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EPA-450/3-90-004
INDUSTRIAL WASTEWATER VOLATILE
ORGANIC COMPOUND EMISSIONS ---
BACKGROUND INFORMATION FOR
BACT/LAER DETERMINATIONS
CONTROL TECHNOLOGY CENTER
SPONSORED BY:
Emission Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Air and Energy Engineering Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Center for Environmental Research Information
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
January 1990
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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EPA 450/3-90-004
INDUSTRIAL HASTEWATER VOLATILE
ORGANIC COMPOUND EMISSIONS —
BACKGROUND INFORMATION FOR
BACT/LAER DETERMINATIONS
by
Jeffrey Elliott
Sheryl Watkins
Radian Corporation
P.O. Box 13000
Research Triangle Park, North Carolina 27709
EPA Contract No. 68-02-4378
Work Assignment Manager
Penny E. Lassiter
Emission Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Prepared for:
Control Technology Center
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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ACKNOWLEDGEMENT
The Industrial Wastewater Volatile Organic Compound Emissions'—Background
Information for BACT/LAER Determinations Revised Draft was prepared for EPA's
Control Technology Center (CTC) by J. Elliott and S. Watkins of Radian
Corporation. The work assignment manager was Penny Lassiter of the EPA's
Office of Air Quality Planning and Standards (OAQPS). Also participating on
the project team were Bob Blaszczak, OAQPS and Chuck Darvin, Air and Energy
Engineering Research Laboratory (AEERL).
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PREFACE
The purpose of this document is to provide technical information to
States on estimating and controlling volatile organic compounds (VOC)
emissions from the collection and treatment of industrial wastewaters for Best
Available Control Technology (BACT) and Lowest Achievable Emission Rate (LAER)
determinations. This document currently applies to four industries: the
Organic Chemicals, Plastics, and Synthetic Fibers (OCPSF) Industry; the
Pesticide Industry; the Pharmaceutical Industry; and the Hazardous Waste
Treatment, Storage, and Disposal Facilities Industry. However, this list
could be expanded to include additional industries as information becomes
available.
The Control Technology Center (CTC) was established by EPA's Office of
Research and Development (ORD) and Office of Air Quality Planning and
Standards (OAQPS) to provide technical assistance to State and Local air
pollution control agencies. Three levels of assistance can be accessed
through the CTC. First, a CTC HOTLINE has been established to provide
telephone assistance on matters relating to air pollution control technology.
Second, more in-depth engineering assistance can be provided when appropriate.
Third, the CTC can provide technical guidance through publication of technical
guidance documents, development of personal computer software, and
presentation of workshops on control technology matters.
The technical guidance projects, such as this information document,
focus on topics of national or regional interest that are identified through
contact with State and Local agencies. In this case, the CTC became
interested in distributing information to States on controlling VOC emissions
from industrial wastewaters. The technical document addresses new and
modified major sources, as defined in Parts C and D of the Clean Air Act
(CAA). Steam stripping to remove the organic compounds in certain wastewater
streams at the point of generation (prior to contacting the atmosphere) is the
recommended control strategy.
The document presents a description of the sources of organic containing
wastewater, VOC emission estimation procedures for treatment and collection
system units, and available VOC emission control strategies. In addition,
secondary impacts and the control costs associated with steam stripping are
present.
iv
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TABLE OF CONTENTS
Section Page
Acknowl edgement i i i
Preface 1 v
List of Tables vii
List of Figures xii
Glossary of Acronyms xv
Conversion Factors xvii
1.0 INTRODUCTION 1-1 '
2.0 INDUSTRY DESCRIPTIONS 2-1
2.1 Organic Chemicals, Plastics, and Synthetic Fibers
Manufacturing 2-5
2.2 Pesticides Manufacturing 2-7
2.3 Pharmaceuticals Manufacturing 2-10
2.4 Hazardous Waste Treatment, Storage, and Disposal
Facilities (TSDF) 2-13
2.5 Pulp, Paper and Paperboard and Builders' Paper and Board
Mills Industry 2-15
2.6 References 2-23
3.0 VOC EMISSIONS DURING WASTEWATER COLLECTION AND TREATMENT 3-1 *
3.1 Sources of Organic-Containing Wastewater 3-1
3.2 Sources of Air Emissions 3-2 '
3.3 Example Waste Stream Collection and Treatment System
Schematics 3-34
3.4 References 3-47
4.0 VOC EMISSION CONTROL EQUIPMENT 4-1
4.1 Waste Minimization 4-1
4.2 Organic Compound Removal 4-3
4.3 VOC Emission Control from Collection and Treatment
System Components 4-19
4.4 Add-On Controls 4-37
4.5 References 4-51
5.0 ENVIRONMENTAL IMPACTS OF STEAM STRIPPING 5-1 '
5.1 Impacts on VOC Emissions Using a Steam Stripper 5-1
5.2 Secondary Air Impacts 5-4 '
5.3 Cross-Media Impacts 5-11
5.4 Energy Impacts 5-11
5.5 References 5-13
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TABLE OF CONTENTS (continued)
Section paqe
6.0 CONTROL COST ANALYSIS OF STEAM STRIPPER SYSTEM 6-1
6.1 Steam Stripper System 6-1
6.2 References ' 5.20
Appendix A - Emission Estimates
A.I Collection and Treatment System Components A-l
A.2 Fraction Emitted During Collection and Treatment (Fe). . . . A-80
A.3 Emissions Reduction /\_90
A.4 References ....... A-98
Appendix B - Estimation of Air Emission Factors From Airflow in
Wastewater Collection Systems B-l
B.I Introduction [ B_3
B.2 Discussion of the Use of Collection System Emission
Factors 5.4
B.3 Methods and Results '.'.'.'.'.'.'.'.'.'.'.'.'.'.'. B-5
B.4 A Comparison of Theoretical Predictions to Measure Values. . B-31
Appendix C - Physical/Chemical Properties C-l
C.I References .'..'.'!!! C-4
Appendix D - Steam Stripper Performance Data
Test Data Summary - Site A D-l
Test Data Summary - Site B '.'.'.'.'.'.'.'.'. D-7
Test Data Summary - Plant G D-13
Appendix E - Draft EPA Reference Mehods 25D and 25E
Method 25D - Determination of the Volatile Organic Concentration of
Waste Samples £-1
Method 25E - Determination of the Vapor Phase Organic
Concentration in Waste Samples E-17
Appendix F - Example Facility Analysis
F.I Introduction F-l
F.2 Overview of Example Facilities '.'.'.'.'.'.'.'.'. F-l
F.3 Emissions Estimates F-14
F.4 Steam Stripper VOC Removal '.'.'.'.'.'.'. F-18
F.5 Test Method Concentration F-26
F.6 References ....... F-31
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LIST OF TABLES
Number Page
2-1 Wastewater Generation by Industry 2-3
2-2 Priority Organic Compounds That Are VOC 2-4
2-3 Generic Chemical Processes 2-6
2-4 Pollutant Concentration Data Presented in Section 114
Responses 2-8
2-5 Quantities of Wastes Managed in Subtitle D Surface
Impoundments 2-16
2-6 Percent of Subtitle D Surface Impoundments Accepting Industrial
Waste by Acreage Category 2-17
2-7 Number of Small Quantity Generators by Industry Group and
Quantity of Waste Generated 2-18
2-8 Mill Population 2-21
3-1 Emission Sources in Wastewater Collection and Treatment
Systems 3-6
3-2 Dimensions for Example Waste Stream Collection and Treatment
Units 3-39
3-3 Example Wastewater Stream 3-41
3-4 Emission Estimate for Example Waste Stream Schematic I 3-42
3-5 Emission Estimate for Example Waste Stream Schematic II 3-43
3-6 Emission Estimate for Example Waste Stream Schematic III 3-44
3-7 Summary of the Estimated Annual VOC Emissions from Each of the
Example Waste Stream Schematics 3-46
4-1 Design and Operating Basis for the Steam Stripping
System 4-9
4-2 Steam Stripper Organic Compound Removal Performance 4-15
4-3 Potential VOC Emission Reductions through Enclosing of Collection
System and Covering Oil/Water Separator with a Fixed Roof
Vented to a Control Device 4-30
4-4 Potential VOC Emission Reductions through Enclosing of
Collection System and Covering Oil/Water Separator with
a Floating Roof 4-31
vii
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LIST OF TABLES (continued)
Number Page
5-1 Summary of the Estimated Annual VOC Emission Impacts to the Air
from Each of the Example Waste Stream Schematics Developed in
Chapter 3 5.2
5-2 Combustion Pollutant Emission Factors 5-5
5-3 Annual Fuel Use for Steam and Electricity Generation 5-6
5-4 Summary of Combustion Pollutant Emissions Associated with a
Steam Stripper 5-8
6-1 Estimation of Basic Equipment Cost for a Steam Stripping
Unit 6.5
6-2 Estimation of Total Capital Investment for a Steam Stripping
Unit 6-7
6-3 Estimation of Total Annual Cost for a Steam Stripping Unit ... 6-10
6-4 Summary of the Estimated Annual VOC Emissions from Each of
the Example Waste Stream Schematics Developed in Chapter 3 ... 6-14
6-5 Removal Efficiencies and Overall Emission Reduction 6-15
6-6 Summary of the Estimated Annual VOC Emissions Reduction from
Each of the Example Stream Schematics Developed in Chapter 3 . 6-16
6-7 Steam Stripper Cost Effectiveness 6-17
A-l Wastewater Collection and Treatment System Components. ... A-2
A-2 Emissions Estimates for Drains A-8
A-3 Emission Estimates for Manholes A-9
A-4 Emission Estimates for Trenches A-10
A-5 Estimation Technique for Junction Boxes A-12
A-6 Emission Estimates for Junction Boxes A-14
A-7 Sample Calculations for Junction Boxes A-16
A-8 Estimation Technique for Lift Stations A-20
A-9 Emission Estimates for Lift Stations A-22
vm
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LIST OF TABLES (continued)
Number Page
A-10 Sample Calculations for Lift Stations A-24
A-ll Estimation Technique for Sumps A-28
A-12 Emission Estimates for Sumps A-29
A-13 Sample Calculations for Sumps A-30
A-14 Estimation Technique for Equalization Basins A-34
A-15 Emission Estimates for Equalization Basins A-38
A-16 Sample Calculations for Equalization Basins A-39
A-17 Estimation Technique for Clarifiers A-47
A-18 Emission Estimates for Clarifiers A-49
A-19 Sample Calculations for Clarifiers A-50
A-20 Estimation Technique for Biological Treatment Basins .... A-54
A-21 Emission Estimates for Biological Treatment Basins A-58
A-22 Sample Calculations for Biological Treatment Basins A-59
A-23 Estimation Technique for Treatment Tanks A-68
A-24 Emission Estimates for Treatment Tanks A-70
A-25 Sample Calculations for Treatment Tanks A-71
A-26 Estimation Technique for Oil/Water Separators A-74
A-27 Emission Estimates for Oil/Water Separators A-76
A-28 Sample Calculations for Oil/Water Separators A-77
A-29 Estimation Technique for Weirs A-81
A-30 Emission Estimates for Weirs A-83
A-31 Sample Calculation for Weirs A-84
A-32 Summary of Emission Factors for Collection and Treatment
System Components A-89
A-33 Cumulative Fraction Emitted During Collection and Treatment for
Example Waste Stream Schematic I A-91
IX
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LIST OF TABLES (continued)
Number paqe
A-34 Cumulative Fraction Emitted During Collection and Treatment for
Example Waste Stream Schematic II A-92
A-35 Cumulative Fraction Emitted During Collection and Treatment for
Example Waste Stream Schematic III A-93
A-36 Emission Reduction for Example Waste Stream Schematic I. . . A-94
A-37 Emission Reduction for'Example Waste Stream Schematic II . . A-95
A-38 Emission Reduction for Example Waste Stream Schematic III. . A-96
B-l Emission Estimates for Dilute Aqueous 1,3-Butadiene Solutions
Flowing Through Sewer Networks (fraction emitted) B-9
B-2 Emission Estimates for Dilute Aqueous Toluene Solutions
Flowing Through Sewer Networks (fraction emitted) B-9
B-3 Emission Estimates for Dilute Aqueous Naphthalene Solutions
Flowing Through Sewer Networks (fraction emitted) B-10
B-4 Emission Estimates for Dilute Aqueous 1-Butanol Solutions
Flowing Through Sewer Networks (fraction emitted) B-10
B-5 Emission Estimates for Dilute Aqueous Phenol Solutions
Flowing Through Sewer Networks (fraction emitted) B-ll
B-6 Emission Estimates from an Open-Trench Section in a
Wastewater Collection Network B-ll
B-7 Partition Coefficients of Compounds Used in Emission
Estimates B-12
B-8 Screening Values for Air Velocities at Sewer Openings. . . . B-32
B-9 A Comparison of Measured and Predicted Air Velocities at
Sewer Openings B-33
C-l Targeted Organic Compounds and Their Physical Properties
at 25oC C-l
C-2 Organic Compound Properties C-2
C-3 Partition Coefficients for Selected Organic Compounds at
Various Temperatures C-3
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LIST OF TABLES (continued)
Number Page
D
Site A
1 Bulk Stream Characterization D-5
2 Component Stream Characterization D-6
Site B
1 Bulk Stream Characterization D-ll
2 Component Stream Characterization D-12
Site G
1 Bulk Stream Characterization D-17
2 Component Stream Characterization D-18
F-l Example Facility 1 Wastewater Stream Characteristics .... F-2
F-2 Example Facility 2 Wastewater Stream Characteristics F-3
F-3 Example Facility 3 Wastewater Stream Characteristics F-4
F-4 Example Facility 4 Wastewater Stream Characteristics .... F-5
F-5 Example Facility 5 Wastewater Stream Characteristics .... F-6
F-6 Example Facility 6 Wastewater Stream Characteristics .... F-7
XI
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LIST OF FIGURES
Number
Page
3-1 Typical wastewater collection and treatment scheme 3-4
3-2 Typical drain configuration 3.7
3-3 Typical manhole configuration 3-10
3-4 Typical junction box configuration 3-13
3-5 Typical lift station configuration 3-16
3-6 Typical trench configuration 3-19
3-7 Typical weir configuration 3-22
3-8 Typical oil-water separator configuration 3-24
3-9 Typical equalization basin 3-27
3-10 Typical clarifier configuration 3-29
3-11 Typical aerated biological treatment basin 3-32
3-12 Example Waste Stream Schematic I 3-36
3-13 Example Waste Stream Schematic II 3-37
3-14 Example Waste Stream Schematic III 3-38
4-1 Continuous steam stripper system 4-6
4-2 Predicted steam stripper organic compound removal efficiencies
based on Henry's Law Constant for the compound 4-17
4-3 P-leg and seal pot configurations for drains 4-21
4-4 Gas tight cover for collection system components 4-23
4-5 Storage tank covers 4-25
4-6 Typical air-supported structure 4-35
4-7 Carbon canister unit 4-40
4-8 Schematic diagram of thermal incinerator system 4-43
4-9 Schematic diagram of catalytic incinerator system 4-45
4-10 Steam-assisted elevated flare system 4-47
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LIST OF FIGURES (continued)
Number Page
4-11 Schematic diagram of a shell-and-tube surface condenser 4-50
5-1 Positive and negative air impacts of steam stripper control
(controlled boiler) 5-9
5-2 Positive and negative air impacts of steam stripper control
(uncontrolled boiler) 5-10
6-1 Continuous steam stripper system 6-2
6-2 Summary of total capital investment versus wastewater feed
rate 6-8
6-3 Summary of unit operating costs versus wastewater feed
rate 6-12
6-4 Cost effectiveness versus wastewater feed rate Example Facility
Schematics I, II, and III 6-18
A-l Typical drain configuration A-4
A-2 Typical manhole configuration A-5
A-3 Typical trench configuration A-6
A-4 Typical junction box configuration A-13
A-5 Typical lift station configuration A-21
A-6 Typical equalization basin A-37
A-7 Typical clarifier configuration A-48
A-8 Typical aerated biological treatment basin A-57
A-9 Typical oil/water separator configuration A-75
A-10 Typical weir configuration A-82
A-ll Example Waste Stream Schematic I A-86
A-12 Example Waste Stream Schematic II A-87
A-13 Example Waste Stream Schematic III A-88
xm
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LIST OF FIGURES (continued)
NMmber Paqe
B-l Simplified Flow Diagrams B-6
D
Site A
1 Diagram of Plant A steam stripper system and sampling
locations n.7
Site B U J
1 Diagram of steam stripper at Site B with sampling
locations n.q
Plant G
1 Diagram of Plant G steam stripping process with sampling
locations D_15
F-l Example Facility One. Treatment Configuration and
Collection System F-8
F-2 Example Facility Two. Treatment Configuration and
Collection System F-9
F-3 Example Facility Three. Treatment Configuration and
Collection System p_10
F-4 Example Facility Four. Treatment Configuration and
Collection System F-ll
F-5 Example Facility Five. Treatment Configuration and
Collection System F-12
F-6 Example Facility Six. Treatment Configuration and
Collection System F-13
xiv
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GLOSSARY OF ACRONYMS
API = American Petroleum Institute
BEC - Base Equipment Cost
CAA - Clean Air Act
CAS = Chemical Abstract Services
CO = Carbon monoxide
CTC » Control Technology Center
CWA = Clean Water Act
EPA = Environmental Protection Agency
ESP = Electrostatic Precipitator
fe = fraction emitted, emission factors
FR = Federal Register
H = Henry's Law Constant
H20 = Water
1pm = liters per minute
MGD = Million Gallons per Day
NOX = Nitrogen oxides
NPDES = National Pollutant Discharge Elimination System
NSPS = New Source Performance Standard
OAQPS = Office of Air Quality Planning and Standards
OCPSF = Organic Chemicals, Plastics, and Synthetic Fibers Manufacturing
Industry
OSW = Office of Solid Waste
OWRS = Office of Water Regulation and Standards
PEC = Purchased Equipment Cost
PM = Particulate Matter
POTW = Publicly Owned Treatment Works
ppm = parts per million by weight
RACT = Reasonably Available Control Technology
SIC = Standard Industrial Classification
S02 = Sulfur dioxide
TAC = Total Annual Cost
TCI = Total Capital Investment
xv
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TSDF = Hazardous Waste Treatment, Storage, and Disposal Facilities
VO = Volatile Organics (this is the organic concentration as detected by
draft EPA Reference Method 25D).
VOC = Volatile Organic Compounds (VOC) refers to all organic compounds
except the following compounds that have been shown not to be
photochemically reactive: methane, ethane, trichlorotrifluoro-
ethane, methylene chloride, 1,1,1-trichloroethane, trichlorofluoro-
methane, dichlorodifluoromethane, chlorodifluoromethane, trifluoro-
methane, dichlorotetraf1uoroethane, and chloropentaf1uoroethane.
(See 45 FR 48941, July 22, 1980.)
xvi
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CONVERSION FACTORS FROM METRIC TO ENGLISH UNITS
To Obtain
Btu
Btu
Btu/ft3
Btu/hr
Btu/sec
cubic ft
cubic ft/sec
feet
ft of H20 @ 4°F
gal (USA, liquid)
inches
gal/hr/ft2
mechanical hp
pounds
pounds/gal (USA, liquid)
square ft
Multiply
Kw-hr
J
KJ/m3
Watts (J/s)
Kw
cubic meters
liters/min
meters
N/m2 (Pa)
liters
centimeters
1/hr/m2
Kw
Kg
Kg/m3
square meters
By
3413
0.0009486
0.02688
3.4127
0.94827
35.314
0.0005886
3.281
0.0003346
0.2642
0.3937
0.02455
1.3410
2.2046
0.008328
10.764
XVI1
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1.0 INTRODUCTION
Under the prevention of significant deterioration (PSD) provisions of
Part C of the Clean Air Act (CAA), a new major stationary source or a major
modification shall apply best available control technology (BACT) for each
pollutant regulated under the CAA that it would have the potential to emit in
significant amounts. Similarly, under the nonattainment new source review
(NSR) provisions of Part D of the CAA, a major new or modified source in a
nonattainment area shall apply controls to attain the lowest achievable
emission rate (LAER). A new major stationary source refers to any source
within these source categories which emits, or has the potential to emit,
100 tons per year of VOC. A major modification refers to a physical change in
or a change in the method of operation of a stationary source which results in
a net increase in potential emissions of 40 tons per year of VOC.
The purpose of this document is to provide technical information to
States on 1) estimating emissions of volatile organic compounds (VOC) from the
collection and treatment of industrial wastewaters, and 2) BACT and LAER
determinations for controlling emissions of VOC from industrial wastewaters.
This document applies to four industries: the Organic Chemicals, Plastics,
and Synthetic Fibers (OCPSF) Industry; the Pesticide Industry, the
Pharmaceutical Industry; and the Hazardous Waste Treatment Storage, and
Disposal Facilities Industry (TSDF). However, this list could be expanded to
include additional industries as information becomes available.
Based on information collected by the Agency, facilities within each of
these industries have the potential to generate wastewaters containing high
concentrations of organic compounds. These wastewaters typically pass through
a series of collection and primary treatment units before treatment is applied
to reduce the concentration of organic compounds prior to discharge. Many of
these collection and treatment units are open to the atmosphere and allow
organic-containing wastewaters to contact ambient air. Atmospheric exposure
of these organic-containing wastewaters results in significant volatilization
of VOC from the wastewater.
These emissions can be reduced by applying one of three control
strategies. The most effective strategy is to apply w?cto minimization
techniques to reduce the organic concentration of the wastewajterrs^jjr,tP_
produce a more manageable wastewater stream through waste segregation or
recycling. Even with waste minimization, some waste streams will be
1-1
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generated. Emissions from these wastewater streams can be reduced by applying
treatment at the point of generation. Numerous controls are suitable in
specific cases, but the most universally applicable treatment technology for
controlling emissions from wastewater generated by these industries is steam
stripping. A third control strategy that may be appropriate for some
situations is to enclose the wastewater collection system and cover all
treatment units up though removal or destruction of the organic compounds.
The organization of this document is as follows. A description of the
industries covered by this document is presented in Chapter 2. The sources of
organic containing wastewater, and the sources of VOC air emissions are
identified in Chapter 3. Chapter 4 presents available VOC emission control
strategies. The secondary impacts and control costs associated with the
recommended control strategy, steam stripping, are presented in Chapters 5
and 6, respectively.
1-2
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2.0 INDUSTRY DESCRIPTIONS
This Control Technology Center (CTC) document is intended to apply to
industrial wastewater generated by new and modified sources within the
following industries:
The Organic Chemicals, Plastics, and Synthetic Fibers Manufacturing
Industry, (OCPSF);
The Pesticides Manufacturing Industry;
The Pharmaceuticals Manufacturing Industry; and
The Hazardous Waste Treatment, Storage, and Disposal Facilities
Industry, (TSDF).
In addition, although not covered by this document, the EPA is in the process
of gathering data on the Pulp, Paper and Paperboard and Builders Paper and
Board Mill Industry (Pulp and Paper Industry). Information is presented in
this chapter on wastewater streams generated by these five industries.
The industry descriptions and wastewater characteristics presented in
this chapter reflect data collected by the EPA on VOC emissions from
industrial wastewater, and work done by the EPA either to develop effluent
guidelines or to evaluate the need to develop effluent guidelines.1"7 The
four industries listed above are included together in this document because
based on the available data, their wastewaters are similar in characteristic
and would have similar control requirements. The wastewater characteristics
such as solids content, organic content, volatility and solubility of organic
constituents, and wastewater volumes are all similar for pharmaceutical,
pesticide, and OCPSF industries as evidenced by the use of steam strippers at
facilities within all of these industries. Since a significant portion of the
waste handled by the TSDF facilities is from one of these three industries,
these wastewaters are also similar in characteristics. The similarities of
these wastewaters are further supported by statements made in the Federal
Register notice promulgating regulations for the pesticide industry.8
Processes in these industries (pharmaceutical and OCPSF) are similar to those
in the pesticides industry and the proposed effluent limitations guidelines
and standards for the OCPSF, Pharmaceuticals, and pesticides categories are
based on the same treatment technologies. This list of these four industries
could expand to include the pulp and paper industry as well as other
2-1
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industries as information becomes available.
Based on information gathered by EPA in developing effluent guideline
limitations, there were approximately 3,500 facilities in 1982 in the four
industries included in this document. These facilities produced approximately
700 million gallons per day (MGD) of wastewater. Table 2-1 presents estimates
of the number of facilities and the quantities of wastewater generated by each
industry. Based on available flow and concentration data, the quantity of
organic compounds in wastewater generated by each of the four industries are
considered significant. In addition, based on the information available on
wastewater characteristics within these industries, similar controls are
applicable and similar control requirements are warranted for new and modified
sources within each industry.
Data collected in developing effluent guideline limitations were obtained
from responses to questionnaires sent under the authority of Section 308 of
the Clean Water Act (CWA) and field sampling and analysis. These data are
typically restricted to 126 pollutants called priority pollutants. Of these,
only 27 are VOC (as listed in Table 2-2). As a result, these data represent a
subset of VOC; those organics that are also priority pollutants. Priority
pollutant data may not, therefore, provide an accurate estimate of the total
organic concentration in wastewater.
The EPA also collected data under the authority of Section 114 of the
Clean Air Act to evaluate emissions of VOC and potentially hazardous air
pollutants from the OCPSF industry. Testing was not required as part of the
Section 114 request, and the data provided represent a combination of actual
sampling data and engineering estimates. Information was also collected
through site visits conducted by EPA to facilities within each of the
industries included in this chapter. During this study, the correlation
between VOC and priority pollutants was found to be highly variable with VOC
content, typically one to six orders of magnitude greater than organic
priority pollutant content for these industries.
The following sections discuss each of the four industries included in
this document, and the pulp and paper industry, in terms of approximate number
of facilities and the number of processes or products. Wastewater
characteristics such as the sources and quantities of wastewater generated,
and the methods of discharge are also provided.
2-2
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TABLE 2-1. WASTEWATER GENERATION BY INDUSTRY
Total Number Daily Wastewater
Of Facilities Generation
Industry (1982) (MGD)
OCPSF
Pesticides
Manufacturing
Pharmaceuticals Manufacturing
TSDF
1,000
119
466
1.909
500
<100
93
16a
TOTAL 3,500 700
"This only represents wastewater generated by the TSDF as landfill leachate,
Actual quantities of organic-containing wastewater handled is much higher.
2-3
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TABLE 2-2. PRIORITY ORGANIC COMPOUNDS THAT ARE VOC
Chemical
Acrolein
Acrylonitrile
—^ Benzene
Bromodi chl oromethane
Bromoform
Bromomethane
Carbon tetrachloride
Chlorobenzene
Chloroethane
2-Chloroethyl vinyl ether
Chloroform
Chl oromethane
Di bromochl oromethane
1,1-dichloroethane
1,2-dichloroethane
1,1-dichloroethene
trans- 1,2-dichloroethene
1,2-dichloropropane
cis-l,3-dichloropropane
1,3-dichloropropane
Ethyl benzene
1,1,2,2-tetrachloroethane
Tetrachl oroethane
Toluene
1, 1, 2 -tri chl oroethane
Trichloroethene
Vinyl chloride
CAS
Number
107-02-8
107-13-1
71-43-2
75-27-4
75-25-2
74-83-9
56-23-5
108-90-7
75-00-3
110-75-8
67-66-3
74-87-3
124-48-1
75-34-3
107-06-2
75-35-4
156-60-5
78-87-5
10061-01-5
10061-02-6
100-41-4
79-34-5
127-18-4
108-88-3
79-00-5
79-01-6
75-01-4
Adapted from References 6.
2-4
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2.1 ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS, MANUFACTURING
Approximately 1,000 facilities are included in the OCPSF industry,
defined as all facilities falling under the following standard industrial
classification (SIC) codes:
2821 Plastics Materials, Synthetic Resins, and Nonvulcanizable
Elastomers;
2823 Cellulosic Manmade Fibers;
2824 Manmade Organic Fibers, except Cellulosic;
2865 Cyclic Organic Crudes and Intermediates, and Organic Dyes and
Pigments; and
2869 Industrial Organic Chemicals, Not Elsewhere Classified.
The OCPSF industry includes a diversity of chemical processes producing a
large number of chemical products. Some facilities within these industrial
categories produce large volumes of a single product continuously while other
facilities may produce various specialty products in short campaigns.
However, despite the diversity of this industry, EPA has determined that 98
percent of all products manufactured are produced by one of 41 major generic
processes. These processes are listed in Table 2-3. The OCPSF industry
generates about 530 MGD of wastewater. About 32 percent of the OCPSF
facilities are direct dischargers (i.e., wastewater is treated on-site and
discharged directly to a water body); 42 percent are indirect dischargers
(wastewater is discharged to a publicly owned treatment works (POTW)), and 26
percent are zero dischargers (no wastewater discharged from the facility).
Estimates for average daily process wastewater flow per plant are 1.22 MGD for
the direct dischargers and 0.24 MGD for the indirect dischargers.9 The
majority of this volume is from cooling water use. Most of the wastewater
collection systems at facilities in the OCPSF industry are underground sewers.
Very few wastewater streams are transported in overhead pipe. In addition, in
some facilities, vigorous aeration of the wastewater prior to biological
treatment is used to improve the biological activity. Based on OAQPS visits
to several facilities in the OCPSF industry, significant potential exists in
this industry for emissions of VOC from wastewater.
2-5
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TABLE 2-3. GENERIC CHEMICAL PROCESSES
1. Acid Cleavage
2. Alkoxylation
3. Alkylation
4. Amination
5. Ammonolysis
6. Ammoxidation
7. Carbonylation
8. Chlorohydrination
9. Condensation
10. Cracking
11. Crystallization/Distillation
12. Cyanation/Hydrocyanation
13. Dehydration
14. Dehydrogenation
15. Dehydrohalogenation
16. Distillation
17. Electrohydrodimerization
18. Epoxidation
19. Esterification
20. Etherification
21. Extraction
22. Extractive Distillation
23. Fiber Production
24. Halogenation
25. Hydration
26. Hydroacetylation
27. Hydrodealkylation
28. Hydrogenation
29. Hydrohalogenation
30. Hydrolysis
31. Isomerization
32. Neutralization
33. Nitration
34. Oxidation
35. Oximation
36. Oxyhalogenation
37. Peroxidation
38. Phosgenation
39. Polymerization
40. Pyrolysis
41. Sulfonation
Taken from Reference 1.
2-6
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Concentrations of organic pollutants are highly variable in process
wastewater generated by OCPSF industry facilities. Table 2-4 presents some of
the concentration data provided by facilities in response to Clean Air Act
Section 114 requests. Table 2-4 lists the pollutants identified in more than
three different wastewater streams and the minimum and maximum concentration
reported for each pollutant. The largest range in concentration was reported
for ethanol. The minimum and maximum concentrations reported for this
pollutant were 199 milligrams per liter (mg/1) and 443,213 mg/1, respectively.
Wastewaters generated in the OCPSF industry may contain moderate levels of oil
and grease or suspended solids but usually not in levels which would preclude
steam stripping. Steam stripping is an effective technology in use at many
facilities in the OCPSF industry for removing organics from wastewater.
Table 2-4 is based on data gathered for this project and is provided for
illustration only. The data is not necessarily all inclusive with regard to
the compounds shown or the concentration ranges presented. The data simply
illustrate that these wastewaters contain a variety of compounds with wide
variations in concentration. Although concentrations for various pollutants
are highly variable, the data indicate that a small number of streams
contribute the majority of the organic compounds in OCPSF wastewater. Organic
quantities were computed for each process wastewater stream where data were
available from facility responses to the Section 114 information requests. In
addition, a total organic quantity representing all the reported streams was
determined by summing the organic quantities computed for each individual
wastewater stream. Based on these data collected from facilities in the OCPSF
industry, approximately 20 percent of the individual wastewater streams were
found to account for 65 percent of the total organic quantity for all the
reported streams.10
2.2 PESTICIDES MANUFACTURING
The Pesticides Manufacturing Industry provides a wide range of chemicals
used to control crop-destroying insects and undesirable vegetation. This
document covers the segment of the pesticide industry that manufactures
pesticide chemical active ingredients. One hundred and nineteen such plants
were identified in development of the 1985 effluent standards (50 FR 40674,
October 4, 1985).8
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TABLE 2-4. POLLUTANT CONCENTRATION DATA PRESENTED IN SECTION 114 RESPONSES
Pollutant
1,3-Butadiene
Acetaldehyde
Acetone
Acrylonitrile
Butane
Butene
Perchloroethylene
Ethylene dichloride
Trichloroethane
Dichloroethane
Ethylene Oxide
Chloroethane
Benzene
Carbon tetrachloride
Methylene chloride
Chloroform
Chlorobenzene
Ethanol
Ethyl benzene
Formaldehyde
Gasoline (C5's thru ClO's)
Hexane
Isobutane
Methyl isobutyl Ketone
Naphtha
Concentration
Minimum
1
20
14
50
700
700
24
5.44
50
273
2
2
0.44
1
0.01
1
0.1
199
0.4
17,485
1,000
90,
0.1
8,888
398
(mg/1 )
Maximum
2,986
2,180
1,220
15,000
1,000
1,000
100
10,110
100
10,110
1,252
300
2,800
29,592
83
400
50
443,213
25
19,487
50,000
10,000
0.2
12,072
14,423
2-8
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TABLE 2-4. (CONTINUED)
Concentration (mq/1)
Pollutant
Naphthalene
Phenol
Propylene Oxide
Styrene
Toluene
Total Organic Compounds
Tri ethyl ami ne
Minimum
0.4
6.2
16.4
5
1
0.05
1,622
Maximum
21
125
2,006
25,524
25,000
1,000,000
100,000
2-9
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These plants produce pesticide products covered under the following SIC codes:
2819 Industrial Inorganic Chemicals, Not Elsewhere Classified
2869 Industrial Organic Chemicals, Not Elsewhere Classified
2879 Pesticides and Agricultural Chemicals, Not Elsewhere Classified
(Nonpesticide products under these SIC codes are excluded.)
The volume of wastewater discharged by facilities in this industry ranges
from less than 10,000 gallons per day to 1 MGD, with over half the facilities
in the industry generating less than 10,000 gallons per day. Discharge
methods vary from plant to plant and one method or a combination of methods
may be used. Forty-five facilities directly discharge wastewater, 38 are
indirect dischargers, and 18 are zero dischargers.
A variety of organic compounds have been detected in pesticides industry
wastewater streams. These include: phenols, aromatics, halomethanes,
clorinated ethanes, nitrosamines, dienes, cyanides, and pesticide compounds.
Sampling data generated during effluent guidelines development on organic
concentrations for the industry are limited to organic priority pollutant
concentration data. High concentrations of halomethanes and chlorinated
ethanes were detected in the pesticide plant wastewaters. The organic
compounds detected in the wastewaters are used as solvents and raw materials
or occur as impurities or by-products. The sources and characteristics of
wastewaters generated by pesticide manufacturing facilities is expected to be
similar to those in the OCPSF industry. Although the wastewater flow rates
from many of the facilities is lower, the organic content and other wastewater
characteristics, such as total suspended solids concentrations, appear to be
similar to those in the OCPSF industry. The pesticide development document
provides detailed information on ten steam strippers in use at Pesticide
Industry plants.3
2.3 PHARMACEUTICALS MANUFACTURING
The Pharmaceutical Manufacturing Industry includes facilities which
manufacture, extract, process, purify, and package chemical materials to be
used as human and animal medications. Four hundred and sixty-six facilities
were identified by EPA as Pharmaceutical Manufacturers. This industry
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as defined in the Federal Register (48 FR 49809, October 27, 1983)11 includes
facilities in the SIC codes:
2831 Which was split in 1987 into:
2835 Diagnostic Substance;
2836 Biological Products Except Diagnostic Substances;
2833 Medicinal Chemicals and Botanical Products;
2834 Pharmaceutical Preparations; and
2844 Perfumes, Cosmetics and Other Toilet Preparations
which function as skin treatment.
Other facilities covered by this document are:
The manufacture of products considered pharmaceutically active by
the Food and Drug Administration;
The manufacture of non-pharmaceutical products made at
pharmaceutical manufacturing facilities that generate similar
wastewater to those from Pharmaceuticals production;
The manufacture of products "which have non-pharmaceutical uses" but
that were "primarily intended for use as a pharmaceutical"; and
Pharmaceutical research.
Pharmaceutical production operations may be batch, semi-continuous, or
continuous. However, the most common method of operation is batch.
Manufacturing in the industry can be characterized by four processes. These
are fermentation; extraction; synthesis; and mixing, compounding, or
formulating.
Fermentation is usually a large scale batch process and involves
fermentation, or controlled growth of specific microorganisms in a reactor
vessel to produce a desired product. The desired product is then recovered
from the fermentation broth using solvent extraction, adsorption,
precipitation and filtration, or ion exchange. Waste streams generated from
fermentation processes include discharges from reactor cleanings and
sterilizations, off-gas scrubber effluents, and occasional off-specification
batches. Solvents used in extracting the product from the broth in the
recovery process may be discharged into the sewers in the waste streams as
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well.
Extraction refers to the extraction and recovery of a small volume of
desired product from naturally occurring sources such as plant roots and
leaves, animal glands, and parasitic fungi. Extraction operations are usually
either batch or semi-continuous. Wastewater discharges from extraction
processes include spent raw materials, solvents used in extractions, and
spills and equipment wash waters.
Chemical synthesis, either through batch or continuous processes (usually
batch), is the most common method of preparing Pharmaceuticals. Synthesis of
Pharmaceuticals involves reaction of the appropriate raw materials and
recovery of the desired product. Effluents from synthesis operations are
highly variable as are the processes where they are generated. Process
solutions, vessel wash wasters, filtrates, concentrates, spent solvents, and
scrubber effluents are all sources of wastewater. Pump seal water, spills,
and cleaning wash waters are additional sources. Any of these sources may
contain significant concentrations of organics.
Mixing, compounding, and formulating operations involve preparation of
the active ingredients into a dosage form for consumer use. The primary
sources of wastewater from these processes are from equipment washings,
scrubber effluents, and spills.
Although wastewater streams from all four processes have the potential to
contain high organic loadings, fermentation and synthesis operations usually
generate larger volumes of wastewater and the wastewaters generated usually
contain higher organic loadings. Based on data gathering efforts by EPA, the
pharmaceutical manufacturing industry discharges significant quantities of
organic compounds in their raw wastewaters.
Discharge practices across the industry vary; 59 percent are indirect
dischargers, 29 percent are zero dischargers, and the remainder are direct
dischargers. Flow data from Clean Water Act Section 308 questionnaires are
limited to the 70 percent of direct and indirect dischargers who provided
responses. Over half the total 80 MGD generated by these respondents resulted
from direct discharges (25 facilities contributed 45 MGD). To better
determine the total industry wastewater generation, EPA estimated the
contribution from the non-respondents at 13 MGD. The total wastewater flow,
therefore, is approximately 93 MGD.
A study by the Pharmaceutical Manufacturers' Association, which focused
on 26 member companies identified a total of 46 volatile organics used by the
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industry.12 These companies represent 53 percent of the domestic sales of
prescription drugs. Industry use of organic compounds is primarily as raw
materials or solvents. An estimated 84 percent of the organic compounds are
recycled and 16 percent are waste organics. Approximately 2.7 percent of the
waste organics are discharged to the sewer.
Because much of the industry uses batch operations, this industry has
more variability in its wastewater flows and organic content. However, in
many cases these wastewaters contain large quantities of organic compounds.
Information gathered on the characteristics and volumes of wastewater
generated in this industry support the inclusion of this industry in this
document. This is supported by the use of steam strippers by at least eight
pharmaceutical manufacturers.4
2.4 HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES (TSDF)7
In 1986, EPA conducted a study to gather data on wastewater produced by
this source category as part of Clean Water Act effluent guidelines
development work. The Domestic Sewage Study, performed by the EPA in response
to Section 3018(a) of the Resource Conservation and Recovery Act (RCRA),
identified TSDF (referred to as Hazardous Waste Treaters (HWT) in that study)
as significant contributors of hazardous wastes to POTW. The EPA has placed
very high priority on development of pretreatment standards for Centralized
Waste Treaters to control toxic and hazardous pollutants.
EPA has divided the TSDF industry into three categories for effluent
guideline purposes:
1. Landfills with leachate collection, including commercial (off-site)
and industrial (on-site) hazardous waste (Subtitle C of RCRA) and
municipal nonhazardous waste (Subtitle D of RCRA) landfills.
2. Hazardous waste incinerators with wet scrubbers (commercial and
industrial).
3. Centralized waste treaters, including commercial, industrial and
federal (Subtitle C of RCRA) TSDF with and without categorical
effluent regulations.
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EPA has identified 1,304 out of 1,909 facilities that would be subject to
effluent guideline regulations if EPA develops any in the future. They break
down as
follows:
Facility Type Direct Discharge Indirect Discharge Other*
Landfill Leachate 173 355 383
Incinerator Scrubber 137 27 109
Centralized Waste Treaters 87 515 ^23
TOTAL 397 907 605
*"0ther" includes off-site disposal at a commercial aqueous waste treatment
facility, deep well injection, and other methods.
Landfill leachates contain high concentrations of toxic organic compounds
and metals, and conventional and nonconventional pollutants. Many organic
compounds are in the range of 1 - 10 mg/1, a few at greater than 100 mg/1.
Total mass in raw wastewater discharges of nonpriority organic compounds range
from 1.8 to 4.7 times greater than priority organic compounds. This industry
produces about 16 MGD of landfill leachate.
RCRA Subtitle D Surface Impoundments.13 Subtitle D surface impoundments
are impoundments that accept wastes as defined under Subtitle D of RCRA.
Subtitle D wastes are all solid wastes regulated under the RCRA that are not
subject to hazardous waste regulations under Subtitle C. These wastes are
defined in 40 CFR Part 257. Specifically, this document applies to process
wastewater produced by generators; small quantity generators; POTW; and TSDF
that is RCRA Subtitle D waste as defined in 40 CFR 257.
These Subtitle D surface impoundments might be used for evaporation,
polishing, storage prior to further treatment or disposal, equalization,
leachate collection, emergency surge basin, etc. They could be quiescent or
mechanically agitated.
A Subtitle D census conducted in 1986 identified 191,822 active surface
impoundments located at 108,383 facilities. The results show that 16,232
Subtitle D surface impoundments accept industrial wastes.
The total nonhazardous waste generation was estimated to be roughly
390,000,000 metric tons per year, with 93 percent of this provided by seven
2-14
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industries: industrial organic chemicals; primary iron and steel; fertilizers
and other agricultural chemicals; electric power generation; plastic and resin
manufacture; industrial inorganic chemicals; and clay, glass, and concrete
products. Table 2-5 shows the quantity of industrial waste managed in
Subtitle D surface impoundments. Table 2-6 shows the number of Subtitle D
surface impoundments accepting industrial waste by acreage category. The
State Subtitle D Consensus estimated that 17,159 Subtitle D surface
impoundments receive industrial wastes from small quantity generators. A
breakdown of total small quantity generator waste by industry is shown in
Table 2-7.
Incinerator wet scrubber liquors contain high concentration of toxic
metals but very few organics at relatively low concentrations. Approximately
15 MGD of incinerator wet scrubber liquors are produced.
Centralized waste treatment facilities typically have high
concentrations of toxic metals and organics. Numerous metals are found from
25 to 1,300 mg/1. Numerous priority organics are found greater than 1 mg/1
and some greater than 10 mg/1. Total mass in raw wastewaters of nonpriority
organics are approximated to be seven times greater than priority organics.
Centralized waste treaters produce approximately 27 MGD.
2.5 PULP, PAPER AND PAPERBOARD AND BUILDERS' PAPER AND BOARD MILLS INDUSTRY
The industry totaled 695 operating facilities at the time of the EPA
development work on the effluent limitations (final rule: 47 FR 52006,
November 18, 19821*). A more recent estimate prepared by EPA in 1989
indicates that there are now 603 facilities in this industry. Table 2-8 shows
a breakdown of the facilities by subcategory as estimated in 1982 and 1989.6
Due to industry diversity, EPA developed three subcategories based on the
similarity in the mills, raw materials used, products manufactured,
production processes employed, mill size, age, and treatment costs. These
subcategories are:
Integrated Mills;
Secondary Fibers Mills; and
Nonintegrated Mills.
2-15
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TABLE 2-5. QUANTITIES OF WASTES MANAGED IN
SUBTITLE D SURFACE IMPOUNDMENTS
Industry Quantity
(Dry Metric Tons)
Electric power generation (SIC 4911) 28,497,800
Fertilizer and other agricultural chemicals
(SIC 2873-2879) 8,640,800
Food and kindred chemicals (SIC 20) NA
Industrial organic chemicals (SIC 2819) 38,058,700
Leather and leather products (SIC 31) 1,200
Machinery, except electrical (SIC 35) NA
Pulp and paper (SIC 26) 579,700
Petroleum refining industry (SIC 29) NA
Pharmaceutical preparations (SIC 2834) NA
Plastics and resins manufacturing (SIC 2821) 30,513,700
Primary iron and steel manufacturing and ferrous
foundries (SIC 3312-3321) 14,563,000
Primary non-ferrous metals manufacturing and
Non-ferrous foundries (SIC 3330-3399) 147.300
Totals: 121,002,200
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TABLE 2-6. PERCENT OF SUBTITLE D SURFACE IMPOUNDMENTS ACCEPTING
INDUSTRIAL WASTE BY ACREAGE CATEGORY
Acreage Category Percent of Impoundments
(Acres) (%)
<0.1 10.8
0.1-0.4 24.8
0.5-0.9 33.6
1-5 17.0
6-10 7.0
11-100 5.8
>100 1.0
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TABLE 2-7. NUMBER OF SMALL QUANTITY GENERATORS BY INDUSTRY
GROUP AND QUANTITY OF WASTE GENERATED13
Industry
Pesticide end users
Pesticide-application services
Chemical manufacturing
Wood preserving
Formulators
Laundries
Other services
Photography
Textile manufacturing
Vehicle maintenance
Equipment repair
Metal manufacturing
Construction
Motor freight terminals
Furniture/wood manufacture
and refinishing
Printing/ceramics
Cleaning agents and cosmetic
Number of Small
Quantity Generators
1,623
9,444
753
193
902
15,646
16,322
9,355
272
224,632
1,795
37,320
12,677
148
3,355
24,640
543
Waste
Quantity
(MT/yr)a
1,122
•8,444
2,373
715
2,333
13,418
10,706
18,052
650
427,287
943
64,652
5,033
161
3,703
18,307
1,569
Other manufacturing
2,564
5,361
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TABLE 2-7. (CONTINUED)
Industry
Number of Small
Quantity Generators
Waste
Quantity
(MT/yr)
Paper industry
Analytical and clinical
laboratories
Educational and vocational
establishments
Wholesale and retail
establishments
Total:
181
6,409
1,179
5,731
377,981
544
7,171
N/Ra
3,876
597,625
"Metric tons per year
bNot Reported
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Integrated mills manufacture paper products or market pulp from wood which is
prepared, pulped, and bleached on-site. Some pulp may be purchased for
blending with pulp produced on-site to achieve the desired paper properties.
Nonintegrated mills manufacture paper products by blending purchased pulps to
achieve the desired paper properties. The Secondary Fibers mills get their
major fiber source from purchased wastepaper. Wastepaper is mildly cooked,
bleached (if necessary) and possibly blended with purchased pulp to achieve
desired paper properties.
The majority of the organics are formed in the pulping and bleaching of
virgin pulp. For this reason, the integrated pulp and paper mills are most
likely to generate waste streams with high organic loadings. Secondary fibers
mills and non-integrated mills do not generate wastewater with concentrations
of organics as high as the streams generated in integrated mills.
Based on EPA data, approximately 49 percent of the pulp and paper mills
are direct dischargers; 34 percent are indirect dischargers; two percent use a
combination of both; and seven percent are zero dischargers. Eight percent of
the pulp and paper mills did not report their method of discharge. The volume
of wastewater discharged averages about 2.8 MGD per facility.
During the pulping process, the lignin present in the wood is broken down
into simpler organic compounds such as methanol and acetone. These soluble
organics are washed from the pulp and are concentrated in the spent pulping
liquor. In the recovery process of this pulping liquor, the organics are
evaporated and condensed. The resulting condensate streams are rich in
organics and are sometimes sewered without treatment. Organics are also
formed as additional lignin breaks down in the bleaching stages. In the
presence of chlorine, chloroform and other chlorinated organics are formed and
are washed from the pulp. These organics are readily volatilized from the
bleach plant wash waters. Digester vent condensates, evaporator condensates,
and bleach plant wash waters may contain high organic loadings. Facilities
visited in 1989 by EPA are using air strippers and steam strippers to lower
organics concentration and total reduced sulfur from their condensate streams,
but some condensate streams are still sewered. Typically, wastewaters
discharged from processes in the pulp and paper industry are discharged into
grated trenches at elevated temperatures. Any controls in place that control
organics have been put in place to control total reduced sulfur emissions and
the resulting odor. No attempts to suppress emissions of volatile organics
from the wastewater collection and treatment systems were noted.
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TABLE 2-8. MILL POPULATION
Subcategory
Market kraft
Dissolving kraft
BCT kraft
Alkaline fine
Unbleached kraft & semi -chemical
Unbleached kraft - liner
Unbleached kraft - bag
Semi -chemical
Dissolving sulfite
Papergrade sulfite
Groundwood CMN
Groundwood fine
Groundwood TMP
Deink - fine
Deink - news
Deink - tissue
Tissue from wastepaper
Wastepaper-molded product
Paperboard from wastepaper
Builders' papers & roofing felts
NI - fine
NI - tissue
NI - lightweight
NI - electrical
NI - fine cotton
NI - filter nonwoven
NI - board
Misc. - integrated
Misc. - nonintegrated
Misc. - secondary fibers
Total Number
(1982)
13
3
9
20
11
17
12
20
6
16
6
9
4
5
4
16
23
20
161
66
32
29
12
6
7
14
16
88
34
16
Estimate
(1989)
14
3
8
24
8
21
5
16
6
11
5
9
7
5
4
21
19
13
132
21
35
22
10
4
6
13
12
91
38
20
Total: 695 603
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The pulp and paper industry has not been included in this document
because of the characteristics of the wastewater and the lack of data.
However, in the future, this industry may be added to the list of industries
required to control wastewaters containing organic compounds. The quantity of
wastewater generated in a typical pulp and paper facility is 2.8 MGD as
opposed to an average of 0.78 MGD in the OCPSF industry. Available data show
lower concentrations of organics in pulp and paper wastewaters than are found
in the four industries covered by this document. The wastewaters in the pulp
and paper industry also typically have higher total suspended solids
concentrations and pH values above 11 or below 3. These characteristics make
the pulp and paper wastewaters less amenable to steam stripping with carbon
steel equipment.
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2.6 REFERENCES
1. Office of Water Regulations and Standards. U. S. Environmental
Protection Agency. Washington, D. C. Development for Effluent
Limitations Guidelines and Standards for the Organic Chemicals and
Plastics and Synthetic Fibers Point Source Category. Volume I (BPT).
EPA 440/1-83/0095 (NTIS PB83-205633), February 1983. pp. 11-39, 94-96,
105-167, 195-198.
2. Office of Water Regulations and Standards. U. S. Environmental
Protection Agency. Washington, D. C. Development Document for Effluent
Limitations Guidelines and Standards for the Organic Chemicals and
Plastics and Synthetic Fibers Point Source Category Volume II (BAT).
EPA 440/l-83/009b (NTIS PB83-205641), February 1983. pp. II-7 - 11-14,
III-l - III-9, IV-10 - IV-78, V-l - V-15, VII-1 - VII-22.
3. Office of Water Regulations and Standards. U. S. Environmental
Protection Agency. Washington, D. C. Development for Effluent
Limitations Guidelines and Standards for the Pesticide Point Source
Category. EPA 440/1-85/079 (NTIS PB86-150042/REB), October 1985.
pp. III-9 - 111-16, VI-4 - VI-47.
4. Office of Water. U. S. Environmental Protection Agency. Washington,
D. C. Development Document for Final Effluent Limitations Guidelines,
New Source Performance Standards and Pretreatment Standards for the
Pharmaceutical Manufacturing Point Source Category. EPA 440/1-83/084
(NTIS PB84-180066/REB), September 1983. pp. 17-33, 49-75, 103-137.
5. Office of Water Regulations and Standards. U. S. Environmental
Protection Agency. Washington, D. C. Development Document for Effluent
Limitation Guidelines and Standards for the Pulp, Paper and Paperboard
Builders Paper and Board Mills Point Source Category. EPA 440/1-82/025
(NTIS PB83-163949), October, 1982. pp. 77-87, 183-235, 363-385.
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6. Meeting notes. Penny E. Lassiter, Environmental Protection Agency,
Chemicals and Petroleum Branch, with Tom O'Farrell, Office of Water
Regulations and Standards, Industrial Technology Division,
March 3, 1989.
7. Office of Water Regulations and Standards. U. S. Environmental
Protection Agency. Washington, D. C. Draft Decision Document for
Hazardous Waste Treatment Industry Effluent Guidelines Development.
EPA Contract No.: 68-01-6947, August 17, 1987.
8. Federal Register, October 4, 1985. Pesticide Effluent Limitations
Guidelines, Notice of Availability. 50 FR 40674.
9. U. S. Environmental Protection Agency. Code of Federal Regulations.
Organic Chemicals and Plastics and Synthetic Fibers; Point Source
Category Effluent Limitations Guidelines Pretreatment Standards; and
Standards of Performance for New Sources. Title 40, Chapter 1,
Subchapter N, Parts 414 and 416. Washington, D. C. Office of the
Federal Register. July 17, 1985. p. 29072.
10. Letter and attachments from Radian Corporation to Penny E. Lassiter,
EPA/OAQPS, July 10, 1987, on the summary of Section 114 responses.
11. U. S. Environmental Protection Agency. Code of Federal Regulations.
Pharmaceutical Manufacturing Point Source Category Effluent Limitations
Guidelines, Pretreatment Standards, and New Source Performance Standards.
Title 40, Chapter 1, Subchapter N, Part 439. Washington, D. C. Office
of the Federal Register. October 27, 1983. p. 49809.
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12 Office of Air Quality Planning and Standards. U. S. Environmental
Protection Agency. Research Triangle Park, North Carolina. Control of
Volatile Organic Emissions from Manufacture of Synthesized Pharmaceutical
Products, OAQPS Guideline Series, EPA-450/2-78- 029 (NTIS PB290-580/0),
December 1978. p 1-1 - 2-5.
13. Office of Solid Waste and Emergency Response. U. S. Environmental
Protection Agency. Subtitle D Study Phase I Report. Washington, D. C.
EPA 530-SW-86-054, October 1986.
14. U. S. Environmental Protection Agency. Code of Federal Regulations.
Pulp, Paper, and Paperboard and the Builders' Paper and Board Mills Point
Source Categories Effluent Limitations Guidelines, Pretreatment
Standards, and New Source Performance Standards. Title 40, Chapter 1,
Subchapter N, Parts 430 and 431. Washington, D. C. Office of the
Federal Register. November 18, 1982. p. 52006.
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3.0 VOC EMISSIONS DURING WASTEWATER COLLECTION AND TREATMENT
In the manufacture of chemical products, wastewater streams are generated
which contain organic compounds. These wastewaters are collected and treated
in a variety of ways. Some of these collection and treatment steps result in
the emission of VOC from the wastewater to the air. This chapter provides a
discussion of the potential VOC emission sources and presents estimates of
emissions for model systems. Wastewater sources are discussed in Section 3.1.
Potential sources of VOC emissions during wastewater collection and treatment
and factors affecting emissions from these sources are discussed in
Section 3.2. Overall VOC emission estimates from three example waste stream
collection and treatment systems are presented in Section 3.3. Development of
emission factors are presented in Appendices A and B.
3.1 SOURCES OF ORGANIC-CONTAINING WASTEWATER
The industries discussed in Chapter 2 differ in structure and manufacture
a wide variety of products. However, many of the chemical processes employed
within these industries use similar organic compounds as raw materials,
solvents, catalysts, and extractants. In addition, many of these processes
also generate similar organic by-products during reaction steps.
Consequently, many of the wastewater streams generated by the targeted
industries are similar in organic content. These organic containing
wastewater streams result from both the direct and indirect contact of water
with organic compounds.
3-1.1 Direct Contact Wastewatpr
Water comes in direct contact with organic compounds due to many
different chemical processing steps. As a result of this contact, wastewater
streams are generated which must be discharged for treatment or disposal. A
few sources of process wastewater are:
Water used to wash impurities from organic products or reactants;
Water used to cool or quench organic vapor streams;
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Condensed steam from jet eductor systems pulling vacuum on
vessels containing organics;
Water used as a carrier for catalysts and neutralizing
agents (e.g., caustic solutions); and
Water formed as a by-product during reaction steps.
Two additional types of direct contact wastewater are landfill leachate
and water used in equipment washes and spill cleanups. These two types of
wastewater are normally more variable in flow and concentration than the
streams previously discussed. In addition, landfill leachate and spill
cleanups may be collected for treatment differently than the wastewater
streams discharged from process equipment such as scrubbers, decanters,
evaporators, distillation columns, reactors, and mixing vessels.
3.1.2 Indirect Contact Wastewater
Wastewater streams which do not come in contact with organic compounds in
the process equipment are defined as "indirect-contact" wastewater. However,
a potential exists for organic contamination of these wastewater types.
Non-contact wastewater may become contaminated as a result of leaks from heat
exchangers, condensers, and pumps. These indirect contact wastewaters may or
may not be collected and treated in the same manner as direct contact
wastewaters. Pump seal water is normally collected in area drains which tie
into the process wastewater collection system. This wastewater is then
combined with direct contact wastewater and transported to the wastewater
treatment plant. Wastewater contaminated from condenser and heat exchanger
leaks are often collected in different systems and bypass some of the
treatment steps used in the treatment plant. The organic content in these
streams can be minimized by implementing an aggressive leak detection program.
3.2 SOURCES OF AIR EMISSIONS
Wastewater streams are collected and treated in a variety of ways.
Generally, wastewater passes through a series of collection and treatment
units before being discharged from a facility. Many of these collection and
treatment system units are open to the atmosphere and allow organic-containing
wastewaters to contact ambient air. Whenever this happens, there is a
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potential for VOC emissions. The organic pollutants volatilize in an attempt
to exert their equilibrium partial pressure above the wastewater. In doing
so, the organics are emitted to the ambient air surrounding the collection and
treatment units. The magnitude of VOC emissions depends greatly on many
factors such as the physical properties of the pollutants, the temperature of
the wastewater, and the design of the individual collection and treatment
units. All of these factors as well as the general scheme used to collect and
treat facility wastewater have a major effect on VOC emissions.
Collection and treatment schemes are facility specific. The flow rate
and organic composition of wastewater streams at a particular facility are
functions of the processes used. The wastewater flow rate and composition, in
turn, influence the sizes and types of collection and treatment units that
must be employed at a given facility. Figure 3-1 illustrates a typical scheme
for collecting and treating process wastewater generated at a facility and the
opportunity for volatilization of organics. Figure 3-1 illustrates wastewater
being discharged from a piece of process equipment into a drain. Drains are
typically open to the atmosphere and provide an opportunity for volatilization
of organics in the wastewater. The drain is normally connected to the process
sewer line which carries the wastewater to the downstream collection and
treatment units. Figure 3-1 illustrates the wastewater being carried past a
manhole and on to a junction box where several process wastewater streams are
joined. The manhole provides an escape route for organics volatilized in the
sewer line. In addition, the junction box may also be open to the atmosphere,
allowing organics to volatilize. Wastewater is discharged from the junction
box to a lift station where it is pumped to the treatment system. The lift
station is also likely to be open to the atmosphere, allowing volatilization
of organics. The equalization basin, the first treatment unit shown in
Figure 3-1, regulates the wastewater flow and pollutant compositions to the
remaining treatment units. The equalization basin also typically provides a
large area for wastewater contact with the ambient air. For this reason,
emissions may be relatively high from this unit. Suspended solids are removed
in the clarifier, and the wastewater then flows to the aeration basin where
microorganisms act on the organic constituents. Both the clarifier and the
aeration basin are typically open to the atmosphere. In addition, the
aeration basin is normally aerated either mechanically or with diffused air.
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Process A
Process C
Drain
V
Manhole
Junction
Box
Process B-
Open
Trench
Lift
Station
Equalization
Basin
Discharge
Underflow
Sump
Sludge
Digester
Waste Sludge
Figure 3-1. Typical wastewater collection and treatment scheme.
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Wastewater leaving the aeration basin normally flows through a secondary
clarifier for solids removal before it is discharged from the facility. The
secondary clarifier is also likely to be open to the atmosphere. The solids
which settle in the clarifier are discharged partly to a sludge digester and
partly recycled to the aeration basin. Finally, waste sludge from the sludge
digester is generally hauled off for landfilling or land treatment.
As mentioned previously, the types of components used to collect and
treat wastewater are facility-specific. Figure 3-1 serves only as an example
scheme for collecting and treating facility wastewater. Table 3-1 presents a
more complete list of components that may be sources of emissions in facility
collection and treatment systems. Although included in Figure 3-1, sludge
digesters are not included in Table 3-1 since they are not considered to be
major emission sources. The following sections will discuss each of the
emission sources listed in Table 3-1. A diagram of each unit is provided
including typical ranges of design parameters. The function of each unit,
emission mechanisms, and factors affecting emissions are also discussed.
Techniques for estimating emissions from each unit are presented in
Appendix A or Appendix B.
3.2.1 Drains
Wastewater streams from various sources throughout a given process are
normally introduced into the collection system through process drains.
Individual drains are usually connected directly to the main process sewer
line. However, they may also drain to trenches, sumps, or ditches. Some
drains are dedicated to a single piece of equipment such as a scrubber,
decanter, or stripper. Others serve several sources. These types of drains
are located centrally between the pieces of equipment they serve and are
referred to as area drains.
Many of the drains discussed above are open to the atmosphere. That is,
they are not equipped with a water seal pot or p-trap to prevent emissions of
organic vapors. A typical open drain configuration is shown in Figure 3-2,
and the typical range of dimensions are listed. As shown in Figure 3-2, a
straight section of pipe, referred to as the drain riser, extends vertically
from the main process sewer line to just above ground level. A process drain
line introduces wastewater to the mouth of the drain.
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TABLE 3-1. EMISSION SOURCES IN WASTEWATER COLLECTION AND TREATMENT SYSTEMS
Wastewater Collection System:
Drains
Junction Boxes
Lift Stations
Manholes
Trenches
Sumps
Surface Impoundments
Wastewater Treatment Units:
Weirs
Oil/Water Separators
Equalization Basins or Neutralization Basins
Clarifiers
Aeration Basins
pH Adjustment Tanks
Flocculation Tanks
Surface Impoundments
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TopVi«w
o.y.^.^v;..^.^.;,:^^-;^
StotVltw
Design Parameter
Drain riser height, L (m)
Drain riser diameter,
(m)
Process drain pipe diameter, D (m)
Effective diameter of drain riser, D (m)
Drain riser cap thickness, DC (cm)
Sewer Diameter, D (m)
Ranoe
0.3 - 1.2
0.1 - 0.3
0.005 - 0.15
0.005 - 0.15
0.5 - 0.7
0.6 - 1.2
Typical
0.6
0.2
0.1
0.1
0.6
0.9
Figure 3-2. Typical drain configuration.
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3'2-1-1 -VOC Emission Mechanise
Emissions occur from drains by diffusive and convective mechanisms * As
wastewater flows through the drain, organics volatilize in an attempt to reach
equilibrium between the aqueous and vapor phases. The organic vapor
concentration in the headspace at the bottom of the drain riser is much
higher than ambient concentrations. Due to this concentration gradient
organics diffuse from the drain into ambient air through the opening at'the
top of the drain riser. In addition, if the temperature of the wastewater
flowing through the sewer is greater than the ambient air temperature, this
temperature gradient will induce air flow from the vapor headspace in the
sewer line. This air flow passes through the drain riser and into the ambient
air. The convective forces created by this air flow establishes convective
mass transfer of the organics. Air flows resulting from wind blowing over or
into the drain, or from wind currents entering another sewer opening and
flowing through the sewer, also aid the mass transfer.
^l2-1'2- factors Af f"-"ng Emissions from Drains Drain emission rates
are affected by a number of factors. These factors include the composition
and physical properties of the organics in wastewater entering the drain and
flowing through the sewer line below the drain, the temperature of the
wastewater, drain design characteristics, and climatic factors.2 The
volatility of the organics in water is the most significant physical property
affecting the rate of emissions from drains. The Henry's Law constant (H) for
an organic compound provides an indication of this physical property Values
for H are determined by measuring the equilibrium concentrations of an organic
compound in the vapor and aqueous phases. However, the organic compound's
vapor pressure and water solubility are sometimes used, when laboratory data
are not available, to estimate values for H. Using these data, the value for
H is estimated by computing the ratio of the organic compound's vapor pressure
to its water solubility at the same temperature. Organic compounds with low
water solubilities and high vapor pressures exhibit the highest values for H
and, therefore, these compounds tend to volatilize into the vapor phase more
readily. Because the temperature of the wastewater affects the Henry's Law
constant, this parameter will affect emissions.
Drain design characteristics also affect emissions. Drain design is
dependent on the flow rate of the wastewater stream. The diameter of the
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drain riser must be large enough to prevent the wastewater from overflowing on
to the ground. As the diameter increases, so does the surface area exposed to
ambient air. This increase in surface area increases the rate of air
emissions. The length of the drain riser from the mouth of the drain to the
process sewer is another design parameter which affects emissions. Pollutants
are more readily emitted to the atmosphere from a short drain riser due to the
smaller resistance to diffusional and convective mass transfer.
Emission rates from a drain are also affected by climatic factors. These
include ambient air temperature and wind speed and direction. Differences in
temperature between the ambient air and the vapors at the bottom of the drain
establish pressure and density gradients across the drain riser. These
gradients generate bulk vapor flow from the sewer headspace to the top of the
drain riser. This bulk flow increases convective mass transfer of organic
compounds to the air surrounding the drain. Wind speed has a similar effect.
As wind moves across the top of the drain riser, it creates an aspirator-like
effect. The lower pressure at the mouth of the drain "pulls" vapors from the
sewer line headspace at the bottom of the drain riser. This pressure
gradient, therefore, increases the convective mass transfer of organic
compounds to air surrounding the drain. Wind blowing into any upstream
opening will also increase the volatilization rate of the organics.
Development of the drain emission factor is presented in Appendix B.
3.2.2 Manholes
Manholes are service entrances into process sewer lines which permit
inspection and cleaning of the sewer line. They are normally placed at
periodic lengths along the sewer line. They may also be located where sewers
intersect or where there is a significant change in direction, grade, or sewer
line diameter. Figure 3-3 illustrates a typical manhole configuration, and
presents typical ranges of manhole dimensions. The lower portion of the
manhole is usually cylindrical, with a typical inside diameter of four feet
to allow adequate space for workmen. The upper portion tapers to the
diameter of the opening at ground level. The opening is normally about two
feet in diameter and covered with a heavy cast-iron plate. The cover usually
contains two to four holes for ventilation so that the manhole cover can be
grasped for removal.
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TopVta*
Design
Manhole diameter, D. (m)
Manhole height, L (m)
Manhole cover diameter, D (m)
Diameter of holes in cover, D (cm)
Manhole cover thickness, H (cm)
Sewer Diameter, D (m)
Ranoe
0.6 - 1.8
0.3 - 1.8
0.4 - 0.7
1.2 - 3.8
0.5 - 0.7
0.6 - 1.2
Typical
1.2
1.2
0.6
2.5
0.6
0.9
Figure 3-3. Typical Manhole Configuration.
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3.2.2.1 VOC Emissions Mechanisms. Emissions occur from manholes by
diffusive and convective mechanisms.3 As wastewater moves through the sewer
lines, organics volatilize in an attempt to reach equilibrium between the
aqueous phase and the vapor headspace in the sewer line. The organic vapor
concentration in the headspace above the wastewater is much higher than the
concentration of organics in the ambient air above the manhole. Due to this
concentration gradient, organics will diffuse from the sewer line into the
ambient air through the manhole openings. In addition, if the temperature of
the wastewater flowing through the sewer is greater than the ambient air
temperature, this temperature gradient will induce air flow from the vapor
headspace in the sewer line. Wind entering through any opening in the sewer
system may also create air flows in the sewer line. This air flow passes
through the manhole openings and into the ambient air. The turbulence created
by this air flow establishes convective mass transfer of the organics and
increases the emission rate from the manhole.
3-2.2.2 Factors Affecting Emissions from Manholes. Emission rates from
manholes are affected by the following types of factors: characteristics of
the wastewater passing through the sewer line below the manhole, manhole
design characteristics, and climatic factors.* Wastewater characteristics
affecting emission rates include wastewater composition and temperature. Both
the concentration and physical properties of the specific organic compounds
present in the wastewater affect the emissions. As previously discussed for
drains, air emissions are higher for organics with greater volatility in water
and higher diffusivity in air. Wastewater temperature affects the volatility
of the compound in water and, therefore, also affects emissions. This effect
can be evaluated by measuring the change in the organic compound's Henry's Law
constant with temperature.
Manhole design characteristics that affect emission rates are: the
manhole diameter, length from the manhole cover down to the sewer line, the
thickness of the manhole cover, and the number and diameter of the vent holes
in the manhole cover. The length from the manhole cover to the sewer line
is the distance organics must diffuse from the wastewater before being emitted
to the ambient air. Therefore, an increase in this length will decrease the
emission rate. The thickness of the cover adds to this diffusional length.
The diameter of holes in the cover along with the number of holes determine
the ultimate surface area available for diffusion and convection of organics
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into the ambient air.
Also similar to drains, climatic factors affecting emission rates are
wind speed and direction and ambient air temperature. As previously
discussed, wind speed will establish an aspirator-type effect at the cover of
the manhole and increase convective mass transfer of the organics into the
air. In addition, differences in temperature between the ambient air and the
headspace air in the sewer line will establish density and thus pressure
gradients between these two locations. These gradients establish flow
patterns as previously discussed. This bulk air flow transports organic
compounds from the wastewater surface to the ambient air, thereby increasing
convective mass transfer. Wind blowing into the sewer system will also aid in
the volatilization of the organics and will increase the emission rate from
the sewer system components. Development of manhole emission factors are
presented in Appendix B.
3.2.3 Junction Boxes
A junction box normally serves several process sewer lines. Process
lines meet at the junction box to combine the multiple wastewater streams into
one stream which flows downstream from the junction box. Generally, the flow
rate is controlled by the liquid level in the junction box. Junction boxes
are normally either square or rectangular and are sized based on the flow rate
of the entering streams. As shown in Figure 3-4, uncontrolled junction boxes
are open to the atmosphere. The range of typical junction box dimensions are
provided at the bottom of Figure 3-4.
3>2<3-1 VOC Emission Mechanisms. Emissions occur from junction boxes
predominantly by convective mass transfer. Organics in the wastewater
volatilize into the ambient air just above the liquid surface in an attempt to
reach equilibrium between the liquid and vapor phases. Since the organic
vapors above the liquid are in contact with the ambient air, these organic
vapors can be swept into the atmosphere by wind blowing across the top of the
junction box.
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/ '/ '/
Design Parameter
Effective diameter, dg (m)
Grade height, h (m)
Water Depth (m)
Surface area (m2)
Range
0.3 - 1.8
1.2 - 1.8
0.6 - 1.2
0.007 - 2.5
Typical Design
0.9
1.5
0.9
0.7
Figure 3-4. Typical Junction Box Configuration.
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3-2'3'2- Factors Affecting Emissions from Junction Boxes. Emission
rates from junction boxes are affected by the following types of factors:
characteristics of the wastewater flowing through the junction box, design of
the junction box, and climatic factors.5 Wastewater characteristics such as
the concentration and physical properties of the specific organic compounds
present in the wastewater have a significant effect on air emissions.
Increases in organic compound concentration and physical properties such as
the compound's volatility in water increase air emission rates. Higher
wastewater temperatures also increase the organic compound's volatility in
water as previously discussed for drains. Therefore, an increase in
temperature will increase the emission rate.
Junction box design characteristics that affect emissions are: the
the fetch to depth ratio, the water turbulence in the junction box, and the
liquid surface area. Fetch is defined as the linear distance across the
junction box in the direction of the wind flow. Depth is represented by the
average liquid level in the junction box. As the liquid depth in the junction
box increases, so does the resistance to liquid phase mass transfer. That is,
organic compounds must overcome more resistance before they reach the water
surface. Once these organics reach the surface, the fetch length provides the
route for volatilization into the ambient air. Therefore, increases in the
fetch to depth ratio for the junction box increase air emissions.
Water turbulence enhances liquid phase mass transfer.6 In completely
smooth flow through the junction boxes, pollutants slowly diffuse to the water
surface to replace the volatilizing pollutants. In turbulent flow through the
junction box, the organic compounds are carried much more rapidly to the
surface by the turbulent water. Therefore, more organic compounds are exposed
to the surface air, and the emission rate is increased. If the sewer lines
feed water to the junction box above the liquid surface, the exposure of
organic compounds to the surface air is also increased. The water spills into
the junction box causing splashing and additional turbulence at the liquid
surface which increases emissions. In addition, wind entering the sewer
system through an upstream component may exit the junction box saturated with
organics. These effects can be minimized by introducing water to the junction
box below the liquid surface. The final design characteristic affecting
emissions is surface area. An increase in surface area at constant depth
increases the hydraulic (water) retention time in the junction box.
Therefore, not only is the area for volatilization increased but so is the
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time available for volatilization to occur.
Ambient wind speed is a climatic factor affecting air emissions. As the
wind speed increases, so does convective mass transfer due to the additional
air turbulence above the wastewater surface. This wind speed effect is more
prominent when the liquid level is closer to the top of the junction box. If
the sewer lines feed the junction box above the liquid surface, wind blowing
into the sewer system through an upstream component may also have an effect on
emissions from the junction box. Development of junction box emission factors
are presented in Appendix A. Appendix B also presents the development of
emission factors for junction boxes. However, the emission estimates
presented in Appendix B are based on the assumption that the major emissions
from a junction box are a result of air leaving the sewer line through the
junction box, in equilibrium with the water in the sewer. Appendix A presents
an emission estimate based on the assumption that evaporation from the
junction box, assisted by turbulence caused by influent streams, is the
primary cause of emissions.
3.2.4 Lift Station
Lift stations are usually the last collection unit prior to the treatment
system, accepting wastewater from one or several sewer lines. The main
function of the lift station is to provide sufficient head pressure to
transport the collected wastewater to the treatment system. A pump is used to
provide the head pressure and is generally designed to operate on and off
based on preset high and low liquid levels. An open top lift station is
illustrated in Figure 3-5. As shown in Figure 3-5, lift stations are usually
rectangular in shape and greater in depth than length or width.
3-2.4.1 VOC Emission Mechanisms. Emissions occur from lift stations
predominantly by convective mass transfer. Organics in the wastewater
volatilize into the ambient air just above the liquid surface in an attempt to
reach equilibrium between the liquid and vapor phases. Since the organic
vapors above the liquid are in contact with the ambient air, these organic
vapors can be swept into the atmosphere by wind blowing across the top of the
lift station.
3-2.4.2 Factors Affecting Emissions from Lift Stations. The factors
affecting emissions from lift stations are similar to the factors affecting
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Pump
Design
Effective diameter, dfi (m)
Width, W (m)
Grade height, h (m)
Water Depth (m)
Surface area (m2)
Ranoe
1.2 - 3.0
1.4 - 3.6
1.8 - 2.4
1.2 - 1.8
1.1 - 7.1
Typical
1.5
1.8
2.1
1.5
1.8
Figure 3-5. Typical Lift Station Configuration.
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emissions from junction boxes discussed in Section 3.2.3.2. These factors
are: the concentration and physical properties of the organics present in
the wastewater, lift station design characteristics, and climatic factors.7
Increases in organic compound concentration and volatility in water increase
the rate of emissions from lift stations. Because increases in temperature
increase the volatility of many compounds, warmer wastewater temperature will
increase the emissions rate of most organic compounds.
The design characteristics which affect air emission rates from lift
stations are: the liquid surface area, the water turbulence in the lift
station, and the fetch to depth ratio. Increases in these design parameters
will increase air emission rates. The hydraulic retention time which is a
function of wastewater flow rate and the liquid volume in the lift station
also has an effect on emissions. An increase in retention time will result in
an increase in air emissions due to the additional time for volatilization.
In addition to these design parameters, operation of the lift station
affects air emissions. The liquid level in a lift station normally rises and
falls based on the wastewater flow to the unit. As the level rises, the
wastewater acts as a piston displacing organic vapors above the liquid
surface into the ambient air. The linear distance between the low and high
level limits in the lift station determine the amount of displacement during
normal operation. As this distance increases, displacement increases and so
does the emission rate. Also, at lower liquid levels, wastewater is normally
spilling into the lift station above the liquid surface. This causes an
increase in turbulence which increases liquid phase mass transfer. Therefore,
volatilization occurs more rapidly above the surface of the rising liquid.
At the higher liquid levels, the sewer lines feeding the lift station are
often submerged which reduces splashing above the liquid surface. Development
of lift station emission factors is presented in Appendix A.
3.2.5 Trench
Trenches are normally used to transport wastewater from the point of
process equipment discharge to subsequent wastewater collection units such as
junction boxes and lift stations. This mode of transport replaces the drain
scenario as a method for introducing process wastewater into the downstream
collection system. In older plants, trenches are often the primary mode of
wastewater transportation in the collection system. Trenches are often
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interconnected throughout the process area and handle pad water runoff, water
from equipment washes and spill cleanups, as well as process wastewater
discharges. Normally, the length of the trench is determined by the general
locations of the process equipment and the downstream collection system units.
This length typically ranges from 50 to 500 feet. Trench depth and width are
dictated by the wastewater flow rate discharged from process equipment. The
depth and width of the trench must be sufficient to accommodate expected as
well as emergency wastewater flows from the process equipment. Figure 3-6
illustrates a typical trench configuration.
3'2-5-1 VOC Emission Mechanisms. Emissions from trenches, like junction
boxes and lift stations, occur predominantly by convective mass transfer. As
wastewater flows through the trench, organic compounds volatilize into the
ambient air above the liquid surface in an attempt to reach equilibrium
between the liquid and vapor phases. Since the organic vapors above the
liquid are in contact with the ambient air, the organic vapors above the
liquid can be swept into the atmosphere by wind blowing across the surface of
the trench. Due to this volatilization, the organic compound concentration
decreases as the wastewater flows through the trench. Therefore, the
volatilization rate decreases somewhat as the wastewater moves downstream from
the point of process equipment discharge.
3-2.5.2 Factors Affecting Emissions from a Trench. The factors which
affect emissions from trenches are: the concentration and physical properties
of the compounds in the wastewater, trench design characteristics, and
climatic factors.8 The effect of organic compound concentration and physical
properties on air emissions from trenches are similar to the effect of these
factors on emissions from well mixed, flow through impoundments (e.g.,
junction boxes, lift stations). Increases in organic compound concentration,
volatility in water, and water temperature will increase air emissions. Wind
speed also similarly affects air emissions from trenches. Increases in wind
speed accelerate air emissions by increasing convective mass transfer.
The trench design characteristics which affect emission rate include the
depth and width of the trench and the hydraulic retention time. Mass transfer
rates increase as the depth of the trench becomes more shallow and the width
of the trench becomes wider. The hydraulic retention time in the trench is a
function of the wastewater flow rate and the volume of the trench. Longer
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Design
Trench length, L (m)
Water depth (m)
Trench depth, h (m)
Trench width, V (m)
15 -ISO
0.3 - 0.9
0.4 - 1.2
0.3 - 0.9
Typical
15.2
0.6
0.8
0.6
Figure 3-6. Typical trench configuration.
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trenches increase the hydraulic retention for mass transfer to take place and,
therefore, will increase air emissions. The grade (slope) of the trench is
also important. Grade will have an effect on the turbulence of the wastewater
flowing through the trench. An increase in turbulence will reduce the liquid
phase resistance to mass transfer and thus increase air emissions.
Development of trench emission factors is presented in Appendix B.
3.2.6 Sumps
Sumps are typically used for collection and equalization of wastewater
flow from trenches prior to treatment. They are usually quiescent and open to
the atmosphere. Typical diameters and depths are approximately 1.5 meters.
3-2-6-1 VOC Emission Mechanism. Emissions occur from sumps by both
diffusive and convective mechanisms. As wastewater flows slowly through the
sump, organics diffuse through the water to the liquid surface. These
organics volatilize into the ambient air above the liquid, and can be swept
into the air by wind blowing across the surface of the sump.
3'2-6-2 Factors Affecting Emissions from a Sump. The factors affecting
emissions from a sump are similar to the factors affecting emissions from an
equalization basin. These factors are: wastewater characteristics, wind
speed, and sump design characteristics. The effects of wastewater
characteristics and wind speed were previously discussed in the sections
concerning junction boxes and lift stations. These two factors will have
similar effects on the rate of air emissions from sumps. The design
characteristics which affect air emission rates from sumps are: the fetch to
depth ratio, the liquid surface area, and the hydraulic retention time. Fetch
to depth ratios vary widely for different sumps. As the fetch to depth ratio
increases, so does the mass transfer rate of organics into the ambient air.
The hydraulic retention time, which is a function of the wastewater flow rate
and volume of the sump, also has an effect on emissions. An increase in
retention time provides additional time for organic compound volatilization to
occur and, therefore, emissions increase. Likewise, an increase in the
surface area of the sump increases the emissions rate. Appendix B also
presents the development of emission factors for sumps. However, the emission
estimates presented in Appendix B are based on the assumption that the major
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emissions from a sump are a result of density differences between the air
leaving the sewer line through the sump and the surrounding air. Appendix A
presents an emission estimate based on the assumption that diffusion from the
water in the sump to the air is the primary cause of emissions.
3.2.7 Weir
Weirs act as dams in open channels. The weir face is normally aligned
perpendicular to the bed and walls of the channel. Water from the channel
normally overflows the weir but may pass through a notch, or opening, in the
weir face. Because of this configuration, weirs provide some control of the
level and flow rate through the channel. This control, however, may be
insignificant compared to upstream factors which influence the supply of water
to the channel. A typical weir configuration is illustrated in Figure 3-7.
3.2.7.1 VOC Emission Mechanism. As shown in Figure 3-7, often the water
overflowing the weir proceeds down stair steps as shown in the figure. These
stair steps serve to aerate the wastewater. The wastewater splashes off each
step increasing the surface area of the water in contact with ambient air.
This action increases diffusion of oxygen into the water which may be
beneficial to the biodegradation process (often the next treatment step).
However, this increased contact with air also accelerates emissions of
volatile organics contained in the wastewater.9'10 The organics volatilize
from the surface of the falling water in an attempt to reach equilibrium
between the liquid and vapor phases. The volatilizing organic compounds are
swept into the ambient air surrounding the weir.
3.2.7.2 Factors Affecting Emissions from a Weir. The major factors
affecting emissions from weirs are: wastewater characteristics, ambient wind
speed, and weir design characteristics. The concentration and physical
properties of the organic compounds in the wastewater have a significant
effect on VOC emissions. The diffusivity in water of the specific organic
compounds present in the wastewater may be the most significant physical
property. Organics must first diffuse through the liquid phase before
volatilizing from the surface of the falling wastewater. Therefore, an
increase in organic compound diffusivity in water tends to increase the air
emissions rate. Wastewater temperature affects diffusivity as well as other
3-21
-------
Pesion
Weir height, h (m)
Range
0.9 - 2.7
Typical
1.8
Figure 3-7. Typical weir configurat
ion.
3-22
-------
compound physical properties and, therefore, has an effect on air emissions.
Ambient wind speed has a significant effect on convective mass transfer.
As the wastewater spills over the weir and splashes down the stair steps,
increased liquid surface area is exposed. Wind sweeps the volatilized
organics away from the liquid surface and carries them into the ambient air.
As the wind speed increases, so does convective transfer of organics by this
mechanism.
The height of the weir is the most significant design characteristic
affecting emissions.11 The height of the weir determines the length of time
that the wastewater stream is falling through the air. Because this is the
time period when the organics are being emitted to the air, an increase in
weir height will increase the magnitude of air emissions. Development of weir
emission factors is presented in Appendix A.
3.2.8 Oil/Water Separator
Oil/water separators are often the first step in the wastewater treatment
plant but may also be found in the process area. The purpose of these units
is to gravity separate and remove oils, scum, and solids contained in the
wastewater. Most of the separation occurs as the wastewater stream passes
through a quiescent zone in the unit. Oils and scum with specific gravities
less than water float to the top of the aqueous phase. Heavier solids sink to
the bottom. Most of the organics contained in the wastewater tend to
partition to the oil phase. For this reason, most of these organic compounds
are removed with the skimmed oil leaving the separator. The wastewater stream
leaving the separator, therefore, is reduced in organic loading. Figure 3-8
illustrates a typical oil/water separator. The separator shown in the figure
is open to the atmosphere.
3.2.8.1 VOC Emission Mechanism. Volatilization of organic compounds
from the surface of an oil/water separator is a complex mass transfer
phenomenon. Most organic compounds tend to partition to the oil phase which
floats on the surface of the separator. The force behind volatilization is
the drive to reach equilibrium between the concentration of organics in the
oil layer and the vapor phase just above this layer. Organic compounds
volatilizing into the vapor phase either diffuse or are swept by wind into the
ambient air surrounding the oil/water separator.
3-23
-------
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Design Parameter
Separator length (m)
Separator width (m)
Retention time (hr)
Ranoe
6.1 - 18.0
4.6 - 10.7
0.6 - 1.0
Typical Design
13.7
7.6
0.8
Figure 3-8. Typical oil/water separator configuration.
3-24
-------
3>2'8-2 Factors Affecting Fmissions from an Oil/Water Separator The
factors affecting emissions from oil/water separators are: characteristics of
the wastewater and oil layers, ambient wind speed, and design characteristics
of the separator.12 The concentration and physical properties of the
organic compounds contained in the wastewater significantly affect emissions.
The diffusivity of the organics in water and in the oil layer affect the mass
transfer rate to the surface of the separator. Diffusivity of the organic
compounds in air affect the rate of mass transfer into the ambient air.
The thickness of the oil layer also affects emissions. Organics that
partition from the wastewater into the oil phase must diffuse through the oil
layer to volatilize. If the separator is operated with a relatively thick
nonvolatile oil layer, this layer may tend to act as a blanket suppressing
emissions from the unit.
Ambient air speed above the oil surface increases convective mass
transfer into the ambient air. Turbulence created by wind moving across the
oil layer helps sweep organics into the ambient air. This effect is similar
to the increase in convective mass transfer due to wind moving across well
mixed, flow through units such as junction boxes and lift stations. The main
difference is the existence of the oil layer which affects volatilization.
Design characteristics affecting emissions include the length and width
of the oil/water separator. The length of the separator in the direction of
the wind has a significant effect on the amount of convective mass transfer.
This effect is similar to the fetch to depth ratio effect discussed for well
mixed, flow through impoundments. An increase in the length of the separator
increases area available for volatilization and, therefore, increases the
emission rate. Development of oil/water separator emission factors is
presented in Appendix A.
3.2.9 Equalization Basins
Equalization basins are used to reduce fluctuations in the wastewater
flow rate and organic content to the downstream treatment processes.
Equalization of wastewater flow rate results in more uniform effluent quality
from downstream settling units such as clarifiers. Biological treatment
performance can also benefit significantly from the damping of concentration
and flow fluctuations. This damping protects biological processes from upset
or failure due to shock loadings of toxic or treatment-inhibiting compounds.
3-25
-------
Figure 3-9 illustrates a typical equalization basin. Normally, these
basins use hydraulic retention time to ensure equalization of the wastewater
effluent leaving the basin. However, some basins are equipped with mixers to
enhance the equalization of organic compounds. Aerators may also be
installed in some equalization basins to accelerate wastewater cooling or to
saturate the wastewater with oxygen prior to secondary treatment.
3.2.9.1 VOC Emission Mechanisms. Emissions occur from equalization
basins by both diffusive and convective mechanisms.13 As wastewater flows
slowly through the basin, organic compounds diffuse through the water to the
liquid surface. These compounds volatilize into the ambient air above the
liquid surface in an attempt to reach equilibrium between the liquid and vapor
phases. Since the organic vapors above the liquid are in contact with the
ambient air, these organic vapors can be swept into the air by wind blowing
across the surface of the basin. If aerators are used in the basin,
organic compounds are convectively transferred to the liquid surface. In
addition, greater wastewater surface area is exposed to the wind and ambient
area above the basin.
3.2.9.2 Factors Affecting Emissions from Equalization Basins. The
factors affecting emissions from equalization basins are similar to the
factors affecting emissions from other well mixed, flow through impoundments.
These factors are: wastewater characteristics, wind speed, and equalization
basin design characteristics.1'1 The effect of wastewater characteristics and
wind speed were previously discussed in the sections concerning junction boxes
and lift stations. These two factors will have similar effects on the rate of
air emissions from equalization basins. The design characteristics that
affect air emission rates from equalization basins are: the fetch to depth
ratio, the liquid surface area, the hydraulic retention time, and the degree
of aeration. Fetch to depth ratios vary widely for different equalization
basins. As the fetch to depth ratio increases, so does the mass transfer rate
of organics into the ambient air. The hydraulic retention time, which is a
function of the wastewater flow rate and volume of the basin, also has an
effect on emissions. An increase in retention time provides additional time
for organic compound volatilization to occur and, therefore, emissions
increase. Likewise, an increase in the surface area of the basin increases
the emissions rate. Also, if the basin is aerated, emissions will occur more
3-26
-------
1.0m freeboard
Plotting aerator
Maximum urface ar«
Minimum allowable
operating
to protact
aerator*
'HHlLd!mini'on$ *'" V*Y with
and
Concrete asour pad*
Design Parameter
Effective Diameter (m)
Surface Area (m2)
Water depth (m)
Retention time (days)
Ranoe
20 -270
300 - 57,000
1 - 8
0.2 - 20
Typical Design
109
9,290
2.9
5
Figure 3-9. Typical equalization basin.
3-27
-------
rapidly from the aerated surface area. Therefore, as the degree of aeration
(and aerated surface area) increases, so do air emissions. Development of
equalization basin emission factors (aerated and nonaerated) is presented in
Appendix A.
3.2.10 Clarifiers
The primary purpose of a clarifier is to separate any oils, grease, scum,
and solids contained in the wastewater. Most Clarifiers are equipped with
surface skimmers to clear the water of floating oil deposits and scum.
Clarifiers also have sludge raking arms which prevent accumulation of organic
solids collected at the bottom of the tank.15
Figure 3-10 illustrates a typical clarifier. Clarifiers are generally
cylindrical in shape. The depth and cross-sectional area of a clarifier are
functions of the settling rate of the suspended solids and the thickening
characteristics of the sludge. Clarifiers are designed to provide sufficient
retention time for the settling and thickening of these solids.
3.2.10.1 VOC Emission Mechanism. Emissions occur from Clarifiers by
both diffusive and convective mechanisms.16 As wastewater flows slowly
through the clarifier, organic compounds diffuse through the water to the
liquid surface. These compounds volatilize into the ambient air above the
liquid surface in an attempt to reach equilibrium between liquid and vapor
phases. Since the organic vapors above the liquid are in contact with the
ambient air, these organic vapors can be swept into the air by wind blowing
across the surface of the clarifier. In addition, Clarifiers are often
equipped with overflow weirs. These weirs provide additional contact with
ambient air as the wastewater flows over the weir and spills into the effluent
collection area.
3-2.10.2 Factors Affecting Emissions from a Clarifier. The factors
affecting emissions from a clarifier are similar to the factors affecting
emissions from other well mixed, flow through impoundments.17 These factors
are: the wastewater characteristics, wind speed, and clarifier design
characteristics. Increases in wastewater temperature, organic concentration
and organic compound physical properties such as volatility and diffusivity in
water increase air emission rates. Likewise, increases in wind speed improve
3-28
-------
Design Parameter
Diameter (m)
Depth (m)
Retention time (hr)
Range
6.1 - 30.5
2.4 - 4.5
1.5 - 7
Typical Design
18.3
3.5
4.0
Figure 3-10. Typical clarifier configuration,
3-29
-------
convective mass transfer and, therefore, also increase air emissions The
design characteristics which affect emission rates from clarifiers are the
liquid surface area, the fetch to depth ratio, and the hydraulic retention
time. Increases in the magnitude of these design parameters increase air
emission rates. Increases in the hydraulic retention time in the clarifier
also increase emissions. Development of clarifier emission factors is
presented in Appendix A.
3-2.11 Biological Treatmpnt. Basins
Biological waste treatment is normally accomplished through the use of
aeration basins. Microorganisms require oxygen to carry out the
biodegradation of organic compounds which results in energy and biomass
production. The aerobic environment in the basin is normally achieved by the
use of diffused or mechanical aeration. This aeration also serves to maintain
the biomass in a well mixed regime. The goal is to maintain the biomass
concentration at a level where the treatment is efficiently optimized and
proper growth kinetics are induced.
The performance of aeration basins is particularly affected by
(1) mass of organic per unit area, (2) temperature and wind patterns,
(3) hydraulic retention time, (4) dispersion and mixing characteristics
(5) sunlight energy, (6) characteristics of the solids in the influent,'and
(7) the amount of essential microbial nutrients present. Basin efficiency
measured as the degree of stabilization of the incoming wastewater, is
dependent on both biological process kinetics and basin hydraulic
characteristics.
Three mechanisms affect the removal of organic compounds in aeration
basins. These mechanisms are: biodegradation, adsorption on to the sludge,
and air emissions.18 Because these three mechanisms compete against each
other, factors affecting the biodegradation and adsorption mechanisms will
have an effect on air emissions. The greater the biomass concentration in the
basin, the greater the removal of organic compounds will be by both
biodegradation and adsorption mechanisms. The biodegradability of a compound
will also affect the removal by biodegradation; as the biodegradability of the
compound increases, so does the rate of biodegradation. Also, because the
microorganisms prefer some compounds more than others, the biodegradation
process is selective and depends on the compound matrix. Octanol-water
3-30
-------
r
partition coefficients are often used to indicate the affinity of a compound
for the organic or aqueous phase. The relative magnitude of this coefficient
provides some indication of organic compound removal by the adsorption
mechanism.
Typically, aeration basins are equipped with aerators to introduce oxygen
into the wastewater.19 The biomass uses this oxygen in the process of
biodegrading the organic compounds. However, aeration of wastewater also
affects air emissions. Increased liquid surface area is exposed to ambient
air, and, due to the turbulence caused by the aerators, the liquid and gas
phase resistances to mass transfer are reduced. Convective mass transfer in
both phases is increased. This transfer mechanism significantly increases ai
emissions compared to quiescent, flow-through type tanks like clarifiers.
However, many of the factors which affect emissions from flow through tanks,
like clarifiers, also affect emissions from aeration basins. The
concentration and physical properties of the organics have a similar effect on
emissions. As the volatility and diffusivities in water and air of the
organic constituents increase, air emissions also tend to increase.
Other factors affecting emissions from aeration basins include wind speed
and basin design characteristics. Figure 3-11 presents a typical aerated
biological treatment basin. Increases in wind speed increase convective mass
transfer from the wastewater in the basin and, therefore, increase air
emissions. However, emissions from aeration basins are not as sensitive to
wind speed effects compared to quiescent basins. Basin design characteristics
which affect emissions include: the quiescent and turbulent surface areas,
the depth of the basin, the design of the aerators, and the hydraulic
retention time of the basin. As the turbulent surface area of the basin
increases, air emissions will also tend to increase due to increased
convective mass transfer of the organic compounds. The depth of the basin
affects mass transfer in the liquid phase. Convective mass transfer in the
liquid phase increases as the basin becomes more shallow, and, therefore, air
emissions also tend to increase. Because the aerators generate the turbulence
that increases the rate of mass transfer in the liquid and gas phases, the
design of these aerators has a significant effect on emissions. The degree of
turbulence these aerators impart to the wastewater is a function of the power
output to the impellers, the impeller speed, and the impeller diameter.
Increases in these design parameters result in additional turbulence of the
wastewater and, for this reason, tend to increase air emissions. The final
3-31
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design parameter affecting emissions is the volume of the basin. As the
volume increases, so does the hydraulic retention time. Increases in the
basin volume provide additional time for removal by all three mechanisms:
biodegradation, adsorption, and air emissions. Therefore, the magnitude of
the increase in air emissions due to the additional retention time depends on
the relative removal rates by the other two mechanisms. Development of
biological treatment basin emission factors (aerated and nonaerated) is
presented in Appendix A.
3.2.12 Treatment Tanks
Flocculation tanks and pH adjustment tanks are typically used for
treatment of wastewater after and before biological treatment, respectively.
In flocculation tanks, flocculating agents are added to the wastewater to
promote formation of large particle masses from the fine solids formed during
biological treatment. These large particles will then precipitate out of the
wastewater in the clarifier which typically follows. Tanks designed for pH
adjustment typically precede the biological treatment step. In these tanks,
the wastewater pH is adjusted, using acidic or alkaline additives, to prevent
shocking of the biological system downstream.
3-2-12-1 VOC Emission Mechanism. Emissions occur from treatment tanks
by both diffusive and convective mechanisms.20 As wastewater flows slowly
through the tank, organic compounds diffuse through the water to the liquid
surface. These organic compounds volatilize into the ambient air above the
liquid and vapor phases. Since the organic vapors above the liquid are in
contact with the ambient air, these organic vapors can be swept into the air
by wind blowing across the treatment tank surface.
3-2-12-2 Factors Affecting Emissions from a Treatment Tank. The
factors affecting emissions from a treatment tank are similar to the factors
affecting emissions from other well mixed, flow-through impoundments.21
These factors are: the wastewater characteristics, wind speed, and design
characteristics of the treatment tank. Increases in the wastewater
temperature, organic compound concentration, and compound physical properties
such as volatility and diffusivity in water increase emission rates to the
air. Likewise, increases in wind speed improve convective mass transfer,
3-33
-------
thereby increasing air emissions. The design characteristics of the treatment
tanks that affect emission rates are the liquid surface area, the fetch to
depth ratio, and the hydraulic retention time. Increases in the magnitude of
these design parameters increase emission rates to the air. Development of
treatment tank emission factors is presented in Appendix A.
3.2.13 Surface Impoundments
Surface impoundments are typically used for evaporation, polishing,
equalization, storage prior to further treatment or disposal, equalization,
leachate collection, and as emergency surge basins. They could be quiescent
or mechanically agitated.
3'2'13'1 VOC Emission Mechanism Emissions occur from surface
impoundments by both diffusive and convective mechanisms. As wastewater
flows slowly through the tank, organic compounds diffuse through the water to
the liquid surface. These organic compounds volatilize into the ambient air
above the liquid and vapor phases. Since the organic vapors above the liquid
are in contact with the ambient air, these organic vapors can be swept into
the air by wind blowing across the surface of the impoundment.
3'2<13-2 factors Affecting Emissions from a Surface ImpoimHmpnt. The
factors affecting emissions from a surface impoundment are similar to the
factors affecting emissions from equalization basins if it is quiescent and
similar to factors affecting emissions from aeration basins if it is
agitated. Emission factor development for a surface impoundment will vary
depending on its purpose.
All characteristics of the impoundment should be reviewed to determine
what type of collection or treatment system it best resembles. Once the
surface impoundment has been characterized, refer to Appendix A for
determination of emission factors.
3.3 EXAMPLE WASTE STREAM COLLECTION AND TREATMENT SYSTEM SCHEMATICS
Emission mechanisms and factors affecting emissions from wastewater
collection and treatment units were presented in the previous section. The
general scheme used to collect and treat process wastewater varies from
3-34
-------
facility to facility and depends on many factors. Some factors which affect
the general scheme used at a particular facility are: the compounds
contained in the wastewater streams leaving different process areas, the flow
rate of these streams, the general equipment layout in the process areas, the
terrain around the facility, and the age of the facility. Also organic
compounds volatilize at different rates from different collection and
treatment units. Therefore, the general scheme used to collect and treat
wastewater at a facility has a significant impact on VOC emissions.
Due to the many factors that affect the general scheme used to collect
and treat facility wastewater, it is not possible to develop example
wastewater streams representing all possible scenarios. In lieu of this,
three example waste stream collection and treatment schemes were developed to
evaluate potential ranges in emissions from different facilities. The
collection and treatment system schematics presented were chosen to represent
a range of emission potentials and are not meant to characterize specific
facilities in the industries covered by this document.
Schematics of the three example waste stream collection and treatment
systems are shown in Figures 3-12, 3-13, and 3-14. Each figure shows the
discharge of a process wastewater stream into the example waste stream
collection system. In each case, the wastewater stream proceeds through the
collection system components and is combined for treatment with other facility
wastewater streams. Dimensions of these collection and treatment system units
are presented in Table 3-2. These dimensions are based on typical designs for
each unit and are within the dimension ranges discussed in Section 3-2.
For purposes of comparison, emissions are estimated for a wastewater
stream with the same flow rate and organic concentration as it flows through
the collection and treatment units in each example schematic. The wastewater
stream is discharged from the process equipment at a flow rate of 300 liters
per minute (1pm) and an overall organic concentration of 2,500 parts per
million (ppm). Table 3-3 provides a description of the example wastewater
stream. This example wastewater stream was designed to contain compounds that
span the range of volatilities to demonstrate a range of emission potentials.
Emissions are estimated from the collection and treatment units in each
example waste stream system using techniques presented in Appendix A. These
emission estimates are presented in Tables 3-4, 3-5, and 3-6 for Example Waste
Stream Schematics I, II, and III, respectively. In each table, emissions are
presented as a fraction of the mass of organic compounds entering the
3-35
-------
Process
Equipment
i5r
\
aln Dr
/ \
1
aln
/
Lift
Station
*i
Sludge
Digester
Discharge
Underflow
Waste Sludge
Figure 3-12. Example Waste Stream Schematic I.
-------
Process
Equipment
Dr
\
i
aln
/
Dr
\
i
aln
/
Junction
Box
H
Discharge -*
Clarlfler K
Underflow
Oil-Water
Separator
Aeration
Basin
Sludge
Digester
Waste Sludge
Figure 3-13. Example Waste Stream Schematic II.
Equalization
Basin
pn Adjustment
Tank
-------
Dr
\
aln
/
— »•
Open
Trench
»
Sump
Junction
Box
Lift
Station
/
*H
Aerated
Equalization
Basin
(A)
CO
CD
Discharge
ph Adjustment
Tank
Waste Sludge
Figure 3-14. Example Waste Stream Schematic III.
-------
TABLE 3-2. DIMENSIONS FOR EXAMPLE WASTE STREAM COLLECTION AND TREATMENT UNITS
Component
Design Parameter
Typical Dimensions
Drain
riser height (m)
riser diameter (m)
process drain pipe diameter
effective diameter of riser
riser cap thickness (cm)
sewer diameter (m)
(m)
(m)
0.6
0.2
0.1
0.1
0.6
0.9
Manhole
Junction Box
Lift Station
Trench
Weir
Oil/Water
Separator
Clarifier
diameter (m)
height (m)
cover diameter (m)
diameter of holes in cover (cm)
cover thickness (cm)
sewer diameter (m)
effective diameter (m)
grade height (m)
water depth (m)
surface area (m2)
effective diameter (m)
width, (m)
grade height (m)
water depth (m)
surface area (m2)
length (m)
water depth (m)
depth (m)
width (m)
height (m)
length (m)
width (m)
retention time (hr)
diameter (m)
depth (m)
retention time (hr)
1.2
1.2
0.6
2.5
0.6
0.9
0.9
1.5
0.9
0.7
1.5
1.8
2.1
1.5
1.8
15.2
0.6
0.8
0.6
1.8
13.7
7.6
0.8
18.3
3.5
4.0
3-39
-------
TABLE 3-2. (Continued)
Component Design Parameter Typical Dimensions
Sump effective diameter (m) 1.5
water depth (m) 1.5
surface area (m2) 1.8
Equalization
Basin effective diameter (m) 109
water depth (m) 2.9
surface area (m2) 9,290
retention time (days) 5
Aeration
Basin effective diameter (m) 150
water depth (m) 2.0
surface area (m2) 17,652
retention time (days) 6.5
Treatment
Tank effective diameter (m) 11
water depth (m) 4.9
surface area (m2) 93
retention time (hr) 2
3-40
-------
TABLE 3-3. EXAMPLE WASTEWATER STREAM
Wastewater Stream Content: Water = 99.75%
Total Organics = 0.25% (2,500 ppm)
Wastewater Flow: 300 1pm
Organic Waste Stream Volatility
Compound Concentration (ppm) Category
Henry's Law (25°C)
(atm-m3/gim)le)
Butadiene
Toluene
Naphthalene
Butanol
Phenol
Total:
500
500
500
500
500
2,500
High
Medium
Medium
Low
Low
1.42 x 10'1
6.68 x 10'3
1.18 x 10'3
8.90 x 10'6
4.54 x 10'7
3-41
-------
TABLE 3-4. EMISSION ESTIMATE FOR EXAMPLE WASTE STREAM SCHEMATIC I
Component*
Drain
Drain
Lift Station
Clarifier
Aerated Biological Treatment
Clarifier
Fraction
EmittedblC
0.13
0.13
0.17
0.017
0.12
0.017
Cumulative
Fraction Emittedb>c
0.13
0.19
0.29
0.30
0.36
0.36
Collection and treatment system components defined in Table 3-2.
Based on wastewater stream described in Table 3-3.
Calculations presented in Appendix A.
3-42
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TABLE 3-5. EMISSION ESTIMATE FOR EXAMPLE WASTE STREAM SCHEMATIC II
Component"
Drain
Drain
Junction Box
Manhole
Oil/Water Separator
Non-Aerated Equalization Basin
pH Adjustment
Aerated Biological Treatment
Clarifier
Fraction
Emittedb-c
0.13
0.13
0.057
0.032
0.31
0.28
0.0062
0.12
0.017
Cumulative
Fraction Emittedb'c
0.13
0.19
0.23
0.23
0.35
0.44
0.44
0.45
0.45
Collection and treatment system components defined in Table 3-2.
Based on wastewater stream described in Table 3-3.
Calculations presented in Appendix A.
3-43
-------
TABLE 3-6. EMISSION ESTIMATE FOR EXAMPLE WASTE STREAM SCHEMATIC III
====!
Component*
Drain
Open Trench
Sump
Junction Box
Lift Station
Manhole
Manhole
Aerated Equalization Basin
pH Adjustment Tank
Weir
Aerated Biological Treatment
Flocculation Tank
Clarifier
Fraction
Emitted"'6
0.13
0.026
0.0035
0.057
0.17
0.032
0.032
n 0.73
0.0062
0.26
ent 0.12
0.0062
0.017
Cumulative
Fraction Emittedb>c
0.13
0.15
0.15
0.19
0.30
0.30
0.31
0.73
0.74
0.80
0.81
0.81
0.81
on°n a?d treatmfnt s>stem components defined in Table 3-2.
on wastewater stream described in Table 3-3
Calculations presented in Appendix A.
3-44
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collection and treatment system. Tables 3-4, 3-5, and 3-6 show the cumulative
fraction of these organic compounds that is emitted at each stage in the
collection and treatment systems for each waste stream system. The cumulative
fraction emitted from Example Waste Stream Schematics I, II, and III are 0.36,
0.45, and 0.81, respectively.
Table 3-7 presents the estimates of annual VOC emissions from each of
these example schematics for various flow rates. From an evaluation of the
results presented in this table, it can be seen that overall VOC emissions are
lowest for Example Waste Stream Schematic I and highest for Example Waste
Stream Schematic III. Because the wastewater stream entering each example
stream is identical, the difference in overall VOC emissions is due to the
presence of different collection and treatment system components in the three
example schematics. Schematic I has the least number of collection and
treatment system components; and, therefore, has the lowest overall VOC
emission factor. Schematic III has the greatest number of collection and
treatment system components and; therefore, the highest overall VOC emission
factor. Although the number of collection and treatment system components may
indicate the emission potential, the characteristics of these components also
affects the emission potential. Sources which are quiescent or have small
surface areas would have lower overall emission factors than sources which are
aerated or turbulent. Clarifiers, treatment tanks, sumps, trenches, and
junction boxes are typically lower emitters than aerated equalization basins,
biological treatment, weirs, lift stations, and drains.
3-45
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TABLE 3-7. SUMMARY OF THE ESTIMATED ANNUAL VOC EMISSIONS FROM
EACH OF THE EXAMPLE WASTE STREAM SCHEMATICS
VOC Emissions (Mg/yr)*
Example
Schematics
Schematic I
Schematic II
Schematic III
Emission
Factor6
(fe) 40
0.36 18.7
0.45 23.9
0.81 42.4
Wastewater
150
70
90
159
Flow
300
140
180
318
Rate (lorn)
455
213
272
482
760
355
445
805
"The assumed wastewater volatile organic concentration is 2,500 ppm. (See
Table 3-3 for the characteristics of the example waste stream.)
Overall cumulative fraction emitted for each Example Waste Stream Schematic
(See Tables A-33 through A-35 in Appendix A.)
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3.4 REFERENCES
1. Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency. Research Triangle Park, North Carolina. VOC
(Volatile Organic Compound) Emissions from Petroleum Refinery
Wastewater Systems - Background Information for Proposed
Standards, Draft EIS. EPA-450/3-85-001a (NTIS PB87-190335),
February 1985.
2. Reference 1.
3. Reference 1.
4. Reference 1.
5. Office of Air Quality, Planning and Standards. U. S.
Environmental Protection Agency. Hazardous Waste Treatment,
Storage, and Disposal Facilities (TSDF) - Air Emission Models,
Draft Report. April, 1989.
6. Reference 5.
7. Reference 5.
8. Lyman, Warren, Ph.D., Reehl, William F., and Rosenblatt, David H.,
Ph.D. Handbook of Chemical Property Estimation Methods.
McGraw-Hill Book Company, New York, New York, 1982. pp. 15-9 to
15-31.
9. Reference 8.
10. Berglund, R. L., and Whipple, G. M. "Predictive Modeling of
Organic Emissions", Chemical Engineering Progress. Union Carbide
Corporation, South Charleston, West Virginia, pp. 46 - 54.
11. Reference 10.
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12. Liang, S. F. Hydrocarbon Losses by Atmospheric Evaporation from
Open Separators, Technical Progress Report, BRC-CORP24-73-F.
(Shell Models).
13. Reference 5.
14. Reference 5.
15. Metcalf & Eddy, Inc. Wastewater Engineering:
Treatment/Disposal/Reuse. McGraw-Hill Book Company, New York, New
York, 1979. pp. 201-222.
16. Reference 5.
17. Reference 5.
18. Reference 5.
19. Reference 15.
20. Reference 5.
21. Reference 5.
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4.0 VOC EMISSION CONTROL EQUIPMENT
As discussed in Chapter 3, VOC emissions during collection and treatment
of industrial wastewater can be significant, and measures to control these
emissions need to be considered. This chapter describes control measures that
can be applied to reduce these VOC emissions. Three control strategies are
discussed in this chapter. The first control strategy is waste minimization
through process modifications, modification of operating practices, preventive
maintenance, recycling, or segregation of waste streams. The second control
strategy is to reduce the organic content of the wastewater through treatment
before the stream contacts ambient air. The third strategy is to control
emissions from collection and treatment system components until the organic
compounds are either recovered or destroyed. Although the third strategy is
feasible in some cases, the more universally applicable treatment technology
is to reduce the quantity of waste generated or reduce the organic content of
the wastewater at the point of generation.
One type of treatment technology available and currently in use at many
facilities is steam stripping. Because steam stripping removes the organic
compounds most likely to be emitted downstream (most volatile compounds), it
is an effective technique for reducing VOC emissions from wastewater.
However, in some applications another organic removal technique may be better
suited. In other cases it may be more reasonable to control emissions up
through removal or destruction of the organic compounds. The purpose of this
section is to present and discuss some of the various emission control
strategies. A general discussion of the application of waste minimization to
control VOC emissions from industrial wastewaters is presented in Section 4.1.
Section 4.2 presents a discussion of organic compound removal technologies.
Section 4.3 presents VOC emission suppression controls from collection and
treatment system components. Add-on control devices are discussed in
Section 4.4.
4.1 WASTE MINIMIZATION
Waste minimization is a general term which includes both source reduction
and recycling. Source reduction refers to reduction or elimination of the
generation of a specific waste at the source. This may be accomplished
through process or equipment modifications, stream segregation, or changes in
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work practices. Recycling includes recovery and/or reuse of potential waste
streams. Waste minimization must be implemented on a process-specific basis.
However, implementation of an aggressive waste minimization program can be an
effective method of reducing emissions of VOC from industrial wastewaters.
Although many of the specific techniques which can be applied to minimize
waste generation are specific to one application, the implementation of any
waste minimization program should follow the guidelines presented below. By
following these guidelines, the most effective steps can be identified and
implemented.
4.1.1 Gather Baseline Data
The first step in any waste minimization program should be to identify
and characterize the individual waste streams. This should include flow rate,
composition, pH, and solids content of the wastewater streams. Although some
of this data might need to be gathered through a sampling program, some of it
may be available from hazardous waste manifests, Superfund Amendments and
Reauthorization Act (SARA) Title III Section 313 release reporting
calculations, permits, monitoring reports, product and raw material
specifications, and other internal records.
4-1-2 Identify and Rank Sources for Reduction
Using the baseline data gathered, a cost allocation system should be
developed to assess treatment and disposal costs to individual waste streams.
Future treatment and disposal costs should be considered in this evaluation,
as should potential liabilities associated with the waste handling and
subsequent treatment and disposal. Once the waste streams have been ranked
and prioritized, methods for controlling these streams can be considered.
4-1.3 Implementation of Reduction/Recycling
In selecting the appropriate method for reducing or eliminating a
wastewater stream, a variety of sources of information can be utilized. EPA's
Pollution Prevention Information Clearinghouse (PPIC), supported by the EPA's
Pollution Prevention Office contains information on case studies and reports
on pollution prevention. PPIC can be accessed by telephone hotline. Other
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valuable sources of information are State assistance programs, vendors, and
consultants.
As waste minimization steps are implemented, it is important that good
record keeping be continued to document which steps were effective and which
ones failed. This is especially important since future regulations may
require percentage reductions in wastes generated. Although some wastewater
streams will still be generated, an effective waste minimization program may
allow more cost-effective handling of these streams.
4.2 ORGANIC COMPOUND REMOVAL
4.2.1 Steam Stripping
Steam stripping is a proven technology which involves the fractional
distillation of wastewater to remove organic compounds. The basic operating
principle of steam stripping is the direct contact of steam with wastewater.
This contact provides heat for vaporization of the more volatile organic
compounds. The overhead vapor containing water and organics is condensed and
separated (usually in a decanter) to recover the organics. These recovered
organics are usually either recycled or incinerated in an
on-site combustion device.
In principle, a multistage steam stripper system can be designed to
achieve almost any level of organic compound removal. In practice, the
achievable VOC emission reductions and associated control costs are highly
dependent on wastewater characteristics such as flow, organic concentration
and composition, and the design of the collection and treatment systems.
As previously discussed, based on industry responses to Clean Air Act
Section 114 information requests, 20 percent of the reported wastewater
streams account for 65 percent of the organics by mass.1 Therefore, it may be
possible to achieve significant VOC emission reduction by controlling a
relatively small number of individual wastewater streams containing organic
compounds. In many cases, it may be possible to combine two or more of these
streams for treatment by the same steam stripper by hard piping these streams
from the point of generation to the steam stripper. As streams are combined,
the cost of control increases, however, cost per stream decreases. In
addition, the emission reduction achieved by controlling the combined streams
increases. This issue is discussed further in the presentation of steam
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stripper costs in Chapter 6.
4-2-1-1 Steam Stripper Process Description. Steam stripper systems may
be operated in batch or continuous mode. Batch steam stripping is more
prevalent when the wastewater feed is generated by batch processes.2 Batch
strippers may also be used if the wastewater contains relatively high
concentrations of solids, resins, or tars. Usually, batch steam strippers
provide a single equilibrium stage of separation. Therefore, the removal
efficiency is essentially determined by the equilibrium coefficients of the
pollutants and the fraction of the initial charge distilled overhead.
Wastewater is charged to the receiver, or pot, and brought to the boiling
temperature of the mixture. Heat is provided by direct injection of steam or
by an external heat exchanger normally referred to as a reboiler. The
overhead vapors are condensed and recovered. The solids, tars, resins,
and other residue remaining in the pot are normally disposed. By varying the
heat input and fraction of the initial charge boiled overhead, the same batch
stripper can be used to treat wastewater mixtures with widely varying
characteristics.
In contrast to batch strippers, continuous steam strippers are normally
designed to treat wastewater streams with relatively consistent
characteristics.3 Design of the continuous stripper system is normally based
on the flow rate and composition of a specific wastewater feed stream or
combination of streams. Multistage, continuous strippers normally operate at
greater organic compound removal efficiencies than batch strippers.
Continuous systems may also offer other advantages (over batch stripping) for
applications involving wastewater streams with relatively high flows and
consistent concentrations. These advantages include more consistent effluent
quality, more automated operation, and lower annual operating costs.
As discussed in the introduction for Section 4.2.1, it may be possible to
achieve significant emission reduction by controlling a relatively small
number of wastewater streams containing organic compounds. Wastewater streams
that are continuously discharged from process equipment are usually relatively
consistent in composition. Such wastewater streams would be treated with a
continuous steam stripper system. However, batch wastewater streams can also
be controlled by continuous steam strippers by incorporating a feed tank with
adequate residence time to provide a relatively consistent outlet composition.
For these reasons, the remaining discussion focuses on continuous steam
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stripping.
A continuous steam stripper system is shown in Figure 4-1. The steam
stripper presented in this figure is a generic stripper. For specific cases,
modifications to the design may provide more effective control. Alternate
feed locations and multiple feed locations are sometimes used. The steam
stripper can also be operated under a vacuum. In addition, steam strippers
may include a reflux stream where the bottoms stream flows into a reboiler to
vaporize and return to the column a portion of the bottoms stream. At least
one steam stripper studied, operated at an altered pH to change the
equilibrium of a reaction of a less volatile compound. The low volatility
compound through this reaction was removed efficiently.
In designing the appropriate steam stripper, these refinements should be
considered. However, the generic steam stripper presented in Figure 4-1 is a
generally applicable control which can be applied to control wastewater
streams with significant concentrations of organic compounds. The purpose,
design, and operation of each of the components of this system (a wastewater
feed tank, feed/bottoms heat exchanger, condenser system, and necessary pumps)
are discussed separately in this section.
The first component in the steam stripper system is the controlled sewer
system or hard piping from the point of wastewater generation to the feed
tank. This is necessary to control emissions prior to steam stripping. The
feed tank collects and conditions the wastewater feed to the steam stripper.
The tank is covered and vented to an on-site combustion device. Sufficient
residence time is provided to ensure that solids, oils, and grease that could
foul the heat exchanger and stripping column are separated from the wastewater
in the feed tank. Residence time in the feed tank also ensures that
wastewater is fed to the steam stripper at a relatively consistent flow rate
and composition.
After the wastewater is collected and conditioned, it is pumped from the
feed tank through the feed/bottoms heat exchanger and into the steam stripping
column. Steam is usually directly injected into the stripper at the bottom of
the column. The wastewater feed is usually introduced into the stripper at
the top of the column as shown in Figure 4-1. As the wastewater flows down
through the column it contacts this steam which is flowing countercurrently up
the column. Organic compounds in the wastewater absorb heat from the steam
and volatilize into the vapor stream. These constituents flow out the tap of
the column with any uncondensed steam.
4-5
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Non-Condensibtes
Control Device -*
Process Wastewater
via Controlled
Sewer or Hard Piping
Water Cooled
Condenser
To Wastewater
Treatment Plant
Feed/Bottoms
Heat Exchanger
Figure 4-1. Continuous Steam Stripper System
-------
A condenser system is used to recover the organic and water vapors
present in the overheads stream. The condensed overheads stream is fed to a
decanter where the organic and water phases are gravity separated. The
organic phase is usually either pumped to storage and then recycled to the
process or burned as fuel in a combustion device. The water phase is returned
to the feed tank and recycled through the steam stripper. Any non-condensable
gases and highly volatile organic compounds not recovered by the condenser
system are routed to an on-site control device such as a carbon adsorber,
boiler, or an incinerator. (In Figure 1, the noncondensables are vented to
the feed storage tank, which is routed to a control device.) If the primary
condenser is not sufficient for condensing a large portion of the organics, it
may be necessary to install a secondary condenser with brine or a refrigerant.
The wastewater effluent leaving the bottom of the steam stripper is
pumped through the feed/bottoms heat exchanger. This serves to heat the feed
stream and cool the bottoms prior to discharge. This exchange of waste heat
also improves the economy of the steam stripper system. After passing through
the heat exchanger, the bottoms stream is usually either routed to an on-site
wastewater treatment plant as shown in Figure 4-1 and discharged to an
National Pollutant Discharge Elimination System (NPDES) permitted outfall, or
is sent to a POTW.
4.2.1.2 Steam Stripper Design and Operation Information on the design
and operation of steam stripper systems is available from studies conducted by
the EPA. During the Industrial Wastewater Project, EPA obtained information
on approximately 15 steam strippers from facility responses to Clean Air Act
Section 114 information requests/ In addition, during this project,
information was gathered on site visits to nine chemical manufacturing
facilities operating steam strippers to remove organic compounds from
wastewater.5"13 The EPA also gathered data on steam stripper operation as a
part of the Hazardous Waste Treatment, Storage, and Disposal Facilities (TSDF)
Project. During this project, data were gathered on three steam strippers
through field testing efforts.1*1'16
The EPA gathered data on steam strippers during the development of
effluent guidelines for the OCPSF, Pesticide, and Pharmaceutical Manufacturing
industries. In response to Clean Water Act Section 308 information requests,
63 OCPSF facilities reported using steam strippers as an in-plant control for
process wastewater.17 A total of 108 steam strippers are reportedly operated
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by these facilities. In addition to these information requests, data on steam
strippers in operation at four OCPSF facilities were obtained through field
testing efforts.18'21 Less data are available for steam strippers in use at
Pesticide and Pharmaceutical Manufacturing industry facilities. Steam
strippers are reportedly used at eight pesticide facilities22 and eight
pharmaceutical facilities.23
The steam stripper systems discussed above are used to treat a variety of
wastewater streams. These wastewater streams vary in flow rate and
composition. In addition, some streams contain relatively high levels of
suspended solids.
Although the wastewater characteristics vary, the basic steam stripper
system shown in Figure 4-1 can be designed and operated to achieve high
organic compound removal efficiencies for most streams. Table 4-1 presents
the design and operating conditions for a steam stripper with an assumed
wastewater feed rate of 300 liters per minute (1pm). The design was developed
using Advanced System for Process Engineering (ASPEN).2* ASPEN is a computer
software program intended for the rigorous design of distillation columns.
The major design parameters in the ASPEN steam stripper model are based on
field experience and published information. These include a pressure drop of
0.41 kPa per meter of packing, 60 percent of calculated flooding for the
packing, and 2.54 cm stainless steel saddles (random dumped packing). In
addition, the following engineering assumptions were made:
Operating pressure of one atmosphere;
Isothermal column operation;
Constant molal overflow (i.e., one mole of aqueous phase vaporized
for each mole of steam condensed); and
Linear equilibrium and operating equations (i.e., Henry's Law is
valid for each organic compound at the concentrations encountered in
the stripping column).
Because the ASPEN Model is a packed tower, some engineering assumptions
were made to approximate a tray column design. ASPEN calculates the number of
transfer units (NTU). A conversion factor of 0.53 theoretical trays per
transfer unit was used by ASPEN to determine the number of theoretical trays.
A tray efficiency of 75 percent was assumed to estimate the actual number of
stages for the column. A tray spacing of 0.46 meters was assumed to estimate
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TABLE 4-1. DESIGN AND OPERATING BASIS FOR THE
STEAM STRIPPING SYSTEM
1. Wastewater Stream Content: water = 99.75%
total organics
2. Wastewater Stream Organic Composition:
0.25% (2,500 ppm)
Organic Compound
Henry's Law Value Waste
Volatility Organic (atm - m3/gmol) Stream
Category Compound at 25°C
High Butadiene 1.42 x 10'1
Medium Toluene 6.68 x 10"3
Medium Naphthalene 1.18 x 10"3
Low Butanol 8.90 x 10"6
Low Phenol 4.54 x 10"7
3. Wastewater Flow: 300 1/min
4. Stripper Operating Period: 24 hr/day
5. Wastewater Storage: Wastewater feed <
% Removal
in
Content (ppm) Stripper*
500
500
500
500
500
x 300 day/yr = 7,200
:ollection tank with t
100
100
99.9
30
2.2
hr/yr
18 hr
8.
9.
retention time
Steam Stripping Column:
Configuration: countercurrent flow, sieve tray column
Steam Flow Rate: 0.06 kg of steam /liter of waste feed
Wastewater Feed Temperature: 35°C
Column Diameter: 0.76 m
Active Column Height: 14.2 m
Total Column Height: 18.3 m
Liquid Loading: 39,900 1/hr/m2
Condenser:
Configuration: Water-cooled
Primary Condenser Outlet Vapor Temperature: 50°C
Overhead Control: Vent to existing on-site combustion or other control
device
Bottoms Control: Feed to existing on-site wastewater treatment facility
or POTW
"Removal efficiency was estimated using ASPEN.2*
design compound.
Benzene was the chosen
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the active column height. To approximate the total column height, 4.1 meters
of nonactive entrance and exit column was assumed.
Using ASPEN, the most cost-effective feasible design for controlling the
model waste streams presented in Chapter 3 was developed. The associated
costs of this steam stripper are presented in Chapter 6.
For purposes of evaluation, the steam stripper system can be separated
into the following three functional sections: collection and conditioning of
the wastewater, steam stripping of the wastewater, and recovery of the steam
stripped organics. Each of these sections is discussed in detail below as
they pertain to well-designed and operated systems.
4.2.1.2.1 Collection and conditioning of the wastewater. In controlling
VOC emissions from wastewaters using a steam stripper, the first necessary
step is to control emissions from the point of wastewater generation to the
steam stripper feed tank. This can be accomplished by hardpiping the
wastewater to the tank, or by controlling the collection system components as
discussed in Section 4.3.1. Next, the steam stripper feed tank should be
controlled by venting to an on-site incinerator or other control device. The
stripper feed tank is used to collect and condition wastewater feeding the
steam stripper. The feed tank is normally sized to provide a desired
hydraulic retention time of 0.5 to 40 hours for the wastewater feed
stream.25'26 However, for controlling individual batch streams, additional
storage capacity may be required. The desired retention time depends
primarily on two factors: (1) the variability in wastewater flow from the
source, and (2) the amount of conditioning required prior to steam stripping.
Additional retention time is required to provide surge capacity for wastewater
streams with highly variable flow rates. As the wastewater flow rate from the
process varies, the level in the feed tank is also allowed to vary to provide
a relatively constant feed rate to the stripper. If the feed tank is
adequately designed, a continuous steam stripper may even be used to treat
wastewater generated by some batch processes. In these cases, the feed tank
serves as a buffer between the batch process and the continuous steam
stripper. During periods of no wastewater flow from the batch process, stored
wastewater is fed to the stripper at a relatively constant rate, and the feed
tank level is allowed to decrease. The tank design is based on an assumed
retention time of 48 hours. This allows sufficient residence time for
multiple batch or continuous streams to be combined to provide a constant
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wastewater composition to the steam stripper.
As mentioned earlier, the desired retention time in the feed tank also
depends on the degree of conditioning required for the stripper feed stream.
Water and organic phases are often present in the stripper feed tank. The
feed tank provides the retention time necessary for these phases to separate
due to density differences. Oils and tars which may also be present normally
partition from the water into the organic phase. This organic phase is
normally either recycled to the process for recovery of the organic compounds
or disposed of by incineration. The water phase is fed to the stripper to
remove the soluble organics. Solids are also separated in the stripper feed
tank. The separation efficiency depends on the density of the solids
dissolved in the process wastewater. Some of the lighter solids may remain
dissolved in the organic or water phases present in the feed tank. However,
the heavier solids will settle to the bottom of the tank. These solids are
normally removed from the feed tank periodically and usually landfilled.
If excessive levels of oils, grease, or solids are present, it may be
necessary to install additional equipment to assist the feed tank in
conditioning the stripper feed stream. In some stripper system designs, the
wastewater first flows through an oil/water decanter before proceeding to the
stripper feed tank.27 The decanter provides an additional separation stage
for removal of oils and grease that could cause fouling and plugging in the
stripper column. However, decanters or oil/water separators used to pretreat
wastewater should be covered and controlled. High dissolved solids levels may
also cause fouling and plugging problems in the column. In these cases, it
may be more efficient to separate the solids prior to the feed tank using
filtration equipment. However, the column internals can sometimes be modified
to accommodate relatively high solids concentrations. High solids levels may
be more of a problem for system components other than the column. These
problems include plugging of the feed/bottoms heat exchanger and cause
excessive wear on the stripper feed and bottoms pumps.
4.2.1.2.2 Steam stripping of the wastewater. Steam stripper columns are
designed and operated to ensure that sufficient contact occurs between the
wastewater containing the organic compounds and the steam which provides the
heat energy. Three main factors affect the degree of contact that occurs in
the column. These are: (1) the dimensions of the column (height and
diameter), (2) the contacting media used in the column (trays or packing), and
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(3) operating parameters such as the steam to feed ratio, column temperatures,
and pH of the wastewater. The organic removal performance of the steam
stripper depends on the degree of contact between steam and wastewater and is,
therefore, a function of the design and operating values selected for these
parameters.
The diameter of the column determines the cross-sectional area available
for liquid and vapor flow through the column. This cross-sectional area must
be sufficient to prevent flooding due to excessive liquid loading or liquid
entrainment due to excessive vapor velocity.28 The cross-sectional area also
affects the liquid retention time in the column. Column diameters reported in
Section 114 responses range from 0.3 m to 1.8 m, and the steam stripper
presented in Table 4-1 has a diameter of 0.76 m.29
The contacting media used in the column plays a major role in determining
the mass transfer efficiency. Generally, steam stripping columns are equipped
with trays or packing to provide contact between the vapor and liquid phases.
Trays are regularly spaced throughout the column and provide staged contact
between the two phases; packing provides for continuous contact. There are
advantages and disadvantages to the use of both trays and packing as the
contacting media in steam stripping columns.30 Trays are generally more
effective for wastewater containing dispersed solids due to plugging and
cleaning problems encountered with packing. In addition, tray towers can
operate efficiently over a wider range of liquid flow rates than packed
towers. Packed towers are often more cost effective to install and operate
when treating wastewater streams that are highly corrosive. Also, the
pressure drop through packed towers may be less than the pressure drop through
tray towers designed for equivalent wastewater loadings. However, packed
towers are seldom designed with diameters in excess of four feet and column
heights may be more limited (compared to tray towers) due to crushing of the
packing located near the bottom of the column.
The column height is determined by the number of theoretical stages
required to achieve the desired VOC removal. The number of theoretical stages
is a function of the equilibrium coefficient of the pollutants and the
efficiency of mass transfer in the column.31 (As mentioned in
Section 4.2.1.2, the number of actual stages was approximated assuming a tray
efficiency of 75 percent.) The steam stripper is a 18.3 m sieve tray
countercurrent flow column, with 31 sieve trays.
In addition to the design factors discussed above, several operating
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parameters affect the organic compound removal performance of steam strippers.
An increase in the steam to feed ratio will increase the ratio of the vapor to
liquid flow through the column. This increases the stripping of organics into
the vapor phase. Because additional heat is provided when the steam rate is
increased, additional water is also volatilized. Therefore, an increase in
the steam to feed ratio is also normally accompanied by an increase in the
steam rate flowing out of the column in the overheads stream.
Steam to feed ratios generally range from 0.01 kg/kg to 1.0 kg/kg. A
steam to feed ratio of 0.06 was assumed for the model steam stripper. The
steam to feed ratio required for high removal efficiency depends strongly on
the temperature of the wastewater feed to the column. If the feed temperature
is lower than the operating temperature at the top of the column, part of the
steam is required to heat the feed. Good column design requires that
sufficient steam flow is available to heat the feed and volatilize the organic
constituents. Steam in excess of this sufficient flow rate helps to carry the
organic compounds out of the top of the column with the overheads stream.
Column operating temperature and wastewater pH also affect organic
compound removal performance.32 Temperature affects the solubility and
equilibrium coefficients of the organic compounds. Usually stripping columns
are operated at pressures slightly greater than atmospheric. Therefore, in
relation with the column pressure, column temperatures usually operate
slightly greater than the normal boiling point of water. Wastewater pH is
often controlled by adding caustic to the feed to ensure that these types of
organic compounds remain in a steam strippable form.33
4.2.1.2.3 Recovery of the steam stripped orqanics. The conceptual
design shown in Figure 4-1 employs a one-stage condenser system. Any
condensables not removed from the vapor stream in the primary condenser are
vented to a control device. The secondary condenser is normally chilled
(brine water or other coolant) to ensure condensation of the more volatile
organic compounds. In Table 4-1, the steam stripper outlet vapor condenser
temperature for the primary condenser is 50°C. The condensed steam and
organics are passed through a decanter to recover the organic phase. The
decanter shown in Figure 4-1 is recovering an organic phase lighter than
water. The organic phase overflows the decanter and is normally pumped to a
storage tank and then recycled to the process. When not recycled, the
recovered organics are usually burned as fuel in an incinerator. The water
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phase in the decanter is recycled to the feed tank for feed to the stripper.
In well designed systems, any noncondensable organic compounds are routed
through the wastewater feed tank to a control device such as an incinerator or
carbon adsorber. This strategy reduces the potential for air emissions from
the steam stripper system. For systems where a primary condenser is not
sufficient for condensing a large portion of the organics, secondary control
may be required. A secondary condenser with brine or a refrigerant as the
cooling agent can be installed to condense most of the organics. The
condensates from the secondary condenser should be sent to a decanter, and the
noncondensables should be vented to a control device.
4.2.1.3 Steam Stripper Removal Performance. The organic removal
performance of five steam stripper systems was measured during field tests
sponsored by the EPA. Information gathered during these testing efforts is
summarized in Appendix C. During each test, samples of the feed and bottoms
streams were obtained to determine the organic removal performance of the
stripper. In addition, data were gathered to evaluate the effect of design
and operating parameters on the performance of each system. These data, along
with performance data provided by a facility using a recently installed steam
stripper, are presented in Table 4-2. The organic removals presented in
Table 4-2 range from 76 percent for Site 7 to greater than 99.8 percent for
Site A. In general, the organic compound removal efficiencies are higher for
the steam strippers treating wastewater containing chlorinated organic
compounds. These chlorinated organic compounds are more easily steam stripped
than organic compounds such as phenol that are more soluble and less volatile
in water. The steam stripper at Site G, however, achieved a relatively high
organic removal efficiency of 92 percent for moderately volatile nitrobenzene
and nitrotoluene constituents. This efficiency is due in part to the column
height for this stripper (19.2 m).
In some cases a facility may already be treating some of their existing
wastewater streams with a steam stripper for product recovery or to meet other
EPA standards such as the vinyl chloride standard. If a facility plans to use
the existing stripper to control wastewaters from a major modification, the
steam stripper system should achieve equal or better organic compound removal
than the recommended steam stripper system. Similarly, if a facility installs
4-14
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TABLE 4-2. STEAM STRIPPER ORGANIC COMPOUND REMOVAL PERFORMANCE
Site
I.D.
A
B
G
7
10
Z
Column Ooeratlon
Column Design Feed Steam: F».rf Oir.fK.^M.. p..^
Organic Height Diameter Rate Ratio Ratio
Compounds (m) (m) (kg/hr) (kg/kg) (kg/kg)
CHC, Benzene NA NA 48,960 0.03 0.03
Chlorobenzene
CHC 3.0" 0.2 1,260 0.1 0.01
Nitrobenzene 19.2 0.46 29,900 0.07 0.01
Nltrotoluene
Benzene 9.8" 0.61 5,452 0.4 NA
Nitrobenzene
Phenol
Nltrophenols
CHC 6.1" 1.07 12,693 NA NA
Chlorinated ethers
Phenol
Chlorinated phenols
Benzene, Toluene 12.2 1.22 68,100 0.020 0.0067
Chlorobenzene
Ethylbenzene
Methylene chloride
Column Performance
Feed Bottoms Organic
Cone. Loading Cone. Loading Compound
(mg/1) (kg/hr) (mg/1) (kg/hr) Removal (I)
5,900 290 9.8 0.5 >99.8
3,900 4.7 5.2 0.005 99.8
634 19 47.8 1.5 92
1.192 6.5 250 1.5 76
*53 5.7 3.4 0.04 99
2,073 118 0.04 0.002 >99.8
"Height of packed section only. Total height Is not available.
NA - Not available.
CHC - Chlorinated hydrocarbons.
-------
a steam stripper other than the steam stripper design in Table 4-1 to treat
wastewater streams from a new source, the steam stripper system should achieve
equal or better removal than the recommended design. This emission reduction
includes emissions which occur between the point of generation and the steam
stripper, from the steam stripper vents, and those that occur downstream from
the stripper. If a facility plans to use a steam stripper that does not meet
the recommended design, additional removal efficiency might be achieved by
adding packing or additional trays to the column if space in the column
allows, or by increasing the steam flow rate. Another alternative would be to
add a secondary treatment system such as a steam stripper system in series or
liquid-phase carbon adsorption on the stripper effluent.
The removal efficiencies used in this document were predicted for the
example waste stream composition using ASPEN. These data are presented in
Table 4-1. As shown, the compounds with high Henry's Law constants were
removed at efficiencies exceeding 99 percent. Figure 4-2 presents a curve
developed to predict removal efficiency of any VOC based on the Henry's Law
constant for the compound. A regression analysis was performed to relate
removal efficiency as a function of Henry's Law constant for the five
compounds in Table 4-1. The result was fraction removed = 1.357 + 0.08677 In
(Henry's Law constant, atm m3/mol). (To get removal efficiency, multiply the
fraction removed by 100.)
4.2.2 Other Organic Compound Removal Technologies
This section presents alternatives to steam stripping for reducing VOC
emissions from industrial wastewaters. Although steam stripping is the most
universally applicable technology for VOC emission reduction from industrial
wastewaters, there are applications where another technology may be more
appropriate. The purpose of this section is to present some of these
alternatives along with a discussion of the technology.
In addition to steam stripping, technologies available for removing
organic compounds from wastewater include air stripping, carbon and ion
exchange adsorption, chemical oxidation, membrane separation, and liquid-
liquid extraction.34 These technologies rely on a variety of mechanisms to
remove organic compounds from wastewater. However, with the exception of air
stripping, the removal efficiencies of these technologies are dependent on
4-16
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ORGANIC COMPOUND REMOVAL EFFICIENCY (%)
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-------
physical properties other than compound volatility in water. As discussed in
Chapter 3, the organic compound property (volatility in water) has a major
impact on air emissions during wastewater collection and treatment.
Therefore, these technologies may not be as generally effective at reducing
air emissions as steam strippers. However, these technologies are used in
different applications by facilities in the targeted industries and may be
effective at removing certain organic compounds. For this reason, a brief
description of each technology is provided below.
The underlying principle for air stripping is vapor-liquid equilibrium.35
By forcing large volumes of air through the contaminated water, the air-water
interface is increased, resulting in an increase in the transfer rate of the
organic compounds into the vapor phase. Although the technology is applicable
to compounds with a wide range of volatilities, controlling the high volume of
air needed to achieve high removal efficiencies on streams with large
quantities organic compounds becomes prohibitive from a design and cost
perspective. In addition, as the air rate through the column is increased,
the cost of the VOC capture device also increases. In most cases, this
capture device is a carbon adsorber. However, in some cases the air stream
can be vented to a combustion device. In practice, air stripping is more
applicable for streams containing dilute organic compound concentrations such
as contaminated ground water.
Chemical oxidation involves a chemical reaction between the organic
compounds and an oxidant such as ozone, hydrogen peroxide, permanganate or
chlorine dioxide. The applicability of this technology depends on the
reactivity of the individual organic compounds. For example, phenols and
aldehydes are more reactive than alcohols and alkyl-substituted aromatics;
halogenated hydrocarbons and saturated aliphatic compounds are the least
reactive.36
Adsorption processes take advantage of compound affinities for a solid
sorbent medium. Often activated carbon or polymeric resins are used as the
medium. Nonpolar compounds can be adsorbed onto the surface of activated
carbon. By contrast, removal by polymeric resins involves both adsorption and
ion exchange mechanisms and is therefore, more effective for polar compounds.
With carbon adsorption, the capacity of the carbon to adsorb the organic
compounds at a given influent concentration varies widely for different
compounds. In addition, the ease of desorption (removal) of the organic
compounds and possible wastewater contaminants from the carbon is highly
4-18
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variable. For these reasons, the feasibility of using carbon adsorption must
be evaluated on a case-by-case basis. A more detailed evaluation of the
applicability of carbon adsorption to organic compound removal from industrial
wastewaters is documented in a memorandum "Evaluation of Carbon Adsorption as
a Control Technology for Reducing Volatile Organic Compounds (VOC) from
Industrial Wastewaters" dated November 30, 1988.37 Two types of membrane
separation processes are: ultrafiltration and reverse osmosis.
Ultrafiltration is primarily a physical sieving process driven by a pressure
gradient across the membrane. This process separates macromolecular organic
compounds with molecular weights of greater than 2,000, depending on the
membrane pore size. Reverse osmosis is the process by which a solvent is
forced across a semi-permeable membrane due to an osmotic pressure gradient.
Selectivity is, therefore, based on osmotic diffusion properties of the
compound and the sizes of the compound and membrane pores.38
Liquid-liquid extraction, sometimes referred to as solvent extraction,
uses differences in solubility of compounds in various solvents as a
separation technique. By contacting a solution containing the desired
compound with a solvent in which the compound has a greater solubility, the
compound may be removed from the solution. This technology is often used for
product and process solvent recovery for two reasons. First, the solvent can
usually be regenerated, and second, the compound of interest can often be
recovered by distillation.
4.3 VOC EMISSION CONTROL FROM COLLECTION AND TREATMENT SYSTEM COMPONENTS
Within an industrial wastewater collection and treatment system, the
individual components represent potential emission sources by providing
contact between wastewater and ambient air. Through the use of physical
covers and water seals, the contact between the wastewater and ambient air can
be minimized, thus suppressing VOC emissions. Suppression controls can be
broken down into four categories: collection system controls, roofs, floating
membranes, and air-supported structures. Suppression controls are discussed
in more detail in the following sections. However, suppressing these VOC
emissions merely keeps the organic compounds in the wastewater until they
reach the next potential VOC emission source. Therefore, these controls are
not effective unless the VOC emissions are suppressed until the wastewater
4-19
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reaches a control device or a controlled treatment tank where the organic
compounds are either removed or destroyed.
4.3.1 Collection System Controls
As discussed in Chapter 3, collection systems are comprised of components
such as drains, junction boxes, sumps, trenches, and lift stations that
provide contact between wastewater and ambient air. These collection system
components provide escape routes for organic compounds contained in
wastewater. Controls can be applied to most of these components to reduce the
potential of VOC emissions during wastewater collection. These controls
involve the use of physical covers and water seals to minimize the contact
between ambient air and the wastewater flowing through the component.
However, these types of controls serve merely to suppress VOC emissions; the
organic compounds remain in the wastewater flowing downstream to the next
potential emission source. For this reason, controls for these collection
system components are only effective if the wastewater flows downstream to an
organic compound removal or destruction device.
For this control strategy, the downstream removal devices are often
oil/water separators and biological treatment units. If sufficient removal of
organic compounds cannot be obtained in these components then an alternative
removal technology should be investigated.
Figure 4-3 presents two commonly used methods for controlling emissions
from drains: p-leg and seal pot configurations. In the p-leg configuration,
water settles in the "P"-bend between the sewer line and the top of the drain
riser. The seal pot configuration provides an external liquid seal. A cap
covers the drain opening, and the bottom edge of the cap extends below the
level of the drain entrance. Wastewater flows into the drain area outside the
cap and then flows under the edge of the cap and into the drain. In both of
these designs, the liquid seal prevents convective transfer of vapors from the
sewer line below the drain. Vapors in the sewer must diffuse through the
water seal to be emitted. Emission reductions for drains are addressed in the
Background Information Document (BID) for VOC Emissions from Petroleum
Refinery Wastewater Systems.39 An emissions reduction study was performed at
a refinery with drains equipped with seal pots having caps that could be
manually removed. Screening results were evaluated for 76 drains both before
4-20
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I
i\n) tr
rv>
77*
/ / / //
0
Figure 4-3. P-leg and seal pot configurations for drains.
-------
and after the cap was removed. A further analysis grouped these drains into
two categories to evaluate whether the uncontrolled leak rate had any effect
on emission reduction. Those with uncontrolled screening values less than
100 ppm of organics were placed in one group while those with values greater
than 100 ppm were placed in a second group. Of the 76 uncontrolled drains
that were screened, 18 had leak rates greater than 100 ppm. Results of
emission reduction vary from approximately zero to 99 percent. Disregarding
outlying data points gives an average VOC emission reduction of approximately
95 percent for seal pots. (Data points were not considered for emission
reductions less than zero or if screening values with the cap on were
excessively high.) In cases where highly contaminated streams are
continuously discharged to the drain or the organic compounds are immiscible
and float on top of the water, the seal is ineffective. If this is the case,
a completely enclosed drain system may be required. With these systems, the
process drain lines are piped directly into the drains, which are connected to
the sewer. A fuel gas purge then sweeps the VOC to a control device.
Use of p-leg seals and seal pots can reduce VOC emissions from drains if
the system is well maintained; however, monitoring of the performance of the
control will be difficult. Best control of emissions is achieved with hard
piping any source of wastewater containing organic compounds to a control
device.
Other collection system components that typically require control are
junction boxes, sumps, and lift stations. Since the design of these three
components are similar, the same technique is effective for controlling VOC
emissions from all three. For these components, a gas tight cover is
typically used. Figure 4-4 presents a schematic of a controlled junction box.
As shown, a gas-tight cover is fitted on the top of the unit, with a vent line
to the atmosphere. Although some VOC emissions do occur from this vent line,
the losses are significantly less than from an uncontrolled unit. For
junction boxes, sumps, and lift stations, a 95 percent control of VOC
emissions is assumed with the application of a gas-tight cover.
Trenches are sometimes used to collect and transport wastewater from
process areas. Since trenches are typically used for collection and transport
of rainwater and wash-down water, as well as process wastewater, they must
have openings and cannot be completely covered. Therefore, a reasonable
technique for controlling emissions from trenches is to install a gas-tight
cover with periodic openings along the length of the trench. These openings
4-22
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•VfNT
OA* TIGHT
COVCH
QJUOE
WATER
Figure 4-4. Gas tight cover for collection system components.
4-23
-------
can then be controlled with a seal pot. As with junction boxes, sumps, and
lift stations, a gas-tight cover applied to trenches is assumed to reduce VOC
emissions by 95 percent.
4.3.2 Roofs
4.3.2.1 Fixed-Roof Tanks/0 A fixed-roof tank is a vertical cylindrical
steel wall tank with a cone-shaped or dome-shaped roof that is permanently
attached to the tank shell (see Figure 4-5). Vents are installed on the roof
to prevent the tank internal pressure from exceeding the tank design pressure
limits and, thereby, causing physical damage or permanent deformation to the
tank structure. The vents can either open directly to the atmosphere, be
equipped with valves that open at specified pressure or vacuum settings, or be
connected to an add-on control device (e.g., carbon adsorption system, vapor
incinerator).
Storage or treatment of wastewater in fixed-roof tanks instead of
open-top tanks reduces VOC emissions. By covering the tank, the wastewater
surface is sheltered from the wind. This decreases the mass transfer rate of
organic compounds in the wastewater to the atmosphere. The extent to which
VOC emissions are reduced depends on many factors including wastewater
composition and organic concentrations, windspeed, and the ratio of the tank
diameter to the depth of the wastewater contained in the tank.
An existing open-top tank can be converted to a fixed-roof tank by
retrofitting the tank with a dome roof. Aluminum, geodesic dome roofs are
available from several manufacturers. These domes have been used successfully
to cover petroleum and chemical storage tanks. The domes are clear-span,
self-supported structures (i.e., require no internal columns be placed in the
tank) that can be installed on open-top tanks ranging in diameter from 5 to
over 100 m.
Although fixed-roof tanks provide large reductions in VOC emissions from
open-top tanks, fixed-roof tanks still can emit significant quantities of VOC.
The major sources of VOC emissions from fixed-roof tanks are breathing losses
and working losses. Breathing losses occur from the expulsion of vapor
through the roof vents because of the expansion or contraction of the tank
vapor space resulting from daily changes in ambient temperature or barometric
pressure. These VOC emissions occur in the absence of any liquid level change
in the tank. Working losses occur from the displacement of vapors resulting
4-24
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flii
Typical fixed roof tank.
External floating roof tank.
Contact Deck Type
Internal floating roof tanks.
Figure 4-5. Storage tank covers.
4-25
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from filling and emptying of the tank.
Breathing and working losses from fixed-roof tanks can be reduced by
installing an internal floating roof, connecting the tank roof vents to an
add-on control device, or installing pressure-vacuum relief valves on the tank
roof vents. For add-on control applications, vapors are contained in the tank
until the internal tank pressure attains a preselected level. Upon reaching
this level, a pressure switch activates a blower to collect the vapors from
the tank and transfer the vapors through piping to the add-on control device.
As a safety precaution, flame arresters normally are installed between the
tank and control device. Other safety devices may be used such as a saturator
unit to increase the vapor concentration above the upper explosive limit.
Add-on control devices for organic vapors are discussed in Section 4.4.
4.3.2.2 Floating Roof Tanks.41 Floating roofs are used extensively in
the petroleum refining, gasoline marketing, and chemical manufacturing
industries to control VOC emissions from tanks storing organic liquids. A
floating roof is basically a disk-shaped structure (termed a "deck") with a
diameter slightly less than the inside tank diameter that floats freely on the
surface of the wastewater in the tank. A seal is attached around the outer
rim of the deck to cover the open annular space between the deck and inside
tank wall. The seal mechanism is designed to slide against the tank wall as
the wastewater level in the tank is raised or lowered. There are two general
types of tank floating roofs: external floating roofs and internal floating
roofs.
Floating roofs are appropriate for wastewater storage tanks and certain
treatment tanks where the presence of the floating cover would not interfere
with the treatment process. Treatment tanks equipped with surface mixing or
aeration equipment cannot use floating roofs. Also, because floating roofs
are in direct contact with the wastewater, the materials selected to fabricate
the deck and seals must be compatible with the wastewater composition.
An external floating roof consists of a single- or double-layer steel
deck that moves within the walls of an open-top tank (see Figure 4-5).
Pontoon sections often are added to the deck to improve floatation stability.
Because the top surface of the deck is exposed to the outdoors, the external
floating roof design must include additional components for rainwater drainage
and snow removal to prevent the deck from sinking, and for cleaning the inside
walls of the tank above the deck to protect the sliding seal mechanism from
4-26
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dirt. A variety of seal types (e.g., metallic shoe seal, liquid-filled seal,
or resilient foam-filled seal) and seal configurations (e.g., mounted above
liquid surface, mounted on liquid surface) can be used for external floating
roofs. Small openings are required on the deck for various fittings such as
vents, inspection hatches, gage wells, and sampling ports.
An internal floating roof consists of a steel, stainless steel, aluminum,
or fiberglass-reinforced plastic deck that is installed inside a fixed-roof
tank (see Figure 4-5). Many internal floating roof designs can be retrofitted
into existing fixed-roof tanks. Because the fixed roof shelters the deck from
weather, internal floating roofs do not need additional components for
rainwater drainage or for seal protection. An internal floating roof is
equipped with the same types of deck fittings used on an external floating
roof, but normally uses a simpler deck seal mechanism (e.g., a single
resilient foam-filled seal or wiper seal). Vertical guide rods are installed
inside the tank to maintain deck alignment. The internal tank space above the
deck must be vented to prevent the accumulation of a flammable vapor mixture.
Floating roof tanks significantly reduce but do not eliminate VOC
emissions. Organic vapor losses termed "standing losses" occur at the deck
seals and fitting openings. The imperfect fit of the deck seals allows gaps
that expose a small amount of the liquid surface to the atmosphere. Small
quantities of vapors that collect in the small openings under the deck can
leak from the deck fitting openings. Standing losses can be reduced by
installing secondary deck seals, selecting appropriate pressure-relief valve
settings, and using tight-gasketed and bolted covers on all other fittings.
Additional organic vapor losses termed "withdrawal losses" occur from
evaporation of the liquid that wets the inside tank wall as the roof descends
during emptying operations.
No emission source test studies of full-sized tanks equipped with
floating roofs have been conducted because of the complexity of erecting an
enclosure around a tank. However, emission test studies of full-sized
floating roof components sponsored by the American Petroleum Institute (API)
were conducted using a pilot-scale tank. The results of these studies in
combination with other data have been used by API and EPA to develop empirical
models that estimate external and internal floating roof tank standing and
withdrawal losses.
For the development of volatile organic liquid storage New Source
Performance Standards (NSPS), EPA analyzed the emission reduction
4-27
-------
effectiveness of using floating roof tanks compared to fixed-roof tanks using
the empirical models. The percentage of reduction in emissions varies with
the tank characteristics (e.g., tank size, vapor pressure of the material
stored in the tank). A model tank was selected for the NSPS analysis that has
a volume of 606 m3, contains a volatile organic liquid having a vapor pressure
of 6.9 kPa, and operates with 50 turnovers per year. The analysis concluded
that, depending on the type of deck and seal system selected, installing an
internal floating roof tank in a fixed-roof tank will reduce VOC emissions by
93 to 97 percent. The analysis also concluded that a similar level of
emission reduction can be achieved using an external floating roof tank.
Tanks used for pH adjustment, equalization, decantation, and settling
could use any of the tank types mentioned above if they are nonagitated.
However, similar tanks and clarifiers which are agitated would be limited to
fixed roofs. Any of the three tank types could be applied to oil/water
separators. Oil/water separators are discussed in more detail below.
RCRA Subtitle D surface impoundments as described in Chapter 2 could
apply floating membrane covers if they are nonagitated. Such impoundments
might be used for evaporation, polishing, storage, equalization, etc. If
these impoundments are agitated, they require air-supported structures erected
over them. Surface impoundments and tanks used for biodegradation could apply
the floating membrane covers if nonagitated or the air-supported structures if
agitated.
In all cases the vapor space within the fixed roof or air-supported
structure should be vented to an add-on control device. These devices are
discussed in more detail in Section 4.4.
4.3.2.3 Oil/Water Separators. The most effective option for controlling
VOC emissions from oil/water separators is to install either a fixed or
floating roof. These roofs control VOC emissions by reducing the oil surface
exposed to the atmosphere, reducing the effects of wind velocity, and reducing
the effects of solar radiation by insulating the oil layer.
Fixed roofs can be installed on most oil/water separators. This can be
done without interfering with the operation of the system by mounting on the
sides of the separator or by supporting with horizontal steel beams set into
the sides of the unit. Gas-tight access doors are usually installed in the
roof for maintenance and inspection. Since the vapor space below fixed roofs
may constitute an explosion or fire hazard, the vapor space is often blanketed
4-28
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with nitrogen and/or purged to a recovery or destruction device.
To eliminate the need for a nitrogen blanket or purge, floating roofs are
sometimes installed on oil/water separators. Floating roofs may be
constructed of plastic or glass foam blocks, aluminum pontoons, or fiberglass.
To prevent the roof from interfering with operation of the flight scraper, the
water level can be raised in the separator so that the top of the oil surface
is above the flight scraper blades.
For both types of roofs, the effectiveness of their emission control is
primarily dependent on the effectiveness of the seals between the roofs and
walls of the separator. If these seals are not well-maintained to prevent
leakage, their VOC emission control capabilities are reduced significantly.
Emission reductions from covering separators are also limited by the method of
controlling vent emissions. If the vent is directed to a control device
rather than the atmosphere, greater emissions reduction will be achieved.
Although very little data are available regarding the VOC emission
reduction achieved by oil/water separators, theoretical analyses have
indicated that a floating roof can reduce emissions from the oil/water
separator by at least 85 percent when equipped with a primary liquid seal and
a secondary seal. Other sources report varying levels of emissions reduction
but give no supporting documentation. The American Petroleum Institute (API)
reports 90 percent to 98 percent reductions of emissions from the separator
and an emission reduction of 96 percent is reported in the Compilation of Air
Pollutant Emission Factors, AP-42. The State of California estimated 90
percent less emissions from the unit when equipped with a floating roof.
Although it is dependent on numerous factors, including effectiveness of the
control device to which the roof vent is directed, an efficiency of 90 percent
is probably most reasonable for a fixed roof. Without any better information,
90 percent reduction of oil/water separator emissions should be assumed in
estimating emissions from a fixed roof, vented to a control device, and 85
percent reduction for a floating roof.
One final concern in evaluating emissions from oil/water separators is
the handling of the recovered oils. Since the oils may contain high
concentrations of organic compounds, care must be taken to minimize VOC
emissions. This can be accomplished by handling the oils and organics in
closed systems equipped with emission controls as well.
Tables 4-3 and 4-4 present oil/water separator analyses performed on
Example Waste Stream Schematic II. In Table 4-3, the oil/water separator is
4-29
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TABLE 4-3. POTENTIAL VOC EMISSION REDUCTIONS THROUGH ENCLOSING OF COLLECTION
SYSTEM AND COVERING OIL/WATER SEPARATOR WITH A FIXED ROOF VENTED
TO A CONTROL DEVICE
Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Total
Fraction Emitted
Through the
Oil/Water
Separator*
FractIon Removed in
OU Layerb
0.11
0.049
0.0099
0.000090
0.0000050
0.03*
CO
O
100 ppm oil
1,000 ppm oil
10,000 ppm oil
Fraction Removed by
Vent Control Device0
100 ppm oil
1,000 ppm oil
10,000 ppra oil
Fraction Passthroughd
100 ppm oil
1,000 ppm oil
10,000 ppm oil
0.0065
0.061
0.34
0.88
0.83
0.54
0.00
0.00
0.00
0.022
0.18
0.57
0.41
0.35
0.18
0.52
0.43
0.20
"A
system components .
Assumes 80 percent of
°Assumes 90 percent of
the organic compounds
organic compounds that
that partition Into
would be emitted In
0.32
0.69
0.78
0.055
0.025
0.018
0.61
0.27
0.19
r, and 99 percent
0.00015
0.0015
0.015
0.00062
0.00062
0.00061
0.999
0.998
0.98
ccduct Ion ox
0.00014
0.0014
0.014
0.000034
0.000034
0.000033
0 . 9998
0.999
0.99
emission from collection
0.070
0.19
0.35
0.27
0.24
0.15
0.63
0.54
0.47
the oil are removed.
an uncontrolled
irator are removed.
Remaining organic compounds pass on to next potential emission point.
-------
TABLE 4-4. POTENTIAL VOC EMISSION REDUCTIONS THROUGH ENCLOSING OF COLLECTION SYSTEM AND
COVERING OIL/WATER SEPARATOR WITH A FLOATING ROOF
Butadiene Toluene Naphthalene 1-Butanol
Fraction Emitted 0.16 0.072 0.014 0.00012
Through the
OlUUater
Separator2
Fraction Removed in
Oil Layerb
100 ppm oil 0.0062 0.022 0.32 0.00015
1,000 ppm oil 0.057 0.17 0.69 0 0015
10,000 ppm oil 0.33 0.56 0.78 0.015
Fraction Pass through0
100 ppm oil 0.83 0.91 0.66 0 9997
1,000 ppm oil 0.78 0.76 0.30 0 999
10,000 ppm oil 0.51 0.37 0.21 0 ' 98
Phenol Total
0.0000068 0.
0.00014 0.
0.0014 0.
0.014 0.
0 . 9998 0 .
0.999 0.
0.99 0.
050
070
18
34
88
77
61
'Assumes 85 percent reduction of emission from oil/water separator, and 99 percent reduction of emission from collection
system components.
^Assumes 80 percent of the organlcs that partition into the oil are removed.
Remaining organic compounds pass on to next potential emission point.
-------
assumed to be controlled with a fixed roof vented to a control device. Three
cases are presented for each of the five representative compounds: 100 ppm,
1,000 ppm, and 10,000 ppm of oil in the wastewater. When an oil/water
separator is covered with a fixed roof and vented to a control device, removal
of organic compounds is achieved in two ways: (1) Organic compounds that
partition into the oil layer are removed with this oil; and (2) Organic
compounds that are volatilized and swept through a nitrogen purge to a vent
control device are recovered or destroyed. For the purpose of this analysis,
99 percent emission reduction was assumed for each collection system
component, and 90 percent of the potential emissions in the oil/water
separator are assumed to be recovered or destroyed in a control device, with
the remaining 10 percent of these potential emissions being emitted.
As shown in Table 4-3, the compounds' vapor pressure and solubility,
and the amount of the organics partitioning into the oil layer (a function of
the octanol-water partition coefficient for the compound, and the total oil
fraction in the water) have significant impacts on the potential removal.
Compounds such as butadiene may be removed reasonably efficiently (54 to 88
percent) by the control device on the oil/water separator vent if they are
controlled efficiently up to the separator. As shown, 11 percent of the
butadiene was emitted prior to removal and a total of 89 percent was removed
by the two mechanisms. Other compounds, such as naphthalene partition into
the oil layer so completely that they can be removed efficiently only if the
oil fraction is sufficiently large. Removal of this compound in the oil
ranged from 32 to 78 percent, depending on the oil concentration. Still other
compounds pass through to the next treatment unit. If these compounds'
emissions are not controlled effectively downstream, very little overall
emission reduction is achieved.
Table 4-4 presents the same scenario as Table 4-3 except the fixed roof
is replaced by a floating roof. Floating roofs are assumed to reduce
emissions by 85 percent but are not vented to a control device. The only
removal mechanism in this case is the removal of the organics that partition
into the oil layer and are removed with the oil. As shown, for most
compounds, this control primarily suppresses the VOC emissions and unless
adequate controls are present downstream, the VOC will be emitted. Of the
five compounds presented, greater than 56 percent removal is only attained for
naphthalene. Naphthalene removal ranges from 32 percent to 78 percent
depending on the oil fraction.
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4.3.3 Floating Membrane Covers*2
A floating membrane cover consists of large sheets of a synthetic
flexible membrane material that floats on the surface of the wastewater.
Individual sheets can be seamed or welded together to form covers applicable
to any size area. Floating membrane covers have been used successfully for
many years to cover the surface of potable water impoundments or reservoirs.
In a "leak tight" application, floating membrane covers have been used to
cover large anaerobic digester lagoons to collect the methane gas for energy
recovery. Thus, floating membrane covers offer good potential as a
suppression device for wastewater surface impoundments.
The material used to fabricate a floating membrane cover for wastewater
unit applications needs to be resistant to chemical and biological degradation
from compounds in the wastewater while also having good strength
characteristics to resist tearing and puncturing. Synthetic materials used
successfully for hazardous waste landfill bottom liners such as high-density
polyethylene (HOPE) or polyvinyl chloride (PVC) are good candidate materials
for floating membrane covers. The material currently preferred by most
floating membrane cover vendors is HOPE.
Although HOPE is buoyant in water, foam floats are normally placed under
the membrane to provide additional flotation. To prevent sinking of the cover
because of accumulation of rainfall on top of the cover, the cover is designed
with sufficient excess material to form troughs that collect rainfall. These
troughs are connected to a pump system. Automatic controls periodically
activate the pumps to drain the accumulated water off the cover. Pressure-
relief valves are also likely to be installed on the cover to provide
emergency venting of any gas buildup under the cover.
The simplest and least expensive method for anchoring a floating membrane
cover is to dig a trench around the impoundment perimeter, insert the edge of
the cover into the trench, and then backfill the trench with earth to secure
the cover. An alternative but more expensive method is to construct a
continuous concrete grade-level footing or short wall around the perimeter of
the impoundment. The cover is then mechanically fastened to the top of the
footing or wall using gaskets for tightness. This method has been
successfully used for the anaerobic digester lagoon applications.
Application of floating membrane covers to wastewater surface
impoundments will require special provisions for impoundment cleaning.
4-33.
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Floating membrane covers for surface impoundments are heavy, weighing over
2 kg/m. Consequently, once the cover is installed, removal of the entire
cover is difficult. Therefore, a section of the cover will need to be removed
and a temporary bracing system devised to provide access to the impoundment by
the cleaning equipment.
The effectiveness of a floating membrane cover depends on the amount of
wastewater surface that is covered and the permeability of the membrane
material to the organic compounds contained in the wastewater. Using a
membrane material with adequate thickness and following good installation
practices will minimize tearing or puncturing the membrane material.
Permeation of the cover is a three-step process that involves the absorption
of the organics by the membrane material, diffusion of the organics through
the membrane, and evaporation of the organics on the air side of the membrane.
The overall cover permeability is a function of the organic composition and
concentration of the wastewater managed in the surface impoundment as well as
the cover material's composition and thickness.
Benchscale study of the floating membrane is ongoing. Laboratory tests
are being performed with different compounds to determine diffusion rates
through the membrane. The benchscale model is set up to be essentially leak
proof. Therefore, diffusion through the membrane is the primary VOC emission
point. Preliminary results show that for some compounds diffusion through the
membrane can be fairly rapid. However, additional results are needed to
provide a complete and accurate evaluation of the method. For the present,
overall suppression efficiency of floating membrane covers applied to
hazardous waste surface impoundments is estimated to be 85 percent.
4.3.4 Air-Supported Structures43
An air-supported structure is a plastic-reinforced fabric shell that is
inflated and, therefore, requires no internal rigid supports. Figure 4-6
shows the major air-supported structure components. The structure shape and
support is provided by maintaining a positive interior pressure (i.e., the
interior pressure is greater than the external atmospheric pressure).
Large electric-motor driven fans are used to blow air continuously or
intermittently through the structure and out a vent system. The interior
pressure is maintained at a constant 10 to 15 kPa for structure inflation.
4-34
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VWYL-COATED
POLYESTER BASE
FABRIC
BIAS HARNESS
NET SYSTEM
INFLATION/HEATINQ
SYSTEM
VEHICULAR
AIR>LOCK
PERSONNEL DOOR
Soureti Air Structure Int«ra*11 on* 1, lac.
Figure 4-6. Typical air-supported structure.
4-35
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Adequate air changes are necessary to prevent the organic vapor concentrations
inside the structure from exceeding the lower explosive limits. A standby
blower system consisting of internal combustion engine driven fans normally is
installed to keep the structure inflated and ventilated in the event of an
electrical power outage. The vent system can discharge directly to the
atmosphere or be connected to an add-on control device.
Large areas can be enclosed by erecting an air-supported structure.
Structures are commercially available ranging in widths from 24 to 91 m wide
and lengths from 24 to 137 m. For larger areas, a number of modules can be
connected together. Air-supported structures have been used as enclosures for
conveyors and coke ovens, open-top tanks, and material storage piles. A
4,000 m3 aerated wastewater treatment lagoon at a specialty chemical
manufacturing plant has been covered by an air-supported structure for more
than four years. Thus, air-supported structures offer good potential as a
suppression device for wastewater surface impoundments that cannot use
floating membrane covers (e.g., surface treatment impoundments using
surface-mounted aeration equipment).
The fabric used for the air-supported structure depends on the size of
the structure, design requirements (e.g., wind and snow loadings), and type of
chemicals to which the fabric's inner side will be exposed. Polyvinyl-
chloride-coated polyester fabric would likely be the material of current
choice for wastewater treatment applications because of the fabric's good
resistance to deterioration from chemical, weather, or ultraviolet sunlight
exposure. The service life of the fabric ranges from 2 to 12 years depending
on the site-specific conditions.
Anchoring the air-supported structure likely will be accomplished by
bolting the edges of the fabric to a continuous, grade-level concrete footing
or beam installed around the perimeter of the surface impoundment. Entrance
into an air-supported structure is through airlocked doors. These doors can
be sized to allow earth-moving equipment to be used inside the structure for
impoundment cleaning operations.
The use of air-supported structures to enclose wastewater impoundments
can result in excessive condensation and high temperatures inside the
structure. An air-supported structure's interior temperatures typically are 5
to 11°C above the ambient temperature. Consequently, during hot summer days,
temperatures inside an air-supported structure can exceed 42°C. Depending on
the severity of these conditions, workers entering the structure may need to
4-36
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follow additional safety procedures and be restricted as to the period of time
they may remain inside the structure. Also, any equipment operating inside
the structure may require more frequent repair or replacement because of
accelerated rust and corrosion of the equipment components.
The effectiveness of an air-supported structure in suppressing VOC
emissions primarily depends on the amount of leakage from the structure and
whether the structure vent system is connected to an add-on control device.
Air-supported structure leaks are usually confined to areas around airlocks,
doors, and anchor points. Leak checks were performed at the air-supported
structure operating at the specialty chemical manufacturing plant. A soap
solution was sprayed around the structure base and fittings to locate leaks,
and measurements were made using a portable hydrocarbon analyzer. Few leaks
were found, and the sizes of the leaks ranged from 20 to 40 ppm. The
operating experience at this facility indicates that proper installation and
maintenance of the air-supported structure can limit leakage to very low
levels.
Because of the low leakage levels attainable, almost all of the organic
vapors contained by an air-supported structure will be ultimately discharged
through the structure's vent system. Therefore, connecting the vent system to
one of the add-on control devices discussed in Section 4.4 will result in an
overall VOC emission control efficiency for wastewater treatment applications
using an air-supported structure that is approximately equivalent to the
efficiency of the control device. These add-on control devices are capable of
achieving control efficiencies in excess of 95 percent.
Operation of an air-supported structure consumes large quantities of
electricity to maintain the positive interior pressure. For example, the
existing air-supported structure covering a 4,000 m3 aerated wastewater
treatment lagoon uses fans with a combined power rating of 26 kW for structure
inflation and ventilation. Annual electricity consumption to operate
continuously a standard 26 kW fan is approximately 250,000 kWh. Application
of air-supported structures to wastewater emission source increases demand for
electricity.
4.4 ADD-ON CONTROLS
Add-on controls are processes applied to capture organic vapors vented
from wastewater emission sources. These controls serve to reduce VOC
4-37
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emissions by destroying organics in the gas stream or extracting organics from
the gas stream before discharging the gas stream to the atmosphere. Add-on
controls for VOC emissions are classified into four broad categories:
combustion, adsorption, condensation, and absorption. General background
information about these types of add-on controls is available in Reference 44.
The type of add-on control best suited for a particular wastewater emission
source depends on the size of the source and the characteristics of the
wastewater in the source.
Combustion destroys the organics in the gas stream by oxidation of the
compounds to primarily carbon dioxide and water. Because essentially all
organics will burn, combustion add-on controls are applicable to all emission
sources for which the organic vapors can be captured. Combustion add-on
controls are thermal vapor incinerators, catalytic vapor incinerators, flares,
boilers, and process heaters.
4.4.1 Carbon Adsorbers'15
Adsorption as applied to air pollution control is the process by which
organic molecules in a gas stream are retained on the surface of solid
particles. The solid most frequently used is carbon that has been processed
or "activated" to have a porous structure. This provides many surfaces upon
which the organic molecules can attach, resulting in a high rate of organic
removal from a gas stream as it passes through a bed of carbon.
Activated carbon has a finite adsorption capacity. When the carbon
becomes saturated (i.e., all of the carbon surface is covered with organic
material), there is no further VOC emission control because all of the organic
vapors pass through the carbon bed. At this point (referred to as
"breakthrough"), the organic compounds must be removed from the carbon before
VOC emission control can resume. This process is called desorption or
regeneration.
For most air pollution control applications, regeneration of the carbon
in the adsorber is performed by passing steam through the carbon bed. The
steam heats the carbon particles, which releases the organic molecules into
the steam flow. The resulting steam and organic vapor mixture is condensed to
recover the organics and separate the water for discharge to a wastewater
treatment unit. An alternative method for regenerating the carbon is to
reduce the pressure of the atmosphere surrounding the carbon particles.
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Vacuum regeneration is used for special carbon adsorber applications when
direct recycling of the recovered organics is desired such as vapor recovery
at gasoline tank truck loading terminals. A detailed description of carbon
adsorption and desorption mechanisms is available in Reference 45.
Two types of carbon adsorption systems most commonly used for VOC
emission control are: fixed-bed carbon adsorbers and carbon canisters. A
fluidized-bed carbon adsorption system has been developed but currently is not
commercially available.
Fixed-bed carbon adsorbers are used for controlling continuous, organic
gas streams with flow rates ranging from 30 to over 3,000 m3/min. The organic
concentration can be as low as several parts per billion by volume (ppbv) or
as high as 25 percent of the lower explosive limit of the vapor stream
constituents. The major components of a fixed-bed carbon adsorber system are
one or more carbon bed units to adsorb the organics, a condenser to convert
the desorbed organics and a steam mixture to a liquid, a decanter to separate
the organic and aqueous phases, and blowers to cool and dry the carbon beds
following desorption.
Fixed-bed carbon adsorbers may be operated in either intermittent or
continuous modes. For intermittent operation, the adsorber removes organics
only during a specific period of the day. Intermittent mode of operation
allows a single carbon bed to be used because it can be regenerated during the
off-line periods. For continuous operation, the unit is equipped with two or
more carbon beds so that at least one bed is always available for adsorption
while other beds are being regenerated.
Carbon canisters differ from fixed-bed carbon adsorbers. First, a carbon
canister is a very simple add-on control device consisting of a 0.21 m3 drum
with inlet and outlet pipe fittings (see Figure 4-7). A typical canister unit
is filled with 70 to 90 kg of activated carbon. Second, use of carbon
canisters is limited to controlling low volume gas streams with flow rates
less than 3 m3/min. Third, the carbon cannot be regenerated directly in the
canister. Once the activated carbon in the canister becomes saturated by the
organic vapors, the carbon canister must be removed and replaced with a fresh
carbon canister. The spent carbon canister is then recycled or discarded
depending on site-specific factors.
The design of a carbon adsorption system depends on the inlet gas stream
characteristics including organic composition and concentrations, flow rate,
and temperature. Good carbon adsorber performance requires that (1) the
4-39
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Figure 4-7. Carbon canister unit.
4-40
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adsorber is charged with an adequate quantity of high-quality activated
carbon; (2) the gas stream receives appropriate preconditioning (e.g.,
cooling, filtering) before entering the carbon bed; and (3) the carbon beds
are regenerated before breakthrough occurs.
Emission source test data for 12 full-sized, fixed-bed carbon adsorbers
operating in industrial applications has been compiled by EPA for a study of
carbon adsorber performance.*6 The analysis of these data concluded that for
well-designed and operated carbon adsorbers continuous organic removal
efficiencies of at least 95 percent are achievable over long periods. Several
units have been shown to continuously achieve organic removal efficiencies of
97 to 99 percent.
An equivalent level of performance for carbon canisters applied to a
wastewater treatment unit is indicated by the results of an emission source
test conducted on carbon canisters installed on the neutralizer tanks for a
wastewater treatment system at a specialty chemicals plant.*7 This device was
designed for odor control and not organic removal. However, 100 percent
removal was measured for 1,2-dichlorobenzene, benzene, toluene, chlorobenzene,
and chloroform. Overall organic removal efficiencies measured for various
hydrocarbon categories ranged from 50 to 99 percent.
High moisture content in the gas stream can affect carbon adsorber
performance for gas streams having organic concentrations less than
1,000 ppm.*8 At these conditions, water molecules compete with the organic
compounds for the available adsorption sites on the carbon particles.
Consequently, the carbon bed working capacity is decreased. Above an organic
concentration of 1,000 ppm, high moisture does not significantly affect
performance. Thus, to obtain good adsorber performance for gas streams with a
high relative humidity (relative humidity greater than 50 percent) and low
organic concentration (less than 1,000 ppm) requires preconditioning the gas
stream upstream of the carbon bed. This can be accomplished using a
dehumidification system, installing duct burners to heat the gas stream, or
diluting the gas stream with ambient air. These gas stream conditions would
most likely occur at locations where a carbon adsorber is used in conjunction
with an air-supported structure enclosing an aerated surface impoundment
containing dilute aqueous hazardous waste.
Carbon bed operating temperature can also affect carbon adsorber
performance. Excessive bed temperatures can result due to the release of heat
from exothermic chemical reactions that may occur in the carbon bed.*9
4-41
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Ketones and aldehydes are especially reactive compounds that exothermically
polymerize in the carbon bed. If temperatures rise too high, spontaneous
combustion will result in carbon bed fires. To avoid this problem, carbon
adsorbers applied to gas streams containing these types of compounds must be
carefully designed and operated to allow sufficient airflow through the bed to
remove excess heat.
4.4.2 Thermal Vapor Incinerators50
Thermal vapor incineration is a controlled oxidation process that occurs
in an enclosed chamber. Figure 4-8 shows a simplified diagram of a thermal
vapor incinerator. One type of thermal vapor incinerator consists of a
refractory-lined chamber containing one or more discrete burners that premix
the organic vapor gas stream with the combustion air and any required
supplemental fuel. A second type of incinerator uses a plate-type burner
firing natural gas to produce a flame zone through which the organic vapor gas
stream passes. Packaged thermal vapor incinerators are commercially available
in sizes capable of handling gas stream flow rates ranging from approximately
8 to 1,400 mVmin.51
Organic vapor destruction efficiency for a thermal vapor incinerator is a
function of the organic vapor composition and concentration, combustion zone
temperature, the period of time the organics remain in the combustion zone
(referred to as "residence time"), and the degree of turbulent mixing in the
combustion zone. Test results and combustion kinetics analyses indicated that
thermal vapor incineration destroys at least 98 percent of non-halogenated
organic compounds in the vapor stream at a temperature of 870°C and achieves a
residence time of 0.75 seconds.36 If the vapor stream contains halogenated
compounds, a temperature of 1,100°C (2,000°F) and a residence time of one
second is needed to achieve a 98 percent destruction efficiency.52
Incinerator performance is affected by the heating value and moisture
content of the organic vapor stream, and the amount of excess combustion air.
Combustion of organic vapor streams with a heating value less than 1.9 MJ/m3
usually requires the addition of supplemental fuel (also referred to as
auxiliary fuel) to maintain the desired combustion temperature.53 Above this
heating value, supplemental fuel may be used to maintain flame stability.
4-42
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Auxiliary fuel
Vent stream
Incinerator
Prahcaur
•xchang*
Exhaust stack
Scrubber
-»>> Scrubber effluent
Figure 4-8. Schematic diagram of thermal incinerator system.
-------
Although either natural gas or fuel oil can be used as supplemental fuel,
natural gas is preferred. Supplemental fuel requirements can be decreased if
the combustion air or organic vapor stream is preheated.
4.4.3 Catalytic Vapor Incinerators54
Catalytic vapor incineration is essentially a flameless combustion
process. Passing the organic vapor stream through a catalyst bed promotes
oxidation of the organics at temperatures in the range of 320 to 650°C.
Temperatures below this range slow down or stop the oxidation reactions
resulting in low destruction efficiencies. Temperatures above this range
shorten catalyst life or may even cause catalyst failure. Oxidation of vapor
streams with a high organic content can produce temperatures well above 650°C.
Consequently, high organic concentration vapor streams may not be suitable for
catalytic incineration. Figure 4-9 shows a simplified diagram of a catalytic
vapor incinerator. The device consists of a chamber where the gas stream
vented from the emission source is heated to the desired reaction temperature
by mixing the organic vapors with hot combustion gas from natural gas-fired
burners. The heated gas mixture then flows through the catalyst bed. The
catalyst is composed of a porous inert substrate material that is plated with
a metal alloy containing platinum, palladium, copper, chromium, or cobalt. A
heat exchange is installed to preheat the vapor stream and, hence, reduce the
amount of fuel that must be burned.
Organic vapor destruction efficiency for catalytic vapor incinerators is
a function of organic vapor composition and concentration, catalyst operating
temperature, oxygen concentration, catalyst characteristics, and the ratio of
the volumetric flow of gas entering the catalyst bed to the volume of the
catalyst bed (referred to as "space velocity"). Destruction efficiency is
increased by decreasing the space velocity. However, a lower space velocity
increases the size of the catalyst bed and, consequently, the incinerator
capital cost. For a specific catalyst bed size, increasing the catalyst bed
temperature allows a higher space velocity to be used without impairing
destruction efficiency.
A series of studies has been sponsored by EPA to investigate the
destruction efficiency of catalytic vapor incinerators used to control organic
and hazardous air pollutants. The results of these studies concluded that
destruction efficiencies of 97 to 98 percent are achievable.
4-44
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Vent stream
.Catalyst bed
If
fuel
»*-
Catalytic
incinerator
\
i
Preheater
heat
y exchanger jl
' / II
'!..,. .. r~ Scrubber
L_
Exhaust stack
Scrubber effluent
Figure 4-9. Schematic diagram of catalytic incinerator system.
-------
The destruction efficiency is reduced by the accumulation of particulate
matter, condensed organics, or polymerized hydrocarbons on the catalyst.
These materials deactivate the catalyst by permanently blocking the active
sites on the catalyst surface. If the catalyst is deactivated, the volatile
organic compounds in the gas stream will pass through the catalyst bed
unreacted or form new compounds such as aldehydes, ketones, and organic acids.
Catalysts can also be deactivated by compounds containing sulfur, bismuth,
phosphorous, arsenic, antimony, mercury, lead, zinc, tin, or halogens.
4.4.4 Flares55
Unlike vapor incinerators, a flare is an open combustion process. The
ambient air surrounding the flare provides the oxygen needed for combustion.
Consequently, a flare does not require blowers to provide combustion air. To
achieve smokeless flare operation, turbulent mixing of the organic vapor
stream with the ambient air at the flame zone boundary can be "assisted" by
injecting steam or air at the flare tip or by releasing the gas stream through
a high velocity nozzle (i.e., a nozzle with a high pressure drop). Flares are
used extensively to burn purge and waste gases from many industrial processes
such as petroleum refinery process units, blast furnaces and coke ovens.
Figure 4-10 shows a diagram of a typical steam-assisted flare
configuration. The knockout drum is used to remove entrained liquids from the
organic vapor stream. A water seal is used to prevent air intrusion into the
flare stack. A pilot burner fired with natural gas is used to ignite the
waste gases.
Flares without assist continuously burn the vapors from the emission
source. A flare equipped with a steam, air, or pressure assist operates on an
intermittent basis. Steam-assisted flares typically are used for burning
large volumes of waste gases released from a process unit during upset or
emergency condition. Air-assisted flares are less expensive to operate than
steam-assisted flares. However, air-assisted flares are not suitable for
large gas volumes because the airflow is difficult to control when the gas
flow is intermittent. Pressure-assisted flares normally are used for
applications requiring ground-level operation.
A series of flare destruction efficiency studies has been performed by
EPA. Based on the results of these studies, EPA concluded that 98 percent
combustion efficiency can be achieved by steam-assisted and air-assisted
4-46
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•riii
fiRv
- -J n
I
AlP UlW
&U L(n»
Figure 4-10. Steam-assisted elevated flare system.
4-47
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flares burning gases with heat contents greater than 11 MJ/m3. To achieve
this efficiency level, EPA developed a set of flare design guidelines. The
guidelines specify flare tip exit velocities for different flare types and
waste gas stream heating values.
4.4.5 Boilers and Process Heaters56
A boiler or process heater can be used for organic vapor destruction.
The organic vapor stream is either (1) premixed with a gaseous fuel and fired
using the existing burner configuration, or (2) fired separately through a
special burner or burners that are retrofitted to the combustion unit.
Industrial boilers and process heaters currently are being used to burn vent
gases from chemical manufacturing, petroleum refining, and pulp and paper
manufacturing process units.
A series of EPA-sponsored studies of organic vapor destruction
efficiencies for industrial boilers and process heaters was conducted by
premixing waste materials with the fuel used to fire representative types of
combustion devices. The destruction efficiency was determined based on the
waste constituent concentrations measured in the fuel feed and stack gases
using a gas chromatograph. The results of one study indicated that the
destruction efficiency for an industrial boiler firing fuel oil spiked with
polychlorinated biphenyls (PCB) was greater than 99.9 percent. A second study
investigated the destruction efficiency of five process heaters firing a
benzene vapor and natural gas mixture. The results of these tests showed
98 to 99 percent overall destruction efficiencies for Cx to C6 hydrocarbons.
Industrial boilers and process heaters are located at a plant site to
provide steam or heat for a manufacturing process. Because plant operation
requires these combustion units to be on-line, boilers and process heaters are
suitable for controlling only organic vapor streams that do not impair the
combustion device performance (e.g., reduce steam output) or reliability
(e.g., cause premature boiler tube failure).
4.4.6 Condensers57 «
Condensation is the process by which a gas or vapor is converted to a
liquid form by lowering the temperature or increasing the pressure. This
process occurs when the partial pressure for a specific organic compound in
4-48
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the vapor stream equals its partial pressure as a pure substance at operating
conditions. For air pollutant control applications, cooling the gas stream is
the more cost-effective method of achieving organic condensation.
There are two major types of condensers: surface condensers and contact
condensers. In a surface condenser the coolant does not contact the vapors or
the condensate. In a contact condenser the coolant and vapor stream are
physically mixed together inside the vessel and exit the condenser as a single
stream.
A shell-and-tube-type heat exchanger is used for most surface condenser
applications (see Figure 4-11). The gas stream flows into a cylindrical shell
and condenses on the outer surface of tubes that are chilled by a coolant
flowing inside the tubes. The coolant used depends on the saturation
temperature or dewpoint of the particular organic compounds in the gas stream.
The condensed organic liquids are pumped to a tank. Additional information
about condenser equipment and operations is available in Reference 58.
The organic compound removal efficiency for a condenser is dependent upon
the gas stream organic composition and concentrations as well as the condenser
operating temperature. Condensation can be an effective control device for
gas streams having high concentrations of organic compounds with high-boiling
points. However, condensation is not effective for gas streams containing low
organic concentrations or composed primarily of low-boiling point organics.
At these conditions, organics cannot readily be condensed at normal condenser
operating temperatures.
A field evaluation of a condenser used to recover organics from a steam
stripping process used to treat wastewater at a plant manufacturing ethylene
dichloride and vinyl chloride monomer was conducted. The measured condenser
removal efficiencies for specific organic constituents ranged from a high
value of 99.5 percent for 1,2-dichloroethane to a low value of six percent for
vinyl chloride.59
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COOLANT INLET
VAPOR OUTLET
VAPOR INLET
COOLANT OUTLET
CONDENSED ORGANICS
Figure 4-11. Schematic diagram of a shell-and-tube surface condenser.
4-50
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4.5 REFERENCES
1. Letter and attachments from Radian Corporation to P. E. Lassiter,
EPA/OAQPS, July 17, 1987, on the summary of data provided in confidential
Section 114 questionnaire responses.
2. Perry, R. H. (ed.), Chemical Engineers' Handbook. 5th ed. New York,
McGraw-Hill Book Co., 1973. pp. 13-50 - 13-55.
3. U. S. Environmental Protection Agency/ORD/HWERL. Preliminary Assessment
of Hazardous Waste Pretreatment as an Air Pollution Control Technique.
EPA-600/2-86/028 (NTIS PB46-17209/A6), March 1986.
4. Reference 1.
5. Trip Report. R. H. Howie and M. A. Vancil, Radian Corporation, to
file. 7 p. Report of May 12, 1987, visit to Allied Fibers.
6. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 10 p. Report of May 22, 1987, visit to Rhone-Poulenc Agricultural
(RP Ag) Company.
7. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 5 p. Report of September 2, 1987, visit to Fritzsche Dodge &
Olcott.
8. Trip Report. D. J. Herndon, Radian Corporation, to file. 5 p. Report
of May 6, 1987, visit to PPG Industries.
9. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 7 p. Report of May 21, 1987, visit to Mobay Chemical Company.
10. Trip Report. D. J. Herndon, Radian Corporation, to file. 11 p. Report
of May 4, 1987, visit to Borden Chemical Company.
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11. Trip Report. D. J. Herndon, Radian Corporation, to file. 5 p. Report
of May 6, 1987, visit to PPG Industries.
12. Trip Report. D. J. Herndon, Radian Corporation, to file. 4 p. Report
May 5, 1987, visit to Union Carbide Corporation.
13. Trip Report. D. J. Herndon, Radian Corporation, to file. 13 p. Report
May 8, 1987, visit to Dow Chemical Company.
14. U. S. Environmental Protection Agency. Hazardous Waste Treatment,
Storage, and Disposal Facilities (TSDF) - Background Information for
Proposed RCRA Air Emission Standards - Volume 2 - Appendices.
Preliminary Draft. March 1988, pp. F-146 to F-149.
15. Reference 14, pp. F-144 - F-147.
16. Reference 14, pp. F-151 - F-155.
17. Memorandum from Herndon, D. J., Radian Corporation, to Industrial
Wastewater file. Summary of facilities reporting use of steam stripping.
May 20, 1988.
18. Environmental Science & Engineering, Inc., and SAIC. Plant No. 4 -
Organic Chemicals Best Available Technology Long-Term Field Sampling.
Prepared for U. S. Environmental Protection Agency, Office of Water
Regulations and Standards. July, 1985.
19. Environmental Science & Engineering, Inc., and SAIC. Plant No. 7 -
Organic Chemicals Best Available Technology Long-Term Field Sampling.
Prepared for U. S. Environmental Protection agency, Office of Water
Regulations and Standards. July, 1985.
20. Environmental Science & Engineering, Inc., and SAIC. Plant No. 7 -
Organic Chemicals Best Available Technology Long-Term Field Sampling.
Prepared for U. S. Environmental Protection agency, Office of Water
Regulations and Standards. July, 1985.
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21. Environmental Science & Engineering, Inc., and SAIC. Plant No. 15 -
Organic Chemicals Best Available Technology Long-Term Field Sampling.
Prepared for U. S. Environmental Protection agency, Office of Water
Regulations and Standards. July, 1985.
22. U. S. Environmental Protection Agency. Code of Federal Regulations.
Pesticide Chemicals Category Effluent Limitations Guidelines,
Pretreatment Standards, and New Source Performance Standards. Title 40,
Chapter 1, Subchapter N, Part 455. Washington, D. C. Office of the
Federal Register. October 4, 1985.
23. U. S. Environmental Protection Agency. Code of Federal Regulations.
Pharmaceutical Manufacturing Point Source Category Effluent Limitations
Guidelines, Pretreatment Standards, and New Source Performance Standards.
Title 40, Chapter 1, Subchapter N, Part 439. Washington, D. C. Office
of the Federal Register. October 27, 1983.
24. Advanced System for Process Engineering (ASPEN). Massachusetts
Institute of Technology for the Department of Energy. DOE/MC/16481-
(3 vols) 1201, 1202, 1203. 1981.
25. Letter from Plant A to Jack Farmer. (Confidential Section 114 response.)
October 1986.
26. Letter from Plant B to Jack Farmer. (Confidential Section 114 response.)
November 1986.
27. Reference 25.
28. U. S. Environmental Protection Agency/ORD/IERL. Process Design Manual
for Stripping of Organics. Cincinnati, Ohio. EPA 600/2-84-139.
August 1984.
29. Reference 25.
30. Reference 22.
4-53
-------
31. Reference 22.
32. Office of Air Quality, Planning and Standards. U. S. Environmental
Protection Agency. Hazardous Waste Treatment, Storage, and Disposal
Facilities (TSDF) - Background Information for 'Proposed RCRA Air Emission
Standards, Preliminary Draft. March 1988.
33. Reference 5.
34. Weber, Walter J. and Edward H. Smith, "Removing dissolved organic
contaminants from water," Environmental Science Technology., Vol. 20, No.
10, pp. 970-979, 1986.
35. Office of Air Quality Planning and Standards. U. S. Environmental
Protection Agency. Research Triangle Park, North Carolina. Air
Stripping of Contaminated Water Sources - Air Emissions and Control. EPA-
450/3-87-017 (NTIS PB88-106166), August 1987.
36. Cheremisinoff, Paul N., "Haz Waste Treatment and Recovery Systems".
Pollution Engineering. Vol. XX, No. 2, pp. 52 - 61. February, 1988.
37. Memorandum from Elliott, J. A., Radian Corporation, to Industrial
Wastewater File, Evaluation of Carbon Adsorption as a Control Technology
for Reducing Volatile Organic Compounds (VOC) from Industrial
Wastewaters. November 30, 1988.
38. Reference 34.
39. U. S. Environmental Protection Agency. VOC (Volatile Organic
Compounds) Emissions from Petroleum Refinery Wastewater Systems -
Background Information for Proposed Standards. EPA-450/3-85-001a.
February 1985, pp. 4-4 to 4-6.
40. Reference 32, pp. 4-6 to 4-11.
41. Reference 39, pp. 4-9 to 4-11.
4-54
-------
42. Reference 39, pp. 4-12 to 4-14.
43. Reference 39, pp. 4-14 to 4-17.
44. Office of Air Quality Planning and Standards. U. S. Environmental
Protection Agency. Control Techniques for Volatile Organic Emissions
from Stationary Sources. Draft Report. 3rd Edition. March 1986,
pp. 3-1 to 3-83.
45. Office of Air Quality Planning and Standards. U. S. Environmental
Protection Agency. Carbon Adsorption for Control of VOC Emissions:
Theory and Full Scale system Performance. Draft. Radian Corporation.
EPA Contract No. 68-02-4378/20. June 6, 1988.
46. Reference 45.
47. Reference 14, pp. F-132 to F-136.
48. Reference 39, pp. 4-25 to 4-27.
49. Reference 45.
50. Reference 39, p. 4-27 to 4-28.
51. Reference 44.
52. Reference 44.
53. Reference 39, p. 4-27.
54. Reference 39, pp. 4-29 to 4-32.
55. Reference 39, pp. 4-32 to 4-34.
56. Reference 39, p. 4-35.
57. Reference 39, pp. 4-35 to 4-36.
4-55
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58. Reference 45.
59. Reference 39, p. 4-36.
4-56
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5.0 ENVIRONMENTAL IMPACTS OF STEAM STRIPPING
The purpose of this chapter is to evaluate the environmental impacts
associated with steam stripping. Analysis of the environmental impacts
includes an evaluation of the air and water pollution impacts, impacts on
waste disposal, and impacts on energy use. An assessment of these impacts is
presented for a steam stripper (as described in Chapter 4) applied to each of
the three example wastewater streams described in Chapter 3.
5.1 IMPACTS ON VOC EMISSIONS USING A STEAM STRIPPER
Chapter 4 describes the design, operation, and performance of steam
stripper systems. Steam stripping is a pretreatment control technique
that removes organic compounds from wastewater before the wastewater contacts
the ambient air. By effectively removing organic compounds from wastewater,
steam stripping reduces the potential for VOC emissions to the air during
downstream wastewater collection and treatment and improves water quality.
However, the steam stripper system, if not controlled and operated properly,
can be a source of VOC emissions. Section 5.1.1 quantitatively presents VOC
emission reductions achievable for the example waste streams presented in
Chapter 3. Section 5.1.2 presents a qualitative discussion on air toxics, and
Section 5.1.3 presents a qualitative discussion of potential VOC emissions
that can occur from the steam stripper.
5.1.1 VOC Emissions Reduction
The VOC emission reduction achievable by steam stripping a wastewater
stream is based on the stripper design, as discussed in Chapter 4, and the
characteristics of the wastewater streams such as flow rate, composition, and
organic concentration. Table 5-1 presents a summary of the VOC air emission
impacts from the three example waste stream schematics described in Chapter 3.
Uncontrolled emissions and emissions after application of the steam stripper
system described in Chapter 4 are estimated for the three example waste stream
schematics described in Chapter 3 and are included in this table.
5-1
-------
TABLE 5-1. SUMMARY OF THE ESTIMATED ANNUAL VOC EMISSION
DEVELOPED IN CHAPTER 3
IMPACTS TO THE AIR FROM EACH OF THE EXAMPLE WASTE STREAM SCHEMATICS
cn
Example Waste Stream I*
Flow Rate
(Ipm)
40
150
300
455
760
Uncontrolled
VOC Emissions
(Mg/yr)
19
70
140
210
360
Controlled
VOC Emiss ionsb>c
(Mg/yr)
0.4
1.5
2.9
4.4
7.3
Example Waste Stream II*
Uncontrolled
VOC Emissions
(Mg/yr)
24
90
180
270
460
Controlled
VOC Emissionsb>d
(Mg/yr)
1.8
6.6
13
20
33
Example Waste Stream III*
Uncontrolled
VOC Emissions
(Mg/yr)
42
160
320
480
810
Controlled
VOC Emiss ionsb>e
(Mg/yr)
8.4
31
63
95
160
*The emissions are based on the example wastewater stream described in Table 3-3.
bControlled VOC emissions are those emissions which will occur from the wastewater after steam stripping.
°Based on an emission reduction of 98X (See Appendix A, Section A.3) for Example Waste Stream I with application of steam stripping.
dBased on an emission reduction of 93X (See Appendix A, Section A.3) for Example Waste Stream II with application of steam stripping.
'Based on an emission reduction of SOX (See Appendix A, Section A.3) for Example Waste Stream III with application of steam stripping.
-------
5.1.2 Air Toxics
This guidance document is written for the control of VOC emissions.
However, there are other environmental benefits gained from controlling VOC
emissions from industrial wastewater. Of particular concern are VOC which are
considered hazardous air pollutants. Hazardous air pollutants are addressed
in Section 112 of the Clean Air Act (CAA). A compound is currently placed on
the intent to list if it is scientifically determined that the compound poses
a serious health risk to humans. Standards are then written to regulate
emissions of that compound. Amendments to the Clean Air Act are expected to
be passed by Congress early in 1990. The amendments call for technology-
based rather than health-based standards for hazardous air pollutants. In
these amendments, 191 chemicals are listed as hazardous air pollutants. A
pollutant is added to the list if it is known to cause or can reasonably be
anticipated to cause in humans any of the following: (1) cancer or
developmental effects; or (2) serious or irreversible reproductive
dysfunctions, neurological disorders, heritable gene mutations, other chronic
health effects, or adverse acute human health effects.
Of the 191 listed hazardous air pollutants, approximately 90 percent are
VOC. Therefore, for those wastewater streams requiring control of VOC,
emissions of hazardous air pollutants could also be significantly reduced.
5.1.3 Steam Stripper Contribution to VOC Emissions
A properly operated and controlled steam stripper can achieve reductions
in VOC emissions from industrial wastewaters. However, if improperly designed
or operated, the steam stripper may be a source of VOC emissions to the air.
The operating principle of a steam stripper is that steam is contacted
with wastewater to provide heat for vaporization of the organic compounds.
This produces an overhead vapor that is concentrated in organic compounds
from which the organic compounds can be recovered by condensing and decanting.
If the condenser system for the steam stripper does not adequately
condense the overhead stream, and is not vented to a control device, the steam
stripper may become a concentrated VOC emission source. Other potential
emissions from the steam stripper are from the feed tank and decant tank.
These tanks would typically have a concentrated organic layer on top of the
wastewater and should be vented to a control device (e.g., boiler, process
5-3
-------
heater, carbon adsorber).
5.2 SECONDARY AIR IMPACTS
This section evaluates the secondary emissions associated with steam
stripping. These secondary emissions are then compared to the VOC emission
reductions for the three example waste streams.
Secondary air impacts may occur from two sources: combustion of fossil
fuels for steam and electricity generation, and handling or combustion of the
recovered organics. Fuel combustion for steam and electricity generation is a
source of combustion pollutants - particulate matter (PM), sulfur dioxide
(S02), nitrogen oxides (NOJ, carbon monoxide (CO), and VOC.
The secondary emissions presented in this section are estimated using EPA
emission factors which are presented in Table 5-2.1 These factors assume that
steam is generated on site, and electricity is purchased from a local electric
utility. Assumptions concerning the fuel composition and boiler efficiencies
achieved by the respective generators are based on information compiled by
EPA and the Energy Information Administration.2'3 Adjustments to these
values to accommodate emission reductions by existing control devices are made
assuming typical controls and control efficiencies presented in these sources.
The industrial boiler used for steam generation is assumed to have a
capacity of less than 150 million BTU. An efficiency of 80 percent is
assigned to the industrial boiler as an average expected value. It is assumed
to be controlled for S02, PM, and NOX emissions using desulfurization (90
percent removal efficiency), an electrostatic precipitator (ESP, 99 percent
removal efficiency), and flue gas recirculation (assuming the mid-range of 40
percent removal efficiency), respectively.*'5 For the purpose of estimating
secondary emissions, a fuel composition based on national fuel use for
industrial boilers was used. This fuel composition is: natural gas at 45
percent, residual oil at 28 percent, distillate oil at seven percent and coal
at 20 percent.2 Table 5-3 presents a summary of the annual fuel usages for
steam and electricity generation. These values are based on the steam
stripper design presented in Chapter 4 at the 300 1pm flow rate. The steam
requirement, assuming a boiler efficiency of 80 percent, is
3.3 x 1010 kilojoules per year. Average heating values are 2.6 x 10"5 m3/KJ
for natural gas, 2.4 x 10"8 m3/KJ for residual oil, 2.6 x 10'8 m3/KJ for
distillate oil, and 2.8 x 104 KJ/kg for coal.
5-4
-------
TABLE 5-2. COMBUSTION POLLUTANT EMISSION FACTORS
Steam/Electricitv Generation
Natural Gas (kg/105 m3)
Residual Oil (kg/m3)a
Distillate Oil (kg/m3)3
Pulverized Coal (g/kg)
PM
4.8
1.6
0.24
60b
S02
1.0
19.0
17.0
29. Oc
NOX
440
6.6
2.4
11
CO
64
0.60
0.60
0.30
VOC
2.2
0.034
0.024
0.035
"Assumes 1.0% sulfur content in the fuel oil.
bFactor derived from the EPA emission factor given as IDA, where A = % ash in
coal which was assumed to be a typical value of 12%.
cFactor derived from the EPA emission factor given as 39S, where S = % sulfur
in coal which was assumed to be the mid-range at 1.5%.
5-5
-------
TABLE 5-3. ANNUAL FUEL USE FOR STEAM AND ELECTRICITY GENERATION8
Fuel
Steam Generation
Natural Gas
Residual Oil
Distillate Oil
Coal
Electricity Generation
Natural Gas
Residual Oil
Distillate Oil
Coal
Percent
Composition19
45
28
7
20
22
11
11
56
Annual
Use
3.8 x 105 sm3/yr
220 m'/yr
59 m'/yr
2.3 x 105 kg/yr
2.0 x 103 sm'/yr
0.92 m'/yr
0.99 m3/yr
6.9 x 103 kg/yr
'Based on steam stripper design in Chapter 4 at the 300 1pm flow rate case.
bBased on national fuel use for industrial and electrical generating boilers.2
5-6
-------
An electric generator is assumed to use boilers with a higher
efficiency (85 percent for this example). The fuel composition, based on
national fuel use for electrical generation, is: natural gas at 22 percent,
distillate oil at 11 percent, residual oil at 11 percent, and coal at
56 percent. The electrical requirement for the 300 1pm case is 82,820 kWh/yr
(see Table 6-3), or 333 MMBtu/yr, based on an 85 percent boiler efficiency.
Annual fuel usages are presented in Table 5-3.
Estimated emissions, based on these assumptions are calculated as
follows:
uncontrolled emissions = annual fuel use x emission factor, and
controlled emissions = (1 - uncontrolled emissions x control efficiency).
The resulting emission estimates are presented in Table 5-4.
An evaluation of the emission estimates reveal that combustion pollutants
associated with electricity generation are small compared to those generated
during steam production. In general, combustion pollutant emissions for PM,
S02, NOX, CO and VOC are the result of steam needs with a small percentage
added, one to ten percent, to account for electricity demand.
Air impacts are presented graphically in Figures 5-1 and 5-2. The values
for combustion pollutants are the sum of the contributions from steam and
electricity generation.
Handling of the recovered organics may also contribute to secondary air
impacts resulting from disposal options. Incineration, for example, produces
combustion pollutants. If the recovered organics are recycled, however, they
do not contribute to the secondary air impacts. The recovered organics could,
in fact, be used as an alternate energy source, i.e., to generate some of the
steam required by the stripper. Although combustion of the organics will
produce combustion pollutants as mentioned above, emissions of S02 and PM
would generally be less than those generated by fossil fuel combustion. This
is due primarily to two factors: (1) most organic compounds do not contain
sulfur, which emits S02 when burned; and (2) organic compounds inherently do
not contain inorganics, which are emitted as particulates when burned.
5-7
-------
TABLE 5-4. SUMMARY OF COMBUSTION POLLUTANT EMISSIONS
ASSOCIATED WITH A STEAM STRIPPER
PM
SO,
NO,
CO
VOC
Steam Generation*'1*
Natural Gas (Mg/yr)
Distillate Oil (Mg/yr)
Residual Oil (Mg/yr)
Coal (Mg/yr)
Subtotal (Mg/yr)
Controlled Emissions (Mg/yr)
Electrical Generation1*'0
Natural Gas (Mg/yr)
Distillate Oil (Mg/yr)
Residual Oil (Mg/yr)
Coal (Mg/yr)
Subtotal (Mg/yr)
Controlled Emissions (Mg/yr)
Total Controlled Emissions
(Mg/yr)
0.0181
0.0141
0.342
13.8
14.2
0.142
0.000952
0.00238
0.0144
0.415
0.433
0.00433
0.146
0.00363
1.00
4.13
6.73
11.9
1.19
0.000190
0.169
0.174
0.202
0.546
0.0546
1.24
1.66
0.141
1.45
2.42
5.67
3.40
0.0873
0.0238
0.0611
0.0727
0.245
0.147
3.55
0.242
0.0353
0.132
0.0690
0.478
0.478
0.0127
0.00595
0.00555
0.00208
0.0263
0.0263
0.504
0.00846
0.00141
0.00737
0.00805
0.0253
0.0253
0.000444
0.000238
0.000310
0.000242
0.00124
0.00124
0.0265
"Fuel composition for steam generation is based on 45, 28, 7, and 20 percent
natural gas, residual oil, distillate oil, and coal, respectively.
bS02, NOX, and PM controls reduce emissions by 90, 40, and 99 percent,
respectively.*'5
°Fuel composition for electricity generation is based on 22, 11, 11, and
56 percent natural gas, residual oil, distillate oil, and coal, respectively.
5-8
-------
2
o
8
UJ
400
350 -
300 -
250 -
200 -
150 -
Example Schematic
100 -
50 -
P{%^'&\
VOC Reduction
-50
PM
VOC Emission Reduction
Emissions Increase
SO,
NOV
CO VOC
Figure 5-1. Air Impacts of Steam Stripper Control (Controlled Boiler)
-------
I
o
UJ
400
350 -
300 -
250 -
200 -
150 -
100 -
50 -H
-50
Example Schematic
VOC Reduction
VOC Emission Reduction
Emissions Increase
IN
PM
SC>,
CO
VOC
EXXXXXH
Figure 5-2. Air Impacts of Steam Stripper Control (Uncontrolled Boiler)
-------
5.3 CROSS MEDIA IMPACTS
Other environmental impacts may result from implementation of steam
stripper control. A major impact from the use of steam strippers is the
improvement in the quality of the wastewater being discharged either directly
from the treatment facility or from a POTW into a natural body of water.
Also, as mentioned in Section 5.2, organics recovered from the steam stripper
can be used as an alternate energy source.
Other impacts include waste disposal, additional demand for non-renewable
fuel resources, and the demand of nutrients for biodegradation. Waste
generation may arise from three possible sources: disposal of recovered
organics, solids removed during feed pretreatment, and control of system vent
emissions.
Although an increase in waste generation may occur for non-recyclable
organics which cannot be used as supplemental fuel and for cases where
treatment is required prior to stripping, it is important to recognize that
these organic and/or solid wastes would most likely have been removed from the
wastewater anyway (via the air (organics only), an oil/water separator, a
clarifier, or activated sludge unit (solids only), for example).
System vent emissions may be sent to a combustion device, thereby
generating combustion pollutants, or collected on a sorbent medium that,
unless regenerated on site, requires disposal. However, the secondary impacts
caused by these types of combustion pollutants are negligible. If sorbent
wastes are present, they may adversely impact the soil and/or water depending
on whether it is disposed of or regenerated. Therefore, if these disposal
methods are necessary, measures should be taken to control emissions from
these potential air emission sources.
Another potential impact from steam stripping of organic compounds is the
demand of nutrients for biodegradation. If a biobasin is included in the
treatment system after the steam stripper, the quantity of nutrients entering
the biobasin will be reduced. This may reduce the efficiency of the system.
5.4 ENERGY IMPACTS
The additional fuel demand to generate steam and electricity for the
steam stripper system reduces available non-renewable resources: coal, oil,
5-11
-------
and natural gas. This is partially offset if the recovered organics are used
as supplementary fuel or if they are recycled (recycling reduces the facility
demand for petroleum-derived feedstocks). It also reduces VOC emissions that
could result if the recovered organics had to be disposed of in a waste
management facility.
5-12
-------
5.5 REFERENCES
1. Office of Air Quality Planning and Standards. U. S. Environmental
Protection Agency. Research Triangle Park, North Carolina. Compilation
of Air Pollutant Emission Factors. Volume I: Stationary Point and Area
Sources. 4th ed., AP-42 (NTIS PB86-124906/REB), September 1985, and
AP-42-SUPPL-A (NTIS PB87-150959/REB), October 1986. pp. 1.1-2, 1.3-2,
1.4-2.
2. Office of Air Quality Planning and Standards. U, S. Environmental
Protection Agency. Research Triangle Park, North Carolina. Fossil Fuel
Fired Industrial Boilers - Background Information. Volume I:
Chapters 1-9 Draft EIS. EPA-450/3-82-006a (NTIS PB82-202573) March 1982.
p. 3-12-18.
3. Energy Information Administration. U. S. Department of Energy.
Washington, D. C. Electric Power Quarterly, April - June 1984.
DOE/EIA-0397(84/2Q) October 1984. pp. 19, 20.
4. Reference 1. pp. 1.3-9, 1.3-4.
5. Reference 1. pp. 1.1-5,6.
5-13
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6.0 CONTROL COST ANALYSIS OF STEAM STRIPPER SYSTEM
6.1 STEAM STRIPPER SYSTEM
Steam strippers were discussed in Chapter 4 as an effective emission
control strategy. The costs of installing a steam stripper system for removal
of organic compounds from industrial wastewater streams for the three example
waste stream schematics presented in Chapter 3 are presented in this section.
A typical steam stripper system design is presented in Figure 6-1. The
wastewater stream is pumped into a storage tank where solids can settle, and
some separation of the organic and aqueous phases will occur. Vapors that
escape through the pressure/vacuum vent are controlled by an existing
combustion or other control device. The wastewater is then pumped to the
steam stripper where organics are stripped from the wastewater stream and
carried out of the column with the overhead stream. All of the water and most
of the organics in the overhead stream are recovered by the condenser unit.
The organic phase of the liquid collected from the overhead stream is
recovered from the decanter. The aqueous phase is recycled to the wastewater
feed stream. Vapors which are not recovered in the condenser are vented to
the feed storage tank, which is controlled by an existing combustion or other
control device (e.g., boiler, process heater, carbon adsorber). The bottoms
from the steam stripper are sent to an on-site plant wastewater treatment
facility or to a POTW. In the following sections steam stripper capital
costs, annualized costs, and cost effectiveness are presented for the three
example waste stream schematics.
6.1.1 Basis For Capital Costs
The total capital investment (TCI) for a steam stripper system includes
the basic equipment costs (BEC), all auxiliary equipment costs, and direct and
indirect installation costs. The BEC is the sum of the price of each
component of the steam stripper system. Total capital investment is composed
of the purchased equipment costs (PEC), direct installation costs, and
indirect installation costs. The PEC is composed of the BEC, auxiliary piping
and equipment costs, instrumentation, freight and sales tax. The BEC is
estimated using published engineering cost estimation techniques. The TCI
required for a new steam stripper system is calculated as a direct function of
6-1
-------
Non-Condenslbtes
Control Device
Process Wastewater
via Controlled
Sewer or Hard Piping
Ogantes
Water
Feed Tank
Storage -«—
•€
Overhead Receiver
Water Cooled
Condsnsor
To Wastewater
Treatment Plant
Feed/Bottoms
Heat Exchanger
-Steam
Figure 6-1. Continuous Steam Stripper System
-------
the BEC. These estimation procedures are described more specifically in the
following section.
6.1.1.1 Basic Equipment Costs (BEC). Design of the base equipment
comprising the steam stripper system shown in Figure 6-1 is based on
information gathered by EPA1'2, and design evaluations performed using
Advanced System for Process Engineering (ASPEN)3, a computer software program
for design of distillation columns. Representative wastewater organic
concentrations were developed from the information gathered by EPA. The steam
stripper system equipment design and operating parameters were then chosen
through a design evaluation performed using ASPEN.
The wastewater stream organic concentration and total wastewater
throughput vary widely within the target industries. An organic concentration
of 2,500 ppm (0.25 percent) at various wastewater throughputs is chosen to
represent the wastewater streams for the example schematics. (A sensitivity
analysis was performed using ASPEN for a range of organic concentrations. The
results showed that removal efficiency varied little within an organic
concentration range of 300 to 30,000 ppm.) In addition, a wide variety of
organic chemical compounds are present in the wastewater streams. To
represent this range, a group of five organic compounds are chosen based on
ranges of Henry's Law constants.
The wastewater storage tank is sized to provide a desired retention time
of 48 hours for the stripper feed stream, assuming five batch and/or
continuous streams are to be combined for treatment by the same steam
stripper. Each batch and/or continuous process wastewater stream was assumed
to require approximately 300 m of connective piping.
All equipment in the steam stripper system was designed by ASPEN. The
steam stripper column is designed as a sieve tray unit with countercurrent
flow. The column is operated at a typical steam to wastewater feed ratio of
0.06 kg of steam per liter of wastewater. The liquid loading of the column is
39,900 liters per hour per square meter (1/hr/m2). Based on ASPEN results, an
average removal of 67 percent is predicted for the five compounds.
A sensitivity analysis was performed to determine the effect of the
column height on the total annualized cost. ASPEN was run at column heights
varying from 11.6 to 30.5 meters with all other variables remaining constant.
The resultant difference in the ASPEN generated total annualized cost between
the shortest and tallest columns was approximately 1.5 percent. Due to the
6-3
-------
relatively small difference in annual costs, emphasis was placed on generating
a design that would be most cost-effective, be within practical design
parameters, and would remove virtually 100 percent of the highly volatile
compounds. (The controlling compound used for design purposes was benzene.)
A column height of 18.3 meters with a total of 31 sieve trays is used for the
steam stripper unit.
The overheads from the steam stripper are recovered with a condenser unit
consisting of a water-cooled condenser. The condenser is designed for an
outlet vapor temperature of 50°C with an overall heat-transfer coefficient (U)
of 1,000 joules per square meter per second per degree Kelvin (j/m2/s/°K).
The organic phase of the overhead stream is recovered from the overheads
decanter. The overhead vapor from the secondary condenser is assumed to be
vented to the feed storage tank which is routed to an existing on-site
combustion or other control device.
The bottoms from the steam stripper are fed to the existing wastewater
treatment facility. Prior to discharge from the stripper system, the bottoms
pass through a feed preheater to enhance the efficiency of the steam stripper.
The overall heat transfer coefficient used by ASPEN for the feed preheater is
1,000 j/m2/s/°K.
Wastewater is pumped to the feed/bottoms heat exchanger from the stripper
to the feed/bottoms heat exchanger (bottoms stream), to the collection pot
from the decanter, and from the collection pot to storage.
A total of five vents in the storage tank and decanter are vented to a
flare.
Steam stripper costs are estimated using the equipment size generated by
ASPEN.3 The cost of each piece of process equipment is determined from
standard chemical engineering cost estimation manuals, textbooks, or journal
articles. The cost estimating techniques presented in these sources are based
upon the size or capacity of the equipment and are derived from actual
construction projects. Table 6-1 summarizes the estimated equipment costs
calculated for each component, the estimated size or capacity, and the
reference or information source used to obtain the cost estimate for 300 1pm.
The initial estimates were based on the equipment costs for the year in which
the textbook or journal article was published. These costs were then adjusted
to January 1986 dollars using the Chemical Engineering fabricated equipment
index for the appropriate month and year. The cost for each individual
component was summed to yield the BEC for the example wastewater stream.
6-4
-------
TABLE 6-1. ESTIMATION OF BASIC EQUIPMENT COST FOR A STEAM STRIPPING UNIT
Equipment
Component
Feed Tanks
Feed Preheater
(Shell and Tube)
Steam Stripping
Tray Column
Primary Condenser
(Water Cooled,
Shell & Tube)
Overhead Collection
Decanter
Flame Arrester
Pumps (4)
TOTAL BASE EQUIPMENT
Equipment
Size8
970 m3
240 m2
0.76 m diameter
18.3 m height
22 m2
2.5 m3
One arrester per
ventline
6100 total Watt
COST (BEC)
Construction
Material
Carbon Steel
Carbon Steel
Carbon Steel
Trays-Stainless
Carbon Steel
Carbon Steel
NA
Stainless Steel
Equipment Cost
Costsb Reference
$68,
$29,
000 4
000 4
$76,000 5,6
$ 5,
$ 4,
$
$38,
$220,
500 7
200 8
500 9
000 7
000
*Based on 300 1pm wastewater flow
January 1986 dollars
NA = Not Applicable
6-5
-------
6.1.1.2 Total Capital Investment (TCI).10 The TCI required to install a
new steam stripper unit is calculated as a direct function of the BEC value.
The TCI value is composed of three separate components; PEC, direct
installation costs, and indirect installation costs. The TCI for the steam
stripper unit and the values of each component of the TCI are presented in
Table 6-2. The PEC is calculated by multiplying the BEC times an appropriate
percentage value. These values are selected from ranges recommended in cost
estimation reference documents. Piping costs are implicitly included in the
direct installation costs; however, auxiliary piping (i.e., additional piping
for the combination of wastewater streams and vapor vent lines for storage
tanks) are accounted for separately in the PEC. Instrumentation, sales tax,
and freight are also components of the PEC. The PEC is used to estimate the
steam stripper system direct installation costs and indirect installation
costs. Each of these costs is calculated by multiplying the PEC by an
appropriate percentage value. The direct installation costs include items
such as electrical wiring, insulation, equipment support and erection, and
painting of equipment. The indirect installation costs include engineering,
construction and field expense, construction fee, start-up and testing, and
contingency. The total of PEC, direct installation costs, and indirect
installation costs yields the TCI. The TCI can also include costs for
buildings, off-site facilities, land, working capital, and yard improvements;
however, these costs are not typically included in the PEC for a steam
stripper system.
6.1.1.3 Total Capital Investment versus Wastewater Throughput. The TCI
for installing a new steam stripper system is compared to the wastewater
throughput in Figure 6-2. TCI is presented for both carbon and stainless
steel construction versus flow rates of 40, 150, 300, 455, and 760 1pm.
Stainless steel construction costs are included for comparison of streams with
corrosive wastewater (i.e., very high or low pH). Equipment costs for
stainless steel were developed from the same sources as for carbon steel.
Generally, a factor for material of construction was used for conversion of
carbon steel to 304 stainless steel. As shown in Figure 6-2, the TCI is a
direct function of the wastewater flow rate to the steam stripper unit with
stainless steel construction being more costly than carbon steel.
6-6
-------
TABLE 6-2. ESTIMATION OF TOTAL CAPITAL INVESTMENT FOR A STEAM STRIPPING UNIT»'b
Cost
Component
Cost
Factor
Component
Cost*
Total Capital
Investment
Cost
Reference
Direct Equipment Costsb
Base Equipment Cost (BEC)
Piping6
Instrunentaton
Sales Tax and Freight
Purchased Equipment Cost (PEC)
Direct Installation Costs
Foundations and Supports
Electrical
Erection and Handling
Painting
Insulation
TOTAL DIRECT INSTALLATION COST
Indirect Installation Costs
Engineering and Supervision
Construction & Field Expense
Construction Fee
Start-up and Testing
Contingency
TOTAL INDIRECT INSTALLATION COST
TOTAL CAPITAL INVESTMENT (TCI)
TABLE 6-1
$33.48/m
0.1*[BEC * Pipe]
0.08 * CBEC + Pipe]
12X of PEC
IX of PEC
40X of PEC
1X of PEC
IX of PEC
10X of PEC
10X of PEC
10X of PEC
1X of PEC
3X of PEC
$220,000
$53,000
$27,000
$24,000
$39,000
$3,300
$130.000
$3,300
$3,300
$33,000
$33,000
$33,000
$3,300
$9,800
$320,000
$180,000
$110,000
$610,000
11
12
12
12
12
12
12
12
12
12
12
12
12
^January 1986 Dollars ~~~~~~" ~~~
Based on 300 Ipm wastewater flow.
Additional piping for combination of five wastewater streams is assumed to total approximately 1500 meters.
Vapor vent lines required for storage tanks, and decanters. Each vent line was assumed to be 11 m in
length and constructed of 5.1 cm diameter schedule 40 steel pipe.
6-7
-------
00
s
I
ll
2.3 -r
2.2 -
2.1 -
2 -
1.9 -
1.8 -
1.7 -
1.6 -
1.5 -
1.4 -
1.3 -
1.2 -
1.1 -
1 -
0.9 -
0.8 -
0.7 -
0.6 -
0.5 -
0.4 -
0.3 -
• Stainless Steel
+ Carbon Steel
—I"
200
I 1
400
Wastewater Feed Rate (Ipm)
600
800
Figure 6-2. Summary of Total Capital Investment versus Wastewater Feed Rate
-------
6.1.2 Basis for Annualized Costs
The total annualized costs (TAC) are the costs incurred to operate the
steam stripper process unit throughout the year. The annual operating costs
are composed of direct and indirect charges. The TAC and each of its
components are presented in Table 6-3.
Direct annual costs are composed of the expenses which are incurred
during normal operation of the steam stripper process. These costs include
utilities, labor, and maintenance activities. Three types of utilities are
required to operate the steam stripper process unit; electricity, steam, and
cooling water. Electricity is required to operate pumps and other electrical
components included in the system. The electricity required for the pumps is
calculated assuming a developed head of approximately 120 feet of water, a
pump efficiency of 64 percent, and using design flow rates to each pump. The
steam costs are estimated using the design steam loading; 0.06 kg steam per
liter of wastewater feed. The cooling water cost is calculated using water
requirements necessary for the overhead primary condenser. Other direct costs
include labor and maintenance. Labor cost is calculated by multiplying the
estimated number of hours required to operate a steam stripper process unit
(0.5 hour/shift) times a $12.00/hr labor rate. The supervisory and
administrative costs are estimated as 15 percent of operating labor. The
maintenance costs are composed of labor and materials. Maintenance labor cost
is estimated with 0.5 hours/shift operation times a $13.20/hour labor rate.
Maintenance materials cost is 100 percent of maintenance labor cost.
The indirect operating expenses are incurred regardless of the operating
status of the steam stripper system. The cost of overhead is estimated to be
60 percent of all labor and maintenance costs. The remaining components of
the indirect annual costs are a percentage of the TCI. Property taxes and
insurance are both estimated to be one percent of the TCI while administrative
charges are estimated to be two percent of the TCI. The capital recovery for
the steam stripper system is calculated based on a 15-year equipment life at
an interest rate of 10 percent.
Another aspect of the TAC included in this estimate is the
recovery credit. This factor accounts for any cost credits which may result
from the organics being recovered from the overheads stream. There are
several alternatives for handling the recovered organics. If steam is
6-9
-------
TABLE 6-3. ESTIMATION OF TOTAL ANNUAL COST FOR A STEAM STRIPPING UNIT*'b
Cost
Component
Cost
Factor
Annual
Consumption
Annual
Cost
Cost
Reference
Direct Annual Costs
Utilities
Electricity
Steam
Water
Labor
Operating Labor
Supervision & Admin
Maintenance
Labor
Materials
TOTAL DIRECT ANNUAL COST (TDAC)
Indirect Annual Costs
Overhead
Property Taxes
Insurance
Administrative Charges
Capital Recovery (CR)
$0.0463/kUhr 44,000 kUhrc
$6.98/Mg 11,000 Mgd
$0.053/1,000 liter 470,000,000 liters*
$12.00/hr 450 hrs
15X of Op. Labor
$13.20/hr 450 hrs
100X of Ma int. Labor
60X of All Labor
and Materials
IX of TCI
1X of TCI
2X of TCI
10X a 15 yrs
TOTAL INDIRECT ANNUAL COST (TIAC)
RECOVERY CREDIT (RC)
TOTAL ANNUAL COST (TAC)
ANNUAL WASTE THROUGHPUT (AWT)
COST PER UNIT UASTEWATER ($/MG)
COST PER LITER WASTEWATER FEED
TDAC + TIAC
130,000 Mg/yr
TAC/AWT
($/l) TAC/FLOW 160.000,000 l/yr
$2,000
$76,000
$25,000
$5,400
$810
$5,900
$5,900
$120,000
$11,000
$6,200
$6,200
$12,000
$80,000
$120,000
$10,000f
$230,000
$1.70
$0.0014
13
13
14
12
12
12
12
12
12
12
12
"January 1986 dollars
Based on 300 Ipm wastewater flow
C150 kUhr/day, 300 days/yr
d37,000 kg/day, 300 days/yr
e1,600,000 liters/day, 300 days/yr
Recovery credit based on approximately 28,000 KJ/Kg
6-10
-------
produced on-site, the recovered organics can be used as fuel for the existing
boiler. The money saved by not having to purchase conventional fuels (i.e.,
fuel oil or natural gas) is the recovery credit. Another option is to reuse
the recovered organics in the manufacturing process. The organics can be
recycled directly to the process in some cases. In other cases, the organics
must be separated by distillation before reuse. The costs saved in the
purchase of raw materials is the recovery credit; however, this may be offset
by the cost of distillation for the recovered organics. Another option for
the recovered organics is to sell them to a chemical manufacturer who will
recover the separate components of the waste organic stream. However, a
cost-effective use for the recovered organics may not exist in all cases. In
this case, the plant would have to pay for disposal of the collected organics.
Although there are several options available for disposal or use of the
recovered organic stream, for this cost estimate it is assumed that the
organics can be used as fuel for an existing boiler. A heating value of
approximately 28,000 KJ/Kg was calculated for an organic composition developed
from Table 2-4.
The organic compounds used to calculate the heating value were chosen
based on the highest concentration values of the compounds reported in the 114
responses: acrylonitrile, carbon tetrachloride, ethanol, formaldehyde,
styrene, toluene, and triethylamine. The cost of generating steam is reported
to be 2 to 3 times more than the fuel cost in Perry's Chemical Engineering
handbook.15 Therefore, to assess a cost savings for burning organics in place
of a typical fuel used (i.e., coal, distillate/residual oil, etc.), the
typical fuel cost was assumed to be the steam cost divided by 2.5. The
resulting fuel cost is SI.3 x 10'6/KJ. The recovery credit is calculated by
multiplying the VOC removal per year by the calculated organic compound
heating value and the estimated fuel cost.
The estimated unit annual cost for the steam stripper system at
300 1pm is $1.74/Mg of wastewater treated. The cost per liter of wastewater
at this flow rate was estimated to be $0.0014/1. Annual costs were also
estimated for four other plant sizes to assess the impact of plant size on
annual operating costs. The same estimation techniques used for the steam
stripper unit were used to estimate the annual operating costs for steam
stripper units treating 40, 150, 455, and 760 1pm of wastewater. The results
of these cost estimates are presented graphically in Figure 6-3. Unit
operating costs versus flow for both carbon and stainless steel construction
6-11
-------
a
O
0.011
0.01 -
0.009 -
0.008 -
0.007 -
0.006 -
0.005 -H
0.004 -I
0.003 -
0.002 -
0.001
• Stainless Steel
+ Carbon Steel
200
I
400
Wastewater Feed Rate (Ipm)
I
600
800
Figure 6-3. Summary of Unit Operating Costs versus Wastewater Feed Rate
-------
are presented. For the carbon steel system, total annual costs (TAG) ranged
from $100,000/yr for the 40 1pm flow rate to $420,000/yr for a 760 1pm
wastewater system. The stainless steel system is more costly with the TAG
ranging from $220,000/yr (40 1pm) to $640,000/yr (760 1pm).
6.1.3 Cost Effectiveness
The cost effectiveness is defined as the total annualized cost per Mg of
VOC emission reduction. The cost effectiveness of steam stripping was
calculated for each of the example waste stream collection and treatment
system schematics described in Chapter 3 (see Section 3.3). The cost
effectiveness was based on a wastewater stream containing 500 ppm (each) of:
1,3-butadiene, toluene, naphthalene, 1-butanol, and phenol. Using the
emission factors (fe) generated in Chapter 3, the annual VOC emissions were
estimated using the following equation:
Q x 0.001 m3/! x 525,600 min/yr x 2.5 x 10'3 Mg/m3 x fe = VOC emissions
where;
Q = wastewater flow rate (1pm)
fe = emission factors generated in Chapter 3 (see Table 6-4).
The VOC emissions from each stream were calculated at five separate wastewater
flow rates (Q) ranging from 40 1pm to 760 1pm. The VOC emissions for each of
the example wastewater stream schematics at the various flow rates are shown
in Table 6-4.
The example waste stream schematics defined in Section 3.3 do not include
any type of VOC emission control system. By installing a steam stripper
system before wastewaters are exposed to ambient air, VOC emissions could be
greatly reduced. Table 6-5 presents controlled and uncontrolled fraction
emitted, predicted removal efficiencies for each compound, average organic
compound removal efficiency, and VOC emission reduction for each example waste
stream schematic applied to the design steam stripper. Table 6-6 presents the
estimated annual emissions reduction for the three example waste stream
schematics based on the predicted emissions and removal efficiencies. The
cost effectiveness for each example waste stream schematic at five different
flow rates is presented in Table 6-7 based on the estimated emission
6-13
-------
TABLE 6-4. SUMMARY OF THE ESTIMATED ANNUAL VOC EMISSIONS FROM
EACH OF THE EXAMPLE WASTE STREAM SCHEMATICS
DEVELOPED IN CHAPTER 3
Exampl e
Schematic
Schematic
Schematic
Schematic
VOC Emi
Emission
Factorb
(fe) 40
I 0.35 19
II 0.45 24
III 0.81 42
ssions (Mg/yr)a
Wastewater
150
70
90
160
Flow Rate
300
140
180
320
(lorn)
455
210
270
480
760
360
460
810
"The assumed wastewater organic concentration is 2,500 ppm. (See Table 3-3
for wastewater characteristics).
bOverall cumulative fraction emitted for each example schematic.
(See Tables A-33 through A-35 in Appendix A.)
6-14
-------
TABLE 6-5. REMOVAL EFFICIENCIES AND OVERALL EMISSION REDUCTION
Uncontrolled Fe*
Example Schematics
Controlled Fec
Example Schematics
Compound
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Average
I
0.92
0.47
0.34
0.052
0.00079
0.36
II
1.0
0.74
0.30
0.22
0.017
0.45
III
1.00
0.997
0.99
0.72
0.32
0.81
Frb
1.00
1.00
0.999
0.31
0.022
0.67
I
0
0
0.00045
0.036
0.00077
0.0074
II
0
0
0.00038
0.15
0.016
0.033
III
0
0
0.0013
0.50
0.31
0.16
Emission reduction = [1 - (controlled fe/uncontrolled fe)] * 100
Example Schematic I Emission Reduction (Mg/yr): 0.98
Example Schematic II Emission Reduction (Mg/yr): 0.93
Example Schematic III Emission Reduction (Mg/yr): 0.80
'Uncontrolled cumulative fraction emitted for each compound. See
Tables A-33 through A-35 of Appendix A.
bFraction removed by the steam stripper is based on ASPEN results for the
design steam stripper.3
Controlled fraction emitted for each compound. Controlled fe =
uncontrolled fe (1-fr).
6-15
-------
TABLE 6-6. SUMMARY OF THE ESTIMATED ANNUAL VOC EMISSIONS REDUCTION
FROM EACH OF THE EXAMPLE WASTE STREAM SCHEMATICS
DEVELOPED IN CHAPTER 3
VOC Emission Reduction (Mg/yr)"
Example
Schematic
Schematic
Schematic
Schematic
Emission
Reduction11
(%) 40
I 98 18
II 93 22
III 80 34
Wastewater
150
69
83
130
Flow Rate
300
140
170
260
Horn)
455
210
250
390
760
350
420
650
"The assumed wastewater organic concentration is 2,500 ppm. (See Table 3-3
for wastewater characteristics).
Determined from ASPEN removal efficiencies and the cumulative uncontrolled
fractions emitted for each model plant.3
6-16
-------
TABLE 6-7. STEAM STRIPPER COST EFFECTIVENESS
Wastewater Flow Rate (1pm)
40 150 300 455 760
Total Annual Costs
(TAC)b $100,000 $160,000 $230,000 $290,000 $420,000
Schematic I
Schematic II
Schematic III
Cost Effectiveness (dollars/Mg VOC
5,500 2,300 1,700
4,500 1,900 1,400
2,900 1,200 890
emission reduction)*
1,400
1,200
760
1,200
1,000
650
"The assumed wastewater organic concentration is 2,500 ppm. (See Table 3-3
for wastewater characteristics). Emission reduction was determined from
ASPEN removal efficiencies and the cumulative uncontrolled fractions
emitted for each example collection and treatment schematic.3
Calculated in Section 6.1.2
6-17
-------
reductions presented in Table 6-6. Estimates of cost effectiveness are
presented graphically in Figure 6-4 for both carbon and stainless steel
construction. As shown in Figure 6-4, the cost effectiveness of steam
stripping is nearly independent of process throughput at wastewater flow rates
greater than 300 1pm. However, at flow rates less than 200 1pm, the cost
effectiveness is almost inversely proportional to the total wastewater flow
rate. As expected, cost effectiveness for stainless steel construction is
greater than that for carbon steel.
6-18
-------
10
13 -y
12 -
11 -
10 -
9 -
8 -
7 -
6 -
5 -
4 -
3 -
2 -
1 -
0 - -
—T~
200
Example Schematic l-Stainless Steel
Example Schematic Il-Staintess Steel
Example Schematic Ill-Stainless Steel
Example Schematic l-Carbon Steel
Example Schematic Il-Carbon Steel
I 1
400
Wastewater Feed Rate (Ipm)
T~
600
Figure 6-4. Cost Effectiveness versus Wastewater Feed Rate for
Example Stream Schematics I, II, III
800
-------
6.2 REFERENCES
1. Letter from Plant B to Jack Farmer (Confidential Section 114 response.)
November 1986.
2. OWRS data, June 12, 1985. JRB/SAIC. "Costing Documentation and National
New Information."
3. Advanced System for Process Engineering (ASPEN). Massachusetts
Institute of Technology for the Department of Energy. DOE/ME/16481-
(3 vols) 1201, 1202, 1203. 1981.
4. Corripio, A. B., K. S. Chrien, and L. B. Evans. Estimate Costs of Heat
Exchangers and Storage Tanks via Correlations. "Chemical Engineering",
January 25, 1982. p. 125.
5. Peters, M. S., and K. D. Timmerhaus. Plant Design and Economics for
Chemical Engineers. 3rd ed. New York, McGraw-Hill Book Company. 1980.
pp. 768 - 773.
6. Corripio, A. B., A. Mulet, and L. B. Evans. Estimate Costs of
Distillation and Absorption Towers via Correlations. "Chemical
Engineering", December 28, 1981. p. 180.
7. Hall, R. S., W. M. Vatavuk, J. Matley. Estimating Process Equipment
Costs. "Chemical Engineering", November 21, 1988. p. 66-75.
8. Reference 5, p. 886.
9. Telecon. Gitelman, A., Research Triangle Institute with Hoyt
Corporation. September 8, 1986. Cost of flame arresters.
10. U. S. Environmental Protection Agency. EAB Control Cost Manual.
Section 2: Manual Estimating Methodology. 3rd Edition. Draft. Office
of Air Quality Planning and Standards. Research Triangle Park, North
Carolina. June 1986. p. 2-27 - 2-31.
6-20
-------
11. Richardson Process Plant Construction Estimation Standards: Mechanical
and Electrical. Volume 3, Richardson Engineering Services, Inc., Mesa,
Arizona, 1988. pp 15-40: Pipe costs were adjusted to January 1986
dollars.
12. Vatavuk, W. M., and R. B. Neveril. Part II: Factors for Estimating
Capital and Operating Costs. "Chemical Engineering". November 3, 1980.
p. 157 - 182.
13. Memorandum from Peterson, Paul, RTI, to Susan Thorneloe, EPA/OAQPS.
"Basis for Steam Stripping Organic Removal Efficiency and Cost Estimates
Used for the Source Assessment Model (SAM) Analysis". January 18, 1988.
14. Reference 10, p. 4-29.
15. Perry, R. H., and C. H. Chilton. Chemical Engineers' Handbook. 5th ed.
New York, McGraw-Hill Book Company. 1973. p. 25-12.
6-21
-------
APPENDIX A
EMISSION ESTIMATES
-------
APPENDIX A
Wastewater collection and treatment systems are comprised of a variety of
components. A list of the most common components is presented in Table A-l.
Because these components are often uncovered and provide contact between
wastewater and ambient air, there is the potential for VOC emissions from each
of these components. The purpose of this appendix is to present emission
estimates for these components and the mass transfer models that were used to
perform these estimates. In addition, three example stream schematics were
developed by combining individual collection and treatment system components
in different scenarios. Cumulative emissions from these three example
schematics are also presented in this appendix.
A.I COLLECTION AND TREATMENT SYSTEM COMPONENTS
Emission estimates for individual collection and treatment system
components and the mass transfer models used to estimate these emissions are
presented in this section. The emission estimates are based on five example
pollutants and typical physical dimensions for the components. The five
pollutants are: 1,3-butadiene, toluene, naphthalene, 1-butanol, and phenol.
The overall emissions from each component are determined by summing the
emissions of these five individual pollutants.
The physical dimensions assigned to each component are based on
information gathered by EPA during the Industrial Wastewater project. During
this project, 19 chemical manufacturing facilities and 2 pharmaceutical
facilities were visited to obtain information on wastewater generation,
collection, and treatment.1"21 During the visits, plant personnel provided data
on the dimensions for these components (i.e., the treatment system components
listed in Table A-l). Also, during the visits, tours were conducted to
evaluate components in the wastewater collection systems. Information
gathered during these tours as well as "best engineering judgment" were used
to develop "typical" dimensions for these components (i.e., the collection
system components listed in Table A-l).
A-l
-------
TABLE A-l. WASTEWATER COLLECTION AND TREATMENT SYSTEM COMPONENTS
Collection System Components
Treatment System Components
Drains
Manholes
Junction Boxes
Sumps
Trenches
Lift Stations
Oil-Water Separators
Equalization Basins
Clarifiers
Treatment Tanks
Weirs
Aeration Basins
A-2
-------
As discussed in Chapter 3, the emission mechanisms and factors affecting
emissions from many of these collection and treatment system components are
relatively similar. For this reason, similar mass transfer models are used to
estimate emissions from many of the components. The models used to estimate
emissions from drains, manholes, and trenches are presented in Section A.1.1.
Emissions from junction boxes, lift stations, sumps, equalization basins,
clarifiers, treatment tanks, and aeration basins are presented in Section
A.1.2 along with the mass transfer models used for these components.
Emissions and emission models for oil-water separators and weirs are presented
in Section A.1.3 and A.1.4, respectively.
A.1.1 Emissions from Drains. Manholes, and Trenches
As discussed in Chapter 3, the wastewater flowing into process drains and
trenches and through underground sewer lines is often greater than the ambient
air temperature. For this reason, the air in the headspace at the bottom of
the drain riser and in the sewer line may also be greater than the ambient air
temperature. Due to this temperature difference, the density of the ambient
air is greater than the air in the headspace at the bottom of the drain riser
and in the sewer line. Drains, manholes, and trenches provide escape routes
for this less dense air to flow into the ambient air above these components.
In addition, as wastewater flows through the drain risers, or into trenches it
may entrain air flow into the sewer line. This air will escape from the sewer
system from downstream drains and manholes or downstream in the trench. Wind
blowing into the sewer line or the trench also increases the rate of
emissions. Because of these factors, drains, manholes, and trenches are
potential emission sources.
Emissions from drains and manholes were estimated based on the factors
discussed above at temperatures of 40°C, 30eC, and 30°C, respectively.
(Temperatures were chosen based on engineering judgement and the assumption of
25eC ambient temperature.) Typical drain, manhole, and trench configurations
are shown in Figure A-l, A-2, and A-3, respectively. Emissions from drains
are based on the average of three cases: (1) emissions due to the entrainment
of air with the wastewater flowing through the drain into the sewer system,
(2) emissions due to wind blowing into the drain, and (3) emissions due to the
less dense air flowing from the sewer out the drain riser. Emissions from
A-3
-------
Top VltW
/•
/ t
T
H.
Vl«w
Design Parameter
Drain riser height, L (m)
Drain riser diameter, Drf (m)
Process drain pipe diameter, D (m)
Effective diameter of drain riser, D (m)
Drain riser cap thickness, D (cm)
Sewer Diameter, D (m)
Ranoe
0.3 - 1.2
0.1 - 0.3
0.005 - 0.15
0.005 - 0.15
0.5 - 0.7
0.6 - 1.2
Typical Design
0.6
0.2
0.1
0.1
0.6
0.9
Figure A-l. Typical drain configurati
on.
A-4
-------
TopVtav
SMtVtow
Design Parameter
Manhole diameter, Dd (m)
Manhole height, L (m)
Manhole cover diameter, DC (m)
Diameter of holes in cover, 0 (cm)
Manhole cover thickness, HC (cm)
Sewer Diameter, DS (m)
Range
0.6 - 1.8
0.3 - 1.8
0.4 - 0.7
1.2 - 3.8
0.5 - 0.7
0.6 - 1.2
Typical Design
1.2
1.2
0.6
2.5
0.6
0.9
Figure A-2. Typical Manhole Configuration.
A-5
-------
Design Parameter
Trench length, L (m)
Water depth (m)
Trench depth, h (m)
Trench width, W (m)
Range
15 -150
0.3 - 0.9
0.4 - 1.2
0.3 - 0.9
Typical Design
15.2
0.6
0.8
0.6
Figure A-3. Typical trench configuration.
A-6
-------
manholes are also based on the average of three cases: (1) emissions due to
the less dense air flowing out of the sewer headspace into the ambient air,
(2) emissions from wind blowing into the upstream end of a sewer which is
obstructed from air flow after the manhole, and 3) emissions from wind blowing
through the sewer line under the manhole. Emissions from trenches are based
solely on the diffusion of the organics from the flowing wastewater stream.
(See Appendix B for the development of emission factors for drains, manholes,
and trenches). The emission estimates for drains, manholes, and trenches are
presented in Tables A-2, A-3, and A-4, respectively.
A.1.2 Emissions from Junction Boxes, Lift Stations. Sumps, Equalization
Basins. Clarifiers. Treatment Tanks, and Aeration Basins
During the Hazardous Waste Treatment, Storage, and Disposal Facilities
(TSDF) project, EPA developed mass transfer models to estimate air emissions
from surface impoundments and open top tanks.22 These models are used in this
appendix to estimate emissions from junction boxes, lift stations, sumps,
equalization basins, clarifiers, treatment tanks, and aeration basins. The
models are based on two-film resistance theory. That is, the resistance to
mass transfer is assumed to occur at the interface between the liquid
(wastewater) and vapor (ambient air) phases. Individual mass transfer
coefficients are used to account for these liquid and vapor phase resistances.
These individual coefficients are functions of the following parameters: the
physical properties of the wastewater pollutants, the design and operation of
the collection or treatment system component, and the conditions of the
ambient air surrounding the component (e.g., temperature, wind speed).
Overall mass transfer coefficients can be determined from the estimated values
for the individual coefficients. Then, the general approach used by the
models is to apply mass balances around the component and use the overall
coefficients to estimate pollutant air emissions. This same general approach
is used to estimate emissions from the components discussed in this section.
The specific models, assumptions, and component dimensions used to estimate
emissions from each component are presented below.
A-7
-------
TABLE A-2. EMISSION ESTIMATES FOR DRAINS
Fraction Emitted, Fe
Compound (T=408C)
1,3-Butadiene 5.7E-01
Toluene 6.1E-02
Naphthalene 1.1E-02
1-Butanol 8.7E-05
Phenol 4.4E-06
A-8
-------
TABLE A-3. EMISSION ESTIMATES FOR MANHOLES
Fraction Emitted, Fe
Compound (T=30'C)
1,3-Butadiene 1.5E-01
Toluene 8.2E-03
Naphthalene 1.5E-03
1-Butanol 1.1E-05
Phenol 5.7E-07
A-9
-------
TABLE A-4. EMISSION ESTIMATES FOR TRENCHES
Compound Fraction Emitted, Fe
(T - 30°C)
1,3-Butadiene 5.9E-02
Toluene 4.5E-02
Naphthalene 2.5E-02
1-Butanol 4.1E-04
Phenol 2.1E-05
A-10
-------
A.1.2.1 Junction Boxes
The general approach used to estimate emissions from junction boxes is
presented in Table A-5. Wastewater flowing through the junction box is
assumed to be turbulent and well mixed. Correlations are available that can
be used to estimate liquid phase coefficients for mechanically aerated
impoundments. Although junction boxes are not mechanically aerated, these
correlations are used to estimate liquid phase coefficients to account for the
wastewater turbulence in the junction box. Air emissions can occur as a
result of air entering the sewer system at some point prior to the junction
box (i.e., from a manhole or drain). However, it is expected that this type
of occurence is rare and the effect on total VOC emissions is small. As seen
in Table A-5, the correlation for kL requires a value for the power input
(POWR) to the aerator. Metcalf and Eddy, Inc., suggest a range of 0.5 to 1.0
hp/1,000 ft3 for mixing in an impoundment.23 Because the junction box is
assumed to be well mixed, a power input of 0.5 hp/1,000 ft3 is used for this
parameter in the correlation to estimate kL. As shown in Table A-5,
individual gas phase mass transfer coefficients are estimated from
correlations developed by MacKay and Matasugu. These individual liquid and
gas phase coefficients are used to estimate overall mass transfer coefficients
for the organic compounds (Step II in Table A-5).
Because the wastewater in the junction box is well mixed, the bulk
concentration is equal to the effluent concentration. This bulk concentration
provides the driving force for volatilization. Step III in Table A-5 shows
the equation for determining the value for this parameter. The overall
emission rate for each compound is estimated by determining the product of the
following three variables: (1) the liquid surface area in the junction box,
(2) the overall mass transfer coefficient for the organic compound, and
(3) the concentration of the organic compound in the effluent leaving the
junction box (Step IV in Table A-5).
A typical junction box configuration is shown in Figure A-4. Emission
estimates for the junction box are based on the typical design dimensions
shown in the figure. Table A-6 presents the fraction emitted from the
junction box for five example organic compounds. The emission rates presented
in the table are based on a wastewater flow rate through the junction box of
150 1/min. The wastewater is assumed to be at a temperature of 35°C. Each of
the five organic compounds are assumed to be present in the wastewater feed at
A-ll
-------
TABLE A-5. ESTIMATION TECHNIQUE FOR JUNCTION BOXES
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Thibodeaux:
kL (m/s) = [8.22 x 1CT9 J (POWR) (1.024)7-20 Ot 106 MWL/(VavpL)]
Vapor Phase. 1^:
Mackay and Matasugu:
kc (m/s) = 4.82 x 10'3 x (U10)°-78 x (ScJ'0'67 x (d.)'0'
'0'11
II. Equation for calculating the overall mass transfer coefficient, K:
1/K = l/kL + l/(K.qkJ
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QC0/(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
A-12
-------
Qra*
Design Parameter
Effective diameter, d (m)
Grade height, h (m)
Water Depth (m)
p
Surface area (m)
Range
0.3 - 1.8
1.2 - 1.8
0.6 - 1.2
0.007 - 2.5
Typical Design
0.9
1.5
0.9
0.7
Figure A-4. Typical Junction Box Configuration.
A-13
-------
TABLE A-6. EMISSION ESTIMATES FOR JUNCTION BOXES
Compound
Henry's Law Constant
H, atm - m3/9"K)l
(25eC)
Henry's Law Constant
H, atm -
(35'C)
Fraction
Emitted, Fe
(T=35CC)
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
1.91E-01
1.10E-02
2.48E-03
1.83E-05
1.04E-06
1.2E-01
9.8E-02
6.8E-02
1.9E-03
1.1E-04
A-14
-------
a concentration of 500 ppm. The fraction emitted of each organic compound
from the junction box is estimated by dividing the mass of the compound
emitted by the mass of that compound in the wastewater. A sample calculation
for junction boxes is provided in Table A-7.
A.1.2.2 Lift Stations
The general approach used to estimate emissions from lift stations is
presented in Table A-8. Wastewater flowing through the lift station is
assumed to be turbulent and well mixed. For this reason, the correlations
applicable to mechanically aerated impoundments are used to estimate liquid
phase mass transfer coefficients for lift stations. Similar to the procedure
used for junction boxes, a power input of 0.5 hp/1,000 ft3 is used in the
correlation to estimate kL. As shown in Table A-8 (Section I), individual gas
phase mass transfer coefficients are estimated from correlations developed by
MacKay and Matasugu. These individual liquid and gas phase coefficients are
used to estimate overall mass transfer coefficients for the organic compounds
in the wastewater (Step II in Table A-8).
Because the wastewater in the lift station is well mixed, the bulk
concentration is equal to the effluent concentration. This bulk concentration
provides the driving force for volatilization. Step III in Table A-8 shows
the equation for determining the value for this parameter. The overall
emission rate for each organic compound is estimated by determining the
product of the following three variables: (1) the liquid surface area in the
lift station, (2) the overall mass transfer coefficient for the organic
compound, and (3) the concentration of the organic compound in the effluent
leaving the lift station (Step IV in Table A-8).
A typical lift station configuration is shown in Figure A-5. Emission
estimates for the lift station are based on the typical design dimensions
shown in the figure. Table A-9 presents the fraction emitted from the lift
station for five example organic compounds. The emission rates presented in
the table based on a wastewater flow rate through the lift station of
150 1/min. The wastewater is assumed to be at a temperature of 30°C. Each of
the five organic compounds are assumed to be present in the wastewater feed at
a concentration of 500 ppm. The fraction emitted of each compound from the
lift station is estimated by dividing the mass of the compound emitted by
A-15
-------
TABLE A-7. SAMPLE CALCULATIONS FOR JUNCTION BOXES
Component: Junction Box
A = 0.656 m2
de = 0.91 m
depth = 0.91 m
F/D = 1
Q = 2.52 x 10'3 ms/s
t = 236.9 s
T = 35'C
U10 = 4.47 m/s
Compound: Toluene
CL = 500 ppm = 5 x 10"A g/cm3
MW = 92.0 g/gmol
Dw = 1.10 x 10'5 cm2/s (35eC)
Da = 8.70 x 10'2 cm2/s
H = 1.10 x 10"2 atm-m3/gmol (35eC)
J = 3 Ib O^hr-hp
Ot = 0.83
Nx = 1
d = 61 cm
w = 126 rad/s
Fraction agitated = 1
Submerged air flow = 0 m3/s
D
ether
8.50 x 10'6 cnrys
Water and Air Properties:
pw = 1 g/cm3
uw = 7.23 x 10'3 g/cm-s
p. - 1.20 x 10'3 g/cm3
ua = 1.81 x 10'* g/cm-s
D02/w = 3.19 x 10"5 cm2/s
MWa = 29 g/gmol
MWW = 18 g/gmol
A-16
-------
TABLE A-7. SAMPLE CALCULATIONS FOR JUNCTION BOXES
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
kL (m/s) = [8.22 x 1
-------
TABLE A-7. SAMPLE CALCULATIONS FOR JUNCTION BOXES
(Continued)
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x ID'3 (U10}° 78 (ScG)-°-67 (d.)'0-11
a. Calculate ScG:
ScG = U./P.D.
ScG = 1.81 x ID'4 g/cm-s/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
b. Calculate kg:
kg (m/s) = 4.82 x 1CT3 (4.47 m/s)°'78 (1.734)-0'67 (0.91 m)'0'11
kg (m/s) = 4.82 x 1CT3 (3.215) (0.692) (1.0104)
kg = 0.0108 m/s
3. Calculate overall mass transfer coefficient, K:
l/kL + l/(K.qkB)
a. Calculate Keq:
Keq = H/RT
Keq = 0.0110 atm-m3/gmol/[(8.21 x 10"5 atm-m3/gmol-eK) (308°K)]
Keq =0.434
b. Calculate K:
1/K = l/kL + l/(K.qk,)
1/K = l/(4.59 x 10-*) + 1/[(0.434) (0.0108)]
1/K = 2.179 x 103 + 2.133 x 102
K (m/s) = 4.18 x 1(T*
A-18
-------
TABLE A-7. SAMPLE CALCULATIONS FOR JUNCTION BOXES
(Continued)
4. Calculate concentration of toluene at vapor-liquid interface, CL:
CL - Q CyCKA + Q)
CL = (2.52 x 1(T3 m3/s) (5 x 10'* g/cm3) (106 cm3/m3)/
[(4.18 x 10'* m/s) (0.656 m2) + (2.52 x 10'3 m3/s)]
CL = 450.9 g/m3
5. Calculate air emissions, N.:
(N.)T (Mg/yr) = K CL A
(N.)T (Mg/yr) = (4.18 x 10"1 m/s) (3600 s/hr) (7200 hr/yr) (450.9 g/m3)
(0.656 m2) (Mg/106 g)
(NJT = 3.21 Mg/yr
6. Calculate fraction of toluene emitted from a junction box, fe:
(fe)T = (NJT/(QCJ
(fe), = (3.21 Mg/yr)/[(2.52 x 10'3 m3/s) (3600 s/hr) (7200 hr/yr)
(5 x 10'4 g/cm3) (106 cm3/m3) (Mg/106 g)]
(fe)T = 0.0982
A-19
-------
TABLE A-8. ESTIMATION TECHNIQUE FOR LIFT STATIONS
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Thibodeaux:
kL (m/s) = [8.22 x 10'9 J (POWR) (1.024)1-20 Ot 106 MWy
(DW/D02, J°'5
Vapor Phase, 1^:
Mackay and Matasugu:
kc (m/s) = 4.82 x 1CT3 x (U10)0'78 x (ScJ'0-67 x (de)-°'n
II. Equation for calculating the overall mass transfer coefficient, K:
1/K « l/kL + l/(KeqkG)
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QC0/(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
A-20
-------
W?SWW^Sid"^B<*W9WB»!»WW!\d
Pump
Jfi
Design Parameter
Effective diameter, d (m)
Width, W (m)
Grade height, h (m)
Water Depth (m)
2
Surface area (m )
Range
1.2 - 3.0
1.4 - 3.6
1.8 - 2.4
1.2 - 1.8
1.1 - 7.1
Typical Design
1.5
1.8
2.1
1.5
1.8
Figure A-5. Typical Lift Station Configuration.
A-21
-------
TABLE A-9. EMISSION ESTIMATES FOR LIFT STATIONS
Compound
Henry's Law Constant
H, atm -
(25eC)
Henry's Law Constant
H, atm -
(30-C)
Fraction
Emitted, Fe
(T=308C)
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
1.65E-01
8.61E-03
1.73E-03
1.29E-05
6.97E-06
3.6E-01
2.9E-01
1.8E-01
3.6E-03
2.0E-04
A-22
-------
the mass of that compound in the wastewater. An example calculation for lift
stations is provided in Table A-10.
A.1.2.3 Sumps
The technique used to estimate emissions from sumps is presented in
Table A-ll. Individual mass transfer coefficients are estimated based on
correlations used for quiescent surface impoundments. Overall mass transfer
coefficients are estimated based on values obtained for the individual
coefficients. The wastewater flowing through the sump is assumed to be
well-mixed. Therefore, the effluent concentration is the driving force for
air emissions. The overall coefficients, the liquid surface area in the
clarifier, and the wastewater effluent concentrations for each organic
compound are then multiplied together to estimate the emission rate of each
organic compound.
Table A-12 presents the fraction emitted for five example organic
compounds. The emission rates are based on a wastewater flow rate of 150 1pm
through the sump. Each of the five organic compounds are assumed to be
present at a concentration of 100 ppm. The wastewater is assumed to be at a
temperature of 30°C. An example calculation for sumps is shown in Table A-
13.
A.1.2.4 Equalization Basins
The technique used to estimate emissions from equalization basins is
presented in Table A-14. Equalization basins may be non-aerated or aerated.
Emission estimates for these cases are shown in Steps (1) and (2) in the
Table A-14. The major difference in the two procedures is the calculation of
the individual mass transfer coefficients. Individual mass transfer
coefficients for the non-aerated case are estimated based on correlations used
for quiescent surface impoundments. Individual mass transfer coefficients for
the aerated case are estimated based on correlations used for mechanically
aerated surface impoundments. Overall mass transfer coefficients (in both
cases) are estimated based on values obtained for the individual coefficients.
The overall coefficients, the liquid surface area in the equalization basin,
and the wastewater effluent concentrations for each organic compound are then
multiplied together to estimate the emission rate of each organic compound.
A-23
-------
TABLE A-10. SAMPLE CALCULATIONS FOR LIFT STATIONS
Component: Lift Station
A = 1.824 m2
de = 1.524 m
depth = 1.524 m
F/D = 1
Q = 2.52 x 1CT3 ms/s
t - 1,103 s
T = 30°C
U10 = 4.47 m/s
J = 3 Ib
Ot = 0.83
Nx = 1
d = 61 cm
w =126 rad/s
Fraction agitated = 1
Submerged air flow = 0 m3/s
Compound: Toluene
CL = 500 ppm = 5 x 10"4 g/cm3
MW = 92.0 g/gmol
Dw = 9.74 x 10'6 cm2/s (30°C)
Da = 8.7 x 10"2 cm2/s
H = 8.61 x 10'3 atm-m3/gmol (30CC)
Water and Air Properties:
pv = 1 g/cm3
uw = 8.01 x 10"3 g/cm-s
pa = 1.20 x 10'3 g/cm3
ua = 1.81 x 10-* g/cm-s
D02>w = 2.83 x 10'5 cm2/s
MWa = 29 g/gmol
MWW = 18 g/gmol
A-24
-------
TABLE A-10. SAMPLE CALCULATIONS FOR LIFT STATIONS
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
kL (m/s) = [8.22 x 10'9 J(POWR) (1.024)1-20 (Ot x 106) (MWw/(VavpJ)]
a. Calculate POWR:
POWR = 0.5 hp/1000 ft3 x 35.31 ft3/m3 (A x depth)
POWR = 0.0005 hp/ft3 x 35.31 ft3/m3 x (1.824 m2 x 1.524 m)
POWR = 0.049 hp
b. Calculate V:
V = Volume x fraction agitated, ft3
V = (19.6 ft2 x 5 ft) (1)
V = 98 ft3
c. Calculate av:
av = area/volume, ft'1
av = 19.6 ft2/98 ft3
av = 0.2 ft'1
d. Calculate kL:
kL (m/s) = [8.22 x 10'9 (3 Ib 02/hr-hp) (0.049 hp) (1.024)10]
[0.83 x 106 (18 g/gmol)/(98 ft3) (0.2) (1 g/cm3)]
[9.74 x 10'6 cm2/s / 2.83 x 10'5 cm2/s]°'5
kL (m/s) = (1.53 x ID'9) (.762245) (.586)
kL = 6.83 x 10'4 m/s
A-25
-------
TABLE A-10. SAMPLE CALCULATIONS FOR LIFT STATIONS
(Continued)
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x 1CT3 (U10)°-78 (ScJ'0'67 (dj'0'
'0'11
a. Calculate ScG:
ScG = 1.81 x 10-* g/cm-s/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
b. Calculate kg:
kg (m/s) = 4.82 x 10'3 (4.47 m/s)°'78 (1.734)-0'67 (1.524 m)"0'11
kg (m/s) = 4.82 x lO'3 (3.215) (0.6916) (0.9547)
kg = 0.0102 m/s
3. Calculate overall mass transfer coefficient, K:
1/K = l/kL + l/(K.qk.)
a. Calculate Keq:
Keq - H/RT
Keq = 0.00861 atm-nrYgmol/[(8.21 x 10'5 atm-m3/gmol-°K) (303°K)]
Keq =0.346
b. Calculate K:
1/K = l/kL + l/(K.qk.)
1/K = 1/6.83 x ID'' + 1/[(0.346) (0.0102)]
1/K = 1464.1 + 283.3
K (m/s) = 5.73 x 10-4
A-26
-------
TABLE A-10. SAMPLE CALCULATIONS FOR LIFT STATIONS
(Continued)
4. Calculate concentration of toluene at vapor-liquid interface, CL:
CL = Q cytKA + Q)
CL = (2.52 x 10'3 m3/s) (5 x 10'* g/cm3) (106 cm3/m3)/
[(5.73 x 1Q-* m/s) (1.824 m2) + (2.52 x 10'3 m3/s)]
CL = 353.4 g/m3
5. Calculate air emissions, Na:
(NJT (Mg/yr) = K CL A
(NJT (Mg/yr) = (5.73 x 1(T4 m/s) (3600 s/hr) (7200 hr/yr) (353.4 g/m3)
(1.824 m2) (Mg/106 g)
(NJT = 9.57 Mg/yr
6. Calculate fraction of toluene emitted from a lift station, fe:
(fe)T = (N.)T/(QCJ
(fe)T = (9.57 Mg/yr)/[(2.52 x 10"3 m3/s) (3600 s/hr) (7200 hr/yr)
(5 x 10'A g/cm3) (106 cm3/m3) (Mg/106 g)]
(fe)T = 0.293
A-27
-------
TABLE A-ll. ESTIMATION TECHNIQUE FOR SUMPS
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Mackay and Yeun
(for F/D <14 and U10 >3.25 m/s):
kL = 1.0 x 1CT6 + 144 x 10'* x (U*)2'2 x (ScJ'0'5,
where
U* <0.3
where
U* (m/s) = 0.01 x U10 x (6.1 + 0.63 x U10)°'5
and
ScL = uL/(pLDJ
Vapor Phase. kG:
Mackay and Matasugu:
kc (m/s) = 4.82 x 10'3 x (U10)0'78 x (ScJ'0'67 x (dj'0 u
II. Equation for calculating the overall mass transfer coefficient, K:
1/K = l/kL + 1/d^U
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QCy(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
A-28
-------
TABLE A-12. EMISSION ESTIMATES FOR SUMPS
Compound
Henry's Law Constant
H, atm - m3/gmol
(25'C)
Henry's Law Constant
H, atm - mYgmol
(30'C)
Fraction
Emitted, Fe
(T=30°C)
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
1.65E-01
8.61E-03
1.73E-03
1.29E-05
6.97E-07
5.6E-03
5.0E-03
4.7E-03
2.1E-03
1.9E-04
A-29
-------
TABLE A-13. SAMPLE CALCULATIONS FOR SUMPS
Component: Sump
A = 1.824 m2
de = 1.524 m
depth = 1.524 m
F/D = 1.0
Q = 2.52 x ID'3 m3/s
t = 1,103 s
T = 30°C
U10 = 4.47 m/s
Compound: Toluene
Ci = 100 ppm = 1 x 10"4 g/cm3
MW = 92.0 g/gmol
Dv = 9.74 x ID'6 cm2/s
Da = 8.70 x 10'2 cm2/s
H = 8.61 x 10'3 atm-mVgmol
Dether = 8.5 x ID"6 cm2/s
Water and Air Properties:
pw = 1 g/cm3
utf = 8.01 x 10~3 g/cm-sec
p. - 1.20 x 10'3 g/cm3
ua = 1.81 x 10'4 g/cm-s
A-30
-------
TABLE A-13. SAMPLE CALCULATIONS FOR SUMPS
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
a. Calculate U*:
U* (m/s) = 0.01 x U10 (6.1 + 0.63 x U10)°'5
U* (m/s) = 0.01 x 4.47 m/s (6.1 + 0.63 x 4.47 m/s)0'5
U* = 0.1335 m/s
b. Calculate ScL:
ScL - uw/(pwDw(T))
ScL = 8.01 x 10'3 g/cm-s/[(l g/cm3) (9.74 x 10'6 cm2/s)]
ScL = 822
c. Calculate kL:
kL (m/s) = 1.0 x 10"6 + 144 x 10"4 (U*)2.2 (ScL)'0'5
kL (m/s) = 1.0 x 10'6 + 144 x 10'4 (0.1335)2'2 x (822)'° 5
kL = 6.98 x 10"6 m/s
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x 10'3 x (U10)°-78 (ScJ'0'67 (d.)'0-11
a. Calculate ScG:
ScG - ua/(paDa(T))
ScG = (1.81 x 10'4 g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
b. Calculate kg:
k6 (m/s) = 4.82 x 10'3 x (4.47 m/s)°'78 (1.734)'0'67 (1.524 m)'0-"
kg (m/s) = 4.82 x 10"3 x (3.215) (0.692) (0.955)
kg = 0.0102 m/s
A-31
-------
TABLE A-13. SAMPLE CALCULATIONS FOR SUMPS
(Continued)
3. Calculate overall mass transfer coefficient, K:
1/K = 1/KL + l/(Keqkg)
a. Calculate Keq:
Keq = H/RT
Keq = 8.61 x 10'3 atm-m3/gmol/[(8.21 x 10'5 atm-m3/gmol-eK) (303°K)
Keq = 0.346
b. Calculate K:
1/K = l/kL + l/(K.qk.)
1/K = (1/6.98 x 10'6 m/s) + [1/(0.346) (0.0102 m/s)]
1/K = 143266 + 283.4
K = 6.96 x 10'6 m/s
4. Calculate concentration of toluene at vapor-liquid interface, CL:
CL = Q C,/(KA + Q)
CL = (2.52 x 10-3 m3/s) (1 x 10'* g/cm3) (106 cm3/m3)/
[(6.96 x 1CT6 m/s) (1.824 m2) + (2.52 x 10'3 m3/s)
CL = 99.5 g/m3
5. Calculate air emissions, Na:
(NJT (Mg/yr) = K CL A
(N.)T (Mg/yr) = (6.96 x 10'6 m/s) (3600 s/hr) (7200 hr/yr)
(99.5 g/m3) (1.824 m2) (10~6 Mg/g)
(NJT = 0.0328 Mg/yr
A-32
-------
TABLE A-13. SAMPLE CALCULATIONS FOR SUMPS
(Continued)
6. Calculate fraction of toluene emitted from a sump, fe:
(f.)t = (NJT/QC,
(fe)T = (0.0328 Mg/yr)/[(2.52 x 10'3 m3/s) (3600 s/hr) (7200 hr/yr)
(1 x 10'* g/cm3) (106cm3/m3) (10'6 Mg/g)
(fe)T = 5.02 x ID'3
A-33
-------
TABLE A-14. ESTIMATION TECHNIQUE FOR EQUALIZATION BASINS
(1) Non-Aerated Basins
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Springer et al (for 14 3.25 m/s):
kL (m/s) = [2.605 x 1CT9 (F/D) + 1.277 x 1(T7J x (U10)2 x (Dw/Dether}2/3
Vapor Phase, k,-:
MacKay and Matasugu:
kG (m/s) = 4.82 x 1CT3 x (U10)0'78 x (ScJ'0'67 x (dj'0-11
II. Equation for calculating the overall mass transfer coefficient, K:
1/K = l/kL + l/(KeqkG)
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QC0/(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
(2) Aerated Basin
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
kL (m/s) = [8.22 x 10'9 J (POWR)(1.024)T-20 Ot 106
(Dw/D02iW)°-5
A-34
-------
TABLE A-14. ESTIMATION TECHNIQUE FOR EQUALIZATION BASINS
(Continued)
Gas Phase
Reinhardt:
kc (m/s) = 1.35 x 10-3-7 (Re)1'42 (P)°-* (Scc)° 5 (Fr)'0'21 (DaMWyd)
II. Equation for calculating the overall mass transfer coefficient, K;
1/K = l/(kj + l/d^kj
where
Keq = Equilibrium constant = H/RT
Equation for calculating overall mass transfer coefficient for
combined quiescent and turbulent areas:
K = K^ + MjJ/tAp + AT)
where
Kp = overall mass transfer coefficient for quiescent area,
KT = overall mass transfer coefficient for turbulent area,
AQ = quiescent surface area, and
AT = turbulent surface area.
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QCy(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
A-35
-------
Figure A-6 presents a typical equalization basin. Emission estimates for
the equalization basin are based on the typical design dimensions shown in the
figure. Table A-15 presents emission estimates for typical aerated and non-
aerated equalization basin designs. The emission rates were based on a
wastewater flow rate of 1,000 gpm through the equalization basin. Each of the
five organic compounds were assumed to be present at a concentration of 10
ppm. The wastewater is assumed to be at ambient temperature for the purposes
of the calculation. An example calculation for equalization basins is shown
in Table A-16.
A.1.2.5 Clarifiers
The technique used to estimate emissions from clarifiers is presented in
Table A-17. Individual mass transfer coefficients are estimated based on
correlations used for quiescent surface impoundments. Overall mass transfer
coefficients are estimated based on values obtained for the individual
coefficients. The wastewater flowing through the clarifier is assumed to be
well-mixed. Therefore, the effluent concentration is the driving force for
air emissions. The overall coefficients, the liquid surface area in the
clarifier, and the wastewater effluent concentrations for each organic
compound are then multiplied together to estimate the emission rate of each
organic compound.
A typical clarifier is shown in Figure A-7.24 Emission estimates for the
clarifier are based on the typical design dimensions shown in the figure.
Table A-18 presents the fraction emitted for five example organic compounds.
The emission rates are based on a wastewater flow rate of 1,000 gpm through
the clarifier. Each of the five organic compounds are assumed to be present
at a concentration of 10 ppm. The wastewater is assumed to be at ambient
temperature for the purposes of the calculation. An example calculation for
clarifiers is shown in Table A-19.
A.1.2.6 Emissions from Aerated and Non-Aerated Biological Treatment Basins
Mass transfer correlations used during the TSDF project to estimate
emissions from activated sludge units and disposal impoundments with quiescent
surfaces are used to estimate emissions from aerated and non-aerated
biological treatment basins, respectively. These techniques are presented in
A-36
-------
I.Omfraaboard
Floating aarator
Maximum wrfaca araa
Minimum raquirad
operating (aval
Minimum allowabja
opariting
toval to protact
floating aarator*
daaign and «t
vary with
•courpad1
Design Parameter
Effective Diameter (m)
2
Surface Area (m)
Water depth (m)
Retention time (days)
Range
20 -270
300 - 57,000
1 - 8
0.2 - 20
Typical Design
109
9,290
2.9
5
Figure A-6. Typical equalization basin.
A-37
-------
TABLE A-15. EMISSION ESTIMATES FOR EQUALIZATION BASINS
Compound
Non-Aerated
1,3 Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Aerated
1,3 Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Henry's Law Constant
H, atm - mVgmol
(25'C)
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
Fraction
Emitted, Fe
4.3E-01
4.0E-01
3.8E-01
1.8E-01
1.6E-02
l.OE+00
9.9E-01
9.88E-01
6.1E-01
7.7E-02
A-38
-------
J - 3 Ib Oj/hr-hp
Ot. - 0.83
Fraction agitated = 0.24
Submerged air flow = 0 m3/s
Nj = 6
d = 61 cm
w = 126 rad/s
TABLE A-16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
Component: Equalization basin
(1) Aerated Basin
A - 9,290 m2
de = 108.7 m
depth = 2.895 m
F/D = 37.56
Q = 0.063 m3/s
t = 5 days
T = 25°C
U10 = 4.47 m/s
Compound: Toluene
Ci = 10 ppm = 1 x 10~5 g/cm3
MW = 92.0 g/gmol
Dw = 8.60 x 10'6 cm2/s
Da = 8.70 x 10'2 cm2/s
H = 6.68 x 10"3 atm-m3/gmo1
Dether = 8.5 x ICT6 cm2/s
Water and Air Properties:
pw = 1 g/cm3
uw = 8.93 x 1CT3 g/cm-s
pa = 1.20 x 1CT3 g/cm3
ua = 1.81 x 10"' g/cm-s
D02_w = 2.5 x ID'5 cm2/s
A-39
-------
TABLE A- 16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
MW. = 29 g/gmol
MWW = 18 g/gmol
1. Calculate liquid mass transfer coefficient, kL:
kL (m/s) = [8.22 x 10'9 J(POWR) (1.024)1-20 (Ot x 106) (MWJ/(VavpJ]
a. Calculate POWR:
POWR = 0.5 hp/1000 ft3 x 35.31 ft3/m3 (A x depth)
POWR = 0.0005 hp/ft3 x 35.31 ft3/m3 (9290 m2 x 2.895 m)
POWR = 475 hp
b. Calculate V:
V = Volume x fraction agitated
V = (100000 ft2 x 9.5 ft) (0.24)
V = 228000 ft3
c. Calculate av:
av = area/volume
av = 100000 ft2/(950000 ft3)
av = 0.1053 ft'1
d. Calculate kL:
kL (m/s) = [8.22 x 10'9 (3 Ib 02/hr-hp) (475 hp) (1.024)5
(0.83 x 106) (18 g/gmol)/ [(228000 ft3) (0.1053 ft'1)
d 9/cm3)]] [(8.60 x ID'6 cm2/s)/(2.5 x 10'5 cm2/sec)]°
kL (m/s) = (1.318 x 10'5) (622) (0.586) = 4.80 x 10'3 m/s
A-40
-------
TABLE A- 16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 1.35 x 1CT7 (Re)1'42 (P)0'4 (ScG)0'5 (Fr)'0'21 (D.MWyd)
a. Calculate Re (Reynold's Number):
Re = d2 wp./ua
Re = (61 cm)2 (126 rad/s) (1.20 x 1(T3 g/cm3)/1.81 x 10'4 g/cm-s
Re = 3.11 x 106
b. Calculate P (Power Number):
P = PX 9c/(P«d*V)
where
Px = 0.85 (POWR) (550 ft-lbf/s-hp)/^
Pj = 0.85 (475 hp) (550 ft-lb£/s-hp)/6
P! = 37000 ft-lbf/s
so,
P = (37000 ft-lbf/s)(32.17 lbm ft/s2 - lbf)/[(lg/cm3) (28317 cm3/ft3)
(lb.,/453.6 g) (61cm(ft/30.48 cm))5 (126 rad/s)3]
p = (1190290 Ibm/s3)/(4.009 x 109
p = 2.97 x 10-'
c. Calculate ScG (Schmidt Number):
ScG -
ScG = (1.81 x 10'* g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
A-41
-------
TABLE A-16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
2. (Continued)
d. Calculate Fr (Froude Number):
Fr = d* w2/9c
Fr = (61 cm/30.48 cm/ft) (126 rad/s)2/(32.17 lbffi-ft/lbf-s2)
Fr = 987.65
e. Calculate kg:
kg (m/s) = 1.35 x ID'7 (Re)1'42 (p)°•* (Scc)°-5 (Fr)"0'21 D.MWyd
kg (m/s) = 1.35 x ID'7 (3.11 x 106)1-42 (2.97 x lO'4)0-4 (1.734)05
(987.65)'0-21 (8.70 x 10'2 cm2/s) (29 g/gmol)/(61 cm)
kg = 1.11 x 10'1 m/s
3. Calculate overall mass transfer coefficient, K:
1/K = l/kL + l/(Keqkg)
a. Calculate Keq:
Keq = H/RT
Keq = (6.68 x 10'3 atm-m3/gmol)/[(8.21 x 10'5 atm-m3/gmol -°K) (298°K)]
Keq =0.273
b. Calculate K:
1/K = (4.80 x ID'3 m/s) + [1/(0.273) (1.11 x 10'1 m/s)]
1/K = 208 + 33
K = 4.15 x 10'3 m/s
4. Calculate overall mass transfer coefficient for combined quiescent and
turbulent areas, K (weighted by area):
Turbulent area = 0.24 x A = 0.24 (9290 m2)
Turbulent area = 2230 m2
Kj = 4.15 x 10'3 m/s
A-42
-------
TABLE A-16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
4. (Continued)
Quiescent area = (Total Area-Turbulent Area) = 9290 - 2230
Quiescent area = 7060 m2
KQ (m/s) = 4.52 x 10'6
K (m/s) = [(4.52 x 10'6 m/s) (7060 m2) + (4.15 x 10'3 m/s) (2230 m2)]/
(2230 m2 + 7060 m2)
K = 9.98 x 10'* m/s
5. Calculate concentration of toluene at vapor-liquid interface, CL:
CL = QCy(KA + Q)
CL = (0.063 m3/s) (1 x 10'5 g/cm3) (106 cm3/m3)/
[(9.98 x 1C"4 m/s) (9290 m2) + (0.063 m3/s)]
CL = 0.0675 g/m3
6. Calculate air emissions, Na:
(NJT (Mg/yr) = K CL A
(NJT (Mg/yr) = (9.98 x 10'4 m/s) (3600 s/hr) (7200 hr/yr) (0.0675 g/m3)
(9290 m2) (ID'6 g/Mg)
(NJT = 16.22 Mg/yr
7. Calculate fraction of toluene emitted from an aerated equalization
basin, fe:
(fe)T = N./QC,
(fe)T = (16.22 Mg/yr)/[(0.063 m3/s) (3600 s/hr) (7200 hr/yr)
(1 x ID'5 g/cm3) (106 cm3/m3) (10'6 Mg/g)]
(fe)T = 0.993
A-43
-------
TABLE A-16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
Component: Equalization basin
(2) Non-Aerated Basin
A = 9,290 m2
de = 108.7 m
depth = 2.895
F/D = 37.56
Q = 0.063 m3/s
t = 5 days
T = 25°C
U10 = 4.47 m/s
Compound: Toluene
CA = 10 ppm = 1 x 10"5 g/cm3
V(, = 92.0 g/gmol
Dw = 8.60 x 10'6 cm2/s
Da = 8.70 x ID'2 cm2/s
H = 6.68 x 10"3 atm-m3/gmol
Dether = 8.5 x ICT6 cm2/s
Water and Air Properties:
pw = 1 g/cm3
uw = 8.93 x 10~3 g/cm-s
pa = 1.20 x 10'3 g/cm3
ua = 1.81 x 10"' g/cm-s
A-44
-------
TABLE A-16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
kL (m/s) = [2.605 x 10'9 (F/D) + 1.277 x 10'7] (U10)2 [D,/Dether]0-67
kL (m/s) = [2.605 x 10'9 (37.56) + 1.277 x 10'7] (4.47 m/s)2
[(8.6 x 10-6cm2/s)/(8.5 x 10-6cm2/s)]0-67
kL = 4.53 x 10'6 m/s
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x lO'3 (U10)0'78 (ScG)-°-67 (dj'0'11
a. Calculate ScG:
ScG = ua/(paDJ
ScG = (1.81 x ID'4 g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
b. Calculate kg:
kg (m/s) = 4.82 x 10'3 x (4.47 m/s)0'78 (1.734)'0-67 (108.7 m)'0'11
kg (m/s) = 4.82 x 1CT3 x (3.215) (0.692) (0.597)
kg = 0.0064 m/s
3. Calculate overall mass transfer coefficient, K:
1/K = l/kL + l/(Keqkg)
a. Calculate Keq:
Keq = H/RT
Keq = (6.68 x 1CT3 atm-m3/gmol)/[(8.21 x 10'5 atm-m3/gmol-°K) (298'K)]
Keq = 0.273
b. Calculate K:
1/K = 1/4.53 x 10'6 m/s + [1/(0.273) (0.0064 m/s)]
1/K = 220750 + 572.3
K = 4.52 x 10'6 m/s
A-45
-------
TABLE A-16. SAMPLE CALCULATIONS FOR EQUALIZATION BASINS
(Continued)
4. Calculate concentration of toluene at vapor-liquid interface, CL:
CL = Q cyKA + Q
CL = [(0.063 m3/s) (1 x 10'5 g/cm3) (106 cm3/m3)]/
[(4.52 x 10'6 m/s) (9290 m2) + (0.063 m3/s)]
CL = 6.00 g/m3
5. Calculate air emissions, Na:
(NJT (Mg/yr) = K CL A
(NJT (Mg/yr) = (4.52 x 10'6 m/s) (3600 s/hr) (7200 hr/yr)
(6.00 g/m3) (9290 m2) (10'6 Mg/g)
(NJT = 6.532 Mg/yr
6. Calculate fraction of toluene emitted from a non-aerated equalization
basin, fe:
(fe)T = (N.
(fe)T = 6.532 Mg/yr/[(0.063 m3/s) (3600 s/hr) (7200 hr/yr)
(1 x 10'5 g/cm3) (106 cm3/m3) (10'6 Mg/g)]
(fe)T = 0.400
A-46
-------
TABLE A-17. ESTIMATION TECHNIQUE FOR CLARIFIERS
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
LiQuid Phase. kL:
Mackay and Yeun
(for F/D <14 and U10 >3.25 m/s):
kL = 1.0 x 10'6 + 144 x 10'* x (U*)22 x (ScJ'0'5,
where
U* <0.3
where
U* (m/s) - 0.01 x U10 x (6.1 + 0.63 x U10)°-5
and
ScL = uL/(pLDJ
Vapor Phase. 1^:
Mackay and Matasugu:
kc (m/s) = 4.82 x 10-3 x (U10)°-78 x (ScJ'0'67 x (dj'0'11
II. Equation for calculating the overall mass transfer coefficient, K:
1/K = l/kL + l/(KeqkJ
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QC0/(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
A-47
-------
Ortvtumt
gffUMntWM
OfWOff Pfp0
Design Parameter
Diameter (m)
Depth (m)
Retention time (hr)
Range
6.1 - 30.5
2.4 - 4.5
1.5 - 7
Typical Design
18.3
3.5
4.0
Figure A-7. Typical clarifier configuration.
A-48
-------
TABLE A-18. EMISSION ESTIMATES FOR CLARIFIERS
Compound
Henry's Law Constant
H, atm - mVgmol
(T = 25°C)
Fraction
Emitted, Fe
1,3 Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
2.8E-02
2.5E-02
2.4E-02
7.8E-03
5.6E-04
A-49
-------
IHDLL «-iy. bA..PLh CALCULATIONS FOR CLARIFIERS
Component: Clan'fler
A = 262.7 m2
de = 18.29 m
depth = 3.505 m
F/D = 5.22
Q = 0.0639 m3/s
t = 4 hr
T = 25°C
U10 = 4.47 m/s
Compound: Toluene
Ci = 10 ppm = 1 x 10"5 g/cm3
MW = 92.0 g/gmol
Dw = 8.60 x 10'6 cm2/s
Da = 8.70 x 10'2 cm2/s
H = 6.68 x 10"3 atm-m3/gmol
Dether = 8.5 x 10-6 cm2/s
Water and Air Properties:
pw = 1 g/cm3
uw = 8.93 x 10"3 g/cm-s
pa = 1.20 x ID'3 g/cm3
ua = 1.81 x 10"4 g/cm-s
A-50
-------
TABLE A-19. SAMPLE CALCULATIONS FOR CLARIFIERS
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
a. Calculate U*:
U* (m/s) = 0.01 x U10 (6.1 + 0.63 x U10)°-5
U* (m/s) = 0.01 x 4.47 m/s (6.1 + 0.63 x 4.47 m/s)°'5
U* = 0.1335 m/s
b. Calculate ScL:
ScL = 8.93 x 10'3 g/cm-s/[(l g/cm3) (8.60 x 10'6 cm2/s)]
ScL = 1,038
c. Calculate kL:
kL (m/s) = 1.0 x 10'6 + 144 x 10'* (U*)2'2 (ScJ'0'5
kL (m/s) = 1.0 x 10"6 + 144 x 10'* (0.1335)2'2 x (1038)'0'5
kL = 6.32 x 10"6 m/s
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x 1CT3 x (U10)0.78 (ScG)-°'67 (dj'0'11
a. Calculate ScG:
ScG = (1.81 x 1CT4 g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
b. Calculate kg:
kg (m/s) = 4.82 x 1CT3 x (4.47 m/s)°'78 (1.734)-0'67 (18.29 m)'0'11
kg (m/s) = 4.82 x 10'3 x (3.215) (0.692) (0.726)
kg = 0.0078 m/s
A-51
-------
A-iy. SAMPLE CALCULATIONS FOR CLARIFIERS
(Continued)
3. Calculate overall mass transfer coefficient, K:
l/kL + l/(Keqkg)
a. Calculate Keq:
Keq = H/RT
Keq = 6.68 x 10'3 atm-m3/gmol/[(8.21 x 10'5 atm-m3/gmol-*K) (298eK)]
Keq = 0.273
b. Calculate K:
1/K = l/kL + l/(K«qkg)
1/K = (1/6.32 x 10'6 m/s) + [1/(0.273) (0.0078 m/s)]
1/K = 158228 + 469.6
K = 6.30 x 10'6 m/s
4. Calculate concentration of toluene at vapor-liquid interface, CL:
CL = Q C1/(KA + Q)
CL = (0.0639 m3/s) (l x 10'5 g/cm3) (106 cm3/m3)/
[(6.30 x 10'6 m/s) (262.7 m2) + (0.0639 m3/s)]
CL = 9.75 g/m3
5. Calculate air emissions, Na:
(NJT (Mg/yr) = K CL A
(NJT (Mg/yr) = (6.30 x 10'6 m/s) (3600 s/hr) (7200 hr/yr)
(9.75 g/m3) (262.7 m2) (10'6 Mg/g)
(NJT = 0.418 Mg/yr
6. Calculate fraction of toluene emitted from a clarifier, fe:
(fe)T = (NJ./QC,
(fe)T = (0.418 Mg/yr)/[(0.0639 m3/s) (3600 s/hr) (7200 hr/yr)
(1 x 10'5 g/cm3) (106cm3/m3) (10'6 Mg/g)]
(fe)T = 0.0253
A-52
-------
Table A-20. For aerated basins, the overall mass transfer coefficient is
calculated by considering that the liquid surface is made up of both turbulent
and quiescent areas. This overall mass transfer coefficient is estimated
using the individual liquid and gas phase coefficients for both areas.
Biodegradation is also included in the emissions model as a competing
mechanism since biodegradation and volatilization are both significant organic
compound removal mechanisms from these units. The removal rate by the
competing biodegradation mechanism is more difficult to predict because of its
strong dependency on the organic compound characteristics, basin design and
operating parameters, and the influent organic compound concentration. For
these emissions estimates, the effluent concentration is calculated from the
organic compound biorate constant, the active biomass, and the influent
concentration. The fraction of the compound emitted is then calculated using
this effluent concentration and the overall mass transfer coefficient.
A typical aerated biological treatment basin is shown in Figure A-8.25
Emission estimates for the aerated basin are based on the typical design
dimensions shown in the figure. Table A-21 presents emission rates for
typical aerated and non-aerated biological treatment basins. The emission
rates are based on influent organic compound concentrations of 40 g/m3 for
each of the five organic compounds. The wastewater is assumed to be at
ambient temperature for the purposes of the calculation. Example calculations
for both aerated and non-aerated biological treatment basins are shown in
Table A-22.
A.1.2.7 Emissions from Treatment Tanks
The technique used to estimate emissions from flocculation and pH
adjustment tanks is presented in Table A-23. Individual mass transfer
coefficients are estimated based on correlations used for quiescent surface
impoundments. Overall mass transfer coefficients are estimated based on
values obtained for the individual coefficients. The wastewater flowing
through the tank is assumed to be well-mixed. Therefore, the effluent
concentration is the driving force for air emissions. The overall
coefficients, the liquid surface area in tanks, and the wastewater effluent
concentrations for each organic compound are then multiplied together to
estimate the emission rate of each organic compound.
A-53
-------
TABLE A-20. ESTIMATION TECHNIQUE FOR BIOLOGICAL TREATMENT BASINS
(1) Aerated Basin
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Thibodeaux:
kL (m/s) = [8.22 x 10'9 J (POWR)(1.024)T-20 Ot 106
Gas Phase
Reinhardt:
kc (m/s) - 1.35 x ID'7 (Re)1'42 (P)°-4 (ScG)0'5 (Fr)'0'21 (DaMWyd)
II. Equation for calculating the overall mass transfer coefficient, K;
1/K = l/(kj + l/(KeqkG)
where
Keq = Equilibrium constant = H/RT
Equation for calculating overall mass transfer coefficient for
combined quiescent and turbulent areas:
K = KQ/V, + KTAT)/(Ap + AT)
where
Kq = overall mass transfer coefficient for quiescent area,
KT = overall mass transfer coefficient for turbulent area,
AQ = quiescent surface area, and
AT = turbulent surface area.
A-54
-------
TABLE A-20. ESTIMATION TECHNIQUE FOR BIOLOGICAL TREATMENT BASINS
(Continued)
III. Equation for calculating the effluent concentration for a well-
mixed system:
a - K' - (KA/Q) + 1
b = KSK' + (V/Q) K^b, - C0
c = -KSC0
CL = [-b + (b2 - 4ac)°'5]/(2a)
where
K,^ = maximum biorate, g/s-g biomass
Ks = half saturation constant, g/m3
bL = Active biomass, g/m3
C0 = inlet organic compound concentration, g/m3
CL = effluent organic compound concentration, g/m3
IV. Equation for calculating the fraction emitted from a well-mixed
system:
f. =
.
(2) Non-Aerated Basins
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Springer et al (for 14 3.25 m/s):
kL (m/s) = [2.605 x 10" (F/D) + 1.277 x 10'7] x (U10)2 x (Dw/Dether)2/3
Vapor Phase. 1^:
MacKay and Matasugu:
k; (m/s) = 4.82 x ID'3 x (U10)0'78 x (ScJ'0'67 x (dj'0-11
A-55
-------
TABLE A-20. ESTIMATION TECHNIQUE FOR BIOLOGICAL TREATMENT BASINS
(Continued)
II. Equation for calculating the overall mass transfer coefficient, K:
1/K = l/kL + l/^kj
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the effluent concentration for a well-
mixed system:
a = K' = (KA/Q) + 1
b = KSK' + (V/Q) K^b, - C0
c = -KSC0
CL = [-b + (b2 - 4ac)°'5]/(2a)
where
K^ = maximum biorate, g/s-g biomass
Ks = half saturation constant, g/m3
bL = Active biomass, g/m3
C0 = inlet organic compound concentration, g/m3
CL = effluent organic compound concentration, g/m3
IV. Equation for calculating the fraction emitted from a well-mixed
system:
fe = KA(VQC0
A-56
-------
Coblt Tits
Surf oca
Mechanic ol
Aerators
A
\
X \
t I
' I
I
/ \
/ X
/ f
V'
V
/
I '
Ov«rflo«
W«ir
«•
• Wa«t«wat«r
! InM Manifold
Design Parameter
Effective Diameter (m)
o
Surface Area (m )
Water depth (m)
Retention time (days)
Typical Design
150
17,650
2.0
6.5
Figure A-8. Typical A*raUd Biological Treatment Basin
A-57
-------
TABLE A-21. EMISSION ESTIMATES FOR BIOLOGICAL TREATMENT BASINS
Fraction Emitted, Fe
Compound (T=25°C)
Aerated
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Non-Aerated
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
2.9E-01
1.2E-01
1.7E-01
4.1E-02
1.9E-05
2.2E-01
6.0E-02
1.2E-01
3.0E-01
3.9E-04
A-58
-------
TABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
I. Component: Aerated Basin Containing Biomass
A = 17,652 m3 J = 3 Ib O^hr-hp
de = 149.9 m Ot = 0.83
depth = 1.981 m Nx - 8
V = 34,972 m3 d - 61 cm
F/D =75.67 w = 126 rad/s
Q = 0.0623 m3/s Fraction agitated - 0.24
t = 6.5 days Submerged air flow = 0 m3/s
T = 25°C bi = Active biomass = 4 g/1
U10 =4.47 m/s Biomass solids =0.00 m3/s
Compound: Toluene
C0 = 40 ppm = 40 g/m3
MW = 92.0 g/gmol
Dw = 8.60 x 10'6 cm3/s
Mw = 8.70 x 10'2 cm3/s
H = 6.68 x 10"3 atm-m3/gmo1
Dether = 8.50 x ID'6 cm3/s
Kffiax = 73.5 mg/gbiomass-hr = 2.04 x 10"5 g/gbiomass/s
Ks = 30.6 mg/1 - 30.6 g/m3
Water and Air Properties:
pw = 1 g/cm3
uw = 8.93 x 10"3 g/cm-s
ua = 1.81 x 10'* g/cm-s
D02/w = 2.5 x 10'5 cm3/s
MWa = 29 g/gmol
A-59
-------
IABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
kL (m/s) = [8.22 x 1(T9 J(POWR)(1.024)T-20(Ot x 106) (MW,/(VavPJ)]
(DW/D02,J°-5
a. Calculate POWR:
POWR (hp) = 0.5 hp/1000 ft3 x 35.31 ft3/m3 (A x depth)
POWR (hp) = 0.0005 hp/ft3 x 35.31 ft3/m3 (17652 m3 x 1.9812 m)
POWR = 617.43 hp
b. Calculate V:
V (ft3) = Volume x fraction agitated
V (ft3) = 34,972 m3 (3.28 ft3/m3)
V = 296180 ft3
c. Calculate av:
av = area/volume, ft"1
av = 17,652 m3/[(34,972 m3) x (3.28 ft/m)]
av = 0.1538 ft'1
d. Calculate kL:
kL (m/s) = [8.22 x 10'9 (3 Ib 02/hr-hp) (617.43 hp) (1.024)5]
[0.83 x 106 x 18 g/gmol/I(296180 ft3) (0.1538 ff1) (1 g/cm3)]]
[8.60 x 10'6 cm3/s)/(2.50 x 10'5 cm3/s)]°-5
kL (m/s) = (1.71 x 10'5) (327.97) (0.5865)
kL = 0.00329 m/s
A-60
-------
TABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) - 1.35 x ID'7 (Re)1 " (P)0-* (ScG)° 5 (Fr)'0'21 (D.MWyd)
a. Calculate Re (Reynold's Number):
Re = d2 wp./ua
Re = (61 cm)2 (126 rad/s) (1.20 x 10'3 g/cm3)/(1.81 x 10"* g/cm-s)
Re = 3.11 x 106
b. Calculate P (Power Number):
P - PI 9c/(Pvd*V)
where
Px = 0.85 (POWR) (550 ft-lbf/s-hpJ/Nj
Pj = 0.85 (475 hp) (550 ft-lbf/s-hp)/8
Px = 36,081 ft-lbj/s
so,
P = (36,081 ft-lbf/s)(32.17 lbm ft/s2 - lb£)/
[(lg/cm3) (Iby453.6 g) (28317 cm3/ft3)
[(61cm)(ft/30.48 cm)]5 (126 rad/s)3]
P = 2.895 x 10"4
c. Calculate ScG (Schmidt Number):
ScG - ua/(paDJ
ScG = (1.81 x 10'* g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10"2 cm3/s)]
ScG = 1.734
d. Calculate Fr (Froude Number):
Fr = d* w2/gc
Fr = (61 cm/30.48 cm/ft) (126 rad/s)2/(32.17 lbm-ft/lbf-s2)
Fr = 987.65
A-61
-------
IABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
2. (Continued)
e. Calculate kg:
kg (m/s) = 1.35 x 1(T7 (3.11 x 106)1'*2 (2.895 x 10'*)°•* (1.734)° 5
(987.65)-0'21 (8.70 x 10'2 cm3/s) (29 g/gmol)/(61 cm)
kg = 0.110 m/s
3. Calculate overall mass transfer coefficient, K:
1/K = l/kL + l/(K.qk.)
a. Calculate K:
K = H/RT
K = (6.68 x 10"3 atm-m3/gmol)/[(8.21 x 10'5 atm-m3/gmol-eK) (298°K)]
K = 0.273
b. Calculate K:
1/K = l/kL + l/(Keqkg)
1/K = (1/0.00329 m/s) + [1/(0.273) (0.110 m/s)]
1/K = 303.95 + 33.30
K = 0.00296
4. Calculate overall mass transfer coefficient for combined quiescent and
turbulent areas, K (weighted by area):
Turbulent area = 4236.5 m3
K = 0.00296
Quiescent area = 13415.5 m3
a. Calculate quiescent liquid mass transfer coefficient, kL:
kL (m/s) = [2.611 x lO'7 (U10)2 [Dw/Dether]2/3
kL (m/s) = [2.611 x ID'7 (4.47 m/s)2 [(8.60 x 10-6cm2/s)/
(8.50 x 10-6cm3/s)]°-667
kL = 5.25 x 10'6 m/s
A-62
-------
TABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL iKEAL.tNl BAMNb
(Continued)
4. (Continued)
b. Calculate quiescent vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x 10-3 (U10)0'78 (Scc)-°-67 (d.)"5'11
kg (m/s) = 4.82 x 10"3 x (4.47 m/s)°'78 (1.734)'0-67 (149.9 m)'0 n
k, (m/s) = 4.82 x 1(T3 x (3.215) (0.6916) (0.5763)
k, = 0.00618 m/s
c. Calculate quiescent overall mass transfer coefficient, K:
1/K = l/kL + l/(Keqkg)
1/K = 1/5.25 x 10"6 m/s + [1/(0.273) (0.00618 m/s)]
1/K = 190480 + 593
K = 5.24 x 10'6
d. Calculate K:
K (m/s) = [K^ + IVWtAp + AT]
K (m/s) = [(5.24 x 10'6 m/s) (13415.5 m3) + 2.96 x 10'3 m/s)
(4236.5 m3)]/(13415.5 m3 + 4236.5 m3)
K = 7.15 x 10'4 m/s
5. Calculate the effluent concentration for toluene for a well-mixed system,
CL:
CL (9/m3) = (-b 4 (b2 - 4ac)°'5]/(2a)
a. Calculate a:
a = K' = (KA/Q) + 1
= [(7.15 x 10-* m/s)(17,652 m2)/(0.0623 m3/s)] + 1
= 203.7
A-63
-------
TABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
5. (Continued)
b. Calculate b:
b = Ks K' + (V/Q) ^ bi - C0
= [(30.6 g/m3)(203.7) + (34,972 m3/0.0623 m3/s)
(2.04 x 10'5 g/gbiomass-s)(4.0 g/1)(1,000 1/m3) - 40 g/m3]
= 6,233 + 45,806 - 40 - 52,000 g/m3
c. Calculate c:
c - -KSC0
= (-30.6 g/m3)(40 g/m3) = -1,224 g2/m6
d. Calculate CL:
CL (g/m3) = [-52,000 g/m3 + [(52,000 g/m3)2 - 4(203.7)
(-1,224 g2/m6)]°-5]/(2(203.7))
= 0.02352 g/m3
e. Calculate the fraction emitted for a well-mixed system, fe:
fe = KAC^QC,
- (7.15 x 10'* m/s)(17,652 m3)(0.02352 g/m3)/[(0.0623 m3/s)(40 g/m3)]
= 0.119
II. Component: Non-Aerated Basin Containing Biomass
A = 1,500 m2 bi = Active biomass = 0.05 g/1
de = 43.7 m Biomass solids = 0.00 m3/s
depth = 1.8 m
V = 2,700 m3
F/D = 24.28
A-64
-------
TABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
Q = 0.00156 m3/s
t = 20.03 days
T = 25°C
Ulo = 4.47 m/s
Compound: Toluene
C0 = 40 ppm = 40 g/m3
MW = 92.0 g/gmol
Dw = 8.60 x 10'6 cm'/s
Mw = 8.70 x 10'2 cm3/s
H = 6.68 x 10"3 atm-m3/gmol
Dether = 8.5 x ID'6 cm'/s
K^ = 73.5 mg/gbiomass-hr = 2.04 x 10"5 g/gbiomass/s
Ks = 30.6 mg/1 = 30.6 g/m3
Water and Air Properties:
pw = 1 g/cm3
uw = 8.93 x 10~3 g/cm-s
pa = 1.20 x 10'3 g/cm3
ua = 1.81 x 10"A g/cm-s
1. Calculate liquid mass transfer coefficient, kL:
kL (m/s) = [2.605 x 10'9 (F/D) + 1.277 x 10'7] (U10)2 [Dw/Dether]° 67
kL (m/s) = [2.605 x 10'9 (24.28) + 1.277 x 10'7] (4.47 m/s)2
[(8.6 x 10-6cm2/s)/(8.5 x 10'6cm2/s)]°-67
kL = 3.84 x 10'6 m/s
A-65
-------
IABLL A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x 10'3 (U10)°-78 (Scc)-° 67 (de)'0'11
a. Calculate ScG:
ScG = uy(p.DJ
Scc - (1.81 x 10'* g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm3/s)]
ScG * 1.734
b. Calculate kg:
kg (m/s) = 4.82 x 10'3 x (4.47 m/s)°'78 (1.734)-0'67 (43.7 m)'° ]
kg (m/s) = 4.82 x 10'3 x (3.215) (0.692) (0.660)
kg = 7.08 x 10'3 m/s
3. Calculate overall mass transfer coefficient, K:
1/K = l/kL + l/(Keqkg)
a. Calculate Keq:
i-0.11
Keq = H/RT
Keq = (6.68 x 10'3 atm-m3/gmol)/[(8.21 x 10'5 atm-m3/gmol-'K) (298°K)]
Keq =0.273
b. Calculate K:
1/K = 1/3.84 x 10'6 m/s + [1/(0.273) (7.08 x 10"3 m/s)]
1/K = 260400 + 517.4
K = 3.83 x 10'6 m/s
4. Calculate the effluent concentration for toluene for a well-mixed system,
CL:
CL (g/m3) = [-b + (b2 - 4ac)°'5]/(2a)
A-66
-------
TABLE A-22. SAMPLE CALCULATIONS FOR BIOLOGICAL TREATMENT BASINS
(Continued)
4. (Continued)
a. Calculate a:
a = K' = (KA/Q) + 1
= [(3.83 x 10'6 m/s)(l,500 m3)/(0.00156 m3/s)] + 1
- 4.683
b. Calculate b:
b = K, K' + (V/Q) !<_ bi - C0
= [(30.6 g/m3)(4.683) + (2,700 m3/0.00156 m3/s)
(2.04 x 10'5 g/gbiomass-s)(0.05 g/1)(1,000 1/m3) - 40 g/m3]
= 143.30 + 1,765.4 - 40 = 1,869 g/m3
c. Calculate c:
c - -KSC0
= (-30.6 g/m3)(40 g/m3) = -1,224 g2/m6
d. Calculate CL:
CL (g/m3) = [-1,869 g/m3 + [(1,869 g/m3)2 - 4(4.683)
(-1,224 g2/m6)]°'5]/2(4.683)
= 0.6538 g/m3
e. Calculate the fraction emitted for a well-mixed system, fe:
fe = KAC^QC,,
= (3.83 x 10'6 m/s)(1,500 m2)(0.6538 g/m3)/[(0.00156 m3/s)(40 g/m3)]
- 0.0602
A-67
-------
TABLE A-23. ESTIMATION TECHNIQUE FOR TREATMENT TANKS
I. Equations used for calculating liquid and vapor mass transfer
coefficients:
Liquid Phase. kL:
Mackay and Yeun
(for F/D <14 and U10 >3.25 m/s):
kL = 1.0 x 1(T6 + 144 x 10"* x (U*)2'2 x (ScL)'°-5,
where
U* <0.3
where
U* (m/s) = 0.01 x U10 x (6.1 + 0.63 x U10)°'5
and
ScL = ur/(pLDJ
Vapor Phase, 1^:
Mackay and Matasugu:
k,, (m/s) = 4.82 x lO'3 x (U10)0'78 x (ScJ"0'67 x (dj'0'11
II. Equation for calculating the overall mass transfer coefficient, K:
1/K = l/kL + l/(KeqkG)
where
Keq = Equilibrium constant = H/RT
III. Equation for calculating the bulk concentration of the organic
compound:
CL (g/m3) = QCy(KA + Q)
IV. Equation for calculating air emissions, Na:
Na (Mg/yr) = K CL A
A-68
-------
Emission estimates based on typical design dimensions for the tanks are
shown in Table A-24. Table A-24 presents the fraction emitted for five
example organic compounds. The emission rates are based on a wastewater flow
rate of 1,000 gpm through the tanks. Each of the five organic compounds are
assumed to be present at a concentration of 10 ppm. The wastewater is assumed
to be at ambient temperature for the purposes of the calculation. An example
calculation for the tanks is shown in Table A-25.
A.1.3 Oil-Water Separators
A theoretical model for predicting VOC emissions from separators has been
developed by the Shell Oil Company.26 The general procedure employed by this
model to estimate emissions is presented in Table A-26. The model takes into
account wind flowing over the oil/water surface with a logarithmic wind
profile. A mass transfer coefficient can be calculated using regressed curves
that Shell developed. This mass transfer coefficient is used to calculate the
volatilization of each compound from the oil surface into the atmosphere.
The model assumes that the volatilization of each component is not affected by
the compound matrix in the oil layer. The model also assumes that mass
transfer through the liquid is much faster than mass transfer into the gas
phase (above the liquid surface). That is, the gas phase resistance is
controlling.
A typical oil-water separator is shown in Figure A-9.27 Emission
estimates for the oil-water separator are based on the typical design
dimensions shown in the figure. Table A-27 presents the fraction emitted for
five example organic compounds. The emission rates are based on a wastewater
flow rate of 4,000 gpm through the oil-water separator. Each of the five
organic compounds are assumed to be present at a concentration of 500 ppm.
The wastewater is assumed to be at 30°C for the purposes of the calculation.
An example calculation for oil-water separators is shown in Table A-28.
A.1.4 Weirs
Mass transfer correlations developed from volatilization-reaeration
theory were used to estimate emissions from weirs.25 The general procedure
A-69
-------
TABLE A-24. EMISSION ESTIMATES FOR TREATMENT TANKS
Compound
Henry's Law Constant
H, atm - mYgmol
(25'C)
Fraction
Emitted, Fe
1,3 Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
l.OE-02
9.2E-03
8.6E-03
2.9E-03
2.1E-04
A-70
-------
TABLE A-25. SAMPLE CALCULATIONS FOR TREATMENT TANKS
Component: Treatment Tank. (Non-Aerated)
A = 92.9 m2
de = 10.9 m
depth = 4.8768 m
F/D = 2.23
Q = 0.063 m3/s
t = 2 hr
T = 25eC
U10 = 4.47 m/s
Compound: Toluene
CL = 10 ppm = 1 x 1(T5 g/cm3
MW = 92.0 g/gmol
Dw = 8.60 x 10"6 cm2/s
Da = 8.70 x ID'2 cm2/s
H = 6.68 x 10"3 atm-mVgmol
D.ther = 8.5 x ID'6 cm2/s
Water and Air Properties:
pw = 1 g/cm3
uw = 8.93 x 10~3 g/cm-s
pa = 1.20 x 10~3 g/cm3
ua = 1.81 x 10'4 g/cm-s
A-71
-------
TABLE A-25. SAMPLE CALCULATIONS FOR TREATMENT TANKS
(Continued)
1. Calculate liquid mass transfer coefficient, kL:
a. Calculate U*:
U* (m/s) = 0.01 x U10 (6.1 + 0.63 x U10)°'5
U* (m/s) - 0.01 x 4.47 m/s (6.1 + 0.63 x 4.47 m/s)0-5
U* = 0.1335 m/s
b. Calculate ScL:
ScL = uw/(pwDJ
ScL = 8.93 x 10'3 g/cm-s/[(l g/cm3) (8.60 x 10'6 cm2/s)]
ScL = 1,038
c. Calculate kL:
kL (m/s) = 1.0 x 10'6 + 144 x 10'4 (U*)2-2 (ScJ'0'5
kL (m/s) = 1.0 x 10'6 + 144 x 10'4 (0.1335)2'2 x (1038)'0'5
kL = 6.32 x 10'6 m/s
2. Calculate vapor mass transfer coefficient, kg:
kg (m/s) = 4.82 x 10'3 x (U10)0'78 (ScJ'0'67 (de)'0'11
a. Calculate ScG:
ScG = uy(p.D.)
ScG = (1.81 x ID'4 g/cm-s)/[(1.20 x 10'3 g/cm3) (8.70 x 10'2 cm2/s)]
ScG = 1.734
b. Calculate kg:
kg (m/s) = 4.82 x 10'3 x (4.47 m/s)0'78 (1.734)-°-67 (10.9 m)'0'11
kg (m/s) = 4.82 x 10'3 x (3.215) (0.692) (0.769)
kg = 0.00824 m/s
A-72
-------
TABLE A-25. SAMPLE CALCULATIONS FOR TREATMENT TANKS
(Continued)
3. Calculate overall mass transfer coefficient, K:
1/K = l/kL + l/(Keqkg)
a. Calculate Keq:
K.q - H/RT
K.q = 6.68 x 10'3 atm-m3/gmol/[(8.21 x 10'5 atm-m3/gmol'K) (298°K)]
Keq =0.273
b. Calculate K:
1/K = l/kL + l/(Keqkg)
1/K = (1/6.32 x 10'6 m/s) + [1/(0.273) (0.00824 m/s)]
1/K = 158230 + 445
K = 6.30 x 10'6 m/s
4. Calculate concentration of toluene at vapor-liquid interface, CL:
CL = Q Cy(KA + Q)
CL = (0.063 m3/s) (1 x 10'5 g/cm3) (106 cm3/m3)/
[(6.30 x 10'6 m/s) (92.9 m2) + (0.063 m3/s)]
CL = 9.91 g/m3
5. Calculate air emissions, Na:
(NJT (Mg/yr) = K CL A
(NJT (Mg/yr) = (6.30 x 10'6 m/s) (3600 s/hr) (7200 hr/yr)
(9.91 g/m3) (92.9 m2) (10'6 Mg/g)
(NJT = 0.150 Mg/yr
6. Calculate fraction of toluene emitted from a treatment tank, fe:
(fe)T = (NJ^QC,
(fe)T = (0.150 Mg/yr)/[(0.063 m3/s) (3600 s/hr) (7200 hr/yr)
(1 x 10'5 g/cm3) (106cm3/m3) (10'6 Mg/g)]
(fe)T = 0.00921
A-73
-------
TABLE A-26. ESTIMATION TECHNIQUE FOR OIL-WATER SEPARATORS
I. Calculate concentration of the organic compound in bulk liquid, CL
CL(gmol/m3) = QCytMW, x Q),
II. Calculate partial pressure at oil -air interface, p*
p* = H x CL
III. Calculate Schmidt number on vapor side Scc:
ScG = u./(paD.)
IV. Calculate non-dimensional downwind distance, Sqig:
Sqig = (0.064 x Ulo x L) (DJ,
V. Calculate curves defined in shell model, k^ and k^
a. k^ = 0.328 Sqig'0-227 + 0.298 Sqig'0'127, for ScG = 1
b. k^ = 0.431 Sqig'0-129 for ScG = 5
VI. Interpolate between the two curves using calculated Schmidt number,
kyalpha:
k^alpha = k^, - [(5 - Sc6)/(5 - 1) x
VII. Calculate local mass transfer coefficient, k,,,:
!(» = (k^alpha) x alpha
VIII. Calculate concentration of the organic compound at vapor-liquid
interface, CL:
CL (gmol/m3) = p*/RT
IX. Calculate emission of the organic compound from oil -water separator,
(NJi
(NaK - k. x CL x L x W, mol/s
X. Calculate fraction emitted of the organic compound from oil -water
separator, fe
- (NJ./QC,
A-74
-------
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Platform
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balloon ttoppara, for diverting
flowt and for elaaning taparator
faction. Slulea gataa or gata valvaa
may ba inataiiad if daalrad
Sklmmad Oil Pump
CovarPorabay
if Daalrad
oil Wufmwars
nan
Chain aprock*
Wood Plight tcrappac
Oil Aatantton •affla Wffuaton Oavto*
'/•meat tafflat
^^"V^^^^f «^^^^^^^^WW
Oil Ratantlon Baffta
Design Parameter
Separator length (m)
Separator width (m)
Retention time (hr)
Range
6.1 - 18.0
4.6 - 10.7
0.6 - 1.0
Typical Design
13.7
7.6
0.8
Figure A-9. Typical oil/water separator configuration.
A-75
-------
TABLE A-27. EMISSION ESTIMATES FOR OIL/WATER SEPARATORS
Compound
Henry's Law Constant
H, atm - mVgmol
(25*C)
Henry's Law Constant
H, atm -
(30'C)
Fraction
Emitted, Fe
(T=30°C)
1,3-Butadlene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
1.65E-01
8.61E-03
1.73E-03
1.29E-05
6.90E-07
l.OE+00
4.7E-01
9.0E-02
6.9E-04
3.7E-05
A-76
-------
TABLE A-28. SAMPLE CALCULATIONS FOR OIL/WATER SEPARATORS
Component: Oil-Water Separator
L = 1,371 cm
w = 762 cm
depth = 244 cm
Q = 4000 gal/min
F, = QC, = 126.18 g/s
T = 30eC
P - 1 atm
R = 82.05 atm-cmVgmol
k, = 0.0056 cm2/s
alpha = 4.3147 cm2/s
U10 = 447 cm/s
Compound: Toluene
CL = 500 ppm = 5 x ID'4 g/cm3 pa = 1.20 x 10'3 g/cm3
MW = 92.0 g/gmol ua = 1.81 x 10'* g/cm/s
Du = 9.74 x 10'6 cm2/s
Da = 8.70 x 1C'2 cm2/s
H = 8.61 x 10"3 atm-mVgmol
1. Calculate concentration of toluene in bulk liquid, CL:
CL (gmol/m3) = F, (264.17 gal/m3) (60 s/min)/(MW x Q)
CL (gmol/m3) = 126.18 g/s (264.17 gal/m3) (60 s/min)/
(92.0 g/gmol) (4,000 gal/min)
CL = 5.435 gmol/m3
A-77
-------
TABLE A-28. SAMPLE CALCULATIONS FOR OIL/WATER SEPARATORS
(Continued)
2. Calculate partial pressure at interface, p*:
P* - H x CL
p* = (8.61 x 1(T3 atm-m3/gmol)(5.435 gmol/m3)
p* = 0.0468 atm
3. Calculate Schmidt number on vapor side ScG:
Scc - uy(p.DJ
ScG = (1.81 x 10'* g/cm/s) / [(1.20 x 10'3 g/cm3 x 0.087 cm2/s)]
ScG = 1.734
4. Calculate non-dimensional downward distance, Sqig:
Sqig = 0.064 x U10 x L/Da
Sqig = 0.064 (447 cm/s) (1371 cm)/(0.087 cm2/s)
Sqig = 450,823
5. Calculate curves defined in shell model, k(Dal and k,^:
a. k^ = 0.328 Sqig-0-227 + 0.298 Sqig'0'127, for ScG < 1
k^ = 0.328 (450,823)-°'227 + 0.298 (450,823)-°-127
k^ = 0.017 + 0.057
K-l = 0.074
b. k^ = 0.431 Sqig-0-129 for ScG = 5
Kn.5 - 0.0804
6. Interpolate between the two curves using calculated Schmidt number,
kyalpha:
kn/alpha = k^ - [(5 - ScG)/(5 - 1) x
kyalpha = 0.0804 - [(5 - 1.734) (0.0804 - 0.074)/4]
k^/alpha = 0.0804 - (0.8165 x 0.0064)
kyalpha = 0.0753
A-78
-------
TABLE A-28. SAMPLE CALCULATIONS FOR OIL/WATER SEPARATORS
(Continued)
7. Calculate local mass transfer coefficient, k,,,:
k,,, = (k^/alpha) alpha
k,. = 0.0753 x 4.3147 cm/s
k,,, = 0.3247 cm/s
8. Calculate concentration of toluene at vapor-liquid interface, CL:
CL (gmol/m3) = P*/RT
CL (gmol/m3) = 0.0468 atm/[(82.05 atm-cm3/gmoleK) (303eK)]
CL (gmol/m3) = 1.88 x 10'6 gmol/cm3 x 106 cm3/m3
CL = 1.88 gmol/m3
9. Calculate emission of toluene from an oil-water separator, (NJT:
(NJT = Kn x CL x L x W, mol/s
(N.)T = (0.3247 cm/s) (1.88 gmol/m3) (1371 cm)
(762 cm) (m3/106cm3)
(N.)T = 0.638 gmol/s
(N.)T = 0.638 gmol/s (3600 s/hr) (7200 hr/yr)
(92.0 g/gmol) (10'6 Mg/g)
(N.)T = 1522 Mg/yr
10. Calculate fraction emitted of toluene from an oil-water separator, fe:
(fe), - (NJ./F,
(fe)T = (0.638 gmol/s) (92.0 g/gmol)/(126.18 g/s)
(fe)T = 0.465
A-79
-------
used to estimate emissions based on this theory is presented in Table A-29.
According to this theory, the mass transfer rate of each organic compound
present in the falling wastewater is controlled by the liquid phase
resistance. The gas phase resistance is assumed to be negligible due to the
degree of convective mass transfer in this phase. Reaeration rates and
physical properties of oxygen are used to estimate the liquid phase resistance
to mass transfer. The diffusivity in water of each organic compound are
compared to the diffusivity in water of oxygen. The rate of emissions of each
organic compounds are then based on this ratio as well as the height of the
weir.
A typical weir configuration is shown in Figure A-10. Emission estimates
for the weir are based on the typical design dimensions shown in the figure.
Table A-30 presents the fraction emitted for five example organic compounds.
Each of the five organic compounds are assumed to be present at a
concentration of 10 ppm. The wastewater is assumed to be at ambient
temperature for the purposes of the calculation. An example calculation for
weirs is shown in Table A-31.
A.2 FRACTION EMITTED DURING COLLECTION AND TREATMENT (Fe)
Three example waste stream systems were developed to evaluate potential
VOC emissions from different collection and treatment scenarios. Schematics
of these example collection and treatment systems are shown in Figures A-ll,
A-12, and A-13. The individual components discussed in Section A.I were used
to develop the three example schematics. The emission factors (fe) presented
for each collection and treatment system component are used in a generalized
procedure to estimate VOC emissions from each wastewater stream. The
procedure, in estimating the fraction emitted from a component in the system,
accounts for the cumulative fraction emitted prior to that component. For
example, if the overall emission factor from a component is 0.2 and the
cumulative fraction emitted prior to that component is 0.4, then the actual
fraction emitted is 0.12 [0.2(1 - 0.4)]; the emission factor, 0.2, is applied
only to the fraction of the original organic compounds reaching the component.
The fraction of the original organic compounds passing on in the water to the
next component is 0.48 (1 -0.4 - 0.12). The emission factors, or fractions
emitted, for the individual collection and treatment system components
discussed in Section A.I are summarized in Table A-32.
A-80
-------
TABLE A-29. ESTIMATION TECHNIQUE FOR WEIRS
Volatilization - Reaeration Theory
C0 = Ct exp (-KD(i))
where
MD - Mo2)[(DtfK/D02(W;i0-75
I. Calculate KD (02)
KD(02) = 0.16h
II. Calculate KD(i)
KD(i) = KD(02) [(DjyDo^J0'75
III. Calculate fraction emitted, fe
, = exp (-KD(i))
A-81
-------
T
h
1
Design Parameter
Weir height, h (m)
Range
0.9 - 2.7
Typical Design
1.8
Figure A-10. Typical weir configuration.
A-82
-------
TABLE A-30. EMISSION ESTIMATES FOR WEIRS
Compound
Henry's Law Constant
H, atm - m3/gnu>l
(25'C)
Fraction
Emitted, Fe
1,3 Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
1.42E-01
6.68E-03
1.18E-03
8.90E-06
4.54E-07
2.9E-01
2.5E-01
2.3E-01
2.6E-01
2.6E-01
A-83
-------
TABLE A-31. SAMPLE CALCULATION FOR WEIRS
Volatilization - Reaeration Theory
C0 = C, exp (-KD(i))
where
Mi) = MOiHdUiAa.vl0-75
and
M02) = 0.16h
where
C0 = effluent concentration of toluene
Ci = influent concentration of toluene
h = 4 ft
T = 25°C
(Dw)t = 8.60 x 10'6 cm2/s
D02iW = 2.50 x 10'5 cm2/s
First, calcualte KD(02)
KD(02) = 0.16H
KD(02) = 0.16 (4) = 0.64
Then, calculate KD(i)
Mi) = MOamDjyD^J0-75
KD(i) = 0.64 [(8.60 x 10"6)/(2.50 x 10'5)]0-75
KD(i) = 0.287
Now, calculate fraction emitted
C0 = Ct exp (-KD(i))
rearrange
= exp (-KD(i))
A-84
-------
TABLE A-31. SAMPLE CALCULATION FOR WEIRS
so,
C./C, = exp (-0.287)
eye, = 0.750
and, the fraction emitted is:
(f.) « 1 - (Co/CJ = 1 - 0.750 = 0.250
A-85
-------
Process
Equipment
Drain
Y
!
Dr
\
!
aln
/
Lift
Station
^
3>
I
CO
*• Discharge
Sludge
Digester
Underflow
Waste Sludge
Figure A-11. Example Waste Stream Schematic I.
-------
Procaaa
Equipment
Drain
V
Drain
Oll-Watar
Separator
Equalization
Baaln
00
Dlacharge
rlflor r*
Underflow
Aeration
Baaln
!
ph Adjuatmant
Tank
Sludga
Dlgaatar
Waata Sludga
Figure A-12. Example Waste Stream Schematic II.
-------
Drain
Op«n
Trench
top
Sump
Junction
Box
Lift
Station
H
Aerated
Equalization
Basin
GO
00
Dlacharg*
ph Adjustment
Tank
WaaU Sludg*
Figure A-13. Example Waste Stream Schematic
III.
-------
TABLE A-32. SUMMARY OF EMISSION FACTORS FOR COLLECTION AND TREATMENT SYSTEM COMPONENTS
00
10
Emission Factor (Fe)
Component
Drain
Manhole
Junction Box
Lift Station
Sump
Open Trench
Equalization Basin
(Non-Aerated)
(Aerated)
Clarifier
Biobasin
(Aerated)
(Non-Aerated)
Treatment Tank
Oil -Water Separator
Weir
1,3-Butadiene
5.7E-01
1.5E-01
1.2E-01
3.6E-01
5.6E-03
5.9E-02
4.3E-01
l.OE+00
2.8E-02
2.9E-01
2.2E-01
l.OE-02
l.OE+00
2.9E-01
Toluene
6.1E-02
8.2E-03
9.8E-02
2.9E-01
5.0E-03
4.5E-02
4.0E-01
9.9E-01
2.5E-02
1.2E-01
6.0E-02
9.2E-03
4.7E-01
2.5E-01
Naphthalene
1.1E-02
1.5E-03
6.8E-02
1.8E-01
4.7E-03
2.5E-02
3.8E-01
9.9E-01
2.4E-02
1.7E-01
1.2E-01
8.6E-03
9.0E-02
2.3E-01
1-Butanol
8.7E-05
1.1E-05
1.9E-03
3.6E-03
2.1E-03
4.1E-04
1.8E-01
6.1E-01
7.8E-03
4.1E-02
3.0E-01
2.9E-03
6.9E-04
2.6E-01
Phenol
4.4E-06
5.7E-07
1.1E-04
2.0E-04
1.9E-04
2.1E-05
1.6E-02
7.7E-02
5.6E-04
1.9E-05
3.9E-04
2.1E-04
3.7E-05
2.6E-01
Overall VOC
1.3E-01
3.2E-02
5.7E-02
1.7E-01
3.5E-03
2.6E-02
2.8E-01
7.3E-01
1.7E-02
1.2E-01
1.4E-01
6.2E-03
3.1E-01
2.6E-01
-------
The fractions of the five example organic compounds emitted from each
example waste stream system are listed in Table A-33, A-34, and A-35. As seen
in the tables, the overall fraction emitted for each organic compound is the
highest for Example Waste Stream Schematic III. For example, for toluene, the
overall fraction emitted was 0.47, 0.74, and 1.0 from Example Waste Stream
Schematics I, II, and III, respectively. For phenol, the compound with the
lowest Henry's Law constant, the cumulative fraction emitted remained
relatively low; 7.9 x 10"*, 1.7 x 10'2, and 3.2 x 10"1 for Example Waste Stream
Schematics I, II, and III, respectively.
A.3 EMISSIONS REDUCTION
Emission reduction measures the efficiency of removal for a control
technique. Removal efficiencies for the model steam stripper are presented in
Chapter 4, while the fraction emitted for each example waste stream is
summarized in Section A.2. For steam stripping of wastewaters containing
organic compounds, the emission reduction is dependent on the mass of organics
in the wastewater, the removal efficiency of the control technique, and the
fraction of organic compounds that would be emitted from the wastewater.
Tables A-36 through A-38 summarize the emission reduction as well as the
uncontrolled and controlled emissions for Example Waste Stream Schematics I,
II, and III, respectively. The following sample calculations for Example
Waste Stream Schematic I at 300 1pm illustrate the method used to estimate
emission reductions.
Initial Organic Compound Loading in Wastewater:
300 1/min * 500 mg/1 * 1 g/103mg * 1 Mg/106g * 60 min/hr * 24 hr/day
* 365 days/yr = 79 Mg/yr per compound
Uncontrolled Emissions!
ex. Toluene - Fe x Initial Loading
0.47 * 79 = 37 Mg/yr
A-90 )
-------
TABLE A-33. CUMULATIVE FRACTION EMITTED DURING COLLECTION AND TREATMENT
EXAMPLE WASTE STREAM SCHEMATIC I
VO
Cumulative Fraction Emitted
Component
Drain
Drain
Lift Station
Clarifier
Aeration Basin
Clarifier
1,3-Butadiene
5.7E-01
8.2E-01
8.8E-01
8.9E-01
9.2E-01
9.2E-01
Toluene
6.1E-02
1.2E-01
3.8E-01
3.9E-01
4.7E-01
4.7E-01
Naphthalene
1.1E-02
2.3E-02
2.0E-01
2.1E-01
3.4E-01
3.4E-01
1-Butanol
8.7E-05
1.7E-04
3.8E-03
1.2E-02
5.2E-02
5.2E-02
Phenol
4.4E-06
8.9E-06
2.1E-04
7.7E-04
7.9E-04
7.9E-04
Overall
0.13
0.19
0.29
0.30
0.36
0.36
-------
TABLE A-34. CUMULATIVE FRACTION EMITTED DURING COLLECTION AND TREATMENT
FOR EXAMPLE WASTE STREAM SCHEMATIC II
vo
rv>
Cumulative Fraction Emitted
Component
Drain
Drain
Junction Box
Manhole
Oil -Water
Separator
Non-aerated
Equalization
Basin
pH Adjustment
Tank
Aeration Basin
Clarifier
1,3-Butadiene
5.7E-01
8.2E-01
8.4E-01
8.6E-01
l.OE+00
l.OE+00
l.OE+00
l.OE+00
l.OE+00
Toluene
6.1E-02
1.2E-01
2.1E-01
2.1E-01
5.8E-01
7.2E-01
7.2E-01
7.4E-01
7.4E-01
Naphthalene
1.1E-02
2.3E-02
8.9E-02
9.1E-02
1.7E-01
2.7E-01
2.7E-01
3.0E-01
3.0E-01
1-Butanol
8.7E-05
1.7E-04
2.1E-03
2.1E-03
2.8E-03
1.8E-01
1.9E-01
2.2E-01
2.2E-01
Phenol
4.4E-06
8.9E-06
1.2E-04
1.2E-04
1.6E-04
1.6E-02
1.7E-02
1.7E-02
1.7E-02
Overall
0.13
0.19
0.27
0.23
0.35
0.44
0.44
0.45
0.45
-------
TABLE A-35. CUMULATIVE FRACTION EMITTED DURING COLLECTION AND TREATMENT
FOR EXAMPLE WASTE STREAM SCHEMATIC III
10
u>
Cumulative Fraction Emitted
Component
Drain
Open Trench
Sump
Junction Box
Lift Station
Manhole
Manhole
Aerated
Equalization
Basin
pH Adjustment
Tank
Weir
Aeration Basin
Flocculation
1,3-Butadiene
5.7E-01
6.0E-01
6.0E-01
6.5E-01
7.7E-01
8.1E-01
8.4E-01
l.OE+00
l.OE+00
l.OE+00
l.OE+00
l.OE+00
Toluene
6.1E-02
l.OE-01
1.1E-01
2.0E-01
4.3E-01
4.4E-01
4.4E-01
l.OE+00
l.OE+00
l.OE+00
l.OE+00
l.OE+00
Naphthalene
1.1E-02
3.6E-02
4.1E-02
1.1E-01
2.6E-01
2.7E-01
2.7E-01
9.9E-01
9.9E-01
9.9E-01
9.9E-01
9.9E-01
1-Butanol
8.7E-05
5.0E-04
2.6E-03
4.5E-03
8.1E-03
8.1E-03
8.1E-03
6.1E-01
6.1E-01
7.1E-01
7.2E-01
7.2E-01
Phenol
4.4E-06
2.6E-05
2.2E-04
3.3E-04
5.3E-04
5.3E-04
5.3E-04
7.7E-02
7.8E-02
3.2E-01
3.2E-01
3.2E-01
Overall
0.13
0.15
0.15
0.19
0.30
0.30
0.31
0.73
0.74
0.80
0.81
0.81
Tank
Clarifier
l.OE+00
l.OE+00
9.9E-01
7.2E-01
3.2E-01
0.81
-------
TABLE A-36 EMISSION REDUCTION FOR EXAMPLE WASTE STREAM SCHEMATIC I
Compound
Toluene
Naphthalene
1,3-Butadiene
Phenol
3* Butanol
<£>
Total VOC
Fraction
Removed
by Stripper
1.0
1.0
1.0
0.022
0.30
Uncontrolled
Loading
( Mg/yr )*
79
79
79
79
79
400
Controlled
Loading
(Mg/yr)
0.000
0.000
0.000
77
52
130
Fraction
Emittedb
0.47
0.34
0.92
0.001
0.052
Uncontrolled
Emissions
(Mg/yr)
37
27
72
0.06
4.1
140
Controlled
Emissions
(Mg/yr)
0.000
0.000
0.000
0.061
2.7
2.8
Percent
Emission
Reduction
(%)
100%
100%
100%
2.4%
0%
98%
"Calculated at 300 1pm, 500 ppm per compound, 365 days/yr.
"Table A-33.
-------
TABLE A-37. EMISSION REDUCTION FOR EXAMPLE WASTE STREAM SCHEMATIC II
VO
tn
Compound
Toluene
Naphthalene
1,3-Butadiene
Phenol
Butanol
Total VOC
Fraction
Removed
by Stripper
1.0
1.0
1.0
0.022
0.30
Uncontrolled
Loading
(Mg/yr)a
79
79
79
79
79
400
Controlled
Loading
(Mg/yr)
0.00
0.00
0.00
76
52
130
Fraction
Emittedb
0.74
0.30
1.0
0.017
0.22
Uncontrolled
Emissions
(Mg/yr)
59
23
79
1.3
17
180
Controlled
Emissions
(Mg/yr)
0.00
0.00
0.00
1.3
11
13
Percent
Emission
Reduction
(*)
100%
100%
100%
2.2%
30%
93%
"Calculated at 300 1pm, 500 ppm per compound, 365 days/yr.
bTable A-34.
-------
TABLE A-38. EMISSION REDUCTION FOR EXAMPLE WASTE STREAM SCHEMATIC III
VO
en
Fraction
Removed
Compound by Stripper
Toluene 1.0
Naphthalene 1.0
1,3-Butadiene 1.0
Phenol 0.022
Butanol 0.30
Total VOC
Uncontrolled Controlled
Loading Loading Fraction
(Mg/yr)a (Mg/yr) Emitted"
79
79
79
79
79
400
0.00 1.0
0.00 0.99
0.00 1.0
77 0.32
52 0.72
130
Uncontrolled
Emissions
(Mg/yr)
79
79
79
25
57
320
Controlled
Emissions
(Mg/yr)
0.00
0.00
0.00
24
38
60
Percent
Emission
Reduction
(%)
100%
100%
100%
2.2%
30%
80%
"Calculated at 300 1pm, 500 ppm per compound, 365 days/yr.
"Table A-35.
-------
Controlled Emissions:
ex. Toluene -
Uncontrolled Loading * (1 - fraction removed (fr) by stripper) * fe
79 * (1 - 1) * 0.47 = 0
Total % of Emission Reduction (ER) for VOC
Uncontrolled Emissions - Controlled Emissions
Uncontrolled Emissions
140 - 2.8 / 140 * 100 = 98%
A-97
-------
A.3 REFERENCES
1. Trip Report. D. J. Herndon, Radian Corporation, to file. 11 p. Report
of May 4, 1987, visit to Borden Chemical Company.
2. Trip Report. D. J. Herndon, Radian Corporation, to file. 4 p. Report
May 5, 1987, visit to Union Carbide Corporation.
3. Trip Report. D. J. Herndon, Radian Corporation, to file. 13 p. Report
May 8, 1987, visit to Dow Chemical Company.
4. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 10 p. Report of May 22, 1987, visit to Rhone-Poulenc
Agricultural (RP-Ag) Company.
5. Trip Report. D. J. Herndon, Radian Corporation, to file. 5 p. Report
of May 6, 1987, visit to PPG Industries.
6. Trip Report. R. H. Howie and M. A. Vancil, Radian Corporation, to file.
7 p. Report of May 12, 1987, visit to Allied Fibers.
7. Trip Report. D. J. Herndon, Radian Corporation, to file. 7 p. Report
of May 7, 1987, visit to Rohm & Haas Texas, Inc.
8. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 7 p. Report of May 21, 1987, visit to Mobay Chemical Company.
9. Trip Report. D. J. Herndon, Radian Corporation, to file. 6 p. Report
of May 29, 1987, visit to General Electric.
10. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 7 p. Report of September 3, 1987, visit to E. I. duPont
de Nemours Company (Deepwater, New Jersey).
11. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 6 p. Report of September 2, 1987, visit to Fritzsche Dodge &
Olcott.
12. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 6 p. Report of September 1, 1987, visit to Vista Chemical
Company.
13. Trip Report. D. J. Herndon and S. K. Buchanan, Radian Corporation, to
file. 5 p. Report of September 3, 1987, visit to CIBA-GEIGY
Corporation.
14. Trip Report. D. J. Herndon, Radian Corporation, to file. 4 p. Report
of March 1, 1988, visit to Morflex Chemical Company, Incorporated.
15. Trip Report. D. J. Herndon, Radian Corporation, to file 4 p. Report
of March 8, 1988, visit to Burroughs Wellcome.
16. Trip Report. D. J. Herndon, Radian Corporation, to file 5 p. Report
of September 9, 1987, visit to Monsanto Company.
A-98
-------
17. Trip Report. D. J. Herndon, Radian Corporation, to file. 5 p. Report
of March 31, 1988, visit to Shell Deer Park Manufacturing Complex.
18. Trip report. D. J. Herndon, Radian Corporation, to file. 4 p. Report
of February 19, 1988, visit to Ethyl Corporation.
19. Trip Report. D. J. Herndon, Radian Corporation, to file. 5 p. Report
of March 30, 1988, visit to Hoechst-Celanese.
20. Trip report. D. J. Herndon, Radian Corporation, to file. 4 p. Report
of March 31, 1988, visit to E. I. duPont deNemours and Company (LaPorte,
Texas).
21. Trip Report. J. A. Elliott, Radian Corporation, to file. 4 p. Report
of September 18, 1989, visit to Glaxo, Incorporated.
22. Office of Air Quality, Planning and Standards. U. S. Environmental
Protection Agency. Hazardous Waste Treatment, Storage, and Disposal
Facilities (TSDF) - Air Emission Models, Draft Report. April 1989.
23. Metcalf and Eddy, Inc. Wastewater Engineering. New York, McGraw-Hill.
1972. p. 519.
24. Process Design Manual for Suspended Solids Removal, U. S. Environmental
Protection Agency, Technology Transfer, January 1975. EPA-625/1-75-
003a.
25. Metcalf and Eddy, Inc. Wastewater Engineering. New York, McGraw-Hill.
1972. p. 525.
26. Liang, S. F. Hydrocarbon Losses by Atmospheric Evaporation from Open
Separators, Technical Progress Report, BRC-Corp-24-73-F. (Shell Models)
27. Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency. Research Triangle Park, NC. VOC (Volatile Organic
Compound) Emissions from Petroleum Refinery Wastewater System -
Background Information for Proposed Standards, Draft EIS.
EPA-450/3-85-001a (NTIS PB87-190335), February 1985.
A-99
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APPENDIX B
ESTIMATION OF AIR EMISSION FACTORS
FROM AIRFLOW IN WASTEWATER COLLECTION SYSTEMS
-------
APPENDIX B
ESTIMATION OF AIR EMISSION FACTORS
FROM AIRFLOW IN WASTEWATER COLLECTION SYSTEMS
B.I INTRODUCTION
The purpose of the theoretical analysis of wastewater collection
systems is to obtain air emission factors that can be used to estimate the
release of volatiles into the atmosphere. As a volatile waste constituent
is discharged into a collection system, it can be emitted into the atmos-
phere through air flowing through the collection system. Air can enter and
leave a collection system by openings in drains, open channels, channels
with grates, openings in manhole covers, junction boxes, sumps, and other
openings. Estimation of the flow of air in a collection system unit
(drain, manhole) relative to the flow of wastewater flowing under the
collection system unit permits an estimation of the fraction of the
volatile constituent lost to the atmosphere as it passes under the unit.
The assumptions that were made to characterize chemical sewer designs
include the following:
• The design depth in the drain channel is assumed to be half
full.
• The flow in the channel for estimating fractional emissions
is assumed to be 80 percent of design depth. (Lower depths
result in higher emissions.)
The air exiting the system is assumed to be at equilibrium
with the volatiles in the channels.
• A typical wind is assumed to be 3.5 mph.
The emission factors for the collection units are sensitive to the
magnitude of the flow rates in the channels. The loss of volatiles in the
channels could be less than the equilibrium amount if the rate of mass
B-3
-------
transfer from the bulk of the wastewater to the air were to limit the rate
of air emissions. This mass transfer rate is expected to be sensitive to
the depth in the channel, with equilibrium not achieved for high flows of
air across deep channels. For the case of channel depths at a fraction of
the design depths and relatively low air rates (manhole covers and enclosed
collection systems), the assumption of equilibrium is expected to be
appropriate.
Since the air emission factors are sensitive to environmental factors
such as temperature, humidity, and wind pressure, the measured air emis-
sions from wastewater collection systems are expected to be variable.
B.2 DISCUSSION OF THE USE OF COLLECTION SYSTEM EMISSION FACTORS
The emission factors developed in this report are expressed in terms
of fraction of material in the sewer main emitted per unit. When the path
of the waste placed in the collection system is specified, the amount of
material remaining in the original waste stream is recalculated each time
the waste flows under a potential emission source (drain connection,
manhole, lift station, sump, etc.):
Emissions from unit = amount present x unit emission factor
New amount present - amount present - emissions from unit.
The following example illustrates how the toluene emissions from a
waste discharge into a collection system can be estimated. The waste flows
into an open trench drain. Forty feet downstream, additional waste flows
into the trench for an additional 20 ft. The flow in the trench discharges
into a drain. The subsurface channel in the sewer has an additional drain
connection and a manhole before discharge into a covered sump with a vent.
Amount
Emission present, Emissions,
Unit factor g g
Open trench drain (40 ft) 0.045 100 4.5
Open trench drain (20 ft) 0.022 95.5 2.1
Drain 0.08 93.4 7.5
Drain connection 0.08 85.9 6.7
Manhole at junction 0.0083 79.2 0.66
Covered sump with vent ' 0.11 78.5 8.6
Overall collection units 0.30 70 30
B-4
-------
This application of the unit emission factors to a wastewater collec-
tion system for toluene wastes indicates that a substantial fraction of the
original toluene in the waste can be lost due to airflows in the collection
system. Another way of interpreting these data is that for every 70 g of
toluene that enter the wastewater treatment plant, 30 g are emitted in the
collection system before reaching the wastewater treatment plant (43
percent).
These emission factors for wastewater collection systems are not
expected to be applicable for all systems. They are for a wastewater
collection system designed to aerate the wastewater, either for safety, for
corrosion reduction, or for odor control. There are a number of equipment
changes that can reduce the air emissions to levels much lower than can the
system presented here. Emissions can be reduced by using covers for sumps,
manhole covers with fewer and smaller openings, seals on drain openings, or
solid metal covers for trenches; by purging the system with excess water;
and by other methods. Emissions from the collection systems presented here
can be increased also by high winds, discharge of steam into the sewer,
open sumps, open junctions, complex collection systems with many units
(potential emission sources) before discharge, and other factors.
It is possible that the emission factors presented in this report will
be modified in the future. Factors that could be used to improve the
accuracy of the emission factors include considering mass transfer at the
liquid gas interface and using Monte Carlo simulations of collection system
characteristics.
B.3 METHODS AND RESULTS
B.3.1 Overview
Air emissions factors are presented for induced airflow in sewer
systems accepting hazardous aqueous waste. The major sources of induced
airflow into and out of a sewer system are process drains, manholes, and
junction boxes. The emission factors are generated for five different
organic compounds: 1,3-butadiene, toluene, naphthalene, 1-butanol, and
phenol.
Ten cases for induced airflow in sewers are illustrated in Figure B-l.
Cases Al, A2, and A3 illustrate potential airflows from process drains.
B-5
-------
/J\
A1
A2
I'
A3
rt
B1
B2
B3
C1
l
D1
C2
\fs=L
n rifl-i
02
t
C3
Legend:
A Process drains
B Manholes
C Sewer lines
D1 Covered sump
02 Drain grate
Figure B-1. Simplified flow diagrams.
B-6
-------
Cases Bl, 82, and B3 illustrate air emissions from manholes. Cases Cl, C2,
and C3 illustrate airflow out of sewer lines. Case Dl represents emissions
from a covered sump with an open vent, and Case D2 illustrates airflow out
of drain grates. The following brief paragraphs describe some of the
assumptions used in estimating the induced flow of air:
• Case Al estimates airflow into a drain annulus induced by
water flow. The air drawn in will escape somewhere and be
in equilibrium with the water at that point.
• Case A2 estimates airflow into a sewer through a drain
annulus. No water is flowing into the drain. The air comes
to equilibrium with the water flowing in the sewer and
escapes at some point upstream or downstream of the drain.
• Case A3 estimates airflow from saturated air rising from a
drain annulus due to a density difference between the air in
the sewer and the ambient air. No water is flowing through
the drain. The air is drawn in at a point upstream or down-
stream of the drain and reaches thermal and chemical equi-
librium with the wastewater flowing in the sewer by the time
it reaches the drain.
• Case Bl estimates airflow from manhole cover vents caused by
a density difference between air in the sewer and the ambi-
ent air. The air flowing out of the vents is in thermal and
chemical equilibrium with the water flowing in the sewer at
that point.
• Case B2 estimates airflow through manhole cover vents
induced by wind blowing in the upstream end of a sewer that
is blocked off after the manhole. The air is in equilibrium
with the water in the manhole.
• Case B3 estimates the airflow from manhole cover vents
induced by wind blowing in one end of a sewer and flowing
past the manhole to some point downwind. The air is in
equilibrium with the water in the sewer at the manhole. No
drains or vents are in the line between the upwind sewer end
and the manhole.
• Case Cl estimates the airflow induced by wind blowing in one
end of a sewer and out another. The air is in equilibrium
with water at the downwind end of the sewer.
• Case C2 estimates the airflow into the sewer from a junction
box induced by water flow through the junction box. This
air escapes somewhere (e.g., the next junction box down-
stream) in equilibrium with the water flowing through at
that point.
B-7
-------
• Case C3 estimates airflow from the discharge end of a
partially filled sewer resulting from density differences
between the ambient air and the warm humid air in equilib-
rium with the wastewater.
Case Dl estimates the airflow induced through a stack on an
enclosed sump. Air is in equilibrium with the wastewater
and is drawn into the system at some point upstream or
downstream of the sump.
• Case D2 estimates airflow from an open trench based upon
mass transfer in the rapid flowing water.
Tables B-l through B-7 describe the estimated fraction of the volatile
organic emitted from the three components of the sewer investigated for
five different compounds that differ in volatility.
The airflow induced by the wind is sensitive to the geometry of the
source, the direction of flow of the wind, and the velocity of the wind.
Because of the large numbers of significant factors that could conceivably
influence the rate of emissions due to wind, the emission estimates are
presented as a range, with zero as the lower bound of the range and a
combination of values from the three cases as the upper range. The choice
of a specific value to be used for estimating emission factors from induced
airflow in the sewer component is also presented in Tables B-l to B-7. In
some cases, the effects of the various mechanisms for airflow can be
additive, but in some cases the effects would tend to cancel each other.
B-3-2 Description of Case Al Calculations
Case Al considers airflow into a drain induced by wastewater dis-
charged to the sewer through a pipe inserted in the drain. The air is
assumed to be drawn into the annulus with a velocity equal to that of the
flowing water at the air/water interface. The velocity of the induced air
is assumed to decrease to zero at the wall of the drain. The assumed air
velocity profile has not been experimentally confirmed. The air drawn into
the drain is assumed to escape at some other point in the system after
coming to equilibrium with the wastewater. In relatively tight systems or
systems with long runs of sewer between openings, the resistance to airflow
will inhibit this mechanism of air induction.
B-8
-------
TABLE B-l. EMISSION ESTIMATES FOR DILUTE AQUEOUS 1,3-BUTADIENE
SOLUTIONS FLOWING THROUGH SEWER NETWORKS3
(FRACTION EMITTED)
Case 1
Case 2
Case 3
Typical
Drains
0.63
0.73
0.54
value 0.63
aCase Al is Unit A with Case
(A) Manholes (B)
0.087
0.21
0.147
0.15
1 conditions.
TABLE B-2. EMISSION ESTIMATES FOR DILUTE AQUEOUS
SOLUTIONS FLOWING THROUGH SEWER NETWORKS
(FRACTION EMITTED)
Case 1
Case 2
Case 3
Typical
Drains
0.073
0.113
0.053
value 0.08
(A) Manholes (B)
0.0045
0.0123
0.008
0.0083
Sewers (C)
0.95
0.79
0.56
0.77
TOLUENE
Sewers (C)
0.48
0.148
0.057
0.23
B-9
-------
TABLE B-3. EMISSION ESTIMATES FOR DILUTE AQUEOUS NAPHTHALENE
SOLUTIONS FLOWING THROUGH SEWER NETWORKS
(FRACTION EMITTED)
Case 1
Case 2
Case 3
Typical
Drains (A)
0.014
0.022
0.0098
value 0.015
Manholes (B)
0.0008
0.0022
0.0014
0.0015
TABLE B-4. EMISSION ESTIMATES FOR DILUTE AQUEOUS
SOLUTIONS FLOWING THROUGH SEWER NETWORKS
(FRACTION EMITTED)
Case 1
Case 2
Case 3
Typical
Drains (A)
0.0001
0.00017
0.00007
value 0.00012
Manholes (B)
0.000006
0.000017
0.000011
0.00001
Sewers (C)
0.14
0.030
0.02
0.06
1-BUTANOL
Sewers (C)
0.00123
0.00023
0.00008
0.0005
B-10
-------
TABLE B-5. EMISSION ESTIMATES FOR DILUTE AQUEOUS PHENOL
SOLUTIONS FLOWING THROUGH SEWER NETWORKS
(FRACTION EMITTED)
Case 1
Case 2
Case 3
Typical value
Drains (A)
0.0000053
0.0000086
0.0000038
0.000006
Manholes (B)
3-10-7
8.5»10-7
5.5»10-7
6-10-7
Sewers (C)
0.000063
0.000012
0.0000041
0.000026
TABLE B-6. EMISSION ESTIMATES FROM AN
OPEN-TRENCH SECTION IN A
WASTEWATER COLLECTION NETWORK
Compound
Partition
coefficient
(Y/X)
Fraction
emitted to air
1,3-butadiene
Toluene
Naphthalene
Butanol
Phenol
7,900
371
65.6
0.494
0.0252
0.059
0.045
0.025
0.0004
0.0002
B-ll
-------
TABLE B-7. PARTITION COEFFICIENTS OF COMPOUNDS USED IN
EMISSION ESTIMATES3
Compound
1,3-Butadiene 4000
Toluene 371
Naphthalene 55.5
1-Butanol 0.494
Phenol 0.0252
aMole fraction in gas phase/mole fraction is aqueous waste.
B-12
-------
The calculation requires the following inputs: flow rate of waste-
water, ratio of wastewater pipe area to drain pipe area, partition coeffi-
cient applicable to the pollutant of interest at the wastewater tempera-
ture, concentration of wastewater stream, and temperature of the ambient
air. The molar air density is calculated at the ambient temperature based
on the ideal gas law assuming an ambient pressure of one atmosphere. The
influent flow rate of volatile organics is calculated from the mass flow
rate of wastewater and the mass fraction of volatile organics in the
wastewater. The influent air linear flow rate is calculated as one-fourth
the linear wastewater flow rate based on the assumed airflow profile. This
is converted to a molar airflow rate by multiplying by the area ratio
(drain pipe area to wastewater pipe area) and the molar density of air.
The fraction emitted is calculated by multiplying the dimensionless parti-
tion coefficient by the ratio of molar flows of air to the total molar flow
of air and water.
Specify: area ratio of sewer segment (Arr), dimensionless
partition coefficient, K, dimensionless
air temperature, Ta, K
Assume: water density, 0.0555 mol/cm3
air velocity profile (as described above)
air density by ideal gas law, 0.0121/T mol/cm3
Calculate: F = fraction emitted:
F =
(Arr)(0.25)(0.0121/Ta)K
a
arr
4
4
4
4
13,
13,
13,
(Arr)(0.25)(0.0121/TJK
a
K Ta
371 298
371 273
0.5 298
0.5 273
371 298
371 273
0.5 298
0.5 273
+ 0.0555
F
0.21
0.23
0.00037
0.00040
0.48
0.50
0.00125
0.00137
13.7
Note that, within the limits of the assumption, a smaller wastewater
pipe flowing at an equivalent volumetric flow rate will induce a greater
airflow (and cause greater emissions) due to its higher linear velocity.
B-13
-------
Note also that slightly greater emissions will occur on cooler days because
more moles of denser ambient air will be drawn in (it is assumed that this
air will come to thermal equilibrium with the wastewater before it escapes
from the system).
B.3.3 Description of Case A2 Calculations
Case A2 considers airflow into A drain and through the sewer. No
water is flowing down the drain. The pressure creating the airflow is due
to changes in wind velocity. The air pressure is estimated from the maxi-
mum pressure obtained from wind flowing at 160 cm/s (3.5 mph) with the
pitot tube pointed into the wind. The drain would not normally be oriented
into the wind, but wind flow patterns and pressures are expected to be
influenced by the location of the drain relative to wind, buildings, sumps,
etc.
The air flowing into the drain is assumed to escape at some other
point in the system after coming to equilibrium with the wastewater. The
frictional drag on the drain and in the headspace of the sewer will deter-
mine the flow of air in response to the pressure exerted by the wind.
The maximum pressure exerted by the wind is calculated based on a
solution of the Bernoulli equation:
dP = i/2 pi (2 gc)
where:
dP = calculated pressure, g force/cm2
i/ = wind velocity, 156 cm/s (3.5 mph)
p = density of air at 25 °C, 0.0012 g/cm3
gc = 980.665 g-cm/gF-s?.
This value of the maximum pressure is equated to the energy of the air
velocity in the sewer and the frictional losses in the sewer:
dP//j = (1 + Ke + 4 F L/D Arr2+ 4 F L2/D2 + Kl) t/2/2gc ,
B-14
-------
where:
dP = pressure, 0.015 g force/cm2
p = density of air, g/cm3
Ke = diameter change coefficient, 0.31
F = friction factor of air, 0.006
L = length of sewer, 1,220 cm
D = equivalent diameter of the headspace in the sewer, 40.4 cm
(four times the hydraulic radius)
Arr = area ratio of sewer segment
L2 = length of drain, 61 cm x 2 drains = 122 cm
D2 = diameter of drain, 20.3 cm
Kl = loss coefficient, 4
gc = 980.665 g-cm/gF-s2.
Solving for V, the velocity of air in the drain is 62 cm/s (122 ft/min).
The sectional area of the headspace is 1,830 cm2, permitting a calculated
airflow of 20,000 cm3/s. The molar density of the air is 4.0»10'5
mol/cm3); a molar airflow rate is then calculated as (8.79«105 cm3/s)
(3.9»10-5 mol/cm3), or 0.81 mol/s. The flow rate of volatile organics in
the air at equilibrium with the initial concentration of volatile organics
in the water is as follows:
(0.81 mol/s)(371)(0.0005 g toluene/g water)(18 g water/mol) or 2.7 g/s .
The fraction of volatile organics present in the air at equilibrium is
independent of concentration (as long as K is a constant). The fraction of
volatile organics in the air is the ratio of the mass flow in the air
divided by the sum of the mass flow in the air and water:
f = 2.77(21.1 + 2.7) = 0.11 .
General assumptions and calculations:
Air temperature 25 °C
Relative humidity 50 percent
Sewer temperature 30 CC
Friction factor for air 0.006
B-15
-------
Wind velocity 156 cm/s (3.5 mph)
Radius of sewer 30.48 cm (12 in.)
Depth of liquid in sewer 24.4 cm (9.6 in.)
Headspace hydraulic radius 10.9 cm
Flow of water in sewer 42,000 cm3/s
Headspace area in sewer 1,830 cm?
Density of air at 25 °C 0.0012 g/cm3
K partition coefficient (Y/X) 371
Weight fraction volatile organics in water 0.0005
Flow of volatile organics in sewer water 21.1 g/s
Molar density of air in sewer 0.00004 mol/cm3.
B.3.4 Description of Case A3 Calculations
Case A3 considers airflow up from a drain induced by density differ-
ences between the ambient air outside the manhole and the warm humid air in
the sewer. No water is flowing in the drain. The wastewater in the sewer
is assumed to be flowing in a direction perpendicular to the airflow
through the vents; the air is assumed to be saturated with water and at
chemical and thermal equilibrium with the wastewater. In the case consid-
ered, the drain is assumed to be 10 cm (4 in.) in diameter and 61 cm (2 ft)
long. Frictional losses through both the drain and the sewer are consid-
ered, based on a friction factor of 0.06. The height of the "stack" is
assumed to be 61 cm (2 ft). This is the vertical distance between the
level of the water in the sewer and the drain. Ambient conditions are
assumed to be 25 °C and 50 percent relative humidity. The wastewater
temperature is assumed to be 30 °C.
The densities of ambient air and warm humid sewer air are calculated,
and the density difference across the drain system is calculated as
8.39»10"5 g/cm3. The maximum pressure from density differences is the
product of the density difference and height. This value of the maximum
pressure from density differences is equated to the energy of the air
velocity in the sewer and the frictional losses in the sewer:
dP//> = (1 + Ke + 4 F L/D Arr2+ 4 F L2/D2 + Kl) i/2/2gc ,
where:
dP = pressure, 0.00195 g force/cm2
p = density of air, 0.0012 g/cm3
B-16
-------
Ke = diameter change coefficient, 0.31
F = friction factor of air, 0.006
L = length of sewer, 610 cm
D = equivalent diameter of the headspace in the sewer, 43.6 cm
(four times the hydraulic radius)
Arr = area ratio of sewer segment, 0.219
L2 = length of drain, 61 cm
D2 = diameter of drain, 20.3 cm
Kl = loss coefficient, 3
gc = 980.665 g-cm/gF-s2.
Solving for V, the velocity of air in the sewer is 4.8 cm/s (9.5 ft/min).
The sectional area of the headspace is 1,828 cm2, permitting a calculated
airflow of 8,853 cm3/s. The molar density of the air is 4.0»10-5 mol/cm3;
a molar airflow rate is then calculated as (8,853 cm3/s)(4.0»10'5 mol/cm3),
or 0.356 mol/s. The flow rate of volatile organics in the air at equilib-
rium with the initial concentration of volatile organics in the water is as
follows:
(0.356 mol/s)(371)(0.0005 g/g)(18 g/mol) or 1.19 g/s .
The fraction of volatile organics present in the air at equilibrium is
independent of concentration (as long as K is a constant). The fraction of
volatile organics in the air is the ratio of the mass flow in the air
divided by the sum of the mass flow in the air and water:
f = 1.19/(21.3 + 1.19) = 0.053 .
General assumptions and calculations:
Air temperature 25 °C
Relative humidity 50 percent
Sewer temperature 30 ec
Friction factor for air 0.006
Radius of sewer 30.48 cm (12 in.)
Depth of liquid in sewer 24.4 cm (9.6 in.)
Headspace hydraulic radius 10.9 cm
Flow of water in sewer 42,000 cm3/s
Headspace area in sewer 1,828 cm2
B-17
-------
Density of saturated air at 40 °C 0.00117 g/cm3
Density of air at 25 CC 0.0012 g/cm3
K partition coefficient (Y/X) 371
Weight fraction volatile organics in water 0.0005
Flow of volatile organics in sewer water 21.3 g/s
Molar density of air in sewer 0.00004 mol/cm3.
B.3.5 Description of Case Bl Calculations
Case Bl considers airflow from the vents in a manhole cover induced by
density differences between the ambient air outside the manhole and the
warm humid air in the sewer. The wastewater in the sewer is assumed to be
flowing in a direction perpendicular to the airflow through the vents; the
air is assumed to be saturated with water and at chemical and thermal
equilibrium with the wastewater. In the case considered, the manhole cover
is assumed to have four vent holes of 2.5 cm (1 in.) diameter. Frictional
losses through the manhole are assumed negligible relative to losses
through the manhole cover vents. The height of the "stack" is assumed to
be 67 cm (2 ft). This is the vertical distance between the level of the
water in the sewer and the manhole cover. Ambient conditions are assumed
to be 25 °C and 50 percent relative humidity. The wastewater temperature
is assumed to be 30 °C.
The densities of ambient air and warm humid sewer air are calculated,
and the density difference across the manhole cover is determined. The gas
velocity through the manhole cover vents was then calculated from the
density difference using the equation for a sharp edged orifice:
= 0.61 (2 gc h «-'-*0-5
where:
v = linear velocity through the vent hole, cm/s
gc = gravitational constant, 981 cm/s2
h = height of manhole, 61 cm (2 ft)
Lp = density difference of air above and below manhole, 3.2»10'5
g/cm3
p = density of warm humid air, 0.00117 g/cm3.
(Frictional losses through the thickness of the cover are negligible.)
B-18
-------
The air velocity is converted to a volumetric flow rate by multiplying
by the cross-sectional area of the vent holes, 20 cm? (0.022 ft?). Based
on this airflow, 710 cm3/S( the wastewater flow in the sewer, and a parti-
tion coefficient appropriate for the compound of interest at the wastewater
temperature, the fractional emission is calculated. (The wastewater flow
is 2,360 mol/s and was calculated from an assumed sewer size, slope,
roughness, and an assumed wastewater depth in the sewer.) The fraction
emitted is calculated as F = GK/(GK + L):
0.0285 x 371 . .....
0.0285 x 371 + 2,360 = °-0045
where:
F = fraction emitted through cover vents, dimensionless
G = airflow rate from the cover vents, 0.0285 mol/s
K = 371, air/water partition coefficient for compound of inter-
est at wastewater temperature, dimensionless
L = wastewater flow rate through sewer, 2,360 mol/s.
B-3.6 Description of Case B2 Calculations
Case B2 estimates airflow through manhole cover vents resulting from
wind blowing into the upstream end of a sewer. The air flows down the
sewer to the manhole where further airflow is obstructed. This might occur
where a sewer ends at a pump sump or where a change in pipe size or slope
results in a completely filled pipe with no air space. The airflow rate is
estimated by calculating the air velocity through the manhole cover vents
that would result in a frictional head loss equal to that available from
the wind blowing into the upstream end of the sewer. Frictional losses
through the sewer, the manhole, and the cover thickness are assumed to be
negligible in comparison to losses through the cover vents.
Frictional losses through the cover vents are calculated using an
equation for flow through a sharp-edged orifice:
B-19
-------
where:
v = linear velocity through vent cover, cm/s
t/w = wind velocity, 156 cm/s (3.5 mph)
p& = ambient air density, 0.0012 g/cm3
ps = density of warm humid air in sewer, 0.00117 g/cm3.
The manhole cover is assumed to have four vents of 2.5 cm (1 in.)
diameter. The wind velocity in the direction of the sewer is assumed to be
156 cm/s (3.5 mph). The factor of 0.61 is an orifice coefficient that will
be approximately constant for the range of flows considered.
The molar airflow rate can be calculated from the linear velocity
through the cover vents by multiplying by the total area of the four vents,
20 cm2 (0.022 ft?), and dividing by the molar density at the warm humid
sewer conditions, 0.00004 mol/cm3. The wastewater flow rate in the sewer
is implicitly specified on the basis of assumed sewer depth, diameter,
slope, and roughness (2,360 mol/s).
The fractional emission of volatiles is calculated from the molar flow
rates of air and water, and a dimensionless partition coefficient appropri-
ate for the compounds of interest at the wastewater temperature:
r _ GK _ „
GK + L u
where:
G = airflow rate, 0.0793 mol/s
K = 371, dimensionless partition coefficient.
L = water flow rate, 2,360 mol/s.
B.3.7 Description of Case B3 Calculations
Case B3 considers emissions from manhole cover vents over a flowing,
partially filled sewer. Air resulting from wind blowing in one end of the
sewer is flowing in the upper portion of the sewer. The direction of the
airflow relative to the water flow is not considered; it is assumed that
the air in the sewer is at thermal and chemical equilibrium with the waste-
water at the location of the manhole.
B-20
-------
The air velocity resulting from the wind pressure is calculated from a
Bernoulli equation based on frictional losses through the unfilled section
of the pipe:
f 2 fi i°-5
v - \v D ID (1 + K=M * RO
I w 'V^s v D 'J ou
where:
v = linear velocity of air through unfilled section of sewer
cm/s '
j/w = velocity of wind, cm/s
pa = density of ambient air, 0.0012 g/cm3
/>s = density of humid air in sewer, 0.00117 g/cm3
f = friction factor for air, assumed constant at 0.006 dimen-
sionless
L = length of sewer, 4,570 cm
D = equivalent diameter (four times the hydraulic radius) of
unfilled section of sewer, 40.4 cm.
The velocity is then used to calculate the pressure drop through the
shorter length of sewer between the manhole and the discharge end of the
sewer:
4 f L ,,2 p
AP = 2 G D = °-0064 •
where:
AP = pressure drop through sewer between manhole and discharqe
end, g force/cm^ y
Ls = length of sewer between manhole and gas exit, 3,050 cm
Gc = gravitational constant, 981 g cm/g forced.
This pressure (0.0064 g force/cm?) is then used as the driving force
in the equation for flow through a square-edged orifice to calculate the
linear velocity of air emitted from the manhole cover vents:
B-21
-------
*c = 0.61 (2 Gc AP//>S)°'5 = 63 cm/s ,
where:
t/c = linear velocity through the cover vents, cm/s
0.61 - orifice coefficient (dimensionless) appropriate for the veloc-
ity range expected.
Note that the above equations can be combined:
i/c = 0.61 (fLs i/2/D)°'5 = 63 cm/s .
The linear velocity can be converted to a molar flow rate by multiply-
ing by the cross-sectional area of the vents, 20 cm2 (four vents each
2.5 cm [1 in.] in diameter assumed in the example), and the molar density
of warm humid air at the wastewater temperature, 4«10"5 mol/cm3. The
wastewater flow rate, 2,360 mol/s, has been implicitly specified in the
example from the depth, diameter, slope, and roughness of the sewer. The
fraction of organics emitted is calculated from the molar flow rates and a
dimensionless partition coefficient appropriate for the compound of inter-
est at the wastewater temperature:
F = GOT = °-008
where:
F = fraction of organics emitted through manhole cover vents
G = airflow rate through manhole cover vents, 0.051 mol/s
K = partition coefficient, 371, dimensionless
L = wastewater flow rate, 2,360 mol/s.
B.3.8 Description of Case Cl Calculations
Case Cl considers air blowing directly into one end of a sewer, reach-
ing thermal and compositional equilibrium within the sewer and exiting a
junction box.
The maximum pressure exerted by the wind is calculated based on a
solution of the Bernoulli equation:
B-22
-------
dP = „< pi(2 gc) ,
where:
dP = calculated pressure, g force/cm2
v = wind velocity, 156 cm/s (3.5 mph)
p = density of air at 25 °C( 0.0012 g/cm3
gc = 980.665 g-cm/gF-s2.
• 0-0.5 , forced .
This value of the maximum pressure is equated to the energy of the air
velocity in the sewer and the frictional losses in the sewer:
dP//j = (1 + 4 F L/D) i/2/2gc ,
where:
dP = pressure, gforce/cm2
p = density of air, g/cm3
F = friction factor of air, 0.006
L = length of sewer, 4,570 cm (150 ft)
D = equivalent diameter of the headspace in the sewer 40.4 cm
(four times the hydraulic radius)
gc = 980.665 g-cm/gF-s2.
Solving for V, the velocity of air in the sewer is 80 cm/s (1.8 mph). The
sectional area of the headspace is 1,828 cm2, permitting a calculated air-
flow of 146,000 cm3/s. The molar density of the air is 4-10-5 mol/cm3; a
molar airflow rate is then calculated as (1.46-1Q5 cm3/s) (4«10-5 mol/cm3),
or 5.8 mol/s. The concentration of volatile organics in the air at equi-
librium with the initial concentration of volatile organics in the water is
as follows:
(5.8 mol/s)(371)(0.0005 g/g)(18 g/mol) or 19.4 g/s .
The fraction of volatile organics present in the air at equilibrium is
independent of concentration (as long as K is a constant). The fraction of
B-23
-------
volatile organics in the air is the ratio of the mass flow in the air
divided by the sum of the mass flow in the air and water:
f = 19.4/(21.1 + 19.4) = 0.48 .
General assumptions and calculations:
Air temperature 25 °C
Relative humidity 50 percent
Sewer temperature 30 »c
Friction factor for air 0 006
Wind velocity !56 cm/s (3<5 h)
n It* y,**"^ • 30.48 cm (12 in.)
Depth of liquTd in sewer 24.4 cm (9.6 in.)
Headspace hydraulic radius 10.9 cm
Flow of water in sewer 42J196 cn)3/s
Headspace area in sewer 1 828 cm2
Density of air at 25 «C 0!o012 g/cn.3
K partition coefficient (Y/X) 371
Weight fraction volatile organics in water 0.0005
Flow of volatile organics in sewer water 21.1 g/s
Molar density of air in sewer 0.00004 mol/cm3.
B-3-9 Description of Case C2 Calculations
Case C2 estimates airflow into a sewer from a junction box, induced by
water flow in the sewer. This air reaches thermal and compositional equi-
librium within the sewer and is discharged from the sewer at the next
junction box.
The velocity profile for the surface of the water in the sewer is
assumed to be given by the following empirical relationship:
= 8.5 + 2.5 ln(Y/e) , [Y > e]
where:
t/+ = velocity quotient, the ratio of the velocity to the friction
velocity
e = surface roughness, cm
Y = distance from a point on the surface to the nearest wall-
surface interface, cm.
The average velocity in the sewer is estimated as 38.7 cm/s integrating the
above equation for average flow. The average surface velocity was 42.2
B-24
-------
cm/s. The perimeter of the surface was 60 cm, and the perimeter of the
sewer headspace was 108 cm. The average velocity of the airflow was estab-
lished as follows:
42.2
J
This average air velocity is 36 percent of the water velocity in the
sewer. This estimated ratio of air velocity to water velocity compares
favorably to a reported percentage of 35 by Pescod and Price (Journal WPCF.
vol. 54, no. 4 (April 1982), p. 393) for laminar airflow due to liquid
drag. The estimated Reynolds number for the above flow conditions suggests
that the flow of air may be in the transitional zone. The assumption of
laminar flow of air may have overestimated the flow of air by 20 percent.
The estimated velocity of air in the sewer is 15 cm/s (0.33 mph). The
sectional area of the headspace is 1,828 cn»2, permitting a calculated air-
flow of 27,000 cm3/s. The molar density of the air is 4-10-5 mol/cm3; a
molar airflow rate is then calculated as (2.7-104 cm3/s)(4.10-5 mol/cm3), or
1.08 mol/s. The flow rate of volatile organics in the air at equilibrium
with the initial concentration of volatile organics in the water is as
follows:
(1.08 mol/s) (371) (0.0005 g/g)(18 g/mol) or 3.61 g/s .
The fraction of volatile organics present in the air at equilibrium is
independent of concentration (as long as K is a constant). The fraction of
volatile organics in the air is the ratio of the mass flow in the air
divided by the sum of the mass flow in the air and water:
f = 3.617(21.1 4 3.61) = 0.146 .
General assumptions and calculations:
Air temperature 25 °C
Relative humidity 50 D~rrpnf
Sewer temperature 30 S*
Friction factor for air 0.006
B-25
-------
Radius of sewer 30.48 cm (12 in.)
Depth of liquid in sewer 24.4 cm (9.6) in.)
Headspace hydraulic radius 10.9 cm
Flow of water in sewer 42,196 cm3/s
Headspace area in sewer 1,828 cm2
Density of air at 25 °C 0.0012 g/cm3
K partition coefficient (Y/X) 371
Weight fraction volatile organics in water 0.0005
Flow of volatile organics in sewer water 21.1 g/s
Molar density of air in sewer 0.00004 mol/cm3
Reynolds number for airflow 2,110
Average velocity of water 39 cm/s
Surface velocity of water 42 cm/s
Roughness of sewer wall 0.21 cm (0.007 ft)
Slope of sewer 0.000431.
B.3.10 Description of Case C3 Calculations
This calculation considers airflow from the discharge end of a partial-
ly filled sewer to the influent end of the sewer resulting from a density
difference between the cooler ambient air and the warm humid air in equilib-
rium with the wastewaters. The air flowing from the sewer is assumed to be
in thermal and chemical equilibrium with the wastewater. Air and water flow
countercurrently.
The ambient temperature and relative humidity and the wastewater
temperature are used to calculate the density difference; the slope and
length of the sewer are used to calculate the elevation difference producing
the "stack effect." Based on the length, diameter, and depth in the sewer,
the frictional resistance to airflow is determined as a function of air
velocity. The air velocity is calculated from a balance of the "stack
effect" and the frictional losses using a form of the Bernoulli equation:
v -- [2 gc Lp\\lpl(\ + 4 FL/D)]0'5 ,
where:
v = velocity of air through the sewer headspace, 5.2 cm/s
gc = acceleration of gravity, 981 cm/s2
A/> = density difference between ambient air and warm humid air in
sewer, 3.2»10'5 g force/cm2
B-26
-------
h = elevation difference determined from sewer length and slope
6.6 cm
p - density of warm humid air in sewer, 0.00117 g/cm3
F = friction factor for airflow through sewer, assumed constant
at 0.006, dimensionless
L = sewer length, 4,570 cm
D = diameter of circle having equivalent area to the cross
section of the sewer headspace, 40.4 cm.
This velocity is converted to a molar flow rate by multiplying by the
cross-sectional area of the headspace in the sewer, 1,828 cm2, and the
molar density of air at the wastewater temperature, 4.0»10"5 mol/cm2.
Water flow rate (2,360 mol/s) is specified implicitly by the slope,
diameter, depth, and roughness of the sewer. The fraction of influent
volatile organics that is emitted is calculated from the molar flow rates
of water and air and the dimensionless partition coefficient for the
compound of interest at the wastewater temperature. Air emitted from the
sewer is assumed to be in equilibrium with influent wastewater. The frac-
tional emissions are calculated as:
F = ^-j- = 0.057 ,
where:
G = airflow rate, 0.382 mol/s
K = 371, dimensionless partition coefficient for compound of interest
L = wastewater flow rate, 2,360 mol/s.
B.3.11 Description of Case Dl Calculations
Case Dl considers emissions from a stack on a sump. The stack was
designed to promote the discharge of fumes above workers' heads so that
their exposures to environmental releases would be reduced. Case Dl uses a
method identical to Case A3 to estimate the airflow due to the stack
effect.
Case Dl considers airflow up from a sump through a vent induced by
density differences between the ambient air outside the sump and the warm
B-27
-------
humid air in the sewer. The wastewater in the sewer is assumed to be
flowing in a direction perpendicular to the airflow through the vents; the
air is assumed to be saturated with water and at chemical and thermal
equilibrium with the wastewater. In the case considered, the vent is
assumed to be 10 cm (4 in.) in diameter and 366 cm (12 ft) long. Fric-
tional losses through both the drain and the sewer are considered, based on
a friction factor of 0.06. The height of the "stack" is assumed to be
366 cm (12 ft). This is the vertical distance between the top of the sump
and the vent top. Ambient conditions are assumed to be 25 °C and 50 per-
cent relative humidity. The wastewater temperature is assumed to be 30 °C.
The densities of ambient air and warm humid sewer air are calculated,
and the density difference across the vent system is calculated as 3.2»10~5
g/cm3. The maximum pressure from density differences is the product of the
density difference and height. This value of the maximum pressure from
density differences is equated to the energy of the air velocity in the
sewer and the frictional losses in the sewer:
dP//j = (1 + Ke + 4 F L/D Arr2+ 4 F L2/D2 + Kl) j/2/2g
where:
dP = pressure, 0.0117 g force/cm?
p = density of air, 0.0012 g/cm3
Ke = diameter change coefficient, 0.378
F = friction factor of air, 0.006
L = length of sewer, 3,048 cm
D = equivalent diameter of the headspace in the sewer 43 6 cm
(four times the hydraulic radius)
Arr = area ratio of sewer segment, 0.055
L2 = length of drain, 366 cm
D2 = diameter of stack, 10 cm
Kl = loss coefficient, 3
gc = 980.665 g-cm/gF-s2.
B-28
-------
Solving for V, the velocity of air in the sewer is 11 cm/s (21 ft/min).
The sectional area of the headspace is 1,830 cm2, permitting a calculated
airflow of 20,000 cm3/s. The molar density of the air is 4.0»10-5 mol/cm3;
a molar airflow rate is then calculated as (20,000 cm3/s)(4.0«1Q-5
mol/cm3), or 0.8 mol/s. The flow rate of volatile organics in the air at
equilibrium with the initial concentration of volatile organics in the
water is as follows:
(0.8 mol/s)(371)(0.0005 g/g)(18 g/mol) or 2.7 g/s .
The fraction of volatile organics present in the air at equilibrium is
independent of concentration (as long as K is a constant). The fraction of
volatile organics in the air is the ratio of the mass flow in the air
divided by the sum of the mass flow in the air and water:
f = 2.7/(21.3 + 2.7) = 0.11 .
General assumptions and calculations:
Air temperature
Relative humidity
Sewer temperature
Friction factor for air
Radius of sewer
Depth of liquid in sewer
Headspace hydraulic radius
Flow of water in sewer
Headspace area in sewer
Density of saturated air at 40 °C
Density of air at 25 °C
K partition coefficient (Y/X)
Weight fraction volatile organics in water
Flow of volatile organics in sewer water
Molar density of air in sewer
25 «C
50 percent
30 °C
0.006
30.48 cm (12 in.)
24.4 cm (9.6 in.)
10.9 cm
42,000 cm3/s
1,830 cm?
0.00117 g/cm3
0.0012 g/cm3
371
0.0005
21.3 g/s
0.00004 mol/cm3.
B.3.12 Description of Case D2 Calculations
Case D2 considers emissions from open trenches around process equip-
ment. These trenches are used to collect process wastes, tank cleaning
wastes, unplanned leaks, and water. Air blows across the top of a grate
covering the open top channel of the trench.
B-29
-------
The depth of flow in the channel is 7.6 cm (3 in.), the velocity is
76 cm/s (1.5 ft/s), and the length is 12.2 m (40 ft). The mass transfer
coefficient of the gas phase is assumed to be one-half the value for
surface impoundments (Kg = 0.0065/2 m/s). The more rapid flow would tend
to increase the mass transfer coefficient and the grate covering would tend
to decrease the mass transfer coefficient. The liquid mass transfer
coefficient is calculated by Owens, Edwards, and Gibbs (Int. J. Air Wat.
Poll., vol. 8 (1964), pp. 469-486):
Kal = (21.6 v0.67/H1.85)(K/Ko) ,
where:
Kal = liquid mass transfer coefficient, 176 /day,
V = velocity, 1.5 ft/s,
H = depth, 0.25 ft, and
K/Ko = ratio of mass transfer coefficients of toluene and air, 0.477.
The overall mass transfer coefficient is obtained by summing the resistance
of the two regions of mass transfer in series:
1/Ka = 1/Kal + H/(C Kg K • 0.000736) ,
where:
Ka = 149/day
Kal = 280
H = 0.25 ft
C = 24.3,600/12/2.54-100 (ft/day) (s/m)
Kg = 0.00325 m/s
K = 371 (Y/X).
The residence time in a 40-ft length of channel is 40 ft (1.5 ft/s) or 27 s
or 3.1»10~4 days. The fraction lost during flow through the 40-ft channel
is estimated with the following equation:
f = 1 - EXP (-Ka t) = 0.045 .
B-30
-------
Therefore, 4.6 percent of toluene is estimated to be emitted over the 40-ft
section of channel.
B.4 A COMPARISON OF THEORETICAL PREDICTIONS TO MEASURED VALUES
Several industrial plants were visited that have wastewater collection
systems. Screening measurements were made at these sites with an Alnor
velometer (low-velocity probe) to evaluate the magnitude of sewer
emissions. Of primary concern was to determine the magnitude of the
measured airflow velocities and to compare these measured velocities with
the predicted velocities.
Based upon the results of the velocity screening measurements, the
following observations can be stated:
• The velocities from the openings in the wastewater collec-
tion systems were variable, but the general range of
velocities from the different sources overlapped
(Table B-8).
• The preliminary results of using the model for site specific
conditions was favorable, with reasonable agreement (factor
of 2) between the predicted and measured velocities (Table
B-9).
• To improve the agreement between the model results and the
observed sewer velocities, representative model plant
parameters were used in the theoretical estimations.
Examples of sources that were modified include open drains
under grates (higher emissions than predicted) and sealed
drain systems (lower emissions than predicted).
• Some of the sealed sewer systems that were observed could be
considered as a control technology relative to other more
open sewer systems.
General comments offered about the plant visits include the following:
• The collection system at the first refinery may not have
been representative of collection systems at other chemical
plants and refineries. The refinery representative said
that a substantial amount of effort had been directed to
reducing collection system emissions.
• The collection systems at the paper mills may be more
typical of chemical plants than the systems at the first
refinery. Open-grated drains may be common around process
equipment, perhaps because they can trap wastes from both
unexpected spills and planned cleanups.
B-31
-------
TABLE B-8. SCREENING VALUES FOR AIR VELOCITIES AT SEWER OPENINGS
Unit
Location
Velocity at opening3
ft/min ft/s
Chemical sewer
Drain grate
Chemical sewer
Open drain
Manhole (1-in. dia. opening)
Open drain
Closed drain
Opening
Sump opening
Sample point drain
Sample point drain
Chemical sewer sump
Drain opening
Horizontal flow in sewer
Manhole cover
Manhole cover
/"* -A.
Grate over sewer
/* j.
Grate
Lift station opening
Lift station opening
Floor drain (2 x 1 ft)
Floor trench (1-2 ft/s)
Floor trench
Main drains between process
units
f i i «
bmall vent on main sewer
Grate on main sewer
*s , ,
Grate on main sewer
Grate open drain
Grate at end of trench
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Refinery 1
Pulp Mill 2
Pulp Mill 2
Pulp Mill 2
Pulp Mill 3
Pulp Mill 3
Pulp Mill 3
Pulp Mill 3
Pulp Mill 4
Pulp Mill 4
Pulp Mill 4
Pulp Mill 4
Pulp Mill 4
Pulp Mill 4
Pulp Mill 4
Pulp Mill 4
Pulp Mill 5
80
65
200
40
60
120
150
Ob
110
50
300
100-150
50-100
50
40-50
60
50
50
0-50
100
>300
150
160-170
50
100
3
2
1.3
1.1
3.3 .
0.66
1.0
2
0-2
2.5
1.8
0-1
0.83
5.0
1.7-2.5
0.83-1.7
0.83
0.67-0.83
1
0.83
0.83
0-1
1.7
5
2.5
2.7-2.9
0.83
1.7
"measurea witn an Alnor velometer, low-velocity probe. Feet per second
were reported without corresponding feet per minute obtained by visual
inspection of plume rise.
bNo measured velocity, but visual observation of slow fumes leaving drain.
B-32
-------
TABLE B-9. A COMPARISON OF MEASURED AND PREDICTED AIR VELOCITIES
AT SEWER OPENINGS
Unit
Drain
Manhole cover
Manhole cover
Average drain velocities
Average manhole cover
opening velocities
Average junction opening
velocities
Location
Refinery 1
Pulp Mill 2
Pulp Mill 2
Velocity at openinq
Measured
65,40,60,120
300
100-150
67
198
88
(ft/min)a
Predicted
122 (A2)b
124 (B3)
191 (B2)
84
1?fi
66
with an Alnor velometer, low-velocity probe.
based on a wind velocity of 3.5 mph (300 ft/minj.
Predicted values
bWind effect (3.5 mph) probably overestimates emissions because actual
wind velocity was lower (tall process units, wind direction different
from stack emissions at high elevation).
B-33
-------
APPENDIX C
PHYSICAL/CHEMICAL PROPERTIES
-------
TABLE C-l. TARGETED ORGANIC COMPOUNDS AND THEIR PHYSICAL PROPERTIES AT 25eCa
Organic
Compound
Toluene
Naphthalene
Phenol
1,3-butadiene
1-Butanol
Molecular
Weight
(g/gmol )
92.0
128.2
94.1
54.1
74.1
Density
(9/cm3)
0.87
1.14
1.07
0.62
0.81
Henry's
Constant
(atm-m3/
gmol)
6,. 68 x 10'
1 1 ft ». 1 A"
J.18 x 10
4.54 x 10"
J.42 x 10-
2D«
(cm2/seca)
8.6 x 10'6
7.5 x 10'6
9.1 x 10'6
].08 x 10'
o •an v irr
D.
(cm /sec)
8.7 x 10'2
5.9 x 10'2
8.2 x lO'2
2.49 x 10"
o nn v in-
8.90 x 10'
D
"Reference 1.
C-l
-------
TABLE C-2. ORGANIC COMPOUND PROPERTIES
Compound
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Vaoor
25'C
(nun Hg)
2095
30
0.23
6.5
0.341
Pressure
loo'c
(atm)
16.7
0.73
0.024
0.51
0.054
Partition'
Coefficient
25'C
(Y/X)
7889b
371
66
0.49
0.025
Partition*
Coefficient
100'C
(Y/X)
47717C
279
28.7
9.4
7.7
Biorated
(mg/g
biomass-
hr)
0.39
73.48
42.47
32.43
97.0
"Reference 2.
bEstimated based on Henry's Law constant (H):
Partition coefficient (K) = H (atm.m3/gmol) (1 x 106 cm3/m3)
(1/1 atm total pressure) (1 gm H20/cm3)(l gmol H20/18 gm H20)
Estimated from: K25 VP100/VP25
where
Reference 1.
K25 = partition coefficient at 25'
VP25 = vapor pressure at 25°C
VPioo * vapor pressure at 100'C
C-2
-------
TABLE C-3. PARTITION COEFFICIENTS FOR SELECTED ORGANIC COMPOUNDS AT VARIOUS TEMPERATURES'
Temperature
°C 1,3-Butadiene
I . Purge and Trap
8010/846
8030/846
EPA/RTI
EPA 624
CARB 401
II. Steam Distillation
EPA
AQMD
III. Headspace
EPA/TRC
EPA/TRC
25
85
25
25
100
100
25
90
7,889
3,602
7,889
7,889
23.5
12,672
12,672
7,889
39,370
1-Butanol
0.49
7.62
0.49
0.49
0.239
9.4
9.4
0.49
8.21
Ki Values
Naphthalene
65.56
36.1
65.56
65.56
0.0345
28.7
28.7
65.56
33.6
Phenol
0.025
6.17
0.025
0.025
0.00486
7.7
7.7
0.025
6.68
Toluene
371.
297
371.
371.
0.
279
279
371.
291
11
11
11
639
11
"Reference 2.
-------
C-l. REFERENCES
1. Office of Air Quality, Planning and Standards. U.S. Environmental
Protection Agency. Hazardous Waste Treatment, Storage, and Disposal
Facilities (TSDF) - Air Emission Models, April 1989.
2. "Preliminary Evaluation of Test Methods for Volatile Organics in
Hazardous Wastes: Batch Steam Stripping/Distillation." Office of Air
Quality Planning and Standards, U.S. Environmental Protection Agency,
February 4, 1988.
C-4
-------
APPENDIX D
STEAM STRIPPER PERFORMANCE DATA
-------
REFERENCES
Site A:
"Field Test and Evaluation of the Steam Stripping Process at B.F.
Goodrich, La Porte, TX". Research Triangle Institute. Prepared for the
U.S. EPA, Cincinnati, Ohio. EPA Contract No. 68-03-3253, December 5,
1986.
Site B:
"Post Sampling Report for 01 in Chemical, Rochester, New York." Metcalf
and Eddy. Prepared for the U.S. EPA, Cincinnati, Ohio. September, 1986,
Plant G:
"Hazardous Waste Pretreatment for Emission Control: Field Tests of Steam
Stripping/Carbon Adsorption at Plant G," Research Triangle Institute, EPA
Contract No. 68-02-3253, Work Assignment No. 5, August 1986.
-------
TEST DATA SUMMARY
SITE A
D-l
-------
1.0 FACILITY DESCRIPTION
Wastewater from the production of 1,2-dichloroethane is collected in a
feed tank, from which the waste is pumped into the steam stripper column. The
organics are stripped from the waste and condensed overhead in a series of two
condensers. The entire condensate, both aqueous and organic phases, is
recycled to the production process. The effluent stream from the stripper
column is sent through a heat exchanger to help preheat the feed stream and is
then sent to a wastewater treatment facility.
A schematic of the steam stripping system is shown in Figure 1. No
design information is available for the tray steam stripper column.
Typically, the feed rate is about 850 L/min to the column operating at 136
kiloPascals (kPa). Steam is fed at 446 kPa and unspecified temperature at a
rate of about 1,700 kg/hr.
2.0 STEAM STRIPPER SAMPLING AND ANALYSIS
Sampling and process measurement locations are detailed on the process
diagram in Figure 1. Sampling was conducted over two days with samples taken
five times at 2-hour intervals on each day. Liquid grab samples were
collected in 40-ml volatile organic analyzers (VOA) vials. Gas vent samples
were collected in evacuated stainless steel canisters. Process data were
collected during the testing at half-hour intervals throughout the testing.
Process operation data collected included feed, effluent, condensate, and
steam flow rates, temperatures of the feed, effluent, and condensate, and the
steam pressure.
The organic compounds in the water samples were analyzed by a purge and
trap procedure with separation and quantification performed by gas
chromatography/mass spectroscopy (GC/MS) analysis (EPA Method 624). The
organic phase in the condensate was analyzed by direct injection gas
chromatography. The vent gas analysis procedures were detailed in the site-
specific test and quality assurance plan dated July 7, 1986, but were not
presented in the report.
D-2
-------
1 Wastewater 1
Treatment |
Wastewater
Feed
Tank
i
(Heat
Exchanger
50,760 kg/hr
~®
Process
Water
y 84 C 48,960 kg/hr
1 Stripper Influent *
Stripper
108 *C
Stripper
Effluent
fr 1 ~~ 1 v$> 3.IUsec
ixjnuonaer •-•• — *j Conuenser 1 U — ^ — »» vapors
/Vent
y^
34 -C
1,440 kg/hr
i
Recycled
Condensate
^ 1.700 kg/hr steam
446 kPa Generation
(§) -SampleLocation
Figure 1. Diagram of Plant A steam stripper system and sampling
locations.
-------
Stream flow and concentration data were used to characterize all process
streams around the steam stripper. Averages of all flow and concentration
data taken were used in preparing the summaries of these data as shown in
Tables 1 and 2. Table 1 presents the flow rate, temperature, and pressure of
streams entering and leaving the steam stripper. Table 2 presents composition
data for each of these streams as well as organic removal efficiencies. The
overhead removal percentage was calculated on the basis of influent and
effluent flows from the stripper. The composition data available for the
condensate is presented in Table 2, but is not used to calculate removal
efficiencies. This is done because of the need to see the actual amount of
organic removed from the wastewater and because of the incompleteness of the
condensate data.
D-4
-------
en
Site A
TABLE 1. 'BULK STREAM CHARACTERIZATION
Influent to Effluent from Overhead CondensateC
Parae»ter Stripper* Stripper* Aqueous Organic Stea*
Flw Rate (kg/hr)" 48.960 50.760 1.200 240 1.700
Temperature («C) 64 108 34 34 NA
Pressure (kPa) NA 136 NA NA 446
Unit Ratio (kg/kg) - - ...
Influent
SteaM
-
-
-
28.8
NA - Not Available
•Snown as Stripper Influent 1n Figure 1.
bSho»n as Stripper Effluent In Figure 1.
cShovn as Recycled condensate In Figure 1. The entire compensate st
and aqueous flows are presented separately here.
Calculated as average of all flew rates Measured during testing.
Is recycled, but the organic
-------
Site A
TABLE 2. COMPONENT STREAM CHARACTERIZATION
O
cn
Influent
Component
1 .2-Dlchloroe thane
Chloroform
Benzene
Carbon Tetrachlorlde
Chlorobenzene
Chloroe thane
1.1-Olchloroe thane
1 . 1 -D 1 ch 1 oroe thene
1,2-dlchl oroe thene
Methylene Chloride
Tetrachl oroe thene
1 , 1 ,2-TMchl oroe thane
Trlchloroe thene
Vinyl Chloride
Total VO
Mater
Total
to Str loner
Flow
(kg/hr)
270d
13
0.0098
0.083
0.017
0.47
0.54
0.23
0.44
0.059
0.069
0.37
0.24
0.41
290
48,6709
48.960h
Conc.«
(ppM)
5.600
270
0.20
1.7
0.34
9.6
11
4.7
8.9
1.2
1.4
7.5
4.8
8.4
5,900
-
~
Effluent
fro. S
Flow
(kg/hr)
0.0049
0.48
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.5E-4
2.SE-4
0.50
50,7609
50,760"
i tripper Anna
Cone.* Flow
(pp*v) (kg/hr)
0.097 4.3
9.6 0.41
0.005f
o.oos'
o.oos'
o.oos'
0.005'
0.005'
o.oos'
0.005'
0.005'
0.005' ,-
0.005'
o.oos'
9.8 4.7
1,2009
1,200"
Overhead P*ti
IQUS
Conc.«
(ppaw)
3.600*
340*
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
3,900
_
-
b
Organic
Flow
(kg/hr)
210
11
-
_
-
-
-
-
-
-
_
_
_
-
220
209
240"
Conc.«
(pp.)
880.000*
47.000*
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
927,000
—
-
Overhead
Removal c
(Mt.X)
99.998
96
97
99.7
99
99.9S
99.9S
99.9
99.9
99.6
99.6
99.9
99.9
99.9
99.8
—
-
NA - Not analyzed for this component
•Average of concentrations Measured during testing.
bNot used for calculation of re*»a1 efficiencies because of need to deter*tne actual organic reioved and tnco-pleteness of
contort sate analyses.
Calculated as: (1 - (Effluent fro» strlpper)/(Influent to stripper)) x 1001.
^Sa«ple calculattoni (Average component concentration. POM) x (Average flow rate) x (lO^ppM)'1 - exponent flow rate.
•Only chlorofor. and 1.2-dlchloroethane were analyzed In the condensate. Because of the use of average flows and average
concentrations, the coiponent MSS balance for these co*onents My not be close as was usually obtained at a given sailing tie*.
All concentrations .ere below detection ll.lt. One-half of 11.lt used for calculation purposes.
^Balance of flow after accounting for organlcs.
Average of flow rates Measured during testing.
-------
TEST DATA SUMMARY
SITE B
D-7
-------
1.0 FACILITY DESCRIPTION
A process waste stream consisting of methylene chloride, water, salt, and
organic residue is fed to the steam stripper in which much of the organic
compounds is stripped and taken overhead. The overhead vapor is condensed,
with the aqueous phase being recycled to the column and the organic phase
stored for reuse. The bottom stream is used to preheat the incoming waste and
is then either sent to a publicly owned treatment works or back into a tank
for the feed stream, depending on whether the effluent meets discharge limits.
If the midpoint temperature of the stripping column is above a given set
point, the effluent meets limitations and is sent to the treatment facility.
A schematic of the steam striper system is shown in Figure 1. The
stripping column contains 10 feet of 5/8 inch pall rings and has a diameter of
eight inches. The waste stream feed rate is approximately 19 L/min with an
overhead organic product rate of about 0.28 L/min. Steam was fed at a
pressure range of 190-320 kiloPascals (kPa), although the temperature and rate
were unspecified.
2.0 STEAM STRIPPER SAMPLING AND ANALYSIS
Desired sampling and process measurement locations are detailed on the
process diagram in Figure 1. All process data recorded during sampling are
presented also. Sampling of the influent and effluent was conducted
approximately hourly for five hours on the first day and for 12 hours on the
second day, although a shut down and restart delay of six hours occurred the
second day because of instrument difficulties. Liquid grab samples were
collected in either a glass or stainless steel beaker and then distributed
into individual glass bottles for analysis. A composite sample of the organic
product was collected in glass bottles after completion of the test. Gas vent
samples were collected in evacuated glass sampling bulbs. Process data
collected included feed flow rate, column, feed, effluent and vent
temperatures, and steam pressure.
Vent gas was analyzed using chromatography with a flame ionization
detector (GC/FID) (Method 18). The volatile organic compounds in the liquid
samples were analyzed by gas chromatography/mass spectrometry (GC/MS)
D-8
-------
Wastewater
Treatment
Process
Waste Feed"
Tank
VD-12
Effluent
50'C
1,
Off-Spec
Waste
(If applicable)
Tank
VD-15
35»C /
1,260kg/hr /
Preheat
Exchanger
25 -
Wat
f
J I
Cooling
Water
22'C
67gpm
26 BC 4.4 kg/hr Vent to
i — r*- Atmosphere
96 *C
Condenser
Packed
Column
16 kg/hr
101 *C
308 kPa
120 kg/hr
RD 02
Steam
Generation
Gravity
Separator
17 kg/hr
Organic
Product
- Sample Location
Figure 1. Diagram of Steam Stripper at Si te B with Sampling Locations
-------
(Method 8240). Material and energy balances and stream flow and concentration
data were used to characterize all process streams around the steam stripper.
Summaries of the flow and concentration data gathered during the test are
shown in Tables 1 and 2. Table 1 presents the flow rate, temperature, and
pressure of streams entering and leaving this steam stripper process. Table 2
presents composition data for each of these streams as well as organic removal
efficiencies.
D-10
-------
SITE B
TABLE 1. BULK STREAM CHARACTERIZATION
Parameter
Organic
influent* Ef,,uentb
Flow Rate (kg/hr)
Temperature (°C)
Pressure (kPa)
Unit Ratio (kg/kg)
1,260
35
NA
1,360
50
NA
17'
NA
NA
NA - Not Available
aShown as Process Waste Feed In Figure 1
cShown as Effluent in Figure 1. 9
W 2r§an1c Product in Figure 1.
120'
NA
308e
Average.
Influent/
"?""*
selected as weighted
D-JJ
-------
o
I
I—i
ro
Site B
TABLE 2. COMPONENT STREAM CHARACTERIZATION
Component
Methylene Chloride
Chloroform
Carbon Tetrachlortde
Total VO
Water
Total
Inf limit
Flow Concentration
(kg/hr) (ppmw)
<.SC 3,600d
0.066 52
0.0019 1.5
4.6 3,600
1,25S»
1,260
Eff 1u«it
Flow Concentratlo
(kg/hr) (ppM»
0.0003* 0.22
0.0072 5.3
0.0001* 0.09
0.0076 5.6
1.360*
1 ,360b
QrarhMd CQ.ndjmsa.tt'
Organic Overhead
in Flow Concentration Removal 9
(kg/hr) (ppmw) (Wt.«)
0.088 5.200 99.99
0.019 1,100 89
2.1E-5* 1.2 95
0.107 6,300 98
16.9*
17
•Balance of total flow after accounting for organlcs.
"Calculated fro* material and energy balances using Measured flows.
cSample calculation!
(Component Concentration, ug/L) x (Flow rate, L/hr) x (10'9 kg/ug) - Component flow rate
Component Concentration Is an average of the grab samples t. ken during testing.
"Calculated from component and total flow rates.
""* M~ tH* d-t*Ct' "•"• °W"h'1f th* d't-Ctl0n 11"1t
°f
calculating
Calculated asi
(1 - (Effluent flow)/( Influent flow)) x 100».
-------
TEST DATA SUMMARY
PLANT G
D-13
-------
1.0 FACILITY DESCRIPTION
Wastewater from a feed tank is pumped to the steam stripping column where
the organics are steam stripped in the column and condensed in the overheads.
The stripped organics are separated from the condensed steam in the organic
condensate tank. The aqueous layer is recycled from the organic condensate
tank to the feed tank. The organic phase is sent to a vented storage tank.
From there, the organics are transferred to tank trucks and taken off site for
resale as fuel. Effluent from the steam stripper is passed through a liquid-
phase carbon adsorption unit to recover any residual organics in the stream.
The effluent is then pH adjusted and discharged to surface water.
A schematic of the steam stripping system is shown in Figure 1. The
steam stripping column is 19.2 meters high with an internal diameter of 0.46
meters. The column is packed with 3.17 m3 of 2.5 cm diameter stainless steel
rings. The steam stripper operates with a liquid to gas (L/G) ratio ranging
from 55 m3/m3 at the bottom of the column to 24 m3/m3 at the top of the column.
Steam is fed to the column at approximately 130'C and 365 kiloPascals (kPa)
pressure at a feed to steam ratio of 14.7 kg/kg.
2.0 STEAM STRIPPER SAMPLING AND ANALYSIS
Sampling and process measurement locations are detailed on the process
diagram in Figure 1. Sampling was conducted over a 2{ hour period with an
average of four samples collected from each sampling point. Liquid grab
samples were collected in 40 ml volatile organic analyzer (VOA) bottles. Gas
vent samples were collected in evacuated stainless steel canisters. Process
operating data were collected over a 4i hour period to ensure that the process
was operating at steady state. Process data collected included feed, steam,
and vent gas flow rates, temperatures, and pressures.
Vent gas was analyzed using GC headspace analysis method (Method 5020).
The volatile organic compounds in the liquid samples were speciated and
quantified by direct injection GC. Confirmation of GC peak identification was
carried out by gas chromatography/mass spectrometry (GC/MS) on selected
samples (Method 8240). Material and energy balances and stream flow and
concentration data were used to characterize all process streams around the
D-14
-------
27'C
29,900 kg/hr
58'C
B1
Heat
Exchanger
2-VOC)
Carbon
Adsorber
3-VOC
|B2
Feed.F
Distillate, D
Steam
Stripping
Packed
Column
4
Liquid, Gas,
L G
0.46m
(1.5ft)
dia
Bottoms, B
f
19.2m
(63ft)
Vent, V
0.34 kg/hr
~^HMM
6-VOC
Condensate
Tank
C, Condensate
O, Organics
"(4-VOC
Organic
Sump
•Steam, S-
_> Sampling Location
129'C
2033 kg/hr
364 kPa
Steam
Generation
Figure 1. Diagram of Plant G Steam Stripping Process with Sampling Locations
D-15
-------
steam stripper and carbon adsorption unit. Summaries of the flow and
concentration data gathered during the test are presented in Tables 1 and 2.
Table 1 presents the flow rate, temperature and pressure of streams entering
and leaving the steam stripper and carbon adsorption unit. Table 2 presents
composition data for each of these streams as well as organic removal
efficiencies.
The steam stripper removal percentage was calculated based on the
influent and effluent flows for the stripper. The composition data for the
overhead streams is present, but is not used to calculate removal
efficiencies. This is done to show the actual removal of organics from the
waste stream. This also minimizes any background interference effects for the
wastewater. By looking at the same bulk stream of liquid, the same liquid
background is present, allowing for consistency between samples.
D-16
-------
PLANT G STEAM STRIPPER
TABLE 1. BULK STREAM CHARACTERIZATION
Parameter
Flow Rate (kg/hr)
Temperature (°C)
Pressure (kPa)
Unit Ratio (kg/kg)
Influent Effluent Effluent fro*
to Stripper* fro* Stripper'' Carbon Adsorber'
29,900 31.490 31,490
83 112 58
204.3 204.3
-
Overhead Condensate
Aqueous0 Organic"1
427.6 15.4
100« 100«
101.3 101.3
-
Steam Inf luent/SteaM
2,033
128.8
364.3
14.7
•Shown as Feed, F In Figure 1
bSho»n as Bottom, B In Figure 1
cShown as Condensate, C In Figure 1
dShown as Organic, 0 In Figure 1
•Assumed to operate at stea* condensation temperature
'Shown as B2 In Figure 1
-------
o
I
>—'
00
PLANT G STEAM STRIPPER
TABLE 2. COMPONENT STREAM CHARACTERIZATION
Effluent
Influent
Component
Nitrobenzene
2-N!troto1uene
4-Nttrotoluene
Water
Total
Flow
(kg/hr)
15. id
2.33
1.53
29.881*
29,900b
Cone.
(pp-w)
SOS
78
51
634
Fra Strionar
Flow
(kg/hr)
1.29
0.076
0.139
31,488*
31,490b
Cone.
41
2.4
4.4
47.8
From Carbon
Adsorber
Flow Cone.
(kg/hr) (ppw)
<0.02S <0.8
<0.02S 98
>67
>82
>95
•Balance of total flow after accounting for organlcs
"Calculated from Material balances using Measured flows and concentrations
C0oe to accuracy of concentration Measurements
<*SaMple calculations 505 pp»w x 29.900 kg/hr x (10* pprnw)'1 • 15.1 kg/hr
•Values represent MlnlMuM removal efficiencies due to component concentrations below analytical detection Halts
fNot used for calculation of removal efficiencies because of the need to calculate actual amount of organic removed
from the waste stream and to MlntMlze background Interference effects.
Calculated ast (1- (Effluent from str1pper)/(Influent to stripper)) x 1001.
-------
APPENDIX E
DRAFT EPA
REFERENCE METHODS 25D AND 25E
-------
METHOD 25D--DETERMINATION OF THE VOLATILE ORGANIC CONCENTRATION OF
WASTE SAMPLES
Introduction
Performance of this method should not be attempted by persons
unfamiliar with the operation of a flame ionization detector (FID) or a
electrolytic conductivity detector (ELCD) because knowledge beyond the
scope of this presentation is required.
1. Applicability and Principle
1.1 Applicability. This method 1s applicable to the determination
of the volatile organic concentration of hazardous waste.
1.2 Principle. A sample of waste is collected at a point before
the waste is exposed to the atmosphere such as 1n an enclosed pipe or
other closed system that 1s used to transfer the waste after generation
to the first hazardous waste management unit. The sample 1s then
heated and purged with a stream of nitrogen to separate the organic
compounds. Part of the sample is analyzed for carbon content, as
methane, with an FID, and part of the sample is analyzed for chlorine
content, as chloride, with an ELCD. The volatile organic concentration
is the sum of the carbon and chlorine content of the sample.
2. Apparatus
2.1 Sampling. The following equipment is required:
E-l
-------
2.1.1 Static Mixer. Installed in-line or as a by-pass loop, sized
so that the drop size of the dispersed phase is no greater than 1000
microns (/<). If the installation of the mixer is in a by-pass loop,
then the entire waste stream shall be diverted through the mixer.
2.1.2 Tap. Installed no further than two pipe diameters
downstream of the static mixer outlet.
2.1.3 Sampling Tube. Flexible Teflon, 0.25 in. ID. NOTE:
Mention of names or specific products does not constitute endorsement
by the Environmental Protection Agency.
2.1.4 Sample Container. Borosilicate glass or
polyterafluoroethylene (PTFE), 15 to 50 ml, and a Teflon lined screw
cap capable of forming an air tight seal.
2.1.5 Cooling Coll. Fabricated from 0.25 in. ID 304 stainless
steel tubing with a thermocouple at the coil outlet.
2.2 Analysis. The following equipment is required:
2.2.1 Purging Apparatus. For separating the organic compounds
from the waste sample. A schematic of the system 1s shown in Figure 1.
The purging apparatus consists of the following major components.
2.2.1.1 Purging Chamber. A glass container to hold the sample
while it 1s heated and purged with dry nitrogen. Exact dimensions are
shown in Figure 2.
The cap of the purging chamber is equipped with three fittings: one
for a mechanical stirrer (fitting with the #11 Ace thread), one for a
thermometer (top fitting), and one for the Teflon exit tubing (side
fitting) as shown in Figure 2.
E-2
-------
Vcnl
CALIBRATION GAS
VALVE
FLOW
METER
i
CO
PLOW
COALESCING METER
PURGING . FILTER
CHAMBER 4
^ „
M
l
Adsoi bciil
Tube
[7 HECD]
NITROGEN
I
I /
FLOW ••" *"'
REGULATOR
CONSTANT TEMPERATURE
BATH
% BYPASS VALVE
CALIBRATION
GAS
FIGURE 1
-------
ROTAMETER
BATH HEATER/
CONTROLLER
STIRRING
MOTOR
PURGING CHAMBER
FIGURE 2
TODHTI-XTOKS
OIL HA 11
COALESCING MI/ILK
-------
The base of the purging chamber is a 50-mm inside diameter (ID)
cylindrical glass tube. One end of the tube is fitted with a 50-mm
Ace-thread fitting while the other end is sealed. Near the sealed end
in the side wall is a fitting for a glass purging lance.
2.2.1.2 Purging Lance. Glass tube, 6-mrn ID by 15.25 cm long, bent
into an el shape. The el end of the tube is sealed and then pierced
with fifteen holes each 1 mm in diameter.
2.2.1.3 Mechanical Stirrer. Stainless steel or PTFE stirring rod
driven by an electric motor.
2.2.1.4 Coalescing Filter. Porous fritted disc incorporated into
a container with the same dimensions as the purging chamber. The
details of the design are shown in Figure 3.
2.2.1.5 Constant Temperature Bath. Capable of maintaining a
temperature around the purging chamber and coalescing filter of 75 +
5eC.
2.2.1.6 Three-way valves. Two, manually operated, stainless
steel.
2.2.1.7 Flow Controller. Capable of maintaining a purge gas flow
rate of 6 + .006 l/m1n.
2.2.1.8 Rotameters. Two for monitoring the air flow through the
purging system (0-20 1/min).
2.2.1.9 Sample Splitters. Two heated flow restrlctors. At a
purge rate of up to 6 l/m1n, one will supply a constant flow of 70 to
100 ml/min to the analyzers. The second will split the analytical flow
between the FID and the ELCD. The approximate flow to the FID will be
40 ml/min and to the ELCD will be 15 ml/min, but the exact flow shall
E-5
-------
Ooo
mo
CTi
o
cl
w
OJ
HEIGHT-SOOmnr
CTE
THERMOMETER
-------
be adjusted to be compatible with the individual detector and to meet
its linearity requirement.
2.2.1.10 Adsorbent Tube. To hold 10 g of activated charcoal.
Excess purge gas is vented through the adsorbent tube to prevent any
potentially hazardous materials from entering the laboratory.
2.2.2 Volatile Organic Measurement System. Consisting of an FID
to measure the carbon content, as methane, of the sample and an ELCD to
measure the chlorine content.
2.2.2.1 FID. An FID meeting the following specifications is
required:
2.2.2.1.1 Linearity. A linear response (+ 5 percent) over the
operating range as demonstrated by the procedures established in
Section 5.1.1.
2.2.2.1.2 Range. A full scale range .of 50 pg carbon/sec to 50 /
-------
2.2.2.2.3 Data Recording System. Analog strip chart recorder or
digital integration system compatible with the output voltage range of
the ELCD.
3. Reagents
3.1 Sampling.
3.1.1 Polyethylene Glycol (PEG). 98 percent pure with an average
molecular weight of 400. Remove any organic compounds already present
in the PEG before it is used by heating it to 250eC and purging it with
nitrogen at a flow rate of 1 to 2 1/min for 2 hours.
3.2 Analysis.
3.2.1 Sample Separation. The following are required for the
sample purging step:
3.2.1.1 PEG. Same as Section 3.1.1.
3.2.1.2 Silicon, Mineral, or Peanut 011. For use as the heat
dispersing medium in the constant temperature bath.
3.2.1.3 Purging Gas. Zero grade nitrogen (N2), containing less
than 1 ppm carbon.
3.2.2 Volatile Organic Measurement. The following are required
for measuring the volatile organic concentration:
3.2.2.1 Hydrogen (H2). Zero grade H2, 99.999 percent pure.
3.2.2.2 Combustion Gas. Zero grade air or oxygen as required by
the FID.
3.2.2.3 FID Calibration Gases.
3.2.2.3.1 Low-level Calibration Gas. Gas mixture standard with a
nominal concentration of 35 ppmv propane in N2.
3.2.2.3.2 Mid-level Calibration Gas. Gas mixture standard with a
nominal concentration of 175 ppmv propane in N2.
E-8
-------
3.2.2.3.3 High-level Calibration Gas. Gas mixture standard with a
nominal concentration of 350 ppmv propane in N£.
3.2.2.4 ELCD Calibration Gases.
3.2.2.4.1 Low-level Calibration Gas. Gas mixture standard with a
nominal concentration of 20 ppmv 1,1-dichloroethene in N£.
3.2.2.4.2 Mid-level Calibration Gas. Gas mixture standard with a
nominal concentration of 100 ppmv 1,1-dichloroethene in N2-
3.2.2.4.3 High-level Calibration Gas. Gas mixture standard with a
nominal concentration of 200 ppmv 1,1-dichloroethene in N2.
3.2.2.5 Water. Deionized distilled water that conforms to
American Society for Testing and Materials Specification D 1193-74,
Type 3, is required for analysis. At the option of the analyst the '
KMn04, test for oxidlzable organic matter may be omitted when high
concentrations are not expected to be present.
3.2.2.6 N-Propanol. ACS grade or better.
3.2.2.7 Electrolyte Solution. For use 1n the conductivity
detector. Mix together 500 ml of water and 500 ml of n-propanol and
store in a glass container.
3.2.2.8 Charcoal. Activated coconut, 12 to 30 mesh.
4.0 Procedure
4.1 Sampling.
4.1.1 Sampling Plan Design and Development. Use the procedures in
chapter nine of the Office of Solid Waste's publication, Test Methods
for Evaluating Solid Waste, third edition (SW-846), as guidance 1n
developing a sampling plan.
4.1.2 Waste in Enclosed Pipes. Sample at one of the locations
described in Section 1.2 in order to minimize the loss of organic
E-9
-------
compounds. Assemble the sampling apparatus as shown in Figure 4.
Install the static mixer in the process line or in a by-pass line.
Locate the tap within two pipe diameters of the static mixer outlet.
Prepare the sampling containers as follows: Pour into the
container an amount of PEG equal to the total volume of the sample
container minus 10 ml. PEG will reduce but not eliminate the loss of
organic compounds during sample collection. Weigh the sample container
with the screw cap, the PEG, and any labels to the nearest 0.01 g and
record the weight (mst). Before sampling, store the containers in an
ice bath until the temperature of the PEG is less than 4'C.
Begin sampling by purging the sample lines and cooling coil with at
least four volumes of waste. Collect the purged material in a separate
container and dispose of 1t properly.
After purging, stop the sample flow and direct the sampling tube to
a preweighed sample container, prepared as previously described of this
section. Keep the tip of the tube below the surface of the PEG during
sampling to minimize contact with the atmosphere. Sample at a flow
rate such that the temperature of the waste is less than 10°C. Fill
the sample container and Immediately cap it (within 5 seconds) so that
a minimum headspace exists 1n the container, store immediately in a
cooler and cover with ice.
Alternative sampling techniques may be used upon the approval of
the Administrator.
4.2 Sample Recovery. Remove the sample container from the cooler,
and wipe the exterior of the container to remove any extraneous ice,
water, or other debris. ReweTgh the sample container and sample to the
nearest 0.01 g, and record the weight (msf). Pour the contents of the
E-10
-------
WASTE LINE
FROM SOURCE
S
STATIC MIXER
OPTIONAL PUMP
f
VALVES
REDUCER dM" TUBE
TEI-LON OK STAINLESS STI-EI.C'Oil.
ICE HATH
I— SAMIM.IiCONTAINI-.K
-------
sample container into the purging flask, rinse the sample container
three times with PEG, transferring the rinsings to the purging flask
after each rinse. The total volume of PEG in the purging flask shall
be approximately 50 ml. Add approximately 50 ml of water. Assemble
the purging apparatus as shown in Figure 1, leaving the purging chamber
out of the constant temperature bath. Adjust the stirring rod so that
it nearly reaches the bottom of the chamber. Position the sparger so
that it is within 1 cm of the bottom but does not interfere with the
stirring rod. Lower the thermometer so that it extends into the
liquid.
4.3 Sample Analysis. Turn on the constant temperature bath and
allow the temperature to equilibrate at 75 + 5°C. Turn the bypass '
valve so that the purge gas bypasses the purging chamber. Turn on the
purge gas. Allow both the FID and the ELCD to warm up until a stable
baseline is achieved on each detector. Pack the adsorbent tube with 10
g of charcoal. Change this after each run and dispose of the spent
charcoal properly. Place the assembled chamber in the constant
temperature bath. When the temperature of the liquid reaches 75 + 5«c,
turn the bypass valve so that the purge gas flows through the purging
chamber. Begin recording the response of the FID and the ELCD.
Compare the readings between the two rotameters in the system. If the
readings differ by more than five percent, stop the purging and
determine the source of the discrepancy before resuming.
As the purging continues, monitor the output of the FID to make
certain that the separation is proceeding correctly and that the
results are being properly recorded. Every 10 minutes read and record
E-12
-------
the purge flow rate and the liquid temperature. Continue the purging
for 30 minutes.
4.4 Water Blank. Transfer about 60 ml of water into the purging
chamber. Add 50 ml of PEG to the purging chamber. Treat the blank as
described in Sections 4.2 and 4.3 beginning with the fifth sentence of
Section 4.2.
5. Operational Checks and Calibration
Maintain a record of performance of each item.
5.1 Initial Performance Check of Purging System. Before placing
the system in operation, after a shutdown of greater than six months,
and after any major modifications, conduct the linearity checks
described in Sections 5.1.1 and 5.1.2. Install all calibration gases
at the three-way calibration gas valve. See Figure 1.
5.1.1 FID Linearity Check and Calibration. With the purging
system operating as 1n Section 4.3, allow the FID to establish a stable
baseline. Set the secondary pressure regulator of the calibration gas
cylinder to the same pressure as the purge gas cylinder and Inject the
calibration gas by turning the calibration gas valve, to switch flow
from the purge gas to the calibration gas. Continue the calibration
gas flow for approximately two minutes before switching to the purge
gas. Make triplicate injections of each calibration gas (Section
3.2.2.3), and then calculate the average response factor for each
concentration (Rt)i as well as the overall mean of the response factor
values, R0. The instrument linearity is acceptable if each Rt is
within 5 percent of R0 and if the relative standard deviation (Section
6.9) for each set of triplicate Injections is less than 5 percent.
E-13
-------
Record the overall mean value of the propane response factor values as
the FID calibration response factor, R0.
5.1.2 ELCD Linearity Check and Calibration. With the purging
system operating as in Section 4.3, allow the ELCD to establish a
stable baseline. Set the secondary pressure regulator of the
calibration gas cylinder to the same pressure as the purge gas cylinder
and inject the calibration gas by turning the calibration gas valve to
switch flow from the purge gas to the calibration gas. Continue the
calibration gas flow about two minutes before switching to the purge
gas. Make triplicate injections of each calibration gas (Section
3.2.2.4), and then calculate the average response factor for each
concentration, Rtn, as well as the overall mean of the response
factors, Ron. The instrument linearity is acceptable if each Rth is
within 10 percent of Roh and 1f the relative standard deviation
(Section 6.9) for each set of triplicate Injections 1s less than 10
percent. Record the overall mean value of the chlorine response
factors as the ELCD response factor, Ron.
5.2 Dally Calibrations.
5.2.1 FID Daily Calibration. Inject duplicate samples from the
mid- level FID calibration gas (Section 3.2.2.3.2) as described in
Section 5.1.1, and calculate the average dally response factor (DRt).
System operation is adequate if the DRt is within 5 percent of the R0
calculated during the initial performance test (Section 5.1.1). Use
the DRt for calculation of carbon content 1n the samples.
5.2.2 ELCD Daily Calibration. Inject duplicate samples from the
mid-level ELCD calibration gas (Section 3.2.2.4.2) as described 1n
Section 5.1.2 and calculate the average daily response factor DRtn.
E-14
-------
The system operation is adequate if the DRth is within 10 percent of
the R0h calculated during the initial performance test (Section 5.1.2).
Use the DRth for calculation of chlorine in the samples.
5.3 Analytical Balance. Calibrate against standard weights.
6.0 Calculations
6.1 Nomenclature.
Ab = Area under the water blank response curve, counts.
As = Area under the sample response curve, counts.
C = Concentration of volatile organlcs 1n the sample, ppmw.
Cc = Concentration of FID calibration gas, ppmv.
Ch = Concentration of ELCD calibration gas, ppmv.
DRt = Average daily response factor of the FID, fig C/counts.
DRth " Average daily response factor of the ELCD, fig Cl-/counts.
mco = Mass of carbon, as methane, in the FID calibration
standard, fig.
mch = Mass of chloride 1n the ELCD calibration standard, fig.
ms = Mass of the waste sample, g.
msc = Mass of carbon, as methane, in the sample, fig.
msf = Mass of sample container and waste sample, g.
msh - Mass of chloride 1n the sample, fig.
mst = Mass of sample container prior to sampling, g.
myo = Mass of volatile organics in the sample, fig.
Pa = Ambient barometric pressure in the laboratory, Torr.
Qc = Flowrate of calibration gas, l/m1n.
tc = Length of time standard gas is delivered to the analyzer,
m1n.
Ta = Ambient temperature in the laboratory, °K.
£-15
-------
6.2 Mass of Carbon, as Methane, in the FID Calibration Gas.
mco = k2 Cc tc Qc (Pa/Ta) Eq. 1
where k2 = 0.7694 x 10-3 0g C-°K/ PPMV-Torr
6.3 Mass of Chloride in the ELCD Calibration Gas.
mch = k3 Ch tc Qc (Pa/Ta) Eq. 2
where k3 = 1.1371 x 10-3 /jg C1-°K/ PPMV-Torr
6.4 FID Response Factor.
Rt * mco/A Eq>3
6.5 ELCD Response Factor.
Eq> 4
6.6 Mass of Carbon, as Methane, in the Sample.
msc = DRt (As - Ab) Eq> 5
6.7 Mass of Chloride in the Sample.
")sh = DRth (As - Ab) Eq. 6
6.8 Mass of Volatile Organics in the Sample.
m * msc + msh Eq. 7
6.9 Relative Standard Deviation.
n
RSD = -100/x [E-(xi-x)2/(n-l)]l/2 Eq. 8
E-16
-------
6.10 Mass of Sample.
ms = msf - mst Eq. 9
6.11 Concentration of Volatile Qrganics in Waste.
C = mvo/ms Eq>10
METHOD 25E—DETERMINATION OF VAPOR PHASE ORGANIC CONCENTRATION
IN WASTE SAMPLES
Introduction
Performance of this method should not be attempted by persons
unfamiliar with the operation of a flame ionlzatlon detector (FID) nor
by those who are unfamiliar with source sampling because knowledge
beyond the scope of this presentation is required.
1. Applicability and Principle
1.1 Applicability. This method is applicable for determining the
vapor pressure of waste samples from treatment, storage, and disposal
facilities (TSDF).
1.2 Principle. A waste sample 1s collected from a source just
prior to entering a tank. The headspace vapor of the sample is
analyzed for carbon content by a headspace analyzer, which uses an FID.
2. Interferences
2.1 The analyst shall select the operating parameters best suited
to his requirements for a particular analysis. The analyst shall
produce confirming data through an adequate supplemental analytical
technique and have the data available for review by the Administrator.
3. Apparatus
3.1 Sampling. The following equipment is required:
E-17
-------
3.1.1 Sample Containers. Vials, glass, with butyl rubber septa,
Perkin-Elmer Corporation Numbers 0105-0129 (glass vials), B001-0728
(gray butyl rubber septum, plug style), 0105-0131 (butyl rubber septa),
or equivalent. The seal shall be made from butyl rubber. Silicone
rubber seals are not acceptable.
3.1.2 Vial Sealer. Perkin-Elmer Number 105-0106, or equivalent.
3.1.3 Gas-Tight Syringe. Perkin-Elmer Number 00230117, or
equivalent, pipe:
3.1.4.1 Static mixer. In-line or by-pass loop, sized so that the
drop size of the dispersed phase is no greater than 1000 pm. If the
mixer is installed as a by-pass loop, the entire waste stream shall be
diverted through the mixer.
3.1.4.2 Tap.
3.1.4.3 Tubing. Teflon, 0.25-in. ID. Note: Mention of trade
names or specific products does not constitute endorsement by the
Environmental Protection Agency.
3.1.4.4 Cooling Coll. Stainless steel (304), 0.25 1n.-ID,
equipped with a thermocouple at the coil outlet.
3.2 Analysis. The following equipment 1s required:
3.2.1 Balanced Pressure Headspace Sampler. Perkln-Elmer HS-6, HS-
100, or equivalent, equipped with a glass bead column instead of a
chromatographic column.
3.2.2 FID. An FID meeting the following specifications is
required:
3.2.2.1 Linearity. A linear response (±5 percent) over the
operating range as demonstrated by the procedures established 1n
Section 6.1.2.
E-18
-------
3.2.2.2 Range. A full scale range of 1 to 10,000 ppm CH4. Signal
attenuators shall be available to produce a minimum signal response of
10 percent of full scale.
3.2.3 Data Recording System. Analog strip chart recorder or
digital integration system compatible with the FID for permanently
recording the output of the detector.
3.2.4 Thermometer. Capable of reading temperatures in the range
of 30° to 60eC with an accuracy of ±0.1°C.
4. Reagents
4.1 Analysis. The following items are required for analysis:
4.1.1 Hydrogen (H2). Zero grade.
4.1.2 Carrier Gas. Zero grade nitrogen, containing less than l"
ppm carbon (C) and less than 1 ppm carbon dioxide.
4.1.3 Combustion Gas. Zero grade air or oxygen as required by the
FID.
4.2 Calibration and Linearity Check.
4.2.1 Stock Cylinder Gas Standard. 100 percent propane. The
manufacturer shall: (a) certify the gas composition to be accurate to
±3 percent or better (see Section 4.2.1.1); (b) recommend a maximum
shelf life over which the gas concentration does not change by greater
than ±5 percent from the certified value; and (c) affix the date of gas
cylinder preparation, certified propane concentration, and recommended
maximum shelf life to the cylinder before shipment to the buyer.
4.2.1.1 Cylinder Standards Certification. The manufacturer shall
certify the concentration of the calibration gas 1n the cylinder by (a)
directly analyzing the cylinder and (b) calibrating his analytical
E-19
-------
procedure on the day of cylinder analysis. To calibrate his analytical
procedure, the manufacturer shall use, as a minimum, a three-point
calibration curve.
4.2.1.2 Verification of Manufacturer's Calibration Standards.
Before using, the manufacturer shall verify each calibration standard
by (a) comparing it to gas mixtures prepared in accordance with the
procedure described in Section 7.1 of Method 106 of Part 61, Appendix
B, or by (b) calibrating it against Standard Reference Materials
(SRM's) prepared by the National Bureau of Standards, if such SRM's are
available. The agreement between the initially determined
concentration value and the verification concentration value shall be
within ±5 percent. The manufacturer shall reverlfy all calibration "
standards on a time interval consistent with the shelf life of the
cylinder standards sold.
5. Procedure
5.1 Sampling.
5.1.1 Sampling Plan Design and Development. Use the procedures 1n
chapter nine of the Office of Solid Waste's publication, Test Methods
for Evaluating Solid Waste, third edition (SW-846), as guidance 1n
developing a sampling plan.
5.1.2 Sample according to the procedures in chapter nine of SW-
846, or, if sampling from an enclosed pipe, sample according to the
procedures described below.
5.1.2.1 The sampling apparatus designed to sample from an enclosed
pipe is shown In Figure 1, and consists of an 1n-l1ne static mixer, a
tap, a cooling coil Immersed 1n an 1ce bath, a flexible Teflon tube
connected to the outlet of the cooling coll, and a sample container.
£-20
-------
STATIC IN-LINE MIXER —
OPTIONAL PUMP
REDUCER (;" TUBE FITTING)
TEFLON OR S'AINLESS r
ICE BATH
SAMPLE CONTAINER
Figure I. Schematic of sampler equipped with
static mixer and cooling coil.
E-21
-------
Locate the tap within two pipe diameters of the static mixer outlet.
Install the static mixer in the process line or in a by-pass line.
5.1.2.2 Begin sampling by purging the sample lines and cooling
coil with at least four volumes of waste. Collect the purged material
in a separate container. Consider the purged material hazardous waste
and dispose of it properly.
5.1.2.3 After purging, stop the sample flow and transfer the
Teflon sampling tube to a sample container. Sample at a flow rate such
that the temperature of the waste is <108C «50°F). Fill the sample
container halfway (±5 percent) and cap it within 5 seconds.
5.1.2.4 Store the collected samples in 1ce or a refrigerator until
analysis.
5.1.2.5 Alternative sampling techniques may be used upon the
approval of the Administrator.
5.2 Analysis.
5.2.1 Allow one hour for the headspace vials to equilibrate at the
temperature specified 1n the regulation. Allow the FID to warm up
until a 5.2.2 Check the calibration of the FID dally using the
procedures 1n Section 6.1.2.
5.2.3 Follow the manufacturer's recommended procedures for the
normal operation of the headspace sampler and FID.
5.2.4 Use the procedures 1n Sections 7.4 and 7.5 to calculate the
vapor phase organic vapor pressure 1n the samples.
5.2.5 Monitor the output of the detector to make certain that the
results are being properly recorded.
E-22
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6. Operational Checks and Calibration.
Maintain a record of performance of each item.
6.1 Use the procedures in Sections 6.1.1 to calibrate the
headspace analyzer and FID and check for linearity before the system is
first placed in operation, after any shutdown longer than 6 months, and
after any modification of the system.
6.1.1 Calibration and Linearity. Use the procedures in Section
6.2.1 of Method 18 of Part 60, Appendix At to prepare the standards and
calibrate the flowmeters, using propane as the standard gas. Fin the
calibration standard vials halfway (±5 percent) with deionized water.
Purge and fill the airspace calibration standards in triplicate at
concentrations that will bracket the applicable cutoff. For a cutoff
of 5.2 kPa (0.75 psi), prepare nominal concentrations of 30,000,
50,000, and 70,000 ppm as propane. For a cutoff of 27.6 kPa (4.0 psi),
prepare nominal concentrations of 200,000, 300,000, and 400,000 ppra as
propane.
6.1.1.1 Use the procedures in Section 5.2.3 to measure the FID
response of each standard. Use a linear regression analysis to
calculate the values for the slope (k) and the y-1ntercept (b). Use
the procedures in Sections 7.2 and 7.3 to test the calibration and the
linearity.
6.1.2 Dally FID Calibration Check. Check the calibration at the
beginning and at the end of the dally runs by using the following
procedures. Prepare two calibration standards at the nominal cutoff
concentration using the procedures in Section 6.1.1. Place one at the
beginning and one at the end of the dally run. Measure the FID
E-23
-------
response of the daily calibration standard and use the values for k ana
b from the most recent calibration to calculate the concentration of
the daily standard. Use an equation similar to 251-2 to calculate the
percent difference between the daily standard and Cs. If the
difference is within 5 percent, then the previous values for k and b
may be used. Otherwise, use the procedures in Section 6.1.1 to
recalibrate the FID.
7. Calculations
7.1 Nomenclature.
A = Measurement of the area under the response curve, counts.
b = y-intercept of the linear regression line.
Ca = Measured vapor phase organic concentration of sample, ppm as
propane.
Cma = Average measured vapor phase organic concentration of
standard, ppm as propane.
Cm = Measured vapor phase organic concentration of standard,
ppm as propane.
Cs = Calculated standard concentration, ppm as propane.
k = Slope of the linear regression line.
Pbar - Atmospheric pressure at analysis conditions, mm Hg (1n.
Hg).
P* = Organic vapor pressure 1n the sample, kPa (psi).
P = 1.333 X 10-7 kPa/[(mm Hg)(ppm)], (4.91 X 10-7 psi/[(1n.
Hg)(ppm)])
7.2 Linearity. Use the following equation to calculate the measured
standard concentration for each standard vial.
E-24
-------
Cm = k A + b Eq< 25E_1
7.2.1 Calculate the average measured standard concentration (Cma) for
each set of triplicate standards and use the following equation to
calculate the percent difference between Cma and Cs.
Cc - C
Percent Difference = — x 100 Eq. 25E-2
cs
The instrument linearity is acceptable if the percent difference is within
five for each standard.
7.3. Relative Standard Deviation (RSD). Use the following equation
to calculate the RSD for each triplicate set of standards.
100 E (Cm - Cma)2
RSD - . Eq> 25E_3
cma n-1
The calibration is acceptable if the RSD 1s within five for each standard
concentration.
7.4 Concentration of organics in the headspace. Use the following
equation to calculate the concentration of vapor phase organics in each
sample.
Ca = k A + b Eq. 25E-4
E-25
-------
7.5 Vapor Pressure of Organics in the Headspace Sample. Use the
following equation to calculate the vapor pressure of organics in the
sample.
P* = p Pbar Ca Eq< 25E-5
E-26
-------
APPENDIX F
EXAMPLE FACILITY ANALYSIS
-------
APPENDIX F
EXAMPLE FACILITY ANALYSIS
F.I INTRODUCTION
The purpose of this document is to provide technical information to
States on best available control technology (BACT) and lowest achievable
emission rate (LAER) determinations for controlling emissions of VOC from
industrial wastewaters. Steam stripping is an effective control technology,
however, other controls which achieve the same performance can be applied. To
determine which wastewater streams should be controlled, the impacts of
applying various control options to a set of example facilities that collect
and treat industrial wastewater were evaluated.
The purpose of this Appendix is to present the background information to
support the development of a set of example facilities. Section F.2 presents
a description of the example facilities, and Section F.3 presents the method
used to predict the VOC emissions from these facilities. The methods used to
predict steam stripper removal and test method concentration are presented in
Sections F.4 and F.5, respectively. Section F.6 presents a brief discussion
on hazardous air pollutants.
F.2 OVERVIEW OF EXAMPLE FACILITIES
The example facilities were developed from responses to questionnaires
sent out by the Office of Air Quality Planning and Standards (OAQPS) in the
Organic Chemicals, Plastics, and Synthetic Fibers (OCPSF) industry under the
authority of Section 114 of the Clean Air Act. This information was
supplemented with information gathered by the Office of Water Regulations and
Standards (OWRS) under Section 308 of the Clean Water Act and with information
collected by OAQPS during site visits.
Six example facilities were developed from this information. These
facilities are examples of wastewater collection and treatment systems found
in the targeted industries discussed in Chapter 2 of this document. Tables
F-l through F-6 present the characteristics of the individual wastewater
streams for each of these example facilities. Figures F-l through F-6 show
the treatment and collection system configurations for each example facility.
F-l
-------
TABLE F-l. EXAMPLE FACILITY I WASTEWATER STREAM CHARACTERISTICS
Stream Flow
ID (1pm)
1 28
2 568
3 568
4 118
101
6 909
7 663
8 568
9 1,278
4,800
Organic
Concentration
(mg/1 )
11,995.0
1,250.0
9,935.0
6,520.0
12,000.0
364.0
414.0
59.0
191.0
VOC Test
Uncontrolled Controlled VOC
Method Fraction
Concentration Emitted
(mg/1 ) (wt%)
1,740.1
1,289.0
10,325.8
6,727.9
5,280.0
443.3
526.1
71.1
87.5
18.26
75.10
39.61
63.59
11.52
45.53
45.11
61.18
16.35
VOC
Emissions
(Mg/yr)
32.69
280.22
1174.73
257.81
73.26
79.16
68.7956
10.77
20.98
1,998
VOC Emission
Emissions Reduction
(Mg/yr) (Mg/yr)
27.90
0.04
0.17
0.04
46.09
0.01
0.00
0.04
13.62
88
4.7876
280.1816
1174.5520
257.7653
27.1710
79.1460
68.7956
10.7364
7.3538
1,910
VOC
Emission
Reduction
(wt%)
14 64
99.99
99.99
99.98
37.09
99.99
100.00
99.65
35.06
76
-------
TABLE F-2. EXAMPLE FACILITY 2 WASTEWATER STREAM CHARACTERISTICS
Stream
ID
1
2
3
4
5
6
Flow
(1pm)
0.08
0.003
0.002
0.003
0.10
0.004
Organic
Concentration
(mg/1 )
5.0
8.4
0.4
25.7
0.5
0.9
VOC Test
Method
Concentration
(mg/D
6.1
0.6
0.5
31.3
0.6
1.1
Uncontrolled
Fraction
Emitted
(wt%)
92.20
98.84
92.50
91.46
92.50
100.00
VOC
Emissions
(Mg/yr)
0.00
0.00
0.00
0.00
0.00
0.00
Controlled
VOC
Emissions
(Mg/yr)
0.00
0.00
0.00
0.00
0.00
0.00
VOC
Emission
Reduction
(Mg/yr)
0.0002
0.0000
0.0000
0.0000
0.0000
0.0000
VOC
Emission
Reduction
(wt%)
106.91
1.22
106.60
107.25
106.48
92.02
87
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TABLE F-3. EXAMPLE FACILITY 3 WASTEWATER STREAM CHARACTERISTICS
Stream
ID
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Flow
(1pm)
47
45
6
31
710
454
38
950
685
1,022
449
175
568
16
Organic
Concentration
(mg/i)
700.0
1.0
460.0
1,460.0
101.0
80.0
300.0
1,500.4
49.0
10,207.5
1,005.0
611.0
222.7
361.0
VOC Test
Method
Concentration
(mg/i )
854.0
1.2
563.8
1,655.8
123.2
97.4
315.0
1,067.1
51.0
10,616.2
1,046.5
744.9
269.0
376.3
Uncontrolled Controlled VOC
Fraction
Emitted
(wt%)
56.93
96.67
45.41
63.55
41.78
41.85
51.46
1.90
65.26
38.68
41.63
53.48
54.77
42.63
VOC
Emissions
(Mg/yr)
9.91
0.02
0.62
14.98
15.75
7.99
3.07
14.20
11.52
2121.17
98.65
30.07
36.40
1.31
VOC Emission
Emissions Reduction
(Mg/yr)
0.00
0.00
0.00
0.00
0.00
0.00
0.00
8.53
0.00
0.31
0.01
0.00
0.01
0.00
(Mg/yr)
9.9111
0.0228
0.6234
14.9826
15.7430
7.9935
3.0714
5.6713
11.5164
2120.8610
98.6400
30.0672
36.3992
1.3114
VOC
Emission
Reduction
(wt%)
99.99
99.99
99.99
99.99
99.99
99.99
99.99
39.93
99.99
99.99
99.99
99.99
99.99
99.99
5,196
2,366
2,357
96
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TABLE F-4. EXAMPLE FACILITY 4 WASTEWATER STREAM CHARACTERISTICS
Stream
ID
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Flow
(1pm)
76
466
5,300
303
719
630
0
95
176
650
60
9
10
5
6
8,503
Organic
Concentration
(mg/1 )
800.0
170.0
60.0
60.0
60.0
55.0
250.0
1,220.0
840.0
1,260.0
110.0
1,100.0
200.0
60.0
800.0
VOC Test
Method
Concentrat
(mg/1)
976.0
151.3
50.4
50.4
50.4
38.5
192.5
1,085.8
722.4
970.2
77.7
790.0
158.0
51.0
648.0
Uncontrolled Controlled
Fraction
ion Emitted
(wt%)
61.82
26.30
31.14
30.56
32.40
33.21
35.29
29.97
36.07
20.46
32.73
47.90
34.36
37.41
32.16
VOC
Emissions
(Mg/yr)
19.68
10.94
52.05
2.92
7.35
6.05
0.01
18.19
28.03
88.05
1.13
2.36
0.36
0.06
0.77
238
VOC
Emissions
(Mg/yr)
0.00
5.02
15.08
0.85
2.13
1.70
0.00
8.34
4.05
52.49
0.30
0.06
0.04
0.04
0.16
90
VOC
Emission
Reduction
(Mg/yr)
19.6800
5.9227
36.9689
2.0737
5.2207
4.3467
0.0071
9.8446
23.9789
35.5582
0.8266
2.2985
0.3166
0.0125
0.6080
148
VOC
Emission
Reduction
(wt%)
99.99
54.13
71.03
71.03
71.03
71.90
86.93
54.13
85.55
40.38
73.26
97.43
87.93
21.78
79.16
71
-------
TABLE F-5. EXAMPLE FACILITY 5 WASTEWATER STREAM CHARACTERISTICS
cr>
Stream
ID
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Flow
(1pm)
9
9
47
47
41
11
70
11
82
607
1
1
16
6
Organic
Concentration
(mg/l)
4,000.0
1,100.0
10,000.0
20,000.0
15,000.0
234.0
60,000.0
242.0
7,100.0
58.0
22,000.0
10,000.0
5,000.0
5,000.0
VOC Test
Method
Concentration
(mg/1 )
52.0
14.3
130.0
18,800.0
13,050.0
203.6
39,510.0
159.2
7,636.0
47.7
19,320.0
7,700.0
4,350.0
3,950.0
I
Fraction
Emitted
(wt%)
17.89
17.89
17.89
75.22
14.34
14.34
19.48
19.39
50.51
35.63
54.53
2.80
19.42
21.54
Jncontrolled
VOC
Emissions
(Mg/yr)
3.56
0.89
44.51
374.19
46.44
0.20
431.13
0.28
153.91
6.59
3.18
0.14
8.05
3.61
Controlled
VOC
Emissions
(Mg/yr)
2.97
0.74
37.08
0.06
13.53
0.06
185.42
0.12
18.95
5.17
1.16
0.08
1.19
0.44
VOC
Emission
Reduction
(Mg/yr)
0.5941
0.1481
7.4267
374.1323
32.9178
0.1420
245.7092
0.1596
134.9550
1.4178
2.0254
0.0562
6.8571
3.1731
VOC
Emission
Reduction
(wt%)
16.69
16.69
16.69
99.99
70.88
70.88
56.99
56.94
87.69
21.52
63.63
40.38
85.19
87.93
959
1,077
267
810
57
-------
TABLE F-6. EXAMPLE FACILITY 6 WASTEWATER STREAM CHARACTERISTICS
Stream
ID
1
2
3
4
Flow
(1pm)
114
189
423
151
Organic
Concentration
(mg/1)
1,352.0
3,258.0
20.9
1,268.0
VOC Test
Method
Concentration
(mg/1)
1,124.2
2,574.0
17.0
1,065.1
Uncontrolled
Fraction
Emitted
(wt%)
95.89
75.34
85.34
100.00
VOC
Emissions
(Mg/yr)
77.39
244.22
3.97
100.93
Controlled
VOC
Emissions
(Mg/yr)
1.16
21.38
0.19
0.01
VOC
Emission
Reduction
(Mg/yr)
76.2347
222.8404
3.7741
100.9139
VOC
Emission
Reduction
(wt%)
98.51
91.25
95.09
99.99
878
427
23
404
96
-------
Process
Figure F-1. Example Facility One.
Treatment Configuration and Collection System.
00
-------
Process A 1
Process B 2
Process C 3
ProcessD 4
Process E 5
Process F
Non-Aerated
Equalization
Basin
Figure F-2. Example Facility Two.
Treatment Configuration and Collection System.
-------
Process A 1
Process G 8
Process H 9
Process I 10
Process J
Process K 12
Process L 13
Figure F-3. Example Facility Three.
Treatment Configuration and Collection System.
-------
Process
Figure F-4. Example Facility Four.
Treatment Configuration and Collection System.
-------
Process
Non-areated
Biotreatment
Basin
Figure F-5. Example Facility Five.
Treatment Configuration and Collection System.
in
«*
r»
oo
-------
Process A 1
Process B 2
Process C 3
Process D 4
Trench
Sump I I^Manhote) »^Manhote) l^^ManhoW.
Sump
^Manhole
Junction
Box
Equalization
Basin
\
I
Treatment
Tank
Aeration
Basin
Figure F-6. Example Facility Six.
Treatment Configuration and Collection System.
r-
r-
00
-------
F.3 EMISSIONS ESTIMATES
For each of the wastewater streams in the example facilities presented in
the previous section, an estimate of the uncontrolled VOC emissions was
developed. This section describes the development of these VOC emission
estimates.
Estimated VOC emissions are a function of the configuration of the
example facilities and of the properties of the specific organic compounds
present in the wastewater streams. The fraction emitted (fe) for each
compound within a wastewater stream is an estimate of the fraction of that
compound that would be emitted from the wastewater stream during collection
and treatment and is dependent on the Henry's Law Constant for that compound.
In Chapter 3, fe was developed for five compounds that represent a range of
volatility using several collection and treatment system configurations. The
five compounds in order of increasing volatility were: 1) Phenol; 2)
1-Butanol; 3) Naphthalene; 4) Toluene; and 5) 1,3-Butadiene. Appendix A
presents detailed calculations of fe for these five compounds for various
collection and treatment configuration systems.
Correlations of fe as a function of Henry's Law constant were developed
from the five compounds for each type of wastewater emission source. This was
done for each collection and treatment source by constructing a plot of fe
versus the Henry's Law constant for the five pollutants. These data were then
fitted to a curve. The least-square curve fitting method was applied to all
of the data and the best curve was chosen based on an optimum fit of R2 = 1.0.
(R2 is a statistical measure of reliability of the relationship between the
fraction emitted and Henry's Law constant values.) Table F-7 presents a
summary of the results for these regressions, by collection and treatment
source. (Weirs were not included in any of the example facility schematics.)
Because these equations approximate fe, very high H values may result in fe
values greater than 1. In addition, very low H values may result in fe values
less than 0. When this occurs, fe is set to 1 for values greater than 1, and
fe is set to 0 for values less than 0.
As a compound flows through the treatment scheme, a fraction of the
compound is emitted into the surrounding air. The fraction of the compound
entering the first source in the treatment scheme is 1.0. Some portion (fex)
of this initial quantity is emitted from this first source in the
F-14
-------
TABLE F-7. SUMMARY OF RESULTS-LEAST SQUARE FIT FOR
fe VS. HENRY'S LAW CONSTANT
Source
Least Square Fit
Drain
Manhole
Junction Box
Sump
Trench
Lift Station
Oil-Water Separator
Equalization Basin -
aerated
Equalization Basin -
fe = 0.0100 + 3.973 * (H)
fe = 0.0003814 + 1.04 * (H)
fe = 1.658 * (HJ0.592
fe = 0.007384 + 0.0004385 * In (H)
fe = 0.06595 + 0.005006 * In (H)
fe = 6.0118 * (H)0.6421
fe = 21.4034 * (H)0.8797
fe = 1.345 + 0.06927 * In (H)
0.997
1.000
0.902
0.876
0.937
0.910
0.968
0.757
non-aerated
Clarifier
Treatment Tank
Biobasin
Biobasin
Weir
(aerated)
(non-aerated)
fe = 0.5752 + 0.0331 * In (H)
fe = 0.03759 + 0.002351 * In (H)
fe = 0.01374 + 0.0008558 In (H)
fe = 1.001 - 1.0028 * Fbioa
fe = 0.7489 - 0.7883 * Fbion
fe = 422.8 * (Dw, i)0.6373
0.844
0.890
0.889
1.000
0.940
1.000
fe = fraction VOC emitted
H = Henry's Law Constant, atm . m3/moL
R2 = measure of the reliability of the relationship between the fe and H
values. The optimum value for R2 is 1.
F-15
-------
collection/treatment scheme and the fraction pass through (fp^l-fej enters
the next source. This fraction pass through is multiplied by the fe from the
second source (fe2) to get the adjusted fraction emitted, Afe. The pass
through of this second source is (fp2) and is equal to (fpx - (fe2 x fpj).
Each source is treated in this manner until the compound reaches the point of
discharge and becomes the effluent. The total or overall fraction emitted is
the sum of Afe for each source.
There are two exceptions to this approach. If the source is an aerated
or non-aerated biobasin, the biodegradation is assumed to be acting on each
pollutant in the wastewater. If it is an oil-water separator, a fraction of
each pollutant partitions in the oil layer on top of the wastewater and is
removed in the recovered oil.
The degree of biodegradation for each pollutant was estimated using the
draft CHEMDAT.7 program (developed by OAQPS1). The program was run for 8
different compounds representing 8 surrogate categories for both aerated and
non-aerated biobasins. These categories were created for groupings of
pollutant biorate and Henry's Law constant. The eight categories are: 1) High
Henry's Law Constant, high biorate (HHHB); 2} High Henry's Law Constant,
medium biorate (HHMB); 3) High Henry's Law Constant, low biorate (HHLB); 4)
Medium Henry's Law Constant, high biorate (MHHB); 5) Medium Henry's Law
Constant, medium biorate (MHMB); 6) Medium Henry's Law Constant, low biorate
(MHLB); 7) Low Henry's Law constant, high biorate (LHHB); and 8) Low Henry's
Law Constant, medium and low biorate (LHMB, LHLB). Table F-8 presents a
summary of the surrogate categories and their corresponding fraction
biodegraded. The ranges of Henry's Law Constant and biorate are also included
for each surrogate category.
To compute the fraction pass-thru from an impoundment with
biodegradation, an adjusted fraction emitted (Afe) and an adjusted fraction
biodegraded (Afb) are calculated:
Adjusted fe (Afe) = fecomponent i x pass-thru from previous source
Adjusted fb (Afb) = fbcomponent , x pass-thru from previous source
The fraction pass-thru from the biobasin is then calculated by subtracting the
Afe and Afb from the influent pass-thru.
The amount of pollutant partitioning into the oil phase in an oil water
separator was estimated using the octanol-water partition coefficient (Kow).
F-16
-------
TABLE F-8. SUMMARY OF SURROGATE CATEGORIES
Surrogate Category
Fraction
Biodegradated (fb)
aerated non-aerated
High Henry's Law Constant, high biorate (HHHB)
High Henry's Law Constant, medium biorate (HHMB)
High Henry's Law Constant, low biorate (HHLB)
Medium Henry's Law Constant, high biorate (MHHB)
Medium Henry's Law Constant, medium biorate (MHMB)
Medium Henry's Law Constant, low biorate (MHLB)
Low Henry's Law Constant, high biorate (LHHB)
Low Henry's Law Constant, medium and
low biorate (LHMB, LHLB)
0.747
0.814
0.638
0.966
0.975
0.980
0.998
0.998
0.812
0.519
0.071
0.824
0.793
0.092
0.950
0.745
High Henry's Law Constant > 10"3, atm m3/moL
Medium Henry's Law Constant 10"3 to 10"5, atm m3/moL
Low Henry's Law Constant <10"5, atm m3/moL
High Biorate >10, mg vo/g biomass/hr
Medium Biorate 1 to 10 mg vo/g biomass/hr
Low Biorate <1, mg vo/g biomass/hr
F-17
-------
Kov is the solubility in oil divided by the solubility in water. This
coefficient is estimated by the following equation:
Kow = EXP (7.494 - ln[Cs]) Ref.3
where: Cs - solubility in water - vapor pressure (mmHg)
760 * H (atm m3/moL)
To determine the fraction removed in the oil-water separator the water in
the oil-water separator was assumed to contain 1000 ppm oil. Therefore, the
mass fraction of each organic compound in the oil is:
x011 = 1 - [0.999/(0.999 + 0.001 K0JJ
A more detailed description of this procedure is provided in "Distribution of
VOC's in the Oil and Water Phases Using the Octanol-Water Coefficient", dated
May 23, 1988.2
The fraction of VOC removed from the oil-water separator was assumed to
be 80 percent of the VOC that partitioned into the oil phase.3 The fraction
VOC pass-thru from the oil water separator is the fraction pass-thru from the
previous source, minus the adjusted fraction emitted from the oil water
separator, minus the adjusted fraction VOC removed.
A sample calculation for Example Facility 1, Stream 1, is presented in
Table F-9. (Figure F-l presents the stream schematics for this facility.)
F.4 STEAM STRIPPER VOC REMOVAL
This section discusses the method used to predict VOC removal, and the
associated emission reduction, through application of a steam stripper. The
design of this steam stripper is presented in Chapter 4, and the
associated control costs are shown in Chapter 6 of the attached document.
Removals of individual compounds were predicted using Advanced Systems for
Process Engineering (ASPEN), a computer software program.
Table F-10 presents the steam stripper removal efficiencies predicted by
ASPEN for five compounds. From these data, an equation relating predicted
removals to the compound's Henry's Law constant at 25"C was developed. This
equation is also presented in Table F-10. Figure F-7 presents this
relationship graphically.
F-18
-------
TABLE F-9. UNCONTROLLED EMISSIONS - SAMPLE CALCULATION
EXAMPLE FACILITY: 1
STREAM: 1
FLOW RATE: 28.4 1pm
ORGANIC CONCENTRATION: 245 mg/1 Ethylene oxide
2180 mg/1 Acetaldehyde
9570 mg/1 Ethylene glycol
Nomenclature
fe - mass fraction of VOC emitted
H - Henry's Law Constant, atm m3/moL (T = 25°C)
fbion - mass fraction biodegraded in a non-aerated biobasin
fbioa - mass fraction biodegraded in an aerated biobasin
Afe - adjusted mass fraction of VOC emitted
fp - mass fraction of VOC pass through to next collection or treatment
configuration
fb - adjusted mass fraction biodegraded in aerated or non-aerated biobasins
Cfe - cumulative mass fraction of VOC emitted
E - VOC emissions, Mg/yr
flow - flow rate of the stream, 1/hr
cone - concentration of individual organic compound, mg/1
Properties Ethvlene oxide Acetaldehyde Ethvlene olvcol
H (atm-m3/mol) 1.42E-04 9.50E-05 1.03E-07
fbioa 0.966 0.966 0.998
F-19
-------
TABLE F-9. (Continued)
A- Fraction Emitted by Component
Drain = 0.0100 + 3.973 * (H)
Sump = 0.007384 + 0.0004385 * ln(H)
Manhole = 0.0003814 + 1.04 * (H)
Nonaerated Equalization Basin =
0.5752 + 0.0331 * ln(H)
Aerated Biobasin =
1.001 - 1.0028 (fbioa) 0.0323
Clarifier = 0.03759 + 0.002351 * ln(H) 0.0168
B. Adjusted fraction emitted, (Afe)
fe
Ethvlene oxide Acetaldehvde Ethvlene
0.0106
0.0350
0.000529
0.282
= fpl.1 * fea
fPi = fi-i * Afe, - fr - fb
fbi = (fbion or fbioaKfp,-!)
0.0104
0.0332
0.000480
0.269
0.0323
0.0158
fp«, = 1.0
0.0100
0.0329
0.000382
0.0427
0.000206
-0
F-20
-------
TABLE F-9. (Continued)
ETHYLENE OXIDE
Component
Drain
Drain
Sump
Manhole
Manhole
Nonaerated
Equalization Basin
Nonaerated
Equalization Basin
Aerated Biobasin
Clarifier
Clarifier
fe
0.0106
0.0106
0.0350
0.000529
0.000529
0.282
0.282
0.0323
0.0168
0.0168
Afe
0.0106
0.0105
0.00343
0.000516
0.000515
0.275
0.197
0.0162
1.32E-05
1.30E-05
ffi
0.989
0.979
0.975
0.975
0.974
0.700
0.502
7.85E-04
7.72E-04
7.59E-04
fb
—
—
—
—
—
—
—
0.485
—
F-21
-------
TABLE F-9. (Continued)
ACETALDEHYDE
Component
Drain
Drain
Sump
Manhole
Manhole
Nonaerated
Equalization Basin
Nonaerated
Equalization Basin
Aerated Biobasin
Clarifier
Clarifier
fe
0.0104
0.0104
0.00332
0.000480
0.000480
0.269
0.269
0.0323
0.0158
0.0158
Afe
0.0104
0.0103
0.00325
0.000469
0.000468
0.262
0.262
0.0168
1.44E-05
1.42E-05
ffi fb
0.990
0.979
0.976
0.976
0.975
0.713
0.521
9.14E-04 0.503
9.00E-04
8.85E-04
F-22
-------
TABLE F-9. (Continued)
ETHYLENE GLYCOL
Component
Drain
Drain
Sump
Manhole
Manhole
Nonaerated
Equalization Basis
Nonaerated
Equalization Basis
Aerated Biobasin
Clarifier
Clarifier
fe
0.0100
0.0100
0.000329
0.000382
0.000382
0.0427
0.0427
0.000206
- 0
- 0
Afe
0.0100
0.00990
0.000322
0.000374
0.000374
0.0418
0.0400
0.000185
- 0
- 0
fft
0.99
0.980
0.980
0.979
0.979
0.937
0.897
0.00182
0.00182
0.00182
fb
—
—
—
—
—
—
—
0.895
—
F-23
-------
TABLE F-9. (Continued)
D. Cumulative fraction emitted, CFE
n
Cfe = z AfBi
i = 1
n = number of VOC in the stream
Cfe
Component Ethylene oxide Acetaldehvde Ethvlene glvcol
Drain 0.0106 0.0104 0.0100
Drain 0.0211 0.0207 0.0199
Sump 0.0245 0.0240 0.0202
Manhole 0.0250 0.0244 0.0206
Manhole 0.0256 0.0249 0.0210
Nonaerated Equalization Basin 0.301 0.287 0.0628
Nonaerated Equalization Basin 0.498 0.479 0.103
Aerated Biobasin 0.514 0.496 0.103
Clarifier 0.514 0.496 0.103
Clarifier 0.514 0.496 0.103
F-24
-------
TABLE F-9. (Continued)
E (Uncontrolled Emissions in Mg/yr) = (fe * flow(l/hr)) * cone (mg/1)
* 8760 yr/hr * 10"9 Mg/mg
EEthyi«ne oxide = (0.514 * 28.4 1 pm * 60 min/hr ) * (245 mg/1)
* 8760 hr/yr * 10'9 Mg/mg = 1.88 Mg/yr
= (0.496 * 28.4 1pm * 60 min/hr ) * (2180 mg/1)
* 8760 hr/yr * 10'9 Mg/mg =16.1 Mg/yr
giycoi= (0.103 * 28.4 1pm * 60 min/hr ) * (9570 mg/1)
* 8760 hr/yr * 10"9 Mg/mg = 14.7 Mg/yr
Evoc = 32.7 Mg/yr
F-25
-------
The equation predicts that compounds with a Henry's Law constant greater than
or equal to 1.63 x 1CT2 removal isessentially 100 percent. This equation was
used to predict removals for all compounds in the example facility analysis.
The predicted removal efficiencies and uncontrolled emissions for the
individual compounds were used to calculate the emission reduction and cost
effectiveness associated with steam stripping each of the individual
wastewater streams. A sample calculation of emission reduction is presented
in Appendix A of the attached document.
F.5 TEST METHOD CONCENTRATION
In the example facility analysis, the VOC emissions (controlled and
uncontrolled), the VOC emission reduction, and the cost effectiveness of
control were calculated based on the actual organics present in the wastewater
and the predicted fraction which would be emitted. However, the decision as
to whether a stream should be controlled is based on the volatile organics
measured using a test method. EPA has developed a draft test method to
measure volatile organics known as Method 25D (see Appendix E). Test method
procedures and operating parameters were chosen such that the test method
detects the volatile organics that are expected to be emitted. The test
method procedure calls for the analysis of the wastewater sample in a 50/50 by
volume polyethylene glycol (PEG) and water dispersion medium. This sample is
purged at a rate of 6 liters per minute for 30 minutes at 75 degrees Celsius.
The test method measures only carbons and halogens present in the
wastewater and adjusts this based on an average molecular weight. Carbons are
measured with a flame ionization detector (FID) and halogens (as chloride) are
measured with a Hall electrolytic conductivity detector (HECD).
The Emissions Measurement Branch (EMB) has tested several compounds and
percent recoveries, or the fraction measured by the method. Due to the
limited number of pollutant results available, however, a theoretical
estimation method was developed in order to estimate the percent recovery for
the compounds in the example facility analysis. The theoretical method uses
the compound structure to predict response correction factors for the FID and
HECD and Henry's law constants in the PEG medium. From these estimates a
percent recovery is predicted.
Table F-ll presents a summary of the predicted percent recoveries used
for compounds contained in the example facility analysis.
F-26
-------
TABLE F-10. STEAM STRIPPER REMOVAL EFFICIENCIES PREDICTED BY ASPEN
Compound
1,3-Butadiene
Toluene
Naphthalene
1-Butanol
Phenol
Henry's Law
0.142
0.00668
0.00118
0.0000089
0.000000454
Removal Efficiency %
100
100
99.9
30.1
2.2
1.357 + 0.08677*ln (Henry's Law Constant, atm m3/mol), R2 = 0.887
F-27
-------
ORGANIC COMPOUND REMOVAL EFFICIENCY (%)
0)
_L
ID
O
w
o
o
_J_
3
w 3
• M
m
i
OT
-------
TABLE F-ll. PREDICTED TEST METHOD PERCENT RECOVERIES
USED IN THE EXAMPLE FACILITIES ANALYSIS
Pollutant Percent Recovery
1,3-Butadiene 119
1-Butanol 77
2,4-Dimethyl phenol 4.7
2,4-Dinitrophenol 1.4
Acenaphthene 123
Acetaldehyde 70
Acetone 89
Acetonitrile 74
Acrylonitrile 87
Aldicarb 2.2
Aniline 24.5
Benzene 122
Butyraldehyde 87
Carbon tetrachloride 103
Chloroaniline(p) 29
Chlorobenzene 116
Chloroethane 105
Chloroform 102.3
Chloronaphthalene(2) 120
Dibutyl phthalate 35.5
Dichlorobenzene(o) 113
Dichloroethane(l,2) 104
Dichloropropane(l,2) 106
Dichloropropylene 106
Diethyl ether 86
Dimethylamine 71
Di-n-octylphthalate 43
Ethyl benzene 120
Ethylene amines 71
F-29
-------
TABLE F-ll. (CONTINUED)
Pollutant Percent Recovery
Ethylene dichloride 104
Ethylene glycol 0.42
Ethylene glycol monoethyl ether 23
Ethylene oxide 71
Fluoranthene 69
Hexane 108
Isobutyl alcohol 85
Isopropanol 79
Isopropyl acetate 79
Isopropylether 94
Methanol 32
Methyl chloride 104
Methylene chloride 102
Methyl isobutyl ketone 95
Naphthalene 124
n-Butyl acetate 81
n-Butyl alcohol 77
n-Propyl acetate 77
Phenol 5.7
Propionaldehyde 72
Propylene glycol 1.3
Propylene oxide 84
Pyridine 72
Styrene 123
Tetrachloroethane(l,l,2,2) 101
Tetrachloroethylene 105
Toluene 121
Trichloroethane(l,l,l) 82
Trichloroethane(l,l,2) 97
Trichloroethylene 105
Vinylidene chloride 106
Xylene 121
F-30
-------
F.6 HAZARDOUS AIR POLLUTANTS
The primary focus in controlling VOC emissions is to reduce atmospheric
ozone concentrations. However, other environmental benefits may result from
the control of VOC. A large number of VOC are considered hazardous air
pollutants. Of the 191 hazardous air pollutants listed in the proposed 1990
Clean Air Act (CAA) amendment, 90 percent are VOCs. Hazardous VOC are widely
used in the industrial processes considered in this document. Seventy-nine
percent of the VOC loadings in the example facility analysis are hazardous air
pollutants. Therefore, reduction of VOC as illustrated with the addition of
steam strippers to the example facilities results in a significant reduction
of hazardous air pollutant emissions.
F-31
-------
F.6 HAZARDOUS AIR POLLUTANTS
The primary focus in controlling VOC emissions is to reduce atmospheric
ozone concentrations. However, other environmental benefits may result from
the control of VOC. A large number of VOC are considered hazardous air
pollutants. Of the 191 hazardous air pollutants listed in the proposed 1990
Clean Air Act (CAA) amendment, 90 percent are VOCs. Hazardous VOC are widely
used in the industrial processes considered in this document. Seventy-nine
percent of the VOC loadings in the example facility analysis are hazardous air
pollutants. Therefore, reduction of VOC as illustrated with the addition of
steam strippers to the example facilities results in a significant reduction
of hazardous air pollutant emissions.
F-31
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t. MIPORTNO.
EPA - 450/3-90-004
*. TITLI
TECHNICAL WOKT DATA
imm joMumtaan em eft* UMIM ov/br*«
a*tewaer V°lati1e
Compound Emissions—
n un m
Background Information for BACT/LAER Determinations
a. RlCIHtNT* ACCESSION NO.
I. Rt^ORT DATS
^January 1990
7. AUTHOftlS)
Jeffrey Elliott and Sheryl Watkins
8. HRFOHMING ORGANIZATION CODE
ToRGANlZATION REPORT MC
t. PERFORMING ORGANIZATION NAMI AND AOORfj
Radian Corporation
Post Office Box 13000
Research Triangle Park, North Carolina 27709
2. SPONSORING AGENCY MAMS AND ADDRESS—
Office of Air Quality Planning and Standards
u. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
15. SUPn.tMUNTA«Y NOTis"
IT NO.
68-02-4378
*. SPONSORING AGENCY CODE
agencie
on rnnt^Tl n nr
new an5 Sod ??Pd
Steam Jtr?ni^t
of PP
VOC
9Ulda?Ce Pr°Jects« such as this information document, focus on topics of
rftV™ identified throu9h contact with State and' Local
TC became inter«ted, in distributing information to States
industria1 ^astewaters. The technical document addres e,
sou^es, as defined in Parts C and D of the Clean Air Act (CAA)
Ve th€ Ot~9anic comP°unds ^ certain wastewater streams at the point
l° "nta^tin9.the atmosphere) is the recommended control strategy
* 3 descriPt1on of the sour«s of organic containing wastewfter,
tro 1 rJS" dures.for t^^"* and collection system units! and available
a^oHrt >S I strategies. In addition, secondary impacts and the control costs
associated with steam stripping are presented.
17.
KJV WOHOS AND QOCUMKNT ANALYSIS
DESCRIPTORS
Air Pollution
Pollution Control
Steam Stripping
Volatile Organic Compounds
BACT/LAER Guidance
Industrial Wastewater
.l01NTI»H*S/OftN
TgRMS
Air Pollution Control
Industrial Wastewater
COSATi Field/Croup
Release unlimited
18. SECURITY CLASS ^nUT*
unclassified
20. SSCURITY CLAM tTtUt p«n""
unclassified
21. NO. OF
350
22.
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