o
Committee on the
Challenges of
Modern Society
EPA/600/R-93/012a
February 1993
Demonstration of Remedial
Action Technologies for
Contaminated Land and Groundwater
Final Report
Volume 1
Number 190
North Atlantic Treaty Organization
1986-1991
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COMMITTEE ON
THE CHALLENGES OF
NATO/CCMS MODERN SOCIETY
Number 190
FINAL REPORT
Volume 1
Demonstration of Remedial Action Technologies
for Contaminated Land and Groundwater
Pilot Study Directors
Donald E. Sanning, United States - Director
Vokler Franzius, Germany - Co-Director
Esther Soczo, The Netherlands - Co-Director
Participating Countries
Canada Germany
Denmark The Netherlands
France United States
Observer and Other Countries
Austria Norway
Italy Turkey
Japan United Kingdom
Authors
Thomas O. Dahl Donald E. Sanning
Merten Hinsenveld James W. Schmidt
Stephen C. James Michael A. Smith
Norma Lewis Sjef Staps
Robert F. Olfenbuttel, author and General Editor
1986-1991
&f} Printed on Recycled Paper
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Abstract
This publication reports on the results of the NATO/CCMS Pilot Study "Demonstration of Remedial Action Tech-
nologies for Contaminated Land and Ground Water" which was conducted from 1986 through 1991. The Pilot
Study was designed to identify and evaluate innovative, emerging and alternative remediation technologies and to
transfer technical performance and economic information on them to potential users.
Twenty-nine remediation technology projects were examined which treat, recycle, separate or concentrate con-
taminants in soil, sludges, and ground water. The emphasis was on in situ and on-site technologies; however, in
some cases, e.g., thermal treatment, fixed facilities off-site were also examined. Technologies included are: ther-
mal, stabilization/solidification, soil vapor extraction, physical/chemical extraction, pump and treat ground water,
chemical treatment of contaminated soils, and microbial treatment.
This report serves as a reference and guide to the potential application of technologies to various types of con-
tamination; it is not a design manual. Unique to this study is the examination and reporting of "failures" as well as
successes.
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Acknowledgements
The Pilot and Co-Pilot Study Directors thank all who made significant contributions to the work of the Pilot Study:
Those representing their countries made a major contribution to the direction of the Study by recommending
projects within their respective countries which would be of particular interest to this Study, and by discussing the
regulatory and general environmental technology situations in their countries.
The various chapters were written by the respective authors after reviewing reports prepared on the Case Studies
for the meetings of the Study Group.
Good use was made of the NATO/CCMS Fellowship Program to further enhance the value of the Study and a
number of Fellows contributed directly to the preparation of this report. Robert Olfenbuttel of Battelle also served as
the general editor for the report, supported by Virginia R. Hathaway of JACA Corp., editor.
Expert speakers, often supported by NATO/CCMS travel funds, participated in the workshops and conferences of
the Pilot Study and contributed to the work of the Pilot Study Group.
Until his retirement, the NATO/CCMS International Staff was represented by the former CCMS Director, Mr. Ter-
rance Moran. Dr. Deniz Beten replaced Mr. Moran and attended the Fifth International Meeting.
Ms. Naomi Barkley of the Office of Research and Development, Risk Reduction Environmental Laboratory, Super-
fund Technology Demonstration Division, U.S. Environmental Protection Agency served as Task Project Manager
for this project.
The names and addresses of all participants in the Study Group are given in Volume Two.
iii
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Contents: Volume 1
Foreword i
Abstract ii
Acknowledgements iii
Figures x
Tables xi
Chapter 1
Introduction . 1
Donald E. Sanning and Robert F. Olfenbuttel
1.1 Background 1
1.2 Structure of the Study 1
1.2.1 Categories of the Technologies Examined 2
1.2.3 How the Technology Information is Presented 2
1.2.4 Summary of Conclusions 3
1.3 Contributions by CCMS Fellows 3
1.4 Contents of Volume 2 3
Chapter 2
Thermal Technologies 7
Stephen C. James and Gregory L Stacy
2.1 Introduction 7
2.2 Case Studies Chosen 11
2.2.1 Case Study 2-A: Rotary Kiln Incineration, The Netherlands . . . 11
2.2.2 Case Study 2-B: Indirect Heating in a Rotary Kiln, Germany 12
2.2.3 Case Study 2-C: Off-site Soil Treatment, Japan 13
2.2.4 Case Study 2-D: Electric Infrared Incineration, United States 13
2.2.5 Case Study 2-E: In Situ Vitrification, United States 14
2.3 Background of the Case Studies as a Group 14
2.4 Performance Results 14
2.5 Residuals and Emissions 15
2.6 Factors To Consider for Determining Applicability of the Technology 17
2.7 Costs 20
2.8 Future Status of Case Study Processes and Thermal Technologies as a Whole 21
Chapter 3
Stabilization/Solidification Technologies 23
Merten Hinsenveld
3.1 Introduction 23
3.1.1 Place of the Techniques in a Broad Sense 23
3.1.2 The Stabilization/Solidification Process 24
3.2 Case Studies Chosen 25
3.2.1 Case Study 3-A: In Situ Lime Stabilization (EIF Ecology), France 25
3.2.2 Case Study 3-B: Petrifix Process (TREDi), France 25
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3.2.3 Case Study 3-C: Portland Cement (Hazcon, presently IM-Tech), United States 25
3.3 Background of Case Study Sites as a Group 25
3.4 Performance Results .25
3.5 Residuals and Emissions 27
3.6 Factors to Consider for Determining the Applicability of the Technology 27
3.6.1 Limitations and Restrictions on the Use of the Technology 27
3.6.2 Steps in Determining the Applicability of S/S Treatment 28
3.7 Costs 29
3.7.1 General Cost Factors 29
3.7.2 Costs Of The Hazcon Treatment System 30
3.8 Future Status of Case Study Processes and the Technology as a Whole 30
Chapter 4
Soil Vapor Extraction Technologies 33
Norma Lewis
4.1 Introduction . . . . 33
4.2 Case Studies Chosen 35
4.2.1 Case Study 4-A: In Situ Soil Vacuum Extraction, The Netherlands 35
4.2.2 Case Study 4-B: Vacuum Extraction of Soil Vapor, Verona Well Field Superfund Site,
United States ,. . . 36
4.2.3 Case Study 4-C: Venting Methods, Hill Air Force Base, United States 36
4.2.4 Additional Case Studies, United States 36
4.3 Background of the Case Study Sites as a Group . 37
4.4 Performance Results 38
4.4.1 Analytical Procedures 38
4.4.2 General Effectiveness of the SVE Process 38
4.4.3 Removal of Nonhalogenated Solvents . 39
4.4.4 Removal of Gasolines and Jet Fuels 39
4.4.5 Removal of Halogenated Solvents 40
4.4.6 Usefulness for Enhancing In Situ Biodegradation . 40
4.5 Residuals and Emissions 41
4.6 Factors to Consider for Determining Applicability of the Technology 43
4.7 Costs 44
4.8 Future Status of Case Study Processes and the SVE Technology as a Whole 48
Chapter 5
Physical/Chemical Extraction Technologies 53
Merten Hinsenveld
5.1 Introduction 53
5.1.1 Place of the Techniques in a Broad Sense 53
5.1.2 Principle of Extraction Techniques 54
5.1.3 Principle of Electro-reclamation '..'.' . . . . 55
5.2 Case Studies Chosen .55
5.2.1 Case Study 5-A: High Pressure Soil Washing (Klockner), Germany 55
5.2.2 Case Study 5-B: Vibration (Harbauer), Germany . . 55
5.2.3 Case Study 5-C: Jet Cutting Followed by Oxidation (Keller), Germany ........... .56
vi
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5.2.4 Case Study 5-D: Electro-reclamation (Geokinetics), The Netherlands 56
5.2.5 Case Study 5-E: In Situ Acid Extraction (TAUW/Mpurik), The Netherlands 56
5.2.6 Case Study 5-F: Debris Washing, United States . . . . 56
5.3 Background of the Case Study Sites as a Group 56
5.4 Performance Results 56
5.5 Management of Residuals 58
5.6 Limitations or Restrictions to the Use of the Techniques 58
5.7 Costs 58
5.7.1 Fixed Costs . . . 58
5.7.2 Variable Costs 60
5.7.3 Total Costs ..- 61
5.8 Future Status of Case Study Processes and Extraction Technologies as a Whole 62
Chapter 6
Pump and Treat Ground Water 65
J.W.Schmidt
6.1 Introduction 65
6.2 Case Studies Chosen 65
6.2.1 Case Study 6-A: Decontamination of Ville fVlercier Aquifer for Toxic Organics, Ville
Mercier, Quebec, Canada. . . ... 66
6.2.2 Case Study 6-B: Evaluation of Photo-oxidation Technology (Ultroxฎ International),
Lorentz Barrel and Drum Site, San Jose, California, United States. 66
6.2.3 Case Study 6-C: Zinc Smelting Wastes and the Lot River, Viviez, Averyron, France .... 67
6.2.4 Case Study 6-D: Separation Pumping, Skrydstrup, Denmark .67
6.3 Background of the Case Study Sites as a Group 68
6.4 Performance Results 69
6.4.1 Effectiveness of Aquifer Remediation at Ville Mercier 69
6.4.2 Effectiveness of Treatment Technologies 69
6.4.3 Lessons Learned on How to Improve Effectiveness 70
6.5 Residuals and Emissions : 71
6.6 Factors and Limitations to Consider for Determining Applicability of the Technology 71
6.6.1 Application of Pump and Treat 71
6.6.2 Application of Ground Water Treatment Technologies 71
6.6.3 Availability of the Technologies 72
6.7 Costs 72
6.8 Future Status of Case Study Processes and the Technology as a Whole 73
6.8.1 Air Stripping and Activated Carbon 73
6.8.2 Photo-oxidation Technologies 74
6.8.3 Precipitation Technology 75
Chapter 7
Chemical Treatment of Contaminated Soils: APEG 77
Michael A. Smith
7.1 Introduction ......;.. 77
7.1.1 Applicability 77
7.1.2 Variations on the APEG Process 78
VII
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7.1.3 Operational Requirements .78
7.2 Case Study Chosen ! ..;.....................:.. 79
7.2.1 Background . . , 79
7.2.2 The KPEG Demonstration Project . : . . .:.'... ... 80
7.3 Performance Results 80
7.4 Residuals and Emissions 80
7.5 Limitations .80
7.5.1 Inherent in the Technology .80
7.5.2 Health and Safety ^ ..:....... 80
7.6 Costs 82
7.7 Factors to Consider for Determining Applicability of the Technology . . . . .82
7.8 Future Status of the Technology . . 82
Chapters
Microbial Treatment Technologies . . ..'-. .'." ;................. 85
SJefStaps
8.1 Introduction ... . . . . . . . . ... . . , 85
8.2 Case Studies Chosen ... . ; ...... . . ....... 86
8.2.1 In Situ Projects . . . . ]' . . . . ... '. ; . . : . ..... .. , ......... 86
8.2.1.1 Case Study 8-A: Aerobic/Anaerobic In Situ Degradation of Soil and Ground
Water, Skrydstrup, Denmark .86
8.2.1.2 Case Study 8-B: In Situ Biorestoration of Soil, Asten, The Netherlands ....... 86
8.2.1.3 Case Study 8-C: In Situ Enhanced Aerobic Restoration of Soil and Ground Water,
Eglin Air Force Base (AFB), United States .86
8.2.2 Ex Situ Projects . 86
8.2.2.1 Case Study 8-D: Bidlogical Pre-treatment of Ground Water, Bunschoten, The
Netherlands 86
8.2.2.2 Case Study 8-E: Rotary Composting Reactor for Oily Soils, Soest, The
Netherlands 87
8.3 Background of the Case Study Sites as a Group 88
8.4 Performance Results 89
8.4.1 Common Effectiveness of Process Units 90
8.4.2 Effectiveness of the Rotating Composting Bioreactor on Diesel Fuel 91
8.4.3 Lessons Learned on How to Improve Effectiveness 91
8.4.4 Lessons Learned In Site Preparation and Testing 91
8.5 Residuals and Emissions 92
8.6 Factors and Limitations to Consider for Determining Applicability of the Technology 92
8.7 Costs 93
8.8 Future Status of Case Study Processes and Microbial Treatment as a Whole 94
8.8.1 Future Status of Case Studies 94
8.8.2 Future Status of Microbial Treatment in General 94
Chapter 9
Selecting Remedies at a Complex Hazardous Waste Site 97
Thomas O. Dahl
9.1 Introduction 97
9.2 Interim Studies/Remedies 98
viii
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9.3 Litigation - ........ 99
9.4 The Remedial Investigation/Feasibility Study (RI/FS) Process .99
9.5 Stringfellow Site RI/FS 102
9.6 Remedy Selection at Stringfellow . . . 105
9.7 Conclusions 106
Chapter 10
Conclusions and Recommendations 109
Donald E. Sanning and Robert F. Olfenbuttel
10.1 Introduction 109
10.2 Specific Technology Chapter Conclusions . . . ....;.% ...... ..... . . . . . . . 109
10.2.1 Chapter 2: Thermal Technologies ,.,.,,......... 109
10.2.2 Chapter 3: Stabilization/Solidification (S/S) Technologies 110
10.2.3 Chapter 4: Soil Vapor Extraction (SVE) Technologies 110
10.2.4 Chapter 5: Physical/Chemical Extraction Technologies 110
10.2.5 Chapter 6: Pump and Treat Ground Water . 110
10.2.6 Chapter 7: Chemical Treatment of Contaminated Soils: APEG 111
10.2.7 Chapter 8: Microbial Treatment Technologies 111
10.2.8 Chapter 9: Selecting Remedies at a Complex Hazardous Waste Site ........... 111
10.2.9 Appendix: In Situ Vitrification . . . . . ...'.:. . . . .\ ....'. .'.' :'. . 112
10.3 General Conclusions . . . 112
10.3.1 Remediation . . ....... . . . . . . .". . . 112
10.3.2 Technology Transfer .'. .'. . >['. .,, .'.'-..,."", . .-. . : .... ........ 114
10.3.3 Research 114
10.4 Recommendations ,..,.,.....,. 115
IX
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Figures
Figure 4-1. Soil vapor extraction system 34
Figure 4-2. Two types of soil venting systems, (a) Use of passive vapor wells to prevent
migration of off-site contaminant vapors, (b) Water table rise caused by the
applied vacuum 44
Figure 4-3. Guidelines for deciding if SVE is applicable 45
Figure 5-1. The basic processes in extraction installations 54
Figure 7-1. Schematic diagram of a typical glycol dehalogenation treatment facility 78
Figure 7-2. APEG reactions 79
Figure 7-3. Block diagram of internal flow of materials 81
Figure 8-1. Cross-section of the soil with an overview of the restoration process 87
Figure 8-2. Eglin AFB Site profile 88
Figure 8-3. Flow diagram of the RBCs and compost filters 89
Figure 8-4. Biological treatment process in the rotating bioreactor. 89
Figure 9-1. Location of the Stringfellow Waste Disposal Site 98
Figure 9-2. General site configuration by 1972 for disposal operations 98
Figure 9-3. U.S. Superfund remedy selection process 100
Figure 9-4. Approximate location of TCE contaminated ground water that extends from the
Stringfellow Site into Glen Avon 104
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Tables
Table 1 -1. Conclusions for NATO/CCMS final report; demonstration of remedial action
technologies for contaminated land and ground water
Table 2-1. Numbers and types of hazardous waste incineration facilities in the United States.
Table 2-2. Hazardous waste incineration facilities in Europe.
Table 2-3. Site data from U.S. hazardous waste incinerator projects
Table 2-4. Performance data for various U.S. hazardous waste incinerator projects
Table 2-5. European Community emission limits for municipal incinerators
Table 2-6. Typical incinerator operating conditions in the EC, as reported by manufacturers. .
Table 2-7. Methods to develop cleanup standards by country . . ."
Table 2-8. Waste characteristics suitable for electric infrared incineration . . .
Table 2-9. Typical costs of incineration of contaminated soils (in US$, 1988)
Table 3-1. Problem handled in these NATO/CCMS case studies
Table 3-2. Limitations of the case study techniques.
Table 3-3. Summary of estimated treatability costs for metals (x1000 US$, 1989)
Table 3-4. Estimated costs for the Hazcon System (in US$, 1989). . .
Table 4-1. Summary of SVE case study information
Table 4-2. Reduction of weighted average TCE levels in soil, Groveland Well Site (TCE
concentration in mg/kg)
Table 4-3. Characteristics limiting SVE feasibility - contaminant, soil, and site characteristics.
Table 4-4. Factors affecting SVE treatment costs
Table 4-5. Terra Vac economic model (in US$, 1989). .
Table 4-6. Verona Well Field SVE costs (in US$, 1990)
Table 4-7. TCAAP Site D Estimated construction and operating costs (in US$)
Table 4-8. TCAAP Site G Estimated construction and operating costs (in US$)
Table 4-9. Capital cost estimation of SVE components (in US$, 1990)
Table 5-1. Problems handled in the NATO/CCMS case studies
Table 5-2. Limitations to the use of the case study techniques
Table 5-3. Summary of annual fixed costs (in US$ 1990)
Table 5-4. Summary of variable costs per tonne soil (in US$, 1990)
Table 5-5. Total costs of extractive treatment per tonne soil (in US$, 1990)
Table 6-1. Sources of contamination at case study sites
Table 6-2. Principal contaminants at the Ville Mercier, and the Lorentz Barrel and Drum sites.
Table 6-3. Performance results for Ville Mercier, and Lorentz Barrel and Drum sites
Table 6-4. Performance results for Lot River site
Table 6-5. Ville Mercier operating costs, (x 1,000 CDN$)
Table 6-6. Estimated capital and operating costs associated with three Ultroxฎ system units
(in US$, 1990 )
Table 6-7. Lot River operating costs (in French francs)
Table 8-1. Costs of control techniques by levels of pollutant removal efficiency (in US$). . . ,
Table 9-1. Stringfellow Site technical studies ,
Table 9-2. Stringfellow Site treatability studies
. 4
. 8
. 8
. 9
. 16
. 18
. 18
. 19
. 20
. 20
. 26
. 28
. 30
. 31
. 37
. 40
. 46
. 47
. 48
. 48
. 49
. 49
. 50
. 57
. 59
. 61
. 62
. 62
. 68
. 68
. 69
. 70
. 73
. 74
. 74
.94
102
102
XI
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Table 9-3. Summary of remedial alternatives resulting from the Stringfellow Site feasibility
study 105
Table 9-4. Estimated cost comparison of revised remedial alternatives - overall site remedy 106
XII
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1
Introduction
Donald E. Banning
United States Environmental Protection Agency
Office of Research & Development, Cincinnati, Ohio 45268
United States
Robert F. Olfenbuttel
Waste Minimization and Treatment, BatteHe-Columbus Division
505 King Avenue, Columbus, Ohio 43201
United States
1.1 Background
Ground water and soil contamination are among
the most complex and challenging environmental
problems faced by most countries today. This chal-
lenge results from a number of significant factors, such
as the complex geochemical, physical and biological
nature of contaminated subsurface soils and ground
water; limited knowledge regarding the behavior and
interaction of pollutants within these environmental
matrices; and the sheer magnitude of the contamina-
tion. These factors, in turn, limit the application and
effectiveness of conventional waste treatment tech-
nologies and result in high remediation costs.
As a result, there is an ongoing need for more reli-
able, cost-effective cleanup technologies to address
these problems and many governmental and private
organizations, in many countries, have committed
resources to the development, test and evaluation,
and demonstration of technologies to meet this need.
The ongoing challenge to these organizations is how
to maximize the value of these technology advance-
ments and effectively transfer the information to
people responsible for making decisions and im-
plementing remedial actions.
Consequently, a NATO Committee on the Challen-
ges of Modern Society (NATO/CCMS) Pilot Study was
conducted from 1986 through 1991 for the purpose of
identifying and evaluating innovative, emerging, and
alternative remediation technologies, and transferring
technical performance and economic information on
them to potential users. A specific and important ob-
jective of the Study was to identify "lessons learned"
from the technology demonstrations, including not only
the successes but also those which illustrated technol-
ogy failures or limitations. The latter type of informa-
tion is rarely presented in conferences and/or
discussed in the technical literature but is very impor-
tant for making informed decisions that involve critical
time and monetary requirements. It is also useful for
defining priorities in research and development
programs.
1.2 Structure of the Study
The Pilot Study Group examined a total of 29 dif-
ferent remediation technology projects conducted by
non-NATO sponsored organizations, within member
countries, over the five year course of the Study.
These technologies treat, recycle, separate or con-
centrate contaminants in soil, sludges and ground
water matrices. In some cases, such as for thermal
treatment, fixed facilities off-site were studied, al-
though the emphasis was on in situ and on-site biologi-
cal, chemical/physical and thermal waste treatment
technologies. The study did not include barrier walls
or technologies in which containment was a primary
technique.
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Chapter 1
1.2.1 Categories of the Technologies Examined
For the purposes of this Study, three categories of
technologies in various stages of development were
examined with respect to their possible use in the
cleanup of polluted sites. They are:
ซ Alternative technologies: A technology that is fully
proven in routine use for end-of-pipe treatment;
however, performance and cost data is not readily
available.
ปInnovative technologies: A technology at the pilot
or field scale for which performance or cost infor-
mation is not complete, thereby impeding its use
for remediation. In general, innovative technology
requires field testing to prove its effectiveness
before it is considered proven and available for
use in remediation.
" Emerging technologies: A technology at a stage
where successful bench testing has been con-
ducted and pilot-scale evaluation is now required
to determine its potential for use in remediation
(James and Banning 1989).
The 29 technology projects covering these
categories served as a primary source for the discus-
sion and results presented in this report. However,
this project-specific information was supplemented by
data from other sources, such as Fellows of the
NATO/CCMS, guest expert speakers at the interna-
tional meetings of the Pilot Study, and the collective
experiences and knowledge of the writers. As such,
the information provided in the following chapters rep-
resents a synthesis of all this information, not a com-
pilation of the details of each project. In this way, the
report serves as a reference to the relative state-of-
the-technologies discussed. It is not intended to be a
manual on technology applications but as a guide to
the potential application of technologies to various
types of contamination.
1.2.3 How the Technology Information is
Presented
Chapters 2 through 8 present the results of the Pilot
Study by technology area. They include the following
technologies:
ป Chapter 2: Thermal Technologies. This chapter
discusses the type and use of thermal tech-
nologies in various projects examined under the
NATO/CCMS Pilot Study, both fixed facilities and
transportable incineration systems. Thermal
processes are technologies designed to break
down hazardous waste through either combustion
or pyrolysis by exposure of the waste material to
high temperature in a controlled environment.
Chapter 3: Stabilization/Solidification Tech-
nologies. In this chapter, a general description is
given of cement based stabilization-solidification
techniques. Stabilization-solidification (S/S)
refers to techniques that aim at preventing migra-
tion of contaminated material into the environment
by forming a solid mass.
Chapter 4: So/7 Vapor Extraction Technologies.
Soil vapor extraction (SVE), also known as in situ
venting (ISV), is a process that uses air to remove
volatile organic compounds (VOC's) and some
semivolatile organic compounds (SVOC's) from
the vadose (unsaturated) zone.
Chapter 5: Physical Chemical Extraction Tech-
nologies. A wide range of processes can fit within
this broad category of technology. Under this
Pilot Study the following processes were chosen
and are discussed in this chapter: ex situ extrac-
tion of organic and inorganic contaminants; in situ
jet cutting followed by oxidation of organic con-
taminants; in situ acid extraction of heavy metals;
and in situ electro-reclamation of heavy metals.
Chapter 6: Pump and Treat Ground Water. This
chapter discusses the extraction of contaminated
ground water from the subsurface, followed by
treatment of the water at the surface to remove
the pollutants. Treatment can be by means of
physical/chemical/biological technologies.
Chapter 7: Chemical Treatment of Contaminated
Soils: APEG. This chapter discusses the chemi-
cal dehalogenation of contaminated soils using an
alkaline metal hydroxide with polyethylene glycol
(APEG). Processes of this type are applicable to
soils and soil-like materials (after excavation) con-
taminated with either aromatic or aliphatic
chlorinated organic compounds, although the lat-
ter require more rigorous treament conditions. It is
of particular interest for the treament of soils con-
taminated with polychlorinated biphenyls (PCB's).
Chapter 8: Microbial Treatment Technologies. A
large number of organic contaminants can be
degraded by microorganisms. This technology is
discussed in terms of the basic biological soil
remediation techniques of in situ biodegradation,
landfarming and composting, and bioreactors.
Each of the technology chapters is organized in the
following manner:
Introduction: A description of the technology, in-
cluding basic principles of the process and where
it potentially can be applied.
ป Case Studies Chosen: A summary of each of the
projects evaluated, including why the project was
chosen for evaluation. Available details on each
project are presented in Volume 2.
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Introduction
Background of the Case Study Sites as a Group:
A synthesis of pertinent information from the
projects that will help readers understand the
range of the technology's application in these
studies. This includes the type, concentration
and sources of contamination, type of soil/ground
water matrices containing the contamination, and
the main lessons learned, if any, in the application
of the technology.
Performance Results: An assessment of the
results from the case studies, including whether
project objectives were met, whether the technol-
ogy processes as a whole showed a common ef-
fectiveness, and lessons learned, if any, in con-
taminated site preparation and operational test-
ing.
Residuals and Emissions: A discussion of multi-
media residuals and emissions, if any, associated
with the technology processes that need attention
when evaluating the potential application of these
processes to contaminated sites.
Factors and Limitations to Consider for Determin-
ing the Application of the Technology. A sum-
mary of important factors limiting the application
of the technology processes including whether
they are in situ or above ground techniques; type
of soils, contaminants and contaminant con-
centrations they can potentially treat; level of
cleanup they may be limited to; requirements for
treatability/pilot studies; availability; etc.
Costs: An overview of major capital, operating
and maintenance cost factors that need to be con-
sidered by remediation planners; typical costs
and/or costs specific to case studies are given in
some chapters.
Future Status of Case Study Processes and
Technology as a Whole: A summary of the state
of the technology and its expected role in future
site remediations.
The process of selecting technologies for cleaning
up a complex hazardous waste site is a difficult, but
necessary process, and one in which countries use a
variety of approaches suitable for their needs. There-
fore, in addition to the technology discussions, a
separate chapter on Selecting Remedies at a Complex
Hazardous Waste Site is included (Chapter 9) to
describe the remedy selection process used by the
United States Environmental Protection Agency (U.S.
EPA) and to examine remedial selection problems of
mutual concern for many countries.
1.2.4 Summary of Conclusions
One of the major accomplishments of this Pilot
Study is that it demonstrated the need to exchange
technical and economic information on contaminated
land and ground water iremediation technologies. It
resulted in an extensive set of conclusions regarding
specific technologies, remediation in general, technol-
ogy transfer and research needs. The conclusions are
based on the technology case studies examined
during the Study, as well as on expert speaker presen-
tations and special studies carried out by the Fellows
of the Pilot Study.
The conclusions reached from this Study reveal
both the strengths and weaknesses of current tech-
nologies as well as what efforts are needed to increase
the effectiveness of remediation tools and their ap-
plication. The conclusions are summarized in Table
1-1 and fully discussed in Chapter 10 on Conclusions
and Recommendations. Chapter 10 also provides the
recommendations made by the Study members to the
NATO/CCMS Council for future actions by that or-
ganization.
Insert Table 1-1
1.3 Contributions by CCMS Fellows
The Pilot Study was significantly aided by the
NATO/CCMS Fellowship program. There were twelve
NATO Fellows associated with this Pilot Study. Nine
Fellows conducted associated studies and submitted
project reports to the Pilot Study under guidance of the
Pilot Study Directors. Three Fellows contributed to the
preparation of the Final Report. The Fellows repre-
sented private, university and governmental organiza-
tions in Germany, Italy, The Netherlands, Turkey, the
United Kingdom, and the United States. Their ac-
tivities covered the range of technologies evaluated
under the Pilot Study, including the development and
evaluation of biological treatment technologies; chemi-
cal destruction techniques; ground water behavior; and
the removal of toxic metals from soil and ground water.
Many of their reports have been and are planned to be
published in professional journals.
1.4 Contents of Volume 2
Volume 2 of this report contains appendices cover-
ing the following information:
Statements by the countries involved in this Pilot
Study discussing their regulations and other over-
view topics (Appendix 1 -A)
NATO/CCMS guest speakers' presentations (Ap-
pendix 1-B)
Final reports by the NATO/CCMS Fellows (Ap-
pendix 1-C)
Summaries and detailed information, when avail-
able, on specific case studies of projects ex-
-------
Chapter 1
Table 1-1. Conclusions for NATO/CCMS final report; demonstration of remedial action technologies for contaminated
land and ground water.
This tablo presents a summary of the conclusions arising from the Pilot Study. They are first presented by specific technology
areas represented by the chapters in this report; these are followed by general conclusions on remediation, technology transfer and
research needs. These conclusions are based on the technology demonstration case studies as well as expert speaker
presentations and special studies carried out by Fellows of the Pilot Study. The numbering corresponds to paragraph numbers in
Chapter 10.
10.2 Specific Technology Area Conclusions
10.2.1 Chapter 2: Thermal Technologies
10.2.1.1 Existing high temperature incineration (on- and off-site) successfully destroys organic contamination; however, not all
nations allow its use for chlorinated compounds.
10.2.1.2 LoW temperature thermal desorption is a successful technology for treating volatile and semivolatile wastes.
10.2.2 Chapter 3: Stabilization/Solidification IS/S) Technologies
10.2.2.1 S/S has been proven for the immobilization of most inorganics.
10.2.2.2 Long term effectiveness data is not available.
10.2.2.3 Scientifically based S/S leaching tests would provide a more easily comparable data base than is available today.
10.2.3 Chapter 4: Soil Vapor Extraction (SVEI Technologies
10.2.3.1 SVE is a viable technology for unsaturated zone remediation of volatile and semivolatile contaminates.
10.2.3.2 Off-gases can be treated by conventional technologies.
10.2.4 Chapters: Physical/Chemical Extraction Technologies
10.2.4.1 Conventional extractive techniques have limited in situ applications.
10.2.4.2 Above ground extraction methods are powerful techniques.
10.2.4.3 Etectroreclamation deserves to be extensively investigated.
10.2.5 Chapter 6: Pump and Treat Ground Water
10.2.5.1 Pump and treat is a limited technology for remediating aquifers.
10.2.5.2 Air stripping and activated carbon, as illustrated in this case study (i.e., Ville Mercier), were only partially effective
treatment processes.
10.2.5.3 An ultraviolet radiation/oxidation process (Ultrox) was effective in reducing the concentration of volatile organics in
ground water to acceptable levels. , ' .--..
10.2.5.4 A precipitation process involving the use of lime and sodium sulfide was effective in reducing the concentrations of
zinc and cadmium to acceptable levels. , ,..-',.
10.2.6 Chapter 7: Chemical Treatment of Contaminated Soils: APEG Treatment
10.2.6.1 The long term stability and behavior of the products of partial dechlorination in APEG processes require investigation.
10.2.6.2 The combination of thermal pyrolysis and APEG treatment applied at Wide Beach, New York, USA, was successful iri
reducing PCB concentrations to below target cleanup levels.
10.2.7 Chapter 8: Microbial Treatment Technologies
10.2.7.1 Bioromodiation process scale-up from laboratory to the field is difficult.
10.2.7.2 There is a need for both data on oxygen behavior in the subsurface and improved methods of providing oxygen for in
situ bioromodiation.
10.2.7.3 There is a need for further research on bioavailability and achievable concentrations.
10.2.7.4 Soil inoculation has not been proven to enhance in situ bioremediation.
10.2.7.5 Permeability is a key factor in applying in situ bioremediation.
10.2.8 Chapter 9: Selecting Remedies at a Complex Hazardous Waste Site
10.2.8.1 Remediation should strive to be a complete solution.
10.2.8.2 Treatability studies must be conducted as early as possible for effective remedy selection, and technologies should be
judged by their overall performance.
10.2.9 Appendix: In Situ Vitrification
10.2.9.1 Vitrification is a promising technique for treating mixed organic and inorganic wastes.
-------
Introduction
Table 1-1. (Continued)
10.3 General Conclusions
10.3.1 Remediation
10.3.1.1 Energy efficiency practices influence plant design and, therefore, processing costs in different countries.
10.3.1.2 Treatment and permanent solutions are preferred.
10.3.1.3 Integrated technology treatment systems are needed for site remediation.
10.3.1.4 Field treatability/pilot studies should be conducted for each technology under consideratioin, under the range of
potentially applicable site field conditions.
10.3.1.5 Technology scale problems need to be addressed in design and testing.
10.3.1.6 A mass balance approach to remediation is desirable.
10.3.1.7 Technology remedies that transfer contaminants from one media to another should be avoided, if possible.
10.3.1.8 All remediations require proper operation and management.
10.3.1.9 Long term monitoring of permanent remediation may be necessary to ensure that cleanup goals are met.
10.3.1.10 Basic records should be preserved.
10.3.2 Technology Transfer
10.3.2.1 Uniform data collection is needed.
10.3.2.2 Independent technology evaluations are needed for effective technology transfer.
10.3.2.3 The NATO/CCMS network is an important source of information.
10.3.3 Research
10.3.3.1 There is a continuing need for development of new technologies and use of common research protocols.
10.3.3.2 Scientific understanding of processes is essential in order to ensure against formation of harmful end products.
10.3.3.3 Standardization of analytical methods is needed.
10.3.3.4 Techniques are needed to remove contamination beneath urban structures without significance disturbance to ongoing
activities.
REFERENCES
James, S.C. and Sanning, D.E. Summary of the NATO/CCMS conference - The demonstration of remedial
action technologies for contaminated land and ground water, in: Journal of the Air and Waste Manage-
ment Association, Vol. 39, No. 9, September 1989, p. 1179.
-------
-------
Thermal Technologies
Stephen C. James and Gregory L Stacy
United States Environmental Protection Agency
Office of Research & Development, Cincinnati, Ohio 45268
United States
ABSTRACT
Based on the site and waste characteristics of a site, thermal treatment may be most efficient. Thermal processes
are technologies/systems designed to break down hazardous waste through either combustion or pyrolysis by
exposure of the waste material to high temperature in a controlled environment. Thermal processes can, in a matter
of seconds, destroy waste materials that might otherwise not be able to be destroyed by natural or other treatment
processes.
This chapter on thermal technologies discusses the type and use of thermal technologies and various projects
examined under the NATO/CCMS Pilot Study, both fixed facilities and transportable incineration systems. In the
United States, the majority of fixed facilities are dedicated to the treatment of hazardous wastes generated and sent
to a facility for treatment. Transportable systems are primarily used for the cleanup of uncontrolled sites (Superfund
sites). While the United States intends to treat waste on site, many countries transport the contaminated material to
the hazardous waste treatment facility.
2.1 Introduction
Hazardous waste thermal technologies have been
selected and implemented for remediation at many
contaminated sites. This technology can be used for
the treatment of contaminated liquids, sludges, soils,
debris, and air streams. The most common incinera-
tion technology used is rotary kiln. Other types of in-
cineration are infrared incineration, liquid injection,
hearth, fluidized beds, circulating beds, pyrolysis
processes, plasma systems, and various kinds of in-
direct heating systems. Incineration is a proven
means of destruction for many organic wastes and
should be considered as a possible treatment for the
cleanup of most toxic waste sites.
An incineration system includes a number of sub-
systems including the following:
Waste pretreatment
Waste screening
Size reduction (grinding)
Waste mixing
Waste feed
Belt conveyers
Augers
Apron feeders
Hoppers
Chutes
Pumps (for liquids, sludges, oils)
Screw conveyers
Ram feeders
Combustion unit
Rotary kiln or secondary combustion chamber
Liquid injection
Fluidized bed or circulating bed
Infrared
Thermal desorption
Heat recovery (optional - not normally applicable
to on-site, transportable incineration systems)
Air pollution control equipment to treat
Products of incomplete combustion
-------
Chapter 2
- Minimized in combustion chamber and after-
burner
Afterburners can significantly reduce the
toxicity of the exhaust gas from an in-
cinerator
Particulate emissions
- Venturi scrubber
Wet electrostatic precipitator
Electrostatic precipitator
- Quench systems
- Fabric filter
Acid gases
- Packed towers
Spray towers
Spray dryers
ซ Residue handling and disposal
Ash
- Solidification
- Use as fill material on-site, or dispose of it
off-site
Scrubber water used to cool ash
Liquids
- Neutralization
- Filtration
- Precipitation (metals)
- Clarification
- Carbon adsorption or air stripping (for small
amounts of organics which are sometimes
recovered in scrubber water)
- Discharge to a municipal wastewater treat-
ment system after successful pretreatment
using one or more of the above options.
Tables 2-1 and 2-2 list the number and capacities
of various hazardous waste incineration systems in the
United States and hazardous waste incineration
facilities in Europe. Table 2-3 lists specific site data
from all U.S. projects.
Rotary kiln Incinerators are slightly inclined (3
percent), refractory-lined, rotating cylinders. Their
primary use is the combustion of organic solids and
sludges and other contaminated waste such as
product, contaminated soils, and liquids with a high
heating value. Rotary kiln incineration involves the
controlled combustion of organic waste under net
Table 2-1. Numbers and types of hazardous waste in-
cineration facilities in the United States.
Table 2-2. Hazardous waste incineration facilities in
Europe.
Technology
Rotary kiln
Fluldlzod bed
Liquid injection
Hearth
Number of units
42
15
95
32
Company
INDAVER
Kommunekemi
SARP
SARP
TREDI
SIDIBEX
TREDI
GSB
ABR
ZSM
HIM
Broerius
Boskalis Esdex
ATM
AVR-Chemi
Eooteohniek II
NBM
Ecotechniek I
Cleanaway
Reohem
Location
Belgium, Antwerp
Denmark, Nyborg
France, Bassens
France, Limay
France, Salaise
France, Sandouville
France, St. Vulbas
Germany, Ebenhausen
Germany, Herten
Germany, Schwabach
Germany, Wiesbaden
The Netherlands, Barneveld
The Netherlands, Ijrnuiden
The Netherlands, Moerdijk
The Netherlands, Rotterdam
The Netherlands, Rotterdam
The Netherlands, Schiedam
The Netherlands, Utrecht
UK, Brentwood
UK, Pontypool
Capacity
(metric
tons/yr)
50,000
50,000
20,000
50,000
40,000
35,000
6,000
100,000
30,000
30,000
45,000
25,000
4,000
60,000
40,000
80,000
60,000
55,000
40,000
13,000
oxidizing conditions (the final oxygen concentration is
greater than zero).
Wastes and auxiliary fuel are injected into the high
end of the kiln and passed through the combustion
zone as the kiln slowly rotates. Rotation of the com-
bustion chamber creates turbulence and improves the
degree of combustion. Retention time in the kiln can
vary from several minutes to an hour or more. Wastes
are substantially oxidized to gases and ash within the
combustion zone. Ash is removed at the lower end of
the kiln. Flue gases are passed through a secondary
combustion chamber and then through air pollution
control units for paniculate and acid gas removal.
The typical hazardous waste kiln is a cylinder with
an outside diameter of 3 to 4 meters, an inside
diameter of 2.5 to 3 meters, and a length of 11 to 13
meters. Typically, 5 tonnes of material will be charged
into the unit. Actual loads will be determined by the
-------
Thermal Technologies
Table 2-3. Site data
Vendor
AET
Canonie
Canonie
Canonie
Canonie
Chemical Waste Mgt.
Ensoo
Ensco
Ensco
Ensco
Ensco
Ensco
GDC Engineering
Harmon
Harmon
Harmon
IT Corporation
IT Corporation
IT Corporation
IT Corporation
Kimmins
Ogden
Ogden
Ogden
O.H. Materials
O.H. Materials
O.H. Materials
O.H. Materials
O.H. Materials
O.H. Materials
O.H. Materials
from U.S. hazardous
Site Name
Valdez
Ottati & Goss
Canon
South Kearny
McKin
confidential
Union Carbide
Lenz Oil
Sydney Mines
NCBC
Bridgeport
Smithville
Rubicon
Bog Creek
confidential
Prentiss
Motco
Cornhusker
AAP
Louisiana AAP
Sikes Pits
La Salle
confidential
Swanson River
Stockton
Goose Bay
Gas station
Rail yard
Twin City AAP
Rail yard
Florida Steel
Rail yard
waste incinerator projects.
Site Location
Valdez, Alaska
Kingston, New Hampshire
Bridgewater, Massachusetts
South Kearny, New Jersey
Gray, Maine
northeast, United States
Seadrift, Texas
Lemont, Illinois
Brandon, Florida
Gulfport, Mississippi
Bridgeport, New Jersey
Canada
Geismar, Louisiana
Howell Twp., New Jersey
Alabama
Prentiss, Mississippi
Lamarque, Texas
Grand Island, Nebraska
Minden, Louisiana
Crosby, Texas
La Salle, Illinois
Sacramento, California
Kenai, Alaska
Stockton, California
Goose Bay, Canada
Cocoa, Florida
Pennsylvania
New Brighton, Minnesota
Pennsylvania
Indianatown, Florida
Cleveland, Ohio
Source of
Contamination
Crude oil spill
Solvent treatment
Solvent recycling
Solvent recycling
Waste treatment &
disposal
PCB spills
Chemical manufacturing
Waste oil
Waste oil lagoon
Herbicide storage
Used oil recycling
PCB transformer leaks
Chemical manufacturing
Paint/solvent disposail
Gasoline tank leak
Wood treatment
Styrene tar disposal pits
Munitions plant pits
Munitions plant lagoon
Chemical waste pits
PCB capacitor
manufacturing
Town gas site
Oil pipeline compressor
oil
Underground tank oil
leak
PCB's
Petroleum tank leak
Repetitive spills
Munitions plant
Diesel tank spill
Steel mill used oils
Refueling station
Project
Status
Finished
Finished
Contracted
Finished
Finished
Contracted
Contracted
Finished
Finished
Finished
Ongoing
Contracted
Ongoing
Ongoing
Finished
Finished
Ongoing
Finished
Finished
Contracted
Contracted
Contracted
Ongoing !
Ongoing
Ongoing
Finished
Finished
Finished
Finished
Finished
Finished
Site Size
(tonnes)
7,200
5,900
16,300
1 6,300
31,800
23,600
9,100
20,000
90,700
' 6,350
47,200
20,400
540
8,300
72.6OO
40,800
90,700
309,400
62,600
20,400
72,600
14,500
3,600
900
1,400
1,800
1,200
16,300
1 ,400
-------
Chapter 2
Table 2-3. (Continued)
Vendor
Sito Rocl. Systems
Site Rocl. Systems
Sito Rocl. Systems
Soil Remediation Co.
SoilToch
TOI Services
Thermodynamics Corp.
U.S. Waste Thermal
Processes
U.S. Waste Thermal
Processes
U.S. Waste Thermal
Processes
Vortac site contractors
Vesta
Vesta
Vesta
Vesta
Vesta
Wostinghouso/
Haztoch
Wostinghouso/
Haztoeh
Woston
Woston
Woston
Woston
Woston
Site Name
Koch Chemical
Gulf Oil
Sun Oil
multiple sites
Waukegan
Harbor
Chevron
S. Crop
Services
gas station
confidential
confidential
Vertac
Nyanza
Rocky Boy
S. Crop Service
Am. Crossarhn
Fort A.P. Hill
Peak Oil
La Salle
Revenue
Letterkenny
Tinker AFB
Paxton Avenue
Lauder Salvage
Site Location
Kansas
multi-sites
multi-sites. South Carolina
multi-sites
Waukegan, Illinois
El Segundo, California
Delray Beach, Florida
Temecula, California
California
San Bernadino, California
Jacksonville, Arkansas
Ashland, Massachusetts
Havre, Montana
Delray Beach, Florida
Chehalis, Washington
Bowling Green, Virginia
Tampa, Florida
La Salle, Illinois
Springfield, Illinois
Chambersburg, Pennsylvania
Oklahoma City, Oklahoma
Chicago, Illinois
Beardstown, Illinois
Source of
Contamination
Tank bottoms
Oil spills
Oil spills
Gas and oil leaks/spills
Marine motor
manufacturing
API sludges
Crop dusting operation
Petroleum tank leak
Oil spills
Oil spills
Chemical manufacturing
Dye manufacturing
Wood treatment
Crop dusting operation
Wood treatment
Army base
Used oil recycling
Transformer
reconditioning
Army depot
Air Force base
Waste lagoon
Metal scrap salvage
Project
Status
Contracted
Contracted
Contracted
Finished
Contracted
Contracted
Finished
Finished
Contracted
Finished
Contracted
Finished
Ongoing
Finished
Finished
Finished
Finished
Finished
Finished
Finished
Finished
Ongoing
Finished
Site Size
(tonnes)
600
16,300
2,700
18,100
27,200
1,600
,900
6,800
490
5,900
900
1,600
1,600
800
180
6,350
27,200
900
450
900
14,500
7,700
thermal input to the kiln rather than the mass load.
The heat source is either a hazardous waste or an oil
or natural gas flame directed axially down the kiln.
The typical hazardous waste secondary chamber is
sized sufficiently to achieve a 2 second residence time
for combustion gases at 2,200 *C.
Electric Infrared Incineration systems use silicon
carbide elements to generate thermal radiation
beyond the red end of the visible spectrum. Waste to
be treated passes through the unit on a noncorrosive
steel belt and are exposed to the heat generated by
the radiation. Organics are driven from the waste
material. Off-gases pass into a secondary chamber
that is heated via supplemental gas or fuel oil for com-
plete destruction of the organics. Flue gases are
treated by a scrubber system and the residual ash is
collected for further treatment and/or disposal. Normal
operating temperatures are 1,600 to 1,800 ฐC in the
10
-------
Thermal Technologies
primary chamber and 1,900 to 2,200 ฐC in the secon-
dary chamber.
Fluidized bed incinerators consist of a refractory-
lined vessel containing a bed of inert, granular, sand-
like material. In operation, combustion air is forced
upward through the bed, which fluidizes the material at
a minimum critical velocity. The heating value of the
waste plus any auxiliary fuel maintains a desired com-
bustion temperature in the vessel. The heat of com-
bustion is transferred back into the bed, and the
agitated mixture of waste, fuel, and hot bed material in
the presence of fluidizing air provides a combustion
environment that resists fluctuations in temperature
and retention time due to moisture, ash, or Btu content
of the waste.
A variation of the fluidized bed is the circulating
fluidized-bed (CFB) combustor. This process uses
higher air velocity and circulating solids to create a
larger and highly turbulent combustion zone for the ef-
ficient destruction of organics and the retention of
resultant acid vapors. The key to this combustion
technology is the hydrodynamic behavior of the
fluidized bed. Conventional fluidized beds are general-
ly well understood. They are characterized by the
clearly defined gas bubbles. Units of this type operate
at gas velocities of 2 to 3 m/s (depending on particle
size). The main difference between circulating and
fluidized beds is the gas velocity. CFB's operate at
gas velocities from 5 to 10 m/s. These gas velocities
give rise to rapid carry over of solids from the top of the
vessel. In order to replenish solids in the vessel, the
CFB systems have developed a solids separation and
return loop. This enables the bed material to be in
constant contact with the waste material.
Fluidized bed technology can be operated at lower
temperatures than other thermal systems because of
the high mixing energies aiding the combustion
process. This mixing offers high thermal efficiency
while minimizing auxiliary fuel requirements and
volatile metal emissions.
Liquid-injection incineration systems are usually
refractory-lined chambers (horizontal, vertical up or
down), generally cylindrical, and equipped with a
primary combustion and secondary chamber. The
waste is burned directly in a burner or injected into the
flame zone or combustion zone of the incinerator
chamber through nozzles. Critical to the operation of
this type of incineration system is the atomizing nozzle
used to convert the liquid stream into finely atomized
droplets.
Multiple-hearth incinerators are used for destroy-
ing solids and heavy sludges. Waste material enters
the combustion chamber at the top and drops through
a series of refractory hearths until noncombustible
residues fall to the bottom of the unit. This method is
useful for the recovery of metals from the waste feed.
Plasma systems use a plasma-arc device to create ex-
tremely high temperatures (25,000 'C). Gaseous
emissions (primarily hydrogen and carbon monoxide),
acid gases in the scrubber, and ash components in the'
scrubber water are the residuals. These systems are
applicable to liquid waste only because of the injection
systems employed.
In situ vitrification (ISV) uses an electric current to
melt soil or sludge at extremely high temperatures of
1,600 to 2,000 ฐC. This destroys organic pollutants by
pyrolysis. Inorganic pollutants are incorporated within
the glass-like vitrified mass. Water vapor and organic
pyrolysis by-products are captured in a hood, which
draws the contaminants into an off-gas treatment sys-
tem that removes particulates and other pollutants.
The vitrification process begins by inserting large
electrodes into contaminated zones containing suffi-
cient soil to support the formation of a melt. An arran-
gement (usually square) of four electrodes is placed to
the desired treatment depth in the volume to be
treated. Because soil typically has low electrical con-
ductivity, flaked graphite and glass frit are placed on
the soil surface between the electrodes to provide a
starter path for electric current. The electric current
passes through the electrodes and begins to melt soil
at the surface. As power is applied, the melt continues
to grow downward, at a rale of 2.54 to 5.08 cm/h. In-
dividual settings (each single placement of electrodes)
may grow to encompass a total melt mass of 907 ton-
nes and a maximum width of 10.7 meters. Single-set-
ting depths as great as 7.6 meters are considered
possible.
Depths exceeding 5.8 meters have been achieved
with the existing large-scale ISV equipment. Adjacent
settings can be positioned to fuse to each other and to
completely process the desired volume at a site.
Stacked settings to reach deep contamination are also
possible. The large-scale ISV system melts soil at a
rate of 3.6 to 5.4 tonne/h. Because the void volume
present in paniculate materials (20 to 40 percent for
typical soils) is removed during processing, a cor-
responding volume reduction occurs. After cooling, a
vitrified monolith results, with a silicate glass and
microcrystalline structure. This monolith possesses
structural and environmental properties.
2.2 Case Studies Chosen
The following discussion summarizes the thermal
projects in this NATO/CCMS Pilot Study by participat-
ing countries.
2.2.1 Case Study 2-A: Rotary Kiln Incineration,
The Netherlands
A national inventory taken in 1981 revealed that the
soil contamination problem in The Netherlands was far
greater than was first thought. The survey identified
about 4,000 cases of possible soil contamination.
However, this figure has since risen to around 7,500.
11
-------
Chapter 2
Since 1982, much experience has been gained with
soil cleanup techniques. In particular, thermal and ex-
traction processes passed the technological develop-
ment stage and are applied on a large scale for various
types of soil contamination.
Ecotechniek has two thermal soil treatment plants,
one In Utrecht, and one near Rotterdam. The latter
installation has a maximum treatment capacity of 50
metric tons per hour. The contaminated soil is treated
in the rotary kiln by direct heating at a temperature of
up to 550 ฐC with a residence time of about 7-15
minutes. The resulting vapors are afterburned at a
temperature of 850-1,000 ฐC and a residence time of
1-2 seconds. The afterburner limits the emission of
hydrocarbons, CO, and HCN. Heat exchangers permit
the reuse of the energy released. Measures to limit
emission include a wet scrubber (SO2) and a fabric fil-
ter (dust). The wash water from the wet scrubber is
cleaned and partly recycled for cooling the cleaned
soil. The process is suitable for the removal of
aromatic and aliphatic hydrocarbons (up to 10,000
mg/kg), cyanides (up to 400 mg/kg), and polynuclear
aromatic hydrocarbons (PAHs) (up to 800 mg/kg).
The installation is suitable for all types of soil. It is
especially the moisture content, the organically-bound
nitrogen and sulfur content of the soil, and the type of
contamination that influence the costs. These vary be-
tween Dfl 100 and Dfl 190 per metric ton. (One Dfl is
approximately U.S. $0.5, October 1987.)
To date, much experience has been gained for the
treatment of contaminated soil from former gasworks
sites and soil contaminated by leaking fuel tanks. A
trial cleanup of soil contaminated with chlorinated
hydrocarbons is planned. The treatment of two types
of soil have been evaluated in particular with respect
to:
"Easy to clean" soils: sandy soil, chiefly con-
taminated with cyanides and polynuclear aromatic
hydrocarbons (PAHs), derived from a former gas-
works site; and
ซ"Difficult to clean" soils: clayish soil and rubble,
chiefly contaminated with PAHs and mineral oil,
derived from a site where various wastes had
been dumped.
They were evaluated with respect to cleanup of the
soil and air emission during the treatment.
The results showed that residual concentrations of
mineral oil and cyanides amply met the requirements
for both types of soil. For some of the PAHs, the quite
strict requirements were not met for soil originating
from the dump site. In the case of the gasworks soil,
higher residual concentrations of (Borneff) PAHs were
allowed. As expected, no removal of heavy metals
took place.
The results of air pollution monitoring show that the
requirements set for emissions onto the air were met
during the treatment of both types of soil. (For more
information on this project, see Appendix 2-A.)
2.2.2 Case Study 2-B: Indirect Heating in a Rotary
Kiln, Germany
The Ruhr Valley of Germany has several former
gasworks and coking plants. Contamination at these
sites is due to process waste as well as spills. The soil
is contaminated with aromatic and aliphatic hydrocar-
bons. The site at Unna-Boenen is a former coke oven
plant with an area of 250,000 m2. The site is divided
into three areas: coal area site, coking oven site, and
acid resin storage. Volatile organic compounds
(VOC's) may be as high as 5 percent of the waste by
weight. Other contaminants such as pesticides,
PCB's, and heavy metals are present up to 1 percent
by weight of the soil. In addition to the examination of
various technologies for the cleanup of the site, an in-
direct thermal heating technology was investigated.
This system, designed by Ruhrkohle Urnwelttech-
nik of Unna Boenen (Germany), is based on a closed-
cycle indirect thermal treatment (pyrolysis) process.
Treatment of contaminated soil begins with mechani-
cal crushing of the soil (to a maximum size of 50 mm).
The crushed soil is stored in a feed hopper and travels
from the hopper to the kiln by means of a double helix
screw conveyer. This permanently filled conveyer
seals the kiln system at approximately 1.5 mbar
depression, which prevents the escape of dust or
pyrolysis gas. The crushed soil then passes through a
rotary kiln 22 meters in length. In the kiln, tempera-
tures between 450 and 600 ฐC release volatile
material. Temperatures are obtained by heating the
outer shell of the rotary kiln with 18 natural gas
burners. Water cools the treated soil that is returned to
the original site. Post-combustion of the released
gases occurs in a secondary chamber. In this cham-
ber temperatures reach a maximum of 1,300 ฐC. After
quenching and scrubbing, the gas exits through the ex-
haust stack.
The system was completed in May 1988 and began
shakedown in July. Over 2,720 tonnes of soil have
been decontaminated in the trial testing. The effec-
tiveness of the soil decontamination increased for
grain sizes less than 50 mm in diameter. Operational
problems with the ash removal screw, which resulted
in overheating of the ash removal system and sub-
sequent obstruction, have been corrected. The design
of the plant enables it to be transported and reused at
different locations. The operators planned full-time
operation of the system with the ability to process ap-
proximately 45,360 tonnes of contaminated soil per
year. (For more information on this project, see Ap-
pendix 2-B.)
12
-------
Thermal Technologies
2.2.3 Case Study 2-C: Off-site Soil Treatment,
Japan
The electro-chemical industrial facility was used
from 1917 to 1979 primarily for the production of soap,
bleaching powder, hydrogen chloride, organic com-
pounds, and, later, sodium hydroxide. It is located in a
residential area in Tokyo and is highly contaminated
with mercury and lead; this contamination was dis-
covered in 1979 when the company stopped operation
and dismantled the facility in order to relocate the fac-
tory. The mercury contamination was generally limited
to the surface soils with an average concentration of
36,800 ppm (maximum concentration of 156,000
ppm). About 56,000 m? of contaminated soil with mer-
cury levels above 2 mg/kg were required to be treated
before redevelopment of the site could occur. Based
on the level of mercury contamination, off-site thermal
treatment and on-site containment processes were
selected. All soils with mercury levels above 10 mg/kg
were to be sent off-site for incineration. All other soils
below this level were treated on-site using immobi-
lization and containment.
About 6,000 drums of contaminated soils were sent
to the Nomura Kosan Co., a firm specializing in the
refining of mercury. Cost of the thermal treatment was
US$330/tonne plus a transportation cost of
US$81/tonne. The treatment facility is equipped with a
vertical multistage rotary furnace called a Herreshoff
Furnace. The mercury contaminated soil was treated
at temperatures from 600 to 800 ฐC. Volatile mercury
vapors were condensed on the inner wall of a con-
denser. Crude mercury was recovered from the soot
and refined into a commercial grade product with a
purity of 99.99 percent. Slag from the furnace was
placed in an on-site secure landfill. Trace amounts of
mercury and acid gas components in the flue gas were
removed from the exhaust gas by adsorption and
neutralization. (For more information on this project,
see Appendix 2-C.)
2.2.4 Case Study 2-D: Electric Infrared
Incineration, United States
Beginning in the 1950's, Peak Oil, an oil refiner,
operated a used-oil processing facility in Brandon,
Florida. Various waste streams from the refining
operation were dumped into a natural lagoon located
on the property. The lagoon quickly became con-
taminated with PCB's and lead from the waste
material. This led to the contamination of the shallow
aquifer system that was the source of the local drinking
water supply. Because of the continuing contamination
of the aquifer from the lagoon, the United States En-
vironmental Protection Agency (U.S. EPA) initiated a
project to remove the contents of the lagoon and the
contaminated soil under and around the lagoon. This
amounted to approximately 7,000 tonnes of sludge
and soil contaminated with PCB's and lead.
The U.S. EPA selected electric infrared incineration
for the cleanup operation. In November 1986, a
transportable unit was brought to the site on five
separate trailers. Once on-site, the units were con-
nected together on new or existing concrete pads
prepared for the cleanup operations. The connected
components formed the 22-meter long primary Com-
bustion unit (PCC), the 24-meter long secondary com-
bustion unit (SCC), an emission control system, and a
process management and monitoring center.
Electric infrared incineration technology (originally
developed by Shirco Infrared Systems, Inc. of Dallas,
Texas) is a mobile thermal processing system that
uses electrically powered silicon carbide rods to
generate heat for volatilization of organics from waste
in the primary incineration chamber. Waste is fed into
the primary chamber on a wire mesh belt and exposed
to temperatures up to 1010 ฐC by the infrared radiant
heat. Ash material from the primary is quenched and
gas emissions are put through a control system for
neutralization and paniculate removal. Technology
demonstrations were conducted on the full and pilot-
scale units at two Superfund sites: Peak Oil site in
Florida and Rose Township site in Michigan. Both
sites contained PCB's arid high concentrations of lead.
In both cases, testing and "evaluation proved that the
technology could successfully destroy PCB's; the sys-
tem achieved greater than 99.99 percent DRE's
(destruction and removal efficiencies). In addition, the
system was tested for its ability to retain and fix lead in
the ash. the lead in the ash was not fixed since it
could be easily removed via leach testing. This was
determined by the Toxicity Characteristic Leaching
Procedure (TCLP) which is a United States testing pro-
cedure.
This technology is applicable for the treatment of
organic contaminants contained in soils or sludges.
Since the waste is fed into and through the system on
a wire mesh belt, only solid material can be processed
through the unit. Liquid organic wastes can only be
handled if they are mixed with a solid material before
processing.
Testing has demonstrated the ability of the'electric
infrared incineration technology to:
Achieve organic destruction greater than the
Resource Conservation and Recovery Act
(RCRA) standard of 99.99 percent ORE
Achieve destruction of dioxins and furans greater
than the RCRA standard of 99.9999 percent ORE
Achieve destruction of PCB's greater than the
Toxic Substances Control Act (TSCA) standard of
99.9999 percent
Achieved HCl RCRA performance standard of 99
percent removal
13
-------
Chapter 2
ป Achieved RCRA paniculate emission standard of
180 mg/dscm (dry standard cubic meters).
(For more information on this project, see Appendix
2-D.)
2.2.5 Case Study 2-E: In Situ Vitrification, United
States
In-situ vitrification (ISV) involves the in-situ melting
of contaminated solids in soils. An array of four
electrodes is placed to the desired treatment depth.
As current flows through the soil, it is heated to the
melting temperature of the soil (typically 1600-2000
ฐC). Once molten, the mass becomes the primary con-
ductor and heat transfer medium, allowing the process
to continue. The molten mass grows downwards and
horizontally as long as power is applied. A recent test
treated a zone 8 m (27 ft) square by about 6 m (20 ft)
deep (about 900 tonnes at a bulk density of 2,200
kg/m3) and took 7 to 10 days to complete. The treated
mass takes several months to a year or more to cool,
although the collection hood can be removed after a
few hours. Once one setting Is completed, the equip-
ment Is moved to an adjacent area; neighbouring
blocks will fuse together. The process may be applied
to contaminated natural soils, but also to other natural-
ly occurring soil-like materials and solid process was-
tes, Including slits, sediments, sludges and tailings.
As a result of the ISV process, individual con-
taminants may:
ซ Undergo chemical and/or thermal destruction
Enter the off-gases from which they can then be
removed
ป Be chemically or physically Incorporated into the
resultant solid product.
In tests at various scales, it is claimed that the
process is applicable to soils containing volatiles,
semf-volatlles, and refractory (non-volatile) organic
compounds and inorganics (heavy metals), a variety of
radioactive materials, and a broad range of combus-
tible, metallic, and inorganic scrap materials (e.g.
paper, plastic, wood, drums, concrete, rock, asphalt). It
is also claimed that drummed organic wastes can be
treated.
The ISV process results in a 20 to 40 precent
reduction in volume for typical soils. Once processing
is completed, clean backfill is placed over the residual
monolith to restore site levels. As cooling continues
additional subsidence may occur.
In the United States this technology is available
from only one commercial vendor (Geosafe Corpora-
tion) and has been under development by Battelle
Memorial Institute since 1980. However, the main
clean-up project that the technology was to comple-
ment could not go ahead because the vendor of the
technology withdrew it from the market. This decision
was prompted by an accident that occurred in March
1991 during large scale testing which resulted in a fire
and destruction of some equipment. The company
took the view that although the accident "involved only
non-hazardous materials,.. such an event could have
unacceptable consequences if it were to happen at a
hazardous waste site." The company did "not consider
it prudent to proceed with commercial large-scale
operations if there is any reasonable chance of recur-
rence of this event.." However, some work is continu-
ing with the U.S. Department of Energy. (For more
information on in situ vitrification, see Appendix 1-C.)
2.3 Background of the Case Studies as a
Group
Thermal treatment has been used for many years
to treat a variety of waste products generated from the
manufacturing of products. Over the last several
years, thermal treatment has been used widely in the
cleanup of remediation sites. Primarily, this technol-
ogy has been used in the treatment of contaminated
soils, sludges and sediments; in addition it is some-
times used to treat liquids. Principally, this technology
Is used to treat organic contamination. However, one
case study reports on the recovery of mercury from
contaminated soil.
The case studies represent a cross section of
problems that may be found at sites throughout any
country and also represent thermal technologies that
are currently available. Three case studies (Germany,
The Netherlands and United States) report on
problems that are very common to all countries.
These case studies represent the treatment of
aromatic and aliphatic hydrocarbons (former gasworks
site), waste oil contaminated with PCB's (former waste
oil refiner), and various other organic contamination
that was improperly disposed of at these facilities. As
can be seen from the results, thermal treatment offers
a very high level of destruction of the organic waste.
The other case study (Japan) discusses the removal of
mercury from soil from a former electro-chemical
facility.
In each case study, defined cleanup goals were
met. However data on the effectiveness of each case
study varies widely. Very little information was
provided on waste feed preprocessing or residual han-
dling. Cost information that documented the complete
cost of using thermal technologies was also missing.
More information on performance and costs are
needed to accurately assess the technology overall.
2.4 Performance Results
When properly designed, constructed and
operated, thermal technologies should be able to treat
waste to appropriate regulatory levels while address-
14
-------
Thermal Technologies
ing other technical issues and operating as a cost-
effective unit.
General examination of performance data for ther-
mal technologies indicate that various types of system
problems occur. One parameter which usually affects
the performance of a thermal unit is the compatibility of
the feed with the feed system. The feed system can
consist of belt conveyors, augers, hoppers, chutes,
pumps, screw conveyors, and ram systems. The feed
system must be reliable and capable of continuous
operation even when the feed varies widely in size,
density, moisture content, and other properties. The
feed system must also be capable of reducing the size
of the incoming feed if necessary and must be reliable.
If this is not the case, both the technical performance
of the unit and the projected cost to operate the unit
will be affected. A feed system which constantly fails
or can not produce the projected throughput to the
thermal unit will adversely affect the project. In
general, problems of this nature will lengthen the time
to complete the job and this will negatively affect the
project economics.
In addition to the feed system, other operating con-
ditions that can have impact on the operation of the
unit are: waste pretreatment; type of combustion unit;
air pollution control equipment used to treat-products
of incomplete combustion, paniculate emissions, and
acid gases; and residue handling and disposal for both
ash and liquids.
Results from the NATO/CCMS case studies show
that soils of smaller grain sizes are the most success-
ful. Also, transportation (either moving a mobile in-
cinerator system to the site or transporting the waste
feed to an off-site incinerator) is critical in the selection,
efficiency, and economics of a system. Most of the
case studies discussed obtained a destruction and
removal efficiency of 99.99 percent. In addition to
these results, Table 2-4 shows design and operating
parameters and performance data for various thermal
units in the United States; see also Table 2-3 for more
site information on these projects.
2.5 Residuals and Emissions
Actions undertaken to remediate a site using in-
cineration or to operate a hazardous waste incinera-
tion facility must meet specific performance and
regulatory requirements and will require monitoring to
assure compliance. The following may be required to
protect human health and the environment:
Performance, design, or action-specific require-
ments such as air emission standards, water dis-
charge standards, and land disposal require-
ments for the ash. In general, each country has
developed their own standards for this category.
Ambient/chemical-specific requirements which
set health risk-based concentration limits based
on emission limits and ambient air quality stand-
ards.
Other regulatory (local) requirements that pertain
to the construction or operation of such an in-
cineration system.
Incineration systems will also require monitoring to
assure compliance with any regulatory requirements
that have been imposed on the operation of the sys-
tem. Incineration systems will generally be required to
perform continuous monitoring for CO and NOx. In ad-
dition, continuous monitoring will generally be required
for combustion temperature (primary and secondary
chamber), waste feed rate, SOa, particulates, HCI, and
various other parameters based on the waste feed and
on permit requirements.
Under RCRA in the United States, standards for in-
cinerator performance include:
Principal organic hazardous constituents (POHC)
of each waste feed must be destroyed and/or
removed to a removal efficiency (ORE) of 99.99
percent. These hazardous organics are the most
abundant and most difficult to burn. Dioxins and
RGB's must achieve a ORE of 99.9999 percent.
Particulate emissions must not exceed 180
mg/dscm, corrected to 7 percent oxygen in the
stack gas.
Gaseous hydrogen chloride (HCI) emissions must
be controlled to a maximum of 8.8 kg/h, or be
removed to 99 percent efficiency.
RCRA standards for incinerator operation, monitor-
ing, and inspection, as well as procedures for granting
permits are also specified. Incinerator owners and
operators must also comply with general facility stand-
ards and administrative requirements for all hazardous
waste management facilities. In the United States,
many states also have their own standards which are
more stringent than the national RCRA standards. In
this situation the more stringent standards must be
met.
Compliance with the above specifications and re-
quirements is determined by incinerator performance
during trial burns or duringi probationary operation.
This operation also determines the incinerator's perfor-
mance and the optimal operating conditions.
The collected data is then submitted to the U.S.
EPA with the application for permit. After review by
the U.S. EPA and by state agencies, a RCRA permit is
developed. The permit establishes operating require-
ments, standards for carbon monoxide in the stack ex-
haust gas, waste feed rate, combustion temperature,
and combustion gas flow rate. The permissible values
of each of these may be unique to each incinerator.
Performance data submitted by the applicant ensures
15
-------
Chapter 2
Table 2-4. Performance data for various U
Vendor
AET
Cnnonio
Canonie
Canonie
Canonie
Choniical Waste
Mgt
Ensco
Ensco
Ensco
Ensco
Ensco
Ensco
GDC Engineering
Harmon
Harmon
Harmon
IT Corporation
IT Corporation
IT Corporation
IT Corporation
Kimmins
Ogdon
Ogden
Ogden
O. H. Materials
O. H. Materials
O. H. Materials
O. H. Materials
O. H. Materials
O. H. Materials
O. H. Materials
Site Reel. Sys.
Site Rocl. Sys.
Site Reel. Sys.
Soil Romod. Co.
SoilTooh
Site name
Valdez
Ottati & Goss
Canon Bridgewater
South Kearny
McKin
confidential
Union Carbide
Lenz Oil
Sydney Mines
NCBC
Bridgeport Rental
Smithville
Rubicon
Bog Creek
confidential
Prentiss Creosote
Motco
Cornhusker AAP
Louisiana AAP
Sikes Pits
La Salle
confidential
Swanson River
Stockton
Goose Bay
gas station
rail yard
Twin City AAP
rail yard
Florida Steel
rail yard
Koch Chemical
Gulf Oil
Sun Oil
multiple sites
Waukegan Harbor
,S. hazardous waste
Indicator compound
Petroleum
hydrocarbons
Volatile organics
Total VOC
Volatile organics
Trichloroethylene
PCB's
Hydrocarbons
Hydrocarbons
Dioxin
PCB's
PCB's
Petroleum
hydrocarbons
PAH's
PCB's
Trinitrotoluene
Trinitrotoluene
Total PNA's
PCB's
PCB's
Total hydrocarbons
PCB's
Benzene, toluene.
xylene
Diesel oil
PCB's
Diesel oil
PCB's
Petroleum
hydrocarbons
Toluene, xylene
Benzene, toluene.
xylene
Petroleum
hydrocarbons
PCB's
incinerator projects.
Contam-
inant
cone, in
treated
soil
(mg/k)
<0.2
<0.1
<0.1
<2.0
<5.0
<5.0
<15
<100
<2
"
<1.3
<1.3
<100
<2.0
<0.1
<1
<0.1
<100
<2
<100
<2
<50
<0.1
<50
Particulate
Trial emissions
burn (mg/dNm3
required @7% C)2)
Yes <69
No
No
Yes <69
Yes
Yes 14
No
Yes 39
Yes
Yes
Yes
Yes 34
No
Yes 25
Yes
Yes 39
Yes
Yes <183
Yes
Yes < 1 1 4
Yes <183
Yes
Yes 25
No
Yes 1 28
Yes 89
No
Yes
RCRA
permit
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
TSCA
permit
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
No
Yes
No
Yes
Yes
No
No
No
No
16
-------
Thermal Technologies
Table 2-4. (Continued)
Vendor
TDI Services
Thermodynamics
Corp.
U.S. Waste
Thermal Proc.
U.S. Waste
Thermal Proc.
U.S. Waste
Thermal Proc.
Vertac site
contractors
Vesta
Vesta
Vesta
Vesta
Vesta
Westinghouse/
Haztech
Westinghouse/
Haztech
Weston
Weston
Weston
Weston
Weston
_._
. .
Chevron Refinery
S. Crop Services
__ ^
Indicator compound
BOAT
Pentachlorophenol
Contam-
inant
cone, in
treated
soil
(mg/k)
0.003
Trial
burn
required
Yes
Particulate
emissions
(mg/dNm3
@7% 02)
80
RCRA
permit
No
No
TSCA
.permit
No
No
gas station
confidential
confidential
Vertac
Nyanza
Rocky Boy
S. Crop Services
American Crossarm
Fort A. P. Hill
Peak Oil
La Salle
Revenue,
Letterkenny Depot
Tinker AFB
Paxton Avenue
Lauder Salvage
Total hydrocarbons
Total hydrocarbons
Total hydrocarbons
.Dioxins
Nitrobenzene
Pentachlorophenol
DDT
Dioxin
Dioxin
PCB's
PCB's
PAH's
Benzene, toluene,
xylene
Trichloroethylene
RCRA constituents
PCB's
<0.2
<0.001
<0.001
<2
<0.33
<2
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes..
No
No
No
Yes
Yes
18
183
46
69
25
46
<183
<183
46
No
No
No
No .
No
No
No ,
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
. No
Yes
compliance with the permit. Performance data
reported for each test run includes:
Carbon monoxide in the stack exhaust gas
Waste feed rate
Combustion temperature
* Combustion gas flow rate
ORE results
Particulate emissions results
HCI results.
Normal fluctuations in the parameters should also
be reported.
Table 2-5 lists the European Community (EC) re-
quirements for new municipal incinerator plants.
Again these are not the only standards or the most
stringent standards. Before these standards were im-
plemented, a more stringent set of standards had been
proposed for Germany. Table 2-6 lists typical in-
cinerator operating conditions in the EC.
The incineration system must not only meet emis-
sions standards, but it must also meet other cleanup
standards. Methods to develop these standards vary
between countries and within countries. Table z-f
summarizes some of these.
2.6 Factors To Consider for Determining
Applicability of the Technology
Waste properties affect incineration performance.
Treatability testing using the specific waste from the
contaminated site will allow investigation and iden-
tification of these potential problem areas and will pro-
vide data on the applicability of the actual waste
stream for a specific technology. Prior to treatabilrty
testing, complete laboratory analysis for the fo lowing
key physical and chemical properties of the waste feed
matrix are recommended: density, moisture content,
heating value, noncombustible ash content, particle
size analysis, flash poiint, elemental analysis/composi-
tion pH, metal species and concentrations, and or-
ganic species and concentrations. Treatability testing
that includes bench or pilot scale testing will establish
17
-------
Total dust
Motels
Pb+Cr+Cu+Mn
Ni+As
Cd
Ho
HCl
HF
CO
Total organlcs (as C)
lean Community emission limits
New
>5
30
1 5
1
0.1
0.1
50
2
300
100
=) 20
for municipal incinerators.
Plant**
. lant Existing Plant**
<5 >6 1-6 <,
100 100 150 600
5
1
0.1
0.1
100
4
300
100 100 100 100
20
at 273 ฐK> 101'3 kpa-
or 9% co* dry-
!h!ซ!w9/6 ฐf reco.mmended operating parameters for
Sfhin ฑn{T!llerCial U-nit 10 assure oAmum operation
SSSi T'ft0ry ^qu'rements. For incineration tech-
Includes5-' ฐrmatlon necessary for treatability testing
ซ Chemical composition of the waste feed
ป Heat of combustion of the waste feed
* Viscosity
* Corrosivity
ปIgnitability
ซ Reactivity
Polymerization
ซ Solfds content of waste feed
Metal content of waste feed.
Once treatability tests are conducted, data
developed from the tests will help in deciding what ad-
ditional information is needed. This could include:
Feed preparation data (materials handling)
Baseline operating conditions (residence times
and temperature in the primary and secondary
chamber) '
* Energy consumption estimates
Ash storage and post treatment requirements.
These treatability tests and appropriate analyses
will prov.de data on the expected performance of a
Incinerator type
^***^*^*l^ i i.
Liquid injection
Fumo
Rotary kiln
Afterburner hearth
Primary chamber
Secondary chamber
Fluidizod bed
Combustion zone
temperature, ฐC
.
980-1650
700-820
650-1260
1100-1370
650-980
760-1200
760-1100
Combustion gas
residence time, S
- _
0.3-2.0
0.3-0.5
2 hours (solids)
1.0-3.0
1.5-2.5
1 .0-5.0
Excess air, %
stoichiometric
120-250
50-200
50-250
1 20-200
30-200
200-400
100-15O
18
-------
Thermal Technologies
Table 2-7. Methods to develop cleanup standards by country.
Canada
Only Quebec has a formalized approach. A comprehen-
sive list of generic criteria adapted from the "Dutch List"
(see The Netherlands) is used for initial guidance and
screening, with site-specific risk assessments as appropri-
ate. ,
Denmark
No national approach; control by local governments. Use
"Dutch List" for general guidance and screening as well
as existing Danish standards where available. Final deci-
sion on a particular site based on site-specific consider-
ations. Formalized risk assessment methods now under
development.
France
No national approach; control by local governments. Use
qualitative risk assessments. If pollution is by natural
substance, must reference background levels. Develop-
ment of standards for soil pollution now under consider-
ation.
Germany
No national approach; control by provincial governments.
Use of "Dutch List" with consideration given to local
conditions. German "Guides/Threshold" values for soil
contamination now under development based on soil pro-
tection policy initiated in 1985.
The Netherlands
National policy for maintaining soil "multi-function-
ality." Generic criteria (A-B-C levels) for evaluating
significance of pollution enacted in 1983 (often re-
ferred to as the "Dutch List"). Reference values
for good soil quality (new A-level) enacted in
1987. Contaminated land must be cleaned to
multi-functional quality (A-level) unless it is techni-
cally or financially unfeasible or environmentally
harmful to do so.
United Kingdom
No national system. National guidance on "Trigger
Concentrations" for some contaminants commonly
found on industrial sites often considered for rede-
velopment.
United States
For NPL (National Priorities List) sites (i.e. Super-
fund), use federal and state requirements where
available and formal site-specific risk assessment
methodologies. For non-NPL sites, procedures
vary widely by state and government jurisdiction,
and include either generic criteria background
levels, or levels determined by site-specific formal
risk assessment methodologies.
commercial scale unit. This information will be used to
determine compliance with regulations on incineration
technologies. Before any treatability testing starts,
performance criteria for the technology and limits on
the various emission streams needs to be determined.
For thermal technologies, the following need to be con-
sidered for regulatory compliance monitoring:
Physical and chemical characteristics of the feed
ORE levels for designated compounds and the
presence of PIC's (products of incomplete com-
bustion) in the stack gas
Levels of HCI and particulates in the stack gas
Oa, CO, COa, NOx and SOx concentrations in the
stack gas
Levels of various compounds (metals, dioxins) in
the ash
Levels of various compounds (dioxins, PCB's,
etc.) and other parameters (pH, TOC, etc.) in the
scrubber water.
Following waste feed analysis and treatability test-
ing, an assessment for compliance with governmental
regulations for incineration must be conducted.
Based on the evaluation of technology performance
parameters, information on both physical and chemical
characteristics of the waste matrix is necessary to
determine the suitability of that particular waste for
thermal processing and the possible need for waste
preparation and pretreatment. Table 2-8 presents a
range of waste characteristics that are suitable for the
electric infrared incineration system. An applicable
range of waste characteristics needs to be prepared
for each technology under consideration.
Site requirements for the operation of the various
fixed or transportable incineration technologies are dif-
ferent, based primarily on the throughput of the tech-
nology. A thorough description of the technology
including major components and on-site needs is re-
quired. At a fixed facility, many of these needs can be
addressed in the design and location of the facility.
However, the requirements for a transportable system
can determine or affect the selection of a technology.
When considering the use of any incineration system,
the following characteristics are important considera-
tions:
Climate
Geology
Topography.
Other requirements include:
19
-------
Chapter 2
Table 2-8. Waste characteristics suitable for electric in-
frared incineration.
Characteristics
Applicable Range
Morphology
Particle size
Moisture content
Density
Hosting value
Orgonics (including
POHC's)
Chlorine
Sulfur
Phosphorous
PH
Alkali metals
Heavy metals
Solid (soil)
Semi-solid
Oily sludge (solid phase)
5 microns (2 inch) diameter
0-50 %wt (no free liquids or
free-flowing sludges)
480 - 2082 kg/m3
0 - 23,244 Joules/g
0-100 %wt (determined by
pre-operation testing)
0 - 5 %wt
0-5 %wt
0 - 300 ppm
5-9
0 - 1 %wt
0-1 %wt (determined by pre-
operation testing)
Utilities including water, electrical, fuel, and
telephone. Water will be required for the process,
equipment and personnel decontamination, and
drinking purposes. Electricity will be required for
the process, offices, laboratories, and monitoring
equipment. Telephone service is essential, espe-
cially for emergency response.
ป Support Facilities including office and laboratory
space, pad for setting up the system, pad for
decontamination, sanitary facilities, parking area,
and a visitors area must be defined.
"Support Equipment may include monitoring
wells, excavation equipment, waste feed storage,
decontamination equipment, sampling equipment,
scales, forklift, analytical equipment, and health
and safety equipment.
ซ Services and Supply. A security service may be
needed to patrol the site when personnel are not
on the site. Office supplies and sampling supplies
will be needed.
Site Preparation, Equipment Setup, and Feed
Preparation. Site development needs and im-
provements must be complete before arrival of
the unit and any field activities begin.
In addition to the site requirements, other prepara-
tions relating to the operation of the technology need
to be considered. These are referred to as material
handling requirements. They can include waste ex-
cavation, feed preparation, and ash handling systems.
2.7 Costs
Incineration costs will vary significantly from site to
site. Unfortunately, costs are sources of controversy
during site remediation. The relatively high costs of
incineration often eliminate it as a treatment option.
This being the case, it is very important to conduct an
accurate cost assessment. The following provides
some preliminary background information on this topic.
The total cost of an incineration system varies with
several factors, including:
System capacity
Types of feedstocks
Regime (i.e., slagging vs ashing)
Length to diameter (L/D) ratio for rotary kilns
Type of solids discharge system
Type and capacity of afterburner
. Type of auxiliary fuel used
Regulations.
The cost of waste treatment also varies consider-
ably from site to site; any estimate should include the
following:
Site preparation
Permitting and regulatory requirements
Capital equipment
Start-up
Labor
Consumables and supplies
Utilities
Table 2-9. Typical costs of incineration of contaminated soils (in US$, 1988).
Capacity (tonnes/h)
Unit cost ($/tonne)
Centralized rotary kiln system
Onsite incineration
Smell site (<4,500 tonnes)
Medium site (4,500 to 18,000 tonnes)
Largo site (> 18,000 tonnes)
Commercial unit
<4.5
4.5 to 9.0
>9.0
330 to 720
1100 to 1360
330 to 880
110 to 440
Not Including the cost of transportation, removal of soils from the ground, or storage.
20
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Thermal Technologies
Effluent treatment and disposal
Residuals/waste shipping and handling
Analytical services
Maintenance and modifications
Demobilization.
Table 2-9 presents the estimated costs of incinerat-
ing contaminated soils in both on-site and off-site in-
cineration systems. These costs do not include
transportation, storage, or removal of the soil from the
ground.
Thermal treatment vendors generally prefer to bid
on projects where a processed waste is ready to feed
into their unit. Quotes are also based on the assump-
tions that the residue from the unit will meet discharge
standards and that the thermal unit can operate at
capacity for the length of the job. Failure to adequately
plan the technical requirements and estimate the costs
of a site remediation project can result in cost overruns
and possibly an incomplete remediation.
In addition to capital cost data, operational and
maintenance (O&M) cost data from previous studies
(pilot- or field-scale) need to be collected. O&M costs
include labor, power, fuel, chemicals, and main-
tenance needed to operate the system. The O&M cost
will also include costs for health and safety considera-
tions, and regulatory requirements, such as permitting.
Because of the various types of thermal treatment
technologies, prices will vary widely. The range in
price between low temperature (thermal desorption
technology) and high temperature incineration varies
widely. Reported ranges for thermal technologies are
between US$60 and US$1,300 per tonne. To ade-
quately assess the costs 'for an individual project, the
above cost categories must be rigorously examined.
2.8 Future Status of Case Study
Processes and Thermal
Technologies as a Whole
Incineration has been a selected option for site
remediation and for the destruction of organics for
many years. Several incineration manufacturers have
been in business for many years. Changes in the ther-
mal technologies have been introduced as a result of
changing environmental regulations. With the applica-
tion of thermal technologies to site remediation, these
technologies now must deal with a wide spectrum of
organic and in some cases inorganic contamination in
the waste matrix. With increasing environmental
monitoring and further understanding of thermal
destruction processes, manufacturers and operators of
thermal technologies have kept pace in the design and
operation of these units. Concerns over the transpor-
tation of waste off-site during site remediation has led
to the development of mobile (transportable) units.
Each of the types of units discussed in this chapter has
undergone modification either by the original users or
by others using the same technology. These modifica-
tions have addressed meeting or exceeding environ-
mental standards and controlling the costs of operating
thermal technologies.
REFERENCES
Cudahy, J.J. and Troxler, W.L. Thermal remediation industry contractor survey. 1m Journal of Air and
Waste Management Association, 40(8), August 1990.
Evans, G.M. Estimating innovative technology costs for the SITE program. 1m Journal of Air and Waste
Management Association, 40(7):1047-1051, July 1990.
Freeman, H.M. Standard handbook of hazardous waste treatment and disposal, McGraw-Hill, 1988, Chap-
ters 2, 8.
Handbook: Permit writer's guide to test burn data, hazardous waste incineration. EPA/625/6-86/012, U.S.
Environmental Protection Agency, Cincinnati, Ohio, September 1986.
House of Lords Select Committee on the European Communities. Air pollution from municipal waste in-
cineration plants. HMSO, Great Britain, 1989.
James, S.C. Guidance for the field demonstration of remediation technologies. Jo: Journal of Air and
Waste Management Association, 40(5), May 1990.
NATO/CCMS Fourth International Conference. Demonstration of remedial action technologies for con-
taminated land and ground water. Angers, France, 5-9 November 1990.
NATO/CCMS Pilot Study. Demonstration of remedial action technologies for contaminated land and ground
water. Fourth International Workshop, Oslo, Norway, 13-15 March 1990.
Shirco Infrared Incineration System: Applications analysis report. EPA/540/A5-89/010, U.S. Environmental
Protection Agency, Cincinnati, Ohio, June 1989.
21
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Chapter 2
Soczo, E.R. and Versluijs, C.W. Review of soil treatment techniques in The Netherlands. National Institute
of Public Health and Environmental Protection, Laboratory for Waste Materials and Emissions, Bil-
thoven, The Netherlands.
Superfund Engineering Issue: Issues affecting the applicability and success of remedial/removal incinera-
tion projects. EPA/540/2-91/004, U.S. Environmental Protection Agency, Cincinnati, Ohio, February
1991.
Technology Evaluation Report: SITE program demonstration test: Shirco infrared incineration system, Peak
Oil, Brandon, Florida. EPA/540/5-88/002a, U.S. Environmental Protection Agency, Cincinnati, Ohio,
September 1988.
Technology Evaluation Report: SITE program demonstration test: Shirco pilot-scale infrared incineration
system at the Rose Township Demode Road Superfund site. EPA/540/5-89/007a, U.S. Environmental
Protection Agency, Cincinnati, Ohio, April 1989.
22
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Stabilization/Solidification Technologies
Merten Hinsenveld
University of Cincinnati, Department of Civil and Environmental Engineering
741 Baldwin Hall (ML 71), Cincinnati, Ohio 45221-0071
United States
ABSTRACT
Cement-based stabilization/solidification (S/S) tephniques attempt to prevent migration of contaminants into the
environment by forming a solid mass. The techniques chosen in the Pilot Study were: (1) Hazcon (United States),
applying ex situ treatment with Portland cement; (2) EIF Ecology (France), applying surface treatment with lime; and
(3) TREDI (France), using the Petrifix process. Only one of them (Hazcon, presently IM-Tech) yielded enough
information for evaluation.
The case study processes accepted in the NATO/CCMS Pilot Study all apply generic binders, such as cement,
pozzolanic material, or lime. No case studies applying other binders were submitted. In all cases, the combination
of metals mixed with organic components and a large site to be treated were the major incentives for applying S/S
treatment.
S/S may lead to a substantial increase in the total volume of waste (more than 100 percent). Consequently, it is
possible that the treated material cannot be accommodated at the original site. Heavy metals in these processes are
retained in the stabilized product by physical entrapment and precipitation.
In the Hazcon case, extensive leaching data exist on the treated soil. However, only limited leaching data are
available, on the original untreated wastes. This makes an evaluationpf the process difficult. From the available data
it can be concluded that the process leads to a strong reduction of the leachate concentrations. A reduction factor of
100 for lead, the predominant metal at the site, was seen during a demonstration on site, using the TCLP test. Similar
results were observed for zinc. For organic contaminants the process is generally not effective.
The Hazcon case provided extensive cost data from which an indication of the gieneral cost factors may be
obtained.
3.1 Introduction
3.1.1 Place of the Techniques in a Broad Sense
Stabilization/solidification (S/S) refers to techniques
that attempt to prevent migration of contaminated
material into the environment by forming a solid mass.
The two terms are generally used together. Stabiliza-
tion refers to rendering the material insoluble;
solidification refers to the process of converting a liquid.
or sludge-like waste into a solid form by adding a
binder. Even for materials already in solid form, like
soil, the process is referred to as, "S/S" treatment. In
practice the terms stabilization and immobilization are
often used as shorthand for stabilization/solidification.
Solidification solely to improve handling characteristics
will not be considered in this chapter.
Many S/S technologies have been proposed and
tried in the past ten years. Some of them are
proprietary, involving the addition of adsorbents and
solidifying agents. The S/S binders can be divided into
two major groups:
Inorganic binders, such as cement, lime, kiln dust,
fly ash, silicates, clay, and zeolites
-------
Chapters
Organic binders, such as asphalt, polyethylene,
resins, epoxies, urea formaldehyde, polyesters,
and organophilic clays.
This chapter deals with stabilization processes
using generic binders, such as Portland cement, lime,
and fly ash.
The advantage of organic binders often is their
ability to stabilize highly soluble wastes and to chemi-
cally bind organic contaminants. This is not possible
with cement and pozzolanic materials. Organic
binders, however, are more expensive than cement
and pozzolans, and may be undesirable from an en-
vironmental point of view. Their application, therefore,
has been limited to specific wastes, such as nuclear
waste and highly toxic industrial waste.
Besides the use of binders for immobilization of
contaminants, thermal methods (vitrification) may be
used. Vitrification is a promising technique, since it
combines destruction of organic contaminants with the
incorporation of metals in the resulting glass-like
matrix. See Chapter 2 for a general description of this
technology. The high cost involved in treatment and
the difficulty of permitting, however, are likely to
hamper the application of vitrification on a large scale.
S/S may be used in a variety of applications. In situ
treatment is used when excavation is undesirable for
health reasons (e.g., dust emissions) or simply to
avoid the cost of excavation. It refers to mixing the soil
in situ with a hollow auger mixer through which the
water-binder mix is pumped into the soil. This techni-
que will not be described in this chapter.
Another application is S/S surface treatment, in
which only the top layer of contaminated soil is treated.
This application attempts to reduce the amount of
water penetrating the waste, and does not stabilize the
complete waste. Surface treatment reduces leaching
of contaminants from the untreated waste underneath,
but has too limited neutralization capacity for long-term
durability. Surface treatment will be briefly discussed in
one of the case studies. S/S treatment is mainly used
in the United States, Canada, and France. In countries
where waste is evaluated on the basis of concentration
limits rather than on leaching behavior, S/S technology
may be used, for those wastes which cannot be
treated otherwise, to produce a material that can be
more easily landfilled.
3.1.2 The Stabilization/Solidification Process
Conceptually, S/S treatment with cement, poz-
zolanic material, or combinations of them is simple. It
consists of mixing the contaminated material with a
binder after or during the addition of (often proprietary)
chemicals. This is followed by the setting and harden-
ing of the mix. The added chemicals may alter the
solubility or redox potential of the waste to be stabi-
lized or may prevent retardation of the hydration
process. This, in turn, may improve the binding of the
contaminants to the matrix. The essential elements in
the process are: (1) pretreatment, (2) mixing, and (3)
casting and curing.
1. Pretreatment. In ex situ applications, the
material is sieved down to a certain particle size that
can be accommodated in the process equipment. If the
waste characterization indicates that the contaminants
are concentrated in a particular particle fraction of the
waste, pretreatment should also seriously be con-
sidered to reduce the amount of waste to be treated. If
the waste contains a large amount of water, dewater-
ing may be necessary to remove excess water that
cannot be accommodated in the final solidified waste
form. Contaminants present in the excess water may
be precipitated and stabilized as well. Homogenizing
the waste improves the consistency of the stabilized
product and the performance of the process. Before
mixing the waste with the binders, chemicals can be
added to convert the contaminants to a non toxic or a
less soluble form.
2. Mixing. Mixing waste and binders can be done
ex situ or in situ. Ex situ mixing is more controllable
and attempts to produce a stable waste form by pump-
ing the mix into a mold. Mixing is the most critical step
in the process. Although it is conceptually simple,
many vendors have difficulty in executing this step for
two reasons:
Insufficient homogeneity of the original waste
Insufficient capability to adequately disperse the
waste in the binder mix.
Insufficient mixing leaves waste forms that have a
large variability in performance and may contain large
clumps of pure waste. This lowers the integrity of the
final waste form.
3. Casting and curing. The waste-binder mix is
pumped into a mold or a lagoon. When cast into a
small mold, the mix should preferably set rapidly, so
that the mold is available for a new cast quickly. In
case of a lagoon hardening, timing is less critical, but
still important since the mix is introduced in the lagoon
in layers that should set before the next layer is intro-
duced.
If the stabilized material is deposited on a noncon-
trolled landfill the integrity of the material, as well as
the leachate concentrations, should be monitored. It
may be necessary to treat the waste a second time if
the release increases to unacceptable proportions.
Although many experts believe that the major part
of the contaminants will ultimately be released, the
concentrations in the leachate at any one time can be
low enough to pose no direct hazard to the environ-
ment. However, if the waste leaches for an extended
period of time, the environment will become largely
loaded with contaminants unless the contaminants are
24
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Stabilization/Solidification Technologies
remineralized and components are incorporated into
soil organic matter.
3.2 Case Studies Chosen
Knowledge about S/S treatment processes is rapid-
ly increasing. The case studies discussed in this chap-
ter do not represent the most recent status of the
technology. Furthermore, the technologies presented
do not, by far, represent the full range of S/S technol-
ogy now available. The technologies chosen for the
NATO/CCMS Pilot Study only serve as a general il-
lustration of the available technology.
Three case studies in which three different vendors
applied their technology where chosen for the
NATO/CCMS Pilot Study. These are:
EIF Ecology (France), applying surface treatment
with lime
TREDI (France), using the Petrifix process
Hazcon (United States), applying ex situ treat-
ment with Portland cement.
The problems handled by the manufacturers are
summarized in Table 3-1. The rationale behind the
choice of these technologies is indicated below.
3.2.1 Case Study 3-A: In Situ Lime Stabilization
(EIF Ecology), France
In this study, described in Appendix 3-A, on-site
stabilization at two sites in France was evaluated
(Sites A and B in Appendix 3-A). The immobilization
process consisted of mixing the material with lime. The
sites are contaminated with a variety of hydrocarbons
and heavy metals. The study was chosen because the
NATO/CCMS members felt it useful to evaluate the
practice of S/S treatment in France. Since the
remediation was already completed at the start of the
NATO/CCMS Pilot Study, these sites provided limited
information.
3.2.2 Case Study 3-B: Petrifix Process (TREDI),
France
The Petrifix process was used by TREDI to stabi-
lize contaminants at two sites in France. These sites
are also described in Appendix 3-A as Sites C and D.
Site C is a former industrial disposal site, con-
taminated with a variety of contaminants, mainly
chromium, sulfates, and sulfides. The study was
chosen for the same reasons as the EIF process.
3.2.3 Case Study 3-C: Portland Cement (Hazcon,
presently IM-Tech), United States
The Hazcon process (presently IM-Tech) is a
proprietary process using a patented nontoxic chemi-
cal called Chloranan (U.S. EPA 1989). Chloranan is
claimed to neutralize the inhibiting effects that organic
contaminants normally have on the hydration of ce-
ment-based materials. The process is described in Ap-
pendix 3-B and was chosen for three reasons. First,
because the study resulted in a detailed evaluation of
the process, and can be regarded indicative of the
results to be obtained with other cement stabilization
techniques. Second, because the technique was ap-
plied on a waste containing large amounts of organic
components. Third, because the process is available
on a commercial scale making an economic evaluation
possible. (For more information on this project, see
Appendix 3-B.)
3.3 Background of Case Study Sites as a
Group
The cases accepted in the NATO/CCMS Pilot
Study all apply cement, pozzolanic material, or lime.
These binders are the most generic ones used to date.
No case studies applying other binders were sub-
mitted. In all case studies, the combination of metals
mixed with organic components plus a large site to be
treated was the major incentive in applying S/S treat-
ment.
3.4 Performance Results
Leachability of the contaminants after S/S treat-
ment is largely reduced due to the insoluble state of
the contaminants, physical encapsulation in the waste
form, and chemical binding to the matrix. The perfor-
mance of S/S treatment is primarily measured by
standard leaching tests, a.s required by regulatory
authorities. At present, only short-term tests are avail-
able. Ongoing international research in predicting the
release rate as a function of environmental variables
(such as soil pH, chemical composition of the contact-
ing ground water, waste characteristics, and binder
characteristics) should lead to more adequate tests.
Major improvements in this area can be expected in
the years to come.
A wide variety of leaching tests is available at
present. Most are required by regulatory agencies, but
have a poor scientific background. Test results are,
therefore, difficult to compare and it is usually unclear
what they measure, since leaching mechanisms are
still poorly understood. Examples of leaching tests are:
Toxicity Characteristic Leaching Procedure, or
TCLP (United States)
Multiple Extraction Procedure, or MEP (United
States)
American Nuclear Society test method 16.1, or
ANSI 6.1 (United States)
Waste Extraction Test, or WET (United States)
SOSUF test (The Netherlands)
25
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Chapters
Table 3-1. Problem handled in these NATO/CCMS case studies.
Process/technique
Manufacturer
Country
City
Area |mj)
Depth (m)
Amount of soil to be
Lime stabilization
EIF-Ecology
France
Site A: Marais de Ponteau-Lavera
Site B: Bourron Marlotte
Site B: 4,200
Site B: 6-7
Site A: 22,000 m3
Petrifix
TREDI
France
Site C: Nesle-Somme
Site D: Bellay-Ain
Site C: 5
Site D: 2.5
Site C: 6,804 tonnes
Portland cement
Hazcon (presently IM-Tech)
United States
Douglassville, PA
Total of five areas in the
site: 200,000
Unknown
200,000 m3
treated
Source
Type of soil
Typo and
concentrations of
contaminants
Main lesson learned
Site B: 22,680 tonnes
Site A: Industrial residues of the
Lavera petrochemical plant (sludges
and sediments)
Site B: Industrial residues from an old
refinery plant (mainly acid tars and
filtration residues)
Site A: Not known
Site B: Top layer - light and viscous
material; middle layer - aqueous
liquid; bottom layer - sticky material
(composition unknown)
Site D: 8,165 tonnes
Site C: Industrial residues
Site D: Sludges from tannery
plant wastewater treatment
Site C: Black-colored sludges
and silty material
Site D: Not known
Site A: Not known Site C: Concentrations in
Site B: Not known leachate: COD up to 450
mg/l; iron up to 47 mg/l;
ammonia up to 80 mg/l;
traces of copper and zinc
(concentrations in the
material itself unknown)
Site D: Chromium 8,700
mg/kg; sulfide 475 mg/kg;
sulfates 500 mg/kg;
nitrogen 350,000 mg/kg
(35%)
Absence of data concerning the original waste characteristics and
concentrations makes evaluation and technology transfer impossible.
Oil recycling facility, with
wastewater sludge,
recycling oil, and filtercake
Five different wastes:
Site A: Oily sludge from
wastewater treatment
Site B: Oily filtercake
Site C: Oil and oily water
Site D: Sludge (landfarming
area)
Site E: Plant processing
area
Lead 3,000 - 22,000
mg/kg (0.3-2.2%); oil and
grease 10,000 - 250,000
mg/kg (1-25%); VOC's 0-
150 mg/kg; semivolatile
organics 12-530 mg/kg;
PCB's 1.2-54 mg/kg; pH
2.6-7.0
Leachate characteristics of
treated material along are
not sufficient for a good
evaluation; leachate quality
from both treated and
untreated waste was
identical. The raw material
feed system and the
blender may be critical in
the process.
26
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Stabilization/Solidification Technologies
AfNOR Standard Test X31 210 (France). This
test, to be used in France, strongly resembles the
United States TCLP.
Since leaching tests only provide limited informa-
tion concerning long-term performance, several other
tests, relating to the integrity of the waste form under
various environmental conditions may be carried out,
such as:
Homogeneity of the final product, which is also an
indicator of the performance of the mixing opera-
tion
Physical performance, such as strength
Influence of weather conditions, such as freeze-
thaw and wet-dry performance
Acid neutralization capacity, which relates to the
ability of the stabilized product to neutralize acids.
Although the formation of a monolith is desirable to
guarantee the encapsulation of the contaminants, it is
recognized that the performance of nonmonolithic or
"soil-like" waste forms may be as good or better than
monolithic waste forms (Barth and McCandless 1989).
EIF Ecology. The information provided by this ven-
dor was too limited to be able to evaluate the perfor-
mance.
TREDI. As in the EIF Ecology stabilization, little is
known about the performance of the TREDI stabiliza-
tion.
Hazcon. The primary goal of the evaluation of the
Hazcon process was to compare contaminant mobility
of the untreated versus treated soil. Although exten-
sive leachate data exist on the treated soil, only limited
data are available on the original untreated wastes.
This makes a comparison difficult. From the available
data it can be concluded that the process leads to a
strong reduction of the leachate concentration. A
reduction factor of 100 for lead, the predominant metal
at the site, was seen during the SITE demonstration
using the TCLP. Similar results were observed for zinc.
For organic contaminants, the process is generally not
effective. In most cases the extracts from the TCLP
leaching tests of untreated soil were found to be identi-
cal to those of the treated soil. Some data available on
the treatment of petroleum refinery wastes, however,
showed sharp reductions in leachate concentration
after waste treatment (U.S. EPA 1989). This indicates
that there might be selected applications where immo-
bilization of organics occurs. During the project,
numerous operating difficulties were encountered by
Hazcon. Main shortcomings were encountered in the
raw material feed system and in the blender. It is
believed that improvements in this field can largely im-
prove operations.
3.5 Residuals and Emissions
Stabilization/solidification leads to a strong in-
crease in the total, volume of waste. Since increases of
more than 100 percent are normal, the treated material
often cannot be accommodated in the original site and
must be landfilled elsewhere. If the treated waste is
very wet, a part of the process water must be cleaned.
The resulting sludge, however, may be recycled back
into the system.
The S/S process produces heat, which can lead to
emission of hazardous components. Most of the
VOC's were volatilized during the Hazcon operation. In
cases where a large amount of VOC's is present, the
process should be executed in a closed system, where
the VOC's can be trapped and subsequently treated.
An inherent feature of isolidified waste is its leach-
ing ability. If improperly landfilled, most of the con-
taminants may eventually leach out. If the stabilized
waste is properly landfilled, (i.e., the landfill is properly
lined to prevent contact with ground and rain water)
leaching into the environment is not a problem. Ade-
quate maintenance of a landfill in this respect is of
major importance.
3.6 Factors to Consider for Determining
the Applicability of the Technology
3.6.1 Limitations and Restrictions on the Use of
the Technology
S/S technology can be considered for two major
reasons. The first is that no other treatment methods
are available for the particular site. This is specifically
true for wastes containing heavy metals mixed with
small amounts of organic contaminants. The second
reason is that the technique is more cost effective than
other techniques.
Generally the cement- or lime-based binders have
not been proven successful in stabilizing organic com-
ponents. Although it may be possible to treat material
containing organic components by adding certain
chemicals to prevent the unwanted effect of the or-
ganic contaminants on the cement hydration, the or-
ganic contaminants themselves are not well retained in
the stabilized waste form. Cement-based stabilization
techniques are, therefore, only applicable to wastes in
which metals are the main source of contamination
and where the release of organic contaminants is not
considered a main problem. The technique should not
be applied when the organics are highly toxic or where
large amounts of volatile organic contaminants are
present.
A drawback of S/S technologies is their ques-
tionable long-term durability. Analyses of crushed
samples show that there often is hardly any chemical
binding, which implies that most of the contaminants in
the solidified waste form are essentially mobile and will
27
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Chapter 3
eventually leach out of the stabilized material. Physical
entrapment and adsorption, however, strongly reduce
the velocity of release.
Another drawback of S/S technology is that it re-
quires large amounts of chemicals and leads to sub-
stantial volume increases of the stabilized products.
Especially for dry materials like soil, an increase of
more than 100 percent can be expected. Volume in-
creases up to 140 percent have been reported. This
means that the disposal site needs to be more than
double the size of the original site. In designing dump
sites this factor will have to be taken into account.
A summary of the limitations related to the case-
study projects is given in Table 3-2.
concentrations. The metals, however, are essentially
mobile. The stabilized material should, therefore, be
deposited on a controlled dump site with adequate
drainage and treatment facilities to prevent migration
into the environment.
3.6.2 Steps in Determining the Applicability of S/S
Treatment
A general five-phase investigation, to assess the
possible application of immobilization, is given by
Barth and McCandless (Barth and McCandless 1989)
and consists of:
Table 3-2. Limitations of the case study techniques.
Manufacturer
Technique
EIF-EcoIogy
Lime Stabilization
TREDI
Petrifix
Hazcon (presently IM-
Tech)
Cement plus additives
InJEx situ
Feature of process used
Long-term effect
Release mechanism
In situ
Heavy metals are partly encapsulated;
buffering capacity is the main cause of
delayed release.
If the waste is not stored dry,
contaminants will be released
Release is partly governed by diffusion.
The waste form easily disintegrates,
enlarging surface area. Utilization of
acid neutralization capacity is the major
release factor.
In situ
Ex situ
Heavy metals are encapsulated and precipitated; some
chemical binding may occur.
If the treated waste is not stored dry, contaminants will
be released.
Release is partly governed by diffusion and accelerated
when the waste form breaks up, due to increase of
surface area. Utilization of acid neutralization capacity
is thought to be a major release factor.
Typo of soil; fraction of No limitations
fines, organic* and rubble
Type of contaminants
Concentration of
contaminants
Volume increase
No limitations
No limitations
Organics are not immobilized; volatile organics may be released.
No limitations No limitations No limitations
Depends largely on water content; dry solids will lead to an increase of 100-140%.
In the EIF Ecology process, the contaminants are
essentially trapped due to the low solubility in the high
pH environment of the mix. Release, therefore, strong-
ly depends on the acid neutralization capacity of the
stabilized product. In general, lime as a sole binder is
not very effective.
In the Hazcon process, heavy metals are retained
in the stabilized product mostly by physical entrapment
and precipitation. The buffering capacity of the stabi-
lized material leads to a strong reduction in leachate
1. Site sampling
2. Waste acceptance/project planning
3. Waste characterization
4. Binder screening
5. Performance testing.
1. Site sampling. Many techniques are available
for taking a representative sample. In most cases, site
sampling for bench testing can be aimed at obtaining
either a "worst case" sample and/or an "overall
28
-------
Stabilization/Solidification Tecfinofogfes
average" sample. The choice depends on the nature of
the waste and the quality and amount of data available
to the planner. For the treatability study, a sample of at
least 130 kg is recommended (Earth and McCandless
1989). An assessment of variability of the waste is im-
portant for determining the size and number of
samples to be taken.
2. Waste acceptance. Generally, laboratory per-
mits are restricted to certain components and wastes.
An analysis of a representative sample should give in-
formation on the type of laboratory needed for the
treatability study. Furthermore, the waste acceptance
investigation should provide information about pos-
sible health aspects that have to be accounted for in
the study.
3. Waste characterization. Prior to binder screen-
ing and performance testing, the waste is charac-
terized to obtain information needed to plan S/S
treatment. Important objectives of the waste charac-
terization are to:
ป Assess the possibility of applying additional tech-
niques in order to reduce the amount of waste to
be treated. In case the contaminants are con-
centrated in a fraction of specific particle size, a
separation technique might be considered.
Obtain information concerning components that
are known inhibitors to the hydration and setting
of cement and pozzolans.
Leaching behavior of the original waste is important
because it gives information on the potential effective-
ness of the S/S treatment. In some cases it has been
established that leaching rates after stabilization were
higher than before treatment, making the application of
S/S somewhat dubious. Establishing the original con-
centration of the total and soluble fraction of the con-
taminants to be immobilized is important in terms of
interpretation of leachability studies.
4. Binder screening. Since S/S represents a rela-
tively new alternative in remediation, little technical in-
formation, empirical or otherwise, is available to
assess its potential (Barth and McCandless 1989).
Many factors influence the performance of the waste-
binder mix. Some important factors are: soil type, con-
taminant type, and contacting liquid (rain water, acid
leachate, sulphate-containing ground water, etc.).
A first step in the possible consideration of immobi-
lization is mix design. The basis of a mix design is the
assessment of binder characteristics and waste char-
acteristics, separately and in combination, leading to
an estimate of appropriate mix compositions. Center
Hill Research Laboratories (University of Cincinnati
1990) establishes so-called design windows (possible
compositions), derived from pH-solubility curves and
acid neutralization capacity-pH curves. Although the
establishment of design windows yields information on
waste-binder mixes, treatability studies are a neces-
sary second step in the assessment of immobilization
as an environmentally sound remedial alternative.
Since only limited theoretical information is available
on selection of binders for a specific waste, trial and
error approaches are followed. In general, three binder
mixes are considered: Portland cement, cement-kiln
dust mixtures, and lime fly ash mixtures. Apart from
possible ad-hoc combinations, a standard trial com-
bination of binder-to-waste mixes may be applied.
Barth and McCandless (Batth and McCandless 1989)
propose trying the nine possible combinations of the
three most widely used binders (Portland cement type
I, cement kiln dust, and lime fly ash type F) and three
binder-to-waste ratios (0.1,0.3, and 0.6).
Other parameters, such as the water-to-cement
ratio (W/C factor) and slump, are assessed according
to established civil engineering practices. Based on
the results of the trial mixes, further optimization is car-
ried out.
5. Performance testings. After the composition of
the binder mix is determined in the laboratory, the sta-
bilized specimen must be tested on a larger scale. In
laboratory tests, performance testing aims at improv-
ing the binder mix and determining the expected
leachate concentrations as measured by standard
leaching tests and physical integrity tests. The
laboratory tests generally result in a fine tuning of the
binder-waste mix under optimal conditions. Since in
practice the actual stabilization is performed with field
equipment under less ideal circumstances, pilot tests
are necessary to obtain information on the perfor-
mance of the actual field stabilization. Mixing, for in-
stance, may be the critical step in the field.
3.7 Costs
3.7.1 General Cost Factors
Currently (1991), little cost information is publicly
available. In the NATO/CCMS case studies, costs of
treatment were only available for Hazcon. The costs of
this particular process are summarized in section 3.7.2
below. However, the following general cost factors for
applying S/S treatment should be taken into account,
at a minimum.
Costs of treatability studies. S/S, more than other
technologies, is an art rather than a science. The per-
formance of the technology is established by trial and
error, rather than by design. Consequently, treatability
studies may represent a substantial part of the total
costs, and the cost of these studies may be an impedi-
ment to the application of the technology.
Barth and McCandless (Barth and McCandless
1989) give an indication of the costs involved in as-
sessing the potential of an S/S technique. These costs
are summarized in Table 3-3 and apply only to metal-
containing wastes. Two cases are indicated in Table
3-3: for wastes containing metals only, and for wastes
29
-------
Chapter 3
Table 3-3. Summary of estimated treatability costs for metals (xlOOO US$, 1989).
Site sampling *
Wosto acceptance
Waste characterization
Binder screening
Performance testing
TOTAL ESTIMATED COSTS
Labor
8.0
13.1
7.7
14.9
16.1
59.8
'Metals Only
Analysis
.-
3.9
5.2
3.8
5.8
18.7
Total
8.0
17.0
12.9
18.7
21.9
78.5
Metals
Labor
8.0
13.1
7.7
18.9
17.6
65.3
Plus Non-Volatile
Analysis
3.9
13.5
25.9
39.6
82.9
Organics
Total
8.0
17.0
21.2
44.8
57.2
148.2
'Estimated average; highly project-specific.
containing a combination of metals and nonvolatile or-
ganlcs. It should be realized that the estimated costs
only serve as an indication of the potential costs in-
volved. As can be seen, the analytical costs are by far
the most significant factor in the total cost of a
treatability study when complex wastes are involved.
Regulatory costs. The costs of permitting and en-
vironmental monitoring of operations for any regulatory
authority may be substantial. Costs vary widely in each
country. In countries following a federal system (e.g.,
Germany and the United States), the regulations may
vary substantially within the country as well.
Site preparation costs. These costs include ac-
cess to feedstocks and providing utilities needed for
the plant to operate. They also include installation of
equipment to support the operation such as storage
tanks, pumps, and piping. Site preparation costs can
be strongly influenced by site geology, proximity to
residential areas, quantity and type of contaminants,
and local costs of labor, utilities, and raw materials.
Treatment costs. These costs are generally given
by the vendor of the technology. In the Hazcon case,
operations are assumed to be 7 days per week and 24
hours per day. Any reductions in this schedule would
add to the remediation costs by increasing the costs
per tonne of treated waste. A vendor generally incor-
porates a profit factor of about 10 percent into the es-
timated costs.
Costs for additional landfilling and cleaning of
process water. The site may not be able to accom-
modate the largely increased volume of the waste after
treatment (more than 100 percent). Costs for additional
landfilling of the treated material can be substantial.
Site completion. This includes the removal of sup-
port equipment at the completion of the cleanup as
well as activities related to further use of the site and
possible long-term monitoring.
3.7.2 Costs Of The Hazcon Treatment System
A cost' analysis of the Hazcon system (now IM-
Tech) has been made by the U.S. EPA (U.S. EPA
1989). A summary of these costs is given in Table 3-4.
It should be noted that Table 3-4 only provides an in-
dication of some of the costs involved in S/S treatment.
3.8 Future Status of Case Study
Processes and the Technology as a
Whole
The future status of the stabilization technology as
a whole largely depends on the policies adopted in a
specific country. Countries relying on concentration-
based threshold values to evaluate hazardous waste
are not likely to adopt the stabilization technology. In
some countries, mixing a waste with another material
is considered dilution of waste and is prohibited even if
this dilution brings the concentration below certain
threshold values.
In general, it can be stated that stabilization techni-
ques (i.e., landfilling of stabilized waste) should be
avoided if treatment techniques are readily avajlabje.
However, in many current industrial processes, as well
as in households, large amounts of unspecific mixed
waste are produced. To clean these wastes would re-
quire so many conventional treatment steps, that treat-
ment in these cases is not a realistic option. As long as
industry continues to produce these unbeatable mixed
wastes in large amounts, landfilling will be necessary.
Stabilization techniques to pretreat these wastes may
be an option to consider.
The processes discussed in this chapter are not yet
optimized. Fundamental research is needed in a num-
ber of areas, such as development of adequate test
methods to assess the long-term durability of stabi-
lized waste, assessment of binding mechanisms in
30
-------
Stabilization/Solidification Technologies
Table 3-4. Estimated costs for the Hazcon System (in US$, 1989).
Demonstration Test
chemical consumption2
Reduced chemical consumption2
136 kg/min
on-stream
factor3
1044 kg/min
on-stream
factor3
136 kg/min
on-stream
factor3
90%
70%
90%
70%
90%
70%
Startup and fixed costs
Operator training 0.84 0.84
Site mobilization 0.83 0.83
Depreciation costs 0.25 0.32
Insurance and taxes 0.25 0.32
Labor costs
Salaries and living expenses 50.32 64.70
Administration 0.25 0.32
Raw materials ,
Cement 50.00 50.00
Chloranan 66.67 66.67
Utilities
Fuel 1.00 1.29
Electricity 0.03 0.03
Water 0.08 0.08
Other costs
Analytical 5.65 6.50
Facility modifications 0.25 O.32
Site demobilization 0.83 0.83
TOTAL* 188 206
0.84
0.83
0.11
0.11
6.56
0.11
50.00
66.67
0.84
0.83
0.13
0.13
8.44
0.13
50.00
66.67
0.23 0.29
0.07 0.07
2.26 2.40
0.12 0.14
0.83 0.83
137
139
0.84
0.83
0.25
0.25
50.32
0.25
33.33
44.44
1.00
0.03
0.08
5.65
0.25
0.83
149
0.84
0.83
0.32
0.32
64.70
0.32
33.33
44.44
1.29
0.03
0.08
6.50
0.32
0.83
167
1044 kg/min
on-stream
factor3
90% 70%
Equipment
Support
Equipment rentals
Contingency
2.25
8.05
0.25
2.25
10.36
0.32
6.75
1.05
0.11
6.75
1.35
0.13
2.25
8.05
0.25
2.25
10.36
0.32
6.75
1.05
0.11
6.75
1.35
0.13
0.84
0.83
0.11
0.11
6.56
0.11
33.33
44.44
0.84
0.83
0.13
0.13
8.44
0.13
33.33
44.44
0.23 0.29
0.07 0.07
2.26 2.40
0.12 0.14
0.83 0.83
98
100
'Estimated accuracy of the reported costs is -30% + 50% or less.
2A higher amount of chemicals was used during the demonstration test. The reduced chemical consumption refers to
33% of the demonstration test amount used.
''The stream factor indicates the continuing performance of the installation (a lower on-stream factor produces
higher costs per ton of treated material).
4Rounded to whole dollars.
Source: adapted from U.S. EPA 1989.
stabilized waste forms, and methods to improve bind-
ing. Engineering improvements such as providing ade-
quate mixing in the field and assessment practices
such as characterization of the raw wastes should be
further standardized and improved.
in terms of scientific advancement, it would be
desirable to have leaching tests that have a sound
scientific background. Most presently used tests do not
provide fundamental infonmation about the leaching
process. Because waste-binder mixes are not required
to be specified to a great esxtent, test results from dif-
ferent waste-binder mixes can be related only very
marginally.
31
-------
Chapters
REFERENCES
Barth, E.F. and McCandless, R.M. et al. Treatability assessment planning guide for Solidification/stabiliza-
tion of contaminated soils, U.S. EPA Risk Reduction Engineering Laboratory, October, 1989.
U.S. EPA. Hazcon solidification process, Douglassville, PA - applications analysis report, EPA/540/A5-
89/001, May 1989.
University of Cincinnati. Solidification/stabilization treatablity assessment report, Kassouf-Kimmerling Bat-
tery (KKB), NPLsite, September, 1990.
32
-------
Soil Vapor Extraction Technologies
Norma Lewis
United States Environmental Protection Agency
Office of Research and Development, Cincinnati, Ohio 45268
United States
ABSTRACT
Soil vapor extraction (SVE) has been useful for soils contaminated with gasoline, solvents and other volatile
organic compounds, and some semivolatile organic compounds.
v^TS^tt^
Ser to the air and to condensed wastewater streams. It can also be used with m,crob.al treatment.
also discussed.
4.1 Introduction
Soil vapor extraction (SVE), also known as in situ
venting (ISV), can be a cost-effective remediation
process for soils to remove volatile organic com-
pounds (VOC's) and some semivolatile organic com-
pounds (SVOC's) from the vadose zone. The vadose
zone is the subsurface soil zone located between the
surface soil and the top of the water table.
SVE technologies have been used to remove vapor
from landfills since the 1970's. During the 1980's, SVE
was used extensively to remediate contaminated soil
from leaking underground storage tanks. Only recent-
ly has SVE been used to remediate contaminated haz-
ardous waste sites. This technology can be useful at
sites where there are interferences or obstructions,
such as buildings and highways that generally have
sub-bases of porous material. In general, SVE is used
in conjunction with other technologies since it transfers
contaminants from soil and ground water to air and to
condensed wastewater streams.
^^
The process of SVE is characterized by air being
drawn through the soil. As the air passes through the
series of soil pores, it follows paths of lower resistance
(i.e., through zones of high air permeability). Air,
which is drawn through pores that contain con-
taminated vapor and liquids, carries the vapor away
(advent the vapors). Contaminants will vaporize from
one or more of the condensed phases (aqueous, ad-
sorbed) replacing the vapors that were carried away in
the air stream. Continued vaporization occurs to main-
tain the vapor-condensed phase equilibrium that was
established before the contaminants were removed.
This process will continue until all of the condensed
phase organics are removed from the higher per-
meability soil. Contaminants in lower permeability
zones will not be removed by advection since the air
stream will continue to flow through the higher per-
meability soil. If the contamination is located some
distance from the air flow, the vapor must diffuse to the
air stream before it can be removed. The diffusion
-------
Chapter 4
process would then limit the rate of contaminant
removal by the SVE process (U.S. EPA 1991 a).
, I!ฃ.baslc Pnenฐmena controlling the performance
of SVE systems are, therefore, based on vapor
transport mechanisms. The effectiveness of this vent-
ing operation is dependent on three main factors:
The chemical composition of the contaminant
ป The rate of the vapor flow through the vadose (un-
saturated) zone
The flow path of the carrier vapors relative to the
tocation of the contaminant (Hutzler, Murphy and
Gierke 1988).
Compounds exhibiting vapor pressures over 0 5
cmi Can be most readilv extracted using SVE (U S
EPA 1991a). When expressed in terms of the air-
water partitioning coefficient, compounds that have
values of dimensionless Henry's Law constants
greater than 0.01 are more likely to be removed by
-------
Soil Vapor Extraction Technologies
aggregation, and stratification. Soil moisture content
or degree of saturation is important because it is easier
to extract vapor from drier soils. As the size of a soil
aggregate decreases, the time required for the dif-
fusion of the chemical out of the immobile regions also
increases. Clayey or silty soils may be effectively ven-
tilated by the usual levels of vacuum developed in a
soil vapor extraction system (Camp, Dresser and
McKee 1987; Terra Vac 1987). (The levels of vacuum
developed in SVE systems can range from 7 to 760
mm Hg; however, usual levels range from 50 to 130
mm Hg [Hutzler, Murphy and Gierke 1988].)
It must be recognized that soils with high clay or
humic content generally provide high sorption potential
for VOC's and thus can inhibit the volatilization of con-
taminants (U.S. EPA 1991a). The success of the soil
vapor extraction in these soils may depend on:
The presence of more conductive strata as would
be expected in alluvial areas
Relatively low moisture contents in the finer-
grained soils (Hutzler, Murphy and Gierke 1988).
Application of proper scientific and engineering
principles are necessary for reliable cost-effective sys-
tem design and to ensure desired treatment results.
Design considerations include the number of installa-
tion wells, well spacing, well location, and well con-
struction, including the vapor treatment system. To
date, a typical SVE system design consists of a single
extraction well network which feeds a common vapor
treatment system. However, modular system designs
can be used to remove VOC's from specific con-
taminated areas or from areas with differing con-
taminant concentrations. Modular system design,
although more capital intensive, allows for rapid chan-
ges in operations; this allows for optimizing the sys-
tem. It permits the shutdown of various segments of
the system once remediation of that area has been
completed, thereby reducing operating costs. It also
allows the operation of one segment of the system to
be continuous while another segment is operated on
an intermittent basis.
In some cases, subsurface soil conditions can be
modified to facilitate the application of the SVE tech-
nology. For example, it may be necessary to lower the
ground water level to enlarge the unsaturated zone;
this would allow adsorbed volatile organics an oppor-
tunity to vaporize. At sites where the ground water is
lowered, the extracted ground water may require treat-
ment. In some cases, application of techniques such
as radio frequency (RF) heating can be considered to
increase soil temperature; this would increase the
volatility of the contaminants and enhance con-
taminant removal.
In addition to extracting VOC's, SVE can be used to
stimulate biodegradation of less volatile contaminants
by supplying air (oxygen) to the subsurface soils at the
same time. Although oxygen is usually the rate limiting
parameter for aerobic biodegradation, other biological
factors, such as availability of nutrients, require
evaluation when considering using SVE in this way.
(See the chapter on microbial treatment, below, for
further discussion of this application.)
After the contaminated vapors have been removed
from the subsurface soil, treatment may be required to
condense/concentrate or destroy the contaminants in
the air/vapor stream before it can be discharged into
the atmosphere. There are a variety of technology op-
tions available for treating these vapors. For vapor
streams with high concentrations of VOC's, condensa-
tion, thermal incineration, or catalytic oxidation are ap-
plicable options. For more dilute vapor streams,
gas-phase activated carbon adsorption can be used.
For very dilute vapor streams, if local regulations per-
mit, direct discharge into the atmosphere may be al-
lowed. Other methods, such as biological treatment,
ultraviolet oxidation, and dispersion also have been
applied. The type of treatment chosen will depend on
the composition and concentration of the contaminants
in the extracted vapor stream (U.S. EPA 1991 a).
As operational experience with the SVE technology
has developed, it has been learned that vapor/liquid
separators are frequently needed prior to the vapor
treatment device. Such separators need to be sized
large enough to provide ample protection for the vapor
treatment system which follows. This means that
vapor/liquid separators should be slightly oversized,
rather than sized specifically for the downstream
equipment. The separated ground water and conden-
sate collected from the vapor treatment may have to
be treated as a hazardous waste.
In the remainder of this chapter, case studies are
presented to illustrate specific applications of the SVE
technology. In addition, residuals and emissions,
costs, factors to consider for determining applicability
of the technology, and the future status of the SVE
system are discussed.
4.2 Case Studies Chosen
The case studies which are presented in the follow-
ing discussion are intended to illustrate how SVE has
been applied to a wide range of site and soil condi-
tions, as well as to various contaminant types and con-
centrations. These include three case studies chosen
for this NATO/CCMS Pilot Study and three additional
studies from the United States. The latter are included
to provide a broader information base on the SVE
technology.
4.2.1 Case Study 4-A: In Situ Soil Vacuum
Extraction, The Netherlands
This case study has two sites, known as Site 1 and
Site 2. Site 1 was contaminated with solvents (up to
2200 mg/kg d.m. toluene); Site 2 was heavily con-
35
-------
Chapter 4
laminated with gasoline (11,000 to 18,000 mg/kg
dm.). There were two objectives of this project: to
study the SVE removal effectiveness for contaminants
located beneath structures as well asto study the ef-
fectiveness of in situ biological degradation of residual
organics stimulated by the perfusion of air into the sub-
surface soils. The contaminants at both sites were in
fine- to coarse-grained sands. Details of this case
study are presented in Appendix 4-A.
4.2.2 Case Study 4-B: Vacuum Extraction of Soil
Vapor, Verona Well Field Superfund Site,
United States
The Verona Well Field site located in Battle Creek,
Michigan had several distinct contaminated areas
within 100 acres. During routine testing of the city's
drinking water supply, volatile organic compounds
(VOC's) were discovered in 10 of the 30 production
wells. The contamination plume extended over an
area of approximately 1.3 km2 (0.5 mi2) and contained
VOC concentrations as high as 1,800 ppb in both the
ground water and soil. The contaminated soil con-
sisted of fine- to coarse-grained sand with traces of
clay and silt. The objective of the project was to
remove VOC's from the unsaturated zone within the
contaminated boundary (Danko, McCann and Byers
1990). To accomplish this, the ground water had to be
lowered from 2 meters to 3 meters below the ground
surface to enlarge the unsaturated zone. An abstract
of this case study is presented in Appendix 4-B.
4.2.3 Case Study 4-C: Venting Methods, Hill Air
Force Base, United States
The United States Air Force Engineering and Ser-
vices Laboratory began a research project with Oak
Ridge National Laboratory to conduct a full-scale test
of In situ soil venting at a jet fuel (JP-4) spill site. The
site chosen for the test was a fuel yard at Hill Air Force
Base (AFB), Utah where a 100,000 liters (27,000 gal-
lon) JP-4 spill had occurred. The site was selected for
several favorable characteristics, including nearly ideal
geohydrology, significant JP-4 contamination in the
soil, logistical support, and the opportunity to under-
take tests of different venting configurations. A sum-
mary of this case study is presented in Appendix 4-C.
4.2.4 Additional Case Studies, United States
The following case studies are presented to typify
other applications of SVE. These case studies have
been well documented and therefore provide com-
prehensive evaluations of performance results for dif-
ferent SVE system configurations and site and
contaminant conditions.
Groveland Well Site, Massachusetts. A
performance evaluation of the Terra Vac, lnc:'s
vacuum extraction system was conducted during a
56-day demonstration test run at a Superfund site in
Groveland, Massachusetts. This site was
contaminated with degreasing solvent and cutting oils.
Total contamination at the site was estimated at
between 1,360 to 13,600 kg (3,000 and 30,000 Ib) of
VOC's with much of the heavy subsoil contamination
located beneath a building (U.S. EPA 1989a).
The objectives of this field test were:
To determine how well the technology would
remove VOC's from the vadose zone
To assess effectiveness in various soil types
To correlate declining recovery rates with time
To correlate VOC concentration in soils with those
in extracted vapors.
This case study is summarized in Appendix 4-D.1.
Paint Warehouse Fire, Dayton, Ohio. An
undetermined quantity of paints and paint solvents
escaped into the soils at a paint warehouse in Dayton,
Ohio, as the result of a catastrophic fire. Even though
water was not used to fight the fire, uncombusted
material still penetrated the soil and spread through
the unsaturated zone. Less than six weeks after the
fire, several VOC's were detected in nearby city wells.
Rapid VOC removal from the porous soils in the
vadose zone was needed to reduce further
contamination of the ground water.
The objective of this project was to document the
use of SVE for the rapid removal of the VOC's. In ad-
dition, the modular SVE system configuration
developed for remediating the site was also the subject
of study. Refer to Appendix 4-D.2 for the case study
abstract.
Twin Cities Army Ammunitions Plant (TCAAP).
This case study covers two site locations (Site D and
Site G), at the TCAAP located at New Brighton,
Minnesota. Site D was a solvent leaching pit/burn
area and covered an area of 0.2 hectare (0.5 acre).
Site G consisted of landfill material contaminated with
VOC's and some metals. The SVE systems used for
remediating both of these sites began operation in
1986 and are the longest operating and the largest
SVE systems to date (U.S. EPA 1990a). The criteria
used in selecting these sites for study were:
Duration of the SVE system operations
Quality of the initial site characterization
Amount and availability of operational data
Willingness of site owners/operators to participate
in the project
Site characteristics, such as soil type, con-
taminant type, and size.
Two separate pilot systems were installed to test
several design and performance variables. System 1
was designed to evaluate tetrachloroethylene TCE
36
-------
Soil Vapor Extraction Technologies
Table 4-1. Summary of SVE case study information.
Case study
The Netherlands
- Site 1
- Site 2
Verona
Hill AFB
Groveland
Dayton fire site
Principal
contaminant
Toluene
Petroleum products
VOC's
Jet fuel
TCE, MC
Toluene
Level of
contamination
2,200 nig/kg
11,000-18,000
mg/kg d.m.*
1 mg/kg
Not specified
TCE:2,500 mg/kg
Not specified
Soil type
Fine to coarse sand
Fine to gravel sand
Fine to coarse sand
Medium to fine sand
Medium sand to
gravel
Sandy soil with clay
Depth to
ground
water
7 meters
2 meters
7.5 meteirs
Not
specified
Not
specified
13.5 to 15
Vapor treatment
Activated carbon
Biological purification
Activated carbon then
catalytic oxidation
Catalytic incineration
Vapor-liquid separator,
activated carbon
Vapor-liquid separator
TCAAP
- Site D
- Site G
TCE, TCA, toluene
TCE
VOC's: 50 to
8,000 mg/kg
VOC's: 22 to 960
mg/kg
Arsenal sand
Fill with underlying
clay
49.5 meters Vapor carbon system
39 meters Activated carbon
*d.m. = dry matter or dry weight (d.w.)
removal from soils with relatively low VOC contamina-
tion (less than 2.3 mg/kg). The second system was a
larger design to remove TCE with higher concentra-
tions up to 5,000 mg/kg. Appendix 4-D.3 contains an
abstract of this case study.
4.3 Background of the Case Study Sites
as a Group
Table 4-1 summarizes the applications of SVE for
the various case studies. The case study sites share
several common traits. They all involve the extraction
of volatile organic compounds from porous to
moderately porous vadose zone soils. The con-
taminated soil types found at the case study sites were
principally soils characterized by their high air conduc-
tivity. In general, these were fine- to coarse-grained
sands, although other soil types including some silts
and clays were present. Typically, the soil hydraulic
conductivities ranged between 10^ to 10-8cm/s.
The sources of contamination varied between sites.
They include releases of contaminants from under-
ground storage tanks, landfills, waste handling prac-
tices, and contamination resulting from a fire.
The contaminants requiring remediation included:
Chlorinated solvents
ซ Gasoline
JP-4 (a jet fuel)
Nonhalogenated solvents.
These classes of compounds are typical of those
for which SVE is used. They all have a majority of
constituents which are highly volatile.
These case studies also represent a diversity of
site-specific conditions for SVE application. For ex-
ample, they illustrate the application of SVE for rapid
remediation of sites recently contaminated to prevent
ground water contamination; the remediation of sites
with contaminants which have resided in the environ-
ment over time; and the remediation of sites which
have obstructions such as buildings that limit the ap-
plication of invasive techniques. Additionally, they il-
lustrate the differing system configurations, using
vertical and horizontal venting, that can be used. Also,
these case studies demonstrate how SVE can be used
to stimulate in situ biological degradation to effect
removal of less volatile contaminants as well as
residual volatile contaminants remaining in the soil.
The SVE processes were used at each of the sites
as an integral part of a treatment train. One of the
most significant differences between the SVE systems
presented involves the treatment techniques used for
the off-gases. Depending on the contaminant con-
centrations in the extracted vapor stream, the treat-
ment of the off-gases included:
Direct discharge for air streams which contained
very dilute VOC concentrations
37
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Chapter 4
Vapor phase activated carbon for low volume/low-
to-moderately contaminated air streams
To catalytic oxidation for more highly con-
taminated air streams.
4.4 Performance Results
For each of the case studies performance results of
the SVE system were collected. The following discus-
sion presents these results, and the key design criteria
and analytical procedures used in their determination.
4.4.1 Analytical Procedures
To evaluate the performance of SVE systems, it is
important to quantify the amount of VOC's removed,
the amount of these contaminants remaining in the
soil, and the time for remediation. Further, additional
data is needed for operating the air pollution equip-
ment used to treat the extracted vapors. The following
discussion illustrates some of the techniques used for
accomplishing these tasks.
The techniques used at the Groveland site typify
the procedures used to measure VOC removal. The
quantification of VOC's removed was done by measur-
ing:
ปThe gas volumetric flow rate by rotameter, and
wellhead gas VOC concentration by gas
chromatography (GC)
"The amount of VOC's adsorbed in the activated
carbon canisters by desorption into CSg, followed
byGC.
VOC flow rates were measured and tabulated for
each well section separately.
In general similar approaches were used in all of
the case studies to determine residual contaminants in
the subsurface soils. These included the collection of
soil, soil gas, and ground water samples, and analyz-
ing these samples for the parameters of concern. At
the TCAAP site soil gas probes were used in
boreholes drilled during the initial site assessment to
determine the residual soil gas in the subsurface. Be-
cause these were already drilled the number of
boreholes required later for assessing the SVE perfor-
mance was reduced, thereby reducing costs as-
sociated with this testing.
To collect data about the extracted vapors, vapors
extracted from both SVE systems at the TCAAP were
continuously monitored for moisture content, tempera-
ture and pressure. Similar data was collected in most
of the case studies which required vapor treatment.
Additionally, air emissions were monitored throughout
the operation, initially on a daily basis, and then on a
weekly basis. The frequency of sampling was ad-
justed when the data reflected trends indicating a
stability of the extraction process. To gain an under-
standing of the SVE process, in addition to evaluating
the performance of the system, other procedures were
used at The Netherlands Site 1. These were the
modeling of the SVE action duration, the study of the
horizontal versus vertical aerodynamical conductivity
of the soil, and the measurement of bacterial activity.
For the duration factor, the input parameters were the
estimated airflow in the subsoil, the sorptive properties
of the subsoil in relation to the contaminants, and the
physical/biological properties of the contaminants at
soil temperature. Air flow and tracer velocity measure-
ments in relation to the applied negative pressure
gradient in the subsoil were made for use in the model.
At this site, the horizontal directional aerodynamical
conductivity of the soil was found to be about 150
meters per day (500 ft/d); in the vertical direction, it
was about 70 to 90 meters per day (230 to 300 ft/d).
4.4.2 General Effectiveness of the SVE Process
SVE worked best at sites contaminated with VOC's
having Henry's Law constants greater than 0.01 or
vapor pressures greater than 0.5 mm Hg. However,
less volatile constituents can also be removed by SVE,
but removal efficiencies are reduced as the volatility
decreases. SVE has been shown to remove VpC's
from fine- to coarse-grained sands with permeabilities
ranging between 10-3 to 10'8 cm/s. Although per-
meability (hydraulic conductivity) is frequently used as
a criterion for SVE applicability, air-filled porosity of a
soil is a more important factor.
In general, SVE has been demonstrated to be ef-
fective for the removal of VOC's from vadose zone soil
up to depths of 180 meters (600 ft). Soil with moisture
content up to 30 percent can be effectively remediated.
(Ground water levels can be lowered to increase the
vadose zone.) Soils with high clay and/or humic con-
tent will tend to adsorb the VOC's present and thereby
slow vaporization. Thus adsorption can affect the level
of remediation obtainable in such soil; that is, the soil
cleanup levels may not be achievable by SVE alone.
Johnson, et al. (1990) suggest that SVE is capable
of removing approximately 90 percent of the volatile
contaminants with a vapor pressure greater than 0.5
mm Hg. This rule of thumb is generally supported by
the case study data and provides a starting point for
estimating how much material can be removed and
how much will remain in the subsurface.
To date, insufficient data exists to permit develop-
ment of empirical relationships for VOC removal ef-
ficiencies for specific contaminants in various soil
types. Based on the case studies presented, the mass
removal rates vary greatly from site to site. The mass
removal rates were observed to range up to 2300 kg/d
(5000 Ib/d). Average mass removal rates typically
ranged between 5 and 30 kg/d. The rate at which con-
taminants were removed over the project life differed.
In several of the case studies, there was an initial
38
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Soil Vapor Extraction Technologies
sharp decline in the VOC mass removal rate followed
by a period of gradual decline; this ultimately leveled
off as residual cpntaminant concentrations ap-
proached zero. It is believed that this is characteristic
behavior for sites where the contaminants have
resided in the subsurface for some time and in which
the moisture content of the soil is low. In other cases,
mass removal rates increased over time and then
declined gradually before leveling off as the VOC con-
centrations in the extracted vapor approached zero.
Preliminary indications are that this occurs at sites
where the moisture content is high and the soil
porosity is low. Since only limited data exist on SVE
applications, the performance results for the case
studies can only provide an indication of the effective-
ness of SVE applications for given contaminants and
specific site conditions.
Operationally, the Groveland case study indicates
that once the VOC concentration in the extracted
vapor leveled off (as it approached zero), the extrac-
tion process can be terminated for approximately two
days and then restarted. (The time required to reach
this leveling-off point was estimated to be 150 to 200
days, based on modeling.) By stopping the extraction
process, equilibrium in the air spaces can be rees-
tablished. If, when the extraction process is begun
again, the VOC concentration does not increase above
the concentration which was observed when the
process was stopped, it can be concluded that the
maximum removal efficiency achievable by the SVE
process has been obtained. If, however, an increase
in the VOC concentration is observed in the extracted
vapor, it can be concluded that vaporization is still oc-
curring. At this point, intermittent operation of the SVE
system can be used until the concentration of the ex-
tracted vapor does not increase after the process has
been stopped.
4.4.3 Removal of Nonhalogenated Solvents
Performance results from Site 1 in The Netherlands
show that, within four months of operation, ap-
proximately 580 kg (1300 Ib) of toluene was withdrawn
from the contaminated area. Initial concentrations of
toluene in the fine- to coarse-grain sand ranged up to
2200 mg/kg. Concentrations of up to 8000 mg of
toluene/m3 were measured in the withdrawn soil vapor
(up to 40 g/m3 in a specific extraction well).
At the Dayton Site, the soil volume to be treated
was divided into four cells, based on the air flow rate
which could be provided by a pumping unit. Each of
the four cells was brought on line for two week inter-
vals. The system recovered 1690 kg (3720 Ib) of
VOC's during the first 73 days of operation. After 56
weeks of operation, over 3600 kg (8000 Ib) of VOC's
had been recovered from the site. By April 1988,
composite off-gas VOC measurements had fallen to
less than 1 ppm. At the same time, VOC concentra-
tions in the unconfined aquifer had, for almost two
months, been at nondetectable levels for all hydrocar-
bon species identified prior to treatment. By June
1988, all off-gases extracted from the shallow, un-
saturated soil were below 1 ppm. All perched water
extracted from the vacuum wells yielded VOC con-
centrations below action levels accepted by Ohio's
EPA and the cleanup activities were halted. (Ground
water VOC action levels were established for the
ketones as follows: acetone, 810 ng/L; MIBK, 260
; and MEK, 450 ng/L.)
4.4.4 Removal of Gasolines and Jet Fuels
At The Netherlands Site 2, the soil was heavily con-
taminated with 11,000 to 18,000 mg/kg petroleum
products. Over the first year of operation, the SVE
system extracted approximately 1 ,900 kg (4200 Ib) of
volatile organics from the soil, and approximately 800
kg (1800 Ib) was broken down in the soil by microbial
action; (thus, a total of nearly 2,700 kg (6000 Ib) of
gasoline was removed or broken down). Nine months
after beginning the SVE process, the soil-air vapor
withdrawal rate was increased from 25 to 50 m3/h (15
to 30 cfm). The concentration of volatile gasoline com-
pounds was 3 g/m3. After an additional ten weeks, the
SVE air extraction rate was increased once again to 63
m3/h (37 cfm). To keep the concentrations of the con-
taminants in the extracted-air at about the same level,
the extraction rate was increased during the clean up
period. This was necessary for the efficient operation
of the biological treatment plant. There were no limita-
tions caused by the geological situation.
At Hill AFB, approximately 50,000 kg (110,000 Ib)
of JP-4 hydrocarbons had been extracted in the vented
soil gas between start-up in December 1988 and Oc-
tober 1 , 1989. The contaminated area was determined
to be 37 meters by 37 meters (122 ft by 122 ft) to a
depth of 15 meters (50 ft) below the land surface. The
highest soil gas hydrocarbon concentrations had
dropped from 1 79 percent of the lower explosion limit
(LEL) in February 1989, to 88 percent LEL in April
1989. Also, the concentration of hydrocarbons in ex-
tracted gas from the entire venting system dropped
from 38,000 ppm hexane equivalent in December
1988, to 500 ppm hexane equivalent in October 1989
(Downey and Elliott 1990).
During these 9 months of operation at Hill AFB,
SVE volatilization removed 47,500 kg (105,000 Ib) of
VOC's and another 6,800 to 9,000 kg (15,000 to
20,000 Ib) were converted by biodegradation. Soil
hydrocarbon levels were reduced by 95 percent, and a
corresponding drop of 99 percent was noted in soil gas
levels. Only 7 percent of the post operation soil
samples exhibited total hydrocarbon levels greater
than the 100 mg/kg cleanup criterion used. \
At the Verona Well Field site, VOC's at concentra-
tions as high as 1800 mg/kg were located in a plume
covering approximately 1 .3 kma (0.5m2) ;and extending
39
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Chapter 4
downward from the surface to 7.5 meter (25 ft).
Results described here come from both the pilot and
full-scale operation at the Verona Well Field site. The
pilot system, which operated for 69 hours during a 2-
month period beginning in November 1987, extracted
about 1360 kg (3000 Ib) of VOC's from the vadose
zone. The full-scale SVE system began operation in
March 1988 and, after 25 months of operation, had
removed approximately 19,500 kg (43,000 Ib) of
VOC's. The TVOC's extracted per day dropped from
49 kg/d (108 Ib/d) initially to less than 45 kg/d (100
Ib/d) by May 1990. By September 1990, this amount
became less than 2.2 kg/d (5 Ib/d).
4.4.5 Removal of Halogenated Solvents
At the Groveland Well site, analysis indicates that a
total of 588 kg (1,297 Ib) of VOC's were extracted over
the 56-day test period. The soil porosity ranged from
40 to 50 percent, and was nearly the same for both the
clay and sands over the 7-meter (24 ft) depth of the
wells. The permeability/hydraulic conductivities
ranged from 10'4cm/sforthe sands to 10-8cm/sforthe
clays. The majority of the contamination resided
above the clay layer. Table 4-2 shows the reduction
of weighted average TCE levels in the soil during the
56-day demonstration test. This weighted average
level was obtained by averaging soil concentrations
obtained every 0.9 meters (2 ft) by split spoon sam-
pling methods over the entire 7-meter (24-ft) depth of
the wells. The largest reduction in TCE soil concentra-
tion, about 95 percent, occurred in Extraction Well 4,
which had the highest initial level of contamination.
The majority of the soil borings taken after the test
gave VOC levels that were not detectable (U.S. EPA
198 9 a).
The two SVE systems at TCAAP have shown the
ability to remove significant quantities of VOC's from
the soils. The Site D system removed a total of 49,200
kg (108,460 Ib) of solvents between January 1986 and
May 1990; and VOC concentrations at Site D
decreased generally four orders of magnitude. The
pretreatment concentrations of TCE varied widely over
the site and ranged from nondetectable up to 7 million
jig/kg. Of the 26 post-treatment soil samples col-
lected, only five detected TCE above the detection
limit; the highest concentration was 29 u.g/kg.
TCAAP Site D soils consist of predominantly silica
sand with a porosity ranging from 36.7 to 39 percent
and permeabilities ranging between 5.7 x 10'4 and 3.5
x 10'3 cm/s. The soil moisture content ranged from 1.7
to 14 percent. Over the first four months of operation,
the mass removal rate ranged from 7 to 16 g/d. After
four months of operation, a deep vent was installed, 46
meters (150 ft), and removal rates increased to 24 g/d.
At this site, because the soil was silica sand, soil ad-
sorption did not play a significant role; thus, the
volatilization phenomenon was the rate controlling
factor.
Table 4-2. Reduction of weighted average TCE levels
in soil, Groveland Weli Site (TCE concentra-
tion in mg/kg).
Extraction Well
1
2
3
4
Monitoring Well
1
2
3
4
Pre-
treament
33.98
3.38
6.89
96.10
1.10
14.75
227.31
0.87
Post-
treatment
28.31
2.36
6.30
4.19
0.34
8.98
84.50
1.05
Percent
reduction
13.74
30.18
8.56
95.64
69.09
39.12
62.83
- '
Source: U.S. EPA April 1989
VOC concentration in TCAAP Site G soils and fill
materials decreased generally two orders of mag-
nitude. The pretreatment concentrations varied from
non-detectables up to 400,000 ng/kg of TCE. Many
samples were in the 10,000 to the 100,000 M9/kg
range. As of May 17, 1990,,an estimated 45,000 kg
(100,000 Ib) of VOC's had been removed from Site G
since remediation began in January 1986. Of the 245
post-treatment soil samples collected, only seven indi-
cated TCE concentrations above the detection limit
with the highest concentration being 420 u.g/kg (U.S.
EPA1990a).
Initially, the removal rates at Site G showed a sharp
decline and a more gradual decline during later opera-
tions. Mass removal rates, beginning at approximately
2300 kg/d (5000 Ib/d), decreased to 450 kg/d (1000
Ib/d) within 14 days. After 76 days, mass removal
rates had dropped to approximately 90 kg/d (200 Ib/d).
They then dropped to 23 kg/d (50 Ib/d) after 195 days,
and to 0.45 to 4.5 kg/d (1 to 10 Ib/d) after 1060 days of
SVE operation.
The soil types present in the landfill area (Site G)
were heterogeneous and consisted of fill material, con-
struction debris, office trash and industrial waste. As a
result, adsorption of contaminants onto landfill material
played a more important role in the release of the VOC
under SVE application.
4.4.6 Usefulness for Enhancing In Situ
Biodegradation
Another important mechanism of remediation using
SVE is biodegradation which can directly affect the
40
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Soil Vapor Extraction Technologies
amount of residual organic contamination remaining in
subsurface soil. The increased oxygen levels in the
soil gas due to infiltration of atmospheric air can stimu-
late biological activity. In the case studies which
evaluated this effect, the SVE process enhanced in
situ biodegradation of nonhalogenated materials such
as toluene, gasoline, and aviation fuels. In the other
case studies, the effect SVE may have had on
biodegradation was not evaluated. However, it would
be expected that, if microbial populations and sufficient
nutrients were present, degradation may have been
occurring simultaneously with vaporization. Thus, in
recent spills where microbial populations have not had
a chance to develop, it is less likely that SVE will
stimulate biodegradation than at sites where the con-
taminants have resided in the subsurface for an ex-
tended period of time.
At Hill AFB, it was found that bioactivity was
responsible for 13 to 17 percent of the total hydrocar-
bon removal during the first 70 days of venting. Over
the 9 months of operation, a total of 6,800 to 9,000 kg
(15,000 to 20,000 Ib) were converted by biodegrada-
tion. Over the study period, the percent of total
hydrocarbon removal attributable to biodegradation
remained essentially the same.
Similarly at the two sites associated with The
Netherlands case study, biodegradation was used to
enhance remediation efforts. At Site 1, under aerobic
conditions, toluene and other hydrocarbons were
found to biodegrade in situ under the conditions
provided by the SVE perfusion of air. The rate of
biodegradation of toluene, per kilogram of soil, was es-
timated to be approximately 2 mg C/kg/d (Spuy et al.
1990; U.S. EPA 1990b). At Site 2, in situ biodegrada-
tion of the less volatile fraction of the gasoline was en-
hanced by application of the SVE process. It was
estimated that, over the first year of operation, ap-
proximately 800 kg (1800 Ib) of the gasoline con-
stituents in the soil were biologically degraded without
the addition of nutrients.
Although halogenated solvents are not as readily
biodegradable as nonhalogenated solvents, they still
can be broken down in the subsurface environment.
No observations of subsurface biological activity were
noted, or sought, in the case studies involving
halogenated VOC's. Those case studies for which an
assessment of in situ bioremediation activities as-
sociated with SVE applications have been conducted
involved nonhaloaenated volatile organic con-
taminants, such as those found in solvents and fuels
4.5 Residuals and Emissions
Air emission problems could be created by using
the SVE system if the vapor stream were not treated.
In some cases, vapor treatment may not be required
for systems that produce a very low emission rate of
easily degradable chemicals. The decision to treat
vapor must be made in conjunction with air quality
regulators. If vapor treatment systems are required,
technologies available for this purpose include liq-
uid/vapor condensers, gas-phase granular activated
carbon, incinerators, and catalytic converters.
Liquid/vapor condensers (separators) are generally
used for raw material recovery and/or as a pretreat-
ment device for removing VOC contaminants prior to
other control devices. For SVE systems, condensers
are used to protect blowers and increase the efficiency
of the vapor treatment system. Condensers are also
used as the primary control device for emission
streams with concentrations greater than 5,000 ppm.
Variability in VOC concentration will decrease the
overall control efficiencies olf condensers. Removal ef-
ficiencies for condensers are typically less than that for
the other three techniques, ranging from about 50 to
80 percent using chilled water. Removal efficiencies
approaching 90 percent are possible using subzero
refrigerants such as ethylene glycol or freon, but this
significantly increases capital and operating costs
(U.S. EPA 1989c). The entrained ground water and
condensate brought up through the SVE system may
have to be treated as a hazardous waste, depending
on the types and concentration of the contaminants.
Once entrained or condensed material has been
removed from the vapor stream, other treatment tech-
niques can be used to remove the remaining VOC's
from the vapor stream. Carbon adsorption is most
commonly applied as a pollution control technique
and/or for solvent recovery. It can be applied to very
dilute mixtures of VOC's but typically performs better
with concentrations exceeding 700 ppm. Carbon ad-
sorption units can be designed to achieve efficiencies
of 99 percent. Actual efficiencies may be somewhat
lower, ranging from 60 to 90 percent, depending upon
inlet concentration and factors such as stream
temperature, moisture content (relative humidity), and
maintenance. Usually, dehumidification is necessary if
high humidity (i.e., relative humidity greater than 50
percent) is present. Cooling the stream is usually re-
quired if the stream temperature exceeds 65 ฐC (150
T). Carbon adsorption can usually handle variable
input stream conditions. Removal efficiencies are not
affected when flow rates arid concentrations vary sig-
nificantly. Carbon adsorption performs best with com-
pounds having a molecular weight between 50 and
150 g/mol, or organic compounds containing between
four to ten carbon atoms.
If air emissions control or vapor treatment is re-
quired for an SVE installation, a vapor phase granular
activated carbon (GAG) adsorber system probably will
be the most practical system, depending on chemical
emissions rates and VOC kivels. Gas-phase GAC re-
quires heating of the extracted air to control the relative
humidity in order to optimize the carbon usage rate.
As the fraction of water increases, the capacity for the
target chemical decreases and the carbon replace-
41
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Chapter 4
ment rate increases. The spent carbon may be con-
sidered as a hazardous waste depending on the con-
taminants (Hutzler, Murphy and Gierke 1988).
Two different methods are used to apply carbon ad-
sorption to SVE systems. One method uses a fixed
bed regenerative system allowing reuse of the carbon
bed, while the other uses carbon canisters which can-
not be reused. Fixed bed systems have higher capital
and annualized costs relative to carbon canisters. As
such, fixed bed systems are generally used when high
gas volumes require treatment, and cleanup duration
is extended. Carbon canister systems are generally
used for low gas volume extraction processes. (U.S.
EPA 1991 a).
Since carbon adsorption is a conventional technol-
ogy for the removal of organics from a vapor stream,
little emphasis was placed on evaluating its perfor-
mance in the case studies. Only when the carbon ad-
sorption systems were found to affect the overall cost
of the remediation were they compared, in economic
terms, with other vapor treatment systems.
Thermal incineration is widely used to control a
variety of emission streams containing VOC's. This
treatment is capable of handling a broader range of
compounds compared to other techniques. Destruc-
tion efficiencies exceeding 99 percent for VOC con-
centrations above 200 ppm, as well as destruction
efficiencies exceeding 95 percent for concentrations
as low as 50 pprn, are obtainable. However, this sys-
tem is not well suited for streams with variable flow
rate conditions since this tends to change mixing and
residence times from design values, and therefore
lowers combustion efficiency. Therefore, the system
performs best with relatively constant flow rates and
with dilute mixtures of VOC's in the air stream. Sup-
plemental fuel is required to maintain combustion,
especially if treating dilute VOC streams. This tends to
increase operating costs and makes this technique
less desirable (U.S. EPA 1989c).
Catalytic converters are similar to thermal in-
cinerators in design and operation except that they use
a catalyst to enhance combustion. The catalyst allows
the reaction to take place at lower temperatures, there-
by reducing the amount of supplemental fuel neces-
sary relative to thermal incineration. Typical design
efficiencies for this technique are usually around 95
percent, although 99 percent is quoted in some cases.
Actual efficiencies may be somewhat lower (e.g., 90
percent) depending upon operational and main-
tenance practices. This technique is not as broadly
applicable as thermal incineration because the catalyst
Is more sensitive to pollutant characteristics and
process conditions. In addition, compounds such as
halogens (e.g., chlorinated hydrocarbons), lead, mer-
cury, tin, zinc, and phosphorous may damage the
catalyst and severely affect performance. Therefore
catalytic converters are not usually selected as a VOC
control system when metals and/or halogenated con-
taminants are present. This method is usually chosen
for nonhalogenated compounds over thermal incinera-
tion for SVE sites because of lower operating costs
(U.S. EPA1989C).
In two of the case studies, catalytic oxidation was
used to destroy the organics present in the extracted
vapors. At the Hill AFB demonstration, during the 9-10
month operation of the SVE system, 95 percent of the
vapors extracted were passed through one of two
catalytic oxidation units. The first unit was a 14 nrvVmin
(500 ft3/min) fluidized bed unit that operated for eight
months. The second was a 28 m3/min (1000 ftS/min)
fixed bed unit that used a precious metal catalyst and
was operated for six months. There was a period of
four months when the two units operated together to
treat the venting off-gases. The fixed bed was
operated between 240 and 330 ฐC (470ฐ and 625 ฐF)
while the fluidized bed unit was operated between 330
and 370 ฐC (625 and 700 ฐF).
Results showed that the fluidized bed unit had an
average 89 percent destruction efficiency and the fixed
bed unit had a 97 percent destruction efficiency. In
this study, it was found that the fixed bed system could
not handle the large flow rate of highly concentrated
VOC's. Because the process is one of oxidation or
burning of the contaminants, the heat released in the
process caused the fixed beds to get so hot that the
end of the bed would melt. Temperature safety con-
trols can be used to prevent this from happening.
However, such controls limit the amount of con-
taminant that can be treated. Because of better heat
transfer, the fluidized bed unit can handle the higher
concentration flow rates. Its disadvantage is that the
system needs a catalyst. At the Hill AFB site, ap-
proximately 70 kg (150 Ib) of catalyst were added to
the reactor over the eight month operation.
The Air Force, at Eglin AFB in Florida, conducted a
pilot-scale catalytic oxidation unit test on fuel con-
taminants which had been air stripped from ground
water. The unit used an electric preheater to raise the
inlet gas temperature to 540 ฐC (1000 *F) before pass-
ing it through a precious metal fixed bed catalyst reac-
tion chamber. Although this technology resulted in
on-site destruction of the organic contaminants,
hydrogen sulfide that was stripped out of the water
caused a chemical reaction in the catalytic oxidation
unit which effectively and rapidly deactivated the
catalyst (U.S. EPA November 1990). This illustrates
the need for a good understanding of the chemical
constituents comprising the vapor stream and for as-
sessing the impact of those constituents on the
catalyst.
Catalytic oxidation was also used at the Verona
Well site when activated carbon costs became exces-
sive. From March 1988 to January 1990, the VOC
contaminants were removed from the vapor stream by
42
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Soil Vapor Extraction Technologies
activated carbon adsorption. At that time, the carbon
vapor extraction treatment system was replaced by an
on-site catalytic oxidation technology for cost reasons.
(Carbon adsorption costs were three times as great as
that for catalytic oxidation.) Of the VOC's present in
the vapor stream, TCE proved to be the hardest to
destroy by this technology and therefore was used as
the indicator of destruction efficiency. At 415 *C (780
ฐF), average TCE discharge concentrations of 204 ppb
were found in the stack emissions-this is about 60
percent of the discharge limit. At 446 ฐC (835 ฐF), the
level of TCE dropped to 35 ppb. As a result of these
findings, the catalytic oxidation system was operated
at 427 ฐC (800 ฐF) without any difficulties.
In summary, vapor phase activated carbon was
used for extraction systems where there was a low
volume of gas extracted and remediation time was ex-
pected to be short. Limited data indicated removal ef-
ficiencies of 90 to 99 percent. Costs for activated
carbon systems used to treat air streams with high
VOC concentrations were found to be excessive. The
major cost factor attributable to the high costs was as-
sociated with regeneration. In such cases, catalytic
oxidation, an alternative to vapor-phase activated
carbon, was found to be a more cost effective vapor
treatment technique. In particular, at the Verona Well
Field site, it was shown that catalytic combustion of off
gases could reduce the emissions to below 100 ppb
(the allowable discharge level) at approximately one
third the cost.
As noted previously, other residuals produced can
include aqueous waste streams from liquid/vapor
separators and ground water extracted to lower the
water table. Conventional treatment techniques in-
cluding biological treatment and/or activated carbon
can be used to treat these waste streams. At The
Netherlands Site 2, however, these aqueous waste
streams were treated with the vapor stream in a com-
mon biological treatment system.
In this single treatment process (referred to as a
biological purification system), the gasoline vapor with
an organic loading of approximately 210 g/h was
treated along with extracted ground water which had
an organic load of approximately 8 g/h (15 m3/h at 0.5
g/m3)(U.S. EPA1990b).
4.6 Factors to Consider for Determining
Applicability of the Technology
One must "realize that there are practical limitations
on the final soil contamination levels that can be
achieved with soil venting systems. Knowledge of
these limits is necessary to realistically set cleanup
criteria and design effective venting systems. Maxi-
mum efficiency of a venting operation is limited by the
equilibrium partitioning of contaminants between the
soil matrix and vapor phases. The maximum removal
rate is achieved when the vapor being removed from
an extraction well is in equilibrium with the con-
taminated soil" (Johnson et al. 1990). Models for
predicting this maximum removal rate have been
presented by Mariey and Hoag (1984) and Johnson et
al. (1988). The former considered only compositions
in a residual free-phase, while the latter also con-
sidered the effects of sorption and dissolution proces-
ses (Johnson et al. 1990).
Venting also presents the possibility of inducing
migration of off-site contaminant vapors toward the ex-
traction wells. If this occurs, the scope, cost and time
for remediation can be significantly impacted, due to
the influx of these off-site contaminant vapors. A pos-
sible solution to this problem is to install a vapor bar-
rier, using vents, at the perimeter of the contaminated
zone. Alternatively, by allowing vapor flow into the
perimeter ground water monitoring wells, a vapor bar-
rier would be formed to block the migration of these
off-site contaminants. In some situations it may be
necessary to install passive air injection wells, or
trenches (Figure 4-2a) (Johnson et al. 1990).
Application of vacuum extraction systems may also
cause a water table rise. When contaminated soils lie
just above the water table, they can become saturated
by the rise in the water table. Where the water table
rise equals the vacuum (that point expressed as an
equivalent water column height, i.e., in mm H2O) the
maximum rise occurs. The recommended solution is
to install a dewatering system, with ground water
pumping wells located as dose to the vapor extraction
wells as possible. The dewatering system must be
designed to ensure that contaminated soils remain ex-
posed to vapor flow (Figure 4-2b) (Johnson et al.
1990).
Uncertainties which appear to limit SVE include
lack of precise information on site heterogeneities and
contaminant location; inability to predict cleanup
schedules; and uncertainty regarding the ability of the
technology to achieve cleanup goals. These areas of
uncertainty must be recognized when conducting
treatability tests, pilot testing, when performing
detailed analysis of alternatives, and when implement-
ing the technology for site remediation (U.S. EPA
1991b). Figure 4-3 (Johnson et al. 1990) provides a
guideline for deciding if a soil vacuum extraction
process is applicable to a particular site.
Table 4-3 summarizes the factors that limit SVE ap-
plication. It discusses reasons for the potential limita-
tions, presents the data collection requirements that
identify these limitations, and indicates at which phase
of the technology selection process it becomes impor-
tant. In the United States, this process consists of:
A prescreening phase, where all possible ap-
propriate technologies for the given contaminants
are identified
43
-------
Chapter 4
Vapor
Extraction
Veil
(b)
OH-site
Contamination
Unsaturated
Soil Zone
Vapor
Extraction
Well
Passive Air Injection Well
or
Perimeter Ground Water Monitoring Well
Saturated
Soil Zone
Water Table upwelling
Caused by Vacuum
Source: Johnson et al. 1990.
Figure 4-2. Two types of soil venting systems, (a) Use of passive vapor wells to prevent migration of off-site con-
taminant vapors, (b) Water table rise caused by the applied vacuum.
ป A remedy screening phase, where the number of
technologies considered is reduced to a manage-
able number based on site-specific conditions
A remedy selection phase, where the remaining
viable technologies are evaluated for technical
and economic merits to permit technology selec-
tion
ปA remedy design phase, which involves those
treatability studies and design activities needed to
permit the construction of the facilities.
Some requirements apply before the prescreening
phase is initiated. These consist of the compilation of
data from literature and data base sources, and from
sfte-specific assessments, investigations, and charac-
terizations. (See related discussion in the chapter
below on selecting remedies at a complex hazardous
wsate site.)
4.7 Costs
Treatment costs for sites depend on various condi-
tions such as:
* Site size, and extent of contamination
ซ Regulatory requirements for permits, and opera-
tion
ซ Site-specific and chemical-specific conditions
ซ Site cleanup criteria.
Therefore, costs should be estimated on a case-by-
case basis.
Treatability data collected can be very useful in
generating cost estimates. These estimates will be
more precise when they are based on pilot-scale data.
Table 4-4 relates data collected during treatability
studies to the major components affecting SVE costs.
The cost of pumping which is associated with the num-
ber of wells, can be significant. Instrumentation, and
analytical costs for monitoring the process will also af-
fect system costs (U.S. EPA 1991 a).
In general, a cost analysis addresses both capital
costs, and operating and maintenance costs. Capital
costs include both depreciable and nondepreciable
cost elements. Depreciable costs include direct costs
for site development, capital equipment, and equip-
,ment installation. Indirect costs include:
Engineering services prior to construction
Administrative tasks, such as permitting
Construction overhead and fee
ป Contingencies.
Nondepreciable costs include those direct costs as-
sociated with purchased engineering and technical
services for the development of operating procedures
manuals and operator training, etc. (U.S. EPA 1989a).
Operating and maintenance costs include variable,
semivariable, and fixed cost elements. Variable
operating cost elements include utilities and
residual/water disposal costs. Semivariable costs in-
clude unit labor and maintenance costs, and laboratory
analyses. Fixed costs include depreciation, insurance,
and taxes (U.S. EPA 1989a).
An economic model for the Terra Vac vacuum ex-
traction system at the Groveland Well site is presented
in Table 4-5. This model illustrates the relative dis-
tribution of capital, operating and maintenance and
fixed costs and the major elements of each. The costs
presented are based on the transportable skid-
mounted unit that may not be permanently installed at
the site. , -
44
-------
Soil Vapor Extraction Technologies
No
No
No
further
action
No
Process
Leak or spill discovered
Emergency response & abatement
Site characterization
Exposure assessment
Regulatory review
Yes
Define clean-up objectives
Screen treatment alternatives
Air permeability test
Ground water pump test
System design
System operation & monitoring
Output
Background review
Site characteristics:
Subsurface characteristics
- Soil stratigraphy
- Characteristics of distinct soil layers
(permeability estimates, soil types)
- Depth to ground water
- Ground water
- Seasonal water table fluctuations
- Aquifer permeability (estimate)
- Subsurfact & above-ground temperature
Contaminate delineation
- Extent of free-phase hydrocarbon
- Extent of soluble contaminant plume
- Composition of contaminant
- Soil vapor concentrations (optional)
Removal rate estimates
Vapor flowrate estimates
Final residual levels & composition
Air permeability of distinct soil layer
Radius of influence of vapor wells
Initial vapor concentrations
Drawdown determination
Radius of influence
Pumping rate determination
- Number of vapor extraction wells
- Vapor well construction
- Vapor well spacing
- Instrumentation
- Vapor treatment system
- Flowrate (vacuum) specifications
- Venting recovery rates
- Changes in vadose zone contamination
Source: Johnson et al. 1990.
(Target levels based on
exposure assessment)
Figure 4-3. Guidelines for deciding if SVE is applicable.
45
-------
Chapter 4
Table 4-3. Characteristics limiting SVE feasibility - contaminant, soil, and site characteristics.
Reason for limiting application
Data collection requirements
Application of data
CONTAMINANTS
Low volatility (vapor
pressure)
High density, high water
solubility
SOIL
Low air permeability
High humic content
High moisture content
Low temperature
High clay content
PH
Low porosity
SITE
Distribution and quantity of
contaminants
Variable soil
conditions/characteristics
Stratigraphy, heterogeneity
Buried debris
Indicative of low potential for
contaminant volatilization
Contaminant identification
Tendency to migrate to saturated zone Contaminant identification
which is less efficient for SVE
Hinders movement of air through soil
matrix
Inhibits volatilization, high sorption of
VOCs, need for column test
verification
Hinders movement of air through soil
and is a sink for dissolved VOC's.
May require consideration of water
table depression
Lowers contaminants' vapor pressures
Loss of structural support through the
drying of clay
Hinders movement of air through soil;
need for field permeability tests
Material selection
Hinders movement of air through soil;
need for field air permeability tests
May not be cost effective; will require
overall definition of contamination and
potential NAPL* pools; need pilot-
scale verification
Inconsistent removal rates "short
circuiting" or bypassing contaminated
zones
Affects well design and placement,
and SVE design; need field air
permeability tests and/or pilot-scale
verification
Inconsistent removal rates; need field
air permeability and/or pilot-scale
verification
Field air permeability test
Analysis for organic matter
Soil temperature
Shrinkage limit tests
Field air permeability, moisture
content
Porosity (calculated) specific
gravity, bulk density
Soil mapping, soil gas survey,
site characterization
Soil mapping and
characterization (type, particle
size, porosity)
Field air permeability
(distribution) tests
Remedy screening
Remedy screening
Remedy selection
Remedy screening
Analysis of soil moisture content All phases
All phases
Remedy screening
Remedy selection
Remedy design,
remedy selection
All phases
Remedy selection
Remedy screening
Remedy selection
Site history, geophysical testing Remedy screening
*Non-aquoous phase liquids
Source: U.S. EPA March 1, 1991
To provide an indication of SVE project costs, three
examples from the case studies cited are presented.
Table 4-6 identifies the costs for the Verona Well Field
Site work in Michigan. These costs indicate the overall
costs for various aspects of the project. Of interest is
the comparison of the activated carbon vapor treat-
ment system, which was initially installed, to the
catalytic oxidation process which later replaced the ac-
46
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Soil Vapor Extraction Technologies
Table 4-4. Factors affecting SVE treatment costs.
Component affected
Factors governing component
selection
Data required
Number of extraction wells
Passive wells (inlet) and air
injection wells
Depth of wells
Vacuum pump or blower
Vapor/liquid separator
Surface seals
Radius of influence
Extent of contamination
Air flow distribution
Depth to impermeable layer
Vacuum level and air flow rate
Liquid (water) removal rates
Air flow distributions
Surface water infiltration
Water table depression pumps Depth to water table
Pressure profile from air permeability and pilot tests;
mathematical model to optimize selection1
Contaminant distribution
Air permeability tests; pilot tests, number of vapor
extraction wells
Depth to bedrock2; depth to water table
Air permeability tests, pilot tests, number of vapor
extraction wells
Moisture content, vapor flow rates (oversized mist
eliminator recommended)
Air permeability tests, pilot tests, mathematical modeling
of air flow patterns
Rainfall, permeability for surface soils
Depth to water table
Off-gas treatment
Liquid (water) treatment
Operating costs
Water infiltration rates
Contaminant removal rates,
contaminant identities, moisture
content after vapor/liquid
separation
Site water removal rates
Size of SVE system, cleanup time,
analytical costs, and residuals
disposal costs
Site hydrological behavior
Air permeability tests, pilot tests; moisture content
during pilot tests
Site hydrological behavior, moisture content in off-gas,
contaminant concentrations in water
All of the above plus cleanup time predictions based
upon mathematical modeling and prior experience
1ln general, specify more wells than predicted by the mathematical model
location and subsurface conditions.
20n some sites, SVE may be the only available technology for application
than wells bored into soils.
Source: U.S. EPA March 1, 1991
as optimum because of uncertainties in the contaminant
to fractured bedrock. These wells will be much more costly
tivated carbon system for vapor treatment (McCann
1990).
Construction and operating cost summaries for the
TCAAP case study (Site D and G) are presented in
Tables 4-7 and 4-8, respectively. Remediation of Site
D soils have been estimated at US$451,000 or
US$22/m3 (US$17/yd3) soil. Air emission controls
were not required for the Site D system. Site G soils
have been treated at an estimated cost of US$969,000
or US$17/m3 (US$13/yd3) soil.
To provide general assistance in developing a
rough SVE cost estimate, Table 4-9 presents capital,
and operating and maintenance costs for each of the
SVE system components over typical operating size
ranges. Capital and certain operating costs may be
approximated by determining the system size and mul-
tiplying unit size estimates by the values given in the
table (U.S. EPA 1991a). It also presents costs for
polyvinyl chloride (PVC) and stainless steel (SS)
materials of construction for extraction well construc-
tion. The compatibility of the contaminant and other
soil chemical characteristics with the well and piping
materials needs to be assessed before system con-
struction. For example, stainless steel will not perform
well under very corrosive or high chloride conditions.
Similarly, PVC may be attacked by certain organic
compounds. The surest way to establish the ap-
propriate materials of construction is to consult ven-
dors of these products. It should be noted that
vapor/liquid separators have been included as an in-
47
-------
Chapter 4
Table 4-5. Terra Vac economic model (in US$, 1989).
Cost components $/tonnes
Sito preparation 3.12
Permitting and regulatory
Equipment
Contingency (10% of direct costs) .31
Startup and fixed cost
Operations procedures/training .44
Mobilization and shakedown .92
Depreciation (10% of direct costs) .31
Insurance and taxes (10% of direct costs) .31
Labor costs 3.05
Supplies - Raw materials
Supplies - Utilities
Electricity .44
Effluent treatment 14.14
Residual disposal 8.27
Analytical
During operation 1.59
Protest and posttest analyses 18.36
Facility modifications
(10% of direct costs) .31
Sito demobilization .36
TOTAL 51.93
Based on equipment capital cost of $50,000 for treating
approximately 5,440 tonnes of contaminated soil. Does
not Include profit for the contractor.
Source: U.S. EPA July 1989
Table 4-6. Verona Well Field SVE costs (in US$, 1990).
COST COMPONENTS
Design of pilot-scale unit, full-scale
construction, and startup
$500,000
Carbon adsorption system and total cost $610,000
of carbon
Catolytio oxidation system $187,000
Operations including utilities, process $305,000
monitoring and maintenance
UNIT COSTS
Cleanup of contaminated soil $30/m3
Cleanup of contaminants $79/kg
Source: Personal communication
tegral part of the SVE system. However, vapor treat-
ment processes which are dependent on the con-
taminants and concentrations are not included.
4.8 Future Status of Case Study
Processes and the SVE Technology
as a Whole
At the Dayton site and the two sites in the Twin
Cities Army Ammunitions Plant case study, SVE
remediation has been completed; at the Verona Wells,
Hill AFB and the Groveland sites, remediation con-
tinues.
Future technology applications seems highly
promising as the process has several advantages.
Soil vapor extraction can be effectively used for remov-
ing a wide range of volatile chemicals under a wide
range of conditions. The process can be part of a
remediation effort and used along with other treatment
processes. Air injection has the advantage of control-
ling air movement, but injection systems need to be
carefully designed. Volatile chemicals can be ex-
tracted from clays and silts but at a slower rate. Inter-
mittent operation is more efficient under these
conditions. The intermittent blower operation is
probably more efficient in terms of removing the most
chemical with the least energy. The design and opera-
tion of these systems can be flexible enough to allow
for rapid changes in operation, thus, optimizing the
removal of chemicals. Equipment used for SVE sys-
tems is readily available and easy to operate. To
protect down stream air pollution control equipment,
air/water separators should probably be installed in
every system. Such devices are inexpensive and easy
to construct.
As with any in situ process, it is usually impossible
to do a complete materials balance on a given site be-
cause most sites have an unknown amount of VOC's
in the soil and in the ground water. As a result, it is
difficult to establish when the cleanup has been com-
pleted. To determine if contaminants are continuing to
vaporize, SVE processes could be operated on an in-
termittent basis for a period of time after the VOC con-
centrations in the extracted vapors have approached
zero. This technique can help to limit the soil boring
and ground water data on residual contamination re-
quired to demonstrate that cleanup objectives have
been attained. Although many aspects of the SVE
technology are understood, additional information
which would be of assistance to engineers and opera-
tions personnel needs to be developed. Documenta-
tion of case studies where difficulties resulting from the
misapplication of the technology or operating problems
would be useful. All too often, only success stories are
documented. However, failures or marginal succes-
ses can provide more insights into factors which need
to be considered in other applications. These can be
particularly useful when a thorough investigation/ as-
48
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Soil Vapor Extraction Technologies
Table 4-7. TCAAP Site D Estimated
Description
CAPITAL
System installation
Subtotal
OPERATIONS AND MAINTENANCE2
Labor3
Professional labor
Craft labor
Subtotal
Operations
Electricity
System monitoring
Subtotal
TOTAL
construction and operating costs (in US$).
Units Cost/Unit ($) Cost ($)
257,000
1000 hours 50/h 50,000
1 500 hours 30/h 45,000
1 ,770,000 kWh 0.04/kWh 71,000
160 samples 175/sample 28,000
Total ($)
257,000
95,000
99,000
451,000
'Cost information supplied by TCAAP (U.S. EPA July 1990). Does not include design, construction supervision, vent sampling,
or safety monitoring.
2Total over operating period (February 86-May 90).
Estimated as 70 percent of Site G information (see Table 4-8).
sessment of the failure identifies the cause(s) of that
failure.
It is known that temperature affects the volatility of
organic compounds and therefore the efficiency of the
SVE process. Under what conditions and for what
contaminants would it be cost effective to consider
technologies such as RF heating to increase the soil
temperature in order to extract organic contaminants
or speed remediation? Would heated air injection
serve the same purpose, and what effect would it have
on extraction rates? How would implementation of
such techniques change the overall efficiency of the
process for different soil types?
Table 4-8. TCAAP Site G Estimated construction and operating costs (in US$).
Description
CAPITAL
System installation
Vapor treatment system
Subtotal
OPERATIONS AND MAINTENANCE2
Labor
Professional Labor
Craft labor
Subtotal
Operations
Electricity
System monitoring
Carbon changeouts
Subtotal
TOTAL
Units Cost/Unit (ง)
1400 hours 50/h
2200 hours 30/h
2,400,000 kWh 0.04/kWh
180 samples 210/sample
16 changes 14,300/change
Cost (ง)
257,000
213,000
70,000
66,000
96,000
38,000
229,000
Total ($)
, 470,000
136,000
363,000
969,000
'Cost information supplied by TCAAP (U.S. EPA July 1990). Does not include design, construction supervision, vent sampling,
or safety monitoring. . , '. .... , .,
2Total over operating period (February 86-May 90).
49
-------
Chapter 4
Table 4-9. Capital cost estimation of SVE components (in US$, 1990).
Capital
Component
PVC1
304 SS2
Other
Extraction Well Construction
Drilling
Casing
5cm $7-$10/m
10cm $10-$16/m
15cm $23-$29/m
Screen
5cm $7-$13/m
10cm $16-$23/m
15cm $33-$49/m
Sand or gravel
Piping
5 cm $3-$7/m
10cm $7-$13/m
15cm $20-$33/m
20 cm $39-$527m
Valves (ball)
5 cm $60
10cm $150
15cm $700
20cm $1,300
Joints (elbow)
5 cm $11
10cm $50
15cm $100
20 cm $460
Water table depression pumps (45-95
gpm)
Surface seals
Bontonite
Polyethylene (.254 mm)
HOPE
Asphalt
Blower (rotary or ring)
0-28 dNnvVmin
8-14dNm3/min
28 dNnvVmin
Vapor/liquid separators
(3,800 L to 7,600 U
Instrumentation
Vacuum gauge
Flow (Annubar)
Sampling port
Gas chromatograph/FID
$2,000 to $5,000/well
$39-$46/m
$75-$82/m
$118-$131/m
$49-$56/m
$89-$102/m
$134-$151/m
$31-$36/m
$72-$82/m
$111-$125/m
$171-$180/m
$1,000
$2,000-$2,200
$3,200
$5,000
$20
$52
$300
$560
$20-46/m3
$3,700
$99/m2
$2.70/m2
$6/m2
$6/m2
$5,000 to $25,000
$13,000
$40,000
$3,500 to $17,500
$50-$75
$300
$20-$30
$20,000 (if purchased;
usually rented)
'Polyvinyl chloride
'Stainless stool
Source: U.S. EPA March 1, 1991
50
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Soil Vapor Extraction Technologies
At this time, SVE systems are often designed with
flexibility so that changes can be made during
remediation. Although such system flexibility is
desirable, it also can increase costs. Since there have
been numerous installations of the SVE system under
a wide range of site, soil and contaminant conditions; it
appears that an analysis of these applications could
provide useful information to design engineers as well
as operating personnel. Johnson et al. (1990) have
supplied a beginning for the development of such
guidelines. This needs to be expanded to reflect "les-
sons learned" from SVE applications. For example,
operating criteria need to be established outlining
those conditions when a system should be operated in
the intermittent extraction mode rather than a con-
tinuous extraction mode.
Little attention has been paid to the effect of
naturally occurring organics on extraction rates or the
ultimate removal efficiencies. Since such soil com-
ponents can adsorb organic contaminants, to what ex-
tent do they reduce the effectiveness of the process?
It has been found that SVE can be used to enhance
in situ biodegradation of a number of nonhalogenated
VOC's and other semivolatile compounds in subsur-
face soil. Similar information is needed for a wider
range of organics and site conditions. And more work
is needed to examine SVE and bioremediation as a
process rather than looking at each technology in-
dividually.
Since buildings and other interferences can be
found at many sites where VOC contamination occurs,
it is likely that it will be necessary to remediate con-
taminated soils near these structures. What special
techniques (e.g., horizontal drilling) could be used
under these conditions? Would using SVE result in
transporting vapors into the building or could they be
vented away? Additionally, at the Dayton, Ohio fire
site, it was found that VOC vapor could be transported
through concrete. Is asphalt similarly affected? The
answers to these questions would be useful in deter-
mining what cap configurations and construction
materials should be used.
Other technical issues that need to be resolved in-
clude the effectiveness of forced or passive vapor in-
jection wells; other means of controlling vapor flow
paths; well-documented demonstrations for removing
contaminants from low-permeability soils; the pos-
sibility of decreasing residual contaminant levels in
water-saturated zones by air sparging/vapor extrac-
tion; and optimal operation schemes for multiple vapor
extraction well systems (U.S. EPA 1991a).
Alternative treatment methods for off-gasses
provides an other area for future investigations. For
example, an Advanced Oxidation Process is being
studied for the destruction of VOC's in air; this work is
being conducted at the Lawrence Livermore National
Laboratory under U.S. EPA Superfund Innovative
Technology Evaluation (SITE) program. The destruc-
tion mechanism is based on photolytic oxidation of
contaminants using a newly developed ultraviolet (UV)
light source, consisting of a pulsed-plasma xenon
flashlamp that generates extremely intense UV emis-
sions. These UV emissions are better suited for or-
ganic contaminant destruction than conventional
mercury-based UV lamps because the photon flux is
shorter in wavelength and higher in intensity. Prelimi-
nary experimental results indicate that the proposed
UV flashlamp treatment scheme will yield high VOC
destruction rates. This process can be coupled to the
gas venting system and creates no secondary waste
stream.
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Danko J P McCann M.J. and Byers, W.D. Soil vapor extraction at a Superfund site in Michigan. Presenta-
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1990.
Downey, D.C., and Elliott, M.G. Performance of selected in situ soil decontamination technologies: An Air
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51
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Chapter 4
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U.S. EPA. Soil vapor extraction technology: Reference handbook. EPA/540/2-91/003, Risk Reduction En-
gineering Laboratory, Cincinnati, Ohio, February 1991 .
P, K fฐ,r condu?ting treatability studies under CERCLA: Soil vapor extraction. Risk Reduction
Engineering Laboratory, Office of Emergency Remedial Response and Office of Solid Waste and Emer-
gency Response. Revised Final Draft March 1 , 1991
52
-------
Physical/Chemical Extraction Technologies
Merten Hinsenveld
University of Cincinnati, Department of Civil and Environmental Engineering
741 Baldwin Hall (ML 71), Cincinnati, Ohio 45221-0071
United States
ABSTRACT
Six case studies, covering a broad spectrum of techniques, were chosen for this t>4ATO/CCMS Pilot Study: ex
situ extraction (two case studies); In situ acid extraction (one case study); in situ jet cutting followed by oxidation
(one case study); electro-reclamation (one case study); and debris washing (one case study).
The ex situ extraction techniques (Kiockner and Harbauer) mainly differ in scrubber technology and the
combination of particle separation techniques. The two techniques clean the soil mainly through removal of the heavi y
contaminated fines from the soil. Their best result is generally obtained for sandy soils. Both techniques are available
on a commercial scale.
The applicability of in situ extraction techniques in general, where removal of the heavily contaminated fine
particles is not possible, is limited to sandy soils. The In situ acid extraction technique (TAUW/Mourik) is applicable
for sand only The site contained cadmium pollution and was ideally suited forthe technique (sandy soil, low adsorptive
capacity, homogeneous). The cleaning results were better than expected; the results are considered an ideal case.
The technique is available on a full scale.
The in situ jet cutting technique (Keller) is capable of removing contaminated soil with the simultaneous
replacement of clean stabilized soil. This makes the technique in principle applicable for cleanup activities underneath
buildings. The oxidation was applied on the easily oxidizable contaminants (e.g., phenols) in the removed son. i ne
technique is available on a pilot scale.
In situ electro-reclamation (Geokinetics) is a new technique for heavy metals removal. Whereas the other
techniques are applicable to sandy soils, electro-reclamation can be applied to clean clayey soils contaminated with
heavy metals At present no other technique exists for heavy metals removal from clayey soils. The technique uses
the flow of water which is induced by applying an electrical field to the soil, but the removal mechanism is not yet
fully understood. A full-scale system is operable. Promising results have been obtained with cleanup of soil and
sludge contaminated with copper, zinc, lead, and arsenic.
5.1 Introduction
5.1.1 Place of the Techniques in a Broad Sense
This chapter concentrates on ex situ and in situ ex-
traction, in situ jet cutting followed by oxidation, and in
situ electro-reclamation. These techniques were sub-
mitted as case studies to the NATO/CCMS Pilot Study.
The case study techniques belong to a group
generally referred to as physical-chemical treatment
techniques. They aim at removal or destruction of con-
taminants and are generally executed in an aqueous
environment. Examples of other techniques in this
group are: particle separation techniques, flotation
techniques, and reduction and dechlorination techni-
ques.
Ex situ extraction, as presently applied in soil clean-
ing, mainly refers to a combination of particle separa-
tion techniques and dissolution and dispersion in an
-------
Chapter 5
aqueous environment. This chapter only deals with
aqueous extraction agents. The use of organic sol-
vents to, for instance, extract PCB's from soils and
sediments, is in development and approaching com-
mercial scale. When organic solvents are used, the
technique is referred to as solvent extraction. Solvent
extraction is not discussed in this section.
The term "extraction" was adopted in the early
stages of development, beginning in the 1980's, be-
cause it was believed that contaminants could easily
be extracted from the soil. At present we know that,
because contaminants are heavily adsorbed onto the
fines (particles smaller than 63 m), the cleaning in
these installations is mainly due to the separation of
these heavily contaminated fines from the bulk of the
soil. Therefore the term "classification" techniques
would have been more appropriate.
In situ extraction has been applied to a limited ex-
tent, because separation of heavily contaminated fines
is not possible. It is, therefore, limited to those cases
where the soil does not contain adsorptive materials.
The case study described in this chapter is an example
of such an ideal site.
In situ jet cutting followed by oxidation is a rather
unique case study in that the soil is removed by jet
cutting as opposed to being excavated, and backfilled
after treatment. In the case study described in this
chapter, no particle separation techniques were ap-
plied. The easily oxidizable contaminants were ideal
for applying this technique. It may, therefore, be con-
sidered a best case example.
Electro-reclamation has very recently been intro-
duced in the field of soil treatment. Little experience
with this technique has been gained so far. The techni-
que applies an electrical field to the soil. It either
creates an electrical driving force for the contaminants
themselves, called electro-phoresis, or it induces water
flow, called electro-osmosis, in which dissolved con-
taminants may be entrained. This technique is espe-
cially suitable for removal of heavy metals from clayey
soils. There are presently no other techniques avail-
able for these "difficult" soils.
5.1.2 Principle of Extraction Techniques
The basic processes in extraction installations con-
sist of (1) pre-screening of the soil, (2) mixing with an
extracting agent, (3) fluid-solids separation, (4) treat-
ment of the cleaned soil, and (5) water purification and
sludge treatment. (See Figure 5-1.)
Extraction installations may incorporate a variety of
other techniques besides the actual extraction. In
general, particle separation techniques (separation on
size and/or density), chemical treatment (mainly oxida-
tion), and flotation techniques are integral components
of extraction installations. In principle the same
process scheme will be applied for the oxidation tech-
nique, but without significant separation of the fines
Contaminated soil
I
Pretreatment
I
Coarse material
Water
Chemicals
Scrubbing and
extraction
Extracting
agent ซ
Phase
separation
After-treatment
Cleaning of
extracting agent
I
Sludge
Cleaned soil
Sourco: Hlmonvold 1990.
Figure 5-1. The basic processes in extraction installa-
tions.
and with the water purification step consisting of oxida-
tion only.
Flotation techniques in the present extraction instal-
lations are only used to clean the process water, but
they may also be used to clean soil. This latter applica-
tion, however, requires special knowledge, so that only
a few firms have specialized in this (very powerful)
technique. Most firms using extractive methods do not
have the required knowledge for this application. Flota-
tion as a soil cleaning technique is available on full
scale in The Netherlands, but is not referred to in this
chapter.
Most of the cleaning efficiency in extraction installa-
tions, in general, is from the removal (separation) of
the heavily contaminated fines from the soil. The
chemicals added in the scrubber, mostly NaOH and
some soaps, mainly serve as dispersing agents to
keep these fine particles in suspension.
The process of extraction-classification can
economically be applied to soils with a combined fines
and organic matter content of less than about 30 per-
cent. There is a simple reason for this limitation: fines
are difficult to dewater and lead to huge amounts of
sludge. For example: one tonne of soil containing 30
percent fines leads to about 0.6 tonne of contaminated
sludge (compared to the original soil, the water content
of the fines is roughly doubled) and 0.7 tonne of clean
soil; the waste stream has been reduced by only 40
percent. In exceptional cases, the contaminants con-
tained in the fines may be destroyed by oxidation or
other techniques. In that case there is no limitation on
the amount of fines. In general, however, part of the
fines will consist of organic matter, and removal of the
54
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Physical/Chemical Extraction Technologies
fines prior to oxidative treatment will largely reduce the
amount of oxidants to be used for destruction of the
contaminants.
It will be clear from the above that the applicability
of in situ extraction techniques is quite limited because
removal of heavily contaminated fine particles is often
not possible.
5.1.3 Principle of Electro-reclamation
Electro-reclamation is a rather new technique for
heavy metals removal from soils in situ. The principle
of the movement of water, charged particles, and ions
in a saturated porous medium when subjected to an
electrical field is well known. The principles of
electrophoresis and electrolysis are widely used in
analytical measurements; the movement of water is
utilized in practice and includes dewatering and con-
solidation of soils in foundation engineering
(Casagrande 1983). The technique has also been
used for desalting agricultural land. The possibilities
and limitations in environmental applications, however,
are still a subject of research.
Researchers do not quite agree on whether the
primary removal mechanism for the heavy metals from
soil is electro-osmosis, electrophoresis, electrolysis, or
a combination of mechanisms. The removal efficiency
can possibly be improved by using acoustic waves in
addition to the electrical field - a technique known to
enhance dewatering of sludges or leaching of waste
(U.S. EPA 1990) - or by the addition of acid (Lageman
et al. 1990). Oxidation and reduction reactions in-
duced by the electrical field are also a subject of study.
Electrochemical studies have shown that an acid
front is generated at the anode, migrating in time from
the anode towards the cathode (U.S. EPA 1990).
Metallic electrodes as well as metallic objects (e.g.,
drums and pipes) in the soil will either corrode and
thus interfere with the removal of heavy metals or be
coated with metals. Therefore, graphite electrodes are
often used in the field and metallic objects should be
removed prior to treatment.
In general the flow of water will be directed from the
anode to the cathode due to the net positive charge of
the solute. Depending on this charge, the complexes
will either move to the cathode or to the anode. Water
flowing towards the cathode is pumped off, together
with the dissolved ions. A solution of HCI or NaCI is
infiltrated at the anode to replace the removed ions,
preventing an equilibrium from establishing. Promis-
ing results have been obtained when cleaning up soils
and sludges contaminated with heavy metals like Cu,
Zn, Pb, and As. In principle, the technique is applicable
for most types of soil, but is particularly applicable to
cleaning clayey soils. For cleaning very permeable
and sandy soils, a conventional in situ extraction might
be cheaper. The technique also shows possibilities for
cleaning soils and sludges in storage facilities.
5.2 Case Studies Chosen
The five case studies chosen for this pilot study
cover a broad spectrum of techniques:
Ex situ extraction (two case studies)
Oxidation (one case study)
In situ extraction (one; case study)
Electro-reclamation (one case study).
In this section, a brief description of each of the
case studies will be given.
5.2.1 Case Study 5-A: High Pressure Soil Washing
(Klockner), Germany
The high pressure soil washing system was
developed in The Netherlands by BSN in the middle
1980's and adapted by KIScknerto German specifica-
tions. The installation has a commercial scale of about
13 to 36 tonne/h. A description is given in Appendix
5-A. The most characteristic aspect of the process is
the use of a high pressure water jet to scrub the soil
particles. Nozzle pressures of up to 350 bar can be
applied. Pretreatment of the soil is purely mechanical,
consisting of sieving the rubble fraction (lumps greater
than 6 cm) on a coarse screen. The fraction smaller
than 6 cm is fed to the high pressure water jet in which
the aggregated particles are disintegrated. The
process was selected in the NATO/CCMS Pilot Study
for a number of reasons. Firstly, because of its
simplicity: pretreatment is simple and no chemicals are
added. Secondly, because of its large scale and the
experience built up over the past 5 years. Up to the
present, some 300,000 tonnnes of contaminated soil
have been treated with this and the following installa-
tion. The installation can be purchased and is fully
commercial. Thirdly, the process can be used to treat
soils contaminated with a combination of volatile or-
ganic contaminants (which are stripped out of the soil
by the air entrained in the water jet) and heavy metals.
Volatile components are not removed in extraction in-
stallations that do not apply high pressure.
5.2.2 Case Study 5-B: Vibration (Harbauer),
Germany
This case study, reported in Appendix 5-B, involves
the cleaning of soils contaminated with oil residuals.
The primary characteristic of this process is the use of
a mechanical vibration scrubbing system. The case
study was chosen for a number of reasons; the most
important was its claim of being able to clean the soil
down to a particle size of 0.015 mm (usually conven-
tional extraction installations can go down to about
0.050 mm). This low cut off size leads to a strong
reduction in the amount of sludge produced. The ven-
dor claims that the exceptionally low particle size of
0.015 mm can be reached by a combination of a wide
55
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Chapters
variety of particle separation techniques. The installa-
tion has a commercial scale.
5.2.3 Case Study 5-C: Jet Cutting Followed by
Oxidation (Keller), Germany
This case study describes the oxidation of soil con-
taminated with phenols and cresols. The soil is
removed from the underground by a cutting water jet
and simultaneously replaced by clean soil. The actual
cleaning is done ex situ. Originally the technique was
used for stabilizing the underground for foundation pur-
poses, but it has been adapted for treating con-
taminated soils. The contaminated soil that is brought
up by the water jet could be cleaned by a number of
wet techniques, but the company involved has no ex-
perience in doing so and chose to use a simple oxida-
tion technique. The study was selected for the
NATO/CCMS Pilot Study because of the possibility of
applying a wet cleaning technique for soils underneath
buildings without the need of tearing these buildings
down. In this respect it could be classified as an in situ
technique. The technique is also interesting because,
by using only an oxidation technique without any
separation techniques, no sludge is produced.
5.2.4 Case Study 5-D: Electro-reclamation
(Geoklnetlcs), The Netherlands
This case study describes the use of an electrical
field to remove heavy metals from clay soils. The study
is reported in Appendix 5-D, including an excellent
description of the principle of the technique. The site
studied in this case was contaminated with arsenic
caused by a former timber preservation impregnating
plant. Field experiments have been conducted by a
number of researchers, but problems at the electrodes
occurred. Geokinetics claims to have mastered this
problem. The case study was chosen because of the
application of this new technique which can be applied
In situ to remediate clayey soils contaminated with
heavy metals. For these soils, no alternative techni-
que is presently available.
5.2.5 Case Study 5-E: In Situ Acid Extraction
(TAUW/Mourik), The Netherlands
This case study, the results of which are described
in Appendix 5-E, deals with the in situ cleaning of a
sandy soil contaminated with cadmium. The cadmium
contamination, caused by a photographic paper fac-
tory, was bleached into the soil in a liquid form. This
case study was chosen because the problem studied
here represents a best case for in situ extraction: a
very mobile contaminant in a permeable soil having
low adsorptive capacity.
5.2.6 Case Study 5-F: Debris Washing, United
States
This technology applies to the decontamination of
metallic debris, such as transformer casings, drums,
and miscellaneous scrap metal which is often found at
hazardous waste sites. Because the rest of this chap-
ter discusses technologies for the cleaning of soil,
greater detail about debris washing will not be included
in this chapter. However, considerable detail on debris
washing can be found in Appendix 5-F.
5.3 Background of the Case Study Sites
as a Group
Table 5-1 shows an overview of the different case
study sites. It can be concluded that there is little
resemblance between these sites, showing the wide
range of application of physical chemical techniques.
As can be expected, however, most sites applying ex-
traction contain sandy soils, leading to an acceptable
amount of sludge produced. Acceptable may be
defined to mean that cleanup costs plus the cost of
sludge disposal are less than or equal to the disposal
of the contaminated soil. For the Klfickner installation
(Case Study 5-A), the fraction smaller than 0.063 mm
ends up in the sludge, whereas for the Harbauer sys-
tem (Case Study 5-B) only the fraction smaller than
0.015 mm becomes sludge. The site on which in situ
extraction was applied (Case Study 5-E) was extreme-
ly sandy and is an exceptional site. The electro-
reclamation study (Case Study 5-D) involved clayey
soils. This technique is exceptional in a sense that it is
the only technique capable of cleaning these difficult
soils.
In the in situ acid extraction (Case Study 5-E), there
were no fines and no organics at all present in the soil.
The amount of organics in the jet cutting oxidation
case study (Case Study 5-C) did not seem to influence
the performance of the oxidation process. The case
study on electro-reclamation and the in situ acid ex-
traction case study can be regarded as opposites in
that electro-reclamation works with clay soils having a
low permeability, whereas in situ acid extraction only
works when the soils are very sandy and show a high
permeability. If soil is very permeable and has a low
adsorptive capacity, extraction is cheaper than electro-
reclamation. Electro-reclamation is needed in case the
soil is very impermeable.
5.4 Performance Results
In extraction, cleaning results strongly depend on
the form in which contaminants are present in the soil
and the grain size distribution, Generally difficult to
clean are soils containing a large fraction of particles
smaller then 0.060 mm or soils containing a large
amount of organic material. In ex situ extraction, the
fines end up in the sludge. A small fraction of highly
adsorptive particles in the soil make the ex situ extracr
tion easier, because separating this fraction from the
soil removes most of the contaminants as well.
56
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Physical/Chemical Extraction Technologies
Table 5-1. Problems handled in the NATO/CCMS case studies.
Process/
Technique
Manufacturer
Country
City
Area (m2)
Depth (m)
Source of
contamination
Type of soil
Type and
concentration of
contaminants
Amount of soil to be
treated (tons)
Main lesson learned
High pressure soil
washing
Klockner
Germany
Berlin
unknown
unknown
Scrap metal, copper
refinery
Sandy soil, less than
20% clay
Heavy metals,
halogenated
hydrocarbons, non-
halogenated
hydrocarbons
100,000
Vibration
Harbauer
Germany
Berlin
1 6,000
unknown
Oil recovery
Sandy soil
Halogenated
hydrocarbons.
aromatics, oil
unknown
Jet cutting/
oxidation
Keller
Germany
Hamburg
unknown
unknown
Disinfectant
factory
Sand, clay and
peat
Phenols, cresols
unknown
-
Electro-
reclamation
Geokinetics
The Netherlands
Lopperisum
unknown
1-2
Timber
impregnating
plant
Clay
Arsenic 400-500
mg/kg
450
Presence of
metal objects
can have a large
influence on
cleaning results
In-situ acid
extraction
TAUW/
Mourik
The Netherlands
Soestduinen
6,000
unknown
Photographic
paper factory
Sandy soil
Cadmium
45,000
Adsorptive
capacity and
permeability as
measured in
laboratory differs
from practice
A major difficulty encountered in interpreting the
results of the case studies was the absence of inde-
pendently obtained data. Data available from the com-
mercial vendors involved generally represent their best
results (mostly in sandy soils). Presenting cleaning
results of sandy soils generally leads to higher clean-
ing efficiencies than would be obtained on the average
in practice. In the jet cutting oxidation case study
(Keller, Case Study 5-C), only easily oxidizable con-
taminants were present.
The electro-reclamation case study has a some-
what different position in that the technique is used for
soils that are difficult or impossible to clean with other
techniques.
High pressure soil washing (Case Study 5-A,
Kldckner). The case study of Klockner, shows dif-
ferences obtained in cleaning efficiency ranging from
35 to 100 percent. These differences cannot be ex-
plained, due to insufficient information provided by the
vendor. The soil treated by Klockner is an easily
cleanable sandy soil containing about 1.6 percent par-
ticles smaller than 0.063 mm.
Vibration (Case Study 5-B, Harbauer). The soil
cleaned with the Harbauer system contains more fines
than the soil treated in the Klockner case (37 percent
smaller than 0.1 mm) and is probably more difficult to
clean without getting a large amount of sludge. How-
ever, Harbauer claims to produce a residue of only 2
percent, meaning that most of the fines above 0.015
mm were not heavily contaminated or could be
cleaned and subsequently separated. We have been
unable to check these claims. The cleaning efficiency
for mineral oil, PAH's, phenol, and cyanide ranged
from 86 to 100 percent.
Water Jet followed by oxidation (Case Study 5-
C, Keller). In contrast to the two extraction techniques
(Klockner and Harbauer), no particle separation tech-
niques were used in this project. The results show a
destruction efficiency of more than 90 percent for
phenol. Reaction time needed ranged from 0.5 h to 3
h, mainly depending on the degree of destruction and
the amount of organic material in the soil.
Electro-reclamation (Case Study 5-D,
Geokinetics). The Geokinetics case study shows that
removal of arsenic from a clay soil is possible, bringing
concentrations down from more than 250 ppm to about
100 ppm and lower. In particular, one part of the site
was difficult to clean, due to the presence of metal ob-
jects that functioned as preferential conductors for the
57
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Chapters
electrical current, thereby delaying the movement of
the contaminants in their vicinity.
An important lesson learned from this experience is
the need to identify metal objects in the soil and
remove them before electro-reclamation is applied.
In situ acid extraction (Case Study 5-E,
TAUW/Mourlk). The TAUW/Mourik case study can be
regarded as an example of an in situ acid extraction
under ideal conditions. The soil cleaned is very perme-
able and contains hardly any adsorbing material. The
results of a trial were so good that the initial cleaning
goal was brought down from 5 mg-Cd/kg to 2.5 mg-
Cd/kg. It was found that the desorption of cadmium in
practice was better than was expected on the basis of
laboratory studies. The permeability of the deeper
layers of soil was found to be quite different from the
permeability of the top soil.
5.5 Management of Residuals
In ex situ extraction techniques the main cleaning
mechanism, in general, is the separation of the fines
from the soil. In most cases, fines are the fraction of
particles smaller than about 0.063 to 0.030 mm (an
exact definition of 'lines" is not useful). Separating this
fraction from the soil leads to the production of sludge,
which is generally the main drawback of extractive
methods. Sludge consisting mainly of fines is con-
sidered non-cleanable and is disposed of in a control-
led dump site. Harbauer is the only vendor that claims
to be able to clean the fraction between 0.050 mm and
0.015 mm, therefore producing only limited amounts of
sludge. However, past experience in The Netherlands
has shown that it is doubtful that this will hold true in
general. In the relatively few cases where the con-
taminants are not heavily adsorbed to the fine fraction,
the contaminants entered the soil in a solid form. (This
could very well explain the exceptional result obtained
In the Harbauer case study).
If oxidation is used, production of sludge can be
avoided. This is, however, only possible for organic
contaminants that are easily oxidizable, e.g., phenols.
The In situ extraction techniques produce a sludge
containing only the extracted contaminants and the
added chemicals in a concentrated form, the volume of
which amounts to only a small percentage of the soil
cleaned. The electro-reclamation technique also
produces a small amount of sludge from the water
purification unit.
5.6 Limitations or Restrictions to the Use
of the Techniques
If the right combination of particle separation
processes are used in combination with extraction,
there are few restrictions for these techniques in
general. Contaminated soils are considered non-
cleanable if the contaminants are equally adsorbed to
the entire soil fraction (equal distribution over particle
size and particle density) and when the contaminants
are relatively insoluble, thus making separation of any
fraction and flushing with a water-based solvent
useless.
Application of the oxidation technique is limited to
well oxidizable contaminants. Other oxidizable
material present will largely increase the amount of
oxidant used. Trials in using oxidants in The Nether-
lands showed very limited applicability.
For in situ techniques aiming at removal of con-
taminants, the contaminants must be readily soluble in
an aqueous solvent and not be heavily adsorbed onto
the soil particles. This will only be true for a limited
number of cases, such as the TAUW/Mourik case
described earlier. Since the mechanism of cleaning by
electro-reclamation has not been explained, little can
be said about its limitations in this respect.
Any soil that is cleanable in situls also cleanable in
installations, but there are additional costs for excava-
tion and handling of the material. A major drawback of
in situ techniques in general is the difficulty of deter-
mining accurate results because of the difficulty in ob-
taining, without significant cost, accurate concentration
profiles, both before and after the remediation opera-
tion. Table 5-2 gives an overview of the limitations of
the different techniques addressed in this Pilot Study.
5.7 Costs
In this section an overview is given of some major
cost factors that determine the total cleaning costs in
an extractive installation. The costs of electro-reclama-
tion, in situ acid extraction, and jet cutting followed by
oxidation were not available at this time.
The general overview of costs involved in extractive
cleaning of soil has been drawn from past experience
with extractive cleaning of soils in The Netherlands
(Hinsenveld 1990). The costs apply to installations
such as the Harbauer and Klockner systems, each of
which will be largely determined by cost factors men-
tioned in this section. The cost factors are applicable to
a lesser extent to the Keller installation, since this in-
stallation is simpler than the other extraction installa-
tions from a treatment point of view.
This discussion of costs is not claimed to be com-
plete and care must be taken to take cost factors into
consideration that are not addressed here, such as
cost factors that are specific for an installation, a
project, a country, and so on.
The costs are given in 1990 US$.
5.7.1 Fixed Costs
Location. An extractive installation is constructed
on an emission controlled site. The costs for such a
site include:
58
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Physical/Chemical Extraction Technologies
Table 5-2. Limitations to the use of the case study techniques.
Process/Technique High pressure soil
washing
Manufacturer Klockner
Technique available Germany, The
in Netherlands
In/Ex situ Ex situ
Type of soil Preferably sandy soils.
Not suitable for clay
Fraction of fines Not more than 30% of
the particles smaller than
0.063 mm and organics
Fraction of organics
Fraction of rubble No limitations
Type of No limitations
contaminants
Concentrations of No limitations
contaminants
Production of sludge Double the amount of
the fraction smaller than
0.015 and of the fines
Remarks Buildings on
contaminated site must
be torn down.
Vibration
Harbauer
Germany
Ex situ
Preferably sandy
soils.
Not suitable for
clay
Not more than
20% smaller than
0.015 mm
Not more than
30% smaller than
0.063 mm and
organics
No limitations
No limitations
No limitations
Double the
amount of the
fraction smaller
than 0.063 and
of the organics
Buildings on
contaminated site
must be torn
down.
Jet cutting/
oxidation
Keller
Germany
In situ soil
cutting; ex situ
treatment
Preferably sandy
soils
No limitations
High content of
organic material
leads to
excessive
oxidant use
No limitations
Only easily
oxidizable
components i.e..
phenol;
heavy metals are
not removed
High
concentrations
lead to high
oxidant use
Not produced
Technique can
be used
underneath
standing
buildings.
Electro-
reclamation
Geokinetics
Australia, The
Netherlands
In situ
Suitable for both
sandy material
and clay. For
sand, flushing
might be cheaper
No limitations
No limitations
No limitations
Only proven for
heavy metals
High
concemtrations
can leiad to high
use of electricity
Little; highly
concentrated
Technique can be
used underneath
standing
buildings; Metallic
objects in the
ground leads to
insufficient
cleaning and high
electricity costs.
In situ acid
extraction
TAUW/
Mourik
The
Netherlands
In situ
Sand, with
high
permeability
Not more than
a few percent
smaller than
0.1 mm
Must be very
low or absent
No limitations
Only acid
soluble heavy
metals
High
concentrations
can lead to
high flushing
costs
Little; highly
concentrated
Technique can
be used
underneath
standing
buildings.
Note: A large fraction means more than 30% of the contaminated soil.
59
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Chapter 5
ป The annual costs of the installation site, including
maintenance of the site itself. These amount to
about US$150,000 to US$270,000. These costs
also incorporate a number of facilities of which the
most important are: the construction of fluid-tight
underlining, runoff water control and a secondary
impermeable barrier (about US$50 to US$80/m2;
these costs are roughly doubled in case a hood is
needed), and the facilities needed at the site. For
a s'rte of an average size of 10,000 to 20,000m2,
the investment, including fences, weigh bridges, a
carwash facility etc., is estimated to be about
US$750,000 to US$1,500,000.
ซ Catchment and treatment of percolation water.
Percolation water from other parts of the site is
generally caught separately. It includes surface
runoff from the covered contaminated soil, sur-
face runoff from parts of the site that are not in
use, and surface runoff from roads. Only if the
contamination is unacceptably high will this runoff
be treated. Annual costs, depending on the size of
the s'rte and the type of contaminant range from
about US$60,000 to US$90,000. This brings the
total estimated annual costs of the location to
about US$210,000 to US$360,000.
Water discharge. The costs of discharge are lar-
gely dependent on the size of the site and arrange-
ments made by the local government. Estimated
annual costs range from US$20,000 to US$30,000.
Installation of soil cleaning equipment. The in-
vestments needed for the soil cleaning installation, the
sludge treatment unit, and the treatment of process
water are difficult to specify for every unit separately,
because of major differences between the installa-
tions. For Installations presently used in The Nether-
lands, these costs range roughly from US$2,500,000
to US$4,500,000. With a depreciation of 5 years and
including necessary maintenance and replacement,
the annual costs amount to US$660,000 to
US$1,200,000.
Operation of the Installation. For a direct opera-
tion of a soil cleaning installation, treatment of process
water, filter press sieving, and logistics, some four to
six people are needed. In most countries, this person-
nel frequently must have completed on-s'rte hazardous
waste management training and be certified to work on
the site. The training generally includes practice in the
field of inhalation protection, first aid, and fire abate-
ment. Annual costs amount to US$240,000 to
US$300,000.
Process control and development. Process con-
trol, making and evaluating test cleaning, and the
evaluation of technology developments are mostly
done by an engineer of academic level. Annual costs
amount to US$90,000 to US$120,000.
Shovels and trucks. Input of soil into the installa-
tion, on a coarse sieve, is done with help of a shovel or
a front-end loader. Another truck is needed for remov-
ing the sludge from the containers. These vehicles
generally need pressurized cabins and an air filter. The
costs amount to US$90,000 to US$150,000 per year.
Licenses. Most commercial firms use one or more
licenses. Different arrangements have been made in
the past for payment. Payment at once, followed by a
yearly depreciation or payment per year per tonne
cleaned material are general practices. Estimated
costs range from US$60,000 to US$90,000.
Canteen, showers, and offices. Buildings and
normal costs like water, electricity, heating, telephone,
and the cleaning of work clothes and offices amount to
annual costs of about US$60,000 to US$90,000.
Other costs. In the field of soil remediation, costs
of insurance, permits, administration, accountants,
bank guarantees, etc., can be quite substantial. Fur-
thermore, costs concerning the establishment and
control of safety procedures, medical checkup of
workers, advice from medical doctors as well as costs
for depreciation of measurement devices must not be
forgotten. These annual costs are estimated to range
from US$90,000 to US$120,000.
Direction and acquisition. The pre-project ac-
quisition and specification of the work can be quite dif-
ficult in this field. Estimated costs amount to
US$60,000 to US$90,000.
A summary of fixed costs is given in Table 5-3.
These total fixed costs must be divided by the total
amount of cleaned soil (approved tonnes). With an an-
nual production of 22,700 tonnes at the lowest and
40,800 tonnes at the highest investments, the fixed
costs amount to US $68 and US$63 per tonne, respec-
tively of cleaned soil.
5.7.2 Variable Costs
Deposit of soil before treatment. The soil on ar-
rival has to be deposited and covered at the site. The
trucks used for this operation must be washed before
leaving the site again. The cost of this operation
strongly depends on the frequency of deposit. Costs
are about US$1 to US$2 per tonne of soil.
Analysis. In order to verify the indicated concentra-
tions and types of contaminant, as well as to assess
the expected sludge to be generated after treatment of
the soil, samples are taken and analyzed during the
process of depositing the soil. Analyses are also con-
ducted for assessing process parameters to minimize
emissions and residues and to indicate the expected
quality of the end product (e.g., cleaned soil, sludge).
These costs strongly depend on the homogeneity of
the soil and the amount of soil being cleaned. Es-
timated costs are US$2 to US$7 per tonne of soil. ,
60
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Physical/Chemical Extraction Technologies
Table 5-3. Summary of annual fixed costs (in US$ 1990).
Cost item
Location
Discharge
Install soil cleaning equipment
Operation of installation
Process control and
development
Shovels and trucks
Licenses
Canteen, showers and offices
Other costs
Direction and acquisition
Lower
values
210,000
18,000
660,000
240,000
90,000
90,000
60,000
60,000
60,000
60,000
Higher
values
360,000
30,000
1 ,200,000
300,000
120,000
1 50,000
90,000
90,000
1 20,000
90,000
TOTAL ANNUAL FIXED
COSTS 1,548,000 2,550,000
TOTAL PER TONNE SOIL 68 63
Electricity and water. Energy is needed for most
of the unit operations. Water is needed, because the
soil and the sludge leave the installation with an in-
creased water content compared to the original soil.
These costs strongly depend on the amount of soil
cleaned per hour and the amount of sludge produced
from the soil. More fines lead to both higher electricity
costs as well as a higher water demand. Estimated
costs range from US$2 to US$4 per tonne of soil.
Chemicals. Depending on the system used in the
extractive soil cleaning installations, the following
chemicals may be used: chemicals for pH condition-
ing, emulsifiers and demulsifiers, coagulants, floc-
culants, and flotation aids. The costs will be a function
of" the type and concentration of contaminants, the
chemical composition of the soil, and the sludge con-
tent. Costs range from US$4 to US$7 per tonne of soil.
Filter material. Cleaning of process water and air
is sometimes done by means of sand filters and active
carbon filters. Both types of filters must be processed
afterwards (i.e., regenerated or deposited). The costs
involved strongly depend on the type and concentra-
tion of contaminants and are in the range of US$1 to
US$3 per tonne of soil.
'Safety and occupational health. Depending on
the risk factors, personal protection is needed. In some
cases the presence of a safety and occupational
health specialist is required. Costs are estimated as
US$2 to US$7 per tonne of soil.
Reuse of the cleaned soil. This is still a problem.
In case the concentrations; are very low (for instance,
at the Dutch reference levels), the soil can be used
multi-functionally. In many cases, the cleaning com-
pany pays for the transportation costs of this material.
At higher residual concentrations, the cleaned soil can
sometimes be used in asphalt production installations.
The costs, therefore, depend on the type and con-
centration of the residual contaminants and on the
transport distance. Typical costs in The Netherlands
range from zero to US$10 per tonne of soil.
Ultimate disposal of cleaned soil depends on
regulatory requirements. It should be noted that even
when the soil is cleaned to trace concentrations of con-
tamination, the public will likely be very reluctant to
allow reuse of the cleaned soil (psychological factors).
Reuse of rubble, etc. Rubble and gravel mixed
with other soil particles which are separated from the
soil may require treatment, depending on the composi-
tion. These coarse materials may be reused in road
building, but are often deposited at a landfill site. The
costs per tonne of material depend on the composition
of the material, type and concentration of the con-
taminants, and the distance of transport. A range may
be indicated as US$17 to US$66 per tonne of rubble.
For soil containing 10 percent rubble and other non-
soil materials, this amounts to US$2 to US$7 per tonne
of soil.
Reuse of sludge. The mineral fraction (mostly the
fraction smaller than 0.063 mm to 0.030 mm) is trans-
ferred from the soil to the water phase and finally ends
up in the sludge. Usually the sludge will be processed
by a mechanical dewatering unit. The sludge, in
general, contains the larger part of the contaminants
(most contaminants are heavily adsorbed on this frac-
tion). Deposit of this material may be expensive due to
its high concentrations of contaminants, such that only
controlled and permitted landfills will accept the
sludge. The cost of disposal will be dependent on the
amount of the minimal fraction in the soil (fraction
smaller than 0.063 mm to 0.030 mm), the distance of
transport, and the cost of landfilling. A soil with 10 per-
cent mineral content leads to estimated costs of dis-
posal of US$7 to US$46 per tonne of soil. If the sludge
has to be treated before deposit, by solidifica-
tion/stabilization techniques: for example (see Chapter
3), the costs will be a multiple of the above mentioned
figures.
A summary of variable costs is given in Table 5-4.
5.7.3 Total Costs
From the inventory above it is clear that the costs of
cleaning soil depend on a large number of factors. This
inventory is based on experience in The Netherlands;
this should be borne in mind when calculating the
costs for other countries. Some of the item costs
probably will be very different and the costs given here
61
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Chapters
Table 5-4. Summary of variable costs per tonne soil (in
US$, 1990).
Cost Item
Lower
values
Upper
values
Deposit of soil before
treatment
Analysis
Electricity and water
Chemicals
Filter material
Safety
Rouse of cleaned material
Rouse of rubble, etc.
Deposit of sludge
TOTAL VARIABLE COSTS
2
2
4
1
2
0
2
7
21
7
4
7
3
7
10
7
46
93
should, therefore, not be used as a direct reference for
estimating costs. Furthermore it is expected that a
number of other costs not mentioned here might be
added to the calculation for certain countries. The
above method of calculating the treatment costs
should, therefore, only serve as an example of how a
Table 5-5. Total costs of extractive treatment per tonne
soil (in US$,1990).
Lower
values
Higher
values
Total fixed costs 68 63
Total variable costs 21 93
TOTAL COSTS OF TREATMENT 89 156
rough calculation might proceed. The total costs of
treatment are indicated in Table 5-5.
In general, the costs for treatment in The Nether-
lands on the basis of 10 percent rubble and 10 percent
sludge will vary between US$89 and US$156. In the
above mentioned inventory, general administration
costs and the costs of profit have also been omitted.
Commercial firms add in general about 10 percent to
15 percent to the above mentioned figures for this pur-
pose. In addition research and development costs
have been omitted.
5.8 Future Status of Case Study
Processes and Extraction
Technologies as a Whole
As indicated, extractive methods are suitable for a
large range of soils and a large range of contaminants.
The ex situ extraction methods are powerful techni-
ques for soils containing heavy metals as well as or-
ganic contaminants. For soils containing a combination
of metals and organics, there are presently no other
techniques available. For soils containing only or-
ganics, thermal techniques are generally more effec-
tive. A further improvement of the extraction
installations by using new separation techniques is ex-
pected. The use of organic solvents and supercritical
extraction techniques are being investigated at the mo-
ment. These techniques might further enlarge the ap-
plicability of the extraction techniques, but are
generally more expensive. The Keller technique, using
only oxidation, has a limited applicability. The jet cut-
ting method used in the cleanup operation, however,
might be useful to reduce the costs of cleanup under
buildings, because the buildings would not need to be
dismantled.
In situ extraction techniques will probably continue
to play only a marginal role in the cleanup of con-
taminated sites dye to their limited applicability.
However, the electro-reclamation technique could
prove to be a powerful technique for solving problems
associated with cleaning clayey soils and sludges, but
is still under development. For in situ cleaning of clay
soils containing heavy metals, electro-reclamation is
the only technique available at the present time. For
that reason, electro-reclamation deserves to be invesr
tigated intensively in order to assess its potential.
62
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Physical/Chemical Extraction Technologies
REFERENCES
demonstration of a pi.ot-sca.e debris washing system. Journa.
Casagrande, L.J. Boston Society of Civil Engineers, 69 (2) 1983, pp 255-302.
^kf ฐuฐ'' W" a?? Sff"98' GA Elซ=ปro-reclamatlon: State of the art and future developments
Dordrechl!T9e9noV Va" **" Brink (8ds0> Contaminated Soil >9ฐ- Kluwer Academic Pub
U.S. EPA Technology evaluation report: Design and development of a pilot-scale debris decontamination
system, Volume 1. EPA/540/5-91/006a, U.S. Environmental Protection ^
innฐVative tecnnolฐ9y evaluation program: Technology profiles. EPA/540/5-
63
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Pump and Treat Ground Water
James W. Schmidt
Wastewater Technology Center, Rockdiffe Research Management, Inc.
867Lakeshore Road, Burlington, Ontario L7R 4L7
Canada
ABSTRACT
Four pump and treat ground water case studies were chosen for the Pilot Study. The first three deal with an
evaluation of treatment technologies. The first of these evaluates the use of more conventional processes: air stripping
and activated carbon adsorption at full scale; the second concerns advanced photo-oxidation technology (at pilot
scale). Generally, the types of contaminants treated were volatile organic compounds and a few other nonvolatiles
such as phenols and PCB's. The third evaluates the use of precipitation and clarification for removing cadmium and
zinc from contaminated ground and surface waters from an old zinc smelting operation.
The final case study deals with minimizing the quantity of water to be treated with a concurrent reduction in the
amount of contaminants to be treated. A particular well pumping technique was examined also at pilot scale at the
W3STS sitG in Dฉnm3rk.
contaminants from the aquifer. In addition, con-
taminants that are adsorbed or held by the soil par-
ticles may be desorbed from the soil particles,
maintained in solution in the ground water, and
pumped out at the extraction well.
In all cases, for decontamination to be effective,
sources contributing to the contamination of the
ground water must be removed, such as, sludge
ponds, buried drums, and nonaqueous phase liquids in
the soil matrix.
6.2 Case Studies Chosen
In terms of system design for pump and treat, the
hydrogeological and geochemical properties of the
aquifer must be known, as well as the behavior of the
contaminants within the aquifer and the ground water.
Extraction wells can be designed from basic hydrologic
principles to ensure that an appropriate "cone of in-
fluence" exists.
There are a number of factors to be considered in
designing a treatment sys;tem. These are indicated
briefly here and elaborated on in Section 6.6. One
6.1 Introduction
This chapter deals with pump and treat technology,
with the primary emphasis on treatment technologies
for pumped ground water. Outlined in this chapter are
four case studies, the performance of various tech-
nologies, lessons learned, costs, factors to be con-
sidered for using the technologies and, finally, the
future of the technologies demonstrated.
Pump and treat technology consists of the extrac-
tion of contaminated ground water from the subsur-
face, followed by treatment of the ground water at the
surface to remove the contaminants. Treatment can
be by means of physical/chemical technologies,
biological treatment technologies, or any appropriate
combination of these.
The application of pump and treat technology can
be considered for essentially two cases: containment
of the contaminants in the ground water to within a
confined zone thereby preventing the spread of the
contamination, and decontamination of the aquifer. In
this latter case, injection wells may be installed
"upstream" of the pumping well(s) to help flush the
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Chapters
consideration is the actual treatment process(es) that
will be used. The treatment processes will be a func-
tion of the type and quantity of contaminants present
as well as the volume of ground water to be treated.
The quantity of contaminants and volume of water to
be treated can also impact significantly on treatment
costs. This factor may be overlooked but it is highly
desirable to examine the possibility of reducing the
volume of water to be treated and, if possible, the
quantity of contaminants to be treated. It is essential
that the treated ground water and any residuals or
emissions meet the regulatory requirements.
To partially illustrate these points, four case studies
were chosen. One case study illustrates flow and con-
taminant minimization and the other three illustrate
various ground water treatment technologies.
One other case study is outlined in Chapter 8 below
which also relates to this chapter on pump and treat
technologies. This case study is biological pretreat-
ment of ground water, The Netherlands (Lin-
dane/Bunschoten). An additional project report is
included in Appendix 1-C: on-site in situ reclamation:
membrane filtering and biodegradation, Denmark
(former gas works site/Fredensborg).
6.2.1 Case Study 6-A: Decontamination of Vllle
Mercler Aquifer for Toxic Organlcs, Vllle
Mercler, Quebec, Canada.
This case study was chosen for two reasons. First-
ly, it Is a demonstration of a full scale "pump and treat"
system, the first in Canada and perhaps North
America, designed to decontaminate an aquifer.
Secondly, an evaluation of the treatment technologies
employed (a combination of "air stripping" and ac-
tivated carbon) was being undertaken by Environment
Canada.
Site. From 1968 to 1972 some 40,000 m3 of waste
oils and liquid industrial wastes from chemical and
petrochemical industries in the vicinity of Montreal,
Quebec were dumped in a lagoon in an old gravel pit
located near Ville Mercier, Quebec. The dump site
was closed in 1972. Over the next 10 years, as a
result of several investigations, it was determined that
about 30 km2 of the aquifer supplying drinking water
for several local communities was contaminated.
The gravel pit is located in a sand and gravel esker
of f luvio-glacial origin. The sand and gravel extend to
a depth of roughly 30 meters and overlie fractured
dolomite and sandstone bedrock. The most con-
taminated zone extends over an area of about 2 km2
down gradient from the lagoon.
The climate in the area is typically temperate, with
snow and rain averaging about 254 cm per year. Cold
weather extends generally from mid October through
mid April.
Treatment System. The installation became
operational in 1984. Three ground water extraction
wells were located down gradient from the lagoon and
provided a flow of 65 L/s to the treatment plant. The
primary treatment processes involve air stripping to
oxidize and precipitate iron and manganese and to
remove volatile organic compounds (VOC's); coagula-
tion and flocculation with alum and polymer addition;
sedimentation and rapid sand filtration to remove iron
and manganese and other suspended solids. Ac-
tivated carbon is used to remove the remaining organic
compounds. More detailed information is provided in
the references at the end of this chapter and in Appen-
dix 6-A.
6.2.2 Case Study 6-B: Evaluation of
Photo-oxidation Technology (Ultra*1*
International), Lorentz Barrel and Drum
Site, San Jose, California, United States.
This case study was chosen because it was the
evaluation of a photo-oxidation process to treat or-
ganics in a contaminated ground water. This technol-
ogy was evaluated under the Superfund Innovative
Technology Evaluation (SITE) program of the United
States Environmental Protection Agency (U.S. EPA).
The demonstration took place in February and March
1989 at a former drum recycling facility in San Jose,
California.
Site. In 1947, Lorentz Barrel and Drum began its
drum recycling operations. Drums were received from
over 800 private companies as well as military bases,
research laboratories and county agencies in Califor-
nia and Nevada. The drums generally contained
residual aqueous wastes, organic solvents, acids,
metal oxides, and oils. Residual wastes from drums
and wastewaters were disposed of in an on-site
drainage ditch routed to a large sump. Prior to 1968,
wastewater from the sump was discharged to the
storm drain system. In subsequent years, discharge
was to the sanitary sewer. This practice was discon-
tinued between 1983 and 1984. Subsequently, liquid
wastes were reportedly reduced in volume by evapora-
tion, put in drums, and disposed of off-site as hazard-
ous wastes. In 1987, the facility ceased operation and
the U.S. EPA Regional Office in California assumed
lead agency responsibility for site remediation and in-
itiated a remedial investigation/feasibility study. When
the company began operations, the site consisted of
25.9 hectares. Since then half has been sold. The
highest contamination levels are suspected to be in the
remaining 13 hectares.
The surface soils are silt and clay (about 1 meter)
underlain by sand and gravel, about 7 meters below
which there is a clay aquitard. The water table occurs
at a depth of approximately '6 meters. The shallow
ground water flow appears to follow the ground surface
topography flowing towards a local watercourse,
Coyote Creek, about 0.8 km away. ' :
66
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Pump and Treat Ground Water
The climate in the area has warm, dry summers
and cool, wet winters. Normal average rain fall is 353
mm (13.9 inches) most of which occurs from Novem-
ber through April.
Treatment Process. The Ultroxฎ technology (a
registered trademark of Ultrox International) simul-
taneously uses ultraviolet radiation, ozone and
hydrogen peroxide to oxidize dissolved organic con-
taminants (including chlorinated hydrocarbons and
aromatic compounds) found in ground water or was-
tewater.
The objectives of the technology demonstration
were to:
Evaluate the ability of the technology to treat the
44 volatile organic contaminants found in the
ground water at the site
Evaluate the effects of major process parameters
on process performance
Evaluate the efficiency of the ozone decomposer
unit in treating off-gas from the reactor
ซ Develop information useful for evaluating whether
this technology is suitable for other hazardous
waste sites with similar conditions.
Five variables examined during the 10-day pilot
scale test included hydraulic retention time, ozone
dose, hydrogen peroxide dose, UV radiation intensity,
and influent pH level. To facilitate the test program,
three indicator VOC's were selected: trichloroethylene
(TCE) 1,1-dichloroethane (1,1-DCA) and 1,1,1-
trichloroethane (1,1,1-TCA). At a flow rate of 14 Lpm
3.75 gpm, the reactor retention time was 40 minutes.
This was varied between 20 and 60 minutes. Addition-
al details are presented in the references at the end of
the chapter and in Appendix 6-B.
6.2.3 Case Study 6-C: Zfnc Smelting Wastes and
the Lot River, Viviez, Averyron, France
This case study was chosen because it repre-
sented an example of a "pump and treat" system and
the contaminants of concern were metals (in contrast
to organics).
Site. Zinc production in Viviez was started in the
1870's. Until 1930, a thermal process was used to ex-
tract the zinc from the ore with the wastes being dis-
posed of on a hillside near the plant. After 1930, an
electrometallurgic process was used and again the
wastes were deposited near the plant. The total, now,
is about 700,000 tonnes. Water percolating through
the wastes dissolves cadmium and zinc which reach
the ground water and eventually, surface water. In
1987, it was calculated that 37 kg/d of cadmium were
reaching the Lot River. Hydrogeological studies were
undertaken to better define the hydrodynamic be-
haviour of the alluvial aquifer, the hydraulic relation-
ship between the waste heap and the aquifer, and the
surface water regime in the vicinity of the heap. Addi-
tional water analyses were done on various chemical
parameters as well.
In 1988, action was taken to cover ponds on the
heap, to relocate the smallest storage piles, and collect
contaminated surface and ground water. With these
actions, the cadmium flux was reduced by 94 percent
to 2 kg/d. Several additional actions, such as flushing
parts of the heap and diverting surface water, resulted
in reduced quantities of contaminated water to be
treated.
Treatment Process. The treatment is performed
in a batch mode with 320 to 800 m3 of contaminated
water collected in any one day. The process involves
the addition of lime in several reactors followed by the
addition of sodium sulfide. Polymer is added to the
clarifier to ensure effective settling of the sludge and to
ensure that the effluent objectives are met. The
sludge is dewatered on a filter press and sent off-site
for metal recovery. The effluent is discharged to a
receiving water. Additional work is underway to further
reduce the quantity of water (and contaminants) to be
treated and, hopefully, reduce the cost of treatment.
Additional details are presented in Appendix 6-C.
6.2.4 Case Study 6-D: Separation Pumping,
Skrydstrup, Denmark
This case study was chosen because it
demonstrated the use of a novel pumping technique,
separation pumping, to reduce the volume of ground
water and the quantity of contaminants to be treated.
Site. In the period 1963-1974, chemical waste
from a refrigerator factory was dumped in a gravel pit
near Skrydstrup in western Denmark. The ground
water was considerably contaminated by 1,1,1
trichloroethane and organic phosphorus. The waste
was excavated in 1986. The drums with chlorinated
solvents were sent for destruction and the con-
taminated soil was placed in a special waste disposal
site for treatment. (For more details, refer to Appendix
6-D.) The pollution plume has been found up to 1.5
km downstream and to a de;pth of 25 meters.
Technique. This technique relies on simultaneous
pumping from the top and bottom of a fully penetrating
well through the polluted section of the aquifer. The
objective is to reduce the volume of water requiring
treatment. In a test well, during the period July-Oc-
tober 1989, from 50 to 65 percent of the total water
pumped was within acceptable limits of contaminants -
obviously a significant reduction in the volume of water
that would have to be treated. In the subsequent
period, November 1989 to March 1990, the pump
ratios had to be changed such that only 10 percent of
the total discharge was within acceptable limits; still,
however, producing a reduction in the volume to be
treated. Additional pilot scale experiments with en-
67
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Chapters
couraging results were also completed in a limestone
aquifer and a chalk aquifer. As these were only pilot
scale experiments, no cost data are available yet for
full scale application. Additional details are provided in
Appendix 6-D.
6.3 Background of the Case Study Sites
as a Group
Only three of the four case studies mentioned
above will be used to demonstrate the performance of
treatment technologies. Before describing the perfor-
mance results, background information is provided on
the sources and types of contaminants, some site
characteristics, and the success in remediating one
aquifer. The sources of contamination are set out in
Table 6-1.
Table 6-1. Sources of contamination at case study sites.
Site
Ville Mercier
Lorentz Barrel and
Drum
Lot River
Source
Waste dump in a rural area
containing primarily organic
wastes and oils. Some PCB's
detected.
Decommissioned industrial site in
an urban area.
Old industrial site near an urban
area.
Table 6-2. Principal contaminants at the Ville Mercier, and the Lorentz Barrel and Drum sites.
A. Villa Mercier
B. Lorentz Barrel and Drum'
Phenols'
1,2-Dichloroethane (1.2 DCA)'
1,1,1-Trichloroethano (1.1.1-TCA)1
1,1,2-TrichloroethanD (1.1,2-TCA)
Trichloroethylene (TCE)1
Chloroform
Chlorobonzone
Trans 1,2 Diohloroathylene
PCB's1
Iron
Manganese
Benzene2
Benzyl Chloride
Bis (2-chloroisopropyl) ether
Bromobenzene
Bromodichloromethane
Bromoform
Bromoethane
Carbon tetrachloride
Chloracetaldehyde
Chloral
Chlorobenzene
Chloroethane3
Chloroform3
1-Chlorohexane
2-Chloroethyl vinyl ether
Chloromethane
Chloremethyl methyl ether
Chlorotoluene
Dibromochloromethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Dichlorodifluoromethane
1,1 -Dichloroethane2'3
1,2-Dichloroethane3
1,1-Dichloroethylene3
Trans-1,2-dichloroethylene3
Diohloromethane
1,2-Dichloropropane3
1,3-Dichloropropylene
Ethyl benzene
1,1,2,2-Tetrachloroethane
1,1,1,2-Tetrachloroethane
Tetrachloroethylene3
Toluene
1,1,1-Trichloroethane2'3
1,1,2-Trichloroethane
Trichloroethylene2'3
Trichlorofluoromethane
Trichloropropane
Vinyl Chloride
Xylenes
Arsenic4
Barium*
Chromium*
Cobalt*
Iron
Manganese
Molybdenum*
Nickel*
Vanadium*
Zinc*
'Contaminants selected to evaluate the performance of the technology.
'Contaminants selected as "indicator" VOC's to guide the test program at Lorentz.
'Principal contaminants measured for test work.
4Motals found in wells on-site but not reported in test work.
Table 6-2 identifies the principal contaminants at
Ville Mercier and Lorentz Barrel and Drum. Volatile
organic compounds (VOC's) and some PCB's were
found at both sites. In the case of Lot River, the con-
taminants of concern are the toxic metals, zinc and
cadmium.
68
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Pump and Treat Ground Water
The site characteristics of the case studies were
significantly different. As the focus of the chapter is
primarily on treatment technologies, the type and
range of site characteristics are not particularly
relevant.
6.4 Performance Results
6.4.1 Effectiveness of Aquifer Remediation at Ville
Mercier
It was anticipated that the aquifer would be
remediated within a period of five years based upon
the predesign hydrogeological investigations, the site
investigations that were conducted as part of the 1989
study clearly indicated that this did not occur nor would
it likely occur within the foreseeable future. The
reason for this was that, when additional monitoring
wells were placed and sampled, significant quantities
of nonaqueous phase liquids (NAPL) were found
throughout the soil and into the fractured bedrock.
Thus, although the pumping appeared to be effectively
constraining the down gradient movement of con-
taminants, it was obvious that the aquifer could not be
remediated until some means was found to remove the
NAPL.
6.4.2 Effectiveness of Treatment Technologies
Each of the treatment systems'.at the three sites
were judged using a similar basis, i.e., that the ef-
fluents and emissions had to meet regulatory stand-
ards. The specific objectives to be met are presented
in Tables 6-3 and 6-4. The effectiveness of the treat-
ment systems at Ville Mercier and Lorentz Barrel and
Drum was assessed by how well they removed the
contaminants of concern priimarily VOC's and if the ef-
fluent criteria were met. For the Lot River case study,
the process was assessed on its ability to reduce zinc
and cadmium.
Ville Mercier. A review of the results of the perfor-
mance of the treatment plant from 1984 to 1989 (Ap-
pendix 6-A) and during the two sampling campaigns
undertaken in 1989 reveals that there were a number
Table 6-3. Performance results for Ville Mercier, and Lorentz Barrel and Drum sites.
Results in figlL (unless otherwise noted)
Compounds
Ville Mercier
Objective
Results
Lorentz Barrel and Drum
Results6
Objective4 Run 12" Run 13e
Iron (mg/L)
Manganese (mg/L)
RGB's
Phenols
Benzene
Chloroform
Chloroethane
1 , 1 -Dichloroethane
1 ,2-Dichloroethane
1 , 1 -Diohloroethylene
Trans-1 ,2-Dichloroethylene
1,1,1-Triohloroethane
1 ,1 ,2-Trichloroethane
Trichloroethylene
1 ,1 ,2,2-Tetraohloroethane
Tetrachloroethylene
1 ,2-Diohloropropane
Vinyl Chloride
Any other VOC
0.30
0.05
0.01
2.0
50
50
33
50
4.5
50.00
0.02 0.01
nil
78.0 27.0
620 1 23
nil nil
441 25.0
1 1 .0 1 .0
5.0
5.0
5.0
5.0
1.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
0.5
low
low
0.23
0.74
0.00
3.80
0.92
0.00
0.00
0.43
0.55
0.045
0.19
2.60
0.11
low
low
0.45
0.81
0.00
4.20
1.00
0.00
0.00
0.49
0.63
0.045
0.091
2.90
0.12
Ville Mercier - Oxidation-air stripping followed by suspended solids removal and activated carbon. Lorentz Barrel and
Drum - Ultroxฎ process consisting of the use of hydrogen peroxide, ozone and ultraviolet light.
2Campaign conducted 4 months after granulated activated carbon (GAC) replacement; period - two weeks.
3Campaign conducted immediately after GAC replacement; period - six weeks.
""Regulatory threshold.
'Thirteen volatiles identified - only 3 common to both sites.
6Mean values; Runs 12 and 13 were replicate runs.
69
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Chapter 6
Table 6-4. Performance results for Lot River site.
Effluent
pH
Suspended solids
Phosphorus
Hydrocarbons (total)
Motals (total)
(Zn + Cu + Ni + Al
+ Fo + Cr + Cd +
Pb + Sn)
Zino
Cadmium
Monthly average
Maximum daily
Objective
5-9
<30 mg/L
< 10 mg/L
<5 mg/L
< 1 5 mg/L
<5 mg/L
0.2 mg/L
0.4 mg/L
Results (daily
average)
8.5-9
N/A
N/A
N/A
N/A
0.5 - 3.0 mg/L
0.03- 0.18 mg/L
N/A ป Not available
of problems associated with various unit operations in
the treatment train. The initial unit operation, consist-
ing of a packed column, was designed for iron oxida-
tion and, to some extent, stripping of the VOC's. Iron
was oxidized effectively; however, the column packing
quickly became coated with an iron colored scale.
Removing the scale added to maintenance of the sys-
tem. The packed column had not been designed as an
efficient air stripping device and therefore the perfor-
mance results for VOC's are inferior to those expected
from a column designed specifically as an air stripper.
The carbon columns failed to perform as well as
required, so effluent quality objectives were not consis-
tently met. For example, 1,2-DCA "broke through" the
carbon within two to three weeks after replacement.
This may have been due to factors such as competi-
tive adsorption with other VOC's or generally with the
other organics present measured as "total organic
carbon", or simply because 1,2-DCA is poorly adsor-
bable.
Significant changes in the influent concentration of
VOC's likely impacted on the performance of the treat-
ment train as well. As an example, the concentration
of 1,2-DCA increased about ten times over what was
expected from the initial pump well tests. Therefore, in
summary, a number of factors contributed to the in-
ability of the treatment system to consistently meet the
effluent objectives.
Lorentz Barrel and Drum. The Ultroxฎ process
was evaluated for a period of 10 days during which five
variables were examined and 13 runs conducted.
Given an initial set of conditions based upon a
treatability study, the objective of the evaluation was to
determine a set of operating parameters under which
the process effluent would meet the permit require-
ments. The objective was met and a set of operating
conditions was defined.
The preferred operating conditions, determined in
the demonstration are the following:
Electricity 11 kw/h operation (24 UV lamps
operating)
Ozone 110 mg/L
H2Oa-13mg/L
ป Influent pH - 7.2 (unadjusted)
Retention time - 40 minutes
Flow rate-14 L/min
Reactor - 568 liters wet volume
ป Cooling water -13 L/min.
Lot River. Although information on the treatment
process was provided, there was no information
provided on the long term operation of the treatment
process. The data provided indicate that for the me-
tals of concern, zinc and cadmium, the effluent objec-
tives were easily met.
6.4.3 Lessons Learned on How to Improve
Effectiveness
Ville Mercier. Because of the unexpected finding
of NAPL at the site several years after the treatment
system had been operating, the need for comprehen-
sive hydrogeological/geochemical investigations to be
undertaken prior to initiating the pump and treat sys-
tem was clearly underscored.
As noted, a number of factors impacted on the per-
formance of the treatment system. As a result, the fol-
lowing needs have been identified:
Comprehensive treatability studies should be un-
dertaken prior to design. These should be at
bench and pilot scale (preferably at the site to be
cleaned up).
More comprehensive hydrogeologic/geochemical
information should be obtained before a remedia-
tion scheme is implemented.
Ground water treatment plants should be
designed with flexibility so that the performance
can be optimized under variable influent condi-
tions.
As an integral part of the 1989 Ville Mercier study, a
pilot plant was constructed and operated to determine
if a different combination of unit operations would be
appropriate to treat the ground water. The pilot plant
study was conducted from January through July 1989.
The unit operations tested and selected as being
appropriate for a treatment train were:
70
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Pump and Treat Ground Water
ซ Diffused aeration followed by sand filtration for
iron removal
ป Optimized, packed, air stripping column for the
removal of VOC's
, Activated carbon for polishing purposes (TOC's,
phenolics).
Because the air stripping column was optimized ori
the basis of 1,2-DCA being the limiting contaminant, it
was found that the existing discharge objectives could
be met using only this unit operation (with pretreatment
for iron removal).
Lorenfz Barrel and Drum. The period of the tech-
nology evaluation was limited to 10 days. Although an
appropriate set of operating conditions was defined to
meet the objective of the demonstration, these were
not necessarily either an optimum set or the most cost
effective.
Lot River. It is difficult to draw significant con-
clusions given the limited information provided. How-
ever, it should be noted that the usefulness of
minimizing the volume of contaminated water and the
quantity of pollutants to be treated appeared to, have a
significant impact on the treatment system and the
receiving water. The treatment process, as designed,
effectively removed the metals of concern to accept-
able levels.
6.5 Residuals and Emissions
Ville Mercler. From this plant, there were air emis-
sions, sludge from the clarifier and spent activated
carbon.
The air emissions were acceptable to the local
regulatory authority, the Ministry of the Environment of
Quebec (MENVIQ). The sludge was analyzed for a
variety of chemicals and found acceptable for disposal
in a local sanitary landfill. The spent activated carbbn
was returned to the supplier in the United States for
regeneration.
Lorentz Barrel and Drum. A "Decompozon" unit
(for which no process or technical details were
provided) was employed to destroy residual ozone and
residual VOC's that were present in the "air emission.
This unit successfully reduced the contaminants to ac-
ceptable levels.
Lot River. The residual from the process was a
sludge containing significant concentrations of zinc
and cadmium. The sludge was dewatered, using a fil-
ter press producing a cake of 20-30 percent solids con-
taining zinc (25 to 35 percent), cadmium (0.2 to 0.5
percent), and calcium (1.5 to 6 percent). The dried
sludge was shipped off-site for metal recovery.
6.6 Factors and Limitations to Consider
for Determining Applicability of the
Technology
6.6.1 Application of Pump and Treat
The nature of the "pump and treat" technology
limits its use to situations where a realistic quantity of
water can be pumped out of a contaminated aquifer
within a reasonable period of time, particularly if the
goal is to decontaminate the aquifer.
This technology will only be applicable to situations
where the soils are relatively permeable, and where
the contaminants in the ground water are well defined,
both in terms of the chemical nature of the con-
taminants and their behaviour in the soil and ground
water matrix.
All sources of contamination must be removed in
order for the cleanup to be successful. This includes
obvious sources such as buried tanks, drums, etc.,
and also less obvious sources, such as "pockets" of
nonaqueous phase liquids.
6.6.2 Application of Ground Water Treatment
Technologies
Comprehensive hydrogeological and geochemi-
cal characterization of the site must be completed
in order to identify the treatment system design
requirements, such as the volume of flow; the
quantity, type and nalture of contaminants; and
probable variability in contaminant concentra-
tions.
Application of Air Stripping and Activated Carbon
Appropriate treatability studies should be con-
ducted to identify the design parameters for the
air stripper and activated carbon adsorbers. At
this stage, pretreatment requirements should be
identified and appropriate design parameters
developed.
Effective removal of volatile organic compounds
and other adsorbable organic compounds will be
accomplished when the process train is properly
designed.
Pretreatment will be required for the removal of
iron and manganese, oil and grease and
suspended solids.
If metals are present, some form of additional
treatment (pre or post) will have to be incor-
porated into the treatment train.
Chemicals may need to be added to control
microbiological growths in the various units.
71
-------
Chapter 6
ป Air emissions may or may not be acceptable to
the regulatory authorities; a number of tech-
nologies exist to control the emissions from air
strippers.
Means of disposal of activated carbon (and any
other process residues) needs careful considera-
tion; the spent carbon may be considered a haz-
ardous waste.
Application of Photo-oxidation Technology
"The chemistry of the process is quite complex
when a number of different organics are being
treated. Therefore the process cannot be mathe-
matically modelled, nor can oxidant dosage be
based on stoichiometric relationships to the or-
ganics present. This means that the appropriate
operating conditions and oxidant dosages can
only be determined through treatability experi-
ments at an appropriate scale.
" Effective for removal of volatile organic com-
pounds and other nonvolatile organic compounds.
ซ There are no residues generated by the process.
Electrical power requirements for the process are
significant and require careful consideration.
" Hydrogen peroxide is the only chemical required
and must be readily available. This is not seen as
a significant problem.
ป Pretreatment will be required for the removal of
iron and manganese, oil and grease, and
suspended solids.
ปIf metals are present, some form of additional
treatment (pre or post) will have to be incor-
porated into the process train.
Based on the gas chromatography (GC) and gas
chromatography/mass spectroscopy analysis per-
formed for VOC's, semivolatile organics and
PCB's/pesticides, no new compounds were
detected in the treated water. The organics
analyzed by GC methods represent less than 2
percent of the total organic carbon (TOC) present.
Very low TOC removals occurred, which implies
that partial oxidation of organics (and not com-
plete conversion to COa and HaO) took place in
the system.
ซVariability in the concentration of influent con-
taminants to the process must be carefully con-
sidered as the operational parameters for the
process can only be set for a given set of influent
concentrations. Presumably, continuing
treatability testing would be required to determine
the appropriate level of the operating parameters
for a significant change in the influent concentra-
tion of organic compounds. Another option to ac-
commodate variability may be the installation of
equalization capability.
Presumably, there is no limit on the concentration
of organics that can be successfully treated. The
limiting factor will be cost, primarily for oxidants
and for power: ultraviolet (UV) lights are relatively
inefficient, e.g., 0.1 percent.
Application of Precipitation Technology
Treatability studies at an appropriate scale are es-
sential.
Effective for removal of cadmium and zinc and
many other heavy metals.
Variability of the volume of water to be treated will
impact on system design, e.g., tank sizes required
and must be carefully considered.
Not all metals can be removed using lime and
sodium sulfide and, therefore, the solubility of me-
tals in relation to pH must be carefully considered.
Residual sludge may present a disposal problem
in some jurisdictions. Recovery of the metal
values appears to be an attractive option.
The quantity of lime required for precipitation is
relatively insensitive to the concentration of me-
tals to be treated. However, the quantity of
sodium sulfide to be used is a direct function of
the quantity of metals to be treated.
6.6.3 Availability of the Technologies
All the technologies are commercially available.
However, they have to be appropriately designed to
suit the site and contaminated ground water charac-
teristics. Technologies and process trains can either
be designed by consultants, or proprietary "commer-
cial packages" can be purchased from various sup-
pliers.
6.7 Costs
Ville Mercier. The plant was constructed and be-
came operational in 1984. The total capital cost for the
treatment facility including the purge wells was
Cdn$3.1 million (Simard 1987). The operating costs
for the plant are set out in Table 6-5. Over the period
of operation from 1984 to 1987, it can be seen that the
unit operating costs decreased significantly from
US$0.70 to US$0.39/m3 and was projected to
decrease to US$0.32/m3. It should be noted that the
relative cost of the activated carbon is a significant ex-
pense and, therefore, steps to minimize this cost would
be desirable.
-------
Pump and Treat Ground Water
Table 6-5. Ville Mercier operating costs, (x 1,000 CDN$).
FIXED COSTS2
VARIABLE COSTS3
Maintenance
Electricity
Chemicals
Activated carbon
SUPPLEMENTARY COSTS4
TOTAL COSTS
Volume treated (10egal)
Operating time (%)
UNIT COSTS (Cdn$/103 gal)
(US$/m3)
1984/85
270.0
11.0
41.1
60.3
222.7
172.7
777.8
181.8
34.5
4.30
0.70
1985/86
307.0
16.5
57.9
108.0
271.0
65.6
826.0
284.0
54.1
1 2.90
0.48
1986/87
283.7
22.4
59.8
145.0
210.3
152.6
873.8
369.1
70.3
2.37
0.39
1987/881
212.9
22.0
76.0
168.0
290.0
133.8
902.7
420.0
80.0
2.15
0.35
1988/891
212.9
23.2
79.8
176.4
304.4
139.1
935.8
472.5
90.0
1.98
0.32
nagement, personnel, maintenance of works and equipment, disposal of sludges and domestic wastes supply of tools and
varlTmaterials, drinking water, telephone and alarm services, insurance program, control analyt.ca. costs, and upkeep of the
access road.
including those set out in the table plus cleaning of the purge wells.
'Including purchase and repair of mechanical equipment, minor modifications, and techn.cal stud.es needed for sound plant
management.
Lorentz Barrel and Drum Site. Table 6-6 was ex-
tracted from an "Applications Analysis Report"
prepared for the U.S. EPA (U.S. EPA 1990) on the
Ultroxฎ technology. These costs are order-of-mag-
nitude estimates (-30 to +50 percent) as defined by the
American Association of Cost Engineers. A more
detailed explanation of the derivation of these costs
can be obtained from the report. The significance of
the utility costs as the size of the units increase should
be noted although the relative cost per liter treated
decreases.
For the purpose of this economic analysis, it is as-
sumed that the system will be operated in a continuous
mode, 24 hours a day, 7 days a week, for one year.
During this period, the unit should treat approximately
40 million liters in the 75L/min unit, 200 million liters in
the 375 L/min unit, and 500 million liters in the 950
L/min unit. One year was chosen as the period of time
for this analysis so that reliable annual operating and
maintenance costs could be determined. Based on
these data, unit operating costs were calculated and
are presented in Table 6-6. Numerous assumptions
with respect to the mode of operation of the units were
made and these are outlined in greater detail in the
U.S. EPA report.
Lot River. No information was provided on the
capital costs of the system. However, operating cost
data were provided and are set out in Table 6-7.
6.8 Future Status of Case Study
Processes and the Technology as a
Whole
6.8.1 Air Stripping and Activated Carbon
The design of air stripping and activated carbon
processes is highly developed and well understood.
Mathematical models exist for both processes. The
design of processes to treat the emissions from an air
stripper are also well developed. However, the Ville
Mercier experience reinforces the need for careful con-
sideration of the types of ntaminants to be treated
for successful process design and performance.
Both unit operations can be designed by qualified
consultants. Proprietary systems are also commer-
cially available. Recently, several novel proprietary air
strippers, which supposedly have advantages over
packed towers, have come onto the market place.
Areas anticipated for research and development re-
late to more cost-effective processes for the treatment
of air emissions from air strippers. In part, this is ex-
pected because of the likelihood that regulatory agen-
cies will not allow untreated air emissions from air
strippers in the future.
Future developments may relate to the use of more
specific resins for the recovery of organics from liquid
or gaseous streams, or to the use of membrane tech-
nologies, such as pervaporation to remove the or-
73
-------
Tabla 6'6. Estimated capital and operating
Item
CAPITAL COSTS
Sito preparation costs
Permitting and regulatory costs
Capital equipment costs
Startup and fixed costs
Site demobilizing costs
Total One-Time Costs
OPERATING & MAINTENANCE COSTS
Labor costs
Supply and consumable costs
Utility costs
Effluent monitoring and disposal costs
Residuals and waste shipping, handling, and
transporting costs
Analytical costs
Equipment repair and replacement
costs
Total Annual Operation and Maintenance Costs
CALCULATED UNIT COST, US$ PER 3750L
costs associated with three Ultroxฎ system
units (in US$,
1990).
Treatment Flow Rate
75 L/min
36,000
3,500
70,000
32,000
2,000
143,500
6,600
10,500
1 2,000
3,000
1,000
24,000
4,000
61,100
5.82
375 L/min
55,000
7,500
150,000
32,000
3,000
247,500
6,600
1 6,500
58,000
3,000
5,000
24,000
22,000
135,100
2.57
950 L/min
75,000
13,000
260,000
32,000
4,000
384,000
6,600
20,800
145,000
3,000
7,000
24,000
33,000
239,400
1.82
ganics, condense them into a small volume, and either
purify them or destroy them using other processes.
6.8.2 Photo-oxidation Technologies
The Uitroxฎ technology is one example of a class of
technologies generally called "advanced oxidation
processes". A number of competing processes which
are a variation of the Ultroxฎ technology are commer-
cially available. Some of these use only the oxidants
Ha02 and Oa; others use medium pressure UV lamps
In combination with H2O2 or O3.
Advances will come as we increase our under-
standing of the process and can therefore more readily
define optimum process operating conditions.
Other advances are likely to occur in the areas of
reductag power consumption, ameliorating the effects
of foulants, such as iron and manganese, and combin-
ing the process with membrane technologies to treat a
broader mix of contaminants.
As there are no residuals from these processes and
when operating experience is gained with these
processes, the future looks promising as regulations
with respect to the treatment of emissions become
more stringent. (It should be noted, however that
there may be residuals associated with pretreatment
processes.)
Table 6-7. Lot River operating costs (in French francs).
Chemicals
Handling
Energy
Analyses
Maintenance
Personnel
TOTAL
CALCULATED UNIT COSTS/M3**
2,460 F/d
600 F/d
2,190 F/d
260 F/d
1,890 F/d
2,830 F/d
10,230 F/d
12 to 33 F/m3
US S 2 to US$6/m3
(approx.)
*5 French francs = approximately US$1.
"Cost is variable depending upon the flow to the plant which
can vary from 20 to 50 m3/h.
74
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1
Pump and Treat Ground Water
6.8.3 Precipitation Technology
This technology is readily available and can either
be designed or can be purchased as a "turnkey" pack-
age from a number of vendors.
The technology is highly developed. Residuals in
effluents may be lowered through the use of "tertiary"
processes after clarifiers. These generally consist of
either granular media filtration or membrane "filtration".
Both processes are commercially available.
If sludge disposal is a serious problem, specific
resins or "adsorbents" may be used as an alternative,
thus eliminating sludge production. However, the me-
tals must then be removed from the resins or adsor-
bents and preferably recovered, with any chemicals
used being recycled. Obviously if simply another
sludge is produced, there is no point in using this alter-
native.
REFERENCES
Aquifer decontamination for toxic organics: the case study of Ville Mercier, Quebec. Final Report Vol. Ill by
the SNC Group for the Wastewater Technology Center, December 1991.
Goubier, R. Vieille montagne. in: Proceedings, NATO/CCMS Fourth International Conference, Demonstra-
tion of Remedial Action Technologies for Contaminated Land and Ground Water, Angers, France,
1990. p. 28.
Halevy, M., Booth, R. and Schmidt, J. Assessment of ground water treatment at Ville Mercier, Quebec, la:
Proceedings, NATO/CCMS Third International Conference, Demonstration of Remedial Action Tech-
nologies for Contaminated Land and Ground Water, Montreal, Canada, 1989. p. 36.
Lewis, N., Topudurti, K. and Foster, R. A field evaluation of the UV/oxidation technology to treat con-
taminated ground water at a hazardous waste site, in: Proceedings, NATO/CCMS Third International
Conference, Demonstration of Remedial Action Technologies for Contaminated Land and Ground
Water, Montreal, Canada, 1989. p. 60.
Mattel, R. Groundwater contamination by organic compounds in Ville Mercier: new developments. In:
Proceedings, NATO/CCMS Second International Conference, Demonstration of Remedial Action Tech-
nologies for Contaminated Land and Ground Water, Bilthoven, The Netherlands, 1988. p. 144.
Nilsson, B. and Jakobsen, R. The separation pumping technique, in: Proceedings, NATO/CCMS Fourth In-
ternational Conference, Demonstration of Remedial Action Technologies for Contaminated Land and
Ground Water, Angers, France, 1990. p. 48.
Proceedings: A symposium on advanced oxidation processes for the treatment of contaminated water and
air. Toronto, Canada. June 4 and 5,1990. Environment Canada, Wastewater Technology Center
Burlington, Ontario.
Schmidt, J. Aquifer decontamination for toxic organics, Ville Mercier, Quebec, Csinada. In: Proceedings,
NATO/CCMS First International Workshop, Demonstration of Remedial Action Technologies for Con-
taminated Land and Ground Water, Karlsruhe, Germany, 1987. p. 51.
Simard, G. and Lanctot, J.P. Decontamination of Ville Mercier aquifer for toxic organics. in: Proceedings,
NATO/CCMS First International Meeting, Demonstration of Remedial Action Technologies for Con-
taminated Land and Ground Water, Washington, D.C., U.S.A., 1987. p. 135.
Technology Evaluation Report. SITE program demonstration of the Ultroxฎ international ultraviolet radia-
tion/oxidation technology. Prepared for Risk Reduction Engineering Laboratory, ORD, U.S. Environ-
mental Protection Agency, Cincinnati, Ohio, April, 1990.
U.S. EPA. Ultraviolet radiation/oxidation technology. Applications Analysis Report. EPA/540/A5-89/012,
U.S. Environmental Protection Agency, Cincinnati, Ohio, 1990. 69 pp.
75
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Chemical Treatment of Contaminated Soiis: APEG
Michael A. Smith
Clayton Environmental Consultants, Ltd.
68 Bridgewater Road, Berkhamsted, Hertfordshire HP4 1JB
United Kingdom
ABSTRACT
The conversion of halogenated compounds (particularly PCB's) in contaminated soils into far less harmful
products may be carried out using an alkaline metal hydroxide with polyethylene glycol (APEG). Processes of this
type are applicable to soils and soil-like materials (after excavation) contaminated with either aromatic or aliphatic
chlorinated organic compounds; the latter require more rigorous treatment conditions.
In general terms, the reagent (APEG) dehalogenates the pollutant to form a gylcol ether and/or a hydroxylated
compound and an alkali metal chloride which are water soluble. There are many variants of the general process,
many covered by patents etc. The most widely used version uses potassium hydroxide in combination with
polyethylene glycol to form a polymeric alkoxide anion referred to as KPEG. The end products of the technology are
regarded as nontoxic and having minimal environmental impact.
7.1 Introduction
This chapter is about the chemical treatment, or
dehalogenation, of soils contaminated with chlorinated
organic compounds, using an alkaline metal hydroxide
with polyethylene glycol (APEG). A schematic draw-
ing of an APEG application is shown in Figure 7-1.
The soil is screened to remove debris and large ob-
jects, homogenized, and reduced in size to allow treat-
ment in the reactor without the soil binding to the mixer
blades and to permit close contact of the contaminants
with the reagents. Because water inhibits the reaction,
it may be necessary to dry the soil before treatment.
Typically the reagents are mixed thoroughly with
the contaminated soil in a reactor which is heated to
100 to 180 ฐC (the range 25-150 ฐC has also been
quoted (U.S. EPA 1989b). The reaction proceeds for 1
to 5 hours depending upon the type, quantity and con-
centration of the contaminants. The treated material
goes from the reactor to a separator where the reagent
is removed and can be recycled.
During the reaction, water vaporizing from the reac-
tor is condensed and collected for further treatment or
recycling through the washing process, if required.
Carbon filters are used to trap any volatile organics
that are not condensed. The soil is washed with water
to remove residual reagents and products, and
neutralized by the addition of acid. It is then dewatered
before disposal. The treated soil may be returned to
beneficial use with appropriate amendment with fer-
tilizers etc.
7.1.1 Applicability
APEG processes are applicable to contaminants in
soils, sludges, sediments and oils. These processes
are mainly used to treat chlorinated aromatic or
aliphatic organics such as polychlorinated biphenyls
(PCB's), polychlorinated clibenzo-p-dioxins (PCDD),
polychlorinated dibenzofurans (PCDF's),
polychlorinated terphenyls (PCTP's), chlorobenzenes,
and some halogenated pesticides and herbicides.
The concentrations of PCB's treated are reported
to be as high as 45000 mg/kg (4.5 percent); con-
centrations in this case were reduced to less than 2
mg/kg per individual PCB congener (U.S. EPA 1990).
However, there are reported to be limitations to the
-------
Chapter?
Waste Treatment
141
^ ฐM".
Soils and ^pp^c 7<
>. ป*"ป. X"V .4 tf-^^
Wll*rl * l**^
r|
ES Wasn Water ^/ ^ wisri WnMDf '
Reactor ฃ to Recyao ^ ฃ to Rปcyaซ J
Now oaoCMd Iron GMBQO Rซm*dtfbon Carp, Icr Booz. Aปซo A Hamilton Inc
Figure 7-1. Schematic diagram of a typical glycol dehalogenation treatment facility.
process with regards to lower weight Arociors; DMSO-
based processes may not work on Aroclor 1240 for
example (see below).Polychlorinated dibenzo-p-
dioxins (PCCD's - "dioxins") and poiychlorinated
dibenzofurans (PCDF's - "furans") have been treated
to nondetectable levels at ng/kg (parts per trillion) sen-
sitivity (U.S. EPA 1990).
APEG technology, preferably using the reagent
KTEG (potassium tetraethylene glycol), will
dehalogenate aliphatic compounds but higher
temperatures and longer reaction times are required
than for aromatic compounds.
7.1.2 Variations on the APEG Process
The most widely used variant of the process uses
potassium hydroxide (KOH) with polyethylene glycol
(PEG) to form a polymeric alkoxide anion, referred to
as KPEG. This acts as an effective nucleophile and as
a phase-transfer catalyst (Komel and Rogers 1985).
The presence of oxygen is an essential requirement of
the process. The reactions involved are shown
schematically in Figure 7-2.
In some KPEG reagent formulations to treat
chlorinated aromatics, dimethyl sulfoxide (DMSO) is
added to reduce the reaction time. Sofolane (SFLN -
tetrahydrothiophene) may also be used to accelerate
the reaction.
Although potassium hydroxide has been the most
widely used reagent, sodium hydroxide has been used
In the past and may be used increasingly in the future
because of lower costs. Other possibilities include
combinations of potassium or sodium hydroxides with
tetraethylene glycol (ATEG).
Proprietary variations include the "APEG-PLUS"
treatment system which uses potassium hydroxide
with DMSO marketed by the Galson Remediation Cor-
poration and one offered by SDTX Technologies Inc
who own the Fuller Institute patents (e.g. Pytlewski
andKrevitz 1983).
The United States Environmental Protection Agen-
cy (U.S. EPA) has devoted effort to the development of
KTEG (potassium tetraethylene glycol) processes for
the treatment of halogenated aliphatic compounds
(Kernel and Rogers 1985; Harden and Ramsay 1986;
Rogers and Kernel 1987). When KTEG is used, a
dehydrohalogenation reaction occurs. Halogenated
compounds with one carbon atom react to form carbon
dioxide and potassium halide. Compounds containing
more than one carbon react to form acetylene (Rogers
and Kernel 1987; Harden and Ramsay 1986). KTEG
has been shown on a laboratory scale to work with
compounds such as ethylene dibromide, carbon
tetrachloride, ethylene dichloride, chloroform and
dichloromethane (Harden and Ramsay 1986; Rogers
and Kernel 1987).
7.1.3 Operational Requirements
Land is required for the operating plant, and for the
safe and secure storage of reagents, soil to be treated,
oversize material prior to crushing or disposal, and for
treated soil pending certification that treatment has
been;effective.
78
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Chemical Treatment of Contaminated Soils: APEG
HO-PEG + KOH
Aryl-ci + KO-PEG
Aryl-0-PEG
> KO-PEG -f H2O (1)
> Aryl-O-PEG + KC1 ....(2)
> Aryl-OH + Vinyl-PEG (3)
Note: In reaction (1) the polyethylene glycol (PEG) is reacted
with potassium hydroxide to form the reactive KPEG species. This
preparative step may be performed directly in the contaminated
matrix or externally. Reaction (2) takes place takes place over a
wide temperature range from ambient to about HOC. Reaction (3)
represents the conversion of the ether linked PEG/Aryl moeity to
a phenolic with consequent release of a vinyl terminal
polyethylene glycol.
Equation (4) below represents this overall reaction.
R-(C1)_+ A-PEG
-OR1
AC1
Figure 7-2. APEG reactions.
A supply of water is required. Energy is required to
dry the materials to be treated, heat the reaction ves-
sel, and to dry the treated materials. Electric power
and a steam generating plant will be required; accord-
ing to the U.S. EPA (U.S. EPA 1989b), a full-scale
dehalogenation plant with a batch capacity of 60 m3
(80 yd3) requires an average of 670 kilowatts, (U.S.
EPA 1989b). Such a plant might be expected to treat
120-150 m3 (160-200 yd3) in one working day.
On-site analytical facilities, including extraction
equipment and gas chromatography/mass
spectrometry, are required to monitor inputs and out-
puts from the process. Perimeter air monitoring may
be required.
Contaminated soils and reagents are hazardous
and a safety plan is required to ensure personnel
safety, safety in plant operation, and to protect.the en-
vironment.
7.2 Case Study Chosen
Only one case study was included in the
NATO/CCMS Pilot study: the U.S. EPA's SITE (Super-
fund Innovative Technology Evaluation) Demonstra-
tion at Wide Beach, New York (U.S. EPA 1989a; U.S
EPA 1991b; U.S. EPA 1991 a). This involved applica-
tion of a KPEG process to the treatment of PCB-con-
taminated soils in combination with a complex four-
stage "thermal processor".
7.2.1 Background
The Wide Beach site is located in a residential area
south of Buffalo, New York. From 1968-1978, PCB
(Aroclor 1264) contaminated waste oil was used for
dust control on local roads at Wide Beach. About
155,000 liters of oil were applied. Following installa-
tion of a sewer in 1980, excavated contaminated soil
was used as fill in residential gardens (yards) and a
community recreation area.
Soil contamination in the area ranged from 0,18 to
1026 mg/kg in samples collected from residential
driveways, roadways and drainage ditches. PCB con-
centrations in excess of 10 mg/kg were detected at
depths of up to 1 meter in the soil in drainage ditches;
in general, these concentrations reached only to about
0.15 to 0.3 meters in depth. It was estimated that
21,700 tonnes (15-16,000 m3) of soil were con-
taminated; about 43,000 tonnes of soil were actually
processed.
A cleanup target of not more than 2 mg/kg was set
(U.S. EPA 1989a; AOSTRA 1990).
79
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Chapter?
7.2.2 The KPEG Demonstration Project
The remedial action at Wide Beach consisted of:
Excavating soils with PCB concentrations greater
than 10 mg/kg from all areas
Excavating contaminated asphalt material from
roadways for disposal off-site, with uncon-
taminated material being retained for reuse
Treating the PCB contaminated soils in a con-
tinuous process using an Anaerobic Thermal
Processor (ATP) in association with a KPEG
process
Using the cleaned soil as fill in excavated areas
ป Repaving the roadways and driveways
ซ Treating perched water in the sewer trench (this
water has been found to contain up to 10 ng/l
PCB's).
Afterthe work was completed, the residences were
thoroughly cleaned to remove any stray dust, etc.
(See Figure 7-3 for the overall flow of materials. See
Appendix 7-A for a more detailed discussion of the
process.)
7.3 Performance Results
The continuous-processing ATP technology was
demonstrated in May 1991. Key findings of the
demonstration were:
ซ The ATP unit removed PCB's in the contaminated
soil to levels below the desired cleanup con-
centration of 2 mg/kg. PCB concentrations were
reduced from an average concentration of 28.2
mg/kg in the contaminated feed soil to an average
concentration of 0.043 mg/kg in the treated soil.
ซ The ATP does not appear to create dioxins and/or
furans.
ป No volatile or semivolatile organic degradation
products were detected in the treated soil. There
were also no leachable VOC's or SVOC's
detected in the treated soil.
No operational problems affecting the ATP's
ability to treat the contaminated soil were ob-
served.
7.4 Residuals and Emissions
There are three main process streams: the treated
soil, the wash water and, possibly, air emissions.
The treated soil will need to be analyzed to deter-
mine if it meets treatment objectives and/or regulatory
requirements for disposal or re-use. The soil's acidity
must be adjusted to a suitable value before disposal or
reuse.
Research by the U.S. EPA has shown the by-
product compounds to be neither toxic nor otherwise of
concern (see for example Komel and Rogers 1985).
However this will only be the case if the process is
carried out properly and dechlorination is complete. If
full dechlorination is not achieved, toxic residual
materials may remain (see Limitations below).
Waste wash water should contain only trace
amounts of contaminants and reagents, and should
meet appropriate discharge standards enabling it to be
disposed to public sewer or surface water, subject to
the usual licensing and regulatory requirements.
7.5 Limitations
Factors limiting the effectiveness of glycolate treat-
ment include highly concentrated contaminants
(greater than 5 percent), high water content (greater
than 15 percent), low pH (less than 2.0), high humic
content (soil), and the presence of alkaline-reactive
materials (e.g., aluminium or other metals).
7.5.1 Inherent in the Technology
Although shown to be effective for a wide range of
chlorinated hydrocarbons in a range of media, there
are limitations to its effectiveness with regard to certain
compounds such as lighterweight Aroclors (e.g., 1240,
1242) and hexachlorobenzene. This has been at-
tributed, at least in the case of the latter (Rogers et al.
1991), to steric hindrance caused by the bulky nature
of the attacking nucleophilic reagent, polyethylene
glycoxide.
The apparent lack of information on the long term
stability of the resulting products in the soil environ-
ment may also be limiting in some applications be-
cause it may be considered that the initial nontoxic
nature of the reaction products can not be guaranteed
to last.
These potential difficulties appear to be overcome
in the combined thermal and KPEG treatment used at
Wide Beach which appears to result in complete
destruction of PCB's through combined chemical and
thermal action.
7.5.2 Health and Safety
Treatment of certain chlorinated aliphatics in high
concentrations with APEG may produce compounds
that are potentially explosive (e.g. chloroacetlylenes)
and/or cause a fire hazard. The use of DMSO or
similar reagents may result in the formation of highly
flammable volatile organics (e.g., methyl sulphide).
Alkaline reactive materials such as aluminium can
result in formation of hydrogen. Vapors from heating
oily soils, which are often the matrix in which PCB's
are found, can also create such potential problems as
80
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Chemical Treatment of Contaminated Soils: APEG
a i
a>
.2
s
(0
I
TJ
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81
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Chapter?
fires and noxious fumes. These potential problems
can all be overcome by appropriate process design.
The process must also be conducted with care be-
cause of the elevated temperatures and production of
steam, the use of caustics in the process, and the
acids used in neutralization. If DMSO is used, care
must be taken to prevent contact of DMSO with skin. It
is a powerful solvent and skin penetrant, and enhan-
ces transport of PCB's through the skin, thus increas-
ing the risk of exposure. KTEG processes are
exothermic and can produce vinyl halides as inter-
mediate compounds. Special considerations will there-
fore apply in the design of plants to operate these
processes (Harden and Ramsay 1986).
7.6 Costs
In September 1990 US$, costs were put at $220-
550/tonne ($200-500/short ton).
One vendor quoted the average cost of treatability
studies as US$2000-3000 depending on the chemistry
of the target contaminant(s). Treatment costs were es-
timated to be $130-390/m3 ($100-$300/yd3) depending
on site-specific factors (U.S. EPA 1989b).
Costs at the Wide Beach demonstration site had
been estimated (U.S. EPA 1989a) as likely to be about
$6,000,000 to treat about 15,000 m3 (20,000 yd3) of
soil to achieve a level not greater than 2 mg/kg, i.e.,
about $390/m3 ($300/yd3). In practice, the contract
value for the work was $15,500,000. Information on
the details of this value is not available, nor is informa-
tion on the cost of treating the larger than expected
volume of soil (23,000 m3) that was actually treated.
7.7 Factors to Consider for Determining
Applicability of the Technology
Studies on materials to be treated should include
determination of the nature and quantities of individual
organic compounds present, and investigation of the
presence of moisture, alkaline metals, organic matter
content (humic content), clay content, glycol extrac-
tables content, presence of "multiple phases" and total
organic halides, and other factors that have the poten-
tial to affect processing times, effectiveness and costs.
The major difficulty is devising means to reduce
processing times sufficiently to permit practical treat-
ments to be effected.
Laboratory treatment studies should be carried out
to determine optimum operating factors such as type
and quantity of reagent to use, temperature and treat-
ment time.
7.8 Future Status of the Technology
The KPEG technology demonstrated in Wide
Beach has been selected for application for treatment
of soils and sediments containing 500 to 500,000
mg/kg PCB's at Waukegan Harbour north of Chicago
(de Percin 1991).
Batch processes of this type have also been shown
to be effective in terms of reducing contaminant levels
to acceptable concentrations in a number of applica-
tions (for example see Peterson 1990).
Variants of the process are available from a num-
ber of vendors. It is expected that work will continue to
incorporate the dechlorination process with other treat-
ment steps to ensure effective application to a range of
contaminants and media. In addition, it is expected
that efforts will be made to overcome the limitations to
effectiveness mentioned above.
It should be noted however, that competitor tech-
nologies are being developed. One process in par-
ticular is catalytic transfer hydrogenation (Rogers et al.
1991) in which hydrogen is the reacting nucleophile. It
is claimed that this process overcomes the problems of
steric hindrance associated with the use polyethylene
gylcol, and is thus capable of bringing about total
dechlorination with formation of non-toxic reaction
products.
In contrast, reports that quick lime might be an ef-
fective treatment agent for PCB's have been shown
not to be true (U.S. EPA 1991 c; Sedlaket al. 1991).
REFERENCES
AOSTRA Taciuk processor performing soil cleanup. The TARpaper, Vol.13, No.4,1990.
de Percin, P. SITE demonstration of the TACIUK thermal desorption process at the Outboard Marine Corp.,
Waukegan Harbour, Illinois Site, 1991. Appendix 7-D to this report.
Harden, J. M. and Ramsay, G. C. Catalytic dehydrohalogenation: A chemical destruction method for
halogenated organics. EPA/600/2-86/113, U.S. Environmental Protection Agency, Cincinnati, 1986.
Heller, H. Poultice method for extracting hazardous spills. U.S. Patent 4483716,1984.
Komel, A. and Rogers, C. PCB destruction: a novel dehalogenation reagent. IQ: Journal of Hazardous
Materials, 12,161-176,1985.
Peterson, R. L. Methods for decontaminating soil. U.S. Patent 4447541, 1984.
82
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Chemical Treatment of Contaminated Soils: APEG
Peterson, R. L. Method for reducing content of halogenated aromatics in hydrocarbon solutions. U.S.
Patent 4530228, 1985.
Peterson, R. L. Method for decontaminating soil. U.S. Patent 4574013,1986.
Peterson, R. L. APEG-Plus: dechlorination of soils and sludges. In: Proceedings of the Symposium Haz-
ardous Waste Treatment: Treatment of Contaminated Soils, Cincinnati, Ohio, (Air & Waste Manage-
ment Association, Pittsburgh 1990) pp. 94-99,1990.
Pytlewski, L. L. and Krevitz, K. Method for decomposition of halogenated organic compounds U S Patent
4400552,1983.
Rogers, C. J. and Kernel, A. Chemical destruction of halogenated aliphatic hydrocarbons. U S Patent
4675464, 1987. :
Rogers, C. J., Kernel, A. and Sparks, H. L. Base catalyzed decomposition of toxic and hazardous chemi-
cals. U.S. Environmental Protection Agency, Cincinnati, 1991.
Sedlak, D. L., Dean K. E., Armstrong, D. E., and Andren, A. W. Interaction of quicklime with
polychlorobiphenyl-contaminated solids, in: Environmental Science and Technology, Vol 25 No 11
1936-1940,1991. '
Taciuk, W. The AOSTRA-TACIUK thermal pyrolysis/desorption process, 1991. Appendix 7-B to this report.
Taciuk, W. and Ritcey, R. M. PCB decontamination of soils and sludges with the Taciuk process. In:
Proceedings HAZTECH CANADA, 4th Annual Environmental Conference, Calgary, 1991.
U.S. EPA. Chemical on-site treatment utilizing KPEG process at Wide Beach, New York. Emergency
Response Division, U.S. Environmental Protection Agency, November 1989.
U.S. EPA. Innovative technology: glycolate dehalogenation. U.S. Environmental Protection Agency, Direc-
tive 9200.5-245S, 1989.
U.S. EPA. Chemical dehalogenation treatment, in: APEG Treatment. U.S. EPA Engineering Bulletin
EPA/540/2-90/015. U.S. Environmental Protection Agency, 1990.
U.S. EPA. Demonstration plan for the Taciuk Thermal Processor at the Wide Beach development site:
Demonstration Program Draft Report, U.S. Environmental Protection Agency. March 1991.
U.S. EPA. AOSTRA-SoilTech anaerobic thermal processor treats PCBs in soils at Wide Beach develop-
ment Superfund site in Brant, New York. U.S. Environmental Protection Agency, Cincinnati. 1991.
U.S. EPA. Fate of polychlorinated biphenyls (PCB's) in soil following stabilization with quicklime.
EPA/600/2-91/052, U.S. Environmental Protection Agency Office of Research and Development
Washington DC, 1991.
83
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8
Microbial Treatment Technologies
SjefStaps
Grontmij nv
P.O. Box 203, 3730 AE De Bilt
The Netherlands
ABSTRACT
A large number of organic contaminants can be degraded by microorganisms. The compounds can vary from
easily degradable compounds like monocyclic aromatics to more xenobiotic compounds like chlorinated aliphatics.
Basically, biological soil remediation techniques can be divided into three groujps: in situ biodegradation,
landfarming and composting, bioreactors.
An advantage of biological treatment is its cost-effectiveness. On the other hand, the treatment period is relatively
long, ranging from a few weeks for composting up to a few weeks to several years for in situ biorestoration. Also,
when treating soil biologically, it is typical that, depending on the type of soil and contaminant, some residual
concentrations will remain after treatment. It has to be determined whether these low residual concentrations can
be regarded as safe.
Given the high level of international research in microbial treatment, it is expected that the scope of application
will be broadened in the coming years.
This NATO/CCMS Pilot Study included five case study reports regarding microbial treatment. In addition, as a
NATO/CCMS Fellowship project, the study "International evaluation of in situ biorestoration of contaminated soil and
ground water" was conducted. These studies are discussed in this chapter.
8.1 Introduction
A large number of organic contaminants can be
degraded by microorganisms. The compounds can
vary from easily degradable compounds like
monocyclic aromatics (e.g., benzene) to more
xenobiotic compounds (e.g., trichloroethylene, a
halogenated hydrocarbon).
Biological treatment techniques for contaminated
soil and ground water aim at optimizing conditions for
promoting biodegradation of organic compounds
therein. These factors are related to characteristics of
the chemical compound, soil, and the indigenous
population of microorganisms.
The chemical compound and its degradation path-
way are decisive for the environmental characteristics
to be chosen. For example, an aerobic environment
should be chosen in the case of nonhalogenated con-
taminants, and an anaerobic environment should be
chosen in most cases of halogenated contaminants,
since the fastest degradation occurs under these con-
ditions.
The purpose of biological treatment is the degrada-
tion of contaminants to harmless intermediates and
end products to such a degree that the remaining con-
centrations of contaminants and degradation products
are below the applicable standard. The ultimate goal is
to reach complete mineralization of the contaminants,
that is, degradation into CO;> and HaO.
Basically, biological soil remediation techniques
can be divided into three groups:
In situ biodegradation
Landfarming and composting
-------
Chapter 8
Bioreactors.
The first technique is applied In situ; the latter two
are applied on- or off-site.
In situ biodegradation of soil and ground water aims
at the stimulation of the biological degradation of con-
taminants in the subsurface environment. Usually a
recirculation system for ground water is installed. Con-
taminated ground water is treated above ground, after
which oxygen and, if necessary, nutrients are added to
the water that infiltrates the soil, in order to stimulate
the indigenous microorganisms to degrade con-
taminants. The ground water treatment can consist of
an air stripper for volatile contaminants or a biological
treatment for dissolved contaminants.
Also, activated carbon filters are often used. Con-
taminants in the exhaust air from an air stripper can be
removed by means of activated carbon or a biofilter
with compost.
In addition to In situ biorestoration by means of
recirculation of water, venting can be applied in order
to stimulate the indigenous microorganisms to degrade
contaminants and to remove volatile contaminants in
the unsaturated zone.
With landfarming, contaminated soil is spread out
over a certain land surface up to a thickness of about
0.40-0.60 meters. If necessary, nutrients are added.
Regularly, the soil is mixed by means of agricultural
implements in order to increase the biological
degradation.
Composting is a treatment similar to landfarming.
However, the soil is placed on heaps and materials
such as wood chips or compost are usually added to
facilitate the oxygen distribution through the heaps.
Bioreactors are used to treat more recalcitrant com-
pounds, such as polynuclear aromatic hydrocarbons
(PAH's). A soil-water(-air) system is used, in which
several environmental factors can be controlled and
maximized for optimal degradation.
8.2 Case Studies Chosen
The NATO/CCMS Pilot Study included five case
studies regarding both in situ and on- or off-site
microbial treatment technologies. In addition to these
case studies, a NATO/CCMS Fellowship project under
the Pilot Study was conducted: "International evalua-
tion of in situ biorestoration of contaminated soil and
ground water (Staps 1990)." In this Fellowship project,
21 in situ biorestoration projects in The Netherlands,
Germany, and the United States were visited and
evaluated. Because of the evaluating character of the
Fellowship project, its results run through the "in situ"
part of this chapter as a continuous thread.
A short description of the case studies is given
below. Longer discussions are included in Appendix
8.
8.2.1 In Situ Projects
8.2.1.1 Case Study 8-A: Aerobic/Anaerobic In Situ
Degradation of Soil and Ground Water,
Skrydstrup, Denmark
The purpose of the project was to verify whether
full-scale cleanup of ground water is possible using in
situ biodegradation of chlorinated solvents.
Four separate research approaches to biorestora-
tion have been initiated:
Biodegradation of chlorinated solvents in con-
taminated soil
Aerobic biodegradation of chlorinated solvents by
addition of methane
Aerobic biodegradation of chlorinated solvents in
the unsaturated zone by co-metabolism by oxida-
tion of methane and/or propane gas
Anaerobic biodegradation of chlorinated solvents
in the contaminated zone by addition of sodium
acetate.
8.2.1.2 Case Study 8-B: In Situ Biorestoration of Soil,
Asten, The Netherlands
The objective of this research and demonstration
project is to study the technical and financial feasibility
of in situ biorestoration of a subsurface soil con-
taminated with oily substances. The approach of the
project started from a literature study (1983) and
laboratory research, continued with column studies,
and is ending up with a full-scale cleanup (started in
1990). Field data are currently not available. A
simplified schematic is shown in Figure 8-1.
8.2.1.3 Case Study 8-C: In Situ Enhanced Aerobic
Restoration of Soil and Ground Water,
Eglin Air Force Base (AFB), United States
The project includes a full-scale biodegradation re-
search project at a JP-4 jet fuel spill site on Eglin AFB
near Ft. Walton Beach, Florida, United States. A treat-
ment system was designed to compare the operational
benefits and limitations of the following three hydrogen
peroxide/nutrient application methods:
Injection wells
Infiltration galleries
Spray irrigation.
Figure 8-2 shows the system flow diagram.
8.2.2 Ex Situ Projects
8.2.2.1 Case Study 3-D: Biological Pre-treatment of
Ground Water, Bunschoten, The Nether-
lands
The subject of this project is the pretreatment of
ground water contaminated with hexachloro-
86
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Microblal Treatment Technologies
IN SITU BIORESTORATION OF A SUBSOIL
stripping
1000-2000
>2000
100 - 1000
(mg gasolinei/kg)
discharge
Figure 8-1. Cross-section of the soil with an overview of the restoration process.
cyclohexane (HCH, a pesticide), chlorobenzene, and
benzene. The project concerns some small-scale ex-
periments with a trickling filter and a rotating biological
contactor. A simplified schematic is shown in Figure
8-3. The applied method is based on the following four
main processes:
Washing of contaminants from the soil by en-
hanced recirculation of purified water
Purification of the pumped-up water by reverse
osmosis (RO)
Biological purification of the concentrate of RO
(without inoculation)
, In situ biodegradation of contaminants in the soil.
; The present concept will be tested in a large-scale
pilot project in The Netherlands.
8.2.2.2 Case Study 8-E: notary Composting Reactor
for Oily Soils, Soest, The Netherlands
This biological treatment method was developed for
off-site decontamination of oil-contaminated soil at
field capacity. First, laboratory-scale studies were car-
ried out in order to determine the optimum environ-
mental conditions for oil degradation. Then the
(research) project was carried out at a former
municipal solid waste composting installation. The soil
was treated in the rotating bio reactor, in which the soil
temperature, oxygen, moisture, and nutrient levels can
be adjusted. A schematic of the biological treatment
process in the rotating bioreactor is shown in Figure
8-4.
87
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Chapter 8
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INFLUENCE
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\
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O RECOVERY MEU.
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^ EJECTION WELL
Figure 8-2. Eglln AFB Site profile.
8.3 Background of the Case Study Sites
as a Group
When regarding the group of case study sites, it is
evident that there is considerable heterogeneity. For
example, the contamination sources include a chemi-
cal waste disposal site, a (former) gas and kerosene
station, and a pesticide production facility. A municipal
composting installation was also studied in relation to
biodegradation.
These sources were responsible for the following
range of contaminants:
CWorinated solvents
Petrol
JP-4 (an aviation fuel)
ป Hexachlorocyclohexane (HCH, a pesticide) in dif-
ferent forms
ซ Diesel oil.
These contaminants are typical of the compounds
that generally can be biologically degraded. They
range from the easily degradable petrol to the more
recalcitrant chlorinated compounds. Typically, the in-
dividual projects have to deal with a specific group of
contaminants like mono-aromatic hydrocarbons,
polynuclear aromatic hydrocarbons, or chlorinated
hydrocarbons. Each of these groups has its own re-
quirements for degradation.
Another example of the diversity of the project sites
is that some required the treatment of soil, some of
ground water, and some of both soil and ground water.
Biodegradation was applied within the projects as fol-
lows:
In situ treatment of both soil and ground water (in
combination with on-site biological and chemi-
cal/physical treatment).
On-site treatment of the ground water (both with
and without physical/chemical treatment). :
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MIcroblall Treatment Technologies
On-site treatment of the soil (after excavation).
In two cases, the treatment was combined with ex-
cavation; in one case the waste from a chemical waste
disposal site was excavated, after which in situ bio res-
toration of the ground water was applied. In a second
case, the soil was biologically treated on site after
being excavated.
8.4 Performance Results
In general, degradation results were assessed in
relation to the original site concentrations of the con-
taminants (percent degradation). In order to get insight
into the risks of the intermediate or residual concentra-
tions, standards like the Dutch Examination
Framework for Soil Pollutants were used in several
projects.
from raw water basin
to raw water basin
RBC's
Figure 8-3. Flow diagram of the RBCs and compost filters.
Figure 8-4. Biological treatment process in the rotating bioreactor.
89
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Chapter 8
Different countries require widely varying clean-up
standards. For example, a project in The Netherlands
started with a concentration level of mineral oil in the
soil that in Germany is regarded to be a sufficient level
of reclamation.
8.4.1 Common Effectiveness of Process Units
IN SITU BIORESTORATION
In situ biorestoration can technologically and finan-
cially compete with other technologies when it is ap-
plied at a suitable location and the process is well run.
The remediation time can vary between a couple of
months and several years, and is largely dependent on
the initial concentrations, the kind of contaminants, the
soil structure, and the cleanup requirements.
In The Netherlands, an Examination Framework for
soil pollutants has been set up. In this Framework,
three different indicative values can be distinguished:
* A - Reference value
ป B - Indicative value for further investigation
ป C - Indicative value for cleaning up.
In principle, the A-value must be reached when
cleaning contaminated soils in The Netherlands.
Residual concentrations below B-level, or even un-
detectable levels, have been reached with in situ
biorestoration in projects for petrol, kerosene, diesel
oil, fuel oil, mineral oil, and certain chlorinated
hydrocarbons (e.g., 4-chloro-2-methylphenol) (Staps
1990).
In situ blodegradatlon of contaminated ground
water (Case Study 8-A). Laboratory tests showed that
tetra-chioroethylene (PCE), trichloroethylene (TCE)
and 1,1,1-trichIoroethane (TCA) in sewage sludge can
be degraded under anaerobic conditions. Lower
chlorinated compounds are formed.
It was not possible to achieve anaerobic degrada-
tion of PCE, TCE or TCA in laboratory tests on sedi-
ment from the Skrydstrup aquifer. This might be due
to the fact that there has not been a restricted
anaerobic environment in the upper part of the aquifer.
It was possible to build up a methane-oxidizing
blomass which was able to degrade TCE and 1,1,1-
TCA, but not PCE.
The ground water at Skrydstrup contains high con-
centrations of chlorinated aliphatics. Therefore, the
toxicHy of 1,1,1-TCA and TCE towards a mixed culture
of methane-oxidizing bacteria was examined in batch
experiments. The consumption of methane was in-
hibited, even by small concentrations of 1,1,1 -TCA and
TCE. A total inhibition of the methane consumption
was observed at a TCE concentration of 13 mg/L,
whereas a total inhibition was not observed at a 1,1,1-
TCA concentration of 103 mg/L. Experiments also
showed that the presence of methane inhibited the
degradation of TCE.
Accumulation of dichloroethanes and
dichloroethenes was observed in the leachate from the
two sites of excavated soil from Skrydstrup, showing
that anaerobic biodegradation had occurred at both
sites. A significant amount of the contaminants from
both sites has been removed, but it could not be deter-
mined how much had been removed by biodegrada-
tion and how much had been removed by other
processes, such as stripping.
A pilot plant for aerobic on-site biodegradation of
chlorinated aliphatics in ground water has been estab-
lished at Skrydstrup. The plant was operated with dif-
ferent hydraulic retention times, in order to optimize
the degradation of the chlorinated aliphatics. It was
possible to obtain degradation of TCE of 40 percent
with a hydraulic residence time of 3.5 hours. At the
same time, a methane consumption of 85 percent was
observed. Degradation of TCA did not occur. About 10
percent of 1,1,1-TCA and TCE were stripped. The
plant was operated with alternating addition of
methane to avoid competition between methane and
chlorinated aliphatics, but it did not result in an in-
creased degradation of TCE.
EX SITU BIODEGRADATION
Rotating biological contactor for biodegrada-
tion of HCH in ground water (Case Study 8-D).
Over 90 percent removal of HCH, benzene, and
chlorobenzene in the rotating biological contactor
(RBC) can be attributed to biodegradation. Volatiliza-
tion and adsorption onto the sludge are of minor impor-
tance to the total removal. aHCH and yHCH show a
degradation rate of up to 70 percent. 8HCH shows little
breakdown, while eHCH and (3HCH concentrations in
the RBC remain constant. The mineralization of con-
taminants is complete; there were no metabolites
found with gas chromatography/mass spectroscopy
analysis.
Rotary composting bioreactor (Case Study 8-E).
The production-scale trials of the rotary composting
bioreactor indicate that, at a soil temperature of ap-
proximately 22 ฐC, the oil can be degraded. This
process starts with concentrations up to 6000 mg oil/kg
dry soil, and drops within one week to a residual con-
centration, varying from less than 50 to 350 mg/kg dry
soil. In this process, the greatest microbial activity oc-
curs in the first 3-4 days. In processes where other
circumstances are present (temperature, oxygen con-
tent, humidity), results will be different.
Compost filter. Compost filters can be used to
treat off-gas, mainly from air strippers that are used to
remove volatile components from ground water on
site. The system is based on adsorption of the con-
taminants on compost material, followed by
biodegradation by microorganisms. Generally, perfor-
mances of compost filters for treatment of air show
poor results (i.e., approximately 70 percent for a broad
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Microbial Treatment Technologies
range of compounds). This is regardless of whether
there is a mixture of compounds or an individual com-
pound present.
8.4.2 Effectiveness of the Rotating Composting
Bioreactor on Diesel Fuel
The approach in Case Study 8-E of using a com-
posting installation for biological treatment of soil con-
taminated with diesel fuel is rather unique.
Consequently, it has unique effectiveness for a biologi-
cal system. Relatively low residual concentrations
(less than 50-350 mg oil/kg dry soil) can be achieved in
a relatively short time period (one week).
8.4.3 Lessons Learned on How to Improve
Effectiveness
In situ biorestoration. Recirculation of the ex-
tracted ground water has positive effects on soil
biodegradation. The reason for this is not yet precisely
known. It might be due to the fact that surfactants,
which are produced by microorganisms, are recircu-
lated through the contaminated soil. Another explana-
tion can be that the recirculating water contains
degradation products, which can more easily be
broken down than the original contaminants. In this
way, there is an extra stimulation of the microbial ac-
tivity, which influences the total biodegradation.
The positive effect of the addition of surfactants is
still questionable. Fundamental research and practical
experience indicate that the effect on degradation is
negative. Detergents that can be applied need to be
biodegradable (the original contamination should not
be replaced by contamination with surfactants). How-
ever, in several research projects microorganisms
preferred these surfactants as a food source and
degraded the original contamination less than before
surfactant addition.
When applying surfactants, clogging problems also
occurred, due to complex interactions between soil
surfactants, soil particles, contaminants, and microor-
ganisms.
Addition of microorganisms to the subsoil, with the
aim of enhancing the biodegradation, is being used by
a few companies on a field scale. These microor-
ganisms can either be selected in the laboratory or can
be cultured at the laboratory after being sampled from
the contaminated site. Although this approach has
some potentially beneficial effect, it has not been
proved to date. Cost-benefit calculations are unavail-
able.
The experiences with hydrogen peroxide (H2O2) as
a supplemental oxygen source are not consistent with
respect to effectiveness. While in the Asten project
hydrogen peroxide was chosen as the most promising
oxygen source after laboratory research, the results
with H2O2 in the Eglin project are very disappointing.
Currently, there is no explanation for this difference in
results. The differences may be due to enzymatic
breakdown of H2O2 or due to abiotic degradation.
Another cause could be the different temperatures
in Florida and The Netherlands. As long as the ef-
ficiency of hydrogen peroxide cannot be predicted,
preliminary (field) treatability testing is necessary when
considering its application.
Venting of volatile contaminating compounds in the
unsaturated zone and treatment of these components
above ground can be a cost-effective method for
removal compared to in situ biorestoration by means of
recirculation of water. Apart from the volatilization of
contaminants, venting will enhance biodegradation be-
cause of the extra oxygen supply. Also combinations
of venting in the unsaturated zone and the application
of a water recirculation system can be cost-effective.
Off-site biorestoration. The application of an off-
site rotating bioreactor for degrading oily contaminants
(Case Study 8-E) is one waiy of improving the effec-
tiveness of off-site biological! soil treatment compared
to other biological techniques like landfarming and in
situ biorestoration.
8.4.4 Lessons Learned In Site Preparation and
Testing
The success of in situ biorestoration, as all in situ
technologies, largely depends on the permeability of
the soil. Since the soil itself is used as a bioreactor, the
permeability is the gate to the degradation. When per-
meability is limited, in situ biorestoration is adversely
affected.
If the permeability of the soil allows in situ biores-
toration, the most important limitation (for oily con-
taminants) is usually oxygen supply. In fact, in
demonstration projects, oxygen is always the limiting
factor. Understanding the behavior of oxygen in the
subsoil and the possibilities for enhancing oxygen
supply are the prime technological challenges to im-
proving in situ biorestoration effectiveness.
Because of the general complexity of soils, the
degradation process can never be predicted complete-
ly. Therefore, preliminary testing and evaluation, both
in the laboratory and in field tests, will always be
necessary. The field tests should include oxygen
utilization rates and potential clogging problems.
These clogging problems can occur as a result of the
reaction of oxygen with iron or manganese present in
the soil. Clogging can also be caused by excessive
bacterial growth, due to the stimulation of microbial ac-
tivity.
Biodegradation is necessarily limited to those or-
ganic compounds that can be degraded biologically.
To date, there is a broad range of compounds that
have been proved in principle to be biologically
degradable. As research continues, more and more
compounds can be added. Continued research and
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Chapter 8
demonstration will be needed to achieve biodegrada-
tion in the field.
Some contaminants seem to be only biodegradable
in the presence of other, easily degradable con-
taminants. This degradation is called co-metabolism.
For example, chlorinated alkenes can be degraded in
the presence of oxygen and methane, while methane-
oxidizing bacteria (methanotrophs) obtain energy from
the oxidation of methane. The enzyme
monooxygenase, which then is formed, brings about
the degradation of chlorinated alkenes (McCarty et al.
1989;Janssen etal. 1987).
Inoculation with (selected) microorganisms has not
been shown to improve degradation results. In most
cases, the indigenous population, which has been
adapted to the specific contamination present, can be
stimulated in order to reach comparable degradation
results. It is expected that the strategy and technology
of isolating and selecting microorganisms will be most
beneficial for very specific contaminants.
8.5 Residuals and Emissions
The residuals and emissions from biological treat-
ment can be divided into the following categories:
ซ Residual concentrations of contaminants and in-
termediates in soil and ground water
Emissions of contaminants and intermediates
with the ground water being discharged
ซ Emissions of contaminants and intermediates into
the air.
When treating soil biologically, it is typical that,
depending on the type of soil and contaminant, some
residual concentrations will remain after treatment. It
has to be determined whether these low residual con-
centrations can be regarded as safe. Attention should
also be paid to compounds that can be formed by
faiodegradation and in certain cases appear to be
resistent to further degradation.
A similar problem is the presence of residual con-
centrations in the ground water; site-specific charac-
teristics determine whether or not low concentrations
of contaminants should be accepted as safe in the
ground water to be discharged.
The above mentioned subjects of concern are also
applicable to the exhaust air from either soil venting,
(biological) ground water treatment, or composting.
Petrol-contaminated soils should not be treated in a
rotating bioreactor without provisions to reduce emis-
sions of volatile aromatics into the air. At the Soest
project no significant emissions of aromatics from
dlesel-polluted soils were measured. However, at the
beginning of the incubation, hydrocarbon emissions of
up to a lew hundred mg/m3 may sometimes occur.
The use of activated carbon to treat air emissions is
a relatively expensive treatment method; consequent-
ly, a compost filter is potentially very welcome. How-
ever, the effectiveness of compost filters generally is
rather poor. Catalytic oxidation can be a good alterna-
tive for larger amounts of contaminants in air to be
treated.
8.6 Factors and Limitations to Consider
for Determining Applicability of the
Technology
A general advantage of biorestoration is the fact
that it is an "environmentally sound" technology; there
is very little or no generation of waste products. Atten-
tion should be paid, however, to the formation of inter-
mediates, which in some cases, can be more harmful
than the original contaminant (for example
tetrachloroethylene degrading to vinyl chloride).
Another advantage of biological treatment is its
cost-effectiveness. Off-site landfarming will generally
be cheaper than alternative techniques like thermal
treatment or soil washing after excavation. On the
other hand, the treatment period is relatively long,
ranging from a few weeks for composting up to one or
two seasons for landfarming.
In situ biorestoration is often more cost-effective
than in situ soil washing, largely due to the shorter time
period that is needed for cleanup.
As mentioned earlier, it is typical that biological
treatment will leave some residual concentrations of
contaminants in the soil. This is caused by limitations
in the "bio-availability" of contaminants at low con-
centration levels. The problem of bio-availability is not
fully understood. Several factors might play a role.
The concentrations may be too low to be favorable as
an energy source for the microorganisms, or the con-
centrations can be too low to induce the production of
certain enzymes necessary for biodegradation.
In certain countries, such as The Netherlands, the
limited capability of microbial treatment to reach low
residual concentrations may lead to limited or no pos-
sibilities for application. For example, the relatively low
residual concentration of less than 50-350 mg/kg dry
soil achieved in the Soest project is still higher than the
A-level defined in the Interim Soil Clean-up Act (50
mg/kg dry soil for soil containing 10 percent organic
matter). ' '."..
As regards in situ biorestoration, the permeability of
the soil is a very important parameter. Generally, a Kf-
value of 10'5 m/s is regarded as being the minimum
permeability required for successful application.
When considering the use of biological treatment,
the following should be considered:
Biological treatment in general
, ป Biodegradability of contaminant(s)
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Microbial! Treatment Technologies
Microbial parameters (total cell count, nitrifiers,
denitrifiers, hydrocarbon degraders)
Inoculation
Oxygen and redox conditions
Oxygen demand (TOC, DOC, BOD)
Ntotai, NH4+, NOa, NOa concentrations
Phosphate concentration
Nutrient demand
Contaminant degradation rate
Bio-availability
pH
Temperature
Concentration of potential toxic components
Mass balance (contribution of biodegradation ver-
sus vaporization)
Formation and fate of intermediates
Residual concentrations of contaminant and inter-
mediates.
In situ biorestoration
Partition of contaminants in soil and ground water
Soil permeability
(Geohydrological) isolation
Fe and Mn concentrations
Heterogeneity of the soil
Behavior of the oxygen source in the subsoil and
effectiveness of providing oxygen to microor-
ganisms.
Biological treatment of ground water
Partition of contaminants in soil and ground water
Soil permeability.
Ex situ biological soil treatment
ป Consequences for excavation and transport
Partition of contaminants in soil and ground
water.
When cleaning up contamination of both the soil
and ground water, the partition of contaminants be-
tween soil and ground water is important. Most con-
taminants will be present both in an adsorbed form on
soil particles and in a dissolved form in the ground
water. The monitoring of the cleanup process can at
first be based on the concentrations of contaminants in
the ground water. When low concentrations in the
ground water have been reached and there is a very
slow decline in concentrations, the recirculation
process should be stopped for a while in order to allow
the concentrations in soil and ground water to reach a
new equilibrium. This must be repeated several times.
Only when the concentrations in the ground water do
not rise after a period of rest and the concentrations in
the soil are sufficiently low, can termination of the
remedial action be considered.
8.7 Costs
In situ biorestoration. A wide range of site- and
system-characteristics and remedial objectives influen-
ces the total costs for in situ biorestoration projects.
Included are:
ซ Geology and soil structure
Type and concentrations of contamination
ซ Distribution of contamiinants in the subsoil
Total surface and volume of the contaminated
area
System characteristics: recirculation, water and
gas treatment, etc.
In the case of the Asten site (Case Study 8-B), total
costs for in situ biorestoration of a sandy soil and
ground water contaminated with petrol are estimated
to be about 70-80 percent of the costs for excavation
and treatment off-site. As regards total costs, a great
advantage of in situ biorestoration for industrial sites is
the fact that commercial activities can be continued
during the cleanup period; because the process occurs
largely in the soil itself, there is no need for stopping
industrial activities.
For smaller sites, like petrol stations, costs vary be-
tween 40 and 250 US$/m3 (1990). For larger sites,
costs are estimated up to 150 US$/m3. Of these costs,
operating and maintenance costs account for about
two-thirds of the total costs. Generally, approximately
one-third of the cost is due to preliminary research and
installation costs, which occur in about equal amounts
(Staps1990).
If applicable, in situ biorestoration will in many
cases be more cost-effective than other techniques,
such as incineration, or soiil washing of the excavated
soil plus treatment of the ground water (approximately
70-170 US$/m3 excluding excavation and transport
costs).
On-site biological treatment of ground water.
The on-site treatment of HCH-contaminated ground
water with the rotating biological contactor (RBC) is es-
timated to lead to a cost reduction of at least 30 per-
cent (with costs ranging from US$102,000 to
US$130,000) compared to using activated carbon plus
physical/chemical treatment alone (costing
US$175,000). In Table 8-1, treatment costs are given
in relation to treatment techniques and removal ef-
ficiencies. For a combined biological/physical/chemical
treatment, costs have been calculated for three dif-
ferent biological removal efficiencies. Also costs for a
one-stage physical/chemical treatment without biologi-
cal pretreatment are given.
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Table 8-1. Costs of control techniques by levels of pollutant removal efficiency (in US$).
Removal efficiency, RBC
Costs
HCH
70%
60%
20%
0
Benzene/
Chlorobenzene
95%
95%
60%
0
RBC
55,000
45,000
17,500
-
Activated
carbon
7,500
10,000
50,000
100,000
Physical/
chemical
installation
40,000
50,000
62,500
75,000
Total
102,500
105,000
130,000
175,000
8.8 Future Status of Case Study
Processes and Microbial Treatment
as a Whole
8.8.1 Future Status of Case Studies
Results of demonstration tests on applying biologi-
cal treatment as a substitute to airstripping at the
Skrydstrup site (Case Study 8-A) are promising.
Therefore, additional experiments will be carried out
and full-scale treatment is likely to be applied. As the
operation of the airstripping unit brings along high
energy costs, biological methods are regarded as a
very relevant alternative to bring down operation costs.
The monitoring of soil will continue with additional
microbiological investigations in the two compart-
ments.
The laboratory and column studies related to the
Asten site (Case Study 8-B) were finished in 1989. The
full-scale cleanup was started in 1990 and is expected
to be finished in 1992.
Because of the poor results obtained in using
hydrogen peroxide at the Eglin site (Case Study 8-C)
and cost estimates that were very high for cleanup, the
Air Force decided not to cleanup the site with in situ
bforestoratfon.
The research project related to RBC-application for
on-stte ground water treatment at Bunschoten (Case
Study 8-D) was finished. Because of the project
results, rt was recommended that more biological tech-
niques like RBC's should be applied in ground water
remedial action, especially for (chlorinated) aromatic
contaminants.
Based on the results of the rotating bioreactor at
Soest (Case Study 8-E), it cannot be guaranteed that
the A-ievel for mineral oil, required by The Nether-
lands, will be achieved by soil treatment in the bioreac-
tor. Therefore, there are no practical applications for
this kind of biological cleaning of oil-contaminated soil
in The Netherlands.
8.8.2 Future Status of Microbial Treatment In
General
Given the level of international research in the area
of microbial treatment, it is expected that the scope of
application will be broadened in the coming years.
More compounds will be proven to be susceptible to
microbial degradation. Thus, the importance of
microbial treatment might improve in the future. How-
ever, the status of microbial treatment will depend on
the residual concentrations that can be reached and
the standards that have been set by the authorities.
For example, in The Netherlands, the applicability of
microbial degradation is limited because of the relative
severely standards.
Available research indicates that there is a factor
called "bio-availability", which refers to limits on the
availability of the contaminants in the soil to the water.
In order to be available for microorganisms, the con-
taminants must be dissolved in the water. Bio-
availability is of major concern for compounds with a
low water solubility. This is one of the current
obstacles for broadening the field to the further ap-
plication of microbial treatment.
As regards the range of compounds that can be
degraded by means of microbial treatment, there can
be a further extension of applicability to other com-
pounds like PAHs or other chlorinated compounds.
The permeability of the soil will remain a specific limita-
tion for the application of in s/fc/biorestoration.
The status of microbial treatment for ground water
is expected to have more possibilities for growth, be-
cause here the microbial treatment is often followed by
a polishing step, for example, with activated carbon.
The philosophy here is that every bit of biological
degradation that can happen first helps reduce total
treatment costs when alternative and more expensive
technologies must be added at the end.
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Microblal Treatment Technologies
REFERENCES
Janssen, D.B., Grobben, G. and Witholt, B.H. Toxicity of chlorinated aliphatic hydrocarbons and degrada-
tion by methanotrophic consortia. in: O.M. Neijssel, R.R. van der Meer and K.C.A.M. Luyben, (Eds.),
Proceedings of the Fourth European Congress on Biotechnology, Vol. 3. Elsevier Science Publishers,
Amsterdam, 1987.
McCarty, P.L., Semprini, L. and Roberts, P.V. Methodologies for evaluating the feasibility of in situ
biodegradation of halpgenated aliphatic ground water contaminants by methanotrophs. Proceedings,
AWMA/EPA Symposium on Biosystems for Pollution Control, Cincinnati, Ohio, Feb. 21-22,1989.
Staps, S. International evaluation of in situ biorestoration of contaminated soil and ground water RIVM-
report no. 73878006,1990.
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Selecting Remedies at a Complex Hazardous Waste Site
Thomas O. Dahl
United States Environmental Protection Agency
National Enforcement Investigations Center, Denver, Colorado 80225
United States
ABSTRACT
Selecting remedies at a complex hazardous waste site is a difficult but necessary process. Countries use a variety
of approaches. This chapter uses the Stringfellow Site in California, United States (U.S.) as a case study to describe
the process used by the United States Environmental Protection Agency (U.S. EPA) and examine remedial selection
problems of mutual concern to many countries. The environmental problem at the Stringfellow Site and the remedy
selection process are described. Major conclusions include:
Selecting remedies at a complex site requires a methodical approach to move from uncertainty to rational
decisions.
Flexibility within the process must be maintained to address inevitable unforeseen circumstances.
ป Conducting treatability studies as eariy as possible and arriving at conclusions from interim remedies are
important in effective remedy selection.
Constructing remedies is not the final chapter in cleaning up complex sites; long term monitoring is required
to validate remedial hypotheses and to determine success.
9.1 Introduction
Selecting remedies at a complex hazardous waste
site is a difficult, but necessary process. A variety of
approaches are used by countries. The process
selected by a given country is driven by such variables
as sense of urgency, philosophical approach, degree
of experience and funds available. To illustrate the
process used by the U.S. and to highlight areas of
mutual concern for many countries, a case study is in-
cluded below. This case study describes the remedy
selection process at a U.S. site.
During the 1950's, southern California was under-
going rapid post-war industrial growth. One unfor-
tunate outcome was the generation of increasing
amounts of hazardous waste. Consequently, the State
of California began seeking safe disposal sites for
these waste products. This search led to Pyrite
Canyon, a box canyon on the southern slopes of the
Jurupa Mountains, approximately 80 kilometers (50
miles) east of Los Angeles, California (see Figure 9-1).
nderlying the shallow alluvium in Pyrite Canyon is
bedrock of metamorphic arid igneous origin. It was
reasoned that the combination of the bedrock floor, a
cemented alluvial cone, and the construction of a con-
crete barrier dam across the surface drainage channel
could provide a suitable location for a disposal site.
In 1955, the Stringfellow Quarry Company received
a permit to operate a hazardous waste disposal facility
in the canyon. The 6.9 hectares (17 acres) disposal
site was operated from 1956-1972 and consisted of as
many as 20 surface impoundments (see Figure 9-2).
About 200 industries sent 130 million liters (34 million
gallons) of liquid industrial process wastes containing
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Chapters
Figure 9-1. Location of the Stringfellow Waste Disposal
Site.
spent acids and caustics, solvents, pesticide by-
products, metals, and other inorganic and organic con-
taminants to the site by trucks which discharged the
wastes into the ponds.
In 1968, site operators noted soil discoloration on
the downgradient side of the concrete barrier dam.
Over the next several years, the site had an increasing
number of problems. These problems included surface
water overflow during heavy rains, and the ap-
pearance of inorganics in ground water at the site
monitoring well which was over 1,000 meters (3,400
feet) downgradient from the site. These events cul-
minated in November 1972 with the voluntary closing
of the site and, despite subsequent efforts to reopen it,
the site's land use permit was revoked in 1974. Sub-
sequently, the site reverted to the State of California
because the owners had not paid taxes.
9.2 Interim Studies/Remedies
Between 1975 and 1982 the State of California
conducted studies and implemented interim remedies
at the site, though with limited budgets. The studies
determined that:
ป The cemented alluvial cone was underlain by an
alluvial, permeable stream channel extending to
about 27 meters (90 feet) below grade.
100- 0 100' CTO-
SCALE IN FEET
LtOENP
ป CONCRETE DAM
ป COLLECTION SUM*
AREAS CONSIDERED
T0 " CONTAMINATED
FROMFONOSFRAV
Figure 9-2. General site configuration by 1972 for dis-
posal operations.
The bedrock underlying the downgradient end of
the site and the concrete barrier dam were frac-
tured, providing potential pathways for off-site
contaminant migration.
Ground waters were entering the site from
upgradient springs.
Permeable, alluvial materials existed next to both
ends of the concrete barrier dam, providing addi-
tional potential pathways of contaminant migra-
tion.
Site-related contaminants, including metals and
chlorinated organics, were found in ground waters
at and downgradient from the site.
Interim remedial actions conducted during this
period included:
Millions of liters of on-site pond liquids were
hauled off-site for disposal.
Pond bottoms and soils from the northern half of
the disposal site were excavated down to bedrock
and moved to the southern half of the site.
Lime kiln dust was disked into surface materials
of the southern half of the site; kiln dust was
placed over the entire disposal site. These ac-
98
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Selecting Remedies at a Compllex Hazardous Waste Site
tions were taken in an unsuccessful effort to
neutralize the highly acidic wastes.
French drains were placed along bedrock lows in
the northern half of the site to carry subsurface
liquids to a sump from which they could be
pumped to off-site storage and disposal.
* An east-west clay-core barrier dam approximately
240 meters (800 feet) long was constructed near
the old concrete dam, from canyon wall to canyon
wall and from surface to bedrock.
A french drain was placed at the upgradient base
of the clay core barrier dam to take hydraulic
pressure off the dam and carry liquid to two
sumps for pumping to off-site storage and dis-
posal.
Silica gel was injected into fractured bedrock un-
derlying the clay core dam in an effort to seal frac-
tures.
The disposal site was covered with an ap-
proximately 0.3 meter (1 foot) layer of clayey
material, and then a 0.3 meter (1 foot) layer of
topsoil.
A surface drainage system was installed on the
sides of the disposal site to carry uncontaminated
runoff around the site.
A 14-well monitoring network was installed
downgradient from the site.
Approximately 760 cubic meters (1,000 cubic
yards) of DDT-contaminated soil were removed
from the site and disposed of offsite.
Two mid-canyon extraction wells were con-
structed approximately 600 meters (2,000 feet)
downgradient from the barrier dam.
In 1980, things changed in many ways when the
U.S. passed the Comprehensive Environmental
Response, Cleanup and Liability Act (referred to as
"Superfund") to deal with abandoned hazardous waste
sites such as Stringfellow. In 1982 the site was placed
on the U.S. EPA's National Priority List (NPL) as
California's highest ranked site. Including the site on
the NPL made it eligible for Superfund remedial action
money.
9.3 Litigation
Work done at the Stringfellow site up to 1982 was
significant but not sufficient to fully define the areal and
vertical extent of contamination or to mitigate all con-
tamination. By the fall of 1982, U.S. EPA had iden-
tified approximately 200 industries that had sent
wastes to the site. Under Superfund, U.S. EPA
notified these industries, as well as former
owners/operators/transporters, that they had been
identified as Potentially Responsible Parties (PRP's)
and tried to have them acpept responsibility for neces-
sary studies and remedies.
Efforts toward a, PRP-led cleanup failed, and in
April 1983 the U.S. and State of California filed suit
against 31 of the PRP's in U.S. District Court. The
industries involved represented over 80 percent of the
liquid volume that had been disposed at the site.
These litigation efforts continue in one of the most
heavily litigated cases in the U.S. While these efforts
continue, U.S. EPA pays for the necessary
studies/remedies with the intent of recovering costs
from the responsible parties. In addition, the U.S. EPA
and the State of California meet regularly with a techni-
cal committee of PRP companies to discuss site
developments and to encourage PRP participation in
necessary studies/remedies;.
9.4 The Remedial Investigation/Feasibility
Study (RI/FS) Process
In 1983, the U.S. and State of California decided to
conduct a Remedial Investigation/Feasibility Study
(RI/FS) at the Stringfellow site to determine the areal
and vertical extent of contamination, assess risks, and
select remedies.
The process which U.S. EPA uses to select
remedies is specified in the National Oil and Hazard-
ous Substances Pollution Contingency Plan (NCP)
and is shown in Figure 9-3; the process seeks to
gather progressively more and more detailed informa-
tion. Once the agency receives information that there
may be a problem, it conducts a Preliminary Assess-
ment, which'makes use of readily available information
to see if further action is necessary. If it is, a Site In-
spection is conducted which gathers more extensive
information, perhaps including some sampling.
Data collected during the Preliminary Assess-
ment/Site Inspection phases are put into a site scoring
model. If the numeric score is high enough, the site is
placed on the National Priorities List and a RI/FS is
conducted. Throughout the process, investigators
must be aware of the need for short term actions (e.g.,
removal of leaking drums, construction of a security
'fence, etc.); these are termed "Removal Actions" by
the U.S. EPA. Similarly, if it becomes apparent during
the often lengthy RI/FS process that interim remedial
actions are called for (e.g., construction of a leachate
treatment plant), they should be started rather than
waiting for the whole process to be completed.
Once a decision has been made to conduct a
RI/FS, a planning or Scoping phase is begun. This
phase includes activities such as:
Meeting with study participants to discuss impor-
tant issues and assign responsibilities.
99
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Chapter 9
FROM:
Preliminary
Assessment
Site
Inspection
NPL
Listing
SITE ; TREATABILITY
CHARACTERIZATION: INVESTIGATIONS
SCOPING
OF THE
RI/FS
DEVELOPMENT
AND
SCREENING
OF
ALTERNATIVES
DETAILED
ANALYSIS OF
ALTERNATIVES
TO:
Remedy
Selection
Record of
Decision
Remedial
Design
Remedial
Action
Figure 9-3. U.S. Superfund remedy selection process.
Evaluating existing data to develop a conceptual
site model to assess the problem as it is under-
stood at the time and to identify potential ex-
posure pathways and health and/or environmen-
tal receptors.
Beginning limited field investigations, if existing
data are not adequate to scope the project.
Identifying preliminary remedial action objectives
for each contaminated medium, and likely
remedial actions. These will change with time as
more information becomes available, but concep-
tualizing early is extremely useful.
ซIdentifying the preliminary criteria that will apply to
site characterization and remediation. There can
be many of these, particularly if several regulatory
agencies exist; if criteria can be identified early,
the site investigators can use them as work goes
on.
ป Determining data needs and the level of analytical
and sampling certainty required for additional data
collection. For example, initial data may show
that a problem exists but may not be enough to
define actual risks or select remedies.
ซ Evaluating the need and setting the schedule for
treatability studies to better evaluate potential
remedial alternatives.
Designing a data collection program that
describes sampling and analytical requirements.
Often jt is difficult to balance between a concern
for controlling costs and perfection. However,
one must not forget that the resulting process
must yield conclusions that can be defended and
from which the site can be characterized and the
problem solved.
Developing a work plan that documents the scop-
ing process and outlines anticipated future tasks.
Identifying health and safety protocols required
during field investigations and preparing a site
health and safety plan. As one learns more about
the problem, these may have to change to reflect
greater or lesser threats.
Meeting with the community and developing a
community relations plan. The studies and
remedy implementation may take much time; and
it is extremely important to establish a program
that both keeps the public well informed and asks
for its input.
Once the scoping phase of the RI/FS process is
completed, a Site Characterization phase is begun.
This consists of:
Conducting field investigations. Some of the
primary effort includes defining the areal and ver-
tical extent of contamination and degree of threat
100
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Selecting Remedies at a Complex Hazardous Waste Site
to health and the environment. Determining how
much data to collect is always a difficult task, and
as mentioned earlier requires a balance between
a concern for controlling cost and perfection.
ซ Analyzing field samples. Many analytical techni-
ques, some at high cost, are available to the in-
vestigator. Again there must be a balance which
gets the job done without spending too much of
the available funds on the analyses and leaving
too little for the remedies. Much attention must
also be given to quality assurance/quality control
methods to assure that the investigator can draw
conclusions that can be defended.
Evaluating the results of the data analysis to char-
acterize the site and develop a baseline risk as-
sessment. The baseline risk assessment is
designed to provide an evaluation of the potential
threat to human health and the environment if
there was no remedial action. It provides the
basis for determining whether or not remedial ac-
tion is necessary and for justifying the remedial
actions. The assessments include contaminant
identification, exposure and toxicity assessments,
and risk characterization. Where possible, as-
sumptions (such as dose/response relationships,
standard ingestion rates for receptors, etc.)
should be standardized to remove variables from
this difficult analysis.
Determining if data are sufficient for developing
and evaluating potential remedial alternatives. As
field investigations continue and data are
analyzed, new concerns often arise beyond those
which were identified at the beginning. For ex-
ample, additional contaminants may be identified
which are not treatable by the same technologies
(e.g., extractable versus volatile organics).
Therefore, it is not uncommon to have to rescope
investigative approaches to address these con-
cerns. The use and acceptance of such a
dynamic process is very important. If the process
is rigid, the result may be a well conducted, but
entirely inadequate investigation.
The Development and Screening of Alternatives
phase of the RI/FS process is one which can be
described as iterative, but in fact is part of the neces-
sary thought process which begins at the time of Scop-
ing. It includes:
Identifying remedial action objectives. As dis-
cussed above, the earlier these can be identified
the better so that the investigations can be
designed to address them.
Identifying potential technologies that will address
these objectives. Often there will be a variety of
technologies that are potentially applicable. For
example, if there is a volatile organics comtamina-
tion problem, both activated carbon and air strip-
ping are potentially applicable technologies.
Later evaluations may demonstrate that one is
more appropriate for use than the other (e.g., be-
cause of cost, presence of other organics, etc.).
Screening the technologies. Various criteria are
possible; the U.S. EPA uses effectiveness, im-
plementability, and cost. In general, one should
use a set of criteria that eliminates technologies
that are not applicable. For example, if the
presence of a particular contaminant makes a
technology ineffective, or if the necessary depths
of application are not achievable, those tech-
nologies should be screened out. The screening
mechanism selected should attempt to balance
the desire to reduce options as quickly as pos-
sible against the desire; to leave options open for
finally selecting the "right" remedial option.
Assembling technologies into remedial alterna-
tives that address the problem. Again the U.S.
EPA uses the criteria of effectiveness, implemen-
tability, and cost. Effectiveness focuses primarily
on whether the alternative protects human health
and the environment. Implementability focuses
on the technical aspects (i.e., the ability to con-
struct and successfully operate) and administra-
tive aspects (e.g., the ability to obtain approvals
for using the alternative). Cost focuses on rela-
tive comparisons between alternatives, recogniz-
ing that a high degree of accuracy is not possible
at this stage. There i;> a wide range of alterna-
tives which can be developed. The U.S. EPA
develops a range which has as its upper end an
alternative which prevents, as much as possible,
the need for any long term management of
residuals and untreated wastes. The lower end of
the range is a "no action" alternative. The best
approach is to find a cost-effective alternative that
satisfies the upper end of the range. However,
this is not always possible for any number of
reasons, including the important variables of high
costs and technical uncertainty.
If available data are insufficient to evaluate the
remedial alternatives, Treatability Investigations
(bench and/or pilot scale) may be necessary. The
point at which these can be conducted varies; they
should be conducted as early as possible within the
process. In some cases the need can't be predicted
until the screening process has begun. For example,
as studies continue and more data become available,
it may become clear that a certain technology seems
to be promising (i.e., anticipated cost or performance).
In these cases, extra time will be required to perform
the necessary treatability studies and then resume the
remedial selection process.
101
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Chapter 9
The next step in the RI/FS process is the Detailed
Analysis of Alternatives. The criteria which are used
by U.S. EPA for this analysis are:
Overall protection of human health and the en-
vironment
ซ Compliance with "applicable or relevant and ap-
propriate requirements" (ARAR's)
Long term effectiveness and permanence
Reduction of toxicity, mobility, or volume through
treatment
ป Short term effectiveness
Implementability
Cost
ป State acceptance
ป Community acceptance.
Each alternative is analyzed against each criterion
and then compared against one another. This iden-
tifies strengths and weaknesses so that U.S. EPA can
evaluate the alternatives and prepare a Proposed
Plan. This plan, which summarizes the remedial alter-
natives and identifies a preferred alternative, is
presented to the public for comment. After considering
the comments received, U.S. EPA documents the
remedial alternative chosen in a Record of Decision.
Then the selected alternative is designed and con-
structed.
Successful construction of facilities is not the end of
the process. It is extremely important that a com-
prehensive monitoring system be designed and imple-
mented. Since there is not enough long term
experience with remedies, it is a good idea to start with
a system that errs on the high side for monitoring
points, parameter coverage, and frequency of sam-
pling. As experience is gained, these can be
diminished or modified to reflect new information. It is
also important to select and use statistical techniques
to characterize cleanup over time. Apparent changes
may be subtle or misleading, and statistical sig-
nificance is necessary for decisions over time. Initial
predictions of cleanup times should be viewed with
caution, as considerable uncertainty often accom-
panies the necessary calculations.
9.5 Stringfellow Site RI/FS
Beginning in 1984, a large number of technical site
studies (see Table 9-1) and treatability studies (see
Table 9-2) were conducted at and near the Stringfellow
Site as part of the RI/FS process. Most of these were
conducted under the direction of the State of California
and the U.S. EPA. Several were conducted for com-
panies that had originally sent wastes to the site. Be-
Table 9-1. Stringfellow Site technical studies.
Environmental (soil, air, water) sampling
Geology/hydrology
Fault/fracture survey
Geophysical
- Electromagnetic conductivity
- Resistivity
- Seismic
Soil gas sampling
Hydraulic testing
Ground water modeling
Air modeling
Risk assessments
cause it was increasingly clear that completion of the
RI/FS process for this complex problem would take
much time, numerous additional interim remedies were
implemented. To date, these have included:
Table 9-2. Stringfellow Site treatability studies.
Reverse osmosis
Carbon adsorption optimization
Carbon regeneration
Incineration
Metals precipitation
Air stripping
Ultraviolet oxidation
Dewatering tunnel (conceptual study)
Ion exchange
Stabilization/solidification
Rotating biological contactor
Ultrafiltration
Additional technology evaluations (ongoing)
' Provision of an alternate drinking water supply to
approximately 500 residents of nearby Glen
Avon, California to protect them from potential
hazard exposure.
' Diversion of surface waters around and from the
on-site area to prevent contamination.
102
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Selecting Remedies at a Complex Hazardous Waste Site
Interception and diversion of shallow uncon-
taminated ground water upgradient of the site.
Improvement of surface drainage patterns.
Construction of a pretreatment plant in the mid-
canyon area to remove metals and organics from
on-site, mid-canyon and lower canyon extracted
ground waters. Treatment includes lime and
sodium hydroxide additions for metals removal
and activated carbon for organics removals.
Treated waters are taken to a sewer drop station
and then discharged offshore in the Pacific
Ocean. The plant began operation in late 1985,
and by January 1992 had successfully treated
about 170 million liters (45 million gallons) of con-
taminated ground water.
Installation of a subsurface french drain
downgradient from the barrier dam to intercept
shallow, contaminated ground water for later
treatment at the pretreatment plant.
Installation of additional mid-canyon extraction
wells to improve the efficiency of the capture sys-
tem. The intercepted water is sent to the pretreat-
ment plant.
Establishment of a systematic ground water
monitoring program to detect any encroachment
of site-related contaminants.
Installation of a lower canyon extraction well sys-
tem approximately 1,200 meters (4,000 feet)
downgradient from the barrier dam to capture
ground water contaminants that otherwise would
flow into the community (PRP companies imple-
mented this interim remedy).
In 1987 the Remedial Investigation (Rl) report was
released to the public; some of the major conclusions
included:
On-site Conditions
Approximately 83 million liters (22 million gallons)
of contaminated ground water are held in uncon-
solidated soil and rock material on-site. An un-
determined amount of contaminated ground water
is in the fractured bedrock underlying the site.
Contaminated ground water was found as deep
as 60 meters (200 feet) below land surface in
bedrock wells.
Most contaminants on-site were found in the
. ground water; the on-site soil (alluvium/fill) is not a
,, primary source of mobile contaminants (solvents,
metals, etc.). Mobile contaminants were found al-
most exclusively in the ground water.
Contaminated ground water is moving
downgradient from the site, leaving the site al-
most entirely through the fractured bedrock under
the subsurface barrier wall. Sulfates were found in
percentage concentrations, heavy metals in 10O's
of mg/L, and volatile and extractable organics in
mg/L ranges.
ซ The site contains over 600,000 cubic meters
(800,000 cubic yards) of unconsolidated soil and
rock (alluvium, decomposed rock and metamor-
phic rock) that contains contamination.
The on-site barrier/extraction system intercepts
and recovers over 80 percent of the potential
ground water leakage from the site.
ซ The composition and distribution of on-site con-
taminated soils, rocks, and ground water are ex-
tremely heterogeneous.
Soils beneath the low permeability site cover but
above the water table are principally con-
taminated with pesticides, polychlorinated
biphenyls (PCB's), parachlorobenzene sulfonic
acid (p-CBSA), a DDT by-product, and traces of
slightly water soluble organic compounds. These
soils are also acidic and contain several heavy
metals at levels above natural background.
ซ" The pesticides and PCB's in the unsaturated
soil/fill on-site are immobile. The remaining low
levels of soluble organiics and metals can be mo-
bilized by leaching through ground water infiltra-
tion.
The on-site soil/fill below the water table has
many of the same insoluble organic compounds
in it as the unsaturated zone; however, levels of
water soluble organics and heavy metals are
much higher and appear to be associated with the
ground water.
Downgradient Conditions
ซ A plume of contaminated ground water extends
over 3 kilometers (2 miles) downgradient from the
site and ranges from 60 meters (200 feet) to
about 270 meters (900 feet) wide (Figure 9-4).
The Stringfellow-related contaminants found in
this plume under the community of Glen Avon in-
clude several organic solvents (trichloroethylene,
chloroform, chlorobenzene, dichlorobenzene),
sulfate, and p-CBSA.
Heavy metals in the ground water extend about
600 meters (2,000 feet) downgradient from the
site; they have been tied up or precipitated out in
the aquifer materials upgradient of this point.
Under 1985/86 water level conditions, which are
affected by significant mid-canyon extraction,
ground water flux past canyon cross sections is
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Chapter 9
SUBSURFACE CLAY
BARRIER mm GEL
INJECTION BENEATH^.
ON-StTEAReA
>,ซ,**"*""ป ^TVป
v'! "*<^
, HID CANYON TREATMENT
Figure 9-4. Approximate location of TCE contaminated ground water that extends from the Stringfellow Site into
Glen Avon.
estimated to increase from about 45 to 57 liters
per minute (12 to 15 gallons per minute) in the
upper portion of Pyrite Canyon below the site, to
about 110 liters per minute (28 gpm) just north of
Highway 60 (1,500 meters or 5,000 feet
downgradient of the site).
ป The two original mid-canyon extraction wells are
estimated to extract about 50 to 60 percent of the
total ground water flow through the mid-canyon.
The addition of five more interception wells in the
mid-canyon in late 1986 increased this fraction.
" Contaminated surface runoff can discharge from
the site during sustained rainfall. Under present
conditions, no measurable amounts of surface
water contamination have been found further than
600 meters (2,000 feet) downgradient of the site.
ซ Surface soils within 300 meters (1,000 feet) south
of the site have been contaminated at concentra-
tions above existing environmental standards.
Within the zone extending about 300 meters
(1,000 feet) downgradient of the barrier,
measurable contamination by site-related con-
taminants was also found in subsurface soils.
Public Health Evaluation
Before starting interim abatement actions in 1980,
the pathways for exposure to the contaminants in-
cluded air, surface water, soils, and ground water;
now, the primary exposure pathway of concern is
migrating contaminated ground water.
The combined maximum lifetime risk from ex-
posure to ground water contaminated with
trichloroethylene (TCE) and chloroform in the
community area, if used for drinking water, ex-
ceeds the U.S. EPA's risk guidelines (i.e., a car-
cinogenic risk ranging from 1 in a million to 1 in
10,000 cancer occurrences).
Without site remediation and ground water
cleanup, the contaminants which have already
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Selecting Remedies at a Complex Hazardous Waste Site
migrated below the mid-canyon extraction system
will continue to; migrate downgradient, adding to
the risk of exposure for the local community.
Air emissions modeling indicates that, even if the
on-site cap/cover were removed to excavate the
underlying contaminated materials, there would
be only a minimum threat to the residents of Glen
Avon.
Contaminated surface soils in the first 300 meters
(1,000 feet) downgradient from the site's subsur-
face barrier system are a potential risk to in-
dividuals in Pyrite Canyon by breathing in air-
suspended dust under severe wind conditions.
Continual airborne dust from this zone will not
reach the community area, and the levels of soil
contamination in this zone are not an ingestion or
skin contact health risk.
Subsurface soils within 600 meters (2,000 feet)
downgradient of the site are accumulating
precipitated and adsorbed contaminants from
migrating ground water. While there is no human
health threat now, this zone must be considered a
secondary contamination source during remedia-
tion planning.
9.6 Remedy Selection at Stringfellow
The data compiled during the technical and
treatability studies were evaluated to determine ap-
propriate remedies. As part of the Feasibility Study
released in 1988, 86 technologies were screened for
potential application; 30 were retained for remedial al-
ternatives selection. Seven remedial alternatives were
chosen from these technologies and were analyzed in
detail using the nine criteria discussed earlier.
The seven remedial alternatives ranged from the
no action alternative to one which included incineration
of on-site contaminants (Table 9-3). As one would ex-
pect, these alternatives spanned a wide range of an-
ticipated costs. A "low cost" alternative, the on-site
natural flushing and downgradient plume cleanup op-
tion, was estimated to have a 30-year present worth
cost (assuming a 7 percent discount rate) of ap-
proximately US$131 million (1989 $). A "high cost" al-
ternative, the on-site soil incineration and
downgradient plume cleanup option, was estimated to
cost about US$742 million (Table 9-4).
A Preferred Alternative was selected which in-
cluded:
Dewatering the on-site area with extraction wells
Implementation of soil-gas extraction for volatile
organics removal in the on-site area, if field tests
prove favorable
Diversion of surface drainage away from the site
Table 9-3. Summary of remedial alternatives resulting
from the Stringfellow Site feasibility study.
Remedial Alternative 1
The no action alternative, would involve discontinuing on-site
(Stream A) and mid-canyon (Stream B) ground water
extraction and treatment that is presently performed. Also,
there would be no effort to minimize the generation of
contaminated leachate from the on-site area; or to clean up or
stop the further migration of the downgradient plume.
Remedial Alternative 2
Natural flushing of the on-site area, and downgradient plume
cleanup.
Remedial Alternative 3
On-site dewatering, extraction and treatment of on-site
leachate, and downgradient plume cleanup.
Remedial Alternative 4A
On-site dewatering, extraction and treatment of on-site
ieachate, in situ soil-gas extraction, in situ soil flushing, and
downgradient plume cleanup.
Remedial Alternative 4B
On-site dewatering, extraction and treatment of on-site
leachate, in situ soil-gas extraction, selective soil excavation
of higher contamination areas, soil treatment and redisposal
on-site, in situ soil flushing, and downgradient plume cleanup.
Remedial Alternative 5
On-site dewatering, extraction and treatment of on-site
leachate, full excavation of all cliggable soil, soil treatment
followed by redisposal on-site into the excavation, and
downgradient plume cleanup.
Remedial Alternative 6
On-site dewatering with extraction and treatment of on-site
leachate, in situ soil-gas extraction, additional treatability
studies of on-site soil contamination, and downgradient plume
cleanup.
i Continued extraction, treatment and sewering of
contaminated ground water from the on-site, mid-
canyon and lower canyon areas,
| Extraction, treatment and reinjection of ground
water back into the community area
i Additional studies to determine whether there is a
feasible method for further addressing on-site soil
and bedrock contamination
i Installation of a multilayered cap in the on-site
area.
105
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Chapters .
Table 9-4. Estimated cost comparison of revised remedial alternatives - overall site remedy.
RA No. 2
RANo. 3
RA No. 4A
RA No. 4B
RANo. 5
Total estimated
capital costs (million
US$)
Total estimated
present worth costs
7% discount rate
(million US$)
$40.7
$131.2
$44:2
$156.2 "
$55.5
"$197.8
$253.3
$392.3
$630.9
$741.7
RA*No. 6
Approximate time
until ground water
cleanup is achieved
(years)
Zone 1
Zone 2
Zone 3
Zone 4
448
162
40
25
Never
162
40
25
' 65
46 '
40
25
60
46
40
25
63
46
40
25
*'*
46
40
25
$64.7**
$186.0**
"RA No. 6 Is the DHS/EPA Preferred Alternative.
"Estimated time and costs for cleaning up Zone 1 are not clear at this time", the results of"on-going pilot tests of soil treatment
processes and evaluations based on EPA's nine Superfund criteria may affect what future on-site actions are taken.
The selection of ground water treatment and dis-
posal methods will address heavy metals, organics
and Inorganics, depending upon levels of contamina-
tion, and desired end uses for the treated water.
Treatability studies and experience with operating
the interim pretreatment plant which began operation
in late 1985 provided valuable information on how to
effectively treat the ground waters and what problems
to anticipate. When trying to deal with a complex site
such as the Stringfellow Site, numerous interactions
and interferences may occur. For example, on-site
ground waters at Stringfellow contain percent levels of
sulfates. When these waters are treated for metals
removal by lime addition, a large amount of gypsum
sludge is also generated. These metals/inorganics-
laden sludges in turn are disposed of off-site as, haz-
ardous wastes.
Another example of potentially hidden costs results
from the large percentages of organics that cannot be
identified by conventional gas chromatography/mass
spectroscopy (GC/MS) methods. Only about 5 per-
cent of the organic carbon in on-site ground waters at
Stringfellow is identifiable by the GC/MS methods;
therefore, more activated carbon is necessary for treat-
ment than would be predicted by using the GC/MS
results. It was also discovered that some ground
waters that appeared to be treatable by air stripping
from the standpoint of the volatiles were, in fact, not
since other compounds caused frothing which
prevented effective stripping. Making these types of
discoveries early in the remedial process is invaluable
in scoping potential remedies and selecting effective
remedies.
To date, the U.S. and State of California govern-
ments have spent approximately US$110 million on
the site. The estimated present worth cost of the
Preferred Alternative, not including implementation of
additional technologies following the planned
treatability studies, is an additional approximately
US$186 million. Cost estimates are assumed to
potentially vary by -30 to +50%.
In September 1990, the U.S. EPA signed a Record
of Decision (ROD) to implement some of the items
contained in the Preferred Alternative. Another
Record of Decision will be necessary in the future to
reflect the treatability study outcome and to make final
cleanup goals/remedy decisions. To implement the
September 1990 ROD, the U.S. EPA convinced PRP
companies to come forward, negotiate and take over
implementation of the ROD elements. Obligations un-
dertaken by the PRP's will require work into the late
1990's. Once a final ROD is issued by U.S. EPA, addi-
tional negotiations will commence regarding remedial
work that could last for the foreseeable future.
9.7 Conclusions
Selecting remedies at a complex hazardous waste
site requires a methodical approach to successfully
move from uncertainty to rational decisions. It is also
necessary to keep the investigative process flexible in
order to deal with inevitable unforeseen circumstan-
ces. As noted in this chapter as well as in others in
this report, applying lessons learned from interim
remedies and conducting treatability studies as early
as possible are also important to effective remedy
selection.
The remedial efforts conducted over the past 15
years at the Stringfellow Site have been extremely
time-consuming and costly but are, nonetheless, rep-
resentative of what can happen when there is the com-
bination of a complex problem, an aggressive
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Selecting Remedies at a Complex Hazardous Waste Site
environmental regulation, a litigation atmosphere, and
ah aroused public. Cleanup of Stringfellow site-related
contamination is, at best, many years away, The.coiv
struction of remedies is not the final chapter in clean-
ing up Complex sites such as this; long term monitoring
is required to validate remedial hypotheses and deter-
mine success. Hopefully, lessons have been and will
continue to be teamed from sites such as Stringfellow
that will be helpful to others in solving hazardous
waste site problems.
REFERENCES
California Department of Health Services. Stringfellow hazardous waste site feasibility study (Draft Final).
Sacramento, California, June 30,1988.
California Department of Health Services. Stringfellow hazardous waste site remedial investigation (Draft
Final). Sacramento, California, June 1,1987.
National Oil and Hazardous Substances Pollution Contingency Plan (NCP). 40 CFR 300,55FR8666, March
8,1990.
U.S. Environmental Protection Agency. Guidance for conducting remedial investigations and feasibility
studies under GERCLA (interim final). EPA/540/G-89/004, OSWER Directive 9355.3-01, October 1988.
107
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10
Conclusions and Recommendations
Donald E. Banning
United States Environmental Protection Agency
Office of Research & Development, Cincinnati, Ohio 45268
United States
Robert F. Olfenbuttel
Waste Minimization and Treatment, Battelle-Columbus Division
505 King Avenue, Columbus, Ohio 43201
United States
10.1 Introduction
One of the major accomplishments of this Pilot
Study was that it demonstrated the need to exchange
technical and economic information on contaminated
land and ground water remediation technologies. The
conclusions are first presented by the specific technol-
ogy chapters in this report, followed by general obser-
vations on remediation, technology transfer and
research needs. The conclusions are based on the
case studies, expert speaker presentations, and spe-
cial studies carried out by Fellows of the Pilot Study.
In addition to the conclusions, a number of recom-
mendations were made by the participants in this Pilot
Study to the North Atlantic Treaty Organization's Com-
mittee on the Challenges of Modern Society
(NATO/CCMS) in a separate Summary Report to this
final report. They address potential actions that could
be taken to increase technology development and
technology transfer for site remediation.
10.2 Specific Technology Chapter
Conclusions
The following conclusions were reached on the
basis of the case studies included in the Pilot Study, as
well as related experiences and observations of the
Study's participants. They include specific technology
needs that could be met through research, develop-
ment and demonstration activities.
10.2.1 Chapter 2: Thermal Technologies
10.2.1.1 Existing high temperature incineration (on-
and off-site) successfully destroys organic
contamination; however, not all nations
allow its use for chlorinated compounds.
High temperature incineration is a successfully
documented remediation technology that can be ap-
plied for treatment of sludges, soils, liquids and air ef-
fluents contaminated with various organic constituents.
This technology has been successfully applied in
many NATO countries, although the thermal treatment
of chlorinated organics is not allowed in at least one
country, The Netherlands,, because of concern for for-
mation of dioxins and/or furans. The technology is
currently offered by several vendors in many countries
and extensive documentation exists on its costs and
performance.
10.2.1.2 Low temperature thermal desorption is a suc-
cessful technology for treating volatile and
semivolatile wastes.
This technology, which generally operates at
temperatures below 800 "C, allows for the desorption
of volatile and semivolatile constituents from solid and
semi-solid waste. The removed constituents,
entrained in an air stream, are then processed through
a secondary treatment unit, usually a secondary com-
bustion chamber. Metal and other nonvolatile waste
components come out in the residual ash stream and
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Chapter 10
can be further processed, if necessary, for final dis-
posal.
10.2.2 Chapter 3: Stabilization/Solidification (S/S)
Technologies
10.2.2.1 S/S has been proven for the immobilization of
most inorganics.
S/S technologies, used as an isolation technology,
have been shown to be effective with many inorganic
contaminants, but not with materials containing or-
ganic chemicals.
10.2.2.2 Long term effectiveness data is not available.
The long term effectiveness of these processes has
not been proven, especially when they are applied
under field conditions (weathering, leaching, structural
durability, etc.).
10.2.2.3 Scientifically based S/S leaching tests would
provide a more easily comparable data
base than is available today.
A variety of S/S teaching tests exist today, most of
which do not have a common technical basis nor a
readily understood knowledge of their physico/chemi-
cal processes. It is, therefore, rarely possible to com-
pare S/S leaching results due to the lack of data on the
physfochemical forms of the waste treated, the chemi-
cal basis of the S/S mix, the process design used, and
the final product pH. It would be helpful, therefore, if
current leaching tests had a more fundamental and
uniformily understood basis.
10.2.3 Chapter 4: Soil Vapor Extraction (SVE)
Technologies
10.2.3.1 SVE is a viable technology for unsaturated
zone remediation of volatile and semi-
volatile contaminants.
The SVE technology has been demonstrated to be
viable for the removal of volatile and some semivolatile
organic compounds from vadose (unsaturated) zone
soils that have sufficient air conductivity. These soil
types typically include porous soils such as fine- to
coarse-grained sands. The presence of water in the
pore spaces impedes the vapor transport into the
gaseous phase. This can be overcome by lowering
the ground water level in the area of contamination.
10.2.3.2 Off-gases can be treated by conventional
technologies.
There are a wide variety of technology options
available for the treatment of off-gases. These include
activated carbon, condensation, and thermal destruc-
tion processes. A number of new technologies are
currently under development which may provide a
wider range of cost-effective alternatives for treating
the extracted vapors.
10.2.4 Chapter 5: Physical/Chemical Extraction
Technologies
10.2.4.1 Conventional extractive techniques have
limited in situ applications.
In situ extraction techniques will probably play only
a marginal role in the cleanup of contaminated sites
due to their limited applicability to soils with high per-
meability.
10.2.4.2 Above ground extraction methods are power-
ful techniques.
Conventional above ground extraction methods are
powerful techniques for a large range of soils contain-
ing heavy metals as well as organic contaminants, but
are limited in the soil size fraction they can effectively
clean. One of the major drawbacks of ex situ extrac-
tion techniques is, however, the production of sludge.
10.2.4.3 Electroreclamation deserves to be extensive-
ly investigated.
Electro reclamation is a promising new technology
for the in situ cleanup of clayey soils contaminated with
heavy metals. There currently is no other technique
that shows the same possibilities.
10.2.5 Chapter 6: Pump and Treat Ground Water
10.2.5.1 Pump and treat is a limited technology for
remediating aquifers.
The pump and treat operation that started out in
1984, as described in this chapter, was intended to
remediate the aquifer within 5 years. Although
remediation has been limited, the pump and treat
operation continues to perform as a barrier technology
for inhibiting the further migration of contaminants.
The case reflects other remediation industry pump and
treat experiences that shows, in general, that ground
water extraction and treatment is not an effective ap-
proach by itself for the ultimate remediation of aquifers
to health-based cleanup concentrations.
10.2.5.2 Air stripping and activated carbon, as il-
lustrated in the case study Ville Mercier,
were only partially effective treatment
processes.
The air stripping unit, described in this case study,
was one of the earliest designed systems for treating
both ferrous iron and volatile organic contaminants in
ground water. Activated carbon was used with the unit
to capture nonvolatile organics and residual volatile or-
ganics. However, this approach was found to be only
partially successful in treating contaminated ground
water. Subsequently, a pilot-scale study at this site
using an alternative iron removal process involving dif-
fused air combined with sand filtration, effectively
removed the iron to acceptable levels. This approach,
combined with an alternative air stripping system
designed to remove the most difficult contaminant,
110
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Conclusions and Recommendations
rather than volatile contaminants generally, effectively
reduced the organics to acceptable levels.
10.2.5.3 An ultraviolet radiation/oxidation process
(Ultrox) was effective in reducing the con-
centration of volatile organics in ground
water to acceptable levels.
10.2.5.4 A precipitation process involving the use of
lime and sodium sulfide was effective in
reducing the concentrations of zinc and cad-
mium to acceptable levels.
10.2.6 Chapter 7: Chemical Treatment of
Contaminated Soils: APEG
10.2.6.1 The long term stability and behavior of the
products of partial dechlorination in APEG
processes require investigation.
10.2.6.2 The combination of thermal pyrolysis and
APEG treatment applied at Wide Beach,
New York, USA, was successful in reducing
PCB concentrations to below target
cleanup levels.
10.2.7 Chapter 8: Microbial Treatment
Technologies
10.2.7.1 Bioremediation process scale-up from
laboratory to the field is difficult.
The complex physical, chemical and biological na-
ture of the subsurface environment makes both
laboratory testing and pilot-scale field evaluations
(treatability studies) essential elements of a successful
approach to remediation. Generally, either bench
and/or pilot-scale studies in the laboratory need to be
followed by pilot and/or full-scale testing in the field.
10.2.7.2 There is a need for both data on oxygen be-
havior in the subsurface and improved
methods of providing it for in situ
bioremediation.
Since oxygen is both the limiting and most expen-
sive factor in most applications of in situ bioremedia-
tion, it is important to gain insight into oxygen supply
and behavior in the subsurface. Further experimenta-
tion with oxygen delivery techniques is needed. One
promising technique is the use of soil vapor extraction
methods. The combined effect of vapor extraction and
biodegradation appears to provide a method for
achieving remediation of a wide range of organic con-
taminants.
10.2.7.3 There is a need for further research on
bioavailability and achievable residual con-
centrations.
To date, bioremediation of contaminated soil al-
ways leaves some residual concentrations of con-
taminants which may be acceptable, depending on
site-specific remediation objectives. These residual
concentrations can be higher or lower than what is al-
lowed, depending on a number of possible factors,
particularly the apparent nonavailability of the con-
taminants to indigenous microorganisms. This can be
a restriction for application of biological techniques.
Since bioremediation is often a relative cheap alterna-
tive to other remediation technologies, there exists a
need for further research on bioavailability and over-
coming its impediment to complete site remediation.
10.2.7.4 Soil inoculation has not been proven to en-
hance in situ bioremediation.
Although artificially supplied microorganisms are
expected to have some beneficial effect, this has not
been proven. A major obstruction is that soil microor-
ganisms tend to adsorb onto (soil) particles, and con-
sequently cannot be transported over long distances in
the subsoil. Another impediment may be the inability
of artifically supplied microorganisms to tolerate real-
world subsurface conditions and/or compete with in-
digenous populations.
10.2.7.5 Permeability is a key factor in applying in situ
bioremediation.
Apart from the biodegradability of typical con-
taminants, permeability is the key parameter which de-
termines the applicability of in situ biorestoration.
Permeability affects the contact of the microorganisms,
contaminants and the oxygen being supplied to sup-
port the biodegradation process.
10.2.8 Chapter 9: Selecting Remedies at a
Complex Hazardous Waste Site
10.2.8.1 Remediation should strive to be a complete
solution.
Once a remediation sites has been identified, an as-
sessment of critical problems must be made. Impacts
from the site on the environment and health need to be
addressed and relevant cleanup goals established.
Remediation efforts can be phased and monitored so
that problems are solved in a timely fashion. Once the
planned remediation actions have been completed,
long term monitoring may be needed to determine if
the remedial actions have been successful overtime.
10.2.8.2 Treatability studies must be conducted as
early as possible for effective remedy selec-
tion, and technologies should be judged by
their overall performance.
Conducting treatability studies as early as possible
is essential to effective selection of remedies. The
consequence of not doing them until late in the selec-
tion process may be unnecessary delays in construct-
ing remedies. The consequence of not doing them at
all may be ineffective remedies. In addition, tech-
nologies should be judged by their overall perfor-
mance, including generation of new waste streams
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Chapter 10
and long term performance, and not by cleaning
results only.
10.2.9 Appendix: In Situ Vitrification
10.2.9.1 Vitrification is a promising technique for treat-
ing mixed organic and inorganic wastes.
Heavy metals combined with organic contaminants
still pose problems in the present treatment schemes
and treatment trains may be needed to address this
problem. It is not expected that this will change in the
future. Vitrification combines the advantages of a ther-
mal process (destroying the organic contaminants)
with immobilization of the inorganics. Furthermore, it
leads to a final product showing a considerable resis-
tance to leaching.
10.3 General Conclusions
In addition to the specific technology area con-
clusions discussed in Section 10.2, the participants of
the Pilot Study reached the following conclusions that
apply to most if not all of the case studies, as well as
conclusions derived from special studies of the Fel-
lows and guest expert speakers to the Pilot Study.
10.3.1 Remediation
10.3.7.1 Energy efficiency practices influence plant
design and, therefore, processing costs in
different countries.
Energy costs in the United States (U.S.) are very
much lower than those in Europe. This may have in-
fluenced plant design, since one might expect more
attention to have been paid to energy efficiency in
plants designed in, for example, Germany, than those
designed in the U.S. Thus, simply multiplying energy
costs fora plant operating in the U.S. to give an energy
cost for a similar plant in Europe may be misleading
(leading to a high estimate of operating costs) because
the European designer would take care not to use so
much energy (but possibly have a higher capital cost,
in consequence). Similar considerations might apply
to attitudes to how labor-intensive operation of a plant
is.
Therefore, care should be taken when comparing
costs of different technologies, and when considering
the application of a technology in a country other than
that in which it was developed. Allowance must be
taken of variable factors such as energy and labor
costs, which will not only influence operating costs
directly, but also plant design and associated capital
costs.
10.3.1.2 Treatment and permanent solutions are
preferred.
Remediations based on technologically permanent
solutions are preferred. Successful remediation re-
quires treatment of the waste source. Containment
technologies may only provide temporary solutions
leading to the potential need for additional remediation
at a future date.
10.3.1.3 Integrated technology treatment systems are
needed for site remediation.
The complexity of contaminated sites and multiple
pollutants requires a multidisciplinary use of engineers
and scientists to solve the problems. Similarly, multi-
technology solutions offer the potential to be more ef-
fective in cleaning up sites than the historical use of
single technology systems. A combination of tech-
nologies can facilitate the preprocessing and treatment
of contaminated soils and ground water, as well the
postprocessing of residuals.
Modular designed integrated treatment trains can
provide system flexibility in optimizing specific process
units to treat different contaminants of varying con-
centrations within various media. This modular arran-
gement also allows the addition or withdrawal of
processing units within the system, as needed, as well
as allowing users the opportunity to insert and
evaluate new/upgraded technologies as they become
available. Modular design requires additional up-front
design but may result in lower capital and operating
costs than conventional one-technology designs.
This integrated systems approach also applies to
situations where there are multiple areas of con-
tamination on a given "site" and where it makes more
sense to use specific technologies on each area,
rather than trying to make one technology solve all of
the contamination problems, the challenge is to get
away from the traditional idea of one technology "fits
all."
10.3.1.4 Field treatability/pilot studies should be con-
ducted for each technology under con-
sideration, under the range of potentially
applicable site field conditions.
This conclusion of the first NATO/CCMS study on
contaminated land is reaffirmed by this NATO/CCMS
Pilot Study. The complex physical and chemical na-
ture of the subsurface environment makes both
laboratory testing and pilot-scale field evaluations
(treatability studies) essential elements of a successful
approach to remediation. Generally, either bench
and/or pilot-scale studies in the laboratory need to be
followed by pilot and/or full-scale testing in the field.
These treatability studies should indicate if the technol-
ogy is applicable to the waste and provide information
on the optimal level of treatment effectiveness that the
technololgy can achieve. Bench- and pilot-scale reac-
tor evaluations must be tailored to each specific ap-
plication in order to obtain the maximum amount of
credible data at minimum costs and establish the basis
for follow-on field evaluations.
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Conclusions and Recommendations
10.3.1.5 Technology scale problems need to be ad-
dressed in design and testing.
Care must be taken in translating technologies from
bench to pilot to demonstration or full-scale so that all
aspects of the scale up are taken into account (e.g,
reactor design, materials and residuals handling).
The scale up of pilot-scale systems to full-scale
operating systems can often result in unforeseen dif-
ficulties which need to be addressed in the design.
Careful consideration is needed of how design vari-
ables (e.g., wall effects, mixing efficiencies, flow pat-
terns, fugitive emissions, retention times) can change
as a result of system scale up. To overcome some of
these problems, particularly for technologies which
have not yet been widely used, operating flexibility can
be built into the system by modular design, by provid-
ing the ability to vary feed rates and by providing surge
capacity at various points throughout the system. It is
important that adequate design attention be paid to all
unit operations and that vendors of similar equipment
are contacted to obtain information on scale up
problems. However, care must be exercised when
using vendor information because frequently their
scale up procedures are based more on experience
and testing of a particular waste using proce-
dures/protocols that they have developed. Although
these testing procedures may work, the design prin-
ciples involved may not be fully developed or under-
stood.
, 10.3.1.6 A mass balance approach to remediation is
desirable.
For all projects, remediation design should be
based on a firm understanding of the mass and types
of pollutants involved, the current location of all of the
mass remaining in the subsurface, and the chemical,
physical and biological processes controlling the
movement and fate of the mass from the subsurface.
Usually, however, knowing any one of these is rare for
in situ remediation, let alone all of them. While it is
desirable to conduct all remediation from a mass
balance perspective, experience shows that it will be
practically impossible to obtain a true mass balance in
either in situ or above ground processes because of
the heterogeneity of the subsurface environment,
limitations of investigation tools and current technology
to accurately determine and/or predict the fate and be-
havior of the contaminants, such as their direction and
rate of movement, spacial distribution and concentra-
tion.
Nevertheless, all technology application evalua-
tions should be planned and conducted on a mass
balance basis since it provides a rational and fun-
damental structure for asking specific questions and
obtaining specific information that is necessary for
determining contaminant fate and behavior, for
evaluating and selecting treatment options, and for
monitoring treatment effectiveness at both laboratory
and field scale sized operations.
70.3.1.7 Technology remedies that transfer con-
taminants from one media to another
should be avoided, if possible.
Remediation activities sometimes transfer con-
tamination from one media, such as contaminated soil,
to another media (e.g., air). Therefore, it is advisable
to review all the pollutant emission pathways which
could result from remediation activity. If any emission
is possible, its impact on treatment effectiveness and
surrounding media should be evaluated. Under such
scrutiny, some technologies may be rejected because
emission control and/or the additional treatment
needed to lessen its impact on other media may
change the feasibility of the overall planned remedia-
tion effort.
10.3.1.8 All remediations require proper operation and
management.
Implementing technologies that have been proven
using field demonstration-scale treatability studies is
not enough to ensure success of the remediation ac-
tivities. The overall effectiveness of a remediation
scheme, which may include many interrelated ele-
ments of civil engineering works and soil and/or
ground water cleanup technologies, will depend heavi-
ly on the care with which the individual processes are
operated in the field; site and operating conditions
may change over time and skilled people are needed
to adjust technologies to these changes and/or remove
them from operation if they don't meet expectations.
Similarly, a strong quality assurance program needs to
be in place and activities carried out by a dedicated,
effective management team.
70.3.1.9 Long-term monitoring of permanent remedia-
tion may be necessary to ensure that
cleanup goals are met.
Construction of soil and ground water remedies is
not the endpoint for determining whether environmen-
tal protection concerns have been satisfied. Com-
prehensive, long term monitoring is essential to assure
that the required remedies are implemented, operated
and maintained, and ultimately are successful. This, in
turn, requires that long term oversight be conducted by
well trained personnel.
10.3.1.10 Basic records should be preserved.
A major challenge in evaluating current and emerg-
ing technology effectiveness to that used in the past is
that there is usually insufficient data available on which
to base an evaluation, particularly for in situ remedia-
tion activities. Therefore, it will be advantageous to fu-
ture remediation planners if records of site
investigations and associated remediation activities
are preserved for future reference and evaluation.
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Chapter 10
10.3.2 Technology Transfer
10.3.2.1 Uniform data collection Is needed.
There is a critical need for the establishment/use of
a uniform data reporting methodology that can be
universally applied. Various data base systems are
available and in use. However, input of consistent
data into these systems and easy access to them will
benefit all users. One particularly critical area of infor-
mation needed in these data bases is the cleanup
standards used at each site since these provide the
basis (remediation goal) upon which technologies
have been shown to be effective or not. The cleanup
standards are also important since there are no current
internationally agreed on standards and those ap-
plicable in one nation or state may not be pertinent in
another.
10.3.2.2 Independent technology evaluations are
needed for effective technology transfer.
Since reporting systems and data bases are only
as good as the data in them, a major challenge to the
remediation community is obtaining reliable, credible
data in a timely fashion. Projects in the field of
remediation techniques for contaminated soil are so
different in approach, execution and demands for
cleanup, that comparison of technology and results is
difficult if not impossible without organized, consistent
preplanned evaluations.
To overcome these difficulties, demonstrations of
technologies are needed that are well designed from a
mass balance point of view and objectively monitored,
analyzed and reported on by those who do not have a
vested interest in the technology itself. When properly
designed, executed and documented, such field trials
and demonstrations on a variety of site and ground
water matrices will not only verify the strengths and
limitations of technology but also provide a credible
basis for technology transfer and application. These
actions require a serious commitment of support by
governments to do so because no private organiza-
tions will have the capability to do this in a concerted,
consistent manner.
This NATO/CCMS Pilot Study has shown the
benefits to be gained from such well designed, sup-
ported, and independently monitored field scale
demonstrations for the evaluation of soil and ground
water treatment technologies. The participants of fu-
ture NATO/CCMS Pilot Studies of a similar character
would further enhance the utility of future candidate
demonstrations by providing guidance on project
design and information needs which would maximize
their value as case studies.
10.3.2.3 The NATO/CCMS network is an important
source of information.
In order to share the successes and failures of
technologies used within the hazardous waste treat-
ment arena, continued, positive interactions between
NATO members are needed. Often successful ap-
plications of technologies are addressed in public
forums and the literature with little attention paid to
those efforts which were not totally successful or that
were outright failures. It is more likely that the free
exchange of information and technology developments
will encourage all aspects of environmental research
and development when there are avenues available
which promote interaction and communication such as
the NATO/CCMS Pilot Study Group. It has provided a
valuable network for information exchange that other-
wise would not have been available.
10.3.3 Research
7 0.3.3.1 There is a continuing need for development
of new technologies and use of common re-
search protocols.
The technical limitations and or cost of present
technologies indicate that ongoing research and
development (R & D) is needed to improve the effec-
tiveness of current technologies and provide new treat-
ment alternatives. There is also a need for the
development of guidance to aid in the design and con-
duct of research, pilot-scale, and demonstration
studies in order to maximize their value to potential
users.
As in the case of remediation, it is essential in all
research studies on treatment or contaminant tech-
nologies that all materials used are fully characterized,
in terms of their chemical, physical, mineralogical and
microbial composition.
10.3.3.2 Scientific understanding of processes is es-
sential in order to ensure against formation
of harmful end products.
As in the case of remediation activities, processes
can be shown to be "effective" by relatively simple test-
ing (e.g., showing that the targeted contaminant
detected in the feed material is no longer present in the
treated material), but it is not a sufficient basis for ac-
ceptance of a treatment technology since toxic inter-
mediates, byproducts and residuals may be formed.
Therefore, a thorough understanding of the treatment
process mechanisms involved is required in order to
avoid such undesirable occurrences.
7 0.3.3.3 Standardization of analytical methods is
needed.
There is a lack of standardization of analytical
methods used within the worldwide hazardous waste
community and, in fact, within each country. As a
result, there can be confusion about what the data
means and the conditions under which the data was
obtained and analyzed. Under such circumstances,
data can be misinterpreted or appear inconclusive. A
level of confidence in the interpretation of data can be
established underworld wide acceptable standardized
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Conclusions and Recommendations
analytical methods. Concurrently, greater attention is
needed in the area of experimental design and in es-
tablishing the hypotheses which define what data are
needed and the quality of that data, which in turn es-
tablishes the analytical methods. Then data collected
can and should be interpreted in view of the questions
it was set out to answer as defined by the experimental
design. In addition, it would be beneficial to the haz-
ardous waste community if qualified organizations had
ongoing programs to both evaluate new analytical
techniques and update the analytical standards cor-
responding to use of those techniques.
10.3.3.4 Techniques are needed to remove contamina-
tion beneath urban structures without sig-
nificant disturbance to ongoing activities.
The remediation of contaminated sites in urban
areas raises a particular need for in situ technologies
that can be applied around and beneath buildings, in-
frastructure and services, with minimal disturbance to
artifacts or to the environment.
10.4 Recommendations
The following recommendations were made by the
participating members to the NATO/CCMS.
10.4.1 CCMS is invited by the Pilot Study Director to
commend this report to NATO Council for
approval.
All of the participants in this phas'e of the study
need to be commended for their professionalism, tech-
nical expertise and cooperation. The Pilot Study
Director particularly thanks the two Co-pilot Countries,
Germany and The Netherlands for their assistance.
All of the Fellows need to be complimented on their
technical quality and input to the study. The Expert
Speaker activities within the study were a stellar suc-
cess in providing an intellectual stimulus to all of their
participating Countries. Over and above the technical
successes of the study, a camaraderie was estab-
lished between the participating country repre-
sentatives that led to many spinoff activities between
different Countries and in different areas of environ-
mental technologies. Professional enhancement and
recognition increased for many of the participants.
Conference participation and publications resulting
from this Study were numerous throughout both
Western Europe and North America and these proved
to be valuable technology transfer activities that
provided information being generated within the Study
to the rest of the environmental community in a timely
manner.
Therefore, the NATO/CCMS is invited to commend
this Final Report to member governments and draw
their attention to the technical information and the Con-
clusions and Recommendations contained herein.
10.4.2 Continue the NATO/CCMS Pilot Study to in-
clude reporting on the field demonstration
of technologies and on new/emerging tech-
nologies.
Ongoing problems with waste management prac-
tices in all countries continue the need for advancing
the state-of-the-art in remediation technologies. The
current phase of the NATO/CCMS Pilot Study on this
topic provided an excellent forum for technology ex-
posure and technology transfer among countries.
Therefore, it is recommended that this Study continue
into a second phase. Since in situ and on-site
remediation usually takes time, this second phase will
enable member countries to see how well the tech-
nologies perform during complete remediation ac-
tivities. It will also enable current members, and
additional countries that haive expressed an interest in
the Study, to take advantage of data from new field
demonstrations. In addition, it will provide them the
opportunity to report on developments in national
legislation and regulations, as well as exchange tech-
nical information on ongoing work in the development
of new technologies, and potentially avoid duplication
of research projects.
10.4.3 Continuation of the current NATO/CCMS Pilot
Study should also include cleanup criteria,
project design methodologies, and
documentation of completed remediations.
The continuation of this NATO/CCMS Pilot Study
can advance the state-of-the-art in remediation tech-
nologies by including related areas of interest to
decisionmakers. These include an examination of
cleanup criteria used by various countries,
methodologies used in the design of research, pilot
and field demonstration projects, and documentation
of completed remediations that examines suc-
cess/failure, costs, field problems, etc.
10.4.4 Encourage participation of NATO and
nonNATO countries in the continuation
study.
Past participation has been a two-way reward for
participating Pilot Study mesmbers. Not only have par-
ticipants learned but have also shared their experien-
ces with others. The sharing of knowledge from the
current Pilot Study, coupled with an increased ex-
change of information with new participants, can en-
hance technology transfer and remedial action
progress.
10.4.5 NATO/CCMS should encourage more active
participation by all member countries.
The NATO/CCMS should encourage membership
within Pilot Studies, whether as full participants or as
observers, by as many countries as possible. It should
draw the attention of member countries to the way in
which membership can open the doors for researchers
and regulators, within and outside central government,
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Chapter 10
and to high quality technology exchange programs. It
should, therefore, encourage member countries to
adopt formal observer status, even if the country itself
wishes to have only minimal active participation at the
official level. The NATO/CCMS is also requested to
encourage member countries to give greater publicity
to the activities of Pilot Study Groups and to the related
Fellowship program.
10,4.6 Encourage participation under the NA TO
Science Committee to establish a scientific
program and advance study institute for soil
and ground water contamination issues.
There are significant deficiencies in our fundamen-
tal understanding of subsurface soil and ground water
systems and the complicated interactive processes
which control contaminant behavior and fate within
those systems. Without profound scientific advances
In our understanding of these phenomena, site inves-
tigation and treatment technologies will likely be slow,
risky, expensive, and poorly effective.
Therefore, the NATO Scientific Committee is en-
couraged to establish a special scientific program for
addressing fundamental gaps in understanding these
phenomena. Such a program should include a
Science Fellowships Programme, an Advanced Study
Institute, Advanced Research Workshop(s), as well as
collaborative research grants, including both NATO
and nonNato researchers.
70.4.7 NATO/CCMS should support the transfer/ap-
plication of results of current study through
workshops and seminars within NATO and
nonNATO countries.
Mindful of the contaminated land problems known
to exist in certain nonparticipant NATO countries, and
In many nonNATO countries, including those in East-
em and Central Europe, the Pilot Study Group recom-
mends that NATO arrange a series of workshops and
seminars specifically in those places, in order to aid in
the dissemination of the results of the present study.
10.4.8 The NATO/CCMS should encourage annual
technology transfer reports from each of its
individual pilot studies.
This Pilot Study showed the value to member
countries of frequent publications and verbal presenta-
tions on the status and results of the its activities.
Therefore, all Pilot Study Directors and technical par-
ticipants are encouraged to publish an annual report
on the progress of their Study in either international
conferences or journals, or both. Publication in both
Europe and North America is encouraged.
10.4.9 Create a more formal interface of the continued
pilot study with OECD, EC and other inter-
national groups.
Throughout the first phase of the pilot study there
was minimum involvement/representation from other
international groups such as OECD and EC at the
meetings. On two occasions the Pilot Study Director
visited OECD and conducted a briefing for Waste
Policy Management officials. The EC attended and
presented at one meeting over the five year period. It
is recommended that the NATO/CCMS lend its sup-
port to the various interested Pilot Studies to formalize
and increase the participation of other international
groups.
10.4.10 A budget for writing the final report should be
established to encourage final report
preparation.
Researchers generally have a limited budget for
activities not directly involving their regular work. At
present, the preparation of final reports is a spare time
activity. Furthermore, not all studies provide the infor-
mation necessary for a detailed final report and addi-
tional information acquisition is needed in some cases.
Because contributions to the NATO/CCMS study are
not directly profitable to the institution in which the re-
searchers are employed, it is desirable that NATO pro-
vide a financial incentive to employers to give
contributors time to work on NATO/CCMS reports
during regular working hours. This would also make
the acquisition of additional information (telephoning,
writing letters) easier.
U.S. GOVERNMENT PRINTING OFFICE, 1993 -750 -002/ 609S"t
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