United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park, NC 27711
EPA-450/1-91-001
March 1991
Air/Superfund
&EPA
AIR / SUPERFUND
NATIONAL TECHNICAL
GUIDANCE STUDY SERIES
Emission Factors for Superfund
Remediation Technologies
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AIR/SUPERFUND NATIONAL TECHNICAL
GUIDANCE STUDY SERIES
Emission Factors for Superfund
Remediation Technologies
Prepared by:
Patrick Thompson
Adrienne Inglis
Bart Eklund
Radian Corporation
Austin, Texas
Contract Number 68-02-4392
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12t/i Floor
Prepared for: Chicago, IL 60604-3590
Mr. James Durham
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
March 1991
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DISCLAIMER
This report has been reviewed by the Office of Air Quality Planning
and Standards, U.S. Environmental Protection Agency, and has been
approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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TABLE OF CONTENTS
Page
1.0 INTRODUCTION 1
2.0 EMISSION FACTORS SUMMARY 5
3.0 THERMAL TREATMENT TECHNOLOGIES 8
4.0 AIR STRIPPING 21
5.0 SOIL VAPOR EXTRACTION TECHNOLOGIES 29
6.0 STABILIZATION AND SOLIDIFICATION TECHNOLOGIES 39
7.0 CHEMICAL AND PHYSICAL TREATMENT TECHNOLOGIES ... 45
8.0 BIOTREATMENT AND LAND TREATMENT TECHNOLOGIES . . 59
REFERENCES REF-1
APPENDIX: SAMPLE CALCULATIONS
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LIST OF TABLES
Page
2-1 Emission Factors for Superfund Clean-Up Technologies 6
2-2 Hourly Emission Factors for Superfund Clean-up Technologies 7
3-1 Off-Site Incineration Stack Emission Factors and Estimated Emissions 18
3-2 On-Site Incineration Stack Emission Factors and Estimated Emissions
on Demonstration Testing of Shirco Infrared Incinerator 20
4-1 Emission Factors for Different Size Superfund Site Air Strippers 28
5-1 Summary of Emissions Data for SVE Systems 34
5-2 Terra-Vac In Situ Vacuum Extraction System Estimated Emissions ... 38
6-1 Typical Ranges of Emissions from Soil Handling Activities 44
7-1 Summary of Measured Removal Efficiencies and Stripping Contribution 52
7-2 Estimated Air Emissions Ultrox Field Testing:
Trichloroethylene Removal 53
7-3 Estimated Air Emissions Ultrox Field Testing:
1,1-Dichloroethane Removal 54
7-4 Estimated Air Emissions Ultrox Field Testing:
1,1,1-Trichloroethane Removal 55
in
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LIST OF FIGURES
Page
3-1 Generalized Process Flow Diagram for Thermal Treatment 9
3-2 Process Flow Diagram for Commercial Rotary Kiln Incinerator 16
3-3 Process Flow Diagram for Shirco Incinerator 19
4-1 Process Flow Diagram for Air Stripper System 22
4-2 Stripper Efficiency vs henry's Law Constant, Parameter = G/L
(vol./vol.) Low Efficiency Range 25
4-3 Stripper Efficiency vs henry's Law Constant, Parameter = G/L
(vol./vol.) High Efficiency Range 26
5-1 Generalized Process Flow Diagram for Soil Vapor Extraction 32
5-2 Process Flow Diagram for Terra Vac In-Situ Vacuum Extraction System 36
6-1 Process Flow Diagram for Stabilization and Solidification Technologies 40
7-1 Typical Equipment Set-Up for Ultrox International Ultraviolet
Radiation/Oxidation Technology 49
7-2 Detailed Flow Schematic of Ultrox International Ultraviolet
Radiation/Oxidation Technology 50
7-3 CF Systems Organics Extraction Process Schematic 57
8-1 Process Flow Diagram for Biotreatment 61
IV
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SECTION 1
INTRODUCTION
BACKGROUND
The U.S. Environmental Protection Agency (EPA) Air Program Office (Office of
Air Quality Planning and Standards) and the Regional Air Offices have been given the
responsibility to evaluate air impacts from Superfund sites and to advise Superfund
Regional Offices on appropriate clean-up actions. The Air/Superfund Coordination
Program, under the direction of the EPA Air Program Office, was begun to facilitate this
effort. An important part of this program is the analysis of air impacts from various
remedial options. These analyses are frequently required for planning purposes prior to
actual remediation. They are, therefore, dependent on the ability to estimate emissions,
rather than on field measurement approaches.
Work to estimate emissions from cleanup activities has already been done under
the Air/Superfund Coordination Program, including a manual summarizing estimation
techniques for emissions from remedial activities at abandoned hazardous waste sites -
Volume III of the National Technical Guidance Series (NTGS). This manual (1)
provides simple emission estimation procedures based on a mass balance approach and
notes the general lack of predictive models for most remedial activities. Emissions of
Volatile Organic Compounds (VOCs) from soils handling operations such as excavation
and dumping have also been studied under the Air/Superfund Coordination program (2).
Simple screening models to evaluate air impacts from many of the remediation
technologies considered in this document are also under development (3).
The EPA recognizes the need to develop simple estimation techniques for air
emissions from Superfund remediation activities. The work presented in this document
attempts to address this need, by developing emission factors for six Superfund clean-up
technologies.
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TECHNICAL OBJECTIVES AND APPROACH
The overall objective of this program was to develop an easy-to-use tool for
decision makers to predict the air emissions associated with Superfund remediation
actions. The specific objectives of this project were three-fold:
1) To develop process descriptions and process flow diagrams for common
Superfund site treatment technologies;
2) To identify the emission points and types of pollutants associated with each
technology; and
3) To summarize available air emissions data and develop emission factors.
As part of meeting these goals, six different remediation technologies were
examined:
1) Thermal Treatment;
2) Air Stripping;
3) Soil Vapor Extraction;
4) Solidification and Stabilization;
5) Physical and Chemical Treatment Methods; and
6) Biotreatment and Land Treatment.
For each of the six technologies a literature review was conducted to develop a
process flow diagram and identify emission points, as well as to analyze available air
emissions data. For most of the technologies examined, emission factors were based on
available data as well as assumed "typical" operating conditions for Superfund site
remediation. Where possible, however, emission factors were based on actual operating
data from site studies.
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LIMITATIONS OF THE WORK
Developing air pollutant emission factors for any process is a challenging task. A
limited data set must be used to generalize about a wide-spectrum of process conditions.
Developing emission factors for the processes used to remediate Superfund sites is an
even greater challenge. Many of the cleanup processes used at Superfund sites are
emerging technologies and have short operating histories. For these technologies, data
on which to base an emissions factor are very limited. Furthermore, each Superfund site
possesses its own unique obstacles to cleanup. These obstacles, in turn, may force
modifications to the cleanup hardware or operating conditions which could effect air
emissions.
The development of air pollutant emission factors applicable to the maximum
number of site conditions and site locations required assumptions regarding the rate and
scope of the clean-up effort, the type of wastes being treated, the number and nature of
emission release points, and so on. Assumptions were based on what is "typical" and
"reasonable" for Superfund site remediations. Obviously, the diverse nature of sites on
the National Priorities List (i.e. Superfund) results in the emission factors being more
applicable to some sites than others.
ORGANIZATION OF TECHNICAL NOTE
The remainder of this technical note is divided into seven sections. Section 2
presents a summary of the emission factors developed in this study. Each of the other
six sections are devoted to one of the six cleanup technologies examined (thermal
destruction, air stripping, soil vapor extraction, solidification and stabilization,
physical/chemical treatment, and biotreatment/land treatment). These sections are each
divided into four parts: 1) a process description of the cleanup technology; 2) a review
of air emission points and typical pollutants for the technology; 3) a summary of
available emissions data and correlations; 4) a discussion of the emission factor
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generated for that technology; and 5) where possible, a case study illustrating the
development of the emission factor.
Example calculations are included as an appendix to this technical note.
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SECTION 2
EMISSION FACTORS SUMMARY
EMISSION FACTORS
Table 2-1 shows air pollutant emission factors for the six Superfund cleanup
technologies examined in this report. Emission factors are presented for total VOCs,
criteria pollutants, total metals, and acid gases. For technologies where it is difficult to
define "typical" operating conditions, emission factors are shown for a particular
commercial process.
Many of the emission factors given in Table 2-1 are built upon several
assumptions and may be more applicable to some sites or commercial processes than
others.
ESTIMATED HOURLY EMISSIONS
Table 2-2 shows estimated hourly emission factors for the technologies discussed
in this report. Hourly emission factors are based on "reasonable" operating conditions
for Superfund remediation actions. These estimates may not be applicable to some
clean-up programs.
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TABLE 2-1. EMISSION FACTORS FOR SUPERFUND CLEANUP
TECHNOLOGIES
Technology
Air Stripping
Sofl Vapor Extraction
Solidification and Stabilization
Physical and Chemical Treatment Methods
Ultrox Oxidation
Pollutant Uncontrolled Emissions
Factor
Controlled Emissions Factor
Thermal Treatment
Rotary Kiln Incineration
Infrared Incineration
VOC
Metals
HO
HF
so2
PM
CO
NO,
VOC
Metals
HC1
HF
so2
PM
CO
N0x
0.1 g/kg VOC in waste feed
50.0 g/kg metal in waste feed
1.03 g/kg a in waste feed
1.05 g/kg F in waste feed
2.00 g/kg S in waste feed
11,750 mg/m3 flue gzis
50.0 ppmv flue gas
100.0 ppmv flue gzis
0.1 g/kg VOC in waste feed
50.0 g/kg metal in waste feed
1.03 g/kg Q in waste feed
1.05 g/kg F in waste feed
2.00 g/kg S in waste feed
Not Available
25.0 ppmv flue gas
100.0 ppmv flue gas
0.1 g/kg VOC in waste feed
50.0 g/kg metal in waste feed
0.01 g/kg Q in waste feed
0.01 g/kg F in waste feed
0.10 g/kg S in waste feed
72 mg/m3 flue gas
0.1 g/kg VOC in waste feed
50.0 g/kg metal in waste feed
0.01 g/kg Q in waste feed
0.01 g/kg F in waste feed
0.10 g/kg S in waste feed
180 mg/m3 flue gas
VOC Emissions equal total mass
VOC in Influent Water
°-l g/g VOC in water
VOC Emissions equal total mass 0.05 g/g VOC Removed from Soil
VOC in Influent Water
VOC 0.6 g/g/ VOC in soil No Controls Typically Applied
VOC 0.2 g/g VOC in water No Controls Typically Applied
Biotreatment and Land Treatment
Flow Through Treatment w/Mechanical Aeration VOC
Quiescent Flow-Through Treatment VOC
Disposal Impoundment VOC
Land Farming (24-hour Total Emissions) VOC
Land Fanning (20-day Total Emissions) VOC
-80 g/g VOC in water
.10 g/g VOC in water
.14 g/g VOC in water
•36 g/g VOC in water
.90 g/g VOC in water
No Controls Typically Applied
No Controls Typically Applied
No Controls Typically Applied
No Controls Typically Applied
No Controls Typically Applied
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TABLE 2-2. HOURLY EMISSION FACTORS FOR SUPERFUND CLEANUP
TECHNOLOGIES
Technology
Physical and Chemical Treatment Methods
Ultrox Oxidation
Biotreatment and Land Treatment
Flow Through Treatment w/Mechanical Aeration
Quiescent Flow-Through Treatment
Disposal Impoundments
Land Fanning (24-hour Average)
Land Farming (20-day Average)
Estimated
Pollutant Controlled Hourly
Emissions (g/hr)
Thermal Treatment
Rotary Kiln Incineration
Infrared Incineration
Air Stripping
Small-Size Unit
Medium-Size Unit
Large-Size Unit
Soil Vapor Extraction
Solidification and Stabilization
VOC
Metals
HC1
HF
SO2
PM
CO
NOX
VOC
Metals
HC1
HF
SO2
PM
CO
NOX
VOC
VOC
VOC
VOC
VOC
340
170
1.4
0.4
17
4,260
3,510
11,530
10.0
5.0
0.04
0.01
0.5
16.2
2.7
16.0
342
1,704
3,420
1,250
5,460
VOC
VOC
VOC
VOC
VOC
VOC
4.5
4,800
720
48.6
1,500
188
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SECTION 3
THERMAL TREATMENT TECHNOLOGIES
PROCESS DESCRIPTION
A broad range of technologies fall into the category of thermal treatment or
incineration. The most common incineration technologies include liquid injection, rotary
kiln, and multiple hearth (4,5). For Superfund site clean-ups any of these options may
be used. Superfund site remediations by thermal treatment fall into two general
categories: 1) on-site treatment using a transportable incinerator, or 2) off-site treatment
where contaminated soils or solvents are shipped to a larger, permanent unit.
In general terms, thermal destruction of hazardous waste is an engineered process
in which controlled combustion is used to reduce the volume of an organic waste
material and render it environmentally safe. Thermal treatment is a flexible process
capable of being used for many waste types including gases, liquids, solids, and sludges.
Figure 3-1 shows a generalized process flow diagram for thermal treatment
systems. A typical system includes the waste feed system, primary and (in most cases)
secondary combustion chambers, and exhaust gas conditioning system.
At the front-end of a hazardous waste incineration system is the waste feed
process. The configuration of the waste feed system is determined by the physical
characteristics of the waste. Solid wastes, normally packed in fiber drums, are
introduced to the combustion chamber by means of a conveyor or pneumatic rams.
Other solid wastes may require shredding or preheating before introduction to the
incinerator. Liquids are injected into the incinerator by means of an atomization
nozzle (s) which uses steam or compressed air as an atomization fluid. Liquids with
entrained solids may require screening to prevent clogging of the atomizer nozzle.
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Clean Flue Gas
Fuel
Contaminated
Soil or Groundwaler
Fuel
Primary Air
KILN
Off-Gas
Secondary Air
SECONDARY
REACTION
CHAMBER
(AFTERBURNER)
PARTICIPATE
REMOVAL
STACK
Ash to Disposal
Figure 3-1. Generalized Process Flow Diagram for Thermal Treatment.
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Gases are usually fed to the incinerator through ductwork and a blower. If the waste
stream contains oxygen, dilution air is frequently added to the gas stream so that the
resulting mixture is below its explosion limit.
The largest part of the waste destruction usually takes place in the primary
combustion chamber. As mentioned earlier, the chamber may be a rotating kiln, open
hearth, or other design. Gases formed in the primary combustion chamber are then
routed to a secondary combustion chamber, or afterburner, where any unburned
hydrocarbons or products of incomplete combustion such as CO, can be fully oxidized.
After the combustion gases leave the incinerator, they may be routed through a
variety of air pollution control devices including gas conditioning, particulate removal,
and acid gas removal units. Gas conditioning is accomplished with equipment such as
waste heat boilers or quench units. Typical particulate removal devices include venturi
scrubbers, wet or dry electrostatic precipitators, ionizing wet scrubbers, and fabric filters.
Acid gas removal units include packed, spray, or tray tower absorbers; ionizing wet
scrubbers; and wet electrostatic precipitators.
IDENTIFICATION OF AIR EMISSION POINTS AND TYPICAL POLLUTANTS
The air emissions associated with full-scale thermal treatment are primarily stack
emissions of combustion gas. However, there may be some additional evaporative
emissions from equipment leaks and waste handling. Full-scale, off-site incineration
units typically vent all emissions from waste handling and transfer activities to the
combustion chamber as make-up air. The air emissions for on-site incinerators are
similar to off-site units, except that waste handling activities have a greater likelihood of
being uncontrolled. For off-site units, typical incinerator stacks will be 50-75 ft high.
For transportable on-site units stack heights may be in the range 15-40 ft. The fugitive
emissions sources associated with thermal treatment will likely be ground-level.
10
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Emissions from both on-site and off-site incinerators include: undestroyed
organics, products of incomplete combustion (PICs), metals, paniculate matter, nitrogen
oxides (NOX), carbon monoxide (CO), and acid gases. The cause of each of these
pollutants is discussed below.
Unburned Hydrocarbons
In general, incinerators treating wastes from Superfund sites must achieve a
required destruction and removal efficiency (DRE) of at least 99.99% for RCRA wastes
and 99.9999% for PCB- or dioxin wastes. The remaining 0.01% or 0.0001% of the can
be assumed to through the system uncombusted (1).
Products of Incomplete Combustion
In the combustion process some reaction may produce a number of simpler
organic compound, called PICs. PICs may include dioxin, formaldehyde, and
benzo(a)pyrene and other polynuclear aromatic hydrocarbons. PIC formation is not
restricted to the combustion chamber; the reactions which produce PICs may continue to
occur in the combustion gases as they travel through the incineration system and out the
exhaust gas (1,6).
Metals
The metals introduced to the incinerator via the waste feed stream are not
destroyed. Depending on their boiling point, they can either be volatilized or remain as
solids. Volatilized metals will exit the stack as a gas or they will condense or adsorb
onto particles in the stack gas stream. Non-volatilized metals can be fluidized and swept
up into the combustion gas or leave the incinerator in the bottom ash.
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Particulate Matter
The waste feed, auxiliary fuel, and combustion air can all serve as sources for
paniculate emissions from an incineration system. Particulate emissions may result from
inorganic salts and metals which either pass through the system as solids or vaporize in
the combustion chamber and recondense as solid particles in the stack gas. High
molecular weight hydrocarbons may also contribute to paniculate emissions through
several possible mechanisms. RCRA requirements for particulate emissions call for a
limit of 0.08 grains/dscf corrected to 7% O2.
Nitrogen Oxides
Achieving high levels of destruction of organic wastes is directly related to
combustion chamber temperature: the higher the temperature, the greater the DRE of
organics. Unfortunately, the fixation of nitrogen and oxygen to form NOX also increases
with combustion temperatures. NOX emissions caused by this mechanism are referred to
as thermal NOX Also if there are bound nitrogen atoms in the waste, e.g. amines. In
such cases, two stage combustion or emissions controls may be needed.
Carbon Monoxide
Carbon monoxide emissions are generally low (<25 ppmv) in commercial
incinerators due to the high operating temperatures and excess oxygen maintained in the
process.
12
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Acid Gases
Hazardous was incineration will also produce acid gases. These include oxides of
sulfur (SOX), and halogen acids (HCI, HF, and HBr). The sulfur, chlorine, fluorine, and
bromine contents of the waste and fuel feed determine the emission levels of their
respective acid gases. The concentrations of these elements range widely amongst
different wastes; consequently, the resulting acid gas emissions will also show wide
variability. Furthermore most incinerators will be equipped with some type of flue gas
treatment system to control acid gas emissions. Control efficiencies will typically range
from 85-99%. Units treating wastes from Superfund sites will generally be required to
meet RCRA requirements governing HCI emissions. These requirements limit HCI
emissions to 4 Ibs/hr or mandate a control efficiency of 99%, whichever i$ less stringent.
SUMMARY OF AIR EMISSION DATA AND CORRELATIONS
The wide variety in design and operation of incinerators makes it difficult to
identify a single emissions factor for each contaminant. Some general equations,
however, can be developed from a mass balance approach to provide general guidelines
for estimating emissions. Separate correlations for each pollutant of concern are
presented.
Unburned Hydrocarbons
An emission rate for unburned hydrocarbons can be generated from a mass
balance on the incinerator system:
ERj = (l-(DREi/100))(Ci)(mw)
where: ER; = emission rate for pollutant i (g/hr);
DREj = destruction efficiency (assume 99.99% if not known);
= total mass flow rate of waste feed (kg/hr); and
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Cj = waste feed concentration for pollutant i (g/kg).
Products of Incomplete Combustion
Emissions of PICs, both the amount and the type, will vary greatly from unit to
unit depending on design and waste feed. Data is currently unavailable to generate a
single emission factor.
Metals
Metals are not destroyed in the incineration process. They leave the system via
either the bottom ash or the stack gas. There are currently no correlation available for
determining the partitioning of metal emissions in incineration systems. An upper limit
on emissions can be estimated by assuming all the metals present in the feed are emitted
in the stack gas. If stack data is available for the incinerator in question, metals
emissions rates can be estimated from:
ERj =
where: ERj = emission rate for metal i (g/hr);
Cj = concentration of metal i in the feed (g/kg);
m^, = mass flow rate of waste (kg/hr); and
% MEj = metal emitted to air expressed as a percentage of metal fed (See
Reference #1).
Acid Gases
The production of acid gases (HC1, SO2, and HF) is determined by the respective
chlorine, sulfur, and fluorine contents in the waste and fuel feed streams. A conservative
approach to calculating the air emissions of these acid gases is to assume complete
conversion of Cl, S, and F into their respective acid gas products. These equations
follow the form:
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ERi =
where ERj = emission rate for acid gas i (g/hr);
Cj = concentration of element (Cl, S, or F) in waste (g/kg);
RJ/J = stoichiometric ratio of acid gas to element (kg/kg);
m^, = mass flow rate of waste (kg/hr); and
%CEj = control efficiency of acid gas treatment system.
Nitrogen Oxides and Carbon Monoxide
In general, incinerator systems are not considered significant sources of NO
emissions. NOX is usually only a concern for wastes with high nitrogen content. Typical
NOX emissions for an incinerator may be on the order of 100-200 ppmv (dry basis), or
expressed on a fuel basis, 0.12-0.33 Ibs per MMBtu.
CO emissions from incinerators are also not considered a major problem. Most
systems are designed to be fired with excess air (i.e. oxygen rich) to ensure complete
combustion of organic material to carbon dioxide CO2. Vendors typically guarantee CO
emissions less than 100 ppmv (dry basis). Actual measured CO levels are often lower.
CASE STUDY: OFF-SITE INCINERATION
Process Description
A common method for Superfund site remediation is off-site incineration. This
involves removing the contaminated soil or water from the site and transporting it to a
commercial incinerator for disposal. The most common type of incinerator used in this
application is the rotary kiln, based on the dependability and versatility of this design.
Figure 3-2 shows a schematic of a typical rotary kiln incinerator with afterburner.
15
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SECONDARY
AIR FAN
Auxiliary Fuel
Energetic
Waste
Liquids
SECONDARY
COMBUSTION
CHAMBER
Clean
Flue Gas
QUENCH
PRIMARY AIR FAN
Process Water
FLUE GAS
TREATMENT
SYSTEM
STACK
To Ash
Disposal
Figure 3-2. Process Flow Diagram for Commercial Rotary Kiln Incinerator.
16
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Emission Factors
The correlations described in the preceding section were used to generate
emissions factors for off-site incineration. These emission factors are only for stack
emissions. In addition, emission estimates were generated for a typical incinerator
assuming a heat duty of 63 MM Kilojoules/hours (60 MMBtu/hr) and a stack gas
flowrate of 986 m3/min (35,000 SCFM). Based on a heating value of 18,590 kJ/kg
(8,000 Btu/lb) for waste material, this corresponds to a feed rate of 3,400 kg/hr (7,500
Ibs/hr). Table 3-1 shows the estimated emissions factors and emissions rates.
Other emissions associated with the handling and storage of contaminated soils
should be estimated using published emission factors.
CASE STUDY: ON-SITE INCINERATION
Process Description
Superfund site remediation is occasionally accomplished using on-site incineration.
This involves moving a transportable incinerator unit to the site. One type of incinerator
demonstrated in this application is the Shirco Infrared Incineration System (7,9). Figure
3-3 shows a schematic of the Shirco, which uses infrared heating in the primary
combustion chamber in place of fossil fuels.
Emission Factors
The correlations described earlier were used with field data to generate emission
factors for the Shirco incineration system. These emission factors, along with estimated
emissions, are shown in Table 3-2. Again, only stack emissions are considered.
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TABLE 3-1. OFF-SITE INCINERATION STACK EMISSION FACTORS AND
ESTIMATED EMISSIONS3'0
Pollutant
VOC
Metals
HC1
HF
Uncontrolled Emission
Factor and Units
0-1 gAg waste feed
50.0 g/kg metal in
waste feed
1.028 g HCl/g Cl in
waste feed
1.053 g HF/E F in
Controlled Emission
Factor and Units
NA
NA
0.010 g HCl/g Cl in
waste feed
0.011 B HF/g F in
Estimated
Controlled
Emissions
(g/hr)
340
170
1.4
04
SO,
waste feed
2.000 g SO2/g S in
waste feed
waste feed
0.100 g SO2/g S in
waste feed
bBasis for Emissions Estimates: Waste Characterization
Waste LHV:
Cl in Waste:
F in Waste:
S in Waste:
Metal in Waste:
18,590 KJ/kg
4.0%
1.0%
5.0%
0.1%
17.0
Paniculate Matter
cod
NOYd
11,750 mg/m3
50.0 ppmv flue gas
100.0 ppmv flue gas
72 mg/m3
NA
NA
4,260
3,510
11,530
aBasis for Emissions Estimates: Typical Incinerator
Heat Load: 63 MM Kilojoules/hour
Waste Feed: 3,400 g/hr
Stack Gas Flow: 986 nr/min
cBasis for Emissions Estimates: Acid Gas Scrubbing Efficiency
HC1 Removal Efficiency: 99%
HF Removal Efficiency: 99%
SO2 Removal Efficiency: 95%
Emission factors for CO and NOX may also be expressed in kg/MMKJ or Ib/MMBtu
CO: 0.05 kg/MMKJ or 0.12 Ib/MMBtu
0.15 kg/MMKJ or 0.33 Ib/MMBtu
NOX:
18
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Contaminated Soil
Inlrared Heating
EMERGENCY BYPASS STACK
Clean Flue Gas
PRIMARY
COMBUSTION
CHAMBER
BELT CONVEYOR
ToPOTW
Figure 3-3. Process Flow Diagram for Shirco Incinerator.
19
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TABLE 3-2. ON-SITE INCINERATION STACK EMISSION FACTORS AND
ESTIMATED EMISSIONS BASED ON DEMONSTRATION
TESTING OF SfflRCO INFRARED INCINERATOR
Pollutant
voc
Metals
HC1
HF
Uncontrolled Emission
Factor and Units
0.1 g/kg waste feed
50.0 g/kg metal in
waste feed
1.028 g HCl/g Cl in
waste feed
1.053 g HF/g F in
Controlled Emission
Factor and Units
NA
NA
0.010 g HCl/g Cl in
waste feed
0.011 e HF/g F in
Estimated
Controlled
Emissions
(g/hr)
10.0
5.0
0.041
nnn
waste feed
waste feed
SO2
Paniculate Matter
CO
NOY
2.000 g SO2/g S in
waste feed
NA
25.0 ppmv flue gas
100.0 ppmv flue gas
0.100 g SO2/g S in
waste feed
180 mg/m3
NA
NA
0.500
16.2
2.7
16.0
aBasis for Emissions Estimates: Typical Incinerator
Waste Feed: 100 g/hr
Stack Gas Flow: 1.5 nr/min
^asis for Emissions Estimates: Waste Characterization
Cl in Waste: 4.0%
F in Waste: 1.0%
S in Waste: 5.0%
Metal in Waste: 0.1%
cBasis for Emissions Estiamtes: Acid Gas Scrubbing Efficiency
HC1 Removal Efficiency: 99%
HF Removal Efficiency: 99%
SO2 Removal Efficiency: 95%
Emission factors do not include the fuel requirements to produce the infrared radiation.
20
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SECTION 4
AIR STRIPPING
PROCESS DESCRIPTION
Air stripping is a mass transfer process in which volatile contaminants in water are
evaporated (stripped) into air. The contaminated water is introduced at the top of a
packed-tower through spray nozzles and allowed to slowly flow down through the column
or tower. The packing media acts to retard the water flow and increase the effective
surface area of the system. Air is introduced countercurrent to the direction of water
flow. The saturated air containing the volatiles is emitted from the top of the column or
routed to a control device.
Figure 4-1 shows a typical air stripping tower. The treatment system may also
contain wells, separators, and vessels for treating inorganic contaminants (10,12).
IDENTIFICATION OF AIR EMISSION POINTS AND TYPICAL POLLUTANTS
The primary source of emissions from air stripping is the stripper exhaust, and
VOCs are the major pollutants of concern. Depending on the concentration and nature
of the VOCs present in the exhaust, some type of treatment such as carbon adsorption or
catalytic oxidation may be required. For systems without control devices, the exhaust is
vented through a short stack, typically a (3-6 ft) pipe, at the top of the column. For
systems with control devices, the airflow from the column is usually vented down to the
control device at ground level. A short stack (15-20 ft) is then used after the control
device (10,12).
21
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Mist Eliminator —
Distribution Tray •
(7
Blower
Air
1
To Atmosphere
Packed
Column
T
Pump
Well
Pump
To Water Treatment
and Distribution
Figure 4-1. Process Flow Diagram for Air Stripper System.
22
-------
The key design parameters effecting emissions from an air stripping unit include:
Groundwater VOC concentration;
Volatility (Henry's Law Constant) of the VOCs;
Groundwater temperature;
Air temperature;
Air water contact time;
Air/water contact ratio; and
Use and efficiency of control device.
In addition to the exhaust stack, other emission sources may exist. Any place
upstream of the air stripping tower where water is in direct contact with the atmosphere,
such as separators, holding tanks, treatment tanks, or conduits, is an emission source.
Fugitive losses from pumps, valves, and flanges are usually not significant due to the
dilute nature of the water contamination.
SUMMARY OF AIR EMISSIONS DATA AND CORRELATIONS
The most accurate and precise way to estimate air emissions from an existing air
stripper is to measure the air flowrate and exit gas contaminant concentrations under
typical operating conditions. The most accurate and precise way to estimate air
emissions from a planned air stripper is to use an air stripper design manual or software
program that includes an air emissions prediction option (12). In many cases, however,
actual measurements or detailed design simulations are not feasible. Therefore, an
alternative approach is given below to allow estimation of emissions using a minimal
number of input parameters.
As noted above, the important parameters affecting the emission rate for a given
compound from an air stripping unit include: the concentration of the contaminant in
the influent to the stripper, the influent flowrate, the stripping efficiency of the tower,
23
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and the effectiveness of any control technologies that are in place. The stripping
efficiency will depend on a number of factors including: the compound's Henry's Law
constant, the type of packing material in the tower, and the gas to liquid contact ratio
within the tower. Emissions for specific compounds from systems without any emission
control devices can be estimated as follows:
i = (Ci)(LR)(SEi/100)(0.06)
where ERj = emission rate for contaminant i (g/hr);
Cj = concentration of species i in influent water (mg/L or ppm);
LR = influent liquid flowrate (L/min);
SEj = stripping efficiency (%); and
0.06 = a constant (g-min/mg-hr).
For a well-designed unit, a stripping efficiency of 100% for volatile organic
compounds is a reasonable, conservative assumption. Alternatively, the stripping
efficiency of each contaminant can be determined from the ratio of gas to liquid (G/L
ratio) in the tower and the log of the Henry's Law constant as shown in Figures 4-2 and
4-3 for low and high efficiency ranges (see Reference 3 for data for selected organic
compounds). A conservative G/L ratio is 50 m3 air/m3 of water treated (12).
The use of a control device can reduce emissions by one to two orders of
magnitude (i.e. 90-99% control). This can easily be incorporated into the equation for
estimating emissions:
j = (Ci)(LR)(SEi/100)(l-%CEi/100)(0.06)
where: ERj = emission rate for contaminant i (g/hr);
C; = concentration of species i in influent water (mg/L or ppm);
LR = influent liquid flowrate (L/min);
SEj = stripping efficiency (%);
%CEj = control efficiency of stripper exhaust treatment (%); and
0.06 = a constant (g-min/mg-hr).
24
-------
/ /
/ /
-4 -3 -2
Log (Henry's Law Constant, atm-m3/gmole)
Figure 4-2. Stripper efficiency vs. Henry's Law constant, parameter
low efficiency range.
= G/L (vol./vol.)
25
-------
99.99
99.9
o>
£ 99
LLI
O>
c
"5.
Q.
c/5 90
-5
- G/L =10
G/L = 20
G/L = 50
G/L =100
G/L = 200
G/L =400
^, ~ .
r-*. — j. - .-• i_
'-"' liiT'"-—vgr.'—-
-4 -3 -2
Log (Henry's Law Constant, atm-m3/gmole)
-1
Figure 4-3. Stripper efficiency vs. Henry's Law constant, parameter = G/L (vol./vol.)
high efficiency range.
26
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EMISSION FACTORS
The correlations described in the preceding sections were used to generate a VOC
emission factor for air stripping. Assuming a stripping efficiency of 100% and a control
device efficiency of 90%, VOC emissions are 0.1 g VOC emitted/g VOC in the influent
water. With a stripping efficiency of 100%, uncontrolled emissions are simply equal to
the mass of VOC in the influent water.
Alternatively, the VOC emission factor can be converted to a g/hr basis for
different air stripper designs. Table 4-1 shows three unit sizes typical for Superfund
cleanup. Assuming a VOC influent concentration of 100 ppm (100 mg/L), uncontrolled
emission factors are 57, 284, and 570 g/hr for the small, medium, and large units,
respectively. Based on a 90% control efficiency, controlled emission factors are 5.7, 28.4,
and 57.0 g/hr.
27
-------
TABLE 4-1. ESTIMATED EMISSIONS FOR DIFFERENT SIZE SUPERFUND
SITE AIR STRIPPERS
Typical Superfund
Parameter
Total Influent Liquid Flowrate
Exhaust Gas Flowrate
Air/Liquid Ratio
Stripping Efficiency
Uncontrolled Emissions3
Controlled Emissionsb
Units
L/min
m3/mi
n
—
%
g/nr
g/hr
Small
570
29
50
99+
3,420
342
Medium
2,840
140
50
99 +
17,040
1,704
=====
Unit Size
Large
5,700
285
50
99 +
34,200
3,420
fBased on influent pollutant concentration of 100 mg/L.
''Based on influent pollutant concentraiton of 100 mg/L and a control efficiency of 90%.
28
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SECTION 5
SOIL VAPOR EXTRACTION TECHNOLOGIES
PROCESS DESCRIPTION
One technology used for for the treatment of contaminated soil at National
Priority List (Superfund) sites is soil vapor extraction (SVE). By nature, SVE is
employed on-site and is often used in conjunction with other remedial measures such as
the removal (pumping) of any liquid hydrocarbon layer that is present and air stripping
of contaminated ground water. In general terms, soil vapor extraction removes volatile
organic constituents from contaminated soil by creating sufficient subsurface air flow to
strip contaminants from the vadose (unsaturated) zone by volatilization. Complete
removal may not be possible unless the source of vapors (e.g. hydrocarbon lens on
groundwater) is also removed. As the contaminant vapors are removed, they may be
vented directly to the atmosphere or treated in a number of ways:
1) activated carbon adsorption;
2) catalytic oxidation; or
3) thermal incineration.
The first two treatment options are the most commonly used at Superfund sites.
The criteria for determining the usefulness of soil vapor extraction for a particular
site are numerous (13-20). The contaminants generally must have vapor pressures
greater than 1.0 mm Hg at 20°F to ensure effective removal. This technique may be
used in a variety of soil types but clearly soil porosity, grain size, moisture content and
stratification must be taken into consideration when planning this type of remediation.
This method is generally less costly than treatment involving excavation and can usually
be implemented without disrupting any concurrent normal business operations at the site.
If a large amount of contaminants is present in the ground water, the contaminated
29
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water should usually be treated first to remove this source of vapors, followed by soil
vapor extraction to remediate the vadose zone.
A few potential problems may arise in implementation of soil vapor extraction,
but effective solutions to most problems exist. When there is some concern that
contaminant vapors from a nearby site may be drawn in by the vacuum, air inlet wells
may be placed around the perimeter of the Superfund site to limit remediation to the
site under treatment. To avoid channelized flow, butterfly valves may be placed on the
extraction wells so that they may be shut down if necessary. If contaminated water is
extracted in the process, a liquid phase treatment system is usually installed.
As the vapors are removed from the soil they are either discharged to the
atmosphere or treated to reduce air emissions. If the hydrocarbon content is high
enough, direct combustion is possible. However, because concentrations typically drop
significantly during removal, natural gas or some other fuel may be needed to maintain
combustion. In some cases, the wells may be shut down for a period of time to allow
subsurface vapor pressures to re-equilibrate, thus yielding concentrations sufficient to
sustain a flame. For lower levels of hydrocarbons, catalytic oxidation may be effective.
Carbon adsorption systems are often used but they may be costly to implement and are
generally not acceptable for high-humidity gas streams.
Evidence of unusually high carbon dioxide levels indicates that some sites may
experience enhanced subsurface biodegradation that may be partially or wholly a result
of soil vapor extraction (21). Subsurface air flow may promote growth of aerobic
hydrocarbon degraders which feed on the organic contaminants by improving the level of
available oxygen for the microbes. At one site, carbon dioxide concetrations in the soil
gas were 8.5%; much higher than the 0.03% or 0.04% typically present in the
atmosphere. Rough calculations indicated that up to 40% of the gasoline was destroyed
by degradation. Other sources of organic material such as co-disposed municipal waste
30
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were not considered and may have been partially responsible for the high carbon dioxide
levels.
Figure 5-1 shows a generalized process flow diagram for the soil vapor extraction
process. Typical systems include extraction wells, monitoring wells, air inlet wells,
vacuum pumps, vapor treatment devices, vapor/liquid separators and liquid phase
treatment devices.
IDENTIFICATION OF AIR EMISSION POINTS AND TYPICAL POLLUTANTS
The air emissions associated with soil vapor extraction systems come primarily
from the stack and from the treatment of the contaminated water extracted. Stack
heights are typically 12-30 feet and usually only one stack is used. Additional releases of
volatile organics occur while sampling and installing the wells. Fugitive emissions are
considered negligible due to the negative pressure throughout most of the system.
Besides the stacks, the only area of positive pressure includes the liquid phase pump and
liquid treatment system. Because the stream is in the liquid phase, minimal fugitive
emissions are likely.
Emissions include untreated volatile organics from the extraction process as well
as any products that may be associated with the vapor and liquid treatment systems.
Vapor treatment systems are usually catalytic oxidation or activated carbon adsorption
canisters. Liquid treatment systems are usually liquid phase carbon or air stripping. Due
to the variety of technologies used, stack emissions may include products of incomplete
combustion, nitrogen oxides, paniculate matter, carbon monoxide, acid gases and any
other possible products of these technologies. Of primary concern, however, are the
volatile organics emitted from the point sources.
31
-------
Clean Flue Gas
Clean Flue Gas
Figure 5-1. Generalized Process Flow Diagram for Soil Vapor Extraction.
32
-------
SUMMARY OF AIR EMISSIONS DATA AND CORRELATIONS
Air emissions data for several SVE systems are summarized in Table 5-1. The
data are from a variety of soil vapor extraction systems. Overall there is little detailed
published information about SVE systems, making it difficult to assess the
representativeness of this sample.
No practical theoretical models for predicting emissions or recovery rates for SVE
systems exist at this time. Because of the complex nature of subsurface gas flow, pilot-
scale demonstrations at every site are typically performed to evaluate the applicability
and effectiveness of SVE as a treatment option. Some general equations can be
developed from a mass balance approach to provide a simple method to estimate
emissions from soil vapor extraction.
Air emissions can be estimated with the following equation for soil vapor
extraction systems:
Ei = Ru(l - (%CEM/100))+ R^l - (%CEv>i/100))
where: Ej = emission factor for soil contaminant "i" (g/hr);
RIJ = removal rate of contaminant "i" in liquid phase (g/hr);
%CE1?i = % control efficiency of liquid treatment device;
RYJ = removal rate of contaminant "i" in vapor phase (g/hr); and
%CEV)i = % control efficiency of vapor treatment device.
Removal rates can be 500-600 kg/day or higher and control efficiencies (when
applicable) range from 60-99%. In one 1989 SVE assessment, only about half of the
sites listed used any VOC control equipment. (15)
33
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TABLE 5-1. SUMMARY OF EMISSIONS DATA FOR SVE SYSTEMS
No. of
Systems
Source Surveyed
Crow (1987)a 13
Parameter
Flowrate per well
Removal
Exhaust Gas
Concentration
Units
cfm
Ib/day
ppmv
Range or Value
5.3 - 300
2-250
20 - 350
Approximate
Average
80
60
100
Hutzler
(1989)b
19 Total Flowrate
Treatment:
- None
- Carbon
- Catalytic Incineration
- Combustion
Removal Rate
cfm
# systems
Ib/day
3 - 5,700
9
6
1
1
4-430
800
100
PES (1989)c 17 Total Flowrate
Pollutant Concentration
_^ Control Efficiency
cfm
ppmv
25 - 11,300
150 - 38,000
90- 99
2,200
4,000
95
Guidelines for Design, Installation, Operation, and Evaluation of Subsurface Ventilation Systems. Draft
Report preapred by Radian Corporation for the American Petroleum Institute (API). July 23, 1987.
Hutzler, N J., B.E. Murphy, and J.S. Gierke. Review of Soil Vapor Extraction System Technology. In
Proceedings of HazMat West 1989 Conference, Long Beach, CA, November 7-9, 1989. pp512-536.
PES, Inc. Soil Vapor Extraction VOC Control Technology Assessment. EPA-450/4-89-017. U.S. EPA,
Research Triangle Park, NC, September 1989.
34
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EMISSION FACTORS
The correlations described above are useful for determining a VOC emission
factor for soil vapor extraction. If 95% effective carbon adsorption systems were used to
treat both vapor and liquid phases then VOC emissions would be 0.05 g VOC emitted/g
VOC in contaminated soil. A default value for uncontrolled emissions from SVE
systems can be assumed to be 250 kg/day of total VOCs. Based on 10-hours of
operation on average per day ("pulsed" operation), uncontrolled emissions are 25,000
g/hr. Controlled emissions, assuming a control device efficiency of 95%, are 1,250 g/hr.
CASE STUDY: TERRA VAC IN SITU VACUUM EXTRACTION SYSTEM
GROVELAND, MASS.
Process Description
Terra Vac Incorporated has developed a vacuum extraction system designed to
remove volatile organic contaminants from the vadose zone. At the Groveland,
Massachusetts Superfund site, the contaminated air stream was treated with two sets of
activated carbon canisters (17-19). Due to weather conditions, liquid water was extracted
as well, so a vapor-liquid separator was included to remove contaminated water to a
holding tank. The process design is shown in Figure 5-2.
Characterization of Air Emissions
Because no biodegradation was taking place in this case, the compounds released
to the atmosphere were the same as those found in the soil. By far the most
predominant contaminant removed was trichloroethylene, although 1,1,1-trichloroethane,
trans-1,2-dichloroethylene, and tetrachloroethylene were also extracted.
35
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Clean Flue Gas
CARBON CANISTERS
TANK
TRUCK
PUMP
VAPOR-LIQUID
SEPARATOR
EXTRACTION WELLS
^TT^ /J^/\
EXTRACTION WELLS
•Jk
•*•
jC
°c
o
o
)*
1
H^M
}^
O
c
o
0
^c
»«m.
0
c
o
^
O i
Soil Surface
• —
Contaminated
Soil
^ Vapors ^
~ — • — —
•y-
o
c
O
O
f
c
o
"^
•*
v_x-
JT
(
*
°(
0
0
)c
•X
c
of
o
o
jC
IK
Vadose Zone
MONITORING
WELLS
r Table
MONITORING
WELLS
STACK
Figure 5-2. Process Flow Diagram for Terra Vac In Situ Vacuum Extraction System.
36
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Emission Factors
Table 5-2 shows emissions factors for each of the four contaminants. The
estimated total VOC peak emission factor is 9.57 g/hr. This includes 6.3 g/hr of stack
emissions and 3.3 g/hr of evaporative emissions since the contaminated water was not
treated on-site. Appendix A describes the mass transfer model used to estimate
evaporative emissions.
37
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TABLE 5-2. TERRA-VAC IN SITU VACUUM EXTRACTION SYSTEM
ESTIMATED EMISSIONS
Pollutant
TCE
DCE
TRI
PCE
Totals
Molecular
Weight g/mol
131.29
96.94
133.41
165.83
Peak
Uncontrolled
Stack
Emissions
g/hra
5,210.0
274.0
36.0
18.0
5,538.0
=^=^==^=
Peak
Controlled
Stack
Emissions
g/hrb
5.91
0.31
0.04
0.02
6.29
Evaporative
Emissions
g/hrc
3.29
0.0
0.0
0.0
3.29
Total
Emissions
g/hrd
9.20
0.31
0.04
0.02
9.57
Uncontrolled emissions equal removal rate of each contaminant.
Based on a 99.75% overall control efficiency for two carbon adsorption canisters in
series.
Evaporative emissions from contaminated water storage.
Total stack and evaporative emissions.
KEY:
TCE - trichloroethylene
DCE - trans-1,2-dichloroethylene
TRI - 1,1,1-trichloroethane
PCE - tetrachloroethylene
38
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SECTION 6
STABILIZATION AND SOLIDIFICATION TECHNOLOGIES
PROCESS DESCRIPTION
Stabilization and solidification technologies are gaining increased use as Superfund
site remediation methods. The goal of these processes is to immobilize the toxic and
hazardous constituents in the waste, usually contaminated soil or sludge. This can be
accomplished by several means:
1) Changing the constituents into an immobile (insoluble) form;
2) Binding them in an immobile, insoluble matrix; or
3) Binding them in a matrix which minimizes the material surface exposed to
solvents (groundwater) which could leach the hazardous constituents.
Several types of stabilization and solidification technologies exist as alternatives
for remedial action. A few of these processes involve in-situ treatment, however, most
generally require excavation and other soil handling activities. Nearly all the
commercially available stabilization and solidification technologies are proprietary.
The basic steps in most solidification and stabilization processes are the same.
Figure 6-1 shows a typical process. Solidification and stabilization processes are usually
batch operations, but may be continuous. Wastes are first loaded into the mix bin
(wastes are sometimes dried before addition to the bin), and other materials for the
solidification or stabilization are added. The contents of the bin are then thoroughly
mixed. After a sufficient residence time, the treated waste is removed from the bin (22-
24). The material is usually formed into blocks and allowed to cure for up to several
39
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Excavation of Contaminated
Soil or Sludge
Waste Returned to Ground
Where Mixture Hardens and Traps
Contaminants
Addition of Binding
or Stabilizing Agent
(Typical matenals used
include Fly Ash, Portland
Cement, Cement Kiln Dust,
and Lime Kiln Dust)
Treated Soil or Sludge
Figure 6-1. Process Flow Diagram for Stabilization and Solidification Technologies.
40
-------
days. The blocks can then be placed in lined excavations on-site. It should be noted
that this description does not apply to in-situ treatment methods, which use a variety of
techniques (from applied high voltage to injection of stabilizing agents) to immobilize the
contaminated waste in-place without excavation or soils handling (25,26).
Typical raw materials used in stabilization processes include fly ash, portland
cement, cement kiln dust, lime kiln dust, or hydrated lime. Other additives that may be
used to solidify or encapsulate wastes include asphalt, paraffin, polyethylene, or
polypropylene.
IDENTIFICATION OF AIR EMISSION POINTS AND TYPICAL POLLUTANTS
The primary source of air emissions from stabilization and solidification processes
is volatilization of organic contaminants in the waste. Volatilization can occur during
waste handling activities such as soil excavation and transport or during the process of
mixing the binding agents with the waste. Also, some evaporative emissions will occur
from waste even after stabilization, especially during the curing period immediately after
the blocks are formed. Lab studies, though, have shown that the largest fraction of
volatile loss occurs during the mixing phase because heat may be required to assist
mixing or generated by exothermic stabilization reactions (27).
In general, VOC emissions form stabilization and solidification processes will
depend on the type and concentration of the VOCs in the waste, the duration and
thoroughness of the mixing, the amount of heat generated in the process, and the
average batch size processed. The longer or more energetic the mixing and processing,
the greater likelihood that organic compounds will volatilize. The volatile losses will also
increase as the temperature of the waste/binder, mixture increases. Binding agents with
high lime contents generally cause highly exothermic reactions. The batch size influences
volatilization by affecting the mean distance a volatilized molecule has to travel to reach
41
-------
the air/solid interface at the surface of the stabilized waste. The larger the block of
material, the lower the rate of volatilization.
In addition to volatile emissions, stabilization and solidification processes will
generate fugitive dust emissions. Possible sources of fugitive dust emissions include
storage of raw materials, preparation of the binding agents, transfer of wastes into the
mixing bin, removal of the treated material from the mixing bin, and replacement of the
material at the site after processing.
SUMMARY OF AIR EMISSIONS DATA AND CORRELATIONS
Little information exists about the fate of volatile contaminants in wastes treated
by stabilization and solidification methods. A literature search found no available field
data on air emissions at Superfund sites using this type of remediation technology.
Laboratory studies, however, have estimated that 40-80% of the volatile contaminants in
the treated waste eventually evaporate (27). Experiments also show that most of the loss
occurs within 60 minutes of mixing the waste with binding agents.
Based on the laboratory tests, the simple expression given below can be used to
estimate VOC emissions from stabilization and solidification processes:
where: ERj = emission rate for contaminant i (g/hr);
Q = concentration of species i in contaminated soil (g
contaminant/kg soil);
M = mass rate of soil treated (kg/hr); and
= percentage of contaminant i volatilized.
Paniculate matter emissions for stabilization and solidification processes can be
estimated using emission factors for soil handling. Typical ranges of emissions for
handling of contaminated soil are shown in Table 6-1.
42
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EMISSION FACTORS
The correlation given in the preceding section was used to generate a VOC
emission factor for stabilization and solidification processes. Assuming 60% of the
volatile contaminants evaporate, VOC emissions are 0.6 g VOC emitted/g VOC in the
contaminated soil.
Alternatively, the VOC emission factor can be converted to a g/hr basis for a
typical stabilization process. Assuming the stabilization equipment can treat 91,000 kg of
soil per hour (100 tons/hr) and that the waste contains 0.1 g VOC/kg soil (100 ppm), the
estimated emission factor is 5,460 g/hr.
43
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TABLE 6-1. TYPICAL RANGES OF EMISSIONS FROM SOIL HANDLING
ACTIVITIES
Activity PM Ertiissions Factor3*
Excavation 0.002-0.086 kg/metric ton
0.015-0.220 kg/metric ton
Transport:
Unpaved Roads 1.3 kg/VKT
Dry Industrial Paved Roads 0.022-0.15 kg/VKT
Heavily-loaded Roads 0.093-0.12 kg/VKT
Dumping 0.005-0.05 kg/metric ton
0.015-0.03 kg/rnetric ton
==B=======_^ 0.025-0.16 kg/metric ton
Units are kilograms per metric ton of soil moved or kilograms of emissions per
vehicle kilometer traveled (VKT).
From Reference 1.
44
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SECTION 7
CHEMICAL AND PHYSICAL TREATMENT TECHNOLOGIES
PROCESS DESCRIPTIONS
A broad range of technologies fall under the heading of physical and chemical
waste treatment methods. Included in this category are emerging technologies such as
ozone treatment of polluted groundwater, in-situ steam stripping of contaminated
disposal sites, and solvent extraction of contaminated soil.
In general terms, a chemical treatment method is one in which a reactive
compound (or compounds) is added to the contaminated groundwater or soil to react
with pollutants and form less harmful products. As the name implies, the effectiveness
of this type of treatment depends greatly on the chemical properties of the pollutants.
An example of this type of method is ozone treatment of contaminated groundwater. In
this process, contaminated groundwater or wastewater is mixed in a continuous reactor
with ozone and other oxidizing agents. The oxidizers react with the organic
contaminants to form CO2 and water.
Physical treatment involves the addition of energy or another treatment agent to
physically transfer the pollutants to another state in which they are easier to dispose of
or treat. The path of physical transfer can be adsorption, absorption, dissolution, or a
change of state such as evaporation. An example of this method is solvent extraction of
contaminated soil. In this process a solvent is mixed with soil contaminated by organic
pollutants to cause the organics to dissolve in the solvent phase. The solvent can then be
recovered and reused, while the contaminant can be biologically treated, incinerated, or
disposed of in another manner.
45
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IDENTIFICATION OF AIR EMISSION POINTS
The air emissions associated with chemical and physical waste treatment
techniques that may be used at Superfund sites have not been adequately characterized
for most methods. A broad spectrum of technologies are included in this category, and
the types and sources of air emissions may vary greatly. For most chemical and physical
treatment methods, however, the emissions of primary concern are VOCs; with emissions
of semi-volatile organic compounds and paniculate matter also of potential concern.
Emissions are usually from either ground level area sources or low-level point sources.
Point sources are typically associated with the treatment method, while area sources are
usually associated with the handling of contaminated soil or water.
In general, there are two types of process air emission sources that can be
associated with chemical and physical treatment. First, transfer of the contaminants from
the liquid- or solid-phase to the air may be an inherent consequence of the treatment
method. For example, in-situ steam stripping volatilizes a significant fraction of the soil
contaminants. In some cases, these air emissions are controlled by add-on control devices
such as carbon adsorption units. Second, fugitive emissions can be generated as a by-
product of the treatment method. For instance, in ozone treatment of contaminated
water, trace emissions of unreacted organic contaminants and ozone may occur.
Additional fugitive emissions from physical and chemical treatment methods can
result from leaking valves, pumps, and flanges in the unit, as well as from transfer or
handling of the untreated contaminated material.
SUMMARY OF AIR EMISSION DATA AND CORRELATIONS
The wide variety of physical and chemical treatment methods and the lack of
published information makes it difficult to summarize air emissions data or develop air
emissions factors. Some general equations, though, can be developed from a mass
46
-------
balance approach to provide a simple method to estimate emissions from these
technologies.
Emissions of original groundwater or soil contaminants that are transferred to the
air can be estimated by the following equation for physical and chemical treatment
methods:
EJ = Ci(V)(Reff/100)(Tfrac/100)(l-%CEi/100)
where: EJ = Air emissions of soil or water contaminantj (g/hr);
Cj = Concentration of contaminant; in soil or water (g/m3);
V = Volume flowrate of soil or water being treated (m3/hr);
Reff = Overall removal efficiency of treatment technology (%);
Tfrac = Fraction of removed contaminant transferred to air (%); and
%CEj = Control efficiency of any add-on air emission control device (%).
Air emissions of byproducts from the treatment method can be estimated from a
similar relationship:
where: Ei = Air emissions of soil or water contaminantj (g/hr);
C; = Concentration of contaminantj in soil or water (g/m3);
V = Volume flowrate of soil or water being treated (m3/hr); and
Reff = Overall removal efficiency of treatment technology (%).
Air emissions from other fugitive sources can be estimated from predictive models
and published emission factors, or can be measured directly (2,3,28).
47
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CASE STUDY FOR SUPERFUND CHEMICAL WASTE TREATMENT- ULTROX
INTERNATIONAL ULTRAVIOLET RADIATION/OXIDATION TECHNOLOGY
Process Description
Ultrox International has developed a technology that uses three oxidants: ozone,
hydrogen peroxide, and UV radiation to destroy organic contaminants in water with low
suspended solids levels. This technology is currently being tested at facilities across the
country on groundwater contaminated with trichloroethylene, tetrachloroethylene, vinyl
chloride, pentachlorophenol, phenol, and various other organics (28).
The Ultrox process can be described as a catalytic ozonation process where the
oxidation of contaminants occurs either by direct reaction of the oxidants added or by
reaction of the hydroxy radicals with the contaminants. Factors that affect the
effectiveness of the Ultrox process include the type of waste treated, the hydraulic
retention time, ozone dose, hydrogen peroxide dose, UV radiation intensity, and influent
pH. Removal can also be dramatically affected by the presence of other species in the
system which consume oxidants. These species include anions such as carbonates,
bicarbonates, sulfides, nitrites, bromides, and cyanides, as well as trivalent metals. The
process is enhanced by the presence of iron which catalyzes the hydrogen peroxide
reactions. Also, the UV radiation is more effective for clear solutions.
From an equipment perspective, the Ultrox process is simple. It consists primarily
of a reactor, ozone generator, and a catalytic ozone decomposer which decomposes any
unreacted ozone back to oxygen. Figure 7-1 shows a typical equipment set-up, and
Figure 7-2 provides a more detailed flow schematic.
48
-------
Trealed Off Gas
CATALYTIC OZONE DECOMPOSER
ULTROX
UV/OXIDATION
REACTOR
Makeup
Water
WATER CHILLER
Trealed Effluent
to Discharge
OZONE GENERATOR
Ground Water
from Wastewaier
Feed Tank
Hydrogen Peroxide
from Feed Tank
AIR COMPRESSOR
Figure 7-1. Typical Equipment Set-Up for Ultrox International Ultraviolet Radiation/
Oxidation Technology.
49
-------
Needle Valve
(typical) *
Rotameler
(lypical)
Ozone M;inilold
Ozone
Irom Ozone
Generator
UVLamp
(typical) "
STAINLESS
STEEL
REACTOR
->
-^
0
o
0
o
o
o
-
o-*-
Overflow Weir
(typical)
**
O
o
0
o
o
o
o
O
o
o
o
o
-
CZ3-*
J
-^.
0
o
o
o
o
o
V.
_x^
o
0
o
0
o
o
-
o-*J
•^ Headspace
^
O
o
o
o
o
o
o
}
h^-
*
0
o
o
o
0
LZ>
i-i
*-
-A
^
O
o
o
o
o
o
^
^V.
O
O
o
o
0 0
o
-
CD-J
r
^
0
o
0
o
o
/
^
O
o
o
0
Ci
O
-
»
3-1
-*s»_
o
o
o
0
o
o
Hydrogen Peroxide •
Ozone Oilluser
(lypical)
CATALYTIC
OZONE
DECOMPOSER
Sight Glass
nil
TREATED
EFFLUENT
STORAGE
TANK
Effluent
Sample Tap
Contaminated Waler
Figure 1-2. Detailed Flow Schematic of Ultrox International Ultraviolet Radiation/
Oxidation Technology.
50
-------
Characterization of Air Emissions
Two types of process emissions are associated with the Ultrox process. First,
there may be some unreacted ozone emitted through the decomposer. However,
because of the high reactivity of ozone, these emissions are usually small.
Concentrations below 0.1 ppmv in the off-gas were measured in field testing. When the
decomposer failed, though, concentrations exceeding 10 ppmv were observed (28).
The largest emissions from the Ultrox process occur as a result of the ozone
bubbling through the contaminated water and stripping VOC. The contribution of
stripping to the total removal is a function of how difficult the compound is to oxidize.
In field testing, stripping accounted for a significant fraction of the total removal of
trichloroethane and dichloroethane. Conversely, the extent of stripping was low for vinyl
chloride and tetrachloroethylene because these compounds contain double bonds
between the carbon atoms and are easier to oxidize.
For the Ultrox process, the equation given before can be used to estimate the
quantity of VOC emissions:
Ei= Ci(V)(Reff/100)(Tfrac/100)
Based on field testing, appropriate default values for highly oxidizable compounds, ones
with carbon-carbon double bonds, are in the range Reff is 90-95% and Tfrac equals 1-10%.
For less oxidizable compounds Reff is in the range of 50-80% and Tfrac varies from 10-
90%.
Table 7-1 summarizes the removal efficiencies measured for different pollutants
during field testing of the Ultrox process, as well as the estimated contribution of
stripping to the overall removal. Tables 7-2 through 7-4 show estimated air emissions for
the Ultrox process, generated using field data.
51
-------
TABLE 7-1. SUMMARY OF MEASURED REMOVAL EFFICIENCIES AND
STRIPPING CONTRIBUTION
Measured % Measured %
Contaminant Removal Stripped
Trichloroethylene 76-99 2-26
1,1-Dichloroethane 30-69 4.37
1,1,1-Trichloroethane 37-85 12-99
Vinyl Chloride N/A 0-13
52
-------
TABLE 7-2. ESTIMATED AIR EMISSIONS ULTROX FIELD TESTING-
TRICHLOROETHYLENE REMOVAL
Average
Influent Cone.
Contaminant Run (mg/m3)
Tnchioroethyiene 1 86
2 55
3 64
4 56
5 50
6 73
7 70
8 59
9 65
10 57
11 57
12 52
13 49
AVERAGE 61
Ratio of Air
to Water
Flowrates
2.1
2.3
2.1
2.0
2.1
4.5
1.0
4.5
4.5
4.3
4.6
4.4
4.3
3.3
Measured
% Removal
95.0
96.0
94.0
94.0
88.0
98.0
76.0
99.0
98.0
97.0
98.0
99.0
99.0
94.7
Measured
% Stripped
2.0
3.4
2.7
3.0
3.5
1.2
1.2
7.5
6.6
9.4
24.0
7.0
26.0
15
Estimated Air
Emissions
(mg/hr)a
37.1
40.8
36.9
35.9
35.0
19.5
14.5
99.5
95.5
118.0
304.5
81.8
286.5
92.7
% Air
Emissions
(g/g-feed)
1.9
3.3
2.5
2.8
3.1
1.2
0.9
74
6_5
9.1
23J
6.9
25.7
7.3
a Based on an estimated flowrate of 100 gpm contaminated water.
53
-------
TABLE 7-3. ESTIMATED AIR EMISSIONS ULTROX FIELD TESTING'
1,1,-DICHLOROETHANE REMOVAL
Average
Influent Cone.
Contaminant Run (mg/m3)
1.1-Dichloroethane 1 n_5
2 10
3 10
4 12
5 10
6 11
7 13
8 9.8
9 11
10 10
11 11
12 11
13 10
AVERAGE 11
Ratio of Air
to Water
Flowrates
2.1
2.3
2.1
2.0
2.1
4.5
1.0
4.5
4.5
4.3
4.6
4.4
4.3
3.3
Measured
% Removal
46.0
69.0
35.0
32.0
36.0
54.0
30.0
52.0
54.0
62.0
50.0
65.0
60.0
49.6
Measured
% Stripped
7.4
9.1
9.9
7.4
17.0
1(5.0
4.9
23.0
16.0
27.0
4-1.0
34.0
37.0
19.4
Estimated Air
Emissions
(mg/hr)a
8.9
14.3
7.9
6.5
13.9
21.6
4.3
26.6
21.6
38.0
55.0
55.2
50.4
24.9
9c Air
Emissions
(g/g feed)
3.4
6.3
3.5
2.4
6.1
8.6
1.5
12.0
8.6
16.7
22.0
22.1
T? ")
10.4
Based on an estimated flowrate of 100 gpm contaminated water.
54
-------
TABLE 7-4. ESTIMATED AIR EMISSIONS ULTROX FIELD TESTING'
1,1,1-TRICHLOROETHANE REMOVAL
Average
Influent Cone.
Contaminant Run (mg/m3)
1.1.1-Tnchloroethane 1 4.0
2 3.7
3 3.8
4 3.9
5 4.1
6 3.9
7 4.7
8 3.5
9 4.3
10 3.4
11 3.8
12 3.3
13 3.2
AVERAGE 4.0
Ratio of Air
to Water
Flowrates
2.1
2.3
2.1
2.0
2.1
4.5
1.0
4.5
4.5
4.3
4.6
4.4
4.3
3.3
Measured
% Removal
70.0
83.0
65.0
53.0
66.0
73.0
37.0
80.0
83.0
82.0
80.0
87.0
85.0
72.6
Measured
% Stripped
43.0
34.0
31.0
29.0
29.0
65.0
12.0
85.0
58.0
73.0
99.0
76.0
75.0
54.5
Estimated Air
Emissions
(mg/hr)a
27.3
23.7
17.4
13.6
17.8
42.0
4.7
54.1
47.0
46.2
68.4
49.6
46.3
35.2
% Air
Emissions
(g/g feed)
30.1
28.2
20.2
15.4
19.1
47.5
44
68.0
48.1
59.9
79.2
66.1
63.8
42.3
a Based on an estimated flowrate of 100 gpm contaminated water.
55
-------
Other air emissions from handling untreated waste must be estimated using other
predictive models or emission factors (2,3,28).
Emission Factors
Based on the data presented above, an overall emission factor for the oxidative
treatment of volatile compounds in contaminated water can be estimated as 0.2 g VOC
emitted/g VOC present in influent water. This estimate is an average value based on
field data for all three compounds studied.
Assuming an influent flowrate of 100 gpm and an initial contaminant
concentration of 1.0 g/m3, an overall emission can also be estimated as 4.5 g VOC
emitted/hr of operation.
CASE STUDY FOR SUPERFUND PHYSICAL WASTE TREATMENT-
CF SYSTEMS ORGANICS EXTRACTION SYSTEM
Process Description
The CF Systems Pit Cleanup Unit (PCU) uses a liquified propane/butane mixture
to extract organic contaminants from soil or sludges (30). Figure 7-3 shows the process
schematic. In the CF Systems process, the soil or sludge is diluted with water to make a
pumpable slurry, and then fed to a first extractor where it is mixed with the liquified gas
solvent. After the extractor, the mixture goes to a decanter where it is separated into
two immiscible layers. The water and solids underflow then moves to the a second series
of extractors, while the overflow is sent through a filter into the solvent recovery column.
After the second decanter, the bottoms product passes to the treated sediment product
tanks.
56
-------
V F
\K,
Basket T r
~^" Strainer * *
t i
& Pressure ^
__. A Letdown A
1 k. ) \ Valves ]
o — *
'
i .— • , ,— . : ?
? i w ' i i i i .
J L I — _ 1 1 i — L i
Extractor
t2
v^__^>
f i i i r \ '
i
i
t ^ f r^i
Treated
Decanter Extractor Decanter „ _
Sediment
<2 #1 jti
1 J *' Product
i 1 I 1 I Tank
^**- r"^ ^- r-1^ 11
\ \ ^
1 • : !
1
1
1
; : •
T
i
i
S
y
\
• i
J-i
Treated
Sediment
Product
Tank
»2
w
!
t
4
i
I
-£
A
r~~
•'-©-:
A-A
Compressor Compressor
i
i
i
i
i
i
Extract
Product
Tank
>-T
•
T :
*
T
^^" V
Cartndge
Filler
-X-—
^ ^
Solvent
Recovery
Column
C1 \
^
=>
=3
/ 1
Legend
Feed
Propane-Butane Solvent
Propane/Organics Mixture
Extracted Organics
Processed Sediments
Figure 7-3. CF Systems Organics Extraction Process Schematic.
57
-------
Factors that influence the effectiveness of the CF Systems process include:
extractor pressure, extractor temperature, feed flowrate, solvent flowrate, feed-to-solvent
ratio, and feed viscosity.
Characterization of Air Emissions
Two types of process emissions are associated the CF Systems PCU. First,
fugitive emissions may occur from leaking valves, pumps, and flanges in the unit.
Second, episodic or short term emissions may occur as a result of an overpressure of one
of the vessels. To control these upsets, the unit is designed so that material is vented to
a relief header which directs the stream to a blowdown tank where solids and liquids are
removed. The gases from the blowdown tank then pass through an activated carbon
filter to remove organic contaminants in the propane gas. The propane is then passed
through a flame arrestor and vented to the atmosphere.
Emission Factors
The lack of published air emissions data makes it difficult to develop emission
factors or correlations for the CF Systems PCU. However, fugitive losses from this unit
may be estimated using published emission factors if an estimate of the number of
components (pumps, valves, flanges) is available (28).
58
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SECTION 8
BIOTREATMENT AND LAND TREATMENT TECHNOLOGIES
PROCESS DESCRIPTION
In biological treatment of hazardous waste, microorganisms are used to degrade
or oxidize hazardous organic compounds in soil or water. When the growth of these
microbes is enhanced both by the increased availability of oxygen and moisture, and the
presence of hydrocarbons as feedstock, a significant amount of waste can be effectively
oxidized. Treatment can be accomplished in-situ, such as in land treatment methods, or
by pumping waste into a batch or continuous reactor.
Land treatment of a waste can be described as the application of waste onto land
and/or incorporation into surface soil, sometimes with the addition of fertilizer or soil
conditioner. The moisture content and waste loading are also controlled. Land
treatment may include landfarming, land application, land cultivation, land irrigation,
land spreading, soil farming, and soil incorporation. Wastes added to the soil
environment are subject to decomposition, leaching, volatilization, and assimilation
(31,32).
The main purpose of this in-situ treatment is to employ the microbiological
activity of the upper layers of the soil to decompose organic waste constituents into
carbon dioxide and water. Since the upper soil layer contains the largest microbial
population, land treatment is generally confined to the soil plow-zone or zone of
incorporation, i.e., the first six to eight inches of material. Waste oils and sludges are
generally applied to soil by surface spreading or subsurface injection. Wastes can be
effectively mixed into the zone of incorporation using a disk or rototiller (32).
59
-------
The direct biotreatment of liquid or slurry waste differs greatly from land
treatment (in-soil or in-situ) methods, and is a far more effective and common hazardous
waste treatment method. In this approach, the liquid waste is pumped from the
contaminated sump or pit into a bioreactor, where biological solids are mixed with waste,
The types of reactors can vary greatly, from batch tanks to flow through impoundments.
When high levels of biodegradation are desired the reactor is usually well aerated and
the biological solids level maintained near 1%. Figure 8-1 shows a schematic of a flow-
through system used for treating wastewater.
IDENTIFICATION OF AIR EMISSION POINTS AND TYPICAL POLLUTANTS
For land-farming operations, the primary air emissions are emissions from area
sources such as the block of contaminated soil being treated. For surface impoundments,
emissions also come from area sources. However, for batch bioreactors, the primary
source of emissions is usually a process vent. In all cases, the emissions of concern are
VOCs and PM when soil handling operations are required.
Air emissions from land treatment processes are influenced by waste
characteristics such as biodegradability and volatility, as well as soil type, temperature,
loading rate, mode of application, and tilling frequency. Other activities that are likely
to occur in conjunction with land treatment processes that may generate air emissions
included storage and handling operations.
For surface impoundments, the primary environmental factors, in addition to the
biodegradability and volatility of the waste, which influence air emissions are
temperature and wind speed. Emissions tend to increase with an increase in surface
turbulence due to wind or mechanical agitation. Temperature effects emissions by
promoting microbial growth. At temperatures outside the band for optimal microbial
activity, volatilization will increase (33-36).
60
-------
Air Emissions from Bioreactor
through Process Vent
BIOREACTOR
/ /
CLARIFIER
Contaminated
p
\
Recycle Sludge
f
Treated
"^ water bftiuent
Figure 8-1. Process Flow Diagram for Biotreatment.
61
-------
Emissions from batch reactors are also in part determined by reactor design
parameters such as the amount of air or oxygen used to aerate the waste. Higher gas
flow will strip more volatiles out of solution and increase air emissions.
SUMMARY OF AIR EMISSIONS DATA AND CORRELATIONS
Estimating VOC emissions from biotreatment processes is a complicated task.
Over the past fifteen years a wide array of models have been developed to estimate the
relative contributions of biodegradation and volatilization to waste removal. Currently,
several public-domain PC models, developed by the U.S. EPA, are available for
estimating air emissions from a variety of biotreatment operations, principally surface
impoundments. The two most commonly used models are ChemDat-7 and the Surface
Impoundment Modeling System (SIMS).
Both ChemDat-7 and SIMS are based on mass transfer and biodegradation
models developed by the U.S. EPA (36). The mass transfer model uses two-film
resistance theory, along with the characteristics of the impoundment, to estimate overall
mass transfer coefficients for each pollutant. The biodegradation model assumes Monod
kinetics to estimate a biodegradation rate.
Both ChemDat-7 and SIMS have limitations and drawbacks. Both models
perform all calculations for 25°C and rely on physical property and kinetic data that are
not always readily available for the modeled compounds. Funhermore, SIMS is limited
only to flow-through or disposal impoundments and is not applicable to estimating land-
farming emissions.
Detailed models have not yet been developed for estimating emissions from batch
bioreactors. These types of processes are, for the most part, developmental and difficult
to generalize. As noted before, emissions from these system are usually through a
process vent.
62
-------
The simplest method for estimating emissions from all types of biotreatment
processes is to use a mass balance approach. For continuous systems, such as flow-
through impoundments treating contaminated water, the following correlation is
applicable:
j = (q/l,000)(V)(%Vj/100)
where: ERj = emission rate for contaminant i (g/hr);
Cj = concentration of species i in contaminated water (mg/L);
V = volume rate of water treated (L/hr); and
Vj = percentage of contaminant i volatilized.
The percentage of each contaminant which is volatilized will vary greatly
depending on the physical properties of the contaminant and the impoundment design
and biological activity. Based on earlier research and modeling for benzene in a
mechanically aerated impoundment (34), as much as 80% may be volatilized. In a
quiescent impoundment, evaporative losses will likely be significantly lower since there is
no stripping effect to increase volatilization. For benzene only 12% of the loading to a
quiescent impoundment is estimated to be lost through volatilization (34).
For batch biotreatment systems, such as disposal impoundments, portable covered
reactors, or landfarms, the relationship given below can be used to estimate air
emissions:
ER; = (q/100)(V)(%Vj/100)/(t)
where: ERj = emission rate for contaminant i (g/hr);
Cj = concentration of species i in contaminated waste (mg/L);
V = volume waste or wastewater treated (L);
Vj = percentage of contaminant i volatilized; and
t = residence time in treatment system.
63
-------
Again, the percentage of each contaminant which is volatilized will depend on the
physical properties of the contaminant and the design of the treatment system, based on
earlier EPA research (34), the percentage of benzene volatilized from a disposal
impoundment over a six-month period is estimated to be 14%. For land-farming,
emissions will be significantly higher because of lower biological activity. The fraction
volatilized in the first 24 hours after application is estimated to be as high as 36%. After
20 days evaporative losses are likely to have reached 90% of the total volatiles originally
applied to the soil.
The estimates of the fraction volatilized for both continuous and batch
biotreatment systems are based on mass transfer models developed by the EPA (34).
The emission models for waste water treatment systems use Henry's Law and two-film
diffusion theory to estimate volatilization. Monod Kinetics are to calculate the
contribution of biodegradation to removal. For land-farming, emission models assume
the presence of an oil film on the soil surface.
Emission Factors
The correlations given in the preceding section were used! to generate VOC
emission factors for biotreatment and land-treatment processes. For mechanically
aerated flow-through impoundments, assuming 80% volatilization, VOC emissions are
0.80 g VOC emitted/g VOC in waste. For quiescent impoundments, volatilization will
be on the order of 10%, so VOC emissions are expected to 0.1 Og VOC emitted/g VOC
in the waste.
For a batch disposal impoundment, VOC emissions are estimated to be 0.14 g
VOC emitted/g VOC in the waste. For land-treatment, emissions over the first 24 hours
are estimated to be 0.36 g VOC emitted/g VOC in the waste. After 20 days, though,
land treatment emissions increase to 0.90g VOC emitted/g VOC in the waste.
64
-------
Alternately, these emission factors can be converted to a g/hr basis for typical
treatment processes. Table 8-1 shows these estimates and the bases used to generate
them.
65
-------
TABLE 8-1. ESTIMATED EMISSIONS FOR BIOTREATMENT AND
LANDTREATMENT PROCESSES
Treatment Process
Flow through Impoundment
w/Mecfaanical Aeration
Quiescent
Basis
1.0 M3/min
1.0 M3/min
Estimated
Residence VOC Waste
Time Concentration
NA 100.0
NA 1000
===^^====
Emissions Factor
(g VOC emitted/
g VOC in waste)
0.80
0.12
=====
Estimated
Emission
Rate
(g/hr)
4,800.0
7200
Disposal Impoundment
Land Farming
15,000 M3 6 months
1,000 M3 waste
1,000 M3 waste
24 hours
20 days
100.0
100.0
100.0
0.14
036
0.90
48.6
1,500.0
187.53
66
-------
REFERENCES
1. Air/Superfund National Technical Guidance Study Series, Volume HI:
Estimation of Air Emissions from Cleanup Activities at Superfund Sites.
Report No. EPA-450/1-89-003. U.S. EPA, Research Triangle Park, NC, 1989.
2. Draft Report: Field Measurements of VOC Emissions from Soils Handling
Operations at Superfund Sites. Prepared by Radian Corporation for U.S.
EPA, Office of Air Quality Planning and Standards, Research Triangle Park
NC, February 1990.
3. Radian Corporation, "Estimation of Air Impacts for Air Stripping of
Contaminated Water". EPA Contract No 68-02-4464, WA 91-112 January 4
1991. y '
4. Lee, C.C., G.L. Huffman, and D.A. Oberacker. Hazardous/Toxic Waste
Incineration. Journal of the Air Pollution Control Association, Volume 36,
Number 8. EPA, Cincinnati, OH. August 1986.
5. Cheremisinoff, P.N. Special Report: Hazardous Materials and Sludge
Incineration. Pollution Engineering, Volume 18, Number 12, pp. 32-38.
December 1986.
6. Trenholm, A. and D. Oberacker. Summary of Testing Program at Hazardous
Waste Incinerators. Proceedings - Annual Solid Waste Research
Symposium, Cincinnati, OH. Report No. CONF-8504112. U.S. EPA,
Cincinnati, OH, 1985.
7. Applications Analysis Report: Shirco Infrared Incineration System. Report
No. EPA-540/A5-89/010. U.S. EPA, Cincinnati, OH, 1989.
8. Technology Demonstration Summary: Shirco Pilot-Scale Infrared
Incineration System at the Rose Township Demode Road Superfund Site
Report No. EPA-540/S5-89/007. U.S. EPA, Cincinnati, OH, April 1989.
9. Technology Demonstration Summary: Shirco Electric Infrared Incineration
System at the Peak Oil Superfund Site. Report No. EPA-540/S5-88/002.
U.S. EPA, Cincinnati, OH, January 1989.
10. Byers, W.D. "Control of Emissions From an Air Stripper Treating
Contaminated Groundwater." Environmental Progress. Vol 7 No 1
February 1988. ' ' '
REF-1
-------
11. Cummins, M.D., JJ. Westrick. "Feasibility of Air Stripping for Controlling
Moderately Volatile Synthetic Organic Chemicals." U.S. EPA, Office of
Drinking Water, Cincinnati, Ohio, 1986.
12. Air/Superfund National Technical Guidance Study Series: Air Stripper
Design Manual. Report No. EPA-450/1-90-003. U.S. EPA, Research
Triangle Park, NC, May 1990.
13. Guidelines for Design, Installation, Operation, and Evaluation of Subsurface
Ventilation Systems. Draft Report Prepared by Radian Corporation for the
American Petroleum Institute (API). July 23, 1987.
14. Hutzler, NJ., B.E. Murphy, and John S. Gierke. Project Summary: State of
Technology Review - Soil Vapor Extraction Systems. Report No EPA-
600/S2-89/024. U.S. EPA, Cincinnati, OH, January 1989.
15. Soil Vapor Extraction VOC Control Technology Assessment. Report No
EPA-450/4-89-017. U.S. EPA, Research Triangle Park, NC, 1989.
16. "In Situ Vapor Extraction" in The Hazardous Waste Consultant. Vol. 5, Issue
5. September/October 1987.
17. Technology Evaluation Report: SITE Program Demonstration Test Terra
Vac In Situ Vacuum Extraction System Groveland, Massachusetts Volume I
Report No. EPA-540/5-89/003a. U.S. EPA, Cincinnati, OH, April 1989.
18. Technology Demonstration Summary: Terra Vac In Situ Vacuum Extraction
System Groveland, Massachusetts, Volume I. Report No. EPA-540/S5-
89/003. U.S. EPA, Cincinnati, OH, May 1989.
19. Applications Analysis Report: Terra Vac In Situ Vacuum Extraction System
Groveland, Massachusetts, Volume I. Report No. EPA-540/A5-89/003 U S
EPA, Cincinnati, OH, July 1989.
20. "A Practical Approach to the Design, Operation, and Monitoring of In Situ
Soil-Venting Systems." Ground Water Monitoring Review. Spring 1990.
21. "Vapor Extraction System Uses Above-Grade Vapor Destruction Train" in
The Hazardous Waste Consultant. Vol. 7, Issue 1. January/February 1987.
22. Handbook for Stablilization/Solidification of Hazardous Wastes. Report No
EPA-540/2-86/001. U.S. EPA, Cincinnati, OH, June 1986.
REF-2
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23. Technology Demonstration Summary: International Waste Technologies In
Situ Stabilization/Solidification Hialeah, Florida. Report No. EPA-540/S5-
89/004. U.S. EPA, Cincinnati, OH, June 1989.
24. "Using an Organophilic Clay to Chemically Stabilize Waste Containing
Organic Compounds." Hazardous Materials Control. Vol. 3 No. 1,
January/February 1990.
25. Roulier, M., J. Ryan, J. Houthoofd, H. Pahren, and F. Custer. Remedial
Action, Treatment and Disposal of Hazardous Waste: Proceedings of the
Fifteenth Annual Research Symposium. "In Place Treatment of
Contaminated Soil at Superfund Sites: A Review." Report No. EPA-600/9-
90/006. U.S. EPA, Cincinnati, OH, February 1990.
26. "In Situ Vitrification" in The Hazardous Waste Consultant. Vol. 8, Issue 1.
January/February 1988.
27. Weitzman, L., L. Hamel, P. dePercin, B. Blaney. Remedial Action,
Treatment and Disposal of Hazardous Waste: Proceedings of the Fifteenth
Annual Research Symposium. "Volatile Emissions from Stabilized Waste".
Report No. EPA-600/9-90/006. U.S. EPA, Cincinnati, OH, February 1990.
28. AP-42: Compilation of Air Pollutant Emission Factors, Fourth Edition. U.S.
EPA, Office of Air Quality Planning and Standards, Research Triangle Park,
NC. September 1985.
29. Technology Evaluation Report: SITE Program Demonstration of the Ultrox
International Ultraviolet Radiation/Oxidation Technology. Report No EPA-
540/5-89/012. U.S. EPA, Cincinnati, OH, January 1990.
30. Technology Evaluation Report: CF Systems Organics Extraction System New
Bedford, Massachusetts. Report No. EPA-540/5-90/002. U.S. EPA,
Cincinnati, OH, January 1990.
31. American Petroleum Institute. Landfarm Air Emissions. API Publication
No. 4500, Health and Environmental Sciences Department. March 1989.
32. Hazardous Waste Land Treatment. Report No. EPA-540/5-90/002. U.S.
EPA, Washington D.C., September 1980.
33. Eklund, B., A. Green, B. Blaney. Evaluation of Industrial Aerated
Wastewater Treatment Systems as Air Emission Sources.
REF-3
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34. Hazardous Waste Treatment, Storage, and Disposal Facilities (TSDF) -- Air
Emission Models. Report No. EPA-450/3-87-026. U.S. EPA, Research
Triangle Park, NC, November 1989.
35. Technical Note: Protocols for Calculating VOC Emissions from Surface
Impoundments Using Emission Models. Prepared by Radian Corporation for
Clyde E. Riley, U.S. EPA, Office of Air Quality Planning and Standards
Research Triangle Park, NC, December 1984.
36. Background Document for the Surface Impoundment Modeling System
(SIMS). Report No. EPA-450/4-89-013b. U.S. EPA, Research Triangle Park
NC, September 1989.
REF-4
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APPENDIX
SAMPLE CALCULATIONS
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EMISSIONS FROM THERMAL DESTRUCTION
(Section 3)
Air Emissions from Off-Site Rotary-Kiln Incineration (Controlled)
Emission Factors:
0.1 g VOC / kg VOC in Waste
50 g Metals / kg Metal in Waste
0.01 g HQ / g Cl in Waste
0.01 g HF / g F in Waste
0.10 g SO2 / g S in Waste
72 mg PM / m3 flue gas
50 ppmv CO / m3 flue gas
100 ppmv NOX / m3 flue gas
Assumptions:
Incinerator
Stack Gas Flow
Waste Fed
Heat Load
986 m3/min
3,400 kg/hr
63 MM KJ/hr
Waste Characterization
Cl in waste
F in waste
S in waste
Metal in waste
4.0%
1.0%
5.0%
0.1%
Estimated Control Efficiencies for Acid Gas Scrubbing
HC1
HF
SO-,
99%
99%
95%
A-l
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EMISSIONS FROM THERMAL DESTRUCTION
(Section 3)
Hourly Emissions:
VOC: 3«g,- «
nr g waste kg waste
g VOC/hr
kg Waste 1 kg M in waste
HC1: 3,400 kg waavQ4kgCli[;01LjLjg=04
hr kg waste g F
hr kg waste g F
s04
so 3.400 kg wa^e,-05 kg S^O 8 SO
hr k waste S *
PM: -xI!;nx^_=4j260 pM/hr
m3 mm hr 1,000 mg
.
_ x...( g
.0236 M3 106 gmole Air hr gmole *
A-2
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SAMPLE CALCULATIONS FOR AIR STRIPPING
(Section 4)
Air Stripping Emissions from Controlled Source
Emission Factor
0.1 g VOC Emitted
g VOC in Contaminated Water
Hourly Emissions from Large Unit
Assumptions:
Liquid Flowrate 5,700 L/min
VOC Cone. 100 mg/L
Total VOC Treated/Stripped per hour:
5/700JL x UOmg x 60min ^ g
min L hr 1,000 mg
Emissions:
0.1 g VOC Emitted x 34,200 g VOC in Water = 3,420 g VOC Emitted
g VOC in Water 1 hr hr
A-3
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SAMPLE CALCULATIONS FOR SOIL VAPOR EXTRACTION
(Section 5)
Stack Emissions from Soil Vapor Extraction
Emission Factor
0.05 g VOC Emitted
g VOC Removed From Soil
Hourly Emissions
Assumptions:
250 Kg VOC removed per 10 hr workday
Emissions:
250 kg VOC x 1 day x 1,000 g ^ 0.05 g VOC Emitted = 1,250 g VOC Emitted
day 10 hr 1 kg g VOC Removed hr
A-4
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SAMPLE CALCULATIONS FOR EVAPORATIVE EMISSIONS
FROM SVE AT THE GROVELAND, MA SITE
(Section 5)
Estimated Evaporative Emissions from Semi-Closed Tank of Contaminated Water
(100 ppm)
Apply Simple Mass Transfer Model (Two-Film Resistance Theory)3
where: Q = evaporative emissions flux (g/m2-5);
KJ = overall mass transfer coefficient (m/s);
Cj = concentration of contaminant (mol/nr); and
Mj = molecular weight of contaminant (g/mol).
In turn, the overall mass transfer coefficient is given by the equation:
_L = J_ + RT
where: Ky = liquid film mass transfer coefficient for contaminant i (m/s);
Kjg = gas film mass transfer coefficient for contaminant i (m/s); and
Hj = Henry's Law Constant for contaminant i (atm-m3/mol).
calculated from the correlations of Mackay and Yuenb.
= 1.0 x 1CT6 + 144 + KT4 U* Scf0-5
U* = friction velocity
.01 (6.1 x .63 U^)0-5
U10 = wind speed at 10 m above water surface
= 0 for semi-covered tank at Groveland
Scj = Schmidt Number for Liquid Film
Mwater
= viscosity of water
Pw = density of water
Diw = diffusivity of contaminant i in water
A-5
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SAMPLE CALCULATIONS FOR EVAPORATIVE: EMISSIONS
FROM SVE AT THE GROVELAND, MA SITE
(Section 5)
calculated from correlation of Mackay and Yuenb.
= 1.0 x ID"3 + 46.2 x ID'3 U* (Sc )-°-67
Scg = Schmidt Number for gas film 8
"air
^ air
viscosity of air
density of air
diffusivity of contaminant i in air
Total Evaporative Emissions:
Ej = emissions from contaminated water
Qi = emissions flux (g/m2«S)
A = surface area of water (m2)
Estimated Stack Emissions:
Assume uncontrolled VOC emission rate is equal to recovery rate of VOCs:
Uncontrolled Emissions = Recovery Rate
= 5,538 gVOC/hr
A-6
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SAMPLE CALCULATIONS FOR EVAPORATIVE EMISSIONS
FROM SVE AT THE GROVELAND, MA SITE
(Section 5)
Calculate controlled VOC emission rate using control efficiency for carbon
canisters:
100,
= 5,538 * l - 22^
I 100
= 6.29 g/hr
Notes:
Mackay, D., and P J. Leinonen. "Rate of Evaporation of Low-Solubility Contaminants
from Water Bodies to Atmosphere". Environmental Science and Technology. Vol. 9,
No. 13. December 1975.
b Mackay, D., and A.T.K. Yuen. "Mass Transfer Correlations of Organic Solutes from
Water" Environmental Science and Technology. Vol. 17, No. 4. April 1983.
A-7
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SAMPLE CALCULATIONS FOR SOLIDIFICATION/STABILIZATION
(Section 6)
Emissions from Stabilization/Solidification Processes
Emission Factor
0.6 g VOC
g VOC in Contaminated Soil
Hourly Emissions From Typical Process
Assumptions: 100 tons soil processed/hr
\ ton lb
0.1 g VOC/kg Soil (100 ppm)
Total VOC in soil processed:
91,000 kg soil 0.1 g VOC _ 9,100 g VOC
hr kg soil hr
Emissions
9,100 g VOC x 0.6 g VOC emitted = 5,460 g VOC emitted
hr g VOC intreated hr
A-8
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EMISSIONS FROM CHEMICAL/PHYSICAL TREATMENT METHODS
(Section 7)
Emissions from Chemical/Physical Treatment Methods
Emission Factor
0.2 g VOC Emitted
g VOC Treated
Hourly Emissions (From Ultrox Process Testing)
Assumptions: influent flowrate 100 gpm
100 gpm* -3785 M»
264.17 gallons
VOC influent cone. l.Og/M3 (1 ppm)
Total VOC treated (g VOC/hr):
.3785 M3 x 60 min 1.0 g = 22.71 g VOC Treated
min hr M3 hr
Emissions:
22.71 g VOC Treated 0.2 g VOC Emitted = 4.5 g VOC Emitted
hr g VOC Treated hr
A-9
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EMISSIONS FROM BIOTREATMENT SYSTEMS
(Section 8)
Flow-Through Impoundments with Mechanical Aeration
Emission Factor
0.8 g VOC Emitted
g VOC in Waste
Hourly Emissions
Assumptions
Influent Flowrate 1 M3/min
VOC Influent Concentration 100 g/M3 (100 ppm)
Total VOC Treated (g VOC/hr)
! M3 x 60min x 100 g = 6,000 g VOC Treated
min hr M3 hr
Emissions
6,000 g VOC Treated x .8 g VOC Emitted _ 4,800 g VOC Emitted
hr g VOC in Waste hr
Quiescent Impoundments
Emission Factor
0.12 g VOC Emitted
g VOC in Waste
A-10
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EMISSIONS FROM BIOTREATMENT SYSTEMS
(Section 8)
Hourly Emissions
Assumptions
Influent Flowrate 1 M3/min
VOC Influent Concentration 100 g/M3 (100 ppm)
Total VOC Treated (g VOC/hr)
1— x 6Q min * 1QO g . 6,000 g VOC Treated
min hr 3 hr
Emissions
6 000 g VQC Treated x .12 g VOC Emitted = 720 g VOC Emitted
hr g VOC in Waste hr
Disposal Impoundment
Emissions
0.14 g VOC Emitted
g VOC in Waste
Hourly Emissions
Assumptions
Impoundment Size 15,000 M3
VOC Influent 100 g/M3
Disposal Time 6 months
A-ll
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EMISSIONS FROM BIOTREATMENT SYSTEMS
(Section 8)
Total VOC Treated (g VOC)
15,000 M3 x HOLM. . 1,500,000 g VOC
M3
Emissions
1,500,000 g VOC x -14 g VOC Em*tted x 1 x 1 month x 1 day _ 48.6 g VQi
g VOC in Waste 6 months 30 days 24 hour ~ h
Land Farming
Emission Factor
0.36 g VOC Emitted2
g VOC in Waste
Hourly Emissions
Assumptions
Volume of Waste 1,000 M3
VOC Concentration 100 g/M3
Treatment Time 24 hours
A-12
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EMISSIONS FROM BIOTREATMENT SYSTEMS
(Section 8)
Total VOC Treated (g VOC)
1,000 M x _ = 100,000 g voc
M3
Emissions
100,000 g VOC x °'36 g VOC Emitted x 1 = 1,500 g VOC Emitted
g VOC in Waste 24 hours hour
Time between impoundment turnovers.
Based on 24-hour period.
A-13
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