07 treatment tech reference guide for pops lli

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Remediation Treatment Technologies:

Reference Guide for Developing Countries Facing

Persistent Organic Pollutants

by

Loretta Li, Ph.D., P.Eng.

Associate Professor

Department of Civil Engineering

The University of British Columbia

6250 Applied Science Lane

Vancouver, B.C. V6T 1Z4

to

Dr. Mohamed EISA, Chief of POPs Unit

UNITED NATIONS INDUSTRIAL DEVELOPMENT ORGANIZATION

(UNIDO)

Vienna International Centre

P.O. Box 300, A-14000 Vienna

Austria


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i

Table of Contents

PageList of Tables ..................................................................................................................... iii

List of Figures .................................................................................................................... iv

Acknowledgements..............................................................................................................v

Disclaimer.......................................................................................................................... vi

1. Introduction.................................................................................................................1

2. Methodology...............................................................................................................2

3. Full Scale Technology Profiles...................................................................................2

4. Development of a Screening Matrix...........................................................................3

4.1. Logistics..........................................................................................................4

4.2. Grading System for the Developed Screening Matrix....................................8

5. The Potential for Improvement of Existing Remediation Techniques .......................9

6. Address the Potential Improvement of Incinerator.....................................................9

6.1. Methodology.................................................................................................10

6.2. Incineration of Hazardous Waste Materials/POPs........................................10

6.3. Conclusion ....................................................................................................15

7. Address the Potential Improvement of Landfilling for POPs...................................15

7.1. Methodology.................................................................................................16

7.2. Landfilling: Engineered Landfill for Hazardous Waste Materials/POPs .....16

7.3. Conclusion ....................................................................................................19

Appendix A Overviews of established, demonstrated and emerging technologies........21

A-1 Incineration ...................................................................................................22

A-2 Bioremediation (DARAMEND

& XenoremTM) ........................................29

A-3 Solvent Extraction.........................................................................................41

A-4 Vitrification (PACT, PLASCONTM& GeoMeltTM) .....................................45


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A-5 Solidification/Stabilization ...........................................................................50

A-6 Gas Phase Chemical Reduction ....................................................................56

A-7 Alkali Metal Reduction (Sodium Reduction) ...............................................61

A-8 Pyrolysis and Gasification ............................................................................64

A-9 Ball Milling/ Mechano-Chemical Dehalogenation (MCDTM) ......................70

A-10 Thermal Desorption ......................................................................................74

A-11 Supercritical Extraction (SCE) .....................................................................83

A-12 Soil Washing.................................................................................................92

A-13 Chemical Dehalogenation...........................................................................100

A-14 Phytoremediation ........................................................................................105

Appendix B Soil Effect on Cost of Technology ...........................................................111

Appendix C Treatment Technology Combinations......................................................117

Appendix D Chemical abbreviations, synonyms and trade names of 12 POPs

identified by UNIDO in the Stockholm Convection................................119

Bibliography ..................................................................................................................122


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List of Tables

Page

Table 1 The list of reviewed technologies ......................................................................3Table 2 Proposed screening matrix system choosing an appropriate technology

for a specific site in each developing country....................................................6

Table 3 Grading System for screening matrix ................................................................8

Table B1 Soil Characteristics Affecting Cost of Remedial Technology ((USEPA

1989; Evans 1990; USEPA 1991a; USEPA 1992b; USEPA 1994b;

USEPA 1995b; USEPA 1997; USEPA 2004a; USEPA 2005) .....................113

Table B2 Critical Characteristics Affecting Cost Ranges for Technology

Alternatives for Remediating POP- Contaminated Soil and Sediment

(Dvila et al., 1993) .......................................................................................114

Table B3 Cost Summary of Each Technology and the Estimated Cost in 2007

U.S. Dollars using Construction Cost Index..................................................115

Table B4 Annual Construction Cost Index....................................................................116


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List of Figures

Page

Figure C1 Common combinations of treatment technologies applied in remedialactions (USEPA 2004b).................................................................................118


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ACKNOWLEDGEMENTS

Special acknowledgment is given to Dr. John R. Grace of the Department of Chemical

and Biological Engineering at The University of British Columbia for his contributions to

the section on combustion technology; Tamer Gorgy, my Ph.D. student, who performed a

literature search and prepared a compilation of existing technologies; Dr. Raymond Li of

CH2MHILL for his cooperation and thoughtful suggestions during the preparation of this

report.

I also express my special thanks to the United Nation Industrial Development

Organization (UNIDO) for its financial support for this project.


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DISCLAIMER

This report compiles information on a wide range of technologies for remediation of

POPs in soil and stockpiles based on available published and unpublished information

available to the author. In preparing this review, technical literature and reports from

various organizations have been surveyed. Note that the evaluation is based on existing

available information, some of which may not be complete or fully accurate.

This report is provided as a reference guide, but it is not intended to provide guidance

regarding selection of a specific technology or vendor. It also should not be construed in

any manner as constituting endorsement, recommendation or discouragement for the useof any trade name or commercial product.


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1. Introduction

Persistent organic pollutants (POPs), originating from a variety of human

activities (agricultural and industrial), are toxic chemical compounds that resist chemical

and biological breakdown in the environment. POPs can be conveyed for thousands of

miles through air or water currents, and may be found in remote ecosystems far from

their source, even in locations where POPs have never been used (EUROPA 2007).

Through bioaccumulation, animals, like humans, higher in the food chain, are more likely

to have higher concentrations of these pollutants, often to the degree that the substances

may cause cancer, as well as neurological and immune system disorders (USEPA 2007,

OMoE 2005).

The United Nations Environment Programme (UNEP) Stockholm Convention on

Persistent organic Pollutants is a global agreement intended to protect human health and

the environment from POPs. It was signed on May 23 2001 and entered into force on

May 17 2004. Parties to the Stockholm Convention agree to the management and control

of POPs (UNEP 2003). Because of their adverse health effects and associated

environmental hazards, remediation of POPs in stockpiles and soils has been underway in

many developed countries. Unfortunately, industrialization of many developing

countries has resulted in extensive use of these chemicals, causing serious environmental

pollution and resulting in serious negative social impacts.

Many advanced soil remediation techniques have been commercialized and

adopted in industrialized and developed countries. These include Gas Phase Chemical

Reduction (GPCR), Mechanochemical dehalogentation (MCD),and Thermal Desorption.

Some promising techniques such as Base Catalyzed Decomposition (BCD) and Sonic

technology are still either at the laboratory stage or at the pilot study. However, due to

the financial constraints, many advanced technologies are unlikely to be adopted by the

developing countries. The success of finding suitable and affordable technologies is

critical in solving problems in the developing countries.


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The objective of this report is to review existing commercially available and

sustainable techniques of remediating POPs and to explore the potential for adopting or

improving existing remediation techniques for use in developing countries.

Existing technologies are first summarized. A set of criteria is then provided as

an aid to developing countries in identifying which technology is most suitable in each

case based on country specific factors and site-specific conditions.

2. Methodology

Both well developed and commercialized combustion and non-combustion

technologies for remediation of POPs in soil and stockpiles are summarized here, basedon available information. In preparing this review, technical literature and reports from

various organizations have been surveyed. Sources which are especially useful are:

USEPA Reference Guide to Non-Combustion Technologies for Remediation of

Persistent Organic Pollutions in Stockpiles and Soil (2005)

UNEP, Science and Technology Advisory Panel (STAP) of the Global

Environmental facilities (GEF) Review of Emerging, Innovative

Technologies for the Destruction and Decontamination of POPs and the

Identification of Promising Technologies for Use in Developing

Countries (2004)

IHPA and North Atlantic Treaty Organization (NATO) Committee on the

Challenges of Modern Society (CCMS) Pilot Study Fellowship Report

Evaluation of Demonstrated and Emerging Remedial Action

Technologies for the Treatment of Contaminated Land and Groundwater

(Phase III) (2002)

3. Full Scale Technology Profiles

As listed in Table 1, Appendices 1 to 14 of this report provide overviews of

established, demonstrated and emerging technologies for remediation of POPs-

contaminated soils and sediments. The information there includes process descriptions,


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site requirements, estimated costs, by-products, and performance (covering where

possible laboratory-, bench, pilot- and full-scale test results). The advantages and

limitations of the various technology options, as well as their applicability in developing

countries are also considered briefly.

Table 1. The list of reviewed technologies

Technology Appendix

Incineration 1

Bioremediation (DARAMEND& XenoremTM) 2

Solvent Extraction 3

Vitrification (PACT, PLASCONTM& GeoMeltTM) 4

Solidification/Stabilization 5

Gas Phase Chemical Reduction 6

Alkali Metal Reduction (Sodium Reduction) 7

Pyrolysis (STARTECH) 8

Established

Ball Milling/ Mechano-Chemical Dehalogentaiotn

(MCDTM)

9

Thermal Desorption 10

Super Critical Extraction (SCE) 11

Soil Washing 12

Demonstrated

Chemical Dehalogenation 13

Emerging Phytoremediation 14

4. Development of a Screening Matrix

Screening Matrices are common tools for screening potentially applicable

commercialized technologies for POPs remediation projects. A matrix allows the user to

screen in-situ (with a few exceptions) technologies to treat POPs for countries at various

stages of development. The US Federal Remediation Technologies Roundtable (FRTR

2007) has developed a similar screening matrix for remediation technologies.


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In this report, three sets of criteria have been developed to form the screening

matrix. The matrix provides a foundation for decision-making and for choosing an

appropriate technology for a specific site in each developing country. The matrix can be

readily expanded as more commercial technologies become available.

4.1. Logistics

The criteria for comparison are based on on-site technology (in-situ/ex-situ)

except for landfilling and incineration. All the criteria are grouped under three major

headings: (a) technical considerations, (b) health and environmental considerations, and

(c) economic considerations. These three subtitles are intended to encourage a wide-

ranging evaluation of the technologies, not only including financial factors, but also

taking into consideration technical and environmental criteria. Equal weight is applied

here to each criterion, but weighting factors can be established to reflect the differing

relative importance of different criteria in each jurisdiction. However each factor should

at least be considered in all cases. Note that the evaluation is based on existing available

information, some of which may not be complete or fully accurate.

(a) Technical considerations

Site Specific Requirements:

Soil Temperature Dependence

Soil Moisture Dependence

Particle Size Distribution of Soil

Permeability/Clay Content

Organic matter (insufficient data and information to be included in the

matrix)

Space available

Proximity of population or sensitive sites

Resource/Technical Requirements:

Pretreatment

Power/energy/fuel

Water quantity, quality and seasonal variations


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Chemicals

Equipment

Monitoring

Skilled labour

Transportation: roads, rail, canals, etc.

Off-gas treatment

Post-treatment

Excavation

(b) Health and Environmental Considerations

Impact on the local, regional and global environment in all aspects, i.e. air,

water, soil and sediments

Hazardous by-product(s)

Worker health and safety

Odours, aesthetic factors

(c) Economic considerations

Pretreatment cost

Labour cost

Monitoring cost

Power/fuel cost

Equipment cost

Installation/decommissioning cost

Operating and maintenance cost

Disposal cost

Transportation cost

Water cost

Intellectual property cost

Post treatment cost

Influence on regional economy

Table 2 displays the proposed matrix system for considering these various factors.


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Table 2. Proposed screening matrix system choosing an appropriate technology for a specific site in each developing country

Combustion Non Combustion

IncinerationThermal

DesorptionSuper Critical

Extraction Phytoremediation Bioremediation GPCRSolvent

Extraction

In/Ex situ Ex Ex Ex/In Ex In In/Ex Ex Ex

On Site/Off site On site Off site On Site On Site On Site On Site On Site On site

Efficient 99.99% 99.99% 93-99.8% 99.99% 60-80% 99.99% 95-99%

Estimate cost ($/m3) * 140-360 350-450/350-700 122-154* partial cost 147-626 55-360 500-630 125-400

Technical Consideration

Site Specific Requirement

Soil Temperature Dependence 1 1 2 2 2 3 3 1

Soil Moisture Dependence 3 3 3 3 3 3 3 3

Particle Size 2 2 3 3 2 3 2 2

Permeability/clay content 1 1 1 1 1 3 1 3

Space Requirement 2 1 2 2 1 3 2 3

Resource Requirement

Pretreatment 2 2 2 3 1 1 3 2

Power 3 1 3 1 1 1 3 3

Water 1 1 1 3 2 3 1 2

Chemical/enemzy 1 1 1 3 1 3 3 3

Monitoring 3 1 3 3 1 1 3 3

Skill Labour 3 1 3 3 1 2 3 3

Transportation 1 3 1 1 1 1 1 1

Off Gas Treatment 2 1 3 3 1 1 3 1

Post Treatment 1 1 1 3 1 1 1 3

Excavation 3 3 3 3 1 1 3 3

Sub total 29 23 32 37 20 30 35 36


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Table 2 (continued)

Combustion Non Combustion

IncinerationThermal

DesorptionSuper Critical

Extraction Phytoremediation Bioremediation GPCRSolvent

Extraction Health & Environm ental

ConsiderationImpact to Environment 2 2 1 1 1 1 1 1

Bi-products

Hazardous 3 3 1 1 1 1 3 1

Sub total 5 5 2 2 2 2 4 2

Financial Consideration

Pretreatment Cost 1 1 3 3 1 1 3 2

Labour cost 2 2 2 3 3 2 2 3

Monitoring Cost 3 1 3 3 2 2 3 3

Power/fuel Cost 3 1 3 2 1 1 3 1 Equipment Cost 3 2 3 3 1 1 3 2 Installation/DecommissioningCost 2 1 3 3 1 1 3 2

Operational & Maintenance Cost 2 1 3 3 2 2 3 2

Chemical (or equivalent) Cost 1 1 1 3 1 2 3 3

Disposal Cost 1 3 1 1 1 1 1 1

Transportation Cost 1 3 1 1 1 1 1 1

Water Cost 1 1 1 3 2 3 1 1

Patent Cost 1 1 3 3 1 1 3 1

Post Treatment Cost 1 1 1 3 1 1 3 3

Sub total21 18 25 31 17 18 29 23

Rating Code : 1 - No/Low

2 - Average

3 - Yes/high

* See Appendix A for detail information on cost


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4.2. Grading System for the Developed Screening Matrix

The symbols used in the treatment technologies screening matrix are simple.

Table 3 provides an explanation of this grading system.

Table 3. Grading System for screening matrix

Rating Code Explanation

1 - No/Low Low degree of intensity or not required - in cost, negative impact or

skilled labour

2 - Average Average degree of intensity - in cost, negative impact or skilled labour

3 - Yes/high High degree of intensity or requirement - in cost, negative impact or

skilled labour

In this matrix evaluation, the lower the score, the better the technology for a

specific site. Completing the matrix is a valuable tool for the site owner, as well as for

government agents who are responsible to determine which available technology is most

suitable for managing POPs. Each criterion can be weighted by multiplication by

weighting factors, accounting for the varying importance of different attributes. The

sum of all scores, multiplied by the corresponding weighting factors results in a total

qualification grade for comparing alternatives and selecting the best technology for the

specific site subject to its own local and specific conditions. The weighting factor for

each item can be adjusted upward or downward as circumstances change, depending on

local factors. Note that there is no a priori methodology to assign the right weighting

factors for the criteria in Table 2. It is up to site owners to assign the appropriate

weighting factor for each criterion based on local priorities and regulatory requirements.

For example, the cost of water and energy can vary radically between difference

communities, so that their weighting factors are likely to differ. Also, the regulatory

requirements for developing countries can differ greatly from those of developed

countries. Therefore, again the corresponding weighting factors with respect to

environmental impacts are likely to differ in such cases.


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5. The Potential for Improvement of Existing Remediation Techniques

Many of the remediation technologies described in the previous sections are

proprietary and protected by patents. Know-how needed to exploit existing technologies

can also be proprietary to design firms or other private interests. Because of the

competition between technologies for the existing market and differences in local

conditions, there may well be potential for improvement of proprietary techniques, or for

adaptations that would make them more suitable to local situations in developing

countries.

Incineration and landfilling are the two most common technologies which are

unlikely to require consideration of patents. Although they have been in practice in manycountries for many year, they are still have potential for improvement, e.g. those based on

the directorate of the Stockholm Convention. The facilities must exist for safe and

appropriate reuse and/or reformulation; they must present no additional unacceptable

hazards, and they must benefit both people and the environment.

6. Address the Potential Improvement of Incinerator

Incineration is a combustion technology which if not designed or operating

optimally, can create products of incomplete combustion such as polychlorinated

dibenxo-p-dioxins (dioxins) and polychlorinated dibenzo-p-furans (furans). Note that

dioxins and furans are often synthesized de novo, i.e. formed downstream, at an

intermediate temperature range e.g. ~400C. According to Carroll (2003) the key to

reduction of generation and emissions of dioxins and furans (PCDD/Fs) is proper design

and operation of the combustor. The uniformity of conditions is significant because

problems often occur when part of the stream by-passes the hot zone. Attention alsoneeds to be paid to free radical reactions which can result in the synthesis of a wide

variety of compounds, some of which are harmful. Specification and operation of

pollution control equipment requires utilization of good combustion practices, often

expressed as the "Three T's": Time in the combustion zone, Temperature of combustion

and combustion gases, and strong Turbulence to ensure good mixing and favourable


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contacting with oxygen. Successful governmental policy reflects these requirements as a

condition for operation of incinerators, especially those burning toxic and other special

wastes. With more research on combustion and careful attention to detail, incineration is

one of the best and most economic technologies for POPs.

6.1. Methodology

In preparing this section, I have relied on:

Review of a number of recently published papers and unpublished material relating to

incineration of POPs, PCBs and emissions of dioxins/furans.

Input from a world-recognized process engineer and research scientist, with

experience related to combustion of a wide range of materials, reactors, high-

temperature processes, and air pollution control, including special waste incineration.

Some available material with respect to the Canadian experiences at the Swan Hills,

Alberta facility and the Sydney Tar Ponds, Nova Scotia facility are used for

illustration purposes.

6.2. Incineration of Hazardous Waste Materials/POPs

Incineration of waste materials is commonly employed as a method for converting

waste carbonaceous materials into relatively harmless substances, mostly carbon dioxide,water and ash. The flue gas also includes oxides of nitrogen (NOx) and sulphur (mostly

SO2), as for combustion of fossil fuels; when the combustible material contains chlorine,

hydrogen chloride (HCl) is also a product. Control of these three gases is standard,

practiced routinely, e.g. in furnaces, boilers and power generation. Inevitably small

amounts of other undesirable products like carbon monoxide (CO) will also be present in

the flue gas. Traces of highly undesirable products of combustion, in particular products

of incomplete combustion, such as chlorinated dioxins and furans, also occur in

combustion processes. The major objective in incineration is to keep the concentrations

of these substances to extremely low and tolerable levels, while effectively destroying the

waste materials fed to the incinerator.


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The main challenges facing the designers and operators of an incinerator for

destroying POPs are:

Effective destruction and removal efficient (DRE) for the waste material;

Minimization of the production and emission of noxious pollutants, like

dioxins and furans, which can be formed in incineration systems.

Effective control of the emissions of heavy metals.

Controlling the emissions of standard combustion pollutants like NOx, SO2,

CO and particulates.

These will be considered in turn, followed by some general observations.

(a) Destruction of POPs (e.g. PCBs) and Other Fed Waste Materials

A rotary kiln is the most common type of hazardous waste incinerator. This type

of high-temperature reactor is also often employed in cement-making, limestone

calcination and pulp and paper operations. Waste liquid and/or solids are fed into one

end of a slightly-inclined rotating cylinder which has been heated (by auxiliary fuel such

as oil) to approximately 1200C or more. The temperature is maintained at that level by

the calorific value of the waste stream, supplemented if needed by fossil fuel such as oil

or natural gas. The wastes are lifted and dropped repeatedly by the revolving furnace,

leading to effective contact with combustion air. Excess air is employed (i.e. more than

required for stoichiometric combustion) in order to promote complete burning of the

wastes. Typically 30 - 50% excess air is recommended. The standards required for the

incinerator need to be fixed, but previous experience (Grace 2007) with rotary kiln

furnaces has shown that they are capable of meeting usual incinerator standards of six

nines (99.9999%) destruction of PCBs, and four nines (99.99%) destruction of

polyaromatic hydrocarbons like naphthalene and anthracene. Well-designed and properly

operating commercial incinerators exceed these values, frequently by a factor of 10 to

100. Operating conditions which are most important to achieve high DREs are the mean

temperature level, temperature uniformity, sufficient excess oxygen concentration (e.g.

>4% oxygen by volume in the flue gas), uniform feeding, and turbulence or other

effective contacting mechanisms in the furnace. To further improve the combustion

efficiency, the off-gases are fed to a secondary combustion chamber (often called an


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afterburner), to assist in oxidizing any unburnt gases. In addition, downstream pollution

control devices, such as scrubbers, filters and/or electrostatic precipitators, are added to

capture fine particulates (fly ash) and gaseous component which would otherwise escape.

A revolving fluidized bed incinerator has demonstrated destruction with at least

six nines efficiency for coke wastes (tar containing a number of potentially harmful

constituents, in particular polycyclic aromatic hydrocarbons (PAHs), PCBs, and heavy

metals, as well as small amounts of volatile organic compounds). Tests by Jia et al.

(2005) of Natural Resources Canada have also indicated that tar sludge can be efficiently

destroyed in circulating fluidized bed combustors. These combustors operate at

significantly lower mean temperatures (typically 850 - 900C, though with greater

temperature uniformity than rotary kilns.) PCB wastes, with much higher concentrations

than those of the tar sludge, are also routinely incinerated in the rotary kiln incinerators at

Swan Hills in Alberta, Canada, with DREs well in excess of six nines. Rotary kiln

incinerators in other countries have had similar success. When problems are

encountered, these can often be related to materials handling in delivering the wastes to

the incinerator, not to the incinerator itself. For example, with Sydney tar ponds wastes in

Nova Scotia, Canada, incineration failed in tests carried out two decades ago due to

problems in pumping the sludge material up hill to the level of the incinerator (Campbell

2002).

(b) Minimization of Dioxins, Furans and Other Products of Incomplete Combustion

Considerable work has been completed in a number of countries on the

mechanisms by which it is possible to form and emit noxious substances, in particular

poly-chlorinated dioxins and furans, in combustion facilities. Some of the key factors

needed to minimize their generation are the same as those cited above with respect to

achieving high destruction and removal efficiencies, i.e. high and uniform temperatures,

uniform feeding, sufficient excess oxygen, effective gas/waste contacting through

turbulence, and proper downstream separation devices. In addition, it is very important

that the cooling of the flue gases through the temperature interval from ~ 400 to 300C be

as quick as possible to prevent de novosynthesis of dioxins and furans downstream of the


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incineration chambers. These stipulations are generally well-known to operators of

incinerators. If an experienced vendor is chosen, with a well designed and effectively

operated and maintained incinerator, it should be possible to operate within normal

hazardous waste limits.

(c) Emissions of Heavy Metals

Some wastes and by-products contain small amounts of heavy metals, which are

present in the material fed to the incinerator. For instance, in coke tar, the metals of

concern are likely to be arsenic, beryllium, cadmium, chromium, copper, lead, mercury,

nickel, selenium, silver, vanadium and zinc. It is important to minimize emissions of

these metals. Mercury is the most volatile of these metals, and its control depends on

effective capture of fly ash entrained by the flue gases, i.e. on efficient gas-solid

separation in the off-gases. Standard separation techniques like scrubbers, bag filters and

electrostatic filters are available to control such emissions. The less-volatile metals are

likely to end up predominantly in the bottom ash. Careful controls can ensure that the

heavy metals emissions satisfy the applicable codes, both in terms of emissions and levels

at point of impingement. Residual (fly and bottom ashes) from the incinerator could be an

issue and must be disposed of and handled properly.

(d) Emissions of Standard Combustion Pollutants

Incinerators must also meet standard emission limits for pollutants (e.g. acid gases

like SO2 and NOx, as well as CO) commonly controlled in stationary combustion. There

is a need to keep the oxygen concentration in the flue gas higher than about 4% to

achieve uniform combustion with good burnout. If this is done, emissions of CO and

unburnt hydrocarbons should be low. The need to control mercury and other heavy

metals also requires effective capture of particulates, so that particulate emissions should

be well controlled by filters, scrubber or precipitator. If opacity is controlled, this should

also be readily achievable given the other controls. Given the oxidizing conditions, gases

like hydrogen sulphide and ammonia will not be problematic.


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(e) Materials Handling Issues

An incinerator is only as good as its auxiliaries, with continuous and uniform

feeding being of the utmost importance. This can sometimes be overlooked. Special

attention to handling and feeding of the waste is needed. As noted above, an attempt to

utilize incineration for Sydney Tar Ponds sludge failed because of materials handling

issues. An accident at the Swan Hills facility in the 1990s was also attributed to materials

handing problems.

(f) Continuous Operation

It is preferable for incinerators to maintain operation night-and-day once

incineration has been started up and to have scheduled shutdowns only in frequently, e.g.

once per year, since steady state continuous operation facilitates trouble-free operation.

(g) Pilot-Scale Testing

Pilot scale testing of POPs burning may be required to prove the successfulness of

the design combustion conditions and operation for a given waste material. Some

companies and government laboratories have pilot scale facilities that can be used for this

purpose. Normally, the test results should be conservative in that a full-scale incinerator

will have greater residence times than those in a pilot unit, and therefore if the pilot unit

meets the requirements, the full-scale should also do so.

(h) Operation and Maintenance

The safety of any technology can be compromised by improper operation or

failure to provide proper maintenance. It is not only vital that proper equipment be

chosen, designed, fabricated, installed and commissioned, but that the operations and

maintenance be at the top level for the full period of operation. The role of government

in assuring quality and continuity of operation is vital to the safety of incinerator

facilities.


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(i) Monitoring and Emissions Testing

Standard substances like oxygen, NOx, SO2, CO, unburnt hydrocarbons and HCl

should be monitored continuously. Their levels can provide a good overall indication

that the incinerator is working properly, and upsets can be detected, e.g. through a sudden

drop in oxygen level and increase in off-gas CO concentration. Testing for complex

organics like dioxins/furans, PAHs and PCBs requires specialized stack testing. While

this would normally be done annually, it is appropriate to conduct additional tests in the

first year in addition to the initial testing required for acceptance of an incinerator.

6.3. Conclusion

Incineration is a widely-practised technique for destroying wastes, including those

containing POPs. Well designed, well constructed and well maintained incinerators with

appropriate monitoring, downstream air pollution control and stack, can often be an

appropriate technique for destruction of hazardous organic substances.

7. Address the Potential Improvement of Landfilling for POPs

Landfilling is a technique which can contain the migration of POPs. Since

landfilling does not normally destroy POPs, every effort has to be used to prevent the

migration. Proper lining and monitoring are required to ensure that there is no leakage

from the landfill containment system. The engineer/control landfill can be considered as

a temporary measured until the destructive technologies for POPs become available for

developing countries, which provide environmental sustainability and fall within

economical affordability.

Developing countries should follow the most up-to-date requirements and

technologies to build landfills which are suitable to handle the disposal of POPs. Two

types of liners can be used: flexible membrane and clay liners. Measurement of the liner

compatibility is critical to success. Flexible membranes deteriorate over time, particular

when they are chemically incompatible with the leachate. Flexible membranes contain

pinholes and therefore cannot be made leak-free. Organic chemical solutions affect the


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hydraulic conductivity of clay liners. Therefore, it is suggested that a flexible membrane,

compatible with POPs, underlain by a clay liner, is the minimum requirement of a landfill

for disposal of POPs. Although there is no universal method to test the compatibility,

two test methods have been promoted (EPA 1992c). They are NSF (National Sanitation

Foundation) Standard No. 54 and EPA Test Method 9090.

Local soil materials or waste materials with high adsorptivity and low hydraulic

conductivity could be explored for possible use as containment barrier materials. If

appropriate for adoption, these materials can benefit the local economy and may possibly

gain a global market for such a material for containment purpose.

7.1. Methodology

In preparing this section, I have relied on the following:

Review of a number of recently published papers and some unpublished

material relating to landfill, clay liner, properties of POPs and soil minerals.

Personal experience with landfill liners, waste containment systems, soil-

contaminant interactions, mobility/immobility of contaminants, and

remediation of contaminated sites, including those involving organic

contaminants. Some available material with respect to experiences in different research and

consulting projects related to remediation of contaminants in soils and landfill

liner studies.

7.2. Landfilling: Engineered Landfill for Hazardous Waste Materials/POPs

Landfilling is generally regarded as the most economical and practical method for

disposal of large volumes of municipal and industrial solid wastes. Land disposal has

been in practice throughout human history. Traditionally waste was dumped in

depressions (e.g. holes left after quarries and gravel were mined) or in open spaces

without any lining system. This led to air, soil and water pollutions, and also to landfill

fires. In developing countries where there is a lack of environmental awareness,

economical means and technological infrastructure to use other treatment options, waste


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will continue to be discarded onto land, whether or not it is regarded as an option for

POPs. Many POPs are still being stored or disposed onto land, regardless of the

development level of the country.

Many environmental problems from landfill sites arise due to lack of

understanding of science, including geology, hydrogeology, soil conditions, properties of

contaminants and the resulting leachate. The legitimate environmental concern with

respect to landfilling is whether pollutants contained in, or generated from, the wastes can

be safely contained in landfills. Flexible membrane liner or clay liners (waste

containment barriers) are frequently installed at waste disposal sites as a means of

preventing pollutant migration and minimizing or eliminating the potential for

groundwater contamination. In this section, I focus on the improvement of clay liners

because many countries have access to clay minerals which may be suitable barrier

materials. These include smectite/bentonite, vermiculate and illite. In using clays as a

liner material in landfill construction, one relies on the effectiveness of the clay barrier to

impede transport of contaminants due to the low permeability of the barrier. In addition,

the ability of the clay barrier to adsorb (accumulate) contaminants (Li and Li 2001) can

make a very useful contribution to the attenuating capability of the clay liner.

Waste containment barriers are in the form of landfill liners and covers, lagoon

liners, and slurry walls. However, the use of cay barriers below waste disposal sites to

protect underlying groundwater resources has become a contentious issue following

experimental and field evidence of failure due to clay-leachate incompatibility and other

factors such as the mineralogical and physical properties (e.g. wetting/drying of clays that

may cause cracking of the liner. Siting and construction of a landfill can be as important

as selection and design of the liner system.

(a) Landfill SitingAttention must be paid to the local geological and hydro-geological situation in

selecting a landfill site. Avoid:

Flood-hazard areas and wetlands


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Areas subject to heavy rainfall

Highly permeable soil (i.e. silt, sand, gravel)

Public water supply watersheds

Groundwater aquifers, recharge areas, areas with high water tables

Limestone bedrock

Designated parks, forests, historic areas, and wildlife refuges

Seismic-risk zones

Environmental impacts must be assessed for environmental impacts (i.e. air

pollution, noise, water pollution, soil contamination and ecological risks); consider

economic impacts also; then plan for preventive and mitigation measures.

(b) Liner materialsLocal clay minerals (montmorillolite, vermiculite, illite and kaolinite) and soil

minerals (zeolite) should be explored as possible liner barrier materials for their

adsorptivity, compatibility and hydraulic conductivity for POPs. The methodology and

approach have been outlined by Li and Li 2001, Li and Denham 2000 and others

(http://www.civil.ubc.ca/people/faculty/lli/li_personalpage.html). Clay is an inexpensive

material, widely used as a barrier in containment systems because of its low hydraulic

conductivity (k) and high adsorptivity. However, the surface of clay is hydrophilic

because of the strongly hydrated metal ions (principally Na+ and Ca2+) occupying the

cation exchange sites (Li and Denham 2000). Hydrophobic organic contaminants (HOCs)

such as POPs are repelled by this environment and are therefore not adsorbed well by

natural clay. Thus, HOCs in landfill leachate may pass through clay barriers and into

ground or surface waters. It is possible to make clays more adsorptive to HOCs by using

cationic surfactants (Li and Denham 2000). These surfactants consist of a cationic,

hydrophilic moiety and a non-ionic, hydrophobic moiety. The cationic ends of the

surfactant molecules using simple ion exchange reactions replace the native inorganic

cations on the clay surface. The modified clay is called organoclay. Large portions of the

organoclay surface are rendered hydrophobic due to the hydrophobic moieties of the

surfactant molecules. Thus, organoclay adsorbs many HOCs very well. Clay/soil


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minerals such as zeolite and bentonite can be modified and adsorb HOC. The inclusion of

organoclay in a clay barrier can effectively immobilize hydrophobic organic chemicals.

Organic matter is an important constituent of soils with very high cation exchange

capacity and very high specific surface areas. It partitions organic contaminants onto its

surface. Admixing organic matter into soil liners may increase the retention ability of

contaminants because many surface functional groups are available on soil organics for

forming complexes (Sparks 1995). There is a lack of studies addressing alternative

materials or reuse waste materials that would improve POPs compatibility.

(c) Construction and Design

A landfill site needs to have a sound design with daily cover, and a leachate

collection and removal system. The construction must ensure a safe and secure landfill.

Proper training of skilled workers is also needed.

(d) No co-disposal of municipal or other wastesMost POPs are hydrophobic or have low solubility. However, in landfill situation

when these are interactions with other organic solvents or humic substance, POPs have

been detected in landfill leachates.

(e) Composite Landfill LinersDepending on the locally available material, landfill liners can be composite liners

or admixed with different materials which achieve the high retention capacity and low

hydraulic conductivity with POPs. Detailed tests of materials need to be conducted before

implementation to ensure that the environment is protected.

7.3. Conclusion

Lined/engineered landfill could be an option to temporary store POPs for

developing country. Hazardous waste landfill design criteria have been set by many

developed countries such as Canada, Australia, USEPA, and EU, and can be adopted.

Local natural materials should be explored for use as landfill liners. Understanding of the


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Appendix A Overviews of Established,

Demonstrated and Emerging Technologies


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A-1 Incineration

Overview

Incineration treats POPs in solids and liquids by subjecting them to temperatures

typically greater than 500oC in the presence of oxygen. These conditions cause

volatilization, combustion, and destruction of the organic compounds. The technology

can be scaled-down, with trailer-mounted versions of conventional rotary kiln and

fluidized bed incinerators in existence. At large sites where the cleanup will require

several years, it may be feasible to construct an incinerator onsite. Economic reasons are

often the key factor in determining whether mobile, transportable, fixed, or off-site

commercial incineration will be provided at a given site. In addition to the furnace,

incinerator systems also include subsystems for waste preparation and feeding,

combustion of feed, air pollution control (APC), and residue/ash handling (Oppelt 1987).

The three major wastestreams generated by incineration are solids from the incinerator

and the associated APC system, water from the APC system, and gaseous emissions from

the incinerator (Freeman and Harris 1995).

The applicability of incineration to the remediation of POP- contaminated soil or

sediment may be limited by the types and concentrations of metals present in the waste to

be treated. When soil or sediment containing metals is incinerated, some metals

vaporize, reacting to form other metal species, while less volatile metals remain with the

soil residuals. Metals in ash, scrubber sludge, or stack emissions, if improperly managed,

can result in potential exposures and adverse health effects (USEPA 1992a). For

example, lead, a metal commonly found associated with polychlorinated biphenyl (PCB)-

contamination, volatilizes at most incinerator operating temperatures and must be

captured before process off-gases are released into the atmosphere (USEPA 1992a). It is

therefore essential to adequately characterize the metal content of the soil or sediment

when considering incineration systems for treatment of PCB and other POPs.


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Weber (2007) describes three mechanisms that affect the emissions of

polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans

(PCDFs) for high-temperature incinerators:

(a) Formation of PCDDs/PCDFs within the high-temperature zone due to free radical

reactions.

(b) Emission of PCDD/PCDF precursors from high temperature processes and

formation of PCDDs/PCDFs in the cooling zone.

(c) Formation of PCDDs/PCDFs via degradation of products of incomplete thermal

destruction (soot, polyaromatic hydrocarbons (PAHs), etc.) in the cooling zone.

If POPs waste and its associated thermal decomposition products are exposed to

elevated temperatures for sufficient residence times, the POP components can be virtually

completely destroyed. For combustion, the times required for destruction are typically

only milli-seconds for gaseous compounds in the active flame zones. On the other hand,

combustion times of the order of seconds may be required for complete destruction of

small solid particles. A combustion temperature of 850oC and residence time of 2s,

respectively, are generally believed sufficient to destroy all chlorinated organic molecules

including PCBs and PCDDs/PCDFs (Weber 2007). However, this relies on all waste

elements travelling through the hot zones something that is difficult to achieve.

For sufficient safety margins state-of-the-art hazardous waste incinerators are

required to operate at temperatures above 1100oC and with a residence time in excess of

2s (Weber 2007). Conditions in cement kilns are even more severe (temperature

>1400oC and several second residence time). Therefore for such facilities, bypassing

around the hot zone has the greatest potential impact on total PCDD/PCDF formation (ifstable operation is maintained) (Weber 2007). This is probably similar for other high

temperature technologies, which can operate steadily at appropriate high temperatures

and sufficient residence time. In addition, all high temperature technologies will face the

challenges of PCDD/PCDF formation during cooling (so-called de novo synthesis),

posing the additional challenge of investigating, minimizing and documenting these


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formations, while also ensuring that off-gas streams cool rapidly through the temperature

range of ~250 - 500C (Weber 2007).

Treatment Process

The primary stages in the incineration process are waste preparation, waste feed,

combustion, and off-gas treatment. Waste preparation includes excavation and/or

transporting the waste to the incinerator. Depending on the requirements of the

incinerator, various equipment is used to remove oversized particles and obtain the

necessary feed size for soil and sediments (USEPA 1997). Blending of the soil or

sediment and size reduction are sometimes required to achieve uniformity of feed size,moisture content, temperature, and contaminant concentrations (USEPA 1989).

The waste feed mechanism, which varies with the type of incinerator, must introduce the

waste smoothly and continuously into the combustion system. The feed mechanism sets

the requirements for waste preparation. Bulk solids are usually shredded; contaminated

media are usually ram or gravity fed (USEPA 1992a). The combustion reactor usually

consists of one of three major systems: rotary kiln, infrared furnace, or circulating

fluidized bed. The primary factors affecting the design and performance of the system arethe uniformity of feeding, the temperature at which the furnace is operated, the time

during which the combustible material is subjected to the high temperature (residence

time and time distribution), and the turbulence required to control (APC) equipment to

remove particulates and capture and neutralize acid gases. APC equipment includes

cyclones, venturi scrubbers, wet electrostatic precipitators, bag-houses, and packed

scrubbers. Rotary kilns and infrared processing systems may require both external

particulate control and acid gas scrubbing systems. Circulating fluidized beds do not

require scrubbing systems because limestone can be added directly into the combustor

loop; however, they are likely to require a downstream system to remove particulates

such as cyclones, bag filters or electrostatic precipitators (USEPA 1992a; USEPA 1997).


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Site Requirements

The site should be accessible by truck or rail, and a graded or gravel area is

required for setup of onsite mobile systems (USEPA 1997). Concrete pads are required

for some equipment (e.g., rotary kiln). For a typical commercial-scale unit, 2 to 5 acres

are required for the overall system site including ancillary support. A stack of height

exceeding that of local buildings and trees should be available or provided as part of the

project. Standard high-voltage, three-phase electrical service is generally needed. A

continuous water supply must be available at the site. Various ancillary equipment may

also be required, such as liquid or sludge transfer and feed pumps, ash collection and

solids handling equipment, personnel and maintenance facilities, and process-generated

waste treatment equipment. In addition, a feed-materials staging area, decontamination

trailer, ash handling area, water treatment facilities, and a parking area may be required

(USEPA 1992a). Special handling measures should be provided to hold any process

residual streams until they have been tested to determine their acceptability for disposal

or release. Depending on the site and the nature of the waste, a method to store waste that

has been prepared for treatment may also be necessary. Storage capacity depends on

waste volume and equipment feed rates (USEPA 1992a).

Cost

The cost of incineration includes the relatively fixed costs of site preparation,

permitting, and mobilization/demobilization; and variable operational costs, such as

labour, utilities, and auxiliary fuel. Average costs of the treatment system were said to

range from $140- $360/m3 (1989 dollars) (USEPA 1997).

By-products

Three major waste streams generated by incineration are solid ash from the incinerator

and any solids captured by the APC system, water from the APC system, and gaseous

emissions from the incinerator.


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Ash is commonly either air-cooled or quenched with water after discharge from

the combustion chamber. Dewatering or solidification/stabilization of the ash may also

have to be applied since the ash could contain leachable metals at concentrations above

regulatory limits. The alkalinity of the matrix may influence the leachability of the ash

(USEPA 1989).

The flue gases from the incinerator should treated by an APC system such as an

electrostatic precipitator, scrubber or filter before discharge through a stack. A high- or

low-pH liquid waste may be generated by the APC system, specifically by a scrubber or

wet precipitator. This liquid waste may contain high concentrations of chlorides, volatile

metals, trace organics, metal particulates, and other inorganic particulates. Wastewater

requiring treatment may be subjected to neutralization, chemical precipitation, reverse

osmosis, settling, evaporation, filtration, or carbon adsorption before discharge (USEPA

1997).

Performance

Incineration technologies were selected as the remedial action at 65 U.S.Superfund sites with VOC and SVOC- contaminated soil or sediment (USEPA 1991a;

USEPA 1993). Incinerator performance is most often measured by comparing initial PCB

concentrations in feed materials with both final concentrations in the ash and

concentrations present in off-gas emissions. In all the reported pilot and field scale

studies, removal efficiencies exceeded 99.99% (USEPA 1997).

Advantages and Limitations

A well designed incinerator will have the following advantages:

Capability of the highest overall degree of destruction and control for the broadest

range of hazardous waste streams. The technology has effectively treated soils,

sludges, sediments, and liquids containing all organic contaminants found at wood


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preserving sites, such as PCDDs/PCDFs, PCP, PAHs, and other halogenated and

nonhalogenated VOCs and SVOCs (Oppelt 1987; USEPA 1997).

Treatment can achieve stringent cleanup levels.

Broad application capability, for example with respect to different POP-contaminated

soils.

The limitations of this treatment technology are:

The inorganic components of hazardous wastes are not destroyed by the process,

mostly reporting to the bottom ash, and thus requiring either further treatment or

disposal under stringent regulatory procedures.

Continuous perfectly stable operation of a man-made facility operated by humans

with heterogeneous or variable feed streams is unattainable. Technical defects, fatigue

of construction materials and sensors, mistakes of operators, problems in power

supply etc. sometimes lead to unstable operation. This may lead to some

PCDD/PCDF/POPs emission (Weber 2007).

Performance can be limited by the physical properties and chemical content of the

waste stream, if not accounted for in the system design. Oversized particles (e.g.,

stones, debris) can hinder processing and can cause high particle loading from fines

carried through the process. Feeds with high moisture content increase feed handlingand energy requirements.

Applicability to Developing Countries

Incineration is a viable treatment method since many countries possess the

infrastructure of incineration systems for municipal solid waste disposal and cement

kilns. These facilities can use the contaminated soil as part of the fuel source, if the

system is upgraded to include APC systems, and maintain proper ash treatment or

disposal methods.

Where there are high precipitation rates or where contaminated site is in a flood

hazard plain, there may be problems with incineration, since the soil has to be predried to


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provide the desired outcome, with minimal dioxin/furan emissions. Also high moisture

content soils require more energy needs to achieve dryness.


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A-2 Bioremediation (DARAMEND & XenoremTM)

Overview

Bioremediation usually refers to the use of microorganisms to break down

complex organic contaminants into simpler compounds. The technology usually involves

enhancing natural biodegradation processes by adding nutrients, oxygen (if the process is

aerobic), and in some cases, microorganisms to stimulate the biodegradation of

contaminants. Anaerobic processes utilize microorganisms that are capable of degrading

contaminants in the absence of oxygen. Bioremediation is typically performed by adding

essential nutrients, adjusting moisture levels, and controlling the concentration of oxygen

in the treatment area or vessel. Microorganisms already present in the soil may be

biodegraders, or additional strains may be introduced.

Solid-phase bioremediation uses conventional soil management practices, such as

tilling, fertilizing, and irrigating, to accelerate microbial degradation of contaminants in

above-ground treatment systems. If necessary, highly contaminated soils can be diluted

with clean soils in order to reduce the contaminants to levels conducive to

biodegradation.

Composting uses bulking agents, such as straw or wood chips, to increase the

porosity of contaminated soils or sediments. Additional components may be added to

increase nutrients and readily available degradable organic matter. These additives

include manure, yard wastes, and food-processing wastes. The resulting mixture often

favours the growth of thermophilic microorganisms which are capable of degrading theorganic contaminants of concern (USEPA 1997).

In-situ bioremediation is accomplished by providing electron acceptors (e.g.,

oxygen and nitrate), nutrients, moisture, or other amendments to soils or sediments,

without disturbing or displacing the contaminated media. In-situ bioremediation is often


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used in conjunction with traditional pump-and-treat and soil flushing groundwater

systems, in which the treated water is amended, as required, to stimulate microbial

activity. It is then re-injected into the zone of contamination. An example of that is

bioventing, where vacuum extraction wells, air injection wells, or both are installed and

operated at relatively low flow rates, providing increased oxygen to the microorganisms

in the soil (NRC 1993).

There are several commercialized bioremediation bio-amendment substances that

are in use. These include: using blood meal, DARAMENDand XenoremTM.

Treatment Processes

Bioremediation can occur under anaerobic or aerobic conditions. These will be

presented separately in the following paragraphs.

Anaerobic Bioremediation

In anaerobic bioremediation, bacteria replace chlorine substituents with electron-

donating hydrogen (from H2) on the organic molecule. Under anaerobic conditions, PCB,

PCDD and PCDF reduction is known to occur as a co-metabolic process, where thesecompounds are transformed during the metabolism of another compound. However,

PCDDs and PCDF have shown resistance to breakdown. There are 2 known

dechlorinating organisms for PCBs, o-17 and DF-1 which depend on 2,3,5,6

tetrachlorobiphenyl (tetraCB) for growth and require acetate to survive (Cutter et al.,

2001).

Anaerobic bioremediation can involve two major remedial actions: bio-

stimulation and bio-augmentation. Bio-stimulation involves addition of a primer to

galvanize a targeted dechlorinating population. Primers include FeSO4, which provides

free sulfate, consumed by sulfate reducers. The bioenergetics favour sulfate reducers

over methanogens. This process is favourable for in-situ applications because it is cheap

and environmentally benign (Bedard et al., 1996). In addition, the procedure can


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introduce halogenated organics to prime processes which are recalcitrant to degradation

(Abraham et al., 2002). Bio-augmentation, involves enriching a contaminated site with

organisms capable of degrading the targeted compound.

Anaerobic degradation of POPs is generally faster than aerobic degradation.

Anaerobic degradation usually involves dechlorination, which has little effect on the total

mass of the target contaminant, but can reduce toxicity by targeting highly chlorinated

congeners (Mondello 2002). Hence dechlorination is sometimes used prior to aerobic

remediation to decrease the reluctance of contaminants to undergo biodegradation.

Usually a sequential of anaerobic and aerobic processes yields better overall degradation

results.

No practical and effective universal systems for bioremediation of PCBs, Dioxins

and furans in soil have been developed for several reasons. PCBs, PCDD/Fs are mixtures

of congeners having different physical and chemical properties. Microorganisms cannot

use PCBs, PCDD/Fs as source of carbon and energy growth. Thus they have no selective

advantage by which they expend energy to perform these reactions (Wiegel and Wu

2000; Smidt and de Vos 2004). It is also difficult to promote successful cometabolic bio-

transformation. The available data are limited, and major differences between lab-scale

and site conditions often exist (Zhang and Bennett 2005). Contaminants can be more bio-

available in the laboratory than on site. In addition, discrepancies are also common in

reported results due to volatilization, redistribution of congeners, and partitioning to

equipment in lab studies (Mondello 2002; Wu et al., 2002; Zhang and Bennett 2005). In

laboratory-scale studies, bacteria are commonly made more competitive or conditions are

adjusted to their favour (Mondello 2002; Wu et al., 2002; Zhang and Bennett 2005).

Aerobic Bioremediation

Aerobic degradation of POPs can be carried out by a variety of aerobes acting

synergistically. The degradation usually attacks lightly-chlorinated congeners (e.g. in

PCBs 5 or fewer) (Bedard et al., 1996; Abraham et al., 2002).


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Studies have shown that a broad range of gram-negative and gram-positive

bacteria can breakdown PCBs. The range is narrower for PCDD/Fs. Extensive research

found strains of PCB-degrading-bacteria, especially in contaminated soils: Enterobacter

sp. SA-2, Ralstonia sp. SA-4, and Pseudomonas sp. SA-6. e.g., Achromobacter sp.,

Alcaligenes, sp., Acinetobacter sp., Corynebacterium sp., Rhodococcus sp., Burkholderia

sp. and Pseudomonas sp. that can metabolize PCBs or, in the case of congeners

containing one or two chlorines, use them as a sole source of carbon and energy

(Adebusoye et al., 2007). Burkholderia xenovorans LB400 and Rhodococcus sp. strain

RHA1 are two of the more promising strains for application in the aerobic stage of a PCB

biotreatment process because of their abilities to degrade a wide range of PCB congeners

(Rodrigues et al., 2006). However, like other PCB-degrading microorganisms, they have

only limited ability to grow on PCBs, so repeated addition (bio-augmentation) would be

required for bio-treatment (Rodrigues et al., 2006).

In-situ bioremediation takes place in the vadose zone of soils and in the top few

millimetres of sediments, ensuring aerobic conditions. This often leads to the production

of chlorobenzoic acid (CBA) due to enzymatic degradation of the ring resulting in fewer

attached chlorine atoms, with release of the second ring as CBA. If accumulated, CBA

itself can be toxic (Abraham et al., 2002). Rodrigues et al (2006) reported that PCB

degraders cannot catalyze degradation CBA, with the consequence being a buildup of the

metabolite.

Performance

Aerobic Studies

Bench, Laboratory and Pilot Scale Studies

Laboratory scale studies commonly experience greater effectiveness than field

treatment because they are conducted under more controlled, uniform and favourable

conditions than in the field (NRC 1993). Laboratory studies can provide upper limit

results, but caution must be exercised when forecasting results expected in full scale and

field bioremediation. Most reported studies have been done on PCB bioremediation in


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particular on Aroclor, including 1221,1242 and 1254 incubated in aerated sludge reactors.

The mono- and dichlorinated PCBs rapidly degraded and the rate decreased as percent

chlorine of Aroclors increased (Mondello 2002). Studies on high-density PCB-degrading

bacteria suspended in buffer solution with a PCB mixture revealed that degradation

occurred, except to Aroclor 1254 (Furukawa et al., 1983).

In bioreactor studies, PCB reduction was up to 80% in bench scale systems

(Mondello 2002). Degradation of Aroclor 1248, 1254 and 1260 has been studied in 8

different types of agricultural and forest soils (Mondello 2002). Results showed

degradation rates up to 80%. The least degraded mixtures were those containing highly-

chlorinated congeners like 1254 and 1260.

Field Studies

Field studies results show less degradation than in laboratory investigations. The

following provides some examples of recorded field studies:

(a)Glenn Falls, NY (Mondello, 2002)

The site consisted mainly of sandy soil contaminated with Aroclor 1242, at levels

of 50-500 mg/kg. Many di- and trichlorobiphenyls were degraded.

The study attempted to stimulate the process by adding Pseudomonas strain

LB400 (which is known to degrade a wide variety of PCBs). Laboratory scale

test, showed 85% degradation.

In the field study the strain was repeatedly dosed over a designated area for a

period of 4 months.

Only 20% of the PCBs degraded.

In an adjacent plot, which was repeatedly dosed with nutrient solution and no

bacteria introduction relying only on native microorganisms, there were negligible

degradation.


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After 373 days, hexa- to nona-CBs decreased from 68% to 26%. However, TriCB

increased. Overall there was no net reduction in total PCB concentration.

(b)Anaerobic Bioremediation of Toxaphene using Blood Meal (USEPA 2005)

This method uses blood meal as a nutrient to the native anaerobic bacteria. The

contaminated soil was treated for toxaphene by bio-stimulation. The soil was

mixed with blood meal and saturated with water (0.3 m above the soil).

In ex-situ systems, the soil was placed on lined cells, covered and incubated for

several months.

The by-products from this process were lower chlorinated chlorobenzenes,

chloride ions and cell mass, in addition to H2S and methane.

An attempt to treat chlorobenzenes by blood meal under aerobic conditions

achieved 90% dechlorination.

Anaerobic-Aerobic Remediation

Aerobic bacteria do not degrade highly chlorinated compounds such as PCBs.

Coupled systems of anaerobic and aerobic phases may be implemented, where highly

chlorinated compounds are dechlorinated, to enhance aerobic degradation.

DARAMEND

and XenoremTM

are commercialized technologies utilized in this

coupled system.

DARAMEND

(USEPA 2005)

The process includes addition of DARAMEND (which contains nutrients and zero-

valent iron) with water to produce an anoxic phase causing bio-stimulation.

Periodic tilling of the soil is performed to promote oxic conditions. Watering and

tilling are performed several times to achieve effective treatment. The technology can be implemented using land-farming techniques for ex-situ or in-

situ conditions:

o Ex-situ requires excavated soil to be placed on lined cells after removal of

debris.


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o In-situ is only applicable for surface soil or soil within reach of tilling

equipment. The soil must be screened to remove large debris.

By-products of concern are the leachate produced, if cells are not covered on top to

prevent exposure to rainfall.

This technology is generally not feasible for highly contaminated soils.

XenoremTM

This is a patented technology developed by Stauffer Management Company, a

subsidiary of AstraZeneca Group PLC of Mississauga, Ontario, Canada. Recently,

this technology was sold to the University of Delaware (USEPA 2005). It is an ex-

situ bioremediation technology utilizing aerobic and anaerobic cycles with enhanced

composting (USEPA 2005). The anaerobic conditions promote dechlorination of

organochlorine compounds. The duration of the anaerobic phase is determined by

bench-scale studies. At the end of the anaerobic phase, the amended soil is mixed

again creating aerobic conditions (USEPA 2005; Rubin and Burhan 2006).

XenoremTM treats low-strength wastes containing chlordane,

dichlorodiphenyltrichloroethane (DDT), dieldrin and toxaphene.

Organic amendments such as manure and wood chips are added to the contaminated

soil. This can increase the final amended soil volume by as much as 40% (Rubin andBurhan 2006).

The metabolic activity is increased due to the presence of high levels of nutrients

from the amendment, depleting the oxygen content and creating anaerobic conditions

(USEPA 2005; Rubin and Burhan 2006).

The anaerobic and aerobic cycles are repeated until the desired contaminant

reductions are achieved (USEPA 2005; Rubin and Burhan 2006).

The organic amendments are reportedly spent after 14 weeks (USEPA 2005; Rubin

and Burhan 2006).

This technology was applied in a full-scale cleanup at the Stauffer Management

Company Superfund site in Tampa, Florida (Jackson and Gray 2001).

o The site is the location of a pesticide manufacturing and distribution facility

that operated from 1951 to 1986 (Jackson and Gray 2001).


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o Soil was contaminated with chlordane, dichlorodiphenyldichloroethane

(DDD), dichlorodiphenyldichloroethylene (DDE), DDT, dieldrin, molinate,

and toxaphene.

o The technology was applied to two batches of soil.

o DDD, DDE, DDT and toxaphene were reduced by 65%, 68 %, 88 %, and 94

%, respectively; however, neither batch achieved the site cleanup goals for

DDT and toxaphene (USEPA 2005; Rubin and Burhan 2006).

Site Requirements

Space requirements depend on the specific technology employed. In general, in-

situ applications do not require large areas. Installation of infiltration galleries and wells

to circulate amendment-laden water, however, requires from several hundred to several

thousand square meters of clear surface area (Mondello 2002; USEPA 2004b; USEPA

2005). During ex situ applications, more open space is typically required to accommodate

equipment.

Cost

Cost varies from $55 to $360/m3(2005 dollars) (USEPA 2005) .

Costs at the higher end mainly apply to ex-situ, and mechanical bioremediation.

technologies.

Vendor-related technologies, such as DARAMEND and XeonremTM

, incur high

costs if exported.

By-products

Offensive odours from anaerobic degradation.

More soluble chlorinated compounds, needing further treatment.

Chloride ions.


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Leachates generated from uncovered systems.

Biomass from microorganisms.

Minerals and salts from completely degraded compounds.

Advantages and Limitations

Advantages of bioremediation are:

Both in-situ and ex-situ bioremediation technologies have been shown to be

successful in treating both water-soluble and relatively insoluble compounds. Organic

compounds that are highly soluble in water may biodegrade rapidly, particularly in

slurry-phase systems. In general, the rate of biodegradation of a given compound is

proportional to the solubility of that compound in water.

Slurry-phase bioremediation also has the advantage of allowing more precise control

of operating conditions (e.g., temperature, mixing regimes) than solid-phase or in situ

applications. Slurry-phase systems utilizing tanks can be operated under anaerobic or

aerobic conditions, either sequentially in the same tanks, or in series with multiple

vessels. Slurry-phase bio-remediation allows improved contaminant monitoring due

to increased homogeneity of the contaminated media.

Solid-phase bioremediation and composting offer several advantages common to

slurry-phase operations and other ex-situ treatment technologies: better process

control, increased homogeneity, and improved contaminant monitoring. In addition,

treatment units can be built to accommodate large quantities of media.

Composting also enriches the treated soil, providing nutrients for revegetation

(Petkewich 2001). In situ bioremediation minimizes the need for excavation and

transport of contaminated soils, sediments, or sludges.

Energy costs required for bioremediation treatment are typically less than for

alterative remedial approaches.


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Limitations include:

Many factors affect the success of bioremediation. The physical form, amount,

location, and distribution of contaminants have major impacts on the degree to which

contaminants are degraded (Downwy et al., 2004).

Biodegradable contaminants may undergo mineralization (complete degradation to

inorganic constituents); however, incomplete degradation (ending with the formation

of organic intermediates) is also possible.

Soil characteristics, including particle size distribution, moisture content, and

permeability, also affect the success of bioremediation.

Soil and contaminant characteristics affect bioavailability (the extent to which

contaminants can be degraded by microorganisms).

The contaminated soil must not exceed 10 % by volume of the treated soil (Bedard et

al. 1996).

Bioavailability of contaminants in soil can decrease with time, as the contaminants

age and become more strongly sorbed to soil particles.

Bioremediation is slower than many other technologies and may require frequent

monitoring during startup. Monitoring and sampling will also be necessary to

determine when prescribed cleanup levels have been achieved.

Temperature, moisture content and pH values below or above the optimal range for

the microorganisms retard or halt bioremediation. In some cases, excessive biomass

growth may impede further remediation.

Bioremediation has not proven to be effective on PCDDs/PCDFs.

Breakdown of contaminants may generate more toxic by-products or contaminants

which are mobile.

Chlorinated compounds used as bioaugmentation, may cause increased contamination

by chlorinated compounds at the site. Ex-situ remediation practices require large surface areas to treat large quantities of

contaminated soil. This is a disadvantage for heavily populated countries where land

is very expensive.

Aerobic remediation is not applicable to sites prone to flooding, because water

logging leads to anaerobic conditions.


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In addition to these general limitations, in situ and, to a lesser extent, solid-phase

bioremediation present potential difficulties in determining the performance of the

treatment. Contaminant spatial heterogeneity, fate and transport, and sorption

dynamics all lead to variability in results across the site and over time. Sorption

dynamics are particularly important for composting, since contaminants may bind

strongly to the added organic matter, reducing bioavailability. Degradation rates,

therefore, may be limited by desorption kinetics rather than microbial activity.

Especially when recalcitrant contaminants such as PCBs are present. PCBs are often

tightly bound to soil particles, resisting enzymes of dechlorination and making it

difficult to establish and stimulate PCB organisms in remediation sites (Abraham et

al., 2002).

Applicability to Developing Countries

Many bioremediation options are affordable.

If contaminated land is expensive, then time-consuming technologies are likely to be

infeasible.

Countries with extreme weather conditions require more controlled treatment

environments since bioremediation technologies are sensitive to moisture content and

temperature.

Many developing countries are subject to high precipitation and to flooding

conditions. In this case, aerobic remediation is only feasible if conducted in protected

sites or ex-situ locations.

Ex-situ bioremediation involving soil spreading requires large surface areas,

especially when large quantities of soil are contaminated. For highly populated

countries suffering from lack of free land, ex-situ remediation tends to be veryexpensive.

In-situ bioremediation technology can be promising for areas with relatively moderate

climates. Technologies involving farming equipment are feasible, since such

equipment is often already present in such areas.


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A-3 Solvent Extraction

Overview

Solvent extraction is an ex-situ process in which contaminants are separated from

soils, sludges, and sediments, thereby reducing the volume of waste that must be treated.

In the process, the contaminated soil or waste material is brought into contact with a fluid

that selectively dissolves the contaminants.

Treatment Process

The primary stages of the solvent extraction technology are media preparation,

contaminant extraction, solvent/media separation, contaminant collection, and solvent

recycling. Waste preparation includes excavation or moving the waste material to the

process where it is normally screened to remove debris and large objects. Depending

upon the process vendor and whether the process is semi-batch or continuous, the waste

may need to be made mobile (pumpable) by the addition of a solvent or water.

In the extractor, the soil or sediment and solvent are contacted with each other,

and the organic contaminant dissolves into the solvent. The extraction behaviour

exhibited by this technology is usually similar to other mass-transfer-controlled

processes, like liquid-liquid extraction, although equilibrium considerations often become

limiting factors when the time of contacting is long. It is important to conduct a

laboratory-scale

treatability test to determine whether mass transfer or equilibrium is likely to be the

controlling factor, since the controlling factor is critical to the design of the unit and to

the determination of whether solvent extraction technology is appropriate for treatment of

the particular waste.


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After a predetermined extraction time, the solid and the fluid are separated, and

the target contaminants are concentrated in the extraction fluid. The number and length

of the extraction stages are selected based on the remediation criteria, i.e. to achieve the

required degree of extraction. The extracted organics are removed from the extractor

with the solvent and go to a separator, where the pressure and/or temperature is changed,

causing the organic contaminants to separate from the solvent by forming different

phases (Rowe 1987). The solvent is then recycled to the extractor, and the concentrated

contaminants are removed from the separator (Rowe 1987).

Soil properties affect the efficiency of the treatment method. Optimal soil

conditions for treatment include less than 15% clay in the soil and less than 20% moisture

in the soil (USEPA 1995b). Higher moisture contents require drying of the soil and /or

solvent distillation to reduce accumulation of water in the solvent.

Soils containing more than 20% moisture must be dried prior to treatment.

Excess water dilutes the solvent, reducing contaminant solubilization and transport

efficiency (USEPA 1995b). Water buildup in the stock solvent requires the addition of a

distillation step to maintain solvent integrity. Excessive clay concentrations require

additional wash cycles and physical handling to reduce clay aggregate size (USEPA

1995b).

Site Requirements

Typical commercial-scale units (50 to 70 tons per day) may require a total

treatment area of 930 m2 and a power supply (USEPA 1995b). Water must also be

available at the site (USEPA 1995b).

Cost

One time start-up (including capital) cost is estimated at $175,000 for a commercial

unit.


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Average treatment cost range between $125-$400/m3 (in 1995 dollars) (USEPA

1995b)

By-products

There are three main by-product streams generated by this technology:

The extract containing concentrated contaminants, after the organic contaminants

being separated from the solvent, which requires further treatment.

The treated soil or sludge may need to be dewatered before being returned to the site.

Water involved in the process. The volume of the water depends on the inherent

dewatering capability of the liquid-solid separation process, the specific water

requirement for feed slurrying, and the initial water content of the soil or sediment

(USEPA 1997).

Performance

Solvent extraction technologies have been selected as the remedial action at

several U.S. Superfund sites. This section briefly summarizes pilot and full-scale studies.

Laboratory, Bench and Pilot Scale Studies

Treatability pilot studies on different PCB contaminated soils of different soil

properties have been conducted, with varying number of wash cycles. The process

resulted in a removal efficiency of 95-99%, with better removal as the number of wash

cycles increased (USEPA 1995b).

Full Scale Studies Removal efficiency at 4 U.S. Superfund sites contaminated with PCBs was 99%

(USEPA 1997).

A full scale study of solvent extraction on DDT-contaminated soil resulted in a 98.8%

contaminant reduction (USEPA 1995b).

07 treatment tech reference guide for pops lli

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