PB88-131271
TECHNICAL RESOURCE DOCUMENT TREATMENT TECHNOLOGIES
FOR HALOGENATED ORGANIC CONTAINING WASTE
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
DEC 87
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
NTIS
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PB88-131271
TECHNICAL RESOURCE DOCUMENT TREATMENT TECHNOLOGIES
FOR
HALOGENATED ORGANIC CONTAINING WASTE
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
DECEMBER 1987
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
11
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FOREWORD
As hazardous waste continues to be one of the more prominent
environmental concerns to the people of the United States and other
countries throughtout the world, there are continuous needs for research
to characterize problems and develop and evaluate alternatives to addressing
those problems. The program of the Hazardous Waste Engineering Research
Laboratory are designed to contribute to satisfying these research needs.
This Technical Resource Document for Treatment Technologies for
Halogenated Organic Containing Wastes compiles available information on
those technologies. It is intended to provide support for the land
disposal prohibition, currently being considered by the EPA, and to
provide technical information for those individuals and organizations
concerned with the subject waste streams. Those wishing additional
information on the various technologies should contact the Hazardous
Waste Engineering Research Laboratory.
Thomas R. Hauser
Director
Hazardous Waste Engineering Research Laboratory
111
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ABSTRACT
This halogenated organics technical resource document (TRD) is one of a.
series of five TRDs that are being prepared by the Hazardous Waste Engineering
Research Laboratory. It provides information that can be used by
environmental regulatory agencies and others as a source of technical
information describing alternatives to the land disposal of nonsolvent
halogenated wastes. These alternatives include waste minimization/recovery,
treatment, and disposal of waste streams. Although emphasis is placed on the
presentation of performance data for proven technologies, information dealing
with the applicability of other emerging technologies is presented as well.
Halogenated organic constituents of concern include all listed
halogenated organics not classified as solvents, dioxins, or polychlorinated
biphenyls. An estimated 24.2 million gallons of these nonsolvent halogenated
wastes were generated in 1981. Of this total, about 3.2 million gallons were
land disposed.
The treatment technologies discussed in this TRD include biological
treatment as well as the following physical, chemical, and thermal treatment
technologies:
Physical Treatment Chemical Treatment Thermal Treatment
Distillation Wet Air Oxidation Incineration
Evaporation Supercritical Water Molten Glass
Steam-Stripping UV/Ozone Oxidation Molten Salt
Solvent Extraction Chemical Dechlorination Pyrolysis
Carbon Adsorption In Situ Vitrification
Each treatment system, plus solidification/fixation processes for treatment
residuals, is examined with regard to the following factors:
1. Process description, including design and operating parameters,
pretreatment requirements, and post—treatment of residuals;
2. Performance data available from bench, pilot, and full-scale studies;
3. Cost of treatment; and
4. Present status of the process.
A final section provides approaches to identifying and selecting appropriate
technologies for specific halogenated organic compound bearing waste streams.
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CONTENTS
Foreword ill
Abstract iv
Figures vii
Tables x
Acknowledgement xv
1. Introduction 1-1
Purpose 1-1
Document Organization and Content. 1-3
2. Waste Characteristics, Generation, and Management 2-1
Identification and Characterization of Halogenated
Organic Wastes and Their Constituents 2-1
Classification of Hazardous Organic Wastes 2-12
Halogenated Organic Waste Generation and Management. . . 2-12
3. Pretreatment , 3-1
4. Waste Minimization Processes and Practices. 4-1
Source Reduction 4-2
Recycling/Reuse. 4-3
Waste Exchange 4-9
S. Physical Treatment Technologies 5-1
Distillation ; . . . 5-3
Evaporation Processes. 5-22
Steam Stripping 5-40
Liquid - Liquid Extraction 5-65
Carbon Adsorption 5-85
Resin Adsorption 5-115
6. Chemical Treatment Processes. 6-1
Wet Air Oxidation 6-2
Supercritical Water Oxidation 6-24
Ultraviolet/Ozone Oxidation 6-39
Chemical Dechlorination 6-55
7. Biological Treatment Methods 7-1
Process Description 7-1
Demonstrated Performance .. 7-2
Cost 7-13
Overall Status 7-15
8. Incineration Processes 8-1
Overview 8-2
Process Description 8-14
Performance of Hazardous Waste Incinerators in the
Destruction of Halogenated Organic Wastes 8-28
Costs of Hazardous Waste Incineration 8-38
Status of Development 8-48
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CONTENTS (continued)
9. Emerging Thermal Treatment Technologies 9-1
Circulating Bed Combustion 9-2
Catalytic Fuluidized Bed Incineration 9-13
Molten Glass Incineration 9-21
Molten Salt Destruction 9-26
Pyrolysis Processes 9-34
In Situ Vitrification 9-50
10. Land Disposal of Residuals 10-1
Solidification/Chemical Fixation 10-2
Macroencapsulation 10-7
11. Considerations for System Selection 11-1
General Approach 11-1
Assessment of Alternatives 11-4
Appendices
A. Chemical and Physical Properties of Halogenated Organic
Compounds ..... A-l
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FIGURES
Number Page
5.1.1 Basic schematic for batch and continuous fractionation
systems 5-6
5.1.2 McCabe-Thiele diagram for distillation 5-7
5.1.3 Reclamation of cold cleaning solvents via small batch stills
(15 gpd) 5-16
5.1.4 Reclamation of cold cleaning solvents via medium batch stills
C55 gpd) 5-17
5.1.5 Reclamation of cold cleaning solvents via a large continuous
still (250 gpd) 5-18
5.2.1 Cross section of agitated thin film evaporator 5-23
5.2.2 Treatment train using an agitated thin film evaporator 5-2.6
5.2.3 Selection of LUWA Evaporators based on waste viscosity. .... 5-28
5.2.4 Required heat transfer surface area for distilling low boiling .
organics and concentrating aqueous solutions 5—30
5.2.5 Required heat transfer surface area for dehydrating heavy
pastes and stripping wastes to low residual organics 5-31
5.2.6 Heat transfer and evaporation rates in LUWA Thin Film
Evaporators ...... 5-32
5.3.1 Typical steam stripping process 5-41
5.3.2 Hausbrand diagram for various halogenated organic liquids
at 1 atmosphere 5-43
5.4.1 Schematic of extraction'process 5—66
5.5.1 Carbon adsorption flow diagram 5-92
5.5.2 Carbon bed configurations .... 5-98
Vll
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FIGURES (continued)
Number Page
5.6.1 Phenol removal and recovery system - solvent regeneration of
Amberlite adsorbent 5-120
6.1.1 Wet air oxidation general flow diagram 6-4
6.1.2 4.5 MGD wastewater treatment facility 6-14
6.1.3 Installed plant costs versus capacity .... 6-16
6.1.4 Unit operating costs versus unit flow rate 6-17
6.2.1 Temperature-density diagram 6-26
6.2.2 Properties of water at 250 atm 6-28
6.2.3 Schematic flow sheet of MODAR process 6-30
6.3.1 Schematic of top view of ULTROX pilot plant by General Electric
(ozone sparging system omitted) 6-45
6.4.1 Probable reaction mechanism 6-57
8.1 Flow sheet of an incineration plant for hazardous wastes. . ... 8-17
8.2 Rotary kiln incinerator with liquid injection capability. . . . 8-22
8.3 Cross-section of a fluidized-bed furnace .• 8-27
8.4 Purchase cost of liquid injection system. ° 8-43
8.5 Purchase cost of rotary kiln system 8-43
8.6 Purchase cost of hearth incinerators 8-44
8.7 Purchase cost of waste heat boilers 8-44
8.8 Purchase cost of scrubbing systems receiving 500 to 550°F gas . 8-45
8.9 Purchase costs for typical hazardous waste incinerator
scrubbing systems receiving 1800 to 2200°F gas. ....... 8-45
9.1.1 CBC incineration pilot plant located at GA Technologies .... 9-3
9.1.2 Chemical reactions that occur in CBC combustion chamber .... 9-4
9.2.1 Typical components of a catalytic incinerator . . 9-13
Vlll
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FIGURES (continued)
Number Page
9.2.2 Flow Diagram of B.F. Goodrich CATOXID process 9-15
9.2.3 Calculated conversion efficiencies for several organic
materials 9-17
9.2.4 Effect of fouling materials, poisons, and suppressants
on catalyst activity ......... 9-17
9.2.5 Comparison of measured €2*1013 oxidation rates and
calculated rates from regression 9-18
9.2.6 Comparison of measured C2C1^ oxidation rates and
calculated rates from regression 9-18
9.2.7 Catalyst deactivation during oxidation of dry C£Cl4 .... 9-19
9.3.1 Dirt purifier and hazardous waste incinerator 9-22
9.4.1 Molten salt combustion system 9-27
9.5.1 Continuous pyrolyzer 9-35
9.5.2 Pyroplasma process flow .diagram ....• 9-39
9.5.3 Advanced electric reactor ' 9-44
9.5.4 High temperature fluid wall process configuration for the
destruction of carbon tetrachloride 9-46
9.6.1 Operating sequence of in situ vitrification 9-51
9.6.2 Off-gas containment and electrode support hood. 9-52
9.6.3 Cost of in situ vitrification for TED wastes as functions of
electrical rates and soil moisture. 9-53
11.1 Halogenated organic waste management options 11-2
11.2 Simplified decision.chart for aqueous and mixed aqueous/organic
waste stream treatment 11-9
11.3 Simplified decision chart for organic liquid waste stream
treatment 11-10
11.4 Approximate ranges of applicability of treatment techniques as
a function of organic concentration in liquid waste streams . 11-13
IX
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TABLES
Number Page
1.1 Scheduling for Promulgation of Regulations Banning Land
Disposal of Specified Hazardous Wastes 1-2
2.1 RCRA-Listed Wastes Containing Halogenated Organic Compounds
(HOCs) 2-2
2.2 Halogenated Organic Compounds in the RCRA D, P, and' U Waste
Codes 2-3
2.3 Constituent Concentrations in K Type Halogenated Process
Wastes 2-4
2.4 Waste Categorization Based on Physical State 2-13
2.5 Waste .Quantity Data for Halogenated Process Wastes 2-16
2.6 Summary of Existing Waste Treatment Technologies 2-18
4.1 Recovery Processes Summary ..........o. 4-5
5.1.1 Commercially Available Solvent Stills 5-19
5.2.1 Keys to Selecting Kontro Thin Film Evaporators 5-27
5.2.2 Typical Agitated Thin Film Evaporator Design Characteristics. . 5-33
5.2.3 Hourly Costs of LUWA Thin Film Evaporator 5-35
5.2.4 Capital Cost Recovery Components for Onsite ATFE Recovery
Systems 5-36
5.3.1 Henry's Law Constants . . 5-47
5.3.2 Steam Stripping Performance 5-52
5.3.3 Steam Stripping Costs for Wastewater Streams Containing
Contaminants of Varying Henry's Law Constant 5-56
5.3.4 Cost Components for Onsite Steam Stripping Halogenated Organic
Compounds Recovery. 5-58
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TABLES (continued)
Number Page
5.3.5 Steam Stripping Cost Estimates as a Function of Throughput,
Volatile Organic Compounds Content and Disposal Method. . . . 5-60
5.4.1 KV Values for Aqueous/Organic Systems 5-71
5.4.2 Rv Values for Aqueous/Organic Systems . 5-73
5.4.3 Results of Solvent Extraction Studies 5-77
5.4.4 Estimated Costs for a Liquid-Liquid Extraction System 5-79
5.4.5 Advantages and Disadvantages of Extraction Types 5-80
5.5.1 Waste Characteristics that Affect Adsorption by Activated
Carbon 5-87
5.5.2 Influence of Substituent Groups on Adsorbability 5-88
5.5.3 Summary of Carbon Adsorption Capacities 5-90
5.5.4 Properties of Several Commercially Available Carbons 5-96
5.5.5 Typical Properties of Powdered Activated Carbon 5-97
5.5.6 Treatability Rating of Some Halogenated Organics Utilizing
Carbon Adsorption 5-103
5.5.7 Compounds Reported in Waste Streams Being Treated by Full-
Scale, Granular Activated Carbon Units 5-105
5.5.8 Results of Adsorption Isotherm Tests on Toxic Chemicals .... 5-106
5.5.9 Direct Costs for Carbon Adsorption. ... 5-107
5.5.10 Indirect Costa for Carbon Adsorption 5-109
5.5.11 Carbon Adsorption Costs 5-110
5.6.1 Physical Properties of Adsorbents 5-117
5.6.2 Removal of Polynuclear Aromatics, Chlorinated Pesticides, and
Polychlorinated Biphenyls From Two Types of Spiked Miami Tap
Water 5-123
5.6.3 Cost of Adsorbents. 5-125
5.6.4 Design Criteria—Trinalomethane Removal .... 5-126
xi
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TABLES (concinued)
Number Page
5.6.5 Cost Comparison—GAC VS. Resin 5-127
6.1.1 Bench-Scale Wet Air Oxidation of Pure Compounds 6-10
6.1.2 Priority Pollutant Removals Using a PACT™/Wet Air Regener-
ation System for Domestic and Organic Chemicals Wastewater. . 6-13
6.1.3 WAO Costs Versus Flow 6-18
6.2.1 Dielectric Constants of. Some Common Solvents 6-25
6.2.2 MODAR Treatment Costs for Organic Contaminated Aqueous Wastes . 6-35
6.3.1 Relative Oxidation Power of Oxidizing Species 6-40
6.3.2 Dissociation Energies for Some Chemical Bonds 6-43
6.3.3 Design Data for a 40,000 gpd (151,400 L/day) ULTROX Plant . . . 6-46
6.3.4 Typical Results of UV/Ozone Irradiation ... ... 6-48
6.3.5 Equipment Plus Operating and Maintenance Costs; 40,000 gpd
UV/Ozone Plant. 6-50
6.4.1 Dechlorination Processes 6-56
6.4.2 Preliminary Economic Analysis of In Situ and Slurry Processes . 6-60
7.1 Examples of Microorganisms that Can Degrade Halogenated Organic
Compounds 7-3
7.2 Research on Microbial Degradation of Halogenated Organic
Compounds 7-8
7.3 Concentrations of 2,4,5-T in Soil Treated With Pseudomonas
Cepacia AC100 7-9
7.4 Zero-Order Rate Constants for Commercial and Mixed Liquor
Bacterial Populations 7-12
7.5 Degradation of Organopollutants by P. Chrysosporium 7-12
7.6 Costs for Biological Treatment 7-14
8.1 Heat of Combustion Based on Physical State and Chlorine
Content 8-8
Xll
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TABLES (continued)
Number Page
8.2 Operating Parameters of Hazardous Waste Liquid Injection
8.3
8.4
8.5
8.6
8.7
8.8
8.9
8.10
8.11
8.12"
9.1.1
9.1.2
9.4.1
9.4.2
9.5.1
9.5.2
10.1
10.2
10.3
Operating Parameters for Rotary Kilns
Operating Parameters of Fluidized Bed Incinerators. ......
Waste Destruction Efficiencies Achievable by Incineration . . .
Incineration Facilities Tested
Survey of Hazardous Waste Incinerators - Costs of Incineration
and Cost Impacting Factors
Summary of Cost Data Compiled by Mitre Corporation, 1981. . . .
Number of Hazardous Waste Incinerators in Service in the
U.S.A
Summary of Incineration Technologies.
Circulating Bed Incinerator vs. Conventional incinerators . . .
PCB Combustion Tests in Sodium-Potassium-Chloride-Carbonate
Melts .
Summary of Operating Parameters and Results for Huber AER
Research/Trial Burns
Compatibility of Selected Waste Categories with Different Waste
Present and Projected Economic Considerations for Waste Solid-
8-20
8-24
8-26
8-30
8-33
8-34
8-36
8-40
8-46
8-50
8-55
9-6
9-11
9-30
9-32
9-42
9-48
10-3
10-4
10-7
Xlll
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TABLES (continued)
Number Page
10.4 Estimated Costs of Encapsulation 10-8
11.1 Guideline Considerations for the Investigation of Waste Treat-
ment Technologies 11-6
11.2 Treatment Processes Potentially Applicable to Halogenated
- Waste 11-12
11.3 Summary of Halogenated Organic Treatment Processes 11-15
11.4 Major Cost Centers for Waste Management Alternatives. ..... 11-19
xiv
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ACKNOWLEDGEMENT
The authors would like to thank Harry M. Freeman, the Hazardous Waste
Engineering Research Laboratory Work Assignment Manager, for his assistance
and support throughout the program. The authors also extend thanks to other
members of the HWERL staff for their assistance and to the many industrial
representatives who provided design, operating, and performance data for the
waste treatment technologies.
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SECTION 1
INTRODUCTION
Section 3004 of Che Resource Conservation and Recovery Act (RCRA), as
amended by the Hazardous and Solid Waste Amendments of 1984 (HSWA), prohibits
the continued placement of RCRA-regulated hazardous wastes in or on the land,
including placement in landfills, land treatment areas, waste piles, and
surface impoundments (with certain exceptions for surface impoundments used
for the treatment of hazardous wastes). The amendments specify dates by which
these prohibitions are to take effect for specific hazardous wastes as shown
in Table 1.1. After the effective date of a prohibition, wastes may only be
land disposed if: (1) they comply with treatment standards promulgated by the
Agency that minimize short-term and. long-term threats arising from land
disposal; or (2) the Agency has approved a site-specific petition
demonstrating, to a reasonable degree of certainty, that there will be no
migration from the disposal unit for as long as the waste remains hazardous.
In addition, the statute authorizes the Agency to extend the effective dates
of prohibitions for up to 2 years nationwide if it is determined that there is
insufficient alternative treatment, recovery or disposal capacity.
PURPOSE '
This Technical Resource Document (TRD) for halogenated organic wastes
identifies recovery and treatment alternatives to land disposal for these
wastes and provides performance data and other technical information needed to
assess potentially applicable alternatives. This document is one of a series
of documents designed to assist regulatory agency and industrial personnel in
meeting the land disposal bans promulgated by the 1984 RCRA Amendments.*
^Technical Resource Documents for dioxin and solvent bearing wastes were issued
earlier in 1986. The treatment of halogenated solvents has been discussed in
the solvent TRD and these solvent compounds are not specifically addressed in
this document.
1-1
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TABLE 1.1. SCHEDULING FOR PROMULGATION OF REGULATIONS BANNING
LAND DISPOSAL OF SPECIFIED HAZARDOUS WASTES
Waste category
Effective date*
• Dioxin containing waste
• Solvent containing hazardous wastes
numbered F001, F002, F)03, F004, F005
• California List
-Liquid hazardous wastes, including free liquids
associated with any solid or sludge containing:
- Free or complex cyanides at >_1, 000 mg/L
- As >500 mg/L "~
- Cd ~>100 mg/L
- Cr-^6 £500 mg/L
- Pb >500 mg/L
- Hg >20 mg/L
- Ni ][134 mg/L
- Se ^100 mg/L
- Tl _>130 mg/L '
-Liquid hazardous wastes with:
- pH <2~.Q
- PCBs >50 ppm
- Hazardous wastes containing halogenated organic
compounds in total concentration >lt 000 mg/kg
I
Other listed hazardous wastes (§§261.31 and 32), for
which a determination of land disposal prohibition
must be made :
- One-third of wastes
- Two-thirds of wastes
- All wastes
Hazardous wastes identified on. the basis of
characteristics under Section 3001
Hazardous wastes identified or listed after enactment
11/8/86
11/8/86
7/8/87
7/8/87
7/8/87
8/8/88
6/8/89
5/8/9U
5/8/90
Within 6 months
*Not including underground injection.
1-2
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Although emphasis is placed on performance data, technical factors affecting
the performance of recovery/treatment alternatives, including restrictive
waste characteristics, are discussed to assist in the evaluation of options to
land disposal. Cost data are also presented to assist in the evaluation and
ultimate selection of treatment/recovery technologies.
DOCUMENT ORGANIZATION AND CONTENT
The following section (Section 2) will identify the nonsolvent
halogenated wastes of concern, including the constituents of concern for each
specific RCRA waste code designation. Available information concerning waste
stream characteristics, generation, and management practices will also be
provided in Section 2. Remaining sections (Sections 3 through 10) will
discuss, respectively; pretreatment, recovery practices, and all potentially
applicable physical, chemical, biological, incineration, other thermal
treatment processes and approaches to land disposal of residuals. Each
treatment process will be reviewed with regard to the following four factors:
1. Process description, including design and operating parameters,
pretreatment requirements, and post-treatment of residuals;
2. Performance data available from bench, pilot, and full-scale studies;
3. Cost of treatment; and
4. Present status of the process.
A final section (Section 11) will provide approaches to identifying and
selecting appropriate technologies for halogenated organic compound bearing
waste streams. Although emphasis is placed on technical performance, cost
data will also be presented and discussed to assist in process selection.
1-3
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SECTION 2
WASTE CHARACTERISTICS, GENERATION, AND MANAGEMENT
IDENTIFICATION AND CHARACTERIZATION OF HALOGENATED ORGANIC WASTES AND THEIR
CONSTITUENTS
The halogenated organic wastes addressed in this TRD are listed by RCRA
code in Table 2.1. The wastes consist of RCRA D code pesticide wastes, listed
because of EF toxicity; specific K code process wastes; and P and U code
wastes containing specific halogenated organic compounds (HOCs). As noted in
the table, many of the K code process wastes contain halogenated organic
compounds that are used as solvents. Although these waste streams will
generally be amenable to the recovery/treatment processes discussed in this
TRD, a more detailed and relevant discussion of the properties and management
of halogenated solvent compounds can be found in the solvent TRD.
A total of 78 nonsolvent halogenated organic compounds are constituents
of concern within the 120 waste streams listed in Table 2.1. These
constituents are identified by chemical compound name in Table 2.2 for the D,
0, and P Codes comprising the halogenated organic waste category.
Constituents found in the specific process waste stream K codes, along with
their concentrations, are listed in Table 2.3. The data in Table 2.3 were
assembled in the Reference 2 study and were compiled from four previous EPA
sponsored programs.
An examination of Table 2.3 shows that the composition and constituent
concentrations of many of the specific waste streams is subject to wide
variability both within and among the four programs shown in the table. A
fairly detailed analysis of the data provided by the four data sources can be
found in Reference 7. As noted in References 2 and 7, the waste character-
ization efforts are subject to a great deal of uncertainty. Very little
sampling data were available to characterize the waste streams, and estimates
2-1
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TABLE 2.1. RCRA-LISTED HASTES CONTAINING HALOGENATED ORGANIC COMPOUNDS (HOCs)
Waste
category
DOXX
KXXX
PXXX
UXXX
Totals
Total Total
number number
listed in containing
Part 261 HOCs (X)
17 6 (35) D012,
76 27 (36) K001,
K020a,
K041,
K098,
107 23 (21) POQ4,
P033,
P058,
233 64 (26) U006,
U029,
U041a,
U049,
U073,
U132,
U185,
U233,
433 120 (28)
Listing of specific hazardous waste codes
containing one or more HOCs
D013,
K009a,
K021a,
K042a,
K099,
P017,
P035,
P059,
U017,
U030,
U042,
U060,
U081,
U138,
U192,
U235,
D014,
KOIO8,
K028a,
K043,
K105a
P023,
P036,
P060,
U020,
U033,
U043,
U061,
U082,
U142,
U207,
U237,
D015,
K015a,
K029a,
K073a,
P024,
P037,
P090,
U023,
U034,
U044a,
U062,
U097,
U150,
U212,
U240,
D016,
K016a,
K030a,
K085a,
P025,
P043,
P095,
U024,
U035,
U045a,
U066,
U127,
U156a,
U224,
U242,
D017
K017a,
K032a,
K095a,
P026,
P050,
P118,
U025,
U036,
U046a,
U067.
U128,
U158,
U230,
U243,
K018a,
K032,
K096a,
P027,
P051,
P123
U026,
U038,
U047,
U068,
U129,
U183,
U231,
U246,
K019a,
K033,
K097,
P028,
P057,
U027,
U039,
U048,
U072,
U130,
U184,
U232,
U247
aContains or represents a specific halogenated organic compound addressed in the solvent TRD.1
Source: Reference 2.
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TABLE 2.2. HALOGENATED ORGANIC COMPOUNDS IN THE RCRA D, P, AND U HASTE CODES
D012 Eldrin
DO13 Lindane
0014 Meehoxychlor
P004 Eldrin
P017 Broooacecone
P023 Chloroacetaldehyde
P024 p-chloroadniline
P025 Indonechacin
P026 l-(o-chlorophenyl)thiourea
P027 3-chloroproprionitrile
P028 Benzyl chloride
P033 Cyanogen- chloride
P035 2,4-D
P036 Dichlorophenylarsine
P037 Dieldrin
U006 Acetyl chloride
U017 Benzal chloride
U020 Benzenesulfonyl chloride
U023 Benzotrichloride
U024 Bi*(2-chloroeChoxy) methane
U02S Bif(2-ehloroethyl) echer
0026 K,N-Bis(2-chloroethyl) naphthyl amine
U027 Bi*(2-chloroi*opropyl) eeher
U039 Bromooeehane
U030 4-Bromophenyl phenyl echer
U033 Carbony1 fluoride
U034 Trichloroacetaldehyde
0035 Chlorambucil
0036 Chlordane
U038 .Chlorobenzilace
U039 p-chloro ui eresol
U041 l-chloro-2,3-epoxy propane
U042 2-ehloroethyle vinyl echer
0043 Vinyl chloride
0044 Chloroform
U045 Chloromechane
U046 Chlorooechyl methyl echer
U047 2—chloronaphchalene
0048 2-chlorophenol
U049 4-chloro-o-toluidine HC1
U060 DDD
U061 DDT
0062 Diallace
U066 1,2-dibromo—3-ehloropropane
U067 1,2-dibroooechane
0068 DibromoneChane
0072 p-dichlorbbenxene
0015 Toxaphene
D016 2,4-0
D017 2,4,5-TP (silvex)
P043 Vinyl chloride
P050 Endosulfan
P051 Endrin
POS7 Fluoroacecanide
POS8 Fluoracetic acid (Na sale)
P059 Hepcachloc
P060 laodrin
P090 PenCachlorophenol
P09S Phoigene
P118 TrichlorooeChanechiol
P123 Toxaphene
U073 3,3~dichlorobenzidene
0081 2,4-dichlorophenol
U082 2,6-dichlorophenol
0097 Dimechylcarbomyl chloride
0127 Hexachlorobenzene
0128 Hexachlorobucadiene
0129 Lindane
0130 Hexachloropencadiene
0132 Hexachlorophene
0138 Methyl iodine
0142 Kepone •
0150 Melphalan
0156 Methyl chlorocarbonace
0158 4,4'-methylene Bis(2-chloroaniline)
0183 Pencachlorobenzene
0184 Pencachloroechane
0185 Pencadhlororonicrobenzene
0192 Pronaaide
0207 1,2,4,5-cecrachlorobenzene
0212 2,3,4,6-eecrachlorophenol
0224 Toxaphene
0230 2,4,5'Crichlorophenol
0231 2,4,6-trichlorophenol
0232 2,4,5-trichlorophenoxy acetic acid
0233 Silvex (2,4,5-TP)
0235 Tria(2,3-dibromopropyl) phosphate
0237 Oracil mustard
0240 2,4-D Sales & EsCers.
0242 Pencaehlorophenol
0243 Hexachloropropene
0246 Nyanogen bromide
0247 Mechoxychlor
2-3
-------
TABLE 2.3. CONSTITUENT CONCENTRATIONS IN K TYPE HALOGENATED PROCESS WASTES
N>
RCRA
hazardoua
waste
number neacriptinn
uaing creoaote and/or
pentachlorophennl
KIW) nialillalion bottom* from
the production of acetal-
debyde from ethvlene
KOin Dlatillation bottoms from
dehyde from ethylene
Halogenated organic compound
conat Ituenta
Fentachlorophenol
-Chlnrophenol
-chloro-m-creeol
rlchlorophenola
etrachlorophenola
enio( h) f luoranthen*
,4-Dichlorophennl
,4,6-Trichlorophenol
2 , 1, 7 , 8-Tetrachlorndihento-p-
dioxln (TCOO)
Pentachlorodihenzo-p-dioKina
HeNachlarodlhenzo-p-dioxinB
Tet rachlorod iheniof urana
Pent achlnrodlbeniof urana
He iiachlorodi hen tnf urana
lleptachlorodihencofiirana
Octachlorodihenzof urana
Heptachlnrddlhento-p-dinxina
Higher chlorophenola
Tetrachloroethvlene
Chloroform
Acetyl chloride
Chloral
Chloroacet aldehyde
Chloroform
Methvlene chloride
Methyl chloride
Acetyl chloride
Chloral
Chloroacet aldehyde
Chloroform
Methylene chloride
Methyl chloride
Conatituent concentrat iona given In the
aourcea of waate cltaracteriiat ion data
H-F-T
Model HITRF. MITRE
Report3 WP81U0046S* WP83000655
7M NA 1.0 i 10*
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
i.nnn
s.nnn
I.nnn
1,000 <\non
l.n in'
ft. 8 in*
11.9 « in* n.i in*
2.0 « in* <«.n in*
<4.n in*
<4.n in*
following
(aw/kg):
JRft
Aaaociatea6
(centinued)
-------
TABLE 2.3 (continued)
10
Ul
RCRA
hat ardoua
waste
numhe r
HOIS
Itnifi
HO 17
Halocenated organic conpound
Heacription - conatituenta
Diatillatinn bulimia fro* nentvl chlnride
the diilillalinn of heniyl Hnnochlorobentene
chloride Reniotr ichloride
Rental chloride
Trichlornbenkenn
Tet rachlnrohencene
Pentachlorohennene
Hexachlorobentene
Heavy enda or diatillation llexachlnroethane
reaiduea froei the production llexachlnrnhenxene
of carbon letrachloride Heaachlornbutadiene
Carbon tetrachlnride
Tel rachloroethylene
Tetrachloroelhan*
Trichlnroethylene
Chlorobenxenea
Chlornpropanea
Chloroforn
Pent achlnroe thane
lleavv chlorinated tara
nichlorohiphenvl
• dilnroprnpenea
Heavy endi (alill hottoaa) Cplchlornhvdr in
from the purification cnlum hiaCchlnrowthvl) ether
in the pr oil. ic lion of hieO-chlnroethvl) ether
eplchlornhvdrin Trichlornpropane
Oichlnropropanola
Chlorinated aliphatlca
2-chloroallyl alcohol
l-f.hloro-2tl-hydroxypropane
Propyl chlorfdea
laopropyl chloridea
1 ,2-nichloropropane
Dichloropropyl ethera
W-E-T
Model MITRE
Report1 W81MJ0465*
s.ion i.n x in*
r.*nn \.n in*
S.n in*
4. inn <5.n in*
<^.n in*
<<>.n in*
410 x
1.5 x in* >vo x in*
X 10 - 1 X
x 10* - 5 x
100 - 1
inn - i
< i (nnc
1 i in* - l x
410
1 x 10* - *» x
in*
in*
in*
in*
«
e
10*
• I03
M 10^
,
10
in*
Ml
*i x 10*
-------
TABLE 2.3 (continued)
RCftA
hazardous
waste
number Rescript ion
KOIB Heavy ends Frn» the frac-
tional ion column in ethyl
chloride production
KOI9 Heavy end* frrm the dia-
dichloride in ethvlene.
dichlnride production
Halopenated organic compound
const ituenta
Kthylene Dlchloridr ( 1 ,7-Dichloro-
ethane)
Trichlnroe.lhylene
Hexachlorohutadiene
llffnachlorohencentf
Heavy chlorinated organic*
Elhvl chloride
nichlornethylenes
Chlorinated butanes
Chloroforai
Ethylene dichloride
1 1— T ii-h-lfi rl an*
1 , ,2-Trichloroethane.
1 , .2,2-Tetrachlorne thane
1 * »' 1 2-Te tr ach loroe thane
HP achloroethane
Tr chloroethy lene
Te rachloroMhylen*
Pent achloroethane
Carhon tetrachlorfde
Chlorofor*
Vinyl chloride (chloroethy lent)
Vinyl idene chloride ( 1 , l-Dichloro-
eth'vlene)
-Ch!orn-?-brn«oe thane
-Chloro-4-elhylhenane
-Chloroethylbentene
.2,3-chloro-l.l-buradtene
, 1-Dichlorohent en«
,4-Dlchlorohencene
kichlorohcHadf ene
tl-0ichloropropane
,1-DJchlornpropane
-Hethyl-)-chloroheniene
Chlorobenzene
Cnnntituent concentrations Riven in Che following
W-E-T
Nnilc 1 HITRR HITKE JR5
Report1 UP8IU0046S4 WP83000655 A>>oci«t<>6
. I.I « 10s 1 > in* - ^ > 10*
1.2 i in' i.i » 10* i > in* - i > ios
2.15 « in*
?.n « in*
A.J » 10*
l.o « in'1 7.0 ii 10* •> * 10*
2.2 ii 10* 1 ii 10* - 1 x 10*
inn - 5 « 10*
100 - 5 * 10*
2.0* s 10* 1.0 10* >5.0 » 10*
2.4? x in* 1.9 10* 2.82 x in* too - ltonn
i.« in*
1.21 x in* ).« in* 1.25 x in* i x in* - i « in*
1.21 x in* 1.9 in* I.2S x in*
1 x 10* - 1 X 10*
ion - i.noo
1 x in4 - i x 10*
1.000 - 1 x 10*
1 x in* - i x 10*
1 I 10*- - 1 x 10*
I • in*
• i x 10*
2 x 10*
i.nno
7
R.s x in*
(continued)
-------
TABLE 2.3 (continued)
Constituent concentration! (riven In the following
RCRA
hazardous
waste
number Description
KOI9
(cnnt.)
K020 Heavy end* from the rtist il-
lation of vinyl chloride In
vinyl chloride monomer
production
Halogenated organic compound
conat ftuenta
1 , 1 ,2-Trichloropropane
Heavy chlorinated tars
1 ,4-Dichloro-2-hutene
Ethyl idene chloride ( 1 ,1-DJcliloro-
ethane)
Cj chlorinated nrpanica
Ftnylene dfchlorlde
1,1, l-Trlchloroethane
1,1, ?-Tr ichlnroethanff
1 • 1 ,2.?-Tetrachloroethane
1,1,1 ,?-Tetrachloroe thane
Trichloroethvlene
Tetrachloroethylene
Carbon tetrachlnride
Chloroforai
Vinyl chloride
Vinvlidene chloride
l-Chlorohutane
1.7-Dichlorohutane
Dlchtorobiitcnea
Chlornhenzene
1 ,2-OfchloroheKane
2-Chlnroethannl
1 ,4-Plchlorohutan* ,
Pent achlorne thane
He xachloroe thane
1.2.3-Trlchlorohtitana A
1 ,2,1-Trichloropropane
Bia(2-chlnroethyl) ether
1,2,4-Trichlorobutann
Freons (soluble and insoluble
•aterlal
Toxaphene
Trichlorophenol
1 , l-Dlchloroe thane
Chlorobutadienei
H-K-T
Model HITRE NITRE
Report1 HP8IUUOi.65* W83000655
\1">
J.I8 » 10'
2.4J > in' J.2i M 10*
11.000 * 3.5 » in'
2.7} « in' 2.R » 10'
s.o > in*
2.11 x in' i.o > 10'
2.000
9.000 2,800
1.0 > in* 2,800
I > in* 2.800
2.000 I « 10*
1 • 10*
1 • 10* S AOO
1,000
s.noo
l.a • in*
i.n i in*
6,000
j.noo
1,000
s.ooo
4.000
9.000 1.74 x 10*
8.000
2.0 > 10* 4.71 x 10*
2.0 x 10*
1.0 > 10*
2.01 x 10'
4.71 x 10*
JRB
Auocietee0
1 x 10* - 1
1 x 10* - 1
1 x 10' - i
1 x 10* - •>
1.000 -
1 ,000 -
100 -
1 x 10* - 5
1 x 10' - i
100 -
1 x 10' - 1
-------
TABLE 2.3 (continued)
pi~n*i
hazardous
waste
j niiathe r De sc r i pt i on
K02I Aqueous spent ant lawny
catalyst waste froM fluoro*
•ethanes production
K02A Spent catalyst from th«
the production of 1,1,1-
trlchloroethane
at ram stripper jn the
production of 1,1,1-
trichloroethane
K> •
A
i
ends fro* the combined
ethylene and tetrachloro-
ethylene
fro* the production of
chlordane
l
Naloaenated organic compound
conat ituenta
Carbon tetrachlorfde
Chloroforai
1 tl , l-Trichlornethane
Vjnvl chloride
Acetyl chloride
1 , 1 ,2,2-Telrechloroethane
Pent achlorne thane
Oichloroethanea
Cthvlene dichloride
I.l.l-Trichloroethane
Vinyl chloride
Vin«lfdene chloride
Chlornfnra
lleaachloronenxene
lleaachlnrobutadiene
1,1. 1 ,2-Tet rachloroethane
\ , 1 , 2, J-Tet rachloroethane
Ethylene dichloride
Tetrachloroethylene
Trichloroethylenc
Pent ach 1 oroethane
1 , l-nlchloroethane
Chlorobencenea
Chloroethanea
Cblorobutadienea.
1 , 1 ,2-Trichloroetbane
Tara .
Heaachlorocyclopentadiene
Chlorinated cyclic cnnpounda
(continued)
Conatltuent concentrat fona given in the following
aourcea of waate characteriaat ion data (na./k|t):
W-E-T
Model HITRK HITKE JOB
Report1 M>aiWOO«6i* WP83000655 Aaaociat«a(
I.OOO
1.97 a 10* 1.0 a 10* 100 - 1 a 10*
1.0 • IO*
2.71 a 10*
1.16 a 10* .
1.4 a 10*
1 a 10* - < a 10*
A.l a 10* .1 a 10*
1.7 a 10* .7 a 10*
.0 a 10*
.0 a 10*
.0 a 10*
2n M in^ ? n M in^
*li It III Z.'l • IU
1.18 a 10* 1.1(1 a 10*
4 0 • 10
6.1 a 10* 6!) a 10*
2.1 a 10* 2.1 a IO*
6,000
A. 5 a 10*
4.S a 10*
1.1 a 10*
NA
NA °
NA
NA
NA
NA
NA
-------
TABLE 2.3 (continued)
RCRA
hazardous
watte
nunher
icnti
KOU
Deccript ton
cvc Inpentadiene In lh*
production of chlorttanr
Filter aolldt fro. (he fil-
er*! ton of henachlorn-
cyc lopentadiene in the
production of chlordane
. Halogenated organic cmvpound
conat ituenta
Chi"*! °r°*iyC °J*n * rne
llexachlnroheniene
Pentachlornbenten*
Hexach 1 oroc vc 1 opent ad 1 ene
llexachlnrnhenxene
PtintAchlorobenzen*
Dictilornhenseneai N.O. S.
Constituent concentrations given in the following
. M-F.-T
Model MITRE HITRft JRB
Riport1 M>BIMO«6S4 WP83000655 Ai.oci.te.6
NA 7.14 H 10^
NA '
J.i7 > Ift5
».l* « 10*
J.O > 10^
i.o * in*
1.0 x 10^
10
WU trtttmfat iluil(« from
Che-product ion of Inxaphene
Tonaphene
1.0 i in4
1.0 > in'1
K042
KIU1
K071
Heavy «n«1i or ditt 1 1 lat ion
reiiduei Irim the Hiitll-
latioo nf tetrachloro-
beoiene in the production
of J.4.S-T
2(6-nichlorophenol wante
frn«i the prnduction of
2,4-0
Chlorinated hydrocarhon
waate fro« the purification
*tep of the diaphrapai cell
procen in ing graphite
anodea in chlorine
production
lleiachlorohenzeoe
o-nichlorohenzene
Chlorohencene
2,4-nichlorophenol
2,6-Olchlorophenol
?,4 .6-Trichlorophenol
rhlorophenol polynera
rhloroforw
Carbon tetrachloride
Hmachlnroe thane
Trichloroethane
Tet rach 1 oroe t hy 1 ene
Dichloroethylene
1 1 1 ,2.2-Tet racliloroetliane
Pent achl oroe thane
NA
NA
NA
NA
NA
NA
NA
7.4 > 10* 7.4 > 10*
I.I a 10* I.I > 10s
n.n « 10*
1.0 « 10*
6,000
1.0OO
t.ooo
1.1 « 10*
7.4 * 10*
I.I a 10*
ft.n . 10*
1.0 « 10*
1.) a 10*
(continued)
-------
TABLE 2.3 (continued)
N>
*-•
O
RCRA
haiardmm
waste
number De ac r i pt i on
mat
KC9S
K096
K097
KQ98
Distillation or fraction-
al ion column hottona f ron
the production of pono-
chlorobenxenp
Distillation hottona frrtm
the production of 1,1,1-
trichloroethane
Heavy ends fro* the heavy
ends column froai the produc-
tion of 1 , 1 , l-trichloro-
ethanp
fr°
1 > 10* - 5 x 10*
1 x 10* - 1 i 10*
100 - 1 x 10*
1 ,000 - i x 10*
1,000 - 1 x 10*
ion - 1,000
(centInued)
-------
TABLE 2.3 (continued)
Conatltunnt concentration* given In
RCRA
hazardous
waste
number He ac ripe inn
llalogenated organic cn*pound
const ituenla
W-E-T
Nmle 1
Report3
NITRE
NP81VM046S'1
MITRE
W83000655
the following
lata dig/kg):
JRB
Associates'
Kins
Untreated wastewater frosi
the production of 2,4-0
Separated aqueous atrean
fron the reactor product
washing strp in the produc-
tion of chlorohensenes
7,4 -0 i ch I orophenn I
2,4,6-Trichloroplienol
Dichlorophenols
TCOD
TCDD isnaiers
TCDF laoswra
Chlorophenols
Chlorohencene
I,7-Dichlnroheniene
?,4,6-Trichlnrophenol
1,4-nichloroheniene
100 - 1.0 x 10*
-------
were based on survey studies of limited scope and reliability. EPA is in the
process of updating the data base to provide more reliable information related
to the characteristics of the specific waste streams and the quantities
generated.
\
CLASSIFICATION OF HAZARDOUS ORGANIC WASTES
Several approaches have been proposed for classifying wastes in a manner
that would provide meaningful insight into the applicability of treatment
technologies. ' ' Although many of these approaches were devised for
solvents, including halogenated solvents, they are for the most part, equally
applicable to other halogenated organics.
In an attempt to provide a meaningful classification system, the
halogenated organic compounds were grouped in,Reference 2 by their chemical
structure and functionality. However, the Reference 2 study members and
others involved in selection of treatment technologies have concluded that
other factors are generally more important in assessing treatability. The
halogen content and the physical nature of the waste matrix were identified as
key .factors. Table 2.4 lists the halogenated organic compounds of concern by
their physical state (gaseous, liquid, or solid) at 25°C in order of their
halogen content. Other factors which are useful in assessing the
applicability of recovery/treatment technologies for these halogens
(e.g. vapor pressure, functionality, solubility, octanol water partition
coefficients, and heat of combustion) are provided in Appendix A.
HALOGENATED ORGANIC WASTE GENERATION AND MANAGEMENT
As shown in Table 2.5, estimates of the quantities of wastes generated
obtained from the above sources of information (i.e., those used to
characterize waste stream composition) and EPA's National Survey Data Base
2
differ widely. The data shown is for the specific waste stream codes (K
type) and for the six pesticide codes (D012 through D017). Little or no
information is available concerning the U and P waste codes for specific
halogenated organic constituents.
2-12
-------
TABLE 2.4. WASTE CATEGORIZATION BASED ON PHYSICAL STATE
RCRA
waste
code
Compound name
Molecular
formula
Molecular
weight
Halogen
content
(Z by weight)
Caseous Compounds (Q25°C)
U043
U033
P033
0045
P095
0029
Liquid
P043
U062
U020
U038
U048
P02&
0030
P036
TO97
U042
TO41
0156
P027
U024
D027
0046
U017
P023
0006
0025
Vinyl chloride
Carbonyl fluoride
Cyanogen chloride
Methyl chloride
Car bony 1 chloride
Methyl bromide
Compounds (@2S*C)
Diiaopropyl fluorophoaphate
Dial late
Benzene sulfonyl chloride
Echyl-4,4'-dichlorobenzilate
2-Chloropheno 1
Benzyl chloride.
1-Bromo— 4— phenoxy benzene
Dichlorophenyl arsive
Dimethyl carbamoyl chloride
2-Chloroethylvinyl ether
Epichlorohydrin
Methyl chlorocarbonate
3-Chloropropionitrile
Bis(2-chloroethoxy) methane
Bis(2-chloroisopropyl) ether
Chloromethoxymethan*
Benzal chloride
Chloroacetaldehyde
Acetyl chloride
Bia(2-chloroethyl) ether
C2H3C1
cr2o
CC1B
CH3C1
CC120
CH3B&
C6H14F03P
C10Hi7Cl2HOS
C6H5C102S
C16Hl4Cl203
C6H5C10
C7H7C1
C12H9B20
C6H5AaCl2
C3H6C1NO
C4H7C10
C3H3C10
C2H3C102
C3H4C1U ' .
C5H10C1202
C6*i2Cljp
C2H5C10
C7H6C12
C2H3C10
C2H3C1
C4H8Cl20
62.5
66
61.5
50.5
98.9
9.5
184
270.2
176.6
325.2
128.6
126.6
249
222.9
107.6
106.6
92.5
94.5
89.5
173.1
171.1
80.5
161
78.5
98.9
143
57 Cl
58 F
58 Cl
70 Cl
72 Cl
84 Br
10 F
13 Cl
20 Cl
22 Cl
28 Cl
28 Cl
32 Br
32 Cl
33 Cl
33 Cl
38 Cl
38 Cl
40 Cl
41 Cl
42 Cl
44 Cl
44 Cl
45 Cl
45 Cl
50 Cl
(continued)
2-13
-------
TABLE 2.4 (continued)
-- —
RCBA
waste
code
U023
P017
0235
0034
0130
0128
0066
0067
0184
0138
0068
Solid
P025
P038 ,
P026
0047
0150
0035
0039
P037
0026
.0158
P024
0192
0237
0073
D014,
0247
— _ -
Compound name
Benzotrichloride
Bromoacetone
Tris(2,3=dibromopropyl) phosphate
Trichloroaceta Idehyde
Hexachlorocyc lopendadiene
Hexachlorobutadiene
1 ,2-Dibromo-3-chloropropane
Ethylene dibrooide
Pentachloroethane
Methyl iodide
Methylene bromide
Compounds (325*C)
Indomethacin
Fluoraeetic acid (Na salt)
o-(l-chlorophenyl) thiourea
2-Chloronaphthalene
Melphalan
Chloraobucil
p-chlore- n-eresol
Fluoroacetamide
Chloraaphazine .
4,4'-Methylene-bis-2-chloroaniline
p-chloroaniline
Pronamide
Oracil mustard
3,3 '-dichlorobenzidine
Methoxychlor
Molecular
formula
C7H5C13
C3H5Be
C9H15Br6P04
C2HC130
C5C16
C4C16
C3H5Br2Cl
C2H4Br2
C2HC15
CH3I
CH,Br2
C2H2FN.02
C7H7C1S2
C10H7C1
C13H18C12H202
c14H19ci2uo2
C7H7C10
C2H4FMO
Ct4H15Cl2H
CpH12Cl2N
C6H6C1H
C12HUC12HO
C8HUC12N302
C12H10C12N2
C16H15C1302
Molecular
weight
195.5
137
697.7
147.4
272.8
260.8
236.4
187.9
202.3
142
' 173.9
137
187
162.6
305
304.2
142.6
77
268.2
267.2
127.6
256.1
252.1
253.1
345.7
Halogen
content
(Z by weight)
54 Cl
58 Br
69 Br
72 Cl
78 Cl
82 Cl
68 Br/15 Cl
85 Cl
88 Cl
89 I
92 Br
10 Cl
19 F
19 Cl
22 Cl
23 Cl
23 Cl
25 Cl
25 F
26 Cl
27 Cl.
28 Cl
28 Cl
28 Cl
28 Cl
31 Cl
(continued)
2-14
-------
TABLE 2.4 (continued)
RCRA
waste
code
D016,
P035
D017,
U233
0232
0060
0082
0081
0061
0132
P050
0231
0230
P037
D012,
P051
P060
P004
0185
0212
0207
P059
P090,
0242
0036
D015,
P123,
0224
0183
0142
D013,
0129
Compound name
2,4-D
2,4.5-TP
2.4,5-T
DDD
2 , 6-Dichloropheno 1
2 ,4-Di.chlorophenol
DDT
Hexachlorophene
Endosulfan
2,4, 6-Trichloropheno 1
2,4, 5-Trichloropheno 1
Dieldrin
Endrin
Isodrin
Aldrin
Pentachloronitrobenzene
2,3,4, 5-Tecrachloraphenol
1,2, 4 ,5-Tetrachlorobenzene
Heptachlor
Pentachlorophanol
Chlordane
Toxaphene
Pencachlorobenzene
Kepone
Lindane
Molecular
formula
C8«6C12°3
C9H7C1303
C8H6C1303
Cl4HlO«4
C6H4Cl20
C6H4C120
C14H9Cl5
C13B6C1602
C9H6C1603S
C6H3C130
C6H3C130
C12H8C160
C12H8C160
C12H8C16
c12a8«6
C6C15K02
C6H2C140
C6H2C14
C10H5C17
C6HC150
C10"6«8
C10H10C18
C6HC15
C10C1100
C6H6C16
'Molecular
weight
221
269.5
255.5
320.1
163
163
354.5
406.9
406.9
197.5
197.5
380.9
380.9
365
365
. 295.4
231.9
215.9
373.4
266.4
409.8
413.8
250.3
490.7
290.9
Halogen
content
(Z by weight)
32 Cl
40 Cl
42 Cl
44 Cl
44 Cl
44 Cl
50 Cl
52 Cl
52 Cl
54 Cl
54 Cl
56 Cl
56 Cl
58 Cl
58 Cl
60 Cl
61 Cl
66 Cl
67 Cl
67 Cl
69 Cl
69 Cl
71 Cl
72 Cl
73 Cl
0127 Hexachlorobenzene
284.8
75 Cl
2-15
-------
TABLE 2.5. WA.STE QUANTITY DATA FOR HALOGENATED PROCESS WASTES
(Waste Quantity from
National
Survey data
base8 W-E-T Model/ICF3
K001 10,980 35,700
K009 \ 399,500
K010
K015
K016
K017
K018
K019
K020
K021
K028
K029
K030
K032
K033
K034
K035
K041
K042
K043
K073
K085
K095
K096
K097
K098
K099
26,300
8,380
1,600
6,360
35,400
80,300
52,700
270
610
1,300
48,400
43,000
-
•" -
-
5,000
— •
-
340
4,500
35,500
3,200
—
-
-
K105 520
0012
D013
D014
D015
D016
D017
_
-
14,435
-
-
•
the Following Sources
MITRE4
86,709
565,000
25,000
50
3,200
8,599
35,000
8,192
125,795
-
580
1,240
61,299
- •
-
-
27,000 - 52,000
17,000
—
—
125,000
6,615'
-
5,090
-
.
—
-
_
-
_
-
—
—
(MT/YR)
MITRE5
56
45
9
-
3,628
-
2,834
15,900
2,504
-
-
-
-
-
14
3
.-
.
- .
-
1,361
57
-
-
-
-
-
-
_
2,268
-
-
-
~
JRB6
-
-
-
23,817
7,403,100
6,858
22,499
27,515
—
1,201
-
-
-
-
-
-
-
-
-
-
435
-
-
-
13,377
-
-
_
-
-
-
-
—
Source: Adapted from Reference 2.
2-16
-------
The National Survey data are roughly comparable to more recent data
rec
10
9
developed by Westat for the Office of Solid Waste and reported in a recent
review of treatment technologies for nonsolvent halogenated organics.
Westat estimated that the mflTn^nii quantity of various subgroups of halogenated
organic wastes generated is as follows:
Estimated maximum
Halogenated quantity generated^
Organic subgroup (10^ gal/yr)
Pesticides (D wastes) 7.6
Specific processes (K wastes) 12.5
Single constituents (U and P wastes) 4.1
Total: . 24.2
National survey estimates of treatment process utilization for nonsolvent
halogenated organic wastes is 31.2 million gallons of halogenated organic
wastes per year. The estimate compares well with the above estimate of 24.2
million gallons generated per year, recognizing that some double counting
exist for wastes that are handled in multiple processes. An estimated
3.1 million gallons (roughly 10 percent) of the 31.2 million gallons treated
q
are land disposed. A summary of existing waste treatment technologies that
could be applied to the treatment of these land disposed wastes is provided in
Table 2.6. As indicated, the applicability of treatment technologies was
determined largely by the physical form of the wastes. Other factors related
to constituents properties and cost will play roles in selecting the best
treatment for a specific waste.
Despite uncertainties in the data base, it is important to note that the
quantities of halogenated organic wastes generated and managed are not large.
Halogenated solvent waste generation was estimated at about 2,600 million
ret
9
gallons/year, roughly 100 times greater than the 31 million gallons/year
estimate for nonsolvent balogenated organic wastes provided by Westat.'
2-17
-------
TABLE 2.6. SUMMARY OF EXISTING WASTE TREATMENT TECHNOLOGIES
Waste category
Land disposed
waste volume
(gal/yr)
Existing treatment technology
Comment
*-*
00
High chlorine'content
KXXX wastes
Halogenated aqueous
KXXX wastes
Halogenated aqueous sludge
KXXX wastes
Halogenated high inorganic'
KXXX liquid wastes
Halogenated potential
gases
1,673,977 (liquid) Liquid injection incineration/waste
blending/caustic scrubbing
612,291 (solid) Rotary kiln incineration
0
23,970
128
Filtration/steam stripping/carbon
adsorption
Waste blending/liquid injection
incineration
Rotary kiln incineration
Rotary kiln incineration with high
efficiency scrubber
Solidification/land disposal
Liqoid injection incineration/
caustic scrubbing
~4,000 Btu/lb
~4,000 Btu/lb
~4,000 Btu/lb
~ 4,000 Btu/lb
~1,000 Btu/lb
Unknown Btu
content
Halogenated potential
solids
Other halogenated organics
with inorganic solids
Total
68,216
759,274
3,137,860
Rotary kiln incineration with
caustic scrubbing
Rotary kiln incineration with
caustic scrubbing
Assumed
Btu/lb
Assumed
Btu/lb
~4,000
~1,000
Source: Reference 1.
-------
REFERENCES
1. Breton, Marc, et al. Technical Resource Document; Treatment Technologies
for Solvent-Containing Wastes. Prepared for U.S. EPA, HWEBL, Cincinnati,
Ohio under Contract No. 68-03-3243, Work Assignment No. 2. August 1986.
2. Arienti, Mark, et al. Technical Assessment of Treatment Alternatives for
Wastes Containing Halogenated Organics. Prepared for U.S. EPA, OSW,
Washington, D.C. under Contract No. 68-01-6871, Work Assignment No. 9.
October 1984.
3. ICF, Incorporated. The RCRA Risk-cost Analysis Model Phase III Report.
Submitted to the U.S. EPA, Office of Solid Waste, Economic Analysis
Branch. March 1, 1984.
4. MITRE Corporation. Composition of Selected Hazardous Waste Streams.
Working Paper WP-81W00465. November 1981.
5. MITRE Corporation. Composition of Hazardous Waste Streams Currently
Incinerated. Working Paper WP-8300065. April 1981.
6. Letter Report from J. Harris, JRB Associates, to M. Scott, ENVIRON.
May 21, 1984.
7. Roeck, D., et al. Assessment of Wastes Containing Halogenated Organic
Compounds and Current Disposal Practices. Report prepared for U.S. EPA,
OSW, Washington, D.C. under Contract No. 68-01-6871, Work Assignment
No. 2. October 1984.
8. Westat. National Survey of hazardous Waste Generators and Treatment,
Storage and Disposal Facilities Regulated Under RCRA in 1981. Office of
Solid Waste, U.S. EPA. 1983.
9. Dietz, S., et al. National Survey of Hazardous Waste Generators and
Treatment, Storage and Disposal Facilities Regulated under RCRA in 1981.
Prepared by Westat, Inc..for U.S. EPA, Office of Solid Waste. April 1984.
10. Turner, R. J. Treatment Technologies for Hazardous Wastes, Part V:
Nonsolvent Halogenated Organics JAPCA. June 1986.
11. Allen, C. C., and B. L. Blaney. Techniques for Treating Hazardous Waste
to Remove Volatile Organic Constituents. JAPCA, Vol. 35, No. 8.
August 1985.
2-19
-------
12. Blaney, B. L. Alternative Techniques for Managing Solvent Wastes.
Journal of the Air Pollution Control Association, 36(3): 275-285.
March 1986.
13. Engineering-Science. Supplemental Report on the Technical Assessment of
Treatment Alternatives for Waste Solvents. Washington, D.C.: U.S.
Environmental Protection Agency. 1985.
2-20
-------
SECTION 3
PRETREATMENT
Most of Che halogenated organic waste streams require some sort of
pretreatment before they are introduced to ,the final treatment process.
Pretreatment is needed to modify restrictive waste stream characteristics that
affect process performance. Generally some sort of phase separation will be
required to remove either solid materials that can adversely affect process
efficiency or operation (e.g., through plugging of fuel atomization nozzles or
packed bed adsorption towers) or an aqueous phase that can drastically lower
waste stream Btu values.
Frequently, phase separation permits a significant volume reduction,
particularly if the hazardous component is present to a. significant extent"in
only one of the phases. Furthermore, by concentrating the hazardous portion
of the stream, sequential processing steps may be accomplished more readily.
Phaserseparation processes usually are mechanical, inexpensive and simple, and
can be applied to a broad spectrum of wastes and waste components.
Emulsions are generally very difficult to separate. Heating, cooling,
change of pH, salting out, centrifugation, API separators, and other
techniques may all be tried, but there is no accurate way to predict
separation. Appropriate methods can only be developed empirically for any
given waste stream.
Conceptually, the simplest separation process is sedimentation, or
gravity settling. The output streams will consist of a sludge and a
decantable supernatant liquid possibly containing both organic and aqueous
fractions. A closely related process and the phase separation technique in
most common use is filtration. Cent rifugation is essentially a high gravity
sedimentation process whereby centrifugal forces are used to increase the rate
of particle settling.
3-1
-------
The basic concept in all the above processes for settleable slurries is
to get the solid phases or water to separate from the organic phase, through
the use of gravitational, centrifugal or hydrostatic forces. Such forces
generally do not act on colloidal suspended particles.
The simplest and most commonly used colloidal separation process is
flocculation. Ultrafiltration, another possible separation technology, has
many industrial applications, but has yet to demonstrate its full potential.
The major phase separation desired in the handling of sludges is
dewatering. Vacuum or press filtration are the processes in most common use.
Some research has been done on simple freezing, but the process is not well
developed and the work that has been done is not promising.
Sludges and slurries (colloidal or separable) in which the liquid phase
is volatile may be treated by either evaporation or distillation. Solar
evaporation is very commonly used, however, the impact of the emission of
volatile organics to the atmosphere should be considered. Engineered
evaporation or distillation systems would normally be operated if recovery of
the liquid is desired.
In the case of halogenated organic waste treated by incineration or other
thermal destruction technologies, blending the waste stream with other organic
compounds may be required to adjust heat content or reduce halogen content to
meet a prescribed specification. Blending and/or heating may also be required
to adjust viscosity to ensure proper atomization of a water treated by liquid
injection incineration.
- In addition to phase separation and/or modification of the waste
properties through mixing or heating, some sort of treatment may be required
to separate components. Component separation can be achieved physically by,
3-2
-------
for example, distillation of volatiles or use of solvent extraction processes,
or chemically by neutralization or precipitation. Pretreatraent options are
•
numerous and must be tailored to the waste stream and the process used for
final treatment.
Extensive descriptions of pretreatment technologies (e.g., demulsifica-
tion, filtration, centrifugation, sedimentation, flotation, evaporation, size
reduction, neutralization and precipitation) 'can be found in the technical
literature, including references cited in the following discussions of
recovery/treatment processes. These discussions of alternative technologies
have been structured to. include considerations of pretreatment requirements.
Although pretreatment processes are generally simple, low cost operations,
their impact must be considered in any assessment and ultimate selection of
alternative technologies.
3-3
-------
REFERENCES
1. Berkowitz, J. B., et al. Unit Operations for Treatment of Hazardous
Industrial Wastes. Noyes Data Corporation; Park Ridge, New Jersey. 1978.
3-4
-------
SECTION 4
WASTE MINIMIZATION PROCESSES AND PRACTICES
Waste minimization consists of two distinct aspects of hazardous waste
management: source reduction and recycling/reuse. Source reduction refers to
preventive measures taken to reduce the volume or toxicity of hazardous wastes
generated at a facility; recycling/reuse refers to procedures and processes
aimed at the recovery of generated wastes or their reuse, e.g., as a fuel.
Very little is known about the extent of waste minimization practices
undertaken by generators or reprocessors of halogenated organic waste
streams. However, despite the fact that data sources generally fail to draw a
distinction between halogenated solvents and halogenated organic compounds, it
is unlikely that halogenated organic wastes a*re reprocessed off site to the
extent that are halogenated solvent wastes. This can be attributed to two
reasons. First, many of the halogenated organics are higher molecular weight
materials that are not as amenable to recovery by distillation or stripping
practices as are the lower molecular weight halogenated solvents. Second, far
less halogenated organic wastes are generated than are halogenated solvents,
and as in the case of pesticides, generation often occurs in a dispersive
pattern. Thus, waste collection and establishment of processing routines is
more difficult. Onsite waste recovery activities are also probably less
frequent for the halogenated organic industry than for the solvent sector. As
noted, recovery is generally more difficult. Incineration of distillation
bottoms containing many of the high molecular weight halogenated- organics
would appear to be the primary method of disposal, especially if the bottoms
are not suitable for process recovery.
4-1
-------
4.1 SOURCE REDUCTION
Source reduction is defined as any onsite activity which reduces the
volume and/or hazard of waste generated at a facility.- Source reduction
represents a preventive approach to hazardous waste management, since the
reduction of hazardous waste volume reduces problems associated with waste
handling, treatment, disposal, and liability. Source reduction practices may
impact all aspects of industrial processes generating hazardous wastes,
including raw materials, equipment, and products. A primary motivation for
plants to implement certain source reduction practices is the potential
economic benefit they may accrue. These economic benefits increase as
restrictions on waste management practices become more stringent.
Waste source reduction practices vary widely from plant to plant,
reflecting the variability of industrial processes and waste characteristics.
In general, source reduction practices may be classified as follows:
• Raw material substitution;
• Product reformulation; • • .
• Process redesign/modification; and
• Waste segregation.
The extent to which these activities are practiced is unknown, although
certain mandatory actions resulting from regulatory restrictions or outright
bans on the use of certain pesticides and other halogenated compound
intermediates have occured within the halogenated organic chemical process
industries. Examples of waste minimization practices also include equipment
modernization, e.g., use of new distillation equipment to maximize overhead
and bottom product separation. Another approach to source reduction based on
waste segregation has been reported by the North Carolina Department of.
Natural Resources and Community Development. A North Carolina firm
formulating pesticide mixtures was able to reduce their hazardous waste
generations by over 45,000 pounds per year by installing bag houses on each
product line and returning collected dust to the product line as raw material
feed. The company realized a 10 month payback period on an initial investment
of £96,000 for each baghouse.
4-2
-------
Review of documented case studies on source reduction indicates that
these practices have been applied in more instances to solvent wastes than any
*
other waste type. Additionally, it appears that source reduction practices
are used more frequently for chlorinated solvents, especially 1,1,1-trich-
loroethane and methylene chloride, although similar practices may be
applicable to other halogenated organics. With respect to cost savings, the
data appear to indicate that source reduction of large generating sources may
yield annual savings of tens of thousands of dollars. Savings in the hundreds
of thousands of dollar may even be possible if source reduction practices
eliminate the need for unit operations such as air pollution controls.
Regulatory trends appear to be moving toward the promotion of source
reduction at sites generating hazardous wastes. The EPA has recently proposed
requirements that generators certify institution of hazardous waste reduction
programs (51 FR 10177, March 24, 1986). This would involve the institution at
generator sites of programs to reduce the volume or toxicity of hazardous
wastes to a degree determined by the generator to be economically
practicable. Generators must also certify that their current method of
management is the most practicable method available to minimize present and
future threats to human health and the environment.
Three states currently have established source reduction/pollution
prevention programs: North Carolina, Minnesota, and Massachusetts. In
addition, Tennessee has established a "pilot program", and Kentucky,
California, Maryland, and Washington have programs currently in development.
These programs vary from State to State but, in general, include information
exchange, technical assistance, and economic incentives to companies to
encourage development of their program.
2—13
The reader is referred to other EPA and state publications and the
solvent TRD (Section 5) which address approaches to source reduction.
Although most of the literature is focused on solvent reduction, the same
general technological principles will apply.
4.2 RECYCLING/REUSE
According to EPA guidance issued on January 4, 1985, "recycling" was
defined as practices in which wastes are: 1) reclaimed, or 2) reused. A
reclaimed waste is one which is processed or treated through some means to
4-3
-------
purify it for subsequent reuse, or to recover specific constituents for
reuse. Reused wastes are those which serve directly as feedstocks, without
any treatment. Recycling of wastes may be done by either the original
generator or other firms.
The recovery of halogenated organic constituents from their waste
materials can be accomplished in several ways. The preferred recovery method
is determined by both constituent and waste matrix characteristics. Volatile
materials can be recovered by evaporation/fractionation processes. Solids can
be recovered as residues from evaporative processes. Organics can be
selectively extracted from liquids (generally aqueous) or solids by an organic
solvent. Very little is known about the extent of recovery practices as
applied to halogenated organic waste streams. However, an examination of
available data for the specific K type waste streams shown previously in
Table 2.3 indicate that constituent concentrations are high enough to warrant
application of recovery processes. Many of the components are low molecular
weight halogenated organic solvents which can be volatilized leaving the
higher molecular weight components as principal constituents of the
distillation bottoms. Conceivably, some of these bottom constituents are.
suitable for recycle. • In other cases, further evaporation or destruction by
incineration may be preferred.
The use of recovery processes is generally highly dependent on the value
of the products which can be recovered or produced. For example, the
viability of the chlorinolysis process is highly dependent on the demand for
its product, carbon tetrachloride. If the demand for this material is low,
then the price will probably be low and the process will not be economically
viable.
In addition, recovery processes are dependent on the feasibility of
disposing of the waste material. In the past, when land disposal of wastes
was relatively inexpensive, recovery processes were rarely considered.
However, with increasing land disposal costs and a potential ban on land
disposal of some wastes, recovery processes become economically feasible
and/or necessary.
Distillation, extraction, and steam stripping are possible unit recovery
processes. Conceptual systems designs which utilize these unit processes are
described below and summarized in Table 4.1 for some K type halogenated
organic wastes.
4-4
-------
TABLE 4.1. RECOVERY PROCESSES SUMMARY
Uaate code
K030
K0| 7
KOI9
aate atreaai n
Hritachlorobutadiene 771
Chlorohenzenea 71
Chloroethanea 3t
Chlorobut ad J ene It
Tara and otncra IOZ
17.000 KKR/yr
Oichlornhydrin 440 KK(/yr
Chloroethers 560 KKR/yr
Trichloropropane 2800 KKR/vr
Tara, Rosins,
and Others 170 KKR/yr
1.2-dlchloroethsne 211
1,1,2-trlchlnroelhane IBS
1,1 1 ,2-tet rachloroethane 18T
Tara IX
1.400 KKR/yr
c ry pr p
CD Steasi stripper rhlorohensenes 1
Chloroetlianes *
(2) ftteen stripper Chlorohutadienea 1 .
Infill KKa/ur
1 lOil KK|l/Vr
' reeve \tA to process
Hexachlorobutadiene
4740 KKR/yr
flO KKR/«r
(2) Evaporation
nichlornhyilrin
(1) Distillation 440 KKa/yr
" — , — '
To process
Trichlnrnpropane
2470 KKR/yr
• To process
CD Distlllstion Ethvlene dichlnride
2A4 KKR/yr
To process
1 , l-dlchlornethylene
110 KKR/yr
Storage
1,1,2-trichloroethylene
111 KKR/yr
StoraRe
Tara Capital coat: $7)1,900
1200 KKft/vr
O|h«>ra Net annual
coat: -$4.136,600
Clilnrorthers 560 KKR/yr
Others 170 KKR/yr Het annual
coat: .2,000
Cheaiical land diapnaal
Ralcliw hydroiide 122 KKR/yr Capital cost: $221.400
Tara 14 KKR/yr
Water 1422 KKg/yr Net annual
Calciim chloride 118 KKR/yr coat: -tl.200
Other 249 KKR/yr
(continued)
-------
TABLE 4.1 (continued)
Waate code Waste atreaat in Recovery prnceaa
K02I Antimony penta- (I) Dechlnrinat Ion
chloride (Shf.l,) IS.O KKR/yr utilising 7.4 KKg/vr
CCI* 4.4 KKsVyr of elhylene
Organic! 0.8 KKR/vr trichloride
(2) Filtration
()) Chlorlnation
utilising 1.) XKR/yr
of ant (atony
trichloride and •
4.7 KKR/vr of
chlorine
! Distillation
Recovered producta Waate sires* out
Antiainnv pent "chloride Tara 1.1 KKg/yr
18. 0 KKi/yr
Chr.ical landfill
Cni4 4.4 KKK/vr
To proceaa
Kthylene pentachloride
12.1 KX(/vr
Storaite
*Preons - To proceaa Tara O.OR KKR/vr
CCl± 4.4 KKit/yr To chiMalcal landfill
• To process i
ShCI^ 18.0 KKR/yr
To process
Cost (1977 cost)
Capital coat: $168,000
Net annual
coat: I 100. 000
Capital coat: t8 1,700
Net annual
coat: )R.4iO
' Source: Reference IS.
-------
Alternative Treatment Process For K030 Waste—Heavy Ends from the Production
of Perchloroethylene
This recovery scheme involves steam stripping of the waste stream to
separate out the light ends which consist of chlorobenzenes, chloroethanes,
and chlorobutadienes. These light ends are then recycled as feed stock
components to the perchloroethylene chlorinator.
The bottoms from this stream stripping operation consist mainly of
hexachlorobutadiene along with tars and other heavy materials. This stream
would subsequently be fractionated in a second stripping column to produce a
pure hexachlorobutadiene stream overhead while the bottoms consist of tarry
materials. The recovered hexachlorobutadiene could be sold for use as a
liquid phase chlorination medium, and the tarry material would have to be
incinerated.
Assuming a throughput of 12,000 KKg of heavy ends per year, 9,240 KKg of
hexachlorobutadiene could be recovered and sold. In addition, more than
1,500 KKg/yr of "lights" are recovered and can be recycled into the production
process'.
Alternative Treatment Process for K017 Waste—Heavy Ends from the Purification
Column in the Production of Perchloroethylene
This recovery process involves extracting epichlorohydrin and
dichlorohydrin from the waste stream using water and recycling the dried
epichlorohydrin and dichlorohydrin back to the process.
The raffinate from the extractor would contain mainly trichloropropane
and chloroethers. This stream could be fractionated to recover
trichloropropane overhead. The bottoms would contain some trichloropropane
and the chloroethers. This stream would have to be disposed of by
incineration.
For a waste volume of 4,000 metric tons per year, this treatment scheme
should be able to reduce the amount of waste material to 1,000 metric tons.
Assuming 80 percent effectiveness of the treatment process, 315 KKg of
epichlorohydrin and 2,000 KKg of trichloropropane would be recovered.
4-7
-------
Alternative Treatment Process For K019 Waste—Heavy Ends from the Distillation
of Ethylene Dichloride in Ethylene Dichloride Production
This recovery process involves distillation of the ethylene dichloride
remaining in the heavy ends using a thin film evaporator. The distillate,
consisting mainly of ethylene dichloride, would be returned to the process.
Other recovery steps involve dehydrochlorination with a slurry of calcium
hydroxide. The bottoms from the distillation column would contain
^Z-'
1,1^2-trichloroetbane and 1,1,1,2-tetrachloroethane. In the first
dehydrochlorination reactor, the trichloroethane would be converted to
1,1-dichloroethylene at a temperature of 50°C. In the second
dehydrochlorination reactor, the tetrachloroethane is converted to
1,1,2-trichloroethylene at 100°C.
A typical plant producing 136,000 MT per year of vinyl chloride monomer •
would generate 1,400 KKg/yr of ethylene dichloride still bottoms. Utilizing
the recovery scheme detailed above, it would be possible to recover over
300 metric tons of 1,1-dichloroethylene, which would be used in the production
of copolymeric materials and 1,1,1-trichloroethane. In addition, 280 metric
tons of ethylene dichloride and 330 metric tons of trichloroethylene would be
recovered.
Alternative Treatment Process for K021 Waste—Spent Reactor Catalyst from
Fluorocarbon Manufacture
This waste stream consists largely of antimony pentachloride (SbCl_)
contaminated with carbon tetrachloride and other organics, as shown in
Table 4.1. In the past, this waste has been landfilled. Two processes for
recovery of the catalyst have been proposed. The first one involves
dechlorinating the antimony pentachloride in the presence of ethylene
trichloride, resulting in the precipitation of antimony trichloride. The
reaction is:
SbCl5 + EtCl3 > SbCl3
4-8
-------
Subsequently, the SbCl. is filtered off and rechlorinated to form antimony
pentachloride which is returned to the fluorocarbon process. The filtrate is
separated by distillation into carbon tetrachloride, ethylene trichloride,
ethylene pentachloride and still bottoms. Each of these materials can be sold
or reused in the process except for the still bottoms. These would be drummed
and treated.
The second method for recovery of the spent catalyst involves
distillation of the waste stream into several components: light ends
(predominately freons), carbon tetrachloride, antimony pentachloride, and
still bottoms. The antimony pentachloride is recovered and returned to the
hydrofluorinator, and the lights and the carbon tetrachloride are reused in
the fluorocarbon manufacturing process.
4.3 WASTE EXCHANGE
Reuse of wastes may be accomplished either by the generator itself, or
through sales to a commercial processor. Marketing of wastes for reuse is
often facilitated through use of waste exchanges. Waste exchanges are
institutions which serve as brokers of wastes or clearing- houses for
information on wastes available for reuse. In some waste exchanges, potential
buyers of wastes are brought into contact with generators, while other waste
exchanges accept or purchase wastes from a generator for sales to other
users. Waste exchanges are considered by EPA to be of great potential value
in future waste management because, through waste exchanges, recycling
practices may be increased.
In general, the "exchangeability" of a waste is enhanced by higher
concentration and purity, quantity, availability, and higher offsetting
disposal costs. Some of the limitations to waste exchangeability are the high
costs and other difficulties associated with transportation and handling,
costs of purification or pretreatment required, and, in certain cases, the
effect on process or product confidentiality. In general, waste exchange
involves transfer of products from large, continuous processors to small,
batch processors, or products from high purity processors (e.g., pharma-
ceutical manufacturers) to low purity processors (e.g., paint manufacturers).
4-9
-------
Waste exchanges are operated by both private firms and public organiza-
tions. Several public waste exchanges are listed below:
• California Waste Exchange (California);
• Canadian Waste Materials Exchange (Ontario);
• Chemical Recycle Information Program (Texas);
• Colorado Waste Exchange (Colorado);
• Georgia Waste Exchange (Georgia);
• Great Lakes Regional Waste Exchange (Michigan);
• Industrial Materials Exchange Service (Illinois);
• Industrial Waste Information Exchange (New Jersey);
• Inter-Mountain Waste Exchange (Utah);
• Louisville Area Waste Exchange (Kentucky);
• Midwest Industrial Waste Exchange (Missouri);
• Montana Industrial Waste Exchange (Montana);
• Northeast Industrial Waste Exchange (New York);
• Piedmont Waste Exchange (North Carolina);
• Southern Waste Information Exchange (Florida);
• Techrad (Oklahoma);
• Tennessee Waste Exchange (Tennessee);
• Virginia Waste Exchange (Virginia);
• Western Waste Exchange (Arizona); and
• World Association for Safe Transfer and Exchange (Connecticut).
The following is a list of the private material exchanges currently in
bus iness:
• Zero Waste Systems, Inc. (California);
• ICM Chemical Corporation (Florida);
4-10
-------
• Environmental Clearinghouse Organization - ECHO (Illinois);
• Americal Chemical Exchange - ACE (Illinois);
• Peck Environmental Laboratory, Inc. (Maine);
• New England Materials Exchange (New Hampshire);
• Alkem, Inc. (New Jersey);
• Enkarn Research Corporation (New York);
• Ohio Resource Exchange - ORE (Ohio); and
• Union Carbide Corporation (in-house operation only; West Virginia)
4-11
-------
REFERENCES
1. North Carolina Department of Natural Resources and Community
Development. Accomplishments of N.C. Industries, Case Summaries.
January 1986.
2. Minnesota Waste Management Board. Hazardous Waste Management Report.
1983.
3. Huisingh, D., et al. Proven Profit from Pollution Prevention.
Conference draft. The Institute for Local Self-Reliance, Washington,
DC. July 1985.
4. Roeck, D. R., et al. GCA Technology, Inc. Hazardous Waste Generation
and Source Reduction in Massachusetts. Bedford, MA. Contract No.
84-198, MA Dept. of Env. Mgt., Bureau of Solid Waste Disposal, June
1985 (Draft).
5. Kohl, Jerome, P. Moses, and B. Triplett. Managing and Recycling
Solvents: North Carolina Practices, Facilities and Regulation.
Industrial Extension Services, School of Engineering, North-Carolina
State University, Raleigh, NC. December 1984.
6. Versar, Inc. National Profiles for Recycling/A Preliminary Assessment,
Draft. EPA Contract No. 68-01-7053, U.S. EPA, OSW, Waste Treatment
Branch. July 1985.
7. Hobbs, B., and R. R. Hall, GCA Technology, Inc. Study of Solvent
Reprocessors. Bedford, MA. EPA Contract No. 68-01-5960 (Draft),'
U.S. EPA, OSW, Office of Chemical Control, January 1982.
8. Radminsky, Jan, et al. Department of Health Services, Alternative
Technology and Policy Development Section. Alternative Technology
for Recycling and Treatment of .Hazardous Wastes, Second Biennial
Report. California, July 1984.
9. Engineering-Science. Supplemental Report on the Technical Assessment of
Treatment Alternatives for Waste Solvents. Washington, D.C. U.S.
Environmental Protection Agency. 1985.
10. Noll, K. D., et al., Illinois Institute of Technology. Recovery, Reuse
and Recycle of Industrial Waste. Chicago, IL. EPA-600/2-83-I14, U.S.
EPA/ORD, Cincinnati, OH. November 1983.
4-12
-------
SECTION 5
PHYSICAL TREATMENT TECHNOLOGIES
The physical treatment processes discussed in this halogenated organic
waste TRD are:
5.1 Distillation,
5.2 Evaporation (thin film evaporators),
5.3 Steam Stripping,
5.4 Liquid-Liquid Extraction,
5.5 Carbon Adsorption, and
5.6 Resin Adsorption.
These physical processes generally do not result in the destruction of
waste constituents and provide opportunities for recovery of valuable
components. The first three processes are largely dependent on the volatility
of the constituents to effect evaporation from the waste matrix. These
technologies are considered more applicable to halogenated solvents which are
generally lower in molecular weight and more volatile than the halogenated
organic compounds considered in this document. However, as noted in Section 2,
many of the K type waste streams considered here contain halogenated solvents
in addition to other halogenated organic constituents. Thus, application of
technologies such as distillation, evaporation, and steam stripping will produce
an overhead fraction consisting of low molecular weight halogenated solvents and
a bottom fraction consisting of higher molecular weight organics.
5-1
-------
Liquid-liquid extraction (solvent extraction) is widely used in the
chemical process industry but has not yet been extensively employed for
treatment of hazardous wastes. It may possibly be utilized to advantage to
separate components that can not be separated by processes based on
differential volatilization. Extraction processes are applicable to both
aqueous and organic matrices, although partition coefficients are greatest for
aqueous/organic combinations.
Adsorption is highly applicable to most of the high molecular weight
halogensted organic compounds considered in this TRD. It is usually used to
remove small quantities of organic contaminants from aqueous waste streams
although it is sometimes used as a pretreatment followed by a biological
finishing process.
Some level of residual contamination of the waste stream(s) can be
expected for the other physical treatment processes. These processes will
require subsequent post-treatment (e.g., incineration of distillation bottoms,
adsorption/biological treatment of steam stripper aqueous condensate) in order
to meet surface water discharge (e.g., NPOES, POTW) or land disposal
<
requirements.
The physical treatment processes (and the other treatment processes
discussed in following sections) are considered within the framework of four
major areas; i.e., 1) process description including pretreatment and
post-treatment requirements, 2) demonstrated performance in field and
laboratory, 3) cost of treatment, and 4) overall status of the technology.
Discussions of the various types of treatment processes applicable to
halogenated organic waste streams are contained in Sections 5.0 through 10.0.
These are followed by a review section (Section 11.0) that addresses
approachestto identifying potential treatment processes or process
combinations that are likely to meet treatment requirements in the most cost
effective manner.
5-2
-------
5.1 DISTILLATION
Distillation is primarily a recovery operation that is most applicable to
the low boiling organic components addressed in the solvent TRD. However,
distillation is also applied to other segments of the organic chemical
industry, including halogenated organic compound waste streams of interest
to this TRD. As noted in Section 2, mnay of these specific waste streams
are K type wastes which contain both halogenated organics and halogenated
solvents. Depending upon their relative volatilities, these mixed wastes
can be recovered as overhead constituents or as overhead and bottom
fractions. For the specific K type waste streams shown in Section 2, the
latter case is most likely. As discussed in the examples of recovery
processes for selected K type waste streams (Section 4), the bottoms
stream can be further purified by a subsequent fractionation, or used
directly as feedstock to a production process. Lacking value as a feedstock
to a production process. Lacking value as a feedstock raw material,
incineration is usually the preferred ultimate disposal option.
Distillation is often useful as an auxilliary to other treatment
processes. For example, it may be used to separate mixtures of solvent
and solute resulting from liquid extraction processes .or from wash solvents
used to regenerate resin adsorbents. Because it is such an important
process it is discussed in some detail below. However, the reader is
referred to the solvent TRD,1 Perry's Chemical Engineers' Handbook^ and
other references for additional details concerning design and performance.
3-10.
5.1.1 Process Description
Distillation is a separation technique that operates on the principle of
differential volatility. More volatile constituents can be enriched or
separated by heating and volatilizing from dess volatile constituents.
Distillation systems fall into one of four general categories.
1. Batch distillation;
2. Continuous distillation;
3. Batch fractionation; and
4. Continuous fractionation.
5-3
-------
Fractlocation is distinguished from distillation through the use of
multiple distillation steps in tray or packed towers to separate two or more
volatile components of the waste feed into distinct fractions. In batch
distillation, the system is charged with a given quantity of a waste
(generally a liquid although some solids can be tolerated if minimum heat and
mass transfer levels can be achieved) and heated indirectly with steam or
oil. Coils or the vessel wall act as the heat transfer surface. Heating
continues until a predetermined fraction of the volatile components is
removed, as indicated by the time/temperature profile of the charge within the
still. At this point, heating is discontinued and the bottom product
(i.e., less volatile residues) are removed.
For the halogenated organic K type waste streams, the bottoms may
represent the halogenated constituent which can be returned to the process as
feedstock. In other cases, further fractionation may be required to recover a
waste product of sufficient quality for reuse or sale. In many cases, it will
be expeditious to maintain a residue that can be handled readily and/or
incinerated; i.e., waste that is pumpable and.has Btu value. In any event, it
must be recognized that complete removal of volatiles will not be feasible.
Attempts to reduce volatile content to low levels can result in- compound
destruction, equipment fouling and excessive operating costs. Optimal removal
efficiencies must balance the benefits of overhead recovery against the .costs
of equipment maintenance and the cost benefits of still bottom disposal or
reuse.
Continuous distillation functions much the same as batch distillation,
except that continuous charging and bottoms removal results in steady-state
operation. Alternatively, waste feed or removal of the bottoms product can
take place at specific intervals resulting in semi-continuous operation. Con-
tinuous bottoms removal generally implies that the stream is a pumpable liquid.
In response to economic incentives to recycle and minimize wastes,
several small stills have been recently developed which yield high percent
recovery as a result of design features such as removable liners for bottoms
disposal. Many can be operated under vacuum with batch bottoms removal to
approach nearly 100 percent recovery. Although aimed at the solvent recovery
market, they can be applied to halogenated organic compounds provided the
vapor pressure of the compound is sufficient under operating conditions and
thermal decomposition is not a factor.
-------
The separation of mixtures requires multiple distillations or
fractionation since adequate separation of fluids with similar boiling ranges
is not achievable in a single stage. Fractionation column designs include the
use of multiple trays or packing to maximize surface area so that rising
vapors are intimately contacted with falling condensate (reflux). These
columns can be operated as batch or continuous units. Figure 5.1.1 shows
basic process- schematics for batch and continuous fractionation systems.
Fractional distillation is a very well developed industrial technology
that has been studied extensively for many years, particularly by the
petrochemical industry. Vapor-liquid equilibrium data provide the basis for
evaluating the feasibility of fractionation. A McCabe-Thiele diagram, which
graphically illustrates the fractionation process, is shown in Figure 5.1.2.
The figure shows the minimum number of theoretical column stages required to
effect separation; i.e., 100 percent efficiency at total reflux. In certain
cases, relative composition differences between the liquid and vapor phase
might be so small as to render the separation economically unfeasible. The
vapor-liquid equilibrium (VLE) data must be evaluated to determine
f •
sepafational feasibility. It is evident from studying the McCabe-Thiele
diagram (Figure 5.1.2) that if the vapor and liquid composition lines are
close enough, many equilibrium stages will be required. Detailed discussions
of fractional distillation theory and practice, including the use of
well-developed models for predicting separation, can be found in chemical
engineering texts such as the section on distillation in Kirk-Ottimer's
Lit
2
Encyclopedia of Chemical Technology, the literature sources cited therein,
and in Perry' s Chemical- Engineers' Handbook.'
In continuous fractipnation, feed is constantly charged to the column at
a point which provides the specified top and bottoms product. The section of
the tower above the feed point is the rectifying or enriching section, and the
section below the feed point is the stripping section. A reboiler is
connected to the bottom of the fractionation tower to provide the reboil heat
needed for added reflux and better fractionation of complex mixtures. Batch
fractionation differs in that the charge is introduced at the bottom of the
tower. As a result, it is possible to obtain a distillate of high purity, but
recovery of volatile component(s) must proceed in a step-wise manner. As the
more volatile constituent is taken off, the reflux and thus, energy consump-
tion, must be increased to maintain overhead product purity. Eventually, the
5-5
-------
VAPOR
1
COLUMN
//£>«r /^
CONDENSER
REFLUX
OVERHEAD
PRODUCT
Tnrfrrcfi
L
BOTTOM PRODUCT
•
.§
v»
Vi
*
FfCO
*
I
*
>
"
%
g
«t
Vj
1
1
^L^
^^
•" t COHilt HStH
I..I , ^
d 1 ..^
1 1 COLO
ACCUMULATOR!. WATCH
• j
* flr;— T^-=T'..-=.IT^
r~^H
§ PISTILLATE *
1
** "VJ REFLUX
^31 PUUP F
FEED
PLATE
VAPOR argoiLFR
A — ' — « 1 1
fl=< 1 ||-> ^ • STfAM
\ 'A
LIQUID 1 °*~ COMDEMS
• ^
BOTTOMS PRODUCT
BATCH FRACTIONATION
CONTINUOUS FRACTIONATION
Figure 5.1.1. Basic schematic for batch and continuous fractionation systems.
-------
-------
overhead quality decreases to the point where it must be removed and stored
separately until the next most volatile component(s) is enriched enough to
generate a useful product. However, batch fractionation does permit handling
of wastes with higher dissolved solids content which would foul the stripping
zone surfaces in a continuous feed column.
5.1.1.1 Restrictive Waste Characteristics—
Batch Distillation
Batch distillation equipment has undergone considerable development in
recent years, particularly that of interest to the small quantity generator.
Almost any liquid waste can be processed in commercially available equipment,
including high solids, ignitable, and potentially explosive mixtures. However,
there are some restrictions which affect safety and product purity that should
be considered. Although, from the standpoint of safety, they are less
critical for halogenated organics which are generally nonignitable under
normal operating conditions.
Typically, at least 40°C between autoignition point and boiling point is
required for safe distillation of high purity mixtures. Autoignition
temperatures for most volatile compounds can be found in the National Fire
12
Protection Association's "Fire Protection Guide for Hazardous Materials."
Heptane is generally considered to have the lowest autoignition point (399°F)
9
of commonly recovered organics. For this reason (to minimize risk of
explosion), many manufacturers design units which are limited to a maximum
temperature of 365'F.
While many small stills are explosive proof, the potential for explosion
should be evaluated, especially for highly volatile mixtures. Autoignition
temperatures of ignitable wastes may pose particular handling problems in
distillation units. Some of the particular waste streams addressed in this
document can contain constituents with low autoignition points.
Most halogenated organics are nonflammable but are susceptible to thermal
decay. Thermal decay occurs at low temperatures relative to autoignition
points. For low autoignition point and low decomposition temperature
compounds, vacuum operation is an option that is available in many of the
5-8
-------
currently marketed batch stills. Additional capital and operating expenses
are at least partially offset by the reduced boiling temperature and higher
potential recovery rates.
Solids content, which is a critical limitation for continuous
distillation and fractionation processes, is less critical for batch
distillation or continuous feed with batch bottoms removal. In particular,
jacketed and immersion heated boilers with provisions for easy bottoms removal
are capable of achieving high recovery rates. Residual low boiling components
remain in the bottoms produced from these operations, but potential volatile
component removal efficiencies are usually greater than 90 percent, regardless
of initial solid constituent concentration. In many cases, the distillation
occurs over a long enough period of time such that potentially reduced mass
diffusion and heat transfer do not greatly reduce the overall effectiveness of
the' recovery process.
Continuous Distillation
Continuous distillation of wastes is subject to the same constraints that
apply to batch distillation in terms of operating temperature, i.e., auto-
ignition temperature, boiling point, and thermal decay. However, the
distinction between batch and continuous bottoms removal greatly affects the
applicability and achievable performance for certain waste types.
Continuous feed, batch bottoms removal units are essentially the same as
batch units in terms of processing capabilities. Continuous feed units have
greater capital costs, since they do require some additional control features
(i.e., level control), but are more automated thereby requiring less labor.
These units are preferred for high throughput applications where labor costs
become a higher fraction of total costs than capital equipment outlays.
The continuous feed, continuous bottoms removal units are different in
that the achievable recovery is controlled by the ultimate disposition of the
bottoms. Continuous bottoms removal implies that the bottoms remain fluid.
In cases where bottoms become highly viscous, ultimate recovery is limited by
equipment processing constraints. These materials are more optimally
processed in thin-film-evaporators which are capable of achieving high
recovery rates and throughputs in a shorter period of time (see Section 5.2).
5-9
-------
Scraped-surface stills also increase the ultimate recovery but by a smaller
amount. Thus, continuous bottoms recovery stills are best suited to
recovering wastes that are non-fouling and that remain pumpable after
separation.
Batch Fractionation
Fractionation is a multi-stage process used for separating volatile
mixtures when the value of the pure component products justifies the
additional expenses associated with separation. In the case of solvents, pure
components can be sold for 80 to 90 percent of the virgin price whereas blends
13
typically sell for only 50 to 60 percent of virgin prices. Batch
fractionation can handle a higher solids content waste form relative to
continuous fractionation since these materials do not come into contact with
the packing or trays. However, the quantity and nature of the solids in the
waste may become a limitation depending upon the design of the heat transfer
unit. Excessive fouling may interfere with heat transfer resulting in higher
energy costs, reduced throughput, and additional labor. Agitated units are
available to reduce the potential problems due to fouling.
Continuous Fractionation
As opposed to batch fractionation, continuous fractionation is reserved
for materials which are essentially void of dissolved and suspended solids.
The feed enters at a mid-point in the column where it comes into intimate
contact with tray or packing surfaces. Labor costs associated with cleaning
these units justify pretreatment in either a distillation or evaporation
unit. Also, the bottoms product will have to be treated to remove the
nonvolatile hazardous constituents.
5.1.1.2 Operating Parameters and Design Criteria—
Distillation and fractionation processes are based on the evaporation and
condensation of constituents. Operating parameters of critical importance for
all units are process temperature and pressure. Higher operating pressures
are routinely used for low boiling point constituents to avoid the use of
5-10
-------
energy intensive refrigeration to achieve condensation. This is particularly
true for fractionation processes which requires greater reboiler and condenser
duties as a result of occurring reflux. Additionally, distillation units,
particularly small batch units capable of processing up to 60 gallons per
hour, are often equipped with vacuum capability. High temperatures combined
with low pressure makes high recoveries possible, even for high boiling
constituents.
Other parameters that must be considered include batch time, viscosity
(flow and mass transfer), reflux ratio, and the location of feed introduction
to fractionation columns. Batch time is chosen based on economics, desired
recovery, and restrictive waste characteristics. Certain units may be
susceptible to fouling or viscosity problems. High viscosity wastes are best
treated in agitated thin-film evaporators (see Section 5.2).
Reflux rate and feed tray location are process variables strictly
applicable to fractionation, with feed tray designation applicable
specifically to continuous fractionation. Reflux rate or ratio is set based
on the economic evaluation of product purity versus utility costs. High
reflux ratios produce higher purity products but are more energy intensive.
In addition, the high internal flow rates often establish the need for either
larger units, or lower throughputs. Optimal feed location in a column will be
at the point of intersection of the rectifying and stripping operating
lines.
The reader is referred to numerous chemical engineering texts,.including
2 1*0
Perry and Kirk-Othmer , for more extensive discussions of distillation
equipment operation and design. The solvent TRD also includes an appendix
describing design features and cost of small, commercially available
9
distillation equipment.
5.1.1.3 Treatment Combinations-
Distillation pretreatment options consist of filtration, centrifugation
and other physical means to separate solids from the liquid stream, and
decanting to separate gross sediment and immiscible fluids.
Post-treatment methods used for overhead product include further
refinement through separation of mixtures into pure components. This is
performed to enhance the value of the recovered overhead or to meet product
5-11
-------
purity specifications. Fractional:ion is usually performed on low molecular
weight organics (e.g., solvents), which have already been separated from
nonvolatile constituents. It is also a typical regeneration technique for
solvents used in liquid-liquid extraction. In cases where the distillate
product consists of two phases, decanting is a typical post-treatment
procedure. If water is soluble in the overhead to an extent which exceeds
product purity specifications, the overhead stream will undergo some form of
drying to remove the water. Commonly employed drying methods include
molecular sieve, calcium chloride, ionic resin adsorption, and caustic
extraction.
Post-treatment options for bottoms products depend on the physical form
and cost of the material. Approximately two-thirds of recycled solvent
bottoms generated by commercial recyclers are used as is or blended with
higher Btu products for use as a fuel. For blends containing expensive
halogenated constituents, there are cases where liquids are added prior to
distillation to promote maximum removal of the halogenated constituents by
keeping the bottoms fluid. Other post-treatment options consist of further
solid-liquid separation for organic liquids and sludges, organic removal or
extraction processes for aqueous wastes., and thermal destruction techniques.
Solid-liquid separations can be accomplished by physical means such as
centrifugation, filtration, decanting and extraction.- Dilute aqueous wastes
can be treated through air or steam stripping, carbon or resin adsorption, or
biological treatment as described in other sections.
5.1.2 Demonstrated Performance
A number of studies have been cited by EPA as demonstrating the
14
feasibility of solvent recovery by distillation processes. Although
residual solvent concentrations in treated wastes were always high enough to
require additional treatment, all these studies demonstrated significant
economic benefits. A discussion of these studies is provided in the solvent
TRD. Unfortunately, very little information was found in the literature
pertaining to the treatment of nonsolvent halogenated wastes. However, 13 of
the 27 specific K type wastes represent distillation bottoms. An examination
of the constituent concentration data previously shown in Table 2.3 would
5-12
-------
suggest that further recovery of both halogenated solvents and compounds could
be achieved by a subsequent bottoms redistillation or treatment by other
technologies. Four alternative treatment procedures have been identified in
Reference 15, three of which identified distillation as a key technology for
waste streams KOI7, R019, K021, and K030. EPA is undertaking work to further
examine alternatives for these and other specific K type waste streams
containing halogenated organics.
5.1.3 Cost of Treatment
Cost data developed for solvent recovery applications is addressed in the
solvent TRD and references cited therein. As noted in the solvent TR1), the
Naval Energy and Environmental Support Activity (NEESA) has assessed the costs
of small to moderate sized batch stills and larger continuous stills, with
results reported in Reference 16. NEESA developed the following methodology
to evaluate the economics of a solvent reclamation program.
Data Requirements:
D - Cost of distillation unit ($)
E - Recovery efficiency of still (decimal fraction)
I * Cost of installation ($)
M - Cost of additional labor (varies with size and operational
requirements of still; assume $0 for under 3,500 gallons per year,
$2,500 between 3,500 and 13,000 gallons per year, and £7,500 for
over 13,000 gallons per year)
S - Cost of halogenated organic (^/gallon)
U - Cost of utilities in reclaiming halogenated organic (^/gallon)
V - Volume of halogenated waste generated (gallons)
W - Waste disposal costs for halogenated waste and still bottoms
(i/gallon)
(A/P:i:n) - Appropriate capital recovery factor to evaluate payback
period.
5-13
-------
These parameters, modified to represent halogenated organics rather than
solvents, may be combined to form an equation representing the parameter
interactions at specific pay back periods as follows:
V[ES+(1-E)W] - (A/P:i:n) (D-H) - UV - M = 0
Using this expression it is possible to calculate break-even volumes for
various applications and payback periods.
NEESA has estimated the costs of reclamation for various types of
solvents, including mineral solvents. The example for mineral solvents is
reproduced below to illustrate the magnitude of costs one might expect for the
recovery of halogenated organic wastes. Many of these wastes, like mineral
spirits, tend to have relatively low cost, low volatility, and high boiling
points (mineral spirits boiling range is 150 to 200°C). These factors make
cost-effective recovery high volume dependent because of the more expensive
reclamation equipment required and the low value of the recovered organic.
Payback periods were calculated using the cost equation and the assumptions
listed below.
Assumptions:
Cost of Still (d): $8,600 for under 3,500 gallons per year
$17,700 for 3,500-13,000 gallons per year
$45,000 for 13,000-60,000 gallons per year
Installation Cost (I): 1.5 D
Recovery Efficiency (E): 0.95
Additional Manpower (M): See original assumptions
Organic Constituent Cost (S): $1.75 per gallon
Utility Costs (U): $0.05 per gallon
Waste Disposal Costs (W): $2.00 per gallon, $3.00 per gallon
Discount 'Factor (i): 10 percent
Due to the high sensitivity to waste disposal costs for the small (15 gpd) and
medium (55 gpd) size distillation units, economic analyses were conducted
using three disposal costs. For the large distillation unit (250 gpd) where
5-14
-------
the waste disposal cost is less influential, the economic analysis was
conducted at the median disposal cost of $2.00 per gallon. NEESA originally
assumed a $0.25 per gallon utility cost. Case studies conducted by GCA and
others report utility costs to be on the order of $0.05 per gallon. Working
with the basis provided by NEESA, payback period curves were generated for the
reduced utility costs in as shown Figures 5.1.3 to 5.1.5.
5.1.4 Overall Status
5.1.4.1 Availability/Application—
Distillation and fractionation are two of the most established unit
operations. Many firms provide design services and manufacture equipment.
The Chemical Engineers Equipment Buyers' Guide provides a comprehensive list
of suppliers. In December 1985, the Naval Energy and Environmental Support
Activity (NEESA), presented the results of a package distillation equipment
9
manufacturer's survey. The document provides detailed price, option
(including safety features), and specification information for products from
17 different manufacturers of small batch and continuous units (<6.Q gallons
per hour). Table 5.1.1 lists some of the general specifications of the stills
that were considered. Appendix B of the solvent TRJ
information including capital purchase information.
that were considered. Appendix B of the solvent TRD provides more detailed
5.1.4.2 Environmental Impact--
The environmental impact of distillation processes for halogenated
organic waste recovery should be minimal. Apart from questions related to the
disposal of still bottoms, other emissions, including air emissions from the
condenser, do not appear to be significant.
5.1.4.3 Advantages and Limitations—
Distillation would appear to be a key technology for the recovery or
minimization of many halogenated organic wastes. Based on well understood
principles, its implementation is relatively straightforward and its economic
benefits can be appreciable.
5-15
-------
5.0OOr-
4,000
- 3.003
2.000
1.000
W = Waste Disposal Cost
W- $1.00/pJlon
W - 12.00/failon
J I ! L I I » > i I
4 6
Payback Period (yean)
10
Figure 5.1.3. Reclamation of cold cleaning solvents via small
batch stills (15 gpd).
Source: Reference 16.
5-16
-------
8,000
S>
Q.
CO
c
03
CJ
III
6.000
4,000
2.000
W = Waste Disposal Cost
— —.W_L H- OO/ ga_l_lon_
4 6
PAYBACK PERIOD (years)
10
Figure 5.1.4. Reclamation of cold cleaning solvents via medium
batch stills (55 gpd).
Source: Reference 16.
5-17
-------
03
O
O
c.
09
c
a
a
*»*
ui
25,000
20,000
15,000
10,000
5,000
W = Waste Disposal Cost
W= 52. OO/gallon
10
PAYBACK PERIOD (years)
Figure 5.1.5. Reclamation of cold cleaning solvents via a large
continuous still (250 gpd).
Source: Reference 16.
5-18
-------
TABLE 5.1.1. COMMERCIALLY AVAILABLE SOLVENT STILLS
Manufacturer
Alt. Resource Mgmt
Baron-Blakeslee
Branson.
Brighton
Cardinal
DC I
Disti
Finish Engineering
lloyt
Lenape
Phillips
Progressive Recovery
Raraco
Recyclene
Unique Industries
Venus
Westinghouse
Solvent types
All
llalogenated
llalogenated
All
llalogenated
All
All
All
All
llalogonated
Halogenated
All
llalogenated
All
llalogenated
All
llalogenated
Maximum Explosion Vacuum
b.p.(F) proof available
500 X X
350
350
500 X X
350 X
500 X - X
500 X X
500 X X
350 X
350
350
500 XX
350
420 X
350
210 X
350
Water
separator Heating
X Electric/Steam
X Electric/Steam
X Electric/Steam
X Hot Oil/Steam
' Electric
X Dir. Steam Injection
X Hot Oil/Steam
Electric/Steam
Hot Oil
X Electric
X Electric/Steam/Caa
Hot Oil/Steam
Electric/Steam
Hot Oil
X Electric/Steam/Gas
Electric
X Electric
Cooling
Water
Water/Refrig
Water/Refrig
Water
Refrig
Water
Water
Water
Water
Water/Kefrig
Water
Water
Water/Air
Water
Water/Kefrig
Water/Kef rig
Water/Refrig
Source: Reference 9.
-------
REFERENCES
1. Breton, M., et al. Technical Resource Document: Treatment Technologies
for Solvent Containing Wastes. Final Report prepared for U.S. EPA,
HWERL, Cincinnati, Ohio, September 1986.
2. Perry, R. H., et al. Chemical Engineers' Handbook, Sixth Edition.
McGraw-Hill, 1984.
3. Gavlin, A. Benagali and W. Lagdon. Case Studies of Solvent Recovery Via
Continuous Processing. AIChE Symposium Series, 76(192): 46-50, 1980.
Paper presented at September Symposium of AIChE Annual Meeting, New York,
NY, November 1977.
4. Peters, M. S« and K. D. Timmerhaus, Plant Design and Economics for Chemical
Engineers, McGraw-Hill, 1980.
$
5. Shulka, H. M., and R. E. Hicks, Water General Corp. Process Design Manual
for Stripping of Organics. EPA-600/2-84-139, U.S. EPA/IERL, Cincinnati,
Ohio, August 1984.
6. Yeshe, P. Low-Volume, Wet-Scrap Processing. Chem. Eng. Progress, 80(9):
33-36, September 1984.
7. GCA, Waste Minimization Case Studies for EPA HWERL, Contract 68-03-3243,.
1986.
8. Higgens, T. E. CH2M Hill, Reston, VA. Industrial Processes to Reduce
Generation of Hazardous Waste at DOD Facilities, Phase 2 Report,
Evaluation of 18 Case Studies. July 15, 1985.
9. Naval Energy and Environmental Support Activity, Assessment of Solvent
Distillation Equipment, NEESA 20.3 - 012, December 1985.
10. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons,
New York, NY, 3rd Edition. 1978.
11. Allen, C., et al. Field Evaluations of Hazardous Waste Pretreatment as
an Air Pollution Control Technique. Report prepared for U.S. EPA, ORD,
Cincinnati, Ohio under Contract No. 68-02-3992. April 1985.
12. National Fire Protection Association, Fire Protection Guide for Hazardous
Materials, 9th Edition, 1986.
5-20
-------
13. Horsak, R. D., et al., Pace Company Consultants and Engineers, Inc.
Solvent Recovery in the United States: 1980-1990. Houston, TX.
Prepared by Harding Lawson Associates, January 1983.
14. U.S. EPA Office of Solid Waste. Background Document for Solvents to
Support 40 CFR Part 268 Land Disposal Restrictions. Volume II. Analysis
of Treatment and Recycling Technologies for Solvents and Determination of
Best Available Demonstrated Technology. U.S. EPA Public Docket.
January 1986.
15. Arienti, M., et al. Technical Assessment of Treatment Alternatives for
Waste Containing Halogenated Organics. Final Report by GCA Technology,
Inc. to OSW under Contract No. 68-01-6871, Work Assignment No. 9,
October 1984.
16. Nelson, W. L., Naval Energy and Environmental Support Activity (NEESA),
In-House Solvent Reclemation, Port Heuneme, CA. NEESA 20.3-012,
October 1984.
5-21
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5.2 EVAPORATION PROCESSES
Available equipment designs used for evaporation/distillation include
e
simple stills, flash evaporators, forced circulation evaporators, and falling
film and agitated thin film evaporators. All designs are capable of
concentrating nonvolatile components of waste mixtures. However, in cases
where fouling, foaming, high viscosity, thermal degradation, or other factors
present potential operational problems, agitated thin film evaporators (ATFEs)
provide the most versatile service. They also represent the most
effective, high volume evaporation equipment which is capable of reducing
viscous wastes to low residual organics. This is a direct result of high
mass transfer rates achieved through turbulence. For these reasons, a
majority of large commercial solvent recycling companies use ATFEs as
indicated by several industry surveys.
The emphasis in this section will be on the agitated thin film designs
because of their widespread use and applicability in reclaiming wastes which
are too viscous or otherwise too difficult to recover in conventional
distillation equipment. Although used extensively for recovery of solvents,
they will also be applicable .to the recovery of many halogenated organic
wastes. •
5.2.1 Process Description
Liquid waste is fed to the top of ATFEs where longitudinal blades mounted
on a motor driven rotor maintain the waste against the heat transfer surface;
i.e., the inside wall of the cylindrical vessel. This surface is enclosed in
a heating jacket which usually employs steam or hot oil as the heating medium
(temperatures up to 650°F).
The agitation and liquid film are maintained by the blades as they move
along the heat transfer surface. The blade tips typically travel at 30 to
40 feet per second at clearances of 0.007 to 0.10 inches which creates high
turbulence (see Figure 5.2.1). This facilitates efficient heat and mass
transfer, shortens required waste residence time, and creates a degree of
mixing that maintains solids or heavy molecular weight solutes in a manageable
suspension without fouling the heat transfer surface. Mass diffusivities in
5-22
-------
Turbulent Liquid Film
on Intrude Wall.
Figure 5.2.1. Cross section of agitated thin film evaporator.
Source: The LUWA. Corporation
Bulletin EV-24, 1982.
Reference 3.
5-23
-------
2
ATFEs can be increased by 1,000 Co 10,000 times over nonagitated designs.
To further promote separation, the unit is usually operated under vacuum
conditions which permits lower temperature processing of thermally unstable
mixtures.
Finally, thermodynamic properties of the waste and ATFE operating
pressure set a limit on ultimate recovery imposed by vapor-liquid equilibrium
constraints. Material will boil when its vapor pressure reaches the operating
pressure of the ATFE. Waste vapor pressure for miscible fluids is equal to
the sum of the partial pressure of each volatile species. Partial pressure of
each component is, in turn, equal to its molar concentration multiplied by the
pure component vapor pressure and a constant which is dependent on the
ideality of the solution. Thus, operating pressure and partial pressure
determine the minimum attainable (i.e., equilibrium) concentration of each
volatile species in solution. High separation efficiency will be associated
with low system pressure, high pure component vapor pressure, high activity
coefficient, high Henry's Law constant, and low solubility (solubility
decreases with temperature). Theoretically,.very high separations can be
achieved for highly volatile compounds in systems of low liquid phase
miscibility. . -
Ultimate recovery will depend on the extent to which equilibrium is
achieved which will be limited by diffusive resistance to mass transfer and
residence time in the system. For viscous wastes, economical recovery is
limited by waste viscosity as a result of decreasing diffusivity of volatile
compounds through the waste as its. viscosity increases. As diffusivity
decreases, resistance to overall mass transfer into the gas phase increases.
However, this effect is less pronounced in ATFEs relative to other evaporator
designs due to high turbulence and large exposed waste surface area.
Residual solvent concentrations below 1,000 ppm have been routinely
achieved and a concentration below 100 ppm can be achieved if conditions are
optimal. However, except, in unusual circumstances (e.g., immiscible fluids),
the sole use of ATFE cannot be expected to yield residual concentrations of
volatiles in the low ppm range.
5-24
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5.2.1.1 Pretreatment and Post7Treatment Requirements—
A schematic of an ATFE and associated pretreatment and post-treatment
options is shown in Figure 5.2.2. As shown, the pretreatment techniques most
commonly applied to wastes'undergoing ATFE are a distillation/evaporation
process aimed at removal of light ends, oil or suspended solids, or a
dissolved solids concentration process. The most cost-effective application
of an ATFE is in treating viscous wastes which are generally not amenable to
treatment using other, less expensive evaporation processes. In many cases,
the source of these wastes will be bottoms products from conventional
evaporation/distillation processes. These processes have been described
previously (Section 5.1).
Constraints on acceptable waste viscosities differ between manufacturers
and specific unit types. In general, specially designed ATFEs can process
wastes with viscosities up to 1,000,000 cps. This is shown in Table 5.2.1 and
Figure 5.2.3 which present equipment selection guides for evaporator products
1 4
based on waste viscosity. '
Post-treatment methods are also identified in Figure 5.2.2. These
basically include further refinement of the overhead product through water
removal or separation of product mixtures, and further recovery or disposal of
bottom products.
The recovered overhead may be used as is or further purified through
decanting, dehydration or fractionation. In cases where the waste feed is a
mixture of organic compounds, separation by fractional distillation is
sometimes justified by the increased value of the separated components.
Further recovery of bottoms from ATFE treatment of. organic wastes is
generally not considered practically achievable in liquid handling equipment.
However, in some cases a drum dryer, centrifuge or other solids handling
equipment might be employed depending on the nature of the waste. The residue
is often solidified and landfilled, incinerated, or burned as fuel if the Btu
value, chlorine content, ash content and viscosity are within required
specifications. In some cases the bottoms may be suitable for process reuse.
Further treatment of aqueous ATFE bottoms will generally be required to
remove remaining volatiles and other contaminants. Candidate technologies
include steam and air stripping, carbon adsorption, or biological treatment if
toxic contaminant concentrations are low.
5-25
-------
FEED
FRETREATMENT
OPTIONS
AGITATED
THIN FILM EVAPORATION
POST-TREATMENT
OPTIONS
WASTE FEED
K
CONVENTIONAL
DISTILLATION OR
EVAPORATION .
DECANTING OR OTHER
LIQUID/SOLID
SEPARATIONS (e.g.
SKIMMING, CENTRIFUGING)
AGITATED
THIN FILM
EVAPORATOR
DECANTING
DRYING
FRACTIONATION
REUSE AS IS
PRODUCT
BOTTOMS
FUEL BLENDING
INCINERATION
SOLIDIFICATION
& DISPOSAL
DRYING
PHYSICAL SEPARATION
OF LIQUIDS AND SOLIDS
(e.g., CENTRIFUGING,
SETTLING)
REUSE AS IS
Figure 5.2.2. Treatment train using an agitated thin film evaporator.
-------
TABLE 5.2.1. KEYS TO SELECTING KONTRO THIN FILM EVAPORATORS
Liquid
Property
Horizontal Vertical High
Agitated Agitated Viscosity
Thin F.ilm Thin Film ATFE
Evaporator Evaporator (Film Truder)
Low viscosity ++ ++
10,000 cps or less
Medium viscosity +* •»• - •
up to 50,000 cps
High viscosity X X ++
up to 1,000,000 cps
Slurry + +
Conventional
Evaporator
-
X
X
X
High vacuum evaporation ++ ++ ++ ++
High concentration ++
Residence
time control ++ +
X
Note: ++ = Particularly suitable
+ = Suitable
- a Usable in special cases
X = Unusable
Source: Reference 4.
-------
00
Evaporator Type
Natural Circulation 1
Falling Film
Circulating
Agitated Thin Film
Agitated Thin Film
(reinforced)
High Viscosity ATF
(film t ruder)
Applicable Viscosity Range (cps)
10-3
'777777
10-2
777777
f J2f rf
10-1
// S/7S
V/ '
I
' ////
f/'y^J
10
//xWx
V / /
102
/"/ / jf /
103
// / /" y
k//
104
^////y
105
'
106
Source: Reference 1.
Figure 5.2.3. Selection of LUWA Evaporators based on waste viscosity.
-------
5.2.1.2 Operating Parameters and Design Criteria—
ATFEs are suited to treatment of concentrated, nonvolatile organic wastes
contaminated with water or other more volatile organics. It is also suitable
for treating aqueous wastes with volatile organic concentrations above
5 percent which are not amenable to treatment using less expensive
conventional evaporation/distillation technologies. Typically, waste
viscosity (feed or bottoms) is the restrictive waste characteristic which
results in adoption of ATFE as the preferred technology. Consequently,
pretreatment requirements are less stringent and may be limited to gross solid
removal or waste concentration through decanting.
Operating system temperature and pressure are limited by waste type and
equipment design. Temperature must be higher (0 to 30°F) than the boiling
point of the material which is to be recovered as the overhead product, and
sufficiently high to maintain a minimum waste viscosity. Maximum design
temperature (less than 650°F) may be further restricted by explosion limits or
by the decomposition temperature of the recoverable materials; the latter is
of particular concern for some halogenated organics (Section 5.1). Operation
at low pressure reduces the temperature required to reach the boiling point.
It also enables higher recovery rates to be achieved, as discussed
previously. The lower limit of pressure is restricted by cost and equipment
design. Typical system pressures range from 2 to 760 mm Hg.
For a given flow and desired recovery, an ATFE system has to be designed
to produce a specific evaporation rate. Evaporation rate depends on
temperature and pressure as discussed above, heat transfer surface area, waste
type and heat transfer coefficient. Figure 5.2.4 and 5.2.5 show the
relationship between heat transfer surface area, waste type, and evaporation
rate for a Cherry-Burrel ATFE (Turba-film processor). Figure 5.2.6 shows
the same relationship, based on unit area of heat transfer surface, for a LUWA
ATFE. As shown, high heat transfer area is required to evaporate solvents
from aqueous wastes and highly viscous materials; e.g., waxes and pastes.
Aqueous wastes, because of their low viscosity, are often handled in
conventional evaporation equipment.
5-29
-------
tr
o
a.
HI
X
DC
Ul
s
UJ
6000
5000
4000
3000
2000
1000
DISTILLING LOW BOILING ORGANICS
CONCENTRATING AQUEOUS SOLUTIONS
20
40
60
80
10O
120
140
TURBA-FILM PROCESSOR HEAT TRANSFER
AREA (FT2)
Figure 5.2.4. Required heat transfer surface area for distilling low
boiling organica and concentrating aqueous solutions.*
*Source: Cherry-Burrell, Reference 5.
5-30
-------
w
JO
tr
o
0.
O
HI
x
QC
UJ
O
ui
6000
5000
4000
3000
2000
1000
D DEHYDRATING HEAVY PASTES
M STRIPPING TO LOW RESIDUAL ORGANIGS
20
40
60
80
100
120
140
TURBA-FILM PROCESSOR HEAT TRANSFER
AREA (FT2)
Figure 5.2.5. Required heat transfer surface area for dehydrating heavy
pastes and stripping wastes to low residual organic3.*
*Source: Cherry-Burrell, Reference 5.
5-31
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;Sp«dfc Evaporation Rtto EA [-T
Heating Medium: dry and saturated steam
A Concentration of aqueous solutions
B Dehydration of organics
C Distillation of organics
D Stripping of low boilers from organics
E Reboiler service
F Solvent reclaiming
G Deodorization
Heating Medium: Dowtherm or hot oil
H Distillation of high-boiling organics
I Stripping of high boilers
J Reboiler service
Figure 5.2.6. Heat transfer and evaporation rates in LUWA.
Thin Film Evaporators.
Source: Reference 3.
5-32
-------
Typical ATFE system operating data are summarized in Table 5.2.2. As
shown, heat transfer surface area, steam consumption and cooling water
requirement vary directly with overhead recovery rate. However, electricity
requirement drops per unit of overhead quantity recovered thus providing a
slight drop in unit operating costs as capacity increases. Throughput of
ATFEs is generally high. If wastes are generated in low quantities, package
distillation units capable of handling high solids waste may be more
economical (see Section 5.1).
TABLE 5.2.2. TYPICAL AGITATED THIN FILM EVAPORATOR DESIGN CHARACTERISTICS
Overhead
recovery
(gal/hr)
40
85
130
240
500
Heat
transfer
surface
area
(ft2)
4.2
8.8
13.4
25
51.2.
Utilities3
Heat ing
Btu/hr
(1,000)
79
168
251
474
989
Cooling
water
(gpm)
5
11
16
30
63
Electricity
(KW)
1.5
1.5
3.5
3.5
4 '
System
dimensions '
L x W x'H,
(ft)
4 x 6 x 10
4 x 6 x 11.5
4 x 6 x 13
5 x 8 x 11.5
5 x 8 x 14
aBased on an average latent heat of vaporization of 175 Btu/lb and preheating
feed by 200"F.
Source: Reference 6.
Commercially available evaporator equipment design parameters are
2
summarized as follows. Evaporators range from 1 to over 400 square feet of
heat transfer surface with liquid throughput ranging as high as
250 Ib/hr/ft . Overhead to bottoms splits for lightly contaminated fluids
can be as high as 100 to 1 with controlled residence times of up to
100 seconds. Blade tip speeds of nonscraping designs average 30 to 40 ft/sec
while scraping blades average 5 to 10 ft/sec. Some units come equipped with
variable clearance while scraping blades are typically spring mounted or
maintain contact with the wall as a result of centrifugal force. Operating
temperatures range up to 650°F and pressure ranges from 2 ram Hg to atmospheric.
5-33
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5.2.2 Demonstrated Performance
Actual performance data from commercially operated units, conducted in
accordance with EPA Quality Assurance/Quality Control requirements, are
limited to EPA sponsored studies of halogenated solvents as reported by GCA
7 2
(1986) and the Research Triangle Institute (1984). These data, and
a
associated cost data are present in the solvent TRD. None of the units
studied demonstrated a capability of reducing volatile concentration in the
bottoms product to low ppm levels. These data are applicable to halogenated
organic wastes provided adjustments are made for differences in the factors
such as relative volatilities.
5.2.3 Cost of Treatment
7 2
Cost estimates obtained by GCA and RTI during their case studies to
assess solvent recovery using ATFEs were discussed in the solvent TRD. As
noted in. the solvent TRD, good agreement was obtained for the various cost
estimates developed by the two studies and another estimate developed by the
g
Pace Company. These estimates are applicable-to halogenated organic wastes
provided volatilities, recoveries, viscosities and other factors remain •
comparable. Generally somewhat higher costs can be anticipated for the higher
molecular weight, less volatile halogenated organics due to increased energy
or lower throughput.
GCA estimated an hourly cost of operation of $77.98 as shown in.
Table 5.2.3. Assuming an annual recovery of 940,000 gallons of waste solvent
and a capital recovery factor of 17.5 percent, total cost per gallon ranged
from $1.12 to $2.08 depending upon the composition of the feed, the product
recovery, and the time of processing. RTI determined processing costs for an
ATFE unit at about $1 per gallon when organic is stripped as the overhead
product and $1.50 per gallon when water is stripped overhead with the organic
becoming the bottom product. Pace estimated costs of $0.85 per gallon with
the major cost difference resulting from a higher projected recovery rate and
higher assumed bottoms disposal costs. Costs based on feed rate were almost
identical as were the capital cost estimates of about $300,000 for a 5 square
meter heat transfer surface area unit. Capital cost estimates developed by
Pace are shown in Table 5.2.4 for ATFE units of different size.
5-34 •
-------
TABLE 5.2.3. HOURLY COSTS OF LUWA THIN FILM EVAPORATOR
Cost
Expenses ($/hour)
Fuel 8.00
Auxiliary Chemicals 0.72
Electricity 2.60
Laboratory 9.37
Operating Labor 15.76
Maintenance Labor 14.58
Spare Farts 12.69
(Repair and Maintenance)
Regulatory Compliance 6.30
Insurance Ot69
Capital Depreciation 7.27
Total 77.98
In addition to hourly cost, the generator pays $0.26/gallon to dispose of
still bottoms to an incinerator.
Source: Reference 7.
5-35
-------
TABLE 5.2.4. CAPITAL COST RECOVERY COMPONENTS FOR ONSITE ATFE
RECOVERY SYSTEMS
Nominal feed rate
(gph)
Process Equipment
Tanks
Subtotal (1)
Engineering, Electrical,
Instrumentation (202 of (1))
Subtotal (2)
Contingency 152 of (2)
TOTAL
Thin
100
126,000
18,500
144,500
28,900
173,400
26.000
199,400
film evaporator
350
212,900
37,000
249,900
50,000
299,900
45,000
344,900
500
264,900
74,000
338,900
67,800
406,700
61,000
467,700
Source: Reference 9.
5-36
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5.2.4. Overall Status of Process
5.2.4.1 Availability--
AXFEs are widely used in a number of industries (e.g, the solvent
recovery industry) due to their unique ability to process viscous wastes
relative to other evaporation/distillation technologies. Evaporators and
accessory equipment can be obtained from a number of manufacturers in various
sizes and configurations. Ten firms are identified as suppliers of the ATFE
in the 1986 edition of McGraw-Hill's Chemical Engineering Equipment Buyers'
Guide. Major producers include Blaw-Knox (Buffalo, NY), Cherry Burrell
(Louisville, KY), LUWA (Charlotte, NC), Kontro (Orange, MA), Pfaudler
2
(Rochester, NY) and Artisan Industries (Waltham, MA).
5.2.4.2 Application—
Evaporators can be used to recover solvents and other volatile organics
from both organic and aqueous waste streams provided the treated waste does
not exceed viscosity limits imposed by the system design (see Table 5.2.1)
operating temperature. Excessive solids content will increase viscosity and
foul heat transfer surfaces; Therefore, some pretreatment for gross solids
removal may be required. . -
In practice, recovery to low residual organics is limited by viscosity
due to increased resistance to mass transfer. This resistance is partially
offset in an ATFE due to the high turbulence generated in the vessel.
Recovery is also limited by operating pressure* since this pressure determines
the equilibrium concentration of volatiles remaining in the waste. Finally,
recovery of organics from waste streams may not be economical unless the
2
recoverable organic content is greater than 6 to 8 percent. A rough cost
analysis based on raw material purchase and disposal costs supports this
figure. However, wastes with recoverable concentrations of as little as 3 to
5 percent may be profitably recovered when processed in existing, high volume
onsite facilities which are underutilized.
ATFEs are likely to find more widespread use relative to conventional
distillation equipment. Land disposal restrictions and limitations on halogen
content in supplemental fuels will compel recyclers to pursue higher recovery
rates when processing halogenated organic wastes.
5-37
-------
5.2.4.3 Environmental Impacts—
In selecting evaporators as a recovery technology for volatiles it should
be recognized that, except in isolated cases, further treatment of the bottoms
stream will be required to meet EPA land disposal or NPOES discharge
requirements. Air emissions from the overhead condenser have been identified
2
as a potentially significant source of VOC emissions by KTI. VOC
concentration averaged 41.1 and 34.4 mg/L at the vacuum pump outlet at two
units tested. However, no estimates of total release of emissions were
provided. Emission rate would be greatest during process start-up. It would
increase if air was leaking into the system, noncondensible gases were being
formed, or if the condenser became overloaded. Vacuum pump emissions controls
should be examined as a potential additional cost since treatment requirements
(e.g., carbon adsorbers) may be necessary to avoid adverse environmental
impacts.
5.2.4.4 Advantages and Limitations—
Evaporation as a means of recovering useful halogenated organics is a
common unit operation used by a variety of industries. It also finds
application in removing water or other volatiles from viscous, non-volatile
fluids with recovery value. The ATFE unit's most significant advantage over
other recovery processes is its ability to handle viscous liquids. However,
its cost must be compared to that of less expensive, conventional recovery
technologies (e.g., distillation) and their associated residual treatment
costs; e.g. thermal destruction, solidification, and land disposal. The cost
of the entire treatment train will ultimately dictate selection of the optimal
recovery technique.
5-38
-------
REFERENCES
1. Kappenberger, P. F., P. G. Bhandarkar. LUWA Ltd., Process Engineering
Division. Zurich, Switz. Thin Film Technology in Environmental
Protection. Chemical Age of India V. 36(1). January 19S5.
2. Allen, C. C., et-al. Research Triangle Institute. Field Evaluation of
Hazardous Waste Pretreatment as an Air Pollution Control Technique.
U.S. EPA/ORD, Cincinnati, OH. January 1986.
3. Luwa Corporation, Luwa Thin-Film Evaporator Technology, Bulletin EV-24,
1982.
4. Kontro Company, Bulletin 7510.
5. Cherry-Burrel, ANCO/Rotator Division, Turba-film Evaporator Bulletin.
6. Pfaudler Co., Recover Wash Solvent with the Pfaudler Solvent Recovery
System, Data Sheet 146, Supplement 1.
7. Roeck, D., et al. GCA Technology, Inc. Sampling Data Collected at
Milsolv Corporation, Milwaukee, WI-under Contract No. 68-03-3243 with
the U.S. EPA Office of Solid Waste. December 1986.
8. Breton, M., et al. Technical Resource Document - Solvent Bearing
Wastes. Prepared by GCA Technology Division for U.S. EPA, HWERL under
Contract No. 68-03-3243, Work Assignment No. 2. September 1986.
9. . Horsak, R. D., et al. Pace Company Consultants and Engineers, Inc.
Solvent Recovery in the United States: 1980 - 1990. Houston, TX.
Prepared for Harding Lawson Associates. January 1983.
10. Chemical Engineering Equipment Buyers' Guide. McGraw Hill. 1986
5-39
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5.3 STEAM STRIPPING
5.3.1 Process Description
Steam stripping by steam injection, usually into a tray or packed
distillation column, is used in both industrial chemical production and waste
treatment to remove volatile organic chemicals from waste streams. This unit
operation is most effectively applied to aqueous solutions for the removal of
volatile components that are immiscible in water. It can also be used for
stripping organic solutions when water forms low boiling point azeotropes and
does not adversely affect overhead or bottoms quality. The presence of water
must either be acceptable to or economically separable from the final product
to achieve product purity specifications.
Steam stripping is commonly employed to separate halogenated and certain
aromatic compounds from water. It is less effectively used to recover
miscible organics such as ketones or alcohols. The process is preferable to
conventional distillation processes for recovering high yields of contaminated
wastes which would otherwise foul heat transfer surfaces. It is more
economical and effective than air stripping for recovering wastes with high
concentrations of volatiles and wastes with low volatility.
Figure 5.3.1 illustrates a typical steam stripping process. Waste enters
near the top of the column and 'then flows by gravity countercurrent to the
steam. As the waste passes down through the column, volatile compounds within
the waste are lost to the steam/organic vapor stream rising from the bottom of
the column. The concentration of volatile compounds in the waste reaches a
minimum at the bottom of the column. The overhead vapor is condensed as it
exits the column and the condensate is then decanted to achieve solvent/water
separation. Reflux may or may not be used, depending upon the desired
composition of the overhead stream.
2
The common uses for steam distillation can be summarized as follows:
1. To separate relatively small amounts of a volatile impurity from a
large amount of material.
2. To separate appreciable quantities of low solubility, higher boiling
point materials from nonvolatile wastes. This requires that the
separable materials form low boiling point azeotropes with water.
5-40
-------
WASTE FEED
FROM
PROCESS
REFLUX (DECANTED AQUEOUS PHASE)
ED
WASTE
STORAGE/
PRETREATMENT
TANK
PREHEATE
R
OVERHEAD
VAPOR
INDIRECT
HEATING
COUNTERFLOW
STEAM
STRIPPING
COLUMN
I
t
NON-CONTACT
COOLING WATER
TREATED AQUEOUS
WASTE DISCHARGE
TO REBOILER, STORAGE
OR POST-TREATMENT
-RECOVERED ORGANIC
PHASE TO STORAGE
OR POST-TREATMENT
DIRECT STEAM
ADDITION
Figure 5.3.1. Typical steam stripping process.
-------
3. To recover materials which are thermally unstable or react with
other waste components at the boiling temperature.
4. To recover materials which cannot be distilled by indirect heating
even under low pressure, because of their high boiling temperatures.
5. To recover materials in instances where direct-fired heaters cannot
be used because of ignition or explosion hazards.
Theoretical Considerations—
The residual streams from steam stripping of aqueous wastes typically
consist of decanted overhead products and treated waste stream bottoms. The
stripped waste is sewered and undergoes additional treatment (e.g., carbon
adsorption) as necessary to further reduce contaminant levels. Depending on
specified purity, decanted overhead (usually organic) is either used directly
or further purified through processes such as drying or fractionation. The
overhead aqueous phase is typically returned to the stripping column if even
slight solubility exists between water and the organic components.
Using steam in distillation permits a more complete separation of
immiscible liquids at lower temperatures than non-steam distillation for the
same conditions of total pressure or vacuum* The essential feature of an
immiscible system is that each liquid phase exerts its own total vapor
pressure, regardless of the quantity .of the other liquid phase. At constant .
system pressure, the presence of steam reduces the total vapor pressure which
is required to induce boiling, thereby lowering system temperature
requirements. This permits separation of compounds which could not be
accomplished through conventional distillation due to polymerization
(e.g., cresols, vinyl-type monomers) or thermal decomposition
(e.g., halogenated compounds) of waste constituents.
The Hausbrand diagram is very useful in steam distillation calcula-
2
tions. As shown in Figure 5.3.2, it plots the total system pressure
(760 mm Hg) minus the water vapor pressure versus temperature. The
intersection of the water curve with the ordinary vapor pressure curves of the
other materials gives the temperature at which steam distillation can take
place (in this case at 1 atmosphere pressure).
5-42
-------
800 r
700 -
600 -
300
PRESSURE
(mmHg)
400 •
300 -
200 -
100 -
-WATER (760-Pw)
PENTACHLOROETHANE
1,1,2 TRICHLOROETHANE
75 100
TEMPERATURE (°C)
Figure 5.3.2. Hausbrand diagram for various halogenated
organic liquids at 1 atmosphere.
5-43
-------
While the Hausbrand diagram makes possible a quick determination of the
temperature at which a steam distillation takes place, it also presents
graphically the molar content of the vapor. In the case of the compound
1,1,2-trichloroethane, the intersection point comes at 86°C. During steam
distillation, the vapor emitted consists of 1,1,2-trichloroethylene with a
partial pressure of about 320 mm and water vapor with a partial pressure of
440 mm Hg. The corresponding weight fraction of the halogenated compound in
the vapor is 83.6 percent. Since most of the halogenated organics have much
higher molecular weights than water, the distillate is much richer by weight
than would appear from the diagram.
With the exception of certain acids, most organic compounds produce
minimum boiling point azeotropes with water. This phenomenon is
characteristic of mixtures with dissimilar molecular species with activity
coefficients greater than unity. Most halogenated organic compounds fall into
this category as manifested by their limited solubility in water.
A minimum boiling point azeotrope forms at a temperature below that of
the boiling point of the pure compounds. Unless this azeotrope is shifted to
more favorable equilibrium conditions through lowered operating pressure or
addition of a chemical complexor (entrainer), it will act to limit the
concentration which can be achieved in the overhead product. With some
organic mixtures, water can act as an entrainer to preferentially distill
compounds by creating a low boiling point azeotrope.
As compounds become dissimilar, they tend to approach liquid
immiscibility (e.g., chlorinated aromatics in water). Their equilibrium vapor
concentration will be essentially constant over an increasing range in liquid
concentrations and only begin to deviate from this level at very high or very
low liquid concentrations. Generally, the azeotrope will occur within the
liquid immiscibility composition range forming a heterogeneous overhead
product which can easily be separated into two phases. Examples clarifying
this and other concepts are provided below.
As noted above and shown in Figure 5.3.2, water and 1,1,2-trichloro-
ethane, two slightly immiscible liquids, boil at 86°C (1 atm) to form a
heterogeneous azeotrope consisting of 83.6 percent 1,1,2-trichloroethylene.
The normal boiling point of pure 1,1,2-trichloroethylene (113.7°C), is
substantially higher than the azeotrophic boiling point, thus heating costs
5-44
-------
are reduced in the presence of steam. The overhead product readily separates
into two phases, the upper layer consisting of 99.55 percent water and the
lower layer consisting of 99.5 percent 1,1,2-trichloroethylene (specific
gravity = 1.443) . Thus, steam distillation is readily applied to this
compound, particularly if it must be removed from polymerizable, nonvolatile
materials which can foul distillation equipment at the normal boiling point.
Steam stripping is also effective in instances where water acts as an
entrainer to shift the vapor-liquid equilibrium toward more desirable
conditions. For example, mixtures can shift toward higher concentrations of
the less ionic component in the overhead product in the presence of steam.
Benzene-alcohol overhead products resulting from steam stripping are more
highly concentrated with benzene relative to normal distillation and separate
into two phases upon condensing (e.g., benzene and isopropanoI/water),
thereby further separating the components. Additional information
regarding azeotrope theory and azeotropic and extractive distillation can be
4 5
found in standard engineering texts. '
In the absence of azeotrope data for particular wastes, the principal
indices used to predict steam stripping feasibility of halogenated organics
from aqueous wastes are their boiling points and Henry's Law constants.
Compounds with boiling points less than 150°C (i.e., volatile compounds), have
good steam stripping potential, as do compounds with Henry's Law constants
greater than 10 atm-m /mole. The Henry's Law constant expresses the
equilibrium distribution of a compound between vapor and liquid for dilute
solutions. It is roughly proportional to the product of vapor pressure and
the reciprocal of solubility, thus taking into consideration the miscibility
of the compound in the liquid phase. Therefore, increasing the value of the
Henry's Law constant also correlates with increasing favorability of
volatilization through the use of steam stripping.
Henry's Law constant is expressed as the ratio of mass per unit volume in
air to mass per unit volume in water. The expression is:
u 16.04 PM
H TS
5-45
-------
Where P is the vapor pressure in mmHg, M is Che gram molecular weight, T is
the temperature in °K, and S is the solubility of the solute in milligrams per
liter. The values obtained in this fashion are about 40 times greater than
values of Henry's Law constant calculated in units of atm-m /mole. Values
of Henry's Law constant are shown in Table 5.3.1 for a number of halogenated
solvents and compounds addresses in this TRD. The compounds have been divided
into three groups. A representative compound from each group was used to
assess the cost of steam stripping in Section 5.3.3.
It should be noted, however, that a study performed by the U.S. EPA/
OAQPS suggested that the use of Henry's Law constants given in the
literature for some chemicals could result in underestimating the required
contact time and overestimating the removal efficiency of steam stripping. As
part of the study, Henry's Law constants were calculated from headspace and
liquid composition sampling data. These calculated constants were
substantially less than their corresponding literature values, but did provide
good correlation with test data. It is recommended- that vapor-liquid
equilibrium data be established through headspace analysis and activity
coefficient models for more complex solutions. Alternatively, relative
volatilities in non-ideal situations can be modeled through the use of •
8
partition coefficients and critical constants.
5.3..1.1 Pretreatment and Post-Treatment Requirements--
Certain waste characteristics affect the viability of steam strippi
a waste treatment technique. Restrictive waste characteristics include:
High solubility of the organic compound in water; usually more than
1,000 ppm;
Organic compounds with high boiling points (more than 150°C);
VOC concentrations in excess of 10 percent; above this
concentration, distillation may be more cost effective; and
Suspended solids concentrations in excess of 2 percent or the
presence of materials that tend to polymerize at operating
temperatures; these can cause fouling of packing material and
eventual plugging of equipment.
5-46
-------
TABLE 5.3.1. HENRY'S LAW CONSTANTS (Hi) (mg/m3/mg/m3)
High Mi*
(3 x loMo
Medium Hi
(i
-------
Pretreatment requirements for wastes, therefore, consist of reducing high
concentrations of volatiles, solids, and polymerizable organics. Highly
concentrated volatile wastes are more economically pretreated through
conventional evaporation/distillation technologies. The diluted bottoms
product can then be treated via steam stripping.
Solids, metals, oil, and grease concentrations can be reduced through a
variety of pretreatment techniques as discussed in Section 3.0. These include
precipitation, coagulation, flocculation, centrifugation, membrane separation
processes, flotation and other chemical/physical separation processes. For
example, fouling of packing material with oxidized iron and manganese can be
reduced through pretreatment via lime precipitation. Membrane separation
processes are effective in removing high molecular weight compounds. Since
these compounds are typically nonvolatile, and thus not amenable to steam
stripping, pretreatment methods using membrane separation techniques
compliment steam stripping removal efficiency while reducing column fouling.
Post-treatment is generally required of both the overhead and bottoms
streams. Data show that steam stripping may be capable of reducing organic
concentrations in wastewater bottoms to levels which meet the land disposal
ban treatment standards. However, due to economic considerations,
conventional wastewater treatment methods (e.g., adsorption, air stripping,
biological or chemical treatment) are more commonly employed to remove
residual organic levels from aqueous streams.
Concentrated organic bottoms such as those containing high boiling point
or solid halogenated organics must be separated from the condensed steam
through decanting, centrifugation, and other physical separation techniques.
In some cases these bottoms may be recycled. Overhead products undergo
liquid-liquid separation, typically through decanting followed by dehydrating
of the recovered organic. Depending on its organic content levels, the
decanted aqueous stream is reprocessed through the stripper or treated via
other wastewater treatment processes. Alternatively, it could be used along
with a portion of the stripped wastewater bottoms to generate steam if the
boilers are properly equipped to accommodate the presence of volatile
10
components.
5-48
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5.3.1.2 Design Characteristics and Operating Parameters—
Stripping towers operate in a batch or continuous mode. Generally, batch
stripping is of less commercial interest. It is reserved for low volume
processing or for staged stripping of streams with multiple volatile
components which have different boiling points. Continuous operation more
effectively separates components of comparable volatility, provides higher
purity of separated products, and uses less stripping medium for the same
degree of separation, particularly when stripping to low levels of organics.
Three modes of flow are possible: cocurrent, countercurrent, and
crossflow. Cocurrent flow, being least efficient, is not usually used, while
crossflow operation is often preferred to counterflow since it provides
greater transfer efficiency over a wider operating range.
A tower can be operated isothermally or adiabatically. Steam stripping
is typically performed isothermally; i.e., temperature is constant along the
length of the tower. The feed is usually preheated to the boiling point
before entering the tower to minimize steam requirements and, consequently,
treated waste volume.
Reflux involves condensing a portion of the vapors from the top product
and returning it to the tower. This.can enhance separation by .increasing the
concentration of the stripped organics in the vapor stream. This occurs
because condensation of vapor in the column is required to heat the.refluxed
liquid to its bubble point. This condensation increases the concentration of
strippable components in the liquid stream which, in turn, will increase their
equilibrium vapor concentrations. This effect is more important as the
solution components become more miscible in one another.
Similarly, for miscible fluids, introducing the feed at a lower tray in
addition to refluxing can increase the concentration of organics beyond that
obtainable by reflux alone. Addition of reflux shifts the distribution in the
column from rectifying to stripping zones. A column designed with variable
feed plate location can accommodate this shift, as well as changes in waste
feed, to permit column operation at maximum efficiency.
The optimal height of the rectifying zone depends on the waste being
treated. If feed enters at the top of the column (i.e., no rectifying zone),
the limiting overhead concentration is given by the vapor equilibrium with the
feed. As the rectifying zone is increased, the overhead concentration is
similarly increased and approached the azeotropic concentration limits.
5-49
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Finally, stripping can be carried out in two types of towers. Tray
towers provide staged contact between liquid and vapor streams.
Alternatively, packed towers allow for continuous contact between the two
phases. Packed towers are less expensive, have low liquid hold-up, low
pressure drop, and are preferred for low pressure operation and treatment of
corrosive, foaming, or viscous liquids. However, tray columns have been
more widely used in the past and consequently are more predictable in their
performance. Tray columns are more flexible since they operate efficiently
over a wide range of flow rates and can be readily adapted to process multiple
feeds or sidestreams. They are also more easily cleaned and are,
therefore, preferred for processing wastes with high concentrations of metals,
solids, or polymerizable materials.
Steam stripper design is ultimately dependent on the waste character-
istics, throughput, and desired residual characteristics. Thus, tower height,
diameter, packing material, and bed volume (or type and number of trays),
materials of construction, and use of ancillary equipment (e.g., reflux, heat
exchangers) are highly specific to the waste being treated. For example, a
survey of commercial steam strippers currently in use to treat pollutants
revealed tower diameter ranges of 1.0 to 9.5 feet, column height ranges of 10
to 180 feet, and throughputs ranging from 230 gpd to as high as 500,000 gpd.
In typical applications of stripping volatiles from aqueous wastes, steam
requirements range from 10 to 30 mole percent of the feed at system pressure
of 1 atm and 100°C. Steam consumption is directly related to the
equilibrium vapor pressure of the material being stripped and its resistance
to diffusion through the waste. The latter determines the extent to which
equilibrium conditions are approached, and becomes increasingly important as
the concentration of volatile species is diminished. Equipment manufacturers
provide steam consumption data for stripping organic streams which are
appropriate if significant volatile quantities remain in the bottoms product.
For example, one manufacturer reported 1,236 Ib/hr of steam required to steam
distill spent mineral spirits in a 100 gph capacity still. Processing xylene
on the same unit would require 829 Ib/hr whereas toluene steam requirements
would be only 419 Ib/hr.10
The reader is referred to design methodologies and cost estimation
procedures which have been developed in the literature for more information on
steam stripping design, optimization, and cost effectiveness. ' ' >5>7»
. 5-50
-------
5.3.2 Demonstrated Performance
As in previous sections dealing with distillation and thin film
evaporation, very little data are available concerning the recovery of
nonsolvent halogenated compounds by steam stripping. Most of the available
data concern halogenated solvents (see Reference 2). However, the same
concepts apply to nonsolvent as apply to solvent halogenated compounds.
Azeotrophic behavior, including the use of the Hausbrand diagram, and relative
volatilization rates as indicated by Henry's Law constant can be used to
assess waste stream constituent behavior in steam stripping equipment.
Compounds in Table 5.3.1 which possess moderate to high Henry's Law constants
are good candidates for treatment by steam stripping. However, steam
stripping could be considered for other halogenated organics if, for example,
decomposition would result from recovery by distillation.
Some performance data for halogenated organic compounds are reported in
References 9, and 12 through 16. The removal data shown in Table 5.3.2., are
reported for low molecular weight halogenated organics, including some
-------
TABLE 5.3.2. STEAM STRIPPING PERFORMANCE
Influent
(mg/L)
Effluent
(mg/L)
Percent
removal
Stripper 1
Dichloromethane
Carbon tetrachloride
Chloroform
1,430
<665
<8.81
<0.0153
<0.0549
1.15
>99.99
>99.99
<86.9
Stripper 2
D i c hloromethane
Chloroform
1,2-Dichloroethane
Carbon tetrachloride
4.73
<18.6
<36.2
<9.7
<0.0021
<1.9
4.36
<0.030
>99.95
89.8
<88.0
99.7
Stripper 3
Methyl en e chloride
Chloroform
1,2-Dichloroethane
34
4,509
9,030
<0.01
<0.01
<0.01
>99.97
>99.99
>99.99
Source: Reference 14.
5-52
-------
halogenated constituents can be stripped. Depending on relative volatility, an
optional tradeoff between column height, reflux, steam rate, operating
pressure, and post-treatment costs can be established.
Treatment cost data presented in the literature were generally not useful
for predicting total waste treatment costs for a range in waste
13
characteristics. RTI presented cost data for four batches of solvent
waste. These data were for specific wastes treated in an offsite facility
and, therefore, were not indicative of general onsite processing costs. Water
General presented a detailed design and treatment cost modeling approach.
This methodology does not include an evaluation of post-treatment costs or
cost reductions achieved through waste constituent recovery. For dilute
wastewaters, these can effectively be ignored since they are relatively small
and offset one another. However, these costs can represent significant
fractions of total waste processing costs for more concentrated wastes, and
therefore, must then be taken into consideration.
Two cost analyses are presented below. The first provides capital and
operating cost equations for steam stripping of dilute wastewater streams. It
is based on a review of actual onsite steam stripping installations performed
by JRB Associates4 The second analysis, performed by GCA, is appropriate
for developing cost estimates for more concentrated wastes. This analysis
takes into consideration three residual disposal options (wastewater
treatment, use as a fuel, and incineration) and discusses the impact of
various waste characteristics and cost centers on overall processing costs.
Steam Stripping Costs for Wastewater Streams—
JRB analyzed cost and design data for 15 industrial steam strippers used
to recover secondary materials or organic priority pollutants from wastewaters
that flowed into secondary biological treatment systems. Steam strippers
used to recover or recycle primary products/raw materials were excluded from
this analysis since they differ in design from units used to treat
wastewater. In addition, tray towers were chosen for use in the analysis
instead of packed towers since tray tower data were more readily available.
Capital and operation and maintenance (O&M) costs were normalized to 1980
dollars using the appropriate Engineering News Record indices. Where
installation costs were not provided, they were assumed to be 50 percent of
5-53
-------
capital costs. Capital costs include: stripping columns, feed tanks, feed
preheaters, condensers, decanters, organic phase pumps, bottom pumps, and
existing equipment modifications. O&M costs include: operation and
maintenance labor, maintenance materials, steam, and electricity.
An analysis was performed to determine a mathematical relationship
between capital and O&M costs and significant steam stripper design parameters
such as contaminant volatility, wastewater flows, column diameter, and column
height. The results of this analysis showed that capital costs were best
related to the diameter (D, in inches) and height (H, in feet) of the column,
while O&M costs were best related to the diameter and wastewater flow (Q, in
million gallons/day) as follows:
Capital cost (in million dollars) - 0.246 - 2.88 x KT4 (D)
+ 1.546 x 10"6 (D2 H)
O&M cost (in million dollars) » 3.68 x 10~3 (D) + 0.809 (Q) - 0.023
Overall, predicted capital costs were within a factor of 3 of reported
costs, O&M cost estimates were, within a factor of 5, .and costs per gallon of
treated waste were within a factor of 3.7 of actual values. With an annual
capital recovery factor of 0.177, capital costs accounted for an average of
26 percent of total cost per gallon of treated waste. Excluding one facility
which had low capacity utilization (largest diameter tower but lowest flow
rate), costs jjer gallon of treated waste averaged 0.9 cents per gallon with a
range of 0.14 to 20.4 cents per gallon. Costs for four packed towers,
excluded from the analysis, averaged 1.12 cents per gallon. Since flow rates
to these units were only one-fourth of that in the average tray column, the
cost difference may be attributable to economies of scale.
The above data are applicable to steam stripping costs for continuous
flow columns treating dilute (i.e., less than 1 percent) organic contaminated
aqueous wastes. They do not include waste pretreatment and bottoms
post-treatment costs or net cost benefits derived from material recovery.
Overhead products consist of a volatile organic-water mixture which requires
further treatment; e.g., distillation or additional stripping. Additional
overhead processing costs may be offset by benefits resulting from recovery
5-54
-------
(e.g., reduced raw material purchase requirements) and therefore these costs
can be neglected. Bottoms post-treatment will be required if organic compound
concentrations continue to exceed disposal limits or if the waste is still
considered to be hazardous due to the presence of other nonvolatile
contaminants. Post-treatment by activated carbon, biological treatment, or
other methods add roughly 2 cents per gallon to waste treatment costs.
JRB also attempted to determine cost variability as a function of
contaminant volatility. JRB used the design methodology provided by Water
General Corporation to determine variability in column height and capital
cost required to strip compounds with different Henry's Law constants. Water
General's methodology involves calculation of a stripping factor which is
proportional to Henry's Law constant, .the vapor/liquid flow ratio, and the
reciprocal of tower operating pressure.
JRB assumed a steam-to-liquid feed ratio of 10 percent and atmospheric
column operating pressure. Costs were based on stripping to a maximum
residual VOC concentration of 1 ppm. Minimum column diameter was set at
1.0 feet and minimum height at 10 feet to reflect wastewater processing
equipment currently in use. '
Table 5.3.3 summarizes the resulting cost data based on the above
assumptions. As shown, cost per gallon of waste treated shows little
variability between compounds with different volatility. However, if JRB's
column size constraints were removed, the data would show lower treatment
costs for wastes with highly volatile constituents and low flow rates. Also,
operating costs would constitute a higher fraction of total costs since
optimal operating conditions would, in some cases, be represented by higher
steam rates instead of increases in column height.
Steam Stripping Costs for Nonaqueous Wastes—
GCA performed a cost analysis for steam stripping of nonaqueous wastes
using three nominal flow rates (10, 50, and 500 gpb) and three disposal
12
methods; i.e. wastewater treatment, use as a fuel, incineration. The cost
of stripping concentrated wastes (i.e., greater than 1 percent organic
constituents) is highly dependent on disposal method. These disposal methods
were selected because they represent a wide range in stripped product
characteristics (i.e., aqueous, concentrated organic with Btu value such as
5-55
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TABLE 5.3.3. STEAM STRIPPING COSTS FOR WASTEWATER STREAMS CONTAINING CONTAMINANTS
OF VARYING HENRY'S LAW CONSTANT
Henry* s Law
constant range Example compound
**1
Greater than 10 1,1,1-Trichloroethane
—o —3
10 to 10 Acrylonitrile
-4
Leas than 10 Nitrobenzene
-
: *
Flow
Rate
(MGD)
1.0
0.10 ,
0.01
1.0
0.10
0.01
1.0
0.10
0.01
Height
(ft)
t
10.0
10.0
19.6
14.2
18.8
30.9
36.1
42.9
65.2 '
Diameter
(ft)
6.28
2.11
1.00
6.28
2.11
1.00
6.28
2.11
1.00
Capital
Cost
($MM)
0.312
0.249
0.247
0.349
0.257
0.249
0.540
. 0.281
0.257
O&M
Cost
UMM)
1.06
0.151
0.029
1.06
0.151
0.029
1.06
0.151
0.029
t
Unit cost
U/gal)a
0.36
0.63
2.30
0.36
0.63
2.30
0.37
0.64
2.40
aAasinning 312 operating days/year and an annual capital recovery factor of 0.177.
Source: Adapted from JRB. Reference No. 7.
-------
oil, and highly contaminated organic material) and disposal costs. Other
major cost variables considered included capital, installation, maintenance,
labor, overhead and utility costs and value of recovered organics.
Capital costs for process equipment, tanks, engineering, electricity
and instrumentation were taken from the literature.^ A contingency of
15 percent and an annualized cost of 17.7 percent of the total were
assumed as summarized in Table 5.3.4. Maintenance costs for steam strippers
were based on an EPA estimate of 4.13 percent of annualized capital
cost.11 Labor costs were assumed to be $14.42/hour including overhead.1?
Labor usage was assumed to range linearly from 0.5 to 3.0 operators for
the flow rates under consideration, with a base case operating time of
2,080 hours/years.
Utility costs were assumed to average $0.04/gallon of recovered
volatiles. This value is based on the cost of steam ($3.00/million Btu)ll,
electricity ($0.04/KWH), and cooling water ($0.25/1,000 gallons) necessary
to separate and condense volatiles from an organic-water mixture. This
value will vary depending on the material to be recovered. For example,
at 1'percent volatile organic concentration, utility costs range from
approximately 2 cents (e.g., acetyl chloride) to 7 cents (e.g., hexachloro-
butadiene) per gallon of recovered organic, depending primarily on the
compound's boiling point in the mixture. Utility costs for more highly
concentrated waste depend on both the boiling temperature and heat of
vaporization of the constituent to be separated, and range from roughly
3 to 6 cents a gallon of recovered compound. ' Since utility costs
generally represent a small fraction of total treatment costs, an average
value of 4 cents per gallon was assumed.
Three methods of bottoms disposal were used in this analysis. Waste-
water treatment technologies such as adsorption and.biological treatment
were assumed to cost 2 cents per gallon. Organic bottoms which could be
used as a fuel substitute were assumed to cost $0.20/gallon and bottoms
which required incineration (e.g., liquid injection) were assumed to cost
$2.00/gallon.
Finally, recovered organic compound (95 percent recovery) was assumed
to have a value of $2.00/gallon for the purposes of calculating overall
unit cost of waste treated. Although many halogenated organics have
higher purchase prices, this value was used since many recovered materials
will be in the form of less valuable mixtures or require additional
treatment to achieve purity specifications.
5-57
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TABLE 5.3.4. COST COMPONENTS FOR ONSITE STEAM STRIPPING HALOGENATED
ORGANIC COMPOUNDS RECOVERY: (EXAMPLE CASE WITH 30 PERCENT
HALOGENATED ORGANIC CONTENT AND BOTTOMS USED AS FUEL)
Nominal feed rate (gpb)
Capital costs
Process equipment
Tanks
Subtotal (1)
Engineering, electrical,
instrumentation (20Z of (1))
Subtotal (2)
Contingency (15Z of (2))
Subtotal (3)
10
8,000
18,500
26,500
5,300
31,800
4,800
36,600
50
39,000
18,500
57,500
11,500
69,000
10,400
79,400
500
72,000
74,000
146,000
29,200
175,200
26,300
201,500
Annualized capital cost (17.7Z of
Subtotal (3))
Operating and maintenance costs3
Maintenance (4.13Z of annualized
capital cost)
Labor ($30,.000/man-year
including overhead)
Utility costs (44/gallon of
recovered solvent)
Compound recovery benefit cost
($2/galIon of recovered compound)
Disposal cost ($0.20/gallon)
Net O&M cost
Total capital and O&M cost
Cost/gallon of waste treated
Threshold cost of recovered compound
($/gallon)
6,478
268
14,054
580.
15,000 22,800
237
1,186
35,666
1,473
90,000
11,856
(11,850) (59,300) (592,800)
3.391 16.953 169.530
7.046 (17.781) (3J9.941)
13.524 (3.727) (284.275)
0.65 (0.04) (0.27)
4.24
1.83
1.00
^Numbers in parenthesis represent revenues.
5-58
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Table 5.3.4 provides an example cost analysis for Creating waste
containing volatile organics and using the residual bottoms product as a
fuel. Table 5.3.4 summarizes the results of the cost analysis for wastes
ranging from 1 to 70 percent volatile organics for the three bottoms disposal
scenarios. Cost figures are presented on the basis of cost per gallon of
waste treated and threshold cost per gallon of volatile organics recovered.
Table 5.3.5 presents steam stripping costs as a function of throughput,
volatile organic compound content and disposal method. The table demonstrates
that stripping costs increase dramatically with increasing bottoms disposal
cost, particularly for high flow rate units. For example, at 10 gpm and
10 percent organic content, disposal costs for wastewater treatment account
for only 4 percent of total treatment costs. This fraction jumps to 16 and
66 percent for disposal, by fuel and non-fuel incineration, respectively. At a
feed rate of 500 gpm, disposal costs became even more significant, accounting
for 24, 61, and 93 percent of total costs as more expensive disposal methods
are used. These costs are lower for wastes with higher percentages of
recoverable organics. However, disposal costs remain significant for
high-volume units with nonaqueous bottoms products, unless they too can be
reused as a product stream.
As capacity and percent recoverable volatile organic increase, total
treatment cost becomes increasingly sensitive to the value of recovered
overhead. For example, at 10 gpm with 10 percent volatile organics in the
waste, the total value of recovered overhead is 16 percent of processing costs
(assuming a $2.00 value per gallon of recovered overhead and using bottoms as
fuel). This percentage jumps to 113 percent as volatile organic content in
the feed increases to 70 percent, and increases further to 554 percent of
processing costs if capacity is then increased to 500 gpm. Thus, unit value
of recovered organics has an increasingly significant impact on processing
economics as throughput and percent recoverable organics increase.
Utility costs show a similar relationship to throughput and recoverable
organics content. For wastes with less than 10 percent volatile organics,
utility costs are only a few percent of total costs. At high flow rate and
high volatile organic content, however, these costs become significant. For
example, at 500 gpm and 70 percent volatiles in the feed, utilities account
for 11 percent of total processing costs when bottoms are used as fuel
(2.6 percent when bottoms are incinerated).
5-59
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I
••' I
TABLE 5.3.5. STEAM STRIPPING COST ESTIMATES AS A FUNCTION OF THROUGHPUT, VOLATILE ORGANIC
COMPOUNDS CONTENT AND DISPOSAL METHOD
Bottoms
disposal
method
Waatewater
treatment
/
Use as fuel
Incineration
Organic
content in
waste (%)
1
5
10
10
30
50
70
10
30
50
70
Cost (*)/gal
of waste
10 gph 50 gph
1.05
0.98
0.89
1.05
0.65
0.24
(0.17)
2.00b
2.00b
1.36
0.61
0.36
0.29
0.21
0.37
(0.04).
(0.45)
(0.85)
2.00b
1.43
0.68
(0.07)
treated8
500 gph
0.12
0.06
(0.03)
0.13
(0.27)
(0.68)
(1.09)
1.93
1.19
0.44
(0.31)
Cost (t)/gal
10 gph
108.00
21.79
11.01
13.11
4.24
2.46
1.70
b
t
b
4.83
2.88
of organic
50 gph
38.58
7.95
4.08
5.90
1.83
1.02
0.67
b
6.98
3.39
1.85
recovered8
500 gph
14.59
3.15
1.68
3.39
1.00
0.52
0.31
22.36
6.15
2.89
1.49
8Numbers in parenthesis represent revenues.
"Cost of treatment via steam stripping exceeds incineration cost of raw waste ((2.00/gallon),
therefore, incineration represents the lower cost alternative.
-------
In contrast to disposal and utility costs, capital and labor represent
the primary costs of processing low volume, dilute wastes. Capacity
utilization is more critical for low volume units since capital costs are
distributed over the total volume of waste processed. For example, increasing
processing time from 8 to 16 hours per day reduces processing costs by
16 cents per gallon for 10 gpm units versus only 1 cent per gallon for 500 gpm
strippers.
5.3.4 Overall Status of Process
5.3.4.1 Availability—
Steam stripping is a commonly applied waste treatment technology for
separating low solubility halogenated organic compounds from water or low
volatility organics (e.g., oil). The EPA has identified 27 industrial steam
stripping wastewater treatment units; 11 units used by the pesticides
industry, and 8 steam strippers (packed towers) used by a pharmaceutical
manufacturer. GCA's analysis of the commercial solvent recycling industry
showed 25 percent of the reclaimers using steam distillation. This technology
is directly applicable to waste streams containing halogenated organic
compounds provided relative volatiles are sufficient to effect separation.
5.3.4.2 Application-
Steam stripping is commonly used as a pretreatment method, particularly
when applied to concentrated solvent wastes. In many cases it can be used to
reduce solvent concentrations to levels which permit direct discharge,
although it is often more cost-effective to use other treatment methods for
final bottoms processing. The extent to which steam stripping is applied to
halogenated organic compound wastes is unknown, but it should be equally
effective for many of these compounds. Steam stripping of wastewater streams
is typically followed by biological treatment or adsorption systems for final
effluent polishing. Stripped organic waste bottoms can be decanted and used
as fuel provided that chlorine content has been sufficiently reduced in the
stripper or diluted with other fuels. In the case of nonvolatile compounds,
reuse of bottoms product as a feedstock may be possible.
5-61
-------
5.3.4.3 Environmental Impact—
Post-treatment of both the overhead and bottoms streams is usually
required to attain proposed effluent standards, although in certain instances
the organics concentration in the bottoms stream may be below proposed
standards. Overhead products typically undergo liquid-liquid separation
through decanting to achieve effluent specifications. However, the organic
compound may require drying and the aqueous phase may require further
treatment to remove dissolved organics. Air emissions from column vents can
be significant and should, at least, be monitored.
5.3.4.4 Advantages and Limitations-
Steam stripping is preferrable to other physical separation technologies
in the following instances:
• Treating wastes which contain high solids or polymerizable materials
which would otherwise foul heat transfer surfaces;
• Treating wastes which contain constituents that form low boiling
point azeotropes with water, particularly those which require low
processing temperatures due to thermal degradation; and
• Treating wastes to low residual organic compound content,
particularly when the bottoms product would be rendered unpumpable
in the absence of water.
Steam stripping is not well suited to treating wastes in which either the
overhead or bottoms.are difficult to separate from water. It is better
utilized for separating organics which decant readily and have low
solubilities in water (e.g., halogenated organics) and less applicable to
treating water soluble wastes such as alcohols.
5-62
-------
REFERENCES
1. Allen, C. C., and B. L. Blaney. Techniques for Treating Hazardous Waste
to Remove Volatile Organic Constituents. Research Triangle Institute
performed for U.S. EPA HWERL. EPA-600/D-85-127, PB85-218782/REB. March
1985.
2. EHerbe, R. W., Steam Distillation/Stripping. The Rust Engineering
Company. In: Handbook of Separation Techniques for Chemical Engineers.
McGraw-Hill Book Company, New York, N.Y. 1979.
3. Weast, R. C., Handbook of Chemistry and Physics. 65th Edition, CRC
Press, Cleveland, OH. 1984-1985.
4. Perry, R. H., Chemical Engineers' Handbook, 6th Edition, McGraw-Hill
Book Company, New York, N.Y. 1984.
5. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons,
New York, N.Y., 3rd Edition. 1978.
6. U.S. EPA Office* of Solid Waste. Background Document for Solvents to
Support 40 CFR Part 268 Land Disposal Restrictions. Volume II. Analysis
of Treatment and Recycling Technologies for Solvents and Determination of
Best Available Demonstrated Technology. U.S. EPA Public Docket. January
1986.
7. JRB Associates and Science Applications International Corporation.
Costing Documentation and Notice of New Information Report. Draft Report
prepared for U.S. EPA. June 1985.
8. U.S. EPA Office of Solid Waste. Analysis of Organic Chemicals, Plastics
and Synthetic Fibers (OCPSF) Industries Data Base. U.S. EPA Public
Docket. January 1986.
9. Arienti, M., et al. GCA Technology Division, Inc. Technical Assessment
of Treatment Alternatives for Wastes Containing Halogenated Organics.
Draft Report prepared for U.S. EPA Office of Solid Waste under EPA
Contract No. 68-01-6871. October 1984.
10. Michigan Department of Commerce. Hazardous Waste Management in the Great
Lakes: Opportunities for Economic Development and Resource Recovery.
September 1982.
5-63
-------
11. Shukla, H. M., and R. E. Hicks. Water General Corporation, Waltbam, MA.
Process Design Manual for Stripping of Organics. Prepared for U.S. EPA
IERL. EPA-600/2-84-139. August 1984.
12. Breton, M., et al. Technical Resource Document - Solvent Bearing
Wastes. Prepared by GCA Technology Division, Inc. for HWERL, CIN under
Contract No. 68-03-3243, Work Assignment No. 2, September 1986.
13. Allen, C. C., Research Triangle Institute, and Simpson, S., and G. Brant
of Associated Technologies, Inc. Field Evaluation of Hazardous Waste
Pretreatment as an Air Pollution Control Technique. Prepared for U.S.
EPA HWERL under EPA Contract No. 68-02-3992. January 1986.
14. Jett, G. M. Development Document for Expanded Best Practicable Control
Technology, Best Conventional Control Technology, Best Available Control
Technology in the Pesticides Chemicals Industry. Effluents Guidelines
Division, U.S. EPA. EPA-440/l-82-079b. November 1982.
15. Coco, J. H., et al. Gulf South Research Institute, New Orleans, LA.
Development of Treatment and Control Technology for Refractory
Petrochemical Wastes. U.S. EPA, ADA, OK. EPA-600/2-79-080. April 1979.
16. Stover, E. L., and D. F. Rincannon. Contaminated Ground Water
Treatability - A Case Study. Journal of the American Water Works
Association. June 1983.
17. Horsak, R. D., et ale Pace Company Consultants and Engineers, Inc.
Solvent Recovery in the United States: 1980-1990. Houston, TX.
Prepared for Harding Lawson Associates. January 1983.
5-64
-------
5.4 LIQUID - LIQUID EXTRACTION
Liquid - liquid extraction is the separation of constituents of a liquid
solution by transfer to a second liquid, immiscible in the first liquid, but
for which the constituents have a preferential affinity. Although not a
commonly used waste treatment technology, liquid-liquid extraction has
potential for removal of many organic constituents from effluent waste
streams. Liquid extraction can be attractive in cases where the solutes in
question are toxic or non-biodegradable, where the solutes are present at
sufficiently high concentrations to provide economic recovery value, when
steam stripping would be rendered less effective by low solute volatility or
formation of azeotropes, or when high solute concentrations increase activated
carbon adsorption costs to excessive.levels. Historically, its general
application to wastewater treatment has been limited to removal of high
concentrations (5 percent or greater) of phenol and phenolic compounds. Steam
stripping is not very effective on phenolic compounds because of their low
Henry's Law constants and activated carbon adsorption is not feasible at these
high concentrations.
5.4.1 Process Description *
The liquid-liquid extraction process'is shown in Figure 5.4.1. The
typical process includes the following basic steps:
1. Extraction of organic pollutants from wastewater,
2. Recovery of solute from the solvent phase or extract, and
3. Removal of solvent from treated wastewater or raffinate.
The first extraction step brings two liquid phases (feed and solvent)
into intimate contact to allow transfer of solute from the feed to the
solvent. Any method by which single or multistage mass-transfer processes can
be conducted can conceivably be used .to conduct liquid extractions. For
example, an extractor unit can be a mixer-settler device in which feed and
solvent are mixed by agitation, then allowed to settle and separate into two
5-65
-------
SOLVENT and SOLUTE
UNTREATED
WASTEWATER
EXTRACT!*
RAFF)
(WATER and
NATE
SOLVENT)
SOLVENT
REMOVAL
SOLVENT
SOLVENT
RECOVERY
and
SOLUTE
REMOVAL
^SOLUTE j
TREATED WATER
Figure 5.4.1. Schematic of extraction process.
-------
liquid streams. Alternatively, it can be a column in which two liquids are
brought into contact by counter-current flow caused by density differences.
The process yields two streams, the cleaned stream, or raffinate, and the
extract, or solute-laden solvent stream.
The second step, solvent regeneration, can be accomplished by a second
extraction or distillation. For example, a second extraction with caustic may
be. used to extract phenol from light oil (the primary solvent in dephenolizing
coke plant wastewaters).
Distillation is a more common solvent regeneration process. Potential
difficulties with distillation may arise if azeotropes are formed, or if the
relative volatilities of the solvent and the extracted compound are close
enough to hinder separation.
The third step, removal of solvent in the treated wastewater or
raffinate, is necessary when solvent concentrations are great enough to create
solvent losses that would add significantly to the process cost or have a
detrimental environmental impact. Solvent removal can be accomplished by a
number of technology options. When treating large quantities of dilute
wastes, an additional extraction step usually cannot economically compete with
other technologies such as stripping, biological or adsorption post-treatments.
5.4.1.1 Pretreatment Requirements for Different Waste Forms and
Characteristics--
Pretreatment is necessary to remove material which will interfere with
•
the mass transfer of the organic contaminant into the solvent extract.
Reduced mass transfer efficiency results in the need for higher
solvent/aqueous phase ratios to obtain desired levels of extraction. Thus,
any emulsion or organic phase droplets should normally be removed prior to
treatment. Solids, to the extent that they retain sorbed contaminants or
hamper column performance, should also be removed. In certain cases dissolved
solids can also affect partitioning of the solute(s), and removal or addition
of dissolved solids may be desirable to enhance the separation. Similarly,
changes in temperature may also modify partitioning behavior. Phase
distribution data, if not available in the literature, will generally have to
be developed in the laboratory. An estimation method based on vapor liquid
data for binary systems can be used to estimate the distribution of an organic
compound (at low concentrations) between water and an organic solvent.
5-67
-------
5.4.1.2 Operating Parameters—
In the simplest case of liquid extraction, the solvent is added to a
liquid mixture, causing a second liquid phase to form. It may be desirable to
add a salt to an aqueous phase to enhance the activity of a component, causing
it to transfer into a nonaqueous phase in which the salt is insoluble.
Similarly, adjusting the pH of an aqueous phase containing organic acidic or
basic solutes will depress their ionization potential and cause them to
concentrate in the nonaqueous solvent phase. It is also often helpful to
change the temperature of the phases in contact to give the most favorable
equilibrium at each step of the extraction.
Theoretically, any aqueous organic waste can be treated by extraction.
However, determining potential feasibility requires a series of analyses to
assess overall system applicability. Much depends on how residual solvent is
to be removed from the treated water stream, how the solvent is to be
regenerated, and what restrictions exist for each unit operation.
In general, extraction is best suited for waste streams of consistent
composition to assure satisfactory performance. In cases where performance is
less important, acceptable ranges in waste characteristics become broader, as
in th6 case where extraction is to be used as a pretreatment. For example,
when several waste streams are to be combined for final treatment, a single
waste stream with higher constituent concentration may be extracted to reduce
the load on the final treatment process.
As noted in Perry's Chemical Engineers' Handbook, the removal mechanisms
in extraction are primarily physical, since the solutes being transferred are
ordinarily recovered without chemical change. The physical equilibrium
relationship on which such operations are based depend mainly on the chemical
characteristics of the solutes and solvents. The use of a solvent that
chemically resembles one component of a mixture more than the other components
will lead to concentration of .that like component in the solvent phase.
The choice of solvent is a key factor in evaluating the utility of liquid
extraction as a means of removing hazardous organic compounds from aqueous
waste streams. Perry, et al.,1 lists characteristics which must be assessed
in selecting a solvent. These are:
5-68
-------
• Selectivity-the ability of a solvent to extract the organic
contaminant preferentially from the aqueous phase. It is a
numerical measure that is equal to the ratio of the distribution
constants of contaminant and water in the solvent. As such, it is
analogous to relative volatility as used in distillation. Poor
selectivity (ratios near unity) means large solvent feed ratios and
a large number of extraction stages will be needed for good
separation.
• Recoverability-the solvent must be recoverable from both extract and
raffinate. Since distillation is the usual recovery method,
relative volatilities of all components should be favorable and low
latent heats for volatile'solvents are desirable.
• Distribution Coefficient-the distribution coefficient of the
contaminant should be large in order to achieve selectivity and
reduce equipment size and costs.
• Contaminant Solubility-the solubility of the extracted contaminant
in the solvent should be high in order to reduce solvent
req ui rement s.
• Solvent Solubility-the solubility of the solvent in the aqueous
phase should be low. This will generally increase selectivity and
the range of waste stream concentrations that can be handled, and
reduce costs of solvent recovery or makeup.
• Density-a difference in density is essential since the flow rates
and separation of the two phases is directly affected.
• Interfacial Tension-the interfacial tension should be large to
assist in the coalescence of dispersed phase droplets.
• Other-other des.irable solvent properties are low corrosivity, low
viscosity for higher mass transfer rates, nonflammability, low
toxicity, and low cost.
A guide to solvent selection may be provided by binary critical solution
temperatures of solute components with prospective solvents. The solvent
having the lower critical solution temperature with the solute compound will
be more selective in an extraction from the aqueous phase.
A significant quantity of data have been collected for the distribution
of pollutants in water and various extractive solvents. These values, called
equilibrium distribution coefficients (K_.), generally express the
equilibrium concentration of the solute as the ratio of the weight percent in
solvent relative to water:
5-69
-------
where: Xog the weight fraction of organic solute in the solvent
phase, and
Xoa is the weight fraction of organic solute in the aqueous
phase, both at equilibrium.
K_ values for the octanol/water system for the halogenated organic
compounds of interest are provided in Appendix A. These data represent just a
small fraction of the data available in the literature for ternary systems
consisting of water and two organic compounds. For example, a number of
references are provided in Perry along with distribution coefficients for
over 200 selected water/organic solute/organic solvent systems which include
some of the organic compounds of concern. Values of K_ that are specific to
the compounds of concern are provided in a number of recent publications.
These data, of use in assessing the potential of liquid-liquid extractions as
a treatment technology are provided in Table 5.4.1 and in Table 5.4.2. These
2
data were reported in the AIChE Symposium Series (1981) by S. T. Hwang,
using References 3 through 6 as additional data sources.
Higher values of K^ (or K.J mean that less solvent is required to
extract a given amount of solute from the wastewater which usually translates
into a less expensive extraction processes. The ratio of the distribution
coefficients of solvent systems for extraction of a specific compound from
water is a measure of the relative amounts of solvent that must be employed to
achieve a given level of extraction. As shown in the table, distribution
coefficients increase with increasing chlorine content, paralleling the
solubility behavior of these compounds in water. In general, chlorinated
compounds would appear to be well suited for recovery by extraction, however,
distribution coefficients are only one of the many solvent properties that
8
must be considered.
The Chemical Engineers' Handbook, Kirk Othmer (Reference 7) and other
background materials present calculation and design methods that can be used
to assess the applicability of liquid-liquid extraction to specific waste
streams. The techniques generally involve the use of equilibrium distribution
data to develop equilibrium and operating line curves. These can be used to
5-70
-------
TABLE 5.4.1. KV VALUES FOR AQUEOUS/ORGANIC SYSTEMS8
1
Solute
carbon tetrachlorlde
( tetrachloromethane) .
chlorobengene
1,2,4-trlchlorobentene
hexachlorobencene
,2-dichtoroethane
, \ , l-trlchloroethane
lexachloroe thane
, l-dlchloroethane
, 1 ,2-t richioroethane
,1,2,2-tetrachloro-
e thane
chloroethane
bla (chloroethyl) ether
bla (2-chloroethyl>
ether
2-chloroethyl vinyl
ether (nixed)
2-chloronnphthalene
2 ,4,6-trlchlorophenol
parachlorometa crelol
chloroform
(trlchloronethane)
2-chlorophennl
1 ,2-dlchlorobcntene
1,3-dichlorobensene
1 ,4-dlchlorobeniene
1 , 1-dlchloroethylene
1 ,2-trana-dlchloro-
ethylene
2,4-dichlorophenol
1 , 2-d ichloropropane
1 ,3-dlchlaropropylene
( 1 , 3-dichloropropene)
biB(2-chlorolaopropyl
ether
bi>(2-chloroethoxy)
fricresyl
phosphate
480
250
17,000
91,000
31
81
11,000
SI
74
75
28
21
IS
33,000
1,374
188
80
90. 5
2,700
2,700
2,800
1,100
700
304
120
120
162
7
Undecane
380
260
12,000
290,000
10
120
3,500
56
70
27
31
19
35
2,500
9
l.S
46
0.9
1,900
2,800
830
1,000
260
3
12S
130
430
9
H1BK
930
1,200
20,000
750,000
38
220
9,600
140
220
8$
62
90
34
28,000
4,900
667
117
432.2*
3,800
4,600
2,500
1,200
840
1,080
330
4SO
430
8
Trldecane
300
200
10,000
200,000
8
110
2.500
52
64
20
30
17
31
2,200
9
1.5
44
0.9
1,600
2,400
600
900
210
3
114
120
360
8
Bensene
2,200
2,900
66,000
IxlO7
100
270
62 ,000
100
200
590
43
82
60
29,000
144
25
88
15
11,000
13,700
12,600
2,750
1,500
46
275
370
850
15
Solvent
laobutylene
1,200
685
15,000
68,000
41.6
190
8.600
94
no
61
so
36
. 57
5,000
27
5
76
3
2,300
3,500
2,000
1,200
710
9
200
230
980
26
Iiobutane
810
445
10,000
37,000
24
150
5,300
70
80
37
40
22
45
2,500
7
1.2
57
0.7
1,600
2,500
1,260
960
510
3
ISO
160
680
17
n-butyl
acetate
870
1,200
19,900
7x10*
37
210
9,400
140
210
85'
60
90
30
29,000
2,610
357
116
255.8
3,800
4,580
2,400
1,100
810
580
320
450
350
6
laobutyl
acetate
900
1,060
19,000
6.9xl05
36
210
9,000
130
200
80
60
80
33
25,000
4.123
563
111
272
3,500
4,350
2,300
1,120
810
911
340
420
410
•8
Dliaopro-
pyl ether
990
460
14,400
5.2x10*
32
150
7,600
68
86
60
37
24
44
8.000
1,580
217
56
IDS
2,300
3,400
2,000
1,150
830
351
ISO
150
630
14
Octanol
436
692
18,200
1.5x10*
38
92
8,800
138
224
86
35
94
20
24,000
2,400
1,260
93
141
2,400
2.400
2,455
999
738
562
30S
. 474
176
3
(continued)
-------
TABLE 5.4.1 (continued)
Solvent
Trlcreayl
Solute plioophate
ncthylene chloride
(dlchloroM thane)
methyl chloride
(chloromethane)
methyl broalde
(bromnroethane)
broraofom
(tcibromoethane)
dichlorobronoraethane
trichlorofluro-
raethane
dichlorodif luro
methane 2,
chlorodlbromoaethane
hexachlorobutadie'ne
hexachlorocyclopen-
tadiene 26,
\SpeclClc Gravity
D ° Specific Gravity
13
9
412
143
22
563
400
30
288
000
of Solvent
of Water
Undecane
15
10
460
140
22
690
7,400
28
90
25,000
Grans !
* Cram
HIBK
SO
18
960
530
62
980
6,700
' 140
270
40,360
Solute/1.000
Trldecane
12
9
450
130
20
650
6,000
26
99
20,900
•1 Solvent
Benzene
106
14
7 SO
500
SO
770
•
5,300
120
9,500
86,000
laobutylene
36 "
14
680
240
36
1,120
38,000
53
180
52.000
leobutane
26
11
550
160
27
950
33,000
32
86
34,000
• n-butyl
acetate
50
18
960
540
62
"
939
5,000
140
280
36,900
lapbutyl
acetate
46
17
930
490
59
955
6,330
130
240
37,600
Dlisopro-
pyl ether
24
11
530
160
27
850
15,000
34
140
37,000
Octanol
72
30
1,000
610
63
740
4,500
173
299
2.4«104
Solute/1, 000 ml Hater
-------
TABLE 5.4.2. Ky VALUES FOR AQUEOUS/ORGANIC SYSTEMS8
Solute
carbon tetrachloride
(tetrachloroaethane)
hlorobentene
,2,4-trlchlorobenxene
exachtorobencene
,2-dlchlorocthnne
, 1. 1'trichloroethane
lexachloroethane
, 1-dlchloroethane
, 1 , 2-t r tchloroethane
,1,2,2-tetra-
chloroethane
chloroethane
bla(chloroethyl) ether
bi>(2-chloroethyl>
ether
2'chloroethyl vinyl
ether (nixed)
2-chloronaphthalene
2.4,6-t rtclilorophenol
parachlorometa creaol
chloroform (trlchloro-
methane)
2-chlorophenol
1 ,2-dlchlorobcnxene
I ( 3-d ichlorobensene
1 ,4-d Ichlorobenxene
3, 3-dichlorobenxldine'
1, l-dlchloroethylene
1,2-trana-dichloro-
ethylene
2,4-dlchlorophenol
1,2-dlchloropropane
1,3-dichloropropylene
(1,3-dlchloropropene)
4-chlorophenyl phenyl
ether
Cumene
1,460
1,080
35,000
2.6xt06
72
196
2.4x10*
66
108
229
33
34
*2
1.6x10'*
1,650
225
56
110
5,970
7,800
5,800
|
1,900,
1,300
364
170
168
3,000
Meaityl
oxide
770
1,700
19,900
6.3xl05
34
212
8,183
163
256
75
67
114
3.7x10*
2.450
348
134
200
4,000
4,560
2,170
4
990
738
560
369
555
972
HEK
690
3,480
19.600
4.7x10'
30
221
6,600
200
309
60
79
148
4.9x10*
2,950
404
162
200
4,057
4,500
1,788
10
870
665
650
440
703
808
Ethyl
acetate
668
2,360
17.000
4.2x10*
28
208
6,100
186
278
54
75
129
23
41,000
4.027
550
150
265
3,560
4,047
1,656
6
840
640
890
404
632
784
Ethyl
ether
1,200
1,000
20,000
7.5xlOJ
40
239
1x10*
127
174
82
61
63
5*
1.9x10*
2,721
372
103
. 179
3,400
4,660
2,570
6.2
1,360
982
600
396
333
3.178
Solvent
Ethyl
beniene
1,266
1,450
43,000
4.2x10°
55
22
2.8x10*
93
165
261
40
64
50
2x10*
200
34
79
20
7,327
9.295
6,000
3
2,127
903
62
234
315
5,670
n-hexanol
236
1,180
9,090
1.2x10*
14
96
1.184
130
202
22
50
92
3.8x10*
1,980
270
109
130
2,248
2.240
673
17
359
294
437
250
492
73
EDO
2,329
3,700
73,000
1.9xl07
1*2 .
212
9x10*
55
115
963
25
38
1x10*
322
56
48.3
J?
1.2x10*
1.5x10*
1.8x10*
30
2,770
1,768
102
158.8
180
8,500
Toluene
1,570
1,660
51,000
5.7xl06
70
248
3.7x10*
101
184
340
43
72
54
2.3x10*
89
16
86
9
5.670
1x10*
7,766
3
2,400
1.100
28
259
246.8
7,300*
Xylene
2,069
2,500
75.700
6.8xl06
92
388
4.7x10*
163
290
432
70
110
"S
3.5x10*
70
12
138
'
1.3x10*
1.6x10*
9.9xl03
4
3,800
1,488
22
407
548
8,300
n-hexane
866
610
18,500
8x10*
24
177
8,600
73
95
66
39
28
50
4.000
7
1.2
60
0.7
2,880
4,280
1,968
0.09
1,330
562
3
170.05
178.8
4,500
(continued)
-------
TABLE 5.4.2 (continued)
Solvent
Solute Cumene
4-broMophenyl' phenyt
ether
bis(2-chloroisoprophyl)
ether
bia(2-ehloroethoxy)
methane
•ethylene chloride
(dichloroaethane)
•ethyl chloride
(chloronethnne)
•ethyl bronide
(broraomethane)
bromoCom
( tribromomethane)
dlchlorobromoae thane
trlchlorof luro~
•ethane
dichlorodif luro
•ethane
chlorodib ronome t hane
hexachlorobutadlene
hexachlorocyc lopen*
tadlene 5.
tetrachloroethylene
toluene
trichloroethylene
vinyl chloride
DDT
lleptachlor
Heptachlor epoxide
a- .. Specific Gravity
% D * Specific Gravity
2,090
656
12
46
10
509
208
10
701
5,127
41
1,450
5x10* 3
5,500
1,100
175
19
of Solvent
of Water
Meaityl
oxide
149
287
5
69
20
1,090
682
71
925
4,180
197
212
.6x10*
8,700
606
1,074
58
Grama !
' Craaa
MEK
241
256
5
106
24
1,300
880
89
1,000
4,600
272
158
4x10*
1.1x10*
527
1,320
63
iolute/1,000 i
Solute/1,000
Bthyl.
acetate
211
253
5
89
22
1,200
778
61
975
23,000
217
115
1.6x10*
1.1x10*
506
1,220
62
•1 Solvent
•1 Hater
Ethyl
ether
4,437
881
21
49
16
864
166
52
• 1,200
2.1x10*
88
227
5.8x10*
5,100
919
771
65
Ethyl
bentene
4,610
662
12
59
14
700
418
44
718
4,571
104
1,000
60,000
7,100
1,290
595
42
n-hexanol
46
31
0.4
58
20
1,049
696
61
454
269
250
40
1x10*
5,200
170
840
15
BDC
2.7x10*
518.7
8
114
9
414
218
28
501
2,578
41
2.1x10*
6.2x10*
17,000
2,674
144
10
Toluene
6,580
751
14
68
15
751
462
48
771
4,500
115
4,140
69,000
8,200
1,690
650
45
Xylene
7,400
1,066
19
101
24
1,249
714
77
1,249
7,180
181
4,976
975,000
1.2x10*
2,080
1,030
74
n-hexane
582
761
18
10
11
550
188
29
894
14,880
17
277
4.7x10*
1,400
708
416
49
9.1x10*
I. 1x10*
4x10*
-------
provide graphical calculations of the number of theoretical stages required to
achieve desired extraction levels. The general method is analogous to the use
•
of McCabe-Thiele diagrams to assess distillation performance. Formulas, such
as the Kremser equations, are also available that quantitatively express the
effect of flow variations on exit concentration levels. The use of such
techniques (in conjunction with laboratory data) provide the basis for
determining equipment size and post-treatment requirements and, therefore, the
costs and applicability of the liquid extraction process.
5.4.1.3 Post-Treatment Requirements—
The post-treatment requirements of a liquid-liquid extraction process are
determined by many of the system component properties discussed above. For
u
example, solvent solubility in the aqueous phase will determine the need for
further treatment to eliminate solvent discharge with the treated waste
stream. The relative volatilities of the solute and solvent will affect the
ease of their separation following extraction. Careful selection of solvent
and proper design .can minimize the cost and difficulty of such processes.
Those technologies most commonly used for raffinate post-treatment are
established technologies such as steam or air stripping, carbon adsorption,
and biological treatment. Distillation will probably be used to separate
solvent and solute. These technologies are discussed in detail in other
sections of this report.
5.4.2 Demonstrated Performance
The use of liquid-liquid extraction for the treatment of aqueous organic
waste streams has been limited. Application of the technology has been
primarily for the treatment of phenol contaminated waste streams from the
petroleum and coal processing industries. Liquid-liquid extraction has proven
to be particularly well suited because of difficulties involved in removal of
phenol from these waste streams by steam stripping and adsorption.
Actual performance data for halogenated organic compounds are limited to
bench and pilot runs conducted under EPA auspices to assess the extractability
of priority pollutants from industrial waste streams. Solvent extraction was
explored in one EPA sponsored program as a method of treating wastewaters from
5-75
-------
9
petroleum refineries and petrochemical plants. Results were obtained from
9
the use of both spray columns and rotating disc contactors (RDC). However,
data for halogenated organic compounds are limited to a few compounds;
i.e., etbylene dicbloride, chloroacetaldehyde, and trichloroacetaldehyde.
Two earlier studies ' conducted by the EPA summarized available
solvent extraction data as shown in Table 5.4.3. These and other related data
from the same studies can also be found in Reference 12, the U.S. EPA
Treatability Manual.
A more relevant EPA sponsored study was conducted to determine the
13
feasibility of pesticide extraction from process waste streams. The study
examined partition coefficients for several pesticide (including DDT;
toxaphene; chlordane; 2,4-D; and bromacil) and solvent (n-butyl chloride,
monopropyl ether, hexane, pentane, and diethyl ether) combinations. The
boiling points of the five solvents considered were in the 34°C-78°C range.
Efficiencies in excess of 99.9 percent for synthetic DDT solutions using
hexane as the extraction solvent were obtained in a bench scale rotary disk
contactor. DDT concentrations ranged from 0.015 to 0.39 percent. Subsequent
tests with process stream effluents also indicated'that efficiencies in excess
of 99 percent were attainable. .As discussed below, costs were estimated and
compared favorably with carbon absorption.
5.4.3 Cost of Treatment
As noted in EPA's Treatability Manual, it is quite difficult to predict
costs of solvent extraction because of the wide variety of systems, feed
streams, and equipment that may be involved. However, in Volume IV of the
Treatability Manual, the EPA does present some cost data based on a waste
phenol feed of 45,000 Ibs/hr containing 1.5 percent phenol by weight and a
similar toluene solvent feed rate. (K_ • 2 for the phenol/toluene/water
distribution coefficient.) The unit is a rotating disc contactor containing .
an equivalent of about five theoretical stages to produce a wastewater
discharge containing 75 ppm phenol. Using the equations provided in Kirk
Othmer (Volume 9, Liquid-Liquid extraction), approximately five additional
theoretical stages would be required to achieve a discharge level of 21 ppm
which is slightly above the design residual phenol level of the entering
solvent stream.
5-76
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TABLE 5.4.3. RESULTS OF SOLVENT EXTRACTION STUDIES
Description of scudv
Chemical
Acrolein
Acrylonicrile
Chlorobenzene
Study
type*
R
R
R
Study Influent
•type" cone.
U
U
U 600 ppm
Result! of study Comments
Extractable v/xylene.
Solvent recovery by
ueotropic distillation.
Extractable w/ethyl echer.
3 ppm effluent cone, uiing
bis-chloroethyl ether
Chloroethane
1,1-Dichloroethane
Hexachloroethane
1,1,2,2-Tetrachloro-
ethane
1,1, 1-Trichloroethane
1,1,2-Trichloroethane
Dichloroetbylene
Ethylene Bichloride
L,B
p, c
D .
:*
49 ppm
23-1,804
ppm 8
2.76-
3.76 L/ain
chloroform solvent.
Extractable w/ethyl ether
and benzene.
Extraceable v/alcohols
and aroaacics.
Extraceable v/alcohols,
aromacics and ethers.
Extractable v/aromatics,
alcohols and ethers.
Extraceable w/aromatics,
alcohols and ethers.
Extractable v/alcohols
and aromatics.
Extractable v/aromatics,
methanol and ethers.
Kerosene effluent cone.
2 ppm; Cio"cl2 *tf~
luent cone. 1* ppm.
A 5.5:1 vater to solvent
ratio gave 94-961 reduc-
tion. Cjo-Cj^ P**~
affin solvent at .5:1 to
16.5:1 vater to solvent
ratio showed 94-991
reduction.
Solvent extraction
v/kerosene & C1(j-
Cj2 hydrocarbon
at 7:1 solvent to
vastevater ratio.
Wascevater contained
14 other halocarbons
including 30-350 ppm
1,1,2-trichloroethirae
and 5-197 ppa 1,1,2,2-
catrachloroethane. A
532 L/min extractor
v/1,000 ppm influent
estimated to have a
capital cost of
5315,000 and total
annual cost of 1143,000
ineluding credit for
recovered EDO.
'Describes the scale of the referenced study:
B - Batch Flov F - Pilot Scale
C - Continuous Flov R - Literature Reviev
L - Laboratory Scale
Source: Reference 10.
•Reference 11.
Describes the type of vastevaeer used in the
referenced study:
I - Industrial Wastevater
U - Unknovn
5-77
-------
The costs are presented in Table 5.4.4 with capital costs modified by ENR
index adjustment from 3119 to 4230 (Hay 1986) and minor changes made in. the
costs of toluene and power to represent May 1986 values. The annual costs of
$917,000/year represent costs in excess of $21 per 1,000 gallons of treated
wastewater, up from the value of $17 per 1,000 gallons provided in
Reference 12 (1980 dollars). Assuming capital costs are related to size
(number of stages) through a 0.7 exponential factor as indicated in
Reference 12, the capital costs shown in Table 5.4.4 would increase from $1.5
to over $2.4 million to achieve a discharge level of 21 ppm phenol in the
effluent wastewater. Total annual operating costs would be well in excess of
$30/1,000 gallons.
The above costs are far higher than the costs of $2/1,000 gallons
estimated in the Reference 13 study for a 300 million gallon per year plant.
Costs for carbon absorption were estimated at $3-$10/1,000 gallons.
Conceptual designs and economic analyses were also carried out for
several cases in the Reference 8 study. These include extraction of
nitrobenzene with diisobutyl ketbne (DISK - a low boiling solvent), and
extraction of acrolein by methyl isobutyl ketone (MIBK/, n-butyl acetate,
toluene, and 1,1,2,2-tetrachloroethane (all high boiling solvents). The costs
(1982 dollars) range from $5-$13/l,000 gallons and appear to be in reasonable
agreement with the costs of Reference 12, given the differences in base year
and operating volumes and concentrations.
5.4.4 Overall Status of Process
5.4.4.1 Availability--
Altbough liquid-liquid extraction processes have not been widely applied
to the treatment of waste streams, they are extensively used within the
chemical process industry to affect separations and recoveries. Table 5.4.5
lists a number of processing equipment units which can be used for
liquid-liquid extractions. Advantages and disadvantages of each type are
listed in the table. These are discussed in more detail in References 1, 7,
12 and other standard texts dealing with separation processes. There are a
number of commercial suppliers of liquid-liquid extraction equipment and
accessory equipment such as that needed for the regeneration of solvent and
removal of solvent from the wastewater effluent.'
5-78
-------
TABLE 5.4.4. ESTIMATED COSTS FOR A LIQUID-LIQUID EXTRACTION SYSTEM
Operating Characteristics
Value
Water/phenol/feed
Toluene feed
Discharge water
Extraction column
Loss of toluene/cycle
Electrical requirements
(column only)
Operation
45,000 Ib/hr containing 1.52 phenol (by we);
temperature is 110'F.
45,000 Ib/hr (containing 20 ppra phenol from
steam stripper reecycle).
Contains 75 ppm phenol.
Rotating disc type; 6 ft diameter, 60 ft high;
made from carbon steel; contains 50 compartments
and equivalent of about 5 theoretical stages.
(Equilibrium distribution coefficient of phenol
between toluene and water is about 2.)
Approximately 0.IZ/cycle.
One 10 hp electric motor.
330 d/yr; 24 hr/d.
Fixed capital costs based on an ENR index of 4,230 (Hay 1986) are estimated to
be $1,500,000 (up from an estimate cost of $1,000,000 provided by Reference 12
in 1980). Estimation of annual operating cost-is presented below.
Cost item
Direct operating cost
Labor
Operating
Maintenance
Chemicals - Toluene
Materials
Steam
Power
Annual
quantity
12,000 man hr
15,000 gal
33 106 Ib
150,000 tcWh
Cost per unit
quantity
S16/hr
41.35
S5/1.000 Ib
S0.05/kWh
Annual cost3 £
192,000
16,000
208,000
20,300
16,700
165,000
7 . 500
Total
Total indirect
Operating Cost
Total annual
operating cost3
917,500
aExciudes annual credit for phenol recovery.
Source: Reference 12 (modified to represent May 1986 dollars).
5-79
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TABLE 5.4.5. ADVANTAGES AND DISADVANTAGES OF EXTRACTION TYPES
Class of equipment
Advantages
Disadvantages
Mixer-Settlers
A
o
Gravity Columns
Spray Column
Packed Column
Tray Column
Mechanically
Agitated Columns
Agitated Column
Pulsed Column
Centrifugal
Extractors
Reliable scaleup
Good contacting
Handles wide flow ratio
Low headroom
Many stages available
Low capital cost
Low operating cost
Simple construction
Handles wide flow ratio
(tray column)
Handles suspended solids
(spray column)
Good dispersion
Reasonable cost
Many stages possible
Relatively easy scaleup
Handles systems of high
interfacial tension
Handles low density difference
and high interfacial tension
between phases
Low holdup
Low space requirements
Small inventory of solvent
Handles stable emulsions
Large holdup
High power costs
High capital costs
Large floor space
Interstage pumping may be required
Extensive backmixing (spray, packed column)
Limited throughput with small density difference
Cannot handle high flow rate (packed column)
High headroom
Low efficiency (spray column)
Difficult scaleup
Internals subject to fouling (packed column)
Limited throughput with small density difference
Cannot handle emulsifying systems
Cannot handle high flow ratio
High capital cost
High operating cost
High maintenance cost
Limited number of stages in single unit
Subject to fouling
Source: References 9-12.
-------
5.4.4.2 Application-
Integration of equipment into an overall system for successful treatment
of waste streams will require considerable analysis of the waste stream of
interest and the candidate processes. Liquid-liquid extractions are most
useful when separations involve materials that are not easily separated by
distillation or other treatment processes. Generally, liquid-liquid
extractions of water streams are conducted to remove materials which have high
water solubility and therefore almost invariably a low Henry's Law constant.
Air or stream stripping do not appear to be viable options for wastes of this
type. Liquid-liquid extractions may be particularly applicable when the
relative volatilities of solute/solvent compounds make separation by
distillation difficult or when high waste concentrations make carbon
adsorption uneconomical. Most of the halogenated organics addressed in this
TRD are only sparingly soluble in water although some of the lower molecular
weight.compounds do exhibit appreciable solubility (see Appendix A).
Extraction of the soluble compounds could be viable. Solvent extraction of
emulsified material might also be considered provided mass transfer
considerations are acceptable. This would have to be determined
experimentally.
.Solvent choice and design parameter options are many and varied.
Although design and operation of a liquid-liquid extraction system to achieve
acceptable effluent levels is theoretically possible, existing experimental
and field data for halogenated and other organics indicate that most units, as
presently designed and operated, fall short of this goal.
5.4.4.3 Environmental Impact-
Properly designed and operated, the liquid-liquid extraction process does
not appear to pose significant environmental problems. Both process exit
streams contain potential contaminants that must be addressed as part of the
process. The solvent will contain solute (contaminant in the feed) that must
be removed if the solvent is to function adequately in recycle. The treated
waste stream (assuming all significant tface3 of contaminant have been trans-
ferred to the solvent) could contain dissolved solvent which may or may not be
significant and warrant additional treatment. Since these potential conditions
are recognized and must be dealt with by system designers, the environmental
impacts of a viable liquid-liquid extraction system should be minimal.
5-81
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5.4.4.4 Advantages and Limitations—
Some potential advantages of liquid-liquid extraction processes are:
• Recovery of costly materials can be accomplished with little threat
of thermal decomposition or chemical interaction.
• Recovery (separation) of materials which have similar relative
volatilities or adsorption isotherms can be achieved.
Some potential limitations of liquid-liquid extraction are:
• Some residuals will generally be present in both the raffinate and
extract streams, thus, some provision must be made for their removal
and subsequent disposal.
• Economics may not be favorable.
• Deviations that limit the extent of removal may occur upon scale-up.
5-82
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REFERENCES
1. Perry, R. H., et al. Editors; Chemical Engineers' Handbook, Sixth
edition, McGraw Hill Book Company, NY. NY. 1984.
2. Hwang, S. T., Treatability of Toxic Waste Water Pollutants by Solvent
Extraction. AIChE Symposium Series, No. 209 "Waste-1980", 1981.
3. Earhart, J.P., Extraction of Chemical Pollutants from Industrial
Wastewaters with Volatile Solvents, U.S. EPA, Ada, Oklahoma,
EPA-600/2-76-220, December 1976
4. Leo, A., C. Hansch, and D. Elkins, "Partition Coefficients and Their
Uses," Chemical Reviews* n.» 525(1971).
5. Earhart, J. P., K. W. Won, H. Y. Wong, J. M. Prausnitz, and C. J. King,
"Recovery of Organic Pollutants via Solvent Extraction," Chem. Eng.
Prog., May, £7 (1977)
6. Murray, W. J., L. H. Hall, and L. B. Kier, "Molecular Connectivity III:
Relationship to Partition Coefficients," J. of Phar* Sci., 64. 1978(1975)
7. Kirk-Othmer. Encylopedia of Chemical Technology, Third Edition,
Volume 9. A Wiley-Intrascience Publication. 1978.
8. King, C. J., D. K. Joshi, and J. J. Senetar, University of California,
Berkeley, Department of Chemical Engineering. Equilibrium Distribution
Coefficients for Extraction of Organic Priority Pollutants From
Water-II. EPA-600/2-84-060b, February 1984.
9. Earhart, J. P., et al. University of California, Berkeley Department of
Chemical Engineering. Extraction of Chemical Pollutants from Industrial
Wastewaters with Volatile Solvents. EPA 600/2-76-220. PB226241.
December, 1976
•
10. Dryden, F. E., J. H. Mayes, R. J. Planchet, and C. H. Woodard. Priority
Pollutant Treatability Review. EPA Contract No. 68-03-2579, U.S.
Environmental Protection Agency, Cincinnati, Ohio, 1978.
11. Coco, J. H., et al. Development of Treatment and Control Technology for
Refractory Petrochemical Wastes. EPA-600/2-79-080, U.S. Environmental
Protection Agency, Ada, Oklahoma, 1979. 236 pp.
5-83
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12. U.S. EPA Treatability Manual, Volume III, EPA-600/2-82-001a. September
1981.
13. Reynolds, S.L., "Extraction of Pesticides From Process Streams Using High
Volatility Solvents". IN: International Conference on New Frontiers for
Hazardous Waste Management. EPA 600-9-85-025, September 1985.
5-84
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5.5 CARBON ADSORPTION
Adsorption is a widely-used process for the removal of organic
contaminants from gas or liquid waste streams. Activated carbon is the most
commonly used adsorbent. Largely nonpolar, carbon is particularly effective
for the removal of hydrophobia, high molecular weight organic compounds from
aqueous streams. Thus, it is a good adsorbent for many of the halogenated
organic compounds considered in this document. Activated carbon adsorption
must be considered a potentially viable treatment technology for many
halogenated organic-bearing wastewater streams, either as a primary treatment
for moderately high (up to 0.5 percent) concentrations of organic compounds or
as a secondary polishing type treatment for much lower levels of
contamination. The cost effectiveness of adsorption is dependent on flow
rates and concentrations of the organic contaminants and on the adsorptive
capacity of the carbon for the contaminants. Adsorption should be cost
effective for concentrations of organic compounds up to about 1,000 mg/L, and
could be cost effective for concentrations up to 5,000 mg/L. For
concentrations above 5,000 mg/L, other unit processes are generally more cost
2
effective, unless nondestructive chemical regeneration can be used to
recover the adsorbed materials.
Activated carbon is available in powder (PAC) or granular (GAG) form.
GAG is more commonly used because its larger size is more amenable to handling
in the equipment used to achieve contact and regeneration. Both types of
carbon adsorbent have large contact surface areas, far in excess of their
nominal external surface areas. Surface areas, resulting from a network of
internal pores 20 to 100 angstroms in diameter, are of the order of 500 to
1,500 square meters per gram. Porosities can be as large as SO percent. The
adsorption capacity of an activated carbon for a contaminant is a function of
the surface area and the surface, binding process and can approach 1 gram per
gram of carbon.
Adsorbent binding forces result from the interaction of the contaminant
surface molecules with the carbon surface atoms. The attractive forces are
generally weaker and less specific than those of chemical bonds and, hence,
the term physical adsorption is used to describe the binding mechanism. The
effective attractive range is small and the adsorbed material is generally
5-85
-------
present only as a monolayer upon the adsorbent surface. The process is
considered analagous to condensation of gas molecules, or to crystallization
from a liquid. The process is reversible, and molecules held at the surface
will subsequently return to the fluid stream. The length of time elapsing
between adsorption and desorption is dependent upon the intensity of the
surface forces. Adsorption is a direct result of this time lag. Because
adsorption is a reversible process, the carbon surface can be regenerated
either thermally or chemically; e.g., by solvent extraction. However, high
temperature thermal regeneration (which destroys the adsorbed organics) is
generally required to insure effective removal of adsorbed -contaminants.
Water solubility and carbon affinity are two properties that, in general,
correlate with the adsorption of hazardous contaminants onto activated
carbon. Generally, less soluble organic materials are more effectively
adsorbed. Several factors are associated with decreased water solubility of
organics and, as a result, correlate with increased adsorption. . These
include: high molecular weight, low polarity, low ionic character, low pH. for
weak organic acids or high pH for weak organic bases, and aromatic
structures. As a rule of thumb, molecules of higher molecular weights are
f
attracted more strongly to activated carbon than are molecules of lower
molecular weights. Strongly ionized or highly polar compounds are more water
4
soluble and are usually poorly adsorbed. Compounds with solubilities of
less than 0.1 g/mL in water and molecular weights between 100 to 1,000 are
considered moderately to highly adsorbable.
Several other aspects of molecular structure also affect adsorbability.
In general, branch-chain compounds are more adsorbable than straight-chain
compounds. Increasing hydrocarbon unsaturation also tends to decrease
solubility and increase carbon adsorption. Thus, unsaturated organics such as
ethylenes tend to more readily adsorb on carbon than saturated compounds such
as ethanes. Table 5.5.1 identifies the specific waste characteristics that
affect adsorption. Table 5.5.2 summarizes the influence of substituent
chemical groups on adsorbability.
The adsorption of organic compounds by adsorbents is usually determined
in the laboratory through adsorption isotherm tests. These tests measure, at
a given temperature, the amount of substance adsorbed and its concentration in
the surrounding solution at equilibrium. Isotherms provide information on the
5-86
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TABLE 5.5.1. WASTE CHARACTERISTICS THAT AFFECT ADSORPTION
BY ACTIVATED CARBON
A. General
1. Polar, low-molecular weight compounds with high degrees of
solubility are poorly adsorbed.
2. Conversely, nonpolar, high-molecular weight compounds with limited
solubility tend to be preferentially adsorbed.
B. Molecular Structure
1. Branched-chain compounds are more adsorbable than straight-chain
compounds.
2. Type and location of substituent groups also affect the degree to
which a compound may be adsorbed from solution. Table 5.5.2 gives
some general guidelines as to how substituent groups affect
adsorbability.
C. Effect of pH
1. The affect of pH on carbon sorbent equilibrium varies significantly
from compound to compound. Adsorption isotherms for some compounds
are affected dramatically, whereas others show no significant change
as a function of pH.
2. Dissolved organics generally adsorb most efficiently at that pH
which imparts the least polarity to the molecule. For example, a
weak organic acid can be expected to adsorb best at a low pH value.
D. Temperature Effects
1. Adsorption reactions are generally exothermic; therefore lower
temperatures favor adsorption. However, shifts in adsorbaoility
within the range of temperatures normally encountered in waste
stream applications are generally small.
E. Physical Form
1. Carbon adsorption is suitable for aqueous wastes, nonaqueous liquids
and gases.
2. The oil and grease concentration should be less than 10 mg/L.
3. Suspended solids concentrations higher than about 10-70 mg/L will
cause clogging of the bed.
Source: Adapted from Reference 5.
5-87
-------
TABLE 5.5.2. INFLUENCE OF SUBSTITUENT GROUPS ON ABSORBABILITY
Substituent Nature of influence
Hvdroxyl Generally reduces adsorbabi.Li.ty; extent of decrease
depends on structure of host molecule.
Amino Effect similar to that of hydroxyl but somewhat greater;
many amino acids are not adsorbed to any appreciable
extent.
Carbonyl . Effect varies according to host molecule; glyoxylic is
more adsorbable than acetic but similar increase does
not occur when introduced into higher fatty acids.
Double bonds Variable effect as with carbonyl.
Halogens Variable effect, but generally increased adsorbability.
Sulfonic Usually decreases adsorbability.
Nitro Often increases adsorbability.
Aromatic rings Greatly increase adsorbability.
Source: Adapted from Reference 5.
5-88
-------
relative affinity of an organic compound for the adsorbent and the adsorption
capacity. Thus, isotherm tests can be useful in making qualitative
evaluations of different carbons for adsorption of specific components from a
given waste stream.
Isotherms data are frequently evaluated using the Freundlich Equation,
which describes the adsorbability characteristics of a constituent for a given
carbon. This equation can be expressed as follows:
i - kCf1/n (1)
m f
where: x • mass of adsorbate, mg
m » mass of dry adsorbent, g
k » constant, adsorbability indicator
Cf « solution concentration at equilibrium, mg/L
1/n • constant, adsorption intensity
Values of k and 1/n for a compound are found by a plot of experimentally
determined carbon adsorption data in which values of x/m are plotted against
Cf on log-log paper.
The adsorption data are useful in estimating the relative effectiveness
of an adsorbent for organic compounds. However, care must be exercised in
assessing performance when the waste stream contains a large number of
competing contaminants. It is possible to develop equilibrium equations that
apply to multi-component systems, as noted in standard texts on adsorption and
Perry's Chemical Engineers' Handbook. However, most users will rely on
laboratory scale carbon adsorption/isotherm tests to assess performance and
design an appropriate system for a specific waste stream.
Carbon adsorption capacities are summarized in Table 5-5.3 for several
halogenated organic and other separate compounds. The capacity, x/m,
corresponds to the constant, k, expressed as mg compound per gram of carbon,
when the equilibrium concentration of the.compound is 1.0 mg/L. The compounds
have been ranked in decreasing order of their capacity (k value) as determined
by isotherm tests using Filtrasorb 300 activated carbon.
5-89
-------
TABLE 5.5.3. SUMMARY OF CARBON ADSORPTION CAPACITIES
Compound
Adsorption3
capacity, mg/g
Compound
Adsorption*
capacity, mg/g
Heptachlor
Heptachlor epoxide
Endoaulfan sulfate
End r in
Aldrin
PCB-1232
beta-Endosulfan
Die Id tin
Hexachlorobenzene
Anthracene
DDT
alpha-BHC
3, 3-Dichlorobenzidine
2-Chloronaphthalene
Hexachlorobutad iene
gamma-BBC (lindane)
Chlordane
4-Chlorophenyl phenyl ether
Chlorobenzene
1 ,2-Dibromo-3-chloro-propane
2-Chlorophenol
5 Bromouracil
Toluene i
Phenol
Carbon tetrachloride
1, 1 ,2 ,2-Tetrachloroethane
Dichlorobromofflethane
Trichlorofluoromethane
Dibromochloromethane
Chloroform
1, 1-Dichloroe thane
Benzene
1,220
1,038
686
666
651
630
615
606
450
376
322
303
300
280
258
156
245
111
91
53
51
44
26
21
11
11
7.9
5.6
4.8
2.6
1.8
1.0
PCB-1221
DDE
Benzidine dihydrochloride
beta-BHC
alpha-Endosulfan
4,4' Methylene-bis-
(2-chloroaniline)
2,4-Dichlorophenol
1 , 2 ,4-Trichlorobenzene
2,4, 6-Tric hloropheno 1
Pentachlorophenol
Naphthalene
l-Chloro-2-nitrobenaene
1 ,2-Dichlorobenzene
p-Chlorometacresol
1,4-Dichlorobenzene
1 , 3-Dichlorobenzene
Hexachloroethane
p-Xylene
Ethylbenzene
Tetrachloroethene
Trichloroethene
bis( 2-Chloroiaopropy 1) ether
Bromoform
bia(2-Chloroethoxy) methane
1,2-Dichloropropene .'
1 , 2-Dichloropropane
1, 1-Dichloroethylene
2-Chlorocthyl vinyl ether
1,1, 1-Trichloroechane
Methylene chloride
242
232
220
220
194
190
157
157
155
150
132
130
129
124
121
118
97
85
53
51
28
24
20
11
8.2
5.9
4.9
3.9
2.5
1.3
aAdsorption capabilities are calculated for an equilibrium
concentration of 1.0 mg/L at neutral pH.
Source: Reference 6.
5-90
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5.5.1 Process Description
A schematic of a carbon adsorption system utilizing a prefilter and a
multiple hearth furnace regeneration system is shown in Figure 5.5.1. In the
regeneration process, adsorbed material is driven from the carbon surface by
thermal forces. However, other methods (e.g., extraction or steam stripping)
can be used to drive off adsorbed material held largely by physical rather
than chemical forces. Regeneration is usually complete, although some loss of
effective surface area over time (3 to 8 percent per cycle) can result from
build-up of bard to remove adsorbent, attrition, and other mechanisms.
Collection or destruction of the desorbed material will also be necessary for
these regeneration processes.
Carbon adsorption is applicable to single-phase aqueous solutions
containing low concentrations of organic contaminants (up to 0.5 weight
2 4
percent) and inorganic contaminants (up to 0.1 weight percent). It is
also applicable to some organic liquid solutions (e.g., those consisting of a
poorly adsorbed solvent and a readily adsorbed solute), although it is less
likely that the selectivity will approach that for adsorption from a water
stream.
Carbon adsorption may be used as a pretreatment process for conventional
biological treatment, but is more frequently used as a polishing step for
biological treatment effluent to remove compounds that are resistant to
biodegradation. In this capacity, it is generally used for high volume waste
streams which contain.dilute organic constituents.
5.5.1.1 Pretreatment Requirements—
Pretreatment of the feed to carbon adsorption columns is often required
to improve performance and/or prevent operational problems. As discussed in
Reference 7, there are four primary areas where pretreatment for different
waste forms and characteristics may be required. These include:
1. Equilization of flow and concentrations of primary waste
constituents.
2. Filtration.
5-91
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SPILL I
VOLATILIZATION I
INCOMING
PROCESS WASTE
WASTE STORAGE
TANK
MULTI-MEDIA
PREFILTER
tT
I I
I FUGITIVE
EMISSIONS
GRANULAR
ACTIVATED
CARBON COLUMNS
DISCHARGED
EFFLUENT
SPENT CARBON
STORAGE TANK
MULTIPLE HEARTH
FURNACE/CARBON
REGENERATION
I
I FURNACE
I EMISSIONS
REGENERATED
CARBON
STORAGE
TANK
Figure 5.5.1. Carbon adsorption flow diagram.
Source: Reference 3.
-------
3. Adjustment of pH.
4. Adjustment of temperature.
Equalization of flow and concentrations of primary waste constituents—It
is generally assumed that both the flow to the GAC columns and the
concentration of the primary waste constituent, namely the halogenated organic
compound in the feed, are constant. Such is not generally the case, and since
variations in either flow or concentration can have a detrimental impact on
system performance, it is necessary to make provisions to equalize flow and
minimize concentration surges.
Flow equalization is accomplished by employing a surge tank of sufficient
capacity to accommodate flow variations. The result is a constant flow rate
to the GAC columns. Concentration equalization can be handled by employing
surge tanks in the same manner as flow equalization. However, provisions must
be made for mixing tank contents prior to discharging to the GAC columns.
Mixing prevents concentration surges which can lead to premature column
leakage and breakthrough. Conversely, low concentration swings can result in
premature regeneration of an underloaded GAC column.
Filtration--l£ is a general requirement for GAC processes that the feed
of the column be low in suspended solids. In treating solvent and ignitable
waste streams, it has been suggested that solids concentrations greater than
50 tng/L will interfere with column operation. In addition to solids
removal, many additional waste contaminants can interfere with carbon
adsorption of solvent and ignitable waste streams. For example, if calcium or
magnesium are present in concentrations greater than 500 mg/L, these
4
constituents may precipitate out and plug or foul the column. Oil and
grease in excess of 10 mg/L can interfere in column operation. Lead and
mercury are also of concern because they may compete for adsorption sites and
Q
are difficult to remove from the carbon during the regeneration cycle. The
presence of many other compounds can influence adsorption as they compete for
available adsorption sites on the carbon surface.
For efficient use of GAC for treating halogenated organic waste streams,
removal of suspended solids and other waste contaminants noted above must be
achieved by pretreatment with, for example, multi-media pressure filters.
5-93
-------
Such filters are very compatible with fixed bed adsorption processes and can
be readily integrated into a total design. Other possibilities include
membrane filtration when a highly clarified feed is desired; ultrafiltration
if high molecular weight (over 1,000) contaminants are present in the raw
waste; and reverse osmosis to concentrate a feed containing numerous dissolved
species, both organic and inorganic. Obviously other pretreatments
(e.g. precipitation, clarification) will be needed to remove dissolved solids
such as calcium and magnesium.
Adjustment of pH—GAG adsorption systems are sensitive to changes in pH.
If the contaminants to be removed are either weakly acidic or weakly basic,
then the pH of the feed will effect their adsorption. Weakly acidic organics
are most readily adsorbed in the nonionized state and consequently a low pH
(acid) favors adsorption. Weakly basic compounds such as aniline or
dimethylamine are also most readily adsorbed in their nonionized state and,
therefore, adsorption is favored by high pH (alkaline). The adsorption of
neutral organic compounds is unaffected by pH.
The control of the feed pH should perhaps be considered a subcategory of
the previously discussed concentration/equalization requirement. It can be
readily controlled by applying pH measurement and feedback control for acid or
base addition to the equalization system at the surge tank to achieve the
desired pH feed to the GAG adsorption columns.
Adjustment of Temperature—Temperature adjustment is rarely required in
GAG adsorption processes.. High feed temperature could lead to increased VOC
emissions to air in an open gravity feed system and is unfavorable for
adsorption and retention of volatile constituents. If the possibility for
temperature surges exists, temperature moderation through flow equalization
should be considered.
5.5.1.2 Operating Parameters-
Process design activities must take into account a number of equipment
design parameters to develop a system which is optimal for the characteristics
of the waste or wastes to be treated. The design parameters will be
considered in terms of both the adsorption system and the regeneration or
desorption system.
5-94
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Adsorption System—Isotherms, determined in a laboratory, measure the
affinity of activated carbon for the "target" adsorbates in the process
liquid. This provides data for determining the amount of carbon which will be
required to treat the full scale process stream. Carbon requirements will be
based on a limiting constituent for which attainment of effluent limitations
is the most difficult. However, adsorption isotherms can vary widely for
different carbons, and isotherm data cannot be used interchangeably.
Table 5.5.4 gives properties of some commercially available granulated
activated carbons. Properties of a typical powdered activated carbon are
shown in Table 5.5.5. Adsorption properties of the two types of carbon are
generally comparable. The principal difference is in the particle size; the
fine size of the PAC makes it unsuitable for use in the contacting and
regeneration equipment used for GAG applications.
A typical continuous adsorption system consists of multiple columns
filled with activated carbon and arranged in either parallel or series. Total
carbon depth of the system must accommodate the "adsorption wavefront";
i.e., the carbon depth must be sufficient to purify a solution to required
specifications after equilibrium has been established. Bed depths of 8 to
40 feet are common. Minimum recommended height-to-diameter ratio of a column
is 2:1. Ratios greater than 2:1 will improve removal efficiency, but result
in increased pressure drop for the same flow rate. Optimum flow rate must be
determined in the laboratory for the specific design and carbon used. For
2
most applications, 0.5 to 5 gpm/ft of carbon is common.
Various configurations are available for GAG adsorption applications.
Based on influent characteristics, flow rate, size and type of carbon,
effluent criteria and economics, each design is unique in its mode of
operation. Figure 5.5.2 illustrates several arrangements typically used for
GAG adsorption systems.
The adsorption beds of both series and parallel design can be operated in
either an.upflow or downflow direction. A dbwnflow mode of operation must be
used where the GAG is relied upon to perform the dual role of adsorption and
filtration* Although lower capital costs can be realized by eliminating
pretreatment filters, frequent backwashing of the adsorbers is required.
2
Application rates of 2 to 10 gallons per minute per square foot (gpm/ft )
5-95
-------
TABLE 5.5.4. PROPERTIES OF SEVERAL COMMERCIALLY AVAILABLE CARBONS
PHYSICAL PROPERTIES
Surface area, m2/g (BET)
Apparent density, g/cm^
Density, backwashcd and drained, lb/g^
Real density, g/cm^
Particle density, g/cnr
Effective size, mm
Uniformity coefficient
Pore volume, cnr/g
Mean particle diameter, ma
SPECIFICATIONS
Sieve size (U.S. std. series)3
Larger than Mo. 8 (max. X)
Larger than Mo. 12 (max. Z)
Smaller than No. 30 (max. Z)
Smaller than No. 40 (max. Z)
Iodine No.
Abrasion No. minimum
Ash (Z)
Moisture as packed (max. Z)
ICI
America
Hydrodarco
(lignite)
600 - 650
0.43
22
2.0
1.4 - 1.5
0.8 - 0.9
1.7
0.95
1.6
8
—
5
—
650
b
b
b
Calgon
Filtrasorb
300
(bituminous) ,m
950 - 1050
0.48
26
2.1
1.3 - 1.4
0.8 - 0.9
1.9 or less
0.85
1.5 - 1.7
8
—
5
—
900
70
8
2
Westvaco
Nuchar
WV-L
(bituminous)
1000
0.48
26
2.1
1.4
0.85 - 1.05
1.8 or less
0.85
1.5 - 1.7
8
—
5
—
950
70
7.5
2
Wicco
517
(12x30)
(bituminous)
1050
0.48
30
2.1
0.92
0.89
1.44
0.60
1.2
—
5
5
—
1000
85
0.5
1
sizes of carbon are available on request from the manufacturers.
available data from the manufacturer.
— Not applicable to this size carbon.
TYPICAL PROPERTIES OF. 8 X 30-MESH CARBONS
Total surface area, o^/g
Iodine number, min
Bulk density, lb/ft^ backwashed and drained
Particle density wetted in water, g/cm^
Pore volume, cnH/g
Effective size, ma
Uniformity coefficient
Mean particle dia. , mm
Pittsburgh abrasion number
Moisture as packed, max.
Molasses RE (Relative efficiency)
Ash
Mean-pore radius
Lignite
carbon
600 - 650
500
22
1.3 - 1.4
1.0
0.75 - 0.90
1.9 or less
1.5
50 - 60
9Z
100 - 120
12 - 18Z
33 A
Bituminous
coal carbon
950 - 1,050
950
26
1.3 - 1.4
0.85
0.8 - 0.9
1.9 or less
1.6
70 - 80
22
40-60
5 - 82
14 A
Source: Reference 9.
5-96
-------
TABLE 5.5.5. TYPICAL PROPERTIES OF POWDERED ACTIVATED CARBON (PETROLEUM BASE)
Surface Area m2/g(BET) 2,300 - 2,600
Iodine No. 2,700 - 3,300
Methylene Blue Adsorption (mg/g) 400 - 600
Phenol No. 10-12
Total Organic Carbon Index (TOGI) 400 - 800
Pore Distribution (Radius Angstrom) 15-60
Average Pore Size (Radius Angstrom) 20 - 30
Cumulative Pore Volume (cnrVg) 0.1 - 0.4
Bulk Density (g/cm3) 0.27 - 0.32
Particle Size Passes: . 100 mesh (wtZ) 97 - 100
200 mesh (wtZ) 93 - 98
325 mesh (wtZ) 85 - 95
Ash (wt%) 1.5
Water Solubles (wtZ) 1.0
pH of Carbon 8-9
Source: Re ference 5.
5-97
-------
in
out
in
i
out
UPFLOW IN SERIES
DOWNFLOW IN SERIES
1
I
out
in
UPFLOW IN PARALLEL
1
i:i:;j;:|:|:;ii
i
T
III
I
t
ijjj::;:'::::!:!;
i
out
DOWNFLOW IN PARALLEL
out
MOVING
BED
Figure 5.5.2. Carbon bed configurations.
Source: Reference 10.
5-98
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are employed, and backwash rates of 12-20 gpm/ft are required Co achieve
bed expansions of 20-50 percent. The use of supplemental air increases
efficiency of the backwashing.
Prefiltration is normally required to prevent blinding upflow-expanded
beds with solids. In this configuration, smaller particle sizes of GAG.can be
employed to increase adsorption rate and decrease adsorber size. Application
rates can be increased even to the extent that the adsorbent may be in an
expanded condition.
The design arrangements offer the following advantages and limitations as
noted in Reference 10:
Method
Adsorbers in Parallel
Adsorbers in Series
Moving Bed
Upf low-expanded
Comments
For high volume applications
Can handle higher than average suspended
solids (<65-70 ppm) if downflow
Relatively low capital costs
Effluents from several columns blended,
therefore, less suitable where effluent
limitations are low
Large volume systems.
Easy to monitor breakthrough at tap
between units
Effluent concentrations relatively low
Can handle higher than average suspended
solids (<65-70 ppm) if downflow
Capital costs higher than for parallel
systems
Countercurrent carbon use (most
efficient use of carbon)
Suspended solids must be low (<10 ppm)
Best for smaller volume systems
Capital and operating costs relatively
high
Can use such beds in parallel or series
Can handle high suspended solids (they
are allowed to pass through)
High flows in bed (~-15 gpm/ft2)
The above systems are not generally used with powdered activated
carbons. The PAC systems now used involve mixing the PAC with the waste
stream to form a slurry which usually can be separated later by methods such
5-99
-------
as filtration or sedimentation. PAC is generally used simultaneously with
biological treatment to enhance organic removal by biological processes.
Regeneration—The economic success of an adsorption system usually
depends on the regenerability of the adsorbent. The exception is where there
are very long adsorption or loading cycles due to very low concentrations of
halogenated organic constituents in the inlet feed. This type of system
usually operates on a "throw away" basis. If very large quantities of
adsorbent are involved, then regeneration and reuse are required for
economical operation. The regeneration techniques employed in industry are
thermal regeneration, steam regeneration, and acid or base regeneration.7
Solvent washing or biological treatment are other methods that are
occassionally used for regeneration. Solvent recovery, if possible, can lead
to adsorbent recovery with attendant cost benefits. Thermal regeneration is
the most commonly applied technique for GAG systems, since this is the only
method that can generally ensure effective regeneration.
Thermal regeneration involves high temperatures and a controlled gaseous
atmosphere. Regeneration of spent carbon can be considered to take place in
three distinct phases. First, wet carbon is dried at a temperature range of
approximately 100 to 150°C. Water and some low boiling point organics will be
removed during this process but higher boiling point organics such as
1,4-dichlorobenzene (b.p. 173aC) will remain. Next, the temperature is raised
to 250 to 750°C where more tightly bonded and higher boiling point organics
are removed by vaporization. An inert gas atmosphere can be employed to
minimize oxidation. Finally, the temperature is raised to 800 to 975°C where
residues and tars that may have accumulated are reacted and driven off the
carbon surface. Steam is sometimes used to assist removal. Even with careful
control, GAG losses are reported to be 3 to 8 percent/cycle due to both
oxidation and mechanical attrition.- Regeneration furnaces have been designed
to conduct all three steps of drying, vaporization under inert gases, and
regeneration separately in different zones. Multiple hearth furnaces and
f luidized-bed furnaces are two types of thermal regenerators commonly found in
commercial use.
5-100
-------
Steam regeneration can be used to displace the liquid in the adsorber
bed, heat the adsorbent and, finally, strip the halogenated organics from the
GAG. However, not all halogenated organics, particularly some of the high
molecular weight pesticides, are volatile enough to permit steam
regeneration. Average pressures of one to three atmospheres are utilized with
steam flow rates of 0.5 to 4 Ibs/min/ft . The amount of steam required
depends upon the size of the carbon bed. The majority of steam used in
regeneration is used to heat the carbon bed to the necessary temperature for
vaporization to occur. The heat capacities of the adsorbed constituents and
their heats of vaporization do not represent a large fraction of the total
steam requirement. Thus units for steam usage are typically expressed as
Ib steam/lb carbon.
As discussed in the pretreatment section, the adsorption of weak organic
acids and bases from aqueous solutions is dependent upon pH. Therefore, if
the adsorbed organic is acidic, regeneration with a basic solution is
feasible. Conversely, basic constituents can be regenerated with an acidic
solution. Acid or base regeneration is not as widely used as other
regeneration techniques, but nonetheless, some organics such as cresols and
etbylene diamine have been successfully recovered commercially by base and-
acid regeneration, respectively. Solvent regeneration (with possible benefits
resulting from sorbent recovery) may also be possible although removal of all
sorbed materials is not likely.
5.5.1.3 Post-Treatment Requirements—
•
Air and water discharges from carbon adsorption systems employing carbon
•regeneration can be relatively innocuous. Under proper design and operating
conditions, the treated water will generally be suitable for discharge to
surface waters. Other aqueous streams such as backwash, carbon wash and
transport waters are recycled or sent to a settling basin. Emissions will
result from thermal reactivation, but when afterburners and scrubbers are
used, the controlled emissions are essentially non-polluting. In some
installations, particulatea must be removed from the air stream (e.g., via a
cyclone and baghouse) resulting in a solid waste.
5-101
-------
5.5.1.4 Treatment Combinations—
The high cost associated with the treatment of moderate to high total
organic carbon (TOO) wastes and the ineffectiveness of carbon as an adsorbent
for many low molecular weight water soluble organic compounds has impacted the
use of carbon adsorption as a waste treatment technology. Except when used
alone as a polishing step for low levels of adsorbable materials in aqueous
streams, carbon adsorption is usually employed in a "treatment train" with
other treatment processes to achieve maximum efficiency at reduced cost.
An extensive discussion of treatment trains employing carbon adsorption
can be found in References 12 and 13.
5.5.2 Demonstrated Performance
Information gathered from activated-carbon manufacturers and industry
indicates that many granular-activated carbon systems are being used for the
treatment of hazardous aqueous organic compound bearing wastes and
wei
.11
wastewaters. A 1982 EPA study found that over 100 GAG systems were being
used nationally to treat industrial wastewaters. Another report
documented the use of PAG at seven and four facilities in the United States
•and Japan, respectively.
Despite the large number of units in use, data for full-scale
applications are incomplete. A major shortcoming of the available data base
dealing with the removal of halogenated organics from aqueous waste streams by
activated carbon, is the sparsity of performance data for higher concentration
(0.1 percent) levels. In addition, most of the data found in the literature
do not consider the removal of individual compounds from concentrated waste
streams, although data for BOD, COD, TOG, and other parameters are fairly
common. Data for individual compounds provided in EPA's background document
for solvents (Reference 4) are, with few exceptions, for treatment of influent
concentrations at the part per billion level. All data presented, however,
indicate that levels acceptable for direct discharge can be reached for
essentially all solvents of concern. Equal or better performance can be
anticipated for most of the halogenated organic compounds. Treatability
ratings of some halogenated organics are shown in Table 5.5.6. Ratings are
high for most of these compounds, particularly the higher molecular weight,
5-102
-------
TABLE 5.5.6.
TBEATABILITY RATING OF SOME HALOGENATED ORGANICS
UTILIZING CARBON ADSORPTION
Priority pollutant
Removal racing*
benzene
chlorobenzene
1,2,4-trichlorobenzene
hexachlorobenzene
hexachloroethane
bis(chloromethyl)ether
bis(2-chloroethyl)ether
2-chloroethyl vinyl ether
2-chloronaphthalene
2,4,6-trichloropheno1
parachlorometa cresol
2-chlorophenol
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-dichlorobenzene
3,3'-dichlorobenzidine
2,4-dichlorophenol
4-chlorophenyl phenyl ether
bis(2-chloroisopropyl)ether
bis(2-chloroethoxy)methane
bromoform (tribromomethane)
n
dichlorobromomethane
ehlorodibromomethane
hexachlorobutadiene
hexachlorocyclopentadiene
pentachlorophenol
vinyl chloride
PCB-1242 (Arochlor 1242)
PCB-1254 (Aroehlor 1254)
PCB-1221 (Aroehlor 1221)
PCB-1232 (Aroehlor 1232)
PCB-1248 (Aroehlor 1248)
PCB-1260 (Aroehlor 1260)
PC3-1016 (Aroehlor 1016)
M
H
H
H
H
M
L
H
H
H
a
H
H
H
H
H
H
M
M
H
M
M
H
H
H
L
H
H
H
H
H
H
H
*Note: Explanation of Removal Ratings.
Category H (high removal)
adsorbs at levels >100 mg/g carbon at C(f) » 10 mg/L
adsorbs at levels >100 mg/g carbon at C(£) <1.0 mg/L
Category M (moderate removal)
adsorbs at levels >100 mg/g carbon at C(f) » 10'mg/L
adsorbs at levels <100 mg/g carbon at C(f) <1.0 mg/L
Category L (low removal)
adsorbs at levels <100 mg/g carbon at C(f) » 10 mg/L
adsorbs at levels <10 mg/g carbon at C(f) <1.0 mg/L
C(f) - final concentrations of priority pollutants at equilibrium.
Source: Reference 14.
5-103
-------
aromatic compounds. Thus, Che utility of adsorption as a treatment process
hinges on the economics of the specific situation, which in turn depend
primarily on the costs of regeneration.
Data taken from Reference 5 have been summarized in Table 5.5.7. These
data provide results of full scale GAC systems. Because of the sparsity of
information concerning system design and operating conditions, including
carbon loading, no attempt has been made to include such information in the
table. Additional data demonstrating effective (99+ efficiency) removal of
pesticides from aqueous waste streams is shown in Table 5.5.8. However, these
data were obtained for loadings that were in the ppb range. While indicative
of the effectiveness of carbon adsorption as a polishing step, the data do not
demonstrate effectiveness for the higher end (up to 5,000 mg/L) of the
reported cost effective range.
No data were found for systems using PAC, although PAC and GAC should
exhibit little, if any, difference in adsorption.performance. As noted
previously, the most significant difference between the two sorbents is in
their particle size. The fine particle size of PAC is not suitable for use in
contacting equipment normally used for GAC systems.
5.5.3 Cost of Carbon Absorption
The cost of carbon adsorption treatment can be described in terms of
capital investment and operation and maintenance costs. Capital costs consist
of direct and indirect expenses. For the small scale system, direct capital
investment costs include the purchase of a waste storage tank, a prefilter,
carbon columns, a waste feed pump, piping and installation. For the large
scale system, additional direct capital investment costs include storage tanks
for spent and regenerated carbon, a multiple hearth furnace and automatic
controls.
A model has been developed by ICF, Inc. (Reference 17) for calculating
carbon adsorption costs. Table 5.5.9 contains the equations used in this
model to calculate direct capital costs as a function of carbon consumption
rate and storage volume. Indirect capital costs include the costs of
engineering, construction, contractor's fee, start-up expenses, spare parts
inventory, interest during construction, contingency and working capital.
5-104
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TABLE 5.5.7. COMPOUNDS REPORTED IN WASTESTREAMS BEING TREATED
BY FULL-SCALE, GRANULAR ACTIVATED CARBON UNITS
Concentration
(mg/L)
Pollutant
Benzene
para-Chlorbnitrobenzene
2-Ch loropbeno 1
4-Ch loropheno 1
2,4-D
2,4-D
2 , 6-Dicblorophenol
2 ,4-Dichlorophenol
Dieldrin
Repone
Pentacb loropbeno 1
Pentacbloropbenol
Toxaphene
2,4, 6-Tr ich loropheno 1
Influent
590
11.6
8.67
5.64
3,600
58.4
3.47
42.6
0.011
4
10
120
0.036
35
Effluent
210
0-0093
0.62
0.010
0.010
0.037
0.26
0.64
0.00001
0.0001
0.0001
49
0.001
0.01
Removal (%)
64
99.9
92.8
99.8
99.99
99.9
92.5
98.5
99.91
99.99
99.99
59
97.2
99.97
Source: Reference 5.
5-105
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TABLE 5.5.8. RESULTS OF ADSORPTION ISOTHERM TESTS ON TOXIC CHEMICALS
Compound
Aldrin
Dieldrin
Endrin
DDT
DDD
DDE
Toxaphene
Arochlor 1242 (PCB)
Arochlor 1254 (PCB)
Initial Carbon treated
concentration concentration Organic
pH g/L g/L reduction %
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
7.0
48
19
62
41
56
38
155
45
49
1.0
0.05
0.05
0.1
0.1
1.0
1.0
0.5
0.5
97.9
99+
99+
99+
99+
97.4
99+
98.9
98.98
Capacity3
30
15
100
11
130
9.4
42
25
7.2
of toxic chemicals adsorbed/g of carbon.
Source: Reference 15.
5-106
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TABLE 5.5.9. DIRECT COSTS FOR CARBON ADSORPTION3
Carbon consumption
rate
(Ibs/day)
Direct capital
costs
(*)
Direct operation and
maintenance costb
($/yr)
Less than 400
Greater than 400
l,256(c)-603 + 140(s)-54 29(c)-6 + 350(c)(cp) +
619(c).168(h) + 5(c)(p)
14,231(c)-522 + 140(s)-54
58(c)'657 + 35(c)(cp)
105(c)-455(h) +
25,012-383(c)(p) +
1.49 106(c)(f)
where: c " carbon consumption rate in pounds per day
s * storage volume in gallons
cp » carbon price in dollars per pound ($0.8/lb)
h ™ hourly wage rate in dollars per hour ($14.56/hr)
p <• power price in dollars per kilowatt-hour ($0.05/KWh)
f " fuel price (natural gas) in dollars per Btu ($6xlO~°/Btu)
aCost estimates were developed for three model treatment systems (three
small scale and three large scale systems). The cost estimates for these
systems were then used to develop a cost equation in the form of a power
curve.
power requirement is derived from the equipment specifications.
Source: Reference 17.
5-107
-------
These costs are expressed as percentages of either direct capital costs or the
sum of direct and indirect capital costs as summarized in Table 5.5.10.
Direct and indirect capital costs are assumed to be incurred in year zero.
Operation and maintenance costs also consist of direct and indirect
costs. Direct operation and maintenance costs (in 1984 dollars) include the
operating labor and electricity and carbon consumption. Table 5.5.9 also
contains the equations used in the model to calculate direct operation and
maintenance costs. As with the capital costs, the model considers operation
and maintenance costs for carbon consumption rates less and greater than
400 Ibs/day. For large-scale systems, the operation and maintenance costs
also include the. natural gas consumption necessary for the furnace. .Indirect
operation and maintenance costs include costs for insurance and overhead.
Based on the RCRA Risk-Cost Analysis Model, Table 5.5.11 shows carbon
adsorption costs for 100, 400, 1,000 and 2,500 gal/hr processes.
5.5.4 Overall Status of Process
5.5.4.1 Availability—
Activated carbon adsorption is a widely used technology for treating
waste streams containing organic compounds, including many hazardous
halogenated compounds. Its ability to treat solvents and other organics has
been demonstrated at bench, pilot, and full-scale'levels by many firms.
Manufacturers of activated carbon produce carbons to fit variable service
needs. Companies that use these activated carbon systems, both GAG and PAC,
are numerous as documented in several literature sources (see References 5,
13, and 18). Equipment designers and suppliers can be found in the Chemical
Engineering Equipment Buyers' Guide published by McGraw-Hill, New York, NY.
Many of these firms will provide assistance in developing a treatment system
for specific waste streams.
5.5.4.2 Application—
Activated carbon adsorption systems are widely used in industry to
process chemical product streams as well as waste streams. The technology has
proven to be effective as a pretreatment for aqueous wastes prior to their
introduction into biological treatment systems. Concurrent treatment of waste
streams with PAC and biological treatment has also proven to be effective.
5-108
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TABLE 5.5.10. INDIRECT COSTS FOR CARBON ADSORPTION
Item
Percent
of direct
capital
costs
Percent of the
sum of direct
and indirect
capital costs
Percent
of total
annual cost*
Indirect Capital Costs
Engineering and
Supervision
Construction and
Field Expenses
Contractors Fee
Startup Expenses
Spare Parts Inventory
Interest During
Construction
Contingency
Working Capital
Indirect Operation and
Maintenance Coats
Insurance, Taxes,
General
Administration
System Overhead
12
10
7
5
2
10
0
0
0
0
0
0
15
18
0
0
0
0
0
0
10
aThe total annual cost is defined as the sum of the total capital cost
multiplied by the capital recovery factor and the total operation and
maintenance costs.
Source: Reference 17.
5-109
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TABLE 5.5.11." CARBON ADSORPTION COSTS3
Quantity processed
(gal/nr)
100 400 1,000 2,500
Capital Expenditures
Capital Cost Including Installation'1
(51,000) 59 561 904 1,462
Annual Operation and Maintenance ($l,000)c
Energy
Labor
Carbon
Other
Capital Recovery
Total Annual Cost
Cost/1,000 gald
2
23
«7
1
10
42e
210e
11
35
27
5
99
177
221
27
53
67
10
160
317
159
68
80
lt>8
18
259
593
119
are based on the RCRA Risk-Cost Analysis Model.1-7
^Capital costs for the 100 gal/hr system include waste storage tank,
prefilter, carbon columns, waste feed pump, piping and installation; the
other flow levels (400, 1,000, 2,500) include these units plus storage
tanks for spent and regenerated carbon, a multiple hearth furnace and
automatic controls.
cThese costs are based on the following data:
carbon price • $0.8/lb
hourly wage rage • Sl4.56/hr
power price * $0.05/kwh
fuel price (natural gas) • $6 x 10~6/Btu
capital recovery factor " 0.177
"Unit costs are based on 2000 hours of operation per year.
^Modified to reflect a direct relationship between carbon requirement and
quantity processed.
*Note: 1984 dollars, prices are similar to 1986 values.
5-110
-------
However, the most common application of carbon adsorption systems would appear
to be as a polishing step for low concentration level effluents from other
treatment technologies. The use of carbon adsorption systems for treatment of
wastes containing 0.5 percent or greater organic concentration levels is not
considered to be cost effective. Other technologies should be considered at
these concentrations, unless regeneration can be used to achieve recovery of
valuable adsorbed compounds.
Removal efficiencies which permit direct discharge can usually be met by
GAG systems for most halogenated organics. However, performance will depend
upon the specifics of waste stream contamination, including the need for
pretreatment, post-treatment, and other aspects of system operation.
5.5.4.3 Environmental Impacts—
Environmental impacts can result from emissions during the regeneration
of carbon. However, there will be no serious environmental impacts if the
exit gases are treated by a control system; e.g.,'an afterburner and/or
scrubber, and in some cases, a particulate filter. Where the carbon is
chemically regenerated (acid, base, or solvent), the regeneration stream will
require future treatment; e.g., incineration or distillation to remove the
organic contaminants. .
The recovery or reuse of desorbed solutes from the. adsorption process
presents opportunities for both cost savings and reduction of environmental
impacts. Disposal of desorbed solutes as waste materials can be costly and
also result in an environmental hazard. Therefore,recycling of solute
following desorption and recovery should be considered and practiced if
possible.
5.5.4.4 Advantages and Limitations—-
The principal advantages of carbon adsorption technology is its ability
to achieve low effluent concentration levels for a large number of compounds,
including many halogenated organics. The technology appears particularly
applicable to high molecular weight compounds such as the chlorinated
pesticides. It is also applicable to the treatment of many compounds which
are normally toxic and resistant to biological treatment. Material recovery
may also be possible if regeneration methods other than thermal regeneration
can be used.
5-111
-------
Limitations are largely associated with high capital and operating costs,
particular^ when thermal reactivation must be used. Thermal reactivation, the
most effective means of regeneration, is cost effective only for relatively
large installations (i.e., greater than 1000 Ibs/day) and for wastes with
relatively low (less than 1 percent) organic concentrations. The technology
is sensitive to other impurities such as suspended solids and oil and grease,
thus, some degree of pretreatment is usually required to ensure effective
performance. The adsorption process is also not effective for many low
molecular weight and highly water soluble organics. However, most of the
halogenated organics considered in this document do not fall into the low
molecular weight, water soluble categories and are usually effectively
adsorbed.
5-112
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REFERENCES
1. Berkowitz, J.B. et al. Physical, Chemical and Biological Treatment
Techniques for Industrial Waste. Noyes Data Corporation; Park Ridge, New
Jersey. 1978.
2. Rizzo, J.L. Calgon Carbon Corporation. Letter to Paul Frillici, GCA.
June 11, 1986.
3. ICF Inc. Survey of Selected Firms in tbe Commercial Hazardous Waste
Management Industry: 1984 Update. Final Report to U.S. EPA,
Section II. OSW Washington, DC. 1985.
4. U.S. EPA Background Document for Solvents to Support 40 CFR Part 268,
Land Disposal Restrictions, Volume II. January 1986.
5. IT Enviroscience, Incorporated. Survey of Industrial Applications of
Aqueous-Phase Activated-Carbon Adsorption for Control of Pollutant
Compounds from Manufacture of Organic Compounds. Prepared for U.S. EPA
IERL; EPA-600/2-83-034, PB-83-200-188. April 1983.
6. Dobbs, R.A., and J. Cohen. Carbon Adsorption Isotherms for Toxic
Organics. EPA-600V 8-80-023. April 1980.
7. Slejko, F.L. Applied Adsorption Technology, Chemical Industry Series,
Volume 19. Marcel Dekker, Inc. NY, NY. December 1985.
8. Perrich, J.R., Editor. Activated Carbon Adsorption for Wastewater
Treatment. CRC Press Inc., Boca Raton, Florida. 1982.
9. U.S. EPA. Activated Carbon Treatment of Industrial Wastewater-Selected
Papers. EPA-600/2-79-177. Robert S. Kerr Environmental Research
Laboratory. August 1979.
10. Lyman, W.J. Carbon Adsorption, In: Unit Operations for Treatment of
Hazardous Industrial Wastes. Pollution Technology Review No. 47, Noyes
Data Corporation, Park Ridge, NJ. 1978.
11. Meidl, J.A., Zimpco Inc. PAC Process. Engineering and Management. June
1982.
12. Breton, M. et al. Technical Resource Document - Treatment Technologies
for Solvent-Containing Wastes. Prepared for HWERL, Cincinnati under
Contract No. 68-03-3243, Work Assignment No. 2. August 1986.
5-113
-------
13. Touhill, Shuckrow & Associates, Inc. Concentration Technologies for
Hazardous Aqueous Waste Treatment. Pittsburg, PA. EPA-600/2-81-019.
14. U.S. EPA. Treatability Manual, Volume III. EPA-600/2-82-001a, U.S. EPA
ORD, Washington, DC. 1981.
15. Hager, D.G., Calgon Corp. "Wastewater Treatment by Activated Carbon."
Chemical Engineering Progress. October 1976.
16. U.S. EPA. Development Document for Effluent Limitation Guidelines and
Standards for Petroleum Refining Point Source Category.
EPA-440/1-82-014. October 1982.
17. ICF, Inc. RCRA Risk-Cost Analysis Model, Phase III, U.S. EPA, OSW.
March 1984.
18. Radian Corporation. Full-Scale Carbon Adsorption Applications Study.
EPA-600/2-85-012. May 1984.
5-114
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5.6 RESIN ADSORPTION
Resin adsorption is an alternative treatment technology for the removal
of organic contaminants £rom aqueous waste streams. The underlying principle
of operation is similar to that for carbon adsorption; organic molecules
contacting the resin surface are held on the surface by physical forces and
subsequently removed during the resin regeneration cycle. Resin adsorbents
can be made from a variety of monomeric compounds which differ in their
polarity and thus, their affinity for different types of compounds. The
choice of resin type can lead to an adsorbent tailored specifically for
effective removal of special classes of compounds. For example, hydrophobia
resins such as those prepared from styrene - divinyl benzene monomers, are
most effective for nonpolar organics and bonding is largely the result of
Van der Waal's forces; acrylic based resins on the other hand are more polar
and dipole-dipole interactions may play the major role in the binding of polar
molecules to the resin surface. The general concept is that like molecules
attract. Polar resins will attract polar organics; nonpolar compounds will be
attracted by the more hydrophobic or nonpolar resins.
A significant aspect of resin adsorption is that the bonding forces are
usually weaker than those encountered in granulated activated carbon (GAG)
adsorption . Regeneration can be accomplished by simple, nondestructive means
such as solvent washing, thus providing the potential for solute recovery.
Thermal regeneration (generally not possible with resin adsorbents because of
their temperature sensitivity) is usually required for carbon adsorbents,
eliminating the possibility of solute recovery. The resins differ in many
other respects from activated carbon adsorbents. In addition to differences
in the ease and usual methods of regeneration associated with the chemical
nature of the two adsorbents, there are significant differences in shape,
size, porosity and surface area. Resin adsorbents are generally spherical in
shape rather than granular, and are smaller in size and lower in porosity and
surface area than GAG adsorbents. Surface areas for resins are generally in
2 2
the range of 100-700 m /g, as opposed to 800-1,200 m /g for activated
carbon. Adsorptive capacities are thus less for the resin adsorbents,
although the chemical nature and the pore structure of the resin can be
tailored to enhance the selectivity of the resin and, therefore, its
5-115
-------
adsorption capacity for specific organic components. Other notable properties
of resin adsorbents include their nondusting characteristics, their low ash
content, and their resistance to bacterial growth. The last characteristic is
primarily a result of the fine pore structure which inhibits bacterial
intrusion. Pore diameter and other physical properties of resin adsorbents
are shown in Table 5.6.1.
Another significant difference between resin and carbon adsorbents is
their cost. Resin adsorbents are much more expensive. They generally will
not be competitive with carbon for the treatment of waste streams containing a
number of contaminants with no recovery value. However, resin adsorption
should be considered if material recovery is practical, selectivity is
possible, and for cases where carbon regeneration is not effective. Like
carbon adsorption systems, resin adsorption can produce an effluent with low
levels of contaminant concentrations, particularly in cases where contaminants
are well characterized and few in number. Resin adsorption combined with
carbon adsorption may be effective for certain waste streams containing a
number of contaminants.
t
5.6.1 Process Description . '
Resin adsorption systems are designed and operated in similar fashion to
GAC systems. A principal difference will be in the regeneration step;
regeneration of the resin is usually performed in situ with aqueous solutions
or solvents. Solute recovery from the regeneration liquor will also be
required, with distillation the most likely method.
5.6.1.1 Fretreatment Requirements—
Polymeric adsorbents require pretreatment of feed streams to remove
suspended solids, oils and greases, and to adjust pH and temperatures, as
appropriate. Suspended solids in the influent should be less than 50 mg/L
and, in the case of oil and grease, less than 10 mg/L to prevent clogging of
the resin bed. The control of pH may be necessary to prevent resin attack
and to enhance adsorbability. Low temperature will also generally enhance
adsorption. Resin adsorbents, although generally resistant to chemical attack
because of their cross-linked structure, should not be brought into contact
5-116
-------
TABLE 5.6.1. PHYSICAL PROPERTIES OF ADSORBENTS
I
I—'
>—•
^J
Manufacturer
Rohm and Haas
Mitsubishi
Adsorbent
Amberlite XAD-2
Araberlite XAD-4
Amberlite XAD-7
Amberlite XAD-8
Amber sorb XE-347
Araberaorb XE-348
Diaion HP-10
Diaion HP-20
Diaion HP-30
Chemical
nature
Polystyrene
Polystyrene
Acrylic Ester
Acrylic Ester
Polymer Carbon
Polymer Carbon
Polystyrene
Polystyrene
Polystyrene
Pore
volume
(cm3/g)
0.68
0.96
0.97
0.82
0.41
0.58
0.64
1.16
0.87
Surface
area
(m2/g)
300
725
450
160
350
500
500
720
570
Pore
diameter
average
(A)
100
50
85
150
200, 15a
200, 15a
b
70
b
Surface
polarity
Low
Low
Intermediate
Intermediate
Low.
Intermediate
Low
Low
Low
aAverage pore diameter of the macropores and micropores, respectively.
"Average pore diameter not available.
-------
with compounds such as chemical oxidants and functional reagents which may
degrade the resin or poison adsorption sites. High levels of dissolved
solids, particularly inorganic salts, do not compete with organics for
adsorption sites, and their presence may in some instances increase the
adsorption of organics.
Pretreatment options are similar to those proposed previously for carbon
adsorption systems. For example, filtration or coagulation/sedimentation type
separations can be used for suspended solids, and flotation/extraction
procedures can be used for removal of oils and greases. Each pretreatment
option will result in a residual which may or may not require additional
processing prior to disposal. .
There are no definite limitations on the upper or lower contaminant
concentration levels that can be treated. An upper limit of 8 percent (for
phenol) is suggested in Reference 1, however, this is to maintain cycle time
and regeneration frequency within reasonable limits. As with carbon
adsorption, the efficiency of resin adsorption (weight of adsorbed material
per weight of adsorbent) is greater at high concentrations.
5.6.1.2 Operating Parameters—
The design of a resin adsorption system requires the development of basic
information such as feed stream flow rate, contaminant concentration, and
adsorbent type and capacity. Other information such as flow rate variations,.
suspended solid level, pH, and temperature will be required to ensure that
adequate pretreatment precautions and operating practices are followed.
The choice of adsorbent type can be guided by the concept that attractive
forces will be greatest for similar molecules. The solubility concept is also
useful in identifying regeneration solvents. The similarity of the adsorbate
in the regeneration solvent is quite important. The solvent not only must be
capable of overcoming the attractive forces of adsorbate/adsorbent but must
also remove the adsorbate in the smallest possible volume.
Although the relative strengths of the attractive forces between solute,
solvent, and resin can be predicted through the use of solubility
4
parameters, there is no practical method for determining the actual
capacity of an adsorbent for contaminants, particularly those existing in
complex waste streams. It is, therefore, necessary to carry out experimental
5-118
-------
studies to determine working capacities for candidate adsorbents. Costs may
also be prohibitive, and activated carbon may often be a more attractive
adsorbent, particularly where solute recovery is not desirable or practical.
Assuming a resin adsorbent can be found that can achieve required
treatment levels, additional tests will be required to identify and select a
regeneration process. The selection of a regeneration solvent can be guided
by use of solubility parameters. However, other factors such as cost of
solvent regeneration and adsorbate recovery must be considered. Distillation
appears to be the most likely solvent and solute recovery technology assuming
a solvent/solute match can be found that is amenable to such a separation
process.
Design of a resin adsorption process operation would include the
following steps as a general procedure: 1) determine wastewater effluent
purity desired, 2) select adsorbent and determine adsorption capacity,
3) select regeneration process based on bench or pilot scale tests, 4) size
adsorbent bed, 5) check loading run length and determine if it is compatible
with the regeneration time cycle, 6) repeat 4 and 5 until loading and
regeneration cycles are compatible, 7) determine bed dimensions by hydraulic
considerations, 8) design and size pumps, storage tanks, pretreatment
equipment and auxiliary equipment.
As noted in Reference 1, a system for treating low volume waste streams
will commonly consist of two beds. One bed will be on stream while the second
is being regenerated as shown in Figure 5.6.1.
The adsorption bed is usually fed downflow at flow rates in the range of
0.25 to 2 gpra per cubic foot of resin; this is equivalent to 2-16 bed
volumes/hr, and thus contact times are in the range of 3-30 minutes. Linear
2
flow rates are in the range of 1-10 gpm/ft . Adsorption is stopped when the
bed is fully loaded and/or the concentration in the effluent rises above a
certain level. A time of 30 minutes may not be adequate for attainment of
minimum concentration levels. EPA has suggested that limited contact times
may play an important role in reducing column loadings in the field to values
6
less than those predicted from isotherm testing. Reference was made to a
study which attributed carbon contact times of greater than 230 minutes to
applications which requires high degree of pollutant removal. Although rapid
5-119
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PHENOLIC
HASTE
POIYMCRIC
AO
•I
HAITI
lOlVEHT
MAKE Uf
£_
(£)
HATER
RECOVERED
SOLVENT
roiYMERIC
AOSORIER
•1
11
R
DISTIllATIOII
COIUMN «l
SOIVENTAIATIR
r>^i
WATtR TO
IIWtR
ni WOlATATtR AZEOTHOPt
(R«T«*« U Muftrnt CjtaMl
OlSniLATIOIt
COLOMH ml
JOlVlMTMATEII/PHEIIOt
OPAHATOII
DISnilATIOH*
CgiUMM U
fHEHOUttATER
I
mcnvnm
tot
PNUTOL
Column #3 utiliad w*wn higMy pun plwnol is raouind.
. ta/kr
KMnel
Wanr
ACMOM
TeiH -
0
284
21.736
22.000
(?)
14<0
1400
®
4
4
©
26«
•
J73 -
© + ®
< 10 own
23.207
4
/ 23^1
Figure 5.6.1. Phenol removal and recovery system - solvent
- regeneration of Amberllte adsorbent.
Source: Reference 1.
5-120
-------
adsorption kinetics are attributed to resin adsorbents, caution should be
exercised in assessing the contacting time requirements and design and
operating features needed to meet acceptable concentration levels.
Regeneration of the resin bed is performed in situ with basic, acidic,
and salt solutions or recoverable nonaqueous solvents being most commonly
used. Basic solutions may be used for the removal of weakly acidic solutes
and acidic solutions for the removal of weakly basic solutes; hot water or
steam could be used for volatile solutes; and methanol and acetone are often
used for the removal of nonionic organic solutes. A prerinse and/or a
postrinse with water will be required in some cases to remove certain
contaminants such as salts. As a rule, about three bed volumes of regenerant
will be required for resin regeneration; as little as one-and-a-half bed
volumes may suffice in certain applications.
The use of steam as the regenerating agent should be considered; steam
regeneration for volatile organics may provide some cost benefits in that it
can reduce the need for subsequent treatment to separate the waste solvent
from the dissolved organics. However, the condensed steam may also require
additional treatment prior to discharge to also eliminate dissolved organics.
When using steam regeneration for polymeric adsorbents, one must consider
the upper temperature limit of the resin in choosing the steam pressure. The
styrene based polymeric adsorbents are usually stable to 200°C; acrylic based
resins up to 150°C. Since the adsorbed solvent and other organic constituents
can cause the adsorbent resin matrix to swell and weaken, removal of these
constituents by steaming could result in disruption and breakup of the resin
matrix. Therefore, adsorbent stability is of concern when using steam
regeneration and should be studied using multi-cycling tests to confirm the
integrity of the adsorbent before proceeding with design of the regeneration
system.
Steam requirements are normally significantly lower for the polymeric
adsorbents than those for granular activated carbon to achieve a certain
desorption level of a given constituent. The reason for this is that the
attractive forces binding the organic constituent to the adsorbent are much
lower for the polymeric adsorbent.
5-121
-------
5.6.1.3 Post-Treatment Requirement—
Assuming effluent goals are realized, the post-treatment requirements are
restricted to treatment of the regeneration effluent. Other possible waste
streams requiring further processing could include the washing effluents (if
required for the prerinse and/or postrinse of the resin), the regeneration
solvent, and the condensed regeneration steam. Requirements will depend upon
the process scheme used.
5.6.1.4 Treatment Combinations-
Resin adsorption will normally be given consideration in applications for
which carbon adsorption would be considered as a potentially viable treatment
alternative. However, it will not generally be economically competitive with
carbon adsorption. In certain situations a combination of resin and carbon
adsorption could be used to advantage. For example it may be attractive as a
polishing step to remove specific contaminants (particularly if the
contaminants have recovery value) passing a carbon adsorption bed, e.g., polar,
low molecular weight compounds.;
5.6.2 Demonstrated Performance
Resin adsorption technology is not as established as activated carbon
adsorption is for full scale treatment of waste streams containing halogenated
organic contaminants. Studies have been conducted to determine the
performance of resins as adsorbents for several types of organic chemical
compounds. The results of one such study for pesticides is shown in
Table 5.6.2. Although high efficiencies were obtained, the initial pesticide
concentrations were in the ppm range and did not approach the higher levels
(8 percent) suggested in Reference 1 as appropriate for the technology.
Further information concerning the performance of resin adsorbents for removal
of halogenated and other organic solvents is provided in Reference 8.
5-122
-------
TABLE 5.6.2. REMOVAL OF POLYNUCLEAR AROMATICS, CHLORINATED PESTICIDES,
AND POLYCHLORINATED BIPHENYLS FROM TWO TYPES OF SPIKED
MIAMI TAP WATER
Dibromochlorophenol
Hexac hlorobenzene
BHC ( 1,2, 3,4,5, 6-hexa-
chlorocyclohexane)
BHC (1,2,3,4,5,6-hexa-
chlorocyclohexane)
Aldrin
Heptachlor
Ambersorb
Water Ab
81.5
98.6
98.7
98.9
92.5
97.6
Z Removed (66,800 BV)a
XE-340 FS-400
Water Bc Water Ab Water Bc
99.4 94.3 100
99.9
100
99.8
95.3
99.8
aBed depth, 2.5 ft; column diameter, 1 in.; flow rate, 1.2 gpm/ft3
(decreasing to 0.6 near end of test); BV, 386 ml; EBCT, 6.2 min
(increasing to 12 min near end of test); duration, 320 days.
"18 ppm Cl2 needed for breakpoint chlorination, 7.2 ppm TOC in finished
water.
C5 ppm Cl£ needed for breakpoint chlorination, 5 ppm TOC in finished
water.
Source: Reference 7.
5-123
-------
5.6.3 Cost of Resin Adsorption
Resin adsorbents are quite expensive (Table 5.6.3). The cost exceeds
that of granular activated carbon (GAG) ($0.80 to $1.00 per pound). However,
the economics of using resins or polymeric adsorbents may in certain cases be
more favorable than those for granular activated carbon.
Thermal regeneration costs for GAG adsorption systems are quite high and
carbon losses are of the order of 3 to 8 percent per regeneration. Even
though macroreticular (resin) adsorbents cost more per pound, they are
relatively cheaper to regenerate and regeneration does not result in any
appreciable adsorbent loss. Thus, smaller beds and more frequent
regenerations may be economically viable with resin adsorbents.
Design criteria for a one million gallon per day treatment plant are
shown in Table 5.6.4. Assuming influent concentrations of 300-1,000 ppb, the
operation is designed to remove greater than 90 percent of the incoming
contaminant. A comparable GAG system is analyzed simultaneously for
comparison. The capital and operating costs for each system are given in
Table 5.6.5. It can be seen that both the capital investment and the •
operating costs are lower when the more expensive (by volume) adsorbent is
used. This comes about primarily because fewer and smaller contactors are
utilized and expensive thermal regeneration furnaces are not required.
The resin system looks very promising because of the many assumptions
made concerning design and performance, e.g., high capacity, rapid kinetics,
and a 5 year resin lifetime. The assumptions have not yet been demonstrated.
Moreover, the design is for a waste influent loading (1 ppm) that is extremely
low for an industrial waste stream. Costs, already high relative to many
other technologies, will increase drastically as influent loadings (and system
size) increase.
However, the example does indicate that resin adsorption may be more
economical than carbon adsorption. Similar reasoning has been applied in
Reference 1 where costs have been estimated for resin adsorption applied to
three different waste streams. Costs ranged from $38.60 per 1,000 gallons for
a phenol recovery system (at 5 percent phenol in waste) to $0.83 per
1,000 gallons for a chlorinated pesticide removal system. In the latter case,
the cost of a GAC treatment system was estimated at $1.33 per 1,000 gallons.
5-124
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TABLE 5.6.3. COST OF ADSORBENTS3
Adsorbent
Amberlite XAD-2
Amberlite XAD-4
Anberlite XAD-7
Amberlite XAD-8
Chemical nature
Polystyrene
Polystyrene
Acrylic ester
Acrylic ester
Cost $/ft3b
282.95
355.05
223.25
337.25
3Personal communication with Rohm and Haas Company,
Fluid Process Chemicals Department, Philadelphia, PA,
April 3, 1986.
"At a bulk density of 37 Ibs/ft , costs are roughly
$6 to $10 per pound.
5-125
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TABLE 5.6.4. DESIGN CRITERIA— TRIHALOMETHANE REMOVAL
Adsorbent
Parameter
Ambersorb XE-340
Granular activated
carbon
Density
Nominal Flowrate
Contactors
On-stream Time
Regeneration
Type
Time/Contactor
Absorbent
Lifetime
37 lb/ft3
6.0 gpm/ft3
1.25-min EBCTa
58 ft3 each
2 on-sCream
1 regeneration/standby
3.3 days
in-place steam
8 hr-
5 yr
(fouling limited)
25 lb/ft3
1.0 gpm/ft3
7.48-min EBCTa
348 ft3 each
2 on-stream
1 regeneration
1 standby
20 days
thermal reactivation
11 days
8 months
<§ 82 loss/cycle
Design Basis: 1.0 mgd average flow, 1.43 mgd peak flow.
aEmpty bed contact time.
Source: References 9 and 10.
5-126
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TABLE 5.6.5. COST COMPARISON—GAC VS. RESIN3
1.0 tngd Plant
Capital Cost
Contactor, Pumps,
Regeneration Facilities
Plus 252 for Engineering
Contingencies
Adsorbent Cost
Total
Operating Costs
Adsorber Power
Regeneration Fuel
Solvent Regeneration.
Adsorbent Makeup
Resin
$350,000
$ 45,000
@ $7.00/lb
$395,000
$/yr ^/l.OOO gal
7,100 1.945
3,000 . 0.822
6,188 1.695
9,000 2.466
(5 yr)
Granular Activated
Carbon
$950,000
$ 20,000
i $0.55/lb
$970,000
$/yr ^/l.OOO gal
3,550 0.973
4,203 1.152
18,000 4.932
(82 loss/cycle)
Subtotal $25,288 6.928
$25,753 7.057
Capital Related Costs
(exclude adsorbent):
Depreciation 92
Maintenance 32
Property Overhead 22
Quality Control
49,000 13.420
9.000 2.460
22
133,000 36.438
9.000 2.460
Total $83,288 1,000 gal
46.
$167,753 1,000 gal
aNo specific GAC or resin product. Values taken at average costs.
Source: References 9 and 10.
5-127
-------
The cost data are outdated (from the 1970's); costs in 1986 dollars would be
about 50 percent greater, based on changes in the chemical engineering plant
cost index.
The high costs of resin adsorption for the treatment of moderate to high
concentration contaminant levels can only be justified in situations where
cost benefit is realized from product recovery. In the case of the phenol
recovery system used in the example above, credit from the sale of phenol
exceeded total annual operating costs, therefore justifying use of the process
on an economics basis.
5.6.4 Overall Status
5.6.4.1 Availability--
Resin adsorption technology parallels that for carbon adsorption.
Equipment requirements are similar and available from a number of
manufacturers serving the chemical process industries. However, there appears
to be some question about the commercial availability of many of the resin
adsorbents for which data are reported in the literature. Ambersorb XE-340,
for example, manufactured by Rohm and Haas and the subject of numerous
technical studies, is not available in commercial quantities. The
availability of some other resin adsorbents may also be questionable.
5.6.4.2 Application—
Because of their expense, resins are-not commonly used full-scale to
remove organics from wastewaters. There is also little publicly available
information on current or proposed industrial applications. Information of a
general nature does report that resins are being used for color removal from
dyestuff and paper mill waste streams, for phenol removal, and for polishing
of high purity waters.
The following applications have been identified as being particularly
attractive for resin adsorption technology.
• Treatment of highly colored wastes where color is associated with
organic compounds
5-128
-------
• Material recovery where solvents of commercial value are present in
high enough concentration to warrant material recovery since it is
relatively easy to recover solutes from resin adsorbents
• Where selective adsorption is an advantage and resins can be
tailored to meet selectivity needs
• Where low leakage rates are required; resins exhibit low leakage
apparently as a result of rapid adsorption kinetics
• Where carbon regenerations is not practical, e.g., in cases when
thermal regeneration is not safe
• Where the waste stream contains high levels of inorganic dissolved
solids which drastically lowers carbon activity; resin activity can
usually be retained, although prerinses may be required.
5.6.4.3 Environmental Impacts—
The only major environmental impacts resulting from resin adsorption
systems are associated with the disposal of the regeneration solution and the
extracted solutes when they can not be recycled. Distillation to recover
solvent and incineration of the separated solute are likely treatment/disposal
options. Air emissions would have to be considered as a result of these
treatment processes.
^
5.6.4.4 Advantages and Limitations—-
As noted, resin adsorption appears to offer advantages in certain
situations; e.g., for treatment of highly colored wastes, for material
recovery, where low leakage is required, and in instances where carbon
adsorption is not practical. The advantages of resin adsorption are a result
of ttieir potential for selectivity, rapid adsorption kinetics, and ease of
chemical regeneration.
Major limitations of resin adsorbents result from: 1) the generally
lower surface area and usually lower adsorption capacities than those found in
activated carbon; 2) possible susceptibility to fouling due to poisoning by
materials that are not removed by the regenerant; and 3) their relatively high
cost. The high cost of the resin may be balanced by its ease of regeneration
and their predicted long lifetimes in situations where carbon must be
thermally regenerated and carbon losses become appreciable (up to 10 percent).
5-129
-------
REFERENCES
1. Lyman. W.J., Resin Adsorption in: Unit Operations for Treatment of
Hazardous Wastes, Pollution Technologies Review No. 47. Noyes Data
Corporation, Park Ridge, New Jersey, 1978.
2. Rohm and Haas Company, Fluid Process Chemicals Department,
Amber-Hi-Lites, Winter 1980 (Technical Bulletin).
3. Neely, J.W. and E.G. Isacoff, Carbonaceous Adsorbent For the Treatment of
Ground and Surface Waters, Marcel Dekker, Inc, New York, N.Y., 1982.
4. Mark, H., et al. Encyclopedia of Polymer Science and Technology,
Cohesive-Energy Density. Vol. 3, p. 833. John Wiley & Sons, Inc., 1970.
5. Slejko, F.L., Applied Adsorption Technology, Chemical Industry Series,
Marcel Dekker, Inc, New York, N.Y. 1985.
6. U.S. EPA, Background Documents for Solvents to Support 40 CFR Part 268
Land Disposal Restrictions, Volume II, January 1986.
7. Symons, J.M., J.K. Carswell, J. DeMarco, and O.T. Love, Jr., Removal of
Organic Contaminants from Drinking Water Using Techniques Other Than GAC
Alone, A Progress Report, U.S. EPA, Cincinnati, 1979.
8. Breton, M. A., et al. Technical Resource Document - Treatment
Technologies for Solvent - Containing Wastes. Prepared for U.S. EPA,
HWERL, Cincinnati under Contract No. 68-03-3243, Work Assignment No. 2.
August 1986.
9. U.S. EPA. Synthetic Resin Adsorbents in Treatment of Industrial Waste
Streams, EPA 600/2-84-105, May 1982.
10. McGuire, M.J. and Sublet, I.A., Activated Carbon Adsorption of Organics
from the Aqueous Phase, Volume 2; Economic Analysis Employing Ambersorb
XE-340 Carbonaceous Adsorbent in Trace' Organic Removal from Drinking
Water, Ann Arbor Science 1980.
5-130
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SECTION 6
CHEMICAL TREATMENT PROCESSES
.The chemical treatment methods discussed in this section include some
processes which could equally well be classified as thermal processes
(i.e., wet air and supercritical water oxidation) since the general result of
these high temperature processes is the conversion of the organic contaminants
to fundamental products of oxidation such as carbon dioxide and water. Other
technologies, like the other oxidation processes do not achieve total
destruction and must be considered as pretreatment steps for a second
treatment technology, usually a biotreatment process. The processes addressed
in this section are:
r
6.1 Wet Air Oxidation
6.2 Supercritical Water Oxidation
6.3 Other Chemical Oxidation Processes
6.4 Oechlorination Processes
Discussions of these chemical treatment processes are provided using the same
format as was used for the discussions of physical treatment processes in the
previous section. Parallel discussions for the above processes can also be
found in the TRD for solvent-containing wastes.
6-1
-------
6.1 WET AIR OXIDATION
Wet air oxidation (WAO) is the oxidation of dissolved or suspended
contaminants in aqueous waste streams at elevated temperatures and pressures.
It is generally considered applicable for the treatment of certain organic-
containing media that are too toxic to treat biologically and yet too dilute
1 2
to incinerate economically. ' The leading manufacturer of commercially
available WAO equipment reports that WAO takes place at temperatures of 175 to
320°C (347 to 608°F) and pressures of 2,169 to 20,708 kPa (300 to
3,000 psig). Although the process is operated at subcritical conditions
(i.e., below 374°C and 218 atmospheres), the high temperatures and the high
solubility of oxygen in the aqueous phase greatly enhances the reaction rates
over those experienced at lower temperatures and pressures. In practice, the
three variables of pressure, temperature and time are controlled to achieve
the desired reductions in contaminant levels.
In addition to serving as the source of oxygen for the process, the
aqueous phase also moderates the reaction rates by providing a medium for heat
transfer and heat dissipation through vaporization. Generally, pressures are
maintained above the vapor pressure of water to limit water evaporation rates,
thus limiting the heat requirement for the process. The reactions proceed
without the need for auxiliary fuel at feed chemical oxygen demand (COD)
3
concentrations of 20 to 30 grams per liter. The extent of contaminant
destruction will depend upon the wastes to be oxidized and the reaction
conditions. Typically, 80 percent of the organic contaminants will be
oxidized to CO. and H.O. Residual organics will generally be low
molecular weight, biodegradable compounds such as acetic acid and formic acid.
However, halogenated aromatic compounds, e.g. chlorobenzenes and many
pesticides, are resistant to wet air oxidation. Information concerning the
extent .of reduction achievable and the nature of the residuals for these
compounds is largely unknown. Wet air oxidation should definitely be
considered a pretreatment alternative for waste streams containing these
difficult to oxidize halogenated compounds. A secondary treatment
(e.g., biological treatment), will generally be needed to achieve acceptable
destruction levels.
6-2
-------
6.1.1 Process Description
^
A schematic of a continuous WAO system is shown in Figure 6.1.1. The
Zimmerman WAO System, as shown in the figure, has been developed by Zimpro,
Inc., Rothschild, Wisconsin. It represents an established technology for the
treatment of municipal sludges and certain industrial wastes. Full scale
treatment of halogenated organic compound wastes has not yet been
demonstrated. However a 10 gpra pilot unit has been used to treat pesticides,
solvent still bottoms and general organic wastes at a commercial waste
3 6^}
treatment facility in California. ' As will be noted later, the
effectiveness of WAO as an alternative to land disposal for certain
halogenated organic containing waste streams will depend upon a number of
factors including the molecular structure and concentration of the
contaminants and the processing conditions. ' '
In the WAO process, the waste stream containing oxidizable contaminants
is pumped to a vertical bubble tower reactor using a positive displacement,
high pressure pump. The feed stream is preheated by heat exchange with the
hot, treated effluent stream. Air (or pure oxygen) is injected following the
high pressure pump. Steam is added as'required to increase the temperature
within the reactor to a level necessary to.support the oxidation reactions in
the unit. As oxidation proceeds, heat of combustion is liberated. At feed
COD concentrations of roughly 2 percent the heat of combustion will generally
be sufficient to bring about a temperature rise and some vaporization of
«
volatile components. Depending upon the temperature of the effluent following
heat exchange with the feed stream, energy recovery may be possible or final
cooling may be required. Following energy removal, the oxidized effluent,
consisting mainly of water, carbon dioxide, and nitrogen, is reduced in
pressure through a specially designed automatic control valve. The effluent
liquor is 'either suitable for final discharge (contaminant reduction achieves
acceptable standards) or is now readily biodegradable and can be sent to a
biotreatment unit for further reduction of contamination levels; Similarly,
noncondensible gases can either be released to the atmosphere or passed
through a secondary control device (e.g., carbon adsorption unit) if
additional treatment is required to reduce air contaminant emissions to
Q
acceptable levels.
6-3
-------
cr>
OXIDIZABLE
WASTE
FEED
PUMP
PROCESS
HEAT
EXCHANGER
REACTOR
AIR COMPRESSOR
PCV
TREATED
WASTEWATER
Figure 6.1.1. Wet air oxidation general flow diagram. \
Source: Reference 4.
-------
The pressure vessel is sized Co accommodate a. fixed waste flow and
residence time. Based on the characteristics of the waste, a combination of
time, temperature, pressure, and possibly catalyst can be utilized to bring
about the destruction of many halogenated organic contaminants.
6.1.1.1 Fretreatment Requirements for Different Waste Forms and
Characteristics—
Very little discussion is found in the literature concerning the physical
form of wastes treatable by WAO. However, WAO equipment.and designs have been
used successfully to treat a number of municipal and industrial sludges.
According to a Zimpro representative, wastes containing up to 15 percent COD
(roughly equivalent to 7 to 8 percent organics) are now being treated
successfully in commercial equipment.
Treatment of solid bearing wastes is dependent upon selection of suitable
pump designs and control devices. WAO units used for activated carbon
regeneration now operate at the 5 to 6 percent solids range. Treatment of
higher solid levels is not precluded by fundamental process or design
limitations. Column design must also be consistent with the need to avoid
settling within the column under operating flow conditions. Thus,
pretreatment to remove high density solids (e.g., metals by precipitation) and
accomplish size reduction (e.g. filtration, gravity settling) would be
required for some slurries. It should be noted that ,the WAO unit operated by
Casmalia Resources in California does not accept slurries or sludges for
treatment. This may be a result of design factors precluding their
14
introduction into the system.
Several bench scale studies have been conducted to determine the
susceptibility of specific compounds to wet air oxidations. Results of these
studies and other studies have been summarized in the literature. ' ' '
The results indicate that the following types of compounds can be destroyed in
wet air oxidation units:
a Aliphatic compounds, including those with multiple halogen atoms.
Depending upon the severity of treatment, some residual oxygenated
compounds such as low molecular weight alcohols, aldehydes, ketones,
and carboxylic acids might be present, but these are readily
bio treatable.
6-5
-------
Aromatic hydrocarbons, such as toluene and pyrene are easily •
oxidized.
Halogenated aroma tics can be oxidized provided there is at least one
nonhalogen functional group present on the ring; the group should be
an electron donating constituent such as an hydroxyl, amino, or
methyl group.
Halogenated aromatics, such as 1,2-dichlorobenzene, PCBs, and TCDDs,
are resistant to oxidation under conventional conditions although
these compounds are destroyed to a greater extent as conditions are
made more severe or catalysts are employed. However, Casmalia
Resources does not accept chlorinated aromatics.^
Casmalia Resources also does not accept for WAO treatment wastes
containing highly volatile organics like Freon which would enter the
unit in the gas phase, and tin, which is corrosive to heat exchanger
surface s.^
Batch process results obtained in the laboratory are applicable to continuous
process design for pure compounds and complex sludges, i.e., specific compound
destruction is similar and predictable for pure compounds and those compounds
contained in complex industrial wastes. '
6.1.1.2 Operating. Parameters—
Although operation of a WAO system is possible, by definition, under all
subcritical conditions; i.e., below 374°C and 218 atm (3,220 psig),
commercially available equipment is designed to operate at temperatures
ranging from 175 to 320°C and at pressures of 300 to 3,000 psig.
Of all variables affecting WAO, temperature has the greatest effect on
reaction rates. In most cases, about 150°C (300°F) is the lower limit for
appreciable reaction. About 250°C (482°F) is needed for 80 percent reduction
of COD, and at least 300°C (572°F) is needed for 95 percent reduction of COD
within practical reaction times. Destruction rates for specific constituents
2
may be greater or less than that shown for COD reductions.
Initial reaction rates and rates during the first 30 minutes are
relatively fast. After about 60 minutes, rates become so slow that generally
2
little increase in percent oxidation is gained in extended reaction.
An increase in reaction temperature will lead to increased oxidation but
generally will require an increase in system pressure to maintain the liquid
phase and promote wet oxidation. A drawback to increasing the temperature and
6-6
-------
pressure of Che reaction is the greater stress placed on the equipment and its
components, e.g., the increased potential for corrosion problems. Corrosion
is controlled by the use of corrosion resistant materials such as titanium.
As noted by Zimmerman, et al., the object of WAO is to intimately mix the
right portion of air with the feed, so that under the required pressure,
combustion will occur at a speed and temperature which will effectively reduce
the organic waste to desired levels. Pressures should be maintained at a
level that will provide an oxygen rich liquid phase so that oxidation is
maintained. Charts and curves are provided in Reference 5 to aid 'in the
determination of waste heating value, stoichiometric oxygen requirement, and
the distribution of water between the liquid and vapor phases at given
temperatures and pressures.
Previous experience with the design of wet oxidation systems has shown
that batch results are applicable to continuous process design when the oxygen
transfer efficiency is 90 percent (11 percent excess air) or less. A model
was developed to gain insight into the key system parameters using a common
industrial waste stream and fixed temperature, residence time, and COD
reduction. The model was also used to estimate costs for the system. Ifs
value, as a predictive tool, along with that o.f supplementary kinetic
studies of batch wet oxidation, is limited by the spar3ity of experimental
data concerning reaction products and their phase distributions at the
elevated temperatures and pressures encountered during WAO.
6.1.1.3 Post-Treatment Requirements—
The use of WAO to meet acceptable treatment levels halogenated organic
a
for wastes has not yet been demonstrated. As will be noted later, WAO has
been used under certain conditions to achieve destruction levels that are
essentially complete. However, for the most part, this level of performance
has.been achieved for specific compounds oxidized in batch reactors under
conditions that are more rigorous than those normally used in commercial
systems.
Destruction levels will vary for different compounds in complex waste
mixtures and there is evidence that certain of the low molecular weight WAO
breakdown products (e.g., methanol, acetone, acetaldehyde, formic acid, etc.)
are resistant to further oxidation. Thus, under typical WAO operating
6-7
-------
conditions it is likely that both contaminant residuals (unreacted halogenated
organics) and low molecular weight process by-product residuals may be
present. While it is entirely possible that imposition of more stringent
operating conditions will serve to reduce these residuals to acceptable
levels, the manufacturers and users of commercial WAO systems stress that the
major applications involve the pretreatment of waste, usually for subsequent
biological treatment.
Even under conditions that are favorable for wet oxidation, it is also
likely that certain contaminants or byproducts, particularly some of the more
volatile components, will partition between the vapor phase and the liquid
phase. The partitioning will be a function of operating conditions and the
contaminant partial pressure. The Henry's Law constant at the temperature of
operation will fix the distribution; however, Henry's Law constant is .not
generally known under most conditions of WAO system operation. Although a
method of estimation has been proposed by researchers at Michigan
Technological University, empirical tests will be necessary to establish
vapor and liquid phase residuals and some post-treatment of both streams may
be necessary. Existing post-treatment methods for the liquid generally
involves bacteriological treatment. Although the results of post-treatment
schemes for vapors from the WAO system have not been found in the literature,
a two-stage water scrubber/activated carbon adsorption system has been used to
treat WAO vapor emissions. Presumably carbon adsorption or scrubbing
systems could be routinely employed if necessary.
6.1.1.4 Treatment System Combinations—
Most of the commercial WAO systems in operation today are employed as
pretreatment devices to enhance the biotreatability of municipal and
industrial wastes. Wet air oxidation is also used as a means of regenerating
spent activated carbon used as an adsorbent. In the latter case the WAO
regenerates the activated carbon through oxidation of the organics adsorbed on
the carbon surfaces.
The application of WAO to industrial organic wastes has generally been
limited to treating specific, homogeneous waste streams, including soda
pulping liquors at pulp mills and n-nitrosodimethylamine and acrylonitrile
wastes. However, WAO has been used since 1983 to treat varied waste streams
6-8
-------
at the Casmalia Class I disposal site, located near Santa Maria, California.
Phenolics, solvent still bottoms, and other organic wastes have all been
treated at Casmalia, in certain instances in conjunction with a powdered
activated carbon treatment system and a two-stage scrubber-carbon adsorption
19
system for vapor treatment.
Treatment of specific waste streams to meet acceptable halogenated
organic effluent levels by a WAO system is not precluded, as evidenced by some
of the performance data shown below for removal of specific contaminants.
However, in most instances reaction conditions would have to be tailored to
the waste stream and pollutant. Generally an increase in the
pressure/temperature conditions normally employed by the users of WAO systems
would be required. Equipment problems associated with the more stringent
operating conditions would have to be considered.
6.1.2 Demonstrated Performance of WAO Systems
8
As noted by EPA, full scale use of WAO technology is well demonstrated
for the treatment of municipal sludge but full scale treatment of halogenated
organic wastes is not demonstrated. However, data showing the WAO destruction
of specific organic compounds including some halogenated organics of concern
to EPA, have been provided in the literature. These data are largely the
result of bench scale testing, but do include results of pilot-scale and
full-scale performance tests. The data indicate that WAO can be effective in
treating specific organic contaminants, including many industrial wastewaters
containing halogenated organics. However, chlorinated organics appear to be
the most difficult compounds to destroy. Residuals in both the gas and liquid
phase would also have to be considered on a case by case basis if WAO
technology is to be used for the treatment of specific halogenated organic
compound containing waste streams.
6.1.2.1 Bench-Scale Studies—
Bench scale studies of the destruction of specific organic substances by
1 8 15
wet oxidation have been conducted at Zimpro, Inc. ' ' Some of these data
are shown in Table 6.1.1. The tables include destruction data for halogenated
organic compounds and for halogenated solvents in order to illustrate the
6-9
-------
TABLE 6.1.1. BENCH-SCALE WET AIR OXIDATION OF PURE COMPOUNDS
Compound
Arocblor 1254
Carbon Tetrachloride
Chlorobenzene
Chloroform
1-Ch loronaph t ba 1 ene
2-Chloropheno 1
2-Ch loropbeno 1
2,4-Dichloroaniline
1 , 2-Dichlorobenzene
1 , 2-Dicbloroetnane
Hexacblorocyclopentadiene
Repone
Pentach loropbeno 1
Pent acb loropbeno 1
2,4,6-Trichloroaniline
Wet
oxidation
conditions
"C/minutes
320/120
275/60
a275/60
275/60
a275/60
275/60
320/60
*275/60
*320/60
275/60
300/60
a280/60
275/60
320/60
a320/120
Starting
concentration
Cmg/L)
20,000
4,330
5,535
4,450
5,970
12,400
12,400
259
6,530
6,280
10,000
1,000
5,000
5,000
10,000
Final
concentrat ion
(mg/L)
7,400
12
1,550
3
5
625
17
0.5
2,017
13
15
690
902
6
2.5
Percent
destroyed
63.0
99.7
72.0
99.9
99.91
95.0
99.9
99.8
69.1
99.8
99.9
31.0
82.0
99.9
99.9
Catalyzed.
6-10
-------
effect of operating variables, catalysts, and chemical structure on the
effectiveness of wet air oxidation. Further detail on treatment of
20
halogenated solvents can be found in the TRD for solvents.
As shown in Table 6.1.1, most compounds were destroyed to an appreciable
extent at 320°C. As noted above, the halogenated organic devoid of other
functional groups (i.e. chlorobenzene, dichlorobenzene, Arochlor PCS, and
kepone) were the most resistant to oxidations. The oxidation resistant
compounds showed a marked increase in destruction efficiency with temperature
through the 275°C to 320°C range. Presumably destruction efficiencies would
be somewhat higher at even more elevated temperatures.
Although no attempt was made to measure vapor phase residuals,
Reference 15 does present data for liquid phase residuals. Formic acid and
acetic acid were identified in these residue in amounts representing as much
as 20 weight percent of the original charge of the specific test compound.
However, the two low molecular weight acids formed are readily biodegradable
by conventional treatment methods. Thus, it was concluded that wet oxidation
of the waste constituents followed by biotreatment would yield an effluent
suitable for discharge to a publicly owned treatment plant.
6.1.2.2 Pilot-»Scale Studies—
The results of several pilot scale studies have been reported in the
literature. The flow rates of systems used in these studies ranged from
2.5 to 28.9 gallons per hour (0.23 to 2.6 cubic meters per day).
Only one series of pilot-scale tests were conducted with a wastewater
containing a halogenated organic pesticide/herbicide (2j5-dichloro-6-
nitrobenzoic acid). Removal was 90.5 percent. In another test series,
unexpectedly high destruction efficiencies of 98.2 percent were obtained for
1,2-dichlorobenzene, a compound that was not readily oxidized in the
bench-scale tests. The higher than anticipated efficiency was attributed to
synergetic effects due to interaction with break down products (free radicals)
of other contaminants. Enhanced oxidation has been noted in other tests of
multicontaminant industrial waste streams.
6-11
-------
6.1.2.3 Full-Scale Studies—
Several full-scale studies have been conducted at the Casmalia Resources
facility in Santa Barbara County, California using a skid mounted WAO systems,
capable of 10 gallon per minute flow rate for waste materials with a COO of
40 g/liter. Tests have been conducted oh wastewater containing phenolics,
organic sulfur, cyanides, nonhalogenated pesticides, solvent still bottoms,
and general organics. In the case of the general organic wastewater, COD was
A
reduced 96.7 percent to a level of 2.5 g/liter. During this test the wet
oxidation unit was operated at 277°C (531°F), 1550 psig, and a residence time
of 120 minutes. For the solvent still bottoms, the unit was operated at an
average reactor temperature of 268°C (514°F), a reactor pressure of
1,550 psig, and a nominal residence time of 118 minutes. COD, BOD, and IOC
2
reductions of 95.3, 93.8, and 96.1 percent, respectively, were measured.
However, no specific organic compound destruction efficiencies were reported
for solvents or halogenated organics.
6.1.2.4 Studies of Treatment Systems Using WAO—
The use of pilot-scale and full-scale treatment systems combining
I'M
PACT (powdered activated carbon addition to the reaction basin of an
activated sludge process) with wet air oxidation regeneration have been
18 21
reported in the literature. ' Reference 21 reports destruction
efficiencies of greater than 99 percent for several priority pollutants
present in a domestic and organic chemical wastewater not treatable by
conventional biological treatment systems (see Table 6.1.2).
Reference 18 presents results obtained during treatment of RCRA
wastewater and CERCLA ground water at the Bofors-Nobel facility in Muskegon,
Michigan. Cleanup at the site was conducted in accordance with the system
schematic shown in Figure 6.1.2. Two WAO units are used, one dedicated solely
to detoxification, the other used primarily as a carbon regeneration unit with
occasional use as an additional detoxification unit. Although no data are
provided for specific organic solvent components of the waste, an average
efficiency of 99.8 percent is stated for toxics in the feed.
6-12
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TABLE 6.1.2. PRIORITY POLLUTANT REMOVALS USING A PACT™/WET AIR
REGENERATION SYSTEM FOR DOMESTIC AND ORGANIC
CHEMICALS WASTEWATER3
Parameter
Benzene
Cb lorobenzene
1,2, 4-Tr icblorobenzene
1,1, 1-Tr ichloroethane
2,4,6-Trichlorophenol
Chloroform'*
2-Cbloropheno 1
1 , 2-D ich lorobenzene
1 , 3-Dichlorobenzene
3 ,4-Dichloropbenol
Dicblorobromometbane
Pentacblorophenol
Toluene
Influent
WD
907
' 597
62
7
81
87
98
113
67
116
2.3
35
1,195
Effluent
WO
3.0
3.7
ND
ND
ND
25
ND
ND
ND
1
ND
ND
2
Removal •
efficiency
(%)
99.6
99.3
~100
~100
- 100
71
~ 100
- 100
~ 100
99
- 100
~ 100
99.8
a4.0 bour aeration time; regeneration temperature * 230°C.
Drinking water background exceeds 50 yg/L chloroform.
Source: Reference 21.
6-13
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HIGH STRENGTH to
TOXIC WASTES |
1
1
T DILUTE
t- PROCESS WASTE. ^
*• LANDFILL *
LEACHATE Nl
ZIMPRO
WAO
ACID CAUSTI
1 I
:UTRALIZATI(
C
'
ZIMPRO ^ A»U m . **ine>ii i
^
>N
VIRGIN PHOSPH.
CARBON ACID POLYMER
MAKEUP I I
* 1 MUSKFGON
. — " ^ A_¥|j 1 ^ C.UUIM 1 T
PACT™ PACT™ WWTP
AERATION 1 SETTLING
1 '
THICKENER
Figure 6.1.2. 4.5 MGD wastewater treatment facility, i
Source: Reference 18. i
-------
6.1.3 Cost of Treatment
6.1.3.1 Wet Air Oxidation Costs—
•
Treatment costs for wet air oxidation systems will be affected by a
number of parameters including the amount of oxidation occurring, the
hydraulic flow, the design operating conditions necessary to meet the
treatment objectives, and the materials of construction. These factors
account for the band of capital costs shown in Figure 6.1.3. The figure was
taken from Reference 2 and updated to reflect changes in the 1982 to 1986
Chemical Engineering (CE) plant cost index. The costs do not include any
costs associated with pretreatment of the feed or post-treatment of the vapor
phase component of the treated liquor. However, post-treatment costs were
included in another capital cost estimate of $2.45 million (adjusted to 1986
4
using the CE plant cost index) for a 20 gpm plant. This estimate is within
the capital cost band shown in Figure 6.1.3.
Operating costs for the wet oxidation unit are shown in Figure 6.1.4.
These data were also derived from data given in Reference 2 with adjustment
made for the costs of labor and cooling water. As noted in Reference 2, power
accounts for the largest element of cost. This power cost is primarily the
result of air compressor operation. Additional power for supplying energy for
the oxidation of very dilute wastewaters would be at most 500 Btu/gallon. The
associated costs for this energy would be less than one (1) cent/gallon.
Total costs, capital plus operating, on a per unit of feed basis,
requires assumptions on life cycle, depreciation, taxes, and current interest
rates for the capital cost. One avenue for financing that has been used
commercially, common lease terms, are 5 years and 20 percent value at end of
term.* Table 6.1.3 illustrates the effect on total costs per unit of feed.
At Casmalia Resources, the prices (April 1985) for treatment of wastes
are computed based on the oxygen demand of the material. Prices range from a
minimum of $120 per ton to a maximum of $700 per ton versus $15 per ton for
14
the land disposal of low risk wastes.
*As3ume charges of fcl7/£l,000 per month based on total installed cost.
6-15
-------
-w-l
o
w
o
o
O
IU
CO
I
I
10 20 30 40 50
WET OXIDATION PLANT CAPACITY, gpm
60
70
Figure 6.1.3. Installed plant costs versus capacity.
6-16
-------
4.5
4.5
4.0
1986 cost: Power-$0.05/KWH; C.W.-$0.25/1000 gallon;
maintenance-1% capital cost; labor-$30,000/yr/operator.
4.0
3.5
3.5
3.0
3.0
-------
TABLE 6.1.3. WAO COSTS VERSUS FLOW
Hydraulic
flow (gpm)
2.0
10
20
40
Cost elements
operating
23
6
3
2-3
per gallon,
capital
31
7
5
4-5
cents
total
54
13
8
6-8
6.1.3.2 Comparison of WAO Costs with Other Alternative Treatment Costs-—
A cost comparison between a 20 gpm WAO system and a comparable incinerator
was presented in Reference 4 for a wastewater containing 7 percent COD. It
was concluded that, although the installed capital cost for WAO was 50 percent
higher than that for incineration, operating costs were appreciably less
($132,000 annual operating cost for WAO versus $463,500 for incineration in
1979 dollars) despite a charge for scrubbing of the WAO off gases and an
operating surcharge for BOD discharges to an average municipal wastewater
treatment plant. It was concluded that total operating costs including
amortization favor WAO when the fuel value of the waste organics is low (less
^
than approximately 50 g/liter Chemical Oxygen Demand).
Other sources of cost data, including comparative costs, are References 3
and 16. Reference 3 notes that WAO is generally less expensive than
incineration when the COD concentration ranges between 10 to 150 g/liter.
Rough cost estimates of from about 10 to 50 cents per gallon were proposed
depending upon type of waste, concentration, and amount to be treated. For
comparison, landfilling costs of 12 to 25 cents per gallon for drummed wastes
were provided. Reference 16 provides cost data for a WAO system designed to
treat a 7 percent COD waste at a 10 gallon per minute treatment rate. Net
operating costs of i>90,780 per year (December 1980) were estimated, a value
roughly equivalent to 3 cents per gallon, assuming a zero rate of return on
investment. This relatively low operating cost was compared to a landfilling
cost of roughly 4l per gallon for barrelled waste and $0.55 to SO.75 per
6-18
-------
gallon for bulk waste. Although WAO costs were roughly two orders of
magnitude greater than typical costs for secondary biological municipal
wastewater treatment, the cost of fcO.07 per pound of COD removed was suggested
as comparable to the typical municipal charge to industry of $0.05 to $0.10
per pound of COD removed.
Another source of cost data, Reference 22, provides data showing that
costs are a strong function of the contaminant type, its concentration, and
the amount of waste to be treated. Costs ranged from $0.12 per pound of
pentachlorophenol to 31.04 per pound of hexachlorobutadiene treated.
6.1.4 Overall Status of WAO Process
6.1.4.1 Availability and Application of WAO Systems—
The WAO process is available commercially, and reportedly well over
150 units are now operating in the field treating municipal and various
13
industrial sludges. The process is used predominately as a pretreatment
step to enhance biodegradability. Only a few units are now being used to
treat industrial wastes. These include the 10 gallon per minute unit at
Casmalia Resources in California and other units operating at Bofors-Nobel in
Muskegon, Michigan and Northern Petrochemical in Morris, Illinois.
The oxidation of specific contaminants in waste streams by the wet
oxidation process is not highly predictable. Equipment manufacturers rely
largely on the result of bench-scale results to tailor the design of
full-scale WAO continuous units for specific wastes. Full-scale data confirm
the results of WAO performance data obtained in bench and pilot-scale
studies. The use of WAO for halogenated aromatic compound bearing wastes
may pose particularly difficult problems and its use as a pretreatment should
be considered with caution.
6.1.4.2 Energy and Environmental Impacts—
As noted, the process is thermally self-sustaining when the amount of
oxygen uptake is in the 15^-20 g/liter range. Below this range, some energy
input will be required to initiate and sustain reaction. However, the energy
requirement will be appreciably less than that required for incineration.
6-19
-------
The environmental impacts of WAO will hinge upon the residuals remaining
after treatment. Wet scrubbing and carbon adsorption cleanup systems have
been used to treat the HC1 formed as a product of chlorinated organic
oxidation and to remove volatile organics from the waste off gases. Residuals
in the liquid phase may also require post treatment if, for example,
100 percent conversion to CO. and H.O " not realized when treating
halogenated contaminants. The available data do suggest that some form of
post treatment of both liquid and vapor phases will be required to meet EPA
treatment standards.
6.1.4.3 Advantages and Limitations—
There are several advantages associated with the use of WAO as noted by
the developer and stated in Reference 2.
1. The process is thermally self-sustaining when the amount of oxygen
uptake is in the 15-20 grams/liter range.
2. The process is well suited for wastes that are too dilute to
incinerate economically, yet too toxic to treat biologically.
3. Condensed phase processing requires less equipment volume than gas
phase processing.
4. The products of WAO stay in the liquid phase. Offgases from a WAO
system are free of NOX, S02, and particulate. Water scrubbing
and, if need be, carbon adsorption or fume incineration are used to
reduce hydrocarbon emissions or odors.
5. WAO also has application for inorganic compounds combined with
organics. The oxidation cleans up the mixture for further removal
of the inorganics. WAO can detoxify most of the EPA priority
pollutants. Toxic removal parameters are in the order of
99+ percent using short-term, acute, static toxicity measurements.
Limitations of the WAO process relate to the sensitivity of destruction
efficiency associated with the chemical nature of the contaminant, the
possible influence of metals and other contaminants on performance, the
unfavorable economics associated with low and high concentration levels, and
the presence of residuals in both the vapor and liquid phases which may
require additional treatment. Costly materials of construction and design
6-20
-------
features may also be required for halogetiated wastes which will form corrosive
reaction products or require extreme temperature/pressure conditions to
achieve destruction to acceptable levels. In particular, chlorinated aromatic
compounds are more resistant to degradation and can result in the production
of HC1 byproducts.
6-21
-------
REFERENCES
1. Dietrich, M.J., T.L. Randall, and P.J. Canney. Wet Air Oxidation of
Hazardous Organics in Wastewater, Environmental Progress, Vol. 4, No. 3,
August 1985.
2. Freeman, H. Innovative Thermal Hazardous Treatment Processes, U.S. EPA,
Hazardous Waste Engineering Research Laboratory, Cincinnati, Ohio, 1985.
3. California Air Resources Board. Air Pollution Impacts of Hazardous Waste
Incineration: A California Perspective, December 1983.
4. Wilhelmi, A.R., and P.V. Knopp. Wet Air Oxidation - An Alternative to
Incineration, Chemical Engineering Progress, August 1979.
5. Zimmerman, F.J., and D.G. Diddams, The Zimmerman Process and its
Applications in the Pulp and Paper Industry, TAPPI Vol. 43, No. 8,
August 1960.
6. Copa, William, James Heimbuch, and Phillip Schaeffer. Full Scale
Demonstration of Wet Air Oxidation as a Hazardous Waste Treatment
Technology. In: Incineration and Treatment of Hazardous Waste,
Proceedings of the Ninth Annual Research Symposium, U.S. EPA
600/9-84-015, July 1984.
7. Copa, William, Marvin J. Dietrich, Patrick J. Cannery, and
Tipton L. Randall. Demonstration of Wet Air Oxidation of Hazardous
Waste. In Proceedings of Tenth Annual Research Symposium, U.S. EPA
600/9-84-022, September 1984.
8. U.S. Environmental Protection Agency, Background Document for Solvents to
Support 40 CFR Part 268, Land Disposal Restrictions, Volume II,
January 1986.
9. Reible, Danny D., and David M. Wetzel. Louisiana State University, A
Literature Survey of Three Selected Hazardous Waste Destruction
Techniques In Proceedings of Ninth Annual Symposium on Land Disposal of
Hazardous Waste. May 2-4, 1983.
10. Randall, T.R. Wet Oxidation of Toxic and Hazardous Compounds.
Zimpro, Inc. Technical Bulletin 1-610, 1981.
6-22
-------
11. Canney, P.J., and P.T. Schaeffer. Detoxification of Hazardous Industrial
Wastewaters by Wet Air Oxidation. Presented at 1983 National AIChE
Meeting, Houston, TX, March 27-31,-1983.
12. Baillod, C. Robert, and Bonnie M. Faith. Wet Oxidation and Ozonation of
Specific Organic Pollutants, U.S. EPA 600/52-83-060, October 1983.
13. Telephone Conversation with A. Wilhelmi on April 3, 1986.
14. Metcalf & Eddy, Inc. Hazardous Waste Treatment Storage and Disposal
Facility - Site Evaluation Report, Casmalia Resources, Casmalia,
California, Publication NS J-1074, April 8, 1985.
15. Randall, Tipton L., and Paul V. Knopp. Detoxification of Specific
Organic Substances by Wet Air Oxidation, Journal WPCF, Vol. 52, No. 8,
August 1980.
16. Baillod, C.R., R.A. Lamporter, and B.A. Barna. Wet Oxidation for
Industrial Waste Treatment, Chemical Engineering Progress, March 1985.
17. Baillod, C.R., B.M. Faith, and D. Masi. Fate of Specific Pollutants
During Wet Oxidation and Ozonation, Environmental Progress, August 1982.
18. Meidl, J.A., and A.R. Wilhelmi, PACT™/Wet Oxidation: Economical
Solutions to Solving Toxic Waste Treatment Problems. Paper presented at
Indiana Water Pollution Control Association Annual Meeting,
August 20, 1985.
19. California Department of Health Services, Alternative Technology for
. Recycling and Treatment of Hazardous Wastes, Second Biennial Report,
July 1984.
20. Breton, M. A., et al* Technical Resource Directive - Treatment
Technologies for Solvent Containing Wastes. Prepared for U.S. EPA,
HWERL, Cincinnati Under Contract No. 68-03-3243, Work Assignment No. 2,
August 1986.
21. Randall, T.L. Wet Oxidation of PACTR Process Carbon Loaded with Toxic
Compounds. Paper presented at 38th Industrial Waste Conference, Purdue
University, West Lafayette, Indiana, May 10-12, 1983.
22. Miller, R.A., and M.D. Swietoniewski. IT Enviroscience The Destruction
of Various Organic Substances by a Catalyzed Wet Oxidation Process, Work
Done Under U.S. EPA Contract No. 68-03-2568, 1982.
6-23
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6.2 SUPERCRITICAL WATER OXIDATION
Supercritical water oxidation is a technology that has been proposed for
the destruction of organic contaminants in wastewaters. It is basically an
oxidation process conducted in a water medium at temperatures and pressures
that are supercritical for water; i.e., above 374°C (705"F) and
218 atmospheres. In the supercritical region, water exhibits properties that
are far different from liquid water under normal conditions; oxygen and
organic compounds become totally miscible with the supercritical water (SCW)
and inorganic compounds, such as salts, become very sparingly soluble. When
these materials are combined in the SCW process, organics are oxidized and any
inorganic salts present in the feed or formed during the oxidation are
precipitated from the SCW.
The oxidation reactions proceed rapidly and completely. Reaction times
are less than 1 minute, as compared to reaction times of about 60 minutes used
in the subcritical wet air oxidation (WAO) process. Moreover, the reaction is
essentially complete. Carbon and hydrogen atoms within the organic
contaminants are reacted to form CO, and H_0 (residuals such as the low
molecular weight organic acids and alcohols found in the treated WAO effluent
are.not found in the SCW process effluent). Heteroatoms (e.g., chlorine and
sulfur) are oxidized to their corresponding acidic anion groupings. These
anions, and those occurring naturally in the feed, can be neutralized by
cation addition to the feed, and the total inorganic content of the waste,
save that soluble in the SCW, can be precipitated and recovered by mechanical
separators operating at SCW conditions.
6.2.1 Process Description
In the supercritical region, water exhibits properties that are far
different from liquid water at normal ambient conditions. The density,
dielectric constant, hydrogen bonding, and certain other physical properties
change significantly with the result that SCW behaves very much like a
I •
moderately polar organic liquid. Thus, solvents such as n-heptane and
benzene, for example, become miscible with SCW in all proportions. On the
other hand, the solubility of salts such as sodium chloride (NaCl) is as low
6-24
-------
as 100 ppm and that of calcium chloride (CaCl_) as low as 10 ppm. These
solubilities are far different from those found under ambient conditions where
the .solubilities of NaCl and CaCl- are about 37 weight percent and up to
70 percent, respectively (Josephson, 1982).
The solubility characteristics of SOW are strongly dependent upon
2
density. A temperature-density diagram is shown in Figure 6.2.1. The
critical point which is located on the dome of the vapor-liquid saturation
curve is at 374°C and 0.3 gram/cubic centimeter. The supercritical region is
that above 374° and the 218 atmosphere isobar. Near the critical point
(e.g., between 300° and 450°) the density varies greatly with relatively small
changes in temperature at constant pressure.
Insight into the structure of the fluid in this region has been obtained
from measurements of the static dielectric constant, values of which are shown
3 4
in Figure 6.2.1. ' The dielectric constants of some common solvents are
given for comparison in Table 6.2.1.
TABLE 6.2.1. DIELECTRIC CONSTANTS OF SOME COMMON SOLVENTS
Carbon dioxide 1.60
n-Hexane 1.89
Benzene 2.28
Ethyl ether 4.34
Ethyl acetate * 6.02
Benzyl alcohol 13.1
Ammonia 16.9
Isopropanol 18.3
Acetone 20.7
Ethanol 24.3
Methanol 32.6
Ethylene glycol 37.
Formic acid 58.
Source: Reference 5.
The dielectric constant is a measure of the degree of molecular
association. While dielectric constant is not the sole determinant of
solubility, the solvent power of water for organics is consistent with
variations in the dielectric constant. According to Figure 6.2.1, as
temperature rises along the saturated liquid-vapor curve the dielectric
6-25
-------
(j
a
UJ
600
500
400
300
200
100
0
= 10
0.05 O.I 0.2
DENSITY (g/cm3)
£°80
0.5 1.0
Figure 6.2.1. Temperature-density diagram.
\ Source: Reference 2.
6-26
-------
constant (normally at about 80 due largely to strong hydrogen bonding)
decreases rapidly despite only small changes in density. The large decreases
in the dielectric reflect the strong dependence of hydrogen bonding forces on
distance, with small decreases in density leading to large.decreases in
dielectric constant. At 130°C (d » 0.9 g/cm ), the dielectric constant is
3
about 50, which is near that of formic acid; at 260°C (d = 0.8 g/cm ) the
dielectric constant is 25 similar to that of ethanol. At the critical point
the dielectric constant is 5, and little, if any, residual hydrogen bonding is
present. The major contribution to the dielectric constant is due to
dipole-dipole interactions, which gradually decrease with density.
Depending upon the pressure and temperature, the dielectric constant can
be varied to achieve values similar to those of moderately polar to nonpolar
organic solvents. Solubility behavior parallels the changes in dielectric and
at some points supercritical conditions are reached and the components are
miscible in all proportions.
The solubilities of inorganic salts in water exhibit different behavior
from that shown by the organic compounds. At 250 atmospheres, the
solubilities of salts reach a maximum at 350-400°C. Beyond the maximum, the
solubilities drop very rapidly with increasing temperature. For example, NaCl
solubility is above 40 weight percent at 300°C and 100 ppm at 450°C; *CaCl
has a maximum solubility of 70 percent at subcritical temperatures which drops
to 10 ppm at 500°C.2
The properties of water, as a function of temperature, are summarized in
Figure 6.2.2. The figure shows that water goes through a complete reversal in
solubility behavior between 300-500°C. Above 450°C, inorganic salts are
2
practically insoluble, and organic substances are completely miscible.
Given the complete miscibility of oxygen and organic contaminants in the
supercritical fluid and the high temperature of operation, oxidation reactions
proceed rapidly and completely. In the MODAR process described below,
organics, air and water wastes are brought together at 250 atmospheres and at
temperatures above 400°C. The heat of oxidation is released within the fluid
and results generally in a rise in temperature to 600-650°C.
The products of supercritical water reforming are subjected to oxidation
while under these homogenous (i.e., single phase) supercritical conditions.
The residence time required for oxidation is very short, which greatly reduces
the volume of the oxidizer vessel.
6-27
-------
Faint
77 Hi
TvwraM
•c « ' 100
•I U**I4
1.0
Critic*)
600 I MO
300 MO $00 MO
•ur Jfcmr |0t
-------
When toxic or hazardous organic chemicals are subjected to SOW oxidation,
carbon is converted to CO. and hydrogen-to H-0. The chlorine atoms from
chlorinated organics are liberated as chloride ions. Similarly, nitrogen
compounds will produce nitrogen gas, sulfur is converted to sulfates,
phosphorus to phosphates, etc. Upon addition of appropriate cations
(e.g., Na+, Mg++, Ca++), inorganic salts'are formed.
The heat of oxidation is sufficient to bring the supercritical stream to
temperatures in excess of 550°C. At these conditions, inorganic salts have
extremely low solubilities in water. Inorganic salts are precipitated out and
readily separated from the supercritical fluid phase. After removal of
inorganics, the resulting fluid is a highly purified stream of water at high
temperature and high pressure. The fluid is used as a source of
high-temperature process heat by generating steam.
A schematic flow sheet for the MODAR process as applied to liquid wastes
is presented in Figure 6.2.3. This figure and subsequent discussion was
provided by MODAR, Inc.
The process consists of the following steps:
A. Feed . ' - '
1. Organic waste materials in an aqueous medium are pumped-from
atmospheric pressure to the pressure in the reaction vessel.
2. Oxygen, stored as a liquid, is pumped to the pressure of the
reaction vessel and then vaporized.
%
3. Feed to the process is controlled to.an upper limit heating value of
1800 Btu/lb by adding dilution water or blending higher heating
value waste material with lower heating value waste material prior
to feeding to the reactor.
4. When the aqueous waste has a heating value below 1,800 Btu/lb, fuel
may be added in order to utilize a cold feed to the oxidizer.
5. Optionally for wastes with heating value below 1,800 Btu/lb, a
combination of preheat by exchange with process effluent and fuel
additon, or preheat alone may be used.
6. When organic wastes contain heteroatoms which produce mineral acids,
and it is desired to neutralize these acids and form appropriate
salts, caustic is injected as part of the feed stream.
6-29
-------
(
;
— •
. — --
Fee
-^
d
•N*.
C
Aqueous
Waste
/— n
— C7
Auxiliary
.auaclc
/— n
— C7
) Oxygen
r? — I
\J 1
Vaporixai
Reaction
Salt Sep
L
J
i
ai
md
at
Steaa
2nd Sf,am l_
~\V rl ' 1 i-— Gas
Oxidtzer T~^
__L_
Cas-Liquid
— • Oxidlzer
1 ' Liquid
(water)
Sale
Separator
Cooling and Pressure Letdown and
ion Beat Recovery Effluent Discharge
Figure 6.2.3. Schematic flow sheet of NODAR process.
Source: Reference 6.
6-30
-------
7. A recycle stream of a portion of the supercritical process effluent
is mixed with the feed streams to raise the combined fluids to a
high enough temperature to ensure that the oxidation reaction goes
rapidly to completion.
B. Reaction and .Salt Separation
1. Because the water is supercritical, the oxidant is completely
miscible with the solution; i.e., the mixture is a single,
homogenous phase. Organics are oxidized in a controlled but rapid
reaction. Since the oxidizer operates adiabatically, the heat
released by the readily oxidized components is sufficient to raise
the fluid phase to temperatures at which all organics are oxidized
rapidly.
2. Since the salts have very low solubility in SOW they separate from
the other homogenous fluids and fall to the bottom of the separation
vessel where they are removed.
3. The gaseous products of reaction along with the supercritical water
leave the reactor at the top. A portion of the supercritical fluid
is recycled to the SCW oxidizer by a high temperature, high pressure
pump. This operation provides for sufficient heating of the feed to
bring the oxidizer influent to optimum reactor conditions.
4. The remaining reactor effluent (other than that, recycled) consisting
of superheated SCW and carbon dioxide is cooled in order to
discharge 002 an<* water at atmospheric conditions.
C. Cooling and Heat Recovery
1. Most of the heat contained in the effluent is used to generate steam
for use outside the MODAR Process.
2. The heat remaining in the effluent stream is used for lower level
heating requirements and is also dissipated.
0. Pressure Letdown
1. The cooled effluent from the process separates into a liquid water
phase and a gaseous phase containing primarily carbon dioxide along
with oxygen which is in excess of the stoichiometric requirements.
2. The separation is carried out in multiple stages in order to
minimize erosion of valves as well as to optimize equilibria.
3. Salts are removed from the separator as a cool brine through
multiple letdown stages and are either dried (and water recovered)
or discharged as a brine depending upon client requirements.
6-31
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6.2.1.1 Pretreatment Requirements-
Very little information exists in the literatute to assess pretreatment
requirements for the process and its feed streams. The process reportedly can
handle slurries, thus, filtration or some other solids removal process may not
o
be required or even desirable if the contaminant is partitioned in the feed
between the aqueous phase and the suspended solids. Similarly, the need to
remove inorganic constituents may not exist since these constituents will
precipitate under the supercritical conditions of operation and presumably
will be removed by the mechanical separator shown in Figure 6.2.3. Adverse
effects such as interference with pump operations, abrasion of internal parts,
and fouling of internal surfaces resulting from existing or formed solids are
possible problem areas but were not considered such by MODAR.
6.2.1.2 Operating Parameters—
The operating conditions are specified by MODAR as follows:
• Form of Feed Materials: Aqueous slurry or solution of organics.
• Temperature Range: 400°-650°C (750°-1200°F)
• Pressure Range: 220-250 atm
• Residence Time Range: Less than one minute
• Energy Type and Requirements: Thermal, to reaction conditions, with
provisions for useful recovery of
latent heat of oxidation.
These conditions are capable of achieving destruction efficiencies in
excess of 99.999 percent. The technology should be applicable to all
halogenated organics considered in this TRD. The principal question related
to the applicability of the technology is associated with cost, including the
durability of the system under the harsh supercritical conditions.
6.2.1.3 Post Treatment Requirements—
Because the oxidation reactions go essentially to completion and
provision can be made for neutralization and removal of inorganic products and
feed stock components the post treatment requirements should be minimal. Off
6-32
-------
gases from the subcritical treated effluent should be largely CO 2 and H~0
and liquid effluent residuals will consist mainly of dissolved salts at the 10
to 100 ppm levels. These salts will consist, at least in part, of salts
resulting from the addition of caustic to neutralize the halogen acids formed
during the oxidation of halogenated compounds in the waste.
Along with N-, N-0 may also be a possible off gas component from the
SOW oxidation of nitrogen containing organics. A possible N-0 component
would not be considered an air contaminant since there is no evidence
involving it in the series of complex chemical reactions producing
photochemical smog.
Apart from the modest impacts anticipated as a result of N»0 emissions
and the dissolved inorganic salt loading of the liquid effluent the only other
residual stream requiring possible attention is the largely solid inorganic
stream from the separator. EP toxicity could be a characteristic of possible
concern for some wastes.
6.2.1.4 Treatment Combinations-
SCW oxidation systems can be considered for aqueous waste streams
containing one or more weight percent of organic constituents. Below
1 percent, other treatment technologies appear to have a cost advantage. The
highest practical organic content again will depend upon costs; specifically
the cost of SCW oxidation versus incineration for wastes in the 10 to 20
weight percent and higher range. Largely unproven, the SCW oxidation system
will, if cost effective, function as a finishing technology discharging
effluents that can be expected to meet acceptable levels of discharge.
6.2.2 Demonstrated Performance
The destruction of organic contaminants is a function of reactor
temperature and residence time. MODAR reports that a reactor temperature in
the range of 600 to 650°C (1120° to 1200°F) and a 5 second residence time are
sufficient to achieve destruction efficiencies of 99.999 percent. Higher
temperatures could be used to reduce the residence time. However, at a
5 second reaction time, the reactor cost is a small fraction of total capital
cost and, thus, there is not much incentive to reduce reactor volume by
operating above 650°C.
6-33
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Theoretically, increasing residence time will also result in increased
destruction efficiency. The oxidation kinetics appear to be first order in
organic concentration. Assuming perfect mixing and first order kinetics at
all concentrations, doubling the residence time could result in a doubling of
the destruction efficiency. Thus, a 99.999 percent efficiency could become
99.99999999 (ten nines).
MODAR has conducted more than 200 laboratory (bench) and pilot plant
tests in order to study the technical feasibility of SCW oxidation for a
variety of organic contaminants. In most cases MODAR does not attempt to
measure destruction and removal efficiency to the greatest possible
precision. Test objectives are rather to measure the levels of organic carbon
in the liquid effluent, and in most cases, residual levels are below detection
limits of the analytical equipment. Consequently, destruction removal
efficiency, which may be claimed in many of MODAR's tests, are limited to
between 99.9 percent and 99.99+ percent by precision of the analytical
equipment (See Reference 8). When the objective is to demonstrate the maximum
degree of waste destruction, richer feeds and more sensitive analytical
equipment are used. Tests of this sort (e.g., on dioxins) show destruction
and removal efficiencies of more than 99.9999 percent . Equal or greater
destruction efficiencies could be expected for most if not all halogenated
organic compounds of concern.
6.2.3 Cost of Treatment
The most significant operating cost factor is the cost of oxygen
consumed. Although compressed air can be used as the source of oxygen, the
cost of power as well as the high capital cost of appropriate compressors has
led MODAR to use liquefied oxygen as the primary oxygen source. Oxygen demand
and heat content of an organic waste are usually directly related, and
therefore the heating value of the waste and waste throughput can be used to
make a preliminary estimate of waste treatment costs.
Table 6.2.2 presents waste treatment costs based on an aqueous waste with
a 10 percent by weight benzene-equivalent and a heat content of 1,800 Btu/lb.
This is the optimal heat content of a cold feed for this process to attain a
reactor exit temperature of 600 to 650°C. Other factors on which the costs in
6-34
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Table 6.2.2 are based are: the system is installed at the site of the waste
generator; the units are owned and operated by the waste disposer; and the
units are not equipped with power recovery turbines.
TABLE 6.2.2. MODAR TREATMENT COSTS FOR ORGANIC CONTAMINATED AQUEOUS WASTES
Waste capacity Processing cost3
Gal /day
5,000
10,000
20,000
30,000
Ton/day
20
40
80
120
$/gal
$0.75 - $2.00
$0.50 - $0.90
$0.36 - $0.62
$0.32 - $0.58
$/ton
$180
$120
$ 86
$ 77
- $480
- $216
- $149
- $139
aBased upon an aqueous waste with 1,800 Btu/lb heating value (equivalent to
a 10 percent organic waste). Does not include energy recovery value of
approximately $0.05 per gallon.
Source: Reference 6.
If the waste has a fuel value of greater than 1,800 Btu/lb, the cost will
be higher per unit of waste processed. In treating a waste with a higher
organic content, it is recommended that the waste is diluted to a 10 percent
benzene-equivalent. Therefore, the increase in cost will be in proportion to
the increase in organic content.
If the waste has a heat content of between 5 and 10 percent benzene-
equivalent, fuel can be added to the waste to bring the heat content up to
10 percent benzene-equivalent without appreciable cost increases. If,
however, the waste is very dilute (2 to 3 percent benzene-equivalent), it is
more economical to use a combination of fuel with regenerative heat exchange.
6.2.4 Overall Status of Process
6.2.4.1 Availability—
A pilot plant with capacity to oxidize 30 gal/day of benzene equivalent
has been in operation at MODAR'a laboratory as well as at a field site since
late 1984. As a result of these activities,.the MODAR SCW oxidation process
6-35
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has been declared commercial and design of the first plant is underway. The
plant will be installed late in 1987 and will treat 10,000 to 30,000 gallons
of aqueous waste per day.
6.2.4.2 Application—
SOW oxidation would appear to be applicable to aqueous wastes containing
1 to 20 weight percent organics. As noted in previous discussions above,
complete destruction of all halogenated organics can be anticipated on the
basis of evidence presented by the developer. The high efficiency of
destruction can be related to the unique and stringent conditions associated
with SOW oxidation which unites oxygen and organic contaminants under
relatively high temperatures and pressures.
Restrictive waste characteristics have not been identified in the
literature as a problem. The effect of heteroatoms (halogens) and their
reaction products can be anticipated and steps taken to essentially eliminate
any deleterious impacts. However, the applicability of solid content wastes
to SOW oxidation systems may be problematical. The effectiveness of removal
of precipitated inorganic salts by the mechanical separators proposed for the
MODAR system may also be a problem. In the absence of particle size and flow
and design data it is difficult to predict mechanical separator performance,
although separation should be enhanced under the low density SCW conditions.
If particles are present, abrasion-problems could occur both within the
oxidation system and in any subsequent system designed to recover energy from
the treated stream.
Supercritical fluid technology is also being considered for a number of
applications other than that concerned with the destruction of organic wastes,
e.g., supercritical fluid extractions, including the extraction of adsorbed
components from granular activated carbon. Fluids such as CO-, ethane, and
ethylene can be used at critical temperature and pressure conditions which are
much less severe than those of SCW. However, no data were found which
relates the performance of such systems to the extraction of halogenated
organics from wastes.
6-36
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6.2.4.3 Environmental Impacts—
Liquid, solid, and gaseous emissions are generated from the SOW oxidation
process. Gaseous emissions consist primarily of carbon dioxide with smaller
amounts of oxygen and nitrogen gas. Effluent gas cleaning is not required.
N-0 is the most abundant nitrogen oxide in the atmosphere. It does not
appear to interact with the nitrogen dioxide photolytic cycle. Any N-0
which might be in the gaseous effluent is not classified as an atmospheric
pollutant.
Solid emissions consist of the precipitated inorganic salts. When
halogenated compounds are processed, halogen salts will be formed, and
2
similarly sulfur is converted to sulfates, and phosphorous to phosphates.
Liquid effluents consist of a purified water stream. Although no data
are available for halogenated organic contaminants, six nines destruction has
been measured for dioxins. On the basis of these data it is anticipated that
essentially all halogenated compounds will be found only at the ppb level.
6.2.4.4 Advantages and Limitations—
The developer states that the MODAR process for supercritical water
oxidation of organics is an improvement in:
• enhanced solubility of gases including oxygen and air in water,
which eliminates two-phase flow;
• rapid oxidation of organics, which approaches adiabatic conditions
as well as high outlet temperatures, and very short residence times;
• complete oxidation of organics, which eliminates the need for
auxiliary offgas processing;
• removal of inorganic constituents, which precipitate out of the
reactor effluent at temperatures above 450"C (840°F); and
• recovery of the heat of combustion in the form of supercritical
water, which can be a source of high-temperature process heat.9
The above advantages are generally relative to the wet air oxidation process
which could be considered as an alternative technology to SOW oxidation. The
limitations of the process have yet to be determined through commercial
operation. Potential limitations relate to cost and equipment limitations due
to the stringent temperature and pressure requirements.
6-37
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REFERENCES
1. Josephson, J. Supercritical Fluids. Environmental Science and
Technology. Volume 16, No. 10. October 1982.
2. Thomason, T. B. and M. Mode11. Supercritical Water Destruction of
Aqueous Wastes. Hazardous Waste. Volume 1, No. 4. 1984.
3. Quiat, A. S. and W. L. Marshall. Estimation of the Dielectric Constant
of Water to 800°, J. Phys. Chem., 69, 3165. 1965.
4. Uematsu, M. and E. U. Franck. J. Phys. Chem. Reference Data, 9(4),
1291-1306. 1980.
5. Franck, E. U. Properties of Water in High Temperature, High Pressure
Electrochemistry in Aqueous Solutions (NACE-4). p. 109. 1976.
6. Sieber, F. MODAR Inc. Review of Draft Section, Supercritical Water
Oxidation. May 16 1986.
7. National Academy of Sciences, Medical and Biological Effects of
Environmental Pollution: Nitrogen Oxides. 1977.
8. Mode 11, M., G. Gaudet, M. Simson, G. T. Hong, and K." Biemann.
Supercritical Water Testing Reveals New Process Holds Promise, Solid
Wastes Management. August 1982.
9. Freeman, H. Innovative Thermal Hazardous Waste Treatment Processes.
U.S. EPA, HWERL Cincinnati, Ohio. 1985.
6-38
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6.3 ULTBAVIOLET/OZONE OXIDATION
Chemical oxidation processes in addition to the wet air and supercritical
water oxidation processes discussed previously, are potential options for the
treatment of hazardous organic wastes. Oxidants such as ozone, hydrogen
peroxide, and potassium permanganate are among the strongest oxidants known
(see Table 6.3.1) and are used industrially to treat specific waste streams
containing phenols, cyanides, organic sulfur compounds, and other rapidly
oxidized organics. The use of these oxidants alone and in combination with
ultraviolet light, for the treatment of hazardous waste streams has been
3 4
described in the solvent TRD and the dioxin TRD and other publica-
5—14
tions. As noted in Reference 3 and other references, ozone and other
commercial oxidants are not generally effective oxidants for halogenated
organics. Nevertheless, the potential for their use has been studied and
oxidation processes have achieved some success in treating aqueous waste
streams containing chlorinated pesticides. These processes must be considered
developing technologies. Only the most prominent process, UV/ozone oxidation,
is discussed here; other potentially useful processes are described in the
previously cited references. It should be noted that at the present time most
chlorinated aliphatic compounds must be considered nonreactive. The
applicability of UV/ozone treatment for waste streams containing these
compounds will require careful experimental documentation.
6.3.1 Process Description
Ozone, as an oxidant, is sufficiently strong to break many carbon-carbon
bonds and even to cleave aromatic ring systems. Oxidation of organic species
to carbon dioxide, water etc., is not improbable if ozone dosage and contact
times are sufficiently high, although many compounds are highly resistant to
ozone degradation. These compounds, which include oxalic and acetic acids,
ketones, and chlorinated aliphatic organics, are not affected significantly by
treatment conditions (1 to 10 mg/liter concentration levels and 5 to 10 minute
contact times) normally used for treating drinking waters or for disinfecting
4
wastewaters.
6-39
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TABLE 6.3.1. RELATIVE OXIDATION POWER OF
OXIDIZING SPECIES
Species
Fluorine
Hydroxyl radical
Atomic oxygen
Ozone
Hydrogen peroxide
Perhydroxyl radicals
Permanganate
Hypochlorous acid
Chlorine
Oxidation
potential,
volts
3.06
2.80
2.42
2.07
1.77
1.70
1.70
1.49
1.36
Relative
oxidation
power3
2.25
2.05
1.78
1.52
1.30
' 1.25
1.25
1.10
1.00
aBased on chlorine as reference (• 1.00)
Source: References 1 and 2.
6-40
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Ozone has been used for years in Europe to purify, deodorize, and
disinfect drinking water. More recently, it has been used in the waste
treatment area to oxidize phenolic and cyanide wastewaters. Cost
considerations and mass transfer factors limit the use of ozonation to
applications involving 1 percent or lower contaminant concentration levels.
Since oxidation by ozone occurs nonselectively, it is also generally used only
for aqueous wastes which contain a high proportion of hazardous constituents
versus nonhazardous oxidizable compounds, thus focusing ozone usage on
contaminants of concern. Ozonation may be particularly useful as a final
treatment for waste streams which are dilute in oxidizable contaminants, but
which did not quite meet effluent standards.
Ozone is generated onsite by the use of corona discharge technology.
Electrons within the corona discharge split the oxygen-oxygen double bonds
upon impact with oxygen molecules. The two oxygen atoms formed from the
molecule react with other oxygen molecules to form the gas ozone, at
equilibrium concentration levels'of roughly 2 percent in air and 3 percent in
oxygen (maximum values of 4 and 8 percent, respectively). Ozone must be
produced onsite (ozone decomposes in a matter of hours to simple, molecular
^
oxygen). Primarily, because of this, and solubility limitations ('300 mg/L
is considered a high dose level),15 ozonation is restricted to treatment of ^
streams with low quantities of oxidizable materials. Using a rule of thumb,
two parts of ozone are required per pound of contaminant. A large commercial
ozone generator producing 500 Ib/day of ozone could treat 1 million
gallons/day of wastewater containing 30 ppm of oxidizable matter, or
equivalently, 3,000 gallons/day of wastewater containing 1 percent of
2
oxidizable matter.
While direct ozonation of industrial wastewater is possible and is
practiced commercially, other technologies have been combined with ozonation
to enhance the efficiency and rate of the oxidation reactions particularly for
difficult to oxidize compounds such as halogenated organics. These
. technologies, which supply additional energy to the reactants, involve the use
of ultraviolet light or ultrasonics. The use of ultraviolet light has
received the most attention and will be the subject of further discussion.
6-41
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Ultraviolet (UV) radiation is electromagnetic radiation having a
wavelength shorter than visible light, but longer than x-ray radiation. The
energy content of light increases as the wave length decreases. For wave
lengths in the UV region the energy is sufficient to break chemical bonds and
bring about rearrangement or dislocation of molecular structures. The energy
corresponding to the absorption of a quantum (photon) of light is 95 kilo
calories per gram-mole for UV light with a wave length of 3,900 angstroms and
is 142 kilo calories per grant-mole for a wave length of 2,000 angstroms.
Table 6.3.2 lists the dissociation energies for many common chemical
bonds, along with the wavelength corresponding to the energy at which UV
photons will cause dissociation. As can be seen from the data in Table 6.3.2,
bond dissociation energies range from a low of 47 cal/gmole for the peroxide
bond to a high of 226 kcal/gmole for the nitrogen triple bond. Of particular
interest in the case of dioxins is the C-C1 bond, with a dissociation energy
of 81 kcal/gmole, corresponding to an optimum UV wavelength of 353 nm. For
reference purposes, this can be compared to the violet end of the visible
spectrum with a wavelength of about 420 nm. Thus, the UV radiation of
interest is in the electromagnetic spectrum close to visible light.
6.3.1.1 Pretreatment Requirements—
Due to the nonselective nature of the ozonation reactions it is important
that the concentration levels of nonhazardous, but oxidizable, contaminants in
the feed stream be reduced as much as possible prior to treatment. The strong
electrophilic nature of ozone imparts to it the ability to react with a wide
variety of organic functional groups, including aliphatic and aromatic
carbon-carbon double and triple bonds, alcohols, organometallic functional
groups, and some carbon-chloride bonds. It is important to recognize that
many functional groups can be present which compete for the oxidant and can
add significantly to the cost of treatment.
The waste to be treated should also be relatively free of suspended
solids, since a high concentration of suspended solids can foul the columns
often used to bring about contact between ozone and the aqueous phase
contaminants. When ozonation is combined with UV radiation,a high
concentration of suspended solids also can impede the passage of UV radiation
and reduction reaction rates.
6-42
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TABLE 6.3.2. DISSOCIATION ENERGIES FOR SOME CHEMICAL BONDS
Bond
Dissociation
energy
'Ucal/gmoD
Wavelength
to break bond
(nm)
c-c
c-c
c=c
C-C1
C-r
C-H
C-N
C=N
C-N .
c-o
C=O (aldehydes)
0=0 (ketones)
C-S
c=s
Hydrogen
H-ti
Nitrogen
N-N . '
N=N
N=N
N-H (NH)
N-H (NH3)
N-0
N=0
Oxygen
0-0 (02)
-o-o-
0-H (water)
Sulfur
S-H
S-N
S-0
82.6
. 145.8
L99.6
81.0
116.0
98.7
72.8
147.0
212.6
85.0
176.0
179.0
65.0
166.0
104.2
52.0
60.0
226.0
85.0
102.0
48.0
162.0
119.1
47.0
117.5
83.
115.
119.
'346.1
196.1
143.2'
353.0
246.5
289.7
392.7
194.5
134.5
334.5
162.4
159.7
439.9
172.2
274.4
540.8
• 476.5
126.6
336.4
.280.3
595.6
176.5
240.1
608.3
243.3
344.5
248.6
240.3
Source: Legan, R.W. 1982.
6-43
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6.3.1.2 Operating Parameters—
To effectively bring about the UV assisted reaction of ozone with organic
contaminants, it is important that mass transfer of ozone and its reactants
through the gas-liquid interface be maximized. Also, to increase ozone
solubility in water, temperatures should be maintained as low as possible and
pressures as high as possible. However, conditions such as high temperature,
high pH, and high UV light flux favor ozone decomposition. Under these
conditions reactivity rates may increase, although costs may also increase due
to less efficient use of ozone. Decisions will have to be made on a
case-by-case basis to establish the most effective operating conditions.
Several commercial designs are available for the conduct of gas/liquid
reactions which bring reactants into contact as effectively as possible. The
types of reactor designs available range from mechanically agitated reactors
to more complex spray, packed, and tray type towers. Their advantages and
limitations are discussed in detail in many standard texts and publications
(for example, see References 5 through 7).
The process of UV/ozone treatment operates in the following manner. The
influent to the system is mixed with ozone and then enters a reaction chamber
where it flows past numerous ultraviolet lamps as it travels through the
chamber (see Figure 6.3.1). Flow patterns and configurations are designed to
maximize exposure of the total volume of ozone-bearing wastewater to the high
energy UV radiation. Although the nature of the effect appears to be
influenced by the characteristics of the waste, the UV radiation enhances
oxidation by direct.dissociation of the contaminant molecule or through
excitation of the various species within the waste stream. In industrial
systems, the system is generally equipped with recycle capacity. Gases from
the reactor are passed through a catalyst unit, destroying any volatiles,
replenished with ozone, and then recycled back into the reactor. The system
has no gas emissions.
Regardless of the reaction mechanisms, there appears to be no doubt that
the combination of ozonation with UV leads to increased oxidation rates.
Typical design data for a 40,000 gal/day UV/ozone treatment process are shown
in Table 6.3.3. The plant is designed to reduce a 50 ppm PCS feed
concentration to a 1 ppm effluent.
6-44
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UV lamps
A
Of
O 0
o
O
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Soent 03
Gas out
Flow distributor
Waste water in
Solid state
controlled
gear pump
Figure 6.3.1.
Schematic of top view of ULTROX pilot plant by General Electric
(ozone sparging system omitted) (Edwards, B. H., 1983).
Source: Reference 6.
6-45
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TABLE 6.3.3. DESIGN DATA FOR A 40,000 GPD
(151,400 L/DAY) ULTROX PLANT
Reactor
Dimensions:
Meters (LxWxH) 2.5 x 4.9 x 1.5
Wet volume, liters 14,951
UV lamps:
Number of 65 watt lamps 378
Total power, KW 25
Ozone Generator
Dimensions:
Meters (LxWxH) 1.7 x 1.8 x 1.2
gms ozone/minute . 5.3
kg ozone/day 7.7
Total power, kW 7.0
Total energy required 768
(KHH/day)
Source: Reference 16.
6-46
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6.3.1.3 Post-Treatment Requirements--
Post-treatment of industrial wastewaters that have been contacted with
ozone will involve elimination of residual ozone, usually by passing the
effluent through a thermocatalytic unit as shown in Figure 6.3.1. Some
by-product residuals may be formed in the feed water and some contaminants, if
present, will not undergo reaction. Compounds considered unreactive probably
will include many chlorinated aliphatic compounds. If these compounds are
present in the waste, technologies other than ozonation should be considered.
6.3.1.4 Treatment Combinations—
Apart from the employment of UV excitation with the ozonation process,
ozonation can be considered as a finishing step for waste streams which have
been treated by other technologies, principally biotreatment systems. It has
also been tested with some success as a means of enhancing biotreatability.
Although the use of ozonation in combination with other technologies such as
biological treatment is a possible halogenated organic waste treatment
alternative, it is not a demonstrated technology for industrial wastevaters,
despite its extensive use and success in treating and disinfecting relatively
clean drinking waters.
*
6.3.2 Demonstrated Performance
The limited information available deals primarily with pesticides,
although some information regarding halogenated solvents and PCB/dioxins is
3 4
presented in the solvent and dioxin. TRDs, respectively. Pesticides
reportedly susceptible to ozonation alone include Aldrin, Benzene
2
Hexachloride, DDT, and Dieldrin. Greater than 99.9 percent destruction of
DDT using ozone at the 10 ppm level over a 30 minute time interval was
reported in Reference 17. However, the data were obtained at the bench scale
level using concentrations in the ppb range. Typical results of UV/Ozone as
reported in Reference 18 are provided in Table 6.3.4. It was noted that in
37 tests on wastewaters containing PCBs the maximum effluent concentration
measured was 4.2 ppb. Equivalent destruction efficiencies for dioxins were
also reported in Reference 4. Other halogenated compounds identified as
economically treated include aldrin, chlorinated phenols, dieldrin, endrin,
ethylene chloride, kepone, methylene chloride, and pentachlorophenol.
6-47
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TABLE 6.3.4. TYPICAL RESULTS OF UV/OZONE IRRADIATION
** •
k
Pesticide
DDT
PGP
Malathion
PCB
. Solution
temperature
30
30
25
22
Ozone
concentration
(ppm)
10
10
50
10,000
UV light
concentration
(w/1)
1.32
1.32
1.32
—
Apparent
percentage
detoxification
>,99.1
>99.3
>99.8
99.6
Starting
pesticide
concentration
(ppm)
0.057
71.0
55.0
0.046
Residual
pesticide
concentration
(ppm)
< 0.0005
<0.5
<0.1
0.0002
Total
time
elapsed
(min)
30
15
' 30
—
Source: Reference 18
-------
6.3.3 Cost of Treatment
Table 6.3.5 lists the costs for a 40,000 gpd UV/Ozone plant for which
design data were shown in Table 6.3.3. Cost estimates were based on waste-
water containing SO ppra PCS, designed to achieve an effluent PCB concentration
of 1 ppm. Costs were considered to be competitive with activated carbon. The
unit cost for treatment of the waste .is greatly affected by whether or not the
cost for a monitoring system is included. The cost of PCB destroyed is in
excess of fclO/pound. PCB data were used for costing purposes because of its
availability. However, the costs will increase substantially if ozonation is
to be used as treatment for a waste containing 1 percent organic contaminants.
This is 200 times the concentration used to develop the costs in Table 6.3.5.
Assuming capital equipment costs follow a simple "sixth-tenths" factor scaling
relationship, the costs of the reactor and generator would be about $3,000,000
(or 24 times the costs shown in Table 6.3.4) for treatment of this higher con-
centration. Scale factors would be variable for the operating and maintenance
cost items listed in Table.6.3.4. The net result of scale-up to handle, the
more concentrated waste would drastically increase the cost/1,000 gallons
treated,-but would also result in far lower costs when calculated on the basis
of the amount of contaminant destroyed. Costs of roughly $10/pound of contam-
inant destroyed would be reduced to an estimated ^I/pound, assuming comparable
efficiencies. Destruction efficiencies, however, may be adversely affected at
higher concentrations due to mass-transfer and other considerations. Thus,
the cost benefits per pound of contaminant destroyed, as stated above, may not
be fully achievable. Ozone usage and the corresponding costs are dependent on
the concentration of oxidizable species in the waste stream. The amount of UV
radiation used depends on quantum yield which can vary widely depending upon
waste characteristics and process condition. An optimal tradeoff must be made
on the basis of pilot-scale or full scale test results.
6.3.4 Overall Status of Process
6.3.4.1 Availability--
Ozonation equipment is available commercially from several manufacturers
within the United States. The Chemical Engineers' Equipment Guide published
by McGraw Hill lists nine manufacturers of ozone generators and 10 manufac-
6-49
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TABLE 6.3.5. EQUIPMENT PLDS OPERATING AND MAINTENANCE
COSTS; 40,000 GPD UV/OZONE PLANT
Reactor " $ 94,500
Generator 30.000
$124,500
0 & M Costa/Day
Ozone generator power $4.25
DV lamp power 15.00
Maintenance 27.00
(Lamp Replacement.)
Equipment Amortization
(10 years <§ 10%) 41.90
Monitoring labor 85.71
TOTAL/DAY • $173.86
Cost per 1,000 gals
(3,785 liters) with
monitoring labor $4.35
Cost per 1,000 gals
without monitoring labor $2.20
Source: Reference 16.
6-50
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turers of ozonators. The latter classification includes films that usually
provide the ozone generator, the reactor, and auxiliaries such as the
catalytic unit for destruction of ozone from the treated stream. The status
of UV/ozonation is far less advanced. Processes such as the Ultrox process
have been concerned with highly refractory compounds such as PCBs. Equipment
specifically designed and available for UV/Ozonation of industrial
wastewaters, is not available as a standard commercial item.
6.3.4.2 Application—
Ozonation, alone, generally cannot be used as a sole treatment technology
for wastes which are resistant to oxidation such as chlorinated aliphatic
hydrocarbon wastes, and for wastes containing contaminants which form stable
intermediates that are resistant to total oxidation. Ozonation appears best
suited for treatment of very dilute waste streams, similar to those streams
treated by the ozone based water disinfection processes now used in Europe.
It does not appear to be cost competitive or .technically viable for most
industrial waste streams where organic concentration levels are 1 percent or
higher. However, it may be viable for certain specific wastes with high
levels of a* contaminant of special concern and high reactivity e.g. Dioxins.
The combination of ultraviolet light and ozone does appear to greatly enhance
destruction efficiency, but available data are not sufficient to identify
specific waste streams that are treatable. Pesticide waste streams appear
most likely to be treatable.
6.3.4.3 Environmental Impact—
Assuming adequate destruction of a contaminant by ozonation, the
principal environmental impact would appear to be associated with ozone in the
effluent vapor and liquid streams. However, thermal decomposition of ozone is
effective and is used commercially to destroy ozone prior to discharge.
Unreacted contaminants or partially oxidized residuals in the aqueous effluent
may be a problem necessitating further treatment by other technologies.
Presence of many such residuals will generally result in selection of a more
suitable alternative technology.
6-51
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6.3.4.4 Advantages and Limitations—
There are several factors which suggest that ozonation may be a viable
technology for treating certain dilute aqueous waste streams: '
• Capital and operating costs are not excessive when compared to
incineration provided oxidizable contaminant concentration levels
are less than 1 percent.
• The system is readily adaptable to the onsite treatment of hazardous
waste because the ozone can and must be generated onsite.
• It can be used as a preliminary treatment for certain wastes;
e.g., preceeding biological treatment.
b-52
-------
REFERENCES
1. Prengle, H. W., Jr. Evolution of tbe Ozone/UV Process for Wastewater
Treatment. Paper presented at Seminar on Wastewater Treatment and
Disinfection witb Ozone., Cincinnati, Ohio, 15 September 1977.
International Ozone Association, Vienna, VA.
2. Harris, J. C. Ozonation. In: Unit Operations for Treatment of
Hazardous Industrial Wastes. Noyes Data Corporation, Park Ridge, N.J.
1978.
3. Breton, H. A. et al. Technical Resource Document; Treatment Technologies
for Solvent-Containing Wastes. U.S. EPA HWERL. Contract
No. 68-03-3243. August 1986.
4. Arienti, M. et al. Technical Resource Document: Treatment Technologies
for Dioxin-Containing Wastes. Prepared for U.S. EPA, HWERL, Cincinnati,
under Contract No. 68-03-3243, Work Assignment No. 2. August 1986.
5. Rice, R. G. .Ozone for tbe Treatment of Hazardous Materials. In:
Water-1980; AICHE Symposium Series 209, Vol. 77. 1981.
6. Edwards, B. H., Paul1in, J.. N., and K. CogbIan-Jordan. Emerging
Technologies for the Destruction of Hazardous Waste - Ultraviolet/Ozone
Destruction. In: Land Disposal: Hazardous Waste. U.S. EPA
600/9-81-025. March 1981.
7. Ebon Research Systems, Washington, D.C. In: Emerging Technologies for
tbe Control of Hazardous Waste. U.S. EPA 600/2-82-011. 1982.
8. Rice, R. G., and M. E. Browning. Ozone for Industrial Water and
Wastewater Treatment, an Annotated bibliography. EPA-600/2-80-142,
U.S. EPA RSNERL, Ada, OR. May 1980.
.9. Rice, R. G., and M. E. Browning. Ozone for Industrial Water and
Wastewater Treatment, A Literature Survey. EPA-600/2-80-060. U.S. EPA
RSKERL, Ada, OK. April 1986.
10. International Ozone Institute, Inc., Vienna, VA. First International
Symposium on Ozone for Water and Wastewater Treatment. 1975.
11. International Ozone Institute, Inc., Vienna, VA. Second International
Symposium on Ozone Technology. 1976.
6-53
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12. Hackman, E. Ellsworth. Toxic Organic Chemicals-Destruction and Waste
Treatment. Park Ridge, NJ, Noyes Data Corp., 1978.
13. Sundstrom, D. W., et. al. Destruction of Halogensted Aliphatics by
Ultraviolet Catalyzed Oxidation with Hydrogen Peroxide. Department of
Chemical Engineering, The University of Connecticut. Hazardous Waste and
Hazardous Materials, 3(1): 1986.
14. Chillingworth, M. A., et al. Industrial Waste Management Alternatives
for the State of Illinois, Volume IV - Industrial Waste Management
Alternatives and their Associated Technologies/Processes, prepared by GCA
Technology Division, Inc. February 1981.
15. U.S., HWERL, Cincinnati Innovative and Alternative Technology Assessment
Manual, Ozone Oxidation. EPA 430/9-78-004, February 1980.
16. Arisman, R. K., and R. C. Musick. Experience in Operation of a UV-Ozone
Ultrox Pilot Plant for Destroying PCBs in Industrial Waste Effluent.
Paper presented at the 35th Annual Purdue Industrial Waste Conference.
May 1980.
17. Dillon, A. P., Editor. Pesticide Disposal and Detoxification Pollution
Technology Review No. 81, Noyes Data Corporation, Farm Ridge, NJ. 1981.
18. Arienti, et. al. Technical Assessment of Treatment Alternatives for
Wastes Containing Halogensted Organics, Final Report to OSW, Washington
D.C. under Contract No. 68-01-6871, Work Assignment No. 9, August 1984.
6-54
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6.4 CHEMICAL DECHLORINATION
6.4.1 Process Description
Chemical dechlorination methods have been developed as possible
alternatives to incineration or land disposal for halogenated organic
compounds such as PCS3. Researchers have found that in order to decrease
the degree of toxicity, as well as the chemical and biological stability of
chlorinated compounds, it is not necessary to totally break down the molecular
structure. Instead, the formation of a compound considered harmless and
environmentally safe can be achieved through a reaction system that will
result in the cleavage of C-C1 bonds or the rearrangement of the chlorinated
molecule. Although several different dechlorination methods exist, all of the
processes are based primarily on two technologies; the "Goodyear process"
developed by Goodyear Tire and Rubber, and the NaPEG system developed by the
Franklin Research Institute. Thus far, they have been studied as technologies
for the destruction of highly toxic wastes such as FCBs and dioxins. However,
they should be applicable to the destruction of all halogenated organics. The
characteristics of these processes are summarized in Table 6.4.1.
The Goodyear Process was originally developed to reduce PCS laden heat
transfer fluids from slightly above 500 ppm to less than 10 ppm. The reaction
chemistry is based on the use of a sodium-naphthalene reagent to form sodium
chloride and an inert, combustible sludge. The reagent is produced by
2
disolving molten sodium and naphthalene in tetrahydrofuran. However, the
reactivity of metallic sodium with water necessitates the use of an air free
anhydrous reaction vessel to prevent rapid generation of hydrogen or loss of
reagent through the formation of NaOH.
Since Goodyear has decided not to pursue the marketing of this process,
several companies such as SunOhio, Acurex (now being marketed by Chemical
Waste Management), and PPM Inc, have entered the field. Generally, they have
modified the process by substituting proprietary reagents for naphthalene,
which is a priority pollutant. These processes are also intended for
treatment of PCB contaminated oils (50-500 ppm) and require pretreatment to
remove water and inorganics such as soil. Typically, these processes cannot
handle PCB concentrations greater than 10 percent, and most are not suitable
for sludges, soils, sediments, and dredgings.
6-55
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TABLE 6.4.1. DECHLORINATION PROCESSES
Proceaa description
Compounds end fora*
of waste treated
Destruction Capabilities
Residuali
Comments
PCB (SunOhio)
• ptoprietsry sodium reagent
used to strip sway chlorine
e oil la aiiied with reagent
and sent to resctor
• Mixture is then centrlfuged
degassed and filtered
Acurex (CWM)
e proprietary aodium reagent
used to atrip chlorine
• contaminated oil la filtered,
and mixed with reagent
e reaction takes piece In
processing tsnk
• liquid hydrocarbon streams,
i.e. PCB contaminated oil
frosi transformers
• cannot be uaed on aqueoua
or soil wsatee
• 250 ppm PCB to 1 ppm
e 3000 ppm to below 2 with
aeveral passes
• can be used on PCB contaminated • PCB feeds ss high aa IOZ
oils and soils effectively treated
• elso effective on transformer
oil contaminated with
2,1,7,8-TCDO
« 2.3,7,8-TCDD reduced
from 200-400 ppt to 40 ppt
• metal chlorides
e polyphenyls
• trested oil
• treated oil
e sodium hydroxide
effluent
e polyphenol sludge
• mobile, continuous process
• moisture and contaminant
removal required as
pre-treatment
• moderate temperature and
pressure
• pure PCBs destroyed at
ISO ml/min
• mobile, batch operation I
i
a pretreatment needed to j
remove water, aldehydes i
and acids from trsnsformer
oils I
• non-toxic solvent used to I
extract PCBa from aoil ;
APEG
• sodium polyethylene glycol
resgent (NaPEC) used for PCB
• Potassium Polyethylene Glycol
used for TCDO
a reagent la added to contamin-
ated material in the presence
of air, and can be sprayed on
• PCB oils and aoila
e TCDD contaminated soils
• also tested on hexachlorocyclo-
hexane, hexachlorobensene, PCP,
DDT, KEPONB, Tri- and Tetra-
chlorobenxenea
• PCB destruction 99.991
e 2,3,7,8-TCDD reduced from
3JO ppb to 101 ppb
• Other halogenated
organlca >99.99I
e aodium chloride
e oxgenated biphenyla
a decontsmlnated
material
a hydrogen gaa
• Involves the application of
reagent In the presence of
sir or oxygen
0 water increases reset ton
times and decreases the
degree of chlorlnation
• temps, sbove 100*C required
for fast destruction
PPH
• proprietary sodium reagent
used for chlorine stripping
e reagent Is sdded to contam-
inated oil and left to react
• sulId polymer formed Is
filtered out
e PCB contaminated oil
• TCDD detoxification will be
Investigated soon
• aqueoua waste and soil not
treated
e 200 ppm PCB reduced
to below 1 ppm
• aolid polymer
e decontaminated oil
• mobile, batch process,
700 gsl/hr
• polymer is produced at
a rate of 55 gal per
10,500 gal oil treated
• polymer is regulated and
•met be landftiled
Source: Reference 1.
-------
A more promising technology is the NaPEG or APEG process, originally
developed in 1980 by Pytlewski, et al., at the Franklin Research
4
Institute. The intent was to devise a"reaction system that would decompose
PCBs and halogenated pesticides in an exothermic and self-sustaining manner.
The dechlorination reagent was formed by reacting alkali metals such as sodium
with a polyethylene glycol (M.W. 400) in the presence of heat and oxygen.
The reaction mechanism involves a nucleophilic substitution/elimination and
the oxidative degradation of chlorine through the generation of numerous free
radicals. The process reactivity can be "tuned" or directed at various
aliphatic or aromatic systems by varying the molecular weight of the
polyethylene glycol. Two emerging technologies based on the APEG system
are currently under development at the Galson Research and the Sea Marconi
Corporations. The Galson Research process involves a series of processes for
the degradation of chlorinated benzenes, biphenyls and dioxins from
contaminated soils. The system, which was developed under EPA sponsorship, is
based on the more reactive KPEG (potassium-based) reagent, in conjunction with
a sulfoxide catalyst/cosolvent. A probable reaction scheme is presented in
Figure 6.4.1.
ROH + KOH —> ROK + . HOH
OUfCCC POTASSIUM jHJUQy'fPB WATB?
KC!
POTUSUM
cucwce
ROH
QLYOOU
Figure 6.4.1. Probable reaction mechanism.
Source: Galson Research Corporation.
6-57
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The Sea Marconi's chemical process, called CDP-Process, was first
developed for the decontamination of PCB-laden mineral oils. However, the
system has been more recently applied to materials and surfaces exposed to
contaminants coming from fire or explosion of PCS equipment. The chemistry
involves reaction with high-molecular weight polyethylene glycol in the
presence of a weak base and a peroxide. No application to aqueous media can
be expected from these processes due to their sensitivity to water.
The mode of operation of each of the above processes is basically the
same with some slight variations. Each of the processes is a batch process
except for the PCBs process which is continuous. All of the processes have
been designed to be mobile. Waste throughput for these processes is generally
2
in the range of 500 to 1,000-gallons per hour for a PCS contaminated oil.
For contaminated soils and other types of waste, the throughput would be
different.
Another approach to dechlorination of halogenated organics is employed in
the light activated reduction of chemicals (LARC). The LARC processes, which
uses UV light and hydrogen gas to degrade extracted chlorinated hydrocarbons,
was developed by Atlantic Research Corporation (U.S. Patent 4,144,152 awarded
to Judith Kitchens of ARC). However, despite its initial promise as demon-
strated by its ability to destroy halogenated organics such as Aroclor 1254,
3 fc
8
kepone, and tetrabromophthalic anhydride, the process has not been actively
pursued, primarily because of economic considerations.
The processes have been designed primarily for the treatment of oils
2
contaminated with 500 to 5,000 ppm of PCBs. Some work has also been done
3
on the treatment of wastes with low concentrations of dioxin . All of the
processes, except for the APEG process, require pretreatment to remove water
and inorganics such as soil from the waste. The Acurex process can treat
contaminants in a suitable solvent at virtually any concentration. The Acurex
process is reported to be able to treat wastes with* up to a 10 percent
concentration of contaminants. If wastes are more concentrated than this,
9
they are diluted before addition of the reagent. In addition, compounds
with phosphorus, sulfur, alcohols and acids are troublesome. The alcohols and
acids interfere with the free radical reaction, upon which the dechlorination
process is based. The PCBs and PPM processes are more limited in their
applicability. Both cannot be used to treat soil contaminated wastes or
wastes with any moisture content.
6-58
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6.4.2 Demonstrated Performance
These processes should be applicable to most types of highly halogenated
compounds. The sodium polyethylene glycol reagent used in the APEG process
was also used on the following compounds in place of PCBs: he.xachlorocyclo-
hexane, hexachlorobenzene, tri- and tetrachlorobenzenes, pentachlorophenol,
DDT, kepone, and chloroethylsulfide. These compounds were dechlorinated
rapidly and completely as noted in the proceedings of the sixth annual
4
symposium on the treatment of hazardous waste.
The destruction efficiency of PCS contaminated material is in the
99 percent range for each of the processes as can be seen in Table 6.4..1.
Equal or greater efficiencies should be achievable for most other halogenated
organic compounds in liquid streams. Further detail regarding the performance
of the processes in degrading toxic compounds such as the PCBs and dioxins can
be found in Reference 10.
0
6.4.3 Cost of Treatment . .
. . At this time, costs are very well established for the decontamination of
PCB contaminated oils. These costs are dependent on several variables:
• concentration of pollutant;
• quantity and characteristics of the material to be treated;
• reagent costs; and
• the resale value of the treated material.
The cost of treating bulk quantities of PCB-contaminated oil using the
SunOhio PCBs process will about $3.00 per gallon. Costs will vary depending
upon contamination level, onsite or offsite treatment, transportation, and
ultimate disposition of the oil. Costs for treating transformer oil will be
higher (5- to 9 dollars or more per gallon) with a minimum charge of i>25,000
per transformer. The average cost in early 1980 for the Acurex process was
$2.40 per gallon or $0.70 per kilogram of oil treated.
6-59
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Based upon the APEG laboratory field research that has been conducted
over the past several years, a preliminary economic evaluation of this
dechlorination process has been attempted . Specifically, Galson Research
Corporation, in conjunction with the U.S. EPA-HWERL, has roughly estimated the
costs for APEG dechlorination using two hypothetical field scenarios. These
costs, as shown in Table 6.4.2 below, indicate that there is approximately a
$2057ton difference between the in situ process (operating on a 1 acre-3 feet
deep contaminated area) and the slurry process (with excavation and 3 reactor
systems operating). This difference comes from the fact that in the slurry
APEG process, reagent recovery is possible which reduces the total cost of the
process by approximately 65 percent.
TABLE 6.4.2. PRELIMINARY ECONOMIC ANALYSIS OF IN SITU AND SLURRY PROCESSES
(Peterson, R.L., et al., 1985)
Cost, fc/ton soil
Cost item
Capital recovery
Setup and operation
Reagent
Total costs
In situ
31
65
200
296
Slurry
17
54
20
91
6.4.4 Status of Development
6.4.4.1 Availability/Application—
The non-APEG processes are available both as fixed and mobile units, from
the developers or operators. These firms are Chemical Waste Management,
SunOhio, PPM Inc. and Goodyear. These processes are used exclusively for the
treatment of PCB-contaminated oils, although the processes should be
applicable to moisture free liquid organic wastes containing halogenated
6-60
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organic constituents. Similarly the AFEG process, now being tested by Galson
Research Corporation and EPRI, should be capable of destroying virtually
all balogenated organics.
The limiting factor in all cases will be cost.
6.4.4.2 Environmental Impacts—
The residuals from these processes are listed in Table 6.4.1. Each of
these processes result in the production of a polyphenol type material which
is nontoxic and can be readily bandied. Acurex has estimated that it takes
about 2,000 gallons of treated oil to produce one drum of sludge and
associated liquid. The chlorine atoms which have been removed from the PCB
compound leave as sodium chloride in the sodium hydroxide effluent. Air
emissions from this process are minimal because the destruction process occurs
under an inert nitrogen atmosphere. PPM and PCBs result in similar
polyphenol/salt type residues which contain less than 2 ppm of PCB and can
therefore be readily handled.
The residuals from the APEG process, however, are somewhat different
because oxygen is involved in the reaction. Oxygenated biphenyls are formed
along with sodium chloride and hydrogen gas. the products are reportedly
nontoxic. Incineration would appear to be the preferred disposal method for
all solid wastes.
6.4.4.3 Advantages/Limitations—
The dechlorination processes discussed here represent proven technology
for the dehalogenation of organic compounds such as PCBs and dioxins.
Equivalent performance can be expected for other halogenated compounds.
However, the costs are high and residuals are produced that will require
further treatment, probably incineration for the solid residuals.
6-61
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REFERENCES
1. Weitzman, L. et al., "Disposing Safely of PCBs: What's Available, What's
on the Way." Power, February 1981.
2. Gin, W. et al., Technologies for Treatment and Destruction of Organic
Wastes as Alternatives to Hand Disposal, State of California Air
Resources Board, August 1982.
3. Nunno, T. et al., Technical Assessment of Treatment Alternatives For
Wastes Containing Halogenated Organics. GCA Report to U.S. EPA/OSW, under
Contract 68-01-6871, WA No. 9. 1985.
4. U.S. EPA, Treatment of Hazardous Waste, Proceedings of the Sixth Annual
Research Symposium, pg. 72. EPA-600/9-8-011, March 1980.
5. Ibid pg. 197.
6. Telephone Conversation with Charles Rogers, U.S. EPA, Cincinnati, Ohio,
May-15, 1986.
7. Valentine, R. S. LARC-Light Activated Reduction of Chemicals. Pollution
Engineering. February 1981.
8. Kitchens, J. Atlantic Research Corporation. Telephone conversation with
M. Arienti of GCA. August 1986.
9. Wallbach, D. Acurex Corporation. Telephone conversation with M. Arienti
of GCA. October 2, 1984.
10. Arienti, M. et. al. Technical Resource Document - Treatment Technologies
for Dioxin-Containing wastes. Prepared for HWERL Cincinnati under
Contract No. 68-03-3243, Work Assignment No. 2. August 1986.
11. Fisher, M. SunOhio. Telephone conversation with N. Surprenant of GCA.
August 1986.
12. Weitzman, L. Acurex Corporation, Cincinnati, Ohio. Telephone
conversation with M. Jasinski. June 4, 1986.
13. Peterson, R. L. et. al. Chemical Destruction/Detoxification of
Chlorinated Dioxins in Soils. Paper presented at Eleventh Annual
Research Symposium on Incineration and Treatment of Hazardous Waste. EPA
600/9-85-028. September 1985.
6-62
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SECTION 7
BIOLOGICAL TREATMENT METHODS
7.1 PROCESS DESCRIPTION
Biological treatment involves the degradation of organic compounds by
microorganisms. Conventional biological treatment processes include activated
sludge, aerated lagoons, aerobic and anaerobic digestion, trickling filters,
rotating biological contactors, and composting. For a detailed description of
these processes, one can refer to a number of texts on wastewater
12
treatment. ' In each of these processes, there exists a population of
microorganisms which are either suspended in a liquid medium, as in the
activated sludge process, or attached to some solid surface, as.in the
trickling filter process. The microorganisms metabolize the organic
constituents of the waste to carbon dioxide and water if the process is
aerobic, or carbon dioxide and methane if the process is anaerobic. When
treating toxic compounds, such as many halogenated organics, only partial
degradation may occur and the end products may be as toxic as the initial
compound. In addition, many of these compounds may be removed by some
mechanism other than biodegradation. Processes that require aeration may
cause volatile constituents in the waste stream to be air stripped prior to
degradation, while hydrophobic compounds with a high octanol/water partition
coefficient may be adsorbed by biological matter or other solids in the
was test ream and subsequently be removed as part of the settled sludge.
Therefore, compounds that may appear to have been biodegraded are sometimes
merely transferred from the liquid to the air or solid phase.
In treating wastes containing halogenated organic compounds, the
effectiveness of the system in removing these compounds is dependent primarily
on the microorganisms that are present. Most of these compounds are manmade
and, therefore, natural microorganisms did not originally have the ability to
degrade these compounds. Through exposure to the compounds, however, some
7-1
-------
groups of microorganisms have developed enzymatic systems resistant to the
3 4
toxic compounds and with a capability to degrade them at a slow rate. '
Microorganisms that have demonstrated an ability to degrade halogenated
organic compounds are listed in Table 7.1. Treatment systems that are
innoculated with these types of microorganisms may have the ability to remove '
these compounds.
7.2 DEMONSTRATED PERFORMANCE
7.2.1 Removal in Conventional Systems
In the past, the primary function of biological treatment systems has not
been to remove toxic organic pollutants, but to remove the conventional,
easily biodegradable organic compounds. Recently, however, the biodegradation
of toxic compounds has received increasing attention due to its potentially
lower cost versus other treatment technologies, and a number of studies have
been conducted. In one study, a municipal wastewater stream treated by a
conventional activated sludge process was spiked with a number of priority
pollutants including toxaphene, lindane, pentachlorophenol, and
heptachlor. The concentration of each of these compounds was 50 yg/L
except for toxaphene which was 150 yg/L. The treatment system included a
primary clarifier, an aeration basin, and a secondary clarifier. The primary
sludge, return activated sludge, and final effluent were sampled over a
312 day period to determine whether the compound was biodegraded, air
stripped, or adsorbed as it passed through the treatment system. As shown in
the table below, each compound responded differently. The only similarity was
that biodegradation was not the primary removal mechanism for any of the
compounds.
Percent
Percent biodegraded Percent in
Compound adsorbed or stripped final effluent
Toxaphene 58 40 2
Heptachlor 68 25 7
Lindane 20 25 55
Pentachlorophenol 28 0 72
7-2
-------
TABLE 7.1. EXAMPLES OF MICROORGANISMS THAT CAN DEGRADE HALOGENATED ORGANIC COMPOUNDS
Compound
Organ 1 ma
Condition
Remarks/Products
Aliph.il lea
Trichloroethnne
Trichloroiae thane
Trichloroethane, trichloromethane, methyl
chloride, chloroethane, dlchloroethane,
vinylidiene chloride, trichloroethylene,
tecrauhloroethylene, taethylene chloride,
dibromochloromethane, brooochloroatethane
Trichloromcthanee, trichloroethylene,
tetrachloroethylene
Tricliloroethane, trichlorogiethane,
tetrachloromethane, diehloroethane,
dibroiauchloromethane, 1,1,2,2-tetra-
chloroethane, bls-(2-chloroisopropyl)
ether, bromoform, broaodichloromethane,
trichlorofluorome thane, 1, 1-dichloroethylene,
1,2-dichloroethylene, I,3-dlchloropropylene,
1,2-tranadichloroethylene
Aromatic compounds
1,2-; 2,3-; 1,4-dichlorobenzeno; p-; M-;
o-chlorobenzoate; 3,4-; 3,5-dichlorobenzoate,
3-mcthyl benxoate; A-chlorophenol
llenachlarobenzene, trlchlorobentene
1,2,3- and l,2,A-trichloroben
-------
TABLE 7.1 (continued)
Compound
Organieaa
Condition
Reaarka/Producta
! Methoxychlor
Ac role in
Aldrin
Endoaulfan
End r i n
Chlorodimefora
Kopone
Polycyclic aroaatic hydrocarbona (halogenated)
PCBa (mono- and dichlorobiphenyla)
4-chlorobiphenyl; 4,4-dichlorobiphenyl;
3.3'-dichlorobiphenyl •
Pesticides
2. 4-D
2. 4. 5-T
Nocardla ap., Streptoaycea ap. (5)
Aerobactar aerogenea (1)
Site water (alerobe«)
Site water (aicrobea)
Sewage aludge
Fungi, bacteria, aoil antlnoaycetea
Paeudoiaonaa ap. Hicrococcua ap.,
yeaat (4)
Sewage aludge
ChloreUa (2), OacillatorU (3)
Treataent lagoon aludge
Paeudoiaonaa, Vibrio, Spirillun,
Plavobacteriun
Achroaobacter
Chrooobacter Baclllua (1), Nocardla (S)
fungi
Paeudoaonaa
Alcaligenea Eutrophua
Paeudoaonaa cepacia
(AC1100)
ae
ae/an
ae
an
ae
an
ae
l,l-dichloro-2,2-bie(p-a»thoxyphenol)ethyleiu
l,l-dichloro-2,2-bia(p-Betlioiiyphenol)-
ethane
O'Hydroxypropionaldeliyde
Dieldrin by eposidation
(8)
Endosulfen (2), endodiol (I).
endohydroether (5)
Soil organiaaa, aldehydea and ketonus with
5 to 6 chlorine atoms (1)
(8)
4-Chloro-o-foraotoluidiene, 4-chloro-o-
toluidiene, i'chloroanthranilic acid,
n-forayl-5-chtoroanthranilic acid,
auapected autagena i
(8), Coaetaboliaa
Biodegradation appeara to be inversely
related to extent of chlorination
High level dehalogenaae, aajor end product
C02
4-Chloro-4'hydroxybiphenyl; 4,V-dichloro-3-
hydroxybiphenyl; chlorinated bunxoic acid
Full aineralitation
(continued)
-------
TABLE 7.1 (continued)
Compound
Organlaua
Condition
Remarka/Producta
Toxaphene
lleptachlorobornane
Lindane
Dieldrin
Ul
POT (l,r-bia(p-chlarophenyl)-2.2.2-
trichloroethane)
Corynebacteriua pyrogenea (I) an
Hicromonoapora chalcea (5) ae
Bovine ruaten fluid (7) an
Chlorella vulgaria (2) ae(T)
Chlaaydamonaa reinhardtli ae
Chloatecidiuoi ap., Paeudomonaa (I) an
Soil bacteria ' an
t. Chryaoaporiun ae
Sewage aludga * an
Anacyatia nldulana (1) an
Agmeneloum quardiplicatua (3) . an
Paeudomonaa (1)
Rumen fluid (7) an
Actlnoaycetea on/an
Klebaiella pneumoniae (1) B. coll, an
Aerobacter aerogenea,' Paeudomonaa,
Cloatridiua, Proteua -vulgaria
llexacltlorobornane (8)
Pentachlorocyclohexane (non-tuxic) (8)
-3,
-------
TABLE 7.1 (continued)
Conpound
Organisms
Condition
Remarks/Products
DDT
P. Chrysosporiua
Fussrium oiyiparun (4)
Hucor altering (4)
Cyllndrotheca, Closteriua (2)
DunalielU (2)
Anaerobic sludge (7)
Nocardia, Streptomyces (S)
llydrogenomonaa (1)
ae Complete Mineralisation
ae Complete mineralization; no DDT in 10-14 days
ae Come tabo lisa
ae DDE (alow) (9)
ae IDE, DDE, DDKS, DDOH (8)(9)
an IDE rapid
ae DDE (9)
an/ae 10 products, simplest was PCPA; 9 products,
simplest wa DBF
DDT—(only p,p'-DDT considered here)
DDE(TDE)—l'-bis(p-chlorophenyl)-2,2-dichloroethane
DDE—l,l'-bis(p-chlorophenyl)-2,2-dlchloroethylene
DBF—4,4'-dlchlorobenxophenone
DDHS—l,l'-bis(p-chlorophenyl)2-chloroethane
PCPA—p-chlorophenyl acetic acid
DOHA—l,l'-bia(p-chlorophenyt)-2-chloroethylene
DDO1I—l,l'*bis(p-chlorophenyl)-2-hydroxyethane
BHC—1,2,1,4,3,6-hexachlorocyclohexana
(I) Bacteria
(2) Algae
(1) Blue-green algae
(4) Fungi
(S) Actinomycetes
(6) Photosynthetic bscteria
(7) Consortium of anaerobices
(B) Reductive dechlorlnation
(9) Dehydrodochlorination
ae—aerobic (may be ae/an)
an—anerobic (either anoxlc or fastidious)
Source: Reference 5.
-------
One point that should be made, however, is that no attempt was made to
optimize the system for the removal of the priority pollutants. The primary
purpose of an activated sludge treatment system such as this is to reduce the
Chemical Oxygen Demand (COD) and the Total Suspended Solids (TSS) of the waste
stream. These removals averaged, respectively, 89 and 95 percent. If the
system had been inoculated with a microbial population that had been
acclimated to the toxic constituents, and a longer solids retention time had
been used, the removal by biodegradation may have been greater. As it was,
the majority of the toxaphene and heptachlor were removed by adsorption, and '
the majority of the lindane and pentachlorophenol were not removed at all.
In another study, the concentration of several pesticides in the influent
and effluent of a municipal wastewater treatment system was measured.
These measurements indicated that biodegradation was the removal mechanism for
16 to 55 percent of the influent 2,4-D that ranged in concentration from 8 to
40 ug/L. The measurements also indicated that DDT was transformed to DDE or
DDD, and that aldrin degradation produced the compound dieldrin. This
illustrates the fact that the products of biodegradation are sometimes as
toxic as the original compounds.
7.2.2 Research on Specific Microorganisms
In addition to research on the fate of compounds in conventional
biological treatment systems, a number of researchers have studied the removal
of halogenated and other toxic organic compounds by acclimated bacterial
populations and other microorganisms. The results of some of these projects
are summarized in Table 7.2. In most of these projects, natural bacterial
populations from sewage, river water, or soil were slowly exposed to waste
containing halogenated compounds (HOCs) after which a population was developed
that could utilize the HOC-as a food and energy source.
For example, in the first project listed in Table 7.2, microorganisms
from several waste dumping sites (such as Love Canal) were collected and
placed in a chemostat along with other microorganisms of known capabilities.
2,4,5-T was added to the chemostat in gradually increasing concentrations over
a period of 8 to .10 months until the bacterial population could utilize
2,4,5-T as its sole food and energy source. The bacteria isolated from this
culture were identified as Pseudomonas cepacia. strain AC1100. Table 7.3
7-7
-------
TABLE 7.2. RESEARCH ON MICROBIAL DEGRADATION OF HALOGENATED ORGANIC COMPOUNDS
Compound
Microorganism
Degradation
achieved
Comments
Reference
2,4.5-T
2.4-0
3,5-DCB
PeneachlorophenoI
2,4-D
Pseudooonas Cepacia,
AC1100
Pseudooona* (Cram
sewage sludge)
Pseudononas (from
sewage sludge)
Flavobacteriua (from
Biver water)
Pseudoaonaa,
Alealigones Eutrophua
Lindane, DOT •
2,3,7,8-TCDO,
3.4,3'.4'-Tetra-
chlorobiphenyl
Halogenaced
Benzoates
Chlorinated
Benzenes
Phanerochaete •
Chrysosporiun
(White Roe Fungus)
Meehanogenic bacteria
from lake sedinent
and sewage sludge
Developed from
primary sewage
981 reduction froa
starting concentra-
tion of 1,000 ppm in
I week.
100 mg/L reduced to
less than I mg/L in
six days; 100 ug/L
reduced Co less than
20 ug/L in 3 days.
100 mg/L reduced to
less than 10 mg/L
in 6 days; 100 ug/L
reduced Co less Chan
20 ug/L in 3 days.
100 ppm in soil
mineralized in I week;
degradation did not
occur at initial
concentration of
500 ppm.
Percent degradation
not presented t but
both types of
bacteria showed rapid
degradation of 2,4-D
after an extended
(80-120 hr) lag
period
90Z degradation of
DDT after JO days;
9.3Z of DDT mineral-
ized to COj after
60 days.
Mineralized halo—
genated aromatics Co
COj and CH&
90-100Z degradation
of several ehloro-
benzenes from initial
concentration* of
10 ug/L.
experiments conducted
on contaminated soil
2,4-D was the only
carbon and energy
source; 3-day lag
period before rapid
growth.
sane as above
Bacteria adapted to
PC? degradation after
a 2-3 week exposure in
saturated stream
sediments; optimum
conditions: 20Z water,
Temp • 24-35*C
No degradation of
2,4-D occurred when
glucose was added as
an alternate substrata
Chatterjee ec al, 1982;
Kilbane et al, 19839
Kim and Maier, 1986l°
same as above
Martinson et al, 1986ll
Roy and Micra, 1986*
12
DehaltOgenation did not
depend on number of
halogen scorns but on the
type of halogen and
position on eromacic
ring
%
Hicrobial population
was grown on either
glass beads or granular
activated carbon in a
25 em upflow column
Bumpus ec al, 198S
Suflica ec al, 1982.U
Bouwer and McCarthy, 198214
7-8
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TABLE 7.3. CONCENTRATIONS OF 2,4,5-T IN SOIL TREATED WITH
PSEUDOMONAS CEPACIA AC100a Cug/g of soil)
Concentration of 2,4,5-T (yg/g of soil)
Sample
1
2
3
4
5
6b
7b
Initial
1,000
2,500
5,000
10,000
20,000
1,000
10,000
1 Week
30
35
280
9,000
17,000
940
11,200
2 Weeks
20
20
70
3,500
11,900
1,100
10,800
3 Weeks
20
20
25
2,050
4,300
1,100
10,800
6 Weeks
60
20
20
488
1,410
1, 120
9,095
^Samples treated with 5 x 10? micro-organisms per g of soil.
^Controls—-no micro-organisms added.
Source: Reference 9.
7-9
-------
shows the effectiveness of this bacteria in degrading 2,4,5-T in soil at
concentrations of up to 20,000 ppm. The researchers plan to develop bacterial
strains for degrading other compounds such as 2,3,7,8-TCDD, using the same
8 9
method, which they call plasmid assisted molecular breeding. '
In other studies listed in Table 7.2, research was conducted to determine
the effect of factors such as contaminant concentration and the presence of
alternate substrates on the degradation of HOCs. Kim and Maier of the
University of Minnesota investigated the degradation of 2,4-D and
3,5-dichlorobenzene (DCS) by acclimated cultures derived from municipal sewage
sludge. They found that the acclimated cultures could degrade the
compounds over a wide concentration range (10 yg/L to 100 mg/L). They also
found that when a nutrient broth was added (to act as an alternate substrate),
the rate of degradation of the HOCs was increased except at low
concentrations. In all cases, however, both substrates were utilized
concurrently.
4,
In a similar study, when 2,000 mg/L of glucose was used as an
alternate substrate along with 1,500 mg/L of 2,4-D. the glucose was degraded
at a normal rate, but no degradation of 2,4-D occured. In this study, as in
the previous study, the bacterial population was derived by selective
enrichment of municipal sewage sludge. In this case, however, the degradation
was undertaken by a pure culture of bacteria of the genus Pseudomonas, while
in the previous case the degradation was by a mixed culture that was
predominantly, but not solely Pseudomonas. This illustrates another point,
namely that degradation by mixed cultures is frequently more successful than
by pure cultures. This point was further demonstrated when pure cultures of
Pseudomonas and Alcaligenes Eutrophus were mixed. Degradation of 2,4-D by
this mixed culture occurred without the initial 5 day lag period that existed
when pure cultures of either of the bacteria were used. The researchers
attribute this to the fact that the enzyme systems in the two microorganisms
are not identical, and instead they complement each other.
The superior degradation of HOCs by diversified microbial populations is
further demonstrated by a study that compared the degradative capabilities of
a municipal mixed liquor with three commercial bacterial populations. In this
study, phenol, 2-chlorophenol, and 2,4-D were added to batch reactors which
had been seeded with one of four different bacterial populations. As shown in
7-10
-------
Table 7.4, the rate of degradation of each of the compounds was higher in the
reactor that had been seeded by the municipal mixed liquor than it was in any
of the reactors that had been seeded with the commercial preparations. The
three commercial preparations, which had supposedly been preconditioned to the
compounds, did not achieve high rates of degradation primarily because of
their narrow population diversity. Conversely, the mixed liquor contained a
diverse population of microorganisms that could quickly adjust to varying
substrates. The highest degradation rates were achieved when either of the
three commercial preparations were mixed with the municipal mixed liquor.
One point that was emphasized in another study is that in order to
enhance biodegradation, particularly in soils, physical parameters such as
water content, pH, oxygen availability, and bacterial concentration must be
optimized. This particular study involved degradation of pentachlorophenol in
soil by Flavobacterium. One of the most important factors affecting the rate
of PGP removal was the water content of the soil. The greatest amount and
rate of PCP removal occured at a water content in the range of 15 to
20 percent. The research also indicated that the optimum temperature range
was 24 to 35°C. No significant mineralization was observed at 12 or 40°C. In
addition, PCP degradation did not occur when PCP concentration exceeded
500 ppm.
Not all of the microorganisms identified as having the ability to degrade
HOCs are bacteria. Recent investigations of the white rot fungus,
Phanerochaete chrysosporium, have demonstrated the ability of this lignin
degrading organism to mineralize several toxic compounds including lindane,
12
DDT, 2,3,7,8-TCDD, and 3,4,3'4'-Tetrachlorobiphenyl. As shown in
Table 7.5, the rate of degradation was highest for lindane. Over 20 percent
was fully mineralized in 60 days. In model degradation studies
g^ Chrysosporium degraded 50 percent of the DDT initially present within the
first 30 days.- Four percent of the initial DDT had been fully mineralized to
C0_ while the remainder had either been incorporated in the organism, or was
present as an intermediate in the pathway between CO- and DDT. These
intermediates were identified as being ODD,, dicofol, and 4,4'-dichlorobenzo-
phenone. At 30 days, additional glucose was added to the 10 mL culture, and
after 18 more days, more than 90 percent of the initial DDT had been
degraded. The researchers feel that this microorganism would be extremely
7-11
-------
TABLE 7.4. ZERO-ORDER RATE CONSTANTS FOR COMMERCIAL AND MIXED LIQUOR BACTERIAL POPULATIONS (ppm/hr)*
(values in parentheses are Che rate constants divided by MLSS-in ppm/hr/I,000 ppra MLSS)
phenol
2-chlorophenol
2,4-D
Livingston
(mixed
liquor)
82(34)
11(5)
0.6(0.5)
Hydrobac
25(230
2(2)*
BI-CHEM
52(37)
4(3)**
LLMO
9(8)
0.4(0.4)
Livingston
+Hydrobac
130(57)
21(9)
0.7(0.5)
Livingston
+BI-CHEM
131(57)
.28(12)
0.2(0.2)
Livingston
+LLMO
101(44)
47(20)
0.4(0.3)
* Average values
**Por runs III&IV
TABLE 7.5. DEGRADATION OF ORGANOPOLLUTANTS BY P. CHRYSOSPORIUM
K>
Radiolabeled substrate
Lindane
Benzo( a)pyrene
DDT
TCDD
3,4,3',4'-TCB
2,4,5,2',4',5'-HCB*
Initial rate of
degradation to *-*C02
(pmoles/day)
11.3
7.5
2.7
1.2
0.7
2.4
evolved as '
(pmoles)
30 days
190.8
117.2
48.0
27.9
13.8
44.2
l*C02
60 days
267.6
171.9
116.4
49.5
25.1
86.0
Percent of
Radiolabeled
substrates evolved
as 14C02 in 60 days
21.4
13.8
9.3
4.0
2.0
1.7
*Substrate concentration was 1.25 nmoles/10 ml for all ^c-radiolabeled compounds except
8,4,5,2',5'-HCB. Because of its low specific radioactivity a concentration of 5.0 nmoles/10 mL
was used for 2,4,5,2',4',5'-HCB.
-------
useful in degrading organopollutants that are physically adsorbed to soils and
sediments. In this state, the pollutants may not be available for uptake and
metabolism by microorganisms. However, JP^ chrysosporium secretes
extracellular fungal enzymes that degrade large, insoluble particles to
smaller substituents which may then be internalized and biodegraded. In
addition, P. chrysosporium is highly nonspecific in its degradative
capabilities and degradation will occur even under low substrate conditions.
Each of these characteristics is desirable for treating contaminated soils and
sediments.
7.3 COST
Biological treatment has conventionally been used to treat aqueous wastes
containing biodegradable organic compounds. A typical activated sludge plant
will consist of an equalization basin, an activated sludge basin with surface
aerators, a clarifier with activated sludge recycle, and some type of sludge
dewataring unit such as a vacuum filter or centrifuge. The cost of a system
such as this will be a function of the organic content of the wastewater (BOD)
and the flow rate. Capital and operating coats for a 1 mgd and a 5 mgd system
are presented in TaBle 7.6.
The cost of treating wastes- containing toxic constituents such as
halogenated organic compounds is difficult to estimate due to the lack of
experience in such projects. If specific bacterial populations are required
to attain full degradation of the waste, a major portion of the cost may go
into research and development as opposed to equipment and construction. In
addition, hazardous wastes are frequently not liquid waste streams, but
instead they are contaminated soils or sludges. In this case, conventional
biological processes such as activated sludge or trickling filters cannot be
employed unless the contaminant is first leached from the soil. Otherwise,
biological treatment will involve the adaption of indigenous bacteria to the
contaminants, or innoculation of the soil with microorganisms that have been
acclimated to the contaminant. In either case, it will be necessary to
maintain optimal temperature, water content, pH, oxygen availability and
nutrient concentration in the soil to attain maximum biodegradation.
7-13
-------
TABLE 7.6. COSTS FOR BIOLOGICAL TREATMENT3
Item
1 mgd
Facility size
5 mgd
Direct Capital ($1,000)
Indirect Capital ($l,000)b
Total Capital
Direct O&M ($l,000/yr)
Indirect O&M ($l,000/yr)c
Total O&M
$2,753
2.552
$5,305
$ 485
$ 7,010
6.433
$13,443
$ 145 $ 529
340 878
$ 1,407
Closure. ($1,000)
Annual Revenue Requirement
($l,000/yr)
Unit Cost ($/lb BOD)
$ 482
$ 871
$ 2,303
$ 2,376
$ 0.37/lb $ 0.21/lb
aUpdated from June 1983 to October 1986 using ENR construction cost index.
b92Z of direct capital costs.
C5Z of total capital costs plus 102 of total annual cost.
Source: Reference 16.
7-14
-------
7.4 OVERALL STATUS
Biological treatment of wastes containing halogenated organic compounds
is not a common practice because many of the compounds are not readily
degraded by naturally occurring microorganisms. Instead, this type of waste
is more commonly incinerated or treated by carbon adsorption. However, recent
research has led to the development of microbial populations that do have the
ability to degrade some of these compounds. It is possible that, in the near
future, these microbes will be used in biological treatment systems to remove
halogenated organic compounds. At the present time, however, biological
processes as the sole method of treatment of these wastes is only in a
developmental stage. Biological treatment is still useful, in reducing the
overall organic content of a wastestream. For example, in one case, leachate
from a landfill containing toxic industrial wastes was being treated by
activated carbon adsorption. The carbon removed the toxic contaminants, but
the carbon usage rate was exceedingly high due to the presence of many
nontoxic organic compounds. Therefore, a biological treatment system was
installed to remove the biodegradable organic compounds and reduce the organic
load to the carbon adsorbers. This significantly reduced the carbon
exhaustion rate and the overall cost of treatment. This example
demonstrates that although biological treatment may not always be used for the
removal of specific halogenated compounds, it is still be useful in removing
conventional pollutants.
7-15
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REFERENCES
1. Metcalf and Eddy, Inc. Wastewater Engineering; Treatment/Disposal
Reuse. McGraw-Hill, Second Edition. 1979.
2. Nemerow, Nelson, L. Industrial Water Pollution; Origins, Characteristics
and Treatment. Addison-Wesley. 1978.
3. Ghosal, D. et al. Microbial Degradation of Halogenated Compounds.
Science, 228, 4696, 135-142. 1978.
4. Roy, D., and S. Mitra. Biodegradation of Chlorophenoxy Herbicides."
In: Incineration and Treatment of Hazardous Wastes: Proceedings of the
Eleventh Annual Research Symposium. EPA/600-9-85-028.
5. Kobayashi, H., and B. E. Rittman. Microbial Removal of Hazardous Organic
Compounds. Environmental Science and Technology, 16(3) 170A-181A. 1982.
6. Petrasek, A. C., et al. Fate of Toxic 'Organic Compounds in Wastewater
Treatment Plants. J. Water Pollut. Control Fed. 55, 1286-1295. 1983.
7- Saleh, F. Y., et al. Selected Organic Pesticides, Occurrence,
Transformation, and Removal from Domestic Wastewater. J. Water Pollut.
Control Fed. 52, 19-29. 1980.
8. Chatterjee, D. K., and A. M. Chakrabarty. Genetic Rearrangements of
Plasmids Specifying Total Degradation of Chlorinated Benzoic Acids. Mol.
Gen. genetics, 188, 279-285.
9. Kilbane, et al. Detoxification of 2,4,5-Trichlophenoxyaxetic Acid from
Contaminated Soil by Pseudomonas Cepacia. Applied and Environmental
Microbiology, 45. May 1983.
10. Kim, C. J., and W. J. Maier. Acclimation and Biodegradation of Chlorinated
Organic Compounds in the Presence of Alternate Substrates. J. Water
Pollut. Cont. Fed. 58, 157-163. 1986.
11. Martinson, M. M., et al. Microbial Decontamination of Pentachlorophenol in
Soils, Surface Waters, and Ground waters. Presented before the Division
of Environmental Chemistry, American Chemical Society, New York.
April 1986.
7-16
-------
12. Bumpus, J. A., et al. Biodegradation of Environmental Pollutants by the
White Rot Fungus Phanerochaete Chrysosporium. In: Incineration and
Treatment of Hazardous Waste: Proceedings of the Eleventh Annual
Research Symposium. EPA 600/9-85-028.
13. Suflita, J. M., et al. Dehalogenation: A Novel Pathway for the Anaerobic
Biodegradation of Haloaromatic Compounds. Environ. Sci. Technol. 218,
1115-1116. 1982.
14. Bouwer, E. J. , and P. C. McCarty. Removal of Trace Chlorinated Organic
Compounds by Activated Carbon and Fixed-Film Bacteria. Environ. Sci.
Technol. 16, 836-843. 1982.
15. Lewandowski, G., et al. Biodegradation of Toxic Chemicals Using
Commercial Preparations. Environmental Progress 5, 212-217. 1986.
16. ICF, Incorporated. The RCRA Risk—Cost Analysis Model Phase III Report.
Submitted to the U.S. EPA, Office of Solid Waste, Economic Analysis
Branch, March 1, 1984.
17. Ying, Wei-Chi, et al. Biological Treatment of a Landfill Leachate in
Sequencing Batch Reactors. Environmental Progress, 5, 41-50. 1986.
7-17
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SECTION 8
INCINERATION PROCESSES
Incineration is a principal alternative to land disposal for wastes
containing halogenated organics. Despite the low heat of combustion and high
thermal oxidation stability (TOS) exhibited by many of the halogenated
organics, incineration represents an established, if costly, means of
achieving effective thermal destruction. A number of incineration
technologies, including liquid injection incinerators, rotary kilns, fixed and
multiple hearth incinerators, and fluidized-bed incinerators have demonstrated
the ability to meet RCRA incineration standards for the destruction of
halogenated organic3. As noted in the solvent TRD,*• many industrial boilers
and process furnaces are also capable of achieving RCRA destruction and
removal efficiency (ORE) standards for halogenated solvents, including
chlorinated aromatics. However, pollution control equipment may be required
to meet RCRA particulate and HC1 emission standards if significant quantities
of wastes are introduced as feed.
Incineration facilities permitted to operate by EPA under RCRA are
2
required to achieve at least a three-tiered environmental standard.
1. They must achieve a destruction and removal efficiency (DRE) of
99.99 percent for each principal organic hazardous constituent
(POHC);
2. They must achieve a 99 percent HC1 scrubbing efficiency or emit less
than 4 Ib/hr of hydrogen chloride; and
3. They must not emit particulate matter in excess of 0.08 grains/dscf,
(0.18 grams/dscm) corrected to 7 percent oxygen.
Other standards which may affect the decision to incinerate halogenated
organic wastes include limitations on the generation of CO, SO , NO , and
X J%
toxic air pollutant; e.g., toxic metals. To become permitted, an incineration
8-1
-------
facility must submit to .a full scale evaluation of design and performance.
This evaluation includes a trial burn monitored by EPA, demonstrating the
ability to perform to expected levels for various wastes. Most large
incinerators are equipped with control systems to limit both particulate
matter and acid gas emissions. The latter control system is needed to remove
halogen acids such as HC1, a product of chlorinated organic compound
incineration, in cases where the chlorine content of the feed is sufficient to
exceed the 4 Ib/hr HC1 emission limitation. The need for particulate control
systems will depend in large measure on the ash content of the feed. The
emission standard of 0.18 g/dscm (63 ng/joule for a 19,000 Btu/lb fuel)* is
well below the EPA emission factors of 6 and 23 ng/joule for distillate and
4,
residual fuel oils, respectively. Thus, particulate standards appear
obtainable for many wastes, particularly when blended with conventional
fuels. Most incinerators operating in 1981 were not equipped with air
pollution control devices, probably because these facilities handled only low
ash, nonhalogenated liquid wastes for which control measures were not
necessary.
, Costs of incineration are higher than most hazardous waste management
alternatives because of the large energy input requirements and cost of
environmental controls. Costs vary widely depending upon waste
characteristics, incinerator design, and various operational considerations.
Costs of commercial incineration were found to vary from approximately
i0.10/lb to *3.00/lb.
«
8.1 OVERVIEW
8.1.1 Incineration Theory
The term incineration normally refers to the destruction of organic
wastes by combustion or thermal oxidation. The reaction sequence which takes
place in the destruction of a hazardous waste involves a complex series of
pyrolysis, free radical, and oxidation reactions. Several intermediate stages
occur before a halogenated organic waste feed is oxidized into its final
product, depending upon the chemical composition of the waste and the design
and operation of the incinerator. Extensive discussion of incinerator theory
8-2
-------
may be found in several recent publications, including the proceedings of
several conferences and symposia (References 5 through 13).
Efficient oxidation depends upon three parameters: temperature, time,
and availability of oxygen. Combustion temperature affects the rate of
reaction, and thus the time needed to achieve the desired destruction
efficiency. Residence time or dwell time is determined by the incinerator
size, combustion gas flow rate, turbulence and the rate at which waste is
processed. Availability of oxygen, or adequate contact of waste and oxygen is
achieved by turbulence and the use of excess air (addition of more air than
the stoichiometric amount needed for combustion).
Oxidation occurs when organic materials are heated in the presence of
oxygen. A second type of reaction, pyrolysis, is chemical change resulting
from heat alone (in the absence of oxygen). It normally involves the breaking
of chemical bonds and the formation of new, smaller organic molecules.
Because oxidation causes a more complete destruction of waste, most
incinerators promote this reaction, with pyrolysis occurring incidentally.
The exception occurs with pyrolytic incinerators, in which pyrolyzed products
are generated intentionally.' Usually, the products of pyrolysis are
14
subsequently oxidized to reclaim their heat content.
The typical chemical reaction scheme for incineration of hazardous wastes
containing chlorinated organics is shown below:
C^Cl, + M 02
waste mixture + stoichiometric volume
including noncombustible of oxygen
solid (M)
C02 + H20 + HC1 + M
most common reaction products
'* [C12 + CaHjjCl,. + others]
plus other species including incompletely combusted species and
noncombustible species
In practical operations, the incinerator is operated to minimize the
formation of the second group of products listed above. The formation of
organics as byproducts is considered a consequence both of inefficient
8-3
-------
operation and the contribution of organics from fuels and reformation. The
formation of Cl- gas, which is highly toxic, is very undesirable because it
is relatively difficult to remove from stack gases by conventional air
pollution control systems. In practice, almost all chlorine is emitted as UC1
as a result of auxiliary fuel addition. Auxiliary fuel is often utilized as
much for its contribution of hydrogen to suppress Cl. formation as for its
^ t
contribution to the overall heat value of the combustion mixture.
Although the kinetics of incineration are highly complex, the overall
high rate of reaction allows the general reaction scheme to be described in
terms of first order kinetics:
where CA = concentration of constituent A in the waste
k • reaction rate coefficient
t * time
The reaction rate coefficient is a function of waste and operating
characteristics, as indicated below:
k -
where A « Arrhenius coefficient (characteristic parameter)
*
E - activation energy (characteristic parameter)
R * universal gas constant
T « absolute temperature
Thus, the most significant factors impacting the destruction of wastes in
an incinerator include the temperature, time, turbulence, and concentration of
principal constituents. This observation has been supported by practical
experience, although there is no absolute level of these factors that has been
correlated with DRE or formation of products of incomplete combustion
(PICs).5
-------
8.1.2 Applicability of Incineration to Wastes Containing Halogenated Organics.
The determination of the applicability of incineration and specific
incineration technologies to the management of hazardous wastes is based upon
waste physical and chemical characteristics. The overall ability to
incinerate a specific waste is a function of the relative ease with which the
materials may be fed to the combustion system, the ignitability and
combustibility of the materials during the oxidation/pyrolysis process, the
relative hazardousness of potential combustion byproducts (dictating
post-combustion handling and control), and the general impact on the system
from their incineration. Several chemical and physical characteristics of the
wastes must be considered in determining whether incineration is technically
and/or economically feasible, what incinerator design will handle a waste most
effectively, and what form of pretreatment should be performed to enhance
performance. As a result of their halogen content, halogenated organic
hazardous wastes, in general, are considered difficult to incinerate. Apart
from system/emission problems posed by HC1 generation, halogenated organics
have lower heats of combustion and normally higher thermal oxidation stability
(TOS) values than their nonhalogenated counterparts. The following tentative
guidelines can be drawn for the TOS of halogenated organics:
1. Chlorinated aromatic3 such as chlorobenzene, PCB and
chloronaphthalene appear to have the highest TOS values of any of
the Appendix VIII constituents.
2. Halogen substitution seems to increase TOS in the following order:
F > Cl > Br.
3. Halogenation does not increase the TOS of all organic compounds.
Halogenation of straight-chain olefins, for example, may result in a
TOS decrease.
4. For aromatic compounds, TOS appears to increase with increasing,
halogen substitution.
Hazardous-wastes- to be burned in an incinerator, including halogenated
lie hazardous wastes, may be clas
<
to their incinerability, as follows:'
organic hazardous wastes, may be classified into two basic categories relative
.9
8-5
-------
I. Combustible wastes which sustain combustion without the use of
auxiliary fuels (i.e., heat content above 8500 Btu/lb); and
2. Noncombustible wastes which will not sustain combustion without the
use of auxiliary fuels.
All combustible wastes are obviously applicable to incineration, but this may
not be the best disposal option for such substances. Instead, combustible
wastes may be better handled in fuel burning devices such as industrial
boilers specially designed to burn hazardous wastes, which would make more
effective use of the recoverable heat energy from these substances. The
primary focus of this discussion will be on noncombustible wastes.
Non-combustible wastes exhibit characteristics which limit their
combustibility. Whether or not these limitations will present a technological
or economic barrier to incineration must be determined.
The primary waste characteristics which determine relative abilities of
wastes to be incinerated include the following:
• Physical form;
• Heat content/heat of combustion;
• Autoignition temperature/thermal stability;
• Moisture content.
These are discussed below in terms of their effect on the incineration process.
Physical Form—
The physical form of a waste is the primary factor in the selection of an
appropriate incineration technology. Although some technologies, such as
rotary kilns, can handle all physical forms, others such as liquid injection
incineration and fluidized-bed incineration cannot. For certain wastes,
pretreatment by filtration, size reduction, heating, or blending may be
sufficient to ensure applicability of the last two technologies.
Heat of Combustion—
The_heat of combustion of a halogenated organic is the amount of heat
energy produced when the substance is totally oxidized. Wastes with a higher
heat of combustion usually produce a higher flame temperature when burned
8-6
-------
which will, in turn, produce a higher destruction efficiency. Although the
concept of using the beat of combustion to rank relative incinerability has
been questioned, ' apparently with some validity, heats of combustion
above a minimum value are needed to stabilize flames in conventional liquid
19
burners.
Wastes with a heat content above 8,500 Btu/lb are considered fuels, and
can be burned in facilities regulated under RCRA Subpart D. These wastes can
sustain combustion in most furnaces. Between approximately 2,500 and
8,500 Btu/lb wastes may require auxiliary fuels to sustain combustion. Below
2,500 Btu/lb, wastes require auxiliary fuels and, in many cases, other forms
20
of pretreatment before incineration. A good example of low Btu content
wastes are those with high moisture contents, which sometimes require
dewatering before incineration can be conducted. High moisture and chloride
contents both limit incinerability. Heat of combustion for several
halogenated organics are listed in Table 8.1 in the order of their physical
state and chloride content. The correlation between heat of combustion and
chlorine content is pronounced.
' " <
Autoignition Temperature/Other Incineration Indicators—
Autoignition Temperature (AIT) as well as several other temperature-
based experimental parameters, have been used as indicators of relative ease
of incineration. AIT is defined as the temperature at which a waste will
first sustain combustion. In theory, the lower the AIT of a material, the
lower the required combustion temperature and, thus, the easier it will be to
incinerate.
Results of field tests at various facilities were compared with the
results predicted by heat of combustion, AIT, and several other indices of
thermal destruction. The most useful predictive procedure proved to be a gas
phase thermal stability method using an oxygen deficient pyrolytic
environment. Field stability rankings could be predicted from laboratory data
9
in 70 percent of the cases evaluated. However, additional study will be
required to fully assess means of predicting TOS.
8-7
-------
TABLE 8.1. HEAT OF COMBUSTION BASED ON PHYSICAL STATE AND CHLORINE CONTENT
00
KCRA
waste
code
Liquid
U062
U048
F02B
DO 30
P036
U097
U042
U041
P027
U024
U027
U046
PU23
U006
U025
U023
POI7
DO 34
DUO
U128
Compound name
compounds (g25*C)
Diallate
2-Chlorophenol
Benzyl chloride
l-Bromo-4-phenoxy benzene
Dichlorophenyl arsive
Dimethyl carbamoyl chloride
2-Chloroethylvinyl ether
Epichlorohydrin
3-Cliloropropionitrile
Bis(2-chloroethoxy) methane
Bia(2-chloroiaopropyl) ether
Ch lororaethoxyuethane
Chloroacet aldehyde
Methyl chloride
Bia(2-chloroethyl) ether
Benzotrlchloride
Bromoacetone
Trichloroacet aldehyde
llexachlorocyc lopendad iene
llexachlorobutadiene
Molecular
formula
C10II17C12NOS
C6HjC10
C7H?C1
C12II9B20
C6llsAaCl2
C3II6C1NO
CAII7C10
CjlljCIO
C3IIAC1H
C5H10C12°2
C6ili2Cl20
C2n5cio
c2u3cio
CjlljCl)
cAn8ci2o
U7lljCl3
CjlljBe
CjllCljO
c5ci6
C«C16
Molecular
weight
270.2
128.6
126.6
• 249
222.9
107.6
106.6
92. 5
89. 5
173.1
171.1
80. 5
78. 5
98.9
143
195.5
137
147.4
272.8
260.8
Halogen
content
(X by weight)
13 Cl
28 Cl
28 Cl
32 Br
32 Cl
33 Cl
33 Cl
38 Cl
40 Cl
41 Cl
42 Cl
44 Cl
45 Cl
45 C
50 Cl
54 Cl
58 Br
72 Cl
78 Cl
82 Cl
Heat of
combustion
(Btu/lb)
10,120
12,400
11,120
10,510
4,160
9,140
9,340 '
9,340
8,100
8,300
8,870
6,260
5,260
4,990
6,080
7,020
4,790
1,440
3,780
3,820
(continued)
-------
TABLE 8.1 (continued)
oo
RCRA
waste
code
U066
U184
Solid
P026
U047
U035
U039
P057
U158
P024
U192
U237
U073
D014.,
U247
U016,
P035
1)017,
U233
U232
U060
U082
Compound name
l,2-Dibromo-3-chloropropane
Pentachloroethane
Compounds (g25"C)
o-(l-chlorophenyl) thiourea
2-Chloronaphthalene
Chlorambucll
p-chloro-m-cresol
Fluoroacet amide
4.4'-Hethylene-bis-2-chloroaniline
p-chloroaniline
Pronamlde
Uracil mustard
3,3'-dichlorobenxidine
Hethoxychlor
2,4-D
2.4,5-TP
2.4.5-T
DDD
2,6-Dichloroplienol
Molecular
formula
C3H5Br2Cl
C21IC15
C;II7C1H2
Cio»7C»
C,4Hj9Cl2N02
C?H7C10
C2HAFNO
C13II12C12H
C6H6C1M
C12IIUC12NO
C8IIUC12N302
C12"lOCl2N2
C16H15C13°2
caii6ci2o3
C9H7C1303
C8n6ci3o3
Cl4»10Cl4
C6U4C120
Molecular
weight
236.4
202.3
187
162.6
304.2
142.6
77
267.2
127.6
256.1
252.1
253.1
345.7
221
269.5
255.5
320.1
163
Halogen
content
(Z by weight)
68 Br
83 total
15 Cl
88 Ci
19 Cl
22 Cl
23 Cl
25 Cl
25 F
27 Cl
28 Cl
28 Cl
28 Cl
28 Cl
31 Cl
32 Cl
40 Cl
42 Cl
44 Cl
44 Cl
Heat of
combustion
(Btu/lb)
2,660
954
9,540
—
10,670
9,140
5,830
8,710
11,052
10,300
7,200
10,300
10,060
6,520
10,040
5,160
9,250
6,860
(continued)
-------
TABLE 8.1 (continued)
00
I
RCRA
waste
code
U081
U061
U132
P050
U231
U230
P037
D012,
P051
P004
U185
U212
U207
P059
P090,
U242
U036
0015,
P123,
U224
U183
U142
U127
Compound name
2 ,4-Dichlorophenol
DDT
Hexachlorophene
Endoaulfan
2,4,6-Trichlorophenol
2,4, 5-Tr Ichlorophenol
Dieldrin
Endrin
Aldrln
Pentachloronltrobenzene
2,3,4,5-Tetrachlorophenol
1 ,2 ,4 , 5-Tetrachlorobenrene
lleptachlor
Pentachlorophenol
Chlordane
Toxaphene
Pentachlorobenzene
Kepone
llexachlorobenzene
Molecular
formula
C6n4ci2o
C14H9C15
C13H6C16°2
C9II6C1603S
C6H3C130
C6lljCljO
C12H8C160
C|2II8C160
cl2H8ci6
C6C15N02
C6II2C140
C6II2CIA
cloii5ci7
C6IIC1S0
C10"6C18
C!0"l0c^8
c6nci5
C10C110°
C6«»6
Molecular
weight
163
354.5
406.9
. 406.9
197.5
197.5
380.9
380.9
365
295.4
231.9
215.9
373.4
266.4
409.8
413.8
250.3
490.7
284.8
Halogen
content
(X by weight)
44 Cl
50 Cl
52 Cl
52 Cl
54 Cl
54 Cl
56 Cl
56 Cl
58 Cl
60 Cl
61 Cl
66 Cl
67 Cl
67 Cl
69 Cl
69 Cl
71 Cl
72 Cl
75 Cl
Heat of
combust ion
(Btu/lb)
6,860
8,120
6,880
4,190
5,180
5,180
6,230
6,210
6,750
2,920
4,010
4,700
5.330
3,760
4,880
4,500
3,690
3,870
3,220
-------
Moisture Content—
Moisture reduces the incinerability of a waste. In the combustion
process, water will absorb heat energy and vaporize, but will not oxidize or
pyrolyze. This will tend to reduce the heat energy available to assist
combustion. Water may also absorb combustion intermediates and waste
components and thus limit their availability for combustion.
The requirement to drive off moisture increases the overall stress on
incineration systems and their operating costs. Certain incinerator designs,
including fixed hearth furnaces and rotary kilns, are not equipped to handle
high moisture content wastes. Moisture content may be reduced by dewatering
pretreatments, but these tend to be expensive. The most common way of dealing
with high moisture content wastes is to blend them with solid wastes or other
high heat content materials.
Ash Content (Solids/Metals/Thermally Inert Materials Content)—
Ash content is a major factor in determining the type of incinerator, air
pollution control equipment, and ash recovery system required, and is often
directly used in incineration pricing structures. Rotary kiln and hearth type
incinerators are, in general, more applicable to wastes with higher ash
content, while liquid injection and fluidized-bed incinerators are less
applicable. Fluidized-bed incinerators have a particular limitation to wastes
containing sodium salts which tend to fuse within the bed, leading to process
21
failure. The costs of incinerating wastes with higher ash content are
higher primarily due to increased air pollution control and ash recovery
costs. Many incineration facilities appear to use ash content as a factor in
determining the price of incinerating wastes. One facility contacted, for
example, indicated that they charged an extra 1 cent per pound per each
22
percent of ash content.
It is conceivable that blends of halogenated organic containing wastes
with fuel oils may meet RCRA particulate emission standards without the need
for particulate. control devices. As noted previously, the RCRA particulate
emission standard for incinerators, 0.18 g/dscm, represents an emission level
that is above the EPA AP-42 emission factor levels for distillate and residual
fuel oils. If a hazardous waste fuel blend with a heating value not
noticeably different from fuel oils, is burned, the RCRA particulate emission
8-11
-------
factor will be of the order of 50 ng/J (versus 6 and 37 ng/J for the
distillate and residual fuel oils, respectively). The ash content
corresponding to the 0.18 g/dscm RCRA standard assuming a similar blend and
stoichiometric emission of ash as particulate is 0.28 percent at 7 percent
oxygen.
Chloride Content--
The chloride content of a waste is directly related to the formation and
emission of HC1. -The RCRA emission standard for HC1 of 4 Ib/hr will be
exceeded by most incinerators burning wastes containing more than nominal
levels of chlorine. For example, the emission standard will be exceeded by a
3.8 x 10 Btu/lb input unit burning a 19,000 Btu/lb waste with a chlorine
content of 2 percent. Thus, most incinerators burning, chlorinated organic
wastes will require a high level of blending or installation of acid gas
scrubbers to meet RCRA standards.
The chloride concentration is also related to the overall corrosivity of
combustion byproducts. As a result, most incinerators establish a limiting
chloride concentration for their systems. It is common for this limit to fall
under 3 percent by weight. Most incinerators also appear to have established
surcharges for chloride content. One facility stated that an additional
charge of 0.2 cents per pound per each 1 percent of chloride was common
22
practice in the industry.
Viscosity—-
Liquid injection incinerators require wastes feedstocks which are
pumpable and atomizable. Common limits for pumping and low pressure atomizing
of fuel oils are 10,000 ssu or less and 100 ssu or less, respectively. These
same limits can be applied to waste incineration and are commonly met by
heating of the waste, blending with fuel oil, or both.
Viscosity limits also affect the compatibility of wastes with other
incinerator types. Fluidized-bed incinerators also require that liquid wastes
be pumpable in order to achieve effective dispersion in the bed. Conversely,
low viscosity wastes may pass through the heating zone of a multiple hearth
incinerator too rapidly for effective destruction.
8-12
-------
8.1.3 Strategy for Assessment of Incinerability
Incineration is a potential option for the disposal of halogenated
organic-containing wastes. An approach to assessing incineration as an option
and identifying the best incineration technology for the specific waste of
concern is provided in Reference 20. It involves the following steps:
1. Determine whether the waste can be physically introduced to the
combustion zone as is, or if pretreatment is required. This
determination is based upon physical form and viscosity. For
example, if the waste is a liquid with low viscosity, it can be
atomized and, thus, may best be incinerated in a liquid injection
system.
2. Determine the overall physical effect of the waste on the
incineration system. This consideration is primarily based upon the
physical form, solids content., and corrosivity of a waste. These
factors may be such that the incineration of the waste will rapidly
lead to process failures due to debilitation of equipment.
Refractory linings, for example, are highly susceptible to chipping
and cracking by large solid particles.
3. Determine if auxiliary fuel should be used. This determination is
commonly made solely on the basis of the heat of combustion. For
example, wastes with a heat of combustion below 2,500 Btu/lb are
almost always mixed with a fuel or blended'with a high Btu waste.
4. Determine the temperature and residence time requirement for
effective combustion. This determination is largely based on
characteristics such as moisture content. Many incinerator designs
operate with a specified residence time or temperature range.
5. Determine the disposal or handling method required for combustion
byproducts other than gaseous products. This consideration is
largely based upon the solid/metal/thermally inert material
concentration of the waste. Wastes with a high ash concentration,
for example, may require a continuous ash removal system.
6. Determine if air pollution controls are required. This
consideration is largely based upon the chloride and ash content of
a waste. Most wastes containing more than a very small amount of
chloride will require a scrubber to remove acid gases. Need can be
calculated assuming emissions are directly related to input.
7. Determine if relevant environmental standards can be met. This
determination, again, is based upon chloride and/or ash
concentration. Most incinerators operate with a chloride
8-13
-------
concentration limit. If Che chloride content is too high, the air
pollution control system will not be adequate to limit emissions to
the applicable standard.
8. Determine the relative costs of the various incinerator options. It
is important to note that the technology "with the lowest base cost
may not be the most cost-effective alternative, should one of the
factors listed above come significantly into play.
Although incineration is a potential option for disposal of halogenated
organics, the wide spectrum of properties found in these compounds of concern
require that each waste stream be carefully characterized and appraised.
Generally, many of the aromatic, highly halogenated compounds are not ideal
candidates for incineration for the following reasons:
• Many are solid compounds which would require special handling or
blending if they are to be used in liquid injection incinerators;
• The high chloride content will limit commercial facility
availability and normally require air pollution control systems;
• Heating values will be low and thermal oxidation stabilities will be
high, generally increasing the difficulty of combustion and the
formation of products of incomplete (PIC) combustion; and.
• High levels of blending will almost' invariably be required to ensure*
destruction and protect equipment, thus increasing the size of the
facility and its cost.
Factors which favor incineration as an option include the resistance of these
halogenated compounds to destruction by other options, including biological
treatment.
8.2 PROCESS DESCRIPTION
There are numerous incineration system designs available to handle the
wide variation of chemical and physical characteristics found in hazardous
wastes. Hazardous waste incineration technologies range from those with
widespread commercial application and many years of proven effective
performance, to those currently in development. As many as 67 companies may
8-14
-------
23
be involved in the design and development of hazardous waste incinerators,
with more expected as limitations on land disposal of hazardous wastes
increase. Several incineration technologies have been demonstrated to be
effective for a wide range of hazardous wastes. They comprise about
80 percent (by number) of the U.S. market. a> They include:
• Liquid injection incinerators
• Rotary kilns
• Fluidized-bed incinerators
• Fixed hearth incinerators, particularly the starved air or pyrolysis
type units, and
• Multiple hearth incinerators.
The first two (and the fixed hearth units) are the most widely used for
the disposal of hazardous wastes. A description of the first three types of
units listed above will be provided here, following a brief discussion of
basic components common to all incinerators. The hearth type incinerators,
particularly the fixed hearth unit, are also used extensively, but data on
their ability to handle hazardous wastes have hot been widely published in the
literature. Discussions of the design and operation of these systems can be
found in the literature.
8.2.1 Basic Components of Incineration Systems
All incineration systems are designed in consideration of the four basic
elements of combustion: temperature, time, turbulence, and concentration.
" 24
Temperature is the most important element of an incineration system. The
heat requirements govern the method by which heat energy is supplied and
sustained within the combustion chamber, and governs many of the pretreatment
operations conducted. Residence time requirements impact the size of the
combustion chamber, as the volume of the combustion zone must be sufficient to
allow for completion of thermal destruction. Turbulence is strictly a
function of incinerator design. Elements such as baffles, rotation, or
changes in direction within the combustion chamber increase turbulence (and,
8-15
-------
therefore, enhance mixing of wastes and oxygen to allow for more effective
performance). Concentration governs the oxygen input requirement, as
sufficient air must be supplied to insure complete combustion of hazardous
constituents.
There are essentially five component parts common to any incineration
facility, as shown in Figure 8.1 and discussed below.
1. Material Storage and Preparation—Waste materials are received,
analyzed, stored and prepared for input into the incinerator. In
this initial step of the incineration process, the waste
characteristics which may affect the performance of the incinerator
are identified. If necessary, pretreatment operations are conducted
to mitigate these characteristics. In some cases, wastes are
rejected for incineration when pretreatment will not render them
"incinerable".
Common methods of pretreatment include preheating, chemical
neutralization, filtration/sedimentation of suspended solids and
water, and distillation.
2. Waste Feed Mechanism—The waste feed mechanism is the means by which
waste materials are input into the combustion chamber of an
incinerator. Feed mechanisms also control the volume of waste
present in the chamber at any moment, and thus control waste
residence time. Feed mechanisms also play a key role in creating
surface area, to increase combustion rate, and .in developing
turbulence within the combustion system. Dispersion of wastes is
particularly critical in liquid injection and fluidized-bed
inc inera tors.
3. Combustion System—Combustion systems perform three functions:
1) heating of waste materials to vaporize and pyrolyze them;
2) mixing of wastes with combustion air; and 3) oxidation and
subsequent formation and separation of combustion products.
Heat Recovery—Heat recovery systems are often employed with
incineration of hazardous wastes in order to achieve greater cost
effectiveness. Generally, heat recovery is accomplished by either
standard heat exchange equipment or waste heat boilers which burn
the waste byproducts. There are generally two limitations in heat
recovery. First, the cost benefits of heat recovery must justify
the expense of the heat recovery system, including design,
installation, and maintenance. Second, heat recovery systems should
not be used if they lead to a more difficult waste management
problem; i.e., form new pollutants of concern, or require difficult
maintenance such as cleanup of waste byproducts plugging the heat
recovery system.
8-16
-------
TANK FOR TANK f Oft TANK FOn DIENOINa FUEL Oft.
V.ATEO WAI6R- SPECIAL TAJIK TANK
SOtLUlE IHSOCUOIE BATCHES
HOUlOS LIQUIDS
00
STACK
fon soto VVASIES ron PAS rv wsv
AFHSUQ
BtOnAOI
FEED
INCUKHAIIOK
HEAT RECOVEHV
OFF-OA3 CIEANIMJ.
NEUIRAllt>IIOM
Figure 8.1. Flow sheet of an incineration plant for hazardous wastes.
Source: Babcock Krauas-Maffei Induatrieanlagen GMBH
(Revised by P.Adie),25. i
-------
5. Solid and Liquid Waste Control—Air pollution control devices are
required if the combustion process produces air pollutants at levels
exceeding applicable emission? standards. Most commonly, the
primary pollutants of concern generated by incineration of hazardous
wastes are partial late matter and hydrochloric acid (HC1) vapor.
Air pollution control is often, but not always, used at hazardous
waste incinerators. Incineration processes produce solid and liquid
waste streams which must be managed. These streams are usually not
hazardous themselves. Ash produced in combustion is collected
either continuously (e.g., a screw conveyor built into the bottom of
the combustion system), or periodically by manually cleaning the
combustion chamber. Sludges can be produced by air pollution
control or heat recovery systems, and are removed periodically from
the process systems. Liquid wastes are produced by air pollution
control or heat recovery systems, and are removed periodically from
the process systems. Liquid wastes produced by air pollution
scrubbers or quench towers are continuously treated. In most cases,
ash may be disposed of in a landfill, as may dried sludges. Liquid
wastes may be subject to wastewater treatments before discharge.
8.2.2 Liquid Injection Incinerators
Liquid Injection (LI) incinerators are the most widely used hazardous
waste incineration systems in the United States, accounting for 64 percent of
23
the total number of waste incinerators currently in use. LI systems may
be used to incinerate virtually any liquid hazardous waste, due to their very
basic design and high temperature and residence time capabilities. Liquid
injection incinerators generally represent the most effective system available
for hazardous wastes that can be processed to produce a pumpable and
atomizable feedstock, from both a technical (i.e., destruction efficiency)
and economic perspective..
Liquid injection incinerator systems typically employ a basic, fixed
hearth combustion chamber. Pretreatment systems to blend wastes and fuels, to
remove solids and free water, and to lower viscosity through heating, are
often used in conjunction with liquid injection incinerators. Ash recovery
systems may not be required, at least on a continuous basis, because many
liquid hazardous wastes fired in an LI system contain low volumes of ash or
Q
suspended solids.
8-18
-------
The liquid waste feed system is the key element of the LI process.
Liquid injection incinerators operate as "suspension burners", whose
combustion efficiency (and hence destruction efficiency for constituents of
hazardous wastes) is dependent upon the extent to which the feed mechanism can
disperse the liquid waste within the combustion chamber and provide sufficient
area for contacting waste with combustion air. There are two atomizer designs
commonly employed in LI systems, denoted as fluid systems and mechanical
systems. Typical characteristics of several atomizer designs are described in
detail in Reference 26.
Once liquid wastes enter into the liquid injection incinerator and are
ignited at the burner, efficient combustion is achieved by proper mixing of
combustion air and waste to create a turbulent flow of waste throughout the
combustion chamber. Combustion temperature capabilities of the systems can be
very high, reaching over 3000°F in many cases. Table 8.2 summarizes operating
parameters for typical hazardous waste liquid injection systems.
Applicability of hazardous wastes to liquid injection incinerators is
generally limited by the extent to which they may be atomized, and the
physical effect they may have on the incinerator equipment (most notably, on
the atomizer). The primary restrictive waste characteristics of interest are
the liquid viscosity, solids content, and .corrosivity. Wastes with low heat
value may also be restricted from burning in a liquid injection incinerator.
In some cases, the applicability of an LI incinerator may be extended by
the use of multiple injection systems. In this way, an injector may be fitted
to more specific ranges in waste characteristics allowing a broader range of
overall usage without requiring pretreatment. As discussed earlier, certain
atomization device designs are better suited to more viscous or high suspended
solids containing wastes than others. In addition, the use of multiple
injection points may allow for coincineration of incompatible wastes.
8.2.3 Rotary Kiln Incinerators
Rotary kiln (RK) incinerators have found widespread application in the
U.S. for management of hazardous wastes, both at chemical manufacturing and at
hazardous waste facilities. MITRE estimated that rotary kilns comprised
12.3 percent of the total number of hazardous waste incinerators in
8-19
-------
TABLE 8.2. OPERATING PARAMETERS OF HAZARDOUS WASTE LIQUID INJECTION
INCINERATORS
Form of Waste Feed: Liquid wastes only
Limiting liquid viscosity for atomization is
typically 16,000 centistokes
Limiting solids content may be as high as 10% by
weight undissolved solids
Limiting solid particle size may be as high as
1/8 inch diameter
5 - 150 x 106 Btu/hr
25,000 Btu/hr.ft3 (typical)
1,000,000 Btu/hr.ft3 (maximum)
Operating Temperature Range: 1200 - 3000°F
Residence Time Range: 0.5-2.0 sees
Excess Air: 20Z (typical)
For nitrogen-containing wastes, excess air
requirements may be 65-95%
Heat Input Capacity Range:
Heat Release:
Pressure:
0.5 - 4 in H20 (typical)
Source: MITRE, 1982 (Reference 23).
8-20
-------
operation. Rotary kiln systems are considered the most versatile of the
established incinerator technologies. Liquid, solid, and slurried hazardous
wastes may all be burned in .rotary kilns, without extensive adaptation of the
design for specific waste types.
Rotary kiln systems employ a fairly basic design concept. As depicted in
Figure 8.2, the typical rotary kiln system involves two-stage combustion of
waste materials with primary combustion occurring in the rotary kiln followed
by secondary combustion of gaseous byproducts. Heat recovery, ash recovery,
and air pollution control devices are usually included in the overall system.
Combustion byproducts are most often scrubbed for both particulate matter and
acidic byproducts; e.g., HC1. Heat recovery is employed in the majority
23
(—70 percent, according to recent estimates) of cases.
Pretreatment of hazardous wastes is not often required for incineration
in a rotary kiln, because of the great versatility of the system. The most
common preparatory operations conducted at rotary kiln incinerators include
size reduction, mixing of liquid wastes with solid wastes, and chemical
neutralization. Wastes with an average heating value of 4,500 Btu/lb are
reported adequate to sustain combustion at kiln temperatures between 1600 and
1800°F. In those cases where auxiliary fuel is required, No. 2 fuel oil is
used most often. Size"reduction of solid wastes, via crushing and grinding
operations, is a common preparatory operation. This is often done both to
preserve the life span of the kiln refractory lining and to increase the
combustion efficiency of the system. Mixing of liquid wastes with solid
wastes helps to increase the liquid waste residence time and thus enhance
destruction efficiency. Highly corrosive wastes are often neutralized by
chemical treatment before being fed to the rotary kiln. This helps preserve
23
the working life of the kiln refractory.
Waste materials, following pretreatment, are fed to the elevated end of
the rotary kiln* Waste feed mechanisms employed are typically simple hoppers
which feed a regulated amount of material to the kiln. Waste materials flow
through the rotary kiln as a consequence of the rotation and the angle of
inclination. The kiln is often designed with baffles, which serve to regulate
the flow rate through the unit, generally resulting in increased residence
times. The rotation of the kiln serves to enhance the mixing of waste with
combustion air and provides continuously renewed contact between waste
8-21
-------
00
ON1INC.
CM
MONI ions
CONVCYOR
flBIR PACKS
IPAMflllOOJ
SAMPIINC (MAIN
ASH RESIDUE
SAMPLE
7
IWOBAHOllMf
SLURRY rilO
SCRUIItN
UOUIO SAMPLE
DRATI f ANS
SIACK
DISCIIARCf
SCRUBBLR WAIIR
Figure 8.2. Rotary kiln incinerator with liquid injection capability.
-------
material and the hot walls of the kiln. Combustion air is fed either
concurrently or countercurrently. One .feature of a rotary kiln is that it may
be operated under substoichiometric (oxygen deficient) conditions to pyrolyze
certain wastes.
As combustion of the waste progresses, ash flows to the bottom of the
unit and is conveyed to the ash recovery system. Gaseous combustion products
are exhausted to the secondary combustion unit.
Secondary combustion generally takes place in a fixed hearth type unit,
where gaseous products of combustion, including completely combusted waste
components, combustible waste products, and fly ash are fired. The gaseous
products from the secondary combustion chamber are normally then passed
through heat recovery and air pollution control systems, while ash is
collected and transported to the ash recovery facility.
Most rotary kiln systems are equipped with a multistage scrubber system
to control particulate matter and acid byproducts of combustion. Heat
recovery systems are often used not only for the conservation of energy, but
also to reduce temperatures to allowable levels prior to introduction to the
scrubbers. Typical operating parameters for a rotary kiln system are shown in
Table 8.3. . .
Rotary kilns are generally large systems, and thus require a large
capital expenditure. Due to their energy requirements, the operating costs
associated with rotary kiln systems may also be higher than other incinerator
systems. Their versatility may lead, however, to benefits measurable in
overall reduced costs for hazardous waste management; cost, considerations are
further discussed later in this section.
8.2.4 Fluidised-Bed Incinerators
Fluidized-bed (FB) incineration systems represent a new incineration
technology which has not yet made a significant commercial impact in the
established incinerator market. Although fluidized-bed processing units were
developed nearly 50 years ago and have found extensive application both in
chemical processing and, more recently, in sewage sludge incineration, the
development of FB systems capable of destroying wastes containing hazardous
components is still in its early stages. As indicated in MITRE's 1982
8-23
-------
TABLE 8.3. OPERATING PARAMETERS FOR ROTARY KILNS
Form of Wastes Fed
Thermal Capacity
Typical Overall System Flowrate
gas flow
pressure drop
solid feed rate
liquid feed rate
Combustion Temperature
1st chamber (Rotary Kiln)
secondary chamber
Residence Time
gases
solids
Rotational Speed
Leng th-to-r Diameter
Excess Air
Refractory Life
Liquid, solid, slurry. Virtually any
waste may be fired to a Rotary Kiln.
1 - 150 x 106 Btu/hr (Rotary Kiln)
20,000 Btu/hr (secondary combuster)
47,000 acfm @ 2200°F
10 - 25 in H20
10,000 Ibs/hr
3,000 Ibs/hr
500 - 2300°F
1600 - 2800°F
0.5 - 3.0 sees -
Highly variable, depending on
viscosity, angle of inclination,
rotation of kiln
12 revolutions/hr (typical)
2:10 (typical)
60 - 150%
24 - 30 months
Source: MITRE, 1981 (Reference 23).
8-24
-------
23
survey, only nine fluidized-bed units, representing 2.6 percent of the
total number of hazardous waste aystems-in operation, had been put into actual
service at hazardous waste processing facilities. The basic fluidized-bed
system is depicted in Figure 8.3. Fluidized-beds are always oriented
vertically. Feed and air flow are balanced to achieve fluidization in the
bed. The fluidized-bed promotes turbulence and serves as an excellent heat
transfer medium, thus assisting combustion. As will be discussed later, the
fluidized-bed material can be chosen to react directly with combustion
production such as HC1, thus minimizing subsequent air pollution control
requirements.
Operating parameters for fluidized-bed incineration are shown in
Table 8.4. Operating temperatures are lower than those found in other types
of incinerators. However, the long residence times and the excellent
distribution of thermal energy within the bed are sufficient to provide
excellent destruction efficiency of organic solvents.
The usage of a fluidized-bed incinerator may be limited by certain
chemical characteristics of a hazardous waste. In general these restrictive
waste characteristics are those properties which may affect the fluidity of
the bed itself. The key to the effectiveness of an FB incinerator is the
ability of the bed to display certain liquid-like physical properties. Those
wastes with characteristics which lead to either an increase or decrease in
bed particle mobility are not suitable for FB incineration. The primary waste
characteristics identified as potentially restrictive include sodium content,
corrosivity, moisture content, and fusible ash content.
Sodium content has been identified as the most significant property of
concern, in determining the applicability of fluidized-bed incinerators to the
treatment of a facility's hazardous wastes. Certain sodium salts, most
notably sulfates and nitrates, may form eutectic complexes with other
inorganic salts present in the bed which serve to bind bed particles together
27
and thus destroy the fluidity of the bed.
8-25
-------
TABLE 8.4. OPERATING PARAMETERS OF FUJIDIZED BED INCINERATORS
Feed Materials
Capacity
Operating Temperature
Residence Time
gaseous
solids
Pressure Drop
Excess 02
Air Flow Rate
Typical Bed Thickness
Preheat Requirements
Air Pollution Control
S tartup and Shutdown
Bed Particle Size
Granular solids, sludges, slurries are best; can
handle liquids, bulk solids as well
2 - 200 x 106 Btu/hr heat input
1600 - 1850°F in combustion zone
5-10 sees.
no limit
90% of height of fluidized bed (in H20)
30 - 50%
2.5 - 8.0 ft/sec
6 - 8 ft
4000 Btu/lb H20 for cold windbox
Acid scrubber
Partial late scrubber
Quench tower
Rapid startups and shutdowns possible; continuous
feed not necessary
20 - 80 mesh inert
Source: Reference 23.
8-26
-------
*»• EXHAUST AND ASH
SAND FEED
THERMOCOUPLE
WASTE INLET
FLUIOIZING
AIR INLET
:•••:• x-x SAND BED :•:•:
PRESSURE TAP
SIGHT GLASS
BURNER
TUYERES
STARTUP
PREHEAT
BURNER
FOR HOT
WINOBOX
Figure 8.3. Cross-section of a fluidized-bed furnace.
Source: Reference 25.
8-27
-------
Highly corrosive wastes pose a different threat to the integrity of the
fluidized-bed. The fluidity of the fluidized-bed is dependent upon
maintenance of a certain bed particle density and size distribution. Thus,
reactions which alter these properties are detrimental to the effective
operation of the bed. Corrosion of the bed may therefore lead to a loss of
fluidization and result in significantly lower destruction efficiencies than
are typically achieved by this type of incineration system.
Wastes with very high moisture content may reduce the overall
effectiveness of the fluidized-bed system. Wastes containing more than
75 percent moisture, by weight, may require temperatures or residence times
23
which are not practical for an FB system. Fretreatment of wastes to
reduce high moisture content is highly recommended for fluidized-bed
incineration. Numerous standard dewatering techniques may be employed,
including fractionation, filtration, and settling.
The consequences of a high concentration of fusible solid byproducts of
waste combustion are very much the same for fluidized-bed incineration as
those associated with the formation of inorganic salt eutectic mixtures
described earlier. These materials may impair the fluidity of the bed by
binding the granular solids into large, nonfluid solids.
- • - •
8.3 PERFORMANCE OF HAZARDOUS WASTE INCINERATORS IN THE DESTRUCTION OF
HALOGENATED ORGANIC WASTES
Most of the available incinerator performance data detail the destruction
of low molecular weight halogenated organic wastes, which generally may be
categorized as solvent wastes, these studies are discussed in detail in
Reference 1, as well as in many sources available in the open literature.
More recently, however, there has been some study of the. applicability and
performance of incineration technologies to the full range of halogenated
organic wastes.
The relative scarcity of data for nonsolvent halogenated waste is not
./•
surprising since this waste category accounts for less than 10 percent of the
total (solvent and nonsolvent) halogenated organic waste generated in the
United States. Available nonsolvent balogenated organic waste incineration
data may be classified in two areas: pesticide waste; and highly chlorinated
8-28
-------
halogens of high thermal stability; e.g., halogenated aromatic compounds such
as hexachlorobenzene. Much of the data-were generated during studies of the
destruction of PCBs in incinerators. Although PCB wastes are not considered
in this document as part of the nonsolvent halogenated organic waste category,
their destruction characteristics in incinerators may be quite comparable to
those wastes that do fall into this category. In addition, studies of PCB
destruction have often tested compounds such as hexachlorobenzene as "PCB
surrogates". The incinerability of certain halogenated organic wastes has
also been subject to study because of their appearance in certain common
industrial wastes streams. As a class they are regarded as thermally stable,
28
and they are suspected of being high temperature precursors of PICs.
Waste destruction efficiencies for a variety of halogenated pesticides,
PCBs, and nonsolvent halogenated organics, determined in several full scale
and pilot scale programs, were summarized in Reference 14. The data, shown in
Table 8.5, demonstrate that 99.99 percent DREs can be achieved for all wastes
in several types of incinerators.
Pesticide destruction levels, shown in Table 8.5, are relatively high,
even for highly chlorinated compounds such as tbxaphene and kepone. The data
are similar'to an extensive tabulation of destruction efficiencies measured
for several chlorinated pesticides incinerated in a variety of pilot and
40
commercial scale incinerators. Halogenated organic pesticides identified
in Reference 40 include aldrin; chlordane; dieldrin;. 2,4-0; 2,4,5-T; herbicide
orange, kepone, and toxaphene. These pesticides exhibited DREs in excess of
99.99 percent in all but 3 of 80 test data points reported as a result of
several EPA, Canadian Government and industry-sponsored programs.
EPA's Combustion Research Facility (CRF) at Pine Bluff, Arkansas has been
involved in studies of the destruction of hexachlorobenzene (HCB) and
2
1,2,4-trichlorobenzene (1,2,4-TCB) in a 1.8 x 10 Btu/hr rotary kiln using
propane as a primary fuel. These two compounds were tested because they were
recognized as thermally stable compounds suspected as being precursors of
PICs. The CRF facility consistently produced ORE values above 99.99 percent
8-29
-------
TABLE 8.5. WASTE DESTRUCTION EFFICIENCIES ACHIEVABLE BY INCINERATION
I
1
1
Waate 'type
Phenoxy herbicide
Kepone
' Kepone , iewdge sludge
!
PCBs 11. 11 in fuel oil)
DDT (201 enuUion in fuel oil)
00 PCBi (375 g/1 of Aroclor 1242
( in oil)
u>
o
1 PCBs (SO fpm in sewage sludge)
Vinyl chloride
Polyvinyl chloride
e Polyvinyl chloride, vinyl
chloride •onomer
• Sludge (12% water)
• Liquid; crystalline, paniculate
PCB capacitors (haomeral 1 led)
i a PCBs, paper and plastics, ash
' • Solid waste
Incinerator type
Cstalytic
Liquid injection
(pilot acale)
Rotary kiln
(pilot scale)
Not specified
Mot specified
Rotary cement kiln
Multiple hearth
Laboratory test
equipment:
vapor phaae
Rotary kiln
Rotary kiln
Major operating parameters
Residence time
Temperature (*C) (sec)
480 Not stated
1090 ' 2
*
Kiln: 500
Afterburner:
1090 2
3
870 to 980 3
Not specified Not specified
Maximum: 790 : O.I
Gas exit temp.:
615
760 O.S
Kiln: 870 2 to 3
Afterburner:
980 to 1090
1310 to 1330 '2)
Kiln: 1250 3.2
Afterburner:
1330
Waste destruction
efficiency (X)
"complete
.destruction"
99.99991
99.9999
99.992 to 99.995
> 99. 9999
99.99998
91.7 to 97.1
99.9
^99.996
99.999 '
99.999
Reference and comment a
Paul ion (Reference 32). Detection
Unit used to measure "complete
destruction" was not specified.
Csrnes (Reference 33). This test was
conducted with the afterburner portion
only of the rotary kiln system below.
Carnea (Reference 33).
Elliot (Reference 34).
Elliot (Reference 34).
Ackerman (Reference 35). Citing work
done by the Swedish Hater Air
Pollution Research Institute. i
Ackerman (Reference 35).
Lee (Reference 36). Idealized
incinerator (plug flow, isothermal).
TRU (Reference 37), pp. 5, 22, 23.
TKH ( Reference "17 ) i»n 5 22 23
TRU (Reference 37), pp. 5, 22, 23.
(continued)
-------
TABLE 8.5 (continued)
'
Waate type
25X DOT (Emulaiflable
concentrate)
10X OUT duat
MX Aldrin (enuleif lable
concentrate)
19Z Aldrin (granular)
00
I
U> 601 Toxaphene (esnilalf table
*~* concentrate)
20X Toxaphdiie dust
llexachlorocyctopentadlene waate
• Mixture of chlorinated toluenea
a Pentanea and benzenea liquid;
suspended partlculate
"Based on the respective pesticide
b
Major operating paraaetera
Residence time
Incinerator type Temperature CO (sec)
Pilot scale, type 1000 2
not clearly apeclfied • .
Pilot acale, type 1000 2
not clearly apeclfied
Pilot acale, type 1000 2
not clearly specified
Pilot acale, type 1000 2
not clearly specified
Pilot scale, type • 1000 2
not clearly apeclfied
Pilot acale, type 1000 2
not clearly specified
Liquid Injection 1350 to 1380 0.17 to 0.18
plus all related apecies in the Incinerator off gas.
• ii^i i» i i
Waste destruction
efficiency (X)
99.992"
(vapor only)
99.995"
(vapor only)
99.992"
(vapor only)
99.999"
(vapor only)
99.995"
(vapor only)
99.995"
(vapor only)
> 99. 999
Reference and conwents
MRl (Reference 38), pp. 3, 4 (source
for next 5 entries). Range: 99.97 to
99.998Z (includes residue). b
Range: 99.99 to 99.997X (includes
residue).0
Range: 99.995 to 99.9995Z (Includes
residue). b
Range: 99.996 to 99.9998X (includes
residue). b
Range: 99.995 to 99.992Z (Includes.
residue). b
Range: 99.995 to 99.997X (includes
residue).6
TRW (Reference 39), pp. 5, 22, 23.
.
ta cover a range o operating
-------
for refractory FOHCs (HCB and 1,2,4-TCB). ' ORE values were higher for
1,2,4-TCB Chan for HCB under comparable.residence time/temperature
conditions. A large number of PICs, including the two POHCs, were identified
in the flue gas; under some conditions POHC output from the afterburner was
28
greater than the POHC input.
As noted in Reference 1, all halogenated solvents of concern, including
the halogenated organics chlorobenzene and the dichlorobenzene have been
effectively destroyed by incineration processes. A summary of recent
EPA-sponsored field tests of commercial and industrial incinerators is
provided in Table 8.6. Although most of the halogenated organics identified
in the table could be considered as solvents, the ORE for all halogenated
organics present at levels above 1000 ppm in the waste feed exceeded
99.99 percent. However, candidate POHCs present at levels less than 500 ppm
did not always meet the 99.99 percent DRE standard. This concentration effect
is under study by the EPA.
DRE values for specific halogenated organics were also obtained during
these field tests, as shown in Table 8.7. Achievement of 99.99 percent DRE
was not always realized at the conditions of test. An extensive discussion of
the results of the test data are provided in Reference 29 and summarized in
Reference 1. As noted, the data show that:
"1. Extensive analysis of organics emissions data provided the following
insight into the factors affecting DRE:
• DREs for the incinerators tested were generally above
99.99 percent. The average DRE for volatile organic
constituents was found to be 99.992 percent.
• .DRE appears to be strongly correlated to concentration of the
POHC in the waste feed. POHCs at higher waste feed
concentrations were observed to be destroyed or removed to a
higher degree. The phenomenon that caused this relationship
was not identified.
• Analyses of data collected on this program showed no clear
correlation between DRE and heat of combustion for POHCs.
• Data compiled from the eight tests were not sufficient to
define parametric relationships between residence time,
temperature, heat input, or 02 concentrations and DRE.
8-32
-------
TABLE 8.6. INCINERATION FACILITIES TESTED
ORE*
(number
at
Facility Control device Uesce nines) b
HCI
concrol
(average)
Average
parciculace
emissions
(g/dscf)
Commercial roeary kiln
liquid incinerator
(37 aiUiaa Bcu/hr)
Commercial fixed-hearth,
tvo-icage ineineracor
(2; million Stu/hr)
Onsice cvo-seage Liquid
ineineracor
(6 million Bcu/hr)
Commercial fixed-hearth
cvo-scage incinerator
(2 oillion Btu/hr)
Onsice liquid injection
ine ineracor
(4.3 million Btu/hr)
areial fixed-hearth
mo-stage ineineracor
(10 million Btu/hr)
Onaite rotary kiln wich
liquid injection
(35 million 3cu/hr)
Commercial fixed*hearch
two-stage incinerator
(75 million 3tu/hr)
Packed-toner adaorber,
ionizing vet scrubber
Electrified gravel bed
filter; packed-tower
adsorber
Packed-toner adsorber
Hone
Hone
None
VenCuri scrubber with
cyclone separators and
packed-cover adsorbers
Venturi scrubber
Drummed, aqueous, liquid 3.3 99.4Z 0.67
organic vaste with carbon
tetrichloride, TCS,e per-
chloroechylene, toluene,
phenol
Liquid organic and aqueous 4.i 98.31 0.173
aqueous weace wich chloro-
form, carbon tetrachloride,
TCE, toluene, perchioro—
echylene
Liquid organic waste with 4-i 99.71 0.027
carbon tecrachloride,
dichlorobenxene, TC£,
chlorobenzene, chloro-
oathana, aniline, phosgene
Liquid organic waece wich 4.7 4 lb/hrd 0.089
TCE, carbon cecrachloride,
toluene, chlorobenzene
Liquid organic waste wich 6.7 4 lb/hrd 0.092
•naline, diphenyLamina,
mono- and dinicrobenzene
Aqueoua and organic liquid 4.3 4 Ib/hr** 0.40
waace wich carbon cecra-
chloride, TCE, benzene,
phenol, perchloroechylene,
toluene, mechylachyl kecone
Liquid organic, paine waace 5.3 99.91 0.01
and filter "cakes uich
mechylene chloride, chloro-
form, benzyl chloride,
hexachloroechane, toluene,
TCE, carbon tetrachloride
Aqueous and organic liquids 4.6 98.31 0.075
and sold waace wich mechy-
lene chloride, chloroform,
carbon cecraehloride,
hesachlorocyelopencadiene,
coluene, benzene, TCE
*De3truc:ion and removal efficiency (mass weighted average for all POHCa).
b?or example, 99.995* ORE » i.5 nines.
CTCE • tricaloroechylene.
dNo HCu control device; waste La low in total organic chlorine concent.
Sourc»: Reference 5.
8-33
-------
TABLE 8.7. SUMMARY OF RESULTS OF INCINERATOR TEST PROGRAMS
No. Average waate
of feed rate
Facility rum (Iba/hr)
Plant C 3 243
Upjohn
Plant G 3 ' PCS Coke
126
OO
9 Plant II 4 Solid Wastes
£ 542.1
Plant I* 4 Liquid waste
and Ho. 2 fuel
Waste characteristic*
Ash Chloride Moisture
Waste constituent* Z Z Z
Chlorobenxene 0.19 21 NA
sr-Dichlorobensene
o-Dlchlorobeniene
p-Dlchlorobcniene
1 , 2 ,4'Tr ichlorobenxene
Phosgene
Benxyl Chloride
llexachloroethane
Benxene — 2.5. 3.0
Tetrachloroethylene
Toluene.
Chlorobenxene
Hexachlorocyclopentadiene
Chlordane
Hexachlorobutadiene
llexachlorocyclopentadiena — 25.
Average incinerator value
Temper- Reaidcnce
ature time Heat input 02, ORE
•C aec 10° Ibs/hr stack Z Z
1116 5.2 6.2 8.2 99.934
99.920
99.997
99.9977
99.67
99.997
99.9995
99.99
99.9848
99.9017
99.9947
99.897
99.99
99.999
99.98
1430 - 0.17 - 7.4 6.4 99.99
1870 0. 18
Performance
IIC1.
Particulate emission
Emissions removal
130 Bg/dscm 99.7SZ
I
NA NA
NA • Not available.
Source: Reference 29.
'From Reference 30.
-------
• The data from the eight tests suggest that POHC levels in
scrubber water and ash were generally very low or
nondetectable. These data suggest that the majority of POHCs
are destroyed rather than merely transferred to another media
in the incineration process.
• Some Appendix VIII compounds detected in the stack (primarily
trihalomethanes) appear to be stripped from the scrubber water
by the hot stack gas. Trihalomethanes detected in the scrubber
inlet water were not detected in the effluent water. The
effect can be lower measured/calculated DREs even though the
destruction mechanisms may not be affected.
2. Evaluation of organic emissions data for compounds classified as
Products of Incomplete Combustion (PICs are Appendix VIII compounds
detected in the stack which were not found in the waste feed in
concentrations above 100 yg/g) led to the following observations:
• Stack gas concentrations of PICs were typically as high as or
higher than those for POHC compounds in the stack.
• PIC output rate infrequently exceeded 0.01 percent of POHC
input rate. (The 0.01 percent criterion was proposed in FR
Vol. 45, No. 197, October 8, 1980.)
• The three likely mechanisms that explain the presence of most
PICs are:
a. Poor DREs for Appendix VIII compounds present at low
concentration (*<100 yg/g) in the waste feed;
b. Input of Appendix VIII compounds to the system from
sources other than waste feed (e.g., scrubber water); and
c. Actual intermediate products of combustion reactions or
products of complex side reactions including recombination.
• Data from the tests suggest that benzene, toluene, chloroform,
tetrachloroethylene, and naphthalene have a high potential for
appearing as byproducts of the combustion of organic wastes.
• A summary of the PICs detected in this study are given in
Table 8.8.
3. Compliance with the particulate standard of 180 mg/Nm was not
achieved at half of the sites tested. Particulate control devices
were operated at five of the eight facilities, and two of these five
failed to achieve the standard. Two of the three facilities without
control devices also failed the particulate standard. Data from
this study suggest that any facility firing wastes with ash content
greater than 0.5 percent will need a particulate control device to
meet the standard.
8-35
-------
TABLE 8.8. PICs POUND IN STACK EFFLUENTS
PIC
Benzene
Chloroform
Bromodichlorome thane
D ibr omoc h lor ome thane
Bromoform
Naphthalene
Ch lorobenz ene
Tetrachloroethylene
1, 1, 1-Trichloroethane
Hexachlorobenzene
Methylene chloride
o-Nitrophenol
Phenol
Toluene
Bromoch lo rome thane
Carbon disulfide
Methylene bromide
2,4,6-Trichlorophenol
Bromomethane
Ch loromethane
Pyrene
Fluor an th ene
Dichlorobenzene
Trich lorobenzene
Methyl ethyl ketone
Diethyl phthalate
o-Chlorophenol
Pentachlorophenol
2,4-Dimethyl phenol
Number
of sites
6
5
4
4
3
3
3
3 .
3
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Concentrations
(ng/L)
12-670
1-1,330
3-32
1-12
0.2-24
5-100
1-10
0.1-2.5
0.1-1.5
0.5-7
2-27
25-50
4-22
2-75
14
32
18
110
1
%
3
1
1
2-4
7
3
7
2-22
6
1-21
Source: Reference 29.
8-36
-------
4. UC1 emissions were generally easily controlled to meet one of the
two criteria specified in the regulations—less than 1.8 kg HCl/hr
or greater than 99 percent removal efficiency."
In addition to the effluent data discussed above, the study included
analyses of two other residuals, ash and the scrubber liquor from the air
pollution control device, at four sites. The results of the analyses indicate
that both ash and scrubber liquor contain concentration levels that are at
acceptable levels for the compounds analyzed.
Summaries of additional tests of full scale incinerators are reported in
1 *
the solvent TRD. Data were provided for two test programs conducted at
rotary kiln incinerators using wastes containing nonsolvent chlorinated
organics. Incinerator standards of 99.99 percent DRE were met for all test
compounds as follows:
Compound Range of DREs Reported
Hexachloroethane 99.99
Trichlorobenzene 99.992-99.995
2,4-Dichlorophenol . 99.999
»
2,4,6-Trichlorophenol 99.999
Correlations between residence time and temperature with DRE were observed, as
expected, in both studies.
Very little data were found, other than shown in Table 8.6, for the
destruction of nonsolvent halogenated organics in fixed hearth and multiple
hearth incinerators and fluidized-bed incinerators although data for
halogenated solvents are available from several test programs. Available data
do indicate that 99.99 percent DREs are achievable for halogenated solvents.
Similar DREs can be anticipated for nonhalogenated organics.
Several recent EPA sponsored studies have examined the destruction
efficiency of halogenated organics in industrial boilers and process kilns
used in the lime, cement, and aggregate industries. Extensive data have
been obtained for halogenated solvents indicating that, in most cases,
incinerator DRE standards can usually be met. Most units for which data are
available also achieved the particulate emission standard of 0.08 grams/scf or
" 8-37
-------
less although ash content data were not available. ' Particulace
emissions appear to increase with an increase in chlorine content. These
increases were attributed to a lowering of ESP efficiency due to changes in
both the electrical resistivity of the particle and the particle size
distribution of the particulate emissions.
8.4 COSTS OF HAZARDOUS WASTE INCINERATION
The overall costs associated with the incineration of hazardous wastes
are high relative to other hazardous waste treatment or disposal methods.
Incineration facilities require large capital costs due to the size and
complexity of the systems involved, and the requirements associated with the
handling of hazardous wastes and their combustion products. Operating costs
are high, primarily due to the large energy input required, and also as a
consequence of large raw material costs and stringent environmental control
requirements. Incineration costs are difficult to specify, in general,
because in each situation the number of factors impacting costs is large.
These factors may be classified fundamentally as follows:
»
• Waste characteristics;
• Facility design characteristics; and
\
• Operational characteristics.
The general significance of many of the factors affecting incineration costs
will be discussed in detail below.
Waste Characteristics
The chemical and physical properties of a waste considered for
incineration govern the type of incinerator selected, the processing capacity,
environmental controls employed, pretreatment employed, required maintenance
and equipment lifespan, and operational parameter levels. Several waste
characteristics which significantly affect the costs of incineration are
described below:
8-38
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• Physical State—Physical state dictates the type of incinerator and
the type of waste feed mechanism selected. Liquid injection
incinerators, for example, are applicable only to liquid vastes.
Limited data available on prices charged by commercial incinerators
suggest that solid and sludge wastes are more expensive to
incinerate than liquid wastes.
• Heat Value—Heat value is used as a measure of auxiliary fuel
requirement. The higher the heat value of a waste, the less fuel is
required to sustain combustion.
• Rheological Characteristics—The way in which liquid viscosity of a
waste changes with temperature is important in determining the need
for preheating, waste feed mechanism, and incinerator type. Some of
the wastes are easily handled at higher temperatures, while others
maintain viscosities which render them nonpumpable and/or
nonatomizable over practical limits of temperature.
• Water Content—Water content of a waste strongly affects temperature
and destruction efficiency of the combustion system. In some cases,
dewatering of wastes is conducted as a pretreatment operation.
• Chloride Content—The chloride content of a waste has strong bearing
on the air pollution control methods employed at an incinerator.
High levels of chlorine necessitate acid gas scrubbing and also
require combustion methods which prevent the formation of toxic
chlorine gas.
• Ash Content/Heavy Metals Content—The amount of ash which will be
formed in combustion, and the nature of the ash is related to the
inorganic salt and heavy metal content of a waste to be incinerated,
and greatly affects the particulate matter air pollution control
requirement and the ash collection and disposal system design.
• Volatile Content—The presence of volatile low flash point
components should be considered. If such materials are present in
significant amount special pretreatment or precautions must be taken.
The impact of various waste characteristics on incineration costs may, in some
cases, be measured directly. A survey was conducted of a cross-section of
hazardous waste incineration facilities operating commercially in the United
States, and it revealed that pricing structures are often established based on
11 23 41—45
certain waste characteristics. ' 'As shown in Table 8.9 chloride
content and ash content commonly are used to establish surcharges based on
additional air pollution control requirements. The physical form of the waste
may also be seen as leading to price differentials. In general, solid and
sludge wastes cost more to incinerate than liquid wastes.
..8-39
-------
TABLE 8.9. SURVEY OF HAZARDOUS WASTE INCINERATORS - COSTS OF INCINERATION AND COST IMPACTING FACTORS
CO
1-
o
Facility
A
B
C
D
B
Incineration
system
Liquid Injection/
Rotary Kiln
Liquid Injection/
Rotary Kiln
Liquid Injection/
Rotary Kiln
Liquid Injection
Liquid Injection/
Rotary Kiln
i
Costa to incinerate hazardous wastes
Type of waste
Blendable* aqueous
Blendable organic
Directly-burned aqueous
Directly-burned organic
Directly-burned sludges
or solids
Liquids
Solids and sludges
Any
Liquids
Bulk liquids
Drummed liquids
Drummed solids
'Cost (t)
0.18/lb
0.2675/lb
0.2050/lb
0.2850/lb
O.S/lb
39/55 gal. drum
125/55 gal. drum
0.25/lb
0.86/gallon
1.93/gallon
230/drum
300/drum
Additional costs
Basis
Phase separation
Chloride content or
ash content
Chloride content or
ash content
Suspended solids
Metals (e.g. chromium)
Chlorine
Handling fee
"Approval" charge
Cost
0.3475/lb
N/A
0.002/lb per
chloride or
0.01/gal per
<*>
each 1Z of
ash content
1Z content
0.0005/100 ppm/gallon
0.02/gal per
25/drum
150/job
1Z chlorine
°Blendable defined as a waste with a viscosity of below 10,000 SSU.
! Source: References 11, 23, 24, 41-45.
-------
Facility Characteristics
Facility characteristics, i.e., the design and size of incineration unit
equipment, are measured in terms of capital costs. Capital costs for
incineration facilities are high relative to many other hazardous waste
management technologies, which are generally less complex and less sensitive
to thermal and mechanical tolerances. For each incineration technology, there
is a large variation in the designs available commercially, and great
differences in the pricing policies of manufacturers. As a result, it is
difficult to specify a range of costs for any particular type of system.
To determine the cost of a hazardous waste incineration facility, several
key factors must be assessed. Several of the key factors influencing capital
costs are:
• Size requirements—flow rates, heat input capacities, exhaust rates,
etc.;
• Equipment lifespan;
• Pretreatment requirements;
• Heat recovery;
• Environmental control requirements;
• Feed mechanisms; and
• Equipment availability.
The size requirements of the system have the most bearing on capital costs,
while the environmental control equipment costs may be the largest element of
the overall capital costs. The capital costs of a particular hazardous waste
incineration system are strongly affected by the overall availability of that
technology. Certain systems, such as liquid injection incinerators, are
manufactured by many companies. Other technologies, most notably the newer
type systems, are manufactured by a few or, in many cases, only one company.
Capital cost data available for hazardous waste incineration systems were
limited. Several manufacturers of incineration systems were contacted, but
most were reluctant to specify costs for their systems because the cost for a
8-41
-------
specific application is dependent upon so many different factors. A study
' 3
conducted by McCormack, et al., provided cost estimation curves for several
of the established hazardous waste incineration technologies: liquid
injection, rotary kilns, and hearth incinerators. These cost curves,
including estimation curves for heat recovery systems (waste heat boiler) and
acid gas scrubbing systems, are presented in Figures 8.4 through 8.9. This
information was generated in 1982, and has been updated to reflect the changes
in the Chemical Engineering Plant Index between May 1986 and the date for
which costs were estimated in Reference 3. A study conducted by MITRE
Corporation in 1981, in which several visits were made to incinerator
manufacturers, generated additional cost data summarized in Table 8.10.
In general, it may be noted that certain hazardous waste technologies are
considered to be more expensive in terms of capital costs than are others.
Rotary kilns are most expensive. Relative capital costs for the five
established incineration technologies are as follows in order of decreasing
cost:
• Rotary Kiln
• Fluidized-Bed
• Multiple Hearth
• Liquid Injection
• Fixed Hearth
Operating Characteristics
Numerous factors impact the operating costs of a hazardous waste
incineration facility. The most significant factor governing operating costs
is energy usage. Energy is used in incineration to heat wastes during
combustion, and to operate materials transport and control systems. In many
cases, the energy usage of an incineration system is large enough to justify
the costs of installing and operating heat recovery systems. A summary of
other important operating characteristics affecting the costs associated with
incineration is presented below:
8-42
-------
1.000
«•» Mtvlc*, cblorlaacrt organic* tad ulu
. ltu/hr)°'5U*
Lithe hydrocarbon*, aonchlorluud orj»ntc»
10
(•illlm ky/hr)
Figure 8.4. Purchase cost of liquid injection system (May 1982),
10.000
5.000
2,000
w 1,000
s
300
200
100
.' »tu/hr)
0.478
I t II I I t_.i_ I A
10
20
30 100
telllloa tco/br)
Figure 8.5. Purchase cost of rotary kiln system (May 1982),
Source: Reference 3.
-------
1.000
100
MO
too
•8
20
10
C*c«torr A
, C
-------
s
r*
•
•
l.ooo
300
200
100
X)
20
10
12 3 w 20 jo
lalac fu novrau, q- (1,000 acta)
Figure 8.8. Purchase cost of scrubbing systems receiving
500 to 550°F gas (July 1982).
1.000
X 200
20
10
» ' US
[V. -fa]"'
7U7
3 10 20 90 100 200 300
l
-------
TABLE 8.10. SUMMARY OF COST DATA COMPILED BY MITRE CORPORATION, 1981
Incineration
Facility technology
Capacity
(MMBtu/hr)
Capital cost ($)
Description of cost factors
Fluidized Bed 10
oq
2 "Packaged"
Rotary Kiln
3 Rotary Kiln 37.5
700,000
40-50,000/(100 Iba/hr)
800,000
Without energy recovery.
Scale-up factor for cost
estimation is 0.6 exponent.
Installed cost, including
heat recovery and air
pollution control.
Not installed. Includes one
item of air pollution control.
Estimated installation cost
was 20 percent.
4 Rotary Kiln
5 Rotary Kiln
80-150
0.5
1.02
1.24
14.1
17.0
90
10-15 x 106
600,000
1.9 - 2.2 x
2.34 - 2.66 x
2.66 - 3.04 x
3.25 - 3.65 x
8.5 x 106
106
106
106
106
Total installed cost.
Total installed.
All not installed.
Total installed.
(continued)
-------
TABLE 8.10 (continued)
Incineration
Facility technology
Capacity
(MMBtu/hr)
Capital cost ($)
Description of cost factors
00,
Liquid Injection 5
Fixed Hearth
Liquid Injection 18
70
Combined Liquid 150
Injection and
Rotary Kiln
10 Liquid Injection 30
11 Pyrolysis
150,000
300,000
150,000
300,000
500,000
1.5 x 10e
2.2 x 106
400-500,000
3,000 Ibs/hr 1 x 106
6,000 Iba/hr 4 x 106
Base cost, not installed, no APC,
heat recovery.
Total installed with APC.
Base cost, no APC or heat
recovery, not installed..
Installed with APC.
Not installed.
Total installed cost.
Scale-up factor is exponent -
0.65.
Not installed. No APC, heat
recovery.
Estimated cost of APC given
is 1.2 x 106.
With boiler and scrubber, not
installed.
Including heat recovery, no APC
installed.
Source: Reference 23.
-------
• Residence Time—Residence time affects the volume of the combustion
chamber, secondary combustion requirement, and the exhaust rate.
Residence time may be increased by employing devices such as baffles
or recirculation blowers.
• Temperature—Temperature affects the volume and type of the
incinerator refractory lining, volume of insulation for other
systems, and the need for heating and cooling systems.
• Raw Materials Usage—A variety of raw materials are used in
incineration systems, including chemical agents, fluidized-bed
. granular material, scrubber and cooling tower water, sorbents, and
oxygen. The consumption of these materials leads to additional
costs.
• Maintenance—Maintenance requirements for incineration systems are
considered high due to the number of systems involved and the
thermal and mechanical stresses under which they operate. The
maintenance of refractory linings, for example, is considered a
particularly significant cost consideration.
• . Disposal—Disposal of solid and liquid combustion byproducts can be
very expensive depending on the characteristics of the materials
produced. In some cases, systems are limited in applicability based
on disposal costs of, for example, heavy metals containing wastes.
Because of the uncertainties in many of the above items, it is difficult to
assign meaningful values to elements of operational costs. These factors,
however, have been considered by operators in assigning differential costs
based on waste characteristics (see Table 8.9).
8.5 STATUS OF DEVELOPMENT
8.5.1 Hazardous Waste Incinerator Manufacturing Industry
Several surveys have been conducted to determine the number of companies
currently involved in the development, manufacture, and installation of
hazardous waste incineration systems. ' ' ' Investigation of the
current hazardous waste incinerator market in 1982, indicates that there are
approximately 67 companies known to be actually involved. This number may not
necessarily include the number of companies who are developing newer, more
innovative thermal technologies. The conventional technologies offered by
8-48
-------
these commercial companies are summarized in Table 8.11. In general, the
following conclusions, drawn by the MITRE Corporation in 1982, are supported
by these data:
• "About 342 incinerators have been put into hazardous waste service
since January 1969. These units were manufactured by 29 companies,
all of which were based in the United States at the time the units
were delivered. Within the past year one of these companies (BSP
Envirotech) was purchased by a West German firm, the Lurgi
Corporation. The count of 342 units is believed to be reasonably
accurate, but cannot be exact for the following reasons:
- A number of small vendor companies have disappeared since
1969. These companies have probably manufactured a few
incinerators which are still in use, but their existence could
not be determined.
- Incinerators originally sold for hazardous waste disposal or
for nonhazardous wastes could be operating, at least part time,
on the other waste.
Some incinerators have been manufactured strictly in accordance
with a customer's specifications and the manufacturing company
has no knowledge of, or declines to speculate on, the nature of
the purchaser's wastes.
- A few incinerators which have been manufactured since January
1969 are probably no longer in use. A vendor will not
generally know this.
- A few incinerators manufactured since 1969 cannot fulfill the
design function and are not operating. Vendors will not
voluntarily acknowledge these.
• The most common type of hazardous waste incinerator is liquid
injection, representing 64.0 percent of all hazardous waste
incinerators in service. This type of incinerator is not designed
to operate on liquids containing any significant amount of salts or
other suspended or dissolved solids.
• The next most common types of hazardous waste incinerators are the
fixed hearth (FH) and the rotary kiln (RK), with 17.3 and
12.3 percent, respectively, of the total manufactured. Both of
these types of units will dispose of solid wastes, liquid wastes,
and/or fumes.
• Although there are nine companies offering fluidized-bed (FB)
incinerators, only nine such units are in hazardous waste service.
Apparently most of these nine companies believe that the market is
potentially good for this technology.
8-49
-------
TABLE 8.11. NUMBER OF HAZARDOUS WASTE INCINERATORS IN SERVICE IN THE U.S.A.
Type
Liquid Injection
Rotary Kiln
Fixed Hearth3
Multiple Hearth
Fluidized Bed
No. of
companies
offering
22
17
15
2
9
No. in
H.W. service
219-231
42
64
7
9
Range of
capacities
3-300 mmBtu/hr
1-150 mmBtu/hr
200-2500 Ibs/hr
1000-1500 Ibs/hr
N/A
Numerical
share of
market (%)
64
12.3
18.5
2.0
2.6
aIncludes other hearth-type systems including Pulse Hearth (2), Rotary
Hearth (2), Reciprocating Grate (1).
N/A - Information not available.
Source: MITRE, 1982 (Reference 23).
6-50
-------
• Two companies are actively marketing fused salt bath technology, but
there are no units in service or under construction yet.
• Of about 219 liquid injection units in service, about 129
(59 percent) were produced by two companies, John Zink and Trane
Thermal. The data furnished by Zink are not well verified. Of 23
companies marketing LI incinerators, 8 have sold no units to date.
However, several of the 8 indicate that sales are imminent.
• Of the 17 companies offering rotary kiln incinerators, 8 have sold
none to date.
• Of the 9 companies offering fluidized-bed incinerators, 5 have sold
none to date.
• Of a total of 57 companies offering 14 types of incinerators, 28
have sold no units in the United States. (Several companies
represent European technologies and all have sold at least one unit
each in Europe.
• The fact that 28 (of the total of 57 companies) have not sold any
units to date is indicative of the extent of: 1) new technology
being made available in the United States by both U.S. and foreign
companies; 2) the formation of new corporate ventures in the field
of technology; and 3) efforts by European companies to invade the
U.S. market. It is therefore believed that the market, or
technology, is not static at this, point in time.
• Two companies are allegedly developing new technology,, which they
would not describe at this time. It is known that other companies
are researching other techniques for hazardous waste incineration,
but these techniques are not described in this report. The new
processes included plasma, microwave plasma, and several unusual
fluidized-bed techniques."^
A comparative assessment of the available incinerator technologies and a
discussion of their advantages and limitations has been provided in
Reference 1 and in many of the other references cited which provide an
overview of hazardous waste incineration. Manufacturers are identified in the
survey studies such as Reference 23; listings of equipment manufacturers can
also be found in McGraw Hill's Chemical Engineering Equipment Buyers' Guide.
8.5.2 Environmental Impacts of Incineration
Incineration processes potentially affect the environment through
generation of air emissions, and liquid, sludge, and solid wastes. As a
result, EPA has established environmental standards of performance for
8-51
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incinerators in .the RCRA permit process. Most incinerators must be equipped
with appropriate air pollution control systems, leading to higher capital and
operating costs. Environmental impacts associated with incineration are,
therefore, a significant factor in the determination of the appropriateness of
incineration as a management option for hazardous wastes.
*
8.5.2.1 Air Emissions--
Air emissions of pollutants produced in incineration are a primary area
of environmental concern. Emissions may be generated from the incinerator
stack and from fugitive emission sources. Emissions from incinerators
primarily consist of the following "criteria" pollutants: oxides of nitrogen
and sulfur, and particulate matter. Other air pollutants of concern include
undestroyed organics such as benzene, toxic heavy metals (in particles),
hydrochloric acid, and other acid gases.
As part of the RCRA permit process, incinerators must demonstrate their
ability to achieve various performance 'levels established by EPA. Among the
performance criteria are emission standards for hydrochloric acid gas and
particulate matter. These standards are:
1. Hydrochloric acid emissions are limited to a rate of 4 Ib/hr or, if
• acid gas scrubbing is employed, a scrubbing efficiency of 99 percent
or greater; and
•
2. Particulate matter emissions are limited to 0.08 grains per dry
standard cubic feet of flue gas at 7 percent oxygen (180 milligrams
per dry standard cubic meter).
Emissions from incinerators are also regulated under Federal NESHAPS and state
air toxics program standards. These may affect, in particular, the emissions
of heavy metals such as lead or mercury vapors.
Available technologies for the control of emissions from hazardous waste
incinerators include devices to control emissions of particulate matter, acid
gases, oxides of sulfur, and possibly oxides of nitrogen. Gaseous pollutant
control devices include various wet and dry scrubbers. Both wet and dry
scrubbing systems are effective in removing acid gases, although the dry
scrubbing systems are newer and, as a result, not as well established as the
- tt-52
-------
wet systems. Oxides of nitrogen emissions can sometimes be minimized by the
use of combustion modifications which reduce the peak flame temperature in an
incinerator.
For control of particulate matter, the primary candidates are the wet and
dry electrostatic precipitators (ESPs), ionizing wet scrubbers, and
baghouses. Conventional scrubbers are not very effective in the removal of
fine particulate matter. Particulate matter control devices must be compatible
with the acid removal device. A wet acid scrubber is more compatible with a
wet ESP or the ionizing wet scrubber than with a baghouse. Since baghouses
are compatible only with a dry gas system, the use of baghouses on hazardous
waste incinerators is not as prevalent as ESP usage. Properly designed
baghouses and ESPs are both effective particulate matter control devices.
Discussion of the various types of emission control devices used on hazardous
waste incinerators and their control efficiency capabilities can be found in
numerous texts and publications dealing with air pollution control and
incineration.
8.5.2.2 Liquid and Solid Wastes Generation—
Wastes formed both in the combustion unit and in pretreatment and air
pollution control systems constitute a potential environmental hazard which
must be -properly managed. Presence of hazardous materials in the incinerator
ash, scrubbing liquor, and scrubber sludges is primarily dependent upon two
factors: composition of wastes fed; and destruction effectiveness of the
incinerator. The primary constituents of concern in these residues are
thermally inert materials such as toxic heavy metals. Toxic organic compounds
are generally not a significant contaminant of these streams, owing to good
destruction efficiencies.
Ash from incineration—Incinerator ash formed during the combustion
reaction consists almost entirely of thermally inert materials (metals and
other inorganics) introduced in the waste feed. Ash, not emitted with the
combustion flue gas, generally collects at the bottom of the incinerator
units. Many incinerator designs include a conveyor system which continuously
removes ash from the bottom of the unit for subsequent disposal. Contaminated
ash is now commonly disposed of in a Class I landfill. As noted in
S-53
-------
Reference 29, ash residuals from incineration have been found to be suitable
for landfill disposal. Alternatives to direct landfilling, if required, could
include encapsulation/solidification treatments.
Scrubber liquor/scrubber sludges—Scrubber systems, which directly
contact the gaseous byproducts of combustion with liquid (or solid) media,
most commonly water, may produce contaminated liquid or solid waste streams.
The primary contaminants of such streams are toxic solid particles carried as
fly ash, acids such as hydrochloric acid formed in combustion, and various
organic products of incomplete combustion. The quantity, quality, and types
of liquid wastes formed from the control equipment is dependent on the
constituents of the waste feed, destruction efficiency, and collection
efficiency.
Liquid effluents from scrubber and quench systems usually will undergo
neutralization and removal of solids before they are discharged to local •
sewage systems. A very common practice is to discharge these streams to
settling ponds (volatilization of organics from these ponds is not considered
a significant problem). Sludges are commonly treated in a sewage sludge
incinerator, or are dewatered and directly landfilled. Residual analysis of
29
scrubber liquor and sludges have indicated that they are essentially free
of organic materials.
8.5.3 Summary
The advantages and disadvantages of the various incineration technologies
available for the destruction of hazardous wastes are presented in
Table 8.12. In general, most of the common incineration technologies might be
of limited applicability to halogenated organic wastes, depending upon the
individual characteristics of the waste.
8-54
-------
TABLE 8.12. SUMMARY OF INCINERATION TECHNOLOGIES
Incineration
method
Liquid Injection
Rotary Kiln
Limitations
Feedstock muat he atoml'cable;
relatively free of
part iculatea
Requlrea large batch
throughput to be practical
Advantages
Can proceaa all typea
of hasardoue liquid j
Can proceaa virtually
any type of vaate;
Disadvantages
remove Impurities, heat,
and blend
Requirea air pollution
controla
Approximate
Capital
$4-500,000 tor 30 HllUtu/hr
(installed, with heat
recovery and APC 1982)
$4-000-50, 000(1 00 */hr)
$10-15 x 105 for 80-150
costa
Operating
tt-250/IOOO gal
.2500-1000/
ton/day
or economical
can coinclnerate
varioua typea of waatea
MMBtu (total installed,
1982)
Fluidlzi*tl Red Requirea large batch
throughput; United to
liquids or non bulky aolida;
no aodlum aalt waatea
Can proceaa laany
waatea typea;
good temperature response
in proceaaing
Requirea periodic bed
replacement; requlrea
air pollution controla
$700,000 for 10 MMBtu
(total installed, no heat
recovery, 1982)
N/A
Fixed Hearth Requirea afterburner;
can't burn liquids if
use continuous ash recovery
Can achieve very high
combustion temperatures;
low maintenance required
Not energy-efficient;
requlrea higher teopera-
turea and realdence timea
$3-400,000 for 10 MMBtu
(installed, 1982)
»O.S/|b
Multiple Hearth
Requires afterburner;
can't burn bulky aolida,
corrosi ves
Beat for aludge incin-
eration; low capital
coat
Possible high maintenance
coata; not energy efficient
N/A
N/A
Source: Engineering-Science (Reference 48).
-------
REFERENCES
1. Breton, M., et al. Technical Resource Document—Treatment Technologies
for Solvent Containing Wastes. Prepared for U.S. EPA, HWERL, Cincinnati,
under Contract No. 68-03-3243. Work Assignment No. 2. August 1986.
2. Federal Register 1982, 47, 27516-35.
3. McCormack, R. J., et al. Cost for Hazardous Waste Incineration.
Capital, Operation and Maintenance, Retrofit. Acurex Corporation,
Mountain View, CA. Noyes Publications, Park Ridge, NJ. 1985.
4. U.S. EPA. Compilation of Air Pollution Emission Factors. Third Edition
including Supplements 1 through 15. Publication No. AP-42. August 1982.
5. Oppelt, E. T. Hazardous Waste Destruction, Environmental Science and
Technology, V01. 20, No. 4. 1986.
6. Hanson, L., et al. Hazardous Waste Incinerator Design Criteria.
EPA-600/2-79-178. TRW, Inc., Redondo Beach, CA. Prepared for U.S.
Environmental Protection Agency, Industrial Environmental Research
Laboratory,.Cincinnati, OH. October 1979.
7. Kee, K. C., H. J. Jahnes, D. C. Macauley. Thermal Oxidation Kinetics of
Selected Organic Compounds. In: 71st Annual Meeting of the Air
Pollution Control Association, Houston, TX. June 23-30, 1978.
8. Advanced Environmental Control Technology Research Center. Research
Planning Task Group Study - Thermal Destruction. EPA-600/2/-84-025.
Prepared for U.S. Environmental Protection Agency, Industrial Engineering
Research Laboratory, Cincinnati, OH. January 1984.
9. U.S. EPA. Incineration and Treatment of Hazardous Waste: Proceedings of
the llth Annual Research Symposium. EPA-600/9-85-028. Articles cited
include:
(a) Olexsey, R., G. Huffman, and G. Evans. "Emission and Control of
By-Products from Hazardour Waste Combustion Process;"
(b) Gorman, P., and D. Oberacker. "Practical Guide to Trial Burns at
Hazardous Waste Incinerators;"
(c) Westbrook, W., and E. Tatsch. "Field Testing of Pilot Scale APCDs
at a Hazardous Waste Incinerator;"
8-56
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(d) Clark, W. u., ec ai. ••emergency Analysis of Hazardous Waste
Incineration: Failure Mode Analysis for Two Pilot Scale
Incinerators";
(e) Bellinger, B., J. Graham, D. Hall, and W. Rubey. "Examination of
Fundamental Incinerability Indices for Hazardous Waste Destruction."
(f) Kramlich, J., E. Poncelet, W. R. Seeker, and G. Samuelsen. "A
Laboratory Study on the Effect of Atomization on Destruction and
Removal Efficiency for Liquid Hazardous Wastes";
(g) Chang, D., and N. Sorbo. "Evaluation of a Pilot-Scale Circulating
Bed Combustor with a Surrogate Hazardous Waste Mixture";
Ch) Evans, G. "Uncertainties and Incineration Costs: Estimating the
Margin of Error"; and
(i) Graham, J., D. Hall, B. Dellinger. "The Thermal Decomposition
Characteristics of a Simple Organic Mixture".
10. Lee, R. C., N. Morgan, J. L. Hansen, G. M. Whipple. Revised Model for
the Prediction of the Time-Temperature Requirements for Thermal
Destruction of Dilute Organic Vapors, and Its Usage for Predicting .
Compound Destructability. In: 75th Annual Meeting of the Air Pollution
Control Association, New Orleans, LA. June 20-25, 1982.
11. Incineration and Treatment of Hazardous Waste: Proceedings of the 8th
Annual Research Symposium. EPA-600/9-83-003. Articles cited include:
(a) Frankel, J., N. Sanders, and G. Vogel. "Profile of the Hazardous
Waste Incinerator Manufacturing Industry":
(b) Vogel, G. A., Frankel, I., and N. Sanders. "Hazardous Waste
Incineration Costs":
(c) Staley, L. J., G. A. Volten, F. R. O'Donnell, and C. A. Little. "An
Assessment of Emissions from a Hazardous Waste Incineration
Facility"; and
(d) Johnson, S. G., S. J. Yosium, L. G. Reeley, and S. Sudar.
"Elimination of Hazardous Wastes by the Molten Salt Destruction
Process."
12. PEDCo, Inc. Evaluation of the Feasibility of Incinerating Hazardous
Waste in High-Temperature Industrial Processes. EPA-600/2-84-049.
Prepared for U.S. Environmental Protection Agency, Industrial
Environmental Research Laboratory, Cincinnati,.OH. February 1984.
13. Air Pollution Control Association. Technical Conference on the Burning
Issue of Disposing of Hazardous Wastes by Thermal Incineration.
April 29-30, 1982. Hilton Gateway, Newark, NJ. Articles cited include:
8.-S7
-------
(a) Deneau, K. S. "Pyrolytic Destruction of Hazardous Waste";
(b) Austin, D. S., R. E. Bastian, and R. W. Wood. "Factors Affecting
Performance in a 90 million Btu/hr Chemical Waste Incinerator:
Preliminary Findings'.1;
(c) Bierman, T. J. and J. C. Reed. "Determination of Principal Organic
Hazardous Constituents (POHCs) in Hazardous Waste Incineration"; and
(d) Sesaverns, G. A., D. R. J. Roy, and W. B. Rossnagel. "Air Pollution
Control Technology: For Hazardous Waste Incineration".
14. Arienti, M., et al. Technical Assessment of Treatment Alternatives for
Wastes Containing Halogenated Organics. Prepared for U.S. EPA, OSW Under
Contract No. 68-01-6871. Work Assignment No. 9. October 1984.
15. Clark, J. N. and J. J. Cudahy. Impact of the Resource Conservation and
Recovery Act on the Design of Hazardous Waste Incinerators. In:
Detoxification of Hazardous Waste. Ann Arbor Science Publishers. 1982.
16. Cudahy, J. J., W. L. Troxler and L. Sroka. Incineration Characteristics
. of RCRA Listed Wastes. U.S. EPA Contract No. 68-03-2568. Work Directive
T-7021. Industrial Environmental Research Laboratory, Cincinnati, OH.
17. Tsang, W., and W. Sbaub. Chemical Processes in the Incineration of
Hazardous Materials. Paper presented at the American Chemical Symposium
on Detoxification of Hazardous Wastes. New York, NY. August 1981.
18. Guidance Manual for Hazardous Waste Incinerator Permits. Report SW-966.
EPA, Washington, D.C., 1983.
19. Senkan, S. M. Combustion Characteristics of Chlorinated Hydrocarbons.
In: Detoxification of Hazardous Waste. Ann Arbor Science Publishers.
1982.
20. Martin, E. J., and L. W. Weinberger, et al. Practical Limitation of
Waste Characteristics for Effective Incineration. Presented at the
Twelfth Annual Research Symposium on Land Disposal, Remedial Action,
Incineration, and Treatment of Hazardous Waste. Sponsored by U.S.
Environmental Protection Agency, Hazardous Waste Engineering Research
Laboratory, Cincinnati, OH. April 21-23, 1986.
21. Edwards, B. H., J. N. Paullin, K. CoughIan-Jordan. Emerging Technologies
for the Control of Hazardous Wastes. Ebon Research Systems, Washington,
D.C., Noyes Data Corporation, Park Ridge, NJ. 1983.
22. Marti, Bruce. Telephone Conversation with M. Kravett, GCA Technology
Division, Inc. Chemical Waste Management, Inc., Chicago, IL. February
1986.
23. MITRE Corporation. Survey of Hazardous Waste Incinerator Manufacturers,
1981. MITRE Corporation, METREK Division, McLean, VA. 1982.
-8-58
-------
24. Cross, F. C. Hazardous Waste Incinerators—Operational Needs and
Concerns. Cross/Tessitore and Associates, P.A., Orlando, PL. In:
Hazardous Waste and Environmental Emergencies—Management, Prevention,
Cleanup, and Control. March 12-14, 1984.
25. State of California Air Resources Board. Air Pollution Impacts of
Hazardous Waste Incineration: A California Perspective. Technical
Support Document. A Report to the California State Legislature.
Prepared by the California Air Resources Board. December 1983.
26. MITRE Corporation, Working Paper. Liquid Injection Incinerator Burner
Performance. WP-83W00393. MITRE Corporation, METREK Division, McLean,
VA. October 1983.
27. Kiang, Y. H., and A. A. Metry. Hazardous Waste Processing Technology.
Ann Arbor Science Publishers, Inc. Ann Arbor, MI. 1981.
28. Lee, C. E. and G. L. Hoffman. An Overview of Pilot-Scale Research in
Hazardous Waste Thermal Destruction. In: International Conference on
New Frontiers for Hazardous Waste Management. U.S. EPA-600/9-85-025.
September 1985.
29. Trenholm, A., P. Gorham, and G. Sungclaus. Performance Evaluation of
Full Scale Hazardous Waste Incinerators. EPA-600/2-84-181. Midwest
Research Institute, Kansas City, MO. Prepared for U.S. Environmental
Protection Agency, Office of Research and Development, Cincinnati, OH.
November 1984.
30. U.S. EPA. Destroying Chemical Wastes in Commercial Scale Incinerators
Facility Report No. 1. SW-122c.l. U.S. Environmental Protection Agency,
Office of Solid Waste, Washington, D.C. 1977.
31. Mournighan, R. E., et al. Hazardous Waste Incineration in Industrial
Processes: Cement and Lime Kilns. In: International Conference on New
Frontiers for Hazardous Waste Management. U.S. EPA-60079-85-025.
September 1985.
32. Paulson, E. G. How to Get Rid of Toxic Organics. Chemical Engineering.
October 17, 1977. pp. 21-27.
33. Carnes, R. A. Combustion Characteristics of Hazardous Waste Streams.
Presented at the 71st Annual Meeting of the Air Pollution Control
Association. No. 77-19-1. June 20-24, 1977.
34. Elliot, W. H. and W. B. McCormack. Incineration of Hazardous Substances.
Presented at the 70th ANnual Meeting of the Air Pollution Control
Association. .No. 77-19.1. June 20-24, 1977.
35. Ackerman, D. G., et al. Guidelines for the Disposal of PCBs and PCB
Items by Thermal Destruction (DRAFT) by TRW, for U.S. EPA, Industrial
Environmental Research Laboratory, Contract No. 68-02-3174. May 1980.
36. Lee, Kun-Chieh, et al. Thermal Oxidation Kinetics of Selected Organic
Compounds, presented at the 71st Annual Meeting of the Air Pollution
Control Association, 78-58.6, Houston, Texas. June 25-30, 1978.
8T59
-------
37. Hanson, L., and S. Unger. Hazardous Material Incinerator Design Criteria,
by TRW, for U.S. EPA, Office of Research and Development.
EPA-600/2-79-198. October 1979.
38. Ferguson, T. L., et al. Determination of Incinerator Operating
Conditions Necessary for Safe-Disposal of Pesticide's, by Midwest Research
Institute, for U.S. EPA, Office of Research and Development.
EPA-600/2-75-041.
39. Ackennan, D. G., et al. Destroying Chemical Wastes in Commercial Site
Incinerators, Final Report—Phase II, by TRW and Arthur D. Litle, Inc.
for U.S. EPA, Office of Solid Waste, SW-155c. November 1977.
40. Dillon, A. P., Editor. Pesticide Disposal and Detoxification. Noyes
Data Corporation, Park Ridge, NJ. 1981.
41. IGF Incorporated. RCRA Risk/Cost Policy Model - Phase III Report.
Prepared for U.S. Environmental Protection Agency, Office of Solid Waste,
Washington, DC. 1984.
42. Anderson, R. Telephone Conversation with M. Kravett, GCA Technology,
Inc. IT Corporation, Martinez, CA. April 1986.
43. Warren, P. Telephone Conservation with M. Kravett, GCA Technology,
Inc. Stablex Corporation, Rock Hill, SC. April 1986.
44. Garcia, G. Telephone Conversation with M. Kravett, GCA Technology,
Inc. TWI, Inc., Sauget, IL. April 1986.
45. Bell, R. Telephone Conversation with M. Kravett, GCA Technology,
Inc. Systech Corporation, Paulding, OH. April 1986.
46. A Profile of Existing Hazardous Waste Incineration Facilities and
Manufacturers in the United States. PB-84-157072. EPA, Washington,
DC. 1984.
47. National Survey of Hazardous Waste Generators and Treatment, Storage and
Disposal Facilities Regulated Under RCRA in 1981. U.S. Government
Printing Office Order No. 055000-00239-8. EPA, Washington, DC. 1984.
48. Engineering-Science. Final Report. Technical Assessment of Treatment
Alternatives for Waste Solvents. Prepared for U.S. Environmental
Protection Agency, OSW, Technology Branch. November 1983.
8-60
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SECTION 9
EMERGING THERMAL TREATMENT TECHNOLOGIES
With the passage of the 1984 amendments to RCRA banning the land disposal
of hazardous wastes, thermal treatment of hazardous wastes has become an
increasingly attractive option. Accordingly, there has been a great deal of
interest shown in the development of new technological approaches to thermal
treatment. HWERL has identified 21 "innovative thermal processes for treating
or destroying hazardous organic wastes", many of which are applicable to
balogenated organic 'wastes.
Emerging thermal treatment technologies include modifications of
conventional incineration technologies (e.g., the circulating bed incinerator)
as well as more unconventional approaches to thermal destruction, e.g., the
plasma arc pyrolysis system. The technologies included here, and discussed
below, are:
L. Circulating Bed Combustion
2. Catalytic Fluidized Bed Incineration
3. Molten Glass Incineration
4. Molten Salt Destruction
5. Pyrolysis Processes
6. In Situ Vitrification
Discussions of these and other technologies can also be found in Reference 1
2 3
and the TRDs for solvents and dioxins. ' In general, the thermal
technologies discussed here can be applied to the destruction of any
balogenated organic.
9-1
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9.1 CIRCULATING BED COMBUSTION
Circulating bed combustion (CBC) systems constitute an innovation in
fluidized bed incineration technology. These systems utilize high air
velocities and recirculating granular bed materials to maintain and achieve
combustion of waste under fluidized bed conditions. The circulating bed
material also can be chosen for its chemical characteristics to bring about
reaction and neutralization of certain products of combustion such as sulfur
oxides and hydrochloric acid. CBC systems are applicable to solids, liquids,
slurries, and sludges, over a wide range of heat values and ash contents.
Numerous performance tests have been conducted which indicate that circulating
bed combustion can achieve very high destruction and removal efficiencies,
while limiting other pollutant emissions to acceptable levels. CBC systems
can offer both technological and economic advantages over established
fluidized-bed incineration systems primarily due to the increased turbulence
of the system. CBC systems operate at higher air velocities, and are not
limited, as are fixed bed units, to the narrow range of design velocities
needed to maintain fluidization. At the same time, they limit entrainment and
carry over of bed material.
9.1.1 Process Description
The circulating bed combustion process, depicted in Figure 9.1.1,
represents a design innovation to standard fluidized bed (FB) incineration
systems. The CBC system is designed to handle all forms of waste, including
solids, liquids, and sludges.
The primary operating unit, the circulating bed combustor, incorporates a
two-chamber design consisting of a combustion chamber and a hot cyclone
chamber, as shown in Figure 9.1.1. The bed material used, limestone
(CaCO.), is fed to the system concurrently with the waste material.
Limestone is used because it readily reacts with sulfur and chlorine
combustion products to form relatively innocuous salts such as CaCl2 and
CaSO,. The general reaction scheme for the CBC process is as shown in
Figure 9.1.2. Waste material is fed to the system either before the
combustion loop for solids and sludges, or just at the start of the loop for
9-2
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Figure 9.1.1. CBC incineration pilot plant located at GA Technologies
Source: Reference 4.
9-3
-------
REACTANTS IN'
I
(HYDROCARBONS] i
(SULFUR COMPOUNDS)
1
(LIMESTONE]
l
(CHLORINE COMPOUNDS)
FERMEDIATES FINAL PRODUCTS
1 . ,
» *
V—+ ^°T , ._, . frtsn^j
1' ... * en i 1GYPSUM)
CT (SALT)
\
Figure 9.1.2. Chemical reactions that occur in CBC combustion chamber.
Source: Reference 4.
9-4
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liquids. As stated by the manufacturer, the CBC requires no specialized waste
atomization or other injection mechanism, due to the inherently high level of
turbulence in the system which ensures good distribution of waste feed.
During operation of the system, a high velocity stream of heated air (15 to
20 feet/sec.) entrains the material and carries it up the combustion column.
As the waste flows upward, combustion occurs, and the byproducts are
dispersed. The gaseous products, primarily CO. and water yapor, flow out
the top of the combustor. The acidic byproducts such as HC1 react with the
limestone to form inorganic salts (generally these form as particulates).
They and other solid byproducts flow downward through the hot cyclone, in
which solids and gases are further separated. The hot flue gases pass first
to a heat exchange system, then to a particulate control device, before being
vented through the exhaust stack. Ash eventually settles within the
combustion column and falls to a screw conveyor (as shown in Figure 9.1.1)
where it is transported to ash recovery.
The operating conditions are as shown below.
Waste Feed: Applicable to any physical form - granular
solids, liquids, sljidges, slurries
Temperature Range: 1400-1600°F (760-870°C)
Residence Time;
Gas Phase: 2-3 seconds
Solids: 10 seconds to 10 hours.
Capacity (Ibs/hr): See Table 9.1.1
Energy Type and Requirements:
Thermal: Sensible and latent heat; self-sufficient
for wastes up to 85 percent water content
Electrical: Blower and feeder operation—approximately
30 HP for 2 MMBtu/hr incinerator
Capacities, shown in Table 9.1.1, are dependent upon the type of waste fed to
the unit. As noted, the data were furnished by the developer; commercial
units covering the range of capacities have not yet been constructed.
9-5
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TABLE 9.1.1. CIRCULATING BED COMBUSTION UNITS
Customer
Startup Pud
Output
(MMBtu/hr) Application
USA-GA
GA Technologies Inc.
San Diego, CA
USA - Pyropower
Gulf Oil Exploration
Bakersfield, CA
California Portland
Cement Co.
Colton, CA
B. F Goodrich
Henry, IL
Central Soya
Chattanooga. IN
General Motors Corp.
Pontiac, Ml
Colorado Ute Electric
Utility
•MM^^^MH^BB
1982
operating
1983
operating
1984
under
construction
1985
1985
1986
1987
Varied
Coal, coke,
and limestone
Coal and
limestone
Coal and
limestone
Coal and
limestone
Coal, limestone,
and plant wastes
Coal and
limestone
2 MW (t)
50
209
123
105
370
1000
Pilot plant
Enhanced oil
recovery
Cogeneration
Process steam
Process steam
Cogeneration
Electrical
generation
Nucla, CO
Foreign ~ Ahlatrom
Hans Ahlstrom
Laboratory
Karhula, Finland
Pihlava Board Mill
Finland
Suonenjoki, Finland
Kemira Oy, Finland
Kauttua, Finland
1976
operating
1979
operating
1979
operating
1980
operating
1981
operating
varied
Peat, wood.
and coal
Peat, wood,
and coal
Zinciferous
sludge
Peat, wood,
and coal
2N
50
22
—
22(
MW(t)
Pilot plant
Cogeneration
District heating
Sludge incineration
Cogeneration
(continued)
9-6 .
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TABLE 9.1.1 (continued)
Customer
Foreign (cont'd)
Hyvinkaa, Finland
Skelleftea, Sweden
Ruzomberok,*
Czechoslovakia
Hylte Bruk, Sweden
Koskenkorva Distillery
Finland
Kemira Chemical
Finland
Zdlstoff und
Papierfabrik
Frantschach AG
Carinthia, Austria
Ahlstrom
Varkaus, Finland
Neste Lampo Oy
Mantsala, Finland
Bord Na Mona
Ballyforan, Ireland
Oriental Chemical Co.
Inchon. Korea
Ostersunds
Fjarrvarme AB
Ostersund, Sweden
Papyrus AB
Kopporfors, Sweden
Metsaliiton Teollisuus
Oy
Aanekoski, Finland
Kereva Power .Company
Kereva. Rnland
Startup
^••MBM^^H^
1981
operating
1981
operating
1982
operating
1982
operating
1982
operating
1982
operating
1983
operating
1983
operating
1983
operating
1984
1984
1985
1985
1985
1985
FtMl
Coal, peat, oil,
and municipal
wastes
Peat, wood,
and coal
Sewage sludge
Peat and coal
Peat and oil
Peat and oil
Bark, brown coal.
and sludge
Wood waste
Coal-water
mixture
and coal
Peat and oil
Petroleum, coke,
and coal
Peat, wood chips.
and coal
Bark, peat, and
coal
Wood waste,
peat.
coal, and oil
Coal and
limestone
Output
(MMBtu/hr)
85
22
—
157
63
173
188
68
10
61
330
85
190
258
102
Application
District heating
District heating
Sludge incineration
Cogeneration
Process steam
Cogeneration
Cogeneration
Cogeneration-
retrofit
Heating-
firetube design
Cogeneration
Cogeneration
Heating
Cogeneration
Retrofit
Utility-heating
Source: Reference 2.
9-7
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Waste streams of primary environmental concern in the CBC process are:
(a) the acidic byproducts and organic products of incomplete combustion
(PICS); and (b) hazardous heavy metals or other solid byproducts remaining in
the ash. To date, performance testing has indicated that acid or PICs in the
flue gas stream are not usually significant. The ash will be handled as a
solid waste. If hazardous materials exist, they will be disposed of in an
appropriate manner.
9.1.2 Demonstrated Performance
A pilot-scale CBC was tested by the California Air Resources Board in
cooperation with the manufacturer, GA Technologies, in 1983. The testing
involved a surrogate, waste mixture .which had a heating value of 8000 Btu/lb
and included organic compounds such as xylene, ethylbenzene, toluene,
hexachlorobenzene, Freon, and carbon tetrachloride. The CBC unit operated at
a capacity of 0.5 MMBtu/hr, and a temperature of below 1600°F (870°C).
A DRE of 99.99 percent or greater was achieved for all principal organic
constituents. Emissions of hydrochloric acid met EPA standards by use of a
limestone sorbent in the bed.
Some of the conclusions drawn by Chang and Sorbo in Reference 6 are
presented below:
1. The DRE of volatile and semi-volatile POHCs under less than optimum
combustion conditions met RCRA requirements (99.99 percent DRE).
2. Total volatile PIC formation was found to correlate well with CO and
THC, normalized to fuel flowrate (C02). Penetration of volatile
chlorinated PICs (based on total chlorine content of the fuel)
exceeded 1 x 10~*. PIC benzene appeared in substantial
concentrations in several samples and was not correlated with any
conventional combustion parameters.
3. The DRE dropped sharply when the bed temperature fell below 700°C.
Temperature appeared to be a major factor in the destruction of the
fluorinated compounds and a moderate correlation between sulfur
hexafluoride, DRE and temperature was observed.
4. The CBC seemed to behave as a plug-flow reactor, susceptible to
pockets of non-stoichiometric air/fuel mixtures passing through the
bed causing increased PIC formation. This observation suggests the
importance of the fuel feed system on CBC performance and should be
evaluated carefully by permitting authorities.
9-8
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GA Technologies, the developer, has reported more than 7,500 hours of
performance testing conducted under the auspices of DOE, EPRI (Electric Power
Research Institute), TVA, and a number of commercial sponsors. These tests
were conducted at the company's 2 x 10 Btu/hr test unit in San Diego, CA.
The system has been tested with a variety of fuels and wastes to establish the
combustion efficiency and the pollutant removal efficiency of the system
relative to specific waste types. For halogenated organic waste types, the
system has generally shown a DRE above 99.99 percent, and an HC1 capture of
99 percent and above. Particulate emissions downstream of the unit's fabric
filter baghouse have been measured at 0.002 grains per standard cubic foot,
well below the RCRA incinerator standard. In summary, DREs found for POHCs
existing in the organic wastes are as shown below:
Compound
Ethylbenzene
Trichloroethane
Vinyl chloride
1,2-trans-dichloroethylene
1,2-dichloroethane
PCBs
Pentachlorophenol
DRE
99.99
99.999
99.9999
99.99
99.99
99.9999
99.992
Temperature (°F)
1600 (871°C)
1600
1600
1600
1600
1800 (982°C)
9.1.3 Cost of Treatment
The costs of circulating bed incinerators according to GA Technologies
Inc., are equivalent to the costs of conventional fluidized bed systems and
less than those for rotary bed incinerators. Additional cost savings will
also result from control of pollutants, such as those resulting from chlorine
and sulfur in the waste, through addition of dry limestone to the bed.
Chlorine capture efficiencies are reported to exceed 99 percent, a condition
that meets EPA incinerator requirements. EPA requirements for particulate
emissions will require the use of pollution control equipment, e.g., ESPs or
baghouses. Overall cost of incineration was estimated to range from $31 to
$235 per metric ton for PCBs, pesticides, and halogenated solvents. Costs for
nonsolvent halogenated organics should be similar.
9-9
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9.1.4 Status of Technology
Circulating bed combustion systems are in operation worldwide, for many
process applications. However, there are no CBC incinerators operating
specifically as hazardous waste incinerators. Although, as the manufacturer
points out, many of the wastes disposed of by currently operating CBCs contain
hazardous constituents. A listing of the operating units, submitted by the
company, is shown in Table 9.1.1. GA Technologies is the only manufacturer of
CBC technology. In terms of market potential, the company provides the
general comparison between existing technologies and CBC shown in Table 9.1.2.
While the CBC concept and available performance data are promising,
additional data are needed' to validate DREs and establish air emission levels
for particulates, PICs, chlorine based pollutants, and other possible toxics.
As noted in Reference 6, plug-flow reactor behavior, if it occurs, could lead
to incomplete combustion and high emission levels of contaminants in the feed.
9-10
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TABLE 9.1.2. CIRCULATING BED INCINERATOR VS. CONVENTIONAL INCINERATORS
Item
Cost
Capital
Operating
Circulating Bed
$
$
Bubbling Bed
$ + scrubber
+ extra feeders
4- foundations
$ + more feeder
maintenance
•f more limestone
+ scrubber
Rotary Kfln
$S (double)
+ scrubber
4- afterburner
S$ + more auxiliary
fuel
4- kiln maintenance
+ scrubber
Pollution control
POHCs
CI.S.P
NO,, CO
Upset Response
Effluent
Feeding
No. of Inlets
Sludge Feeding
Solids Feedsize
Fly-Ash Recycle
Unit size
Land area
Efficiency
Thermal, %
Carbon, %
Feeder, hp
In minimum-temperature
combustor
Dry limestone in combustor
Low due to turbulence,
staged combustion
Slump bed; no pollution
Dry ash
1 -solid
1 -liquid
Direct
Leas than 1 in.
Inherent (50 to 100 X
feedrate)
Smaller
>78
>98
Minimum
In high-temperature
combustor or afterburner
Downstream scrubber
High: bubbles bypass and
poor fuel distribution
Bypass scrubber pollution
released
Wet ash sludge
5-solids
5-liquids
Filter/atomizer (5 each)
Less than % to V, in.
Difficult mechanical/
pressure (10 X feedrate
max)
Larger (over 2X)
<75
<90
High
In afterburner
Downstream scrubber
High NO,: hot afterburner
Bypass scrubber pollution
released
Wet ash sludge
1-solids
2-liquids
Filter/atomizer (2 each)
Larger, but shredded
Not done
Larger (over 4X)
<70
High
• SI ConwBMn: mm • ia. X 2&4
Source: GA Technologies, Inc.
9-11
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9.2 CATALYTIC FLOIDIZED BED INCINERATION
The combustion temperatures required for high level destruction of wastes
and, hence, the operating costs associated with an incinerator may be
significantly reduced through the use of catalysts. Catalysts serve to
increase the rate of oxidation by adsorbing reactants onto active sites, thus
increasing their localized concentration. By increasing the reaction rate,
less energy input is required to achieve component destruction efficiencies
which are substantially similar to conventional incinerator systems. Thus, a
catalytic incinerator operating at temperatures on the order of 500 to 600°F
lower may destroy certain species as effectively as a conventional system
(Reference 7).
Catalytic incinerators have been proven effective as a fume abatement
(air pollution control) device for many years. Such systems typically employ
a static catalyst bed into which material flows and oxidation ensues (see
Figure 9.2.1). The catalyst bed may be either a single "honeycomb"-type unit,
or a bed of pellets or uniquely-designed pieces (not unlike the packing
materials used in packed-tower scrubber systems). Such systems have not been
proven effective, however, in the incineration of streams contaiping high
particulate loadings or high concentrations of halogens. As stated' in
Reference 9, the performance life of a catalyst may be seriously deteriorated
by the effect of plugging or corrosion, especially by HC1. Excessively high
localized temperatures will also tend to deactivate the catalyst in a shorter
time period.
Beginning in the 1970*s, studies began to indicate that, while problems
could not always be entirely eliminated, the continuous replacement of a
portion of the catalyst bed during normal operation could allow continuing
operation at high efficiency, even in the presence of poisoning agents. This
criterion could be satisfied by a fluidized bed reactor into which catalyst
could be added, and from which withdrawals could be made during operation.
The use of a fluidized bed could also provide some protection against catalyst
poisoning because of the self-abrading action of the catalyst particles in the
bed, which continuously cleans the surfaces available for activation. Such
9r-12
-------
and *C
Burner
Preheat section
Filter/,,
mixer
and *C
Catalyst
bed
Recife, damper
/or secondary
heat exchanger
Secondary
VjL/addition
Figure 9.2.1. Typical components of a catalytic incinerator.
AP and °C indicate pressure drop and heated
gas, respectively. (Reference 8)
9-13
-------
systems have been researched by several different manufacturers, both as an
independent system or as a system to be used in combination with another waste
treatment technology. Although the overall status of catalyzed fluid bed
incineration is still in an early development stage some promising results
have reportedly been observed relative to incineration of halogenated organic
wastes.
9.2.1 Process Description
The catalytic fluidized bed incineration process would appear to be
essentially identical to a standard fluidized bed incinerator process, with
the exception of the bed materials. An example of this process is the
"CATOXID" process designed by BF Goodrich, as shown in Figure 9.2.2.
It is likely that pretreatment of the waste stream would be even more
important in catalytic fluidized bed incineration processes, given the
negative effect that high particulate loadings and high halogen concentrations
would have on the catalyst bed. It is also, necessary to remove waste
constituents such as sodium salts which may contribute to the clogging
(defluidization) of the bed. Information detailing the specifics of the
processes currently in development is limited in availability, particularly
with respect to the catalyst materials being used. For more detailed
information on the fluidized bed incineration process, the reader is advised
to refer to Section 8.
9.2.2 Demonstrated Performance
Performance data relative to catalytic fluidized bed incineration in
general, and their performance in the destruction of balogenated organic
compounds in particular, are limited. The three primary studies which appear
to have been conducted to date were summarized by Manning (Reference 7).
Hardison and Dowd (Reference 10) described the performance of a
pilot-scale catalytic unit of 0.91m in diameter with a 15cm bed of propriety
catalyst. In the disposal of a refinery waste stream, the unit oxidized
9-14
-------
HEAT
RECOVERY
PRODUCT
CHLORINATED
BY-PRODUCT
FEED TANK
AIR
T
HYDROGEN CHLORIDE
CARBON OXIDES
NITROGEN OXYGEN
STEAM
DRUM
BOILER
FEED WATER
CATOXID
REACTOR
Figure 9.2.2.
Flow diagram of B. F. Goodrich CATOXID process.
(Reference 7)
9-15
-------
98 percent of the feed organic materials while operating at a combustion
temperature of approximately 820°F and a residence (catalyst contact) time of
150 milliseconds, as illustrated in Figure 9.2.3. It was claimed that the
catalyst deactivation rate was low, as illustrated in Figure 9.2.4.
Unfortunately, the article failed to detail which catalyst materials were
involved in the test.
In 1981, Rockwell (Reference 11) announced that a two stage fluidized bed
process bad achieved a destruction efficiency of greater than 99.9999 percent
for PCBs and PCB surrogates during a test burn of a sample of transformer
coolant (52 percent by weight PCB, 48 percent trichlorobenzene). The
combustion temperatures during this test reportedly were at or below 1300°F.
The system combined a conventional fluidized bed reactor, which also contained
a sodium carbonate sorbent for HC1 and a chromia-catalyzed secondary fluidized
bed reactor which oxidized any materials not combusted in the first unit.
Benson reported in 1979 (Reference 12) on the results achieved by the
largest scale catalytic oxidation process for chlorinated hydrocarbons, the
BF Goodrich CATOXID process. At temperatures below 1000°F, a feedstock
containing several low molecular weight hydrocarbons was oxidized "essentially
to completion". In this process, catalyst life was reported to be indefinite
and was not reported to have been significantly poisoned by the chlorinated
species. Manning's own results, as shown'in Figures 9.2.5 and 9.2.6,
indicated "effective oxidation for several chlorocarbons". While the
poisoning of the catalyst clearly was shown in this study to be directly
proportional to cblorocarbon feed rate or concentration (see Figure 9.2.7),
Manning concluded that extended operation may be possible at only slightly
reduced rates if feed stoicbiometry (specifically the H/C1 ratio in the mixed
feed) is controlled. Manning further concluded that, while a catalyzed system
may not be best for a large-scale commercial waste disposal facility handling
diverse waste materials, it may be applicable to usage in the chemical process
industry, where much of the volume of HOC waste is presently being treated
onsite. In this environment, where the waste streams are less variable in
composition and volume, the application of catalytic oxidation in fluidized
bed reactors offers more immediate potential. This observation is
substantiated by the pattern of usage of the technology to date.
9-16
-------
too
o
«7S
-------
00 2.0 4.0 6.0
CALCULATED RATE.U103)
8.0 1O.O
g moles
12.0
g cot - nr
Figure 9.2.5. Comparison of measured C.HC1. oxidation rates
and calculated rates from regression. (Reference 7)
50.0
L 40-° ~
o» a>
LU
tr
z
LU
HI
Q.
X
LU
30.0 -
2O.O -
10.0 -
0.0 10.0 20.0
CALCULATED
30.0 4O.O 5O.O
g molas C2[
g cot - hr
Figure 9.2.6. Comparison of measured C0CTA oxidation rates
(Reference 7)
and calculated rates from regression.
9-18
-------
1OO
C2CI4 IN FEED ( Mole V. )
A 1.58
O 0.83
10 20 3O
CATALYST TIME ON STREAM. HOURS
Figure 9.2.7. Catalyst deactivation during
oxidation of dry C7C1,.
(Reference 7)
9-19
-------
9.2.3 Costs
Because the fluidized bed catalytic incineration systems are still in a
relatively early stage of their development, detailed cost information is not
available. In general, however, the capital costs would be expected to
closely reflect the costs of conventional fluidized bed incinerators. The
catalyst materials used, typically made from exotic materials, would tend to
add, perhaps significantly, to the overall capital cost. The higher capital
costs could be more than offset, however, by.the significant savings in
operating costs due to reduced fuel consumption. Such systems would be
expected to involve somewhat higher maintenance costs, particularly for the
•»
destruction of HOC wastes which will poison the catalyst pellets.
9.2.4 Status of Development
The fluidized bed catalytic incineration system is primarily in the early
stages of its development as a waste disposal technology. Several units,
however, appear to have been installed at industrial facilities. Hardison and
Dowd reported that two commercial units manufactured by Air Resources, Inc.
were designed and placed into operation, including one destroying chlorinated
organics at a chemical maunfacturing facility. The BF Goodrich CATOXID
process has also been implemented at several Goodrich plants, including one at
toe Calvert City VCM complex which handles all of the chlorinated by product
streams at the plant. Benson reported that several CATOXID units are in
operation worldwide.
9--20
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9.3 MOLTEN GLASS INCINERATION
Molten glass incinerators (MGI) are electric furnace reactors in which a
pool of molten glass is used both as a means of destroying hazardous organic
wastes and/or as a means for encapsulating the solid byproducts of hazardous
waste treatment. The system utilizes furnaces similar to those used
extensively in the glass manufacturing industry. Combustible hazardous wastes
of virtually any physical form or chemical composition may be destroyed
effectively in MGI systems. The system is considered particularly attractive
for the destruction of highly toxic organic wastes, wastes containing heavy
metals, and contaminated soils. Solids introduced with the waste feed and
many solid products of combustion become incorporated in a glass matrix,
rendering them environmentally inert and land disposable. Molten glass
systems are being studied by two separate firms (Battelle Northwest and
Penberthy Electromelt International) as hazardous waste treatment devices.
The process is considered to have certain technological and economic
advantages over other established incineration technologies.
9.3.1 Process Description
The molten glass furnace is a tunnel-shaped reactor, lined with
refractory brick, in which a pool of glass is maintained in a molten state by
electric current passing through the glass between submerged electrodes. Such
furnaces are used extensively in the glass manufacturing industry. The unit
is designed to withstand temperatures as high as 1260°C (2300°F), and
corrosion by acidic gases. MGI systems, as designed, will be equipped with
heat recovery and air pollution control systems, and can be combined with a
preconditioning beater or primary incineration unit, as depicted in
Figure 9.3.1.
In the absence of a primary incineration unit, wastes can be fed directly
to the furnace chamber, above or into the pool of molten glass. Solids,
slurries, and highly viscous liquids are usually charged via a screw feeder.
Liquids may also be sprayed into the chamber through nozzles located at the
top of the unit. Combustion air is fed to the system from two locations, one
near the top (as shown in Figure 9.3.1), and the other nearer to the surface
9-21
-------
srl
o
CO
00
w
t-l
o
o
c
CO
co
03
3
O
•a
CO
ff.
•a
c
CO
If
CO
o
w
• H
Q
en
•
o\
cu
CO
u
s
-------
of the pool on the opposite side, in order- to maximize the turbulence within
the reaction space. The temperature within the chamber is maintained at
2300°F. Residence time of gases within the chamber is about 2 seconds
although this can be increased if desired by reducing load. Residence time of
solids within the glass will be appreciably longer, and is measured in terms
of hours. Several furnace sizes accomodating various waste feed rates are
available^.
During operation, volatile waste materials mix with air, ignite, and
react in the space above, and at the surface of, the pool of molten glass.
The solid products of combustion, dir, and other noncombustible materials
(e.g., heavy metal contaminants or the solid waste being treated) will be
incorporated into the glass bed. Gaseous products flow out of the chamber
through a series of ceramic fiber filters which catch most of the particulate
matter. The hot gases, consisting primarily of C02, water vapor, and HC1
(if chlorinated organics are incinerated), then pass through a heat exchanger
for heat recovery (heat is used to warm the combustion air, as shown in
Figure 9.3.1). The exhaust gases flow next to a series of water spray-type
scrubbers. The first- spray chamber is designed to use a slightly alkaline
scrubbing liquor to capture acidic vapors. Water is used in the other spray
chamber (or chambers) to remove remaining particulates and other scrubbable
vapors. The gases are then reheated above' the dewpoint and passed through
charcoal and HEPA filters before being vented out thet stack. The entire
systems if maintained under negative pressure by means of the exhaust
blower. 13
After a period of usage, the molten glass bed, with the solid waste
materials incorporated, is tapped out of the chamber into metal canisters and,
after cooling, is sent to a disposal facility. The ceramic filters, which
eventually become loaded with particulate matter, can be disposed of by
dissolving them in the molten glass bed. The glass bed can also be used to
encapsulate the sludge from the spray chambers, the spent charcoal and HEPA
filters.
Major advantages of the molten glass incineration system are its
applicability to many forms of hazardous waste and the encapsulation of
residuals in a nonleachable glass matrix. Performance testing, and data
generated from commercial usage of MGI units in the chemical processing
9-23
-------
industry, while limited, have shown no significant difference in the
effective operation of such systems for wastes of different physical forms
and widely varying chemical composition. However, preheating and chemical
treatment of wastes are often used tfo aid combustion and reduce system
maintenance and down time. The waste related factors which may be of the
greatest particular concern are moisture, metals and inorganics content.
The significance of these characteristics are discussed below.
A high concentration of water in waste will necessitate additional
energy input to the system and may affect destruction efficiencies.
Penberthy has set a moisture content limit of 20 percent (by weight) for
its systems.13- Since many wastes contain water at levels higher than
this, pretreatment of the waste will be needed. Pretreatment systems which
can be used include evaporation and sedimentation. Dewatering options may
be somewhat limited for certain wastes, due to characteristics such as
volatility and miscibility with water.
Metals and minerals which are constituents of wastes pose a problem
to the effective operation of molten glass incinerators. Those materials
which are denser than the molten glass will tend to accumulate near the
bottom of the furnace. (Battelle reports that its process, which involves
intermixing of molten glass and waste, achieves 95 percent detention of
nonvolatile heavy metals.)1 Eventually, due to their electrolytic properties,
they may affect the operation of the metal electrodes. Penberthy has
recommend the usage of sumps to collect and localize setting metal particles.
Such systems have been found to be effective in reducing the effect of
metals on furnace operation.^
9.3.2 Demonstrated Performance
No data, demonstrating DREs or quantifying exhaust gas emissions, are
available for halogenated organic wastes or any other wastes. These data
are needed if this technology, which appears promising in concept, is to
be utilized for hazardous waste treatment.
9-24
-------
9.3.3 Cost of Treatment
Costs will depend to an appreciable extent upon the need for pretreatment
and tbe demands placed on the system used to clean exhaust gases.
9.3.4 Status of Technology
Molten glass incinerators are available commercially from Penberthy
Electromelt International Inc. for use as chemical processing units.. Battelle
Northwest, another company involved in the development of MGI systems, has not
yet produced equipment on a commercial scale. The Penberthy system has not
been sold or permitted specifically as a hazardous waste incinerator to date.
However, despite the lack of information concerning its application to
hazardous wastes, the technology would appear to offer certain definite
advantages. Anticipated advantages are as follows:
• Able to achieve significant waste volume reduction
• Able to destroy almost all forms of hazardous waste, largely
independent of physical state or chemical composition
«
• Heat recovery and air pollution control built into system
*
• Solid byproducts transformed via glass encapsulation to
environmentally safe state. The encapsulates are resistant if.not
inert to chemical reaction, leaching, and fracture. They probably
can be disposed of in landfills
• System is small in size, can be transportable
• Equipment used is relatively simple, representing basic technology
that has been applied in heavy .industry for 30 years
Limitations, also largely conjectural at this stage, include the following:
• Unproven technology. There is no knowledge of long term operation
and maintenance requirements, or how performance would be affected
by long term usage with wastes
• Energy costs and capital costs are relatively high
• Control system as described may be inadequate for exhaust gases of
the type anticipated from hazardous waste destruction
9-25
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9.4 MOLTEN SALT DESTRUCTION
Molten salt incinerators involve the combustion of waste materials in a
bed of molten salt. Using the molten salt incineration process, "organic
wastes may be burned while, at the same time scrubbing in situ any
objectionable byproducts of that burning and thus preventing their emission in
the effluent gas stream." Molten salt incinerators were developed by
Rockwell International, specifically to burn hazardous organic wastes and, as
designed, are applicable to both liquid and solid waste streams. However,
wastes with high ash content or a high percentage of water or noncombustible
material are not good candidates for molten salt destruction.
9.4.1 Process Description
The molten salt destruction process has been under development by
Rockwell International since 1969. The original intent was to use the
process to gasify coal. A variety of salts can be used, but the most recent
studies have used sodium carbonate (Na.CO.) and potassium carbonate
U2C03) in the 1450°F to 2200°F (790°C to 1200°C) temperature range.
As shown in a schematic of the Rockwell process (Figure 9.4.1), the waste
is fed to the bottom of a vessel containing the liquid salt along with air or
oxygen-enriched air. The molten salt is maintained at temperatures of
800-1,000°C (1500 to 1850°F).16 The high rate of heat transfer to the
waste causes rapid destruction. Hydrocarbons are oxidized to carbon dioxide
and water. Constituents of the feed such as phosphorous, sulfur, arsenic, and
the halogens react with the salt (i.e., sodium carbonate) to form inorganic
melt
1,15
salts, which are retained in the melt. The operating temperatures are low
enough to prevent NO emissions.
Eventually, the build-up of inorganic salts must be removed from the
molten bed to maintain its ability to absorb acidic gases. Additionally, ash
introduced by the waste must be removed to maintain the fluidity of the bed.
Ash concentrations in the melt must be below 20 percent to preserve fluidity.
9-26
-------
UQUID WASTE FEED
COMBUSTION AIR
SOLID WASTE FEED
SALT QUENCHING CHAMBER
EXHAUST STACK
AND/OR GAS
CLEANING EQUIPMENT
MOLTEN SALT OEMISTER
^ SECONDARY REACTION ZONE
MOLTEN-SALT
LEVEL CONTROL
.MOLTEN SALT
WASTE ENTRANCE
NOT DRAWN TO SCALE
TO SALT RECOVERY
Figure 19.4.1. Molten salt combustion system
Source: Reference 14.
9-27
-------
Melt removal can be performed continuously or in a batch mode.
Continuous removal is generally used if the ash feed rates are high. The melt
can be quenched in water and the ash can be separated by filtration while the
salt remains in solution. The salt can then be recovered and recycled. Salt
losses, necessary recycle rates, and recycling process design are strongly
dependent on the waste feed characteristics. '
9.4.1.1 Waste Characteristics and Pretreatment Requirements—
Molten salt destruction (MSD) systems are limited in their applicability
to various hazardous wastes. Although the system is capable of handling
hazardous wastes in both the liquid and solid state, MSD is in practice
limited to the incineration of hazardous organic wastes which have a
relatively low percentage of solids or inorganics. Slurried wastes and most
"dry" solid wastes (e.g., contaminated soils) are not good candidates for
incineration by MSD. When ash accumulates in the bed, it tends to form a
waste matrix which eventually affects bed fluidity, the overall transfer of
heat and capacity for waste byproduct neutralization within the molten mass.
Thus, 20 percent ash was determined to be the limit to which the system could
effectively,operate.
Wastes with high water content may limit the effectiveness of the molten
salt destruction process. As moisture content increases, the waste will
require more fuel and combustion air, to the point where the reactor volume is
limited. Thus, many wastes must be dewatered by pretreatment to ensure that
they are effectively destroyed in the MSD.
Discussion with Rockwell indicated that there is no established
pretreatment system designed as part of the MSD system. However, separation
technology to remove solids and to dewater wastes prior to incineration in a
MSD unit must be considered.
9.4.1.2 Operating Parameters—
The operating parameters for a molten salt unit are:
• Temperature Range: 800-1000°C (1500-1850°F)
• Residence Time:
Gas Phase Approximately 5 seconds
Liquid or Solid Phase Hours
9-28
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• Energy Requirement: Natural gas or oil to beat salt bed;
Auxiliary fuel for noncombustible wastes;
Power for exhaust
• Available Capacity: Commercial units available at 2,000 Ibs/hr;
Pilot scale in use operating at 250 Ibs/hr
• Operating Limitations: Heat generation: MSD requires a cooling
system to prevent operational failures
9.4.1.3 Post-Treatment Requirements—
Altbougb post-treatment requirements have not yet been defined, it is
likely that treatment will be required to remove products of combustion that
are not scrubbed out of the exhaust gases by the molten salt. These products
of combustion could include particulates, POHCs and PICs. Solid residues
(i.e., used salt) must be reprocessed or disposed.
9.4.2 Demonstrated Performance
Rockwell International has built two bench scale combustors (0.5 to
2 Ib/hr), a pilot plant (55 to 220 Ib/hr), and a portable unit
(500 Ib/br). They have also built a 200 Ib/hr coal gasifier based on the
molten salt process. Destruction efficiency tests have been conducted at the
bench and pilot scale levels. While no data were found to demonstrate the DRE
of the molten salt destruction technology for the halogenated organics, data
showing five nines to eleven nines DRE for certain organic compounds have been
obtained.
Many wastes have been tested in the bench scale unit. Chemical warfare
agents, including Mustard HD, a chlorinated organic, have been destroyed at
efficiencies ranging from 99.999988 to 99.9999995 percent. Other chemicals
that have been destroyed using the molten salt combustion process include:
chlordane, malathion, Sevin, DDT, 2,4-D herbicide, tar, chloroform,
perchloroethylene distillation bottoms, trichloroethane, tributyl phosphate,
and PCBs.16
The PCB trial combustion data are presented in Table 9.4.1. The
destruction efficiency at the lowest operating temperature, 700°C (1300°F),
exceeded 99.99995 percent. The average residence time'of the PCB in the
9-29
-------
TABLE 9.4.1. PCB COMBUSTION TESTS IN SODIUM-POTASSIUM-CHLORIDE-CARBONATE
MELTS
Temp
(°C)
870
830
700
895
775
775
Scochiometric
air
(1)
145
115
160
180
125
90
Concentration
of KC1, NaCl
in melt
Cwt %)
60
74
97
100
100
100
Extent of PCB
destruction3
-------
melted salt was 0.25 to 0.50 seconds, based on gas velocities of 1 to 2 ft/sec
through the 0.5 ft of melt.
Hexachlorobenzene (HCB) and cblordane destruction were tested in the
pilot plant facility. Feed rates for HCB and cblordane were as high as
269 Ib/hr and 72 Ib/hr, respectively. Bed temperatures ranged from 1685° to
1805°F (920°C to 985°C) and residence times were in the 2 to 3 second range.
HCB destruction efficiencies ranged from 99.9999999 to 99.999999999, and
chlordane destruction efficiencies ranged from 99.99999 to 99.999999. The
results of the pilot-scale tests are summarized in Table 9.4.2..
As shown in Table 9.4.2, very high DREs were noted for both compounds.
HC1 emissions were below 100 ppm, and no Cl« gas or phosgene gas was
detected. Particulate emissions were measured, but were found to be quite
low, and analysis showed that particulate matter was nonhazardous. The
improved performance in the pilot scale reactor was attributed to greater
residence times.
9.4.3 Costs of Treatment
Detailed estimates of costs for molten salt destruction have not been
«
formulated. Based on the performance of the bench- and pilot-scale MSD units,
it is speculated that general operating costs will be low, but that the
initial capital costs will be high. Molten salt destruction operating costs
should be lower than established technologies such as rotary kilns. Operating
temperatures are low and the process does not require a complex air pollution
control system and associated appurtenances, (although emission data are
needed to verify this), or ash recovery and transport systems.
9.4.4 Status of Technology
Molten salt destruction systems are a proprietary design of the Rockwell
International Corporation. Rockwell began development of the MSD system in
1969, obtaining several patents for the technology. By 1980, the system was
made available for commercial-scale .application, at a capacity of 2000 Ibs/hr,
for destruction of specific waste types. The company constructed, and
currently maintains three different sized units, including a bench-scale
(2 Ibs/br) unit, and a pilot-scale (200 Ib/hr) unit, and a full scale
9-31
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TABLE 9.4.2. SUMMARY OF PILOT-SCALE TEST RESULTS
PCB Chlordane
Combustor Feed Rate 20.9 - 122.0 12.1 - 32.7
(Ib/hr)
Combustor Off-gas
- mg/m3 2.7 x 10~4 - 7.1 x 10~2 5.3 x 10~3 - 6.8 x 10"2
- ppmv 2.3 x 10~5 - 6.1 x 10~3 3.2 x 10'4 - 4.1 x 10"3
Bagbouse
- mg/m3 6 x 10~6 - 1.6 x 10~4 3.6 x 10~4 - 4.4 x 10"3
- ppmv 5.2 x 10~7 - 1.4 x 10~5 2.1 x 10~5 - 2.6 x 10"4
Spent Melt (ppmv) 0.001 - 0.104 0.0044 - 1.2.
NOX (ppmv) 70 - 125 0.5 - 630
HC (ppmv) 35 - 110 0.4 - 60
Particulate (mg/m3) 6.2 x 10~3 - 0.107 4.1 x 10~3 - 1.75 x 10~2
DRE (2) 11-9's - 9-9's 8-9's - 7-9's
Note: The pH of the liquid in a small sampling scrubber in the off—gas line
remained basic throughout the test indicating essentially no HC1
emission.
Source: Reference 1.
9^32
-------
(2000 Ibs/br) unit, for demonstration of molten salt incineration
capabilities. However, no commercial scale units bave been sold by the
company to date. Rockwell has indicated that development of this technology
has been curtailed, due in part to the limited demand encountered.. Rockwell
will maintain their demonstration units and considers future development of
HSD a possibility.
As demonstrated in the molten salt destruction process performance tests,
HSD systems have certain distinct advantages as an incineration technology
alternative. The limitations of the system however, may prove to severely
limit its further development.
Advantages--
• Achievement of high destruction efficiencies for many wastes,
including highly toxic and highly halogenated wastes;
• Low NOX and heavy metal emissions
• Retention of halogens and metals in a manageable salt matrix;
• Compact size. The process has few moving parts and acts, as its own,
highly efficient scrubber for acid combustion gases;
• Especially well-suited to wastes whose combustion results in
liberation of acids;
• Improved reliability due to simple design;
• Increased waste throughput possible
Limitations—
• Generally restricted to certain types of organic hazardous wastes;
• Sensitive to high ( 20 percent) ash content in wastes;
• Molten salt is corrosive to all but specific engineering alloys.
Material and construction costs will therefore be high, and
management of spent salt beds will be difficult;
• No commercial applications to date, thus, no existing record of
long-term performance and operation and maintenance requirements
9-33
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9.5 PYROLYSIS PROCESSES
Pyrolysis reactors are systems in which destruction of waste contaminants
is accomplished by applying sufficient thermal input to bring about bond
t
fracture and molecular decomposition. No oxidation reactions are involved in
these processes. Pyrolysis reactors can achieve very high destruction
efficiencies for wastes, including difficult to dispose wastes such as
dioxins. A variety of pyrolysis systems have been developed, including
continuous and batch furnace pyrolyzers, the plasma arc reactor, and the high
temperature fluid wall reactor. These are described below.
9.5.1 Furnace Pyrolysis Systems
9.5.1.1 Process Description—
The pyrolysis system shown in Figure 9.5.1 consists of three major
components: a continuous rotary furnace, a rich fume secondary combustion
chamber, and a heat recovery unit. The furnace is similar to furnaces
employed to treat metals and other materials requiring controlled thermal
treatment. Waste is continuously fed to a rotating belt which passes through
an indirect-fired, oxygen-free pyrolytic chamber. The waste is heated to
between 540°C UOOO°F) and 870°C (1600°F). Volatiles in the waste or
resulting from pyrolysis are driven off leaving behind inert materials,
metals, and other inorganics, which are continuously removed from the moving
belt. The volatile gases, containing organic compounds and products of
pyrolysis such as H, and HC1, are combusted in the rich fume reactor to
complete the destruction of any organic materials present. These gases then
flow through a waste heat boiler or a similar device used to recover energy.
Although some HC1 formed by pyrolysis is removed through contact with alkaline ,
components (either in the waste or added to the feed deliberately for that
purpose), it is conceivable that some type of air pollution control device
might be needed to control acid gas emissions. Reportedly other pollutants
such as particulates and nitrogen oxides will not be a problem because of the
low turbulence level within the pyrolysis chamber and the reducing atmosphere
of pyrolysis, respectively.
9-34
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Waste heat boiler *
Combustion
air blower \
Rotary hearth
furnace "-
Refiuctory duct work.
Rich fume
reactor and
dwell chamber
Figure 9.5.1. Continuous pyrolyzer.
Source: Reference 18.
9-35
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Although wastes with a wide range of chemical characteristics may be
treated in a pyrolytic incinerator, certain wastes are clearly better candi-
18
dates than others. As noted by Midland-Ross, the developer, pyrolysis
systems work best for wastes which fall into the following categories:
1. Too viscous to atomize in liquid incinerators, yet too fluid for
spreader-stoker incinerators.
2. Low melting point materials that foul heat exchangers, spall
refractories, and complicate residue discharge.
3. High residue materials (ash), with easily entrained solids, that
would generally require substantial stack gas cleanup.
4.• Material containing priority pollutants with excessive vapor
pressure at incineration temperatures.
5. Any material, drummed or loose bulk, where controlled thermal
treatment is desired to make clean gases for heat recovery or for
discharge to the atmosphere.
Operating conditions for the components of the two types of pyrolyzers (batch
and continuous) produced by Midland-Ross are as follows:
Pyrolyzer
• Temperature Range:
• Residence Time Range:
• Auxiliary Fuel Requirements:
I
Rich Fume Incinerator (Reactor)
• Temperature Range:
• Residence Time Range:
Commercial System
• PyroBatch Systems:
• PyroTberm Systems:
650e-870°C
U200°-1600°F)
15-30 minutes (continuous systems)
4-6 hours (batch systems)
Natural gas, fuel oils, and/or
electrically-fired
980°-1200°O
(1800°-2200°F+)
1.0-2.0 seconds
1,000 Ib/load to 30,000 Ib/load
500 Ib/hr
9-36
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9.5.1.2 Demonstrated Performance—
A Midland-Ross batcb pyrolysis system, operated by the McDonnell Douglas
Company in St. Charles, Missouri, was RCRA permitted in 1984 after a series of
trial burns using wastes with five POHCs with 50-70 percent chlorinated
hydrocarbons. Average DREs for the five POHCs during the trial burns were
99.9999 percent (six nines). Removal efficiency for HC1 was 99.9 percent, and
particulate emissions were 0.035 grains per dry standard cubic foot. No
other data appear to be available.
9.5.1.3 Cost of Treatment—
As noted in Reference 1, the developer states the following with regard
to cost.
"Our cost estimates are proprietary information and are supplied
only to customers with whom we have projects. To date, most of our
clients' wastes applications are different from one another, hence
project capital costs are also different. However, inherent
benefits of pyrolytic incineration help our clients realize
significant overall project cost reductions relative to direct
incineration systems."
9.5.1.4 Status of Technology—
Both batch and continuous pyrolysis units are supplied commercially by
the Midland-Ross Corporation. The company also maintains a research facility
and offers complete bench and pilot test facilities.
The pyrolysis systems are particularly suited for sludges and solid
wastes because of the long residence times that can be employed to assist
19
destruction. In addition to the potential to destroy all organics and to
handle difficult waste types, pyrolysis systems, as noted by the developer,
offer the following advantages:
1. Salts and metals (inert materials) with moderate melting points are
not liquified because the pyrolyzer operates at a design temperature
below the melting points of most salts and metals.
2. Since the same salts and metals are normally not vaporized,
refractory spalling, surface fouling, and formation of inert aerosol
condensates are all greatly reduced.
S-37
-------
3. Particulate emissions with most types of pyrolyzers are greatly
reduced because the waste is not agitated or contacted with
turbulent gases during pyrolysis, so particulate cleanup devices
in many ca'ses are not needed to meet Federal standards.
4. Waste-borne NOX is redacted in a pyrolysis atmosphere to N2 and
H20. Hence, NOX emissions from the process are considerably
1owe T.
5. Chlorinated or halogenated materials (e.g., hydrochloric acid)
typically liberated by thermal treatment of a waste can be adsorbed
by caustics present in, or added to, the feed prior to pyrolysis.
This often leads to a reduction in emissions of HC1 and SOX from
50 to 90 percent.
6. Leaching of metals and salts from the carbonaceous residue (char) is
reduced because they are exposed to a reducing atmosphere throughout
the process, and they tend to be physically or chemically tied up in
the char.
7. Overall, gas cleanup equipment is greatly reduced or not required to
pyrolytically treat the same waste materials treated by direct
.incineration.
9.5.2 Plasma Arc Pyrolysis
9.5.2.1 Process Description—
In this process, under development by Pyrolysis Systems Inc. of Welland,
Ontario, waste molecules are destroyed by the action of a thermal plasma
field. The field is generated by passing an electric charge through a low
pressure air stream thereby ionizing the gas molecules and generating
temperatures up to 10,000°C.
A flow diagram of the plasma pyrolysis system is shown in Figure 9.5.2.
The plasma device is horizontally mounted in a refractory-lined pyrolysis
chamber with a length of approximately 2 meters and a diameter of 1 meters.
The colinear electrodes of the plasma device act as a plug-flow atomization
zone for the liquid waste feed, and the pyrolysis chamber serves as a mixing
zone where the atoms recombine to form hydrogen, carbon monoxide, hydrogen
chloride, and particulate carbon. The approximate residence times in the
atomization zone and the recombination zone are 500 microseconds and 1 second,
respectively. The temperature in the recombination zone is normally
maintained at 900-1200°C (1650°F - 2190°F).21
9-38
-------
Off GASES TO fLME
\uaaucicMaattfua
WSOWOUWOQWH-
kUSSSEUCTMJYlWT
Figure 9.5.2. Pyroplasma process flow diagram.
Source: Reference 20.
9-39
-------
After the pyrolysis chamber, the product gases are scrubbed with water
and caustic soda to remove hydrochloric acid and particulate matter. The
remaining gases, a high percentage of which are combustible, are drawn by an
induction fan to the flare stack where they are electrically ignited. In the
event of a power failure, the product gases are vectored through an activated
carbon filter to remove any undestroyed toxic material.
The treatment system that is currently being used for testing purposes is
rated at 4 kg/minute of waste feed or approximately 55 gal/hour. The product
gas production rates are 5-6 m /minute prior to flaring. To facilitate
testing, a flare containment chamber and 30 ft. stack have also been added to
the system. The gas flow rate at the stack exit is approximately
3 21
36 m /minute.
A major advantage of this system is that it can be moved from waste site
to waste site as desired. The entire treatment system, including a
laboratory, process control and monitoring equipment, and transformer and
21
switching equipment, are contained on a 45 foot tractor-trailer bed.
Two residual streams are generated by this process. These are the
exhaust gases that are released up the stack as a flare, and the scrubber
water, stream. Since the product gas (after scrubbing) is mainly hydrogen,
carbon monoxide, and nitrogen, it burns "with a clean flame after being
ignited. Analysis of the flare exhaust gases, presented in the following
section, indicates virtually complete destruction of toxic constituents.
The scrubber water stream is composed mainly of salt water from
neutralization of HC1 and particulates, primarily carbon. Analyses of the
scrubber water for the waste constituent of concern (e.g., carbon
tetrachloride (CC1.) and PCB in the feed material) have shown that the
constituents were present at low ppb concentrations. The quality of scrubber
water generated would depend on the water feed rate and corresponding product
gas and scrubber waste flowrates. During a test in which 2.5 kg/min of waste
containing 35 to 40 percent CC1, was fed to the reactor, a scrubber water
21
effluent flowrate of 30 liters/minute was generated.
The reactor as it is currently designed can only be used to treat liquid
waste streams with viscosities up to that of 30 to 40 weight motor oils.
Particulates are removed by a 200 mesh screen prior to being fed into the
reactor. Contaminated soils and viscous sludges cannot be treated.
9-40
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9.5.2.2 Demonstrated Performance--
The plasma arc system bas been tested using several liquid feed
materials, including carbon tetracbloride (CC1,), polycblorinated biphenyls
(PCBs), and methyl ethyl ketone (HER).
Table 9.5.1 presents the results of tbree test burns conducted in
Kingston, Ontario using carbon tetrachloride in the feed material. The carbon
tetrachloride was fed to the reactor along with ethanol, methyl ethyl ketone,
and water at a rate of 1 kg of CC1,/minute. The duration of each of these
tests was 60 minutes, and stack gas flowrates and temperatures averaged 32.5
dry standard cubic meter/minute (dscm/min) and 793°C (1460°F), respectively.
As can be seen in the table, the destruction and removal efficiency (DRE) of
CC1, in each of the tests was high, exceeding six nines. In addition, the
concentration of HC1 in exhaust gases was less than the upper limit of 1.8
kg/hr required by RCRA guidelines. As far as FCBs are concerned, the
destruction and removal efficiency in each of the tests was greater than 6
nines, and in some cases reached 8 nines. Similar or better results can be
anticipated for most halogenated brganics.
9.5.2.3 Costs of Treatment—
The approximate capital cost of a unit similar to the one tested would be
21
ie range of 1 to 1.5 million dollars. Mor<
available once a commercial unit has been built.
21
in the range of 1 to 1.5 million dollars. More accurate figures will be
9.5.2.4 Status of Technology—
The construction and testing of the plasma arc system is being jointly
sponsored by the New York State Department of Environmental Conservation
CNYDEC) and the U.S. EPA Hazardous Waste Engineering Research Laboratory
(HWERL). The project is comprised of four phases, which are:
Phase 1: Design and construction of the mobile plasma arc system by the
contractor, Pyrolysis Systems, Inc. (PSI).
Phase 2: Performance testing of the plasma arc system at the Kingston,
Ontario, Canada test site.
Phase 3: Installation of the plasma arc system and additional
performance testing at Love Canal, Niagra Falls, N.Y.
Phase 4: Demonstration testing, as designated by NYDEC.
9-41
-------
TABLE 9.5.1. CARBON TETRACHLORIDE TEST RESULTS
Parameter
Chlorine Mass Loading (%)
Scrubber Effluent
CCl4(ppb)
mg/hr
Flare Exhaust
CCl4(ppb)
mg/hr
ppm(v/v)
Ibs/hr
CO
ppm(v/v)
Ibs/hr
HC1
mg/dscm
kg/hr
Destruction Removal Efficiency
Test 1
35
1.27
2.29
0.83
12.1
106
1.02
48
0.28
1
1
99.99998
Test 2
40
5.47
9.85
0.43
4.9
92
0.69
57
0.26
137.7
0.25
99.99998
Test 3
35
3.26
5.87
0.63
7.2
81
0.02
81
" 0.37
247.7
0.44
99.99998
Source: Reference 20.
9-42
-------
Phase 1 cook place in 1982 and Phase 2, the results of which have been
presented above, was completed in early 1986. Phase 3 will be initiated later
in 1986.
The plasma technology is being jointly marketed by Westinghouse Electric
Corporation Waste Technology Services Division and PSI. Once the system has
been properly tested, they plan to lease these units to companies or
organizations that require the system for waste clean up. The current system
is only designed to handle liquid wastes. Future plans by PSI and Westinghouse
include the design of units which could handle contaminated soil and other
22
solid wastes.
9.5.3 High Temperature Fluid Wall (HTFW) Destruction - Advanced Electric
Reactor
9.5.3.1 Process Description—
The HTFW reactor was originally developed by Thagard Research of Costa
Mesa, California. However, the J.M. Huber Corp. of Borger, Texas has.
developed proprietary modifications to this original design. The reactor,
called the Advanced Electric Reactor (AER), is shown in Figure 9.5.3. The
reactor.is a thermal destruction device which employs radiant energy provided
by electrically heated carbon electrodes to heat a porous reactor core. The
heated core then radiates beat to the waste materials. The reactor core is
isolated from the waste by a blanket of gas formed by nitrogen flowing
radially through the porous core walls.
The only feed streams to the reactor are the waste material and the inert
nitrogen gas blanket. Therefore, the destruction is by pyrolysis rather than
oxidation. Because of the low gas flow rate and the absence of oxygen, long
gas phase residence times can be employed, and intensive downstream cleanup of
off gases can be achieved economically.
Destruction via pyrolysis instead of oxidation significantly reduces the
concentrations of typical incineration products such as carbon dioxide and
oxides of nitrogen. The principal products formed during treatment of
balogenated organics would be hydrogen, chlorine (if calcium oxide is added to
the reactor, calcium chloride is formed instead), hydrochloric acid, elemental
23—25
carbon, and free-flowing granular material.
9.-43
-------
7. EXPANSION BELLOWS
COOLING MANIFOLD
4. POWER
^^m^+p^^pf tf^^\ f
ASSEMBLY
6. END PLATE
a
70. RADIATION
HEAT SHIELD
77. HEAT SHIELD
72 COOLING JACKET
POVVEfl CMMP
5. RADIATION
DEFLECTOR
7. ELECTRODE
CONNECTOR
9. POROUS CORE
13. RADIOMETER PORT
. BLANKET GAS INLET
(TYPICAL)
Figure 9.5.3. Advanced electric reactor [Huber]
9--44
-------
A process flow diagram for the AER is shown in Figure 9.5.4. The waste,
if it is a solid, is released from an air tight feed bin through a metered
screw feeder into the top of the reactor. If it is a liquid, it is fed by an
atomizing nozzle into the top of the reactor. The waste then passes through
the reactor where pyrolysis occurs at temperatures of approximately 4500°F
(2480°C) in the presence of nitrogen gas. Downstream of the reactor, the
product gas and waste solids pass through two post-reactor treatment zones,
the first of which is an insulated vessel which provides additional high
temperature (2000°F or 1090°C) and residence time (S seconds). The second
post-reactor treatment zone is water-cooled, and its primary purpose is to
cool the gas prior to downstream particulate cleanup.
Off gas cleaning equipment includes a cyclone to collect particles which
do not fall into the solids bin, a bag filter to remove fines, an aqueous
caustic scrubber for acid gas and free chlorine removal, and two banks of five
parallel activated carbon beds in series for removal of trace residual
organics and chlorine.
The stationary pilot scale reactor which has been used for testing
various wastes at Huber's Borger, Texas facility consists of a porous graphite
tube, 1 foot in diameter and 12 feet high, enclosed in a hollow cylinder with
a double wall cooling jacket. This pilot unit is capable of processing
5,000 tons/yr of waste. Huber also has a 3 inch diameter mobile unit which
has been transported to hazardous waste sites for testing purposes.
The AER cannot currently handle two-phase materials (i.e., sludge); it
can only burn single-phase materials consisting of solids, or liquids, or
gases alone. ' Generally, a solid feed must be free flowing,
nonagglomerating, and smaller than 100 mesh (less than 149 micrometers or
24
0.0059 inches). However, depending on the required destruction, solids
smaller than 10 mesh may be suitable. Soils should be dried and sized before
being fed into the reactor.
The operating parameters as described by References 25 and 27 are as
follows:
• Residence Time 0.1 seconds
(100 mesh solids)
• Gas Flow Rate 500 scfm for 150 ton/day
9-45
-------
POST
REACTOR
ZONES
SOLID
WASTE
BIN
AIR TIGHT FEED BIN
MOUNTED ON A HOPPER
METERED
SCREW FEEDER
ELECTRIC
REACTOR
SAMPLE POINT I
FAN BAG FILTER
mru
CYCLONE
SLIDE
VALVE
MAKEUP WATER
AND NoOH
STACK
CAUSTIC
SCRUBBER
Figure 9.5.4.
High temperature fluid wall process configuration for
the destruction of carbon tetrachloride [Huber],
9-46
-------
Gas Phase 5 seconds
Residence Time
(at 2500°F or 1370°C)
9.5.3.2 Demonstrated Performance—
In 1983, Thagard conducted a series of tests on PCB-contaminated soils
27
using a 3-inch diameter research reactor. The results of these tests
showed an average ORE of 99.9997 percent. The destruction efficiency was
found to be independent of the feed rate in the 50 to 100 g/m range at
2343°C. Pyrolysis products other than carbon and hydrogen chloride were not
detected using a GC with electron capture detection. It was concluded that
the method for dispersing the feed into the reactor needed improvement.
Problems with slagging in the reactor occurred that were believed to be
related to the small diameter of the reactor and also to the design of the
fluid wall flow. After modifications, additional tests on a 6-inch prototype
reactor were conducted by Tbagard using hexachlorobenzene dispersed on carbon
27
particles; 99.99991 percent destruction efficiency was achieved.
J. M. Huber Corporation purchased the patent rights and made further
26
improvements to the process. The J.M. Huber Corporation then began tests
in its stationary reactor system which has a diameter of 12 inches. Included
in this system are: an insulated post-reactor vessel, a water-jacketed
cooling vessel, a cyclone, a baghouse, a wet scrubber, and an activated carbon
bed. Several research burns have been conducted with this system. Results
and operating parameters for pertinent burns are summarized in Table 9.5.2.
A series of four trial PCB-burna were conducted during September 1983
using a synthesized mixture of Aroclor 1260 and locally available sand to
1 24
obtain a total concentration of 3000 ppm PCBs. ' After treatment, the
sand had a PCB content ranging from 0.0001 to 0.0005 ppm (0.1 to 0.5 ppb).
The destruction and removal efficiency was measured to be 99.99960 to
99.99995 percent. Additional studies were conducted with the 12 inch diameter
reactor using soils contaminated with octachlorodibenzo-p-dioxin (OCDD) and
carbon tetrachloride. Seven nines DRE (99.99999 percent) were reportedly
achieved at feed rates up to 2500 Ibs/br.
9-47
-------
TABLE 9.5.2. SUMMARY OF OPERATING PARAMETERS AND RESULTS
FOR HUBER AER RESEARCH/TRIAL BURNS
Condition
PCBs
(Sept. 1983)
CC14
(May 1984)
Dioxins
(Oct/Nov 1984)
Reactor Core
Temperature (°F)
Waste Feed
Rate (Ib/min)
Nitrogen Feed
Rate (scfm)
Z-DRE
4100
15.5-15.8
147.2
99.99999
3746-4418
1.1-40.8
104.3-190.0
99.9999
3500-4000
0.4-0.6
6-10
99.999
Source: References 24 and 28.
9-48
-------
9.5.3.3 Cost of Treatment—
Operating costs will vary depending on the quantity of material to be
processed and the characteristics of the waste feed. Pretreatment may be
necessary for bulky wastes having a high moisture content. Typical energy
requirements for contaminated soils range from 800 to 1000 kwh/ton.
The Huber process is not cost competitive with standard thermal
destruction techniques (such as the rotary kiln) for materials with a high Btu
23 26
content. ' It is cost-effective for wastes with a low Btu content
(e.g., highly chlorinated compounds) because unlike standard thermal
destruction techniques, the Huber process does not require supplementary fuels
to obtain the necessary Btu content for incineration.
Cost estimates for processing contaminated soil at a site containing more
than 100,000 tons of waste material were approximately £365 to $565/ton in
1985. The cost breakdown for this estimate was 12 percent for maintenance,
7 percent labor, 29 percent energy, 18 percent depreciation and 34 percent for
29 30
other costs (permitting, setup, post-treatment, etc.). ' These costs
have recently been updated. The new costs are expected to be released in
1986.26
9.5.3.4 Status of Tecbnology—
Huber "maintains two fully equipped reactors at their pilot facility in
24"
Borger, Texas. The smaller reactor, which is equipped for mobile
operation, has a 3-inch core diameter and a capacity of 0.5 Ib/min. The larger
reactor is commercial scale with a 12-inch core diameter and a capacity of
50 Ib/min. Both of these reactors are used primarily for research purposes.
In May 1984, the Huber reactor was certified by the EPA under TSCA to burn
PCBs wastes. Recently, the U.S. EPA and the Texas Water Commission jointly
issued J.M. Huber Corporation a RCRA permit which authorizes the incineration
of any non-nuclear RCRA hazardous waste (including dioxin-containing wastes)
31
in the Huber Advanced Electric Reactor. This was the first commercial
permit issued under RCRA for treating dioxin-containing wastes. The
J.M. Huber Corporation intends to use the permit for research and development
of a full-scale transportable AER. Huber does not intend to operate a
hazardous waste disposal operation, but rather to construct and market
stationary and/or mobile units for use by companies or organizations involved
26
in hazardous waste destruction.
3-49 .
-------
9.6 IN SITO VITRIFICATION
In situ vitrification (ISV) was originally developed by Battelle Pacific
Northwest Laboratories as a means of stabilizing in-place high level nuclear
waste. More recently, however, ISV has been studied as a means of destroying
soils contaminated with chlorinated organic wastes, including PCBs and dioxin
wastes, and heavy metals. The system was patented in 1983.
In situ vitrification converts contaminated soils, or sludges, into a
solid glassy matrix through melting by electrical heating. As depicted in
Figure 9.6.1, the process begins when graphite electrodes are placed into the
ground in a square array. A conductive path is established by placing
graphite over the soil between the electrodes. Electrical current is passed
between the electrodes, creating high temperatures (1700°C or 3100°F) which
melt the soil, and pyrolyze the organic waste constituents. Gaseous effluents
which are produced are collected by a hood over the area and are exhausted to
off-gas treatment systems. When pyrolysis is complete, current is shut off
and the mass cools to form a glass-like material. A picture of the system is
presented in Figure 9.6.2, showing the enclosed hood.
Battelle engineers-have developed 30, 500, and 3,750 kw size units. The
small unit produces up to a ton of vitrified mass per setting, the 500 kw unit
produces approximately 10 tons per setting, and the large unit produces 400 to
800 tons per setting.
The cost estimates reported by PNL, and discussed below for transuranic
(TRU) wastes treated by the ISV process, account for charges associated with
site preparation, consumable supplies such as electrical power, and
operational costs such as labor and annual equipment charges.
Specifically, for variations in manpower levels, power source costs, and
degree of heat loss, it was determined that the costs for TRU waste
vitrification ranges from 160 to 360 S/m to vitrify to a depth of
5 meters. These costs are a function of many variables, but are most
sensitive to variations in the amount of moisture in the soil and the cost of
electrical power in the vicinity of the process. Figure 9.6.3, developed by
PNL, illustrates the variation in total costs as a function of both electrical
power costs and the moisture content of the TRU soil which was experimentally
treated. The vertical line represents the value beyond which it is more cost
34
effective to lease a portable generator.
9-50
-------
\o..
Cn I
GRAPHITE
AND FRIT
STARTER
VITRIFIED SOIL/WASTE
Figure 9.6.1. Operating sequence of in situ vitrification.
Source: Reference 32. .
-------
Figure 9.6.2. Off-gas containment and electrode support hood.
Source: Reference 32.
9-52
-------
400
300
s «•
100
I , ' "II
46 8
Qvetrieal fUtw (C/kWh)
. 10
Figure 9.6.3. Cost of in situ vitrification for TRU wastes as functions
of electrical rates and soil moisture [Fitzpatrick, 1984].
.9-53
-------
Recently, PNL has assessed the cost implications for ISV treatment of
three additional waste categories; i.e., industrial sludges and hazardous
waste (PCB) contaminated soils at both high and low moisture contents.
Representatives at PNL indicated that for industrial sludges with moisture
contents of 55 to 75 percent (classified as a slurry), the total costs would
range from $70 to $130/m . Additionally, treatment of high (greater than
25 percent) moisture content hazardous waste-PCB contaminated soil would cost
approximately $150 to. $250/m versus costs of $128 to $230/m for low
(approximately 5 percent) moisture content PCB contaminated soil.
As these recent data and past TRU waste cost data suggest, the moisture
content of the contaminated material treated is particularly important in
influencing treatment costs; high moisture content increases both the energy
and length of time required to treat the contaminated material. Furthermore,
PNL representatives suggest that treatment costs are also influenced by the
degree of off-gas treatment required for a given contaminated material,
i.e., ISV application to hazardous chemical wastes will likely not require as
^
sophisticated an off-gas treatment system as would TRU waste treatment.
PNL has recently assessed the treatment of and costs associated .with
hazardous waste contaminated soils. Specifically, during the summer of 1985,
tests were conducted for the Electric Power Research Institute (EPRI) on PCB
contaminated.soil. While the draft report on these tests has been completed,
it has not been published and/or made available to date. However, an EPRI
project summary publication, dated March 1986, entitled "Proceedings: 1985
EPRI PCB Seminar" (EPRI CS/EA/EL 4480), has recently been made available to
EPRI members. Preliminary results suggest that a destruction/removal
efficiency (DRE) of six to nine nines was achieved from the off-gas treatment
system and that a vitrification depth of 2 feet was achieved. Additional
information will soon be available to the public. PNL expects to continue
with research in the area of hazardous waste soils.
9-54
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2. Breton, M. A., et al. Technical Resource Document: Treatment
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19. Daiga, V. Telephone conversation with M. Kravett, GCA Technology
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24. Schofield, William R., Oscar T. Scott, and John P. DeRany. Advanced
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Rotary Kiln Incinerator. Presented HAZMAT Europa 1985 and HAZMAT
Philadelphia 1985.
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Enforcement, under EPA Contract No. 68-01-6769, Work Assignment No.
84-120. GCA-TR-84-109-GCO). March 1985.
26. Boyd, James. J.M. Huber Corporation. Telephone Conversations with Lisa
Parrel1, GCA Technology Division, Inc. January 28, 1986; April 3, 1986;
May 1, 1986.
27. Horning, A.W., and H. Masters. Rockwell International, Newbury Park,
California. Destruction of PCB-Contaminated Soils With a
High-Temperature Fluid-Wall (HTFW) Reactor. Prepared for U.S. EPA,
Office of Research and Development, Municipal Environmental Research
Laboratory, Cincinnati, Ohio. EPA-600/D-84-072. 1984.
28. Roy F. Weston, Inc. and York Research Consultants. Times Beach,
Missouri: Field Demonstration of the Destruction of Dioxin in
Contaminated Soil Using the J.M. Huber Corporation Advanced Electric
Reactor. February 11,1985.
29. Lee, Kenneth W., William R. Schofield, and D. Scott Lewis. Mobile
Reactor Destroys Toxic Wastes in "Space". Chemical Engineering.
April 2, 1984.
30. Freeman, -Harry M. Hazardous Waste Destruction Processes. Environmental
Progress. Volume 2, Number 4. November 1983.
31. Hazardous Materials Intelligence Report (HMRI). First Commercial Dioxin
Incineration Permit Granted to J.M. Huber. January 24, 1986.
32. Buelt, J. L. and S. T. Freim. Demonstration of In-Situ Vitrification for
Volume Reduction of Zirconia/Lime Sludges. Battelle Northwest
Laboratories. April 1986.
33. Oma, K. H. et al. 1983. In-Situ Vitrification of Transuranic Wastes:
Systems Evaluation and Applications Assessment. PNL-4800, Pacific
Northwest Laboratory, Richland, Washington.
34. Fitzpatrick, V. F., et al. 1984. In Situ Vitrification - A Potential
Remedial Action Technique for Hazardous Wastes. Presented at the 5th
National Conference on Management of Uncontrolled Hazardous Waste Sites,
Washington, DC
35. Buelt, J. L. Battelle Memorial Institute, Pacific Northwest
Laboratories. Telephone conversation with Michael Jasinski. GCA
Technology Division, Inc. 1986.
9.-S7
-------
SECTION 10
LAND DISPOSAL OF RESIDUALS
All treatment processes leave residuals that, at a minimum, must be
characterized to ensure that land disposal is achievable without risk to human
health and the environment.
Even processes such as incineration that are carried out to achieve
essentially total destruction of organic constituents can produce residuals
such as ash and scrubber waters. These residuals can be hazardous; e.g., as a
result of concentration of EP toxicity metals in the ash or POHCs and PICs in
scrubber waters. In such cases, measures such as fixation and encapsulation
may be required for the ash to eliminate the characteristics of EP toxicity
and further treatment (e»g., Carbon adsorption) may be needed to provide an
aqueous stream suitable for discharge. The discussion here will concentrate
on examining the status of solidification and fixation processes and other
techniques designed to isolate and contain wastes within a stable,
non-leachable medium.
As noted in Reference 1, chemical fixation involves the chemical
interaction of the hazardous waste constituents with the fixation medium.
Solidification is a process in which the waste is physically entrapped within
a solid, essentially continuous, nonporous matrix. A third process,
microencapsulation, relies on containment of the waste within a coating or
outer enclosure; e.g. a sealed glass vessel.
Despite the interest shown in immobilization techniques and some
generalizations made concerning their applicability to organic containing
wastes, there are little, if any, data provided in the literature. Most
techniques described must be considered physical processes and few can be
considered to represent chemical fixation. Even if fixation could be
demonstrated, little is known concerning the long term stability of the matrix
-10-1
-------
and the possible breakdown products over time. The processes described below,
will require further study to demonstrate their effectiveness for halogenated
organic wastes. The extent of their future use will depend upon the
regulatory criteria now being established by EPA for fixation/encapsulation
processes.
10.1 SOLIDIFICATION/CHEMICAL FIXATION
Solidification can be used to chemically fix or structurally isolate
halogenated organic wastes to a solid, crystalline, or polymeric matrix. The
resultant monolithic solid mass can then be safely handled, transported, and
disposed of using established methods of landfilling or burial.
Solidification technologies are usually categorized on the basis of the
principal binding media, and include such additives as: cement-based
compounds, lime-based pozzolanic materials, thermoplasts, and organic polymers
(thermosets). The resulting stable matrix produces a material that contains
the waste in a nonleachable form, is nondegradable, and does not render the
land it is disposed in unusable for other purposes. A brief summary of the
compatibility and cost data for selected waste solidification/
stabilization systems is presented in Tables 10.1 and 10.2.
Cement Based Systems
These systems utilize type I Portland cement, water, proprietary
additives, possibly fly ash, and waste sludges to form a monolithic, rock-like
mass. In an EPA publication, several vendors of cement based systems
reported problems with organic wastes containing oils, solvents, and greases
not miscible with an aqueous phase. Although the unreactive organic wastes
become encased in the solids matrix, their presence can retard setting, cause
swelling, and reduce final strength. These systems are most commonly used
to treat inorganic wastes such as incinerator generated wastes and heavy metal
sludges.
10-2
-------
TABLE 10.1. COMPATIBILITY OF SELECTED WASTE CATEGORIES WITH DIFFERENT WASTE
SOLIDIFICATION/STABILIZATION TECHNIQUES
Waste
coaponent
Cement
bsaed
Lime •
baaed
Therao'plaallc
oolldlflcallon
Treatment Typ*
Organic
polyaer
«
Surface
encapsulation
Self-
ceaentlng
techniques
Claaalftcatlon and
aynlhellc mineral
formation
Organlcai
1.
J.
Orgenlc
aolvenla and
olla
Solid organ-
lea (e.g..
plastics.
realne. tare)
Hay Impede
aetllng, may
aacapa aa
vapor
Good --of ten
Increase*
durability
Many Impede aet-
llng. may ascspe
aa vapor
Good — often
Increeaee
durability
Organlca may
vaporise on
heating
foaalble uae aa
binding agent
Hay ratard eel
of polyaara
Hay ratard eel
of polymer*
Huet first be
abaorbad on
aolld matrix
Coapetlble—meny
encapaulatlon
matartala are
plastic
fire danger
on healing
rire danger
on healing
Wsetee decoapoee et
high lemperalurea
Uesles decompose at
high lemperalurea
Inorganics:
1.
I.
1.
4.
S.
4.
Acid waatea
Oxldlaera
Sulfatea
Hal Ida*
Heavy metels
led lose live
•alertale
Cement will
neutral lae
aclda
Compel tbla
Hay retard aet-
tlng and
cauae apalllng
unleaa ipeclal
ceaent la uaed
bally leached
Iroa ceaent,
may ratard
aetllng
Compatible
Coapstlble
Compatible
Coapatlbla
~
Hay retard aat,
moat are
eaatly leached
Compatible
Compatible
Can be neutral-
ised before
Incorporation
Hay cauaa
•atrli break
down, fire
Hay dehydrate
and rehydrale
c cue Ing
apllttlng
Hay dehydrate
Compatible
Compatible
Compatible
Hay cauaa
malrli braak
down
Compatible
Coapa I Idle
Acid pH aolu-
blllsea aetal
hydroaldea
Coapatlbla
Can be aeutrel—
Ised before
Incorporation
May cauae
deterioration
of encapaulat-
Ing aaterlale
Compatible
Coapstlble
Coapa llble
Compatible
May be neu-
tralised to
fora aul-
fate aalta
Compatible If
eulfetee
ere preeant
Compatible
Compatible H
eulfatea
are alao
preaent
Compatible If
aulfete*
ere preaenl
Compatible If
aulfatea
are preaent
Can be neutral laed
and Incorporeted
High leaperaturee
may cauae unde-
able react lone
Compatible In many
cases
Compatible la many
caaea
Compatible In many
caaee
Compatible
•Urea-formaldehyde resin.
Source: Reference 2.
-------
TABLE 10.2. PRESENT AND PROJECTED ECONOMIC CONSIDERATIONS FOR WASTE
SOLIDIFICATION/STABILIZATION SYSTEMS
Type of treatment
system
Cement-based
Pozzolanic
Thermoplastic
(bitumen-based)
Organic polymer
(polyester system)
Surface encapsulation
(polyethylene)
Self-cementing
Class i f icat ion/nine ra 1
synthesis
Major
materials required
Portland Cement
Lime Flyash
Bitumen
Drums
Polyester
Catalyst
• Drums
Polyethylene
Gypsum (fro™ waste)
Feldspar
Unit
cost of
material
i0.03/lb
$0.03/lb
$0.05/lb
*27/drum
$0.45/lb
ll.ll/lb
in/drum
Varies
**
$0.03/lb
Amount of
material required
to treat 100 Ibs
of raw waste
100 Ib
100 Ib
100 Ib
0.8 drum
43 Ib of
polyester-
catalyst mix
Varies
10 Ib
Varies
Cost of
material required
to treat 100 Ibs
of raw waste
$ 3.00
1 3.00
$18.60
$27.70
$ 4.50*
**
— —
Trends in price
Stable
Stable
Keyed to Oil Prices
Keyed to Oil Prices
Keyed to Oil Prices
Stable
Stable
Equipment
costs
Low
Low
Very high
Very high
Very high
Moderate
High
Energy
use
Low
Low
High
High
High
Moderate
Very high
*Based on the full cost of t91/ton.
"Negligible but energy cost for calcining are appreciable.
Source: Reference 2.
-------
Lime Based (Pozzolanic) Techniques
Pozzolanic concrete is the reaction product of fine-grained aluminous
siliceous (pozzolanic) material, calcium (lime), and water. The pozzolanic
materials are wastes themselves and typically consist of fly ash, ground blast
furnace slag, and cement kiln dust. The cementicious product is a bulky and
heavy solid waste used primarily in inorganic waste treatment such as the
solidification of flue gas desulfurization sludge. However, biological and
paint sludges have been treated, although high concentrations (greater
than 20 percent) of organics tend to prevent the formation of a high strength
product.
Thermoplastic Material
In a thermoplastic stabilization process, the waste is dried, heated
(260-450°F), and dispersed through a heated plastic matrix. Principal binding
media include asphalt, bitumen, polypropylene, polyethylene, or sulfur. The
resultant matrix is resistant to leaching and biodegradation, and the rates of
loss to aqueous contacting fluids are significantly lower than those of cement
or lime based systems. However this process is not suited to wastes that act
as solvents for the thermoplastic material. Also there is a risk of fire or
secondary air pollution with wastes that thermally decompose at high
2
temperature.
Organic Polymers (Thermosets)
Thermosets are polymeric materials that crosslink to form an insoluble
mass as a result of chemical reaction between reagents, with catalysts
sometimes used to initiate reaction. Waste constituents could conceivably
enter into the reaction, but most likely will be merely physically entrapped
within the cros si inked matrix. The crossi inked polymer or thermoset will not
soften when heated after undergoing the initial set. Principal binding agents
or reactants for stabilization include ureas, phenolics, epoxides, and
polyesters. Although the thermosetting polymer process has been used most
frequently in the radioactive waste management industry, there are
- 10-5
-------
formulations that may be applicable to certain organic contaminants. It is
important to note that the concept of thermoset stabilization, like
thermoplastic stabilization, does not require that chemical reaction take
place during the solidification process. The waste materials are physically
trapped in an organic resin matrix that, like thermoplastics, may biodegrade
and release much of the waste as a leachate. It is also an organic
material that will thermally decompose if exposed to a fire.
New Technology
An EPA sponsored study recently indicated that most solidification
processes in current use (silicates, lime, and cement), including those
described above, stabilize contaminants through microencapsulation rather than
chemical fixation. Microencapsulation is a process that entraps micro and
macroscopic particles individually as the fixative solidifies. An inorganic
polymer that is a candidate for true chemical fixation is the HWT product
series marketed by International Waste Technologies. The HUT series is a set
of inorganic, irreversible colloidal polymers which improve on a successful
Japanese approach which has been used in Japan for over 10 years.
In the HWT fixation process, there is a two-step reaction in which the
toxic elements and compounds are complexed first in a rapid reaction and then
permanently complexed in the building of macromolecules which continue to grow
over a long period of time. Step one of the detoxification reaction is the
blending of contaminants and HWT chemicals to achieve a homogeneous state so
that all the toxic compounds are exposed. This blending generates
irreversible colloidal structures and ion exchanges with toxic metals and
organics. Step two is the generation of an irreversible, three-dimensional,
macromolecule which provides the crossiinking framework. The vendor claims
that both inorganic and organic wastes are treatable in either concentrated or
dilute form, although pretreatment may be necessary. Table 10.3 shows the
effect of the inorganic polymer on samples of FOB and PGP. The levels of
toxic compounds before and after treatment were determined by EPA approved
laboratory testing. A company spokesman indicated that data on the
effectiveness of HWT on concentrated trichloroethylene still bottoms will be
Q
available in the near future.
10-6
-------
TABLE 10.3. SUMMARY OF TEST RESULTS ON TOXIC ORGANICS
Toxic
organic
PCS
PCP
HWT - 20
weight
percent
15
15
15
15
Concentration
Untreated
1,140
1,800
9,200
11,000
(ug/L)
Treated
0.006
0.069
0.337
450
Source: International Waste Technology.
International Waste Technology has estimated average treatment levels by
HWT compounds run between 8-15 percent by weight of waste with HWT compounds
costing between 12-25«f/lb. The company estimates that heavy metal electric
arc furnace dust could be treated for {319/ton while chemical still bottoms
(halogenated hydrocarbons, benzene compounds, phenols in pure state) would
cost &90-100/ton in materials costs for low volumes of waste. The bases for
these cost estimates are not entirely clear. As a fixant for low molecular
weight organics, it would appear that HWT amounts far greater than 8 to
15 percent by weight of waste would be required. At an assumed level of 50:50
HWT/waste, costs would range from fcl20-250/toh for HWT material with
additional costs required for transportation, processing, and disposal.
10.2 MACROENCAPSULATION
Encapsulation is often used to describe any stabilization process in
which the waste particles are enclosed in a coating or jacket of inert
material. A number of systems are currently available utilizing
polybutadiene, inorganic polymers (potassium silicates), portland cement,
polyethylene, and other resins as macroencapsulation agents for wastes that
have or have not been subjected to prior stabilization processes. Several
different encapsulation schemes have been described in Reference 7. The
resulting products are generally strong encapsulated solids, quite resistant
10-7
-------
to chemical and mechanical stress, and to reaction with water. Wastes
• (nonsolvent) successfully treated by these methods and their costs are
summarized in Tables 10.4.
TABLE 10.4. ESTIMATED COSTS OF ENCAPSULATION
Process Option Estimated Cost
Resin Fusion:
Unconfined waste SllO/dry ton
55-gallon drums $0.45/gal
Resin spray-on Not determined
Plastic Welding $253/ton • $63.40/drum
(80,000 55-gal drums/year)
Source: Reference 7.
•»
These technologies could be considered for stabilizing organic wastes
but are dependent on the compatibility of the' organic waste and the encap-
sulating material. Additional research is needed concerning the interaction
of organic wastes and stabilization materials and the durability of the
matrix, if the safe disposal of wastes and.treatment residuals to be
raaHzed through these processes. EPA is now in the procass of developing
criteria which stabilized/solidified wastes must meet in order to make them
acceptable for land disposal.9
10-8
-------
REFERENCES
1. Breton, M. et al. Technical Resource Document: Treatment Technologies
for Solvent-Containing Wastes. Prepared for U.S. EPA, HWERL, Cincinnati,
OH under Contract No. 68-03-3243, Work Assignment No. 2. August 1986.
2. Guide to the Disposal of Chemically Stabilized and Solidified Waste,
EPA SW-872, Sept. 1980.
3. Environmental Laboratory U.S. Army Engineer Waterways Experiment Station,
Survey of Solidification/Stabilization Technology for Hazardous
Industrial Wastes, EPA-600/2-79-056.
4. McNeese, J. A., Dawson, G. W., and Christensen, D. C., Laboratory studies
of fixation of Kepone contaminated sediments, in "Toxic and Hazardous
Waste Disposal," Vol. 2 Pojasek, R. B., Ed., Ann Arbor Science, Ann Arbor,
Michigan. 1979.
5. Stabilizing Organic Wastes: How Predictable are the Results? Hazardous
Waste Consultant. May 1985 pg. 18.
6. Thompson, D. W., and Malbne, P. G., Jones, L.W., Survey of Available
Stabilization Technology in Toxic and Hazardous Waste Disposal, Vol. 1,
Pojasek, R. B., Ed. Ann Arbor Science, Ann Arbor, Michigan. 1979.
7. Lubowitz, H. R. Management of Hazardous Waste by Unique Encapsulation
Processes. Proceedings of the Seventh Annual Res.earch Symposium.
EPA-600/9-81-002b.
8. Newton, Jeff, International Waste Technology, Personal communication with
Steve Palmer, GCA Technology, Inc. 1986.
9. Wiles, C. Hazardous Waste Engineering Research Laboratory, U.S. EPA,
Private Communication; and Critical Characteristics and Properties of
Hazardous Waste Solidification/Stabilization, HWERL, U.S. EPA, Contract
No. 68-03-3186 (in publication).
10-9
-------
SECTION 11
CONSIDERATIONS FOR SYSTEM SELECTION
Waste management options consist of three basic alternatives: source
reduction, recycling/reuse, and use of a treatment/disposal processing system
or some combination of these waste handling practices (see Figure 11.1).
Recovery, treatment, and disposal may be performed onsite in new or existing
processes or through contract with a licensed offsite firm which is
responsible for the final disposition of the waste. Selection of the optimal
waste management alternative will ultimately be a function of regulatory
compliance and economics, with additional consideration given to factors such
as safety, public and employee acceptance, liability, and uncertainties in
meeting cost and treatment objectives.
Many of the technologies discussed in previous sections can be utilized
to achieve high levels of halogenated organic removal or destruction; however,
practicality will limit application to waste streams possessing specific
characteristics. Since many processes yield large economies of scale, waste
volume will be a primary determinant in system selection. The physical and
chemical nature of the waste stream and pertinent properties of its
constituents, including many of those properties identified in Appendix A,
will also determine the applicability of waste treatment processes. Treatment
will often involve the use of more than one technology in a system designed to
progressively recover or destroy hazardous constituents in the most economical
manner. Incremental costs of hazardous waste constituent removal will
increase rapidly as low concentrations are attained.
11.1 GENERAL APPROACH
All generators of hazardous wastes will be required to undertake certain
steps to characterize regulated waste streams and to identify potential
11-1
-------
WASTE
FEED
Is)
REUSE OF
RECOVERED
PRODUCT
SALE
OF
RECOVERED
PRODUCT
REUSE OR
RECYCLING
SYSTEM
WASTE
GENERATING
PROCESS
SOURCE
REDUCTION
TREATMENT/
DISPOSAL
SYSTEM
N-
IIAZARDOUS
WASTE
DISCHARGE
Figure 11.1. Halogenated organic waste management options.
-------
L
treatment options. Treatment process selection should involve the following
fundamental steps:
1. Characterize the source, flow, and physical/chemical properties of
the waste.
2. Evaluate the potential for source reduction.
3. Evaluate the potential for reuse or sale of recycled halogenated
organics and other valuable waste stream constituents.
4. Identify potential treatment and disposal options based on technical
feasibility of meeting the required extent of waste constituent
removal or destruction. Give consideration to waste stream
residuals and fugitive.emissions to air.
5. Determine the availability of potential options. This includes the
use of offsite services, access to markets for recovered products,
and availability of commercial equipment and existing onsite systems.
6. Estimate total system cost for various options, including costs of
residual treatment and/or disposal and value of recovered organic
product. Cost will be a function of items 1 through 5.
7. Screen candidate management options based on preliminary cost
estimates. . . '
8. Use mathematical process modeling techniques and lab/pilot scale
testing as needed to generate detailed treatment system design
characteristics and processing capabilities. The latter will define
product and residual properties and identify need for additional
treatment.
9. Perform process trials of recovered product in its anticipated end
use applications or determine marketability based on projected
stream characteristics.
10. Perform a detailed cost analysis based on modeling and performance
results.
11. Final system selection based on relative cost and other
considerations; e.g., safety, acceptance, liability, and risks
. associated with data uncertainties.
Key system selection steps are discussed in more detail below.
11-3
-------
11.2 ASSESSMENT OF ALTERNATIVES
Waste Characterization
The first step in identifying appropriate waste management alternatives
to land disposal involves characterizing the origin, flow, and quality of
generated wastes.. An understanding of the processing or operational practices
which result in generation of the waste forms the basis for evaluating waste
minimization options. Waste flow characteristics include quantity and rate.
Waste quantity has a direct impact on unit treatment costs due to economies of
scale in both treatment costs and marketability of recovered products. Flow
rate can be continuous, periodic, or incidental (e.g., spills) and can be
relatively constant or variable. This will have a direct impact on storage
requirements and treatment process design; e.g., continuous or batch flow.
Waste physical and chemical characteristics are generally the primary
determinant of waste management process selection for significant volume
wastes. Of particular concern is whether the waste is pumpable, inorganic or
organic, and whether it contains recoverable materials, interfering compounds
or constituents which may foul heat or mass transfer surfaces. Waste
properties such as corrosivity, reactivity, ignitability, heating value,
viscosity, concentrations of specific chemical constituents, biological and
chemical oxygen demand, and solids, oil, grease, metals and ash content need
to be determined.to evaluate applicability of certain treatment processes.
Individual constituent properties such as solubility, vapor pressure, partition
coefficients, thermal stability, reactivity with various biological and
chemical (e.g., oxidants and reductants) reagents, and adsorption coefficients
are similarly required to assess treatability. Finally, variability in waste
stream characteristics will necessitate overly conservative treatment process
design and additional process controls. Variability will adversely affect
processing economics and marketability of recovered products.
Source Reduction Potential
Source reduction potential is highly site specific, reflecting the
diversity of industrial waste generating processes and product requirements.
Source reduction alternatives which should be investigated include raw
11-4
-------
material substitution, product reformulation, process redesign and waste
' segregation. The latter may result in additional handling and storage
requirements, while differential processing cost and impact on product quality
may be more important considerations for the other alternatives. Source
reduction should be considered a highly desirable waste management
alternative. In the wake of increasing waste disposal and liability costs, it
has repeatedly proven to be cost effective while at the same time providing
for minimal adverse health and environmental impact.
Recycling Potential
As part of the waste characterization step, the presence of potentially
valuable waste constituents should be determined. Economic benefits from
recovery and isolation of these materials may result if they can be reused in
onsite applications or marketed as saleable products. In the former case,
economic benefits result from decreased consumption of virgin raw materials.
This must be balanced against possible adverse effects on process equipment or
product quality resulting from buildup or presence of undesirable
> '
contaminants. Market potential is limited by the lower value of available
quantity or demand. Market potential will be enhanced with improved product
purity, availability, quantity, and consistency.
Identifying Potential Treatment and Disposal Options
Following an assessment of the potential for source reduction and
recycling, the generator should evaluate treatment systems which are
technically capable of meeting the necessary degree of halogenated organic
removal or destruction. Guideline considerations for the investigation of
treatment technologies are summarized in Table 11.1. The treatment objectives
for a waste stream at a given stage of treatment will define the universe of
candidate technologies. Possible restrictive waste characteristics
(e.g., concentration range, flow, interfering compounds) may further reduce
the number of candidate technologies. Consideration must be given to
pretreatment options, for eliminating restrictive waste characteristics, to
-11-5
-------
TABLE 11.1. GUIDELINE CONSIDERATIONS FOR THE INVESTIGATION OF
WASTE TREATMENT TECHNOLOGIES
A. Objectives of Treatment;
Primary function (pretreatment, treatment, residuals treatment)
Primary mechanisms (destruction, removal, conversion, separation)
Recover waste for reuse (fuel, process feed)
- Recovery of specific chemicals, group of chemicals
Polishing for effluent discharge
Immobilization or encapsulation to reduce migration
- Overall volume reduction of waste
Selective concentration of hazardous constituents
- Detoxification of hazardous constituents
B. Waste Applicability and Restrictive Waste Characteristics;
- Acceptable concentration range of primary & restrictive waste
constituents
- Acceptable range in flow parameters
Chemical and physical interferences
C. Process Operation and Design;
-• Batch versus continuous process design
Fixed versus mobile process design
' - Equipment design and process control complexity
- Variability in system designs and applicability
Spatial requirements or restrictions
- Estimated operation time (equipment down-time)
Feed mechanisms (wastes and reagents; solids, liquids, sludges,
slurries)
Specific operating temperature and pressure
Sensitivity to fluctuations in feed characteristics
- Residuals removal mechanisms
- Reagent requirements
- Ancillary equipment requirements (tanks, pumps, piping, heat
transfer equipment)
- Utility requirements (electricity, fuel and cooling, process and
make-up water)
D. Reactions and Theoretical Considerations;
Waste/reagent reaction (destruction, conversion, oxidation,
reduction)
Competition or suppressive reactions
- Enhancing conditions (specify chemicals)
- Fluid mechanics limitations (mass, heat transfer)
- Reaction kinetics (temperature and pressure effects)
Reactions thermodynamics (endothermic/exothermic/catalytic)
(continued)
11-6
-------
TABLE 11.1 (continued)
E. Process Efficiency:
- Anticipated overall process efficiency
- Sensitivity of process efficiency to:
feed concentration fluctuations
reagent concentration fluctuations
process temperature fluctuations
process pressure fluctuations
toxic constituents (biosysterns)
physical form of the waste
other waste characteristics
- Acceptable range of fluctuations
F. Emissions and Residuals Management;
- Extent of fugitive and process emissions and potential sources
(processing equipment, storage, handling)
- Ability (and frequency) of equipment to be "enclosed"
- Availability of emissions data/risk calculations
- Products of incomplete reaction
- Relationship of process efficiency to emission data
Air pollution control device requirements
- Process residuals (cooling and scrubber water, bottom ash, fly ash,
fugitive/.residual reagents, recovered products, filter cakes,
sludges)
- Residual constituent concentrations and leachability
- Delisting potential
G. Safety Considerations;
Safety of storing and handling wastes, reagents, products and
residuals
Special materials of construction for storage and process equipment
- Frequency and need for use of personnel protection equipment
- Requirements for extensive operator training
- Hazardous emissions of wastes or reagents
- Minimization of operator contact with wastes or reagents
- Frequency of maintenance of equipment containing hazardous materials
- High operating temperatures or pressures
- Difficult to control temperatures or pressures
Resistance to flows or residuals buildup
- Dangerously reactive wastes/reagents
- Dangerously volatile wastes/reagents
11-7
-------
required treatment of process emissions and residuals, and to opportunities
• for by-product recovery. System design will be based on the most difficult
compound to remove or destroy.
A number of approaches to selecting potential treatment technologies for
halogenated solvent and halogenated organic waste streams have been
proposed . Many of these references also provide cost information to
assist the user in making a final determination of the cost effectiveness of a
process. The distinction between halogenated solvents and other halogenated
organics as related to the applicability of recovery/treatment processes is
obscure in many cases. Physical and chemical properties can exhibit a high
degree of similarity and both solvent and nonsolvent compounds coexist as
significant constituents of many specific waste streams, including many of the
K type wastes included in the halogenated organic category. One scheme that
specifically addresses the management of solvent bearing wastes is also
directly applicable to nonsolvent halogens. In the Reference 3 scheme,
management alternatives, including recycle/reuse, destructive treatments such
as those resulting from thermal oxidations, and treatments for the removal of
solvent constituents prior to land disposal, are reviewed. The reference .
%
discusses the applicability of these waste management alternatives to waste
streams having various physical characteristics. Several waste treatment
techniques are described including incineration, agitated thin film
evaporation, fractional distillation, steam stripping, wet oxidation, carbon
adsorption, and activated sludge biological treatment.
• For the purposes of discussing treatment approaches, wastes can be
divided into three broad categories: 1) aqueous and mixed aqueous/organic
liquids, 2) organic liquids, and 3) sludges. As defined, aqueous streams
have water contents of 95 percent or higher, while organic streams are
described as containing 50 percent or more organic liquids. Mixed
aqueous/organic streams fall in between. Sludges are streams with solids
.content greater than 2 percent. Decision charts for aqueous and mixed
aqueous/organic liquids and for organic liquid waste stream treatment are
provided in Figures 11.2 and 11.3. Discussion of these charts in Reference 3
identifies some possible treatment options and stresses the importance of the
possible need for treatment of residuals.
11-8
-------
SLUDGE
SLUDGE
TREATMENT
AND/OR
DISPOSAL
SLUDGE
OFFCASCS
AMD OVERHEAD
SLUDGE
AQUEOUS OR
KIJCED HASTE
YES
PHYSICAL
SEPARATION
ORGANIC
FRACTION
AQUEOUS
FRACTION
PRELIMINARY
TREATMENT
AQUEOUS
STREAM
ORCANICS
TRAHSFORMAIIO
OR REMOVAL
TRANSFORMATION
OFFGASES
6 SLUDGES
REMOVAL
ORGANIC
COMPONENT
SEPARATION
AQUEOUS
STREAM
AQUEOUS
STREAM
- POLISHING
TREATED AQUEOUS
STREAM
Figure 11.2. Simplified decision chart for aqueous and mixed aqueous/organic
waste stream treatment.
Source: Reference 3.
11-9
-------
ASH
INCINERATE
INCINERATE
INCINERATE
ORGANIC
RESIDUE
ORGANIC
LIQUID WASTE '
REUSE OR
INCINERATE
AS IS?
GROSS
SOLIDS
REMOVAL
NEEDED?
REUSE
OR
INCINERATE?
ORCANICS
SEPARATION
REQUIRED?
COMPONENT
SEPARATION
AQUEOUS OR
SLUDGE STREAM
TREATMENT
AND/OR
DISPOSAL
REUSE
PHYSICAL
SEPARATION
ORCANICS
SLUDGE
SLUDGE
TREATMENT
AND/OR DISPOSAL
REUSE
ORGANIC PRODUCT
Figure 11.3. Simplified decision chart for organic liquid
waste stream treatment.
Source: Reference 3.
11-10
-------
The treatment processes potentially applicable to the three broad
categories of waste are shown in Table 11.2. The identification of potentially
applicable treatment processes should be considered as tentative since the
treatments used will depend upon specific waste stream characteristics (not
fully defined by the three general waste categories) and the purpose of the
treatment. In addition, other innovative and emerging technologies described
in previous sections of this document (or in the solvent and dioxin TRDs) could
also be considered as applicable processes for some of these waste categories.
In addition to physical form, concentration of organic constituents
within the waste is a principal determinant in assessing the applicability of
a treatment process. Concentration ranges for which treatment processes are
generally applicable are shown in Figure 11.4. Generally, techniques used for
wastes with organic concentrations over 10 percent are applicable to lower
concentrations as well, but other processes are generally more economical.
Other waste characteristics which affect process selection are waste
viscosity, solids content, volatility, solubility and contaminant type.
Viscosity is important in that it indicates whether the waste stream is
sufficiently fluid to undergo treatment. If not, high temperature to improve
flow properties or treatment such as incineration in a kiln may be required.
The presence of excess solids can cause plugging of certain equipment
(e.g., packed towers) and necessitate solids removal prior to treatment.
Dissolved solids may also require removal if they precipitate or otherwise
interfere with process performance. Solubility and volatility are indicators
of the ease of removal of a volatile compound by processes such as
distillation or stripping. Finally, the type of contaminant will play a role
in process selection. Certain types of compounds may be susceptible to
reaction and degradation, and may, as in the case of many halogens, produce
.corrosive byproducts and be inherently low in Btu value.
As discussed previously, halogen content is a major factor in determining
the extent to which an organic compound can be reacted or destroyed. Halogen
contents of nonsolvent halogensted organics are listed in Table 2.2. The
extent of halogenation will affect many of the key physical and chemical
properties of the halogen compounds (see Appendix A), and thereby, determine
the relative ease.and practicality of thermal destruction, biodegradability,
dehalogenation, and other approaches to chemical detoxification and
destruction.
11-11
-------
TABLE 11.2. TREATMENT PROCESSES POTENTIALLY APPLICABLE TO HALOGENATED WASTES
Aqueous and
mixed aqueous/
Process organic wastes
Preliminary Treatment
pH adjustment
Dissolved solids precipitation
Phase Separation
Solids removal
Drying
Organic f ract ion
Organic Component Separation
Steam stripping
Carbon adsorption
Fractional distillation
Resin adsorption
Solvent extraction
Organic Compound Destruction
Incineration
Biological degradation
Chemical oxidation
Wet air oxidation
Supercritical water
Supercritical water oxidation
Stabilization/Solidification
Y
Y
Y
NA
Y
Y
Y
Y
Y -,
Y
Y
Y
"Y
Y
Y
, Y
NA
Organic
wastes
NA
NA
Y
Y
Y
Y
NA
Y
Y
Y
Y
NA
NA
NA
NA
NA
NA
Sludges
NA
NA
NA
Y
Y
Y
NA
Y
NA •
Y
Y
NA
NA
Y
NA
NA
Y
Y = Yes
NA = Generally not applicable.
Source: Adapted from Reference 3.
il-12
-------
Fractional Distillation
Chtmlcal Oildatlon
1
Steam Stripping
Incineration
Solvent Extraction
Air Stripping
-f-
I 1
Risln Adsorption
1
Carbon
Adsorp
tlon
0*on«/UV Radiation
LEOEND
• ; COMMERCIALLY APPLIED
POTENTIAL EXTENSION
Wet Air Oildollon
1-^ 1
Supercritical Water
I
Drying
H
Thin Film Evaporation
I 1 I
0.01
0.05 0.1
10
0.5 1.0 5
INITIAL % ORQANICS
Figure 11.4. Approximate ranges of applicability of treatment techniques as a
function of organic concentration in liquid waste streams.
Source: Reference 12.
90
100
-------
The general susceptibility of halogenated solvents to biological,
chemical, and thermal treatment has been summarized in Reference 12. As noted
therein, other researchers have provided similar qualitative assessments of
the applicability of treatment processes for specific compounds.
Reference 11, for example, provides a numerical rating assessing the
applicability of many of the waste treatment processes considered here to
various W-E-T model streams and their constituents. Although this rating
system was developed for assessing the treatment of volatile components within
the waste stream, it contains information concerning the treatability of many
of the nonsolvent halogenated organics addressed in this TRD.
The volativity of solvent and nonsolvent halogenated organics is often a
key distinction between these two categories of halogenated compounds.
Although volatilities (and other properties) are similar for many halogens,
the nonsolvent category contains many high molecular weight compounds,
(e.g., most of the pesticides) which exist as solids at 25°C. Many of these
will not be amenable'.to recovery by distillation and similar processes or will
appear as constituents of the bottoms product resulting from such processing
operations. In many cases, further recovery may not be possible because of
volatility or thermal stability considerations-and ultimate disposal by
incineration may be required. Solidification/encapsulation may be another
disposal option for such residuals.
The advantages and limitations of the treatment processes discussed in
this document are summarized in Table 11.3; Incineration and other thermal
destruction processes are discussed first in the table because of their
general applicability to the treatment of halogenated organic wastes. As
noted by Blaney and others, incineration may well prove to be the ultimate
disposal method, at least for sludges for which halogenated organic recovery
is impractical. Incineration will also be the major method used to dispose of
still bottoms following recovery operations. However, the extent to which
incineration will be used for these difficult to treat wastes will depend to
some extent on the technical and regulatory requirements that will be imposed
on performance of solidification/stabilization technologies.
Some of the technologies discussed in Table 11.3 are not generally
intended to be used as final treatment processes. Agitated thin film
evaporation and distillation, for example, are concerned primarily with
11-14
-------
TABLE 11.3. SUMMARY OF HALOGENATED ORGANIC TREATMENT PROCESSES
Process
Inc i nerat ion
Liquid' injection
incineration
Rotary kiln
incineration
FluldUed bed
Incineration
Fixed/multiple
hearths
Applicable waate streams
All punpable llqulda
provided wastes can be
blended to Btu level of
8500 Btu/lb. Some solids
removal may be neceaaary
to avoid plugging noulea.
All waatea provided Btu ,
level la Maintained.
Liquids or nonbulky
solids.
Can handle a wide
variety of waatea.
Stage of development
Estimated that over 219
unlta are in uae. Moat
widely used Incineration
technology.
Over 40 unlta in aervlce;
•oat veraatile for waate
destruction.
Nine unlta reportedly
in operat lon~clrculat Ing
bed unlta under
development.
Approximately 70 unita
in uae. Old technology
Performance
Excellent deatructlon
efficiency (>99.99X).
Blending can avoid
probleraa aaaociated
with residuals, e.g., IIC1.
Excellent deatructlon
efficiency (>99.99I).
Excellent destruction
efficiency (>99.99Z).
Performance nay be
marginal for halogenated
Reaiduals generated
ISt, poaaibly some PICs,
and HCI. Little ash if
solids removed in pre-
treatment processes.
equirea APCUa. Process
esiduals ahould be accep~
able If charged properly
nd treated for acid gaa
• emoval.
Aa above.
As above.
Industrial kilns
Generally all. wastes, but
Btu level, chlorine content,
and other impurity content
nay require blending to
control charge characteristics
and product quality.
for Municipal waste '
conbuation*
Only a few unita now
burning hazardous waste*
Usually excellent
destruction efficiency
(>99.99X) because of
long residence tinea and
high temperatures.
As above.
Other Thermal Technologies
Circulating bed
conbuator
Molten glaaa
Incineration
Molten Halt
de s t rue t i on
Liquids or nonbulky
solids.
Almost all wastes, provided
Moisture and metal impurity
levels are within
limitations.
Not suitable for high
(>20X) ash content
wastea.
Only one U.S. manufac-
turer. No unlta treating
hazardous waate.
Technology developed
for glass manufacturing
Not available yet aa a
haxardoua waate unit,,
Technology under develop-
ment a ince 1 969 but
further development on
hold.
Manufacturer reports
high efficlenciea
(>99.99Z).
No performance 'data
available, but DREs
ahould be high
(>99.99I).
Very high destruction
ef f ic ienc ies for
organica (six nines
for PCBa).
Bed material additives
can reduce HCI emissions.
Residuals ahould be
acceptable.
pill need APC device fur HCI
and possibly PICs; solids
retained (encapsulated) in
molten glass. '
Needs some APC devices
retained in salt.
(continued)
-------
TABLE 11.3 (continued)
trace**
Applicable waste itreaiu
Stage of development
Performance
Residuals generated
Furnace pyrolyals • Most designs suitable
units for ill waatet.
Plasma arc
pyrolyalt
Fluid wall
advanced
electric
reactor
In altu
vitrification
Present dealgn suitable
only for liquids.
Suitable for all wastes
• If sotlda pretreated to
enaure free flow.
Technique for treating
contaminated soils, could
possibly be extended to
slurries. Alao uae aa
solidification process.
Physical Treatment Methods
Distillation
Evaporation
Steam Stripping
Liquid-Liquid
Extraction
This la a process used to
recover and sepsrste volatile
organics. Fractional distil-
lation will require solids
removal to avoid plugging
columns.
Agitated thin fllsj units
can tolerate higher levels
of solids and higher
viscosities than other
types of stills.
A simple distillation
process to remove volatile
organics from aqueous solu-
tions. Preferred for tow
concentrations and organics
with low solubilities.
Generally suitable only for
liquids of low solid content.
One pyrolysls unit RCRA
permitted. Certain
designs available
commercially.
Commercial design appears
itamlnent, with future
modifications planned
for treatment of sludges
and solids.
Ready for commercial
development. Teat unit •
permitted under RCRA.
Mot commercial, further
work planned.
Technology well developed
and equipment available
from many suppliers;
widely practiced technology.
Technology Is well developed
snd equipment Is
available from several
suppliers; widely
practices technology.
Technology well developed
snd available.
Technology well developed
for industrial processing.
Very high destruction
efficiencies possible
(>99.99Z). Possibility
of PIC formation.
Efficiencies exceeded
six nines In tests with
solvents.
Efficiencies have
exceeded alx nines.
No data available, but
DRBa of over six nines
reported.
Separation depends upon
reflux (99* percent
achievable). This is
a recovery process.
This Is a volatile orgsnlc
recovery process.
Typical recovery of
60 to 70 percent.
Not generally considered
a final treatment, but
can achieve low residual
organic levels.
Can achieve high efficiency
separations for certain
organic/waste combinations.
TSP emissions lower than those
from conventional combustion;
will need APC devices for IIC1.
Certain wastes may produce ah
unacceptable tarry residual.
Requires APC devices for
HCP and TSP, needs flare
for II2 and CO
destruction.
Requires APC devices for
TSP and HC1.
Off gas system needed
to control emissions
to air. Aah contained
In vitrified soil.
Bottoms will usually contain
levels of volatlles in excess
of 1,000 ppm; condenaate
may require further treatment*
Bottoms will contain
volatiles. Generally
suitsble for incineration.
Aqueous treated stream
will probably require
•polishing. Further
concentration of over-
head stesm generally
required.
Organic compound solubility
In aqueous phase should
be monitored.
(continued)
-------
TABLE 11.3 (continued)
Process
Applicable waste stressis
Stage of development
Performance
Residuals genersted
Csrbon Adsorption
Resin Adsorption
Suitable for low solid,
low concentration
aqueous waste streams.
Suitable for low solid
waste streams. Consider
for recovery of valuable
compounds.
Chemical Treatment Proceaaea
Wet «lr
oxidation
Supercritical
water oxidation
UV/Osonatlon
I Dechlorlnation
Suitable for aqueoue
liquid., al.o possible
for alurrlea. Organic
concentrationa up to 15X.
For liquid* and alurrlea
containing optimal
concentration, of about
IDS organic*.
Oxidation with oxone
(a*alated by UV)
•uitable for low aolld,
dilute aqueou* aolutlone.
Dry .oil. and «ollda.
Biologies! Treatment Method*
Aerobic technology aultable
for dilute waetea although
aone conatltuent* will be
resistant.
Technology well developed;
used as polishing treatment.
Technology well developed
In industry for special
realn/organtc compound
combinat Ions. Appl icabi ll.ty
to waste atreams not demon-
strated.
High temperature/
preaaure technology,
widely uied a* pretreatment
for municipal sludges, only
one manufacturer*
Supercritical condition*
•*y Impose demand* on
•y*tem reliability.
Commercially available
In 1986.
Now uaed a. a pollahlng
atep for w**tewatera.
Not fully developed*
Conventional treatment*
have been uied for yeara.
Can achieve low levels of
organica in effluent.
Can achieve low levels 6f
organics in effluent.
Pretreatment for
biological treatme
Some compound*
reliit oxlditlon.
Supercritical condition*
achieve high deatructlon
efficiencies (>99.99Z)
for all constituent!.
Not likely to ichleve
reildual level* In
the low ppm range for
moat waate*.
Destruction efficiency
of over 99X reported
for dloxio.
Nay be u*ed a* final
treatment for apeciflc
unite*, may be pretreat-
ment for reslstsnt *pecle*.
Adsorbate must be
processed during
regeneration. Spent
carbon and wastewater
nay also, need treatment.
Adsorbste oust be
processed during
regeneration.
Some residues likely which
need further treatment.
Residuals not likely to
be • problem. Halogen*
can be neutralised in
process.
Residual contamination
likely; will require
additional processing of
off gases.
Residu*! contamination
•eema likely.
Realdual contamination
likely; will usu.lly
•require additional
processing.
-------
recovery/reuse. Others like wet air oxidation and liquid-liquid extraction
are pretreatment processes than can be used to make a waste amenable to a
finishing step such as biological treatment.
Ultimately, the selection of a specific treatment system from the list of
potentially applicable processes will depend on cost, availability, and site
specific factors. These considerations are discussed below.
Management System Cost Estimation
The relative economic viability of candidate waste management systems
will be the primary determinant of ultimate system selection. This must be
evaluated on the basis of total system costs which includes the availability
of onsite equipment, labor and utilities, net value of recovered products and
treatment/disposal processing costs. Costs for a given management system will
also be highly dependent on waste physical, chemical, and flow
characteristics. Thus, real costs are very site specific and limit the
usefulness of generalizations. The reader is referred to the sections on
specific technologies for data on costs and their variability with respect to
flow and waste characteristics. Major cost centers which should be considered
are summarized in Table 11.4.
Modeling System Performance and Pilot Scale Testing
Following a preliminary cost evaluation which will enable the generator
to narrow his choice of waste management options, steps must be taken to
further finalize the selection process. These could involve the use of
mathematical models to predict design and operating requirements. However,
models often sacrifice accuracy for convenience and are not always adequate
for complex waste streams. Laboratory data, or pilot plant and full-scale
data, may ultimately be needed to confirm predicted performance. In fact,
some data may be needed as model inputs for predicting system behavior.
Processes which rely on Henry's Law constant are a good example of the
need for experimentally documented data. Removal efficiency approximations
using Henry's Law constant based on a ratio of pure compound vapor pressure to
-------
TABLE 11.4. MAJOR COST CENTERS FOR WASTE MANAGEMENT ALTERNATIVES
A. Credits
Material /energy recovery resulting in decreased consumption of
purchased raw materials
- Sales of waste products
B. Capital Costs*
- Processing equipment
Ancillary equipment (storage tanks, pumps, piping)
Pollution control equipment
Vehicles
Buildings, land
Site preparation, installation, start-up
C. Operating and Maintenance Costs
- Overhead, operating, and maintenance labor
- Maintenance materials
Utilities (electricity, fuel, water)
- Reagent materials
- Disposal, off site recovery and waste brokering fees
- Transportation
- Taxes, insurance, regulatory compliance, and administration
D. Indirect Costs and Benefits
Impacts on other facility operations; e.g., changes in product
quality as a result of source reduction or use of recycled materials
- Use of processing equipment for mangement of other wastes
*Annual costs derived by using a capital factor:
CRF-
Where: i » interest rate and n = life of the investment. A CRF of 0.177 was
used to prepare cost estimates in this document. This corresponds to
an annual interest rate of 12 percent and an equipment life of
10 years.
11-19
-------
its solubility often overestimate stripping by as much as two orders of
2
magnitude. However, if Henry's Law constant is obtained experimentally
using headspace analysis and batch stripping methods, it can be effectively
used to estimate equilibrium partitioning behavior.
Many models are useful for predicting constituent behavior in separation
processes. These models are based on thermodynamic equilibrium partitioning
and may also include kinetic factors to establish separation performances.
Perry's Chemical Engineers' Handbook and other Chemical Engineering textbooks
are sources of information about such models. Standard analytical
packages are also available to predict the fate of waste stream contaminants
as they are exposed to unit operations such as stripping and distillation.
The need for experimental data will depend upon the complexity of waste
stream/process interactions. Equipment manufacturers are often able to
provide experimental equipment and models to establish process parameters and
cost, including the costs required for disposal of residuals.
11-20
-------
REFERENCES
1. Allen, C. C., and B. L. Blaney. Techniques for Treating Hazardous Waste
to Remove Volatile Organic Constituents. Research Triangle Institute for
EPA HWERL. EPA-600/2-85-127 PB85-218782/REB. March 1985.
2. Allen, C. C., and B. L. Blaney. Techniques for Treating Hazardous Waste
to Remove Volatile Organic Constituents. JAPCA, Vol. 35-, No. 8.
August 1985.
3. Blaney, B. L. Alternative Techniques for Managing Solvent Wastes.
Journal of the Air Pollution Control Association, 36(3): 275-285.
March 1986.
4. Ehrenfeld, J., and J. Bass, Arthur D. Little, Inc. Evaluation of
Remedial Action Unit Operations at Hazardous Waste Disposal Sites.
Cambridge, MA, Noyes Publication.
5. Bee, R.W., et al. The Aerospace Corporation. Evaluation of Disposal
Concepts for Used Solvents at DOD Bases. Report No. TDR-0083(3786)-01.
February 1983.
6. U. S. EPA Technologies and Management Strategies for Hazardous Waste
Control. U. S. EPA Office of Technology Assessment. 1983.
7. U. S. EPA Superfund Strategy. OTA-ITE-252, U. S. EPA Office of
Technology Assessment. April 1985.
8. White, R. E., Busman, T., and J. J. Cudahy, et al.,IT Enviroscience, Inc.
New Jersey Industrial Waste Study (Waste Projection and Treatment).
Knoxville, TN. EPA/600/6-85/003. May 1985.
9. Michigan Department of Commerce. Hazardous Waste Management in the Great
Lakes: Opportunities for Economic Development and Resource Recovery.
September 1982.
10. Spivey, J. J. et al., Research Triangle Institute. Preliminary
Assessment of Hazardous Waste Pretreatment as an Air Pollution Control
Technique. U. S. EPA/IERL. 15 March 1984.
11. Engineering-Science. Supplemental Report on the Technical Assessment of
Treatment Alternatives for Waste Solvents. Washington, D. C.: U. S.
Environmental Protection Agency. 1985.
T.l-21
-------
12. Breton, M., et al. Technical Resource Document: Treatment Technologies
for Solvent-Bearing Wastes. Report prepared for U.S. EPA, HWERL,
Cincinnati, OH under Contract No. 68-03-3243, Work Assignment No. 2.
August 1986.
13. Arienti, M., et al. Technical Resource Document: Treatment Technologies
for Dioxin-Containing Wastes. Report prepared for U.S. EPA, HWERL,
Cincinnati, OH under Contract No. 68-03-3243, Work Assignment No. 2.
August 1986.
14. Perry, J. H., et al. Chemical Engineers' Handbook. Sixth Edition, McGraw
Hill. 1984.
15. Henley, E., and J. D. Seader. Equilibrium-Stage Separation Operations in
Chemical Engineering, John Wiley and Sons, Inc., New York. 1981.
16. McCabe, W. L., and J. C. Smith. Unit Operations of Chemical Engineering
(Third Edition), McGraw-Hill Book Company, New York, 1979.
17. Treybal, R. E. Liquid Extraction, Second Edition, McGraw-Hill Book
Company, New York, 1963, pp 359, 376.
18. Holland, C. D. Fundamentals and Modeling of Separation Processes,
Prentice Hll, New York. 1975.
11-22
-------
APPENDIX A
CHEMICAL AND PHYSICAL PROPERTIES
OF HALOGENATED ORGANIC COMPOUNDS
-------
TABLE A-l. CHEMICAL AND PHYSICAL PROPERTIES OP HALOGENATED ORGANIC COMPOUNDS3
Compound
«. IIALOCCNAtED AUMUTICS
Alaanaa
HathyUna chlorlda
1,1, 1-trlchloroatbant
Carbon tatrachlorlda
I,l,2-lrlchloro-l,2,2-trllluoro>thant
TrlchlorofluoroMthana
chloroform
Halhylana bro.ld.
Methyl chlarlda
if
A llaiachloroalhana
l,2,)-trlchloropropaua
1,2-dlchloroathant
1,1,2-trichloroathana
1,1,2,2-Utrachloroatbana
1,1,1,2-tatrachloroathana
IrlchloroTClhaoalblol
Molacular
CAS Ho. forawta
73-09-2 CBjOlj
71-33-6 CjHjClj
56-23-5 CC14
76-13-1 CjCljfj
73-69-4 CClJf
67-66-3 CHClj
74-93-) CHj8r2
74-87-3 CHjCl
67-72-1 CjClj
96-18-4 CjMjClj
107-06-2 C,H4Cla
79-00-3 CjljClj
79-34-3 CjH,CI4
6)0-18-4 CjHjCl^
CHCljS
Nailing
Holaciilar point
•light CO
84.9
133.4
1)3.8
187.4
137.4
119.4
173.9
30.3
237
147.4
99
133.4
167. •
167. 8
131.3
-93
-30.4
-22.9
-34.4
-111
-64
-32.7
-97.7
187
(aubl.)
-14
-33
-13
-43
-70
•oiling Vapor
point praaaura
1 740 lorr 1 20-23'Ck
CO (lorr)
39.8
74.1
76.8
48
23. a
' 62
97
-24
187
(aubl.)
136
84
113.7
144
IM
362. «
96.0
89.55
270
667.4
160
40
3,800
0.4
2
M
19
5
• 13.9
Vapor
denallr
(alr-1)
2.9
4.6
5.3
6.5
4.7
4.12
6.03
1.8
8.2
5.0
3.35
4.6
5.8
Liquid
denaltt
1.3)»
l.)4»
1.39"
1.56»
1.49"
1.49
2.5
0.99l-JJ
,.0,20/4
1.42»'«
l.232«/«
1.4«'0/4
• 1.60»0/4
1.60
Solubility
In iratar
(•g/1)
20.000"
930"
7esl°
10"
1.100"
a, ooo
11.7"
4,000 cc/l
(vapor)
30"
213
8,000
4,300
2,900
2)6
Log
octanol
vatar
partition
coelf Iclani
1.23
2.17
2.64
2.00
2.3)
1.97
0.91
3.34
1.3
2.17
2.56
1.0
Haorv'a Lav
conalaal
3.19 •
4.92 i
3.01 •
4.) I
3.8) •
3.39 •
8.14 •
4.83 I
2.8 •
1.35 i
7.42 >
3.8 •
1.) •
10-1
10-1
10-1
W-2
10-2
10-1
10-1
10-1
10-1
10-1
•o-«
io-«
10-2
(eontlotitd)
-------
TABLE A-l (continued)
Compound
Huhyl lironldt
l.l-ditro»»-)-chloroprop»*
?.,,0/»
0.94
0.94
I.I?
1.44
I.Mll'H
0.41"'*
Soluhllltt
in water
900><>
i.ooo"
4,)00J°
mo"
l,100Jn
1.700*°
14*°
11
'•'"""
100
5II.MI.
1,700
I1O
1,000
,10
l.ioo"
octanol
water Ntnrv't Law
partition cnnttant
I.I 1.1 • 10-'
1.0 1.41 > 10-*
,.„ . ,n-»
1.1* • 1.**
1.74 1.4 i I"*"
l.ll 1." » IP*'
).7 1.1 • in-J
l.JO 1.1 . |0-*
l.«l J.n > in-'
-.71 1.17 « in-'
1.74 1.01 • in*'
0.* 1.6 • in*-
(continued)
-------
TABLE A-l (continued)
CAS No. fornuU
•oil UR Vapor
Kelt Ing point prcaiur* Vapor Liquid
Holrcul.tr point • 160 (orr * IO-f$*Cb oVnaltv demit?
wvljtht CD CO (lorr) (air-1) (*/•!>
Lot
octane)
Solubility wmt9T flenrv'c Law
In wattr pertltlnn conttant
Uft/l) coefflcUnt Ut*r-n»V«ol«>V
Vlnflld«n* chlorld*
1,4-d.ehloeo-J-buttnt
l,}-tr«n*)-dlchloro*thyltnt
HenachIoropropen*
CycIIc Compoundn
Llndani>c
II*aaehtorocyc lnp*?n|adi*n*>
Uracl I *u»t«rdc
*-
Ch1oro*e*ield*hvdc
Trlchloroacvtaldelivd*
75-l»-4
11}
>ta.«
-in.i 11.*
J.I MI
-JO 48
111 ' 111
-« !14
IM
(det.l
«>.«
500
0.01
.01
l.JJ 1. »»
»•'»
l.M I.J6
J.OOO20 1.41
Imolubl.
600«>
17**
Sparlnply
10-'
1.41 ».I3 » IO'1
Nliclblt -0.4 ?.* • 10-'
n »•• '•'I0/' r,«irs.iubi.
Rpicklorohvnr In
Aclo«
Fluorocccllc acid, aodlim
-J6 114
(dee.)
I.I*11* l.l»'«'» *4.flOO -0.4 1.11 » in-
Very Soluble
•roaoaccton*
1.6)" Uparlnltl?
(continued)
-------
TABLE A-l (continued)
I
1
Compound
[th.ta
IIa(chloroa*thyl)atlMr
lta(2-chloroalbyl)albar
lla(2-cblorolaopropyl)actaar
2-chlorcxlbyl >loyl atbar
ChloroawlhoayMthaoa
llad-chloroalboaylMthana
Nltroa.o Coapouoda
J-chloroproplonllrlla
Cyanogen cblorlda
• t
lluoroacatan,ldac
Cyaooa.an broailda
Uracll auatard'
*. HALOGQUUD AJUMUIICS
atpi.o.a
Chlorobaoaaoa
o-dlchlorotanaaoa
Bollloa Vapor
Maltlai point pr.aaui. Vapor Liquid
Holacular Holacular point ( 740 tort 1 20-25*Cb danalty daoalty
CAS Ho. lormla treifht CO CO (ton) (alr-1) (»/•!)
141-M-l Cj^CljO 115.0 -41.5 104 JO.O 1.97 1.12lo/«
111-44-4 C4N|C1]0 14J -15 171 0.71 4.91 1. 21*0/4
1M-60-1 CjHjjCljO 171.1 -97 1*9 0.15 6.0 1.11
110-75-1 C4«;C10 106.4 -70.J 109 16.1 1.0610/4
I07-W-1 CjHjCIO 10.1 -101.5 59.5 1.06
111-91-1 CjljoCljOj 171.1 -11.1 111 <0.1
141-76-7 CjN4ClN 19.1 -51 ' 174 650 1.1 1.14»
506-77-4 CC1M 61.3 -4.5 11.1 • 1.000 1.91 1.22*/4
640-19-7 C,N4rNO. 77 101
SOt-69-J ClrN 101.9 12 61 100 2.0220/4
66-7J-1 C-H.-tl-N-O, 212.1 20»
' " * * (dae.)
108-90-7 Ct*jCl 111.6 -41.4 111 I.I . J.M 1.11
91-50-1 CtH4Clj 147 . -17.4 UO.l 1 5.01 1.10
Lo|
octaool
Solubility oalar
la ntar partition
(M/D co.lllcl.at
ll.OOOi d.c.- O.M
10.100 1.5S
1,700 1.51
15.000) dac. 1.11
dac.
11,000 1.2ft
45.000
JO.OOO11 0.64
fraaly -1.05
Slowly dac.
In CM
.P...MU
4BI 2.14
145 J.M
Haory'a Lav
conataot
2.1 a 10-4
2.14 a 10->
1.51 a ID'4
2.16 a ID' *
1.71 a 10-'
J.9J a IO-J
(cmtlMad)
-------
TABLE A-l (continued)
CoMpound
Hn«cti lorobenttnt
rant «ch 1 orobtnttn*
Dichloropfttnylirslfit
lenient •ulfonyl chtorM*
l-brotM-t-phenoxy bcnttot
•-dlehtarobcnttne
I.V-o'lehloroBtnililntf
•f nl achloronl t robontint
, l.l.4,)-lttr>cKlorobtnitn<
>
O\ 1,1,4-Trlchlorobenttnt
Arrnr*
Bvntfl chlorldt
••niotflchloridr
Icnul cMotid.
Chlor«»bucllc
4-chloro-l-««thyl b*nt«nMlntc
Helllnl
HolvculAr Holcctflar point
CAI No. lorwlo «ljh« CO
118-74-1 C(Clt 184.8 111
608-*]-) cn"clj 1'°-) "
646-18-n C^jAtClj 118. «
04.1 4)
•)-6«-t c^em 141.6 17
lolllno Vipor
point prvstur*
$ 760 torr • 10-1)*C*
CO (torr)
11) l.08t>IO->
in t»-.''>nltl
*.64 I.0»" n.ll" 6.18 1.70 > IK''
8.6 |.6I 0.14" '->
1.18" ImolDblo
).l)
).08 I.I910'* 111" l.M 1.61 • in-'
5.07 1.44.""^ 80" 1.19 1.71 K ln~'
4.0" 1.01
(pR 6.9)
in. 1 1.71 Proct. Iniol.
7.4 I.861"* O.l*1 4.71
6.1) 1.17 19 4.18 1.1 i IP''
4.14 I.IO10"" Iniol. CU; 1. 10 ).ll • I""1
o«. m
6.77 I.1810" leictl «lth 4.16 1.1 • 10'*
I.161'"* ln«olublt
Inioluhlt
8plrln(lT
(continued)
-------
TABLE A-l (continued)
loll Inn V.por
Melting fK>l«t pr«Mort
Holceutir Molecular point t 760 torr ' JO- J5*C^*
Conpoiinil CAS No. forxili Ml«ht CO (*C) dorr)
rt«lph«•>
*.«'-«lh,Un« Mtc ?HW-18-5 r|,"|1cliHO "*•' "J • '•' ' I0"%
o-loluldlnt h;nol tt-V-S C^NjCIO IK. 6 ».l OS 1.1
p-chloro-»-cr«>ol W- \t\-t C;H;CIO 141.6 64 111
' l,4-nol 170-81-J ft"4cl,° 1" 4* "° O.II
l.6-illcliloroph«nol (7-6S-0 C.N C| 0 It) IS lit 1.0
T .641
^j 1.4.6-trUhloroph.nol ««-0*-l C^BjCljO lt».S «l 144 I7*-*
Ht««chloropl»iwc TO-ln-4 c,,"4CI,ini >0*>* '**
2)4 6'tctraehlnrophcnol \K-tO-l r H Cl O 1)1. t M 1M {I^O
l.4,S-lrlchloroph«nol t»-tS-4 C^HjCljO l«l.1 «l 1)1 A l"
M«tho.»chlorc »l-4)-) c,4"|tclj°| >**•' '•
(Chlorok>otll>t«) '* '* * '
octvnol
».por Liquid SolubllltT ««t«r
(•Ir-l) («/.!) («/l) cocrrlcUnt
Prut. Imol.
1.44
U"
Very lolublt
t.l l.ti 14*° J.OI
1.16 11,300 I. IS/1. It
1.8JO 1.11/1.10
S.6I 1. )•••'*> 4.60010 !.»»
t.« 140 l.t
Pr«ct. Inlol.
1.0 1.6^0^4 Inioluhl* 4.1
6-« l.l" 1.1*0 l.ll
1.41*' 0.04**
I.Sf Slightly
Henrv'i L«w
Ut«J/»l.)
8.81 > 10-*
».!« » 10"'
6.66 » 10-*
4.0 • ID"'
1.1 > 10-6
(conttdurd)
-------
TABLE A-l (continued)
Compound
ODD1
DDIC
Rtuchloroph«Mc
rolfmiclur Compounds
Chloruph»fta«
l-chloroMphlh«llorobtalldlMc
HtlphiUli0
4,4'-MtkfltM kU(l-chloroHlllo<)c
rranuld*1
o-toluldlot kfdrochlortdo1
HoltcaUr Moltculir
CAS Mo. loravU nl|ht
;i-M-a cui10ci4 310.1
10-19-J C14B,Clj 314.1
70-30-4 cu»jcl»°j 40t.t
494-03-1 C14iJ}Cljll Ml.l
J1-J8-7 C10I,C1 1*1.*
10*-47-t C(H(C1M 117.*
C;U;C1I2* 117
301-03-3 C^HjjCljNOj 304.1
91-94-1 C,,.,^!,!., 113.1
14«-«l-3 Cj^.CljUjO, 301
101-14-4 C,j)(uCIj», U7.1
139JO-M-1 C|]B||CljllO JH.l
•14-11-1 C;«toCUI 143.*
lolllol Tlpor
HilltM polit niourt Vapor Liquid
poUt t 740 tort 1 JO-SJ'C11 dtoollr dtultf
CO CO (tort) (.U-l) (!/•!)
Ill 1.01 i 10-* 11.0
101 1(1 1.9 i 10-'
11 110
19.1 lit 0.017 1.41
71.1 131 0.011 4.41 1.43*9/4
14*
4)
11 141
131
HI (die.)
99-107 1.44
111 *.} x 10-1
111 141
Solubility
la mite
(M/D
0.1.0"
0.0034"
Prut. luol.
Sp>rlD|ljr
».74»
Solub. lo HM
ImolubU
tpartogly
4.0"
(pU 4.9)
Frut. Imol.
11"
Tory oolublo
U|
ocUool
ntor Htorj'i U«
p«rtltloi conotut
c( (•l*-a)/Ml«)
1.98 1.14 • 10- >
4.M
4.11 6.11 i 10-'
1.83
4
3.01
-------
TABLE A-l (continued)
1
Compound
C. HAUKDUttD rlSTICIDU
Hydrocarbon loaactlcldaa
Undana'
Hetboirchlor'
DDOC
D0tc
1 , 1-dl broM-I-chloropropana c
Etnrlana dlbronlda'
Cyclodlana loatctleldaa
i Eoilrlo
l| • Chlordana
\o ;
' Haptachlor
Aldrln
Dlaldrla
laodrln
Eodoaulian
brbaaata Inaacllcldaa
cblocarbaut*
Holacular HoUcular
GAS No. fonuU valiht
}«-«»-» CjHjClj »0.»
71-41-} CjjIjjCljO j 14}. 7
72-54-*. CM»10«4 no. I
JO-19-J CUD,C»} 154.5
J.-11-8 cyijlr^l 11*. 4
106-9J-4 C^lr, 1*7.*
71-20-* CjjBjGljO ItO.t
57-74-* C10HtCl, 40*.*
7»-44-« C10«jCl| 171.4
109-OO-J C,2M(C1, I**-'
*0-)7-l CuHtCItO MO.*
4.5-71-. CU1.,C», 10
UJ-19-7 CjUjCljOjS 40*.*
JJOJ-W-4 C|0Ri;ClNOi 170.1
(olllni taper
Haltlni point praaiuo Vapor Liquid
point t 7*0 tore 1 20-15'C11 danaitf danaltr
CO CO (torr) (alr-1) (»/al)
111 111 . 0.01 • 10.0 1.I720/*
». 1.41»
111 1.01 I 10-* 11.0
10* 1(5 1.* l 10-'
1*6 O.I l.Oa'O/'C
10 111 11 t.5 !.;»'«
111-110 1 i 10-'
105 175 t 1 M V| 1 i 10-1 |t. i l.»15/15
(5 140 t 2 a. H| 1 i 10-* it.* Ii57
104 1.1 • 10-'
17* . 1.1 i 10"* 11.1 1.75
141
70-100 1.0 i 10-1
15-M 150 t * na> If 1.5 l HT* 1.11
oetaool
tolubllltr natar » torf 'a La*
In ntar partition conatant
(•I/D cotlllclant (atB-iVanla)
171* 1.72 7.1 i W*
0.04"
0.1*** l.M 2.1* • 10"s
O.OOJ41' 4.9*
1.000*1 1.0 1.4} • 10'*
4.50030 *.«! l 10"*
0.2* ).« 1 • 10-'
.00* 2.7* 4.* I 10->
.OH**-** 5.05 1.4* I 10-1 j
0.271' 5.00 «.** o W*
0.1..»-« «.}» 5.1 . 10-»
i
14
(coatlauad)
-------
TABLE A-l (continued)
Compound '
DlMthrl earbamifl chloridt
PhenoiT Hilda and lalta
J.4-0
1,4,1-tp (8II..«)
1.4.1-T
Caaplunaa
Toiaphent
Onanephoflptiorua Co»pounda
Dllropropjrl fluorophoaphate
Naltlnl
Molecular Molecular point
CAS Mo. formula v.ljht CO
lf-44-1 CjHtClim lO'.t -11
•4-7J-? caBtclj°j I" I*0-1
•l-II-l C.R^IjOj lit. I 110
tl-74-5 C^jCljOj Dt.t |]l
IOOI-1S-I CJ0H10CI§ 4IJ.8 6J-90
CjH^rOjt 1(4 -Hi
loll In, »i(ror
point prtalura Vapor Liquid
• '60 lorr * 10-J5*Cfc d.nill, danall;
Cc) (torr) (alr-l) (,/.!)
166 ).I1 1.61
160 0.4"° 1.6] I.4J"
HI O.I • I0~> 1.1
IJO (d.c.) fl.J-0.4 14.1 1.6}
4« » 1 tm 0.11* 1.J4 1.01
to,
octanol
Solubllltr water ltanrv*a taw
In watar partition conatant
(•»/!' eoclflclant («t»-«'/«ol«)
.«,» ,..,
1*0" 1.4
111"
1 1.1 4. I* > 10"'
11,400 I.M
ui-to-o
440.? liO HO' ' 1 > 10"'
1S6.I 111 . 1.1 « I0~>
u»
(contlmtd)
-------
TABLE A-l (continued)
HoUcular
c*l Ha. forauli
Nolteular
«tl«hl
lollloi
Heltlits point
V.por
CO
totr a JO-JVC1"
CO A (torr)
Vepor . Liquid
deitilly denolty
(elr-l) («/.!)
octanol
Solubility wetcr Nenry'e Lew
In weter partition conelent
(«t/l) coefficient le)
D. NISCCLLANCOUI COMPOUKDS
Phoe|ene (cerbonyl chloride)
Acelyl chloride
Cerbonyl fluoride
Nethyl cklorocerbonete
TrU(!,)-elbroi>oproprl>phoephele
II-J6-1
)i)-SO-4
6*
M.I
-III
-lit
-114
I.I
II
-II.I
71
I.tit
n»
i. H"/*
I.I4-H*
I.IJ'O/*
1.14
Very lll|htly
eol.t dee.
-O.I?
SlUhtly »ol.,
dee.
1.0"
•Source: Arlentl, M.. et >1. dee Reference 1 - Project Sunury).
bHote: 1 torr - 1 m Hg.
', 'Indicates compounds which are listed in nore than one (unctional group category.
------- |