COMMITTEE ON EPA 542-R-98-001a
THE CHALLENGES OF June 1998
MODERN SOCIETY www.clu-in.com
www.nato.int/ccms
NATO/CCMS Pilot Study
Evaluation of Demonstrated and
Emerging Technologies for the
Treatment and Clean Up of
Contaminated Land and
Groundwater
PHASE
FINAL REPORT
Number 219
NORTH ATLANTIC TREATY ORGANIZATION
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NATO/CCMS Pilot Study, Phase II Final Report
CONTENTS
Chapter 1: INTRODUCTION 1-1
1.1 BACKGROUND 1-1
1.2 STRUCTURE OF THE STUDY 1-3
1.3 HOW THE INFORMATION IS PRESENTED 1-6
1.4 RELATIONSHIP TO OTHER CCMS PROGRAMS 1-8
1.4.1 Contributions by CCMS Fellows 1-8
1.4.2 CCMS Study Visit Program 1-9
1.5 CONTRIBUTIONS BY EXPERT SPEAKERS 1-9
1.6 CONCLUSIONS AND RECOMMENDATIONS 1-9
1.7 REFERENCES 1-9
Chapter 2: TECHNICAL OVERVIEW 2-1
2.1 INTRODUCTION 2-1
2.2 DEVELOPMENT STATUS 2-1
2.3. INSITUVS. EX SITU 2-2
2.4 TECHNOLOGIES EMPLOYED 2-2
2.5 CONTAMINANTS TREATED 2-2
Chapter 3: PROCESS-BASED REMEDIATION METHODS 3-1
3.1 INTRODUCTION 3-1
3.2 BASIC OPTIONS AND CLASSIFICATION OF METHODS 3-1
3.3 CIVIL ENGINEERING-BASED METHODS 3-2
3.4 PROCESS-BASED METHODS 3-3
3.4.1 Ex Situ Methods for Solids and Liquids 3-3
3.4.2 Ex Situ Treatment of Groundwater and Other Contaminated Liquids 3-6
3.4.3 In Situ Methods for Soils 3-8
3.4.4 In Situ Treatment of Groundwater 3-12
3.5 REFERENCES 3-15
Chapter 4: IN SITU TREATMENT 4-1
4.1 INTRODUCTION 4-1
4.2 CASE STUDIES 4-2
4.2.1 Project 1: Trial of Air-Sparging of a Petroleum-Contaminated Site 4-4
4.2.2 Project 2: Bioremediation of Petrochemicals Following a Major Fire 4-5
4.2.3 Project 3: Bioclogging of Aquifers for Containment and Remediation of Organic
Contaminants 4-5
4.2.4 Project 4: Remediation of Methyl Ethyl Ketone Contaminated Soil and
Groundwater 4-6
4.2.5 Project 6: In Situ/On-Site Remediation of Wood Treatment Soils 4-6
4.2.6 Project 9: Demonstration of an In Situ Process for Soil Remediation Using Well
Points 4-7
4.2.7 Project 12: Groundwater and Soil Remediation at a Former Manganese Sulfate
Production Plant 4-7
4.2.8 Project 15: Combined Chemical and Microbiological Treatment of Coking Sites . . 4-8
4.2.9 Project 16: Combined Vacuum Extraction and In Situ Stripping of Chlorinated
Vapors 4-9
4.2.10 Project 18: Biological In Situ Remediation of Contaminated Gasworks 4-9
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4.2.11 Project 23: Modeling and Optimization of In Situ Remediation 4-10
4.2.12 Project 35: Combined In Situ Soil Vapor Extraction Within Containment Cells and
Subsequent Ex Situ Bioremediation 4-11
4.2.13 Project 37: Bioventing of Hydrocarbon-Contaminated Soils in the Sub-Arctic . . 4-12
4.2.14 Project 41: In situ Microbial Filters 4-13
4.2.15 Project 42: In Situ Pneumatic Fracturing and Bioremediation 4-13
4.2.16 Project 43: Multi-Vendor Bioremediation Technology Demonstration 4-14
4.2.17 Project 47: In Situ Electroosmosis (Lasagna™ Process) 4-15
4.2.18 Project 49: Characterization of Residual Contaminants in Bioremediated Soils and
Reuse of Bioremediated Soils 4-16
4.3 REVIEW OF CASE STUDIES AS A GROUP 4-17
4.4 ENVIRONMENTAL IMPACTS AND HEALTH AND SAFETY 4-19
4.5 COSTS 4-20
4.6 APPLICABILITY OF IN SITU TECHNOLOGIES 4-20
Chapter 5: PHYSICAL-CHEMICAL TREATMENT 5-1
5.1 INTRODUCTION 5-1
5.1.1 Overview of Chapter 5-1
5.1.2 Generic Description of Technology Group 5-1
5.2 CASE STUDIES CHOSEN 5-3
5.2.1 Group 1: Typical Soil Washing (Project 30) 5-3
5.2.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36) 5-4
5.2.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19, 27,
31, and 33) 5-7
5.2.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)5-15
5.2.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) 5-19
5.3 BACKGROUND OF CASE STUDIES AS A GROUP 5-24
5.4 PERFORMANCE RESULTS 5-24
5.4.1 Analytical and Assessment Procedures 5-24
5.4.1.1 Group 1: Typical Soil Washing (Project 30) 5-26
5.4.1.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36) . 5-27
5.4.1.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19,
27, and 31) 5-27
5.4.1.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44,
and 47) 5-29
5.4.1.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) 5-30
5.4.2 General Effectiveness 5-31
5.4.3 Overall Performance 5-35
5.4.3.1 Group 2: Soil washing and biological treatment (Projects 24, 26, and 36) . . 5-35
5.4.3.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19,
27, and 33) 5-37
5.4.3.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 31, 32,
44, and 47) 5-37
5.4.3.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) 5-40
5.5 RESIDUALS AND EMISSIONS 5-40
5.5.1 Soil Washing 5-40
5.5.2 Combined Treatments 5-40
5.5.2.1 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36) . 5-41
5.5.2.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10, 17, 19,
27, 31, and 33) 5-43
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5.5.2.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44,
and 47) 5-43
5.5.2.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40) 5-43
5.6 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE
APPLICABILITY OF THE TECHNOLOGY 5-44
5.6.1 Typical Soil Washing 5-46
5.6.2 Soil Washing and Other Treatment 5-47
5.6.3 Physical-Chemical Technologies 5-48
5.6.4 Photo-Oxidation Technologies 5-49
5.7 COSTS 5-50
5.8 FUTURE STATUS OF THE CASE STUDY PROCESS AND THE TECHNOLOGY AS
A WHOLE 5-53
5.8.1 General Remarks 5-53
5.8.2 Characterizing Contaminated Material 5-53
5.8.3 Optimizing Performance of Unit Processes 5-53
5.8.4 Investigating Cost-Effectiveness of Treatment Combinations 5-53
5.8.5 Investigating Residuals 5-54
5.9 REFERENCES 5-54
Chapter 6: BIOLOGICAL TREATMENT PROCESSES: INTRODUCTION AND EX SITU
APPROACHES 6-1
6.1 INTRODUCTION 6-1
6.2 GENERAL OVERVIEW 6-1
6.2.1 Biological Processes, In General 6-1
6.2.2 Main Process Variations (by Biological Process) 6-3
6.2.3 Main Process Variations (by Mode of Application) 6-4
6.2.4 Combinations with Abiotic Processes 6-6
6.2.5 Extensive Approaches 6-7
6.2.6 Groundwater Treatment 6-7
6.2.7 Indications for Using Ex Situ Treatment Technologies 6-8
6.3 CASE STUDIES CHOSEN 6-9
6.4 BACKGROUND OF CASE STUDIES AS A GROUP 6-9
6.5 PERFORMANCE RESULTS 6-14
6.5.1 Project 6: In Situ/On-Site Bioremediation of Soils Contaminated with Organic
Pollutants: Elimination of Soil Toxicity with DARAMEND® 6-14
6.5.2 Project 8: Biodegradation/Bioventing of Oil-Contaminated Soils 6-14
6.5.3 Project 11: On-Site Biological Degradation of PAHs in Soil at a Former Gasworks
Site 6-15
6.5.4 Project 15: Bioremediation of Soils from Coal and Petroleum Tar
Distillation Plants 6-16
6.5.5 Project 24: Combined Remediation Technique for Soil Containing Organic
Contaminants: Fortec 6-16
6.5.6 Project 25: Slurry Reactor for Soil Treatment 6-17
6.5.7 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry
Phase Bioreactors) 6-17
6.5.8 Project 28: Use of White-Rot Fungi for Bioremediation of Creosote-Contaminated
Soil 6-17
6.5.9 Project 31: Decontamination of Metalliferous Mining Spoil 6-18
6.5.10 Project 35: Combined In Situ Soil Vapor Extraction within Containment Cells
Combined with Ex Situ Bioremediation and Groundwater Treatment 6-18
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6.5.11 Project 36: Investigation of Enhancement Techniques for Ex Situ Separation
Processes, Particularly with Regard to Fine Particles 6-18
6.5.12 Project 43: Multi-Vendor Bioremediation Technology Demonstration Project . . . 6-19
6.5.13 Project 49: Characterization of Residual Contaminants in Bioremediated Soil and
Reuse of Bioremediated Soil 6-19
6.5.14 Project 54: Treatment of PAH- and PCP-Contaminated Soil in Slurry Phase
Bioreactors 6-20
6.6 GENERAL DISCUSSION OF PROJECTS 6-20
6.7 RESIDUALS AND EMISSIONS 6-21
6.8 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE
APPLICABILITY OF THE TECHNOLOGY 6-23
6.9 COSTS 6-25
6.10 FUTURE STATUS OF THE CASE STUDY PROCESSES AND THE TECHNOLOGY
AS A WHOLE 6-25
6.11 ACKNOWLEDGEMENT 6-27
6.12 DISCLAIMER 6-27
6.13 REFERENCES 6-27
Chapter 7: EX SITU THERMAL METHODS 7-1
7.1 INTRODUCTION 7-1
7.2 MAIN PROCESS VARIATIONS 7-1
7.3 DESCRIPTION OF MAIN PROCESS VARIATIONS 7-2
7.3.1 Thermal Desorption 7-2
7.3.2 Incineration 7-5
7.3.3 Vitrification 7-6
7.4 DETERMINATION OF EFFECTIVENESS 7-6
7.5 CASE STUDIES CHOSEN 7-7
7.5.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process 7-7
7.5.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using New
On-Site Technique 7-11
7.5.3 Project 19: Cleaning Mercury-Contaminated Soil Using Combined Washing and
Distillation Process 7-12
7.5.4 Project 20: Fluidized Bed soil Treatment Process—BORAN 7-13
7.5.5 Project 21: Mobile Low-Temperature Thermal Treatment Process 7-14
7.6 REVIEW OF CASE STUDIES AS A GROUP 7-14
7.7 PERFORMANCE RESULTS 7-15
7.7.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process 7-15
7.7.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using New
On-Site Technique 7-17
7.7.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process 7-18
7.7.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN 7-19
7.7.5 Project 21: Mobile Low-Temperature Thermal Treatment Process 7-19
7.8 ENVIRONMENTAL IMPACTS 7-19
7.8.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process 7-19
7.8.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique 7-20
7.8.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process 7-20
7.8.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN 7-20
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7.8.5 Project 21: Mobile Low-Temperature Thermal Treatment Process 7-20
7.9 HEALTH AND SAFETY 7-21
7.9.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process 7-21
7.9.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique 7-21
7.9.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process 7-22
7.9.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN 7-22
7.9.5 Project 21: Mobile Low-Temperature Thermal Treatment Process 7-22
7.10 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE
APPLICABILITY OF THE TECHNOLOGY 7-22
7.10.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process 7-22
7.10.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique 7-23
7.10.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process 7-23
7.10.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN 7-23
7.10.5 Project 21: Mobile Low-Temperature Thermal Treatment Process 7-23
7.11 COSTS 7-23
7.11.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process 7-24
7.11.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique 7-24
7.11.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process 7-24
7.11.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN 7-24
7.11.5 Project 21: Mobile Low-Temperature Thermal Treatment Process 7-25
7.12 CONCLUSIONS AND PROGNOSIS 7-25
7.13 REFERENCES 7-25
Chapter 8: STABILIZATION/SOLIDIFICATION PROCESSES 8-1
8.1 INTRODUCTION 8-1
8.1.1 Main Process Variations 8-2
8.1.2 Ex situ Methods of Application 8-3
8.1.3 In Situ Methods of Application 8-4
8.2 CASE STUDIES CHOSEN 8-5
8.2.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process) 8-6
8.2.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides
onto Unconventional Sorbents 8-8
8.4 PERFORMANCE RESULTS 8-9
8.4.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process) 8-9
8.4.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides
onto Unconventional Sorbents 8-9
8.5 RESIDUALS AND EMISSIONS 8-10
8.5.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process) 8-10
8.5.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides
onto Unconventional Sorbents 8-10
8.6 HEALTH AND SAFETY 8-10
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8.6.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process) 8-10
8.6.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides
onto Unconventional Sorbents 8-10
8.7 COSTS 8-11
8.8 FUTURE STATUS OF CASE STUDY PROCESSES AND TECHNOLOGY AS A
WHOLE 8-11
8.9 REFERENCES 8-11
Chapter 9: OTHER REMEDIATION TECHNOLOGIES 9-1
9.1 INTRODUCTION 9-1
9.2 PROJECTS IN THE SITE INVESTIGATION STAGE 9-1
9.2.1 Project 51: Sobeslav, South Bohemia Wood Treatment Plant 9-1
9.2.2 Project 56: Spolchemie a.s.—Mercury-Contaminated Site 9-2
9.3 PROJECTS FOR WHICH REMEDIAL OPTIONS HAVE BEEN SELECTED, BUT
NOT IMPLEMENTED 9-2
9.3.1 Project 55: Czechowice Oil Refinery Project 9-2
9.4 PROJECTS FOR WHICH THE SELECTED REMEDIAL OPTION DOES NOT FIT IN
THE CATEGORIES OF TECHNOLOGIES HIGHLIGHTED IN THE OTHER
TECHNOLOGY CHAPTERS 9-3
9.4.1 Project 22: Environmental Evaluations of Former Soviet Military Bases in Hungary 9-3
9.4.2 Project 39: Management of Soil Vapors at the Basket Creek Site 9-4
9.4.3 Project 50: Integrated Rotary Steam Stripping and Enhanced Bioremediation for In
Situ Treatment of VOC-Contaminated Soil (Cooperative Approach to Application of
Advanced Environmental Technologies) 9-5
9.4.4 Project 53: In Situ Bioremediation of Chloroethene-Contaminated Soil 9-6
Chapter 10: INTEGRATION OF TECHNOLOGIES 10-1
10.1 INTRODUCTION 10-1
10.2 BASIC OPTIONS AND CLASSIFICATION OF APPROACHES 10-1
10.2.1 Technical Factors 10-2
10.2.2 Organizational Factors 10-2
10.3 CASE STUDIES CHOSEN 10-3
10.3.1 Project 1: Field Trial of Air Sparging of a Petroleum-Contaminated Aquifer . . . 10-5
10.3.2 Project 9: Field Demonstration of an In Situ Process for Soil Remediation Using
Well Points 10-5
10.3.3 Project 10: Recovery of Inorganic and Organic Contaminants from Soil 10-5
10.3.4 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique 10-6
10.3.5 Project 15: Combined Chemical and Microbiological Treatment of Coking
Sites/Bioremediation of Soils from Coal and Petroleum Tar Distillation Plants .... 10-6
10.3.6 Project 19: Cleaning Mercury-Contaminated Soil Using a Combined Washing and
Distillation Process 10-6
10.3.7 Project 24: Combined Remediation Technique for Soil Containing Organics:
Fortec 10-6
10.3.8 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry
Phase Bioreactor) 10-7
10.3.9 Project 27: Soil Washing and Chemical Dehalogenation of PCB-contaminated
Soil 10-7
10.3.10 Project 31: Decontamination of Metalliferous Mining Wastes 10-7
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10.3.11 Project 32: Cacitox™ Soil Treatment Process 10-7
10.3.12 Project 33: In-pulp Decontamination of Soils, Sludges, and Sediments 10-7
10.3.13 Project 36: Enhancement Techniques for Ex Situ Separation Processes
Particularly with Regard to Fine Particles 10-8
10.3.14 Project 42: In Situ Pneumatic Fracturing and Biotreatment 10-8
10.3.15 Project 47: In Situ Electro-Osmosis (Lasagna™ Project) 10-8
10.4 REVIEW OF CASE STUDIES AS A GROUP 10-8
10.5 PERFORMANCE RESULTS 10-10
10.5.1 Overview 10-10
10.5.2 Separation of Fractions 10-10
10.5.3 Mobilization of Contaminants 10-12
10.5.4 Increase of Availability 10-13
10.5.5 Sequential Removal of Contaminants 10-14
10.6 FACTORS AND LIMITATIONS OF INTEGRATED TECHNOLOGIES 10-15
10.6.1 Separation of Fractions 10-15
10.6.2 Mobilization of Contaminants to Enhance Treatment 10-15
10.6.3 Increase of Availability of Contaminants to Treatment 10-16
10.6.4 Sequential Removal of Different Types of Contaminants 10-16
10.7.5 General and Concluding Aspects Regarding Integration of Technologies 10-16
10.7 COSTS 10-18
10.8 GENERAL CONCLUSIONS 10-18
10.9 ACKNOWLEDGEMENTS 10-18
Chapter 11: REMEDIATION TECHNOLOGY RESEARCH NEEDS 11-1
11.1 INTRODUCTION 11-1
11.2 LESSONS FROM PREVIOUS NATO/CCMS STUDIES 11-3
11.3 THE PRESENT STUDY 11-4
11.4 REFERENCES 11-6
Chapter 12: CONCLUSIONS AND RECOMMENDATIONS 12-1
12.1 INTRODUCTION 12-1
12.2 GENERAL CONCLUSIONS 12-1
12.3 GENERAL TECHNICAL CONCLUSIONS 12-2
12.4 RESEARCH NEEDS 12-6
12.5 RECOMMENDATIONS TO CCMS 12-6
12.6 REFERENCES 12-8
Appendix I—COUNTRY REPRESENTATIVES A-I-1
Appendix II—CCMS FELLOWS A-II-1
Appendix III—GUEST SPEAKERS A-III-1
Appendix IV—PROJECT SUMMARIES
Available through the Internet at http://clu-in.com or http://www.nato.int/ccms
Appendix V—FELLOW STUDIES A-V-i
PREFACE A-V-i
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NATO/CCMS Pilot Study, Phase II Final Report
Quality Management Systems and the Remediation of Contaminated Land
Dr. Bob Bell and Mr. Richard Failey, SGS Environment, Colwyn Bay, U.K A-V-1
Groundwater Contamination in Portugal: Overview of the Main Problems
Maria Teresa Chambino, Institute Nacional de Engenharia e Tecnologia Industrial (INETI),
Institute de Tecnologias Ambientais/Dep. Tecnologias Ambientais, Portugal A-V-6
Critical Review of Air Sparging and In situ Bioremediation Technologies
Domenic Grasso, The School of Engineering, University of Connecticut, Kenneth L Sperry,
Envirogen, Lawrenceville, NJ, and Susan Grasso, Environ, Princeton, NJ A-V-20
The Cost of Remedial Action
Dr. Mary R. Harris, Monitor Environmental Consultants Ltd, Birmingham, U.K. ... A-V-25
Changing Approaches to Remediation
Merten Hinsenveld, TSM Business School, University of Twente, Enschede,
The Netherlands A-V-31
Use of Remedial Clean-Up Technology in Portugal
Maria Jose Macedo, Hovione - Sociedade Quimica SA, Loures, Portugal A-V-32
Experiences with the Performance of In Situ Treatment Technologies
Dr. Robert L. Siegrist, Environmental Science & Engineering Division, Colorado School of
Mines A-V-35
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NATO/CCMS Pilot Study, Phase II Final Report
TABLES
Table 1.1: List of Projects Included in CCMS Study on Remediation Technology 1-4
Table 2.1: Projects Included in NATO/CCMS Pilot Study, Classification by Technology
(February 1997) 2-3
Table 2.2: Projects Included in NATO/CCMS Phase II Pilot Study, Classification by Media and
Contaminants 2-6
Table 4.1: In Situ Projects 4-3
Table 4.2. Estimated Costs of Technology Application 4-20
Table 6.1: Projects Reviewed and References 6-2
Table 6.2: Overview of Selected Projects 6-10
Table 6.3: Outline of Treatment Processes By Project 6-11
Table 6.4: Biogenie Case Studies 6-14
Table 6.5: Project 11 Treatments 6-15
Table 6.6: Residuals and Emissions 6-22
Table 6.7: Key Factors Limiting Performance 6-24
Table 6.8: Cost Information by Project 6-26
Table 7.1: Projects Involving Ex Situ Thermal Treatment 7-7
Table 7.2: Input Materials 7-15
Table 7.3: Thermal Treatment Process 7-16
Table 7.4: Performance Information 7-17
Table 7.5: Mercury Concentrations in Waste Streams Treated in Project 19 7-18
Table 7.6: Summary Results of Pilot-Scale Trials 7-19
Table 7.7: Cost Data 7-23
Table 10.1: Factors Limiting Effective Treatment with Only One Technology and the General
Options to Overcome the Limitations 10-3
Table 10.2: Projects Involving Integration of Treatment Technologies 10-4
Table 10.3: Goal of Combination, Input Materials in Terms of Medium Treated, Contaminants
Present, Types of Technologies Combined and Scale of Project 10-9
Table 10.4: Categories of Integration of Technologies and Respective Criteria 10-11
Table 10.5: Performance Data of the Separation of Fractions Category 10-11
Table 10.6: Performance Data of the "Mobilization of Contaminants to Enhance Treatment"
Category 10-13
Table 10.7: Performance Data of the "Increase of Availability of Contaminants to Treatment"
Category 10-14
Table 10.8: Performance Data of the "Sequential Removal of Different Types of Contaminants"
Category 10-15
Table 10.9: Cost Data (to the extent available) 10-19
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Phase II Final Report
NATO/CCMS Pilot Study
Evaluation of Demonstrated and Emerging
Technologies for the Treatment and Clean Up
of Contaminated Land and Groundwater
June 1998
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NOTICE
This Phase II Pilot Study Final Report was prepared under the auspices of the North Atlantic Treaty
Organization's Committee on the Challenges of Modern Society (NATO/CCMS) as a service to the
technical community by the United States Environmental Protection Agency (U.S. EPA). Production of
the document was funded by U.S. EPA's Technology Innovation Office under the direction of Michael
Kosakowski. Michael A. Smith of Berkhamsted, U.K., served as the principal editor for the report.
Final editing and formatting services were provided by Environmental Management Support, Inc., of
Silver Spring, Maryland, under U.S. EPA contract 68-W6-0014. Mention of trade names or specific
applications does not imply endorsement or acceptance by U.S. EPA.
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NATO/CCMS Pilot Study, Phase II Final Report
Chapter 1: INTRODUCTION
Michael A. Smith
M.A. Smith Environmental Consultancy
1.1 BACKGROUND
Groundwater and soil contamination are among the most complex and challenging environmental
problems faced by many countries. The problems involve a number of technical issues, including the
means of identifying contamination, understanding contaminant behavior in the environment, and
mitigating the potential adverse affects to human health and the environment. There are also a number
of non-technical issues to be considered, such as the social, economic, and psychological impacts of
contamination on individuals and communities, and the need to rejuvenate old urban and industrial areas.
The NATO Committee on the Challenges to Modern Society (NATO/CCMS) has organized a number
of pilot studies on the technical aspects of contaminated land. The first pilot study (Box 1.1), which ran
from 1980-1984, included an assessment of available remediation methods and a number of other topics.
This led to the Phase I Pilot Study (Box 1.2) from 1986-1991 for the purpose of identifying and
evaluating innovative, emerging, and alternative technologies and transferring the technical performance
and economic information to potential users.
Twenty-nine demonstration projects were shared by the pilot study participants. A specific and important
objective of this study was to identify "lessons learned" from the technology demonstrations—not only
the successes but also those lessons that illustrated technology failures or limitations. Attention was paid
not only to the technologies themselves, but to the practical, operational, and organizational aspects of
implementation. Information on limitations and practical aspects of implementation is rarely presented
at conferences or discussed in the technical literature, but is very important for making informed
decisions involving critical time and monetary requirements. It is also useful for defining priorities in
research and development.
The success of the Phase I Pilot Study led to the inception of the Phase II Pilot Study in 1992. Phase
II was conducted similarly to Phase I, but was extended in scope to include technologies at an earlier
stage of development.
This report provides:
• the background and organization of the Phase II Pilot Study;
• a short description of each of the more than 50 projects included in the study;
• characterization of the projects in a variety of ways including, for example, by the technologies used,
their development status, and contaminants treated;
• a critical review of the project results in a series of technology-based chapters; and
• the conclusions and recommendations arising from the study.
The organization of the pilot study, a summary of its achievements, key conclusions, and
recommendations to the NATO/CCMS have also been published in a separate Overview Report (1).
1-1
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NATO/CCMS Pilot Study, Phase II Final Report
Technologies are frequently classified as emerging, innovative, or demonstrated. Emerging technologies
are at a stage where successful bench-scale testing has been conducted and pilot-scale evaluation is
required to determine its potential for use in remediation. Innovative technologies are at the stage where
pilot- or field-scale testing is being conducted and performance or cost information is incomplete. In
general, innovative technologies require field testing to prove their effectiveness before they can be
considered proven and available for use in remediation. Finally, demonstrated technologies have
undergone properly designed independent field evaluation to determine their performance under carefully
monitored conditions.
What is viewed as an innovative technology in one country may be regarded as established in another.
What is considered as established in one country may not be used widely in others because of doubts
about its effectiveness1. The term "innovative" often applies to the application of a technology rather
than to the principles underlying it. While truly innovative technologies remain a goal, there is also a
need for better information and understanding of established processes or means of ensuring that their
capabilities are fully realized in practice.
Box 1.1: The First NATO/CCMS Pilot Study on Contaminated Land (1980-84)
The first NATO/CCMS Pilot Study on contaminated land was conducted from 1980 to 1984.
Seven countries participated in the study: Canada, Denmark, the Federal Republic of Germany,
France, the Netherlands, the United Kingdom (U.K.), and the United States (U.S.).
The Pilot Study culminated in publication of a report (2), which provided a state-of-the-art
review of measures available for dealing with contaminated sites and of a number of related
topics. It also provided the participating countries with a common basis for understanding the
problems posed by contaminated sites and how they might be addressed. A chapter entitled
"Long-Term Effectiveness of Remedial Measures," provided the basis for three principal
conclusions of the Pilot Study:
• Systems based on isolation of the contamination (e.g., covering systems) are vulnerable to
loss of effectiveness with time; like many other engineered projects they have a finite life;
• The development of on-site and in situ processes resulting in the removal or destruction of
contaminants is to be encouraged as providing a one-time final solution; and
• Very few of the technologies described have been sufficiently proven in applications specific
to the treatment of contaminated land.
The initial NATO pilot study led to an extensive exchange of information between participants,
the formation of a professional and scientific network that continues to this day, and the
initiation of bilateral programs of cooperation.
An example is stabilization/solidification. While widely applied in the United States, it has only limited
application to date in Western Europe.
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Box 1.2: The Phase I Study (1986-1991)
The formal title of the Phase I Pilot Study was "Demonstration of Remedial Action
Technologies for Contaminated Land and Groundwater. " This Pilot Study was intended to be a
practical, rather than a desk-based exercise, although it continued to provide a forum for the
exchange of information on policy developments in the participating countries. It was co-piloted
by Germany, the Netherlands, and the United States, and ran from 1986 to 1991. Seven
countries participated formally throughout the study. A number of other countries attended at
least one meeting on a less formal basis or through the CCMS Fellowship Program.
The objectives of the Phase I Pilot Study were to:
• identify and evaluate innovative, emerging, and alternative remediation technologies and to
transfer technical performance and economic data to potential users; and
• identify "lessons learned" from the technology demonstrations, including not only the
successes, but lessons illustrating technology failures or limitations.
A total of 29 demonstration projects from several countries were included in the Phase I Pilot
Study. The results of demonstration projects were critically reviewed at the pilot study meetings
so that "lessons learned" could be distilled.
The final report (3) published by the U.S. Environmental Protection Agency (USEPA) comprises
a principal volume, which presents the lessons learned and technology classifications, and
supporting volumes, which contain the individual project reports, reports by CCMS Fellows,
papers presented by expert speakers, and other supporting material arising from the Pilot
Study.
1.2 STRUCTURE OF THE STUDY
The Phase II Pilot Study was intended to provide a means for information and technology exchange
between participating countries; information was also exchanged on regulatory and policy developments.
The primary vehicles for the exchange were the Pilot Study members' critical review of projects
submitted by the participating countries (Table 1.1), and technical presentations and themed discussions
at the meetings of the Pilot Study members. The technical work of the Pilot Study members was
enhanced by work on special topics by a number of CCMS Fellows2 (Section 1.4).
The Phase II Pilot Study was modeled on the Phase I study but included technologies that were in an
early stage of development, as well as those that were ready for full-scale demonstration.
The CCMS awards a number of Fellowships each year to meet travel and subsistence costs for projects related
to on-going Pilot Studies. Fellows (i.e., the recipients of fellowships) are encouraged to attend meetings of the
Study Group. Fellows have made important contributions to all three CCMS projects on contaminated land.
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NATO/CCMS Pilot Study, Phase II
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Table 1.1: List of Projects Included in CCMS Study on Remediation Technology
Country
Australia
Austria
Canada
Czech Republic
Denmark
France
Germany
Hungary
Project
Number
1
2
3
4
5
6
7
8
9
10
51
56
11
12
13
14
15
16
17
45
18
19
20
21
52
22
Title
Trial of air-sparging of a petroleum-contaminated aquifer
Bioremediation of petrochemicals following a major fire
Bioclogging of aquifers for containment and remediation of organic contaminants
Remediation of methyl ethyl ketone contaminated soil and groundwater
In situ bioremediation, bioavailability, and process control with different soil types
In s/fu/on-site bioremediation of industrial soil contaminated with organic pollutants: elimination of soil toxicity with
DARAMEND6
Demonstration of thermal gas-phase reduction process
Biodegradation/bioventing of oil-contaminated soils
Field demonstration of an in situ process for soil remediation using well points
Integrated treatment technology for the recovery of inorganic and organic contaminants from soil
Sobeslav, South Bohemia wood treatment plant
Spolchemie a.s.— mercury-contaminated site
On-site biological degradation of PAHs in soil at former gasworks site
Groundwater and soil remediation at former manganese sulfate production plant
Rehabilitation of a site contaminated by tar substances using new on-site techniques
Ozone treatment of contaminated groundwater
Combined chemical and microbiological treatment of coking sites/bioremediation of soils from coal and petroleum tar
distillation plants
Combined vacuum extraction and in situ stripping of chlorinated vapors
Treatment of polluted soil in a mobile solvent extraction unit
Bioremediation of soils from coal and petroleum tar distillation plants
Biological in situ remediation of contaminated gasworks
Cleaning of mercury-contaminated soil using a combined washing and distillation process
Fluidized bed soil treatment process— BORAN
Mobile low-temperature thermal treatment process
Permeable treatment beds
Environmental evaluations of former Soviet military bases in Hungary
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Country
Netherlands
Norway
Sweden
Switzerland
Turkey
United Kingdom
United States
Project
Number
23
24
25
53
26
27
28
54
49
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
47
50
55
Title
Modeling and optimization of in situ remediation
Combined remediation technique for soil containing organic contaminants: Fortec®
Slurry reactor for soil treatment
In situ bioremediation of chloroethene-contaminated soil
Treatment of creosote-contaminated soil (soil washing and slurry phase bioreactor)
Soil washing and chemical dehalogenation of PCB-contaminated soil
Use of white-rot fungi for bioremediation of creosote-contaminated soil
Treatment of PAH- and PCP-contaminated soil in slurry phase bioreactors
Characterization of residual contaminants in bioremediated soil and reuse of bioremediated soil
Sorption/solidification of selected heavy metals and radionuclides onto unconventional sorbents
Using separation processes from the mineral processing industry for soil treatment
Decontamination of metalliferous mining spoil
Cacitox™ soil treatment process
In-pulp decontamination of soils, sludges, and sediments
Chemical fixation of soils contaminated with organic chemicals
In situ soil vapor extraction within containment cells combined with ex situ bioremediation and groundwater treatment
Enhancement techniques for ex situ separation processes, particularly with regard to fine particles
Bioventing of hydrocarbon-contaminated soils in the subarctic environment
Demonstration of Peroxidation Systems, Inc., Perox-Pure™ advanced oxidation technology
Management of soil vapors at the Basket Creek site
An evaluation of the feasibility of photocatalytic oxidation and phase transfer catalysis for destruction
water (in situ treatment of chlorinated solvents)
In situ microbial filters
In situ pneumatic fracturing and in situ bioremediation
Multi-vendor bioremediation technology demonstration project
Enhanced in situ removal of coal tar: Brodhead Creek Superfund Site
In situ electro-osmosis (Lasagna™ project)
of contaminants from
Integrated rotary steam stripping and enhanced bioremediation for in situ treatment of VOC-contaminated soil (cooperative
approach to application of advanced environmental technologies)
Czechowice oil refinery project
NOTE: There are no Project Nos. 45, 46 or 48. Project 5 from Austria was withdrawn.
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NATO/CCMS Pilot Study, Phase II Final Report
The objectives were to:
exchange technical information on demonstrated technologies;
exchange information on the development of emerging and innovative technologies; and
recommend, develop, and adopt uniform data reporting methods for results of technology studies (demonstrations, bench, pilot, and other technology studies).
The third objective was intended to facilitate evaluation of the probable performance of a technology, based on a country's environmental, health, or risk standards.
The need for better reporting standards was identified during the Phase I Pilot Study. However, the nascent stage of technical developments in many countries
did not permit this need to be fully addressed. It is anticipated that the development of better reporting standards will be addressed further during the planned Phase
III Pilot Study.
A number of the conclusions drawn from the Phase I Pilot Study report were addressed during the Phase II Pilot Study. For example, Fellowship projects addressed
the costs and the design of demonstration projects. The organization of the Phase II Pilot Study is described in Box 1.3.
1.3 HOW THE INFORMATION IS PRESENTED
Chapter 2 presents an overview of the Phase II Pilot Study. It lists the 52 projects included in the study
and classifies them in several ways, including by their development status and whether in situ or ex situ
methods were employed.
Chapter 3 provides an overview of process-based remediation methods and is intended to show how the
different technologies discussed in later chapters relate to one another. The terminology used here and
elsewhere in the report generally corresponds to with that being developed by the International
Organization for Standardization (ISO) (4).
Chapters 4 to 9, which are generally organized as shown in Box 1.4, present the results of the Pilot
Study by technology area as follows:
• Chapter 4, In Situ Treatment;
• Chapter 5, Physical-Chemical Treatment;
• Chapter 6, Ex Situ Biological Treatment;
• Chapter 7, Thermal Treatment;
• Chapter 8, Stabilization/Solidification; and
• Chapter 9, Other (includes all projects not easily dealt with in the other chapters).
The broader topic of integrated treatment systems is addressed in:
• Chapter 10: Integration of Technologies.
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Box 1.3: Organization of the Phase II Pilot Study
Formal members of the Pilot Study held either "participant" or "observer" status. Each
country nominated a representative to attend Pilot Study meetings3, and these representatives
invited others from their countries to take part in meetings and activities. The major part of the
Phase II Pilot Study was completed during international meetings attended by:
• country representatives;
• technical experts representing Pilot Study projects;
• leading international experts invited to speak on topics of interest to the Pilot Study;
• nominated guests of the host country; and
• Pilot Study Fellows.
Individual country representatives nominated projects of potential interest to the Phase II Pilot
Study, and the representatives as a group voted whether or not to accept them. The Pilot Study
strived to maintain a balance between long-term and short-term projects4 across a range of
technologies. Projects that were accepted were expected to produce interim reports and a final
project report within the Pilot Study's lifetime. Throughout the Pilot Study, project presentations
were open to technical scrutiny and critical review. These discussions have been used in
conjunction with each project's interim and final presentations as the basis for information
presented in this report.
Each country was limited to a maximum of four active projects within the Pilot Study at any
one time, although during the course of the study, countries could replace completed projects
with new ones. Germany, the United Kingdom, and the United States all had more than four
projects accepted over the lifetime of this study.
The Phase II Pilot Study was at the forefront of technology development and application.
Hence, projects that might be regarded in some countries as state-of-the-art or innovative, such
as applications of thermal treatment, may not have been accepted into Phase II if they were
previously considered in Phase I. Where an established technology was accepted, it was
generally because the project focused on a novel application or involved a fundamental
investigation that offered potentially significant improvements in process optimization.
3 "Participants" are countries that had a technical project accepted within the Pilot Study while "observers" are
formal members of the Pilot Study, but did not contribute projects. Some countries have been represented by
individuals, such as the CCMS Fellows, and were not formal members of the Pilot Study.
4 Long-term projects involve technologies that are being developed in the laboratory and might not be
commercially available for another 5-10 years. Short-term projects involve technologies being evaluated in full
field-scale trials and are therefore near-market applications.
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Box 1.4: Organization of Technology Chapters
Introduction: A description of the technology including basic principles of the process and its
potential application. A fuller description is provided in Chapter 3.
Case studies included: A brief summary of the projects evaluated, including why the project
was chosen for evaluation. More detailed summaries of each project are provided in Appendix
IV (Volume 2).
Background of the case studies as a group: A synthesis of pertinent information from the
projects to help the reader understand the range of applicability of the technology. This
includes the type, concentration, and sources of contamination, as well as the type of media
that can be treated. The lessons learned in the application of the technology are also presented.
Performance results: An assessment of the results of the case studies, including whether project
objectives were met, whether the technology was effective, and lessons learned in site
preparation and operational testing.
Residuals and emissions: A discussion of the residual materials and emissions, if any,
associated with the technology that should be considered when evaluating the potential
application of these processes to contaminated sites.
Factors and limitations to consider for determining the technology's applicability: Identification
of both technical and non-technical aspects.
Costs: An overview of major capital, operating, and maintenance cost factors that need to be
considered by remediation planners. Typical costs or costs specific to case studies are provided
in some chapters.
Prognosis for technology: A summary of the state of the technology and its expected role in
future site remediation, including an identification of future research needs.
Conclusions and recommendations
1.4 RELATIONSHIP TO OTHER CCMS PROGRAMS
1.4.1 Contributions by CCMS Fellows
The CCMS Fellowship Program made an important contribution to the success of the Phase II Pilot
Study, as it did to the earlier studies on the remediation of contaminated soil and ground-water. It enabled
the participation of a number of experts from countries that would not otherwise have had a presence
in the Pilot Study. It also enabled a wider range of topics to be covered.
Ten NATO Fellows participated in the Phase II Pilot Study. Nine Fellows conducted associated studies
and submitted reports to the Pilot Study under the guidance of the Pilot Study Directors. One acted as
the editor of this report, and two others contributed to its preparation. The Fellows came from private,
university, and governmental organizations in Germany, Portugal, the Netherlands, Turkey, the United
Kingdom, and United States. Their activities examined a range of topics, including national approaches
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to environmental problems, costs and economics, quality management, innovative approaches to large-
scale remediation projects, and performance assessment of in situ treatment methods. The Fellows and
the subjects of their studies are listed in Appendix II. The Fellows' summary reports are provided in
Appendix V.
1.4.2 CCMS Study Visit Program
Participation of a number of individuals, particularly expert speakers, was made possible by travel funds
provided under the CCMS Study Visit Program.
1.5 CONTRIBUTIONS BY EXPERT SPEAKERS
Invited expert speakers (see Appendix III) attended all of the meetings, which often lead to an in-depth
discussion of a particular subject area. Where relevant, these discussions have been taken into account
in the preparation of this report.
1.6 CONCLUSIONS AND RECOMMENDATIONS
One of the major achievements of the Phase II Pilot Study is that it has demonstrated the benefits of
exchanging technical and economic information on the remediation of contaminated land and
groundwater. Conclusions regarding specific technologies, remediation in general, technology transfer,
and research needs were drawn from the Pilot Study. The conclusions and recommendations are based
on an analysis of the results of Pilot Study projects, and on the contributions of expert speakers, CCMS
Fellows, and the numerous other participants in the Study Group meetings.
The conclusions and recommendations reflect both the achievements to date in devising effective
treatment technologies and the gaps in the methods available to treat some of the more difficult
problems. The conclusions are presented in Chapter 12, which also includes the recommendations made
to the CCMS/NATO Council following the Study Group's deliberations.
1.7 REFERENCES
1. U.S. Environmental Protection Agency, Evaluation of Demonstrated and Emerging Technologies for
Treatment and Clean-up of Contaminated Land and Groundwater: Overview Report, EP A/542-R-98-
OOlb, 1998.
2. Smith, M. A. (editor), Contaminated Land: Reclamation and Treatment
Plenum (London) 1985.
3. U.S. Environmental Protection Agency, NATO/CCMSPilotStudy: Demonstration of Remedial Action
Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, 1993, EPA/600/R-
93/012a.
4. International Organization for Standardization, ISO DIS 11074-4: Soil Quality - Vocabulary: Part
4: Terms and Definitions Relating to the Rehabilitation of Soils and Sites
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Chapter 2: TECHNICAL OVERVIEW
Michael A. Smith
M.A. Smith Environmental Consultancy
2.1 INTRODUCTION
While the objective of the Pilot Study was to evaluate applications of particular technologies, a large
proportion of the projects involved more than one technology. For example, some involved the use of
integrated treatment systems combining more than one technology type, and others involved the
application of different more than one technology to address different aspects of site contamination (e.g.,
more than one contaminated medium). Other projects involved:
• large-scale remediation projects for which the remediation strategy had yet to be developed (e.g.,
Projects 51 and 56);
• theoretical studies (e.g., Project 23); and
• strategic scientific studies (e.g., Project 49).
Because the projects are classified below in a variety of ways, they may be counted two or three times,
and not all projects may be included in each analysis. Furthermore, the categorization of projects is, in
part, at a matter of judgment, and alternative categorizations to those presented here are possible.
The projects have been classified as follows:
• by the development status of the technology;
• whether they are in situ, ex situ technologies, or a combination of both;
• by the type of technology used;
• by the contaminants treated; and
• whether they involve a single technology, mixed technologies, or integrated treatment systems.
Table 2.1 summarizes the 52 "active" projects in the Pilot Study. Additional information can be obtained
from the project summaries, which are provided separately (Appendix IV). The project summaries
contain a technical abstract providing a synopsis of the author's written and oral reporting, but are not
a critical review of the material presented. The technical contact for the project is also provided in each
summary.
2.2 DEVELOPMENT STATUS
Forty-nine of the 52 pilot study projects were technology based. The Pilot Study accepted technical
projects in two stages of development: emerging and demonstration. For the purposes of this report an
emerging technology is defined (see Chapter 1) as being at bench- or pilot-scale, while a demonstrated
technology is one implemented at field- or full-scale. Demonstrated technologies are usually at or near
to commercial application. There was almost an even split of projects within the Pilot Study examining
emerging and demonstrated technologies.
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2.3. IN SITU VS. EX SITU
There were 18 projects using in situ technologies, 26 projects using ex situ technologies, six projects
using both in situ and ex situ technologies, and two projects for which the remediation strategy has yet
to be decided.
2.4 TECHNOLOGIES EMPLOYED
For the purposes of this report,the technologies described in each technical project were broadly
classified as one of five types: biological, chemical, physical-chemical, stabilization/solidification, and
thermal. The additional categories of "integrated" and "mixed" are used to describe combinations of
technologies used as part of an overall remediation strategy. Integrated refers to approaches where two
or more technologies are used simultaneously or in series to treat a specific site problem. "Mixed"
projects involved two or more technologies to treat different contaminated areas or media across a site
as part of an overall remedial strategy.
The classification of projects was as follows (Note that some projects are counted more than once.):
Technology Number of
Projects
Biological
Physical-chemical
Chemical
Thermal
Stabilization/Solidification
Other
24
29
4
5
2
4
Examples of Technologies
bioventing, biopiles, slurry reactors, white rot
fungi
soil vapor extraction, soil washing, solvent
extraction, ultraviolet treatment
photochemical oxidation, ozone treatment,
sorption, leaching
thermal desorption, incineration, thermal
vitrification
chemical fixation, grouting
site characterizations, free-product recovery
systems
There were 23 projects that relied upon a single technology, 19 that used integrated technologies, seven
mixed technologies, and three that did not involve treatment.Typical combinations were soil vapor
extraction with in situ biotreatment, soil washing followed by biotreatment, and soil washing followed
by thermal treatment.
2.5 CONTAMINANTS TREATED
Forty of the 52 projects were concerned only with the treatment of organic contaminants including
polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and BTEX compounds
(benzene, toluene, ethylbenzene, and xylenes). Six projects dealt exclusively with metals, while six dealt
with both inorganic and organic contaminants. One project focused on remediation of inorganic sulfates
and cyanides. A matrix showing the contaminants treated for each project is presented in Table 2.2.
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Table 2.1: Projects Included in NATO/CCMS Pilot Study,
Classification by Technology (February 1997)
Project
1
2
3
4
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Title
(Chapter in which Project is Addressed)
Trial of air-sparging of a petroleum-contaminated aquifer
(Chapters 4 & 10)
Bioremediation of petrochemicals following a major fire
(Chapter 4)
Bioclogging of aquifers for containment and remediation of
organic contaminants (Chapter 4)
Remediation of methyl ethyl ketone contaminated soil and
groundwater (Chapter 4)
In s;Mon-site bioremediation of industrial soils contaminated
with organic pollutants: elimination of soil toxicity with
DARAMEND® (Chapters 4 & 6)
Demonstration of thermal gas-phase reduction process
(Chapter 7)
Biodegradation/bioventing of oil-contaminated soils (Chapter 6)
Field demonstration of an in situ process for soil remediation
using well points (Chapters 4 & 10)
Integrated treatment technology for the recovery of inorganic
and organic contaminants from soil (Chapters 5 & 10)
On-site biological degradation of PAHs in soil at a former
gasworks site (Chapter 6)
Groundwater and soil remediation at a former manganese
sulfate production plant (Chapter 4)
Rehabilitation of a site contaminated by tar substances using a
new on-site technique (Chapters 7 & 10)
Ozone treatment of contaminated groundwater (Chapter 5)
Combined chemical and microbiological treatment of coking
sites/ bioremediation of soils from coal and petroleum tar
distillation plants (Chapters 4, 6, & 10)
Combined vacuum extraction and in situ stripping of
chlorinated vapors (Chapter 4)
Treatment of polluted soil in a mobile solvent extraction unit
(Chapter 5)
Biological in situ remediation of contaminated gasworks
(Chapter 4)
Cleaning mercury-contaminated soil using a combined
washing and distillation process (Chapters 5, 7, & 10)
Fluidized bed soil treatment process — BORAN (Chapter 7)
Mobile low-temperature thermal treatment process (Chapter 7)
Environmental evaluations of former Soviet military bases in
Hungary (Chapter 9)
Modeling and optimization of in situ remediation (Chapter 4)
Technology
Physical-
chemical
Biological
Biological
Physical-
chemical
Biological
Physical-
chemical
Thermal
Biological
Physical-
chemical
Physical-
chemical
Biological
Physical-
chemical
Thermal
Physical-
chemical
Chemical
Chemical
Biological
Physical-
chemical
Physical-
chemical
Biological
Physical-
chemical
Thermal
Thermal
Thermal
-
Physical-
chemical
Biological
In situl
ex situ
In situ
Ex situ
In situ
In situ
In situ
In situ
Ex situ
Ex situ
Ex situ
In situ
In situ
Ex situ
In situ
Ex situ
Ex situ
Ex situ
In situ
Ex situ
In situ
Ex situ
Ex situ
Ex situ
-
In situ
Single/
integrated/
mixed
Integrated
Single
Single
Integrated
Single
Single
Single
Integrated
Integrated
Single
Mixed
Integrated
Single
Integrated
Integrated
Single
Single
Integrated
Single
Single
Integrated
Research
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NATO/CCMS Pilot Study, Phase II
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Project
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
Title
(Chapter in which Project is Addressed)
Combined remediation technique for soil containing organic
contaminants: Fortec® (Chapters 5, 6, & 10)
Slurry reactor for soil treatment (Chapter 6)
Treatment of creosote-contaminated soil (soil washing and
slurry phase bioreactor) (Chapters 5, 6, & 10)
Soil washing and chemical dehalogenation of PCB-
contaminated soil (Chapters 5 & 10)
Use of white-rot fungi for bioremediation of creosote-
contaminated soil (Chapter 6)
Sorption/solidification of selected heavy metals and
radionuclides onto unconventional sorbent (Chapter 8)
Using separation processes from the mineral processing
industry for soil treatment (Chapter 5)
Decontamination of metalliferous mine spoil (Chapters 5, 6, &
10)
Cacitox™ soil treatment process (Chapters 5 & 10)
In-pulp decontamination of soils, sludges, and sediments
(Chapters 5 & 10)
Chemical fixation of soils contaminated with organic chemicals
(Chapter 8)
In situ soil vapor extraction within containment cells combined
with ex situ bioremediation and groundwater treatment
(Chapters 4 & 6)
Enhancement techniques for ex situ separation processes,
particularly with regard to fine particle (Chapters 5, 6, & 10)
Bioventing of hydrocarbon-contaminated soils in the subarctic
environment (Chapter 4)
Demonstration of Peroxidation Systems, Inc., Perox-Pure™
advanced oxidation technology (Chapter 5)
Management of soil vapors at the Basket Creek site (Chapter
9)
An evaluation of the feasibility of photocatalytic oxidation and
phase transfer catalysis for destruction of contaminants from
water (in situ treatment of chlorinated solvents) (Chapter 5)
In situ microbial filters (Chapter 4)
In situ pneumatic fracturing and in situ bioremediation
(Chapters 4 & 10)
Multi-vendor bioremediation technology demonstration project
(Chapters 4 & 6)
Enhanced in situ removal of coal tar: Brodhead Creek
Superfund Site (Chapter 5)
Technology
Physical-
chemical
Biological
Biological
Physical-
chemical
Biological
Physical-
chemical
Chemical
Biological
Stabilization/
solidification
Physical-
chemical
Physical-
chemical
Biological
Physical-
chemical
Physical-
chemical
Stabilization/
solidification
Physical-
chemical
Physical-
chemical
Biological
Physical-
chemical
Chemical
Physical-
chemical
Physical-
chemical
Biological
Biological
Other
Biological
Physical-
chemical
In situl
ex situ
Ex situ
Ex situ
Ex situ
Ex situ
Ex situ
Ex situ
Ex situ
Ex situ
Ex situ
Ex situ
In situ
In situ
Ex situ
Ex situ
In situ
Ex situ
Ex situ
Ex situ
In situ
In situ
In situ
Ex Situ
Ix situ
Single/
integrated/
mixed
Integrated
Single
Integrated
Integrated
Single
Single
Single
Integrated
Integrated
Integrated
Single
Mixed
Integrated
Single
Single
Single
Single
Single
Integrated
Mixed
Single
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Project
47
49
50
51
52
53
54
55
56
Title
(Chapter in which Project is Addressed)
In situ electro-osmosis (Lasagna™ project) (Chapters 4, 5, &
10)
Characterization of residual contaminants in bioremediated soil
and reuse of bioremediated soil (Chapter 6)
Integrated rotary steam stripping and enhanced bioremediation
for in situ treatment of VOC-contaminated soil (Cooperative
approach to application of advanced environmental
technologies) (Chapter 9)
Sobeslav, South Bohemia wood treatment plant (Chapter 9)
Permeable treatment beds (to be addressed in the Phase III
report)
In situ bioremediation of chloroethene-contaminated soil
(Chapter 9)
Treatment of PAH- and PCP-contaminated soil in slurry phase
bioreactors (Chapter 6)
Czechowice oil refinery project (Chapter 9)
Spolchemie a.s. — mercury-contaminated site (Chapter 9)
Technology
Physical-
chemical
Biological
Biological
Physical-
chemical
Biological
Biological
Containment
Physical-
chemical
Chemical
Biological
Physical-
chemical
Biological
Biological
Physical-
chemical
-
In situl
ex situ
In situ
Ex situ
In situ
Ex situ
In situ
In situ
Ex situ
In situ
Ex situ
-
Single/
integrated/
mixed
Integrated
Research
Mixed
Mixed
Integrated
Mixed
Single
Mixed
Other
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NATO/CCMS Pilot Study, Phase II
Final Report
Table 2.2: Projects Included in NATO/CCMS Phase II Pilot Study,
Classification by Media and Contaminants
PROJECT
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
MEDIUM
'o
C/3
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Groundwater
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
CONTAMINANT
>
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
<3
o
85
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Pesticides/PCBs
•
•
•
•
•
•
v>
o
31
Q_
•
•
•
•
•
•
•
•
•
Inorganics
•
•
•
•
•
•
•
•
•
•
•
•
•
NOTES
benzene, xylene, petroleum hydrocarbons
benzene, phenol, acrylonitrile
BTEX
MEK, oil, gasoline, turpentine, kerosene
project withdrawn
aliphatic and aromatic hydrocarbons, phthalates, chlorophenols
TCE, 1,2-DCE, methylene chloride, toluene, ethylbenzene, PCBs, benzidine,
benzene, vinyl chloride, chlorobenzene, PAHs, lindane, dieldrin, chlordane,
DDT metabolites
BTEX, PAHs, mineral oil, grease, pentachlorophenols
BTEX, aliphatic hydrocarbons
PAHs, lead, copper, zinc
PAHs
sulfate, cyanide
coal tar, PAHs, BTEX, phenols, cyanides, heavy metals, ammonium compounds
phenols, aliphatic and aromatic hydrocarbons, BTEX, acetone, ethanol,
chlorinated solvents, petroleum hydrocarbons
PAHs, phenols, cyanides
PCE
BTEX, PAHs, PCBs
PAHs, extractable lipophilic organics
mercury
PAHs, PCBs
BTEX, PAHs, mineral oils, lignite tar oil, mercury, TNT
jet fuel, including DNAPL
VOCs
mineral oils, PAHs, chlorophenol, lindane
mineral oil, PAHs
PAHs
PCBs
PAHs
lead, cadmium, copper, cesium-137, strontium-90
PAHs, phenols, heavy metals, cyanides
lead, zinc
heavy metals, radionuclides
copper, zinc, chromium, arsenic
chlorinated hydrocarbons, PAHs, benzene and benzene derivatives, phenolics,
PCBs, organophosphorus/sulphurous compounds
BTEX, PAHs, phenols, heavy metals, cyanides
PAHs, diesel fuel
jet propellant #4
TCE, PCE, 1,1,1-TCA, 1,1 -DCA
TCE, PCE, toluene, MEK, MIBK, lead, mercury
BTEX
TCE
benzene, toluene, xylenes
TCE, PCE, DCE, acetone, MEK, toluene
BTEX, PAHs, coal tar
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NATO/CCMS Pilot Study, Phase II
Final Report
PROJECT
NO.
45
46
47
48
49
50
51
52
53
54
55
56
MEDIUM
s
•
•
•
•
•
•
•
Groundwater
•
•
•
•
•
•
•
CONTAMINANT
(/)
O
9
•
•
•
•
•
<3
i
•
•
•
•
Pesticides/PCBs
•
•
v>
o
31
Q_
•
•
•
Inorganics
•
•
•
NOTES
accidental replication of project #15
project withdrawn
TCE
project withdrawn
unspecified hydrocarbons
unspecified VOCs
PAHs, phenols, heavy metals
various contaminants
TCE, PCE
PAHs, PCP
oil refinery organics
mercury
NOTES:
BTEX = benzene, toluene, ethylbenzene, and xylenes
DCE = dichloroethene
DDT = dichlorodiphenyltrichloroethane
DNAPL = dense, non-aqueous phase liquid
MEK = methyl ethyl ketone
MIBK = methyl isobutyl ketone
PAHs = polycyclic aromatic hydrocarbons
PCBs = polychlorinated biphenyls
PCE = tetrachloroethene
PCP = pentachlorophenol
PHCs = petroleum hydrocarbons
SVOCs = semivolatile organic compounds
TCE = trichloroethene
TNT = trinitrotoluene
VOCs = volatile organic compounds
2-7
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NATO/CCMS Pilot Study, Phase II Final Report
Chapter 3: PROCESS-BASED REMEDIATION METHODS
Michael A. Smith
M.A. Smith Environmental Consultancy
3.1 INTRODUCTION
A risk assessment is usually used in deciding whether or not to eliminate or reduce the risks posed by
a contaminated site. If the risks need to be reduced, a remediation strategy must be developed to address
them. For sites designated for development, the remediation strategy also must address engineering
requirements, such as minimum load-bearing capacities, and management objectives, such as making a
profit.
This chapter provides an overview of the available process-based remediation methods for controlling
risk. It draws extensively on the lessons learned from the Phase I Pilot Study (1), which also contributed
to the development of the primary reference for this chapter (2). Descriptions of specific methods are
provided in subsequent chapters.
In general, the suitability of a remediation method depends on many factors including: contaminated
media, contaminants, remediation objectives, current status of the site, location of the site, time available
to complete the treatment, and money available to pay for the treatment.
3.2 BASIC OPTIONS AND CLASSIFICATION OF METHODS
The three basic approaches to remediation are:
• risk avoidance by changing the intended use of the land, re-routing a sewer, etc.;
• elimination of the risks by removing or destroying contaminants; and
• control of risks to an acceptable level by reducing contaminant concentrations or by containing
the contaminants, such as installing barriers between the contaminants and potential receptors.
The remediation strategy developed for a particular site may combine all three approaches and several
different methods.
The methods may be classified as1 civil engineering-based methods, such as excavation, containment
using cover systems and vertical barriers, and hydrogeological controls; or process-based methods.
Process-based methods can be further classified on the basis of the underlying physical-chemical
principles involved. For the purposes of this report, they are classified according to the following generic
processes: thermal, chemical, biological, physical, and stabilization/solidification.
This allocation is a matter of judgment. For example, vitrification, considered a thermal method in this
classification scheme, may be viewed by others as a solidification process. The generic processes are
1 The terminology employed throughout this report is generally consistent with that proposed by the International
Organization for Standardization (ISO) in its draft document: CD 11074-4: Soil Quality Vocabulary — Part 4
Terms and definitions relating to rehabilitation of soils and sites.
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frequently combined in treatment trains so that, for example, soil washing becomes the prelude to
chemical or biological treatment.
Process-based methods may be applied ex situ—after contaminated soil or ground-water has been
removed from the ground for treatment—or in situ—without removing the contaminated media from the
ground. Ex situ treatment may be performed onsite or offsite.
Although civil engineering approaches are discussed only briefly in this chapter, often they are used in
conjunction with process-based methods.
3.3 CIVIL ENGINEERING-BASED METHODS
Civil engineering-based methods, may be an essential precursor to the application of a process-based
method involving ex situ treatment. Furthermore, civil engineering-based methods, such as vertical
barriers and lowering the water table, can also be essential to the application of an in situ treatment, such
as soil vapor extraction. Issues to be addressed during the excavation of contaminated media for
subsequent treatment include:
• delineation of the volume of material to be removed;
• compliance with excavation specifications to ensure that all material that should be removed has
been removed;
• control of potential environmental impacts as well as other impacts, such as emissions to the
atmosphere and traffic movements;
• engineering support, such as controlling water levels, required for excavation to proceed;
• ancillary support, such as the treatment of contaminated groundwater;
• facilities required for temporary storage;
• source and specification of clean replacement material, including chemical composition; and
• planning and permissions, including permits.
Careful consideration must be given to pre-treatment requirements of civil-engineering-based methods,
such as particle size and moisture content of the contaminated media. In addition, hydraulic measures
are often essential components of remediation systems. The extraction or infiltration of groundwater may
be used to:
• control groundwater levels, enabling excavation to take place;
• control groundwater levels in conjunction with physical barriers as part of a long-term
remediation strategy;
• control groundwater levels and flow directions so that in situ treatment, such as soil flushing or
soil vapor extraction, can be applied;
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NATO/CCMS Pilot Study, Phase II Final Report
• extract ground-water for ex situ treatment (pump-and-treat) and return the treated water to the
ground; and
• infiltrate water as part of an in situ treatment process.
Extracted groundwater may be contaminated and require either disposal to the local sewer system or on-
site or off-site treatment.
Vertical barriers, which can be designed in a number of ways (3, 4, 5, 6), are used to control the
migration of contaminated groundwater and soil gas. They are frequently used in conjunction with
hydraulic measures to control the groundwater plume or with an active or passive system to control gas
emissions. When used as the primary remediation method, vertical barriers must be designed to last,
sometimes for decades. When used as an adjunct to another treatment method (for example, to control
the groundwater flow rate, flow direction, and level), they usually need to last for a much shorter time.
As a permanent solution, vertical barriers have several disadvantages. No matter how well designed and
installed, barriers perform satisfactorily only for a limited time, albeit possibly several decades.
Eventually, they have to be replaced unless steps have been taken to remove the original hazard or the
potential for migration decreases with time as can occur at gas-producing sites. Because experience is
limited in the use of vertical barriers under all environmental conditions, predicting performance is
difficult.
3.4 PROCESS-BASED METHODS
3.4.1 Ex Situ Methods for Solids and Liquids
Several generic methods are available for the ex situ treatment of solids (e.g., soils, sediments, sludges,
and filter cakes) and liquids (e.g., groundwater, surface water, and wastewater). Treatment aims to
remove, destroy, or modify contaminants, rendering them unavailable to potential human and
environmental targets. Whether an ex situ method can be applied at a site is determined by the nature
and distribution of the contaminants, and by the physical, chemical, and in some cases, biological
properties of the media to be treated.
Many generic methods generate waste streams that may require further treatment or disposal. This may
take place onsite, using for example mobile or transportable treatment systems, or at off-site fixed
treatment facilities. The decision to treat contamination onsite or offsite depends on a number of factors,
including availability and cost of on- and off-site facilities; available time scales; and site-specific
factors, such as the location of the site relative to off-site treatment centers, space available for on-site
treatment and temporary storage, and availability and capacity of local services, such as power, drainage,
and water supply.
On-site treatment generally requires:
• appropriate approvals for operating the treatment equipment;
• preparation of the site to receive the treatment plant and equipment;
• appropriate site services and support facilities to protect occupational and public health and
safety and the environment;
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NATO/CCMS Pilot Study, Phase II Final Report
• installation and commissioning of the treatment plant; and
• temporary storage and materials-handling facilities for feedstocks, products, and wastes.
When the use off-site facilities is expected, it is important to:
• comply with legal requirements on the transfer of controlled wastes and the discharge of
hazardous effluents;
• make arrangements for temporary storage and pre-treatment requirements prior to transfer;
• ensure adequate protection of the workforce, public, and environment during transfer operations;
and
• agree on transport routes and permissible shipping rates.
Factors requiring special attention during the selection, design, and implementation of any remedy
include:
• properties of the material to be treated in relation to potential applicability, effectiveness, and
constraints;
• need for treatability studies;
• materials handling requirements;
• engineering aspects, such as ancillary engineering support;
• operational aspects, such as electrical and water services required;
• testing for compliance and performance to demonstrate that target concentrations and other
specifications can be achieved;
• potential for integration with other remedial measures; and
• compatibility with engineering and management objectives.
To assess the applicability and potential performance of ex situ treatment methods, information is
required on the contaminants present (e.g., types, concentrations, speciation, and distribution) and the
physical, chemical, and biological properties of the material to be treated. The data on applicability and
performance should be tailored to meet the specific requirements of the method, or methods, intended
for use. In most cases, this involves collecting supplementary data beyond that necessary for the risk
assessment and initial remedy selection. Treatability studies are likely to be required to select, design,
and implement the remedy.
Many ex situ treatment methods are specific to particular types of contaminants and are sensitive to
variations in feedstock composition. Comprehensive data on the composition of the material are needed
to ensure:
• applicability to the contaminants present;
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NATO/CCMS Pilot Study, Phase II Final Report
• applicability to the material to be treated;
• applicability to the contaminant concentration range that needs to lie within the range that can
be treated;
• absence of any interfering or inhibitory substances;
• feedstocks in the correct physical form for processing;
• maintenance of optimal processing conditions; and
• accurate predictions of the waste stream composition so that appropriate pollution control
measures can be provided and suitable disposal and discharge arrangements can be made.
Several factors determine how effective the treatment method will be in producing material that
consistently achieves pre-defined remedial objectives, such as residual contaminant concentrations. These
factors include the composition, physical condition, and homogeneity of the feedstocks; presence of
inhibitory or interfering substances; and conditions that affect the ability to maintain the process at
optimal levels. Factors that can limit the effectiveness of ex situ methods of treatment include:
• inappropriate particle size preventing effective contact between treatment reagents and
contaminants;
• heterogeneous feedstocks leading to variable performance and quality of the treated product;
• inappropriate matrix types, such as clay or humic soils in soil washing technologies or overly
coarse material in thermal treatment technologies;
• complex contaminant mixtures leading to antagonistic or unproductive reactions, or interference
in the main process reaction; and
• sub-optimal processing conditions leading to poor or variable performance.
When selecting, designing, or implementing remedial strategies that include ex situ treatment methods,
effectiveness must be defined. The potential effectiveness of the method should always be considered
in the context of its ability to meet the prescribed standard, such as allowable residual concentrations
of contaminants in treated material or compliance with teachability criteria.
Although low residual contaminant concentrations may appear to provide the most direct means of
assessing effectiveness, they may not always be a sufficient measure of the ecological quality of soil or
other treated material. A number of treatment methods, including biological and chemical methods, can
produce toxic intermediates or fail to adequately treat low concentrations of highly toxic substances.
Thus, direct measures of toxicity may be required.
All ex situ treatment operations should be subject to compliance and performance testing. Typically, such
tests include assessing the potential for exposure of personnel to hazardous materials and measuring the
composition of emissions to the atmosphere, discharges to the sewer, and any material landfilled onsite
or offsite. Performance evaluations include:
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NATO/CCMS Pilot Study, Phase II Final Report
• On-going monitoring of treatment performance, measured, for example, as interim quality
inspections on samples of processed material; and
• Final validation of the quality of the treated product to confirm that it conforms to pre-defined
remediation objectives. Validation may include a variety of measurements, such as total
concentrations of residual contamination in the treated product, concentrations of hazardous
substances in leachates prepared under standard conditions, and measurements of the physical
condition (e.g., strength development) of the treated product.
Post-treatment validation programs vary depending on the methods used, contaminants treated, volume
of material handled, and variability of the feedstocks.
Long-term testing of material processed in ex situ systems is unlikely to be required although long-term
monitoring may be necessary where stabilized/solidified material has been returned to the site. Long-term
monitoring may involve periodic removal and chemical/physical analysis of cores of treated material.
In addition, groundwater monitoring wells may have to be installed to determine long-term changes in
water quality.
3.4.2 Ex Situ Treatment of Groundwater and Other Contaminated Liquids
Where soils are treated using ex situ methods, such as soil washing, the treatment and/or disposal of
process waters and effluents usually form part of the overall treatment system. Contaminated waters
requiring ex situ treatment include:
• surface waters, such as ponds and lagoons;
• groundwater collected during pump-and-treat operations;
• groundwater removed incidentally as a result of excavation and other engineering operations;
• effluents from the pre-treatment of solids (e.g., dewatering of dredged sediments or industrial
sludges);
• aqueous liquids extracted from contaminated soil and waste;
• leachates collected from waste deposits and contaminated sites;
• contaminated water from in situ soil flushing or washing, and chemical treatment operations;
• process effluents from ex situ treatment of solids (e.g., soil washing and chemical treatment);
and
• effluents from the decontamination of plant and equipment, using, for example, high pressure
water jets.
Contaminated waters may contain only one or a small number of contaminants present over a relatively
narrow concentration range, or they may contain complex mixtures of contaminants at wide-ranging or
very high concentrations. In addition, these concentrations may fluctuate over time, and the volumes of
liquid to be treated and time scales may vary considerably. For example:
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NATO/CCMS Pilot Study, Phase II Final Report
• Process and decontamination effluents associated with the ex situ treatment of solids arise only
during the operational phase of remediation, and the total volumes of effluents to be treated may
be relatively small; and
• Treatment of large volumes of contaminated ground-water may be necessary over extended time
periods, particularly where source control measures are not possible and groundwater
remediation is the only feasible means of reducing contamination hazards.
Options other than on-site treatment of contaminated water may be available. Two examples are
discharge to an existing sewage treatment plant, possibly after some initial pre-treatment, or transfer by
tanker to a central treatment facility.
Treatment methods developed for drinking water, process water, sewage treatment, and industrial effluent
can be adapted, provided that the physical, chemical, and biological properties of the liquid to be treated
and the design and operational requirements of the treatment system have been considered. Several
methods have been specially developed for the treatment of contaminated groundwater.
Contaminated waters from land remediation projects usually require treatment in an integrated treatment
train in order to overcome variations in contaminant types and concentrations, flow rates, and physical
properties. Treatment trains usually conform to the following basic sequence: pre-treatment, primary
treatment, secondary treatment, and tertiary treatment or polishing. As liquid moves through the
treatment train, it becomes progressively cleaner. Trace levels of contamination are removed in the
tertiary treatment stage. In conventional applications, treatment trains are normally constructed as
permanent installations.
A number of treatment methods or options may be available at each stage of the treatment train. The
methods selected depend on their compatibility; the physical, chemical, and biological properties of the
liquid; and quality of the water to be achieved on completion of treatment.
The liquids must be well characterized at the outset in order to provide for appropriate treatment stages
and adequate capacity for expected variations in concentration and flow. In modern industrial plants, care
is taken to ensure that effluents from processes having different treatment requirements are not
unnecessarily mixed in, thereby adding to the technical difficulties and costs of downstream treatment.
For instance, effluents with inorganic and organic contaminants are not mixed because they have
different treatment requirements. Particular attention should be given to the potential for biological and
mineralogical fouling of treatment systems.
The information needed to design a treatment system for a contaminated land application is similar to
other systems. However, the system design must take into account the:
• variable nature of water;
• common presence of contaminant mixtures and the inability to control for them;
• range of contaminant concentrations frequently present;
• temporary status of the treatment plant (with the exception of some groundwater treatment
operations); and
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NATO/CCMS Pilot Study, Phase II Final Report
• the fact that systems often have to be installed in less than optimal physical conditions, such as
working space, services, terrain, and access.
The relatively short-term nature of many contaminated land projects, compared to conventional water
and wastewater treatment applications, presents a number of potential design problems. The conventional
treatment plant is usually designed and constructed to last for 20 years or more depending on the life
expectancy of the equipment. Contaminated land projects are typically much shorter. The shorter time
scales have implications for the commercial availability and operational efficiency of the treatment plant,
and for the cost of designing the treatment system. For instance:
• Appropriate plants may not be available "off-the-shelf;"
• Commercially available plants may not operate as effectively on a small scale due to design
constraints; and
• Cost may be very high relative to the volume of material to be treated.
During the life cycle of a groundwater treatment project, significant changes may occur in the basic
parameters that determined the selection and design of the initial treatment system. When designing
groundwater treatment systems, it must be understood that:
• Management of the hydraulic regime, including the extraction and recharge rates, should be
considered an integral part of the overall design of a pump-and-treat system;
• Flow rates may be controllable within limits (allowing for a choice of plant size) or dictated by
hydrogeological factors, such as the pumping rate required to control plume migration—all of
which may change during the lifetime of the project;
• Because contaminant concentrations decrease with time, different treatment processes may be
required at different stages of a project in order to maintain technical effectiveness and economy
of operation;
• Relatively small plant sizes may mean high operating costs compared to capital costs; and
• A point probably will be reached when ex situ treatment ceases to be more effective than natural
degradation or dispersion processes—this point may occur before target concentrations are
reached. If this occurs, a period of passive management, such as monitoring, will be required
until target concentrations are achieved.
3.4.3 In Situ Methods for Soils
In situ treatment methods avoid the above-ground environmental impacts and costs associated with
excavation and extraction. Some methods are particularly attractive for application on operating sites and
other sites where buildings and structures need to be preserved.
In situ technologies for treating soil and similar materials can be classified like their ex situ counterparts
on the basis of the underlying treatment principle, such as physical separation and biological degradation.
In addition, a distinction can be made between those methods that seek to remove, destroy, or stabilize
contaminants by introducing a treatment agent into the ground, and those that act directly on the ground,
such as electroremediation and in situ vitrification.
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NATO/CCMS Pilot Study, Phase II Final Report
Typically, the aim of in situ remediation is to treat the saturated or unsaturated zones, although some
integrated systems are capable of treating both. Methods for the treatment of soil and soil-like materials
(including soil water and gas) and methods intended to treat ground-water and associated strata may be
used separately or in an integrated system. In situ treatment methods may be combined with pump-and-
treat methods to treat contaminated groundwater. Soil flushing, in situ bioremediation, and soil vapor
extraction may be combined in an integrated remediation scheme. Heat may be introduced to aid
bioremediation or vapor extraction, and electrokinetic techniques may be used to enhance penetration
of chemical or stabilization agents.
Typical in situ systems:
• deliver a treatment agent or agents in liquid, gas, or energy form;
• recover products; and
• dispose of or treat products, although the aim of many methods is to produce only non-harmful
products or safely "lock-up" contaminants in situ.
The engineering, legal, and operational issues that must be addressed in all in situ applications are
generally the same as those for ex situ treatment:
• site characterization and pilot studies to determine potential applicability, effectiveness, and
constraints;
• testing for compliance and performance; and
• compatibility with engineering objectives.
Thorough characterization of the chemical contaminants and physical properties of the contaminated
matrix is essential for a proper evaluation of the feasibility of particular in situ treatments. Also, the
mode of action, which usually involves in-ground treatment, often at significant depths, imposes unique
constraints on treatment applicability and feasibility. Site characterization should be tailored to meet the
specific requirements of the method, or combination of methods, that may be applied. This almost
certainly requires supplementary investigations beyond those that estimate risk. Bench and pilot-scale
treatability studies are frequently required.
Accurate identification of all contaminants present, combined with treatability data, is essential because
of the danger that a treatment adopted to remedy some contaminants could lead to adverse or counter-
productive reactions with other contaminants. This may result in increased toxicity or mobility. An
understanding of the physical characteristics of a site is essential for all in situ techniques, especially
those requiring infiltration of treatment agents. Information on the engineering properties of the ground
is required, especially if heavy equipment is used or if the remedial action itself could lead to
unfavorable ground changes, such as increased soil density, volume, or instability.
The effectiveness of in situ treatment methods is determined by a variety of factors, including:
• nature, extent, and distribution of contaminants;
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NATO/CCMS Pilot Study, Phase II Final Report
• contact achieved between contaminants and treatment agents, and often the extent to which the
contaminants can be solubilized (Conductivity and penetration can be enhanced by a variety of
means);
• accessibility of the contaminants on a micro- and macro-scale;
• control over processing conditions in the ground which are not visible, especially when working
at considerable depth;
• extent to which treatment agents can be delivered to the site of action;
• ability to effectively remove treatment products and excess agents from the ground; and
• time available for treatment in terms of access to the site and natural factors, such as
groundwater flow rates.
Minimal information is available on the long-term effectiveness of in situ treatment methods that do not
remove or destroy contaminants. Effectiveness is limited by the actual contamination as well as the
perception of contamination. A system design based on an inadequate understanding of the contamination
and site characteristics may not be sufficient to treat the actual situation. Flexible and robust designs that
can be modified as treatment proceeds are essential.
In situ techniques are likely to be most effective when applied to specific types of contaminants in
homogeneous ground conditions or at least well defined heterogeneous ground conditions. Monitoring
undertaken during processing and for a considerable time after treatment is likely to be required to fully
demonstrate effectiveness over time.
Often engineering or hydraulic measures must be employed to contain in situ methods of treatment or
to increase the volume of soil available for treatment. For instance, if the groundwater table needs to
be lowered, consideration must be given to whether the mobility of contaminants will increase. This can
occur when a floating layer of contaminants enters the saturated zone. In addition, lowering the
groundwater table may adversely affect trees and other vegetation, and alter the level and flow of surface
water bodies. In situ treatment may have significant implications on the engineering properties of the
ground and hence on any subsequent construction works. For example:
• Infiltration/extraction operations may affect the stability of the neighboring buildings, plant, and
services;
• Density and volume increases may result from the addition of solidification/stabilization reagents
or grouts; and
• Changes in load-bearing capacity must be taken into account in designing foundations.
The delivery systems used to deliver treatment agents to the sub-surface and to recovery systems may
be propelled by gradients, such as hydraulic, pressure, chemical, temperature, and electrochemical/
electrokinetic gradients. Systems based on air or gas are driven by similar potentials.
Where aqueous fluids are to introduced into the ground, facilities for preparing, storing, and
"reconditioning" recirculated extraction solutions must be provided. Treatment agents may be hazardous
and potentially polluting and thus require appropriate storage and handling arrangements. Also, recovered
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NATO/CCMS Pilot Study, Phase II Final Report
treatment solutions or gases, and incidental emissions, such as those from heat treatment, require
appropriate treatment or disposal.
The site geology and hydrogeology may be such that treatment agents are diverted away from target
areas, thereby limiting effectiveness and possibly leading to the contamination of surrounding ground.
For water-based systems, an initial test of the delivery system using water only or water with a tracer
usually is necessary to make sure the recovery system is adequate.
Delivered materials are typically liquids but may be gases (such as those used in soil vapor extraction
and bioremediation), vapors, slurries, or solids. Recovery systems involve fluid flows (gases, liquids, and
emulsions) and may require enhancement by modifying the physical or chemical attributes of the
contaminants or pathways.
Problems associated with installing and operating delivery and recovery systems include:
• presence of structures, plant, and services;
• presence of physical obstacles, such as boulders, drums, concrete debris, and hard rock;
• depth restrictions that affect the integrity and performance of the system;
• ensuring the penetration of aqueous fluids where hydraulic conductivity is less than about 10~6
to 10"5 m/sec;
• presence of contaminants with low solubilities;
• adsorption of contaminants onto clay minerals or organic matter;
• existence of fractures or other secondary porosity that create paths of high conductivity in
bedrock of otherwise low conductivity;
• absence of an underlying low-permeability layer that precludes migration of delivered materials
and treatment products;
• whether remedial action is progressing as planned;
• whether remediation targets (standards) have been achieved;
• whether any contaminants or treatment agents have migrated beyond the operational area;
• composition of extracted fluids or emissions, which could provide information on progress and
treatment/disposal requirements;
• presence and nature of any fugitive emissions to the atmosphere;
• validating that treatment has been fully effective; and
• determining whether the engineering properties of the ground have been affected by the
treatment.
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Procedures for monitoring soil and groundwater are likely to be required in most applications of in situ
technologies. The basis for deciding compliance in terms of pre-defined remediation criteria, and the
statistical basis for accepting that compliance has been achieved, should be decided before monitoring
is carried out. Although most in situ methods affect both solid and liquid media, these media can be
affected separately when parallel treatment processes are used. Monitoring procedures vary depending
on the purpose of the testing and the methods used, but they typically include (7):
• installing monitoring wells for collecting groundwater samples as well as assessing groundwater
and contaminant movement at the site;
• monitoring recovery streams to determine the quantity of contaminants removed;
• analyzing cores of treated material to determine residual concentrations or other properties, such
as teachability of stabilized/solidified soils; and
• monitoring process streams, such as treated groundwater or air from soil vapor extraction
systems, to determine quality prior to discharge.
Monitoring data can be used in making process stream and mass balance calculations, which are used
to establish how effective in situ treatment is in removing contaminants. Such calculations are important
because demonstrating the effectiveness of in situ treatment can be difficult in the presence of
heterogeneous ground conditions, poor accessibility of contaminants, low degree of mixing, and
migration of contaminants away from the zone of treatment due to the remedial action itself. Experience
has shown that concentrations of contaminants in groundwater recovery streams may decrease initially,
but then increase after a period of inaction as contaminants move back into the groundwater system from
the fine pore structure or other locations in the ground. Similar behavior can be observed when soil
vapor extraction is applied to ground containing zones of low gas permeability within strata of higher
permeability. Long-term monitoring, well beyond the point at which remedial action appears to be
complete, is often required to confirm that remediation has been fully effective.
3.4.4 In Situ Treatment of Groundwater
In situ treatment of groundwater requires water to pass through a treatment zone where injection of
agents in solution or in gaseous form cause degradation or promote natural degradation of contaminants;
or a solid substrate exists that supports physical separation of the contaminants by adsorption, chemical
or biological degradation, or reduction in toxicity.
These two processes may be used in combination. In situ treatment of groundwater may be combined
with in situ treatment of the unsaturated zone. Soil vapor extraction coupled with microbial treatment
is an example of this type of combination. In situ groundwater treatment also may be combined with
pump-and-treat operations. The flow of groundwater through or to the treatment zone may be the result
of natural gradients; induced by pumping from vertical or horizontal wells, or by infiltration of water;
or achieved through injection of heated water or steam.
Regulatory authorities should always be consulted prior to applying such methods to obtain relevant
permissions for installing and operating injection and extraction wells, and for deliberately introducing
chemical agents into the environment.
In situ groundwater remediation requires a thorough understanding of the hydrogeology of the site and
its environs, and usually requires the prior removal or containment of the source of the contamination
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and removal of free product. As for all in situ methods, ensuring contact between contaminants and the
treatment agent is the major practical difficulty. Contaminants may be adsorbed onto mineral surfaces
and held in capillary pores. Effective long-term treatment requires that these contaminants be released
into the groundwater. A variety of means may be used to promote the movement of contaminants
through the subsurface. These include hydrofracturing, electrokinetic techniques, injection of steam or
hot water, and surfactant flushing.
Because contaminant mobility is different at each site, any in situ treatment method must take into
account the characteristics of the contaminants present. Contaminants partition between liquid, soil, and
vapor phases in amounts characteristic of the contaminants, aquifer materials, organic content, and other
geochemical factors. For many contaminants, these associations vary and may not be completely
reversible. Modeling groundwater and contaminant movement is often required to design the treatment
system.
Significant amounts of groundwater flow—both horizontally and vertically—may occur through limited
parts of the aquifer, and the direction and rate of flow may be markedly different at different depths.
This can result from spatial variability in the permeability of water, or as a result of density or other
contaminant characteristics. Thus, neither the bulk water flow nor the distribution of contaminants can
be assumed to be homogeneous.
Principal treatment methods for in situ groundwater contamination include:
• oxidation of contaminants by introducing oxidizing agents, such as oxygen, ozone, hydrogen
peroxide, and permanganate;
• enhancement of natural biological degradation processes;
• air-stripping of volatile organic compounds;
• adsorption on, or reaction with, reactive materials, such as those in a chemical barrier; and
• biological degradation within an active barrier.
Planning and management requirements typically associated with these methods include:
• obtaining appropriate approvals to install and operate extraction and infiltration wells and to
introduce treatment agents into the groundwater;
• obtaining appropriate approval to install and operate a treatment plant;
• preparing the site to receive the installation, including preparing any reagent storage or handling
facilities; and
• monitoring to measure boundary effects, check progress, and determine the completion point.
Technical specifications should ensure:
• appropriate controls over treatment agents and other materials used during treatment;
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• proper provisions for locating, installing, operating, and maintaining injection wells, barrier
systems, and associated storage facilities; and
• satisfactory monitoring arrangements, particularly to determine the end point of treatment.
Care is required in the selection and design of an in situ groundwater treatment system to ensure that:
• any chemical introduced into the ground during treatment does not itself become a pollutant;
• mobilization of contaminants other than those that are the primary object of the treatment or are
naturally present is prevented; and
• treatment end products are not more harmful than the original compound.
A full understanding of the contamination and the geological, hydrogeological, and geochemical
characteristics of the site is required to effectively design and implement the remedy. Detailed
information is necessary on a range of physical-chemical properties of the contaminants, including
sorption characteristics, volatility, partitioning, and chemical and microbial degradability.
A range of laboratory investigations, such as treatability studies, development of sorption isotherms, and
column and microcosm experiments, are necessary to determine contaminant transport and transformation
parameters, assist in developing a full understanding of site conditions, and enable evaluation of
alternative methods of treatment. When microbial treatment is used, laboratory studies usually are
required to determine if the native populations of microbes can degrade the contaminants, and if minerals
are present to promote maximum activity at ambient groundwater temperature and under aerobic
conditions. Natural conditions may be anaerobic or only slightly aerobic. Data on the quantity of
contaminants present and the porosity of the aquifer can be used to calculate theoretical oxygen
requirements for degradation and the volumes of air or water (saturated with air or oxygen) needed to
supply the oxygen. Similar calculations can be made for the unsaturated zone.
Relatively scarce information is available on the long-term effectiveness of most in situ groundwater
methods, and much of it originates only from field trials. However, the use of hydrogen peroxide as an
oxygen source at petroleum contaminated sites to enhance biological degradation rates, and sparging to
strip volatile contaminants and encourage biological degradation, are established techniques.
Effectiveness may be enhanced by using techniques, such as hydrofracturing or pneumatic fracturing,
surfactant flushing, electrokinetics, and hot water and steam flushing, to promote the movement or
penetration of treatment agents or contaminants. However, many of these systems are themselves at an
early stage of development.
Chemical and other forms of treatment requiring the introduction of agents into the ground are limited
by the fact that groundwater flows within an aquifer in a plug flow manner, providing very minimal
natural mixing. Therefore, introduced agents tend to be pushed ahead of water entering the treatment
zone. Such difficulties may be overcome by using systems designed to induce mixing, such as the UVB
system (Project 43).
Precipitation and polymerization may lower hydraulic conductivities near the injection wells making
closely spaced wells necessary for effective treatment. Microbial growth close to points of nutrient and
oxygen injection may have a similar effect.
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In general, permeable barriers can be used only in relatively shallow aquifers because the trench must
be excavated to a layer of low permeability. However, it may be possible to design fence-and-gate
systems to operate effectively where contamination is restricted to the upper portion of an aquifer. In
1992, the Technology Innovation Office (TIO) of the USEPA identified in situ groundwater treatment
as a critical area requiring research and development. TIO surveyed available technologies and ongoing
research and development on chemical, biological, and physical treatments that alter the toxicity of
contaminants, enhance their removal, or improve the mobility of non-aqueous phase liquids (8). The
report concluded that the range of techniques available was very limited; at the present rate of
development, alternative technologies may not be available for three to five years; and of the 15
technologies under development, most were at the bench- or pilot-scale stage.
3.5 REFERENCES
1. U.S. Environmental Protection Agency, NA TO/CCMS Pilot Study: Demonstration of Remedial Action
Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, 1993, EPA/600/R-
93/012a.
2. Harris, M.R., S.M. Herbert, and M. A. Smith, "Remedial Treatment for Contaminated Land, Volumes
I to XII: Selection and Classification of Available Methods," Construction Industry Research and
Information Association, London, 1995-1997, Special Reports 101-112.
3. Harris, M.R., S.M. Herbert, and M.A. Smith, "Remedial Treatment for Contaminated Land, Volume
VI: Containment and Hydraulic Measures," Construction Industry Research and Information
Association, London, 1996, Special Report 106.
4. Privett, K.D., S.C. Matthews, and R.A. Hodges, "Barriers, Liners and Cover Systems for
Containment and Control of Land Contamination," Construction Industry Research and Information
Association, London, 1996, Special Report 124.
5. Building Research Establishment, "Slurry Trench Cut-off Walls to Contain Contamination," Building
Research Establishment Digest, Garston, 1994, 395.
6. "1997 International Containment Technology Conference and Exhibition, St. Petersburg, Florida,
USA, February 9-12, 1997'," Land Contamination and Reclamation, 1997, 5(3), [Special Issue]
7. Harris, M.R., S.M. Herbert, and M.A. Smith, "Remedial Treatment for Contaminated Land, Volume
III: Site Investigation and Assessment," Construction Industry Research and Information Association,
London, 1995, Special Report 103.
8. U.S. Environmental Protection Agency, In Situ Treatment of Contaminated Ground Water: An
Inventory of Research and Field Demonstrations and Strategies for Improving Ground Water
Remediation, 1993.
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Chapter 4: IN SITU TREATMENT
Mark Smith
European Office of Aerospace Research and Development
Cathy Vogel and Alison Thomas
Tyndall Air Force Base
4.1 INTRODUCTION
Environmental remediation technologies can be broadly divided into two categories: ex situ and in situ.
Ex situ technologies treat contaminated materials after gross removal and transport of contaminated
media to the treatment facility. Actual treatment often occurs onsite—reducing costs, risks, and
administrative burden incurred with hazardous material portage. In contrast, in situ technologies apply
the remediation process directly to the contaminants, with little or no gross movement of hazardous
material.
The cost of environmental remediation is, to a large degree, directly proportional to the amount of
material handled in the process. When large masses of earth or water are removed and cleaned, costs
are incurred for both the physical handling of the material—large fractions of which may be
uncontaminated—and for application of the treatment process in order to ensure complete
decontamination. Deep contamination can involve extensive excavation of uncontaminated overburden.
In addition to direct costs, excavation of contaminated soil is often impractical due the presence of
overlying structures.
In situ processes attempt either to destroy the contaminants where they are found or, at the very least,
to remove the contaminants from the contaminated matrix. Post-extraction physical separations are
avoided or minimized, even if destruction or recovery is necessary. The technical challenge common to
all of these processes involves moving mass to some desired area, moving reagents (oxygen, nutrients,
oxidants, etc.) to the contaminants, or moving the contamination to some subsurface treatment zone.
In general, in situ processes require less capital outlay than ex situ treatments. Material handling
requirements are lower, transportation costs are avoided, and post-process treatment (e.g., landfilling)
is avoided. In situ processes are also less invasive, which is often the reason for their use, as in the case
of treatment under a building. On the other hand, in situ treatments, especially biotreatments, are
generally slower and require longer implementation. In many circumstances, such as in the sale of
property, the need to act quickly can outweigh the lower capital costs.
In situ strategies frequently use biological processes to destroy contaminants. Bioremediation uses
microorganisms to transform the hazardous organic contaminants into harmless products, such as carbon
dioxide and water. Microorganisms require mineral nutrients and a carbon and energy source (food) to
carry out these biodegradation processes. Ideally, the target contaminant will be the food source, and
sometimes a treatment process can be designed around fortuitous incidental biochemical reactions.
Microbes also require a terminal electron acceptor to complete the circuit of reactions by which they
survive. The most familiar electron acceptor is oxygen, but certain other oxidized ionic species, such as
nitrate, sulfate, or ferrous iron, can support bacterial growth. Several other factors (e.g., temperature and
pH) affect the efficiency of these processes. Degradation capabilities of microorganisms have been used
for decades to treat municipal and industrial wastes. Recent advances in biotechnology allow these
processes to be applied to hazardous chemicals in situ.
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In general, petroleum hydrocarbons can serve as primary growth substrates for bacteria. The ease of
biodegradability of a hydrocarbon is inversely proportional to its molecular weight and complexity.
Short-chain aliphatic hydrocarbons and simple aromatic molecules are fairly readily consumed, while
large, polycyclic aromatic hydrocarbons (PAHs) are more recalcitrant. Synthetic organic compounds,
such as chlorinated solvents (tetrachloroethene [PCE], trichloroethene [TCE], carbon tetrachloride, etc.),
are much more resistant to biodegradation. Chlorinated solvents cannot serve as growth substrates for
most microorganisms, but can nonetheless be degraded or transformed by populations that grow on other
substrates. TCE, for example, can be transformed and even mineralized by a variety of microorganisms
growing on different organic compounds, including methane, phenol, toluene, propane, methanol, and
n-butane. The current challenge for bioremediation is the encouragement of microorganisms to degrade
these manufactured compounds.
Bioremediation can be very effective for removing contaminants that serve as growth substrates,
particularly if low concentrations of the contaminants are present in an appropriate environment.
Bioremediation can provide a cost-effective alternative to traditional technologies (e.g., air stripping,
carbon sorption, and excavation) for a wide range of natural organic compounds, such as motor or jet
fuel. Biological treatment offers a permanent and often less expensive solution than strictly physical
treatments, because microorganisms convert toxic organic compounds to environmentally benign
products. However, bioremediation is no panacea. In situ bioremediation systems are often integrated
with other remediation technologies to effect total cleanup.
Physical processes will also be considered as in situ for purposes of this study if the intent of the process
is to physically remove only the contaminant from the contaminated media. As an example, air sparging
is intended to remove volatile organic compounds (VOCs) from groundwater. This judgment could be
debated, as such a process still merely transfers contamination from water-saturated soil to air, which
often still requires post treatment. However, as opposed to the pumping and treating of groundwater, air
sparging promises several advantages in material handling, as well as certain challenges associated with
the physical transfer of matter at the contaminated area, and it is appropriate to discuss these processes
here.
Knowledge of contaminant location and physical state in the subsurface is critical in implementing in
situ remediation techniques. In the vadose or unsaturated zone, contamination may exist as a vapor
phase, adsorbed to particles, dissolved in the thin film of water surrounding soil particles, or as a non-
aqueous phase liquid (NAPL). Contamination in the saturated zone might consist of residual saturation
or material trapped within the soil matrix, matter sorbed to solids, a pool of NAPL, or dissolved material
in the groundwater. Each situation can pose unique challenges to the remediation engineer.
Each of the technologies examined by the Phase II Pilot Study offers innovations over more traditional,
mass-intensive approaches to remediation. As they are implemented, a greater understanding of the
dynamic interaction of contamination with the subsurface is gained. Comparing and contrasting the
results of these demonstrations suggests further innovations, as well as contextual evaluation of the
technologies themselves.
4.2 CASE STUDIES
Of the 52 remediation projects examined by the pilot study, 18 were either fully in situ implementations
or involved partial in situ treatment. Of these 18, 11 provided sufficient detail by the end of the pilot
study from which to draw conclusions. These projects consisted mainly of biological treatments of
organic contaminants. Table 4.1 shows those projects considered to be totally or significantly in situ in
nature, with country of origin and a basic description. More information is provided in the sections that
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Table 4.1: In Situ Projects
Project
Number
Title
Description
1 Trial of air-sparging of a
petroleum-contaminated aquifer
Field trials of air sparging combined with soil
vapor extraction (SVE) to determine the increase
of extracted VOCs.
Bioremediation of petrochemicals
following a major fire
In situ flushing/bioremediation process
substantially reduced the total soil contamination
burden at the site and, as a consequence, greatly
reduced the potential migration of contamination
offsite. Phenol-degrading microorganisms were
encouraged to proliferate. In situ application was
only part of overall cleanup strategy.
Bioclogging of aquifers for
containment and remediation of
organic contaminants
Strategy entails using biomass, polysaccharide
and gas production to decrease soil permeability.
Pilot Study report is limited to laboratory studies
and modeling.
Remediation of methyl ethyl
ketone contaminated soil and
groundwater
Strategy includes a combination of pump and
treat for free-phase product and SVE for volatile
and adsorbed contamination. In situ
bioremediation is planned to treat residual
contamination within the basalt aquifer after
pumping operations are complete.
In situ/on-site bioremediation of
wood treatment soils
Daramend process. Land farming with
amendments. Highly effective for relatively
shallow contamination (in situ) or for excavated
soils (ex situ application)
Demonstration of an in situ
process for soil remediation
using well points
Field demonstration of a combined in situ soil
flushing and bioremediation technology for BTEX
and other petroleum hydrocarbons.
12 Groundwater and soil
remediation at a former
manganese sulfate production
plant
In situ treatment involving accelerating the
leaching process with an aggressive leachant, and
collecting leachate in a drainage system.
15 Combined chemical and
microbiological treatment of
coking sites
Bench-scale microbiological treatment of aromatic
hydrocarbons with and without oxidizing
pretreatments (bench-scale)
16 Combined vacuum extraction and
in situ stripping of chlorinated
vapors
NOVOC™ wells and SVE wells and blowers
remove contamination as a gas stream for
treatment above ground by carbon adsorption.
18 Biological in situ remediation of
contaminated gasworks
Large-scale injection and extraction of water
through a contaminated zone leached
contaminants. This process was later used to
introduce nutrients into the ground and to raise
soil temperature by preheating the infiltration
water.
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23 Modeling and optimization of in
situ remediation
Investigation of several aspects of remediation
models including economic and time constraints
as well as technical considerations.
35 In situ SVE within containment
cells combined with ex situ
bioremediation and groundwater
treatment
Partial in situ application for dual-phase vacuum
extraction. On-site treatment of materials in
lagoons and biopiles.
37 Bioventing of hydrocarbon-
contaminated soils in the sub-
arctic
Study investigating economic viability of soil
heating to promote bioventing in cold soils.
Considerable detail is available including an
economic analysis.
41
In situ microbial filters
Resting-state methanotrophic bacteria can degrade
TCE. Exploiting this capability, the bacteria are
raised in a bioreactor, and the biomass is injected
into the subsurface through a borehole where they
attach to the solid rock matrix creating an
inoculated subsurface zone. After an attachment
period to allow fixation and establishment of the
microbiological community, groundwater is
extracted from the borehole resulting in the flow
through the impregnated zone.
42 In situ pneumatic fracturing and
in situ bioremediation
Tight soils hamper in situ technologies such as
SVE, bioventing, air sparging, and other air and
nutrient injection techniques. Hydraulic and
pneumatic fracturing are enhancement
technologies to increase treatment efficiency of in
situ techniques by increasing the permeability of
the soils.
43 Multi-vendor bioremediation
technology demonstration project
Three technologies were tested, including two
aquifer stripping wells and a co-metabolic
bioventing process using added methane and
ammonia.
47 In situ electroosmosis (Lasagna™
process)
Contaminants are directed through treatment
zones under the influence of electroosmosis.
49 Characterization of residual
contaminants in bioremediated
soil and reuse of bioremediated
soil
Bioremediated soil was chemically characterized,
and its environmental behavior was evaluated by
cultivating various plant species.
follow. The project number corresponds to extended project summaries found in Appendix IV. Note
that Project 47, which is discussed in this chapter, is also discussed in Chapter 5, Physical-Chemical
Treatment.
4.2.1 Project 1: Trial of Air-Sparging of a Petroleum-Contaminated Site
Leaking pipes beneath a gas station in Adelaide, South Australia, contaminated the soil and groundwater
with up to 2,100 mg/L petroleum hydrocarbons, up to 1.5 mg/L benzene, and up to 20 mg/L xylene.
Contamination occurred as dissolved, adsorbed, vapor, and minor free phases. The adsorbed phase
occurred as a relatively thin and widespread zone above the water table at a depth of 7.5 m. Three trials
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were conducted to determine the effectiveness of air sparging in combination with vapor extraction at
this site.
The study found that air sparging substantially increased the amount of VOCs that could be removed
by vapor extraction from soil and groundwater. The initial increase in extraction rate was short-lived,
however, and slowed dramatically after only a few days operation. The zone of influence and rate of
recovery of VOCs were highly dependent on local geology. Air sparging also produced mounding of
the water table around the sparge well, which may have forced contaminants away from the extraction
wells. Based on the results of the trials, air sparging was abandoned as a remediation strategy at this site.
4.2.2 Project 2: Bioremediation of Petrochemicals Following a Major Fire
A major fire at a petrochemical facility near Melbourne, Australia resulted in the widespread
contamination of soil and groundwater with phenol, benzene, and acrylonitrile from damaged storage
tanks. A site investigation found phenol concentrations as high as 24,000 mg/kg in near-surface soils and
700 mg/L in the groundwater, making bioremediation problematic due to the toxicity of phenol to
bacteria. Following extensive laboratory studies, a flushing-biotreatment system was investigated at field
scale.
A field study was undertaken on a 1,600-m2 area of soil. The site was prepared by plowing gypsum and
slow-release nutrients into the soil. Contaminated water was flushed through the soil, recovered, and
treated in a bioreactor. Phenol concentrations decreased rapidly in the top 0.6 m of soil after treatment
commenced. Monitoring of soil microbiology showed high concentrations of phenol-degrading bacteria
(up to 5xl07/g) were being maintained. Two months after in situ treatment began, phenol concentrations
in the groundwater rose to 1,000 mg/L, and then gradually declined to about 1 mg/L.
In situ treatment was only one aspect of this project. The overall remediation scheme for the site also
included disposal of some contaminated fire water, storm water, and groundwater to local sewage works
for aerobic lagoon biotreatment; ultraviolet (UV) peroxidation of fire water and storm water; and soil
vapor extraction (SVE) and sparging of VOCs.
4.2.3 Project 3: Bioclogging of Aquifers for Containment and Remediation of Organic
Contaminants
Recent studies have suggested a correlation between increased microbial biomass density in aquifer
materials and reduced saturated hydraulic conductivity of aquifers. This process, termed "bioclogging,"
is believed to result from several different processes, such as the production of low solubility gaseous
end products, the excretion of extra-cellular polysaccharides, and the increase in bacterial cell numbers.
The objective of this project was to investigate the potential benefits of bioclogging to provide a
temporary partial subsurface containment of contaminated areas, and to act as a site for enhanced
biodegradation of organic contaminants. Only laboratory results were reported to the Phase II Pilot
Study, and no bioclogging in the field had yet been attempted.
Test leachate containing growth medium, glucose, and sodium nitrate was passed through a 0.5-m long,
by 0.08-m diameter column at a constant volume flux density of 0.11 nrVday. Results showed that
polysaccharide production can lead to at least one order of magnitude reduction in column hydraulic
conductivity. The study also suggested that after initial delivery of amendments (e.g., nutrients), the
reduction in hydraulic conductivity appeared to be long-lived. The most rapid change in K^ occurred
in the first 18 hours of the experiment, with further slow reductions after 50 hours.
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4.2.4 Project 4: Remediation of Methyl Ethyl Ketone Contaminated Soil and Groundwater
This Pilot Study project reports on the development and implementation of a site remedial strategy that
incorporates in situ recovery of free product and contaminant vapors. Geology at the site consists of a
thin layer of clay and reworked soil overlying basaltic lava flows to a depth of 30 m. The basalt is an
extremely heterogeneous aquifer comprising discontinuous, very low to moderately permeable layers
with occasional interconnecting joints and fractures. There are three free product contaminant plumes
present in the aquifer: a lubrication oil plume, a methyl ethyl ketone (MEK) plume, and a mixed plume
containing benzene, toluene, ethylbenzene, and xylene (BTEX), motor fuel, turpentine, and kerosene.
The plumes cover an area of greater than 7 ha.
The initial remedial strategy consisted of a combination of pump-and-treating free phase product and
SVE for volatile and adsorbed contamination. Since contaminant distribution can be distinguished as
three separate plumes, the remediation plan addressed separate recovery and treatment systems for each
of them. Floating free product was recovered from a network of boreholes with specially designed "top
loading" pumps. These modified displacement pumps use compressed air to pump the recovered fluid
to the surface. Uncontaminated water was injected around each plume to force free product towards the
recovery wells. Vapor extraction was conducted simultaneously to take advantage of the dewatered
ground.
Recovered vapor, free product, and groundwater were treated at the surface in a treatment compound
comprising a three-stage oil/water separator, a heated air stripper for groundwater treatment, discharge
of treated wastewater to a municipal sewer, and a thermal destruction system (using a methane gas
carrier to ensure full product combustion) to treat all hydrocarbon waste streams from the air stripper
as well as the vacuum manifold system. When operated at 760°C and a retention time of 0.5 seconds,
the system ensured total destruction of hydrocarbons. Emissions met the 10 mg hydrocarbon/m3
objective.
Full-scale remediation commenced with recovery of a large volume of free product with an associated
high concentration of dissolved contamination. Two years later, remediation was on-going with an
average rate of groundwater recovery on the order of 50,000 L/day. The rate of hydrocarbon recovery
declined significantly over time. In situ bioremediation was being considered to treat the residual
contamination within the basalt aquifer after pumping operations were completed.
4.2.5 Project 6: //? S/fu/On-Site Remediation of Wood Treatment Soils
DARAMEND® bioremediation carefully cultivates desirable microorganisms through soil preparation
and addition of nutrients. Soil amendments are incorporated into the contaminated soil and homogenized
to supply biologically available water, nitrogen, phosphorous, micronutrients, and oxygen to support
biodegradation of the contaminants. The amendments also reduce the acute toxicity of the soil's aqueous
phase by transiently adsorbing contaminants and providing surfaces for microbial adhesion and
development of biofilms. The composition of DARAMEND® organic amendments is soil-specific and
based upon the results of a thorough physical and chemical characterization (e.g., texture, moisture
retention, carbon:nitrogen ratio, nutrient profile, and concentrations of target compounds) and treatability
studies of the soil or waste. Soil moisture content is also strictly controlled.
The process was applied ex situ to excavated, PAH-contaminated harbor dredgings; in situ to petroleum
hydrocarbon-contaminated soil in the Arctic, and in situ to soil at a wood treatment plant.
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Harbor sediments were treated for 46 days, which resulted in an 84% reduction in total PAH, from 1,146
mg/kg to 187 mg/kg. A control plot (tillage only) showed a 40% reduction. Benzo(a)anthracene
reduction for unpretreated sediment, pretreated sediment, and control sediment was 60%, 58%, and 30%,
respectively.
At the Arctic site, pilot in situ plots were covered by temporary greenhouses to control soil moisture
content and to increase soil temperatures through solar heating. Three DARAMEND® formulations were
tested, and after 10 days, 89%, 62%, and 75% reductions in total petroleum hydrocarbons (TPH) were
observed. No TPH reduction was observed in the control plot.
After 254 days in the ex situ demonstration at the wood treatment plant, PAHs were reduced 94%, from
1,710 mg/kg to 98 mg/kg; chlorophenols 96%, from 352 mg/kg to 13.6 mg/kg; and TPH by 87%. The
control area showed a reduction of 41%, but no reduction in either chlorinated phenols or TPH was
observed. Toxicity, as measured by earthworm mortality and seed germination, was eliminated or greatly
reduced only in the treated soil.
4.2.6 Project 9: Demonstration of an In Situ Process for Soil Remediation Using Well
Points
The treatment process consisted of a recirculation system with injection and extraction wells. A
surfactant/co-surfactant solution is injected into the well points to mobilize soil contaminants. The
extracted contaminated soil washings were sent to an effluent treatment plant. Biodegradation of the
remaining hydrocarbon residual located in the subsurface was stimulated by injecting nutrients and air
or hydrogen peroxide via the well points. The project scope included laboratory-scale selection of
surfactants, in situ soil washing tests using the selected surfactant, in situ biodegradation testing of
residual hydrocarbons and the contaminated washing solution, and subsequent monitoring to verify
contaminant removal. Over 50 types of surfactants and co-surfactants were tested to establish pairings
and concentrations required to extract over 95% of the hydrocarbons from the contaminated soil.
4.2.7 Project 12: Groundwater and Soil Remediation at a Former Manganese Sulfate
Production Plant
On-site disposal of about 45,000 m3 of hazardous waste at a former manganese sulfate plant in the
municipality of Tinglev, Denmark, left severe contamination of the soil and groundwater. Groundwater
was contaminated with high concentrations of manganese, sulfate, and cyanide. Solid wastes, leachate,
and contaminated groundwater all required treatment. Traditional remediation of the solid waste by off-
site incineration and off-gas treatment was estimated to cost 8-13 million ECU (U.S.$9-10 million).
Paper to pilot scale studies were used to investigate alternatives.
Conceptually, the leachate and most contaminated groundwater could be collected for treatment by
constructing drains beneath the wastes. Leaching of wastes could be accelerated by installing a system
at the top of the wastes to distribute suitable treatment agents. It was estimated that leaching at a
liquid/solid ratio of 2-3 annually (40-60 times the natural rate) would leach contaminants from the solids
in 7-10 years. Between 160,000 and 240,000 m3 of leachate would have to be treated and cleaned each
year.
Ex situ batch processing of the wastes was also investigated. Sodium hydroxide was shown in pilot
studies to leach sulfate and cyanide effectively from the production waste. Another waste material, which
had been used to clean the coal gas, contained fine particles that did not allow for efficient flow of
leachant.
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Five possible methods for treating the leachate and contaminated ground-water were considered:
biodegradation, chemical precipitation, chemical oxidation, evaporation, and reverse osmosis.
Evaporation and reverse osmosis were not evaluated experimentally because economic analysis indicated
they would be too expensive. Pilot-scale tests of leachate biodegradation required continuous supervision
and were laborious, and the biomass was insensitive to fluctuations in pH. Therefore, bioremediation was
not evaluated further. Precipitation of the sulfate with barium chloride was determined to be impractical
because high residual barium levels would result in precipitation and aquifer clogging if reinjected, or
require expensive post-treatment if disposed of elsewhere. Thus, precipitation was also rejected for
technical and economic reasons. Laboratory experiments showed that UV light destroyed complex
cyanides in the range of 1-25 parts per billion (ppb) within 10 minutes.
Both ex situ batch and in situ remediation processes were proposed for the sulfate-rich solid waste. In
the ex situ batch process, solid waste would be mixed with water in an impoundment to leach the sulfate.
Effective leaching required retention times as high as 120 hours. An improved design consisted of a
fluidized bed batch treatment.
In situ treatment would involve accelerating the leaching process by using pH neutral groundwater or
an aggressive leachant containing sodium hydroxide on the waste, and collecting leachate in collection
drains. It was suggested that at a liquid/solid ratio of 20, the leachate derived from pH-neutral water
would have a concentration acceptable for being returned to the groundwater. A pilot-scale treatment
facility was constructed onsite consisting of heaped waste that was leached using a sodium hydroxide
solution. Objections to this technology are due to the use of chemicals during treatment.
It was concluded that batch treatments are unlikely to be feasible due to high treatment costs, long
treatment times, and costly effluent disposal. In situ treatment may be more viable although it will take
a long time.
Treatment of the cyanide-contaminated waste was evaluated using accelerated in situ leaching and an
ex situ batch process. In situ treatment was unsuccessful at pilot-scale because the waste heap was
clogged by fine particles. Ex situ batch processing was evaluated at bench-scale using both sodium
hydroxide solution and neutral water. Solid/liquid separation from the alkali leach proved extremely
difficult, and cyanide was incompletely leached by the neutral water. It was therefore concluded that
treatment of the cyanide wastes was not feasible due to lengthy treatment times and high costs.
In conclusion, the sulfate-contaminated wastes could be treated by an in situ method although the
treatment times could be lengthy and disposal of effluent costly. Viable options include leaving the
wastes on the site, covering it with clean soil and planting vegetation. Another option may be to cover
the wastes with a protective membrane. The cyanide-contaminated wastes are not suitable for on-site
treatment and should be excavated and removed for incineration or other treatment. Final disposition of
the site was not reported to the Pilot Study.
4.2.8 Project 15: Combined Chemical and Microbiological Treatment of Coking Sites
Disposal sites of wastes (including coal tars) from the petroleum refinery industry are often characterized
by high concentrations of total hydrocarbons (up to 2,200 mg/kg in soil and 4,800 mg/kg in settling
ponds), phenols (3-10 mg/kg), PAHs (850-1,500 mg/kg), and cyanides (10-300 mg/kg). In this project,
PAH-degrading bacteria were identified and the practical bioremediation of PAHs within the
contaminated soils was evaluated. The ability of an oxidation pretreatment to enhance subsequent
bioremediation was also assessed.
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Pilot-scale assessments were conducted with five different fungi and nine bacterial isolates in a
recirculating bioreactor. Biopiles were continuously mixed and aerated with amendments of straw, saw
dust, and uncontaminated soil. Inorganic nutrients were added to the system using a proprietary time-
release nutrient. Three oxidizing pretreatments (hydrogen peroxide, sodium hypochlorite, and ozone)
were assessed by mixing them as amendments into the biopiles during their construction.
The results after 2 months of the trial showed that only four of the bacterial isolates and none of the
fungi significantly degraded PAHs in the soil tested. The high concentrations of tar present in the soil
made it difficult to turn and mix the material which may have reduced contaminant accessibility. Despite
these difficulties, degradation rates of 75% for PAHs after 12 months, 75% for phenols after 7 weeks,
and 50% for cyanides after 2-3 months were reported. No information was provided on the relative
efficacy of each organism.
Considerable additions of oxidizing agents were required to observe any enhanced decrease in PAH
concentrations. The addition of a catalyst, such as ferrous sulfide, was found to reduce the amount of
nutrient necessary. In 19 weeks, 1,000 mg/kg PAH was reduced to 50 mg/kg with pretreatment by
hydrogen peroxide and ferrous sulfide catalyst.
4.2.9 Project 16: Combined Vacuum Extraction and In Situ Stripping of Chlorinated
Vapors
NOVOC™, an in situ VOC removal system, is based on an air-lift pumping technology that uses air
injection. A remediation system installed at a former pigment manufacturing facility consisted of a series
of NOVOC™ wells and SVE wells and blowers. Contaminants included PCE and heavy metals. Initial
PCE concentrations ranged from 0.085-3.7 mg/L in groundwater and from 10 mg/kg to greater than
5,000 mg/kg in soil. The negotiated cleanup level for PCE was 1 mg/L in groundwater and 50 mg/kg
in soil.
The NOVOC™ system operated for a period of 22 months. System efficiency was controlled quarterly
and consisted of collecting water samples from monitoring wells adjacent to the remediation wells.
Results from the final soil and groundwater sampling showed that the target concentration of 1 mg/L
in groundwater was achieved. PCE concentrations measured in the NOVOC™ wells after the system had
been turned off for a 1-month period ranged from 200-565 mg/L.
4.2.10 Project 18: Biological In Situ Remediation of Contaminated Gasworks
This Pilot Study project followed the progress of a 3-year in situ bioremediation project of a former
gasworks site. The specific test area was located beneath a tar/ammonia separating sump, where spills
and leaks had contaminated the ground beneath. Maximum contamination was located at a depth of 5-7
m. Soil recovered from this zone contained up to 55,000 mg/kg of extractable, lipophilic organics and
14,000 mg/kg of PAHs. The intent of this project was to optimize natural degradation processes by
controlled addition of oxygen and nutrients.
The test area was sealed off from its surroundings by constructing walls into an impervious clay
aquielude at 17 m depth, forming a test cell. The water level in the test cell was lowered below the level
of contamination to enhance air flow and promote aerobic degradation of hydrocarbons. A network of
lances was sunk into the ground to serve as injection and extraction points for oxygen, with the goal of
achieving homogeneous horizontal subsurface air flow. Above ground, an irrigation system was installed
for vertical seepage of inorganic nutrients and moisture into the soil.
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An objective of the project was to chart changing concentrations of leachable contaminants during the
course of the experiment. This was achieved by using a dedicated infiltration and extraction well to flush
the soil at long intervals during the test period. This process was later used to introduce nutrients into
the ground and to raise soil temperature by preheating the infiltration water.
Using 4-ringed PAHs as conservative tracers to compare initial to final organic contents, the researchers
reported that 54% of total PAHs present in the soil were degraded after 2.5 years of remediation.
Assuming that the hydrocarbons consumed were predominantly aromatic, the oxygen consumed and
carbon dioxide produced (which were monitored) account for 2,400 kg of organic material mineralized.
Maximum degradation rates were seen when the soil was warmed either by flushing with warm air or
water, or by natural warming during the summer months. Rapid degradation was also supported by
supplying oxygen by air flushing, rather than as dissolved oxygen in water. This latter observation
reinforced the desirability of lowering the water table below the level of contamination to facilitate
aeration of the contaminant zone.
Assessing exactly the efficiency of bioremediation in the field was difficult due to the extreme
heterogeneity of the subsoil. Analysis of contaminant composition suggested that the most available
components of the tar oil were readily biodegraded. Water was repeatedly flushed through the
contaminant zone (10-20 fold flushing of mobile soil pore water volume) approximately every three
months to extract elutable contaminants. During the 3 years of bioremediation, the chemical oxygen
demand (COD) levels thus recovered were reduced by about 83%, while dissolved organic carbon
(DOC) dropped about 76%. Over the same period, there was a parallel decrease of 97% in the
concentration of PAH.
The main limitation to biodegradation appeared to be the bioavailability of contaminants. Although in
some places the soil still contains relatively high concentrations of PAHs, the hazard potential of the
contaminated site was reduced considerably.
4.2.11 Project 23: Modeling and Optimization of In Situ Remediation
In situ remediation of contaminated soil and water is widely perceived to offer the greatest potential for
enhancing performance and reducing treatment cost. However, its commercial implementation has been
limited by the perception that current methods are unreliable and their treatment duration unpredictable.
The unpredictability of full-scale in situ treatment is not solely due to the heterogeneity of field sites,
but also due to economic and time constraints on the preliminary collection of field data. Treatment
design and predicted performance are often based on bench-scale studies used in combination with
models incorporating subjective default data values. The results are often misleading and overly
optimistic. This Pilot Study project reported on several aspects of an investigation into the modeling of
in situ treatment with an overall goal of enhancing and optimizing treatment performance.
A literature survey indicated that although several groundwater models existed, soil air models for
predicting the performance of SVE were relatively immature. A spreadsheet model to predict SVE
performance for sites contaminated with up to three VOCs linked differential equations to a mass
balance maintained on the spreadsheet. Model outputs included the cumulative amount of contaminants
extracted and soil contaminant concentration, both as a function of time. Parameters and expressions
within the model accounted for equilibrium sorption to organic matter, transfer from liquid to vapor
phase, and contaminant interactions, diffusion, biodegradation, and time dependence. The model output
was used to determine expected treatment durations. Four case studies were evaluated using the
predictive model with one laboratory-based study, two on-site studies, and another conducted in situ.
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Another model examined changes in contaminant concentration in extracted water as a function of time
to predict the treatment duration of in situ soil flushing. The model combined a simple predictive model
with statistical simulation to account for variabilities and uncertainties in the input parameters. Assuming
a homogeneous distribution of site parameters, soil flushing duration was predicted to achieve the
remedial target for groundwater contaminant concentration in three years. A more realistic scenario
accounting for site heterogeneity resulted in treatment times on the order of decades. The authors
stressed that a higher quality of soil investigation was necessary in order to generate a realistic prediction
of remediation duration and cost.
A mechanistic model of in situ bioventing, dubbed ECOSAT, was developed and calibrated with data
from laboratory batch and column bioventing tests. Mechanistic models allow for scenario calculations,
which may help to develop site-specific soil investigation strategies, to evaluate different combinations
of remediation techniques, and to design and optimize the process control of the selected techniques. The
calibrated model was used to predict bioventing performance, and the predictions were compared to ten
full-scale soil venting projects. Comparison of idealized geology with field data revealed that predictions
based on averaged properties are too optimistic—the observed duration of the remediation is longer than
predicted. The deviation between estimated and observed duration of remediation differ by up to one
order of magnitude. The stagnation of biotreatment suggests that a significant fraction of contamination
is unavailable to the treatment process.
The ECOSAT model was used to more fully investigate the "stagnation" phenomenon. The study
concluded that nonequilibrium phenomena, particularly diffusion-controlled mass transfer from areas of
the soil where convective flow was absent, were the dominant factors in treatment stagnation. The model
was also used to compare continuous vapor extraction with intermittent extraction. Results showed that
treatment times for either method were approximately the same since they were dependent upon the
slowly diffusing contaminant fraction. However, the intermittent extraction technique provided oxygen
to the bioavailable water-soluble contaminants much more efficiently, promoting biodegradation as the
dominant contaminant removal process. In contrast, the continuous extraction method rapidly reduced
the concentration of available contaminants through volatilization, not through biodegradation.
4.2.12 Project 35: Combined In SituSo\\ Vapor Extraction Within Containment Cells and
Subsequent Ex Situ Bioremediation
An area of 7.9 ha was significantly contaminated with coal carbonization wastes from a cokeworks plant.
Contaminants included BTEX, PAHs, phenols, heavy metals, and cyanides. The site is underlain by
reworked soil, sand and gravel to a depth of 2-4 m, and groundwater was encountered within this
interval. The original site investigation indicated that both soil and groundwater were highly
contaminated. In particular, the groundwater was found to be contaminated across the entire site with
phenol, oil, and PAHs. NAPL was evident at certain locations, and oil was seeping into the nearby river.
Benzene and other VOCs were also detected in significant concentrations.
A deep cut-off slurry wall was installed to allow safe excavation up to 5 m and to prevent discharges
of contaminants directly into the river. Following dewatering, solid material was excavated. Solids
unsuitable for treatment were placed directly into an on-site encapsulation facility. The remaining
material was then screened and either air dried and reused or treated by ex situ bioremediation to remove
oil and PAH contamination. Treated materials were used as backfill to reinstate the excavated
contaminated area.
Dual-phase vacuum extraction (DVE) was implemented by dividing the area into a series of treatment
cells. The DVE system used an applied subsurface vacuum to draw contaminant vapors and free product
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to the surface for separation and treatment. At the surface, free product was separated from the
ground-water in a separator tank, and volatile organic vapors were adsorbed onto activated carbon filters.
In order to facilitate free product removal, dewatering trenches were dug in some areas of the site. The
DVE process was operated for 46 weeks. Severe weather conditions often caused problems during DVE
treatment because of freezing of supporting pipes and equipment. The goal of the treatment was to
remove free product and reduce VOC concentrations (particularly benzene) to safe levels for excavation,
rather than as a complete remedial treatment in itself.
Extracted groundwater was treated as follows in a succession of holding lagoons and reactors: (1)
floating product are removed by skimming reception/buffer lagoons; (2) heavy metals are removed by
hydroxide precipitation; (3) cyanide is treated by oxidation; (4) sulfide is treated by oxidation; (5) pH
is corrected; (6) filtration using sand filters and activated carbon filters; (7) ammoniacal nitrogen is
oxidized in a biological treatment plant. Inoculum from a local sewage works was found to perform far
better than commercially available inocula. Treated groundwater was discharged to a soakaway along
the river.
Treatment beds (biopiles) to treat some of the solids were constructed over a high density polyethylene
(HDPE) membrane and clay liner. Runoff was collected in an HDPE-lined ditch and was reapplied to
the treatment beds. Aeration was provided continuously via a network of air injection pipes. Effectively
treated material was re-used on site.
A reed bed has been planned to treat any residual contamination following site reinstatement. It is
envisioned that the reed bed will need to accommodate a groundwater flow of 30-50 m3/day.
4.2.13 Project 37: Bioventing of Hydrocarbon-Contaminated Soils in the Sub-Arctic
This technology demonstration was carried out on a 0.4-ha area at an arctic air base that had been
contaminated with JP-4 jet fuel to a depth of nearly 3 m. The site is underlain by a mixture of sand and
gravel, with increasing silt content to 3 m, the depth of the water table. Total petroleum hydrocarbon
(TPH) levels ranged from 100-3,000 mg/kg. A field evaluation of bieventing was undertaken to
determine whether and to what degree soil warming can enhance the effectiveness of bioventing of JP-4
and to determine whether soil warming promoted a higher rate of biodegradation all year round.
The demonstration area was divided into four test plots, which were used to test four different soil
warming techniques:
(1) warm water system: Groundwater collected via an extraction well was pumped through an electrical
heater and warmed to around 35°C before re-infiltration. Insulation was placed over the ground
surface to retain heat;
(2) heat tape system: Strips of heat tape were buried to a depth of 1 m in the test plot and warmed at
a rate of 16 W/m2. Insulation was placed over the plot to retain heat;
(3) solar test: Insulation placed over the ground during the winter months was replaced with plastic
mulch sheeting during the spring and summer to capture solar heat and passively warm the soil;
(4) control test: Both the warm water and heat tape systems were operated for two years from summer
to summer over the demonstration period. The solar and control plots were monitored for 3 years.
No soil warming.
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Soil temperatures in the warm water and heat tape plots were consistently 10°C higher than in the solar-
heated and control plots, resulting in average biodegradation rates three- to four-times higher in the
warmer plots than in the solar and control plots. After the heating systems were switched off,
biodegradation rates in these plots decreased below that of the control, suggesting that the
microorganisms may have adapted to the higher temperatures. TPH removal in the warmed plots was
an order of magnitude higher than in the solar heated and control plots. Warm water was most effective,
followed by heat tape. In all cases, soil TPH and BTEX levels dropped dramatically, indicating that
bioventing resulted in significant contaminant removal. In general, air emissions of benzene vapor in the
control plot were higher when the bioventing system was on than when it was off, but were still well
below regulatory limits.
From demonstration data, the estimated costs per volume of soil treated were comparable in all cases,
ranging from U.S.$31.67-$34.16 per m3for a 5,000 m3 site with an average TPH level of 4,000 mg/kg.
Soil heating significantly decreased treatment time (from nearly 20 years to about three), however, so
that the decision to use soil heating in conjunction with bioventing becomes a choice about project
duration and budget allocation. Doubling initial TPH level increased the cost estimates by only 13-26%
4.2.14 Project 41: In situ Microbial Filters
Cultured methanotrophic bacteria injected into the subsurface through a borehole attach to the solid rock
matrix creating an inoculated subsurface zone. After an attachment period to allow fixation and
establishment of the microbiological community, groundwater is extracted from the borehole therefore
drawing the flow through the impregnated zone. It was concluded that a 100-mm thick biofilter
established at the site provided complete breakdown of TCE for a period of eight weeks, and had a
reduced degradation capacity for an additional eight weeks. The demonstration was reported to be
successful, although regulatory guidelines for TCE were not met in the treated water. The authors
concluded that this was due to a high concentration of co-contaminants, including chlorofluorocarbon
and methane, which were degraded preferentially to TCE. Remedial costs were claimed to be up to 50%
lower than pump-and-treat, with applicability problems being associated with large fast-flowing plumes
with contaminant concentrations less than 10 mg/L.
4.2.15 Project 42: In Situ Pneumatic Fracturing and Bioremediation
By increasing the permeability of the soil to liquids and vapors, removal of contaminants by SVE and
biodegradation can be accelerated. Hydraulic and pneumatic fracturing increase treatment efficiency of
in situ techniques by creating fissures in the soil, which act as conduits for air and water. Hydraulic
fracturing utilizes pressurized water while pneumatic fracturing utilizes pressurized air to create cracks
in low permeability and highly consolidated sediments. Aerobic processes dominate at the fracture
interfaces and, to a limited distance, into the soil away from the fracture.
Initial characterization of the test site revealed low permeability soils and benzene, toluene, and xylenes
(BTX) contamination. Over a one-year period, the site was pneumatically fractured, and nitrate and
ammonium salt were periodically injected to enhance aerobic and anaerobic biodegradation. Off-gasses
from monitoring wells were analyzed for BTX, carbon dioxide, methane, and oxygen to monitor the
progress of treatment. Additional soil corings were analyzed to measure the change in extent of site
contamination during remediation. Carbon mass balances were also performed to evaluate treatment
efficiency.
Fracturing increased subsurface permeability by a factor of 40 within an effective radius of
approximately 6 m. Results from soil sampling at the end of the demonstration showed a 79% reduction
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in BTX concentrations in the soil. Cores from three distinct depths taken before and after remediation
showed a 22-kg decrease in BTX. Biodegradation accounted for over 82% of total BTX mass removal
during the 12-month study period. Based on periodic soil-gas sampling, 14% of BTX was removed by
SVE. Other mechanisms accounted for 4% of the BTX loss.
4.2.16 Project 43: Multi-Vendor Bioremediation Technology Demonstration
This comparison of three treatment technologies took place at an abandoned hazardous waste disposal
site containing very high concentrations of chlorinated and non-chlorinated solvents such as TCE, PCE,
MEK, and toluene. Specific technical objectives of this study included determining whether the use of
naturally-occurring microorganisms can effectively remediate VOCs present in the unsaturated zone,
generating field data for simultaneous evaluation of different biological processes, and evaluating the
ability of the in situ and ex situ approaches to meet site specific remedial objectives.
The site consisted of a clay cap over mixed fill, which was comprised of hazardous waste and soil fill.
Beneath the mixed fill is a thin silty-clay layer with numerous fine silty-sand lenses. Beneath the fill is
sandy silt glacial till. Work during the trial revealed that a plastic liner was present between the fill
material and the natural soil creating a perched water table.
The first technology was a co-metabolic bioventing approach, consisting of extraction wells linked to
a central blower. The output of the blower was connected to the injection wells via ports to allow inputs
of ambient air, methane, and anhydrous ammonia. The methane was intended to boost co-metabolic
processes degrading chlorinated VOCs. The ammonia was intended as a bioavailable nitrogen source.
The blower operated for approximately 2 hr/day for nearly 5 months. The material treated turned out
to be relatively lightly contaminated, with many samples meeting treatment targets in advance of
treatment. The installation of the technology was complicated by the plastic liner and perched water,
which were not expected based on the available site investigation information. The system achieved the
compliance target; however, contaminant levels were already low in the test area—particularly for
methyl isobutyl ketone (MIBK) and PCE—and data for acetone and MEK could not be interpreted
because of difficulties with their detection limits. Using demonstration data, the treatment cost was
U.S.$52/m3, and the duration of treatment was 12 months1.
The second technology consisted of biopiles constructed on twin layers of high density polyethylene
(HDPE) supported by earthen berms. The HDPE was covered by a layer of sand for protection and
drainage. The surface of the pile was covered by a similar felt, sand, and HDPE construct. Aeration was
via extraction pipes in the lower sand layer connected to a fan with passive air injection pipes in the
upper sand layer. Liquids could be percolated into the biopile via a sprinkler system. Air and liquid
movement was intended to optimize conditions for biological activity within the piles. Two piles were
set up: one with continuous aeration, and the other with discontinuous aeration to allow the development
of alternating periods of aerobic and anaerobic activity within the piles. The materials treated within the
piles were the most grossly contaminated site materials. The treatment was made more difficult by the
fine texture of the soil, which impeded aeration and water movement. The intermittent aeration pile
possibly did not achieve conditions suitable for aerobic activity. Neither the continuously nor
intermittently ventilated biopiles achieved compliance, although both substantially degraded the VOCs.
Based on demonstration data, the treatment cost was U.S.$71/m3, and the duration was 9 months1.
'The cost bases for each of three technologies were not the same. For instance, the co-metabolic bioventing
estimate included costs associated with permitting, while the UVB estimate did not.
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The third technology was a vacuum vaporization (UVB™) well. The basic unit was a 400-mm diameter
steel water well with upper and lower screens inserted to a depth of 8 m below the ground surface. A
submersible pump in the bottom zone of the well pumped groundwater through an in-line bioreactor
packed with granular activated carbon. The treated water was discharged back into the soil through the
upper screen. The bioreactor unit was integrated with an air stripping function, both to remove VOCs
and to oxygenate the groundwater prior to discharge. The extraction of groundwater from the lower zone
and discharge to the upper zone was intended to circulate water around the well to create a zone of
enhanced stripping and biodegradation activity. Installation of the well was complicated by the plastic
liner and an unexpectedly shallow water table. After 5 months, when the other trials were completed,
samples from the UVB treatment area indicated little significant contaminant reduction; compliance was
achieved for PCE only. A longer treatment period was recommended for this type of technology. After
14 months, compliance was also achieved for MIBK and TCE (based on 45 usable data points). Using
demonstration data, the treatment cost was U.S.$240/m3, and the duration was 14 months1.
4.2.17 Project 47: In Situ Electroosmosis (Lasagna™ Process)
The Lasagna™ process is intended to deliver treatment agents to contaminants in low permeability soils
and to render in situ treatments more feasible. The process depends on electroosmosis, whereby low
voltage electrical current applied to electrodes creates an electric field to mobilize contaminants through
low-permeability soil toward treatment zones. These zones, installed in close proximity through the
contaminated material, contain materials (e.g., sorbents, catalytic agents, microbes, oxidants, buffers,
etc.,) to sorb or degrade contaminants. Placing the treatment layers close to each other minimizes the
time needed for electroosmotic transport. Intermittent reversal of electrical polarity reverses liquid flow
and appears to increase the efficiency of contaminant removal as well as allowing complete
sorption/degradation by passing contaminants several times through the treatment zones. Reversed flow
minimizes the pH extremes that occur at the electrodes when the system is operated in one direction.
Various configurations of the technology are possible. The Pilot Study project used a vertical
configuration at a site contaminated with TCE. The case study was carried out in two phases: Phase I
evaluated the overall effectiveness of coupling electrokinetics and carbon adsorption treatment zones,
and Phase II examined the use of iron filings in the treatment zone to dehalogenate TCE in a
commercial-scale demonstration .
The demonstration site covers an estimated area of 557 m2 and extends to a depth of 15 m. TCE
concentrations in soil are as high as 1,523 mg/kg, but average around 84 mg/kg. Concentrations increase
with depth, and the highest concentrations are believed to occur at depths from 6-9 m. The test site was
about 4.6 m x 3 m on the surface and 4.6 m deep. A control area was built next to the test area and was
isolated from it hydraulically. The vertical configuration tested at the site consisted of steel panel
electrodes and treatment zones made of wick drains containing granular activated carbon. A direct
current of approximately 40 volt/m applied to the electrodes caused groundwater to flow from the anode
to the cathode at about 13 mm/day. The induced pH gradient caused problems such as soil drying and
cracking and the formation of metal and mineral deposits at the cathode. Pumping water from the
cathode to the anode reduced these problems.
Soil samples collected at the demonstration site before and after the test showed that the process
removed 98%-99% of the TCE from the tight clay (a reduction from 100-500 mg/kg to an average of
1 mg/kg). Carbon canisters used to collect soil vapors accounted for around 50% of the original TCE.
The remaining removal of TCE may be attributed to passive diffusion, evaporation, in situ degradation,
non-uniform distribution of the contaminant in the soil, or incomplete extraction of the compound from
the activated carbon before analysis.
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Results suggest the process is also effective for removing residual dense non-aqueous phase liquid
(DNAPL). At most soil sampling locations with TCE concentrations greater than 225 mg/kg (which is
indicative of residual DNAPL) the Lasagna™ process reduced these levels to less than 1 mg/kg.
A more extensive field investigation incorporated reactive treatment zones, such as iron filings, to
destroy TCE in situ. Preliminary results show that the iron filings can dechlorinate TCE, producing
relatively innocuous end-products such as chloride ion, ethane, and ethene. Potential intermediate
products, like dichloroethene and vinyl chloride, are associated with the surface of the filings.
An engineering evaluation and cost analysis for the vertically-configured process estimates a treatment
cost of U.S.$52-118/m3 of clay soil containing TCE at a depth of 12-15 m and over an area of 0.4-0.8
ha. With optimized electrode spacing, improved ability to install treatment zones and electrodes at closer
spacing, and mass-produced prefabricated materials resulting from wider use of the technology, costs
are expected to fall to U.S.$26-52/m3. These costs exclude those for analyses, waste disposal, etc.
4.2.18 Project 49: Characterization of Residual Contaminants in Bioremediated Soils and
Reuse of Bioremediated Soils
The emission levels expected during the reuse of remediated soil were estimated by means of laboratory
and field tests. For all investigations, hydrocarbons were extracted by Soxhlet extraction using
tetrachloromethane, and hydrocarbon content was evaluated by infrared spectroscopy. In further
discussion, total petroleum hydrocarbon (TPH) content is defined as the total solvent extractable material
(TSEM) after removing polar compounds with alumina.
The remediated soil used for all tests contained 780 mg/dry kg TSEM and 430 mg/dry kg TPH, the
hydrocarbon originating from EL heating oil. The content of PAH was below 2.8 mg/kg and was not
subsequently measured.
Most of the residual contaminants remaining in bioremediated soil consisted of apolar, low-volatility
compounds (boiling points >280°C). Small quantities of polar compounds (e.g., fatty acids and long-
chain alcohols) were also detected in individual fractions. On the whole, however, the compounds were
very hydrophobic, with octanol/water distribution coefficients greater than 106.
The second phase of the project involved investigating the environmental behavior of residual
contaminants in the bioremediated soil after being applied as topsoil. The processes investigated were
biodegradation, teachability due to precipitation, and volatilization. The teachability of the residual
contaminants to percolating water was investigated in laboratory tests by means of shake and column
leachate tests and by means of a lysimeter test outdoors. The initial total hydrocarbon content was of
the order of 0.09 mg total hydrocarbons (THC) per liter, but rapidly declined thereafter. After less than
one average annual precipitation throughput, the THC content in the percolating water was already below
the drinking water limit of 0.02 mg/L. The leached quantity of contaminants corresponded to 0.1% of
the total hydrocarbon content in the soil material. Extrapolation of these measurements indicated that
only about 1% of the residual contaminants would leach out, even after 100 years' precipitation. DOC,
which includes all the polar and apolar organic compounds dissolved in the water, ranged from 4.3-15
mg/L in the leachate from bioremediated soil, which is comparable to that of gravel. In comparison, the
DOC of garden soil is about 107 mg/L.
Further biodegradation of the residual contaminants was observed when the soil was used to cultivate
red clover or rye-grass, or left fallow or regularly plowed. Over 28 months, residual contamination
declined about 13%, with no significant differences between the cultivation types. Since only small
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quantities of residual contaminants leached out or were emitted into the air over the whole trial period,
the reduction in the TSEM/THC contents can be attributed to biodegradation.
The germination and growth of 36 plant species on both remediated soil and garden soil (control) were
investigated in greenhouse trials. The plants developed normally on both soil materials and showed no
phenotypical changes of any kind. Eight crops and eight wild herbs grown in deliberately contaminated
soil showed a slightly increased plant yield over the controls after 30 days. The effect was not
statistically significant, but these results clearly show that the contaminants added to the soil did not
inhibit growth.
DIN-S4 leachates showed no significant acute toxic effects on the water-flea (Daphnia magna). The
residual contaminants in successfully bioremediated soil are slightly soluble, difficult to volatilize, and
undergo further biodegradation only over prolonged periods. Since the anticipated emissions are very
low, no risks to humans or the environment are expected.
4.3 REVIEW OF CASE STUDIES AS A GROUP
As discussed in Chapter 2, Pilot Study projects were nominated and selected by a vote of Country
Representatives. The selections, therefore, reflect a desire of a particular panel of experts to review
representative or interesting new technologies available at that time, and should in no way be construed
as either a random sampling of available technologies or representing any relative abundance or
popularity of technologies. The in situ technologies chosen range from modeling efforts, to laboratory
studies, to field studies and full-scale remediation projects.
The period of the Pilot Study saw the rapid development and deployment of bioventing as a remediation
strategy for hydrocarbons in the vadose zone. Bioventing is similar to vacuum extraction, but whereas
vacuum extraction is used as a means to remove contaminant vapors from the soil for recovery or
disposal, bioventing is aimed at promoting microbial destruction of the contaminants before they reach
the atmosphere. Variables affecting the effectiveness of bioventing are the capacity of microorganisms
in the soil to metabolize hydrocarbons; the bioavailability of the hydrocarbons; temperature; and proper
control of air flow to supply sufficient oxygen while minimizing venting of volatilized contaminants.
While in some ways epitomizing "innovative" technology, bioventing had by 1993 become a widely-
accepted alternative to traditional excavate-and-dispose solutions. Extensions to the technology were
being sought to apply bioventing to hydrocarbon contamination in cold climates, to tight soils, and to
the cleanup of more recalcitrant contaminants, like chlorinated hydrocarbons.
The demonstration of arctic region bioventing (Project 37) and the demonstrations of co-metabolic
bioventing (Project 43) both achieved these to some degree. In Project 37, soil warming was applied to
promote biodegradation, and the economics of the use of soil warming were evaluated. It was shown
that the cost of bioventing with or without soil warming was about the same, but that soil warming
significantly accelerated cleanup. The decision to use soil heating in conjunction with bioventing then
becomes a choice about project duration and budget allocation, in the context of government imposed
or negotiated cleanup agreements. The estimated cost of less than U.S.$35/m3 is still significantly less
than typical dig-and-haul rates of U.S.$100/m3 or more.
Project 43 showed some promise as well, but the validation of co-metabolic bioventing based on the one
demonstration presented is equivocal. In situ concentrations of contaminants decreased, but some of the
target chlorinated compounds were already within regulatory limits at the demonstration site, and
degradation of other compounds, (e.g., toluene) was disappointing.
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Project 18 assessed the applicability of bioventing to the contaminated soils on a pilot scale at a former
gasworks site. Assessing exactly the efficiency of bioremediation in the field was difficult due to the
extreme heterogeneity of the subsurface. Analysis of contaminant composition suggested that the more
available tar oil components were readily biodegraded. The main limitation to biodegradation appeared
to be the bioavailability of contaminants.
Similar to bioventing are land farming and "biopile" technologies (Projects 6 and 15). These
technologies depend upon soil microbiology to perform the transformations necessary for cleanup, but
are applied to relatively shallow depths and depend upon air diffusion, natural convection, or plowing
for aeration. Several successes for the Daramend® process (Project 6) were reported to the Pilot Study,
including one at an arctic site and demonstrations involving a variety of soil types and contaminants.
The successes of this technology are attributed to the application of proprietary amendments to the soil,
which improve the bioavailability of contaminants and meet coincident microbial nutritional
requirements. A similar effort (Project 15) attempted to apply this kind of treatment on PAHs in a
biopile. Partial success was reported for PAH degradation, but significant difficulties were encountered
due to the tarry nature of the contaminated soil. A biopile was also part of the overall strategy in Project
35.
Soil flushing was attempted in two demonstrations to avoid more invasive efforts. A former manganese
sulfate plant in Denmark was severely contaminated with sulfate and cyanide (Project 12). While sodium
hydroxide solution was shown in laboratory studies to effectively leach sulfate, limited soil porosity
prevented effective in situ application, necessitating further disposal or treatment of the leachate. The
cyanide contamination was found to be unsuitable for on-site treatment. Final resolution of the treatment
plan was not reported to the Pilot Study, but the project was illustrative of practical limitations
encountered in the field. Project 9 reported attempts at flushing contaminants with surfactant and co-
surfactant aqueous solutions, but final outcome of these efforts were not reported.
One of the Pilot Study projects was a hybrid between land farming and leaching. Project 2 leached water
through amended soil and recovered the leachate for treatment in a bioreactor. Successful destruction
of the contaminating phenolic compounds occurred in both the soil and the bioreactor.
The delivery of treatment to the contaminants is an alternative to remote treatment. Project 41 involved
a conceptual demonstration that created a subterranean zone of resting-stage methanotrophic bacteria
known to dechlorinate TCE. This "biofilter" provided a treatment zone capable of dechlorinating TCE
in eight weeks at a cost approximately half that for a pump and treat system. Operational limitations
include interference by other substances such as methane and chlorofluorocarbon and difficulty in
capturing a fast-moving plume, given the necessarily slow draw rate of contaminated water through the
biofilter.
Aquifer stripping and SVE are regarded in this report as in situ treatments, although the actual treatment
of the contaminants occurs ex situ. Project 4 applied SVE after dewatering, to take advantage of the
increased unsaturated volume. Project 1, applied air sparging to a petrol-contaminated site, in conjunction
with SVE. The amount of volatile hydrocarbons removed by vapor extraction when sparging commenced
initially increased, but the increase was short-lived and slowed dramatically after only a few days
operation. Two competing and patented aquifer stripping technologies were introduced during the early
1990's, and examples were included in the Pilot Study inventory. NOVOC™ (Project 16) is based on
an air-lift pumping technology using air injection. NOVOC™ was demonstrated for 22 months at a PCE-
contaminated site and reduced the PCE concentration in the aquifer from up to 3.7 mg/L to less than
1 mg/L. In Project 43, a UVB™ well pumped water from the aquifer, aerated to remove VOCs, and
discharged it back to the subsurface. The system of extracting water from the lower zone and
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discharging it to the upper zone was intended to circulate water around the well and create a zone of
enhanced stripping biodegradation activity. Compliance at the site was achieved in 14 months for both
MIBK and TCE, at a cost of U.S.$240/m3. Project 35 applied a subsurface vacuum to draw contaminant
vapors and free product to the surface for separation and treatment in a process called DVE. Applied
after dewatering, DVE in this instance was intended to reduce the benzene concentration at the site to
a level safe for excavation.
Remediation is the removal of a mass of contamination from a mass of natural materials, and the energy
and effort applied to separate these two masses are the fundamental problems requiring both
technological and economic solutions. The technology becomes more intensive and the costs increase
when the contaminated soil has low porosity, either because of inherent soil properties or due to fouling
by the contaminant. Two Pilot Study technologies addressed the subject of these "tight" soils. Bioventing
can be used in tight soils once pneumatic fracturing has been applied to increase their porosity. An
increased porosity makes contaminants more accessible and facilitates the introduction of air into the
subsurface. In Project 42, the site was pneumatically fractured, and nitrate and ammonium salt were
periodically injected to enhance aerobic and anaerobic biodegradation. Fracturing increased subsurface
permeability up to 40 fold within an effective radius of approximately 6 m. Biodegradation accounted
for over 82% of the total BTX mass removed; the remaining loss was accounted for by SVE and other
losses. Project 47, dubbed the Lasagna™ process, used electroosmotic transport to move contaminated
groundwater through treatment zones. In the Pilot Study demonstration, TCE was dehalogenated in a
treatment zone of iron filings. TCE concentrations in the soil were reduced from 100-500 mg/kg to an
average of 1 mg/kg.
An unusual application of biological processes is bioclogging. The combination of cells, polysaccharide,
and gases produced can reduce the hydraulic conductivity in an area for temporary partial subsurface
containment of contamination and to act as a site for enhanced biodegradation of organic contaminants.
In Project 3, biomass was made to grow in particular regions. However, only laboratory results were
reported to the Pilot Study, and no bioclogging in the field had yet been attempted.
Project 23 took a detailed look at technical and economic models of in situ remediation. In one of the
studies, the anticipated duration of remediation was three years, assuming homogeneous distribution of
site parameters, and several decades when accounting for site heterogeneity. Similar calculations changed
duration projections by an order of magnitude, just by accounting for heterogeneity. Modeling of
bioventing through a diffusion-controlled region suggested that intermittent convection promoted
biodegradation over vapor extraction as the dominant means of mass removal.
4.4 ENVIRONMENTAL IMPACTS AND HEALTH AND SAFETY
For the most part, those sites that selected in situ technologies are those with hydrocarbon contamination
ranging from lighter petroleum fractions to PAHs. In some cases, chlorinated hydrocarbons were present.
The typical strategy was to destroy the contaminants in the subsurface, reducing the chance for toxic
exposure to workers or the general public compared to traditional methods. Vapor extraction methods
involve plumbing that carries contaminants directly to treatment, which also reduces the risk of exposure.
Fugitive emissions are typically very low, providing for very little adverse environmental impact.
Project 49 found that the risk from the bioremediated soils was extremely low. Extensive tests of
bioremediated soils originally contaminated with EL heating oil showed very low teachability, no
toxicity to a number of different plants, and leachates non-toxic to Daphnia water fleas. These studies
strongly support the idea that residual limits should be based upon toxicological data and not upon
analytical capabilities.
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4.5 COSTS
Costs for the five Pilot Study in situ technologies that provided an economic analysis ranged from
U.S.$26-$240/m3, and these costs were estimated based on limited field data and operating assumptions.
Actual costs of any technology at any given site are notoriously dependent on actual site parameters, but
the data in Table 4.2 indicate that the costs of in situ technologies are likely to be competitive for a
number of applications. In Project 12, the in situ technologies evaluated were deemed too expensive,
lengthy, or inadequate to apply. However, neither was an excavation-and-incinerate or landfill strategy
deemed suitable. The final disposition of the site is not known, but some type of impermeable cap was
being considered.
Table 4.2. Estimated Costs of Technology Application
Project
Number
6
12
37
43
47
Project
In situ/on-site bioremediation of
wood treatment soils
Groundwater and soil remediation
at a former manganese sulfate
production plant
Bioventing of hydrocarbon-
contaminated soils in the sub-arctic
Multi-vendor bioremediation
technology demonstration project
In situ electroosmosis (Lasagna™
process)
Technology Costs (U.S.S)
$46/m3 (in situ) or $96/m3 (ex. situ), excluding
treatability studies and disposal of hazardous
oversize screenings. $92/m3 (in situ) or $140/m3
(ex situ) including disposal.
deemed too expensive
$31. 67-34. 16/m3
See Appendix IV for assumptions and other
details.
Co-metabolic in situ bioventing: $52/m3
biopiles: $71/m3
UVB™ well: $240/m3
See Appendix IV for assumptions and other
details.
$26-52/m3 expected with mass-produced
prefabricated equipment. Otherwise, $52-118/m3
4.6 APPLICABILITY OF IN SITU TECHNOLOGIES
The most successful in situ technologies were those directed toward simple hydrocarbons in the vadose
zone, i.e., some form of bioventing or land farming. Complicating factors involve mass transfer and
bioavailability because tight clayey soils or tarry deposits prevent the intimate contact of microbes,
oxygen, water, contaminants, and other nutrients necessary to carry out the destruction of the
contaminant. Cold temperatures pose no great threat to implementing bioremediation—provided one is
willing to heat the soil or wait longer for success.
SVE has also come into its own during this period, with several enhancements being demonstrated.
Extension of bioventing and SVE through pneumatic fracturing of tight soils is notable.
Aquifer stripping entered the remediation scene during this Pilot Study period and met with mixed
success. These technologies appear to be most effective in relatively homogeneous aquifers contaminated
with highly volatile contaminants. Microbial filters, as demonstrated to the Pilot Study, show promise
in chlorinated hydrocarbon contamination, but still require further development. Electroosmotic transport
of contaminants through treatment zones is also promising.
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Attempts to extend bioremediation to PAHs have met with mixed success, due to the recalcitrance of
the substrate. Land farming was somewhat more successful than bioventing toward these contaminants.
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Chapter 5: PHYSICAL-CHEMICAL TREATMENT
Alex Lye and Robert Booth
Water Technology International Corporation, Burlington, Ontario, Canada
5.1 INTRODUCTION
5.1.1 Overview of Chapter
This chapter presents information for 16 projects that investigated physical-chemical techniques to treat
soils, sediments, other solid media, and groundwater containing a variety of chemicals. Most of the
chapter deals with soil washing, because it was the most frequently used technology for pretreating solid
contaminated media. Contaminated concentrates that resulted from soil washing were subsequently
treated by biological and physical-chemical technologies. Only six projects investigated physical-
chemical technologies without soil washing as a pretreatment.
To make meaningful comparisons of data reported for the projects, the projects were grouped as follows:
• Group 1: Typical soil washing;
• Group 2: Soil washing and biological treatment;
• Group 3: Soil washing and physical-chemical treatment;
• Group 4: Physical-chemical treatment (no soil washing); and
• Group 5: Photo-oxidation treatment.
The project summaries presented in Section 5.2 provide an overview of the projects but do not contain
all information, such as performance data and criteria achieved. This excluded information is discussed
elsewhere in the chapter and in the project summaries (Appendix IV). However, key points of the
technologies are contained in Table 5.1.
For the purposes of this chapter, soil washing includes unit processes such as screening, attrition
scrubbing, hydrocycloning, etc., as well as enhancements such as flotation, magnetic separation, and
gravity separation.
Finally, it must be noted that the authors of this chapter summarized and compared data contained in
available reports. Data are presented as they were reported for the various projects. Final reports were
not available for some projects, while documents for others did not provide detailed information. As a
result, there are limitations to the data comparisons and observations made by the authors.
5.1.2 Generic Description of Technology Group
Typical Soil Washing
As a pretreatment for excavated material, soil washing exploits the fact that contaminants are often
preferentially adsorbed to the fine particles. This approach relies on physical processes to separate a
small volume of contaminated material from the bulk of relatively uncontaminated material. Current
commercial soil washing processes remove mainly fine fractions (<0.063 mm) containing the highest
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concentrations of contaminants. The remaining coarse fraction (>0.063 mm) is relatively clean. The clean
material is often reused as "inert" fill.
Separating the contaminated fines often results in lower costs for overall treatment, because it is only
this smaller volume of contaminated material, not all the original material, that requires further treatment
or disposal. The contaminated material is shipped to a controlled landfill or treated further by a variety
of processes that destroy, immobilize, or recycle the contaminants.
Soil washing is economically feasible only if the volume reduction is large enough to provide financial
benefits. According to a report (7) on an extensive review of commercial and pilot-scale soil washing
systems, soil washing is most effective on soils containing less than 30-35% clay and silt, i.e., particles
smaller than 0.063 mm. At higher percentages of these fines, the volume reduction is not large enough
for the process to be economical. In addition, difficulties arise in handling these materials, separating
the contaminated and uncontaminated materials, and handling the products.
Despite these problems for soils rich in fines, soil washing may be seen as a cost-effective treatment if
the technology overcomes difficulties presented by the high levels of silt and clay. Possible solutions
include enhancing soil separation techniques and developing processes to treat the fine fractions
downstream.
Soil Washing Combined with Other Technologies
With some soils, physical treatment alone will not reduce the absolute concentration of contaminants to
acceptably low levels. For soils containing more than 30% clay and silt by weight, physical pretreatment
could reduce the volume of contaminated material requiring downstream treatment. Pretreatment may
also present the separated contaminant concentrate in a form suitable for the downstream process, e.g.,
bioslurry, solvent extraction, and vacuum distillation. Case studies in this chapter illustrate soil washing
combined with biological or physical-chemical treatment such as vacuum distillation, photo-oxidation,
biodegradation, and chemical dehalogenation.
Physical-Chemical Treatment (No Soil Washing)
Some of the downstream processes mentioned above may be used directly on contaminated material that
was not previously washed. Some of the case studies in the chapter examine processes such as:
• solvent extraction and treatment of extracts by stabilization (for heavy metals);
• leaching and treatment of leachate; and
• in situ electro-osmosis and adsorption.
Like soil washing, these conventional technologies experience difficulties in treating contaminated
materials where the fines exceed 30-35%. When the levels of fines are this high, methods such as
thermal treatment and solvent extraction become more expensive, while others such as biological
treatment take a longer time.
Photo-Oxidation Treatment
This chapter restricts the discussion of photo-oxidation treatment to ultraviolet (UV) radiation and
hydrogen peroxide (H2O2) to treat groundwater.
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5.2 CASE STUDIES CHOSEN
This section summarizes each of 14 projects as a case study. The projects are discussed in groups as
follows:
• Group 1: Typical soil washing (Project 30);
• Group 2: Soil washing and biological treatment (Projects 24, 26, and 36);
• Group 3: Soil washing and physical-chemical treatment (Projects 10, 17, 19, 27, 31, and 33);
• Group 4: Physical-chemical treatment (no soil washing) (Projects 32, 44, and 47); and
• Group 5: Photo-oxidation treatment (Projects 14, 38, and 40).
Some of the projects are also discussed in other chapters: Project 47 in Chapter 4; Projects 24, 26, and
31 in Chapter 6; Project 19 in Chapter 8; and Projects 10, 24, 26, 31, 32, 33, and 47 in Chapter 11.
5.2.1 Group 1: Typical Soil Washing (Project 30)
Project 30: Using Separation Processes From The Mineral Processing Industry For Soil Treatment
Investigators evaluated the applicability of particle separation techniques from the mineral processing
industry to treat contaminated soil from sites in the U.K. This technique of soil washing by physical
separation used established and innovative mineral processing equipment to separate soil into fractions
of varying contaminant concentrations. The majority of tested soils contained clay and fines at high
levels normally considered uneconomical for soil washing. These soils contained arsenic, complexed
cyanides, and metals such as Hg, Cr, Cu, Pb, Ni, and Zn. Organics in the samples included polycyclic
aromatic hydrocarbons (PAHs) and petroleum hydrocarbons.
Laboratory studies assessed the potential of physical processes to separate the contaminated soils into
various fractions. These processes consisted of grain-size separation, attrition scrubbing, specific gravity
partitioning, froth flotation, and magnetic separation. The studies confirmed that contaminants in the
tested soils appeared to occur preferentially in particular soil fractions. Unfortunately, this preferential
distribution was not always sufficient, so that fractions with the lowest concentrations of contaminants
could be reused as inert landfill.
A pilot-scale investigation with the Warren Spring Laboratory's National Environmental Technology
Centre's (WSL/NETCEN) soil washing plant examined soils from a former metal processing works and
gasworks. Both soils were included in the laboratory studies. Material from the former gasworks
consisted of building rubble, wastes and soil. A relatively high clay content (around 30%) made handling
difficult. To exploit the physical properties of the soil and contaminants, the WSL/NETCEN soil washing
plant was designed to transfer contaminants from the soil to a water-based suspension. This plant, with
a throughput of 0.5-1.0 tonne/hr, compared froth flotation and a multi-gravity separator (MGS) for
separating fine particles. Altogether, treatment processes consisted of coarse sizing, further sizing,
attrition scrubbing and classification, and contaminant concentration.
The effectiveness of the process was measured by comparing the levels of contaminants in treated and
untreated soil. In the pilot-scale tests using froth flotation, residues with low levels of contaminants (i.e.,
treated material) made up around 48% by weight of the original feed. For similar tests with an MGS
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instead of froth flotation, the residues with low levels of contaminants totaled around 50% of the original
feed. Compared to the rest of the feed, these residues contained markedly lower levels of PAHs,
petroleum hydrocarbons, cyanide, Pb, and As. Comparing data on contaminants in the two types of
residues (i.e., froth flotation and MGS) revealed that the flotation residues contained higher levels of
PAHs and petroleum hydrocarbons, but lower levels of Pb and cyanide. Arsenic levels did not differ
much between the two residues.
Samples from the former metal reprocessing works produced a small proportion of dense material
(specific gravity >2.8) with very marked concentrations of contaminants. Despite this separation of
contaminants into the dense fraction, the remaining bulk of treated material contained unacceptable levels
of contaminants. According to a project report, researchers re-assessed results of the Toxicity
Characteristic Leaching Procedure (TCLP) of the soil and then re-considered the role of physical
treatment in a treatment train to reduce the hazard.
For the soil from the former gasworks, the researchers suggested improving separation of fractions then
destroying concentrated contaminants in the fine clay and silt fraction as a cheaper option to treating the
entire soil. The recommended approach could consist of an enhanced soil washing process to improve
separation, an in-line bioslurry reactor to destroy contaminants, or a combination of the two. The
resulting treated fines may form a sludge that could be disposed of as a contaminant-free waste.
The pilot-scale soil washing plant featured process water containment and recirculation, and carbon
filters to extract volatile contaminants from emissions. Wastes and sludges from the plant received
further treatment at downstream processes or were shipped to a licensed landfill. The reports did not
contain information on costs.
5.2.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36)
Project 24: Combined Remediation Technique for Soil Containing Organic Contaminants: FORTEC9
Developed by Heidemij Realisatie of the Netherlands, the Fortec® (Fast Organic Removal Technology)
process combines hydrocyclone separation, photo-oxidation, and bioslurry technologies to treat soils
contaminated with heavy aliphatic hydrocarbons (oils) and PAHs. A multi-staged configuration of
hydrocyclones selects specific soil fractions that contain the majority of the contaminants. A clean sand
fraction and heavily contaminated sludge result. The technology has been developed through bench- (25
m3) and pilot- (50 m3) scale to its current demonstration-scale of 300 nrVbatch.
Depending on the composition of the feed material, the sludge may be pretreated before it enters the
slurry bioreactor. Pretreatment involves photo-oxidation (using high-pressure mercury UV lamps and
H2O2) or a physical process in a batch reactor. This step transforms contaminants that are difficult to
biodegrade into readily biodegradable ones.
The batch slurry bioreactor has a retention time of 3-20 days depending on the matrix being treated.
Nutrients (nitrogen and phosphorus) are added as required. Once biotreatment is complete, the slurry is
allowed to settle. The resulting effluent is recycled, while a belt filter press dewaters the sludge.
While photo-oxidation pretreatment enhances the biodegradation of PAHs, it is not required for more
readily biodegradable contaminants. Initial studies showed that concentrations of 400-5,000 mg/kg
mineral oil in contaminated soil could be reduced to the objective of 100 mg/kg in eight days without
photo-oxidation pretreatment. In contrast, data showed that photo-oxidation helped degrade PAHs in soil
and chlorophenol in groundwater. The pretreatment reduced PAHs from 30 mg/kg to 5-10 mg/kg in 15
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days and chlorophenol from 200 ug/L to approximately 50 ug/L in 25 hours. It was suggested that the
enhanced degradation resulted from the breakdown of soil organic matter and subsequent release of
sorbed PAHs rather than to the oxidation of PAH molecules themselves. Without photo-oxidation
pretreatment, PAHs were not degraded, while chlorophenols were reduced to only 100 ug/L.
Two demonstration tests were undertaken: one on sandy soil contaminated with heavy crude oil and one
on sediment contaminated with mineral oil and PAHs. Soil washing was used as the pretreatment step
to separate the fines from the larger soil or sediment fractions. Fines rich in organics were then treated
in the 300-m3 bioslurry reactor designed to maintain a minimum dissolved oxygen concentration of 2
mg/L and a set temperature between 15-30°C.
The results of these demonstrations showed that soil contaminated with up to 14,500 mg/kg of crude oil
was treated to less than 3,000 mg/kg (in recombined fractions). Sediment contaminated with up to 2,000
mg/kg PAHs and 20,000 mg/kg mineral oil was treated to levels of 150 and 2.5 mg/kg respectively.
Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry Phase Bio-reactor)
The project investigated combining soil washing (especially using froth flotation) and slurry-phase
bioremediation to remediate soils contaminated with 3- and 4-ring PAHs. The project consisted of bench-
scale treatability studies and pilot-scale remediation.
The bench-scale biotreatability studies involved first isolating and screening soil microorganisms to
evaluate their tolerance to PAHs and their ability to degrade these contaminants. Subsequent experiments
with selected microorganisms provided optimum conditions for biodegradation of these compounds in
slurry reactors.
The pilot-scale plant set up at the Norwegian State railways site in Lillestrom, Norway, combined froth
flotation as a pretreatment for soil washing, a 1-tonne/hr soil washing plant, and a 454-L bioslurry
reactor. This phase of work tested four excavated soils made up of sand, silt, clay, and sawdust/sand
from the railway site, as well as two soils from another location. Investigators evaluated single and
blended commercial anionic and cationic surfactants used with a foamer at water temperatures between
10-50°C and pH of 7-11. The biotreatment phase of the study tested indigenous microorganisms as well
as patented PAH degraders. Parameters for biostimulation included nitrogen (N) and phosphorous (P),
pH, aeration, surfactant, and temperature.
Bench-scale investigations of soil washing revealed that the most effective combination of one of the
cationic collectors and a foamer removed 90-95% of PAHs from sandy soils. Increasing water
temperature or pH provided no significant benefits and was incompatible with the downstream biological
treatment. At the pilot-scale, soil washing at a loading rate of 550-859 kg/hour removed 20-90% of
PAHs from two clay soils. The cleaned soil fraction contained 15-1,500 mg/kg PAHs. Clayey soils
impaired the efficiency of soil washing and resulted in less than optimum performance.
The pilot-scale bio-reactor tested five 60 L batches of sludge resulting from soil washing two clayey
soils. During treatment of the sludges, which contained 14-20% solids, PAH concentrations fell by up
to 97% after 6 days. Oxygen uptake decreased during this time corresponding to a decrease in
bioavailable PAHs in the bioslurry. An interim report noted that the native populations of PAH degraders
"appeared to be sufficient to achieve residual PAH concentrations ranging from 55-200 mg/kg after a
6-day retention time."
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A Microtox 15-minute bioassay revealed that the combined soil washing and biological treatment
reduced toxicity by a factor of 10. Soil washing itself reduced the relative toxicity only slightly. The
bioslurry treatment accounted for most of the reduced toxicity. Costs for various aspects of the
remediation approach for the site were estimated at U.S.$160/m3 for excavation, sorting and backfilling,
U.S.$300/m3 for washing, and U.S.$530/m3 for biological treatment.
Project 36: Enhancement Techniques for Ex Situ Soil Separation Processes, Particularly with Regard
to Fine Particles
This pilot study examined the feasibility of extending soil washing processes to soils containing a high
proportion of fine particles. The investigation focused on physical separation techniques and equipment
used to treat fine mineral ores and industrial minerals. Tested soils contained a high proportion of fines
and were contaminated with organic compounds. The studies investigated a variety of processes that
included disaggregation, sizing, and classification of particles, attrition scrubbing, dewatering, and
integration with slurry-phase biological treatment.
For the laboratory- and pilot-scale studies, two tested soils were both rich in clays. One soil from a
former industrial site contained 62% soil particles less than 0.063 mm and was contaminated with diesel
fuel. The other soil from a former gasworks facility had up to 43% soil particles less than 0.063 mm and
contained PAHs, total petroleum hydrocarbons (TPH), and complexed cyanides. Laboratory tests served
to characterize the soils and help design the pilot-scale studies. The tests evaluated disaggregation,
screening, classifying at fine sizes, attrition scrubbing, and removal of misplaced or "entrained" particles.
For the pilot plant tests, investigators used small-scale commercial separation and concentration
equipment. Tests were conducted as a number of batch processes, with material from one process being
collected and used as feed for further processes.
Contaminated fines were sometimes treated by froth flotation and specific gravity separation. The froth
flotation approach, seen as an alternative to ultrafme hydrocycloning, consisted of a coal collector and
frother. A part of the study tested 10 common organic flocculants and three inorganic coagulants to
choose a flocculant/coagulant that produced relatively large compact floes that settled rapidly. Work
included settling tests and capillary suction tests.
Ten-liter air-sparged reactors provided a temperature-controlled environment for biological treatment.
These investigations evaluated the biodegradability of different contaminated fine fractions at different
temperatures, and with and without nutrients.
The bulk of contamination in the diesel-contaminated soil occurred in the fraction smaller than 0.002
mm. Pretreatment with a rotary ball mill partially filled with steel balls or pebbles disaggregated the soil
particles and produced a slurry amenable for separation. Up to four additional sequential stages of
hydrocycloning substantially reduced the concentration of contaminants in the coarse fraction. The
resulting contaminant-reduced fraction accounted for 68.7% of the original soil.
Froth flotation, tested on the fraction smaller than 0.01 mm, did not significantly reduce contamination
in the non-floating product. Of the 13 organic and inorganic coagulants/flocculants examined, calcium
hydroxide at a dose rate of 100 g/tonne of solids produced a floe with the lowest moisture content after
filtration.
After 28 days of treatment in the slurry reactor, fines separated from the diesel-contaminated soil
retained only 20% of their original contamination. Despite this reduction, treated fines contained
relatively high levels (2,300 mg/kg) of TPH, down by 80% from the original 12,000 mg/kg.
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Despite their success with diesel-contaminated soil, physical separation and slurry phase biological
processes experienced difficulties treating fines in the gasworks soil. Disaggregating this soil involved
a tumbling mill system, sometimes preceded by a high pressure water-sprayed screen. Laboratory studies
revealed that attrition scrubbing had little benefit because fine aggregated particles and contaminant-
coated particles were minimal.
Froth flotation and specific gravity separation, unlike sizing and multi-staged classification, were able
to concentrate contaminants in specific fractions. Froth flotation proved best on the 0.01-0.063 mm
fraction, producing a non-floating fraction that accounted for 69% of the original untreated material.
Three stages of froth flotation reduced PAH contamination by 61%, petroleum hydrocarbons by 54%,
and cyanide by 39%. Specific gravity separation on the 0.01-0.063 fraction reduced PAHs, petroleum
hydrocarbons, and cyanide contamination by 68%, 76%, and 14%, respectively. Despite these reductions,
treated fractions could not be reused because they still contained unacceptable levels of contaminants.
Biological slurry treatment of the fine fractions failed to significantly reduce levels of the contaminants.
After 28 days of treatment, PAHs fell by 40-50%, and petroleum hydrocarbons by up to 20%. Cyanide
remained unchanged.
Residuals include clean treated soil materials and others that did not achieve remediation guidelines.
Clean material could be reused onsite, while partially clean materials have to be dewatered and disposed.
Water from soil washing and bioslurry treatment would also have to be treated before disposal.
For treatment to be more cost-effective than disposal of the untreated soil, the cost for transporting and
disposing of such material must exceed £40-60 (U.S.$65-100) per tonne. Total operating costs were
estimated at £23-37 (U.S.$38-60) per tonne of treated material.
The results of the study suggested that ex situ separation processes may be cost-effective for soils
containing more than 30-35% of particles smaller than 0.063 mm. However, further work should assess
the extent of application of this approach. This work may examine the mineralogy of clay particles, as
well as how the exchange capacity of these particles influences adsorption/desorption of contaminants
and subsequent dewatering.
5.2.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10,17,19,27, 31,
and 33)
Project 10: Integrated Treatment Technology for the Recovery of Inorganic and Organic
Contaminants from Soil
This technology uses an integrated process to recover metals and organic compounds from soils and
sediments. The process combines physical and hydrometallurgical steps to recover metals, and physical-
chemical methods for organics. The combination provides a technology capable of recovering organic
and inorganic contaminants simultaneously.
The first step involves separating the finer fraction of material, normally associated with contaminants,
for further treatment. Coarse screens remove the fraction greater than 75 mm, which is usually clean and
normally returned to the site. Material less than 75 mm goes through sequential soil washing separation
methods, which break down soil aggregates, separate ferrous metal, and produce fractions of different
sizes.
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The resulting slurry, free of coarse metal fractions, is then treated with proprietary reagents and
conventional flotation equipment to extract a product rich in organic contaminants. If further treatment
is required, the organic-depleted slurry passes to a hydrometallurgical circuit where fine metal
contaminants that were not recovered physically are leached into solution then extracted with Vitrokele™
metal-selective absorbents. The resulting metal-rich filtercake is recycled, while the remaining slurry is
washed, dewatered, and disposed as a clean material.
The intended uses for treated materials govern the degree of treatment required to satisfy the relevant
criteria and the consequent overall costs. For example, sediments to be used as lake-fill may require an
extra hydrometallurgical leach and counter-current Vitrokele™ adsorption unit to achieve lake-fill
guidelines. Sediments for on-shore use as fill may not require this step.
Tallon Metal Technologies, Inc. conducted bench-scale tests with sediments from Hamilton Harbour,
Ontario, Canada. The sediments contained high concentrations of organic contaminants (PAHs, oil and
grease), metals such as Pb, Zn, Cd, Cu, and Ni, as well as a total organic carbon (TOC) load that
exceeded 10%. A 20-kg test sample was made up of approximately 92% material smaller than 100 um
and 75% smaller than 50 um. Metals such as Cd, Cr, Fe, Mn, Ni, Pb, and Zn exceeded the "severe
effect level" base on Ontario's sediment quality guidelines. The bench-scale treatment approach included
flotation, magnetic separation, and gravity separation techniques.
The results showed that cleaned tailings represented around 40% of the original sediment feed, but
contained only 4.1% of the total oil and grease, 4.9% of the PAHs, less than 2% of the total Pb, and
11% of the total Zn. In contrast, Cd, Ni and Fe were also reduced but remained at 24-30% of the
original load.
The organic product contained 27% of the total mass and captured 62% and 74% of the original oil and
grease and PAHs, respectively. It was also enriched in Pb, Zn, Cd, Ni, and Fe at 81%, 60%, 54%, 54%,
and 32%, respectively, of the original content.
Based on the bench-scale investigation, the treatment process for Hamilton Harbour sediments would
consist of screening, magnetic separation, concentration of organics by flotation, and a hydrometallurgi-
cal extraction if required to remove residual Zn, Cu, Ni, and Pb from feeds to the leach circuit. For this
treatment, the contractor estimated a cost of Cdn$75-100 (U.S.$52-69)/tonne, assuming at least 20,000
tonnes require treatment.
The technology was tested on soils from two industrial sites: the Ataratiri site in Toronto, Ontario,
Canada, and a site in Longue Pointe, Quebec, Canada. The soils exceeded industrial guidelines for reuse
for some heavy metals and inorganics. Ataratiri soils contained PAHs, while those from Longue Pointe
were contaminated with metals such as Pb, Cu, and Zn.
Pretreatment of Ataratiri soils resulted in a metal concentrate, suitable for recycling, containing as much
as 55% by weight iron. "Clean" fractions that made up around 95% by weight of the feed material were
within Ontario's residential criteria for some contaminants, but within industrial criteria for PAHs. The
treatment reduced benzo(b)fluoranthene from 14 mg/kg to 4 mg/kg, a value that exceeds residential
guidelines. Treatment reduced Zn from 4,026 mg/kg to 360 mg/kg, but Cu remained unchanged at 100
mg/kg. An added hydrometallurgical step proved effective for treated soils that still exceeded industrial
guidelines. When soils were treated by this extra recovery step, higher percentages of the original feed
material achieved industrial or residential guidelines.
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For Longue Pointe soils, the technology incorporated hydrometallurgical extraction and Vitrokele™
adsorption because most of the Pb contamination occurred in fine particles in the soil. Soil treated this
way contained as little as 7% of its original Pb content (as high as 11,800 ug/g), and met regulatory
limits for industrial or residential use.
At Ataratiri and Longue Pointe, recovered contaminant metal products were of low mass, rich in metals
and suitable for recycling off-site in the steel or base metal industries. Recovered organic contaminants
were low in mass, enriched in oil and grease and PAHs, and suitable for on-site or off-site treatment by
a secondary technology.
According to the technology vendor, the integrated approach for organic and inorganic contaminants is
economically attractive over one that uses two independent treatments.
Project 17: Treatment of Polluted Soil in a Mobile Solvent Extraction Unit
The ORG-X mobile solvent extraction unit, originally designed to remove viscous non-aqueous phase
liquids (NAPLs), such as PAHs and tars, from excavated soils at manufactured gas plants, is modular
and usually mounted on five trailers. Under this NATO/CCMS Pilot Study, the ORG-X process was
combined with other technologies to treat PAHs, polychlorinated biphenyls (PCBs), petroleum
hydrocarbons, and heavy metals in different soil types.
After first screening contaminated soil to remove a coarse clean fraction (>#4 mesh), contaminated fines
are mixed with anon-chlorinated, non-toxic, biodegradable solvent at ambient temperature. An extraction
auger enhances dissolution of organics from soil in the resulting slurry and partially separates the cleaned
fines from the solvent laden with organics. The solvent then passes to a decanter where the entrained
fines settle. After settling, fines are returned to the initial mixing tank, and spent solvent is decanted and
sent to a vaporizing recovery unit. Solvent recovered from this unit is recycled to the initial mixing tank
while organics form a concentrated contaminated oil, which requires subsequent treatment.
Soil from the extraction auger goes to a dryer that evaporates residual solvent, condenses it, and sends
it to the vaporizing unit. The treated dry soil is then either stabilized if contaminants such as heavy
metals are present, or is reused. Traces of solvent in cleaned soils are claimed to be innocuous and
biodegradable.
The feed rate depends on the soil type and ranges from two to five tonnes/hour. Treatment costs vary
from U.S.$75-200/tonne depending on the volume of material to be treated.
Tests were conducted with 12-200 tonnes of media (silty sand, loamy soil, and sediment) contaminated
with PAHs, coal tar, petroleum hydrocarbons, heavy metals, and PCBs. Extraction reduced levels of
PAHs from 250-2,000 mg/kg to 6-30 mg/kg, and PCBs from 200-500 mg/kg to 1-6 mg/kg (98%
reduction). Treated materials were used as fill or treated further to stabilize metals.
The solvent formulation, protected by trade secret, which is non-specific and thus provides excellent
extraction for a wide range of organic contaminants. These include crude oil, machining oils, PCBs,
pesticides, and herbicides. A key feature of the system's design is its ability to treat finer particles with
adsorbed contaminants.
The ORG-X mobile solvent extraction unit operates best under optimum moisture content and grain size.
In one case study, the soil moisture content of 20% made the soil more difficult and costly to treat. The
process achieves higher efficiency on sandy material, but is being improved for fine-grained soils.
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The technology vendors reported that cost savings increase as the volume of material to be treated
increases, for example:
• 2,000 tonnes: approximately U.S.$200/tonne
• 20,000 tonnes: just under U.S.$100/tonne
• 100,000 tonnes: about U.S.$60/tonne
Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing and Distillation
Process
The large-scale Harbauer soil washing and vacuum distillation plant was evaluated at a site in
Marktredwitz, Germany. The site contained 57,000 metric tonnes of soil and debris contaminated with
mercury, solvents, chemical waste, and treatment residuals. Mercury occurred at concentrations of 300-
5,000 mg/kg. The project's remediation goal was to clean the contaminated soil and debris to meet
criteria for landfilling.
This was reported as the first full-scale application of vacuum distillation technology. This unit is
containerized, transportable, and equipped with systems to treat process water and off-gas. During the
3-year period of operation, the unit processed 57,000 tonnes at the rate of 150 tonnes/day.
Vacuum distillation eliminates drawbacks associated with conventional thermal processes. For example,
the moderate heating does not change the mineral structure of treated soils.
In this technology, soil washing first concentrates mercury in a fine fraction (as small as 0.1 mm to as
large as 8 mm). During subsequent vacuum distillation, the fines concentrated with mercury are heated
in a rotating drum to 350-450°C under reduced pressures of 50-150 hPa. Reduced pressures (rather than
higher temperatures) lower the boiling points of contaminants and result in lower energy costs. Also,
vacuum distillation releases only 1/20 to 1/30 of emissions normally encountered with incineration.
Volatile mercury is recovered by condensation. Treated soils containing more than 50 mg/kg mercury
are passed through the process again.
In addition to soil washing and vacuum distillation, the system incorporates processes to treat water and
off-gases. Water treatment consists of thickeners, flocculants, a sand filter, and activated carbon filters.
The sand filter removes very fine particles while the carbon adsorbs organic contaminants that may be
present in the process water. An ion exchanger completes treatment before water may be discharged to
a sanitary sewer.
In the remediation project, 15,000 tonnes were treated at a rate of 150 tonnes daily during the first year
of operation. Soil containing mercury up to 1,900 mg/kg achieved levels below the target of 50 mg/kg,
and often reached 10 mg/kg. Treated off-gases and water also achieved relevant target levels.
Monitoring the plant revealed that the operation met emission standards. Under the low-oxygen
environment of vacuum distillation, secondary oxidation does not occur, so dangerous organic residues
like dioxin are not formed.
Residuals to be disposed of or recycled were condensed mercury, spent ion-exchange resin, and a fine-
grained precipitation sludge from the water treatment unit.
Costs for treatment, according to results from a U.S. SITE demonstration project, were estimated at
U.S.$320/tonne.
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In addition to its application for mercury in the remediation project, the combined process can be used
to treat crude oil fractions, halogenated hydrocarbons, PAHs, cyanides, and metal compounds that can
be vaporized.
Project 27: Soil Washing and Chemical Dehalogenation of PCB-Contaminated Soil
Soil washing and chemical dehalogenation were used to treat 1,288 tonnes of excavated material
contaminated with PCBs. This material came from a site in Oslo, Norway, where insulator oils
containing PCBs had leaked from transformer equipment and contaminated soil with up to 2,000 mg/kg
PCBs.
The three-year project included bench-scale studies on soil washing followed by pilot-scale and full-scale
washing. Dehalogenation investigations were conducted at bench-scale and full-scale. The Pilot Study
focused on a combined system of water-based soil washing and dehalogenation, because this
combination had not been applied before in Norway. Both processes were novel in that country, and
reductive dehalogenation was itself innovative.
Duplicate bench-scale soil washing treatability experiments with a laboratory-scale flotation cell tested
these variables: water temperature, pH, five surfactants, and a foamer (methylisobutylcarbanol). The
additives and soil were mixed for a fixed conditioning period, then aerated for a fixed period. The foam
and remaining clean soil were collected and analyzed for PCBs.
Soil washing involved first separating and sorting debris, then treating the soil in a soil washing plant.
For this treatment, the plant consisted of three processes to separate the remaining contaminated
materials into two size fractions (>0.1 mm and <0.1 mm) and to surface-wash them. The contaminated
fines (<0.1 mm), having passed through a conditioning mixing tank and a double flotation cell, were
trapped in a foam in the cell. The trapped material, laden with contaminants, was coagulated and
flocculated with an organic polymer, then thickened and dewatered.
The full-scale soil washing operation did not achieve its performance target for volume reduction
because the levels of fine particles were higher than expected. Washing reduced the volume of material
by 60%, not 70% as expected. The excess particles overloaded the system with solids, and soil that
should have been clean after one washing had to be washed again. As a result of the reduced
performance, washing produced 780 tonnes of clean soil and around 400 tonnes of sludge containing
PCBs to be destroyed.
The dehalogenation technology tested at the pilot-scale involved first drying soil to 10% moisture, then
adding a reducing agent and exposing the mixture to a reducing environment. The final report
documenting results of the pilot-scale dehalogenation investigation was not available for this review.
In terms of performance for PCBs, the duplicate bench-scale soil washing experiments on samples with
around 1,000 mg/kg PCBs achieved 80-95% removal of PCBs. The remaining soil (clean fraction)
contained residual PCBs at 40-50 mg/kg.1 The full-scale soil washing operation treated 1,400 tonnes
of soil containing 50-300 mg/kg PCBs (dry weight). All batches achieved the performance criterion of
less than 10 mg/kg PCBs.
'Authors' note: In the absence of mass balance data, the percent removal cannot be verified. It is possible that
the laboratory work aimed to achieve a specific concentration of PCBs in the clean fraction rather than a targeted
percent removal.
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The report did not contain information on performance in terms of discharged water. This water could
contain no more than 10 ug/L PCBs, that translates to a loading of less than 200 mg/day.
The interim report did not contain information on the full-scale dehalogenation studies, or on the eco-
toxicological tests to evaluate the risk associated with clean and treated soil to be redeposited at the site.
Leachates from TCLP tests of treated material provided information on the toxicity of the biphenyl by-
products.
The soil washing operations generated residuals, but no gaseous emissions. Coarse material and treated
fines were returned to the original excavation and capped. All wash water was collected, analyzed for
PCBs, and treated if required before discharge to a sewer.
Treated soil contained residual PCBs, by-products formed during treatment, and chemicals used to
promote dehalogenation of the PCBs. All of these compounds posed possible environmental hazards.
To evaluate these hazards, a suite of eco-toxicological tests was conducted on leachate generated from
samples treated according to the TCLP.
For the full-scale soil washing operations, equipment costs were estimated at U.S.$75,000 and operations
at U.S.$380/tonne. These amounts include handling materials, and analyses (approximately U.S.$767
tonne). Costs for dehalogenation were not available.
Project 31: Decontamination of Metalliferous Mine Spoil
The Water and Environment Division of the Welsh Office commissioned a study to evaluate methods
for decontaminating metalliferous spoil from abandoned mines in mid and north Wales. This study aimed
to determine if current metal-processing could be used to reprocess old metalliferous spoil materials to
recover metals of some value and to reduce the environmental impact of the spoil.
Laboratory-scale studies evaluated the mineral processing techniques on lead-zinc mine spoil materials
from five unreclaimed former metal mines. This evaluation, the first phase of a two-part study, set out
to identify promising treatment options for detailed examination in the second phase. Researchers first
characterized spoil material then examined techniques involving gravity separation, froth flotation,
chemical leaching and biological extraction.
Characterization of the mine spoil revealed that concentrations of Pb and Zn in the whole spoil samples
were up to 20% and 15% by mass, respectively, but Cu and Cd were in the range of parts per million.
Lead was concentrated in the finer particle sizes of the spoil. Results also showed that a fine-grained,
compact, clay-like spoil saturated with water created anaerobic conditions, which inhibited oxidation and
allowed minerals to retain their sulfide forms. In contrast, a sandy spoil allowed extensive oxidation to
occur and convert Pb and Zn minerals to their more easily leached sulfate forms.
In this study, differences in particle density and surface chemistry for the separation of spoil particles
were evaluated using dense media (so called "sink and float") and froth flotation tests. An MGS was
further examined for density separation at pilot-scale. Laboratory-based density separation consistently
reduced metal concentrations (<2 weight %) in the lighter spoil fractions, which represented over 90%
of the total sample weight. The heavier concentrate contained up to 32% Pb and 5% Zn by weight.
Although treated material was significantly cleaner than original spoil, these levels still greatly exceeded
U.K. soil guidelines. The pilot-scale MGS treatment produced similar results on the fraction of spoil less
than 0.5 mm. Results showed that the MGS can concentrate almost 70% of the metals into a mass of
less than 10% of the original spoil. The residue has a combined metal assay of 2.5%.
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For most of the tested spoils, froth flotation performed poorly but achieved reasonable performance
where spoils remained un-oxidized. Additives showed little promise in terms of producing marketable
concentrates or significantly more acceptable (i.e., low metal) tailings. The effectiveness of this
technique depended critically upon the mineralogy of the spoil. Un-weathered material, rich in sulfides,
showed better segregation of contaminants into the concentrate.
Leaching metal contaminants from the spoil by a variety of chemical agents, such as sulfuric acid,
sodium hydroxide, diethylenetriamine, and by using ferric bacteria inoculum, was evaluated on
unprocessed spoil and treated fractions from the density and froth flotation tests. Effective chemical
leaching depended on the degree of spoil weathering. Generally, sulfuric acid and diethylenetriamine,
leached 2-33% of the Pb and 12-64% of the Zn. Sodium hydroxide leaching of weathered spoil
mobilized 25-92% of the Pb and 3-23% of the Zn in unprocessed spoil.
To evaluate the extent to which metals remaining in reprocessed (by gravity separation or froth flotation)
residues would be leached and hence be of environmental concern, the residues were subject to chemical
and biological leaching. This leaching removed 2-5% of the remaining contaminants, indicating a
resistance to leaching in residual material. Bacterial leaching proved to be ineffective for Pb but removed
significant amounts of Zn from the spoil.
Project 33: In-Pulp Decontamination of Soils, Sludges, and Sediments
This project consisted of bench-scale and demonstration-scale development of a treatment technology
by Davy International Environmental Division of the U.K. and Kommunekemi of Denmark. The process
combines conventional ex situ soil washing techniques with an innovative chemical treatment stage. A
major expected advantage is the ability of the approach to remove contaminants from fine sized soil
fractions such as silt and clay. Two measures used to extract contaminants are:
• leaching using acidic or alkaline reagents followed by adsorption to activated carbon or ion exchange
resin; and
• adsorption by activated carbon or cation exchange resins in direct contact with a soil slurry.
Contaminating substances then may be desorbed from the recovered carbon or ion exchange resin that
is then recycled.
Test materials consisted of contaminated soils and sediments. Soils came from a reclaimed site
contaminated with arsenic from a catalyst; a gasworks facility containing Zn and Pb; a wood preserving
site contaminated with Cu, Cr, and As; and chlor-alkali and gas metering sites with Hg contamination.
A sediment sample containing Zn, Pb, and Fe was collected from Hamilton Harbour in Ontario, Canada.
Zn, Pb, Fe, and Mn levels in the sediment exceeded Ontario's "severe effect" guidelines, while Cu, Cr,
and Ni levels ranged between the "severe effect" and "limited effect" levels. This summary highlights
work done on samples from the wood preserving site, the chlor-alkali site, and the harbor. Project reports
did not contain information on the other samples.
Small pilot-scale leaching experiments examined inorganic and organic acids, alkalis, and chelating
reagents under various conditions. The results showed that mild leaching was inadequate for obtaining
target contaminant concentrations in the solid residue. The most effective leachant, sulfuric acid,
removed 90-97% of the contaminants from the soil. Cu, Zn, and Cr were removed to below target levels,
but As exceeded the target of 30 mg/kg.
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Adsorption tests on leachate from soils from the wood preserving site were carried out with ion
exchange resins, activated carbon, and magnetite to treat the leachates. Compared with the other
adsorbents, the ion exchange resins removed the most Cu, Cr, and Zn from the leachate. Acid resins
adsorbed from 75-100% of the Cu, Cr, and Zn but only 20-60% of the As.
A 10-kg sample of the soil from the wood preserving site was treated at bench-scale using the unit
operations of physical separation and chemical leaching which had been identified from the experimental
studies. The treated soil had a lower metal content than the feed material. Copper fell from 360 mg/kg
to 22 mg/kg, Cr from 621 mg/kg to 74 mg/kg, Zn 414 mg/kg to 68 mg/kg, and As from 1,204 mg/kg
to 112 mg/kg. Only As exceeded its preliminary treatment target of 30 mg/kg. Further work focusing
on protocols that take As speciation into account showed that chelating agents leached up to 52% of As.
Combining flotation, screening, and hydrocycloning achieved 60% removal in 80% of a soil but the
residual still exceeded target levels. Multiple acid leaching reduced As from 650 mg/kg to 22 mg/kg,
but at a relatively high cost.
Trials with the Hg-contaminated soil used oxidative compounds and complexing agents such as nitric
acid, hydrochloric acid, and sodium hypochlorite. To improve extraction of mercury, the approach
included size separation to remove fines and was operated at higher temperatures. Ion exchange resins
developed for mercury adsorbed the metal slowly. As a result of difficulties with this approach, a
thermal option was investigated. Preliminary tests revealed that by heating contaminated materials to
around 800°C, treated soils achieved regulatory targets for mercury.
Work with Hamilton Harbour sediment showed that the Ontario guidelines for sediment could be met.
Leaching tests were conducted with mineral and organic acids. Strong mineral acids dissolved
contaminants as well as Ca and Fe in 90 minutes. Since these two metals, as well as organic
contaminants would compete with the metal contaminants during adsorption, a two-stage leaching
approach was tested as a way to eliminate this competition. This involved a mild acid to dissolve iron
first, followed by a strong acid to attack the contaminants. The presence of organic contaminants had
little impact on the removal of metals.
Tests with several adsorbents pointed to chelating resins as the likely candidates. These resins proved
to be more selective than activated carbon or magnetite for the contaminant ions over the other metal
ions. The high level of Fe in solution inhibited the adsorption of contaminants, and thus required
pretreatment such as magnetic separation to remove iron particles from the sediment before leaching.
Precipitation to remove metals from the leachate was somewhat ineffective because some metal remained
in solution and required further processing.
The process generates a variety of residuals and emissions some of which require further treatment or
disposal. Decontaminated solids may require final treatment such as pH adjustment and dewatering
before being disposed. For most metal extractions, acid is used to remove metals from the resin,
resulting in a concentrated solution of metals which may be treated by precipitation, reduction or
electrowinning to recover metals, or may be disposed of at a secure disposal site or encapsulated. In the
case of sediments, the leach stage may produce gas emissions if anaerobic activity produces sulfides.
These emissions, noted during leach tests with sediments from Hamilton Harbour, may require gas
scrubbing in a scaled-up commercial plant. Decanted water from excavated sediment may also have to
be treated.
Treatment costs are expected to be high (no data or expected costs were provided) if the process
demands aggressive leaching with oxidative and complexing agents as well as elevated temperatures for
enhanced leaching.
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Although principally applicable to metal contamination, the technology may be adapted (by using carbon
as an additional adsorbent) to handle organic contaminants. Plans to develop the technology further
include investigating surfactants, solvents and other agents to extract organic contaminants and to
combine this with adsorption by activated carbon. The applicability of the technology would depend on
its ability to achieve regulatory requirements.
5.2.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)
Project 32: CACITOX™ Soil Treatment Process
This innovative technology aims to chemically treat soils containing significant silt and clay fractions
for which conventional soil washing techniques are not cost-effective. The technology potentially can
treat contaminated soils and sediments while not depositing unacceptable by-products into the matrix
or destroying the matrix itself.
The CACITOX™ process involves soil leaching, soil/leachate separation, and leachate treatment. The
proprietary leaching process uses a three-component mixture consisting of low concentrations of
carbonate, oxidants, and complexing agents such as carboxylic acids. This mixture, which is used at
near-neutral pH and ambient temperature, reacts with contaminated materials and converts insoluble or
absorbed contaminants into soluble complexes. The oxidant helps dissolve certain metals that occur in
their less soluble forms. As a result of its high selectivity, the leaching reagent minimizes secondary
waste.
A combination of precipitation and ion exchange removes dissolved inorganic contaminants from the
leachate. This stage of treatment may include innovative approaches such as electro-deposition/polishing
to recover valuable by-products or to minimize the volume of secondary waste. Precipitated contaminants
may be conditioned to ensure they meet requirements for disposal. This conditioning may involve
dewatering, containerization, or encapsulation. Chemical processes destroy organic contaminants in the
extract.
Treated soils can be used again because the leaching process uses low concentrations of the mild
chemicals. Hydrocyclones or mixer settlers separate the leached soil from the leachate. A filter press or
belt filter then dewaters separated soil, that was washed to remove residual reagent.
When used with a range of aqueous leaching reagents, CACITOX™ initially experienced more difficulty
decontaminating soils with high clay content than those containing sand. As a result, further work
focused on fine-grained soils to satisfy one of the aims of the project to treat soils with significant clay
and silt content.
Experiments with soils containing "high" levels of heavy metals showed that the leaching process
achieved Dutch B and Canadian Residential Values for all metals except Cd and As. A report claimed
that optimizing the formulation and process variables could enable the technology to achieve target
values for these two metals. Added organic contaminants reduced initial leaching efficiencies by 1-2%.
However, leaching removed 98% of these organics. Leaching with CACITOX™ achieved removal
efficiencies comparable to leaching with mineral acids. However, the proprietary reagent dissolved less
than 10% of the soil matrix, while the mineral acids removed 40%.
During trials to leach radionuclides from test soils, a single contact with the CACITOX™ reagent mixture
removed 52-76% of the Pu, Am, Np, Sr, and Ra, but only 2% of the Cs. Limited data for removal of
radionuclides from a contaminated site show how repeated contacts could improve removal.
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In summary, the CACITOX™ technology can process materials containing high levels of fines like silt
and clay and can selectively dissolve actinides and heavy metals from other wastes. Because the
CACITOX™ process treats inorganic contaminants, it requires other technologies for treating mixed
wastes. The final report mentioned that using low concentrations of mild chemicals resulted in low costs,
but did not provide supporting data. The pilot-scale transportable plant has a capacity of 10 kg/hour, but
can be easily scaled up to 100 kg/hr.
Project 44: Enhanced In Situ Removal of Coal Tar: Brodhead Creek Superfund Site
During the operation of a former gasworks plant from 1888 to 1944, waste coal tars were disposed onsite
in an open pit. Over time, the coal tars migrated into the subsurface, where they collected 6-9 m below
ground surface in a natural depression formed at the geological boundary between coarse gravels and
silty sands. A layer of coal tar (dense non-aqueous phase liquid—DNAPL) was shown to be polluting
0.12-ha of the underlying aquifer and a nearby river. A larger 3-acre (1.22-ha) area of residual
contamination is also present.
Remediation efforts focused on recoverable coal tar in an area with an estimated 22,700 L of DNAPL
because it was believed to represent the major source of groundwater pollutants; however, the dissolved
groundwater contaminants were not addressed. A slurry cut-off wall was constructed to protect the river
from further pollution. Excavation of the contaminated soil was not considered practical, so an
innovative in situ treatment known as Contained Removal of Oily Wastes (CROW) was selected. CROW
is a thermally enhanced in situ recovery process that uses hot water injected at the perimeter of the
contaminated area to reduce the density and viscosity of tar to a level where it can be pumped to the
surface for further treatment and disposal. The rate at which the heated water is injected into the ground
is is used to control the displacement and temperature of the tar material so that it is forced towards the
of extraction wells. Lateral containment is achieved by carefully controlling injection and extraction rates
to isolate the affected areahydraulically. A layer of cooler groundwater above the area of active recovery
prevented mobilized fluids from migrating vertically and condensed contaminants that were volatilized
by the heated water below.
Preliminary treatability studies on coal tar samples were used to determine the optimum temperature and
injection/extraction rates required for full-scale operation. These studies indicated that coal tar in soils
could be reduced to a residual saturation of 60-70%.
Full-scale operation was based on a pattern of six injection wells surrounding two extraction wells in
the center of the contaminated area. Well screens focused injection and extraction flows at the depth of
contamination. A greater amount of water was extracted than injected to hydraulically isolate the
contaminated area. The design flow for injection of heated water was 378 L/min and 435 L/min for
recovery of the water and coal tar mixture. However, much lower injection rates were actually attained
because iron precipitate that formed around the injection well screens significantly reduced operational
performance. This problem was partially solved by installing agitators in the injection wells, but flow
rates remained low (114-132 L/min). The system operated at 71°C instead of the expected 93°C because
the water heater was designed for high flows and could not heat the water to the required temperatures
at the lower flows. The reduced flow rate and lower operating temperature extended the treatment time
to 10 months, approximately twice the expected treatment time. A higher injection temperature of 96°C
was achieved in January 1996 with the installation of the new heater.
At the ground surface, the initial treatment step was to separate the coal tar from the water. The coal
tar was incinerated, and the water was treated by removing the dissolved inorganics (primarily iron and
manganese) through oxygenation and pH adjustment of the water. The precipitated inorganics were
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removed by gravity separation. (The inorganics required removal because they were found to inhibit the
coal tar separation process and foul the system.) The treated water was reheated and reinjected into the
subsurface. A lesser amount was injected than was extracted to maintain hydraulic isolation. The
overdraw of water was treated in a fluidized bed reactor followed by granular activated carbon units and
then discharged into Brodhead Creek.
The performance standard for the CROW process was to continue operating the system until the
cumulative recovery of coal tar dropped to 0.5% or less per pore volume of water flushed through the
contaminated zone. This was based on previous operational experiences at a similar site where achieving
this specification meant that 98.5% recovery of recoverable tar had been attained. Planned groundwater
sampling will assess the overall effectiveness of the treatment. During December 1995, a cumulative
flow of 3.1 pore volumes resulted in recovery of 602 L of tar. Over a 10-month period of operation, 29
pore volumes of hot water were flushed through the formation, and a total of 5,400 L of coal tar was
recovered as pure tar.
Groundwater contaminants and residual coal tar remain at the site. A "No-Further Action" record of
decision was issued for groundwater and residual coal tar contamination because of technical
impractibility considerations.
Project 47: In Situ Electro-Osmosis (Lasagna™ Project)
In the Lasagna™ in situ treatment process, electro-osmosis moves dissolved contaminants to treatment
zones, where they are degraded or adsorbed. This process can be operated in a horizontal or vertical
configuration. The vertical configuration consists of outer layers that act as either positively or negatively
charged electrodes and promote electro-osmosis. Sheet piling, trenching, and slurry walls can be used
to create vertical treatment zones, in between the outer electrodes. In the horizontal configuration, which
is installed by hydraulic fracturing or related methods, treatment layers occur between the upper and
lower layers that make up the electrodes. These electrodes may contain graphite or other granular,
electrically conductive materials.
Site characteristics and contaminants determine the configuration to use. In general, the vertical
configuration is more applicable to contamination occurring within about 15 m (50 ft) of the surface.
The horizontal configuration works best for deeper contamination.
The NATO/CCMS case study was limited to the field demonstration of electro-osmosis, using the
vertical configuration to transport and adsorb trichloroethene (TCE) at the U.S. Department of Energy's
Paducah Gaseous Diffusion Plant in Kentucky. The case study was carried out in three phases. Phase
I, conducted January-May 1995, evaluated the overall effectiveness of coupling electrokinetics and
carbon adsorption treatment zones. In 1996, the Phase Ha commercial-scale demonstration examined iron
filings in the treatment zone to dehalogenate TCE. This work was conducted to depths of about 14m
(45 ft) and with a wider spacing between the treatment zones. The full-scale Phase II cleanup will take
place if the Phase Ha tests successfully reduce TCE levels in soil to 5.6 mg/kg.
The field study lasted for 120 days. A key objective was to successfully demonstrate coupling electro-
osmosis to flush TCE from the clay soil (hydraulic conductivity <10"9 m/sec) and adsorption to remove
the contaminant from the pore water. The test site was about 4.6 m x 3 m (15 ft x 10 ft) on the surface
and 4.6 m (15 ft) deep. A control area was built next to the test area and isolated from it hydraulically.
The vertical configuration tested at the site consisted of steel panel electrodes and treatment zones made
of wickdrains containing granular activated carbon.
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A direct current of around 40 volt/m applied to the electrodes caused ground-water to flow from the
anode to the cathode at about 13 mm/day. The induced pH gradient caused problems such as soil drying
and cracking, and metal and mineral deposits at the cathode. Pumping water from the cathode to the
anode reduced these problems. Operating parameters during this period were:
• Power requirements: 105 volts and 40 amperes
• Electro-osmotic flow rate: 4-5 L/hr
• Average soil temperature: 25-30°C
Soil samples collected throughout the demonstration site before and after the test showed that the process
removed 98-99% of the TCE from the tight clay. TCE levels in the soil were reduced from 100-500
mg/kg to an average of 1 mg/kg. Sampling and analyzing the carbon revealed how much dissolved TCE
was adsorbed in the treatment zones and provided mass balance data. These carbon samples accounted
for around 50% of the original TCE. The remaining TCE reduction may be attributed to passive
diffusion (5%), evaporation (5%), in situ degradation of TCE, non-uniform distribution of the
contaminant in the soil, or incomplete extraction of the compound from the activated carbon before
analysis.
The results suggest the process is effective for removing residual DNAPL as well. At most soil sampling
locations with TCE concentrations of more than 225 mg/kg—indicative of residual DNAPL in soil pores
—the process reduced these levels to less than 1 mg/kg.
A more extensive field investigation incorporated material such as iron filings in reactive treatment zones
to destroy TCE in situ. The first part (Phase Ha) of this two-stage investigation, to be conducted on 20
times more soil than was treated in the preliminary field investigation, will try to resolve scale-up
questions, verify cost estimates for treatment, and evaluate how the zero-valent iron performs.
Preliminary results of the Phase Ha demonstration at the site in Kentucky show that treatment zones with
iron filings can dechlorinate TCE, producing relatively innocuous end products such as chloride ion,
ethane, and ethene. Other potential intermediate products like dichloroethene and vinyl chloride are
associated with the surface of the filings.
Residuals and emissions include off-gases resulting from evaporation, and the treatment layers. At the
test site in Kentucky, TCE losses by evaporation accounted for 5% of the mass balance. These off-gases
did not require treatment. If treatment zones are determined to be a hazardous waste, removing and
disposing them may be an issue.
An engineering evaluation and cost analysis for the vertically configured process estimates a treatment
cost of U.S.$52-118/m3 of clay soil containing TCE at a depth of 12-15 m and over an area of 0.4-0.8
ha. With optimized electrode spacing, improved ability to install treatment zones and electrodes at closer
spacing, and mass-produced prefabricated materials resulting from wider use of the technology, costs
are expected to fall to U.S.$26-52/m3. These costs exclude those for analyses, waste disposal, etc.
The Lasagna™ process reportedly offers promise for treating water-soluble organic and inorganic
contaminants, and mixed wastes in low-permeability soils as well as in groundwater. For highly non-
polar contaminants, surfactants introduced into groundwater or incorporated into treatment zones will
solubilize the organics. The process has been shown to be effective in treating residual DNAPL as well.
Larger scale demonstrations need to be conducted to confirm the effectiveness of using zero-valent iron
to degrade contaminants. The horizontal configuration using biological treatment zones also needs to be
evaluated.
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5.2.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)
Project 14: Ozone Treatment of Contaminated Groundwater
This project examined biological and advanced oxidation treatment of ground-water contaminated by
leachate from an abandoned quarry located at Vaucelles, France. Between 1963 and 1972, this quarry
served as a site for disposal of various chemical wastes.
After an initial site investigation to confirm the source and extent of contamination, the project focused
on examining optional treatments for contaminated groundwater to achieve acceptable drinking water
limits. The water contained a wide variety of organic compounds such as chlorinated and non-chlorinated
solvents at concentrations of 0.8-360 mg/L.
The selected approach combined biological pre-treatment and a UV/ozone oxidation system. The
biological process is seen as a way to degrade chlorinated contaminants into a form more amenable for
photo-oxidation. A membrane filter that separates activated sludge from purified water was claimed to
be better than the conventional process by producing five times less sludge. In the second treatment step,
photo-oxidation degrades compounds remaining in the biologically purified water. Tested treatment
combinations were:
• ozone, and ozone/UV without biological treatment; and
• ozone, ozone/UV, and ozone/H2O2 after biological treatment.
Pilot testing showed that the combined biological/photo-oxidation treatment was more effective than
photo-oxidation alone. The combination reduced chemical oxygen demand (COD) by 90-95%, TOC by
80%, and volatile organic compounds (VOCs) by 100%. The report did not mention investigations to
identify by-products.
In terms of costs, achieving the goal that treated water should achieve drinking water guidelines for
VOCs was estimated to cost FF15 million (U.S.$2.5 million) in capital cost and FF23.7 million (U.S.$4
million) annually. Alternatively, discharge to a surface water body would cost FF10 million (U.S.$1.7
million) at first, and only FF1.7 million (U.S.$280,000) annually.
Project 38: Demonstration of Peroxidation Systems, Inc., Perox-Pure™ Advanced Oxidation
Technology
The Perox-Pure™ UV/oxidation technology combines UV radiation and hydrogen peroxide to treat
groundwater contaminated with a variety of organic compounds. Other components such as acid and base
feed systems may be added to the treatment train to ensure successful treatment of the contaminants.
Adding acid to the water feed reduces the pH (<5.5) to minimize interferences by bicarbonates and
carbonates. Following treatment, adding a base increases the pH to normal levels (6.5-7.5) so that
discharged water meets designated criteria.
The Perox-Pure™ UV/Oxidation treatment technology was evaluated under the USEPA Superfund
Innovative Technology Evaluation (SITE) program at a site at the Lawrence Livermore National
Laboratory in California. Evaluation of the technology's performance at three other sites was used to
support findings for the SITE demonstration.
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At the Lawrence Livermore National Laboratory site, shallow groundwater was contaminated with TCE
and tetrachloroethene (PCE) at concentrations around 1,000 ug/L and 100 ug/L, respectively. The SITE
technology demonstration intended to:
• determine the ability of the technology to remove VOCs from groundwater under different operating
conditions;
• find out if treated water achieved applicable disposal requirements at the 95% confidence level; and
• estimate treatment costs.
A secondary objective was to identify by-products formed during treatment.
The Perox-Pure™ system effectively achieved the California drinking water action levels and U.S. federal
drinking water maximum contaminant levels for the five compounds studied. Quartz tube wipers kept
the quartz tubes clean and prevented scaling, which is detrimental to contaminant removal efficiencies.
Bioassay tests results demonstrated that the effluent was acutely toxic to freshwater test organisms. This
toxicity may have been caused by the residual hydrogen peroxide rather than by treatment by-products.
The following three case studies summarize work and findings to demonstrate the technology for:
• wastewater containing acetone and isopropanol (IPA);
• groundwater contaminated with TCE; and
• groundwater contaminated with pentachlorophenol (PCP).
The first study, at the Kennedy Space Center in Florida, tested the photo-oxidation system as a
replacement for the existing carbon adsorption treatment for wastewater. The replaced system could not
achieve the required discharge level of 0.5 mg/L. In contrast, effluent from the new oxidation system
met all of the discharge criteria, including the demineralization discharge standards, in less than the
specified 24-hour maximum treatment time. The system was efficient enough to allow treatment of the
wastewater in a flow-through mode rather than a batch mode at a flow rate of 18.9 L/min (5 U.S.
gal/min), a hydrogen peroxide dosage of 100 mg/L, and 10 kilowatts of power for a period of 20 hours
per day.
For the second study, the Perox-Pure™ technology was used to treat well water containing 50-400 mg/L
of TCE. Because the well was located in the middle of a large residential area in Arizona, the treatment
was chosen because of its low-visibility and quiet operation. When treatment was conducted at a flow
rate of 510 L/min (135 U.S. gal/min) and 15 kW of power, TCE was consistently treated to a level
below the analytical detection limit of 0.5 ug/L.
A full-scale Perox-Pure™ system treated groundwater contaminated with PCP at levels up to 15 mg/L
for the third study conducted on the property of a chemical manufacturing company in Washington in
1988. Continued operation confirmed that the Perox-Pure™ system could destroy the PCP to below the
target level of 0.1 mg/L. To obtain this result, the system operated at a flow rate of approximately 265
L/min (70 gal/min), a hydrogen peroxide concentration of 150 mg/L, and a power requirement of 180
kW. A pretreatment system oxidized and removed high levels of iron. To reduce the scaling tendency,
acid was added to decrease the pH of water to about 5.0. The photo-oxidation system featured automatic
devices to keep the reactors clear.
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Treatment costs for three of the four tests were U.S.$0.95-1.3/m3 (U.S.$3.60-5.00 per 1,000 U.S.
gallons). Treating well water in the second case study cost only U.S.$0.07/m3 (U.S.$0.28 per 1,000 U.S.
gallons). These costs exclude those for capital.
Project 40: An Evaluation of the Feasibility of Photocatalytic Oxidation and Phase Transfer Catalysis
for Destruction of Contaminants from Water (In Situ Treatment of Chlorinated Solvents)
Photocatalysis is an emerging treatment technology that uses an advanced oxidation process based on
generating hydroxyl radicals using UV light in the presence of a semi-conductor catalyst, such as
platinum-coated titanium oxide. The Hand D process uses a fixed-bed catalyst with the semi-conductor
fixed to a silica gel support. Pretreatment of groundwater by removing suspended matter and inorganic
ions is conducted by a series of filters and ion-exchange columns. Dissolved oxygen levels are increased,
as necessary, to supply oxidants for the destructive oxidation process. The UV light is provided by
natural sunlight.
The project researched development of highly photoactive catalysts and a fixed-bed photocatalytic
process to destroy toxics in air and water. It also researched development of a treatment process using
adsorption to remove contaminants and advanced oxidation processes (AOPs) to regenerate spent
adsorbents. The developed technologies were field tested at Tyndall Air Force Base (AFB), K.I. Sawyer
AFB, and the Wausau Water Treatment Plant.
Some of the photocatalysts used in the laboratory studies were modified on their surfaces with noble
metals, or changed by doping with transition metals to extend the photocatalyst's response to visible
light. Artificial light and UV sources and solar radiation were used to evaluate the photoactivities of
these catalysts for destroying model compounds. Results showed that platinum-coated Aldrich titanium
oxide (Pt-Aldrich-TiO2)—a surface-modified catalyst—performed best for destroying hydrophobic
compounds. The laboratory-developed, platinum-coated Michigan Technology University TiO2 catalyst
performed best for hydrophilic compounds.
The supports tested for fixed-bed photocatalysts consisted of random packing and structured materials.
These supports were chosen for their adsorption capacity, UV transmission, and mass transfer properties.
Silica-based materials were included to test how they performed at destroying organic compounds, and
some of them were surface-modified to increase their adsorption capacity. Investigations excluded
electron-rich materials that could scavenge reactive radicals and diminish the efficiency of photocatalysis.
Researchers developed a unique procedure involving heating and annealing to prepare supported catalysts
for fixed-bed reactors. During solar experiments, the fixed-bed processes were optimized with respect
to the type of catalyst and dosage, support type and size, and preparation methods. Destruction of a
model compound was tested under various UV irradiance, influent concentration, pH, and hydraulic
loading. Tanning lamps tested on the same fixed-bed process tested the destruction of several other
compounds in air and water. Two reactor designs consisted of a catalyst added as a slurry and passed
through a lighted reactor, and a catalyst attached to a support in a lighted fixed-bed reactor.
Tests with the fixed-bed photocatalysts revealed that Pt-Aldrich-TiO2 supported on silica gel completely
mineralized TCE in water (8 mg/L) in one contact time of 1.3 minutes. This destruction rate was 16
times better than observed for an optimized slurry of a commercially-available photocatalyst (Degussa
P25).
Increasing the adsorption capacity of a silica-based support improved the overall destruction kinetics.
Silica gel modified to increase surface hydrophobicity and the adsorption capacity for non-polar organic
water pollutants increased the adsorption capacity for trichloroethene (TCE) in water by more than a
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factor of five. When used as a support for Pt-TiO2, the modified silica gel showed faster overall
degradation kinetics for TCE than did the unmodified silica gel.
For experiments with contaminants in the gas-phase, results showed faster destruction kinetics than in
the aqueous phase. This suggests the option to strip volatile compounds followed by gas-phase
destruction by photocatalysis. For trichloroethane (TCA), a relative humidity of 25% yielded the best
destruction rate. On the other hand, toluene destruction increased with increasing vapor content. The
fixed-bed approach provided high light efficiency. The reported ratio of organic molecules destroyed to
UV photons required was 40%—much higher than the 5% value commonly reported. Phosgene and
carbon monoxide, two major toxic by-products in air-phase photocatalysis, were not found above
regulated levels.
Developing the combined processes of adsorption followed by regeneration consisted of using a fixed-
bed system adsorber to remove and accumulate organic compounds, and regenerate the spent adsorbent
using homogeneous AOP, photocatalysis, or a combination of steam and photocatalysis. For
homogeneous AOP, hydrogen peroxide/ozone and UV light/hydrogen peroxide were used for destructive
adsorbent regeneration. Both of these options consumed three to six times more oxidants in the
regeneration process than would be needed to destroy the contaminants in water directly by conventional
AOP. Regeneration appeared to be limited by adsorbate desorption from the interior to the exterior
adsorbent surface. Neither option is feasible because the desorption rate is too slow, and therefore too
much oxidant is required to regenerate the adsorbents.
In testing photocatalysis for destruction of adsorbed contaminants and regeneration of adsorbents
simultaneously, the catalysts were impregnated onto the adsorbent before being used to adsorb organics.
The first test consisted of using UV illumination to test photocatalysis alone for regenerating the spent
adsorbents and destroying the contaminants. Results showed that desorption of adsorbates from the
interior to the exterior of an adsorbent limited the regeneration process. Thus, temperature played a
leading role in photocatalytic regeneration, and increasing temperature enhanced regeneration rate much
more effectively than increasing light intensity. Using heat to increase the desorption rate and match the
photocatalytic oxidation rate is one way to maximize the photolytic regeneration efficiency.
Saturated steam was used to overcome this problem of slow desorption rates. Heating promoted the
kinetics of photocatalysis and AOP processes by desorbing organic contaminants on the interior of the
adsorbents and moving them to the exterior for oxidation. Thus, steam followed by photocatalysis was
found to be an effective way to regenerate spent adsorbents and to clean up the regeneration fluid (off-
steam or steam condensate).
At Tyndall AFB, a solar photocatalytic process was used to remediate fuel-contaminated groundwater
containing BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) at greater than 2 mg/L. Two
options were tested: (1) a solar photocatalytic fixed-bed process using Pt-TiO2 supported on silica; and
(2) fixed-bed process with Pt-TiO2 impregnated adsorbents alone or combined with Pt-TiO2 supported
on silica gel. During option 1, ionic species fouled the catalysts and inhibited destruction, so the water
was pretreated to remove suspended particulates and ionic species and to increase dissolved oxygen.
Following pretreatment, catalyst photo-activity continued undiminished after 25 days of operation. The
BTEX compounds were destroyed with 6.5 minutes of empty bed contact time on rainy days. Test
results with various flow rates, reactor diameters, influent concentrations, solar irradiances and weather
conditions confirmed the potential application of the process. Treatment cost was estimated at
U.S.$5.52/1,000 U.S. gallons (U.S.$1.46/m3).
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During option 2, two different reactor design configurations were tested. The first design was a
continuous flow configuration with three fixed-bed reactors in series. The first and third reactors were
packed with platinum-coated TiO2 supported on silica gel supports. The second reactor was packed with
a photocatalyst-impregnated adsorbent. In daylight, the incoming organic compounds were destroyed in
the first reactor. At night, the organics were adsorbed onto photocatalyst-impregnated adsorbent in the
second reactor; the adsorbed organics were either mineralized or partially mineralized in the second
reactor during daylight. The remaining organics or destruction by-products were destroyed in the third
reactor. Because organic compounds can be adsorbed during periods of insufficient sunlight, the process
can treat water continuously. Like option 1, option 2 was also affected by catalyst fouling. After four
days of operation, the process was apparently unable to destroy any more BTEX compounds. An ion
exchange unit was added to the system and satisfactory BTEX destruction was resumed; however, the
third reactor still did not perform well, presumably due to fouling species desorbed from the second
reactor.
In the second design, a reactor packed with photocatalyst-impregnated adsorbents was used to remove
the organics during darkness. During daylight, the adsorbent was taken off-line and regenerated by
passing heated water through the reactor. The hot water was then passed through a fixed-bed reactor
packed with platinum-coated TiO2 supported on silica gel supports to destroy any residual desorbed
organics or by-products. The strategy behind this design was to have an 18-hour adsorption period
followed by a 6-hour regeneration period during which the solar irradiance is strong enough to destroy
most contaminants.
The spent adsorbents were regenerated in the presence of sunlight while passing hot water (90°C)
counter-current to the flow direction during the adsorption process. The desorbed organics from the
regeneration process were destroyed in the subsequent fixed-bed photoreactor. The process was examined
for 10 adsorption and regeneration cycles. The efficiency (ratio of organics removed and destroyed to
organics adsorbed) of the process to regenerate the adsorbents was examined for each cycle. Overall,
21% of the total influent BTEX was destroyed, and 98% of the BTEX was removed from the waste
stream. The detention times required for 99.9% destruction of TCE (5 mg/L), TCA (5 mg/L), and
toluene (115 mg/L) were 2.15 seconds, 11.2 seconds, and 40 seconds, respectively. While the process
appears to be effective for 10 cycles, more cycles are required to determine whether steady-state is
achieved.
At K.I. Sawyer AFB, the unit used a fixed-bed photocatalyst and a solar panel made up of 80 tubular
reactors to treat chlorinated compounds in groundwater. The design included a water pretreatment unit,
which included a turbidity filter, a bubble-less oxygen contactor, and ion-exchange columns. The reactor
was a modified solar thermal reactor panel with 80 plastic tubes mounted in parallel. The capacity for
each reactor panel was designed as 0.25 U.S. gallons per minute. On a sunny afternoon, the panel
destroyed 95% TCE, which was present in groundwater at 100 ug/L, within a two-minute contact time.
At the Wausau Water Treatment Plant, fixed-bed adsorption removed and accumulated organic
compounds. The spent adsorbents were regenerated off-line with steam followed by photocatalysis. The
groundwater contained chlorinated compounds and BTEX. Direct photocatalytic oxidation was not
effective for regenerating spent adsorbent loaded with contaminated groundwater because nuisance
substances in the water fouled the catalyst. Tests combining steam regeneration followed by
photocatalysis of steam condensate showed that carbon adsorbent was not effectively regenerated and
lost a significant amount of capacity. Background organic matter in the water may have caused this loss
of efficiency. Based on the results of chloride yield with all the tested adsorbents, steam regeneration
did not appear to destroy significant amounts of the sorbed chlorinated compounds.
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5.3 BACKGROUND OF CASE STUDIES AS A GROUP
Table 5.1 presents key information on the projects. In terms of media treated, Projects in Groups 1-4
dealt with contaminated solids, while Group 5 projects addresses groundwater contamination. Project
44, which is in Group 4, addressed DNAPL contamination in a gravel layer, but not the dissolved
groundwater contaminants. In general, the contaminated solids consisted of soils and sediments
containing a high content of fines. The fines made up 12.5-63% of the parent material. Metalliferous
spoil examined for Project 31 also had a high proportion of fines.
Organic and inorganic compounds were present in some of the contaminated solid media. Typical
concentrations of organic contaminants were 200-5,000 mg/kg petroleum hydrocarbons, 30-2,000 mg/kg
PAHs, and around 120-1,000 mg/kg PCBs. One site contained a concentration of 100-500 ppm TCE,
while another reported chlorophenols at 200 ug/L. Heavy metal contamination attributed to individual
species included Pb (up to 12%), Zn (up to 5%), Cu (360 mg/kg), Cr (621 mg/kg), Hg (300-5,000
mg/kg), and As (1,204 mg/kg). At one site, total metals were detected at 32-650 mg/kg, while cyanides
were detected at 2,000-3,000 mg/kg.
Treatment technologies generally consisted of soil washing and groups of other treatments that included
biological or physical-chemical treatment. Soil washing usually involved screening, scrubbing and
particle size separation. Specialized techniques such as flotation and density and gravity separation were
sometimes used to obtain better separation of clean fractions and contaminated concentrates. Other
groups of treatments that did not include soil washing relied upon physical-chemical or photo-oxidation
technologies.
5.4 PERFORMANCE RESULTS
5.4.1 Analytical and Assessment Procedures
Common analytical and assessment approaches were adopted for all the projects regardless of the
contaminants or media to be treated, the technology being used, or the targeted criteria.
For projects with a soil washing component, the contaminated soil or sediment was first characterized
with respect to particle size distribution and the concentration of organic and inorganic contaminants in
the various particle fractions. Soil washing products were also checked for distributions of mass and
contaminants.
For all projects, the effectiveness of the processes was determined by comparing the levels of
contaminants in treated and untreated materials. All streams were reportedly sampled to measure flows
in the slurry, solids, and water. These data were sometimes used to provide a mass balance. Contaminant
concentrates and products low in contamination were analyzed to determine the degree of contaminant
reduction.
Agency-approved procedures were used to determine characteristics such as pH, moisture content, and
organic and inorganic constituents. For example, analytical approaches included USEPA procedures for
digesting samples, atomic absorption spectrophotometry (AAS) for metal content of aqueous samples,
gas chromatography (GC) for mineral oil, and x-ray fluorescence (XRF) to determine the mineralogy
of the soil and sediment. Specialized methods (e.g., DEXSIL L2000 PCB/chloride analyzer) were
sometimes required.
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Final Report
Table 5.1: Classification of the 14 Case Studies by Technology Used
Project
Number
Group 1:
30
Group 2:
24
26
36
Group 3:
10
17
19
27
31
33
Media
Treated
Soil Washing
Soil (mainly
clayey)
Soil Washing
Soil,
sediment
Soil (sandy
and clayey)
Soils with
high fines
content
Soil Washing
Soil,
sediment
Soil,
sediment
Soil, debris
Soil, other
solids
Metalliferous
spoil
Soil with
high fines,
sediment
Contaminants
Treated
Only
Heavy metals,
inorganic cyanides,
PAHs, petroleum
hydrocarbons
Contaminant
Concentrations
Heavy metals (32-
650 mg/kg); PAHs
(184 mg/kg);
petroleum hydro-
carbons (200 mg/kg)
Technology
Used
Soil washing
Treatment
Process
Particle size
separation
and Biological Treatment
PAHs, heavy
aliphatic
hydrocarbons (oils),
chlorophenols
PAHs (3- and 4-ring)
from creosote
Diesel, PAHs, TPH,
complexed cyanides
and Physical-Chemical
Heavy metals (Pb,
Zn, etc.), PAHs
PAHs, PCBs,
petroleum
hydrocarbons, metals
Solvents, chemical
waste, Hg
PCBs
Pb, Zn, Cu, Cd
Heavy metals (Cu,
Cr, Zn, As), Hg
400-5,000 mg/kg
mineral oil; 30 mg/kg
PAHs; 200 ug/L
chlorophenol
180-3,500 mg/kg
PAHs
2,000-4,000 mg/kg;
TPH; 200-300 mg/kg
PAHs; 2,000-3,000
mg/kg cyanides
Treatment
11,800 ug/gPb;
7,400 ug/gZn; 12.15
ug/g pyrene
250-2,000 ppm
PAHs; 200-500 ppm
PCBs
300-5,000 mg/kg Hg
120-1,000 mg/kg
PCBs
up to 12% Pb; up to
5% Zn; Cu and Cd in
ppm range
360 mg/kg Cu;
621 mg/kg Cr;
414 mg/kg Zn;
1,204 mg/kg As
Soil washing,
bioslurry reactor,
photo-oxidation
Soil washing,
bioslurry
Soil washing,
bioslurry
treatment
Soil washing,
hydrometallurgy
Soil washing,
solvent extraction
Soil washing,
vacuum
distillation
Soil washing,
chemical
dehalogenation
Gravity separa-
tion, flotation,
chemical leach-
ing, biological
extraction
Combined soil
washing and
chemical
treatment
Particle size
separation,
biodegradation
Flotation,
biodegradation
physical
separation,
bioremediation
Particle size
separation, metal
recovery, chemi-
cal destruction
of organics
Particle size
separation,
extraction (for
organics),
stabilization
Particle size
separation,
distillation,
condensation
Particle size
separation,
dehalogenation
Particle size
separation,
leaching and
extraction
Leaching and
adsorption
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Final Report
Project
Number
Group 4:
32
44
47
Group 5:
14
38
40
Media
Treated
Contaminants
Treated
Contaminant
Concentrations
Technology
Used
Treatment
Process
Physical-Chemical Treatment
Soil with
high clay and
silt content
Gravelly soil
and ground-
water
Soil (clay)
Heavy metals,
radionuclides,
organics
Coal tar DNAPL
TCE
DNAPL over 0.12 ha
100-500 ppm TCE
Leaching
Thermally
enhanced
recovery of coal
tar
Electro-osmosis,
in situ treatment
Oxidation,
complexing,
precipitation, ion
exchange
Coal tar: ex situ
incineration.
Water: ex situ
precipitation,
fluidized bed
reactor, and
filtration
Electro-osmosis,
adsorption
Photo-Oxidation Treatment
Groundwater
Groundwater,
wastewater
Groundwater
Chlorinated solvents,
esters, phenols,
BTEX, etc.
TCE, PCE, acetone,
IP A, PCP
BTEX, TCE, other
chlorinated solvents
0.8-360 mg/L
1,000 ug/L TCE;
100 ug/L PCE; 15
mg/L PCP
100 ug/L TCE,
others not given
Combined
biological and
photo-oxidation
Advanced
oxidation and
chemical
oxidation
Adsorption and
advanced
oxidation
Activated
sludge, ozone,
UV/ozone,
ozone/H2O2
UV radiation
and O3/H2O2 or
H2O2
Highly photo-
active catalysts
and fixed-bed
photocatalysis
Treatability studies were often conducted on various contaminants and matrices. During these studies,
measurements of the initial and final concentrations of the contaminants provided information to assess
the probable performance of planned full-scale operations.
Full-scale treatment plants were monitored to ensure they met operational requirements. In some cases,
concentrations of contaminants in emissions and discharges were measured and compared to specified
target levels. For technology evaluations conducted under the SITE program, routine operation of a
treatment plant followed SITE protocols.
Finally, treatments were assessed in terms of their ability to achieve regulatory targets and criteria or
the hazards posed by treated materials. Microtox or a suite of ecological tests were sometimes used to
assess hazards associated with contaminants, residual process additives, and by-products in treated
materials.
5.4.1.1 Group 1: Typical Soil Washing (Project 30)
Comparing the levels of contaminants in treated and untreated soil showed the effectiveness of the
process. All streams were sampled to measure flows in the slurry, solids, and water, and data were
compiled to provide a mass balance. Contaminant concentrates and products low in contamination were
analyzed to determine the degree of contaminant reduction.
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Batch processes (for jigging coarse material and the MGS for separating sand and silt) were incorporated
into the overall materials balance to determine how the entire circuit performed.
5.4.1.2 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36)
Soil Washing
Test materials were first characterized according to the approaches summarized above. Preliminary
experiments first determined the percentages of sand, fines, and coarse material in soil and sediment test
samples. Soil washing was evaluated with bench-scale and small-scale commercial equipment and a pilot
plant. Following soil washing, test material and the resulting wash fractions were analyzed to determine
initial and final concentrations, respectively, of contaminants. This information was used to determine
if contaminants in these fractions were significantly reduced so that the fractions could be reused or
discharged, or required further treatment.
Biological Treatment
To assess the biological phase of the treatment, researchers measured initial concentrations of
contaminants in the soil wash concentrates and compared them with final concentrations of contaminants
after a known treatment period. The final concentrations of contaminants in the recombined treated
fractions (from soil washing and biological treatment) were also measured.
To assess the impact of biological activity, experiments focused on measuring contaminant degradation
over time, comparing the carbon dioxide concentration in the headspace to the concentration in the
atmosphere, and monitoring biological activity expressed as the respiration rate (mg O2/g-hr).
Microtox was used in Project 26 to measure the acute toxicity of water-extractable components of the
soils. Test results assessed hazards associated with the soils that could not be quantified by chemical
analyses, and also the formation of possible toxic intermediates from the biological process.
5.4.1.3 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10,17,19, 27,
and 31)
Characterization
Where mentioned in project reports, characterization of contaminated material involved determining
particle size distribution and analyzing sub-samples of the separated fractions for organics and
inorganics. Preparing materials consisted of screening soil samples at various sizes (e.g., 20 mm, 6 mm,
and 2 mm and with a standard set of screens) sometimes down to 45 um. Yields at each screen size
were calculated as dry weights and used to prepare particle size distribution curves.
Each major fraction was digested using standard USEPA procedures and analyzed for contaminants and
other soluble species. For the content of inorganics, digested samples were analyzed by methods such
as AAS. In the project on metalliferous spoil (Project 31), the mineralogy of the separated fractions was
examined by XRF. For XRF, samples were subjected to a 0-100° scan against standard results for lead
sulfide, lead sulfate, and lead carbonate. Analytical procedures for Project 33 consisted of USEPA
Method 3010 for acid digestion of aqueous samples and extracts for total metals for analysis by FLAA
or ICP spectroscopy, and Method 3050 for acid digestion of sediments, sludges, and soils. The
investigators modified recommended procedures by using hydrochloric and nitric acids in the USEPA
protocols, since the use of hydrofluoric acid in U.K. laboratories is restricted.
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Soil Washing
Soil washing was conducted at bench-, pilot-, and full-scale. To assess this technology, feed material
as well as contaminant concentrates and various separated fractions were weighed and analyzed for
contaminants such as oil and grease, and metals. Samples were sometimes analyzed in duplicate or
triplicate.
Physical-Chemical Treatment
In general, performance was assessed by checking mass and contaminant distributions in feed and
recovered products. This approach was taken for investigations from bench-scale treatability to full-scale
application. Analyses were usually conducted in a laboratory, but for Project 27, PCB analyses were
done in the field with a DEXSIL L2000 PCB/chloride analyzer.
At full-scale, plants were sometimes monitored to ensure that they met operational requirements. For
a technology evaluation conducted under the USEPA SITE program, routine operation of the plant work
followed SITE protocols. As an example, instruments at the field site for Project 27 monitored air for
particle-bound and free PCBs.
Because different technologies were used to treat soil wash fractions, different assessment procedures
were applied during subsequent work with these wash fractions. In froth flotation tests (Project 31), for
example, the technology was initially assessed in a 2.5-L Denver flotation cell under conventional
conditions practiced widely in the base metal industry to recover sulfide minerals. Similarly, a
preliminary leach program with several types of soils (Project 33) tested various inorganic and organic
acids, as well as alkaline and chelating reagents under various conditions. Samples of the soil wash
mixture, which were withdrawn and analyzed periodically, revealed concentrations of metals in both the
solid and liquid fractions. Adsorption tests with the leachates involved first screening a variety of
adsorbents then obtaining adsorption isotherms for candidate adsorbents.
Only one report documented quality assurance and quality control (QA/QC) procedures. For Project 33,
where work was conducted on Hamilton Harbour sediment, Davy International Environmental Division
and the Wastewater Technology Center (WTC) in Burlington, Ontario, agreed on a program of
laboratory work and a QA program. As agreed with the WTC, a full USEPA quality assurance project
plan was inappropriate for the laboratory work. However, to obtain quality data and have confidence in
the pilot plant design, control actions included performing analyses in duplicate, testing blanks and
spiked samples (approximately 10% of samples over the whole program), performing elemental mass
balances for each test, and completing an independent audit.
Overall Assessment
This overall assessment concerns criteria/targets used to assess the performance of the technologies in
this group.
In terms of targets, mercury emissions from vacuum distillation used for Project 19 were measured, and
concentrations were compared to a specified level of 50 ug/dscm. Mercury was measured in the feed
and treated stream to evaluate the performance of the technology and to determine if the residual had
achieved the target of 50 mg/kg. Mercury in cleaned water for discharge to a sewer had to achieve a
target level of 10 ug/L. For Project 27, the Norwegian Pollution Control Authority proposed the test
methods and acceptance criteria for PCB reduction and eco-toxicological tests. A 70% guideline was set
for volume reduction. This agency also recommended a suite of ecological tests (biodegradation, acute
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toxicity, and bioaccumulation) to evaluate risk associated with the clean soil and dehalogenated sludge
that would remain onsite. These tests were conducted on leachate generated from samples treated
according to the TCLP. The potential risks included residual PCBs as well as residual process additives
and by-products of the chemical dehalogenation process. To assess performance, criteria for PCBs were
less than 10 mg/kg for soils; less than 10 ug/L for water to be discharged; and less than 100 ug/100 cm2
for non-porous scrap for landfilling.
Other regulatory agencies also established criteria or targets to assess performance. This applied to
Project 31, which investigated reprocessing techniques such as gravity separation, froth flotation,
chemical leaching, and biological extraction for metalliferous mine spoil. To determine the effectiveness
of the treatments on various types of spoil, residual levels of metals in treated spoil were compared with
U.K. soil guidelines for corresponding metals. To determine the extent to which metals in original spoil
and reprocessed residues could be leached and hence be of environmental concern, both materials were
subjected to chemical and biological leaching. The procedure for chemical leaching tests was a modified
version of the shake-flask test described in the Acid Rock Drainage Prediction Manual published by the
Canadian Center for Mineral and Energy Research (CANMET). Laboratory microcosms were set up to
investigate how oxidative microbial activity affected metal teachability. These studies simulated natural
biological processes that occur when the residues are exposed to air and water, and quantified losses of
metals from such a weathered deposit.
Finally, for Project 33, the technology on in-pulp decontamination of soils, sludges and sediments was
assessed in terms of its ability to achieve low absolute regulatory levels (e.g., Danish, U.K., and Dutch)
and teachability criteria recommended by the U.S.
5.4.1.4 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32, 44, and 47)
Characterization
For Projects 32 and 47, characterization of test material comprised determination of particle size
distribution, mass distribution, and distribution of heavy metals (Project 32 only) across the size
fractions. Project 44 involved initial laboratory studies on the coal tar and soil to obtain data for system
design. The specific gravity of the coal tar was determined, and the optimum temperature for the injected
water was determined to be 68°C. It was estimated that 60% of the coal tar in the soil could be removed
with 98% of the removable tar being recovered after 19 pore volumes were flushed through the surface.
Piezometers were installed to define the areal extent of the coal tar.
Treatment Assessment
For Project 32 (CACITOX™ treatment), differences in contaminant removal effectiveness for varying
levels of heavy metal contaminants were determined using a range of tests, including tests on soils
spiked at "high" (1,000-22,500 mg/kg) and "low" (10-450 mg/kg) concentrations of these metals. To
assess the decontamination efficiency of the treatment for radionuclides, researchers spiked USEPA
simulated soil matrices with individual radioisotopes of Pu, Am, Np, Sr, Cs, and Ra.
In Project 44, the recovery of coal tar was measured and compared to performance specifications.
Performance specifications required treatment to continue until results showed that there was less than
0.5% additional recovery of coal tar per pore volume of water flushed through the contaminated zone.
To evaluate the performance of the in situ Lasagna™ technology (Project 47), soil samples and sampling
cassettes were analyzed to assess the TCE removal efficiency. Twelve soil borings were completed
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before and after the demonstration. The soil samples collected from each boring were analyzed to assess
how TCE concentration changed at each location. Also, cassettes from 12 treatment zones and from the
control zone were analyzed to determine the amount of TCE they collected. The data were used to
perform a mass balance.
Overall Assessment
To evaluate the success of a given formulation or process change in the leaching process (Project 32)
for heavy metals, concentrations of these metals in the feed and product were compared against Dutch
B values and Canadian Residential values for heavy metals in soil. The CROW process used in Project
44 was considered successful although it did not achieve expected operating conditions and recovery of
contaminants. Groundwater sampling was planned to assess the overall effectiveness of the treatment.
No overall assessment criteria were reported for the in situ demonstration of the Lasagna™ technology.
5.4.1.5 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)
Unlike the projects in the other groups, Group 5 projects solely involved technologies for treating
groundwater. Biological treatment (Project 14), chemical treatment (Project 38), and adsorption (Project
40) accompanied photo-oxidation, the main technology for each project.
Characterization
Investigators characterized groundwater by analyzing samples for contaminants of concern and other
parameters. For Project 14, concentrations of organic contaminants as well as COD, TOC and adsorbed
organic halogens (AOX) were determined first for untreated groundwater. In addition to conducting gas
chromatography/mass spectrometry (GC-MS) analysis of influent samples for VOCs, investigators
working on Project 38 determined toxicity of influents by subjecting them to bioassay tests with
waterfleas and minnows. As discussed in Section 5.2.5, a number of laboratory tests were conducted
during Project 40 to optimize the photoactivities of photocatalysts and to optimize the supports for fixed-
bed photocatalysts.
Treatment Assessment
To assess the biological pretreatment coupled with an ozone/UV combination process, researchers
measured COD, TOC, VOC, and AOX levels as a function of ozone concentrations. For Project 38,
samples were taken at several locations to evaluate the treatment system's efficiency. GC-MS analysis
of influent and effluent samples for VOCs were used to indicate levels of intermediate organic
compounds created during treatment. Other analyses included parameters such as total organic halogens
(TOX), AOX, TOC, total carbon, and purgeable organic carbon. To obtain reliable data, USEPA-
approved sampling, analytical, and QA/QC procedures were followed. For toxicity assessment, influents
and effluents were subjected to bioassay tests with waterfleas and minnows.
Overall Assessment
Projects 14 and 38 were assessed in terms of their ability to achieve target levels of contaminants or
toxicity limits. The combined biological and photo-oxidation treatment was required to achieve
acceptable drinking water limits. The effectiveness of the Perox-Pure™ system was measured in terms
of its ability to achieve the California drinking water action levels and U.S. federal drinking water
maximum contaminant levels for the five compounds studied. However, neither project report listed the
numerical values for the target limits. However, for a separate study involving treatment of groundwater
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containing TCE, the discharge level for the treatment was set at 0.5 mg/L. Bioassay tests also
demonstrated whether the effluent was toxic to freshwater organisms.
The effectiveness of the systems tested at Tydall AFB and K.I. Sawyer AFB for Project 40 were
assessed in terms the destruction rates of contaminants. The effectiveness of the system tested at the
Wausau Water Treatment Plant was not measured because fouling of the catalyst inhibited destruction
of the adsorbates.
5.4.2 General Effectiveness
This section of the chapter examines the performance of soil washing when it was used alone or in
combination with other technologies. In the latter cases where soil washing was used as a pretreatment
to provide a contaminant concentrate for further treatment, this review considers the performance of the
pretreatment step only.
Unfortunately, some data on soil washing are not available for reporting or comparison here. Instead of
documenting the effectiveness of soil washing and the add-on treatments separately, some investigators
provided information on the overall performance for pretreating the feed and treating the concentrate.
Another part of this chapter focuses on this overall performance.
It is somewhat difficult to compare reported performance of soil washing because the projects did not
use the same unit processes. For example, one project examined hydrocycloning only, while others
incorporated sizing, scrubbing, froth flotation, magnetic and gravity separation, etc. Thus, effectiveness
will be measured in terms of targets and criteria mentioned in Section 5.4.1.
Table 5.2 provides data on contaminated material before and after soil washing and on the treatment
processes used. Where results were not provided, a notation has been made. Performance data in Table
5.2 also identify if treated materials achieved their target criteria.
Data for these projects confirm reported observations that washing efficiency was dependent on the
composition of the soil, and specifically that particle size distribution plays an important role in washing
effectiveness. In general, the process is very efficient on sandy material, but fine-grained materials
containing relatively high percentages of silt and clay were more difficult to treat. As reported in the
Introduction, soil washing is most effective on soils containing less than 30-35% clay and silt.
As demonstrated in Project 36, additional treatments or several passes of the same unit process overcame
treatment difficulties presented by materials high in fines. Investigators deliberately tested material
containing up to 62% of particles less than 0.063 mm to test the feasibility of extending soil-washing
processes to such materials. The results confirmed that three stages of froth flotation or gravity
separation succeeded in significantly reducing levels of contaminants in the clean fraction. Despite these
reductions, contaminants in the treated fraction were still significant making it unsuitable for reuse.
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Table 5.2: Performance of Soil Washing Only
Project
Contaminant Levels1
Media
Treatment Processes
Performance2
10 (B) TOC, >10%; high concentrations of Sediment
PAHs and O&G; 92% metals in
<100 um fraction; 75% metals in
<50 um fraction
10 (P) 4,026 mg/kg Zn; 100 mg/kg Cu Soil
Flotation, magnetic and gravity
separation
17 (F) Not provided
19 (P) Not provided
24 (F) Crude oil up to 14,500 mg/kg
24 (F) High levels of mineral oil and
PAHs (no data given)
26 (B) 180-3,500 mg/kg PAHs
26 (P) 100-11,000 mg/kg PAHs
27 (B) up to 1,000 mg/kg PCBs
27 (P) 10-100 mg/kg PCBs
Soil, sediment
Soil, debris
Sandy soil (77%
sand, 12.5%
fines, 10.5%
coarse)
Sediment (40%
sand, 55% fines,
5% coarse)
Sandy soils
Clayey soils
Soil
Soil
Screening, solvent extraction
Soil washing, vacuum
distillation
Multi-step hydrocyclone
Multi-step hydrocyclone
Screening, flotation
Screening, flotation
Screening; flotation
Screening, flotation
Tailings: 40%; O&G, 4.1%; PAHs, 4.9%; Pb, 2.9%;
Zn, 11%; Cd, Ni, and Fe, 24-30%
Organic concentrate: 27%; O&G, 62%; PAHs, 74%;
Pb, 81%; Zn, 68%; Cd, 54%; Ni, 54%; Fe, 32%)
Clean: 95%: 360 mg/kg Zn; Cu unchanged. Achieved
industrial guidelines for PAHs and residential
guidelines for some contaminants.
Metal concentrate: Fe, 55%
No data on screening.
No data on soil washing.
Sand fraction: 87.5%; 130 mg/kg crude oil
Coarse fraction, 10.5%
Fine fraction: 12.5%; 110,000 mg/kg crude oil
Sand fraction: no data; hydrocarbons, 100 mg/kg
Fine fraction: no data; 20,000 mg/kg hydrocarbons;
1,000-2,000 mg/kg PAHs
Washed fraction: 20-185 mg/kg PAHs
Concentrate: no data
Washed fraction: 24-1,250 mg/kg PAHs
Concentrate: 480-6,000 mg/kg PAHs
Clean fraction: 40-500 mg/kg PCBs
Clean fraction: 0.7-5.0 mg/kg PCBs
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Project
Contaminant Levels1
Media
Treatment Processes
Performance2
27 (F) 50-300 mg/kg PCBs
30 (P)
184 mg/kg PAHs; 937 mg/kg TPH; Clayey soil
2,332 mg/kg CN; 650 mg/kg Pb;
32 mg/kg As
1,288 tonnes Screening, flotation
soil; Fines, 63%
(30% not
expected)
Sizing, scrubbing, flotation
30 (P)
163 mg/kg PAHs; 939 mg/kg TPH; Clayey soil
2,340 mg/kg CN; 733 mg/kg Pb;
32 mg/kg As
Sizing, scrubbing, multi-
gravity separation
31 (B) Pb, 20%; Zn, 15%
31 (P) Not provided
31 (B) Pb, 9.8%; Zn, 2.3%
Pb in fines; fine- Gravity separation
grained material,
anaerobic; coarse
material, aerobic
<0.5 mm Multi-gravity separation
fraction of spoil
<180 urn
fraction un-
oxidized spoil
33 360 mg/kg Cu; 621 mg/kg Cr; 414 Soil, sediment
mg/kg Zn; 1,204 mg/kg As
36 (P) 3,000-4,000 mg/kg TPH Soil, 62%
O.063 mm
Froth flotation
Screening, hydrocycloning,
flotation
Sizing
780 tonnes clean fraction (60%)
400 tonnes PCB-enriched sludge
Clean: 48%; 48 mg/kg PAHs; 250 mg/kg TPH; 1,242
mg/kg CN; 540 mg/kg Pb; 18 mg/kg As
Fines: 29%; 170 mg/kg PAHs; 1,523 mg/kg TPH;
3,423 mg/kg CN; 1,000 mg/kg Pb; 54 mg/kg As
Concentrate: 24%; 476 mg/kg PAHs; 1,694 mg/kg
TPH; 3,191 mg/kg CN; 441 mg/kg Pb; 33 mg/kg As
Clean: 50%; 39 mg/kg PAHs; 188 mg/kg TPH; 1,651
mg/kg CN; 577 mg/kg Pb; 18 mg/kg As
Fines: 29%; 170 mg/kg PAHs; 1,523 mg/kg TPH;
3,422 mg/kg; 1,001 mg/kg Pb; 54 mg/kg As
Concentrate: 21%; 450 mg/kg PAHs; 1,931 mg/kg
TPH; 2,494 mg/kg CN; 735 mg/kg Pb; 35 mg/kg As
Light fraction: >90%; <2% metals; exceeded U.K.
guidelines
Concentrate: <10%; Pb, 32%; Zn, 5%
Light: 90%: metals, 2.5%
Concentrate: 10%; metals, 70%
Tailings: Pb, 3.0-3.5%; Zn, 0.1-1.1%
No information on performance.
Clean fraction: 68.7%; 200-210 mg/kg TPH
Fines: 26-31%; 12,000 mg/kg TPH
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Project Contaminant Levels1
36 (P) 200-300 mg/kg PAHs; 2,000-3,000
mg/kg TPH; 2,000-3,000 mg/kg
CN
Media
Gasworks soil,
43% O.063 mm
Treatment Processes
3 stages of froth flotation;
gravity flotation. Applied to
separate 0.01-0.63 mm
fraction.
Performance2
Clean fraction from froth flotation: 69%. PAHs
reduced by 61%, TPH by 54%, and CN by 39%.
Clean fraction from gravity separation: PAHs reduced
by 68%; TPH reduced by 76%; and CN reduced by
14%.
Notes:
1 Data are presented in the units that appeared in the various project reports.
2 Washed media and concentrate provided as percentage of feed.
(B)= bench-scale (F)= full-scale
(P)= pilot-scale O&G= oil and grease
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NATO/CCMS Pilot Study, Phase II t r c
Project 27 demonstrates how an unanticipated high quantity of fines impaired soil-washing performance
and required changes to the treatment. The higher than anticipated fines (63% rather than 30%)
overloaded the system with solids and reduced performance. A volume reduction of 60%—not the
targeted 70%—was achieved. Treated material often did not achieve target levels for PCBs and had to
be washed again.
In summary, the projects demonstrated that soil washing may require several unit processes before
treated materials can achieve target criteria. While this goal is desirable, it must be pointed out that
performance should take into account the ability of the processes to produce a concentrate suitable for
downstream treatment.
5.4.3 Overall Performance
To complement the discussion above on the performance of soil washing alone, this section of the report
presents overall performance for the treatments, which may or may not have included soil washing. Data
are presented for Group 2 on soil washing and biological treatment, Group 3 on soil washing and
physical-chemical treatment, Group 4 on physical-chemical treatment, and Group 5 on photo-oxidation
treatment.
5.4.3.1 Group 2: Soil washing and biological treatment (Projects 24, 26, and 36)
Table 5.3 summarizes data for projects conducted at the bench-scale to full-scale. Demonstration projects
used soil washing as a pretreatment followed by bioslurry treatment of contaminant concentrates. To
achieve better degradation rates, photo-oxidation was used as an added pretreatment in Project 24 to
convert contaminants such as PAHs to readily biodegradable forms.
Materials tested in Project 24 consisted of a sandy soil contaminated with crude oil and a sediment
contaminated with mineral oil and PAHs. In experiments conducted at the pilot scale, soil washing and
biodegradation reduced mineral oil in soil from 400-5,000 mg/kg in the original feed to less than 100
mg/kg in the biologically-treated material. Biological treatment lasted 3-8 days. For treating soil
contaminated with PAHs, pilot-scale investigations supplemented biological treatment with UV/H2O2
pretreatment. This combined photo-oxidation and biological treatment reduced PAH levels in soil wash
concentrates from 30 mg/kg to 2-4 mg/kg in recombined soil in 15 days. PAH availability to UV/H2O2
pretreatment appears to be a rate-limiting factor. For soil washing and biological treatment at the full
scale, crude oil levels in a soil fell from 14,500 mg/kg to less than 3,000 mg/kg (in recombined
fractions). Similarly, soil washing a contaminated sediment resulted in a sludge with up to 2,000 mg/kg
PAHs and 20,000 mg/kg hydrocarbons. After 30-32 days of treating the sludge biologically, residuals
contained 2,000 mg/kg hydrocarbons and 200 mg/kg PAHs.
When the froth flotation fraction of a diesel-contaminated soil (Project 36) containing 12,000 mg/kg TPH
was treated in a bioslurry reactor, the TPH concentration fell by 81%. However, treated solids still
contained relatively high TPH (2,300 mg/kg). Similarly, biological treatment of fines generated by froth
flotation and specific gravity separation of a gasworks soil failed to significantly reduce levels of
contaminants. After 28 days of treatment, PAHs fell by 40-50%, and petroleum hydrocarbons by up to
20%. Cyanide remained unchanged.
Photo-oxidation pretreatment of soil-washed residues enhanced the subsequent biodegradation of PAHs,
but was not required for more readily biodegradable contaminants such as mineral oil. As demonstrated
in Project 24, pretreatment enhanced subsequent biological treatment which reduced PAHs from 30
mg/kg to 5-10 mg/kg in 15 days. PAHs were not biodegraded without this pretreatment. In contrast, the
pilot-scale bioreactor tested batches of sludge resulting from soil washing two clayey soils in Project 26.
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Project
24 (P)
24 (P)
24 (F)
24 (F)
26 (B)
26 (P)
36 (P)
36 (P)
36 (P)
Notes:
Table 5.3
Treated Media and
Contaminants
400-5,000 mg/kg mineral oil in
soil
30 mg/kg PAHs in soil
14,500 mg/kg mineral oil in
sandy soil (77% sand, 12.5%
fines, 10.5% coarse)
Mineral oil and PAHs
(concentrations not provided) in
sediment (40% sand, 55% fines,
5% coarse)
180-3,500 mg/kg PAHs in sandy
soil
41-12,000 mg/kg PAHs in clay
soils
Diesel fuel (3,000-4,000 mg/kg
TPH) in fine-grained soil (62%
O.063 mm)
200-300 mg/kg PAHs; 2,000-
3,000 mg/kg petroleum
hydrocarbons; 2,000-3,000 mg/
kg cyanide in fine-grained soil
200-300 mg/kg PAHs; 2,000-
3,000 mg/kg petroleum
hydrocarbons; 2,000-3,000 mg/
kg cyanide in fine soil
Overall Performance of Soil Washing and Biolog
Soil Washing Performance
Not provided
Not provided
Fines: 110,000 mg/kg mineral oil;
Clean: 130 mg/kg mineral oil
Sand fraction: 100 mg/kg
hydrocarbons;
Sludge: 20,000 mg/kg hydrocarbons;
1,000-2,000 mg/kg PAHs
Clean fraction: 17-185 mg/kg PAHs
Clean fraction: 30-1,500 mg/kg
PAHs;
sludge: 2,400-3,750 mg/kg PAHs
Clean fraction: 200-210 mg/kg TPH;
fines: 120,000 mg/kg TPH
Flotation clean fraction: 80-117
mg/kg PAHs; 920-1170 mg/kg TPH;
1,220-1,830 mg/kg CN
Gravity clean fraction: 62-93 mg/kg
PAHs; 460-690 mg/kg TPH; 1,680-
2,520 mg/kg CN
ical Treatment
Biological Treatment
Treatment
(Before) (After) Time (days)
Not provided
Not provided
110,000 mg/kg
mineral oil
Sludge (see
previous cell)
180-52,000
mg/kg PAHs
2,400-3,750
mg/kg PAHs
120,000 mg/kg
TPH
Not provided
Not provided
<100 mg/kg mineral oil 3-8
2-4 mg/kg PAHs in recombined 15
soil
22,000 mg/kg mineral oil in 40
treated sludge; <3,000 mg/kg in
recombined soil
2,000 mg/kg hydrocarbons; 200 30-32
mg/kg PAHs
55-4,800 mg/kg PAHs
55-200 mg/kg PAHs 6
2,300 mg/kg TPH 28
Slurry reduced PAHs by 40-50%, 28
hydrocarbons by 20%; CN
unaffected
Slurry reduced PAHs by 40-50% 28
and hydrocarbons by 20%. CN
unaffected.
(P)= pilot-scale
(F)= full-scale
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After 6 days of treatment, PAH concentrations fell by up to 97% (from 2,400-3,750 mg/kg to 55-200
mg/kg). A project report claimed that indigenous PAH degraders could achieve residual PAH
concentrations ranging from 55-200 mg/kg after a 6-day retention time.
According to data collected during the biological treatment for Project 24, toxicity was reduced
significantly. Since soil washing itself accounted for little of the reduced toxicity, it was concluded that
bioslurry treatment accounted for most of the reduced toxicity.
5.4.3.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10,17,19, 27,
and 33)
Table 5.4 summarizes data for projects conducted at the bench-scale to full-scale. Physical-chemical
treatments applied to the soil wash concentrates were leaching and adsorption (Projects 10 and 33),
solvent extraction (Project 17), vacuum distillation (Project 19) and chemical dehalogenation (Project
27). Because little similarity exists among these treatments, their performances will be assessed
individually.
When used on concentrates containing heavy metals, leaching and adsorption reduced metal
concentrations in treated materials by between 60-95%. In both cases, metal residuals fell within
regulatory industrial and residential limits. However, the in-pulp leaching and adsorption method used
in Project 33 appeared to be better than the approach used for Project 10. The metal content in the first
case was lower, but the relative removal was higher than observed in the second case.
Materials treated by solvent extraction, vacuum distillation, and chemical dehalogenation reportedly
achieved their regulatory targets. Solvent extraction removed almost 98% of PAHs and PCBs from soil
that originally contained between 250-2,000 mg/kg PCBs and 200-500 mg/kg PCBs. Chemical
dehalogenation achieved a similar level of success on soil wash concentrates with PCBs in the same
concentration range. However, data suggest that when compared with these technologies, vacuum
distillation achieved the highest removal. Treated soil contained less than 1% of the original organic
contaminants and only around 3% of the mercury. Altogether, vacuum distillation will likely perform
better than the others because it can remove volatile organic and inorganic contaminants from
contaminated materials.
5.4.3.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 31, 32, 44, and
47)
Table 5.5 summarizes data for projects conducted at the bench-scale to full-scale. The table identifies
the NATO project number and the scale of the investigation, characteristics of the tested material, and
overall performance of the treatment.
Physical-chemical treatments applied to unwashed contaminated material were leaching and adsorption
(Project 31), leaching and extraction (Project 32), in situ thermally enhanced recovery (Project 40), and
in situ electro-osmosis and adsorption (Project 47). Because little similarity exists among these
treatments, their performances is assessed individually.
Of all the reprocessing techniques tested (others discussed for Project 31 under Group 3), leaching of
oxidized Pb minerals with alkalis like sodium hydroxide displayed the highest potential for removing
metals from spoil thereby resulting in the lowest concentrations of metals in the residue. Sodium
hydroxide released 25-92% of the Pb and 3-23% of the Zn in un-reprocessed spoil containing 7.5% Pb
and 0.1% Zn. These releases correspond to 1.5-5 tonnes Pb and 0.1-1.2 tonnes Zn per 100 tonnes spoil.
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Table 5.4: Overall Performance of Soil Washing and Physical-Chemical Treatment
Project „ , , . _ , Contaminants in
„ , Contaminants in Feed „ ^ ^
Number Concentrate
10 (P) 2,112 mg/kg Pb; 950 mg/kg Cu; 4 Not applicable
mg/kg Cd; 2,535 mg/kg Zn
10 (P) Pb as high as 11,800 ug/g Not applicable
17 (F) Silty sand, loamy soil, and Not provided
sediment (250-2,000 mg/kg PAHs;
200-500 mg/kg PCBs; 2,000 mg/kg
heavy organics
19 (P) 32,000 mg/kg PAHs; 102,000 mg/ Not provided
kg TPH; 1,728 mg/kg CN; 8,000
mg/kg HG; 100,000 mg/kg TNT;
3,400 mg/kg lindane
19 (F) Hg up to 1,900 mg/kg 100 urn - 8 mm;
contaminant
concentrations not given
27 (B) PCBs at unknown levels 250 mg/kg PCBs
33 (B) 1,204 mg/kg As; 360 mg/kg Cu; Information not provided
621 mg/kg Cr; 414 mg/kg Zn
Notes:
(B)= bench-scale
(F)= full-scale
(P)= pilot-scale
Overall Performance
Soil solids after leaching: 1,070 mg/kg Pb; 480 mg/kg Cu; 0
mg/kg Cd; 1,050 mg/kg Zn
Soil solids after metal adsorption: 898 mg/kg Pb; 289 mg;kg
Cu; <1 mg/kg Cd; 286 mg/kg Zn;
Recovery= Pb, 57%; Cu, 70%; Cd, >90%; Zn, 67%. Metal
residuals within regulatory industrial (1,000 mg/kg) and
residential (500 mg/kg) limits
Clean material (7% original Pb) met regulatory industrial
and residential criteria
Treated material (6-30 mg/kg PAHs; 1-6 mg/kg PCBs; 20
mg/kg heavy organics
Treated soil: <1 mg/kg PAHs; <10 mg/kg TPH; <10 mg/kg
CN; 0.5-4.0 mg/kg Hg; 0.4 mg/kg TNT; 0.0002 mg/kg
lindane
Treated material (Hg 10-50 mg/kg); below target of 50 mg/
kg.
Treated concentrate (PCBs <1 mg/kg); below target of 10
mg/kg.
Treated product: 112 mg/kg As; 22 mg/kg Cu; 74 mg/kg Cr;
68 mg/kg Zn. Corresponding targets are 30, 100, 160, and
100 mg/kg, respectively.
Treatment
Processes
Leaching and
adsorption
Leaching and
adsorption
Solvent
extraction
Vacuum
distillation
Vacuum
distillation
Chemical
dehalogenatio
n
Leaching and
adsorption
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Table 5.5: Overall Performance of Physical-Chemical Treatment Without Soil Washing
Project
Number
31 (P)
32 (F)
32 (F)
44 (F)
47 (P)
Notes:
Characteristics of
Contaminated Media
Un-reprocessed metalliferous
spoil: Pb, 7%;Zn, 0.1%
Soil with 46% silt/clay: total
heavy metals 1,000- 22,500
mg/kg;
Soil spiked with radionuclides
Gravelly soil with coal tar
DNAPL
Soil with TCE averaging 72.6
mg/kg
Overall Performance
Sodium hydroxide leached 25-92% Pb
and 3-23% Zn.
Sulfuric acid leached 2-33% Pb and 12-
64% Zn.
Treated material achieved Dutch B values
and Canadian residential values for Cr,
Ni, Cu, Zn, and PB, but not for As or Cd.
Treated material contained 24-48% of Pu,
U, Ru, Am, Np, and Sr.
5,400 L of pure coal tar was removed
Treated soil contained 1.1 mg/kg TCE;
removal efficiency 98%;
Treatment
Processes
Aggressive leaching
Mild leaching and
extraction
Leaching and
extraction
DNAPL: thermally
enhanced recovery,
incineration
Water: precipitation,
fluidized bed
reactor, filtration
Electro-osmosis and
adsorption
(F)= full-scale (P)= pilot-scale
Other leach tests showed that sulfuric acid was more effective at leaching Pb from un-oxidized spoil than
from oxidized material. The acid leached 2-33% Pb and 12-64% Zn. By comparison, tests with
reprocessed spoil showed that the acid leached only 2-5% of the original Pb, suggesting that the residual
Pb is resistant to acid leaching.
As demonstrated for Project 32, using the CACITOX™ reagent to leach a 46% silty clay soil containing
a variety of heavy metals at concentrations in the range of 1,000-22,500 mg/kg resulted in simultaneous
removal of metals. The treated material achieved Dutch B values and Canadian Residential values for
Cr, Ni, Cu, Zn, and Pb, but not for As and Cd. The researchers reported that if the conditions were
optimized, all metals would have met the criteria. In tests of soil spiked with radionuclides, a single
leach removed between 52 and 76% of Pu, U, Ru, Am, Np, and Sr. Multiple contacts could have
resulted in better removal of these radionuclides.
When the Lasagna™ technology was applied to a contaminated site (Project 47), TCE concentrations
were reduced on average from 72.6 mg/kg to 1.1 mg/kg, which translates to an average removal
efficiency of 98%. At sampling locations where the initial concentrations were as high as 225 mg/kg,
indicative of residual DNAPL in soil pores, the process reduced these concentrations to less than 1
mg/kg in all but one sample. Upward diffusion of TCE from untreated soil may explain the single
discrepancy of 17.4 mg/kg TCE. TCE reduction in a control area averaged at around 45%, falling from
89.9 m/kg to 49.5 mg/kg. These data, when compared to those from the demonstration area, confirm the
effectiveness of the Lasagna™ process for removing TCE from soil.
Mass balance accounted for 50% of the pre-demonstration TCE. The remaining 50% may be attributed
to passive diffusion (5%), evaporation (5%), in situ degradation of TCE, non-uniform distribution of
TCE in the soil, or incomplete extraction of TCE from the activated carbon (taken from the treatment
layer) before analysis.
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5.4.3.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)
Table 5.6 summarizes the performance data for the Group 5 projects. The table identifies the scale of
the investigation, characteristics of the tested ground-water and wastewater, and overall performance of
the photo-oxidation treatment.
While all three projects used photo-oxidation, Project 14 included biological treatment with activated
sludge to improve performance. The project report did not explain how the biological step improved
performance, or why it was necessary. However, the combined approach reduced dissolved constituents
by 80-85%, eliminated VOCs, and lowered COD from 239 ppm to undetectable levels.
For the three tests conducted under Project 38, the photo-oxidation technology generally achieved
regulatory targets and reduced contaminants to below detection levels. For a technology demonstration
conducted at the Lawrence Livermore National Laboratory facility, groundwater contained TCE and PCE
at 1 mg/L and 0.1 mg/L, respectively. Treated water contained TCE and PCE at levels below detection
limits, while TCA and chloroform occurred at levels slightly above detection limits. In another study
where the technology was used to treat well water containing 50 to 400 mg/L TCE, effluents consistently
achieved levels below the analytical detection limit of 0.5 ug/L. Also, at a full-scale treatment for
groundwater containing PCPs as high as 15 mg/L, the system destroyed the contaminants to below the
target level of 0.1 mg/L.
5.5 RESIDUALS AND EMISSIONS
5.5.1 Soil Washing
Table 5.7 identifies residuals (i.e., soil/sediment, water, and concentrates) and emissions (air) from soil
washing only. For projects that used soil washing as a pretreatment to provide a concentrate for further
treatment, residuals and emissions for the subsequent treatments are covered under the project groups
to follow.
As seen in the examples in Table 5.7, soil washing residuals usually include the following:
• Wastewater from sizing and classifying material. This water is usually recycled, but may eventually
require treatment before disposal.
• Concentrates that may be treated further to destroy or stabilize contaminants, or to extract useable
products.
• Treated material that may be reused or recycled if it meets regulatory criteria, or disposed of at a
landfill, incinerated, etc., if it does not.
• Off-gases that may contain volatile contaminants, which may be removed by techniques such as
adsorption by activated carbon.
5.5.2 Combined Treatments
Residuals from combined treatments consist of those identified for soil washing in Table 5.7, as well
as others unique to the treatments used on contaminant concentrates. Residuals discussed below pertain
mainly to treatment of the concentrates.
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Table 5.6: Overall Performance of Photo-Oxidation Treatment of Contaminated Water and
Wastewater
Project
Number
14 (F)
38 (F)
38 (F)
38 (F)
40 (F)
40 (F)
40 (F)
40 (F)
Notes:
Characteristics of contaminated
water/wastewater
239 ppm COD; chlorinated
solvents, esters, phenols, BTEX,
etc., at 0.8-360 mg/L
Groundwater: TCE 1 mg/L; PCE
0.1 mg/L
Drinking water: TCE 50-400 mg/L
Groundwater: PCPs up to 15 mg/L
Groundwater: contained total BTEX
compounds greater than 2 mg/L
Groundwater: 100 ug/L TCE
Groundwater: 100 ug/L TCE
Groundwater: contained chlorinated
solvents and BTEX compounds at
unspecified concentrations
(F)= full-scale BTEX= benzene, toluene,
Overall Performance
COD undetected; dissolved organic constituents reduced by
80%-85%; VOCs eliminated.
TCE (99.9% removal) and PCE (98.7% removal) below
detection limits in treated water; TCA and chloroform slightly
above detection limits.
Effluents below analytical detection of 0.5 ug/L.
PCPs in treated water below target level of 0.1 mg/L.
Ionic species initially fouled the catalysts and inhibited
destruction. Following treatment to remove suspended
particulates and ionic species, catalyst photo-activity did not
decrease after 25 days of operation. BTEX compounds were
destroyed within 6.5 minutes of empty bed contact time on
rainy days.
>21% of total influent BTEX destroyed; 98% of BTEX
removed from waste stream.
>95% of TCE was destroyed within a 2-minute contact time.
Direct photocatalytic oxidation did not effectively regenerate
spent adsorbent because nuisance substances in the ground-
water fouled the catalyst. Tests combining steam regeneration
followed by photocatalysis of steam condensate showed that
carbon adsorbent was not effectively regenerated an lost a
significant amount of capacity. Background organic matter in
the water may have caused this loss of efficiency. Also,
steam regeneration did not appear to destroy significant
amounts of the sorbed chlorinated compounds.
ethylbenzene, and xylenes
5.5.2.1 Group 2: Soil Washing and Biological Treatment (Projects 24, 26, and 36)
The main residuals from biological treatment are process water and sludge. Table 5.8 identifies residuals
(soil/sediment, water, and concentrate/other) associated with biological treatment of soil wash
concentrates for the three Group 2 projects.
Only one of the three projects reported recycling of the process water, and it is not clear what was done
for the other projects. Contaminants in treated concentrate achieved regulatory guidelines or remained
at unacceptable levels. Clean material derived from Project 24 was described as having no residuals,
while Microtox analysis of treated material from Project 26 revealed that toxicity had been reduced
significantly. In contrast, unacceptable levels of contaminants remained in fines treated in Project 36.
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Table 5.7: Residuals and Emissions Associated with Soil Washing
Project
Number
10
17
19
24
26
27
30
31
33
36
Soil/Sediment
Treated sediment material
achieved industrial limits
for Pb, Cd, and organics.
Not suitable as off-shore
fill.
Treated material used as
fill, or treated further to
stabilize metals.
Not reported
Not provided
Not provided
Non-porous debris disposed
in a landfill; porous debris
registered as hazardous
waste for incineration;
coarse fraction (>0.1 mm)
returned to excavation and
capped
Not provided
Residue contained total
metals exceeding U.K.
guidelines for soils. Metals
are leachable.
Provided for overall
treatment, not for soil
washing only.
Residue contaminant-
reduced, but unsuitable for
reuse. Contamination levels
still significant.
Water
Wastewater from sizing and
classifying material
Not reported
Wastewater treated
chemically to form a
precipitation sludge.
Disposed in a hazardous
waste facility. Water
polished with activated
carbon.
Not provided
Not provided
Wash water treated if it
contained PCBs, then
recirculated or discharged
to a sewer.
Process water was
contained and recirculated.
Not provided
Decanted water
Not provided
Air
Not reported
Not reported
Off-gases
treated with
activated
carbon.
Not provided
Not provided
No off-gases
generated
Carbon
filters, which
extracted
volatile
contaminants,
created
emissions.
Not provided
Off-gases
may be
produced
Not provided
Concentrate/Other
Inorganic concentrates
for disposal or recovery
of metals; organic
concentrate for
secondary treatment
Concentrate treated by
solvent extraction.
Light-weight particles
and spent activated
carbon treated by
vacuum distillation.
Concentrate treated
biologically.
Concentrate treated
biologically.
Concentrate treated by
chemical
dehalogenation.
Wastes and sludges
received further
treatment or shipped to
a licensed landfill.
Not provided
Concentrate leached and
metals adsorbed.
Concentrate treated
biologically.
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Table 5.8: Residuals Associated with Biological Treatment of Soil Wash Concentrates
Project
Number
24
26
36
Soil/Sediment
Clean soil with no residuals;
treated fractions recombined.
Not applicable
Not applicable
Water
Effluent from
biodegradation
was recycled.
Not provided
Not provided
Concentrate/Other
Not clear what was done with sludge treated
biologically.
Microtox analysis of water-extractable
components of treated concentrate showed
significantly reduced toxiciry.
Treated fines contained unacceptable levels of
contaminants.
5.5.2.2 Group 3: Soil Washing and Physical-Chemical Treatment (Projects 10,17,19, 27,
31, and 33)
The type of physical-chemical treatment used on soil wash concentrates determined the nature and
quality of residuals. Table 5.9 identifies residuals (soil/sediment, off-gases, and concentrate/other)
associated with physical-chemical treatment of soil wash concentrates for five of the six Group 3
projects. For four of these projects in this group, treatment consisted of further concentrating the
contaminants to provide a recoverable product or a smaller volume of contaminated material for disposal.
These treatments resulted in products such as a metal-rich filter cake, oil, and mercury. The treated
materials were usually suitable for reuse or disposal. If carbon filters were used in the treatment, they
contained captured volatile contaminants.
Only Project 27 examined chemical destruction of PCBs in the concentrate. Based on bench-scale studies
only, the treated material contained acceptable residual PCBs.
5.5.2.3 Group 4: Physical-Chemical Treatment (No Soil Washing) (Projects 32,44, and 47)
Like the Group 3 projects already discussed, the type of physical-chemical treatment used on
contaminated materials treated by Group 4 projects determined the nature and quality of residuals. Table
5.10 identifies residuals (soil, sediment, water, off-gases, and concentrate/other) associated with physical-
chemical treatment (no soil washing) for three projects.
In Projects 31 and 32, treated materials were reused or disposed. One of these materials had to be
washed before disposal to remove residual leachant. In the case of Project 47 (in situ treatment of TCE
contaminated soil), soil retained around 1 mg/kg TCE after treatment. The physical treatments concentra-
ted the contaminants further rather than destroying them. Because of this, contaminant-rich products
resulted. These consisted of metal-rich concentrates as well as treatment cartridges that captured TCE.
Only Project 47 reported residuals in off-gases and water.
5.5.2.4 Group 5: Photo-Oxidation Treatment (Projects 14, 38, and 40)
When used to treat contaminated groundwater, photo-oxidation—with or without biological treatment—
resulted in few residuals (water, off-gases, and concentrate/other) as noted in Table 5.11. Treated
groundwater contained low levels of contaminants that could be discharged directly or treated further
before being sent to a municipal treatment facility.
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Table 5.9: Residuals Associated with Physical-Chemical Treatment of Soil Wash Concentrates
Project
Number
Treatment Process
Soil/Sediment
Off-Gases
Concentrate/Other
10 Metal recovery,
chemical destruction
of organics
17 Solvent extraction,
stabilization
19 Distillation
27 Chemical
dehalogenation
33 Leaching, adsorption
Treated sediment material
achieved industrial limits
for Pb, Cd, and organics.
Could be used as fill on-
shore or offshore.
Traces of solvent in cleaned
soils. Claimed to be
innocuous and biodegrad-
able
Not provided
Not applicable
Treated material was
disposed.
Not Metal-rich filter cake for off-
applicable site recycling
Carbon filters Oil concentrate requires
with treatment, recycling, or
recovered disposal.
vapors
Not provided Spent ion-exchange resins for
recycling; condensed mercury.
Not provided Treated concentrate contained
<1 mg/kg PCBs.
Gaseous Acid used to remove metals
emissions was recycled. Concentrated
may require solution of metals may be
scrubbing treated by precipitation,
reduction, or electrowinning
to recover metals, or
encapsulated or disposed.
Precipitated residues may
require fixation before
disposal.
Photo-oxidation treatments normally do not result in sludge or spent media requiring further processing,
handling, or disposal. Ideally, end-products include water, carbon dioxide, halides, and in some cases
organic acids. However, although Project 14 included a biological step, the reports did not mention how
a biological sludge was treated or the levels of residual contaminants.
GC/MS analysis of influent and effluent samples examined for Project 38 revealed no new target
compounds or other tentatively identified compounds being formed during treatment. The report for
Project 14 did not mention work to identify possible by-products resulting from the ozonation treatment.
Finally, treated water may have retained unused hydrogen peroxide: investigators for the study at the
Lawrence Livermore Laboratory (Project 38) reported residual hydrogen peroxide in the effluent.
5.6 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE APPLICABILITY
OF THE TECHNOLOGY
Several factors determine the success of physical-chemical technologies. As most of the case studies
dealt with in this chapter involved soil washing as a pretreatment stage, consideration is given below
to this technology both when used alone and in combination with other technologies. The final part of
this section examines the factors governing the applicability of physical-chemical treatment not involving
soil washing.
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Table 5.10: Residuals Associated with Physical-Chemical Treatment of Contaminated Materials (No
Soil Washing)
Project Treatment
Number Process
3 1 Froth flotation,
gravity
separation,
density
separation
32 Leaching,
complexation,
precipitation, ion
exchange
44 Thermally
enhanced
recovery
47 Electro-osmosis,
adsorption
Soil/Sediment
Treated spoil was
disposed or reused.
Treated soil was
washed to remove
residual leaching
agent, dewatered,
then reused
Soil and ground-
water concentrations
were not provided.
Recovered coal tar
DNAPL was
incinerated.
Soil treated in situ
contained <1 ppm
TCE.
Water
The effluent has
to be addressed.
Options include
conventional
metal adsorption
filters.
Not reported
Groundwater was
treated and was
either reinjected
or discharged to
Brodhead Creek
Recycling water
from the cathode
to the anode
eliminates
effluent.
Off-gases Concentrate/Other
Not reported Compared to other
treatments, alkali
leaching provides the
residue with the
lowest concentration
of metals.
Not reported Precipitated
contaminants may be
reconditioned
(contained or
encapsulated).
Electro-deposition/
polishing the leachate
may recover valuable
products or minimize
secondary waste.
Not reported Sludge and spent
carbon from treatment
of groundwater and
the recovered DNAPL
must be disposed.
Evaporation Treatment layers with
produces captured TCE may
contaminant require disposal as a
vapors hazardous waste.
Table 5.11: Residuals Associated with Photo-Oxidation Treatment of Groundwater
Project
Number
Water
Off-Gases Concentrate/Other
14 Dissolved contaminants were reduced by 80-85%. Water Not
was treated again before being sent to treatment plant or provided
discharged to a stream.
38 Treated water has TCE and PCE below the detection limit None
of 0.5 ug/L. Chloroform slightly exceeds detection limits, generated
Effluent may contain residual H2O2;
38 For a full-scale treatment, treated water contained 0.1 None
mg/L PCP. generated
40 Concentrations of residual contaminants varied, depending Not
on the system tested. provided
Sludge. No mention of
the levels of residual
contaminants.
Not applicable
Not applicable
Not provided, but
presumably sludge from
water pretreatment and
spent catalyst and
support materials.
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5.6.1 Typical Soil Washing
General Issues
This ex situ separation process could potentially be applied cost-effectively to materials with less than
30-35% of particles less than 0.063 mm. When the concentration of fines exceeds this range,
conventional soil washing may have to include other treatments (e.g., flotation, density and gravity
separation), washed material will have to be reprocessed, or several cycles of the same treatment (e.g.,
hydrocycloning) may have to be implemented. Another option includes using the CACITOX™ technology
(Project 19) which is claimed to be effective for soils containing a high content of silt and clay, a
characteristic that presents difficulties to other treatment technologies—including soil washing.
If low absolute standards cannot be achieved with a single technology, pretreatment by flotation or size
separation may be used to complement a treatment process. Pretreatment may reduce the volume
requiring downstream treatment and may also present the separated contaminant concentrate in a form
suitable for the downstream process (e.g., bioslurry).
For soil washing pretreatment and companion treatment technologies to be viable, the treatment process
on the separated contaminated fines has to be rapid. Otherwise, long treatment periods will cause
problems when matching commercially viable throughput of physical processes with relatively slow
treatments such as biological processes.
Coarse-grained soils would not benefit much from soil washing and accompanying treatments. As
explained for Project 33 which used soil washing and in-pulp extraction, coarse-grained soils containing
metals can be easily leached, filtered and washed. Extracted metals can then be precipitated or adsorbed
from the resulting wash and leachate. In contrast, the washing step becomes more difficult for soils high
in fines.
Material Characteristics
When soil washing is used as a pretreatment for other technologies, accurate determination of feed
material characteristics is a crucial step. These characteristics have a key influence on the choice of the
most efficient technologies to treat soil wash concentrates, and on how the selected technology performs.
Single unit operations can then be combined to provide tailor-made solutions to deal with the
contamination. However, it is important to note that for complex sites with many sources of
contamination, the contaminated material may not behave consistently during the separation process.
Thus, the chosen technology should be able to cope with variations in the chemical and physical
composition of the feed.
For example, the ORG-X solvent extraction unit (Project 17) operates best under optimum moisture
content and grain size. Soil moisture content of 20% in one case made the soil difficult and more costly
to treat. The process achieves higher efficiency on sandy material, but is being improved for fine-grained
soils. Similarly, the mineralogy of clay particles in a soil matrix may influence the overall treatment
process. The exchange capacity of different clay minerals affects the degree to which contaminants can
be adsorbed or desorbed, and strongly influences the characteristics of subsequent dewatering.
In contrast, some treatment technologies are insensitive to variations in soil types. Vacuum distillation
(Project 19), for example, can effectively treat materials such as gravel, sandy soils, fine-grained soils
(up to 90% silt and clay although at a reduced throughput); slags, concrete and brick debris, etc.
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Contaminant Characteristics
Physical and chemical properties of contaminants to be treated influence the applicability of
technologies. For example, vacuum distillation (Project 19) is suitable for volatile contaminants with
boiling points of 350-400°C at pressures of 50-150 hPa. In terms of biological treatment, candidate
contaminants must be amenable to biological degradation. Other factors influencing the applicability of
a technology are operating parameters and maintenance requirements of equipment used in the treatment
processes.
Treatment Criteria and Characteristics of Residuals
With some soils, physical pretreatment alone will not reduce the absolute concentration of contaminants
to acceptably low levels. However, by combining this pretreatment with other approaches such as
biodegradation and chemical treatment, treated material may achieve the regulatory criteria. Thus, the
applicability of a treatment system would depend on its overall ability to achieve regulatory
requirements.
A technology that may not achieve absolute regulatory criteria should not necessarily be discounted as
a treatment option. As shown in Project 33, in-pulp extraction provides an attractive option for removing
metals from pulp generated by leaching a contaminated soil high in fines. The project's report notes that
achieving low absolute levels can be difficult and costly. On the other hand, teachability criteria could
be achieved easily.
Before using soil washing pretreatment and companion treatments, property owners should clarify the
intended use or disposal of treated materials and soil wash concentrates. This is a key point because it
determines which soil washing processes should be used to achieve this goal. For example, if treated
material is to be disposed of at a secure landfill, the feed will require less rigorous treatment than a
material for reuse on an industrial or residential property.
If destruction of a soil matrix is not desirable, strong acids should not be used for treatment because they
can significantly impair the integrity of a soil matrix. In contrast, weak extractants such as those used
in the CACITOX™ technology (Project 32) do not destroy the matrix and thus be potentially be used
treat contaminated soils and sediments when this is an important consideration.
5.6.2 Soil Washing and Other Treatment
With some soils, soil washing alone will not reduce the absolute concentration of contaminants to
acceptably low levels. Combining this treatment with other proven extraction, destruction, or
concentration approaches may reduce contaminants in treated media to meet acceptable criteria. The
proven technologies must be combined in such a way that each technique is properly integrated and the
overall performance better than could be achieved with a single unit application alone.
An alternative approach, claimed to be more economically attractive than one using two independent
treatments in sequence, is one that combines treatment of inorganic and organic contaminants in a single
unit operation.
In a combined treatment approach that includes soil washing, the selectivity of the companion
technology for contaminants determines its applicability to soil wash concentrates. Biological treatments,
for example, can be applied only to contaminants that are biodegradable. Similarly, the CACITOX™
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technology is claimed to selectively dissolve and extract heavy metals and transuranic elements from
other wastes.
Soil Washing and Biological Technologies
This combination of technologies is restricted to soil and sediment with a low content of organic matter
and contaminated with high concentrations of biodegradable organic compounds, such as mineral oil and
PAHs. High molecular weight PAHs biodegrade slowly, and the limited bioavailability of these
compounds restricts degradation to even lower rates. Limited bioavailability of PAHs results from
adsorption of these compounds to the organic soil matrix. As seen in Project 24, using a UV/H2O2
pretreatment to break down the organic matrix and release the PAHs can increase this bioavailability.
The combination of soil washing and slurry-phase treatment provides a viable option for treating
contaminated soil. The washing step reduces the volume of material requiring treatment by up to 80-90%
and can function as the prerequisite mixing operation for microorganisms, nutrients, and contaminants.
Under optimal conditions (e.g., pH, temperature, and nutrients) during the bioslurry phase, indigenous
degraders in the contaminated material may significantly increase removal of contaminants.
For the overall treatment to be viable, the degradation process on separated contaminated fines has to
be rapid. Otherwise, long degradation periods will cause problems when coupling commercially viable
throughput of physical processes with relatively slow biological processes.
Soil Washing and Physical-Chemical Technologies
Soil washing pretreatment should reduce the volume of material requiring downstream treatment and also
present the separated contaminant concentrate in a form suitable for the downstream physical treatment.
If the feed to soil washing contains organic and inorganic contaminants, the organic and inorganic
concentrates should be separated for subsequent treatment.
To be applied successfully for treating a contaminant concentrate, physical-chemical technologies have
to complement each other. For example, if a treatment involves leaching contaminated materials and
subsequently adsorbing metals, the leached metals have to be in a form suitable for adsorption. As
demonstrated in Project 33, ion exchange resins work well for Cu, Cr, and Zn. However, these resins
experienced difficulties removing As because the metal forms un-dissociated arsenic acid, which is
unavailable for ion exchange, at the low pHs needed to dissolve arsenates. At high pHs, the ion exists
in solution but preferentially adsorbs onto iron precipitates formed under these conditions.
The degree to which physical-chemical treatments destroy a soil matrix may be significant. When this
is a concern, other technologies may have to be considered. The CACITOX™ technology, for example,
which employs "weak extractants," potentially can treat contaminated soils and sediments without
destroying the matrix.
5.6.3 Physical-Chemical Technologies
Like biological treatments, physical-chemical technologies treat specific contaminants and media. The
Lasagna™ process (Project 47) demonstrates this selectivity, because it offers promise for treating water-
soluble organic and inorganic contaminants and mixed wastes in groundwater and low-permeability soils.
For highly non-polar contaminants, surfactants introduced into groundwater or incorporated into
treatment zones will solubilize the organics. The process has been shown also to be effective in treating
residual DNAPLs. If contaminated soil has a relatively high permeability, other treatment processes may
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be more effective or more economical than the Lasagna™ process. The CACITOX™ process also
demonstrates this selectivity by dissolving and extracting heavy metals and transuranic elements from
other wastes.
For in situ treatment, the spatial distribution of contamination may influence how a technology is
applied. Contaminated material within 10m of the surface may be easily excavated for treatment on the
surface. However, when contamination occurs at depths greater than 10 m, it is usually treated in situ.
A similar rationale applies to using the Lasagna™ technology. The vertical configuration of the
technology is more appropriate for contamination near the ground surface. For deeper contamination,
installing horizontal treatment zones provides a better option. Finally, if contaminant concentrates are
determined to be hazardous wastes, treating, removing and disposing of them may be an issue and may
prove costly.
5.6.4 Photo-Oxidation Technologies
Photo-oxidation treatment does not transfer or concentrate contaminants that may require further
treatment or costly disposal. Treated water can be disposed onsite or offsite. Options for on-site disposal
include groundwater recharge or temporary on-site storage for sanitary use. Off-site disposal options
include discharge into surface water bodies, storm sewers, and sanitary sewers. Depending on permit
requirements, discharged water may have to be adjusted for pH. Factors influencing the applicability of
photo-oxidation can be grouped into four categories: site characteristics, influent characteristics, operating
parameters, and maintenance requirements.
Site Characteristics
Site characteristics can influence the application of the technology. Site-specific factors include support
systems (e.g., extraction wells, facility for treatment, and equalization tanks), site area and preparation,
climate, utilities, and services and supplies.
Influent Characteristics
In general, minimal pretreatment is required. If needed, it usually consists of oil and grease removal,
suspended solids removal, metals removal, or pH adjustment to reduce carbonate and bicarbonate levels.
Under a given set of operating conditions, contaminant removal efficiencies depend on the chemical
structure of the contaminants. Removal efficiencies are high for organic compounds with double bonds
(e.g., TCE, PCE, and vinyl chloride) and aromatic compounds (e.g., benzene, toluene, xylene, and
phenol) because these compounds are easily oxidized. Organic compounds without double bonds (e.g.,
TCA and chloroform) are not easily oxidized and are more difficult to remove.
Contaminant concentration also influences the technology's effectiveness. The system is most effective
for contaminant concentrations lower than 500 mg/L. At higher concentrations, the technology can be
combined with others such as air stripping. For highly contaminated water, the system can be operated
in a "flow-through with recycle" mode. In this arrangement, part of the effluent is recycled through the
oxidation unit to improve overall removal efficiency.
Other chemical species in influents may consume oxidants and place an additional load on the system.
These species, known as scavengers, include anions such as bicarbonate, carbonate, sulfide, nitrite,
bromide and cyanide. Metals in reduced states (e.g., trivalent chromium, ferrous iron, manganesian ion)
are also likely to be oxidized. Under alkaline conditions, these reduced metal species can cause other
concerns. For example, trivalent chromium can be converted to the more toxic hexavalent form, while
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ferrous and manganous ions can be converted to insoluble forms which precipitate to create suspended
solids that can build up on the quartz tubes housing the UV lamps. Natural organic compounds such as
humic acids (often measured as TOC) are also potential scavengers.
Suspended solids, oil, and grease pose potential problems because they can build up on the quartz
sleeves, reduce UV transmission and so decrease treatment efficiency.
Operating Parameters
The main operating parameters are hydrogen peroxide dose, influent pH, and flow rate. Treatment unit
configuration, contaminated water chemistry, and contaminant oxidation rates determine the hydrogen
peroxide dose. A hydrogen peroxide splitter allows the operator to inject hydrogen peroxide to the
oxidation unit influent and directly to any of the individual oxidation reactors. Influent pH controls the
equilibrium among carbonate, bicarbonate, and carbonic acid. When carbonate and bicarbonate
concentrations exceed 400 mg/L, lowering the influent pH to between 4 and 6 improves the efficiency
by shifting the carbonate equilibrium to carbonic acid that is not a scavenger. In general, increasing the
hydraulic retention time improves treatment effectiveness by increasing the time available for
contaminant destruction.
Maintenance Requirements
Regular maintenance by trained personnel is essential for the successful operation of photo-oxidation
systems. The lamp assembly is the only major system component requiring regular maintenance. Other
components of the system can be checked monthly.
5.7 COSTS
Table 5.12 summarizes information on contaminants and media treated, pretreatment and other treatments
used, reported treatment costs, and qualifiers regarding the costs. Some of these costs are based on actual
remediation projects, while others are estimated from results of bench- and pilot-scale investigations. In
another approach (Project 47), a cost model examined a contamination scenario and predicted treatment
costs. The currencies used for costs are those used in project reports.
The costs in Table 5.12 should be treated with caution. The reports for some of the projects did not
differentiate between capital and operating costs; and generally did not clearly state if the costs were for
treatment only, exclusive of excavation, handling and disposal. However, for Project 26 the cost of
excavation, sorting and backfilling was reported as U.S.$160/m3 and the cost of washing as U.S.$300/m3.
Cost-effectiveness and costs will be highly site-specific and will depend on factors that influence
treatment. For example, the nature of the material determines the need for various types of specialized
pretreatment processes such as magnetic separation, flotation, and density separation. If material
contaminated with organic and inorganic compounds contains relatively high concentrations of fines,
specialized treatments will require additional handling of material and result in higher costs. As
demonstrated in Project 19, the rate of utilization of a soil washing plant influences treatment costs. Cost
decreases as the rate of utilization increases. The size of a treatment plant also has an impact on cost.
For example, for the groundwater treatment conducted during Project 38, a larger plant, if required,
could offer lower treatment costs.
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Table 5.12: Reported Costs for Different Options Used to Treat Contaminated Media
Project
Number
Group 1:
30
Group 2:
24
26
36
Group 3:
10
17
19
27
Contaminants and
Media Treated
Typical Soil Washing
32-650 mg/kg metals;
184 mg/kg PAHs; 200
mg/kg TPH
Treatment
Processes
Particle size
separation, froth
flotation, gravity
separation
Overall Cost
(per m3 unless other
units given)
Not provided.
Comments
Soil Washing and Biological Treatment
14,500 mg/kg crude
oil in soil; PAHs in
sediment
180-3,500 mg/kg
PAHs in sandy and
clayey soil
2,000-4,000 mg/kg
TPH; 200-300 mg/kg
PAHs; 2,000-3,000
mg/kg CN in soils
high in fines
Hydrocycloning
photo-oxidation,
bioslurry
Flotation, bioslurry
Size separation,
bioslurry
Not provided
Excavation, sorting,
backfilling (U.S.$160/
m3); washing
(U.S.$300/m3);
biological (U.S.$530/
m3)
£23-£37 (U.S.S38-
61)/tonne of treated
material
Pretreatment by photo-
oxidation and hydro-
cycloning can be expensive,
depending on the ratio of
sand to fines and the
organic matter content
Treatment is more cost-
effective only if
transporting and disposing
of untreated Mattel exceeds
£40-60 (U.S.S65-
100)/tonne.
Soil Washing and Physical-chemical Treatment
4,026 mg/kg Zn; 100
mg/kg Cu in soil
250-2,000 mg/kg
PAHs; 200-500 mg/kg
PCBs in soil and
sediment
875 mg/kg Hg in
sandy loam and loam
soils
50-300 mg/kg PCBs
in soil and other solids
Flotation, magnetic
separation, leaching
of metals and
adsorption
Size separation,
solvent extraction,
oil recovery
size separation,
scrubbing, vacuum
distillation
Particle size
separation, chemical
dehalogenation
U.S.$75/tonne
U.S.$200/tonne for
2,000 tonnes;
U.S.$100/tonne for
20,000 tonnes;
U.S.$60/tonne for
100,000 tonnes
U.S.$320/tonne
Soil washing alone
cost U.S.$380/tonne
Estimated cost for treating
500,000 tonnes of soil
containing PAHs and
metals.
Rate of utilization of the
soil washing plant
influences treatment costs.
Soil wash treatment costs
U.S. $22 I/tonne if util-
ization is 25%, but drops to
$70/ tonne if utilization is
100%.
Costs for dehalogenation
were not provided.
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Project
Number
31
33
Group 4:
31
32
44
47
Group 5:
14
38
40
Contaminants and
Media Treated
Metals in mine spoil
360 mg/kg Cu; 621
mg/kg Cr; 414 mg/kg
Zn; 1,204 mg/kg As
Treatment
Processes
Particle size
separation, flotation
Particle size
separation, leaching,
adsorption
Overall Cost
(per m3 unless other
units given)
Not available.
For proposed scale-up
plant, cost estimated
at£70-£80(U.S.$115-
130)/tonne.
Comments
The project was not at the
stage where meaningful
costs could be calculated.
Treating Hg-contaminated
soil by aggressive leaching
and complexing agents
requires costly unique
construction materials for a
treatment plant.
Physical-Chemical Treatment (no soil washing)
Metals in mine spoil
Heavy metals and
radionuclides in
clay/silt soil
Coal tar DNAPL in
gravelly soil
TCE in clay
Leaching,
adsorption
Oxidation,
complexation,
precipitation, ion
exchange
Thermally enhanced
recovery
Electro-osmosis
Not available.
Not provided.
Total cost:
approx. U.S.S1.8M
U.S.$52-118/m3;
The project was not at the
stage where meaningful
costs could be calculated.
Report noted that using low
concentrations of mild
chemicals for leaching
yielded low costs, but did
not provide supporting data.
Cost for removing 5,400 L
of recoverable coal tar and
treating groundwater before
reinjection or discharge.
Costs obtained from a cost-
optimization model; 1-2
acre site with TCE at depth
of 12-15 m (40-50 ft)
electrode installation
accounts for 20-40% of the
overall cost.
Photo-Oxidation Treatment (no soil washing)
0.8-360 mg/L
chlorinated
compounds in
groundwater
1,000 ug/L TCE; 100
ug/L PCE; 15 mg/L
PCP in groundwater
and wastewater
BTEX and chlorinated
solvents (Tyndall
AFB)
Biodegradation,
photo-oxidation
Chemical oxidation,
photo-oxidation
Adsorption and
photocatalysis
15 million FF
(U.S.$2.5 million)
capital costs; 23
million FF (U.S.$3. 9
million) annual costs
U.S.$2-3/m3 for a 190
L/min unit
U.S.$1.46/m3
Costs for achieving
acceptable drinking water
limits. To achieve surface
water discharge, costs
would be U.S. $1.7 million
for capital, and U.S. 12.9
million annually.
Unit costs increase as the
size of the treatment unit
gets smaller and
contaminants become more
difficult to oxidize.
The unit cost is for treating
BTEX-contaminated water
using a solar photocatalytic
fixed-bed process (Pt-TiO2
supported on silica gel).
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In summary, unit costs will vary from site to site. However, these costs may sometimes be offset by the
sale of concentrate produced by treatments although none of the project reports provided evidence that
recovered concentrates were actually sold for profit.
5.8 FUTURE STATUS OF THE CASE STUDY PROCESS AND THE TECHNOLOGY AS A
WHOLE
5.8.1 General Remarks
Physical-chemical methods, used alone or in combination with other technologies in a treatment train,
have proved capable of treating mainly fine-grained materials contaminated with organic and inorganic
contaminants. Despite their successes, these technologies have limitations that restrict their ability to treat
certain types of media and contaminants effectively. If planned investigations reveal ways to overcome
these limitations, the future of physical-chemical technologies will lie in their ability to cost-effectively
treat a wide range of contaminants in a wide variety of media. This section of the chapter presents some
of the issues that could have an impact on the future of the technologies.
5.8.2 Characterizing Contaminated Material
Soil washing provides a reliable way to treat contaminated solids, and specialized treatments like
flotation enhance the overall physical separation of clean and contaminated materials. For the approach
to be most effective, material to be treated must be properly characterized. When feed material is
properly characterized, unit processes can be tailored to site-specific contamination situations.
5.8.3 Optimizing Performance of Unit Processes
Unit processes have proven excellent for media such as sand and gravel, but need to be improved for
fine-grained soils where more than 30-35% of particles are less than 0.063 mm. In terms of other
physical characteristics of contaminated materials, future investigations should investigate the feasibility
of treating sediments and sludges with high water content.
Improved performance in the separation methods is required to increase the weight of the clean fraction
and reduce the volume of contaminated concentrate. Obtaining better effectiveness at this separation
stage of treatment could improve the performance of downstream treatments.
Optimizing plant operation may lead to lower levels of contaminants, a key requirement if reuse of
treated material is required, and residual contaminants are otherwise unacceptably high. For example,
the pilot-scale MGS described in Project 31 achieved a combined metal assay of 2.5% in the residue.
Optimizing the MGS could result in higher separation efficiencies. Similarly, for soil washing and
bioslurry treatment demonstrated in Project 26, using longer retention times or adding special microbial
cultures were proposed as ways to achieve further reductions in contaminant concentrations in treated
materials.
5.8.4 Investigating Cost-Effectiveness of Treatment Combinations
Preliminary investigations conducted for some of the case studies identified specific treatments that may
perform better if combined with others. This observation confirms that the future of physical-chemical
technologies lies in their ability to be used both alone and in existing and new combinations for treating
contaminated materials. For example, a proposed new combination consists of MGS physical separation
and chemical leaching as a potentially effective two-stage process for decontaminating metalliferous
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mine spoil. This combination needs further investigation with larger volumes and varieties of spoil
samples before being used in the field.
Some existing combinations have proved to be cost-effective in some situations, but investigations
should confirm their full range of application. For example, further investigations should assess the
extent of application of the combined soil washing/slurry biodegradation processes which can likely be
applied cost-effectively. Long degradation periods will cause problems when combining commercially
viable throughput of physical processes with relatively slow biological processes. To enhance the
viability of the treatment, further work should investigate ways to achieve rapid biodegradation to a
reusable product. As an example, further work for Project 36 could investigate if continuous biological
treatment can reduce the contaminant levels in fewer than the reported 28 days.
Similarly, many water treatment systems combine the Perox-Pure™ technology with carbon adsorption,
air stripping, and biological treatment. Depending on the influent water quality and treatment objectives,
the technology can be paired with others to produce a more cost-effective solution than any single
process.
5.8.5 Investigating Residuals
The physical and chemical characteristics of residuals from physical-chemical treatments are key
attributes when considering the applicability and acceptability of the treatments for any particular
application. For example, two key factors will be their ability to achieve regulatory requirements for the
reuse and recycling of treatment chemicals, and the use or disposal of treated materials and concentrates.
Projects 31 and 47 illustrate considerations of regulatory requirements for residuals.
Further investigations should focus on the feasibility of reprocessing metalliferous mine spoil (Project
31) by single-stage physical separation or two-stage physical-chemical treatment to achieve regulatory
criteria for treated material to be redeposited onsite. Tests of treated material should examine the
susceptibility of residual tailings to biological leaching. If this leaching does occur, leached metals may
contaminate surface water and groundwater.
The formation of potentially harmful intermediates may limit the applicability of emerging technologies.
In the Lasagna™ technology (Project 47), for example, result show that iron filings in treatment zones
can decontaminate TCE resulting in innocuous end products such as chloride ion, ethane, and ethene.
While the technology satisfies regulatory criteria for these compounds, more attention has to be paid to
potential intermediate products such as dichloroethene (DCE) and vinyl chloride. These products tend
to be associated with the iron surface.
5.9 REFERENCES
1. Pearl, Mike and Peter Wood (1994). Review of Pilot and Full Scale Soil Washing Plants. AEA
Technology, National Environmental Technology Centre, Oxford, 113p.
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Chapter 6: BIOLOGICAL TREATMENT PROCESSES: INTRODUCTION AND EX
SITU APPROACHES
R. Paul Bardos
r3 Environmental Technology Ltd.
6.1 INTRODUCTION
This chapter reviews the projects presented at the Pilot Study that focused on, or included in a
significant way, ex situ biological treatments. These are listed in Table 6.1. All of these projects
investigated the treatment of solid materials rather than groundwater. This chapter also provides a brief
overview of biological treatment with particular regard to ex situ approaches and appropriate situations
for their use. It summarizes the case studies and then discusses them with regard to:
• performance;
• residuals and emissions;
• applicability;
• costs; and
• prognosis for the future.
Where possible, project references that are in the public domain have been provided. Some of the
projects dealt with in this chapter are also dealt with in other chapters: Projects 24, 26, 31 and 36 are
dealt with in Chapter 5, and Projects 15, 24, 26, 31, and 36 are dealt with in Chapter 11.
6.2 GENERAL OVERVIEW
6.2.1 Biological Processes, In General
Innovative treatments are often described as ex situ or in situ. Ex situ refers to processes applied to
excavated soil either onsite or offsite. In situ refers to processes occurring in unexcavated soil, which
remains relatively undisturbed. Treatment processes can also be categorized according to their general
operating principles (5, 32), for instance: biological, chemical, physical, solidification or thermal.
For ease of discussion, materials are considered in this chapter as three basic types in the context of
materials handling: groundwater, soil, and slurry, where slurry is some mixture of soil and groundwater
or added water from another source. "Soil" is used to describe the solid phase material. However, in
reality, the solid phase materials encountered and treated encompass a far broader range of materials,
including, but not limited to topsoil, subsoil, and other natural regolith, fill, waste deposits and industrial
process residues, sediment, demolition debris, vegetation, and refuse. In many cases, remediation of
bedrock is required. Typically, treatment of bedrock—if it is attempted at all—is approached in situ, so
it is not considered in this chapter. Some materials onsite are liquid or semisolid in nature, such as
sludges and coal tars. So far as ex situ biological approaches are concerned, these are treated either by
mixing with a solid material or by treatment in a bioreactor in some form of suspension or slurry
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treatment (25). In some cases, the semi-solid material to be treated is a process residue from an earlier
non-biological treatment process such as soil washing.
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Table 6.1: Projects Reviewed and References
Project
Number
6
8
11
15
24
25
26
28
31
35
36
43
49
54
Project Title
In situ/on-site bioremediation of industrial soils contaminated with organic pollutants:
elimination of soil toxicity with DARAMEND® (55, 57)
Biodegradation/bioventing of oil-contaminated soils (35, 45)
On-site biological degradation of PAHs in soil at a former gasworks site (33)
Combined chemical and microbiological treatment of coking sites/bioremediation of
soils from coal and petroleum tar distillation plants
Combined remediation technique for soil containing organic contaminants: Fortec
Slurry reactor for soil treatment (30, 39)
Treatment of creosote-contaminated soil (soil washing and slurry phase bioreactors)
(16, 17)
Use of white-rot fungi for bioremediation of creosote-contaminated soil
Decontamination of metalliferous mining spoil (59)
In situ soil vapor extraction within containment cells and combined with ex situ
bioremediation and groundwater treatment (47)
Enhancement techniques for ex situ separation processes, particularly with regard to
fine particles (43, 60)
Multi-vendor bioremediation technology demonstration project (24, 31)
Characterization of residual contaminants in bioremediated soil and reuse of
bioremediated soil
Treatment of PAH- and PCP-contaminated soil in slurry phase bioreactors
Biological processes for the remediation of contaminated land depend on one or more of four basic
processes: (1) biodegradation; (2) biological transformation to a less toxic form (e.g., for metals); (3)
biological accumulation into biomass; or, conversely, (4) mobilization of contaminants for downstream
recovery. In general, established commercial processes are limited to those based on biodegradation.
The vast majority of practical biological treatments exploit degradation (5, 8, 13, 38, 56) and are
variously described as bioremediation, bioreclamation, biotreatment or biorestoration. Contaminated sites
are also commonly revegetated to improve their stability and aesthetic appeal and to reduce windblow
of contaminated dust (18).
Concerns about current biological processes include:
• Their susceptibility to inhibition by toxic contaminants (13) (e.g., for example heavy metals)
although some biodegradation processes appear quite robust (26);
• The low biodegradability and or bioavailability of some common organic pollutants, found with other
more degradable contaminants (34). (Current research includes the use of chemical pre-treatments
to enhance biodegradability (1) and treatment of an increasing number of compounds is found to be
feasible, for example chlorinated solvents (11));
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• Residual concentrations of contaminants after treatment, whose environmental significance is not
known (34, 44); and
• The mobilization and release of potentially toxic, partially degraded contaminants from in situ
treatments (12, 27, 40).
6.2.2 Main Process Variations (by Biological Process)
Degradation and Transformation
Biodegradation describes the decomposition of an organic compound into smaller chemical subunits
through the action of organisms. Both aerobic and anaerobic degradation pathways exist, although there
are some differences in the types of compound that will degrade under aerobic and anaerobic conditions
(3). Principally, soil microorganisms (bacteria, fungi, and actinomycetes) are responsible for bioremedia-
tion processes, but some researchers are interested in prospects for plants and algae (13, 53). As
summarized below, plants may be of more immediate use in the accumulation of contaminants or as a
means of stimulating soil microbial activity. These approaches are known collectively as
"phytoremediation" and are regarded as an important emerging technology for future research^, 34, 49).
Completely degraded compounds are said to be "mineralized," and the end products of the aerobic
degradation of chlorinated hydrocarbon might be carbon dioxide, water, and chloride ions. Guthrie (23)
describes this as "ultimate biodegradation." He defines "acceptable biodegradation" as breakdown to
below toxic levels, and "primary biodegradation as a structural change in the parent molecule. Primary
biodegradation is more commonly referred to as "biotransformation."
Biotransformation may be of use in biological treatment of contaminated soil, but has not been exploited.
It has the drawback that further transformations could regenerate toxic forms. In addition, biotransforma-
tion can be accompanied by an enhancement in toxicity.
Biodegradation may proceed via enzymic activity on compounds adsorbed into cells or through the
activity of extracelluar enzymes active outside the confines of the cell. Cells also use enzymes to
generate free radicals or peroxide ions that attack organic compounds, particularly insoluble compounds
(2, 5, 13). In many cases, organic compounds do not readily enter microbial cells since the compounds
are either sorbed to soil surfaces, are too large, or are physically incapable of being sorbed into cells.
Bioavailability is regarded as one of the key limiting factors for bioremediation (34).
More complex compounds may not be completely degradable by single organisms, but are degraded by
consortia of organisms, or in some cases may not be completely degradable in any circumstance. Some
organic compounds may be coincidentally degraded as a result of microbial activity against other
substrates, a process called "cometabolism." An example of this is the use of methane oxidation to
degrade some chlorinated solvents (14). There are a number of organic compounds, such as
tetrachloroethene (PCE), whose degradation is not energetically favorable to microorganisms. However,
in some cases, under anaerobic conditions, these compounds may be biodegraded. The compound does
not serve as an energy source or carbon source, but is used as an electron acceptor, i.e., it is reduced
during the conversion of other organic materials (40).
It is likely that several of these processes may occur simultaneously in practical bioremediation
treatments; however, some techniques are designed to capitalize on particular microbial processes, such
as the use of fungal lignase systems to degrade recalcitrant organic contaminants like pentachlorophenol
(PCP) and polycyclic aromatic hydrocarbons (PAHs) (26).
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Inorganic compounds may also be changed by microorganisms, either by direct metabolism (as in the
oxidation of sulfur or the methylation of mercury) or indirectly through the release of ligands or acids
(6). These processes may mobilize inorganic contaminants such as heavy metals. There may be potential
applications for mobilization as a means of stripping inorganic contaminants from soils, and several laboratory-
and pilot-scale initiatives based on microbial mobilization are underway (5). Arsenic and some heavy
metals may be converted into volatile methylated forms by microbial activity (also referred to as
"biotransformation"). However, the toxicity of the methylated compounds may raise serious issues of
operational safety and environmental emissions from such an approach.
Other Processes
Biological immobilization of contaminants is common, for example, the sorption of metals or organic
compounds to plant roots. The bioavailability of sorbed compounds may be reduced by this process, but
the effect is temporary, depending on the lifetime of the root. Contaminants would be mobilized as the
supporting plant matter was degraded. There is some evidence that PAHs may be irreversibly adsorbed
into soil humus (51); however, the usefulness of this in land remediation may be limited by current
approaches to hazard assessment based on total soil concentrations of contaminants.
Biological accumulation of contaminants by plants and fungi is a well-known phenomenon. The potential
use of plants that accumulate metals in their leaves and shoots is being investigated as a possible means
of removing metals from contaminated soils (7). The approach seems particularly suited to shallow
contamination arising, for example, from sewage sludge disposal or atmospheric deposition of metal-rich
dusts. More recently, interest has emerged in combining accumulation of contaminants with energy
forestry to achieve use of the land during the remediation process.
Commercially Available Processes
At present, the great majority of commercially available bio-remediation techniques assist the
biodegradation of fairly readily degradable contaminants: mononuclear aromatics (e.g., benzene toluene,
ethylbenzene, and xylenes); simple aliphatic hydrocarbons (e.g., mineral oils and diesel fuel) and lower
PAHs (2-, 3- and 4-ringed) (8). However, full-scale applications of bio-remediation to treat more
complex contaminants (such as pentachlorophenol, chlorinated solvents and possible more difficult
PAHs) are taking place, and some successes are being reported (11). Recently, the use of metal
accumulation by plants has also begun to be exploited in full-scale practical applications (58).
6.2.3 Main Process Variations (by Mode of Application)
Ex situ application of biological processes allows better process control—in particular, the breaking
down of soil material into small particles (e.g., by cultivation, grading, or conversion into a slurry). This
overcomes one of the major limitations of in situ processes, which is ensuring the accessibility of the
contaminant to the treatment (9). Ex situ processes can be divided into four basic groups (8):
(1) Shallow cultivation, where contaminated soil is cultivated in a treatment bed or in situ by cultivating
the surface layers of a specially prepared area of a contaminated site (e.g., Project 6);
(2) Windrow turning, where piles of contaminated soil often mixed with organic materials such as bark
are turned on a regular basis using processes akin to green waste composting (e.g., Project 11);
(3) Biopiles, where static piles of contaminated soil are vented and irrigated using processes akin to
static pile waste composting (e.g., Project 8); and
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(4) Bioreactors where groundwater or a soil slurry is treated in a reaction vessel (e.g., Project 25).
Cultivation
50 cm
(Till Depth)
The term "landfarming" has been used to
describe cultivation processes, but is avoided here
to avoid confusion with the treatment of oily
sludges by cultivation on land, which is also
known as landfarming. Methods vary from simple
to advanced techniques—which are all largely
based on agricultural practice. Contaminated soil
is spread over a surface, typically to a thickness
of about 0.5 m. The soil is regularly mixed and
tilled to improve soil structure and oxygen
supply. Water can be supplied to adjust the
moisture content and supply inorganic nutrients to
the system. In many applications the treatment
bed is placed over an impermeable membrane to
ensure complete collection of leachate. Spray
irrigation/recirculation of leachate is also common
practice. An example configuration is provided in Figure 6.1.
Windrows
<10 mm soil for treatment and amendments
• •. Sand'(IG'cm) -
HOPE Geotextile •
. Sand-(10'cmS. '.
Figure 6.1: Section Through a Treatment Bed
(based on Project 6)
Screened Soil and
amendments turned weekly
Leachate drain'
Hard Stand
Figure 6.2: Windrow Treatment (schematic)
Treatment techniques using windrows are similar
to approaches used for waste composting, for
example, of urban and agricultural wastes. Soil is
placed in thick layers or heaps (see Figure 6.2).
Materials such as wood chips, bark, or compost
are often mixed in to improve the soil structure
and increase aeration. Regular turning and tilling
is often carried out to further improve aeration.
Specialized equipment using technology borrowed
from the waste composting industry is typically
used for this purpose. In most cases, true
composting (i.e., a controlled aerobic, solid-phase
thermophilic process) does not take place.
Furthermore, amendments tend to be added to condition the soil, rather than as part of an integrated
waste management approach, which perhaps remains an under-exploited opportunity.
Biopttes
Excavated soil is placed in a static heap (i.e., no mechanical turning or tilling is conducted). Nutrients
and water are added to the contaminated soil by percolation or along a network of internal galleries. The
conditions in the piles are monitored and optimized through aeration and water supply. An example
schematic (based on Project 35) is provided in Figure 6.3. The principal distinction between biopiles and
windrow-based systems is the use of active aeration and irrigation. Biopiles are closely allied to the
aerated static pile technique for waste composting (52), although refinements such as feedback control
based on temperature, moisture, and partial pressure of oxygen (pO2) are less frequent in soil treatment
than aerated static pile composting. The technology has a longer history for waste composting, and there
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Bed height
2.5m
Aeration —•
supply I
main
Graded
material for .—y
treatment •••»'
Aeration Pipe
Monitoring Probe
Haul Road
Basal layer (e.g., gravel, clay)
Leachate-' Collection
System
' Prepared1 s/irfaqe' /' /'
Impermeable
Membrane
Figure 6.3: Example Biopile Configuration (based on Project 35)
would appear to be still some capacity for technology transfer to soil treatment (e.g., combined aeration
and turning technologies).
Bioreactors
Pre-treated soil (e.g., soil with particles >4-5 mm removed) are slurried with water and treated in a
purpose built reactor system with a mechanical agitation device. Within the reactor, controls on
temperature, pH, nutrients, and oxygen supply can be amended to gain the maximum contaminant
degradation rates using either microorganisms indigenous to the soil or specially added cultures.
Bioreactors can range from treatment lagoons
(38) to contained in-vessel systems (19), and the
sophistication of engineering approach can vary
accordingly. Bioreactors can also operate in the
solid phase. Although infrequent for soil remedia-
tion, this is a common approach for waste treat-
ment. Waste compost bioreactors often incorpor-
ate an ability to turn and mix materials, as well
as to simply aerate. The technology is robust, and
again there may be opportunities for technology
transfer to soil remediation (20, 48). An example
slurry-phase bioreactor (based on Project 25) is
illustrated in Figure 6.4.
6.2.4 Combinations with Abiotic Processes
Soil +
sediment inflow
§ Sand fractions
- Fine fractions
Slury !
recycle
Outflow fines
Outflow sand
Slurry
Air
Figure 6.4: Principle of the DITS Reactor with
the Dual Injection Manifold at the Bottom of the
Reactor (based on Project 25)
The difficulties of remediating complex
contamination problems with individual process
technologies has led to the development of
process integration, which combines unit process treatments to provide an effective overall treatment (43,
54). Two examples follow:
Bioventing, which can be applied in situ or ex situ in treatment beds, is an integrated technology that
combines biodegradation and volatilization. A significant problem for biological treatment has been
to supply the active microbial population with sufficient nutrients and oxygen to ensure rapid
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biodegradation. In bioventing, soil vapor extraction (SVE) is used to supply oxygen as well as a
means of removing volatile organic compounds (VOCs) from soil. Bioventing is far more efficient
at delivering oxygen to soil microorganisms than systems that use recirculated groundwater. Project
8 used bioventing to treat soil ex situ.
• Project 24 is a pilot-scale investigation that combined hydrocyclone treatment with separate
"cleaned" sandy fractions from a process residue, which was then sequentially treated by photo-
oxidation and biodegradation.
Treatment integration in general within the Pilot study projects is discussed in Chapter 11.
6.2.5 Extensive Approaches
Intensive treatments, such as soil washing or incineration, use relatively complex equipment and plants,
and require a lot of resources for initiation, running, and support. Therefore, they tend to be costly.
Extensive technologies operate over a longer period with low maintenance, cost, and energy require-
ments. Approaches being considered include reducing contaminant concentrations, environmental
mobility, and availability and toxicity, or enhancing natural attenuation processes. Techniques include
hyper-accumulator plants and enhanced rhizosphere-mediated biodegradation, and fixation by minerals.
In addition to cost savings, they tend to have less impact on soil quality than their intensive counterparts.
Indeed, biologically based extensive methods such as the promotion of in situ biological activity by plant
roots actually may enhance soil structure and fertility. The development of extensive treatments is of
particular interest to industrial holders of contaminated land as potential low cost treatments over the
lifetime of existing industrial plant operation (12, 44).
Extensive approaches considered to date are mostly in situ techniques (11). However, ex situ approaches
include techniques based on waste composting, and are particularly appropriate where there is a -
possibility of synergy between the treatment of hazardous wastes and other organic wastes such as
sewage sludge or green wastes.
6.2.6 Groundwater Treatment
Contaminated groundwater is treated in three main contexts:
(1) As part of a system where it acts as carrier to transport contamination from soil to the treatment
process(es), for example, in pump-and-treat systems (32);
(2) When it is removed to lower the water table for treatment of contaminated ground; and
(3) As effluent treatment prior to re-infiltration or discharge to surface water.
A permanent solution to groundwater contamination will always require the reduction of contamination
in the aquifer and the source of contamination.
Where groundwater is treated above ground, biological approaches include:
• a variety of bioreactors (5, 46);
• treatment within a soil mass (e.g., through the irrigation of a biopile, windrow, or treatment bed);
and
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• combined treatment with solids in slurry bioreactors.
The majority viewpoint is that simple approaches to pump-and-treat, using groundwater as a carrier to
effect an in situ treatment, are rarely effective; this has led to the emergence of more elegant approaches
(37). These can be divided into two broad and overlapping categories: treatment zones and active
containment.
Treatment zones improve in situ remediation by treating contamination in a smaller, more clearly defined
and better optimized subsurface volume to address typical limitations of in situ remediation, such as
process and emissions control, and to ensure contaminant availability and accessibility. Treatment zones
employ groundwater as a "carrier" for the contamination.
Contamination may be directed or mobilized to the in situ treatment technology by processes such as
the natural groundwater flow, managed groundwater flow (e.g., funnel and gate systems (50)\ or by
manipulation such as by using electroosmosis. This approach has a cross-over with ex situ techniques
in several ways:
• The operating principle of the in situ treatment zone may be contained in some form of removable
cartridge or cassette, in which case, it may be considered as a buried ex situ system;
• The treatment system may be entirely or partially above ground; and
• More complex permutations are possible, for example, where a fairly dispersed in situ technique is
used to mobilize contaminants, which are then contained and collected for further treatment above
ground.
Active containment, or use of treatment walls, is a special case of an in situ treatment zone that treats
migrating contaminants, usually dissolved in groundwater or in the vapor phase, where the source cannot
be treated. Active containment targets treatment of the pathway rather than the source. It aims to
overcome the perceived limitations of passive containment measures (which physically restrict migration
of contaminants) such as doubts over long-term barrier integrity and treatment of contaminants.
The control of the contaminant plume can be visualized in terms of a control surface or boundary
beyond which contaminant levels are "acceptable." The treatment system may or may not act at this
surface. For example, a treatment process may be remote from the boundary where subsequent natural
degradation and attenuation also plays a part in contaminant destruction. Active containment deals with
migrating contaminants. At its most elegant, active containment does not contain groundwater, but
contains the contaminants by destroying them or removing them from the groundwater (28).
6.2.7 Indications for Using Ex Situ Treatment Technologies
Within the process industries sector and among much of the research community, there is great interest
in developing in situ treatment technologies because of their perceived advantages in terms of cost and
environmental impact. These advantages are clearest when remediation can proceed over significant
periods of time, and perhaps when in situ treatments are compared with excavation and transportation
to the intensive ex situ treatment plants.
However, the availability of time is a critical limitation to the use of in situ treatments for many
situations, for example, where an acute risk exists or a redevelopment is planned. Furthermore, in situ
applications are limited by subsurface conditions. Even where in situ techniques are applied, many in
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situ treatment approaches still require the removal of concentrated hot spots. In addition, practical site
reclamation for redevelopment often requires removal of debris and site materials. In such cases, ex situ
treatment may be performed to reduce the volume of material requiring disposal offsite through materials
recovery, or to render the materials more environmentally benign.
Ex situ treatment may take place onsite (e.g., for minimization of material taken off site) or at a remote
site (e.g., to recycle re-usable components and render contamination "safe"). The costs of mobilizing a
treatment plant usually means that on-site treatment is only cost effective above some threshold of
volume of material to be treated. Many countries, including Canada, Denmark, Germany, and the
Netherlands, have off-site biological treatment plants for contaminated site materials. However, an
opportunity that has yet to be broadly exploited is synergy with recycling and reuse of contaminated site
materials and other wastes, for example, construction wastes, civic amenity wastes, or compostable
wastes. Indeed, the longer-term goals of sustainable waste management and sustainable approaches to
dealing with contaminated land are seen not only as an opportunity for synergy, but requiring an
integrated approach if the best opportunities for either are to be realized. An interesting illustration of
this is where an old landfill must be excavated and removed for redevelopment. A particular interest may
be the stationing of an off-site treatment plant at landfills where the opportunities for co-treatment with
materials from different sites and waste streams is greatest (21).
There also may be opportunities for synergy among the needs of sustainable waste management,
recovery of materials from land remediation, and the improvement of marginal land. In this context,
marginal land refers to land that could be remediated, but whose remediation is not possible from a
strictly commercial viewpoint. An example is the possibility of linkage among land remediation, waste
management, and sustainable energy forestry. The opportunity is the long-term reuse of waste (e.g., as
compost or site engineering materials such as gravel substitutes) in ongoing productive use of marginal
land for non-food uses. This may be particularly appropriate for former coal fields, providing new jobs
as well as environmental improvement and sustainable waste management into the long term. However,
it could be appropriate for a wide range of marginal land types.
6.3 CASE STUDIES CHOSEN
The Pilot Study projects chosen as case studies for this chapter are listed in Table 6.1.
6.4 BACKGROUND OF CASE STUDIES AS A GROUP
Table 6.2 describes the Pilot Study projects involving ex situ treatment in terms of the type of
technology configuration (as described in Section 6.2). Projects in the Pilot Study cover the four modes
of treatment application described in Section 6.2.3. The majority of these projects examine exploiting
biodegradation. However, one project examines bioleaching (mobilization of metals by reducing pH
through the action sulfur-oxidizing bacteria). Another is an investigation of the risks posed by a variety
of inorganic and organic contaminants. Table 6.3 outlines the process investigated for each project.
Detailed project summaries are provided in Appendix IV.
Although site details are lacking for some projects, those sites for which details are reported are mainly
wood preservation plants or other sites with PAH contamination, including gasworks and coking works.
PAH and oil degradation are the main processes reported, although some projects also considered PCP
degradation. One project considered treatment of chlorinated and non-chlorinated solvents.
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Table 6.2: Overview of Selected Projects
Project
6 In situ/on-site bioremediation of industrial soil
contaminated with organic pollutants:
elimination of soil toxicity with
DARAMEND®
8 Biodegradation/bioventing of oil-contaminated
soils
1 1 On-site biological degradation of PAHs in soil
at former gasworks site
1 5 Combined chemical and microbiological
treatment of coking sites/bioremediation of
soils from coal and petroleum tar distillation
plants
24 Combined remediation technique for soil
containing organic contaminants: Fortec
25 Slurry reactor for soil treatment
26 Treatment of creosote-contaminated soil (soil
washing and slurry phase bioreactor)
28 Use of white-rot fungi for bioremediation of
creosote-contaminated soil
3 1 Decontamination of metalliferous mining spoil
35 In situ soil vapor extraction within
containment cells combined with ex situ
bioremediation and groundwater treatment
36 Enhancement techniques for ex situ separation
processes, particularly with regard to fine
particles
Technology Type
Cultivation (full-scale)
Biopile + monthly
turning (full scale)
Windrow (+ "passive"
aeration) (full-scale)
Biopile ("pilof'-scale)
Bioreactor (part of a
treatment train)
(pilot-scale)
Bioreactor (pilot-scale)
Bioreactor (part of a
pilot-scale treatment
train)
Laboratory-scale R&D
Laboratory-scale R&D
on "bioleaching" of
heavy metals
Biopile (part of a full-
scale integrated
approach)
Laboratory-scale
bioreactors (part of a
pilot-scale treatment
train)
Input Material for Treatment
Screened soil (<100 mm) + proprietary
amendment
(a screen size of 250 mm was also
mentioned)
Screened soil + organic amendments
Screened soil (<80 mm) + organic
amendments
Soil + organic amendments / untreated
soil
Soil slurry and sediment slurry
contaminated with PAHs or
hydrocarbons
Clay -rich soil and harbor sediment
contaminated with PAHs
Soil slurry (PAHs)
Soil, examined degradation of higher
PAHs
Mine spoil (metals)
Screened and "vented" soil (various
organinc and inorganic contaminants)
Soil slurries from a diesel
contaminated soil, and a gasworks soil
Site Details
Main results from Domtar Site, Toronto,
Canada. Former wood preserving site
that used PCP, and PAH-contaminated
sediments from Hamilton Harbour
Boucerville (contaminated by
transformer oils) Jonquiere (former rail
station) Canada plus brief data from
other sites
Frederiksberg Gasworks, Denmark
Not specified, France
Various, not specified, The Netherlands
Mijdrecht and Petroleumhaven, The
Netherlands
Former wood preserving facility
(creosote contamination) , Lillestrom,
Norway
Former wood preserving facility
(creosote contamination) , Southern
Norway
Former metalliferous mine sites, Wales,
U.K.
Derwenthaugh Cokeworks, U.K. (PAH
contamination, cyanides, VOCs and
metals)
Unspecified U.K. locations
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Project
43 Multi-vendor bioremediation technology
demonstration project
49 Characterization of residual contaminants in
bioremediated soil and reuse of bioremediated
soil
54 Treatment of PAH- and PCP-contaminated soil
in slurry phase bioreactors
Technology Type
Biopile (full-scale)
Laboratory-scale R&D
Bioreactor (pilot-scale)
Input Material for Treatment
Soil contaminated with chlorinated and
non-chlorinated solvents
Soils treated at a full-scale ex situ
biological treatment plant, various
residual contaminants tested for.
Soil (PAHs, PCP)
Site Details
Sweden 3-Chapman site, Sweden, New
York, USA, an abandoned hazardous
waste disposal area.
Unspecified location(s), Switzerland
A closed wood preservation plant (PAH
contaminated), oil storage plant (PCP
contaminated), Sweden
Table 6.3: Outline of Treatment Processes By Project
Project
Process Outline (see Project Summary for further Information)
In situ/on-site bioremediation
of industrial soil
contaminated with organic
pollutants: elimination of soil
toxicity with DARAMEND®
The technology is a proprietary system: DARAMEND® bioremediation. It is targeted at a range of organic contaminants
including aliphatic and aromatic hydrocarbons, chlorinated phenols, and phthalates. The test results reported to the Pilot Study
focused on PAH and PCP in the range of 1,000s and 100s of mg/kg. The treatment is based around a proprietary soil
amendment. Its composition varies from site to site depending on soil analyses. The amendments are based on plant materials
and increase the water holding capacity of the soil. They include slow-release nutrients and surfaces that sorb contaminants
with the claimed effects of reducing their toxicity to microbial activity and also increasing their accessibility to degraders.
Soil amendments are introduced at 1-5% by weight using conventional agricultural equipment followed by regular cultivation.
For "ex situ" application, soil or sediment to be treated is transported to the treatment area and homogenized by tilling with a
power take-off driven rotary tiller. During the remediation process, soil moisture content is maintained within a narrow range
with drip irrigation. The DARAMEND® amendment is also cultivated directly into to the surface of the contaminated site,
which is termed an "in situ" application. Pilot Study reports also suggest its use in biopile applications. It is conceivable that
the amendments could also be applied in windrow and solid-phase bioreactor systems.
Biodegradation/bioventing of
oil-contaminated soils
Biogenie has developed a biopile-based, ex situ bioremediation technique whereby soil is heaped in contained areas, such as
on an asphalt pad with drainage collection, and supplied with oxygen, moisture, and nutrients to enhance natural degradation
processes. The test results center on soils contaminated with oil and grease in the range of 104 mg-kg"1. The project also
discussed the use of biofilters for emissions control from the process (see project summary). Since the beginning of the Pilot
Study the company has also carried out a large number of commercial remediation projects. Results from 24 of these projects
were presented in 1996, total tonnage nearly 400,000 tonnes. On the basis of these projects, the company calculated average
degradations of 75% for mineral oil and grease; 99% for BTEX; 95% for PCP; 90% for total PAH including 99% for
naphthalene.
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Project
Process Outline (see Project Summary for further Information)
11 On-site biological degradation
of PAHs in soil at former
gasworks site
Windrow-based treatments were tested for their ability to reduce PAH concentrations at pilot-scale (20-30 m3) after laboratory
and microcosm studies on <4-mm fraction. The soil was screened at 80 mm. The tests were performed on sandy soil
containing total PAH at about 400 mg-kg"1. After mixing soil was spilt into test windrows. Windrows tested different
amendments (wood chips, compost, none) and the impact of adding nutrients (N, P, K) and Ca or detergent solution was
examined.
15 Combined chemical and
microbiological treatment of
coking sites/bioremediation of
soils from coal and petroleum
tar distillation plants
Investigations encompassed the use of bioreactors and biopiles at pilot-scale to treat PAH & hydrocarbon contaminated soil
(103 mg/kg. Biopiles were made of contaminated soil/wastes mixed with organic amendments (straw, sawdust, uncontamina-
ted soil). The effect of adding oxidizing agents (hydrogen peroxide, sodium hypochlorite, and ozone) during biopile
construction was also evaluated.
24 Combined remediation
technique for soil containing
organic contaminants: Fortec
Fortec® consists of three unit operations combined in series: multi-step hydrocyclone separations, UV/hydrogen peroxide
photochemical pretreatment, and slurry-phase bioremediation. It deals with more recalcitrant contaminants in fine fractions (a
common soil washing residual). The photo-chemical oxidation is designed to transform recalcitrant organic compounds into
more readily biodegradable compounds. The bioreactor is slurry based and operates at mesophilic temperatures (10-25°C).
Mixing is achieved by slurry recirculation and reactor operates on a batch-wise process, residence time 3-20 days. The
reactor has been tested at up to 300 m3 as part of an integrated soil washing process. Testing has been carried out on soils
contaminated with diesel oil and PAH.
25 Slurry reactor for soil
treatment
This project treats excavated clay soils and sediments contaminated with organic compounds, such as mineral oil and PAH.
The treatment technology described is the Slurry Decontamination Process (SDP), which combines separation processes with
a microbiological slurry reactor. The bioreactor is used to treat a <4 mm fraction produced by removal of debris (>60 mm),
grinding, and sieving. The basic bioreactor configuration has been tested up to 4 m3. The process uses a cascade of
bioreactors. A key aspect of the configuration is the triangular base and the turbulent flow produced with the bioreactor to
maintain the soil particles in suspension, mix and grade them by particle size. Coarse particles settle out in the first
bioreactor. Subsequent bioreactors treat the finer fractions and the more recalcitrant contamination attached to them or
remaining in solution or suspension. Testing has focused on mineral oils and PAHs.
26 Treatment of creosote-
contaminated soil (soil
washing and slurry phase
bioreactor)
This project is an investigation into the remediation of three and four ring PAHs contaminated soils using a process that
combines soil washing (especially froth flotation) with slurry-phase bioremediation. The project consisted of bench-scale
treatability studies and pilot-scale remediation trials. Bioslurry testing was carried out initially at bench-scale (1 L), and at
454 L, using fines slurry from froth flotation in a tonne/hour soil washing plant. PAH degradation was determined.
28 Use of white-rot fungi for
bioremediation of creosote-
contaminated soil
Laboratory-scale testing was carried out to determine the potential of white and brown rot fungi to degrade PAHs in soil
from an abandoned wood preservation site contaminated with creosote. Testing consisted of screening a limited number of
fungal types for their capacity to degrade PAH and determine their requirements for optimal degradation performance at
mesophilic temperatures (20°C), such ase lignin-rich substrates. Subsequently, 60-L batches were tested. Pilot-scale testing
due in 1995/96 has been delayed.
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Project
Process Outline (see Project Summary for further Information)
31 Decontamination of
metalliferous mining spoil
This project investigated a variety of treatments for dealing with metalliferous mining wastes. Biological investigations
centered on ferric bacterial leaching (Thiobacillus spp) of metals from metalliferous mine tailings and from a fine fraction
residue from MGS (a particle separation process exploiting density—see Chapter 5). The investigations aimed to understand
both the potential of "bioleaching" as a treatment, and as a factor causing the release of metals from tailings and residues in
the environment. Investigations were carried out at bench-scale.
35 In situ soil vapor extraction
within containment cells
combined with ex situ
bioremediation and
groundwater treatment
Investigation of the former Derwenthaugh Cokeworks site identified an area of 7.9 ha that was significantly contaminated
with coal carbonization wastes from the original plant including BTEX, PAHs, phenols, heavy metals, and cyanides. The
remedial scheme involved four stages: (1) Installation of a cut-off wall to protect the adjacent river from further pollution and
to allow safe excavation (to a depth of 5 m) of the contaminated ground; (2) Installation of wells for Dual Phase Vapor
Extraction (DVE) to remove VOCs and free phase product; (3) Use of wells to abstract contaminated groundwater for surface
treatment; and (4) Excavation and biological treatment of contaminated ground. A biopile technique was used to treat 28,000
m3 of material in four batches using continuous forced aeration over 2-3 months. All material was screened at 100 mm, with
oversize being crushed and then re-used on site if found acceptable.
36 Enhancement techniques for
ex situ separation processes,
particularly with regard to
fine particles
Laboratory-scale, slurry-phase bioreactors (10-L) were used to test the potential for biodegradation of contaminants in
fractions of soil from a gasworks site and from a site contaminated by diesel (locations not revealed). Fractions had been
produced from a pilot-scale soil washing plant and had been stored briefly prior to testing. Two fractions of diesel-
contaminated soil were tested: 0.002-0.01 mm and O.002 mm. One fraction of gasworks soil was tested (O.063 mm). Test
periods were 10-14 days, and the bioreactor operated at mesophilic temperatures (15°C or 25°C). The effect of nutrient
amendments was also evaluated.
43 Multi-vendor bioremediation
technology demonstration
project
The biopile treatment investigated was one of three technologies investigated at field-scale at the Sweden 3-Chapman site.
The other two were in situ approaches and are discussed in Chapter 4. The site is an abandoned hazardous waste disposal
area containing very high concentrations of chlorinated and non-chlorinated solvents such as trichloroethylene,
tetrachloroethene, 2-butanone (MEK) and toluene. Materials were tested at pilot-scale (76 m3 biopiles). Discontinuous and
continuous forced aeration was tested. Irrigation was via a sprinkler system.
49 Characterization of residual
contaminants in
bioremediated soil and reuse
of bioremediated soil
Mineral oil products are major pollutants found at contaminated sites in Switzerland. Certain residual pollutants remain after
soils contaminated with oil products have been bioremediated. The emission levels to be expected during the reuse of
remediated soil were estimated in laboratory and field tests. The remediated soil material used for all tests came from various
minor oil spills (primarily involving EL heating oil) and was combined before being sent as a single batch to a bioremedia-
tion plant. The contaminant content in the fine material (<2 mm) was 780 mg (TSEM) and 430 mg/kg (TPH), in each case
related to the dry content of the sample. The PAH content (according to EPA) was below 2.8 mg/kg and was not measured
subsequently. The project was subdivided into the following operational stages: (1) physical and chemical characterization of
the residual contaminants; (2) environmental behavior of the residual contaminants; (3) effects of the residual contaminants
on the environment; and (4) evaluation of the environmental acceptability by means of a risk assessment.
54 Treatment of PAH- and PCP-
contaminated soil in slurry
phase bioreactors
Eko Tec has carried out several full-scale remedial actions at contaminated sites across Sweden. This project reports on the
intended use of these reactors to treat 3,000 metric tons of creosote-contaminated soil containing 1,000-10,000 mg/kg PAHs
and 100 metric tons soil contaminated with 500-1,000 mg/kg PCP. Small-scale bioreactors were used to treat approximately 1
m3 of each contaminated soil. Pilot-scale testing was scheduled for 1996/97 but results have not yet been reported.
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6.5 PERFORMANCE RESULTS
6.5.1 Project 6: In S/fu/On-Site Bioremediation of Soils Contaminated with Organic
Pollutants: Elimination of Soil Toxicity with DARAMEND®
A 216-m2 test plot and a 12-m2 control plot were compared using ex situ treatment beds (Table 6.3).
Total PAH removal was in excess of 90%, and total chlorophenol removal was just below 90% using
the DARAMEND® technology (55). These removals were about double the removals found for the
control plot, which was left unattended over the treatment period (254 days). Removals for individual
PAH and chlorophenol compounds showed some variation, (from 41% to 98%). Higher-ring PAH
compounds were more recalcitrant. Tests of toxicity to earthworms and seeding emergence also indicated
amelioration through treatment. Total petroleum hydrocarbon (TPH) removal in the test plot was 87%.
Interestingly, a zero value for the TPH removal was recorded for the control plot, despite the reported
removals of PAHs and chlorophenols. The fate of compounds was not reported (e.g., disappearance into
humic materials versus degradation). The vendor has provided further case study information where
similar treatment performances were achieved.
6.5.2 Project 8: Biodegradation/Bioventing of Oil-Contaminated Soils
Field tests at Boucherville and Jonquiere reported total hydrocarbon removals of around 70%. The
contractor, Biogenie, also presented summary data from 25 practical remediation projects. The
cumulative amount of material treated was around 400,000 "tons." (Note the exact unit of measurement
was not specified). These case studies are listed in Table 6.4. Biogenie reports average removal
efficiency for a variety of contaminant classes: mineral oil and grease, 75%; benzene, toluene,
ethylbenzene, and xylenes (BTEX), 99%; PCP, 95%; and total PAHs, 90%, with 99% removal for
naphthalene.
Table 6.4: Biogenie Case Studies
Type of Site
Gas station (decommissioning and underground
storage tank replacement)
Former diesel power station
Manufactured gas plant
Refinery
Former petroleum depot
Industrial yard and waste lagoon
Others (railroad yard, electrical substation, etc.)
TOTAL:
Number of Sites
8
5
1
2
3
2
4
25
Amount of Material
Treated (tons1)
174,800
78,200
75,000
40,500
10,000
7,000
4,700
390,200
1 The original reports do not specify whether "tons" refers to metric tons (tonnes), U.S. short tons
(2,000 Ibs), or Imperial long tons (2,240 Ibs).
Aging has been suggested as a major factor in reducing the degradability of mineral oil and grease.
Some projects were halted as soon as regulatory criteria were met. Pile temperatures may be on the order
of 50°C, so some loss of organics through volatilization will take place. However, based on the tests at
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Jonquiere, Biogenie believes that more than 99% of contaminant removal is due to degradation. No other
information on fate of compounds was reported. Field-scale performance tends to be less than the
potential treatment performance based on bench-scale test work. This indicates some potential for further
optimization of the full scale treatment. The trade-off is whether such optimization is achievable at a
reasonable cost and within a reasonable treatment duration.
6.5.3 Project 11: On-Site Biological Degradation of PAHs in Soil at a Former Gasworks
Site
Ten turned-windrow configurations were tested (Table 6.5), and the authors compared: "ordinary"
sampling with analysis shortly after sampling; freeze drying for sample preservation; and freezing of
samples for sample preservation.
Table 6.5: Project 11 Treatments
Windrow *
IG Control
IB Control
2G
2B
3G
3B
4G
4B
5G
5B
Amount of soil
(m3)
33
21
19
19
20
20
32
32
33
36
Aeration2
-
-
Turning
Aeration
Turning
Aeration
Turning
Turning
Turning
Turning
Treatment at
initiation of test
-
-
+ 11 m3 wood chips
+ 11 m3 wood chips
+ 10 m3 compost
+ 10 m3 compost
+ detergent solution
+ detergent solution
-
-
Treatment in the test
period
Addition, as required,
of:
- NPK fertilizer
- calcium nitrate
- water
Addition of detergent
solution to windrows
4G and 4B
Notes:
1 (1G-5G): Windrows located outside.
(1B-5B): Windrows located inside.
2 Aeration by turning of soil with excavator (a total of 10 times during the test period).
Aeration via air drains in the bottom of the windrow from where air is drawn (around 50 m3/hour).
3 A 5% detergent solution was added three times during the test period. A total of 1.6 g of detergent/kg of
soil was added to test windrow 4G, and 2.6 g of detergent/kg of soil was added to test windrow 4B.
The sample preservation route had a strong impact on reported findings. For freeze-dried samples no
significant differences between PAH removal for the different treatments were found. However, some
differences were found for analyses of ordinary samples. Significant degradation (at the 5% level)
compared with the starting concentration was found for both indoor and outdoor control batches, and
for batches that had detergent addition and were turned. In addition, the indoor batch with turning but
not detergent addition also showed significant total PAH removal. The remaining piles, including piles
with compost addition (turned or otherwise), showed no significant decrease in total PAH concentration.
It appears that turning is beneficial except that the control batches that were not turned also showed
significant decreases in total PAH concentration. This study shows the difficulties in interpreting
biodegradation data. The data are strongly affected by the sample preservation and subsequent analytical
approach. Furthermore, results vary greatly for individual PAHs. The authors suggest that bioavailability
was a limiting factor for PAH removal and was affected by aging and sorption of the PAH to soil
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surfaces. It may also be that the relatively low initial levels of PAH in the soil (400 mg/kg in total)
affected treatment performance, although this is not suggested by the authors. The low initial
concentration may have meant a much smaller pool of available degradable PAHs, and hence a much
slower initiation of biological action.
6.5.4 Project 15: Bioremediation of Soils from Coal and Petroleum Tar Distillation Plants
Biopiles and recirculating bioreactors were used to screen 14 fungal and biological isolates. However,
no detailed results were provided for this project.
6.5.5 Project 24: Combined Remediation Technique for Soil Containing Organic
Contaminants: Fortec
The process concept uses a hydrocyclone treatment to separate the sandy fraction from finer soil grains.
The fines are then treated biologically in a batch mode slurry reactor (3% solids) with a retention time
of 3-20 days. The test work investigated whether a photochemical treatment of the hydrocy clone-treated
soil before biological treatment led to further reductions in residual contaminant concentrations in the
treated residues. The photochemical pretreatment consisted of ultraviolet (UV) irradiation and addition
of hydrogen peroxide.
The pilot-scale reactor had a capacity of 25 m3, and its contents were mixed by air sparging and slurry
pumping. The initial charge of biomass was 1 m3 of activated sludge from sewage treatment. Subsequent
batches were seeded with recycled biomass from earlier runs. Reactor effluent was recycled to a process
water "buffer." Nitrogen and phosphorus amendments were made during processing, based on initial
contaminant loadings. Processes were carried out at ambient temperatures (10-16°C).
Tests on mineral oil contaminated soil (input loadings 400-5,000 mg/kg) set a target residual concentra-
tion of 100 mg/kg. Treatment times to reach this target were found to be in the range 3-8 days. The
sandy fractions separated by hydrocyclone treatment generally contained less than 50 mg/kg mineral oil.
No detectable benefit of photochemical pretreatment was found.
Tests on PAH-contaminated soil (input loading 30 mg/kg) used target residual concentrations of 1 mg/kg
and 20 mg/kg. Only slight PAH removal from the fines fraction took place in the absence of photo-
chemical pretreatment. With pretreatment, PAH levels decreased to around 5-10 mg/kg after 15 days
treatment in the bioslurry reactor. If the fines fraction and sandy fraction were recombined, final residual
PAH concentrations would be in the order of 2-4 mg/kg, which is lower than 20 mg/kg and close to 1
mg/kg. The accumulation of organic effluents in the process effluent was not severe.
Further studies on high molecular weight PAH compounds concluded that degradation rates were limited
by contaminant bioavailability, which decreased due to strong adsorption of these compounds to organic
matter in the soil. The photochemical pretreatment appeared to act as a mechanism for destroying the
soil organic matter and increasing contaminant bioavailability. Comparative results showed that
pretreatment significantly increased slurry phase biological degradation of PAH compounds. Sixty-nine
percent of the PAH compounds were degraded after 12 days for the pretreated sample compared with
26% for the sample without photochemical pretreatment. It was concluded by the authors that
photochemical destruction of soil organic matter enhances subsequent degradation but the technique
would be limited to soils with a naturally low soil organic matter content (tests of the 300-m3 reactor
were not reported in detail).
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Tests on (5-HCH (lindane), including chemical pretreatment, resulted in no biological degradation of the
contaminant. It was concluded that the chemical stability of (5-HCH was too high for this combined
process.
6.5.6 Project 25: Slurry Reactor for Soil Treatment
Pilot-scale tests (1 m3) were conducted, and removal rates of 95% for oil contamination (Petroleumhaven
clay soil) and 90% for total PAH (Mijdrecht sediment) were achieved in under two weeks. Starting
concentrations were 800 mg/kg and 300-400 mg/kg respectively. A lower removal of oil contamination
was found for the Mijdrecht sediment (80%). Process losses to volatilization were checked using capture
of VOCs in filters and found to account for 1% or less of contaminant removals.
6.5.7 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry
Phase Bioreactors)
Bench-scale tests indicated that:
• PAH degrading organisms could be isolated from the creosote contaminated soil, and under optimal
culture conditions, 94% of PAHs was degraded in 7 days (after acclimation); and
• PAHs could be concentrated by froth flotation.
Pilot-scale test work using a 454-L bioslurry reactor examined the treatment of PAH concentrates from
froth flotation. Process optimization was carried out for biostimulation using nutrient (nitrogen and
phosphorous) addition, pH amendment, aeration, addition of surfactants and temperature control. Tests
were carried out on five 600-L batches from two clay-rich soils of solids content 14-20%. These initial
tests resulted in 97% PAH removal—better than the bench-scale finding. Residual PAH concentrations
were 71-200 mg/kg, from starting concentrations of 480-6,000 mg/kg. The removal of PAHs was found
to correspond with oxygen uptake indicating that aerobic biodegradation had taken place. Addition of
commercially available inocula was not found to be necessary at pilot-scale.
6.5.8 Project 28: Use of White-Rot Fungi for Bioremediation of Creosote-Contaminated
Soil
Screening tests were conducted using the white-rot fungi Pleurotus ostreatus and Trametes versicolor
and the brown-rot fungus Lentinus leptinus. The tests were used to evaluate different lignin substrates,
such as wheat straw, wood chips (birch or pine), and newspaper, and to determine the influence of pH,
aeration, and addition of compost. Tests were carried out either on petri dishes or in 1-L Erlenmeyer
flasks. Following these tests, Pleurotus ostreatus was investigated further using wheat straw as the lignin
substrate.
Contaminated soils were incubated with straw and fungus for 8 weeks at 20°C. A range of supplements
was added (peat, compost, potato pulp). Degradation performance was dependent upon the number of
aromatic rings in each PAH compound ranging from up to 70% degradation for 3-ring PAHs to less than
35% for 5-ringed PAHs.
Further bench studies (using 60-L batches) investigated the impact on degradation of indigenous
microbial populations as a pretreatment, followed by fungal inoculation. The pre-inoculation incubation
period was two months. After inoculation, samples were incubated for a further three months. Samples
incubated with bark prior to fungal inoculation were found to show the greatest PAH degradation. This
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benefit was reduced if fertilizer was also added during the pre-inoculation incubation period. Degradation
of PAH was greater at 20°C than at 8°C; however, the benefit of preliminary incubation with bark was
greater for the lower temperature. Compared with controls, degradation of PAHs, but not heterocyclic
compounds, was enhanced by the fungal inoculation.
Radiolabelling of the PAH compounds was used to enable tracing of treatment metabolites to be
conducted. These produced the contradictory findings that no accumulation of intermediate metabolites
was detected, yet mineralization rates were low.
6.5.9 Project 31: Decontamination of Metalliferous Mining Spoil
Biological leaching due to microbial generation of sulfuric acid from sulfide was investigated for a
highly oxidized sandy spoil (Frongoch); fine particle size sulfitic material (Y Fan); and high metals
content tailings (Cwmerfyn). Ten-gram samples were subjected to a standard bioleaching test (from the
Canadian Centre for Mineral and Energy Research) which was not described. Aliquots were tested of
untreated material ("head"); residues remaining after soil washing (as described in Chapter 4); and a
heat-treated aliquot (500°C for 18 hours) intended to simulate oxidation through weathering in the long
term. The residues remaining after soil washing tended to have a lowered content of lead, zinc,
cadmium, and sulfur.
Heat-treated samples showed higher zinc leaching than untreated samples. In all cases, the initial rate
of bioleaching of zinc was high but then declined. The authors concluded that bioleaching can lead to
significant movement of zinc from the solid to the aqueous phase. In regards to using bioleaching as a
treatment, the authors concluded that it would be ineffective for lead. Lead would be rapidly precipitated
as sulfate and hence remain in the solid phase. It was also regarded as less suitable than chemical
leaching for zinc removal. However, bioleaching may have a significant environmental impact for zinc
spoils, even if reprocessed, in cases where iron sulfide is also present and conditions are aerobic.
6.5.10 Project 35: Combined In Situ Soil Vapor Extraction within Containment Cells
Combined with Ex Situ Bioremediation and Groundwater Treatment
Initial laboratory-scale studies discounted the need for using inocula in the proposed biopile system.
Nutrient addition and aeration were found to enhance biodegradation at this scale. However, at full-scale,
attempts to reproduce optimization through nutrient addition were not found to be cost effective.
Following the main works, it was noted that the main factors affecting the degradation process were
aeration and ambient temperature. Attempts to replicate the laboratory conditions indicated as beneficial
showed no cost benefits at full-scale. Significant reductions in the contaminant levels were achieved
through redistribution and volatilization. Often these processes alone were enough to achieve the
specified criteria, with no further action required. A key contribution to success is careful management
of material batches and the screening of materials before placement in the biopiles. Treatment targets
were set by the local regulatory authorities to allow reuse of the treated material onsite. No additional
information on removal rates was reported.
6.5.11 Project 36: Investigation of Enhancement Techniques for Ex Situ Separation
Processes, Particularly with Regard to Fine Particles
Bench-scale (10 L) bioreactor degradation of organic contaminants produced from a pilot-scale soil
washing plant was investigated. Soil washing treatment residues for a gasworks soil and a diesel
contaminated soil were tested.
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For the gasworks soil, the <0.063 mm fraction was tested. Management of pH was difficult, with large
decreases in the first 4 days of operation requiring correction. In addition, CO2 was consumed by the
process over this period of time. The authors believe this was due to the stimulation of chemolithotropic
organisms, such as Thiobacillus, metabolizing sulfide compounds in the gasworks material. Three
bioreactor tests were carried out: one at 12°C, one at 12°C with added nitrogen (N) and phosphorous
(P), 25°C operation with added N and P. The best performance came from the 25°C treatment, but still
only 40-50% of PAHs and 20% of TPH were removed after 28 days. There was no indication of cyanide
degradation. It was suggested that the initial problems with acidification reduced the potential for PAH
degradation.
Greater success was achieved for the diesel-contaminated soil. The size fractions 0.002-0.01 mm and
<0.002 mm were treated. (Note that the performance of the soil washing stages is discussed in Chapter
4). A single test of degradation in a bioreactor at 15°C with no additives was carried out for the 0.002-
0.01 mm fraction. Three tests were carried out for the <0.002 mm fraction: 15°C no additions; 15°C plus
N and P, 25°C plus N and P. Two flushes of activity were noted for the <0.002 fractions tested, the first
over the initial three days of treatment, and a second less intense flush some 8 to 10 days later. The
authors postulated that during the first flush microorganisms degraded readily available substrates, and
then a period of acclimation took place to deal with more complex substrates, resulting in the second
flush of activity (as measured by CO2 release). The size of the flush was enhanced by both temperature
and nutrient addition. Similar removal rates for TPH (80%) were observed for both the 15°C and 25°C
treatments with N and P addition. The removal rate for the 15°C treatment was around 20% without
nutrient addition, similar to the removal rate found for the <0.002 to 0.01 mm fraction, which was also
tested at 15°C without nutrient addition. The duration of all four tests was 28 days.
6.5.12 Project 43: Multi-Vendor Bioremediation Technology Demonstration Project
Aeration of two 76-m3 test piles (Table 6.3) was found to be difficult because of the fine texture of the
soil being treated. Average removal percentages of VOCs by the biopile technologies ranged from 43-
99%, depending on the compound.
Soil clean-up goals were set by the New York State Department of Environmental Conservation for six
VOCs: acetone, 200; methyl ethyl ketone (MEK), 600; methyl isobutyl ketone (MIBK), 2,000; PCE,
2,500; trichloroethene (TCE), 1,500; and dichloroethene (DCE), 600 ug/kg. Ninety percent of the tested
samples were to meet these targets to achieve compliance (success) in the test.
Only 79% of the samples from the biopile treatment met these limits, so on these grounds it was deemed
unsuccessful. Stripping and volatilization accounted for some of the VOC removal. The treatment
duration was nine months. The aeration used was negative forced aeration (i.e., air was sucked through
the piles). Evidence from conventional composting technology is that negative aeration tends to be less
effective for process optimization, especially for finely-textured materials such as sewage sludges (52).
However, positive aeration would require containment of the process to prevent the release of VOCs.
6.5.13 Project 49: Characterization of Residual Contaminants in Bioremediated Soil and
Reuse of Bioremediated Soil
The availability of residual contaminants remaining after biological treatment was tested by leaching
tests. Biodegradability studies and bioassays of the residues' toxicity were also performed. The nature
of the treatment process was not specified, only that it was a commercial treatment plant, presumably
ex situ and offsite. Dissolved organic carbon levels in the leachate of the treated soil were comparable
to those from gravel. The residual organic contaminant levels, while detectable, were found to be only
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slowly leachable and only slowly biodegradable. Only around 10% degradation was observed over a two-
year period. No negative impact was found on the growth yield for a number of plant species compared
with controls in growth trials. Indeed, a significant enhancement was reported. Patterns of plant growth
were normal. Ecotoxicity tests (using Daphnia and Vibrio flcheri) did not detect significant toxicity from
soil leachates. A qualitative risk assessment based on the experimental findings concluded only a low
possibility of adverse effects on human health and the environment from residual contaminants in the
treated soil.
6.5.14 Project 54: Treatment of PAH- and PCP-Contaminated Soil in Slurry Phase
Bioreactors
A trial using a 1-m3 Eko Tec bioreactor over 28 days was carried out at 24-28°C. Biostimulation and
bioaugmentation were conducted. Input material was screened at 2-3 mm, and the total PAH concentra-
tion was 859 mg/kg. The residual concentration after treatment was 75 mg/kg. In a second trial, the Eko
Tec bioreactor was evaluated in parallel with a 450-L EIMCO reactor. In this case, concentrations of
total PAHs were 313 mg/kg and 164 mg/kg, respectively. Both bioreactors yielded total PAH levels of
48 mg/kg after 28 days. Emissions of VOCs were found to be negligible. Eko Tec also reported a PCP
treatment trial, using soil with an initial PCP level of 630 mg/kg. Redox conditions were varied from
anaerobic to aerobic over a 6-week period. The exact nature of the process was not described. The PCP
level after treatment was reported to be 80 mg/kg. An unspecified composting treatment was also found
to reduce PCP levels over a 4-month period, with initial and treated concentrations of 126 mg/kg and
75 mg/kg, respectively. The full-scale process will be included in the Phase III Pilot Study.
6.6 GENERAL DISCUSSION OF PROJECTS
The general level and quality of information provided in a number of projects is inadequate to support
a detailed discussion. However, the following points were worthy of note.
Ex situ biological treatments, with the possible exception of bioslurry reactors, are rapidly becoming
established technologies for contaminated solids. The number of full-scale demonstrations and commer-
cial projects has increased for several of the treatment approaches included in the Pilot Study, in
particular for biopile and cultivation-based approaches. These approaches appear to be robust and
relatively simple treatments for organic contaminants including simple alkanes and aromatics, as well
as for more recalcitrant compounds such as 3- and 4-ringed PAHs and PCP. However, this is not a uni-
form picture. Biological treatments may fail to reach desired targets, even where there are good
experimental reasons to believe that they should succeed. The reasons for this often appear to be
associated with the texture of the contaminated medium, its organic matter content, and its age (Section
6.8).
While it is hard to make a generalization, it does appear that the technical "know-how" of the
remediation contractor is also a key factor to success. The likelihood of success for solid phase
treatments appears to be related to the "ingredients" in the mix of materials used, and to relatively
simple process changes. Examples of these simple changes include how to improve porosity for fine-
grained soils, how to improve activity for low initial concentration or for aged contaminants, and how
best to optimize the flow of air and water.
One issue that is well-known in waste composting but has been little reported in biopile projects is that
of "edge effects." Materials at the edge of a static pile or treatment bed may be affected by greater
variations in process conditions such as temperature, moisture, or nutrient supply, but conversely have
better access to oxygen. The significance of edge effects is that treatment effectiveness depends on
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where the contaminated material is in the pile, bed or windrow. The idea of zones of activity is
recognized in composting (22, 52) as a particular problem for static systems. As a result, turning is
commonly employed for windrows, for actively aerated "piles," and in-vessel to ensure that edge effects
have no lasting impact on overall treatment effectiveness and to reduce heterogeneity of the treated
product through mixing.
Bioslurry reactors have not seen widespread adoption at a practical scale. However, treatment in
bioslurry reactors, as indicated by some of the Pilot Study projects, may extend the range of biologically
treatable contaminants, for example to include higher PAHs. However, this technology is also more
expensive and creates a need for dewatering of the treated product and, as a result, process water
handling. One application where bioslurry reactors may have a competitive edge is in situations where
a material is already in a liquid or semi-liquid form. Examples examined by Pilot Study projects are
treatment concentrates from soil washing.
The majority, if not all of practical ex situ biological treatments, rely on biodegradation processes
mediated by bacteria—mostly as a direct carbon source for microbial growth. Fungal lignolytic activity
has long been recognized as a possible means of extending the range of biologically treatable contamin-
ants, to more insoluble and recalcitrant compounds (Section 6.2.2). Of course, many such contaminants
may be biodegradable ultimately by bacteria, but the lignolytic attack mediated by nonspecific enzymes
and free radicals may be faster. It may be conjectured that fungi may offer the opportunity to extend the
range of contaminants treatable in simple solid phase systems, to include those currently regarded as
being practically biodegradable only in bioslurry reactors.
As a final comment, there appear to be two sets of competing factors that fundamentally determine the
effectiveness of an ex situ biological treatment:
• The competing needs to use pore space for air and water movement, discussed below in the context
of forward and reversed aeration, but also evident in trying to supply solutions (e.g., of nutrients or
detergents) at the same time as supplying air; and
• The need to mobilize and render contamination available to facilitate biodegradation (which typically
means moving it to gaseous or liquid phase), versus the need to limit process emissions of
contaminants in vented air or in leachate.
6.7 RESIDUALS AND EMISSIONS
Residuals and emissions generated from the projects are summarized by project in Table 6.6. Whether
collected or left to disperse, gaseous and aqueous phase emissions are likely for any biological treatment
(ex situ or in situ) based on biodegradation. Gaseous emissions in process air or that leave the surface
of treatment beds or windrows comprise VOCs that are stripped and not biodegraded. Forced aeration
tends to increase the amount of VOCs stripped and volatilized. The amount of VOCs lost to volatiliza-
tion is dependent on the nature of the contamination. Amounts recorded for semivolatiles such as PAHs
were low, but were high for solvents.
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Table 6.6: Residuals and Emissions
Project
6
8
11
15
24
25
26
28
31
35
36
43
49
54
In w'/M/on-site bioremediation of industrial soil
contaminated with organic pollutants
BiodegradatioiVbioventing of oil-contaminated
soils
On-site biological degradation of PAHs in soil
at a former gasworks site
Combined chemical and micro-biological
treatment of coking sites
Combined remediation technique for soil
containing organic contaminants: Fortec
Slurry reactor for soil treatment
Treatment of creosote-contaminated soil (soil
washing and slurry phase bioreactor)
Use of white-rot fungi for bioremediation of
creosote-contaminated soil
Decontamination of metalliferous mining spoil
in situ SVE within containment cells combined
with ex situ bioremediation and groundwater
treatment
Enhancement techniques for ex situ separation
processes, particularly with regard to fine
particles
Multi-vendor bioremediation technology
demonstration project
Characterization of residual contaminants in
bioremediated soil and reuse of bioremediated
soil
Treatment of PAH- and PCP-contaminated soil
in slurry phase bioreactors
Comments on Residuals and Emissions
No leachate generation was recorded. Oversize
screenings were the main process residue.
Leachate is reportedly recirculated to irrigate the
biopile, but no information on generation rates was
provided. Vented air is treated by a biofilter card,
which apparently removes 85% of the VOC's passing
through it. Oversize rejects may also be a significant
process residual.
Pilot trial. No practical information reported.
Not reported.
Process and dewatering effluent not recycled elsewhere
in the soil washing plant may be a significant
emission. (For residues from the washing stage see
Chapter 4.)
Process effluent and water from solids removal that are
not recycled, oversize reject material, and process air
emissions.
Process effluent and water from solids removal that are
not recycled, process air emissions. (For residues from
the washing stage see Chapter 4.)
Not applicable.
See comments in text.
For the biopile process, vented air (significant VOC
removals due to volatilization were reported) and
leachate.
Presumably bioreactor and dewatering effluent.
Presumably bioreactor process air.
VOCs in process air emissions.
Not applicable.
Screened oversize (>2-3 mm) and presumably excess
water from bioreactor and dewatering operations.
Not all of the biopile or bioreactor studies reported here record the steps being taken to treat process air.
Reversed aeration (suction) is a common approach to ensuring that process air from aeration of biopiles
can be collected; for example for subsequent treatment in a biofilter (e.g., a peat bed). Reversed aeration
is not, however, optimal for enhancing the degradation process, particularly as particle size decreases.
A recognized effect of reversed aeration in waste composting (22) is that the pile retains a higher
moisture content and that moisture is drawn to the center of the pile to points of suction. This effectively
clogs the system's air supply, reducing the amount of air that can be delivered to the system.
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Steps to contain process water and leachate containment were reported for many trials. However,
treatment of the process water was not typically described, but presumably relied on capture and
recirculation.
Most biological processes are intended to destroy contaminants rather than collect them in a solid waste
residual. Nonetheless, residual contaminants are commonly detected in treated soils after processing. It
appears from Project 49, which deals with residuals from biological treatment, that such residuals can
be effectively inert, at least in terms of risk management. However, that should not be taken as a blanket
assumption.
The most common solid process residue is over-size material after screening prior to biological
treatment. While this may not be important for an approach integrated with, for example, a soil washing
plant, it could lead to large volumes of solid residues for approaches centered on a biological treatment
such as a biopile. One possibility is to crush such materials and incorporate them in the biopile if testing
indicates they require treatment.
6.8 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE APPLICABILITY
OF THE TECHNOLOGY
The majority of ex situ treatment technologies with established track records are relatively simple to
apply and relatively robust in the hands of an experienced operator. Table 6.7 lists key factors and
limitations found for the various projects discussed in this chapter including:
• Biodegradability and bioavailability (which may be linked to the age and initial concentrations of
the contaminants as well as the sorptive capacities of the solid matrix);
• Dewatering and water handling for slurry-based processes;
• Dealing with edge effects and heterogeneity and ensuring adequate process control (e.g., air and
water supply) for solid-phase technologies;
• The texture of the treated material (content of fine particles); and
• The distribution of contaminants by particle size for slurry-based systems.
Two other interesting observations were made:
(1) Project 36 postulated that interactions between different biological processes could limit the success
of slurry-phase treatment of soil at gasworks sites. It was also suggested that sulfide oxidation
leading to changes in slurry pH might have limited subsequent biodegradation of PAHs.
(2) Based on the results of several of the Pilot Study projects, laboratory-, bench-, and pilot-scale tests
do not always predict the performance of full-scale treatment.
In the absence of an adequate fundamental understanding, know-how appears to be a key factor in
process prediction: both in interpreting test data, and in knowing which tests to carry out. This comment
links back to the earlier comment that in general treatment performance may be linked to empirical
operational expertise of the practitioner.
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Table 6.7: Key Factors Limiting Performance
Project
6
8
11
15
24
25
26
28
31
35
36
43
In s/Ytt/on-site bioremediation of
industrial soil contaminated with
organic pollutants: elimination of
soil toxicity with DARAMEND®
Biodegradation/bioventing of oil-
contaminated soils
On-site biological degradation of
PAHs in soil at a former
gasworks site
Combined chemical and
microbiological treatment of
coking sites
Combined remediation technique
for soil containing organic
contaminants: Fortec
Slurry reactor for soil treatment
Treatment of creosote-
contaminated soil (soil washing
and slurry phase bioreactor)
Use of white-rot fungi for
bioremediation of creosote-
contaminated soil
Decontamination of metalliferous
mining spoil
In situ soil vapor extraction
within containment cells
combined with ex situ
bioremediation and groundwater
treatment
Enhancement techniques for ex
situ separation processes,
particularly with regard to fine
particles
Multi-vendor bioremediation
technology demonstration project
Comments on Factors Limiting Performance
• Proportion of more recalcitrant organics (e.g., higher PAHs).
• Ambient conditions and their impact on possible leachate generation.
• Maximum treatment depth (in situ application) of 0.6 m.
• Proportion of oversize material.
• Biodegradability/availability.
• Proportion of oversize material.
• Temperature, although piles can be air heated.
• Soil texture. Heavier soils are harder to treat, which increases costs
because of their more difficult materials handling properties and
often extended treatment time.
• Aging, which was thought to have reduced the biological treatability
of the PAHs, along with sorption to soil particles.
• Turning the windrows?
• Initial concentration of PAHs? (related to aging factor).
No relevant information provided.
• Contaminant distribution by particle size.
• Biodegradability/treatability by photooxidation.
• Soil composition (texture and organic matter content).
• Contaminant distribution by particle size.
• Contaminant bioavailability and biodegradability.
• Presumably contaminant distribution by particle size.
• Contaminant bioavailability and biodegradability.
• Optimization of the biodegradation process in the reactor.
No relevant information provided.
Bioleaching was not recommended as a treatment option.
• Treatment is more difficult for heavier, less porous fractions.
• The main process factors affecting the degradation process at full
scale were aeration and temperature.
• Process optimization through nutrient addition was not found to be
cost effective at full-scale.
• Dewatering the treated slurry. Up to 57% solids could be achieved
after 10 minutes of filtration at 1,600 Kpa with calcium hydroxide
as a coagulant.
• Temperature and nutrient addition strongly affect bioreactor
performance.
• The nature of the contaminated matrix (e.g. , sulfide content. See
text).
• Bioavailability and biodegradability of contaminants.
• Soil texture affects aeration.
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Project
49
54
Characterization of residual
contaminants in bioremediated
soil and reuse of bioremediated
soil
Treatment of PAH- and PCP-
contaminated soil in slurry phase
bioreactors
Comments on Factors Limiting Performance
Not applicable (see text).
No relevant information provided. Limitations are presumably similar
to bioreactors in general.
6.9 COSTS
Scant cost data could be compiled for most projects. What could be gleaned is summarized in Table 6.8.
However, it would be wise to treat the data in Table 6.8 with a great deal of caution. Costs are strongly
dependent on site specific factors, and cost data were reported in different years.
6.10 FUTURE STATUS OF THE CASE STUDY PROCESSES AND THE TECHNOLOGY AS
A WHOLE
The pilot study projects discussed here as case studies are an interesting cross-section of the biological
treatments applied to solid materials and slurries. Dealing with the technology overall first, it is clear
that ex situ biological treatments are an effective means of dealing with many contamination problems
and offer great advantages over in situ approaches in terms of process control, monitoring and
assessment, and treatment duration. These advantages come at a premium. This premium encompasses
the possibility of higher costs, a more intrusive response, and greater visible generation of process
residuals and emissions. In some situations, the specific circumstances of a site's redevelopment make
this premium worth paying for the ex situ treatment advantages.
Across Europe, great attention is being paid to the treatment of wastes in general, with a desire to reduce
the volumes of material being landfilled, more specifically the disposal of biodegradable or chemically
active wastes. These desires are manifest in the latest Landfill Directive draft and the intention for a
Directive on composting. It would therefore seem likely that possibilities for synergy in the co-treatment
of different waste types will be of increasing interest. It also seems likely that landfill operators and
waste management companies will become more open to treatment-based waste management solutions.
It may be that these two factors will extend to wastes arising from contaminated sites and offer new
opportunities for offsite and integrated treatment plant. Ex situ treatment also offers the opportunity for
on-site recycling, and it does seem likely that future redevelopment projects will take a more strategic
and integrated view of risk reduction, waste minimization, and construction requirements.
Biopile, windrow, and treatment bed approaches are now well established approaches and because of
their track record and the know-how acquired for them, these approaches seem set to be used more
widely. So far as fundamental advances are concerned, the best place to look for these might be around
the resolution of the two process conflicts outlined in Section 5: air versus water movement; and
mobilization versus containment.
Bioslurry bioreactor technologies are under active development, but at present are not easily cost-
competitive. However, bioreactors for slurries are likely to continue to be a useful approach for specific
circumstances, such as the treatment of sludges from soil washing.
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Table 6.8: Cost Information by Project
Project
6 In s/Yw/on-site bioremediation of industrial soil
contaminated with organic pollutants: elimination of soil
toxicity with DARAMEND®
8 Biodegradation/bioventing of oil-contaminated soils
1 1 On-site biological degradation of PAHs in soil at a
former gasworks site
15 Combined chemical and microbiological treatment of
coking sites
24 Combined remediation technique for soil containing
organic contaminants: Fortec
25 Slurry reactor for soil treatment
26 Treatment of creosote-contaminated soil (soil washing
and slurry phase bioreactor)
28 Use of white-rot fungi for bioremediation of creosote-
contaminated soil
3 1 Decontamination of metalliferous mining spoil
35 In situ soil vapor extraction within containment cells
combined with ex situ bioremediation and groundwater
treatment
36 Enhancement techniques for ex situ separation processes,
particularly with regard to fine particles
43 Multi-vendor bioremediation technology demonstration
project
49 Characterization of residual contaminants in
bioremediated soil and reuse of bioremediated soil
54 Treatment of PAH- and PCP-contaminated soil in slurry
phase bioreactors
Comment
In situ unit costs are estimated to be U.S. $46-
92/m3, and ex situ process costs are estimated
to be U.S.$96-140/m3 (1995).
Based on the 24 case studies reported,
0-5,000 tons, $45-90/ton;
5,000-25,000 tons, $30-45/ton; and
>25,000 tons, $15-30/ton.
The type of "ton " is not specified, nor is it stated whether
Canadian or U.S. dollars are used.
Not applicable.
Not applicable.
Cost data not provided.
Cost data not provided.
Estimated to be U.S.$530/m3 of froth flotation
sludge (1993).
Not applicable.
Not applicable.
The biological treatment costs were not
separately reported.
The authors felt that reporting treatment
would be misleading as they depend on
many site-specific factors.
costs
too
Estimated to be U.S.$71/m3 (1996).
Not applicable.
Not reported.
Bioreactor technologies for the solid phase may be a suggestion for useful future development, taking
advantage of existing waste composting technology and know-how. In-vessel treatments, particularly
those involving mixing, offer advantages over cultivation, biopile, and windrow systems including better
containment, process control and monitoring, as well as improved product homogeneity and elimination
of edge effects. An opportunity for such enhanced process control is to make better use of fungal
processes, which tend to be inhibited above 50°C, or to achieve sequential aerobic and anaerobic effects.
More complex ex situ biological treatments may tend to be most easily installed as fixed plant, perhaps
as part of an integrated wastemanagement system.
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6.11 ACKNOWLEDGEMENT
Note the author acknowledges the support of the Environment Agency for England and Wales and the
U.K. Department of the Environment Transport and the Regions (DETR) which supported his attendance
of the Pilot Study. However, the views expressed in this paper are those of the authors only and do not
necessarily reflect the views of the Department of the Environment. The work of Ian Martin (now with
the Environment Agency) is also acknowledged. Mr. Martin is a co-author of several of the papers that
this summary chapter draws upon.
6.12 DISCLAIMER
Reference to any individual or organization or mention of any proprietary name or product in this report
does not confer any endorsement by the author, nor the Environment Agency, nor DETR.
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Chapter 7: EX SITU THERMAL METHODS
Michael A. Smith
M.A. Smith Environmental Consultancy, U.K.
7.1 INTRODUCTION
Thermal treatment methods use heat to remove or destroy contaminants (1). Some methods also
encapsulate contaminants that cannot be volatilized or burned. Processes vary with respect to:
• the heat source (e.g., heated air or another gas, open flame, or liquid heat-transfer medium) and
method of application (direct or indirect contact);
• operating temperature;
• phasing of the process (i.e., one or more stages);
• the equipment used to contain the thermal process and provide heat and mass transfer (e.g., a rotary
kiln or fluidized bed reactor);
• the materials handling methods used both before and after treatment; and
• methods used to collect and contain and treat air and other emissions from the process.
7.2 MAIN PROCESS VARIATIONS
Three main types of thermal treatment can be identified for contaminated soils, sediments, sludges, filter
cakes (e.g., from soil washing) and similar materials:
(1) Thermal desorption in which contaminants are removed from the feedstocks at relatively low
temperatures and then destroyed or collected from the gas stream in a subsequent stage;
(2) Incineration (thermal destruction) in which contaminants are destroyed at high temperature; and
(3) Vitrification in which very high operating temperatures destroy some contaminants and trap others
in a glassy product.
The thermal process projects reviewed in this chapter involved either thermal desorption or incineration,
and the introductory sections that follow concentrate on these forms of treatment. In practice, there is
no clear technical distinction between thermal desorption and incineration, since thermal desorption of
contaminants occurs during incineration of soils or other solids, and partial combustion of desorbed
organic compounds often occurs within a desorber unit or downstream in a fume incinerator, depending
on the design.
Existing industrial thermal processors, such as cement kilns and coal-fired boilers, are also sometimes
used for organic-rich residues. Other thermal processes can be used for specific contaminants; for
example, retorts have been specified by the USEPA for the treatment of mercury-contaminated soil.
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7.3 DESCRIPTION OF MAIN PROCESS VARIATIONS
7.3.1 Thermal Desorption
Thermal desorption methods physically separate volatile and semivolatile1 contaminants from soils,
sludges, and sediments. They do not generally result in a high degree of thermal decomposition of
contaminants, although temperature variations between different systems may allow for some localized
oxidation or pyrolysis. The thermal desorption unit is only one part of a treatment train; some
pretreatment of feedstocks and post-treatment of treated soil or separated contaminants is usually
required.
Efficient separation can occur at temperatures of up to 600°C, although temperatures may reach 900°C
during the primary stage in some specialized systems. In practice, many systems operate at relatively
low solids temperatures; even polychlorinated biphenyls (PCBs) can be removed at 450-500°C. An
important design parameter is the length of time that soils remain at the target temperature.
Separated contaminants, water vapor, and particulates must be collected and treated. Typically, this is
done using conventional methods of condensation, adsorption, incineration, filtration, etc. The methods
are selected according to the nature and concentration of contaminants, regulatory regime, and economics
of the system employed. It may be possible to recover separated contaminants for reuse. Thermal
desorption systems that employ combustion or other oxidation processes for treating the off-gas can
accomplish the same goal as incineration—i.e., destruction of contaminants.
Two basic configurations are available:
(1) Direct systems, in which heat is transferred by convection, radiation from heated air (or another gas),
or an open flame to the contaminated feedstock; and
(2) Indirect systems, in which heat is transferred by conduction from the heat source to the contaminated
feedstock.
Project 7, in which soil was floated on molten metal, can be regarded as a directly heated system, while
Project 13 involved two indirectly heated stages. A classification of thermal desorption systems is shown
in Figure 7.1. In practice some commercial types occupy a hybrid position and are capable of operating
in different modes. Most systems of both types employ rotary kilns, although more innovative systems
use various types of conveyors (e.g., screw, paddle, mixing, or belt). Fluidized beds are also under
development (see Project 20).
The achievable solids-treatment temperature is a function of the temperature of the heating medium as
well as the heat transfer area and the heat burden posed by the feedstock. Both directly and indirectly
heated desorbers can be classified as low- or high-temperature systems. High-temperature desorbers can
achieve solids temperatures comparable to some incinerators, depending on the design, operating
conditions, and the volatility and thermal characteristics of the contaminants. In the U.S., many thermal
desorption units are regarded as low-temperature systems and are employed for soils contaminated with
hydrocarbon fuel. Evolved water and volatile compounds may be swept from the processor using an inert
gas such as nitrogen or oxygen-deficient (<4 % by volume) combustion off-gas (see Project 13).
1 What matters is whether the contaminants of concern are volatile under the conditions of temperature, etc.,
in the desorber. The terms "volatile" and "semivolatile" are here used as in much USEPA literature.
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Thermal desorption
Direct systems
Indirect systems
Open flame
Separate burners
Heated shell
Conveyor
Infra-red heated
Fired or Heattransferfluid
electrically may circulate through
heated conveyor flights
and jacket
x Conveyor
Classified as directly heated
since there is no barrier
between the heat source
and the soil
Note: In some texts the term 'direct' is confined to those systems employing an open flame.
Figure 7.1: A Classification of Thermal Desorption Systems
Depending on the pretreatment handling processes used and the temperatures applied during treatment,
thermal desorption may not significantly alter the physical properties of the soil or its ability to support
vegetation, although resident microbial populations will have been affected. Provided the material
conforms to all site-specific remediation standards, it may be returned for reuse onsite. At high operating
temperatures, however, the natural organic constituents of the soil (e.g., humic acids) are broken down.
This reduces the utility of the treated product for landscaping. Furthermore, changes in mineral properties
may lead to a loss of cohesiveness, and the loss of water from clay matrices may render them potentially
reactive (pozzolanic).
Directly Heated Processes
Direct processes usually take place in a rotary kiln into which externally heated air or gas is introduced
or an open flame provided. Energy requirements vary according to the moisture content of the
contaminated feedstocks, the maximum bed temperature required, ambient temperatures, maximum gas
combustion temperatures, and the extent to which heat is transferred and recovered from the kiln exhaust
gases.
Indirectly Heated Processes
Indirect methods operate by transferring heat across a metal surface, either from a fired or electrical
furnace adjacent to the desorber or from a heated fluid, such as steam, flue gas, air, heat transfer liquid
or molten salt. Indirect heating can be carried out in a rotary unit (similar to a rotary calciner) with a
furnace shell surrounding the rotating desorber, or in conveyor systems equipped with a travelling belt
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or pipes or hollow augers through which a heat transfer medium (such as steam, oil, or molten salts) is
fed.
In the conveyor systems, screw conveyors or hollow augers are used to transport the soil or other
feedstock, continuously through an enclosed trough. Hot oil or steam circulates through the conveyor
or auger to heat the soil. Molten salts have seen limited use. A heat transfer fluid is commonly pumped
through the walls of the trough for additional heat transfer. One, two, or four augers may be arranged
in a trough to provide mixing during the heating and conveying process. More than one trough system
can be run in series to achieve the bed temperature and residence time required. A clean sweep gas, such
as nitrogen or steam, typically is used to convey the vaporized contaminants and water from the troughs.
The sweep gas also may be used to minimize oxidation of the contaminants by reducing the availability
of oxygen. The maximum bed temperature is limited by the properties of the heat transfer fluid and the
materials used to construct the equipment. It also depends on the speed at which soils are conveyed
through the trough(s) and the operating temperature of the heat transfer fluid. Advantages of this type
of desorption unit include simplicity of operation and temperature control, as well as reduced generation
of fines or dust.
A typical indirectly fired rotary unit consists of an outer furnace that is heated and a rotary inner drum
that contains the contaminated soil. The soil is primarily heated by direct contact with the drum and by
radiation from the drum walls. The efficiency of indirect systems relies on the provision of a large heat
exchange area. Compared to directly heated rotary kiln systems, a much smaller volume of gas (approxi-
mately 300 nrVtonne of treated soil) is discharged from the desorber. As a result, secondary combustion
and gas cleaning systems are smaller and more economical to construct compared to those of direct
systems. However, construction costs for indirect systems may be high due to the complexity of the heat
exchanger.
Gas Collection and Treatment
Gas collection and treatment arrangements vary according to the design of the plant, whether it is
directly or indirectly heated, its capacity and the type of contaminants being treated. Regulatory
requirements on acceptable emissions are also important, as is the availability of a water supply and
discharge facility. Gas collection and treatment systems in common use include:
• combustion of volatile contaminants at high temperatures (up to 1,400°C) in an afterburner followed
by gas cleaning and discharge through a stack;
• thermal treatment at moderate temperatures (200-400°C) using catalysts (e.g., nickel or zinc/ copper)
to assist oxidation, followed by gas cleaning and discharge through a stack;
• for indirect heating systems, conventional low-temperature scrubbers using water or organic solvents,
and activated carbon absorption; and
• for indirect systems, condensation of volatile compounds with possible recovery.
A combination of systems may be necessary to comprehensively treat all the constituents present in the
gas phase exiting the primary desorber.
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7.3.2 Incineration
Incineration (thermal destruction) destroys contaminants at high temperature (800-1,200°C). Specifically,
incineration is a high-temperature oxidation reaction between combustible substances and oxygen under
controlled conditions of retention time, temperature, and turbulence within a single- or multiple-stage
combustion chamber2. Although organic contaminants are destroyed in the process, air pollution control
equipment must be provided to collect and treat combustion products, particulates, and volatile metals
present in exhaust gases. Incineration of soils and sediments involves volatilization and desorption of
water and organic contaminants (and some inorganic contaminants), as in thermal desorption. A
secondary combustion chamber to complete oxidation of the volatilized materials is generally required.
The high temperatures used during incineration have implications for the reuse of the treated soil due
to changes to the physical, chemical, and biological properties of the material. Changes in soil texture
together with the loss of natural organic constituents, reduce the ability of treated material to support
vegetation and may affect engineering properties. The loss of soil structure and organic content also may
increase the teachability of any heavy metals remaining in the treated product. Further treatment, e.g.,
stabilization/solidification (Chapter 8), may therefore be required before the material is acceptable for
reuse.
A wide range of incineration techniques have been developed for the treatment of contaminated soils,
sediments, and sludges, including direct-fired rotary kilns, fluidized beds, and infrared belt conveyor
systems.
Direct Fired Rotary Kiln Incinerators
Direct fired rotary kiln incinerators typically contain a primary and a secondary combustion chamber.
The primary chamber is a cylindrical, sloping, rotating, refractory-lined shell in which the soil is dried
and heated by firing fuel or liquid wastes with a high calorific value. The secondary combustion chamber
provides additional capacity for any contaminants not destroyed at the primary stage. Soil may move
with, or counter to, the direction of gas flow. The kiln can be designed to operate in an oxidation mode
or pyrolysis (anoxic) mode, with the latter generating smaller volumes of flue gas. Rotation and
inclination provide the necessary mixing and heat transfer functions. Gases exiting the secondary
combustion chamber pass through a multi-stage gas cleaning plant.
Fluidized Beds
Fluidized beds have been used for the treatment of waste liquids and sludges and, on a more limited
scale, of contaminated soils and sediments. In these systems, air or combustion gases are used to develop
and maintain a fluidized bed of solid particles derived from sand or the inorganic residue from the soil
or waste being treated. The continuous movement of the solids in the bed promotes rapid heat and mass
transfer, and hence destruction of the contaminants. Continuous removal of bed solids is required for the
treatment of soil or sediments. Additional fuel is added as necessary to maintain a bed temperature of
between 700-1,200°C, although temperatures must be limited to prevent sintering. Particulates escaping
the bed are generally recovered in a cyclone and returned to the combustion chamber if treatment is
incomplete.
2 Thermal processors also can be operated at high temperatures under anoxic conditions, so that pyrolysis
(reductive degradation) of organic substances occurs.
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Infrared Incinerator Systems
Infrared systems use infrared radiant heat (generated by electrically powered silicon carbide elements)
to heat organic wastes to combustion temperatures. A typical configuration comprises an infrared
primary chamber, a gas-fired secondary combustion chamber, an emissions control system, and a control
center. Mobile infrared incineration systems have been developed for use in the United States.
7.3.3 Vitrification
Vitrification destroys contaminants by oxidation and thermal decomposition and immobilizes residual
contaminants in a vitreous product. The advantages of vitrification over other thermal treatment
processes are that it produces fewer air emissions and a solid residue with favorable leaching
characteristics.
Vitrification systems consist of a melter, heat recovery system, air pollution control system, and storage
and handling for feedstock and raw materials. There are various configurations for melters, some of
which are multi-chamber and others which use mechanical agitation. Energy requirements are significant
where feedstocks have a high mineral content. The most common melters are heated by electrical
currents passed through the melt mixture from electrodes. Variations between melters include the method
of introducing feed, the degree and type of mixing, electrode design, and the means of achieving
complete combustion of organic compounds. More recent melter designs utilize alternative methods of
introducing heat and have different heat and mass transfer characteristics.
Typical melt temperatures are about 1,500°C. Sufficient glass-forming material (silicate) must be present
to produce a proper melt that will result in a durable vitrified product. This may require the addition of
fluxing agents. Molten product is continuously drawn off the melter either into containers for cooling,
solidification, and handling, or through some type of cooling process to produce granular solids.
Emissions of the more volatile metals is a potential concern, and air pollution control systems must be
highly efficient. Process residues include glass/vitrified waste, molten metal (not produced as a separate
phase in most processes), scrubbing and cooling liquors, and off-gases.
Commercial vitrification systems have been developed for the treatment of contaminated soils and
sediments in the U.S. where a number of vendors have field-, bench- and pilot-tested the technology.
Most of these systems were modifications of different types of glass-making furnaces, and development
was directed initially towards radioactive or other highly hazardous solid wastes. One commercial facility
in the United States was used to treat organic wastes for several years.
7.4 DETERMINATION OF EFFECTIVENESS
The effectiveness of both thermal desorption and incineration (thermal destruction) systems should be
judged on the basis of their ability to achieve target residual concentrations while complying with
emission limits to air, etc.
The primary technical factors governing the performance of thermal desorption processes are the
maximum bed temperature achieved; the total residence time; the content of organic contaminants and
water; contaminant characteristics; and medium (e.g., soil) properties.
Since the basis of the processes is the physical removal of contaminants from the medium by
volatilization, bed temperature directly determines end point concentrations. The degree of mixing and,
where applicable, sweep gas rate will also affect the effectiveness of the process.
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The primary technical factor affecting performance of thermal destruction (incineration) systems is also
the maximum bed temperature of the solids. Overly large particle sizes lead to poor performance. A high
proportion of fines leads to high dust loading in the downstream air pollution control system.
7.5 CASE STUDIES CHOSEN
The projects reviewed for this chapter are listed and described in Table 7.1. Brief descriptions of the
projects are provided in Sections 7.5.2 to 7.5.6. Project summaries can be found in Appendix IV.
Table 7.1: Projects Involving Ex Situ Thermal Treatment
Project
7
13
19
20
21
Demonstration of thermal gas-phase
reduction process
Rehabilitation of a site contaminated
by tar substances using a new on-site
technique
Cleaning mercury -contaminated soil
using a combined washing and
distillation process
Fluidized bed soil treatment process —
BORAN
Mobile low-temperature thermal
treatment process
Description
Key feature is the high temperature (850°C) thermal reduction
unit. Contaminants in soils are volatilized in a specially
designed thermal desorber and then injected into the unit.
Contaminated aqueous phases are vaporized before injection.
Successfully demonstrated by USEPA's SITE Program in 1992.
Integrated soil washing and two-stage thermal treatment
employing ventilated tent to reduce atmospheric emissions.
Integrated soil washing and vacuum distillation plant used to
treat mercury-contaminated soil and debris. Started operation in
1993.
Fluidized bed thermal desorption plant with high-temperature
afterburner intended to treat soils and residues from soil
washing plants. Full-scale, but regarded as test plant by the
design/operating company. In September 1996, the plant was
undergoing modifications to overcome feed problems.
Low-temperature (<300°C) sealed processor employs steam
injection. Pilot plant successfully operated in 1994 and 1995.
Three projects (Projects 7, 20 and 21) involved the use of ex situ thermal treatment as the main
treatment element, and two (Projects 13 and 19) used ex situ thermal treatment as the second element
of a treatment train. In both cases, the first element was a soil washing process.
7.5.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process
The ECO LOGIC thermo-chemical process employs hydrogen to chemically reduce organic compounds
to mineral components at temperatures of about 900°C. Soils are treated with the aid of a novel thermal
desorber involving use of a molten metal bath. A technology demonstration at the Middleground Land-
fill, Bay City, Michigan, U.S., was conducted in 1992 under the USEPA's Superfund Innovative
Technology Evaluation (SITE) Program with partial funding from the Canadian and Ontario govern-
ments. The wastes processed were oily PCB contaminated water, high-strength PCB oils, and PCB-
contaminated soil.
Background
The Middleground Landfill accepted municipal wastes for approximately 40 years. A 1991 investigation
indicated elevated levels in groundwater of trichloroethene (TCE), PCBs, 1,2-dichloroethene, methylene
chloride, toluene, and ethylbenzene. The groundwater contained lesser concentrations of benzidine,
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benzene, vinyl chloride, chlorobenzene, polycyclic aromatic hydrocarbons (PAHs), lindane, dieldrin,
chlordane, and DDT metabolites.
Technical Concept
The ECO LOGIC thermo-chemical process employs hydrogen to chemically reduce organic compounds
to mineral components at temperatures of about 900°C. Chlorinated hydrocarbons, such as PCBs and
polychlorinated dibenzo-p-dioxins, are converted to methane and hydrogen chloride, while non-
chlorinated organic compounds, such as PAHs, are reduced to methane and ethene. Incomplete
reduction/combustion in the system may result in benzene formation (as noted below, residual benzene
was a problem in the demonstration project. Ethene produced by contaminant breakdown may undergo
additional conversion to methane. Methane reacts with water vapor to form hydrogen and carbon
monoxide. The hydrogen chloride is removed in a caustic soda scrubber downstream of the processor.
The reformed process gas can then be recirculated in the system or used as fuel in various stages of the
process. The absence of free oxygen in the reactor inhibits dioxin and furan formation. The process
employs automatic monitoring to maintain optimum operating conditions.
The reactor feed is dependent upon the soil or waste being treated. Aqueous streams, such as
groundwater, are preheated in a vaporizer using steam from a boiler that is fired by propane or process
gas, before injection. When soils or sediments are to be processed, they are first pretreated in a linked
thermal desorption unit (TDU), in which the soil or sediment is floated on a bath of molten tin.
Volatilized contaminants are sent to the reactor through a separate port. Contaminated solids, such as
transformer parts, can be handled in sequencing batch vaporizer chambers. The process is shown
schematically in Figure 7.2.
Recirculating Gas
Exhaust
Gas
9
00°C^
\
Reactor
900°C
*
Sci
jbt
er
35°C „
o
Scrubber
Water
Make-up
Propane.
. Air
Reactor ,, Sludge
Gnt Decant
Stack Gas
Water
Clean Steam
150°C
—<
Boiler
Hydrocarbon
Gas
O
Compressed
Storage
Thermal
Desorptton Unit
| bteam
M .'
^
Combustion
Air
• Propane
' Condensate
Figure 7.2: Reactor and Thermal Desorption Unit Schematic Diagram
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The Demonstration Reactor
The demonstration-scale reactor (Figure 7.3) was 2 m in diameter and 3 m tall, mounted on a 15-m
drop-deck trailer. This trailer carried a scrubber system, a recirculation gas system, and an electrical
control center. A second trailer held a propane boiler, a waste preheating vessel, and a waste storage
tank.
To Scrubber
Waste Injection Ports
Reactor Steel Wall
Fibreboard Insulation
Refactory Lining
Electric Heating Elements
Ceramic-coated Central
Steel Tube
To Grit Box
Figure 7.3: The ECO LOGIC Reactor
In the demonstration, a heat exchanger evaporated contaminated aqueous feedstock to form steam and
a concentrated liquor. Atomizing nozzles sprayed the heated liquor and associated particulates into the
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reactor; a separate set of atomizing nozzles injected the PCB-rich oil directly into the reactor.
Compressed hydrogen-rich recirculation gas passed through a gas-fired heat exchanger and entered the
top of the reactor tangentially. The tangential entry swirled the fluids to provide effective mixing. As
indicated in Figure 7.3, the swirling mixture travelled downwards in the annulus formed by the reactor
wall and the central ceramic-coated steel tube, past electrically heated silicon carbide elements. These
elements heated the mixture to 900°C. At the bottom of the reactor, the mixture entered the central tube
and flowed upwards to the outlet of the reactor. The reduction reactions occurred as the gases travelled
from the reactor inlets to the scrubber inlet.
Heavy particulates dropped out of the gas stream and collected at the base of the reactor in a grit box.
The gas leaving the reactor was scrubbed using a caustic alkaline (pH 9) wet scrubber, which removes
steam, particulates, and gases such as hydrogen chloride. Ninety-five per cent of the exhaust gases
(reheated to 500°C) were recycled, and 5% were used as a supplementary fuel for the propane-fired
boiler. The boiler produced steam, which was used in the heat exchanger and burned the reformed gas.
The exhaust from this boiler was the only source of emissions to air from the process.
Thermal Desorption Unit
The TDU desorbs organic compounds at 500-600°C into a hydrogen-rich carrier gas from soil supported
on a molten tin bath. Hydrogen and tin are used because they do not react. Tin offers favorable
properties: high density, low vapor pressure, high surface tension (which means it does not "wet" the
soil and enter the pores), high thermal conductivity, and good solvent properties for heavy metals such
as lead, cadmium, and arsenic.
Some of each volatile metal present passes to the reactor, some dissolves in the molten tin bath, and the
remainder stays in the soil. Non-volatile metals remain in the treated soil. Quench water cools the soil
before disposal.
During the demonstration, a hopper with a screw feed dropped waste soil onto the tin bath. The screw
feeder provided a gas seal between the hydrogen and the outside air. Once inside the TDU, the soil
floated on the molten tin. A paddle wheel removed treated soil from the end of the tin bath and fed it
to the quench tank.
Materials Processed
The wastes processed were oily PCB contaminated water, high-strength PCB oils, and PCB-contaminated
soil extracted directly from the landfill. The tests on the two liquid wastes yielded information on reactor
performance; the tests on the soil yielded information on the functioning of the complementary thermal
desorption unit.
A liquid pool of waste within the landfill provided feedstock for the tests. Tetrachloroethene (PCE) was
added to the feedstocks to serve as a tracer to determine destruction efficiencies (DEs)3. The reactor
program treated approximately 2.6 tonnes of wastewater contaminated with 3,757 mg/L PCBs and 3,209
mg/L PCE at a rate of 1.73 kg/min, and 0.2 tonnes of waste oil containing 25.4% PCBs and 6,203
mg/kg PCE at a rate of 0.385 kg/min. Additional feedstock contaminants included fluoranthene,
DE is a measure of the system's ability to destroy organic compounds, as measured around the system and all output
streams. DE(%) = {(l-Massortpl]1)/Masslnpl]1}*100.
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naphthalene, phenanthrene, other PAHs, chlorobenzene, chlorophenol, methyl chloride, toluene, and
various metals.
Two runs were conducted with the TDU on PCB-contaminated soil. The two runs treated 1 tonne of soil
contaminated with 627 mg/kg PCB and 14,693 mg/kg hexachlorobenzene (HCB).
7.5.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using NewOn-
Site Technique
This on-site remedial demonstration project combining excavation of tar-contaminated soil followed by
on-site ex situ thermal desorption was carried out at an old gasworks site in a densely populated area
of Copenhagen. The excavation was performed inside a ventilated tent. The project was regarded as a
demonstration of a new on-site technique.
Background
The Valby Gasworks was one of the largest in Copenhagen with an operating capacity of up to 300,000
m3 coal gas/day. Site investigation results showed a wide distribution of contaminants in the soil and
groundwater including coal tars, phenols, ammonium compounds, cyanides, and heavy metals. One area
of the site contained two tar reservoirs that had been partially filled with demolition debris after site
closure. A large amount of tar was left at the base of the reservoirs. The upper part was filled with
rainwater mixed with tar substances. The total amount of contaminated material in the two reservoirs
was about 12,000 tonnes.
The objective of the demonstration project was to remediate the heavily contaminated soil and debris
within and around the pits using an approach that minimized off-site migration (for example as air
emissions) since the site was located in an urban area.
Technical Concept
Free-phase tar and heavily contaminated materials were excavated within the tent, which covered an area
of 40 m by 50 m (with a height of up to 10 m). The air within the tent was cleaned using three powerful
extraction ventilators connected to a two-stage filter system consisting of particle and active carbon
filters. About 60% of ventilation air was blown in actively as fresh air at the end of the tent away from
the extraction fans; the remaining 40% came from general leakages.
Although on-site thermal desorption is claimed to be suitable for treating tar contaminants, it was
considered uneconomical to treat all of the excavated material in this manner. Therefore, a soil washing
system was used to provide a volume reduction step by producing clean fractions in the particle size
ranges of greater than 50 mm and 2-50 mm through screening and high pressure spray washing. All solid
fractions were dewatered before further treatment or reuse, and the contaminated process effluent was
recycled and treated before discharge. It was observed that tar removal efficiencies were increased
through using recycled water. Elevated levels of ammonia in the recycled water (up to 20,000 mg/L)
were believed to have assisted tar solvation. The contaminated fraction (<2 mm) was treated using the
thermal desorption process.
The thermal treatment plant consisted of two separate indirect heat treatment units: the first operating
at 250-300°C, while the second operated at 800-900°C. In the first stage water and volatile substances
were evaporated from the contaminated materials The off-gas was treated using a particulate dust trap
and an air/oil/water separator and condenser. The second stage was used to volatilize the heavier tar
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substances, which were then recovered in an air/tar condenser. Each treatment unit was transported in
a standard 12 m x 9 m container and had a maximum operating capacity of 2.5 tonnes/hr. However,
during operation, its practical operating capacity was only 1 tonne/hr—the limiting factor being the rate
at which energy could be transferred from the reactor walls to the material. Treated material had a
residence time of approximately 3 hours inside the reactors. After treatment, the decontaminated soil was
cooled using a closed single axle screw conveyor with a box cover to prevent dust emissions.
The first stage desorber was a specially designed, indirectly heated rotary unit operated in a strictly
controlled atmosphere, which was slightly over-pressurized and secured by inert gas. The processor was
heated by a closed-loop thermal fluid (boiler). The slight excess pressure led the gaseous hydrocarbons
and steam to the controlled condensation stage. Non-condensable gases (nitrogen, argon, methane,
hydrogen, etc.) were removed from the condenser and fed to the oil-fired burner of the Stage-2
processor. Stage 2 employed an indirect rotary heat exchanger with an external shell temperature of
1,100°C produced by oil burners.
7.5.3 Project 19: Cleaning Mercury-Contaminated Soil Using Combined Washing and
Distillation Process
The Marktredwitz Chemical factory in Germany, which was established in 1786, manufactured various
mercury compounds (including agrochemicals) and mineral acids. Site investigations in the early 1980s
found that the buildings, soil, and groundwater were heavily contaminated with mercury and other
contaminants. Mercury concentrations ranged from 400-3,300 mg/kg on the surfaces of brickwork, from
1,000-4,000 mg/kg in the soil, and up to 200 mg/L in the wastewater. This led to closure of the factory
in 1985. The Pilot Study project reported on the remedial operations employed including:
• Dismantling of the production plant, which involved removal of highly contaminated wall plastering
and supporting pipework for disposal in a secure on-site facility (approximately 5,000 tonnes);
• Protection of the River Kosseine, which flows adjacent to the site, using a sheet piling wall and a
pump-and-treat system;
• Demolition of the old factory building;
• Excavation of soil and debris to an average depth of 5 m across the entire site followed by refilling
to prepare the entire site for further urban redevelopment. Contaminated material was transported
offsite for treatment and disposal. A large off-site monofill waste disposal area was prepared where
treated material and slightly contaminated material (<50 mg/kg mercury) was disposed.
• Treatment of excavated soil and debris at an off-site treatment plant, which was constructed as a
semi-mobile (i.e., transportable) operation consisting of several modularized containers. This project
is the first full-scale application of vacuum distillation technology applied to debris and soil
contaminated by volatile and semivolatile substances like oil, mercury, and the lighter fractions of
tar.
The distillation unit is used in combination with a soil washing plant that separates out the highly
contaminated silt and clay soil fractions to form a pretreatment concentrate for thermal treatment. The
soil washing plant includes the following processes: crushing of material and screening at 0.05 m; wet
screening and density separation of slurried contaminated material; attrition scrubbing to remove fine
particles from coarser material; and dewatering and waste stream categorization. The sand and rubble
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fraction is discharged as clean fill. The fine fraction (<0.008 mm) is concentrated in thickeners,
dewatered in a chamber filter press, and then transferred to the vacuum distillation unit.
The thermal treatment process is a two-stage system involving thermal desorption at 100°C to reduce
material moisture content followed by vacuum distillation at the higher temperature. Treated material
exiting Stage 1 has a reported moisture content of about 1%. Volatilized contaminants and steam are
recovered from the off-gas using condensers. In the vacuum distillation reactor contaminated waste is
heated to temperatures between 350-450°C at a pressure of 50-150 hPa and the volatilized contaminants
recovered from the off-gas. By using reduced pressures rather than higher temperatures it is claimed that
overall energy consumption is significantly reduced and that off-gas volume is less than l/30th of that
produced by an incineration plant. After treatment, the treated soil is water cooled in a rotating drum
to an average temperature less than 50°C and is recombined with the coarse-grained material from the
soil washing plant. Treated soil with residual concentrations greater than 50 mg/kg are treated again.
The Harbauer soil treatment plant is a full-scale, commercial, transportable plant. The plant is a modular
system, and the process units are preassembled in about 60 containers (3-m wide, 3-m high, 10-14 m
long). The plant is gas-sealed; internal air is kept and treated; noise-reduced equipment is used; and soil
underlying the site is protected by a bottom-sealing system.
About 57,000 tonnes of soil were treated between 1993 and 1996, with an average daily throughput of
150 tonnes. Besides routine monitoring during operation, the technology demonstration was conducted
according to the USEPA's SITE Program protocols.
7.5.4 Project 20: Fluidized Bed soil Treatment Process—BORAN
The BORAN thermal fluidized bed soil treatment process plant has been designed primarily to treat slurry
residues from soil washing plants. It is designed to treat contaminants such as PAHs and PCBs. The
plant is operated by its designers and manufacturers, and while intended to be a commercial operation,
is also intended to be used as a full-scale test bed for design modifications. The basic technology is in
use for waste treatment and a number of other applications.
Before the contaminated soil is fed into the furnace, it is screened in a vibrating bar sizer with a cut-
point at 20 mm. Material greater than 20 mm is transferred elsewhere for alternative treatment and safe
disposal. Material less than 20 mm is fed into the furnace.
The furnace is fitted with two over-bed screw feeders for soils and four in-bed feed points for fine
residues. A bed temperature of 900°C is maintained to ensure that the organic content of the soil is fully
oxidized and destroyed. The combustion chamber is rectangular with one side wall being inwardly
inclined to act as a deflector plate and a limit to bed expansion. Preheated air is injected into the
chamber to ensure that feedstock (contaminated soil), combustion gases, and the bed materials are
circulated rapidly in an elliptical path within the combustion chamber. The controlled circulation
produces lateral mixing and turbulence, which reportedly enhances combustion efficiency.
Immediately downstream of the reactor is a hot gas cyclone, which is capable of removing up to 85%
of the soil and fines expected to be carried by the fast moving off-gas stream. The cyclone is designed
to remove up to 7.5 tonnes of particles per hour. This material is cooled from approximately 900°C to
180°C using water-cooled screw feeders before it is transferred to three storage silos as a clean product.
The majority of the treated soil is collected at this stage, although some of the coarser particles sink to
the base of the fluid bed within the furnace and are collected as a heavy ash product.
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After the hot gas cyclone the off-gas stream passes to an afterburner where it is heated to 1,200°C by
an oil-fired heater. The flue gas enters the treatment chamber at the top, passes down the center of the
chamber, and exits at the base. The afterburner gases are directed at high velocity and tangentially to
the flue gas stream to mix turbulently with the flue gas at the top of the chamber. At the base of the
chamber, a water bath with an immersed screw feeder extracts any soft entrained material. When the
afterburner is in use the following quench chamber reduces the temperature of the flue gas back to
900°C. A heat exchanger system uses the flue gases to preheat air about to be injected into the main
furnace. The flue gas cleaning plant consists of a primary and a secondary system. Primary absorption
of inorganic gases, such as hydrogen chloride and sulfur dioxide, is achieved by mixing finely powdered
limestone into the flue gas stream. The limestone is subsequently collected in a baghouse. In the
secondary absorption system any residual organic compounds, including dioxins and furans, are collected
by activated brown coal coke filters. Fouled coke is incinerated in the furnace.
No performance data for this technology were available.
7.5.5 Project 21: Mobile Low-Temperature Thermal Treatment Process
Many commercially available thermal treatment plants for contaminated soil are based on rotary kilns
operating at temperatures above 500°C, although some hydrocarbons are volatile at temperatures below
300°C. Use of lower operating temperatures, where appropriate, would reduce the environmental and
economic cost of treatment significantly.
Ruhrkohle Umwelttechnik GmbH have been operating thermal treatment facilities for contaminated soil
since 1986. In 1990, they began developing a mobile low-temperature treatment system for a range of
soil contaminants (such as volatile hydrocarbons, chlorinated solvents, and various forms of mercury)
with the following objectives: to reduce overall treatment costs compared with high temperature
treatment; to reduce plant transport costs in order to increase applicability of on-site treatment to smaller
remediation projects; to improve performance and cost effectiveness of thermal treatments for fine-
grained (especially clay-rich) soils; and to shorten project initiation times by developing a process that
did not require regulatory permitting for any off-gas or effluent emissions.
The process involves heating soil of less than 15 mm grain size in a gas-tight evaporator to 290°C under
continuous agitation for 30-45 minutes. Direct heating is achieved by mixing the soil with a hot medium
such as steam. Volatilized contaminants are collected from the off-gases by a multi-step condensation
system. Contaminants such as chlorinated solvents and mercury are separated from the condensed steam
which is cleaned and reused. Further contaminant separation may be carried out to produce low boiling
point and high boiling point products to increase their recycling value. The cooled off-gas (at about 5°C)
is cleaned further using an activated carbon filter for organic contaminants and an unspecified chemical
adsorption unit for inorganics (such as mercury) before discharging to the atmosphere. The treated soil
is cooled to about 60°C and water added to raise soil moisture content to 7-10%.
7.6 REVIEW OF CASE STUDIES AS A GROUP
Projects 7, 20 and 21 used ex situ thermal methods as the main element of treatment, while Projects 13
and 19 used ex situ thermal methods as the second element of a treatment train (the first element of
which was a soil washing process). Project 20 (fluidized bed treatment) assumed that some enrichment
of organic contaminants in the feedstock would take place elsewhere, for example, in a soil washing
plant. Tables 7.2 and 7.3 describe the input materials and thermal treatment processes of the projects,
respectively.
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Table 7.2: Input Materials
Project
7 Demonstration of
thermal gas-phase
reduction process
13 Rehabilitation of a site
contaminated by tar
substances using a new
on-site technique
19 Cleaning mercury-
contaminated soil using
a combined washing
and distillation process
20 Fluidized bed soil
treatment process —
BORAN
21 Mobile low-temperature
thermal treatment
process
Medium
Soil, groundwater,
and oily waste.
Soil and
demolition debris.
Soil and debris.
Designed for soil
and slurry residues
from soil washing
plants.
Soil.
Contaminants
Chlorinated hydrocar-
bons, including PCBs
and HCB, PAHs,
chlorobenzene,
chlorophenol, methyl
chloride, PCE, toluene,
metals.
Coal tars.
Mercury.
Designed for PAHs,
PCBs, etc.
Volatile hydrocarbons
and 5- and 6-ringed
PAHs.
Pretreatment/
Fraction treated
Soil homogenized to provide
uniform feed. Volatile compounds
in soil desorbed and subjected to
gas-phase reduction.
Oil injected directly into gas-
phase reduction unit.
Concentrate from pre-treatment of
aqueous phases injected directly
into reduction unit.
First stage soil washing. The
fraction <2 mm was subjected to
thermal desorption.
First stage soil washing. The
fraction 0.1-8 mm was subjected
to thermal desorption under
vacuum.
Simple screening to remove >20
mm material for treatment
elsewhere (plant does not have
crushing equipment).
Fraction <15 mm subjected to
steam injection.
7.7 PERFORMANCE RESULTS
Performance results of each project are summarized in Table 7.4 and discussed in more detail in the
paragraphs that follow. There are no results for Project 20 as this plant had not become operational by
the time the study ended.
7.7.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process
The runs employing liquid feeds confirmed the feasibility of the gas-phase reduction process for treating
PCBs and other chlorinated organic compounds, producing a fuel gas from contaminated liquids that
yielded environmentally acceptable air emissions. In general, the reactor system destroyed PCBs
effectively, reducing them to lighter hydrocarbons.
Theoretically, the overall effectiveness of the destruction process could depend on the functioning of
both the reactor system's gas phase reduction process (which produced the reformed gas), and the
propane and reformed-gas fired boiler. Destruction and removal efficiencies (DREs)4 for PCBs in the
DREs compare the mass flow rate of selected feedstock compounds, in this case PCBs, to their mass flow
rate in the boiler stack gas. DRE(%)= {(1-Mass^J/Mass, t)}*100.
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scrubbed reformed gas essentially were equal to the DREs at the boiler stack. This shows that
combustion of the reformed gas in the boiler is not required to complete PCB destruction.
Stack emissions generally met stringent regulatory standards. However, average benzene concentrations
in the stack gas (corrected to 7% oxygen) and scrubber liquor required close monitoring. Benzene
emissions (73-113 ug per dry standard cubic meter [dscm]) exceeded the regulatory limit. The scrubber
liquor required either disposal as a Resource Conservation and Recovery Act (RCRA) waste or recycling
through the system for additional treatment.
Demonstrated DREs for PCBs ranged from 99.9999 to 99.99999%. Demonstrated DEs for PCE was
99.99%. There was no net formation of dioxin or furan.
The TDU did not operate to specification. The most important finding was inefficient desorption from
soil during one of the runs. The DE for HCB ranged from 72.13 to 99.99%.
Table 7.3: Thermal Treatment Process
Project
7 Demonstration of
thermal gas-phase
reduction process
13 Rehabilitation of a site
contaminated by tar
substances using a
new on-site technique
19 Cleaning mercury-
contaminated soil
using a combined
washing and
distillation process
20 Fluidized bed soil
treatment process —
BORAN
21 Mobile low-tempera-
ture thermal treatment
process
Process
Thermal desorber
using molten metal
bath for soil, etc.
Gas-phase reduction
Two-stage thermal
desorption. Both
stages employed
indirect heating.
Two-stage thermal
desorption: (1) to
remove water; and
(2) vacuum distill-
ation at 50-150 hPa.
Fluidized bed
Afterburner
Sealed thermal
desorption with
steam injection.
Temperature
500-600
850
Stage 1: 250-300
Stage 2: 800-900
Stage 1: 100
Stage 2: 350-400
900
1,200
270-290
Fate of contaminants
Degraded to hydrogen
chloride, hydrogen,
methane, ethene, etc.,
depending on feeds-
tock. Recirculated or
removed by wet
scrubbing.
Condensed.
Condensed
Condensed, if not
thermally degraded.
Condensed.
Fate of
treated
material
Fate of
treated water
and soil not
indicated in
reports.
Coarse (>2
mm) washed
material
backfilled
onsite.
Fate of
thermally
treated
material not
clear.
Landfilled
with
untreated
materials
containing
<50 mg/kg
mercury.
No operating
results
available.
No informa-
tion
available.
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Table 7.4: Performance Information
Project
7 Demonstration of thermal
gas-phase reduction
process
13 Rehabilitation of a site
contaminated by tar
substances using a new
on-site technique
19 Cleaning mercury-
contaminated soil using a
combined washing and
distillation process
20 Fluidized bed soil
treatment process —
BORAN
21 Mobile low-temperature
thermal treatment process
Contaminant Concentrations
Input
Soil: 1,000 mg/kg PCBs
Oil: 25.4% PCBs, 0.6% PCE
Water: 3,757 mg/kg, PCB
3,209 mg/kg, PCE
(tracer)
1,500-80,000 mg/kg total tars.
Median value is 11,000 mg/kg.
400-3,000 mg/kg Hg on
surface of brickwork
1,000-4,000 mg/kg Hg in soil
No information
Mineral oil, 3.8%
Heavy mineral oil, 2.2%
Light tar oil (PAH C2.6), 0.45%
Tar oil (C2.6), 0.5%
TNT, 180 mg/kg
Mercury, 11,000 mg/kg
900 mg/kg
300 mg/kg
Output
0.6 mg/kg in soil
from desorber
22 mg/kg total tars
Average from
January 1995:
20 mg/kg Hg
No information
60 mg/kg
1,000 mg/kg
2 mg/kg
20 mg/kg
4.5 mg/kg
85 mg/kg
25 mg/kg
5 mg/kg
Removal Efficiency
PCB DE1 for soil up
to 99.9%
PCB ORE2
99.9999%+
PCB DE1
99.8%
No overall figures.
No information.
No information.
Notes: ' Destruction efficiency (DE) is a measure of the system's ability to destroy organic compounds as
measured around the system and all output streams. DE(%)= (l-Massoutput/Massmput) x 100
2 Destruction and removal efficiencies (DREs) compare the mass flow rate of selected feedstock
compounds to their mass flow rate in the boiler stack gas. DRE(%)= {(l-Massstack)/Massmput)} x
100
7.7.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using NewOn-
Site Technique
Analysis of the "clean" products of the soil washing process proved difficult due to the heterogeneity
of the coarse material, which comprised pieces of brick, concrete, and stones. Only limited chemical
analysis of the coarse washed fraction (2-50 mm) was conducted. Reliance was largely placed on visual
inspection. Ammonia in the recycled wash water enhanced washing efficiency. However, as tar
concentrations in the recycled wash water built up, washing efficiency decreased because at high tar
concentrations, the water lost its ability to emulsify the tar.
Concentrations of total tars in the fine concentrate (<2 mm) treated at the thermal treatment plant were
found to range between 1,500 mg/kg and 83,000 mg/kg. The fine concentrate was regarded as of optimal
grain size and homogeneity for the thermal treatment. Because of the variable nature of the feed material
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and the 3-hour plug-flow operation, it was difficult to match input and output samples. The characteris-
tics were therefore expressed statistically; the distribution of values for both was approximately log
normal.
Treatment efficiency was reported to be in the order of 99.8% with total tar concentrations reduced to
22 mg/kg from a median input of 11,000 mg/kg. Comparable performance was achieved for individual
PAHs including benzo(a)pyrene, which was reduced from a median value of 100 mg/kg to less than 0.1
mg/kg.
7.7.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing
and Distillation Process
Results of Routine Plant Monitoring
About 57,000 metric tons of soil were successfully treated between 1993 and 1996; the daily average
throughput was about 150 metric tons. Thorough monitoring of the plant showed that all requirements
were met during operation of the system. Emissions were found to be well below the specified criteria.
Long-term plant monitoring has shown that residual concentrations are well below 50 mg/kg, even if
peaks of very high input concentrations amount to more than 5,000 mg/kg mercury (Table 7.5). Trial
runs done with mercury-contaminated soil from another site showed that a clean-up criterion of 2 mg/kg
can be reliably met using an appropriate plant configuration.
Table 7.5: Mercury Concentrations in Waste Streams Treated in Project 19
Unit
soil washing plus
vacuum distillation
vacuum distillation
water treatment
stack gas
Period
Sept. 93-Oct. 94
Nov. 94-Oct. 95
Nov. 95-Feb. 96
Oct. 95-Apr. 96
1993-96
1993-96
Average Concentration of Mercury
Feed Stream
(mg/kg)
average- 500
peaks up to 5,000
-
-
-
Treated Stream
(mg/kg)
23
19
7.9
3.6
(see Section 3.2)
(see Section 3.2)
Treatment
Criteria
50 mg/kg
-
10 ug/L
50 ug/dscm
Results of a Technology Demonstration Under USEPA 's SITE Program
The Harbauer Treatment System was the subject of a technology demonstration in a joint project of the
German Federal Ministry of Science, Education, Research and Technology and the USEPA. The
technology demonstration was done according to the SITE protocols during routine operation of the
plant. Based on the SITE demonstration results, the following conclusions were drawn about the
Harbauer soil washing and vacuum distillation soil treatment technology:
• Average total mercury concentrations in the treated sandy loam and loam soils were reduced from
875 mg/kg to less than 18 mg/kg (95% confidence level).
• Average total mercury removal efficiencies for the soils ranged from 98-99%.
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• Average Toxicity Characteristic Leaching Procedure (TCLP) mercury concentrations in the soil
leachates were reduced from 82 ug/L to less than 6 ug/L.
• The average mercury concentration in treated process water discharged to the municipal sewer was
5 ug/L.
• The average mercury concentration in the treated stack gas discharged to the atmosphere was 2.92
ug per normal cubic meter (However, these measurements were not made during the same test runs
as the demonstration soil samples that were collected.).
7.7.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN
There are no results for Project 20 because the plant was not operational by the time the Phase II Pilot
Study ended.
7.7.5 Project 21: Mobile Low-Temperature Thermal Treatment Process
Pilot-scale trials (Table 7.6) were carried out during 1994 and 1995 to evaluate process performance and
to aid design of a commercial scale plant. In many cases, the observed concentration of contaminants
in the process water was low or below detection limits. Steam injection enhanced volatilization of certain
contaminants at a particular temperature. The results showed that at 270°C, and at low steam injection
rates, a treated soil sample still contained up to 35 mg/kg of 5- and 6-ringed PAHs. At higher injection
rates but at the same temperature this residual concentration dropped to about 10 mg/kg.
Table 7.6: Summary Results of Pilot-Scale Trials
Contaminant
Mineral oil in clay soil
Heavy mineral oil
Light tar oil (PAH C2-C4)
Tar oil (PAH C2-C6)
Mercury in sandy soil
in clay soil
in clay soil
Trinitrotoluene (TNT)
Temperature
(°C)
240
270
270
240
280
330
320
210
Stripping
Steam
(kg/hr)
6
5
6
6
4
6
6
8
Input
Concentration
(mg/kg)
38,000
22,000
4,500
5,000
300
900
11,000
180
Output
Concentration
(mg/kg)
60
1,000
2
50
5
25
85
4.5
7.8 ENVIRONMENTAL IMPACTS
7.8.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process
During the tests, continuous emission monitors measured the concentrations of the criteria air pollutants
at the stack: nitrogen oxides (NOX), sulfur dioxide (SO2), total hydrocarbons (THC), and carbon
monoxide (CO). Each of these pollutant concentrations were well under the level established in the
Michigan Department of Natural Resources (MDNR) permit.
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The demonstration boiler operated between high and low fire, depending on the system's steam
requirements. The test analyses showed out-of-range spike concentrations of THC and CO, which are
indicators of combustion efficiency, during low-fire operation, most notably during treatment of the
wastewater when cycling between high- and low-fire conditions.
Hydrogen chloride emissions were well below the MDNR permitted level of 4 Ibs/hr (1.81 kg/hr or 99%
removal); average stack concentrations ranged from 0.66 mg/dscm at 109 mg/hr to 0.81 mg/dscm at 198
mg/hr. Removal efficiencies reached 99.98%.
Process residuals comprised reactor grit, scrubber sludge, scrubber decant, scrubber liquor, compressed
tank condensate and stack gas—and when the TDU was used, treated soil. The reactor grit contained
PCBs, PAHs, and other organic compounds. However, ECO LOGIC intend to recirculate the grit through
the reactor in a full-scale plant. Scrubber residuals also contained metals and a variety of organic
compounds, but again recycling through the plant should be possible.
7.8.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique
Washed coarse material (>2 mm) was returned to the excavation. The disposal route for thermally treated
fine materials is not clear from the report.
One of the key elements of the project was to avoid emissions to atmosphere by the use of a ventilated
tent. Air emissions from the thermal treatment process were destroyed by feeding them to the Stage-2
oil burner.
One of the projects key conclusions concerned the noise associated with the remedial process. It was
found that with a measured level of about 60 dB(A) at the working site it was difficult but practical to
meet the maximum permitted noise level of 50 dB(A) at the site boundary.
Water from the tar reservoirs was used in the soil washing process and treated in a plant (1 m3/hr
capacity) comprised of an oil skimmer, cellulose filter for particulates and an active carbon filter.
7.8.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing
and Distillation Process
Precipitation sludge from the water treatment system was disposed in subsurface hazardous waste storage
facilities. Spent ion exchange resin was reactivated off-site for recycling. Condensed mercury was
disposed off-site for reuse or proper disposal. During plant operation, nearly 30 tonnes of mercury were
recovered. Treated wastewater and treated off-gas were subject to constant on-line monitoring. Treatment
criteria of 10 ug/L and 50 ug/dscm, respectively, were achieved.
7.8.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN
No performance data available because the plant was not operational by the end of the Phase II Pilot
Study.
7.8.5 Project 21: Mobile Low-Temperature Thermal Treatment Process
No information on emissions was provided.
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7.9 HEALTH AND SAFETY
7.9.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process
The principal health and safety concerns were the physical hazards common on construction and
remediation sites, chemical use, equipment integrity, and process control.
The chemical hazards arise from the use of propane, liquified nitrogen and oxygen, hydrogen, industrial
chemicals, and hazardous feed materials. In addition, the process generates methane. Standardized
industrial procedures provided adequate guidance for storing, transporting and handling these materials.
There should be no undue concern associated with hydrogen usage in the process. Well-established and
proven procedures are available for safe hydrogen storage and use. Hydrogen is no more or less
dangerous than gasoline or methane, but it must be handled with regard to its unique properties.
Verification of system integrity is essential for process safety. Hydrogen is more difficult to contain
because of its small molecular size. Therefore, interfaces of equipment, instruments, and piping must
be leak-free. To provide additional safeguards, the process is operated at a slight positive pressure to
prevent oxygen ingress, internal oxygen concentrations are monitored, and gas feeds (propane and
hydrogen) maintained at low pressure to minimize the likelihood of pipeline breaks. The plant is fitted
with an automatic safety system which initiates plant shutdown in the event of a number of hazardous
situations occurring.
7.9.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique
During excavation, the release of volatile substances was very high. Although a ventilation rate of three
air exchanges per hour was maintained, it was still necessary for workers within the tent to use personal
protection. Two principal levels of protection were provided:
• chemically resistant suits with fresh-air supply through an air tube for manual work involving direct
contact with heavily contaminated material; and
• fabric coveralls combined with a fresh-air mask with multi-filter in all other work operations.
Excavator operators either used a fresh-air mask with multi-filter or were supplied with a pressurized
cabin with filtered air supply.
The effectiveness of the chemically resistant suits was checked. Volatile tar substances such as BTEX
compounds (benzene, toluene, ethylbenzene, and xylenes), phenols and naphthalene, could not be
detected inside the suits.
Both of the desorber units were protected by two independent systems:
(1) Jets spraying water on the hot internal surface thereby producing steam. This steam has three
functions: (a) as a start up procedure to remove air/oxygen from internal hot parts before feeding
materials; (b) to keep the system over-pressurized relative to atmospheric pressure during operation;
and (c) back-up in shutdown situations, when steam production from wet material decreased.
(2) Nitrogen was added automatically to the processor if the internal pressure dropped below
atmospheric pressure.
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7.9.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil Washing
and Distillation Process
No information was provided.
7.9.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN
No information was provided.
7.9.5 Project 21: Mobile Low-Temperature Thermal Treatment Process
No information was provided.
7.10 FACTORS AND LIMITATIONS TO CONSIDER FOR DETERMINING THE
APPLICABILITY OF THE TECHNOLOGY
7.10.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process
The SITE Program concluded that the ECO LOGIC process efficiently treated liquid wastes containing
oily PCBs and other organic compounds, and water containing PCBs, other organic compounds, and
metals. Stack emissions met stringent regulatory levels. The principal residual stream—the scrubber
effluent—concentrated metals and some organic compounds (benzene, PCBs, PAHs), indicating that
additional treatment, such as recycling through the process, might be required prior to disposal. However,
throughput reliability was only 20-55% of design and system availability was 24% indicating that system
reliability needs improvement. A number of technical problems were encountered during operation of
the plant and are recorded in the SITE program report. The boiler should be operated at firing rates and
air/fuel ratios that prevent the spikes of THC and CO observed during the trial.
The reactor system is best suited for processing liquids and TDU off-gases and water vapor. The waste's
organic content limits the demonstration-scale system's feed rate because of the reformed gas generation.
ECO LOGIC plans to improve throughput by storing excess reformed gas after compressing it. Future
users should consider the implications, logistics, and costs of this approach.
The TDU did not perform to design specifications. The USEPA categorized the TDU test data as a
system proof-of-concept rather than as a comprehensive evaluation of a fully developed unit. The TDU
only achieved acceptable desorption efficiencies at the expense of throughput. In addition, ECO LOGIC
experienced material handling problems with the TDU feed. The combination of feed problems and
inadequate organics desorption showed a need for further development. Nevertheless, the demonstration
did show that the TDU can desorb PCBs and that satisfactory treatment in the reactor system was
possible.
Cold-weather operations may inhibit efficient destruction because of the incremental amount of energy
required to heat the reactor. In addition, frozen feedstock liquids would require melting prior to
treatment, and liquid residuals could freeze in the unheated storage tanks. Winterization, including heat
tracing, is necessary to provide adequate feedstock and to ensure uninterrupted processing.
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7.10.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique
The only specific difficulty noted in the report was the reduction in effectiveness of the soil washing
plant as the concentration of tarry substances built up in the recycled wash water. This could presumably
be overcome by introducing a greater proportion of fresh water. This has also been noted as a limitation
in other soil washing operations.
Operation within a tent successfully limited emissions to the atmosphere from soil handling although
noise remained a potential problem. However, containment in this way, does increase the potential risks
to workers compared to working in the open when emissions can rapidly disperse into the air. However,
avoidance of weather extremes may help to reduce the potential for accidents due to difficult working
conditions.
7.10.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process
No specific limitation regarding the technology were noted in the report. However, it emerged during
analysis of the results of the USEPA-German Bilateral project that the analytical method used to
determine PAH concentrations in the untreated and treated soils is important. In particular, the extraction
method used as some methods will tend to underestimate the proportion of the more volatile PAHs
present, and other methods will tend to underestimate the less volatile fraction. Reliable assessment of
effectiveness may, therefore, require use of more than one analytical method in parallel.
7.10.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN
No performance data available because the plant was not operational by the end of the Phase II Pilot
Study.
7.10.5 Project 21: Mobile Low-Temperature Thermal Treatment Process
No specific limitations were noted in the project reports.
7.11 COSTS
Cost data are summarized in Table 7.7.
Table 7.7: Cost Data
Project
7
13
19
20
21
Demonstration of thermal gas-phase
reduction process
Rehabilitation of a site contaminated by tar
substances using a new on-site technique
Cleaning mercury -contaminated soil using a
combined washing and distillation process
Fluidized bed soil treatment process —
BORAN
Mobile low-temperature thermal treatment
process
Cost information
Liquids: U.S.$l,840-2,205/ton
Soil: U.S.$550-695/ton
Total cost U.S.$2.6M, of which 70% is directly attributable
to soil and ground water treatment.
Total cost estimated to be DM 150M.
Plant not operated.
Costs of a full-scale plant are estimated to be about DM
150-250 (U.S. $90-160), depending on the contaminants
(1996 prices). The report suggested the process would not
be economical for remedial actions of less than 100 tonnes.
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7.11.1 Project 7: Demonstration of Thermal Gas-Phase Reduction Process
The 12 categories established for the SITE Program5 formed the basis for the cost analysis of the
treatment of liquid wastes. Costs relate to the reactor system, processing an average 2.2 kg/min, as
operated at the Middleground Landfill site. For this estimate it was assumed that 378 m3 (100,000 U.S.
gallons) of wastewater and 114 m3 (30,000 U.S. gallons) of waste oil were stockpiled for treatment.
Based on the economic analysis, the estimated cost (1994 U.S. dollars) for treating liquid wastes similar
to those at the Bay City site ranged from U.S.$2,205/tonne (60% utilization factor) to U.S.$1,840 (80%
utilization factor). The most important element affecting cost is labor (52%), followed by site preparation
(15%), supplies (12%), and start up/mobilization (12%).
Demonstration site preparation costs were U.S.$127,400. Capital costs (for the reactor and immediately
associated equipment, but excluding the TDU) for a commercial operation are estimated to be
U.S.$585,000.
Similarly, the costs of treating contaminated soils were estimated. These were estimated at
U.S.$695/tonne (at a 60% utilization factor) and U.S.$550/tonne (80% utilization factor). Important
elements affecting cost are fuel (67%), equipment (11%), and labor
7.11.2 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique
The total project cost was about 18M DKK (about U.S.$2.6M) of which 15M DKK (about 70%) was
for contracted clean up costs. The total cost included:
Personnel costs (consultant and contractor) 13%
Operation and maintenance 7%
Establishment and rental of the tent 7%
Soil, air and water cleaning costs 70%
Analytical costs 1%
Miscellaneous 2%
7.11.3 Project 19: Cleaning of Mercury-Contaminated Soil Using a Combined Soil
Washing and Distillation Process
The estimated treatment cost was 480 Deutsche Marks (DM) per tonne, which is approximately
U.S.$320/tonne (assuming 1.5 DM= U.S.S1).
7.11.4 Project 20: Fluidized Bed Soil Treatment Process—BORAN
No projected costs for an operational process were provided.
Site preparation, permitting and regulatory, capital equipment, mobilization and start-up, operations labor, supplies, utilities, effluents,
residuals, analytical, repair and maintenance, demobilization.
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7.11.5 Project 21: Mobile Low-Temperature Thermal Treatment Process
According to Ruhrkohle, the costs of cleaning soil using a full-scale plant based on this process would
be about 150-250 DM/tonne (U.S.$90-160), depending on the contaminant(s). The cost depends on the
plant equipment required and waste disposal costs.
An important factor influencing costs is the quantity of soil to be treated at a particular site. Ruhrkohle
accepts that a mobile plant cannot compete with stationary plants when only a small amount of soil is
to be treated (for example, mobilization costs would be disproportionally high). However, for larger
quantities of soil, treatment of the contaminants such as mineral oils and PAHs in the mobile plant
should be less expensive, because on-site cleaning does not involve transport costs for the soil and does
not require any expenditure for obtaining permits. It can be installed rapidly and operated under German
law without the need for time-consuming applications for approvals to set up and operate.
7.12 CONCLUSIONS AND PROGNOSIS
As a group, the projects showed that thermal treatment plants can provide a technically satisfactory
means of dealing with a wide range of organic contaminants and with mercury. They also showed that
thermal treatment can be integrated well with pretreatment processes such as soil washing that are
intended to reduce the volume of material to be treated. Unfortunately, the promising fluidized bed
technology described under Project 20 did not become operational during the study.
Project 13 illustrated the benefits and practicality of operating even complex on-site operations under
cover thereby limiting possible impacts from emissions within an urban area; however, noise may still
remain a problem. Containing the operations under a tent may increase risks to workers from emissions
that might otherwise rapidly disperse into the air.
The thermal processor employed in Project 11 appears to be uniquely versatile in being able to handle
contaminated soils, waste waters and non-aqueous phase liquids (NAPLs).
Costs will remain a limiting factor for the technologies described here, hence pretreatment to reduce the
amount of contaminated material to be treated is important. The cost of U.S.$550-695/tonne of soil
quoted for the Eco Logic process (Project 7) is only likely to be justified for treatment of difficult
contaminants such as PCBs. Costs for processing of less difficult materials such as PAHs and hydro-
carbon oils are most likely to come from measures to reduce energy requirements, which are much more
expensive in Europe than in the United States, and to increase throughput of mobile plants of a given
size.
7.13 REFERENCES
1. Harris, M.R., S.M. Herbert, and M.A. Smith. Remedial treatment for contaminated land: Ex-situ
remedial methods for soils, sludges and sediments, Construction Industry Research and Information
Association, London, Special Publication 108, 1995.
2. Anderson W.C. (editor). Monograph on innovative remediation technology: thermal desorption
American Academy of Environmental Engineers (Annapolis, MA) 1994.
3. Anderson W.C. (editor). Monograph on innovative remediation technology: thermal destruction
American Academy of Environmental Engineers (Annapolis, MA) 1994.
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Chapter 8: STABILIZATION/SOLIDIFICATION PROCESSES
Michael A. Smith
M.A. Smith Environmental Consultancy
8.1 INTRODUCTION
Stabilization/solidification methods (sometimes called immobilization methods) change the physical state
of a contaminated material, such as solidifying a contaminated sludge. In addition, chemical stabilization
can reduce the "availability" of contaminants to potential targets, usually by containment within a solid
product of low permeability. Harris (1) and the American Academy of Environmental Engineers (2) have
recently reviewed stabilization/solidification methods.
Stabilization involves adding chemicals to the contaminated material to produce more chemically stable
constituents, for example, is the formation of virtually insoluble metal hydroxides. Stabilization may not
result in an improvement in the physical characteristics of the material. For instance, the material may
remain as a relatively mobile sludge, but the stabilization process will have reduced the toxicity or
mobility of the hazardous constituents within it.
Solidification involves adding reagents to the contaminated material to reduce the material's fluidity or
friability and to prevent access by external mobilizing agents, such as wind or water, to the contaminants
contained in the solid product. Solidification does not necessarily require that chemical reactions occur
between contaminants and the solidification agent, although such reactions may take place depending
on the nature of the reagent.
In practice, many commercial systems and applications involve a combination of stabilization and
solidification processes. Solidification follows stabilization to reduce exposure of the stabilized material
to the environment through, for example, formation of a monolithic mass of low permeability.
Although volatile constituents may be driven off (because heat is often generated) and some hydrolysis
of chlorinated organic compounds may occur during the application of some processes, the destruction
or removal of contaminants is not the objective of stabilization/solidification.
Contaminants may become available once again if the physical or chemical nature of the treated product
alters in response to changes in the external environment, such as exposure to an acidic discharge or
leachate or physical breakdown of a compacted soil mass due to freezing and thawing. Solidified
products also may be subject to internal degradation reactions over time (e.g., the oxidation of sulfides
to form expansive sulfates). Key points for selecting a stabilization/solidification method are therefore:
• its ability to achieve and retain the desired physical properties, chemically stabilize or permanently
bind contaminants, and contain (physically entrap) contaminants over the long-term; and
• the methods to be used to determine treatability and short- and long-term performance.
The effectiveness of stabilization/solidification methods depends on:
• proper characterization of the material to be treated so that the most appropriate formulation can be
selected:
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• effective contact between the contaminants and treatment reagents—for many systems this can be
achieved by ensuring a high degree of chemical and physical consistency of the feedstock, and the
use of appropriate mixing equipment;
• control over external factors, such as temperature, humidity, and amount of mixing after gel forma-
tion, since these affect the setting and strength development processes and the long-term durability
of the product; and
• absence of substances that inhibit the stabilization/solidification process and development of the
required physical characteristics, or pretreatment to render such substances harmless, such as by
sorbent addition.
Treatability studies are always required to establish anticipated effectiveness and materials handling
requirements.
Because most stabilization/solidification methods involve the addition of solid reagents to the
contaminated material, some increase in the final volume of the treated product can be expected.
Increases in the range 30-130% are typical (4). A major advantage of most stabilization/solidification
methods is that they improve the handling characteristics of sludges and other high-water content
materials, and may confer additional structural strength on contaminated material. Sometimes these are
the primary reasons for their use, and they may be an important consideration for contaminated sites
undergoing redevelopment. Stabilization/solidification methods are readily applied onsite using mobile
mixing and blending equipment.
Most commercial stabilization/solidification systems are derived from established hazardous waste
treatment techniques and use relatively simple equipment and conventional reagents (binders) to
immobilize the contaminants. Systems may be classified according to the primary stabilization agent
used: cement-based, pozzolan-based, silicate-based, thermoplastic-based, or polymer-based systems. In
practice, a combination of these reagents may be employed. The formulations actually used on a
commercial basis are often proprietary in nature.
In the U.S., stabilization/solidification is considered an established technology for the treatment of certain
inorganic forms of contamination, and long-term monitoring data are available on the performance of
solidified wastes in the field (4, 5, 6). Stabilization/solidification techniques have also been used in
Europe for the treatment of hazardous waste. However, doubts remain over their long-term performance.
These doubts arise from the chemical and physical nature of the processes themselves and from observed
deficiencies in the quality of application in the field (and in fixed plant). In addition, methods of testing
and predicting performance are not well developed and are the subject of continuing debate (7).
Proprietary formulations for the treatment of organic contaminants prior to the use of conventional
binders are available in the U.S., but practical experience in their application is limited.
8.1.1 Main Process Variations
Processes can be grouped according to the reagents used to achieve stabilization/solidification and
conveniently categorized into three main groups:
(1) Those based on inorganic cementitious systems including Portland cement, pozzolans, hydraulic
slags, and lime.
(2) Those using organic binders, including asphalt emulsions, bitumen, and other thermoplastics.
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(3) Other systems, such as those using sulfur as a binder (2).
Other materials used in cementitious systems include cement kiln dust, lime kiln dust, and steel slag
fines. Depending on the source, cement kiln dust may contain variable proportions of reactive calcium
silicates, free lime, partially reacted and possibly pozzolanic clay minerals, and alkali sulfates.
With the exception of proprietary lime and thermoplastic-based methods, which can be applied to solids
contaminated with organic residues, one of the principal limiting factors associated with conventional
stabilization/solidification systems is that even very low concentrations of organic contaminants may
interfere with setting and hardening processes. Thus, recent research has addressed the development of
methods that can treat materials contaminated with both organic and inorganic contaminants. One
approach involves the use of organophilic clays to preferentially absorb organic contaminants (see
discussion of Project 34 below). Treated material then undergoes conventional stabilization/solidification
to immobilize the inorganic constituents and provide a secondary layer of protection around the clay-
bound organics. Other potentially useful adsorbents include ion exchange resins, activated carbon, and
zeolites.
8.1.2 Ex situ Methods of Application
Ex situ stabilization/solidification methods can be applied in three main ways:
(1) Plant processing, in which contaminated material is excavated and then mixed with stabilization/
solidification reagents in a plant specifically designed for the purpose or adapted from other
applications, such as concrete batching and mixing plants.
(2) Direct mixing, in which contaminated material is excavated and transported to a designated area
of the site. The material is then spread out in layers, and the reactive ingredients are added and
mixed in using a mechanical plant. Direct addition and mixing may be used to treat contami-
nated sludges and sediments present in lagoon areas and ponds.
(3) In-drum processing, in which binders are added to contaminated material contained in a drum
or other container. After mixing and setting, the product is disposed in the drum.
Plant processing has considerable advantages: it ensures adequate mixing and reduces unacceptable
environmental impacts due to the release of particulates and vapors. Three principal steps are employed
in the application of plant processing:
• pretreatment, for example to dewater, grade, or homogenize the material to be treated, or to
concentrate the contaminants (e.g., by soil washing);
• mixing of waste with active ingredients either to form a pumpable slurry or a material that can be
placed using standard earth moving/engineering equipment; and
• placement and curing.
Curing of pumpable material requires maintenance of appropriate temperature and humidity to promote
stabilizing reactions and proper development of physical properties. Curing may take place in molds or
in disposal lagoons. With low-moisture content material, curing occurs at the final disposal site. When
treated material is placed in lagoons, care should be taken to prevent the formation of "cold joints,"
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which would allow water easy access and allow excessive accumulation of contaminated free water
(bleeding).
Effective treatment usually requires a relatively high ratio of treatment agent to feedstock. The amounts
used affect chemical stabilization capacity, permeability, and the long-term strength and durability of
the product.
The required amount of water varies with the system and can be very important. For instance, in cement-
based systems, the water:cement ratio is an important factor in the development of early and long-term
properties of the system. Water is a reactive component of the system. Lower water contents are
generally preferred.
The options for final disposal should be taken into account when deciding on the acceptability of a
particular application. What is permitted depends on the nature of the product and may vary among
countries. In some cases, a full containment landfill may be required. In contrast, there are reported cases
(8, 9) where treated material has been used successfully as a construction base. In these cases, the
material is placed and compacted in thin layers to agreed specifications using standard engineering
procedures.
8.1.3 In Situ Methods of Application
Stabilization/solidification reagents may be introduced into the ground using soil mixing equipment (e.g.,
contra-rotating hollow stem augers through which treatment agents are injected) or by pressure injection
using techniques analogous to conventional grouting.
Only the former method has been developed on a commercial scale, and the discussion that follows is
restricted to such systems. The latter concept was examined in a report for the U.K. Department of the
Environment in 1982 (10), and two principal disadvantages were identified:
• difficulty in ensuring even permeation of the treatment agent in the ground; and
• treatment depth limitations (in excess of about 2 m) because of a need for sufficient overburden
pressure to withstand the injection pressures required (the report indicated that this might be
overcome by temporary surcharging).
Stabilization/solidification, when applied to material in lagoons, is typically performed using
conventional construction equipment, such as backhoe excavators and draglines. Effective mixing is very
difficult to achieve. The primary purpose of these operations is usually to improve the physical
characteristics of the material (11).
The in-ground mixing process developed in the U.S. by International Waste Technologies and Geo Con,
Inc., was evaluated under the USEPA Superfund Innovative Technology Evaluation (SITE) Program in
1988 (12). Other in situ stabilization/solidification processes are under development and scheduled for
demonstration under the SITE program (13, 14). An established ground improvement (solidification)
technique, using jet grouting, also has potential for application (see Box 8.1).
As with ex situ stabilization/solidification processes, the product obtained after treatment typically should
comprise a dense, homogeneous material with favorable leaching and weathering characteristics, low
permeability (<10"5m/s), and good (>0.34 MPa) unconfmed compressive strength. Unlike ex situ systems,
where the physical properties of the excavated material can be determined in advance of processing and
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some pretreatment preparation is possible, the effectiveness of in situ applications relies on adequate
characterization of the ground at the treatment location to optimize the mixing conditions.
Box 8.1: Soilcrete® Jet Grouting
In this process, soil is loosened by the high pressure action of water, often sheafed in a cone
of air (jet-cutting). The loosened soil is partially removed to the surface via air-lift pressure as
the remaining soil is simultaneously mixed with cementitious or cement/bentonite grout.
Columns can be made to overlap, thus treating all of the soil. The columns have diameters of
0.5-1.8 m, depending on soil type. Compressive strengths of up to 10 MPa can be achieved in
granular soils and 5 MPa can be achieved in cohesive soils. Some binding of inorganic
contaminants can be expected. Permeabilities in the range 10~6-10~9 m/s can be achieved.
A variation of the jet-cutting process, in which the soil is displaced by clean material
introduced at the base of the hole, has been applied to permit ex situ treatment of the
displaced soil.
8.2 CASE STUDIES CHOSEN
Only two stabilization projects were included in the pilot study:
• Project 34 Chemical fixation of soils contaminated with organic chemicals (Envirotreat); and
• Project 29 Sorption/solidiflcation of selected heavy metals and radionuclides on to unconventional
sor bents.
Conventional stabilization/solidification methods, such as those based on cementitious and pozzolanic
materials, have been applied with limited success to treat soils with organic contaminants. Project 34
involved the development of a range of modified organophilic clays with the goal of overcoming these
limitations in an in situ stabilization/solidification application based on cementitious binders. Following
laboratory trials to develop the optimum combination of modified clays and other ingredients, the
technology was tested at field scale on a site contaminated with a variety of inorganic and organic
substances.
Project 29 involved a laboratory-scale investigation of the use of solid wastes, such as red muds and coal
fly ashes, to absorb toxic heavy metals and radionuclides from water (a fixation or stabilization process)
followed by solidification of the metal-loaded solid wastes in a cement-based system.
Both projects focused on the pre-solidification stabilization stage with the intention of providing
adsorptive media for organic and inorganic contaminants, respectively. Both are intended to be used with
cement-based solidification processes.
The projects differ in that the:
• Project 34 uses a tailor-made (possibly expensive) organophilic clay, while Project 29 seeks to use
readily available, inexpensive waste materials; and
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• Project 34 is intended for the treatment of soils, while the Project 29 is intended for the treatment
of effluents.
The projects are summarized below. Additional detail is provided in Appendix IV, Project Summaries.
8.2.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process)
The Envirotreat process uses modified smectite clays that contain reactive species. The process is
primarily targeted at organic contaminants, but also has the capability to treat cationic and anionic heavy
metal species by a combination of ion-exchange processes and chemical interaction with pillaring agents
and other intercalatants. The technology uses modified continuous-flight auger drilling and injection
techniques. The treatment materials are injected in slurry form into the ground and mixed with the
contaminated soil in situ.
Commercially available organophilic clays are typically made by the substitution of quaternary
ammonium salts into phyllosilicate clay matrices (e.g., montmorillonite). The primary objective of this
project was to modify these clays through intercalation (i.e., substitution of the cations between clay
layers) to improve stabilization of organic contaminants by:
• increasing the size of the interlamellar spacing within the clays to accommodate large molecules,
such as poly chlorinated biphenyls (PCBs) and poly cyclic aromatic hydrocarbons (PAHs); to increase
the effective surface area; and to increase the potential reactivity by introducing selected pillaring
agents;
• optimizing the polarity of the interlamellar environment to increase the absorption and adsorption
of organic contaminants;
• providing a reactive environment on interlamellar clay surfaces to chemically bind contaminants
permanently; and
• providing an active medium for effective treatment of heavy metals (both cationic and anionic) and
other inorganics by cation exchange processes and/or interaction with the intercalated species (which
then can be immobilized within the cementitious matrix following alkaline precipitation).
An advantage of using tailored organoclays is that a clay can be manufactured to treat a specific group
of contaminants by manipulating the type and amount of intercalating agents used. Envirotreat's goal was
to produce a range of clays with varying hydrophobicity and chemical composition to deal with five
different groups of organic compounds.
Following laboratory trials to develop the clays and additional efforts to optimize the auger design, a
field trial was carried out on a site occupied since the turn of the century by a variety of industrial
operations, including a chemical waste "quarantine store," chemistry laboratory, flammables store, battery
bank, engine testing areas, underground storage tanks, and nucleonic laboratory. Likely contaminants
included flammable materials, solvents, concentrated sulfuric acid, oils, gasoline, and radioactive species.
Site characterization seems to have been very limited in terms of the range of contaminants analyzed
and the number of samples (3) analyzed. The maximum value for PAHs (six carcinogenic compounds
selected by the World Health Organization [WHO]) was 12 mg/kg—well below the U.K. threshold value
for residential development (50 mg/kg for 16 USEPA PAHs). Maximum copper, lead, and zinc
concentrations were 635, 3,330, and 785 mg/kg, respectively.
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Prior to field operations, a laboratory program was conducted to determine the type of intercalated clay
to be used; the proportions of cement, fly ash, and clay for the grout; and the optimum soil:grout ratio.
The clay formulation used was A13+ pillared and Fe3+ exchanged (spiked) and then treated with benzyl
quaternary ammonium salt. The modified clay was produced as a suspension at Birmingham University
and transported to the site in steel drums. The clay concentration was 20 g/L (2.5 times more dilute than
that used in laboratory treatment trials).
The grout was injected using a prototype auger fitted to a conventional piling rig that produces 900-mm
diameter columns either individually or overlapping. The columns were formed by advancing the auger
into the soil to the required depth of the column, mixing the soil in place during the auger descent, and
then injecting the grout slurry into the soil with simultaneous mixing on the auger withdrawal. The
overall volume increase, measured at the end of the second day, was about 1 m3, which represents an
increase of about 6.5%. For this demonstration, columns with 50% overlap were chosen, and several
different optimized mixes were evaluated in adjacent columns. An area of 6 m2 to a depth of 2.5 m was
treated in the trial. Cores aged 50 days (taken at 44 days), 70 days (taken at 57 days), and 1 year
(presumed to have been taken at 57 days) from each column were tested in the laboratory against the
treatment criteria outlined below.
The effectiveness of the various treatments in the laboratory and field was assessed based on:
• unconfmed compressive strength by an American Society for Testing and Materials (ASTM) method
(greater than 350 kPa after 28 days of curing);
• teachability, based on the USEPA Toxicity Characteristic Leaching Procedure (TCLP), which uses
an aggressive acid leaching medium, with respect to six WHO PAHs (total PAHs less than 10 ug/L
and benzo(a)pyrene less than 0.5 ug/L) and chromium, copper, lead, and zinc with target levels 50
times the U.K. drinking water limits; and
• a final leachate pH in the TCLP leachate (between 8-10 following 28 days curing) to ensure low
metal solubility (this was later amended to a pH of 7-11).
Durability (freeze/thaw and wet/dry) and permeability tests (less than IxlO"9 m/s) were used as secondary
evaluation criteria. ASTM test procedures were used for the initial freeze/thaw tests on laboratory
prepared materials, but the test method was subsequently modified as it was judged too harsh in relation
to typical U.K. weather conditions.
The results on the cores taken at 44 and 57 days were judged to be satisfactory. All unconfmed
compressive strength values exceeded the target value of 350 kPa and were greater than the equivalent
(28-day) laboratory results. This was particularly true for the mixes containing quick lime. The total
concentrations of the six WHO PAHs in the leachates were all below 2 ug/L and often below the 0.02
ug/L detection limit. Also, the individual leachate values for benzo(a)pyrene were within the target value
of less than 0.5 ug/L. All results for chromium, copper, lead, and zinc were satisfactory. Subsequently,
more detailed analyses showed satisfactory performance with respect to a wider range of metals. The
samples survived a modified freeze-thaw test—the ASTM method being considered too aggressive
following the laboratory trials for U.K. conditions. The wet-dry test results were also satisfactory.
However, only one sample satisfied the permeability criterion of less than IxlO"9 m/s; this was probably
due to the presence of natural bentonite.
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Cored samples collected during the site trial were cured under laboratory conditions for 12 months. They
were wrapped in wet cloth and kept in a humidity room. The cores were 75-150 mm in diameter and
had a maximum length of 400 mm.
Samples from all mixes showed an increase in unconfmed compressive strength for those cured for 12
months, compared to those cured for 70 days. Permeability values decreased as expected due to
continuing cement hydration processes. Wet-dry durability testing gave similar results after 12 months,
and freeze-thaw testing was largely inconclusive (all samples failed at very low temperatures as
previously observed).
8.2.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto
Unconventional Sorbents
Cadmium (II) (Cd2+), lead (II) (Pb2+) and copper (II) (Cu2+) are toxic heavy metals that pose a serious
threat to the ecology of receiving water bodies when discharged in industrial wastewater. Cesium-137
(137Cs) and strontium-90 (90Sr), with half lives of 30 years and 28 years, respectively, pose significant
threats to the environment as a result of fallout from nuclear bomb tests and reactor accidents. In recent
years, land burial of radioactive wastes has become a common practice, posing a radioactive
contamination risk to groundwater. In Turkey, 137Cs became a matter of public concern after the
Chernobyl accident, especially due to contamination of tea-growing areas on the Black Sea coast. Milk
products and other biological materials containing 137Cs were also extensively investigated for possible
90Sr contamination.
Various treatment technologies have been developed for the removal of these metals from water. They
include ion exchange, electrodialysis, reverse osmosis, membrane filtration, sludge leaching,
electrowinning, solvent stripping, precipitation, and common adsorption. The cost of adsorptive metals
removal processes is relatively high when pure sorbents, such as activated carbon or hydrated oxides,
are used. Consequently, there is an increasing trend towards substitution of pure adsorbents with natural
byproducts or stabilized solid waste materials. Such materials may also be useful for constructing
"natural barriers" around radioactive waste disposal sites, especially for facilities involving shallow burial
of low-level wastes, to prevent the leakage of radionuclides from the facility to the environment.
The goal of this pilot study project was to develop cost-effective unconventional sorbents, preferably
metallurgical waste solids, for the removal of heavy metals and radionuclides from contaminated water.
The removal capacities of heavy metals (Cd, Pb, and Cu) and radionuclides (137Cs and 90Sr) and the
sorption modeling of red muds and fly ashes were studied. The irreversible nature of sorption needs to
be demonstrated to guarantee non-leachability of metals from the metal-loaded sorbents.
Metal uptake (sorption) and release (desorption) were investigated by thermostatic batch experiments
on coal fly ashes and on red muds, which are alkaline leaching wastes of bauxite from the Bayer process
for the manufacture of alumina. The materials were subjected to a variety of pretreatments prior to the
introduction of the contaminated solutions. The distribution ratios of metals between the solid sorbents
and the aqueous solution were determined as a function of sorbent type, equilibrium aqueous
concentration of metals, and temperature. The breakthrough volumes of the heavy metal solutions were
measured by dynamic column experiments to determine the saturation capacities of the sorbents. The
sorption data were analyzed and fitted to linear adsorption isotherms.
The heavy metal solutions contained up to 10,000 mg/L of Cd, Pb, or Cu made from the corresponding
nitrate salts. No further pH adjustment was made. Solutions containing 137Cs and 90Sr were made by
diluting flacons of standard solutions supplied by Amersham International, Ltd.
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The desorption studies were conducted using distilled water, saturated aqueous carbonic acid (pH=4.75),
and H2CO3/NaHCO3 buffer solutions (pH=7.0) to simulate carbonated groundwater conditions for the
purpose of analyzing risks around waste disposal sites.
The sorbents may serve as effective fixation agents for removing heavy metals from water prior to
solidification for disposal. Although stabilization tests were conducted on the fly ash and red muds, as
well as on the adsorbents after they were loaded with contaminating metals, the detailed results were
not described in the final project report. Solidification of the red muds and fly ash was accomplished
by adding them to a mixture of cement, standard sand, and carefully measured water. When metal-loaded
solid waste was added (up to 20% by mass) to Portland cement-based formulations, the fixed metals did
not leach out from the solidified concrete blocks over extended periods with the exception of Cu2+,
which reached a concentration of 0.4 mg/kg after 8 months in water of pH 8-9. In solid-waste
concentrations below 20%, the compressive strengths and shear strengths of the doped concrete did not
significantly differ from the control concrete. However, there is a critical weight percentage of 10-20%
additives above which the strength declines dramatically.
8.4 PERFORMANCE RESULTS
8.4.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process)
Regardless of the success of laboratory trials, the field trial suffered from a number of deficiencies that
make it difficult to evaluate the effectiveness of the process. The characterization of the site in terms
of the contaminants present and their distribution was poor. The maximum PAH concentration (the total
of six WHO carcinogens) was 12 mg/kg compared to a threshold trigger value of 50 mg/kg (16 USEPA
compounds) for residential development and 1,000 mg/kg for commercial developments, suggesting that
the site was in no need of PAH treatment. In contrast, the metal concentrations were high relative to the
threshold trigger values. The greatest weakness, however, was the lack of any control mixes not
containing the modified clay; thus, the possibility that a similar satisfactory performance could have been
achieved in the absence of the clay cannot be ruled out. The detailed leaching results for metals are not
provided in the reports but it should be noted that the criteria applied (50 times U.K. drinking water
limits) were quite generous.
A calculation shows that the six WHO PAHs in the treated soil would be reduced to about 8.5 mg/kg
compared to 12 mg/kg in the soil due to dilution by the other ingredients. The concentration of modified
clay is about 500 mg/kg. Given the low solubility of the PAHs, the insolubility of the clay, and the
probable inefficient mixing, it seems unlikely the clay could have a profound effect on binding the
PAHs.
8.4.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto
Unconventional Sorbents
The laboratory study showed that:
• Bauxite wastes of alumina manufacture (i.e., red muds) are capable of removing the radionuclides
137Cs and 90Sr as well as other heavy metals from water. Acid- and heat-treated red muds are more
effective in Cs removal than water-washed red muds, but heat treatment is detrimental to the surface
hydroxyl sites, which are important for ion-exchange sorption of 90Sr. Cesium uptake is predominan-
tly irreversible and exothermic and increases with the specific surface area of the sorbent. A rise in
pH favors the exchange sorption of Sr, while the specific adsorption of Cs is negatively affected.
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• Coal fly ashes from thermal power plants are capable of removing 137Cs and 90Sr, as well as other
heavy metals from water. Although acid treatment of fly ash did not result in an improved
adsorption capacity, acid treatment is recommended to prevent trace pollutant leach-out from the
adsorbent into water.
Red muds and especially fly ashes were shown to exhibit a high capacity for heavy metals. The sorption
sequence was Cu > Pb > Cd in accordance with the order of insolubility of the corresponding metal
hydroxides. The metals were held irreversibly and would not leach out into carbonic acid or bicarbonate-
buffered solutions.
Metal-loaded solid wastes could be solidified to an environmentally safe form thereby serving the two-
fold objective of water treatment and solid waste disposal. Thus, the two-fold objective of heavy metal
fixation and metallurgical solid waste disposal could be achieved with the constraint that fly ashes better
serve the purpose of heavy metal fixation than red muds.
Red muds and fly ashes, along with other metallurgical solid wastes and clay minerals, may be utilized
for constructing "natural barriers" (active permeable barriers) around shallow-land burial sites of low-
level radioactive wastes and heavy metal-containing products.
8.5 RESIDUALS AND EMISSIONS
8.5.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process)
No information on residuals or emissions was provided. Likely emissions would be dust that presents
similar hazards to any cement-based system, and possibly volatile organic compounds if temperatures
in the mixed material rise too high (the hydration of cement and lime are exothermic processes).
8.5.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto
Unconventional Sorbents
No information on emissions was provided, but as noted above, prior treatment of the fly ash is
recommended to reduce the possibility that trace elements already present in the ash will leach into the
environment.
8.6 HEALTH AND SAFETY
8.6.1 Project 34: Chemical Fixation of Soils Contaminated with Organic Chemicals
(Envirotreat Process)
No specific information was provided on health and safety. However, the likely hazards are those
associated with any cement- or lime-based system and are primarily those that result from contact with
highly alkaline materials and from chrome in cement. If volatile organic compounds are emitted due to
heating of the mix, additional hazards would be expected.
8.6.2 Project 29: Sorption/Solidification of Selected Heavy Metals and Radionuclides onto
Unconventional Sorbents
No specific issues of health and safety are related to this process, other than those that would ordinarily
attend pretreatment processes. The reports provided no indication of the specific activity of fully loaded
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wastes and whether these activities might pose a health hazard, but the purpose of the treatment is, after
all, to concentrate radionuclides on the solid adsorbent.
8.7 COSTS
No information was provided on costs for either project.
8.8 FUTURE STATUS OF CASE STUDY PROCESSES AND TECHNOLOGY AS A WHOLE
The Envirotreat Process (Project 34) clearly has potential but needs to be employed in better designed
studies that are more likely to reveal the claimed benefits of the active ingredient. The findings of the
pilot field study fail to demonstrate that the technology can bind PAHs or other organic compounds.
The use of wastes as adsorbents needs to be followed up by larger-scale studies, leading in due course
to field trials under practical conditions.
8.9 REFERENCES
1. Harris, M.R., S.M. Herbert, and M.A. Smith, Remedial Treatment for Contaminated Land, Volume
IX: Ex-Situ Treatment of Contaminated Soils, Sediments and Sludges, Construction Industry Research
and Information Association (London) 1995.
2. Anderson, W.C. (editor), Stabilization/solidification, American Academy of Environmental Engineers
(Annapolis, MD) 1994.
3. Hinsenveld, M. Stabilization/Solidification Technologies, In: Demonstration of Remedial Action
Technologies for Contaminated Land and Ground-water, Final Report, Volume 1, pp 53-63, USEPA,
EPA/600/R-93/012a, 1993.
4. USEPA, Corrective Action: Technologies and Applications,
Seminar Publication, EPA/625/4-89/020, 1989.
5. USEPA, Innovative Treatment Technologies Overview and Guide to Information Sources, Office of
Solid Waste and Emergency Response, EPA/540/9-91/002, 1991.
6. Bishop, P.L., "Stabilization/Solidification of Contaminated Soils: An Overview," Proceedings of the
Third International KfK/TNO Conference on Contaminated Soil '90, Arendt, F., M. Hinsenveld, and
W.J. van den Brink, W.J. (edits), Kluwer Academic Publishers (Dordrecht), pp 1265-1274, 1990.
7. Harris, M.R., S.M. Herbert, and M.A. Smith, Remedial Treatment for Contaminated Land, Volume
III: Site Investigation and Assessment, Construction Industry Research and Information Association
(London) 1995.
8. MacKay, M. and J. J. Emery, Practical Stabilization of Contaminated Soils, Land Contamination and
Reclamation, 1:3, pp 144-145, 1993.
9. Emery, J. J., "Stabilization of Industrial Sludge for Fill Applications," Volume 4, Proceedings Seventh
International Congress on the Chemistry of Cement (Paris), 1980.
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10. Barry, D.L., Treatment Options for Contaminated Land (Report to the Department of the
Environment), W.S. Atkins Research and Development (Epsom), 1982.
11. USEPA, Handbook on the In Situ Treatment of Hazardous Waste-Contaminated Soil, EPA/540/2-
90/002, 1990.
12. USEPA, International Waste Technologies/Geo-Con In Situ Stabilization/solidification, Applications
Analysis Report, EPA/540/A5-89/004, 1990.
13. USEPA, Hazardous Waste Control: Nomix® Technology, In: The SuperfundInnovative Technology
Evaluation Program: Technology Profiles, Fifth Edition, pp 100-101, EPA/540/R-92/077, 1992.
14. USEPA, S.M. W. Seiko Inc: In Situ Solidification and Stabilization, In: The Superfund Innovative
Technology Evaluation Program: Technology Profiles, Fifth Edition, pp 156-157, EPA/540/R-92/077,
1992.
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Chapter 9: OTHER REMEDIATION TECHNOLOGIES
Diane Dopkin
Environmental Management Support, Inc., Silver Spring, MD, U.S.
9.1 INTRODUCTION
The projects included in this chapter (22, 39, 50, 51, 53, 55, and 56) were not covered in previous
chapters for the following reasons: (1) the project is still in the site investigation stage; (2) remedial
options have been selected, but not implemented; or (3) the selected remedial option does not fit into
the categories of technologies highlighted in the other technology chapters (in situ treatment, physical-
chemical treatment, ex situ biotreatment, thermal treatment, or stabilization/solidification). The following
sections summarize the findings of these projects. Additional information on these projects is contained
in Appendix IV.
9.2 PROJECTS IN THE SITE INVESTIGATION STAGE
Projects 51 and 56 involve site investigations at contaminated industrial and military properties in the
Czech Republic and will continue into the remediation stage during Phase III of NATO/CCMS Pilot
Study.
9.2.1 Project 51: Sobeslav, South Bohemia Wood Treatment Plant
Since the 1870s, a wood processing plant has been operating on the outskirts of the town of Sobeslav,
located 120 km south of Prague, Czech Republic. Wood products such as railway sleepers and telegraph
poles were treated at the Sobeslav wood processing plant by immersion in boiling tar ("black"
impregnation) or by coating with a mixture of heavy metal salts ("white" impregnation).
In 1990, following a decision to install and upgrade existing process equipment, a site investigation was
performed to determine the extent of soil and groundwater contamination resulting from industrial
operations at the plant. This investigation was completed in December 1996. Soil and groundwater
contaminated with polycyclic aromatic hydrocarbons (PAHs) and metals were identified in an area of
approximately 1-2 km2. The contamination resulted from on-site disposal of tar sludges in poorly lined
pools, discharge of untreated effluent into the Luznice River, and discharges of chemicals from treated
products staged at the site prior to transportation.
Initial concerns about site pollution centered on the foul odors emanating from local drinking water
wells. The odors prompted an investigation by the local environmental health authority, which examined
the results of biological oxygen demand (BOD), chemical oxygen demand (COD), and non-polar
extractable organic analyses of surface water and groundwater samples. The more comprehensive
investigation initiated in 1990 included a detailed site walkover survey, aerial imaging, inspection of
plant life, installation and logging of monitoring wells, chemical sampling of soil and groundwater, and
pump testing to determine subsurface permeability. Although originally intended to be completed in 14
months, the investigation was extended to 35 months because of financial, analytical, and regulatory
difficulties.
During the walkover survey, the principal sources of contamination were identified as a leaking creosote
oil storage tank and seepage from unlined disposal lagoons in the southeast part of the site. Nearly 100
boreholes were drilled, and sandy to sandy clay soils overlying sedimentary clays were found to underlie
the site. Monitoring of the groundwater indicated a light non-aqueous phase liquid (LNAPL) layer up
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to 0.7 m thick at the site. Extensive analysis of soil and groundwater samples confirmed elevated
concentrations (unspecified) of PAHs, heavy metals, and phenols.
An initial investigation of remedial options was carried out by a German consultancy, which studied the
effectiveness of biotreating the contaminated soils. Results showed that an initial decrease in PAH
concentrations was followed by a greater increase in concentrations, which destroyed the degrading
micro-organisms. The study concluded that microbial activity had caused rapid desorption of
contaminants and increased bio-available concentrations to intolerably high levels. Although more
success was achieved during bench-scale testing using in situ groundwater biotreatment, the technique
was unsuccessful during field-scale testing. As a result, it was concluded that soil encapsulation, in
combination with pumping and treating groundwater with gravel filters, was the most cost-effective
remediation solution.
9.2.2 Project 56: Spolchemie a.s.—Mercury-Contaminated Site
The town of Usti nad Labem lies in the a region of North Bohemia known as the "black triangle"
because of the severity of its environmental problems. The Spolek pro chemicke a hutni vyroba
(Company for Chemical and Industrial Production), also known as "Spolchemie," is one of the most
contaminated sites in this region. Spolchemie was founded in 1856 for the production of chlorinated lime
and sodium bicarbonate. The company has since produced pesticides, including DDT and "Agent
Orange," and a variety of other chemicals. More than 30 separate production facilities are known to have
operated at the site, which occupies over 1,000 x 5,000 m2 (>500 hectares or 1,000 acres).
Mercury has been used in electrolysis operations at Spolchemie since 1890. Based on an environmental
audit of the site, it is estimated that the total release of mercury at the site has been greater than 500
metric tons. Liquid mercury has been observed during soil excavations.
Site investigations have been conducted near the electrolysis plant to assess mercury contamination in
soil and groundwater. Mercury concentrations in nine groundwater samples collected in January 1996
ranged from <0.1 ug/L to 154.1 ug/L, and concentrations in 39 soils samples ranged from <0.0001
mg/kg to 707 mg/kg. Concentrations of all but one of the groundwater samples exceed 0.1 ug/L, which
is the Ministry of Environment's Category A threshold concentration for mercury; four samples exceed
5 ug/L, which is the Category C threshold. Furthermore, nine of 39 soil samples exceed the Category
A threshold concentration of 0.3 mg/kg for mercury in soil; six samples exceed the Category C threshold
of 10 mg/kg.
Up to several hundred micrograms per liter of chlorinated hydrocarbons and slightly elevated
concentrations of zinc and copper were also detected in samples at Spolchemie. Remedial options are
being studied.
9.3 PROJECTS FOR WHICH REMEDIAL OPTIONS HAVE BEEN SELECTED, BUT NOT
IMPLEMENTED
The site characterization and risk assessment stages of Project 55 have been completed, and bioventing
and biosparging have been selected to remediate the site.
9.3.1 Project 55: Czechowice Oil Refinery Project
This project involves a working partnership between the U.S. Department of Energy (DOE) and the
Institute for Ecology of Industrial Areas (IETU), an independent organization under the Polish Ministry
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of Environmental Protection. Each phase of the project aims to demonstrate the technology and decision-
making processes involved in site remediation.
The first project initiated by the partnership was the environmental characterization, risk assessment, and
remediation of the Czechowice Oil Refinery, which has operated for nearly 100 years near the city of
Katowice in southern Poland. The refinery uses a catalytic cracking process to refine crude oil. Wastes
from the cracking process were deposited in site lagoons, which are now filled with a thick viscous
sludge. Leakage of the lagoons has contaminated soil and groundwater with several organic compounds.
Environmental characterization of the refinery will consist of a two-phased expedited site characterization
approach using low-cost, simple rapid-response technologies to obtain general site information, followed
by quantitative sampling using direct push technologies for data collection. Risk assessment will involve
the development and refinement of potential exposure scenarios. The scenarios will be combined with
the expedited site characterization results to quantify potential risks from the site to humans and the
environment. The estimates of risk will be compared to appropriate benchmark concentrations for the
contaminants.
Based on preliminary site information, bioventing and biosparging have been proposed to remediate the
lagoons. Bioventing involves the injection of oxygen and nutrients into the subsurface to aerobically
stimulate the indigenous microorganisms to degrade hydrocarbons to carbon dioxide and water. Vertical
injection wells will be installed around the perimeter of the lagoons to aerate and remediate the
contaminated vadose zone. Biosparging will be conducted to treat the lagoon sludge. Biosparging is
similar to bioventing except that the air and nutrients are injected into a liquid, in this case a lined basin
filled with process water. Sludge that has been pH-adjusted or mixed with a surfactant will be added to
the basin in batches. In the implementation of both remediation technologies, the level of microbial
activity, pH, contaminant concentrations, and rate of degradation will be carefully monitored.
9.4 PROJECTS FOR WHICH THE SELECTED REMEDIAL OPTION DOES NOT FIT IN THE
CATEGORIES OF TECHNOLOGIES HIGHLIGHTED IN THE OTHER TECHNOLOGY
CHAPTERS
Projects 22, 39, 50, and 53 involved remedial options not covered by the technologies detailed in the
previous chapters of this report. Project 22 describes the recovery of jet fuel from contaminated
groundwater; in situ bioremediation is proposed to treat residual contamination in the unsaturated zone,
but has not yet been implemented. Project 39 involves the ex situ treatment of groundwater contaminated
with dissolved organic compounds using a chemical oxidation technology.
Project 50 involved demonstration of a groundwater pump-and-treat system coupled with a pervaporation
system to treat groundwater contaminated with dissolved organic contaminants. In addition, in situ rotary
steam and air stripping were demonstrated for the treatment of contaminated soil. In situ bioremediation
has been proposed for further treatment of soil; however, the demonstration has not yet been conducted.
Project 53 involved both laboratory- and pilot-scale studies of in situ biotreatment, using aerobic and
anaerobic zones to mineralize tetrachloroethene (PCE) to ethene.
9.4.1 Project 22: Environmental Evaluations of Former Soviet Military Bases in Hungary
After the withdrawal of the Soviet army from Hungary in 1990, the Hungarian Ministry for Environment
conducted an environmental assessment and damage survey following a method acceptable to both the
Hungarian and Soviet governments. Tokol airbase was one of the sites identified as needing prompt
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remediation because it is located just 600 m from the Danube River and lies atop of the aquifer that
supplies the village of Halasztelek with about 5% of its municipal drinking water. Site investigations
determined that the groundwater was contaminated by free phase and dissolved hydrocarbons from a jet
fuel storage area. Contaminated groundwater from the airfield was migrating slowly towards the
Halasztelek water supply wells.
Recovery operations at Tokol began in August 1991. Recovery of free product from groundwater was
accomplished by depressing the water table to accelerate the flow of groundwater toward large diameter
recovery wells where product was separated using 150 mm diameter Filter Scavenger pumps. By June
1993, approximately 224,000 liters of jet fuel were recovered from 279,000 m3 of pumped groundwater.
By April 1994, the volume of recovered jet fuel was about 700,000 liters.
Remediation at Tokol was accomplished in cooperation with the Danish Agency of Environmental
Protection. The total cost was estimated at U.S.$600M (1994). The study concluded that although
immediate risks to the Halasztelek water supply was reduced, jet fuel sorbed to soil in the unsaturated
zone is still present and poses a long-term source of groundwater contamination. Pilot scale in situ
bioremediation was successful and was recommended as an effective method for further reducing risks
to groundwater quality.
9.4.2 Project 39: Management of Soil Vapors at the Basket Creek Site
The Basket Creek Site, located in Douglassville, Georgia, is an abandoned surface impoundment used
in the 1960's for the disposal of industrial wastes. The disposed wastes were ignited accidently and
burned for several days in 1970. The USEPA initiated emergency action at the site in 1991. Analyses
of soil samples revealed concentrations of toluene, methyl ethyl ketone, methyl isobutyl ketone in
concentrations exceeding 30%; concentrations of trichloroethylene and tetrachloroethylene of up to 8,000
mg/kg; and concentrations of mercury and lead of 400 mg/kg and 5,000 mg/kg, respectively.
Approximately 765 m3 of contaminated soil was present with total organic concentrations ranging from
5-10%.
An in situ soil vapor extraction (SVE) treatability study determined that the soil was not sufficiently
permeable for in situ SVE to be viable, and low temperature thermal desorption was rejected due to the
low flash point of the soil vapor (150°C), which resulted in ignition of a soil sample during the
treatability study. Based on the treatability results, ex situ SVE was selected to treat the contaminated
soil.
Contaminated soil was excavated from the site within a 60-foot by 120-foot (18.3 m by 36.6 m)
ventilated metal enclosure to prevent the escape of untreated vapors. The excavated soil was screened
to remove rock and debris; the screened soil was stockpiled, and ambient air was pumped through the
stockpile via 4-inch (10-cm) diameter slotted horizontal well screens.
Extracted vapors from excavation and SVE were passed through a bag-house for the removal of
particulates and treated with a thermal oxidizer. The thermal oxidizer operated at temperatures of 816-
871°C and had a greater than 95% removal efficiency.
In total, approximately 1,500 m3 of soil were excavated and treated. In addition, 100 tons of screened
rocks and debris, 18 yd3 (13.8 m3) of excavated metal and crushed drums, and 4,250 gallons (16,086
liters) of decontamination water were disposed at appropriate off-site facilities.
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The total cost of the project was $2 million (1993), which was $1 million less than the original estimate
in 1992. The project was interesting in that the soil was not treatable by SVE in situ, but could be
treated by venting ex situ after excavation and screening.
9.4.3 Project 50: Integrated Rotary Steam Stripping and Enhanced Bioremediation for In
Situ Treatment of VOC-Contaminated Soil (Cooperative Approach to Application of
Advanced Environmental Technologies)
This project involves technology demonstrations at the Department of Energy's Pinellas Northeast Site,
located in Largo, Florida, USA. Concentrations of chlorinated volatile organic compounds (VOCs) in
the sandy surficial aquifer at the site range from 10-1,000 mg/L. In January 1995, the following three
technologies were selected for pilot tests at the Pinellas site:
(1) groundwater pump and treat with a pervaporation system to remove VOCs from the pumped
groundwater while eliminating air emissions and the need for costly groundwater pre-treatment;
(2) in situ rotary steam and air stripping to treat the highest concentrations of VOCs in soil and
reduce them to a level of 100 mg/kg; and
(3) nutrient injection to enhance in situ anaerobic bioremediation of soil with VOC concentrations
of 100 mg/kg or less.
A potential cost savings of U.S.$5-10 million was anticipated over the proposed baseline remedial
design, which was a standard 30-year pump-and-treat system using groundwater recovery wells and an
air stripper. Furthermore, the proposed baseline remedial design was not expected to reduce the most
concentrated areas of VOCs to below drinking water standards.
Pervaporation Technology Evaluation
Evaluation of the pervaporation pilot test was conducted from 1995-1996. Two recovery wells pumped
groundwater to the system, which used membranes to allow VOCs to preferentially permeate. Transport
of VOC vapors through the membrane was induced by maintaining a lower vapor pressure on the
permeate side of the membrane than on the side of the influent groundwater. This pressure difference
was achieved by cooling the permeate vapor to make it condense.
The pilot system was capable of treating 1-2 gallons of groundwater per minute. Approximately 6,250
gallons of groundwater with VOC concentrations ranging from 500-1,000 parts per million (ppm) were
treated during the pilot test. Effluent contaminant concentrations were reduced to 1-4 ppm under
optimum operating conditions; however, the efficiency of the system was lowered due to membrane
fouling caused by the precipitation of iron gel. Moderate success was achieved by modifying the system
and adding chemicals to reduce membrane fouling. The only wastes produced during the pilot test were
the permeate and the spent filters used to inhibit membrane fouling. VOCs were successfully
concentrated in the permeate, eliminating air emissions. Full-scale system capital costs for the
pervaporation system to treat 20 gallons per minute are expected to range from U.S.$200,000-275,000;
operating costs are expected to range from U.S.$10-20 per 1,000 gallons (3,785 liters) of treated water.
Rotary Steam and Air Stripping Technology Evaluation
Evaluation of the rotary steam and air stripping pilot test is currently being conducted. The stripping
system injects steam and hot air through a rotating auger to volatilize VOCs sorbed onto soil particles.
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The off-gases are transported by the injected steam and air to a metal hood at the ground surface where
they are treated using a catalytic oxidation system for the destruction of contaminants and an acid-gas
scrubber to eliminate air emissions.
Thus far, the system has effectively reduced the concentrations of chlorinated VOCs in soil from 1,000-
6,000 ppm, to 100-300 ppm, which was the goal for this site. However, several operational problems
were experienced with the total system. In particular, the catalytic oxidation system was unable to handle
the quantity of the vapors generated by the stripping system. As a result, some vaporized VOCs initially
escaped from the metal hood. This problem was subsequently controlled by reducing the injection
pressures. The only wastes generated by the system were from the scrubber. The initial results of the
pilot test indicate that the operational costs will range from U.S.$70-200/yd3 (U.S.$92-260/m3).
Nutrient Injection to Enhance In Situ Anaerobic Bioremediation
The in situ anaerobic bioremediation system recently began operation and has not yet been evaluated.
The system involves a series of horizontal wells and infiltration galleries to control the hydraulic gradient
and supply nutrients to the contaminated zone.
9.4.4 Project 53: In Situ Bioremediation of Chloroethene-Contaminated Soil
In the Netherlands, between 20-30% of heavily contaminated sites have chlorinated hydrocarbons—in
particular, trichloroethene (TCE) and PCE—as a principal constituent. On some sites, the depth to
contamination makes ex situ treatment technically difficult and uneconomical. Therefore, there is a need
to develop in situ remedial techniques for this type of contamination. Biotreatment is particularly
attractive since it offers the potential for remediation without generating any secondary hazardous waste
for further treatment or disposal. However, biodegradation of chloroethenes is technically and
microbiologically complex, and might prove difficult to achieve under field conditions. This Pilot Study
project reports on the development of an in situ biotreatment for chloroethenes from bench-scale studies
to a pilot-scale field application.
Technical Concept
The Tauw Milieu approach to treating chloroethenes exploits both aerobic and anaerobic microbial
processes. Although chloroethenes such as PCE are persistent under aerobic conditions, they can be
dechlorinated sequentially by anaerobic bacteria to TCE, dichloroethene (DCE), vinyl chloride, and
ultimately to ethene. Since the dechlorination of DCE and vinyl chloride are the rate-limiting steps, these
compounds are accumulated under anaerobic conditions as intermediate breakdown products of PCE.
In contrast to PCE, however, less-chlorinated ethenes can be co-metabolically mineralized by aerobic
bacteria. The Tauw Milieu process degrades PCE through stimulation of bacteria in spatially separated
aerobic and anaerobic zones. PCE is degraded anaerobically to TCE and DCE, which are transported
downstream to an aerobic zone where they are mineralized to ethene.
Laboratory Studies
By February 1996, the process had been demonstrated and verified for PCE at the bench scale. These
studies showed that under anaerobic conditions, using formate and methanol as carbon and electron-
donor sources respectively, PCE and TCE were readily dechlorinated to DCE and other intermediaries.
In addition, using toluene or phenol as a co-substrate, TCE, DCE, and vinyl chloride were readily
degraded aerobically. Flask studies with indigenous bacteria from a proposed pilot-scale test site had
similar results.
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In order to evaluate degradation kinetics, a series of column experiments were performed using 0.7-L
columns of site soil through which 200 mL of site groundwater was recirculated. The soil column was
operated anaerobically, spiked with PCE, and supplied with formate or methanol as a carbon source and
electron donor. PCE concentrations initially decreased due to sorption onto column material, but
dechlorinated breakdown products were noted approximately three weeks after start-up. Although
degradation was observed using both formate and methanol, it was concluded that methanol would be
used for the pilot-scale system because of its lower cost and more stable pH profile. The aerobic column
was set up in a similar way to the anaerobic column. It was spiked with PCE and its breakdown
products (TCE, DCE, and vinyl chloride). The daughter products were readily degraded with the addition
of phenol to the column, but PCE degradation was not observed.
Pilot-Scale Study
The pilot-scale remediation study was conducted from August 1995 to September 1996 at a former dry
cleaning facility near the town of Breda. Soil and groundwater was contaminated with PCE over an area
of 1,800 m2 to a depth of 10 m. Concentrations of PCE in groundwater ranged up to 10,000 ug/L. The
unsaturated zone was remediated using soil vapor extraction, and the saturated zone and groundwater
were remediated by a combination of aerobic and anaerobic biodegradation.
The anaerobic biodegradation zone was created by the extraction and injection of groundwater (up to
250 m3 per day) to which methanol and nutrients were added. A total of about 1,100 kg of methanol was
injected. By carefully controlling the hydrogeological environment, anaerobic conditions were created
within the recirculating "groundwater loop." Downstream of this loop, aerobic biodegradation was
supported by slow infiltration of phenol (acting as a co-metabolite) through a series of wells. A well
downstream of the anaerobic treatment zone was used to extract up to 150 m3 of groundwater per day,
in order to prevent the contamination spreading and to provide water for the phenol infiltration process.
Extensive monitoring was conducted to determine the effectiveness and kinetics of the degradation
processes and to mitigate the migration of the contamination plume. Methanol was detected in all
monitoring wells in the anaerobic zone, in concentrations ranging from 120 to 800 umol/L. As soon as
the methanol was detected, anaerobic degradation was observed. PCE was degraded rapidly to DCE;
TCE, vinyl chloride, and ethene were present but did not accumulate significantly.
Under anaerobic conditions, PCE was dechlorinated at rates comparable to those found in the laboratory,
and evidence of complete anaerobic degradation to ethene was found. The aerobic process also proved
successful, with complete degradation of phenol and DCE. The limiting factor associated with in situ
biodegradation of chloroethenes appears to be the availability of suitable electron donors rather than the
presence of microorganisms.
Prognosis
The pilot study proved so successful that the site owner is continuing the remediation, which is expected
to take two to three years.
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Chapter 10: INTEGRATION OF TECHNOLOGIES
Kai Steffens
Probiotec GmbH
10.1 INTRODUCTION
Experience shows that contaminated sites frequently cannot be remediated by a single technology.
Complex contamination problems require the combination of different technologies for either different
contaminated areas and media or for a specific medium exhibiting complex contamination.
However, remediation strategies employing a single treatment technology and those employing a
combination of technologies are commonly more complicated and more expensive than is removal to
a landfill. Consequently, not only technical effectiveness (in terms of ability to achieve remediation
objectives, time requirements, potential environmental impacts, and cost), but also "political" (policy)
factors will influence the choice of strategy. These policy considerations may lead to adoption of
complex treatment systems that otherwise might be rejected in terms of short term costs alone (assuming
comparable technical effectiveness).
In Chapter 2, the terms "integrated" and "mixed" are used to describe combinations of technologies that
are used as part of an overall remediation strategy. In the Phase II Pilot Study, 23 projects used a single
technology, 19 involved an integration of technologies, and seven used different technologies in parallel
("mixed").
The term "integrated" refers to approaches involving process integration where two or more technologies
are used simultaneously or in series to treat a specific problem. The term "mixed" refers to projects
involving two or more technologies to treat different contaminated areas or media at a site as part of an
overall remedial strategy. The individual technologies applied in both the integrated and the mixed
projects are discussed in detail in the other chapters in this report.
This chapter focuses on projects in which treatment technologies were integrated to treat a contaminated
material in two or more stages. The goal is to discuss identified benefits, problems, and general
constraints.
The Pilot Study projects involving integration of treatment technologies are listed and briefly described
in Section 10.3. The general characteristics of the projects are summarized in Section 10.4 Performance
results of the integration are discussed in Section 10.5, while factors and limitations to consider for
determining the applicability of technology integration are dealt with in Section 10.6. Cost information
is provided in Section 10.7. Finally, general conclusions are discussed in Section 10.8.
10.2 BASIC OPTIONS AND CLASSIFICATION OF APPROACHES
Effective and efficient treatment of environmental contamination requires tailor-made solutions meeting
the specific requirements of the media to be treated, of the contaminants to be removed or destroyed,
and of the policy framework within which the project is to be implemented. In many projects, the
contamination problem can be adequately addressed by applying a single treatment technology. However,
problems may occur due to one or more technical or organizational factors:
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10.2.1 Technical Factors
• Difficult-to-treat media, such as soil with high proportion of fine-grained material; mixed solids (soil,
ashes, slags, brick, debris, concrete, plastics, wood, etc.); solids with a high proportion of organic
matter (e.g., peat); low-permeability soils and sediments; fine or uneven distribution of contaminants
(i.e., giving rise to low bioavailability); or large volumes of contaminated material requiring
treatment.
• Contaminants that are difficult to treat due, for example, to physical properties (e.g., low solubility);
chemical properties (e.g., not biodegradable); presence of complex contaminant mixtures (e.g., metals
and organic compounds).
10.2.2 Organizational Factors
• Policy (e.g., generation of secondary waste that would have to be landfilled)
• General project constraints, such as budget; time constraints; space constraints; or lack of community
acceptance (e.g., due to high emissions).
The limitations of the "single" technologies are discussed under their respective chapters in this report.
Frequently, combinations of technologies can overcome these limitations. In many cases, efforts are
made to reduce the amount of material requiring expensive treatment by separating fractions of materials
that can be reused without further treatment or with limited effort. In other cases, materials or
contaminants are difficult to treat, which means that the limitations of a single technology are evident
early in the development of the remediation strategy. In these cases, means of modifying the material's
physical and chemical conditions have to be identified and evaluated in order to allow treatment at all,
or to optimize cost and results.
The organizational factors mentioned above are commonly reduced to the "policy" requirement to avoid
generating secondary wastes that would have to be landfilled.
Technology integration can be generally classified into methods involving
• separation of fractions for volume reduction or to apply different downstream treatments; or
• increasing the availability of contaminants for treatment by mobilizing of contaminants in the
medium to be treated; modifying the chemical or physical properties of contaminants; or employing
treatment trains for sequential removal/treatment of different types of contaminants.
In practice, a combination of these options may be employed in an integrated treatment system to deal
with particularly complex contamination.
Separation of different fractions may be carried out to reduce the volume to be treated using a more
expensive technology or to be treated at all; to separate out fractions that need to be treated differently.
Separation is usually achieved through dry physical separation (e.g., crushing or sieving) or wet physical
separation (e.g., soil washing or other wet mechanical separation processes or flotation with or without
chemical pretreatment). Besides separating out the more contaminated fine grained concentrate, creating
a "clean" coarse fraction may be intended when applying wet mechanical separation processes. One
group of integration options is based on the principle of washing off the contaminants and the (highly)
contaminated fine particles from the surfaces of the coarser particles, leaving the coarse fraction
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relatively "clean." A second group of options uses physical techniques to separate fractions by exploiting
differences in the physical properties (e.g., specific gravity or surface hydrophobicity).
Mobilization of contaminants may be achieved by altering the medium to be treated. Examples include
• in situ methods, such as through fracturing, steam injection, air sparging, or soil flushing with
agents; and
• ex situ methods, such as crushing clay-clumps.
Mobilization may also be achieved by modifying the contaminants to increase availability to microbial
degradation by concentrating or pretreating the contaminants (e.g., partial oxidation of organics).
Treating combinations of different contaminants (e.g., organics and metals) usually will require
application of different processes in sequence. Table 10.1 lists the factors limiting effective treatment
with only one technology and the options to overcome these limitations.
Table 10.1: Factors Limiting Effective Treatment with Only One Technology and the General
Options to Overcome the Limitations
Limiting Factor
Soil with high fines
Mixed solids
Solids with high proportion of organic
material
In situ treatment of low-permeability
sediments
Fine or uneven distribution of
contaminants (low bioavailability)
Large volumes to treat
Low solubility contaminants
Non-biodegradable contaminants
Complex mixtures of contaminants
Options to Overcome Limitation
Separation
/
/
/
/
/
/
Mobilization of Sequential
Contaminants Treatment
/
/
/
/
/
/
/
10.3 CASE STUDIES CHOSEN
The 15 Pilot Study projects reviewed for this Chapter are listed in Table 10.2. Additional information
on the projects is provided in the brief descriptions that follow. Further information is available in the
project summaries found in Appendix IV.
This Chapter focuses on the integration of technologies. The individual technology elements, which make
up the integrated technologies discussed in this chapter, are described and analyzed in detail in the
respective technology-based chapters.
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Table 10.2: Projects Involving Integration of Treatment Technologies
Project
Description
Goal of
Integration
Trial of air sparging of a petroleum-
contaminated aquifer
Field trials of air sparging combined with
soil vapor extraction to determine the
increase of extracted VOCs
Mobilization of
contaminants
Field demonstration of an in situ
process for soil remediation using well
points
Field demonstration of a combined in situ
soil flushing and bioremediation technology
for BTEX and petroleum hydrocarbons
Mobilization of
contaminants
10 Integrated treatment technology for the
recovery of inorganic and organic
contaminants from soil
Integrated ex situ classification and solvent
enhanced soil washing process for metals
and PAHs; separation of metal particles by
classification; solvent extraction of PAHs
and hydrometallurgical leaching of metals
from a slurry (pilot-scale)
Mixed contamin-
ants requiring
different
treatment
13 Rehabilitation of a site contaminated
by tar substances using a new on-site
technique
Integrated soil washing and two-stage
thermal treatment of highly tar-contaminated
fines (full-scale, thermal unit: 1 ton/hr
operating capacity)
Volume
reduction
15 Combined chemical and microbiologi-
cal treatment of coking sites/
bioremediation of soils from coal and
petroleum tar distillation plants
Microbiological treatment of aromatic
hydrocarbons with and without oxidizing
pretreatments (bench-scale)
Increase
availability of
contaminants
19 Cleaning of mercury-contaminated soil
using a combined washing and
distillation process
Integrated soil washing and vacuum distil-
lation plant used to treat mercury contamina-
ted soil and debris (full-scale, 150 tonnes/
day)
Volume
reduction
24 Combined remediation technique for
soil containing organics: Fortec*
Combined hydrocyclone separation,
photochemical treatment, and bioremediation
(demonstration-scale, 300 m3 reactor)
Increase
availability of
contaminants
26 Treatment of creosote-contaminated
soil (soil washing and slurry phase
bioreactor)
Combined soil washing and slurry phase
bioreactor (pilot-scale, 1 ton/hr washing, 600
dm3 reactor)
Volume
reduction
27 Soil washing and chemical
dehalogenation of polychlorinated
biphenyl (PCB)-contaminated soil
Combined soil washing and chemical
dehalogenation (pilot/bench scale, 1.5 ton/hr
washing, bench-scale reactors)
Volume
reduction
31 Decontamination of metalliferous
mining wastes
Laboratory tests of a combination of
flotation and metal-leaching processes (pilot-
scale)
Volume
reduction
32 Cacitox™ soil treatment process
Tests of combined application of soil
washing (for physical separation) and metal
leaching (pilot-scale, 10 kg/hr)
Volume
reduction
33 In-pulp decontamination of soils,
sludges, and sediments
Tests of combined application of soil
washing (for physical separation) and metal
leaching (bench-scale)
Volume
reduction
36 Enhancement techniques for ex situ
separation processes particularly with
regard to fine particles
Tests of combined application of wet soil
separation techniques and biological
treatment of the contaminated fines fraction
(bench-scale)
Volume
reduction
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Project
Description
Goal of
Integration
42 In situ pneumatic fracturing and
biotreatment
Pneumatic fracturing in low-permeability and
over-consolidated sediments increases
permeability and improves the conditions for
in situ remediation (SITE demonstration)
Increase
availability of
contaminants
47 In situ electro-osmosis (Lasagna™
Project)
Fracturing in low-permeability and over-
consolidated sediments increases
permeability and improves the conditions for
in situ remediation, e.g., by electro-osmosis
(demonstration-scale)
Increase
availability of
contaminants
10.3.1 Project 1: Field Trial of Air Sparging of a Petroleum-Contaminated Aquifer
Goal: Mobilization of contaminants to increase removal rate.
Three field trials were carried out at a gas station site in Adelaide, Australia, to determine the effect of
air sparging when applied in combination with soil vapor extraction (SVE). Air sparging caused a
substantial increase in the amount of extracted contaminants in the short term. However, the rate slowed
down within just a few days. This effect probably resulted from a mobilization of contaminants from
the immediate vicinity of the boreholes. The areas and layers with higher permeability were assumed
to exhaust fairly quickly, while the lower permeability layers were only slightly affected by sparging.
The zone of influence was limited to between 3 m and 9 m from the sparging well.
10.3.2 Project 9: Field Demonstration of an In Situ Process for Soil Remediation Using
Well Points
Goal: Mobilization of contaminants to increase removal rate. Treatment of residual concentration with
second technology.
The field demonstration was carried out at a site contaminated with benzene, toluene, ethylbenzene, and
xylenes (BTEX) and aliphatic hydrocarbons. The treatment process consisted of a recirculation system
with injection and extraction wells. During soil flushing, a surfactant/co-surfactant solution was used to
mobilize the contaminants, which were separated in an above-ground effluent treatment plant. The
remaining hydrocarbon contamination was to be subjected to microbial degradation enhanced by the
injection of nutrients and air or hydrogen peroxide into the well points.
10.3.3 Project 10: Recovery of Inorganic and Organic Contaminants from Soil
Goal: Integration of different physical and chemical separation steps suitable for different
contaminants in a treatment train.
A bulk soil sample from two industrial sites in Canada was collected for a pilot-scale evaluation of this
integrated technology. After breaking down clay clods in a wet scrubber, the slurried soil was sorted by
particle size, density, or magnetic susceptibility to produce a contaminant concentrate that was to be
recycled off site. The remaining slurry was subjected to a leaching process involving solvent extraction
for polycyclic aromatic hydrocarbon (PAH) removal and a hydrometallurgical treatment involving
leaching metals selectively and recovering them using metal-selective adsorbents. The pilot tests were
reportedly successful in producing a soil suitable for further use. Full-scale remediation of one of the
sites was decided on using a 600 tonnes/day plant. Estimated costs are U.S.$75/tonne.
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10.3.4 Project 13: Rehabilitation of a Site Contaminated by Tar Substances Using a New
On-Site Technique
Goal: Volume reduction of the material treated thermally, and application of different treatment
technologies suitable for different grain size fractions of soil.
This on-site remedial demonstration project combining excavation of tar-contaminated soil followed by
on-site ex situ thermal desorption was carried out at an old gasworks site in a densely populated area
of Copenhagen. Soil and debris surrounding two tar reservoirs were excavated in a tent and subsequently
treated in a combined soil-washing and thermal-desorption system. Soil washing was used to provide
a volume reduction step by producing clean fractions in the particle size ranges >50 mm and 2-50 mm
through screening and high-pressure spray washing. The contaminated fraction (<2 mm) was treated
using a two-stage thermal desorption process. In the first stage water and volatile substances were
evaporated from contaminated materials. The off-gas was treated using a particulate dust trap and an air/
oil/water separator and condenser. The second stage, operating at higher temperatures, was used to
volatilize the heavier tar substances, which were recovered in an air/tar condenser
10.3.5 Project 15: Combined Chemical and Microbiological Treatment of Coking Sites/
Bioremediation of Soils from Coal and Petroleum Tar Distillation Plants
Goal: Pretreatment of contaminants to optimize biodegradation rates.
PAH-degrading bacteria were identified and the practicality of using bioremediation for PAHs in soil
was evaluated. Furthermore, an oxidation-based pretreatment was examined to assess whether subsequent
bioremediation was enhanced. Very limited information was provided on this project and on the success
of the oxidizing pretreatments. Considerable additions were required to observe any increased
degradation of PAHs. There are indications that ferrous sulfide was used as an oxidizing catalyst.
10.3.6 Project 19: Cleaning Mercury-Contaminated Soil Using a Combined Washing and
Distillation Process
Goal: Volume reduction of the material that was to be treated thermally, and application of different
treatment technologies suitable for different grain size fractions of soil.
The Marktredwitz Chemical factory in Germany was established in 1786 and manufactured various
mercury compounds (including agrochemicals) and mineral acids. Buildings, soil, and groundwater were
heavily contaminated with mercury. A distillation unit was used in combination with a soil washing plant
that separated the highly contaminated silt/clay soil fractions to form a pretreatment concentrate for
thermal treatment. The sand and rubble fraction was disposed as clean fill. The fine fraction (grain size
ranging from <100 urn to <8 mm) was transferred to the vacuum distillation unit. The treated soil was
water cooled in a rotating drum to an average temperature of <50°C and recombined with the coarse-
grained material from the soil washing plant.
10.3.7 Project 24: Combined Remediation Technique for Soil Containing Organics: Fortec
Goal: Volume reduction of material that is to be treated in downstream steps, and pretreatment of
contaminated concentrate to optimize biodegradation rates.
The system combines hydrocyclone separation of soil fractions resulting in separated coarse fractions,
which are either "clean" or can be subjected to additional soil washing. The slurry carrying the fine
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fraction can be treated in a photochemical (UV/H2O2) treatment step if persistent organic contaminants
(e.g., PAHs) are to be treated. The UV/H2O2 treatment partially oxidizes the organics and transforms
these compounds into biodegradable fragments. This photochemical pretreatment may be skipped if
organics are present, since they are more easily biodegraded. The final treatment step of the slurry is
a slurry-bioreactor, which is operated in batch mode.
10.3.8 Project 26: Treatment of Creosote-Contaminated Soil (Soil Washing and Slurry
Phase Bioreactor)
Goal: Volume reduction of the material that is to be treated in downstream steps.
Pilot-scale testing was done using a 1 tonne/hr soil washing unit. "Clean" coarse material was removed.
Soil washing was used as a pretreatment for froth flotation studies, which showed that a cationic
collector and frother removed high percentages of PAHs from the soil. PAH-contaminated slurry was
subjected to a subsequent bioreactor treatment in a pilot-scale unit.
10.3.9 Project 27: Soil Washing and Chemical Dehalogenation of PCB-contaminated Soil
Goal: Volume reduction of the material that is to be treated in downstream steps.
A soil washing unit with an operating capacity of 1.5 tonnes/hr was used for cleaning and separation
of a coarse grain-size fraction. The fines were treated further in a double air flotation cell. The
contaminated sludge from the flotation process was used for bench-scale testings of chemical
dehalogenation. Systems from three different vendors were tested, two of which (both closed reactors)
were successful. Detailed information on the dehalogenation testings was not presented.
10.3.10 Project 31: Decontamination of Metalliferous Mining Wastes
Goal: Volume reduction of the material that is to be treated in downstream steps.
Laboratory-scale studies of mineral processing techniques were carried out on lead- and zinc-containing
spoils from abandoned mine sites in Wales. Separation testing was conducted using dense media ("sink-
and float") and froth flotation cells. Subsequently, leaching tests were done using various chemical
agents. Results show that leaching of unprocessed material is significantly more effective than leaching
of processed material.
10.3.11 Project 32: Cacitox™ Soil Treatment Process
Goal: Volume reduction of the material that is to be treated in downstream steps.
The proprietary reagent converts insoluble or adsorbed contaminants into soluble complexes. Pilot-scale
studies used a plant with a capacity of 10 kg/hr to leach heavy metals and radionuclides from soil.
During application of this technology, soil washing should be applied as a pretreatment step to reduce
the volume by separating out a fine-grained contaminant concentrate.
10.3.12 Project 33: In-pulp Decontamination of Soils, Sludges, and Sediments
Goal: Volume reduction of the material that is to be treated in downstream steps.
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Laboratory- and bench-scale studies of metal leaching processes were carried out using a 10-kg sample
of soil contaminated with copper, chromium, zinc, and arsenic. It is indicated that a preliminary soil
washing process should be used for initial volume reduction by separation of a fine-grained concentrate.
The results of the leaching tests show that arsenic was the contaminant most difficult-to-treat, requiring
multiple acid leaching to achieve low residual concentrations. Other trials were done with mercury-
contaminated soil, including the investigation of a thermal option (heating the material to around 800°C)
to achieve regulatory targets.
10.3.13 Project 36: Enhancement Techniques for Ex Situ Separation Processes
Particularly with Regard to Fine Particles
Goal: Volume reduction of the material that requires further treatment or is to be landfllled.
Laboratory- and pilot-scale tests were done with two soils contaminated with organics. The study
focused on the fate of highly contaminated fine particles in a wet separation processes. Subsequent tests
were conducted using a laboratory-scale slurry bioreactor for treatment of the fines. The study concludes
that wet separation techniques ("soil washing") can be beneficially applied if a substantial fraction of
the soil of grain size >0.002 mm is contaminant free, and if material <0.002 mm is less than 30-35%
by weight of the original feed soil.
10.3.14 Project 42: In Situ Pneumatic Fracturing and Biotreatment
Goal: Improvement of conditions for subsequent in situ treatment.
A field-scale pilot study was done under the USEPA's Superfund Innovative Technologies Evaluation
(SITE) Program. Low-permeability and over-consolidated sediments were subjected to pneumatic
fracturing (by pressurized air) to increase the permeability of the soil to liquids and vapors. In the field
demonstration, permeability was increased by up to 40 times within an effective radius of about 6 m.
This technology can improve the conditions for in situ treatment of low-permeability sediments by SVE
or biodegradation, for example. The results of the field test combining fracturing and bioremediation are
promising.
10.3.15 Project 47: In Situ Electro-Osmosis (Lasagna™ Project)
Goal: Improvement of conditions for subsequent in situ treatment.
The overall concept of the Lasagna™ technology is to introduce treatment zones (zones of high
permeability containing treatment agents) into contaminated areas. Electro-kinetic mechanisms carry
water and contaminants through these zones for treatment in situ or after extraction. To improve
conditions for in situ treatment in low-permeability sediments, hydraulic or pneumatic fracturing may
be employed.
10.4 REVIEW OF CASE STUDIES AS A GROUP
In eight of the 15 Pilot Study projects employing integrated technologies, the primary goal of integration
was to reduce the volume of the material requiring expensive treatment, such as thermal treatment of
organics and mercury (in two projects) or leaching of metals (in three projects). In other cases, wet
physical separation processes were applied to form a fine-grained contaminant concentrate that was
subjected to further treatment: microbial degradation in bioreactors (in two projects) and chemical
dehalogenation of PCBs. Information on various aspects of the projects is summarized in Table 10.3.
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Table 10.3: Goal of Combination, Input Materials in Terms of Medium Treated, Contaminants
Present, Types of Technologies Combined and Scale of Project
Project
Input Materials
Contaminants
Technologies
Combined
Scale
Separation of Fractions
13 Rehabilitation of a site
contaminated by tar
substances using a new
on-site technique
19 Cleaning of mercury -
contaminated soil using a
combined washing and
distillation process
26 Treatment of creosote-
contaminated soil (soil
washing and slurry phase
bioreactor)
27 Soil washing and
chemical dehalogenation
of PCB -contaminated soil
3 1 Decontamination of
metalliferous mining
wastes
32 Cacitox™ soil treatment
process
33 In-pulp decontamination
of soils, sludges, and
sediments
36 Enhancement techniques
for ex situ separation
processes particularly
with regard to fine
particles
Soil and debris
(fraction <2 mm)
Soil and debris
(fraction 0.1-8 mm)
Sandy soil
Soil and debris
(fraction <0.1 mm)
Mine spoils
Most testings with
fine particle soils
No data
2 Soils with fines
(O.063 mm)
contents of 43% and
62%
Tar
Mercury
PAHs
PCBs
Pb, Zn
Heavy metals,
radionuclides
Cu, Cr, Zn, As,
Hg
Diesel fuel,
PAHs
Soil washing and
two-stage thermal
treatment
Soil washing and
vacuum distillation
Soil washing and
slurry-phase
bioreactor
Soil washing and
chemical
dehalogenation
Flotation and
metal leaching
Soil washing and
metal leaching
Soil washing and
metal leaching
Wet soil
separation and
biological
treatment
Full-scale, thermal
unit: 1 ton/hr
operating capacity
Full-scale,
150 tonnes/day
Pilot scale,
1 ton/hr washing,
600-dm3 reactor
Pilot/bench-scale,
1.5 ton/hr
washing, bench-
scale reactors
Laboratory tests
Pilot-scale, 10
kg/hr
Bench-scale
Laboratory- and
pilot-scale
Mobilization of Contaminants to Enhance Treatment
1 Trial of air sparging of a
petroleum-contaminated
aquifer
9 Field demonstration of an
in situ process for soil
remediation using well
points
In situ (water table
at 7.5 m depth)
In situ
VOCs, gasoline
BTEX,
petroleum
hydrocarbons
Air sparging and
SVE
Soil flushing and
bioremediation
Field trials
Field demonstra-
tion
Increase Availability of Contaminants to Treatment
15 Combined chemical and
microbiological treatment
of coking sites/bio-
remediation of soils from
coal and petroleum tar
distillation plants
Soil
Aromatic
hydrocarbons
Oxidizing
pretreatments/
microbiological
treatment
Bench-scale
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24 Combined remediation
technique for soil
containing organics:
Fortec
42 In situ pneumatic
fracturing and
biotreatment
47 In situ electro-osmosis
(Lasagna™ Project)
Sandy soil/fines
Low permeability
sediments
Low permeability
sediments
PAHs,
chlorophenol
Benzene,
toluene, and
xylene
-
Hydrocyclone
separation and
photochemical
treatment and
bioremediation
Pneumatic
fracturing and
biotreatment
Fracturing and
electro-kinetics
Demonstration
scale, 300-m3
reactor
SITE
demonstration
Field
demonstration
Sequential Removal of Different Types of Contaminants
10 Integrated treatment tech-
nology for the recovery
of inorganic and organic
contaminants from soil
Soil
Cu, Pb, Zn, Classification
PAHs and solvent
enhanced soil
washing and
leaching
Pilot-scale
Mobilization of contaminants was the goal in two projects. Both were in situ processes targeting an
increase of the amount of contaminants extracted by conventional methods like SVE and groundwater
pump-and-treat approaches. Both technologies were applied at field demonstration scale.
Low availability of contaminants to treatment was the reason that four projects modified the physical-
chemical properties of the contaminants. Two of these involved an oxidizing pretreatment process for
organics in slurries. In one of these cases, the slurry had been generated by using a wet mechanical
separation process. Unfortunately, the reported data are rather limited in both cases. An evaluation of
the pretreatment effect is therefore restricted to some global assumptions.
Only one of the reviewed projects involved a combined technological approach to a matrix containing
mixed contaminants (organics and metals). The pilot-scale tests of these integrated technologies were
reported to be successful, although the reported data sets are limited.
10.5 PERFORMANCE RESULTS
10.5.1 Overview
The effectiveness of integrating treatment technologies should be judged on the basis of their ability to
achieve the goals of the overall treatment system. However, the primary technical factor for evaluating
the performance of the integration is the degree to which the goals of the integration itself (e.g.,
reduction in the volume of material to be subjected to downstream treatment) are achieved. Table 10.4
lists the categories of the projects reviewed in this chapter together with criteria that can be employed
for the performance evaluation of integration. The costs of integrating the technologies are also discussed
below. Tables 10.5 to 10.8 show the key data for the performance evaluation for the categories.
Information was very limited for some projects.
10.5.2 Separation of Fractions
The integrated technologies involving separation of fractions succeeded in reducing the volume of the
material requiring treatment in more expensive or technically more complicated downstream treatment
processes. In Projects 19, 27, 31, and 36, a significant portion of the soil was separated in soil washing
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Table 10.4: Categories of Integration of Technologies and Respective Criteria
Category
Separation of fractions
Mobilization of contaminants to enhance treatment
Increase of availability of contaminants for treatment
Sequential removal of different types of contaminants
Example criteria
• Volume reduction achieved
• Concentration in separated fractions
• Increase of contaminant mobilization in the
medium
• Increase of destruction caused by pretreatment
• Interferences reducing different treatment effects
Table 10.5: Performance Data of the Separation of Fractions Category
Project
13 Rehabilitation of a site
contaminated by tar
substances using a new
on-site technique
19 Cleaning of mercury-
contaminated soil using
a combined washing
and distillation process
26 Treatment of creosote-
contaminated soil (soil
washing and slurry
phase bioreactor)
27 Soil washing and
chemical
dehalogenation of PCB-
contaminated soil
31 Decontamination of
metalliferous mining
wastes
Contaminants
Tar
Mercury
PAHs
PCB
Pb, Zn
Volume
Reduction
No data
About
30%
No data
60%
90%
Contaminant Concentrations (mg/kg)
Input for
Pretreatment
No data
Average:
500 mg/kg Hg
peaks: 5,000
mg/kg Hg
No data
50-300 mg/kg
20 wt% Pb,
15 wt% Zn
Output of
Pretreatment
Coarse: 13-35 mg/kg
"total tars"
7.9-23 mg/kg Hg
No data
Coarse: <10 mg/kg;
fines (<0.1 mm): no
data
<2 wt% metals in
light fraction;
32 wt% Pb, 5 wt%
Zn in heavy
concentrate
Input for
Downstream
Treatment
Fines: 1,500-
83,000 mg/kg
"total tars,"
median value
11,000 mg/kg
(1.1 wt %)
1,000-4,000
mg/kg Hg in
soils
No data
250 mg/kg
No data
Output of
Downstream
Treatment
median value
22 mg/kg
"total tars"
Average in
January 1995:
20 mg/kg Hg
Flotation: 90-
95% PAH
removal
(sandy soil),
20-90% PAH
removal (clay
soil);
bioreactor:
97% PAH
reduction after
6 days
< 1 mg/kg
Removal rates
from untreated
material:
NaOH: 25-92
% Pb, 3-23%
Zn; H2SO4: 2-
33% Pb, 12-
64% Zn; much
lower removal
from
pretreated
material: 2-5%
"metals"
removed
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32 Cacitox™ soil treatment
process
33 In-pulp
decontamination of
soils, sludges, and
sediments
36 Enhancement
techniques for ex situ
separation processes
particularly with regard
to fine particles
Heavy metals,
radionuclides
Cu, Cr, Zn, As
Two samples:
1) Diesel
2) PAHs
No data
No data
1) fraction
>0.01mm,
68-72%
2) fraction
>0.01mm,
78%
Contaminant Concentrations (nig/kg)
No data
No data
1) 3,000-4,000
mg/kg TPH,
4 mg/kg PAHs
2) 2,000-3,000
mg/kg TPH,
200-300 mg/kg
PAHs
No data
No data
1) fraction >0.01
mm: 200-290 mg/kg
TPH (3-4 hydro-
cyclone repasses)
2) fraction >0.01
mm, 4,200 mg/kg
TPH, 320 mg/kg
PAH
No data
Cu: 360, Cr:
621, Zn: 414,
As: 1,204 mg/
kg
1) Fraction
<0.01 mm,
12,000 mg/kg
TPH
2) fraction 0-
0.063 mm,
413 mg/kg
PAH
Metals
exceeded
Dutch "B"
values; 98%
removal of
organics
Cu: 22, Cr: 74,
Zn: 68, As:
112 mg/kg;
multiple acid
leaching: As
650 down to
22 mg/kg
1) fraction
<0.01 mm,
2,300 mg/kg
TPH
2) fraction 0-
0.063 mm, 214
mg/kg PAH
or flotation processes. The flotation tests in Project 31 resulted in a potentially recyclable metal-rich
concentrate leaving the "light" fraction as an input material for further processing in a metal-leaching
process. This process needs to be optimized to increase contaminant removal. The same is true for
Projects 32 and 33, which also involved leaching processes as a downstream treatment.
The volume reduction effects of the soil washing processes are critically dependent on the fines content
of the original feed soil and the distribution of contamination in the different grain size fractions. In
Projects 19 and 27, volume reduction did not reach the anticipated level. In Project 19, this was caused
by higher-than-expected contamination of the fine-to-medium size fraction, which therefore could not
be treated with the required effect by soil washing alone; it had to be subjected to thermal treatment
together with the fines. The "cutting grain size" of the soil washing had to be increased, resulting in a
larger amount of separated fines.
In Project 27, the fine-grained portion of the feed soil was reported to be much higher than anticipated.
Nonetheless, the reduction by 60% in this case would result in significant savings of costs and effort
during the downstream treatment.
The target volume reduction, or "separation of fractions," was achieved by the different approaches.
However, in the soil washing projects, removing contaminants from the coarse fraction was an additional
goal. It was difficult to achieve cleaning levels and analytically determine the extent of contaminant
removal. Although the reported data sets in this respect are limited, it can be stated that in Projects 13,
19, 27, and 36 (total petroleum hydrocarbon [TPH] sample), a significant cleaning effect was achieved.
In other cases, either no data were reported or the coarse fraction still showed elevated levels of
contaminant concentrations (e.g., Project 36, sample 2).
10.5.3 Mobilization of Contaminants
Performance data for this category are provided in Table 10.6. Only for one of the two projects of this
category were data reported that can be evaluated regarding the effect of combination of technologies.
The field trials of in situ air sparging in Project 1 showed that preferred flow paths of air in the
subsurface were exhausted very rapidly when SVE was supplemented with air sparging. After additional
Volume
Project Contaminants Reduction
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air sparging was applied, the contaminant yield of SVE increased very rapidly and significantly, but
dropped after about 30 hours to very low values.
Table 10.6: Performance Data of the "Mobilization of Contaminants to Enhance Treatment"
Category
Project
1 Trial of air sparging of a
petroleum-contaminated
aquifer
9 Field demonstration of an in
situ process for soil
remediation using well points
Contaminants
volatile organic
compounds
(VOCs),
gasoline
BTEX,
petroleum
hydrocarbons
Status Before
Mobilization
Total
hydrocarbons:
initially: 0.5-0.8
kg/day, before
sparging: 0.1-0.2
kg/day
No data
Status After
Mobilization
Total
hydrocarbons:
0.8-1.5 kg/day
dropped after
30 hours to
<0.1 kg/day
No data
Degree of Increase
About ten times for
about 30 hours.
After 30 hours, drop
due to exhaustion of
preferential flow
paths
No data
From the projects results, it cannot be determined if preferred flow paths were created by air sparging,
or if they were also present and active during the "conventional" SVE. In both cases, air sparging was
beneficial:
• If the preferred flow paths are caused by air sparging, it can be concluded that air sparging is not
a suitable method to enhance an evenly distributed removal of contaminants from a sedimentary
formation by SVE.
• If these flow paths are present no matter if air sparging is applied or not, SVE would be a longer
lasting effort to exhaust these paths and not more. Thus, the trials would have shown in a very short
period of time that SVE does not affect the entire subsurface but only parts of it.
In the future, air sparging could be an option to check the effectiveness of long-term SVE efforts under
the conditions of the particular project.
10.5.4 Increase of Availability
Performance data for projects involving an increase of availability are given in Table 10.7. The effect
of technology combinations in this category is very difficult to evaluate based on the reported data.
Projects 42 and 47 involved site or medium pretreatment. In these cases, fracturing was used—or should
be used—as a method to allow in situ treatment of densely packed sediments with low permeability. It
is unlikely that in situ treatment of these sediments without fracturing would be possible. Therefore,
given that in situ treatment is the only way to handle the problem, the pretreatment by fracturing can
be assumed successful if there is any treatment effect at all. In Project 42, pneumatic fracturing was
shown to increase permeability by up to 40 times. Thus, this appears to be a useful means to apply in
situ processes to a much wider range of cases than in the past.
The oxidizing pretreatment in Project 24 showed a significant increase in biodegradability of PAHs.
PAHs were partly oxidized by physical-chemical treatment (UV/H2O2) and were thus more available for
microbial degradation in a slurry-bioreactor process. Test results for chlorophenol were interpreted as
showing the same effect as the PAH results. It is remarkable that the pretreatment process-step is an
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Table 10.7: Performance Data of the "Increase of Availability of Contaminants to Treatment"
Category
Project
15 Combined chemical
and microbiological
treatment of coking
sites/bioremediation of
soils from coal and
petroleum tar
distillation plants
24 Combined remediation
technique for soil
containing organics:
Fortec
42 In situ pneumatic
fracturing and
biotreatment
47 In situ electro-osmosis
(Lasagna™ Project)
Contaminants
PAHs, phenols,
cyanides
Petroleum
hydrocarbons
PAHs
Chlorophenol
BTEX
trichloroethene
(TCE)
Without
Pretreatment
No data
Petroleum
hydrocarbons
decreased from 400-
5,000 mg/kg down
to 100 mg/kg in 3-8
days
PAHs: no degrada-
tion observed
Chlorophenol:
decreased from 200
to 100 mg/kg in 24
days
No treatment
possible
Vertical electrodes
were used.
Control plot (no
treatment): TCE
decreased from 89.9
to 49.5 mg/kg
With
Pretreatment
PAH decreased
from 800 to 200
(after 12 months);
phenols: 75%
degradation (after 7
weeks); cyanides:
50% removal (after
2-3 months)
Petroleum
hydrocarbons: same
as without
pretreatment
PAHs: decreased
from 30 mg/kg to
5-10 mg/kg in 15
days
Chlorophenol:
decreased from 160
to 60 mg/kg in 24
days
79% reduction in
soil-phase BTEX
TCE decreased
from 72. 6 to 1.1
mg/kg
Degree of
Increase
no data; info
that
considerable
additions were
required to
observe
increased
degradation
Petroleum
hydrocarbons:
no difference
detectable
PAHs: pretreat-
ment allowed
degradation
Chlorophenol:
increase unclear
Fracturing
increased
permeability by
up to 40 times
within 6 m
radius
In the future,
horizontal
electrodes will
be placed by
fracturing
optional part of the capabilities of the soil treatment center in this project. This combination is a
beneficial way to improve flexibility in soil treatment and to overcome impediments to microbial
degradation of PAHs.
10.5.5 Sequential Removal of Contaminants
Performance data for projects involving sequential treatment are given in Table 10.8. In Project 10, an
ex situ classification was combined with a solvent-enhanced soil washing process for metals and PAHs.
The separation of metal particles by sorting resulted in a metal-rich concentrate of the fine particles.
Unfortunately, the concentrate was not characterized in deeper detail in the project report. After this
treatment, the remaining soil contained only 7% of the initial lead content, meeting the regulatory limits
of either 1,000 mg/kg for industrial use or 500 mg/kg for residential use.
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Table 10.8: Performance Data of the "Sequential Removal of Different Types of Contaminants"
Category
Project
10 Recovery of inorganic
and organic contaminants
from soil
Contaminants
Cu, Pb, Zn,
PAHs
Removal in Step 1
Metal concentrates for
potential recycling
contained 55% by weight
of iron
lead was reduced to 7% of
the initial content
Removal in Step 2
Benzo(b)fluoranthene:
decreased from 14 to 4
mg/kg, Zn from 4,000
down to 360 mg/kg, Cu
was not affected by
treatment
The solvent extraction of PAHs from the remaining slurry resulted in significant removal of benzo-(b)-
fluoranthene and a successful hydrometallurgical leaching of zinc. Further optimization should focus on
improving removal of other metals. This project is an example of treatment of different types of
contaminants in sequential steps. The composition and other properties of the treated material were not
reported.
10.6 FACTORS AND LIMITATIONS OF INTEGRATED TECHNOLOGIES
10.6.1 Separation of Fractions
In this category, technologies like soil washing and flotation are included as pretreatment processes.
Important factors to consider, limitations, and integration into treatment trains are discussed below.
Separation by Soil Washing
The portion of fines present in the feed soil and the distribution of contaminants in different grain sizes
determine the volume reduction that can be achieved. If contaminants mainly adhere to fine particles,
and the soil washing process minimizes "misplaced" fines, the volume reduction can be significant.
Minimizing misplaced fines, (in the coarse fraction) together with the efficiency of washing contaminants
off the surface of coarser particles, are the critical factors for the residual contamination in the coarse
fraction.
Separation by Flotation
The portion of material to be removed by exploiting the differences in physical-chemical properties must
be significant. The separated "heavy" material—i.e., metal concentrates—must be very suitable for
metallurgical processes. The flotation process should not hinder downstream processes like leaching of
metals from the "light" fraction, solvent-extraction, or microbial degradation of organics. An example
of interferences between the pretreatment and the downstream treatment of the light fraction by metal-
leaching was given in Project 31. No information was given on the suitability of recycling of
concentrates.
10.6.2 Mobilization of Contaminants to Enhance Treatment
The examples for this category show a potential to improve the treatment of proven technologies like
in situ SVE and groundwater pump-and-treat systems. The effect itself and the duration of the effect may
promote clean-up efficiency and may provide information on conclusions about the future course of the
chosen remedial approach.
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The critical factors for applying SVE in combination with air sparging are the degree to which the
contaminant yield can be increased and the development of this increase. If low soil permeability is the
reason for low yields of extracted contaminants, air sparging might not improve extraction. Project 1
shows that the presence (or formation) of preferred flow paths governs the conditions for this approach.
The other example of an attempt to mobilize contaminants and increase extraction by groundwater
pumping by using surfactants or co-surfactants (Project 9) raises two issues:
• whether increase in solubility from the introduction of the surfactant into the aquifer is always
desirable—this particular issue is of critical importance in discussions with water-control authorities;
and
• the possibility of impediments to microbial degradation caused by the surfactant enhanced extraction
pretreatment should be evaluated in laboratory trials at a reasonable investment of resources.
10.6.3 Increase of Availability of Contaminants to Treatment
The main characteristic of the technology combinations in this category is that without the preliminary
treatment of the subsurface or contaminants, contaminant removal would not be possible. Therefore, the
evaluation of the factors and limitations of the combination of the technologies applied can be limited
to the respective issues brought up in the discussions of the single technologies in the other chapters of
this report.
10.6.4 Sequential Removal of Different Types of Contaminants
This category is represented by Project 10, in which a solvent-enhanced soil washing process for metals
and PAHs was the downstream treatment for the separation of metal particles by sorting. The main
factor is the hindering of the downstream extraction or leaching caused by the flotation process's effects.
The example shows that different leaching process steps probably have to be applied for different metals.
Another factor is the extent to which the pretreatment process can lower the contaminant concentration
levels. Because of the high cost of downstream treatment agents and the severe damage they cause to
the soil structure, the largest potential for optimization of this technology combination is considered to
be the preliminary wet separation process.
10.7.5 General and Concluding Aspects Regarding Integration of Technologies
Factors and Limitations for Ex Situ Treatment
In the projects involving ex situ treatment, thermal treatment, microbial degradation, and chemical
treatment were applied as downstream processes to the wet, mechanically separated fine fractions. Thus,
one of the main characteristics of the wet mechanical separation processes, the generation of highly
contaminated concentrates was matched with technologies targeting these secondary waste streams. Other
ex situ projects involved pretreatment to enhance microbial degradation of organics and sequential
treatment of metals and organics.
Besides the general critical factors for the pretreatment of the soil stated above, the following factors
are important for integrated technology application in practical clean-up projects:
• Interference of physical and chemical pretreatment that hinder or complicate downstream treatment.
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• Availability of two or more compatible technologies in terms of their technological "readiness."
• Throughput capacities per time unit of the technologies must match as well as possible to allow
smooth handling of materials on the site and to avoid interim storage and multiple handling of
materials.
• Condition and properties of materials that have undergone thermal treatment or multiple solvent- and
acid-leaching.
Factors and Limitations for In Situ Treatment
The in situ projects reviewed involved enhancement of treatment by mobilizing contaminants or
improving the subsoil conditions. The critical factors for the application of the in situ pretreatment
technologies of this group are discussed above and in the respective chapter of this report. For the
integration of technologies, the following factors and limitations are important:
• availability of two or more compatible technologies in terms of their technological "readiness."
• cost-effect ratio of the enhancing technology.
• duration of the positive effect.
• environmental impact of substances introduced into the subsurface.
• control of the process, increasingly complicated in combinations of in situ technologies.
In the projects reviewed, a combination of technologies has been shown to make treatment possible, to
increase treatment efficiency, and to adapt the remedial approach to policy requirements such as the
avoidance of secondary wastes that would have to be landfilled.
Especially in the latter respect, the requirement to minimize residues is promoting the application of
integrated technologies. The cost of additional pretreatment or downstream-treatment, however, can be
considered to be the main hurdle for integrated technologies application. Additional cost factors include
additional investigation of treatment options, investment cost for additional plants or equipment, cost for
longer project duration, cost for interim storage and additional handling of material, and fees for
treatment of material in treatment centers.
The policy framework in a region or a country for the decisions in a particular remedial project can be
considered the critical factor for having a real option either to landfill or to treat residues. In some cases
of site clean-up, contaminated soil is disposed at municipal waste landfills. In these cases, prices range
from U.S.$80-150/tonne. If contaminated soil or treatment residues are to be handled as hazardous
wastes, landfilling in state-of-the-art hazardous waste landfills costs about U.S.$ 500-800/tonne. In
Project 27, costs for incineration of PCB-contaminated material was reported to be U.S.$5,000-7,5007
tonne. In the last two cases, many efforts of integrating remedial technologies would be competitive. If
the decision either to treat the soil or to dispose it in a low-cost landfill is more or less left to the
responsible project personnel, in most cases no expensive treatment will be carried out.
In the international remedial marketplace, two factors are under discussion:
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• How many follow-up costs (e.g., monitoring and maintenance of closed landfills) should be included
in the landfilling fees (what is "maintenance" and for how long must it be continued)?
• Should contaminated soil be disposed at municipal waste landfills or at hazardous waste landfills?
The policy decisions made in these respects set the framework for soil treatment. Costs for integrating
technologies in site cleanup, in most cases, are higher than landfilling. Therefore, policy decisions must
support decontamination by establishing a policy for minimizing disposed wastes by treatment.
10.7 COSTS
As shown in Table 10.9, only very limited information was provided on the costs of the studied or
applied technologies. One of the reasons may have been that most of the technologies were only applied
in bench- or pilot-scale testing. In the two full-scale applications of wet mechanical soil separation and
subsequent thermal treatment of the fines fraction (Projects 13 and 19), cost data were reported for the
entire clean-up project. A breakdown of cost showing the relative portions of the two treatment steps
was not reported.
10.8 GENERAL CONCLUSIONS
The examples of technology integration in the Phase II Pilot Study show that significant progress has
been achieved by efforts to:
• optimize cost and energy consumption by reducing materials volumes to be treated thermally;
• improve the conditions for microbial degradation of contaminants;
• improve the conditions to permit treatment of difficult-to-treat media in situ;
• achieve higher removal rates; and
• avoid landfilling of residues.
Although many of the technological approaches to integration of remedial technologies are still at bench-
or pilot-scale, there is a broad spectrum of promising approaches and technologies. The review of
application factors has shown that the limitations inherent in many single technologies can be
compensated for by using integrated technologies. Therefore, it can be stated that integrated treatment
technologies are needed to handle complex projects of site remediation better, faster, and (in the long-
term) more cheaply.
10.9 ACKNOWLEDGEMENTS
The author wishes to gratefully acknowledge:
• The German Federal Ministry for the Environment, Nature Conservation, and Nuclear Safety for
providing financial resources for the preparation of this chapter.
• Prof. Harald Burmeier, representing the Fachhochschule Nordostniedersachsen, Suderburg
(University of Applied Studies and Research), for providing substantial input and helpful comments.
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Table 10.9: Cost Data (to the extent available)
Project
Information on Costs
Separation of Fractions
13 Rehabilitation of a site contaminated
by tar substances using a new on-
site technique
19 Cleaning of mercury -contaminated
soil using a combined washing and
distillation process
26 Treatment of creosote-contaminated
soil (soil washing and slurry phase
bioreactor)
27 Soil washing and chemical
dehalogenation of PCB -contaminated
soil
3 1 Decontamination of metalliferous
mining wastes
32 Cacitox™ soil treatment process
33 In-pulp decontamination of soils,
sludges, and sediments
36 Enhancement techniques for ex situ
separation processes particularly
with regard to fine particles
Project costs are discussed in Chapter 7 of this report; no
breakdown of costs for soil washing and thermal treatment were
provided.
Treatment costs were reported by vendor to be about U.S. $3207
tonne, no further breakdown of costs for soil washing and thermal
treatment provided.
Cost estimates per cubic meter for the remediation of the site:
U.S.$160 for soil handling; U.S.$300 for soil washing; U.S.$530 for
biological treatment.
Bench- and pilot-scale washing tests: U.S. $70,000; 2 tonnes/hr
washing plant: capital cost U.S. $750,000, operation (including
materials handling and analytical costs) U.S.$380/tonne; cost of
dehalogenation: not yet presented.
No data available.
No data available.
No data available.
Based on a bench-scale test sample; treatment cost for a diesel-
contaminated soil was estimated roughly to be U.S. $50-80 in a 20-
tonne/hr plant.
Mobilization of Contaminants to Enhance Treatment
1 Trial of air sparging of a petroleum-
contaminated aquifer
9 Field demonstration of an in situ
process for soil remediation using
well points
No data available.
No data available.
Increase Availability of Contaminants to Treatment
15 Combined chemical and
microbiological treatment of coking
sites^ioremediation of soils from
coal and petroleum tar distillation
plants
24 Combined remediation technique for
soil containing organics: Fortec
42 In situ pneumatic fracturing and
biotreatment
47 In situ electro-osmosis (Lasagna™
Project)
No data available.
No data available.
No data available.
Estimate: U.S.$52-118/m3 for TCE at an approx. 0.5-km2 site with
contamination 12-15 m deep (direct costs of application only).
Sequential Removal of Different Types of Contaminants
10 Integrated treatment technology for
the recovery of inorganic and organic
contaminants from soil
Estimate for full-scale plant (500,000 tonnes to treat): Cdn$100/
tonne
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Chapter 11: REMEDIATION TECHNOLOGY RESEARCH NEEDS
Michael A. Smith
M.A. Smith Environmental Consultancy
11.1 INTRODUCTION
In preparing this report, the authors identified several technology research needs that would be beneficial
to:
• countries in the formulation of national research programs;
• the Phase III CCMS study in scoping its future work; and
• the selection of individual projects for a Phase III study.
Technologies are frequently classified as emerging, innovative, or established. However, what is viewed
as innovative in one country may be regarded as established in another, and what is considered
established in one country may not be used widely in others because of doubts about effectiveness.1 The
term "innovation" often applies to an application of a technology rather than to the principles underlying
the technology. While developing truly innovative technologies remains an important goal, such a focus
should not divert attention from the need for better information and understanding of established
processes and for ensuring that their capabilities are fully realized in practice.
A great wealth of knowledge is available on many technologies, such as soil vapor extraction,
bioventing, bioremediation, and stabilization/solidification, enabling authoritative guidance to be provided
on good practice for many situations. The difficulty is getting this knowledge applied to the myriad of
small projects where these technologies are used. This is not to say that continued research is not
required, but that the barriers to the application of research results must also be tackled. This is not
unique to contaminated land. In areas such as construction, there is a constant battle to ensure that good
practice, established on the basis of past research, is adhered to by practitioners.
As in all areas of research, a variety of topics such as the following need to be recognized:
• Basic scientific research, not directed specifically to solving problems posed by contaminated
land—basic science researchers may have an idea of the potential relevance of their work, but
relevance is not the immediate driving force;
• Strategic applied research of a fairly basic nature into such things as biodegradation mechanisms
and the behavior of contaminants in soil;
• Strategic research leading to a better understanding of how a process works so that
improvements can be made;
• Feasibility testing of concepts derived from basic research;
1 An example is stabilization/solidification. While widely applied in the United States, this technology has only
limited application to date in Western Europe.
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• Pilot-scale and field testing of potentially useful technologies; and
• Development of a new concept or process as a result of a problem discovered during site
investigation for which no adequate technology exists.
Soil and groundwater remediation industries have been established in a number of countries, and in some
cases, as in soil washing in Germany and the Netherlands, some of the plants can be regarded as third
generation. Innovation can be driven by operators seeking to extend the physical and chemical range of
materials that can be treated and effectiveness of treatment, and to lower processing costs so that they
can compete in an increasingly challenging market. Such research by commercial interests is of a
proprietary nature and will only slowly reach the wider scientific and technical community.
Promising technologies can sometimes find rapid application before fullly understanding the processes
involved, and subsequent improvements can follow after initial application. Soil vapor extraction, electro-
remediation, and more recently, active treatment barriers, are examples of such technologies.
In practice, some research needs represent very broad concepts, whereas others relate to improvements
or extensions required for particular technologies. For example, the USEPA identified in 1993 a lack of
technologies for in situ treatment of contaminated groundwater (1).
More recently, a general need has been identified for treatments that are less costly and extensive, which
means they are less dependent on technology and energy, and are likely to have less impact on other
costs. Ideally, treatments should harness time and natural processes to the wheel of remediation. Such
treatment methods have been discussed by Bardos and van Veen (2). These considerations are
particularly appropriate to the large-scale pollution problems in Central and Eastern European countries.
Existing methods are generally too costly for the pollution problems in these countries. Similarly, in
many developing and less developed countries, existing technologies are too expensive. Owners and
operators of industrial facilities, also have a need for similar methods once they have taken the measures
necessary to avoid immediate legal liabilities.
It is important to recognize that scale has a major influence on the costs of any process. The size of
many treatment plants has been limited by the need to be transportable, or at least mobilizable. Even
the largest soil washing plants only handle about 150,000 tonnes/year. This capability is small compared
to, for example, mineral processing plants, where capabilities of 1 million metric tons/year are not
uncommon. This brings into play several factors, such as how remediation is organized and the relative
importance of the costs and environmental impacts of transportation (e.g., to a central transport facility),
compared to those of the actual treatment process.
Cement kilns are used for disposal of hazardous wastes, used oil, and even vehicle tires in parts of
Europe (the energy content is the attraction). In Canada, waste foundry sands and power station fly ash
are used as silica sources. In the United Kingdom, colliery wastes have been used as sources of fuel,
silica, and aluminum. The possibility of using cement plants as a means of treating contaminated soils
merits further investigation, taking into account that the process usually requires large volumes of
reasonably consistent material to ensure product quality and that performance is very sensitive to low
concentrations of some metals in the cement clinker. Obviously, limits on atmospheric emissions would
have to be met and it is important to recognize that the burning of hazardous wastes in cement kilns is
controversial in some countries.
In Western Europe the use of a fast-fix, intensive treatment approach is often driven by the need to
redevelop an area. Remediation is a step in the redevelopment process rather than the end objective. For
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instance, the need to rejuvenate brownfield sites is becoming increasingly important in policy and
research in the United States and has always been a driver in parts of Canada (e.g., the greater Toronto
area of Ontario). In these cases, the overall costs and value of the development can have a greater
influence on the selection of a remedial strategy than the direct remediation costs alone. Time (a costly
commodity to developers) is often an overriding factor leading to the use of off-site strategies, such as
simply excavating and disposing off site, rather than on-site in situ or ex situ treatment.
Although a great range of technologies now exists, many technologies such as bioremediation will only
work on a limited group of contaminants and may be hindered by the presence of other substances (e.g.,
metals hindering the bioremediation of organic compounds). Few technologies can deal with such mixed
contamination, and increasingly, integrated treatment systems are being used. These may involve
sequential treatment in a treatment train or parallel treatment of different fractions following an initial
separation step. This trend is apparent in the Phase II study—20 projects involved the use of integrated
technologies.
Some contamination problems occur on such a scale and are so complex that containment is the only
technically and economically viable solution. However, the effectiveness of containment systems (e.g.,
cover systems, vertical barrier walls) can be reduced with time and require long-term monitoring, repair,
replacement during operation. Containment systems would be more attractive if low cost, minimal
methods could be found to reduce the pollution potential of the contained materials during the lifetime
of the containment system. This situation is very similar to the deliberately constructed mixed waste
landfill that has a finite lifetime. Although highly controversial in other countries, the concept of the
"flushing landfill bioreactor," which is gaining acceptance in the United Kingdom, is relevant. Research
that brings this concept to practical use will in turn aid the development of methods for dealing with old
"problem" hazardous waste sites.
11.2 LESSONS FROM PREVIOUS NATO/CCMS STUDIES
An objective when preparing the final reports of the CCMS Pilot Studies on remediation technologies
has been to identify research and development requirements as well as the general lessons learned. For
the report on the Phase I Pilot Study (3), the authors of individual chapters initially took on this task and
then met to further refine their ideas. Their conclusions are:
• There is a continuing need for development of new technologies and use of common research
protocols;
• Scientific understanding of processes is essential in order to ensure against formation of harmful
end products;
• Standardization of analytical methods is needed; and
• Techniques are required to remove contamination beneath urban structures without significant
disturbance to on-going activities.
The conclusions that were technology specific are listed in Box 11.1 (note that variants of some of these
appear in Chapter 12 as conclusions of the Phase II Pilot Study, together with supporting reasons for
their inclusion).
Several technologies, especially in situ treatments, either fail to destroy or remove contaminants or are
based on principles of immobilization or transformation (e.g., stabilization/solidification processes). The
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long-term performance of these technologies needs to be better understood in terms of risk management
and appropriate environmental quality criteria to be applied during monitoring.
Box 11.1: Conclusions from Phase I Study Indicating a Need for Research2
• The long-term effectiveness of solidification/stabilization processes has not been proven,
especially when these processes are applied under field conditions;
• Electro-reclamation deserves to be extensively investigated—no other technology currently
shows the same potential for treating clay soils;
• Pump and treat is a limited technology for remediating aquifers;
• Scaling up the bioremediation process from the laboratory to the field is difficult;
• Further research is needed on bioavailability and residual concentrations achievable in
bioremediation;
• A mass balance approach to remediation is desirable;
• Uniform data collection is needed to enhance technology transfer; and
• Continuation of the current NATO/CCMS Pilot Study should also include cleanup criteria,
project design methodologies, and documentation of completed remediation projects.
11.3 THE PRESENT STUDY
The projects included in the Phase II Pilot Study do not necessarily provide a true reflection of research
and development needs. However, they do have certain characteristics that possibly provide some
indication of where current interest lies. For example, interest can be identified in:
• coal carbonization sites and the chemicals typically associated with them, such as polycyclic
aromatic hydrocarbons (PAHs), and mixtures of coal-tar chemicals such as creosote;
• in situ treatment methods;
• methods to treat chlorinated solvents;
• ex situ methods for treating metal contamination;
• residuals left after biotreatment;
• all forms of bioremediation; and
• active barriers.
2 The wording in the report has been slightly amended for clarity.
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There are, however, significant gaps in the coverage of the projects. For example, there are very few
projects on groundwater cleanup (although a number of projects dealt with groundwater as part of an
overall remediation strategy). This may, of course, simply be a reflection of a lack of innovative
technologies and their practical applications.
Taking discussions at meetings into account, the general areas where research might be directed are:
• In situ methods for soil treatment, particularly for metals and mixed contaminants;
• In situ methods for groundwater treatment;
• Means for improving the effectiveness and speed of operation of pump-and-treat systems;
• Extensive treatments, requiring fewer resources, but possibly taking more time to achieve a given
level of risk reduction;
• Means of reducing the pollution potential within a contained site through low intensity processes
for the purpose of extending the life of the overall system and achieving an overall
environmental improvement in the long term;
• Test facilities where technologies, considered to have potential negative environmental impacts,
can be tried out at field scale under controlled conditions;
• Improved methods for stabilization/fixation or solidification of organic chemicals;3
• Long-term studies of stabilized/solidified materials, especially the products of in situ treatment;
and
• Better techniques to characterize sites before remediation and to perform evaluations, particularly
of in situ treatments.
The discussion at the Berlin meeting regarding the proposed Phase III study indicated an interest in
including containment systems (e.g., cover systems or vertical barrier walls) within the scope of the
study. There remains a dearth of information on long-term performance, and laboratory and field studies
are required. However, it is important to recognize that these studies must be long-term in nature and
might require 20 or more years to complete. Despite the widespread use of covers in the United
Kingdom, and some research in the early 1980s and currently at the Building Research Establishment,
there is little or no long-term field monitoring.
Additional areas of study that might merit attention include:
• A feasibility study on the use of cement kilns to dispose or treat contaminated soils in Eastern
and Central Europe (Note: As stated above, there is controversy about the burning of hazardous
wastes in kilns in some countries);
3 A conclusion of the Phase I study and various U.S. studies is that the performance of cement-based
stabilization/ solidification processes is one of physical occlusion only, which means there is no chemical
change or fixation of organic species. Project No. 34 tests a method of binding organic chemicals to
organophilic clay minerals before solidification.
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• Investigation of the importance of time (for equilibrium reactions to occur) and the intensity of
mixing in the treatment of soils contaminated with organic chemicals using organophilic clays
and other adsorbents as a prelude to solidification; and
• Development of cost-effective technologies (including sorption and solidification) applicable in
less developed countries as well as highly developed NATO-member countries (e.g., using
readily available wastes as treatment agents).
11.4 REFERENCES
1. U.S. Environmental Protection Agency, In Situ Treatment of Contaminated Ground Water: An
Inventory of Research and Field Demonstrations and Strategies for Improving Ground Water
remediation, 1993.
2. Bardos R.P. and H.J. van Veen, "Review of longer-term or extensive treatment technologies," Land
Contamination and Reclamation, 1996, 4(1), pp 19-36.
3. U.S. Environmental Protection Agency, NATO/CCMSPilotStudy: Demonstration of Remedial Action
Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, 1993, EPA/600/R-
93/012a.
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Chapter 12: CONCLUSIONS AND RECOMMENDATIONS
Michael A. Smith
M.A. Smith Environmental Consultancy
Stephen P. James and Walter W. Kovalick, Jr.
U.S. Environmental Protection Agency
12.1 INTRODUCTION
The Phase II Pilot Study once again demonstrated the benefits of exchanging technical and economic
information on technologies for the remediation of contaminated land and groundwater. This chapter
presents the conclusions and recommendations of the Phase II Pilot Study and contains:
• general conclusions arising from the Pilot Study (12.2);
• general conclusions about remediation and technology transfer (12.3);
• research needs (12.4—see also Chapter 11); and
• the formal recommendations to CCMS arising from this Pilot Study (12.5).
The conclusions are based on the deliberations of the Study Group, results of case studies, expert speaker
presentations, special studies carried out by Fellows of the Pilot Study, and the experience and expertise
of the individual chapter authors.
A number of the conclusions closely parallel those of the previous phase of the Pilot Study (1), further
affirming their importance.
12.2 GENERAL CONCLUSIONS
1) Involvement of more countries led to better and wider awareness of the problems posed by
contaminated land.
A total of 23 countries were involved in the Pilot Study, and 14 contributed projects. The increased
number of countries participating in Phase II undoubtedly increased the overall value and impact of
the technology exchange process. Although more countries took part largely as recipients of
technology information rather than as contributors, the representatives of these countries brought new
insights and priorities to the Pilot Study and were able to make valuable contributions to the
discussions.
2) Presentation of additional full-scale experiences was helpful.
A number of the participants found the case studies involving full-scale remediation, as opposed to
demonstration-, pilot- or bench-scale studies, to be particularly valuable.
3) In a number of countries, remediation strategies are moving from technology-intensive treatment
processes to greater recognition of land use management and extensive approaches, such as natural
attenuation. Further research into these approaches is needed.
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It was apparent during the Pilot Study that there is increasing interest in land use management and
extensive approaches to remediation. While these approaches can be as effective as more intensive
methods, they may take longer to complete. Extensive approaches demand fewer resources and are
less costly; thus, they can be viewed as more sustainable. Extensive remediation options, which are
less dependent on technology and energy inputs, etc., and are likely to have less impact on other
aspects of economic activity, are needed. Cost considerations are particularly appropriate for less-
developed countries having pollution problems that would be prohibitively expensive to treat using
technology-intensive processes.
Consideration of the overall potential environmental, social, and economic impacts of planned
remedial actions are of increasing interest and the subject of formal study in some countries. It
should be noted that taking these issues into account can both increase the level of clean up required
(e.g., in situations where "fit for current or immediate future use" is a prime criterion) and lessen
the level of clean up required (e.g., in a situation where multi-functional land use might otherwise
be required or where groundwater has no economic value).
4) The intended future use of a site is increasingly a determining factor when setting clean-up
objectives and selecting a remediation strategy.
This conclusion reflects the convergence in thinking between those countries that have always seen
land use as an important factor and those that have tended to set clean-up requirements irrespective
of the future use of the land. Consideration of future land use can lead to a better allocation of
scarce resources.
5) All remediation activities require proper operation and management.
The success of field demonstration and treatability studies is not enough to ensure success of the
remediation activities. The overall effectiveness of a remediation scheme, which may include many
interrelated elements of civil engineering works and soil and groundwater clean-up technologies, will
depend heavily on the care with which the individual technologies are operated in the field. Site and
operating conditions may change over time, and skilled people are needed to adjust technologies to
these changes or discontinue them if they do not meet expectations. Similarly, a strong quality
assurance program needs to be in place, and activities must be carried out by a dedicated and
effective management team.
6) Whenever possible, the wider environmental impacts of a chosen remedial strategy should be
considered during remedial selection.
Short-term performance goals should not be the sole factor in technology selection when developing
a remediation strategy. Some remediation strategies may only be effective over a longer time frame,
but may have lower environmental impacts during implementation (e.g., reduced traffic, lower
emissions, and lower energy requirements) .
12.3 GENERAL TECHNICAL CONCLUSIONS
7) Integrated treatment systems are frequently needed for site remediation.
Contamination at many sites can be complex, with different contaminants in different media and
areas. Multi-technology solutions are required for the effective remediation of such sites. Many of
the Phase II projects involved the use of integrated or mixed technologies (see Chapters 2 and 10).
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Modular integrated treatment systems can provide system flexibility by allowing optimization of
specific process units to treat different contaminants of varying concentrations within various media.
This modular arrangement also allows the addition or withdrawal of processing units within the
system and the opportunity to insert and evaluate new or upgraded technologies as they become
available. Modular systems require additional up-front design, but may result in lower capital and
operating costs than conventional one-technology approaches.
The integrated systems approach also applies to sites where there are multiple areas of contamination
and where it is more practical to use specific technologies on each area, rather than trying to make
one technology solve all of the contamination problems (see Chapter 2).
8) Energy efficiency practices influence plant design resulting in varying processing costs between
countries. This may make cost comparisons between countries difficult and leads to the choice of
different technologies to address similar problems.
Variable factors, such as the cost of energy and labor, not only influence operating costs, but also
plant design and associated capital costs. These factors must be taken into account when considering
the application of a technology in a country other than the one in which it was developed.
9) Independent evaluation and verification of technologies and uniform data collection are needed for
effective technology transfer.
The NATO/CCMS Pilot Studies have shown the benefits to be gained from well-designed,
supported, executed, and documented field demonstrations of treatment technologies that are
independently evaluated and verified. Such field demonstrations not only help to confirm the
strengths and limitations of a technology, but also provide a credible basis for technology transfer
and application.
There is a critical need for the establishment of a uniform data reporting methodology for
demonstration projects, etc. Various database systems are available and in use; however, input of
consistent data into these systems and easy access to them will benefit all users. Critical information
needed in these databases includes:
• a minimum data set concerning the site's geological and hydrological setting, the types and
concentrations of contaminants present, etc.
• the clean-up standards used to provide the basis for selecting remediation strategies and for
assessing their effectiveness. The clean-up standards are important because there are currently
no internationally adopted standards or guidelines, and those applicable in one nation or state
may not be pertinent in another.
The identification and/or development of standard protocols for demonstration projects was one of
the objectives of the Phase II Pilot Study. This objective was not achieved, but it was addressed, in
part, by one of the CCMS Fellows and will be considered further in the Phase III Pilot Study.
10) Consensus on analytical methods and quality assurance is needed.
There is a lack of consensus on analytical methods used within the worldwide contaminated-land
community and often within individual countries. As a result, there can be confusion between or
within countries about meaning of the data and how the data were obtained and analyzed. Under
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such circumstances, data can be misinterpreted or appear inconclusive. A greater level of confidence
in the interpretation of data could be established if there were worldwide acceptance of analytical
methods.
In addition, greater attention is needed in the areas of experimental design and quality assurance and
quality control (QA/QC) for identifying data needs and data quality, which in turn determine the
analytical methods. Programs to evaluate new analytical techniques and update analytical standards
would further benefit the contaminated-land community. One forum addressing this issue is the
International Organization for Standardization (ISO) Technical Committee 190 for soil quality.
11) Scientific understanding of processes is essential to avoid forming harmful end-products and
byproducts, ensure process optimization, avoid unwanted transfer of contaminants to other media,
and understand the limits of technical performance.
The demonstrated removal of contaminants from contaminated media is not a sufficient basis for
implementing a treatment technology because toxic intermediates, byproducts, and residuals may
be formed during treatment. A thorough understanding of the treatment process mechanisms
involved is required in order to avoid such undesirable occurrences.
12) Field treatability/pilot studies should be conducted under the range of potential field conditions they
might be realistically applied. Test facilities are required where technologies considered to have
potential negative environmental impacts can be field-scale tested under controlled conditions.
The complex physical and chemical nature 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-scale or pilot-scale studies in the laboratory need
to be followed by pilot-scale or full-scale field evaluations. These evaluations should indicate
whether the technology is applicable to the contaminated medium and should provide information
on the optimal level of treatment effectiveness that the technology can achieve. Bench-scale and
pilot-scale evaluations must be tailored to each specific application in order to obtain the maximum
amount of credible data at a minimum cost and establish the basis for follow-on field evaluations.
13) Field-scale studies aimed at understanding phenomena such as transport of contaminants and
natural attenuation are needed. International collaboration on this effort would increase the value
and diversity of conditions studied and lead to quicker application of results.
Studies of this type are already taking place, particularly in North America. Field laboratories in
which controlled release of contaminants is permitted would be particularly valuable.
14) Technology scale-up problems need to be addressed in design and testing.
Care must be taken in translating technologies from bench- to pilot-scale to demonstration-scale or
full-scale so that all aspects of the scale-up are taken into account. The scale-up of pilot-scale
systems to full-scale operating systems can often result in unforeseen difficulties that need to be
addressed in the design. For instance, design variables (e.g., wall effects, mixing efficiencies, flow
patterns, fugitive emissions, and retention times) can change as a result of system scale-up. To
overcome some of these problems (particularly for technologies that are not widely used), operating
flexibility can be built into the system by modular design, by providing the ability to vary feed rates,
and by providing surge capacity at various points throughout the system.
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15) Long-term monitoring of assumed permanent remediation may be necessary to ensure that clean-up
goals are met.
Construction of soil and groundwater remedies is not the endpoint for determining whether
environmental protection concerns have been satisfied. Focused, long-term monitoring is essential
to ensure that the required remedies are properly implemented, operated, and maintained and
ultimately are successful. This, in turn, requires that long-term oversight is provided by well-trained
personnel and that the necessary institutional controls are put in place to ensure that monitoring is
conducted and appropriate responses to the results of monitoring are taken.
Limiting monitoring to the period in which remediation goals and objectives are first achieved may
yield misleading results. It has been demonstrated both in "pump-and-treat" groundwater systems
and soil vapor extraction systems that "bounce back" can occur as contaminants held in less
permeable zones diffuse out to re-contaminate the apparently clean (and more permeable) zones.
Monitoring must be continued until such phenomena no longer occur to a significant extent.
16) Assessment, remedy selection, and implementation records should be preserved.
A major challenge in evaluating the effectiveness of current and emerging technologies is that there
are usually insufficient data available to evaluate them (particularly for in situ remediation
strategies). Therefore, it would be advantageous to remediation planners if site investigation and
assessment records and the rationale for selecting the remediation strategy are preserved for future
reference and evaluation. Such records are valuable in property transactions and in determining the
suitability of land for a particular use subsequent to remediation. It is also important that the records
reflect "as-built" or "as-operated" systems, rather than just the design intentions.
17) Although treatment and permanent solutions are widely sought, some contamination problems occur
on a scale and complexity for which containment may be the preferred technical and economically-
viable solution. Further information sharing among countries is needed to determine the long-term
effectiveness and state of development of containment systems.
Containment systems can be expected to decline in effectiveness with time, require long-term
monitoring, and possibly require repair or replacement.
18) Studies related to stabilization/solidification processes are required in respect to:
• improved methods for stabilization/solidification of organic chemicals;
• long-term performance of stabilized/solidified materials, especially the products of in situ
treatment;
• the importance of time (to permit equilibrium reactions to occur) and the intensity of mixing in
the treatment of soils contaminated with organic chemicals using organophillic clays and other
adsorbents as a prelude to solidification; and
• development of cost-effective technologies applicable in less-developed countries as well as
highly-developed NATO-member countries (e.g., using readily available wastes as treatment
agents).
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12.4 RESEARCH NEEDS
19) Future work on the NATO/CCMS Pilot Study should include the formulation of the overall scope
of a Phase III CCMS study and the selection of individual projects for inclusion in a Phase III
study.
20) As in all areas of research, it is necessary to recognize that research of a variety of types is
required.
For example:
• basic scientific research not directed specifically to solving the problems posed by contaminated
land—although the researchers may have an idea of potential relevance, this is not the immediate
driving force;
• strategic applied research on such topics as biodegradation mechanisms and the behavior of
contaminants in soil;
• strategic research leading to a better understanding of how a process works so that improvements
can be made;
• feasibility testing of concepts derived from more basic research;
• pilot-scale and field testing of possible technologies; and
• development of a new concept or process as a result of a problem discovered during site
investigation for which no adequate technology exists.
21) Further research is required into the remediation of coal carbonization sites and the chemicals
typically associated with them, such as polycyclic aromatic hydrocarbons (PAHs) and mixtures of
coal tar chemicals.
22) Further research is required into:
• in situ methods for soil treatment particularly for metals and mixed contaminants;
• in situ methods for groundwater treatment, including active barriers;
• improving the effectiveness and speed of pump-and-treat systems; and
• better techniques for site characterization before remediation and for performance evaluation—
particularly of in situ treatments.
12.5 RECOMMENDATIONS TO CCMS
1) The CCMS is invited by the Pilot Study Directors to commend this Phase II Pilot Study Final Report
to the NATO Council for approval.
All the participants in this phase of the study are commended for their professionalism, technical
expertise, and cooperation. The Pilot Study Directors particularly thank the two co-pilot countries,
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Germany and The Netherlands, for their assistance. The CCMS Fellows are complimented on their
technical quality and personal input to the Pilot Study. The Expert Speaker activities were a major
success in stimulating discussion among participants. Over and above the technical successes of the
Pilot Study, a camaraderie was established between participants leading to extensive exchanges of
information outside of the Pilot Study. The progress of the Study was reported via formal interim
reports and numerous papers published in technical journals, and conference proceedings published
in North America, Europe, and Australia. Consequently, the CCMS is invited to commend the Final
Report to member governments and to the governments of the North Atlantic Cooperation Council
(NACC) countries drawing their attention to the technical information, conclusions, and
recommendations it contains.
2) The CCMS is requested to encourage participation of NATO and non-NATO countries in the
continuation study (Phase III Pilot Study).
The participation of NACC and other non-NATO countries has been a feature of the Phase II Pilot
Study with mutual benefit to all involved. The Pilot Study co-pilots will continue to elicit formal
participation by additional countries known to have contaminated land and groundwater programs.
CCMS is requested to draw the attention of member countries to the way in which formal
participation can open doors for researchers, regulators, and others from within and outside
government to high quality technology and information exchange activities and to an extensive
network of professional contacts. The CCMS is asked to encourage member countries to adopt
formal observer status, even if the countries wish to have only minimal active participation at an
official level.
3) The Phase III Pilot Study should maintain liaison with related international activities on
contaminated land.
The benefits to all participants has been enhanced by the parallel activities in policy-orientated areas
(e.g., the International Working Group on Contaminated Land and the Common Forum on
Contaminated Land) and technical areas such as risk assessment through the European Union's (EU)
Coordinated Action on Risk Assessment for Contaminated Sites (CARACAS) and soil quality
through the ISO Technical Committee 190. Liaison should be extended in the Phase III study to
include the EU's Network for Industrially Contaminated Land (NICOLE), the European
Environment Agency's Soil Topic Centre, the World Health Organization's European Centre for
Environment and Health and others involved in this technical area. Close liaison should be continued
with NATO/CCMS Pilot Studies dealing with contamination of military installations.
4) The Phase III Pilot Study should publish an annual progress report and, as appropriate, periodic
technical reports on selected topics.
Preparing a technical report summarizing several years' work requires a considerable effort on the
part of all concerned. It involves not only critical review of submitted information, but also the
gathering of additional technical information and liaison with country representatives and project
authors. Furthermore, there is a considerable editorial effort required to combine the individual
contributions into a coherent final report. Preparation of the Final Report for this and the preceding
Pilot Studies (1,2) has been possible because of the efforts of the volunteer writing teams.
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The remediation of contaminated soil and ground-water is a rapidly evolving field so that there is
a risk that much of the information provided in the Pilot Study report will already be out of date
by the time of publication. It is therefore recommended that this issue be addressed by:
• preparation of an annual report that could be widely distributed and serve as a working tool for
participants to monitor the progress of the Pilot Study, including the introduction and completion
of individual projects;
• the publication from time to time of technical and non-technical reports on specific topics as
seems appropriate; and
• the use of other channels of publication, such as technical journals and conference publications,
to ensure rapid dissemination of the results of individual projects and of the Pilot Study as a
whole.
12.6 REFERENCES
1. U. S. Environmental Protection Agency. NATO/CCMS Pilot Study, Demonstration of Remedial Action
Technologies for Contaminated Land and Groundwater, Final Report, Volume 1, EPA/600/R-
93/012a, 1993.
2. Smith, M.A. (editor). Contaminated Land: Reclamation and Treatment, Plenum (London) 1985.
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Appendix I
COUNTRY REPRESENTATIVES
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NATO/CCMS Pilot Study, Phase II
Final Report
Country Representatives (1998)
COUNTRY
CONTACT
AUSTRALIA
BELGIUM
Gillian King Rodda
Manager, Contaminated Sites
Environment Protection Group
Environment Australia
PO Box E305
Kingston ACT 2604
tel: 61-2-6274-1114
fax: 61-2-6274-1164
E-mail: gillian.king.rodda@ea.gov.au
AUSTRIA Nora Auer
Federal Ministry of Environment, Youth and Family Affairs
Dept. HI/3
Stubenbastei 5
A-1010 Vienna
tel: 43/1-515-22-3449
fax: 43/1-513-1679-1008
E-mail: Nora.Auer@bmu.gv.at
Jacqueline Miller
Groupe d'Etude Habitat/territoire
Brussels University
Avenue Jeanne 44
1050 Bruxelles
tel: +32/2-650-3183
fax: +32/2-650-3189
E-mail: jmiller@resulb.ulb.ac.be
CANADA
Harry Whittaker
Emergencies Engineering Division
Environment Canada
3439 River Road
Ottawa, Ontario, K1A OH3
tel: 613/991-1841
fax: 613/991-1673
E-mail: harry.whittaker@etc. ec. gc. ca
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COUNTRY
CONTACT
CZECH REPUBLIC
Jan Svoma
Aquatest a.s.
Geologicka 4
152 00 Prague 5
tel: 420/2-581-83-80
fax: 420/2-581-77-58
E-mail: aquatest@aquatest.cz
DENMARK
Inge-Marie Skovgard
Contaminated Land Division
Danish Environmental Protection Agency
29 Strandgade
DK-1401 Copenhagen K
tel: 45/3-266-0100 - direct 45/32660397
fax: 45/3-296-1656
E-mail: ims(o),mst.dk
FRANCE
Rene Goubier
Polluted Sites Team
ADEME
BP406
49004 Angers, Cedex 01
tel: +33/41-204120
fax: +33/41-872350
GERMANY
Volker Franzius
Umweltbundesamt
Bismarkplatz 1
D-14193 Berlin
tel: +49/30-8903-2496
fax: +49/30-8903-2285 or -2103
HUNGARY
Pal Varga
National Authority for the Environment
F6 u.44
H-1011 Budapest
tel: 36/1-457-3530
fax: 36/1-201-4282
E-mail: vargap@kik.ktm.hu
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COUNTRY
CONTACT
NETHERLANDS
H. Johan van Veen
The Netherlands Integrated Soil Research Programme
P.O. Box 37
NL-6700 AA Wageningen
tel: 31/317-484-170
fax: 31/317-485-051
E-mail: anneke.v.d.heuvel@spbo.beng.wau.nl
NEW ZEALAND
Raymond S alter
Resource Management Directorate
Ministry for the Environment
84 Boullcott Street
P.O. Box 10362
Wellington
tel: 64/4-917-4000
fax: 64/4-917-7523
e-mail: rs@mfe.govt.nz
NORWAY
Bjorn Bjornstad
Norwegian Pollution Control Authority
P.O. Box 8100 Dep
N-0032 Oslo
tel: 47/22-257-3664
fax: 47/22-267-6706
E-mail: bjorn.bjornstad@sftospost.md.dep.telemax.no
REPUBLIC OF
SLOVENIA
Branko Druzina
Institute of Public Health
Trubarjeva 2-Post Box 260
6100 Ljubljana
tel: 386/61-313-276
fax: 386/61-323-955
E-mail: branko.druzina@ivz.sigov.mail.si
SWEDEN
Ingrid Hasselten
Environmental Protection Agency
Biekholmsterrassen 36
S-106 Stockholm
tel: +48/8-698-1179
fax: +48/8-698-1222
E-mail: inh@environ.se
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COUNTRY
CONTACT
SWITZERLAND
Bernhard Hammer
Federal Office of the Environment, Forests and Landscape
Federal Department of the Interior
Buwal Laupenstrausse 20
3003 Bern
tel: +41/31-322-6961
fax: +41/31-382-1546
TURKEY
Resat Apak
Instanbul University
Faculty of Engineering
Avcilar Campus
Avcilar
34840 Instanbul
tel: 90/212-5911-998
fax: 90/212-5911-997
E-mail: rapak@istanbul.edu.tr
UNITED KINGDOM
Ian D. Martin
Environment Agency
Olton Court
10 Warwick Road
Olton, West Midlands
tel: 44/121-711-2324
fax: 44/121-711-5830
E-mail: ianmartin@environment-agency .gov. uk
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COUNTRY
CONTACT
UNITED STATES
Stephen C. James
U.S. Environmental Protection Agency
National Risk Management Engineering Laboratory
26 Martin Luther King Drive
Cincinnati, OH 45268
tel: +1/513-569-7877
fax: +1/513-569-7680
E-mail: james.steve@epa.gov
Walter W. Kovalick, Jr.
U.S. Environmental Protection Agency
Technology Innovation Office
401 M Street SW (5012W)
Washington, DC 20460
tel: +1/703-603-9910
fax: +1/703-603-9135
E-mail: kovalick.walter@epa.gov
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Appendix II
CCMS FELLOWS
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NATO/CCMS Pilot Study, Phase II
Final Report
NATO/CCMS Fellows1
FELLOW
SUBJECT
Robert M. Bell
Technical Director
Hyder Consulting
c/o Ty Isa Farm
Garth Road
Glan Conway LL28 5TE
Colwyn Bay
United Kingdom
tel: +447(0)1492-580-950 (home)
+447(0)1928-579-955 ext. 53015 (work)
E-mail: bob.bell@hyder-con.co.uk
Quality management systems in the remediation of
contaminated land
Maria Teresa Chambino
INETI
ITA/DTA
Azinhaga dos Lameiros a Estrada do Paco do Lumiar
1699 Lisboa Codex
Portugal
tel: +35/1-1-716-4211
fax: +35/1-1-716-0901
Important issues about the Portuguese situation
Domenic Grasso
Department of Civil Engineering
University of Connecticut
Storrs, CT 06269-3037
USA
Hazardous waste site remediation
tel: +1/860-486-2680
fax: +1/860-486-2298
E-mail: grasso@eng2.uconn.edu
Mary R. Harris
Monitor Environmental Consultants Ltd.
Blakelands House
400 Aldridge Road
Birmingham
B44 8BH
United Kingdom
tel: +44/(0)121-356-5533
fax: +44/(0)121-356-5222
E-mail: mary.harris@monitorec.co.uk
Economic/cost data issues related to innovative
environmental restoration technologies
For information about the CCMS Fellowship Programme, contact NATO's Scientific and Environmental Affairs
Division in Brussels at Tel: +32/2-707-4111 or FAX: +32/2-707-4232. Information can be found on the World
Wide Web at http://www.nato.int/science. Invitations for applications are extended each year through national
NATO coordinators.
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FELLOW
SUBJECT
Merten Hinsenveld
TSM Business School
University of Twente
P.O. Box 217
7500 AE Enschede
The Netherlands
Changing approaches to remediation
tel: +31/53-489-8009
fax: +31/53-489-4848
E-mail: m.hinsenveld@tsm.utwente.nl
Maria Jose Macedo
Hovione - Sociedade Quimica SA
Qt. S. Pedro
Sete Casas
Loures
Portugal
tel: +35/1-1-982-9000
fax: +35/1-1-983-6801-1406
Use of remedial clean-up technology in Portugal
Robert Siegrist
Colorado School of Mines
Environmental Science and Engineering Division
1500 Illinois Avenue
Golden, CO 80401-1887
USA
In situ remediation of organics: process design,
treatment efficiency, and performance assessment
tel: +1/303-273-3490
fax: +1/303-273-3413
E-mail: rsiegris@mines.edu
Michael A. Smith
68 Bridgewater Road
Berkhamsted
Hertfordshire
HP4 1JB
United Kingdom
tel: +44/1442-871500
fax: +44/1442-870152
E-mail: Michael.A.Smith@BTinternet.com
Contributed to preparation of the final report
Kai Steffens
PROBIOTEC gmbh
Schillingsstrasse 333
D 52355 Duren-Giizenich
Germany
Concepts of quality management in testing and
monitoring of innovative technologies for remedial
actions on contaminated land and groundwater
tel: 49/2421-69090
fax: 49/2421-690961
E-mail: info@probiotec.ac-euregio.de
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FELLOW SUBJECT
Hans-Joachim Stietzel Innovative approaches used on large remediation
Bundesministerium fur Umwelt, Naturchutz und projects in Germany
Reaktorsicherheit
Postfach 120629
D-53048 Bonn
Germany
tel: 49/228-305-3432
fax: 49/228-305-2398
E-mail: Hans-Joachim. Stietzel@metronet.de
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Appendix III
GUEST SPEAKERS
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During the Phase II Pilot Study, meetings were held at which numerous experts were invited to make
presentations related to the overall objectives of the study. Most of these invitees and the titles of their
presentations are listed below.
Guest Speakers
GUEST SPEAKER
TITLE OF PRESENTATION
YEAR
Jens Nonboe Andersen
Ramb01, Hannemann & H0jlund
Denmark
Danish assistance in the remediation of Tokol Airbase 1994
(Hungary)
Baldur Barczewski
Grundwasser u.
Germany
Research facility for subsurface remediation
1994
James Barker
Waterloo Centre for
Ground-water Research
Ontario, Canada
Controlled in situ groundwater treatment
1994
Prof. Harald Burmeier
WCI Umwelttechnik GmbH,
Germany
Permeable treatment beds
1997
David Cooper
U.S. EPA
Office of Emergency and
Remedial Response
USA
Risk Assessment in Superfund
1997
Patrick Davoren
Department Primary Industries
and Energy
Canberra, Australia
Rehabilitation of former British nuclear test sites at 1996
Maralinga, South Australia
Dr. Wolfgang Dott
Institut fur Hygiene und
Umweltmedizin, Aachen
Germany
Strategies for in situ bioremediation
1996b
Marco Estrela
Institute de Soluadura e
Qualidade, Centre de
Technologias Ambientais
Portugal
Use of remedial clean-up technology in Portugal
1997
Ayse Filibei
Dokuz Eylul University
Turkey
Solidification of fly ash samples coming from a solid 1993
waste incineration plant
Jan Freijer
University of Amsterdam
The Netherlands
Prediction and optimization of the abiotic environment 1994
in landfarms to enhance biodegradation of
hydrocarbons
Karsten Hupe
Technical University of
Hamburg-Harburg
Germany
Biological soil remediation
1996b
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GUEST SPEAKER
TITLE OF PRESENTATION
YEAR
Steven Hutchins
U.S. EPA
Office of Research and
Development
Ada, Oklahoma
USA
Field demonstration of bioremediation under
anaerobic conditions of a fuel-contaminated aquifer
1997
Rune Dyre Jespersen
Technical Soil Cleaning
Denmark
Electrodialiytic soil remediation (EDSR)
1996
Harald Kasamas
CARACAS Office
Vienna, Austria
CARACAS—The Concerted Action on Risk 1996b
Assessment for Contaminated Sites (in the European 1997
Union)
Nic Korte, Gary Jacobs, and
Tony Palumbo
Oak Ridge National Laboratory
USA
In situ remediation employing redox processes in
reactive barriers and zones
1997
Walter Kovalick, Jr.
U.S. EPA
Technology Innovation Office
USA
Overview of in situ treatment options for metals-
contaminated soils
1996b
Walter Kovalick, Jr.
U.S. EPA
Technology Innovation Office
USA
Treatment walls
1996
Andrew Langley
Environmental Health Branch
Australia
The interface between risk assessment and
remediation: choosing a method of risk assessment
appropriate for Australia
1996
Andrea Leeson
Battelle-Columbus
USA
Results of bioventing studies at over 100 field sites 1994
James Mantle
Rust PPK
Australia
Oil terminal remediation: integration of free product, 1996
dissolved phase and soil vapor recovery and treatment
Dr. Ewa Marchwinska
IETU
Poland
Environmental issues in Poland
1997
Igor Marvan
Grace Dearborn, Inc.
Canada
Evaluation of six near-real-time analytical methods 1996
Mark McNamara
Clough Engineering Group
Australia
Introduction to the Homebush Bay regeneration
project
1996
Annemieke Nijhof
TAUW Milieu bv.
The Netherlands
The NOBIS project
1996b
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GUEST SPEAKER
TITLE OF PRESENTATION
YEAR
Annemieke Nijhof
TAUW Milieu bv.
The Netherlands
Risk assessment bottlenecks
1996b
Mark Noll
Applied Research Associates,
Inc.
Dover AFB
USA
Groundwater remediation field laboratory
1996b
Anna Orlova
University of Maryland
USA
Soil contamination in Russia
1996b
Paul Richter
New Jersey Department of
Environment and Energy
USA
Selection of remedial technologies
1993
Inge-Marie Skovgard
Environmental Protection
Agency
Denmark
The new Danish assistance to Central and Eastern
Europe
1994
Thomas Stauffer
U.S. Air Force
USA
Natural attenuation/degradation of aromatic
hydrocarbons
1996
Brian Ullensvang
U.S. EPA, Region 9
USA
Design and construction of an on-site leachate
treatment plant at the Operating Industries, Inc.,
landfill
1992
Paul Van der Heidje
Colorado School of Mines
USA
The role of modeling in risk assessment and site
remediation engineering
1997
Vilma Wisser
Tauw Milieu bv.
The Netherlands
Contaminated land in industrialized countries
1993
Ken Wangerud
U.S. EPA, Region 8
USA
On-site risk assessment and remediation planning at
lead-contaminated sites in Romania
1997
Geoffrey Williams
British Geological Survey
United Kingdom
Natural attenuation at the U.K. Villa Farm
1997
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Appendix IV
PROJECT SUMMARIES
These summaries are published in a separate document
available on the Internet from:
http://clu-in.com
http://www.nato.int/ccms
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Appendix V
FELLOW STUDIES
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NATO/CCMS Pilot Study, Phase II Final Report
PREFACE
This Volume of the Final Report of the Phase II Pilot Study on the remediation of contaminated land
and groundwater contains contributions from CCMS Fellows who took part in the study. They are
reproduced directly from the texts provided by the authors: they have not been edited other than to put
them into a common format. Contact addresses for the Fellows are provided at the end of the volume.
These papers do not represent the entirety of the contribution of the Fellows to the Pilot Study. Each
Fellow attended one or more of the international meetings and played an active part in discussions at
the meetings. In addition, a number of the Fellows have contributed to the preparation of the Final
Report by writing technology-related chapters (see Volume 1) and preparing extended project summaries
(see Volume 2).
The CCMS Fellowship Programme provides grants towards the travel and subsistence costs of
individuals conducting small studies related to on-going CCMS Pilot Studies. Recipients are encouraged
to attend meetings of the study group with which they are associated. Fellwoships are awarded annually
in response to applications through national CCMS coordinators. For more information on this and other
CCMS programmes, such as the Study Visit Programme, please contact:
CCMS Secretariat
NATO Scientific Affairs Division
B-1110 Brussels
Belgium
tel. +32/2-707-4619
fax. +32/2-707-4232
Information can also be obtained through national CCMS coordinators and on the World Wide Web at:
http://www.nato.int/science.
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Quality Management Systems and the Remediation of Contaminated Land
Dr. P.M. Bell, Hyder Consulting, and Mr. Richard Failey, SGS Environment,
Colwyn Bay, U.K.
1. INTRODUCTION
Quality Management Systems (QMS) are required to be established for the remediation of contaminated
land and waste containment in the expectation that the system will provide a consistent, and maintainable
operation which results in a piece of land that is fit for use and that all information upon which decisions
are made is reliable.
Quality Management Systems (QMS) are used where a contract between two parties requires the
demonstration of capability and assurance to provide the design and supply of a product or service. The
aim is to prevent nonconformity by using a system comprising components and elements subject to
Quality Control and Quality Assurance.
QMS like any system requires a policy, set of objectives and a method of measurement and review to
ensure targets are being met. QMS in the remediation of contaminated land requires a plan giving the
methods used, responsible parties and a system for identifying a non-conformance and implementation
of corrective action.
Quality Assurance (QA) is achieved through planned auditing/inspection of components of the system
against predetermined targets to give confidence that product or service requirements are being met, i.e.,
it is prevention rather than detection of non-conformance.
Quality Control (QC) is the ongoing measurement of conformance to ensure objectives and targets set
by the system are being reached. QC aims to achieve conformity through quantified measurement against
predetermined specifications which may include product standards, etc.
The most common method of ensuring QA/QC is by auditing which determines whether activities
comply with planned arrangements through the assessment of objective evidence. This is discussed later
under verification.
For the remediation of contaminated land a QMS will comprise a three phase system:
• Pre-works design and specification;
• On site operations including materials testing, site sampling and analysis; and
• Post works verification, ongoing monitoring, and guarantees.
Environmental Management Systems (EMS) are a method by which organisations can demonstrate
environmental performance through controlling the impact of their products and services. Many
organisations conduct environmental reviews or audits, but an EMS gives assurances that environmental
performance is in accordance and will continue to meet with the organisations environmental policy and
objectives. Examples include the ISO 140001; and the European Eco-Management and Auditing Scheme
(EMAS) which requires the publication of an auditable statement on the organisations concerns with the
environment.
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The essential elements of an EMS are that the system is based upon the evaluation of environmental
effects, from which all policies, targets, and procedures are based, and that the system is auditable. An
EMS follows QMS principles of control, calibrate, and verify, but also requires continual improvement
in environmental performance.
2. LAND REMEDIATION
EMS in land remediation allows for effective site management and policing of issues and allows the site
manager to pre-empt future problems. One assumes the land remediation process itself is a measure of
continual improvement. The first step in establishing an EMS is a preliminary environmental review
which needs to cover four key areas:
• Legislative requirements of proposed operations; Evaluation of significant effects;
• Examination of existing management practices;
• Assessment of feedback systems in dealing with incidents.
These key areas are considered in relation to internal site management issues, as well as external factors
such as neighbouring land use, road network, planning constraints, etc.
Important elements of any EMS relating to land remediation and waste containment include:
• Policy documents must incorporate principles of Economically Viable of Application of Best
Available Technology (EVABAT). In the U.K., this would include adoption of the waste
management hierarchy outlined in Department of Environment Waste management Paper No. 28,
1991.
• Procedures for waste containment sites will be those outlined in the site working plan and licensing
conditions. For proprietary processes, the procedures relating to site controls are usually outlined in
an Environmental Impact Assessment required as part of planning permission.
• Responsibility includes the identification of management representatives, training of personnel, and
instructions to subcontractors. Current U.K. legislation requires the nomination of a 'Fit and Proper
Person' as representative of waste management expertise; the EMS, however, requires demonstration
of appropriate training at all levels of staff which critically impinge on day to day operations.
• Evaluation of Environmental Effects requires the operator to identify, evaluate, and control all
significant environmental effects. These are to be registered in a "live" document that will be
auditable. Effects to be evaluated include direct effects from operations which may have already
been assessed using risk management principles during the site investigation or site licensing. There
also needs to be consideration of indirect effects which are generally more esoteric and may include
unmanageable issues such as nearest neighbours, or site location and access. The effects from
abnormal operations and accidents also need to be identified and evaluated. This is normal for sites
subject to an EIA under U.K. planning regulations.
The aim of the EMS is to manage significant environmental effects; however, there is guidance as to
what is meant by 'significant' in any current certified system. The determination of a significant effect
is relative in all cases and can only be adjudged through transparent reasoning.
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• A Management Programme will be progressive and a chance to emphasise the positive aspects of
site management and evidence of the application of EVABAT.
• Operational Control is required on an activity from which a significant effect arises and that any
control mechanism is verified. Clear recognition of non-conformance is therefore required for
controls to be effective. For site remediation, operational controls are incorporated in the first phase
of site remediation, site design and construction/remediation methods. This also includes the
establishment of acceptance criteria for each activity that causes a significant effect.
• Verification and corrective actions are to ensure that operational controls are effective. This usually
comprises regular sampling and monitoring regimes during the second and third phase of site
remediation.
• Management Review principles are adopted for EMS as a normal part of QMS to ensure performance
reaches targets. It is the system that is reviewed and not the raison detre for the operation or site
works, since this will have been established in the Environmental Effects Evaluation.
3. U.K. EXPERIENCE
There are currently no formal systems for QMS in the U.K. for site remediation; we still rely largely
on caveat emptor as a means of absolving responsibility. Out of fifteen remediation contractors in the
U.K., only two specifically stated that they have an identifiable QMS in place to ensure the site
remediation process is reliable and that reliability can be demonstrated.
Planning legislation and licensing generally provide checks in the quality of site remediation, although
this can result in major differences in the reasoning for adopting site remediation techniques and the
interpretation of what is acceptable. In many cases, site remediation may be dictated by local politics
and the understanding of local council officers and not necessarily EVABAT/BATNEEC or a proper
evaluation of risk.
For large scale remediation schemes, an Environmental Impact Assessment and accompanying statement
are required. There are obvious and numerous licensing and regulation requirements, particularly for
waste containment as a means of site clean up which will soon be subject to taxation.
Section 78 of the Environment Act 1995, to be implemented in April 1996, allows the regulator to serve
a remediation notice and establishes responsible parties and the means by which remediation will be
undertaken. The courts, however, are not the best place to start the remediation process and the quality
of site remediation may not be uppermost in the polluters mind when paying court fines.
Some contractors and consultants operate a QMS system in accordance with IS09000 and there are
numerous product standards for materials used in the site remediation process.
However, for the U.K. there is currently no standard procedure for documentation for verification of
remedial action.
The Welsh Development Agency (WDA) (the government agency in Wales for remediation and
redevelopment) have produced a Manual on the Remediation of Contaminated Land with the purpose
of outlining its policy and objectives on the quality of land remediation projects.
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The WDA's aim of land remediation is to ensure economic regeneration and environmental improvement
can take place using appropriate technical procedures, the effectiveness of which are confirmed through
appropriate management procedures. This will demonstrate to investors and regulators that remediation
has been carried out to a sufficiently high standard.
It is the WDA's principal policy that remediation schemes comply with legislation and present residual
environmental health risks that are low as are reasonably practicable according to existing and proposed
site use, local setting, and technical and financial constraints. That is, the quality of land remediation
is based upon the principles of risk management and provides a complete record of site remediation.
The manual sets out guidance on procurement associated with site investigations, design
and selection criteria for technologies and materials, and gives guidance for requirements for detailed
design and verification.
The main documentation are the Outline Strategy Document (OSD) and Final Strategy Document (FSD).
The aim of the OSD is to ensure that site design considers and incorporates Best Practicable
Environmental Options and should fulfil those planning requirements for an Environmental Statement,
particularly the review of alternatives and the assessment of risks through accidents and abnormal
operations. In establishing the best practicable environmental option for remediation, the OSD will also
fulfilf those requirements for an effects evaluation identified in ISO 14000. The FSD sets out the
requirements for auditing mechanisms to verify the quality of remediation with the eventual aim of
providing a Certificate of Completion that can be substantiated.
The site remediation process typically involves a consultant undertaking site investigations and designing
remedial works; a contractor undertaking the remedial works; regulatory authorities ensuring regulatory
compliance; a site owner/operator for whom the works are carried out; financial institutions or funding
bodies and solicitor to ensure contractual obligations are met. Further to this, an independent verifier of
works is often employed. These parties require a clear understanding of the remediation process and their
liabilities as well as clarification of any future obligations. A standard documented procedure is therefore
warranted.
Elements for documentation of verification procedures include:
• Description of site conditions and contamination;
• Hazard identification and risk assessment;
• Definition of remedial objectives and standards;
• Selection of preferred strategy;
• Site design for preferred technique;
• Tender preparation and contract documents;
• Variations to works; and
• Certificate of completion and warranties.
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The above elements need to be part of, or referenced in a Verification Report which should provide a
clear understanding of:
• The rationale for remedial action;
• Nature of works carried out;
• Key decisions and responsibilities;
• Regulatory compliance;
• Post remediation status of site; and
• Performance of site works.
The environmental performance of site works will be measured against objectives and standards
established in the first phase of remediation. The first phase of the remediation process also needs to
demonstrate:
• BATNEEC
• Practicality
• Guarantees of performance through demonstration on other sites
• Acceptance of technique by statutory authorities
For the second and third phase of the remediation quality controls will be implemented through an
agreed sampling and monitoring programme. Where a documented EMS has been established,
verification can be limited to an appraisal of whether commitments have been carried out. Otherwise
specific sampling programmes and protocols are required to ensure predetermined standards have been
met.
Most financial and funding institutions require independent measurement to ensure the quality of site
remediation. The establishment of a standard documented procedure will almost certainly provide
substantiated evidence that controls were in place during the entire remediation process and therefore
site warranties can be accepted as collateral.
4. CONCLUSIONS
In the U.K., QMS for site remediation is informal and variable and there is currently no consistent
system by which developers, regulators and funders can have confidence in. Pressure from developers,
legal and financial institutions has resulted in the issue being addressed by government agencies such
as the WDA and the Department of Environment.
By adopting QMS principles, this allows us to build in consistency, reliability, and independent
verification of the remediation process. Such principles may be set out in an EMS which brings together
all phases and elements of site remediation into a reasoned, documented, and measurable or auditable
system that gives objective evidence of verification. This in turn allows all parties in the remediation
process to have a clear understanding of their obligations and can give value to site warranties.
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Groundwater Contamination in Portugal: Overview of the Main Problems
Maria Teresa Chambino, Institute Nacional de Engenharia e Tecnologia Industrial (INETI),
Institute de Tecnologias Ambientais/Dep. Tecnologias Ambientais, Portugal
1. INTRODUCTION
Nowadays in Portugal, there is a progressive degradation of soils and ground-water, mainly as a
consequence of the population growth and industrial development of the last decades. Quite often waste
and wastewater treatment plants are not created according to the new needs and industrialists and farmers
are not yet conscious of the dangers of the uncontrolled deposition of wastes or use of excessive
amounts of fertilizers and pesticides.
Nevertheless soil and groundwater contamination are not yet a priority in Portugal compared to other
european countries. To overcome these problems the creation of a national program of characterization
of soil and groundwater contaminated sites and also the intervention of local authorities is of great
importance.
This paper presents a national overview of the main groundwater contaminated problems. The case of
the industrial site of Estarreja is specifically mentioned because it is a very important one and the most
systematically characterized .
2. MAIN POLLUTION SOURCES
2.1 Industry
The principal industries causing major pollution problems are food processing, pulp and paper,
chemistry, textile, and cattle breeding. These together account for 90% of the total pollution produced.
The major contributions are from pulp and paper (20.9%), textile (12.4%), olive oil (10.6%), pig
breeding (10.2%), wine and derivatives (4.7%), synthetic resins (4.5%), yeast (4.2%), and oil refineries
(3.4%).
Industry is responsible for the consumption of around 16% (800 million m3) of the total water consumed.
Around 80% of this water is consumed in North region and Lisbon area.The sectors consuming most
are textiles and tanning (= 45%) and pulp and paper, and printing (= 25%). The slaughter houses,
tanning, extractive industry and steel works are not important at a national level, but may be important
regionally.
2.2 Agriculture
Agriculture is an important pollution source due to the intense activity in certain areas and the excessive
use of pesticides and fertilizers that contribute to the degradation of superficial and groundwater.
The total yearly water consumption in agriculture is around 3,800 million m3 (= 77% of total
consumption). Of this, the North region has 31%, Lisbon area 35%, Centre 17%, Alentejo 14%, and
Algarve 3%.
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2.3 Urban Areas
The public water supply is = 7% of total consumption or 360 million m3. 67% of this water is for
domestic consumption, 20% for industrial consumption, and 13% for public sector. Portugal has a
consumption of 100 L/inhab/day, which is less than most other european countries. The dependency of
domestic and industrial water supply on groundwater is indicated in Figure 1.
Figure 1: Dependency of domestic and industrial supplies on groundwater
3. MAIN PORTUGUESE REGIONS WITH SERIOUS PROBLEMS OF GROUNDWATER
POLLUTION AND OVEREXPLOITATION
The main problems are presented here. Due to its relevance the Estarreja case, in centre region, is
described in detail in Section 4 below. A general problem is the groundwater contamination by most of
the landfills, in particular in Estarreja, Almada/Seixal and Sines.
3.1 North Region
3.1.1 Organic and Industrial Pollution in River Cavado Sediments
This is an important industrial area. The main activity is textiles but paper, ceramics, food processing,
and slaughter houses are also important.
The water from the Borralha mines contaminates the river with cadmium and copper. Some urban areas
also dispose of their domestic effluents to the river.
An investigation of the river sediments revealed high levels of cadmium, copper, lead, chromium, nickel,
and zinc.
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The groundwater revealed organic contamination. In the nearby urban area of Barcelos 69% of the water
is bacteriologically unsuitable and only 11.5% is chemically unsuitable. This means the water has good
quality in the origin, but becomes contaminated along the way.
3.1.2 Domestic and Industrial Pollution in the Sediments of the Rivers Ave and Affluent
The same situation as the previous one. Contamination by cadmium, chromium, copper, lead, and zinc.
The main industry is textiles, which absorbs around 70% of all the people employed in industry in the
area.
Most of the industrial wastewaters are discharged directly and without any treatment into the rivers. The
situation with regard to sewage discharges the situation is quite similar.
3.2 Centre Region
3.2.1 Lowering of Piezometric Levels in the Baixo Vouga Aquifer
During recent decades, piezometric levels have fallen by tens of meters. From only 1989 to 1993, the
level decreased 5.5 m. Chloride levels over 500 mg/L were detected in the part of the area closer to the
sea.
3.2.2 Industrial Pollution in Caldas de S.Jorge
Toys industrial units, with chromium and nickel plating operations have disposed around 500 L/week
of their effluents, over the years, into wells and on land near the industries. The main pollutants were
chromium, nickel, cyanide, copper, and zinc, and the contamination reached the groundwater.
3.2.3 River Sediments
Near Agueda there are about 120 industrial units with anodizing surface treatments mainly chromium,
nickel, and zinc plating. Around 80-90% of these units have infiltrated their effluents in the soil. The
sediments of river Agueda are contaminated with heavy metals. The sediments of the river Criz
(Tondela) are polluted by effluents of aviculture.
3.3 Lisbon Area
3.3.1 High Nitrate Concentrations
Nitrate levels between 74 and 471 mg/L have been detected in river Sizandro valley. High nitrate levels
were detected in Rio Mai or (325 mg/L), Seixal (274.5 mg/L), Almeirim (226.1 mg/L), and Torres
Vedras (203.5 mg/L).
3.3.2 Disposal Area of Almada
Domestic and industrial wastes were disposed in the old disposal site, with no impermeabilization. The
groundwater are contaminated with heavy metals of industrial origin.
3.3.3 Ridge of Mountains of Aires and Candeeiros
Over the years domestic waste was thrown in pits and this contaminated the groundwater.
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3.3.4 Alcanena
The tanning industry is concentrated in Alcanena, representing 75% of the national production.The
wastewater rejection over the years has contaminated the aquifers near the water lines. A wastewater
treatment plant has now been installed, but there remains the problem of sludges and wastes highly
saturated with chromium.
Due to the industry concentration in this area, it was decided to install a collective treatment plant to
treat the domestic and industrial effluents of almost all the industrial units. The sludges from the
treatment have been deposited on the soil, with no control for over six years.
A new landfill is being built consisting of three impermeable pools. Some sludges are being transferred
to the first pool with 61,000 m3, located 100 m from the treatment plant. This plant is going to be
enlarged to produce 60 nrVday of sludges that will be deposited in the two lagoons with 122,000 m3.
This sludge and waste transfer to the landfill has created atmospheric pollution problems with chromium
acid, hydrogen sulphide, and methylmercaptan.
3.4 Alentejo Region
The main problem in this region is nitrate contamination of groundwater. In the Evora area, around 50%
of the groundwater analysis performed indicate values exceeding the limit value of 50 mg/L. The nitrate
level is also high in Beja.
3.5 Algarve Region
3.5.1 Nitrate
Nitrate levels over the limits were detected in several river sediments, due to agriculture and effluent
disposal.
3.5.2 Groundwater salinization
Several areas around the south coast have problems of groundwater salinization. Besides the problems
of salinization by overexpoitation of the aquifers, salinization also occurs due to the leaching of
saliferous rocks. The main contaminated (saline ?) aquifers are shown in the map in Figure 2.
4. GROUNDWATER CONTAMINATION IN ESTARREJA
4.1 Main Chemical Units
4.1.1 The general situation
This area is one of the most industrialized in the country and presents serious problems of soil and
groundwater contamination due to over forty years of presence of an important chemical complex, with
precarious methods of effluent and waste disposal.
The chemical industrial area of Estarreja includes mainly the following industrial concerns: Quimigal,
Uniteca, and Cires. The first unit to be installed was Quimigal, in 1952, followed by Uniteca in 1959
and Cires in 1963. There is a great interdependence among these units, with exchanges of raw material
and subproducts.
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Polluted and over-exploited groundwater
Polluted groundwater
Over-exploited groundwater
50 Km
Figure 2: Main contaminated aquifers
This industrial area is regarded as a threat to the environment due to the wastes and effluents produced.
Furthermore, it is located on highly permeable soils with a groundwater level that is periodically high,
and near an area of intense agricultural activity highly dependent on groundwater.
Over the years these units have been rejecting large quantities of waste directly on the soil: Uniteca
sludge deposit, 60,000 tonnes; Cires sludge deposit, 300,000 tonnes; and the Quimigal sludge deposit,
80,000 tonnes. These wastes were deposited with no impermeabilization measures.
Until recently, the effluents were disposed to a not impermeable ditch, transporting over several
kilometers arsenic, mercury and other heavy metals and inorganic compounds to the Estarreja river
branch. Some compounds infiltrated through the bottom of the ditch have contaminated the local
groundwater. In addition, during periods of with heavy rain or disposal of large effluent volume, the
effluents have overflown the agricultural land near the ditch.
A few years ago, a pipe was built for effluent transport. Although the ditch has officially ceased to be
used for effluent rejection, effluents with nitrobenzene were detected during a sampling campaign
performed in 1992.
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The atmospheric pollution and the deposition on the soil of several metals and sulphur dioxide from
gaseous emissions will increase the soils acidification.
The effects of this industrial area are felt until the Aveiro estuary, 20 km away, where high levels of
mercury were detected.
The groundwater contamination has reached such a level in many wells that the municipality has been
forced to distribute water for domestic use. Nevertheless the water distribution is not enough for
agricultural purposes.
The volume of groundwater withdrawn over the years has lowered the piezometric level and induced
a gradual salinization. So the industrial units were forced to capture water from the river nearby
(corresponding to 90% of their needs), and use groundwater during summertime.
4.1.2 Quimigal
This plant has been producing, ammonium sulphate since 1952, nitric acid and ammonium nitrate since
1974 and aniline from mononitrobenzene since 1978. The main raw material was pyrites for sulphuric
acid production. This production is now stopped for economic reasons.
Over the working decades, we can foresee the impact of the atmospheric emissions of sulphur dioxide
and sulphuric anhydride, arsenic, mercury, and other metals and the effluents and waste rejection. Some
years ago, a gas treatment system was installed but no protection was made for soil or groundwater. The
dust from the treatment was gathered with the other sludges and wastes.
Waste Production
Around 80,000 tonnes of wastes and sludges were produced over the years—mainly dusts from gaseous
effluents treatments with heavy metals, and sludges from primary treatment contaminated with arsenic
and ashes.
Main Contaminants
• In liquid effluents: aniline, ammonia, arsenic, mononitrobenzene, and benzene
• In wastes: arsenic, lead, zinc, vanadium, other heavy metals
Effluent Treatment
• Incineration for effluent rich in organic matter and activated carbon for inorganic effluents.
• Settling
Raw Materials
• Ammonia, potassium chloride, pyrite, solid sulphur, phosphates, benzene
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4.1.3 Uniteca
This plant produces sodics and chlorates from rock salt through electrolytic cells, using graphite anodes
and mercury cathodes. Some mercury goes to the environment, mainly due to cleaning of the cells,
cleaning of the pavements near the electrolysis area, and wastewater treatment sludges
Nowadays in the European Community, the most important producers of alkaline chlorides no longer
use mercury cells. Nevertheless in Uniteca they are still being used, although there exists a new line with
membrane technology that avoids pollution with mercury.
Main Contaminants
• Liquid effluents with mercury, suspended solids, and sulphuric acid
• Sludges with mercury
• Atmospheric pollutants: sulphur dioxide, nitrogen oxide, particles, mercury, and hydrochloric acid
Raw Materials
Raw materials include sodium chloride, mercury, sodium carbonate, and sulphuric acid. There is a plan
to install a process for mercury removal from the liquid effluents, lowering the mercury level from 25
mg/L to 0.025 mg/L. In the Portuguese legislation, the mercury level allowed in wastewaters is 0.001
mg/L.
4.1.4 Cires
This plant produces synthetic resins, mainly PVC (polyvinyl chloride).
Main Contaminants
• Liquid effluents with vinyl chloride and mercury
• Sludges with calcium hydroxide, wastewater sludges
Effluents Treatment
The effluents are stored in two lagoons before going to the treatment plant. The lagoons are not
impermeabilized and so vinyl chloride can contaminate the groundwater.
Raw Materials
• Hydrochloric acid, vinyl chloride, mercury chloride, and sodium hydroxide
4.2 Sampling
Two different sampling campaigns were performed for groundwater and soil characterization, from 1992
to 1994. In the first campaign, in 1992, samples were collected only from 37 wells and three ditches
covering an area of 15 km2 around the industrial units. In the second campaign, in 1993/94, samples
were collected in 39 monitoring holes. The depth of sampling was in average 5.5 m.
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These data allowed the characterization of the ground-water and the identification of the major pollution
plume, only with season concentration changes.
4.3 Results
4.3.1 Overview
The main concentration values were detected near the industrial units, in the ditches and in the sludges
deposition areas. This concentration flows in the direction of the quaternary aquifer flow, from east to
west. So the highest concentrations are found west of the industrial area. The concentration levels found
in monitoring holes are higher than those found previously in wells. Due to the nonexistence of
legislation for groundwater in Portugal, the comparison is made with legislation for water for human
consumption.
4.3.2 Heavy Metals
Mercury
High values of mercury were found reaching 745 ug/L (the legislation value is 1 ug/L). The areas where
this happened are near the effluent rejection ditches and west of the industrial area.The total mercury
concentration is higher than the dissolved mercury, revealing that mercury is adsorbed by small particles.
A map of mercury concentrations is provided in Figure 3.
The origin of the mercury is mainly the sludge disposal area of Uniteca. Those sludges have mercury
levels from 100-500 mg/kg. In the area where these high mercury levels were detected, the water cannot
be used for human consumption.
Arsenic
High concentrations in groundwater were found, reaching 6,760 ug/L, compared the legislation level was
50 ug/L. The high levels of arsenic come from the sludge disposal area of Quimigal. Also the effluents
from Quimigal presented high levels of arsenic. From 1987 to 1991, the industry effluent had maximum
levels of arsenic of 38,000 ug/L. The average values were 8,355 ug/L and the effluent value allowed
in legislation is 1,000 ug/L.
Zinc
The origin of the zinc is the sludge disposal area. The main pollution area is west of this area and
reaches 204 mg/L, compared to the limit of 0.1 mg/L. Also, near the ditches the values are important.
Iron
The higher concentrations are near the ditches, reaching values of 61 mg/L (legislation value of 0.2
mg/L). So we can see that the heavy metals reach high contamination levels in groundwater.
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125.0
121.0
123.
0)
rH
H
n)
M
rt
Meridians
Figure 3: Groundwater mercury contamination
4.3.3 Anions
Chlorides
The chloride concentrations reach higher values (highest value = 36,540 mg/L) than the legislation
permits (25 mg/L) all over the sampling area. The origin is probably the sludges from Uniteca, which
present chloride values of 7 to 11% in the 60,000 tonnes of sludges. Also, the effluents from Quimigal
present high chloride values, reaching an average between 1987 and 1991 of 630 mg/L.
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Sulphates
Values over three times the legislation limit were found: values of 900 mg/L compared to the limit of
250 mg/L. The origin is the sludge from Uniteca, where calcium sulphate is 10 to 14% of the sludges,
and the effluents from Quimigal that reach values of 2,300 mg/L, compared to the legislation limit of
2,000 mg/L. Some of the sulphate might have been reduced to sulphide and be responsible for the smell
characteristic of the waters in this area.
Nitrates
Values exceeding the legislation value (50 mg/L) were found near the ditches, reaching values of 325
mg/L. Their origin is the effluent rejection and also the fertilization for agriculture. The effluent rejection
between 1987 and 1991 reached values of 5,116 mg/L, hundred times the legislation value.
4.3.4 Organic compounds
There is no mention of organic compounds in the Portuguese legislation for water for human
consumption so reference is made below to international legislation.
Nitrobenzene
In three of the monitoring holes, the level was higher than the U.S. legislation limit for groundwater (20
ug/L), reaching the high value of 2,520 ug/L. This hole is very near to the ditches, indicating the
importance of effluents disposal as a source.
Benzene
The high value of 85.7 ug/L was reached in the same hole where nitrobenzene also reached the
maximum (the limit in USA legislation is 5 ug/L). These two compounds are present in Quimigal
effluents. The sampling campaigns allowed the detection of the area where contaminant concentrations
are higher than the legislation permits. This area is illustrated in Figure 4.
4.4 Solutions Proposed
The Estarreja problem is a complex one due to the long time over which disposals have taken place
(over forty years) and the dispersion of contaminants over a large area. Before the decontamination of
the area, the first step should be the removal and treatment of the main pollution sources: i.e., the
sludges disposal area of Quimigal and Uniteca and the liquid effluent disposal to the ditches.
For the moment, the sludges disposal area should be covered to prevent the rain entering and consequent
leaching and a physical isolation of the area through the injection, in the land and until near the aquifer,
of walls preventing the pollutants migrating. Also, effluent disposal through the ditches should be
stopped and wastewater treatment should also be installed.
There is a project from the Estarreja Municipal Government to treat the wastes by "Chemical Fixation
and Solidification." The sludges from Quimigal and Uniteca would be mixed with Cires sludges, which
are more inactive (mainly calcium hydroxide) and would be used as material for encapsulation.The
sludges and wastes would finally be deposited in a landfill.
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security. For management of industrial wastes, an Integrated System of Waste Treatment (SITRI) was
programmed for the country.
In Estarreja should be installed an incineration unit, together with a project for soil and groundwater
decontamination (Project ERASE) and a project for industrial and domestic wastewater treatment (Project
AMRIA). Also, priority should be given in Estarreja to the installation of clean technology industries.
The incineration installation is somewhat delayed because the NIMBY mentality (not in my backyard)
arrived quickly in Portugal, and through 1995 great opposition was made by the population to the
installation of incineration units or landfills.
5. RESEARCH PROJECTS
In Portugal, very few research projects are dedicated to the problems of groundwater and soils
contamination, and those there are mainly are master theses in the universities. One of the few existing
projects is a European Community project "Experimental Evaluation of Remediation Techniques for
Contaminated Coke Oven Sites." The partners are SiderurgiaNacional, Institute de Ciencia e Tecnologia
dos Materials (ICTM) and Deutshe Montan Tecnologie (DTM).
INETI is subcontracted by ICTM, one of the partners. INETI's activities concern characterization of the
contamination of soils and groundwater in the coke oven site of Siderurgia Nacional by the Institute of
Environmental Technologies (ITA); and strategies for microbial remediation of coke oven contaminated
sites by the Institute of Biotechnology, Chemistry and Food Technologies (IBQTA).
The contamination of soil at operational coke oven sites is due to organic and inorganic toxic compounds
such as mono-aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), phenols, cyanides,
heavy metals, and ammonia. This contamination may be a source of groundwater pollution, especially
when the water table is at shallow depths. Due to the fact that the contaminated site is located near an
estuary, the tide effect can cause a groundwater gradient towards the surface water and cause superficial
water pollution problems.
The objective of this research project is to select the most effective biological treatment technology to
remove phenols, PAHs, and cyanides from contaminated coke oven plant sites still in operation and also
to analyse the groundwater contamination. The program of work was:
• Identification of organic contaminated areas;
• Development of sampling program for soils and groundwater;
• Characterisation of soils and groundwater; and
• Determination of biological treatment efficiencies.
Regarding ITA's activities, the characterisation of soil contamination as well as the mapping of the
extent of pollution was carried out. Individual samples of soil representative of each geological layer
were collected in order to obtain information about the lithology and the contamination of the area.
Twelve trenches were dug with a mechanical excavator, almost all were dug until groundwater level was
reached.
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The contamination found in the coke oven site is mainly due to tar at the top of the first layer. Coke
oven tar is an extremely complex mixture, the main components of which are polycyclic aromatic
hydrocarbons (PAHs), highly toxic. Fluoranthene, phenanthrene, and pyrene have been detected as major
contaminants.
Due to their high chemical stability and low water solubility, the PAHs have low mobility and persist
as soil contaminants. The PAHs were identified by reverse phase high performance liquid
chromatography, and values exceeding 1,000 mg/kg of fluoranthene, phenanthrene and pyrene were
detected. The phenols and total cyanides reached 25.3 mg/kg and 1,420 mg/kg, respectively.
The tar contamination was mapped. In most places tar contamination is only at the surface, but in some
sampling points, it has reached deeper layers down to groundwater level.
In lower soil layers the presence of ammonia was detected in the groundwater in all the trenches. This
contamination is due to ancient accidental spillage and probably also to pipe leaks. In the next project
phase, groundwater contamination is going to be characterised.
Regarding the bioremediation studies, the objective was to determine the potential for bioremediation
of the microbial communities indigenous of the coke oven site through the evaluation of their abilities
to degrade PAHs, particularly those detected as major contaminants. Tests already performed indicate
that mixed culture selected and enriched from soil native microbial populations have the ability to
degrade the predominant PAHs contaminants fluoranthene, phenanthrene, and pyrene.
6. BIBLIOGRAPHY
Goncalves, E. e Boaventura, R., (1989), Sediments as Indicators of River Ave Contamination by Heavy
Metals, International Symposium on Integrated Approaches to Water Pollution Problems, SISIPPA,
Lisboa.
Grupo de Investigacao de Aguas Subterraneas, (1992), Metodologias para a Recuperacao de Aguas
Subterraneas e Solos Contaminados, Partes A e B, LNEC.
Grupo de Investigacao de Aguas Subterraneas, (1994), Metodologias para a Recuperacao de Aguas
Subterraneas e Solos Contaminados, Partes C, D, E e F, LNEC.
Grupo de Investigacao de Aguas Subterraneas, (1995), Desenvolvimento de um Inventario das Aguas
Subterraneas de Portugal, LNEC.
Lobo Ferreira,J.P., (1989), A Groundwater Pollution Case Study: Rio Maior, International Symposium
on Integrated Approaches to Water Pollution Problems, SISIPPA, Lisboa.
Milheiras Costa, A., (1989), Agueda como Exemplo de Solucao Integrada de Poluicao, las Jornadas sobre
Industria e Ambiente, INETI.
Monteiro, H. e Boaventura, R., (1989), Distribuicao de Metais Pesados nos Sedimentos da Bacia
Hidrografica do rio Cavado, International Symposium on Integrated Approaches to Water Pollution
Problems, SISIPPA, Lisboa.
Piano Nacional da Politica de Ambiente, (1994) , M. do Ambiente e Recursos Naturais.
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Santiago,M.F. e Corte-Real Frazao, A., (1993), Lamas das Aguas Residuals Industrials - Caso da
Industria dos Curtumes, Seminario sobre Tratamento e Destine Final de Lamas de Aguas Residuais,
LNEC e DGQA.
Sepulveda, I., (1994), Soil Contamination and Decontamination: Overview of the Portuguese Situation,
Land Contamination & Reclamation, Vol. 2, No. 2.
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Critical Review of Air Sparging and In Situ Bioremediation Technologies
Domenic Grasso, The School of Engineering, University of Connecticut, Kenneth L Sperry,
Envirogen, Lawrenceville, NJ, and Susan Grasso, Environ, Princeton, NJ
1. INTRODUCTION
This review consists of the identification, classification, and analysis of issues of concern (or "critical
issues") frequently encountered during the application of air sparging/biosparging, bioventing,
biostimulation, and biorestoration remediation technologies. This review was prepared for the NATO
Committee on the Challenges of Modern Society, which is evaluating emerging environmental
remediation technologies, in an effort to facilitate future applications of these technologies.
The review utilized a case study approach and included more than 400 sites located in the United States,
Australia, Canada, and Europe. Case studies included bench-, pilot-, and full-scale applications of these
technologies, and explored remediation at a wide variety of sites including:
• petroleum processing/handling facilities;
• wood preserving plants;
• manufactured gas plants;
• military installations; and
• industrial/chemical manufacturing facilities.
At a majority of the sites reviewed, organic compounds in soil and groundwater were the target of
remediation. Elevated levels of heavy metals and inorganic compounds were, however, also present at
many of the sites reviewed. In general, seven classes of compounds were frequently encountered: (1)
aliphatics; (2) substituted benzenes; (3) poly cyclic aromatic hydrocarbons; (4) poly chlorinated biphenyls;
(5) pesticides/insecticides/herbicides; (6) inorganics; and (7) metals.
Critical issues identified in the case studies were categorized according to scale (macro, meso or micro).
A macroscale issue was generally defined as a factor that may complicate the selection and
administration of a remedial technology. Meso- and microscale issues were generally defined as factors
that may adversely affect the performance of a remedial technology. More specifically, mesoscale issues
were related to the physical geologic and hydrogeologic properties of the subsurface, and microscale
issues pertained to biological and physicochemical processes. The review focused primarily on the
detailed evaluation of meso- and microscale critical issues most frequently associated with the
remediation technologies of interest.
Overall, critical issues (macro, meso, and micro) were reported in approximately 35% of all cases
reviewed. More specifically, critical issues were observed with the following frequency for each
technology:
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Technology
Air sparging/biosparging
Bioventing
Biostimulation
Biorestoration
Total Number
87
101
67
104
Sites with
18
31
29
47
Percentage of Sites
21%
31%
43%
45%
The actual number of case studies where critical issues were encountered may be much greater as there
may be reluctance to report such information. The primary types of critical issues observed for each
technology are summarized below.
2. AIR SPARGING/BIOSPARGING
Air sparging/biosparging consists of injecting air (or other gases) under pressure directly into
groundwater-saturated aquifer materials. The objective is to facilitate contaminant transfer from an
aqueous phase (groundwater) to a gaseous phase (in situ air stripping) which is subsequently transported
to the overlying unsaturated zone and removed by traditional soil vapor extraction (SVE) techniques.
In addition to volatilization, air sparging fortuitously stimulates microbial degradation of contaminants
by increasing the concentration of dissolved oxygen in the subsurface (biosparging).
Mesoscale critical issues were observed most frequently followed by macro-scale critical issues.
Reported macroscale issues were associated with regulatory acceptance of these technologies due to their
limited use. A very limited number of air sparging and biosparging case studies reported microscale
issues.
While some of the mesoscale issues observed were related to contaminant distribution and site
hydrogeology, those relating to site geology were observed to most severely compromise air sparging
and biosparging performance. In these cases, geologic stratigraphy (such as lenses of low or high
permeability material), and small variations in soil permeability resulted in preferential air channeling
and poor air distribution through tortuous and asymmetrical air flow pathways.
Preferential air flow reduced the effectiveness of air sparging and biosparging because large
portions of the targeted remediation zone were bypassed by the sparge air.
3. BIOVENTING
Bioventing induces air movement through the unsaturated soil to enhance aerobic biodegradation of
contaminants by supplying oxygen to soil microorganisms. Air movement is usually induced by forced
(active) aeration using injection and extraction wells.
Similar to air sparging/biosparging, mesoscale critical issues were observed most frequently followed
by macro-scale critical issues. Reported macroscale issues were associated with regulatory approval and
acquisition of regulatory permits. Relatively few of the bioventing case studies provided information
detailed enough to accurately identify microscale critical issues. Where microscale critical issues were
observed, however, they were likely associated with biological and/or physicochemical limitations that
adversely affected biodegradation kinetics.
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Mesoscale critical issues observed to most adversely affect system performance were related to site
geology and hydrogeology. More specifically, the effectiveness of bioventing was reduced when the
delivery of oxygen to indigenous microorganisms was hindered by: (1) low permeable soils; and (2)
excessive soil moisture content.
Fine-grained soils (silts and clays) which have a low intrinsic soil gas permeability and a high
field capacity (potential for high soil moisture content) were found to be especially problematic
in the application of bioventing. The combination of these factors decrease effective soil gas
permeability and increase the potential for oxygen diffusion limitations.
4. BIOSTIMULATION
Biostimulation refers to the enhancement of aerobic biodegradation of contaminants in the unsaturated
zone (above the water table) through the addition of electron acceptors, electron donors, and nutrients.
In the case studies reviewed, these amendments were typically delivered to the subsurface using water
or air as a carrier fluid.
Macroscale and microscale critical issues were observed with equal frequency in biostimulation case
studies, while mesoscale critical issues were observed to a lesser degree. Macroscale critical issues
included: (1) difficulty in obtained regulatory approval for use of the technology; and (2) difficulty
obtaining discharge to groundwater permits. The primary mesoscale issue observed involved the non-
uniform delivery of components required to enhance aerobic biodegradation as a result of geologic
heterogeneity.
Microscale critical issues were most often associated with biological and physicochemical processes,
however, in many case studies differentiating between these mechanisms was not possible. The following
were observed:
(1) Biological microscale issues were related to contaminant biodegradation potential, microorganism
metabolic requirements, and contaminant toxicity.
(2) Physicochemical critical issues were related to reduced contaminant bioavailability deriving from
either mass transfer kinetics or dissolution rate limitations.
The predominance of microscale critical issues in the biostimulation case studies reviewed was a
reflection of the contaminant type targeted for remediation. In contrast to the majority of the air
sparging/biosparging and bioventing case studies reviewed, a wide range of large poly cyclic aromatic
hydrocarbons (PAHs) were the target of remediation at the majority of biostimulation case studies
reviewed.
The insoluble and nonvolatile nature of PAHs targeted for remediation in many of the
biostimulation case studies makes them more recalcitrant to biodegradation (and volatilization)
than the lower weight aliphatic and aromatic hydrocarbons that were typically the target of
remediation in the air sparging/biosparging and bioventing case studies discussed.
5. BIORESTORATION
Biorestoration refers to the injection of fluids containing electron acceptors, electron donors, or nutrients
into the saturated zone (below the water table) to stimulate in situ aerobic or anaerobic biodegradation.
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Macroscale critical issues were observed most frequently in the biorestoration case studies reviewed, and
typically involved: (1) difficulty in obtained regulatory approval for use of the technology; and (2)
difficulty in monitoring biorestoration performance.
Mesoscale critical issues were most often related to site hydrogeology. Groundwater flow velocity, as
determined by hydraulic conductivity and hydraulic gradient, was an important factor in the successful
application of biorestoration, as expected.
Informations with low groundwater velocities, the area! extent of biodegradation was limited
because electron acceptors, electron donors, and nutrients were quickly consumed within the
immediate vicinity of injection wells.
Microscale critical issues were most often associated with biological processes in many of the
biorestoration case studies reviewed. Specific hindrances to system performance included:
(1) The biodegradation kinetics of some components of coal tar waste were observed to be rate
limiting.
(2) Microbial inhibition due to elevated levels of arsenic, lead, chromium, and dioxins was also
observed to potentially limit biodegradation.
The slow biodegradation rate of components of coal tar wastes was observed to limit system
performance in some of the biorestoration case studies reviewed. The biodegradation kinetics
of these compounds were potentially limited by contaminant bioavailability. In addition,
microbial inhibition due to elevated concentrations of arsenic, lead, chromium, and dioxins was
suspected of limiting biodegradation rates in some biorestoration case studies discussed.
6. MASS TRANSFER LIMITATIONS—A UBIQUITOUS CRITICAL ISSUE
Although many critical issues were observed to be specific to either air sparging/biosparging, bioventing,
biostimulation, or biorestoration, all the reviewed technologies have one at least one critical issue in
common: diffusion limited mass transfer. The theory and ramifications of diffusion limited mass transfer
were therefore explored in depth. The discussion focused on diffusion limitations:
(1) in bulk aqueous solution where advective flow is minimal or absent; and
(2) from within soil matrices to the surrounding bulk aqueous solution (sorption retarded diffusion).
6.1 Diffusion Limitations in Bulk Solution
In situ technologies discussed herein are inherently susceptible to diffusion limited mass transfer in the
bulk aqueous phase because each technology relies upon fluid flow to either:
(1) deliver components required to enhance biodegradation (electron donors, electron acceptors, and
nutrients); or
(2) to extract contaminants (such as volatilization in air sparging).
Fluid flow in most subsurface environments, however, is not uniform and heterogeneities in the
subsurface can result in preferential flow pathways. Outside these flow pathways, advective fluid flow
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may be minimal or absent. As a result, the primary mechanism for delivering components required to
enhance biodegradation or contaminant extraction in these areas may be governed by molecular
diffusion. A mathematical model was used to explore diffusion times required for oxygen and
contaminants under various subsurface conditions encountered in this review.
Modeling results indicated that extensive diffusion times (ca. years) are required for oxygen and
common contaminants to diffuse short distances (less than 1 m) in regions of the subsurface
where advective fluid flow is minimal or absent.
6.2 Sorption Retarded Diffusion
A sorption retarded diffusion limitation (i.e., diffusion from within the soil matrix to the surrounding
bulk aqueous solution) has been proposed as the primary mechanism responsible for the significant
"tailing effect" in contaminant concentrations which was observed in many of the case studies reviewed.
A bi-modal theory describing desorption from the soil matrix was combined with a radial diffusion
model of transport in an aqueous solution to simulate the tailing effect phenomena. Model simulations
assessed the effects of:
• tortuous and constricting soil pores;
• intra-particle porosity;
• soil fraction organic carbon;
• particle size; and
• contaminant chemical properties.
Model simulations demonstrated that considerable time (ca. years) may be required to desorb
some contaminants from the soil matrix to the surrounding bulk aqueous solution. In addition,
the use of a Freundlich isotherm to represent non-linear sorption in select portions of a soil
matrix resulted in the prediction of significantly higher desorption times.
The ability to uniformly distribute fluid in the subsurface was frequently encountered as a limitation in
the application of the in situ technologies under review due to heterogeneous conditions commonly
present in the subsurface. Without this ability, accomplishing uniform and complete remediation is such
an environment can be difficult, due to diffusion limitations that may exist in the bulk fluid.
Additionally, in most of the case studies reviewed, soils had been contaminated for many decades prior
to remediation, suggesting that sorption retarded diffusion may be responsible for tailing phenomena
commonly observed. As previously discussed, this may severely limit the long-term performance of the
in situ remedial technologies reviewed.
7. REFERENCE
Grasso, Domenic, Kenneth L Sperry, and Susan Grasso. NATO Fellowship Project: A Critical Review
of Air Sparging and In Situ Bioremediation Technologies, The School of Engineering, University of
Connecticut (Storrs, Connecticut, USA) 1997.
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The Cost of Remedial Action
Dr. Mary R. Harris, Monitor Environmental Consultants Ltd, Birmingham, U.K.
1. INTRODUCTION
Considerable efforts have been made over recent years to identify and develop new technologies for the
treatment of contaminated soil and groundwater and to demonstrate their technical performance in the
field. Many of these technologies have the potential to transfer across international boundaries. Some
appear to offer the prospect of dealing with contamination on a "once-and-for-all," as opposed to
"contain and control," basis.
With some notable exceptions, however, there seems to be relatively little reliable information available
to landowners, regulators and practitioners on:
• the cost of different technologies, and how they may compare against more established or traditional
approaches;
• the key cost components of different technologies; and
• how the cost of treatment may be distributed over time.
A lack of reliable cost information can be as important as technical uncertainty in discouraging the wider
uptake and application of new technologies. For example:
• it encourages users to favour the selection of established methods and approaches, where technical
capabilities and costs are already well established and understood;
• it makes it difficult for users to predict at the outset (and with any acceptable degree of accuracy)
what the financial implications of a remedial project may be; and
• it makes it difficult for users to gauge short versus long-term costs and benefits when making
selection decisions, and to justify them financially.
Finally, a lack of information on the cost characteristics of new technologies can hamper their transfer
across international borders because users are unable to make the essential financial adjustments needed
to translate technology costs into a specific national context.
There are, of course, a number of practical difficulties in obtaining reliable financial information.
Examples include:
• commercial confidentiality (on the part of both clients and contractors) on the actual "value" of the
work done, rather the estimated or predicted cost;
• local or temporal cost variations due, for example, to fluctuations in local demand for remedial
goods and services; and
• other site specific factors, such as the nature of the contamination, scale of operations, duration of
the works, extent of other ground improvement or construction activities and their relationship with
remedial action.
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However, opportunities do exist for the systematic collection of financial information. Examples include
national and international research and demonstration programmes, such as this NATO/CCMS study,
and other publicly-funded remedial works, e.g., regulatory-led action and grant-aided redevelopment
schemes.
The development of standardised data collection and reporting procedures can help to ensure that
financial information is consistent, objective and informative. The aim of this Fellowship was to assist
in the development of reliable information on remedial costs and to improve the ability of technology
users to interpret and apply cost information.
2. OBJECTIVES
The main objective of the Fellowship was to develop a standardised framework for reporting information
on the costs of remediation that will:
• help to expand the currently relatively limited information base on remedial costs;
• assist in the international transfer of information on remedial costs;
• allow potential users of different remedial technologies to identify where the main cost burden is
likely to fall;
• alert potential users to the trade-offs (e.g., high capital/low aftercare versus low capital/high
aftercare costs) which may have to be made when selecting particular technologies; and
• help potential users of overseas technologies to identify those cost items (e.g., waste disposal,
energy, labour, etc.) which may vary significantly as a result of country-specific factors.
3. APPROACH
Draft guidance on reporting remedial costs has been developed (see Annex I) based on:
• the cost framework developed in support of the U.S. Environmental Protection Agency Superfund
Innovative Technology Evaluation (SITE) Program;
• research on remedial costs commissioned by the German Federal Environment Ministry; and
• work carried out by the U. S. Federal Remediation Technologies Roundtable Ad Hoc Working Group
on Cost and Performance.
The draft guidance was circulated to Pilot Study Country Representatives for comment. Some comments
have been received and have been incorporated into the current draft. This will be circulated to Pilot
Study members with a request for submission of cost information.
4. ANALYSIS AND REPORTING
It is hoped that sufficient cost data on individual Pilot Study Projects will be available to allow a simple
analysis of the broad cost characteristics of different types of technologies. The responses of Project
Leaders will also be used to refine the cost framework where necessary and to identify the key issues
to be addressed when attempting to interpret or apply cost information.
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It is intended that the findings of the Fellowship will be incorporated into the final Pilot Study report
in the form of a separate chapter on Remedial Costs.
5. ACKNOWLEDGEMENTS
The work reported here was carried out by means of written correspondence with other members of the
Pilot Study and through participation at the following Pilot Study Meetings:
Quebec City, Canada September 1993
Oxford, U.K. September 1994
Nottingham, U.K. May 1995
The assistance of other members of the Pilot Study, and the financial support of NATO and the U.K.
Department of the Environment are gratefully acknowledged.
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ANNEX I: Guidance on Reporting Information on Remedial Costs
A.1. INTRODUCTION
One of the aims of the Pilot Study is to provide information on the cost of remediating contaminated
soil and ground-water. This guidance has been prepared to assist project leaders in collecting and
presenting cost data on their technologies. The information obtained will be used to prepare a Chapter
on costs for inclusion in the Final Pilot Study Report. The guidance supplements that produced by Mike
Smith (see notes of the September 1994 Pilot Study meeting in Oxford) on overall reporting
requirements.
The guidance has been developed with reference to the U.S. Environmental Protection Agency Superfund
Innovative Technology Evaluation (SITE) programme cost framework, research on remediation costs
commissioned by the German Federal Environment Ministry and work carried out by the Federal
Remediation Technologies Roundtable Ad Hoc Working Group on Cost and Performance. Comments
from the Pilot Study Country Representatives have also been taken into account.
It is recognised that not all the projects in the Pilot Study programme will be able to provide cost data
at the level of detail shown; some projects are only just under way, and others are too remote from
commercial realisation to provide meaningful data. Nevertheless, the aim is to provide actual or
estimated costs for the full-scale operation of the technology.
A.2 OBJECTIVES
The main aims of providing cost data on remediation technologies through the NATO/CCMS Pilot Study
are to
• expand the relatively limited information base currently available;
• assist in the international transfer of information on remedial costs;
• inform potential users where the main costs are likely to fall when applying a particular technology;
and
• alert potential users to the trade-offs (e.g., high capital costs/low aftercare costs vs low capital
cost/high aftercare costs) that will have to made when selecting particular types of remedial
technology for use.
It has been suggested that the provision of cost data is of relatively limited value because actual remedial
costs are highly site-specific and some cost items (e.g., energy, labour, waste disposal) can vary
significantly from country to country. However, potential technology users can be made aware of the
limitations associated with the cost data and the need to make appropriate adjustments when attempting
to apply them in individual cases.
It is important therefore to document any important limitations applying to the cost data provided. All
assumptions used to derive cost estimates and any other information essential to the correct interpretation
of the data should be reported.
To facilitate the presentation and analysis of the data, costs should be in national currency and dated.
SI units (e.g., quantities of material treated) should be used throughout.
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A.3 COST BREAKDOWN
Where possible, data should be provided according to the generic cost breakdown provided in Table A. 1.
This shows the different activities that might be carried out during the course of remedial action (left
hand column) against various cost elements (top row). It may be necessary to add activities/cost elements
when submitting data for individual technologies.
Sections A.4 and A.5 give a brief description of the intended scope of the activities/cost elements to be
covered in project submissions. A brief explanation of the items covered by the cost data actually
submitted should be provided.
Table A.l. Actual/Estimated Full-Scale Remediation Costs
Stage
Pre-operational
Operational
Post-operational
Activity
Legal approvals
Site Preparation
Mobilisation
Sub-total
Excavation/extraction
Pre-treatment
Processing
Waste treatment/disposal
Monitoring
I. process control
I. legal compliance
Modification and repair
Public relations
Sub-total
Sub-total
TOTAL
Plant &
Materials
Laboratory
Other
A.4 ACTIVITIES
A.4.1 Pre-Operational Stage
Legal approvals: Costs involved in obtaining regulatory approval for the installation/operation of the
remedial technology. Requirements are likely to vary widely depending on the (national) regulatory
framework, the technology involved and site-specific factors but they will typically include: approval
for installing/constructing items of plant & equipment; consents to make permitted discharges (e.g., to
air, water, sewer); permission to abstract water (e.g., for groundwater remediation work); provision of
environmental impact statements, etc.
Site preparation: Costs involved in preparing the site to receive all necessary plant & equipment. Typical
items to be included are: provision of site security/access; site leveling; provision of hardstanding/storage
areas; ground and surface water protection measures; provision of site services, etc.
Mobilisation: Costs involved in transferring, setting up and commissioning all necessary plant and
equipment.
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A.4.2 Operational Stage
Excavation/extraction: Cost of removing contaminated solids/liquids from the ground prior to treatment
in on or off-site facilities.
Pre-treatment: Costs associated with storing/preparing material for treatment where this can be identified
as a separate part of the process. Typical pre-treatment activities include storing/conditioning, size
classification, grinding, dewatering, drying, etc., of feedstocks.
Processing: The cost of processing/treating contaminated material using physical, chemical, biological
techniques.
Waste treatment/disposal: Cost of transporting/treating/disposing of solid, liquid or gaseous wastes from
the process, including pollution control residues (e.g., spent activated carbon, scrubbing liquors, etc.).
Monitoring: All operational monitoring costs including that required to optimise/control the process (e.g.,
to maintain temperatures, mixing conditions, pH conditions) and ensure legal compliance (e.g., with
respect to atmospheric discharge limits, to protect the health and safety of the workforce).
Modifications/repair: Cost of modifying/repairing plant and equipment.
Public relations: The costs of informing/liaising with third parties, such as the local community.
A.4.3 Post-Operational Stage
Demobilisation/reinstatement: Cost of dismantling, decontaminating and removing items of plant and
equipment, and reinstating the site (where appropriate).
Monitoring: The cost of demonstrating that remedial objectives have been met including one-off
validation (e.g., demonstrating the quality of a product from a soil washing plant) and long-term
monitoring (e.g., demonstrating that an in situ treatment process has reached completion).
A.5 COST ELEMENTS
Plant and equipment: Plant and equipment costs may be reported as capital items (amortisation period
to be specified) or as plant hire costs.
Materials costs: These include all materials consumed during the course of remedial action. Typical
items include treatment chemicals, energy (electricity, diesel), water, health protection equipment,
monitoring equipment not otherwise specified.
Labour costs: These should be reported for all personnel involved in setting-up, operating and
completing the remedial operation. Consultancy and contracting labour costs should be reported
separately where possible. Travel and subsistence costs should be reported under the "other costs"
activity heading.
Analysis: All laboratory analytical support used before, during and after remedial action.
Other costs: All costs not otherwise specified. The items covered under this heading should be specified
and may include permitting/legal fees, travel and subsistence costs, loan charges, insurance, etc.
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Changing Approaches to Remediation1
Merten Hinsenveld, TSM Business School, University of Twente, Enschede, The
Netherlands
In the 1980s, large differences existed amongst the various countries in their approach towards
contaminated sites. By looking at the concentrations in their supposedly clean soils, the Dutch took a
straight forward approach and derived a single concentration per contaminant for a clean soil (so-called
A-value) and a concentration of a polluted soil for which prolonged exposure might lead to health effects
(so-called C-value). The Americans on the other hand choose a more site specific, but cumbersome and
disputable, risk approach. Both approaches were developed on the assumption that the problem of
contaminated sites was limited.
Initially, various countries adopted—with or without modifications—one of these extreme examples.
Experience made two points clear:
(1) the problem was not limited, and
(2) concentration based approaches as well as risk based approaches each have their specific advantages
and disadvantages.
Mixed approaches in various forms and the study of exceptions to the rule is now more common
practice.
Improved understanding of the mechanisms with which the subsoil and the groundwater can and does
cope with a contamination, is changing the approach towards remediation rapidly. With particular
reference to intrinsic bioremediation, the scientific and the regulatory world are both changing from a
problem-solution approach towards a process-oriented approach. Contamination in this approach is more
a process that might be altered, stopped or monitored, than it is a problem.
Finally, the realisation that the tremendous cost of remediation may not be in balance with its benefit,
has provided a growing incentive to the development and use of methods that can weigh the various
cost/benefit elements (economy, environment, health, spacial use) of contaminated sites to provide a tool
for integrated decision making.
1 This fellowship is still in progress and will be extended into the new Pilot Study on remediation starting in 1998.
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Use of Remedial Clean-Up Technology in Portugal
Maria Jose Macedo, Hovione - Sociedade Quimica SA, Loures, Portugal
1. INTRODUCTION
Until recently there was no experience of remedial clean-up of industrial sites in Portugal. Lisbon is
organizing the 1998 World Exposition (EXPO'98) and a site located East of the city was chosen to host
the exposition. This site was formerly occupied by the Petrogal, BP, Mobil and Shell petroleum
companies. Principal activities at the site included petroleum refining and storage, causing soil and
groundwater contamination in several distinct areas. Prior to the existence of the petroleum companies
at the site, there was a sulphuric acid producing plant that caused, in a determined area, contamination
of the soil by arsenic.
ISQ made an audit to the decontamination of this site. A brief description of the decontamination work
is presented.
2. SOIL REMEDIATION AT THE EXPO'98 SITE
The soil was contaminated by several petroleum originated pollutants (benzene, toluene, ethylbenzene,
and xylenes and total petroleum hydrocarbons [TPH]) and arsenic from a previously existent sulphuric
acid plant.
For the site clean-up, several techniques were considered, namely:
• thermal treatment;
• stabilisation;
• soil-vapour extraction;
• biological treatment; and
• excavation and landfilling.
Excavation and deposition in a controlled landfill was finally chosen since it was the technique that
presented a better cost/benefit ratio. Prior to the start of the excavations an excavation plan was prepared.
In this excavation plan, excavation activities to be carried out were described area by area, completed
with drawings and cross-sections. Each excavation area was staked out first, based on the results of the
delineation investigation and the modifications that were included in the excavation plan.
Excavation was done in two phases. After completing a first topographical survey of the area, the non-
contaminated soil was excavated. The limits of the non-contaminated soil were determined during
excavation by means of an oil detection pan. The excavated non-contaminated soil was placed in
stockpiles in the vicinity of the excavated area.
The quantity of excavated non-contaminated soil was determined after doing a second topographical
survey. Excavation of contaminated soil proceeded according to the remediation goals.
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In general, the extent of contamination was quite similar to the expected extent. A total of approximately
300,000 m3 of soil was excavated and landfilled.
The contaminated soil was transported to a landfill. The new designed landfill was situated at the eastern
part of the existing Beirolas landfill in Moscavide, Lisbon. The landfill was constructed with
recompacted clay layers, geotextiles, geonets and liners, to provide a secure storage facility for
contaminated soil. The contaminated soil was transported to the landfill by truck.
There were also large amounts of free product and a large quantity was removed. In total approximately
400 m3 of free product was recovered and removed by tanker truck.
In order to properly excavate to the required depth dewatering of certain excavated areas was necessary.
The water was pumped into a temporary water treatment plant.
The water treatment plant consisted of the following components:
• collection sump with pumps;
• oil/water separator;
• aeration container;
• compost container for treatment aeration air;
• buffer basin for temporary storage;
• sandfilters;
• active-carbon filters;
• end buffer container;
• watermeter; and
• discharge hose to existing sewer.
The contaminated groundwater entered into the oil/water separator, where free product and groundwater
were separated. The free product accumulated in the separator was removed regularly by tankertruck.
The groundwater then entered the aeration container, in which the volatile compounds were dispersed
into the air. The contaminated air was led into the compost container for bio-cleaning. The treated
groundwater was discharged into the buffer basin.
From the buffer basin the water was pumped through the sand filters and the active carbon filters and
then discharged via the end buffer container into the existing sewer. The discharged water was regularly
sampled and analysed. The concentrations of TPH and volatile organic compounds (VOCs) never
exceeded the allowed concentrations.
In total, approximately 5,200 m3 groundwater was treated in the temporary plant.
3. CONCLUSIONS
This is the only case of soil remediation of a previously industrial site in Portugal.
There are some studies being made for the assessment of soil and groundwater contamination in
industrial sites but no remedial actions have been made. One example of a study area is the chemical
complex of the Estarreja industrial area, in Oporto district.
The processing industry, namely the chemical industry, is, in Portugal, the major source of industrial
contamination. Until recently, the solid wastes originating from there were deposited, without any control
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or protective measures in municipal landfills or in landfills belonging to the companies, as was the case
of the Estarreja chemical complex. Thus, there is a large contaminated area with solid wastes from
several production processes.
In 1991, the Environment Ministry started a project aiming to study an adequate methodology for
remediation of contaminated groundwater and soil. The objectives of this study were:
• selection of a study area with problems of soil contamination by industrial wastes
• assessment of present situation, in terms of soil and water quality: (1) elaboration of hydrogeological
studies; and (2) risk analysis
• elaboration of recommendations for the resolution of the problems of the selected area
This study has been made but no remedial actions have started.
At present, there are two factors that make the adoption of state of the art technologies slower in
Portugal than in more industrialised countries:
• the difficult financial situation of Portugal—made worse by the recession in all Europe—does not
allow large investments in remedial projects; and
• the awareness level of the Portuguese population is still extremely low.
The delay that Portugal suffered in its economic development can, however, in the long term become
an advantage, because, due to the low industrialisation in this century, there are not contaminated sites
in such a large number and proclivity (throughout the country) as for instance in Germany. In addition,
it is still possible to avoid strategic errors (future problems) by applying appropriate legislative,
administrative and technological measures.
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Experiences with the Performance of In Situ Treatment Technologies
Dr. Robert L. Siegrist, Environmental Science & Engineering Division, Colorado School of
Mines
1. INTRODUCTION
The overall goal of this study is to explore international experiences gained with the performance of in
situ treatment technologies for contaminated soil and groundwater and to determine the cleanup achieved
as related to time and cost expended compared to predictions made when the in situ technology was
selected. The types of sites of interest include those commonly encountered and where in situ
technologies have been employed. These sites include those contaminated with petrochemicals such as
benzene and/or chlorocarbons such as trichloroethylene. The types of technologies commonly applied
include soil vapor extraction and air sparging for source treatment and increasingly treatment barriers
for interception and plume migration control. As originally conceived, this work is being accomplished
by literature review and critical analysis complemented by interactions with delegates at NATO Pilot
Study meetings and through personal inquiries and correspondence.
While performance of in situ treatment technologies can be assessed with regard to various measures,
one critical question relates to how well did the technology achieve the cleanup goal initially prescribed
in terms of time and cost predictions that were made initially when the technology was selected. This
question is a critical one. The selection, design, and implementation of in situ technologies requires
knowledge of their ability to achieve various cleanup goals and at what cost over what time. If large
expenditures in terms of cost and time are made but the technology does not achieve the goal, then it
could be speculated that savings could have been realized with no loss in risk reduction actually
achieved, if a more realistic goal had been initially prescribed. In so doing, the savings in cost and time
could have been allocated to other sites and overall the reduction in risk in a jurisdiction might have
been greater.
Work on the project started with attendance at the Adelaide meeting of the Phase II Pilot Study held in
February 1996 and will continued into the Phase III Pilot Study.
2. PROJECT SCOPE AND CONCEPTS
For contaminated sites, a conceptual model for risk is generally considered to include several key
elements:
(1) a source of contamination,
(2) transport/fate in the soil and ground water environment, and
(3) the receptors and their exposure pathways and dose-response properties (Figure 1).
If the risk is deemed unacceptably high, risk management is often implemented to reduce or eliminate
the source, beneficially modify the transport/fate properties, or cut-off the exposure of receptors. For
these purposes, in situ remediation technologies are often preferred because they can be implemented
over larger areas with lower site disruption, with lower worker exposure, and generally at lower cost.
Achieving risk reduction via in situ technologies often requires a reduction in concentration and/or mass
of contaminants somewhere prior to exposure occurring.Figure 2 presents a graphical illustration of
contaminant concentration as related to time and cost.
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Contaminated site caused by past land disposal of petrochemicals and
solvents with risk posed to humans by drinking water usage
downgradient from the site...
Volatilization
Drinking water well —
Human exposure by ingestton,
inhalation, dermal contact
Vadoze
zone
Saturated
zone
Sorption /
Degradation ;
;-v--" Receptors
:'fc- and exposures
Transport/fate,,, ;
........,.,..,,..,.,,.:_.
Advection / dispersion
Sorption / degradation
in situ remediation to reduce the source of
contamination by vapor extraction potentially
with sir sparglnfg and some biodegradation,,..
In situ remediation to cut'Off the transport
to receptors by an in situ treatment wall...
Figure 1: Conceptual Model Components for an Organically Contaminated Site and In Situ Remediation to
Achieve a Reduction in Risk
In most remediation cases, extensive time and expense are devoted to characterizing a site, assessing the
risk associated with the nature and extent of contamination present, and selecting and implementing a
remedial action to achieve a prescribed cleanup goal. However, less effort is often expended to evaluate
technology performance over time and to document cleanup goal achievement versus the time and cost
incurred. Such a critical review of technology performance is needed however, to ascertain whether
investments made in characterization, assessment, and remedial action implementation are justified by
the benefits achieved.
Information is being gathered on in situ technologies to enable a critical evaluation of the treatment
efficiency and the risk reductions that have been claimed to be achieved and whether there is adequate
information to support these claims. Moreover, the study will attempt to determine whether the initially
established cleanup goals were in fact achieved at the cost and time predicted. The study will also
explore whether resources could have been more effectively expended by treating more sites to less
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stringent goals that were in fact all that was achieved even when more stringent goals were initially
established.
High uncortainty In praa.ctlonfi tnd abttrvatlons
W*st»d tlmt »na money trying to tchltve
an unachlevalil'i ao*/ *> * tvtn */r».. t
Glmnup gout to ti* tennvte
el utmjtottd tlmt *fid catt
u
10
Figure 2: Illustration of the Relationship Between In Situ Remediation Performance Predictions versus Actual
Achievement as Related to Time and Cost of Remediation
The project will contribute to the objectives of the Pilot Study by providing an independent and critical
understanding of the use of in situ treatment technologies, methods used for their process control, and
their true performance in achieving cleanup goals and associated risk reductions.
Editorial Note:
In addition to the CCMS Fellowship study described here, Dr. Siegrist hosted the meeting of the Phase
II Pilot Study held in Golden, Colorado in March 1997. In addition, during the meeting he made a guest
speaker presentation on In situ remediation of DNAPLs in low permeability media.
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