&EPA
United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
Office of Emergency and
Remedial Response
Washington DC 20460
Office of Research and
Development
Municipal Environmental Resea
Laboratory
Cincinnati OH 45268
Superfund
EPA-540/2-84-003a Sept 198
Review of In-Place
Treatment
Techniques for
Contaminated
Surface
Volume 1:
Technical Evaluation
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EPA-540/2-84-003a
September 1984
REVIEW OF IN-PLACE TREATMENT
TECHNIQUES FOR CONTAMINATED SURFACE SOILS
VOLUME 1:
TECHNICAL EVALUATION
OFFICE OF EMERGENCY AND REMEDIAL RESPONSE
OFFICE OF SOLID WASTE AND EMERGENCY RESPONSE
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
U S Environmental Protection Agency
^uSSl^
Chicago, IL 60604-3D*0
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NOTICE
The information in this document has been funded wholly or in part by the United States Environmental
Protection Agency under Contract No. 68-03-3133 (Task 41) to JRB Associates with a subcontract to the Utah Water
Research Laboratory, and Contract No. 68-01-6160 (Work Order 12) to Arthur D. Little. Inc. It has been subject to the
Agency's peer and administrative review and has been approved for publication. The contents reflect the views and
policies of the Agency. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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FOREWORD
This is one of a series of reports being published to implement CERCLA. otherwise known as Superfund
legislation. These are documents explaining the hazardous response program and, in particular, the technical
requirements for compliance with the National Contingency Plan (NCR), the analytical and engineering methods and
procedures to be used for compliance, and the background and documenting data related to these methods and
procedures. The series may include feasibility studies, research reports, manuals, handbooks, and other reference
documents pertinent to Superfund.
This two-volume report presents information on in-place treatment technologies applicable to contaminated soils
at shallow depths. This volume discusses the selection of the appropriate in-place treatment technology for a particular
site and provides specific information on each technology. Volume 2 provides background information and relevant
chemical data, and is available from NT1S.
Selection of in-place treatment technologies follows the process outlined in the National Contingency Plan. The
type of in-place treatment (extraction, immobilization, degradation, attenuation, or reduction of volatiles) is deter-
mined on the basis of information available from the remedial investigation. Selection of a specific technology
involves assessment of waste, soil, and site-specific variables. The technology is implemented if it is considered more
cost-effective in comparison with the other alternatives.
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ABSTRACT
This two-volume report presents information on m-place treatment technologies applicable to contaminated soils
less than 2 feet in depth. Volume 1 discusses the selection of the appropriate in-place treatment technology for a
particular site and provides specific information on each technology. Volume 2. available through NT1S. provides
background information and relevent chemical data
Selection of in-place treatment technologies follows the process outlined in the National Contingency Plan. The
type of in-place treatment (extraction, immobilization, degradation, attenuation, or reduction of volatiles) is deter-
mined on the basis of information available from the remedial investigation. Selection of a specific technology
involves assessment of waste, soil, and site-specific variables The technology is implemented if it is considered more
cost-effective in comparison with the other alternatives.
Technologies in the five groups mentioned above are discussed according to the following categories of
information:
description.
wastes amenable to treatment.
status of technology.
ease of application.
potentially achievable level of treatment.
reliability of method.
secondary impacts.
equipment and exogenous reagents,
information requirements, and
sources of information.
This report was submitted in partial fulfillment of Contract Nos. 68-03-3113 and 68-01-6160 (Work Order 12) by-
Utah State University and Arthur D. Little. Inc.. respectively, under the sponsorship of the U.S. Environmental
Protection Agency. The report covers the period May. 1982 to September. 1984, and work was completed as of
April 1. 1984.
IV
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CONTENTS
Page
iii
Foreword jv
Abstract vjjj
List of Figures jx
List of Tables x
Acknowledgements
EXECUTIVE SUMMARY 1
1.0 INTRODUCTION 9
1.1 Purpose and Function of the Report 9
1.2 Overview 10
2.0 SELECTION OF IN-PLACE TREATMENT TECHNOLOGY 12
2.1 Introduction 12
2.2 Discussion of In-Place Treatment Technologies 12
2.2.1 Extraction Techniques 12
2.2.2 Immobilization Techniques 15
2.2.3 Degradation Techniques 15
2.2.4 Attenuation 16
2.2.5 Reduction of Volatilization 16
2.3 Development of Alternatives 16
2.3.1 Definement of Objectives 16
2.3.2 Selection of Possible Alternatives 17
2.3.3 Selection of an In-Place Treatment Type 17
2.4 Screening of Alternatives 19
2.5 Detailed Analysis of Alternatives 19
2.5.1 Assessment of Waste, Soil and Site-Specific Variables 20
2.5.1.1 Waste Characteristics 20
2.5.1.2 Site Characteristics 21
2.5.1.3 Waste/Soil System Characteristics 22
2.5.1.4 Laboratory and Pilot-Scale Testing 27
2.5.1.4.1 Statistical Sampling Requirements 28
2.5.1.4.2 Sampling Equipment 28
2.5.1.4.3 Sample Collection, Preservation, Shipping and Storage 28
2.5.1.4.4 Chemical Analysis 28
2.5.1.4.5 Monitoring 28
2.5.2 Selection of In-Place Treatment Technology 29
2.6 Determination of Extent of Remedy 29
2.7 In-place Treatment Information Gaps 29
2.7.1 General Information Gaps 30
2.7.2 Technology-Specific Information Gaps 30
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3.0 TECHNOLOGIES FOR 1N-PLACE TREATMENT 32
3.1 Introduction 32
3.2 Extraction (Soil Flushing) 33
3.3 Immobilization 37
3.3.1 Sorption 37
3.3.1.1 Heavy Metals Addition of Sorbents 39
3.3.1.1.1 Addition of Agricultural Products and By-Products 40
3.3.1.1.2 Addition of Activated Carbon 42
3.3.1.2 Heavy Metals Chelation with Tetren 45
3.3.1.3 Organics Reduction of Soil Moisture 46
3.3.1.4 Organics Addition of Sorbents 50
3.3.1.4.1 Addition of Agricultural Products and By-Products 50
3.3.1.4.2 Addition of Activated Carbon 55
3.3.2 Ion Exchange 56
3.3.2.1 Addition of Clays 57
3.3.2.2 Addition of Synthetic Resins 59
3.3.2.3 Addition of Zeolites 60
3.3.3 Precipitation 62
3.3.3.1 Sulfides 62
3.3.3.2 Carbonates, Phosphates, and Hydroxides 64
3.4 Degradation 69
3.4.1 Chemical 69
3.4.1.1 Oxidation 69
3.4.1.1.1 Soil Catalyzed Reactions 70
3.4.1.1.2 Addition of Oxidizing Agents 72,
3.4.1.2 Reduction 76
3.4.1.2.1 Organics 76
3.4.1.2.2 Chromium 79
3.4.1.2.3 Selenium ' 81
3.4.1.2.4 Sodium Reduction/Dehalogenation for PCBs and Dioxins 82
3.4.1.3 Polymerization 84
3.4.2 Biological 85
3.4.2.1 Modification of Soil Properties 87
3.4.2.1.1 Soil Moisture 87
3.4.2.1.2 Aerobic Biodegradation 89
3.4.2.1.3 Anaerobic B iodegradation 90
3.4.2.1.4 SoilpH 93
3.4.2.1.5 Soil Nutrients 94
3.4.2.2 Addition of Non-Specific Organic Amendments 96
3.4.2.3 Analog Enrichment for Cometabolism 98
3.4.2.4 Augmentation with Exogenous Acclimated or Mutant Micro-organisms 100
3.4.2.5 Application of Cell-Free Enzymes 104
3.4.3 Photolysis 105
3.4.3.1 Addition of Proton Donors HO
3.4.3.2 Enhancement of Volatilization 112
3.5 Attenuation H3
3.5.1 Metals 113
3.5.2 Organics 115
3.6 Reduction of Volatilization H6
3.6.1 Reduction of Soil Vapor Pore Volume 116
3.6.2 Soil Cooling 120
VI
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4.0 MODIFICATION OF SOIL PROPERTIES 122
4.1 Introduction 122
4.2 Control of Oxygen Content 122
4.3 Moisture Control 124
4.3.1 Irrigation 124
4.3.2 Drainage 126
4.3.3 Well Points 126
4.3.4 Additives 126
4.4 Nutrient Additions to the Soil 127
4.5 Control of Soil pH 127
4.6 Modification of Soil Temperature 130
Appendix: Cost Information 133
Bibliography 139
Index 152
Copyright Notice 163
VII
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FIGURES
Figure Page
2-1. Detailed Sequence Phase VI Remedial Action (40 CFR, Part 300 68) 13
2-2. Methodology for Selecting In-Place Treatment Technology. 14
2-3. Exposure Pathways. 17
3-1 Schematic of an Elutriate Recycle System. 35
3-2. Extent of Sorption as a Function of Amount Sorbed and K for 8 = 0.1 and N = 0.9 39
3-3. Adsorption Characteristics of Cd(II) from Synthetic Cd(ID-Plating Wastewaters
(Cd-BF4 Solution) as Affected by pH. 43
3-4. Extent of Cd(II) Adsorption as Affected by Carbon/Cadmium Ratio at Various pH. 43
3-5. Extent of Sorption as a Function of Soil Moisture 0 and KJ. 47
3-6. Extent of Sorption as a Function of Amount Sorbed and K for a Range of Moisture
Contents and N = 07. 4g
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TABLES
Table Page
2-1 General Applicability Matrix 18
2-2. Treatment Variables for In-Place Treatment Technologies 24
3-1. Summary Matrix of Treatment Technologies 34
3-2. Typical Surface Properties of Activated Carbons 42
3-3. Average Concentration of Constituents in Primary and Digested
Sludges from 33 U.S Treatment Plants 51
3-4. Elemental Analyses of Treatment Plant Sludge Samples Expressed as
Ranges on a Dry Weight Basis 52
3-5. Total Amount of Sludge Metals Allowed on Agricultural Land 53
3-6. Effect of Increasing the Concentration ol Muck Soil and Bentomte
Clay on the Adsorption of Herbicides 53
3-7. Cation Exchange Capacity (CEC) for Various Materials 57
3-8. Concentrations in PPM of Herbicide Solutions Added to the
Adsorbents to Give 50 Percent Inhibition of the Test Plant 58
3-9. Solubility Product Constants for Metal Sulfides 62
3-10. Solubility Product Constants for Metal Carbonates. Phosphates.
and Hydroxides 65
3-11. Relative Effect of Crushed Limestone Liner Placed Over Soil on the Prevention
of Heavy Metals in Municipal Solid Waste Landfill Leachate from Migrating 66
3-12. Some Probable Bivalent Metal Complexes with Inorganic Ligands in Soil Solutions 67
3-13. Oxidation Reactivity for Organic Chemical Classes 69
3-14 Some Chemicals that do not Oxidize at Soil and Clay Surfaces 71
3-15. Relative Oxidation Power of Oxidizing Species 72
3-16. Hazardous Products of Ozone Reactions 74
3-17. Chemical Groups that React with Peroxides to Form More Mobile Products 75
3-18. Chemical Reductive Treatment for Degradation of Paraquat in Soil 78
3-19. Biodegradation Rate Constants for Organic Compounds in Soil (day ^ ') 86
3-20. Biodegradation Rate Constants for Organic Compounds in Anaerobic
Systems (day~') 87
3-21. Commercial Microbial Augmentation Products or Processes Used to
Treat Hazardous Waste Contaminated Soils 101
3-22. Compounds or Classes of Compounds that Have Been (or Could be)
Degraded by Commercially Available Microbial Augmentation Productions 103
3-23. Rate Constants for the Hydroxide Radical Reaction in Air with
Various Organic Substances, KQHOin Units of (Mole-Sec)^ ' 107
3-24. Atmospheric Reaction Rates and Residence Times of Selected Organic
Chemicals 108
4-1. Soil Modification Requirements for Treatment Technologies 123
4-2. Liming Materials ' 129
4-3. Mulch Materials 131
ix
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ACKNOWLEDGEMENTS
The Utah Water Research Laboratory (UWRL) prepared the initial draft of this report for EPA's Office of
Research and Development under Contract No. 68-03-3133 (Task 41) to JRB Associates. Ms. Naomi Barkley was the
Project Officer. Dr. Ronald Sims was the principal investigator Dr. Darwin Sorensen. Ms. Judith Sims. Ms. Joan
McLean, Mr. Ramzi Mahmood, Dr. Ryan Dupont, and Dr. Jerry Jurinak contributed to the project. Special thanks are
extended to Ms. Kathy Wagner of JRB Associates and Mr. Donald Sannmg of the Municipal Environmental Research
Laboratory. Cincinnati, OH, for their direction of and valuable contributions to this report.
Arthur D. Little. Inc.. under Contract No 68-01-6160 (Work Order No 12). prepared the Final Report, based on
information contained in UWRL's draft. Ms. Norma Lewis was Project Officer. Mr. Jeffrey Bass, Arthur D. Little's
Project Manager. Ms. Joo Hooi Ong, Dr Joan Berkowitz. and Dr. John Ehrenfeld were principal contributors. Mr.
Bruce Goodwin and Dr Warren Lyman also contributed.
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EXECUTIVE SUMMARY
PURPOSE AND SCOPE
The purpose of this report is to provide state-of-the-art information on in-place treatment technologies for soils
contaminated to a shallow depth. Such situations are commonly encountered when the source of contamination is at or
near the soil surface. Examples include leakage from unpaved drum storage areas, spills in truck and rail transport.
spills in transfer of chemicals, and leakage from shallow lagoons or burial pits.
The in-place technologies discussed have the potential for attenuating, extracting, immobilizing, degrading, or
reducing the volatilization of both inorganic and organic soil contaminants The particular application methods
emphasized in this report are generally limited to contaminated soils that lie above the water table With different
application methods, not discussed m detail in this report, the basic technologies can be adapted to treatment of
contaminants in the saturated zone.
This report has been divided into two volumes. Section 2 of Volume 1 provides a guide for selection of in-place
treatment technologies. Section 3 provides a discussion of each in-place treatment technology, including process
description, information requirements for application of the technology, wastes amenable to treatment, current status
of the technology, ease of application, potentially achievable levels of treatment, reliability of the technology over the
long term, secondary impacts, and equipment materials required to implement the technology. Section 4 discusses
engineering methods for modifying the oxygen content, moisture content, nutrient content, pH and temperature of the
soil to optimize the effectiveness of in-place treatment. In addition, data for estimating the costs of implementing in-
place treatment are provided in Section 4 and in an appendix on cost information.
Background information for characterization and evaluation of immobilization, degradation, and volatilization
processes in waste/soil systems is provided in Volume 2 of the report, available through NT1S.
SELECTION PROCESS FOR IN-PLACE TREATMENT
TECHNOLOGY
The technologies discussed in this report are potentially applicable for immediate removal, planned removal, and
remedial action as defined in the National Contingency Plan (NCP). They could be particularly cost-effective in
situations in which contamination has not yet reached groundwater, but would be expected to do so if no action were
taken. They also have the potential for controlling or preventing further migration of contaminants to groundwater. In
the latter case, in-place treatment of near-surface soils might be sufficient in and of itself to achieve remedial
objectives, or it might be used in conjunction with other source control and offsite remedial actions directed at
containment or cleanup of already contaminated groundwater.
The procedure for selecting appropriate remedial action technologies (including in-place treatment technologies)
is specified in the National Contingency Plan. The prescribed steps are as follows:
Preliminary assessment (scoping) Determination on the basis of available data of the possible need
for remedial response.
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Remedial investigation Gathering of sufficient information, generally through field sampling and
monitoring, to determine the nature and extent of both the problem and the remedial action that may be
necessary.
Setting of objectives Defining the goal(s) or desired end-result(s) of the remedial program. In
general, objectives will include an environmental goal (e.g., reduce exposure via the direct contact,
air, groundwater, and surface water pathways to some level of acceptability) and a cost effectiveness
component (e.g., to achieve the environmental goal(s) using the least cost alternative that is techni-
cally feasible and reliable).
Identification of alternatives with potential for meeting the environmental goal(s) the identification
should be as comprehensive as possible so that the most cost-effective alternative is not overlooked.
Screening alternatives Evaluation of the technical effectiveness, reliability, engineering prac-
ticality, costs (capital, operating, and maintenance), and environmental impacts of implementing each
alternatives.
Refinement and detailed specification of alternatives that pass screening Detailed cost estimation,
including distribution of costs over time; specification and evaluation of an engineering implementa-
tion plan; detailed assessment of how well each alternative meets the remedial objectives; and detailed
analysis of any adverse environmental impacts, mitigation measures, and associated costs.
Selection of the most cost-effective alternative This will generally be the lowest cost alternative of
those analyzed in detail that meets the objectives of the remedial program.
When the remedial investigation shows contamination of near-surface soils as contributing to risk, Table 2-1 should be
consulted to identify the in-place technologies that might be appropriate. In the identification step, the primary
consideration is the chemical nature of the contaminants of concern. In particular, some technologies are designed
primarily to control the release of heavy metals, while others are designed primarily to control the release of organics.
When both types of contaminants are of concern, the possibility of combining two or more in-place technologies to
meet remedial objectives should be considered.
SPECIFIC IN-PLACE TREATMENT TECHNIQUES
There are five major categories of in-place treatment techniques. These are:
Extraction,
Immobilization,
Degradation,
Attenuation, and
Reduction of volatilization.
Specific technologies within each category are discussed briefly below.
EXTRACTION (SOIL FLUSHING)
Extraction is the washing of contaminants from the soil with a suitable solvent such as water, or other aqueous or
non-aqueous solutions. The method is potentially applicable to all types of soil contaminants, provided that a suitable
non-polluting solvent can be found. Effects of the solvent on the physical, chemical, and biological properties of the
soil need to be evaluated. Furthermore, a system for profusing the contaminated area with solvent and for capturing the
elutriate needs to be designed. This might involve flooding the site and collecting the elutriate in a series of shallow
well points or subsurface drains, or appropriate placement of recharge and discharge wells. After treatment, the
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elutriate might be discharged to a receiving water body or sewer, or it might be recycled through the contaminated
area. This technology derives from the mining industry, where it has been used for in-place extraction of metal values
from ores.
IMMOBILIZATION
Immobilization includes a wide range of in-place treatment technologies designed to reduce the rate of release of
contaminants from the soil so that resultant concentrations along pathways of exposure are held within acceptable
limits. The primary immobilization mechanisms are sorption. ion exchange, and precipitation. Sorption is potentially
applicable to both organic and inorganic contaminants. Ion exchange is applicable to organic and inorganic cation and
anion species. Precipitation is limited, for most practical purposes, to heavy metal contaminants.
Sorption of Heavy Metals
Heavy metal contaminants in soil may be immobilized by mixing the contaminated soil with a good adsorbent, or
mixture of adsorbents, for the metals present, or with a metal complexing agent, such as tetren, that binds the metal
into a complex that strongly adsorbs to soil. The adsorbent, or complexing agent, may be mixed into the soil with
conventional power implements or tillers. Suitable adsorbents for heavy metals include various agricultural products
and by-products, such as straw, sawdust, peanut hulls, bark, and activated carbon. For maximum adsorption
efficiency, the pH of the soil generally needs to be above 6.5. To maintain a high pH, lime can"be mixed into the soil
with the adsorbent. The amount of adsorbent added must be sufficient to tie up the releasable heavy metals, and
periodic reliming may be necessary to maintain the treated system at a pH above 6.5.
Tetren-metal complexes are strongly adsorbed to soil clays. For contaminated soils rich in clays, mixing of tetren
(and lime, if the soil is acidic) into the contaminated area may be sufficient to achieve immobilization. If the
contaminated soils are of low clay content, a combination of tetren, clay materials, and lime (if necessary) may be
used. Tetren generally forms 1:1 complexes with metals and, hence, should be added in amounts slightly in excess of
the number of moles of heavy metal contaminants present.
Sorption of Organics
The distribution of an organic chemical between soil and infiltrating precipitation at equilibrium is directly
proportional to the fraction of organic carbon in the soil matrix. Therefore, addition of organic matter can increase the
sorption capacity of the soil, and can be particularly effective for soils with low organic carbon content, such as sand
and gravel. Possible sorbents include sewage sludge, agricultural products and by-products, organic soil materials,
such as soils of the Histosol soil order, and activated carbon. The sorbents may be mixed into contaminated surface
soils using conventional power implements and tillers.
Ion Exchange
Certain clays, synthetic resins, and zeolites have the capacity to release ions of one type and to preferentially
adsorb ions of another type at the vacated lattice position (i.e., to exchange one type of ion for another). Cation
exchangers have replaceable cations,and anion exchangers have replaceable anions.
Increasing the clay content of a soil can increase its capacity to immobilize cationic compounds. The cationic
exchange capacity (CEC) of a soil is defined as the number of milli-equivalents of exchangeable ions per hundred
grams dry weight of soil. Clays tend to have the highest CEC values among natural soils, and typically exchange
calcium ions for cations of heavy metals or organics (see Table 3-7).
Synthetic resins have been developed that carry either exchangeable cations (e.g., Chelex 100) or exchangeable
anions (e.g., Dowex 1-X8).
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Zeolites are a family of crystalline-hydrated alummo silicates with high selectivity and capacity for adsorption of
heavy metal cations. Zeolites are stable over the pH range of 6-12, but begin to degrade around pH 4-5 and below.
Therefore, zeolites should be used only in alkaline or limed soils where the pH is maintained above 6.
Precipitation of Heavy Metals
The addition of sulfides, carbonates, phosphates, and hydroxides to metal-contaminated soils can immobilize
metals by precipitation of a highly insoluble compound. Precipitating agents that may be mixed into the soil by
standard agricultural techniques include lime for hydroxide precipitation, limestone for carbonate precipitation, trebel
superphosphate for phosphate precipitation, and calcium sulfide or sodium sulfide for sulfide precipitation. The use of
phosphate should be avoided if arsenic is present in the soil matrix, because of the potential for the formation and
release of arsenate into infiltrating precipitation. Under some conditions, heavy metals may form soluble phosphate,
carbonate, and hydroxide complexes that are more mobile than the free metal ions. By controlling the rate of addition
of precipitating reagents and the pH of the contaminated soil system, it should be possible to optimize precipitation
over a complex formation.
In-place precipitation of sulfides presents special complications in soil systems. The heavy metal sulfides are
generally the least soluble of the heavy metal compounds. While the solubilities of metal sulfides decrease with
increasing pH (except for arsenic, which precipitates only at pH 5), metal sulfides have very low solubilities, even at a
pH as low as 4. Some heavy metals form soluble sulfide complexes that may be more mobile in the environment than
the free metal ion. Controlled addition of sulfide reagent, controlled pH, and thorough mixing of the contaminated soil
with the precipitating reagent can help to favor precipitation over soluble complex formation. More serious over the
long term is the potential for oxidation of the precipitated sulfides to form soluble metal sulfates under aerobic soil
conditions. Maintenance of a high soil pH-is particularly important, since acid conditions will not only dissolve the
metals, but also lead to the release of hydrogen sulfide. The latter is a highly toxic gas, and the odor, even if
concentrations are below toxic thresholds, can result in a major community relations problem.
CHEMICAL DEGRADATION
Oxidation, reduction, and polymerization reactions may be carried out in-place to transform soil contaminants
into less toxic or less mobile products.
Oxidation
Chemical oxidation of organic contaminants with half-wave potentials less than the redox potential (0.8 volt) of a
well-aerated soil can be oxidized in-place in the presence of clay catalysts. This method is conceptual, and the
oxidation products are not necessarily less toxic or less mobile than the original contaminants. As previously
discussed, increasing the clay content of surface soils can aid in immobilization of contaminants. Clay-catalyzed
oxidation of organics may be an additional benefit, or an undesired side effect, depending upon the products of
oxidation. These should be investigated in laboratory or field treatability studies undertaken to develop design
parameters for in-place treatment with clay.
Introduction of chemical oxidants into the soil system is another method for promoting the oxidation of organics.
Possible oxidizing agents include ozone or hydrogen peroxide. The agents may be applied in water solutions directly
onto the soil surface, injected into the subsurface, or introduced through injection wells. Since oxidants are relatively
non-selective and may act on natural organics in the soil as well as organic contaminants, laboratory and field
treatability studies would be required to assess the reactions that occur and to develop data for design of a full-scale
treatment system if results are favorable.
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Reduction
In-place reduction reactions may be brought about by the addition of reducing agents to the contaminated soil.
Possible reagents include catalyzed metal powders of iron, zinc or aluminum, for example, or sodium borohydride.
These reagents have been shown to degrade toxic organic constituents, although there have been very few demonstra-
tions of in-place treatment of contaminated soils. Catalyzed metal powders can be applied to the soil surface and mixed
into the contaminated soil with conventional agricultural equipment. Sodium borohydride can be applied in an alkaline
water solution via irrigation, subsurface injection, or injection wells.
Hexavalent chromium is highly toxic and mobile in soils, generally in the form of a chromate ion. Trivalent
chromium, the reduced form, is less toxic and readily precipitated by hydroxides over a wide pH range. Hexavalent
chromium is readily reduced in natural soils. Mixing of ferrous iron, leaf litter, or acid compost into the surface soils
can assist in the conversion. Liming of the soil once reduction is complete will precipitate trivalent chromium
hydroxide compounds.
Hexavalent selenium, as selenate, is also highly soluble and mobile in soils. Selenates are readily reduced in
natural soils to elemental selenium, which is virtually immobile, and also to selenites. The solubility and potential
leachability of selenites increases with increasing pH. Hence the high pH that is generally required to immobilize other-
heavy metal contaminants could result in the release of selenium if any is present.
Polymerization
If a soil is contaminated with polymerizable organics such as styrene, vinyl chloride, isoprene, acrylonitrile, or
methyl methacrylate, mixing of iron and sulfates into the contaminated area may catalyze an in-place polymerization
reaction. The polymers are commonly less toxic and less mobile than the monomers from which they are formed.
Generally, a 2:1 ratio of volume of catalysts and activator to volume of contaminant is required. The catalysts and
activator are generally applied separately, and a wetting agent added to promote rapid and uniform dispersion of
solutions through the contaminated area. The technical feasibility of the method and parameters for design of a full-
scale system would need to be established by a combination of laboratory bench-scale and pilot field demonstrations.
BIODEGRADATION
Biodegradation, as the term is used here, refers to the breakdown of organic compounds in soils by the action of
micro-organisms such as bacteria, actinomycetes, and fungi. Treatment generally consists of optimizing conditions of
pH, temperature, soil moisture content, soil oxygen content, and nutrient concentration to stimulate the growth of
micro-organisms that will feed on the particular contaminants present. Alternatively, genetically engineered organisms
may be added to the soil system and conditions established within the soil to optimize their growth. Optimum
conditions of application generally need to be established in laboratory bench-scale studies and small field pilot test
spots. Some of the hazardous constituents present in a contaminated soil may be most readily biodegraded under
aerobic conditions, while others are more readily degraded under anaerobic conditions. Treatment might therefore
consist of alternate aerobic and anaerobic cycles.
While generally biodegradation is used as a detoxification mechanism for organic contaminants in soil, some
micro-organisms will also interact with metallic species. For example, aerobic heterotrophic bacteria oxidize arsenite
to arsenate. Further treatment with ferrous sulfate would then immobilize the arsenic in the form of highly insoluble
ferric arsenate.
PHOTOLYSIS
Photochemical reactions require the absorption of light energy, generally from sunlight in natural systems. Since
light does not penetrate very far into soils, photodegradation of soil contaminants is limited to soil surfaces. The
addition of proton donors in the form of polar solvents, such as methanol, can enhance surface photodegradation of
soil contaminants. For example, photolysis of dioxin (TCDD) on soil surfaces has been reported in the presence of
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methanol. Photodecomposition of PCBs at soil surfaces has been reported in the presence of tnethylamme as a proton
donor.
ATTENUATION
Attenuation is the mixing of contaminated surface soil with clean soil, using conventional power implements or
tillers, so that the concentrations of hazardous components in the mixture are reduced to acceptable levels. Although
potentially applicable to any type of waste, guidelines for acceptable concentration levels in surface soils are available
only for heavy metals. The amount of clean soil required to assure that the mixture lies within an acceptable range is a
practical limitation that needs to be evaluated
REDUCTION OF VOLATILIZATION
If soil contaminants are volatile, and the air transport pathway could lead to adverse exposure, it may be
important to suppress volatilization. This could have the added benefit of retaining compounds within the soil system
for a long enough time to allow for m-place treatment by one of the mechanisms described above. The most practical
method of suppressing volatilization is to reduce the soil vapor pore volume through which the transport of vapors
occurs. This can be done by compaction or addition of water to reduce the air-filled pore spaces within the soil relative
to the water-filled pore spaces. Another technique is to decrease the temperature of the soil, since vapor pressure of
volatile constituents generally decreases with decreasing temperature.
METHODS FOR IMPLEMENTATION OF IN-PLACE TREATMENT
The m-place methods discussed in this report have many elements in common. Most involve application of
absorbents or reagents and thorough mixing with the contaminated soil. Many involve liming for pH control and
adjustment of the moisture content of the soil to optimize conditions of treatment.
Solid or semi-solid agents are typically applied to the soil surface by means of spreaders that may be truck-
mounted, hitch-mounted, or tractor-drawn. Liquids can be applied with hydraulic sprayers or subsurface injectors.
Mixing of treatment agents with the contaminated soil can be accomplished with plows, rotary tillers, subsoilers, disc
harrows, spike harrows, or spring-tooth harrows. Moisture can be controlled with sprinklers and perforated pipe
drains. Tilling, which breaks, mixes, and aerates the soil, tends to increase oxygen content; compaction and flooding
tend to decrease oxygen content. Irrigation increases surface moisture; drainage and well points remove excess water
from the surface. Various additives are also available for moisture control. For example, synthetic substances that
store water can enhance the water retention capacity of the soil; water-repelling agents can accelerate soil drainage and
improve water infiltration and percolation.
RESEARCH NEEDS
There has been little operating experience with the use of in-place treatment of contaminated soils. Since the
National Contingency Plan requires that any alternative selected for implementation as part of a remedial program
must be technically feasible and reliable, research on m-place treatment technologies is critically needed in the
following areas to assure that in-place methods can be properly evaluated as potential remedial alternatives.
1) Information on soil processes interfacing with atmospheric processes (i.e., controlling volatilization
and photodegradation), including:
investigation of photochemical reactions that enhance biodegradation of refractory compounds and
those that can produce toxic or undesired breakdown products;
laboratory and field-scale analysis of the feasibility of using volatilization/photodegradation as a
viable treatment method for volatile/photoreactive hazardous chemicals;
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evaluation of the importance of soil-photochemical reactions to the fate and behavior of photoreac-
tive compounds within the environment;
refinement of containment/transport models that address volatilization, vapor adsorption, biodegra-
dation, and leaching through the soil matrix; and
continued development of rapid partition coefficient estimation methods for predicting compound
partitioning among air/water/soil systems.
2) Information on chemical reactions relating to the transformation and immobilization of constituents in
soil systems, including:
effects of chemical addition (oxidants, reductants, and polymerizing agents) on the soil properties
affecting treatment;
constituent sorption and precipitation studies at concentrations in the soil matrix characteristic of
those found at remedial action sites;
Eh-pH information for metal species in soils at concentrations representative of remedial action site
concentrations; and
behavior of specific metals, viz., arsenic, beryllium, silver, selenium, mercury, and chromium in
soil systems, including the investigation of the reaction of chromium (VI) to chromium (III).
3) Information on biological reactions to stimulate the biodegradation of constituents in soil systems,
including:
potential for combinations of chemical and biological treatment methods for accelerating soil
treatment;
potential for composting of hazardous waste contaminated soil for accelerating biological reactions
and for detoxifying and degrading recalcitrant organic constituents;
i-
evaluation of the biodegradation kinetics and extent of hazardous constituents and metabolites of
hazardous constituents sorbed to clay and soil organic matter;
degradation rates and pathways for chemical classes, including alkyl halides and highly chlorinated
organics (PCBs) in the -soil treatment zone (upper 5 feet of soil); and
information concerning the effectiveness of micro-organism seeding compared with no seeding,
specifically in terrestrial systems.
4) Information on immobilization reactions in the soil/waste system, including:
investigation of enhancement of sorption by adding different sorbents, such as activated carbon,
straw, synthetic resins. (The specific information needed includes application rates of sorbent in
relation to concentrations of contaminant in soil);
continued development of estimation methods for predicting soil adsorption constants by chemical
and physical properties of compounds;
long-term effectiveness of immobilization of sorbed contaminants on soil; and
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effects of solvents on mobility of organic contaminants in soil systems.
5) Information on leaching in the soil/waste system, including:
laboratory experiments to estimate parameters for transport models that can be used to predict
behavior under field conditions;
field instrumentation to validate transport models under imposed environmental conditions.
incorporating the variability under field conditions by designing appropriate sampling stations; and
effect of different environmental conditions, including soil moisture, redox potential, and organic
content on transport parameters.
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SECTION 1
INTRODUCTION
1.1 PURPOSE AND FUNCTION OF THE REPORT
Unplanned and uncontrolled disposal of hazardous wastes frequently results in the contamination of the upper 2
feet of soil. This may severely affect public health, damage terrestrial systems, and destroy or diminish opportunities
for land use. Solutions to problems associated with contaminated sites generally follow the procedure specified in the
National Contingency Plan (NCP). The NCP process, which is presented in Section 2, is required for sites which
receive Federal Superfund money. It also serves as the model for clean-up of non-Superfund sites.
Three types of remedial responses are outlined in the NCP:
Immediate removal;
Planned removal; and
Remedial action.
Immediate removal is employed when there is an "immediate and significant risk of harm to human life or health or to
the environment. . ." (40CFR 300.65). Planned removal involves the continuation of immediate response actions, or
the implementation of remedial measures at sites not on the National Priorities List. Remedial actions are defined as
"responses to realeases on the National Priorities List that are consistent with permanent remedy to prevent or mitigate
the migration of a release of hazardous substances into the environment" (40CFR 300.68). The in-place technologies
discussed in this report are potentially applicable to each type of response. Selection of in-place treatment as a remedial
action response, however, is considered in detail.
The NCP differentiates among initial, source control, and off-site remedial actions. Initial remedial actions are
those measures which prevent immediate exposure while long-term solutions are being considered. A security fence
and temporary cover are examples of initial remedial actions. Source control remedial actions address realized and
potential on-site contamination including, for example, drummed wastes, leaky storage tanks, or contaminated soil.
Source control remedial actions contain the hazardous substances where they are located, or eliminate potential
contamination by treatment or removal. Off-site remedial actions apply to hazardous substances that have migrated
away from the original source of contamination. Off-site measures include provisions for alternative drinking water
supplies or treatment of contaminated aquifers. At a given hazardous waste site, any or all of the three types of
remedial actions may be applicable.
One of the most common problems found at uncontrolled sites is the contamination of soil and underlying strata.
Such contamination arises from leaking drums and tanks, leaking impoundments, direct discharge of wastes in pits,
and leaching from solid residues. When large volumes of soil are contaminated and pose a continuing hazard, the
development of a remedial action plan will almost certainly require consideration of source control options. In-place
treatment is one of a family of source control measures described in the NCP. Others include: no action, excavation
and off-site disposal, on-site treatment (e.g., excavation, treatment, and replacement), and physical containment (e.g.,
cap, hydraulic barrier). In-place treatment can be used to contain the source of contamination (e.g., by immobiliza-
tion), or to remove it through treatment (e.g., by degradation).
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Selection of the appropriate remedial alternative is made through the process outlined in the NCP and is based on
site-specific considerations. In some cases, m-place treatment might be considered the most cost-effective option, as
indicated by the following scenarios:
An industrial facility that has produced heavy metal-based chemicals for the past 50 years is closed
and the owner wishes to sell the land. Soil analyses, however, indicate that several acres of soil (to a
depth of up to 10 feet) at the facility are contaminated with heavy metals on the order of 100 ppm.
Excavation of such large quantities of soil would be prohibitively expensive and the benefit relatively
low, since the facility is in a highly industrialized area. In addition, it is likely that the new owner
would not accept a no-action alternative, and physical containment would interfere with land use.
After further investigation, immobilization through in-place treatment is considered the most suitable
alternative.
A farmer decided to supplement his income by disposing of drummed chemical waste in trenches at
the edge of his property. A fire in the trenches, however, alerted authorities to his activities. Since the
farmer was not able to pay for clean-up, the site was put on the National Priority List making it eligible
for Superfund money. Based on the remedial investigation and feasibility study, Ihe U.S. Environ-
mental Protection Agency decided to excavate and remove the drummed wastes and treat the residual
contaminated soil in place. An impervious cap was also constructed over the trenches and the site
monitored annually.
A train carrying several tankers of various chemicals derailed in a remote area. During the accident, a
piece of track pierced a tank car carrying benzene, creating two large holes from which the chemical
drained. Much of the benzene volatilized immediately. The rest soaked into surface soils. An
emergency crew called to the scene estimated that 25,000 gallons of benzene had spilled from the
tanker, 10,000 gallons of which remained in the surface soils. Because of the remote location,
enhanced microbial degradation was used to remove the benzene from the soil.
The purpose of this report is to provide state-of-the-art information on in-place treatment technologies for
contaminated soil. While many of the technologies discussed are applicable for in-place treatment regardless of the
depth of contamination, treatment of contamination in the upper 2 feet of soil is emphasized. The report is intended to
be used by on-scene coordinators, engineers, regulatory agencies and researchers in evaluating in-place treatment of
contaminated surface soils as a remedial alternative.
The report provides a discussion of the major in-place treatment technologies which can be used to treat
contaminated surface soil. A methodology for selection of the appropriate technology for a particular site and
techniques to modify soil properties are also discussed. The report, however, is not intended to be a guidance manual.
Rather, it provides the technical basis necessary to understand the applicability of in-place treatment technologies as a
source control remedial measure for contaminated surface soil.
1.2 OVERVIEW
This manual has been organized into two volumes. Volume 1 discusses in-place treatment technologies applicable
to contaminated surface soil. Volume 2, available through NTIS, provides background information on the characteri-
zation and evaluation of the fundamental processes applicable to site/soil/waste systems.
Volume 1 contains four sections. Section 1 presents the purpose and function of the report and discusses
information gaps for in-place treatment. Section 2 gives a general discussion of the various in-place treatment
10
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technologies as well as the methodology for selecting the appropriate technology for a particular site. Section 3
presents state-of-the-art information on the technologies. Each technology discussion includes:
description,
wastes amenable to treatment,
status of technology,
ease of application,
potential achievable level of treatment,
reliability of method,
secondary impacts.
equipment and exogenous reagents,
information requirements, and
sources of information.
A summary matrix with a brief evaluation of each technology is also provided. Section 4 briefly discusses soil
modification techniques applicable to several technologies. Soil properties discussed include:
oxygen content,
moisture content,
nutrient content,
pH, and
temperature.
The section also contains a table linking soil modification techniques to in-place treatment technologies.
Volume 2 contains three sections and an appendix of chemical data. Section 1 is an introduction. Section 2
provides information on monitoring soil/waste systems. Section 3 addresses fundamental processes in soil/waste
systems, including site conditions, physical soil properties, soil sorption, soil microbiology, volatilization and
degradation as related to hazardous waste treatment in soil systems. This information is included to provide the user
with additional information for making more complex decisions in the analysis of site/soil/waste systems. It is also
useful for evaluating the application of additional treatment techniques not specifically discussed in this report. The
Appendix provides compound properties and adsorption, degradation and volatilization parameters for various
chemicals. These data are important in assessing soil/waste interactions. A glossary is also provided.
11
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SECTION 2
SELECTION OF IN-PLACE TREATMENT TECHNOLOGY
2.1 INTRODUCTION
Selection of appropriate remedial action technologies follows the procedure specified in the National Contingency
Plan (NCP). This procedure is outlined in Figure 2-1. First, a preliminary assessment, called scoping, is conducted to
determine the type of response expected (initial, source control, or off-site remedial action). Scoping relies on
available information and provides the basis for funding requests. This is followed by a remedial investigation to
determine "the nature and extent of the problem presented by the releases. This includes sampling and monitoring, as
necessary, and includes the gathering of sufficient information to determine the necessity for and the proposed extent
of remedial action." (40 CFR 300.68 (f))- The remedial investigation also re-evaluates the conclusions of the scoping
phase. Alternative remedial technologies are then suggested and screened according to the factors given in the figure.
Finally, the most promising technologies are analyzed in detail and the most cost-effective alternative selected.
Evaluation of in-place treatment technologies is a part of this overall process. The specific methodology for
selecting an in-place treatment technology (beginning with the remedial investigation) is depicted in Figure 2-2. It is
assumed here that the results of scoping indicate source control remedial action to be appropriate. It is also assumed
that contaminated surface soils are involved, so that the technologies in this report are potentially applicable.
This Section begins with a general discussion of in-place treatment technologies, followed by four sections that
parallel the procedure outlined in Figure 2-2. The development of alternatives in selecting in-place treatment type and
the detailed analysis to select appropriate in-place treatment technologies are emphasized. Finally, consideration is
given to information gaps and the need for further research pertaining to in-place treatment as a remedial action
alternative.
2.2 DISCUSSION OF IN-PLACE TREATMENT TECHNOLOGIES
There are five major categories of in-place treatment technologies that can be defined in terms of their primary
action on the contaminants contained within the soil:
1. extraction,
2. immobilization,
3. degradation,
4. attenuation,
5. reduction of volatilization.
2.2.1 Extraction Techniques
Extraction techniques actually remove the undesired contaminant from the soil by dissolution in a fluid which is
subsequently recovered and treated either on site or at another location. This technique offers a more or less permanent
solution to the problems pre-existing at the remedial action site. The problem of ultimate disposal of the contaminants
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Figure 2-1. Detailed sequence - phase VI - remedial action (40 CFR, part 300.68)
Funding
30062
30068iC)e
ptOVidPS tulcqo^tp protection
Sourca: Ehrenfeld and Bass, 1983.
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Figure 2-2. Methodology for selecting in-place treatment technology.
Develop Alternatives
Screen Alternatives I Detailed Analysis of Alternatives
Determine Extent
of Remedy
Compare
to Other
Alternative
Compare
Screened
Alternatives
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is, however, moved to another location and another set of processes. The ultimate treatment and disposal of the
contaminated extraction fluid can often be carried out under more favorable technical conditions, at significantly lower
risk, and at reduced costs compared to other in-place treatment options.
2.2.2 Immobilization Techniques
Immobilization techniques are designed to capture the species within the contaminated soil mass. Immobilization
reduces the tendency of the contaminant to enter the groundwater, surface water, or atmospheric exposure pathways.
The immobilized contaminants, however, remain in the soil, leaving open the possibility for exposure via direct
contact or contaminant migration under changed conditions in the future.
The three major classes of immobilization techniques are: adsorption (sorption), ion exchange, and precipitation.
Adsorption includes techniques designed to capture the contaminants on the soil particles by adjusting the
properties within the soil system. In addition, adsorptive materials, such as activated carbon can be admixed into/the
soil to enhance its inherent adsorptive properties. Adsorption can be applied to both inorganic and organic
contaminants.
Ion exchange is a means for immobilizing inorganic species similar in nature to physical adsorption. Initially
mobile metal ions exchange positions with innocuous cations and become bound to clay particles in the soil system.
Many heavy metal contaminants that pose significant risks are quite tightly bound by common clay minerals. The
activity of natural ion exchange in soils can be enhanced by admixing synthetic ion exchange resins. Such resins can be
tailored to be highly selective for particular metals. Ion exchange techniques are applicable only to inorganic
contaminants.
The final immobilization technique iS precipitation. Inorganic contaminants that are initially soluble are caused to
react and form compounds of very low solubility. The insoluble products are thereby retained by the soil system within
the initially contaminated region instead of being removed by infiltration and groundwater flow. The precipitating
agent can be added directly, for example, in the form of sodium sulfide (Na2S), or it can be generated in-place by a
chemical or biochemical reaction.
2.2.3 Degradation Techniques
The third category of treatment technologies is degradation. This is a family of methods which converts the
contaminant species into an innocuous or less toxic compound or compounds. In general, degradation is applicable to
organic compounds. There are a number of limited cases in which degradation is applicable to inorganic species.
Highly toxic hexavalent chromium, for example, can be reduced to the less toxic trivalent form by the addition of
reducing agents. Degradation is often used in combination with immobilization for inorganic contaminants. Following
the above example, trivalent chromium can be readily precipitated in the hydroxide form. By and large, however, the
degradation techniques are of broader applicability to organic contaminants than to inorganic.
Chemical degradation techniques convert contaminant species by promoting the natural capacity of the soil to
support oxidation or reduction reactions or by adding suitable reagents. Reactive organic compounds, such as vinyl
monomers, may be polymerized in-place by the addition of catalysts to form immobile species.
Biological techniques utilize the action of micro-organisms to break down organic compounds into innocuous or
less toxic metabolic products. The naturally occurring micro-organisms found in nearly every soil system can often be
used to degrade organic contaminants. The soil system may have to be modified to promote the activity of naturally
found organisms. Promotion includes addition of nutrients and aeration of the soil. If the intrinsic micro-organism
flora do not work on some set of contaminants, selectively adapted innoculants or even perhaps genetically engineered
species, can be added to the soil mass.
15
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The last degradation technique involves photodegradation (photolysis). The action of the ultraviolet portion of
sunlight can result in the breakdown of many complex and toxic organic compounds. Organic species brought to the
surface by volatilization or mechanical mixing may be broken down by sunlight incident on the surface. The
compounds must move toward the surface in order for this technique to be practical.
2.2.4 Attenuation
Attenuation, the fourth category of in-place treatment techniques, involves admixing clean soils or other bulking
agents to reduce contamination to an acceptable level. This approach has been used to reduce the hazards due to
ingestion or direct contact.
2.2.5 Reduction of Volatilization
Finally, reduction of volatilization, the last major category of treatment techniques, is applicable to exposure via
the air pathway. Volatile organic contaminants pose a significant risk via this pathway. Techniques for reducing
volatility include those which impede the diffusion of volatile contaminants and others which reduce the inherent
tendency for volatilization to tak*e place. Flow toward the surface can be inhibited by reducing the soil vapor pore
volume. Alternatively, the volatility of the contaminant materials can be reduced by techniques such as cooling the soil
to lower the vapor pressure.
2.3 DEVELOPMENT OF ALTERNATIVES
The first phase in selecting the appropriate in-place treatment technology, as shown in Figure 2-2, is the
development of alternatives. This takes place after scoping and the remedial investigation have been completed. This
means that the type of remedial response has been determined. For this discussion, it is assumed that source control
remedial actions are appropriate, and that information from the remedial investigation is available to determine the
nature and extent of the contamination problem. Such information would include:
type of waste present (organic, inorganic, chemical components),
estimate of waste quantity,
waste form (free liquid, solid, contaminated soil),
waste location (areal extent, depth, relationship to water table),
exposure pathways (groundwater, surface water, air, direct contact),
population threatened (human, environmental).
The remedial investigation provides the basis for the selection processes through the comparison and screening of
initial remedial alternatives.
2.3.1 Definition of Objectives
The first step in developing alternatives is to define the objective of the remedial program. This step, which is not
explicitly specified in the NCR, is iterative and occurs throughout the selection process. The objectives are refined and
modified as new information is obtained. It is necessary, however, to have a clear understanding of the remedial
objectives before considering alternative remedial actions, since selection depends on the desired result.
An objective can be defined as an aim or goal of the remedial program. Based on current legislation, the primary
objective for remedial action at Superfund sites is to reduce risk to an acceptable level, while minimizing cost. The
purpose of the selection process, therefore, is to determine which alternative is most "cost-effective" (defined in 40
CFR 300.68(j) as "the lowest cost alternative that is technologically feasible and reliable and which effectively
mitigates and minimizes damage to and provides adequate protection of public health, welfare, or the environment").
Secondary objectives can be used to further define the primary objective. They may consider a particular exposure
pathway or address other technical requirements, local regulations, or political concerns. Together, the objectives
specify the end-result or outcome desired to be achieved through implementing the selected remedial action
technologies.
16
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Figure 2-3. Exposure pathways.
Surface
Supply
Contaminated Soil
Source: Arthur D. Little, Inc.
mdwater Flow
Figure 2-3 depicts a generalized site containing a large quantity of contaminated soil. The remedial objective at
the site might be to reduce risk (a function of the contamination, the pathways and the receptors) by minimizing
exposure along-each of the pathways depicted (direct contact, air, groundwater, surface water). Alternatively, if there
was no drinking water use downgradient or downstream of the site, the objectives might be to minimize exposure
along the air and direct contact pathways.
2.3.2 Selection of Possible Alternatives
Once objectives have been determined, it is necessary to select alternatives that would meet the objectives from
the many available source control remedial action technologies. For the example in Figure 2-3, a security fence, cap
and slurry wall combination, removal and off-site disposal, on-site treatment, and in-place treatment would all
potentially reduce exposure along each of the pathways. They, therefore, can be considered in the initial development
of alternatives, along with any other technology or combination of technologies which have a similar effect. The
purpose of the initial selection of possible alternatives is to consider as many technologies as possible so that the cost-
effective alternative is not overlooked. Subsequent screening and detailed analysis of alternatives serve to single out
those technologies that are most cost-effective in meeting the objectives.
The remainder of this Section emphasizes the considerations particular to selecting in-place treatment tech-
nologies. The evaluation of other technologies follows a similar path which is not discussed, except where the two
paths converge.
2.3.3 Selection of an In-place Treatment Type
The selection process described herein fits into the two-step procedure commonly used in remedial
investigation/feasibility studies (RI/FS). It begins with a preliminary evaluation of all the potential in-place treatment
methods available and the identification of all those that are potentially applicable to the site, and that are consistent
with the objectives. A very rough screen can be made on the basis of the exposure pathways and the chemical nature of
the contaminants. Table 2-1 shows a general applicability matrix. Reference to this table permits selection of the
family of techniques applicable to any combination of pathway and compound. For example, if the objectives contain
a requirement to reduce the risk from organic compounds via direct contact, then extraction or any of the degradation
techniques would be potentially applicable. None of the immobilization techniques would be useful. On the other
hand, if the objective were to reduce the risk from inorganic species via groundwater, then removal and immobiliza-
tion via adsorption, ion exchange, or precipitation would be potentially applicable. Degradation would have limited
applicability, depending on the specific inorganic species.
.7
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TABLE 2-1. GENERAL APPLICABILITY MATRIX
Technology
Air
Groundwater
Surface
Water
Direct
Contact
Inorganic Organic
EXTRACTION
IMMOBILIZATION
Adsorption
Ion exchange
Precipitation
DEGRADATION
Chemical
Biological
Photolysis
ATTENUATION
VOLATILE REDUCTION
X
-
X
X
X
L
X
X
X
X
X
X
X
X
-
-
X
X
X
X
X
X
X
-
-
X
-
X
X
X
X
-
X
X
X
X
L
L
-
X
L
X
X
L
X
X
X
X
X
X = Potentially Applicable
= Not Applicable
L = Limited Applications
If multiple pathways are involved, as is very often the case, technologies potentially applicable to all pathways
should be considered. For example, dioxin-contammated soils may pose a risk through both ingestion of surface soils
and groundwater contamination. Although immobilization techniques via adsorption would be potential!) applicable
for groundwater, as shown in Table 2-1, the inapplicability of this approach when direct contact is included would rule
it out, or it would at least require adsorption to be used in combination with another technology.
The preliminary screening procedure should be broadly construed. If there is any question, a general class of in-
place treatment should be left in the portfolio of options to be evaluated in the detailed steps further along the process.
Combinations of techniques should also be included in the first round.
The list of potentially applicable alternatives can also be narrowed down by consideration of the time available for
treatment, or by the rough reduction levels if available at this stage of the analysis. Some of the processes take a very
long time (e.g., photodegradation) and may be inappropriate at a site requiring clean-up over a limited time period.
Using only information available from the initial remedial investigation, one may find it possible to eliminate
some of the technologies, or at least note that the likelihood of their feasibility is lower than that of other options
Immobilization techniques depend perhaps more than any other option on the intrinsic properties of the soil system.
Adsorption can be expected to be fairly high in soil systems containing high clay and organic content. Waste sites
where soils are predominantly sandy in nature would probably be poor candidates for techniques based on adsorption,
although additives could be used to enhance the poor intrinsic soil properties.
18
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The effectiveness of any one technique or combination of techniques depends on many site-specific and waste-
specific factors. The procedure for introducing these factors into the evaluation and final selection of the single or
small family of cost-effective techniques is developed in the following sections of this document.
2.4 SCREENING OF ALTERNATIVES
Once a list of alternative technologies and technology combinations has been developed, it then becomes
necessary to narrow the list for further detailed analysis. The three criteria used for this screening are:
costs,
effects of the alternative, and
acceptable engineering practice.
Costs include capital, operating, and maintenance costs. Technologies that are significantly more expensive than other
alternatives without providing a greater degree of benefit or reliability can be excluded from further consideration. For
example, if removal by extraction costs X dollars and removal by excavation costs 10X, excavation would no longer
be considered, assuming that extraction would meet the second and third criteria.
Evaluating the effects of the alternative involves two considerations:
(1) whether implementing the alternative causes adverse environmental effects. Some biodegradation
techniques, for example, produce toxic metabolic products which bio accumulate in the course of
detoxifying the target contaminant(s); and
(2) whether the technology has sufficient capabilities relative to the objectives and associated performance
requirements. In other words, can the technology achieve the required level of source control?
If either consideration produces an unsatisfactory finding, the technology option would not be considered further.
Acceptable engineering practice means that the alternative is feasible, given site-specific conditions, and is
considered an applicable and reliable means of addressing the problem.
These screening criteria are evaluated based on available information according to the judgment of the lead
agency or other decision-makers. The screening should result in a shorter list of technologies to be evaluated in detail.
2.5 DETAILED ANALYSIS OF ALTERNATIVES
The detailed analysis of alternatives involves further investigation in five areas (40 CFR 300.68(0(2)):
1) refinement and specification of alternatives in detail;
2) detailed cost estimation, including distribution of costs over time;
3) evaluation in terms of engineering implementation or constructability;
4) an assessment of how well the alternative meets the remedial objectives; and
5) an analysis of any adverse environmental impacts, methods for mitigating these impacts, and costs of
mitigation.
For in-place treatment technologies these steps involve (1) assessment of waste, soil, and site-specific variables, and
(2) selection (including detailed specification) of an in-place treatment technology within the treatment category.
19
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2.5.1 Assessment of Waste, Soil and Site-specific Variables
Many waste, soil, and site-speific variables affect the technical feasibility and effectiveness of in-place treatment.
Some of these variables can be conveniently established as part of the remedial investigation. Others may require
independent bench-scale or pilot studies directly related to treatability. Each of the important variables is discussed
below under the following sub-headings:
waste characteristics,
site characteristics, and
waste/soil system characteristics.
These discussions are followed by a discussion of laboratory and pilot-scale testing.
2.5.1.1 Waste Characteristics
Soil core and soil pore water samples should be obtained and analyzed to determine the chemical contaminants
present, the areal extent and depth of contamination, and the range of contaminant concentrations at presumed source
locations and along expected pathways of migration.
Soil and groundwater samples from contaminated areas and control (background) areas should be analyzed for:
Elemental and Inorganic Constituents:
Metals and metalloids (As, B, Ca, Cd, Cr, Cu, K, Mg, Mo, Na, Ni, P, Pb, Se, V, Zn),
Total organic carbon (TOC),
Total Kjeldahl nitrogen (TKN),
Sulfate
Chloride.
Organic Constituents:
Priority pollutants (volatiles, acid extractables, and base/neutrals),
Others known or expected to be present, based on past activities at the site.
Based on the analytical results, a list of contaminants within each group that are present at levels in excess of
background should be compiled. Maps should be prepared showing contaminant locations and concentrations.
To assist in evaluating pathways of migration, and in designing in-place treatment processes, the following
physical/chemical properties should be derived from the literature or estimated for each of the identified waste
constituents:
solubility in water (and in other solvents, if flushing is an alternative of interest);
vapor pressure;
soil/water partition coefficient, Koc, for organic waste constituents (Koc is defined as the Freundlich
adsorption coefficient (K) divided by the weight fraction organic carbon (foc) in the soil, i.e., Koc =
K/foc);
20
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Henry's Law Constant (used in evaluating the partitioning of a contaminant between soil pore water
and the vapor phase); this may be derived from the vapor pressure/water solubility ratio for chemicals
of limited water solubility (
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Soil Properties
pH is an important variable in evaluating mobility of many metal contaminants, as well as organic
acids and bases, and in designing several of the in-place processes discussed in this report.
Cation exchange capacity (CEC) is an important determinant of the mobility of metallic species in
soils; if the CEC is sufficiently high to adequately immobilize the heavy metals present in the soil,
no further action may be necessary; if one remedial objective is to reduce heavy metal migration
from expected "no action" levels, a potential in-place treatment method might involve increasing
the intrinsic CEC of the soil.
Redox potential (Eh) is important in determining the stability of various metallic and organic
species in the subsurface environment of the site, and it also might be modified by in-place
treatment.
Organic carbon content is a major variable affecting adsorption, and hence mobility, of organic
species in the subsurface environment.
Microbial content as a function of depth is an important variable, if potentially biodegradable
constituents are present in the waste.
Soil type (e.g., clay, till, sand, fractured bedrock) is a major variable affecting rates and routes of
groundwater migration and contaminant transport.
Hydraulic conductivity is important in determining feasibility and spacing of drains and wells.
Trafficability Factors that affect the mobility and/or placement of equipment on the site, and the
ability to perform tillage and other in-place treatment operations need to be considered in the remedial
action design. Significant variables include: bearing capacity, traction capacity, soil strength, slip-
periness, stickiness, moisture content, clay content, presence of debris, structures and/or vegetation,
and slope of the terrain (topography), as mentioned earlier.
Potentially Exposed Human Populations and Sensitive Ecological Environments
Groundwater and surface water usage, especially downgradient of the site, are important in
evaluating risks and environmental benefits of remedial alternatives.
Size of population and nature of ecological resources downgradient and downv/ind of the site are
also important variables for risk assessment.
2.5.1.3 Waste/Soil System Characteristics
Design and implementation of an in-place treatment process requires information on characteristics of the
waste/soil system as a whole. The important variables are:
Depth of Contamination If contamination is limited to the upper 6-8 inches of the soil and it is well
above the water table, in-place treatment techniques may be much more easily applied than if the
contamination extends well below the plow layer and into the seasonally high water table.
Contaminant Concentrations and Quantities The efficiency and effectiveness of many in-place
processes depend upon both contaminant concentration levels and the total quantity of each contami-
nant present in a given area.
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Treatability Based on the various waste, soil, and system characteristics discussed above, an
analysis can be made of routes and rates of contaminant migration and the potential for damage to
human health and the environment as a function of time under conditions of no action. The in-place
methods discussed in this report are intended for consideration in situations in which naturally
occurring immobilization, degradation, attentuation, and volatilization processes are insufficient in
and of themselves to meet defined objectives within an acceptable time frame. For practical purposes,
therefore, in-place treatment will require physical modification of the waste/soil system and/or
addition of exogenous agents to accelerate the rate of naturally occurring remediation processes or to
induce processes in-place to meet the remedial objectives.
The in-place methods discussed in this report are basically intended to alter the waste, soil, and/or waste/soil
system characteristics determined to exist at the site prior to treatment. Any one of the generic methods under
consideration, however, needs to be specifically adapted to each particular site contamination situation in order to
achieve desired system characteristics after treatment. Table 2-2 summarizes the treatment variables that need to be
determined to assess the capability of in-place treatment alternatives to achieve remedial objectives.
Waste and soil characteristics are useful in prescreenmg in-place alternatives for potential applicability in meeting
remedial objectives. However, the present state of the art of in-place treatment is not sufficiently advanced to have a
comprehensive data base, or to allow calculation of optimum conditions for degradation, detoxification, and/or
immobilization of waste constituents. For those alternatives identified as potentially applicable, bench scale treatabil-
ity studies will generally be necessary to assess technical feasibility further and to establish design parameters for
implementation and costing. The combined use of waste, soil and system characteristics in the assessment of several
generic in-place alternatives is illustrated below.
No Action Alternative
In situations where the intrinsic properties of the soil are adequate to block migration of waste constituents along
pathways of concern, the no action alternative is likely to be the most cost-effective. In all cases, the inherent
assimilative capacity of the soil for the waste constituents of concern should be evaluated (see Overcash and Pal, 1979
and USEPA, 1983).
Even if naturally occurring degradation, immobilization, and attentuation processes are deemed inadequate to
meet remedial objectives, assessment of these processes provides a useful baseline for designing additional in-place
remedial measures. For example, soil systems containing high clay and organic content may adequately immobilize
both heavy metal and organic chemical constituents of waste by natural adsorption processes, provided that the
assimilation capacity of adsorption sites is not exceeded. Waste sites where soils are predominantly sandy would have
little potential for immobilizing waste constituents. No action might be appropriate for the clay soils, but not for the
sandy soils. For two equally contaminated sites of the same size, less additional adsorbent might be required to
immobilize constituents in the clay soil where its natural assimilative capacity has been exceeded than in the sandy
soil.
Extraction Alternative
Flushing or "solution mining" of contaminants requires identification and bench-scale testing of potentially
suitable solvents and the design of a recharge/discharge system to effect flushing in the field.
Immobilization Alternative
Immobilization processes are designed essentially to reduce leaching (or volatilization) of hazardous waste
constituents to acceptable levels. Depending upon the particular waste/soil system, immobilization may be
accomplished through physical or chemical adsorption, ion exchange, or precipitation. In general, immobilization of
contaminants at uncontrolled hazardous waste sites requires the incorporation of physical or chemical adsorbents into
23
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TABLE 2-2. TREATMENT VARIABLES FOR IN-PLACE TREATMENT TECHNOLOGIES
Technology
Treatment Variables
Comments
EXTRACTION
IMMOBILIZATION
Sorption
Ion Exchange
Precipitation
DEGRADATION
Chemical
Solubility of waste constituents
in solvent
Concentrations of waste
constituents
Rate of dissolution of adsorbed
species
Adsorptive capacity of sorbent
for specific waste constituents
Concentrations of sorbates,
including naturally occurring
substances
Soil pH
Soil moisture
Soil/water partition coefficient
(Koc)
Cation (or anion) exchange
capacity of clay, resins, or
zeolites
Concentration of ions in soil
water
SoilpH
Concentration of soluble metals
Stability of precipitate relative
to dissolved species
Soil pH
Oxidation state of metal ions
Soil oxygen content
Reactivity of precipitate
Redox potential of waste/soil
system
Soil oxygen content
Presence of catalyst(s)
Polymerization potential of
wastes
SoilpH
Soil moisture
Soil temperature
Solubilities of constituents vary with
different solvents.
All sorbates compete for adsorptive
capacity of sorbent.
Clays and zeolites are used to treat
cations (metal ions), resms for both
cations and anions.
Sulfides may transform to more solubl
sulfates under long periods of aerobic
soil conditions
Oxidation/reduction products may be
more mobile and/or more toxic than
the parent compound; chemical
oxidants are non-selective and may
preferentially oxidize organic matter
in soils.
(continued)
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TABLE 2-2 (Continued)
Technology
Treatment Variables
Comments
Biological
Photolysis
ATTENUATION
REDUCTION OF
VOLATILIZATION
Biodegradability of waste
constituents (half-life)
SoilpH
Micro-organisms present
(type; population)
Soil oxygen content
Soil moisture
Soil nutrient content
(C:N:P ratio)
Soil temperature
Rates of biodegradation, or
rates of leaching
Absorption spectra of waste
constituents ( > 290-nm wave-
length range)
Half-life of photolysis; photolysis
products
Volatility of waste constituents
(vapor pressure, Henry's Law
Constant)
Site-soil assimilative capacity
Feasibility of mixing uncon-
taminated material with con-
taminated soils
Volatility of waste constituents
and dependence on temperature
(vapor pressure, Henry's Law
Constant)
Soil moisture
Soil temperature
Caution is needed to ensure that con-
taminants are not toxic to micro-
organisms. Chemical-specific micro-
organisms may be encouraged by
manipulating treatment variables.
Photolysis products may be more toxic
than parent compound.
Assimilative capacities are available for
many heavy metals, but not for organics.
Source: Arthur D. Little, Inc.
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the contaminated soil, or the addition of ion exchange or precipitating agents. Optimum additive concentrations are
best determined using laboratory treatability studies with the waste/soil system. Optimum conditions for m-place
immobilization can be selected by varying the treatment parameters and determining the minimum rate of leaching of
the constituents of concern. The minimum achievable leaching rate should then be compared with the desired rate to
meet remedial objectives.
Degradation Alternative
Management of the soil/site system to increase the rate of biodegradation is a potential option to be considered for
sites contaminated with organic chemical wastes. As discussed above, part of the site characterization will involve a
determination of the presence or absence of micro-organisms (e.g., aerobic bacteria, anaerobic bacteria,
actinomycetes, fungi, and,algae) for representative areas of contamination. Part of the waste characterization will
involve analyses to determine the carbon:nitrogen:phosphorus ratio. If the C:N:P ratio is not optimal for micro-
organism growth, bench-scale experiments should be conducted to determine whether adjustment of this ratio will
increase the concentration of micro-organisms in the soil and the rate of biodegradation. These initial experiments
should be done with samples of contaminated soils from the site at dissolved oxygen concentration levels characteristic
of the respective contaminated areas if possible.
Experiments should also be done to determine the effect of various oxygen levels on soil micro-organism count
and rate of biodegradation. If nutrient and oxygen adjustments are insufficient to stimulate the growth of micro-
organisms or to increase the biodegradation rate adequately, experiments might be performed to innoculate the
soil/waste mixture with activated sludge, commercially developed micro-organisms likely to feed on the particular
contaminants in the soil, or soil from the site or control area that has a high micro-organism count. Rates of
biodegradation should be measured systematically as a function of nutrient concentrations, oxygen, and micro-
organisms to establish optimum conditions for degradation.
Once these conditions have been determined, an in-place method capable of achieving these conditions in the
field would have to be designed. There are a number of possibilities. For contaminated areas within 2 feet of the
surface, simple tilling of the surface soils may introduce sufficient oxygen into the system to accelerate the rate of
biodegradation. Depending upon the laboratory results, it may also be necessary to innoculate the surface with
additional micro-organisms, adjust the pH and nutrients, and/or adjust the moisture content. For contaminated areas at
greater depths, oxygen nutrient and possibly micro-organism additions will almost certainly be required to achieve
satisfactory degradation rates. Conceivably, deeper constituents could be flushed out of the soil and reapplied in a
controlled manner to the soil surface for biological treatment as described above for surface contaminants.
In areas where contaminant concentrations are so high as to be toxic to micro-organisms, the contaminated soil
might be mixed with uncontammated soil to reduce overall concentrations to levels that could then be successfully
biodegraded in-place.
In the soil/waste system, biodegradation under the optimum conditions established in the laboratory experiments
will generally compete with leaching, or volatilization of the waste constituents or their intermediate degradation
products. Laboratory experiments should be performed to compare degradation rates with leaching and volatilization
rates. If leaching or volatilization is rapid compared to biodegradation, it may be necessary to modify soil properties
for some distance along the pathways of migration to immobilize the biodegradable constituents.
The laboratory experiments performed to establish the optimum achievable rate of degradation should determine
not only the rate of disappearance of the parent compound, but also the chemical identity and rate of disappearance of
the degradation products over time. The toxicity of partially degraded fractions should be determined either from the
literature or via a bioassay. If the biodegradation products are toxic and do not degrade, then biodegradation would
generally have to be considered infeasible.
26
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Depending upon the nature of the contaminants present and the treatment objectives, chemical reagents may also
have to be incorporated into contaminated surface soils, or injected into deeper contaminated layers, to bring about
detoxification or degradation reactions. Such reactions might involve oxidation, reduction, or polymerization, for
example. Appropriate reagents, reaction rates, and the leachability and toxicity of reaction products will generally
have to be determined by laboratory treatability studies.
Attenuation Alternative
Federal and State guidelines for land application of sewage sludges specify acceptable levels of heavy metal
accumulation in soils (mg/kg). If these or other specified levels are exceeded at a site, they can be attenuated to
acceptable levels by mixing with clean soil. The amount of soil, required is determined by the metal that must be
attenuated to the greatest extent to meet standards. Attenuation is also applicable, in principle, to organic contami-
nants. In practice, assimilative capacities of soils, which must be known to design attenuation systems, have only been
established for heavy metals.
Reduction of Volatiles
Suppression of vapor transport from contaminated soils may be desirable if contaminants or their degradation
products can escape from the untreated soils at levels and rates potentially damaging to target organisms. Simple
models are available to estimate the loss and transport of volatiles from soil systems. These models generally require
data or estimates of the vapor pressure and solubility of the contaminants, as well as knowledge of the meteorological
conditions at the site. Effectiveness of methods to reduce volatiles should be tested in the laboratory to establish design
parameters for a field system (Farmer et al., 1980).
2.5.1.4 Laboratory and Pilot-scale Testing
Laboratory (bench-scale) and pilot-scale testing may be required to evaluate the technical and practical feasibility
of in-place treatment methods for contaminated soil prior to full-scale implementation. Testing may be used to
establish the following at in-place treatment sites:
1) The critical soil level for the waste at which treatment (degradation, detoxification, and/or immobiliza-
tion) is ineffective due to toxicity or mass flow conditions.
2) The rate of degradation or detoxification of organic constituents, i.e., the half-life, and the extent of
immobilization of inorganic constituents.
3) The mobility, toxicity, and biodegradability of partially degraded waste constituents or waste fractions.
4) Criteria for management of the soil and site to enhance the natural ability of the soil to attenuate
constituents by determining optimum conditions for degradation, detoxification, and/or
immobilization.
5) Parameters and constituents that should be monitored to indicate contaminant migration to receiver
systems including groundwater, surface water, and atmosphere.
6) Technical feasibility and potential costs associated with using techniques based on management of the
site/soil assimulative capacity for accomplishing the treatment required for a particular site/soil/waste
system.
In principle, the direct costs for labor and equipment for laboratory or pilot-scale testing, as well as the indirect
costs of delaying implementation until test results are obtained, will be determined by the complexity of the
experimental design. That will depend, in turn, on the number of experimental variables to be controlled and/or
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monitored, the types of equipment required, the length of time and number of samples required to obtain the desired
information with the requisite precision, or reliability, and prior operating experience with the process. Each of these
factors will be specific to the process under study and thus cannot be specified a priori.
Certain elements of the testing program, however, are likely to be common to most other laboratory and pilot-
scale testing programs. Among those elements are statistical sampling requirements, sampling equipment, sample
collection, preservation, shipping and storage, and chemical analysis. Basic considerations and reference sources for
each of these areas are described briefly under the respective headings below.
2.5.1.4.1 Statistical Sampling Requirements
The purpose of sampling is to permit estimation of the properties of interest in a cost- and time-effective manner.
The sampling program chosen to achieve this objective will depend on the precision required of the estimation.
Sampling plans commonly used for soil testing programs include simple random sampling, stratified random
sampling, and systematic sampling. Statistical considerations associated with these and other types of sampling plans
are discussed in detail in Black, 1965; Walsh and Beaton, 1973; and "Guidelines for Data Acquisition and Data
Quality Evaluation in Environmental Chemistry," 1980.
2.5.1.4.2 Sampling Equipment
The sampling equipment used to obtain samples for subsequent testing depends on the type of sample required
and on the soil type and depth from which the sample is to-be obtained. The materials from which the sampling
equipment is constructed must be chosen so that those surfaces in direct contact with the soil will not contaminate the
sample with any species which may interfere in the chemical analysis. General descriptions of the types of equipment
which may be used for soil sampling with directions for their use are in Soil Conservation Service, 1972; and U.S.
EPA, 1982.
2.5.1.4.3 Sample Collection, Preservation, Shipping and Storage
Procedures used for sample-handling and storage will depend on the characteristics to be determined. In the
simplest case, the sample may be air-dried under ambient conditions and subsequently stored in clean containers until
analyses are performed. However, special precautions may be required in cases where the characteristic to be
determined may be affected by the conditions of handling, shipping, and storage. Those precautions may include
addition of chemicals to fix or retard changes in the concentration of the species of interest, freezing the sample, or
performing the analysis at the time of collection. Guidelines for sampling handling and storage are provided in U.S.
EPA, 1982; and American Public Health Association, 1975.
2.5.1.4.4 Chemical Analysis
Methods applicable to the determination of a wide variety of organic and inorganic compounds, elements, anions,
and physical and chemical properties are readily available in the technical literature. Representative sources include:
Walsh and Beaton, 1973; U.S. EPA, 1982; American Public Health Association, 1975; David, 1978; and Purdue
University, 1977.
2,5.1.4.5 Monitoring
In general, laboratory and pilot-scale testing do not simulate field conditions exactly. Therefore, the effectiveness
of the treatment process selected must be monitored after implementation. Soil core and soil pore water in the
treatment zone and along pathways of migration must be sampled and analyzed to determine whether the treatment
process is functioning according to design. Appropriate parameters to monitor would generally be selected from
among the waste constituents expected to be treated, and the degradation products of treatment identified in treatability
studies or in the literature as indicators of the success of treatment. If the treatment process is not as effective in the
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field as had been predicted from the laboratory or pilot studies, improvement may be possible by adjusting operating
conditions. A more complete discussion on monitoring is provided in Volume 2.
2.5.2 Selection of In-Place Treatment Technology
The assessment of waste, soil, and site-specific variables described above will result in identification of
technically feasible in-place treatment technology. Further analysis of each of the technically feasible alternatives is
required to determine which (if any) meet the cost-effectiveness criteria of the National Contingency Plan.
The data assembled for assessing technical feasibility should be sufficient to form the basis of initial detailed
engineering designs and operating specifications for each in-place treatment system. The designs and specifications in
turn form the basis for developing detailed capital, operating and maintenance cost estimates over the lifetime of the
remedial program.
The initial implementation plan should then be examined in some detail, and refined as appropriate. Several
iterations may be necessary. First, the plan should be examined for completeness and logical consistency with respect
to engineering implementation and constructability. Have any steps for successful implementation, operation, and
monitoring been overlooked? Are all steps in logical order? Is the schedule realistic? Have all steps been properly
costed? Next, an assessment needs to be made of how well each alternative meets the remedial objectives. This may
require mathematical modeling of contaminant migration patterns, based on the modified waste/soil system charac-
teristics that would be anticipated if the remedial alternatives were implemented. In addition, any adverse environmen-
tal impacts should be identified and assessed. Methods and costs for mitigating these impacts should be incorporated
into a revised implementation plan. Finally, each in-place treatment process design that meets the remedial objectives
should be rank ordered in terms of annualized cost, and the most cost-effective in-place alternative(s) should be
selected for comparison with other alternatives.
2.6 DETERMINATION OF EXTENT OF REMEDY
The process described above, along with a similar process for other technologies, should provide enough
information to enable selection of the most cost-effective alternative. The results of the analysis for the in-place
treatment alternatives that survive screening are compared with other alternatives that have also been analyzed in
detail. The lowest cost alternative that reduces risk to an acceptable level and meets the other objectives of the remedial
program is then selected.
2.7 IN-PLACE INFORMATION GAPS
The evaluation of the in-place techniques discussed briefly in this section and in more detail in the next section is
hampered by the general lack of information pertaining to remedial applications. The missing information is of two
types. The first is general information about the technologies in any setting, remedial action, land treatment,
agriculture, and the like. A number of the techniques have been developed for and applied in the latter two areas, but
even these are often in the early stages of development.
The second type of information gap is related to specific information on individual technologies. Data on the
natural, intrinsic (assimilative) capacity of soil systems to support these in-place technologies are needed, as are data
on means to enhance the natural capacity by the addition of reagents, or the modifications of the soil/waste system.
To begin to address some of the information gaps described below, the Utah Water Research Laboratory has
initiated studies in cooperation with the U.S. Environmental Protection Agency, Robert S. Kerr Environmental
Research Laboratory to investigate in-place treatment of complex hazardous wastes for application to in-place
remedial action as well as to land treatment systems. The experimental studies focus on high soil concentrations and
assimilation capacities for complex hazardous wastes, and on volatilization of hazardous constituents from soil
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systems. The goal of the work is to be able to relate waste composition on a constituent basis to soil-treatment
capacities. Assimilation capacities with respect to degradation, detoxification, and immobilization will be determined
to generate a data base for establishing the capabilities and limitations for soil 'treatment of hazardous waste
constituents.
2.7.1 General Information Gaps
The ability to utilize in-place treatment will be improved by developing a broader data base containing the
following:
1) Information obtained from the controlled application of complex hazardous wastes (including solid.
liquid, and semi-solid wastes) to soil systems in laboratory or field experiments. Information must
specifically include mass balance for degradation, mobilization, volatilization, photodegradation, and
rates of reaction.
2) Information obtained from /jeW-scale applications of hazardous wastes, either controlled or uncon-
trolled, in which environmental sampling includes waste and soil parameters through the soil profile,
soil core and soil pore-liquid, volatile fugitive emissions, and groundwater.
3) Information obtained from controlled experiments on a field scale, comparing effecliveness of adding
treatment agents (e.g., chemicals, micro-organisms, adsorbents) compared to a non-treatment agent
addition for soil treatment (degradation, transformation, immobilization) of constituents in complex
hazardous wastes.
2.7.2 Technology-specific Information Gaps
Several areas in which specific information concerning in-place treatment is scarce or completely lacking have
also been identified. These areas relate to the treatment processes in a soil system, viz., degradation, transformation,
and immobilization. Such information needed to determine the assimilative capacity, or quantitative ability of the soil
system to prevent contamination of air, groundwater, and surface water is described below.
1) Information on soil processes interfacing with atmospheric processes (i.e., controlling volatilization
and photodegradation), including:
investigation of photochemical reactions that enhance biodegradation of refractory1 compounds and
those that can produce toxic or undesired breakdown products;
laboratory and field-scale analysis of the feasibility of using volatilization/photodegradation as a
viable treatment method for volatile/photoreactive hazardous chemicals;
evaluation of the importance of soil-photochemical reactions to the fate and behavior of photoreac-
tive compounds within the environment;
refinement of containment/transport models that address volatilization, vapor adsorption, biodegra-
dation, and leaching through the soil matrix; and
continued development of rapid partition coefficient estimation methods for predicting compound
partitioning among air/water/soil systems.
2) Information on chemical reactions relating to the transformation and immobilization of constituents in
soil systems, including:
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effects of chemical addition (oxidants, reductants. and polymerizing agents) on the soil properties
affecting treatment;
constituent sorption and precipitation studies at concentrations in the soil matrix characteristic of
those found at remedial action sites,
Eh-pH information for metal species in soils at concentrations representative of remedial action site
concentrations; and
behavior of specific metals, viz., arsenic, beryllium, silver, selenium, mercury, and chromium in
soil systems, including the investigation of the reaction of chromium (VI) to chromium (III).
3) Information on biological reactions to stimulate the biodegradation of constituents in soil systems,
including:
potential for combinations of chemical and biological treatment methods for accelerating soil
treatment;
potential for composting of hazardous waste contaminated soil for accelerating biological reactions
and for detoxifying and degrading recalcitrant organic constituents;
evaluation of the biodegradation kinetics and extent of hazardous constituents and metabolites of
hazardous constituents sorbed to clay and soil organic matter;
degradation rates and pathways for chemical classes, including alkyl halides and highly chlorinated
organics (PCBs) in the soil treatment zone (upper 5 feet of soil); and
information concerning the effectiveness of micro-organism seeding compared with no seeding,
specifically in terrestrial systems.
4) Information on immobilization reactions in the soil/waste system, including:
investigation of enhancement of sorption by adding different sorbents, such as activated carbon,
straw, synthetic resins. (The specific information needed includes application rates of sorbent in
relation to concentrations of contaminant in soil);
continued development of estimation methods for predicting soil adsorption constants by chemical
and physical properties of compounds;
long-term effectiveness of immobilization of sorbed contaminants on soil; and
effects of solvents on mobility of organic contaminants in soil systems.
5) Information on leaching in the soil/waste system, including:
laboratory experiments to estimate parameters for transport models that can be used to predict
behavior under field conditions;
field instrumentation to validate transport models under imposed environmental conditions.
incorporating the-variability under field conditions by designing appropriate sampling stations; and
effect of different environmental conditions, including soil moisture, redox potential, and organic
content on transport parameters.
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SECTION 3
TECHNOLOGIES FOR IN-PLACE TREATMENT
3.1 INTRODUCTION
This section presents detailed information on specific in-place treatment technologies. Each technology was
selected on the basis of its potential or demonstrated ability to augment natural soil processes to accomplish in-place
treatment.
The technology discussions are divided into the five treatment categories presented in Section 2; viz., extraction,
immobilization, degradation, attenuation, and reduction of volatiles. Each discussion is presented in the following
format:
Description a qualitative discussion of the technology and principles on which it is based.
Wastes amenable to treatment a discussion of the kinds of wastes suited to the treatment in terms of
waste type (organic/inorganic), chemical class, or certain required properties of the class.
Status of technology a measure of the availability of the technology and degree to which it has been
demonstrated for soil treatment, "Field" means that it has been used for soil treatment in practice,
either large-scale or in small pilot studies. "Laboratory" means that the technology has been
demonstrated for soil treatment in small experiments in laboratories. "Conceptual'' means either that
it is still purely theoretical, or that it has been used for treatment other than soil treatment but no
laboratory or field work exists for soil treatment.
Ease of application a qualitative description of the relative difficulty of implementing the tech-
nology in the field. "Easy" means that application problems are not expected under most conditions,
while "difficult" means that problems are usually expected. "Easy to difficult" means that ease of
application vanes considerably, depending on site-specific conditions.
Potential achievable level of treatment a description (high, low, variable) of the conceptual or
theoretical level of treatment which could be obtained independent of site-specific considerations. A
"high" potential achievable level of treatment for reduction, for example, means that wastes
applicable to treatment by reducing agents may be effectively degraded by reduction. Site conditions,
however, may interfere with technology performance.
Reliability of method a brief discussion of the long-term effectiveness of the technology, including
reversibility of treatment and retreatment needs. If there is a lack of information on long-term
effectiveness, the reliability is designated as "unknown."
Secondary impacts a discussion of the effects of technology implementation in addition to its
intended primary effect. The impacts discussed include effects on soil properties, site conditions, and
the enhancement or retardation of other in-place treatment processes.
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Equipment and exogenous reagents a brief description of the equipment and materials that may be
required to implement the technology. Additional information on equipment and reagents is presented
in the appendix.
Information requirements a list of information, including waste, soil, and site factors discussed in
Section 2, that is needed for application of the technology.
Sources of information a listing of the publications used in preparing the technology discussions,
including some that are not specifically referenced.
A matrix of important summary information for each of the technologies is presented in Table 3-1.
3.2 EXTRACTION (SOIL FLUSHING)
Description
Removal of soil contaminants can be accomplished through extraction (soil flushing or solution mining). This
involves the elutriation of organic and/or inorganic constituents from soil for recovery and treatment. The site is
flooded with the appropriate flushing solution and the elutriate is collected in a series of shallow well points or
subsurface drains. The elutriate is collected, treated, and/or recycled back into the site. Collection of elutriate is
required to prevent uncontrolled contaminant migration through uncontaminated soil and into receiver systems
including groundwater and surface water. An example of a soil flushing system with elutriate recycle is given in Figure
3-1.
Flushing solutions may include water, acidic aqueous solutions (sulfuric, hydrochloric, nitric, phosphoric, and
carbonic acid), basic solutions (e.g., sodium hydroxide), and surfactants (e.g., alkylbenzene sulfonate). Water can be
used to extract water-soluble or water-mobile constituents. Acidic solutions are used for metals recovery and for basic
organic constituents, including amines, ethers, and anilines, and basic solutions for metals, including zinc, tin, and
lead and for some phenols, complexing and chelating agents, and surfactants (U.S. EPA, 1982).
Addition of any flushing solution to the system requires careful management and knowledge of reactions that may
adversely affect the soil system. For example, a sodium addition as sodium hydroxide to soil systems may adversely
affect soil permeability by affecting the soil sodium absorption ratio. It is not only important to understand the
chemical reaction(s) between solvent and solute, but also between solvent and site/soil system.
For a site contaminated by organic constituents, it may be possible to recycle the elutriate back through the soil
for treatment by biodegradation. Proper control of the application rate, based on hazardous waste land treatment
principles (U.S. EPA, 1983), would provide for effective in-place treatment at soil concentrations that would allow
controlled biodegradation of the waste constituents. Using this approach may eliminate the need for separate processes
for treatment and disposal of the collected waste solution, or at least provide for a combination of pretreatment/land
application that may be considerably more economical than using unit operations alone for treatment of elutriate.
For soils contaminated with inorganic and organic constituents, a combination of pretreatment land applications
where the metal constituent(s) is reduced or eliminated in the elutriate by precipitation, followed by land application of
the elutriate, may be a feasible, cost-effective method of treatment.
Soil flushing and elutriate recovery may also be appropriate for situations where chemical oxidizing or reducing
agents are used to chemically degrade waste constituents resulting in the production of large amounts of oxygenated,
mobile, degradation products. The most conservative and safest approach may be to flush the soil after treatment to
recover and possibly reapply the elutriate in a controlled manner to the soil surface.
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TABLE 3-1. SUMMARY MATRIX OF TREATMENT TECHNOLOGIES
Technology
Wastes Amenable
to Treatment
Status
Potential
Level of
Ease of Application Treatment
Reliability
EXTRACTION
IMMOBILIZATION
Sorption (heavy metals)
Agri. products
Activated carbon
Tetren
Sorption (Organics)
Soil moisture
Agri. products
Activated carbon
Ion Exchange
Clay
Synthetic resins
Zeolites
Precipitation
Sulfides
Carbonates, phosphates
and hydroxides
DEGRADATION
Oxidation
Soil catalyzed reactions
Oxidizing agents
Reduction
Organics
Chromium
Selenium
Soluble organics
and inorganics
Heavy metals
Heavy metals
Heavy metals
Organics, non-
volatile, Kd<10
Organics
Organics, low
water solubility
Cationic components
Certain canonic and
anionic compounds
Heavy metals
Heavy metals
Heavy metals
Aliphatic organics.
other organics
Various organics
Chlorinated organics.
unsaturated aromatics,
ahphatics
Hexavalent chromium
Hexavalent selenium
Laboratory
Field
Conceptual
Laboratory
Conceptual
Laboratory
Field
Laboratory
Laboratory
Conceptual
Conceptual
Laboratory
Limited field
Limited field
Limited field
Limited fielc*
Limited field
Easy Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy - Difficult
Difficult
Easy Difficult
Easy Difficult
Moderate - Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Variable
High
Unknown
High
High
High
Low High
High
Variable
Unknown
High
Unknown
Variable
High
High
High
High
Good
Retreatment
required
Unknown
Unknown
Retreatment
required
Retreatment
required
Unknown
Good
Unknown
Unknown
Fair
Retreatment
requ ired
Good
Good
Retreatment
required
Retreatment
required
Retreatment
required
(continued)
-------
TABLE 3.1 (Continued)
Technology
Wastes Amenable
to Treatment
Status
Potential
Level of
Ease of Application Treatment
Reliability
Sodium reduction
Polymerization
Modification of soil
Properties (biodegradation)
Soil moisture
Soil oxygen aerobic
Soil oxygen anaerobic
Soil pH
Nutrients
Nonspecific organic
amendments
Analog enrichment for
cometabolism
Exogenous acclimated or
mutant micro-organisms
Cell-free enzymes
Photolysis
Proton donors
Enhance volatilization
ATTENUATION
Metals
Organics
REDUCTION OF
VOLATILIZATION
Soil vapor volume
Soil cooling
PCB, dioxin, halogenated
compounds
Aliphatics, aromatics.
oxygenated organic
compounds
Organics
Organics
Halogenated organics
Organics
Organics
Organics, arsemte
wastes
Some organics
with analogs
Various organics
Organics
Some organics, including
TCDD, Kepone, PCB
Specific organics
Metals
Organics
Volatile organics
and inorganics
Volatile organics
Conceptual
Expt. field
Field (Agri )
Field
Conceptual
Field
Field
Laboratory
Laboratory
Field
Laboratory
Field
Conceptual
Field
Limited field
Laboratory
Expt., limited
field
Moderate
Moderate Difficult
Easy Difficult
Easy Difficult
Moderate Difficult
Easy Difficult
Easy - Difficult
Easy Difficult
Easy - Difficult
Easy Difficult
Difficult
Easy Difficult
Easy Difficult
Easy Difficult
Easy -- Difficult
Easy Difficult
Difficult
High
Variable
Low High
Low High
Low High
High
High
Low High
Low High
High
High
High
High
High
High
Low
Medium
Low
Medium
Good
Unknown
Retreatment
required
Retreatment
required
Retreatment
required
Retreatment
required
Retreatment
required
Retreatment
required
Unknown
Retreatment
required
Unknown
Unknown
Good
Good
Good
Retreatment
required
Retreatment
required
Source: Arthur D. Little, Inc.
-------
Figure 3-1. Schematic of an elutriate recycle system.
Spray Application
..,.,
Leachate
' .. ' -jWater Table
Well
Source: Ehrenfeld, J.R., and Bass, J.M., 1983.
Wastes Amenable to Treatment
Both inorganics and organics are suitable for soil flushing treatment if they are sufficiently soluble in an
inexpensive solvent that is obtainable in a large enough volume. Surfactants can be used for hydrophobic organics.
Status of Technology
This technology is currently at the laboratory stage. Studies have been conducted to determine appropriate
solvents for mobilizing various classes and types of waste constituents.
Ease of Application
This technology may be easy or difficult to apply depending on the ability to flood the soil with the flushing
solution and the installation of collection wells or subsurface drains to recover all the applied liquids. Provisions must
also be made for ultimate disposal of the elutriate.
Potential Achievable Level of Treatment
The achievable level of treatment is variable, depending on the contact of flushing solution with waste
constituents, the appropriateness of solutions for the wastes, and the hydraulic conduciivity of the soil. This
technology is more applicable to highly permeable soils because the level of treatment will probably be higher.
36
-------
Reliability of Method
Although the level of treatment may be variable, once the waste components are removed from the soil, the
treatment is not reversible and no additional retreatment is necessary.
Secondary Impacts
The solutions used for the flushing may themselves be potential pollutants. They may have toxic and other
environmental impacts on the soil system and water receiver systems. The soil system after treatment is altered from its
original state. Its physical, chemical, and biological properties may be altered adversely; e.g., the pH may be lowered
by the use of an acidic solvent, or the soil may be compacted from being flooded. These soil properties may have to be
restored to assure that other treatment processes can occur (e.g., biodegradation).
Equipment and Exogenous Reagents
Equipment used for soil flushing include drains and an elutriate collection and distribution system. The solvents
for flushing are required.
Reapplication of collected elutriate may require construction of a holding tank for the elutriate.
Information Requirements
characterization and concentration of waste constituents;
depth, profile, and areal distribution of contamination;
partitioning of waste constituents between solvent(s) and soil;
effects of flushing agent (solvent) on soil physical, chemical, and biological properties;
suitability of site to flooding and installation of wells and/or subsurface drains;
trafficability of soil and site.
Sources of Information
Botre, C, et al., 1978; U.S. EPA, 1982, 1983.
3.3 IMMOBILIZATION
3.3.1 Sorption
The sorption of a pollutant refers to processes which result in a higher concentration of the chemical at the surface
or within the solid phase than is present in the bulk solution of soils. Actual sorption mechanisms are often not known.
Sorption is the major general retention mechanism for many organic compounds and metals. Adsorbed compounds or
ions are in equilibrium with the soil solution and are capable of desorption (Bonazountas and Wagner. 1981).
Several processes are involved in sorption including:
ion exchange.
physical sorption through weak atomic and molecular interaction forces (van der Waal Forces).
37
-------
specific adsorption exhibited by anions involving the exchange of the ion with surface ligands to form-
partly covalent bonds, and
chemisorption involving a chemical reaction between the compound and the surface of the sorbent.
We will discuss ion-exchange separately as another immobilization technology in Section 3 3.2.
Soil sorption is perhaps the most important soil-waste process affecting immobilization of toxic and recalcitrant
tractions of hazardous wastes. Leaching potential and the residence time in soil for constituents which undergo
degradation are directl> affected by the extent of immobilization.
The sorption process is usually described b\ an adsorption isotherm, which expresses the relationship between the
amount of constituent adsorbed onto a solid (soil, activated carbon, zeolite, organic matter, etc ). and the concentra-
tion of solute in solution at equilibrium One frequently used relationship is the Freundlich isotherm, which is
expressed as.
S = KCN (3-1)
where
S = amount of constituent adsorbed per unit drv weight of soil.
K and N are constants, and
C = solution phase equilibrium concentration
The percentage sorbed under natural moisture conditions can be estimated by.
100
% sorbed =
where 9 = fraction soil moisture content (weight basis). When the sorption is linear. N = I. and the percent sorbed is
not a function of the amount sorbed per unit weight of soil (S) However, when the sorption is not linear, the percent
sorbed becomes a function of S. Figure 3-2 shows the percent of chemical sorbed as a function of K values and for
different S values
Desorption of constituents is also important in affecting treatment effectiveness through the extent of release of
chemicals from soil into percolating water moving through the soil. Generally the extent of desorption follows the
Freundlich isotherm, but with constants different from the ones used for adsorption. This is due to hysteresis of a soil
system exhibited during the sorption-desorption cycle Factors directly associated with desorption include the amount
of leachate (soil/water ratio) and the amount of constituent contaminating the soil (soil/constituent ratio). The extent of
desorption will decrease with an increase of these ratios.
Treatment techniques to enhance immobilization of constituents by controlling or augmenting the sorption
process in soils have been developed based on fundamental principles and applied land treatment techniques. These
treatment techniques also provide engineering management tools for affecting treatment of constituents through
degradation, especially biological degradation.
Because the mechanisms involved in the sorption of organics are significantly different from that of heavy metals.
we will discuss these two groups separately.
38
-------
Figure 3-2. Extent of sorption as a function of amount sorbed and K for 6 = 0.1 and N = 0.9.
100 r-
90
T3
I
o
c
O)
u
OJ
D.
80
Legend:
d Soil Moisture Content, = 0.1
Weight Basis
N Freundlich Isotherm =0.9
Exponent
S Amount Sorbed Per Unit
Weight of Soil, /ig/g
B= 0.1
D = 1.0
A= 10
o= 100
0 5 10 15
Value of the Freundlich Isotherm Constant, K
Source: Mahmood and Sims, 1984.
20
3.3.1.1 Heavy Metals Addition of Sorbents
Many heavy metals have a strong affinity for organic matter. The retention of added metals is often well
correlated with soil organic matter Metals are readily chelated and/or complexed by functional groups in organic
matter These include -COOH. phenolic, alcoholic and enohc-OH and carbonyl (C = O) structures of various types.
The stability of these metal-organic complexes increases with pH due to the increased lomzation of the functional
groups. Sorption processes are affected by 1) pH. 2) competing cations. 3) solvent present in a complexed waste. 4)
presence of chelating agents. 5) solution ionic strength, and 61 types of unions present in the soil solution.
Theoretically, the addition of organic matter to a contaminated soil should remove metals from the soil solution.
thus preventing their leaching in groundwater. Organic materials most conducive for use with soils include.
agricultural products and by-prod.ucts. and activated carbon.
39
-------
3.3.1.1.1 Addition of Agricultural Products and By-products for Heavy Metals
Description
The use of various agricultural products and by-products, such as s-trav\A sawdust, peanut hulls, and bark, for the
removal of heavy metals from vvastewater solutions has been recently suggested by Larsen and Schierup (1981) and
Henderson et al. (1977 a.b) Larsen and Schierup ( 198 1) found that 1 gram of barley straw was able to adsorb amounts
ot Zn. Cu. Ph. Ni. and Cd ranging from 4 3 to 15 2 mg. while pine sawdust removed 1.3 to 5 0 mg. The selective
order of metal sorption tor straw was Pb > Cu > Cd = Zn S Ni The concentration of metals and the pH value of the
metal solutions also affected the amount of metals sorbed The obv lous advantage of the use of waste organic materials
compared to the use of other sorbmg materials, such as activated carbon, is the lower cost involved when organic
waste materials are used.
Agricultural products and by-products (e.g . animal manures, plant residues, and food processing wastes) have
been used extensively as soil conditioners. Sewage sludge and animal manures have been used as fertilizer sources and
as soil conditioners. The use of such waste materials for the removal of metals in soils has not-been extensively
studied.
Sewage sludges from municipal areas often contain high concentrations of heavy metals themselves. The use of
such sludges should be avoided. Waste materials may also contain soluble organic matter that chelates metals and
increases their mobility. More research is needed to identify the extent of increased mobility Other factors also affect
the sorption of metals, including the presence of competing cations and the ionic strength of the soil solution.
To obtain maximum sorption of metals by organic matter, soil pH must be adjusted and/or maintained at greater
than 6.5. The addition of organic materials may result in a decreased pH. requiring continued pH adjustment.
Wastes Amenable to Treatment
Heavy metal wastes and organic wastes are amenable to treatment by the addition of organic materials. This
discussion is devoted to heavy metals
Status of Technology
Addition of agricultural materials has been used in the field for soil conditioning. In the laboratory, it has been
conceptually evaluated for use in the removal ot metals from wastewater.
Ease of Application
The quantity of organic material required cannot be predicted from stoichiometnc relationships. Laboratory
sorption studies are required. Liming may be required to maintain the pH of the soil system at greater than 6.5. The
application process may be easy to difficult depending on the trafficabihty of the site and the depth of contamination.
Thorough mixing is required for maximum waste and organic material contact. Because tilling is used, erosion control
techniques may have to be implemented
Potential Achievable Level of Treatment
This is an effective method for removal of metals from wastes However, agricultural products and by-products
are highly susceptible to microbial activity. Degradation of the materials may result in the release of metals. The long-
term level of treatment achievable is probably much smaller than in the short-term unless treatments are repeated.
40
-------
Reliability of Method
As mentioned above, the mineralization of the organic materials may result in the release of the sorbed metals.
Repeated treatments may be necessary periodically. Reliming is likely to be a necessity as well, since mineralization of
the orgamcs would tend to reduce the pH of the soil system. Another important factor is the potential competition ot
the metals with orgamcs which are also sorbable on organic materials.
Secondary Impacts
Organic materials may alter the properties of the soil system including:
degree of structure:
water-holding capacity:
bulk density:
immobilization of nutrients, hindering degradation of organic wastes:
reduction in soil erosion: and
soil temperature.
Organic materials may also result in excessive nitrate levels in receiving waters, depending on the nitrogen
content and degree of mineralization of the material. Since tilling is used to incorporate the organic material into the
soil, wind and water erosion may effect the soil surface adversely.
Equipment and Exogenous Reagents
The equipment used are power implements, tillers, and applicators. Organic material and liming materials are the
exogenous reagents required.
Information Requirements
characterization and concentration of metals present in waste;
depth, profile, and areal distribution of contamination;
soil pH;
adsorptive selectivity and capacity of organic material for metals at the site;
soil biological activity (mineralization potential of organic material); and
trafficability of soil and site.
Sources of Information
Bonazountas,M., and Wagner, J., 1981; Brown, L.S., 1972; Coffey, D.L., and Warren, G.R., 1969; Coun. for
Agri. Sci. &Tech., 1975; Damanakis, M., et al., 1970; Jacobs, L.W., 1977; Ko, W.H., and Lockwood, J.L., 1968;
Shin, Y.,etal., 1970; Tames, R.S., and Hance, R.J., 1969; Taylor, J.M., et al., 1980; U.S. EPA, 1976, 1977, 1978,
1980 1981; Voerman, S., and Tammes, P.M. 1969; Walker., A., and Crawford, D.V., 1968.
41
-------
3.3.1.1.2 Addition of Activated Carbon for Heavy Metals
Description
In water and wastewater treatment, most of the research and development effort related to the use of activated
carbon is oriented toward organics, with relatively little attention being given to inorganics, specifically heavy metals.
The soil literature lacks information on the use of activated carbon as a treatment method. The following discussion is
based on the use of activated carbon in water treatment.
Several factors can contribute to heavy metal removal capability of activated carbon: 1) specific surface area, 2)
pore size and distribution, and 3) surface chemical properties. Huang and Ostoric (1978) suggested that the chemical
reactivity of the surfaces is of major importance. They found that, in general, powdered activated carbon (e.g., Nuchar
S-N and Nuchar S-A) has a low pH at the zero point of charge (zpc) (Table 3-2) and excellent sorption capacity for
heavy metals. Granular activated carbon (e.g., Darco HD 3000 and Filtrasorb 400), having a high pHzpc is rather poor
for metal ion adsorption. The pHzpc value reflects the acidic nature of surface functional groups.
The effect of solution pH on Cd sorption by Nuchar-SA is illustrated in Figure 3-3. The data were obtained from a
batch equilibrium study using a synthetic Cd-fluoroborate-plating wastewater and activated carbon (Huang and Smith,
1981). The initial linear segments illustrate that sorption of Cd by Nuchar-SA increases with pH. Above pH 6 to 7,
precipitation reactions, CdCO3 and Cd(OH)2, become the major mechanism of removal of Cd from solution.
Precipitation reactions have long been used as the method of removing metals from wastewatesr. Precipitation is often,
however, a kinetically slower process than sorption.
Larsen and Schierup (1981) found that granular activated carbon removed from solution 6.2 to 19.5 mg of Zn,
Cu, Pb, Ni, and Cd per g of carbon.
Figure 3-4 illustrates the extent of Cd sorption as affected by the carbon to cadmium ratio. Huang and Smith
(1981), using these data, recommended a carbon-to-metal ratio of 0.25 g/mg at pH 7 for maximum efficiency of
removal of Cd from wastewater. Work by Pillie et al. (1975) indicates that carbon-to-metal ratios of 0.1 g/mg are
needed for maximum efficiencies in treating wastewater. Soils may require ratios in excess of this amount because
sorption is affected by numerous factors, such as the presence of chelating agents, competing cations, and ionic
strength of the soil solution. Sorption of metals by activated carbon occurs over a wide pH range, with maximum
efficiency atapH greater than 6.5. Adjustment of the pH of acid soils with liming materials maybe necessary.
TABLE 3-2. TYPICAL SURFACE PROPERTIES OF ACTIVATED CARBONS
Carbon Type Specif ic Surface Area Particle Size PHzpc
(m2/g) (mm)
Nuchar S-N
Nuchar S-A
Darco HD 3000
Filtrasorb 400
1400-1800
1400-1800
550-650
941
0.04-0.10
0.03-0.10
0.84-4.75
0.90-1.00
5.84
3.84
a
7.10
a. Value not determined, but estimated to be 5-7 based on comparison with values
of other Darco brand granular carbons and observations of pH drift in various solution.
Source: Huang and Smith, 1981. (See Copyright Notice)
42
-------
Figure 3-3. Adsorption characteristics of Cd(ll) from synthetic
Cd(ll)-plating wastewaters (Cd-BF^ solution) as
affected by pH.
250
200
150
O)
2
=5.
5 M Cd
M Cd
M Cd
M Cd
M Cd
M Cd
Cd BF4 Solution
NucharS-A (2.0 g/L)
-0.1 M NaCIO4
Reaction Time = 2 hrs
Room Temperature
05x 10
Q 1 x 10
A2 x 10
O3 x 10
-O4 x 10
V5 x 10
0
8
34567
pH
Source: Huang and Smith, 1981. (See Copyright Notice)
10
Figure 3-4. Extent of Cd(ll) adsorption as affected by carbon/
cadmium ratio at various pH.
O
a
100
80
60
40
20
T
_L
_L
T
pH 4
Cd BF4 Solution
500 ml Suspension
Nuchar SN
Original Cd-conc. = 1 x 10"
0.1 M NaCI04
Room Temperature
M
J_
_L
_L
0
.050
.100
.150
.200
.250
.300
C/Cd (g/mg)
Source: Huang and Smith, 1981. (See Copyright Notice)
43
-------
Activated carbon should be relatively resistant to degradation in the soil environment.
Wastes Amenable to Treatment
Heavy metal wastes (and organic wastes) are amenable to treatment with activated carbon.
Status of Technology
This technology is used conventionally in wastewater treatment, but its use in soil treatment is still conceptual in
nature.
Ease of Application
Liming may be necessary to keep the soil in the pH range of optimum sorption. The application of this technology
is easy to difficult, depending on the trafficability of the soil and site and the depth of contamination. Thorough mixing
is required for maximum contact between the waste and the activated carbon. Because of the tilling that is required for
incorporation of the activated carbon into the soil, controls to prevent erosion from runoff and controls for runon may
have to be installed, depending on the site.
Potential Achievable Level of Treatment
This technology has been effective in wastewater treatment. However, removal efficiency is metal-specific. The
potential achievable level of treatment for metals in soil is unknown because of competition with orgamcs and because
of the number of complicating variables in the soil system.
Reliability of Method
The reliability of this method is unknown. Desorption may be a problem in the long term because of competition
for the activated carbon by organics in the soil. Also, changes in pH in the soil will affect the sorption. Reliming may
be necessary to keep the metals adsorbed on the activated carbon.
Secondary Impacts
Tilled soils are usually more susceptible to water and wind erosion.
Equipment and Exogenous Reagents
The equipment needed includes power implements, tillers, and applicators. Activated carbon and liming
materials are the exogenous reagents used.
Information Requirements
characterization and concentration of metals present in waste;
depth, profile, and areal distribution of contamination;
soil pH;
adsorptive selectivity and capacity of activated carbon for metals at site;
zero point of charge of activated carbon;
trafficability of soil and site.
Sources of Information
Huang and Astoric, 1978; Huang and Smith, 1981; Pillie et al., 1975.
44
-------
3.3.1.2 Heavy Metals Chelation with Tetren
Description
Metals will react with tetraethylenepentamine (tetren) to form stable metal chelates. Most chelating agents, such
as EDTA, will increase metal mobility in soils and their use is to be avoided. Metal complexes with tetren are,
however, strongly sorbed by soil clays, thus immobilizing the metal by enhancement of the natural soil sorption
system. Smeulders et al. (1983) showed that the use of tetren increases the extent of metal sorption by soil clays. Their
study indicated that the addition of tetren to a clay soil ensures the nearly complete sorption of rather large doses of Cu,
Zn, Ni, and Cd, with efficiencies comparable to those for specific adsorption (which is restricted to a very small
fraction of the exchange capacity).
To be effective, tetren must be applied to a soil relatively high in clays. Tetren-metal complexes are not sorbed by
soil organic matter. If tetren is applied to an organic soil low in clays, the tetren-metal complex will remain in the soil
solution and will be susceptible to leaching.
It is possible that the utility of tetren in adsorption to clay-like soils is due to the presence of metallic ions, such as
iron, in the clay. To obtain a better understanding of the long-term stability of the tetren-metal complexes, it will be
necessary to determine the prevalent form(s) of the complex for each metallic species.
It is possible, for example, to form a complex with a metal ion in which several of the amine groups in one tetren
molecule are bonded to the same metal ion. Alternatively, only the terminal amine group (or possibly only the
secondary amine groups) may be available for coordination to the metal of interest. The question of single versus
multiple coordination of the amines to the metal of interest is extremely important, since it directly affects the effective
stability of the resultant complex. For example, if multiple amines are coordinated to a single metal ion, exchange
processes that remove only one amino group will not result in mobility of the metal ion. Indeed, if it is held by the
remaining amino group coordination, subsequent exchange to permit recomplexation of the displaced amine group is
still possible.
In addition, the question of complex type is also important with respect to adsorption to the clay materials. The
higher the number of amine groups that are complexed to the clay substrate, the fewer there are available for the metal
ion of interest. Tetren is a molecule which maximizes the number of amine groups available for metal complexation in
a small stereochemical area, and deserves further study as a fixation method for metals known to form strong amine
complexes.
The stability of tetren-metal complex against decomposition or degradation is not yet known. More research is
also needed on soil factors affecting metal complexation with tetren and resulting sorption by clays, including soil
moisture, pH and the ionic strength of the soil solution.
Wastes Amenable to Treatment
Heavy metal wastes are amenable to treatment with tetren. Tetren will likely form strong complexes with those
metallic species that interact strongly with amines.
Status of Technology
There have been limited studies in the laboratory and greenhouse. It is still at the conceptual stage in the field.
The stability of the tetren-metal complex against decomposition and degradation is not yet known. The soil factors
affecting metal complexation with tetren and the resulting sorption of the complex by clays are not well understood.
These soil factors probably include soil moisture, pH, and the ionic strength of the soil solution.
45
-------
Ease of Application
Tetren should be added in sufficient amounts for the formation of a 1:1 complex with the metals present. To
ensure the formation of such a complex, a ratio of at least 1:1.15 metal/tetren is advisable. Addition of clay materials
may be necessary to increase sorption of tetren-metal complex. Liming may also be necessary if the soil is too acidic.
The application may be easy to difficult, depending on the trafficability of the soil and the site and the depth of
contamination. Thorough mixing is required for maximum contact between the waste and the tetren. Erosion and
runon controls may be necessary because the tilling of the site may increase its susceptibility to erosion.
Potential Achievable Level of Treatment
The achievable level of treatment is potentially high, depending on the characteristics of the soil at the site and the
complexation capacity of tetren for the metals present at the site.
Reliability of Method
The stability of the tetren-metal complex is not yet known. Also, its interaction with soil factors like soil
moisture, pH, and soil ionic strength is not known. These uncertainties affect the predictability of the tetren-metal
complexation effectiveness in soil. If tetren is applied to a soil low in clays, the tetren-metal complex will remain in
solution and be susceptible to leaching. In general, this technology cannot be considered reliable at the present time.
Secondary Impacts
Tilling of the soil to incorporate the tetren may increase the susceptibility of the site to erosion by wind and water.
Equipment and Exogenous Reagents
Equipment needed for the application of this technology includes power implements, tillers, and applicators.
Tetren and liming materials are required. If the soil at the site is low in clay, it might be necessary to incorporate clay
as well.
Information Requirements
characterization and concentration of metals present in waste;
depth, profile, and area! distribution of contamination;
soil pH;
complexation capacity of tetren with metals at site;
clay content of soil at site;
organic matter content of soil at site;
degree of sorption of tetren-complex with soils at site;
trafficability of soil and site.
Sources of Information
Smeulders et al., 1983.
3.3.1.3 Organics Reduction of Soil Moisture
Description
Controlling the moisture content of a soil can be utilized to immobilize constituents in contaminated soils, as well
as allowing for additional time to accomplish biological degradation. Where immobilization of constituents using this
46
-------
technique is to. be followed by anaerobic decomposition in a treatment train, anaerobiosis must be achieved with
techniques other than flooding, such as soil compaction or organic matter addition.
Using the Freundlich isotherm, discussed previously, the percent sorbed under natural moisture conditions can be
estimated by using Equation 3-2 (see subsection 3.3.1). When N is equal to 1 (i.e., linear isotherm). Equation 3-2
becomes:
100
9r sorbed =
(e/Kd)
(3-3)
where Kd is the distribution coefficient of the chemical between soil and soil water and 0 is the soil moisture
content (weight basis). Figure 3-5 shows percent sorbed as a function of Kd for different values of 0.
From Figure 3-5, it is seen that with lower moisture content, the percent of adsorbed chemical is higher.
This is especially important for constituents with relatively small Kd values, i.e., constituents not
strongly sorbed to soil. When the adsorption isotherm is nonlinear (N < 1) for a given amount sorbed
per unit weight soil (S), controlling soil moisture will also follow the same trend as in the case of the
linear isotherm, as shown in Figure 3-6.
Figure 3-5. Extent of sorption as a function of soil moisture 9 and
90
"8
O
GO
c
-------
o>
_Q
O
to
-M
c
V
o
u.
OJ
Q.
90
80
70
60
50
40
30
20
Figure 3-6. Extent of sorption as a function of amount sorbed and K for a
range of moisture contents and IM = 0.7.
100 _
Freundlich Isotherm = 0.7
Exponent
Amount Adsorbed Per Unit =100
Weight Of Soil, M9/g
Soil Moisture Content,
Weight Basis
A = °-1
= 0.2
O = 0.4
I
10 20
Value of the Freundlich Isotherm Constant, K
30
Source: Mahmood and Sims, 1984.
48
-------
Wastes Amenable to Treatment
This technology is more effective for those organics that are not strongly sorbed (K
-------
3.3.1.4 Organics Addition of Sorbents
Organic matter can be used to sorb organics in soil. Sorbents may immobilize the organic constituents, and may
also allow additional time for further treatment by biodegradation. Addition of an adsorbent is also useful for relatively
"immobile" compounds if cracks and fractures exist in the soil which may increase the potential for mobilization and
groundwater contamination. The sorbents which can be used in soils include agricultural products and by-products.
sewage sludges, other organic matter and activated carbon.
3.3.1.4.1 Addition of Agricultural Products and By-Products, Sewage Sludges, and Other
Organic Matter
Description
Addition of organic matter including sewage sludge, agricultural products and by-products, and organic soil
materials to a site/soil/waste system increases the organic content of tjae soil. This is useful both for waste attenuation
(see Section 3.5) and for immobilizing organics in wastes by sorption. Addition of organic matter for increasing the
sorption capacity for toxic constituents is especially important and effective in soils with low organic matter content,
such as sandy and strip-mined soils.
Sludge may be defined as a semi-liquid waste having a suspended solid content ranging between 0-25 percent dry
solids. Sewage sludges are generated by different processes during wastewater treatment. They may be classified
either according to stage of treatment (e.g., primary, secondary, tertiary), or according to the process by which the
sludges were produced (e.g.. activated, digested, etc.). Municipal sludges contain organic and inorganic fractions with
90 percent by weight or more water. Average sludge characteristics of primary and digested sludge are shown in Table
3-3. However, it should be realized that sewage sludge characteristics are quite variable, depending on the source and
type of industries associated with the makeup of wastewater (Table 3-4).
Additional advantages of using municipal sludges in organic waste treatment are:
1. Sewage sludges contain active indigenous populations of micro-organisms with degradative potential.
This enhances the possibility of degrading toxic constituents.
2. Sewage sludges provide necessary nutrients for biodegradation.
A major disadvantage of using sewage sludges is that the heavy metal content of the sludge may increase potential
for groundwater pollution. Therefore, careful management practices are required in terms of application rates of
sludges that have high levels of heavy metal. Table 3-5 shows the accumulation of metals allowed in agricultural land
(assuming it is safe with respect to leaching), based on the cation exchange capacity (CEC) of the soil.
Organic materials have been added to soil systems to increase sorptive capacity for pesticides. Walker and
Crawford (1968) added straw to different soils and noticed an increase in adsorption of four s-triazine herbicides
(atrazine, propazine, prometone, and prometryne). The application rate to achieve immobilization was the amount
necessary to raise the organic matter content of soil to 2.5 percent. If an organic content of soil of 0.5 percent is
assumed, the amount of straw needed is 2 percent or 20,000 ppm, and if a 6-inch depth of incorporation is assumed,
the application rate is 45 tons/hectare. The adsorption capacity of soil mixed with the straw remained constant for 81
weeks.
Other materials that have been investigated include plant roots, muck soil, fungal mycelium, and baker's yeast.
Tames and Hance (1969) have shown that the addition of freshly killed roots of five plants (oats, beans, peas,
cucumber, and radish) to soil increased its adsorptive capacity. The study was conducted with the herbicides atrazine,
diuron. linuron, and monohnuron. The adsorptive capacity of the plant roots, however, was less than the capacity of
soil organic matter. Coffey and Warren (1969) used a muck soil in the adsorption of several herbicides. With low
50
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TABLE 3.3. AVERAGE CONCENTRATION OF CONSTITUENTS IN PRIMARY
AND DIGESTED SLUDGES FROM 33 U.S. TREATMENT PLANTS.
Constituent
Raw or Primary
(geometric mean8)
Digested or Stabilized
(geometric mean')
Nitrogen
Phosphorus
Sulfur
Boron
Cadmium
Cobalt
Copper
Mercury
Manganese
Nickel
Lead
Silver
Strontium
Zinc
% Volatile Solids
Btu/lb (heat of
combustion)
mg/kg except where noted
80,000
9,070
3,100
775
27
410
740
8.2
460
420
1,150
355
175
1,740
74.4
7,910
37,100
16,700
6,010
380
4.3
290
1,270
6.5
475
530
2,210
190
290
2,900
51.9
5,850
a. The nth root of the product of n observed values.
Source: Jacobs, L.W., 1977.
51
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TABLE 3-4. ELEMENTAL ANALYSES OF TREATMENT PLANT SLUDGE SAMPLES
EXPRESSED AS RANGES ON A DRY WEIGHT BASIS
(in mg/kg)a
Chemical Domestic Industrial and Domestic Industrial
Element Wastewaters Wastewaters Wastewaters
Phosphorus
Calcium
Magnesium
Potassium
Sodium
Iron
Aluminum
Zinc
Copper
Nickel
Cadmium
Manganese
Chromium
Cobalt
Lead
Silver
Strontium
Beryllium
Vanadium
Barium
Boron
Mercury
2,900-19,600
4,100-120,000
500-5,400
400-6,000
200-7,000
2,300-12,600
3,800-13,400
1,000-1,800
95-700
1 1 0-400
<1 0-400b
100-300
50-200
20-<400
200-<500
7-100
100-200
<10-<100
<500- 1,000
600-1,000
50-400
1.0-11.2
1 1 ,000-22,800
13,200-40,000
2,700^,300
700-1,700
500-2,300
15,320-47,600
3,850-12,000
800-4,600
960-2,300
200-900
90-240
500-6,100
260-2,650
400-500
760-2,790
20-300
100-1,600
<10-<100
<200-500
700-1,350
c
2.6-5.0
12,700-38,300
32,000-128,000
3,000-7,600
1,600-4,000
800-5,400
64,500-225,000
10,800-70,000
3,200-14,000
1,640-4,700
440-2,800
<40-200
640-6,100
1,240-2,700
<40-500
1,280-8,300
200-1,680
80-2,100
<40-<100
100-2,000
2,600-6,400
c
0.6-3.0
a. EPA analysis data - sludges collected from four plants for each type of wastewater received,
12 treatment plants in all.
b. An unusually high value for Cd obtained from only one sludge source.
c. Analyses not included.
Source: Jacobs, L.W., 1977.
52
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TABLE 3-5. TOTAL AMOUNT OF SLUDGE METALS ALLOWED
ON AGRICULTURAL LAND
Metal
Soil Cation Exchange Capacity (meq/100g)a
<5 5-15 >15
Maximum amount of metal (Ib/acre)
Lead (Pb)
Zinc (Zn)
Copper (Cu)
Nickel (Ni)
Cadmium (Cd)
500
250
125
50
5
1,000
500
250
100
10
2,000
1,000
500
200
20
aDetermined by the pH 7 ammonium acetate procedure.
Source: Jacobs, L.W., 1977.
Herbicide
TABLE 3-6. EFFECT OF INCREASING THE CONCENTRATION OF MUCK SOIL
AND BENTONITE CLAY ON THE ADSORPTION OF HERBICIDES
Concentration of Herbicide in ppm to Give 50%
Root Inhibition of the Test Plant
Control 0.01% 1.0%
(No Adsorbent) Muck Bentonite Muck Bentonite
2,4- D
DNBP
Amiben
DCPA
Dipheramid
0.12
30
6.8
10.5
1.4
0.13
37
6.8
10.5
1.4
0.12
34
8.3
10.5
1.4
0.43
83
11
38
4.3
0.12
36
8.3
10.5
5.1
Source: Coffey, D.L., and Warren. G.F., 1969. (See Copyright Notice)
adsorbent concentrations added to the growth medium (0.01 percent), negligible adsorption was observed for muck
soil. However, when the concentration was increased to 1.0 percent, adsorption was increased for muck soil (Table 3-
6). Ko and Lockwood (1968) have shown that addition of living mycelium (R. Solani) to oxidized soil restored its
ability to immobilize PCNB and dieldrin. Shin et al. (1970) also demonstrated the beneficial effect of myceha (R.
Solani) on soil sorption of DDT. Voerman and Tammes (1969) demonstrated effective sorption of lindane and dieldrin
by baker's yeast. With yeast and mycelia cells, nonliving cells exhibited greater sorption capacity than living cells.
53
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Wastes Amenable to Treatment
Organics are amenable to sorption by organic materials.
Status of Technology
Laboratory studies have been conducted demonstrating the sorptive capacity of various organic materials.
Ease of Application
Organic material may be ground, if necessary, and applied to the soil surface or injected below the surface and
thoroughly mixed with the contaminated soil. Controls to prevent runoff and runon of precipitation may be necessary.
This technology is therefore easy to difficult to apply, depending on the trafficability of the soil and site and the depth
of contamination.
Potential Achievable Level of Treatment
The level of treatment achievable is potentially high.
Reliability of Method
Periodic treatment may be required if wastes are recalcitrant Mineralization of organic materials may release
waste constituents if the additives biodegrade more quickly than the waste.
Secondary Impacts
Organic materials may affect soil properties, including:
degree of structure;
water-holding capacity:
bulk density:
immobilization of nutrients, hindering degradation of organic wastes;
reduction in soil erosion potential;
soil temperature.
Organic materials may also result in excessive nitrate levels in receiving waters, depending on the nitrogen
content and degree of mineralization of the material. Tillage may make the site more susceptible to water and wind
erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are required. Organic materials are the only exogenous reagents
required.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
depth, profile, and areal distribution of contamination;
adsorption isotherm constants for specific added organic material (K, N);
soil pH;
soil biological activity (soil C:N:P ratio, soil oyxgen content, soil moisture, etc.);
trafficability of soil and site.
54
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Sources of Information
Jacobs, 1977; Walker and Crawford, 1968; Tawes and Hance, 1969; Coffey and Warren, 1969; Ko and
Lockwood, 1968; Shin et al., 1970; Voerman and Tammes, 1969.
3.3.1.4.2 Addition of Activated Carbon for Organics
Description
Activated carbon is a very strong sorbent for certain classes of chemicals and has been used extensively in
industrial and advanced domestic wastewater treatment processes. The aggregate structure of activated carbon (i.e.,
the pores distributed as macropores (channels) and micropores (capillaries)) enhances its ability for adsorption.
Powdered activated carbon is the preferred form because of its high surface area to mass ratio (1000 m2/g). Per unit
mass of activated carbon, the powder form offers the advantages of maximum rate of sorption, ease of mixing with the
soil, and maximum extent of contact of waste constituents with carbon.
One assumption used to determine an application rate for activated carbon is that the amount of activated carbon
needed to make constituents unavailable for plant uptake will be enough to immobilize the constituent. Use of this
assumption allows a starting point based on several examples from the literature for short-term treatability studies with
site/soil/waste systems. However, it should be recognized that the amount of activated carbon required varies with type
and amount of constituent and plant involved. Much more research is required with hazardous waste constituents in
different site/soil/waste conditions to develop a useful data base for designing efficient treatability studies and for
determining effective activated carbon application rates.
Activated carbon has been used to reduce phytotoxicity and uptake of pesticides from soil by crops (Ahrens and
Kring 1968; Andersen 1968; Lichtenstein et al., 1968; Coffey and Warren, 1969; Gupta. 1976, Weber and Mrozek.
1979; Strek et al., 1981). Application rates for the compounds used in these studies including PCB's, aldnn. dieldnn.
heptachlor, heptachlorepoxide, atrazine, monuron, bromacil, DPCA, DMPA, C1PC, and trifuralin, varied from 1 to 7
metric ton/hectare. Cost calculations were based on high application rates. For pesticide chemicals, it was demon-
strated that activated carbon was more effective on non-ionic compounds, and that adsorption was sustained for long
periods of time, with negligible desorption. However, for ionic compounds, desorption may be significant
Requirements for activated carbon for other constituents (kg activated carbon per kg constituent) are 10-20 kg/kg
for toluene and 10-100 kg/kg for sodium dodecyl benzene sulfonate (Jensen, 1982). Activated carbon sorption for a
large number of energy processes related pollutants, based on the Freundlich isotherm model, is included in the U.S.
EPA publication, "Carbon Adsorption Isotherms for Toxic Organics" (Dobbs and Cohen, 1980).
Wastes Amenable to Treatment'
Organic wastes, particularly high molecular weight compounds with low water solubility, low polarity, and low
degree of ionization, are amenable to treatment with activated carbon. This treatment has been used on pesticides.
Activated carbon is more effective with non-ionic than ionic compounds. Highly water soluble organics, which often
contain two or more hydrophilic groups, are difficult to remove using activated carbon.
Status of Technology
In the field, activated carbon has been used to immobilize pesticides and herbicides in soils. The long-term
physical and chemical stability of activated carbon in soil systems is unknown.
55
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Ease of Application
Activated carbon may be applied to the soil surface and thoroughly mixed. Wind conditions must be assessed
during application to avoid blowing of carbon. The carbon should be applied during periods of low wind activity or
wetted before application. Alternatively, the carbon may be injected below the soil surface and then thoroughly mixed
with the soil. Activated carbon has been used to immobilize pesticides at rates of 1-7 metric ton/hectare. The ease of
application depends on the trafficability of the soil and the site and the depth of contamination. Controls to prevent
runoff and runon may be necessary because erosion could be a problem.
Potential Achievable Level of Treatment
The level of treatment achievable is dependent on the sorptive capacity of activated carbon for the specific waste
constituents present at the site and the extent of contamination. The treatment achieved may range from low to high.
Reliability of Method
As mentioned earlier, the long-term physical and chemical stability of activated carbon in soil systems is
unknown. Because it has been used in the field successfully for pesticides, it may be considered reliable at least in the
short run. Desorption may be a problem for ionic compounds because of competition with non-ionic compounds which
may be present in the soil.
Secondary Impacts
Immobilization of organics by activated carbon may adversely affect the rate of biodegradation in soils. Tillage
will increase the susceptibility of the site to water and wind erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are needed to apply the activated carbon.
Information Requirements
characterization and concentration of wastes, particularly organic at site;
depth, profile, and areal distribution of contamination;
soil pH;
adsorptive selectivity and capacity of activated carbon for metals at site;
adsorption isotherm constants (K, N) for specific waste constituents;
trafficability of soil and site.
Sources of Information
Ahrens, J.F., and Kring, J.B., 1968; Andersen, A.M., 1968; Lichenstein, E.P., et al.. 1968; Coffey D.L., and
Warren, G.F., 1969; Gupta, O.P., 1976; Weber, J.B., and Mrozek, Jr., E., 1979; Strek, H.J., et al., 1981; Jensen,
R.A., 1982; Dobbs, R.A., and Cohen, J.M., 1980.
3.3.2 Ion Exchange
Ion exchange is a process in which certain minerals and resins in contact with a solution, particularly an aqueous
one, release ions in preference for ions of another type present in the solution. Clay minerals in soil can remove cations
in exchange for an equivalent amount of calcium. Ion exchangers can be classified into two principal types: cationic
and anionic. Cation exchangers have replaceable cations which are exchanged for other cations in the waste.
56
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TABLE 3-7. CATION EXCHANGE CAPACITY (CEC)
FOR VARIOUS MATERIALS
Material CEC Value (m.e./100g)
Humus
Montmonllonite
Vermiculite
Hydrous Mica and chlontes
Kaolinite
Hydrous oxides
200
100
150
30
Source: from Brady, N.C., 1974.
Correspondingly, anion exchangers have replaceable anions which are exchanged for other anions in the waste. Three
types of ion exchangers will be discussed below as technologies usable in soils for immobilization of pollutants in soil.
They are: clays, synthetic resins, and zeolites.
3.3.2.1 Addition of Clays
Description
Clays have high surface areas and are especially effective in immobilizing cationic compounds. A mixture of clay
and organics could be used for wastes containing both ionic and hydrophobic compounds. The cationic exchange
capacity (CEC) of a soil is usually defined as the number of milliequivalents of the ion that can be exchanged per lOOg
dry weight of soil. With clays, the exchanged ion is often calcium:
M++ + [clay] . Ca ^ Ca++ + [clay] . M (3-4)
Among soils, humic material and clays tend to have the highest CEC values. Typical CEC values for various materials
are shown in Table 3-7. Brady (1974) also showed a range of CEC values between 2-60 m.e./lOOg for various soils.
The cation exchange capacity is variable in a particular soil; in most soils the exchange capacity increases with pH
(Brady, 1974).
Bentonite clay (primarily montmorillonite) has been used for inactivating pesticide phytotoxicity (Coffey and
Warren, 1969). Table 3-8 illustrates the sorption of herbicides by bentonite clay at a clay concentration of 25 mg/25 ml
solution. As expected for pesticides in anionic form (Weber et al., 1965), neither amiben nor 2,4-D were sorbed.
Paraquat, a strongly cationic and water-soluble chemical, was strongly sorbed by bentonite. Paraquat cations penetrate
the basal plane of the bentonite, and sorption is relatively irreversible. Hydrogen saturated montmorillonite exhibited
greater adsorption than sodium saturated montmorillonite for pesticides including S-triazines, substituted ureas,
phenyl carbamates, anilines, anilides, and picolinic acids (Bailey et al., 1968).
Wastes Amenable to Treatment
Cationic compounds, both organic and inorganic are amenable to this treatment. This technology is not effective
if the cations to be immobilized are present in the wastes in relatively low concentrations when compared to certain
other cations (e.g., Ca+ + , Na+, Fe+ +, and K + ). The latter cations may overwhelm the exchange capacity of the
clay and low concentrations of the former cations, including those with higher affinities, will not be significantly
exchanged. Landfill leachates and industrial wastes are often concentrated solutions with high total dissolved solids
content (including Na+, Ca+ + , etc.). Trace cations may not be effectively exchanged in these wastes. For heavy
metals, a high pH (greater than 7) would limit the role of ion exchange in preference for precipitation (Bonazountas
and Wagner, 1981).
57
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TABLE 3-8. CONCENTRATIONS IN PPM OF HERBICIDE SOLUTIONS ADDED TO THE
ADSORBENTS TO GIVE 50 PERCENT INHIBITION OF THE TEST PLANT
Herbicide
Tri- Di-
Adsorbent CIPC fluralin 2,4-D phenamid DCPA DNBP Amiben Paraquat
Muck soil
Bentonite
Clay
Control
(no adsorbent)
0.78
0.45
0.26
0.64
0.58
0.14
0.13
0.12
0.12
1.4
1.4
1.4
10.5
10.5
10.5
37
34
30
6.8
8.3
6.8
31.0
81.0
21.0
Source: Coffey, D.L., and Warren, G.F., 1969. (See Copyright Notice)
Status of Technology
Studies have been conducted at the laboratory stage showing immobilization of pesticides by clays.
Ease of Application
The rate of application (mass per volume of soil) is determined in short-term treatabihty studies. Clay is applied to
the soil surface and thoroughly incorporated through the depth of contamination. Runoff and runon controls may be
appropriate if erosion or drainage problems occur. This technology is easy to apply using traditional equipment and
methods. However, if the site is not trafficable, it might be difficult to apply.
Potential Achievable Level of Treatment
For certain cationic compounds, the level of treatment achievable is high. As mentioned earlier, other ions
present in the waste mixture could effectively reduce the immobilization expected.
Reliability of Method
The interactions of ions in the soil system are very complex. This technology is reliable in that the addition of clay
to a soil is likely to cause immobilization of some cations. However, the effectiveness may not be as high as
anticipated from theory or tests in the laboratory.
Secondary Impacts
Clay addition may affect the chemical, physical, and biological properties of natural soil. The extent and type of
effects are dependent on the characteristics of both native soil and added clay. Tillage will increase susceptibility of the
site to erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are necessary to incorporate the clay into the soil.
58
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Information Requirements
characterization and concentration of wastes, primarily ionic forms present;
depth, profile, and areal distribution of contamination;
cationic exchange capacity of clay;
soil pH;
selectivity of clay for cations in waste;
competing, naturally occurring ions at site;
trafficability of soil and site.
Sources of Information
Brady, N.C., 1974; Coffey, D.L., and Warren, G.F., 1969; Weber, J.B., et al., 1965; Bailey, G.W., et al.,
1968; Bonazountas, M., and Wagner, J., 1981.
3.3.2.2 Addition of Synthetic Resins
Description
Synthetic resins consist of a network of hydrocarbon radicals to which ionic functional groups are attached. These
hydrocarbon molecules are cross-linked in a three dimensional arrangement, rendering the resin insoluble. The cross-
linking of these molecules affects the pore structure of the resin. Ions penetrate these pores in order to be exchanged.
Hence, the appropriate resin allows the exclusion of a given size of ions. Synthetic resins can be: 1) those carrying
exchangeable cations (acidic), and 2) those carrying exchangeable anions (basic). The advantage of synthetic resins
over activated carbon is that they are effective in immobilizing ionic compounds. Despite the high cost and lower
sorption capacity of synthetic resins compared with activated carbon, use of synthetic resins is attractive because they
can be made selective for specific compounds. The availability and cost of resins do limit their use in large-scale
situations like those in hazardous waste sites.
Competition from ionic species found naturally in soil is a problem, decreasing the effectiveness of synthetic
resins in the real world.
Wastes Amenable to Treatment
Both organic and inorganics are amenable to treatment with synthetic resins. Cations and anions can be
immobilized on synthetic resins with the right choice of resins.
Status of Technology
Synthetic resins (cationic exchange resin, e.g., Chelex 100, and anionic exchange resin, e.g., Dowex 1-X8) have
been shown to reduce phytotoxicity of pesticides in the laboratory. Synthetic resins have been effective in removing
ionic compounds such as paraquat, DNBP, 2,4-D and amiben from solution.
Ease of Application
The rate of application (mass per volume of soil) should be determined in short-term treatability studies. The resin
is applied to the soil surface and thoroughly incorporated through the depth of contamination. Runoff and runon
controls may have to be installed to prevent erosion and drainage into the site. This technology should be easy to apply
if the depth of contamination is relatively shallow and the site is trafficable.
Potential Achievable Level of Treatment
The achievable treatment level is variably dependent on resin characteristics and competing, naturally occurring
ions in the soil.
59
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Reliability of Method
The long-term desorption and stability of resins in soil systems is unknown at the present time. This increases the
risk of this technology because of the lack of certainty and the unpredictability of the ion-exchange capacity for a
particular ion in natural soils.
Secondary Impacts
Immobilization of organics by synthetic resins may adversely affect rates of biodegradation. Tillage increases the
susceptibility of a site to water and wind erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are necessary to apply resins into the soil.
Information Requirements
characterization and concentration of waste, primarily ionic forms present;
depth, profile, and areal distribution of contamination;
ion exchange capacity of synthetic resin;
soil pH;
selective characteristics for specific ions present at site;
trafficability of soil and site.
3.3.2.3. Addition of Zeolites
Description
Molecular sieve zeolites are crystalline, hydrated aluminosilicates with chemical formulae such as
Na2Al2Si4O12. Ion exchange selectivities in zeolite do not follow the typical rules and patterns exhibited by other
inorganic or organic ion exchangers. Zeolites provide certain combinations of selectivity, capacity, and stability
characteristics superior to the more common organic and inorganic cation exchangers. Breck (1974) presents detailed
information on the properties of zeolites.
Zeolites are highly selective for particular metals. Clinoptilolite and mordenite both show selective sorption of
heavy metals (Sherman, 1978):
Clinoptilolite Cu =£ Zn =£ Cd « Pb
Mordenite Ni < Zn; and Co < Cu < Mn
The maximum theoretical cation exchange capacity for these two zeolites is 2.6 m.e./g. Zeolites have been used to
soften water.
Zeolites are stable over a wide alkaline pH range (6-12) and do not biologically degrade. The chief restriction in
the use of zeolite ion exchangers is their limited acid resistance. Most zeolite ion exchangers should not be employed
below about pH 4-5. At lower pH's, the zeolite will itself degrade. Because of this, it would be recommended that
zeolites be used only in alkaline soils or limed soils (pH greater than 6).
As with all cation exchangers, sorption of metals by zeolite is affected by 1) pH, 2) competing cations, 3) choice
of solvent, 4) presence of complexmg agents, 5) solution ionic strength, and 6) type of anicns present. The effect of
these variables upon the overall ion exchange performance of zeolites is generally less complex and more predictable
than with resin exchangers.
60
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The lack of data, both from laboratory and field studies, on the use of zeolites for metal clean-up in soils makes it
difficult to comment on possible undesirable factors that may be involved. Research is needed on potential long-term
immobilization.
Wastes Amenable to Treatment
Zeolites can be used to immobilize wastes containing heavy metals.
Status of Technology
This technology is conceptual for immobilization of heavy metals in soil systems. It has been used in agricultural
applications for retention of ammonium and potassium. Research is needed to investigate the long-term potential for
metal immobilization, although it is effective for removing heavy metals (especially cadmium, copper, lead, and zinc)
from wastewater
Ease of Application
Liming might be necessary to increase the pH to greater than 6. Thorough mixing is required for maximum
waste/zeolite contact. This technology may be easy or difficult to apply depending on the trafficability of the site and
the depth of contamination.
Practical Achievable Level of Treatment
Zeolites have been found to be effective for removing heavy metals (especially Cd, Cu, Pb, and Zn) from
wastewater. They look promising for use in soils, but research is required to investigate the long-term potential for
melal immobilization.
Reliability of Method
There are a lot of uncertainties associated with this method. At present, its reliability is unknown.
Secondary Impacts
Tillage would increase the susceptibility of the site to wind and water erosion.
Equipment and Exogenous Reagents
The equipment needed are power implements, tillers, and applicators. Zeolites and liming material are also
needed.
Information Requirements
characterization and concentration of waste, primarily ionic forms present;
depth, profile, and areal distribution of contamination;
ion exchange capacity and selectivity for metals at site;
competing naturally occurring ions at site;
soil pH;
trafficability of soil and site.
Sources of Information
Breck, 1974; Sherman, 1978; Coffey, D.L., and Warren, G.F., 1969; Weber, J.B., et al., 1965.
61
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TABLE 3-9. SOLUBILITY PRODUCT CONSTANTS FOR
METAL SULFIDES
Solubility
Product
Substance Equilibrium Constants
Sulfides
Cadmium Sulfide
Cobalt Sulfide
Cupric Sulfide
Ferrous Sulfide
Lead Sulfide
Manganous Sulfide
Mercuric Sulflde
Nickelous Sulfide
Silver Sulfide
Zinc Sulfide
CdS=Cd++ +S
CoS=Co++ +S
CuS=Cu++ +S
FeS=Fe++ +S
PbS=Pb++ +S
MnS=Mn++ +S
HgS=Hg+++S
NiS=Ni+++S
Ag2 S=2Ag+ +S
ZnS=Zn++ +S
6x 1CT27
5x 1CT22
4x 10"36
4x 1(T17
4x 1CT26
8x 1CT14
1 x10-so
1 x10-22
1 x10-50
1x1CT20
Source: Overcash, M.R., and Pal, D., 1979.
(See Copyright Notice)
3.3.3 Precipitation
Another immobilization technology for metals in soils is precipitation. Theoretically, precipitation occurs when
the solubility product of the ions forming the precipitate is exceeded in the solution. Metals may be precipitated as
sulfides. carbonates, phosphates, and hydroxides. We will discuss sulfides separately from the rest because the method
for precipitating sulfides is different from that for precipitating the others.
3.3.3.1 Precipitation as Sulfides
Description
Heavy metals will react with sulfide ions to form insoluble metal sulfides (Table 3-9). These metal sulfides have
very low solubilities, even at acidic pH values. The extent of metal sulfide precipitation is a function of 1) pH, 2) type
of metal, 3) sulfide content, and 4) interfering ions. A high salt content of the waste will reduce the theoretical extent
of precipitation.
With divalent heavy metals the important metal-sulfide reactions are:
H2S
HS~
Me2+
FT -r HS
H+ + S2~
S2~ ^ MeS
(3-5)
(3-6)
(3-7)
The solubilities of metal sulfides decrease with increasing pH (arsenic is an exception, precipitating only at pH
<5). With sulfide precipitation, a residual concentration less than 0.1 mg/1 metal (for Cd, Cu, Pb, and Zn) can be
achieved at 4 « pH =£ 12. Therefore, a single pH level may be used to remove several heavy metals.
62
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Metal sulfides are the least soluble of the metal compounds likely to form in the soil system. Competition from
other anion species present would be negligible. The high stability of metal sulfides makes it possible to precipitate
metals even in the presence of organic liquids such as chelating agents.
The kinetic aspects of dissolution and precipitation reactions involving heavy metals in the soil matrix have not
been studied in detail. Therefore, the time required for maximum precipitation is not known.
Some heavy metals will form soluble sulfide complexes: ZnS22 ~ , HgS22 ~ , HgS2H ~ , AgS ~ , and As2S22 ~ .
The complexed metal may be more mobile than the free-metal ion. Controlled additions of sulfide by accurate control
of pH or sulfide concentration may help prevent the formation of these complexes.
Wastewater treatments have employed several effective sources of sulfide. The sodium salts of sulfide (Na2S or
NaHS) are highly soluble, so that concentrated solutions of sulfide can be prepared. However, addition of Na may
have adverse effects on soil physical properties. Calcium sulfide (CaS) has been used, but must be prepared as a slurry
because of its low solubility. Iron sulfide (FeS) can additionally reduce Cr6 to Cr3 but, because of its very low
solubility, it would not be of practical use in soils as a source of sulfide.
Diking the site, adding gypsum and organic matter, and then flooding the site will provide an anaerobic
environment for the reduction of SO42~ to S2~. This process could be used to provide sulfide for precipitation in
soils having sufficiently high sulfate concentrations. However, the possibility of leaching other hazardous constituents
must be investigated.
Sulfide precipitates in a natural soil system may be an important mechanism for regulating the solution
concentration of heavy metals under reduced conditions only. Sulfides will be oxidized to form soluble metal sulfates
under aerobic soil conditions. However, there is no published literature discussing the use of sulfides for reclaiming
soils contaminated with metals.
Wastes Amenable to Treatment
Inorganic wastes containing heavy metals, particularly metals with highly insoluble sulfides like copper,
cadmium, lead, mercury, and zinc.
Status of Technology
This technology has been used in the field to treat river water and wastewaters. On the laboratory scale, there
have been additional studies with wastewater. The treatment of soils by precipitation of sulfides is purely conceptual at
the present time.
Ease of Application
Theoretically, one mole of sulfide reacts with one mole of divalent metal. At a waste site, metals are encountered
as compounds with various anions. Excess sulfide must be added to ensure that the precipitation is as complete as
possible. Calcium sulfide may be applied as a slurry and incorporated. Sodium sulfide may be applied in an irrigation
system or with sprayers. The soil must be maintained at reduced conditions. Otherwise, the oxidation of precipitated
sulfides to more soluble sulfate compounds may occur under aerobic soil conditions. Runon and runoff controls may
have to be installed depending on whether the site has been tilled.
Potential Achievable Level of Treatment
Excellent treatment of wastewaters containing copper, cadmium, lead, mercury, and zinc has been obtained for
4 =£ pH =£ 12. This technology may prove promising for soil systems, with appropriate soil conditions and careful
management.
63
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Reliability of Method
If the precipitated sulfides are subjected to aerobic conditions for long periods of time, they may be oxidized to
the more soluble sulfates and be leached from the soil into groundwater. Also, if the pH is lowered, the metals will
dissolve, releasing hydrogen sulfide. The soil conditions have to be maintained carefully if the metals are to remain as
immobile precipitates.
Secondary Impacts
The use of sodium sulfide salts may affect soil permeability. However, soils low in clays and native sodium may
be conducive to sodium sulfide treatments without adverse effects. Incomplete sulfide precipitation under reducing
conditions may result in leaching of nonprecipitated metals and other soluble constituents, and the formation of
volatile toxic metal compounds.
Hydrogen sulfide, a poisonous flammable gas with an offensive odor, may be formed in the precipitation
treatment. However, Bhattacharyya et al. (1981) found no formation of H2S gas during sulfide precipitation reactions.
They attributed this to the high reactivity of sulfides and metals. Pillie et al. (1975) noted that the use of a small amount
of NaOH prevented the evolution of H2S gas. The rate of formation of metal-sulfide precipitates in soils may be slow
in comparison with the rate in water. The likelihood of the evolution of H2S will increase as the reactivity of sulfides
and metals decrease. Hydrogen sulfide is neutralized in alkaline soils.
A favorable secondary impact may be a reduction of selenium and chromium as a result of precipitating under
reducing conditions.
Equipment and Exogenous Reagents
If calcium sulfide is used as the source of sulfide, power implements, tillers, and an applicator for applying
slurries are required. Otherwise, if sodium sulfide is used in solution, sprayers or sprinklers may be used.
Information Requirements
characterization and concentration of metals in waste, primarily heavy metals;
depth, profile, and areal distribution of contamination;
soil pH;
soil oxygen content;
solubility of metal sulfide(s);
oxidation/reduction (redox) potential of waste constituents at site;
trafficability of soil and site;
susceptibility of soil permeability to change by addition of sodium.
hydraulic conductivity of soil
Sources of Information
Bhattacharyya, D.,etal., 1981; Pillie, R.J., et al., 1975; Weast, R.C., 1983; King, 1981; Overcash, M.R., and
Pal, D., 1979.
3.3.3.2 Precipitation as Carbonates, Phosphates, and Hydroxides
Description
Theoretically, many metals will form insoluble compounds with carbonates, phosphates, and hydroxides. Table
3-10 lists the solubility product constants for these compounds.
64
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TABLE 3-10. SOLUBILITY PRODUCT CONSTANTS FOR METAL CARBONATES,
PHOSPHATES, AND HYDROXIDES
Substance
Equilibrium
Solubility Product
Constants
Carbonates
Barium carbonate
Cadmium carbonate
Calcium carbonate
Cobalt carbonate
Cupric carbonate
Lead carbonate
Magnesium carbonate
Manganous carbonate
Nickelous carbonate
Silver carbonate
Strontium carbonate
Zinc carbonate
Phosphates
Variscite
Strengite
Octocalcium phosphate
Fluorapatite
Hydroxyapatite
Hydroxides
Aluminum hydroxide
Cadmium hydroxide
Chromic hydroxide
Cobaltous hydroxide
Cupric hydroxide
Ferric hydroxide
Ferrous hydroxide
Lead hydroxide
Magnesium hydroxide
Manganese hydroxide
Mercuric hydroxide
Nickel hydroxide
Zinc hydroxide
BaC03=Ba++ +C03
CdC03=Cd++ +C03
CaC03=Ca++ +C03
CoC03=Co++ +C03
CuC03=Cu++ +C03
PbC03=Pb++ +C03
MgC03=Mg++ 4C03~
MnC03=Mn++ +C0r~
NiC03=Ni++ +CO"
Ag2C03=2Ag+ +C03
SrC03=Sr++ +CO3~
ZnC03=Zn++ +C03
AI(H2PO4) (OH)2 =
AI3++H2P04~+20H~
Fe(H4P04) (OH)2 =
Fe3++H2P04~+2OH~
Ca4H(P04)3 =
4Ca2++H++3P043~
Ca10(P04)6(FH)2 =
10Ca2++6P043~+2F~
Ca,0(P04)6(OH)2 =
10Ca2++6PO43~+2OH~
AI(OH)3=AI+++ +3(OH) ~
Cd(OH)2=Cd++ +2(OH)~
Cr(OH)3=Cr+++ +3(OH) ~
Co(OH)2=Co++ +2(OH) -
Cu(OH)2=Cu++ +2(OH) ~
Fe(OH)3=Fe+++ +3(OH)~
Fe(Qf3)2=Fe++ +2(OH) ~
Pb(OH')2=Pb++ +2(OH)~
Mg(OH)2=Mg++ +2(OH)~
Mn(OH)2=Mn++ +2(OH) ~
HgO+H2O=Hg++ +2(OH)'
Ni(OH)2=Ni++ +2(OH)~
Zn(OH)2=Zn++ +2(OH)~
1.6 x 1CT9
5.2 x 10r12
6.9 x 10"9
8x 10"13
2.5 x 10~10
1.5x 10"13
4x 10"5
9x 10"11
1.4 x 10"7
8.2 x10'12
7x10-10
2x10-10
3x 10"31
1 x 10"3S
1x10-47
4x10-119
2x 10-114
5x 1Q-33
2.0 x 10'14
7x 10'31
2.5 x10'16
1.6 x 1Q-19
6x 10"38
2x TO'15
4x 10'15
8.9 x 1CT12
2x 1Q-13
3x 1CT26
0.6 x10"16
5x10-17
Source: Overcash, M.R., and Pal, D., 1979. (See Copyright Notice)
65
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Santillan-Medrano and Jurinak (1975) obtained experimental data from soil column studies using both Pb and Cd
Their data showed that for the calcareous Nibley soil: 1) the solubility of Pb decreases with increasing soil pH, which
is the usual trend for most heavy metals, 2) lead phosphate compounds could be regulating the activity of Pb2 + ion in
solution, and 3) mixed compound precipitation cannot be precluded between pH 7.5-8 0 because of the convergence of
the solubility isotherms for PbCO3, Pb(OH)2, Pb3(PO4)2 and Pb5(PO4)3Cl. Similar results were seen for the solubility
of Cd in Nibley soil. However, the solubility of Cd is considerably higher than Pb at any pH, and at high pH values the
soil solution is undersaturated with respect to the compounds considered. This research showed that precipitation
reactions involving native soil carbonates, hydroxides, and phosphates are important in regulating solution concentra-
tions of metals added to the soil.
McBnde (1980) concluded that calcite serves as a site for chemisorption of Cd2 at low levels of Cd additions,
while CdCO3 precipitation occurs at higher Cd concentrations. Carbonate surfaces are known to chemisorb other
2 +
heavy metals such as Zn (Jurinak and Bauer. 1956) and Mn (McBride, 1979), providing a mechanism of metal
retention that can lower the solution activity below that predicted by the solubility producl of the least soluble pure
mineral phase. McBride (1980) found that the initial chemisorption of Cd2+ on calcite was very rapid, while CdCO3
precipitation of higher Cd2 concentrations was slow.
Article and Fuller (1979) tested the effectiveness of using a limestone barrier as a landfill liner to retard the
migration rate of metals. The test was conducted in a laboratory column study using a leachate generated from
municipal solid waste. The use of a limestone barrier increased the retention of the metals studied (Be, Cd, Fe, Ni, Zn
and Cr) as is shown in Table 3-11
TABLE 3-11. RELATIVE EFFECT OF CRUSHED LIMESTONE LINER PLACED OVER SOIL ON
THE PREVENTION OF HEAVY METALS IN MUNICIPAL SOLID WASTE LANDFILL
LEACHATE FROM MIGRATING
Pore Volume Displacement to Achieve the Same C/C0a
With Limestone Layer With Soil No Limestone Layer, Soil Only
Element
Be
Cd
Cr (pH 2.5)
Cr (pH 4.0)
Fe
Ni
Zn
1b
30
30
35
28
31
40
30
2
29
35
52
49
31
35
25
3
35
40
85
125
35
30
30
4
30
38
88
144
36
35
32
5
30
35
86
111
30
28
25
6
25
35
35
109
25
24
30
1
10
16
10
2
21
20
10
2
16
18
15
21
26
15
11
3
15
28
5
39
10
11
15
4
15
15
10
25
25
15
18
5
18
18
10
17
10
7
12
6
10
6
6
15
10
10
16
a. Determination used in column studies, where C = concentration of effluent, Co = concentration of
influent. The higher the pore volume displacement, the greater the volume that was passed through
the column to achieve the same C/C0, and therefore the greater the compound was retained in the
column.
Texture
b. Soil Characteristics
1. Davidson
2. Ava
3. Anthony
4. Mohave
5. Kalkaska
6. Wagram
pH
6.2
4.5
7.7
7.3
4.7
4.2
clay
silty-clay-loam
sandy-loam
sandy-loam
sand
loamy-sand
Source: Article, J., and Fuller, W.H., 1979. (See Copyright Notice)
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TABLE 3-12. SOME PROBABLE BIVALENT METAL COMPLEXES WITH
INORGANIC LIGANDS IN SOIL SOLUTIONS
OH
Cl
S04
C03
PO4
MOH+
M(OH)2°
M(OH)3~
M(OH)42~
MCI+
MCI;,0
MCI3~
MCI42~
MHS04+
MS04°
M(S04)22~
MHC03 +
M(HC03)2°
MC03°
M(C03)22~
MH2PO4 +
MHP04°
MPO4"
Source: Mattigod, S.W., et al., 1981. (See Copyright Notice)
For maximum treatment effectiveness, soil pH must be maintained over time In a calcareous soil this should not
pose any problems. In an acid soil, however, the pH of the soil must be adjusted to a pH greater than 6 and maintained
with continued liming of the soil
In determining the amount of CaCO3 to be added to increase the pH and thus precipitate the metals present.
consideration must be given to the lime requirement of the soil. The lime requirement calculation indicates the amount
of lime required to reach a predetermined pH. Lime in excess of this amount will also provide an adsorbing surface for
a number of heavy metals.
When applying relatively soluble treble superphosphate fertilizer |Ca[H2PO4]2l to the soil to precipitate metals as
phosphates, consideration must be given to the competitive interaction for phosphate of the soil constituents. In acid
soils this would be iron and aluminum compounds, whereas excess calcium existing in alkaline soils is competitive for
the phosphate anion.
Maximum insolubility of metal-hydroxides occurs at different pH values for each heavy metal Selection of an
optimum pH for all metals that may be involved in a treatment process is not possible. Because of this. Kim (1980) and
Bhattacharyya et al. (1983) recommended the use of sulfide in treating wastewater for metals. This same pH-
dependency on optimum precipitation is also true for carbonates and phosphates.
Heavy metals may also form soluble phosphate, carbonate, and hydroxide complexes (Table 3-12). These
complexed metals may be more mobile than the free metal ion. Controlled additions of the anions and optimizing pH
for precipitation versus complex-formation may help prevent the formation of these complexes.
The kinetic aspects of dissolution and precipitation reactions involving heavy metals in the soil matrix have not
been studied in any detail. Also, high salt content of any accompanying waste as well as chelating agents and other
competing reactions may reduce performance of these treatments.
Wastes Amenable to Treatment
Inorganic wastes containing metals, particularly heavy metals, are amenable to this treatment.
Status of Technology
Hydroxide precipitation has been used effectively in wastewater treatment of metals. The use of limestone as a
barrier to retard the migration of heavy metals from landfill leachate has been successfully demonstrated in the
laboratory.
67
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Ease of Application
Hydroxide salts are highly corrosive and their direct application to soil is not recommended. Hydroxide ions are
formed when a soil is treated with liming materials, and they are available for hydroxide-metal precipitation reactions
After adjusting soil pH to the optimum pH for precipitation, theoretically, for divalent metals, one mole of carbonate
(two moles of hydroxide) reacts with one mole of metal. However, at a hazardous waste site, the complexity of the soil
matrix and wastes make simple estimates impossible and excess carbonate or phosphate should be used. Treble
superphosphate fertilizer, which is relatively soluble, may be used to provide phosphate ions.
Limestone and treble superphosphate are both easy to handle agricultural chemicals. No special equipment or
safety considerations are necessary. Soil pH must be maintained at a value conducive to maximum insolubility of the
specific metal precipitate. Thorough mixing is required for maximum waste and reagent contact. Controls to prevent
runon and runoff may be necessary because tillage will increase the susceptibility of the site to erosion.
Potential Achievable Level of Treatment
Insoluble metal compounds of phosphate, carbonate, and hydroxide are known to participate in regulating
solution concentrations of metals in natural soil systems. Little, however, is known about using precipitation as a
means of treating metals in soils. The kinetics of metals precipitation in soils may limit the effectiveness of this
treatment. Also, high salt content of waste, as well as any chelating agents and other competing reactions, may reduce
the performance of this treatment.
Reliability of Method
Because precipitation reactions are pH-dependent, it is necessary to maintain the pH of the soil system at high
levels to prevent dissolution of the precipitates and subsequent leaching. Reliming is necessary at intervals.
Secondary Impacts
If arsenic is present in the system, the use of phosphate may cause the release of arsenate to the soil solution.
Heavy metals may form soluble phosphate, carbonate, and hydroxide complexes which are more mobile than the free
metal ion. Tillage will increase the susceptibility of the site to erosion.
Equipment and Exogenous Reagents
Power implements, tillers and applicators are necessary. Calcium carbonate and treble superphosphate fertilizer
are required as the precipitating agents.
Information Requirements
characterization and concentration of metals in waste, primarily heavy metals;
depth, profile, and areal distribution of contamination;
soil pH;
oxidation/reduction (redox) potential of waste constituents at site;
iron and aluminum compounds, calcium (phosphate fixation capacity);
soil arsenic (oxidation state and concentration);
solubility of precipitates (carbonates, phosphates, and hydroxides);
trafficability of soil and site.
68
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TABLE 3-13. OXIDATION REACTIVITY FOR ORGANIC CHEMICAL CLASSES
High
Reactivity
Moderate
Low
Phenols
Aldehydes
Aromatic amines
Certain organic sulfur compounds
Alcohols
Alkyl-substituted aromatics
Nitro-substituted aromatics
Unsaturated alkyl groups
Aliphatic ketones
Aliphatic acids
Aliphatic esters
Aliphatic amines
Halogenated hydrocarbons
Saturated aliphatic compounds
Benzene
Chlorinated insecticides
Source: JRB, 1982.
Sources of Information
Santillan-Medrano, J., and Jurinak, J.J., 1975; Overcash, M.R., and Pal. D., 1979; McBride, M.B., 1979,
1980; Jurinak, J.J., and Bauer, N., 1956; Antiole, J., and Fuller, W.H., 1979; Kim, B.E., 1981; Bhattacharyya, D.,
et al., 1983; Mattigod et al., 1981; Dept. of Army, 1982.
3.4 DEGRADATION
3.4.1 Chemical
Chemicals naturally undergo reactions in soil that may transform them into more or less toxic products, or which
may increase or decrease their mobility within the soil system. Chemical treatment of contaminated soils entails the
reaction of pollutants with reagents, resulting in products which are less toxic, or which become immobilized in the
soil column. These reactions may be classified as oxidation reactions, reduction reactions, and polymerization
reactions.
3.4.1.1 Oxidation
Chemical oxidation is a process in which the oxidation state of an atom is increased. This is accomplished by
removal of electrons or addition of oxygen to the atom. Chemical oxidation represents a significant treatment process
in soil systems. As a result of oxidation, a substance may be transformed, degraded, and/or immobilized in soil.
Oxidation reactions within the soil matrix may occur through management of the natural processes in a soil, or through
addition of an oxidizing agent to the soil-waste complex. Certain compounds are more oxidizable in soils than others.
General oxidation reactivity for organic chemical classes is summarized in Table 3-13.
The following discussion is primarily concerned with the oxidation of organics. Oxidation of heavy metals is not
usually effective as a treatment method because the higher the oxidation state, the more mobile the heavy metal tends
to be. Arsenic is an exception. It is discussed here rather than separately because there is very little information on its
oxidation.
Arsenate (As(V)) is less toxic and forms less soluble compounds than arsenite (As(III)). Treatment, therefore,
consists of oxidizing As(III) to As(V) followed by the addition of 1:1 ferrous sulfate to precipitate ferric arsenate
69
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(FeAsO4), a highly insoluble compound. Aluminum sulfate, zinc sulfate, organic matter, or lime can also be used as a
means of fixing As(V). Volatile arsines are formed under anaerobic conditions which, therefore, must be avoided.
There is a lack of research dealing with methods for oxidation of arsenic. Aeration may be adequate. Also, there is
presently no analytical technique for distinguishing between As(III) and As(V).
3.4.1.1.1 Soil Catalyzed Reactions
Description
Iron, aluminum, trace metals within layer silicates, and adsorbed oxygen have been identified as catalysts
promoting free-radical oxidation of constituents in soil systems (Page, 1941; Solomon, 1968; Theng, 1974; Furukawa
and Brindley, 1973; and Hirschler, 1966). General characteristics of the organic chemicals likely to undergo oxidation
include: 1) aromaticity, 2) fused ring structures, 3) extensive conjugation, and 4) ring substituent fragments.
For oxidation to occur in soil systems, the redox potential of the solid phase must be greater than that of the
organic chemical contaminant. Therefore, the half-cell potentials, E1/2, of chemical contaminants need to be below the
redox potential, 0.8V of a well oxidized soil (Dragun and Baker, 1979).
Another characteristic that is significant with respect to soil-catalyzed oxidation is the solubility of the organic
contaminant. The oxidation reaction site is the hydrophilic clay mineral surface, and sorption to the surface precedes
soil-catalyzed oxidation. Therefore, more water-soluble compounds should be more readily oxidized in clay-catalyzed
systems.
Soil water content (degree of saturation) may also play a very important role in controlling, and therefore
managing, soil-catalyzed oxidation. Greater oxidation of chemical contaminants is expected in less saturated soils
(Dragun and Helling, 1982). Therefore the technique for immobilization by control of soil moisture is completely
compatible with this treatment technique.
Techniques for immobilization by control of soil moisture or by incorporation or addition of uncontaminated soil
should not only augment sorption, but they should also augment clay catalyzed reactions in the soil B-horizon where
the clay fraction of soil is predominant. Thus a physical-chemical and biological treatment system may be achieved in
a layered system through the soil where sorption of hydrophobic constituents occurs in the upper soil layers, or where
organic matter content is high, and chemical reactions for hydrophilic constituents occur in lower soil layers where the
clay fraction predominates. Biological activity may be expected to increase the extent of degradation of constituents as
the retention time of constituents is increased through sorption.
Wastes Amenable to Treatment
Organic wastes which are water-soluble and have half-cell potentials below the redox potential of a well oxidized
soil are amenable to this treatment. Table 3-14 lists chemicals which do not undergo free-radical oxidation at soil and
clay surfaces. Included in this group of chemicals is the aliphatic class of compounds.
Status of Technology
Soil-catalyzed oxidation reactions have been verified in the field for several chemical classes, including
S-triazines and organo-phosphate compounds. Some other compounds have been verified in the laboratory. Other-
wise, this technology is at the conceptual stage.
Ease of Application
If required, clay may be applied to the soil surface and thoroughly incorporated through the depth of contamina-
tion. The site may require installation of drainage systems to reduce soil moisture. Tillage may be used to dry and
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TABLE 3-14. SOME CHEMICALS THAT DO NOT OXIDIZE
AT SOIL AND CLAY SURFACES
Chemical Name
Acetamide
Acetone, anisilidene-
-, dianisilidene-
-, dicinnamylidene-
-, di benzyl idene-
j3-Carotene
Cyclohexylamine
Monoethanolamine
Triethylamine
Source: Dragun, J., and Helling, C.S., 1982.
aerate the soil. Increasing soil temperatures may enhance soil drying and increase the rate of reaction. This treatment
technology requires aerobic soil conditions to be maintained which may be easy or difficult, depending on the site and
the depth of contamination as it affects the ability to incorporate clays.
Potential Achievable Level of Treatment
The level of treatment achievable is variable, depending on the oxidation potential of the waste constituents and
the aeration of the soil.
Reliability of Method
The chemical degradation of a compound does not guarantee less mobile or less toxic products. Care must be
taken that oxidation of the waste will not produce substances more problematic than the parent compounds in the
waste.
Secondary Impacts
Decreased soil moisture may result in possible retardation in microbial activity or increased volatilization of
volatile waste constituents. Volatilization may present a public health hazard, but also may reduce toxic concentrations
to soil micro-organisms. Toxic concentrations may also be reduced by attenuation with the added soil. Other clay-
catalyzed degradation may be enhanced by this treatment. Tillage will increase the susceptibility of the soil to erosion.
Equipment and Exogenous Reagents
Equipment to set up a drainage system may be necessary, together with applicators and tillers to incorporate the
clay.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
potential for oxidation of waste constituents (half-potentials, E1/2);
oxidation products (particularly hazardous products);
solubility of organics;
depth, profile, and areal distribution of contamination;
soil moisture;
soil type and profile;
catalysts for oxidation present in son;
trafficability of soil and site.
71
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TABLE 3-15. RELATIVE OXIDATION POWER OF OXIDIZING SPECIES
Species
Oxidation
Potential
Volts
Relative
Oxidation
Power
Fluorine
Hydroxyl radical
Atomic oxygen
Ozone
Hydrogen peroxide
Perhydroxyl radicals
Hypochlorous acid
Chlorine
3.06
2.80
2.42
2.07
1.77
1.70
1.49
1.36
2.25
2.05
1.78
1.52
1.30
1.25
1.10
1.00
Source: Rice, 1981. (See Copyright Notice)
Sources of Information
Page, 1941; Solomon, 1968, Theng, B.K.G., Furakawa, T., and Brindley, 1973; Hirschler, 1966; Dragun and
Baker, 1979; Dragun and Helling. 1982
3.4.1.1.2 Addition of Oxidizing Agents
Description
Oxidizing agents may be utilized to degrade organic constituents in soil systems. Oxidation reactions are usually
limited in application due to their substrate specificity and pH dependence. Two powerful oxidizing agents considered
for in-place treatment include ozone and hydrogen peroxide. The relative oxidizing ability of these chemicals.
compared with other well known oxidants is indicated in Table 3-15. A serious potential limitation to the use of
oxidizing agents for soil treatment is the additional consumption of the oxidizing agent(s) by nontarget constituents
comprising the soil organic matter.
Ozone is an oxidizing agent that may be used to degrade recalcitrant compounds directly, to create an oxygenated
compound without chemical degradation, and/or to increase the dissolved oxygen level in the water for enhancing
biological activity. Ozone is a colorless gas characterized by a pungent odor and very high oxidation potential.
The rate of decomposition of ozone is also strongly influenced by pH. Ozone reactions are believed to be of two
fundamental types: 1) direct reaction of ozone with the organic compounds, and 2) free radical reaction of ozone,
which involves a hydroxy] free-radical intermediate. Direct reaction of ozone with solute achieves the most rapid
decomposition of solute. At high pH, the hydroxyl free-radical reactions have been observed to dominate over the
direct ozone reactions. Thus the relative rate of ozone reaction can be controlled by adjusting the pH of the medium.
The most efficient and cost-effective uses of ozone in soil system decontamination appear to be in the treatment of
contaminated water extracted from contaminated soil systems through recovery wells, and in the stimulation of
biological activity in saturated soil (Nagel et al., 1982). If the specific organic constituents present in contaminated soil
are relatively biodegradable, ozone treatment may be very effective as an enhancement of biological activity.
However, if a large fraction of the matrix is relatively biorefractory, the amount of ozone that will be required to
directly treat the waste by chemical destruction will be a direct function of the organic matter present in the solution
72
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and in the soil, and will represent a greatly increased cost of treatment. The presence of natural soil organic matter will
greatly increase ozone dosage and consumption necessary to treat the target constituents.
Groundwater contaminated with oil products were treated with ozone to reduce dissolved organic carbon (DOC)
concentration (Nagel et al., 1982). Dosages of 1 gram ozone per gram dissolved organic carbon resulted in residual
water ozone concentration of 0.1 to 0.2 ppm. The treated water was then infiltrated into the aquifer through injection
wells. An increase in dissolved oxygen (DO) in the contaminated water was demonstrated. The increase in DO
increased microbial activity in the saturated soil zone which stimulated microbial degradation of the organic
contaminants. Thus, ozone can be effectively used to treat contaminated water extracted from the soil system and to
stimulate biological activity in deeper saturated zones of contaminated soils.
Hydrogen peroxide is an oxidant that has been successfully used in wastewater treatment to degrade compounds
that are resistant to biological treatment (recalcitrant). It has also been used to modify the mobility of some metals.
Hydrogen peroxide can react in three major ways:
1) Direct reaction with substrate as shown in Equation 3-8, where the peroxide reacts with silver nitrate to form
elemental silver and nitric acid:
2AgNO3 + H2O2 -2Ag + O2 + 2HNO3 (3-8)
2) Hydrogen peroxide can be degraded by UV light to form hydroxyl free radicals as shown in Equation 3-9:
H2O2 + UV 2OH - (3-9)
2,537A
3) It can undergo auto-decomposition in the presence of a metal catalyst as in Equation 3-10:
6 H202 Meta'» 6 H20 + 3 02 (3-10)
Hydrogen peroxide has also been used in conjunction with ozone to degrade compounds which are refractory to either
material individually (Nakayama et al., 1979).
Peroxide, as demonstrated in Equations (3-8) and (3-10), can be used to increase oxygen levels in the soil. A
previous study (Nagel et al., 1982) has shown an increase in microbial activity and microbial degradation of organic
contaminants with increasing oxygen content in soil/groundwater systems.
Hydrogen peroxide is a strong oxidant and, as a result, it is nonselective. If this material is added to the soil, it
will react with any oxidizable material present in the soil. This will be a major concern because the concentration of
natural organic material in the soils may be lowered, resulting in decrease sorption capacity for some organics.
Thus, the effectiveness of peroxide may be inhibited because it simultaneously increases mobility and decreases
possible sorption sites.
Wastes Amenable to Treatment
Organic wastes are amenable to treatment by the addition of oxidizing agents, subject to considerations of the
production of more toxic or more mobile oxidation products.
73
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TABLE 3-16. HAZARDOUS PRODUCTS OF OZONE REACTIONS
Parent Compound Reaction Product Oxidation of Product with Ozone
Aldrin
Heptachlor
DDT
Parathion
Malathion
Dieldrin
Heptachlor epoxide
DDE
Paraoxon
Malaoxon
Very slow
Stable to further oxidation
Nitrophenols, phosphoric acid
Source: Utah Water Research Laboratory.
Some hazardous compounds are known to be non-reactive with ozone. Unreactive chemical species are usually
characterized by inorganic compounds in which cations and anions are in their highest oxidation state, or organic
compounds which are highly halogenated. There are many hazardous chemicals for which no information currently
exists concerning their susceptibility to ozone oxidation
Some general rules concerning chemical destruction of organic constituents include the following.
I) Saturated aliphatic compounds which do not contain easily oxidized functional groups are not readily
reactive with ozone. Examples include saturated aliphatic hydrocarbons, aldehydes, and alcohols.
2) For aromatic compounds, reactivity with ozone is a function of the number and type of substituent(s).
Generally, substituents which withdraw electrons from the ring deactivate the ring toward ozone.
Examples include halogens, nitro, sulfomc acid, carbonyl, and carboxyl groups. Substituents which
release electrons activate the ring toward ozone. Examples include alkyl, methoxyl, and hydroxyl.
The following general patterns concerning reactivity with ozone have been identified:
I) phenol, xylene > toluene > benzene
2) pentachlorophenol < dichloro-, trichloro-, tetrachlorophenol
Ozonation of hazardous pesticides may actually be detrimental in many instances. Table 3-16 presents specific
examples in which reactions of ozone with parent compounds result in the production of hazardous products, which are
often degraded very slowly with ozone.
Hydrogen peroxide has been demonstrated to be effective for oxidizing cyanide, aldehydes, dialkyl sulfides,
dithionate, nitrogen compounds, phenols, and sulfur compounds (FMC Corp., 1979).
Peroxide also reacts with many chemical classes with a resultant increase in mobility for the products (JRB.
1982). Table 3-17 shows chemical groups having incompatible reactions with peroxides (i.e., reaction products are
more mobile).
Status of Technology
Oxidizing agents are used in waste water treatment, but there is little experience with their use in terrestrial
systems. Hydrogen peroxide is used in septic tank drainfields experiencing failure due to biological clogging.
74
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TABLE 3-17. CHEMICAL GROUPS THAT REACT WITH PEROXIDES
TO FORM MORE MOBILE PRODUCTS
Acid chlorides and anhydrides
Acids, mineral, non-oxidizing
Acids, mineral oxidizing
Acids, organics
Alcohols and glycols
Alky I halides
Azo, diazo compounds, hydrazine
Cyanides
Dithio carbamates
Aldehydes
Metals and metal compounds
Phenols and cresols
Su If ides, inorganic
Chlorinated aromatics/alicycles
Source: Utah Water Research Laboratory.
Ease of Application
The soil should not be disturbed to avoid dilution of contaminants in the soil. The oxidizing agents may be applied
in water solutions directly onto the soil surface, injected into the subsurface, or applied through injection wells,
depending on the depth and location of contamination. Loading rates can be determined in short-term treatability
studies.
Application may be moderate to difficult because oxidizing agents are dangerous to handle and require special
treatment. Controls to manage runon and runoff may also be necessary.
Potential Achievable Level of Treatment
The achievable level of treatment is potentially high for wastes susceptible to oxidation, in soils without large
quantities of competing oxidizable substances, and for limited areas of contamination.
Reliability of Method
Because ozone and hydrogen peroxide are very strong oxidizers, they are not particularly discriminating in the
substances which they will oxidize in the soil. As a result, much of the oxidant will be wasted on oxidizing non-target
compounds. Treatment may have to be repeated should initial applications be insufficient, or if the non-target
compounds were more susceptible to oxidation than the oxidizable compounds which were problematic at the site.
Secondary Impacts
Oxidizing agents may result in violent reactions with certain classes of compounds (e.g. metals), and may be
corrosive to application equipment. Their use may also affect soil hydraulic properties (e.g., infiltration rate),
especially in structured soils. Oxidation of soil organic matter may decrease sorption sites for nonoxidizabkr'waste
constituents. Oxygenated degradation products are expected to be more polar than the parent compounds and,
therefore, potentially more mobile. The chemical reaction may produce a large quantity of potentially mobile
constituents in a relatively short period of time, necessitating the installation of recovery wells. The oxygenated
products may also be toxic to soil systems, human health, and the environment. Some products may be more refractory
than the parent compounds. The use of oxidizing agents may also increase the mobility of some metals. Oxidizing
agents may have beneficial effects on microbial degradation processes by adding O2 to the soil water solution.
Equipment and Exogenous Reagents
Power implements are required. If ozone is used, an ozone generator is necessary. Depending on the application
method, an irrigation system, applicators, and/or injection wells may be needed. Exogenous reagents needed are
oxidizing agents, ozone or hydrogen peroxide.
75
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Information Requirements
characterization and concentration of wastes, particularly organics at site;
potential for oxidation of waste constituents (half-cell potentials, E1/2);
oxidation products (particularly hazardous products);
depth, profile, and areal distribution of contamination;
soil and waste pH;
other naturally occurring oxidizable substances in soil at site;
selectivity of oxidizing agent(s) for specific wastes present at site;
trafficability of soil and site.
Sources of Information
Nagel, G., et al., 1982; Nakayama, S., et al., 1979; FMC Corp., 1979; JRB Inc., 1982; Pringle, Jr., H.W.,
1977; Rice, R.G., 1981; Griffin, R.A., and Shimp, N.F., 1978; Metsy, A.A., 1980; Overcash, M.R., and Pal, D.,
1979; Woolson, E.A., 1977.
3.4.1.2 Reduction
Chemical reduction is a process in which the oxidation state of an atom is decreased. Reducing agents are electron
donors, with reduction accomplished by the addition of electrons to the atom. Reduction of chemicals may occur
naturally within the soil system. Certain compounds are more susceptible to reduction than others because they will
accept electrons. Addition of reducing agents to soil to degrade reducible compounds can be used as an in-place
treatment technology.
Reducing agents and conditions of reduction vary with organics and with metals. The following discussion is
divided into organics, chromium, and selenium for ease of organization of the information.
3.4.1.2.1 Organics Addition of Reducing Agents
Description
Chemical reduction using catalyzed metal powders and sodium borohydride has been shown to degrade toxic
organic constituents. Reduction with catalyzed iron, zinc, or aluminum affect treatment through mechanisms including
hydrogenolysis, hydroxylation, saturation of aromatic structures, condensation, ring opening, and rearrangements to
transform toxic organics to innocuous forms.
The use of catalyzed metal powders has been used successfully for aqueous solutions passed through beds of
reactant diluted with an inert solid (Sweeney, 1981). The process may be adaptable to terrestrial application, although
this has not been directly demonstrated at this time. The process has been used successfully on the following specific
constituents:
hexachlorocyclopentadiene PCBs
p-nitrophenol chlordane
trichloroethylene chlorinated phenoxyacetic acid
chlorobenzene di- and tri-nitrophenols
kepone atrazine
76
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Iron powders are preferred for soil systems and are also the most cost-effective and available. Reactions of iron
with some organic constituents are as follows:
1) Removal of halogen atom and replacement by hydrogen in halogenated organic species.
Fe + H2O + RC1 Z- RH + Fe++ 4- OH ~ + Cl ~ (3-11)
An example is the transformation of DDT to DDA.
2 Replacement of a halogen by a hydroxyl group:
Fe + 2H20 + 2RC1 ^ 2ROH + Fe++ + 2C1 ~ + H2 (3-12)
3. Saturation of an aromatic structure.
Fe + 2H2O + RCH = CHR ^ RCH2CH2R -t- Fe+ + + 2OH~ (3-13)
An example is the transformation of chlorobenzene to cyclohexanol
4. Condensation of species:
Fe + 2RC1 ^ R R + 2C1 ~ + Fe++ (3-14)
An example is the condensation of DDT to TTTB.
Consumption of metal occurs through the reactions discussed above and also through reactions of the active metal
with water:
Fe + 2H2O ^ Fe++ + 2OH ~ + H2 (3-15)
The total consumption of metal from these reactions in aqueous solutions of industrial wastewaters produces 1 to
5 mg/1 of metal (Fe+ +) in the solution when low toxicant levels are treated.
Organic chemical constituents in soil may also be chemically reduced through the use of sodium borohydride and
zinc. These chemicals have been successful for in-place, small-scale field experiments with soils (Staiff et al., 1981).
Results of reductive treatment for degradation of paraquat in soil is summarized in Table 3-18. Results indicate that
sodium borohydride and powdered Zn/acetic acid combinations accomplished very effective degradation of paraquat
in soil and sand media. Toxic products that may be produced as a result of reductive treatment and other by-products
were not investigated to any significant extent in this study.
Wastes Amenable to Treatment
Chlorinated organics, unsaturated aromatics and aliphatics, and other organics that are susceptible to reduction
will be amenable to treatment by reducing agents.
Status of Technology
Reduction with catalyzed metal powders has been utilized in wastewater treatment systems. Reduction of
paraquat with sodium borohydride and powdered zinc has been demonstrated in small-scale field plots.
77
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TABLE 3-18. CHEMICAL REDUCTIVE TREATMENT FOR DEGRADATION OF PARAQUAT IN SOIL
Chemical
Paraquat in Soil (ppm)
Treatment
None
NaBH4-soil
NaBH4-sand
Powdered Zn
acetic acid
Initial (1 day)
9,590
None detected
None detected
60
4 Months
6,300
None detected
None detected
69
Comment
Violent foaming
No foaming
Some bubbling
Source: Staiff, D.C., et al., 1981. (See Copyright Notice)
Ease of Application
The soil should not be disturbed prior to treatment to avoid dilution of contaminants in the soil. For metal-
catalyzed powders, stoichiometnc excess of reductant powder should be applied to the soil surface and mixed with the
contaminated soil to achieve maximum contact. For chemical reducing agents, a sodium borohydride-stabilized water
solution should be applied to the soil at 50 percent stoichiometric excess. A solution used in a small-scale study
contained:
Sodium borohydride
Sodium hydroxide
Water
12 ± 0.5%
42 ± 2%
balance
Iron may be more desirable than zinc or aluminum, since iron is naturally present in most soils. Aluminum is
toxic to biological systems and contributes to soil acidity. Soil pH must be maintained at pH 6-8 for maximum
treatment effectiveness. Soil water should be controlled at less than saturated conditions (60-80% of field capacity) to
provide an aqueous environment for reductive reactions to occur while preventing leaching.
Controls may be necessary for runon and runoff management. Depending on the trafficability of the site and the
depth and the extent of contamination, application of this technology may be easy or it may be difficult.
Potential Achievable Level of Treatment
The achievable level of treatment is potentially high for wastes susceptible to reduction, and for limited areas of
contamination. The soil must be without large quantities of competing constituents susceptible to reduction, or the
level of treatment may be greatly decreased.
Reliability of Treatment
Treatment may have to be repeated if the reducing agents are not sufficient because of high levels of naturally
occurring reducible compounds in the soil.
Secondary Impacts
The use of reducing agents may also degrade soil organic matter. The extent of impact on soils is not known at the
present time. The products of reduction may present problems with respect to toxicity, mobility, and degradation.
Little information is available at the present time. The addition of metals to soil adds to the metal contaminant load.
78
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Iron appears to be the least damaging to the soil system, though iron has. a secondary drinking water standard and is of
concern with respect to aesthetics. Addition of metals with acetic acid may possibly increase metal mobility by
decreasing soil pH. Addition of sodium borohydride may adversely impact soil permeability, depending on the type
and content of clay and ionic constituents in the soil solution.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are needed. An irrigation and drainage system is needed to apply the
sodium borohydride and to maintain the soil moisture at an optimum level. Reducing agents are necessary.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
potential for reduction of waste constituents;
reduction products;
depth, profile, and areal distribution of contamination;
soil and waste pH;
soil moisture;
selectivity of reducing agent(s) for specific wastes present at site;
trafficability of soil and site.
Sources of Information
Staiff, D.C., 1981; Sweeney, K., 1981.
3.4.1.2.2 Chromium Addition of Reducing Agents
Description
Hexavalent chromium is highly toxic and highly mobile in soils. Treatment consists of reducing Cr (VI) to Cr
(III), which is less toxic and is readily precipitated by hydroxides over a wide pH range. In a study of the relative
mobility of metals in soils at pH 5, Cr (III) was found to be the least mobile (Griffin and Shimp, 1978).
Acidification agents (such as sulfur) and reducing agents (such as leaf litter, acid compost or ferrous iron) may
serve in the conversion of Cr (VI) to Cr (HI) (Grove and Ellis, 1980). Hexavalent chromium itself is a strong oxidizing
agent under acidic conditions and, as such, Cr (VI) will be readily reduced to Cr (III), even without the addition of
strong reducing agents. After reduction, liming of the soil will precipitate Cr (III) compounds. Precipitation of Cr (III)
occurs at pH 4.5-5.5, so little soitpH adjustment is necessary. Caution is required, however, since trivalent chromium
can be oxidized to Cr (VI) under conditions prevalent in many soils, e.g., under alkaline and aerobic conditions in the
presence of manganese.
Wastes Amenable to Treatment
Wastes containing hexavalent chromium are amenable to this treatment technology.
Status of Technology
Laboratory data support the theory of this treatment method. Treatment of soils has been performed under field
conditions.
79-
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Ease of Application
Acidification requirements for the particular soil need to be determined. Three moles of ferrous sulfate will
reduce one mole of Cr (VI). Excess of this amount will probably be needed to account for other reduction reactions
occurring in the soil. The quantity of organic material cannot be predicted from stoichiometric considerations. Liming
materials, after the acidification and reducing steps, are applied to raise the pH to greater than 5.
Leaf litter and compost are easily applied to soils by standard agricultural practices, if site/soil trafficability is
suitable. Ferrous sulfate may be applied directly to soil or through an irrigation system. Reduction of Cr (VI) must
occur under acidic conditions, followed by liming to precipitate Cr (III). Acidification and liming are standard
agricultural practices.
Runon and runoff controls may have to be installed to prevent erosion and drainage problems.
Potential Achievable Level of Treatment
The potential achievable level of treatment is high.
Reliability of Method
The pH of the system has to be maintained at greater than 5. Reliming may be necessary at intervals to ensure that
the chromium is immobilized in the soil.
Secondary Impacts
Tillage increases the susceptibility of the site to water and wind erosion, and organic materials may have many
effects on soil properties, including:
degree of structure;
water holding capacity;
bulk density;
immobilization of nutrients, hindering degradation of organic wastes;
reduction in soil erosion potential;
soil temperature.
Organic materials may also result in excessive nitrate levels in receiving waters, depending on the nitrogen
content and degree of mineralization of the material.
Equipment and Exogenous Reagents
Power implements, tillers, applicators, and an irrigation system are necessary to apply the reducing, acidifying,
and liming materials.
Information Requirements
characterization and concentration of metals, particularly Cr (VI), arsenic, mercury, and other
constituents whose treatment requirements may be incompatible;
depth, profile, and areal distribution of contamination;
soil pH;
soil organic matter;
acidification, reduction, and liming reaction rates;
80
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trafficability of soil and site.
Sources of Information
Griffin and Shimp, 1978; Grove and Ellis, 1980; Metsy, 1980.
3.4.1.2.3 Selenium Addition of Reducing Agents
Description
Hexavalent selenium (as selenate (SeO42~)) is highly mobile in soils. It is the dominant form of selenium in
calcareous soils. Elemental selenium and selenite (Se(IV)) are less mobile in soils Hexavalent selenium can be
reduced to Se (IV) or Se° under acid conditions. Reduction of selenium occurs naturally in soils. Elemental selenium is
virtually immobile in soils. Se (IV) will participate in sorption and precipitation reactions, but unlike the metals
discussed previously, selenite is an anion (SeO32~) and its potential leachability will increase with increasing pH.
Therefore, at a site that contains selenium as well as other metals, selenium could not be treated if increased pH were
required as part of the treatment for the other metals.
Wastes Amenable to Treatment
Wastes containing hexavalent selenium (SeO42~) that do not contain significant amounts of other metallic
constituents are the most amenable to treatment by this method.
Status of Technology
Studies have been limited to those involving basic chemistry of selenium in soils.
Ease of Application
The soil requires acidification with sulfur or another agricultural acidifying agent to pH 2-3. Acidification
requirements for the particular soil need to be determined experimentally. Leaf litter or compost are easily applied to
soils by standard agricultural practices, if site trafficability is suitable. Ferrous sulfate may be applied directly to soil or
through an irrigation system. Two moles of ferrous sulfate will reduce one mole of Se(VI). Excess of this amount
should be added to account for other reduction reactions that may occur in the soil. The quantity of organic material
cannot be predicted from stoichiometric considerations.
Runoff and runon controls may be necessary to prevent erosion and drainage problems.
Potential Achievable Level of Treatment
The addition of reducing agents speeds up the natural process of selenium reduction in soils. The potential level of
treatment should be high.
Reliability of Method
Once reduction has occurred, the soil must be kept acidic. Reapplication of an acidifying agent may be necessary
as required to maintain the pH to between 2 and 3.
81
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Secondary Impacts
Low pH will adversely affect microbial activity and degradation of organic waste constituents. Tillage increases
the susceptibility of the site to water and wind erosion. Organic materials may have many effects on soil properties,
including:
degree of structure;
water holding capacity;
bulk density;
immobilization of nutrients, hindering degradation of organic wastes;
reduction of soil erosion potential;
soil temperature.
Organic matter may also result in excessive nitrate levels in receiving waters, depending on the nitrogen content
and the degree of mineralization of the material.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are needed to prepare the site and apply the acidifying agent and
reducing agent.
Information Requirements
characterization and concentration of metals, particularly selenium (Treatment of selenium is
incompatible with treatment of all other metals; oxidation state of metallic ions);
depth, profile, and areal distribution of contamination;
soil pH;
soil organic matter;
clay content of soil;
acidification and reduction reaction rates;
trafficability of soil and site.
Sources of Information
Griffin, R.A., and Shimp, N.A., 1978; Sharma, S., and Singh, R., 1983.
3.4.1.2.4 Sodium Reduction!Dehalogenation for PCBs and Dioxins
Description
Several processes to detoxify PCB's and, potentially dioxins have been developed in the past several years. All
employ a sodium-based chemical reagent to remove chlorine from the very stable PCB ancl dioxin molecules. The
residue structures are generally non-toxic or of lower toxicity than the original compound. These processes were
originally developed for the treatment of PCB-containing oils; several have been suggested for application to
contaminated soils. The sodium strips off the chlorine to form sodium chloride (common salt).
One process, Acurex, follows a two-step procedure. First, dioxins (or PCB's) are extracted from the soil with a
special blend of solvents. The solvents are then treated with a proprietary sodium-based reagent to destroy the
contaminants (Mille, G.J., 1982). A second process, developed by the Franklin Research Institute, applies a. reagent
-------
directly to the soil. The reagent is a chemically-modified sodium polyethylene glycol (NaPEG) complex. The reagent
is quite stable, does not contain metallic sodium, and is not sensitive to small quantities of water (Franklin Research
Institute, 1981).
Wastes Amenable to Treatment
PCB's and dioxms are detoxified. Other halogenated compounds will also be attached by the reagents.
Status of Technology
The technology has been applied to the treatment of PCB-containing oils, but is still in the developmental stage
with respect to soil decontamination.
Ease of Application
The reagents are liquids and should be applied relatively easily. They will react with excess moisture and thus
must be applied under carefully controlled conditions.
Potential Achievable Level of Treatment
Results with PCB oils have shown high levels of detoxification. The same levels are potentially realizable in
soils.
Reliability
Once the compounds are dechlorinated, there is no mechanism to reverse the reaction. If the application is
successful in the first place, no further retreatment should be needed.
Secondary Impacts
The reagents are powerful reducing agents and may react with soil organic matter. The consequences of such
reactions are unknown at present.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are needed. Some sort of temporary cover might be needed to keep
rain off of the treatment area until the reactions are complete. Soil may have to be drained or tilled and allowed to dry.
Reducing agents are needed in sufficient quantity to react with the target contaminants and with other waste and natural
constituents.
Information Requirements
**t~
depth, profile, and areal distribution of contamination;
soil moisture content.
soil temperature
Source of Information
Mille, G.J., 1982; Franklin Research Institute, 1981.
83
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3.4.1.3 Polymerization
Description
A polymer is a large molecule built up by the repetition of small, simple chemical units. A polymerization
reaction is the conversion of a particular compound to a larger chemical multiple of itself (Kirk Othmer Encyclopedia
of Chemical Technology, 1982). The resulting polymer often has different physical and chemical properties from the
initial unit and could be less mobile in the soil system.
It has been demonstrated that naturally occurring iron and sulfates in contaminated soil may catalyze initial
polymerization of contaminants. Treatment solutions containing sulfate-related constituents have been successfully
used in polymerization reactions in the soil (Williams, 1982). Acrylate monomer (4200 gallons) contaminating glacial
sand and gravel layers was polymerized m-place by injecting a catalyst, activator, and wetting agent.
Mercer, B.W., etal. (1970), working with grouting materials and polymeric agents, found the process of in-place
immobilization with these agents expensive and complicated by the logistics of obtaining widespread coverage without
an excessive number of injection wells.
Wastes Amenable to Treatment
Chemical polymerization is most effective for immobilization of organic constituents, preferably those with more
than one double bond. General categories of constituents, applicable to polymerization include aliphatic, aromatic.
and oxygenated monomers, such as styrene, vinyl chloride, isoprene, acrylonitnle, etc. For multi-organic contamina-
tion, catalysts and activators necessary to achieve polymerization may interact with one another
Status of Technology
Experimental studies have been conducted in the field.
Ease of Application
A 2:1 ratio of volume of catalyst and activator to volume of contaminant is used. The catalyst and activator should
be applied in two applications and applied separately to prevent reactions before contact with wastes. A wetting agent
is added to promote rapid and uniform dispersion of solutions through the contaminated area. If ground temperature
falls below 50°F, it may be necessary to warm the treatment solution to 50°F before use. Because of the acidic nature
of treatment reagents, corrosion-resistant application equipment is required
If the surficial zone is too shallow to tolerate sufficient injection pressure for dispersing catalyst and activator
solutions, installation of exfiltration galleries (e.g., a 2-inch diameter perforated PVC casing, buried in trenches below
ground surface across the contaminated zone) is required. A riser pipe and manifold header connect each gallery to
solution tanks which contain catalyst and activator.
This technology is moderate to difficult to apply. In a field study, it was found that obtaining widespread
coverage was difficult without an excessive number of injection wells.
Potential Achievable Level of Treatment
The level of treatment achievable is variable, depending on the waste and soil conditions The potential for long-
term immobilization is unknown at this time.
Reliability of Method
The reliability of the treatment is unknown since there is no information on its long-term effectiveness.
84
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Secondary Impacts
The polymerized area may exhibit decreased infiltration and permeability.
Equipment and Exogenous Reagents
Catalysts and activators are needed. Vendors should be consulted as to the equipment to be used.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
potential for polymerization of waste constituents;
polymerization products;
depth, profile, and areal distribution of constituents;
iron and sulfate content in soil;
catalysts and activators present in soil;
trafficability of soil and site.
Sources of Information
Kirk Othmer Encyclopedia of Chemical Technology, 1982; Mercer, B.W., etal., 1970; Williams, E.B., 1982.
3.4.2 Biological
Biodegradation is an important environmental process causing the breakdown of organic compounds. It is a
significant loss mechanism in soil in the mineralization process by which organics are converted to inorganics.
Micro-organisms, principally bacteria, actinomycetes, and fungi, are the most significant group of organisms
involved in biodegradation, and soil environments contain a diverse microbial population. The parameters influencing
the rate of biodegradation are of two types:
1) those that determine the availability and concentration of the compound to be degraded or that affect
the microbial population site and activity; and
2) those that control the reaction rate.
Important parameters affecting biodegradation include pH, temperature, soil moisture content, soil oxygen
content, and nutrient concentration, among many others (Bonazountas and Wagner, 1981).
Table 3-19 shows rate constants of organic compounds in soil. Table 3-20 shows rates in anaerobic systems.
Biological treatment methods are directed toward enhancing biochemical mechanisms for detoxifying or decom-
posing hazardous waste materials in contaminated soils. Soil micro-organisms, principally the bacteria,
actinomycetes, and fungi, are important in decomposition or detoxification processes. Therefore, treatments applied to
the soil to enhance biological processes must not alter the physical environment in such a way that it would severely
restrict microbial growth and/or biochemical activity. In general, this means that soil temperatures should be between
50°C and 60°C (Atlas and Bartha, 1981); soil water potential should be greater than - 15 bars (Sommers et al., 1981),
pH should be between 5 and 9 (Alexander, 1977; Atlas and Bartha, 1981), and oxidation-reduction (red9x) potential
should be between pe + pH of 17.5 to 2.7 (Baas and Becking et al., 1960). Soil pH and redox boundaries should be
carefully monitored when chemical and biological treatments are combined. With these restrictions in mind several
treatments are considered, both tried and theoretical, which may enhance microbial activity in hazardous waste
contaminated soil.
85
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TABLE 3-19. BIODEGRADATION RATE CONSTANTS FOR
ORGANIC COMPOUNDS IN SOIL
(day-1)
Compound
Die-Away
Test Method
14CO2 Evolution
Aldrin, Dieldrin
Atrazine
Bromacil
Carbaryl
Carbofuran
Dalapon
DDT
Diazinon
Dicamba
Fonofos
Glyphosate
Heptachlor
Lindane
Linuron
Malathion
Methyl parathion
Paraquat
Parathion
Phorate
Picloram
Simazine
TCA
Terbacil
Trifluralin
2,4-D
2,4,5-T
0.013
0.019
0.0077
0.037
0.047
0.047
0.00013
0.023
0.022
0.012
0.1
0.011
0.0026
0.0096
1.4
0.16
0.0016
0.029
0.0084
0.0073
0.014
0.059
0.015
0.008
0.066
0.035
0.0001
0.0024
0.0063
0.0013
0.022
0.0022
0.0086
0.0008
0.0045
0.0013
0.051
0.029
Source: Lyman, W.J., et al., 1982.
86
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TABLE 3-20. BIODEGRADATION RATE CONSTANTS FOR ORGANIC COMPOUNDS
IN ANAEROBIC SYSTEMS (day"')
In
Sewage
Compound Die-Away 14CO2 Evolution Sludge
In Soil
1 4.
Carbofuran
DDT
Endrin
Lindane
PCP
Trifluralin
Mirex
Methoxyclor
2,3,5, 6-Tetrachlorobenzene
Bifenox
0.026
0.0035
0.03
0.025
0.0046
0.07
0.0192
9.6
12.72
6.27
Source: Lyman, W.J., et al., 1982.
3.4.2.1 Modification of Soil Properties
Since the activity of micro-organisms is so dependent on soil conditions, modification of soil properties is a viable
method to enhance the microbial activity in the soil. These soil properties are: soil moisture, soil oxygen content, soil
pH, and nutrient content. Details of how to apply the soil modification techniques are given in Section 4.
3.4.2.1.1 Soil Moisture
Description
When natural precipitation is insufficient to maintain soil moisture within a range that is near optimal for
microbial activity, irrigation may be necessary. Although many microbial functions continue in soils at - 15 bars or
drier, optimum biochemical activity is usually observed at soil water potentials of 0.1 to 1.0 bar (Sommers et al.,
1981).
In a review of soil water potential on decomposition processes in soils, including pesticide degradation, Sommers
et al. (1981) suggested that the effect of soil water potential on pesticide degradation is to alter general microbial
activity and to affect the kinds of micro-organisms which are metabolically active in the soil. Ou et al. (1983) observed
rapid mineralization of methyl parathion in soils at -0.1 and -0.33 bar soil moisture tension, along with the
formation of bound residues. The ratio of the degradation products (p-nitro-phenol to p-aminophenol) increased as the
soils became drier. In dry soil (-15 bar), mineralization of methyl parathion and bound residue formation were
slower. Limited experimentation with the effects of soil moisture on degradation indicates that degradation rates are
highest at soil water potential between 0 and - 1 bar.
The degradation of hazardous organic compounds may be accelerated by soil moisture optimization, and this
approach may be sufficient to bring about required degradation, especially for constituents relatively easy to degrade.
However, more rapid treatment of the contaminated soil may be achieved when moisture augmentation is used in
combination with other techniques.
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Wastes Amenable to Treatment
Biodegradable organic compounds are amenable to this treatment.
Status of Technology
Moisture control is widely practiced in agriculture. However, little information is available on the use of moisture
control to stimulate biological degradation of hazardous materials in soil. Most experimental work in the laboratory on
pesticides and other xenobiotic compound degradation has been conducted at or near optimal soil moisture.
Ease of Application
An irrigation and drainage system is required. Irrigation water is applied using standard irrigation practices.
Irrigation should be applied frequently in relatively small amounts, without exceeding field capacity, to minimize
leaching. Depending on the ease of controlling water at the site and on the availability of a suitable water source (e.g.,
transport distance, drilling of new wells, availability and cost of energy for pumping), it may be easy or difficult to
apply this technology. Controls for erosion and proper drainage due to runoff are necessary.
Potential Achievable Level of Treatment
The achievable level of treatment may be low to high, depending on the biodegradability of waste constituents
and suitability of the site and soil for effective moisture control. The effectiveness of this technology may be enhanced
by the use of other treatment techniques to increase biological activity.
Reliability of Method
This technology is reliable in that it has been used in agriculture, but retreatment is necessary.
Secondary Impacts
Leaching of soluble hazardous compounds may occur. Erosion may also be a problem.
Equipment and Exogenous Reagents
An irrigation system and water are required.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant);
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents;
soil moisture;
other soil properties for biological activity (pH, oxygen content, nutrient content, organic matter,
temperature, etc.);
trafficabihty of soil.and site.
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Sources of Information
Bonazountas, M., and Wagner, J., 1981; Atlas and Bartha, 1981; Sommers, L.E., et a!., 1981; Alexander, M.,
1977; Bass et al., 1960; Lyman, W.J., et al., 1982; Ou et al., 1983.
3.4.2.1.2 Soil Oxygen Content for Aerobic Biodegradation
Description
One reason for the common practices of tilling and/or draining the soil in agriculture is to stimulate organic matter
decomposition in an aerobic environment so that nutrients will be mineralized and made available for plant
assimilation. Aerobic metabolism is more energy-efficient, and microbial decomposition processes are, in general,
more rapid under aerobic conditions Although the decomposition of some xenobiotic organic compounds appears to
require anaerobic metabolism, the majority of organisms in soils shown to be active in pesticide and other xenobiotic
compound decomposition are aerobic (Alexander 1977; Pal et al., 1980, Baker and Mayfield, 1980; Brunner and
Focht. 1983; Sims and Overcash, 1981). In many instances, therefore, assuring the aerobiosis of the soil will enhance
the rate of biological decomposition
Tilling the soil for aeration is common practice in agriculture and has been recommended for hazardous waste-
contaminated soil reclamation by practitioners and researchers (Arthur D. Little, Inc., 1976; Thibault and Elliott,
1979). Soils with high water tables that restrict aeration may also be drained using common agricultural techniques.
Wastes Amenable to Treatment
Organic wastes that are acted upon by micro-organisms under aerobic conditions are amenable to treatment. Most
organics fall into this category of compounds.
Methods of Technology
In the field, tilling the soil for aeration is common practice in agriculture to enhance crop-residue degradation.
and it has been recommended for hazardous waste-contaminated soil reclamation.
Ease of Application
If the site is too wet, a drainage system should be installed. The soil is tilled at periodic intervals to achieve
aeration. Controls to prevent runon and runoff of precipitation are necessary. This technology is easy to difficult.
depending on the characteristics of the soil and the site and the trafficability of the site.
Potential Achievable Level of Treatment
The level of treatment achievable is from low to high, depending on the biodegradability of the waste constituents
and the suitability of the site and soil for maintenance of aerobic conditions.
Reliability of Method
Retreatment at periodic intervals is necessary to assure that the soil oxygen is at a sufficiently high level.
Secondary Impacts
Tillage will increase the susceptibility of the site to erosion.
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Equipment and Exogenous Reagents
Power implements and tillers are necessary.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant);
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents;
soil oxygen content;
other soil properties for biological activity (soil moisture, pH, nutrient content, organic matter,
temperature, etc.);
soil texture,
trafficability of soil and site.
Sources of Information
Pal, et al., 1980; Baker, M.D., and Mayfield. 1980. Brunner, W., and Focht, D.D., 1980; Sims, R.C.. and
Overcash, M.R., 1981; Arthur D. Little, Inc., 1976; Thibault, G.T., and Elliott, N.W., 1979; Lyman. W., et al..
1982; Atlas and Bartha. 1981; Bass, J., et al., 1960.
3.4.2.1.3 Soil Oxygen Content for Anaerobic Biodegration
Description
There is increasing evidence that some halogenated xenobiotic compounds may be dehalogenated or completely
degraded under anaerobic conditions (Sulflita, J.M., et al., 1982; Sulflita, J.M., and Tiedje, J.M., 1983; Horowitz,
A., et al., 1983; Sulflita, J.M., et al., 1983; Kobayashi and Rittman, 1982; Pfaender and Alexander, 1972).
Therefore, manipulation of contaminated soil to create an anaerobic, reducing environment to enhance the decomposi-
tion of certain hazardous waste constituents should be considered. Apparently, the redox potential (Eh) of the
environment must be below 0.35V for significant reductive dechlorination to take place, but exact-requirements
depend upon the individual compounds being reduced (Kobayashi and Rittman, 1982). Reductive reactions may be
catalyzed by both abiotic and biochemical means in anaerobic environments.
Once a recalcitrant compound has been altered by reductive reactions under anaerobic conditions, it may be more
amenable to decomposition under aerobic conditions. For example, the reductive dechlorination of 2,4,5-trichlorophe-
noxyacetic acid (2,4,5-T) under anaerobic conditions to 2,4-dichlorophenoxyacetic acid (2,4-D) which is readily
degraded in the soil under aerobic conditions has been described (Munnecke et al., 1982). Laboratory experimentation
may show that anaerobic soil conditions followed by aeration may enhance biological decomposition of some
hazardous waste constituents. However, Marinucci and Bartha (1979) evaluated weekly alterations between anaerobic
and aerobic conditions for enhancement of biodegradation of trichlorobenzenes in soil and found no improvement in
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mineralization rates. The trichlorobenzenes were mineralized most rapidly under continuous aerobic conditions. Other
classes of compounds may not follow this pattern, and more research is needed to further evaluate the potential for
treatment by using alternating anaerobic and aerobic conditions. Longer periods between alternation may be
appropriate.
Arthur D. Little, Inc. (1976), also reported that the only proven method of creating anaerobic conditions is to dike
and flood the soil in a fashion similar to that used to grow rice. They cite unpublished work by W. Farmer at the
University of California at Riverside in which a 1.5-acre DDT-contaminated field was amended with organic matter,
flooded, and the soil temperature increased. Complete transformation of the DDT to ODD was observed in 18 days.
They suggest that, without this treatment, the transformation to DDD would have taken more than 2 years. Flooding
the soil presents opportunities for leaching of hazardous materials from contaminated soil and is probably not advisable
in most hazardous waste-contaminated soils. However, it should be possible to lower the redox potential of the soil by
adding excessive amounts of readily biodegradable organic matter, compacting the soil to reduce oxygen diffusion
through large soil pore spaces, keeping the soil wet without exceeding the gravitational water potential (field capacity),
and perhaps deep mulching to impair oxygen diffusion to the soil surface.
Applications of this method of inducing anaerobiosis have not been identified in the literature as used either in the
field or under laboratory conditions. Reductive dehalogenations or other reductive reactions that lead to decomposition
or detoxification of specific hazardous waste constituents should be verified from the literature or from experimenta-
tion before this treatment is used.
Wastes Amenable to Treatment
Organic wastes that are biodegradable under anaerobic conditions, e.g., halogenated compounds, are amenable to
this treatment.
Status of Technology
In the field, this technology is only conceptual. Neither are there any reported laboratory studies using this
technique.
Ease of Application
Organic materials are applied and incorporated into the soil. Irrigation water is applied using standard irrigation
practices. Irrigation water should be applied in amounts large enough to create anaerobic sites in the soil, but not to
cause leaching. Mulches may also be applied to act as a barrier to oxygen diffusion into the soil. The soil may be
compacted to reduce porosity. Runon and runoff controls are necessary. This technology involves a complex
combination of soil manipulations (i.e., moisture control, organic amendment, compaction, and mulching) and may
range from moderate to difficult to apply.
Potential Achievable Level of Treatment
Depending on the degradative pathway of the constituents, the achievable level of treatment may range from low
to high. This technology may result only in partial degradation, requiring the establishment of aerobic conditions to
complete treatment.
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Reliability of Method
Retreatment is necessary as frequently as required to maintain anaerobic conditions.
Secondary Impacts
This technology may result in the formation of toxic volatile forms of metals (e.g., methylated mercury and
arsines), hydrogen sulfide, and other nuisance odor compounds. Leaching of hazardous constituents may also occur if
water addition is not carefully controlled. Organic materials may have many effects on soil properties, including:
degree of structure;
water-holding capacity;
bulk density;
immobilization of nutrients, hindering degradation of organic wastes;
reduction in soil erosion potential;
soil temperature.
Organic materials may also result in excessive nitrate levels in receiving waters, depending on the nitrogen
content and degree of mineralization of the material.
Equipment and Exogenous Reagents
Power implements, compactors and an irrigation system are necessary The exogenous materials required are
irrigation water and organic materials, e.g., mulches.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant).
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents;
soil oxygen content;
other soil properties for biological activity (soil moisture, pH, nutrient content, organic matter,
temperature, etc.);
soil water holding capacity;
suitability of site to flooding and drainage;
trafficability of soil and site.
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Sources of Information
Sulflita, J.B., et al., 1982; Sulflita. J.M.. et al . 1983; Sulflita. J.M.. and Tiedje. J.M . 1983: Horowitz. A . et
al.. 1983; Sulflita, J.M., et al., 1983; Kobayashi. H.. and Rittman. B.E.. 1982; Pfaender. F.K.. and Alexander. M..
1972; Munnecke, D.M., et al., 1982; Marmucci. A.C.. and Bartha. R.. 1979; Arthur D. Little. Inc.. 1976:
Alexander, 1977; Atlas and Bartha. 1981. Bass et al., 1960; Lyman et al., 1982: Bonazountas. M.. and Wagner. J..
1981; Munnecke, D.M., 1980.
3.4.2.1.4 Soil pH
Description
Depending on the nature of the hazardous waste components contaminating the soil, it may be advantageous to
optimize the soil pH for a particular segment of the microbial population, since microbial community structure and
activity are affected by soil pH (Gray. 1978. Alexander. 1977). Some fungi have a competitive advantage at slightly
acidic pH, while actmomycetes flourish at slightly alkaline pH (Alexander. 1977). Soil pH has also been shown to be
an important factor in determining trie effect various pesticides have on soil micro-organisms (Anderson, 1978) Near
neutral pH values are probably most conducive to microbial functioning in general The recent discovery that fungal
metabolism of polynuclear aromatics (PNAs) is qualitatively similar to mammalian metabolism in that mutagenic
arene oxides (epoxides) are produced as initial oxidation products (Cermglia and Gibson. 1979; Cerniglia et al.. 1979)
suggests that fungal degradation of PNAs in the environment should be discouraged. Although the effect of soil pH on
the formation of epoxides from PNAs has not been demonstrated, it may be advantageous to maintain pH near
neutrality to encourage a relatively higher bacterial activity in soils contaminated with these compounds
It may be necessary to treat contaminated soil with crushed limestone or lime products to raise the pH to the
desired range, or with acid-producing materials or sulfur to lower the pH. Methods for determining the lime
requirement of agricultural soils that take into account the buffering capacity of the soil (McLean et al.. 1966.
McLean, 1982) have been developed, but guidelines for reducing soil pH are not readily available, and the addition of
acidifying agents must be determined experimentally in the laboratory.
Wastes Amenable to Treatment
Organic wastes that are biodegradable are amenable to this treatment.
Status of Technology
Liming is a common agricultural practice. Acidification is much less commonly required.
Ease of Application
A lime requirement test may be performed to determine loading rate for increasing soil pH. Acidification
requirements for a particular soil have to be determined experimentally. Buffering capacity of the waste must also be
considered.
Thorough mixing is required in the zone of contamination to effect pH change. Because the soil is tilled, runoff
and minor controls are necessary to control drainages and erosion. This technology ranges from easy to difficult to
apply, depending on the trafficability of the soil and the depth of contamination.
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Potential Achievable Level of Treatment
The achievable level of treatment is high, depending on the biodegradability of the wastes and the suitability of
the site and the soil.
Reliability of Method
Retiming or reacidification is necessary as treatment progresses.
Secondary Impacts
Dissolution or precipitation of materials within the soil are affected by changes in soil pH. Care must be taken to
assure that hazardous materials do not increase in mobility due to the raising or lowering of soil pH. Tillage increases
the susceptibility of the site to erosion.
Equipment and Exogenous Reagents
Applicators, tillers, and power implements are required. Depending on the wastes and the soil characteristics.
liming or acidifying material is required.
Information Requirements
characterization and concentration of wastes, particularly organics at site:
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant):
biodegradation products (particularly hazardous products);
depth, profile, and area! distribution of constituents;
soil pH;
other soil properties for biological activity (oxygen content, soil moisture, nutrient content, organic
matter, temperature, etc.):
trafficability of soil and site.
Sources of Information
Gray. 1978; Alexander. 1977; Anderson, 1978; Cerniglia. and Gibson. 1979. Cerniglia, et al . 1979; McLean.
1982; McLean, et al., 1966.
3.4.2.1.5 Soil Nutrients
Description
Although most micro-organisms are capable of very efficient extraction of inorganic nutrients from their
environment, their activity may be limited by nutrient availability. This is especially true if available carbon is in large
excess relative to the nitrogen and/or phosphorus required by the micro-organisms that degrade it. Determination of
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soil organic carbon, organic nitrogen, and organic phosphorus allows the determination of its C:N:P ratio and an
evaluation of nutrient availability. If the ratio of organic C:N:Pis wider than about 300:15:1 and available (extractable)
inorganic forms of N and P do not narrow the ratio to within these limits, supplemental nitrogen and/or phosphorus
should be added (Alexander, 1977; Kowalenko, 1978). Excesses or deficits of nitrogen or phosphorus brought about
by addition of any organic amendments should be taken into account, and commercial fertilizers can be used to make
up any deficit.
Adding fertilizer to hasten the decomposition of crop residues is used in agriculture (Alexander, 1977), and this
procedure has been used in the treatment of hazardous waste (oil spill)-contaminated soils (Thibault, and Elliott,
1980). Skujins, et al. (1983) studied the biodegradation of waste oils at a disposal site whose soils were amended with
calcium hydroxide, phosphate, and urea. Within 4 years, 90 percent of the applied oil (added 7.5 percent by weight to
the surface 10 cm) was degraded.
Wastes Amenable to Treatment
Biodegradable organics are amenable to this treatment.
Status of Technology
In the field, this technology is commonly used in agriculture. It has also been used in the treatment of oil wastes.
Ease of Application
Fertilizers are added to the soil using standard agricultural methods. Depending on the nutrient type, physical
state, solubility of the fertilizer, and depth of contamination, the fertilizer is incorporated into the soil as necessary.
Sufficient N and P is applied to ensure that these nutrients do not limit the microbial and metabolic activity. Controls to
manage the runon and runoff from the site are necessary to prevent drainage and erosion problems. This technology
ranges from easy to difficult to apply, depending on trafficability considerations.
Potential Achievable Level of Treatment
If nutrient availability is limiting or retarding microbial degradation or detoxification of organic hazardous waste
constituents, the achievable level of treatment would be high if the site and soil characteristics are suitable.
Reliability of Method
Retreatment may be necessary at intervals as nutrients are used up in the process. Liming and reliming may be
necessary to maintain optimal pH'for biological activity.
Secondary Impacts
Caution must.b_e used in the application of nitrogen to the soil to avoid excessive application. Nitrate or other
forms of nitrogen irfthe soil oxidized to nitrate may be leached to groundwater. Also, some nitrogen fertilizers tend to
lower the soil pH, necessitating a liming program to maintain pH optimal for biological activity. Tillage will increase
the susceptibility of the site to erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are required to apply the fertilizer to the soil.
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Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant);
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents;
soil nutrient (concentration of all essential nutrients, particularly limiting nutrients);
other soil properties (pH, soil moisture, oxygen content, organic matter, temperature, etc.);
trafficability of soil and site.
Sources of Information
Alexander, 1977; Kowalenko, 1978; Thibault and Elliott, 1980; Skujins, et al., 1983; Bass et al., 1960;
Bonazountas and Wagner, 1981; Lyman, et al., 1982; Atlas and Bartha, 1981.
3.4.2.2 Addition of Non-specific Organic Amendments
Description
Stimulating general soil microbial activity and population size through organic matter addition improves the
opportunities for selection of organisms that can degrade hazardous waste components. High microbial activity
provides opportunity for cometabolic processes to act on recalcitrant hazardous waste components. Addition of
manures, plant materials, and/or wastewater treatment digester sludge at levels characteristic of composting may prove
valuable to biological treatment of hazardous waste-contaminated soils (Kaplan, and Kaplan, 1982a; Doyle and
Isbister, 1982).
Extensive laboratory research has shown that supplemental carbon and energy sources can stimulate the
metabolism of xenobiotic, often recalcitrant compounds. The breakdown or transformation of these compounds can be
through cometabolism (Alexander, 1981), or metabolism of the compound may simply be stimulated by the
supplemental carbon and energy source (Yagi and Sudo, 1980). Composting of contaminated soil has been shown to
degrade hexahydro-1,3,5-trinitro-l,3,5-triazine (RDX), while the ring structure of 2,4,6-trinitrotoluene (TNT) was
not mineralized. The TNT residues were apparently strongly sorbed to the compost (Doyle and Isbister, 1982).
Camoni, et al., (1982) demonstrated that addition of organic compost to soil had no significant effect on the half-life (1
year) of 2,3,7,8-TCCD in soil.-The degradation of pentachlorophenol and pentachloronitrobenzene in a laboratory
composting system has also been studied (Sikora, et al., 1982).
Laboratory experimentation may be needed to determine the biochemical fate of given hazardous compounds in
organically enriched soil or compost, and the environmental hazards associated with any residues evaluated (Kaplan
and Kaplan, 1982b). Residues may be more or less toxic than the parent compounds. Residues of hazardous
compounds may not be extractable from organically enriched soil using ordinary solvents, suggesting strong binding to
organic matter or other soil constituents (Doyle and Isbister, 1982; Khan, 1982; Wallnofer, et al., 1981; Bartha, 1980;
Stevenson, 1972). Enzymatic activities of soil micro-organisms can be responsible for coupling xenobiotic compounds
and their breakdown products to soil humic materials (Bollag, 1983; Bollag, et al., 1983; Sjobland and Bollag, 1981;
Liu, et al., 1981; Sulflita and Bollag, 1980; Bollag, et al. 1980; Bollag, et al. 1978). Careful monitoring for bound
hazardous organic compounds, including toxic metabolites of hazardous parent compounds should be performed.
Humus-bound xenobiotic compounds may be slow to mineralize or be transformed to innocuous forms (Khan, 1982;
Chowdhury, et al., 1981). In such cases, increasing the humic content of the soil may not be the method of
choice.
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Microbial decomposition of humic matter that contains bound hazardous organic compounds can release these
compounds to the soil solution, where they are subject to leaching, volatilization, or reattachment to soil organic
matter. This potential mobility of bound hazardous compounds suggests that treatment is not complete until their
absence or safe level in the soil can be demonstrated (Bartha, 1980; Saxena and Bartha, 1983b; Khan and Iverson,
1982).
No examples of field trials of this treatment technique are available. Doyle and Isbister (1982) observed 55
percent degradation of RDX in compost incubated in a greenhouse in 6 weeks. In the same study, TNT levels were
reduced by more than 99 percent within 3 weeks, but very little decomposition (mineralization) was observed.
Aerobic heterotrophic bacteria oxidize arsenite (As + 3) to arsenate (As + 5) with the consumption of 02. An
available reserve of organic matter must be present in the soil for the oxidation to occur. Therefore, when arsenite
contaminates a soil in concentrations that are below toxic levels for soil heterotrophs, it will be possible to oxidize the
arsenite to arsenate by amending the soil with readily available organic matter and maintaining aerobic conditions in
the soil. Oxidation of arsenite in laboratory soil perfusion systems has been described by Quastel and Scholefield
(1953). The microbial biochemistry of arsenic has been reviewed by Alexander (1977) and Konetzka (1977). Further
treatment with ferrous sulfate will form highly insoluble FeASO4.
Wastes Amenable to Treatment
Biodegradable organic wastes and arsenite wastes are amenable to this treatment.
Status of Technology
There are no examples of field trials. Chemical precipitation is usually used to treat arsenite wastes at landfill
sites. Extensive laboratory research has shown that supplemental carbon and energy sources can stimulate metabolism
of even recalcitrant compounds. Experimental soil systems have demonstrated the microbial oxidation of arsenite to
arsenate.
Ease of Application
The quantity of organic material required must be determined in treatability studies. Nonspecific, readily
biodegradable organic matter should be added and mixed into the soil as dry materials or as slurries. The soil moisture
level should be optimized, and frequent mixing is required to maintain aerobic conditions. Runon and runoff controls
are required. This technology is easy or difficult, depending on the trafficability of the soil and site, and the depth of
contamination.
Potential Achievable Level of Treatment
The potential achievable level of treatment ranges from low to high, depending on the solubility, sorption, and
biodegradability of the organic constituents in the waste. Some arsenite may be bound to the soil and will not be
available for oxidation. Available (extractable) arsenite should be quickly and completely oxidized.
Reliability of Method
This technolgy may require reapplications to complete treatment.
Secondary Impacts
Hazardous constituents may be initially bound to organic materials, but later released as organic materials
decompose.
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Under anaerobic conditions, the added organic matter may result in the reduction and methylation of arsenic to
volatile forms. Anaerobic conditions must be avoided. However, anaerobic microsites are known to exist even in well-
aerated soil, and some volatile metal compounds may be produced even in carefully managed soils. Tillage will
increase the susceptibility of the site to erosion.
Organic materials may have many effects on soil properties, including:
degree of structure;
water-holding capacity;
bulk density;
immobilization of nutrients, hindering degradation of organic wastes;
reduction in soil erosion potential;
soil temperature.
Organic materials may also result in excessive nitrate levels in receiving waters, depending on the nitrogen
content and degree of mineralization of the material.
Equipment and Exogenous Reagents
Power implements, tillers, applicators, and proper drainage are required. The exogenous reagent required is
organic material.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant);
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents;
soil organic matter;
other soil properties (pH, soil moisture, oxygen content, nutrient content, temperature, etc.);
trafficability of soil and site.
Sources of Information
Kaplan and Kaplan, 1982a and 1982b; Doyle, Isbister, 1982; Alexander, 1981; Yagi, and Sudo, 1980; Camoni,
et al., 1982; Sikora, et al., 1982; Khan, 1982; Wallnofer, et al., 1981; Bartha, 1980; Stevenson, 1982; Bollag, 1983;
Bollag, et al., 1983; Sjobland and Bollag, 1981; Liu, et al., 1981; Sulflita and Bollag, 1980; Saxena and Bartha,
1983a and 1983b; Khan and Iverson, 1982; Quastel and Scholefield, 1953; Konetzka, 1977; Lyman, et al., 1983;
Bonazountas and Wagner, 1981; Sikora L.J., et al., 1982.
3.4.2.3 Analog Enrichment for Cometabolism
Description
Adding a chemical analog of a hazardous compound to a contaminated soil or to culture media can accomplish
cometabolism of the hazardous compound (Sims and Overcash, 1981; Pal et al., 1980; Furukawa, 1982; Focht and
Alexander, 1970). Apparently, enzymes proliferated by micro-organisms to metabolize an energy-yielding substrate
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with structural similarity to a recalcitrant xenobiotic compound can, in certain cases, transform the recalcitrant
molecule cometabolically (Alexander, 1981). For compounds where the transformation product.of the cometabolic
process is not hazardous or is degradable by other organisms in the soil microbial community, analog enrichment may
be an effective treatment for contaminated soil.
Sims and Overcash (1981) used analog enrichment with phenanthrene to increase the rate of degradation of
benz(a)pyrene, resulting in a decrease of 35 percent in the half-life. Biphenyl has been used to stimulate cometabolic
degradation of PCBs (Furukawa, 1982).
Close chemical analogs to hazardous compounds or their degradation products may be hazardous. Therefore, caia
must be used in selecting and using analog exogenous agents for treatment.
Wastes Amenable to Treatment
Organic waste containing constituent(s) having analogs with high rates of degradation by organisms without
producing toxic products are amenable to treatment.
Status of Technology
No information is available on the field level. In the laboratory, studies that are limited in number and range of
compounds have shown that analog enrichment can accomplish cometabolism.
Ease of Application
Analog compounds are added in amounts large enough to stimulate microbial activity, but not enough to be toxic
to microbial functions or to adversely affect public health and the environment. Treatability studies are required to
determine the feasibility, loading rate, and effectiveness of the analog(s). The analogs may be applied as solids,
liquids, or slurries and mixed thoroughly with the contaminated soil. Fertilization may be required to maintain
microbial activity. Controls may be necessary to prevent drainage and erosion problems. This technology may range
from easy to difficult to apply, depending on the trafficability and the depth of contamination.
Potential Achievable Level of Treatment
The level of treatment may range from low to high, depending on the susceptibility of the hazardous constituent to
cometabolism.
Reliability of Method
The reliability of this technology is unknown.
Secondary Impacts
Tillage will increase the susceptibility of the site to erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are required to apply the analog compounds.
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Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-oganisms present at site;
biodegradability of waste constituents (half-life, rate constant);
availability of structural analog(s) to waste constituent(s);
degradation pathway for analog;
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents;
other soil properties (pH. soil moisture, soil nutrient content, oxygen content, organic matter,
temperature, etc.);
trafficability of soil and site.
Sources of Information
Sims and Overcash, 1981; Pal, et al., Furukawa, 1982; Focht, and Alexander, 1970; Alexander, 1981;
Bonazountas and Wagner, 1981; Lyman, et al., 1982; Alexander, 1977.
3.4.2.4 Augmentation with Exogenous Acclimated or Mutant Micro-organisms
Description
Biological treatment methods described thus far have relied on the stimulation of microbial activity in the soil or
on the natural selection of populations of micro-organisms, which can degrade toxic waste constituents. These
approaches show considerable promise for treating many kinds of organic hazardous waste constituents. However, the
metabolic range of the natural soil microbiota may not include the capability to degrade certain compounds or classes
of compounds. In addition, microbial metabolic specialists may not develop large enough populations under limited
substrate conditions to degrade xenobiotic compounds rapidly enough to meet treatment criteria. In situations such as
these, it may be advisable to add exogenously grown micro-organisms to the soil. Microbial inoculants are available
commercially with the broad range of metabolic capabilities, and experience in their use in both soil and aquatic
systems contaminated with waste chemicals is expanding (Anonymous, 1981, 1982; Thibault and Elliot, 1980; Walton
and Dobbs, 1980; Thibault and Elliot, 1979). Table 3-21 lists suppliers of biological products that have been or may be
used to treat hazardous waste-contaminated soils. Frequently, the application of microbial amendments to the soil is
combined with other treatment techniques such as soil moisture management, aeration, and fertilizer addition.
. Laboratory trials have recently demonstrated the potential of exogenously grown, xenobiotic compound degrad-
ing bacteria to quickly degrade target compounds. Edgehill and Finn (1983) inoculated pentacholorophenol (PCP)
degrading Arthrobacter and observed rapid degradation of PCP (t[/2 < 1 day) when the soil was incubated at 30°C. In
soil treated under a roof where temperatures ranged from 8 to 16°C, PCP degradation was much slower, but mixed
inoculated soil lost PCP faster than the control.
Kilbane et al. (1983) used repeated applications of a "genetically engineered" Pseudornanas cepacia with the
ability to mineralize 2,4,5-tnchlorophenoxyacetic acid (2,4,5-T) obtaining 90 percent to essentially complete removal
100
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TABLE 3-21. COMMERCIAL MICROBIAL AUGMENTATION PRODUCTS OR PROCESSES
USED TO TREAT HAZARDOUS WASTE CONTAMINATED SOILS
Product Product
Vendor Address Name(s) Description
Flow Laboratories
Environmental
Cultures
Division
General
Environmental
Science
Groundwater
Decontamination
Systems, Inc.
Polybac/Cytox
Corporation
Sybron
Biochemical
Ingelwood, CA
Beachwood, OH
Waldwick, NJ
Allentown, PA;
San Francisco, CA;
Gonzales, FL
Birmingham, NJ;
Salem, VA
DBC Plus;
Types A,
A-2,B,F,
and H-1.
LLMO
CDS process
Polysoil
process
Chemical-
biological
augmentation
process
Detoxsol
Formulated from
specifically cul-
tured bacteria
preserved by freeze
drying and air dry-
ing techniques.
Mixture of 7
bacterial strains
(Bacillus,
Pseudomonas,
Nitrosomonas,
Nitrobacter,
Cellulomonas,
Acrobacter,
Rhodopseudomonas)
in liquid suspension.
Technique involves
circulating water
from the soil into
an environmentally
controlled tank.
Nutrients are added
and the water is
aerated. Treated
water is returned to
the soil. Air may be
injected into the soil
to stimulate further
biodegradation.
Mutant bacteria
formulatron, nitro-
gen and phosphorus
fertilizer, and bio-
degradable
emulsifier.
Uses chemical
treatment ahead
of biological
treatment to
shorten treatment
time (currently in
experimental and
demonstration
stages).
Formulation of
mutant bacteria.
buffer nutrients.
growth stimulator,
and detoxifying
agents.
Treatment
25 Ib/acre
(Site
dependent)
(Site
dependent)
100 Ib.
organisms +
400 Ib.
fertilizer
and
emulsifier
if needed.
363 Ib/acre
Price
$/Unit
10.50-
15.80/lb
$16.00/
gallon
$0.02/gal
treated
$27/lb
$/Acre
$263-
395.00
$3227-
8067.00
per
application
$40,300-
161,300
for total
treatment
$9,801 b
a. Includes labor, equipment, and products. Usually 2 to 6 applicati
process.
b. Prices for treatment of areas larger than 2000 ft are negotiable.
i the Polysoil
Source: Utah Water Research Laboratory
101
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of 2,4,5-T from contaminated soil within 6 weeks. When the 2,4,5-T was exhausted, the population of P. cepacia
became undetectable, but when 2,4,5-T was added to the soil 12 weeks after initial treatment, regrowth occurred.
This method may be most effective against one compound or closely related compounds. Toxicity or the inability
of the micro-organisms to metabolize a wide range of substrates may limit their effectiveness.
Recent research advancements in genetic engineering, particularly in interstrain and interspecies genetic transfer,
hold out hope for development of organisms with extraordinary abilities to degrade xenobiotic compounds (Cha-
krabarty, 1982; Johnston and Robinson, 1982; Chakrabarty, 1980). More information is required, however, on the
ability of genetically engineered organisms to survive, grow, and function in the soil environment (Stotsky and
Krasovsky, 1981, Liang et al., 1982).
Wastes Amenable to Treatment
Compounds or classes of compounds which may be degraded by mutant or selected bacterial cultures which are
available commercially are shown in Table 3-22.
State of Technology
This technology has been demonstrated in the laboratory and has been used in several full-scale soil decontamina-
tion operations. Case histories of treatment of chemical spill sites (oil spill, orthochlorophenol spill, and acrylonitrile
spill) reported by Thibault and Elliott (1979, 1980) and Walton and Dobbs (1980) were deemed successful. However,
some hazardous waste clean-up practitioners are skeptical about the use of this technology, since the soil environment
is so important in determining microbial activity and hence the success of applying exogenous organisms
(Anonymous, 1982). More information is required on the ability of exogenous organisms to service, grow, and
function in the soil environment.
Ease of Application
Methods for application are determined in consultation with the vendor of the micro-organisms. The micro-
organisms may be applied in liquid suspension or with a solid carrier. Depending on the method of application, runon
and runoff controls may be necessary. The ease of application depends on the trafficability and the depth of
contamination.
Potential Achievable Level of Treatment
With waste constituents that are susceptible to degradation by the added micro-organisms and when the site and
soil are conducive to microbial activity, the potential level of treatment is high.
Reliability of Method
Relatively long periods of time may be required to complete treatment. Excessive precipitation may "wash out"
the inoculum, necessitating retreatment.
Secondary Treatment
Tillage, if used, will increase the susceptibility of the site to erosion.
Equipment and Exogenous Reagents
These vary according to the micro-organisms used, as recommended by the vendor. Micro-organisms are usually
applied by the vendors.
102
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TABLE 3-22. COMPOUNDS OR CLASSES OF COMPOUNDS THAT HAVE BEEN (OR COULD BE)
DEGRADED BY COMMERCIALLY AVAILABLE MICROBIAL AUGMENTATION PRODUCTIONS
Alcohols
Esters
n-Butyl alcohol
Dimethylammoethanol
Alkyl Halides
Ethylene dichloride (1,2-Dichloroethane)
Methylene chloride (Dichloromethane)
Propylene dichloride (1,2-Dichloropropane)
Amines
Dimethylanilme
Trimethylamme
Aromatic Hydrocarbons
Divinyl Benzene
Polynuclear Aromatic Hydrocarbons (PNA's)
Styrene (Vinyl Benzene)
Chlorinated Aromatics
Polychlormated biphenvls (PCB's)
Methacrylates
Ketones
Acetone
Nitriles
Acrylonitnle
Phenols
Phenol
Metachlorophenol
Orthochlorophenol
Pen tach I oro phenol
Resorcmol (1,3-Benzenediol)
t- Butylcatechol
Crude and refined oils
Emulsifiers
Detergents
Source: Utah Water Research Laboratory
Information Requirements
characterization and concentration of wastes, particularly organics at site:
micro-organisms present at site;
metabolic capability of exogenously grown micro-organisms;
pathogenicity to susceptible populations;
biodegradability of waste constituents (half-life, rate constant);
biodegradation products (particularly hazardous products);
depth, profile, and areal distribution of constituents,
other soil properties (pH, soil moisture, nutrients, oxygen content, organic matter, temperature, etc ):
trafficabihty of soil and site;
climate, particularly precipitation.
Sources of Information
Anon., 1982; Thibault and Elliott, 1979, 1980; Walton and Dobbs. 1980; Edgehill and Finn, 1983; Kilbane. et
al., 1983; Chakrabarty, 1980, 1982; Johnson and Robinson, 1982; Stotsky and Krasovsky, 1981; Bonazountas and
Wagner, 1981; Lyman, et al., 1982; Alexander, 1977.
103
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3.4.2.5 Application of Cell-free Enzymes
Description
Enzymes, produced by micro-organisms, which can transform hazardous compounds to nonhazardous or more
labile products, could possibly be harvested from cells grown in mass culture and applied to contaminated soils. Crude
or purified enzyme extracts are commonly used in industry either in solution or immobilized on glass beads, resins, or
fibers to catalyze a variety of reactions, including the breakdown or transformation of carbohydrates and proteins.
Munnecke, et al. (1982) discussed the enzymology of selected pesticide degradation, and suggested that extracted
(cell-free) enzymes might be used to quickly transform pesticides in soils. They pointed out that a bacterial enzyme
preparation has been used to detoxify organophosphate pesticide waste from containers (Munnecke, 1980), and that
the enzyme parathion hydrolase hydrolyzed 1 percent parathion ordiazinon within 24 hours in contaminated soil.
Enzyme activity can often be preserved in environments which are not hospitable to micro-organisms. Enzymes
could possibly be used in soils with extremes of pH and temperature, high salinity, or high solvent concentrations, i.e.,
in soils where microbial growth may be restricted. In milder soil environments, enzymatic hydrolysis or oxidation of a
compound may make it more susceptible to decomposition by the soil micribiota (Munnecke, et al., 1982).
To function outside the cell in the soil environment an enzyme must not require co-factors or co-enzymes a
requirement that will limit the application of many enzymes. Enzymes may also be chemically and/or biologically
degraded. They may be leached out of the treatment zone, and they may be inactive or have lower activity if they are
bound to clay or humus in the soil. Outside of biochemical and environmental constraints, logistics and costs for
producing enzymes in large enough quantities may limit current use of this concept.
Wastes Amenable to Treatment
Organic wastes primarily are amenable to this treatment.
Status of Technology
Theoretically, enzymes would quickly transform hazardous compounds if they remained active in soil. There
have been laboratory experiments with parathion hydrolase.
Little information is available on the use of this technique in soil. The only example at l.he present time is the work
by Munnecke, et al. (1982). There is no information available from the field.
Ease of Application
For treatment of pesticides, application rates of 1 mg crude protein per 100 mg of pesticide in soil have been
suggested (Munnecke, personal communication, July 1983). Thorough mixing with the soil is necessary. Enzymes are
sprayed on soil in solution or suspension, or spread with solid carrier, using sprayers or fertilizer spreaders. The poor
availability of appropriate enzymes for hazardous waste constituents makes application difficult. Depending on
application method, controls to prevent runon and runoff may be necessary.
Potential Achievable Level of Treatment
Given the appropriate enzyme and if the enzyme remains active in the soil, the potential achievable level of
treatment is high.
Reliability of Treatment
The reliability of this technology is unknown.
104
-------
Secondary Impacts
Enzymatic degradation products may not be less hazardous than parent compound(s). Products may be more
water soluble and/or mobile in the soil. Tillage, if used, will increase the susceptibility of the site to erosion.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are necessary for application of this treatment. Enzymes for treating
hazardous waste constituents are not currently in bulk production. Although increases in the use of industrial enzymes
have been projected (O'Sullivan, 1981), only eight companies accounted for 90 percent of worldwide production in
1981. Five of these companies are located in western Europe. Only 16 enzymes (primarily amylases, proteases,
oxidases, and isomerases) accounted for 99 percent of the 1981 market. This information suggests that specialized
enzyme production, even on a large scale, may be quite expensive. Current prices for bulk enzyme materials range in
price from $1.45 to $164 per pound. If the enzyme can be produced through chemical synthesis, it will be much less
expensive than if it is produced by micro-organsims in fermenters (Miles Laboratories, personal communication, July
1983).
Information Requirements
characterization and concentration of wastes, particularly organics at site;
micro-organisms present at site;
biodegradability of waste constituents (half-life, rate constant);
biodegradation products (particularly hazardous products);
cell-free enzymetic activity for transformation of the compound(s) of interest;
co-factor requirements of enzyme;
stability of enzyme under soil environmental conditions;
depth, profile, and areal distribution of constituents;
other soil properties (pH, salinity, soil moisture, nutrients oxygen content, organic matter, temper-
ature, etc.);
trafficability of soil and site.
Sources of Information
Munnecke, et al., 1980, 1982; O'Sullivan, 1981.
3.4.3 Photolysis
Utilization of the lower atmosphere as a treatment medium requires an analysis of both the photoreaction potential
and the volatility of the compounds of interest. Volatilization and dilution alone are not considered as acceptable
treatment methods. An adequate assessment of the potential for the use of photodegradation requires information
regarding the compound's atmospheric reaction rate (log KQH°) ancl anticipated reaction products. While this
information is available for a selected number of compounds (Cupitt 1980; Lemaire et al., 1980), much more data are
required if photodegradation is to become a viable treatment option.
If a compound is determined to be poorly photoreactive, e.g., a t1/2 in the atmosphere greater than 1 day,
volatilization suppression may be required to maintain safe ambient air concentrations at the site. Volatilization
suppression techniques are described in Section 3.6.
105
-------
Photodegradation is the use of incident solar radiation to carry out photoreaction processes. Both direct photolysis
(photoreactions due to direct light absorption by the substrate molecule) and sensitized photo-oxidation (photoreac-
tions mitigated by an energy-transferring sensitizer molecule) are possible under environmental conditions. Sensitized
photoreactions are characteristically ones of photo-oxidation resulting in substrate molecule oxidation rather than
substrate isomerism, dehalogenation, or dissociation characteristic of direct photolysis reactions.
The rate of photoreaction is influenced by the nature of light reaching the reaction medium, the absorption
spectrum of the reacting species of sensitizer, the concentration of reacting species, the energy yield produced upon
light energy absorption, the nature of the media in which the reaction is taking place, and the interactions that occur
between the contaminant and its surroundings. Overall, reactions are a complicated function of the characteristics
listed above. Photolysis reaction rates and breakdown products are only crudely understood.
Although the occurrence of the soil photoreaction of adsorbed chemicals has been identified, the importance of
this reaction as compared to aqueous or vapor photoreactivity has not been identified. Soil photodecomposition will be
of concern if the compound or compounds remain relatively stationary within the contaminated soil, e.g., high values
of KD (soil:water partition coefficient) and high values for Kw (air:water partition coefficient). Soil characteristics
including soil organic content (Spencer, et al., 1980), transition metal content (Nilles and Zabik, 1975), and soil
pigment content (Hautala, 1978) have been indicated as affecting photochemical reactions within soil systems.
Moisture content and its effect upon chemical partitioning within the air/water/soil matrix within a soil system will also
potentially have a great impact upon soil photoreactions (Burkhard and Guth, 1979; Hautala, 1978).
Information regarding the photolysis of pesticides in air is generally available due to the relatively high volatility
of pesticides and the concern for their transport via the air medium. The major photoreaciion taking place with
pesticides in the atmosphere is oxidation (Crosby, 1971; Plimmer, 1971) involving the OH radical or ozone, of which
the OH radical is the species of greatest reactivity (LeMaire, et al., 1982). Based on a first-order rate of reaction for
vapor phase reactions with OH radical, the half life of a specific chemical species can be estimated if its OH radical
reaction rate constant is known using:
t1/2 = 0.693/K0H°[OH0]) (3-16)
where
t1/2 = time to decrease component concentration by 50% (s)
koH° = OH radical reaction rate constant (cm3/molecule-s)
[OH°] = atmospheric OH radical concentration (4 x 105 molecules/cm3 = 6645 x 10 ~19 moles/cm3)
A number of OH radical reaction rate constants as presented by Klopffer, (1980) and Cupitt, (1980), are given in
Table 3-23. Table 3-24 presents additional constants, as given by Cupitt (1980), along with an estimation of the
likelihood of a photolysis reaction occurring within the ambient atmosphere. Cupitt (1980) indicated that of all
atmospheric removal mechanisms including physical, chemical, and photochemical, the photochemical reactions are
of most significance for most classes of hazardous compounds and should be investigated further as a viable treatment
option.
The use of photochemical reactions for the enhancement of compound biodegradation is an important area of
interest for hazard mitigation from hazardous waste sites. Photolysis reactions are oxidative in nature and would be
expected to aid in microbial degradation through the oxidation of resistant complex structures (Crosby, 1971; Sims and
Overcash, 1983). Photoreactions are limited to soil surfaces due to light extinction within the soil system, but coupled
to soil mixing, they may prove to be highly effective as an in-place treatment technique for relatively immobile
chemical species.
106
-------
TABLE 3-23. RATE CONSTANTS FOR THE HYDROXIDE RADICAL REACTION IN AIR WITH
VARIOUS ORGANIC SUBSTANCES, KQH° 'N UNITS OF (MOLE-SEC)" '
Substance
loga
Acetaldehyde
Acrolem
Acrylonitnle
Allyl chloride
Benzene
Benzyl chloride
Bis (chloromethyl (ether
Carbon tetrachlonde
Chlorobenzene
Chloroform
Chloromethyl methyl ether
Chloroprene
o-,m-,p-cresol*
p-cresol
Dichlorobromo benzene*
Diethyl ether
Dimethyl mtrosamine
Dioxane
Epichlorophydnn
1,2-epoxy butane
Epoxypropane
Ethanol
Ethyl acetate
Ethyl propionate
Ethylene dibromide
Ethylene dicnlonde
Ethylene oxide
Formaldehyde
Hexachlorocycl open tad lene
Maehc anhydride
Methanol
Methyl acetate
Methyl chloroform
Methyl ethyl ketone
Methylene chloride
Methyl propionate
Nitrobenzene
Nitromethane
2-nitropropane
n-nitrosodiethylamme
Nitrosoethy I urea
n-propylacetate
Perchloroethylene
Phenol
Phosgene
Polychlormated biphenyls
Propanol
Propylene oxide
Tetrahydrofuran
Toluene
Trichloroethylene
Vmylidene chloride
o-,m-,p-xylene*
9.98
10.42
9.08
10.23
8.95
9.26
9.38
<5.78
8.38
7 78
9.26
10.44
10.52
10.49
8.26
9.73
10.37
9.26
9.08
9.16
8.89
9.28
9.06
9.03
8.18
8.12
9.08
9.78
10.55
10.56
8.78
8.04
6.86
9.32
7.93
8.23
7.56
8.81
10.52
10 19
989
9.41
8.01
10.01
nonreactii/e
<8.78
9.51
8.89
9.95
9 52. 9 56
9 12
938
998
Source: Adopted from Lemaire, et al. (1980) and Cupitt, (1980)
107
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TABLE 3-24. ATMOSPHERIC REACTION RATES AND RESIDENCE TIMES OF SELECTED ORGANIC CHEMICALS
Compound
kOHx 1012
(cm molecule
sec"1)
Direct
Photolysis
Probability
Physical
Removal
Probability
Residence
Time
(Days)
Anticipated Photoproducts
Acetaldehyde
Acrolein
Acrylonitnle
Allyl chloride
Benzyl chloride
Bio(Chloromethyl)
Ether
Carbon Tetrachlonde
Chlorobenzene
Chloroform
Chloromethyl
methyl ether
Chloroprene
o,m,p-cresole
Dichlorobenzene
Dimethyl Nitrosamme
Dioxane
Dioxin
Epichlorohydrin
Ethylene Dibromide
Ethylene Dichlonde
Ethylene Oxide
Formaldehyde
Hexachlorocyclo-
pentadiene
Maleic Anhydride
16
44a
2
28a
3a
4a
<0.001
0.4a
0.1
3a
46a
55
0.3a
39a
3a
-
2a
0.25
0.22
2a
10
59a
60a
Probable
Probable
Possible
Possible
Possible
Possible
Possible
Probable
_
Possible
Probable
_
Probable
Possible
Possible
Possible
Probable
Probable
Possible
Unlikely
Unlikely
Unlikely
Unlikely
Unlikely
Probable
Unlikely
Unlikely
Unlikely
Probable
Unlikely
Unlikely
Unlikely
-
Unlikely
-
Unlikely
Unlikely
Unlikely
Unlikely
Unlikely
Possible
0.03-0. 7C
0.2
5.6
0.3
3.9
0.02-2.9d
>1 1,000
28
120
0.004-3.9d
0.2
0.2
39
<0.3
3.9
-
5.8
45
53
5.8
0.1-1.2C
0.2
0.1
H2CO, CO:
OCH-CHO, H2CO, HCOOH,
CO 2
H-.CO, HC(0)CN, HCOOH,
CN°
HCOOH, H:CO, CICH2CHO,
chlorinated hydroxy
carbonyls, CICH2COOH
OCHO, Cl, ring cleavage
products chloromethyl-
phenols
HCI + H2CO, CIHCO,
chloromethylformate
CI2CO, Cl°
Chlorophenols, ring
cleavage products
ci2co,cr
chloromethyl and
methyl formate, CIHCO
H2CO, H2C=CCICHO,
OHCCHO, CICOCHO,
H2CCHCCIO, chloro-
hydroxy acids, aldehydes
hydroxymtrotoluenes,
ring cleavage products
chlorinated phenols,
ring cleavage products
a.dehydes, NO
OHCOCH2CH2OCHO,
OHCOCHO oxygenated
formates
-
H2CO, OHCOCHO,
CICH2O(O)OHCO
Bi, BrCH2CH2CHO, H2CO,
Br HCO
CIHCHO, H2CCICOCI,
H2CO, H2CCICHO
OHCOCHO
CO, C02
C 2CO, diacyclchlondes.
kotones, Cl'
CO2, CO; acids, aldehydes
and esters which should
photolyze
108
-------
TABLE 3-24. (Continued)
Compound
\t i 7
KOH x 10 2
(cm molecule
Direct
Photolysis
Probability
Physical
Removal
Probability
Residence
Time
(Days)
Anticipated Photoproducts
Methyl Chloroform
Methylene Chloride
Methyl Iodide
Nitrobenzene
2-Nitro propane
N-IMitrosodi-
ethylamme
Nitrosoethylurea
Nitrosomethylurea
Nitrosomorphohne
Perchlorethylene
Phenol
Phosgene
Polychlormated
Biphenyls
POM (Benzo(a)-
pyrene)
Propylene Oxide
Toluene
Tnchloroethylene
Vinyllidene
Chloride
o-,m-,p-xylene
0.012
0.14
0.0043
0.06a
55a
263
13a
20a
28a
0.17
17a
~0
<1a
1.3
6
2.2
4a
16
Possible
Possible
Possible
Possible
Possible
Probable
Possible
Possible
Possible
Possible
_
-
Possible
Possible
-
Possible
Possible
Unlikely
Unlikely
Unlikely
Unlikely
Unlikely
-
-
-
-
Unlikely
Possible
Possible
Unlikely
Probable
Unlikely
Unlikely
Unlikely
Unlikely
Unlikely
970
83
2900
190
0.2
<0.4
<0.9
<0.6
<0.4
67
0.6
-
>11
8
8.9
1.9
5.2
29
~0.7
H2CO, CI2CO, Cl-
CI2CO, CO, CIHCO, Cl-
H2CO, l°, ICHO, CO
Nitrophenols, ring
cleavage products
H2CO, CH3CHO
aldehydes, nitroammes
aldehydes, nitroammes
aldehydes, nitroammes
aldehydes, ethers
CI2CO, CI2C(OH)COCI,
dihydroxy benzenes,
nitrophenols, ring
cleavage products
C02, Cl°, HCI
hydroxy PCB's, ring
cleavage products
B(a)P-1 ,6-quinone
CH3C(O)OCHO,
CH3C(0)CHO, H2CO,
HC(O)OCHO
Benzaldehyde, cresols,
ring cleavage products,
nitro compounds
CI2CO, CIHCO, CO, Cl-
H2CO, CI2CO, HCOOH
substituted benzaldehydes.
hydroxy xylenes, ring
cleavage products
nitro compounds
a. Rate constant by method of Hendry and Kenley (1979).
b. Material is not expectecPfo exist in vapor phase at normal temperatures. Residence time calculation assumes the chemical is
substantially absorbed on aerosol particles and that the aerosol particles have a residence time of approximately 7 days.
c. The shorter residence time includes a photolysis rate as given in Graedel (1978).
d. Decomposition in moist air is expected. The shorter residence time includes the cited decomposition rate.
e. Values given are averages for the various isomers.
f. Reaction with OCDI is possible; k = 3.6 x 10"10 cm3 molecule"' sec"1, and [OCD1] = 0.2 molecules cm"3 implies a
tropospheric lifetime of 440 years. In addition, slow hydrolysis is expected.
Source: Cupitt, L.T., 1980.
109
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Photolysis of soil contaminants may be enhanced in 2 ways:
(1) by addition of proton donors, and
(2) by enhancing volatilization leading to photodegradation
3.4.3.1 Addition of Proton Donors
Description
Enhanced photodegradation of soil contaminants may be accomplished through the addition of various proton
donor materials to the contaminated soils.
Photolysis of tetrachlorodibenz-p-dioxin (TCDD) on soil surfaces was reported by Crosby, et al. (1971) in the
presence of suitable hydrogen sources in the form of polar solvents, and Plimmer, et al. (1973) indicated that methanol
used as a solvent for TCDD photo-oxidation also acted as a hydrogen donor in the photolysis reaction.
Investigations of feasible in-place treatment methods for contaminated areas surrounding the TCDD release
which occurred near Seveso, Italy, in 1976 have been reported by a number of authors. Wipf, H.K., et al. (1978)
investigated the use of alternative hydrogen donors for the photo-oxidation of TCDD. Solutions of 80 percent olive oil
and 20 percent cyclohexane at 350 L/ha and 40 percent aqueous emulsion with 4 percent biodegradable emulsifying
agent at 400 L/ha were found to produce a thin film on vegetation and other smooth surfaces to provide a maximum
reaction surface for TCDD photolysis. TCDD reductions in excess of 60 percent were observed within 48 hours after
treatment. Under laboratory conditions, the oil and emulsion solutions reduced the half life of TCDD by a factor of 25
upon irradiation with simulated sunlight.
Liberti, et al. (1978) reported a 1:1 solution of ethyl oleate and xylene used as hydrogen donors also resulted in
complete degradation of TCDD on building surfaces in approximately 1 hour at 2 mW/cm2 and 72 hours at 20
H,W/cm2 light intensity.
Dehalogenation of kepone (Dawson, et al., 1978, in Dawson, et al., 1980) and enhanced PBB (Christensen and
Weimer 1979) photolysis have been reported when hydrogen donors in the form of amino groups have been added to
contaminated soils prior to irradiation with sunlight. However, no observable degradation of PCBs in soil was found
with amine-enhanced soil (Meuser and Weimer, 1982).
Soil photodecomposition of PCBs was reported by Occhiucci and Patacchuiola, (1982) and was shown to be
enhanced by the addition of a proton donor, triethylamine, to the waste/montmorillonite system. Addition of
triethylamine resulted in a 2.5 to 5-fold increase in PCB degradation over a 100 hour irradiation period, providing 4 to
18 percent decomposition of the various chlorinated species tested.
The dechlorination reactions described above result from hydrogen abstraction by organic radicals formed upon
irradiation as presented by Bunce (1982). Optimization of this process for soil systems has yet to be accomplished but
appears to represent an area of potential for use in the in-place treatment of stable, nonmobile compounds.
Activated carbon adsorption of organics at hazardous waste sites followed by chemical addition and photolysis
has been reported by React Environmental Crisis Engineers, St. Louis, MO (personal communication, 1983). The site
is impregnated with activated carbon and soils are sampled. The most highly contaminated materials are physically
removed, packaged, and disposed of in an approved hazardous waste disposal facility. The remaining material is
mixed with sodium bicarbonate to increase soil pH, and the material is allowed to photochemically react resulting in
the photolysis of the parent material. The level of treatment is expected to be high to medium. An increase in soil pH is
the major secondary impact of the treatment method.
1 10
-------
Wastes Amenable to Treatment
Photodegradable organic wastes are amenable to this treatment. Generally, this includes compounds with
moderate to strong absorption in the >290-nm wavelength range. Such compounds generally have an extended
conjugated hydrocarbon system or a functional group with an unsaturated hetero atom (e.g.. carbonyl, azo, nitro).
Groups that typically do not undergo direct photolysis include saturated aliphatics, alcohols, ethers, and amines.
Tetrachlorodibenz-p-dioxin (TCDD), kepone, and PCBs have been treated with this method.
Status of Technology
In the field, several hazardous waste sites have been treated by this method. Laboratory studies have demon-
strated the potential for photo-oxidation. However, the potential for the production of hazardous compounds from
photodegradation needs to be further researched.
Ease of Application
Materials which are hydrogen donors are applied and depending on the depth of contamination, the soil is tilled to
expose waste to the light. This may be easy or difficult depending on the trafficability of the site and the depth of
contamination. Runon and runoff controls may be necessary to manage the drainage and erosion.
Potential Achievable Level of Treatment
The level of treatment achievable is potentially high, based on limited experimental data. Effectiveness also
depends on the amount of tillage possible at the site and the depth of contamination.
Reliability of Method
Considering that hazardous compounds may be produced as a consequence of photodegradation, unless the
constituents in the wastes and their photodegradation products are known, this is not a reliable method.
Secondary Impacts
Production of hazardous compounds from the photodegradation of pesticides has been documented, e.g., dieldrin
formation from aldrin, paraoxon formation from parathion, phosgene formation from chloropicrin (Crosby 1971), and
the formation of PCBs from the photoreaction of DDT (Woodrow et al,, 1983). The potential for such occurrences
with additional parent compounds is expected to be high and further research is needed to identify potential toxic
product formation to ensure the safe application of this treatment methodology.
Equipment and Exogenous Reagents
Power implements, tillers, and applicators are required to apply the proton donors.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
absorption spectra of waste constituents (at wavelength >290 nm, molecular absorptivities,
absorption maxima, quantum yield);
photolysis rate constant(s);
products of photolysi's (particularly hazardous products);
volatility of organics (vapor pressure, Henry's Law Constant);
11 1
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depth, profile, and areal distribution of contamination;
light intensity at site;
trafficability of soil and site.
Sources of Information
Cupitt, 1980; Lemaire, et al., 1981; Spencer, 1980; Nilles and Zabik, 1975; Hautala, 1978; Burkhard and Guth,
1979; Crosby, 1971; Plimmer, 1971; Klopffer, 1980; Sims and Overcash, 1983; Plummer, 1973; Wiff, 1978; Liberte,
et al., 1978; Dawson, et al., 1980; Christensen and Weimer, 1979; Meuser and Wierner, 1982; Occhiucci and
Patacchiola, 1982; Bunce, 1982; Woodrow, et al., 1983; Hendry and Kenley, 1979; Graedel, 1978.
3.4.3.2 Enhancement of Volatilization
Description
Enhancing volatilization of compounds from the soil which are susceptible to photodegradation may be a
potential treatment technique. This method involves increasing the bulk density or drying of the soil system to increase
soil vapor pore spaces and subsequently increase the vaporization rate of desired compounds, followed by photodegra-
dation in air.
Wastes Amenable to Treatment
The technique is applicable to compounds of low water solubility, with low KO values, low K\v values, and those
that are highly photoreactive and that, once within the lower atmosphere, would have a relatively short half life (on the
order of hours or preferably minutes). Generally, this includes compounds with moderate to strong absorption in the
>290-nm wavelength range. Such compounds generally have an extended conjugated hydrocarbon system or a
functional group with an unsaturated hetero-atom (e.g., carbonyl, azo, nitro). Groups that typically do not undergo
direct photolysis include saturated aliphatics, alcohols, ethers, and amines.
Status of Technology
This technology is conceptual, based on observed laboratory reaction rates for waste constituents in simulated
atmospheres. No information concerning the enhancement of volatilization to increase photolysis has been reported in
the literature either on laboratory or pilot scale. Theoretically the process can be expected to be effective for
compounds of high volatility and high photoreactivity. Further investigations concerning this process are needed.
Ease of Application
The soil may be tilled to enhance vaporization. Drying of the soil to increase volatilization may be accomplished
by tilling, or by installation of a drainage system. This technology may be easy or difficult to apply, depending on the
trafficability of the site and the depth of contamination. Controls for runon and runoff management may be necessary.
Potential Achievable Level of Treatment
The level of treatment achievable is potentially high for volatile, photoreactive compounds with short
atmospheric half-lives.
Reliability of Method
As with the previous treatment technology, hazardous products may result from photodegradation. Unless there is
sufficient certainty that the constituents in a waste will not produce hazardous photodegradative products, this
technology should not be used.
1 12
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Secondary Impacts
There is evidence of the production of degradation products that are hazardous from several pesticides.
Potentially, this could also be true of other compounds. Tillage used to dry the soil could increase the susceptibility of
the site to eorsion.
Equipment and Exogenous Reagents
Power implements, tillers, and a drainage system are required for this treatment technology.
Information Requirements
A determination of the volatility potential of the compounds of concern through an analysis of their partition
coefficients, along with a determination of their half lives, will allow a determination of the applicability of this
proposed treatment technique to a specific situation. The information requirements are.
characterization and concentration of wastes, particularly orgamcs at site,
absorption spectra of waste constituents (at wavelengths >270 nm, molar absorptivities, absorption
maxima, quantum yield);
photolysis rate constant(s):
products of photolysis (particularly hazardous products);
volatility of organics (vapor pressure. Henry's Law Constant);
depth, profile, and areal distribution of contamination;
soil moisture;
light intensity at site;
trafficability of soil and site
Sources of Information
Burkhard and Guth, 1979; Crosby. 1971; Crosby, et al., 1971; Cupitt. 1980; Hautala. 1978. Klopffer. 1980;
Lemaire, et al., 1982; Nilles and Zabik, 1975; Plimmer, 1971; Sims and Overcash, 1983.
3.5 ATTENUATION
The basic principle of attenuation is the mixing of contaminated soil (or wastes) with clean soil to reduce the
concentrations of hazardous components to acceptable levels. This process is potentially applicable to both inorganics
and organics. However, acceptable concentration limits have been established only for heavy metals.
3.5.1 Attenuation of Metals
Description
Attenuation of metals which accumulate at the soil surface may be accomplished by either mixing subsurface soil
with the top soil, or by applying uncontaminated soil from the adjacent area. Soil may also be purchased from local
contractors, or pure soil materials (e.g., bentonite) may be obtained from commercial suppliers.
The treatment requires no chemical additives and is good for large-scale contaminated areas. It can easily be used
with other treatments, such as pH adjustment, to maximize metal sorption to soils, to enhance its effectiveness.
However, attenuation is generally not applicable for contamination below the plow layer (about 2 feet).
113
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Wastes Amenable to Treatment
This treatment is applicable to all kinds of wastes containing metals. It is particularly applicable to wastes for
which concentrations in soil have been defined. For those wastes which are extremely toxic, destructive treatment
might be more acceptable.
Status of Technology
This technology has been applied in land treatment systems in which the addition of wastes to soil is controlled
and monitored.
Ease of Application
Attenuation for metals may be easy or difficult to apply depending on site/soil trafficability considerations and
depth of contamination. Thorough mixing is required. The site should be evaluated for erosion potential, and erosion
controls and provisions for containment and treatment of runoff instituted as necessary. Controls for the prevention of
runon of precipitation (both surface and subsurface) may also be necessary.
Potential Achievable Level of Treatment
The level of attenuation achievable depends primarily on the concentration and depth of contamination. It could
be high with appropriate site/soil trafficability and if the contamination is not deep into the ground.
Reliability of Method
This method is reliable. However, the mixing of soil or addition of other soil into the site may alter the properties
of the natural soil. Because of the increased mobility of metals with decreased pH, liming and reliming of the site may
be necessary to maintain the metals in the soil if the pH is altered due to the treatment.
Secondary Impacts
The mixing of the soil profile or the addition of different soil may alter the physical, chemical, and biological
properties of the original soil at the site. This may have adverse effects. Tilled soils are also usually more susceptible to
water and wind erosion.
Equipment and Exogenous Reagents
Power implements and tillers are necessary. If new material is added, applicators will be necessary. Liming
material and soil may also be needed.
Information Requirements
characterization and concentration of metals in waste;
depth, profile, and areal distribution of contamination;
soil assimilative capacity of metals, both contaminated and uncontaminated soils;
soil pH;
trafficability of soil and site.
14
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3.5.2 Attenuation of Organics
Description
Attenuation of organics in soil is performed in the same manner as attenuation for inorganics discussed above. In
addition, the potential for a higher percentage of sorbed organics with an increased mass of soil may increase the level
of attenuation for organics. The Freundlich Isotherm used to describe sorption is discussed under Immobilzation
(Section 3.3).
As the amount sorbed per unit dry mass of soil (S in Equation 3.1) decreases, the percent sorbed increases.
Therefore, the incorporation by mixing of endogenous soil layers, or the addition of exogenous soil to contaminated
soil, represents another technology to increase the extent and effectiveness of immobilization of chemical contami-
nants at hazardous waste sites, and may also aid in decreasing toxicity of the contaminated soil to soil micro-organisms
that is due to high concentrations of constituents.
Wastes Amenable to Treatment
This treatment is applicable to all organic wastes. However, organics that are very soluble in water may be more
effectively treated by other methods since large amounts of soil may be required to reduce the mobility of the
compound. If very toxic components are present in the waste, destructive treatment would be the preferable treatment
alternative.
Status of Technology
There is limited field experience in this technology. Addition of dry soils for accomplishing treatment has been
utilized for PCB wastes. Waste oil pits, that held transformer fluid containing PCB's ruptured causing a release of
740,000 liters of oil and acidic water. After dewatering, the oils remaining in the pits were treated by the addition of
dry soil (Eckenfelder, 1970).
Ease of Application
The endogenous soil profile is tilled to mix uncontaminated soil with the contaminated layers. If the desired
attenuation is not reached, imported soil or clay may be applied. This method may be easy or difficult depending on
site/soil trafficability considerations for tillage and incorporation of added soil or clay. Erosion may be a problem due
to tillage. Controls for erosion prevention and containment and runoff treatment may be necessary. Controls for n
prevention of runon of precipitation (both surface and/or subsurface) may also be necessary.
Potential Achievable Level of Treatment
The level of attenuation achievable is potentially high with suitable size, soil, and waste characteristics.
Reliability of Method
The mixing of soil or addition of other soil or clay to the soil system may alter the properties of the natural soil. As
a result, the effectiveness of this method may vary for different compounds, and may not be as expected. However,
this method should be reliable under most conditions.
1 15
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Secondary Impacts
Toxic concentrations to soil organisms may be reduced and biodegradation may be enhanced by this treatment. If
clay is added, clay catalyzed degradation and ion-exchange in the clay surface may also be enhanced. However, the
mixing of the soil profile or the addition of different soil may alter the physical, chemical, and biological properties of
the original soil at the site adversely. Tilled soils are usually more susceptible to water and wind erosion.
Equipment and Exogenous Reagents
Power implements and tillers are necessary. Applicators will be necessary for the addition of new soil or clay.
Information Requirements
characterization and concentration of organic waste constituents;
depth, profile, and areal distribution of contamination;
soil organic carbon content;
soil moisture;
trafficability of soil and site.
Sources of Information
Eckenfelder, Jr., 1970.
3.6 REDUCTION OF VOLATILIZATION
Volatilization from a hazardous waste site may need to be controlled to reduce air emissions or to retain
compounds within the soil system longer to allow for in-place treatment. There are three ways to reduce volatilization
from a site; reduction of soil vapor pore volume, use of physical/chemical barriers, and soil cooling.
3.6.1 Reduction of Soil Vapor Pore Volume
Description
Reduction of soil vapor pore volume for volatilization control is accomplished by modifying the soil system to
reduce the partitioning of a compound into the vapor phase and subsequently reduce its rate of volatilization. Such
modifications include compaction and water addition to reduce the air-filled pore spaces within the soil. These
techniques are especially applicable to those compounds found to represent a high vapor phase mobility potential and a
low water phase partition potential (i.e., for compounds with a KD x Kw product greater than about 50, and a KD
value greater than 10, where KD is the soil:water partition coefficient and Kw is the air.water partition coefficient).
Under these circumstances, addition of moisture does not materially decrease the percent sorbed to the soil
surface, but reduces greatly the soil vapor pore spaces. Air filled porosity is the soil parameter of major significance
affecting volatilization because of increased partitioning onto the soil from the soil vapor phase as the volume of the
vapor phase is reduced due to soil compaction and/or water addition (Farmer, et al., 1980).
Evaluation of the effectiveness of soil modifications on contaminant loss via vapor movement can be made
rapidly using the technique described by Farmer et al. (1980), assuming steady-state vapor flux through a soil cover,
i.e.;
J = - D. (C - CS)/L (3-17)
1 16
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where
J = vapor flux (ng/cm2/d),
Ds = apparent steady-state diffusion coefficient (cm2/d),
C = concentration in the air at the soil surface (ng/cm3),
Cs = concentration in the air at the bottom of the soil layer, i.e., saturation vapor pressure assuming
steady-state (ng/cm3),
L = depth of the soil layer, cm.
Millington and Quirk (1961) have suggested the use of the following equation for apparent diffusion in soil taking
into account the porosity of the soil:
Ds = D0 (Pa10/3/PT2) (3-18)
where:
D0 = diffusion coefficient in air (cm2/d),
Pa = soil air filled porosity, (cm3/cm3),
PT = total soil porosity (cm3/cm3), 1 soil bulk density/particle density,
9 = volumetric water content (cm3/cm3),
while Thibodeaux and Hwang (1982) model apparent soil diffusion using total soil porosity and tortuosity:
Ds = D0PT/t (3-19)
where
t = soil tortuosity.
Equation (3-17) then becomes:
J = - D0 (Pa10/3/PT2) (C - C3)/L (3-20)
or:
J = - D0 (PT/t) (C - CS)/L ' (3-21)
Using oxygen as a reference, diffusion coefficients of other compounds can be estimated using:
DA = 0.178 cm2/s (32/MA)05 (3-22)
1 17
-------
where:
DA = air diffusion coefficient for compound A (cm2/s) in air at 0°C
MA = molecular weight of compound A (fi.g/mole)
Temperature corrections are made to the above value according to:
DA2 = DAiOyTi)05 (3-23)
where:
DAI. DA2 = diffusion coefficients at temperatures TL and T2, respectively.
A compound's saturation concentration, Cs, may be calculated using the following relationship:
Cs = pM/RT (3-24)
where:
p = compound vapor pressure (mm Hg),
M = compound molecular weight (ng/mole),
R = universal gas constant (L mm Hg/°K mole),
T = absolute temperature (°K).
Laboratory evaluation of hexachlorobenzene (HCB) vaporization from simulated landfill areas has been reported
by Farmer et al. (1980). They found that increases in soil moisture content produced logarithmic decreases in HCB
vaporation (an increase in 9 from 17.24 to 19.58 percent resulted in HCB flux reductions of 20 percent). Water phase
mobility of HCB was not of concern due to HCB's water solubility of only 6.2 fig/1.
Bulk density effects were also shown by Farmer, et al. (1980) to have a large impact on HCB vapor movement.
An increase in bulk density from 0.96 to 1.15 g/cm3 resulted in a 65 percent reduction in HCB flux from the laboratory
landfill units.
Because of the insoluble nature of HCB, its volatilization flux through a water layer was shown to be reduced by a
factor of 870 as compared to uncovered samples (Farmer, et al., 1980). Farmer, et al. indicated an expected similar
reduction in HCB vapor flux to take place upon saturation of contaminated soil systems. Similar results would be
expected for compounds with properties similar to those of HCB. Leaching would be minimized due to the low water
solubility and the slight compound partitioning into the soil water phase.
Wastes Amenable to Treatment
This treatment is useful for most volatile organic (e.g., benzene, gasoline, phenol) and inorganic (e.g., H2S,
NH3, Ra, methyl mercury) compounds. The nature of the waste is also very important. As discussed earlier, these
control technologies are especially applicable to those compounds with a high vapor phase mobility potential and a low
water phase partition potential.
-------
Status of Technology
Reduction of soil vapor pore volume is at the laboratory stage for uncontrolled hazardous waste sites. Decreases
in volatilization of compounds due to water addition and increase in bulk density have been demonstrated from
simulated landfill areas.
Ease of Application
Irrigation water is applied to reduce vapor-filled pore space, but not in such amounts that would cause leaching of
hazardous constituents. Frequent smaller applications are more desirable. This is comparatively easy. Soil may be
compacted to increase bulk density so vapor-filled pore space is reduced.
Potential Achievable Level of Treatment
The achievable level of treatment is potentially low to medium, depending on the waste characteristics. This
technology is most effective for constituents with a high vapor phase potential and a low water phase partition
potential. The achievable level of treatment also depends on site and soil conditions that are necessary for the addition
of soil moisture and for compaction to increase bulk density of the soil.
Reliability of Method
Since soil moisture evaporates, retreatmfent with irrigation water from time to time is essential for effective
reduction in volatilization.
Secondary Impacts
There is a potential for increased liquid phase mobility when water is used if the constituent has a high Kw and
low Koc, i.e., it readily partitions into the water phase and is highly water-soluble. Compaction reduces aeration in the
soil and could adversely affect degradative reactions, e.g., chemical oxidation or aerobic biodegradation. Similarly,
reducing pore volume with increasing soil moisture content would reduce oxygen content.
Equipment and Exogenous Reagents
Irrigation and compaction equipment are required. Irrigation water is the reagent used in this technology.
Information Requirements
characterization and concentration of waste, primarily organics at site;
volatility of organic constituents (vapor pressure, Henry's Law Constant, air/water partition
coefficient, solubility);
sorption of organics in soil (Koc);
depth, profile, and areal distribution of contamination;
bulk density, particle density, tortuosity of soil pores, temperature, and organic matter content of soil;
soil moisture content;
precipitation at site;
trafficability of soil and site.
Contaminant Kw and KD or KOc estimates will provide information necessary to indicate the relative importance
of vapor and solution phase transport and will dictate appropriate control methods for the compounds.
1 19
-------
Sources of Information
Fanner, et al., 1980; Millington and Quirk, 1961; Thibodeaux, and Hwang, (1982).
3.6.2 Soil Cooling
Description
Soil cooling may be used to decrease the temperature of soil systems to reduce the vapor pressure of volatile
constituents and correspondingly reduce their volatilization rate. The technique may enhance treatment by other means
through the retention of compounds for longer periods of time within the soil system.
One means of lowering soil temperature is by the use of cooling agents applied to the soil surface. Greer, and
Gross, (1980) found solid carbon dioxide (dry ice) to be more effective than liquid carbon dioxide, liquid nitrogen, or
ice in reducing ethyl ether vaporization from a liquid pool. They observed ethyl ether vapor concentration reductions
from 8300 to 96 ppm with dry ice addition. Dry ice resulted in a liquid pool temperature of 85°C for 80 minutes at an
application rate of 250 kg/2.7 m3. Liquid nitrogen produced - 120°C temperatures but required 1025 kg to reduce
concentrations from 93,000 to 116 ppm, and was found more difficult to work with than the dry ice. Because of the
effectiveness of solid carbon dioxide and its minimal risks for response personnel during its application, it was the
cooling agent of choice (Greer and Gross, 1980).
Modifications to the soil surface may also result in cooler soil temperatures (Baver, et al., 1972). Vegetated soils
are usually cooler in the summer but warmer in the winter. Soils with more moisture warm up more slowly in the
spring. Irrigation can be used for cooling in the summer. Tillage of the soil creates a surface barrier reducing heat flow
from the surface to the subsurface. Mulched soils are cooler in spring, winter, and fall, while summer temperatures are
similar between mulched and bare plots.
Soil temperature control is discussed in greater detail in Section 4.
Wastes Amenable to Treatment
Volatile organics are the most suitable wastes for this technology.
Status of Technology
Experimental and limited field applications of cooling agents have been conducted only on liquid spills, and no
reports are available on soil surface cooling for vapor mitigation. Soil cooling by soil surface modification is used in
agricultural operations.
Ease of Application
Cooling agents are continually applied to soil surface with spray equipment for liquefied agents or with grinding
and spreading equipment for solid agents. Mulch is applied by standard agricultural methods. Water is applied at
frequent intervals through irrigation systems in small amounts. The use of cooling agents would be difficult due to the
low temperature and the reactions that occur upon application of low-temperature materials. Soil modifications using
mulches, tilling, and other techniques vary in difficulty depending on trafficability considerations.
Potential Achievable Level of Treatment
The effectiveness of soil cooling is related to the degree of temperature reduction possible. Cooling agents are
more effective than soil modifications, but are not likely to be practical because of cost.
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Reliability of Method
Soil modification techniques are more reliable than cooling agents. The latter would not be reliable for large areas
or for long periods of time, and the extremely low temperatures obtainable would be unnecessary. Retreatment of soil
surface modification techniques is necessary.
Secondary Impacts
Low temperatures may decrease or inhibit microbial activity. Extremely low temperatures may severely decrease
microbial numbers and/or activity. The application of excessive irrigation water may result in leaching of hazardous
constituents.- Tilling will increase the potential for erosion at the site and actually increase the surface area available for
volatilization.
Equipment and Exogenous Reagents
Mulch, applicators, grinders, tillers, and cooling agents are needed for the technology.
Information Requirements
characterization and concentration of wastes, particularly organics at site;
volatility of organic constituents (vapor pressure, Henry's Law Constant, air/water partition
coefficient, solubility, and particularly their dependence on temperature);
sorption of organics in soil (Koc);
depth, profile, and areal distribution of contamination;
soil moisture;
effectiveness of cooling agents;
trafficability of soil and site.
Sources of Information
Green and Soors, 1980; Baver, et al., 1972.
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SECTION 4
MODIFICATION OF SOIL PROPERTIES
4.1 INTRODUCTION
Implementation of in-place treatment techniques for contaminated soils often involves the modification of soil
properties. Biological degradation, for example, can be enhanced by the addition of nutrients, and immobilization of
heavy metals may require adjustment of soil pH. Soil properties discussed in this section include:
oxygen content,
moisture content,
nutrient content,
pH,
temperature.
This Section emphasizes the mechanics of soil property modification, independent of the treatment technology. Table
4-1 lists the technologies of Section 3, indicating which soil properties may require modification as a part of treatment.
4.2 CONTROL OF OXYGEN CONTENT
Oxygen content in surface soils can be increased primarily through the use of tillage equipment which breaks.
mixes and aerates the soil. Alternatively, oxygen content can be decreased by compaction or increased moisture
content. Aeration of subsurface soils not accessible to tillage equipment can be accomplished using construction
equipment, such as a backhoe, or using a well point injection system.
A variety of equipment is available to aerate surface soils. This equipment, grouped under the category of Tillers.
is described in the appendix. Tilling equipment can also be used to mix wastes or reagents into the soil. Choice of
equipment depends on the amount of soil disturbance or mixing desired, and on site characteristics such as the
rockmess of the soil.
For some processes, such as anaerobic biological degradation, surface soil compaction may be desirable By
reducing pore sizes and restricting reaeration, anaerobic microsite frequency in the soil will increase. Compaction
helps draw moisture to the soil surface. Thus, the problems of leaching that may occur if anaerobiosis were achieved
by water addition would be lessened. If the compaction itself were not adequate to achieve the required degree of
anaerobiosis, water could be added. Less water, however, should be required in a compacted soil than in an
uncompacted soil; thereby minimizing the leaching potential. Volatilization may also be suppressed by surface soil
compaction.
Aeration of soils deeper than about 2 feet can be accomplished by air injection through well points. In one case,
air was injected into a series of 10 wells using diffusers attached to paint sprayer-type compressors. They delivered
about 2.5 cfm to enhance microbial degradation. Various nutrients were added simultaneously. The diffusers were
positioned 5 feet from the bottom of the well and below the water table (Raymond, et al., 1976). Aeration through well
points has been primarily used for saturated soils and has been shown to be effective. Applicability of the technique for
unsaturated soils is not certain.
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TABLE 4-1. SOIL MODIFICATION REQUIREMENTS FOR TREATMENT TECHNOLOGIES
Technology
Oxygen Moisture
Content Content
Nutrient
Content pH
Temperature
EXTRACTION
IMMOBILIZATION
Sorption (heavy metals)
Agri. products
Activated carbon
Tetren
Sorption (organics)
Soil moisture
Agri. products
Activated carbon
Ion exchange
Clay
Synthetic resins
Zeolites
Precipitation
Sulfides
Carbonates, phosphates and hydroxides
DEGRADATION
Oxidation
Soil-catalyzed reactions
Oxidizing agents
Reduction
Reducing agents
Chromium
Selenium
PCBs and Dioxins
Polymerization
Modification of soil properties
(for biodegradation)
Soil moisture
Soil oxygen aerobic
Soil oxygen - anaerobic
Soil pH
Nutrients
Nonspecific org. amendments
Analog enrichment for cometabolism
Exogenous acclimated or mutant
micro-organism
-
-
-
-
-
-
-
-
X
X
X
X
X
X
X
-
-
_
X
X
-
-
-
-
-
-
-
X
-
-
-
-
X
X
-
-
X
-
X
-
X
X
-
-
-
-
-
-
-
-
-
-
-
-
-
X
-
-
X
X
X
X
X
-
-
-
X
X
X
X
X
X
X
X
X
X
-
_
X
-
-
-
-
X
-
-
-
-
-
-
_
-
-
_
X
_
-
X
X
X
(continued)
23
-------
TABLE 4-1 (Continued)
Technology
Oxygen Moisture
Content Content
Nutrtent
Content pH
Temperature
Cell-free enzymes
Photolysis
Proton donors
Enhance volatilization
ATTENUATION
Metals
Organics
REDUCTION OF VOLATILES
Soil Vapor Volume
Soil Cooling
-
:
-
-
-
X
X
-
-
-
-
X
-
X
Source: Arthur D. Little, Inc.
4.3 MOISTURE CONTROL
Control of moisture content of soils at an in-place treatment site may be essential for control and optimization of
some degradative and sorptive processes as well as for suppression of volatilization of some hazardous constituents.
Moisture control may take the form of supplemental water to the site (irrigation), removal of excess water (drainage.
well points), a combination of techniques for greater moisture control, or other methods, such as soil additives.
4.3.1 Irrigation
Irrigation may be accomplished by subirrigation, surface irrigation, or overhead (sprinkler) irrigation (Fry and
Grey, 1971).
With subirrigation, water is applied below the ground surface and moves upward by capillary action. If the water
has high salinity, salts may accumulate in the surface soil, resulting in an adverse effect on soil microbiological
activity. The site must be nearly level and smooth, with either a natural or perched water table, which can be
maintained at a desired elevation. The groundwater is regulated by check dams and gates in open ditches, or jointed
perforated pipe to maintain the water level in soil. The use of such systems is limited by the restrictive site criteria
There may be situations in which a subirrigation system may be combined with a drainage system to optimize soil
moisture content. However, at a hazardous waste site, raising the water table might result in undesirable groundwater
contamination.
Trickle irrigation is a system of supplying filtered water directly on or below the soil surface through an extensive
pipe network with low flow-rate outlets only to areas which require irrigation. It does not give uniform coverage to an
area, but with proper management, does reduce percolation and evaporation losses. For most in-place treatment sites,
this method would probably not be appropriate, but it may find application in an area where only "hot spots" of
wastes are being treated.
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Surface irrigation includes flood, furrow, or corrugation irrigation. Since the prevention of off-site migration of
hazardous constituents to ground or surface waters is a primary restraint on in-place treatment technology, the use of
surface irrigation should be viewed with caution. Contaminated water may also present a hazard to on-site personnel.
In flood irrigation, water covers the surface of a soil in a continuous sheet. Theoretically, water should stay at
every point just long enough to apply the desired amount, but this is difficult or impossible to achieve under field
conditions.
In furrow irrigation, water is applied in narrow channels or furrows. As the water runs down the furrow, part of it
infiltrates the soil. Considerable lateral movement of the water is required to irrigate the soil between furrows. Salts
also tend to accumulate in the area between furrows. Furrow irrigation frequently requires extensive land preparation,
which usually would not be possible or desirable at a hazardous waste site due to contamination and safety
considerations.
In corrugation irrigation, as with furrow irrigation, water is applied in small furrows from a head ditch. However,
in this case, the furrows are used only to guide the water, and overflooding of the furrows can occur.
In general, control and uniform application of water is difficult with surface irrigation. Also, soils high in clay
content tend to seal when water floods the surface, limiting water infiltration.
The basic sprinkler irrigation system consists of a pump to move water from the source to the site, a pipe or pipes
leading from the pump to the sprinkler heads, and the spray nozzles. Sprinkler irrigation has many advantages. Erosion
and runoff of irrigation water can be controlled or eliminated, application rates can be adjusted for soils of different
textures, even within the same area, and water can be distributed more uniformly. Irrigation is also possible on steep,
sloping land and irregular terrain. Usually less water is required than with surface flooding methods, and the amount of
water applied can be controlled to meet the needs of the in-place treatment technique.
There are several types of sprinkler irrigation systems:
1) Permanent installations with buried main and lateral lines;
2) Semi-permanent systems with fixed main lines and portable laterals;
3) Fully portable systems with portable main lines and laterals, as well as a portable pumping plant.
The first two types (especially the first) would likely not be appropriate nor cost-effective for a hazardous waste site
because of the required land disturbance for installation and the limited time period for execution of the treatment.
The fully portable systems may have hand-moved or mechanically moved laterals. To eliminate movement by
hand, the system may have enough laterals to cover the whole area (a solid set system). Portable systems can be
installed in such areas as forests in patterns such as to avoid interference with trees. Mechanically moved laterals may
be divided into three categories: side-roll wheel move; center pivot systems; and traveling sprinklers. The amount of
labor is considerably reduced compared to portable systems, but the cost of the equipment is higher. However, the
health and safety of workers must be considered as well as cost in the choice of an appropriate system.
The side-roll wheel move is a lateral suspended on a series of wheels. The unit is stationary during operation and
is moved while shut off by an engine mounted at the center of the line or an outside power source at one end of the line.
A variation of this system is a continuous travel wheel with a flexible hose, which remains in operation as the wheel
moves across the field.
The center pivot system is a pipeline suspended above ground with various sized sprinklers spaced along its
length. The system is self-propelled and continuously rotates around a pivot point.
125
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The traveling sprinkler consists of a single gun sprinkler mounted on a portable, wheeled unit which is self-
propelled up and down the length of the field.
The choice of an appropriate irrigation system depends on site conditions, costs, and health and safety
considerations for both on-site personnel and off-site populations. The system should be designed by a qualified
specialist such as an agricultural engineer. Preliminary guidelines for designing an irrigation system can be found in
the Sprinkler Irrigation Handbook (Fry and Grey, 1971) and Planning for an Irrigation System (Turner and Anderson,
1980). The latter publication, in addition to technical aspects of irrigation, also discusses sources of water, including
legal rights, and methods of determining irrigation costs.
4.3.2 Drainage
A properly designed drainage system removes excess water and/or lowers the groundwater level to prevent
waterlogging. Surface drainage is accomplished by open ditches and lateral drains, while subsurface drainage is
accomplished by a system of open ditches and buried tube drains into which water seeps by gravity. The collected
water is conveyed to a suitable disposal point. Subsurface drainage may also be accomplished by pumping from wells
to lower the water table. Caution is required at a hazardous waste site to ensure that drainage water disposed off-site is
not contaminated with hazardous substances. Provisions must be made to collect, store, treat, and/or recycle water that
is not acceptable for off-site release. The drainage system should be managed to prevent or minimize contamination
problems.
The design of a drainage system is affected by the topography, soil properties, and water source factors of a site.
The two types of drainage systems are (Donnan and Schwab. 1974):
surface drains used where subsurface drainage is impractical (e.g.. impermeable soils, excavation
difficult), to remove surface water or lower water table;
subsurface drains used to lower the water table. Construction materials include clay or concrete
tile, corrugated metal pipe, and plastic tubing. Selection depends on strength requirements, chemical
compatibility, and cost considerations.
For the design and construction of a drainage system, a drainage engineer should be consulted. The American Society
of Agronomy monograph. Drainage for Agriculture (Schilfgaarde, 1974) contains a complete discussion of drainage.
4.3.3 Well Points
Well points, like subsurface drains, can be used to lower the water table in shallow aquifers. They typically
consist of a series of riser pipes screened at the bottom and connected to a common header pipe and centrifugal pump.
Well point systems are practical up to 10 meters (33 feet) and are most effective at 4.5tmeters (15 feet). Their
effectiveness, however, depends on site-specific conditions, such as the horizontal and vertical hydraulic conductivity
of the aquifer (Ehrenfeld and Bass, 1983).
4.3.4 Additives
Various additives are available to enhance moisture control. For example, the water-retaining capacity of the soil
can be enhanced by adding water-storing substances. Three such synthetic substances were recently evaluated by
Nimah, et al. (1983) for use in arid area soils. They found that available soil water content was increased by two of the
products. Water-repelling agents are available which diminish water absorption by soils. On the other hand, water-
repelling soils can be treated with surface-active wetting agents to improve water infiltration and percolation. Other
soil characteristics which have been modified by surface active agents include acceleration of soil drainage.
modification of soil structure, dispersion of clays, and soil made more compactable. Evaporation retardants are also
26
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available to retain moisture in a soil. Secondary effects of some of these amendments on soil biological activities, other
soil physical properties, soil chemical properties and environmental effects, e.g., leachability and degradability, are
discussed by Brandt, G.H., (1972).
4.4 NUTRIENT ADDITIONS TO THE SOIL
Degradation of organic compounds at a hazardous waste site requires an active population of micro-organisms.
Among other environmetnal factors (e.g., temperature, moisture, pH, etc.), adequate nutrition is vital to maintain the
microbial population at an optimum level. The hazardous wastes being degraded may contribute some necessary
nutrients, but may not supply all that are required or that may be beneficial (e.g., silicon and sodium). If the soil does
not contain an adequate supply of nutrients, the soil must be supplied with the appropriate elements in the form of
fertilizers. A fertilizer is any substance added to the soil to supply those elements required in plant nutrition (Tisdale
and Nelson, 1975).
The number of substances suitable as fertilizers is very large, and their compositions and origins differ
considerably. Classification systems incorporating many aspects of fertilizer origin, use, and characteristics are
presented in Finck (1982). Because of the variety of possible classifications, the choice of an appropriate fertilizer can
be complicated, and an agronomist should be consulted to develop a fertilization plan at a hazardous waste site. A plan
may include types and amounts of nutrients, timing and frequency of application, and method of application. The
nutrient status of the soil and the nutrient content of the wastes must be determined to formulate an appropriate
fertilization plan. Basic textbooks on fertilization include Soil Fertility and Fertilizers (Tisdale and Nelson, 1975),
Fertilizers and Fertilization (Finck, 1982), and Fertilizers and Soil Amendments (Follett, et al., 1981).
The development of a fertilization program not only includes the proper selection of fertilizer form and
determination of correct fertilizer quantities, but also the selection of an application method. Fertilizers must be
transported, stored, and applied so that no chemical or physical changes occur to decrease dispersibility and
effectiveness. Improper handing during transportation and storage may result in the creation of safety hazards due to
moisture absorption, such as increased flammability, explosiveness, and corrosiveness, or the formation of noxious
gases. Improper mixing of fertilizer types before or after application may result in nitrogen losses, immobilization of
water-soluble phosphate, or deterioration of distribution properties due to moisture absorption (Finck, 1982).
In agricultural application, fertilizers are either applied evenly over an area or concentrated at given points, such
as banded along roots. However, at a hazardous waste site, fertilizer will likely be applied evenly over the whole
contaminated area and incorporated by tilling, if necessary. Nutrients can also be injected through well points below
the plow layer.
With broadcast fertilization, the fertilizer can be left on the surface or incorporated with a harrow (2 to 3 cm
deep), a cultivator (4 to 6 cm deep), or with a plow (a layer at bottom of furrow, e.g., 15 cm deep). The depth of
incorporation depends on the solubility of the fertilizer and the desired point of contact in the soil. In general, nitrate
fertilizers move freely, while ammonia nitrogen is adsorbed by soil colloids and moves little until converted to nitrate.
Potassium is also adsorbed and moves little except in sandy soils. Phosphorus does not move in most soils. Therefore,
potassium and phosphorus need to be applied or incorporated to the desired point of use.
4.5 CONTROL OF SOIL pH
Control of soil pH at an in-place hazardous waste treatment site is a critical factor in several treatment techniques
(e.g., metal immobilization, optimum microbial activity). The goal of soil pH adjustment in agricultural application
usually is to increase the pH to near neutral values, since natural soils tend to be acidic.
The areas of the country in which the need for increasing soil pH is greatest are the humid regions of the East,
South, Middle West, and Far West States. In areas where rainfall is low and leaching is minimal, such as parts of the
Great Plain States and the arid, irrigated saline-alkali soils of the Southwest, Intermountain, and Far West States, pH
127
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adjustment is usually not necessary. Some soils, especially those high in carbonates, do require the pH to be lowered.
However, a hazardous waste-contaminated soil may have substances high in pH, thus necessitating soil acidification.
The most common method of controlling pH is liming. Liming is the addition to the soil of any calcium or
calcium-and magnesium-containing compound that is capable of reducing acidity (i.e., raising pH). Lime correctly
refers only to calcium oxide, but is commonly used to refer to calcium hydroxide, calcium carbonate, calcium-
magnesium carbonate, and calcium silicate slags (Tisdale and Nelson, 1975).
The benefits of liming to biological activity are several. At higher pH values, aluminum and manganese are less
soluble. Both of these compounds are toxic to most plants. In addition, phosphates and most micro-elements necessary
for plant growth (except molybdenum) are more available at higher pH. Microbial activity is greater at or near neutral
pH, which enhances mineralization and degradation processes and nitrogen transformations (e.g., nitrogen fixation
and nitrification).
A summary of commonly used liming materials is presented in Table 4-2. The choice of a liming material
depends upon several factors. Calcitic and dolomitic limestones are the most commonly used materials. To be
effective quickly, however, these materials must be ground, because the velocity of reaction is dependent on the
surface in contact with the soil. The finer they are ground, the more rapidly they react with the soil. However, a more
finely ground limestone product usually contains a mixture of fine and coarse particles in order both to effect a pH
change rapidly and still be relatively long-lasting as well as reasonably priced. Many states require that 75 to 100
percent of the limestone pass an 8- to 10-mesh sieve and that 20 to 80 percent pass anywhere from an 8- to 100-mesh
sieve (Tisdale and Nelson, 1975). Calcium oxide and calcium hydroxide are manufactured as powders and react
quickly.
Other factors to consider in the selection of a limestone are neutralizing value, magnesium content, and cost per
ton applied to the land.
Lime requirement for soil pH adjustment is dependent on several soil factors, including soil texture, type of clay,
organic matter content, and exchangeable aluminum (Follett, et al., 1981). The buffering capacity of soil reflects the
ability of soil components to hold a large number of ions in adsorbed or reserve form. Thus, adsorption or inactivation
of H+ ions, or the release of adsorbed ions to neutralize OH- ions provides protection against abrupt changes in pH
when acidic or basic constituents are added to soil. Differences among soils in their buffering capcity reflect
differences in the soil cation exchange capacities and will directly affect the amount of lime required to adjust soil pH.
The amount of lime required is also a function of the depth of incorporation at the site, i.e., volume of soil to be
treated. The amount of lime required to effect a pH change in a particular site/soil/waste system is determined by a
state experimental or commercial soil testing laboratory in short-term treatability studies or soil-buffer tests (McLean,
1982).
Lime requirements may also be affected by acid precipitation and acid-forming fertilizers. A field study in
Connecticut showed that each year the acidity generated by acid precipitation would require 36 kg/ha (32 Ib/A) of pure
calcium carbonate for neutralization (Frink and Voight, 1976).
Lime is usually applied from a V-shaped truck bed with a spinner-type propeller in the back (Follett, et al., 1981).
Uniform spreading is difficult with this equipment, and wind losses can be significant. A more accurate but slower and
more costly method is a lime spreader (a covered hopper or conveyor) pulled by a tractor. Limestone does not migrate
easily in the soil since it is only slightly soluble, and must be placed where needed. Plowing and/or discing surface-
applied lime into the soil may therefore be required.
The application of fluid lime is becoming more popular, especially when mixed with fluid nitrogen fertilizer. The
combination results in less trips across the soil, and the lime is available to counteract acidity produced by the nitrogen.
Also, limestone has been applied successfully to a pharmaceutical wastewater land treatment facility through a spray
irrigation system.
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TABLE 4-2. LIMING MATERIALS
Liming Material
Description
Calcium
Carbonate
Equivalent9
Comments
Limestone, calcitic
Limestone, dolomitic
Limestone, unslaked lime,
burned lime, quick lime
Hydrated lime, staked
lime, builder's lime
Marl
Blast furnace slag
Waste lime products
CaC03, 100% purity
65% CaC03 + 20%
MGCO3, 87% puntyb
CaO, 85% purity
Ca(OH)2, 85% purity
CaC03, 50% purity
CaSi203
Extremely variable in
composition
100
89
151
85
50
75-90
Neutralization value usually
between 90-98% because of
impurities; pulverized to
desired fineness
Pure dolomite (50% MgC03 ana
50%CaC03) has neutralizing
value of 109%; pulverized to
desired fineness
Manufactured by roasting calcitic
limestone; purity depends on
purity of raw materials; white
powder, difficult to handle -
caustic; quick acting; must be
mixed with soil or will harden
and cake
Prepared by hydrating CaO;
white powder, caustic, difficult
to handle; quickly acting
Soft, unconsohdated deposits of
CaCO3, mixed with earth, and
usually quite moist
By-product in manufacture of
pig iron; usually contains
magnesium
a. Calcium carbonate equivalent (CCE): neutralizing value compared to pure calcium carbonate, which has
a neutralizing value defined as 100.
State laws specify a calcium carbonate equivalent averaging 85%.
Source: Follett, R.H., etal., 1981, Tisdale, S.L,and Nelson, W.L, 1975.
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4.6 MODIFICATION OF SOIL TEMPERATURE
Soil temperature is one of the more important factors that controls microbiological activity and the rate of organic
matter decomposition. Soil temperature is also important in influencing the rate of volatilization of compounds from
soil. Soil temperature can be modified by regulating the oncoming and outgoing radiation, or by changing the thermal
properties of the soil (Baver, et al., 1972).
Vegetation plays a significant role in soil temperature because of the insulating properties, of plant cover. Bare soil
unprotected from the direct rays from the sun becomes very warm during the hottest part of the day, but also loses its
heat rapidly during colder seasons.
However, a well-vegetated soil during the summer does not become as warm as a bare soil, and in the winter, the
vegetation acts as an insulator to reduce heat lost from the soil. Frost penetration is more rapid and deeper under bare
soils than under a vegetative cover.
Mulches can affect soil temperature in several ways. In general mulches reduce diurnal and seasonal fluctuations
in soil temperature. In the middle of the summer, there is little difference between mulched and bare plots, but
mulched soil is cooler in spring, winter and fall, and warms up more slowly in the spring. Mulches with low thermal
conductivities decrease heat flow both into and out of the soil; thus, soil will be cooler during the day and warmer
during the night. White paper, plastic, or other types of white mulch increases the reflection of incoming radiation,
thus reducing excessive heating during the day. A transparent plastic mulch transmits solar energy to the soil and
produces a greenhouse effect. A black paper or plastic mulch adsorbs radiant energy during the day and reduces heat
loss at night. Humic substances increase soil temperature by their dark color, which increases the soil's heat
adsorption.
The type of mulch required determines the application method. Mulches, in addition to modification of soil
temperature, are also used to protect soil surfaces from erosion and to reduce water and sediment runoff, prevent
surface compaction or crusting, conserve moisture, and help establish plant cover (Soil Conservation Service, 1979).
A summary of mulch materials is presented in Table 4-3. Commercial machines for spraying mulches are available.
Hydromulching is a process in which seed, fertilizer, and mulch are applied as a slurry. To apply plastic mulches,
equipment which is towed behind a tractor mechanically applies plastic strips which are sealed at the edges with soil.
For treatment of large areas, special machines that glue polyethylene strips together are available (Mulder, 1979).
Irrigation increases the heat capacity of the soil, raises the humidity of the air, lowers air temperature over the
soil, and increases thermal conductivity, resulting in a reduction of daily soil temperature variations (Baver, et al.,
1972). Sprinkle irrigation, for example, has been used for temperature control, specifically frost protection in winter
and cooling in summer and for reduction of soil erosion by wind (Schwab, et al., 1981). Dra.inage decreases the heat
capacity, thus raising the soil temperature. Elimination of excess water in spring causes a more rapid temperature
increase. The addition of humic substances improves soil structure, thus improving soil dramabihty, resulting
indirectly in increased soil temperature.
Several physical characteristics of the soil surface can be modified to alter soil temperature (Baver, et al., 1972).
Compaction of the soil surface increases the density and thus the thermal conductivity. Tillage, on the other hand,
creates a surface mulch which reduces heat flow from the surface to the subsurface. The diurnal temperature variation
in a cultivated soil is much greater than in an unfilled soil. A loosened soil is colder at night and more susceptible to
frost.
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TABLE 4-3. MULCH MATERIALS
Organic
Materials
Quality
Notes
Small gram straw
or tame hay
Corn stalks chopped
or shredded
Wood Excelsior
Wood Cellulose
Fiber
Compost or manure
Wood chips and
bark
g. Sawdust
Pine straw
Undamaged, air dry threshed
straw, free of undesirable
weed seed
Air dried, shredded into
8" to 12" lengths
Burred wood fibers
approximately 4" long
Air dry, non-toxic with
no growth inhibiting
factors
Shredded, free of clumps
or excessive coarse
material
Air dried, free from
objectionable coarse
material
Free from objectionable
coarse material
Air dry. Free of coarse
objectionable material
Spread uniformly at least 1/4
of ground should be visible to avoid
smothering seedling. Anchor either
during application or immediately after
placement to avoid loss by wind or water.
Straw anchored in place is excellent on
permanent seedings.
Relative slow to decompose. Resistant
to wind blowing.
A commercial product packaged in 80-90
Ibs. bales. Apply with power equipment.
Tie down usually.
Must be applied with hydraulic seeder.
Excellent around shrubs. May create
problems with weeds.
Most effective as mulch around orna-
mentals, etc. Resistant to wind blowing.
May require anchoring with netting to
prevent washing or floating off.
More commonly used as a mulch around
ornamentals, etc. Requires anchoring on
slopes. Tend to crust and shed water.
Excellent around plantings. Resistant
to wind blowing.
(continued)
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TABLE 4-3 (Continued)
Other Mulch
Materials
a. Asphalt Emulsion
b. Gravel or Crushed
Stone
c. Wood Excelsior
Mats
d. Jute, Mesh or
Net
Quality
Slow setting
SS-1
Blanket of excelsior fibers
with a net backing on one
side
Woven jute yarn with 3/4"
openings
Notes
Use as a film on soil surface for temporary
protection without seeding. Requires
special equipment to apply.
Apply as a mulch around woody plants.
May be used on seeded areas subject to
foot traffic. (Approximate weight 1 ton
per cu. yd.)
Roll 36" x 30 yards covers 161/2 sq. yds
Use without additional mulch. Tie down
as specified by manufacturer.
Roll 48" x 75 yds. weighs 90 Ibs. and
covers 100 sq. yds.
Source: Soil Conservation Service, 1979.
132
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APPENDIX
TABLE A-1.
COST INFORMATION
EQUIPMENT APPLICABLE TO TREATMENT OF
HAZARDOUS-WASTE-CONTAMINATED SOILS
Power Implements
Tillers: Loosening,
aerating, and/or
mixing the soil
Tractors, Crawler
Tractors, wheel type,
two-wheel drive
Tractors, wheel type
four-wheel drive
Plows, Chisel
Plows, moldboard
Rotary tillers
Subsoilers, chisel
Subsoiler, double
tilling
May be needed when
maximum traction and
stability is needed.
Especially useful on
steep slopes.
Adequate where traction
or power requirements
are less demanding.
Better traction and higher
horsepower available than
with two wheel drive
tractors.
Loosens and aerates soil
to 14 inch depth with
minimum vertical mixing.
Turn and aerate soil 8 to
1 2 inches deep. Poor
mixing, but useful in
rocky soils.
Effective verticle mixing
and aeration of surface
4 to 10 inches of soil.
Combines effects of
plowing and cultivation.
Break up deep soil with
little verticle mixing to
30 inches or more.
Turns surface soil with
moldboard plow then
loosens and mixes subsoil
to 20 inches with a rotary
tiller. Fertilizer or other
agent can be mixed into
the subsoil.
Small, 28 maximum
drawbar horsepower
Large, 300 maximum
drawbar horsepower
Small, 12 maximum
drawbar horsepower
Large, 164 maximum
drawbar horsepower
Small, 12 maximum
drawbar horsepower
Very large, 552
maximum drawbar
horsepower
10 foot width
41 foot width
3-bottom, 2-way
40 inch width,
15 inch rotor
diameter
300 inch width,
21 inch rotor
diameter
13 shank, 270 inch
width
$ 21,800
210,000
6,000
66,500
6,800
*
275,000
1,500
18,700
4,800
1,330
16,600
7,640
each
each
each
each
each
each
each
each
each
each
each
each
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TABLE A-1. (Continued)
Examples of
Function
Tillers (Continued)
Compactors:
Compacting soil
Applicators'
Application of
exogenous
agent(s)
Capacity or Approximate Cost
Equ.pment Principal Use Size Range Cost3 Umts
Harrows, Disc
Harrows, power
Harrows, spike
Harrows, spring
tooth
Rollers
Sprayers, hydraulic
Spreaders, chemical
fertilizer
Spreaders, manure
or dried sewage
sludge
Spreaders, agricultural
limestone
Loosen and aerate surface
soil.
Provide more verticle
mixing than most other
harrows.
Several varieties of power
harrows available which
use rotating (verticle or
horizontal) oscillating, or
reciprocating motion to
loosen and aerate surface
soil.
Break up clods formed
when plowing sticky soil.
Loosen and aerate shallow
surface soil.
Loosen and aerate shallow
surface soil, have vibrating
action.
Compact soil surface,
improve soil moisture
retention, restrict gas
diffusion.
Treatment with relatively
small amounts of fluid
agents, e.g., 20 to 200
gallons per acre.
Apply granular chemical
fertilizers or other agents
in similar form. Some
fertilizer spreaders can
be modified to apply
agricultural limestone.
Apply barnyard manure
or dried sewage sludge.
Apply ground lime or
dolomite to soil for pH
control.
Small hitch
mounted, 450 Ib
Large, pull type,
16,700 Ib
Small, 72 inch
width, 10 inch
working depth
Large, 240 inch
width, 8 inch
working deptb
7 foot wide section
8 foot width
20 foot width
4 foot width
16 foot width
Small, hitch mounted,
7.5-foot treatment
width
Large, hitch mounted,
60-foot treatment
width
Small, self-propelled,
27-foot treatment
width
Large, self-propelled,
70-foot treatment
width
Small, hitch mounted
1 to 2 cu ft capacity
Tractor drawn, 122
cu ft capacity
Tractor drawn, 391
cu ft capacity
Truck mounted
Small, hitch mounted,
12 cu ft capacity
450
32,100
5,000
19,500
160-230
940
2,900
586
1,620
511
9,330
6,730
144,000
214
2,600
9,490
Bid
624
each
each
each
each
each
each
each
each
each
each
each
each
each
each
each
each
each
134
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TABLE A-1. (Continued)
Function
Equipment
Principal Use
Examples of
Capacity or
Size Range
Approximate
Cost8
Cost
Units
Grinders:
Grind plant
Materials
Covers, Mulches.
Soil coverings
and applicators
Irrigation
Drainage
Injectors, liquid
Grinders, tub
Plastic sheeting
Plastic laying
machine
Hydromulching
Sprinkler, hand move
Sprinkler, self-move
Sprinker, self-propelled
Perforated pipe drains
Inject liquid materials
below the soil surface.
Conventional equipment
can inject 1100 gal per
minute of liquid to 16
inches below the surface.
Grind hay or similar plant
material to be used as
organic matter amendment
or mulch.
Cover soil to manage soil
temperature or to suppress
volatilization.
Applies plastic sheeting
over the soil by unrolling
it, buring, and/or gluing
the edges. Mounted on
tractor hitch.
Ground plant materials
(frequently wood fiber)
are sprayed onto the soil
in aqueous slurry.
Chemical binders may
be added to stabilize the
material against the wind.
Apply water to manage
soil moisture and/or soil
temperature. Fertilizers
or other treatment agent
may be applied with the
irrigated water
Lower shallow water
table to improve soil
aeration.
Large, truck mounted.
250 cu ft capacity
Self-propelled
Tractor-drawn
S ton per hour
15 to 25 ton
per hour
2 mil thick
10.5ft wide,
1400 ft. long
10.5 ft wide
Isizes 9 to 20 ft
wide available)
Portable, 1 to
40 acres
Solid set, 1 or
more acres
Motor driven, side
roll, 20 to 80 acres
Center pivot driven
by water, 40-240 acres
Water driven, side
roll, 80-1 60 acres
Costs depend on
depths of drains,
soil hydraulic
conductivity, and
site parameters
15,700
Bid
Bid
12,500
41 ,000
90-95
3,300
1,500 to
1,700
(Includes mulch,
equipment and
labor)
200-500
800-2000
300-500
325-450
275-450
350-500
each
each
each
roll
(140 Ib)
each
pr acre
pr acre
pr acre
pr acre
pr acre
pr acre
pr acre
a. Manufacturers suggested retail prices are used for most agricultural tractors and implements.
b. Larger rotary tillers can be modified to carry fertilizer or other chemical application equipment so that treatment can be done in a single
pass over the soil.
Source: Utah Water Research Laboratory.
135
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TABLE A-2. EXOGENOUS AGENTS, EXCAVATION' AND HAULING COSTS
Identifying Term
Agent
Approximate
Cost
Cost3
Unit
Acidifying Agents
Activated Carbon
Carbonates/Phosphates
Cooling Agents
Excavation and Hauling
Fertilizer
Flushing Agents
Aluminum sulfate
Ferrous sulfate
Ferric sulfate
Liquid ammonium sulfide
Sulfur (crude)
Sulfunc acid
Activated carbon, powder
Activated carbon, granular
Calcium corbonate (limestone)
Triple superphosphate
Liquid and gas carbon dioxide
Liquid nitrogen
Solid carbon dioxide
Water ice
Excavation
Hauling less than 5 miles
Hauling more than 5 miles
Ammonia, anhydrous
Ammonia, aqueous
Ammonium nitrate
Ammonium sulfate
Diammonium phosphate
Phosphoric acid, 52-54%
Phosphate, rock
Potassium chloride, 60-62.4%
Potassium nitrate
Sodium nitrate
Superphosphate, triple
Urea
Blended fertilizers (N-P-K)
16-16-8%
16-16-16
18-46-0
29-14-0
Caustic soda, liquid, 50%
Citric acid
Hydrochloric acid, 20 Bec
Nitric acid, 36°, 38°, 40° Be
Sodium lauryl sulfate, 30%
Sulfunc acid
$235
130
108
235
109-126
20-96
0.55
1.05
6.50-35
127-165
0.12
0.28
0.16
0.03
0.77-4.58b
(Average ~2.10)
0.50
0.25-0.30
135-180
210
91-115
74-79
165
165
23
57
277-284
130
160-165
200-215
220
230
260
230
150-230
0.81
55-115
195
0.29-0.32
20-96
Ton
Ton
Ton
Ton
Ton
Ton
Ib
Ib
Ton
Ton
Ib
Ib
Ib
Ib
yd3
yd3 -mile
yd3-mile
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ib
Ton
Ton
Ib
Ton
(Continued)
136
-------
TABLE A-2. (Continued)
Approximate
Cost"
Identifying Term Agent Cost Unit
Liming Material
Organic Materials
Oxidizing Agents
Precipitating Agent
Proton Donors
Reducing Agents
Resins
Soil/Clay
Agricultural limestone
or dolomite
Lime (85% CaO)
Hydrated lime (85% CaOH)
Animal Tankage
Alfalfa hay
Bone meal, steamed
Castor pomace
Cottonseed meal, 41%
Horse feed (grains and molasses)
Manure, dairy cattle
Molasses
Peanut meal, 50%
Sewage sludge, activated
Hydrogen peroxide, 35-70%
Ozone generator, 22 Ib/day
Potassium permanganate
Ferrous sulfate
9
Methanol
Mineral oil
Vegetable oils
Xylene
Acetic acid
Iron powder
Soda caustic (NaOH-Tech):
Liquid, 50%
Flake, 76%
Granular, 75%
Sodium borohydride powder
Sodium borohydride stabilized
solution, 12%
Anion Exchange
Cation exchange
Bentonite, industrial grade
Kaolin, uncalcined
Top soil
6.50-34
31.25-32.50
32.50-34.50
55
80-120
300
149
215
180
0-1
125
235
80
0.22-0.43
40,000-45,000
2
130
0.48
2.69-2.72
0.22-0.47
1.20-1.60
0.23
1.00
1 50-230
500-570
520
18-19
16
191-197
211-217
94
58
4-10
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Ton
Cubic Foot
Ton
Ton
Ton
Ib
Each
Kilogram
Ton
Gallon
Gallon
Ib
Gallon
Ib
Ib
Ton
Ton
Ton
Ib
Ib
Cubic Foot
Cubic Foot
Ton
Ton
Cubic Yard
(Continued)
137
-------
TABLE A-2. (Continued)
Identifying Term
Sulfides
Tetren
Zeolites
Agent
Ammonium sulfide liquid
Hydrogen sulfide liquid
Sodium sulfide
Tetraethylenepentamine
Clinoptilolite
Approximate
Cost
235
0.11
410-470
1.70-1.78
45-50
Cost3
Unit
Ton
Ib
Ton
Ib
Ton
a. Most costs are wholesale, bulk in train car, tank car, or truckload quantities FOB factories or ports.
b. Depends on equipment type and size. Add 60% for hard or rocky soil, deduct 15% in light soil or
sand (Godfrey, R.S., ed. 1982. Building construction cost data 1983. Robert Snow Means Co., Inc.,
Kingston, MA. 421 p.).
c. Be = Baume.
Source: Utah Water Research Laboratory.
138
-------
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1 5
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INDEX
Acrylate monomer, polymerization of, 84
Activated carbon
in adsorption, 15, 55
cost of, 136t
for heavy metals adsorption, 3, 34t, 39, 42-44, 123t
information needed on, 31
for organics adsorption, 42, 44, 55-56. 110
surface properties of, 42t
synthetic resins compared to, 59
Acurex process, 82
Additives, moisture control enhanced by, 126-127
Adsorption, (sorption), 15, 18t, 34t, 37-38
and attenuation, 115
and Freundlich isotherm, 38, 39(fig), 47, 48(fig), 54, 115
of heavy metals, 3, 34t, 39-46, 123t
by lime, 67
or organics, 3, 34t, 46-56, 123t
and oxidizing agents, 73, 75
in photolysis treatment, 110
and soil, 18, 23, 123t
and soil moisture, 34t, 47, 47(fig), 48(fig), 70, 123t
treatment variables for, 24t
Adverse environmental impacts, in technology selection, 19, 29
Aeration of soils, 122
Aerobic bacteria, and degradation alternative, 26
Aerobic biodegradation, soil oxygen content for, 35t, 89-90, 123t
Aerobic heterotrophic bacteria, as arsenite oxidizer, 5, 97
Aerobic soil conditions
oxidation of sulfides in, 63, 64
and soil-catalyzed oxidation, 71
Agricultural products and by-products. See also Organic soil
materials
and metal adsorption, 3, 34t, 39-41
and organics, 34t, 50, 54, 123t
and soil modification, 123t
Air.water partition coefficient (Kw), 106, 112, 116, 119, 121
Alcohols
as degraded through microbial augmentation, 103t
and direct photolysis, 111, 112
oxidation reactivity for, 69t, 74
and peroxides, 75
Aldehydes, oxidation reactivity for, 69t, 74, 75t
Aliphatic acids, oxidation reactivity for, 69t
Aliphatic amines, oxidation reactivity for, 69t
Aliphatic esters, oxidation reactivity for, 69t
Aliphatic ketones, oxidation reactivity for, 69t
Aliphatic monomers, polymerization of, 84
Aliphatics
and oxidation, 34t, 70
and ozone reactivity, 74
and polymerization, 35t
reduction of 34t
Aliphatics, saturated
and direct photolysis, 111, 112
oxidation reactivity for, 69t
Aliphatics, unsaturated, reduction of, 77
Alkyl halides
as degraded through microbial augmentation, 103t
information, needed on, 31
and peroxides, 75
Alkyl-substituted aromatics, oxidation reactivity for, 69t
Alternatives
detailed analysis of, 2, 19
development of, 2, 14(fig), 16-19
screening of, 2, 19
Aluminum
as catalyst, 70
and pH, 128
as reducing agent, 5, 76, 78
in wastewater sludges, 52t
Aluminum hydroxide, solubility product constant for, 65t
Aluminum phosphate, solubility product constant for, 65t
Aluminum sulfate
in arsenate fixing, 70
cost of, 136t
Amines
as degraded through microbial augmentation, 103t
and direct photolysis, 111, 112
fflushmg solutions for, 33
as proton donors, 110
in tetre-metal complexes, 45
Ammonia (NH3)
cost of, 136t
in fertilizer, 127
and reduction of vapor pores, 118
Ammonium, and zeolites, 61
Anaerobic bacteria, and degradation alternative, 26
Anaerobic biodegradation, and soil, 35t, 46-47, 90-93, 122. 123t
Anaerobic conditions
arsenic reduction and methylation in, 98
to provide sulfides, 63
Analog enrichment for cometabolism, 35t, 98-100, 123t
152
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Anilines
adsorption of, 57
flushing solutions for, 33
Anion(s)
in adsorption, 38
and ozone reaction, 74
selemte as, 81
Anion exchange capacity, 24t
Anion exchangers, 3, 56-57
Anionic compounds, and ion exchange, 34t
Amonic exchange resin, 3, 59, 137t
Applicability matrix, 17, 18t
Aromatic amines, oxidation reactivity for. 69t
Aromatic hydrocarbons, as degraded through microbial
augmentation, 103t
Aromatic monomers, polymerization of, 84
Aromatics
nitro-substituted, 69t
and ozone reactivity, 74
and polymerization, 35t
saturation of, 77
Aromatics, alkyl-substituted, oxidation reactivity for, 69t
Aromatics, unsaturated, reduction of, 34t, 77
Arsenate (As(V)), 69-70
as oxidation product, 5, 97
from phosphate use, 4, 68
Arsenic
and anaerobic condition, 98
analysis for, 20
information needed on, 31
oxidation of, 69-70
and phosphate use, 4, 68
and reduction of chromium, 80
sulfide of, 62, 63
Arsenite (AS(III))
biodegradation of, 5, 97
oxidation of, 69, 70
Arsines, 70, 92
Assessment
of generic in-place alternatives, 23, 26-27
preliminary, 1, 12
of site-specific variables, 21-22
of treatment processes, 2, 29
of water characteristics, 20-21
of waste/soil system characteristics, 22-23
Assimilative capacities
and attenuation, 25t, 27
information gap on, 29
studies on, 29
Atmospheric removal mechanism, photolysis as, 106
Atomic oxygen, oxidation power of, 72t
Attenuation technique, 6, 16, 18t, 35t, 113-116
for metals, 27, 35t, 113-114, 124t
for organic contaminants, 27, 35t, 115-116, 124t
and organic matter, 50
treatment variables for, 25t
Barium, in wastewater sludges, 52t
Banum carbonate, solubility product constant for, 65t
Bench-scale (laboratory) testing, 5, 20, 26, 27-29
Bentonite clay
cost of, 137t
herbicide adsorption by, 53t, 57, 58t
Benzene
oxidation reactivity for, 69t
and ozone reactivity, 74
rate constant for hydroxide radical reaction in air with, 107t
and reduction of vapor pores, 118
Beryllium (Be)
information needed on. 31
and limestone barrier, 66t
in wastewater sludges, 52t
Biological degradation techniques, 5, 15, 18t, 35t, 85
addition of non-specific organic amendments, 35t, 96-98, 123t
with adsorption, 38
aerobic, 35t, 89-90, 123t
anaerobic, 35t, 46-47, 90-93, 122. 123t
analog enrichment for cometabolism, 35t, 98-100, 123t
application,of cell-free enzymes, 35t, 104-105, 124t
with attentuation, 116
augmentation with exogenous acclimated or mutant
micro-organisms, 35t, 100-103, 123t
with extraction, 33
information needed on, 30, 31
modification of soil properties for, 5, 35t, 87-96, 122, 123t
(see also Soil properties, modification of)
and ozone, 72-73
parameters influencing, 85
and peroxide, 73
rate constants for organic compounds in anaerobic systems, 87t
rate constants for organic compounds in soil, 86t
sewage sludges for, 50, 51t
and synethic resin use, 60
treatment vanables for, 25t
and waste/soil system, 26-27
Biological products, lOlt
Bivalent metal complexes, with inorganic ligands in soil
solutions, 67t
Boron, (B)
analysis for, 20
in sludge, 5It, 52t
Cadmium (Cd)
activated-carbon removal of, 42
adsorption of, 42, 43(fig)
agricultural products and by-products for, 40
allowable accumulations of, 53t
analysis for, 20
carbonate of, 65t
hydroxide of, 65t
and limestone barrier, 66t
in sludge, 5It, 52t
solubility of, 66
sulfide of, 62t, 63
tetren for adsorption of, 45
and zeolites, 61
Calcium, (Ca)
analysis for, 20
in ion exhcange, 56, 57
lime as compound(s) of, 128
in wastewater sludges, 52t
153
-------
Calcium carbonate, solubility product constant for. 65t
Calcium hydroxide, and biodegradation of oils, 95
Calcium phosphate, solubility product constant for, 65t
Calcium sulfide, in precipitation, 63, 64
Carbon. See also Activated carbon
as metabolism stimulator. 96, 97
total organic carbon (TOC), 20
Carbonmitrogen.phosphorus (C.N:P) ratio, 25t, 26, 54, 94-95
Carbonates
cost of, 136t
metals precipitation with, 4, 34t. 64-69, 123t
Carbonic acid, as flushing solution, 33
Catalysts, for oxidation, 70 (see also Oxidation)
Cation exchange capacity (CEC), 3, 22, 24t, 57
and allowable metals accumulations, 50, 53t
for clinoptilolite and mordenite, 60
and pH adjustment, 128
for various materials, 57t
Cation exchangers, 3, 56-67
Cationic components, and ion exchange, 34t
Cationic compounds, and ion exchange, 34t, 57, 58
Cationic exchange resin, 3, 59, 137t
Cations, 24t, 74
Cell-free enzymes, application of, 35t, 104-105, 124t
Chelation of metals and chelating agents
in adsorption, 39, 42, 45
in precipitation, 63, 67, 68
Chemical analog, cometabolism through, 98-100
Chemical analysis, 28
Chemical-biological augmentation process, 10It
Chemical degradation techniques, 15, 18t, 34t-35t, 69
with extraction, 33
information needed on, 31
oxidation, 4, 34t, 69-76 (see also Oxidation)
polymerization, 5, 15, 35t, 84-85, 123t
reduction, 5, 34t-35t, 76-83, 123t (see also Reduction)
treatment variables for, 24t
and waste/soil system, 27
Chloride, analysis for, 20
Chlorinated alicycles, and peroxides, 75
Chlorinated aromatics
as degraded through microbial augmentation, 103t
and peroxides, 75
Chlorinated insecticides, oxidation reactivity for, 69t
Chlorinated organics
information needed on, 31
reduction of. 34t, 77
Chlorinated phenoxyacetic acid, reduction of, 76
Chlorine, oxidation power of, 72t
Chlorobenzenes
atmospheric reaction rate and residence time of, 108t
rate constant for hydroxide radical reaction in air with, 107t
reduction of, 76, 77
Chromium (Cr)
analysis for, 20
hydroxide of, 65t
information needed on, 31
and limestone barrier, 66t
in waste water sludges, 52t
Chromium, hexavalent (Chromium VI), reduction of, 5, 15, 34t,
64, 79-81, 123t
Chromium, trivalent (Chromium III), precipitation of, 5, 15,
79, 80
Chromium (Vl)-Chromium (III) reaction, 79
information needed on, 31
with iron sulfide, 63
Clay
as catalyst, 49, 70, 71, 116
cost of, 137t
in ion exchange. 3, 15, 24t, 34t, 56, 57-59, 123t
and tetren-metal complexation, 3, 45
C:N:P (carbon:nitrogen:phosphorus) ratio, 25t, 26, 54, 94-95
Cobalt, in sludge, 5It, 52t
Cobalt carbonate, solubility product constant for, 65t
Cobalt hydroxide, solubility product constant for, 65t
Cobalt sulfide, solubility product constant for, 62t
Cometabolism
analog enrichment for, 98-100
and micTobial activity, 96
Commercial microbial augmentation products and
processes, 101t
Contaminant concentrations and quantities, and technology
selection, 22
Contaminants, inorganic. See Inorganics
Contaminants, organic. See Organics
Compaction. See Soil compaction
Contamination depth. See also Information'requirements
and biodegradation, 26
in metals attenuation, 113, 114
and microbial content, 22
and purposes of this report, 1. 10
and reduction or organics, 78, 79
and synthetic resin treatmenl, 59, 60
and technology selection, 22
Cooling of soil, 35t, 120-121, 124t
Copper (Cu)
activated-carbon removal of, 42
agricultural products and by-products for, 40
allowable accumulations of, 53t
analysis for, 20
carbonate of, 65t
hydroxide of, 65t
in sludge, 5It, 52t
slufide of, 62t, 63
tetren for adsorption of, 45
and zeolites, 61
Corrugation irrigation, 125
Cost-effectiveness
definition of, 16
and possible alternatives, 17
in technology selection, 2, 29
Costs
for exogenous agents, excavation and hauling, 136t-138t
as screening criterion, 19
for testing, 27-28
Cyanide, and peroxides, 74, 75
Data. See Information
DEC Plus, lOlt
ODD, transformation of DDT to, 91
154
-------
DDT
adsorption of. 53
biodegradation of, 86t, 87t, 91
in ozone reaction, 74
photoreaction of. 111
reduction of, 77
Definition of objectives, in technology selection. 16-17
Degradation, and pH, 128
Degradation techniques, 15-16 18t
biological, 5, 15, 28t, 25t, 16, 35t, 85 (see also Biological
degradation techniques)
chemical, 4-5, 15, 18t. 14t, 27. 34t-35t, 69 (see also
Chemical degradation techniques)
in layered system, 70
oxidation. 4, 34t. 69-76, 123t
photolysis, 5-6, 15. 18t, 25t, 35t, 105-113, 123t
polymenzation, 5. 15, 35t, 84-85, 123t
reduction. 5, 34t-35t, 76-83, 123t
and waste/soil system, 24t-25t, 26-27
Dehalogenation
under anaerobic conditions, 90-93
for PCBs and dioxms, 82-83
Depth of contamination See Contamination depth
Detailed analysis of alternatives, 19
Detergents, as degraded through microbial augmentation, I03t
Detoxsol, 1011
Development of alternatives, in technology, 14(fig), 16-19
Dichlorophenol, and ozone reactivity, 74
Dieldnn
adsorption of, 53, 55
biodegradation rate for, 86t
in ozone reaction, 74
as photodegradation production, 111
Diffusers, for aeration, 122
Diffusers of oxygen, 91
Digested sludges, constituents in, 5It
Dioxin (TCDD tetrachlorodibenz-p-dioxm)
atmospheric reaction rate and residence time of, 108t
dechlonnation of, 82-83
multiple pathways of, 18
photolysis of, 5-6, 110
and reduction, 35t
Dissolved organic carbon (DOC), as reduced by ozone, 73
Dissolved oxygen (DO), and ozone treatment, 73
Distribution coefficient of chemical between soil and soil
water (K,,), 47, 49
Drainage, 6, 126
equipment for, 135t
and soil temperature, 130
Ecological environments, and technology selection, 22
EDTA, and chelation of metal, 45
Eh. See Redox potential
Emulsifiers, as degraded through microbial augmentation, 103t
Engineering practice, in screening criterion, 19
Enhancement of volatilization, 35t, 112-113, 124t
Enzymes, cell-free, application of, 35t, 104-105, 124t
Equipment, 6, 133t-135t
sampling, 28
Esters, as degraded through microbial augmentation, 103t
Ethyl ether, vapor reduction for, 120
Ethers
and direct photolysis. 111, 112
flushing solutions for, 33
Evaluation See also Assessment information needed for, 29
(see also Information requirements)
in selection process, 12
Excavation and off-site disposal. 9
Exogenous acclimated or mutant micro-organisms,
augmentation with, 35t, 100-103. 123t
Experimental studies. 29-30 See also Laboratory and
pilot-scale testing
Exposure pathways. 16-17. 17(fig), 18 See also Pathways of
migration
Extraction (soil flushing) techniques, 2-3. 12. 18t. 33. 34t, 36-37
soil modification requirements for. 123t
treatment variables for. 24t
and waste/soil system. 23, 24t
Feme hydroxide, solubility product constant for. 65t
Feme sulfate. cost of. 1361
Ferrous hydroxide, solubility product constant for, 65t
Ferrous sulfate
and arsenic, 5, 97
cost of. I36t. I37t
as reducing agent. 80, 81
Ferrous sulfide, solubility product constant for. 62t
Fertilizer. 127 See also Soil nutrients
cost of. 136t
for oil-spill contamination, 95
Flooding, for anaerobic biodegradation, 91
Flood irrigation. 125
Flow Laboratories. Environmental Cultures Division.
microbial augmentation from, lOlt
Fluorine, oxidation power of, 72t
Flushing, and biodegradation. 26
Rushing agents, cost of, 136t
Flushing solutions, 33
Franklin Research Institute, dechlonnation process bv. 82-83
Freundhch adsorption coefficient or constant (K). 20. 38.
48(fig), 54, 56
Freundhch isotherm, 38, 39(fig), 47, 49(fig), 54. 115
Furrow irrigation, 125
Gasoline, and reduction of vapor pores. 118
CDS process, lOlt
General applicability matrix, 17, 18t
General Environmental Science, microbial augmentation
from, lOlt
Genetic engineering, for degradation capabilities, 5, 102
See also Exogenous acclimated or mutant micro-organisms
Groundwater Decontamination Systems, Inc , microbial
augmentation from, lOlt
Groundwater flow, in technology selection, 21
Groundwater levels, in technology selection, 1, 21
Halogenated compounds, and reduction, 35t
Halogenated hydrocarbons, oxidation reactivity for, 69t
Halogenated organics
and biodegradation, 35t
reduction of, 35t, 77
155
-------
Halogenated xenobiotic compounds, anaerobic biodegrada-
tion of, 90
Hazardous waste, information needed on, 30. See also Heavy
metals; Inorganics; Metals; Organics
Heavy metals. See also Metals; specific metals
activated carbon for, 3, 34t, 39, 42-44. 123t
adsorption of, 3, 34t, 39-46, 123t
agricultural products and by-products for, 3, 34t, 39-41
attenuation of, 27, 35t
chelation of, 39, 42, 45, 63. 67, 68
ion exchange for, 3, 15 (see also Ion exchange)
and ion exchange vs. precipitation, 57
oxidation of, 69
precipitation of, 3, 4, 42, 62-64, 66, 66t, 67-68
in sewage sludge, 50, 53t
solubility of, 66
tetren complexation of, 45-46
and zeolites, 60, 61
Henry's Law Constant, 21, 25t, 111, H3, 119, 121
Herbicides, adsorption of, 50, 53t, 58t
Hexachlorobenzene (HCB), vaporization of, 118
Hexavalent chromium. See Chromium hexavalent
Hexavalent selenium, reduction of, 5, 34t, 64, 81-82, 123t
Human populations, and technology selection, 22
Hydrochloric acid
cost of, 136t
as flushing solution, 33
Hydrogen peroxide, 73, 74, 75
cost of, 137t
oxidation power of, 72t
Hydrogen sulfide
from anaerobic degradation, 92
cost of, 138t
and precipitation, 4, 64
and reduction of vapor pores, 118
Hydroxides, metals precipitation with, 4, 34t, 64-69, 123t
Hydroxyl radical, oxidation power of, 72t
Hypochlorous acid, oxidation power of 72t
Immediate removal, 1, 9
Immobilization techniques, 3, 15
adsorption (sorption), 3, 15, 18t, 24t, 34t, 37-38 (see also
Adsorption)
information needed on, 31
ion exchange, 3-4, 15, 18t, 24t, 34t, 56-61, 123t (see also
Ion exchange
precipitation, 3, 4, 15, 18t, 24t, 34t, 62-69, 123t (see also
Precipitation technique)
and waste/soil system, 23, 24t, 26
Information, from remedial investigation, 16
Information gaps and research needs. 6-8, 29-31. See also
Laboratory and pilot-scale testing
Information requirements
on activated carbon and heavy metals, 44
for adsorption by agricultural products, 41
on analog enrichment, 100
on attenuation of organics, 116
on clay ion exchange, 59
on dechlonnation of PCBs and dioxins, 83
on enhancement of volatilization, 1 13
for enzyme treatment, 105
for extraction, 37
for metals attenuation, 114
for metals-sulfide precipitation, 64
for microbial inoculation, 103
on non-specific organic amendments. 98
on organic matter and organics. 54
for oxidizing agent use, 76
for photolysis, 105, 111-112, 113
on polymerization, 85
on reduction of selenium, 82
on reduction of vapor pores, 119
for soil-catalyzed oxidation, 71
on soil cooling, 121
on soil moisture modification, 88
for soil moisture reduction, 49
on soil nutrient modification. 96
on soil oxygen content, 90, 92
on soil pH, 94
on synthetic resin ion exchange, 60
on tetren-metal complexation, 46
for zeolite ion exchange, 61
Initial remedial actions, 9
Inorganics. See also Heavy metals; Metals
and degradation, 15
and extraction, 34t
general applicability matrix for, 19t
and ion exchange, 15, 57, 59
and precipitation with sulfides, 63
and reduction of vapor pores, 118
and wastewater treatment, 42
In-place treatment, 1, 10
as cost-effective, 10
equipment for, 6, 133t-135t
implementation of, 6, 122
and types of response, 9
In-place treatment techniques
attentuation, 6, 16, 18t, 25t, 27, 35t, 113-116 (see also
Attenuation technique)
degradation, 4-6, 15, 18t, 24t-25t, 26. 34t-35t (see also
Degradation techniques)
extraction, 2-3. 12, 18t, 24t, 33, 34t, 36-37, 123t
general applicability of, 18t
immobilization, 3-4, 15, 18t, 23, 24t. 34t (see also
Immobilization techniques)
reduction of volatilization, 6, 16, 18t, 25t, 27, 35t, 116-121,
124t
selection of, 1-2, 12, 13(fig), 14(fig) (see also Tech-
nology selection)
soil modification requirements for. I23t-I24t (see also
Soil properties, modification of)
summary matrix of, 34t-35t
Ion exchange, 15, 18t, 34t, 56-67
through addition of clays, 3, 15, 24t, 34t, 56, 57-59, 123t
through addition of synthetic resins, 3, 15, 24t, 34t, 59-60. 123t
through addition of zeolites, 3-4. 24t, 34t, 60-61, 123t
in adsorption, 37
with attenuation, 116
treatment variables for, 24t
lomzation, and metal-organic complexes, 39
lomzation rate, and activated carbon, 55
Iron (Fe). See also ferric and ferrous compounds
as catalyst, 70, 84, 85
hydroxides of, 65t
and limestone barrier, 66t
156
-------
phosphate of, 65t
in reduction of chromium, 79
sulfide of, 62t, 63
in wastewater sludges, 52t
Iron powder
cost of, 137t
as reducing agent, 5, 76, 77, 78, 79
Irrigation, 6, 124-126
for anaerobic biodegradation, 91
equipment for, 135t
for reduction of organics, 5, 79
for reduction of soil vapor pores, 119
for soil temperature modification, 130
K (Freundlich adsorption coefficient or constant), 20, 38,
48(fig), 54, 56
Kd (distribution coefficient of chemical between soil and soil
water), 47, 49
KD (soil:water partition coefficient), 47, 106, 112, 116, 119
KO,. (soil/water partition coefficient for organics in soil), 24t
definition of, 20
and reduction of soil moisture, 49
and reduction of soil vapor pores, 119
and soil cooling, 121
Kow (octanol/water partition coefficient), 49
Kw (airwater partition coefficient), 106, 112, 116, 119, 121
Kepone
dehalogenation of, 110
and photolysis, 35t
reduction of, 76
Ketones, as degraded through microbial augmentation, 103t
Laboratory (bench-scale) and pilot-scale testing, 5, 20, 26, 27-29
Lead (Pb)
activated-carbon removal of, 42
agricultural products and by-products for, 40
allowable accumulations of, 53t
analysis for, 20
carbonate of, 65t
flushing solutions for, 33
hydroxide of, 65t
in sludge, 51t,52t
solubility of, 66
sulfide of, 62t, 63
and zeolites, 61
Lime and liming, 4, 128
in arsenate fixing, 70
cost of, 137t
in heavy metals adsorption, 40, 41, 44
materials for, 137t
in precipitation of chromium, 5, 79, 80
and soil pH, 3,93,94
in zeolite treatment, 61
Limestone, 4
cost of, 137t
as liming material, 68, 128, 129t, 137t
as metals-migration barrier, 66, 66t, 67
and soil pH, 93
LLMO, lOlt
Location, in technology selection, 21
Magnesium (Mg)
analysis for, 20
in liiftestone, 128
in wastewater sludges, 52t
Magnesium carbonate, solubility product constant for, 65t
Magnesium hydroxide, solubility product constant for, 65t
Manganese (Mn)
chemisorption of, 66
andpH, 128
m sludge, 51t,52t
Manganese carbonate, solubility product constant for, 65t
Manganese hydroxide, solubility product constant for, 65t
Manganese sulfide, solubility product constant for, 62t
Mass balance, information needed on, 30
Mercury
information needed on, 31
and reduction of chromium, 80
in sludge, 51t, 52t
sulfide of, 62t, 63
Mercury hydroxide, solubility product constant for, 65t
Metal carbonates, precipitation of, 4. 64-69
Metal complexes, with inorganic ligands in soil solutions, 67t
Metal hydroxides, precipitation of, 4, 64-69
Metal phosphates, precipitation of, 4, 64-69
Metal powders, as reducing agent, 5, 76-77
Metals. See also Heavy metals; specific metals
attenuation of, 35t, 113-114, 124t
biodegradation of, 5, 97
flushing solutions for, 33
with oxidizing agents, 75
precipitation of, 42 (see also Heavy metals, precipitation of)
and treatment technologies, 34t, 35t
Metal sulfides, 4, 62t, 62-64
Meteorology and climate, in technology selection, 21
Methylated arsenic, from anaerobic conditions, 98
Methylated arsines, from anaerobic degradation, 92
Methyl (methylated) mercury
from anaerobic degradation, 92
and reduction of vapor pores, 118
Microbial activity
and heavy metals adsorption, 40
andpH, 128
and temperature, 121, 130
Microbial content, 23
Microbial moculants, 100-103
Microbial population, nutrients for, 127
Micro-organisms .
and biodegradation, 5,15, 25t, 26, 85, 87 (see also Soil
properties, modification of)
exogenous acclimated or mutant, 35t, 100-103, 123t
in sewage sludges, 50
Mineralization, 85
under aerobic/anaerobic conditions, 90-91
and heavy metals adsorption, 41
of methyl parathion, 87
and organics adsorption, 54
andpH, 128
Molybdenum (Mo), 20
Monitoring of treatment effectiveness, 28-29
Muck soil, herbicide adsorption by, 50, 53, 53t, 58t
157
-------
Mulches, 130, 131t-132t
equipment for, 135t
for soil cooling, 120
Municipal sludges, 50. See also Sewage sludges
National Contingency Plan (NCP), 1, 9
and definition of objectives, 16
remedial responses in, 9
selection procedures in, 1-2, 12, 13(fig), 14(fig)
source control measures in, 9
and technology selection, 29
National Priorities List, 9
Nickel (Ni)
activated-carbon removal of, 42
agricultural products and by-products for, 40
allowable accumulations of, 53t
analysis for, 20
carbonate of, 65t
hydroxide of, 65t
and limestone barrier, 66t
in sludge, 5It, 52t
sulfide of, 65t
tetren for adsorption of. 45
Nitrates
from anaerobic biodegradation, 92
as fertilizers, 127
from nutrient modification, 95
and organic materials, 41, 54,98
Nitric acid
cost of, 136t
as flushing solution, 33
Nitnles, as degraded through microbial augmentation, 103t
Nitrogen. S«ea/tt>Carbon"nitrogen"phosphorus (C:N:P) ratio
cost of, 136t
with fluid lime, 128
as nutrient addition, 95, 127
in sludge, 5It
total Kjeldahl nitrogen (TKN), 20
Nitrogen transformations, and pH, 128
Nitro-substituted aromatics, oxidation reactivity for, 69t
No action alternative, 23
Non-specific organic amendments, addition of, 35t, 96-98, 123t
Nutrients. See Soil nutrients
Objectives, 2, 16-17
Octanol/water partition coefficient (K0w). 49
Off-site remedial actions, 9
Oils
attenuation of, 115
biodegradation of, 95
as degraded through microbial augmentation, 103t
microbial inoculations for, 102
On-site treatment, 9
Organic carbon content, 22
Organic materials. See also Agricultural products and
by-products; Mulches; Sewage sludges; specific types of material
addition of, 96-98
for anaerobic biodegradation, 91, 92
as biodegradation parameter. 90, 92, 94, 96, 100, 103, 105
CEC of, 57t
cost of, 137t
and metal removal, 39-41
as mulches, 13It
and organics adsorption and attenuation, 3, 50-54
in reduction of chromium, 79, 80
in reduction of selenium, 81, 82
Organics (organic contaminants) See also specific organic
compounds and groups
and activated carbon, 42, 44, 55 -56, 110
adsorption of, 3, 34t, 41, 46-56, 123t
aerobic biodegradation of, 5, 35l, 89
anaerobic biodegradation of, 5, 35t, 90-93
atmospheric reaction rates and residence time of, 108t
attenuation of, 27, 35t, 115-116, 124t
cometabolism of, 35t, 99-100
and degradation, 15 (see also Degradation techniques)
enzyme treatment for, 35t, 104-105, 124t
exogenous micro-organisms for, 35t, 100-103, 123t
general applicability matrix for, I8t
non-specific organic amendments for, 35t, 96-98, 123t
nutrients addition for, 35t, 94-96
oxidation of, 34t, 69-76
photolysis process for, 35t, 110-111
polymerization of, 35t" 84
rate constants for hydroxide radical reaction in air with, 107t
reduction of, 5, 34t-35t, 76-79
soil cooling for, 35t, 120, 121
and soil moisture, 35t, 87-88
soil pH optimization for, 35t, 93-94
in summary matrix of treatment technologies, 34t, 35t
Organic soil matter. See also Organic materials
and heavy metals, 39
and organics adsorption, 50
and ozone, 72-73
and reducing agents, 78
in site information requirements, 41,46, 80, 82, 88, 90, 92, 94,
96,98,100,103,105
Organophosphates
enzyme treatment for, 104
soil-catalyzed oxidation for, 70
Oxidation, 4, 34t, 69-70
through addition of oxidizing agents, 72-76
in photolysis of pesticides, 106
soil-catalyzed reactions, 4, 70-72, 123t
Oxidizing agents
addition of, 72-76
cost of, 137t
soil modification requirements for, 123t
Oxidizing species, 72t, 72-73
Oxygen, dissolved (DO), and ozone treatment, 73
Oxygenated monomers, polymerization of, 84
Oxygen diffusion, reduction of, 91
Ozone, 72-73,74,75
Oxidation power of, 72t
in photolysis of pesticides, 106
Ozone generator, cost of, 137t
158
-------
Paraquat
adsorption of, 57, 58t
biodegradation rate for, 86t
reduction of, 77, 78t
and synthetic resins, 59
Partition coefficient, air:water (Kw)
and enhancement of volatilization, 112
photodecomposition affected by, 106
and reduction of vapor pores, 116, 119
and soil cooling, 121
Partition coefficient, octanol/water (Kow), 49
Partition coefficient, soiliwater (KD)
and adsorption, 47
and enhancement of volatilization, 112
photodecomposition affected by, 106
and reduction of soil vapor pore volume, 116, 119
Partition coefficient, soil/water, for organic waste constitutents
(Koe), 20, 24t, 49, 119, 121
Partition coefficients, and enhancement of volatilization, 113
Partitioning, watervapor, 21. See also Henry's Law Constant
Pathways, exposure, 16-17, 17(fig), 18
Pathways, of migration, 20, 21, 26, 28
PCBs (polychlorinated biphenyls)
and activated carbon, 55
atmospheric reaction rates and residence times for, 109t
attenuation of, 115
cometabolic degradation of, 99
dechlonnation of, 82-83
as degraded by microbial augmentation, 103t
information needed on, 31
and photolysis, 6, 35t, 110, 111
and reduction, 35t, 76
PCNB, adsorption of, 53
Pentachlorophenol (PCP)
degradation of, 96, 100
and ozone reactivity, 74
Peroxide, 73, 74, 75t. See also Hydrogen peroxide
Perpydroxyl radicals, oxidation power of, 72t
Pesticides
and activated carbon, 55, 5o
adsorption of, 50, 57
enzyme treatment for, 104
photolysis of, 106, 111
and soil moisture, 87, 88
and soil pH, 93
and volatilization enhancement, 113
pH. See Soil pH
Phenols
atmosphenc reaction rate and residence time for, 109t
as degraded through microbial augmentation, 103t
flushing solutions for, 33
hydrogen peroxide oxidation for, 74
oxidation reactivity for, 69t
and ozone reactivity, 74
and peroxides, 75
rate constant for hydroxide radical reaction in air with, 107t
and reduction of vapor pores, 118
Phosphates
cost of, 136t
metals precipitation with, 4, 34t, 64-69, -123i
andpH, 128
Phosphoric acid
cost of, 136t
as flushing solution, 33
Phosphorus (P). See also Carbon.nitrogen.phosphorus ratio
analysis for, 20
in fertilizers, 127
in nutrient modification, 95
in sludge, 51t, 52t
Photolysis (photodegradation), 16, 18t, 35t, 105-110
with addition of proton donors, 5-6, 35t, 110-112, 124t
and atomosphenc reaction rates and residence times, 108t-109t
with enhancement of volatilization, 35t, 112-113, 124t
information needed on, 30
treatment variables for, 25t
Physical containment, 9
Pilot-scale testing, 5, 20, 26, 27^29
Planned removal, 1, 9
Polybac/Cytox Corporation, microbial augmentation from, 10H
Polychlorinated biphenyls. See PCBs
Polymer, 84
Polymerization, 5, 15, 35t, 84-85, 123t
Polymerization potential, 24t
Polynuclear aromatics (PNAs), fungal metabolism of, 93
Poly soil process, 10 It
Potassium (K)
analysis for, 20
in fertilizers, 127
in wastewater sludges, 52t
and zeolites, 61
Precipitating agents, cost of, 137t
Precipitation technique, 3, 4, 15, 18t, 34t, 42, 62
for Chromium (III), 5, 15, 79, 80
with extraction, 33
for metal carbonates, phosphates, and hydroxides, 4, 34t,
64-69, 123t
for metal sulfides, 4, 34t, 62-64, 123t
treatment variables for, 24t
Primary sludges, constituents m, 51t
Priority pollutants, analysis for, 20
Products and processes, biological, 1011
Proton donors
addition of, 5-6, 35t, 110-112, 124t
cost of, 137t
Radium (Ra), and reduction of vapor pores, 118
React Environmental Crisis Engineers, 110
Redox potential (Eh), 22, 24t
as biodegradation parameter, 85
in information requirements, 31, 64, 68
and oxidation, 70
for reductive dechlonnation, 90
Reducing agents
addition of, 76-82
cost of, 137t
soil modification requirements for, 123t
Reduction, 5, 34t-35t, 76
of chromium, 5,341,64,79-81, 123t
of orgamcs, 5, 34t-35t, 76-79
of selenium, 5, 34t, 64, 81-82, 123t
of sulfates to sulfides, 63
Reduction of soil vapor pore volume. 35t. 116-120, 124t
159
-------
Reduction of volatilization, 6, 16, 18t, 35t, 116
models for, 27
through reduction of soil vapor pore volume, 6, 35t,
116-120, 124t
through soil cooling, 6, 35t, 120-121, 124t
treatment variables for, 25t
Remedial actions, 1, 9
no-action alternative, 23
objectives of, 16-17
source control, 9, 12, 13(ftg), 16
Remedial investigation, 2, 12, 16, 18
Remedial investigation/feasibility studies (RI/FS), 17
Research needs and information gaps, 6-8, 29-31
Resins, synthetic, 59
cost of, 137t
information needed on, 31
in ion exchange, 3, 15, 34t, 59-60, 123t
Salt, as dechlorination product, 82
Salt content
and heavy metals precipitation, 67
and metal sulfide precipitation, 62
Salts, in furrow irrigation, 125
Sample collection, preservation, shipping and storage, 28
Sampling equipment, 28
Saturated zone
microbial activity in, 73
and technological methods, 1
Scoping, 1, 12, 16
Screening of alternatives, in technology selection, 19
Selection of in-place treatment technologies. See Technology
selection
Selenite (Se(IV)), 81
Selenium (Se)
analysis for, 20
information needed on, 31
Selenium, hexavalent, reduction of, 5, 34t, 64, 81-82, 123t
Sewage sludges, 50
constituents in, 5It
cost of, 137t
elemental analyses of, 52t
heavy metals m, 27, 40, 50, 53t
and orgamcs, 50, 52t, 54
Side effects. See Adverse environmental impacts
Silicon, as required additive, 127
Silver
information needed on, 31
in ozone reaction, 73
m sludge, 51t,52t
Silver carbonate, solubility product constant for, 65t
Silver sulfide, solubility product constant for, 62t
Site-specific characteristics
in technology selection, 21-22
and well-point effectiveness, 126
Site/soil system, and flushing solution, 33
Sludge, 26, 50 See also Sewage sludge
Sodium (Na)
analysis for, 20
and metal-sulfide precipitation, 64
in PCB/dioxm dechlonnation. 82-83
as required additive, 127
in wastewater sludges, 52t
Sodium borohydnde
cost of, 137t
in reduction of orgamcs, 5, 76, 77, 78t, 79
Sodium hydroxide, in reducing agent, 78
Sodium sulfide, 15, 63, 64, 138t
Sodium sulfide salts, 63, 64
Soil(s)
and activated carbon treatment, 42, 44, 55-56
aeration of, 122
CEC of, 57
cost of, 137t
reduction impact on, 78
zeolite use m, 61
Soil catalyzed reactions, 70-72, 123t
Soil characteristics. See Soil properties
Soil compaction, 122
equipment for, 134t
oxygen diffusion reduced by, 91
for reduction of soil vapor pores, 116, 119
Soil contamination depth. See Contamination depth
Soil cooling, 35t, 120-121, 124t
Soil environments
and enzyme use, 104
and exogenous organisms, 102, 103
photodecomposition affected by, 106
Soil flushing. See Extraction techniques
Soil moisture, 24t, 25t, 35t, 87-88, 123t
and adsorption, 34t, 47, 47(fig), 48(fig), 54, 70, 123t
as biodegradation parameter. 25t, 85,90,92, 94,96, 98,
100, 103, 106
control of, 123t-124t, 124-127
in information requirements,31,83, 113, 116
and microbial activity, 71
photodecomposition affected by, 106
reduction of, 46-49
and reduction of volatilization, 25t, 118, 119, 120, 121
and soil-catalyzed oxidation, 70, 71
and temperature, 120
and volatile waste, 71
Soil nutnent content, as biodegradation parameter, 25t, 90, 92, 94,
98, 100,103, 105
Soil nutrients
additions to, 123t-124t, 127
and biodegradation, 35t, 85, 88
modification of, 94-96, 123t
and organic materials, 54
Soil organic matter. See Organic soil matter
Soil oxygen content, 24t, 251
and adsorption by organic matter, 54
for aerobic biodegradation, 35t, 89-90, 123t
for anaerobic biodegradation, 35t, 90-93, 123t
as biodegradation parameter, 25t, 85, 88, 90, 92, 94, 96,
98, 100, 103, 105
control of, 122, 123t-124t
experiments needed on, 26
in information requirements, 64
Soil pH, 22, 24t, 25t, 26, 35t, 92-94. 95, 123t
and activated carbon for heavy metals, 42, 44
and activated carbon for organics, 56
and adsorption, 3, 40, 41, 54
and agricultural products for heavy metals, 41
as biodegradation parameter, 25t, 85, 88, 90, 92, 98,
100, 103, 105
160
-------
andCEC,57
control of, 123t-124t, 127-128, 129t
and geographic region, 127-128
in information requirements, 31, 64. 68, 76. 114
and ion exchange, 24t, 59
and metals precipitation, 4, 24t, 66, 67. 68
and ozone reactions, 72, 76
and reduction of chromium, 79, 80
and reduction of orgamcs, 78, 79
and reduction of selenium. 81,82
under sodium bicarbonate treatment. 110
and soil moisture reduction, 49
and synthetic resin ion exchange, 60
and zeolite ion exchange, 4, 60. 61
Soil properties
and adsorption, 18, 23
and chemical degradation. 15
and metal-sulfide precipitation, 63, 64
modification of, 5, 23, 35t, 87-96, 120, 122-130
and oxidizing agents, 73, 75
in technology selection, 22
Soil temperature, 24t, 25t See also Soil cooling
and anaerobic biodegradation. 91, 92
as biodegradation parameter, 25t, 85, 88. 90, 92, 94, 96,
98, 100, 103,105
modification of, 124t-125t, 130, 131t-132t
and organic matenals, 54
and reduction of volatilization, 25t, 118, 120-121
Soil type, 22
Soil vapor pore volume, reduction of, 35t. 116-120, 124t
Soil.water partition coefficient (KD). 47, 106, 112, 117. 119
Solubility
and extraction, 24t
of heavy metals, 66
and soil-catalyzed oxidation, 70, 71
in waste-characteristic assessment, 20
Solubility product constants
for metal carbonates, phosphates, and hydroxides, 65t
for metal sulfides, 62t
Solution mining. See Extraction technique
Sorption See Adsorption
Sorption of organics in soil. See K^.
Source control remedial actions, 9, 12, 13(fig), 16
Sprinkler irrigation, 125-126, 130
Statistical sampling requirements, 28
Stratigraphy, in technology selection, 21
S-tnazines
adsorption of, 50, 57
soil-catalyzed oxidation for, 70
Strontium, in sludge, 5It, 52t
Strontium carbonate, solubility product constant for, 65t
Studies, on in-place treatment systems, 29-30
Subirrigation, 124
Subsurface aeration, 122
Subsurface drains, 126
Sulfates
analysis for, 20
as catalyst, 84, 85
and sulfide precipitation, 63, 64
Sulfides. See also specific sulfides
cost of, 138t
and precipitation, 4, 24t, 34t, 62-64, 67, 123t
Sulfides, inorganic, and peroxides. 75
Sulfur, in sludge, 5It
Sulfunc acid
cost of, 136t
as flushing solution, 33
Summary matrix of treatment technologies, 34t-35t
Superfund
and NCP process. 9
and objectives, 16
Surface aeration ,122
Surface drams, 126
Surface irrigation, 125
Surfactants, as flushing solutions, 33. 36
Sybron, microbial augmentation from. lOlt
Synthetic resins See Resins, synthetic
TCDD SeeDioxm
TCDP, and photolysis, 35t
Technology selection, 1-2, 13, 29
detailed analysis of alternatives in, 19
development of alternatives in, 14(fig), 16-19
information gaps in, 29-31
laboratory and pilot-scale testing in, 27-29
screening criteria in. 19
site-specific variables in, 21-22
waste-characteristics assessment in, 20-21
waste/soil characteristics assessment in, 22-27
Testing, laboratory and pilot-scale, 5, 20, 26. 27-29
Tetrachlorodibenz-p-dioxin (TCDD). See Dioxm
Tetrachlorophenol, and ozone reactivity, 74
Tetren
and adsorption, 3, 34t, 123t
cost of, 138t
with heavy metals, 45-46
Tillers, 3,6, 122, 133t-134t
Tin, flushing solutions for, 33
Toluene
atmospheric reaction rate and residence time for, 109t
and ozone reactivity, 74
rate constant for hydroxide radical reaction in air with, 107t
Topography, in technology selection, 21
Total Kjeldahl nitrogen (TKN), analysis for, 20
Total organic carbon (TOC), analysis for, 20
Trafficability, 22
and activated carbon for heavy metal, 44
and activated carbon for organics, 56
and adsorption by organic matter, 54
and aerobic biodegradation, 89, 90
and agricultural products for heavy metals, 40, 41
and analog enrichment, 99, 100
and clay ion exchange, 58, 59
and exogenous micro-organisms, 102, 103
and metals attenuation, 114
and non-specific organic amendments, 97, 98
and nutrient modifcation, 95, 96
and organics attenuation, 115
and proton donors, III, 112
and reduction of chromium, 80
and reduction of organics, 78, 79
and reduction of selenium, 81, 82
and soil cooling, 120, 121
and soil pH optimization, 93, 94
16]
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and synthetic resin ion exchange, 59, 60
and tetren-metals complexation. 46
and volatilization enhancement, 112, 113
and zeolite ion exchange, 61
also mentioned in information requirements. 37, 49, 64,
68,71,85,88,92,105,109
Transport models, information needed on, 31
Treatability, and technology selection, 23
Treatment technologies. See In-place treatment technologies
Treatment variables, 24t-25t
Tnchlorophenol, and ozone reactivity, 74
Trickle irrigation, 124
Tnethylamine, as proton donor, 110
Tnvalent chromium, precipitation of, 5, 15, 79, 80
2,4,5-tnchlorophenoxyacetic acid (2,4,5-T)
biodegradation rate for, 86t
pseudomanas fepacia used for, 100, 102
reductive dechlormation of, 90
Wastewaters
activated-carbon use m, 42-44, 55
reduction with catalyzed metal powders in. 77
sewage sludge from, 50, 52t
sulfides for, 63
zeolite use in, 61
Water table, and technology selection, 1,21
Well points, 6, 126
Xenobiotic compounds
anaerobic biodegradation of, 89, 90-93
metabolism stimulated for, 96
microbial inoculation for, 100, 102
and soil moisture, 88
Xylene
cost of, 137t
and ozone reactivity/74
Utah Water Research Laboratory, 29-30
Vanadium (V)
analysis for, 20
in wastewater sludges, 52t
Vapor pressure, 20, 25t
Variables. See Site characteristics; Treatment variables;
Waste charactenstlcs; Waste/soil system charactenstlcs
Volatilization. See also Reduction of volatilization
enhancement of, 35t, 112-113, 124t
information needed on, 30
and temperature, 130
Volatilization suppression, 105, 122
Waste, information needed on, 30. See also Heavy metals;
Inorganics; Metals; Organics
Waste characteristics, in technology selection, 20-21
Waste/soil system characteristics, in technology selection, 22-27
Zeolites
cost of, 138t
in ion exchange, 3-4, 24t, 34t, 60-61, 123t
Zero point of charge (zpc), 42, 44
Zinc (Zn)
activated-carbon removal of, 42
agncultural products and by-products for, 39-41
allowable accumulations of, 53t
analysis for, 20
carbonate of, 65t
chemisorption of, 66
flushing solutions for, 33
hydroxide of, 65t
and limestone barrier, 66t
in sludge, Sit, 52t
sulfate of, 70
sulfide of, 62t, 63
tetren for adsorption of, 45
and zeolites, 61
Zinc powder, as reducing agent, 5, 76, 77, 78, 78t
1.62
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COPYRIGHT NOTICE
Figure 3-3
Figure 3-4
Table 3-2
Table 3-6
Table 3-8
Table 3-9
Table 3-10
Table 3-1
Table 3-12
Table 3-15
Table 3-18
From Huang, C.P., and E.H. Smith 1981. Removal of cadmium(II) from plating waste water
by an activated carbon process. In W.J Cooper (ed.) Chemistry in water reuse, 2:355-400.
Ann Arbor Sci. Publ., Ann Arbor. Ml. Used by permission.
From Huang, C.P., and E.H. Smith. 1981. Removal of cadmium(II) from plating waste water
by an activated carbon process. In W.J. Cooper (ed.) Chemistry in water reuse, 2:355-400.
Ann Arbor Sci. Publ., Ann Arbor, Ml. Used by permission
From Huang, C.P., and E H. Smith 1981. Removal of cadmium(Il) from plating waste water
by an activated carbon process. In W.J. Cooper (ed.) Chemistry in water reuse, 2:355-400.
Ann Arbor Sci. Publ., Ann Arbor, MI Used by permission.
From Coffey, D.L., and G.F. Warren. 1969. Inactivation of herbicides by activated carbon
and other adsorbents. Weed Sci. 17.16-19. Used by permission.
From Coffey, D.L., and G.F. Warren. 1969. Inactivation of herbicides by activated carbon
and other adsorbents. Weed Sci. 17:16-19. Used by permission.
From Overcash, M.R., and D. Pal. 1979. Design of land treatment systems for industrial
wastes theory and practice. Ann Arbor Science, Ann Arbor, Ml. Used by permission.
From Overcash, M.R., and D. Pal. 1979. Design of land treatment systems for industrial
wastes theory and practice. Ann Arbor Science, Ann Arbor, MI. Used by permission.
From Article, J., and Fuller, W.H., 1979. Effect of Crushed Limestone Barriers on
Chromium Attenuation in Soils. J. Environ. Qual. 8:503-510.
From Mattigod. S.W., G. Sposito, and A.L. Page. 1981. Factors affecting the solubility of
trace metals in soils. In Chemistry in the Soil Environment, ASA Special Publication 40.
Used b\ permission.
From Rice. R G 1981. Ozone for the treatment of hazardous materials. Water 1980.
Symposium series. American Institute of Chemical Engineers, 209 (77):79-107. Used by
permission
From Staiff. D C . L.C. Butler, and J.E. Davis. 1981. A field study of the chemical
degradation of paraquat dichlonde following simulated spillage on soil. Bull. Environ.
Contam. Toxicol. 26:16-21. Used by permission.
US GOVERNMENT PRINTING OFFICE 1984 - 759-102/10712
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