SEPA
United Stales
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 2771 1
EPA-eOO/7-78-224
November 1978
Control of Waste and
Water Pollution from
Coal-fired Power
Plants:
Second R&D Report
Interagency
Energy/Environment
R&D Program Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide-range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/7-78-224
November 1978
Control of Waste and Water
Pollution from
Coal-fired Power Plants:
Second R&D Report
by
P.P. Leo and J. Rossoff
The Aerospace Corporation
Environment and Energy Conservation Division
El Segundo, California 90245
Contract No. 68-02-1010
Program Element No. EHE624A
EPA Project Officer: Julian W. Jones
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
ABSTRACT
This is the second annual report of a series summarizing
and assessing the state of research and development in the fields of nonre-
generable flue gas cleaning waste treatment, utilization, and disposal,
as well as water reuse technology for coal-fired utility power plants. It is
based upon information available through November 1976.
Significant results cover the following areas: coal-pile
drainage, ash characterization and disposal, chemical and physical proper-
ties and leaching characteristics of treated and untreated wastes, field
evaluations of treated and untreated waste disposal, assessment of alterna-
tives for the disposal of scrubber wastes in coal mines and the ocean,
physical and chemical properties of gypsum produced from flue gas desul-
furization systems, cost estimates for producing and disposing of gypsum,
flue gas desulfurization potential use of wastes in fertilizer production, and
the economics of alumina production and total power plant water reuse.
Future reports that are to be issued annually will continue to
evaluate the progress of flue gas cleaning waste disposal and utilization
technology. Results not available, but to be included in subsequent reports,
will cover the areas of soil attenuation effects, and conceptualized design
cost analyses for various methods of flue gas cleaning waste disposal, gyp-
sum production, and marketing and assessment of processes for potential
use of wastes in portland cement manufacture and production of sulfur or
sulfuric acid.
ACKNOWLEDGMENTS
This report, prepared by The Aerospace
Corporation, is the result of a continuing cooperative effort of
many individuals and organizations, all of whom have made si§-
nificant contributions to the projects being reported. The au-
thors wish to acknowledge Julian W. Jones, U.S. Environmental
Protection Agency Project Officer, for his guidance and contin-
ued assistance in conducting this study and in providing timely
access to data necessary for the preparation of this report.
11
-------
CONTENTS
ABSTRACT ii
ACKNOWLEDGMENTS ii
FIGURES vii
TABLES rf
CONVERSION TABLE xv
I. INTRODUCTION 1
1. 1 Background 1
1.2 Scope 1
1.2.1 The EPA Program 2
1.2.2 Other Programs 3
1. 3 Technical Basis for This Report 3
II. CONCLUSIONS 11
2. 1 Background 11
2.2 Conclusions and Observations 11
III. RECOMMENDATIONS 15
3. 1 Background 15
3.2 Recommendations 15
IV. SUMMARY 17
4. 1 Approach 17
4.2 Effect of Process Variables 17
4. 3 Physical and Chemical Characteristics of Wastes 19
4. 3. 1 Physical Properties 19
4.3.2 Chemical Properties 23
iii
-------
CONTENTS (Continued;)
4.4 Disposal Economics 26
4.4. 1 Chemical Treatment and Disposal 26
4.4.2 Ponding 26
4.4. 3 Forced Oxidation to Gypsum. . . . k 26
4.4.4 Mine and Ocean Disposal 27
4.4. 5 Alumina Extraction 28
4. 5 Environmental Assessment 29
4. 5. 1 FGC Waste Properties 29
4. 5.2 -Waste Disposal and Dewatering Methods 30
4. 5. 3 Data Base Development 31
4. 6 Disposal and Utilization Alternatives 31
4. 6. 1 Disposal Alternatives 32
4. 6.2 Utilization Alternatives 33
4.7 Power Plant Water Recycle, Treatment, and Reuse ... 34
4.8 Full-Scale Applications 36
V. EPA-SPONSORED RESEARCH AND DEVELOPMENT 37
5. 1 Environmental Assessment of FGC Waste Disposal .... 37
5. 1. 1 FGC Waste Characterization> Disposal
Evaluation, and Transfer of Waste Disposal
Technology (The Aerospace Corporation) 38
5. 1. 2 Shawnee FGD Waste Disposal Field Evaluation
(TVA and The Aerospace Corporation) 85
5. 1. 3 Laboratory and Field Evaluation of FGC
Waste Treatment Processes (U.S. Army
Engineer WES) 97
5. 1.4 Characterization of Effluents from Coal-
Fired Plants (TVA) 127
5. 1. 5 Fly Ash Characterization and Disposal (TVA) . . 142
5. 1. 6 Studies of Attenuation of FGC Waste Leachate
by Soil (U. S. Army Development &
Readiness Command) 149
5. 1. 7 Compilation of Data Base for the Development
of Standards and Regulations Relating to
Land Disposal of FGC Sludge (SCS Engineers). . 163
iv
-------
CONTENTS (Continued)
5. 1.8 Environmental Effects and Control of
Various FGC Sludge Disposal Options
(SCS Engineers) 168
5.2 Process Technology Assessment and New
Technology Development 168
5. 2. 1 Evaluation of FGD Waste Disposal Options
(Louisville Gas and Electric) 168
5.2.2 FGD Waste Leachate-Liner Compatibility
Studies (U.S. Army Engineer WES) 176
5.2.3 Lime and Limestone Wet Scrubbing Waste
Characterization (TVA) 180
5.2.4 Dewatering Principles and Equipment Design
Studies (Auburn University) 200
5. 3 Process Economics Studies 202
5. 3. 1 Conceptual Design and Cost Studies of
Alternative Methods for Lime and Limestone
Scrubbing Waste Disposal (TVA) 202
5.3.2 Gypsum By-Product Marketing Studies (TVA) . . 202
5.4 Alternative FGC Waste Disposal Methods 203
5. 4. 1 Evaluation of Alternative FGC Waste
Disposal Sites (A. D. Little) 203
5. 5 New FGC Waste Utilization Methods 218
5. 5. 1 Lime and Limestone Scrubbing Waste
Conversion Pilot Studies (Pullman Kellogg) ... 218
5. 5. 2 Fertilizer Production Using Lime and
Limestone Scrubbing Wastes (TVA) 218
5. 5. 3 Utilization of Lime and Limestone Scrubbing
Waste in a New Extraction Process (TRW) .... 223
5. 6 Improvement of Overall Power Plant Waste Use 227
5. 6. 1 Water Recycle and Reuse Alternatives
in Coal-Fired Steam-Electric Power
Plants (Radian) 227
5. 6. 2 Treatment of FGC Waste Streams with Vapor
Compression Cycle Evaporation (Resources
Conservation Company) 239
5. 6. 3 Power Plant Cooling Tower Blowdown Recycle
by Vertical Tube Evaporator with Interface
Enhancement (University of California,
Berkeley) 240
5. 7 EPA In-House Research 243
-------
CONTENTS (Continued)
VI. UNIVERSITY-RELATED RESEARCH AND
DEVELOPMENT 245
VII. INDUSTRIAL RESEARCH AND DEVELOPMENT
AND OPERATIONAL APPLICATIONS 249
7. 1 Research and Development 249
7. 1. 1 Electric Power Research Institute 249
7.1.2 New York State Energy Research and
Development Authority 249
7.2 Utility Power Plant Applications 250
VIII. FOREIGN TECHNOLOGY 255
REFERENCES 259
vi
-------
FIGURES
1. EPA Programs Overview: Control of Waste and Water
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Pollution from FGC Systems
EPA Program Evaluation Approach
Viscosity of Desulfurization Sludges "
Permeabilities of Chemically Treated and Untreated
Sludges
Compression Strength of Sludges and Sludge and Fly Ash
Mixtures as a Function of Solids Content
Concentrations of Major Ionic Species from the TVA
Shawnee Lime Scrubber
Viscosity of Desulfurization Sludges
Permeabilities of Chemically Treated and Untreated
Sludges
Compression Strength of Sludges and Sludge-Fly Ash
Mixtures as a Function of Solids Content
Effect of Water Removal by Underdrainage on Load-
Bearing Strength of Lime Sludges
EPA Pilot Plant Forced Oxidation System, Tests
with Fly Ash
EPA Pilot Plant Forced Oxidation System, Tests
Without Fly Ash ,
Concentration of Major Species in Leachate of First-
Stage Slurry Solids of RTP Oxidized Sludges ,
Concentration of Major Species in Leachate of Second-
Stage Slurry Solids of RTP Oxidized Sludges
6
18
20
22
24
47
57
63
64
65
67
68
72
73
vii
-------
FIGURES (Continued)
15. Load-Bearing Strengths of Dewatered Filtered Solids
from RTF Oxidized Sludges Containing 5 Percent
Sulfite 76
16. Simplified Process Schematic for Wet Limestone
Tail-End Scrubber Forced Oxidation Gypsum-
Producing System ' '
17. Simplified Process Schematic for Wet Limestone
Integrated Forced Oxidation Gyp sum-Producing
System 78
18. Cost of Producing Saleable Gypsum as a Function
of Sludge Treatment and Disposal Credit 83
ig. Disposal Cost of Gypsum Produced by Forced
Oxidation Compared to Disposal of Equivalent
Quantity of Sulfite Sludge 84
20. Concentration of TDS and Majdr Species in
Pond A Leachate 91
21. Concentration of TDS and Major Species in
Pond D Leachate 92
22. Concentration of TDS and Major Species in
Pond B Leachate 94
23. Concentration of TDS and Major Species in
Pond C Leachate 95
24. Concentration of TDS and Major Species in
Pond E Leachate 96
25. Grain Size Distribution: (a) Untreated and (b) Treated
Waste 107
26. Grain Size Distribution: Processes B and F Results 108
27. Porosity and Void Ratio of Soils Compared with
Untreated and Treated Wastes 110
28. Leachate Conductivity, Untreated FGD Sludges 115
29. Leaching Results: Sulfate, Sludge No. 100 116
30. Leaching Results: Sulfate, Sludge No. 500 117
viii
-------
FIGURES (Continued)
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
Conductivity Versus Dissolved Solids
Conductivity of Leachate, Sludge No. 100
Conductivity of Leachate, Sludge No. 600
Leachate pH for Untreated and Treated Residues
Means and Ranges of Coal Pile Drainage Analyses
Spatial Distribution of Monitoring Wells at the
Kingston Generating Facility
Topographic Profile Illustrating Wells and Soil Strata ....
Schematic Diagram of Sampling Locations for Coal
and Ash at Colbert Steam Plant Unit 1 . . .
Flow Rate of Water Through Plant A FGD Waste
Flow Rate of Water Through Plant B FGD Waste
Effect of Plant A Waste on the Flow Rate of Water
Through Davidson Soil
Effect of Plant B Waste on the Flow Rate of Water
Through Davidson Soil
Effect of Plant F Waste on the Flow Rate of Water
Through Davidson Soil
Average Leakage Rate of Liner Specimens
Settling Rate: Limestone Slurry
Settling Rate: Effect of Solids Morphology
Thermal Characteristics: Lime System Solids
Thermal Characteristics: Limestone System Solids
Phase II Study Outline . . . . ;
Process Flow Sheet for Producing Solid Granular
Fertilizer Material from Scrubber Sludge
118
119
120
121
133
143
144
146
157
158
159
160
161
189
196
196
. . . 198
198
215
. . . 220
ix
-------
FIGURES (Continued)
51. Proposed Extraction Process 224
52. Total Utilization Concept 226
53. Renovation and Recycle of Power Plant Cooling
Tower Blowdown 242
-------
TABLES
1. Relationship of Projects in FGC Waste and Water
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Program to Areas of Interest
Project Status
FGD Systems Sampled as Data Base
Flue Gas Desulfurization Systems Sampled as Data Base
Relative Change in Concentration of Constituents in the
Scrubber Circuit Liquor: Limestone Process
Range of Concentrations of Chemical Constituents in FGD
Sludges
Net Change in Scrubber Liquor Composition of Major,
Minor, and Trace Constituents Between Initial
and Final Stages in Scrubber System
Composition of Dry Solid Sludge from Three Power Plants . . .
Comparative Analytical Results for TVA Shawnee Lime
Sludge Liquor and Leachate
Comparative Analytical Results for Scholz Sludge
Liquor and Leachate
Comparative Analytical Results for Paddy's Run Sludge
Liquor and Leachate
Comparative Analytical Results for Shawnee Lime
Scrubber Filtrate Liquors
Trace Elements Leached from Shawnee Fly Ash at
Controlled pH
Phase Composition of FGD Waste Solids in Weight Percent ....
Water Retention and Bulk Density Characteristics
4
7
38
40
41
42
43
44
48
49
50
51
53
56
60
xi
-------
TABLES (Continued)
16. Permeability Coefficients of Compacted Untreated
Sludge ....................................... 61
17. Composition of RTF Oxidized Sludges by Wet Chemical
Analysis ..................................... ^0
18. Analysis of Leachates and Filtrates of RTF Forced
Oxidation Samples ............................... 7*
19. Physical Characteristics of RTF Oxidized Sludges ......... 75
20. Operating Premises for New 500-MWe System Wet
Limestone Scrubbing Process ....................... 79
21. Total Incremental Cost for Producing Gypsum by Forced
Oxidation ..................................... 81
22. Estimated Incremental Cost of Producing Gypsum for
Sale or Disposal Relative to the Disposal of Chemically
Treated FGC Wastes ............................. 82
23. Pond and FGC Waste Characteristics .................. 87
24. Characteristics of Cores from Chemically Treated
FGC Wastes ................................... 88
25. Shawnee Disposal Evaluation Input Sludge Analysis
Record ...................................... 89
26. Shawnee Pond Leachate, Sampled January 21, 1976 ......... 90
27. FGC Waste and Chemical Treatment Matrix .............. 98
28. Comparison of Specific Gravities of Untreated and
Treated FGC Wastes ............................. 100
29. Physical Properties of Treated Sludge ................. 101
30. Permeability Test Data for Untreated Sludge ............. 102
31. Permeability Test Data for Treated Sludge .............. 103
32. Unconfined Compression Test Data for Treated Sludge ....... 104
33. Changes in Dry Unit Weight After Compaction of
Sludges Treated by Process B ....................... 105
34. Chemical Characteristics Tests of Untreated and
Treated FGC Wastes ............................. 112
xii
-------
TABLES (Continued)
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
Results of Sludge Digests, Metals
Leachate Data, Lead
FGC Sludge Test Cell Matrix
Leachate Analysis
Chemical Analyses on Samples for Site Surveys
Treatment Materials Being Tested
Second Generation Treatment Processes
Location and Status of Field Site Studies
Analysis of Coal Pile Drainage
Summary of Laboratory Tests and Analyses
Colbert Ash Pond Effluent Survey
Colbert Ash Pond Effluent Monitoring Survey
Sample Analyses
FGD Waste Characteristics
Soils Characteristics
Concentration of Various Metallic Constituents in
FGD Solids
Concentration of Various Metallic Constituents in
FGD Solids Supernate ,
Solubilization of Metals and Chlorides from FGD Wastes ...
Channeling Occurring Waste-Only Columns and Decrease
in Waste Column Depth
Content of Final Report
Sixty- Day Unconfined Compressive Strength of Treated
and Untreated FGD Wastes ,
Additional Laboratory Test Mixtures
114
122
123
124
126
128
129
131
132
135
138
140
147
150
151
152
153
155
156
163
170
174
-------
TABLES (Continued)
57. Permeability of Treated and Untreated Wastes 175
58. Leachate Analyses * ' '
59. Identification of Mixtures for Impoundment Evaluation 179
60. Liner Materials Being Tested 181
61. FGD Wastes 182
62. Evaluation of Sprayon and Admix Test Materials 183
63. Liner Materials Rejected 187
64. Permeability Coefficients Using Water 188
65. Study Outline 205
66. Factors Considered in Ocean Disposal Evaluation 210
67. Chemical Analysis of FGD Sludge Samples 216
68. Preneutralizer Test Conditions 222
69. Basic Characteristics of Power Plants 229
70. Summary of Physical Properties 247
71. FGC Chemical Treatment Processes: Utility Plant
Characteristics Z51
72. FGC Waste Treatment and Disposal Status 253
73. Gypsum-Producing Processes Based on Wet
Lime-Lime stone Scrubbing 256
XIV
-------
CONVERSION TABLE
British
1 inch
1 foot
1 mile
1 square foot
1 acre
1 cubic foot
1 gallon
1 cubic yard
1 pound
1 ton (short)
1 pound per square inch
1 pound per cubic foot
1 ton per square foot
1 part per million
1 British thermal unit
(Btu)
1 pound per million Btu
1 Btu per pound
Metric
2. 54 centimeters
0. 3048 meter
1. 609 kilometers
9,290 square centimeters
4,047 square meters
28,316 cubic centimeters
3. 785 liters
0. 7646 cubic meter
0. 454 kilogram
0. 9072 metric ton
0. 0703 kilogram per square
centimeter
0. 01602 gram per cubic
centimeter
9, 765 kilograms per square
meter
1 milligram per liter (equivalent)
252 calories
0.43 grams per million joules;
1. 80 grams per million calories
2. 324 joules per gram; 0. 555
calories per gram.
XV
-------
SECTION I
INTRODUCTION
1.1 BACKGROUND
A major consideration in controlling pollutants from modern
coal-fired, steam-electric generating plants is the environmental manage-
ment of solid wastes and effluents. Essentially, all the solid wastes, ex-
cluding bottom ash, are generated as a result of air pollution devices to con-
trol sulfur dioxide and fly ash emissions. The solid wastes, in turn, present
their own potential water pollution problems once they are removed from the
control devices for disposal.
The environmental legislation of the past several years pro-
vides the framework for regulation of these effluents and wastes, and the
development of technology to minimize their adverse environmental impacts
has, in a number of cases, required significant research and development
efforts. The need for these efforts was the basis for the formulation of the
programs described in this report.
A significant portion of the efforts in this area is currently
being funded by the U.S. Environmental Protection Agency (EPA). Twenty-
one different EPA projects are either completed or are under way. Work
has also been and is being conducted by utilities and other industrial organi-
zations involved in the treatment and disposal process. In addition, full-scale
systems are currently in operation, and others are in various stages of plan-
ning and implementation.
1.2 SCOPE
The Aerospace Corporation under Task 9 of EPA Contract
No. 68-02-1010 has been contracted to integrate and evaluate the research
and development (R&D) work being performed in the area of power plant waste
disposal and utilization, as well as overall power plant water recycle and
reuse. This report is the second in a series and provides an updated evalua-
tion of the R&D results of the EPA-funded projects, as well as information
available since the first report, on work being performed by other domestic
-------
(U.S. ) and foreign organizations. The assessment of the results and
technology is related to the definition of environmentally sound and economic
disposal of or utilization of FGD wastes and water recycle, reuse, and
treatment. In addition, a summary of the status of full-scale operational
FGD waste disposal systems is reported.
1.2.1 The EPA Program
In late 1974, plans were formulated to greatly expand existing
EPA flue gas desulfurization (FGD) waste disposal R&D efforts. These ef-
forts were aimed at determining pertinent environmental parameters, re-
ducing costs, investigating alternative strategies, and encouraging waste -
product usage. Although the major emphasis was on FGD wastes, the plans
involved consideration of overall power plant waste and water problems, in-
cluding the disposal and utilization of coal ash. The program is currently
entitled "Control of Waste and Water Pollution from Coal-Fired Power Plants"
or, for brevity, "Waste and Water Program. "
The objectives of the Waste and Water Program are to evaluate,
develop, demonstrate, and recommend environmentally acceptable cost-
effective techniques for disposal and utilization of flue gas cleaning (FGC)
wastes and to evaluate and demonstrate systems for maximizing power plant
water recycling and reuse. The projects, in general, fall into one of six
main categories: (1) environmental assessment of FGC waste disposal,
(2) technology assessment development, (3) disposal economics, (4) alterna-
tive disposal methods, (5) utilization of wastes, and (6) power plant water
recycle and treatment for reuse.
The environmental assessment projects include FGC waste
characterization studies; laboratory and pilot field studies of disposal tech-
niques for chemically treated FGD sludges; characterization of coal-pile
drainage, coal ash, and other power plant effluents; and studies of attenuation
of FGC waste leachate by soils. Chemical and physical properties have been
determined by several laboratories for untreated FGC wastes from a total of
13 scrubbers, wastes treated by 5 distinct processes, and gypsum produced
in an EPA laboratory pilot plant facility.
The technology assessment and development efforts include
field studies of untreated and chemically treated FGD wastes, FGC waste
leachate-disposal site liner compatibility studies, studies to correlate waste
solid characteristics with scrubber operating conditions, and dewatering
equipment design studies. The economic studies include cost estimates of
current disposal practices (e.g., ponding, landfill) and by-product marketing
studies. Alternative disposal method studies include both mine and ocean
disposal assessments. Utilization projects include development of a process
for FGC waste conversion (to sulfur and calcium carbonate), pilot studies
of fertilizer production (using the waste as a filler material and a source of
sulfur), use of FGD gypsum in portland cement manufacture, and FGC waste
beneficiation studies. Studies to define methods of minimizing water con-
sumption by electric utility power plants by recycling and reuse of water
from FGC processes and major water-use systems are being conducted,
as well as methods of treating purge streams.
-------
Table 1 shows the relationship of each of the projects to the
areas of interest. Whereas four of the projects are aimed at investigating
one specific area, the others cover several areas of interest. This is to be
expected, since it would be difficult, for example, to fairly assess the tech-
nology of a process without examining both the economics and the environmen-
tal effects. An overview of the EPA program as it relates to the various ele-
ments of the FGC solid waste and liquid effluent generation, treatment, dis-
posal, and utilization is shown in Figure 1. The projects and contractors are
identified and keyed to the elements of the system addressed.
In Section V, each of the projects is discussed, and the current
project status and results are described. These are listed under the heading
of the main area of interest. Table 2 identifies the EPA project officer, con-
tractor project director, start date, and duration of each of the projects, as
•well as the section in which each of these projects is discussed.
1.2.2 Other Programs
Other organizations including utilities and FGD waste fixation
contractors have conducted work on various aspects of the overall disposal
problem that are generally of a site-specific nature. The results of work con-
ducted by United States industrial organizations are discussed in Section VII,
and the status of full-scale operational FGD waste disposal system is also
provided in that section. Section VI provides information on university-
related work, and foreign technology is discussed in Section VIII.
1.3 TECHNICAL BASIS FOR THIS REPORT
This report is based generally on published information avail-
able through November 1976 and subsequent to December 1975, which was the
cutoff date for the first R&D report (Ref. 1). During its preparation, infor-
mation developed from informal contacts was included, as appropriate. An-
nual updating of this report is planned by the EPA.
-------
TABLE i. RELATIONSHIP OF PROJECTS IN FGC WASTE AND
WATER PROGRAM TO AREAS OF INTEREST
Project
FGC Waste Characterization
and Disposal Evaluation
Shawnee FGO Waste Disposal
Field Evaluation
Laboratory and Field Evalua-
tion of FGC Treatment
Processes
Characterization of Effluents
from Coal -Fired Power
Plants
Fly Ash Characterization and
Disposal
Attenuation of FGC Waste
Leachate by Soils
Establishment of Data Base
for FGC Disposal Standards
Environmental Effects
and Control of Various
FGC Sludge Disposal
Options
Evaluation of FGD Waste
Disposal Options
FGD Waste Leachate -
Liner Compatibility
Scrubber Waste
Characterization
Dewatering Principles and
Equipment Design
Conceptual Design-Cost
Studies of Alternative
Methods for FGC Waste
Disposal
Gypsum By-Product
Marketing Studies
Contractor
Aerospace
TVAC and Aerospace1"
U. S. Army WESd
TVAe
TVAe
U.S. Army, Dugway
scsg
scsg
LGfcEh
U.S. Army, WESd
TVAe
Auburn U1
TVAJ
TVAJ
Environmental
Assessment
X
X
X
X
X
#
X.
•«r
X
Technology
Assessment
and Development
X
X
X
X
X
X
X
X
X
X
X
X
Economic
Studies
X
X
X
X
X
Bxoixf- '^m^.-
:v~:»:v3s:-:v::.y'-:-:-\ .-.-. ..
>Kv>>>>^Av:/rv.->X'X>K"vXv'-
v:v:v^:{^Sr/>:v>/»:-:-»:vH
v.v.v.v.v.'.^fl^v.v.v.v.v.v.v//.-.
^^H^;3™&?™
Alternative
Disposal
Methods
X
X
X
Utilization
Methods
Development
X
Overall
Power Plant
Water Use
X
(Continued)
-------
TABLE 1. RELATIONSHIP OF PROJECTS IN FGC WASTE AND
WATER PROGRAM TO AREAS OF INTEREST (Continued)
Project
Evaluation of Alternative
FGC Waste Disposal Sites
Scrubbing Waste Conversion
Studies
Fertilizer Production Using
Scrubbing Wastes
FGD Waste and Fly Ash
Beneficiation
Assessment of Power Plant
Water Recycle and Reuse
Treatment of FGC Waste
Streams by Vapor
Compression Cycle
Evaporation
Power Plant Cooling Tower
Slowdown Recycle by
Vertical Tube Evaporator
with Interface Enhancement
Contractor
A. D. Littlek
Pullman Kellogg 1
TV A)
TRW™1
Radian11
RCC°
U. of California
Environmental
Assessment
X
Technology
Assessment
and Development
X
X
X
Economic
Studies
X
X
X
X
X
Alternative
Disposal
Methods
X
Utilization
Methods
Development
SiHSSSiliSlsiii
•:ss»/s»»Bsa-»ss;s *
Overall
Power Plant
Water Use
' "&™f "- W f ..
" ^f "~ ;»
j-t^? 3f
' - ic* f -_-" •>, -
^ f V.
" jyf
«, * —
Primary area of interest is indicated by shaded areas.
The Aerospace Corporation, El Segundo, California.
CTennes8ee Valley Authority (TVA), Division of Chemical Development. Muscle Shoals, Alabama.
U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi.
TVA, Power Research Staff, Chattanooga, Tennessee.
U.S. Army Materiel Command, Dugway Proving Ground, Utah.
"SCS Engineers, Long Beach, California.
Louisville Gas and Electric Company (LG&E), Louisville, Kentucky.
Auburn University, Auburn, Alabama.
JTVA, Office of Agricultural and Chemical Development (OACD), Muscle Shoals, Alabama.
jt
Arthur D. Little, Inc., Cambridge, Massachusetts.
Pullman Kellogg Company, Houston, Texas.
TRW Systems Group, Redondo Beach, California.
Radian, Inc., Austin, Texas.
Resources Conservation Company, Renton, Washington.
-------
' CHARACTERIZATION OF
EFFLUENTS FROM COAL-FIRED
POWER PLANTS (TVA).A.C.L
• FLY ASH CHARACTERIZATION
AND DISPOSAL ITVA)C.M,H
• ASSESS AND DEMONSTRATE
POWER PLANT WATER REUSE/
RECYCLE (Radian) L,B, K
• EVALUATE USE OF VAPOR COM-
PRESSION EVAPORATOR TO
REDUCE WATER POLLUTION FROM
FGD PROCESSES (RCC). I
• RENOVATE COOLING TOWER
BtOWDOW BY VERTICAL TUBE
EVAPORATOR (U of California). L
• LIME AND LIMESTONE SCRUBBING • FGC WASTE CHARACTERIZATION • LABORATORY AND FIELD EVALU-
WASTE CHARACTERIZATION (TVAI AND DISPOSAL EVALUATION
D,E
1.2.3
(Aerospace) Ej 2 3G, H. K, L, M
' DEWATERING PRINCIPLES AND
EQUIPMENT DESIGN STUDIES
(Auburn U) F
ATI ON OF FGC TREATMENT
PROCESSES (U.S. Army WES)
G, EyH
• EVALUATION OF FGC WASTE
DISPOSAL OPTIONS ILG&EI
G.H
• CONCEPTUAL DESIGN AND COST
STUDIES OF ALTERNATIVE
METHODS FOR LIME AND
LIMESTONE SCRUBBING WASTE
DISPOSAL (TVA) G.H
• LIME AND LIMESTONE SCRUBBING
WASTE CONVERSION PILOT
STUDIES (Pullman-Kellogg)
• FERTILIZER PRODUCTION USING
LIME AND LIMESTONE SCRUBBING
WASTES (TVA) I, J
• SHAWNEE FGD WASTE DISPOSAL
FIELD EVALUATION (TVA and
Aerospace) H, G, E-
• ATTENUATION OF FGC WASTE
LEACHATE BY SOILS (U.S.
Army. Dugwayl H
• ESTABLISHMENT OF DATA BASE
FOR FGC WASTE DISPOSAL
STANDARDS DEVELOPMENT
(SCS EngrlH
• ALTERNATIVE DISPOSAL
METHODS DEVELOPMENT
IA.D. Little) H,
• FGC WASTE LEACHATE- LINER
COMPATIBILITY (U.S. Army
WESIH
• FGD WASTE AND FLYASH
BENEFICIATION STUDIES
(TRW) J. I
• GYPSUM BY-PRODUCT
MARKETING STUDIES (TVA) J
• ENVIRONMENTAL EFFECTS
AND CONTROL OF
VARIOUS FGC SLUDGE
DISPOSAL OPTIONS
(SCS Engr) H, Ej, G
Figure 1. EPA program overview: control of waste and
water pollution from FGC systems.
-------
TABLE 2. PROJECT STATUS
Project Title
of FGC Waste Disposal
FGC Waste Characteriza-
tion, Disposal Evaluation,
and Technology Transfer
Shawnee FGD Waste
Disposal Field
Evaluation
Laboratory and Field
Evaluation of FGC Waste
Treatment Processes
I. Pollution Potential of
Untreated and Chemi-
cally Fixed Sludges
2. Site Survey and Environ-
mental Assessment of
Existing Solid Waste
Disposal Sites
3. Evaluation of Existing
Fixation Technology
Characterization of Effluents
from Coal-Fired Power
Plants
Fly Ash Characterization
and Disposal
Studies of Attenuation of
FGC Waste Leachate by
Soils
EPA Project Officer3
J. W. Jones
Industrial Environmental Research
Laboratory (IERL)
Research Triangle Park, NC
M. C. Osborneb
IERL
Research Triangle Park, NC
R. E. Landreth
Municipal Environmental
Research Laboratory (MERL)
Cincinnatti, OH
M. C. Osborneb
R. A. Venezia
IERL
Research Triangle Park, NC
M. C. Osborneb
R. A. Venezia
IERL
Research Triangle Park, NC
M. Roulier
MERL
Cincinnatti, OH
Contractor Project Director
J. Rossoff
The Aerospace Corporation
El Segundo, CA
A. F. Little
TVA, Division of Chemical
Development
Muscle Shoals, AL
J. Rossoff
The Aerospace Corporation
El Segundo, CA
P. G. Malone
U. S. Army Engineer
Waterways Experiment Station
(WES)
Vicksburg, MS
H. B. Flora
TVA Power Research Staff
Chattanooga, TN
H. B. Flora
TVA, Power Research Staff
Chattanooga, TN
M. Houle
U.S. Army Materiel Command
Dugway Proving Ground
Dugway, UT
Start Date
Nov 1972
Sep 1974
1. Jul
1974
2. Jul
1975
3. Jul
1975
Apr 1975
Apr 1975
Dec 1975
Estimated
Duration, months
50
34
1. 36
2, 24
3. 26
50
42
24
Type of Study
Laboratory
analyses:
technical
and economic
Field
evaluation
1 . Laboratory
2. Laboratory,
field
3. Laboratory
Laboratory,
field
Laboratory,
field
Laboratory
Section Ref-
erenced' in
This Report
5. 1
5. 1. 1
5. 1.2
5. 1.3
5. 1.3. 1
5. 1.3.2
5. 1.3.3
5. 1.4
5. 1.5
5.1.6
(Continued)
-------
TABLE 2. PROJECT STATUS (Continued)
Project Title
Establishment of a Data Base
for FGC Waste Disposal
Standards Development
Environmental Effects and
Control of Various FGC
Sludge Disposal Options
Process Technology Assess-
ment and New Technology
Development
Evaluation of FGD Waste
Disposal Options
FGD Waste Leachate-Liner
Compatibility
Lime and Limestone Wet
Scrubbing Waste
Characterization
Dewatering Principles and
Equipment Design Studies
Process Economics Studies
Conceptual Design and Cost
Studies of Alternative
Methods for Lime and Lime-
stone Scrubbing Waste
Disposal
Gypsum By- Product Marketing
Studie s
Alternative FGC Waste
Disposal Methods
Evaluation of Alternative FGD
Waste Disposal Sites
EPA Project Officer
D. E. Sanning
MERL
Cincinnati, OH
D. E. Sanning
MERL
Cincinnati, OH
M. C. Osborne
IERL
Research Triangle Park, NC
R. E. Landreth
MERL
Cine inn atti, OH
M. C. Osborne
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
J. W. Jonesa
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
Contractor Project Director
C. J. Schmidt
SCS Engineers
Long Beach, CA
C. J. Schmidt
SCS Engineers
Long Beach, CA
R. P. Van Ness
Louisville Gas and Electric Co.
Louisville, KY
Z. B. Fry
U.S. Army WES
Vicksburg, MS
J. L. Crowe
TVA Energy Research
Chattanooga, TN
J. C. Warman
Auburn University
Auburn, AL
H. L. Faucett
TVA, Office of Agricultural and
Chemical Development (OACD)
Muscle Shoals, AL
J. I. Bucy
TVA, OACD
Muscle Shoals, AL
R. R. Lunt
Arthur D. Little, Inc.
Cambridge, MA
Start Data
Dec 1975
Sep 1976
May 1976
Jul 1975
Mar 1975b
June 1976
Jan 1976
Jan 1976
Jul 1975
Estimated
Duration, months
15
24
18
30
28
27
18
12
54
Type of Study
Technical
analysis
Technical
analysi a
Laboratory.
field
Laboratory
Laboratory,
field
Laboratory
Technical and
economic
analyses
Technical and
, economic an
analyses
Technical
analysis, lab-
oratory and
field tests0
Section
5. 1.7
5. 1.8
5.2
5.2. 1
5.2.2
5.2.3
5.2.4
5.3
5.3. 1
5.3.2
5.4
5.4. 1
00
(Continued)
-------
TABLE 2. PROJECT STATUS (Continued)
Project Title
New FCC Waste Utilization
Methods
Lime and Limestone Scrubbing
Waste Conversion Pilot Studies
Fertilizer Production Using
Lime and Limestone
Scrubbing Wastes
FGD Waste and Fly Ash
Benefi elation Studies
Improving Overall Power
Plant Water Use
Assess and Demonstrate
Power Plant Water
Reuse and Recycle
Treatment of Flue Gas
Scrubber Waste Streams by
Vapor Compression
Cycle Evaporation
Power Plant Cooling Tower
Slowdown Recycle by
Vertical Tube Evaporator
with Interface Enhancement
EPA Project Officer
J. W. Jones
IERL
Research Triangle Park, NC
M. C. Osborne
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
J. W. Jones
IERL
Research Triangle Park, NC
M. C. Osborne
IERL
Research Triangle Park, NC
M. C. Osborne
IERL
Research Triangle Park, NC
Contractor Project Director
A. G. Sliger
Pullman Kellogg Company
Houston, TX
J. L. Crowe
TVA, Energy Research
Chattanooga, TN
J. Blumenthal
TRW Systems Group
Redondo Beach, CA
D. M. Ottmers
Radian, Inc.
Austin, TX
L. D. Weimer
Company
Renton, WA
H. H. Sephton
U of California
Berkeley, CA
Start Date
1977
May 1975
Mar 1976
July J975
Jul 1976
Aug 1974
Estimated
Duration, months
11
41
(plus 18 for
field tests)
6
(completed)
13
11
23
Type of Study
Bench, pilot
plant
Pilot plant.
field tests
Conceptual
design, bench,
pilot plant
Analysis of
field data.
computer
simulation
Conceptual
design,
economics.
bench and
pilot plant
tests
Pilot plant
tests
Section
5.5
5.5.1
5.5.2
5.5.4
5.6
5.6.1
5.6.2
5.6.3
aUpdated to reflect current EPA project officers
Change since last report
cPhase II initiated July 1976
-------
SECTION II
CONCLUSIONS
2. 1 BACKGROUND
This report summarizes and assesses the state of research
and development (R&D) in the fields of flue gas cleaning (FGC) waste treat-
ment, disposal, and utilization, as well as water recycle and reuse for coal-
fired utility power plants, with the ultimate objective being directed toward
definition of cost-effective, environmentally acceptable methods. A survey
of the work being conducted indicates that a significant portion of effort is
currently being conducted under the direction of the U.S. Environmental Pro-
tection Agency (EPA). Considerable efforts are also being conducted by
others, including utilities and industrial organizations. Although most of
these efforts are concerned with problems of a site-specific nature, they
contribute to the overall understanding of the technical field under study.
Several EPA studies have been completed, while others have
been expanded in scope. In addition, many of the EPA studies are in early
stages relative to the availability of quantitive data and will require approxi-
mately one to two years to complete. Therefore, firm conclusions regarding
a major portion of the laboratory results to date are not warranted at this
time. However, some conclusions can be drawn relative to the EPA program
scope and its potential to meet program objectives, and observations can be
made on the basis of information currently available. These augment and
expand those provided in the first annual report; the composite is provided in
Section 2.2.
2.2 CONCLUSIONS AND OBSERVATIONS
Federal regulatory guidelines have not been promulgated which
could be used to gauge the effects of flue gas desulfurization (FGD) waste dis-
posal on the quality of groundwater and on land reclamation. The results
from this program are providing a data base for defining waste disposal stan-
dards, predicting effects on groundwater and surface water quality, and de-
termining the structural quality of disposal sites.
11
-------
Specific observations are as follows:
a. Chemical characteristics of FGC wastes have been found
to be a function not only of the properties of coal and
scrubber absorbent but also of the manner in which the
scrubber is operated, primarily, the pH of liquor in the
scrubber. The influence of operating variables on waste
characteristics is being systematically studied as part of
the program.
b. Removal of fly ash upstream of the scrubber does not com-
pletely eliminate the presence of trace elements in leachates
of untreated wastes.
c. Physical and chemical properties of untreated and treated
FGD wastes and liquors for lime, limestone, and double
alkali scrubber systems, using Eastern and Western coals
are reported. The resultant properties are process- and
fuel-dependent.
d. Results of tests of FGC wastes have shown that chemical
treatment significantly improves the structural character-
istics of the FGD waste, reduces the solubility of major
chemical species by a factor of two to four, and reduces
permeability by an order of magnitude or more. No ap-
preciable reduction of the concentration of trace elements
in the leachate has been noted when compared to untreated
wastes. These observations are being borne out by analy-
sis of results from, a field disposal evaluation. Management
of disposal sites to prevent collection of surface water would
be a significant factor in minimizing or eliminating seepage
through the waste. Analysis of groundwater from a field
evaluation site with a low permeability clay soil has shown
that the presence of the disposal ponds has not yet affected
the quality of the groundwater near that site after two years
of observation.
e. Load-bearing strengths acceptable for land reclamation
purposes have been achieved with untreated lime scrubber
sulfite-rich waste placed in an underdrained test disposal
site. Monitoring of physical and leaching characteristics
will continue. Disposal of limestone, sulfite waste, and
gypsum will also be evaluated.
f. With the increased acquisition of quantitative information
anticipated during the program, a data base will be formed
with which to determine the migration of major species and
trace elements from FGD waste disposal sites and to assess
the feasibility and environmental impact of alternative dis-
posal sites such as landfills, ponds, mines, and oceans. A
12
-------
compilation categorizing the power-generating industry,
location of FGD sources, state of the art of FGD system
control technology, current waste treatment and disposal
has been prepared. Consideration of environmental im-
pacts of waste disposal is also included. This data base
is to be expanded so that it can be used by the EPA to
define waste disposal guidelines.
g. The economics of FGD waste disposal and utilization are
being defined in detail and will be available for assess-
ment of the various disposal and utilization options. Engi-
neering estimates of 30-year average total fixation and
disposal costs (capital and operating) for a typical 1000-
megawatt (MW) plant were identified as $7.30 to $11.40
per ton of sludge (1976 dollars and dry weight basis).
These estimates represent the range of costs for three
different chemical treatment processes. The costs equate
to $2.07 to $3.24 per ton of coal and 0.9 to 1.4 mills per
kilowatt hour (kWh). Costs of disposing of untreated FGD
wastes in lined ponds have been reported as approximately
75 percent of the fixation-disposal costs. *
h. Chemical and physical characteristics of pilot plant pro-
duced gypsum by forced oxidation have been determined.
Engineering estimates have indicated that the cost of
saleable gypsum produced by this process can be com-
petitive with domestically mined crude gypsum if appro-
priate cost avoidance credits are taken for chemical
treatment and disposal. The suitability of the material
in actually producing wallboard has not been determined.
The desirability of producing gypsum for disposal can be
competitive with chemical treatment disposal processes
under certain conditions. Factors such as improved
scrubber operation may improve the attractiveness of the
approach.
i. Technically promising candidates that minimize environ-
mental impacts in the disposal of FGD waste in mines
and in the ocean have been identified. Mine disposal,
particularly coal-mine disposal, appears attractive and
is being considered by industry. Ocean disposal is still
under study to better understand the potential effects of
certain chemical and physical characteristics of FGC
waste on the environment. Further study in quantifying
these properties and assessing their impact is currently
under way.
For sites with bases of natural clay, the cost is approximately 40 percent
of fixation-disposal.
13
-------
j. Results, to date, of studies of recycle and reuse of water
from major streams from utility power plants have shown
that much more efficient water use can be obtained, in many
cases without significant expense, and that evaporation sys-
tems are more generally applicable to treating major
streams.
k. An economic study of an alumina extraction process utiliz-
ing FGG waste as a source of calcium has been completed,
and the limitations under which this method of utilization
may be competitive with bauxite have been defined. Sev-
eral key processing steps have also been identified that
require experimental verification.
1. Work performed by utilities and chemical processors has
ranged from laboratory research on processes and charac-
teristics of wastes to field evaluation of pilot plants and
prototype treatment processes. The work has focused on
site-specific problems of waste treatment and disposal
faced by the utilities involved. The Electric Power Re-
search Institute (EPRI) has initiated a project on the dis-
posal of wastes from FGC processes. The published re-
sults and planned effort, in general, complement and aug-
ment the EPA program.
m. As of December 1976, 9 stations have 15 units (7484 MWe)
committed to full-scale chemical treatment and disposal
of FGD wastes through 1979. Of these, five units (2100
MWe) are now in operation, and startup by seven others
(3959 MWe) is planned by the end of 1976. Also, 16 plants
representing 3646 MWe are identified as scrubbing and
disposing untreated lime-limestone scrubbed FGC wastes
in lined or in natural clay unlined ponds in 1976 (Ref. 2).
14
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SECTION III
RECOMMENDATIONS
3.1 BACKGROUND
In the first research and development (R&D) report (Ref. 1),
review and assessment was conducted of all known R&D activities for flue
gas cleaning (FGC) waste treatment, disposal, and water reuse to determine
the completeness of the coverage regarding a total understanding of the prob-
lems and potential solutions. This report updates and augments the informa-
tion previously reported. Generally, the current work, funded primarily by
the U.S. Environmental Protection Agency (EPA), addresses a broad range
of questions that must be answered prior to defining environmentally and
economically sound flue gas desulfurization (FGD) waste disposal methods.
A project sponsored by the Electric Power Research Institute (EPRI) is ex-
pected to expand the data base and provide an independent evaluation of waste
treatment and disposal processes, as well as defining disposal guidelines.
The results from the EPA program, together with work being done by utilities
and other organizations, are forming a significant data base to assist in
achieving the stated objectives.
3.2 RECOMMENDATIONS
At present, no specific change in the direction of the EPA-
sponsored program objectives is recommended. The various projects are
complementary, and negligible duplication of effort has been noted within the
EPA program and between the EPA projects and work being conducted by
others. For complete coverage of the problem, further consideration of the
following recommendations should be given. The first two recommendations
were identified in the first annual R&D report; projects concerning these
recommendations are not yet under way.
a. In laboratory testing conducted as part of the EPA program,
it has been determined that weathering may deteriorate the
physical properties of treated wastes. However, the data
are limited, and followup work is recommended to define
realistic test conditions and quantify the freeze-thaw wet-
dry effects on the strength, permeability, and leaching
characteristics of treated wastes.
15
-------
b. Although the EPA program will result in the compilation
of a data base encompassing the technology and properties
of FGD wastes whereby disposal criteria can be defined
and environmental impacts assessed, a series of detailed
case studies are recommended where conditions at typical
disposal sites in various regions of the United States may
be evaluated. Based on the type of waste produced at each
site, together with geological, climatalogical, and hydro-
logical facto rs_and site management techniques, an assess-
ment of pollutant transport phenomena, environmental
acceptability, and impact of various disposal methods can
be made.
c. In the course of evaluating the results of leaching tests,
it has become apparent that a need exists to develop and
standardize appropriate laboratory test methods to assess
and ultimately predict disposal site pollution potentials of
FGC wastes. Individual laboratories have tended to devise
procedures based on their best appraisal of the problem.
While in most cases the data are useful, results between
laboratories, in most cases, do not correlate. Therefore,
efforts to standardize leaching methods are needed.*
'it should be noted that the EPA Office of Solid Waste has proposed a toxicant
extraction procedure (which involves a shake test with a small sample of the
waste under study) to be used in hazardous waste testing under the Resource
Conservation Recovery Act (RCRA). Efforts are also under way at the
American Society for Testing and Materials (ASTM) to devise a standard
leach test.
16
-------
SECTION IV
SUMMARY
This second report summarizes and evaluates the research
and development (R&D) work conducted during calendar year 1976 in the field
of coal-fired utility power plant flue gas cleaning (FGC) waste treatment,
disposal, and utilization and overall power plant water recycle and reuse.
It supplements the information provided in the first annual R&D report
(Ref. 1). The results of the various projects being funded by the U.S.
Environmental Protection Agency (EPA) and private industry are viewed
with the ultimate objective of recommending environmentally acceptable,
cost-effective waste disposal and utilization methods.
4. 1 APPROACH
Twenty-one EPA projects encompass the areas of (1) techno-
logy and economic assessment of existing FGC waste treatment, disposal,
and utilization processes; (2) development of new or evolving technology-of
treatment, utilization, and disposal; and (3) development of methods to im-
prove overall power plant water use.
Some of the EPA projects have recently been initiated, while
others have been under way for several years. The projects that address
the physical and chemical characterization of the FGC wastes have been
funded for the longest periods. Therefore, considerable information re-
quired in the evaluation process in these areas is available and is summa-
rized (Figure 2). This report includes data available through November 1976;
other significant information published during preparation of this report is
also included.
4.2 EFFECT OF PROCESS VARIABLES
A number of variables affect the chemistry of the various
process streams and result in different chemical characteristics and pro-
perties of the materials to be disposed.
The results were based on chemical analyses of samples
from seven different scrubbers having capacities ranging from 1 to 125 MWe
and were reported as a function of location within a scrubber circuit as well
17
-------
00
POWER
PLANT
t
\
k
r
WATER
RECYCLE
AND REUSE
SECTION 4.7
^ FGC AND
FGD WASTES
i
I
EFFECT OF '
PROCESS
VARIABLES
SECTION 4. 2
UNTREATED
CHARACTERIZE
WASTES:
PHYSICAL AND
.CHEMICAL
SECTION 4.3
DATA BASE
COMPILE
'
CRITERIA
'
DEFINE AND
EVALUATE DISPOSAL
AND UTILIZATION
TECHNOLOGIES
SECTION 4. 3
ENVIRONMENTAL
ASSESSMENT
SECTION 4.5
i
i
ECONOMICS
SECTION 4.4
DISPOSAL AND
UTILIZATION
ALTERNATIVES
SECTION 4.6
Figure 2. EPA program evaluation approach.
-------
as a function of time, pH, absorbent, and coal composition (Ref. 1). These
included the effects of time, pH, and absorbent in scrubber liquor trace
element concentration, as well as the effects of coal composition and solid
and liquid waste trace element concentration.
A systematic evaluation of a number of operating variables
on solid waste properties is being conducted by TVA at their Shawnee
10-MWe scrubber test facility. The specific form in which the sulfite
species appears has been found to be directly related to the type of absor-
bent used (lime or limestone) and independent of the scrubber configuration
[turbulent contact absorber (TCA) or venturi spray tower]. The average
size of the sulfite platelets (crystals) formed from the limestone system
appears to be inversely related to the system stoichiometry; i.e., the better the
limestone utilization, the larger the crystals that are formed. No specific
relationship has been seen in the lime system.
4. 3 PHYSICAL, AND CHEMICAL. CHARACTERISTICS
OF WASTES
4. 3. 1 Physical Properties
Properties that define handling and engineering characteris-
tics of untreated and treated sludges have been presented in the first annual
R&D report (Ref. 1). These included viscosity, bulk density, and dewatering
characteristics; porosity; permeability; and unconfined compressive strength.
Viscosity is a major factor in determining pumping power
requirements. Bulk density data are needed in defining the volume of waste
and disposal site acreage, and dewatering characteristics are important in
defining treatment or conditioning requirements as well as achieving the
potential of reducing bulk densities. Compressive strength provides a mea-
sure of structural quality. Porosity and permeability determine rate of
leachate penetration through the solid waste mass. Therefore, the rate and
quantity of leachate constituents entering the ground, i.e., mass loading,
can be defined.
4.3.1.1 Viscosity
The viscosity of FGD wastes from seven power plants was
presented as a function of solids content in Ref. 3. Properties of six more
wastes were determined and are included in Figure 3. The measured vis-
cosity curves generally exhibited the same shape. The results show that,
of the wastes tested, the maximum solids content of pumpable mixtures
(<20 poise) range from a high of 70 percent for the Arizona Public Service
(APS) Cholla limestone sample to a low of 32 percent for both the Utah
Power and Light (UPL) Gadsby and General Motors Parma (GM) double
alkali samples. Considering this wide range of maximum solids content,
the importance of experimentally determining the viscosity becomes evident.
Considering the similarity of the curve shapes, it is also apparent that the
dewatering properties are significant in defining the range of solids content
over which the fluidity of the mixtures is such that pumping can be
considered.
19
-------
120
100
o
a.
to
O
60
40
20
CURVE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
SLUDGE FLY
GM PARMA DOUBLE ALKALI
UPL GADSBY DOUBLE ALKALI
TVA SHAWNEE LIME
DLC PHILLIPS LIME
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
SCE MOHAVE LIMESTONE
APS CHOLLA LIMESTONE
LG&E PADDY'S RUN CARBIDE LIME
TVA SHAWNEE LIME
TVA SHAWNEE LIMESTONE
GPC SCHOLZ SODA ASH DOUBLE ALKALI
GPS SCHOLZ SODA ASH DOUBLE ALKALI
TVA SHAWNEE LIME
ASH, %
7.4
8.6
40.5
59.7
20.1
40.1
40.9
3.0
58.7
12.4
<1.0
<1.0
<1.0
30.0
40.0
DATE
7/18/74
8/9/74
3/19/74
6/17/74
2/1/73
6/15/74
7/11/73
3/30/73
4/1/74
7/76
9/8/76
9/28/76
6/20/76
6/27/76
9/8/76
10
30
40 50 60
SOLIDS CONTENT, WEIGHT %
70
Figure 3. Viscosity of desulfurization sludges.
20
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Test results suggest that the presence of fly ash in FGD
wastes decreases the viscosity of FGD slurries, but the magnitude of
change is sludge-dependent (Figure 3).
4.3.1.2 Bulk Density and Dewatering Characteristics
The dry bulk density of untreated FGC wastes was reported
(Ref. 3) to be in the range of 0.75 to 1. 01 g/cm3 (47 to 63 pcf), the actual
value being scrubbing-process and coal-source dependent.
For the wastes examined, chemical treatment increases the
dry bulk density to approximately 0.80 to 1. 12 g/m3 (50 to 70 pcf) for wastes
with 0.75 g/cm3 untreated density and 1.28 to 1.76 g/cm3 (80 to 110 pcf)
for those characterized by the higher 1. 01 g/cm3 untreated densities.
Again, the coal source and the scrubbing process appear to affect the values.
Dewatering techniques such as settling, draining, centrifu-
ging, and filtration have a marked effect on the resultant bulk density
(Ref. 1). Generally, the wet bulk density varied from a low of approximately
1.48 g/cm3 (92 pcf), settled, to a high of 1.76 g/cm3 (110 pcf), filtered.
Drained and centrifuged values were intermediate to these extremes. These
values were determined under laboratory conditions and may not necessarily
be representative of results using commercial equipment. However, it is
expected that the trends defined will apply. Results of tests with five addi-
tional sludges have maintained the same trends and values fall within the
ranges previously reported.
Some settling characteristics of wastes from lime and lime-
stone scrubbing processes have been reported by TVA (Section 5.2. 33).
For the wastes examined, no general relationship has yet been determined
between slurry solids content and settling rates because of the strong influ-
ence of solids morphology on this property. However, settling rates and
behavior for materials of similar particulate composition are generally a
function of the slurry solids content, the thicker slurries settling more
slowly.
4.3.1.3 Permeability
The permeability coefficients of untreated wastes were re-
ported to be in the range of !Q-4to 10~5 cm/sec (Figure 4) (Ref. 3). These
values are intermediate to typical values for silty sand and sandy clay,
which are 10"^cm/sec and 5 X 10 cm/sec, respectively. Values as low
as 6 X 10~7 cm/sec have been reported for Louisiana Gas and Electric
(LG&E) Paddy's Run carbide lime untreated wastes (Section 5.2. 1). Conso-
lidation of wastes under pressures of 30 to 100 psi tends to reduce permea-
bility coefficients by factors of from 2 to 5. Chemical treatment tended to
reduce permeability by less than a factor of two in some cases and several
orders of magnitude in others. The chemical treatment process used, in-
cluding the solids content of the treated waste, appears to be the major
factor in the benefit derived.
21
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SAMPLE SOURCES DATE FLY ASH, %
• TVA SHAWNEE LIMESTONE 6/15/74 40.0
o TVA SHAWNEE LIME 3/15/74 40.5
n SCE MOHAVE LIMESTONE 3/30/73 3.0
• GM PARMA DOUBLE ALKALI 7/18/74 7.4
T UPL GADSBY DOUBLE ALKALI 8/9/74 8.6
v DLC PHILLIPS LIME 6/17/74 59.7
A APS CHOLLA LIMESTONE 4/1/74 58.7
X CHEMFIX LAB
0 DRAVO LAB
A IUCS LAB
© POND B TVA SHAWNEE/ DRAVO (Ref. 2)
$ POND C TVA SHAWNEE/ IUCS (Ref. 2)
(g| POND E TVA SHAWNEE/CHEMFIX (Ref. 2)
* PULVERIZED
rZT FAMILIES OF DATA HAVING SAME SLOPES
1 1 1 1 1
,-7 _
0.10
0.20
0.30
0.40 0.50
VOLUME FRACTION OF SOLIDS
0.60
0.70
0.80
0.90
Figure 4. Permeabilities of chemically treated and
untreated sludges.
-------
Weathering such as freezing and thawing has been reported
to break up the monolithic structure of certain treated wastes (Ref. 4). The
permeability of several treated wastes that were mechanically fractured
and powered to simulate extensive weathering exhibited permeability values
approximately the same as for untreated wastes. Fracturing (but not
powdering) and compacting resulted in about one order of magnitude reduc-
tion of permeability relative to the powdered condition (Ref. 1).
4.3.1.4 Compressive Strength
Unconfined compressive strength of untreated wastes are
low, and no specific values are generally reported because the material is
usually too soft to measure. Chemically treated sludges exhibited uncon-
fined compressive strengths ranging from as low as 25 psi to as high as
4500 psi in laboratory studies (Ref. 3). However, commercial processes
being used at power stations today produce values in the range of 25 to
400 psi. A systematic evaluation using LG&E Paddy's Run carbide lime
sludge at various solids content with carbide lime, lime, and portland ce-
ment additives has resulted in unconfined compressive strengths up to
400 psi. Load-bearing strength based on modified soil testing techniques
was reported for ten untreated wastes (Ref. 3) (Section 5. 1. 1.4. 6). The
influence of settling properties and the criticality of the strength over a
narrow range of solids content are illustrated in Figure 5.
4. 3. 2 Chemical Properties
Chemical properties of scrubber waste liquors and solids
and FGC waste leachates have been reported (Ref. 1). More data are
becoming available on FGC waste leaching characteristics as the program
progresses and are being used to define long-term trends.
Chemical, x-ray, and scanning electron microscope analyses
of the solid fractions of the wastes have continued to show the uniqueness
of the characteristics, with properties affected by coal composition and
scrubber operating variables (Ref. 3).
4.3.2.1 Quality of Scrubber Liquors
The range of concentrations of scrubber liquor constituents
were reported (Ref. 3). The soluble chemical content of FGD sludge liquors
typically have approximately 10, 000-mg/i total dissolved solids (TDS)
(steady state), except for double alkali scrubbers, whose liquors have a
much higher TDS (Section V, Table 5). The distribution of trace elements
in systems liquors tends to lie between 0.01 and 1 ppm for all elements
except mercury, which has a concentration distribution of about one-tenth
that of other trace elements.
Some limited data representing the effect of fly ash collection
ahead of the scrubber on trace element concentrations in the sludge liquors
are reported (Ref. 3). From an assessment of the data, fly ash appears to
represent the major source of trace elements in the sludge. The most vola-
tile elemental species (e.g., mercury and selenium) that are scrubbed from
flue gases are present in comparable concentrations regardless of whether
fly ash is collected upstream of the scrubber.
23
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a 150 -
O
I
t/>
O
O SHAWNEE LIME, NO FLY ASH
• SHAWNEE LIME. 40% FLY ASH
A SCHOLZ. NO FLY ASH
A SCHOLZ. 30% FLY ASH
D PADDY'S RUN
0 PHILLIPS
O CHOLLA
• GADSBY
® SHAWNEE LIMESTONE, NO FLY ASH
O SHAWNEE LIMESTONE 40% FLY ASH
60 70
SOLIDS CONTENT, weight %
90
Figure 5. Compression strength of sludges and sludge and fly ash
mixtures as a function of solids content.
-------
4.3.2.2 Leaching Characteristics
4.3.2.2.1 Untreated Wastes
From an overall assessment of leaching data, it was
concluded that for the major species, i.e., sulfate and chloride ions and
TDS, concentration in the leachate decreases rapidly during the first
three pore volume displacements (PVD), where about 90 percent of the
decrease takes place relative to the fifth pore volume (Ref. 3). The
concentrations at the 50th pore volume are approximately the same as at
the 5th.
For untreated wastes, the pH of the leaching solution showed
no discernible effect on the leachate except for the trace elements lead and
zinc, which were leached more readily by acidic conditions. Solubility
testing of fly ash showed only Cd, Cu, and Pb concentrations higher at an
acidic pH of 4. 0 than at 7. 0.
4.3.2.2.2 Treated Wastes
No data in addition to that reported in Ref. 3 was available,
and the following discussion generally repeats the information presented in
the first R&D report (Ref. 1). As with untreated wastes, the reduction of
major species concentrations generally takes place within the first three
pore volumes.
On the basis of laboratory and field test results, it was
reported that the concentration of the TDS in the first pore volume of the
treated leachate is approximately 50 percent of the untreated sludge leachate
(Ref. 3). After the initial flushing period of three to five pore volumes, the
concentrations generally remained constant thereafter, with values from
the treated wastes being approximately 25 to 50 percent of those from the
untreated wastes.
On the basis of somewhat limited leaching tests evaluating
five chemical treatment processes, another laboratory has reported mixed
results relative to improvement in the leachate quality from treated wastes
(Ref. 4). However, further testing is being conducted, as planned, to verify
initial trends and to permit an assessment of the performance of each of the
five individual chemical processes.
The effect of chemical treatment on immobilizing trace
elements was reported previously (Ref. 3); i.e., no discernible difference
was observed when compared to untreated materials because of low concen-
trations and significant scatter in much of the data. With additional leaching
data expected (Ref. 4) and utilization of statistical techniques, it may be
possible to determine the effect of chemical treatment. Also, some evidence
suggests that in certain instances the additives used in the chemical treatment
of FGD wastes may be contributing trace metals to the leachate.
25
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4.4 DISPOSAL. ECONOMICS
4.4.1 Chemical Treatment and Disposal
Engineering estimate costs for disposal of chemically treated
FGC wastes from a 1000-MWe plant burning Eastern coal were reported
previously (Ref. 5) and are repeated here for the convenience of the reader.
The total disposal costs, in 1975 dollars, on a 30-year average are as
follows:
a. Sludge, including fly ash, per ton (dry basis): $7.30 to
$11.40
b. Coal per ton (Eastern): $2. 07 to $3. 24
c. Mills per kilo watt-hour: 0.9 to 1.4
These costs represent the range of estimates for three fixation-
disposal processes. The average annual operating load factor was assumed
to be 50 percent over a 30-year lifetime, with the disposal site 5 miles
away from the power plant. Locating the disposal site 0. 5 miles from the
power plant rather than 5 miles and increasing the annual average operating
load factor from 50 to 65 percent reduces the disposal costs by approximately
9 and 7 percent, respectively. More detailed cost analyses of several dis-
posal processes will be conducted by the Tennessee Valley Authority (TVA),
and results from this study will be reported as they become available.
4.4.2 Ponding
Ponding costs available from Reference 1 are reported herein.
Disposal pond costs are dependent on construction and material factors as
well as land costs. For materials costing $2. 20 to $3. 80 per square yard,
which represent a reasonable range of liner material costs, the disposal
costs on a dry weight basis for a 1000-MW plant are $5.70 to $7.80 per
ton of dry sludge, or approximately 75 percent of those for chemical treat-
ment and disposal.
The cost of underdraining systems is in preparation and is
expected to be available in the next report.
4.4.3 Forced Oxidation to Gypsum
Engineering cost estimates were reported (Ref. 6) for a
tail-end oxidation process approximating the Japanese processes producing
saleable gypsum and an integrated system similar to that being tested at the
EPA Research Triangle Park (RTP) facility by R. Borgwardt. These are
presented in the following table, for a 500 MWe plant, on a 30-year average,
at a load factor of 50 percent, and in 1977 dollars. If a cost-avoidance cre-
dit is taken for not treating and disposing the FGD waste, gypsum produced
by forced oxidation becomes competitive with domestically mined gypsum.
26
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Process
Tail -End
Integrated
Cost, $/ton
dry gypsum
15.62
11.09
Net cost,
$/ton
dry gypsuma
4.84
0.31
Domestic
gypsum
fob at
mine, 1975 $
4.80
4.80
Assuming a disposal cost of $9/ton dry sludge
The above estimates are for 100 percent limestone utilization.
For a calculated 65 percent utilization, the net costs are $6.73 and $2.22
per ton dry gypsum, respectively, for the tail-end and integrated processes.
Conditions under which it may be economically feasible to oxidize and dis-
pose the gypsum are also presented. Since the conditions are somewhat
restrictive, the reader is referred to Section 5. 1. 1. 5. 3 for a more definitive
discussion.
4.4.4
Mine and Ocean Disposal
In conjunction with the work described in Section 5.4. 1 to
assess the potential and the environmental impacts associated with disposal
of FGC wastes in mines and in shallow and deep ocean sites, estimates of
capital and operating costs were made for five ocean disposal and six mine
disposal options. As a basis, a 500-MW power plant, burning typical
Eastern coal (3. 0% S, 10. 0% ash, and 0. 85 Ib of coal/kWh) was assumed
producing 365, 000 tons per year of dry sludge (including ash). The sludge
(with ash) was considered to be available either as a dry filter cake (50
percent solids), a 35 percent solids slurry (thickener underflow), or treated
sludge. No estimates were included for sludge processing such as filtration,
drying, fly ash addition, or treatment. However, in cases where treated
sludge required handling, estimates for excavation of treated sludge from
stabilization ponds were included. Capital costs were based on 1978 com-
pletion of construction and included installed equipment cost for the battery
limits disposal system (transfer, handling, and placement), engineering
and contractors' fees, working capital, owners' expense, startup, and
interest and escalation during construction. Capital investment and opera-
ting costs did not include sludge processing equipment, site preparation,
land cost, auxiliary utilities, or fees for permits.
For untreated sludge, costs including transfer and interme-
diate storage ranged from $3. 00 to $3. 50 per dry ton for onsite disposal
to $6.50 to $8.00 per ton for offsite disposal. Disposal of treated sludge
in surface area mines increased costs approximately $2. 00 to $2. 50 per
ton to account for excavation of stabilization ponds. The estimates did not
include site monitoring costs, which are a strong function of the hydrology,
sludge characteristics, and parameters (species) to be measured. To
determine overall disposal system costs, sludge treatment costs, as appro-
priate must also be added to these transfer and placement costs.
27
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In preparing the ocean disposal cost estimates, it was
assumed that the sludge was produced in an Eastern power plant with ready
access to the ocean and test facilities for berthing disposal craft were avail-
able with sufficient area for installation of a sludge transfer and storage
system. In all cases studied, the system costs utilizing self-propelled
ships were found to be less than for tug-barge combinations because of the
lower capital investment for fewer ships, resulting from their shorter
cycle times.
Disposal of untreated filter cake (with ash) on the Continental
Shelf was estimated as $4. 00 to $5. 00 per dry ton of sludge, with additional
costs of about $2. 00 to $2. 50 per dry ton resulting from excavation of sta-
bilization ponds for treated sludges. Deep ocean (off-shelf) disposal of filter
cake or treated sludge increased costs by $3. 00 to $4. 00 per dry ton more
than shallow (on-shelf) ocean disposal. Disposal of thickener underflow in
the deep ocean was estimated to cost approximately $ 1. 00 more per ton
than filter cake disposal. As with mine disposal costs, these estimates did
not include monitoring costs or sludge treatment costs.
4.4.5 Alumina Extraction
A preliminary process design and economic evaluation of a
method for the utilization of lime and limestone scrubbing wastes has been
completed (Section 5.5.4). The FGC wastes were used as a source of
calcium in the extraction of alumina from low grade domestic ores such as
clays or coal ash. The other principal feedstocks for the process were soda
ash and coal. The products were alumina for use in aluminum production,
elemental sulfur, and dicalcium silicate, an alternative material for use in
producing portland cement.
The process design was based on co-locating the conceptual
processing plant with a 1000-MW coal-burning power plant in order to re-
ceive more than 1, 000, 000 tons per year (TPY) of lime or limestone FGC
scrubber wastes. In addition to scrubber wastes, the process will require,
on an annual basis, 12, 000 tons of soda ash, 300, 000 tons of clay, and
273, 000 tons of coal to produce 70, 000 tons of alumina, 156, 000 tons of
sulfur, and 625, 000 tons of dicalcium silicate. Dicalcium silicate would
be used to feed a cement manufacturing facility producing 860, 000 tons of
portland cement per year.
The results of this study indicate that an alumina extraction
process employing calcium sulfate or sulfite sludge, sodium carbonate, and
kaolin clay as reactants could be commercially feasible under present econo-
mic conditions provided that the alumina extraction plant includes a cement-
producing facility which utilizes the dicalcium silicate by-product from the
alumina extraction process. Should bauxite prices escalate, the estimated
selling price for alumina as output from an alumina plant not possessing a
cement facility may become competitive (Section 5. 5.4).
28
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4.5 ENVIRONMENTAL ASSESSMENT
4. 5. 1 FGC Waste Properties
Data from the various projects are not sufficient for a detailed
overall environmental assessment of the effects of land disposal on water
quality and land reclamation. However, certain trends are emerging and
are summarized herein. It is expected that these will be updated and possi-
bly modified as additional data become available.
It has been determined that untreated waste chemical and
morphological properties tend to be a function of the coal and more impor-
tantly a function of the scrubbing process variables. The morphology tends
to establish the settling and dewatering characteristics of a particular slurry.
Detailed characterization of scrubber solid as a function of scrubber operating
parameters on the properties are being conducted. Furthermore, chemically
treated waste characteristics are also dependent on the treatment process
itself. Prime factors to be considered in the disposal of FGD wastes are as
follows.
4.5.1.1 Structural Strength
Because of their rheological and structural characteristics,
untreated wastes cannot typically support personnel and equipment. Treated
material, depending on the fixation process and the solids content, can be
expected to achieve strengths in excess of those considered minimal for
supporting personnel and equipment and, in some cases, building structures.
The long-range effect of weathering on strength, i.e., the effect of wet-dry
and freeze-thaw cycling, is yet to be defined.
4.5.1.2 Permeability
Permeability coefficients of untreated materials are in the
range 10"* to 10"^ cm/sec. Chemical treatment tends to reduce these
values over a broad range, from negligible to several orders of magnitude,
depending on the process, chemical additive, and the solid content of the
treated material (Sections 4. 3. 3 and 5. 1.3. 1. 1). The long-range effect of
weathering on permeability is yet to be determined.
4.5.1.3 Leachate Concentration
Laboratory and field leaching data have shown that leachate
concentrations of major species, i.e., calcium, sulfate, chloride, and TDS,
in the leachate from chemically treated wastes are about 25 to 50 percent
of the concentrations of major species in untreated materials (Section
5. 1.1.3).
4.5.1.4 Leachate Mass Release
The mass release of major constituents into the soil from
chemically fixed materials is reduced as a result of a 10- to 100-fold
reduction in the permeability of the treated wastes (Section 4. 5. 1. 2), as
29
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well as the reduced solubility of major pollutant constituents (Section 6. 1.3).
Treatment process and mode of disposal, i.e., pond, landfill, or lake,
determine the mass loading of pollutants into the soil, which can amount to
a reduction of one to two orders of magnitude when compared to untreated
materials.
4.5.2 Waste Disposal and Dewatering Methods
4.5.2.1 Field Disposal Evaluation
A project to evaluate and monitor the field-site disposal of
untreated and treated FGC wastes has been under way for approximately
two years at the TVA Shawnee power plant site (Ref. 5). Its purpose is to
determine the effects of several scrubbing operations, waste treatment
methods, disposal techniques, soil interactions, and field operation proce-
dures. Test samples of treated and untreated wastes, groundwater, surface
water, leachate, and soil cores are being analyzed in order to evaluate the
environmental acceptability of current disposal technology.
The analysis of groundwater shows no indication of increases
in concentration levels attributable to the presence of any of the ponds.
The TDS and the concentrations of major constituents in the
supernates of the untreated and treated ponds increased during dry weather
and decreased again when increased rainfall caused additional dilution
(Refs. 5 and 7).
Generally, the TDS, SC>4, Ca, and Cl in the leachate from
untreated ponds reached the input liquor concentration for these constituents
and decreased steadily thereafter. Minor constituents whose concentrations
span a range of six orders of magnitude were relatively constant over the
period monitored (Ref. 5). The analyses of leachate from the ponds con-
taining treated sludge show data trends similar to the untreated ponds;
however, TDS levels consistently remained at a level approximately one-half
that of those found in the input liquor. Six minor constituents remained at
relatively constant levels throughout the monitoring period, with the excep-
tion of the boron level in one treated pond, which increased steadily to a
level approaching that of the input liquor.
Late in 1976, an evaluation was initiated at the TVA Shawnee
site concerning the environmental effects, settling, and structural charac-
teristics of disposing untreated lime wastes in underdrained field impound-
ments. Monitoring of limestone and gypsum evaluation sites was started
early in 1977.
Other field evaluations of FGC waste test impoundments and
full-scale disposal sites are in early stages of implementation by LG&E and
U.S. Army Corps of Engineers, respectively.
30
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4.5.2.2 Liner Evaluation
An experimental program to determine the compatibility and
effectiveness of 18 liner materials with FGD wastes, liquors, and leachates
has been initiated. Material screening tests have been conducted. Materials
have been selected, and testing has begun in test cells. The exposure of
materials to various wastes has been limited, and definitive information is
not available at present. The economics of FGD disposal by ponding is also
being assessed.
4.5.2.3 Soil Attenuation Effects
A study to determine the extent to which heavy metals and
other chemical constituents of FGC wastes may be expected to migrate
through soil in land disposal sites has been initiated. Soil and waste charac-
terization tests are complete. However, work has not progressed to the
point where quantitative information on the migration and attenuation of FGD
waste constituents has been determined.
4.5.2.4 Waste Dewatering Methods
Studies were initiated to determine dewatering characteristics
of FGC wastes and to define areas where improvements can be made in
dewatering equipment or techniques. Since the program is in its early
stages, quantitative information is not available. However, results from
this work are expected to be used in assessing benefits derived from not
only a reduction of dewatering equipment size, but also the waste volume
handled, disposal acreage, and chemical additives.
4. 5. 3 Data Base Development
A study establishing a data base for use in the development of
FGD waste standards has been completed. It includes a categorization of
the power generating industry and the location of FGD waste sources, the
state of the art of FGD system control technology, untreated and treated
waste characterization, and the current practices in sludge treatment and
disposal technology. In addition, such factors as site characterization,
health effects, safety, ecological effects, and land use and aesthetics in
environmental considerations of FGD sludge disposal are included. Existing
and proposed federal and state regulations that may apply to the disposal of
FGD wastes are summarized and discussed. The results of this study sug-
gest chemical and physical regulating parameters, as well as one option
for regulating FGD sludge disposal to land.
4.6 DISPOSAL, AND UTILIZATION ALTERNATIVES
Disposal alternatives being studied include assessment of
the environmental effects of disposal of treated and untreated wastes in
mines and oceans, as well as in landfills and ponds. Experimental and
economic studies evaluating processes to produce usable materials such as
gypsum, elemental sulfur, and alumina are also being pursued.
31
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4. 6. 1 Disposal Alternatives
The preliminary assessment of the technical, environmental,
and economic factors associated with the mine and ocean disposal of FGC
wastes has been completed.
An initial review identifies four general categories of mines
as the most promising candidates: active surface-area coal mines, active
underground coal mines, inactive or mined-out portions of lead or zinc
mines, and inactive or mined-out portions of active underground limestone
mines. In addition to the environmental impacts, each category was re-
viewed with regard to the alternatives for placement, the physical properties
of FGC wastes that would be suitable, the operational impacts, the capaci-
ties, and the availability and accessibility (via transportation systems) for
FGC waste disposal. As a result of this review, the following mines were
determined to be most promising:
a. Active Interior surface-area coal mines
b. Active Eastern and Interior room-and-pillar under-
ground coal mines.
In general, Interior surface-area coal mines appear to be
more promising than Western (Rocky Mountain and Pacific Coast) area
surface coal mines. However, area surface mines both in the Interior and
the West were considered much more promising than Eastern contour sur-
face mines because of the latter's low capacity for FGC wastes and the
difficulty for waste placement because of the steepness of slopes in the con-
tour mines. The problem with the Western surface-area mines is the
greater potential for groundwater contamination, relative to Interior mines,
because of a lower net annual rainfall resulting in less dilution of leachate.
In addition, FGC wastes from Western plants burning low-sulfur coal nor-
mally contain a higher concentration of dissolved salts.
Individual Interior surface-area mines have substantial cap-
acity for receiving FGC wastes, and disposal is considered technically
feasible within existing mine operations. The wastes must be dewatered to
the extent necessary for landfill operations, so that they can be dumped into
a mined-out strip (which can be adjacent to one being mined) and covered
with overburden. Placing FGC waste in the mine void should assist in re-
turning the terrain to its original elevation.
The principal environmental impact anticipated from this
disposal method is an increase in TDS in waters that are recharged by
leachate from the disposal site. This impact may be lessened by placing
part of the overburden in the mined-out strip prior to placing the FGC waste,
thereby elevating the waste above the groundwater table. In addition, dilu-
tion to acceptable TDS levels can be encouraged by maintaining a suitable
distance between the disposal site and the stream or by assuring that the
receiving streams have a sufficiently high flowrate.
32
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In assessing the ocean disposal of FGC wastes, various
methods of transportation and disposal were examined, including surface
craft (e.g., bottom-dump barge and slurry dispersion) and pipeline (outfall).
Various chemical and physical forms of the FGC wastes were also consi-
dered, i.e., sulfite-rich wastes, sulfate-rich wastes, and treated wastes in
both soil-like and brick-like forms. Both Continental Shelf and deep ocean
disposal of the wastes were examined.
Until more definitive data are available, disposal of sulfite -
rich FGC wastes on the Continental Shelf or in the deep ocean does not
appear to be advisable because of protected problems with oxygen demand
and sulfite toxicity (from ingestion by marine life). In addition, it appears
that all soil-like FGC wastes--whether sulfite or sulfate, treated or
untreated--should not be disposed of via quick-dumping surface craft or
pipeline (outfall) on the Continental Shelf. Several options that involve sur-
face craft appear more promising:
a. Dispersed disposal of sulfate-rich FGC wastes on the
Continental Shelf
b. Concentrated disposal of treated, brick-like FGC
wastes on the Continental Shelf
c. Dispersed disposal of sulfate-rich FGC wastes in the
deep ocean
d. Concentrated disposal of both sulfate-rich and treated
FGC wastes in the deep ocean
4.6.2 Utilization Alternatives
Utilization of FGC wastes can be considered as an alternative
to disposal. In this regard, the use of FGD wastes in the manufacture of
fertilizer were reported as being studied by TVA and the Illinois Institute
of Technology (IIT) (Ref. 1). Although a number of problems relating to
preneutralizer operation have been experienced by TVA, potential solutions
are being systematically tested. Experiments on the forced oxidation of
sulfite sludges to form gypsum for potential use in wallboard were conducted
by EPA at RTF (Ref. 8) and by Southern Services at Gulf Power Company
(GPC) Plant Scholz, using the Chiyoda process. Wallboard from Chiyoda
gypsum, a 50/50 blend with the natural material, has been fabricated. The
chemical and physical properties of the gypsum produced by forced oxidation
have been determined. The properties specifically related to manufacturing
wallboard have not been determined.
Engineering estimates on the cost of producing saleable
gypsum, have been made and are summarized in Section 4.4. The detailed
economics studies of various gypsum-producing processes and a survey of
potential markets are also being conducted.
33
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A project to use FGD gypsum in cement manufacturing is
expected to get under way in the near future, as is the pilot plant evaluation
of key steps in a process that uses FGD waste reduced to CaS in a kiln as a
starting material to produce elemental sulfur or sulfuric acid.
A preliminary process design and economic evaluation of a
method for the utilization of lime and limestone scrubbing wastes has been
completed (Section 5.5.4). The FGC wastes were considered as a source
of calcium in the extraction of alumina from low-grade domestic ores such
as clays or coal ash. The other principal feedstocks for the process were
soda ash and coal, the products being alumina for use in aluminum produc-
tion, elemental sulfur, and dicalcium silicate, which is an alternative
material for use in producing portland cement. Although the chemistry of
the process is similar to the lime-soda-sinter reaction, with the exception
that it proceeds in a reducing rather than oxidizing atmosphere, a number
of technical assumptions were made regarding the chemical functioning of
the process. These conditions were identified, and the recommendation
that laboratory testing be conducted to determine the validity of the assump-
tions was made. The economics are discussed in Section 4.4. 5.
4.7 POWER PLANT WATER RECYCLE,
TREATMENT, AND REUSE
This portion of the Waste and Water Program is designed to
evaluate, develop, and demonstrate cost-effective techniques for minimizing
water consumption and discharges through recycle and reuse, as well as
techniques for treatment of in-plant streams for reuse or discharge within
effluent guidelines.
The major limitation in the recycle and reuse of major plant
streams (e.g. , cooling tower blowdown and ash sluice water) is the buildup
of dissolved salts. Chemical treatment to precipitate compounds (e.g.,
calcium sulfate) can increase the number of cycles in the major systems,
but eventually purging of the more soluble salts is required. Treatment of
the purge streams may involve use of expensive techniques such as eva-
porative or membrane processes. Demonstration of the broad-scale appli-
cability of the technology necessary for minimization or elimination of
effluents is expected to be provided by this program.
Five power plants are being studied to examine the alternatives
for minimizing water use and discharges in the major plant systems, e.g.,
cooling towers, ash sluice systems, and wet scrubbers. Several water
treatment systems are being examined to address the problem of dissolved
salts in recycle streams, including vapor-compression cycle evaporation
and vertical tube evaporation with interface enhancement (for better heat
transfer).
Chemical characterization of water streams from three
plants, and computer-assisted simulation of existing plant water utilization
operations were completed. Technical assessments were also completed,
formulating water recycle and reuse options to minimize water requirements
34
-------
and discharges in major plant systems, e.g., cooling towers, ash sluice
systems, and wet scrubbers. Cost estimates of each viable option were
also prepared. The plants were chosen to represent regions in the United
States where water recycle or reuse would be advantageous because of high
water costs, limited availability, or treatment and disposal problems.
The three sites initially selected for this study were the
Four Corners Plant of Arizona Public Service (APS), Comanche of Public
Service of Colorado, and Bowen of Georgia Power Company. The study
has been completed for these locations during the past year, and subsequently
similar studies were initiated for Montana Power Company's Colstrip plant
and Pennsylvania Power and Light Company's Monitor plant.
Chemical analyses of water samples were conducted, and
these results were used as input data to verify a computer model simulating
normal plant operations. Subsequently, evaluation of various water recycle
and reuse options and strategies for each of the representative plants on the
basis of design or design installation, operability, and treatment effective-
ness were made with the aid of the model simulations.
Cooling tower and ash sluicing alternatives included use of
cooling system blowdown to sluice ash operating at various cycles of con-
centration, the effect of CC>2 mass transfer on formation of scale, pH
control, and treating of the discharge water by lime-soda or reverse
osmosis.
Alternatives for the participate scrubbing system include the
effects of using existing tanks as solid-liquid reaction vessels, increasing
tank volumes, recycling ash pond overflow, and reducing the fly ash content
entering the scrubbers. The sensitivity to the various parameters was
determined and reported; several viable options as defined by the techni-
cal assessment were made; and the overall optimum recycle or reuse option
based on technical and economic considerations for each of the three plants
was defined. The results of the study including several alternatives for
each specific site and additional testing to verify that key assumptions have
been made. Overall recommendations for further assessments or field
evaluations are planned and will be available upon completion of the analyses
of the Colstrip and Montour plants.
A series of tests to demonstrate the feasibility of using a
vertical tube, falling film, vapor-compress ion evaporator to concentrate
waste water from an FGD process will be conducted in the near future: one
with a 25-gallon per day bench unit and the other with a pilot size 600-gallon
per day evaporator.
The effectiveness of interface enhancement using a surfactant
to reduce heat transfer requirements was demonstrated as a means of re-
ducing energy and cost of treating and recycling boiler plant wastewater
streams. Tests with 5, 000 and 10, 000-gallon per day evaporation were
conducted.
35
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4. 8 FULL-SCALE APPLICATIONS
A total of 15 plants, representing 9 utilities and totaling
7484 MWe, are currently committed to initiate, by 1979, the chemical treat-
ment of lime-limestone scrubber wastes prior to disposal. Five stations
(2100 MWe) are now in operation; seven (3959 MWe) will start up by the end
of 1977; and three have made definite commitments to begin by 1979. Also,
16 plants representing 3646 MWe are identified as scrubbing and disposing
untreated lime-limestone scrubbed FGC wastes in lined or in natural clay
unlined ponds in 1976 (Ref. 2).
Experience with a limestone wet scrubber, gypsum-producing
system operating on Unit 1 at the Northern States Power Company Sherbourne
generating plant was described recently (Ref. 9). Unit (700 MWe) became
operational in May 1976. The sulfite slurry from the scrubber is air-
oxidized in a reaction tank. The gypsum slurry is thickened and pumped to
a disposal site. Unit 2 (700 MWe) is scheduled to begin operation in
May 1977.
36
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SECTION V
EPA-SPONSORED RESEARCH AND DEVELOPMENT
The U. S. Environmental Protection Agency (EPA) Program
for Control of Waste and Water Pollution from Flue Gas Cleaning (FGC)
Systems is designed to evaluate, develop, demonstrate, and recommend
environmentally acceptable cost-effective techniques for disposal and utili-
zation of FGC wastes, with emphasis on flue gas desulfurization (FGD) waste,
and to evaluate and demonstrate systems for maximizing recycling and reuse
of power plant water. The program currently consists of 20 projects,
encompassing 6 major areas of interest: (1) environmental assessment of
FGC waste disposal and utilization processes including other power plant
effluents, (2) process technology assessment and new technology develop-
ment, (3) process economic studies, (4) alternative FGC waste disposal
methods development, (5) new FGC waste utilization methods development,
and (6) development of methods for improving overall power plant water
utilization.
The scope of the EPA FGC waste and water pollution control
program, is depicted in Figure 1. Projects concerning coal-pile effluents,
fly ash, water, and FGC waste (untreated, treated, and as affected by
scrubber operation) span the entire spectrum of the FGC waste characteriza-
tion and disposal assessment problems.
In this report, the specific projects are discussed separately
under their respective primary categories as indicated in Table 1.
Additional information such as contractor or agency project director, EPA
project director, duration, start date, and type of study are provided in
Table 2.
5. 1 ENVIRONMENTAL ASSESSMENT OF FGC WASTE DISPOSAL
Eight environmental assessment projects are currently under
way. These include FGC waste characterization studies; laboratory and
pilot field studies of disposal techniques for chemically treated FGD sludges;
characterization studies of coal-pile drainage, coal ash, and other power
plant effluents; and studies of attenuation of FGC waste leachate by soils.
37"
-------
5. 1. 1
FGC Waste Characterization, Disposal Evaluation, and
Transfer of Waste Disposal Technology (The Aerospace
Corporation
The Aerospace Corporation, El Segundo, California, is
completing a broad-based study directed toward the determination of environ-
mentally sound disposal of solid and liquid wastes produced in FGD processes.
The desulfurization processes of interest in this program are the lime,
limestone, and double alkali wet scrubbing of flue gases produced in the
combustion of coal in steam power plants. More specifically, problems
associated with FGD waste disposal are being defined, and assessments
are being made of the operational feasibility, performance, and costs of
current disposal methods. In addition, recommendation regarding alter-
native disposal methods based on these findings are being formulated
(Ref. 1). Annual reports are being issued, of which this is the second, in
which FGC waste-related research and development (R&D) activities
sponsored or conducted by EPA, Tennessee Valley Authority (TVA), and
private industry are summarized and assessed.
During this period, emphasis has been placed on enlarging
the data base of the physical and chemical characterization of FGD scrubber
wastes. Three additional sources (Table 3) were included. Alternative
disposal methods encompassing technical and economic factors in producing
TABLE 3. FGD SYSTEMS SAMPLED AS DATA BASE
Power Plant
Tennessee Valley
Authority (TVA),
Shawnee Steam
Plant
Louisville Gas
and Electric Co.,
Paddy's Run Station
Gulf Power Company
Scholz Station
Scrubber
System
Venturi and
spray tower,
prototype
Marble
bed
absorber
Venturi and
spray tower
Scrubbing
Capacity
MW (equiv)
10
70
20
Coal
Source
Eastern
Eastern
Eastern
Absorbent
Lime
Carbide
lime
(slaked lime
waste)
Soda ash,
lime
i7Psll_m by forced^oxi^ation of FGD wast_es__were assessed.. Physical and
chemical properties of gypsum relative to its disposal potential were "deter-
mined. The technical planning, support, and assessment of an EPA FGD
waste disposal field evaluation program was continued. The latter is
reported in Section 5. 1.2.
38
-------
Results reported in the first annual R&D report jRef. 1) are
summarized briefly to place the entire technical program in perspective.
However, details of only the current year's work are provided.
5.1.1.1 Chemical Characterization of Process Streams
Analyses of process streams from seven utility power plants
(Table 4, plants 1 through 7), encompassing a wide range of scrubber
system capacity, coal sources, and absorbent were reported (Ref. 3). The
effect of process variables on the stream characteristics wereincluded and
are summarized as follows:
a. T*he concentrationj^fjnajor chemical species increases
with time from startup~until a steady-staTe~condition~i¥
reached for all species. Trace element concentrations
reach steady-state rapidly and are not affected by the
steady-state conditions of the major species.
b. The system pH is effective in controlling trace element
species only within a defined system where major process
parameters are controlled.
c. Western coals, in general, tend to have lower trace metal
contents than Eastern coals and significantly lower con-
centrations of arsenic, cadmium, mercury, and zinc.
d. The major portion of trace metals found in the sludge
liquor originates from leaching of the fly ash during the
more acid portion of the scrubbing cycle. The contribution
made by the process waters is insignificant relative to the
contribution from coal; in most cases, the contribution of
the absorbent is slight.
5.1.1.2 Chemical Characteristics of Untreated FGC Wastes
Chemical properties of scrubber waste liquors and solids and
FGC waste leachates have been reported (Refs. 1 and 3). Data on wastes
from three additional sources (Table 4, plants 8 through 10) were obtained
during the year and are reported herein.
A description of the chemical analyses is presented in detail
in Reference 3 for both liquids and solids.
Chemical, x-ray, and scanning electron microscope analyses
of the solid fractions of the wastes have continued to show the uniqueness of
the characteristics, with properties affected by coal composition and scrubber
operating variables such as pH, liquid-to-gas ratio, and hold-tank residence
time s.
The effect of process variables on the concentration of chemical
constituents was reported as a function of the location within a scrubber
circuit, as well as a function of the scrubber process itself, i. e., lime,
limestone, and double alkali.
39
-------
TABLE 4. FLUE GAS DESULFURIZATION SYSTEMS
SAMPLED AS DATA BASE
Power Plant
1. TVA Shawnee Steam
Plant
2. TVA Shawnee Steam
Plant
3. Arizona Public Ser-
vice Company,
Cholla Power Plant
4. Duquesne Light Com-
pany, Phillips
Power Station
5. General Motors
Corporation,
Chevrolet -Parma
Power Plant
6. Southern California
Edison, Mohave
Generating Station
7. Utah Power and
Light Company,
Gadsby Station
8. TVA Shawnee
9. Gulf Power Company,
Plant Scholz
10. Louisville Gas and
Electric Company,
Paddy's Run Station
Scrubber
System
Venturi and
spray tower,
prototype
Turbulent
contact
absorber,
prototype
Flooded-disk
scrubber,
wetted film
absorber
Single- and
dual-stage
venturi
Bubble -cap
tower
Turbulent
contact
absorber,
pilot plant
Venturi and
mobile bed,
pilot plant
Venturi and
spray tower,
prototype
Venturi and
spray tower
Marble bed
absorber
Scrubbing
Capacity,
MW (equiv)
10
io
120
410
32
<1
<1
10
20
65
Coal
Source
Eastern
Eastern
Western
Eastern
Eastern
Western
Western
Eastern
Eastern
Eastern
Absorbent
Lime
Limestone
Limestone,
fly ash
Lime
Soda ash,
lime
Limestone
Soda ash,
lime
Lime
Soda ash,
lime
Carbide
lime
Note: Sources 1 through 7 are reported in Reference 3 .
Sources 8 through 10 are reported in this report.
40
-------
The concentrations of major chemical species and trace
elements in FGD wastes decrease as the sludge passes from the scrubber to
the disposal point. However, the constituents are affected differently as they
progress through the scrubbing process. An indication of the end-to-end
(scrubber stage to disposal stream) changes for the concentrations of various
constituents is shown for the limestone process in Table 5 by the relation-
ship of the constituent concentrations of liquors in the scrubber to those in
the disposal material.
The range of concentrations of constituents found in 10 dif-
ferent Eastern and Western scrubber liquors is shown in Table 6. A sum-
mary of the net changes in the liquor stream between the initial (scrubber)
stage and the final stage (disposal stream) for lime, limestone, and double
alkali is shown in Table 7.
TABLE 5. RELATIVE CHANGE IN CONCENTRATION OF CONSTITUENTS
IN THE SCRUBBER CIRCUIT LIQUOR: LIMESTONE PROCESS
Constituent
Calcium
Chloride
Sulfite
Sulfate
Trace Metals
PH
Direction of Change
Decrease
Decrease
Decrease
Decrease
Decrease
Increase
Change from Scrubber Stage
to Disposal Stream
30 to 40%
20%
< 99%
10%
10 to 20%
2 units
5. 1. 1.2. 1
Solids Composition
Dry wastes from three power plants (Table 3), Gulf Power
Company (GPC), Louisville Gas and Electric (LG &c E) Paddy's Run No. 6,
and the EPA two-stage pilot scrubber, were analyzed for their major com-
ponents. The results of these analyses are shown in Table 8.
Each of the samples contained gypsum in excess of 15 per-
cent (dry basis). Neither the Scholz or the Shawnee sample contained a
significant amount of fly ash, but the Paddy's Run sludge contained about
12 percent ash and about 3. 5 percent carbon. The Scholz sludge also con-
tained approximately 4 percent sodium salts from the double alkali process.
On a dry basis, precipitated calcium carbonate amounted to about 10 per-
cent for the Shawnee and Scholz sludges and almost 30 percent for the
Paddy's Run sludge.
41
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TABLE 6. RANGE OF CONCENTRATIONS OF CHEMICAL,
CONSTITUENTS IN FGD SLUDGES
Scrubber
Constituents
Aluminum
Arsenic
Beryllium
Cadmium
Calcium
Chromium
Copper
Lead
Magnesium
Mercury
Potassium
Selenium
Sodium
Zinc
Chloride
Fluoride
Sulfate
Sulfite
TDS
PH
Sludge Concentration Range
Liquors; mg/1
0.03 - 2.0
0.004 - 1.8
0.001 - 0. 18
0.004 - 0. 11
10 - 2600
0.011 - 0.5
0.002 - 0. 56
0.005 - 0. 52
0.1 - 2750
0.00005 - 0.07
5.9 - 760
0.0006 - 2.7
10.0 - 29,000
0.001 - 0. 59
420 - 33,000
0.6 - 58
600 - 84,000
0.9 - 3500
2800 - 162, 700C
4.3 - 12.7
Solids; mg/kg
a
0.6 - 52
0.05 - 6
0.08 - 4
(10. 5) - (26.8)b
10 - 250
8-76
0.23 - 21
-
0.001 - 5
-
2-17
(3.7)
45 - 430
(0.9)
-
(3.5) - (47.3)
(0.2) - (69.2)
Not analyzed.
Parentheses indicate weight percent.
Typical maximum: approximately 10,000 (see Section 5. 1. 1.2.2).
42
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TABLE 7. NET CHANGE IN SCRUBBER LIQUOR COMPOSITION OF
MAJOR, MINOR, AND TRACE CONSTITUENTS BETWEEN
INITIAL AND FINAL STAGES IN SCRUBBER SYSTEM
Constituent
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Nickel (Ni) '
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Zinc (Zn)
Chloride (Cl)
Fluoride (F)
Sulfate (S04)
Sulfite (SO3)
TDS
PH
Limestone*
Increase
X
XX
XX
XX
X
XXX
XX
X
XX
xxxx
Decrease
XXX
X
X
XX
X
xxxx
X
X
X
XX
X
XX
X
X
XXX
xxxx
xxxx
xxxx
No
Significant
Change
(<20%)
XXX
XXX
XXX
XX
XXX
X
XX
XX
xxxx
X
X
xxxx
Lime*
Increase
X
X
X
XX
XX
xxxx
Decrease
XX
X
XXX
X
XX
XX
XX
XXX
X
X
X
X
XXX
XX
XXX
XX
XX
XXX
XX
No
Significant
Change
(<20%)
X
XX
X
xxxx
XX
XX
XX
XX
xxxx
XX
XXX
X
XXX
X
XXX
X
XX
XX
XX
X
Double Alkali*
Increase
X
X
X
X
X
Decrease
X
X
X
No
Significant
Change
(
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TABLE 8. COMPOSITION OF DRY SOLID SLUDGE FROM THREE
POWER PLANTS (WEIGHT PERCENT)
Component
CaS04a
CaS04b
CaSO3C
CaCO3
Insolubles in HC1
Na2S04f
Total
TVA/Shawnee,
Lime (Run F)
19.4
-
69.2
10.3
-
-
98.9
LG&E /Paddy's Run,
Carbide Lime
15.1
-
37.4
29.5
15. 9e
-
97.9
Gulf/Scholz,
Double Alkali
15.3
-
68. 1
10. 1
-
3.7
97.2
Gulf/Scholz
(analysis by
A. D. Little, Inc.)
-
13.9
68. 1
8.2d
-
3. 5
93.7
aExpressed as CaSC^- 2 H2O. Calculated from excess Ca.
bExpressed as CaSC^- 1/2 H2O. 6 Contained 3.5 percent carbon (loss on
Expressed as CaSO,- 1/2 H2O. ignition [LOl]) .
Calculated from Na.
Scanning electron microscope (SEM) examination of the solid
phases of each of the ash-free sludges showed the presence of some fly ash
particles. The trace elements found in the liquors of ash-free sludge may be
explained by the presence of minor quantities of fly ash not removed by the
separator. Also, in addition to condensing the volatile elements such as
Pb and Hg in the scrubber it is probable that the extremely fine fly ash
particles are carried past the separators by the flue gas and are collected in
the scrubber. Since the finest fly ash particles can remain suspended in
the liquors and leachates and pass through the pores of the filters used during
analyses of the liquor, it is possible that these suspended particles are sub-
sequently analyzed as dissolved species. Therefore, not all the reported
concentration levels of trace elements may actually represent dissolved
species.
Additionally, other input ingredients such as the lime and
limestone absorbents may possibly contribute perceptible levels of trace
elements to the liquor.
It is concluded from these data, that removal of fly ash ahead
of the scrubber will not eliminate the trace elements from the sludge liquors
and leachates, but the concentration levels of some trace elements may be
significantly reduced (Section 5. 1. 1. 2. 3. 2).
44
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5.1.1.2.2 Quality of Scrubber Liquors
The range of concentrations of scrubber liquor constituents
from eight scrubber systems from seven utility power plants is shown in
Table 6.
From these data, several observations can be made that reveal
the chemical constituent concentrations that may be expected of liquors in
contact with solids from FGD scrubber systems. Among the trace elements in
the sludge liquors, the upper limits of the ranges of concentrations are between
0. 1 and 1 mg/£ with the exceptions of aluminum, arsenic, and selenium, for
which the highest values did not exceed 3 mg/fe , and for mercury, for which
the highest value was 0.07 mg/i . The range of concentrations of most trace
elements in the liquor was two orders of magnitude. The range of con-
centrations found in the solids is similar. However the absolute level of
the concentrations in the solids is greater than the liquor by a factor of 100.
The concentration of Be, Cd, and Hg in the liquids and solids
are generally low in both phases. Concentrations of chromium and zinc
(possibly also copper are high in the solids), but corresponding high con-
centrations are not observed in the liquor. Whereas in the first case (Be,
Cd, and Hg), the correlation strongly suggests a concentration limitation
based on input quantities, in the second case, the lack of correlation suggests
that factors relating to system chemistry may be controlling the liquor con-
centrations of these elements. An apparent exception is selenium. It has
the broadest concentration range in the liquor (nearly four orders of
magnitude) but has the narrowest concentration range in the solids (factor
of eight). In this case, the sample that contributed the high solids content
had the lowest pH of all samples analyzed.
Among the major chemical species, the concentrations and
range of concentrations were reported as strong functions of the chemical
parameters of the system. Sodium, as an example, ranges from a low
value of 10 mg/j? to nearly 5 percent by weight. The later quantity being in
the liquid phase of the double alkali systems. When high values of sodium
and sulfate, or chloride, are present, significant amounts of sodium salts
can be expected in the solids. As was expected, the solids sample having
the highest sulfite content also had the lowest sulfate content. One of the
more important chemical parameters in the sludge liquors is the total dis-
solved solids (TDS) content. Because of the recycle of scrubber liquor and
because water is evaporated in the scrubber, the TDS can be expected to
be relatively high. In most cases, it can be typically described at
10,000 mg/J . Higher values of about 150,000 ppm were observed for the
double alkali samples wherein the solids had not been washed to remove
soluble salts. In another instance where a salt brine was used as makeup
water, the TDS was high and consistent with the makeup water concentration.
Values lower than 10,000 were observed in two systems during startup and
a third system in a partial open-loop operation. From these data, it is
reasonable to expect values of TDS in scrubber liquors to be approximately
10,000 mg/l for steady-state systems, except in cases having exceptional
circumstances, and these cases can usually be identified from system design
parameters, e.g., the percent solids in the water stream (degree of water
recycled), chloride content of coal, and addition of soluble salts such as
MgO.
45
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5.1.1.2.3 Leachate Characteristics
In previously reported studies (Ref. 1), leaching tests were
continued until 50 pore volumes had been displaced. In most cases it was
observed that 90 percent of the decrease in concentration of major leachable
species had taken place after three pore volumes had been displaced. In the
studies currently being reported, leaching was not continued beyond 10 pore
volume displacements (PVD). The leaching tests were performed under
aerobic conditions; other details of the procedures are given in Ref. 3.
Leaching curves were defined by analyzing for TDS at approxi-
mately five different PVD values. Complete analyses for major and minor
constituents were made only on the first and last leachate PVD sample. ;
Figure 6 illustrates the concentrations of major ionic species (804, Cl, Ca,
and Mg or Na) and TDS for the sludge leachates obtained from a TVA
Shawnee lime scrubber operation. It shows the results of leaching ashfree
lime sludge and sludge remixed with 40-wt % fly ash. For additional com-
parison, the concentrations of major species and TDS of the sludge liquor
(filtrate taken from vacuum filter) have also been plotted. The TDS in the
leachates of both sludge samples decreased from initial values comparable
to that of the filtrate and leveled off at 2000 to 2500 mg/4 after three pore
volumes had been displaced. This is approximately the solubility of the
calcium sulfate. Similarly, the sulfate leveled off at about 1000 to 1500 mg/jf .
The calcium concentrations of both samples remained relatively constant at
about the 600 mg/jf level. In contrast, the magnesium and chloride concen-
trations decreased to below the 100 mg/jj level. The filtrate and leachate
analytical data are also shown in Table 9. Data from the LG&E Paddy's Run
and the Gulf Power Plant Scholz from Reference 6 are given in Table 10.
Although TDS was high for the Scholz double alkali material, approximately
160,000 ppm, it was due primarily to the presence of sodium sulfates. The
sodium sulfate fraction was completely leached by the third PVD, and the
TDS exhibited calcium sulfate saturation levels.
The leachate from the L.G&E sludge at the 10th pore volume
differed from the leachate samples of all the other sludges after extended
leaching. In that material, the TDS and SO. concentrations did not level off
at their characteristic gypsum saturation level of 2200 and 1300 m.g/JL .
Lower values^observed for the 10th PVD leachate sample from the LG&E
Paddy's Run sludge represents under-saturation of the leaching water and
indicates that most of the gypsum may have been already dissolved so that
saturation was no longer possible.
5.1.1.2.4 Effect of Fly Ash on Leachate Components
Chemical analyses for major components and for 10 selected
trace elements are reported for the sludge JLiquors and leachates from the
three power plants (Tables 9 through IT). Analyses for" SHawne"e~sTudge
filtrate liquor a.nd for leachate samples frornjleaching tests of both the ash-
free sludge and the sludge and fly ash mixture "are given in Table 12. "Results
for both ash-free sludge from Gulf Scholz and sludge containing 30 percent
fly ash are given in Table 10.
46
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.10,000
< 5,000
o
o
NO FLY ASH
40% FLY ASH
O — IDS — •
A _ S04 — A
D — cr — •
0 — Ca — •
O — Mg — •
234567
AVERAGE PORE VOLUME DISPLACEMENT
Figure 6. Concentrations of major ionic species from the
TVA Shawnee lime scrubber
47
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TABLE 9. COMPARATIVE ANALYTICAL RESULTS FOR TVA SHAWNEE
LIME SLUDGE LIQUOR AND LEACHATE
Concentrations in m.g/1
Constituent
pH
TDS
Arsenic
Beryllium
Boron
Cadmium
Calcium
Chromium
Copper
Lead
Magnesium
Mercury
Potassium
Selenium
Sodium
Zinc
Chloride
Fluoride
Sulfate
Without Fly Ash
9/8/76 Run F
Filtrate
8.0
10260
0. 058
<0.001
76
0.013
650
0. Oil
0.005
0.010
1730
<0. 00006
24
0.078
137
<0.001
1320
1.9
4500
9/8/76 Run F Leachate
First Pore
Volume
8.3
4480
35
690
0.025
0.011
<0.002
400
14
75
0.007
550
2.6
2150
Fifth Pore
Volume
7.1
1770
0.120
<0.001
3
0.013
450
0.010
<0.002
<0.002
30
0.00006
2
<0.0004
47
0.01
128
2.5
1100
Run F + 40% Fly Ash Leachate
First Pore
Volume
7.9
4330
65
600
0.010
<0.002
<0.005
310
7
72
0.003
400
6
2700
Seventh Pore
Volume
7.4
2430
0.360
<0.001
16
0.010
640
0.004
<0.002
<0.005
10
0.00024
4
0.051
42
0.02
130
1.2
1450
48
-------
TABLE 10.
COMPARATIVE ANALYTICAL RESULTS FOR SCHOLZ
SLUDGE LIQUOR AND LEACHATE
Concentrations in
Constituent
pH
TDS
Arsenic
Beryllium
Boron
Cadmium
Calcium
Chromium
Copper
Lead
Magnesium
Mercury
Potassium
Selenium
Sodium
Zinc
Chloride
Fluoride
Sulfate
6/20/76 Run with No Fly Ash
Leachate
Filtratea
12.1
155700
43
12
0. 1
320
53600
5000
24
80000
First Pore
Volume
12.5
9140
5
1000
—
—
— •
<0.01
—
43
2260
1070
48
3700
Sixth Pore
Volume
12.3
3550
<0.004
<0.001
<0.5
0.016
1100
0.0025
<0.002
0.005
<0.01
0.00030
1
<0.0004
12
0. 007
310
13
1160
6/27/76 Run with Fly Ash
Leachate
Filtrate*
12.0
162700
40
..-_
7
0.1
380
55300
4900
4
84000
First Pore
Volume
10.4
17330
<0.5
550
0.2
74
4720
1050
3
10100
Ninth Pore
Volume
9. 1
2140
0.019
<0.001
<0.5
0.010
800
0.024
<0.002
<0.002
0.3
0.00024
11
<0.0004
82
0.013
134
0.9
1415
alncomplete analyses for filtrate samples is a consequence of insufficient sample quantity.
49
-------
TABLE 11. COMPARATIVE ANALYTICAL RESULTS FOR PADDY'S RUN
SLUDGE LIQUOR AND LEACHATE
Concentrations in mg/J
Constituent
pH
TDS
Arsenic
Beryllium
Boron
Cadmium
Calcium
Chromium
Copper
Lead
Magnesium
Mercury
Potassium
Selenium
Sodium
Zinc
Chloride
Fluoride
Sulfate
Filtrate
8.9 •
24230
0.011
<0.001
18
O.OZ5
515
0.054
0.0045
<0.005
3400
0.00006
760
0.0028
260
0.003
5600
<1
15000
Leachate
First Pore
Volume
7.4
5240
2
410
<0. 0008
0. 004
<0. 002
470
125
40
0.015
410
<0. 1
2800
Tenth Pore
Volume
8.1
1650
0.023
<0.001
<0.5
0.004
260
<0.0008
<0.002
<0. 002
70
0.00006
21
0.006
3
0. 005
157
<0. 1
920
50
-------
TABLE 12.
COMPARATIVE ANALYTICAL RESULTS FOR SHAWNEE
LIME SCRUBBER FILTRATE LIQUORS
Concentrations in m.g/1
Constituent
pH
TDS
Arsenic
Beryllium
Boron
Cadmium
Calcium
Chromium
Copper
Lead
Magnesium
Mercury
Potassium
Selenium
Sodium
Zinc
Chloride
Fluoride
Sulfate
With Fly Ash
3/19/74
9.4
2800
0. 15
0.026
--
0.03
660
0.03
0.05
0.01
24
0.07
11
0.09
36
0.01
1050
1.4
900
5/16/74
8.8
8400
0.01
0.05
--
0.013
2420
0.02
0.04
0.13
200
<0.05
27
1.9
109
0.02
4200
3.0
1250
6/27/74
8.7
9400
0.02
<0.002
46
0.11
2520
0.03
0.002
0.33
420
<0.001
28
<0.02
127
0.08
4900
3.3
800
Run F
with 40%
FlyAsha
7.9
4330
--
--
65
--
600
0.010
•C0.002
<0.005
310
--
7
--
72
0.003
400
6
2700
Without Fly Ash
8/23/76
Run E
8.9
5650
<0.004
<0.001
9
0.025-
1450
0.008
<0.003
0.010
220
<0. 00006
22
0.022
130
0.002
1850
1.3
1100
9/8/76 Run F
Liquor
8.0
10260
0.058
<0.001
76
0.013
650
0.011
0.005
0.010
1730b
<0. 00006
24
0.078
137
<0.001
1320
1.9'
4500
First PVD
8.3
4480
--
--
35
--
690
0.025
0.011
<0.002
400
--
14
--
75
0.007
550
2.6
2150
aFly ash admixed to fly ash-free sludge, first pore volume.
Magnesium added to lime to evaluate absorbent efficacy.
51
-------
When comparing the trace element concentration levels in
samples with and without fly ash, differences exceeding 100 percent were
reported as being considered significant in order to offset uncertainties
resulting from analytical procedures and techniques.
Trace element concentrations are given in Table 12 for TVA
Shawnee lime sludge filtrate liquors from Run E (8/23/76) and Run F (9/8/76),
in which the fly ash was removed ahead of the scrubber, and from three runs
made early in 1974 (Ref. 3), in which the fly ash was present and scrubbed
from the flue gas. The pH of each of the liquors is in the range of 8 to 9.
The 3/19/74 sampling was taken for a starting run. The high
Mg content of Run F was due to the^ deliberate addition of MgO to the lime as
part ~o~f~the~ TVA~— Bechtel test program. Examination of Table 12 shows
that with a single exception the results, for Run E and Run F, all liquors are
comparable in concentration to the lowest value of the three samples that
contained fly ash or, in several cases, range between the lowest and the
median values for the 1974 runs. Zn appears as the single exception and is
definitely lower in the Run E and Run F filtrates.
Reports of the leachate analyses (Table 9) (Ref. 3) for Shawnee
Run F ash-free sludge and sludge to which 40 percent fly ash had been added
showed five trace element concentrations that were greater in the sludge
and ash leachate, four approximately the same in both leachates, and two
higher in the ash-free sludge. Only for B and Se were the differences greater
than by a factor of three. However, the As, Hg, and Zn levels in the leachate
of the sludge-fly ash mixture are higher than those in the Run F filtrate
liquor. Also, the last PVD of leachate showed higher Zn concentrations than
the first PVD. For the greater amounts of observed Zn to be released, it
was postulated that the trace element Zn is incorporated in sulfite or
carbonate solid phases whose solubilities are sufficiently greater at the
slightly lower pH's of the last leachate samples. A similar pattern was
observed for the Zn concentrations in the leachates from the Paddy's Run
sludge (Table 11). The behavior of As and Hg may also have been a con-
sequence of their release from a solid phase during leaching.
Inasmuch as sampling of scrubber sludge containing fly ash
had not been planned for the Runs E and F time period leaching tests, data
from recent sludges are not available for comparing the leachate from
sludges containing fly ash that was scrubbed with the flue gas and presum-
ably was exposed to a much lower pH during the scrubbing operation. Such
a comparison can be made for the leachates from the two Gulf Scholz sludge
samples shown in Table 10. However, the pH range of the double alkali
process used at the Gulf Scholz plant was too high to expect acid leaching
of fly ash during the scrubbing operation." The high pH of the liquors (> 12)
causes the virtual absence of Mg, which was precipitated as the hydroxide
and only began to reappear in the leachates after elution had reduced the
pH to below 9. Examination of the data of Table 10 shows that of the trace
elements listed, only As and Cr are found in higher concentrations in the
leachate from the sample that contained fly ash. The much lower pH of the
leachate sample from the Scholz sludge containing fly ash may also be
52
-------
responsible for the higher concentrations of these two elements. It is
noteworthy that the fluoride concentrations are higher in the liquors and
leachates of the ash-free sludge.
5. 1. 1.2.5
Effects of pH on Trace Element Solubility
Fly ash obtained from TV A Shawnee was mixed in the pro-
portion of two parts of mechanically separated ash to one part of electro-
statically separated ash to lime sludge from Run F. To this mixture, dilute
HC1 was added as required to maintain a constant pH. Two acid equilibra-
tions, one at pH 4. 0 and the other at pH 7. 1, were continued until the pH
remained constant. The mixture was then stirred for 24 hours.
The concentrations of trace elements measured in the solutions
at pH 4 and pH 7 are shown in Table 13. Only the concentrations of Cd, Cu,
and Pb appeared to be significantly higher in the sample at pH 4, than in the
sample at pH 7. The selenium concentration was higher in the neutral sample
at pH 7 than in the acidic extract. Of all the trace element concentrations
measured in these fly ash tests, only the concentrations of Cd, Cu, and Pb
in the sample at pH 4 were found to be significantly higher than the values
for these elements measured in the sludge-fly ash leaching tests. The con-
centration levels of all other trace elements in the fly ash leachate were
comparable to those in the sludge-fly ash extract except for the concentra-
tions of As, which were lower than those measured in the sludge-fly ash
leaching tests.
TABLE 13.
TRACE ELEMENTS LEACHED FROM SHAWNEE
FLY ASH AT CONTROLLED pH
Concentrations in m#
PH
Arsenic
Beryllium
Cadmium
Chromium
Copper
Lead
Mercury
Selenium
Sodium
Zinc
4.0
0.039
<0.001
0.036
0.006
0.036
0.022
0.00012
0.006
10
0.01
7. 1
0.058
<0.001
0.009
0.009
0.003
<0.005
0.00015
0.026
10
0.005
aShawnee fly ash mixture of two parts mechanically separated ash and
one part electrostatically separated ash.
53
-------
5.1.1.3 Chemical Characteristics of Treated Waste
Since no additional leaching experiments of chemically treated
waste were planned during this phase of the program, a summary of the
findings provided in the first annual R&D report (Ref. 1) are summarized in
the following paragraphs.
As with untreated wastes, the reduction of major species con-
centrations generally takes place within the first three pore volumes.
On the basis of laboratory and field test results, it was re-
ported that the concentration of the TDS in the first pore volume of the
treated leachate is approximately 50 percent of the untreated sludge leachate.
After the initial flushing period of 3 to 5 pore volumes, the concentrations
generally remained constant thereafter, with values from the treated wastes
being approximately 25 to 50 percent of those from the untreated wastes.
The effect of chemical treatment of immobilizing trace ele-
ments is not discernible at present when compared to untreated materials
because of low concentrations and significant scatter in much of the data.
With additional leaching data, statistical techniques may be useful to deter-
mine the effect of chemical treatment. Also, some evidence suggests that
in certain instances the additives used in the chemical treatment of FGD
wastes may be contributing trace metals to the leachate.
5. 1. 1.4 Physical Properties
The determination of disposal, handling, and transportation
techniques for FGD wastes will be strongly influenced by the physical be-
havior of the wastes and the resultant costs. The applicability of some
disposal methods may be limited or restricted by physical properties of
FGD wastes resulting from the particular state in which they are formed,
i. e. , water content, crystalline phase composition, and particle size and
distribution. In the previous year (Table 4) (Ref. 3), experimental tests
were conducted to characterize 15 FGD wastes from 7 power plant scrubbing
facilities. These included pilot, prototype, and full- scale units ranging
from 1- to 410 -MWe capacities. In each case, the material from each
facility was received as it would be for its normal state of disposal, and
testing was directed toward the application of the results in landfilling and
land reclamation situations.
_____ ^^^riqd^ covered by this report, fiye^ additional
samples from three plants (Table 4), were tested. Selected tests were also
conducted on FGD wastes to which fly ash was recombined to wastes initially
collected without the ash to determine the effect on physical characteristics
in the event more favorable structural properties resulted from these
combinations .
The physical parameters investigated included specific "gravity
and bulk density as a function of solids content, water retained as a result
of various dewatering techniques, viscosity of slurries at various solids
54
-------
contents, permeability as a function of particle packing, and compactibility
and load-bearing strength as a function of solids content.
5.1.1.4 Solids Characterization
The physical properties of liquid-solid mixtures are dependent
upon the characteristics of both the liquid and the solid constituents as well
as the interaction between them. The FGD wastes contain four principal
crystalline phases: calcium sulfite, calcium sulfate, fly ash, and unreacted
limestone or precipitated calcium carbonate. These solid phases exist as
fine particulates suspended in an aqueous liquor which is usually saturated
with ions of these solids. In addition, ions from dissolved sodium chloride
or calcium chloride are also present.
The relative amounts of each of the solid crystalline phases
are dependent upon many system design and operating parameters and in-
clude (1) the sulfur content of the coal and the efficiency of SO^ removal,
(2) the fly ash in the flue gas entering the scrubber and the fly ash removal
efficiency of the system, (3) the stoichiometric ratio of reactants added
relative to the sulfur content and the reactant utilization efficiency, and (4)
the amount of oxidation of the sulfur products that takes place in the system.
In addition, each crystalline phase and the characteristic of each phase will
have some influence on the behavior of the waste.
5. 1. 1.4.2 Solids Composition
The composition of the solids fraction of each of the wastes
sampled was determined by chemical means and is presented in Table 14;
the analytical techniques used are described in Reference 3. The wide
range in composition for each of the major solid constituents reflects the
various design differences that exist among scrubber systems/.' Systems
having high-efficiency fly ash collection facilities upstream of the scrubber
are contrasted sharply with those systems having less efficient collection
methods. The calcium sulfate content of the sludge reflects the tendency of
the calcium sulfite to be oxidized, the oxidation usually occurring in the
scrubber or reaction tank.
5.1.1.4.3 Viscosity
The viscosity of the liquid waste is a measure of its pump-
ability, which affects both the mode and cost of sludge transport.
The results of viscosity tests for ten sludges (Ref. 10) show
that pumpable mixtures (< 20 poise) range from a high solids content of
70 percent to a low solids content of 30 percent (Figure 7).
The waste materials produced in FGD systems contain finely
divided particulate materials suspended in an aqueous medium and consist of
three major phases having markedly different morphologies: calcium sulfite,
calcium sulfate, and fly ash. It is both the particle size distributions and
phase morphologies that are believed to influence the viscosity of the sludges.
55
-------
TABLE 14. PHASE COMPOSITION OF FGD WASTE SOLIDS IN WEIGHT PERCENT'
Atomic
Formula
CaSO • 2H2O
CaSOj. 1/2H2O
CaS04- 1/2H2O
CaC03
MgSO4' 6H2<3
Other
Na2S04- 7H2O
NaCl
CaSO4a
CaSj010a
Fly Ash
Total
TVA Shawnee
Limestone,
2/1/73
21.9
18. 5
38.7
4. 6
20. 1
103.8
TVA Shawnee
Limestone,
7/12/73
15.4
21.4
20. 2
3.7
40.9
101. 6
TVA Shawnee
Limestone,
6/15/74
31.2
21.8
4.5
1.9
40. 1
99. 5
TVA Shawnee
Lime,
3/19/74
6.3
48.8
2.5
1.9
40. 5
100.0
SCE Mohave
Limestone,
3/30/73
84. 6
8. 0
6.3
1. 5
3.0
103.4
GM Parma
Double Alkali,
. 7/17/74
48.3
12.9
19.2
7.7
6.9
7.4
101.4
APS Cholla
Limestone,
4/1/74
17.3
10.8
2. 5
14. 3C
58.7
103.6
DLC Phillips
Lime,
6/17/74
19.0
12.9
0.2
9.8
59.7
101. 3
UPL Gadsby
Double Alkali,
8/9/74
63.8
0.2
10.8
17.7
8.6
101. 1
Shawnee
Lime,
9/8/76
19.4
69.2
10.3
<1.0
98.9
LG&E
Lime,
7/76
15. 1
37.4
29. 5b
3.5d
7.8
12.4b
101.0
Gulf-
Scholz,
6/20/76
15. 3
68. 1
10. 1
<1.0
97.2
Phases not explicitly measured; presence deduced from x-ray study.
The carbide lime used as absorbent is an acetylene manufacturing plant waste by-product, and is reported to contain 2 to 2-1/2 percent silica and 3 to 8 percent CaCO,.
^Soluble salt, phase not determined.
Carbon.
in
-------
CURVE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
SLUDGE FLY
GM PARMA DOUBLE ALKALI
UPL GADS BY DOUBLE ALKALI
TVA SHAWNEE LIME
DLC PHILLIPS LIME
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
TVA SHAWNEE LIMESTONE
SCE MOHAVE LIMESTONE
APS CHOLLA LIMESTONE
LG&E PADDY'S RUN CARBIDE LIME
TVA SHAWNEE LIME
TVA SHAWNEE LIMESTONE
GPC SCHOLZ SODA ASH DOUBLE ALKALI
GPS SCHOLZ SODA ASH DOUBLE ALKALI
TVA SHAWNEE LIME
ASH, %
7.4
8.6
40.5
59.7
20.1
40.1
40.9
3.0
58.7
12.4
<1.0
<1.0
<1.0
30.0
40.0
DATE
7/18/74
8/9/74
3/19/74
6/17/74
2/1/73
6/15/74
7/11/73
3/30/73
4/1/74
7/76
9/8/76
9/28/76
6/20/76
6/27/76
9/8/76
120
100
LU
—
O
" 80
fc
in
O
O
5 60
40
20
10
30
40 50 60
SOLIDS CONTENT. WEIGHT %
70
Figure 7. Viscosity of desulfurization sludges
57
-------
Both calcium sulfate and calcium sulfite scrubber waste
products tend to have particle sizes in the same range as fly ash, between
1 and 100 |j.m. However, fly ash is formed as spheres; sulfite wastes are
platey or rosettes; and sulfates are blocky in shape. Unreacted precipitated
CaCO, from the limestone (or lime process) is usually present in the waste
and contributes an additional shape parameter.
Whereas particle shape, particularly platey sulfite particles,
has been suggested as the cause of the rheological nature of sludge, in the
viscous-fluid behavior of these sludges it is not apparent that the sulfite
phase plays a decisive role. On the other hand, the data clearly suggest
that fly ash decreases the viscosity of a sludge and high pH (of a double
alkali system) increases it. Although particle shape, size, and distribution
appear to influence viscosity behavior, the precise effect each may have is
not clear from published results. In an instance with double alkali sludge,
the results tend to suggest that agglomeration of the fine particles, rather
than their presence, also affected viscosity.
Considering the lack of characterization data, the importance
of experimentally determined data for system design parameters is apparent.
5.1.1.4.4 Water Retention and Wet Bulk Density
The water retention and, conversely, the dewatering charac-,
teristics of FGD wastes are important to the various disposal techniques in
that they affect the volume of the disposal basin, the waste handling methods,
and the condition of the wastes in their final disposal state. The water re-
turned to the scrubbing system reduces the need for makeup water and also
reduces the pollution potential associated with the liquid phase at the dis-
posal site. Bulk density is then a consequence of the dewatering charac-
teristics of a waste.
The effectiveness of the dewatering method and the ability of
a sludge to be dewatered is a function of a number of solids characteristics,
including the size and distribution of particles, and the crystalline structure
of the particles, which are a function of the system as well as its operating
parameters, including the type of coals. Generally, four dewatering
methods are used: settling, settling by free drainage, vacuum filtration,
and centrifugation. The results are almost exclusively based on laboratory
experiments.
The effectiveness of a dewatering operation, i. e. , the relative
quantity of water that remains with the solid after performing the dewatering
operation, is characterized by the wet bulk density of a sludge.
The sludges with the best overall dewatering characteristics
are those with coarse particle size distributions, generally those produced
by the limestone scrubber systems. TTie'double alkali systems produce
the finest particle size distributions and have the poorest dewatering
characteristics.
58
-------
The highest density is obtained principally by vacuum-assisted
filtration in most sludges and by centrifugation in a few cases. In all cases,
relatively small density differences resulted from these two dewatering
methods.
In most sludges, there is very little difference in the density
when dewatered by settling or settling followed by free drainage, although
the latter always exhibits higher densities because of the lower retrention
from its free draining condition. While free draining may not produce a
significant improvement in bulk density, the slight gain coupled with its
associated solids content in some cases may significantly affect its load-
bearing strength (Section 4. 3.2).
Generally, the wet bulk density ranges from a low of approxi-
mately 1.48 g/cm^ (92 pcf) for settled sludges to a high of 1.76 g/crn^
(110 pcf) for vacuum filtered (Table 15). Drained and centrifuged values
were intermediate to these extremes, with the drained values being slightly
higher than the settled and centrifuged slightly lower than the filtered. These
values were obtained under laboratory conditions and may not be representa-
tive of results for commercial equipment use. However, it is expected that
the defined trends will apply.
No general relationship has yet been determined between
slurry solids content and settling rates because of the strong influence of
solids morphology on this property.
An interesting phenomenon was reported (Ref. 10) with freely
drained Shawnee lime sludge to which fly ash had been added. The solids con-
tent was adjusted to approximately 25 percent to simulate clarifier underflow.
When poured into a test container, the coarser fly ash particles (typically
50 |j.m in diameter) settled more rapidly than the sulfur-phase particles
(typically 20 ^.m) in diameter) and formed a fly ash layer on the filter paper
used as a retainer. Although supernate drained through the paper as in all
other cases without the fly ash layer, the presence of a fly ash layer beneath
the sludge appeared to aid the dewatering process. The resultant process was
nearly as effective as vacuum filtration. Because water retention in fly ash is
relatively low, supernate water pass es freely through the fly ash layer, creat-
ing air voids. It was postulated that, since the fly ash is contiguous with the
sulfur-phase particles, surface tension forces between the fly ash particles
and water are capable of overcoming the surface tension between the sulfur-
phase particles and water. Thus, water is also removed from the sludge as
it passes through the fly ash layer. The net consequence of this action is
that more effective dewatering takes place.
5.1.1.4.5 Permeability
Thejx>llution potential of sludge liquor into groundwaters is
governed by the mobility of leaching waters, which is limited by the coefficient
of permeability of the various media through which this leachate must pass.
Permeability of leaching waters through the waste defines
an upper limit to the amount of leachate that enters the subsoil. The amount
of liquid and the level of contamination of this liquid are jointly responsible
for the pollution potential of any given waste disposal site.
59
-------
TABLE 15. WATER RETENTION AND BULK DENSITY CHARACTERISTICS
Dewatering Method
Scrubber System
Lime
Limestone
Double alkali
Settled
Percent
Solids
40-48
47-67
37-40
Density,
g/cc
1.34-
1.40
1.39-
1.65
1.30-
1.35
Settled and
Drained
Percent
Solids
43-53
56-67
41-44
Density,
g/cc
1.36-
1.50
1.44-
1.67
1.33-
1.44
Centrifuged
Percent
Solids
50-57
60-77
50-62
Density,
g/cc
1.39-
1.52
1.56-
1.86
1.38-
1.62
Vacuum Filtered
Percent
Solids
56-57
53-80
55-58
Density,
g/cc
1.48-
1.54
1.48-
1.78
1.50-
1.61
-------
A The permeability coefficients of untreated wastes range from
2 X 10" to 5 x 10-^ cm/sec (Ref. 3). The permeability coefficient of un-
treated sludges has been shown to be a function of the volume fraction of
solids in the waste. These values are intermediate to typical values for
silty sand and sandy clay, which are 10~4 cm/sec and 5 X 10~° cm/sec,
respecitvely. Values as low as 6 X 10~7 cm/sec have been reported for
LG&E carbide-lime untreated wastes. Sludge without fly ash has been found
to have permeabilities about five times greater than the sludge with fly asn,
with the solids fraction nearly identical for both materials. The difference is
believed to be related to agglomeration of the fine sludge particles, which
respond in a manner similar to coarser materials. When fly ash replaces
the sludge particles, the solids fraction does not change, but the fly ash,
having a broad particle size distribution, fills pore passages such that the
rate of water passage through the waste is reduced.
Consolidation of untreated wastes under pressures of 30 to
100 psi reduces the void fraction and also reduces permeability coefficients
by factors of from 2 to 5 (Table 16). The higher solid volume fraction,
resulting from compaction or consolidation, and the decrease in permeability
TABLE 16.
PERMEABILITY COEFFICIENTS OF COMPACTED
UNTREATED SLUDGE
Sludge
Source
TVA Shawnee Lime
(6% fly ash)
TVA Shawnee Lime
(40% fly ash)
LG&E
(12% fly ash)
Gulf Scholz
(0% fly ash)
Gulf Scholz
(30% fly ash)
Sampling
Date
9/8/76
9/8/76
11 /76
6/20/76
6/27/76
Fractional
Solids
Volume
0.35
0.33
0.47
0.42
0.41
0.25
0.21
0.37
0.34
0.36
0.34
Permeability
Coefficient
cm/sec
8.9 X lO'6
1.9 X 10"5
7.3 X 10-6
i. 1 x io~5
1.4 X 10'5
8.4X 10-6
3.4 X 10-5
1.4X ID"4
4.4 X ID'4
4.8X 10-5
8.3 X ID'5
Consolidation
Pressure, psi
100
30
100
30
30
100
30
100
30
100
30
61
-------
appear to be a function of the size of the sludge particles and the size and
distribution of the fly ash particles. Consolidation of sludge at the base of
a 40-foot-deep disposal site will decrease permeabilities to about 1 X 10"
cm/sec at the surface. This value appears to represent the lower limit of
untreated waste permeabilities expected in the field.
Chemical treatment tends to reduce permeability by less than
a factor of 2 in some cases and several orders of magnitude in others
(Figure 8).
5.1.1.4.6 Compressive and Load-Bearing Strength
The structural characteristics of wet FGD sludge affect its
use where land reclamation is desired. Therefore, the load-bearing
strength of the sludge is an important factor in planning for acceptable
disposal of FGD waste.
Unconfined compressive strengths of untreated wastes are
low, and generally no specific values are reported because the material is
usually too soft to measure.
Chemically treated sludges exhibit unconfined compressive
strengths ranging from approximately 25 to 4500 psi in laboratory studies.
However; commercial processes being used at power stations today produce
values in the range of 25 to 400 psi (Ref. 10).
Recently, load-bearing strengths as a function of the solids
content of wastes dewatered by settling, with underdraining such that sur-
face drying occurs, have been reported (Ref. 6) for a number of power plant
FGD sludges (Figure 9). These results reinforce previous observations
(Ref. 11) that sludges may be dewatered to critical and narrow ranges of
solids content, above which the load-bearing strengths increase rapidly to
values well above the minimum for safe access of personnel and equipment.
However, the critical concentration appears to be-unique for each waste
tested, and correlation with other physical or morphological characteristics
was not apparent. Field evaluations (Ref. 7) of underdrained ponds of lime
and limestone sludges have shown these materials to be capable of supporting
light construction equipment. Load-bearing strengths in excess of 20 psi
were reached.
The development of load bearing strength of various TVA
Shawnee power plant lime sludge and fly ash mixtures as a function of the
time the waste was allowed to dewater by settling and with the water removed
in an underdrained condition is shown in Figure 10. The strength of settled
wastes without draining is also illustrated. In the latter case, low bearing
strengths are exhibited even after an extended settling period. As a result
of under drainage, high strengths were developed within several days. With
limestone underdrained wastes, high load bearing strengths, e. g. , 12 kg/
cm^, were developed approximately 5 to 10 days after the same values were
attained for lime wastes handled in a similar manner.
62
-------
10
,-3
JUT4
10
10
-7
10
,-8
o--
*
J-o*
PONDB
1.6 x 10
5.5 x 10
,-8
SAMPLE SOURCES DATE FLY ASH, %
• TVA SHAWNEE LIMESTONE 6/15/74
o TVA SHAWNEE LIME 3/15/74
o SCE MOHAVE LIMESTONE 3/30/73
• GM PARMA DOUBLE ALKALI 7/18/74
T UPL GAOSBY DOUBLE ALKALI 8/9/74
V DLC PHILLIPS LIME 6/17/74
A APS CHOLLA LIMESTONE 4/1/74
X CHEMFIX LAB
0 DRAVO LAB
A 1UCS LAB
© POND B TVA SHAWNEE /DRAVO (Ref. 2)
$) POND C TVA SHAWNEE /I UCS (Ref. 2)
(g) POND E TVA SHAWNEE/ CHEMFIX (Ref. 2)
* PULVERIZED
r^T FAMILIES OF DATA HAVING SAME SLOPES
40.0
40.5
3.0
7.4
8.6
59.7
58.7
0.10
0.20
0.30
0.40 0.50 0.60
VOLUME FRACTION OF SOLIDS
0.70
0.80
0.90
Figure 8. Permeabilities of chemically treated and untreated sludges.
-------
Ov
it"-1
O SHAWNEE LIME, NO FLY ASH
• SHAWNEE LIME, 40% FLY ASH
A SCHOLZ. NO FLY ASH
A SCHOLZ. 30% FLY ASH
D PADDY'S RUN
0 PHILLIPS
O CHOLLA
• GADSBY
e SHAWNEE LIMESTONE, NO FLY ASH
O SHAWNEE LIMESTONE 40% FLY ASH
60 70
SOLIDS CONTENT, weight
80
90
Figure 9. Compression strength of sludges and sludge/fly ash
mixtures as a function of solids content.
-------
250
en
200
150
o
I
to
o
5!
§ 100
50
30% 55/60 1
58/66
45/55 J
EFFECT OF WATER REMOVAL BY
UNDERORAINAGE ON LOAD-BEARING
STRENGTH OF LIME SLUDGES
NOTE:
a. PERCENTAGES REFER TO THE
AMOUNT OF ASH AS A
FRACTION OF THE SOLIDS
b. SOLIDS CONTENT OF
NON DRAINED SLURRY: 45%
WATER REMOVAL BY
UNDER DRAINAGE-
55/60 REFERS TO INITIAL
AND FINAL SOLIDS CONTENT
NON-
DRAINED
5 10
SLUDGE SETTLING TIME, DAYS
Figure 10. Effect of water removal by underdrainage on
load-bearing strength of lime sludges.
15
-------
The effect of rewetting dewatered wastes with the equivalent
of 1/2 inch of rainfall is also reported (Ref. 6). A loss in load-bearing
strength was observed. However, its recovery, when allowed to drain,
appeared to be comparable to the initial buildup.
5.1.1.5 Gypsum From Forced Oxidation of RTF Pilot Plant
Limestone Scrubber Sludge
R. Borgwardt of EPA, RTP, has been conducting pilot plant
scale experiments evaluating the forced oxidation of sulfite sludges from
the limestone and lime scrubbing of SO-, from flue gas. The experiments
were designed to determine limestone utilization, oxidation efficiency,
settling rates, and bulk densities of the gypsum product. The pilot plant
system consisted of a first-stage spray tower and a second-stage TCA loop
(Figures 11 and 12). The first-stage loop contained a holding tank, or tower,
equipped for air sparging to oxidize the sulfite. A portion of the oxidized
slurry was bled off to a vacuum drum filter. Burner combustion products
simulated flue gas with SC>2 and HC1 being introduced into the gas stream.
Fly ash was introduced, when desired, with the limestone in the second-
stage loop.
To augment the numerous chemical analyses and physical
property measurements being made at RTP and reported by Borgwardt
(Ref. 8), Aerospace conducted additional characterization tests on filter
cake and slurries from the first- and second-stage loopp of samples from
two runs utilizing limestone scrubbing, one with and the other without added
fly ash. Scanning electron microscope (SEM) and x-ray examinations were
made of crystalline phases, and wet chemical analyses were made for
major constituents of both the solid and liquid phases. Also, the leaching
characteristics of the solids were determined. Physical properties such as
bulk densities, compressive strengths, and permeabilities were also
measured on samples from the two runs.
5.1.1.5.1 Chemical and Leaching Characteristics
SEM, x-ray, and wet chemical analyses were made of the
filtered solids and solids from the first- and second-stage slurries. All
the measurements are in substantive agreement with each other as to the
composition of the solids.
It was shown that (1) the second-stage slurry contained
primarily hydrated calcium sulfite, CaSCy 1/2 H-O, with a small amount of
gypsum; (2) both the first-stage slurry and the filtered solids were primarily
gypsum with small amounts (< 1 and < 6 percent, respectively) of CaSO,' 1/2
H2O; and (3) the filtered solids contained more CaSO,- 1/2 H-O than did the
first-stage slurry. The presence of CaSO_. 1/2 H2O in the quantities ob-
served in the filtered solids was not due to incomplete oxidation in the first
stage and is not indicative of the basic characteristics process.
The presence of sulfite in the filter solids was not due to
incomplete oxidation in the first-stage loop, but was determined to be the
result of an unscheduled modification of the plumbing whereby a portion of
66
-------
2590 ppm S02
RUN SEP 29 - OCT 3
FLY ASH ADDITION
SCRUBBER EFFLUENT LIQUOR
TOTAL S AS S03 2660
S02 1250
C02 41
Ca 2640
Cl 5500
pH 4.3
S02
5.66
I 2910 ppm S02
AIR
35 Ib/hr
LIQUOR
TOTAL S AS S03 2300
S02 870
C02 28
Ca 2520
5 9Pm Cl 5440
Mg 770
pH 4.5
SATURATION 1.2
SOLIDS
TOTAL S AS S03 346
S02 15
C02 5
Ca 179
OXIDATION = 0.95 U
UTILIZATION - 0.97
TO FILTER
SETTLING RATE = 2.0cm/min'
SETTLED DENSITY =• 0.91 g/mi*
16 gph pH 5.4
. S02 • 520 ppm
_1_ 15.5 gpm
AP
8 in. H20
LI/VIESTONE + FLY ASH
25.0 Ib/hr
50.8% SOLIDS
"*^ BYPASS
I
47 gal
06
1
47 gal
f
47 gal
LIQUOR
TOTAL S AS S03 1820
S02
C02
Ca
Cl
Mg
PH
SATURATION
SOLIDS
TOTAL S AS SO,
S02
COo
Ca
260
1%
1600
3230
640
5.6
1.0
306
218
30
186
OXIDATION = 0.11
UTILIZATION • 0.82
FIRST STAGE
SECOND STAGE
Figure 11. EPA pilot plant forced oxidation system, tests with fly ash.
-------
00
S027.71 Ib/hr
HCI 0.15 Ib/hr
6.8% 02
LIQUOR
TOTAL S AS S03 1880
S02 390
Ca 2420
Cl 4180
pH 4.4
SATURATION 1.14
SOLIDS (12%)
TOTAL S AS S03 503
S02 55
C02 7
Ca 271
OXIDATION - 0.86
UTILIZATION - 0.93
TO FILTER
SETTLING RATE = 2 cm/min
SETTLED DENSITY = 0.88
(60% solids)
BYPASS
s*
3000 ppm S02
6.7 gpm1
I
(L/G
AIR
17.9 Ib/hr
(2.8x)
psig
10
in.
•i
15.8
min
18 ft
106
gal
0
L-fr
OXIDATION
TOWER
12
ft /sec
AP
2.0
in. H20
735 ppm
so
pH 3.9
FIRST STAGE
'2 = 720 ppm
(76%)
21 gpm
RUN DEC 1 - 5, 1975,
12 fps, NO FLY ASH
12
ft/sec
OQOOOOO
rgggW9S
AP
7.0
in. H20
pH5.1
(IIG 64)
SOLID SPHERES
3-in. BED DEPTH
25.4 Ib/hr
•LIMESTONE + FILTRATE
36.2% SOLIDS
\ **
47 gal
•
\
\
47 gal
cP
•
\
\
47 gal
aP
2.2 min 2.2 min 2.2 min
SECOND STAGE
Grams dry solid per ml final settled volume
LIQUOR
TOTAL S AS S03 1270
S02 190
C02 260
Ca 1430
Cl 2260
pH 5.5
SATURATION 1.07
SOLIDS (8%)
TOTAL S AS SO, 455
S02 257
C02 78
Ca 309
OXIDATION = 0.29
UTILIZATION = 0.74
Figure 12. EPA pilot plant forced oxidation system!', tests without fly ash.
-------
the second-stage bypassed the first-stage loop to control the solids content
in the second stage. In addition, the quantative results of the wet chemical
analyses verified conclusively that complete oxidation of calcium sulfite to
gypsum was achieved in the first-stage loop (Table 17).
Calcium, magnesium, chloride, sulfate, and TDS were re-
ported for the filtrates from both samplings. The results are shown in
Table 18. Mass and charge balance calculations were included; the results
are expressed as ratios in Table 18. The close proximity to unity of these
ratios corroborates the results of the chemical analyses. Since the
analytical data appear to indicate saturation of the filtrates with gypsum, a
solubility ratio was also determined. It was defined as the product of the
measured calcium and sulfate ion concentrations, divided by the theoretical
solubility product constant, corrected for the effect of ionic strength. These
ratios also are approximately unity, also signifying gypsum saturation.
5.1.1.5.1.2 Leaching Test Results
Leaching test results of RTP lime stone-scrubbed FGC
gypsum wastes from sludge samples of September 30, 1975 (with fly ash)
and December 4, 1975 (without fly ash) are outlined in Table 18,
Based on the drying conditions used in the TDS determination,
it was reported that the CaCl~- 2H-O in the solids was not dehydrated when
the sample was brought to constant weight. A correction to reduce the TDS
by the molecules of H_O in the hydrated CaCl- was applied and reported.
The results for the filtered solids and first-stage slurries
show that after two to three PVD of water have passed through the samples,
gypsum, the principal ingredient of both materials, starts to dissolve and
produces a leachate that is saturated with calcium and sulfate ions.
Each one of the samples of Table 18 is saturated with gypsum
except for two of the second-stage slurry samples at 10 and 22 PVD whereby
the gypsum supply has been essentially depleted. These two are saturated
with calcium sulfite. From this point on, the calcium is supplied by the
dissolution of hydrated calcium sulfite, although the anion found in the
leachate will be sulfate because of the rapid oxidation of sulfite ions.
The concentrations of TDS and major constituents in leachate
from the first-stage slurry samples have been plotted against pore volume
displacement in Figure 13. In both samples, the TDS in the leachates
reached the same minimum gypsum (saturation) value after about three PVD.
The value was unchanged even when the leaching was continued until more
than 30 pore volumes had been displaced. The concentrations of magnesium
and chloride were reduced as leaching progressed, but sulfate remained
relatively constant, and calcium was only partially removed (Table 18). The
computed solubility ratios also supported the fact that each of the leachate
samples was saturated with gypsum.
69
-------
TABLE 17. COMPOSITION OF RTF OXIDIZED SLUDGES BY
WET CHEMICAL ANALYSIS
Sample Designation
Sampled 9/30/75,
Contained Fly Ash
First- Stage Slurry
Second- Stage Slurry
Filtered Solids
Sampled 12/4/75,
Contained No Fly Ash
First-Stage Slurry
Second- Stage Slurry
Filtered Solids
Total Solids
(% of Slurry)
11.3
12.4
64.9
b
Composition of Solids, Percent by Weight, Dry
Fly Ash
40. 0
38.4
38.6
CaSO4- 1/2 H2Oa
62.5
7.8
52.7
94.6
11.8
86.4
CaSO3' 1/2 H2O
<0. 5
41.4
5.7
0.7
51.8
9.5
CaC03
<0. 5
11.4
4.9
8.0
37.0
r
Drying process converted gypsum to CaSO,' 1/2 H_O.
b
Not determined.
-------
TABLE 18. ANALYSIS OF LEACHATES AND FILTRATES OF
RTF FORCED OXIDATION SAMPLES
Sample /Date
First-Stage
Slurry Solids
(9-30-75)
First-Stage
Slurry Solids
(1Z-4-75)
Second-Stage
Slurry Solids
(9-30-75)
Second-Stage
Slurry Solids
(12-4-75)
Filtered
Solids
(9-30-75)
Filtered
Solids
(12-4-75)
Filtrate
(9-30-75)
Filtrate
(12-4-75)
Contains
Fly Ash
Yes
No
Yes
No
Yes
No
Yes
No
No. of
Pore Vol.
Displacements
0. 7
26. 4
1.0
10. 3
0.3
9.6
0.9
22. 1
0.6
11. 1
0.5
-
14. 4
-
Concentration in mg/l
TDS
6820
2180
5860
2160
6770
300
5070
330
7100
2190
10100
2310
9230
10490
TDS
Corrected
5840
2140
4775
2120
5855
270
4290
300
6010
2120
8100
2260
7595
8515
Sb
5140
2130
5110
1620
5270
310
4290
380
5470
2065
7940
2100
7290
7750
^C
0. 88
0.99
1.07
0. 76
0.90
1.14
1.00
1. 27
0. 91
0.97
0. 98
0.93
0.96
0. 91
Ca
1300
550
1280
540
950
120
1080
100
1220
560
2170
500
1420
2200
so4
1540
1500
1450
1000
1910
150
1500
220
1600
1400
1250
1500
1800
1130
Cl
2000
80
2160
80
1870
40
1530
60
2220
90
4040
100
3330
3980
Mg
300
0. 3
220
0.04
540
0. 3
180
0. 3
430
15
480
0.2
740
440
Ionic
Strength
0. 15
0.06
0. 14
0.05
0.16
0.01
0.12
0.01
0. 16
0.06
0.23
0.06
0.22
0.23
Solubility
Product
Ratiod
1.16
1.19
1. 12
0.92
0.97
0.08e
1. 17
0. 10e
1.03
1. 13
0.94
1. 11
0.96
0.89
aMeasured TDS corrected for • 2 H2O in CaCl2 • 2 H2O. (Ca) X (SO4'/KCaSO with KCaSO corrected for ionic strength.
bS = sum of Ca, SO4> Cl, Mg ions. ^CaCO was ueed-
cMass ratio: S/TDS(corrected)-
-------
8000:
6000
: 4000
CONTAINED
NO FLY ASH
CONTAINED
FLY ASH
2000
10 20 30
AVERAGE PORE VOLUME DISPLACEMENT
Figure 13. Concentration of major species in leachate of
first-stage slurry solids of RTP oxidized
sludges.
During leaching, the soluble magnesium and calcium chlorides
were washed out of the bed with the residual liquor, leaving the crystalline
gypsum to saturate the leaching water. The ionic strength decreased as the
chlorides were removed, thus reducing the solubility of gypsum.
The results of leaching tests for the filtered solids were
reported as similar to those for the first-stage slurries. The TDS leveled
out at the same saturation value of about 2200 mg/jf .
The results shown in Figure 14 and the data of Table 18 on the
leachate characteristics of the second-stage slurries illustrate the difference
in composition between the second-stage and first-stage solids. The same
initial pattern of changing TDS with PVD that was observed for the first-stage
and filtered solids samples only persists to about five pore volumes. The
TDS concentration (Figure 1), particularly the one for the sample that con-
tained no fly ash, began to level off at the gypsum saturation content of about
2200 mg/S. and then decreased to about 300 mg/j? when 20 pore volumes were
displaced. The sulfate concentrations in the final leachate samples from the
second-stage slurries were about 1/10 of the amount in the final leachates
of the filtered solids or the first-stage slurries.
72
-------
8000
7000
6000
,5000
i1
§.
>3000
2000
1000
CONTAINED
NO FLY ASH
O
D
A
0
V
CONTAINED
FLY ASH
TOS
Cl
Mg
10 20
AVERAGE PORE VOLUME DISPLACEMENT
Figure 14. Concentration of major species in leachate of
second-stage slurry solids of RTP oxidized
sludges.
The inflection points on the TDS curves for the solids from
the second-stage slurries correspond to the gypsum being depleted. Initially,
the available gypsum in the leachate was beds (8 and 12 percent, Table 17)
and was ultimately depleted, leaving only calcium sulfite hemihydrate. This
was confirmed by x-ray diffraction measurements on the leachate bed solids
made at the conclusion of the leaching tests.
In assessing the overall material balance at PVDs of less than
1.0, i.e., TDS versus Ca, SO., Cl, and Mg, better agreement was obtained
with those samples without fly ash than with those that had fly ash in the
scrubber slurry. This indicates that;the major species were encompassed
by Ca, SO., Cl, and Mg for the no fly ash case, whereas some significant
additional constituents were leached when fly ash was present. It is also
apparent that, after many PVDs (> 10), the concentrations^ the major
species were virtually the same whether or not fly ash was initially present.
5. 1. 1.5.2
Physical Characteristics
Measurements were made of permeability coefficients, void
fraction, water retention, density, unconfined compressive strength, and
load-bearing strength of fly-ash-free gypsum, calcium sulfite, and gypsum
73
-------
mixed with 5 to 10 percent calcium sulfite. The effects of fly ash on the
properties of the various materials were also reported. A summary of the
physical properties is provided in Table 19.
Permeability coefficients for the gypsum and calcium were
approximately 1 X 10~4 cm/sec. The predominantly sulfite gypsum samples
tended to be slightly higher than the 1 x 10-4 value and the calcium sulfite
slightly lower.
The pore volume fractions of these solids range from 0. 5 to
0. 65 of which from 30 to 50 percent remain filled with water when the cast
samples are allowed to drain and dry in the ambient air until firm enough for
compressive strength measurements. For both samples, with and without
added fly ash, the second-stage solids show the largest pore volume frac-
tions (and the lowest densities), and the filtered solids retained the largest
percentage of water. In all cases, the pore volume fractions of the samples
which contained no fly ash were slightly higher, and their densities were
somewhat lower than for the corresponding samples which contained fly ash.
A comparison of the results of unconfined compressive
strength measurement for the two sets of samples (with and without fly ash)
shows that when wet the corresponding solids in both sets have comparable
strengths. When dry, the samples which did not contain fly ash had higher
levels of unconfined compressive strength. Furthermore, for both sets of
samples, the first-stage solids (gypsum) when wet showed substantially
higher compressive strength than the second-stage solids (calcium sulfite).
However; this difference did not persist in the first-stage solids when the
samples were completely dry; the gypsum without fly ash tended to remain
higher.
When the gypsum contained 5^p 10 percent calcium sulfite,
the wet unconfined strength was approximately that oFthe sulfite. The pre-
sence of fly ash did not seem to affect the unconfined compressive strength
of the drained solids. The effect of fly ash on the compressive strength of
the dry solids resulted in measurably lower values than did samples without
it.
Load-bearing strengths were measured on both samples of
filtered solids, with and without fly ash, using an adaptation of the standard
bearing ratio test for soils (ASTM D-1833-73). These gypsum samples,
which contained 5 percent sulfite, exhibited strength characteristics of
sludge containing typical sulfite-sulfate ratios of 3 to 4.
Measurements were repeated after further dewatering of the
solids. Results for the filtered solids with and without fly ash are plotted in
Figure 15. Although the measurements were terminated prematurely for
the sample containing fly ash, the curves are similar for the two samples
except that the rapid increase in strength with increasing solids content occurs
at about 10 percent higher solids content for the sample containing fly ash.
74
-------
TABLE 19. PHYSICAL CHARACTERISTICS OF RTF OXIDIZED SLUDGES
Sample Designation
Water
Content,
%
Density,
g/cm3
(wet)
Sampled 9/30/75, Contained Fly Ash
First-Stage Slurry
Second- Stage Slurry
Filtered Solids
Sampled 12/4/75, Co
First-Stage Slurry
Second- Stage Slurry
Filtered Solids
10
14
18
ntained No
15
14
18
1.4
1.2
1.5
Fly Ash
1.3
1.0
1.35
Unconfined
Compressive
Strength, kg /cm2
(wet) (dry)*
4.4
1. 1
1.4
4.2
1.8
0.7
0.5
0.9
3.0
1.9
1.6
Density,
g/cm7
(dry)
1.3
1.0
1.2
1. 1
0.8
1. 1
Pore
Volume
Fraction
0.50
0.60
0.50
0.55
0.65
0.55
Permeability
Coefficient,
cm/sec
1. 6X 10"4
8. IX 10"5
_5b
4. 5X 10 D
1. IX 10"4
9. 6X 10"5
1. IX 10'4
a50°C, vacuum.
Test specime.n was prepared -by "rodding" slurry during initial drainage.
Ol
-------
176
150-
125-
100
75
50
25
NO FLY ASH
WITH 39% FLY ASH
65 70
SOLIDS CONTENT, WEIGHT %
75
5. 1. 1.5.3
Figure 15. Load-bearing strengths of dewatered
filtered solids from RTF oxidized
sludges containing 5 percent sulfite.
Estimated Costs of Gypsum-Producing Processes
Engineering cost estimates were made for producing wallboard-
grade gypsum from forced oxidation of limestone-scrubbed FGD sulfite-rich
wastes (Ref. 6). Two basic processes were considered: a tail-end system
incorporating an oxidation tower, which approximates the Japanese processes,
and an integrated system, which represents the pilot plant installation of
Borgwardt at RTF and is being tested at the TVA Shawnee plant with its
10-MWe venturi and spray tower scrubber (Figures 16 and 17). The estimates
are meant to illustrate the range of costs for saleable-grade gypsum produced
from SO_ abatement processes. The costs were also evaluated for converting
FGC wastes to a high gypsum content for disposal in the event that the
physical and chemical properties of the gypsum and fly ash mixture were
favorable for environmentally sound disposal above ground or in a landfill.
Results of the calculations indicated that, for a 500-MWe tail-
end forced oxidation system, total capital costs are approximately 20 percent
greater than for a base case system that included particulate removal by
an electrostatic precipitator (ESP) and a limestone scrubber system producing
76
-------
OXIDATION
TOWER
FLUE
GAS
AIR
COMPRESSOR
-0;
ELECTROSTATIC
PRECIPITATOR
(ESP)
MAJOR ADDITIONAL
EQUIPMENT REQUIRED
IS SHOWN WITHIN
DOTTED LINES
Figure 16. Simplified process schematic for wet limestone tail-end scrubber
forced oxidation gypsum-producing system
-------
001
NOTE: MAJOR ADDITIONAL
EQUIPMENT REQUIRED
IS SHOWN WITHIN
DOTTED LINES
DEMISTER
WASH
SPRAY
TOWER
ELECTROSTATIC
PRECIPITATOR
(ESP)
VENTURI
SCRUBBER
CENTRIFUGE
|
OXIDA-
TION
TANK
THICKENERJ
I AIR
I COMPRESSOR
I J
r
LIMESTONE
SLURRY
Figure 17. Simplified process schematic for wet limestone integrated
forced oxidation gypsum-producing system.
-------
sulfite-rich sludge, but did not include sludge disposal costs. A schematic
of the basic particulate removal and scrubber system, considered as the
baseline, and the major additional equipment to oxidize the sulfite-rich
slurry are depicted in Figure 16. It illustrates a two-stage (venturi and
spray tower) limestone wet-scrubber system, with an oxidation tower in-
corporated in the system to oxidize the sulfite-rich slurry to gypsum. In
order to produce saleable material with a sufficiently low moisture content,
centrifugation was included. Capital equipment costs for the integrated
system (Figure 17) are 13 percent more than the base case scrubber (as
compared to 20 percent for the tail-end system. The integrated system most
nearly represents the pilot plant system tested by Borgwardt of EPA (Ref. 8)
and currently being evaluated at the TVA Shawnee power plant, Paducah,
Kentucky, by Bechtel and TVA at the 10-MWe level.
The operating premises and^waste production data fojr a
500-MWe boiler are summarized in Table 20. For this estimate, the gypsum
production costs were assumed to be independent of the base case scrubber
system capital and annual operating costs inasmuch as gypsum modifications
were estimated and reported on an incremental basis. On this basis, the
effect of forced oxidation can be compared directly to the waste disposal
costs by chemical treatment and landfill or by a number of other disposal
options.
TABLE 20. OPERATING PREMISES FOR NEW 500-MWe SYSTEM
WET LIMESTONE SCRUBBING PROCESS (1977;DOLLARS)
Coal burned: 9.6x10 tons/yr (3^5% S, 12% ash,
30 years life, 50% average operating load factor, 4380 hr/year
Coal burned:
0.88 Ib/kWh)
Q
kWh generated: 21.8x10 /yr
_ _ .. .. e - 5 -- -
Dry sludge: 1.93 X 10 tons/yr (including 0.87 X 10 tons/yr
fly ash)
90% SO- removal and 0.65 limestone utilization factor
5
Limestone consumption: 1. 25 X 10 tons/yr
The major pieces of additional equipment required for oxidizing
the sludge with the tail-end system includes oxidation towers, pumps, air
compressors, and centrifuges. Individual equipment costs were taken from
Reference 12 and corrected to 1977 on the basis of factors obtained from
Reference 13. The total increase in costs for the these items was
$10. 14 X 10^ for the tail-end system. A significant savings in equipment
costs can be realized with the integrated system by use of an ion oxidation
tank instead of a tower. The corresponding increase in capital equipment
costs above the base case is $6. 64 X
79"
-------
The estimate of $10. 14 x 10 results in a cost of $17. 51 and
$15. 62 per ton of dry gypsum for limestone utilization factor of 0. 65 and
of 1.0, respectively (Table 21). It does not consider the cost incurred of
disposing the waste if the sludge were not oxidized. Based on a midrange
value of $9.00 per dry ton for FGC sludge chemical treatment and disposal
(Ref. 14), which would offset the gypsum processing costs, and assuming a
$3.00 per ton fly ash disposal cost, the net cost of producing gypsum in a
tail-end systems is $6. 73 and $4. 84 per dry ton for the 0. 65 and 1.0 utiliza-
tion factors, respectively (Table 22). The effect of improved limestone
utilization is highly significant in reducing the net gypsum cost. A larger
effect in reducing the production cost is by considering an integrated system.
With the economies resulting with that mode of operation, the estimates
are $2. 22 and $0.31 per dry ton, respectively, for utilization of 65 and
100 percent. Tests have shown (Ref. 8) that a utilization of virtually
100 percent can be achieved with the process.
Tests have also indicated that the settling properties of
gypsum are significantly superior to that of calcium sulfite (Ref. 1). There-
fore, smaller thickeners are needed for reduction of plant captial costs.
For the tail-end oxidation systems (Figure 18) and 100 percent
limestone utilization, a $9 per ton chemical treatment and disposal avoidance
cost results in a gypsum cost comparable to the 1975 fob price for domestic
gypsum. At lower treatment costs forced oxidation costs of tail-end systems
are not as favorable; at greater than $9 per ton, they become increasingly
attractive. For the integrated system, the entire range of cost avoidance
costs of $7 to $11 per dry ton are competitive with the mined gypsum.
In considering disposal of gypsum, informal reports have
indicated the potential for better, trouble-free scrubber operation operating
in a forced oxidation mode. The costs of gypsum disposal were also investi-
gated to determine if favorable conditions existed. For instance, if for the
hypothetical 500-MWe plant, an FGC sludge chemical treatment and dis-
posal cost of $9.00 per ton of dry sludge was estimated as being needed to
achieve environmentally sound disposal, oxidizing the waste to gypsumj^n an^
integrated plant would result in a cost of $6.44 per ton of dry gypsum less than
chemically treating and disposing the equivalent calcium sulfite and fly ash
FGC sludge that would have been produced. Since the gypsum mixture would
require disposal, the $6.44 per ton can be considered the maximum gypsum
(and fly ash) disposal cost that could be incurred to be equivalent to a $9.00
per dry ton FGC chemical treatment and disposal cost. For the integrated
approach (Figure 19) of forced oxidation of limestone scrubber wastes, the
costs of producing gypsum for sale are generally competitive with domestically
mined material for limestone utilization of 65 to 100 percent and with fixation
costs of $7 per dry ton or greater. If disposal is considered, the advantages
are narrowed somewhat, and only the high (approximately 100 percent)
limestone utilization and treatment costs of $8 per dry ton or greater become
competitive if the gypsum and fly ash mixtures are disposed in a landfill or
underdrained site.
80
-------
TABLE 21. TOTAL INCREMENTAL COST FOR PRODUCING GYPSUM BY
FORCED OXIDATION
500 MWe System, 1977 Dollars
Forced Oxidation
Cost Increment
Capital cost
Annual charge @ 18%b
Annual labor
Limestone @ $6 /ton
Total
$/ton coal
Mills /kWh
$/ton dry gypsum
Total
Tail- End
$10. 14X 106
Integrated
6. 64 X 106
Annual
Tail- End
Integrated
Utilization Factor
0.65
1.82X 106
0. 58 X 106
d
$ 2.40X 106
2.50
1.09
$17.51
1.0
1.82X 106
0. 58 X 106
(0.26X 106)
$ 2. 14X 106
2.22
0.98
-$15.62
0.65
1.20X 106
0. 58 X 106
_d
1.78X 106
1.85
0.82
13.00
1.0
1.20X 106
0. 58 X 106
(0. 26 X 106)
1. 52 X 106
1.58
0.70
11.09
Relative to wet limestone scrubbing without waste disposal, 30-year life plant, 50-percent average
load factor.
Reference 5,
°Prorated, based on scrubber system operation. Data derived from Reference 11.
Included in scrubber costs. The limestone was used at 1. 0 utilization factor = 81X10 tons/yr.
00
-------
TABLE 22.
ESTIMATED INCREMENTAL COST OF PRODUCING GYPSUM FOR SALE
OR DISPOSAL RELATIVE TO THE DISPOSAL OF CHEMICALLY TREATED
FGC WASTES (1977 DOLLARS)
All costs are converted to $/ton dry gypsum except as noted j
$/ton dry gypsum
Fly ash disposal
Sludge treatment and ,
disposal cost avoidance
Cost avoidance, filtering
Total incremental cost
of gypsum per ton (dry)
S/ton coal
Mills/kWh
Saleable
Tail- End System
Integrated
System
Disposala
Tail- End
Integrated
Utilization Factor
0. 65
17. 51
1.90
(12. 68)e
NAPf
6.73
0.96
0.42
1.0
15. 62
1.90
(12.68)
NAP
4.84
0.68
0.30
0.65
13.00
1.90
(12.68)
NAP
2. 22
0.32
0. 14
1.0
11.09
1.90
(12.68)
NAP
0.31
0.04
0.02
1.0
9.55
NAP
(12.68)
(0.55)
(3.68)
(0.52)
(0.23)
1.0
6.79
NAP
(12.68)
(0.55)
(6.44)
(0.90)
(0.40)
Estimated at $9. 00/ton dry sludge that would have been produced;
1.93X 105 tons/yr total. Includes 0.86 X 105 tons/yr fly ash.
bTotal production: 1. 37 X 10 tons/yr (dry), 500 MWe plant, 30 years life, 50% average
load factor, wet limestone scrubbing, forced oxidation.
°Estimated at $3. 00/ton dry fly ash (unlined ponding).
Gypsum includes 0. 86 X 10 tons/yr fly ash.
Parentheses denote a negative value.
Not applicable.
CO
-------
10
9
8
7
o
5? 5
0
-1
-2
-3
500-MWe PLANT, 30-yr LIFE
50% AVERAGE OPERATING LOAD FACTOR
WET LIMESTONE SCRUBBING, FORCED OXIDATION
LIMESTONE
UTILIZATION
U.S. MINED CRUDE
GYPSUM, FEB 1975
7
8
9
10
11
12
FGC WASTE TREATMENT AND DISPOSAL COST AVOIDANCE,
$/ton dry sludge (including ash)
Figure 18. Cost of producing saleable gypsum as a function of
sludge treatment and disposal credit (1977 dollars).
83
-------
-C
. «/»
l_ ro
CO ^
o ^
o
O -
Q_ O
CO C
OS
CO
12
11
10
9
8
7
6
5
4
3
2
1
0
500-MWe PLANT, 30-yr
LIFE,5055. AVERAGE
LOAD FACTOR,
WET LIMESTONE SCRUBBING,
FORCED OXIDATION, 100%
LIMESTONE UTILIZATION ^INTEGRATED
TAIL-END
NOTE: COST OF FORCED
OXIDATION PLUS GYPSUM
DISPOSAL BREAK-EVEN
EQUALS SULFITE SLUDGE
DISPOSAL COST
I
78 9 10 11
SULFITE SLUDGE DISPOSAL COST,
$/ton dry sludge (including ash fly)
12
Figure 19. Disposal cost of gypsum produced by forced oxidation
compared to disposal of equivalent quantity of sulfite
sludge (1977 dollars).
In summary, the potential selling cost of gypsum produced in
the integrated systems results in generally favorable economic trends relative
to chemical treatment and disposal costs of dry waste of $7 to $11 per dry
ton. An approximately $2 per ton reduction in the cost of producing the
gypsum can be achieved by improving limestone utilization from 65 to 100 per-
cent. Disposal by landfill and underdraining of gypsum and fly ash mixtures
appear to be marginally competitive with fixation costs at $8 per dry ton;
gypsum economics improve with increasing fixation costs.
For tail-end systems operating with 100 percent limestone
utilization, gypsum production for sale is marginally competitive if fixation
costs are envisioned in the $8 to $9 per ton range. Forced oxidation
economics improve with increasing fixation costs. Limestone utilization of
less than 90 percent tends to make this method of utilization noncompetitive
with chemical treatment. The economics of disposal of gypsum and fly ash
mixtures from a tail-end system do not appear to be competitive with
chemical treatment.
84
-------
5.1.2 Shawnee FGD Waste Disposal Field Evaluation
(TVA and The Aerospace Corporation)
This project was initiated to evaluate and monitor the field site
disposal of untreated and treated FGC wastes. Its purpose is to determine the
effects of several scrubbing operations, waste treatment methods, disposal
techniques, soil interactions, and field operation procedures. Test samples
of treated and untreated wastes, groundwater, surface water, leachate, and
soil cores are being analyzed in order to evaluate the environmental accept-
ability of current disposal technology. This program will provide a broad
data base for the evaluation of controlling flue gas SO- by combining evalua-
tions of scrubber performance and sludge disposal at The same site, while
laboratory analyses are conducted concurrently on the same methods. Also
on the basis of this program, engineering estimates of total costs (capital and
operating) projected for full-scale FGD waste treatment and disposal were
made (Ref. 5).
The site selected for the evaluation was the TVA Shawnee
power station at Paducah, Kentucky. Two 10-MWe prototype flue gas
scrubber systems, one a UOP turbulent contact absorber (TCA) and the
other a Chemico venturi and spray tower. Each are capable of using lime
and limestone absorbent. The wastes that they produced were placed in five
disposal ponds on the plant site. Two of the ponds contain untreated wastes;
each of the remaining ponds contains wastes chemically treated by one to
three commercial contractors.
The Bechtel Corporation (the scrubber facility test director)
provided the technical interface relating the scrubber test facility to the
disposal evaluation.
The Aerospace Corporation has been providing program
planning and coordination and is conducting selected chemical analyses,
Data evaluation, costing estimates, and reporting are also Aerospace re-
sponsibilities. TVA has provided the on-site support relating to all pond
construction and maintenance, filling of untreated ponds, and providing FGD
waste for treatment. Sample collection, analysis, climatalogical and hydraulic
data collection, and photographic documentation services are also performed
by TVA. Chemical treatment of the waste was performed by Chemfix, Inc. ,
Pittsburgh, Pennsylvania; Dravo Corporation, Pittsburgh, Pennsylvania; and
IU Conversion Systems, Inc. (IUCS), Philadelphia, Pennyslvania.
The program began in September 1974 with the filling of the
first untreated pond and is scheduled to continue through 1977. Reports on
the findings from the second year and updating the first-year results have
been published recently (Ref. 7). The highlights of the second-year findings
are included herein. Future plans include the evaluation of untreated wastes
under other disposal conditions including the disposal of gypsum.
Initially the evaluation included five sites, each occupying
approximately 0. 1 acre. Two of these sites contained untreated sludge, and
three contained sludge that had been chemically treated. During 1976, the
program was expanded to provide for the construction of three additional
85
-------
containments. One, an underdrained site, was filled in October 1976 with
untreated lime sludge admixed with fly ash. The second, also underdrained,
was filled in early 1977 with untreated limestone and fly ash waste, and the
third was scheduled for filling later during 1977 with gypsum produced by
forced oxidation.
In addition to plans for evaluating the environmental accept-
ability of the disposal of oxidized sulfite sludge (gypsum), recommendations
have been made to retire an untreated pond simulating reclamation of the
site. The sludge would be covered with earth and landscaped. Leachate
monitoring would be continued. In addition, evaluation of runoff character-
istics of a sloped treated sludge pond has been recommended to simulate
a landfill. The runoff would be collected and analyzed.
5. 1.2. 1 Analytical Results
5. 1.2. 1. 1 Chemical Properties
The FGD disposal field evaluation program at the Shawnee
steam plant has been under way since September 1974. The program is
being conducted to assess various disposal techniques and field operating
procedures involving FGD sludge on the environmental quality of the dis-
posal site. Currently, six disposal ponds are under evaluation, the sixth
one having been added in 1976. Construction has been completed for two
additional ponds to be filled early in 1977. A summary of the sludge types
being used and data on the respective ponds are shown in Table 23.
All ponds are being monitored for leachate, supernate, and
groundwater quality, and for the characteristics of the soil on the pond
bottom. Sludge cores are also evaluated on those ponds containing chemically
treated material. The significant results and trends observed to date are
summarized in the following paragraphs.
Additional data have been acquired since the last report
(Ref. 7), from the analyses of supernate, leachate, groundwater; and soil
and treated material cores. Since the strength and permeability of the fixed
and untreated wastes are some of the more significant of these data as they
impact the environment, these results are repeated in Table 24 (Ref. 13).
A detailed analysis of the input liquor for each of the ponds is
provided in Table 25.
Concentrations of the various constituents in samples taken
January 21, 1976 are shown in Table 26.
Generally the TDS in the leachate from untreated ponds reached
the input concentration and decreased steadily thereafter. The trends for the
concentrations of TDS, SO4> Ca, and Cl are shown in Figures 20 and 21.
Minor constituents whose concentrations span a range of six orders of
magnitude were relatively constant over the period monitored.
86
-------
TABLE 23. POND AND FGC WASTE CHARACTERISTICS
Pond
A
B
C
D
E
G
Scrubber
Venturi-
spray
tower
TCA
Venturi-
spray
tower
TCA
TCA
Venturi-
spray
tower
Absorbent
Lime,
filter cake
Limestone,
clarifier
underflow
Lime,
centrifuge
cake
Limestone,
clarifier
underflow
Limestone,
clarifier
underflow
Lime,
centrifuge
cake
Untreated
Solids
Content,
Weight %
46
38
55
38
38
38
42
Fly Ash
Solids
Content,
Weight %
43
40
45
38
38
38
40a
Treatment
Contractor
Untreated
Dravo
IUCS
Untreated
Untreated
Chemfix
Untreated
Fill and Treatment
Date
Sep 24 - Oct 8, 1974
Apr 7-15, 1975
Mar 31 - Apr 23, 1975
Oct 11-20, 1974
Jan 13 - Feb 5, 1975
Dec 3-7, 1974
Oct 5, 1976
a20 percent admixed with sludge prior to disposal, and 20 percent layered in approximately
a 9:2 sludge-to-ash depth ratio.
00
-------
TABLE 24. CHARACTERISTICS OF CORES FROM CHEMICALLY TREATED FGC WASTES
Sample
Source
and Date
Pond Ec
2/27/75
Pond Bd
6/12/75
Pond CC
5/29/75
6/12/75
Unconfined Compressive
Strength, psi
Weta
103 to 133
27 to 33
410 to 510
Dryb
95 to 165
40 to 46
470 to 540
3
Density, g/cm
Weta
1.40 to 1.46
1.36 to 1.44
1.67 to 1.70
Dryb
0.69 to 0.73
0. 59 to 0. 62
1.05 to 1.08
Water
Content,
wt %
51.0 to 51.5
56.9 to 57.8
36. 5 to 37.0
Estimated
Fractional
Pore
Volume
0.71 to 0.73
0.75 to 0.76
0.57 to 0. 58
Water
Permeability,
cm/ sec
1. 5 to 2.7X 10"5
6.9X 10"5
5.5X 10":?
5.5X 10"'
Wet: as received.
Dry: after oven drying.
cSamples from Ponds E and C were taken from locations free of surface water.
Pond B was kept underwater continuously as in the case of disposal upstream of a dam.
00
00
-------
TABLE 25. SHAWNEE DISPOSAL EVALUATION INPUT
SLUDGE ANALYSIS RECORD
Concentrations in mg/i ; solids analyses in wt%
Fill Date
Liquor Analysis:
pH
Alkalinity
COD
Conductivity
Arsenic
Boron
Calcium
Lead
Magnesium
Mercury
Selenium
Sodium
Chloride
Sulfate
Sulfite
TDS
Solids Analysis:
Fly Ash
Calcium Carbonate
Calcium Sulfate
Calcium Sulfite
Total Solids
pH
Pond
A
10/74
8.3
61
-
1Z.O
0.024
44
2100
-
290
<0.0001
0.005
-
4600
1525
4
8560
-
.
.
-
-
8.3
B
4/75
8.9
76
140
5.3
0.004
97
1060
<0.02
2.5
<0. 00024
0.02
17
1850
1875
3
5160
34.9
14.2
10.7
30.3
35. 1
, 8.9
C
4/75
8.9
111
140
11.1
0.002
34
2720
<0.01
33
<0. 00008
0.018
46
4700
1575
45
9240
40.3
0
9.7
38.8
55.5
8.9
D
10/74
9.2
303
130
7.1
-
93
1880
<0.02
50
-
.
56
2950
1500
56
6750
33.2
18.6
10.9
29.4
32.6
9.2
E
12/74
9.4
302
110
7. 1
0.004
80
1800
<0.01
12
0.00033
0.014
41
2700
1400
32
6190
34.2
18.3
9.4
27.9
42.0
9.4
89
-------
TABLE 26. SHAWNEE POND LEACHATE, SAMPLED JANUARY 21, 1976
Concentrations in mg/i
Constituent
Aluminum
Antimony
Arsenic
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Nitrogen
Potassium
Selenium
Silicon
Silver
Sodium
Tin
Vanadium
Zinc
Carbonate
Chloride
Fluoride
Phosphate
Sulfate
TDS
pH
Pond
A
9.2
0.78
0.059
<0.004
45
0.002
1400
0.06
<0.05
<0.05
0.20
<0.01
90
0. 33
<0. 00008
2.0
<0.05
0.79
78
0.014
-
0.036
66
0. 32
0.08
<0.05
<40
2300
2.9
<0.04
1300
5860
8.2
B
3.0
0. 18
0.011
<0.004
1.3
<0.002
525
0.02
<0.05
<0.05
0.05
0.01
27
0.47
0.0007
0. 11
<0.05
3.61
109
0.009
.
0.022
83
<0.08
<0.08
<0.05
<1
520
0.05
0.08
1100
2540
7.4
C
2.6
0. 12
0.021
<0.004
1.0
<0.002
575
0.03
<0.05
<0.05
0. 18
<0.01
9
0. 19
0.0012
0.45
<0.05
<0.010
425
0.022
0.48
0.038
143
0.08
<0.08
<0.05
<20
1050
0.4
0. 12
1175
3540
6.9
D
3.8
0.40
0. 34
<0.004
1. 3
<0.002
675
0. 11
<0.05
<0.05
0. 10
<0.01
37
<0.05
0.00115
0.34
<0.05
0.74
13
0.004
0.012
17
<0.08
0.08
<0.05
<1
970
3.0
0.24
1375
2970
7.8
E i
0.2
0. 10
0.076
<0.004
0.5
<0.002
30
0.01
<0.05
<0.05
0.20
<0.01
0.4
<0.05
0.0007
0. 32
<0.05
0.52
425
0.005
0.60
0.010
540
0.08
0.29
<0.05
<50
520
1.75
<0.04
1075
2640
8.1
90
-------
vD
8000
7000
en
E
z-5000
P4000
LU
O
3000
82000
1000
0
O
a c\
O Ca
CLOSED SYMBOLS - AEROSPACE ANALYSES
OPEN SYMBOLS - TVA ANALYSES
I
0
10
20
30 40 50 60
WEEKS AFTER POND FILLING
10/7/74 12/16/74 2/24/75 5/5/75 7/14/75 9/22/75 12/1/75
CALENDAR DATES
70
OTDS
80
90
2/9/76 4/19/76 6/28/76
Figure 20. Concentration; of TDS and major species in Pond A leachate.
-------
7500
tv)
INPUT LIQUOR TDS • 5375 tng//
AVERAGE (2nd filling!
20
3/10/75
O TDS
D Cl
& S04
O Ca
Closed Figure-Aerospace Analysis
Open figure-TVA Analysis
NOTE: 1st lilting completed on 10/20/74
2nd filling completed on 2/3/75
30
5/19/75
40 50 60
WEEKS AFTER FIRST POND FILLING
7/28/75 10(5/75 12/15/75
CALENDAR DATES
70
2)23/76
90
7/12/76
100
9/2006
Figure 21. Concentration of TDS and major species in Pond D leachate.
-------
The analyses of leachate from the ponds containing treated
sludge show data trends similar to the untreated ponds; however, TDS levels
consistently remain at a level approximately one-half that of those found
in the input liquor. The results of these analyses are presented in Fig-
ures 22 through 24 for Ponds B, C, and E, respectively. Six minor con-
stituents remained at relatively constant levels throughout the monitoring
period, with the exception of the boron level in Pond C, which increased
steadily to a level approaching that of the input liquor.
The TDS and the concentrations of major constituents in the
supernates of the untreated ponds decreased with time from initial values
corresponding to the values measured in the input liquor. After the initial
decrease, fluctuations were observed in which concentrations increased
during dry weather and decreased again when increased rainfall caused
additional dilution.
For the treated ponds, the concentrations of major constituents
and TDS in the supernate varied as a function of dry and wet weather during
the monitoring period and did not exceed values of one half to two thirds of
the corresponding constituent concentration in the input liquor.
The analysis of groundwater shows no indications of increases
in concentration levels attributable to the ponds. For samples from the Pond
A well, there is a discernible trend showing a decrease in the TDS level
toward the end of the monitoring period. In the Pond D well samples, the
concentrations of calcium and sulfate remained relatively constant during the
monitoring period, whereas the concentration of chloride and TDS increased
uniformly. The groundwater well for Pond D was monitored for 13 weeks
prior to the first filling of the pond, and inasmuch as the increasing trends
for chloride and TDS extend back to the beginning of the monitoring period
it is not apparent that the increase is attributable to the sludge liquor of
Pond D. In addition, the concentrations of chloride and TDS in the leachate
of Pond D show decreasing trends during the same period.
Analysis of groundwater from wells near the treated ponds
shows that the major constituents and TDS remain essentially constant over
a monitoring period starting as early as 22 weeks prior to filling, and no
trends attributable to the presence of the ponds have been observed.
5.1.2.1.2 Physical Properties
Physical property data on treated material from Reference 13
is presented in Table 24. The compressive strength of untreated sludge
when placed in undrained ponds, such as Ponds A and D, has been too low to
permit walking on its surface, i. e. , less than 3 psi.
In preparation for the filling of Pond G, laboratory tests were
conducted on ash-free lime filter cake (obtained from the Chemico venturi
and spray tower scrubber) remixed with fly ash in a quantity representing
40 weight percent of total solids. Samples were allowed to settle or drain
to obtain bearing strength measurements as a function of settling or draining
time. The test results showed that undrained settling alone would not produce
93
-------
5000 ,-
4000
^
en
3000
2000
o
o
o
1000
0
10
4/14/75 6/23/75
O IDS
D Cl
A S04
O Ca
CLOSED SYMBOLS - AEROSPACE ANALYSES
OPEN SYMBOLS - TVA ANALYSES
20 30 40 50
WEEKS AFTER POND FILLING
9/1/75 11/8/75 1/19/76 3/29/76
CALENDAR DATES
TDS
60 70
6/7/76 8/16/76
Figure 22. Concentration! of, TDS and major species in Pond B leachate.
-------
Ul
5000t-
4000 -
CT>
E
3000 -
o
h-
CC.
LU
o
O
O
2000
1000 -
0
4/21/75
O IDS
D Cl
A S04
O Ca
10
6/30/75
CLOSED SYMBOLS - AEROSPACE ANALYSES
OPEN SYMBOLS - TVA ANALYSES
20 30 40 50
WEEKS AFTER POND FILLING
9/8/75 11/17/75 1/26/76 4/5/76
CALENDAR DATES
6/14/76 8/23/76
Figure 23. Concentration of TDS and major species in Pond C leachate.
-------
vD
s*
E
2?
o
\—
<
O
O
O IDS
D Cl
A S04
O Ca
o Na
CLOSED SYMBOLS - AEROSPACE ANALYSES
OPEN SYMBOLS - TVA ANALYSES
5000
4000
3000
2000
1000
30 40 ^50 60
WKKS AFTER POND FILLING
12/2/74 2/10/75 4/21/75 6/30/75 9/8/75 11/17/75 2/26/76 4/5/76 6/14/76 8/23/76
CALENDAR DATES
Figure 24. Concentration, of! TDS and major species in Pond E leachate.
-------
bearing strengths above 40 psi after a settling time of 13 days. Samples
which were allowed to drain, however, showed significant increases in
bearing strength. Samples in which half the fly ash was remixed in the sludge
and the other half placed in layers showed bearing strengths greater than
20 psi in 12 hours and exceeded 50 psi in 24 hours. This layered structure
was selected for the filling of Pond G. During filling, personnel could walk
on the surface between 2 and 10 hours after placing the sludge and fly ash in
the pond. Equilibrium values of solids content and bearing strength are not
available at this time but will be provided in future reports.
Soil cores were taken and tested by TVA during the construc-
tion of groundwater wells for the new ponds. The results show that the clay
soil has a dry density of 1.6 to 1. 8 gm/cm.3, a permeability coefficient of
10~" to 10 cm/sec, and natural moisture content of 15 to 21 weight percent.
5. 1. 3 Laboratory and Field Evaluation of FGC Waste Treatment
Processes (U.S. Army Engineer
Studies are being conducted by the U.S. Army Engineer Water-
ways Experiment Station (WES), Vicksburg, Mississippi, to evaluate chemical
treatment (fixation) and environmental effects associated with the disposal of
five FGC wastes. The program also includes evaluation of the chemical
treatment of five industrial wastes. The industrial wastes are outside the
scope of this report and will not be specifically discussed herein. However,
the treatment and evaluation of the pollutant potential of these wastes parallels
those originating in the FGC processes.
The program has been divided into three areas encompassing
the following tasks:
a. Assessment of the pollution potential of the leaching of
untreated and chemically fixed FGC wastes
b. Site survey and environmental assessment of existing
solid waste disposal sites
c. Evaluation of existing FGC waste fixation technology
Under the first task, assessment of the pollution potential of
the wastes, five chemical processes were used to treat five FGC wastes
(Table 27). The processes are being evaluated by means of leaching column
studies and physical and chemical testing of untreated and treated wastes.
Pollution assessment leaching column experiments are scheduled for a period
of two years. An interim report presenting the results of physical properties
of untreated wastes after approximately eight months and treated wastes
after about four months has been published (Ref. 4). A detailed summary and
the test analyses conducted were provided in the first annual publication of
this report (Ref. 1) and will not be repeated herein except to the extent of
providing continuity for this report. During this past year, modifications
were made to this task which included the addition of lysimeter testing to
determine the leachability of untreated and treated FGC wastes under
simulated environmental conditions and/or reduction in the number of
97
-------
TABLE 27. FGC WASTE AND CHEMICAL, TREATMENT MATRIX
Code
No.
100
400
500
600
1000
Type of FGC
Waste
Lime process,
eastern coal
Lime stone
process,
eastern coal
Double -alkali
process,
eastern coal
Limestone
process,
western coal
Double -alkali
process,
western coal
Percent
Sulfur
1.67
1.32
2.00
0.60
0.46
Percent
Solids
41.6
23.0
37.0
13.9
44.2
Process Designation
A
X
X
X
X
X
B
X
X
X
X
X
E
X
X
X
X
X
F
X
NA
NA
X
NA
G
X
X
X
X
X
X: Waste treated by processor and being tested in column
NA: Not applicable.
Processes A, B, E, F, and G include (not listed in alphabetic order):
• cement and fly ash additive,
• proprietary additive with pH adjustment,
• cement and sodium silicate additive,
• proprietary additive with pH adjustment, and
• fly ash and lime additive.
98
-------
column leachate analyses. Samples will continue bo be taken from the
triplicate columns, but only one is expected to be analyzed, with the remain-
ing two held in the event additional analyses are deemed necessary. Addi-
tional details are provided in Section 5. 1.3. 1.2.
In order to accelerate the acquisition of a data base in assessing
the pollutant migration and environmental impact from FGC wastes on land
disposal sites, the second task, to survey and characterize existing disposal
sites, is being conducted. Its primary goal is to establish the extent of
pollutant migration from existing disposal sites, the relationship to site
history and disposal operations, and the establishment of site selection
criteria. The geology, hydrology, and chemistry of the sites and their
surrounding media will be studied. Evaluation of the site data is expected
to continue for two years.
The third task of the study involves the evaluation of existing
fixation technology. A list of fixation processors currently available has
been compiled and their respective areas of application have been identified.
Another objective is the development of a methodology for selection and
application of fixation technology based on economic analysis and process
evaluation. The latter includes the defintion and development of a screening
test for rapid and accurate assessment of the potential environmental impact
associated with the fixation and disposal of FGC wastes. ' The evaluation
phase of this task is expected to extend over a two-year period.
5. 1. 3. 1 Assessment of Pollution Potential of Leaching of Untreated
and Chemically Fixed FGC Wasted
Five chemical treatment processes have been used with five
FGC wastes (Table 27). The processes are being evaluated by means of
leaching-column and physical and chemical testing of the untreated and
chemically fixed wastes. The principal objectives of this task are:
a. To assess the application of fixation technology for
retarding the leaching (mass transport) of pollutants
from selected FGC wastes
b. To assess the leaching potential of those wastes
c. To determine the physical stability of the fixed wastes
and its relationship to disposal operations
d. To evaluate the potential role of fixation of FGC wastes
as a pretreatment process prior to ultimate disposal
5. 1. 3. 1. 1 Physical and Engineering Properties
Testing to characterize the untreated and fixed wastes has
been completed (Ref. 4). The available physical and engineering properties
are summarized in Tables 28 through 33. Physical properties describe the
particle structure of the sludge, while engineering properties are used to
evaluate the sludge as a mass and to predict its reaction to applied loads.
99
-------
TABLE 28. COMPARISON OF SPECIFIC GRAVITIES OF
UNTREATED AND TREATED FGC WASTE
Sludge
100
400
500
600
1000
Specific Gravity
Untreated
2.41
2.51
2.85
2.53
2.99
Treatment Process
A
2.41
2.47
2.57
2.52
2.45
B
2.58
2.35
2.74
2.57
2.84
E
2.54
2.55
2. 72
2.57
2.61
F
2.46
G
2.70
2.49
2.50
2.41
2.44
Blank spaces indicate processors did not fix that sludge.
100
-------
TABLE 29. PHYSICAL PROPERTIES OF TREATED SLUDGE
Sludge
A-100
A-400
A-500
A-600
A-1000
B-100
B-400
B-500
B-600
B-1000
E-100
E-400
E-500
E-600
E-1000
F-600
G-100
G-400
G-500
G-600
G-1000
b
Specific
Gravity
2.41
2.47
2.57
2.52
2.45
2.58
2.35
2.74
2.57
2.84
2.54
2.55
2.72
2.57
2.61
2.46
2.70
2.49
2.50
2.41
2.44
Water
VV CfcbC X
Content,
23.8
24.2
41.4
15.6
23.7
77.5
69.5
67.3
88.9
70.9
6.4
8.7
6.5
10.7
0.7
3.7
10.7
7.6
13.3
17.0
Void
Ratio
0.860
0.768
1.377
0.663
0.958
2.711
1.794
2.150
2.811
2.717
0.671
1.072
0.822
0.601
0.987
0.996
1.737
2.198
1.991
1.617
Porosity,
46.2
43.4
57.9
39.9
48.9
73.1
64.2
68.3
73.8
73.1
40.2
52.2
45.1
37.5
49.7
49.1 '
63.5
68.7
66.6
61.8
Bulk
Unit
Weight, c
lb/ft3
100.1
108.3
95.5
109.3
96.6
77.0
89.0
90.8
79.6
81.5
101.1
82.7
99.3
110.9
82.7
81.0
62.7
52.5
56.9
68.1
Dry
Unit
Weight,
lb/ft3
80.9
87.2
67.5
94.6
78.1
43.4
52.5
54.3
42.1
47-7
94.9
76.1
93.2
100.2
82.0
78.1
56.8
48.8
50.3
58.2
Tests conducted using 60°C oven for drying.
Value determined using one sample; all others are average for
three samples.
Sample air-dried prior to determination of unit weight.
101
-------
TABLE 30. PERMEABILITY TEST DATA FOR UNTREATED SLUDGE
Sludge
R-100
R-400
R-500
R-600
R-900
R-1000
Solids,
%
54.8
63. 1
51. 1
59.8
59.2
45.0
69.9
77.5
43.9
50.3
40.5
42.4
Water
Content, a> b
%
82.5
58.6
95.7
67.0
145.6
121.6
43.0
29.4
128.2
98.7
146.5
136.1
Dry
Unit
Weight, a
lb/ft3
58.8
64.4
57.9
70.1
30.3
36.0
86.9
103.6
46.8
53.1
43.2
48.9
Void
Ratio
1.559
1.336
1.706
1.235
4.872
3.942
0.818
0.525
2.682
2.245
3.321
2.817
Coefficient of
Permeability,
cm/sec
3.610 X 10~5
1.070 X 10~5
9.498 X 10"5
7.784 X 10~6
4.373 X 10"5
2.505 X 10"5
2.013 X 10"5
1.439 X 10"5
3.524 X 10"5
2.834 X 10"5
8.461 X 10"5
6.536 X 10"5
All drying done in 60° C oven. Note two sets of data for each sludge.
Dry weight basis.
Corrected for water at 20° C.
102
-------
TABLE 31. PERMEABILITY TEST DATA FOR TREATED SLUDGE
Sludge
A- 100
A-500
A-600
A-900
A- 1000
B-100
B-400
B-500
B-600
B-1000
E-100
E-400
E-500
E-600
E-1000
F-600
G-400
G-500
G-600
G-1000
Solids,
78.1
67.6
86.2
83.3
78. 1
82.0
82.6
65.4
59.2
58. 1
77.0
91.0
75.2
80.0
90.1
97.0
93.5
98.4
91.7
63.7
Water
Content, a' b
28.3
47.8
16.1
19.5
27.8
21.9
21.2
52.7
68.8
71.9
30.9
11.3
33.4
24.7
10.4
3.7
7.7
2.9
9.1
56.8
Dry
Unit
Weight. a
lb/ft3
76.9
62.3
92.5
68.0
73.7
60.0
63.7
54.2
44.4
45.1
81.0
72.5
77.9
88.3
77.3
78.1
53.1
50.6
53.0
54.0
Void
Ratio
0.956
1.575
0.701
1.369
1.075
1.684
1.303
2.156
2.613
2.931
0.958
1.196
1.180
0.881
1.108
0.966
1.927
2.084
1.837
1.821
Coefficient of
Permeability, c
cm /sec
2.057 X 10'6
1. 124 X 10"7
4.308 X 10"7
3.847 X 10"5
8.953 X 10"7
-4d
1.590 X 10
1.082 X 10"5
4.563 X 10"5
3.968 X 10"5
6.625 X 10"5
_4d
7.935 X 10
2.518 X 10"6
4.540 X 10"11
3.571 X 10"8
7.328 X 10"7
5.007 X 10"6
5.241 X 10"5
_4d
1.388 X 10 *
1.224 X 10"4
4.047 X 10"5
All drying done in 60° C oven.
Dry weight basis .
f* o
Corrected for water at 20 C.
Value questionable because flow restriction caused by sample support
may have influenced flow through sample.
103
-------
TABLE 32.
UNCONFINED COMPRESSION TEST DATA
FOR TREATED SLUDGE
Sludge
A-100
A-500
A-600
A-1000
B-100
B-400
B-500
B-600
B-1000
E-100
E-400
E-500
E-600
E-1000
F-600
G-400
G-500
G-600
G-1000
Initial
Dry Unit
Weight
lb/ft3
80.9
67.6
94.6
78. 1
41.7
65.4
58.3
44.2
53. 5
95.0
82.7
93.3
100.3
82.7
69.6
56.8
48.8
50.3
58. 2
Undrained
Shear
Strength, a
lb/in2
11.85
22.28
21.37
17.66
11.62
Unconfined
Compressive
Strength,
lb/in2
100
188
403
337
23
44
43
35
23
2574
719
2200
4486.
1374
396
242
86
126
144
Modulus
of
Elasticity,
lb/in2
1. 10 X 104
3.03 X 104
7.50 X 104
1. 10 X 105
3.57 X 103
3.64X 103
1.00 X 104
3.39 X 103
1. 10 X 103
4.50 X 105
1.26 X 105
3. 10 X iof
1.67 X 10°
2.45 X 105
5.00 X 104
9. 10 X 104
1.59 X 104
1.64 X 104
5.28 X 104
Taken as one-half unconfined compressive strength.
Significant for soil-like sludges only. Blank spaces
indicate nonsoil-like sludges.
104
-------
TABLE 33. CHANGES IN DRY UNIT WEIGHT AFTER
COMPACTION OF SLUDGES TREATED
BY PROCESS B
Sludge
B-100
B-400
B-500
B-600
B-1000
Dry Unit Weight3"
Without
Compaction,
lb/ft3
43.4
52.5
54.3
42.1
47.7
Maximum
after
Compaction,
lb/ft3
42.9
56.9
51.5
41.9
50.5
Change
due to
Compaction,
lb/ft3
-0.5
+4.4
-2.8
-0.2
+2.8
Optimum
Moisture
Content,
%
82.5
47.0
65.0
89.5
73.5
aDrying performed in 60°C oven.
15 -blow compaction test; 7400 ft-lb/ft compactive effort.
105
-------
The approach taken by WES was to characterize the wastes by evaluation of
their physical and engineering properties as determined by standard tests
and procedures applied to soils. In addition to assessing the effects of the
fixation process by evaluating the change in properties resulting from fixation,
characterization may be possible by comparison of results with typical values
of familiar materials such as soil-cement, concrete, and soils.
5.1.3.1.1.1 Untreated Wastes
In comparison with soils, the untreated FGC sludges are
generally of low density and low water content. The specific gravities, how-
ever; are comparable to soils, indicating that structural rearrangement of
the particles are expected to result in densities of the same magnitude as
those of soils. The high porosities of the sludges give an indication of
the loosely packed nature of the sludges; the total volume of most samples
exceeded 50 percent voids.
On the basis of the grain size distribution (Figure 25), the
sludges were classified as silt (ML) under the Unified Soil Classification
System (USCS) and as silt and silt loam under the U.S. Department of
Agriculture (USDA) system. On this basis, general characteristics were
predicted. The untreated sludges contain a high percentage of particles
that pass the number 200 sieve, which is usually indicative of low permeabil-
ity, < 10~^cm/sec. Strength is also expected to be low. Soils of low density
are generally so loosely packed that little intergranular friction is developed,
and shear strengths are correspondingly low in the absence of cementation.
Prior to treatment, sludges were characterized by low densities
and low water content, leading to the anticipation of low shear strength (2 to
8 psi) and low permeability (< lO-^cm/sec). Porosity is high, and improve-
ment in the quality of the sludges should be accomplished by restructuring
the particle matrix to provide a tighter packing arrangement. Comparison of
the physical properties of the untreated sludges to soils is presented in
Table 28.
5.1.3.1.1.2 Treated Wastes
The grain size distribution of nine sludges treated by Process
B and of one sample treated by Process F were determined and reported
(Ref. 4). The treated wastes exhibited characteristics similar to silt (ML)
and silty sand (SM) based on the USCS system. Sludges fixed by Process B
were classified as loam or as fine sandy loam under the USDA system.
Grain size distribution curves illustrating the effects of Processes B and F
on a limestone sludge from a plant using Western coal is shown in Figure 26.
A comparison of the grain size curves for sludges treated with
Process B with those of untreated sludges shows that the process had little
effect on the particle size distribution. Particle sizes of the fixed sludges
were essentially in the same range as those of the untreated sludges. The
slight change in gradation for B-treated wastes was not uniform for all sludges.
All B-treated sludges were reported to remain similar to the untreated sludges
in texture and were considered similar to silty soils.
106
-------
O
100
901
: so
i
j 70
i 60
j 50
• 40
30
20
10
0
500
U.S. STANDARD SIEVE
OPENING IN INCHES
643 Itt 1 « ft V4 3 4
U.S. STANDARD
SIEVE NUMBERS
7101416 203040 50 70 100140200
HYDROMETER
30
40
50
60
70
o
>-
oo
ct.
LU
to
40
CO
DC
50 {/)
o:
60 o
70 i_
Z
UJ
80 O
UJ
90 °-
100 50
10 5 1 0.5 0.1 0.05
GRAIN SIZE IN MILLIMETERS
0.01 0.005
100
0.001'
b.SLUDGE 400 (Eastern Coal, Limestone Absorbent)
Figure 25. Grain size distribution: (a) untreated and (b) treated wastes.
107
-------
O
100
90
80
70
60
50
40
30
20
10
0
U.S. STANDARD SIEVE U.S. STANDARD
OPENING IN INCHES SIEVE NUMBERS
6 43 2 IV, 1 * 14 y. 3 4 5 710 14 16 20 30 40 50 70 100140 200
HYDROMETER
I II II II II I I I II TT1-K
BOSTON
BLUE
\CLAY -
OTTAWA SAND1,
F-600
I I
,0 ,_
20 —
30
>-
CO
40
50 10
OL
60 O
O
70 t
90
O
a:
LLJ
CL
100
500 100 50 10 5 0.5 0.1 0.05 0.01 0.005 0.001
GRAIN SIZE IN MILLIMETERS
SLUDGE 600 (Western Coal. Limestone Absorbent)
Figure 26. Grain size distribution: Processes B and F results.
108
-------
In general, treatment of the sludges tended to reduce specific
gravity although a few values were slightly higher after treatment. Changes
were not reported as process-dependent. The specific gravities are reported
in Table 28. Values were in the range of common minerals and soils such
as kaolinite, dolomite, and bauxite.
Bulk density, i. e. , air-dry unit weight, did not exhibit as
wide a range of values after treatment as before treatment. The range of
values for all treated sludges was reported as 65. 7 Ib/ft3 to 105.9 Ib/ft3,
while for untreated sludges values ranged from 47.4 lb/ft3 to 157. 2 lb/ft3.
There were some large reductions, as well as some increases, in bulk
density resulting from treatment, but none appeared to be dependent upon
the type of treatment process.
Dry density, i. e. , oven-dry unit weight (samples dried at
60° C), was generally lower after treatment by Process B and considerably
higher after fixation by Process E. The dry densities of sludges fixed by
Process E are in the range of lightweight clays and silts.
A large increase in water content resulted from treatment
of sludges by Process B. Water contents for B-treated sludges ranged from
2 to 37 times those of the untreated sludges. Sludges treated by Process E
remained at low water contents, in the range of the untreated sludges. All
water contents are shown in Table 29.
Porosity and void ratio remained about the same after treat-
ment by Process B. Process E resulted in lower values of porosity and
void ratio. Comparisons of sludges, untreated as well as fixed, with soils
in terms of void ratio and porosity were compared and are presented in
Figure 27.
5.1.3.1.1.3 Engineering Properties
The results of three standard engineering properties tests
were reported on selected fixed sludges. A 15-blow compaction test was
conducted on 9 samples of sludges fixed by Process B to determine the
density-moisture relationships of the fixed sludges. The compressive
strengths of specimens of sludges treated by Processes E and F were
determined by performing unconfined compression tests. Durability of
sludges fixed by Process E was determined by the wet-dry brush test.
Results of the compaction test were reported and are sum-
marized in Table 33. The results show that sludges fixed with Process B
exhibit low dry densities and high optimum moisture contents when compared
to basic soil types. A comparison of the dry densities of sludges fixed with
Process B before and after the application of the compactive effort of the
15-blow compaction revealed that in two cases, B-400 and B-1000, a more
dense material resulted. Furthermore, samples B-100 and B-600 were
'unaffected by the test, and another sample, B-500, had higher densities
before the compaction.
109
-------
POROSITY, %
0
WE
GR
SI
Ml
)
0.
33
0.50
OTTAWA
SAND
1
UNIFORM SILT
0.60 0.67 0.71 0.75 0.78 0.80
1
SANDY OR SILTY CLAY
;
/
LL-GRADE
AVEL, SA
LT, CLAY
XES
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i
CLAY (30-50% clay sizes)
,
nl
ND,
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c
r\7Or
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JlH
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2.5 3.0 3.5 4.0 4.
VOID RATIO, e
Figure 27. Porosity and void ratio of soils compared with untreated and treated wastes.
-------
The unconfined compressive strengths of samples of sludges
fixed by Processes C, E, and F after curing are also reported (Table 29).
Additionally, the modulus of elasticity was determined from the stress-strain
curve for each of the treated sludges. Sludges fixed by Process E lost their
soil consistency and became quite hard, apparently undergong a cementation
process. Compressive strengths of sludges fixed by Process E were com-
parable to those of low strength concrete (3000 psi at 28 days). The stress-
strain measurements also showed that sludges fixed by Process E were
brittle, failure occurring at low strains. However, sludges fixed by Pro-
cess F failed at very high strains, indicating an elastic consistency, though
compressive strengths were lower than the sludges fixed by Process E.
A wet-dry brush test was performed as a measure of durabil-
ity on samples fixed by Process E. These sludges performed fairly well,
generally surviving the 12 cycles, at which time the test was terminated in
accordance with the ASTM test procedure. The weight loss reported for
samples fixed by Process E was in the range of 7 to 16 percent.
5.1.3.1.2 Chemical Properties
The leaching tests are aimed at measuring the rate of pollutant
migration into an aqueous medium. One hundred sixty-two columns have
been assembled to simulate the dispersed flow and leaching of pollutants at
surfaces or cracks within the treated waste matrix.
For treated wastes, a leaching surface-to-sludge volume ratio
of approximately 1.0 to 1. 5 is being tested. A treated sludge core, 3 inches
in diameter and with a volume of approximately 0. 25 ft , has been placed
within a 4-inch (inner diameter) transparent-plastic column, and the annular
space has been filled with polypropylene pellets. The leachate flow rate is
controlled to maintain a fluid velocity in the range of 10~5 to 10~"cm/sec.
This rate has generally been achieved for all samples of treated wastes,
on the basis of flow patterns established for these leaching columns. The
control of flow rate through the untreated wastes is a function of the waste
permeability itself and is not subject to control methods.
Two leaching fluids were used to represent both sides of the
pH spectrum and to provide some insight into the effect of leaching pH, one
fluid being water saturated with carbon dioxide having a pH of 4. 5 to 5.0
and the other being deionized water buffered with boric acid with a pH of
7. 5 to 8.0. The columns are triplicated for each leaching solution. Analysis
of data has indicated no significant differences in leachate pollutant concentra-
tion from either of the two leaching solutions. Therefore, based on results
achieved through mid-1976, use of the slightly alkaline leaching solutions has
been discontinued; that with the nominal pH of 4. 7 will continue to be used in
the study. A modification in the numbers of leachate analysis from the
columns has been implemented. Triplicate columns will still be maintained
and sampled quarterly, but only one sample will be analyzed (Table 34). The
remaining two samples will be retained in the event results warrant additional
analyses.
Ill
-------
TABLE 34. CHEMICAL CHARACTERISTICS TESTS OF UNTREATED
AND TREATED FGC WASTES
Chemical Analysis: Concentration as a Function of Time
Cations
Arsenic
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Zinc
Anions
Chloride
Cyanide
Fluoride
Nitrite
Nitrate
Sulfate
Sulfite
Organic
Chemical oxygen demand
Total organic carbon
Leachate pH
Leachate Electrical Conductivity, ^mhos/cm
112
-------
A new task has been incorporated into the program. It is to
determine the leaching effects of placing untreated and treated FGC sludges
in a sanitary landfill environment and to determine the leachability under
such environmental conditions. The experiments will be carried out by the
use of lysimeters, and investigative efforts are being designed to minimize
the scale effect of the small laboratory lysimeters to maintain comparability
of results with field conditions. Additional information is provided in
Section 5. 1. 3. 1. 3.
5.1.3.1.2.1 Untreated Wastes
Characteristics of the untreated wastes were reported in
Reference 15 and are outlined in this section.
The results of the digests of the FGD sludges for metals are
summarized in Table 35. The major metal species appear to be a reflection
of the type of absorbent employed in the scrubber. The heavy metals that
are present to a consistent degree in the sludges include chrome, nickel,
and lead. In the case of the limestone and double alkali scrubbers, a
possible correlation may be made with respect to coal source. For the
limestone scrubber, the Western coal sludge is consistently higher for all
metals included in the analysis; for the double alkali scrubbers, the reverse
situation is true.
Conductivity measurements of the column leachates, which
are indicative of the TDS, are shown in Figure 28. For most of the FGD
sludges studied, there is an initial high concentration followed by a subse-
quent decline.
The leaching of lead was reported as an example of the type
of results being obtained. These are summarized in Table 36. The trends
observed are similar to the conductivity (TDS) data, i. e. , a high concentra-
tion followed by a drop and leveling off. Data similar to that for lead may
be used in assessing the environmental impact associated with the leaching
of metals from FGD wastes.
5.1.3.1.2.2 Treated Wastes
Typical treated waste leachate analyses for sulfate and TDS
were published in References 4 and 15 and presented in the last report
summary (Ref. 1) (Figures 29 and 30). Figures 31 through 33 from Refer-
ence 4 are repeated here for the convenience of the reader. The results
and data acquired subsequently are being analyzed and will be presented in
the next report. Pertinent data relative to pH characteristics are discussed
in the following paragraphs.
The pH for untreated and fixed sludge specimens are presented
in Figure 34. These data are reported as the mean values for all leachate
replicates over the sampling period, from the pH 4. 7 buffered leach solution,
and represent a spatial representation of pH for comparative purposes
between samples.
113
-------
TABLE 35. RESULTS OF SLUDGE DIGESTS, METALS
Parameter
Be
Ca
Cd
Cr
Cu
Mn
Mg
Ni
Pb
Zn
Co
Mo
Na
Sludge Number
100
400
600
500
1000
Concentration, ppm, dry weight basis
10.4
63, 500
2.8
98.2
'87. 3
159.2
5, 630
137.4
54.1
166.1
35.8
23.6
17, 100
3.9
158, 700
12.9
90.6
169.7
251.8
18, 700
215.3
155.3
330.8
4.4
147.1
40, 200
23.7
196, 250
17.7
131.9
239-8
595. 7
33, 900
202.4
287.8
333.7
46.7
140.5
99, 500
2.4
69, 100
22.6
54.1
90.9
169.7
9, 740
123.5
131.6
228.6
2.7
98.4
28, 200
0.01
59, 200
3.1
24.5
38.5
40.3
5,430
75.4
64.9
67.2
0.05
4.8
18,700
114
-------
150,000,
100,000
100
I ' I I
LEGEND
I
Q LIME, EASTERN
• LIMESTONE, EASTERN
o LIMESTONE, WESTERN
DOUBLE ALKALI, EASTERN
DOUBLE ALKALI, WESTERN
50
100 150 200 250 300 350
ELAPSED TIME, days
Figure 28. Leachate conductivity, untreated FGD sludges.
115
-------
50.000,—
10.000
en
1000
100
*
*--*
r- I
- 1
H
* *
/
LEGEND
A PROCESS A
A PROCESS B
O PROCESS E
• PROCESS F
• PROCESS G
D RAW SLUDGE
10' kxJ-O-6-
0 40
fc-r
80 120 160
ELAPSED TIME, days
200 240
Figure 29. Leaching results: sulfate, sludge No. 100.
116
-------
50.000
10.000
en
e
1000
100
10
A
A
O
D
LEGEND
PROCESS A
PROCESS B
PROCESS E
PROCESS G
RAW SLUDGE
0
40
120
ELAPSED TIME,
Figure 30. Leaching results: sulfate, sludge No. 500.
117
-------
6500.-
6000 -
1000
0 1000 2000 3000 4000 5000 6000
• DISSOLVED SOLIDS, mgtf
Figure 31. Conductivity versus dissolved solids.
118
-------
150,000
100,000
o
-C
£ 10,000
C_3
o
o
1000
100
LEGEND
A PROCESS A
A PROCESS B
OPROCESS E
• PROCESS F
DRAW SLUDGE
I
I
I
40 80 120 160
ELAPSED TIME, days
200 240
Figure 32. Conductivity pf leachate, sludge No. 100.
119
-------
150,000
100,000
t/
o
LEGEND
A PROCESS A
A PROCESS B
O PROCESS E
• PROCESS F
O RAW SLUDGE
0 40 80 120 160 200 240
ELAPSED TIME, days
Figure 33. Conductivity of leachate, sludge No. 600.
120
-------
(
RESIDUE
CATEGORY
100
400
500
600
1000
PH
) 1 2 3 4 5 6 7 8 9 10 11 12 13 I
1 1 1 1 1 1 1 1 1 1 1 1 1
RAW SLUDGE A
FIXATION PROCESS ^v vv
A
V V V
A E B
A
V VV
A B E
A
VV W
AF EB
1 1 I 1 1 I 1 1 1 1 A 1 1 1
V V V
A E B
Figure 34. Leachate pH for untreated and treated residues.
-------
TABLE 36. LE AC HATE DATA, LEAD
Elapsed Time,
days
1
7
14
21
28
42
Sludge Number
100
400
500
600
1000
j\
Concentration, fig/j?
98
6
6
1
1
1
17
15
3
1
1
1
22
1000
500
330
220
240
71
22
26
--
1
1
870
780
360
490
7
5
Lead background level is 4 fig/£.
It was suggested in Reference 4 that pH may have a predomi-
nant effect on leaching characteristics and be related to observed pollutant
mobility, particularly for the metals which are less mobile at a high pH due
to formation of insoluble hydroxides.
5. 1.3. 1.3
Environmental Effects
An evaluation of the potential effects of placing untreated and
treated FGD wastes in a landfill environment is the objective of this recently
defined 52-month task. Experiments will be conducted, using lysimeters.
The test conditions are being designed to minimize the scaling factor effect
of the lysimeter data as it relates to field conditions.
Untreated and treated FGC sludges will be placed in cells
which are 3 ft in diameter and 6 ft deep. The cells will be constructed or
lined with nonreactive material capable of withstanding stresses due to tem-
perature changes, loading conditions, and any other physical loads as may
result from movement. The cells will be located in a controlled environ-
ment. Their number and distribution are identified in Table 37.
Distilled water will be applied weekly, at the rate of 24 inches
per year, to the top layer of material. Temperature and redox potential
will be monitored by temperature sensors and platinum electrodes in the soil
122
-------
TABLE 37. FGC SLUDGE TEST CELL MATRIX
Sludge
Untreated
Treated, Processor 1
Treated, Processor 2
Type 1
lia
14
17
Type 2
12
15
18
Type 3
13
16
19
Refers to test cell identification number.
layers. Three inches of nonreactive silica gravel will be placed in tha
bottom of each lysimeter. Soil will be placed on top of the gravel to a depth
of one foot in all lysimeters and compacted so that no direct channeling
occurs. The cells are being designed such that leachate samples can be
obtained below the soil layer and at the soil-sludge interface. The intent
is to determine any improvement in the quality of the leachate after passing
through the soil.
Sources of the soil and FGD wastes are being selected to more
nearly simulate in-situ disposal conditions. The soil used in the lysimeters
will be chemically and physically characterized initially and after termination
of the 3-year leaching experiment. The soil parameters that will be mea-
sured are pH, texture, total iron (Fe), free iron oxides (FexOy), total
aluminum (Al), free and/or exchangeable aluminum oxides (A1XOV), exchange-
able Fe, total manganese (Mn), manganese oxides (MnxOy), exchangeable
Mn, water soluble Mn, and the major type of clay mineral present in the
clay fraction. A distilled water and dilute hydrochloric acid leach of the
soil will be conducted and the resulting solutions analyzed for Cr, Hg, Ni,
Pb, Cu, As, Be, Cd, Se, V, and Zn. It is expected that by combining the
data from the two leaching systems with the data on the chemical parameters
listed, information on the effect of leachate on soil under a disposal site
can be obtained.
Leachate will be sampled, and the pH, electrical conductivity,
and temperature will be determined. The leachate will then be analyzed
for the constituents shown in Table 38. The sampling frequency and analyti-
cal schedule is being determined cooperatively by the WES Principal Inves-
tigator and the EPA Project Officer.
123
-------
TABLE 38. LEACHATE ANALYSIS
Aluminum Mercury Vanadium
Arsenic Magnesium Zinc
Beryllium Manganese Sulfate
Boron Sodium Chloride
Cadmium Phosphorous Sulfite
Chromium Potassium Nitrite
Copper Nickel Nitrate
Calcium Lead Ammonium
Iron Selenium Cyanide
Total organic carbon (TOC)
Total dissolved solids (TDS)
Chemical oxygen demand (COD)
124
-------
5. 1.3.2 Site Survey and Environmental Assessment of
Existing Solid Waste Disposal Sites
The site investigation task is divided into preliminary investi-
gative, sampling, analysis, and environmental assessment. It is expected
that candidate site characteristics related to history, waste characteristics,
geology, and hydrology will be defined and quantified. A total of three FGD
disposal sites have been selected. A boring and sampling program is also
being defined. Samples of the waste, soil, bore water, and groundwater
•will be taken and analyzed for chemical constituents and partition of
pollutants (Table 39).
The principal goal of this task is to investigate contaminant
migration from disposal sites and relate findings to site history and disposal
operations. Background samples from outside the disposal site will be ob-
tained for baseline data and comparative purposes.
The basic objectives for this task have been defined as
follows:
a. Qualify and quantify general site characteristics related to
history, residue characteristics, geology, and hydrology
b. Develop and execute a sampling schedule based on the
results of (a) for residue, soil, and groundwater
c. Analyze the samples for physical and chemical properties
including the partitioning of pollutants
d. Obtain an assessment of land disposal as a function of
waste category, disposal operations, and environmental
factors
The first R&D report (Ref. 1) indicated that a number of
contacts had been made with companies known to have operational FGD sludge
disposal sites, and one site has been visited and rejected for study because
of geologic conditions. Since that time, two sites in the Midwest have been
tentatively selected, with a third one being confirmed. Borings have been
completed at the latter site, and others are expected to be taken as soon
as approval for study of the other sites is received.
5.1.3.3 Evaluation of Existing FGC Waste Fixation Technology
During this portion of the study, a compilation of FGC waste
treatment processes currently available will be made and their respective
areas of application identified. The development of a methodology for
selection and application of fixation technology based on economic analyses
and process evaluation is also planned. The latter task includes the definition
and development of a screening test for rapid and accurate assessment of
the potential environmental impact associated with the fixation and disposal
125
-------
TABLE 39. CHEMICAL ANALYSES ON SAMPLES FOR SITE SURVEYS
Arsenic
Beryllium
Cadmium
Chromium
Cyanide
Copper
Mercury
Magnesium
Manganese
Nickel
Iron
Lead
Selenium
Zinc
Sulfite
Sulfate
Boron
Chloride
Vanadium
Nitrite
Nitrate
Hydrocarbons
Total organic carbon
of FGC wastes. The program is currently under way and is expected to
extend over a two-year period. Specific program objectives include:
a. Development of a rational method for selection and
application of fixation technology based on economic
analysis and process evaluation
b. Development of a screening test for fast and accurate
environmental analysis of fixation methodology (to
include physical and leach testing)
c. Compilation of a list of fixation processes currently
available and their respective areas of application
The same FGC wastes that were evaluated in the pollution
potential task (Table 27) will be treated with a number of materials selected
on the basis of a survey of identified second generation FGC waste treatment
processes and of the Corps of Engineers soil and dust control materials and
methods.
126
-------
The list of candidate materials identified in Reference 1 has
been expanded, and the materials listed have been tested (Table 40). Limited
testing, appropriate to define optimum concentration of additives, will be
performed. The screening criteria which are being defined will be developed
to evaluate the efficacy of potential fixation processes and also the environ-
mental effects of solid waste on a disposal site.
Each potential chemical fixative is being screened in the
following manner: Specimens of each FGD sludge type are mixed
with fixative at rates of 0, 5, 10, and 15 percent of the dry sludge weight and
allowed to air dry. Following the mixing, but prior to air drying, a portion
from each mix is oven-dried. Water is added to the oven-dried samples
until each specimen lies under approximately one inch of water. The portions
of the samples left to air dry thus far have usually assumed a solid or semi-
solid (form) condition. However, the samples that were oven-dried and
then immersed in water usually became soft to fluid.
Four samples of each chemical will also mixed with each of
the five sludge types at the rate of 15 percent of the dry sludge weight. The
testing methodology to be applied to these samples is currently being defined.
Contact was made with approximately 25 chemical treatment
organizations (manufacturers and processors) to elicit their participation
in the program to evaluate second generation processes. Those indicating
interest in participating are listed in Table 41. Final determination as to
the extent of participation of each processor has not been defined.
5. 1.4 Characterization of Effluents from Coal-Fired
Power Plants (TVA)
This interagency-funded program with TVA is being conducted
by the Power Research Staff, Chattanooga, Tennessee, Studies of liquid-
and solid-related effluents are under the cognizance of Julian W. Jones, the
EPA Industrial Environmental Research Laboratory (IERL), Research
Triangle Park, North Carolina; studies of gaseous effluents are under Ron A.
Venezia, also of IERL. This report addresses the work in the liquid-and
solid-waste areas only.
The water- and solid-waste program is comprised of 5 tasks
extending over a period of approximately 38 months. A final report is planned
for late 1978. Chemical properties of coal pile drainage will be characterized
and quantified. A second task will be an assessment of the adjustment of pH
on the physical and chemical composition of ash pond effluents for purposes of
meeting effluent standards. The frequency of sampling and analysis for an
effective ash pond monitoring program will be defined, and a monitoring
system designed and tested. An assessment of the total residual chlorine,
its components (free and combined), and chlorinated organics discharged
from a once-through cooling system will be conducted; lastly, the effects of
coal ash leachate on groundwater quality will be characterized and quantified.
The status of the various tasks as of November 15, 1976 are summarized in
1Z7
-------
TABLE 40. TREATMENT MATERIALS BEING TESTED
Calcium carbide
Lime
Cement
Arquard 2HT
TACSS 025 (also a 20% sample)
Asphalt emulsion (67.8% asphalt)
AM 9
Fly ash
TACSS T020 NF (also a 20% sample)
Arothane 170
Aropol 7110
Chrome lignin
Sodium silicate
Aniline furfural
TACSS C400
TACSS C7a
TACSS STa
aTo be tested.
128
-------
TABLE 41. SECOND GENERATION TREATMENT PROCESSES
I. U. Conversion Systems, Inc.
Research Center
P.O. Box 331
Plymouth Meeting, PA 19462
215/825-1555
Contact: Dr. Steve Taub
Wehren Engineering Corp.
East Main Street Extended
Middletown, NY 10940
914/342-5881
Contact: Mr. Dennis Fenn
Protective Packaging, Inc. (NECO)
328 Production Court
Jeffersontown, KY 40299
502/491-8300
Contact: Mr. Bruce Goreham
DRAVO Corporation
Product Research
Neville Island
Pittsburgh, PA 15225
412/771-1200
Contact: Mr. Laszlo Pasztor
CHEMFIX, Inc.
505 McNeilly Road
Pittsburgh, PA 15226
412/343-8611
Contact: Mr. Ronald Polosky
Air Frame Mfg. fk Supply Co.,
(TACSS)
7407 Fulton Avenue
North Hollywood, CA 91605
213/875-2094
Contact: Mr. Robert F. Jenson
Werner & Pfleiderer Corp.
160 Hopper Avenue
Waldwich, NJ 07463
201/652-8600
Contact: Mr. John E. Steward
Aerojet Energy Conversion Co.
P. O. Box 13222
Sacramento, CA 95813
816/355-2255
Contact: Mr. Roy E. Jones
Chem Nuclear Systems, Inc.,
P.O. Box 1866
Bellevue, WA 98009
206/747-5331
Contact: Mr. C. D. Johnson
Environmental Technology Corp.
289 Casa Drive
Pittsburgh, PA 15241
412/431-8586
Contact: Mr. Albert R. Kupiec
ANEFCO Company
151 East Post Road
White Plains, NY 10601
914/946-4631
Contact: Mr. John Murphy
United Nuclear Industries
Commercial Division
1201 Jadwin Avenue
Richland, WA 99352
509/946-7661
Contact: Mr. Harold W. Heacock
Sludge Fixation Technology
Orchard Park, NY
129
-------
the following paragraphs. A tabulation of the sites being studied as part of
the various tasks are shown in Table 42.
5.1.4.1 Characterization of Coal Pile Drainage
The Kingston and Colbert steam plants were selected as sites
for the coal pile drainage characterization studies. Composite samples were
taken at Kingston of the surface runoff pumped to the ash pond. Pumped
volume is being correlated with rainfall.
Sampling has been delayed at Colbert because of equipment
failures. As a result of information obtained during the Kingston study, it
has prompted a change in sampling strategy. Samples at Kingston were
weekly composites and were reported to vary with the rainfall regime.
Samples to be taken at Colbert -will be composite samples of individual storms
and are expected to define more clearly the effect of rainfall intensity and
duration in establishing the character of coal pile drainage.
Elution tests of the coal and analysis of elutriate are being
conducted. In addition to determining the chemical species in the liquid
phase, coal pH, neutralization potential, and potential acidity tests will be
performed on each coal sample. The pH of the coal is being determined,
and modifications of techniques used for coal mine overburden analyses are
being considered.
Abundant information on the acid potential of coal mine over-
burden is reported to be available but very little on coal. If the data from
the tests on potential acidity of coal correlate favorably with overburden data,
it may reduce the number of coal samples that will be analyzed. SOXHLET
extraction is being used for obtaining analysis of the acid potential.
Sampling is nearly complete at Kingston, with the collection
of 19 weekly composite surface runoff samples. Results of the analyses
from the samples are reported in Table 43 and summarized in Figure 35.
Concentrations of Cr, Pb, Hg, Ba, Cd, Ti, Be, and Sb were consistently
low or below detection limits and were not reported. Matrix interferences
prevented the determination of chlorides. Sampling at the Colbert steam
plant was initiated in November.
Mass flows of several constituents were reported for the month
of June 1976. The total flow for this month was 3. 19 million gallons
with a requirement of 9. 7 X 105 equivalents of base for neutralization to pH 7.
During this period, 12 tons (1. 1 X 104 kg) of iron, 4 tons (3.6 X 103 kg) of
aluminum, 800 Ib (360 kg) of manganese, 80 Ib (36 kg) of nickel, and 30 Ib
(14 kg) of copper, along with large quantities of sulfate, suspended solids,
and hardness were leached from the coal pile.
An analysis was performed of a rainfall sample collected
during a storm that occurred on June 29 and 30. The storm had a duration
of 33 hours, with a total precipitation of 1. 35 in (3.43 cm). Total precipitation
130
-------
TABLE 42. LOCATION AND STATUS OF FIELD SITE STUDIES
Task
Paragraph
Discussed
Remarks
Characterization of Coal
Pile Drainage
Effects of pH Adjustment
on Ash Pond Effluent
Design of Monitoring Program
for Ash Pond Effluents
Chlorinated Once-Through
Condenser Cooling Water
Discharge Study
5.1.4.1
5. 1.4.2
5.1.4.3
5.1.4.4
Effect of Coal-Ash Leachates
on Ground Water Quality
5.1.4.5
Sampling and analysis is under way at
Kingston. Problems associated with
the sampling equipment have delayed
sampling at Colbert. Resolution is
expected shortly.
Colbert, Kingston, and Paradise.
Colbert and Kingston.
may be selected. )
(Another site
The Kingston plant was originally
selected for study. However, pre-
liminary studies indicated that the
intake water pH was high and varied
seasonally. Because of these widely
varying conditions, further testing
was dropped, and the John Sevier plant
was selected as the eite for future work.
The Kingston and Colbert generating
plants were selected as the site for
this investigation. Soil core samples
were taken and monitoring wells were
installed at Kingston. A one-year
sampling program is planned. Because
of geological complications at Colbert,
the Widow's Creek plant was selected
as a replacement. Field work, soil
sampling, and monitoring of the well
installation were completed recently.
-------
TABLE 43. ANALYSIS OF COAL PILE DRAINAGE
Week
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
pH
2.9
2.6
2.8
2.5
3.0
2.9
3.0
3.0
2.9
2.8
2.3
3.0
2.9
3. 0
3.1
2.6
2.5
3.0
2.3
Acid
7. 0 pH
mg/1 a.s
CaCO3
1700
1100
5300
2200
2400
1400
300
3700
5500
6100
1700
5900
3900
7100
5900
3600
340
3100
Conductivity
|j.mhos /cm
2400
2400
5200
4600
4000
4200
5300
5600
9500
5400
4400
5900
5500
3700
4700
4400
so4
Dissolved
Solids
Suspended
Solids
Fe
Mn
Cu
Zn
Al
Ni
Ca
Mg
As
Se
mg/l
2600
1800
4500
3100
6600
2700
4500
4600
7200
7400
1800
7800
9500
7600
9600
3700
4000
3800
3200
2500
9400
6800
7500
3100
5900
7400
11000
13000
3500
12000
6300
16000
14000
7600
8400
4700
550
110
150
140
120
8
2300
1400
210
440
280
46
480
61
170
75
1900
39
510
300
1800
1100
790
840
240
580
620
760
.1700
470
1800
1000
1400
1600
790
750
780
27.0
8.9
33.0
31.0
31.0
31.0
11.0
23.0
34.0
39.0
32.0
14.0
33.0
31.0
41.0
45.0
28.0
27.0
26.0
0.56
0.43
1.30
0.84
0.73
0.89
0.62
1.10
1.10
1.40
1.10
0.59
1.10
0.71
0.63
1.40
0.60
0.58
0.70
3. 7
2. 3
6. 3
5.4
5.1
5.1
2.6
6.6
5.6
9.2
16.0
10.0
8.1
5.3
13.0
9.9
4.6
4.1
4.0
190
66
350
300
270
240
78
240
310
370
350
96
440
260
380
250
430
220
180
1.70
0.74
3.50
2.30
2. 20
2.40
1.20
2.50
2.70
3.90
3.90
1.40
4.00
2.30
4.30
4.50
2.20
1.80
1.60
240
190
400
31
220
340
230
320
320
330
370
260
280
300
490
430
300
350
320
1. 2
64
320
270
220
260
7.6
160
210
340
350
95
380
320
480
440
17
27
150
0.010
0.010
<0.045
0.150
0.110
0.070
0.040
0.360
0.310
-
0.600
0.080
0.180
0.260
0.005
0.200
0.084
0.310
0.180
0. 030
<0. 002
<0. 002
<0. 002
0.006
0.008
0.006
0.005
0.011
0. 008
0.008
0. 003
0. 001
0.002
0.001
0.004
0.001
0.001
OJ
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-------
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: DISSOLVED CONDUCTIVITY:
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Figure 35. Means and ranges of coal pile drainage analyses.
-------
for June was 4.74 in (12.04 cm). Concentrations of several constituents
were analyzed in the rainfall sample, and loadings were extrapolated for the
month of June. Calculated values were 8. 0 Ib (3. 6 kg) of iron, ll.Blb
(5.2 kg) of aluminum, 0. 6 Ib (0. 27 kg) of manganese, 2.91b(13. kg) of
nickel, 4.0 Ib (1. 8 kg) of copper. Thus, contaminants in rainfall were
considered to be insignificant except for copper, which appeared to contribute
13 percent of the copper in the runoff. Another sample was collected for
analysis during October 1976.
5.1.4.2 Effects of pH Adjustment and Suspended Solids Reduction on
Trace Metals and Power Plant Ash Pond Effluent
In this study, an assessment and quantification is being made
of the chemical and physical composition of ash pond effluent after the pH
of the ash pond is adjusted. Mathematical modeling and laboratory settling
tests are being made in addition to physical and chemical characterization
of ash pond suspended solids from the Colbert, Kingston, and Paradise
plants.
A mathematical model and computer iteration method has
been developed that simulates the batch settling characteristics of fly ash
and bottom ash in a continuous ash pond system. The model permits use of
batch settling mechanisms to compute the necessary retention time in an
ash pond for a predefined suspended solids removal efficiency.
A summary of the tests and analyses being conducted is pro-
vided in Table 44. The ash settling characteristics will be evaluated in re-
lation to the original percentage of ash content in the sluice water, specific
gravity of ash, and particle size of ash.
Kinetic studies were performed to investigate the rate of pH
change and dissolved solids released when fly ash was contacted with
Tennessee River water. It was reported that for fly ash having neutral and
alkaline fly ash sluice waters containing 0.5 to 3 percent suspended solids
concentrations, the equilibrium curves of pH leveled off within three hours
after ash and river water contact. The equilibrium concentrations of con-
ductivity leveled off within four hours. For fly ash resulting in acid ash
sluice water and containing 0. 5 to 3 percent suspended solids concentrations,
both the equilibrium curves of pH and conductivity leveled off within 30 min-
utes after ash and water contact.
The dissolved and suspended nature of trace metals in ash
pond discharges was investigated. Grab samples from Colbert and Kingston
steam plant ash pond discharges, as well as samples from all other TVA
fossil-fired plants, were analyzed for several trace metals. Based on pre-
liminary data, some general conclusions were reported for cadmium,
chronmium, copper,, iron, lead, manganese, and zinc. Their removal may
be facilitated by adjusting the pH to 8 or 9 and by increasing removal of
suspended solids. Arsenic and selenium were found to be exceptions.
134
-------
TABLE 44. SUMMARY OF LABORATORY TESTS AND ANALYSES
Power
Plant
Colbert
Kingston
Paradise
Sluice Water pH
Intake
7.7 - 8.6
Neutral
Acid
Entrance to
Ash Pond
8.0 - 12.5
jl>
Ash Pond W
Adjusted to
6 . 0 and
9.0
9.0
6.0 and
9-0
Sluice Water Settling Tests
i
O
o
U
Yes
Yes
Yes
,0
41
%
hw
0.03
ash-to-
water
ratio
0.03
0.03
•°j.
Ash Pond
Discharge V
Yes
Yes
Yes
aAnalyze for total Al, Ca, Fe, K, Mg, Na, Si, Ti, As, Cd, Cr, Cu, Pb, Hg, Ni, Se, and Zn.
Sixteen trace elements.
(JO
(Jt
-------
Samples of fly ash sluice water representing an ash to water
ratio of 0.03 from the three plants were analyzed for 24 water quality param-
eters, including 16 trace metals. The fly ash sluice water from Paradise was
acid; Kingston, neutral; and Colbert, alkaline. The acidic and alkaline fly
ash sluice waters were then adjusted to pH levels of six and nine, and the
neutral fly ash sluice water was adjusted to a pH of nine only. The quantities
of chemicals required for adjusting pH were proportionate to the ash to water
ratio. After pH adjustment and analysis, trace element concentrations were
found to be greater than the minimum detectable amount in the original
samples.
Quantitative data from the various analyses will be provided
in the next annual report.
5.1.4.3 Design of Monitoring Program for Ash Pond Effluents
This study includes the evaluation of an ash pond monitoring
program to define the sampling necessary to obtain reliable qualitative and
quantitative information.
Data from a preliminary survey performed at Colbert during
October 1975 was reported. Pond profiles on the first two days of the initial
survey showed the pond to be stratified with respect to temperature. A
third pond profile on the third (last) day of the survey showed the pond to be
completely isothermal. Other characteristics, such^as constant dissolved
oxygen levels and uniform pH throughout the pond, were observed. Effluent
samples from the ash pond and untreated sluice water samples were also
collected, and analyses indicated that the suspended solids concentration in
the effluent was less than in the untreated sluice -water. This observation
agrees with an analysis of the weekly untreated water supply effluent data for
the period 1974 to 1975. It was reported that Fe, Cu, and Al associated
with the suspended solids was less in the effluent than in the original sluice
water. The study also showed that Cu, Fe, and Mg dissolved phases decreased
in concentration from the influent to effluent, while As, Al, Ca, and Cr
increased in the dissolved phase. The concentration of zinc remained re-
latively unchanged from intake to effluent. The concentration of lead was
below the detection limit of 10 |o.g/j0 in the intake and effluent. A net increase
in TDS in the effluent was also observed.
Comparison of data for suspended solids, dissolved solids,
alkalinity, and pH during the survey with those taken weekly indicated that
the daily variation was no greater than the weekly variation. Also, no
daily cycles were indicated.
A second survey similar to the preliminary survey was per-
formed at Colbert five months later. By the use of a dye tracer, the deten-
tion time of the ash pond was found to be approximately 12 hours. Two more
pond profiles were obtained in order to determine the chemical and mixing
characteristics of the ash pond. It was found that the ash pond was stratified
with respect to temperature on the first day and completely isothermal on
the third day. The first day was extremely calm, while the third day was
136
-------
windy. Hence, wind affects the mixing of the pond and, therefore, the
detention time. In order to verify the findings of the first survey with respect
to the association of metals with suspended solids, samples were collected to
determine suspended metals directly. This will allow a more accurate
estimate of the suspended metal concentration. Also, the daily variation of
suspended solids, pH, and various trace metals for a longer period was
obtained.
Samples will be collected weekly (on random days of the week)
from the Colbert ash pond for approximately nine months and analyzed for
pH, suspended and dissolved solids, and various trace metals.
Initial chemical analyses from the second ashjpond survey
conducted in February 1976 at Colbert are shown in Table 45. After the
results were obtained, samples footnoted in Table 45 were analyzed for
suspended metals or dissolved metals based on total metal concentration
and suspended solids concentration. When either suspended solids concen-
trations or total metal concentrations were low, suspended metals were not
analyzed. The samples footnoted were chosen for suspended metal analysis.
Only 4 of the 16 effluent samples were analyzed due! to the low suspended
solids concentration in the effluent.
The data in Table 45 confirmed the finding of the first ash
pond survey at Colbert. That is, the total metals concentration does not
vary significantly on a daily basis. On that basis, a weekly sampling pro-
gram was initiated at Colbert with samples collected on a random day of
each week.
The preliminary data available _to date from 16 weeks of the
weekly sampling program are shown in Table 46. Because the data did not
show much variation on a weekly basis, sample analysis was further reduced
and performed on a biweekly basis as of October 7. Samples are to be col-
lected weekly, but stored in the event the data for the fall and winter months
show a greater variation than the previous data. To date, no samples from
this program have been.analyzed for suspended metals because of the extreme-
ly low suspended solids concentrations (usually below 6 mg/j? ) encountered
in the effluent.
5.1.4.4 Chlorinated Once-Through Condenser Cooling
Water Discharge Study
The objective of this study is to quantify and evaluate chlorin-
ated effluent from once-through cooling systems.
A preliminary study was initiated at the Kingston steam plant
to identify free and total residual chlorine levels in the discharge waters
resulting from the chlorination of the condensers on the plant's nine units.
Concentration as a function of time was determined for free and total residual
chlorine for samples collected at the outlet of the condenser discharge water
box on Units 1, 3, 5, 7, and 9. Samples were taken of intake water and were
analyzed for total organic carbon, total carbon, total nitrogen, ammonia
137
-------
TABLE 45. COLBERT ASH POND EFFLUENT SURVEY
February 1976
00 I
Sample
No.
1
2a
3a
4
5a
6
7a
8
9a
10
11
12
13
14
15
16
17
18a
19
20
Date
2/18/76
2/19/76
2/20/76
2/22/76
2/23/76
2/23/76
2/23-24/76
2/24/76
2/24/76
2/24/76
2/24-25/76
2/25/76
2/25/76
2/25/76
2/25-26/76
2/26/76
2/26/76
2/26/76
2/26-27/76
2/27/76
Time
9a.m. -2p.m.
8a.m. - 2 p. in.
8a.m. -2p.m.
2p.m. -8p.m.
8 p. m. - 2 a.m.
2a.m. -8a.m.
8 a. m. - 2 p. m.
2p.m. -8p.m.
8p.m. -2a.m.
2 a. m. - 8 a. m.
8 a. m. - 2 p. m.
2p.m. -8p.m.
8p.m. -2a.m.
2 a. m. - 8 a. m.
8a.m. -2p.m.
2 p. m. - 8p.m.
8p.m. - 2 a. m.
2 a. m. - 8 a. m.
Sample
Location
Intake
Intake
Intake
Intake
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Solids
Susp. ,
mg/1
54
15
16
8
8
4
3
4
5
7
4
3
3
2
2
<1
<1
8
<1
2
Diss. ,
mg/1
100
90
90
110
230
230
220
220
200
200
210
• 200
210
220
210
200
200
210
200
200
Total
mg/1
154
105
106
118
238
234
223
224
205
207
214
203
213
222
212
200
200
218
200
202
Diss.
Sulfate,
mg/1
13
12
6
18
87
87
87
87
89
89
92
92
92
94
92
92
89
94
94
85
Diss.
Silica,
mg/1
5.0
5.0
4.8
6.9
7. 2
6.6
6. 3
6.6
6. 3
6.6
6. 5
6. 3
6.3
6. 3
6. 3
6. 5
6.4
6. 1
6.7
Chromium,
H-g/1
<5
<5
6
<5
7
19
15
<5
11
<5
10
7
23
17
10
23
36
14
8
19
Lead,
«?/!
<10
<10
22
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
<10
NOTE: All metals are total metals.
Chosen for suspended metal analysis.
-------
TABLE 45. COLBERT ASH POND EFFLUENT SURVEY (Continued)
Sample
No.
1
2C
3C
4
5C
6
7C
8
9C
10
11
12
13
14
15
16
17
18C
19
20
Calcium,
mg/1
22
21
21
23
93
9?
110
110
100
94
91
95
87
92
93
98
88
87
90
91
Copper,
mg/1
0.02
0.02
0.24
0.05
<0.01
<0.01
<0.01
<0.01
0.09
<0. 01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Iron,
mg/1
1.7
1. 3
2.2
0.81
0.30
0. 15
0.05
0. 13
0. 14
0. 13
0.09
0.21
0. 16
0.26
0. 10
0.08
0.06
0. 10
0.09
0.09
Manganese,
mg/1
0.07
0.05
0.33
0.05
0.04
0.03
0.02
0.05
0.02
0.01
0.01
0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Magnesium,
mg/1
3. 1
3.2
3.2
3.4
0.5
0.5
0.4
0.4
0.4
0.4
0.4
0.4
0. 4
0.4
0.4
0.4
0. 4
0.4
0. 5
0.5
Zinc,
mg/1
0.03
0.03
0. 14
<0.01
<0.01
0.03
0. 11
0. 16
<0.01
0.05
0.08
0.04
<0.01
0.02
0.02
<0.01
<0.01
<0.01
<0.01
<0.01
Aluminum,
mg/1
2.4
.6
.6
0.9
.7
.7
.6
.6
.7
.7
.9
.9
2.0
2.0
2.0
1.7
1.6
2.0
1.9
1.8
Arsenic,
H-g/1
5
5
5
10
5
10
5
5
5
5
5
5
5
10
20
20
oH
f-"
8.0
7.9
7.7
8.5
10.95
11.0
11.23
11.2
11.3
11.3
11. 1
11.2
11. 3
11.3
11.3
11.3
11.3
11.35
11.3
11. 36
TDS,b
mg/1
91
85
85
90
330
350
420
400
385
400
385
400
400
390
410
395
390
370
350
385
Temp,
°C
14
14.5
13.5
14. 5
15.5
14.5
14. 5
14. 5
15.0
15.0
15.0
15.5
15. 5
15. 5
15.5
NOTE: All metals are total metals.
Based on past data, all intake samples assumed to be less than minimum detectable limit of 5 fig/1.
Field conductivity measurement.
CChosen for suspended metal analysis.
-------
TABLE 46. COLBERT ASH POND EFFLUENT MONITORING SURVEY
Values in mg/jf
Tag
No.
5418
5419
5417
5420
5421
5422
5423
5425
5426
5424
5427
5428
5429
5430
5431
5432
5433
5434
5436
5437
5438
5439
5435
5440
Tur-
bidity
_
-
-
-
-
1.5
1.1
<1.0
1.6
<1.0
1.4
-
2.9
2.0
1.4
1.2
2.4
1.2
11.
<1.0
-
3.5
2.8
2. 1
Al
1.4
2. 2
1.8
1.8
1. 5
1.6
2.5
2.0
2. 5
1.7
2.6
2.2
3. 1
3.2
2.6
3.1
6.1
3.2
2.9
2.4
3.9
3.3
4.8
2.2
Ca
54
-
32
76
65
120
230
140
130
150
120
130
170
130
170
140
140
170
140
73
280
160
120
150
Cr
0.010
0.013
0.025
0. 008
0.032
0.008
0.040
0. 050
0.042
0. 009
0.041
0. 018
0.034
0.021
0.024
0. 018
0.021
0. 025
0.034
0.029
0.009
0.037
0.034
0.027
Cu
<0.01
<0.01
<0.01
0.13
0.02
0.22
0.04
0.05
<0.01
0.09
<0.01
0.03
0.02
0.06
0.11
<0.01
0.04
<0.01
0.02
0.02
0.02
0.02
0.02
<0.01
Fe
0.20
0.16
0.12
0.47
0.28
0.22
0.26
0.10
0.25
0.13
1.0
2.6
0.20
0.17
0.56
0.23
16.
0.15
0.29
0.18
10.
0.19
0.78
0.38
Pb
<0.010
<0.010
<0.010
<0.010
<0.010
<0.010
<0. 010
<0.010
0.230
<0.010
<0.010
<0.010
<0.010
<0.010
<0.010
<0.010
0.019
0.019
0.014
0.011
<0.010
<0.010
<0.010
0.018
Mg
2.9
0.4
3.2
0.9
0.8
14.
0.5
0.6
0.7
0.4
0.6
1.5
0.2
0.3
<0.1
0.2
0.2
0.2
0.3
0.2
4.5
0.8
0.8
0.7
Mn
<0.01
0.02
<0. 01
0. 05
0.02
0.02
0.01
<0. 01
<0.01
0. 02
0.06
0.07
<0.01
<0. 01
0. 11
0.01
0. 39
<0. 01
0. 01
<0.01
0. 23
<0. 01
0.04
0.03
Zn
<0.01
0. 04
<0.01
0. 13
0.02
0.03
0.28
<0.01
<0. 01
0.59
<0.01
0.02
0.09
<0.01
0.02
0.04
0.04
0.06
0.02
<0.01
0.06
0. 05
0.02
0.04
Se
0.018
0.017
-
0.012
0.012
0.015
0.018
0.015
0.017
0.011
0.016
0.017
0.021
0.021
0.013
0.019
0.015
0.016
0.005
0.004
0.020
0.025
0.016
0.020
As
0.080
0.014
0.010
<0.020
0.005
0.025
0.030
0.015
0.015
0.009
0.020
<0.005
0.015
0.020
0.015
<0.005
0.025
0.020
0.025
0.020
<0.005
0.010
0.015
0.012
Dis-
solved
Si
5. 5
7.1
6.5
5.3
4.9
5. 1
5.7
6.4
5.3
6.4
6.2
6.6
7. 1
5.3
7.0
6.8
5.9
6.4
6.5
6.7
7. 1
6.1
6.2
5.4
so4
58
72
-
130
140
190
130
200
220
140
190
180
180
180
200
170
160
160
-
160
180
200
230
220
Dis-
solved
Solids
210
290
340
300
40
280
370
390
350
300
340
350
470
310
460
360
370
370
720
480
430
430
Sus-
pended
Solids
6
2
1
6
6
4
1
2
6
1
4
4
2
10
4
<1
9
17
2
3
2
6
11
8
-------
nitrogen, chlorine demand, total suspended solids, volatile and nonvolatile
chloro-organics, and pH. Also, a sample from the condenser outlet was
analyzed for volatile and nonvolatile chloro-organics.
The results of the preliminary study indicated that the intake
water had a low nitrogen content and a relatively high pH (7. 8 to 8. 5). The
varying pH was due to a change in the intake water source, depending on the
time of year. This pH range results in a 10 to 30 percent HOC1 level, which
is about 80 times more efficient as a biocide than OC1". Because of the high
pH and the variability of the intake water, the plant was dropped as the site
to perform a detailed chlorination study.
The John Sevier plant was then selected for a preliminary
study. On the basis of water quality information and inlet and outlet con-
denser sample analyses it appeared that the plant intake water came from
the same source river and also had a relatively high chlorine demand.
Therefore, the plant was retained as a site to be studied in greater detail
to test and develop a methodology for assessing minimum effective chlorine
dosage for control of biological fouling in steam-electric generating station
cooling systems.
Weekly condenser performance tests and free and total
residual chlorine measurements will be made at the inlet and outlet of the
condenser on each unit, using predefined chlorine feed rates. Also, deter-
mination of water quality parameters is planned to try to correlate with the
chlorine requirements. Using these data, the study will attempt to develop
a methodology for assessing minimum effective chlorine dosage for control
of bio fouling in the cooling system of a steam-electric generating station.
The chlorination rates selected for the four units at John Sevier were as
follows:
a. Unit 1 -- 6000 lb/24 hr for 2-hr duration
b. Unit 2 -- 7500 lb/24 hr for 20 min, twice per day
c. Unit 3 -- 4500 lb/24 hr for 20 min, twice per day
d. Unit 4 -- 6000 lb/24 hr for 20 min, twice per day
Unit 4 represents present and past chlorination practice and
will be used as a control. At least once per week, water entering the cooling
system will be monitored at the intake of each unit for total residual chlorine,
at the inlet to each unit for total residual chlorine, and at the outlet of each
unit for free residual chlorine.
During initial attemps to chlorinate, problems were experi-
enced with the chlorinators in maintaining the rates indicated above. There-
fore, the chlorination study was temporarily halted until a new chlorinator
incorporating a flow meter and recorder is procured and installed. Re-
sumption of the study is expected in the near future.
141
-------
5.1.4.5 The Effect of Coal-Ash Leachates on Groundwater Quality
A field survey was completed at Kingston. Thirteen
monitoring wells were installed at eight locations in and around the ash dis-
posal pond. Figure 36 illustrates their approximate positions, and Figure 37
shows a profile of the ash pond substrata. Wells Nos. 1 and 8 function as
control wells, while Nos. 2 and 3 and 4, 5, 6, and 7, respectively, are
located in the ash pond proper and on the dike.
Continuous soil core samples were taken at all locations, and
when possible the soil water was extracted and analyzed in the field for pH,
conductivity, TDS, calcium, and sulfate. In addition to the above analyses,
97 soil core samples and 44 water samples extracted from the soil cores are
being analyzed for Fe, Cu, Cd, Hg, Zn, Cr, Pb, Al, Ni, Ca, Mg, As, Be,
B, and Se. The cation exchange capacity on the soils will be determined.
Subsoil samples were collected for physical analyses. Determinations of
horizontal and vertical permeabilities of the various strata were conducted
along with grain size distribution, dry densities, percent moisture, and
soil classification. Soil elution tests are also planned. The data are being
analyzed and will be available in the next annual report.
The soils tested generally were of medium to high (89 to
112 pcf) dry density, fine grained, or well-choked with fines, with vertical
permeabilities ranging from 6. 3 X 10-8 to 6. 1 X 10-6 cm/sec and horizontal
permeabilities in the range of 7. 4 x 10-8 to 7. 4 x 10-5 cm/sec.
Transparent plastic columns were packed_with s^ail to a^
density approximating field coliditions, and water taken from well No. 2 in
the old Kingston ash pond was leached through the columns. In all tests
reported thus far, clogging of the columns occurred. This was due to the
precipitation of iron, which was caused by oxidation of the elution water
during the experiment. Future testing will be done under anaerobic
conditions.
Monitoring well and soil sampling at Widows Creek has not
been completed. A total of 19 monitoring wells has been installed. These
include nine ash pond sites, two control sites, and eight scrubber pond sites
(five for trace metals and three for organics). Results of the soils analysis
will be provided in the next annual report.
5.1.5 Fly Ash Characterization and Disposal (TVA)
The objectives of this interagency-funded program with TVA,
Power Research Staff, Chattanooga, are to characterize chemically and
physically coal-fired boiler ashes and waste effluents. In addition, studies
on fly ash handling systems disposal and utilization of fly ash, and treatment
methods for water reuse and recycle will be conducted. Work was initiated
in June 1975, and the final report on the project is planned for December 1979,
Data since the last report from TVA progress reports on
the characteristics of ash have been summarized and evaluated. Also,
chemical and physical analyses of coal, coal ashes, and ash effluents
142
-------
WATTS BAR
RESERVOIR
uo
Figure 36. Spatial distribution of monitoring wells at the Kingston generating facility.
-------
«v;;;WATER TABLE
ASH POND
ASH
EMORY I
ESHALEEi
1098 1464
DISTANCE, m
1830
2196
2562
Figure 37. Topographic profile illustrating wells and soil strata.
-------
are being conducted at the Colbert plant and are planned for the Kingston
plant in order to characterize these materials at two different plants having
different boiler designs and burning different types of coal. The various
methods available for disposal and utilization of fly ash may also be evaluated,
depending on fuel availability. The first phase of the program, scheduled for
completion in June 1978, will conclude with a summary of information on
physical and chemical processes for reusing or recycling sluice water.
Studies of dry and wet ash handling systems may be conducted,
and recommendations may be made relative to the more promising systems
for ash handling, disposal, and utilization alternatives.
The TVA plants at Colbert and Kingston have been selected
for conducting chemical analyses of the streams. Complete stream charac-
terization will be conducted initially for the Colbert plant only (Figure 38).
Some of the work is being performed under another project, "Characteriza-
tion of Effluents from Coal-Fired Power Plants," reported in Section 5. 1.4.
In order to develop sampling procedures and methods, pre-
liminary sampling programs were conducted at the Colbert steam plant.
Sampling sites included the coal scales, pulverizers, mechanical collector,
electrostatic precipitate r (ESP), and pyrite hoppers and their respective
ash slurry streams. Laboratory analyses being performed on samples
from the various streams are listed in Table 47. Some sampling problems
were experienced, primarily with various outages of plant equipment.
Modifications in procedures as a result^of the preliminary sampling pro-
gram were devised.
Conclusions derived from analysis of data from the pre-
liminary sampling program include the following:
a. Chemical analyses for Ca, Fe, S, Al, and Si were
generally consistent in all samples collected.
b. Zn and Cu showed considereable variation between all
samples collected during a three-day sampling period.
c. Variability of the five major species between bottom
ash and mechanical ash slurry were attributed to poor
communication between power plant and sampling
personnel and inadequate flushing of sluice lines
between sample collections.
d. The five primary constitutents (if assumed to be in the
oxide state) accounted for about 90 percent by weight
of the ash.
e. Mass balances relative to incoming coal and slurry
streams were Al, — 2 percent; Ca, + 35 percent,
Fe, + 43 percent; Si, + 25 percent and S, - 98 percent
(lost to stack). The major unbalances were attributed
to difficulty in sampling solids in the two-phase
slurry flows.
145
-------
COAL
SCALES
t
COAL
PULV
1
PYRITE
HOPPER
^"^^"c
»
BOILER
BOTTOM ASH
1
FLY ASH
SLUICE TRENCH
HYDROVACTOR
'L"TJ' J
"
MECH ESP
HOPPER * HOPPER
P<— >
i
r
OVERFLOW H
STACK
r
1 HYDROVACTOR
j
HAIR SEPARATOR
j GRINDER j
O - SLURRY SAMPLING POINT (BA, ESP) |
D - DRY FLY ASH SAMPLING POINT
A- PYRITE SAMPLING POINT
O- COAL SAMPLING POINT
Figure 38. Schematic diagram of sampling locations for coal and ash at
Colbert Steam Plant Unit 1.
-------
TABLE 41'. SAMPLE ANALYSES
Laboratory
Samples
Pulverized Coal (dry)
Pyrite (dry)
Electrostatic Precipitator
Fly Ash (dry)
Mechanical Collector
Fly Ash (dry)
Bottom Ash (BA) Slurry
Settled Solids (14hr)
Water
Suspended
Dissolved
Inflow Water
Suspended
Dissolved
Pyrite
Parameters Analyzed for Each Sample
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Barium (Ba)
Beryllium (Be)
Boron (B)
Cadmium. (Cd)
Calcium (Ca)
Chloride (Cl)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Fluoride
Iron (Fe)
True Specific
Gravity
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Sodium (Na)
Sulfate
Titanium (Ti)
Vanadium (V)
Zinc (Zn)
Field
BA Slurry
Inflow Water
Temperature
pH
Conductivity
Phenol Alkalinity
Total Alkalinity
ORP
147
-------
Improved definition in the data reported here and additional data are
anticipated as full-scale sampling procedures are improved.
A draft of the work plan and experimental design for the task
to investiage physical and chemical processes for recycling or reusing of
ash sluicing water has been prepared.
The report "Characterization of Ash from Coal-Fired Power
Plant" is in publication and is expected to be available early in 1977. Its
purpose is to present a summary of existing data on the chemical and
physical characteristics of ash produced by the burning of coal in steam-
electric generating plants. Several recent studies concerned with the
characteristics of coal, ash, or ash effluents were examined. The focus
included the elemental chemical composition of the coals and their ashes,
with emphasis on the trace inorganic constituents and toxic elements.
Methods for the chemical analysis of ash and coal matrices were examined
to aid the evaluation and comparison of results from studies performed with
different analytical methods. The finer particulates are a particular
source of concern because they have higher concentrations of potentially
hazardous trace elements, pass through collection devices, and are emitted
to the atmosphere in greater proportions than larger particles.
Results from analytical studies of power plant residues were
found to be not always comparable because of differences in analytical
methods used in determining the various elements and in sample preparation
and handling. These sources of error are in addition to the normal inter-
laboratory dispersion present when multiple institutions determine the same
sample by identical preparation and analytical techniques. Recommendations
were made to develop standard analytical practices for trace elements in the
coal and ash matrices.
In evaluating the analytical studies of coal and its combustion
residues, the various sources were regarded as being generally agreed that
elements are partitioned into three main groups with respect to their dis-
tribution in the residues:
a. Group I -- Elements which are approximately equally
distributed in the bottom ash and the fly ash
b. Group II -- Elements which are preferentially concen-
trated in the fly ash as compared to the bottom ash
c. Group III -- Elements which are primarily emitted to
the atmosphere as gaseous species
The theory for this partitioning effect involves the volatilization of some
elements or their compounds in the furance. Later, these vaporous phase
elements recondense completely or partially or are discharged through the
stack as gases. Elements with higher volatilization temperatures than that
reached in the boiler remain about evenly distributed in the two ash fractions
148
-------
(Group I). Others are volatilized and are not cooled sufficiently to condense
(Group III). Elements which do condense generally form fine particles or
are deposited onto the surface of small particles (Group II).
5.1.6 Studies of Attenuation of FGC Waste Leachate by Soil
(U.S. Army Development & Readiness Command)
The U.S. Army Development and Readiness Command
(DARCOM), formerly Army Materiel Command, Dugway Proving Ground,
Utah, is conducting a study to determine the extent to which heavy metals
and other chemical constituents of FGC wastes migrate through soil in land
disposal sites. The experimental FGC program was initiated in December
1975 and will be completed October 1977. The project consists of the fol-
lowing tasks: (1) physical and chemical characterization of wastes, (2) flow
rate studies, and (3) soil column studies.
Six FGC wastes and three fly ash wastes are being applied to
six soils to observe any changes in the physical and chemical properties of
the soils and to quantify the migration of the waste constituents through the
soils. All experimental work and the final report on this group of 9 wastes
is scheduled for completion 24 months after collection of the last waste. An
interim progress report will be published in 1977 covering work through the
end of calendar year 1976.
The FGC wastes and soils are identified and summarized in
Tables 48 and 49.
5. 1. 6. 1 Waste Characterization
Chemical composition of the wastes are being determined
prior to their application to the soil columns. Characterization of the wastes
will include pH, conductivity, TDS, major cations and anions, fluoride ion
and trace metal concentrations.
An analysis of each waste is shown in Table 50. These are
based on digestion of one gram of dry (to constant weight at 105°C) waste
with concentrated hydrochloric and nitric acids. Beryllium and selinium
were not detected. Analysis for boron, fluoride, calcium, magnesium,
sodium, and silicon is planned.
The concentration of the various constituents in the FGD waste
supernate are shown in Table 51. Although the Fe content is high in the
wastes, it is apparently present in insoluble forms as evidenced by the low
concentration in the liquor. Lead appears to be leached from the wastes
more consistently than the other metals. Arsenic and zinc were present
in significant concentrations in some of the liquors.
The solubilization of a number of constituents as a function of
the pH was determined. Ten and 20 percent samples, i. e. , 20 and 40 grams
of dry wastejDejr 200 ml _of^water were titrated with 1.0 N HNO, and 1. 0 N
NaOH, as appropriate, to adjust the pH of the solutions to 5,7, and 9
149
-------
TABLE 48. FGD WASTE CHARACTERISTICS
Desig-
nation
A
B
C
D
E
F
Source
Commonwealth Edison
Co., Will County
Station
Duquesne Light Co. ,
Phillips Power Station
General Motors,
Parma
Arizona Public Service
Co. , Cholla Station
Kansas City Power and
Kansas Gas and
Electric, La Cygne
Station
TVA, Shawnee
Conditions during FGD Waste Sample Collection
Absorbent
Limestone
Limec
(dolomitic)
Double
Alkali
(soda ash
and lime)
Limestone
Limestone
Limed
Coal
Type
Wyoming
Eastern
Ohio
New
Mexico
Missouri
So.
Illinois
% S
NAVa
2.2
2.5
0.3-
0.6
NAV
NAV
Solids
Content, %
40-50b
NAVb
~50b
12-15b
-15%
NAV
Sampling
Location
Thickener
underflow
Thickener
underflow
Filtered
solids
Scrubber
discharge
At pond
near
scrubber
discharge
outfall
From
disposal
site
T~\ — f. -,
ua.ce
15
Oct
1975
20
Oct
1975
21
Oct
1975
27
Feb
1976
22
Mar
1976
24
Mar
1976
PH
10.4
8.8
11. 1
6.2
10.4
NAV
aNot available. Normally high calcium is used.
Including fly ash. Being used on collection date.
-------
TABLE 49. SOILS CHARACTERISTICS
Soils Classification/ Character! sties
Source
North Carolina, Davidson series
Indiana, Chalmers series
Kentucky, Nicholson series
Shawnee Kentucky (fill soil)
Dugway Utah, Sample 1
Sample 2
Type
Clay
Silty loam
Silty clay
NAV
NAV
NAV
Class
Ultisol
Mollisol
Alfisol
NAV
NAV
NAV
% Clay
>60
>90% silt
and clay
>95% silt
and clay
NAV
NAV
NAV
Water
Penetration,
cm/sec
«10~2 to 10"5
»10"5 to 10~7
<*10~5 to 10~7
NAV
NAV
NAV
NAV denotes not available at present.
(J\\
-------
TABLE 50. CONCENTRATION OF VARIOUS METALLIC
CONSTITUENTS IN FGD SOLIDS
Uli
Source
of
Waste
Plant A
Plant B
Plant C
Plant D
Plant E
Plant F
Concentration in mg/kg j
As
900
13000
17700
2000
2200
6700
Be
<200
<200
<200
<200
<200
<200
Cd
700
<200
300
300
1400
400
Cr
2500
600
1100
1500
500
2300
Cu
4400
1700
2600
2400
1800
2700
Ni
2700
1900
2100
2100
3100
2600
Pb
17700
6700
17000
12300
15300
900
S
<1000
<1000
<1000
<1000
<1000
<1000
Zn
23200
4700
10300
5000
62300
14900
Hga
4
11
43
6.7
3. 5
2
Permangante digestion.
NOTE: Beryllium and selenium were not detected.
-------
TABLE 51. CONCENTRATION OF VARIOUS METALLIC
CONSTITUENTS IN FGD SOLID SUPERNATE
Source
of
Waste
Plant A
Plant B
Plant C
Plant D
Plant E
Plant F
Concentration in mg/jf
As
0.09
0.35
<0.05
<0.05
0. 10
<0.05
Ca
560
465
645
670
785
4370
Cd
<0.02
0.02
<0.02
<0.02
<0.02
0.03
Cr
<0. 05
0. 08
0.09
0.05
<0. 05
<0. 08
Cu
<0.02
0.04
<0.02
<0.02
0.03
0.06
Fe
<0.05
0.07
<0.05
0.05
0.05
0. 13
Hg
<0.002
<0. 002
<0.002
<0.002
<0.002
<0. 002
K
167
120
34
15
55
90
Mg
1.9
2300
0.32
195
3.5
4. 5
Na
1200
85
610
1000
58
98
Ni
0.07
0.08
0.05
0. 17
0.07
0. 16
Pb
0. 10
0.35
0. 14
0. 15
0. 10
0.45
Si
2
5
5.5
22
6.5
4
Zn
0.03
0.04
0.02
0.48
0.04
0.04
Ul
uo
-------
(Table 52). As expected, the solubility of the metals generally increased
as the pH decreased. Analyses from plants D, E, and F are being
performed.
5.1.6.2 Flow Rate Studies
In addition to examining the potential for migration of hazard-
ous substances from the FGD and fly ash wastes, any chemical and/or
physical interaction which may take place between the wastes and the natural
clay soils used in the investigations will be determined. Any interactions
between the soils and wastes could affect the suitability of such soils at
disposal sites. Nine wastes using six soils with three replications are
being applied to 162 soil columns. Visual observation of the soils will be
made, and flow rates will be measured to record any changes in soil perme-
ability resulting from possible interactions with the wastes.
JPripr to conducting tests where the waste is placed on the
soil, soil-only and waste-only flow characteristics were conducted.
5.1.6.2.1 Soil-Only Flow Characteristics
Soil columns were prepared by placing a small piece of glass
wool in the bottom of the glass container. Thirty grams of white, washed
quartz sand were placed over the glass wool, and the soil was added in
10-gram segments until the desired height was attained. Each additional
soil segment was tamped 10 to 15 times to pack the soil column to the desired
density of 1. 5 g/cc.
Initially several soil columns of each soil were prepared and
leached to develop a procedure that would produce desired flow rates of
100 to 400 m? /day for each column. A variation of approximately 100 to
150 mf /day between replicates of one soil type was deemed acceptable.
Difficulty was experienced in packing the soil columns to a bulk density of
1. 5 g/cc when dry soil was used. Further, the flow rates of dry soil columns
of the same soil varied considerably. It was concluded that more reproducible
results would be obtained if the soils were moistened slightly before being
compacted.
The flows obtained when Davidson, Chalmers, and Nicholson
soils were compacted at different initial water contents varied greatly. How-
ever, after some experimentation it was determined that Davidson and
Chalmers soils containing 16 percent water and Nicholson soil containing
13 percent water resulted in achieving flow rates within the criterion estab-
lished. A six-foot head of water was maintained on all columns. The soil
column tubes are 1-1/2-inch inner diameter and 16-inch long sections of
glass. Soil depth was established as approximately 50 mm.
5.1.6.2.2 Waste-Only Flow Characteristics
The flow rates for columns containing waste only were also
measured. Results from two samples from each of the six plants were
reported. It was observed that periodic channeling occurred with resultant
154
-------
TABLE 52. SOLUBILIZATION OF METALS AND CHLORIDES FROM FGD WASTES
Source
of
Waste
Plant
A
Plant
B
Plant
C
pH of
Waste
10.4
8. 8
11. 1
Grams Waste
to ZOO ml
Water
20
40
20
40
20
40
20
40
20
40
20
40
20
40
20
40
20
40
pH,
Adjusted
5.0a
5.0a
7.0
7.0
9.0
9.0
5.0
5.0
7.0
7.0
9.0
9.0
5.0
5.0
7. 0
7.0
9-0
9.0
Concentration of Constituents (mg/J?)
Cd
0.21
0.22
0.03
0. 03
<0.02
<0. 02
0.03
0.03
<0.02
0.03
0. 02
0.02
0. 06
0. 11
0.02
0.03
<0. 02
<0. 02
Cr
0. 20
0.44
<0. 05
0.06
<0.05
<0. 05
<0. 05
<0.05
<0. 05
<0. 05
<0.05
<0. 05
0.08
0. 14
<0. 05
0.07
<0. 05
<0. 05
Cu
0.26
0. 50
0.04
0.06
<0. 02
<0. 02
0. 10
0.08
0.02
0.03
<0.02
<0. 02
0. 14
0. 19
0.04
0.07
<0.02
0.02
Fe
0. 34
0. 76
0.08
0. 10
<0. 05
<0. 05
34
45
0.05
0. 07
0.05
0.05
1.8
7.2
0. 10
0. 14
0.06
0.08
Ni
0.80
1.4
0. 14
0. 15
<0. 05
<0. 05
0. 29
0.46
0. 10
0. 10
0.06
0.07
0.65
1. 10
0. 15
0. 20
0.06
0.08
Pb
1.4
3. 1
0. 30
0.40
0. 10
0. 10
0.20
0. 30
0.20
0. 30
0.20
0. 20
0.60
1.00
0.40
0.60
0. 10
0. 20
Zn
2.4
1.8
0.07
0.07
<0.02
0.03
0. 31
0. 38
0.04
0.04
<0.02
0. 03
3.00
4.40
0.02
0.04
<0.02
0.02
Ca
6700
19500
1300
2000
410
420
670
750
550
500
340
310
2800
4450
1870
2520
570
870
Mg
136
290
28
56
2.4
4. 5
730
1380
740
1410
600
960
250
480
50
73
8. 6
20
Na
350
650
335
465
330
490
220
260
170 -
190
290
305
610
575
505
700
465
790
Si
11
7
5
5
2
<1
38
46
8
8
3
3
50
25
7
9
7
9
Cl
104
273
103
196
98
218
271
550
302
642
309
528
43
88
66
109
65
130
aNever reached a stable reading of pH 5. Solution stabilized at pH 5. 6.
(Jl
-------
rapid increases in flow rates. Examples of this characteristics are shown
in Figures 39 and 40. The figures are typical plots of the flow of water
through columns of wastes. Large increases in flow through the wastes are
particularly noticeable in Plants A, B, C, and D. When the flow exceeded
500 mi /day, the waste columns were stirred to break the channels in the
wastes. The flow would immediately decrease. However, new channels
would form, and the flow rate would again increase. Because of the ease
and continual formation of channels in the wastes from Plants A and D,
these columns flow studies were terminated.
The occurrence of channeling and stirring for wastes A, B,
and C are shown in Table 53. The resultant decreases in waste depths are
also shown.
TABLE 53.
CHANNELING OCCURRING WASTE-ONLY COLUMNS AND
DECREASE IN WASTE COLUMN DEPTH
Sample
Plant A
Plant A
Plant B
Plant B
Plant C
Plant C
Occurrence of Channeling,
Days After Start of Test
6, 22, 39
6, 20, 39
4, 25
8, 30
38
Decrease
in Depth,
mm
25
25
1
1
15
1
Percent
Decrease
in Depth
13
13
4
4
8
5
The flow studies in which Plants A, B, C, and D waste were
applied to Davidson soil were terminated in June (except for one Plant B
column). The soil from these columns was saved for chemical analysis. It
was noted that after the wastes that exhibited channeling from Plants A and C
above the Davidson soil columns were stirred, the flow of water through the
soil columns was greatly reduced. However, the flow rates returned in a
few weeks to the previous rates, indicating rapid formation of channels
through the waste.
5. 1.6.2.3
Waste and Soil Flow Characteristics
The effect of wastes on the flow characteristics varied, and
in some cases the presence of waste on the soil affected the flow significantly.
Increases in the flow through Davidson soil after it was treated with wastes
from Plants A, B, C, and D was significant. The wastes from Plants A, C,
and D produced a large increase in two to four weeks. An example from
plant A is shown in Figure 41. The wastes from Plant B produced nearly an
immediate effect upon two of the soil columns; however, the increase in the
third was gradual (Figure 42). The wastes from Plants E and F have produced
little effect upon the infiltration rate in the two months the wastes have been
in contact with the soil (Figure 43).
156
-------
10000
1000
Ul I
100
J
80
0
20
40
TIME, days
60
Figure 39. Flow rate of water through Plant A FGD waste.
-------
10000
» 1000
Ul
00
100
0
20
40
TIME, days
60
80
Figure 40. Flow rate of water through Plant B FGD waste
-------
vO
LEGEND
• NC-6
• • NC-7
* * NC-14
CONTROL
WASTE STIRRED
}END
o
20
40
60 80
TIME, days
100
120
140
Figure 41. Effect of plant A waste on the flow rate of water through Davidson soil.
-------
Q
END
LEGEND
. . NC-6
—— NC-12
* *. NC-22
CONTROL
1 , 1 1 1
0 20
.1,1,1,
40 60
,,1,11(11,
80 100
TIME, days
, t 1 . , . l , , , 1
120 140 16
Figure 42. Effect of Plant B waste on the flow rate of water through Davidson soil.
-------
E
«*
O
LEGEND
- NC-5
NC-21
NC-24
CONTROL
WASTE ADDED
40
TIME, days
60
80
Figure 43. Effect of Plant F waste on the flow rate of water through Davidson soil.
-------
Wastes from Plants A, C, and D caused an increase in the
flow of water through Chalmers soil. However, the increase in flow rates
was not as dramatic as was observed with the Davidson soil. Also, the flow
of water through the Chalmers control columns tended to be more variable
than the Davidson control columns. Wastes E and F are expected to be tested
shortly.
Nicholson soil columns which have been flowing for less than
two months (except for Plant B waste soil columns which were in test about
four months) have produced little effect upon the infiltration rate with any of
the six wastes.
The infiltration of water through Kentucky soil after treatment
with each of the six FGD wastes showed no significant change in flow rate in
approximately three months of exposure.
5.1.6.3 Column Migration Studies
Soil column studies are being conducted to monitor the move-
ment in soil of contaminants leached from the FGD and fly ash wastes.
Compounds of arsenic, beryllium, cadmium, chromium, copper, mercury,
lead, zinc, and fluorides may be present in the soil column leachate. FGD
and fly ash wastes are being applied to 162 soil columns. Each of nine
wastes (six FGD and three fly ash) will be applied to six soils with three
replications of each combination. Leachate migrating through the columns
will be analyzed for the preselected anions or cations present in the waste.
Provisions in the construction of the columns will permit sampling of the
liquid at both the interface between the soil and the wastes and at the base
of the column.
When one or more of the compounds are found in the soil
column effluent, one of the three columns (each combination of waste and
soil is replicated three times) will be removed, sectioned, digested and/or
extracted, and each section analyzed for the compounds of interest. This
process will provide information relative to distribution and mobility of the
compounds through the soil with time. The remaining two columns will
continue to be leached until one or more additional compounds are detected
in the effluent. At the time of the second "breakthrough," one of the two
remaining columns will be taken down, sectioned, and analyzed as pre-
viously described. The last remaining column will be treated with fresh
waste and the leaching continued until a significant change is found in the
composition (pH, conductivity, and/or concentration of metals breaking
through the column) of the effluent.
Leachate samples from the flow rate columns were collected
and were analyzed with emphasis being given to the samples collected from
the Davidson soil waste columns. This was done in order to gain some
insight as to the migration of metals through the soil and to assist with the
design of full-scale migration columns.
162
-------
Analysis of the leachate during the first month of soil
exposure to the waste showed that metals in the leachate decrease to or below
the detection level of the analyses. Initially Ni, Pb, and Zn concentrations
were significant but decreased to the detection limit within two months. As,
Be, Cd, Cr, Cu, and Se were always below the detection limit, K, Mg, and
Na were very high initially but rapidly decreased to a low but detectible level.
Ca remained high throughout the experiment although some decrease was
observed.
Any conclusions regarding the attenuation of Davidson soil
would be premature at this time inasmuch as the results reported were from
data when the column flow rate had not been disrupted by an increase in flow
rate as a result of channeling in either the waste or soil.
5.1.7 Compilation of Data Base for the Development of Standards
and Regulations Relating to Land Disposal of FGC kludge
(SCS Engineers)
A study was initiated in December 1975 with SCS Engineers,
Long Beach, California, to establish a data base for use by EPA in its de-
velopment of FGD waste disposal standards. The final report is currently
in publication, and its availability is expected in the near future.
The data base compilation performed in Phase I of the study
included a categorization of the power generating industry and the location of
FGD waste sources, the state of the art of FGD system control technology,
untreated and treated waste characterization, and the current practices in
sludge treatment and disposal technology.
In addition, the forthcoming Phase II report will address such
factors as site characterization, health effects, safety, ecological effects,
and land use and aesthetics in its environmental considerations of FGD sludge
disposal (Table 54). Existing and proposed federal and state regulations,
that may apply to the disposal of FGD wastes are summarized and discussed.
Potential chemical and physical regulating parameters are identified.
The conclusions drawn about the environmental impact of
FGD disposal were limited because of the broad range of information being
obtained and not yet reported. Significant observations and generalizations
resulting from the Phase I study are outlined here:
a. A potential exists for catastrophic environmental impact
on surface water resources from a dike failure at a pond
containing FGD sulfite sludges. The oxygen demand
exerted by these sludges is sufficient to destroy aquatic
life for long distances. Regulations pertinent to siting and
construction of FGD sludge disposal sites should be suffi-
ciently stringent to provide assurance against massive
accidental discharges. Existing state and federal regulations
on pond and dike construction for phosphate sludges and acid
mine drainage sludges were recommended as a starting point
for development of suitable FGD sludge regulations.
163
-------
TABLE 54. CONTENT OF FINAL REPORT
Industry Categorization
Description of Power Generation Utilities
Location of FGD Users
Existing FGD Systems and Sludge
Control Technology
State of the Art
FGD Systems with Sludge Generation
Control Processes, without Sludge Generation
By-Product Recovery Systems
Marketable Products
Use as an Additive
Specialty Uses
Waste Characterization
Characterization Parameters
Chemical and Physical Characteristics
Treatment and Disposal Technology
Current Practices
Unstabilized
Stabilization Methods
Cost of Disposal Options
Cost of Unit Operations
Cost of Typical Systems
164
-------
TABLE 54. CONTENT OF FINAL REPORT (Continued)
Environmental Considerations
Site Characteristics
Health Effects
Safety
Ecological
Land Use and Aesthetics
Selection of Regulating Parameters
Chemical
Physical
Existing and Proposed Regulation
Solid Waste Disposal
Hazardous Waste Disposal
Wastewater Disposal
Water Quality Criteria
Air Pollution Regulations
Best Practicable Control Technology Currently Available
Guidelines and Limitations
Cost
Economic and Institutional Energy
165
-------
A potential is present for pollution of groundwater
resulting from land disposal of FGD sludges, e. g. ,
ponds and landfills. The assessment of the degree
of potential pollution is considered site-specific and
complex. Some interdependent factors to be con-
sidered in an assessment include the following:
1. The chemical and physical characteristics of
the FGD sludge being disposed, these charac-
teristics being a function of the FGD system
(e.g., flue gas composition, scrubber water
chemistry, and absorbent used), the treatment
provided the waste sludge prior to disposal
(e.g. , dewatering, commercial and noncom-
mercial treatment and stabilization), and time.
The physical and chemical characteristics, in
turn determine the quality and quantity of leachate
generated by the in-place sludge. The leachate
contaminants considered to be of interest are
TDS, Se, Hg, F, B, Pb, and As. None were
reported as exceeding drinking water standards
by more than a factor of 10. The chemical
speciation of these contaminants was recom-
mended as requiring further investigation.
2. The characteristics of the land disposal site,
e.g., soil type, groundwater quality, ground-
water hydrology, geology, meteorology, and
surface terrain pertinent to flood protection
and by-pass of surface waters. These disposal
site characteristics are important in determining
the fate and impact of thejeachate generated by
the in-place FGD sludge.
3. The design of the disposal site. This includes the
need and type of liner, sludge containment area
dimensions (particularly depth), dike construction,
sludge handling and circulation of supernatant,
prevention of public access, safety precautions,
and other design considerations.
4. Since indefinite containment of the waste FGD
sludge contaminants was not considered possible,
time is a significant parameter. Plastic liners
will eventually deteriorate; impervious clays will
allow some seepage; and chemically treated sludges
may lose their integrity. Therefore, in evaluating
land disposal of FGD sludge, the decision is not
whether contaminant release will be allowed, but
rather the rate of contaminant release that is en-
vironmentally acceptable for the present and over
the long term.
166
-------
5. It was recommended that future regulations for
land disposal incorporate the factors defined in
(1) through (4) above. In order to do so, sub-
stantially more interdisciplinary research was
considered necessary to provide the data upon
which to formulate decisions.
c. Available cost information was considered fragmentary
and in some cases difficult to interpret. In order to
determine the future economic impact of proposed FGD
sludge regulations on industry, additional cost estimates
were recommended for FGD management systems en-
compassing improvements.
d. It was concluded that studies of FGD sludge disposal to
date have concentrated heavily on the empirical evalua-
tion of environmental impact and lack any development
of theoretical explanations for the observed behavior.
The areas of groundwater contamination and contaminant
speciation •were particularly cited.
Several areas recommended as requiring basic research,
generally beyond the scope of existing sludge disposal studies, were
identified:
a. A theoretical model that can be used universally to
describe the chemistry, physics, and hydraulics of
groundwater contamination migration
b. Determination of the environmental cost benefit
realized through the use of various sludge disposal
options.
Other areas considered as possible extensions of existing dis
posal research are as follows:
a. Definition of criteria concerning the prevention of
catastrophic release of FGD sludge to surface waters
b. Formulation of a thermodynamic model capable of
predicting species and concentration of constituents
in the liquid and solid phases of FGD sludges
c. Further evaluation of the costs of various FGD sludge
disposal options and the associated economic impact of
regulating FGD sludge disposal
d. An investigation of the effects of scrubber sludge on
handling and disposal equipment
167
-------
e. An evaluation of the environmental impact of disposal
of calcium sulfite waste versus forced oxidation of
gypsum prior to disposal
f. More emphasis on the characterization and disposal
consequences of double alkali sludges, resulting partic-
ularly from the high sodium and ammonium salts
concentration.
5.1.8 Environmental Effects and Control of
Various FGC Sludge Disposal Options
(SCS Engineers)
In this program, which was initiated on September 20, 1976,
SCS Engineers will conduct a two-part study. In one portion, it will develop
and verify a thermodynamic model capable of predicting species and con-
centration of constituents in the liquid and solid phases of FGD sludges
generated under various conditions. The speciation model is expected to
assist in recommending in-process changes to minimize mobilization of
undesirable contaminants in the sludge.
The other part, which will be conducted concurrently with the
modeling studies, will provide a current updating of the economics associated
with the disposal of FGD sludges. The results will be in the form of an
economic development document for use in the promulgation of disposal
guidelines. Completion is expected in December 1978. The scheduling is
designed to take advantage of ongoing economic analyses being conducted by
EPA contractors in the FGC Waste and Water Program and other programs.
5.2 PROCESS TECHNOLOGY ASSESSMENT AND
NEW TECHNOLOGY DEVELOPMENT
The technology assessment and development efforts, totaling
four projects, include (1) field studies of untreated and chemically treated
FGC wastes, (2) FGC -waste leachate disposal site liner compatibility studies,
(3) studies to correlate waste solid characteristics with scrubber operating
conditions, and (4) dewatering equipment design studies.
5.2.1 Evaluation of FGD Waste Disposal Options (Louisville
Gas and Electric)
Studies of various chemical processes for the treatment of
FGC scrubber wastes are being conducted in this 18-month project with
Louisville Gas and Electric Company (LG&E), Louisville, Kentucky. Scrub-
ber wastes from the LG&E Paddy's Run No. 6 are being used. Laboratory
testing and evaluations of treated wastes are nearly completed. Work was
initiated in May 1976. The laboratory test program, all chemical analyses,
and program evaluation are being conducted by Combustion Engineering,
Windsor, Connecticut. The University of Louisville will perform disposal site
tests, field sampling, and physical testing of field samples.
168
-------
Laboratory-scale tests are being conducted to determine
optimum conditions for chemical treatment and physical stabilization of
carbide lime and commercial lime FGC scrubber wastes. Scrubber wastes
have been treated with carbide lime, slaked lime, and portland cement
additives. Some of these formulations contained fly ash.
3 3
The field studied will include eight 25 yd (19 m ) above-
ground impoundments of the treated wastes. Leachate, runoff, and physical
property tests of stabilized and unstabilized wastes are planned. Eight
treated wastes will be selected for evaluation in 100 yd 3 (17 m^) underdrained
disposal ponds. As in the smaller-scale impoundment studies, leachate,
runoff, and physical properties of the wastes will be determined.
An interim report is planned upon completion of the laboratory
studies, approximately eight months after the start of the program. Field
evaluations are scheduled to begin in December 1976 and continue for
approximately one year thereafter. A final report will be issued on the con-
clusion of the program.
5.2.1.1 Laboratory Program
A total of 59 mixtures encompassing a matrix of absorbents,
additives, and fly ash conditions were evaluated using the 60-day unconfined
compressive strength of the mixes as the primary screening parameter.
Permeability tests were also conducted on certain mixtures. The uncon-
fined compressive strength tests were carried out on samples cured for
60 days in a humidity chamber. The permeability determinations were
made on samples confined underwater for 30 days. Final selection for field
demonstration is being based on the amount of additive required and the
permeability. Selected samples of sludge and fly ash mixtures are under-
going four-cycle freeze-thaw tests after a 7 to 8 day curing period. Similar
tests are also planned for commercial lime sludge mixtures.
Wastes taken from the thickener underflow (24 percent solids)
and treated with carbide lime and lime additives we_re_fqund_to_be_too_soft to
measure unconfined compressive strength. All other slurry mixtures, which
were filtered to 42, 55, and 65 percent solids and treated, exhibited strengths
in the range of 7 to 400 psi, with the major portion of the mixes being above
BlTpsi (Table 55). Subsequently, nine commercial lime sludges have been
added to the test matrix (Table 56).
The~perm eabilfty criterion established in this project for
acceptable landfill material was that it be in the range of 10-« to 10"'cm/sec,
a rate similar to that of medium-stiff kaolinite clay. The mixtures selected
for permeability measurements and the data obtained thus far are shown in
Table 57 and have been in the range of about 3 x 10-6 to 6 X 10-?, except for
the mixtures made with the 24 percent solids (thickener underflow), which
were more permeable by a factor of 10. Permeabilities will also be deter-
mined for mixtures outlined in Table 56.
-------
TABLE 55. SIXTY-DAY UNCONFINED COMPRESSIVE STRENGTH OF TREATED
AND UNTREATED FGD WASTES
Sludge
Type
Carbide Lime
Percent
Solids
24
42
55
Additive
Type
Carbide Lime
CaO
Carbide Lime
CaO
CaO
•
Amount,
%
5
25
5
20
5
10
15
3
5
10
5
3
5
10
Fly Ash
to Scrubber
Solids Ratio
1:1
1:1
1:1
1:1
0:1
1:1
60-Day
Unconfined
Compressive
Strength, psi
Too soft
Too soft
Too soft
Too soft
57. 1
64. 1
35.9
47.5
62.8
63.0
29.0
235.8
176.3
270.2
-------
TABLE 55. SIXTY-DAY UNCONFINED COMPRESSIVE STRENGTH OF TREATED
AND UNTREATED FGD WASTES (Continued)
Sludge
Type
Carbide Lime
Commercial Lime
Percent
Solids
55
50
Additive
Type
Carbide Lime
Portland Cement
CaO
Amount
%
0
5
0
3
5
10
3
5
10
3
5
10
3
5
10
3
5
10
Fly Ash
to Scrubber
Solids Ratio
0:1
1:1
0.5:1
1:1
1.5:1
0.5:1
60 -Day
Unconfined
Compressive
Strength, psi
Not available
63.9
101.6
174.6
344.2
382. 7
10.6
10.8
40.9
37.9
19.3
83.4
46.4
69.5
134.2
50.6
60.0
63.5
-------
TABLE 55.
SIXTY-DAY UNCONFINED COMPRESSIVE STRENGTH OF TREATED
AND UNTREATED FGD WASTES (Continued)
Sludge
Type
Commercial Lime
(Continued)
Percent
Solids
50
65
Additive
Type
CaO
(Continued)
Ca(OH)2
Portland Cement
Amount,
%
3
5
10
3
5
10
3
5
10
3
5
10
3
5
10
3
5
Fly Ash
to Scrubber
Solids Ratio
1:1
1.5:1
0.5:1
1:1
1.5:1
0:1
60 -Day
Unconfined
Compressive
Strength, psi
59.1
137. 5
189. 5
86.8
249.0
404. 5
49. 5
150.8
236.0
94.9
187.2
392.6
7.1
61.6
48.9
23.9
27.4
-------
TABLE 55. SIXTY-DAY UNCONFINED COMPRESSIVE STRENGTH OF TREATED
AND UNTREATED FGD WASTES (Continued)
-4,
00
Sludge
Type
Commercial Lime
(Continued)
Percent
Solids
65
Additive
Type
Portland Cement
(Continued)
None
CaO
Ca(OH)2
Amount,
%
3
5
3
5
0
3
5
10
3
5
10
Fly Ash
to Scrubber
Solids Ratio
0.5:1
1:1
1:1
0.5:1
1:1
60-Day
Unconfined
Compressive
Strength, psi
31.0
31.9
53.0
65. 3
21.0
39.4
91.0
74.5
34.6
58.2
54. 7
-------
TABLE 56. ADDITIONAL LABORATORY TEST MIXTURES
Sample
Designation
P17
P18
P19
P20
P21
P22
P23
P24
P25
Sludge
Type
Commercial Lime
Solids,
%
50
50
50
50
50
50
50
50
50
Chemical Treatment
Type
Portland Cement
Portland Cement
Portland Cement
CaO
CaO
Ca(OH)2
CaO
Ca(OH)2
Ca(OH)2
Amount,
%
5
3
5
5
3
3
5
10
3
Fly Ash
to Sludge
Ratio
0.5:1
1:1
1:1
0.5:1
1:1
1:1
1:1
0.5:1
1.5:1
-------
TABLE 57. PERMEABILITY OF TREATED AND UNTREATED WASTES
Sludge
Type
Carbide Lime
Comme r cial
Lime
Percent
Solids
24
42
55
65
50
Additive
Type
Carbide Lime
Carbide Lime
CaO
Carbide Lime
None
Portland Cement
CaO
Percent
5
25
5
15
5
0
3
0
5
0
3
10
3
3
10
3
Fly Ash to
Scrubber
Solids Ratio
1:1
1:1
1:1
1:1
1:1
1:1
1:1
0:1
0:1
1:1
0.5:1
0.5:1
1.5:1
0.5:1
0.5:1
1.5:1
Permeability
Coefficient,
cm/sec
7.6 X 10"5
8.5 X 10"5
2.9 X 10"6
7.7 X 10"7
1. 1 X 10"6
5.7 X 10"?
-------
Leachate analysis for pH, TDS, Cl", SO3 , Cd, Cu, Pb, Hg,
As, SO ~, Ca, Mg, and Se were performed on the 16 mixtures selected as
potential candidates for further impoundment testing.
Table 58 contains the results of leachate analyses obtained
from the 16 permeability tests. As a result of the small sample size, the
first and second pore volumes were combined, and the fifth and sixth volumes
were mixed prior to analysis. In general, trace element concentrations have
been reduced considerably between the first and sixth pore volumes collected.
After a preliminary review of the data, it has been reported
that the carbide sludge and fly ash samples appear to be more susceptible
to the solubilizing of sulfate than the commercial lime mixtures. More
information is required from the field tests before definitive conclusions
on the selection of optimum mixtures can be made.
Selection of some of the carbide lime sludge mixtures for
impoundment evaluation has been made and are identified in Table 59. Two
of the mixtures will be evaluated in both large and small impoundments for
comparison. The commercial lime sludge mixtures will be selected for
demonstration, following completion of leachate tests now under way.
5.2.1.2 Field Disposal Evaluations
Work on the preparation of field disposal sites is being initiated.
The location will be at the LG&E Cane Run plant site. F^eld site evaluation
studies are being performed by the University of Louisville.
3 3
Eight, small, 25 yd (19m ), abov eg round impoundments
and eight large 100 yd^ (76 m ) underdrained disposal ponds are planned.
Chemical analysis of leachate and runoff, as well as physical
property testing of the treated wastes, will be performed for all impounded
wastes.
5.2.2 FGD Waste Leachate-Liner Compatibility Studies
(U.S. Army Engineer WES)
An assessment of the use of liners to contain FGD wastes in
disposal ponds is being conducted by the U.S. Army Engineer WES, Vicksburg,
Mississippi. An experimental program to determine the compatibility and
effectiveness of 18 liner materials with FGD wastes, liquors, and leachates
has been defined. Estimates of liner lifetimes are being made on the basis
of both a one- and two-year exposure of the liners to the wastes. The
economics of FGD disposal by ponding will then be assessed. The cost of
the liner materials and placement will be included, as well as associated
and construction costs. The program was initiated July 1975 and is scheduled
to be conducted over a period of 36 months.
176
-------
TABLE 58. LEACHATE ANALYSES
Sample
(I) PI
P2
(II) P3
P4
(III) P5
(V) P6
(VI) P7
P8
(IV) P9
Pore
Volume
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
Conductivity
(imho/cm
3550
2350
t8180
7370
4090
-
-
_
3750
_
4350
-
-
-
6850
2500
-
-
pH
11.4
11. 1
12.3
12.2
8.4
-
-
.
8.0
_
7.9
-
-
-
7.8
7.5
-
-
TDS,
ppmb
_
_
.
^
2500
-
-
_
2200
_
2600
-
-
-
4100
1500
- .
-
cr,
ppm
115
<5
180
< 5
250
-
-
_
155
_
335
-
-
-
345
<5
-
-
so3",
ppm
_
656
60 '
706
501
-
-
_
201
_
51
-
-
-
30 i
-
-
-
Cd,
ppm
<0.01
<0.01
0.02
0.02
0.02
-
-
_
0.02
-
0.02
-
-
-
0.02
<0.01
-
-
Cu,
ppm
0.02
0.02
0.02
0.02
0.06
-
-
_
0.08
.
0.06
-
-
-
0.06
0.02
-
-
Pb,
ppm
0. 1
0. 1
0. 1
0. 1
0. 1
-
-
_
0. 1
.
0. 1
-
-
-
0.2
0. 1
-
-
Hg,
ppm
0.003
0.002
0.008
0.003
0.002
-
.
_
0.001
-
0.001
-
-
-
0.001
0.002
-
-
As,
ppm
_
0.03
0.04
0.01
0.05
-
-
_
0.07
-
0.05
-
-
-
0.05
0.01
-
-
so4=,
ppmc
1580
1470
1320
1530
1860
-
-
_
1550
.
1940
-
-
-
5390
1960
-
-
Ca,
ppm
300
310
540
590
250
-
-
_
230
.
360
-
-
-
260
300
-
-
Mg,
ppm
0.05
0.05
0.01
0.01
0. 10
-
-
_
0.06
.
0. 14
-
-
-
940
130
-
-
Se,
ppm
0.019
0.006
0.015
0.004
0.034
-
-
_
0.015
_
0.028
-
-
-
0.023
0.002
-
-
-------
TABLE 58. LEACHATE ANALYSES (Continued)
Sample
P10
PH
P12
P13
P14
P15
P16
Pore
Volume
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5&6
1&2
5& 6
1&2
5&6
1&2
Conductivity
jimho /cm
2850
2000
2450
550
2200
420
2650
620
5650
3850
66902
5400
1800
PH
7.8
7.7
8.9
9.2
11.6
9.7
8.0
9. 1
12.2
12. 1
12. I2
12.2
9.3
TDS,
ppmb
1700
1200
1500
300
-
250
1600
370
-
_
-
-
1100
cr,
ppm
10
15
10
<5
<5
<5
20
<5
10
15
<5
<5
15
ppm
40 '
-
60 i
606
851
105
351
210
-
_
452
-
230
Cd,
ppm
0.02
<0.01
0.02
<0.01
<0.01
<0.01
<0.01
<0.01
0.02
<0.01
0.02
<0.01
<0.01
Cu,
ppm
0.02
0.02
0.04
<0.02
0.04
0.02
0.02
<0.02
0.02
0.02
0.06
0.02
<0.02
Pb,
ppm
0. 1
0. 1
0. 1
<0. 1
<0. 1
<0. 1
0. 1
<0. 1
0. 1
0. 1
0. 1
0. 1
<0. 1
Hg.
ppm
0.018
0.001
0.003
0.001
0.002
<0.001
0.069
0.001
0.001
0.002
0.001
0.001
0.001
As,
ppm
0.03
0.03
_
0.02
<0.01
<0.01
0.02
0.03
0.01
<0.01
<0.01
<0.01
0.01
S°4=-
ppmc
1580
1470
1390
280
270
110
1550
260
140
44
840
110
440
Ca,
ppm
320
300
250
70
11
14
200
95
240
160
470
270
6.7.
Mg,
ppm
0. 18
0. 16
0. 17
0.06
0.01
0.02
0.21
0. 12
0.01
0.01
0. 38
0.01
0.02
Se,
ppm
0.003
0.003
<0.001
-
-
-
-
_
-
1 -
•_
NOTE: Superscripts denote the pore volume used in the analysis.
aSamples are marked on the basis of permeability runs (see Table 57 ).
Roman numerals refer to mixtures selected for field demonstration (see' Table 59 ). Samples III, IV, and VI have not been
sufficiently permeable to allow collection of a leachate sample.
The total of the dissolved solids is an approximate value obtained from the conductivity. This approximation can only be made
if the pH is between 5 and 10. Absolute values for TDS cannot be obtained for these samples.
CTotal sulfur is expressed as SO|.
-------
TABLE 59. IDENTIFICATION OF MIXTURES FOR IMPOUNDMENT EVALUATION
Sludge
Type
Carbide Lime
Percent
Solids
24
42
42
55
55
55
Additive
Type
Carbide Lime
Carbide Lime
CaO
Carbide Lime
Carbide Lime
Carbide Lime
Percent
5
5
5
5
3
5
Fly Ash to
Scrubber
Solids Ratio
1:1
1:1
1:1
0:1
1:1
1:1
Impoundment
Designation
Small
s
II
s
-
IV
s
-
VIs
Large
h
^
mi
-
Vl
-
Permeability
Test
Designation
PI
P3
P5
P9
P6
P7
Commercial Lime - Mixtures To Be Selected
-------
A total of 72 test cells approximately 11-13/16 inches inner
diameter, containing the 18 liner materials^ and contacting a layer of 6 inches
of compacted soil has been assembled. A total of four gallons of sludge,
forming a column about eight einches high, is used to inundate the liner.
Approximately two gallons of water (approximately five inches high) covers
the sludge. The test cells are housed in a temperature-controlled environ-
ment and are being pressured at a rate of 2 psi per month to simulate a
disposal site fill cycle. The pressure will be increased until an equivalent
30 -foot sludge depth (20 psi) is reached.
Physical property and durability tests such as weigh.^ thick- _____
ness, density, and tensile strength have been performed on the as-received
membrane liner materials and will be made again in replicate after both a
12- and a 24-month exposure. The leachate from each cell will be mea^ _________
sured and analyzed. Daily monitoring of the test cells is being conducted
to observe if any breakthroughs occur.
Six sprayon-type ^ rnaj;erj.als1_10__additive^ mixed jw_i£h__3Q_il, .and
2 prefabricated membranes are currently under testing (Table 60). The
additives have been mixed with clayey silt soil, or silty sand, to form a
six-inch thick liner. The liner materials are exposed to FGD wastes from
plants burning Eastern coal, one from a lime- scrubbed flue gas and the
other limestone (Table 61).
Screening tests for liner permeability were conducted ^
various liner formulations and materials. The specimens were subjected to
a 2-foot head of water. Silty sand and clayey silt soil were combined with
various proportions of admix materials arid tested. The results are sum-
marized in Table 62. Four admixes (fly ash, cement with fly ash, lime
with fly ash, and aniline-furfural) and one sprayon material (SSK) were
rejected as unsuitable because of excessive permeability (Table 63). Con-
trol tests on the soil permeability were conducted, and the results are
reported in Table 64.
Initial data on the average leakage rate of the four test cells
for each of the liner materials are^sho^nj.n^igujre^:^ Chemical_analy^es
of the leachate are being performed on samples collected from each test
cell.
5.2.3 Lime and Limestone Wet Scrubbing Waste
Characterization (TVAj
The effects of scrubber operating conditions on FGC waste
characteristics are being correlated in this program, which is part of an
interagency agreement with TVA, Power Research Staff, Chattanooga,
Tennessee. The FGC waste materials from the TVA Shawnee scrubber
facility are being characterized and the physical and chemical properties
correlated with scrubber operating conditions. Although FGD sludges have
received extensive physical and chemical characterization in the past, the
total range of variability of the solids and their characteristics as a function
180
-------
TABLE 60. LINER MATERIALS BEING TESTED
Material
Prefabricated Membranes
Total Liner
T-16
Sprayon Type
DCA-1Z95
Dynatech Formulation
267
Uniroyal
Aerospray 70
AC 40
Sucoat
Admixes
Cement
Lime
Cement with Lime
M179
Guartec (UF)
Asphalt Concrete
TACSS 020
TACSS 025
TACSS C400
TACSS ST
Material Type
Elasticized polyolefin
(30 mil)
Black neoprene- coated
nylon- reinforced fabric
Polyvinyl acetate
Natural rubber latex
Natural latex
Polyvinyl acetate
Asphalt cement
Molten sulfur
(10%)b
(10%)
(4% Portland Cement,
6% lime)
Polymer bentonite
blend (4%)
A light grey powder (4%)
(11% cement,
1/2-in. aggregate)
(6%)
(6%)
(15%)
(15%)
Manufacturer
The Goodyear Tire and Rubber Co.
Reeves Brothers, Inc.
Union Carbide
Dynatech Research & Development Co.
Uniroyal, Inc.
American Cyanamid
Globe Asphalt
Chevron Chemical Co.
Dundee Cement Co.
Williams Keith Lime Co.
Dowell Division of Dow Chemical
General Mills
Local Contractors
TakenakaCo., Japan, Distributed in U. S.
by Air Frame Mfg. Co. , Calif.
Takenaka Co., Japan, Distributed in U.S.
by Air Frame Mfg. Co., Calif.
TakenakaCo., Japan, Dis tributed in U . S .
by Air Frame Mfg. Co., Calif.
TakenakaCo., Japan, Distributed in U.S.
by Air Frame Mfg. Co., Calif.
Soil is clayey silt, except where noted by c.
The number in parentheses indicates the application rate in percentage of test material
based on dry soil weight.
Soil is silty sand.
181
-------
TABLE 61. FGD WASTES
Type of FGD Waste
Lime -scrubbed
Limestone -scrubbed
Designation
A
B
Wet Density at
23 °C, lb/ft3
88.8
83.6
Source of Coal
Eastern coal
Eastern coal
Sample Source
Duquesne Light Co.^
Phillips Power Station
Commonwealth Edison,
Will County Station,
Unit No. 1
-------
TABLE 62. EVALUATION OF SPRAYON AND ADMIX TEST MATERIALS
Test Material
Spray on
DCA-1295
Aerospray 70
Dynatech 267
Uni royal
AC 40
SSk
SSk
SSk
Application
Rate
0.75 gsya
0. 75 gsy
0. 75 gsy
0. 75 gsy
0. 75 gsy
0. 75 gsy
1.0 gsy
0. 75 gsy
Soil Type
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
& clayey
silt
Remarks
Penetrated surface 1/16 in. , no leakage.
Penetrated surface 1/32 in. , no leakage.
Penetrated surface 1/64 in. , no leakage.
Penetrated surface 1/64 in. , no leakage.
Penetrated surface 1/64 in. , no leakage.
Penetrated surface 1/32 in., slight
leakage.
The membrane covering the test
specimen ruptured after 5-2/3 days.
Prior to this time, the specimen had
exhibited slight (49 ml total) leakage.
Ineffective on both soil types after
approximately 7 days.
agsy: gallons per sq yd.
00
-------
TABLE 62. EVALUATION OF SPRAYON AND ADMIX TEST MATERIALS (Continued)
oo
Test Material
Admix
Portland Cement
Portland Cement
Cement-Fly Ash
Hyd rated Lime
Lime-Cement
Application
Rate
8%a
10
12
16
20
24
6%
8
10
2% cement,
8% fly ash.
5% cement,
5% fly ash.
8% cement,
2% fly ash.
6%
8
10
2% lime,
8% cement.
8% lime,
2% cement.
5% lime,
2% cement.
Soil Type
Silty sand
Clayey silt
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Remarks
Each specimen leaked. Judged
inadequate as an integral part of a liner
system for this soil type.
No leakage.
Slight leakage.
No leakage.
Started leaking soon after test began.
Judged unacceptable as a linear mate-
rial under stated conditions.
Leaked badly, failed.
Same as cement-fly ash.
aPercentage based on dry soil weight.
-------
TABLE 62. EVALUATION OF SPRAYON AND ADMIX TEST MATERIALS (Continued)
oo
Test Material
Admix (Continued)
Lime -Fly Ash
Fly Ash
M-179
Guartec UF
AM9
Application
Ratea
2% lime,
8% fly ash.
5% lime,
5% fly ash.
8% lime,
2% fly ash.
6,8,10%
4%
8
10
4%
8
10
12
10%
10
Soil Type
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Silty sand
Clayey silt
Silty sand
Remarks
Same as cement-fly ash.
Same as hydrated lime.
None of these specimens leaked, how-
ever, the top of each became soft and
slimy after the 7-day permeability test.
Rejected for use with silty sand soil.
Material will be used in a test cell with
clayey silt soil.
Same remarks as for M-179 above.
Samples shrank approximately 1/32 in.
in the middle of the top portion of each
specimen. Both samples were leaking
after 67 hr of testing.
Samples very soft, specimens leaked
24 ml (av) after 1 hr 45 min.
Percentage based on dry soil weight.
-------
TABLE 62. EVALUATION OF SPRAYON AND ADMIX TEST MATERIALS (Continued)
Test Material
Admix (Continued)
Aniline -Furfural
(2. 1% aniline,
1.2% furfural)
TACSS T-025-NF
TACSS T-020-NF
TACSS T-020-NF
Application
Rate
3.3%
6%
10
15
6%
10
15
6%
10
15
6%
10
15
Soil Type
Silty sand
&: clayey
silt
Clayey silt
Clayey silt
Clayey silt
Silty sand
Silty sand
Silty sand
Clayey silt
Clayey silt
Clayey silt
Silty sand
.Silty sand
Silty sand
Remarks
Both specimens exhibited high com-
pressive strengths and were unaffected
by water but were highly permeable.
Rejected.
No leakage.
27 ml /day leakage.
34 ml /day leakage.
1/4 ml/day leakage.
7. 6 ml /day leakage.
8. 5 ml /day leakage.
No leakage.
No leakage.
No leakage.
No leakage.
No leakage.
One specimen passedr one failed.
00
-------
TABLE 63. LINER MATERIALS REJECTED
oo|
Material
Prefabricated Membranes
T85
T105
Admixes
Fly Ash
Cement with Fly Ash
Lime with Fly Ash
Analine, Furfural
Sp rayon Type
SSK
Reason
Leakage at joint. Did not pursue
study to improve joining methods.
Leakage at joint. Did not pursue
study to improve joining methods.
Excessive permeability
Excessive permeability
Excessive permeability
Excessive permeability
Excessive permeability
Replaced in Test
Program by
T105
T16
TACSS 020
TACSS 025
TACSS C400
TACSS ST
SUCOAT
aSee Table 5.2.2c for mixtures tested.
-------
TABLE 64. PERMEABILITY COEFFICIENTS USING WATER
Conditions
Permeability, cm/sec
6-in. compacted silty sand
6-in. compacted silty sand
with lime sludge
6-in. compacted silty sand
with limestone sludge
81 X 10
49 X 10
47 X 10
-6
-6
-6
6-in. compacted clayey silt
6-in. compacted clayey silt
with lime sludge
6-in. compacted clayey silt
with limestone sludge
16 X 10
7 X 10
1 X 10
-6
-6
-6
The liquid was passed through a porous plastic filter at the
bottom of the test cell. The permeability of the filter was
28,500 X ID-6 cm/sec.
188
-------
LINER MATER IAL
TOTAL LINER
M6
DCA 1295
DYNATECH 267
UN I ROYAL
AEROSPRAY 70
AC 40
SUCOAT
CEMENT
LIME
CEMENT W/ LI ME
M179
GUARTEC (UF)
ASPHALT CONCRETE
TACSS 020
TACSS 025
TACSS C400
TACSS ST
0 10 20 30
AVERAGE DAILY LEAKAGE, m#day
AVERAGE OF FOUR CELLS PER LINER,
AMBIENT PRESSURE
40
Figure 44. Average leakage rate of liner specimens
189
-------
of scrubber operation have not been studied. The goal of the program is to
determine the feasibility of controlling waste characteristics to improve
disposal and utilization economics.
Correlation of the Shawnee scrubber operation and sludge
characteristics is scheduled for completion by the middle of calendar year
1977. During the period March 1975 to June 1976, slurry and solids charac-
terization studies were conducted on 84 samples from the Shawnee Test
Facility TCA and venturi and spray tower scrubbing systems.
Results are reported from the data obtained from analysis of
solids from the following scheduled tests:
a. Mist eliminator testing
b. Magnesium oxide addition
c. Factorial testing
Present plans include examination of solids from the following tests, which
are to be conducted in the future:
a. Variable load
b. Maximum oxidation
c. Fly ash free testing
d. Maximum SO- removal efficiency
e. Reliability testing
The plant operating conditions that appear to be most closely
related to variations in the solids compositions and properties are variable
liquid-gas ratios, presence of fly ash, scaling potential of the mother
liquor (i. e. , degree of CaSO ' 2H~O super saturation), and the control of
oxidation in the solids as indicated by SO. for SO- isomorphic substitution in
the structure of CaSO^ 1/2H-O crystals. The study also gathered data on
the conditions during which optimum crystal growth occurs because of the
significance of this factor on pond site dewatering, filtration rates, and the
liquid entrainment in the solids.
Solids samples obtained from the TCA and venturi and spray
tower scrubbing process loops generally consist of calcium sulfite hemi-
hydrate, fly ash, and gypsum, with trace amounts of unreacted absorbent
and quartz. The calcium sulfite hemihydrate species is generally the major
component (50 to 70 percent) of the solids.
The specific form in which the sulfite species appears was found
to be directly related to the type of absorbent used (lime or limestone) and
independent of the scrubber configuration (TCA or venturi and spray tower).
190
-------
When limestone •was used as the absorbent, the sulfite crystallized
predominantly as well-formed single plates; on the other hand, with lime as
the absorbent, the sulfite appeared as spherical, closely interpenetrating
aggregates. The average size of the sulfite plates formed from the lime-
stone system appears to be inversely related to the system stoichiometry.
No_relationship has been seen in the lime system. Besides the sulfite, fly
ash is one of the more significant of the accessory components in sludge
samples, comprising 20 to 40 percent by weight of the solids composition.
The spheres may be solid or hollow and consist of an amorphous alumino-
silicate material, sometimes containing calcium and/or iron.
The sedimentation behavior of the scrubbing slurry studies
may be described principally as zone settling. Solids morphology was
found to exert a strong influence on settling behavior. In samples with large
proportions of very small plates, settling is inhibited because more liquor
is entrapped upon reaching the compression stage because of a much higher
incidence of interparticle contact.
The initial report of these studies, both qualitative and
quantitative, have used comparative optical, x-ray, infrared, and SEM
investigations of the sludges from the Shawnee scrubbers and provide a
good base for describing the range of variability observed in sludge phases.
Settling rates and bulk densities provide data on the physical properties
of sludges.
At this point in the project, data collection is not complete,
and in many cases no firm conclusions can be drawn between data trends
and process variables. In some cases, definite relationships have emerged,
but these are still subject to further refinement or modification upon com-
pletion of the sampling program.
An important factor that is reported to require further evalu-
ation is the response time of the solids for showing change in characteristics.
This plays a decisive role in characterization of the solids since they are a
function of liquor chemistry and scrubber operation averaged over a pre-
ceding period of time and not one specific increment. The time required for
the solids as a mass to adjust to a specific change and establish a new equili-
brium in terms of chemical composition on morphology can range from one
to three days. Because of this, time correlations will be meaningful only if
these latter factors are representative of some prior finite period of
operation.
5. Z. 3. 1 Characterization Techniques
The initial studies involve a comparative optical, x-ray, in-
frared and SEM analysis of the sludges from the Shawnee scrubbers. Quan-
titative and qualitative data will be obtained to evaluate the variability of the
sludge phases. Settling rates and bulk densities will also be measured.
Scanning electron microscopy and optical microscopy have
been used to provide both qualitative and quantitative information concerning
bulk solids composition, as well as the specific morphological form of the
191
-------
various individual components. Infrared spectrophotometry and x-ray powder
diffraction measurements have been used for semiquantitative analyses of the
dried solids. Specific surface area of the solids was determined as an indica-
tion of solids component morphology.
Several techniques were used which reflected any changes in
crystal structure caused by the substitution of sulfate or carbonate species
into the calcium hemihyrate. Optical microscopy was used to provide the
index of refraction of the substituted component, while its specific unit cell
parameters, which are sensitive to compositional changes, were obtained
from x-ray powder diffractometry. In addition, differential scanning calo-
rimetry (DSC) is being evaluated as an indicator of the ease with which the
sulfite component will undergo dehydration. Because the temperature of
dehydration should, in general, vary inversely with the degree of substitution
of sulfate for sulfite, it is felt that the DSC technique may provide such an
indicator.
5.2.3.2 Solids Morphology
Solids from the TCA and venturi and spray tower scrubbing
process loops are generally comprised of calcium sulfite hemihydrate and
fly ash, with trace quantities of gypsum, unreacted absorbent, and quartz.
The concentration of the calcium sulfite hemihydrate species
is generally 50 to 70 percent of the solids. Therefore, a study of its occur-
rence and morphology was considered important as these factors affect such
considerations as sludge filtration, clarification, and disposal. When
referring to the calcium sulfite hemihydrate crystalline species it is under-
stood that it may be more appropriately described as x(CaSO,) y(CaSO4)'
zH^O where x is much greater than y, and z approaches 0. 5. The specific
form in which the sulfite species Appears is directly related Jp the type of
absorbent used, i. e. , lime or limestone, and is independent of the scrubber
configuration (TCA or venturi-spray tower). The calcium sulfite hemihydrate
component of the solids samples occurred in several forms. When limestone
was used as the absorbent, the sulfite crystallized predominantly as well-
formed single plates with average length-width-thickness dimensions in the
ratio of approximately 25:20:1 microns. While within a given sample the
crystallite size distribution will range over an order of magnitude, the
average size may differ only by a factor of two to three from one sample to
another. While the flat plates described above are the major form observed,
aggregated forms of the sulfite crystals were also observed. This form
was reported to be "not uncommon;" most samples examined from limestone
scrubbed operation contained incidences of this rosette form with a few
samples exhibiting this form as the predominant sulfite occurrence^ The i
maximum reported dimension was 40 microns.
The characteristic form of the sulfite precipitated from
scrubbing liquors where lime isjused a.s the absorbent is generally
spherical with closely interpenetrating aggregates" fouSod"tolKe "almost total
exclusion of other forms. Unlike the Hat plates occuring during limestone
192
-------
- the spherical aggregates averaging approximately 10 microns
in diameter do not show a wide variation in size distribution within a given
sample, although incompletely developed forms and fragments are often
observed.
; A series of tests with the venturi and spray tower scrubber
demonstrated that the sulfite characteristics were independent of the scrubber
operation but dependent on the absorbent. During these tests, the use of lime-
stone as the absorbent was alternated with lime. The results repeatedly show
the spherical sulfite aggregate occurrence when lime was used. With lime-
stone, flat plates predominated. While this morphology-absorbent relationship
was considered to be clearly established, no explanation for this effect is
available at this time.
In a limestone test series in which the chloride ion concen-
tration was much higher than any other condition studied (2. 13 percent), the
aggregates consisted of smaller more densely interpenetrating plates than
were usually observed. The exact cause of this difference has not been
determined.
In lime systems, no definite relationship has been found
between aggregate size and either chemical composition or physical operating
parameters. When limestone is used as the absorbent, however, the average
size of the plate crystals formed in this environment appears to be inversely
related to system stoichiometry, a steadily decreasing average crystallite
size, with increasing Ca:S stoichiometry between 0.98 and 1.63. While no
precise mathematical relationship between crystal size and stoichiometry
was derived, this observation suggests stoichiometries approaching 1.0 in
order to promote faster slurry filtration and clarification.
A previously unreported form of "mixed crystal" was observed,
occurring during the period January 1, 1976 to January 10, 1976, in both the
TCA and venturi and spray tower systems. In this form, a sulfite rosette is
in intimate physical association with a well-developed, although often imper-
fect, gypsum crystal. The gypsum crystals often show a large number of
surface cracks and longitudinal crystal defects. Enlarged views of the areas
of contact between the two forms show what appears to be CaSO' 0. 5H_O
plate crystals growing from the body of the gypsum prism. Occurence of
these mixed crystals was not routinely observed in samples other than those
included in the time period cited and in these samples only in minor (less
than 5 percent) quantitites. These forms may be related to the gypsum-
calcium sulfite hemihydrate solid solutions referred to by Borgwardt
(Ref. 17). Comparison of sample chemical composition and scrubber
operating data for the period of time during which these samples were taken
indicates no excursions from normal values which might be helpful in ex-
plaining the appearance of these mixed forms. No explanation for their
presence is available at this time.
Fly ash is one of the more significant components of the sludge
samples examined to date, comprising 20 to 40 percent by weight of the
solids composition. It is normally present in the form of featureless
193
-------
spheres ranging in diameter from a submicron size up to greater than
100 microns. The spheres may be solid or hollow and consist of an
amorphous aluminosilicate material, sometimes containing calcium and
iron. A portion of the fly ash is magnetic and ranges in quantity from 5 to
60 percent by weight. A small fraction of the fly ash constituent is not
spherical but appears to be irregularly shaped, vesicular particles. Rarely,
CaSO' 0. 5H,O flat plates will be observed to have been precipitated on the
surface of ally ash sphere.
Gypsum and unreacted absorbent was generally observed in
very small quantities (less than 5 percent total). The CaSO ' 2H2
-------
Settling rates and behavior for samples of similar participate
composition are generally dependent on slurry percent soilds, with the thicker
slurries settling more slowly. This is illustrated in Figure 45, in which the
settling rates for some limestone slurries are shown by a plot of interface
position as a function of time. It was observed that thicker (higher percent
solids) slurries have lower settling rates and take longer to reach the
compression stage.
No general relationship between slurry percent solids and
slurry settling rates could be defined because solids morphology also exerts
a strong influence. An example of this effect is the behavior of slurries
obtained from the TCA system on May 14, 1976 and April 12, 1976 (Figure 46).
Although the weight percent solids in both slurries are essentially the same,
the sample taken on April 12, 1976 settled more than three times faster
and attained, when settled to compaction, an ultimate solids weight percent
of 68 percent as compared to 38 percent for the sample taken on May 14,
1976. The micrographs of these solids reveal that while both contained a
predominance of single plates, the sample taken on May 14, 1976 consisted
of a large proportion of very small plates and plate fragments. These
smaller particles inhibit settling and entrap more liquor upon reaching the
compression state as a result of a much higher incidence of interparticle
touching. This limits the amount of liquor that may flow past them during
settling and increases the difficulty with which dewatering can occur.
Because of sample handling and shipping, the static settling
tests performed at Muscle Shoals are conducted from 3 to 10 days after the
samples are originally taken from the process loop. Settling tests conducted
at the Shawnee Test Facility, however, are generally performed within a
short time after acquisition. In addition, settling data at Shawnee are
generated by the Dorr-Oliver method, which differs from a static test in
that the bottom of the test cylinder contains a rake rotated at 1/6 rpm during
the settling test. In order to compare data generated by the two methods
and to evaluate any effects caused by the delay in testing, comparison of
the results obtained by both methods was made. It was concluded that no
significant systematic difference was evident in the results between the two
procedures within the range of sample percent solids studied and within the
context of the types of slurry samples included in the tests.
5.2.3.4 Solids Surface Area
Since the size, shape, and complexity of individual solid
particles in the scrubbing slurry may influence or control processes such as
chemical reaction speed and filtration or dewatering rates, the solids sur-
face area was determined as a measure of the average particle size and com-
plexity of the slurry solids. The method used is based on a nitrogen desorp-
tion method described in Reference 18.
2 The surface area in meters per gram squared range from
1.6 to 7.6 m /g. The average specific area for samples obtained during
lime scrubbing is greater than that measured for samples taken from systems
employing limestone, i.e. , 5.4 for lime and 3. 3 for limestone. These data
195
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0
2816 5-7-76
SOLIDS
2816 3-30-76
17.7% SOLIDS
2816 9-28-
9.7% SOLIDS
I
2816 11-13-75
15.4% SOLIDS
I
0 100 200 300 400
MINUTES
Figure 45. Settling rate: limestone slurry
500
2816 5-14-76
16.9% SOLIDS
2816 4-12-76
.6% SOLIDS
0 100 200 300 400 500
MINUTES
Figure 46. Settling rate: effect of solids morphology
196
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agree with the observation that lime scrubbing tends to precipitate the sulfite
crystals as more complex, interpenetrating forms. The values of specific
surface area were not readily correlated with variations in sulfite crystal
size or complexity (even though this component may comprise, in weight
percent, the majority of the sample) because of masking effects of the wide
variation in quantity and particle size distribution of the fly ash fraction.
Work is in progress to explore possible relationships between the specific
area of a sample and its filterability. In addition, a series of "fly ash-free"
runs begun on the venturi and spray tower system in June 1976 are expected
to provide samples displaying less of the fly ash masking effect and thus
simplify further correlational studies.
5.2.3.5 Thermal Analysis of Solids
Thermal analysis of the dried scrubbing solids has been per-
formed, using a Perkin Elmer DSC-2 in the range 330 to 500° C. This
temperature range was selected in order to study the thermal dehydration of
the CaSCX'O. 5H2O component. It is felt that substitution of carbonate or
sulfate into the sulfite structure will result in either a shift of this compound's
desolvation temperature away from that of the pure compound or exhibit an
increase in complexity of the normally straightforward endothermic desolva-
tion reaction.
Two types of thermal activity were reported. The type of
behavior illustrated in Figure 47 has been observed to predominate in samples
taken from lime systems. A generally straightforward endothermic desolva-
tion of the sulfite is considered to occur only after an initial reaction, which
may represent a gradual desolvation or decomposition of an unknown
compound.
A type of thermal activity which is representative of limestone
systems is shown in Figure 48. In this case, no initial thermal activity is
observed, but the endothermic reaction generally attributed to the sulfite
decomposition clearly consists of at least two components, although inade-
quately resolved. The dashed curve superimposed upon Figure 48 repre-
pared CaSC^-O. 5H2O.
To date, no correlation has been found between the temperature
of reaction as measured and quantities which would measure either SO^. sub-
stitution (infrared spectrophotometric determination of substituted CaSO^) or
disturbances in the CaSO,-0. 5H2O structure (the index of refraction or
length of crystal axes).
Thermal analysis of lime-lime stone scrubbing materials has
been reported in Reference 19. In these studies, synthetic sludges were
prepared by the addition of fly ash to mixtures of the pure components
normally found in such sludges (CaSO • 0. 5H-O, CaSO^Zt^O, and
These mixtures were studied, subjected to differential thermal analysis
(DTA) and thermogravimetric analysis (TGA). The CaSO./0. 5H2
-------
V 4
o>
T
(A) 1816 6/9/76 0730
HEATING RATE - 10 deg min
-1
600
625 650
675
700
725 750
TEMPERATURE, °K-
Figure 47. Thermal characteristics: lime
system solids
8
01
•8
I'
CO
CO
0
(B) 1816 4/3/76 0730
HEATING RATE - 10 deg min
o
O
O
O
ct:
UJ
600 625 650 675 700
TEMPERATURE, °K-
725 750
Figure 48. Thermal characteristics: limestone
system solids
198
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favorably with the results of this program, which indicate an average
decomposition temperature of approximately 390° C. The dehydration
temperature of 367° C for the pure compound is reported in Reference 20,
which also reports a decomposition temperature of 364° C, utilizing DTA
and DSC investigation of the pure compound as prepared in the TVA labora
tory. It is not clear which aspects of the complex thermal behavior of the
samples examined to date are a result of matrix effects and which may be
assigned to reactions of carbonate- or suLfate- substituted CaSO • 0.
species. Studies in progress are intended to clarify this information.
5.2.3.6 Data Handling and Analysis
A series of computer programs have been written to establish
and maintain a slurry sample data base containing all numeric data obtained
from this characterization study and selected analytical and operating data
supplied by the Shawnee Test Facility. This data base provides machine
readable files which are used in ongoing statistical data analysis and report
generation and also allows interactive file updating and correction
capabilities.
Numerical or statistical analysis to determine relationships
between the chemical and physical properties of the scrubbing slurries and
solids and scrubber operating parameters has proceeded along several
lines:
a. Determination of relationships associated with sludge
handling factors, i. e. , settling rates, settled bulk
densities, ultimate settled percent solids, and operating
or chemical parameters such as percent fly ash, average
particle size and morphology, absorbent, and hold tank
residence time.
b. Relating sulfate substitution as indicated by variations
in the index of refraction and length of crystallo graphic
axes to chemical composition, i.e., weight percent
sulfate, stoichiometry, saturation ratio, and pH.
c. Evaluating general system operation as functions of
absorbent used, make per pass ratio, and liquid to gas
ratio.
In the analyses performed to date, some trends have been
indicated, but no unusual significant results have been observed. A signifi-
cant factor in masking possible correlations is the solids response time.
Assuming an abrupt change in adsorbent or additive feed or in scrubber
operating conditions, the time required for the solids to adjust to this change
and establish a new equilibrium in terms of chemical composition or
morphology ranges from one to three days. The importance of this effect
is that a chemical analysis of components in the scrubbing liquor or a
description of scrubber operating conditions at a given point in tim e may
not be related to the chemical composition and morphology of the solids
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taken at that time. Rather, the characteristics of the solids are functions
of liquor chemistry and scrubber operation averaged over a preceding
period of time. Analyses of these data are continuing, particularly concern-
ing sludge handling properties. Multivariate relationships between variables
such as slurry percent fly ash, settling rates, and settled percent solids
are currently under investigation.
5. 2. 4 Dewatering Principles and Equipment Design
Studies (Auburn University)
This study was initiated in June 1976 by Auburn University,
Auburn, Alabama. Overall objectives include the examination of current
dewatering equipment design principles, their applicability to dewatering of
FGC wastes, and the potential for developing more promising continuous
dewatering methods for increasing the throughput or increasing the solids
content of wastes. The economics of the dewatering processes developed
will be considered and included in an overall assessment of their feasibility.
The initial emphasis is on the application of gravity sedimentation to rapid
and inexpensive dewatering of FGC wastes.
Specific tasks include the following:
a. Develop methods for characterizing the physical properties
and behavior of FGC wastes. The characteristic indicator
is used to provide a basis for selection of type of gravity
sedimentation unit; i. e. , continuous or semicontinuous and
lamella or conventional, for determining design specifica-
tions and for directing operations to achieve maximum
dewatering efficiency for any given application.
b. Develop procedures based on existing gravity settling
mathematical modes, with modifications and extensions, to
allow accurate design and analysis of gravity sedimentation
units used in treating FGC wastes.
c. Perform bench-scale and pilot tests to evaluate the feasi-
bility of using gravity sedimentation units for treating FGC
wastes. The effects of system variables such as location
of feed port, design of the feeder head, depth of sludge bed,
and solids throughput rate on dewatering efficiency are to
be evaluated. Gravity sedimentation methods that can best
be utilized in treating FGC wastes will then be recommended.
d. Conduct experiments to determine the best design for the
application of channel promoters. Bench-scale and con-
tinuous pilot tests are to be performed to evaluate the
feasibility of such devices for improving dewatering
efficiency while treating FGC wastes.
e.
Study the filter ability of different types of FGC sludges
having been dewatered previously to different levels. Also
assess the pumping requirements for the different sludges.
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5. 2. 4. 1 Initial Results
A study of those separation processes, particularly
sedimentation (thickening) and filtration, currently accepted as offering the
best means for dewatering FGC wastes has been emphasized early in the
program. The material being used in these studies is carbide lime sludge
from LG&E. Progress made in the sedimentation and filtration studies is
summarized in the following paragraphs.
5.2.4.1.1 Sedimentation Studies
It was reported that stirring had a pronounced effect on the
settling rate in settling column tests. For example, after about a month of
settling, slurry that had been stirred only once had a mean solids concentra-
tion of 20. 7 percent by weight; whereas unstirred slurry had a mean solids
concentration of 37. 7 percent. These early results indicate that much of the
data from past developmental studies at Auburn using phosphatic slimes may
be directly applicable in dewatering studies using FGC wastes.
Batch settling tests of the FGC waste included monitoring of
solids concentration at a specific height above the settling bottom as well as
the height of the solid-liquid interface. These results are being compared to
existing dewatering theories to describe the dewatering mechanism and
characterize settling behavior. Tests were conducted in columns 8 feet high
and 1 foot in diameter, with a 4 feet by 4 inch inner diameter.
5.2.4.1.2 Continuous Settling Studies
Studies to determine the effect of the solids throughput rate
on underflow concentration for a base set of operational conditions were
initiated. These are expected to provide a baseline for comparison in
evaluating the effect of different operational parameters such as sludge
blanket height and feed port location on dewatering efficiency.
A significant observation was made while setting up the pilot
thickener unit which may result in significantly higher dewatering efficien-
cies, as well as better control of the pilot thickener. It was reported that
parametric pumping had a pronounced effect on underflow concentration while
thickening phosphatic slime. The slime was used to simulate the FGC waste and
has settling characteristics similar to those of carbide lime wastes. During
the test, while holding all operational parameters constant and simultaneously
pulsing the slurry feed and underflow flow rates by alternately operating and
stopping the pump, underflow concentration increased by 25 percent above
that obtained during continuous pumping.
5.2.4.1.3 Economics
Based on previous experience, it was reported that a series
of thickeners rather than a single thickener should require the least overall
capital expenditure for a given dewatering load. On the other hand, pumping
costs are higher when multiple thickeners are used. For computation of the
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economically optimal number of thickeners, a computer program was
designed which relates the economic cost relationships and the baseline
solids throughput rate versus underflow concentration curve that will be
established (experimentally).
5. 3 PROCESS ECONOMICS STUDIES
Economic studies are interwoven within most of the various
projects. Assessment of process technology or environmental impact gen-
erally includes an examination of the economics involved. However, those
primarily related to economics are discussed in this section and include (1)
conceptual design and cost studies for current disposal practices and (2)
gypsum by-product marketing studies. Both are being conducted by TVA.
5. 3. 1 Conceptual Design and Cost Studies of Alternative
Methods for Lime and Limestone Scrubbing Waste
Disposal (TVA)
In this study the TVA Office of Agricultural and Chemical
Development, Muscle Shoals, Alabama, is conducting a detailed economic
evaluation of several FGC waste treatment and disposal methods.
In addition to the economics of disposal of an untreated waste,
the Chemfix, Dravo, and IUCS chemical treatment processes are being
examined. These studies are expected to augment those in Reference 5 by
providing more detail costs including the effects of major system variables
and options and the sensitivity to operating conditions for lime and limestone-
based scrubber wastes. Disposal site characteristics, i.e., location,
ponding (with and without liners), and landfill will also be included.
Flowsheets, material balances, equipment and material lists,
layouts and equipment costs, as well as capital investment and revenue
requirements for the 108 cases of four major disposal alternatives, will be
included in a detailed interim report that is expected early in the second
quarter of calendar year 1977.
Currently, the capital costs for all the processes and options
have been defined. The annual operating and lifetime costs will be completed
early in 1977.
A Phase II to this study has been defined, which will evaluate
the economics of (1) forced oxidation of sulfite wastes to gypsum and (2) the
blending of dry fly ash with sludge. This study along with the final report
covering both phases is scheduled for completion in the fall of 1977.
5. 3. 2 Gypsum By-Product Marketing Studies (TVA)
This project is a task to identify the technology, economics,
and market potential for by-product gypsum-producing FGD alternatives. It
is being conducted by TVA, Office of Agricultural and Chemical Development,
Muscle Shoals, Alabama, through an interagency agreement with EPA.
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The current study evolved from a preliminary gypsum study
conducted for EPA by TVA during early 1974 (Ref. 21), followed by a series
of detailed market studies on by-product sulfuric acid and elemental sulfur in
the United States (Ref. 22). The gypsum study indicated that production and
sale of abatement (by-product) gypsum to the wallboard industry in the
United States might offer economic advantages over other waste-producing
alternatives.
Included within the current study, are the design and
economics for the Chiyoda, Dowa, and Kureha commercial gypsum processes.
In addition, a limestone slurry scrubbing process utilizing subsequent oxida-
tion to gypsum is evaluated. Flow diagrams, material balances, and invest-
ment and revenue requirement projections corresponding to a 1978 startup
are included for each of these processes.
The study includes a survey of the gypsum industry, quality
standards for gypsum, and market statistics. In addition, a comprehensive
assessment will be made for marketing the SO? abatement gypsum for -wall-
board and cement manufacturing applications in the United States. The most
likely candidate power plants will be defined, and expected transportation
costs and possible net sales revenue will be projected for the selected plants
on the basis of 1978 total demand estimates as well as prorating on the basis
of various market applications.
Completion of the study is estimated by the end of the first
quarter of the calendar year 1977 at which time a draft report will be avail-
available.
5.4 ALTERNATIVE FCC WASTE DISPOSAL METHODS
The intent of work in this area is to assess the potential and
the environmental impacts associated with disposal of FGC wastes in mines
and in shallow and deep ocean sites.
5. 4. 1 Evaluation of Alternative FGC Waste Disposal Sites
(A. D. Little)
An evaluation of mines and the ocean as FGC waste disposal
alternative sites to ponding and landfilling are being evaluated in this pro-
gram being conducted by A. D. Little, Inc. , Cambridge, Massachusetts.
Phase I, which included an initial assessment of the technical, environ-
mental, regulatory potential and economic aspects of the disposal of
untreated and chemically treated FGC wastes in deep and surface mines and
in the ocean, has been completed. The state of the art on technology related
to disposal operations on detection, monitoring, and control was reviewed as
well as the possible benefits resulting from FGC sludge disposal operations,
e. g. , mine subsidence control and use as a tailings amendment.
Federal regulations applicable to such disposal have been
identified and assessed as to their adequacy in protecting the environment.
An assessment of state regulations was made for Pennsylvania inasmuch as
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it is confronted with the potential of disposing of large quantities of waste,
and its mining regulations were considered as representative of those of
other states. Based on technical feasibility within regulatory constraints, a
number of approaches for implementing ocean or mine disposal systems
were identified.
Phase I focused on environmental effects and operational
safety as the primary considerations; in Phase II, an assessment will be
made of the costs of promising disposal systems including conceptual
designs. In Phase II, recommendations will also include plans for subscale
pilot demonstrations of such a size that design data for full-scale operations
can be obtained.
Phase I was completed in September 1976. Phase II is cur-
rently under way and will continue through March 1977. A Phase I report is
currently in publication (Ref. 23)".
5.4.1.1 Phase I Results
Assessment of the impacts of the waste disposal in mines
and the ocean was conducted. Table 65 presents a general outline of the
various tasks. Significant project tasks were to evaluate the applicability for
mine and ocean disposal and to collect existing data on the physical and
chemical properties of both untreated and treated FGC waste by location,
process type, and potential quantity produced. Sources were primarily from
the U. S. Army WES and The Aerospace Corporation work. It was found that
certain data on the properties of FGC wastes which were essential to dis-
posal in the marine and mine environment had not been determined, and a
limited experimental program to obtain these data was defined.
5.4.1.1.1 Mine Disposal
The impact assessment with regard to overall technical
feasibility was based upon a broad grouping of mines according to the
mineral mined, mine capacity, and method of mining, together with ranges
of sludge characteristics appropriate for each region of the country. While
this assessment yielded general conclusions regarding overall viability of
disposal options, any proposed disposal operation must be evaluated on a
case-by-case basis, considering the site-specific conditions and the charac-
teristics of the sludge. The type of mines considered on the basis of geo-
graphic regions were as follows:
a. Surface area coal mines
b. Underground coal mines
1. Room and pillar mines
2. Longwall mines
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TABLE 65. STUDY OUTLINE
Sludge Characterization
Chemical Properties of Untreated Sludge
Physical and Engineering Properties of Untreated Sludge
Effects of Treatment on Sludge Properties
Mine Disposal
Screening of Alternatives
Regulatory Environment
Environmental Assessment
Technology Assessment
Disposal Criteria
Ocean Disposal
Environmental Assessment
Technology Assessment
Disposal Criteria
Economics of Conceptual Disposal Systems
Coal Mine Disposal
Ocean Disposal
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c. Underground mineral mines
1. Lead-zinc mines
2. Limestone mines
Salt mines were not specifically addressed within the scope of
the FGC waste disposal study because these mines have been assigned to a
higher priority use.
Active, Interior region surface, strip coal mines, active
Interior and Eastern room and pillar underground coal mines were deter-
mined to be the most promising types for disposal of untreated and treated
FGD sludges, for a number of reasons, including their accessibility and
availability of space for disposal of the sludge. Such factors as location,
mining methods, disposal transport and placement methods, and mine
capacity were evaluated in light of geology, water resources, water quality,
and biota. Underground limestone and lead-zinc mines were also considered
technically suitable, but capacity and location were factors that tended to
reduce their attractiveness. Numerous weighting factors were applied, and
for these the reader is referred to in Reference 23.
Following are some general considerations relative to coal
mine disposal and sludge treatment. Disposal of untreated FGD wastes in
surface mines may be acceptable. In some cases, impacts may be reduced
by placement of overburden in the mined out area prior to waste placement
and if sufficient dilution occurs to the leachate prior to entering, or in
mixing with the receiving waters.
Although highly promising, use of underground room and
pillar mines for sludge disposal must be decided according to site-specific
hydrogeology. Because the mine environment is rock and nonalkaline,
attenuation of soluble chemical species is not expected.
In general, data on the effects of sludge treatment on the
concentrations of contaminants, particularly trace elements, in leachate are
not very definitive. However, certain types of sludge treatment solidify the
sludge into a matrix of low permeability. Leachate impacts may be mini-
mized to an insignificant level if an appropriate chemical treatment were
employed, simply as a result of reduced permeability.
The use of untreated FGD sludge mixed with mine tailings as
an amendment for plant growth was judged to be of minimum benefit. It was
determined to be considerably less promising than either limestone or
sewage sludge, which are now used. In underground mines, FGD sludge
placement would result in the potential of lessening acid drainage formation
and long-term subsidence, primarily by sealing exposed coal against air
exposure, which leads to pyritic sulfur oxidation and also leads to pillar
deterioration.
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Recent regulatory attitudes indicate a growing concern for
groundwater protection from seepage or leachate from the disposal of
•wastes. Given the recent Resource Conservation and Recovery Act (RCRA)
of 1976, coverage by existing legislation is considered adequate in coverage
to encompass all aspects of FGD waste disposal. However, because of the
technical difficulties of completely characterizing an underground environ-
ment and of locating monitoring wells, it was concluded that regulation must
rely on guidelines for site selection and waste acceptance and must allow for
case-by-case assessment by professional geologists and geochemists.
Specific conclusions relative to regulatory considerations
were reported as follows:
a. The lead authorities for FGD sludge disposal appear to be
the federal and state environmental protection agencies.
b. The lead legislation is expected to be the RCRA of 1976.
The new RCRA provides for comprehensive regulatory
authority in the area of solid and hazardous waste manage-
ment at the federal level and an institutional framework
for planning and regulatory implementation at the state
level. The RCRA is expected to be the lead legislation to
regulate FGD sludge disposal. In the area of water, both
the Federal Water Pollution Control Act (FWPCA) and the
Safe Drinking Water Act provide authority to regulate under-
ground discharges. Existing laws and regulations appear
to adequately cover transportation of desulfurization wastes
as transportation of similar materials by modes of transport
under consideration is a frequent and familiar practice of
commerce.
c. The combination of federal and state legislation is legally
adequate to protect the environment during and after FGD
sludge disposal; however, regulations are needed with site
selection and waste acceptance guidelines based upon the
characteristics of FGD sludge and research on potential
environmental impacts.
d. Additional legislation and standards may be required to
protect worker health and safety. Administration of the
health and safety requirements needs clarification,
especially between authorities of the Office of Safety and
Health Administration (OSHA) and MESA.
e. Because of the nonpoint source nature of air and water
emissions from FGD sludge disposal and the large varia-
tions in FGD sludge character, disposal must be regulated
on a case-by-case basis.
At the state level, there are laws and regulations which either
enhance the federal laws and regulations or fill gaps in the regulations.
Laws governing mining activities (i. e. , reclamation, sealing, subsidence
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control, and acid mine drainage) and permit regulations for wastewater
effluent, mine drainage, and solid waste disposal sites are covered at the
state level.
In assessing state regulations, Pennsylvania was selected as
a model state. Pennsylvania is an industrialized state with extensive mining
operations and a number of utilities planning or operating FGD systems. The
Department of Environmental Resources (DER) currently has lead responsi-
bility for regulating sludge disposal in mines. The regulating statutes do not
specifically address FGD disposal in mines; however, collectively, the
statutes can be interpreted as providing coverage for all aspects of sludge
disposal.
The DER is considering regulatory amendments to existing
statutes in order to ensure orderly and environmentally sound disposal of
FGD sludge. Some factors regarding mine disposal may be clarified by a
pilot field program recently undertaken by DER under an EPA grant to
evaluate sludge disposal in underground mines.
Recommendations for additional research or information
related to FGD sludge disposal in mines included the following:
a. Additional and more detailed leachate and elutriate data
for both treated and untreated sludges including TOS
levels in both aerobic and anaerobic environments.
b. Development of more definitive data on engineering
properties of untreated sludges and comparison of results
with field data. Specifically, Atterberg Limits Test
(liquid and plastic), consolidation tests, and triaxial com-
pression tests for a representative range of sludges are
needed to determine the ultimate fate (e. g. , stability,
flow potential, and load capacity) of sludge in various
underground and surface mine disposal scenarios.
c. Effects of climate such as freeze-thaw and rewetting of
sludge on its physical and handling properties and on
pollutant mobility.
d. Potential for corrosion of bulkheads (concrete and steel)
by sludge.
e. Potential for SC>2 evolution in disposing of sludge in
underground mines containing acidic waters.
f. Laboratory or field tests of hydraulic and pneumatic
stowing of various sludges to determine handling prop-
erties and define appropriate mine disposal methods.
g. Survey of dust, noise, airborne contaminant, and other
health and safety criteria which disposal must meet and
an evaluation of the levels of dust created during sludge
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handling and placement, particularly during intermediate
storage and in pneumatic and hydraulic stowing in under-
ground mines.
h. Clarification of roles of OSHA and MESA and other health
and safety authorities.
i. Field survey of various mines (coal, limestone, salt, and
lead-zinc) to characterize the alkalinity and acidity of
drainage, the extent of pillar robbing, the pathways and
rate of groundwater flow, and the potential for long-term
subsidence.
5.4.1.1.2 Ocean Disposal
Both deep ocean and Continental Shelf disposal alternatives
were evaluated and included sludge of three different consistencies, i.e. ,
dewatered (untreated), slurry (dispersed), and brick-like (treated).
Numerous environmental and technical factors were considered in the evalua-
tion and are listed in Table 66. Considering these alternatives, two promis-
ing options •were selected for developing conceptual system designs and
associated capital and operating costs, viz., the disposal of untreated FGD
sludge in the deep ocean and treated rock-like sludge on the Continental Shelf.
Several general conclusions emerged from the study. First,
the need exists for case-by-case analysis of the environmental feasibility of
ocean disposal of specific FGD sludges with emphasis being focused on the
type of sludge and disposal, site environmental conditions. Secondly, all con-
trol and monitoring options evaluated appear to be technically feasible.
Economic feasibility was considered less definitive and could serve to limit
the viability of several of the most promising environmental options.
Specific conclusions included the following:
a. The disposal of untreated or treated, soil-like FGD sludges
by bottom dump barge or outfall on the Continental Shelf is
considered environmentally unacceptable.
b. According to available information on sulfite toxicity,
sulfites require an immediate dilution factor greater than
10,000:1 in the dispersed disposal of untreated sulfite-
rich sludges. Technology is not currently available for
attaining such dilution factors for sulfite-rich sludges in
an economical manner. Therefore, the dispersed disposal
of untreated sulfite-rich sludges both on and off the
Continental Shelf was currently not considered to be a
promising option. Further information on organism uptake
and toxicity of TOS may result in a reevaluation of this
conclusion.
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TABLE 66. FACTORS CONSIDERED IN OCEAN
DISPOSAL EVALUATION
Environmental Assessment
Regulatory Environment
Fate and Effects of Ocean Disposal
Physical Transport
Environmental Impact Potential
Benthic Sedimentation
Sludge Suspended in the Water Column
Sulfite-Rich Sludge
Trace Contaminants
Environmental Impact of Applicable Control Option
Restrictions on Sludge Composition
Disposal by Dispersion
Concentrated Bottom Disposal
Chemical Treatment
Deep Ocean Dumping
Technology Assessment
Transportation
Navigation and Surveillance
Monitoring
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With the exception of concentrated disposal of brick-like
treated material, chemical treatment appears to offer few, if any, advan-
tages over the traditional bottom dump of untreated FGD sludge. The sulfite
impacts may be mitigated by chemical treatment, but effects of benthic sedi-
mentation and suspended sludge in the water column would be comparable
to those of untreated material.
Disposal options that appear promising and were recom-
mended for further research are as follows:
a. Dispersed disposal of untreated sulfate-rich FGD sludges
on the Continental Shelf
b. Concentrated disposal of treated, brick-like FGD sludge
on the Continental Shelf
c. Dispersed disposal of untreated sulfate-rich FGD sludges
in the deep ocean
d. Concentrated disposal of both untreated sulfate-rich FGD
sludge and treated FGD sludges in the deep ocean
In considering regulatory factors coupled with the vigilance
in agency attitudes towards ocean dumping, the existing regulations were
reported as adequate in ensuring protection of the ocean environment. How-
ever, several specific recommendations were made:
a. Pending revisions should be adopted to the existing ocean
dumping regulations that would allow for additional
empirical considerations in the determination of limiting
permissible concentrations.
b. Existing absolute limits on permissible concentrations
of mercury and cadmium in solid fractions of wastes
should be reevaluated through consideration of the actual
anticipated long-term availability of the contaminants
on a case-by-case basis.
c. Inherent disincentives to deep ocean dumping, e. g. , extra
monitoring requirements should be reevaluated in light of
the apparent desirability of certain deep ocean disposal
options.
No additional sludge-related legislation concerning ocean disposal was con-
sidered necessary for the present.
The following research needs were identified as being most
important at this time:
a. Development of a body of empirical data concerning dis-
solution rates of various types of treated and untreated
FGD sludges in the representative types of seawater that
would characterize the disposal area environs.
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b. Empirical determination of the uptake of both liquid and
solid constituents of FGD sludges by various marine
organisms. In particular, values for uptake associated
with short-term exposure of pelagic organisms require
investigation.
c. Determination of lethal and sublethal effects thresholds,
a variety of representative marine organisms upon
exposure to FGD sludges. One of the focal points of such
research should be the dynamics of food web transfer of
potential toxicants.
5.4.1.1.3 Economics of Conceptual Disposal System Designs
Basis
Conceptual system designs and general capital and operating
costs were provided for five ocean disposal and six mine disposal options.
As a basis, a 500-MW power plant burning typical Eastern coal (3. 0 per-
cent S, 10. 0 percent ash, and 0. 85 Ib of coal/kWh) was assumed producing
365,000 tons per year of dry sludge (including ash). The sludge (with ash)
was considered to be available either as a dry filter cake (50 percent solids),
a 35 percent solids slurry (thickener underflow), or as treated sludge. No
estimates were included for sludge processing such as filtration, drying, fly
ash addition, or treatment. However, in cases where treated sludge required
handling, estimates for excavation of treated sludge from stabilization ponds
were included. Capital costs were based on 1978 completion of construction
and included installed equipment cost for the battery limits disposal system
(transfer, handling, and placement) engineering and contractors' fees, work-
ing capital, owners' expense, startup, and interest and escalation during con-
struction. Capital investment and operating costs did not include sludge
processing equipment, site preparation, land cost, auxiliary utilities, or
fees for permits. Operating costs include capital charges at 1 7 percent of
total installed cost.
Coal Mine Disposal
Conceptual systems and costs included the disposal of both
filter cake (admixed with ash) and treated sludge in onsite and offsite surface
area coal mines and the disposal of slurried, untreated sludge (with ash) in
onsite underground coal mines. For onsite mines, either truck transport of
filter cake and treated sludge or pipeline transport of thickener underflow
were used in transport of the sludge. For offsite mines, rail haul of either
treated sludge or filter cake was assumed. Preliminary estimates indicated
truck haul and slurry pipeline to be impractical for long-distance sludge
transport.
For untreated sludge, disposal costs including transfer and
intermediate storage ranged from $3.00 to $3. 50 per dry ton for onsite dis-
posal to $6. 50 to $8. 00 per ton for offsite disposal. Disposal of treated
sludge in surface area mines increased costs approximately $2. 00 to $2. 50
per ton to account for excavation of stabilization ponds. The estimates did
212
-------
not include site monitoring costs, which are a strong function of the
hydrology, sludge characteristics, and parameters (species) to be measured.
For determination of overall disposal system costs, sludge treatment costs,
as appropriate, must also be added to these transfer and placement costs.
Ocean Disposal
Conceptual system designs and costs were developed for five
ocean disposal options, two for dumping on the Continental Shelf (25 nmi)
and three for off the shelf (100 nmi) dumping. Estimates included disposal
of both untreated and treated sludge on the shelf and untreated filter cake or
thickener underflow and treated sludge off the shelf. While disposal of un-
treated sludge on the Continental Shelf was not presently considered promis-
ing because of the potentially adverse environmental impacts, it was included
for comparative purposes.
In preparing the conceptual system designs, it was assumed
that the sludge was produced in an Eastern power plant with ready access
to the ocean; i. e. , facilities for berthing barges •were available with suffi-
cient area for installation of a sludge transfer and storage system. Costs
were developed for operations including tug and barge combinations and self-
propelled ships. In all cases, the system costs utilizing self-propelled ships
were found to be less than for a tug-barge combination because of the lower
capital investment resulting from shorter cycle times for ships, therefore
requiring fewer ships.
Disposal of untreated filter cake (with ash) on the shelf was
estimated as $4. 00 to $5. 00 per dry ton of sludge, with additional costs of
about $2. 00 to $2. 50 per dry ton resulting from excavation of stabilization
ponds for treated sludges. Deep ocean (pff-_shelf) disposal of filter cake or
treated sludge increased costs by $3.00 to $4.00 per dry ton more than shallow
(on-shelf) ocean disposal. Disposal of thickener underflow in the deep ocean
was estimated to cost approximately $1. 00 more per ton than filter cake
disposal. As with mine disposal costs, these estimates did not include
monitoring costs or sludge treatment costs.
5.4.1.2 Phase II Study
The Phase II program encompasses four major areas of
study:
a. Sludge characterization and laboratory test procedures
evaluation
b. Mine impact assessment
c. Ocean impact assessment
d. System design and economics
Based on the results of this program, a Phase III study encompassing a
simulation and testing program will be formulated.
213
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In the Phase II characterization tests, tests to determine
chemical, physical, and mechanical properties are being performed to aug-
ment and confirm existing data unique to the disposal and fate of the sludge
constituents in mine and ocean environments. Laboratory tests (Figure 49)
are being performed at A. D. Little, Inc. , and at the New England Aquarium
(NEA) for ocean disposal to clarify impact issues identified during the
Phase I impact assessment. These data will be used as a basis for selecting
sludges for Phase III simulation and demonstration testing. Concurrently,
sampling, analytical, and test procedures being developed or in use for
determining physical and chemical characteristics of sludges will be evalu-
ated. Their applicability to Phase III testing will be determined, and modi-
fications will be defined as appropriate.
Based on the results of the Phase II tests and the evaluation
of impact issues identified during Phase I, refinements and adjustments will
be made to the Phase I environmental and technical assessments. An update
of the regulatory issues are planned as well as a review of control options
and disposal criteria.
Preliminary engineering designs will be prepared for at
least two mine and ocean disposal options, and the handling, storage, and
physical processing required; all transport and intermodal transfer of the
sludge; and sludge placement and environmental impact control measures
including site monitoring will be considered. Estimates will also be pro-
vided for the capital and operating costs for these disposal designs. As a
part of the cost and design efforts, cost tradeoffs and cost sensitive areas
will be identified.
5.4.1.2.1 Project Status
Samples of eight different types of wastes have been selected
on which will be conducted characterization tests appropriate to the waste
type and disposal method. These include double alkali filter cake, with and
without fly ash (high sulfur coal); centrifuged direct lime scrubber sludge
with ash (low sulfur coal); centrifuged gypsum sludge without ash; and direct
lime-scrubbing filter cake without ash (high and low sulfur coal). The
chemical analyses of these sludges is summarized in Table 67. Recently,
sulfate-rich lime and sulfite-rich limestone wastes have been included.
The material balance accountabilities for all samples ranged
between 93 and 100 percent, on the assumption that the major phases are
CaS03- 1/2 H20, CaS04. 2 H2O, CaCO3, MgCO3, and Na2SC>4. The values
reported for acid insolubles may be somewhat low if some of the iron com-
pounds in the fly ash were leached.
The analytical methods for chemical and physical character-
ization of FGD sludges used by other investigators are being evaluated. The
assessment involves a review in the following areas:
a. Chemical analysis procedures for major and trace
constituents
214
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LABORATORY
TESTING
(ocean)
REFINEMENT
OF IMPACT
ASSESSMENT
SYSTEM
DESIGNS
AND
ECONOMICS
• SLUDGE OXIDATION/DISSOLUTION
• WATER COLUMN PHYSICAL EFFECTS
• BOTTOM DISTRIBUTION POTENTIAL
12
SLUDGE
CHARACTERIZATION
to
I-*
(Jl
CHEMICAL
• SULFITE UIVELS AND CHEMICAL
OXYGEN DEMAND OF SLUDGES
AND LEACHATES
• SOLUBILITY AND OXIDATION
RATES OF CALCIUM SULFITE
IN SEAWATER AND GROUND-
WATER
• LEACHING DATA AND EFFECTS
OF TREATMENT ON POLLUTANT
MOBILITY
• EFFECTS OF ASH CONTENT ON
IN SLUDGE
ENGINEERING AND PHYSICAL
• LIQUID AND PLASTIC LIMITS
INDICES
• CONSOLIDATION TESTS
• TRIAXIAL COMPRESSION TESTS
• EFFECTS OF CRYSTAL STRUCTURE
AND FLY ASH ON SLUDGE
DEWATERING CHARACTERISTICS
• REFINE PHASE I ASSESSMENT
• IMPLEMENT LAB DATA AND
CONTRIBUTE TO PHASE III
PLANNING
• DEFINE ADDITIONAL INFORMATION
REQUIRED
SAME AS MINES
t/i
o 5
2
• APPLICABILITY TO OCEAN AND
MINE DISPOSAL
• DEFINE MODIFICATIONS AS
APPROPRIATE
• VERIFY PROCEDURES FOR
PHASE III USE
PHASE 111
»
RECOMMENDATIONS
FOR SIMULATION AND
DEMONSTRATION TEST
PROGRAM
TOS, LEACHABILITY
AND OXIDATION
CORROSION POTENTIAL
(steel and concrete)
S02 EVOLUTION
POTENTIAL
SLUDGE FREEZE-THAW
EFFECTS
SIGNIFICANCE OF
GEOTECHNICAL
ISSUES
EFFECT OF
HYDROGEOLOGY
ON GROUND WATER
< QUALITY
UPDATE REGULATORY
ASSESSMENTS
FUGITIVE EMISSIONS
AND OTHER HEALTH
EFFECTS
PRELIMINARY ENGINEERING
DESIGNS (total of two options)
CAPITAL AND OPERATING
COST ESTIMATES, TRADEOFFS,
AND COST SENSITIVITY
COMPARE WITH PUBLISHED
LANDFILL AND POND DISPOSAL
ESTIMATES
Figure 49. Phase II study outline
-------
TABLE 67. CHEMICAL ANALYSIS OF FGC SLUDGE SAMPLES
Sludge
Dual alkali, clean
filter cake (CEA-1)
Dual alkali, fly ash- containing
filter cake (CEA-2)
Direct lime, fly ash- containing
centrifuge cake (TVA-1)
Direct lime, clean, filter
cake (TV A- 2)
Direct lime (carbide), filter
cake (LGE-1)
Gypsum (CIC-1)
Wt % Solidsa
(as rec'd)
54
57
63
52
47
83
Analysis (millimoles/g dry solids)
Ca
7. 15
4.45
4. 59
7.22
6.99
6.05
TOSb
5.52
2.66
3.85
5.76
5.89
not
done
so4
0.97
0.87
0.70
1.37
0.52
6.04
Na
0.43
0.22
<0.03
<0.03
<0.02
<0.02
Mg
0.25
0.22
0.045
0.074
0.23
0.012
Cl
0.027
0.031
0.052
0.030
0.008
0.004
Wt % Acid
Insoluble0
0.00
30. 8
35.2
0.83
2.94
0. 30
aWeight percent dry solids in the "as received" wet cakes.
Total oxidizable sulfur (calculated as sulfite).
CInsoluble in 1 molar HC1.
-------
b. Physical and engineering properties methods
c. Chemical analysis of groundwater and seawater
d. Sampling techniques for monitoring groundwater and
seawater
It was also recognized that there are no typical mine condi-
tions and that wide variations exist. Therefore, in this phase, the ranges of
likely mine conditions and the sensitivity of any conditions are defined as
being representative in the Phase I report. Impacts and allowable disposal
amounts will depend on the site specific nature of FGD sludge, its placement
and treatment technique, mine hydrogeology, and mine geology. Therefore,
the hydrogeological and geochemical aspects of mine disposal are being
given major emphasis in the impact assessment. Other effects are outlined
in Figure 49.
In reviewing the corrosion resistance of concrete to sulfate
attack, it was determined that Type V cement should be used because of its
low tricalcium aluminate content. An aggregate low in magnesium is needed
to avoid sodium attack; coating any embedded steel with epoxy would lessen
chloride attack. However, it is not known if sulfites will attack concrete in
a manner similar to sulfates. Also synergistic effects, if any, that may
occur when both sulfates and chlorides are present near concrete are also
unknown. It was reported that the state of knowledge for some FGD sludge
parameters is inadequate to accurately define the impact of sludge on con-
crete and embedded steel. It was noted that any tests using Type V cement
require three months curing time before a concrete specimen can be sub-
jected to exposure testing in sludge liquors. Also, any in-field demonstra-
tion using corrosion-resistant concrete must employ this three-month
curing period. Use of a Type V cement, epoxy-coated rods, and a pure
limestone aggregate with a low water-to-cement ratio may increase
materials cost by about 25 percent.
In addition, other efforts during the first half of Phase II have
been to finalize plans and methods for sludge TOS and dissolution methods
and to incorporate modifications to the Phase I report in accordance with the
recent passage of the RCRA of 1976 and the broadened legislative coverage
of the State of Pennsylvania.
In the ocean assessment task, water column drop tests are
being performed in order to determine sludge cohesiveness and behavior.
The effect of water content in the sludge is being investigated, as well as
the effects of rewetting and resettling. Preliminary results indicate that
lime sludge is more cohesive than double alkali; both types eroded more
easily than dredged river bottom material that was used as a basis of com-
parison. Several other sludges are to be tested, and quantitative data will
then be available.
Laboratory programs of bottom dispersion tests have been
completed, and the results are being analyzed. These tests were directed
toward determining the overall stability of sludges on the ocean floor and,
217
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in particular, the critical velocity for sludge erosion and resuspension. In
general, they tend to be consistent with the cohesive properties observed.
The sludge dissolution and TOS oxidation apparatus was
checked in simulated seawater tests. Both seawater and groundwater tests
will be performed.
Refinement of Phase I impact assessment is under way. At
present, the bases for economic evaluation of promising alternatives have
not been fully defined and are not available for inclusion in this report.
5. 5 NEW FGC WASTE UTILIZATION METHODS
Utilization projects include development of (1) a process for
FGC waste conversion (to sulfur and calcium carbonate), (2) pilot studies
of fertilizer production (using the waste as a filter material and a
source of "sulfur)", and (3) use of FGC waste in an alumina extraction
process.
5. 5. 1 Lime and Limestone Scrubbing Waste Conversion
Pilot Studies (Pullman Kellogg)
A study is planned to evaluate the Kel-S process, which
produces elemental sulfur as an alternative to throwaway disposal of FGD
lime and limestone wastes. The project will be approximately 11 months in
duration. It involves a cost-shared contract with Pullman Kellogg, Houston,
Texas, to conduct pilot-plant scale evaluation of several key steps in the
Kel-S process. The project is expected to be initiated in 1977.
The process converts FGD wastes obtained from lime and
limestone scrubbers to elemental sulfur. It also produces calcium car-
bonate, CaCC^, which can be recycled in the SC>2 scrubbing system. FGD
waste will be reduced, using coal as the reactant, to calcium sulfide, CaS,
in a continuously rotating kiln. The CaS is then reacted with hydrogen
sulfide, H2S, which is available from the recovery unit and forms calcium
hydrosulfide, Ca(HS)2- The Ca(HS)2 is dissolved in water and the solution
is filtered. The cycle is closed by reacting the Ca(HS)2 with CC>2-rich gas
available from the drying kiln. The reaction with CG^ forms ^S and also
CaCO^, which is precipitated. Half of the H2S is returned to react with the
CaS, and the remainder is converted to elemental sulfur in a conventional
Glaus unit. The CaCO^ is recycled to the scrubber system.
It is expected that design and operating data will be obtained
to permit scaleup of the process to a prototype integrated system that can
be operated in conjunction with a power plant FGC system.
5. 5. 2 Fertilizer Production Using Lime and Limestone
Scrubbing Wastes (TVA)
The use of lime and limestone scrubbing wastes as a filler
material and source of sulfur in granular fertilizers is being evaluated.
218
-------
The work is being performed by TVA, Office of Agricultural and Chemical
Development, Muscle Shoals, Alabama, as part of an interagency agree-
ment directed toward the evaluation of the utilization or disposal of FGC
wastes.
Results from previous TVA bench-scale laboratory tests and
small field plot application tests with rye grass were sufficiently promising
to warrant additional work on a pilot-plant production basis. In addition to
the pilot plant evaluation, the technical, economic, and environmental
impacts will be studied as a result of producing and using granular fertilizer
from scrubber wastes. Specific tasks include (1) determining compatibility
factors involved in mixing and storing the fertilizer with conventional fer-
tilizer, (2) conducting of field plot tests with the pilot-plant-produced
fertilizer, and (3) assessing the effects of trace and toxic materials relative
to those in conventional fertilizers. Marketing studies of the scrubber-
waste-based fertilizer are also planned.
The process basically consists of mixing phosphoric acid,
HgPC^, and gaseous ammonia with a typical dewatered sludge produced from
lime-limestone scrubbers. The temperature of the mixture is maintained at
approximately 200°F while phosphoric acid and ammonia are metered in at a
predetermined rate. The sludge, acid, and ammonia mixture is maintained
slightly acidic to prevent solidifying in the preneutralizer. After the desired
amount of acid and base are added, the hot mixture is transferred to an
ammoniator-granulator, where further ammoniation causes the slurry to
solidify and form a granular material. A certain amount of partially dry,
undersized material is recycled to the ammoniator-granulator to facilitate
proper granulation. The granular material discharged from the ammoniator-
granulator is dried, cooled, and screened to obtain a fertilizer product with
desirable nutrient and physical characterization.
The pilot plant production and the storage compatibility tests
are scheduled for completion in 1977. Long-term agronomic testing is
planned to begin in 1977 and extend through 1979.
A flow diagram of a typical pilot plant process is shown in
Figure 50. The pilot plant for this study is rated at 3000 Ib/hr.
During initial pilot plant preneutralizer tests using sludge
produced at the 1-MW limestone pilot unit located at the TVA Colbert Steam
Plant, severe foaming occurred during the introduction of sludge, phosphoric
acid, and ammonia into the preneutralizer. The preneutralizer was then
operated -with only the acid and ammonia in the conventional ammonium phos-
phate mode. The sludge and the ammonium phosphate from the preneutralizer
were then fed to the drum granulator. A number of sludge feed rates were
tried, and those resulting in acceptable granulation rates have been defined.
Construction of a specially designed preneutralizer to elimi-
nate the problems encountered was completed. It includes alternative
methods and locations for adding the sludge, acid, and ammonia. Improved
agitation, foam breaking methods, and insulation were included. One of the
219
-------
PHOSPHORIC ACID
IS)
tsJ
O
GAS
TREATMENT
SYSTEM
EXHAUST
FANS
Figure 50. Process flowsheet for producing solid granular fertilizer
material from scrubber sludge.
-------
objectives in the development of the preneutralizer modifications is the
effective utilization of the heat of reaction in reducing the water content of
the incoming sludge.
Initial testing with the modified preneutralizer resulted in an
unacceptable sulfur loss ranging from 78 to 90 weight percent and an
ammonia loss of 34 to 61 weight percent based on input quantities.
The losses are suspected to result from a reaction between
calcium sulfite in the sludge and phosphoric acid.
Calcium sulfite + phosphoric acid > calcium phosphate +
sulfurous acid
3CaSO3 + 2H3P04 *• Ca3(PC>4)2 + 3H2SC>3 (1)
Sulfurous acid + ammonia »• ammonium sulfite
2NH3 - (NH4)2S03 (2)
Laboratory tests indicated that the reaction defined by Eq. (1)
occurs readily at room temperature. Also, past pilot plant experience has
shown that ammonium sulfite formed as in Eq. (2) can be easily lost as a
very fine particulate in the gas stream. This loss would be enhanced by the
agitation and by the stripping action of the water being boiled off in the
preneutralizer.
It is expected that these unwanted reactions can be prevented
by either neutralizing the phosphoric acid before it comes into contact with
the sludge or by oxidizing the calcium sulfite to calcium sulfate before feed-
ing to the preneutralizer. Therefore, tests are being planned to determine
the feasibility of using oxidized sludge in the preneutralizer.
Additional tests (Table 68) were conducted to define preneu-
tralizer operating conditions. These included the effect on ammonia-to-
phosphoric acid ratios and the location of the sludge feed and its flow rate.
Problems including release of SO2, sparger plugging, and
temperature and fluidity control were encountered under the conditions
tested.
It is planned to conduct tests at a pH of 6. 5, where the fluidity
of the product sludge is expected to be at an acceptable level with the pro-
motion of di-ammonium phosphate rather than mono-ammonium phosphate
221
-------
TABLE 68. PRENEUTRALIZER TEST CONDITIONS
ro
NH3 to
H,PO4 mol
Ratio
0.3
1.5
1.5
1.5
pH
1. 6
6.5
6.5
6. 5
Sludge Feed
Rate, gpm
1.0
1.5-2.0
1.5
1.5
Remarks
SO_ released from system. Gas spargers
plugged with slurry due to low gas feed rate.
Temperature in preneutralizer could not
be maintained at 2 gpm.
Difficulty encountered in controlling fluidity
of product slurry.
Relocated sludge feed from bottom to top
of preneutralizer. Change did not improve
operation.
-------
that is formed at a pH of 1.6. Some preliminary testing at a pH of 6. 5 has
shown that mixing is important, and some SC>2 has been driven off as a
result of regions with low pH.
5. 5. 3 Utilization of Lime and Limestone Scrubbing Waste
in a New Extraction Process (TRW)
TRW has completed a preliminary process design and eco-
nomic evaluation of a method for the utilization of lime and limestone
scrubbing wastes, the wastes being a source of calcium in the extraction of
alumina from low-grade domestic ores such as clays or coal ash (Figure 51).
The other principal feedstocks for the process are soda ash and coal. The
products are alumina for use in aluminum production, elemental sulfur, and
dicalcium silicate, an alternative material for use in producing portland
cement.
Present alumina production in the United States is based
exclusively upon the Bayer process or its variations which utilize bauxitic
ore. Domestic production of bauxite is approximately 10 percent of con-
sumption, with dependence for the remaining supply centered on the
Caribbean area and other sources external to the United States. Domestic
reserves have been estimated (1965) at 45 million (MM) tons or 0. 8 percent
of the total world supply. The annual U.S. demand for aluminum metal is
expected to be at least 21.2 MM tons by the year 2000 or approximately
equivalent to 41. 4 MM tons of bauxite ore. Other sources of aluminum exist
in abundance within the continental United States. However, these are in
the form of low-grade clay deposits or thin or deeply buried bauxite deposits.
With the insufficiency of U.S. domestic bauxite reserves, a study to inves-
tigate alternative mineral sources of aluminum and related processes for its
extraction was conducted.
The process design is based on colocating the conceptual
processing plant with a 1000-MW coal burning power plant in order to
receive more than 1,000,000 tons per year (TPY) of lime or limestone FGC
scrubber wastes. In addition to scrubber wastes, the process will require,
on an annual basis, 12,000 tons of soda ash, 300,000 tons of clay, and
273,000 tons of coal to produce 70,000 tons of alumina, 156,000 tons of
sulfur, and 625, 000 tons of dicalcium silicate. Dicalcium silicate would be
used to feed a cement manufacturing facility producing 860,000 tons of
portland cement per year.
The results of this study indicate that an alumina extraction
process employing calcium sulfate and sulfite sludge, sodium carbonate,
and kaolin clay as reactants could be commercially feasible under present
economic conditions provided that the alumina extraction plant includes a
cement producing facility which utilizes the dicalcium silicate by-product
from the alumina extraction process. Should bauxite prices escalate, the
estimated selling price for alumina as output from an alumina plant not
possessing a cement facility may become competitive. Each of the above
conclusions are based upon a sulfur credit of $10. 00 per ton and a sludge
223
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WET SCRUBBER RESIDUE.
CaS04 OR EQUIVALENT—
to
CO
AIR-
CLAY. AI203 2Si02 • 2H20-
MAKEUP Na2C03-
H2S FED TO SULFUR
RECOVERY UNIT
SULFUR
PRODUCT
REDUCTION AND CALCINATION
Na2C03 +
2SiOn
• 2H20
+ REDUCING COMBUSTION GASES
—— Na20 • AI203 + 2Si02 • (2CaO)
+ 4H2S + COMBUSTION GASES
1000 - 1250°C. 0.5 TO 1.0 HR
RESIDENCE TIME
Si02 • 2CaO
SODIUM CARBONATE, Na
2
LEACHING AND SEPARATION
. SEPARATE Na20 • AI20, FROM
Si02 • 2CaO BY LEACHING THE
ALUMINATE WITH Na2C03
SOLUTION-FILTER AND DRY
THE RESIDUAL Si02 • 2CaO
. PRECIPITATE ALUMINUM HYDROXIDE
FROM THE LEACH BY CARBONATION
WITH C02. FILTER AND DRY
. CALCINE THE ALUMINUM HYDROXIDE
TO ALUMINA
. RECYCLE SODIUM CARBONATE
ALUMINA
PRODUCT
DI CALCIUM
SILICATE
PRODUCT
Figure 51. Proposed extraction process
-------
disposal credit of $5. 00 per wet ton (50 percent solids). One of the
utilization processes considered more viable is illustrated in Figure 52.
The selling price for alumina as estimated for this arrangement is $89 per
ton. This value may be compared with the present market value of $160 per
ton (July 1976) and the estimated selling price of $248 per ton, 10 percent
discounted cash flow (DCF) from an unattached alumina plant.
The required selling price for the alumina produced at 10 DCF
would range from $178 to $309 per ton as a function of sludge removal credit,
exclusive of cement manufacture. However, if this alumina plant were
colocated with a 860, 000 TPY portland cement plant selling cement at $40 per
ton, the alumina produced would have a selling price range of $19 to $165 per
ton at 10 percent DCF, depending on sludge removal credit. The alumina
selling price is dependent upon the values of several parameters. Chief
among these are the amount of water in the scrubber sludge, the sludge
credit taken in the accounting, the price of coal to the process, the selling
price of sulfur, and the plant capital and operating costs.
The chemistry of the process is similar to the lime-soda-
sinter reaction except that the reaction proceeds in a reducing rather than an
oxidizing atmosphere. The reaction may be summarized as follows:
Sludge + soda + clay —*- soluble sodium aluminate
+ insoluble dicalcium silicate
or
4CaSO. + Na,CO, + A1..O, = 2SiO_ - 2H,O + reducing combustion
4 2 J £ J d L*
gases ^Na2O-Al203 + 2SiC>2'(2CaO) + 4H2S
+ combustion gases (3)
It has been assumed that this reaction will occur at 1200°C
with coal and a less than stoichiometric amount of oxygen. However, the
chemical functioning of this process is predicated upon several technical
assumptions which require laboratory verification before concluding that the
potential for an extraction process exists. TRW laboratory recommends
bench-scale investigations to confirm the following:
a. Reactions of soda, alumina, calcium, and silica to form
dicalcium silicate and sodium aluminate will proceed in a
reducing atmosphere to achieve high yields.
b. Reaction rates are sufficiently fast to be practical.
225
-------
LIMESTONE
QUARRY
LIMESTONE
375
LIMESTONE
COAL
228
CEMENT
PLANT
J858
COAL MINE
652
POWER PLANT
(1000MW)
COAL
3,325
COAL
250
DICALCIUM SILICATE
SLUDGE
1,365
CLAY
317
ALUMINA
PLANT
PORTLAND
CEMENT
70 I J156
ALUMINA SULFUR
CLAY
STORAGE
SODA ASH
12
LIME
Figure 52. Total utilization concept (quantities in 10 tons/yr)
226
-------
c. Side reactions do not occur which inhibit the formation
of soluble sodium aluminate and thus negate the output of
alumina.
d. Coal in the proper amounts can be used to produce a
reducing atmosphere.
e. The dicalcium silicate by-product possesses the necessary
mechanical properties for compatibility with standard
cement manufacturing.
Other elements of the process not dependent upon the refer-
enced assumptions have been demonstrated in earlier work by the Bureau of
Mines (Refs. 24 and 25) and TRW Systems, Inc. (Ref. 26). Given the
laboratory demonstration of the validity of the process chemistry
assumptions, TRW considers sufficient technical justification exists to
proceed with a development program. No unusual equipment has been iden-
tified, and plant construction can be accomplished with standard items.
TRW has also recommended that an alternative processing
method be considered for study where the principal product is cement. It
would use sand and lime or limestone scrubber sludge as primary feed-
stocks. It would require less capital than the alumina extraction process,
and such a process would be less energy intensive.
5.6 IMPROVEMENT OF OVERALL POWER
PLANT WASTE USE
The program to improve power plant water use effort com-
prises a study of methods to minimize water losses and to recycle or reuse
waste water discharges.
5. 6. 1 Water Recycle and Reuse Alternatives in Coal-
Fired Steam-Electric Power Plants (Radian)
A technical and economic study is being conducted by Radian,
Inc. , Austin, Texas, to assess the options for the recycle or reuse and
treatment of water from coal-fired utility power plants. The primary objec-
tive is to define ways to minimize water consumption and the discharges
of waste water.
Three plants were selected initially for water system charac-
terization and detailed analysis (Ref. 1). Since the last annual report,
two additional power plants have been added to the study. The analyses
include an evaluation of the technical and economic feasibility of various
water recycle and reuse options. The plants were chosen to represent
regions in the United States where water recycle or reuse would be advan-
tageous because of high water costs, limited availability, or treatment and
disposal problems. Other screening criteria included location, availability,
site characteristics, and timing.
227
-------
The first three sites selected were the Four Corners plant of
Arizona Public Service, Comanche of Public Service of Colorado, and Bowen
of Georgia Power Company. The study has been completed for these loca-
tions. During the past year, similar studies were initiated for the Colstrip
plant of Montana Power Company and Montour of Pennsylvania Power and
Light Company. Water and ash samples from these sites have been taken
and are in the process of being analyzed. Analyses were completed for
the first three locations and used in the evaluation. Precipitation kinetic
experiments for CaCo3 and Mg(OH)2 were conducted to define their critical
scaling limits. Characterization of the ash was performed to determine
CC>2 mass transfer between the atmosphere, process vessels, and ash
ponds. Using this input data, a computer model was prepared to simulate
the existing plant operations. With the model, predictions of plant oper-
ations were made for the first three sites. After comparisons with actual
plant operations were made to verify the validity of the models, they •were
used in the technical assessment of various water recycle and reuse
alternatives.
The technical assessment included the evaluation of various
water recycle and reuse options and strategies for each of the represen-
tative plants on the basis of design or design installation, operability, and
treatment effectiveness. The sensitivity to various parameters was deter-
mined and reported. Cost estimates including capital, installation, and
operating costs of the most attractive viable options as defined by the tech-
nical assessment were made, and the overall optimum recycle or reuse
option based on technical and economic considerations for each of the three
plants was defined. The results of the study including recommendations for
each plant, further assessments, testing, or field demonstrations will be
included in the final report, which will be published upon completion of
the analyses for the Colstrip and Montour plants.
The characterization of the existing operations and the pro-
posed recycle and reuse alternatives are summarized in this section.
Details are reported in References 27 through 29. The basic characteris-
tics of each plant are summarized in Table 69.
5.6.1.1 Four Corners Station
The Arizona Public Service Company (APS) Four Corners
station is a five-unit 2150-MW coal-fired electric generating plant located
near Farmington, New Mexico. The coal burned at Four Corners contains
approximately 20 percent ash and 0. 5 to 1.0 percent sulfur and has a heating
value of about 9300 Btu/lb. The plant uses a cooling pond and a bottom
ash wet sluicing for all units, particulate wet scrubbing for Units 1 through 3,
and ESP for Units 4 and 5 (dry ash disposal). Makeup water for the plant is
taken from the San Juan River and stored in Morgan Lake, which serves
as the source for all water used in the system. A periodic blowdown is
taken from Morgan Lake to control the TDS concentration. This blowdown
is discharged to the Chaco River which flows into the San Juan River.
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Table 69. BASIC CHARACTERISTICS OF POWER PLANTS
Utility
Arizona Public
Service
Public Service of
Colorado
Georgia Power Co.
Station
Four Corners
Comanche
Bowen
Location
Farming ton,
New Mexico
Pueblo,
Colorado
Taylor sville,
Georgia
Capacity, MW
1600
350
1595f
Type of
Coolingb
CP
WCT
WCT
Ash
Handling0
WSB
WSF
WSB
WSB
WSF
Particle
Control
Cyclones,
ESP,
venturi
ESP
ESP
so2
Control6
UC
None
None
Reference 20.
Wet cooling tower (WCT); cooling pond (CP).
°Wet sluicing of bottom ash (WSB); wet sluicing of fly ash (WSF).
Electrostatic precipitator (ESP).
Under construction (UC).
Plant capacity as reported in Federal Power Commission (FPC) Form 67 data sheet;
present capacity is 3200 MW (4 units).
-CO,
to
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Cooling water, bottom ash sluicing water, boiler makeup water, and makeup
water for the particulate scrubbing system are taken from Morgan Lake.
In addition to the blowdown stream from Morgan Lake, water leaves the
plant through evaporation from the lake, evaporation from the ash pond,
evaporation in the scrubbers, and ash pond overflow. Some vaporization
also occurs in bottom ash sluicing operations as a result of the high ash
temperature.
Based on computer model simulations, potential scaling
conditions were found at several points in the scrubbing system for low
(2 percent) solids operation. The model had been previously found to ade-
quately represent the existing plant operations when its output was compared
to the chemical analyses of water samples. The scrubber effluent,
thickener overflow, and thickener underflow all were identified as showing
CaSO4-2H2O relative saturations above 1. 3, indicating a tendency to form
gypsum scale. No calcium carbonate scaling was noted. A simulation of
high (9 percent) solids operation showed increased scaling potential in the
system.
Four alternatives were studied for the particulate scrubbing
system:
a. Use existing tanks as solid-liquid reaction vessels
b. Substantially increase tank volume
c. Recycle ash pond overflow
d. Reduce flue gas fly ash content into scrubbers
The study focused primarily on the particulate wet scrubbing
system and subsequent ash disposal for Units 1 through 3. Water is recycled
in the cooling and bottom ash sluicing systems, and the potential for water
recycle-reuse alternatives in these systems was considered slight. Also,
since scaling problems have been encountered in the scrubbing system,
the study of recycle and reuse alternatives at Four Corners addressed the
causes and potential solutions of these problems.
Based on the results of simulating the first alternative, it was
reported that the present system tankage capacity is not sufficient to allow
ample gypsum precipitation to prevent scaling.
3 In the second alternative, increasing the tank capacity to
37,500 m (1. 33 x 10° ft3) was simulated. Gypsum relative saturations were
reduced to levels below the critical level required for the onset of scaling.
Two cases were studied with different scrubber liquid-to-gas ratios (L/G).
The existing L/G of 4. 7 i/mri3 (18. 7 gal/1000 acf) gave a scrubber bottom's
pH of 2. 9 and an L/G of 10. 0 jE/nm3 (39. 8 gal/1000 acf) gave a pH of 3. 9
(assuming 50 percent SO2 removal), indicating that higher L/G's are desir-
able for corrosion control.
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Simulating the third alternative, recycling the ash pond
overflow to the scrubbing system, it was found that the pond overflow has
no significant effect on the gypsum relative saturations in the system. How-
ever, the water makeup requirements are reduced from 70.7 £/sec (1122 gpm)
for alternative two to about 50. 8 i/sec (807 gpm). Also, a simulation with
ash pond overflow recycle using a reaction tank volume of 21,200 m3
(7. 5 x 10^ ft3) showed that a more reasonable reaction tank volume can be
utilized. This simulation showed a gypsum relative saturation of 1. 19 in the
scrubber effluent slurry.
The fourth alternative indicated that reaction tank volume
could be decreased further if portions of the fly ash were removed by dry
methods prior to the scrubbing system. A volume of 8900 m3 (3. 14 x 10^ ft3)
was used to obtain a gypsum relative saturation of 1. 19 in the scrubber
effluent (60 percent of fly ash removed prior to scrubber). Water makeup
requirements were also reduced to 41. 0 £/sec (650 gpm).
The resulting rough-cost estimates of the technically feasible
options, alternatives (a) through (c), indicated that two to three million
dollars would be required to upgrade the particulate scrubbing system so that
scaling potential is eliminated and water requirements reduced. Installed
costs for the least expensive alternatives was case two of alternative (c)
(recycle ash pond overflow, reduced reaction tank volume), which were
$2. 491 X 106. This was followed closely by option (c), $2. 546 X 10&. Alter-
native (b), cases one and two, and alternative (c), case one, showed similar
installed costs of $2. 708 to 3. 313 X 10°. Energy consumption was not
greatly different between alternatives although alternative (c), case one
(increased tank volume, low L/G), indicated a lower energy requirement of
about 2370 kWh/hr less than the other alternatives.
5.6.1.2 Comanche Plant
The Public Service of Colorado Comanche generating station
is a coal-fired system composed of two units, each having a 350-MW capac-
ity, and is located near Pueblo, Colorado. The basic water flow schematics
are the same for both units. The cooling system uses wet cooling towers
to discharge heat. The ash removal system consists of wet sluicing for
bottom ash and ESP and subsequent dry disposal for the fly ash. The bottom
ash slurry is sent to ash ponds for disposal.
Under existing operations, the water entering the system
is first taken from the Arkansas River and stored in a raw water
reservoir. From the reservoir, a small portion of the raw water
(about 7 2/sec or 105 gpm) is sent to the coal handling facilities for dust
suppression. Another portion of the flow from the reservoir is sent to the
ash removal system to sluice bottom ash into the ash ponds. The remainder
of the raw water leaving the reservoir is sent to the Comanche lime
treatment facility to reduce the calcium hardness. The lime sludge pro-
duced during the softening process is sent to a special ash pond, which is
kept separate from the ponds receiving bottom ash slurries. The softened
water is used for service water and for makeup water for the two cooling
systems.
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The water effluent leaves the system via the overflow from
the final polishing pond, which is fed by the two boiler blowdown streams,
the lime sludge disposal pond overflow, and the two bottom ash disposal pond
overflows. The final polishing pond effluent is sent to the St. Charles River.
The remaining system water losses are cooling tower evaporation and drift
and other evaporative losses.
5.6.1.2.1 Cooling System
The station has two cooling systems, one for each unit. The
systems are identical and employ wet cooling towers for evaporative cooling.
The circulating cooling water characteristics are controlled
by the makeup water composition and by the amount of chemical additives
introduced into the system. Sulfuric acid is added for pH control, and zinc
polyphosphate is added to inhibit scaling.
The blowdown stream is maintained at a rate sufficient to keep
dissolved species from concentrating to the point of saturation. Otherwise,
scaling of the line and equipment could result. Present operation of the
Comanche cooling system maintains the blowdown rate so that the makeup
water is concentrated about five times, i. e. , the number of times that dis-
solved species in the makeup water are concentrated in the circulating
water.
5. 6.1. 2. Z Ash Disposal System
The ash disposal system consists of two ash ponds of about
5060 m2 (54, 500 ft^) each. Only bottom ash is being sluiced into the ponds
at present. The fly ash is trucked away in a dry form.
The bottom ash stream sluiced to the ash ponds contains
about one weight percent solids. The sluicing is intermittent; bottom ash
is removed from the ash hopper about six hours per day. The sluice water
comes from two sources, blowdown from the cooling system and untreated
water from the plant raw water reservoir.
Part of the cooling system blowdown stream is diverted for
use as boiler refractory cooling water. This water subsequently flows down
into the bottom ash hoppers where an overflow stream is sent to the ash
ponds. But when bottom ash is being removed, the refractory cooling water
goes out in the bottom ash sluice stream.
The bottom ash sluice stream flow rate to the ash pond is
about 210 cm/sec (7 ft/sec). The sluice lines for the two boiler units are
760 and 590 m (2500 and 1930 ft) long, giving line retention times of about
5.9 and 4. 6 minutes, respectively.
5.6.1.2.3 Technical Alternatives
The water recycle-reuse alternatives for the Comanche plant
are summarized as follows. For purposes of the simulation, the water
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streams were divided into two systems, the cooling system and the ash
handling system. The operating characteristics of the cooling system were
examined first. Then the ash handling system was analyzed in the context
of the possible range of cooling system blowdown streams available for
sluicing. This resulted in evaluating water recycle and reuse alternatives
on the basis of the Comanche water system.
All of the alternative cooling system simulations were per-
formed for summer operation of the cooling towers because summer condi-
tions represent the case of maximum blowdown rates.
The calculated CaCC>3 and CaSC>4 • ZHz® relative saturations
in the recirculating cooling water (8.2 x 10~4 and 0.252, respectively) indi-
cate that the cycles of concentration may be significantly increased without
forming calcium carbonate or gypsum scale. However, a high level of the
silica concentration exists in the makeup water and may require some form
of silica removal, such as lime and soda ash treatment, in order to prevent
silica scaling at higher cycles of concentration. Pilot or bench scale
studies to more accurately quantify silica scaling potentials should be
performed before increasing the cycles of concentration in the cooling
system.
In evaluating cooling system alternatives, simulations were
conducted to determine the effects of operating at increased cycles of
concentration in the towers. Results of simulating cooling tower operations
at 5.0, 7.6 and 15.0 cycles of concentration were obtained. Also, system
sensitivity to composition changes in the makeup water were investigated
by assuming twice the sulfate concentration in the makeup water as that
found in the water sample from the plant for 5. 0, 7. 6, and 13.0 cycles of
concentration.
Three alternatives were examined for ash sluicing. The first
case involved the use of a cooling system blowdown from the towers oper-
ating at five cycles of concentration to sluice fly ash and bottom ash on a
once-through basis. Additional cases were run with this configuration to
determine the effects of CO2 mass transfer in the ash pond and the sluice
tank. No gypsum scale potential was identified in any of the once-through
sluicing cases, but potential scaling of CaCOs and Mg(OH)2 was found to
be present.
However, the possibility was reported that the fly ash slurry
line can be kept free of plugging by the addition of a fly ash slurry reaction
tank and by frequent flushing with water of pH 6 to 7. Pilot or bench- scale
studies are needed in order to size the reaction tank and determine the
quantity of wash water required before implementing fly ash sluicing. This
alternative will result in an ash pond overflow of about 32. 7 t/ sec (518 gpm)
for each unit as compared to the existing configuration pond overflow rate
of about 78 £/sec (1233 gpm). The other two alternatives included the re-
circulation of ash pond liquor and sluicing of bottom ash and dry fly ash
disposal. Fly ash sluicing is included as well as the existing bottom ash
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sluicing for the first two alternatives. For fly ash sluicing, the effects of
CO2 transfer in the pond and in the sluice tank were examined, as well as
the scaling potentials of the system.
From the results of the cooling tower and ash sluice system
simulations conducted, two alternatives for reducing plant discharges with
fly ash sluicing in the system were reported as technically feasible:
a. Cooling system operation at 5. 0 cycles of concentration
(essentially the existing operations) with once-through ash
sluicing. The ash pond overflow may be discharged after
a pH adjustment or can be treated with a brine concentrator
and reverse osmosis unit, with the clean water recycled to
the boiler and cooling tower makeup systems.
b. Cooling system operation at 7. 6 cycles of concentration with
the sluicing of bottom ash by use of recycled ash pond water.
The fly ash would be sluiced by cooling system blowdown
water, 50 percent of which was previously treated with brine
concentration to lower the calcium and sulfate in the ash
sluicing makeup water.
A third alternative was also reported in which dry fly ash was
disposed as is currently done at Comanche. The cooling towers may be
operated at 8.4 cycles of concentration (with lime-soda ash treatment for
silica removal if necessary) providing 16.4 £/sec (260 gpm) blowdown for
boiler refractory cooling for each unit. This water may then be used to
sluice bottom ash on a once-through basis, resulting in an ash pond overflow
or about 15. 1 I/sec (240 gpm) per unit. Zero discharge may be achieved
with this alternative by treating the overflow by brine concentration and
recycling the clean water to the boiler and cooling tower makeup systems.
The first alternative requires the addition of reaction tanks
upstream of the fly ash sluice line to minimize CaCOs and Mg(OH)2 scale
formation in the line. Adjustment of the pH of the ash pond overflow may
be required, depending on the amount of CC>2 transfer occurring in the ash
pond. The calculated pH for equilibrium with respect to CC>2 between the
pond and the atmosphere is 7.9, but the value for no CO2 transfer is 12. 7.
The second alternative also includes adding reaction tanks
in the fly ash sluice system, as in the first alternative. Also, recycle lines
and pumps are required to return a portion of the ash pond liquor for sluicing.
This alternative involves operating the cooling system at 7. 6 cycles of con-
centration, which reduces the ash pond overflow to 14.4 (./sec (229 gpm) for
each unit. However, cooling system scaling may result because of silica.
Chemical studies are needed to be undertaken to investigate if scaling will
occur.
If scaling were to occur at the increased level of concentration,
the silicate concentrations must be lowered by lime-soda ash softening of the
cooling system makeup water instead of solely lime treatment. Approximately
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50 percent of the cooling tower blowdown must be treated to remove calcium
and sulfate to avoid gypsum scaling in the sluice line.
The second alternative can achieve zero-discharge by treat-
ment of the ash pond overflow by a brine concentrator and reverse osmosis
unit. Discharge of the ash pond overflow may require pH adjustment as in
the first alternative, depending on the amount of CO2 transfer in the pond.
The third alternative is not expected to require pH adjust-
ment of the ash pond overflow before discharge because of the insoluble
nature of the bottom ash.
The report (Ref. 28) emphasized here that none of the
alternatives should be implemented prior to conducting bench or pilot
scale experiments to determine the actual size of the reaction tank required
in the sluice system, the quantity and frequency of acid wash water required
to minimize CaCOs and Mg(OH)2 scale formation, and the solubility limits
for silica in the cooling tower system.
5.6.1.2.4 Economics of Implementing Alternatives
Rough cost estimates were provided for the various alterna-
tives described in the previous section. The once-through sluice system and
the recirculating system using cooling system blowdown to sluice fly ash
with 50 percent of the blowdown treated by brine concentration (first alter-
native) is the least expensive option. Operating the cooling system at 5 cycles
of concentration and sluicing the fly ash and bottom ash on a once-through
basis is estimated to be $381, 000 in capital costs and about $48, 000 per year
in operating costs.
By operating the cooling systems at 7. 6 cycles of concentra-
tion with the cooling system blowdown as sluicing makeup (second alternative),
the entire plant ash sluice system requires an initial capital cost of about
$3. 3 million and an operating cost of about $390, 000 per year. The costs
for silica removal, if required, are not included.
If zero discharge of ash pond overflow is desired, the once-
through system becomes more expensive because of the increase in ash pond
overflow requiring treatment. A softening, reverse osmosis, and brine
concentration system to treat ash pond overflow is estimated to require an
additional capital investment of about $8. 28 million with an additional oper-
ating cost of approximately $1. 218 million per year. The total overall
costs would be about $8. 661 million for capital costs and $ 1. 266 million
per year for operating costs.
The additional costs for obtaining zero discharge with the
recirculating system would be about $3. 700 million for capital costs with
$485, 000 per year for operating costs. Overall costs for this case total to
approximately $7. 0 million for capital costs and $877, 000 per year for
operating costs.
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The costs associated with achieving zero discharge with dry fly
ash disposal (third alternative) are about $3.9 million capital costs and
$509, 000 per year operating costs. These costs include brine concentration,
additional piping, and additional pumping costs.
5.6.1.3 Plant Bowen
The Georgia Power Company Plant Bowen is a four-unit
3180-MW coal-fired electric generating station located near Taylorsville,
Georgia. The coal utilized is approximately 11 percent ash and 2.8 percent
sulfur with a heating value of about 11, 500 Btu/lb. Cooling towers and
bottom and fly ash wet sluicing are typical for all of the units.
Makeup water for the plant is taken from the Etowah River
and stored in a makeup pond. Water is removed from the makeup pond at a
design rate of 1. 6 X 10$ 2/min (52, 000 gpm) and used as general service
water, boiler makeup, and cooling tower makeup.
The general service water effluent is split so that 5 percent
of the flow returns to the makeup pond and 95 percent is used as cooling
tower makeup. Water treatment wastes total about 9. 5 0/sec (150 gpm) and
are pumped to the ash pond. The major water consumers at the Bowen
plant are the cooling tower system and the ash handling systems.
5.6.1.3.1 Cooling Tower System
Each of the four units have independent cooling systems with
one cooling tower for each unit. Units 1 and 2 are identical (700 MW) and
have identical cooling towers. Units 3 and 4 are each rated at 890 MW and
also have identical cooling towers. Water circulates between the condenser
and the cooling tower of each unit at a rate of 16, 280 I/sec (258,400 gpm)
for Units 1 and 2 and 19, 350 £/sec (310, 000 gpm) for Units 3 and 4. A
blowdown stream is removed from the circulating water after the condenser.
The water removed as blowdown is replenished with fresh makeup water.
The towers operate at about 1.7 cycles of concentration,
which is defined as the ratio of blowdown species concentration to makeup
species concentrations.
5.6.1.3.2 Ash Handling Systems
Fly ash is collected by ESP at a rate of about 24, 200 kg/hr
(53, 300 Ib/hr) from Units 1 and 2 and about 22, 500 kg/hr (49, 500 Ib/hr)
from Units 3 and 4. All of the collected fly ash is sluiced on a once-through
basis to the ash pond using cooling tower blowdown as sluice water. Sluicing
this amount of fly ash at about 7 percent solids requires 350 i/sec (5500 gpm)
of water.
Bottom ash is periodically sluiced with cooling tower blowdown
to the ash pond also on a once-through basis. Cooling tower blowdown not
used for sluicing fly ash is used to sluice the bottom ash at about 1 percent
solids. This water is discharged when it is not used to sluice the bottom ash.
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5.6.1.3.3 Technical Alternatives
A modular approach was reported to be as used in studying
water recycle or reuse alternatives at Bowen. The major plant water systems
were divided into two subsystems to form separate process simulations. One
subsystem consisted of the cooling towers with associated treatment facilities
(where necessary), hold tanks, and condensers. The other subsystem con-
sisted of the ash handling systems. The effects of increasing the cycles of
concentration in the cooling towers and of poorer quality makeup water
(increased calcium levels) were presented first. Then the use of cooling
tower blowdown in a once-through and a recirculating ash sluice system was
evaluated. The effects of carbon dioxide mass transfer between the atmos-
phere and the pond liquor were also determined.
Sodium carbonate softening of 80 percent of the pond recycle
water was calculated to be necessary on the assumption that no CaSO4'
precipitation occurs in the pond and that all of the cooling tower blowdown
(towers operating at 15 cycles of concentration) is used as makeup water
to the fly ash system. Bottom ash was assumed to be sluiced exclusively
with pond water. Gypsum relative saturation in the slurry was found to be
0.998 and in the pond recycle stream before treatment, 0.863. These rela-
tive saturations will prevent gypsum scaling in the system as they are below
the critical range for scaling of 1.3 to 1.4. Treatment of 80 percent of the
recycle liquor corresponds to removing 2. 7 g-mole/sec calcium from a
206 I./sec (3270 gpm) stream. Treatment inefficiencies were considered in
the calculation.
It was noted that simulations of existing operations indicated
that the cycles of concentration may be greatly increased in the cooling
towers without scaling with respect to calcium sulfate. However, only
limited increases in the cycles of concentration may be implemented before
calcium carbonate reaches saturation. Calcium carbonate scaling potential
can be controlled with acid treatment of the circulating water.
From the results of various cooling tower and ash sluice
system simulations discussed in detail in Reference 29f two alternatives
for reducing plant discharges were reported as technically feasible:
a. Cooling tower operation at 5. 7 cycles of concentration with
acid treatment and once-through ash sluicing with discharge
of ash pond overflow after pH adjustment
b. Cooling tower operation at 15.0 cycles with acid treatment
and recirculating ash sluice water (Na2CC>3 softening of
80 percent of pond recycle), with either discharge of the
ash pond overflow after pH adjustment or treatment of the
overflow with a softening, reverse osmosis, or brine con-
centration unit and recycle of the clean water as boiler
makeup and cooling tower makeup.
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The first alternative will require acid treatment in the cooling
towers and reaction tanks prior to the fly ash sluice line to minimize CaCC>3
and Mg(OH)2 scale formation in the line. Adjustment of the pH of the ash
pond overflow may be required, depending on the amount of carbon dioxide
mass transfer occurring in the pond. The calculated pH for equilibrium with
respect to CC>2 between the pond liquor and the atmosphere is 8.0, whereas
the value for no CC>2 transfer is 12. 0. This alternative would not allow
Bowen to achieve zero discharge without expensive treatment of the ash pond
overflow (255 tf/sec or 4050 gpm) but would reduce the plant makeup water
and discharge rates significantly. The existing ash pond overflow rate for
Bowen is about 1600 t/sec (25, 000 gpm) by this alternative.
If in the future, SC>2 scrubbers will be installed at Bowen, it
was noted that the ash pond overflow could be used as makeup water to the
scrubbing system to make use of the available alkalinity from the ash. How-
ever, the study did not include evaluating the addition of scrubbers at Bowen,
but considered only the cooling and ash handling systems.
Implementation of the second alternative would also require
the addition of acid treatment in the cooling towers and reaction tanks in the
fly ash sluice system as in the first alternative. Treatment of the ash pond
overflow by the lime and soda ash process would reduce the calcium,
magnesium, and silica levels, but sulfate concentrations would reach levels
high enough for gypsum scaling to occur. In addition, recycle lines and
pumps are needed to return a portion of the ash pond liquor for sluicing
and sodium carbonate softening of 80 percent of the pond recycle water.
Zero discharge may be achieved with this alternative by treatment of the
ash pond overflow by a softening, reverse osmosis, brine concentration
unit and return of the cleaned water to the boiler and cooling tower makeup
systems. Discharge of the ash pond overflow may require pH adjustment
as in the first alternative depending on the level of CC>2 transfer in the pond.
It was emphasized in the report (Ref. 29) that neither alter-
native should be implemented before more information is obtained from bench
or pilot scale tests to determine the actual size of reaction tank required in
the sluice system, the quantity and frequency of acid wash water required
to minimize CaCC>3 and Mg(OH)2 scale formation, and the level of gypsum
de super saturation in the pond.
5.6.1.3.4 Economics
The rough cost estimations in 1976 dollars for implementing
either of the technically feasible alternatives are summarized. Capital
costs as well as operating costs are presented. The assumptions used in
calculating these costs are outlined briefly. It is noted (Ref. 29) that these
values were only valid for comparative purposes.
The capital costs for the two technically feasible alternatives
are $79, 700 and $920,400, respectively, for alternatives 1 and 2. The fly
ash slurry tanks were sized based on a 5-minute residence time of the
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slurry to allow most of the ash soluble species to be leached in the tank. One
tank was used for the fly ash slurry from each unit and was assumed to have
one agitator to keep the slurry well mixed.
Pond overflow recycle pumps and piping were sized on the
basis of flows calculated in the simulations. Since both alternatives involve
sluicing the ash at 10-wt% solids, the tank and agitator costs were identical.
The higher capital costs for alternative 2 is the result of the pumps and piping
required for recycling a portion of the ash pond liquor and the Na2CO3 soften-
ing of the pond recycle liquor.
The annual operating costs for the two alternatives are $47, 300
and $243,400. Three major items were included: acid treatment, power
consumption, and softening. Operating the towers at 15.0 cycles of concen-
tration (alternative 2) requires 27 percent more acid than operation at 5. 7
cycles (alternative 1). The power consumption for the second alternate is
estimated as $66, 700 compared to $2600 for the first. The difference was
ascribed to operation of the recycle pumps for the second alternative. A cost
of 2 cents/kWh was used to determine power costs.
It is apparent that the first alternative is significantly less
expensive than the second. However, zero discharge by eliminating the ash
pond overflow discharge is not practical for the first alternative (once-through
ash sluicing) because of the high flow rate of 255 £/sec (4050 gpm).
Additional capital and operating costs for treating the 41 It/sec,
(650 gpm) ash pond overflow from the second alternative were also presented.
The overflow was considered as being treated by a combination of softening,
reverse osmosis, and brine concentration, with the clean water recycled to
the plant boiler makeup system. The additional capital cost for treatment
is about $ 5. 14 million. Therefore, a total capital cost of about $6. 06
million was estimated for achieving zero discharge with a recirculating ash
sluice system. The additional operating costs were reported as approxi-
mately $700, 000 per year with a total of about $942, 000 per year.
5.6.2 Treatment of FGC Waste Streams with Vapor
Compression Cycle Evaporation (Resources
Conservation Company)
This project is being conducted by Resources Conservation
Company (RCC) to demonstrate the practicability of using an RCC brine
concentrator as a means of reducing the volume of waste water discharges
from FGC processes.
The brine concentrator is a vertical tube, falling-film, vapor
compression evaporator that was developed to provide an energy-efficient
process for concentrating waste and blowdown waters. The project includes
a series of bench and pilot scale tests to demonstrate the feasibility of using
the brine concentrator for reducing the waste water volume from FGC
processes.
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The primary objective of this program is to demonstrate a
way to reduce the volume of waste water from a desulfurization process,
by evaporative means without scaling heat transfer surfaces, to less than
4 percent of its initial volume and produce a high quality water stream (less
than 10-ppm TDS) for recycle back to the power plant.
An appropriate program to demonstrate the feasibility of the
brine concentrator for reducing the volume of waste water from FGC
processes requires on-site operation of the concentrator at an SO2 scrubber
installation. The Chiyoda "Thoroughbred 101" scrubber installed at the
Sholz Power Plant of Gulf Power Company in Sneads, Florida, is planned
for the on-site testing because it produces a continuous blowdown stream.
The Chiyoda process removes sulfur dioxide from the flue gas by counter-
current scrubbing with weak sulfuric acid in a fixed bed absorber. The
absorption of SC>2 by f^O gives sulfurous acid (H^SOs), which is catalytically
oxidized to H2SC>4. The concentration of sulfuric acid in the scrubbing liquid
is maintained constant by continuous withdrawal to the crystallizer. In the
crystallizer, this absorbent is partially neutralized by limestone to produce
gypsum. There are two waste streams from the process. One is fly ash
bleed from the prescrubber, and the other is the scrubbing liquid bleed
from the crystallizer for water balance and control of the chloride concen-
tration in the scrubbing liquor. These two waste streams are combined,
neutralized by limestone, and discharged to the liquid waste pond. This
combined neutralized waste water stream will be fed to the concentrator
during the demonstration tests.
The demonstration program is comprised of the following
tasks: (1) evaluation of existing chemical data on waste streams from the
Chiyoda process, (2) glassware evaporation tests to confirm predicted
precipitation levels and to establish operating conditions for bench model
tests, (3) bench model tests (25 gallons per day unit) to verify operating
conditions for the on-site demonstration tests, (4) on-site tests with a pilot
size (6000 gallons per day) evaporator to demonstrate the vapor compres-
sion evaporator's long-term performance in concentrating scrubber waste
water, and (5) estimation of the capital and operating costs for a full-scale
system.
5. 6. 3 Power Plant Cooling Tower Blowdown Recycle by
Vertical Tube Evaporator with Interface Enhancement
(University of California, Berkeley)
5. 6. 3. 1 Background
Industrial cooling accounts for more industrial water use in
the United States than all others combined; about 80 percent of industrial
water use is for heat rejection. Much of this use is on a once-through basis,
the slightly heated water being returned to the environment. Since the
temperature of the rejected coolant is slightly above its previous equilibrium
with the environment, proportionately more will evaporate to readjust to
equilibrium. This in effect degrades the water quality by concentrating dis-
solved solids.
240
-------
The concept of a cooling tower operating with zero discharge
is not new; it is, however, more expensive than both once-through cooling
and partial evaporation followed by discharge of a somewhat concentrated
warm effluent.
Development of a vertical tube foam evaporator (VTFE)
promises economic improvements that should make adoption of cooling
towers and zero discharge more acceptable to industry (Ref. 30). Improved
economy follows from the increased heat transfer performance of VTFE.
This permits either a reduction in the heat transfer surface area required
or increased steam economy.
The interface-enhanced method of evaporating liquids applied
in this study relies on the addition of a few parts per million of a selected
surfactant to the liquid to be evaporated, followed by causing the feed liquid
to flow as a foamy layer over a heated surface (Ref. 31). As a result of this
foamy layer flow, heat transfer from the surface to the feed liquid is aug-
mented by several mechanisms to provide for a significant increase in the
rate of evaporation or heat transfer coefficient.
Vertical tube evaporation (VTE) accounts for more industrial
evaporation in the United States than all other methods used, and its further
improvement by the VTFE method should be of significant value.
In addition, the VTFE process permits the adoption of novel
modes of operation previously only marginally feasible; it could also add
new capabilities to older VTE applications. One such possible improvement,
addressed in this work, is a novel power plant coolant flow that permits the
use of waste heat available within conventional coolant flow diagrams to
renovate the cooling tower blowdown, producing distilled water Jfor boiler
feed, potable use, or recycle as coolant and a dry or slurried salt concen-
trate. Such an improved coolant flow is diagramed in Figure 53. The
work reported here was planned to provide test data and design information
for evaluating feasibility of applying this technique to a preexisting power
plant. The main objectives of adopting such a flow would be to renovate
the cooling tower blowdown at low cost for recycle with zero blowdown,
and to utilize a VTFE facility that would interface readily with normal power
plant operation. This approach, although as yet unproven, provides the
basis for work undertaken in this as well as in a followon project.
5.6.3.Z Results
The results of this work confirm the effectiveness of applying
interface enhancement (Ref. 30) to the evaporation of liquids in reducing
the energy and capital cost requirements for the renovation and recycle of
industrial wastewaters. Interface enhancement, which depends upon foamy
two-phase vapor-liquid flow, induced during the evaporation of a liquid flow-
ing over a heat transfer surface, provides a substantial increase in the rate
of evaporation of the liquid, after the addition of a selected surfactant. This
241
-------
Cs)
BAROMETRIC
CONDENSER
IX X2
COOLANT
MAKEUP
COOLANT
SLOWDOWN
COOLING TOWER
DISTILLATE SOL'DS SLOWDOWN
COOLANT
MAKEUP
Figure 53. Renovation and recycle of power plant cooling tower blowdown.
-------
project included the construction of two new VTE pilot plants. A two-effect
upf low-downflow VTE of 10, 000 gallons per day capacity was constructed
by adding an identical second effect to an existing single-effect, upflow VTE
pilot plant; the second effect was operated in the downflow VTE mode for the
work reported here. This pilot plant was used to obtain comparative data
on the concentration of saline water by upflow VTE and downflow VTE, and
by an interface-enhanced upflow and downflow VTE. These data indicate
that while conventional downflow VTE has a higher heat transfer performance
than upflow VTE, the interface-enhanced method of upflow VTE operation
provides a higher performance than both the interface-enhanced and con-
ventional downflow operations.
A second pilot plant facility assembled for this work was
a 5000 gallons per day vertical tube evaporator-crystallizer (EC), tested
in the downflow mode. This facility was first used with low-temperature
steam heating for crystallizing sodium sulfate and for reducing Mohave
power plant cooling tower blowdown to a 30-fold concentrate, at about 125°F.
The objectives of these tests were to determine the feasibility of renovating
cooling tower blowdown with waste heat available within a conventional power
plant cooling cycle; feasibility was indicated by the test results. Secondly,
this EC was operated with a vapor compressor (VC) in the evaporation tem-
perature range 215 to 224°F. This series of tests was for the concentration,
by both conventional and interface-enhanced modes of operation, of saline
agricultural drainage water and industrial cooling tower blowdown. In each
of these cases, it was found that the heat transfer performance of the VTE
was increased, while its energy requirements were simultaneously reduced,
by applying interface enhancement, except in the case of crystallizing sodium
sulfate.
5.7 EPA IN-HOUSE RESEARCH
EPA has conducted pilot plant experiments on forced oxidation
of FGD scrubber wastes, corresponding to operation with high-sulfur U. S.
Eastern coal (Refs. 8 and 32). Primary objectives of the project include
complete limestone utilization, maximum oxidation efficiency of calcium
sulfite to calcium sulfate, and improved oxidized slurry settling rates. The
second and third objectives are related to determining the feasibility of
forming usable gypsum as a by-product from the FGD scrubbing process.
In order to assess the characteristics of the gypsum from a
utilization standpoint or the suitability of gypsum as a disposal product with-
out the need for further chemical treatment, Aerospace has conducted chemi-
cal and physical characterization tests of oxidized wastes formed under
conditions equivalent to limestone scrubbing, with and without fly ash.
The laboratory study was completed recently on oxidized
samples of filter cake and first- and or second-stage solids which are pri-
marily calcium sulfite. Physical and chemical properties including results
of x-ray and SEM analysis are summarized in Section 5. 1. 1.5.
243
-------
SECTION VI
UNIVERSITY-RE LA TED RESEARCH AND DEVELOPMENT
Several universities were identified in the first summary
report (Ref. 1) as planning or conducting research and development (R&D)
work in the flue gas desulfurization (FGD) waste disposal and utilization
area. These included Auburn University, which is conducting FGD waste
dewatering experiments under EPA sponsorship (Section 5.2.4), and The
Illinois Institute of Technology (IIT), which is studying the applicability of
SO2 from flue gas to form a super phosphate fertilizer. Information not
available on the IIT work for this report is expected in the near future.
The University of Louisville is conducting tests to support
the EPA study being performed by the Louisville Gas and Electric Co.
(LG&E) (Section 5.2. 1). Physical characterization data on six FGD scrubber
wastes have been reported. The LG&E support includes determination or
development of disposal (impoundment) site:
a. Hydrology characteristics
b. Soil permeability
c. Periodic sampling schedule and techniques
d. In-situ strength measurements of the wastes
Laboratory tests on field samples augmenting the field work includes uncon-
fined compression tests and permeability.
The American Society of Testing and Materials (ASTM) soil
mechanics tests to characterize the mechanical properties of six wastes
have been reported (Ref. 33). These include specific gravity, grain size
distributions, plasticity, and compaction. Wastes included samples from
LG&E Paddy's Run (mostly calcium sulfite), Southern Services Plant Scholz
using the ADL-CEA dual alkali process (about 70/30 sulfite-to-sulfate)
Southern Services, Scholz Chiyoda process (mostly gypsum), Kansas City
Power and Light La Cygne (waste and fly ash), and two unidentified foreign
sludges containing primarily sulfite.
245
-------
Triaxial compression tests and a study will be conducted to
investigate the effects of various additives on mechanical properties.
Although it is recognized that FGD sludges are not soils and
soils engineering experience can only be used to a limited degree in predict-
ing field behavior, some observations were reported. Based on the Unified
Soil Classification System (USCS) the Chiyoda and ADL-CEA dual alkali may
be classified as silts of low compressibility and Paddy's Run material, as
a silt of high compressibility. Other properties are summarized in
Table 70.
246
-------
TABLE 70. SUMMARY OF PHYSICAL, PROPERTIES
Source of
Waste
LG&E
Paddy's Run
Gulf Power, Scholz
Chiyoda
Gulf Power, Scholz
ADL-CEA
Kansas City Power
La Cygne
LGfeE
Paddy's Run with
50% Fly Ash
Specific Gravity*
2.49
2. 35
2.56
-
-
Grain Size Fractions
Sand. Size
(>0.074 mm)
0%
18
4
-
-
Silt- Size
(0.002 to 0.074 mm)
97%
76
93
-
-
Clay -Size
(< 0.002 mm)
3%
6
3
-
-
Moisture-Density Relationship
Maximum
Dry Density,
pcf
84.0
94.8
85.3
102.4
91.5
Water Content,
%
31. 3
13.3
26.8
17. 1
25.0
a70°C.
bASTM D422.
CO
-------
SECTION VII
INDUSTRIAL RESEARCH AND DEVELOPMENT
AND OPERATIONAL APPLICATIONS
This section supplements the information reported in Ref.
on the work being performed by various industrial organizations and other
governmental agencies in their treatment of flue gas desulfurization (FGD)
wastes. The operational applications of FGD treatment and disposal in the
United States are also summarized.
7. 1 ' RESEARCH AND DEVELOPMENT
7. 1. 1 Electric Power Research Institute (EPRI)
In December 1976, a project was initiated by EPRI, "By
Product/Wastes Disposal for Flue Gas Cleaning Processes" (Ref. 34). Its
objectives are (1) to develop and maintain a data base on sludge and task
handling procedures, (2) to provide an independent evaluation of sludge fixa-
tion processes, (3) to quantify variables affecting the solubility of trace
elements, (4) to establish guidelines for disposal, and (5) to evaluate sludge
dewatering processes and hard-ware. Michael Baker Corporation and
Radian Corporation are the contractors involved in the task evaluation.
Envirotech is conducting the dewatering task.
7.1.2 New York State Energy Research and Development
Authority (NYSERDA)
A study to investigate the feasibility of using chemically
treated flue gas scrubber waste as artificial fishing reefs was initiated by
NYSERDA (Ref. 35). The research contract was awarded to the Marine
Sciences Research Center of the State University of New York at Stony Brook.
7.1.3 Southern Services
Recent testing of the Chiyoda process the Southern Services
Plant Scholz, Chattahoochee, Florida, has been directed toward a water
saving approach to reduce usage by a factor of two (Ref. 36). Testing was
scheduled to continue through December 1976. In addition, 3000 4 X 12 ft
248
-------
sheets of wallboard were produced for evaluation using a 50/50 blend of
natural gypsum and gypsum produced by the Chiyoda process.
7. 2 UTILITY POWER PLANT APPLICATIONS
Full-scale experience and future plans relating to FGD chem-
ical treatment and disposal by utilities are summarized in Tables 71 and 72.
A total of 15 plants, representing 9 utilities totaling 7484 MWe, are currently
committed to initiate by 1979 the chemical treatment of lime-limestone
scrubber wastes prior to disposal. Five stations (2100 MWe) are now in
operation; seven others (3959 MWe) will start up by the end of 1977, and
three others have made definite commitments to begin by 1979. Also,
16 plants representing 3646 MWe are identified as scrubbing and disposing
untreated lime-limestone scrubbed FGC wastes in lined or in natural clay
unlined ponds in 1976 (Ref. 2).
Experience with a limestone wet scrubber, gypsum-producing
system operating on Unit 1 at the Northern States Power Company Sherbourne
generating plant was described recently (Ref. 9). Unit 1 (700 MWe) became
operational in May 1976. The plant burns Montana subbituminous coal
(8300 Btu/lb 0. 8 percent S and 9. 0 percent ash). The scrubber is a two-stage
venturi and marble bed scrubber. Fifty percent of the SO_ and 99 percent of
the particulate matter in the flue gas are removed.
The sulfite slurry from the scrubber is air oxidized in a
reaction tank. The calcium sulfate slurry is withdrawn at 10 percent total
solids. The gypsum slurry is thickened and pumped to the fly ash pond.
Thickener overflow is returned to the scrubber recirculation tank where it
is used as makeup water in the scrubber system. The slurry in the fly ash
pond is allowed to settle, and the supernate is also returned to the scrubber
recirculation tank.
Unit 2 (700 MWe) is scheduled to begin operation in May 1977.
249
-------
TABLE 71.
FGC CHEMICAL TREATMENT PROCESSES:
UTILITY PLANT CHARACTERISTICS
Utility
Commonwealth Edison
Duqueana Light Co.
Duquesne Light Co.
Southern California
Edison (SCE)
Central Area Power
Coordination (CAPCO)
Group
Ohio Edison Co.
Duqueane Light Co.
Cleveland Electric
Co.
Toledo Edison Co.
Pennaylvania Power
Co. (operator)
Power Station
Will County,
Unit No. 1
Phillips
Elrama
Mohave, Unit No. 1
Mohave, Unit No. 2
Bruce Mansfield,
Unit No. 1
Unit No. 2
Station
Size,
MW
167
410
510
790
790
835
835
Coal Characteristics
•ks
4
1.0 to 2.8
1.0 to 2.8
0.5 to 0.8
0.5 to 0.8
4 to 5
4 to 5
% Ash
10
18
18
10
10
12.5
12.5
Btu/lb
9, 500
11, 300
12,000
11,500
11, 500
11,900
11,900
FGD
Absorbent
Limestone
Slaked lime
Hydrated lime
with switch to
quicklime as
soon as
pos sible
Limestone
(lime
alternative)
Lime
(limestone
alternative)
Lime
Lime
FGD
Installation
Retrofit
Retrofit
Retrofit
Retrofit
Retrofit
New
New
FGD
Startup
Feb 1972
Jul 1973
Nov 1975
Jan 1974
Nov 1973
Apr 1976
Apr 1977
Scrubber
Size,
MW
167
410
510
170
170
835
835
Particulate
Control Device
Upstream of
Scrubbers
ESP used only when FGD
not in use
Mechanical cyclones
followed by ESP,
Research- Cottrell;
Venturis
Mechanical cyclones
followed by ESP;
Venturis
ESP, Research- Cottrell
ESP, Research-CottreU
None
None
Scrubber System
Two venturi and coun-
tercurrent tray ab-
sorber modules;
Babcock k Wilcox
(B 8, W)
One 2- stage variable
throat venturi module
processing 125 MW;
four single-stage
modules processing
remainder; Chemico
Five single-stage
Venturis; Chemico
Vertical TCA module;
Universal Oil Products
(UOP); test completed
Jul 1975
Horizontal 4-stage
counter- current
module; SCE; tests
completed Feb 1975;
170-MW prototype
unit to Public Service
Corners Station
2-stage scrubbers;
Chemico
2-stage scrubbers;
Chemico
By-
pass
Yes
Yea
Yes
Yea
Yes
Ref. in
First
R fc D
Reporta
28,31
28,32
28, 33,
34
28, 35,
36
28, 35,
36
28, 37,
38
28, 37,
38
Ref.
This
Report
2
2
2, 37
2
2
ro
m
o
-------
TABLE 71. FGC CHEMICAL, TREATMENT PROCESSES: UTILITY
PLANT CHARACTERISTICS (Continued)
Utility
Louisville Gas and
Electric Co.
(LG&E)
Columbus and Southern
Ohio Electric
Indianapolis Power
and Light
Allegheny Power
System
Utah Power &
Light Co.
Texas Utilities Co.
Power Station
Paddy's Run, Unit No. 6
Cane Run, Unit No. 4
Cane Run, Unit No. 5
Mill Creek, Unit No. 3
Conesville, Unit No. 5
Conesville. Unit No. 6
Petersburg, Unit No. 3
Pleasants, Unit No. 1
Emery, Unit No. 1
Martin Lake, Unit No. 1
Martin Lake, Unit No. 2
Station
Size,
MW
65
178
183
425
400
400
530
625
415
793
793
Coal Characteristics
%S
3.5 to 4.0
3.5 to 4.0
3.5 to 4.0
3.5 to 4.0
4.5 to 4.9
4.5 to 4. 9
3.0 to 3.5
4.5
0.5
1.0
1.0
% Ash
13
11 to 12
17
17
15
Btu/lb
11, 500
11,500
FGD
Absorbent
Carbide lime
Lime
Lime
Lime
Thiosorbic
lime
Thiosorbic
lime
Limestone
Thiosorbic
lime
Lime
Limestone
Limestone
FGD
Installation
Retrofit
Retrofit
Retrofit
New
New
New
New
New
New
New
New
FGD
Startup
Apr 1973
Aug 1976
Dec 1977
Jul 1977
Jan 1977
Jan 1978
Sep 1977
Mar 1979
Jun 1978
Jan 1977
Oct 1977
Scrubber
Size,
MW
65
178
183
425
400
400
530
625
415
793
793
Participate
Control Device
Upstream of
Scrubbers
ESP
ESP
ESP
ESP
ESP
ESP
ESP
ESP
ESP
Scrubber System -*=
Combustion
Engineering
Marble Bed
American Air Filter
Combustion
Engineering
American Air Filter
UOP
UOP
4 modules; UOP
B 8. W
Chemico
Research- Cottrell
By-
pass
Yes
Yes
Ref . in
First
R b D
Report*
28
28
28
28
28
28
Ref!
This
Report
2
2
2
2
2
2
aReference 1.
to
-------
TABLE 72. FGC WASTE TREATMENT AND DISPOSAL STATUS
Utility
Commonwealth
Edison
Duquesne Light Co.
Duquesne Light Co.
SCE
CAPCO Group
Ohio Edison Co.
Duquesne Light
Co.
Cleveland Elec-
tric Co.
Toledo Ediaon
Co.
Pennsylvania
Power Co.
(operator)
Power Station
Will County, Unit
No. 1 {167 MW)
Phillips (410 MW)
Elrama (510 MW)
Mohave, Unit No. 1
Mohave, Unit No. 2
Bruce Mansfield,
Unit No. 1
(825 MW)
Unit No. 1 (825 MW)
FGC Waste Treatment Processing
Process
Own •with Chicago
fly ash
Calcilox®
IU Conversion
Systems, Inc.
(IUCS) estimated
startup date:
Oct. 1977
IUCS, permanent
plant estimated
startup date:
Nov 1977
IUCS
Dravo
Dravo
Treatment
Material
Lime and
fly ash
Calcilox®
Lime and
fly ash
Calcilox®
Calcilox®
Waste Solids
Content
35 to 45% clarifier
underflow
30 to 40% clarifier
30 to 40% clarifier
underflow.
filtered to approx.
60% solids
35 to 40% clarifier
unde rflo w , f il -
tered to 50 to 60%
solids before
treatment
30% solids clari-
fier underflow
Treatment
Conditions
10% lime and 20%
fly ash (of dry
sludge solids)
10% on dry
s u ge
Treating waste
produced by 210
MW equivalent.
using equipment
from Mohave
site tests
Treated all
sludge from
167-MW sys-
tem for 1 yr
FGC Waste Disposal
Interim
Storage
7-acre onsite
clay-lined
disposal basin
{prior to
Sep 1975)
Three curing
yd , each with
10 to 14-day
capacity
None
None
Transport
Mode
Rotary mix
concrete
truck
Dump truck
Truck, 25-
ton capacity
Treated
waste
pumped to
disposal
site ~7 mi;
pond
supernate
returned
for reuse
Final Disposal Site
Offsite to permanent clay-
lined landfill disposal site
operated by Material
Service Co. since
Sep 1975
•--1 mi from plant; 2-yr
solidifies in place
Landfill ~2 mi from
plant
Landfill of 25,000 tons
for housing, parking lot
construction, streets
and roads in Bullhead
City and Riviera; syn-
thetic aggregate
manufacture
Unlined pond
400 -ft high embankment
dams a 1330-acre
valley
Site estimated to be
adequate for 20 to
25 yr
Ref. in
First
R&D
Report1
29,31
22,32
22,33,
39
25,29,
35,36
25
22,37,
38
Ref.
This
Report
2
2
38
2,
37,
38
Ui!
PO
-------
TABLE 72. FGC WASTE TREATMENT AND DISPOSAL STATUS (Continued)
Utility
LG&E
Columbus and
Southern Ohio
Electric Co.
Indianapolis Power
and Light
Allegheny Power
System
Utah Power and
Light Co.
Texas Utilities Co.
Power Station
Paddy's Runt Unit
No. 6 (65 MW)
Cane Run, Unit
No. 4 (178 MW)
Mill Creek, Unit
No. 3 (4Z5 MW)
Conesville, Unit
No. 5 (400 MW)
Conesville, Unit
No. 6 (400 MW)
Petersburg, Unit
No. 3 (530 MW)
Pleas ants. Unit
No. 1 (625 MW)
Emery, Unit
No. 1 (400 MW)
Martin Lakef Unit
No. 1 (793 MW)
Martin Lake, Unit
No. 2 (793 MW)
FGC Waste Treatment Processing
Process
LGtE
LG«!
-------
SECTION VIII
FOREIGN TECHNOLOGY
Significant published information subsequent to that provided
in References 1 and 37 was not available during this reporting period. It is
noted that cost estimates for the production of gypsum by the Chiyoda, Dowa,
an dLJSureJiaL processes as applied to U.S. conditions are being calculated by
the Tennessee Valley Authority (TVA) and is expected to be published in
the next report (Section 5. 3. 2).
A summary of the major characteristics of the various
Japanese gypsum producing processes (Ref. 40) are summarized in
Table 73.
255
-------
TABLE 73. GYPSUM-PRODUCING PROCESSES BASED ON WET
LIME-LIMESTONE SCRUBBING
Process
Features
Electrostatic
Precipitator (ESP)
Range of Inlet
SO2, ppm
Exhaust Gas
Cooler, type
Scrubber /Absorber,
type
Absorbent
No. of Absorbers
pH Adjusted,
with
SOji Removal
Efficiency, %
O 'd'
Gypsum
Dewatering
Gypsum Moisture
Content, %
Power Plants, in
Operation, MWe
Cost: Capital
Operating
GypsumAJse
Mitsubishi-
JECCO
None
550 - 20,000
Tower
Grid, packed
Lime or
CaCO
1 or 2
6-7,
H2S04
90 - 97
atomizer, air
Thickener and
c entrif uge
8-10
31,
5730
$60 /kW,
NAV
High quality
wallboard,
cement
Mitsui-
Miike
None
1500 - 2350
None
Venturi
CaCO
2
6,
Flue gas
NAV
T
Thickene r and
centrifuge
10 - 15
5,
856
NAV
Usable for
wallboard.
cement
Babcock
Hitachi
None
400 - (500
Venturi
Perforated plate
CaCO.
1
6,
H2S04
90
Rota
air
Thickener and
centrifuge
7-8
5,
1075
NAV
Saleable
Chubu-Mkk
(CM Process)
None
NAV
Spray
Screen
CaCO
1
6,
H2S04
90
air
Thickener and
centrifuge
10 - 12
2,
102
NAV
Wallboard
Kobe Steel
(CAL Process)
None
200 - 400
Yes
NAV
Lime with
CaCl2 added
1
7,
None
90
Air
Centrifuge
10%
(0.5%CaCl2)
2,
240
NAV
Cement
retarder
Sumitomo-
Fuji
Kasui
(More tana
Process)
Yes
800
Yes
Perforated
plate
Lime
1
6,
H2S04
90 - 97
Air
Centrifuge
10 - 12
8,
258
$60 /kW,
NAV
Wallboard,
cement
IHI-
TCA
No
1300
Yes
TCA
Lime
2
NAV,
Yes
90
Air
NAV
10 - 15
3,
210
NAV
NAV
Chemico-
IHI
Yes
NAV
None
Venturi
CaCO,
2
NAV,
H2S°4
80
Air
Thickener
. and cen-
trifuge
NAV
2,
530
NAV
Not sale-
able, ex-
cessive
fly ash
content
Kawasaki
None
NAV
Yes
NAV
Lime/Mg(OH),
CaCO /Mg '*•
'OH>2
NAV
NAV,
H2S°4
NAV
Thickener
and cen-
trifuge
NAV,
0. 5% MgSO4
3,
187
NAV
Cement
retarder
Tsuki-
(TSK
Process)
NAVa
NAV
NAV
Bahco
Lime
NAV
NAV
NAV
V
NAV
NAV
1,
20
NAV
NAV
Nippon
Kokan
t
NAV
b
Spray
tower
Lime
b
b
b
b
b
h
1,
38
_t
b
aNot available.
bSimilar to Mitsubishi - JECCO process.
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TABLE 73. GYPSUM-PRODUCING PROCESSES BASED ON WET
LIME-LIMESTONE SCRUBBING (Continued)
~~ — ^^^ Process
Features ~~ — ^^^
Electrostatic
Precipitator (ESP)
Range of Inlet SO., ppm
Exhaust Gas Cooler,
type
Scrubber, type
pH
Absorbent/Precipitant
No. of Absorbers
SO, Removal
Efficiency, %
Oxidizer
Oxidation Stages,
number
pH, adjusted with
Gypaum
Dewatering
Gypsum Moisture
Content, %
Plants in Operation,
MWe
Cent: Capital
Operating
Gyp sum /Use
aNot available.
Showa Denko
None
NAV a
No
7
Na2SO3/CaCO3
4
95
Air
NAV
NAV, H2SO4
Centrifuge
~9 with +
~300 pptnNa
16,
785
$43/kW/(1973)
4 mills /kWh
Wallboard
Kureha-
Kawasaki
Yes
600 - 1300
Venturi type
type
7
Na2SO3/CaCO3
1
~97
Air
NAV
NAV, H2S04
Centrifuge
< 8%
6,
1900
$50 /kW( 1973)1
NAV
Good quality
gypsum
Nippon Kokan
Yes
250 - 500
Spray tower
6
(NH4)2S03/Ca(OH)2
1 (5 stages)
95
Air
2
4. H2S04
Centrifuge
NAV
1,
46
Available
Good quality
gypsum
Chiyoda
None
600 - 1500
Yes
Packed, tower
NAV
H2S04(Fe+3)/CaCO3
1
i-90
Air
1 (oxidiled in
absorber)
--
Centrifuge
6-10
13,
1390
$65 - 70 kW(1973)
Good quality
gypsum
Dowa
None
400 - 1700
No
Packed Tower
3 - 4
AL2(S04)3/CaC03
1
95
Air
1
--
Centrifuge
NAV
2,
90
$55/kW(1973)
Wallboard, cement.
0.05% Al
Kurabo
None
NAV
Yes
KBCA
<4
(NH4)2S04/Ca(OH)2
NAV
-90
Air
1
4
Centrifuge
9
4,
129
Available
Saleable
Tsukishima
None
750 - 1300
No
NAV
NAV
Na2S03/Ca(OH)2
NAV
NAV
Air
NAV
NAV
Thickener, filter
NAV
4,
228
NAV
NAV
Hitachi.
Tokoyo
Electric
Yes
NAV
NAV
NAV
NAV
Carbon
CaCO3
80 . 90
CaCO
reacting
with dil.
H2S04
NAV
NAV
Centrifuge
10 - 12
1,
150
NAV
,NAV
-------
REFERENCES
1. P. P- Leo and J. Rossoff, Control of Waste and Water Pollution from
Power Plant Flue Gas Cleaning Systems; First Annual R&D Report,
EPA-600/7-76-018, U.S. Environmental Protection Agency,
Research Triangle Park, NC (October 1976).
2. Summary Report - Flue Gas Desulfurization Systems, prepared by
PEDCO-Environmental Specialists, Inc. , for the U.S. Environmental
Protection Agency, Research Triangle Park, NC, Contract No.
68-02-1321 (September-October 1976).
3. J. Rossoff, et al. , Disposal of By-Products From Nonregenerable
Flue Gas Desulfurization Systems: Second Progress Report,
EPA-600/7-77-052, U.S. Environmental Protection Agency, Research
Triangle Park, NC (May 1977).
4. J. L. Mahloch, D. E. Averett, and M. J. Bartos, Jr. , Pollutant
Potential of Raw and Chemically Fixed Hazardous Industrial Wastes
and Flue Gas Desulfurization Sludges; Interim Report,
EPA-600/2-76-182, U.S. Environmental Protection Agency,
Cincinnati, OH (July 1976).
5. R. B. Fling, et al. , Disposal of Flue Gas Cleaning Wastes: EPA
Shawnee Field Evaluation: Initial Report, EPA-600/2-76-070, U.S.
Environmental Protection Agency, Research Triangle Park, NC
(March 1976).
6. J. Rossoff, et al. , Disposal of By-Products from Nonregenerable
Flue Gas Desulfurization Systems; Final Report, Prepared by The
Aerospace Corporation for the U.S. Environmental Protection
Agency, Research Triangle Park, NC, Contract No. 68-02-1010
(to be published).
7. R. B. Fling, et al. , Disposal of Flue Gas Cleaning Wastes: EPA
Shawnee Field Evaluation; Second Annual Report, EPA-600/7-78-024,
U.S. Environmental Protection Agency, Research Triangle Park, NC
(February 1978).
259
-------
8. R. H. Borgwardt, "IERL-RTF Scrubber Studies Related to Forced
Oxidation," paper presented at the U.S. Environmental Protection
Agency, Symposium on Flue Gas Desulfurization, New Orleans,
March 8-11, 1976.
9. R. J. Kruger, J. A. Noer, and T. M. Pryslak, "Sherbourne County
Wet Scrubber System Experience, " Paper presented at the Sulfur
Removal Systems Conference, University of Wisconsin, Madison, WI,
January 6-7, 1977.
10. P. P. Leo and J. Rossoff, Controlling SQg Emissions from Coal-
Fired Steam-Electric Generators: Solid Waste Impact, Vol. II,
EPA-600/7-78-044b, U.S. Environmental Protection Agency,
Research Triangle Park, NC (March 1978).
11. J. Rossoff and R. C. Rossi, Disposal of By-Products from Non-
Regenerable Flue Gas Desulfurization Systems: Initial Report,
EPA-650/2-74-037-a (NTIS No. PB 237-114/AS), U.S. Environmental
Protection Agency, Research Triangle Park, NC (May 1974).
12. H. G. Blecker and T. M. Nichols, Capital and Operating Costs of
Pollution Control Equipment Modules, Vol. II, Data. Manual,
EPA-R5-73-023b, U.S. Environmental Protection Agency,
Washington, DC (July 1973).
13. J. W. Jones, J. Rossoff, and R. C. Rossi, "Flue Gas Cleaning
Waste Characterization and Disposal Evaluation, " Proceedings:
Fourth International Ash Utilization Symposium — St. Louis,
March 1976, U.S. Environmental Protection Agency, Research
Triangle Park, NC (March 1976).
14. J. L. Mahloch, "Chemical Properties and Leachate Characteristics
of FGD Sludges," Paper presented at the AICHE Symposium, Atlantic
City, NJ, August 29-1 September 1976.
15. J. L. Mahloch, "Chemical Fixation of FGD Sludges: Physical and
Chemical Properties," Paper presented at the U.S. Environmental
Protection Agency Symposium on Flue Gas Desulfurization,
New Orleans, March 8-11, 1976.
16. J. Rossoff, et al. , "Disposal of By-Products from Non-Regenerable
Flue Gas Desulfurization Systems: A Status Report, " Proceedings:
Symposium on Flue Gas Desulfurization — Atlanta, November 1974,
Volume I, EPA-650/2-74-126-a (NTIS No. PB 242-572/AS),
U.S. Environmental Protection Agency, Research Triangle Park,
NC (December 1974).
17. H. R. Borgwardt, "Limestone Scrubbing of SO2 at EPA Pilot Plant,"
Progress Report, June 11, 1973.
18. Grob, et al. , American Laboratory, _^ (6), 13-25(1975).
19. Taylor, Combustion, j45 (4), 15-22 (1973).
260
-------
20. Schropfev, Zeitschrift fur Anorg. und Allg. Chemie. 401 (1), 1-14
(1973).
21. P. A. Corrigan, Preliminary Feasibility Study of Calcium-Sulfur
Sludge Utilization~in the Wallboard Industry, TVA S-466, Tennessee
Valley Authority, Muscle Shoals, AL (June 21, 1974).
22. J. I. Bucy, J. L. Nevins, and P. A. Corrigan, "Potential Utilization
of Controlled SOX Emissions from Power Plants in the Eastern United
States," Paper presented at the U.S. Environmental Protection
Agency Symposium on Flue Gas Desulfurization, New Orleans,
March 8-11, 1976.
23. "An Evaluation of the Disposal of Flue Gas Desulfurization Wastes
in Mines and the Ocean -- Initial Assessment," prepared by
Arthur D. Little, Inc. , Cambridge, MA for the U.S. Environmental
Protection Agency, Research Triangle Park, NC, Contract No.
68-02-2334 (to be published).
24. F. J. Cservenyak, Recovery of Alumina from Kaolin by the Liime-
Soda Sinter Process, R. I. 4069, U.S. Dept. of the Interior, Bureau
of Mines, College Park, MD (1947).
25. F. A. Peters, P. W. Johnson, J. J. Henn, and D. C. Kirby,
Methods for Producing Alumina from Clay, R. I. 6927, U.S. Dept.
of the Interior, Bureau of Mines, College Park, MD (1966).
26. Proposal for the Development of a New Process for the Economic
Utilization of the Solid Waste Effluent from Linestone Slurry Wet
Scrubber Systems, Vols. I and II, Proposal No. 27359.000, TRW
Systems Group, Inc. , Redondo Beach, CA (1974).
27. O. W. Hargrove and J. G. Noblett, "Water Recycle/Reuse Alterna-
tives at the Arizona Public Service Four Corners Station, " Radian
Technical Note 200-118-07, EPA Contract 68-03-2339, July 23, 1976.
28. W. Gathman and J. G. Noblett, "Water Recycle/Reuse Alternatives
at the Public Service of Colorado Comanche Plant, " Radian Technical
Note 200-118-09, EPA Contract 68-03-2339, August 23, 1976.
29. J. G. Noblett, "Water Recycle/Reuse Alternatives at the Georgia
Power Company Plant Bowen, " Radian Technical Note 200-118-08,
EPA Contract 68-03-2339, August 17, 1976.
30. Renovation of Power Plant Cooling Tower Slowdown for Recycle by
Evaporation; Crystallization with Interface Enhancement, University
of California, Berkeley, CA, EPA Grant No. R803-257-012-3
(to be published).
31. U.S. Patent No. 3,846,254, November 5, 1974, and foreign
counterpart patents.
261
-------
32. R. H. Borgwardt, "Pilot Evaluation of Methods of Increasing
Limestone Utilization in FGD Scrubbers, " Paper presented at the
Sixty-Eighth Annual Meeting of the American Institute of Chemical
Engineers, Los Angeles, November 16-20, 1975.
33. D. J. Hagerty, Summary; Status of FGD Sludge Testing Program,
University of Louisville, Department of Civil Engineering, Louisville,
KY (November 1976).
34. K. B. Andrews, Research and Development Projects, Electric
Power Research Institute (November 4, 1976).
35. Coal Waste Disposal at Sea, Information pamphlet, New York State
Energy Research and Development Authority, NY.
36. Personal communication: R. Edwards, Southern Services, to
P. P. Leo, The Aerospace Corporation, September 16, 1976.
37. Personal Communication: R. Patton, IU Conversion Systems, to
J. Rossoff, The Aerospace Corporation, April 28, 1976.
38. Personal Communication: H. Mullen, IU Conversion Systems, to
J. W. Jones, Environmental Protection Agency, January 17, 1977.
39. Personal Communication: R. J. Bacskai, IU Conversion Systems,
to P. P. Leo, The Aerospace Corporation, January 17, 1977.
40. J. Ando and G. A. Isaacs, SOg Abatement for Stationary Sources in
Japan, EPA-600/2-76-013-a, U.S. Environmental Protection Agency,
Research Triangle Park, NC (January 1976).
262
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-78-224
2.
3. RECIPIENT'S ACCESSION NO.
Control of Waste and Water Pollution
from Coal-fired Power Plants: Second R&D Report
6. REPORT DATE
November 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
P. P. Leo and J. Rossoff
8. PERFORMING ORGANIZATION REPORT NO.
ATR-79(7297-01)-l
9. PERFORMING ORGANIZATION NAME AND ADDRESS
The Aerospace Corporation
Environment and Energy Conservation Division
El Segundo, California 90245
10. PROGRAM ELEMENT NO.
EHE624A
11. CONTRACT/GRANT NO.
68-02-1010
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND.PERIOD COVERED
Annual; 1/76 - 4/77
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES JERL-RTP project officer is Julian W. Jones, MD-61, 919/541-
2489. EPA-600/7-76-018 was previous report in this series.
16. ABSTRACl
The report is the second of a series summarizing and assessing the state
of research and development in the fields of flue gas cleaning waste treatment,
utilization, and disposal, as well as water reuse technology for coal-fired utility
power plants. Significant areas treated include: coal-pile drainage; ash character-
ization and disposal; chemical and physical properties and leaching characteristics
of treated and untreated flue gas desulfurization (FGD) wastes; field evaluations of
treated and untreated waste disposal; physical and chemical properties of gypsum
produced from FGD systems; cost estimates for producing and disposing of FGD
gypsum; potential use of FGD wastes in fertilizer production; the economics of
alumina production; and power plant water recycle, treatment, and reuse.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Pollution Flue Gases
Electric Power Plants
Coal
Combustion
Water Treatment
Waste Disposal
Desulfurization
Water Reclamation
Gypsum
Fertilizers
Aluminum Oxide
Pollution Control
Stationary Sources
Flue Gas Cleaning
Coal Piles
Coal Ash
13B
10B
21D
21B
07A,07D
08G
02A
07B
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
278
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
263
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