.16 ± 1.30 35.00 ± 1.50 36.66 ± 0.85

*mg/Kg tissue (DW)

Table 6.2 Accumulation of Cr* in A. indica treated with tannery sludge in pot experiment.

In the field experiment, the test plant also showed higher accumulation of Cr in stem tissues. Thus Azadirachta

indica was not only able to tolerate very high concentrations of chromium but also showed appreciable growth

over control plants (Fig.6.5). Similar results have been recorded in 16 Salix clones grown in a field trial (Watson,

2002; Pulford et al., 2002). Therefore, Azardirachta indica could be potentially exploited in phyto remediation

practices like soil reclamation, phyto extraction of metals like Cr from tannery effluent amended soil.

Fig. 6.5. Growth of Azadirachta indica plants in tannery sludge amended soil

27 28 6

Fig. 6.4. Accumulation of Chromium (VI) in different parts of A. indica.

Presence of Cr in the external environment does not lead to any changes in the growth and development pattern

of the plants at the initial low concentrations. While, Hasselgren (1999) found stem biomass production of three

willow clones was enhanced by sludge application rate; it also led to more uniform growth and a greater shoot

number than in control plants. But Sinapsis alba showed reduction in plant height at 200 – 400 mg chromium per

kilogram soil (Hanus and Tomas, 1993).

Parameter Control Cr (VI) Cr (VI) Cr (VI) Cr (VI) Cr (VI)(10 µM) (25 µM) (50 µM) (100 µM) (150 µM)

Shoot 9.48 ±0.6 9.12 ±0.1 8.42 ±0.6 7.63 ±0.3 6.91 ±0.5 6.75 ±0.6length (cm)

Root 6.97 ±0.1 4.06 ±0.4 4.29 ±0.2 3.87 ±0.1 3.98 ±0.2 3.06 ±0.4length (cm)

Total leaf 16.3 ±2.1 16.7 ±0.9 15.6 ±1.1 14.68 ±1.9 14.7 ±2.3 13.73 ±2.3area (cm2)

Shoot dry 0.028 ±0.003 0.028 ±0.006 0.029 ±0.006 0.024 ±0.004 0.015 ±0.006 0.012 ±0.006weight (g)

Root dry 0.099 ±0.009 0.056 ±0.018 0.052 ±0.018 0.045 ±0.07 0.043 ±0.018 0.041 ±0.018weight (g)

Table 6.1 Growth parameters of Azadirachta indica as influenced by Cr(VI) in nutrient medium after

120 h of treatment.

500

400

300

200

100

25 50 100 150

mg

\Kg

dry

wt

Chromium concentration (mM)

0 5 10

Shoot Root

In pot studies also the test plant accumulated higher amount of chromium in the stem followed by roots and

leaves; but the chromium accumulation in the shoot was over 2 and 28 fold when compared to the root and leaf

respectively (Table 6.2). The accumulation of Cr increased with increase in sludge amendments and exposure

periods as observed by Hasselgren (1999). Whereas, Huffman and Allaway (1973) have reported as much as

98% chromium accumulation in the roots of bean plants. The reason for the high accumulation in roots of the

plants could be because chromium is immobilized in the vacuoles of the root cells (Shanker et al., 2004). Khan

(2000) further reported the potential of mycorhiza in protecting tree species Populus euroamericana, Acacia

arabica and Dalbergia sissoo against the harmful effects of chromium contaminated tannery effluent polluted

soil.

Plant Tannery sludge ( % )parts

10 20 40 60 80 100

Root 48.43 ± 0.90 71.43 ± 0.95 94.26 ± 0.86 110.40 ± 0.72 253.03 ± 1.35 341.66 ± 1.60

Shoot 242.13 ± 1.55 451.43 ± 1.25 597.93 ± 0.47 785.26 ± 1.27 896.36 ± 2.85 1021 ± 2.25

Leaves 17.03 ± 1.15 21.93 ± 0.41 25.50 ± 0.72 29.16 ± 1.30 35.00 ± 1.50 36.66 ± 0.85

*mg/Kg tissue (DW)

Table 6.2 Accumulation of Cr* in A. indica treated with tannery sludge in pot experiment.

In the field experiment, the test plant also showed higher accumulation of Cr in stem tissues. Thus Azadirachta

indica was not only able to tolerate very high concentrations of chromium but also showed appreciable growth

over control plants (Fig.6.5). Similar results have been recorded in 16 Salix clones grown in a field trial (Watson,

2002; Pulford et al., 2002). Therefore, Azardirachta indica could be potentially exploited in phyto remediation

practices like soil reclamation, phyto extraction of metals like Cr from tannery effluent amended soil.

Fig. 6.5. Growth of Azadirachta indica plants in tannery sludge amended soil

3029 6

Plant parts Cr mg/Kg (DW)

Root 16.3 ± 0.02

Leaf 5.2 ± 0.02

Stem 471.5 ± 0.16

Table: 6.3 Accumulation of Cr (VI) in different parts of A. indica in field experiment.

6.2 Case Study 2. A Tamil Nadu Experience

In this study, the feasibility of using Salicornia brachiata as a phytoremediator for accumulation of NaCl

present in tannery wastewater. The plants were grown in pots fed with tannery wastewater with varying + -

concentrations of NaCl. The accumulation of Na and Cl increased with increase in salt concentration of tannery

wastewater offered to the plant. The growth of the plants with respect to root and shoot length decreased with an + -

increase in salt concentration. However, the accumulation of Na and Cl increased with time of growth and plant + - density. 51 % of Na and 33% of Cl were absorbed by the plant at an NaCl concentration of 20,000ppm at high

plant density conditions. Based on the results of trials, Salicornia brachiata was grown on open lands in Tamil

Nadu State, India where tannery wastewater was discharged. The TDS levels of the land decreased from 10 +300ppm to 5500ppm at the end of one year by the growth of S. brachiata. The maximum accumulation of Na

-and Cl was observed during the period July to September. The results of the present work indicate that S.

brachiata can be used to accumulation of sodium chloride from tannery wastewater discharged lands, thereby

contributing towards solving TDS problem arising from the leather sector.

•••

•

Plants contribute to biodegradation by their ability to fix metals due to the presence of proteins called

metallothionins. This ability can be harnessed to extract heavy metals from polluted areas. Phytoremediation is

the use of plants to combat the effects of environmental pollution.

There are four essential requirements for such plants

The plant should be able to absorb the metal via roots.

It should transfer the metal to the leaf canopy.

The plant should be able to store and utilize the material

Mobilization of the metal should be possible. i.e. it should be able to fix the metal that can be

absorbed.

There are natural varieties of plants which do such fixation. Hyper accumulators are those plants which can

absorb and accumulate metals to such high levels which in other similar plant species will be hazardous.

Common examples include the Alpine pennycross and bracken fern. The former absorbs Cadmium and Zinc

while the fern is a hyper accumulator of Arsenic. Plants take up the metal pollutant through their roots and it can

be either remediated for reuse or the entire plant disposed as hazardous waste.

The processes are advantageous where other methods of remediation are costly and not practical. However, the

choice of Phytoremediation should also consider the duration, potential effects on food chain, and high toxic

levels of contaminants where it would be difficult to establish the vegetation.

Phytoremediation Technologies: Project Management Requirements

Developing and managing phytoremediation technology systems are similar to any in situ remediation system.

To successfully remediate a particular site, six numbers of the general phases exist which require specific skills

necessary to understand the particular site conditions, treatment mechanism, design layout, and evaluation

parameters:

• Assessment

• Remedy selection

• Designing

• Implementation

• Operation, maintenance, and monitoring (OM&M)

Though discrete, these phases form a continuum and sometimes an iterative process to design an optimal phyto-

remedial-technology system for a contaminated site. The following sections describe unique characteristics and

functions required for each of these phases to reliably apply phyto-remedial-technologies to address impacted

soils, sediments, and/or groundwater.

3029 6

Plant parts Cr mg/Kg (DW)

Root 16.3 ± 0.02

Leaf 5.2 ± 0.02

Stem 471.5 ± 0.16

Table: 6.3 Accumulation of Cr (VI) in different parts of A. indica in field experiment.

6.2 Case Study 2. A Tamil Nadu Experience

In this study, the feasibility of using Salicornia brachiata as a phytoremediator for accumulation of NaCl

present in tannery wastewater. The plants were grown in pots fed with tannery wastewater with varying + -

concentrations of NaCl. The accumulation of Na and Cl increased with increase in salt concentration of tannery

wastewater offered to the plant. The growth of the plants with respect to root and shoot length decreased with an + -

increase in salt concentration. However, the accumulation of Na and Cl increased with time of growth and plant + - density. 51 % of Na and 33% of Cl were absorbed by the plant at an NaCl concentration of 20,000ppm at high

plant density conditions. Based on the results of trials, Salicornia brachiata was grown on open lands in Tamil

Nadu State, India where tannery wastewater was discharged. The TDS levels of the land decreased from 10 +300ppm to 5500ppm at the end of one year by the growth of S. brachiata. The maximum accumulation of Na

-and Cl was observed during the period July to September. The results of the present work indicate that S.

brachiata can be used to accumulation of sodium chloride from tannery wastewater discharged lands, thereby

contributing towards solving TDS problem arising from the leather sector.

•••

•

Plants contribute to biodegradation by their ability to fix metals due to the presence of proteins called

metallothionins. This ability can be harnessed to extract heavy metals from polluted areas. Phytoremediation is

the use of plants to combat the effects of environmental pollution.

There are four essential requirements for such plants

The plant should be able to absorb the metal via roots.

It should transfer the metal to the leaf canopy.

The plant should be able to store and utilize the material

Mobilization of the metal should be possible. i.e. it should be able to fix the metal that can be

absorbed.

There are natural varieties of plants which do such fixation. Hyper accumulators are those plants which can

absorb and accumulate metals to such high levels which in other similar plant species will be hazardous.

Common examples include the Alpine pennycross and bracken fern. The former absorbs Cadmium and Zinc

while the fern is a hyper accumulator of Arsenic. Plants take up the metal pollutant through their roots and it can

be either remediated for reuse or the entire plant disposed as hazardous waste.

The processes are advantageous where other methods of remediation are costly and not practical. However, the

choice of Phytoremediation should also consider the duration, potential effects on food chain, and high toxic

levels of contaminants where it would be difficult to establish the vegetation.

Phytoremediation Technologies: Project Management Requirements

Developing and managing phytoremediation technology systems are similar to any in situ remediation system.

To successfully remediate a particular site, six numbers of the general phases exist which require specific skills

necessary to understand the particular site conditions, treatment mechanism, design layout, and evaluation

parameters:

• Assessment

• Remedy selection

• Designing

• Implementation

• Operation, maintenance, and monitoring (OM&M)

Though discrete, these phases form a continuum and sometimes an iterative process to design an optimal phyto-

remedial-technology system for a contaminated site. The following sections describe unique characteristics and

functions required for each of these phases to reliably apply phyto-remedial-technologies to address impacted

soils, sediments, and/or groundwater.

31 32

• Alexander, Martin. Biodegradation and Bioremediation. San Diego, Academic Press, 1994.15

• Alvarez-Cohen, Lisa. Engineering Challenges of Implementing In Situ Bioremediation. University of

California, Berkeley, California, 1993.

• Flathman, P., D.E. Jerger, J.H. Exner. Bioremediation Field Experience. Boca Raton, Lewis

Publishers, 1994.

• Glazer AN, Nikaido H. 1995 Mcirobial biotechnology: Fundamentals of applied microbiology,

Freeman, New York

• Hasselgren K. 1999. Utilisation of sewage sludge in short-rotation energy forestry: a pilot study. Waste

Manage Res;17:251–62. India. Fourth international conference on the biogeochemistry of trace

elements.

• Jones,B., Wolf,B., Mills,H.A., 1991. Plant analysis handbook: a practical sampling, preparation,

Analysis and Interpretation Guide. Micro-Macro International, Athens, GA. University of California,

Berkeley, USA. June 23-26, pp 771-772.

• Khan AG, Kuek C, Chaudhry TM, Khoo CS and Hayes WJ. 2000. Role of plants, mycorrhizae and

phytochelators in heavy metal contaminated land remediation. Chemosphere;41:197–207.

• King, R.B., G.M. Long, and J.K. Sheldon. Practical Environmental Bioremediation The Field Guide.

Boca Raton, Lewis Publishers, 1998.

• Moncur. M.C, Ptacek. C.J, Blowes. D.W, Jambor. J.L, (2005). Release, transport, and attenuation of

metals from an old tailings impoundment, Applied Geochemistry 20:639–659.

• National Research Council. In Situ Bioremediation When Does it Work? Washington,D.C., National

Academy Press, 1993.

• Papp, J.F., Mineral Commodity Summaries 2001: Chromium, U.S. Department of the Interior, U.S.

Geological Survey, Washington, DC, 2001.

• Pulford ID, Riddell-Black D and Stewart C. 2002. Heavy metal uptake by willow clones from sewage

sludge-treated soil: the potential for phytoremediation. Int. J. Phytoremediation;4:59–72.

References

• Rama Krishna, K and Ligy Philip, 2005., Bioremediation of Cr(VI) in contaminated soils, Journal of

Hazardous Materials B121 (2005) 109–117

• Ramasamy, K. 1997. Tannery effluent related pollution on land and water ecosytems in Raskin, I. and

B.D. Ensley (Eds.), 2000. Phytoremediation of Toxic Metals: Using Plants to Clean up the

Environment, John Wiley, New York.

• Shanker A. K, Djanaguiraman, M., Sudhagar, R., Chandrashekar, C.N and Pathmanabhan G. 2004.

Differential antioxidative response of ascorbate glutathione pathway enzymes and metabolites to

chromium speciation stress in green gram (Vigna radiata (L) R Wilczek, cv CO 4) roots. Plant Sci ,

166:1035– 43.

• Vidali M, 2001. Bioremediation, an overview. Pure Appl. Chem., Vol. 73, No. 7, pp. 1163–1172.

• Watson C, Pulford ID and Riddell-Black D. 1999. Heavy metal toxicity responses of two willow

(Salix) varieties grown hydroponically: development of a tolerance screening test. Environ Geochem

Health; 21:359– 64.

• Watson, C. 2002. The phytoremediation potential of Salix: studies of the interaction of heavy metals

and willows. PhD thesis, University of Glasgow.

• Zahir, Eid. 1996. Characterization and Treatment of the soil of an industrial site contaminated with

Cr(VI), J. Environ. Sci. Health A 31 (1) (1996) 227–247.

31 32

• Alexander, Martin. Biodegradation and Bioremediation. San Diego, Academic Press, 1994.15

• Alvarez-Cohen, Lisa. Engineering Challenges of Implementing In Situ Bioremediation. University of

California, Berkeley, California, 1993.

• Flathman, P., D.E. Jerger, J.H. Exner. Bioremediation Field Experience. Boca Raton, Lewis

Publishers, 1994.

• Glazer AN, Nikaido H. 1995 Mcirobial biotechnology: Fundamentals of applied microbiology,

Freeman, New York

• Hasselgren K. 1999. Utilisation of sewage sludge in short-rotation energy forestry: a pilot study. Waste

Manage Res;17:251–62. India. Fourth international conference on the biogeochemistry of trace

elements.

• Jones,B., Wolf,B., Mills,H.A., 1991. Plant analysis handbook: a practical sampling, preparation,

Analysis and Interpretation Guide. Micro-Macro International, Athens, GA. University of California,

Berkeley, USA. June 23-26, pp 771-772.

• Khan AG, Kuek C, Chaudhry TM, Khoo CS and Hayes WJ. 2000. Role of plants, mycorrhizae and

phytochelators in heavy metal contaminated land remediation. Chemosphere;41:197–207.

• King, R.B., G.M. Long, and J.K. Sheldon. Practical Environmental Bioremediation The Field Guide.

Boca Raton, Lewis Publishers, 1998.

• Moncur. M.C, Ptacek. C.J, Blowes. D.W, Jambor. J.L, (2005). Release, transport, and attenuation of

metals from an old tailings impoundment, Applied Geochemistry 20:639–659.

• National Research Council. In Situ Bioremediation When Does it Work? Washington,D.C., National

Academy Press, 1993.

• Papp, J.F., Mineral Commodity Summaries 2001: Chromium, U.S. Department of the Interior, U.S.

Geological Survey, Washington, DC, 2001.

• Pulford ID, Riddell-Black D and Stewart C. 2002. Heavy metal uptake by willow clones from sewage

sludge-treated soil: the potential for phytoremediation. Int. J. Phytoremediation;4:59–72.

References

• Rama Krishna, K and Ligy Philip, 2005., Bioremediation of Cr(VI) in contaminated soils, Journal of

Hazardous Materials B121 (2005) 109–117

• Ramasamy, K. 1997. Tannery effluent related pollution on land and water ecosytems in Raskin, I. and

B.D. Ensley (Eds.), 2000. Phytoremediation of Toxic Metals: Using Plants to Clean up the

Environment, John Wiley, New York.

• Shanker A. K, Djanaguiraman, M., Sudhagar, R., Chandrashekar, C.N and Pathmanabhan G. 2004.

Differential antioxidative response of ascorbate glutathione pathway enzymes and metabolites to

chromium speciation stress in green gram (Vigna radiata (L) R Wilczek, cv CO 4) roots. Plant Sci ,

166:1035– 43.

• Vidali M, 2001. Bioremediation, an overview. Pure Appl. Chem., Vol. 73, No. 7, pp. 1163–1172.

• Watson C, Pulford ID and Riddell-Black D. 1999. Heavy metal toxicity responses of two willow

(Salix) varieties grown hydroponically: development of a tolerance screening test. Environ Geochem

Health; 21:359– 64.

• Watson, C. 2002. The phytoremediation potential of Salix: studies of the interaction of heavy metals

and willows. PhD thesis, University of Glasgow.

• Zahir, Eid. 1996. Characterization and Treatment of the soil of an industrial site contaminated with

Cr(VI), J. Environ. Sci. Health A 31 (1) (1996) 227–247.

33 34

1. Description of Phyto-Remedial-Technologies:

Phyto-remedial-technologies use plants to remediate various media impacted with different types of

contaminants. While phyto-remedial-technologies are typically applied in situ, hydroponics allows for ex situ

application. Typical organic contaminants (“organics”) such as petroleum hydrocarbons, gas condensates,

crude oil, chlorinated compounds, pesticides, and explosive compounds can be remediated using phyto-

remedial-technologies. Typical inorganic contaminants (“inorganics”) that can be addressed include salts

(salinity), heavy metals, metalloids, and radioactive materials. Phyto-remedial-technologies can potentially

treat soils, sludge, sediments, groundwater, surface water, wastewater, and storm water. This document

includes guidance for remediating soils, sludge, sediments, groundwater, and storm water. The reader is also

referred to other Interstate Technology & Regulatory Council (ITRC) guidance for wastewater, surface water,

and storm water control (ITRC 2003b, 2005a). Likewise, the reader is referred to similar ITRC guidance on

alternative waste containment and management strategies (ITRC 2003c, 2003d, 2006a, 2006b).

The particular phyto-remedial-technology mechanisms used to address contaminants depend not only on the

type of contaminant and the media affected, but also on the cleanup goals. Typical goals include containment

through stabilization or sequestration, remediation through assimilation, reduction, detoxification,

degradation, metabolization or mineralization, or both.

To achieve these goals, the proper phyto-remedial-technology system must be selected, designed, developed,

implemented, and operated using detailed knowledge of the site layout, soil characteristics, hydrology, climate

conditions, analytical needs, operation and maintenance (O&M) requirements, economics, public perspective,

and regulatory protection of the environment. Many phyto-remediation technologies apply basic and

fundamental information collected from different green-work areas like agriculture, forestry, and horticulture

to environmental problems. Therefore, the best starting place for someone relatively new or unfamiliar with

the technology is a simple review of the plant physiological processes that are exploited through phyto-

remedial-technologies.

1.1 Basic Plant Physiology:

Plants typically grow by sending their roots into the soil and producing leaf and woody material (Figure 1-1).

To accomplish these basic growth habits (Taiz and Zeiger 1991), plants use carbon dioxide to harvest light

energy, convert it into chemical energy, and produce carbon biomass through the processes of photosynthesis

in the leaves and cellular respiration. Plants also take up liquid water and dissolved inorganic nutrients through

the root system, transport them throughout the plant in the xylem, and transpire the water through the leaves as

vapor. While carbon dioxide and water vapor are being exchanged, oxygen is also being released to the

environment. Likewise, photosynthetic chemicals (photosynthates or phytochemicals) are transported

throughout the plant in the phloem, even into the root to be exuded into the surrounding soil. The upward

transport in the xylem and downward transport in the phloem, collectively termed “translocation,” depend on

Annexure I. Phyto-Remedial-Technology Technical and Regulatory Guidance and Decision Trees, Revised the continuous water column that exists throughout the plant. Each biological process contributes to the

remediation or containment of contaminants as described in the following subsections.

Inorganic Nutrition: Thirteen essential inorganic plant nutrients (N, P, K, Ca, Mg, S, Fe, Cl, Zn, Mn, Cu, B,

and Mo) are taken up by the root system as dissolved constituents in soil moisture (Table 1-1). These elements

are required by the plant for growth, development, or reproduction and are acquired either passively in the

transpirational stream (see Section 1.1.3) or actively through transport proteins associated with the root

membrane. Once inside the root system, the dissolved nutrients can be transported throughout the remainder of

the plant through the vascular system (xylem).In addition to these essential nutrients, other nonessential

inorganics such as various common contaminants (salts, Pb, Cd, As, etc.) can be taken up as well. Again, this

uptake process can be either passive in the transpirational stream or active by substituting for the essential

nutrient on the transport protein. These processes are relevant to phytoextraction (see Section 1.2.4) and

certain applications of phytoremediation groundcovers (see Section 1.3.3). Since these other inorganics are

not essential to the plant and may represent potential toxins at high concentrations, the plant also contains

various mechanisms to sequester or stabilize these extraneous inorganics and prevent transport into the more

sensitive tissues of the plant. These processes are relevant to phytosequestration mechanisms (see Section

1.2.1) and certain phytostabilisation covers (see Section 1.3.1).

1.2 Mechanisms

The basic physiological processes described in the previous section are the bases for the various phyto-

remedial-technology mechanisms that can be used to clean up contaminated sites. Table 1-3 summarizes the

specific mechanisms along with the applicable cleanup goals. The mechanisms are listed in the same order as

the sequence of how contaminants come into contact with the transpiration stream, rhizosphere, and plant

system. These mechanisms are interrelated and dependent upon the precursors. Therefore, in any given phyto-

remedial-technology application, multiple mechanisms may be involved and can be exploited depending on

the designed application (see Section 1.3).

Summary of phytoremediation-technology mechanisms:

Mechanism Description Cleanup goal

1. Phytosequestration: The ability of plants to sequester certain contaminants in the rhizosphere through

exudation of phytochemicals and on the root through transport proteins and cellular processes

Containment.

2. Rhizodegradation: Exuded phytochemicals can enhance microbial biodegradation of contaminants in the

rhizosphere Remediation by destruction.

3. Phytohydraulics: The ability of plants to capture and evaporate water off the plant and take up and

transpire water through the plant Containment by controlling hydrology.

33 34

1. Description of Phyto-Remedial-Technologies:

Phyto-remedial-technologies use plants to remediate various media impacted with different types of

contaminants. While phyto-remedial-technologies are typically applied in situ, hydroponics allows for ex situ

application. Typical organic contaminants (“organics”) such as petroleum hydrocarbons, gas condensates,

crude oil, chlorinated compounds, pesticides, and explosive compounds can be remediated using phyto-

remedial-technologies. Typical inorganic contaminants (“inorganics”) that can be addressed include salts

(salinity), heavy metals, metalloids, and radioactive materials. Phyto-remedial-technologies can potentially

treat soils, sludge, sediments, groundwater, surface water, wastewater, and storm water. This document

includes guidance for remediating soils, sludge, sediments, groundwater, and storm water. The reader is also

referred to other Interstate Technology & Regulatory Council (ITRC) guidance for wastewater, surface water,

and storm water control (ITRC 2003b, 2005a). Likewise, the reader is referred to similar ITRC guidance on

alternative waste containment and management strategies (ITRC 2003c, 2003d, 2006a, 2006b).

The particular phyto-remedial-technology mechanisms used to address contaminants depend not only on the

type of contaminant and the media affected, but also on the cleanup goals. Typical goals include containment

through stabilization or sequestration, remediation through assimilation, reduction, detoxification,

degradation, metabolization or mineralization, or both.

To achieve these goals, the proper phyto-remedial-technology system must be selected, designed, developed,

implemented, and operated using detailed knowledge of the site layout, soil characteristics, hydrology, climate

conditions, analytical needs, operation and maintenance (O&M) requirements, economics, public perspective,

and regulatory protection of the environment. Many phyto-remediation technologies apply basic and

fundamental information collected from different green-work areas like agriculture, forestry, and horticulture

to environmental problems. Therefore, the best starting place for someone relatively new or unfamiliar with

the technology is a simple review of the plant physiological processes that are exploited through phyto-

remedial-technologies.

1.1 Basic Plant Physiology:

Plants typically grow by sending their roots into the soil and producing leaf and woody material (Figure 1-1).

To accomplish these basic growth habits (Taiz and Zeiger 1991), plants use carbon dioxide to harvest light

energy, convert it into chemical energy, and produce carbon biomass through the processes of photosynthesis

in the leaves and cellular respiration. Plants also take up liquid water and dissolved inorganic nutrients through

the root system, transport them throughout the plant in the xylem, and transpire the water through the leaves as

vapor. While carbon dioxide and water vapor are being exchanged, oxygen is also being released to the

environment. Likewise, photosynthetic chemicals (photosynthates or phytochemicals) are transported

throughout the plant in the phloem, even into the root to be exuded into the surrounding soil. The upward

transport in the xylem and downward transport in the phloem, collectively termed “translocation,” depend on

Annexure I. Phyto-Remedial-Technology Technical and Regulatory Guidance and Decision Trees, Revised the continuous water column that exists throughout the plant. Each biological process contributes to the

remediation or containment of contaminants as described in the following subsections.

Inorganic Nutrition: Thirteen essential inorganic plant nutrients (N, P, K, Ca, Mg, S, Fe, Cl, Zn, Mn, Cu, B,

and Mo) are taken up by the root system as dissolved constituents in soil moisture (Table 1-1). These elements

are required by the plant for growth, development, or reproduction and are acquired either passively in the

transpirational stream (see Section 1.1.3) or actively through transport proteins associated with the root

membrane. Once inside the root system, the dissolved nutrients can be transported throughout the remainder of

the plant through the vascular system (xylem).In addition to these essential nutrients, other nonessential

inorganics such as various common contaminants (salts, Pb, Cd, As, etc.) can be taken up as well. Again, this

uptake process can be either passive in the transpirational stream or active by substituting for the essential

nutrient on the transport protein. These processes are relevant to phytoextraction (see Section 1.2.4) and

certain applications of phytoremediation groundcovers (see Section 1.3.3). Since these other inorganics are

not essential to the plant and may represent potential toxins at high concentrations, the plant also contains

various mechanisms to sequester or stabilize these extraneous inorganics and prevent transport into the more

sensitive tissues of the plant. These processes are relevant to phytosequestration mechanisms (see Section

1.2.1) and certain phytostabilisation covers (see Section 1.3.1).

1.2 Mechanisms

The basic physiological processes described in the previous section are the bases for the various phyto-

remedial-technology mechanisms that can be used to clean up contaminated sites. Table 1-3 summarizes the

specific mechanisms along with the applicable cleanup goals. The mechanisms are listed in the same order as

the sequence of how contaminants come into contact with the transpiration stream, rhizosphere, and plant

system. These mechanisms are interrelated and dependent upon the precursors. Therefore, in any given phyto-

remedial-technology application, multiple mechanisms may be involved and can be exploited depending on

the designed application (see Section 1.3).

Summary of phytoremediation-technology mechanisms:

Mechanism Description Cleanup goal

1. Phytosequestration: The ability of plants to sequester certain contaminants in the rhizosphere through

exudation of phytochemicals and on the root through transport proteins and cellular processes

Containment.

2. Rhizodegradation: Exuded phytochemicals can enhance microbial biodegradation of contaminants in the

rhizosphere Remediation by destruction.

3. Phytohydraulics: The ability of plants to capture and evaporate water off the plant and take up and

transpire water through the plant Containment by controlling hydrology.

35 36

4. Phytoextraction: The ability of plants to take up contaminants into the plant with the transpiration stream

Remediation by removal of plants.

5. Phytodegradation: The ability of plants to take up and break down contaminants in the transpiration

stream through internal enzymatic activity and photosynthetic oxidation/reduction Remediation by

destruction.

6. Phytovolatilisation: The ability of plants to take up, translocate, and subsequently transpire volatile

contaminants in the transpiration stream Remediation by removal through plants.

Example of Phyto-remedial-technologies' Broad Utility: Consider wood-treating facilities where creosote

(organic contaminant) and copper-chromium-arsenic (inorganic contaminants) wood preservations were

used. Often, surface releases directly impact the soil while leaching of the soluble components of both organic

and inorganic contaminants can create commingled groundwater impacts. Assume the groundwater is

relatively shallow but spread across a large area of the site. Different treatment options are possible:

Option 1. Conventional Treatment Train—To address soil impacts, excavation and off-site disposal can

prevent further leaching. Once completed, the groundwater impacts might be addressed using extraction

(groundwater pumping network) to remove contaminants and control plume migration. Once extracted, the

organic constituents in groundwater might be treated through granulated activated carbon (GAC). For the

dissolved inorganic constituents, a reverse osmosis (RO) system might be used as treatment. Once cleansed,

the groundwater would be discharged through a permitted outfall. This scenario uses three steps (excavation,

extraction, treatment) with two treatment technologies (GAC and RO).

Option 2. Phyto-remedial-technology Application—Deep rooted trees planted over the impacted area can

send roots through the impacted soil to access the groundwater. Phytohydraulics can be used to control plume

migration (tree hydraulic barrier application). Phytosequestration of the inorganics and rhizo-degradation of

the organics can be used to treat the surface soils (phytostabilisation cover and phytoremediation groundcover

applications). The dissolved inorganic constituents can be phytoextracted or phytosequestered in the trees

(phytostabilisation cover application) while the organic groundwater constituents can be rhizo-degraded

and/or phytodegraded (would likely not be phytovolatilised given the chemical properties of heavier

hydrocarbon typical of creosote) (phytoremediation tree stand application). No water is discharged. This

scenario uses one step (planting) but with four phyto-remedial-technology applications.

Option 3. Hybrid Approach—Excavation and extraction as in Option 1, but treatment in a constructed

treatment wetland that can address both the organic and inorganic constituents (see ITRC 2003c). This

scenario uses three steps (excavation, extraction, treatment) with one treatment technology. Of course, the

final selection of the remedial approach depends on many other factors besides remedial technologies,

including technical issues, economics, regulatory acceptance, community stakeholders, etc.

However, like all remediation technologies, phyto-remedial-technologies are appropriate only under certain

conditions. The major limitations are depth, area, and time. The physical constraints of depth and area depend

on the plant species suitable to the site (i.e., root penetration) as well as the site layout and soil characteristics.

Phyto-remedial-technologies typically require larger tracts of land than many alternatives. Time can be a

constraint since phyto-remedial-technologies generally take longer than other alternatives and are susceptible

to seasonal and diurnal changes. These limitations should be considered along with several other decision

factors when evaluating a phyto-remedial-technology as a potential remedy (see Section 2.3). Furthermore,

these potential limitations should be considered when assessing the site (see Section 2.2) to determine

immediate “No-Go” situations.

35 36

4. Phytoextraction: The ability of plants to take up contaminants into the plant with the transpiration stream

Remediation by removal of plants.

5. Phytodegradation: The ability of plants to take up and break down contaminants in the transpiration

stream through internal enzymatic activity and photosynthetic oxidation/reduction Remediation by

destruction.

6. Phytovolatilisation: The ability of plants to take up, translocate, and subsequently transpire volatile

contaminants in the transpiration stream Remediation by removal through plants.

Example of Phyto-remedial-technologies' Broad Utility: Consider wood-treating facilities where creosote

(organic contaminant) and copper-chromium-arsenic (inorganic contaminants) wood preservations were

used. Often, surface releases directly impact the soil while leaching of the soluble components of both organic

and inorganic contaminants can create commingled groundwater impacts. Assume the groundwater is

relatively shallow but spread across a large area of the site. Different treatment options are possible:

Option 1. Conventional Treatment Train—To address soil impacts, excavation and off-site disposal can

prevent further leaching. Once completed, the groundwater impacts might be addressed using extraction

(groundwater pumping network) to remove contaminants and control plume migration. Once extracted, the

organic constituents in groundwater might be treated through granulated activated carbon (GAC). For the

dissolved inorganic constituents, a reverse osmosis (RO) system might be used as treatment. Once cleansed,

the groundwater would be discharged through a permitted outfall. This scenario uses three steps (excavation,

extraction, treatment) with two treatment technologies (GAC and RO).

Option 2. Phyto-remedial-technology Application—Deep rooted trees planted over the impacted area can

send roots through the impacted soil to access the groundwater. Phytohydraulics can be used to control plume

migration (tree hydraulic barrier application). Phytosequestration of the inorganics and rhizo-degradation of

the organics can be used to treat the surface soils (phytostabilisation cover and phytoremediation groundcover

applications). The dissolved inorganic constituents can be phytoextracted or phytosequestered in the trees

(phytostabilisation cover application) while the organic groundwater constituents can be rhizo-degraded

and/or phytodegraded (would likely not be phytovolatilised given the chemical properties of heavier

hydrocarbon typical of creosote) (phytoremediation tree stand application). No water is discharged. This

scenario uses one step (planting) but with four phyto-remedial-technology applications.

Option 3. Hybrid Approach—Excavation and extraction as in Option 1, but treatment in a constructed

treatment wetland that can address both the organic and inorganic constituents (see ITRC 2003c). This

scenario uses three steps (excavation, extraction, treatment) with one treatment technology. Of course, the

final selection of the remedial approach depends on many other factors besides remedial technologies,

including technical issues, economics, regulatory acceptance, community stakeholders, etc.

However, like all remediation technologies, phyto-remedial-technologies are appropriate only under certain

conditions. The major limitations are depth, area, and time. The physical constraints of depth and area depend

on the plant species suitable to the site (i.e., root penetration) as well as the site layout and soil characteristics.

Phyto-remedial-technologies typically require larger tracts of land than many alternatives. Time can be a

constraint since phyto-remedial-technologies generally take longer than other alternatives and are susceptible

to seasonal and diurnal changes. These limitations should be considered along with several other decision

factors when evaluating a phyto-remedial-technology as a potential remedy (see Section 2.3). Furthermore,

these potential limitations should be considered when assessing the site (see Section 2.2) to determine

immediate “No-Go” situations.

37

Notes

38

Notes

37

Notes

38

Notes

39

Notes

40

Notes

39

Notes

40

Notes

under HSBC Climate Partnership

Green ChemistrySeries

Module I 1 : Bioremediation

and Phytoremediation

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WWF-India's

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